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Chemokine receptors in the central nervous system: Role in brain inflammation and neurodegenerative diseases
Abstract
Chemokines were originally described as chemotactic cytokines involved in leukocyte trafficking. Research over the last decade, however, has shown that chemokine receptors are not restricted to leukocytes. In the brain, chemokine receptors are not only found in microglia (a brain macrophage), but also in astrocytes, oligodendrocytes and neurons. In this review, we describe the spatial and cellular distribution of chemokine receptors in the brain, distinguishing between constitutively and inducibly expressed receptors. We then discuss possible physiological functions, including neuronal migration, cell proliferation and synaptic activity. Evidence is emerging that chemokine receptors are also involved in neuronal death and hence neurodegenerative diseases. Chemokines may induce neuronal death either indirectly (e.g. through activation of microglia killing mechanisms) or directly through activation of neuronal chemokine receptors. Disease processes in which chemokines and their receptors are likely to be involved include multiple sclerosis (MS), Alzheimer's disease (AD), HIV-associated dementia (HAD) and cerebral ischemic disease. The study of chemokines and their receptors in the central nervous system (CNS) is not only relevant for the understanding of brain physiology and pathophysiology, but may also lead to the development of targeted treatments for neurodegenerative diseases.
... Chemokines, including astrocytes, microglia, and neurons, are expressed in the human CNS from the embryonic stage to adult stage (Westmoreland et al., 2002). CCR5 is mainly distributed in microglia, with lower expression levels in astrocytes and neurons, although all are upregulated in disease states (Xia et al., 1998;Cartier et al., 2005). Numerous experiments have demonstrated that chemokines in the brain function beyond directing immune cell migration, including brain development, neuronal differentiation, neuronal communication, neuron survival, and learning and memory capabilities, directly by affecting neurons, or indirectly through glial cells (Song et al., 2002;Sorce et al., 2011;Wang et al., 2016). ...
... Normal Neural progenitor cells Induces neural progenitor cells to migrate and promotes neuronal differentiation Ji et al., 2004;Park et al., 2009 Neuron Promotes neuronal growth and differentiation during embryonic development Bolin et al., 1998;Park et al., 2009 Modulates neuronal excitability and neurotransmitter release Oh et al., 2002;Musante et al., 2008 Regulates neuronal survival or apoptosis Choi et al., 2013;Radzik et al., 2019 Inhibits hippocampus and cortical plasticity, impairs learning and memory processes Zhou et al., 2016;Necula et al., 2021 Microglia Mediates microglia migration and colonization, which may provide nutritional support, regulation of neuronal development, and removal of toxic debris Polazzi and Contestabile, 2002;Cowell et al., 2006 Astrocytes Regulates the proliferation, survival and differentiation of astrocyte progenitors during embryonic development Bakhiet et al., 2001;Cartier et al., 2005;Necula et al., 2021 Ischemic Tumor cell Promotes tumor cell proliferation and migration Aldinucci and Colombatti, 2014 Pathological pain Neuron Activates neuron ERK to create and maintain pathological pain Piotrowska et al., 2016;Hang et al., 2017;Lu et al., 2017 Reduces the antinociceptive action of opioid receptor agonists Szabo et al., 2002;Chen et al., 2007 (Continued) Frontiers in Cellular Neuroscience | www.frontiersin.org CCR5 plays a role in tumor development or progression in multiple myeloma, classical Hodgkin lymphoma, prostate, breast, gastric, colon, and ovarian cancer, glioblastoma, and melanoma (Brunn et al., 2007;Yu-Ju Wu et al., 2020). ...
... CCR5 and its ligands are overexpressed in both the periphery and brain of AD patients, which activates astrocytes and microglia, leading to amyloid deposits and memory dysfunction. However, some studies have also shown that CCR5 deletion can lead to worsening of AD, which may be due to a compensatory increase in CCR2 (Cartier et al., 2005;Goldeck et al., 2013). The autoimmune disease multiple sclerosis (MS) is a CNS disease with chronic inflammation caused by T cells. ...
Stroke is the world’s second major cause of adult death and disability, resulting in the destruction of brain tissue and long-term neurological impairment; induction of neuronal plasticity can promote recovery after stroke. C–C chemokine receptor 5 (CCR5) can direct leukocyte migration and localization and is a co-receptor that can mediate human immunodeficiency virus (HIV) entry into cells. Its role in HIV infection and immune response has been extensively studied. Furthermore, CCR5 is widely expressed in the central nervous system (CNS), is engaged in various physiological activities such as brain development, neuronal differentiation, communication, survival, and learning and memory capabilities, and is also involved in the development of numerous neurological diseases. CCR5 is differentially upregulated in neurons after stroke, and the inhibition of CCR5 in specific regions of the brain promotes motor and cognitive recovery. The mechanism by which CCR5 acts as a therapeutic target to promote neurorehabilitation after stroke has rarely been systematically reported yet. Thus, this review aims to discuss the function of CCR5 in the CNS and the mechanism of its effect on post-stroke recovery by regulating neuroplasticity and the inflammatory response to provide an effective basis for clinical rehabilitation after stroke.
... Although their primary function involves provoking immune responses by facilitating the precise movement of immune cells, they also exert direct influences on neuronal elements. Chemokines and their associated receptors stand as integral components orchestrating communication between neurons and inflammatory cells [39]. The correlation between change in inflammation markers and change in NFL was much stronger for those who remained suppressed than for those who became suppressed, suggesting that inflammation is more important Figure 2. Box plot of viral detectability and CSF Factor 1. ...
... Although their primary function involves provoking immune responses by facilitating the precise movement of immune cells, they also exert direct influences on neuronal elements. Chemokines and their associated receptors stand as integral components orchestrating communication between neurons and inflammatory cells [39]. The correlation between change in inflammation markers and change in NFL was much stronger for those who remained suppressed than for those who became suppressed, suggesting that inflammation is more important as a driver of neurodegeneration in those who are durably virally suppressed than in those who have not yet achieved suppression. ...
Background:
HIV infection causes neuroinflammation and immune activation (NIIA) and systemic inflammation and immune activation (SIIA), which in turn drive neurodegeneration (ND). Cross-sectionally, higher levels of NIIA biomarkers correlate with increased biomarkers of ND. A more convincing confirmation would be a longitudinal demonstration.
Methods:
PWH in the US multisite CHARTER Aging project were assessed at a baseline visit and after 12 years using standardized evaluations. We measured a panel of 14 biomarkers of NIIA, SIIA, and ND in plasma and CSF at two time points and calculated changes from baseline to the 12-year visit. Factor analysis yielded simplified indices of NIIA, SIIA, and ND.
Results:
The CSF NIIA factor analysis yielded Factor1 loading on soluble tumor necrosis factor type-2 (sTNFR-II) and neopterin, and Factor2, loading on MCP1, soluble CD14, and IL-6. The SIIA factor analysis yielded Factor1 loading on CRP, D-dimer, and Neopterin; Factor2 loading on sTNFR-II. The ND analysis yielded Factor1 loading on Phosphorylated tau (p-tau) and Aβ42; Factor2 loading on NFL. NIIA Factor1, but not Factor2, correlated with increases in CSF NFL (r = 0.370, p = 0.0002).
Conclusions:
Increases in NIIA and SIIA in PWH were associated with corresponding increases in ND, suggesting that reducing neuro/systemic inflammation might slow or reverse neurodegeneration.
... C-C motif chemokine receptor 5 (CCR5), a seven-transmembrane-domain G-protein-coupled receptor expressed in the central nervous system, is stimulated by chemokine ligands CCL3, CCL4, and CCL5 . 22 Recently, studies have shown that NSCs can express CCR5. [23][24][25][26] Thus, NSCs can exhibit chemotactic responses to the relative chemokine ligands; however, few studies have reported the effect of CCL5/CCR5 on the migration of transplanted NSCs in PD. ...
... 39 Evidence is emerging that CCL5 and CCR5 are involved in neurological diseases such as multiple sclerosis, stroke, and Alzheimer's disease. 22,40 Hence, we suspect that ethyl stearate may promote NSCs migration through chemokines and their receptors. The levels of proinflammatory factors and chemokines such as IL-1β, IL-33, CCL2, and CCL5 can be increased in PD. 41 The levels of IL-15 and CCL5 were increased in the PD patients who received levodopa, compared to healthy controls and the patients with PD. 42 Our study showed that ethyl stearate apparently improved the migration of NSCs in vitro, and increased the expression of CCR5 on NSCs both in vitro and in vivo. ...
Background
In recent years, the ability of neural stem cells (NSCs) transplantation to treat Parkinson's disease (PD) has attracted attention. However, it is still a challenge to promote the migration of NSCs to the lesion site and their directional differentiation into dopaminergic neurons in PD. C‐C motif chemokine ligand 5 (CCL5) and C‐C motif chemokine receptor 5 (CCR5) are expressed in the brain and are important regulators of cell migration. It has been reported that ethyl stearate (PubChem CID: 8122) has a protective effect in 6‐OHDA‐induced PD rats.
Methods
Parkinson's disease rats were injected with 6‐hydroxydopamine (6‐OHDA) into the right substantia nigra, and striatum followed by 8 μL of an NSC cell suspension containing 100 μM ethyl stearate and 8 × 10⁵ cells in the right striatum. The effect of transplantation NSCs combined with ethyl stearate was assessed by evaluating apomorphine (APO)‐induced turning behavior and performance in the pole test. Quantitative real‐time reverse transcription–polymerase chain reaction (qRT‐PCR), Western blotting (WB), and immunofluorescence staining were also performed.
Results
NSCs transplantation combined with ethyl stearate ameliorated the behavioral deficits of PD rats. PD rats that received transplantation NSCs combined with ethyl stearate exhibited increased expression of tyrosine hydroxylase (TH) and an increased number of green fluorescent protein (GFP)‐positive cells. Furthermore, GFP‐positive cells migrated into the substantia nigra and differentiated into dopaminergic neurons. The expression of CCL5 and CCR5 was significantly increased after transplantation NSCs combined with ethyl stearate.
Conclusions
These findings suggest that NSCs transplantation combined with ethyl stearate can improve the motor behavioral performance of PD rats by promoting NSCs migration from the striatum to the substantia nigra via CCL5/CCR5 and promoting the differentiation of NSCs into dopaminergic neurons.
... For instance, CXCL12 plays a vital role in regulating neuronal migration during cortical development (6,7). Remarkably, different studies show both chemokines and their receptors expressed in neurons, suggesting an implication of these components in direct neuronal communication (5,8). In homeostasis, neuronal CX 3 CL1 interacts with microglia preventing its activation (9). ...
... However, some chemokines, such as CCL2 after peripheral injury, have been also described to promote axonal regeneration as a result of macrophage recruitment and phenotype modulation (10,14). Meanwhile, although several chemokine receptors are expressed in different neuronal types (8,9), little is known about their functions as autocrine or paracrine messengers on other neurons. ...
While chemokines were originally described for their ability to induce cell migration, many studies show how these proteins also take part in many other cell functions, acting as adaptable messengers in the communication between a diversity of cell types. In the nervous system, chemokines participate both in physiological and pathological processes, and while their expression is often described on glial and immune cells, growing evidence describes the expression of chemokines and their receptors in neurons, highlighting their potential in auto- and paracrine signalling. In this study we analysed the role of nociception in the neuronal chemokinome, and in turn their role in axonal growth. We found that stimulating TRPV1⁺ nociceptors induces a transient increase in CCL21. Interestingly we also found that CCL21 enhances neurite growth of large diameter proprioceptors in vitro. Consistent with this, we show that proprioceptors express the CCL21 receptor CCR7, and a CCR7 neutralizing antibody dose-dependently attenuates CCL21-induced neurite outgrowth. Mechanistically, we found that CCL21 binds locally to its receptor CCR7 at the growth cone, activating the downstream MEK-ERK pathway, that in turn activates N-WASP, triggering actin filament ramification in the growth cone, resulting in increased axonal growth.
... 20,21 CCL27 produced by keratinocytes in which contributes to skin homeostasis 20 and T cell-mediated skin inflammation. 21 Also, The CCL27 and its receptors are expressed in microglia, oligodendrocytes, astrocytes, and neurons which it can have important roles the recruitment of T cells to CNS. 22,23 Recent studies suggest that members of the tumor necrosis factor (TNF) protein family contribute to tissue inflammation and increase of co-morbidities in different immune-mediated diseases. 24,25 TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, 26 has different roles in inflammatory diseases such as stroke, 27 trauma, 28 infections, 29 and MS. 30 The main mechanism of such role is the induction of apoptosis through Fas-associated protein in conjunction with death domain/death-inducing signaling complex (FADD/DISC)/caspase-8in several cell types such as oligodendroglia and neurons. ...
... 40 The CCL27 and its receptors are expressed in microglia, oligodendrocytes, astrocytes, and neurons and can contribute to neuronal death. 22 Interferon β as a treatment option in MS patients may inhibit the production of CCL27 and in this way inhibit CCL27 inflammatory effects. 23 According to our results, BAFF serum levels were significantly higher in MS patients along with a significant positive correlation with the severity of the disease. ...
The pathogenic roles of Interleukine-16 (IL-16), CCL27, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), and B-cell activating factor (BAFF) has been shown in some autoimmune and inflammatory diseases. We aimed to correlate the circulatory changes of such factors with the severity of disease in patients with multiple sclerosis (MS).
This case-control study was conducted on 84 MS patients and 83 healthy controls. We measured the serum levels of IL-16, CCL27, TRAIL, and BAFF in all participants by enzyme-linked immune sorbent assay. Using the expanded disability status scale (EDSS), we evaluated the severity of MS. Finally, we assessed the correlation between serum levels of such factors with the severity of MS.
We found increased serum levels of CCL27, IL-16, and BAFF in patients with MS compared to those in healthy subjects. However, no difference was found in serum levels of TRAIL between the patients and controls. In addition, a significant positive correlation between serum levels of CCL27, IL-16, TRAIL, and BAFF with disease severity according to EDSS score was determined.
We showed higher serum levels of CCL27, BAFF, TRAIL, and IL-16 in MS patients with more severe disabilities than mild forms. Such finding may represent their contribution to the pathogenesis of MS. Blocking such molecules may yield new treatments for MS.
... There are several cytokine and chemokine cues from the environment that are implicated in the persistent neuroinflammation of neurodegenerative diseases. Direct evidence for this was produced in 2005 when Cartier et al. showed elevated levels of pro-inflammatory and apoptotic molecules (IL-1α, CXCR2, CCR3, CCR5, and TGF-β) in post-mortem brain tissue in subjects with Alzheimer's disease (AD) compared to age-matched controls [50]. Like other neurodegenerative diseases, the prognosis of HIV, a life-long viral infection, is intimately mediated by long-lasting dysregulated cytokine pathways. ...
Despite combined antiretroviral therapy (cART) limiting HIV replication to undetectable levels in the blood, people living with HIV continue to experience HIV-associated neurocognitive disorder (HAND). HAND is associated with neurocognitive impairment, including motor impairment, and memory loss. HIV has been detected in the brain within 8 days of estimated exposure and the mechanisms for this early entry are being actively studied. Once having entered into the central nervous system (CNS), HIV degrades the blood–brain barrier through the production of its gp120 and Tat proteins. These proteins are directly toxic to endothelial cells and neurons, and propagate inflammatory cytokines by the activation of immune cells and dysregulation of tight junction proteins. The BBB breakdown is associated with the progression of neurocognitive disease. One of the main hurdles for treatment for HAND is the latent pool of cells, which are insensitive to cART and prolong inflammation by harboring the provirus in long-lived cells that can reactivate, causing damage. Multiple strategies are being studied to combat the latent pool and HAND; however, clinically, these approaches have been insufficient and require further revisions. The goal of this paper is to aggregate the known mechanisms and challenges associated with HAND.
... P2X7R produces chemokines induced by A-b peptides and recruits CD8T cells in brain parenchyma. Chemokines are expressed excessively in vitro and AD mouse models in response to A-b peptides, leading to the inflammatory process and recruitment of immune cells (148). Furthermore, this overexpression of chemokines contributes to the subsequent neurodegenerative process (149). ...
The P2X7 receptor (P2X7R), a non-selective cation channel modulated by adenosine triphosphate (ATP), localizes to microglia, astrocytes, oligodendrocytes, and neurons in the central nervous system, with the most incredible abundance in microglia. P2X7R partake in various signaling pathways, engaging in the immune response, the release of neurotransmitters, oxidative stress, cell division, and programmed cell death. When neurodegenerative diseases result in neuronal apoptosis and necrosis, ATP activates the P2X7R. This activation induces the release of biologically active molecules such as pro-inflammatory cytokines, chemokines, proteases, reactive oxygen species, and excitotoxic glutamate/ATP. Subsequently, this leads to neuroinflammation, which exacerbates neuronal involvement. The P2X7R is essential in the development of neurodegenerative diseases. This implies that it has potential as a drug target and could be treated using P2X7R antagonists that are able to cross the blood-brain barrier. This review will comprehensively and objectively discuss recent research breakthroughs on P2X7R genes, their structural features, functional properties, signaling pathways, and their roles in neurodegenerative diseases and possible therapies.
