Aldose reductase inhibition promotes retinal ganglion cell survival after optic nerve injury

Abstract

Purpose : Optic nerve trauma induces retinal microglia (RMG) activation and causes irreversible retinal ganglion cells (RGC) loss in mammals. Since aldose reductase (AR) is an inflammatory response mediator and is highly expressed in RMG, we investigated the effects of AR inhibition on RMG activation, RGC survival, and axon regeneration in an optic nerve crush (ONC) model.

Methods : BV2 microglia were utilized to study the effects of AR inhibition on cytokine secretion, cell migration, and microglia-retinal organoid co-culture with LPS exposure. Adult animals underwent ONC (OS) or sham (OD) and were treated with AR inhibitor- Sorbinil or DMSO by intraperitoneal injection. Total protein of ONs and retinae was collected for Western blot probing with Iba-1, AR, GFAP, and GAPDH. Cryosections of ONs and retinae were stained with Iba1, Cleaved Caspase 3, GFAP, and DAPI. RGC survival and regenerating axons were observed 1 and 2 weeks post-ONC (pONC). Flatmount retinae were stained with RBPMS for RGC counting. Regenerative axons were visualized by CTB-555. RGC function was detected by pattern ERG. The study was conducted in compliance with ARVO Statement for the Use of Animals in Ophthalmic and Vision Research and approved by IACUC at University of Pittsburgh. All experiments were performed in independent triplicate and considered significant if P < 0.05.

Results : In-vitro, results show that Sorbinil attenuates LPS-induced BV2 activation, migration, and retinal organoid apoptosis in the BV2-organoid co-culture. In-vivo, we observed that Iba-1 and AR protein expression was elevated by ONC and attenuated by Sorbinil in the retina and ON. However, GFAP protein expression was only altered in the retina and reduced by Sorbinil. Detected by cryosection staining, Iba-1+ cells and GFAP+ cells were elevated by ONC and attenuated by Sorbinil. In addition, Sorbinil reduced apoptotic marker expression in the ONC retina. Although experiments of 2 weeks pONC display no change, we did observe that Sorbinil promoted RGC survival, restored RGC function and displayed a trend towards delaying axon degeneration 1 week pONC.

Conclusions : This is the first study to explore the effects of AR inhibition on RMG and RGC in the ONC model. AR inhibition promotes RGC survival, restores RGC function and delays axon degeneration by attenuating RMG activation, which provides a potential therapeutic strategy against ocular inflammatory diseases.

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