Antiviral effects of statins

Introducing statins as possible widely-available drugs for the treatment of viral infections requires an in depth review of their antiviral properties. Despite some inconsistency, a large body of literature data from experimental and clinical studies suggest that statins may have a role in the treatment of viral infections due to their immunomodulatory properties as well as their ability to inhibit viral replication. In the present review, the role that statins may play while interacting with the immune system during viral infections and the possible inhibitory effects of statins on different stages of virus cell cycle (i.e., from fusion with host cell membranes to extracellular release) and subsequent virus transmission are described. Specifically, cholesterol-dependent and cholesterol-independent mechanisms of the antiviral effects of statins are reported.     

Growth inhibition of Candida species and Aspergillus fumigatus by statins

Statins are a class of drugs widely used for lowering high cholesterol levels through their action on 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme in the synthesis of cholesterol. We studied the effects of two major statins, simvastatin and atorvastatin, on five Candida species and Aspergillus fumigatus. The statins strongly inhibited the growth of all species, except Candida krusei. Supplementation of Candida albicans and A. fumigatus with ergosterol or cholesterol in aerobic culture led to substantial recovery from the inhibition by statins, suggesting specificity of statins for the mevalonate synthesis pathway. Our findings suggest that the statins could have utility as antifungal agents and that fungal colonization could be affected in those on statin therapy.     

Biosynthesis and biotechnological production of statins by filamentous fungi and application of these cholesterol-lowering drugs

Hypercholesterolemia is considered an important risk factor in coronary artery disease. Thus the possibility of controlling de novo synthesis of endogenous cholesterol, which is nearly two-thirds of total body cholesterol, represents an effective way of lowering plasma cholesterol levels. Statins, fungal secondary metabolites, selectively inhibit hydroxymethyl glutaryl-coenzyme A (HMG-CoA) reductase, the first enzyme in cholesterol biosynthesis. The mechanism involved in controlling plasma cholesterol levels is the reversible inhibition of HMG-CoA reductase by statins, related to the structural similarity of the acid form of the statins to HMG-CoA, the natural substrate of the enzymatic reaction. Currently there are five statins in clinical use. Lovastatin and pravastatin (mevastatin derived) are natural statins of fungal origin, while symvastatin is a semi-synthetic lovastatin derivative. Atorvastatin and fluvastatin are fully synthetic statins, derived from mevalonate and pyridine, respectively. In addition to the principal natural statins, several related compounds, monacolins and dihydromonacolins, isolated fungal intermediate metabolites, have also been characterized. All natural statins possess a common polyketide portion, a hydroxy-hexahydro naphthalene ring system, to which different side chains are linked. The biosynthetic pathway involved in statin production, starting from acetate units linked to each other in head-to-tail fashion to form polyketide chains, has been elucidated by both early biogenetic investigations and recent advances in gene studies. Natural statins can be obtained from different genera and species of filamentous fungi. Lovastatin is mainly produced by Aspergillus terreus strains, and mevastatin by Penicillium citrinum. Pravastatin can be obtained by the biotransformation of mevastatin by Streptomyces carbophilus and simvastatin by a semi-synthetic process, involving the chemical modification of the lovastatin side chain. The hypocholesterolemic effect of statins lies in the reduction of the very low-density lipoproteins (VLDL) and LDL involved in the translocation of cholesterol, and in the increase in the high-density lipoproteins (HDL), with a subsequent reduction of the LDL- to HDL-cholesterol ratio, the best predictor of atherogenic risk. The use of statins can lead to a reduction in coronary events related to hypercholesterolemia, but the relationship between benefit and risk, and any possible interaction with other drugs, must be taken into account.     

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.     

Statins downregulate ATP-binding-cassette transporter A1 gene expression in macrophages

The ATP-binding-cassette transporter A1 (ABCA1) plays an essential role in cellular cholesterol efflux and helps prevent macrophages from becoming foam cells. The statins are widely used as cholesterol-lowering agents and have other anti-atherogenic actions. We tested the effects of four different statins (fluvastatin, atorvastatin, simvastatin, and lovastatin) on ABCA1 expression in macrophages in vitro. The statins suppressed ABCA1 mRNA expression in RAW246.7 and THP-1 macrophage cell lines and in mouse peritoneal macrophages. The effect was time- and dose-dependent and was abolished by the addition of the post-reductase product, mevalonate. These findings imply that there is a possible modulation of the well-known beneficial effects of the statins on the reverse cholesterol transport pathway.     

