Inflammasome facilitates ganglion cell dysfunction and loss in ocular hypertension glaucoma

Abstract

Purpose : To determine molecular pathways facilitating retinal ganglion cell (RGC) dysfunction and death in response to ocular hypertension (OHT)-induced stress. In this study, we sought to establish the contribution of the inflammasome to RGC pathology in a mouse model of OHT-induced glaucoma.

Methods : Glaucomatous degeneration was induced by intracameral injection of the Ad5-MYOC vector that produced a chronic IOP elevation. Inflammasome activation was detected by IL-1β production, changes in casp1, pycard (ASC), nlrp1, and gsdmD gene expression, and protein accumulation using RT-PCR, Western blot, and immunohistochemistry. Wild type and knockout mouse strains were used to determine the role of the inflammasome in ocular hypertension glaucoma. IL-1β cytokine production was assessed by sandwich ELISA in the vitreous fluid; gene expression changes in the retina, by RT-PCR. Changes in RGC functionality were assessed by PERG recordings; RGC loss was assessed at 8 wks post-OHT induction by direct counts in retinal flat mounts.

Results : Activation of the inflammasome became evident in the inner retinal layer and co-localized with RPBMS⁺ RGCs in C57Bl6 (WT) mice at 2-4 wks after glaucoma induction. This correlated in time with RGC dysfunction, where PERG amplitude was reduced 55.8% in WT eyes with chronic OHT glaucoma. RGC density analysis in these animals showed a loss of 32.3±9.2 % in the central and 28.4±9.2 % in the peripheral retina at 6 wks post-OHT-induction. In contrast, mice are deficient in key inflammasome complex proteins NLRP1, Casp1 and GsdmD did not produce statistically significant changes in PERG amplitude. RGC loss was also blocked, averaging 0.7±11.2% increase in the central and no change in the peripheral retina of NLRP1^-/- eyes; 7.3± 9.2% decrease in the central and 1.3 ±19.5 % increase in the peripheral retina of Casp1^-/- eyes. Immunohistochemistry data in retinal cross-sections showed the absence of Casp1 and a reduction in GsdmD immunolabeling labeling in RGCs in the knockout retinas with induced glaucoma.

Conclusions : Our results show a strong correlation between the elevation of IOP, induction of inflammasome, and RGC pathology in the retina. Our results in mice deficient for inflammasome pathway components revealed the key role of the inflammasome in driving RGC dysfunction and cell death. Drugs inhibitors of inflammasome could protect vision loss in human ocular hypertension glaucoma

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.