Apoptotic injury in cultured human hepatocytes induced by HMG-CoA reductase inhibitors

Aldo-keto reductase-7A2 protects against atorvastatin-induced hepatotoxicity via Nrf2 activation

Atorvastatin (ATO), as a cholesterol-lowering drug, was the world's best-selling drug in the early 2000s. However, ATO overdose-induced liver or muscle injury is a threat to many patients, which restricts its application. Previous studies suggest that ATO overdose is accompanied with ROS accumulation and increased lipid peroxidation, which are the leading causes of ATO-induced liver damage. This study is, therefore, carried out to investigate the roles of anti-oxidant pathways and enzymes in protection against ATO-induced hepatotoxicity. Here we show that in ATO-challenged HepG2 cells, the expression levels of transcription factor NFE2L2/Nrf2 (nuclear factor erythroid 2 p45-related factor 2) are significantly upregulated. When Nrf2 is pharmacologically inhibited or genetically inactivated, ATO-induced cytotoxicity is significantly aggravated. Aldo-keto reductase-7A (AKR7A) enzymes, transcriptionally regulated by Nrf2, are important for bioactivation and biodetoxification. Here, we reveal that in response to ATO exposure, mRNA levels of human AKR7A2 are significantly upregulated in HepG2 cells. Furthermore, knockdown of AKR7A2 exacerbates ATO-induced hepatotoxicity, suggesting that AKR7A2 is essential for cellular adaptive response to ATO-induced cell damage. In addition, overexpression of AKR7A2 in HepG2 cells can significantly mitigate ATO-induced cytotoxicity and this process is Nrf2-dependent. Taken together, these findings indicate that Nrf2-mediated AKR7A2 is responsive to high concentrations of ATO and contributes to protection against ATO-induced hepatotoxicity, making it a good candidate for mitigating ATO-induced side effects.

Inhibitors of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase Decrease the Growth, Ergosterol Synthesis and Generation of petite Mutants in Candida glabrata and Candida albicans

Candida glabrata and Candida albicans, the most frequently isolated candidiasis species in the world, have developed mechanisms of resistance to treatment with azoles. Among the clinically used antifungal drugs are statins and other compounds that inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), resulting in decreased growth and ergosterol levels in yeasts. Ergosterol is a key element for the formation of the yeast cell membrane. However, statins often cause DNA damage to yeast cells, facilitating mutation and drug resistance. The aim of the current contribution was to synthesize seven series of compounds as inhibitors of the HMGR enzyme of Candida ssp., and to evaluate their effect on cellular growth, ergosterol synthesis and generation of petite mutants of C. glabrata and C. albicans. Compared to the reference drugs (fluconazole and simvastatin), some HMGR inhibitors caused lower growth and ergosterol synthesis in the yeast species and generated fewer petite mutants. Moreover, heterologous expression was achieved in Pichia pastoris, and compounds 1a, 1b, 6g and 7a inhibited the activity of recombinant CgHMGR and showed better binding energy values than for α-asarone and simvastatin. Thus, we believe these are good candidates for future antifungal drug development.

Cholesterol biosynthesis modulates differentiation in murine cranial neural crest cells

Cranial neural crest cells (cNCC) are a multipotent embryonic cell population that give rise to a diverse set of cell types. These cells are particularly vulnerable to external metabolic stressors, as exemplified by the association between maternal hyperglycemia and congenital malformations. We were interested in studying the effect of various concentrations of glucose and pyruvate on cNCC metabolism, migration, and differentiation using an established murine neural crest cell model (O9-1). We unexpectedly observed a pattern of gene expression suggestive of cholesterol biosynthesis induction under glucose depletion conditions in O9-1 cells. We further showed that treatment with two different cholesterol synthesis inhibitors interfered with cell migration and differentiation, inhibiting chondrogenesis while enhancing smooth muscle cell differentiation. As congenital arhinia (absent external nose), a malformation caused by mutations in SMCHD1, appears to represent, in part, a defect in cNCC, we were also interested in investigating the effects of glucose and cholesterol availability on Smchd1 expression in O9-1 cells. Smchd1 expression was induced under high glucose conditions whereas cholesterol synthesis inhibitors decreased Smchd1 expression during chondrogenesis. These data highlight a novel role for cholesterol biosynthesis in cNCC physiology and demonstrate that human phenotypic variability in SMCHD1 mutation carriers may be related, in part, to SMCHD1's sensitivity to glucose or cholesterol dosage during development.

The main side effects of statins in clinical practice

Statins have long occupied a central place in cardiovascular medicine, being an integral component of the prevention and treatment of atherosclerotic cardiovascular diseases (coronary heart disease and its main clinical forms, angina pectoris and myocardial infarction; transient ischemic attacks, ischemic strokes, etc.). By blocking a key enzyme of cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA-reductase), statins normalize the parameters of the lipid spectrum, primarily, the serum levels of atherogenic low-density lipoprotein cholesterol. However, in addition to the beneficial effects of statins, side effects are also characteristic, which are a significant problem in modern clinical practice due to the fact that they can cause dangerous disorders, forcing physicians to reduce dosages or completely cancel these drugs. Understanding the side effects and the mechanisms underlying their formation is important for improving the measures for the early detection, prevention and treatment of those disorders. This article discusses such side effects of statins as myotoxicity, hepatotoxicity, nephrotoxicity. The pathogenetic mechanisms underlying these toxic effects of statins are discussed. A particular attention is paid to the effect of statins on the oxidative stress, the mechanisms of oxidative damage to cellular macromolecules (lipids, proteins and DNA) and their potential role in the development of myotoxicity, hepatotoxicity and nephrotoxicity.

Emerging role of ferroptosis in breast cancer: New dawn for overcoming tumor progression

Breast cancer has become a serious threat to women's health. Cancer progression is mainly derived from resistance to apoptosis induced by procedures or therapies. Therefore, new drugs or models that can overcome apoptosis resistance should be identified. Ferroptosis is a recently identified mode of cell death characterized by excess reactive oxygen species-induced lipid peroxidation. Since ferroptosis is distinct from apoptosis, necrosis and autophagy, its induction successfully eliminates cancer cells that are resistant to other modes of cell death. Therefore, ferroptosis may become a new direction around which to design breast cancer treatment. Unfortunately, the complete appearance of ferroptosis in breast cancer has not yet been fully elucidated. Furthermore, whether ferroptosis inducers can be used in combination with traditional anti- breast cancer drugs is still unknown. Moreover, a summary of ferroptosis in breast cancer progression and therapy is currently not available. In this review, we discuss the roles of ferroptosis-associated modulators glutathione, glutathione peroxidase 4, iron, nuclear factor erythroid-2 related factor-2, superoxide dismutases, lipoxygenase and coenzyme Q in breast cancer. Furthermore, we provide evidence that traditional drugs against breast cancer induce ferroptosis, and that ferroptosis inducers eliminate breast cancer cells. Finally, we put forward prospect of using ferroptosis inducers in breast cancer therapy, and predict possible obstacles and corresponding solutions. This review will deepen our understanding of the relationship between ferroptosis and breast cancer, and provide new insights into breast cancer-related therapeutic strategies.

