1438-P: HSPB4 as a Modulator of Retinal Gliosis and Inflammation for Neuroprotection in Diabetic Retinopathy

Introduction and Objective: Chronic retinal inflammation is a central pathological obstacle in diabetic retinopathy, and finding a method of regulating this innate response may be a promising therapeutic avenue for preventing the gradual degeneration of neurons and associated loss of eyesight. One of the main cell types responsible for controlling the inflammatory response in the retina are microglia, which become activated (characterized morphologically) and can have varying expression profiles ranging from pro- to anti-inflammatory. We hypothesize that HSPB4 can attenuate microglia activation to modulate inflammation in the retina. Methods: BV2 microglia were exposed to either LPS [10ng/ml] or a diabetes-like stressor (high glucose [25mM] + TNFα [100ng/mL]) and co-treated with recombinant HSPB4 [500ng/mL] for 24h. The extent of activation was assessed by morphological analyses of the average length of projections and the ramification index. Both LPS and HG+TNFα insults were also applied to primary murine microglia for up to 48h and activation was evaluated similarly. To assess therapeutic potential, BV2s received HG+ TNFα and after 2 and 4h were post-treated with HSPB4. Finally, primary microglia had RNA isolated after 4 and 24h of treatments, and expression of pro- and anti-inflammatory markers were analyzed through qPCR. Results: HSPB4 showed significant reduction of activation in both the BV2 and the primary microglia when treated with LPS or HG+TNFα. Excitingly, this reduction remained present when BV2s were post-treated with HSPB4 after 2 and 4h of HG+TNFα exposure. At the RNA level, the expression of pro-inflammatory markers were not altered by HSPB4 at 4h, but demonstrated a trend of faster resolution by 24h. Conclusion: Altogether, these findings are indicative of HSPB4’s potential in regulating the activation of microglia and downstream inflammatory response. Next steps include further clarification on the duration of HSPB4’s effects, how anti-inflammatory markers are impacted, and whether these are translated from in vitro to in vivo. Disclosure G. Johnson: None. P.E. Fort: Research Support; Current; Boehringer Ingelheim International GmbH. Research Support; Ended; Genentech, Inc. Funding Vision Research Training Program (5T32-EY013934-22), National Institutes of Health (R01-EY020895)