... Ccr5 (~ 35%) in the PFC in defeated female mice compared to the non-defeated controls ( Fig. 2A and Extended Data Fig. 2A). CCR5 is a seven-transmembrane G protein-coupled receptor expressed in microglia, astrocytes and neurons in diverse brain regions [47][48][49][50] . We did not observe similar changes in male mice following CSDS, implicating female specific response of Ccr5 to CSDS. ...
Chronic stress induces changes in the periphery and the central nervous system (CNS) that contribute to neuropathology and behavioral abnormalities associated with psychiatric disorders. In this study, we examined the impact of peripheral and central inflammation during chronic social defeat stress (CSDS) in female mice. Compared to male mice, we found that female mice exhibited heightened peripheral inflammatory response and identified C-C motif chemokine ligand 5 (CCL5), as a stress-susceptibility marker in females. Blocking CCL5 signaling in the periphery promoted resilience to CSDS. In the brain, stress-susceptible mice displayed increased expression of C-C chemokine receptor 5 (CCR5), a receptor for CCL5, in microglia in the prefrontal cortex (PFC). This upregulation was associated with microglia morphological changes, their increased migration to the blood vessels, and enhanced phagocytosis of synaptic components and vascular material. These changes coincided with neurophysiological alterations and impaired blood-brain barrier (BBB) integrity. By blocking CCR5 signaling specifically in the PFC were able to prevent stress-induced physiological changes and rescue social avoidance behavior. Our findings are the first to demonstrate that stress-mediated dysregulation of the CCL5-CCR5 axis triggers excessive phagocytosis of synaptic materials and neurovascular components by microglia, resulting in disruptions in neurotransmission, reduced BBB integrity, and increased stress susceptibility. Our study provides new insights into the role of cortical microglia in female stress susceptibility and suggests that the CCL5-CCR5 axis may serve as a novel sex-specific therapeutic target for treating psychiatric disorders in females.
... As mentioned above, the pathological brain features of AD include extracellular amyloid plaques; in addition, the inflammatory response in AD induces an increase in the number, size, and motor activity of microglia, as well as a morphological alteration, whereby they change from branched (resting) to amoeboid (active). In addition, the microglia surrounding the plaques appear to be positive for activation markers and proinflammatory mediators, including MHC class II, COX-2, TNF-α, and some interleukins [31][32][33][34]. Proinflammatory cytokines, such as TNF-α, IL-1β, and IL-6, can act directly on the neurons to induce apoptosis [35,36], and the activation of caspases and signal-dependent transcription factors, such as NF-κB and AP-1, leads to the production of many amplifiers (e.g., IL-1β, TNF-α, IL-6). ...
Neurodegenerative diseases (NDs) affect millions of people worldwide, and to date, Alzheimer’s and Parkinson’s diseases are the most common NDs. Of the many risk factors for neurodegeneration, the aging process has the most significant impact, to the extent that it is tempting to consider neurodegenerative disease as a manifestation of accelerated aging. However, genetic and environmental factors determine the course of neurodegenerative disease progression. It has been proposed that environmental stimuli influence neuroplasticity. Some clinical studies have shown that healthy lifestyles and the administration of nutraceuticals containing bioactive molecules possessing antioxidant and anti-inflammatory properties have a preventive impact or mitigate symptoms in previously diagnosed patients. Despite ongoing research efforts, the therapies currently used for the treatment of NDs provide only marginal therapeutic benefits; therefore, the focus is now directly on the search for natural products that could be valuable tools in combating these diseases, including the natural compound Andrographis paniculata (Ap) and its main constituent, andrographolide (Andro). Preclinical studies have shown that the aqueous extract of Ap can modulate neuroinflammatory and neurodegenerative responses, reducing inflammatory markers and oxidative stress in various NDs. Therefore, in this review, we will focus on the molecular mechanisms by which Ap and Andro can modulate the processes of neurodegeneration and neuroinflammation, which are significant causes of neuronal death and cognitive decline.
... The reason that the chemokine but not cytokine expression increased in mouse brains 30 days after RI and RCI is not clear yet, but it may be associated with different stages of brain injury since multiple cytokines, including the increased interleukins, have been reported by other groups at early time points [19,21]. While cytokines and chemokines are primarily involved in mediating inflammation, chemokines and their receptors are also essential in facilitating communication between neurons and inflammatory cells, and they play a crucial role in directing immune cells to the brain [41]. We need to be mindful that the specific chemokines associated with brain impairment caused by either RI or RCI are still unclear, and further studies are required to unravel this information. ...
Radiation injury- and radiation combined with skin injury-induced inflammatory responses in the mouse brain were evaluated in this study. Female B6D2F1/J mice were subjected to a sham, a skin wound (SW), 9.5 Gy 60Co total-body gamma irradiation (RI), or 9.5 Gy RI combined with a skin puncture wound (RCI). Survival, body weight, and wound healing were tracked for 30 days, and mouse brain samples were collected on day 30 after SW, RI, RCI, and the sham control. Our results showed that RCI caused more severe animal death and body weight loss compared with RI, and skin wound healing was significantly delayed by RCI compared to SW. RCI and RI increased the chemokines Eotaxin, IP-10, MIG, 6Ckine/Exodus2, MCP-5, and TIMP-1 in the brain compared to SW and the sham control mice, and the Western blot results showed that IP-10 and p21 were significantly upregulated in brain cells post-RI or -RCI. RI and RCI activated both astrocytes and endothelial cells in the mouse brain, subsequently inducing blood-brain barrier (BBB) leakage, as shown by the increased ICAM1 and GFAP proteins in the brain and GFAP in the serum. The Doublecortin (DCX) protein, the "gold standard" for measuring neurogenesis, was significantly downregulated by RI and RCI compared with the sham group. Furthermore, RI and RCI decreased the expression of the neural stem cell marker E-cadherin, the intermediate progenitor marker MASH1, the immature neuron cell marker NeuroD1, and the mature neuron cell marker NeuN, indicating neural cell damage in all development stages after RI and RCI. Immunohistochemistry (IHC) staining further confirmed the significant loss of neural cells in RCI. Our data demonstrated that RI and RCI induced brain injury through inflammatory pathways, and RCI exacerbated neural cell damage more than RI.
... As mentioned above, the brain pathological features of AD include extracellular amyloid plaques; in addition, the inflammatory response in AD induces an increase in the number, size, and 3 motor activity of microglia as well as a morphological change whereby they change from branched (resting) to amoeboid (active). In addition, microglia surrounding plaques appears positive for activation markers and proinflammatory mediators, including MHC class II, COX-2, TNF-α, and some interleukins [18,19]. Proinflammatory cytokines, such as TNF-α, IL-1β, and IL-6, in turn can act directly on neurons to induce apoptosis [20,21], and activation of caspases and signal-dependent transcription factors, such as NF-κB and AP-1, leads to the production of numerous amplifiers (e.g., IL-1β, TNF-α, IL-6). ...
Neurodegenerative diseases (NDs) affect millions of people worldwide, and to date Alzheimer's and Parkinson's disease are the most common NDs. The risk of developing NDs increases dra-matically with age, and genetic and environmental factors can be crucial in their progression. The main feature of NDs is the abnormal presence of specific proteins that can lead to neuronal death, proteotoxic stress, and alteration of catabolic systems, which are major players in the processes of neurodegeneration and neuroinflammation. Despite research efforts to date, the therapies cur-rently in use for the treatment of NDs provide marginal therapeutic benefit, so the focus is now being direct toward the search of natural products that could be a valuable aid in combating these diseases, including the natural compound Andrographis paniculata (Ap) and especially its main constituent Andrographolide (Andro). Preclinical studies have shown that the aqueous extract of Ap is capable to modulate neuroinflammatory and neurodegenerative responses, determining a reduction in inflammatory markers and oxidative stress in various NDs. Therefore, in this review we will focus on the molecular mechanisms through which Ap and Andro are able to modulate the processes of neurodegeneration and neuroinflammation that are major causes of neuronal death and cognitive decline.
... Chemokines are a family of small cytokines, initially studied because of their ability to manage the migration of leukocytes in the respective anatomical locations during inflammatory and homeostatic processes (see [36,37] for a review). Besides their contribution in inflammation, chemokines also play a role in brain development [34,38] and in neurodevelopment disorders, such as autism and schizophrenia [39][40][41][42]. ...
Maternal infections during pregnancy may increase the risk of psychiatric disorders in offspring. We recently demonstrated that activation of peroxisome proliferator-activate receptor‐α (PPARα), with the clinically available agonist fenofibrate, attenuates the neurodevelopmental disturbances induced by maternal immune activation (MIA) in rat offspring. We hypothesized that fenofibrate might reduce MIA-induced cytokine imbalance using a MIA model based on the viral mimetic polyriboinosinic-polyribocytidilic acid [poly (I:C)]. By using the Bio-Plex Multiplex-Immunoassay-System, we measured cytokine/chemokine levels in maternal serum and in the fetal brain of rats treated with fenofibrate, at 6 and 24 hours after poly (I:C). We found that MIA induced time-dependent changes in the levels of several cytokines/chemokines/colony-stimulating factors (CSFs). Specifically, the maternal serum of the poly (I:C)/CTRL group showed increased levels of (i) proinflammatory chemokine macrophage inflammatory protein 1-alpha (MIP-1α), (ii) tumor necrosis factor-alpha (TNF-), the monocyte chemoattractant protein-1 (MCP-1), the macrophage (M-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Conversely, in the fetal brain of the poly (I:C)/CTRL group, interleukin 12p70 and MIP-1 levels were lower than in veh/CTRL group. Notably, MIP-1, TNF-, GRO/KC, GM-CSF, and M-CSF levels were lower in the poly (I:C)/FEN than in poly (I:C)/CTRL rats, indicating the protective role of the PPARα agonist. PPARα might represent a therapeutic target to attenuate the consequences of MIA.
... Pro-inflammatory cytokines and chemokines are significantly elevated in the brain of AD patients compared to healthy controls, as well as in animal models of AD [6][7][8][9]. These neuroinflammatory mediators appear early in the disease time course, suggesting their significant role in AD pathogenesis [8]. ...
Neurodegenerative diseases, including Alzheimer's disease (AD), are major contributors to death and disability worldwide. A multitude of evidence suggests that neuroinflammation is critical in neurodegenerative disease processes. Exploring the key mediators of neuroinflammation in AD, a prototypical neurodegenerative disease, could help identify pathologic inflammatory mediators and mechanisms in other neurodegenerative diseases. Elevated levels of the multifunctional inflammatory protein thrombin are commonly found in conditions that increase AD risk, including diabetes, atherosclerosis, and traumatic brain injury. Thrombin, a main driver of the coagulation cascade, has been identified as important to pathological events in AD and other neurodegenerative diseases. Furthermore, recent evidence suggests that coagulation cascade-associated proteins act as drivers of inflammation in the AD brain, and studies in both human populations and animal models support the view that abnormalities in thrombin generation promote AD pathology. Thrombin drives neuroinflammation through its pro-inflammatory activation of microglia, astrocytes, and endothelial cells. Due to the wide-ranging pro-inflammatory effects of thrombin in the brain, inhibiting thrombin could be an effective strategy for interrupting the inflammatory cascade which contributes to neurodegenerative disease progression and, as such, may be a potential therapeutic target for AD and other neurodegenerative diseases.
... Thus, the CCR may also be involved in leukocyte recruitment in aging CX. This is supported by evidence that GPCRs and CCR receptor levels are also altered in CX from aged rodents (Cartier et al., 2005;Gu et al., 2021). In addition, what can support the suggestion mentioned earlier is that the DEGs of cortical tissue were enriched in several inflammatory signaling pathways in the KEGG results. ...
The mechanism of brain aging is not fully understood. Few studies have attempted to identify molecular changes using bioinformatics at the subregional level in the aging brain. This study aimed to identify the molecular signatures and key genes involved in aging, depending on the brain region. Differentially expressed genes (DEGs) associated with aging of the cerebral cortex (CX), hippocampus (HC), and cerebellum (CB) were identified based on five datasets from the Gene Expression Omnibus (GEO). The molecular signatures of aging were explored using functional and pathway analyses. Hub genes of each brain region were determined by protein-protein interaction network analysis, and commonly expressed DEGs (co-DEGs) were also found. Gene-microRNAs (miRNAs) and gene-disease interactions were constructed using online databases. The expression levels and regional specificity of the hub genes and co-DEGs were validated using animal experiments. In total, 32, 293, and 141 DEGs were identified in aging CX, HC, and CB, respectively. Enrichment analysis indicated molecular changes related to leukocyte invasion, abnormal neurotransmission, and impaired neurogenesis due to inflammation as the major signatures of the CX, HC, and CB. Itgax is a hub gene of cortical aging. Zfp51 and Zfp62 were identified as hub genes involved in hippocampal aging. Itgax and Cxcl10 were identified as hub genes involved in cerebellar aging. S100a8 was the only co-DEG in all three regions. In addition, a series of molecular changes associated with inflammation was observed in all three brain regions. Several miRNAs interact with hub genes and S100a8. The change in gene levels was further validated in an animal experiment. Only the upregulation of Zfp51 and Zfp62 was restricted to the HC. The molecular signatures of aging exhibit regional differences in the brain and seem to be closely related to neuroinflammation. Itgax, Zfp51, Zfp62, Cxcl10, and S100a8 may be key genes and potential targets for the prevention of brain aging.
... 29 The binding of chemokine and receptor leads to the activation of intracellular signaling pathways, such as the mitogenactivated protein kinases (MAPKs), phospholipase C (PLC) pathway, and phosphoinositide 3-kinases (PI3K). 30,31 The MAPKs members including extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK) are activated in the DRG and spinal cord by peripheral nerve injury. 32 Similarly, phosphorylated ERK, p38 and JNK are accumulated, increasing excitability of sensory neurons and thus facilitating mechanical allodynia in trigeminal neuropathic pain models. ...
Background:
Chemokine-mediated neuroinflammation plays an important role in the pathogenesis of neuropathic pain. The chemokine CC motif ligand 7 (CCL7) and its receptor CCR2 have been reported to contribute to neuropathic pain via astrocyte-microglial interaction in the spinal cord. Whether CCL7 in the trigeminal ganglion (TG) involves in trigeminal neuropathic pain and the involved mechanism remain largely unknown.
Methods:
The partial infraorbital nerve transection (pIONT) was used to induce trigeminal neuropathic pain in mice. The expression of Ccl7, Ccr1, Ccr2, and Ccr3 was examined by real-time quantitative PCR (qPCR). The distribution of CCL7, CCR2, and CCR3 was detected by immunofluorescence double-staining. The activation of extracellular signal-regulated kinase (ERK) was examined by Western blot and immunofluorescence. The effect of CCL7 on neuronal excitability was tested by whole-cell patch clamp recording. The effect of selective antagonists for CCR1, CCR2, and CCR3 on pain hypersensitivity was checked by behavioral testing.
Results:
Ccl7 was persistently increased in neurons of TG after pIONT, and specific inhibition of CCL7 in the TG effectively relieved pIONT-induced orofacial mechanical allodynia. Intra-TG injection of recombinant CCL7 induced mechanical allodynia and increased the phosphorylation of ERK in the TG. Incubation of CCL7 with TG neurons also dose-dependently enhanced the neuronal excitability. Furthermore, pIONT increased the expression of CCL7 receptors Ccr1, Ccr2, and Ccr3. The intra-TG injection of the specific antagonist of CCR2 or CCR3 but not of CCR1 alleviated pIONT-induced orofacial mechanical allodynia and reduced ERK activation. Immunostaining showed that CCR2 and CCR3 are expressed in TG neurons, and CCL7-induced hyperexcitability of TG neurons was decreased by antagonists of CCR2 or CCR3.
Conclusion:
CCL7 activates ERK in TG neurons via CCR2 and CCR3 to enhance neuronal excitability, which contributes to the maintenance of trigeminal neuropathic pain. CCL7-CCR2/CCR3-ERK pathway may be potential targets for treating trigeminal neuropathic pain.
... Aβ deposition is accompanied by the activation of the innate immune system. The microglia surrounding Aβ plaques with altered morphology and activation state have higher levels of inflammatory factors [58,59]. In the early stage of AD, activated microglia prevent the accumulation of toxic Aβ by phagocytosis and achieve the protection of neurons. ...
