Effect of 2-aminoethoxydiphenyl borate on the functions of mouse skeletal muscle mitochondria.

This work examined the effect of 2-aminoethoxydiphenyl borate (2-APB) on the functioning of isolated mouse skeletal muscle mitochondria and modeled its putative interaction with mitochondrial proteins. We have shown that 2-APB is able to dose-dependently suppress mitochondrial respiration in state 3 and 3UDNP driven by substrates of complex I and II. This effect of 2-APB was accompanied by a slight dose-dependent decrease in mitochondrial membrane potential and appears to be due to inhibition of complex I and complex III of the electron transport chain (ETC) with IC50 values of 200 and 120 µM, respectively. The results of molecular docking identified putative 2-APB interaction sites in these ETC complexes. 2-APB was shown to dose-dependently inhibit both mitochondrial Ca2+ uptake and Ca2+ efflux, which seems to be caused by a decrease in the membrane potential of the organelles. We have found that 2-APB has no significant effect on mitochondrial calcium retention capacity. On the other hand, 2-APB exhibited antioxidant effect by reducing mitochondrial hydrogen peroxide production but without affecting superoxide generation. It is concluded that the effect of 2-APB on mitochondrial targets should be taken into account when interpreting the results of cell and in vivo experiments.

Mitochondrial Transplantation Therapy Ameliorates Muscular Dystrophy in mdx Mouse Model.

Duchenne muscular dystrophy is caused by loss of the dystrophin protein. This pathology is accompanied by mitochondrial dysfunction contributing to muscle fiber instability. It is known that mitochondria-targeted in vivo therapy mitigates pathology and improves the quality of life of model animals. In the present work, we applied mitochondrial transplantation therapy (MTT) to correct the pathology in dystrophin-deficient mdx mice. Intramuscular injections of allogeneic mitochondria obtained from healthy animals into the hind limbs of mdx mice alleviated skeletal muscle injury, reduced calcium deposits in muscles and serum creatine kinase levels, and improved the grip strength of the hind limbs and motor activity of recipient mdx mice. We noted normalization of the mitochondrial ultrastructure and sarcoplasmic reticulum/mitochondria interactions in mdx muscles. At the same time, we revealed a decrease in the efficiency of oxidative phosphorylation in the skeletal muscle mitochondria of recipient mdx mice accompanied by a reduction in lipid peroxidation products (MDA products) and reduced calcium overloading. We found no effect of MTT on the expression of mitochondrial signature genes (Drp1, Mfn2, Ppargc1a, Pink1, Parkin) and on the level of mtDNA. Our results show that systemic MTT mitigates the development of destructive processes in the quadriceps muscle of mdx mice.