Role of prostaglandins in the proliferation and differentiation of C2C12 muscle cells, induced by a phospholipase A2 isolated from snake venom

Abstract

Muscle quiescent cells, called satellite cells, are crucial elements for the initiation of regeneration events after tissue injury. Once activated, these cells acquire the ability to proliferate and differentiate, until the formation of mature muscle fibers in a synchronized process and regulated by transcription factors. Studies in vivo experimental models have demonstrated that the process of muscle regeneration is accompanied by an inflammatory response characterized by leukocyte influx and release of inflammatory mediators. Among these mediators, the best characterized are cytokines, whose role is related to the quality of muscle regeneration. Given the complexity of the inflammatory response, the role of another set of important mediators, the metabolites derived from arachidonic acid (AA) metabolism, such as prostaglandins, has not been fully elucidated. It is now known that some prostaglandins (PG), such as PGE2, PGI2 and PGJ2, when added to the culture of quiescent muscle cells, can activate or inhibit their proliferation and differentiation. However, it is still unknown that, in addition to leukocytes, the satellite cells themselves have the ability to release these mediators, in order to initiate the process of cell proliferation and differentiation. On the other hand, phospholipases A2 (PLA2s) hydrolyze membrane phospholipids releasing AA. Its metabolism by cyclooxygenases (COX) -1 and COX-2, originates prostaglandins, important second physiological messengers and mediators of inflammatory processes. On the other hand, snake venom PLA2s, such as CB, isolated from Crotalus durissus terrificus snake venom, show structural homology with PLA2s from mammalian group IIA and generally trigger local effects such as myotoxicity, accompanied by reaction Inflammatory. Among the experimental models used in the study of the muscular regenerative process, these secretory PLA2s are useful tools to induce muscle degeneration accompanied by a well-established tissue regeneration pattern, although the effect of these PLA2s on isolated satellite cells is still unknown. Thus, the present study aims to investigate the action of CB on mice satellite cells (C2C12 line) in culture in the presence or absence of inhibitors of COX isoforms and analyzed for: I) cell proliferation and differentiation; II) expression of transcription factors PAX-7, MyoD and MRF-4; III) expression of COX-1 and -2; IV) the release of PGE2, PGI2, PGJ2. The better characterization of the regulation of cell proliferation and differentiation processes, triggered by a muscle injury, by PLA2s and prostaglandins, will increase the knowledge of the role of the inflammatory response in the degenerative and regenerative events of skeletal muscle tissue. Also, clarifying the influence of prostaglandins in these processes may contribute to the identification of new therapeutic targets and the development of more promising therapies for the efficient repair of muscle tissue after injury. (AU)