Mitochondria and Reactive Oxygen Species: The Therapeutic Balance of Powers for Duchenne Muscular Dystrophy

Abstract

Duchenne muscular dystrophy (DMD) is a genetic progressive muscle-wasting disorder that leads to rapid loss of mobility and premature death. The absence of functional dystrophin in DMD patients reduces sarcolemma stiffness and increases contraction damage, triggering a cascade of events leading to muscle cell degeneration, chronic inflammation, and deposition of fibrotic and adipose tissue. Efforts in the last decade have led to the clinical approval of novel drugs for DMD that aim to restore dystrophin function. However, combination therapies able to restore dystrophin expression and target the myriad of cellular events found impaired in dystrophic muscle are desirable. Muscles are higher energy consumers susceptible to mitochondrial defects. Mitochondria generate a significant source of reactive oxygen species (ROS), and they are, in turn, sensitive to proper redox balance. In both DMD patients and animal models there is compelling evidence that mitochondrial impairments have a key role in the failure of energy homeostasis. Here, we highlighted the main aspects of mitochondrial dysfunction and oxidative stress in DMD and discussed the recent findings linked to mitochondria/ROS-targeted molecules as a therapeutic approach. In this respect, dual targeting of both mitochondria and redox homeostasis emerges as a potential clinical option in DMD.

Keywords: DMD therapies; Duchenne muscular dystrophy; antioxidant defense; mitochondria; mitophagy; oxidative stress; redox homeostasis; skeletal muscle.

Figure 1

A functional muscle in healthy people is characterized by a proper balance of the redox system and mitochondrial homeostasis (green arrows). In DMD patients, the alteration of this balance contributes to constant muscle damage (red arrows). Many mitochondrial defects have been described in DMD and among these, excessive production of mitochondrial ROS (mtROS) constitutes one of the main sources of oxidative stress in dystrophic muscles, also enhanced by defects in the redox system. Abbreviations: NADPH oxidases (NOXs); xanthine oxidase (XO); electron transport chain (ETC); neuronal nitric oxide synthase (nNOS).

Figure 2

Schematic representation of mitochondrial defects in DMD.

Figure 3

Schematic representation of main sources of free radicals in DMD.