086 | Kir4.1 channels at the crossroads of oxidative stress and presbycusis: redox imbalance, electrophysiological failure and quercetin-mediated rescue

Sara Spinelli¹, Alessia Remigante², Angela Marino¹, Rossana Morabito¹ | ¹Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Italy; ²Department of Biomedical, Dental and Morphological and Functional Imaging, University of Messina, Italy.

Kir4.1/KCNJ10 is an inwardly rectifying potassium channel highly expressed in intermediate cells of the cochlear stria vascularis, where it plays a pivotal role in potassium ion recycling [1]. By sustaining endolymph high potassium concentration (~150 mM), Kir4.1 is essential for the generation and maintenance of the endocochlear potential, a prerequisite for sensory hair cell depolarization and effective auditory signal transduction [1]. Dysfunction of the stria vascularis and disruption of potassium homeostasis have been widely implicated in the pathophysiology of presbycusis [2]. Oxidative stress is a well-established hallmark of aging and a major contributor to cochlear degeneration in presbycusis, which particularly affects metabolically active structures such as the stria vascularis [3]. However, the molecular targets that relate oxidative damage to impaired cochlear ion homeostasis remain incompletely defined. Based on the redox sensitivity of potassium channels and the critical role of Kir4.1 in cochlear physiology, we hypothesized that oxidative stress may directly impair Kir4.1 expression and function, thereby contributing to presbycusis. To investigate this hypothesis, we examined the relationship between aging, oxidative stress, and Kir4.1 dysfunction using an in vitro model of oxidative stress-induced aging, obtained by the exposure of cell lines to 100 mM D-galactose. Both endogenous and ectopic Kir4.1 activity were evaluated under these conditions. D-galactose exposure induced a pronounced oxidative imbalance, as evidenced by increased intracellular reactive oxygen species levels and thiobarbituric acid reactive substances, along with depletion of protein sulfhydryl groups. In parallel, key components of the cellular antioxidant defense system were disrupted, including catalase and superoxide dismutase activities and GSH/GSSG ratio. Importantly, oxidative stress was associated with a significant reduction in Kir4.1 current density, denoting a functional impairment of the channel. Treatment with the natural flavonoid antioxidant quercetin effectively restored redox homeostasis, normalized antioxidant enzyme activity, and fully rescued Kir4.1 channel function. Taken together, these findings identify Kir4.1 as a previously unrecognized molecular target of oxidative stress and suggest that Kir4.1 dysfunction may represent a mechanistic link between age-related oxidative damage and impaired cochlear potassium recycling in presbycusis. Moreover, our data support the potential of quercetin as a protective agent in preserving Kir4.1 function under oxidative stress conditions, thereby highlighting a novel therapeutic strategy for the prevention or treatment of age-related hearing loss.