Fig 2 - available from: Journal of Neuroinflammation
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Brain blood flow in mice during MCAO. a Representation of brain blood flow before MCAO (as a baseline), after MCAO (when the cerebral artery was occluded), and reperfusion (when the suture was withdrawn from the cerebral artery). b Percentage of brain blood flow reperfusion (reperfusion/before MCAO) among groups. There was no significance on the percentage of brain blood flow reperfusion among groups. n = 11-13 per group
Source publication
Background:
Macrophages are involved in demyelination in many brain diseases. However, the role of macrophages in the recovery phase of the ischemic brain is unknown. The present study aims to explore the role of macrophages in the ischemic brain injury and tissue repair following a 90-min transient middle cerebral artery occlusion in mice.
Metho...
Context in source publication
Context 1
... and reperfusion were validated by monitoring the changes of cerebral blood flow using a laser Doppler flowmetry (Moor Instruments, Axminster, Devon, UK). Animals were included into further charac- terizations when the brain blood flow decreased for at least 80 % compared to the baseline and returned to 80 % of the baseline after suture withdrawal (Fig. 2). The mor- tality rates of animals following MCAO for the control liposome (Vehicle), phosphate-buffered saline (PBS), and clodronate liposome (CLP) groups were 21.4, 14.3, and 18.8 %, respectively. There was no significant difference of the mortality among the ...
Citations
... CLP is widely used to deplete peripheral Mo/MΦs [49][50][51]. These results are consistent with previous studies showing that the depletion of peripheral monocytes prevents in ammation and neurodegeneration in a model of PD [52,53]. ...
Background
Neuroinflammation is a crucial factor in the pathogenesis of Parkinson's disease (PD). Activated microglia in the central nervous system (CNS) and peripherally infiltrating immune cells contribute to the degeneration of dopaminergic neurons. However, how the peripheral immune system leads to neuron loss and whether blocking this response slows disease progression remain largely unknown. Triggering receptor expressed on myeloid cells-1 (TREM-1), a key regulator of inflammation, plays a significant role in the pathogenesis of infection and noninfection-related inflammation. However, the specific role of TREM-1 in PD has not yet been determined. Therefore, the aim of this study was to determine the immune regulation mechanism of monocyte TREM-1 on dopaminergic neurons and motor function in PD.
Methods
First, we evaluated TREM-1 expression and monocyte infiltration in the substantia nigra pars compacta (SNpc) in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP)-related neurotoxic model of PD by western blot, qRT-PCR, and flow cytometry. Second, we determined the level of TREM-1 and the extent of dopaminergic neuronal injury in the SNpc after the depletion of peripheral monocytes. Motor function was assessed by the open field test, pole test, and rotarod test. Third, to determine the actual role of TREM-1 in the PD, we analyzed the effects of TREM-1 inhibition on monocytes infiltration. Assays examining dopaminergic neuron degeneration and neuroinflammation include immunofluorescence, western blot, and qRT-PCR. To corroborate the dopaminergic terminal loss in the striatum we quantified the concentration of dopamine in the striatum using High-performance liquid chromatography (HPLC). Additionally, we conducted an adoptive transfer of TREM-1-producing monocytes from PD model mice to investigate whether monocytes induce dopaminergic neuron injury and motor dysfunction in a TREM-1-dependent manner.
Results
MPTP administration successfully induced subacute PD model and increased peripheral blood inflammatory monocyte levels. Deletion of peripheral monocytes protected against MPTP neurotoxicity in the SNpc. TREM-1 inhibition genetically or pharmacologically dampens the peripheral innate response, reduces the accumulation of infiltrating monocytes, and efficiently prevents dopaminergic neuron injury in the SNpc. Adoptive transfer of TREM-1-producing monocytes from PD model mice was sufficient to induce dopaminergic neurons and motor deficits in naive mice.
Conclusion
These results indicate the critical role of peripheral monocytes in the pathogenesis of PD and suggest that inhibiting monocyte TREM-1 expression is a promising therapeutic approach for the degeneration of dopaminergic neurons in the SNpc in PD patients.
... The monocyte-macrophage phagocytic system stands as a principal driver of inflammation in the context of IRI (31)(32)(33)(34)(35). Our published (36) and unpublished data have demonstrated a notable surge in proinflammatory cytokine levels, both within the affected tissues and in systemic circulation, within the initial 6 hours following resuscitation. ...
