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Inhibition of cholesterol synthesis by squalene synthase inhibitors does not induce myotoxicity in vitro.
Toxicol Appl Pharmacol. 1997 Jul; 145(1):91-8.TA

Abstract

The cholesterol-lowering HMG CoA reductase inhibitors (HMGRI), pravastatin and lovastatin, have been associated with skeletal myopathy in humans and in rats. In a previous in vitro study, HMGRI-induced changes in neonatal rat skeletal muscle cells were characterized by reversible inhibition of protein synthesis and loss of differentiated myotubes at concentrations markedly lower than those inducing enzyme leakage. Myotoxicity was determined to be directly related to inhibition of HMG CoA reductase, since mevalonate, the immediate product of HMG CoA reductase metabolism, abrogated the drug-induced changes. Farnesol, geranylgeraniol, and squalene are metabolites of mevalonate. Squalene, formed from farnesol by squalene synthase, is the first metabolite solely committed to cholesterol synthesis. In contrast, geranylgeraniol, formed by the addition of an isoprene group to farnesol, is the first metabolite uncommitted to cholesterol synthesis. The objective of the present study was to determine the role of inhibition of cholesterol synthesis in HMGRI-induced in vitro myotoxicity. HMGRI-treated neonatal rat skeletal muscle cultures were supplemented with farnesol and geranylgeraniol, and in another study, muscle cultures were exposed to two squalene synthase inhibitors (SSI), BMS-187745 and its prodrug ester, BMS-188494. Endpoints evaluated for both studies included protein synthesis ([3H]leucine incorporation), total cellular protein (a measure of cell loss), intra- and extracellular lactate dehydrogenase activity (a measure of membrane integrity), cholesterol biosynthesis ([14C]acetate incorporation), and morphology. HMG CoA reductase inhibitor-induced morphologic changes and inhibition of protein synthesis were significantly ameliorated by supplementation with farnesol and geranylgeraniol. In contrast to HMGRI-induced in vitro myotoxicity, SSI induced an irreversible, minimal cytotoxicity at close to maximum soluble concentrations. These results indicate that depletion of metabolites of geranylgeranyl pyrophosphate, and not inhibition of cholesterol synthesis, is the primary cause of HMG CoA reductase-induced myotoxicity.

Authors+Show Affiliations

Department of Experimental Pathology, Bristol-Myers Squibb Pharmaceutical Research Institute, Syracuse, New York 13057, USA. in_vitro@ix.netcom.comNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

9221828

Citation

Flint, O P., et al. "Inhibition of Cholesterol Synthesis By Squalene Synthase Inhibitors Does Not Induce Myotoxicity in Vitro." Toxicology and Applied Pharmacology, vol. 145, no. 1, 1997, pp. 91-8.
Flint OP, Masters BA, Gregg RE, et al. Inhibition of cholesterol synthesis by squalene synthase inhibitors does not induce myotoxicity in vitro. Toxicol Appl Pharmacol. 1997;145(1):91-8.
Flint, O. P., Masters, B. A., Gregg, R. E., & Durham, S. K. (1997). Inhibition of cholesterol synthesis by squalene synthase inhibitors does not induce myotoxicity in vitro. Toxicology and Applied Pharmacology, 145(1), 91-8.
Flint OP, et al. Inhibition of Cholesterol Synthesis By Squalene Synthase Inhibitors Does Not Induce Myotoxicity in Vitro. Toxicol Appl Pharmacol. 1997;145(1):91-8. PubMed PMID: 9221828.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Inhibition of cholesterol synthesis by squalene synthase inhibitors does not induce myotoxicity in vitro. AU - Flint,O P, AU - Masters,B A, AU - Gregg,R E, AU - Durham,S K, PY - 1997/7/1/pubmed PY - 1997/7/1/medline PY - 1997/7/1/entrez SP - 91 EP - 8 JF - Toxicology and applied pharmacology JO - Toxicol Appl Pharmacol VL - 145 IS - 1 N2 - The cholesterol-lowering HMG CoA reductase inhibitors (HMGRI), pravastatin and lovastatin, have been associated with skeletal myopathy in humans and in rats. In a previous in vitro study, HMGRI-induced changes in neonatal rat skeletal muscle cells were characterized by reversible inhibition of protein synthesis and loss of differentiated myotubes at concentrations markedly lower than those inducing enzyme leakage. Myotoxicity was determined to be directly related to inhibition of HMG CoA reductase, since mevalonate, the immediate product of HMG CoA reductase metabolism, abrogated the drug-induced changes. Farnesol, geranylgeraniol, and squalene are metabolites of mevalonate. Squalene, formed from farnesol by squalene synthase, is the first metabolite solely committed to cholesterol synthesis. In contrast, geranylgeraniol, formed by the addition of an isoprene group to farnesol, is the first metabolite uncommitted to cholesterol synthesis. The objective of the present study was to determine the role of inhibition of cholesterol synthesis in HMGRI-induced in vitro myotoxicity. HMGRI-treated neonatal rat skeletal muscle cultures were supplemented with farnesol and geranylgeraniol, and in another study, muscle cultures were exposed to two squalene synthase inhibitors (SSI), BMS-187745 and its prodrug ester, BMS-188494. Endpoints evaluated for both studies included protein synthesis ([3H]leucine incorporation), total cellular protein (a measure of cell loss), intra- and extracellular lactate dehydrogenase activity (a measure of membrane integrity), cholesterol biosynthesis ([14C]acetate incorporation), and morphology. HMG CoA reductase inhibitor-induced morphologic changes and inhibition of protein synthesis were significantly ameliorated by supplementation with farnesol and geranylgeraniol. In contrast to HMGRI-induced in vitro myotoxicity, SSI induced an irreversible, minimal cytotoxicity at close to maximum soluble concentrations. These results indicate that depletion of metabolites of geranylgeranyl pyrophosphate, and not inhibition of cholesterol synthesis, is the primary cause of HMG CoA reductase-induced myotoxicity. SN - 0041-008X UR - https://www.unboundmedicine.com/medline/citation/9221828/Inhibition_of_cholesterol_synthesis_by_squalene_synthase_inhibitors_does_not_induce_myotoxicity_in_vitro_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0041-008X(97)98131-X DB - PRIME DP - Unbound Medicine ER -