Carbon monoxide (CO) modulates hydrogen peroxide (H2O2)-mediated cellular dysfunction by targeting mitochondria in rabbit lens epithelial cells

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Mitochondrial components are of great importance for the maintenance of lens transparency. In our previous work, we confirmed that carbon monoxide (CO) can protect human and rabbit lens epithelial cells (LECs) from hydrogen peroxide (H2O2)-mediated apoptosis, while the mechanism remains undefined. Because CO can bind to mitochondrial cytochrome c oxidase (COX), we evaluated the effect of CO on the regulation of mitochondrial biogenesis and function in H2O2-treated rabbit LECs. To evaluate mitochondrial biogenesis, several mitochondrial transcription factors (PGC-1α, NRF-1, and mtTFA) were detected by western blot analysis. To assess cellular metabolism, adenosine triphosphate (ATP) levels and COX enzymatic activity were measured. In addition, mitochondrial permeability transition pores (mPTP) opening, dissipation of mitochondrial membrane potential (ΔΨm), cytochrome c mitochondrial translocation, and apoptotic molecules were also detected to evaluate mitochondrial apoptosis pathway. Furthermore, the interaction of Bcl-2 and COX was assessed by co-immunoprecipitation. Finally, CO-mediated regulation of cellular function was detected in Bcl-2-knockdown cells. Our results confirmed that CO pretreatment restored H2O2-induced down-regulation of mitochondrial transcription factors expression, COX activity and ATP production. Moreover, CO pretreatment attenuated mPTP opening, ΔΨm loss, cytochrome c mitochondrial translocation, and activation of apoptotic molecules. Bcl-2 was identified to bind to COX, and silence of Bcl-2 expression prevented CO-regulated cellular metabolism and cytoprotection. These data suggest that CO modulates H2O2-induced cellular dysfunction by increasing mitochondrial biogenesis, enhancing cellular metabolism, and attenuating mitochondrial apoptosis cascade. Moreover, Bcl-2 expression was vital for CO to regulate cellular metabolism and cytoprotection in LECs.HighlightsCO pretreatment restored H2O2-induced down-regulation of mitochondrial biogenesis in LECs.CO pretreatment increased COX activity and ATP production in H2O2-treated LECs.CO pretreatment attenuated H2O2-induced activation of mitochondrial apoptosis cascade in LECs.Bcl-2 expression was vital for CO to regulate cellular metabolism and cytoprotection in LECs.Abbreviations: Apaf-1: apoptotic protease activating factor-1; ATP: adenosine triphosphate; CO: carbon monoxide; CORM-3: carbon monoxide-releasing molecule-3; COX: cytochrome c oxidase; HO: heme oxygenase; H2O2: hydrogen peroxide; iCORM-3: inactivated CORM-3; JC-1: tetraethylbenzimidazolylcarbocyanine iodide; LECs: lens epithelial cells; MMP: mitochondrial membrane permeabilization; mPTP: mitochondrial permeability transition pore; mtTFA: mitochondrial transcription factor A; ROS: reactive oxygen species; ΔΨm: mitochondrial membrane potential.

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