Membrane depolarization induces calcium-dependent upregulation of Hsp70 and Hmox-1 in skeletal muscle cells

Heat shock proteins (HSPs) are a conserved family of cytoprotective polypeptides, synthesized by cells in response to stress. Hsp70 and heme oxygenase 1 (Hmox-1) are induced by a variety of cellular stressors in skeletal muscle, playing a role in long-term adaptations and muscle fibers regeneration. Though HSPs expression after exercise has been intensely investigated, the molecular mechanisms concerning Hsp70 and Hmox-1 induction are poorly understood. The aim of this work was to investigate the involvement of calcium in Hsp70 and Hmox-1 expression upon depolarization of skeletal muscle cells. We observed that depolarization of myotubes increased both mRNA levels and protein expression for Hsp70 and Hmox-1. Stimulation in the presence of intracellular calcium chelator BAPTA-AM resulted in a complete inhibition of Hsp70-induced expression. It is known that inositol-1,4,5-trisphophate (IP3)- mediated slow Ca2+ transients, evoked by membrane depolarization, are involved in the regulatio

Differential gene expression in skeletal muscle cells after membrane depolarization

Skeletal muscle is a highly plastic tissue with a remarkable capacity to adapt itself to challenges imposed by contractile activity. Adaptive response, that include hypertrophy and activation of oxidative mechanisms have been associated with transient changes in transcriptional activity of specific genes. To define the set of genes regulated by a depolarizing stimulus, we used 22 K mouse oligonucleotide microarrays. Total RNA from C2C12 myotubes was obtained at 2, 4, 18, and 24 h after high K+ stimulation. cDNA from control and depolarized samples was labeled with cyanine 3 or 5 dyes prior to microarray hybridization. Loess normalization followed by statistical analysis resulted in 423 differentially expressed genes using an unadjusted P-value ≤0.01 as cut off. Depolarization affects transcriptional activity of a limited number of genes, mainly associated with metabolism, cell communication and response to stress. A number of genes related to Ca 2+ signaling pathways are induced at 4

Interleukin-6 and neuregulin-1 as regulators of utrophin expression via the activation of NRG-1/ErbB signaling pathway in mdx cells

© 2016 Elsevier B.V. Duchenne muscular dystrophy (DMD) is a neuromuscular disease originated by mutations in the dystrophin gene. A promising therapeutic approach deals with functional substitution of dystrophin by utrophin, a structural homolog that might be able to compensate dystrophin absence in DMD muscle fibers. It has been described that both interleukin-6 (IL-6) and neuregulin-1 (NRG-1; Heregulin-HRG) induce utrophin expression in skeletal muscle. We investigated a possible functional link among IL-6, NRG-1 and utrophin, in normal (C57) and dystrophic (mdx) skeletal muscle cells. Western Blot analysis allowed us to demonstrate that IL-6 (100 ng/mL) induces NRG-1 receptor phosphorylation (ErbB2/ErbB3) in both cell types, in a process that depends on intracellular Ca2 + and metalloproteinase activity; it also induces a transient increase of ERK1 and GABPα phosphorylation only in dystrophic myotubes. Semiquantitative PCR showed that IL-6 treatment increases utrophin mRNA levels j

Abnormal distribution of inositol 1,4,5-trisphosphate receptors in human muscle can be related to altered calcium signals and gene expression in Duchenne dystrophy-derived cells

Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) drive calcium signals involved in skeletal muscle excitation-transcription coupling and plasticity; IP3R subtype distribution and downstream events evoked by their activation have not been studied in human muscle nor has their possible alteration in Duchenne muscular dystrophy (DMD). We studied the expression and localization of IP3R subtypes in normal and DMD human muscle and in normal (RCMH) and dystrophic (RCDMD) human muscle cell lines. In normal muscle, both type 1 IP3Rs (IP3R1) and type 2 IP3Rs (IP3R2) show a higher expression in type II fibers, whereas type 3 IP3Rs (IP3R3) show uniform distribution. In DMD biopsies, all fibers display a homogeneous IP3R2 label, whereas 24 ± 7% of type II fibers have lost the IP3R1 label. RCDMD cells show 5-fold overexpression of IP3R2 and down-regulation of IP3R3 compared with RCMH cells. A tetanic stimulus induces IP 3-dependent slow Ca2+ transients significantly larger and faster in RCDMD c