Pitavastatin Is a Highly Potent Inhibitor of T-Cell Proliferation

Repositioning of approved drugs is an alternative time- and cost-saving strategy to classical drug development. Statins are 3-hydroxy-3-methylglutaryl-CoA (HMG CoA) reductase inhibitors that are usually used as cholesterol-lowering medication, and they also exhibit anti-inflammatory effects. In the present study, we observed that the addition of Pitavastatin at nanomolar concentrations inhibits the proliferation of CD3/CD28 antibody-stimulated human T cells of healthy donors in a dose-dependent fashion. The 50% inhibition of proliferation (IC50) were 3.6 and 48.5 nM for freshly stimulated and pre-activated T cells, respectively. In addition, Pitavastatin suppressed the IL-10 and IL-17 production of stimulated T cells. Mechanistically, we found that treatment of T cells with doses <1 µM of Pitavastatin induced hyperphosphorylation of ERK1/2, and activation of caspase-9, -3 and -7, thus leading to apoptosis. Mevalonic acid, cholesterol and the MEK1/2 inhibitor U0126 reversed this Pitavastatin-mediated ERK1/2 activation and apoptosis of T cells. In summary, our results suggest that Pitavastatin is a highly potent inhibitor of T-cell proliferation, which induces apoptosis via pro-apoptotic ERK1/2 activation, thus representing a potential repositioning candidate for the treatment of T-cell-mediated autoimmune diseases.

A functional long-term 2D serum-free human hepatic in vitro system for drug evaluation

Human in vitro hepatic models generate faster drug toxicity data with higher human predictability compared to animal models. However, for long-term studies, current models require the use of serum and 3D architecture, limiting their utility. Maintaining a functional long-term human in vitro hepatic culture that avoids complex structures and serum would improve the value of such systems for preclinical studies. This would also enable a more straightforward integration with current multi-organ devices to study human systemic toxicity to generate an alternative model to chronic animal evaluations. A human primary hepatocyte culture system was characterized for 28 days in 2D and serum-free defined conditions. Under the studied conditions, human primary hepatocytes maintained their characteristic morphology, hepatic markers and functions for 28 days. The acute and chronic administration of known drugs validated the sensitivity of the system for drug testing. This human 2D model represents a realistic system to evaluate hepatic function for long-term drug studies, without the need of animal serum, confounding variable in most models, and with less complexity and resultant cost compared to most 3D models. The defined culture conditions can easily be integrated into complex multi-organ in vitro models for studying systemic effects driven by the liver function for long-term evaluations.

Atorvastatin induces mitochondrial dysfunction and cell apoptosis in HepG2 cells via inhibition of the Nrf2 pathway

Atorvastatin (ATO) is a 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor widely used to treat hypercholesterolemia. However, clinical application is limited by potential hepatotoxicity. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a master regulator of cellular antioxidants, and oxidative stress is implicated in statin-induced liver injury. This study investigated mechanisms of ATO-induced hepatotoxicity and potential mitigation by Nrf2 signaling. ATO reduced Nrf2 and antioxidant enzyme superoxide dismutase-2 (SOD2) expression in human hepatocarcinoma HepG2 cells. ATO also induced concentration-dependent HepG2 cell toxicity, reactive oxygen species (ROS) accumulation, and mitochondrial dysfunction as evidenced by decreased mitochondrial membrane potential (MMP) and cellular adenosine triphosphate (ATP). Further, ATO induced mitochondria-dependent apoptosis as indicated by increased Bax/Bcl-2 ratio, cleaved caspase-3, mitochondrial cytochrome c release and Annexin V-fluorescein isothiocyanate/propidium iodide staining. Tert-butylhydroquinone enhanced Nrf2 and SOD2 expression, and partially reversed ATO-induced cytotoxicity, ROS accumulation, MMP reduction, ATP depletion and mitochondria-dependent apoptosis. In conclusion, the present study demonstrates that ATO induces mitochondrial dysfunction and cell apoptosis in HepG2 cells, at least in part, via inhibition of the Nrf2 pathway. Nrf2 pathway activation is a potential prevention for ATO-induced liver injury.

Systematic review with a meta-analysis: clinical effects of statins on the reduction of portal hypertension and variceal haemorrhage in cirrhotic patients

BACKGROUND

Statins may improve outcomes in patients with cirrhosis. We performed a systematic review and meta-analysis to evaluate the effect of statins on patients with cirrhosis and related complications, especially portal hypertension and variceal haemorrhage.

METHODS

Studies were searched in the PubMed, Embase and Cochrane library databases up to February 2019. The outcomes of interest were associations between statin use and improvement in portal hypertension (reduction >20% of baseline or <12 mm Hg) and the risk of variceal haemorrhage. The relative risk (RR) with a 95% CI was pooled and calculated using a random effects model. Subgroup analyses were performed based on the characteristics of the studies.

RESULTS

Eight studies (seven randomised controlled trials (RCTs) and one observational study) with 3195 patients were included. The pooled RR for reduction in portal hypertension was 1.91 (95% CI, 1.04 to 3.52; I²=63%) in six RCTs. On subgroup analysis of studies that used statin for 1 month, the RR was 2.01 (95% CI, 1.31 to 3.10; I²=0%); the pooled RR for studies that used statins for 3 months was 3.76 (95% CI, 0.36 to 39.77; I²=75%); the pooled RR for studies that used non-selective beta-blockers in the control group was 1.42 (95% CI, 0.82 to 2.45; I²=64%); the pooled RR for studies that used a drug that was not reported in the control group was 4.21 (95% CI, 1.52 to 11.70; I²=0%); the pooled RR for studies that used simvastatin was 2.20 (95% CI, 0.92 to 5.29; I²=69%); RR for study using atorvastatin was 1.82 (95% CI, 1.00 to 3.30). For the risk of a variceal haemorrhage, the RR based on an observational study was 0.47 (95% CI, 0.23 to 0.94); in two RCTs, the pooled RR was 0.88 (95% CI, 0.52 to 1.50; I²=0%). Overall, the summed RR was 0.64 (95% CI, 0.42 to 0.99; I²=6%).

CONCLUSION

Statins may improve hypertension and decrease the risk of variceal haemorrhage according to our assessment. However, further and larger RCTs are needed to confirm this conclusion.

Effect of simvastatin on bovine intramuscular and subcutaneous adipocytes proliferation and gene expression in vitro

Simvastatin (SIM) is a widely used anticholesterolemic drug that blocks the biosynthesis of cholesterol. However, SIM also has pleiotropic effects on 3-hydroxy-3-methyglutary-CoA reductase (HMGR), cholesteryl ester transfer protein (CETP), and lipoprotein lipase (LPL), which are important genes in the cholesterol biosynthesis and transport processes. We investigated the effects of different concentrations of SIM on the mRNA expression of these genes in bovine intramuscular and subcutaneous adipocytes from the longissimus dorsi muscle and subcutaneous fat tissues of Luxi Yellow cattle. The results showed that SIM treatment showed dose-dependent toxicity on normal adipose cells, but no effect on cell proliferation. SIM decreased HMGR expression in a dose-dependent manner but showed no significant effect on CETP and LPL expression. Thus, SIM may lower the cholesterol content by decreasing the HMGR expression level, but CETP and LPL may be regulated through other mechanisms, which require further investigation.

