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Schematic illustration of the experimental in vivo approach and the incidence of bleedings in APPPS1 transgenic mice. (A) We immunized T-GFP mice with Aβ42 and adoptively transferred these isolated T cells via the tail vein into transgenic or control mice. After a recovery period of one week, a cranial window surgery with dura removal and antibody application of either antibody 10D5 against Aβ or control antibody 16D5 against human tau was performed. Brains were analyzed postmortem 3 to 4 days after passive immunization. (B) In contrast to wildtype mice passively immunized (left image) or APPPS1 transgenic mice immunized with a control antibody against human tau (right image) transgenic mice immunized with anti Aβ antibody developed acute hematomas on both hemispheres as indicated by black arrows (image in the middle).
Source publication
Immunization against amyloid-β (Aβ), the peptide that accumulates in the form of senile plaques and in the cerebrovasculature in Alzheimer's disease (AD), causes a dramatic immune response that prevents plaque formation and clears accumulated Aβ in transgenic mice. In a clinical trial of Aβ immunization, some patients developed meningoencephalitis...
Citations
... Some Ab antibodies were shown to bind to Ab deposits and reduce the plaques via activation of microglia. However, passive immunization of Ab antibodies was also showed to cause microhaemorrage [56,57]. A modified antibody with minimized interaction with Fc-g receptors and complement protein has been shown to reduce microhemorrhage, though with a moderate efficacy, in the reduction of Ab deposits [58]. ...
... For comparison, in IE patients, CMBs have been observed in more than 50% of the cases, at both the IE acute and subacute phases (11). In the literature, only few CMBs animal models are reported (22)(23)(24). Interestingly, we observed similar radiologic pattern of CMBs in IE and NBTE rats. ...
Objectives:
Embolic events from vegetations are commonly accepted as the main mechanism involved in neurologic complications of infective endocarditis. The pathophysiology may imply other phenomena, including vasculitis. We aimed to define the cerebral lesion spectrum in an infective endocarditis rat model.
Design:
Experimental model of Staphylococcus aureus or Enterococcus faecalis infective endocarditis. Neurologic lesions observed in the infective endocarditis model were compared with three other conditions, namely bacteremia, nonbacterial thrombotic endocarditis, and healthy controls.
Setting:
Research laboratory of a university hospital.
Subjects:
Male Wistar rats.
Interventions:
Brain MRI, neuropathology, immunohistochemistry for astrocyte and microglia, and bacterial studies on brain tissue were used to characterize neurologic lesions.
Measurements and main results:
In the infective endocarditis group, MRI revealed at least one cerebral lesion in 12 of 23 rats (52%), including brain infarctions (n = 9/23, 39%) and cerebral microbleeds (n = 8/23, 35%). In the infective endocarditis group, neuropathology revealed brain infarctions (n = 12/23, 52%), microhemorrhages (n = 10/23, 44%), and inflammatory processes (i.e., cell infiltrates including abscesses, vasculitis, meningoencephalitis, and/or ependymitis; n = 11/23, 48%). In the bacteremia group, MRI studies were normal and neuropathology revealed only hemorrhages (n = 2/11, 18%). Neuropathologic patterns observed in the nonbacterial thrombotic endocarditis group were similar to those observed in the infective endocarditis group. Immunochemistry revealed higher microglial activation in the infective endocarditis group (n = 11/23, 48%), when compared with the bacteremia (n = 1/11, 9%; p = 0.03) and nonbacterial thrombotic endocarditis groups (n = 0/7, 0%; p = 0.02).
Conclusions:
This original model of infective endocarditis recapitulates the neurologic lesion spectrum observed in humans and suggests synergistic mechanisms involved, including thromboembolism and cerebral vasculitis, promoted by a systemic bacteremia-mediated inflammation.
... S6) (13). The invasion correlated with increased tissue iron content as quantified by standard morphometric measurements with Prussian blue staining (33). The data summarized in Fig. 4 (A and B) indicate that the depth of A. fumigatus invasion increased with time (days 6 to 12) posttransplant and was associated with a timedependent increase in tissue iron deposition. ...
