Pharmacodynamics and pharmacokinetics of the HMG-CoA reductase inhibitors. Similarities and differences

Ezetimibe alone and in combination lowers the concentration of small, dense low-density lipoproteins in type 2 diabetes mellitus

OBJECTIVE

The effectiveness of the cholesterol absorption inhibitor ezetimibe on LDL subfractions and ultimately on the atherosclerotic risk profile remains controversial. We thus determined the concentration of atherogenic small, dense LDL (sdLDL) in patients with type 2 diabetes and an elevated cardiovascular risk profile.

RESEARCH DESIGN AND METHODS

Multicenter, randomized, open-label 6-week study investigating the effect of ezetimibe 10mg (E), simvastatin 20mg (S) and the combination of ezetimibe-/simvastatin 10/20mg (C) on the concentration of sdLDL separated from fresh plasma by gradient ultracentrifugation in patients with type 2 diabetes (NCT01384058).

RESULTS

Fifty-six patients were screened for sdLDL, 41 were randomized, and 40 patients (12 E, 14 S and 14 C) completed the study. Total and LDL cholesterol fell by 14% (p=0.004) and 15% (p=0.006) with E, 22% (p<0.001) and 32% (p<0.001) with S, and 32% (p<0.001) and 44% (p<0.001) with C, respectively. E reduced the concentration of sdLDL by 20% (p=0.043) whereas S and C reduced sdLDL by 24% (p=0.020) and 33% (p=0.003), respectively, and non-sdLDL by 28% (p=0.004) and 42% (p<0.001), respectively. However, the further drop in sdLDL by adding E to S was not significant.

CONCLUSION

Ezetimibe alone and in combination with simvastatin reduced the concentration of atherogenic sdLDL in patients with type 2 diabetes.

Optimizing secondary prevention: Statin prescribing across East and West London in accordance with NICE guidelines

Objectives

Statins are a well-known primary and secondary prevention drug for cardiovascular disease and NICE guidelines have been issued to identify key indicators for their use. An audit looking into statin prescribing for medical inpatients was carried out in two geographically distinct London hospitals.

Design

A prospective inpatient audit of medical prescription charts was performed. Blood results were reviewed for the inpatients during their admission to identify any contraindications for statin usage (rhabdomyolysis). The medical notes were also reviewed for patient refusal of statin therapy.

Setting

The study was carried out at two distinct hospitals in London. Whipps Cross University Hospital (WCUH) and Chelsea & Westminster Hospital (CWH) are located in East London and West London, respectively. Acute medical, surgical, obstetrics and gynaecology, paediatric and palliative wards were excluded.

Participants

A total of 309 inpatient medical notes and prescription chart data were collected from WCUH (n = 211) and CWH (n = 98).

Main outcome measures

High percentage of hospitalized patients are not prescribed statins despite clear clinical indications for their use. Regardless of geographical and socioeconomic factors between hospitals, statin prescribing remains suboptimal.

Results

The patient demographics in both hospitals were very similar; the mean age at WCUH was 78 ± 15 1SD while at CWH the mean age was 74 ± 15 1SD. The results showed that approximately one-third of patients (30% at WCUH and 33% at CWH) had at least one indication for statin therapy according to NICE guidelines and yet they were not prescribed a statin. Ten percent of patients at WCUH and 13% of patients at CWH had ischaemic heart disease (IHD) and yet were not prescribed statins.

Conclusion

Statin prescription is often overlooked in secondary care with patients being discharged without the appropriate assessment (NICE guidelines), which subsequently means repeat prescriptions are not provided by the GP. This study is the first to show that this problem is not due to resources or geography, but is inherent within the NHS system. Consequently, a revised prescription chart checking system has been suggested for pharmacists and junior doctors.

Cytochrome P450-mediated cardiovascular drug interactions

INTRODUCTION

There are numerous drug-drug interactions (DDIs) related to cardiovascular medications and many of these are mediated via the cytochrome P450 (CYP) system. Some of these may lead to serious adverse events and it is, therefore, essential that clinicians are aware of the important interactions that occur.

AREAS COVERED

An extensive literature search was performed to analyze the CYP-mediated cardiovascular DDIs that lead to a loss of efficacy or potential toxicity. Cardiovascular drugs may be victims or act as perpetrators of DDIs. The paper analyzes CYP-mediated drug interactions concerning anticoagulants, antiplatelet agents, antiarrhythmics, β-blockers, calcium antagonists, antihypertensive medications, lipid-lowering drugs and oral antidiabetic agents.

EXPERT OPINION

Cardiovascular DDIs involving the CYP system are numerous. Additionally, the spectrum of drugs prescribed is constantly changing, particularly with cardiovascular diseases and it is not necessarily the case that drugs that had shown safety earlier will always show safety. Clinicians are encouraged to develop their knowledge of CYP-mediated DDIs so that they can choose safe drug combination regimens, adjust drug dosages appropriately and conduct therapeutic drug monitoring for drugs with narrow therapeutic indices.

Juvenile toxicity assessment of open-acid lovastatin in rats

BACKGROUND

Lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, reduces de novo cholesterol biosynthesis primarily in the liver. Since cholesterol is a major component of brain myelin and peak periods of brain myelination occurs after birth, this study was designed to encompass this period in rats and evaluate the potential neurotoxic effects.

METHODS

The pharmacologically active, open-acid form of lovastatin was administered to groups of 50 Sprague-Dawley rats per sex subcutaneously once daily at dose levels of 0 (vehicle), 2.5, 5, or 10 mg/kg/day beginning on postnatal day 4 and continuing until termination on postnatal day 41 to 51. Physical signs and body weights were monitored during the study. Animals were assessed in a battery of behavioral tests, and at termination a set of animals were examined for gross and histological changes.

