Statins, the cholesterol-lowering drugs cause myotoxicity through phospholipase D-mediated lipid signaling in skeletal C2C12 myoblast cells
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Date
2015-05
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The Ohio State University
Abstract
Cardiovascular diseases (CVDs) are among the leading causes of mortality in the US and worldwide. Cholesterol at high levels in circulation has been established as a major risk factor for CVDs in humans. Statins, the cholesterol-lowering drugs, have been widely used for lowering and controlling the endogenous levels of cholesterol to prevent or treat CVDs. Statins lower cholesterol by inhibiting 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase), the rate-limiting enzyme in the biosynthetic pathway of endogenous cholesterol. On the other hand, statins are known to cause skeletal muscle damage (myotoxicity and myalgia) in humans while administered to lower the circulating cholesterol levels for the treatment of CVDs. However, the mechanisms and treatment of statin-induced myotoxicity and myalgia are not thoroughly established. Phospholipase D (PLD), a membrane phospholipid-hydrolyzing enzyme is ubiquitous and involved in mediating lipid signaling in mammalian cells including the skeletal muscle cells (myocytes). Therefore, we hypothesized that statins would mediate skeletal muscle myocyte damage through activation of the PLD-mediated lipid signaling, and inhibition of PLD activation would protect against the statin-induced myotoxicity. In order to test our hypothesis, we used the well-established C2C12 mouse skeletal muscle myoblast cell line and studied the PLD activation and cytotoxicity in vitro induced by two different widely used statins (mevastatin and simvastatin) by the CVD patients. Our studies revealed that the statins caused dose-dependent (10-100 μM) and time-dependent (4-24 h) activation of PLD (as determined by the [32]P-labeling of cells and thin-layer chromatography of phosphatidylbutanol formation) and cytotoxicity and mitochondrial dysfunction (as determined by the release of intracellular lactate dehydrogenase, suppression of MTT reduction, and alterations in cell morphology) in the C2C12 myoblast cells. Our results also showed that cholesterol replenishment protected against the statin-induced toxicity to the C2C12 cells. Furthermore, our results showed that the novel PLD-specific inhibitor, 5-fluoro-2-indolyl des-chlorohalopemide (FIPI) inhibited the statin-induced PLD activation and cytotoxicity in the C2C12 myoblast cells. For the first time, our current study demonstrated the role of endogenous cellular cholesterol depletion and PLD-mediated lipid signaling in the statin-induced skeletal muscle myocyte damage and emphasized the importance of PLD inhibition in attenuating the statin-induced myotoxicity and myalgia in CVD patients consuming statins to lower the elevated levels of endogenous cholesterol.
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Keywords
Statins, cardiovascular disease, cholesterol, phospholipase D, microbiology, pharmaceuticals