Inhibition of recombinant enzyme 3-hydroxy-3-methylglutaryl-CoA reductase from Candida glabrata by α-asarone-based synthetic compounds as antifungal agents

Due to increasing resistance of Candida species to antifungal drugs, especially azoles, new drugs are needed. The proposed compounds 3 and 4 are analogous to α-asarone (2), a naturally occurring potent inhibitor of HMGR with hypolipidemic and antifungal activity. We used the recombinant enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase of Candida glabrata (CgHMGR) as a model to test the effectiveness of the test compounds. Compounds 3 and 4 demonstrated inhibitory kinetics, having lower IC₅₀ values (42.65 μM and 28.77 μM, respectively) than compound 2 (>100 μM). The docking studies showed better binding energies for compounds 3 and 4 (-5.35 and -6.1 kcal/mol, respectively) than for compound 2 (-4.53 kcal/mol). These findings suggest that the tested compounds are better than their natural analogue. Plaque assays were performed on the C. glabrata strain CBS138 by applying ergosterol or cholesterol to evaluate the possible reversal of the inhibition induced by compounds 2, 3 and 4. Inhibition was easily suppressed in all three cases, recovering the viability of C. glabrata. These results reveal that the CgHMGR model is excellent for testing antifungals. Compound 4 produced the best effect and is herein proposed as a new potent antifungal agent.

Atorvastatin ameliorates early brain injury through inhibition of apoptosis and ER stress in a rat model of subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a severe cerebrovascular disease with very poor prognosis. The aim of the present study was to evaluate the protective effects of atorvastatin on early brain injury (EBI) after SAH using a perforation SAH model. Male Sprague–Dawley rats were randomly divided into four groups: the sham group, the SAH group (model group), SAH + 10 mg.kg⁻¹.day⁻¹ atorvastatin (low atorvastatin group), and SAH + 20 mg.kg⁻¹.day⁻¹ atorvastatin (high atorvastatin group). Atorvastatin was administered orally by gastric gavage for 15 days before operation. At 24 h after SAH, we evaluated the effects of atorvastatin on brain water content, apoptosis by TUNEL assay and scanning electron microscope (SEM), and the expression of apoptosis-related proteins by immunofluorescence and Western blotting analysis. Compared with the sham group, we observed increased brain water content, significant apoptosis, and elevated levels of apoptosis-related proteins including caspase-3, CCAAT enhancer-binding protein homologous protein (CHOP), the 78-kDa glucose-regulated protein (GRP78), and aquaporin-4 (AQP4) in the SAH group. Atorvastatin administration under all doses could significantly reduce brain water content, apoptosis, and the expression levels of caspase-3, CHOP, GRP78, and AQP4 at 24 h after SAH. Our data show that early treatment with atorvastatin effectively ameliorates EBI after SAH through anti-apoptotic effects and the effects might be associated inhibition of caspase-3 and endoplasmic reticulum (ER) stress related proteins CHOP and GRP78.

Hepatotoxicity associated with statins

Treatment with statins is known all over the world. They are generally considered safe at therapeutic doses. Nevertheless, clinical trials are not enough to assess their scarce adverse effects such as idiosyncratic drug induced liver injury (DILI). Due to some conditions, such as concomitant usage (drug-drug interaction using an identical metabolising enzyme) and genetic polymorphisms, there is an increasing concern about their safety. Hepatotoxicity and rhabdomyolysis have begun to appear in published studies. Most of investigations have focused on both these adverse effects and mechanisms of drug induced toxicity. The present review has attempted to compile almost all of the existing studies on the hepatotoxicity of statins but not rhabdomyolysis. The aim of our study is to provide an overview of the studies on the statin-associated hepatotoxicity and to discuss the published studies. The researchers are of the opinion that the research on this topic is incomplete but extremely necessary.

A Multicenter and Randomized Controlled Trial of Bicyclol in the Treatment of Statin-Induced Liver Injury

BACKGROUND The aim of this study was to evaluate the efficacy and safety of bicyclol treatment in statin-induced liver injury. MATERIAL AND METHODS The study included 168 patients with liver injury caused by statins. Patients were randomized into two four-week treatment groups: bicyclol 25 mg three times daily or polyene phosphatidylcholine 456 mg three times daily as control. Serum biochemical indexes were compared before and after treatment. RESULTS Significant differences in alanine transaminase (ALT) levels among the three measurements before and after treatment in the two groups at different time points were observed (p<0.01). There was a significant difference (p<0.01) between two weeks and four weeks after treatment compared to the baseline period. There was a significant interaction (p=0.003) between the two groups and time factors. After two and four weeks of treatment, the ALT levels in the control group (68.20±26.31, 50.71±27.13 respectively) were higher compared to the ALT in the bicyclol group (49.33±21.39, 30.36±17.41 respectively) (p<0.01). After four weeks of treatment, the normalization rates of bicyclol and polyene phosphatidylcholine groups were 74.68% and 46.15%, respectively. The efficacy of bicyclol was significantly better than that of polyene phosphatidylcholine (p<0.05). The incidence of adverse reactions in the bicyclol and polyene phosphatidylcholine groups were 2.53% and 2.56%, respectively, with no statistically significant differences observed between the two groups (p>0.05). CONCLUSIONS These findings suggest that trends of ALT changes in the two groups were different, and the improvement of ALT was more obvious in the bicyclol group. Bicyclol is considered to be safe and effective in the treatment of statin-induced liver injury.

Distribution of androstenedione and its effects on total free fatty acids in pregnant rats

Androstenedione, an anabolic steroid used to enhance athletic performance, was administered in corn oil by gastric intubation once daily in the morning to nonpregnant female rats at a dose of 5 or 60mg/kg/day, beginning two weeks before mating and continuing through gestation day (GD) 19. On GD 20, the distribution of androstenedione and other steroid metabolites was investigated in the maternal plasma and target organs, including brain and liver. The concentration of estradiol in plasma approached a statistically significant increase after treatment as compared with the controls, whereas the levels of androstenedione, testosterone and progesterone were not significantly different from the controls. In the liver, the concentrations of androstenedione and estradiol only were increased in a dose-related manner. None of these steroids was detectable in the brain. Androstenedione treatment also produced changes in the level of selected free fatty acids (FFAs) in the maternal blood, brain, liver and fetal brain. The concentrations of palmitic acid (16:0) and stearic acid (18:0) in the plasma were not significantly different between the controls and treated rats. However, oleic acid (18:1), linoleic acid (18:2) and docosahexaenoic acid (DHA, 22:6) were 17.94 ± 2.06 μg/ml, 24.23 ± 2.42 μg/ml and 4.08 ± 0.53 μg/ml, respectively, in the controls, and none of these fatty acids was detectable in the treated plasma. On the other hand, palmitic, stearic, oleic, linoleic and DHA were present in both control and treated livers. Among the FFAs in liver, linoleic and DHA were increased 87% and 169%, respectively, over controls. Palmitic, stearic and oleic acids were not significantly affected by the 60 mg/kg treatment. These were present in both control maternal and fetal brains, whereas linoleic acid was found only in fetal brain control. DHA was present only in the control maternal brain (0.02 ± 0.02 μg/mg protein) and fetal brain (0.24 ± 0.15 μg/mg protein). The results indicated that androstenedione exhibits significantly different effects on the FFA composition among target organs during pregnancy.