RESULTS

There were no test article-related deaths, physical signs, or effects on preweaning and postweaning body weights during the study. In the behavior tests there were no test article-related effects in the passive avoidance, auditory startle habituation, open-field motor activity, or FOB. No test article-related postmortem findings were observed, including brain weights and histomorphology of brain, spinal cord, eye, optic nerve, or peripheral nerve.

CONCLUSION

Based on these results, the no-effect level for general and neurobehavioral toxicity in neonatal rats was ≥10 mg/kg/day for open-acid lovastatin.

A New Improved RP-HPLC Method for Assay of Rosuvastatin Calcium in Tablets

A reliable and sensitive isocratic stability indicating RP-HPLC method has been developed and validated for assay of rosuvastatin calcium in tablets and for determination of content uniformity. An isocratic separation of rosuvastatin calcium was achieved on YMC C8, 150×4.6 mm i.d., 5 μm particle size columns with a flow rate of 1.5 ml/min and using a photodiode array detector to monitor the eluate at 242 nm. The mobile phase consisted of acetonitrile: water (40:60, v/v) pH 3.5 adjusted with phosphoric acid. The drug was subjected to oxidation, hydrolysis, photolysis and thermal degradation. All degradation products in an overall analytical run time of approximately 10 min with the parent compound rosuvastatin eluting at approximately 5.2 min. Response was a linear function of drug concentration in the range of 0.5-80 μg/ml (r(2)= 0.9993) with a limit of detection and quantification of 0.1 and 0.5 μg/ml respectively. Accuracy (recovery) was between 99.6 and 101.7%. Degradation products resulting from the stress studies did not interfere with the detection of rosuvastatin and the assay is thus stability-indicating.

A population pharmacokinetic-pharmacodynamic model for simvastatin that predicts low-density lipoprotein-cholesterol reduction in patients with primary hyperlipidaemia

Simvastatin (SV), a HMG-CoA reductase inhibitor, is widely used for the treatment of hyperlipidaemia. The objectives of the present study were to develop a population pharmacokinetic-pharmacodynamic (PK-PD) model for simvastatin and to evaluate its usefulness in predicting the dose-response relationship of simvastatin in patients with hyperlipidaemia. The data were obtained from a drug-drug interaction study to assess the effect of aspirin on the PK of simvastatin. Twenty-seven healthy volunteers were given simvastatin 40 mg daily for 14 days in whom aspirin 100 mg q.d. was co-administered after day 8. Full PK studies were performed on days 1, 7 and 14 in addition to trough sampling on days 5, 6, 12 and 13. Low-density lipoprotein-cholesterol (LDL-C) levels were also measured serially. Then, a population PK-PD model for simvastatin and its active metabolite, simvastatin acid (SVA), was developed using mixed effect methods (NONMEM Ver. 6.2). A simple linear PK model with parent and metabolite compartments provided the best fit for the 2647 concentrations of simvastatin and simvastatin acid, and a turnover model was used to describe the change in LDL-C levels. The dose-response curve simulated from the final model and those obtained from the literature overlapped very closely. No influence of aspirin was observed in PK or PD. A simple PK-PD model developed using only 2-week study data from fewer than 30 healthy volunteers successfully predicted the dose-response relationship of simvastatin in patients when compared with published data.

mTORC2 is required for proliferation and survival of TSC2-null cells

Mutational inactivation of the tumor suppressor tuberous sclerosis complex 2 (TSC2) constitutively activates mTORC1, increases cell proliferation, and induces the pathological manifestations observed in tuberous sclerosis (TS) and in pulmonary lymphangioleiomyomatosis (LAM). While the role of mTORC1 in TSC2-dependent growth has been extensively characterized, little is known about the role of mTORC2. Our data demonstrate that mTORC2 modulates TSC2-null cell proliferation and survival through RhoA GTPase and Bcl2 proteins. TSC2-null cell proliferation was inhibited not only by reexpression of TSC2 or small interfering RNA (siRNA)-induced downregulation of Rheb, mTOR, or raptor, but also by siRNA for rictor. Increased RhoA GTPase activity and P-Ser473 Akt were inhibited by siRNA for rictor. Importantly, constitutively active V14RhoA reversed growth inhibition induced by siRNA for rictor, siRNA TSC1, reexpression of TSC2, or simvastatin. While siRNA for RhoA had a modest effect on growth inhibition, downregulation of RhoA markedly increased TSC2-null cell apoptosis. Inhibition of RhoA activity downregulated antiapoptotic Bcl2 and upregulated proapoptotic Bim, Bok, and Puma. In vitro and in vivo, simvastatin alone or in combination with rapamycin inhibited cell growth and induced TSC2-null cell apoptosis, abrogated TSC2-null tumor growth, improved animal survival, and prevented tumor recurrence by inhibiting cell growth and promoting apoptosis. Our data demonstrate that mTORC2-dependent activation of RhoA is required for TSC2-null cell growth and survival and suggest that targeting both mTORC2 and mTORC1 by a combination of proapoptotic simvastatin and cytostatic rapamycin shows promise for combinational therapeutic intervention in diseases with TSC2 dysfunction.

Novel effects of statins in enhancing efficacy of chemotherapy in vitro in nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal cancer (NPC) is a relatively uncommon malignant epithelial cancer seen worldwide. The treatment of NPC has evolved toward combined modality treatment with radiation therapy and chemotherapy. However, chemotherapeutic agents currently have a secondary role, due to their lack of efficacy as curative agents. Recent identification of a novel property of statin drugs raises a promising hope that concurrent use of statins may enhance the efficacy of single-drug chemotherapy in NPC. However, the effects of statins have not been studied before in NPC. In this in vitro study, we demonstrate a unique property of statins that can enhance the efficacy of cisplatin in NPC.

METHODS

Primary human NPC cells (CCL-30) were treated with statins and cisplatin concurrently, and the effects on cell proliferation, apoptosis, and cell colony formation were examined.

