title: Electrical stimulation induces calcium-dependent up-regulation of neuregulin-1β in dystrophic skeletal muscle cell lines.
abstract: Duchenne muscular dystrophy (DMD) is a neuromuscular disease originated by reduced or no expression of dystrophin, a cytoskeletal protein that provides structural integrity to muscle fibres. A promising pharmacological treatment for DMD aims to increase the level of a structural dystrophin homolog called utrophin. Neuregulin-1 (NRG-1), a growth factor that potentiates myogenesis, induces utrophin expression in skeletal muscle cells. Microarray analysis of total gene expression allowed us to determine that neuregulin-1β (NRG-1β) is one of 150 differentially expressed genes in electrically stimulated (400 pulses, 1 ms, 45 Hz) dystrophic human skeletal muscle cells (RCDMD). We investigated the effect of depolarization, and the involvement of intracellular Ca(2+) and PKC isoforms on NRG-1β expression in dystrophic myotubes. Electrical stimulation of RCDMD increased NRG-1β mRNA and protein levels, and mRNA enhancement was abolished by actinomycin D. NRG-1β transcription was inhibited by BAPTA-AM, an intracellular Ca(2+) chelator, and by inhibitors of IP(3)-dependent slow Ca(2+) transients, like 2-APB, Ly 294002 and Xestospongin B. Ryanodine, a fast Ca(2+) signal inhibitor, had no effect on electrical stimulation-induced expression. BIM VI (general inhibitor of PKC isoforms) and Gö 6976 (specific inhibitor of Ca(2+)-dependent PKC isoforms) abolished NRG-1β mRNA induction. Our results suggest that depolarization induced slow Ca(2+) signals stimulate NRG-1β transcription in RCDMD cells, and that Ca(2+)-dependent PKC isoforms are involved in this process. Based on utrophin's ability to partially compensate dystrophin disfunction, knowledge on the mechanism involved on NRG-1 up-regulation could be important for new therapeutic strategies design.
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Independencia 1027, Santiago, Chile. njuretic@med.uchile.cl
authors.forename: Nevenka
authors.initials: N
authors.lastname: Juretić
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Jorquera
authors.forename: Pablo
authors.initials: P
authors.lastname: Caviedes
authors.forename: Enrique
authors.initials: E
authors.lastname: Jaimovich
authors.forename: Nora
authors.initials: N
authors.lastname: Riveros
mesh_terms: D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D017931:DNA Primers; D004558:Electric Stimulation; D020869:Gene Expression Profiling; D006801:Humans; D018482:Muscle, Skeletal; D009136:Muscular Dystrophies / Q000473:pathology*; D020890:Neuregulin-1 / Q000235:genetics / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D017931:DNA Primers; C094131:NRG1 protein, human; D020890:Neuregulin-1; D002118:Calcium