Non-traditional dosing of statins in statin-intolerant patients-is it worth a try?

In this manuscript, three manifestations of statin intolerance will be covered. The first, myopathy, is mostly subjective with variable complaints of myalgias often worsened by exercise, muscle cramping or weakness, and at times associated with a biomarker, elevations in creatine kinase (CK). A rare but serious manifestation can be rhabdomyolysis. The second, liver toxicity, is associated with reversible biochemical increases in transaminases and rarely other liver function tests. Finally, statin-related central nervous system (CNS) toxicity typically defined as cognitive impairment is quite rare and appears to be idiosyncratic. Statin dose alternatives will then be discussed and highlighted in the setting of the new cholesterol-lowering guidelines. Non-statin lipid-altering therapies as well as other alternative therapies will also be reviewed.

Simvastatin modulates mesenchymal stromal cell proliferation and gene expression

Statins are widely used hypocholesterolemic drugs that block the mevalonate pathway, responsible for the biosysnthesis of cholesterol. However, statins also have pleiotropic effects that interfere with several signaling pathways. Mesenchymal stromal cells (MSC) are a heterogeneous mixture of cells that can be isolated from a variety of tissues and are identified by the expression of a panel of surface markers and by their ability to differentiate in vitro into osteocytes, adipocytes and chondrocytes. MSC were isolated from amniotic membranes and bone marrows and characterized based on ISCT (International Society for Cell Therapy) minimal criteria. Simvastatin-treated cells and controls were directly assayed by CFSE (Carboxyfluorescein diacetate succinimidyl ester) staining to assess their cell proliferation and their RNA was used for microarray analyses and quantitative PCR (qPCR). These MSC were also evaluated for their ability to inhibit PBMC (peripheral blood mononuclear cells) proliferation. We show here that simvastatin negatively modulates MSC proliferation in a dose-dependent way and regulates the expression of proliferation-related genes. Importantly, we observed that simvastatin increased the percentage of a subset of smaller MSC, which also were actively proliferating. The association of MSC decreased size with increased pluripotency and the accumulating evidence that statins may prevent cellular senescence led us to hypothesize that simvastatin induces a smaller subpopulation that may have increased ability to maintain the entire pool of MSC and also to protect them from cellular senescence induced by long-term cultures/passages in vitro. These results may be important to better understand the pleiotropic effects of statins and its effects on the biology of cells with regenerative potential.

GGPPS deficiency aggravates CCl4-induced liver injury by inducing hepatocyte apoptosis

GGPPS catalyses the expression of GGPP, a key protein in the mevalonate metabolic pathway. HMG-CoA reductase inhibitor statins can induce liver injury by inhibiting GGPP. However, the function of GGPPS in liver injury has not yet been revealed. In this study, we found that GGPPS increased in liver injury and that GGPPS deletion augmented liver injury and fibrosis. GGPPS inhibition induced hepatocyte apoptosis, inflammation and TGF-β1 secretion, which activated hepatic stellate cells. Our findings imply that GGPPS deletion induces hepatocyte apoptosis, which makes the liver vulnerable to hepatotoxicity.

Protective Effects of N-acetylcysteine Against the Statins Cytotoxicity in Freshly Isolated Rat Hepatocytes

PURPOSE

Hepatotoxicity is one of the most important side effects of the statins therapy as lipid-lowering agents. However, the mechanism(s) of hepatotoxicity induced by these drugs is not clearly understood yet, and no hepatoprotective agent has been developed against this complication.

METHODS

The protective effect of N-acetylcysteine (NAC) against statins-induced cytotoxicity was evaluated by using freshly isolated rat hepatocytes. Hepatocytes were prepared by the method of collagenase enzyme perfusion via portal vein. This technique is based on liver perfusion with collagenase after removal of calcium ion (Ca2+) with a chelator (ethylene glycol tetra acetic acid (EGTA) 0.5 mM). The level of parameters such as cell death, ROS formation, lipid peroxidation, mitochondrial membrane potential (MMP) in the statins-treated hepatocytes were determined. Additionally, the mentioned markers were assessed in the presence of NAC.

RESULTS

Incubation of hepatocytes with the statins resulted in cytotoxicity characterized by an elevation in cell death, increasing ROS generation and consequently lipid peroxidation and impairment of mitochondrial function. Administration of NAC caused reduction in amount of ROS formation, lipid peroxidation and finally, cell viability and mitochondrial membrane potential (MMP) were improved.

CONCLUSION

This study confirms that oxidative stress and consequently mitochondrial dysfunction is one of the mechanisms underlying the statins-induced liver injury and treating hepatocytes by NAC (200 μM) attenuates this cytotoxicity.

Statins, Bcl-2, and apoptosis: cell death or cell protection?

Statins have proven their effectiveness in the treatment of cardiovascular disease. This class of drugs has also attracted attention as a potential treatment for dissimilar diseases such as certain types of cancers and neurodegenerative diseases. What appears to be a contradiction is that, in the case of cancer, it has been suggested that statins increase apoptosis and alter levels of Bcl-2 family members (e.g., reduce Bcl-2 and increase Bax), whereas studies mainly using noncancerous cells report opposite effects. This review examined studies reporting on the effects of statins on Bcl-2 family members, apoptosis, cell death, and cell protection. Much, but not all, of the evidence supporting the pro-apoptotic effects of statins is based on data in cancer cell lines and the use of relatively high drug concentrations. Studies indicating an anti-apoptotic effect of statins are fewer in number and generally used much lower drug concentrations and normal cells. Those conclusions are not definitive, and certainly, there is a need for additional research to determine if statin repositioning is justified for noncardiovascular diseases.

Statin use in primary inflammatory breast cancer: a cohort study

Background:

Some studies have suggested that statins, which have cholesterol-lowering and anti-inflammatory properties, may have antitumor effects. Effects of statins on inflammatory breast cancer (IBC) have never been studied.

Methods:

We reviewed 723 patients diagnosed with primary IBC in 1995–2011 and treated at The University of Texas MD Anderson Cancer Center. Statin users were defined as being on statins at the initial evaluation. Based on Ahern et al's statin classification (JNCI, 2011), clinical outcomes were compared by statin use and type (weakly lipophilic to hydrophilic (H-statin) vs lipophilic statins (L-statin)). We used the Kaplan–Meier method to estimate the median progression-free survival (PFS), overall survival (OS) and disease-specific survival (DSS), and a Cox proportional hazards regression model to test the statistical significance of potential prognostic factors.