RESULTS

Statins caused significant decrease in cell proliferation and viability in NPC. Statins also induced loss of cell attachment, change in cellular morphology, decrease in colony forming units, and loss of sphere formation in soft gel agar, which are the important properties of tumorigenicity in NPC. Furthermore, we found that the effects of statins occur by a mevalonate (MA)-mediated pathway in these cells.

CONCLUSIONS

We demonstrate a unique property of statins that can enhance the antitumor effects of cisplatin in NPC. Statins may act as a relatively safe and cost effective chemoadjuvant agent in the treatment of NPC.

The statin class of HMG-CoA reductase inhibitors demonstrate differential activation of the nuclear receptors PXR, CAR and FXR, as well as their downstream target genes

The therapeutic class of HMG-CoA reductase inhibitors, the statins are central agents in the treatment of hypercholesterolaemia and the associated conditions of cardiovascular disease, obesity and metabolic syndrome. Although statin therapy is generally considered safe, a number of known adverse effects do occur, most commonly treatment-associated muscular pain. In vitro evidence also supports the potential for drug-drug interactions involving this class of agents, and to examine this a ligand-binding assay was used to determine the ability of six clinically used statins for their ability to directly activate the nuclear receptors pregnane X-receptor (PXR), farnesoid X-receptor (FXR) and constitutive androstane receptor (CAR), demonstrating a relative activation of PXR>FXR>CAR. Using reporter gene constructs, we demonstrated that this order of activation is mirrored at the transcriptional activation level, with PXR-mediated gene activation being pre-eminent. Finally, we described a novel regulatory loop, whereby activation of FXR by statins increases PXR reporter gene expression, potentially enhancing PXR-mediated responses. Delineating the molecular interactions of statins with nuclear receptors is an important step in understanding the full biological consequences of statin exposure. This demonstration of their ability to directly activate nuclear receptors, leading to nuclear receptor cross-talk, has important potential implications for their use within a polypharmacy paradigm.

NCI60 cancer cell line panel data and RNAi analysis help identify EAF2 as a modulator of simvastatin and lovastatin response in HCT-116 cells

Simvastatin and lovastatin are statins traditionally used for lowering serum cholesterol levels. However, there exists evidence indicating their potential chemotherapeutic characteristics in cancer. In this study, we used bioinformatic analysis of publicly available data in order to systematically identify the genes involved in resistance to cytotoxic effects of these two drugs in the NCI60 cell line panel. We used the pharmacological data available for all the NCI60 cell lines to classify simvastatin or lovastatin resistant and sensitive cell lines, respectively. Next, we performed whole-genome single marker case-control association tests for the lovastatin and simvastatin resistant and sensitive cells using their publicly available Affymetrix 125K SNP genomic data. The results were then evaluated using RNAi methodology. After correction of the p-values for multiple testing using False Discovery Rate, our results identified three genes (NRP1, COL13A1, MRPS31) and six genes (EAF2, ANK2, AKAP7, STEAP2, LPIN2, PARVB) associated with resistance to simvastatin and lovastatin, respectively. Functional validation using RNAi confirmed that silencing of EAF2 expression modulated the response of HCT-116 colon cancer cells to both statins. In summary, we have successfully utilized the publicly available data on the NCI60 cell lines to perform whole-genome association studies for simvastatin and lovastatin. Our results indicated genes involved in the cellular response to these statins and siRNA studies confirmed the role of the EAF2 in response to these drugs in HCT-116 colon cancer cells.

Systemic and central immunity in Alzheimer's disease: therapeutic implications

Clinical pharmaceutical trials aimed at modulating the immune system in Alzheimer's Disease have largely focused on either dampening down central proinflammatory innate immunity or have manipulated adaptive immunity to facilitate the removal of centrally deposited beta amyloid. To date, these trials have had mixed clinical therapeutic effects. However, a number of clinical studies have demonstrated disturbances of both systemic and central innate immunity in Alzheimer's Disease and attention has been drawn to the close communication pathways between central and systemic immunity. This paper highlights the need to take into account the potential systemic effects of drugs aimed at modulating central immunity and the possibility of developing novel therapeutic approaches based on the manipulation of systemic immunity and its communication with the central nervous system.

Effect of preinjury statin use on mortality and septic shock in elderly burn patients

BACKGROUND

Premorbid statin use has been associated with decreased mortality in septic and trauma patients. This has been ascribed to the pleiotropic, anti-inflammatory effects of HMG-CoA reductase inhibitors. This association has not been investigated in burn victims.

METHODS

A retrospective review of 223 consecutive patients, aged 55 years and older admitted to Vanderbilt University Regional Burn Center from January 2006 to December 2008, was performed. Multivariate regression analysis determined odds ratios of death and sepsis by statin use, adjusting for cardiovascular comorbidities.

RESULTS

Of 223 patients, 70 (31.4%) were taking statins before admission. Mean age and mean total body surface area burn were not significantly different by statin use. The odds ratio of inhospital death was 0.17 (95% confidence interval 0.05-0.57; p = 0.004) if on statins. The odds ratio of mortality when stratified by cardiovascular comorbidities did not change. Sepsis developed in 30 patients (13.5%), with an odds ratio in statin users of 0.50 (95% confidence interval 0.20-1.30; p = 0.155).

CONCLUSION

Preinjury statin use was associated with an 83% reduction in the odds of death after thermal injury. The odds of sepsis decreased by 50%, although not statistically significant. Further study is warranted to investigate the potential benefits of statin therapy in the management of burn victims.

