Browsing by Subject "Microglia"
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Item Blood Inflammatory Exosomes with Age Prime Microglia through Complement Signaling for Negative Stroke Outcomes(2020-05) Zhang, Hongxia; Jin, Kunlin; Forster, Michael J.; Yang, Shaohua; Shi, Xiangrong; Cunningham, J. ThomasThe systemic inflammatory milieu plays an important role in the age-related decline of functional integrity, but its contribution to age-related disease (e.g., stroke) remains largely unknown. Here, we found that activated complement molecules (C1q, C3a, C3b) in serum exosomes increased with age, whereas CD46, a C3b/C4b-inactivating factor, was higher in serum exosomes from young rats. These serum inflammatory exosomes passed the blood-brain barrier and primed the microglial response that led to exacerbation of synaptic loss and motor deficits after ischemic stroke via microglial C3a receptor (C3aR). When aged rats were exposed to serum exosomes from young rats, microglia-mediated synaptic loss was reduced and motor deficits after stroke were improved. Administration of C3aR inhibitor or microglial depletion attenuated synaptic loss associated with the treatment of serum exosome from aged rats, in parallel with improved post-stroke outcome. Our data suggest that peripheral circulating old exosomes act as inflammatory mediators and influence ischemic stroke outcome through a complement-microglia axis.Item C1q propagates microglial activation and neurodegeneration in the visual axis following retinal ischemia/reperfusion injury(BioMed Central Ltd., 2016-03-24) Silverman, Sean M.; Kim, Byung-Jin; Howell, Garreth R.; Miller, Joselyn; John, Simon W. M.; Wordinger, Robert J.; Clark, Abbot F.BACKGROUND: C1q represents the initiating protein of the classical complement cascade, however recent findings indicate pathway independent roles such as developmental pruning of retinal ganglion cell (RGC) axons. Furthermore, chronic neuroinflammation, including increased expression of C1q and activation of microglia and astrocytes, appears to be a common finding among many neurodegenerative disease models. Here we compare the effects of a retinal ischemia/reperfusion (I/R) injury on glial activation and neurodegeneration in wild type (WT) and C1qa-deficient mice in the retina and superior colliculus (SC). Retinal I/R was induced in mice through elevation of intraocular pressure to 120 mmHg for 60 min followed by reperfusion. Glial cell activation and population changes were assessed using immunofluorescence. Neuroprotection was determined using histological measurements of retinal layer thickness, RGC counts, and visual function by flash electroretinography (ERG). RESULTS: Retinal I/R injury significantly upregulated C1q expression in the retina as early as 72 h and within 7 days in the superficial SC, and was sustained as long as 28 days. Accompanying increased C1q expression was activation of microglia and astrocytes as well as a significantly increased glial population density observed in the retina and SC. Microglial activation and changes in density were completely ablated in C1qa-deficient mice, interestingly however there was no effect on astrocytes. Furthermore, loss of C1qa significantly rescued I/R-induced loss of RGCs and protected against retinal layer thinning in comparison to WT mice. ERG assessment revealed early preservation of b-wave amplitude deficits from retinal I/R injury due to C1qa-deficiency that was lost by day 28. CONCLUSIONS: Our results for the first time demonstrate the spatiotemporal changes in the neuroinflammatory response following retinal I/R injury at both local and distal sites of injury. In addition, we have shown a role for C1q as a primary mediator of microglial activation and pathological damage. This suggests developmental mechanisms of C1q may be re-engaged during injury response, modulation of which may be beneficial for neuroprotection.Item COMPLEMENT AND GLIAL ACTIVITY IN THE RETINOCOLLICULAR PATHWAY OF MICE USING A NOVEL MODEL OF GLAUCOMA(2013-04-12) Silverman, SeanPurpose: Glaucoma is a leading cause of irreversible visual impairment and blindness throughout the world. C1q is responsible for axonal pruning in early ocular development and is upregulated in glaucomatous eyes of mice, non-human primates, and humans. We used an inducible mouse model of human primary open angle glaucoma with elevated intraocular pressure (IOP) to examine expression levels of C1q in the retina and superior colliculus (SC), as well as identify changes in cellular homeostasis. Methods: Anesthetized A/J mice were given a single intravitreal injection of Ad5.MYOC.Y437H (5x107 pfu), a mutant glaucoma gene, or Ad5.null control virus. Following injections, conscious IOPs were measured weekly, using a TonoLab tonometer (iCare). Mice were sacrificed at time points between 3 days and 8 weeks. Brains and retinas were harvested for immunofluorescence or immunoblotting studies. Microglia and astrocytes cells were identified using Iba1 and GFAP, respectively. All quantifications were performed using ImageJ Analysis software(NIH). Results: IOPs were significantly increased in the Ad5.MYOC.Y437H eyes (p<0.01) compared to the contralateral un-injected eye and eyes receiving Ad5.null. Clq expression was significantly upregulated in retinas receiving Ad5.MYOC.Y437H (2.69-fold±0.38, p<0.0001) compared to contralateral control retinas (0.7-fold±0.29). Clq upregulation was additionally observed in SC hemispheres receiving neural connections from injected eyes. Mice given Ad5.null vector displayed no elevation of Clq in the visual axis. Additionally, colocalization studies demonstrated significant increases of inner retinal microglia density beginning 2 weeks post injection (0.61%±0.07, p<0.001) and continuing at 4 weeks (0.87%±0.09, p<0.0001) compared to untreated retinas (0.4l%±0.03 and 0.44%±0.03, respectively). No signs of astrogliosis were detected. Conclusions: C1q is actively upregulated in the retina and SC, following mutant myocilin induced ocular hypertention, whereas adenovirus alone had no effect. An increased microglial population in the retina accompanied these changes. This suggests that microglia may sense the increased IOP and play a role in upregulating endogenous C1q. Early glaucoma pathogenesis may result from the reactivation of the ocular developmental roles of C1q and microglia, suggesting new therapeutic targets for future neuroprotective studies.