MCU knockdown attenuates cisplatin-induced damage of auditory cells: potential involvement of PI3K/AKT/mTOR signaling and autophagy-related processes.

INTRODUCTION

The mitochondrial calcium uniporter (MCU) mediates mitochondrial Ca2⁺ uptake, but its involvement in cisplatin-induced ototoxicity remains poorly understood. We investigated MCU expression and its association with cisplatin-induced injury in mouse cochlear basilar membranes and HEI-OC1 cells.

METHODS

MCU protein abundance and localization were assessed by Western blotting and immunofluorescence. MCU expression was genetically reduced by lentiviral knockdown, and Ru360 was used as a pharmacological intervention. Apoptosis-related proteins and transcriptomic changes were evaluated. An acute cisplatin-induced ototoxicity model was established in C57BL/6 mice and assessed using auditory brainstem response (ABR) measurements and outer hair cell counts.

RESULTS

Cisplatin increased MCU expression and reduced SERCA2 expression; the cisplatin-induced increase in MCU was partially reversed by BAPTA-AM and the endoplasmic reticulum stress inhibitor 4-PBA. MCU knockdown did not affect basal cell viability but attenuated cisplatin-induced reductions in viability, TUNEL positivity, and cleaved caspase-3. It was also associated with increased SERCA2 and decreased IP3R, GRP75, and VDAC1 expression. RNA sequencing identified differentially expressed genes enriched in autophagy-related processes and mTOR signaling. MCU knockdown was associated with increased PI3K/AKT/mTOR signaling and changes in Beclin1, LC3B-II, and p62. Ru360 cotreatment partially reproduced the protective phenotype in vitro and was associated with attenuated ABR threshold elevation at selected frequencies and reduced outer hair cell loss in vivo.

DISCUSSION: These findings support an association between MCU-related signaling, PI3K/AKT/mTOR pathway activation, altered autophagy-related markers, and reduced cisplatin-induced cochlear injury.