Invasive pulmonary disease due to the moldAspergillus fumigatuscan be life-threatening in lung transplant recipients, but the risk factors remain poorly understood. To study this process, we used a tracheal allograft mouse model that recapitulates large airway changes observed in patients undergoing lung transplantation. We report that microhemorrhage-related iron content may be a major determinant ofA. fumigatusinvasion and, consequently, its virulence. Invasive growth was increased during progressive alloimmune-mediated graft rejection associated with high concentrations of ferric iron in the graft. The role of iron inA. fumigatusinvasive growth was further confirmed by showing that this invasive phenotype was increased in tracheal transplants from donor mice lacking the hemochromatosis gene (Hfe
-/-
). The invasive phenotype was also increased in mouse syngrafts treated with topical iron solution and in allograft recipients receiving deferoxamine, a chelator that increases iron bioavailability to the mold. The invasive growth of the iron-intolerantA. fumigatusdouble-knockout mutant (ΔsreA/ΔcccA) was lower than that of the wild-type mold. Alloimmune-mediated microvascular damage and iron overload did not appear to impair the host's immune response. In human lung transplant recipients, positive staining for iron in lung transplant tissue was more commonly seen in endobronchial biopsy sections from transplanted airways than in biopsies from the patients' own airways. Collectively, these data identify iron as a major determinant ofA. fumigatusinvasive growth and a potential target to treat or preventA. fumigatusinfections in lung transplant patients.
... In spite of the significant clinical and scientific interest in this field, lack of appropriate animal models has hindered progress in delineating the exact mechanisms involved in CMH development and in the development of treatments to address CMH. The currently used animal models of CMH are amyloid beta (Aβ)- [2][3][4], hypoxia-reoxygenation-, or hypertension-induced [5]. These existing animal models have several disadvantages: (1) CMH development in these models can take up to 15-24 months, (2) invasive surgical procedures are required to exacerbate CMH development, and most importantly, (3) clinically, CMH may develop independent of amyloid deposition, hypoxic brain injury, or hypertension [6]. ...
... Existing mouse models of CMH include mice that over-express mutant amyloid precursor protein to study cerebral amyloid angiopathy (CAA)-associated CMH [2], hypertensive mice [5] to study hypertension-associated CMH, and the hypoxia-reoxygenation-induced CMH mouse model to study high-altitude-associated CMH [33]. In the CAA mouse model, mice spontaneously develop PB-positive lesions by 15-24 months of age [2] and development of CMH can be exacerbated by passive immunization [3,34] or by inducing bilateral common carotid artery stenosis [4]. Two-photon-excited microscopy has been used to induce localized cortical CMH [35], and hyperhomocysteinemia (HHcy) has also been Fig. 4 Sub-acute Prussian blue-positive cerebral microhemorrhages: Significantly higher number of PB-positive stains in LPS (1 mg/kg, at 0, 6, and 24 h; n=9)compared with saline-treated (n=9) mice (comparisons shown in black) (a). ...
... In the existing rodent models [2,3,34,36] and clinically [6], PB staining for hemosiderin is commonly used to detect old CMH in post mortem brain tissues. Further, the current standardized method used to visualize cerebral microbleeds in humans is MRI, which relies on the paramagnetic properties of hemosiderin. ...
