HMGB1 expression and muscle regeneration in idiopathic inflammatory myopathies and degenerative joint diseases.

The High-Mobility Group Box 1 protein (HMGB1) is a known nuclear protein which may be released from the nucleus into the cytoplasm and the extracellular space. It is believed that the mobilized HMGB1 plays role in the autoimmune processes as an alarmin, stimulating the immune response. In addition, muscle regeneration and differentiation may also be altered in the inflammatory surroundings.

Fluvastatin-induced alterations of skeletal muscle function in hypercholesterolaemic rats.

Although statins, the most widely used drugs in the treatment of hyperlipidaemia, are generally accepted as efficient and safe drugs their side-effects on skeletal muscle have been reported with increasing frequency. The lack of an animal model in which these side effects would consistently be observed is one of the important drawbacks in studying statin associated myopathy. To overcome this and enable the studying of the effects of fluvastatin on skeletal muscles an animal model with high blood cholesterol levels was developed.

Contribution from P2X and P2Y purinoreceptors to ATP-evoked changes in intracellular calcium concentration on cultured myotubes.

Although the alteration of purinoreceptor pattern on skeletal muscle is known to accompany physiological muscle differentiation and the pathogenesis of muscle dystrophy, the exact identity of and the relative contribution from the individual receptor subtypes to the purinergic signal have been controversial. To identify these subtypes in cultured myotubes of 5-10 nuclei, changes in intracellular calcium concentration and surface membrane ionic currents were detected and calcium fluxes calculated after the application of the subtype-specific agonists 2'3'-O-(benzoyl-4-benzoyl)-ATP (BzATP), 2-methyltio-ADP and UTP. The effectiveness of these agonists together with positive immunocytochemical staining revealed the presence of P2X(4), P2X(5), P2X(7), P2Y(1) and P2Y(4) receptors.

Differentiation-dependent alterations in the extracellular ATP-evoked calcium fluxes of cultured skeletal muscle cells from mice.

Although extracellular adenosine triphosphate (ATP) has been generally accepted as the regulator of cellular differentiation, the relative contribution of the various purinoreceptor subtypes to purinergic signalling at distinct stages of skeletal muscle differentiation is still poorly understood. Here we measured extracellular ATP-evoked changes in intracellular calcium concentration and surface membrane ionic currents (I (ATP)), calculated the calcium flux (FL) entering the myoplasmic space and compared these parameters at different stages of differentiation on cultured mouse myotubes. The ATP-evoked FL displayed an early peak and then declined to a steady level.

Differential effects of maurocalcine on Ca2+ release events and depolarization-induced Ca2+ release in rat skeletal muscle.

Maurocalcine (MCa), a 33 amino acid toxin obtained from scorpion venom, has been shown to interact with the isolated skeletal-type ryanodine receptor (RyR1) and to strongly modify its calcium channel gating. In this study, we explored the effects of MCa on RyR1 in situ to establish whether the functional interaction of RyR1 with the voltage-sensing dihydropyridine receptor (DHPR) would modify the ability of MCa to interact with RyR1. In developing skeletal muscle cells the addition of MCa into the external medium induced a calcium transient resulting from RyR1 activation and strongly inhibited the effect of the RyR1 agonist chloro-m-cresol.