Perturbed Redox Signaling Exacerbates a Mitochondrial Myopathy

Area of Science:

• Mitochondrial biology
• Cellular respiration
• Muscle physiology

Background:

• Alternative oxidases (AOXs) offer a potential therapeutic strategy for mitochondrial diseases by bypassing damaged respiratory complexes.
• Mitochondrial dysfunction, particularly in skeletal muscle, leads to severe myopathies.
• The role of reactive oxygen species (ROS) in mitochondrial disease pathogenesis and compensatory mechanisms is complex.

Purpose of the Study:

• To investigate the therapeutic potential of AOX in a mouse model of severe skeletal muscle mitochondrial disease.
• To elucidate the impact of AOX expression on disease progression, lifespan, and compensatory pathways.
• To determine the effect of antioxidant treatment on disease severity and survival.

Main Methods:

• Generation of a double mutant mouse model by crossing skeletal muscle-specific COX15 knockout mice with AOX-transgenic mice.
• Assessment of lifespan, myopathy severity, and muscle regeneration capacity in wild-type, KO, and double mutant mice.
• Analysis of reactive oxygen species (ROS) production, AMPK/PGC-1α signaling, and muscle regeneration markers (PAX7, MYOD).
• Evaluation of the effects of N-acetylcysteine (antioxidant) treatment on KO mice.

Main Results:

• Double KO-AOX mutants exhibited decreased lifespan and exacerbated myopathy compared to KO mice alone.
• KO-AOX mice showed reduced ROS production, leading to impaired AMPK/PGC-1α signaling.
• Muscle regeneration, dependent on PAX7 and MYOD, was blunted in KO-AOX mice, hindering compensatory responses.
• Administration of the antioxidant N-acetylcysteine similarly decreased the lifespan of KO mice.

Conclusions:

• AOX expression can worsen mitochondrial myopathy by disrupting ROS signaling and impairing muscle regeneration.
• ROS signaling plays a crucial role in activating compensatory mechanisms in mitochondrial disease.
• Antioxidant therapies may pose risks and could be detrimental in certain mitochondrial disease contexts.
• Findings necessitate a re-evaluation of AOX-based therapies and highlight the importance of ROS signaling in disease pathogenesis.