Preventive effects of bicarbonate on cerivastatin-induced apoptosis

Study of Statin- and Loratadine-Induced Muscle Pain Mechanisms Using Human Skeletal Muscle Cells

Many drugs can cause unexpected muscle disorders, often necessitating the cessation of an effective medication. Inhibition of monocarboxylate transporters (MCTs) may potentially lead to perturbation of l-lactic acid homeostasis and muscular toxicity. Previous studies have shown that statins and loratadine have the potential to inhibit l-lactic acid efflux by MCTs (MCT1 and 4). The main objective of this study was to confirm the inhibitory potentials of atorvastatin, simvastatin (acid and lactone forms), rosuvastatin, and loratadine on l-lactic acid transport using primary human skeletal muscle cells (SkMC). Loratadine (IC₅₀ 31 and 15 µM) and atorvastatin (IC₅₀ ~130 and 210 µM) demonstrated the greatest potency for inhibition of l-lactic acid efflux at pH 7.0 and 7.4, respectively (~2.5-fold l-lactic acid intracellular accumulation). Simvastatin acid exhibited weak inhibitory potency on l-lactic acid efflux with an intracellular lactic acid increase of 25–35%. No l-lactic acid efflux inhibition was observed for simvastatin lactone or rosuvastatin. Pretreatment studies showed no change in inhibitory potential and did not affect lactic acid transport for all tested drugs. In conclusion, we have demonstrated that loratadine and atorvastatin can inhibit the efflux transport of l-lactic acid in SkMC. Inhibition of l-lactic acid efflux may cause an accumulation of intracellular l-lactic acid leading to the reported drug-induced myotoxicity.

[Direct mechanism of action in toxic myopathies]

Toxic myopathies are a large group of disorders generated by surrounding agents and characterized by structural and/or functional disturbances of muscles. The most recurrent are those induced by commonly used medications. Illicit drugs, environmental toxins from animals, vegetables, or produced by micro-organisms as well as chemical products commonly used are significant causes of such disorders. The muscle toxicity results from multiple mechanisms at different biological levels. Many agents can induce myotoxicity through a direct mechanism in which statins, glucocorticoids and ethyl alcohol are the most representative. Diverse mechanisms were highlighted as interaction with macromolecules and induction of metabolic and cellular dysfunctions. Muscle damage can be related to amphiphilic properties of some drugs (chloroquine, hydroxychloroquine, etc.) leading to specific lysosomal disruptions and autophagic dysfunctions. Some agents affect the whole muscle fiber by inducing oxidative stress (ethyl alcohol and some statins) or triggering cell death pathways (apoptosis or necrosis) resulting in extensive alterations. More studies on these mechanisms are needed. They would allow a better knowledge of the intracellular mediators involved in these pathologies in order to develop targeted therapies of high efficiency.

The role of acid-base imbalance in statin-induced myotoxicity

Disturbances in acid-base balance, such as acidosis and alkalosis, have potential to alter the pharmacologic and toxicologic outcomes of statin therapy. Statins are commonly prescribed for elderly patients who have multiple comorbidities such as diabetes mellitus, cardiovascular, and renal diseases. These patients are at risk of developing acid-base imbalance. In the present study, the effect of disturbances in acid-base balance on the interconversion of simvastatin and pravastatin between lactone and hydroxy acid forms have been investigated in physiological buffers, human plasma, and cell culture medium over pH ranging from 6.8-7.8. The effects of such interconversion on cellular uptake and myotoxicity of statins were assessed in vitro using C2C12 skeletal muscle cells under conditions relevant to acidosis, alkalosis, and physiological pH. Results indicate that the conversion of the lactone forms of simvastatin and pravastatin to the corresponding hydroxy acid is strongly pH dependent. At physiological and alkaline pH, substantial proportions of simvastatin lactone (SVL; ∼87% and 99%, respectively) and pravastatin lactone (PVL; ∼98% and 99%, respectively) were converted to the active hydroxy acid forms after 24 hours of incubation at 37°C. At acidic pH, conversion occurs to a lower extent, resulting in greater proportion of statin remaining in the more lipophilic lactone form. However, pH alteration did not influence the conversion of the hydroxy acid forms of simvastatin and pravastatin to the corresponding lactones. Furthermore, acidosis has been shown to hinder the metabolism of the lactone form of statins by inhibiting hepatic microsomal enzyme activities. Lipophilic SVL was found to be more cytotoxic to undifferentiated and differentiated skeletal muscle cells compared with more hydrophilic simvastatin hydroxy acid, PVL, and pravastatin hydroxy acid. Enhanced cytotoxicity of statins was observed under acidic conditions and is attributed to increased cellular uptake of the more lipophilic lactone or unionized hydroxy acid form. Consequently, our results suggest that comorbidities associated with acid-base imbalance can play a substantial role in the development and potentiation of statin-induced myotoxicity.

