Electrical Stimulation Induces Calcium-dependent Up-regulation of Neuregulin-1β in Dystrophic Skeletal Muscle Cell Lines

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-1 beta (NRG-1 beta) 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 Ca2+ and PKC isoforms on NRG-1 beta expression in dystrophic myotubes. Electrical stimulation of RCDMD increased NRG-1 beta mRNA and protein levels, and mRNA enhancement was abolished by actinomycin D. NRG-1 beta transcription was inhibited by BAPTA-AM, an intracellular Ca2+ chelator, and by inhibitors of IP3-dependent slow Ca2+ transients, like 2-APB, Ly 294002 and Xestospongin B. Ryanodine, a fast Ca2+ signal inhibitor, had no effect on electrical stimulation-induced expression. BIM VI (general inhibitor of PKC isoforms) and Go 6976 (specific inhibitor of Ca2+-dependent PKC isoforms) abolished NRG-1 beta mRNA induction. Our results suggest that depolarization induced slow Ca2+ signals stimulate NRG-1 beta transcription in RCDMD cells, and that Ca2+-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. Copyright (C) 2012 S. Karger AG, Basel