Effects of simvastatin on cholesterol metabolism and Alzheimer disease biomarkers

Preclinical and epidemiologic studies suggest a protective effect of statins on Alzheimer disease (AD). Experimental evidence indicates that some statins can cross the blood-brain barrier, alter brain cholesterol metabolism, and may ultimately decrease the production of amyloid-beta (Abeta) peptide. Despite these promising leads, clinical trials have yielded inconsistent results regarding the benefits of statin treatment in AD. Seeking to detect a biological signal of statins effect on AD, we conducted a 12-week open-label trial with simvastatin 40 mg/d and then 80 mg/d in 12 patients with AD or amnestic mild cognitive impairment and hypercholesterolemia. We quantified cholesterol precursors and metabolites and AD biomarkers of Abeta and tau in both plasma and cerebrospinal fluid at baseline and after the 12-week treatment period. We found a modest but significant inhibition of brain cholesterol biosynthesis after simvastatin treatment, as indexed by a decrease of cerebrospinal fluid lathosterol and plasma 24S-hydroxycholesterol. Despite this effect, there were no changes in AD biomarkers. Our findings indicate that simvastatin treatment can affect brain cholesterol metabolism within 12 weeks, but did not alter molecular indices of AD pathology during this short-term treatment.

A simple and sensitive HPLC-UV method for quantitation of lovastatin in human plasma: application to a bioequivalence study

An available, simple, sensitive, and rapid method has been developed for determination of the 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor, lovastatin in human plasma. The analytical procedure involves a one-step liquid-liquid extraction method using atorvastatin as internal standard. Chromatographic separation was carried out on a reversed phase C(18) column using a mixture of 0.05 M phosphate buffer (pH 7) and acetonitrile (44.5 : 55.5, v/v) as mobile phase with UV detection set at 238 nm. The total run time of analysis was 6 min with the retention time of lovastatin being 4.3 min. A complete set of analytical method validation tests were carried out on the method. Accordingly, the method was linear in the wide range of 1-100 ng/ml. The limit of detection (LOD) and limit of quantification (LOQ) for lovastatin were 0.5 and 1 ng/ml, respectively. The method was shown to be precise with average within-run and between-run variations of 10.45+/-6.88 and 8.68+/-5.13%, respectively. The average within-run and between-run accuracy of the method throughout its linear range was 113.33+/-3.98 and 105.72+/-5.07%, respectively. The mean relative recovery of lovastatin from human plasma by the developed method was 88.61+/-7.00%. The applicability of the method in real pharmacokinetic situations was evaluated successfully during a bioequivalence study in 14 fasting healthy male volunteers.

Effect of HMG-CoA reductase inhibitors on activation of human gammadeltaT cells induced by Mycobacterium tuberculosis antigens

Lipid rafts are cholesterol-enriched microdomains which act as a platform for the initiation of T-cell activation. To investigate effect of endogenous cholesterol on lipid rafts formation and activation of gammadeltaT cells, human peripheral blood mononuclear cells were stimulated in vitro with Mycobacterium tuberculosis antigens (Mtb-Ag). Lovastatin and fluvastatin, two 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase (HMGCR) inhibitors, were used to block endogenous cholesterol biosynthesis. The expression of ganglioside GM1 (GM1), a lipid rafts marker, and CD69, an activation marker, and the level of tyrosine phosphorylation in gammadeltaT cells were measured by flow cytometry. The expression and aggregation of GM1 were also detected with laser confocal microscopy. We found that lovastatin and fluvastatin could obviously inhibit tyrosine phosphorylation and expression of GM1 and CD69 in gammadeltaT cells induced by Mtb-Ag. These results collectively indicated that HMGCR inhibitors might interfere with the formation of lipid rafts and inhibit the activation of gammadeltaT cells induced by Mtb-Ag.

Statins inhibit cyclooxygenase-2 and matrix metalloproteinase-9 in human endothelial cells: anti-angiogenic actions possibly contributing to plaque stability

AIMS

Cyclooxygenase (COX)-2 expression is increased in inflammation and angiogenesis and also in atherosclerotic plaques, where it co-localizes with metalloproteinases (MMPs) involved in the fibrous cap weakening. Insight into the regulation of COX-2 and MMP-9 expression suggests the involvement of a Rho-dependent pathway. Because statins interfere with Rho activation, we investigated the statin effect on COX-2 and MMP expressions in the human endothelium.

METHODS AND RESULTS

Simvastatin and atorvastatin were incubated with endothelial cells for 12 h before stimulation with phorbol myristate acetate or tumour necrosis factor-alpha, for times suitable to assess the endothelial tube differentiation on Matrigel and COX-2 and MMPs activities, proteins, and mRNA expressions. At 0.1-10 micromol/L, both statins reduced COX-2 expression and activity, without affecting COX-1. The statin effect was reversed by mevalonate and geranylgeranyl-pyrophosphate and mimicked by the Rho inhibitor C3 transferase, indicating the involvement of Rho in the signal transduction pathway leading to COX-2 expression. In parallel, statins, as well as COX-2 inhibitors, reduced the MMP-9 stimulated release and the endothelial tubular differentiation.

CONCLUSION

In the human vascular endothelium, statins reduce COX-2 and MMP-9 expression and activity. Through this mechanism, statins exert an anti-angiogenic effect possibly contributing to the cholesterol-lowering-unrelated protective effects of statins against plaque inflammatory angiogenesis and rupture.

The genetics of statin-induced myopathy

OBJECTIVE

Our goal was to use genetic variants to identify factors contributing to the muscular side effects of statins.

BACKGROUND

Statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) are usually well tolerated medications, but muscle symptoms, ranging from mild myalgia to clinically important rhabdomyolysis are an important side effect of these drugs and a leading cause of noncompliance. Recent results suggest that genetic factors increase the risk of statin-related muscle complaints. We performed a systematic review of the medical literature to determine genetic factors associated with statin myopathy.

METHODS

We identified English language articles relating statin myopathy and genetic diseases and gene variants via a PubMed search. Articles pertinent to the topic were reviewed in detail.

