Chronic nicotine exposure (via smoking, E-cigarettes) increases oxidative stress in the kidney that sensitizes it to additional injury in experimental models and in the renal patient. The pro-apoptotic p66shc protein-via serine36 phosphorylation that facilitates its mitochondrial translocation and therein cytochrome c binding-generates oxidative stress that leads to injury of renal proximal tubule cells during chronic nicotine exposure. Coenzyme Q10-a clinically safe antioxidant-has been used against nicotine/smoke extract-associated oxidative stress in various non-renal cells. This study explored the anti-oxidant/anti-apoptotic effect of Coenzyme Q10 on nicotine-induced oxidative stress and its impact on p66shc in cultured rat renal proximal tubule cells (NRK52E). We studied the anti-oxidant effect of 10 µM Coenzyme Q10 using various mutants of the p66shc gene and also determined the induction of selected anti-oxidant entities (antioxidant response element, promoter of the manganese superoxide dismutase gene) in reporter luciferase assay during oxidative stress induced by 200 µM nicotine. Our studies revealed that Coenzyme Q10 strongly inhibits nicotine-mediated production of reactive oxygen species and consequent apoptosis that requires serine36 phosphorylation but not mitochondrial translocation/cytochrome c binding of p66shc. While both nicotine and Coenzyme Q10 stimulates the p66shc promoter, only nicotine exposure results in mitochondrial translocation of p66shc. In contrast, the Coenzyme Q10-stimulated and non-mitochondrial p66shc activates the anti-oxidant manganese superoxide dismutase promoter via the antioxidant response elements and hence, rescues cells from nicotine-induced oxidative stress and consequent apoptosis.
Keywords: Antioxidant; Apoptosis; Coenzyme Q10; Nicotine; Oxidative stress; P66shc; Protection.