The deposition of amyloid-beta (Aβ) plaques in the brain is one of the primary pathological characteristics of Alzheimer’s disease (AD). It can take place 20–30 years before the onset of clinical symptoms. The imbalance between the production and the clearance of Aβ is one of the major causes of AD. Enhancing Aβ clearance at an early stage is an attractive preventive and therapeutic strategy of AD. Direct inhibition of Aβ production and aggregation using small molecules, peptides, and monoclonal antibody drugs has not yielded satisfactory efficacy in clinical trials for decades. Novel approaches are required to understand and combat Aβ deposition. Neurological dysfunction is a complex process that integrates the functions of different types of cells in the brain. The role of non-neurons in AD has not been fully elucidated. An in-depth understanding of the interactions between neurons and non-neurons can contribute to the elucidation of Aβ formation and the identification of effective drug targets. AD patient-derived pluripotent stem cells (PSCs) contain complete disease background information and have the potential to differentiate into various types of neurons and non-neurons in vitro, which may bring new insight into the treatment of AD. Here, we systematically review the latest studies on Aβ clearance and clarify the roles of cell interactions among microglia, astroglia and neurons in response to Aβ plaques, which will be beneficial to explore methods for reconstructing AD disease models using inducible PSCs (iPSCs) through cell differentiation techniques and validating the applications of models in understanding the formation of Aβ plaques. This review may provide the most promising directions of finding the clues for preventing and delaying the development of AD.
... Before chronic inflammation develops peripherally in response to increased adiposity, short periods of HFD exposure are associated with an acute, central inflammation in the brainstem and hypothalamus (Astiz et al., 2017;Belegri et al., 2018;Buckman et al., 2015;Guillemot-Legris et al., 2016;Kalin et al., 2015;Thaler et al., 2012;Waise et al., 2015) along with the activation of local astrocytes and microglia (Cartier et al., 2005;Clyburn & Browning, 2019;Thaler et al., 2012). Within the adjacent NTS, morphological changes have been observed in response to acute HFD exposure and chemogenetic activation of DVC astrocytes reduces food intake significantly (MacDonald et al., 2020). ...
Prolonged high‐fat diet (HFD) exposure is associated with hyperphagia, excess caloric intake and weight gain. After initial exposure to a HFD, a brief (24–48 h) period of hyperphagia is followed by the regulation of caloric intake and restoration of energy balance within an acute (3–5 day) period. Previous studies have demonstrated this occurs via a vagally mediated signalling cascade that increases glutamatergic transmission via activation of NMDA receptors located on gastric‐projecting neurons of the dorsal motor nucleus of the vagus (DMV). The present study used electrophysiological recordings from thin brainstem slice preparations, in vivo recordings of gastric motility and tone, measurement of gastric emptying rates, and food intake studies to investigate the hypothesis that activation of brainstem astrocytes in response to acute HFD exposure is responsible for the increased glutamatergic drive to DMV neurons and the restoration of caloric balance. Pharmacological and chemogenetic inhibition of brainstem astrocytes reduced glutamatergic signalling and DMV excitability, dysregulated gastric tone and motility, attenuated the homeostatic delay in gastric emptying, and prevented the decrease in food intake that is observed during the period of energy regulation following initial exposure to HFD. Understanding the mechanisms involved in caloric regulation may provide critical insights into energy balance as well as into the hyperphagia that develops as these mechanisms are overcome. image
Key points
Initial exposure to a high fat diet is associated with a brief period of hyperphagia before caloric intake and energy balance is restored.
This period of homeostatic regulation is associated with a vagally mediated signalling cascade that increases glutamatergic transmission to dorsal motor nucleus of the vagus (DMV) neurons via activation of synaptic NMDA receptors.
The present study demonstrates that pharmacological and chemogenetic inhibition of brainstem astrocytes reduced glutamatergic signalling and DMV neuronal excitability, dysregulated gastric motility and tone and emptying, and prevented the regulation of food intake following high‐fat diet exposure.
Astrocyte regulation of glutamatergic transmission to DMV neurons appears to involve release of the gliotransmitters glutamate and ATP.
Understanding the mechanisms involved in caloric regulation may provide critical insights into energy balance as well as into the hyperphagia that develops as these mechanisms are overcome.
... Some chemokines have pleiotropic properties and activate different receptors (Figure 1), including CCL3/CCR1, CCR5; CCL4/CCR5, CCR8; CCL5/CCR1, CCR3, CCR5; CCL7/CCR1, CCR2; CCR3; CCR5; and CCL11/CCR2/CCR3/CCR5, and some chemokines activate only one receptor, such as CX3CL1-CX3CR1, CXCL25-CXCR9, and CXCL13-CXCR5 [3]. After binding with their ligand, chemokine receptors activate a cascade of intracellular signaling pathways, e.g., mitogen-activated protein kinase (MAPK), phospholipase C (PLC), and phosphatidylinositol 3-kinase (PI3-K), which lead to a wide range of cellular processes, such as chemotaxis, adhesion, cell activation or cell polarization, which amplify the production of cytokines [4][5][6]. GRO, growth-related oncogene; HCC, haemofiltrate CC chemokine; IL, interleukin; IP-10, interferon-inducible protein 10; I-TAC, interferon-inducible T-cell alpha chemoattractant; LEC, liver-expressed chemokine; LCC-1, liver-specific CC chemokine-1; MCP, monocyte chemoattractant protein; MDC, macrophage-derived chemokine; MEC, mammary-enriched chemokine; Mig, monokine induced by interferon γ; MIP, macrophage inflammatory protein; MPIF, myeloid progenitor inhibitory factor; NAP, neutrophil-activating peptide; PF4, platelet factor 4; RANTES, 'regulated on activation, normally T-cell-expressed and -secreted'; SCM-1α/β, single C motif-1 α/β; SDF, stromal-cellderived factor; TARC, thymus-and activation-regulated chemokine; TECK, thymus-expressed chemokine. ...
Chemokines and their receptors participate in many biological processes, including the modulation of neuroimmune interactions. Approximately fifty chemokines are distinguished in humans, which are classified into four subfamilies based on the N-terminal conserved cysteine motifs: CXC, CC, C, and CX3C. Chemokines activate specific receptors localized on the surface of various immune and nervous cells. Approximately twenty chemokine receptors have been identified, and each of these receptors is a seven-transmembrane G-protein coupled receptor. Recent studies provide new evidence that CC chemokine receptor 4 (CCR4) is important in the pathogenesis of many diseases, such as diabetes, multiple sclerosis, asthma, dermatitis, and cancer. This review briefly characterizes CCR4 and its ligands (CCL17, CCL22, and CCL2), and their contributions to immunological and neoplastic diseases. The review notes a significant role of CCR4 in nociceptive transmission, especially in painful neuropathy, which accompanies many diseases. The pharmacological blockade of CCR4 seems beneficial because of its pain-relieving effects and its influence on opioid efficacy. The possibilities of using the CCL2/CCL17/CCL22/CCR4 axis as a target in new therapies for many diseases are also discussed.
... CCR5, a seven-membrane G protein-coupled receptor (GPCR), is highly expressed in microglia and is found to a lesser extent in neurons and astrocytes (Cartier et al., 2005;Fantuzzi et al., 2019;Tran et al., 2007;Westmoreland et al., 2002). CCR5 is enriched in the hippocampal CA1 (Torres-Muñoz et al., 2004), a brain region known to be critical for the acquisition and consolidation of episodic and spatial memories, the latter of which are crucial to successful navigation. ...
While combination antiretroviral therapy (cART) has successfully increased the lifespan of individuals infected with HIV, a significant portion of this population remains affected by HIV-associated neurocognitive disorder (HAND). C-C chemokine receptor 5 (CCR5) has been well studied in immune response and as a co-receptor for HIV infection. HIV-infected (HIV⁺) patients experienced mild to significant amelioration of cognitive function when treated with different CCR5 antagonists, including maraviroc and cenicriviroc. Consistent with clinical results, Ccr5 knockout or knockdown rescued cognitive deficits in HIV animal models, with mechanisms of reduced microgliosis and neuroinflammation. Pharmacologic inhibition of CCR5 directly improved cerebral and hippocampal neuronal plasticity and cognitive function. By summarizing the animal and human studies of CCR5 in HIV-associated cognitive deficits, this review aims to provide an overview of the mechanistic role of CCR5 in HAND pathophysiology. This review also discusses the addition of CCR5 antagonists, such as maraviroc, to cART for targeted prevention and treatment of cognitive impairments in patients infected with HIV.
... Anti-HMGB1 mAbs have proven to be effective in different mouse models of epilepsy (138)(139)(140), reducing also the chronic inflammatory pathways (upregulation of inflammation-related genes, microglial activation, and neuronal cell death). Chemokines are involved at different levels in CNS homeostasis, and have been implicated in the pathogenesis of different CNS diseases, including epilepsy (26,141). In animal models of epilepsy, the administration of a CCL2 transcription inhibitor (Bindarit) or a selective antagonist of the CCR2 receptor (RS102895) suppressed the LPS-induced seizure enhancement (142,143). ...
Introduction
Recent studies prompted the identification of neuroinflammation as a potential target for the treatment of epilepsy, particularly drug-resistant epilepsy, and refractory status epilepticus. This work provides a systematic review of the clinical experience with anti-cytokine agents and agents targeting lymphocytes and aims to evaluate their efficacy and safety for the treatment of refractory epilepsy. Moreover, the review analyzes the main therapeutic perspectives in this field.
Methods
A systematic review of the literature was conducted on MEDLINE database. Search terminology was constructed using the name of the specific drug (anakinra, canakinumab, tocilizumab, adalimumab, rituximab, and natalizumab) and the terms “status epilepticus,” “epilepsy,” and “seizure.” The review included clinical trials, prospective studies, case series, and reports published in English between January 2016 and August 2021. The number of patients and their age, study design, specific drugs used, dosage, route, and timing of administration, and patients outcomes were extracted. The data were synthesized through quantitative and qualitative analysis.
Results
Our search identified 12 articles on anakinra and canakinumab, for a total of 37 patients with epilepsy (86% febrile infection-related epilepsy syndrome), with reduced seizure frequency or seizure arrest in more than 50% of the patients. The search identified nine articles on the use of tocilizumab (16 patients, 75% refractory status epilepticus), with a high response rate. Only one reference on the use of adalimumab in 11 patients with Rasmussen encephalitis showed complete response in 45% of the cases. Eight articles on rituximab employment sowed a reduced seizure burden in 16/26 patients. Finally, one trial concerning natalizumab evidenced a response in 10/32 participants.
Conclusion
The experience with anti-cytokine agents and drugs targeting lymphocytes in epilepsy derives mostly from case reports or series. The use of anti-IL-1, anti-IL-6, and anti-CD20 agents in patients with drug-resistant epilepsy and refractory status epilepticus has shown promising results and a good safety profile. The experience with TNF inhibitors is limited to Rasmussen encephalitis. The use of anti-α4-integrin agents did not show significant effects in refractory focal seizures. Concerning research perspectives, there is increasing interest in the potential use of anti-chemokine and anti-HMGB-1 agents.
... Another main role of chemokines is to attract circulating granulocytes, lymphocytes, and monocytes to the site of injury, resulting in an inflammatory response [125]. Of note, it is now known that chemokines and chemokine receptors are expressed not only by immune cells but also by cells of the nervous system (e.g., neurons and glial cells) [122,126,127] (Box 1). ...
Neuropathic pain (NP) originates from an injury or disease of the somatosensory nervous system. This heterogeneous origin and the possible association with other pathologies make the management of NP a real challenge. To date, there are no satisfactory treatments for this type of chronic pain. Even strong opioids, the gold-standard analgesics for nociceptive and cancer pain, display low efficacy and the paradoxical ability to exacerbate pain sensitivity in NP patients. Mounting evidence suggests that chemokine upregulation may be a common mechanism driving NP pathophysiology and chronic opioid use-related consequences (analgesic tolerance and hyperalgesia). Here, we first review preclinical studies on the role of chemokines and chemokine receptors in the development and maintenance of NP. Second, we examine the change in chemokine expression following chronic opioid use and the crosstalk between chemokine and opioid receptors. Then, we examine the effects of inhibiting specific chemokines or chemokine receptors as a strategy to increase opioid efficacy in NP. We conclude that strong opioids, along with drugs that block specific chemokine/chemokine receptor axis, might be the right compromise for a favorable risk/benefit ratio in NP management.
... Cytokines and chemokines, produced by microglia, neurons, astrocytes, and ECs, can attract leukocytes such as neutrophils, monocytes, and lymphocytes (Kim et al., 2016). Once activated, these cells participate to further increasing the levels of inflammation and inducing neuronal death (Cartier et al., 2005;Ramesh et al., 2013). Of note, proinflammatory cytokines IL-1β and TNF as well as chemokines KC/IL-8/CXCL8 and MIP1α present a biphasic response to 4-min ACC, with a peak at 6-h and a peak at 36-h post-ACC. ...
Aortic aneurism open repair surgery can cause spinal cord (SC) injury with 5–15% of patients developing paraparesis or paraplegia. Using a mouse model of transient aortic cross-clamping (ACC), we have previously found that the expression of proinflammatory microRNA miR-155 increases in motoneurons (MNs) and endothelial cells (ECs) of ischemic SCs, and that global miR-155 deletion decreases the percentage of paraplegia by 37.4% at 48-h post-ACC. Here, we investigated the cell-specific contribution of miR-155 in choline acetyltransferase-positive (ChAT ⁺ ) neurons (that include all MNs of the SC) and ECs to SC injury after ACC. Mice lacking miR-155 in ChAT ⁺ neurons (MN- miR-155 -KO mice) developed 24.6% less paraplegia than control mice at 48-h post-ACC. In contrast, mice lacking miR-155 in ECs (ECs- miR-155 -KO mice) experienced the same percentage of paraplegia as control mice, despite presenting smaller central cord edema. Unexpectedly, mice overexpressing miR-155 in ChAT ⁺ neurons were less likely than control mice to develop early paraplegia during the first day post-ACC, however they reached the same percentage of paraplegia at 48-h. In addition, all mice overexpressing miR-155 in ECs (ECs- miR-155 -KI mice) were paraplegic at 48-h post-ACC. Altogether, our results suggest that miR-155 activity in ChAT ⁺ neurons protects the SC against ischemic injury during the first day post-ACC before becoming deleterious during the second day, which indicates that early and late paraplegias arise from different molecular malfunctions. These results point to the need to develop specific protective therapeutics aimed at inhibiting both the early and late deleterious events after open repair surgery of aortic aneurisms.
... Scale bars represents 50 Further in vitro investigation of IL-16 revealed a direct negative impact on the number of mature PLP expressing oligodendrocytes and reduced levels of de novo myelination. To our knowledge, this is the first investigation to reveal an inhibitory role for IL-16 on myelinating glia, however it is well established that chemokine receptors are present not only on inflammatory cells, but also on astrocytes, oligodendrocytes, and neurons [80]. The receptor for IL16 is CD4 and although typically its expression is found on immune cells it has been reported in neurons, glia, and microglia throughout the brain [81][82][83][84]. ...
One of the therapeutic approaches for the treatment of the autoimmune demyelinating disease, multiple sclerosis (MS) is bone marrow mesenchymal stromal cell (hBM-MSCs) transplantation. However, given their capacity to enhance myelination in vitro, we hypothesised that human olfactory mucosa-derived MSCs (hOM-MSCs) may possess additional properties suitable for CNS repair. Herein, we have examined the efficacy of hOM-MSCs versus hBM-MSCs using the experimental autoimmune encephalomyelitis (EAE) model. Both MSC types ameliorated disease, if delivered during the initial onset of symptomatic disease. Yet, only hOM-MSCs improved disease outcome if administered during established disease when animals had severe neurological deficits. Histological analysis of spinal cord lesions revealed hOM-MSC transplantation reduced blood–brain barrier disruption and inflammatory cell recruitment and enhanced axonal survival. At early time points post-hOM-MSC treatment, animals had reduced levels of circulating IL-16, which was reflected in both the ability of immune cells to secrete IL-16 and the level of IL-16 in spinal cord inflammatory lesions. Further in vitro investigation revealed an inhibitory role for IL-16 on oligodendrocyte differentiation and myelination. Moreover, the availability of bioactive IL-16 after demyelination was reduced in the presence of hOM-MSCs. Combined, our data suggests that human hOM-MSCs may have therapeutic benefit in the treatment of MS via an IL-16-mediated pathway, especially if administered during active demyelination and inflammation.