RESULTS/CONCLUSIONS

Our review suggests that some patients are susceptible to statin myopathy because of pre-existing subclinical inherited muscular disorders, or genetic variation in statin uptake proteins encoded by SLCO1B1 or the cytochrome P enzyme system. Variations in genes affecting pain perception and polymorphism in vascular receptors may also contribute to statin myopathy. None of the variants identified in this review suggested novel metabolic mechanisms leading to statin myopathy.

Investigation of the rate-determining process in the hepatic elimination of HMG-CoA reductase inhibitors in rats and humans

Elucidation of the rate-determining process in the overall hepatic elimination of drugs is critical for predicting their intrinsic hepatic clearance and the impact of variation of sequestration clearance on their systemic concentration. The present study investigated the rate-determining process in the overall hepatic elimination of the HMG-CoA reductase inhibitors pravastatin, pitavastatin, atorvastatin, and fluvastatin both in rats and humans. The uptake of these statins was saturable in both rat and human hepatocytes. Intrinsic hepatic clearance obtained by in vivo pharmacokinetic analysis in rats was close to the uptake clearance determined by the multiple indicator dilution method but much greater than the intrinsic metabolic clearance extrapolated from an in vitro model using liver microsomes. In vivo uptake clearance of the statins in humans (pravastatin, 1.44; pitavastatin, 30.6; atorvastatin, 12.7; and fluvastatin, 62.9 ml/min/g liver), which was obtained by multiplying in vitro uptake clearance determined in cryopreserved human hepatocytes by rat scaling factors, was within the range of overall in vivo intrinsic hepatic clearance (pravastatin, 0.84-1.2; pitavastatin, 14-35; atorvastatin, 11-19; and fluvastatin, 123-185 ml/min/g liver), whereas the intrinsic metabolic clearance of atorvastatin and fluvastatin was considerably low compared with their intrinsic hepatic clearance. Their uptake is the rate-determining process in the overall hepatic elimination of the statins in rats, and this activity likely holds true for humans. In vitro-in vivo extrapolation of the uptake clearance using a cryopreserved human hepatocytes model and rat scaling factors will be effective for predicting in vivo intrinsic hepatic clearance involving active uptake.

Multiple antiplatelet effects of clopidogrel are not modulated by statin type in patients undergoing percutaneous coronary intervention

We investigated whether statin type or dose influenced the inhibition of platelet function induced by clopidogrel in a prospective, open, parallel group study in patients undergoing elective percutaneous coronary intervention. Patients were taking CYP3A4 metabolised atorvastatin (n = 20) or simvastatin (n = 21), non-CYP3A4 metabolised pravastatin (n = 11) or fluvastatin (n = 2), or no statin therapy (n = 5). ADP and TRAP-induced platelet aggregation were measured using optical aggregometry, whole-blood single-platelet counting, and the Ultegra and Plateletworks point-of-care systems. Platelet pro-coagulant activity (annexin V binding and microparticle formation), P-selectin expression and platelet-leukocyte conjugate formation were assessed by flow cytometry. Platelet responses were measured at baseline, 4 h post clopidogrel 300 mg, and after 10 and 28 days with clopidogrel 75 mg daily. Clopidogrel significantly inhibited both ADP and TRAP-induced platelet responses over time, with steady state inhibition achieved by day 10. This was demonstrated by all techniques used. There was no significant effect of statin type or dose on platelet responses by any method at any time-point. In conclusion, statins do not influence the inhibitory effects of clopidogrel on multiple platelet responses, including aggregation, P-selectin expression, platelet-leucocyte conjugate formation and pro-coagulant responses, in patients undergoing elective PCI.

Effects on coronary atherosclerosis by targeting low-density lipoprotein cholesterol with statins

A correlation exists between circulating levels of low-density lipoprotein cholesterol (LDL-C) and risk of cardiovascular disease (CVD). Evidence from clinical trials indicates that reducing LDL-C levels can result in beneficial clinical outcomes in patients at risk of CVD and in high-risk patients with clinical symptoms of CVD. Lipid-lowering agents, of which HMG-CoA reductase inhibitors (statins) are the most effective, protect against the vascular changes seen in the development of atherosclerotic plaque formation. Clinical trials assessing the effects of statins on coronary atherosclerosis using quantitative coronary angiography or intravascular ultrasound showed that statins can reduce progression or even cause regression of atherosclerotic plaque. This improvement of vascular structure after statin treatment is correlated with reductions in LDL-C levels. This appears to be the principal mechanism by which statin therapy reduces cardiovascular risk, with emerging evidence for statin-mediated changes in high-density lipoprotein and C-reactive protein levels contributing to modification of the atherosclerotic plaque.

Functional expression of human HMG-CoA reductase in Saccharomyces cerevisiae: a system to analyse normal and mutated versions of the enzyme in the context of statin treatment

AIMS

Statins - inhibitors of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase - are known to reduce blood cholesterol levels. In this paper, we present a Saccharomyces cerevisiae expression system, which enables quick evaluation of the sensitivity of the wild-type and/or mutant forms of human HMG-CoA reductase towards statins or other drugs.

METHODS AND RESULTS

We analysed the sequence of the HMG-CoA reductase gene in DNA extracted from blood samples of 16 patients with cardiovascular disorders. We applied the yeast system to examine the sensitivity of the wild-type and mutated versions of the hHMG-CoA reductase to different types of statins.

CONCLUSION

The yeast and mammalian HMG-CoA reductases demonstrate structural and functional conservation, and expression of human HMG-CoA reductase in yeast complements the lethal phenotype of strains lacking the HMG1 and HMG2 genes.

SIGNIFICANCE AND IMPACT OF THE STUDY

These data indicate that a yeast expression system can serve to study the influence of selected mutations in human HMG-CoA reductase on the sensitivity of the enzyme to commonly prescribed statins. Our results suggest that this model system is suitable for the development and selection of lipid-lowering drugs as well as for the examination of DNA sequence variations in the context of statin therapy.