Involvement of Monocarboxylate Transporter 4 Expression in Statin-Induced Cytotoxicity

Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are the most widely used cholesterol-lowering agents for prevention of obstructive cardiovascular events. However, statins can cause a variety of skeletal muscle problems, and exercise leads to an increase in statin-induced muscle injury. Exercise induces the protein content of monocarboxylate transporter 4 (MCT4), which is expressed strongly in skeletal muscle and is thought to play a major role in the transport of metabolically important monocarboxylates such as l-lactate. We previously reported that α-cyano-4-hydroxycinnamate, an MCT4 inhibitor, increased the inhibition of growth of RD cells, a prototypic embryonal rhabdomyosarcoma cell line (an RD cell line), as a model of in vitro skeletal muscle, induced by a statin. However, it is unclear whether statin-induced RD cell cytotoxicity is associated with MCT4 expression. We, therefore, examined the relationship between statin-induced cytotoxicity and MCT4 expression in RD cells. Atorvastatin reduced the number of viable cells and upregulated MCT4, but not MCT1, mRNA level in a concentration-dependent manner. MCT4 knockdown suppressed atorvastatin-, simvastatin-, and fluvastatin-induced reduction of cell viability and apoptosis compared with negative control-treated cells. In this study, we demonstrated that MCT4 expression is associated with statin-induced cytotoxicity.

Statin-induced Myopathy in Skeletal Muscle: the Role of Exercise

Statins are widely used drugs to lower cholesterol levels and to reduce the risk of cardiovascular disease. However, it has been reported that statins are associated with adverse side effects of skeletal myopathy. Statin treatment can impair mitochondrial function and induce apoptosis in skeletal muscle in both human and animal models. Ubiquinone plays an essential role in transferring electrons in the mitochondrial electron transfer chain for oxidative phosphorylation. However, statin treatment reduces ubiquinone levels in the cholesterol synthesis pathway, which may be associated with mitochondrial dysfunction. In addition, reactive oxygen species (ROS) production and apoptosis induced by statins may provide cellular and molecular mechanisms in skeletal myopathy. Exercise is the most effective therapy to prevent metabolic and cardiovascular diseases. However, whether exercise provides a benefit to or exacerbation of statin-induced myopathy in skeletal muscle remains poorly investigated. This review will briefly provide a comprehensive summary regarding the effects of statins on skeletal myopathy, and discuss the potential mechanisms of statin-induced myopathy and the role of exercise in statin-induced myopathy in skeletal muscle.

Uremic toxins enhance statin-induced cytotoxicity in differentiated human rhabdomyosarcoma cells

The risk of myopathy and rhabdomyolysis is considerably increased in statin users with end-stage renal failure (ESRF). Uremic toxins, which accumulate in patients with ESRF, exert cytotoxic effects that are mediated by various mechanisms. Therefore, accumulation of uremic toxins might increase statin-induced cytotoxicity. The purpose of this study was to determine the effect of four uremic toxins-hippuric acid, 3-carboxy-4-methyl-5-propyl-2-furanpropionate, indole-3-acetic acid, and 3-indoxyl sulfate-on statin-induced myopathy. Differentiated rhabdomyosarcoma cells were pre-treated with the uremic toxins for seven days, and then the cells were treated with pravastatin or simvastatin. Cell viability and apoptosis were assessed by viability assays and flow cytometry. Pre-treatment with uremic toxins increased statin- but not cisplatin-induced cytotoxicity (p < 0.05 vs. untreated). In addition, the pre-treatment increased statin-induced apoptosis, which is one of the cytotoxic factors (p < 0.05 vs. untreated). However, mevalonate, farnesol, and geranylgeraniol reversed the effects of uremic toxins and lowered statin-induced cytotoxicity (p < 0.05 vs. untreated). These results demonstrate that uremic toxins enhance statin-induced apoptosis and cytotoxicity. The mechanism underlying this effect might be associated with small G-protein geranylgeranylation. In conclusion, the increased severity of statin-induced rhabdomyolysis in patients with ESRF is likely due to the accumulation of uremic toxins.

