MiRNA-634 promotes apoptosis in HEI-OC1 cells by regulating AK4 and AKT/mTOR signaling pathways

Presbycusis, or age-related hearing loss (ARHL), is a complex condition characterized by the progressive accumulation of hearing loss associated with aging. Age-related deafness is caused by inner ear hair cell damage and loss. Previously, we extracted exosomal miRNA from peripheral blood samples of elderly deaf individuals to corroborate the differentially high expression of miR-634. This work examines how miR-634 regulates HEI-OC1 cell death via the downstream target gene AK4 and the AKT/mTOR signaling pathway. KEGG and GO enrichment studies identified miR-634's downstream target gene AK4, followed by a dual luciferase reporter test to evaluate binding. HEI-OC1 cells underwent transfection utilizing miR-634 mimics and vectors for the overexpression and knockdown of AK4. qRT-PCR quantified miRNA, flow double staining detected apoptosis, immunoblotting measured protein, and a fluorescent probe measured ROS. Transfection of HEI-OC1 cells with miR-634 mimics enhanced Caspase-7, Caspase-3, and Bax protein expression, decreased Bcl-2 protein expression, and significantly raised ROS levels. Apoptosis and ROS levels decreased in the AK4-OE group, but Bcl-2 protein and downstream-associated proteins p-AKT and p-mTOR increased. AK4-ShRNA and miRNA-OE showed different changes from AK4-OE. In HEI-OC1 cells, overexpression of AK4 inhibited apoptosis. In contrast, overexpression of miR-634 mimics and AK4 knockdown accelerated apoptosis. miR-634 may facilitate the apoptosis of HEI-OC1 cells by down-regulating AK4 and its downstream associated proteins, p-AKT and p-mTOR. miR-634 and AK4 may serve as targets that induce functional alterations and ultimately lead to the death of inner ear hair cells in individuals with presbycusis.