Retinal neurodegeneration and neovascularization are suppressed by HIF inhibitor topotecan in murine models of retinopathy

Abstract

Purpose : Retinal diseases caused with neurodegeneration and pathological angiogenesis are the major vision threatening disorders in developed countries. Hypoxia-inducible factors (HIFs) are transcriptional factors which regulate angiogenesis, intracellular metabolism, and programed cell death mainly depending on oxygen availability. We hypothesized that ectopic activation of HIFs may contribute to the pathogenesis of the diseases through an abnormal stress response, and reported that a topotecan has a preventive effect against a murine light-induced retinopathy (LIR) model at ARVO 2016. Here we show that topotecan is protective against not only neurodegeneration but also pathological angiogenesis through a common molecular mechanism.

Methods : To investigate therapeutic mechanisms of topotecan against LIR, murine cone photoreceptor cell line 661W cells were treated with vehicle or topotecan, and exposed to a bright light (380 nm, 50W/m², 30 min) with a HIF-luc reporter gene transfection to monitor HIF activation. As a LIR model, 8-week-old BALB/C mice were exposed to 3,000lux white light for one hour and the mRNA expression of hif-1a and HIF target genes in sensory retina were evaluated by qPCR. To evaluate a therapeutic effect of topotecan on pathological angiogenesis, 661W was incubated under 1% oxygen and the mRNA expression of hif-1a and HIF target genes were evaluated by qPCR. Mice in oxygen-induced retinopathy (OIR) model were injected vehicle or topotecan from P12-16 (1.25 mg/kg/day). Retinal neovascular tufts were evaluated on wholemount staining with isolectin-B4. P-value less than 0.05 was considered as statistical significance with Student’s t-test.

Results : A significant HIF activation was observed in 661W cell exposed to a bright light (1.5-fold, p < 0.001), and topotecan suppressed the light-induced HIF activation by 47.9% (p < 0.001). Hif-1a (1.9-fold, p < 0.001) and bnip3 (1.3-fold, p < 0.05) were significantly increased in the retina of LIR. Vegf was significantly increased (3.5-fold, p <0.001) in 661W cells incubated under 1% oxygen, and topotecan significantly suppressed vegf by 28.9% (p < 0.05). In the OIR model, topotecan significantly suppressed neovascular tufts by 26.9% (p < 0.05).

Conclusions : Topotecan has preventive effects against both neurodegeneration and pathological angiogenesis in murine retinae by suppressing hif-1a mRNA and HIF target genes.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.