leupeptins and Muscular-Dystrophies

Congenital muscular dystrophy caused by laminin α2 chain deficiency (also known as MDC1A) is a severe and incapacitating disease, characterized by massive muscle wasting. The ubiquitin-proteasome system plays a major role in muscle wasting and we recently demonstrated that increased proteasomal activity is a feature of MDC1A. The autophagy-lysosome pathway is the other major system involved in degradation of proteins and organelles within the muscle cell. However, it remains to be determined if the autophagy-lysosome pathway is dysregulated in muscular dystrophies, including MDC1A. Using the dy(3K)/dy(3K) mouse model of laminin α2 chain deficiency and MDC1A patient muscle, we show here that expression of autophagy-related genes is upregulated in laminin α2 chain-deficient muscle. Moreover, we found that autophagy inhibition significantly improves the dystrophic dy(3K)/dy(3K) phenotype. In particular, we show that systemic injection of 3-methyladenine (3-MA) reduces muscle fibrosis, atrophy, apoptosis and increases muscle regeneration and muscle mass. Importantly, lifespan and locomotive behavior were also greatly improved. These findings indicate that enhanced autophagic activity is pathogenic and that autophagy inhibition holds a promising therapeutic potential in the treatment of MDC1A.

Topics: Adenine; Animals; Apoptosis; Autophagy; Behavior, Animal; Disease Models, Animal; Drug Therapy, Combination; Fibrosis; Gene Expression Regulation; Injections; Laminin; Leupeptins; Mice; Motor Activity; Muscles; Muscular Atrophy; Muscular Dystrophies; Peripheral Nervous System Diseases; Phenotype; Phosphorylation; Proto-Oncogene Proteins c-akt; Regeneration; Survival Analysis

The present study was undertaken to investigate changes in the muscle fiber when treated with calcium ionophore. Muscles treated with ionophore showed disruption of the plasma membrane of the muscle fiber, delta lesions, marked contraction of the myofibrills, and dissolution of Z lines and I bands. Black granules of calcium pyroantimonate were observed inside the plasma membrane in ionophore-treated muscle fibers without alteration of the other muscle organelles. The density of the intramembranous particles was less in muscle treated with calcium ionophore than in the control muscle. These results support the previous hypothesis that the increased concentration of intracellular calcium activates calcium-activated neutral protease and induces necrosis of the myofiber. The mechanism for the decrease in the density of intramembranous particles is unsolved. However, the disruption of the plasma membrane may not be a direct effect of calcium ionophore on it, but a secondary phenomenon which occurs after the calcium-induced necrosis of the muscle fibers.

Topics: Animals; Calcimycin; Calcium; Cell Membrane; Creatine Kinase; Female; Freeze Fracturing; Leupeptins; Microscopy, Electron; Muscles; Muscular Dystrophies; Rats; Rats, Inbred Strains