Anxiety refers to emotional responses triggered by discrete environmental factors that lead to defensive behaviors. Although the neural circuits underlying anxiety behaviors have been extensively studied, the molecular mechanisms involved in anxiety remain poorly understood. In this study, we explored the role of fam19a5a , a zebrafish ortholog of the human FAM19A5 gene encoding a secreted peptide, in anxiety responses. We conducted gene expression and behavioral analyses. Additionally, we measured the brain neuronal activity and analyzed the transcriptomes to elucidate the cellular and molecular mechanisms underlying the function of fam19a5a in anxiety-like responses. Gene expression analyses revealed a broad expression of zebrafish fam19a5a in anxiety-associated brain regions, including the septum, pallial amygdala, and habenula. Using multiple behavioral paradigms and genetic models for loss-of-function and gain-of-function studies, we demonstrated that loss of fam19a5a significantly reduced anxiety-like behaviors, unlike those previously reported in Fam19a5 knockout mice. Moreover, neuronal overexpression of fam19a5a diminished anxiety-like responses. Neuronal activity analysis revealed altered activity in the septum, pallial amygdala, and habenula in the fam19a5a -knockout brain, without changes in neurotransmitter levels. However, elevated neuronal activity was observed in the preoptic area of the neuronal fam19a5a -overexpressing brain. Transcriptomic analyses revealed upregulation of anti-inflammatory chemokine/cytokine levels and downregulation of pro-inflammatory factor levels in both fam19a5a -knockout and neuronal fam19a5a -overexpressing brains. In summary, our findings suggest that fam19a5a regulates anxiety-like behaviors in zebrafish by modulating the anti-inflammatory chemokine/cytokine signaling pathways.
Background: Alzheimer’s disease (AD) is the most common sort of neurodegenerative dementia, characterized by its challenging, diverse, and progressive nature. Despite significant progress in neuroscience, the current treatment strategies remain suboptimal. Objective: Identifying a more accurate molecular target for the involvement of microglia in the pathogenic process of AD and exploring potential mechanisms via which it could influence disease. Methods: We utilized single-cell RNA sequencing (scRNA-seq) analysis in conjunction with APP/PS1 mouse models to find out the molecular mechanism of AD. With the goal of investigating the cellular heterogeneity of AD, we downloaded the scRNA-seq data from the Gene Expression Omnibus (GEO) database and identified differentially expressed genes (DEGs). Additionally, we evaluated learning and memory capacity using the behavioral experiment. We also examined the expression of proteins associated with memory using western blotting. Immunofluorescence was employed to investigate alterations in amyloid plaques and microglia. Results: Our findings revealed an upregulation of ITGAX expression in APP/PS1 transgenic mice, which coincided with a downregulation of synaptic plasticity-related proteins, an increase in amyloid-β (Aβ) plaques, and an elevation in the number of M1 microglia. Interestingly, deletion of ITGAX resulted in increased Aβ plaque deposition, a rise in the M1 microglial phenotype, and decreased production of synaptic plasticity-related proteins, all of which contributed to a decline in learning and memory. Conclusions: This research suggested that ITGAX may have a beneficial impact on the APP/PS1 mice model, as its decreased expression could exacerbate the impairment of synaptic plasticity and worsen cognitive dysfunction.
Hyperglycemia has been shown to modulate the immune response of peripheral immune cells and organs, but the impact of hyperglycemia on neuroinflammation within the brain remains elusive. In the present study, we provide evidences that streptozotocin (STZ)-induced hyperglycemic condition in mice drives a phenotypic switch of brain astrocytes to a proinflammatory state, and increases brain vulnerability to mild peripheral inflammation. In particular, we found that hyperglycemia led to a significant increase in the astrocyte proliferation as determined by flow cytometric and immunohistochemical analyses of mouse brain. The increased astrocyte proliferation by hyperglycemia was reduced by Glut1 inhibitor BAY-876. Transcriptomic analysis of isolated astrocytes from Aldh1l1CreERT2;tdTomato mice revealed that peripheral STZ injection induced astrocyte reprogramming into proliferative, and proinflammatory phenotype. Additionally, STZ-induced hyperglycemic condition significantly enhanced the infiltration of circulating myeloid cells into the brain and the disruption of blood-brain barrier in response to mild lipopolysaccharide (LPS) administration. Systemic hyperglycemia did not alter the intensity and sensitivity of peripheral inflammation in mice to LPS challenge, but increased the inflammatory potential of brain microglia. In line with findings from mouse experiments, a high-glucose environment intensified the LPS-triggered production of proinflammatory molecules in primary astrocyte cultures. Furthermore, hyperglycemic mice exhibited a significant impairment in cognitive function after mild LPS administration compared to normoglycemic mice as determined by novel object recognition and Y-maze tasks. Taken together, these results demonstrate that hyperglycemia directly induces astrocyte reprogramming towards a proliferative and proinflammatory phenotype, which potentiates mild LPS-triggered inflammation within brain parenchymal regions.
Interleukin-8 (IL-8/CXCL8), an essential CXC chemokine, significantly influences psychoneuroimmunological processes and affects neurological and psychiatric health. It exerts a profound effect on immune cell activation and brain function, suggesting potential roles in both neuroprotection and neuroinflammation. IL-8 production is stimulated by several factors, including reactive oxygen species (ROS) known to promote inflammation and disease progression. Additionally, CXCL8 gene polymorphisms can alter IL-8 production, leading to potential differences in disease susceptibility, progression, and severity across populations. IL-8 levels vary among neuropsychiatric conditions, demonstrating sensitivity to psychosocial stressors and disease severity. IL-8 can be detected in blood circulation, cerebrospinal fluid (CSF), and urine, making it a promising candidate for a broad-spectrum biomarker. This review highlights the need for further research on the diverse effects of IL-8 and the associated implications for personalized medicine. A thorough understanding of its complex role could lead to the development of more effective and personalized treatment strategies for neuropsychiatric conditions.
According to recent findings, Phosphoglycerate Kinase 1 (pgk-1) enzyme is linked to Parkinson's disease (PD). Mutations in the PGK-1 gene lead to decreases in the pgk-1 enzyme which causes an imbalance in the levels of energy demand and supply. An increase in glycolytic adenosine triphosphate (ATP) production would help alleviate energy deficiency and sustain the acute energetic need of neurons. Neurodegeneration is caused by an imbalance or reduction in ATP levels. Recent data suggest that medications that increase glycolysis and neuroprotection can be used to treat PD. The current study focuses on treatment options for disorders associated with the pgk-1 enzyme, GLP-1, and A2A receptor which can be utilized to treat PD. A combination of metformin and terazosin, exenatide and meclizine, istradefylline and salbutamol treatments may benefit parkinsonism. The review also looked at potential target-specific new techniques that might assist in satisfying unfulfilled requirements in the treatment of PD.
Tissue infiltration by circulating leukocytes via directed migration (also referred to as chemotaxis) is a common pathogenic mechanism of inflammatory diseases. G-protein coupled receptors (GPCRs) are essential for sensing chemokine gradients and directing the movement of leukocytes during immune responses. The TNF-α-induced protein 8-like (TIPE or TNFAIP8L) family of proteins are newly described pilot proteins that control directed migration of murine leukocytes. However, how leukocytes integrate site-specific directional cues, such as chemokine gradients, and utilize GPCR and TIPE proteins to make directional decisions are not well understood. Using both gene knockdown and biochemical methods, we demonstrated here that two human TIPE family members, TNFAIP8 and TIPE2 were essential for directed migration of human CD4+ T cells. T Cells deficient in both of these proteins completely lost their directionality. TNFAIP8 interacted with the Gαi subunit of heterotrimeric (α, β, γ) G-proteins whereas TIPE2 bound to phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-triphosphate (PIP3) to spatiotemporally control immune cell migration. Using deletion and site-directed mutagenesis, we established that Gαi interacted with TNFAIP8 through its C terminal amino acids, and that TIPE2 protein interacted with PIP2 and PIP3 through its positively charged amino acids on the α0 helix and at the grip-like entrance. We also discovered that TIPE protein membrane translocation that is crucial for sensing chemokine gradients was dependent on PIP2. Collectively, our work describes a new mechanistic paradigm for how human T cells integrate GPCR and phospholipid signaling pathways to control directed migration. These findings have implications for therapeutically targeting TIPE proteins in human inflammatory and autoimmune diseases.
Maternal infections during pregnancy may increase the risk of psychiatric disorders in offspring. We recently demonstrated that activation of peroxisome proliferator-activate receptor‐α (PPARα), with the clinically available agonist fenofibrate, attenuates the neurodevelopmental disturbances induced by maternal immune activation (MIA) in rat offspring. We hypothesized that fenofibrate might reduce MIA-induced cytokine imbalance using a MIA model based on the viral mimetic polyriboinosinic- polyribocytidilic acid [poly (I:C)]. By using the Bio-Plex Multiplex-Immunoassay-System, we measured cytokine/chemokine levels in maternal serum and in the fetal brain of rats treated with fenofibrate, at 6 and 24 hours after poly (I:C). We found that MIA induced time-dependent changes in the levels of several cytokines/chemokines/colony- stimulating factors (CSFs). Specifically, the maternal serum of the poly (I:C)/CTRL group showed increased levels of (i) proinflammatory chemokine macrophage inflammatory protein 1-alpha (MIP-1α), (ii) tumor necrosis factor-alpha (TNF-α), the monocyte chemoattractant protein-1 (MCP-1), the macrophage (M-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Conversely, in the fetal brain of the poly (I:C)/CTRL group, interleukin 12p70 and MIP-1α levels were lower than in veh/CTRL group. Notably, MIP-1α, TNF-α, GRO/KC, GM-CSF, and M-CSF levels were lower in the poly (I:C)/FEN than in poly (I:C)/CTRL rats, suggesting the protective role of the PPARα agonist. PPARα might represent a therapeutic target to attenuate MIA-induced inflammation.
Neuropathic pain is a debilitating condition that affects millions of people worldwide. Numerous studies indicate that this type of pain is a chronic condition with a complex mechanism that tends to worsen over time, leading to a significant deterioration in patients’ quality of life and issues like depression, disability, and disturbed sleep. Presently used analgesics are not effective enough in neuropathy treatment and may cause many side effects due to the high doses needed. In recent years, many researchers have pointed to the important role of chemokines not only in the development and maintenance of neuropathy but also in the effectiveness of analgesic drugs. Currently, approximately 50 chemokines are known to act through 20 different seven-transmembrane G-protein-coupled receptors located on the surface of neuronal, glial, and immune cells. Data from recent years clearly indicate that more chemokines than initially thought (CCL1/2/3/5/7/8/9/11, CXCL3/9/10/12/13/14/17; XCL1, CX3CL1) have pronociceptive properties; therefore, blocking their action by using neutralizing antibodies, inhibiting their synthesis, or blocking their receptors brings neuropathic pain relief. Several of them (CCL1/2/3/7/9/XCL1) have been shown to be able to reduce opioid drug effectiveness in neuropathy, and neutralizing antibodies against them can restore morphine and/or buprenorphine analgesia. The latest research provides irrefutable evidence that chemokine receptors are promising targets for pharmacotherapy; chemokine receptor antagonists can relieve pain of different etiologies, and most of them are able to enhance opioid analgesia, for example, the blockade of CCR1 (J113863), CCR2 (RS504393), CCR3 (SB328437), CCR4 (C021), CCR5 (maraviroc/AZD5672/TAK-220), CXCR2 (NVPCXCR220/SB225002), CXCR3 (NBI-74330/AMG487), CXCR4 (AMD3100/AMD3465), and XCR1 (vMIP-II). Recent research has shown that multitarget antagonists of chemokine receptors, such as CCR2/5 (cenicriviroc), CXCR1/2 (reparixin), and CCR2/CCR5/CCR8 (RAP-103), are also very effective painkillers. A multidirectional strategy based on the modulation of neuronal–glial–immune interactions by changing the activity of the chemokine family can significantly improve the quality of life of patients suffering from neuropathic pain. However, members of the chemokine family are still underestimated pharmacological targets for pain treatment. In this article, we review the literature and provide new insights into the role of chemokines and their receptors in neuropathic pain.
Background:
Neurodegeneration is progressive cell loss in specific neuronal populations, often resulting in clinical consequences with significant medical, societal, and economic implications. Because of its antioxidant, anti-inflammatory, and anti-apoptotic properties, oxytocin has been proposed as a potential neuroprotective and neurobehavioral therapeutic agent, including modulating mood disturbances and cognitive enchantment.
Methods:
Literature searches were conducted using the following databases Web of Science, PubMed, Elsevier Science Direct, Google Scholar, the Core Collection, and Cochrane from January 2000 to February 2023 for articles dealing with oxytocin neuroprotective properties in preventing or treating neurodegenerative disorders and diseases with a focus on oxidative stress, inflammation, and apoptosis/cell death.
Results:
The neuroprotective effects of oxytocin appears to be mediated by its anti-inflammatory properties, inhibition of neuro inflammation, activation of several antioxidant enzymes, inhibition of oxidative stress and free radical formation, activation of free radical scavengers, prevent of mitochondrial dysfunction, and inhibition of apoptosis.
Conclusion:
Oxytocin acts as a neuroprotective agent by preventing neuro-apoptosis, neuro-inflammation, and neuronal oxidative stress, and by restoring mitochondrial function.
Ischemic stroke involves a series of complex pathological mechanisms, of which neuroinflammation is currently the most widely recognized. C-C motif chemokine receptor 5 (CCR5) has recently been shown to be upregulated after cerebral ischemia. Notably, CCR5 is not only involved in neuroinflammation, but also in the blood-brain barrier, neural structures, and connections. Accumulating experimental studies indicate that CCR5 has a dual effect on ischemic stroke. In the acute phase after cerebral ischemia, the pro-inflammatory and disruptive effect of CCR5 on the blood-brain barrier predominates. However, in the chronic phase, the effect of CCR5 on the repair of neural structures and connections is thought to be cell-type dependent. Interestingly, clinical evidence has shown that CCR5 might be harmful rather than beneficial. CCR5-Δ32 mutation or CCR5 antagonist exerts a neuroprotective effect in patients with ischemic stroke. Considering CCR5 as an attractive potential target, we introduce the current research progress of the entangled relationships between CCR5 and ischemic stroke. Clinical data are still needed to determine the efficacy of activating or inactivating CCR5 in the treatment of ischemic stroke, especially for potential phase- or cell type-dependent treatments in the future.
In neurodegenerative diseases, microglia switch to an activated state, which results in excessive secretion of pro-inflammatory factors. Our work aims to investigate how this paracrine signaling affects neuronal function. Here, we show that activated microglia mediate non-cell-autonomous inhibition of neuronal autophagy, a degradative pathway critical for the removal of toxic, aggregate-prone proteins accumulating in neurodegenerative diseases. We found that the microglial-derived CCL-3/-4/-5 bind and activate neuronal CCR5, which in turn promotes mTORC1 activation and disrupts autophagy and aggregate-prone protein clearance. CCR5 and its cognate chemokines are upregulated in the brains of pre-manifesting mouse models for Huntington's disease (HD) and tauopathy, suggesting a pathological role of this microglia-neuronal axis in the early phases of these diseases. CCR5 upregulation is self-sustaining, as CCL5-CCR5 autophagy inhibition impairs CCR5 degradation itself. Finally, pharmacological or genetic inhibition of CCR5 rescues mTORC1 hyperactivation and autophagy dysfunction, which ameliorates HD and tau pathologies in mouse models.
Cytokines are small, secreted proteins that are known for their roles in the immune system. An accumulating body of evidence indicates that cytokines also work as neuromodulators in the central nervous system (CNS). Cytokines can access the CNS through multiple routes to directly impact neurons. The neuromodulatory effects of cytokines maintain the overall homeostasis of neural networks. In addition, cytokines regulate a diverse repertoire of behaviors both at a steady state and in inflammatory conditions by acting on discrete brain regions and neural networks. In this review, we discuss recent findings that provide insight into how combinatorial codes of cytokines might mediate neuro-immune communications to orchestrate functional responses of the brain to changes in immunological milieus.
