Purchase this article with an account.
Savalan Babapoor-Farrokhran, Monika Deshpandeh, Marisol Cano, James T Handa, Gregg L Semenza, Silvia Montaner, Akrit Sodhi; Hypoxia Inducible Factor-1α Promotes the Survival of Retinal Pigment Epithelial Cells Exposed to Oxidative Stress. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):810.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Oxidative stress has been implicated in the development and progression of age-related macular degeneration (AMD), and anti-oxidant vitamins have been shown to reduce the risk of progression from dry to wet AMD. However, the molecular link between oxidative stress and the development of wet AMD remains poorly understood. The transcription factor hypoxia inducible factor (HIF)-1 regulates the expression of angiogenic mediators that promote the development of choroidal neovascularization (CNV) in wet AMD. Interestingly, regulation of gene expression by HIF-1α has also been implicated in the cellular response to oxidative stress. Here we examine the regulation of HIF-1α and its target genes in RPE cells exposed to oxidative stress.
RPE cells were treated with inducers of oxidative stress (4HNE, tBH and H2O2). Production of reactive oxygen species (ROS) was quantified using dihydroethidium assay. HIF-1α accumulation was assessed by western blot and immunofluorescence. Regulation of HIF-1α target genes was assessed by qPCR and ELISA. HIF-1α was inhibited using RNAi or digoxin. Cell survival was measured using the MTS assay. Results were confirmed in vivo following intraocular injection with 4HNE.
Exposure to oxidative stress resulted in increased protein accumulation and nuclear localization of HIF-1α in RPE cells in vitro and in vivo. HIF-1α, in turn, upregulated the expression of angiogenic cytokines (e.g., vascular endothelial growth factor) by RPE cells; this was effectively inhibited by blocking HIF-1α protein accumulation, supporting HIF-1α as a therapeutic target for the treatment of early CNV. However, inhibition of HIF-1α also prevented the expression of important survival genes and resulted in increased death of RPE cells exposed to oxidative stress.
Although HIF-1α upregulates the expression of angiogenic cytokines that promote the development of CNV, accumulation of HIF-1α in RPE cells exposed to oxidative stress is also necessary for RPE survival, suggesting that HIF-1α may not be a suitable treatment target for patients with AMD. These studies demonstrate a mechanism linking oxidative stress to HIF-1α accumulation and RPE survival under conditions that simulate dry AMD, and suggest that HIF-1α dysregulation leads to over-expression of angiogenic cytokines in the transition from dry to wet AMD.
This PDF is available to Subscribers Only