Myopathy associated with HMG-CoA reductase inhibitors (HMGRIs) and cyclosporin A: evaluation in a rat model

Role of cyclosporin A in the treatment of kidney disease and nephrotoxicity

The clinical use of cyclosporin A (CsA) has led to significant advances and achievements in the field of transplantation and immune diseases. However, the nephrotoxicity of CsA is a major concern in current immunosuppression regimens. CsA causes abnormal kidney function while treating kidney disease, causing problems for clinicians and patients. Evidence of CsA nephrotoxicity is almost always present in transplant recipients after long-term CsA administration (up to 10 years), and similar phenomena occur with other calcineurin inhibitors. In this review, we summarize the mechanisms and influencing factors of CsA for the treatment of primary nephrotic syndrome. The mechanisms of CsA nephrotoxicity, clinical-pathological features, diagnosis, prevention strategies, and risk factors are summarized. We discuss the correlates and mechanisms of the switch between kidney disease prevention and nephrotoxicity of CsA to better understand the function of CsA in the kidney and to provide a basis for the prevention and treatment of CsA nephrotoxicity.

Statins with different lipophilic indices exert distinct effects on skeletal, cardiac and vascular smooth muscle

AIMS

Data concerning the influence of statin lipophilicity on the myotoxic and pleiotropic effects of statins is conflicting, and mechanistic head-to-head comparison studies evaluating this parameter are limited. In order to address the disparity, this mechanistic investigation aimed to assess the effects of two short-acting statins with different lipophilic indices on skeletal, cardiac and vascular smooth muscle physiology.

MATERIALS AND METHODS

Young female Wistar rats were randomised to simvastatin (80 mg kg^-1 day^-1), pravastatin (160 mg kg^-1 day^-1) or control treatment groups. Changes in functional muscle performance were assessed, as well as mRNA levels of genes relating to atrophy, hypertrophy, mitochondrial function and/or oxidative stress.

KEY FINDINGS

There were no significant differences in the mRNA profiles of isolated skeletal muscles amongst the treatment groups. In terms of skeleletal muscle performance, simvastatin reduced functionality but treatment with pravastatin significantly improved force production. Rodents given simvastatin demonstrated comparable myocardial integrity to the control group. Conversely, pravastatin reduced left ventricular action potential duration, diastolic stiffness and Mhc-β expression. Pravastatin improved endothelium-dependent relaxation, particularly in muscular arteries, but this effect was absent in the simvastatin-treated rats. The responsiveness of isolated blood vessels to noradrenaline also differed between the statin groups. The findings of this study support that the effects of statins on skeletal, cardiac and vascular smooth muscle vary with their lipophilic indices.

SIGNIFICANCE

The results of this work have important implications for elucidating the mechanisms responsible for the myotoxic and pleiotropic effects of statins.

The Toxicology of HMG—CoA Reductase Inhibitors: Prediction of Human Risk

The discovery that 3-hydroxy-3-methyglutaryl coenzyme A reductase was a rate-determining step in the biosynthesis of cholesterol led to the discovery of inhibitors of this enzyme. To support the development of these agents (statins) as potential hypocholesterolemic drugs, a variety of preclinical studies were conducted in several animal species. Not unexpectedly due to the central role played by mevalonic acid and its products including cholesterol in development and maintenance of cellular homeostasis, administration of high dosage levels of these agents led to the expression of a broad variety of adverse effects in many different tissues. Using the tools of toxicologic pathology and classical risk assessment, these varied toxicities were evaluated by many groups relative to the conditions of use in human therapy and a perspective was developed on potential human risk. These approaches of mechanism-based risk assessment predicted that most of the adverse effects observed in animals would not be seen under conditions of human use and supported the successful introduction of one of the most important classes of human medicines.

The hepatoprotective effect of the combination use of Fructus Schisandrae with statin--A preclinical evaluation

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Schisandrae is traditionally used as a liver-toning Chinese herb. Recent studies suggested Fructus Schisandrae could prevent high-fat diet-induced hepatic steatosis as well as improving anti-oxidative status within the liver, which is a proposed mechanism against statin-induced liver toxicity.

AIM

The aim of the present study was to determine if the combination use of Atorvastatin (AS) and Fructus Schisandrae aqueous extract (FSE) could (a) exert potent therapeutic effects not only on high-fat diet-induced hyperlipidemia, but also on hepatomegaly (enlarge of liver size) and hepatic steatosis (fatty liver); and (b) reduce side effects caused by intake of statin alone including increased incidence of elevated liver enzymes and liver toxicity in Sprague Dawley rats.

