title: Electrical stimuli are anti-apoptotic in skeletal muscle via extracellular ATP. Alteration of this signal in Mdx mice is a likely cause of dystrophy.
abstract: ATP signaling has been shown to regulate gene expression in skeletal muscle and to be altered in models of muscular dystrophy. We have previously shown that in normal muscle fibers, ATP released through Pannexin1 (Panx1) channels after electrical stimulation plays a role in activating some signaling pathways related to gene expression. We searched for a possible role of ATP signaling in the dystrophy phenotype. We used muscle fibers from flexor digitorum brevis isolated from normal and mdx mice. We demonstrated that low frequency electrical stimulation has an anti-apoptotic effect in normal muscle fibers repressing the expression of Bax, Bim and PUMA. Addition of exogenous ATP to the medium has a similar effect. In dystrophic fibers, the basal levels of extracellular ATP were higher compared to normal fibers, but unlike control fibers, they do not present any ATP release after low frequency electrical stimulation, suggesting an uncoupling between electrical stimulation and ATP release in this condition. Elevated levels of Panx1 and decreased levels of Cav1.1 (dihydropyridine receptors) were found in triads fractions prepared from mdx muscles. Moreover, decreased immunoprecipitation of Cav1.1 and Panx1, suggest uncoupling of the signaling machinery. Importantly, in dystrophic fibers, exogenous ATP was pro-apoptotic, inducing the transcription of Bax, Bim and PUMA and increasing the levels of activated Bax and cytosolic cytochrome c. These evidence points to an involvement of the ATP pathway in the activation of mechanisms related with cell death in muscular dystrophy, opening new perspectives towards possible targets for pharmacological therapies.
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Denisse
authors.initials: D
authors.lastname: Valladares
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Almarza
authors.forename: Ariel
authors.initials: A
authors.lastname: Contreras
authors.forename: Mario
authors.initials: M
authors.lastname: Pavez
authors.forename: Sonja
authors.initials: S
authors.lastname: Buvinic
authors.forename: Enrique
authors.initials: E
authors.lastname: Jaimovich
authors.forename: Mariana
authors.initials: M
authors.lastname: Casas
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics; D000072224:Bcl-2-Like Protein 11; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D017630:Connexins / Q000378:metabolism; D004558:Electric Stimulation; D008565:Membrane Proteins / Q000235:genetics; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D009136:Muscular Dystrophies / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000235:genetics; D051028:bcl-2-Associated X Protein / Q000235:genetics
chemical_list: D051017:Apoptosis Regulatory Proteins; C494827:Bax protein, mouse; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; C529218:CACNA1S protein, mouse; D020746:Calcium Channels, L-Type; D017630:Connexins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C488588:PUMA protein, mouse; C503631:Panx1 protein, mouse; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D051028:bcl-2-Associated X Protein; D000255:Adenosine Triphosphate; D002118:Calcium