Background
Cerebral microhemorrhages (CMH) are tiny deposits of blood degradation products in the brain and are pathological substrates of cerebral microbleeds. The existing CMH animal models are β-amyloid-, hypoxic brain injury-, or hypertension-induced. Recent evidence shows that CMH develop independently of hypoxic brain injury, hypertension, or amyloid deposition and CMH are associated with normal aging, sepsis, and neurodegenerative conditions. One common factor among the above pathologies is inflammation, and recent clinical studies show a link between systemic inflammation and CMH. Hence, we hypothesize that inflammation induces CMH development and thus, lipopolysaccharide (LPS)-induced CMH may be an appropriate model to study cerebral microbleeds. Methods
Adult C57BL/6 mice were injected with LPS (3 or 1 mg/kg, i.p.) or saline at 0, 6, and 24 h. At 2 or 7 days after the first injection, brains were harvested. Hematoxylin and eosin (H&E) and Prussian blue (PB) were used to stain fresh (acute) hemorrhages and hemosiderin (sub-acute) hemorrhages, respectively. Brain tissue ICAM-1, IgG, Iba1, and GFAP immunohistochemistry were used to examine endothelium activation, blood-brain barrier (BBB) disruption, and neuroinflammation. MRI and fluorescence microscopy were used to further confirm CMH development in this model. ResultsLPS-treated mice developed H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. No surface and negligible H&E-positive CMH were observed in saline-treated mice (n = 12). LPS (3 mg/kg; n = 10) produced significantly higher number, size, and area of H&E-positive CMH at 2 days. LPS (1 mg/kg; n = 9) produced robust development of PB-positive CMH at 7 days, with significantly higher number and area compared with saline (n = 9)-treated mice. CMH showed the highest distribution in the cerebellum followed by the sub-cortex and cortex. LPS-induced CMH were predominantly adjacent to cerebral capillaries, and CMH load was associated with indices of brain endothelium activation, BBB disruption, and neuroinflammation. Fluorescence microscopy confirmed the extravasation of red blood cells into the brain parenchyma, and MRI demonstrated the presence of cerebral microbleeds. ConclusionsLPS produced rapid and robust development of H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. The ease of development of both H&E- and PB-positive CMH makes the LPS-induced mouse model suitable to study inflammation-induced CMH.
... APP23 mice develop relatively strong CAA (Calhoun et al., 1999;Kuo et al., 2001) that may be associated with microhemorrhages (Winkler et al., 2001). In some studies using APP transgenic mice passive immunization led to an increase in CAA and microhemorrhages (Pfeifer et al., 2002;Wilcock et al., 2004;Racke et al., 2005;Beckmann et al., 2011;Meyer-Luehmann et al., 2011;Luo et al., 2012). However, other investigations in APP mice showed no such effects (Asuni et al., 2006;Levites et al., 2006). ...
Currently, several immunotherapies and BACE inhibitor approaches are being tested in the clinic for the treatment of Alzheimer`s disease (AD). A crucial mechanism related safety concern is the exacerbation of microhemorrhages, which are already present in the majority of Alzheimer patients. To investigate potential safety liabilities of long-term BACE inhibitor therapy we used aged APP23 mice, which robustly develop cerebral amyloid angiopathy (CAA). T2*-weighted MRI, a translational method applicable in preclinical and clinical studies, was used for the detection of microhemorrhages throughout the entire brain, with subsequent histological validation. Three-dimensional reconstruction based on in vivo MRI and serial Perls` stained sections demonstrated a one-to-one matching of the lesions thus allowing for their histopathological characterization. MRI detected small Perls` positive areas with a high spatial resolution. Our data demonstrate that volumetric assessment by non-invasive MRI is well suited to monitor cerebral microhemorrhages in vivo. Furthermore, three months treatment of aged APP23 with the potent BACE inhibitor NB-360 did not exacerbate microhemorrhages in contrast to Aβ antibody β1. These results substantiate the safe use of BACE inhibitors regarding microhemorrhages in long-term clinical studies for the treatment of AD.
... Furthermore, it is becoming increasingly apparent that more than one drug will be needed to effectively treat AD. Immunization-based therapies to reduce Aß have shown detrimental vascular effects [311,312]. An important implication of the elucidation of mTOR-dependent pathways of vascular damage in AD is that this knowledge may lead to using mTOR inhibitors with drugs to reduce Aß while preserving cerebrovascular integrity and function. ...