Physiologically based pharmacokinetic modeling to predict transporter-mediated clearance and distribution of pravastatin in humans

Hepatobiliary excretion mediated by transporters, organic anion-transporting polypeptide (OATP) 1B1 and multidrug resistance-associated protein (MRP) 2, is the major elimination pathway of an HMG-CoA reductase inhibitor, pravastatin. The present study examined the effects of changes in the transporter activities on the systemic and liver exposure of pravastatin using a physiologically based pharmacokinetic model. Scaling factors, determined by comparing in vivo and in vitro parameters of pravastatin in rats for the hepatic uptake and canalicular efflux, were obtained. The simulated plasma and liver concentrations and biliary excretion profiles were very close to the observed data in rats under linear and nonlinear conditions. In vitro parameters, determined in human cryopreserved hepatocytes and canalicular membrane vesicles, were extrapolated to in vivo parameters using the scaling factors obtained in rats. The simulated plasma concentrations of pravastatin were close to the reported values in humans. Sensitivity analyses showed that changes in the hepatic uptake ability altered the plasma concentration of pravastatin markedly but had a minimal effect on the liver concentration, whereas changes in the ability of canalicular efflux altered the liver concentration of pravastatin markedly but had a small effect on the plasma concentration. In conclusion, the model allows the prediction of the disposition of pravastatin in humans. The present study suggests that changes in the OATP1B1 activities may have a small and a large impact on the therapeutic efficacy and side effect (myopathy) of pravastatin, respectively, whereas those in the MRP2 activities may have opposite impacts (i.e., large and small impacts on the therapeutic efficacy and side effect).

The prince and the pauper. A tale of anticancer targeted agents

Cancer rates are set to increase at an alarming rate, from 10 million new cases globally in 2000 to 15 million in 2020. Regarding the pharmacological treatment of cancer, we currently are in the interphase of two treatment eras. The so-called pregenomic therapy which names the traditional cancer drugs, mainly cytotoxic drug types, and post-genomic era-type drugs referring to rationally-based designed. Although there are successful examples of this newer drug discovery approach, most target-specific agents only provide small gains in symptom control and/or survival, whereas others have consistently failed in the clinical testing. There is however, a characteristic shared by these agents: -their high cost-. This is expected as drug discovery and development is generally carried out within the commercial rather than the academic realm. Given the extraordinarily high therapeutic drug discovery-associated costs and risks, it is highly unlikely that any single public-sector research group will see a novel chemical "probe" become a "drug". An alternative drug development strategy is the exploitation of established drugs that have already been approved for treatment of non-cancerous diseases and whose cancer target has already been discovered. This strategy is also denominated drug repositioning, drug repurposing, or indication switch. Although traditionally development of these drugs was unlikely to be pursued by Big Pharma due to their limited commercial value, biopharmaceutical companies attempting to increase productivity at present are pursuing drug repositioning. More and more companies are scanning the existing pharmacopoeia for repositioning candidates, and the number of repositioning success stories is increasing. Here we provide noteworthy examples of known drugs whose potential anticancer activities have been highlighted, to encourage further research on these known drugs as a means to foster their translation into clinical trials utilizing the more limited public-sector resources. If these drug types eventually result in being effective, it follows that they could be much more affordable for patients with cancer; therefore, their contribution in terms of reducing cancer mortality at the global level would be greater.

Effect of Atorvastatin on Antibody, Interleukin-4 and Gamma-Interferon Production in Mice Immunized with Egg Albumin

Three-hydroxy-3-methylglutaryl CoA reductase inhibitors, also known as statins, are widely used as the drug of choice for the treatment of hyperlipidemia. However, actions beyond that of simply lowering cholesterol levels have been reported. This study aims at evaluating the effect of atorvastatin on antibody interleukin-4 and gamma-interferon production in mice immunized with egg albumin. Antibody levels were determined by an enzyme linked immunosorbent assay and cytokine transcripts by reverse transcriptase-polymerase chain reaction. Results indicated that repeated daily doses of 40 mg/Kg body weight of atorvastatin following immunization suppressed the antibody response in mice to egg albumin. Moreover, a decline in interleukin-4 and gamma-interferon transcripts was observed.

Effects of cyclosporin A and itraconazole on the pharmacokinetics of atorvastatin in rats

AIM

To evaluate the effects of cyclosporin A and itraconazole, which were used as inhibitors of P-glycoprotein (P-gp) and/or cytochrome P450 (CYP) 3A4 on the pharmacokinetics of atorvastatin in rats.

METHODS

The pharmacokinetic parameters of atorvastatin were measured after intravenous (2 mg/kg) and intragastric (10 mg/kg) administration of atorvastatin in rats, which were pretreated with cyclosporin A (5, 10, and 20 mg/kg) or itraconazole (5, 10, and 20 mg/kg).

RESULTS

Compared with the control rats, cyclosporin A and itraconazole altered the pharmacokinetics of atorvastatin significantly. The AUC0-t values of atorvastatin after intragastric administration, pretreated with cyclosporin A (5-20 mg/kg), increased by 32.3%, 61.8%, and 187.2%, respectively, but the CLbile values decreased (P<0.01, 5-20 mg/kg). With pretreatment of itraconazole (5-20 mg/kg), the AUC(0-t) values of atorvastatin increased by 88.2%, 102%, and 123%, respectively, but the CL(bile) values decreased (P<0.01, 5-20 mg/kg).

CONCLUSION

These data indicated that cyclosporin A could be effective in inhibiting the efflux of atorvastatin, and itraconazole could be effective in inhibiting both the metabolism and biliary excretion of atorvastatin.