Since its first description over a century ago, neurodegenerative diseases (NDDs) have impaired the lives of millions of people worldwide. As one of the major threats to human health, NDDs are characterized by progressive loss of neuronal structure and function, leading to the impaired function of the CNS. While the precise mechanisms underlying the emergence of NDDs remains elusive, association of neuroinflammation with the emergence of NDDs has been suggested. The immune system is tightly controlled to maintain homeostatic milieu and failure in doing so has been shown catastrophic. Here, we review current concepts on the cellular and molecular drivers responsible in the induction of neuroinflammation and how such event further promotes neuronal damage leading to neurodegeneration. Experimental data generated from cell culture and animal studies, gross and molecular pathologies of human CNS samples, and genome-wide association study are discussed to provide deeper insights into the mechanistic details of neuroinflammation and its roles in the emergence of NDDs.KeywordsImmune systemPro-inflammatoryNeuroinflammationNeurodegenerationAlzheimer’s diseaseParkinson’s diseaseAmyotrophic lateral sclerosisMultiple sclerosis
In two freestanding volumes, the Textbook of Neural Repair and Rehabilitation provides comprehensive coverage of the science and practice of neurological rehabilitation. Revised throughout, bringing the book fully up to date, this volume, Neural Repair and Plasticity, covers the basic sciences relevant to recovery of function following injury to the nervous system, reviewing anatomical and physiological plasticity in the normal central nervous system, mechanisms of neuronal death, axonal regeneration, stem cell biology, and research strategies targeted at axon regeneration and neuron replacement. New chapters have been added covering pathophysiology and plasticity in cerebral palsy, stem cell therapies for brain disorders and neurotrophin repair of spinal cord damage, along with numerous others. Edited and written by leading international authorities, it is an essential resource for neuroscientists and provides a foundation for the work of clinical rehabilitation professionals.
Chronic mental health problems are common among military veterans who suffered blast-related traumatic brain injuries. The reasons for this association remain unexplained. Male rats exposed to repetitive low-level blast overpressure (BOP) exposures exhibit chronic cognitive and post-traumatic stress disorder (PTSD)-related traits that develop in a delayed fashion. We examined blast-induced alterations on the transcriptome in four brain areas (anterior cortex, hippocampus, amygdala and cerebellum) across the time frame over which the PTSD-related behavioral phenotype develops. When analyzed at 6 weeks or 12 months after blast exposure, relatively few differentially expressed genes (DEGs) were found. However, longitudinal analysis of amygdala, hippocampus and anterior cortex between 6 weeks and 12 months revealed blast-specific DEG patterns with most DEGs unique to one condition. Six DEGs (Hapln1, Grm2, P2ry12, Ccr5, Pbld1 and Cdh23) were found in all three brain regions in blast-exposed animals. Pathway enrichment analysis using all DEGs or those uniquely changed revealed different transcription patterns in blast vs. sham. In particular, amygdala in blast-exposed animals had a unique set of enriched pathways related to stress responses, oxidative phosphorylation and mitochondrial dysfunction. Upstream analysis implicated tumor necrosis factor α (TNFα) signaling in blast-related effects in amygdala and anterior cortex. EIF4e, an upstream regulator of P2ry12 and Ccr5 was predicted to be activated in amygdala. qPCR validated longitudinal changes in two TNFα regulated genes (Ctsb, Hapln1), P2ry12 and Grm2. These studies have important implications for understanding how blast injury damages the brain and implicates inflammation as a potential therapeutic target.
For a long time, astrocytes were considered a passive brain cell population. However, recently, many studies have shown that their role in the central nervous system (CNS) is more active. Previously, it was stated that there are two main functional phenotypes of astrocytes. However, nowadays, it is clear that there is rather a broad spectrum of these phenotypes. The major goal of this study was to evaluate the production of some inflammatory chemokines and neurotrophic factors by primary human astrocytes after pro- or anti-inflammatory stimulation. We observed that only astrocytes induced by inflammatory mediators TNFα/IL-1a/C1q produced CXCL10, CCL1, and CXCL13 chemokines. Unstimulated astrocytes and those cultured with anti-inflammatory cytokines (IL-4, IL-10, or TGF-β1) did not produce these chemokines. Interestingly, astrocytes cultured in proinflammatory conditions significantly decreased the release of neurotrophic factor PDGF-A, as compared to unstimulated astrocytes. However, in response to anti-inflammatory cytokine TGF-β1, astrocytes significantly increased PDGF-A production compared to the medium alone. The production of another studied neurotrophic factor BDNF was not influenced by pro- or anti-inflammatory stimulation. The secretory response was accompanied by changes in HLA-DR, CD83, and GFAP expression. Our study confirms that astrocytes differentially respond to pro- and anti-inflammatory stimuli, especially to inflammatory cytokines TNF-α, IL-1a, and C1q, suggesting their role in leukocyte recruitment.
Extracellular vesicles (EVs) are emerging as powerful players in cell‐to‐cell communication both in healthy and diseased brain. In Parkinson's disease (PD)—characterized by selective dopaminergic neuron death in ventral midbrain (VMB) and degeneration of their terminals in striatum (STR)—astrocytes exert dual harmful/protective functions, with mechanisms not fully elucidated. Here, this study shows that astrocytes from the VMB‐, STR‐, and VMB/STR‐depleted brains release a population of small EVs in a region‐specific manner. Interestingly, VMB‐astrocytes secreted the highest rate of EVs, which is further exclusively increased in response to CCL3, a chemokine that promotes robust dopaminergic neuroprotection in different PD models. The neuroprotective potential of nigrostriatal astrocyte‐EVs is investigated in differentiated versus undifferentiated SH‐SY5Y cells exposed to oxidative stress and mitochondrial toxicity. EVs from both VMB‐ and STR‐astrocytes counteract H2O2‐induced caspase‐3 activation specifically in differentiated cells, with EVs from CCL3‐treated astrocytes showing a higher protective effect. High resolution respirometry further reveals that nigrostriatal astrocyte‐EVs rescue neuronal mitochondrial complex I function impaired by the neurotoxin MPP⁺. Notably, only EVs from VMB‐astrocyte fully restore ATP production, again specifically in differentiated SH‐SY5Y. These results highlight a regional diversity in the nigrostriatal system for the secretion and activities of astrocyte‐EVs, with neuroprotective implications for PD.
The search for a clinically effective therapy for patients with Alzheimer's disease (AD) has been long and arduous. In some circles the recent US Food and Drug Administration (FDA) approval of the human monoclonal antibody, Aducanumab, was viewed as a welcome advance. However, the administrative decision, in the face of a negative review by the members of the FDA neurology advisory board raised many questions concerning its appropriateness. In response the FDA has modified the conditions under which the drug should be administered. Currently, the etiology of AD remains unknown. Thus, application of therapies based on the still controversial amyloid hypothesis deserves critical scrutiny. While successful animal studies based on the hypothesis have stimulated many clinical trials in humans, none of these have shown statistically clinical benefit, raising questions regarding the intrinsic validity of the hypothesis itself. However, each successive trial has benefited from the experiences of those which preceded it. Given these caveats, the relevance of an apparent beneficial response in a subset of Aducanumab treated study participants must be weighed carefully. There are competing hypotheses regarding the etiology and pathophysiology responsible for the development of AD, including tau protein aggregation, acetylcholine deficiency, neuroinflammation, among others, all of which remain controversial. Nonetheless, the newly approved agent, Aducanumab did show some subtle benefit in some mild AD patients. Understanding the current hypotheses and controversies may help better evaluate the limitations and challenges in anti-amyloid therapy and in exploration of more efficacious therapies in treating patients with AD in the future.
Microglial cells are the brain resident macrophages which are involved in maintaining CNS homeostasis. During CNS infections, the microglial cells get activated and trigger immune response. Neuroviral infections often lead to encephalitis, encephalopathy, and meningitis. This chapter highlights the roles of microglial cells during several neuroviral infections. Microglia, as the first responders to neuroviral infections, generate pro-inflammatory and antiviral response, affect the adaptive immune response and perturb the cell death pathways. The mechanisms behind most of these responses are poorly understood and require further studies in order to understand the pathophysiological mechanisms during neuroviral infections.KeywordsMicrogliaNeurotropic virusesNeuroinflammationNeuroviral infection
With the increase in the aging population, age‐related conditions such as dementia and Alzheimer's disease will become ever more prevalent in society. As there is no cure for dementia and extremely limited therapeutic options, researchers are examining the mechanisms that contribute to the progression of cognitive decline in hopes of developing better therapies and even an effective, long‐lasting treatment for this devastating condition. This review will provide an updated perspective on the role of immunity in triggering the changes that lead to the development of dementia. It will detail the latest findings on Aβ‐ and tau‐induced microglial activation, including the role of the inflammasome. The contribution of the adaptive immune system, specifically T cells, will be discussed. Finally, whether the innate and adaptive immune system can be modulated to protect against dementia will be examined, along with an assessment of the prospective candidates for these that are currently in clinical trials.
The seven-transmembrane receptor CX3CR1 is a specific receptor for the novel CX3C chemokine fractalkine (FKN) (neurotactin). In vitro data suggest that membrane anchoring of FKN, and the existence of a
shed, soluble FKN isoform allow for both adhesive and chemoattractive properties. Expression on activated endothelium and
neurons defines FKN as a potential target for therapeutic intervention in inflammatory conditions, particularly central nervous
system diseases. To investigate the physiological function of CX3CR1-FKN interactions, we generated a mouse strain in which the CX3CR1 gene was replaced by a green fluorescent protein (GFP) reporter gene. In addition to the creation of a mutant CX3CR1 locus, this approach enabled us to assign murine CX3CR1 expression to monocytes, subsets of NK and dendritic cells, and the brain microglia. Analysis of CX3CR1-deficient mice indicates that CX3CR1 is the only murine FKN receptor. Yet, defying anticipated FKN functions, absence of CX3CR1 interferes neither with monocyte extravasation in a peritonitis model nor with DC migration and differentiation in response
to microbial antigens or contact sensitizers. Furthermore, a prominent response of CX3CR1-deficient microglia to peripheral nerve injury indicates unimpaired neuronal-glial cross talk in the absence of CX3CR1.
HIV-1 and related viruses require co-receptors, in addition to CD4, to infect target cells. The chemokine receptor CCR-5 (ref. 1) was recently demonstrated to be a co-receptor for macrophage-tropic (M-tropic) HIV-1 strains2-6, and the orphan7 receptor LESTR (also called fusin) allows infection by strains adapted for growth in transformed T-cell lines (T-tropic strains). Here we show that a mutant allele of CCR-5 is present at a high frequency in caucasian populations (allele frequency, 0.092), but is absent in black populations from Western and Central Africa and Japanese populations. A 32-base-pair deletion within the coding region results in a frame shift, and generates a non-functional receptor that does not support membrane fusion or infection by macrophage- and dual-tropic HIV-1 strains. In a cohort of HIV-1-infected caucasian subjects, no individual homozygous for the mutation was found, and the frequency of heterozygotes was 35% lower than in the general population. White blood cells from an individual homozygous for the null allele were found to be highly resistant to infection by M-tropic HIV-1 viruses, confirming that CCR-5 is the major co-receptor for primary HIV-1 strains. The lower frequency of heterozygotes in seropositive patients may indicate partial resistance.
The HIV-1 envelope protein gp120 induces apoptosis in hippocampal neurons. Because chemokine receptors act as cellular receptors
for HIV-1, we examined rat hippocampal neurons for the presence of functional chemokine receptors. Fura-2-based Ca imaging
showed that numerous chemokines, including SDF-1α, RANTES, and fractalkine, affect neuronal Ca signaling, suggesting that
hippocampal neurons possess a wide variety of chemokine receptors. Chemokines also blocked the frequency of spontaneous glutamatergic
excitatory postsynaptic currents recorded from these neurons and reduced voltage-dependent Ca currents in the same neurons.
Reverse transcription–PCR demonstrated the expression of CCR1, CCR4, CCR5, CCR9/10, CXCR2, CXCR4, and CX3CR1, as well as the chemokine fractalkine in these neurons. Both fractalkine and macrophage-derived chemokine (MDC) produced
a time-dependent activation of extracellular response kinases (ERK)-1/2, whereas no activation of c-JUN NH2-terminal protein kinase (JNK)/stress-activated protein kinase, or p38 was evident. Furthermore, these two chemokines, as
well as SDF-1α, activated the Ca- and cAMP-dependent transcription factor CREB. Several chemokines were able also to block
gp120-induced apoptosis of hippocampal neurons, both in the presence and absence of the glial feeder layer. These data suggest
that chemokine receptors may directly mediate gp120 neurotoxicity.
A recently identified chemokine, fractalkine, is a member of the chemokine gene family, which consists principally of secreted,
proinflammatory molecules. Fractalkine is distinguished structurally by the presence of a CX3C motif as well as transmembrane
spanning and mucin-like domains and shows atypical constitutive expression in a number of nonhematopoietic tissues, including
brain. We undertook an extensive characterization of this chemokine and its receptor CX3CR1 in the brain to gain insights
into use of chemokine-dependent systems in the central nervous system. Expression of fractalkine in rat brain was found to
be widespread and localized principally to neurons. Recombinant rat CX3CR1, as expressed in Chinese hamster ovary cells, specifically
bound fractalkine and signaled in the presence of either membrane-anchored or soluble forms of fractalkine protein. Fractalkine
stimulated chemotaxis and elevated intracellular calcium levels of microglia; these responses were blocked by anti-CX3CR1
antibodies. After facial motor nerve axotomy, dramatic changes in the levels of CX3CR1 and fractalkine in the facial nucleus
were evident. These included increases in the number and perineuronal location of CX3CR1-expressing microglia, decreased levels
of motor neuron-expressed fractalkine mRNA, and an alteration in the forms of fractalkine protein expressed. These data describe
mechanisms of cellular communication between neurons and microglia, involving fractalkine and CX3CR1, which occur in both
normal and pathological states of the central nervous system.
The β-chemokine receptor CCR5 is considered to be an attractive target for inhibition of macrophage-tropic (CCR5-using or
R5) HIV-1 replication because individuals having a nonfunctional receptor (a homozygous 32-bp deletion in the CCR5 coding
region) are apparently normal but resistant to infection with R5 HIV-1. In this study, we found that TAK-779, a nonpeptide
compound with a small molecular weight (Mr 531.13), antagonized the binding of RANTES (regulated on activation, normal T cell expressed and secreted) to CCR5-expressing
Chinese hamster ovary cells and blocked CCR5-mediated Ca2+ signaling at nanomolar concentrations. The inhibition of β-chemokine receptors by TAK-779 appeared to be specific to CCR5
because the compound antagonized CCR2b to a lesser extent but did not affect CCR1, CCR3, or CCR4. Consequently, TAK-779 displayed
highly potent and selective inhibition of R5 HIV-1 replication without showing any cytotoxicity to the host cells. The compound
inhibited the replication of R5 HIV-1 clinical isolates as well as a laboratory strain at a concentration of 1.6–3.7 nM in
peripheral blood mononuclear cells, though it was totally inactive against T-cell line-tropic (CXCR4-using or X4) HIV-1.
The critical role of chemokine receptors (CCR5 and CXCR4) in human immunodeficiency virus–type 1 (HIV-1) infection and pathogenesis
prompted a search for polymorphisms in other chemokine receptor genes that mediate HIV-1 disease progression. A mutation (CCR2-64I) within the first transmembrane region of theCCR2 chemokine and HIV-1 receptor gene is described that occurred at an allele frequency of 10 to 15 percent among Caucasians
and African Americans. Genetic association analysis of five acquired immunodeficiency syndrome (AIDS) cohorts (3003 patients)
revealed that although CCR2-64I exerts no influence on the incidence of HIV-1 infection, HIV-1–infected individuals carrying theCCR2-64I allele progressed to AIDS 2 to 4 years later than individuals homozygous for the common allele. BecauseCCR2-64I occurs invariably on a CCR5-+–bearing chromosomal haplotype, the independent effects ofCCR5-Δ32 (which also delays AIDS onset) andCCR2-64I were determined. An estimated 38 to 45 percent of AIDS patients whose disease progresses rapidly (less than 3 years until
onset of AIDS symptoms after HIV-1 exposure) can be attributed to theirCCR2-+/+ or CCR5-+/+ genotype, whereas the survival of 28 to 29 percent of long-term survivors, who avoid AIDS for 16 years or more, can be explained
by a mutant genotype forCCR2 or CCR5.
Phosphoinositide 3-kinases (PI3Ks) regulate fundamental cellular responses such as proliferation, apoptosis, cell motility,
and adhesion. Viable gene-targeted mice lacking the p110 catalytic subunit of PI3Kγ were generated. We show that PI3Kγ controls
thymocyte survival and activation of mature T cells but has no role in the development or function of B cells. PI3Kγ-deficient
neutrophils exhibited severe defects in migration and respiratory burst in response to heterotrimeric GTP-binding protein
(G protein)–coupled receptor (GPCR) agonists and chemotactic agents. PI3Kγ links GPCR stimulation to the formation of phosphatidylinositol
3,4,5-triphosphate and the activation of protein kinase B, ribosomal protein S6 kinase, and extracellular signal-regulated
kinases 1 and 2. Thus, PI3Kγ regulates thymocyte development, T cell activation, neutrophil migration, and the oxidative burst.
