Reactive oxygen species, oxidative stress, and cell death correlate with level of CoQ10 deficiency

Coenzyme Q10 (CoQ10) is essential for electron transport in the mitochondrial respiratory chain and antioxidant defense. The relative importance of respiratory chain defects, ROS production, and apoptosis in the pathogenesis of CoQ10 deficiency is unknown. We determined previously that severe CoQ10 deficiency in cultured skin fibroblasts harboring COQ2 and PDSS2 mutations produces divergent alterations of bioenergetics and oxidative stress. Here, to better understand the pathogenesis of CoQ10 deficiency, we have characterized the effects of varying severities of CoQ10 deficiency on ROS production and mitochondrial bioenergetics in cells harboring genetic defects of CoQ10 biosynthesis. Levels of CoQ10 seem to correlate with ROS production; 10-15% and >60% residual CoQ10 are not associated with significant ROS production, whereas 30-50% residual CoQ10 is accompanied by increased ROS production and cell death. Our results confirm that varying degrees of CoQ10 deficiency cause variable defects of ATP synthesis and oxidative stress. These findings may lead to more rational therapeutic strategies for CoQ10 deficiency. © FASEB.