MATERIALS AND METHODS

We studied 5 groups of Sprague Dawley rats that were given the following treatment for 8 weeks: (i) Normal-chow diet; (ii) High-fat diet (contains 21% fat and 0.15% cholesterol); (iii) High-fat diet (contains 21% fat and 0.15% cholesterol)+0.3% Atorvastatin; (iv) High-fat diet (contains 21% fat and 0.15% cholesterol)+0.45% FSE; (v) High-fat diet (contains 21% fat and 0.15% cholesterol)+0.3% Atorvastatin+0.45% FSE. After 8 weeks of treatment, body weight, adipose tissue and liver mass were measured, and liver and plasma lipid levels were determined to evaluate to effect of FSE with or without AS treatment on diet-induced obesity, hyperlipidemia and hepatic steatosis. Liver enzyme activities, anti-oxidative status and membrane permeability transition were also assessed to determine if FSE could reduce the side effects induced by AS.

RESULTS

From the results, FSE treatment alone resulted in significant inhibitory effect on diet-induced increase in: (a) body weight; (b) fat pad mass (epididymal, perirenal and inguinal fat); (c) liver weight; (d) total liver lipid; (e) liver triglyceride and cholesterol levels; and (f) plasma lipid levels, suggesting FSE has a potential preventive beneficial effect on weight control and lipid metabolism in Sprague Dawley rats with diet-induced obesity. However, FSE supplementation exerted no further beneficial effect on diet-induced metabolic syndrome when it is combined with AS treatment, compared with rats given AS-treatment alone. At the dose of 0.45%, dietary FSE supplementation resulted in: (a) reduced liver enzymes (ALT and AST) levels; (b) reduced macrophage infiltration (CD68); (c) improved liver glutathione levels (anti-oxidative status); (d) reduced liver reactive oxidative species; (e) a trend to reduce calcium-induced membrane permeability transition within the liver. Most importantly, these improvements induced by FSE treatment were not only observed in the livers of rats given high-fat-diet, but also in high-fat-fed rats with atorvastatin-induced hepatotoxicity.

CONCLUSIONS

Taken together, these data suggested FSE has a potential beneficial effect on weight control and lipid metabolism in Sprague Dawley rats with diet-induced obesity, and the combination use of FSE with AS could significantly prevent liver toxicity and anti-oxidative status induced by AS alone.

Rhabdomyolysis secondary to a drug interaction between simvastatin and clarithromycin

OBJECTIVE

To report a case of rhabdomyolysis resulting from concomitant use of clarithromycin and simvastatin.

CASE SUMMARY

A 64-year-old African-American man was admitted to the hospital for worsening renal failure, elevated creatine phosphokinase, diffuse muscle pain, and severe muscle weakness. About three weeks prior to admission, the patient was started on clarithromycin for sinusitis. The patient had been receiving simvastatin for approximately six months. He was treated aggressively with intravenous hydration, sodium bicarbonate, and hemodialysis. A muscle biopsy revealed necrotizing myopathy secondary to a toxin. The patient continued to receive intermittent hemodialysis until his death from infectious complications that occurred three months after admission. There were several factors that could have increased his risk for developing rhabdomyolysis, including chronic renal failure.

DISCUSSION

Clarithromycin is a potent inhibitor of CYP3A4, the major enzyme responsible for simvastatin metabolism. The concomitant administration of macrolide antibiotics and other hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have resulted in previous reports of rhabdomyolysis. Other factors may increase the risk of this drug interaction, including the administration of other medications that are associated with myopathy, underlying renal insufficiency, and administration of high doses of HMG-CoA reductase inhibitors.

CONCLUSIONS

Macrolide antibiotics inhibit the metabolism of HMG-CoA reductase inhibitors that are metabolized by CYP3A4 (i.e., atorvastatin, cerivastatin, lovastatin, simvastatin). This interaction may result in myopathy and rhabdomyolysis, particularly in patients with renal insufficiency or those who are concurrently taking medications associated with myopathy.

Muscle disorders associated with cyclosporine treatment

Alone or as part of a multidrug immunosuppressive regimen, cyclosporine A (CsA) has been reported in isolated case studies as a cause of muscle disorders. We reviewed the current knowledge on muscle toxicity of CsA and discussed the possible role of mitochondrial dysfunction in the genesis of CsA-associated myopathy. A systematic review using Medline(R) and Current Contents(R) databases combined with a manual literature search allowed us to select 56 references. We identified 34 patients with muscle disorders possibly related to CsA, usually manifesting by myalgia or muscle weakness and plasma creatine kinase elevation. Only 2 of 34 patients were treated with CsA alone. Experimental studies have shown that administration of CsA to rats reduces capillary density in extensor digitorum longus, skeletal muscle mitochondrial respiration, and endurance exercise capacity. Cyclosporine has been shown to inhibit the mitochondrial permeability transition pore. Whether identified interactions between CsA and mitochondria can explain CsA-associated myopathy is still unclear.