Results:

In the multivariable Cox model, H-statins were associated with significantly improved PFS compared with no statin (hazard ratio=0.49; 95% confidence interval=0.28–0.84; P<0.01); OS and DSS P-values were 0.80 and 0.85, respectively. For L-statins vs no statin, P-values for PFS, DSS, and OS were 0.81, 0.4, and 0.74, respectively.

Conclusion:

H-statins were associated with significantly improved PFS. A prospective randomised study evaluating the survival benefits of statins in primary IBC is warranted.

Safety of statins

Statins are an established class of drugs with proven efficacy in cardiovascular risk reduction. The concern over statin safety was first raised with the revelation of myopathy and rhabdomyolysis with the use of now withdrawn cerivastatin. Enhanced understanding of the mechanisms behind adverse effects of statins including an insight into the pharmacokinetic properties have minimised fear of statin use among clinicians. Studies reveal that occurrence of myopathy and rhabdomyolysis are rare 1/100000 patient-years. The risk of myopathy/rhabdomyolysis varies between statins due to varying pharmacokinetic profiles. This explains the differing abilities of statins to adverse effects and drug interaction potentials that precipitate adverse effects. Higher dose of rosuvastatin (80 mg/day) was associated with proteinuria and hematuria while lower doses were devoid of such effects. Awareness of drugs interacting with statins and knowledge of certain combinations such as statin and fibrates together with monitoring of altered creatine kinase activity may greatly minimise associated adverse effects. Statins also asymptomatically raise levels of hepatic transaminases but are not correlated with hepatotoxicity. Statins are safe and well tolerated including more recent potent statins such as, rosuvastatin. The benefits of intensive statin use in cardiovascular risk reduction greatly outweigh risks. The present review discusses underlying causes of statin-associated adverse effects including management in high risk groups.

Differential mitochondrial toxicity screening and multi-parametric data analysis

Early evaluation of new drug entities for their potential to cause mitochondrial dysfunction is becoming an important task for drug development. Multi-parametric high-content screening (mp-HCS) of mitochondrial toxicity holds promise as a lead in-vitro strategy for drug testing and safety evaluations. In this study, we have developed a mp-HCS and multi-parametric data analysis scheme for assessing cell responses to induced mitochondrial perturbation. The mp-HCS measurements are shown to be robust enough to allow for quantitative comparison of biological systems with different metabolic pathways simulated by alteration of growth media. Substitution of medium glucose for galactose sensitized cells to drug action and revealed novel response parameters. Each compound was quantitatively characterized according to induced phenotypic changes of cell morphology and functionality measured by fluorescent biomarkers for mitochondrial activity, plasma membrane permeability, and nuclear morphology. Descriptors of drug effects were established by generation of a SCRIT (Specialized-Cell-Response-to-Induced-Toxicity) vector, consisting of normalized statistical measures of each parameter at each dose and growth condition. The dimensionality of SCRIT vectors depends on the number of parameters chosen, which in turn depends on the hypothesis being tested. Specifically, incorporation of three parameters of response into SCRIT vectors enabled clustering of 84 training compounds with known pharmacological and toxicological activities according to the degree of toxicity and mitochondrial involvement. Inclusion of 6 parameters enabled the resolution of more subtle differences between compounds within a common therapeutic class; scoring enabled a ranking of statins in direct agreement with clinical outcomes. Comparison of drug-induced changes required variations in glucose for separation of mitochondrial dysfunction from other types of cytotoxicity. These results also demonstrate that the number of drugs in a training set, the choice of parameters used in analysis, and statistical measures are fundamental for specific hypothesis testing and assessment of quantitative phenotypic differences.

Atorvastatin up-regulate toxicologically relevant genes in rainbow trout gills

There are large and increasing discharges of statins into the aquatic environment. Statins are cholesterol-lowering pharmaceuticals, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, an enzyme in the cholesterol synthesis pathway. Earlier studies have shown that statins will affect the expression of a range of genes in mammalian tissues and this group of pharmaceuticals has also been shown to affect membrane transporters. Changes in gene expression and ion transport in aquatic organisms may have dramatic consequences for the individual. The aim of the present study was to clarify whether waterborne exposure to a selected statin, atorvastatin, would affect gene expression in rainbow trout (Oncorhynchus mykiss) gill or liver or ion regulation in gills. Juvenile rainbow trout were exposed to two atorvastatin acid and atorvastatin lactone concentrations for 7 days (nominal concentrations 200 ng L(-1) and 10 μg L(-1)). The exposures caused up-regulated gene expression in gill, not liver, and only at the lowest concentration. Genes involved in membrane transport (pgp, mrp1), oxidative stress response (sod, mt), apoptosis (bax) and biotransformation (sult2b) were differentially expressed whereas the expression of genes involved in cholesterol biosynthesis (hmgr, fdps) or peroxisomal proliferation (ppar) were not affected. There were no significant changes in gill Na(+)/K(+) ATPase activity following exposure to atorvastatin. The pattern of differentially expressed genes in rainbow trout gills differ from responses previously observed in mammalian tissues following statin exposure.

Occurrence of pharmaceutical compounds in wastewater process streams in Dublin, Ireland

The aim of this work is to establish baseline levels of pharmaceuticals in three wastewater treatment plant (WWTP) streams in the greater Dublin region to assess the removal efficiency of the selected WWTPs and to investigate the existence of any seasonal variability. Twenty compounds including several classes of antibiotics, acidic and basic pharmaceuticals, and prescribed medications were selected for investigation using a combination of membrane filtration, solid phase extraction (SPE) cleanup, and liquid chromatography-electrospray ionization tandem mass spectrometry. Fourteen of the selected compounds were found in the samples. Increased effluent concentrations, compared to influent concentrations, for a number of compounds (carbamazepine, clotrimazole, propranolol, nimesulide, furosemide, mefenamic acid, diclofenac, metoprolol, and gemfibrozil) were observed. The detected concentrations were generally below toxicity levels and based on current knowledge are unlikely to pose any threat to aquatic species. Mefenamic acid concentrations detected in both Leixlip and Swords effluents may potentially exert ecotoxicological effects with maximum risk quotients (i.e., ratio of predicted exposure concentration to predicted no effect concentration) of 4.04 and 1.33, respectively.

Species-dependent sensitivity to contaminants: an approach using primary hepatocyte cultures with three marine fish species

There is limited knowledge about the sensitivity of different fish species to environmental pollutants. Such information is pivotal in risk assessment and to understand why some species appear to be more tolerant to contaminants than others. The aim of the current study was to evaluate whether primary hepatocyte cultures of three marine fish species could be established in the field and whether their sensitivity to selected contaminants would differ. Primary hepatocyte cultures of three marine fish species (plaice, long rough dab, Atlantic cod) were established and exposed for 24 h to copper (20-2500 mg L⁻¹) and statins (1-200 mg L⁻¹). Endpoints were esterase activity, metabolic activity and reduced glutathione (GSH) content, all using fluorescent probes. Flatfish hepatocytes were more susceptible to copper and statin exposure than hepatocytes from cod. This study has shown that species-dependent differences in contaminant sensitivity can be investigated using primary hepatocyte cultures.

