calpain and Peripheral-Nerve-Injuries

Calpain 3 (CAPN3), also known as p94, is a skeletal muscle-specific member of the calpain family that is involved in muscular dystrophy; however, the roles of CAPN3 in muscular atrophy and regeneration are yet to be understood. In the present study, we attempted to explain the effect of CAPN3 in muscle atrophy by evaluating CAPN3 expression in rat gastrocnemius muscle following reversible sciatic nerve injury. After nerve injury, the wet weight ratio and cross sectional area (CSA) of gastrocnemius muscle were decreased gradually from 1-14 days and then recovery from 14-28 days. The active form of CAPN3 (~62 kDa) protein decreased slightly on day 3 and then increased from day 7 to 14 before a decrease from day 14 to 28. The result of linear correlation analysis showed that expression of the active CAPN3 protein level was negatively correlated with muscle wet weight ratio. CAPN3 knockdown by short interfering RNA (siRNA) injection improved muscle recovery on days 7 and 14 after injury as compared to that observed with control siRNA treatment. Depletion of CAPN3 gene expression could promote myoblast differentiation in L6 cells. Based on these findings, we conclude that the expression pattern of the active CAPN3 protein is linked to muscle atrophy and regeneration following denervation: its upregulation during early stages may promote satellite cell renewal by inhibiting differentiation, whereas in later stages, CAPN3 expression may be downregulated to stimulate myogenic differentiation and enhance recovery. These results provide a novel mechanistic insight into the role of CAPN3 protein in muscle regeneration after peripheral nerve injury.

Topics: Animals; Calpain; Cell Differentiation; Cell Line; Disease Models, Animal; Gene Expression Regulation; Gene Knockdown Techniques; Isoenzymes; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy; Myoblasts; MyoD Protein; Peripheral Nerve Injuries; Rats; Regeneration; RNA, Messenger; RNA, Small Interfering; Sciatic Neuropathy

Muscle atrophy is a disease that is usually caused by denervation. The aim of the present study was to determine whether electrical stimulation by semi-implantable electrodes is capable of decreasing the levels of specific proteins associated with sciatic nerve injury-induced muscle atrophy. Male Sprague Dawley (SD) rats with damaged sciatic nerves were maintained on a 12‑h light/dark cycle. Thirty-two SD rats were randomly allocated into 4 groups (each group, n=8). The rats in group C received no electrical stimulation; the rats in groups D, N and DN received electrical stimulation by semi-implantable electrodes during the daytime alone, nighttime alone and both the daytime and nighttime, respectively. Immunoblot assays were performed to detect the expression of cellular proteins associated with muscle atrophy. The number of muscle satellite cells was determined using a microscope, indicating that electrical stimulation increased the number of muscle satellite cells. Immunoblot assay results showed that electrical stimulation reduced the expression levels of cathepsin L, calpain 1 and the ubiquitinated muscle ring finger‑1 (MuRF-1) protein. In conclusion, electrical stimulation by semi-implantable electrodes constitutes a potential method for the treatment of sciatic nerve injury-induced muscle atrophy. The decreased expression levels of the cellular proteins cathepsin L and calpain 1, as well as the ubiquitinated protein MuRF-1, are associated with the attenuation of sciatic nerve injury-induced muscle atrophy.

Topics: Animals; Body Weight; Calpain; Cathepsin L; Electric Stimulation; Electrodes, Implanted; Male; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy; Organ Size; Peripheral Nerve Injuries; Rats; Satellite Cells, Skeletal Muscle; Sciatic Neuropathy; Tripartite Motif Proteins; Ubiquitin-Protein Ligases; Ubiquitinated Proteins