Inhibition of mitochondrial fission protein Drp1 ameliorates skeletal myopathy in the D2-mdx model of Duchenne muscular dystrophy

Although current treatments for Duchenne muscular dystrophy (DMD) have proven to be effective in delaying myopathy, there remains a strong need to identify novel targets to develop additional therapies. Mitochondrial dysfunction is an early pathological feature of DMD. A fine balance of mitochondrial dynamics (fission and fusion) is crucial to maintain mitochondrial function and skeletal muscle health. Excessive activation of dynamin-related protein 1 (Drp1)-mediated mitochondrial fission was reported in animal models of DMD. However, whether Drp1-mediated mitochondrial fission is a viable target for treating myopathy in DMD remains unknown. Here, we treated a D2.B10-<i>Dmd</i>^mdx/J (D2-mdx) model of DMD (9-10 wk old) with mitochondrial division inhibitor 1 (Mdivi-1), a selective Drp1 inhibitor, every other day (intraperitoneal injection) for 5 wk. We demonstrated that Mdivi-1 effectively improved skeletal muscle strength and reduced serum creatine kinase concentration. Mdivi-1 treatment also effectively inhibited mitochondrial fission regulatory protein markers, Drp1(Ser616) phosphorylation, and mitochondrial fission protein 1 (Fis1) in skeletal muscles from D2-mdx mice, which resulted in reduced content of damaged and fragmented mitochondria. Furthermore, Mdivi-1 treatment attenuated lipid peroxidation product, 4-hydroxynonenal (4-HNE), in skeletal muscle from D2-mdx mice, which was inversely correlated with muscle grip strength. Finally, we revealed that Mdivi-1 treatment downregulated the expression of markers of fibrosis [alpha 1 type I collagen (Col1a1), metalloproteinases 2 and 9 (MMP2 and MMP9)] and inflammation [IL-6, monocyte chemoattractant protein-1 (MCP1), and CXC motif chemokine ligand 12 (CXCL12)]. In summary, these results demonstrate that inhibition of Drp1-mediated mitochondrial fission by Mdivi-1 is effective in improving muscle strength and alleviating muscle damage in D2-mdx mice. These improvements are associated with improved skeletal muscle mitochondrial integrity, leading to attenuated lipid peroxidation.<b>NEW & NOTEWORTHY</b> The therapeutic potential of targeting mitochondrial dynamics in treating myopathy in Duchenne muscular dystrophy (DMD) remains unknown. This study is the first to target Drp1-mediated mitochondrial fission to alleviate myopathy in DMD. We reported that Mdivi-1, a pharmacological inhibitor targeting Drp1-mediated mitochondrial fission, was effective in reducing muscle damage and improving skeletal muscle strength in D2-mdx mice. These responses were associated with improved mitochondrial morphology and reduced lipid peroxidation.