HDAC inhibition protects RPE cells from oxidative stress via enhanced mitochondrial fusion, cytoskeletal repair, and Nrf-2 activation

Oxidative stress is a key driver of retinal pigment epithelium (RPE) damage and the development of age-related macular degeneration (AMD). Here, we demonstrate that the histone deacetylase (HDAC) inhibitors vorinostat and trichostatin A (TSA) elicit a coordinated cytoprotective response in RPE cells exposed to rotenone. Both compounds significantly reduced reactive oxygen species (ROS) levels, enhanced mitochondrial fusion, increased mitochondrial ATP production, and improved cell morphology and cell survival in the rotenone-treated cells. In addition, the compounds activated Nrf-2 as evidenced by Keap1 downregulation, increased p62/SQSTM1 expression, and induction of Nrf-2 targets, including heme oxygenase 1 (HO-1). Proteomic analysis of drug-treated cells revealed a significant enrichment of proteins involved in cytoskeletal organization and dynamics. Consistently, specific staining for actin filaments confirmed that vorinostat and TSA preserved cytoskeletal architecture and increased levels of the tight junction protein TJP3 in cells exposed to rotenone. Finally, inhibition of the vorinostat/TSA target HDAC6, or blockade of α-tubulin acetyltransferase, demonstrated that modulation of α-tubulin acetylation could influence ROS levels. Similarly, enhanced mitochondrial fusion by Mdivi-1 reduced ROS accumulation in the rotenone-treated cells. However, these last two interventions did not fully recapitulate the antioxidant effects observed with vorinostat or TSA. Our results identify a multifaceted protective mechanism triggered by HDAC inhibition in oxidatively stressed RPE cells and support the therapeutic repurposing of vorinostat in oxidative stress-driven RPE or retinal degeneration.