Aging is the strongest known risk factor for Alzheimer's disease (AD). With the discovery of the mechanistic target of rapamycin (mTOR) as a critical pathway controlling the rate of aging in mice, molecules at the interface between the regulation of aging and the mechanisms of specific age-associated diseases can be identified. We will review emerging evidence that mTOR-dependent brain vascular dysfunction, a universal feature of aging, may be one of the mechanisms linking the regulation of the rate of aging to the pathogenesis of Alzheimer's disease. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.
... This demonstrates that young splenocytes enhance Aβ clearance in the brain of old AD mice. However, transplanting oSCs increased cerebral Aβ burden, indicating that splenocyte senescence impacts Aβ pathology in AD progression [32]. This result shows that immunosenescence is not only limited to the effect on Aβ clearance, but is also involved in Aβ pathology. ...
Immunosenescence contributes to pathogenesis of Alzheimer's disease (AD) in the elderly. In this study, we explored the effects of young wild type (WT) splenocytes (ySCs) on Alzheimer's disease by transplanting ySCs into APPswe/PSENldE9 transgenic mice. Young WT splenocytes not only prevented AD, but also improved the spatial learning and memory of APPswe/PSENldE9 transgenic mice. Young WT splenocytes enhanced Aβ clearance, decreased astrogliosis and increased systemic growth differentiation factor 11 (GDF11) levels. Splenocytes derived from old AD mouse promoted AD. There was an increased number of regulatory T cells (Tregs) among old AD splenocytes. We suggest that alterations of GDF11 and Tregs are involved in AD progression and that rejuvenation of the immune system is a potential therapeutic strategy in AD.
... Thus, each carries a risk of inducing pathogenic autoimmunity, similar to that which occurred in the AN1792 vaccine clinical trials in AD (Tabira, 2010). This trial, designed to evaluate active immunization with full-length amyloid (Aβ) peptide (a selfantigen) in adjuvant, caused meningoencephalitis in a subset of patients that was subsequently attributed to development of a pathogenic Aβ-specific T-cell response (Delrieu et al., 2012;Meyer-Luehmann et al., 2011). The risk for development of similar pathological responses in SCI patients certainly exists with any of the vaccination approaches described in the preceding sections as each of these have the potential to activate CNS-reactive T-cells. ...
... Some of the reasons for the adverse events are now clear. The initial active immunization with full-length Aβ peptide in adjuvant activated Aβ-reactive Th1 cells that caused autoimmune encephalitis (Delrieu et al., 2012;Meyer-Luehmann et al., 2011). The Aβ-specific T-cell response most likely arose because the Aβ peptide contained T-cell epitopes and/or because of adjuvant effects (Lobello et al., 2012;Morgan, 2011). ...
... This approach is attractive because most individuals would be expected to have pre-existing memory T-cells for tetanus toxin as a result of the public health vaccination program (Davtyan et al., 2013). Because the T-cell responses generated in these newer vaccine approaches are against non-self antigens, they are less likely to induce the pathogenic autoreactive T-cell responses that caused the abrupt termination of previous immunotherapy AD trials (Delrieu et al., 2012;Meyer-Luehmann et al., 2011). These novel vaccination strategies, should they prove successful, could provide new opportunities for development of similar immunotherapies in SCI. ...
... In a previous model of cerebral microbleeds using aged Tg2576 mice, diseased blood vessels could be successfully visualized with Prussian blue staining (Vasilevko et al. 2010;Fisher et al. 2011). In another mouse model of cerebral microbleeds, both H&E and Prussian blue showed comparable results 3 to 4 days post intracranial injection of β-amyloid (Aβ) antibody in APPswe/PS1d9 mice (Meyer-Luehmann et al. 2011). In the present study, based on a previously published model of blood brain-barrier (BBB) permeability alteration (Xaio et al. 2001;Veszelka et al. 2003), we used an even shorter time window (2 days) for cerebral microbleed induction and compared the results obtained with H&E and Prussian blue stains. ...
