Clioquinol induces mitochondrial toxicity in SH‐SY5Y neuroblastoma cells by affecting the respiratory chain complex IV and OPA1 dynamin‐like GTPase

Clioquinol has been thought of as the causative drug of subacute myelo-optic neuropathy (SMON). The underlying mechanisms of clioquinol toxicity, however, have not been elucidated in detail. Here, we revealed that clioquinol (20 μm) suppressed the expression of SCO1 and SCO2 copper chaperones for mitochondrial respiratory chain Complex IV (cytochrome c oxidase) in SH-SY5Y neuroblastoma cells. The assembly of Complex IV components and Complex IV activity were suppressed in clioquinol-treated cells. Clioquinol (10-50 μm) decreased cellular ATP levels in glucose-free media. Clioquinol (10-50 μm) induced OMA1 mitochondrial protease-dependent degradation of the dynamin-related GTPase OPA1 and suppressed the expression of CHCHD10 and CHCHD2 involved in the maintenance of cristae structure. These results suggest that mitochondrial toxicity is one of the mechanisms of clioquinol-induced neuronal cell death.