The chemokine receptor 5 (CKR5) protein serves as a secondary receptor on CD4+ T lymphocytes for certain strains of human immunodeficiency virus-type 1 (HIV-1). The CKR5 structural gene was mapped to human chromosome 3p21, and a 32-base pair deletion allele (CKR5Δ32) was identified that is present at a frequency of ∼0.10 in the Caucasian population of the United States. An examination
of 1955 patients included among six well-characterized acquired immunodeficiency syndrome (AIDS) cohort studies revealed that
17 deletion homozygotes occurred exclusively among 612 exposed HIV-1 antibody-negative individuals (2.8 percent) and not at
all in 1343 HIV-1-infected individuals. The frequency of CKR5 deletion heterozygotes was significantly elevated in groups of individuals that had survived HIV-1 infection for more than
10 years, and, in some risk groups, twice as frequent as their occurrence in rapid progressors to AIDS. Survival analysis
clearly shows that disease progression is slower in CKR5 deletion heterozygotes than in individuals homozygous for the normal CKR5 gene. The CKR5Δ32 deletion may act as a recessive restriction gene against HIV-1 infection and may exert a dominant phenotype of delaying progression
to AIDS among infected individuals.
Unique among known human herpesviruses, Kaposi's sarcoma–associated herpesvirus (KSHV or HHV-8) encodes chemokine-like proteins
(vMIP-I and vMIP-II). vMIP-II was shown to block infection of human immunodeficiency virus–type 1 (HIV-1) on a CD4-positive
cell line expressing CCR3 and to a lesser extent on one expressing CCR5, whereas both vMIP-I and vMIP-II partially inhibited
HIV infection of peripheral blood mononuclear cells. Like eotaxin, vMIP-II activated and chemoattracted human eosinophils
by way of CCR3. vMIP-I and vMIP-II, but not cellular MIP-1α or RANTES, were highly angiogenic in the chorioallantoic assay,
suggesting a possible pathogenic role in Kaposi's sarcoma.
The CC chemokine receptor-1 (CCR1) is a prime therapeutic target for treating autoimmune diseases. Through high capacity screening
followed by chemical optimization, we identified a novel non-peptide CCR1 antagonist, R-N-[5-chloro-2-[2-[4-[(4-fluorophenyl)methyl]-2-methyl-1-piperazinyl]-2-oxoethoxy]phenyl]urea hydrochloric acid salt (BX 471).
Competition binding studies revealed that BX 471 was able to displace the CCR1 ligands macrophage inflammatory protein-1α
(MIP-1α), RANTES, and monocyte chemotactic protein-3 (MCP-3) with high affinity (K
i ranged from 1 nm to 5.5 nm). BX 471 was a potent functional antagonist based on its ability to inhibit a number of CCR1-mediated effects including Ca2+ mobilization, increase in extracellular acidification rate, CD11b expression, and leukocyte migration. BX 471 demonstrated
a greater than 10,000-fold selectivity for CCR1 compared with 28 G-protein-coupled receptors. Pharmacokinetic studies demonstrated
that BX 471 was orally active with a bioavailability of 60% in dogs. Furthermore, BX 471 effectively reduces disease in a
rat experimental allergic encephalomyelitis model of multiple sclerosis. This study is the first to demonstrate that a non-peptide
chemokine receptor antagonist is efficacious in an animal model of an autoimmune disease. In summary, we have identified a
potent, selective, and orally available CCR1 antagonist that may be useful in the treatment of chronic inflammatory diseases.
RAFTK, a novel nonreceptor protein kinase, has been shown to be involved in focal adhesion signal transduction pathways in neuronal PC12 cells, megakaryocytes, platelets, and T cells. Because focal adhesions may modulate cytoskeletal functions and thereby alter phagocytosis, cell migration, and adhesion in monocyte-macrophages, we investigated the role of RAFTK signaling in these cells. RAFTK was abundantly expressed in THP1 monocytic cells as well as in primary alveolar and peripheral blood-derived macrophages. Colony-stimulating factor-1 (CSF-1)/macrophage colony-stimulating factor (M-CSF) stimulation of THP1 cells increased the tyrosine phosphorylation of RAFTK; similar increases in phosphorylation were also detected after lipopolysaccharide stimulation. RAFTK was phosphorylated with similar kinetics in THP1 cells and peripheral blood-derived macrophages. Immunoprecipitation analysis showed associations between RAFTK and the signaling molecule phosphatidylinositol-3 (PI-3) kinase. PI-3 kinase enzyme activity also coprecipitated with the RAFTK antibody, further confirming this association. The CSF-1/M-CSF receptor c-fms and RAFTK appeared to associate in response to CSF-1/M-CSF treatment of THP1 cells. Inhibition of RAFTK by a dominant-negative kinase mutant reduced CSF-1/M-CSF-induced MAPK activity. These data indicate that RAFTK participates in signal transduction pathways mediated by CSF-1/M-CSF, a cytokine that regulates monocyte-macrophage growth and function.
Migration of neuronal precursor cells from the external germinal layer (EGL) to the internal granular layer (IGL) is a crucial process in the development of the mammalian cerebellar cortex. These cells make up the only precursor population known to migrate away from the surface of the brain. We studied the role of the chemokine stromal-derived factor 1 (SDF-1) in the cerebellar tissue of rats and knockout mice and found (i) that it functions as an attractive guidance cue for neuronal migration and (ii) that its secretion from non-neuronal meningeal tissue is important for controlling the migration of embryonic EGL cells
RAFTK, a novel nonreceptor protein kinase, has been shown to be involved in focal adhesion signal transduction pathways in neuronal PC12 cells, megakaryocytes, platelets, and T cells. Because focal adhesions may modulate cytoskeletal functions and thereby alter phagocytosis, cell migration, and adhesion in monocyte-macrophages, we investigated the role of RAFTK signaling in these cells. RAFTK was abundantly expressed in THP1 monocytic cells as well as in primary alveolar and peripheral blood-derived macrophages. Colony-stimulating factor-1 (CSF-1)/macrophage colony-stimulating factor (M-CSF) stimulation of THP1 cells increased the tyrosine phosphorylation of RAFTK; similar increases in phosphorylation were also detected after lipopolysaccharide stimulation. RAFTK was phosphorylated with similar kinetics in THP1 cells and peripheral blood-derived macrophages. Immunoprecipitation analysis showed associations between RAFTK and the signaling molecule phosphatidylinositol-3 (PI-3) kinase. PI-3 kinase enzyme activity also coprecipitated with the RAFTK antibody, further confirming this association. The CSF-1/M-CSF receptor c-fms and RAFTK appeared to associate in response to CSF-1/M-CSF treatment of THP1 cells. Inhibition of RAFTK by a dominant-negative kinase mutant reduced CSF-1/M-CSF–induced MAPK activity. These data indicate that RAFTK participates in signal transduction pathways mediated by CSF-1/M-CSF, a cytokine that regulates monocyte-macrophage growth and function.
Chemokines have been shown to play an important role in leukocyte infiltration into ischemic lesions. Recently, the increased expression of monocyte chemoattractant protein-1 (MCP-1) and cytokine-induced neutrophil chemoattractant (CINC) was observed in experimental stroke models where infiltrated leukocytes were supposed to induce tissue injury, however, the protein level and time course of these chemokines have not been fully elucidated. Therefore, we analyzed the time-dependent production of MCP-1 and CINC in the rat brain after transient middle cerebral artery occlusion (MCAO) by means of specific enzyme-linked immunosorbent assay systems. The MCP-1 levels in the ipsilateral hemispheres increased from 6 h, peaked at 2 days, and thereafter gradually decreased. The peak MCP-1 concentration was 89.2 ± 28.2 ng/g tissue wet weight (mean ± sem, n = 5, 49.3-fold greater than the contralateral value at the same time, P < 0.05), which is supposed to be high enough to exert its biological effects. In contrast, the maximum CINC concentration that corresponded to 2.9 ± 0.7 ng/g tissue wet weight (mean ± sem, n = 5, 55.0-fold greater than the contralateral value at the same time, P < 0.05), was observed at 6 h. In addition, we confirmed the temporal profile of leukocyte subtypes that infiltrated into the ischemic brain, thus, neutrophil infiltration occurred at early stages (1–3 days), followed by massive infiltration of macrophages at later stages (2–7 days). These studies suggest that MCP-1 in cerebral ischemia actually plays a significant role in the migration of macrophages into the lesion and that the differential temporal production of these chemokines contributes to the regulation of infiltrated leukocyte subtypes. J. Leukoc. Biol. 65: 744–749; 1999.
We have evaluated the in vivo distribution of the major human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) coreceptors, CXCR4, CCR3, and CCR5, in both rhesus macaques and humans. T lymphocytes and macrophages in both lymphoid and nonlymphoid tissues are the major cell populations expressing HIV/SIV coreceptors, reaffirming that these cells are the major targets of HIV/SIV infection in vivo. In lymphoid tissues such as the lymph node and the thymus, approximately 1 to 10% of the T lymphocytes and macrophages are coreceptor positive. However, coreceptor expression was not detected on follicular dendritic cells (FDC) in lymph nodes, suggesting that the ability of FDC to trap extracellular virions is unlikely to be mediated by a coreceptor-specific mechanism. In the thymus, a large number of immature and mature T lymphocytes express CXCR4, which may render these cells susceptible to infection by syncytium-inducing viral variants that use this coreceptor for entry. In addition, various degrees of coreceptor expression are found among different tissues and also among different cells within the same tissues. Coreceptor-positive cells are more frequently identified in the colon than in the rectum and more frequently identified in the cervix than in the vagina, suggesting that the expression levels of coreceptors are differentially regulated at different anatomic sites. Furthermore, extremely high levels of CXCR4 and CCR3 expression are found on the neurons from both the central and peripheral nervous systems. These findings may be helpful in understanding certain aspects of HIV and SIV pathogenesis and transmission.
Patients with the acquired immunodeficiency syndrome (AIDS) are subject to a spectrum of central nervous system (CNS) disorders. Recent evidence implicates the human T-cell lymphotropic virus type III (HTLV-III) in the pathogenesis of some of these illnesses, although the cells infected by the virus have yet to be identified. Using in situ hybridization, we examined brain tissue from two patients with AIDS encephalopathy for the presence of HTLV-III RNA. In both cases, viral RNA was detected and concentrated in, though not limited to, the white matter. The CNS cells most frequently infected included macrophages, pleomorphic microglia, and multinucleated giant cells. Less frequently, cells morphologically consistent with astrocytes, oligodendroglia, and rarely neurons were also infected. The findings strengthen the association of HTLV-III with the pathogenesis of AIDS encephalopathy. In situ hybridization can be applied to routinely prepared biopsy tissue in the diagnosis of HTLV-III infection of the CNS.
(JAMA 1986;256:2360-2364)
Human immunodeficiency virus type 1 (HIV-1) uses the chemokine receptors CCR5 and CXCR4 as coreceptors for entry. It was recently demonstrated that HIV-1 glycoprotein 120 (gp120) elevated calcium and activated several ionic signaling responses in primary human macrophages, which are important targets for HIV-1 in vivo. This study shows that chemokine receptor engagement by both CCR5-dependent (R5) and CXCR4-dependent (X4) gp120 led to rapid phosphorylation of the focal adhesion-related tyrosine kinase Pyk2 in macrophages. Pyk2 phosphorylation was also induced by macrophage inflammatory protein-1β (MIP-1β) and stromal cell–derived factor-1α, chemokine ligands for CCR5 and CXCR4. Activation was blocked by EGTA and by a potent blocker of calcium release–activated Ca⁺⁺(CRAC) channels, but was insensitive to pertussis toxin (PTX), implicating CRAC-mediated extracellular Ca⁺⁺ influx but not Gαi protein-dependent mechanisms. Coreceptor engagement by gp120 and chemokines also activated 2 members of the mitogen-activated protein kinase (MAPK) superfamily, c-Jun amino-terminal kinase/stress-activated protein kinase and p38 MAPK. Furthermore, gp120-stimulated macrophages secreted the chemokines monocyte chemotactic protein-1 and MIP-1β in a manner that was dependent on MAPK activation. Thus, the gp120 signaling cascade in macrophages includes coreceptor binding, PTX-insensitive signal transduction, ionic signaling including Ca⁺⁺ influx, and activation of Pyk2 and MAPK pathways, and leads to secretion of inflammatory mediators. HIV-1 Env signaling through these pathways may contribute to dysregulation of uninfected macrophage functions, new target cell recruitment, or modulation of macrophage infection.
We determined incidence and future projections of dementia after AIDS onset in 492 homosexual men with AIDS in the Baltimore/Los Angeles sites of the Multicenter AIDS Cohort Study, 64 of whom developed dementia. We studied various risk factors for dementia, including demographic and clinical features, medical history, markers of immune status before AIDS, and zidovudine use. During the first 2 years after AIDS, HIV dementia developed at an annual rate of 7%. Overall, 15% of the cohort followed through death developed dementia. The median survival after dementia was 6.0 months. Using a proportional hazards model, risk factors for more rapid development of dementia were lower hemoglobin (relative hazard, 0.59 per additional 2 g/dl;p = 0.0005) and body mass index (relative hazard, 0.64 per additional 5 kg/m²; p = 0.05) 1 to 6 months before AIDS, more constitutional symptoms 7 to 12 months before AIDS (relative hazard, 1.68 per additional symptom, p = 0.005), and older age at AIDS onset (relative hazard, 1.60 per decade older; p = 0.009). In a multivariate model, pre-AIDS hemoglobin remained the most significant predictor of dementia. There were no significant risks defined from demographic characteristics, specific AIDS-defining illnesses, zidovudine use before AIDS, or CD4+ lymphocyte count before AIDS. We project that 12 months after the first AIDS diagnosis, 7.1% of survivors will have dementia. The observed association between anemia, low weight, constitutional symptoms, and dementia suggests a role for cytokines inducing both systemic and neurologic disease.
Chemokines are low molecular weight cytokines which act as chemoattractants for infiltrating cells bearing appropriate receptors (CCR) to sites of inflammation. It has been proposed that CCR2 on monocytes is responsible for their recruitment into the central nervous system (CNS) in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, and two previous reports have described resistance of CCR2−/− mice to EAE. The present study examined three different mouse strains with CCR2 deletions for susceptibility to EAE. Animals were studied up to 4 months post-sensitization and were examined by neuropathology, RNase protection assay, in situ hybridization, and in vitro assays. All three strains were found to be susceptible to EAE: C57BL/6 × J129 and Balb c strains, 100%; and C57BL/6, 67%. Unusual in CNS lesions of CCR2−/− mice was an overabundance of neutrophils versus monocytes in wild-type animals. An attempt of the immune system to develop compensatory mechanisms for the lack of CCR2 was evidenced by a corresponding increase in mRNA for other chemokines and CCR. Inasmuch as neutrophils replaced monocytes and led to demyelination, our findings support the concept that promiscuity of chemokines and CCR was able to surmount the deletion of CCR2, still resulting in full expression of this autoimmune disease.
Chemokines belong to an expanding family of cytokines the primary function of which is recruitment of leukocytes to inflammatory sites. Recent evidence has shown their presence in the central nervous system. Because inflammatory responses have been implicated in the pathogenesis of Alzheimer's disease (AD), we studied the expression of CCR3, CCR5, and their ligands in normal and AD brains by immunohistochemistry. CCR3 and CCR5 are present on microglia of both control and AD brains, with increased expression on some reactive microglia in AD. Immunohistochemistry for MIP-1 beta, MIP-1 alpha, RANTES, eotaxin, and MCP-3 (ligands for CCR5 and/or CCR3) revealed the presence of MIP-1 beta predominantly in a subpopulation of reactive astrocytes, which were more widespread in AD than control brains, and MIP-1 alpha predominantly in neurons and weakly in some microglia in both AD and controls. Many of the CCR3(+) or CCR5(+) reactive microglia and MIP-1 beta(+) reactive astrocytes were found associated with amyloid deposits. Immunoreactivity for eotaxin, RANTES, and MCP-S were not detected. Detection of these beta-chemokine receptors on microglia and some of their ligands in reactive astrocytes and neurons as well as microglia suggests a role for this system in glial-glial and glial-neuronal interactions, potentially influencing the progression of AD.