Changes of pulmonary pathology and gene expressions after simvastatin treatment in the monocrotaline-induced pulmonary hypertension rat model

BACKGROUND AND OBJECTIVES

Simvastatin's properties are suggestive of a potential pathophysiologic role in pulmonary hypertension. The objectives of this study were to investigate changes of pulmonary pathology and gene expressions, including endothelin (ET)-1, endothelin receptor A (ERA), inducible nitric oxide synthase (NOS2), endothelial nitric oxide synthase (NOS3), matrix metalloproteinase (MMP) 2, tissue inhibitor of matrix metalloproteinases (TIMP) and caspase 3, and to evaluate the effect of simvastatin on monocrotaline (M)-induced pulmonary hypertension.

MATERIALS AND METHODS

Six week old male Sprague-Dawley rats were treated, as follows: control group, subcutaneous (sc) injection of saline; M group, sc injection of M (60 mg/kg); and simvastatin group, sc injection of M (60 mg/kg) plus 10 mg/kg/day simvastatin orally.

RESULTS

On day 28, right ventricular hypertrophy (RVH) significantly decreased in the simvastatin group compared to the M group. Similarly, right ventricular pressure significantly decreased in the simvastatin group on day 28. From day 7, the ratio of medial thickening of the pulmonary artery was significantly increased in the M group, but there was no significant change in the simvastatin group. The number of muscular pulmonary arterioles was significantly reduced in the simvastatin group. On day 5, gene expressions of ET-1, ERA, NOS2, NOS3, MMP and TIMP significantly decreased in the simvastatin group.

CONCLUSION

Administration of simvastatin exerted weak inhibitory effects on RVH and on the number of muscular pulmonary arterioles, during the development of M-induced pulmonary hypertension in rats. Simvastatin decreased gene expressions on day 5.

Central role of mitochondria in drug-induced liver injury

A frequent mechanism for drug-induced liver injury (DILI) is the formation of reactive metabolites that trigger hepatitis through direct toxicity or immune reactions. Both events cause mitochondrial membrane disruption. Genetic or acquired factors predispose to metabolite-mediated hepatitis by increasing the formation of the reactive metabolite, decreasing its detoxification, or by the presence of critical human leukocyte antigen molecule(s). In other instances, the parent drug itself triggers mitochondrial membrane disruption or inhibits mitochondrial function through different mechanisms. Drugs can sequester coenzyme A or can inhibit mitochondrial β-oxidation enzymes, the transfer of electrons along the respiratory chain, or adenosine triphosphate (ATP) synthase. Drugs can also destroy mitochondrial DNA, inhibit its replication, decrease mitochondrial transcripts, or hamper mitochondrial protein synthesis. Quite often, a single drug has many different effects on mitochondrial function. A severe impairment of oxidative phosphorylation decreases hepatic ATP, leading to cell dysfunction or necrosis; it can also secondarily inhibit ß-oxidation, thus causing steatosis, and can also inhibit pyruvate catabolism, leading to lactic acidosis. A severe impairment of β-oxidation can cause a fatty liver; further, decreased gluconeogenesis and increased utilization of glucose to compensate for the inability to oxidize fatty acids, together with the mitochondrial toxicity of accumulated free fatty acids and lipid peroxidation products, may impair energy production, possibly leading to coma and death. Susceptibility to parent drug-mediated mitochondrial dysfunction can be increased by factors impairing the removal of the toxic parent compound or by the presence of other medical condition(s) impairing mitochondrial function. New drug molecules should be screened for possible mitochondrial effects.

Statin prescriptions and breast cancer recurrence risk: a Danish nationwide prospective cohort study

BACKGROUND

Accumulating evidence suggests that statins affect diseases other than cardiovascular disease, including cancer, and that these effects may depend on the lipid solubility of specific statins. Though many studies have reported an association between statin use and breast cancer incidence, the relationship between statin use and breast cancer recurrence has not been well studied.

METHODS

We conducted a nationwide, population-based prospective cohort study of all female residents in Denmark diagnosed with stage I-III invasive breast carcinoma who were reported to the Danish Breast Cancer Cooperative Group registry between 1996 and 2003 (n = 18,769). Women were followed for a median of 6.8 years after diagnosis. Prescriptions for lipophilic and hydrophilic statins were ascertained from the national electronic pharmacy database. Associations between statin prescriptions and breast cancer recurrence were estimated with generalized linear models and Cox proportional hazards regression with adjustment for age and menopausal status at diagnosis; histological grade; estrogen receptor status; receipt of adjuvant therapy; type of primary surgery received; pre-diagnosis hormone replacement therapy; and co-prescriptions of aspirin, angiotensin-converting enzyme inhibitors, nonsteroidal anti-inflammatory drugs, or anticoagulants. All statistical tests were two-sided.

RESULTS

Most prescriptions for lipophilic statins in the study population were for simvastatin. Exclusive simvastatin users experienced approximately 10 fewer breast cancer recurrences per 100 women after 10 years of follow-up (adjusted 10-year risk difference = -0.10, 95% confidence interval = -0.11 to -0.08), compared with women who were not prescribed a statin. Exclusive hydrophilic statin users had approximately the same risk of breast cancer recurrence as women not prescribed a statin over follow-up (adjusted 10-year risk difference = 0.05, 95% confidence interval = -0.01 to 0.11).

CONCLUSIONS

Simvastatin, a highly lipophilic statin, was associated with a reduced risk of breast cancer recurrence among Danish women diagnosed with stage I-III breast carcinoma, whereas no association between hydrophilic statin use and breast cancer recurrence was observed.

Effects of lovastatin on the pharmacokinetics of diltiazem and its main metabolite, desacetyldiltiazem, in rats: possible role of cytochrome P450 3A4 and P-glycoprotein inhibition by lovastatin

OBJECTIVES

The purpose of this study was to examine the effects of lovastatin on cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp) in vitro and then to determine the effects of lovastatin on the pharmacokinetics of diltiazem and its main metabolite, desacetyldiltiazem, in rats.

METHODS

The pharmacokinetic parameters of diltiazem and desacetyldiltiazem were determined after orally administering diltiazem (12 mg/kg) to rats in the presence and absence of lovastatin (0.3 and 1.0 mg/kg). The effect of lovastatin on P-gp as well as CYP3A4 activity was also evaluated.

KEY FINDINGS

Lovastatin inhibited CYP3A4 enzyme activity with a 50% inhibition concentration of 6.06 µM. In addition, lovastatin significantly enhanced the cellular accumulation of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp. Compared with the control (given diltiazem alone), the presence of lovastatin significantly altered the pharmacokinetic parameters of diltiazem. The areas under the plasma concentration-time curve (AUC) and the peak concentration of diltiazem were significantly increased (P < 0.05, 1.0 mg/kg) in the presence of lovastatin. Consequently, the absolute bioavailability values of diltiazem in the presence of lovastatin (11.1% at 1.0 mg/kg) were significantly higher (P < 0.05) than that of the control group (7.6%). The metabolite-parent AUC ratio in the presence of lovastatin (1.0 mg/kg) was significantly (P < 0.05) decreased compared with the control group.

