Low-dose Simvastatin Increases Skeletal Muscle Sensitivity to Caffeine and Halothane

Area of Science:

• Biochemistry
• Pharmacology
• Cell Biology

Background:

• Statins, like simvastatin, are widely prescribed cholesterol-lowering drugs.
• Myotoxicity is a known side effect of statin therapy.
• Skeletal muscle sensitivity to anesthetic agents like halothane and caffeine can be affected by various conditions.

Purpose of the Study:

• To investigate the impact of simvastatin-induced myotoxicity on skeletal muscle sensitivity to caffeine and halothane.
• To explore the underlying mechanisms related to intracellular calcium handling.

Main Methods:

• Primary cultured neonate rat skeletal myotubes were exposed to varying concentrations of simvastatin (0.01-5.0 μmol/L).
• Cellular viability, morphology, and microstructure were assessed.
• Intracellular calcium concentrations ([Ca2+]i) and responses to caffeine and halothane were measured using fluorescence calcium imaging.

Main Results:

• Simvastatin decreased myotube viability and altered cellular structure in a dose-dependent manner.
• Low-dose simvastatin (0.01 μmol/L) increased sensitivity to high-dose caffeine and halothane, linked to increased sarcoplasmic reticulum Ca2+ storage.
• High-dose simvastatin (1.0-5.0 μmol/L) decreased sensitivity to caffeine and halothane, correlating with greater myotube damage.

Conclusions:

• Simvastatin's myotoxic effects modify skeletal muscle sensitivity to high-dose caffeine and halothane.
• Low simvastatin doses increase sensitivity via enhanced Ca2+ storage, potentially explaining positive caffeine-halothane contracture tests in statin myopathy.
• Severe myotube damage from higher simvastatin doses leads to reduced sensitivity, possibly increasing risks like rhabdomyolysis during anesthesia.