Stretch-induced force deficits in murine extensor digitorum longus muscles after cardiotoxin injection

Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models

Skeletal muscle injuries occur frequently in daily life and exercise. Understanding the mechanisms of regeneration is critical for accelerating the repair and regeneration of muscle. Therefore, this article reviews knowledge on the mechanisms of skeletal muscle regeneration after cardiotoxin-induced injury. The process of regeneration is similar in different mouse strains and is inhibited by aging, obesity, and diabetes. Exercise, microcurrent electrical neuromuscular stimulation, and mechanical loading improve regeneration. The mechanisms of regeneration are complex and strain-dependent, and changes in functional proteins involved in the processes of necrotic fiber debris clearance, M1 to M2 macrophage conversion, SC activation, myoblast proliferation, differentiation and fusion, and fibrosis and calcification influence the final outcome of the regenerative activity.

Chronic administration of a leupeptin-derived calpain inhibitor fails to ameliorate severe muscle pathology in a canine model of duchenne muscular dystrophy

Calpains likely play a role in the pathogenesis of Duchenne muscular dystrophy (DMD). Accordingly, calpain inhibition may provide therapeutic benefit to DMD patients. In the present study, we sought to measure benefit from administration of a novel calpain inhibitor, C101, in a canine muscular dystrophy model. Specifically, we tested the hypothesis that treatment with C101 mitigates progressive weakness and severe muscle pathology observed in young dogs with golden retriever muscular dystrophy (GRMD). Young (6-week-old) GRMD dogs were treated daily with either C101 (17 mg/kg twice daily oral dose, n = 9) or placebo (vehicle only, n = 7) for 8 weeks. A battery of functional tests, including tibiotarsal joint angle, muscle/fat composition, and pelvic limb muscle strength were performed at baseline and every 2 weeks during the 8-week study. Results indicate that C101-treated GRMD dogs maintained strength in their cranial pelvic limb muscles (tibiotarsal flexors) while placebo-treated dogs progressively lost strength. However, concomitant improvement was not observed in posterior pelvic limb muscles (tibiotarsal extensors). C101 treatment did not mitigate force drop following repeated eccentric contractions and no improvement was seen in the development of joint contractures, lean muscle mass, or muscle histopathology. Taken together, these data do not support the hypothesis that treatment with C101 mitigates progressive weakness or ameliorates severe muscle pathology observed in young dogs with GRMD.

Biomimetic affinity purification of cardiotoxin and its pharmacological effects on the nervous system

Cobra venom is a very precious natural resource. The traditional method for purification of cardiotoxin from cobra venom is a multi-step, high cost, and low recovery procedure. By molecular modeling and docking with SYBYL software, we designed and synthesized an affinity ligand, m-aminobenzoic acid, for high efficiency purification of this therapeutically useful Chinese cobra venom cardiotoxin. The one-step recovery of cardiotoxin reached 64% and the purity reached 92% upon purification. The binding capacity of this synthetic ligand was 9.1 mg cardiotoxin/g moist weight gel and the affinity constant for cardiotoxin was 5.5 x 10(3) M(-1). Unlike a natural affinity ligand, this synthetic ligand is highly stable, and has great potential for industrial scale production of cardiotoxin. In addition, we examined the effects of cardiotoxin on the nervous system in a mouse model. Results showed that cardiotoxin could maintain analgesic effects for 120 min with a dose of less than 0.06 mg/kg (2.8% of the LD(50)). Administration of 0.12 mg/kg cardiotoxin could improve scopolamine impairments of memory in mice. These results suggest that cardiotoxin may be a potential drug for nervous system diseases.