Background
Cardiac arrest (CA) is a significant public health concern. There is the high imminent mortality and survival in those who are resuscitated is substantively compromised by the post-CA syndrome (PCAS), characterized by multiorgan ischemia–reperfusion injury (IRI). The inflammatory response in PCAS is complex and involves various immune cell types, including lymphocytes and myeloid cells that have been shown to exacerbate organ IRI, such as myocardial infarction. Purinergic signaling, as regulated by CD39 and CD73, has emerged as centrally important in the context of organ-specific IRI. Hence, comprehensive understanding of such purinergic responses may be likewise imperative for improving outcomes in PCAS.
Methods
We have investigated alterations of immune cell populations after CA by utilizing rodent models of PCAS. Blood and spleen were collected after CA and resuscitation and underwent flow cytometry analysis to evaluate shifts in CD3⁺CD4⁺ helper T cells, CD3⁺CD8a⁺ cytotoxic T cells, and CD4/CD8a ratios. We then examined the expression of CD39 and CD73 across diverse cell types, including myeloid cells, T lymphocytes, and B lymphocytes.
Results
In both rat and mouse models, there were significant increases in the frequency of CD3⁺CD4⁺ T lymphocytes in PCAS (rat, P < 0.01; mouse, P < 0.001), with consequently elevated CD4/CD8a ratios in whole blood (both, P < 0.001). Moreover, CD39 and CD73 expression on blood leukocytes were markedly increased (rat, P < 0.05; mouse, P < 0.01 at 24h). Further analysis in the experimental mouse model revealed that CD11b⁺ myeloid cells, with significant increase in their population (P < 0.01), had high level of CD39 (88.80 ± 2.05 %) and increased expression of CD73 (P < 0.05). CD19⁺ B lymphocytes showed slight increases of CD39 (P < 0.05 at 2h) and CD73 (P < 0.05 at 2h), while, CD3⁺ T lymphocytes had decreased levels of them. These findings suggested a distinct patterns of expression of CD39 and CD73 in these specific immune cell populations after CA.
Conclusions
These data have provided comprehensive insights into the immune response after CA, highlighting high-level expressions of CD39 and CD73 in myeloid cells.
... Analysis of our flow scatter data, however, suggests that CCI injury may be needed to enhance these effects and contribute to the release of an immunoregulatory population. Prior studies in mice confirm the neuroprotective effects of pre-injury depletion with clodronate and also detail the role of non-classical monocytes in tissue damage [3], while studies in rats indicate pre-depletion increases BBB disruption [45] and opposing effects have been observed in stroke outcome [46,47]. These divergent findings may be due to species, model or injury severity differences, or investigative tools which warrant further investigation. ...
... We are the first to show this hyperacute compensatory mechanism using outbred CD1 mice as early as 24 h after brain injury. Others have used altered mouse strains [3], confirmed clodronate effects only prior to injury [48] or used spleen and brain for outcome measures [47,49]. Collectively, however, these studies highlight the key importance of monocytes in pre-clinical models of neurological impairments. ...
Monocytes represent key cellular elements that contribute to the neurological sequela following brain injury. The current study reveals that trauma induces the augmented release of a transcriptionally distinct CD115⁺/Ly6Chi monocyte population into the circulation of mice pre-exposed to clodronate depletion conditions. This phenomenon correlates with tissue protection, blood–brain barrier stability, and cerebral blood flow improvement. Uniquely, this shifted the innate immune cell profile in the cortical milieu and reduced the expression of pro-inflammatory Il6, IL1r1, MCP-1, Cxcl1, and Ccl3 cytokines. Monocytes that emerged under these conditions displayed a morphological and gene profile consistent with a subset commonly seen during emergency monopoiesis. Single-cell RNA sequencing delineated distinct clusters of monocytes and revealed a key transcriptional signature of Ly6Chi monocytes enriched for Apoe and chitinase-like protein 3 (Chil3/Ym1), commonly expressed in pro-resolving immunoregulatory monocytes, as well as granule genes Elane, Prtn3, MPO, and Ctsg unique to neutrophil-like monocytes. The predominate shift in cell clusters included subsets with low expression of transcription factors involved in monocyte conversion, Pou2f2, Na4a1, and a robust enrichment of genes in the oxidative phosphorylation pathway which favors an anti-inflammatory phenotype. Transfer of this monocyte assemblage into brain-injured recipient mice demonstrated their direct role in neuroprotection. These findings reveal a multifaceted innate immune response to brain injury and suggest targeting surrogate monocyte subsets may foster tissue protection in the brain.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12974-024-03032-8.
