Abstract
Purpose :
Photoreceptor (PR) cells receive nearly all their nutritional and oxygen supply from the underlying retinal pigment epithelium (RPE). Retinal detachment (RD), defined as the separation of the retina from the RPE, results in PR hypoxia and activation of hypoxia-inducible factor 1-alpha (HIF-1α). In this study we aimed to explore how HIF-1α regulates downstream cellular pathways involved in PR death versus survival.
Methods :
Retina-RPE separation was created in C57BL/6J mice by injection of 1% hyaluronic acid into the subretinal space. Retinas were harvested and assayed for markers of ER stress, mitophagy and proteasomal degradation. Cultured 661W photoreceptor cells were subjected to hypoxic conditions and assayed for induction of HIF and other pathways associated with cell death such as ER stress, mitochondrial dysfunction, mitophagy and proteasomal degradation.
Results :
Evaluation of retinas 1 day and 3 days post retinal detachment revealed that HIF-1α protein expression was increased by 4.2 fold (p=0.0144) and 2.2 fold (p=0.0465), respectively. In vitro hypoxia similarly elevated HIF-1α expression of 661W cells by a 3-fold (p=0.0570). RD significantly upregulated protein expression of several markers of ER stress, including BIP, CHOP, and IRE1α, and increased the levels of polyubiquitinated proteins by 3.7 fold (p=0.0081). Further, evaluation of 661W cells also indicated hypoxia impaired mitochondrial function, with a loss of mitochondrial membrane potential (ΔΨm), an increase in mitochondrial ROS, and a decrease in intracellular ATP levels.
Conclusions :
Our results indicate the involvement of pathways such as ER stress, mitophagy, mitochondrial dysfunction and proteasomal degradation upon separation of photoreceptors from RPE. Future work will establish the relationship between HIF activation and these downstream regulators of cell death versus survival.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.