Chemokines, small proinflammatory cytokines, are involved in migration of inflammatory cells, but also have a role in normal central nervous system development. One chemokine, growth-related oncogene-α (GRO-α) and its receptor CXCR2, are involved in proliferation and migration of oligodendrocyte progenitors in rats. Here we studied the regional and cell type-specific expression of GRO-α and CXCR2 in the human telencephalon at midgestation, the time that oligodendrocytes are being generated in the human brain. Our results showed that both GRO-α and CXCR2 are predominately expressed by oligodendrocyte progenitors and activated microglial cells in the highly proliferative subventricular zone. This cellular and regional localization suggests that GRO-α/CXCR2 may play a role in human oligodendrocyte proliferation and subsequent migration. We also studied the expression of GRO-α and CXCR2 in brain sections of multiple sclerosis (MS) patients. Consistent with their role in the inflammatory process of MS, both GRO-α and CXCR2 were expressed in activated microglia localized on the border of MS lesions. However, neither GRO-α nor CXCR2 were present in early oligodendrocyte progenitors, a finding that may partially explain why remyelination is not more efficient in MS.
A human cDNA encoding a putative G protein-coupled receptor designated chemokine beta receptor-like 1 (CMKBRL1) was isolated from an eosinophilic leukemia library. Its deduced sequence is similar to 40% identical to previously cloned receptors for the beta chemokines macrophage inflammatory protein-1 alpha (MIP-1 alpha), RANTES, and monocyte chemoattractant protein-1 (MCP-1), which are chemoattractants for blood leukocytes, and is 83% identical to the product of the orphan rat cDNA RES 11, Like the MIP-1 alpha/RANTES receptor, CMKBRL1 is encoded by a small, single-copy gene that maps to chromosome 3p21 and is expressed in leukocytes, However, two screening assays with a broad panel of chemokines failed to identify its ligand, CMKBRL1 mRNA was detectable by Northern blot hybridization in neutrophils and monocytes, hut not eosinophils, and was also found in eight solid organs that were tested with particularly high expression in brain, The RNA distribution of the known beta chemokine receptors was overlapping but distinct from that of CMKBRL1. MIP-1 alpha/RANTES receptor mRNA was detectable in neutrophils, monocytes, eosinophils, and in all eight solid organs tested, with particularly high expression in placenta, lung, and Ever, MCP-1 receptor mRNA was found in monocytes, lung, liver, and pancreas, These results suggest that the ligand for the putative CMKBRRL1 receptor is a beta chemokine that targets both neutrophils and monocytes, Moreover, the RNA distributions suggest that CMKBRL1, the MIP-1 alpha/RANTES receptor, and the MCP-1 receptor may have both overlapping and distinct biological roles.
CXCR4, a seven transmembrane domain G-protein-coupled receptor for the Cys–X–Cys class of chemokines, is one of several chemokine receptors that can act as a co-receptor with CD4 for the human immunodeficiency virus (HIV-1) glycoprotein gp120 [1–3]. CXCR4 can mediate the entry of HIV-1 strains that specifically infect T cells, such as the IIIB strain (see [4] for review). Recent reports indicate that gp120 can signal through CXCR4 [5] and it has been suggested that signal transduction, mediated by the viral envelope, might influence viral-associated cytopathicity or apoptosis [6]. Neuronal apoptosis is a feature of HIV-1 infection in the brain [7,8], although the exact mechanism is unknown. Here, we address the possible role of CXCR4 in inducing apoptosis using cells of the hNT human neuronal cell line; these cells resemble immature post-mitotic cholinergic neurons and have a number of neuronal characteristics [9–15]. We have previously shown that gp120 from the HIV-1 IIIB strain binds with high affinity to CXCR4 expressed on hNT neurons [15]. We now find that both IIIB gp120 and the Cys–X–Cys chemokine SDF-1α can directly induce apoptosis in hNT neurons in the absence of CD4 and in a dose-dependent manner. To our knowledge, this is the first report of a chemokine and an HIV-1 envelope glycoprotein eliciting apoptotic responses through a chemokine receptor.
Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) characterised by perivascular inflammatory cell infiltrates and plaques of demyelination. Chemokines have been shown to play an important role in the activation and directional migration of cells to sites of CNS inflammation. The action of chemokines requires the expression of their complementary chemokine receptors by their target cells. We have examined the expression of the β-chemokine receptors CCR2, CCR3 and CCR5 in post-mortem MS CNS tissue using single- and double-labelling immunocytochemistry techniques. Low levels of CCR2, CCR3 and CCR5 were expressed by microglial cells throughout control CNS tissue. In chronic active MS lesions CCR2, CCR3 and CCR5 were associated with foamy macrophages and activated microglia. CCR2 and CCR5 were also present on large numbers of infiltrating lymphocytes. A smaller number of CCR3-positive lymphocytes were present, but we also noted CCR3 and CCR5 on astrocytes in five of the 14 cases of MS investigated, particularly associated with processes around vessels and at the glia limitans. Ligands for CCR2 and CCR3 include MCP-1 and MCP-3 which were co-localised around vessels with the infiltrating leukocytes, but were also present in unaffected areas of cortex. The elevated expression of CCR2, CCR3 and CCR5 in the CNS in MS suggests these β-chemokine receptors and their ligands play a role in the pathogenesis of MS.
Inflammation has been implicated in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative diseases. We have examined the potential role of some chemokine/chemokine receptors in this process. It is known that CXCR2 is a strongly expressed chemokine receptor on neurons and is strongly upregulated in AD in a subpopulation of neuritic plaques. Here, we show that one of the CXCR2 ligand GROα/KC can be a potent trigger for the ERK1/2 and PI-3 kinase pathways, as well as tau hyperphosphorylation in the mouse primary cortical neurons. GROα immunoreactivity can be detected in a subpopulation of neurons in normal and AD. Therefore, the CXCR2–ligand pair may have a potent pathophysiological role in neurodegenerative diseases.
We give here evidence that Purkinje neurons (PNs) of mouse cerebellar slices studied with patch clamp technique combined with laser confocal microscopy, respond to human IL-8 and GROα by (i) a cytosolic Ca2+ transient compatible with inositol (1,4,5) trisphosphate (InsP3) formation; (ii) an enhancement of the neurotransmitter release; and (iii) an impairment of the long-term depression of synaptic strength (LTD). It was also found the expression of IL-8 receptor type 2 in PN and granule cells by immunofluorescence, immunoblotting and RT-PCR analysis. Considered together these findings suggest that IL-8 and GROα may play a neuromodulatory role on mouse cerebellum.
In an effort to unravel some of the cellular actions of gb-amyloid protein (Aβ), we investigated its effects on interleukin-8 (IL-8) production from human monocytes. Supernatants harvested from cultured monocytes stimulated with the neurotoxic fragment 25-35 of β-amyloid [Aβ(25-35)]contained significant amounts of IL-8. Northern blot analysis demonstrated that Aβ(25-35) also induced IL-8 mRNA accumulation. The effect of Aβ(25–35) on IL-8 mRNA accumulation and secretion was not mimicked by a scrambled Aβ(25–35) peptide, and was not affected by polymyxin B sulphate, which, on the other hand, almost completely abolished the effect of lipopolysaccharide. Our results uncover a new biological action of β-amyloid: that of stimulating the production of a chemokine from monocytes.
The CXC chemokine, IL-8, is a potent chemoattractant of neutrophils and binds to two distinct receptors, termed IL-8R1 and IL-8R2. These receptors share high affinity for IL-8, however, only IL-8R1 is specific for IL-8 whereas IL-8R2 binds other related chemokines, including GROα with high affinity. Stable Jurkat transfectants were generated expressing either functional IL-8R1 or IL-8R2 (J-IL8R1 and J-IL812). Both J-IL8R1 and J-IL8R2 exhibited high affinity IL-8 binding (Kd 3–5nM) with respective receptor densities of23,000 ± 3,000 and18,500 ± 1,500. Pre-treatment of both transfectants with 1.0 μg/mlB. pertussis toxin (PTx) resulted in inhibition of IL-8 mediated intracellular Ca2+ mobilisation and chemotaxis, without altering the receptor's affinity for its ligand. This indicates that both receptors couple to a PTx-sensitive G-protein. Further studies showed that IL-8R1 and IL-8R2 could mediate time-dependent phosphorylation of p42/p44 MAP-kinase. In both transfectants, phosphorylation was maximal at 1–2 min after IL-8 stimulation and could be inhibited by PTx. Stimulation of J-IL8R1 and J-IL8R2 with GROα revealed that this chemokine was a more potent activator of MAP-kinase in J-IL8R2, an observation reflected in the high affinity binding of GROα to IL-8R2. These studies indicate that chemokines are capable of activating protein kinases and with regards to PTx-sensitivity and MAP-kinase stimulation, no significant differences between IL- 8R1 and IL-8R2 post-receptor signalling occur during cell activation by IL-8.
WE report here that, in cultured cerebellar granule cells, the CXC chemokine GRO beta stimulates the signaling pathway of the extracellular signal-regulated kinases, and enhances both evoked and spontaneous postsynaptic currents in patch clamped Purkinje neurons from rat cerebellar slices. The GRO beta-induced enhancement of the excitatory post-synaptic currents evoked by stimulating the parallel fibres is blocked by the inhibitor of the extracellular signal-regulated kinases pathway PD98059, which also reduces both basal frequency of spontaneous post-synaptic currents and mean amplitude of evoked excitatory post-synaptic currents. Our results suggest that GRO beta modulates neurotransmitter release in the cerebellum through the activation of the extracellular signal-regulated kinases pathway. NeuroReport 9: 3601-3606 (C) 1998 Lippincott Williams & Wilkins.
Phosphoinositide 3-kinases (PI3Ks) activate protein kinase PKB (also termed Akt), and PI3Kγ activated by heterotrimeric guanosine
triphosphate–binding protein can stimulate mitogen-activated protein kinase (MAPK). Exchange of a putative lipid substrate-binding
site generated PI3Kγ proteins with altered or aborted lipid but retained protein kinase activity. Transiently expressed, PI3Kγ
hybrids exhibited wortmannin-sensitive activation of MAPK, whereas a catalytically inactive PI3Kγ did not. Membrane-targeted
PI3Kγ constitutively produced phosphatidylinositol 3,4,5-trisphosphate and activated PKB but not MAPK. Moreover, stimulation
of MAPK in response to lysophosphatidic acid was blocked by catalytically inactive PI3Kγ but not by hybrid PI3Kγs. Thus, two
major signals emerge from PI3Kγ: phosphoinositides that target PKB and protein phosphorylation that activates MAPK.
Experimental allergic encephalomyelitis (EAE) serves as a model for autoimmune diseases mediated by T lymphocytes1,2. Following sensitization to rat, mouse or guinea pig myelin basic protein (MBP) in complete Freund's adjuvant, inbred mouse strains PL/J (H–2u, SJL/J (H–2s) and (PL/J × SJL/J)F1((PLSJ)F1) develop EAE3,4. Whereas sensitization to the N-terminal 37 amino-acid peptide of rat or guinea pig MBP [MBP(1–37)] induces EAE in PL/J mice, immunization to the C-terminal peptide (89–169) leads to EAE in SJL/J mice4,5. The immune response to MBP in (PLSJ)F1 mice is not co-dominant; sensitization to the N-terminal peptide induces EAE, while sensitization to the C-terminal peptide does not3,4. We have generated MBP-specific T-cell clones restricted to class II (Ia) antigens of the major histocompatibility complex (MHC) from PL/J and (PLSJ)F1 mice following sensitization to rat MBP. Two such I–Au-restricted T-cell clones that proliferate in response to the encephalitogenic N-terminal MBP peptide and recognize a shared determinant with mouse (self) MBP cause paralysis in 100% of (PLSJ)F1 mice tested. Paralysis is induced even when recipients are injected with as few as 1 × 105 cloned T cells. Relapsing paralysis followed in two-thirds of the recipients after recovery from acute paralysis, whereas one-third developed chronic persistent paralysis, a form of EAE not usually seen. Histopathology revealed intense perivascular inflammation, demyelination and remyelination within the central nervous system of paralysed mice. The experimental disease induced with these clones shares important features with human demyelinating diseases such as multiple sclerosis. This is the first demonstration that T-cell clones that respond to a defined self-antigen can induce clinical and histological autoimmune disease.
Discusses neurologic and immunologic aspects of AIDS-associated dementia (AAD). Important clinical manifestations include impaired mental concentration, slowness of hand movements, and difficulty in walking. In AAD, unlike other types of viral encephalitis, the progressive clinical signs occur without direct infection of neurons by HIV-1 or evidence of autoimmunity induced by the virus. The cells chiefly infected by HIV-1 in the brain are mononuclear phagocytes (i.e., brain macrophages, microglia, and multinucleated giant cells). Neuronal injury mediated by brain macrophages is detailed. The therapeutic potential of the N-methyl-D-aspartate (NMDA) antagonists memantine and nitroglycerin in AAD is addressed. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Background:: Three phenotypes of the antioxidant protein haptoglobin are known: Hp 1–1, Hp 2–1 and Hp 2–2.
Objectives:: To investigate the outcome of HIV infection according to haptoglobin type.
Design and methods:: Haptoglobin phenotypes were determined using starch gel electrophoresis in serum obtained from 653 HIV‐infected Caucasians in the AIDS reference centers of Gent (n = 184), Antwerp (n = 309), and Luxembourg (n = 160). Survival was compared between haptoglobin types using Kaplan‐Meier curves. Plasma HIV‐1 RNA was quantified by reverse transcriptase PCR. Serum iron, transferrin saturation, ferritin, and vitamin C were assayed to evaluate iron‐driven oxidative stress in 184 HIV‐infected patients and 204 controls.
Results:: The haptoglobin type distribution amongst the patients (17.6% Hp 1–1, 49.9% Hp 2–1, 32.5% Hp 2–2) corresponded to that of the controls. Kaplan‐Meier curves showed a higher mortality for the Hp 2–2 group (P = 0.0001; adjusted mortality risk ratio, 1.78; 95% confidence interval, 1.25−2.54). Median survival time was 11.0 years (Hp 1–1 and Hp 2–1) versus 7.33 years (Hp 2–2). Plasma HIV‐1 RNA levels prior to antiviral therapy and their increase over 1 year were highest in Hp 2–2 patients (P = 0.03 and 0.003, respectively). The Hp 2–2 type was associated with higher serum iron, transferrin saturation, and ferritin levels and with low vitamin C concentrations. Furthermore, ferritin concentrations were higher in HIV‐infected patients than in controls (P < 0.0001).
Conclusion:: HIV‐infected patients carrying the Hp 2–2 phenotype show a worse prognosis, which is reflected by a more rapid rate of viral replication (in the absence of antiviral treatment). They also accumulate more iron and oxidize more vitamin C, suggesting that less efficient protection against haemoglobin/iron‐driven oxidative stress may be a direct mechanism for stimulating viral replication.
Objective:: To determine the prevalence of genotypic resistance to nucleoside analogues (NA) in a large group of HIV‐infected individuals in Spain, some of whom had no previous treatment with antiretroviral drugs (antiretroviral‐naive) and some of whom had such experience (antiretroviral‐experienced).
Setting:: Cross‐sectional study in outpatient clinics in three reference hospitals for HIV/AIDS located in Barcelona, Madrid and Seville, Spain.
Patients and methods:: Primary mutant genotypes were examined in plasma HIV RNA collected from 150 antiretroviral‐naive subjects, half in 1993 and the other half in 1997. Furthermore, drug resistance mutations were analysed in plasma collected from another 150 antiretroviral‐experienced patients who had received 2 NA for longer than 1 year, either in sequence as monotherapy or as combination therapy. A line probe assay was used for recognizing mutations conferring resistance to zidovudine (ZDV), didanosine (ddI), zalcitabine (ddC), and lamivudine (3TC). A point‐mutation nested‐PCR assay was used for examining a codon 151 mutation associated with multiple drug resistance.
Results:: One or more mutations associated with primary resistance to NA were seen in 10 antiretroviral‐naive (13.3%) patients in 1993 and in nine (12%) in 1997. In all but two cases, they were associated with ZDV resistance. In contrast, all but six (96%) of the antiretroviral‐experienced subjects harboured drug‐resistant mutant viruses. The codon 184 mutation (associated with resistance to 3TC) was detected in 92% of patients treated with 3TC, but also in 18% of those treated with only ddI or ddC. The codon 215 mutation was found in 67.3% of patients who had been exposed to ZDV; the codon 69 mutation was found in 15% of patients treated with ddC; and the codon 74 mutation was found in only 7.2% of patients treated with ddI. Finally, the codon 151 multidrug resistant mutation was found in four (2.7%) of 150 patients with a longterm exposure to NA.
Conclusions:: Overall, the prevalence of drug‐resistant HIV‐1 genotypes was 12.7% in antiretroviral‐naive patients, most of whom had ZDV‐resistant mutants. There is no evidence of an increase during the last 5 years. However, multidrug‐resistant HIV genotypes are currently circulating in Spain.
