Hybrid Compound SA-2 is Neuroprotective in Animal Models of Retinal Ganglion Cell Death

Abstract

PURPOSE. Determine the toxicity, bioavailability in the retina, and neuroprotective effects of a hybrid antioxidant-nitric oxide donor compound SA-2 against oxidative stress-induced retinal ganglion cell (RGC) death in neurodegenerative animal models. METHODS. Optic nerve crush (ONC) and ischemia reperfusion (I/R) injury models were used in 12-week-old C57BL/6J mice to mimic conditions of glaucomatous neurodegeneration. Mice were treated intravitreally with either vehicle or SA-2. Retinal thickness was measured by spectral-domain optical coherence tomography (SD-OCT). The electroretinogram and pattern ERG (PERG) were used to assess retinal function. RGC survival was determined by counting RBPMS-positive RGCs and immunohistochemical analysis of superoxide dismutase 1 (SOD1) levels was carried out in the retina sections. Concentrations of SA-2 in the retina and choroid were determined using HPLC and MS. In addition, the direct effect of SA-2 treatment on RGC survival was assessed in ex vivo rat retinal explants under hypoxic (0.5% O 2) conditions. RESULTS. Compound SA-2 did not induce any appreciable change in retinal thickness, or in a-or b-wave amplitude in naive animals. SA-2 was found to be bioavailable in both the retina and choroid after a single intravitreal injection (2% wt/vol). An increase in SOD1 levels in the retina of mice subjected to ONC and SA-2 treatment, suggests an enhancement in antioxidant activity. SA-2 provided significant (P < 0.05) RGC protection in all three of the tested RGC injury models in rodents. PERG amplitudes were significantly higher in both I/R and ONC mouse eyes following SA-2 treatment (P 0.001) in comparison with the vehicle and control groups. CONCLUSIONS. Compound SA-2 was effective in preventing RGC death and loss of function in three different rodent models of acute RGC injury: ONC, I/R, and hypoxia.

Biological Correlations and Confounding Variables for Quantification of Retinal Ganglion Cells Based on Optical Coherence Tomography using Diversity Outbred Mice

“…The results found confirmatory evidence that GCC thickness correlates positively to RGC abundance. While several studies analyzed mouse retinas with both OCT and RGC-specific immunostaining [41][42][43][44] , relatively few have tested the correlations between these measurements 5,45 .…”

The Susceptibility of Retinal Ganglion Cells to Optic Nerve Injury is Type Specific

“…ONC is a commonly used model for RGC injury due to TON or glaucoma. Although most of the experiments were performed using similar cross-action forceps, which apply a constant and consistent force to press on the optic nerve by the pressure from the self-clamping action of the forceps, different studies clamped the optic nerve for a different length of time (from 3 s to 60 s) [52][53][54][55][56][57][58]. To determine the potential variation by the ONC procedure on RGC death, we first tested whether various durations of clamping cause RGCs to die to a different extent.…”

Brimonidine is Neuroprotective in Animal Paradigm of Retinal Ganglion Cell Damage

“…Retinal ischemia/reperfusion has been used as a model of retinal injury and has been described in many rodent species ( Osborne et al, 2004 ; Gustavsson et al, 2008 ; Ulbrich et al, 2017 ; Stankowska et al, 2019 ). A validated modified I/R model ( Hartsock et al, 2016 ) ( Hartsock et al, 2016 ) was used in the present study.…”