CONCLUSIONS

It might be considered that lovastatin resulted in reducing the first-pass metabolism in the intestine and/or in the liver via inhibition of CYP3A4 and increasing the absorption of diltiazem in the intestine via inhibition of P-gp by lovastatin.

Hepatotoxicity fears contribute to underutilization of statin medications by primary care physicians

INTRODUCTION

The safety and efficacy of hydroxymethylglutaryl CoA reductase inhibitors (statins) have been extensively demonstrated, but in clinical practice, there remains significant underutilization of these medications. The authors hypothesized that this underutilization could stem in part from fear of liver damage caused by statins. The purpose was to determine whether concern about hepatotoxicity acts as a barrier among primary care physicians to prescribing statins for patients with elevated liver transaminase values and/or underlying liver disease.

METHOD

The survey included 937 primary care physicians from 138 academic centers in the United States, and the following were measured: (1) comparison of statin prescribing for patients with clinical indications and (a) no mention of liver transaminase values, (b) elevated liver transaminase values and (c) underlying liver disease; (2) correlation between perception of statin hepatotoxicity and statin prescribing.

RESULTS

Seventy-one percent of respondents would prescribe statins in scenario 1, (45-year-old woman with low-density lipoprotein 240 mg/dL), whereas only 50% would prescribe statins if the baseline liver transaminase values were elevated to 1.5 times upper limit of normal (P < 0.001). This prescribing rate dropped even further to 40% in scenario 3 (55-year-old man with known coronary disease, low-density lipoprotein 250 mg/dL and hepatitis C). Thirty-seven percent of respondents had falsely elevated perceptions of statin hepatotoxicity risk, and these perceptions correlated inversely with statin prescribing. The method of survey administration prevented calculation of response rate, possibility of response bias exists.

CONCLUSION

Despite extensive data documenting safety of statins, primary care physicians harbor significant hepatotoxicity concerns, and these concerns act as a barrier to statin utilization.

Pharmacokinetic interaction between oral lovastatin and verapamil in healthy subjects: role of P-glycoprotein inhibition by lovastatin

BACKGROUND

Lovastatin is an inhibitor of P-glycoprotein (P-gp) and is metabolized by the cytochrome P450 (CYP) 3A4 isoenzyme. Verapamil is a substrate of both P-gp and CYP3A4. It is therefore likely that lovastatin can alter the absorption and metabolism of verapamil.

METHODS

The pharmacokinetic parameters of verapamil and one of its metabolites, norverapamil, were compared in 14 healthy male Korean volunteers (age range 22-28 years) who had been administered verapamil (60 mg) orally in the presence or absence of oral lovastatin (20 mg). The design of the experiment was a standard 2 x 2 crossover model in random order.

RESULTS

The pharmacokinetic parameters of verapamil were significantly altered by the co-administration of lovastatin compared to the control. The area under the plasma concentration-time curve (AUC (0-infinity)) and the peak plasma concentration of verapamil were significantly increased by 62.8 and 32.1%, respectively. Consequently, the relative bioavailability of verapamil was also significantly increased (by 76.5%). The (AUC (0-infinity)) of norverapamil and the terminal half-life of verapamil did not significantly changed with lovastatin coadministration. The metabolite-parent ratio was significantly reduced (29.2%) in the presence of lovastatin.

CONCLUSION

Lovastatin increased the absorption of verapamil by inhibiting P-gp and inhibited the first-pass metabolism of verapamil by inhibiting CYP3A4 in the intestine and/or liver in humans.

Low dose simvastatin induces compositional, structural and dynamic changes in rat skeletal extensor digitorum longus muscle tissue

Statins are commonly used drugs in the treatment of hypercholesterolaemia. There are many adverse effects of statins on skeletal muscle, but the underlying mechanisms remain unclear. In the present study, the effects of low dose (20 mg/kg) simvastatin, a lipophilic statin, on rat EDL muscle (extensor digitorum longus muscle) were investigated at the molecular level using FTIR (Fourier-transform infrared) spectroscopy. FTIR spectroscopy allows us rapid and sensitive determination of functional groups belonging to proteins, lipids, carbohydrates and nucleic acids simultaneously. The results revealed that simvastatin treatment induces a significant decrease in lipid, nucleic acid, protein and glycogen content. A significant increase in the lipid/protein and nucleic acid/protein ratios was also obtained with simvastatin treatment. Furthermore, an increase in lipid order and membrane fluidity was detected. A decrease in the bandwidth of the amide I band and shifting of the position of this band to higher frequency values in treated muscle indicates structural changes in proteins. Detailed secondary structure analysis of the amide I band revealed a significant increase in antiparallel and aggregated beta-sheet, random coil structure and a significant decrease in beta-sheet structure, which indicates protein denaturation.

Lipophilic but not hydrophilic statins selectively induce cell death in gynaecological cancers expressing high levels of HMGCoA reductase

Recent reports have suggested that statins induce cell death in certain epithelial cancers and that patients taking statins to reduce cholesterol levels possess lower cancer incidence. However, little is known about the mechanisms of action of different statins or the effects of these statins in gynaecological malignancies. The apoptotic potential of two lipophilic statins (lovastatin and simvastatin) and one hydrophilic statin (pravastatin) was assessed in cancer cell lines (ovarian, endometrial and cervical) and primary cultured cancerous and normal tissues. Cell viability was studied by MTS assays and apoptosis was confirmed by Western blotting of PARP and flow cytometry. The expressions of key apoptotic cascade proteins were analysed. Our results demonstrate that both lovastatin and simvastatin, but not pravastatin, selectively induced cell death in dose- and time-dependent manner in ovarian, endometrial and cervical cancers. Little or no toxicity was observed with any statin on normal cells. Lipophilic statins induced activation of caspase-8 and -9; BID cleavage, cytochrome C release and PARP cleavage. Statin-sensitive cancers expressed high levels of HMG-CoA reductase compared with resistant cultures. The effect of lipophilic statins was dependent on inhibition of enzymatic activity of HMG-CoA reductase since mevalonate pre-incubation almost completely abrogated the apoptotic effect. Moreover, the apoptotic effect involved the inhibition of synthesis of geranylgeranyl pyrophosphate rather than farnesyl pyrophosphate. In conclusion, lipophilic but not hydrophilic statins induce cell death through activation of extrinsic and intrinsic apoptotic cascades in cancerous cells from the human female genital tract, which express high levels of HMG-CoA reductase. These results promote further investigation in the use of lipophilic statins as anticancer agents in gynaecological malignancies.

Atorvastatin ameliorates cerebral vasospasm and early brain injury after subarachnoid hemorrhage and inhibits caspase-dependent apoptosis pathway

Backgroud

Cerebral vasospasm (CVS) and early brain injury remain major causes of morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH). Hydroxymethylglutaryl coenzyme A reductase inhibitors, also known as statins, has the neuroprotective effects and ameliorating CVS after SAH. This study was designed to explore apoptosis inhibiting effects of atorvastatin and its potential apoptotic signal pathway after SAH.

