Neuroprotective Effect of Risuteganib on Retinal Neurons in an Excitotoxic Injury Cell Culture Model and a Mechanical Injury Rat Model

Abstract

Purpose : Retinal neuron dysfunction and cell death have been observed across many visual impairment diseases (including age-related macular degeneration, retinitis pigmentosa, glaucoma, and diabetic retinopathy) and treatment options are limited. This study aimed to determine the neuroprotective effect of the investigational drug, risuteganib (RSG), in cultured retinal neuron (RN) cells exposed to excitotoxic damage and retinal degeneration in an experimental optical nerve clamp rat model.

Methods : In RN cells, excitotoxic damage was induced by kainic aid (KA). Primary mouse neuronal cells (n=8) were exposed for 24 h to culture medium only (SSB), 50 µM KA, or KA + 1mg/mL RSG added either 24 h before or after KA treatment. After treatment, the number and viability of cultured cells were measured using WST-8 and LDH assays. The student’s t-test was used for statistical analysis. In an optical nerve clamp study, a total of eight rats were evaluated to assess the protection of ganglion cells. Animals were intravitreally injected 1.28 mg RSG (n=5) or SSB (n=3) 24 h before 60-minute optic nerves crush (ONC), followed by 48 h rest and ganglion cell survival assessment. Wilcoxon Matched-pairs signed ranks test was used for statistical analysis.

Results : Exposure to KA decreased the viability of cultured cells by 40 ± 1.0 % (P<0.05). The cells treated with RSG either before or after KA showed significantly less damage (10 ± 1.5 or 18 ± 1.0 % viability reduction, respectively; p<0.05. LDH assay showed none of the experimental conditions had a detectable alteration in membrane cell structure. Eyes from rats subjected to ONC and injected with vehicle had 10.09 ± 8.622 ganglion cells per field, while those treated with RSG demonstrated 19.46 ± 8.406 ganglion cells per field (p=0.0001).

Conclusions : Our findings showed RSG induced a clear reduction in the cytotoxic effect generated by an excitotoxic condition in cultured retinal neurons. This effect is more prominent when RSG was applied previously to excitotoxicity generated by KA. Additionally, a statistically significant ganglion cell protective effect was observed in the ONC rat model. Altogether, these findings suggest RSG may have neuroprotective properties relevant to human retinal diseases. Nonetheless, additional studies are needed to further clarify this mechanism of action.

This is a 2021 ARVO Annual Meeting abstract.