title: Statins and PPARalpha agonists induce myotoxicity in differentiated rat skeletal muscle cultures but do not exhibit synergy with co-treatment.
abstract: Statins and fibrates (weak PPARalpha agonists) are prescribed for the treatment of lipid disorders. Both drugs cause myopathy, but with a low incidence, 0.1-0.5%. However, combined statin and fibrate therapy can enhance myopathy risk. We tested the myotoxic potential of PPAR subtype selective agonists alone and in combination with statins in a differentiated rat myotube model. A pharmacologically potent experimental PPARalpha agonist, Compound A, induced myotoxicity as assessed by TUNEL staining at a minimum concentration of 1 nM, while other weaker PPARalpha compounds, for example, WY-14643, Gemfibrozil and Bezafibrate increased the percentage of TUNEL-positive nuclei at micromolar concentrations. In contrast, the PPARgamma agonist Rosiglitazone caused little or no cell death at up to 10 muM and the PPARdelta ligand GW-501516 exhibited comparatively less myotoxicity than that seen with Compound A. An experimental statin (Compound B) and Atorvastatin also increased the percentage of TUNEL-positive nuclei and co-treatment with WY-14643, Gemfibrozil or Bezafibrate had less than a full additive effect on statin-induced cell killing. The mechanism of PPARalpha agonist-induced cell death was different from that of statins. Unlike statins, Compound A and WY-14643 did not activate caspase 3/7. In addition, mevalonate and geranylgeraniol reversed the toxicity caused by statins, but did not prevent the cell killing induced by WY-14643. Furthermore, unlike statins, Compound A did not inhibit the isoprenylation of rab4 or rap1a. Interestingly, Compound A and Compound B had differential effects on ATP levels. Taken together, these observations support the hypothesis that in rat myotube cultures, PPARalpha agonism mediates in part the toxicity response to PPARalpha compounds. Furthermore, PPARalpha agonists and statins cause myotoxicity through distinct and independent pathways.
authors.affiliation: Department of Safety Assessment, Merck Research Laboratories, WP45-319, Merck Research Laboratories, West Point, PA 19486, USA. Timothy_Johnson@merck.com
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Johnson
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Zhang
authors.forename: Shu
authors.initials: S
authors.lastname: Shi
authors.forename: Diane R
authors.initials: DR
authors.lastname: Umbenhauer
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D005343:Fibrinolytic Agents / Q000737:chemistry / Q000633:toxicity; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use / Q000633:toxicity*; D007473:Ion Channels; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D024101:Mitochondrial Proteins / Q000096:biosynthesis / Q000235:genetics; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology; D009135:Muscular Diseases / Q000139:chemically induced*; D032448:Myoblasts, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D047492:Peroxisome Proliferator-Activated Receptors / Q000819:agonists* / Q000235:genetics / Q000633:toxicity*; D011743:Pyrimidines / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D000077154:Rosiglitazone; D013844:Thiazoles / Q000633:toxicity; D045162:Thiazolidinediones / Q000737:chemistry / Q000633:toxicity; D013997:Time Factors; D000071246:Uncoupling Protein 2
chemical_list: D005343:Fibrinolytic Agents; C425931:GW 501516; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007473:Ion Channels; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D047492:Peroxisome Proliferator-Activated Receptors; D011743:Pyrimidines; D012333:RNA, Messenger; D013844:Thiazoles; D045162:Thiazolidinediones; D000071246:Uncoupling Protein 2; D000077154:Rosiglitazone; C006253:pirinixic acid; D000255:Adenosine Triphosphate