Evaluation of the effect of LMP-420, an inhibitor of the tumor necrosis factor alpha (TNF-alpha) transcription, in mdx mice submitted to physical activity and in myoblasts and mast cells culture

• Grant number: 07/02855-2
• Support Opportunities: Regular Research Grants
• Start date: October 01, 2007
• End date: September 30, 2009
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: Maria Cristina Ramos Costa
• Grantee: Maria Cristina Ramos Costa
• Host Institution: Universidade de Ribeirão Preto (UNAERP). Campus Ribeirão Preto. Ribeirão Preto , SP, Brazil

Abstract

Duchenne Muscular Dystrophy (DMD) is a degenerative disorder caused by mutations in the gene of dystrophin, a subsarcolemmal protein important to connect actin cytoskeleton to the extracellular matrix. DMD is characterized by muscular weakness resulting from skeletal muscle progressive degeneration and culminates in early death by cardiac or respiratory failure. The mdx mouse, the most utilized DMD model, shows susceptibility to injury, increase of serum creatine kinase levels and muscular degeneration and regeneration cycles. The milder phenotype, when compared to DMD, can be intensified by compulsory physical activity. Muscular degeneration, initially caused by sarcolemma fragility due to dystrophin absence, is exacerbated by a chronic inflammatory process, with the participation of immune cells and inflammatory cytokines. Among them, the tumor necrosis factor alpha (TNF-alpha), which is released by mast cells and injured myofibers, has a key role. Recent studies have shown that the blockage of TNF-alpha, using monoclonal antibodies and a soluble receptor, results in diminished muscular degeneration in the mdx mouse. The objective of this project is to evaluate the effect of LMP-420, a recently developed inhibitor of TNF-alphatranscription, in mdx mice submitted to physical activity and in mast cells and myoblasts cell culture. To this end, 4 week old mdx mice, subcutaneously treated or not treated with 25 mg/kg/day LMP-420, will be submitted to compulsory activity for 5 weeks. The extension of the muscular inflammatory process will be evaluated by serum creatine kinase dosage and quantitative histopathological analyses of gastrocnemius and diaphragm, using the following parameters: the relative muscular area containing inflammatory cells, the proportion of non peripherally nucleated myofibers, the relative area of myofibers with sarcolemmal injury and the relative area of grouped regenerating myofibers. The LMP-420 inhibitory effect on the TNF-alphatranscription will be evaluated by comparative RT-PCR and western blot analyses of the gastrocnemius and diaphragm and also in myoblasts and mast cells in culture. The therapy for DMD is still limited and consists mainly on the use of corticosteroids, with intense adverse effects. The research of novel compounds with systemic and specific action – as LMP-420 – which can stop or retard dystrophinopathy progression is of fundamental importance and can benefit the present generation of boys affected by DMD. (AU)