Translational insight into statin-induced muscle toxicity: from cell culture to clinical studies

Statins are lipid-lowering drugs used widely to prevent and treat cardiovascular and coronary heart diseases. These drugs are among the most commonly prescribed medicines intended for long-term use. In general, statins are well tolerated. However, muscular adverse effects appear to be the most common obstacle that limits their use, resulting in poor patient compliance or even drug discontinuation. In addition, rare but potentially fatal cases of rhabdomyolysis have been reported with the use of these drugs, especially in the presence of certain risk factors. Previous reports have investigated statin-induced myotoxicity in vivo and in vitro using a number of cell lines, muscle tissues, and laboratory animals, in addition to randomized clinical trials, observational studies, and case reports. None of them have compared directly results from laboratory investigations with clinical observations of statin-related muscular adverse effects. To the best of our knowledge this is the first review article that combines laboratory investigation with clinical aspects of statin-induced myotoxicity. By reviewing published literature of in vivo, in vitro, and clinically relevant studies of statin myotoxicity, we aim to translate this important drug-related problem to establish a clear picture of proposed mechanisms that explain the risk factors and describe the diagnostic approaches currently used for evaluating the degree of muscle damage induced by these agents. This review provides baseline novel translational insight that can be used to enhance the safety profile, to minimize the chance of progression of these adverse effects to more severe and potentially fatal rhabdomyolysis, and to improve the overall patient compliance and adherence to long-term statin therapy.

Metabolic Syndrome and Chronic Simvastatin Therapy Enhanced Human Cardiomyocyte Stress before and after Ischemia- Reperfusion in Cardio-Pulmonary Bypass Patients

Metabolic syndrome (MetS) is a set of metabolic alterations including high levels of low-density lipoprotein (LDL), which increase the risk of cardiomyopathy often leading to surgery. Despite inducing myopathy, statins are widely used to lower LDL. Cardiopulmonary bypass (Cpb) causes oxidative stress and metabolic injury, altering mitochondrial expression (Grp75) and endoplasmic reticulum (Grp78) chaperones, apoptotic enzymes (Bcl2 family) and increasing cardiomyocyte lipid/lipofuscin storage. We believe that cardiomyocytes from patients with MetS may be more sensitive to surgical stress, in particular after simvastatin therapy (MetS+Stat). The study group included ten patients with MetS, ten patients with Mets+Stat and ten healthy subjects. Myocardial biopsies were obtained both before and after-Cpb. Grp75, Grp78, Bax, Bcl2, lipids, lipofuscin and fibrosis were evaluated by immuno/histochemistry. MetS cardiomyocytes had higher Grp75, Bax, fibrosis and lipofuscin. MetS+Stat had lower Grp75 and higher Grp78 expressions, high Bax, fewer fibrosis and higher lipofuscin content. Cpb did not vary the fibrosis and lipids/lipofuscin content, although it influenced the chaperones and Bax expression in all groups. These changes were more profound in patients with MetS and even more so in patients with MetS+Stat. The results suggest that MetS and MetS+Stat cardiomyocytes were more highly stressed after-Cpb. Interestingly, simvastatin caused high stress even before-Cpb.