Chemokine receptors dictate the cellular responses to chemokines on target cells. Therefore, the regulation of expression of chemokine receptors is likely a crucial point for the regulation of chemokine action. Here we show that CC chemokine receptor 1 (CCR1) expression by primary mouse astrocytes is increased after transforming growth factor β1 (TGFβ1) stimulation. TGFβ1 caused a pronounced up-regulation of CCR1 mRNA in a concentration- and time-dependent manner. TGFβ1-mediated increase of CCR1 mRNA accumulation resulted in increased CCR1 protein expression and augmented cell migration to a physiological ligand, macrophage inflammatory protein-1α (MIP-1α). The half life of CCR1 mRNA in the presence and absence of TGFβ1 stimulation was comparable, suggesting that TGFβ1-induced CCR1 mRNA accumulation occurred at the transcriptional level. TGFβ1 did not affect CCR1 mRNA expression in hematopoietic cells, indicating that TGFβ1 effect on CCR1 expression in primary astrocytes is cell-type specific. This is the first evidence that TGFβ1 may modulate central nervous system (CNS) inflammation in part by affecting chemokine receptor expression on astrocytes. GLIA 30:1–10, 2000. © 2000 Wiley-Liss, Inc.
Among the chemokine family, fractalkine shows unusual properties: it exists as a membrane-bound and soluble protein, and both fractalkine and its receptor CX3CR1 are expressed predominantly in the central nervous system. In rat cell culture models, the chemokine fractalkine was expressed in neurons and microglia, but not in astrocytes and its receptor exclusively localized to microglial cells, where its expression was downregulated by treatment with the bacterial endotoxin (LPS). In microglial cultures, LPS (10 ng/ml) induced a marked increase in the release of the proinflammatory cytokine tumor necrosis factor-α (TNF-α). The effects of LPS on TNF-α secretion were partially blocked (30%) by fractalkine and the effects of fractalkine were reversed by a polyclonal anti-fractalkine antibody. When microglial-associated fractalkine was neutralized by anti-fractalkine antibody, the LPS response was increased by 80%, suggesting tonic activation of microglial fractalkine receptors by endogenous fractalkine. The effects of the antibody were antagonized by the addition of fractalkine. LPS-activated microglia were neurotoxic when added to neuronal hippocampal culture, producing 20% neuronal death, as measured by NeuN-positive cell counting. An anti-fractalkine antibody produced neurotoxic effects of similar magnitude in this co-culture system and also markedly potentiated the neurotoxic effects of LPS-activated microglia (40% neuronal death). These results suggest that endogenous fractalkine might act tonically as an anti-inflammatory chemokine in cerebral tissue through its ability to control and suppress certain aspects of microglial activation. These data may have relevance to degenerative conditions such as multiple sclerosis, in which cerebral inflammatory processes may be activated. GLIA 29:305–315, 2000. © 2000 Wiley-Liss, Inc.
Abstract It has been shown that human monocytes express monocyte chemoattractant protein-1 (MCP-1), an inflammatry factor, in response to non-fibrillar β-amyloid protein. Reactive microglia and inflammatory factors were reported to be present in β-amyloid deposits (senile plaques) in Alzheimer's disease, suggesting the presence of MCP-1 in senile plaques. To address this issue, we examined MCP-1-immunoreactivity in senile plaques using a mouse monoclonal anti-MCP-1 antibody. Monocyte chemoattractant protein-1 was found immunohistochemically in mature senile plaques and reactive microglia but not in immature senile plaques of brain tissues from five patients with Alzheimer's disease. These findings suggest that MCP-1-related inflammatory events induced by reactive microglia contribute to the maturation of senile plaques.
We have previously developed and characterized isolated microglia and astrocyte cultures from rapid (<4 h) brain autopsies of Alzheimer's disease (AD) and nondemented elderly control (ND) patients. In the present study, we evaluate the inflammatory repertoire of AD and ND microglia cultured from white matter (corpus callosum) and gray matter (superior frontal gyrus) with respect to three major proinflammatory cytokines, three chemokines, a classical pathway complement component, a scavenger cell growth factor, and a reactive nitrogen intermediate. Significant, dose-dependent increases in the production of pro-interleukin-1β (pro-IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory peptide-1α (MIP-1α), IL-8, and macrophage colony-stimulating factor (M-CSF) were observed after exposure to pre-aggregated amyloid β peptide (1–42) (Aβ1–42). Across constitutive and Aβ-stimulated conditions, secretion of complement component C1q, a reactive nitrogen intermediate, and M-CSF was significantly higher in AD compared with ND microglia. Taken together with previous in situ hybridization findings, these results demonstrate unequivocally that elderly human microglia provide a brain endogenous source for a wide range of inflammatory mediators. GLIA 35:72–79, 2001. © 2001 Wiley-Liss, Inc.
The viral chemokine antagonits vMIP-II encoded by human herpesvirus 8 (HHV8) and MC148 encoded by the poxvirus – Molluscum contagiosum – were tested against the newly identified chemokine receptor CCR10. As the CCR10 ligand ESkine / CCL27 had the highest identity to MC148 and because both chemokines are expressed in the skin we suspected MC148 to block CCR10. However, in calcium mobilization assays we found MC148 unable to block CCR10 in micromolar concentrations in contrast to vMIP-II. 125I-MC148 was only able to bind to CCR8, but not to CCR10, CCR11, CXCR6 / BONZO, APJ, DARC or the orphan receptors BOB, EBI-II, GPR4, GPR17, HCR or RDC1. We conclude that MC148 is a highly selective CCR8 antagonist conceivably optimized to interfere with NK cell and monocyte invasion, whereas the broad-spectrum antagonist vMIP-II protects HHV8 by blocking multiple receptors.
Focal cerebral ischemia elicits local inflammatory reaction as demonstrated by the accumulation of inflammatory cells and mediators in the ischemic brain. Interferon-inducible protein-10 (IP-10) is a member of the C-X-C chemokine family that possesses potent chemoattractant actions for monocytes, T cells, and smooth muscle cells. To investigate a potential role of IP-10 in focal stroke, we studied the temporal expression of IP-10 mRNA after occlusion of the middle cerebral artery in rat by means of northern analysis. IP-10 mRNA expression after focal stroke demonstrated a unique biphasic profile, with a marked increase early at 3 h (4.9-fold over control; p < 0.01), a peak level at 6 h (14.5-fold; p < 0.001) after occlusion of the middle cerebral artery, and a second wave induction 10–15 days after ischemic injury (7.2- and 9.3-fold increase for 10 and 15 days, respectively; p < 0.001). In situ hybridization confirmed the induced expression of IP-10 mRNA and revealed its spatial distribution after focal stroke. Immunohistochemical studies demonstrated the expression of IP-10 peptide in neurons (3–12 h) and astroglial cells (6 h to 15 days) of the ischemic zone. To explore further the potential role of IP-10 in focal stroke, we demonstrated a dose-dependent chemotactic action of IP-10 on C6 glial cells and enhanced attachment of rat cerebellar granule neurons. Taken together, the data suggest that ischemia induces IP-10, which may play a pleiotropic role in prolonged leukocyte recruitment, astrocyte migration/activation, and neuron attachment/sprouting after focal stroke.
Macrophage inflammatory protein (MIP)-1α is a chemokine that is associated with Th1 cytokine responses. Expression and antibody blocking studies have implicated MIP-1α in multiple sclerosis (MS) and in experimental autoimmune encephalomyelitis (EAE). We examined the role of MIP-1α and its CCR5 receptor in the induction of EAE by immunizing C57BL / 6 mice deficient in either MIP-1α or CCR5 with myelin oligodendrocyte glycoprotein (MOG). We found that MIP-1α-deficient mice were fully susceptible to MOG-induced EAE. These knockout animals were indistinguishable from wild-type mice in Th1 cytokine gene expression, the kinetics and severity of disease, and infiltration of the central nervous system by lymphocytes, macrophages and granulocytes. RNase protection assays showed comparable accumulation of mRNA for the chemokines interferon-inducible protein-10, RANTES, macrophage chemoattractant protein-1, MIP-1β, MIP-2, lymphotactin and T cell activation gene-3 during the course of the disease. CCR5-deficient mice were also susceptible to disease induction by MOG. The dispensability of MIP-1α and CCR5 for MOG-induced EAE in C57BL / 6 mice supports the idea that differential chemokine expression patterns represent differences in disease mechanism that underlie various models of EAE, and possibly distinct patterns of pathology seen in MS.
CXCR4 is the Gi protein-linked seven-transmembrane receptor for the alpha chemokine stromal cell-derived factor 1 (SDF-1), a chemoattractant for lymphocytes. This receptor is highly conserved between human and rodent. CXCR4 is also a coreceptor for entry of human immunodeficiency virus (HIV) in T cells and is expressed in the CNS. To investigate how these CXCR4 ligands influence CNS development and/or function, we have examined the expression and signalling of this chemokine receptor in rat neurons and astrocytes in vitro. CXCR4 transcripts and protein are synthesized by both cell types and in E15 brain neuronal progenitors. In these progenitors, SDF-1, but not gp120 (the HIV glycoprotein), induced activation of extracellular signal regulated kinases (ERKs) 1/2 and a dose-dependent chemotactic response. This chemotaxis was inhibited by Pertussis toxin, which uncouples Gi proteins and the bicyclam AMD3100, a highly selective CXCR4 antagonist, as well as by an inhibitor of the MAP kinase pathway. In differentiated neurons, both SDF-1 and the glycoprotein of HIV, gp120, triggered activation of ERKs with similar kinetics. These effects were significantly inhibited by Pertussis toxin and the CXCR4 antagonist. Rat astrocytes also responded to SDF-1 signalling by phosphorylation of ERKs but, in contrast to cortical neurons, no kinase activation was induced by gp120. Thus neurons and astrocytes can respond differently to signalling by SDF-1 and/or gp120. As SDF-1 triggers directed migration of neuronal progenitors, this alpha chemokine may play a role in cortex development. In differentiated neurons, both natural and viral ligands of CXCR4 activate ERKs and may therefore influence neuronal function.
Multiple sclerosis (MS) is a common disease of the central nervous system characterized by myelin loss and progressive neurological
dysfunction. An underlying genetic susceptibility plays a clear role in the etiology of MS, likely acting in concert with
an undefined environmental exposure. Full-genome screenings in multiplex MS families have identified several susceptibility
regions, supporting a polygenic model for MS. Among these regions, evidence for weak linkage was observed at 3p/3cen suggesting
the presence of an MS gene(s) of modest effect. Encoded here are two chemokine receptors, CCR5 and CCR2B. We examined the chromosome 3p21–24 region in 125 MS families (322 total affecteds and 200 affected sib-pairs), and performed
genetic analyses of CCR5 and CCR2B loci and two nearby markers (D3S1289 and D3S1300) using both linkage- and association-based tests. No evidence of linkage to MS was observed for any of the tested markers.
Affected relative-pair (SimIBD) and sib-pair analyses (ASPEX), and association testing (sib-TDT) for each locus were also
not significant. However, age of onset was approximately 3 years later in patients carrying the CCR5
Δ
32 deletion (P=0.018 after controlling for gender effects). Thus, chemokine receptor expression may be associated with differential disease
onset in a subset of patients, and may provide a therapeutic target to modulate inflammatory demyelination.
Using the suppression subtractive hybridization (SSH) strategy for differential gene cloning, we identified the induced expression of a rat homologue to murine and human monocyte chemotactic protein-3 (MCP-3) in ischemic brain. The 2.4-kilobase rat MCP-3 gene features high homology in gene structure and sequence to murine MCP-3. The temporal expression of MCP-3 mRNA was examined in brain tissue rendered ischemia by permanent or temporary occlusion of the middle cerebral artery (MCAO). A marked increase in MCP-3 mRNA was observed 12 h post-ischemia, with 49-fold and 17-fold increase (n=4, p<0.01) over control in the permanent or temporary MCAO, respectively. Significant induction of MCP-3 in the ischemic cortex was sustained up to 5 days after ischemic injury. The profile of MCP-3 mRNA induction paralleled leukocyte infiltration and accumulation that occur after focal stroke, suggesting a role for MCP-3 in recruiting these inflammatory cells into the ischemic tissue. Molecular cloning of rat MCP-3 should provide a valuable tool, as demonstrated in the present work, for the investigation of MCP-3 expression and function in rat disease models.
Human immunodeficiency virus type 1 (HIV-1) infection of the brain is associated with neurological manifestations both in adults and in children. The primary target for HIV-1 infection in the brain is the microglia, but astrocytes can also be infected. We tested 26 primary HIV-1 isolates for their capacity to infect human fetal astrocytes in culture. Eight of these isolates, independent of their biological phenotype and chemokine receptor usage, were able to infect astrocytes. Although no sustained viral replication could be demonstrated, the virus was recovered by coculture with receptive cells such as macrophages or on stimulation with interleukin-1β. To gain knowledge into the molecular events that regulate attachment and penetration of HIV-1 in astrocytes, we investigated the expression of several chemokine receptors. Fluorocytometry and calcium-mobilization assay did not provide evidence of expression of any of the major HIV-1 coreceptors, including CXCR4, CCR5, CCR3, and CCR2b, as well as the CD4 molecule on the cell surface of human fetal astrocytes. However, mRNA transcripts for CXCR4, CCR5, Bonzo/STRL33/TYMSTR, and APJ were detected by RT-PCR. Furthermore, infection of astrocytes by HIV-1 isolates with different chemokine receptor usage was not inhibited by the chemokines SDF-1β, RANTES, MIP-1β, or MCP-1 or by antibodies directed against the third variable region or the CD4 binding site of gp120. These data show that astrocytes can be infected by primary HIV-1 isolates via a mechanism independent of CD4 or major chemokine receptors. Furthermore, astrocytes are potential carriers of latent HIV-1 and on activation may be implicated in spreading the infection to other neighbouring cells, such as microglia or macrophages.
The two chemokines, monocyte chemoattractant protein (MCP)-1 and γ-interferon inducible protein (IP)-10, are thought to be involved in the pathogenesis of multiple sclerosis (MS). We measured MCP-1 and IP-10 levels in serum and CSF samples from 38 acute and 25 stable MS patients and from 40 controls. The latter consisted in patients with other inflammatory neurological diseases (OIND) or with non-inflammatory neurological diseases, and healthy controls. CSF MCP-1 levels exceeded those found in serum in all the patients studied as well as in healthy controls. CSF MCP-1 levels were significantly lower in acute MS [468±(S.E.M.) 18 pg/ml] than in stable MS (857±104 pg/ml). When detectable, serum and CSF IP-10 levels were significantly higher in acute MS (serum 331±66 pg/ml; CSF 118±16 pg/ml) than in stable MS (serum 69±7 pg/ml; CSF 25±2 pg/ml). Among OIND patients, those with HIV-1-associated dementia showed high serum and CSF levels of both MCP-1 and IP-10. Those with encephalitis showed high serum and CSF levels of IP-10 and CSF mononuclear pleiocytosis. We also evaluated the effects of 6-methylprednisolone or IFN-β1a therapy on circulating MCP-1 and IP-10 levels. Neither MCP-1 nor IP-10 post-therapy levels varied significantly from baseline values. Our findings suggest that (a) MCP-1 could be constitutively produced within the brain; (b) MCP-1 and IP-10 CSF levels in acute MS vary significantly from those in stable MS, and these variations are inverse; and (c) current MS therapies do not modify circulating levels of MCP-1 and IP-10.
We have evaluated the in vivo distribution of the major human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) coreceptors, CXCR4, CCR3, and CCR5, in both rhesus macaques and humans. T lymphocytes and macrophages in both lymphoid and nonlymphoid tissues are the major cell populations expressing HIV/SIV coreceptors, reaffirming that these cells are the major targets of HIV/SIV infection in vivo. In lymphoid tissues such as the lymph node and the thymus, approximately 1 to 10% of the T lymphocytes and macrophages are coreceptor positive. However, coreceptor expression was not detected on follicular dendritic cells (FDC) in lymph nodes, suggesting that the ability of FDC to trap extracellular virions is unlikely to be mediated by a coreceptor-specific mechanism. In the thymus, a large number of immature and mature T lymphocytes express CXCR4, which may render these cells susceptible to infection by syncytium-inducing viral variants that use this coreceptor for entry. In addition, various degrees of coreceptor expression are found among different tissues and also among different cells within the same tissues. Coreceptor-positive cells are more frequently identified in the colon than in the rectum and more frequently identified in the cervix than in the vagina, suggesting that the expression levels of coreceptors are differentially regulated at different anatomic sites. Furthermore, extremely high levels of CXCR4 and CCR3 expression are found on the neurons from both the central and peripheral nervous systems. These findings may be helpful in understanding certain aspects of HIV and SIV pathogenesis and transmission.