The muscle-specific ubiquitin ligase atrogin-1/MAFbx mediates statin-induced muscle toxicity
Jun-ichi Hanai, … , Vikas P. Sukhatme, Stewart H. Lecker
Jun-ichi Hanai, … , Vikas P. Sukhatme, Stewart H. Lecker
Published December 3, 2007; First published November 8, 2007
Citation Information: J Clin Invest. 2007;117(12):3940-3951. https://doi.org/10.1172/JCI32741.
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Categories: Research Article Cardiology

The muscle-specific ubiquitin ligase atrogin-1/MAFbx mediates statin-induced muscle toxicity

Abstract

Statins inhibit HMG-CoA reductase, a key enzyme in cholesterol synthesis, and are widely used to treat hypercholesterolemia. These drugs can lead to a number of side effects in muscle, including muscle fiber breakdown; however, the mechanisms of muscle injury by statins are poorly understood. We report that lovastatin induced the expression of atrogin-1, a key gene involved in skeletal muscle atrophy, in humans with statin myopathy, in zebrafish embryos, and in vitro in murine skeletal muscle cells. In cultured mouse myotubes, atrogin-1 induction following lovastatin treatment was accompanied by distinct morphological changes, largely absent in atrogin-1 null cells. In zebrafish embryos, lovastatin promoted muscle fiber damage, an effect that was closely mimicked by knockdown of zebrafish HMG-CoA reductase. Moreover, atrogin-1 knockdown in zebrafish embryos prevented lovastatin-induced muscle injury. Finally, overexpression of PGC-1α, a transcriptional coactivator that induces mitochondrial biogenesis and protects against the development of muscle atrophy, dramatically prevented lovastatin-induced muscle damage and abrogated atrogin-1 induction both in fish and in cultured mouse myotubes. Collectively, our human, animal, and in vitro findings shed light on the molecular mechanism of statin-induced myopathy and suggest that atrogin-1 may be a critical mediator of the muscle damage induced by statins.

Authors

Jun-ichi Hanai, Peirang Cao, Preeti Tanksale, Shintaro Imamura, Eriko Koshimizu, Jinghui Zhao, Shuji Kishi, Michiaki Yamashita, Paul S. Phillips, Vikas P. Sukhatme, Stewart H. Lecker

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Figure 9

PGC-1α expression reduces lovastatin-induced atrogin-1 expression and muscle damage in zebrafish embryos.

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PGC-1α expression reduces lovastatin-induced atrogin-1 expression and mu...
(A) Myosin heavy chain staining of representative zebrafish embryo somites following injection of 100 pg PGC-1α cDNA or vehicle in the presence or absence of 0.5 μM lovastatin for 12 hours (left box) or morpholino oligonucleotides against z–PGC-1α (right box). Note that suppression of atrogin-1 protects from statin-induced damage and that suppression of PGC-1α has a similar muscle phenotype as lovastatin treatment. Original magnification, ×200. (B) Quantitation of muscle damage. Classes of morphological phenotypes are as described in Figure 5. Note that at each lovastatin concentration, the injection of PGC-1α cDNA almost completely abolishes the damage caused by lovastatin. Number of embryos quantitated are 137, 112, 139, and 122 for the controls and 120, 103, 108, and 107 for the PGC-1α–injected embryos at the lovastatin concentrations of 0, 0.05, 0.5, and 1.0 μM, respectively. (C) Western blot of atrogin-1 following 0.5 μM, 12 hours lovastatin treatment in zebrafish embryos injected or not with 100 pg PGC-1α cDNA. (D) Muscle fiber diameter was measured following myosin heavy chain staining as described in Methods in embryos injected with atrogin-1 morpholinos or PGC-1α cDNA. At least 500 fibers were measured at each lovastatin concentration. Results were graphed as the ratio of mean experimental fiber size ± SEM/mean control fiber size ± SEM. Control fiber size: 7.58 ± 0.10 μM. (E) Mitochondrial function is diminished by lovastatin treatment of zebrafish embryos. Cells from zebrafish embryos treated with varying concentrations of lovastatin (0–1 μM) were stained with MitoTracker, and fluorescence intensity, reflecting mitochondrial function, was detected by fluorescence-activated cell sorting. Representative data of mean fluorescence intensity from 3 independent experiments are shown. (F) PGC-1α augments mitochondrial staining and protects against lovastatin’s effects in zebrafish embryos. Embryos were injected with PGC-1α cDNA as described in Methods, then treated with lovastatin (0.5 μM) for 24 hours. As in E, dispersed embryonic cells were stained with MitoTracker and detected by FACS. Data are presented as percentage of mean fluorescence intensity in vehicle-treated embryos.