HMG-CoA reductase expression in breast cancer is associated with a less aggressive phenotype and influenced by anthropometric factors

Although several studies have reported on the anti-tumoural properties exerted by 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR) inhibitors (statins), the in vivo expression of HMG-CoAR in human cancer has been considerably less investigated. In our study, we examined the immunohistochemical expression of HMG-CoAR in 511 incident breast cancers within the Malmö Diet and Cancer Study in order to explore its relationship to established clinicopathological and tumour biological parameters. Furthermore, the potential influence of estrogen exposure on HMG-CoAR expression was assessed by performing Cox's proportional hazards analyses of the relationship between the use of hormone replacement therapy (HRT), obesity (waist circumference) and tumour-cell specific HMG-CoAR expression. We found that HMG-CoAR was present in various fractions and intensities in the cytoplasm, sometimes with a membranous pattern, but not in the tumour cell nuclei. The expression of HMG-CoAR was associated with a smaller tumour size (p = 0.02), low histological grade (p = 0.001), low Ki67 index (p = 0.004), ERalpha+ (p = 0.02), ERbeta+ (p = 0.005), and high p27 expression (p = <0.001). The incidence of tumours with a high HMG-CoAR-expression was increased among HRT-users, although this was not statistically significant in a heterogeneity analysis. Obesity was significantly associated with a high HMG-CoAR expression assessed both as a high (>50%) fraction of positive cells (relative risk: 2.06; 95% confidence interval: 1.20-3.51), and a strong staining intensity (2.33: 1.08-5.02). In summary, we demonstrate that HMG-CoAR is differentially expressed in breast cancer and that a high expression is associated with prognostically favourable tumour parameters. Moreover, estrogen related life-style and anthropometric factors might indeed regulate HMG-CoAR expression.

Cholesterol lowering and beyond: role of statins in Alzheimer’s disease

Alzheimer’s disease (AD), the most common form of dementia, is a major health problem with increasing prevalence associated with the increase in life span. Unfortunately, drugs currently used to treat this disorder have only modest therapeutic efficacy. Therefore, there is an urgent need to develop new pharmacological strategies to prevent or delay the onset of AD. As it has been suggested that there is a link between cholesterol and the development of AD, one such strategy could be the inhibition of cholesterol synthesis using HMG-CoA reductase inhibitors (statins). In addition to their cholesterol-lowering properties, statins exert multiple lipid-independent (pleiotropic) effects that may explain some of their beneficial actions. The aim of this article is to summarize the current knowledge on the effects of statins on AD and the mechanisms involved, based on data from in vitro, in vivo and clinical studies, and to provide an overview of the future perspectives in this field.

Class effects of statins in elderly patients with congestive heart failure: a population-based analysis

BACKGROUND

Long-term treatment with statins reduces mortality in patients with congestive heart failure (CHF). Whether statin agents exert a class effect is unknown.

METHODS

We analyzed long-term mortality in Canadian patients aged > or = 65 years who were discharged from hospital with a diagnosis of CHF from January 1998 to December 2002. Administrative data from Quebec, Ontario, and British Columbia were merged. We compared patients prescribed with atorvastatin, simvastatin, pravastatin, and lovastatin.

RESULTS

A total of 15,368 patients hospitalized with a diagnosis of CHF fulfilled the inclusion criteria for this study. In this final dataset, 6670 (43.4%) filled a prescription for atorvastatin, 4261 (27.7%) for simvastatin, 3209 (20.9%) for pravastatin, and 1228 (8.0%) for lovastatin. Clinical characteristics and proportion of days covered with a statin prescription were similar across groups. Drug dosages were relatively low, with 82% of patients who received the agent at a dose of < or = 20 mg. Although controlling for time-dependent covariates representing current use and dosage, as well as for age, sex, coronary artery disease, and several other comorbidities, treatment with pravastatin (adjusted hazards ratio [HR] 0.94, 95% CI 0.83-1.07), lovastatin (adjusted HR 1.02, 95% CI 0.88-1.17), or simvastatin (adjusted HR 0.92, 95% CI 0.83-1.01) had a similar effectiveness to prevent mortality compared to atorvastatin (reference in this analysis) in this population with CHF. Time-dependent exposure to a statin was highly protective against mortality.

CONCLUSIONS

Statins exert a class effect in patients with CHF, when used at a relatively low dose. The favorable effects appear largely independent of drug dosage.

Statin adverse effects : a review of the literature and evidence for a mitochondrial mechanism

HMG-CoA reductase inhibitors (statins) are a widely used class of drug, and like all medications, have potential for adverse effects (AEs). Here we review the statin AE literature, first focusing on muscle AEs as the most reported problem both in the literature and by patients. Evidence regarding the statin muscle AE mechanism, dose effect, drug interactions, and genetic predisposition is examined. We hypothesize, and provide evidence, that the demonstrated mitochondrial mechanisms for muscle AEs have implications to other nonmuscle AEs in patients treated with statins. In meta-analyses of randomized controlled trials (RCTs), muscle AEs are more frequent with statins than with placebo. A number of manifestations of muscle AEs have been reported, with rhabdomyolysis the most feared. AEs are dose dependent, and risk is amplified by drug interactions that functionally increase statin potency, often through inhibition of the cytochrome P450 3A4 system. An array of additional risk factors for statin AEs are those that amplify (or reflect) mitochondrial or metabolic vulnerability, such as metabolic syndrome factors, thyroid disease, and genetic mutations linked to mitochondrial dysfunction. Converging evidence supports a mitochondrial foundation for muscle AEs associated with statins, and both theoretical and empirical considerations suggest that mitochondrial dysfunction may also underlie many nonmuscle statin AEs. Evidence from RCTs and studies of other designs indicates existence of additional statin-associated AEs, such as cognitive loss, neuropathy, pancreatic and hepatic dysfunction, and sexual dysfunction. Physician awareness of statin AEs is reportedly low even for the AEs most widely reported by patients. Awareness and vigilance for AEs should be maintained to enable informed treatment decisions, treatment modification if appropriate, improved quality of patient care, and reduced patient morbidity.

