A novel HIF1α stabilizer prevents apoptosis and promotes a senescence-like phenotype in photoreceptor cells

Abstract Retinal detachment (RD) disrupts oxygen and nutrient delivery to the neurosensory retina, creating a hypoxic environment that can lead to degeneration of photoreceptors (PRs) if left untreated. Hypoxia-inducible factors (HIFs) are central regulators of cellular adaptation to hypoxia, acting to preserve cellular function following oxygen deprivation. We hypothesized that pharmacologic stabilization of HIF1α would protect PRs from hypoxia-induced cell death. To test this, we used the murine cone photoreceptor-like 661 W cell line to evaluate a novel cyclometalated iridium(III) complex, stabilizer 1a, which disrupts the von Hippel-Lindau (VHL)–HIF1α interaction and reduces HIF1α degradation. We compared its effects with dimethyloxalylglycine (DMOG), a well-established cell-permeable inhibitor of HIF prolyl hydroxylase. Stabilizer 1a increased HIF1α accumulation under normoxia and hypoxia and significantly reduced apoptosis induced by hypoxic stress, as demonstrated by reduced cleaved caspase-3 expression and annexin V labeling. Stabilizer 1a was also associated with reduced mitochondrial and total reactive oxygen species (ROS) levels, preserved intracellular ATP levels, and increased markers associated with mitophagy. In addition, stabilizer 1a induced a reversible senescence-like phenotype characterized by increased protein levels of p16 and p21, reduced proliferation, and activation of IL-6 and c-Jun N-terminal kinase (JNK) signaling. Removal of stabilizer 1a restored p21 levels to baseline, supporting a potentially transient adaptive state in response to stress. Further in vivo validation supported these in vitro findings: stabilizer 1a attenuated PR apoptosis after RD, accompanied by increased markers of mitophagy. Together, these findings suggest that short-term HIF1α stabilization with stabilizer 1a is associated with suppression of apoptosis, attenuation of oxidative stress and induction of a transient senescence-like cellular phenotype.