Effect of a high dose of simvastatin on muscle mitochondrial metabolism and calcium signaling in healthy volunteers

Statin use may be limited by muscle side effects. Although incompletely understood to date, their pathophysiology may involve oxidative stress and impairments of mitochondrial function and of muscle Ca(2+) homeostasis. In order to simultaneously assess these mechanisms, 24 male healthy volunteers were randomized to receive either simvastatin for 80 mg daily or placebo for 8 weeks. Blood and urine samples and a stress test were performed at baseline and at follow-up, and mitochondrial respiration and Ca(2+) spark properties were evaluated on a muscle biopsy 4 days before the second stress test. Simvastatin-treated subjects were separated according to their median creatine kinase (CK) increase. Simvastatin treatment induced a significant elevation of aspartate amino transferase (3.38±5.68 vs -1.15±4.32 UI/L, P<0.001) and CK (-24.3±99.1±189.3 vs 48.3 UI/L, P=0.01) and a trend to an elevation of isoprostanes (193±408 vs 12±53 pmol/mmol creatinine, P=0.09) with no global change in mitochondrial respiration, lactate/pyruvate ratio or Ca(2+) sparks. However, among statin-treated subjects, those with the highest CK increase displayed a significantly lower Vmax rotenone succinate and an increase in Ca(2+) spark amplitude vs both subjects with the lowest CK increase and placebo-treated subjects. Moreover, Ca(2+) spark amplitude was positively correlated with treatment-induced CK increase in the whole group (r=0.71, P=0.0045). In conclusion, this study further supports that statin induced muscular toxicity may be related to alterations in mitochondrial respiration and muscle calcium homeostasis independently of underlying disease or concomitant medication.

Statin-induced myopathies

Statins are considered to be safe, well tolerated and the most efficient drugs for the treatment of hypercholesterolemia, one of the main risk factor for atherosclerosis, and therefore they are frequently prescribed medications. The most severe adverse effect of statins is myotoxicity, in the form of myopathy, myalgia, myositis or rhabdomyolysis. Clinical trials commonly define statin toxicity as myalgia or muscle weakness with creatine kinase (CK) levels greater than 10 times the normal upper limit. Rhabdomyolysis is the most severe adverse effect of statins, which may result in acute renal failure, disseminated intravascular coagulation and death. The exact pathophysiology of statin-induced myopathy is not fully known. Multiple pathophysiological mechanisms may contribute to statin myotoxicity. This review focuses on a number of them. The prevention of statin-related myopathy involves using the lowest statin dose required to achieve therapeutic goals and avoiding polytherapy with drugs known to increase systemic exposure and myopathy risk. Currently, the only effective treatment of statin-induced myopathy is the discontinuation of statin use in patients affected by muscle aches, pains and elevated CK levels.

Simvastatin impairs ADP-stimulated respiration and increases mitochondrial oxidative stress in primary human skeletal myotubes

Statins, the widely prescribed cholesterol-lowering drugs for the treatment of cardiovascular disease, cause adverse skeletal muscle side effects ranging from fatigue to fatal rhabdomyolysis. The purpose of this study was to determine the effects of simvastatin on mitochondrial respiration, oxidative stress, and cell death in differentiated primary human skeletal muscle cells (i.e., myotubes). Simvastatin induced a dose-dependent decrease in viability of proliferating and differentiating primary human muscle precursor cells, and a similar dose-dependent effect was noted in differentiated myoblasts and myotubes. Additionally, there were decreases in myotube number and size following 48 h of simvastatin treatment (5 μM). In permeabilized myotubes, maximal ADP-stimulated oxygen consumption, supported by palmitoylcarnitine+malate (PCM, complex I and II substrates) and glutamate+malate (GM, complex I substrates), was 32-37% lower (P<0.05) in simvastatin-treated (5 μM) vs control myotubes, providing evidence of impaired respiration at complex I. Mitochondrial superoxide and hydrogen peroxide generation were significantly greater in the simvastatin-treated human skeletal myotube cultures compared to control. In addition, simvastatin markedly increased protein levels of Bax (proapoptotic, +53%) and Bcl-2 (antiapoptotic, +100%, P<0.05), mitochondrial PTP opening (+44%, P<0.05), and TUNEL-positive nuclei in human skeletal myotubes, demonstrating up-regulation of mitochondrial-mediated myonuclear apoptotic mechanisms. These data demonstrate that simvastatin induces myotube atrophy and cell loss associated with impaired ADP-stimulated maximal mitochondrial respiratory capacity, mitochondrial oxidative stress, and apoptosis in primary human skeletal myotubes, suggesting that mitochondrial dysfunction may underlie human statin-induced myopathy.