... The more phospholipid bilayers and liposomes are ingested by the macrophage, the more clodronate accumulates within the macrophage until it exceeds an intracellular concentration, thereby inducing apoptosis. Indeed, depleting macrophages in the middle cerebral artery occlusion mice model with CL suppressed the activation of microglia in the acute inflammation phase and protected against brain damage 28 . www.nature.com/scientificreports/ ...
Pathological conditions in cochlea, such as ototoxicity, acoustic trauma, and age-related cochlear degeneration, induce cell death in the organ of Corti and degeneration of the spiral ganglion neurons (SGNs). Although macrophages play an essential role after cochlear injury, its role in the SGNs is limitedly understood. We analyzed the status of macrophage activation and neuronal damage in the spiral ganglion after kanamycin-induced unilateral hearing loss in mice. The number of ionized calcium-binding adapter molecule 1 (Iba1)-positive macrophages increased 3 days after unilateral kanamycin injection. Macrophages showed larger cell bodies, suggesting activation status. Interestingly, the number of activating transcription factor 3 (ATF3)-positive-neurons, an indicator of early neuronal damage, also increased at the same timing. In the later stages, the number of macrophages decreased, and the cell bodies became smaller, although the number of neuronal deaths increased. To understand their role in neuronal damage, macrophages were depleted via intraperitoneal injection of clodronate liposome 24 h after kanamycin injection. Macrophage depletion decreased the number of ATF3-positive neurons at day 3 and neuronal death at day 28 in the spiral ganglion following kanamycin injection. Our results suggest that suppression of inflammation by clodronate at early timing can protect spiral ganglion damage following cochlear insult.
... Whereas ablation of peripheral Ly6C low monocytes showed no effect on stroke outcome [116], efficient inhibition of Ly6C high monocyte infiltration significantly worsened stroke outcomes [117]. Several studies have examined the impact of deleting or reducing the infiltration of monocytes showing both positive and negative effects on infarct volume, neurological score, demyelination, and angiogenesis, pointing to the need to further investigate the effects of specific monocyte subpopulations and involved molecular mechanisms on stroke outcomes [58,[118][119][120][121]. ...
Ischemic stroke is a leading cause of disability and mortality. Despite extensive efforts in stroke research, the only pharmacological treatment currently available is arterial recanalization, which has limited efficacy only in the acute phase of stroke. The neuroinflammatory response to stroke is believed to provide a wider time window than recanalization and has therefore been proposed as an attractive therapeutic target. In this review, we provide an overview of recent advances in the understanding of cellular and molecular responses of distinct macrophage populations following stroke, which may offer potential targets for therapeutic interventions. Specifically, we discuss the role of local responders in neuroinflammation, including the well‐studied microglia as well as the emerging players, border‐associated macrophages, and macrophages originating from the skull bone marrow. Additionally, we focus on the behavior of monocytes stemming from distant tissues, such as the bone marrow and spleen. Finally, we highlight aging as a crucial factor modulating the immune response, which is often neglected in animal studies.
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... Interestingly, a model of acute ischemic stroke helped in understanding the role of acute monocyte recruitment in the brain and the role of monocyte-derived macrophages in the brain [47]. While these monocyte-derived macrophages strongly contribute to the first phase of postischemic stroke to reduce brain edema, BBB damage, neuronal apoptosis and cerebral ischemic infarction [48][49][50][51], they also seem to promote inflammation via reactive oxygen species, glutamate and chemokines in a second phase, causing secondary damage [52]. Recently, a study showed their involvement in Alzheimer's disease [53], which will be discussed later. ...
Brain macrophages include microglia in the parenchyma, border-associated macrophages in the meningeal-choroid plexus-perivascular space, and monocyte-derived macrophages that infiltrate the brain under various disease conditions. The vast heterogeneity of these cells has been elucidated over the last decade using revolutionary multiomics technologies. As such, we can now start to define these various macrophage populations according to their ontogeny and their diverse functional programs during brain development, homeostasis and disease pathogenesis. In this review, we first outline the critical roles played by brain macrophages during development and healthy aging. We then discuss how brain macrophages might undergo reprogramming and contribute to neurodegenerative disorders, autoimmune diseases, and glioma. Finally, we speculate about the most recent and ongoing discoveries that are prompting translational attempts to leverage brain macrophages as prognostic markers or therapeutic targets for diseases that affect the brain.
