Abstract
Purpose :
We have previously observed that inactivating Nogo-A, a reticulon protein enriched in Müller glia and in oligodendrocytes, enhanced vascular repair, optic nerve axon regeneration and visual recovery after retinal injury. The mechanisms underlying the effect of Nogo-A in the development of visual defects are not clear. The aim of this study was thus to determine if Nogo-A modulates injury-induced neuroinflammation in the adult mouse retina.
Methods :
Excitotoxic injury was induced by intravitreally injecting different concentrations of NMDA (0.5-40 nmol) in adult mouse eyes. Nogo-A level was followed in the vitreous and in the retina of injected animals by Western blotting. Two days after NMDA injection, Nogo-A-blocking antibody (11C7) or a control antibody (IgG) were injected. Quantitative real-time PCR was performed 1 and 7 days after antibody injection to determine gene expression changes for Nogo-A and its receptors, and inflammation and gliosis markers. Microglia was visualized on retinal flatmounts by immunofluorescence. Western blotting and immunofluorescent analyses were also realized on samples from diabetic patients.
Results :
Full-length and fragmented Nogo-A proteins were upregulated in the mouse vitreous after NMDA-induced injury. This change was correlated with TNFα trimer release. In injured animals, intravitreal injection of 11C7 significantly improved visual function recovery compared with control IgG delivery. The expression of pro-inflammatory molecules, such as TNFα, was strongly downregulated by 11C7. Immunofluorescent stainings suggested that microglia/macrophages were the main source of TNFα in the damaged retina. TNFα immunofluorescence was markedly reduced in response to 11C7 injection. Further Western blot and histological results suggested that TNFα downregulation may result from cofilin inactivation in microglia/macrophages. In addition, the decrease in Vimentin and Gfap mRNAs in 11C7-treated retinal lysates indicated that 11C7 mitigated gliosis, possibly by downregulating P.Stat3. Increased levels of Nogo-A in the vitreous and in the retina were observed in diabetic donors.
Conclusions :
The administration of function-blocking antibody directed against Nogo-A promotes visual recovery after retinal injury. At the same time, the inhibition of neuroinflammation suggests a new function for Nogo-A that could be used to design ophthalmic treatments.
This is a 2021 ARVO Annual Meeting abstract.