Potent inhibition of cicatricial contraction in proliferative vitreoretinal diseases by statins

OBJECTIVE

Despite tremendous progress in vitreoretinal surgery, certain postsurgical complications limit the success in the treatment of proliferative vitreoretinal diseases (PVDs), such as proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR). One of the most significant complications is the cicatricial contraction of proliferative membranes, resulting in tractional retinal detachment and severe vision loss. Novel pharmaceutical approaches are thus urgently needed for the management of these vision-threatening diseases. In the current study, we investigated the inhibitory effects of statins on the progression of PVDs.

RESEARCH DESIGN AND METHODS

Human vitreous concentrations of transforming growth factor-beta2 (TGF-beta2) were measured by enzyme-linked immunosorbent assay. TGF-beta2-and vitreous-dependent phosphorylation of myosin light chain (MLC), a downstream mediator of Rho-kinase pathway, and collagen gel contraction simulating cicatrical contraction were analyzed using cultured hyalocytes. Inhibitory effects of simvastatin on cicatrical contraction were assessed both in vitro and in vivo.

RESULTS

Human vitreous concentrations of TGF-beta2 were significantly higher in the samples from patients with PVD compared with those without PVD. Simvastatin inhibited TGF-beta2-dependent MLC phosphorylation and gel contraction in a dose- and time-dependent manner and was capable of inhibiting translocation of Rho protein to the plasma membrane in the presence of TGF-beta2. Vitreous samples from patients with PVD enhanced MLC phosphorylation and gel contraction, whereas simvastatin almost completely inhibited these phenomena. Finally, intravitreal injection of simvastatin dose-dependently prevented the progression of diseased states in an in vivo model of PVR.

CONCLUSIONS

Statins might have therapeutic potential in the prevention of PVDs.

Effects of strontium fructose 1,6-diphosphate on expression of apoptosis-related genes and oxidative stress in testes of diabetic rats

OBJECTIVE

To investigate the effects of strontium fructose 1,6-diphosphate (FDP-Sr) on testicular dysfunction induced by diabetes.

METHODS

Diabetes was induced by a single injection of streptozotocin (65 mg/kg, i.p.). After 28 days, therapy with three doses (50, 100, and 200 mg/kg per day, p.o.) of FDP-Sr was carried out for another 4 weeks.

RESULTS

The rats exhibited morphological lesions of testes and significant decreases in serum testosterone levels after 2 months of diabetes. Testicular tissues of diabetic rats showed significantly increased malondialdehyde levels and declined glutathione peroxidase activity. Meanwhile, augmented DNA fragmentation was observed, along with downregulated Bcl-2 and upregulated Bax expressions at both mRNA and protein levels. FDP-Sr showed significant antioxidant effects in both in vitro and in vivo experiments, and significantly relieved apoptosis and the decline of serum testosterone caused by diabetes.

CONCLUSIONS

Testicular injury and apoptosis induced by diabetes are partially attributed to the augmented oxidative stress in testicular tissue. FDP-Sr indirectly alleviates these pathologic alterations by suppressing the generation of reactive oxygen species.

Hydrophobic statins induce autophagy in cultured human rhabdomyosarcoma cells

Statins are widely used to treat hypercholesterolemia, but they are associated with muscle-related adverse events, by as yet, inadequately resolved mechanisms. In this study, we report that statins induced autophagy in cultured human rhabdomyosarcoma A204 cells. Potency differed widely among the statins: cerivastatin induced autophagy at 0.1muM, simvastatin at 10muM but none was induced by pravastatin. Addition of mevalonate, but not cholesterol, blocked induction of autophagy by cerivastatin, suggesting that this induction is dependent on modulation of isoprenoid metabolic pathways. The statin-induced autophagy was not observed in other types of cells, such as human hepatoma HepG2 or embryonic kidney HEK293 cells. Muscle-specific abortive induction of autophagy by hydrophobic statins is a possible mechanism for statin-induced muscle-related side effects.