... The use of clodronate to deplete macrophages may have indeterminate effects on vascular function independent of the elimination of adventitial macrophages, as it depletes macrophages throughout the body. We also halved doses 2 and 3 of clodronate, as repeating the original dose led to~25% mortality in the control group (consistent with published studies Ma et al., 2016) and up to 50% mortality in the IBD group. No studies using clodronate in IL10 −/− mice have reported mortality. ...
Introduction: Inflammatory bowel disease involves aberrant immune responses and is associated with both cardiovascular disease risk and altered intestinal blood flow. However, little is known about how inflammatory bowel disease affects regulation of perivascular nerves that mediate blood flow. Previous work found perivascular nerve function is impaired in mesenteric arteries with Inflammatory bowel disease. The purpose of this study was to determine the mechanism of impaired perivascular nerve function.
Methods: RNA sequencing was performed on mesenteric arteries from IL10 −/− mice treated with H. hepaticus to induce disease (inflammatory bowel disease) or left non-gavaged (Control). For all other studies, Control and Inflammatory bowel disease mice received either saline or clodronate liposome injections to study the effect of macrophage depletion. Perivascular nerve function was assessed using pressure myography and electrical field stimulation. Leukocyte populations, and perivascular nerves, and adventitial neurotransmitter receptors were labeled using fluorescent immunolabeling.
Results: Inflammatory bowel disease was associated with increases in macrophage-associated gene expression, and immunolabeling showed accumulation of adventitial macrophages. Clodronate liposome injection eliminated adventitial macrophages, which reversed significant attenuation of sensory vasodilation, sympathetic vasoconstriction and sensory inhibition of sympathetic constriction in inflammatory bowel disease. Acetylcholine-mediated dilation was impaired in inflammatory bowel disease and restored after macrophage depletion, but sensory dilation remained nitric oxide independent regardless of disease and/or macrophage presence.
Conclusion: Altered neuro-immune signaling between macrophages and perivascular nerves in the arterial adventitia contributes to impaired vasodilation, particularly via dilatory sensory nerves. Targeting the adventitial macrophage population may help preserve intestinal blood flow in Inflammatory bowel disease patients.
... However, stroke is also associated with inflammatory cell activation [32], including infiltration of circulating monocytes and macrophages to the core-surrounding penumbra in the days following injury. This amplified neuroinflammation increases the risk of secondary complications after stroke [9,26], suggesting that inflammation may be another link between heart and brain after ischemic cerebral damage. Inter-organ communication within the heart-brain axis contributes to concurrent injury after focal ischemic damage, as evidenced after myocardial infarction with simultaneous neuroinflammation [5,27,40]. ...
Ischemic stroke imparts elevated risk of heart failure though the underlying mechanisms remain poorly described. We aimed to characterize the influence of cerebral ischemic injury on cardiac function using multimodality molecular imaging to investigate brain and cardiac morphology and tissue inflammation in two mouse models of variable stroke severity. Transient middle cerebral artery occlusion (MCAo) generated extensive stroke damage (56.31 ± 40.39 mm ³ ). Positron emission tomography imaging of inflammation targeting the mitochondrial translocator protein (TSPO) revealed localized neuroinflammation at 7 days after stroke compared to sham (3.8 ± 0.8 vs 2.6 ± 0.7 %ID/g max, p < 0.001). By contrast, parenchyma topical application of vasoconstrictor endothelin-1 did not generate significant stroke damage or neuroinflammatory cell activity. MCAo evoked a modest reduction in left ventricle ejection fraction at both 1 weeks and 3 weeks after stroke (LVEF at 3 weeks: 54.3 ± 5.7 vs 66.1 ± 3.5%, p < 0.001). This contractile impairment was paralleled by elevated cardiac TSPO PET signal compared to sham (8.6 ± 2.4 vs 5.8 ± 0.7%ID/g, p = 0.022), but was independent of leukocyte infiltration defined by flow cytometry. Stroke size correlated with severity of cardiac dysfunction ( r = 0.590, p = 0.008). Statistical parametric mapping identified a direct association between neuroinflammation at 7 days in a cluster of voxels including the insular cortex and reduced ejection fraction ( ρ = − 0.396, p = 0.027). Suppression of microglia led to lower TSPO signal at 7 days which correlated with spared late cardiac function after MCAo ( r = − 0.759, p = 0.029). Regional neuroinflammation early after cerebral ischemia influences subsequent cardiac dysfunction. Total body TSPO PET enables monitoring of neuroinflammation, providing insights into brain–heart inter-organ communication and may guide therapeutic intervention to spare cardiac function post-stroke.
