Protective effects of Ca2+ handling drugs against abnormal Ca2+ homeostasis and cell damage in myopathic skeletal muscle cells.
Deficiency of delta-sarcoglycan (delta-SG), a component of the dystrophin-glycoprotein complex (DGC), causes skeletal muscular dystrophy and cardiomyopathy in BIO14.6 hamsters. Here, we studied the involvement of abnormal Ca2+ homeostasis in muscle degeneration and the protective effect of drugs against Ca2+ handling proteins in vivo as well as in vitro. First, we characterized the properties of cultured myotubes from muscles of normal and BIO14.6 hamsters (30-60 days old). While there were no apparent differences in the levels of expression of various Ca2+ handling proteins (L-type Ca2+ channel, ryanodine receptor, SR-Ca2+ ATPase, and Na+/Ca2+ exchanger), muscle-specific proteins (contractile actin and acetylcholine receptor), or DGC member proteins except SGs, BIO14.6 myotubes showed a high degree of susceptibility to mechanical stressors, such as cyclic stretching and hypo-osmotic stress as compared to normal myotubes, as evidenced by marked increases in creatine phosphokinase (CK) release and bleb formation. BIO14.6 myotubes showed abnormal Ca2+ homeostasis characterized by elevated cytosolic Ca2+ concentration, frequent Ca2+ oscillation, and increased 45Ca2+ uptake. These abnormal Ca2+ events and CK release were significantly prevented by Ca2+ handling drugs, tranilast, diltiazem, and FK506. The calpain inhibitor E64 prevented CK release, but not 45Ca2+ uptake. Some of these drugs (tranilast, diltiazem, and FK506) also exerted a significant protective effect for muscle degeneration in BIO14.6 hamsters and mdx mice in vivo. These observations suggest that elevated Ca2+ entry through sarcolemmal Ca2+ channels predominantly contributes to muscle degeneration and that the drugs tested here may have novel therapeutic potential against muscular dystrophy.
Iwata
Yuko
Y
Department of Molecular Physiology, National Cardiovascular Center Research Institute, Fujishiro-dai 5-7-1, Suita, Osaka 565, Japan. yukoiwat@ri.ncvc.go.jp
Katanosaka
Yuki
Y
Shijun
Zhu
Z
Kobayashi
Yuko
Y
Hanada
Hironori
H
Shigekawa
Munekazu
M
Wakabayashi
Shigeo
S
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D003402:Creatine Kinase / Q000378:metabolism; D006224:Cricetinae; D006706:Homeostasis; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009136:Muscular Dystrophies / Q000188:drug therapy / Q000378:metabolism*; D049031:Sarcoglycans / Q000172:deficiency; D016559:Tacrolimus / Q000494:pharmacology; D062367:ortho-Aminobenzoates / Q000494:pharmacology
D015220:Calcium Channels; D049031:Sarcoglycans; D062367:ortho-Aminobenzoates; D003402:Creatine Kinase; C012293:tranilast; D002118:Calcium; D016559:Tacrolimus