Determination of lovastatin in human plasma by ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry and its application in a pharmacokinetic study

A selective, rapid and sensitive ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the quantitative determination of lovastatin in human plasma and its application in a pharmacokinetic study. With mycophenolate mofetil as internal standard, sample pretreatment involved a one-step extraction with tert-butyl methyl ether of 0.2 ml plasma. The analysis was carried out on an ACQUITY UPLCTM BEH C18 column (50 mm x 2.1 mm, i.d., 1.7 microm) with flow rate of 0.35 ml/min. The mobile phase was 20% water and 80% acetonitrile (v/v). The detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI). Linear calibration curves were obtained in the concentration range of 0.08-24.50 ng/ml, with a lower limit of quantification of 0.08 ng/ml. The intra- and inter-day precision (RSD) values were below 15% and accuracy (RE) was -7.6 to 9.3% at all QC levels. The method was applicable to clinical pharmacokinetic study of lovastatin in healthy volunteers following oral administration.

Locally applied Simvastatin improves fracture healing in mice

Background

HMG-CoA reductase inhibitors, statins, are widely prescribed to lower cholesterol. High doses of orally administered simvastatin has previously been shown to improve fracture healing in a mouse femur fracture model. In this study, simvastatin was administered either subcutaneously or directly to the fracture area, with the goal of stimulating fracture repair at acceptable doses.

Methods

Femur fractures were produced in 70 mature male Balb-C mice and stabilized with marrow-nailing. Three experiments were performed. Firstly, 20 mice received subcutaneous injections of either simvastatin (20 mg) or vehicle. Secondly, 30 mice were divided into three groups of 10 mice receiving continuous subcutaneous delivery of the vehicle substance, the vehicle with 5 mg or with 10 mg of simvastatin per kg bodyweight per day. Finally, in 20 mice, a silicone tube was led from an osmotic mini-pump to the fracture area. In this way, 10 mice received an approximate local dose of simvastatin of 0.1 mg per kg per day for the duration of the experiment and 10 mice received the vehicle compound. All treatments lasted until the end of the experiment. Bilateral femurs were harvested 14 days post-operative. Biomechanical tests were performed by way of three-point bending. Data was analysed with ANOVA, Scheffé's post-hoc test and Student's unpaired t-test.

Results

With daily simvastatin injections, no effects could be demonstrated for any of the parameters examined. Continuous systemic delivery resulted in a 160% larger force at failure. Continuous local delivery of simvastatin resulted in a 170% larger force at failure as well as a twofold larger energy uptake.

Conclusion

This study found a dramatic positive effect on biomechanical parameters of fracture healing by simvastatin treatment directly applied to the fracture area.

Pattern of statin exposures reported to Texas poison centers, 1998-2004

Information on the management of potentially adverse exposures to statins is limited. This study examined the pattern of 2331 statin exposures reported to Texas poison control centers during 1998-2004. In particular comparisons were made between exposures among pediatric (age < or = 5 yr) and adult (age > or = 20 yr) patients. The number of exposures increased from 134 in 1998 to 516 in 2004. Of the total exposures, 55% were to statins alone. Of the exposures to statins alone, 57% of the patients were < or = 5 yr of age and 22% were > or = 60 yr of age. The majority of exposures to statins alone (a) involved female patients (53%), (b) were unintentional (94%), (c) occurred at home (91%), (d) were managed on-site/at home (89%), and (e) had a final medical outcome classified as no effect (94%). Pediatric and adult patients differed with respect to patient gender (45 versus 66% female), exposure reason (100 versus 88% unintentional, 1 versus 75% therapeutic error), exposure site (14 versus 2% at other residence), final medical outcome (4 versus 11% minor effect, none versus 4% moderate effects), report of specific adverse clinical exposures (0.2 versus 5% neurological effects, none versus 1% cardiovascular effects), and listed treatments (60 versus 24% decontamination by dilution, 13 versus 6% decontamination by food). In conclusion, reported statin exposures are increasing. The majority of potentially adverse statin exposures reported to poison control centers may be successfully managed at home with favorable outcomes. The pattern of exposures differs with age.

Lovastatin induces the expression of bradykinin type 2 receptors in cultured human coronary artery endothelial cells

Cardioprotective bradykinin type-2 receptors (BK-2Rs) are downregulated in the myocardial endothelium of both human and rat failing hearts. Statins are cardioprotective drugs that reduce the level of plasma cholesterol but also exert cholesterol-independent pleiotropic effects. Here we examined the effect of lovastatin on BK-2R expression in cultured human coronary artery endothelial cells. The effect of lovastatin on the expression of BK receptors in human coronary artery endothelial cells (HCAECs) was examined by real-time PCR, Western blot analysis and immunocytochemistry. Lovastatin induced a time- and concentration-dependent increase in both BK-2R and BK-1R mRNA expression in the cultured HCAECs. Also, the number of functional BK-2Rs capable of inducing BK-mediated NO production and cGMP signaling was increased in the lovastatin-treated HCAECs. Mevalonate, the direct metabolite of HMG-CoA reductase, reversed the effect of lovastatin. Furthermore, lovastatin inhibited Rho activation and a selective inhibitor of Rho-associated kinases, Y-27632, induced a similar increase in BK-2R expression as lovastatin. In contrast, a specific inhibitor of COX-2, NS398, significantly inhibited the lovastatin-induced expression of BK-2Rs. Here we show for the first time that lovastatin induces the expression of BK-2Rs in cultured human coronary artery endothelial cells through a novel cholesterol-independent pleiotropic mechanism that involves RhoA kinase inhibition and COX-2 activation. Thus, reported beneficial effects of statins in cardiovascular diseases may be partly mediated by an increased expression of cardioprotective BK-2Rs in the endothelial cells of the coronary tree. Moreover, the use of COX-2 inhibitors may affect the level of endothelial BK-2Rs in a negative fashion.