... Because vessel leakiness increases over time in these mice (it may take two years for the transgenic animals to fully show microbleeds), the use of Prussian blue was justified (Vasilevko et al. 2010). In another study, 3 to 4 days were sufficient for the use of Prussian blue, as evident from the comparable H&E-and Prussian blue-stained microbleed frequency profiles (Meyer-Luehmann et al. 2011). In the same study, H&E-and Prussian blue-positive staining was observed even in control animals. ...
... This could be due to cardiac perfusion performed in the present, but not in the previous, study. On the other hand, Prussian blue staining was positive in the controls in the present study, which is generally consistent with previous findings (Meyer-Luehmann et al. 2011). As Prussian blue stains for iron deposits that may come from sources other than bleeding, the localized Prussian blue-positive foci within the control group may not be microbleeds. ...
Cerebral microbleeds are microscopic hemorrhages with deposits of blood products in the brain, which can be visualized with MRI and are implicated in cerebrovascular diseases. Hematoxylin and eosin (H&E) and Perl's Prussian blue are popular staining methods used to localize cerebral microbleeds in pathology. This paper compared these two staining techniques in a mouse model of cerebral microbleeds. We used lipopolysaccharide (LPS) to induce cerebral microhemorrhages. C57B6 mice were treated with LPS (5 mg/kg, i.p.) or vehicle at baseline and at 24 hr. The brains were extracted 48 hr after the first injection and adjacent coronal sections were stained with H&E and Prussian blue to compare the effectiveness of the two staining techniques. H&E-positive stains were increased with LPS treatment and were correlated with grossly visible microhemorrhages on the brain surface; Prussian blue-positive stains, by comparison, showed no significant increase with LPS treatment and did not correlate with either H&E-positive stains or surface microhemorrhages. H&E staining is thus a more reliable indicator of acute bleeding events induced by LPS in this model within a short time span.
... This may strongly deplete extrasynaptic ACh levels and disturb the proper functional status of cholinoceptives microglia and/or astrocytes, endothelial, and smooth muscle cells comprising the main component of micro-blood vessels in the brain [75,76]. This may lead to micro-hemorrhages in the brain, a phenomenon that has happened in some of the immunization trials in AD patients [77]. ...
Despite three decades of intensive research in the field of Alzheimer's disease (AD) and numerous clinical trials of new therapeutic agents, cholinesterase inhibitors (ChEIs) are still the mainstay of therapeutics for AD and dementia with Lewy bodies. Pharmacodynamic analyses of ChEIs provide paradoxical observations. Treatment with the rapidly reversible, noncarbamylating ChEIs (donepezil, galantamine, and tacrine) increases acetylcholinesterase (AChE) protein expression, whereas the carbamylating agent, rivastigmine, produces sustained inhibition with no significant change in AChE protein expression. Still, the symptomatic clinical efficacies of all these agents are similar. We report here for the first time that treatment with phenserine, another carbamylating ChEI, produces a sustained but mild inhibition of AChE in cerebrospinal fluid (CSF) of AD patients. We also show that phenserine treatment reverses donepezil-induced elevation of AChE expression. Further analyses on CSF of another larger patient cohort treated with donepezil revealed that, in addition to its main mode of action, donepezil produced two other pharmacodynamics with potentially contradictory outcomes. Donepezil-induced AChE expression favored an AChE-driven amyloid-β peptide (Aβ) aggregation, whereas donepezil itself concentration-dependently counteracted the AChE-induced Aβ aggregation, most likely by competing with the Aβ peptides for peripheral anionic site on the AChE protein. The reduction of AChE protein expression in the donepezil-treated patients by concomitant administration of the carbamylating agent, phenserine, could allow the donepezil molecule to only prevent interaction between Aβ and AChE. The current study suggests that an add-on therapy with a low-dose formulation of a carbamylating agent in patients on long-term donepezil treatment should be explored as a strategy for enhancing the clinical efficacy of these agents in dementia disorders.
