Biphasic Regulation of Intracellular Calcium by Gemfibrozil Contributes to Inhibiting L6 Myoblast Differentiation: Implications for Clinical Myotoxicity

Abstract

Gemfibrozil is the most myotoxic fibrate drug commonly used for dyslipidemia, but the mechanism is poorly understood. The current study revealed that gemfibrozil inhibits myoblast differentiation through the regulation of intracellular calcium ([Ca(2+)]i) as revealed in L6 myoblasts by use of laser scan confocal microscopy and flow cytometry using Fluo-4 AM as a probe. Gemfibrozil at 20-400 μM, could regulate [Ca(2+)]i in L6 cells in a biphasic manner, and sustained reduction was observed when the concentration reached 200 μM. Inhibition of L6 differentiation by gemfibrozil was concentration-dependent with maximal effect noted between 200 and 400 μM, as indicated by creatine kinase activities and the differentiation index, respectively. In differentiating L6 myoblasts, gemfibrozil at concentrations below 400 μM led to no significant signs of apoptosis or cytotoxicity, whereas differentiation, inhibited by 200 μM gemfibrozil, was only partially recovered. A good correlation was noted between gemfibrozil concentrations that regulate [Ca(2+)]i and inhibit L6 myoblasts differentiation, and both are within the range of total serum concentrations found in the clinic. These data suggest a potential pharmacodynamic effect of gemfibrozil on myogenesis as a warning sign, in addition to the complex pharmacokinetic interactions. It is also noteworthy that mobilization of [Ca(2+)]i by gemfibrozil may trigger complex biological responses besides myocyte differentiation. Information revealed in this study explores the mechanism of gemfibrozil-induced myotoxicity through the regulation of intracellular calcium.

Functional KCa1.1 channels are crucial for regulating the proliferation, migration and differentiation of human primary skeletal myoblasts

“…To record the basal intracellular calcium levels and the effects of paxilline in large cell population for a prolonged duration, we recorded continuously by FCM. 21, 22 DM1 myoblasts displayed a significantly higher Indo-1 ratio than normal myoblasts (Figure 2a). Blocking KCa1.1 with paxilline induced an increase in intracellular calcium levels in normal myoblasts and to a lower extent in DM1 myoblasts (Figure 2b).…”

Gemfibrozil disrupts lysophosphatidylcholine and bile acid homeostasis via PPARα and its relevance to hepatotoxicity

“…Abnormally regulated lipid metabolism, high systemic exposure, and differential PPARa abundance in skeletal muscle have been speculated as possible mechanisms (Marcoff and Thompson 2007). Recent studies found that gemfibrozil-induced disturbances in intracellular calcium concentrations and inhibition of myocyte differentiation might play an important role in myotoxicity (Liu et al 2011a, 2012). However, the most common clinically observed toxic reactions with gemfibrozil were cholestatic jaundice and cholelithiasis, especially in patients with a history of gallbladder disease (Roglans et al 2004; Hajdu et al 2009).…”

The PPAR alpha agonist gemfibrozil is an ineffective treatment for spinal cord injured mice

“…Interestingly, several studies have documented a deleterious effect of PPARα activation on myocytes. PPARα-induced myotoxicity has been detected in both human and rat cells in vitro and in a primate in vivo model (Johnson et al, 2005; Liu et al, 2009; Liu et al, 2011; Zhao et al, 2010). Similar to the mice in Study I, primates treated with gemfibrozil displayed significant behavioral deficits.…”