Post-transplant hyperlipidaemia: low-dose lovastatin lowers atherogenic lipids without plasma accumulation of lovastatin

OBJECTIVES

The purpose of the present study was twofold. First, to determine the frequency of hyperlipidaemia after heart transplantation (Tx) in relation to values obtained before Tx. Secondly, to examine the effect of low-dose lovastatin on possible antiatherogenic mechanisms and test the hypothesis that the side-effects are dose-dependent.

SUBJECTS AND DESIGN

Retrospective study of the frequency of hyperlipidaemia disturbances in heart transplant patients. In addition, in a prospective study, the safety and efficacy of incremental low doses of lovastatin up to 20 mg day-1 were studied, with measurements of its plasma concentration in 24 cyclosporin A treated heart (n = 14) and kidney (n = 10) recipients with total cholesterol > 7.5 mmol L-1.

RESULTS

Cholesterol increased markedly after heart transplantation from a pretransplant value of 5.3 (5.0,5.6) mmol L-1 to 6.7 (6.4,7.0) mmol L-1 after 1 year and then remained constant, but this increase was largely due to a 'normalization' since cholesterol decreased significantly during increasing heart failure before transplantation. Treatment with lovastatin decreased total cholesterol by 19% (P < 0.001), primarily by an effect on LDL cholesterol. HDL cholesterol increased by 15% (P < 0.05), whereas triglycerides remained unchanged. Lovastatin also caused a significant reduction in apolipoprotein B of 16%, and lipid peroxidation of 40%, whereas apolipoprotein A-I, fibrinogen, and glycerol were unchanged. Plasma concentration of lovastatin was significantly higher in transplant recipients compared with controls, but there was no accumulation during incremental dosing of lovastatin. The drug was well tolerated without significant symptoms or evidence of myopathy.

CONCLUSIONS

Hyperlipidaemia is common after cardiac transplantation. Treatment with low dose lovastatin is well tolerated and has a favourable effect on atherogenic lipids.

Inhibition of cholesterol synthesis by squalene synthase inhibitors does not induce myotoxicity in vitro

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.

Lovastatin-induced rhabdomyolysis possibly associated with clarithromycin and azithromycin

OBJECTIVE

To describe two cases of rhabdomyolysis in patients taking lovastatin that were precipitated by the use of the newer macrolide antibiotics clarithromycin and azithromycin.

CASE SUMMARIES

In each case, the patients were treated over 5 years with lovastatin and developed rhabdomyolysis that coincided with the completion of a prescribed regimen of a newer macrolide antibiotic. Following intravenous hydration and administration of bicarbonate, the patients' condition resolved without permanent' sequelae.

DISCUSSION

Rhabdomyolysis is a clinical syndrome resulting from the destruction of skeletal muscle that may progress to renal failure Several drugs have been associated with rhabdomyolysis, including lovastatin, a hydroxymethylglutaryl-coenzyme A reductase inhibitor. Erythromycin is a macrolide antibiotic that may increase the risk of lovastatin-induced rhabdomyolysis. To our knowledge, these cases are the first published reports of lovastatin-induced rhabdomyolysis associated with azithromycin and clarithromycin.

CONCLUSIONS

The risk of drug-induced rhabdomyolysis due to the potential interaction between lovastatin and azithromycin or clarithromycin should be considered before the concomitant use of these agents.

Pravastatin. A reappraisal of its pharmacological properties and clinical effectiveness in the management of coronary heart disease

Pravastatin is an HMG-CoA reductase inhibitor which lowers plasma cholesterol levels by inhibiting de novo cholesterol synthesis. Pravastatin produces consistent dose-dependent reductions in both total and low density lipoprotein (LDL)-cholesterol levels in patients with primary hypercholesterolaemia. Favourable changes in other parameters such as total triglyceride and high density lipoprotein (HDL)-cholesterol levels are generally modest. Combination therapy with other antihyperlipidaemic agents such as cholestyramine further enhances the efficacy of pravastatin in patients with severe dyslipidaemias. Available data suggest that pravastatin is effective in elderly patients and in patients with hypercholesterolaemia secondary to diabetes mellitus or renal disease. The benefit of cholesterol-lowering in terms of patient outcomes is currently an area of considerable interest. Recently completed regression studies (PLAC I, PLAC II, KAPS and REGRESS) show that pravastatin slows progression of atherosclerosis and lowers the incidence of coronary events in patients with mild to moderately severe hypercholesterolaemia and known coronary heart disease. Large scale primary (WOSCOPS) and secondary (CARE) prevention studies, moreover, demonstrate that pravastatin has beneficial effects on coronary morbidity and mortality. In WOSCOPS, all-cause mortality was reduced by 22%. Pravastatin is generally well tolerated by most patients (including the elderly), as evidenced by data from studies of up to 5 years in duration. As with other HMG-CoA reductase inhibitors, myopathy occurs rarely (< 0.1% of patients treated with pravastatin): approximately 1 to 2% of patients may present with raised serum levels of hepatic transaminases. Thus, with its favourable effects on cardiovascular morbidity/mortality and total mortality, pravastatin should be considered a first-line agent in patients with elevated cholesterol levels, multiple risk factors or coronary heart disease who are at high risk of cardiovascular morbidity.

