Browsing by Subject "C1q"
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
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 CORRELATIVE INCREASES IN ASTROCYTE, MICROGLIA, AND C1Q IN A MURINE MODEL OF ACUTE GLAUCOMATOUS INJURY(2014-03) Olarte, Neal; Silverman, Sean; Wordinger, Robert J.; Clark, Abbot F.Glaucoma is an injury to cells of the eye indicated by pressure within the eye which can lead to eventual blindness. Microglial cells are a special type of cell within the central nervous system (CNS) that cleans up cellular damage. Astrocytes are another specialized cell which plays a supportive role important for CNS function. C1q is a part of the immune system usually reserved for clearance of bacteria from the body, but has been recently demonstrated to serve other roles. Microglia and C1q have been implicated in mediating retinal damage in mouse models mimicking glaucoma. This study was conducted to investigate if C1q and either microglia or astrocytes, or both, could be involved in brain damage caused by a simulated glaucoma injury. Purpose (a): Glaucoma is a leading cause of blindness worldwide. Recent studies of glaucomatous retinal injury have observed a correlation of upregulated C1q and increased microglial activity. Using the optic nerve crush (ONC) model of glaucoma, we are investigating whether there is an injurious response involving C1q, microglia, and astrocytes within the superior colliculus (SC), the visual center of the mouse brain. Methods (b): Glaucomatous injury was simulated in mice using ONC of the left eye, while leaving the right eye intact. Brain tissue was harvested at 0, 7, 14, and 28 days post-injury, fixed overnight in 4% paraformaldehyde, and paraffin embedded. Following paraffin removal and antigen recovery, immunohistochemistry was performed to label astrocytes (GFAP), microglia (IBA1), and C1q in the SC. Results (c): Beginning 7 days post-injury, there was an increase in astrocytes, microglia, and C1q, with microglia assuming an activated morphology. Astrocytes and C1q remained elevated through 28 days post-injury, with a gradual reduction in microglial density. These results were observed only within the SC contralateral to the injured nerve, the main target of the retinal ganglion cell (RGC) axons from the ONC eye. Increased C1q and astrocyte activity was not observed in the ipsilateral hemisphere; however, there was a slight increase in microglial density. Conclusions (d): Our data support a similar response in the retina and SC of upregulated C1q, resulting from glaucomatous injury. Microglia and astrocytes also appear to be involved in the acute injury phase. Previous studies of retinal glaucomatous injury have shown that early reduction of C1q is protective. Future studies using a C1q-deficient mouse model might also show protective function against SC glaucomatous injury.Item Pathological Mechanisms of Retinal Ischemia/Reperfusion Injury and Potential Targets of Neuroprotection(2015-12-01) Silverman, Sean M.; Clark, Abbot F.; Pang, Iok-Hou; Krishnamoorthy, Raghu R.Neurodegenerative diseases trigger a cascade of pathological mediators including significant accumulation of reactive oxygen species (ROS) and chronic neuroinflammation resulting in widespread neuronal loss. We can effectively mimic these changes in a mouse model of retinal ischemia/reperfusion (I/R) injury. Herein we demonstrate retinal I/R leads to chronic upregulation of C1q expression accompanied by similar long-term activation of microglia and astrocytes, as well as a significant increase in retinal ROS. These changes resulted in morphological and functional degeneration. In addition, we identified the neuroprotective potential of modulating changes in C1q and superoxide by genetic and pharmacological methods. In the retina I/R injury resulted in significant increases in C1q expression, glial activation and cell density by day 3 compared to controls. These changes continued to increase and were sustained through our entire 28 day time course. Similar effects from injury were observed in the superior colliculus (SC), one of the primary visual centers in the brain of rodents. Surprisingly, hemispheres corresponding to both injured and noninjured eyes displayed signs of chronic neuroinflammation by day 21. Using the chemilluminescent compound L-012 we demonstrated a novel method for non-invasive in vivo detection of superoxide in the eye as early as 24 hours post injury. These findings were confirmed with dihydroethidium (DHE) in the retina. Our previous work has characterized inner retinal thinning, loss of retinal ganglion cells (RGCs), and suppression of b-wave amplitudes due to I/R injury. Using C1qa-deficient mice, we show complete morphological protection and ablation of reactive microgliosis. However, astrocytes were unaffected by deletion of C1q, and retinal function was only partially preserved. Two superoxide inhibitors, Apocynin and Tempol, significantly reduced L-012 chemilluminescence 24 and 48 hours after injury. Further, Apocynin treatment completely protected against morphological degeneration in the retina and significantly rescued functional deficits. In conclusion, this study demonstrates the therapeutic potential of modulating either C1q or superoxide for neuroprotection following injury or diseases where they are implicated in pathological loss.