Results

Preserving blood-brain-barrier permeability, decreasing brain edema, increasing neurological scores and ameliorating cerebral vasospasm were obtained after prophylactic use of atorvastatin. TUNEL-positive cells were reduced markedly both in basilar artery and in brain cortex by atorvastatin. Apoptosis-related proteins P53, AIF and Cytochrome C were up-regulated after SAH, while they were not affected by atorvastatin. In addition, up-regulation of caspase-3 and caspase-8 after SAH was decreased by atorvastatin treatment both in mRNA and in protein levels.

Conclusion

The neuroprotective effects of atorvastatin after SAH may be related to its inhibition of caspase-dependent proapoptotic pathway based on the present results.

Synergistic anti-tumor efficacy of lovastatin and protein kinase C-beta inhibitor in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is characterized by hypervascularity and chemoresistance. Protein kinase C (PKC) participates in cancer progression by enhancing anti-apoptotic signals, angiogenesis, and chemoresistance. Statins have a selective anti-cancer effect due to over-expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR) in cancer cells, but statins may also activate PKC. Thus, we hypothesized that simultaneous treatment with statin and PKC inhibitor might synergistically enhance their anti-tumor efficacies against HCCs.

METHODS

Hepatocellular carcinoma cell growth was assessed using MTS assays, apoptotic cell death by DAPI staining, and apoptotic signaling cascades were explored by immunoblotting. An in vivo model of HCC was established in C3H mice intradermally implanted with MH134 cells. Lovastatin and/or a PKC inhibitor (enzastaurin) was subsequently administered. Anti-tumor efficacies were evaluated by measuring tumor volumes and quantifying apoptotic cells and microvessel densities (MVD).

RESULTS

Co-treatment with lovastatin and enzastaurin was found to synergistically suppress HCC cell growth in vitro. Lovastatin induced HCC cellular apoptosis by activating mitochondrial apoptotic signals, and although enzastaurin alone did not induce apoptosis, its addition significantly enhanced lovastatin-induced apoptosis. This enhanced apoptosis was attributed to increased caspase-9 activation in these cells. Moreover, tumor growth was significantly suppressed in mice co-treated with lovastatin and enzastaurin, and percentages of TUNEL-positive cells were significantly increased and MVDs were significantly decreased in those mice.

CONCLUSION

Combinatorial treatment with statin and PKC inhibitor was found to enhance anti-tumor efficacy in vivo and in vitro. Further studies are warranted to prove anti-tumor efficacy of this potential therapy in human HCCs.

Beneficial effects of fluvastatin on liver microcirculation and regeneration after massive hepatectomy in rats

Fluvastatin, the first entirely synthetic statin, has a significant cholesterol-lowing effect comparable with other statins. In addition, it has been shown to inhibit oxidative stress and improve vascular endothelial function. The aim of this study was to clarify the pretreatment effects of fluvastatin on liver function after massive hepatectomy in rats. Six-week-old male Wister rats were divided into two groups: a fluvastatin group (group F), pretreated with oral administration of fluvastatin (20 mg/kg per day) for 2 days before 90% hepatectomy; and a control group (group C), pretreated with vehicle for 2 days before hepatectomy. Animals were sacrificed at 0, 12, 24, 48, and 72 h after hepatectomy. The liver regeneration rate, liver function tests, and hepatic stellate cell activation were examined. The liver regeneration rate in group F was significantly higher at 72 h after hepatectomy (P < 0.05). The serum level of total bilirubin in group F was significantly lower at 48 h after hepatectomy (P < 0.05). Sinusoidal area in group F was maintained histologically. Furthermore, the expression of alpha smooth-muscle actin (alpha-SMA) protein in the liver was inhibited in group F at 48 h after hepatectomy. This study demonstrated the beneficial effects of fluvastatin in a lethal massive hepatectomy model using rats, with improved hepatic regeneration and microcirculations, by inhibiting the activation of hepatic stellate cells.

Interaction of the HMG-CoA reductase inhibitor lovastatin and nitric oxide in cardiomyocyte cell death

AIM

The objective of this study was to examine the interaction ofa 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor (statin) with a nitric oxide (NO) donor from the perspective of the impact on cardiomyocyte cell viability.

METHODS

Embryonic chick cardiomyocytes in culture were treated with a wide range of concentrations of sodium nitroprusside (SNP), which releases NO and also generates toxic reactive nitrogen species. SNP was combined with the HMG-CoA reductase inhibitor lovastatin and cell viability was assessed by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay.

RESULTS

SNP and lovastatin each produced a significant (p < 0.01) concentration-dependent increase in cell death. Using SNP concentrations at or below the ED50, SNP (0.01, 0.1 or 0.5 mmol/l) increased the amount of cell death when combined with lovastatin (1, 10, 50 and 100 micromol/l). At lovastatin concentrations of 50 micromol/l and less, the amount of cell death was consistently similar to the arithmetic sum of SNP and lovastatin, suggesting that there was an additive and not synergistic relationship between SNP and lovastatin. In combination with lovastatin (100 micromol/l), however, the amount of cell death was consistently lower than the calculated expected value and suggested saturation of a common mechanism. The combination of SNP and lovastatin produced the characteristic microscopic changes of apoptosis. Considering that both SNP and lovastatin can activate caspase-3, cells were treated with the caspase-3 inhibitor Ac-DEVD-CHO. This inhibitor produced a significant (p < 0.05) and consistent 30% reduction in the amount of cell death induced by SNP and lovastatin.

CONCLUSION

These data suggest that the cardiomyocyte toxicity from NO continues to be evident uninterrupted by and not accentuated by the presence of an HMG-CoA inhibitor. The cardiac adverse effect of each of these agents utilizes a common pathway involving caspase-3 so that their cardiotoxicity can be blunted by a caspase-3 inhibitor.

Simvastatin enhances induction of inducible nitric oxide synthase in 3T3-L1 adipocytes

The present study was designed to determine whether hydroxymethylglutaryl-CoA reductase inhibitors (statins) modulate the NO production via iNOS in adipocytes stimulated by lipopolysaccharide (L) and tumour necrosis factor-alpha (T). Well-differentiated 3T3-L1 adipocytes significantly produced NO by LT-treatment. Pre-incubation with simvastatin, a lipophilic statin, pravastatin, a hydrophilic one, or Y27632, an inhibitor of Rho kinase, further enhanced the production of NO. The effect of simvastatin was offset by mevalonate and geranylgeranyl pyrophosphate (GGPP) but not by squalene. The mRNA level for iNOS parallelled the NO production. The NF-kappaB was activated by the LT-treatment and was further enhanced by simvastatin, pravastatin or Y27632 addition. Mevalonate and GGPP completely offset the effect of simvastatin. Statins and Y27632 also further increased the interleukin-6 secretion in the LT-treated 3T3-L1 adipocytes. These results suggest that statins, especially lipophilic type, enhance induction of iNOS by inhibiting the small GTP-binding protein signal in adipocytes.