ROS-Induced Activation of DNA Damage Responses Drives Senescence-Like State in Postmitotic Cochlear Cells: Implication for Hearing Preservation

Abstract

In our aging society, age-related hearing loss (ARHL) has become a major socioeconomic issue. Reactive oxygen species (ROS) may be one of the main causal factors of age-related cochlear cell degeneration. We examined whether ROS-induced DNA damage response drives cochlear cell senescence and contributes to ARHL from the cellular up to the system level. Our results revealed that sublethal concentrations of hydrogen peroxide (H₂O₂) exposure initiated a DNA damage response illustrated by increased γH2AX and 53BP1 expression and foci formation mainly in sensory hair cells, together with increased levels of p-Chk2 and p53. Interestingly, postmitotic cochlear cells exposed to H₂O₂ displayed key hallmarks of senescent cells, including dramatically increased levels of p21, p38, and p-p38 expression, concomitant with decreased p19 and BubR1 expression and positive senescence-associated β-galactosidase labeling. Importantly, the synthetic superoxide dismutase/catalase mimetic EUK-207 attenuated H₂O₂-induced DNA damage and senescence phenotypes in cochlear cells in vitro. Furthermore, systemic administration of EUK-207 reduced age-related loss of hearing and hair cell degeneration in senescence-accelerated mouse-prone 8 (SAMP8) mice. Altogether, these findings highlight that ROS-induced DNA damage responses drive cochlear cell senescence and contribute to accelerated ARHL. EUK-207 and likely other antioxidants with similar mechanisms of action could potentially postpone cochlear aging and prevent ARHL in humans.