Temporal inhibition of electron transport chain attenuates stress-induced cellular senescence by prolonged disturbance of proteostasis in human fibroblasts

Abstract

AbstractWe previously developed a stress-induced premature senescence (SIPS) model in which normal human fibroblast MRC-5 cells were treated with either the proteasome inhibitor MG132 or the V-ATPase inhibitor bafilomycin A1 (BAFA1). To elucidate the involvement of mitochondrial function in our SIPS model, we treated cells with an inhibitor of electron transport chain (ETC) complexes I, III, or a mitochondrial uncoupler reagent along with MG132 or BAFA1 and evaluated the induction of premature senescence. SIPS induced by MG132 or BAFA1 was partially attenuated by co-treatment with antimycin A (AA) and rotenone, but not carbonyl cyanide 3-chlorophenylhydrazone (CCCP), in which intracellular reactive oxygen species (ROS) levels, acute mitochondrial unfolded protein responses, and accumulation of protein aggregates were remarkably suppressed. Co-treatment with AA also reversed the temporal depletion of SOD2 in the mitochondrial fraction on day 1 of MG132 treatment. Furthermore, co-treatment with AA suppressed the induction of mitophagy in MG132-treated cells and enhanced mitochondrial biogenesis. These findings provide evidence that the temporal inhibition of mitochondrial respiration exerts protective effects against the progression of premature senescence caused by impaired proteostasis.Graphical abstractGRAPHICAL ABSTRACTCellular senescence is induced by prolonged inhibition of proteasome or lysosome function using MG132 and bafilomycin A1 (BAFA1), respectively. When cells were co-treated with a mitochondrial respiration inhibitor, antimycin A, and MG132 or BAFA1, oxidative stress, mitochondrial unfolded protein response (UPRmt), accumulation of protein aggregates, and mitophagy were suppressed whereas mitochondrial biogenesis was enhanced, resulting in the attenuation of stress-induced cellular senescence (SIPS).