Effects of HMG-CoA reductase inhibitors on growth and differentiation of cultured rat skeletal muscle cells

HMG-CoA reductase inhibitors have been associated with skeletal muscle myopathy, ranging from asymptomatic elevations of serum creatine kinase (CK) activity to rhabdomyolysis. In this study, we assessed the effects of addition of different concentrations of simvastatin and pravastatin on growth and differentiation of cultured primary rat skeletal muscle cells. Protein concentrations, CK activity and percentage CK-MM, which is a parameter for maturation, were determined. Effects were generally stronger if inhibitors were added to both growth and differentiation medium rather than only to differentiation medium. Addition of 25 microM pravastatin caused only a decrease of CK activity. Addition of 1-5 microM simvastatin resulted in a decrease of protein concentration, CK activity and percentage CK-MM, whereas 25 microM simvastatin resulted in cell death. Addition of mevalonic acid or cholesterol could not prevent the effects of 1 microM simvastatin. In addition, 1 microM simvastatin did not influence the cholesterol and phospholipid content of the cells. Superfusion of cultured cells with simvastatin concentrations of 10 microM and higher caused a transient increase of the cytoplasmic calcium concentration followed by an apparent second rise and cell puncture. The results indicate that HMG-CoA reductase inhibitors may affect skeletal muscle cell regeneration in vivo by a direct toxic effect on growth and differentiation.

Approaches to the treatment of hyperlipidemia in the solid organ transplant recipient

OBJECTIVE

To review the literature investigating increased lipid concentrations in transplant recipients and the use of lipid-lowering agents in this population.

DATA SOURCES

Relevant articles were identified from a MEDLINE search using the terms transplantation, hyperlipidemia, immunosuppression, and therapy including diet, gemfibrozil, bile acid sequestrants, nicotinic acid, probucol, and hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors. Selected literature, including controlled studies, was used in this review.

STUDY SELECTION

Articles published since 1970 pertaining to hyperlipidemia in solid organ transplant recipients. Emphasis was placed on clinical trials that investigated approaches to the treatment of hyperlipidemia in transplant recipients.

DATA EXTRACTION

Original articles and reviews were obtained to select material pertinent to the objectives.

DATA SYNTHESIS

Descriptions of lipid concentrations in the transplant patient and treatment approaches used, including potential complications, were reviewed.

CONCLUSIONS

Hyperlipidemia is an important risk factor for coronary heart disease in the solid organ transplant patient. Treatment alternatives include diet modification and, in most cases, pharmacologic intervention that should be based on the type of hyperlipidemia. The HMG-CoA reductase inhibitors are effective agents in the treatment of hyperlipidemia in the transplant recipient and generally are used as single therapy in low dosages to minimize the risk of myositis or rhabdomyolysis.

Comparison of properties of four inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase

Four inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase have been approved for treatment of hypercholesterolemia. Three of these are fungal metabolites or derivatives thereof: lovastatin, simvastatin, and pravastatin. The fourth, fluvastatin, is totally synthetic. Its structure, containing a fluorophenyl-substituted indole ring, is distinct from that of the fungal metabolites. Lovastatin and simvastatin are administered as prodrugs, which undergo in vivo transformation to active inhibitory forms; fluvastatin and pravastatin are administered as active agents. The HMG-CoA reductase inhibitors are all effective in reducing plasma concentrations of low density lipoprotein. They have differing pharmacokinetic properties, which may be of importance in some patients. All of these drugs are very well tolerated, and there do not appear to be major differences in toxicity or adverse effects. When LDL reductions > 30% are needed, simvastatin is the most cost-effective HMG-CoA reductase inhibitor. However, these drugs are most commonly used in dosages that reduce LDL-C by 20-30%. For this degree of LDL reduction, fluvastatin is the most cost-effective HMG-CoA reductase inhibitor.