Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by sustained synovitis. Moreover, this disease is primarily characterized by joint pain, swelling, stiffness, and accompanied by skeletal muscle wasting. Patients with RA suffer from loss of skeletal muscle mass or rheumatoid cachexia, which includes wasting of skeletal muscle tissue. Although the mechanism for the cause is still unknown, it is likely that elevated levels of pro-inflammatory mediators, in particular the cytokines, constitute one of the leading causes of rheumatoid wasting of skeletal muscle. Proliferation and differentiation of muscle quiescent cells (satellite cells) are essential steps for the beginning of muscular tissue regeneration after injury. C2C12 myoblasts have been recognized as relevant tools to study the molecular mechanisms involved in proliferation and differentiation of satellite cells in the process of muscle regeneration. In this context, Lopap (Lonomia obliqua prothrombin activator protein), isolated from bristles of Lonomia obliqua caterpillar, belongs to the lipocalins family. The recombinant form (rLopap) presents pro-coagulant activity, acts directly on the endothelium promoting antiapoptotic effects and increases the expression of molecules involved in tissue remodeling. In addition, Losac (Lonomia obliqua Stuart factor activator) is the first factor X activator purified from a lepidopter secretion. Studies using the native and the recombinant form (rLosac) revealed specificity toward factor X. Besides its role on coagulation, Losac induces proliferation and inhibits death of endothelial cells under stress condition. It also stimulates the release of NO (antiapoptotic activity) and t-PA, a component of fibrinolytic-pathway involved in matrix remodeling. Therefore, they constitute interesting molecules to be explored as potentially active agents in the process of muscle regeneration. This study objectives the identification of potentially novel molecular targets related to muscle regeneration by investigating (1) the effect of hemolin (rLOSAC), lipocalin (rLOPAP) and LOPAP- derived peptides E8, P4, P4CPP, P8 and LOSAC-derived peptides P2, D1, D3 and other venom molecules on proliferation and differentiation of C2C12 myoblast cells stimulated with TNF-± or IL-1², (2) the role of pro- and anti-inflammatory mediators on proliferation and differentiation of C2C12 myoblast cells and (3) the signaling pathways involved in these events.
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