Mitochondrial DNA damage in aging and in apoptosis

This chapter analyzes mitochondrial respiratory chain dysfunction caused by coenzyme Q deficiency. CoQ10 plays a pivotal role in the mitochondrial respiratory chain, distributing the electrons between the various dehydrogenases and the cytochrome segments of the respiratory chain. Being in large excess compared to any other component of the respiratory chain (RC), it forms a kinetically compartmentalized pool. Depending on its redox and protonation status, CoQ10 can react with molecular oxygen to produce superoxides. In particular, the full reduction of b-type cytochromes and the increased formation of unstable ubisemiquinone ensures maximal superoxide production. Besides the pro-oxidant effect of CoQ10, the fully reduced species (ubiquinol) can reduce a number of radical species, including superoxides, therefore acting as an antioxidant. The chapter presents an overview of respiratory chain and ubiquinone. Cellular consequences of CoQ10 depletion along with clinical presentation of coenzyme Q10 depletion are also discussed in the chapter. The chapter elaborates the detection of CoQ10 deficiency and presents the details of supplementation therapy.