... The results showed that macrophage clearance alone and Sanguinarine treatment alone could inhibit tumor growth, (Figure 4B), manifesting in the smallest tumor ( Figure 4C) and the lightest tumor ( Figure 4D). The percentage of CD11b+F4/80+ macrophages significantly decreased in the spleen and tumor tissue treated with macrophage clearance ( Figure S3 and Figures 4F, S6B, E), which is consistent with previous reports (38)(39)(40). In addition, the group treated with CLPs effectively decreased tumor size and load ( Figures 4B-D), indicating that macrophages contribute to neoplastic progression. ...
Tumor-associated macrophage (TAM)-mediated angiogenesis in the tumor microenvironment is a prerequisite for lung cancer growth and metastasis. Therefore, targeting TAMs, which block angiogenesis, is expected to be a breakthrough in controlling the growth and metastasis of lung cancer. In this study, we found that Sanguinarine (Sang) inhibits tumor growth and tumor angiogenesis of subcutaneously transplanted tumors in Lewis lung cancer mice. Furthermore, Sanguinarine inhibited the proliferation, migration, and lumen formation of HUVECs and the expression of CD31 and VEGF by regulating the polarization of M2 macrophages in vitro. However, the inhibitory effect of Sanguinarine on angiogenesis remained in vivo despite the clearance of macrophages using small molecule drugs. Further high-throughput sequencing suggested that WNT/β-Catenin signaling might represent the underlying mechanism of the beneficial effects of Sanguinarine. Finally, the β-Catenin activator SKL2001 antagonized the effect of Sanguinarine, indicating that Sanguinarine can regulate M2-mediated angiogenesis through the WNT/β-Catenin pathway. In conclusion, this study presents the first findings that Sanguinarine can function as a novel regulator of the WNT/β-Catenin pathway to modulate the M2 macrophage polarization and inhibit angiogenesis, which has potential application value in immunotherapy and antiangiogenic therapy for lung cancer.
... Using an anti-CCR2 antibody, MC-21, Watannanit et al. were able to block monocyte recruitment and found that this resulted in decreased tissue expression of the anti-inflammatory genes TGFb, CD163, and Ym1 and functional inability of mice to recover long-term (13). Yet, there are conflicting data in other models (133)(134)(135). In an intracerebral hemorrhage model, Hammond et al. reported that classical monocytes exacerbated acute disability (135). ...
... In an intracerebral hemorrhage model, Hammond et al. reported that classical monocytes exacerbated acute disability (135). Using clodronate liposomes to deplete peripheral macrophages, Ma et al. found that under conditions of macrophage depletion, there was decreased demyelination and brain atrophy in the ipsilateral striatum and enhanced focal microvessel density in the peri-infarct region, all of which have been correlated with longer survival times in ischemic stroke patients (134,136). Further long-term studies of the effects of MoDMs on recovery are needed to better understand these discordant findings regarding the activity and function of MoDMs in the chronic stage. ...
The immune response to ischemic stroke is an area of study that is at the forefront of stroke research and presents promising new avenues for treatment development. Upon cerebral vessel occlusion, the innate immune system is activated by danger-associated molecular signals from stressed and dying neurons. Microglia, an immune cell population within the central nervous system which phagocytose cell debris and modulate the immune response via cytokine signaling, are the first cell population to become activated. Soon after, monocytes arrive from the peripheral immune system, differentiate into macrophages, and further aid in the immune response. Upon activation, both microglia and monocyte-derived macrophages are capable of polarizing into phenotypes which can either promote or attenuate the inflammatory response. Phenotypes which promote the inflammatory response are hypothesized to increase neuronal damage and impair recovery of neuronal function during the later phases of ischemic stroke. Therefore, modulating neuroimmune cells to adopt an anti-inflammatory response post ischemic stroke is an area of current research interest and potential treatment development. In this review, we outline the biology of microglia and monocyte-derived macrophages, further explain their roles in the acute, subacute, and chronic stages of ischemic stroke, and highlight current treatment development efforts which target these cells in the context of ischemic stroke.
