Preventive effects of (-)-epicatechin on retina and pigmented epithelium impaired by sodium iodate (NaIO₃)

Abstract

Purpose : Oxidative stress (OS)-induced damage, and prolonged inflammatory responses are prominent pathophysiological mechanisms underlying geographic atrophy (GA) development. (-)-Epicatechin (epi) is an antioxidant flavonoid that appears to ameliorate OS by improving mitochondrial parameters and decreasing inflammatory cytokines. Here, we evaluated the effectiveness of epi in a NaIO₃-induced retinal degeneration model, as a potential prophylactic strategy for GA.

Methods : Equal number of wild-type (WT) C57BL/6J mice (n = 30) were randomly assigned to an intervention, sham-treated or control group. The intervention and control group received 1 mg/kg/day of epi q24h PO diluted in a vehicle (H₂O, pH 5-6). Shams-treated received only the vehicle. After 15 days of treatment, intervention and sham-treated mice were injected with 30 mg/kg of NaIO₃ diluted in PBS on the right retro-orbital venous sinus and were followed by an additional 5 days. Controls were PBS-injected. We planned to perform indirect immunofluorescence (IF) for OS markers (PPRAγ, pATK) on flat-mount retinas and retinal pigment epithelium (RPE)-choroids. Also, western-blot for SOD2 and Gpx1, and qPCR of key inflammatory genes in vitro (IL-1β, CCL2, VEGF, TNF-α). RPE-choroids were stained with phalloidin (red). RPE degeneration ratio was obtained by fluorescence slide scanning and analysis.

Results : RPE degeneration ratio was significantly decreased in epi-fed mice compared to sham (p = 0.0018). Gene expression analysis in vitro, showed a rapid up-regulation of inflammatory cytokines in NaIO₃ exposed retinas [e.g. IL-1β Epi(-)/NaIO₃(+) 1.132, Epi(+)/NaIO₃(+) 0.8223 fold-induction, p = 0.0571]. This effect was ameliorated by epi-treatment. Additionally, epi-fed mice and exposed to NaIO₃ had lower SOD2 protein expression than the sham-treated group [Epi (-)/NaIO₃ (+)].

Conclusions : Taken altogether, our preliminary results might be suggestive of an early prophylactic benefit with dietary supplementation of (-)-epicatechin in mice. This might be impactful for GA patients. Further corroboration in other animal models is warranted.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Flat-mount RPE-choroid indirect immunofluorescence Phalloidin (red). A. Control group. B. Sham-treated group. C. Intervention group.