Effects of inhibiting CoQ 10 biosynthesis with 4-nitrobenzoate in human fibroblasts

Abstract

Coenzyme Q 10 (CoQ 10) is a potent lipophilic antioxidant in cell membranes and a carrier of electrons in the mitochondrial respiratory chain. We previously characterized the effects of varying severities of CoQ 10 deficiency on ROS production and mitochondrial bioenergetics in cells harboring genetic defects of CoQ 10 biosynthesis. We observed a unimodal distribution of ROS production with CoQ 10 deficiency: cells with <20% of CoQ 10 and 50-70% of CoQ 10 did not generate excess ROS while cells with 30-45% of CoQ 10 showed increased ROS production and lipid peroxidation. Because our previous studies were limited to a small number of mutant cell lines with heterogeneous molecular defects, here, we treated 5 control and 2 mildly CoQ 10 deficient fibroblasts with varying doses of 4-nitrobenzoate (4-NB), an analog of 4-hydroxybenzoate (4-HB) and inhibitor of 4-para-hydroxybenzoate:polyprenyl transferase (COQ2) to induce a range of CoQ 10 deficiencies. Our results support the concept that the degree of CoQ 10 deficiency in cells dictates the extent of ATP synthesis defects and ROS production and that 40-50% residual CoQ 10 produces maximal oxidative stress and cell death. © 2012 Quinzii et al.