L-NAME improves the morphology and necrosis of skeletal muscle by activating PINK1-PARKIN mediated mitophagy in mdx mice

Background

This study investigates mitophagy in Duchenne muscular dystrophy (DMD, OMIM #310200), focusing on how nitric oxide synthase (NOS) inhibition improves muscle tissue pathology by affecting mitophagy, which is implicated in muscle weakness due to dystrophin deficiency and may affect DMD-related cardiomyopathy and respiratory problems.

Methods

Histopathological analysis, immunofluorescence staining, Western blot were used to study the mitophagy status of the tibialis anterior muscle in mdx mice without treatment or mdx mice administered L-NAME (L-N^G-nitro arginine methylester), an inhibitor of NOS. For in vitro experiment, the effect of S-nitrosylation enzyme, N6022, on mitophagy in C2C12 cells was assessed using TEM (transmission electron microscopy), and Western blot.

Results

Mdx mice showed dystrophic muscle pathology and elevated LC3 (microtubule-mssociated protein 1 light chain) and VDAC (voltage-dependent anion channel) expression, indicating increased mitophagy. Reduced PINK1 (PTEN-induced putative kinase 1) and PARKIN (E3 ubiquitin ligase PARK2) levels suggested incomplete mitochondrial clearance. L-NAME treatment improved muscle morphology and reduced necrosis, partially restoring mitophagy by increasing LC3 without matching VDAC upregulation. However, PINK1 and PARKIN were further reduced, suggesting mitophagic inefficiency. In C2C12 cells, GSNOR(S-nitrosoglutathione reductase) inhibition via N6022 elevated nitrosylation, impaired mitophagy, and caused mitochondrial accumulation with increased PINK1 but unchanged PARKIN, highlighting a critical role of nitrosylation balance in mitophagy regulation.

Conclusions

NOS inhibition may serve as a key point for further research on the progression of DMD disease and as a potential therapeutic target for this incurable disease.