Induction of macrophage elastase (MMP-12) gene expression by statins

The statins (including mevastatin and lovastatin) are a widely prescribed class of serum-cholesterol lowering drugs that function by inhibiting 3-hydroxymethylglutaryl coenzyme A (HMG CoA) reductase activity and cellular sterol synthesis. Statins are also widely being appreciated for their inhibitory effects upon inflammation, primarily mediated through direct regulation of inflammatory gene expression. Here we report that statins are also capable of increasing the expression of macrophage elastase (MMP-12). The induction of MMP-12 in mouse macrophages by statins is specific for HMG CoA reductase inhibition, rescued by mevalonate and not observed after inhibition of subsequent steps in the cholesterol biosynthetic pathway. Modulation of cholesterol metabolism may lead to changes in MMP-12 expression and subsequent impacts during physiological and pathophysiological states. We conclude that statins, in addition to their previously described anti-inflammatory properties, may promote the production of some proteinases from activated macrophages.     

Binding thermodynamics of statins to HMG-CoA reductase

The statins are powerful inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMG-CoA reductase), the key enzyme in the cholesterol biosynthetic pathway, and are among the most widely prescribed drugs in the world. Despite their clinical importance, little is known about the binding thermodynamics of statins to HMG-CoA reductase. In this paper, we report the results of inhibition kinetics and microcalorimetric analysis of a representative type I statin (pravastatin) and four type II statins (fluvastatin, cerivastatin, atorvastatin, and rosuvastatin). Inhibition constants (K(i)) range from 2 to 250 nM for the different statins. Isothermal titration calorimetry (ITC) experiments yield binding enthalpies (DeltaH(binding)) ranging between zero and -9.3 kcal/mol at 25 degrees C. There is a clear correlation between binding affinity and binding enthalpy: the most powerful statins bind with the strongest enthalpies. The proportion by which the binding enthalpy contributes to the binding affinity is not the same for all statins, indicating that the balance among hydrogen bonding, van der Waals, and hydrophobic interactions is not the same for all of them. At 25 degrees C, the dominant contribution to the binding affinity of fluvastatin, pravastatin, cerivastatin, and atorvastatin is the entropy change. Only for rosuvastatin does the enthalpy change contribute more than 50% of the total binding energy (76%). Since the enthalpic and entropic contributions to binding originate from different types of interactions, the thermodynamic dissection presented here provides a way to identify interactions that are critical for affinity and specificity.     

Cost-effectiveness of the use of low- and high-potency statins in people at low cardiovascular risk

Background:

Although statins have been shown to reduce the risk of cardiovascular events in patients at low cardiovascular risk, their absolute benefit is small in the short term, which may adversely affect cost-effectiveness. We sought to determine the long-term cost-effectiveness (beyond the duration of clinical trials) of low- and high-potency statins in patients at low cardiovascular risk and to estimate the impact on Canada’s publicly funded health care system.

Methods:

Using Markov modelling, we performed a cost-utility analysis in which we compared low-potency statins (fluvastatin, lovastatin, pravastatin and simvastatin) and high-potency statins (atorvastatin and rosuvastatin) with no statins in a simulated cohort of low-risk patients over a lifetime horizon. Model outcomes included costs (in 2010 Canadian dollars), quality-adjusted life-years (QALYs) gained and the cost per QALY gained.

Results:

Over a lifetime horizon, the cost of managing a patient at low cardiovascular risk was estimated to be about $10 100 without statins, $15 200 with low-potency statins and $16 400 with high-potency statins. The cost per QALY gained with high-potency statins (v. no statins) was $21 300; the use of low-potency statins was not considered economically attractive. These results were robust to sensitivity analyses, although their use became economically unattractive when the duration of benefit from statin use was assumed to be less than 10 years.

Interpretation:

Use of high-potency statins in patients at low cardiovascular risk was associated with a cost per QALY gained that was economically attractive by current standards, assuming that the benefit from statin use would continue for at least 10 years. However, the overall expenditure on statins would be substantial, and the ramifications of this practice should be carefully considered by policy-makers.Although statins improve survival and reduce the risk of cardiovascular events in populations at high and moderate risk,¹ their effectiveness and cost-effectiveness in low-risk populations is less certain.² This uncertainly is due in part to low-risk patients being less likely to have cardiovascular events over the short term. For instance, in the recent Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) study³ — a large randomized trial comparing cardiovascular outcomes in low-risk patients randomly assigned to receive either rosuvastatin or placebo — the risk of death or nonfatal myocardial infarction over three years was 2.5% in the rosuvastatin group and 3.5% in the placebo group, which represented a large relative, but small absolute, risk reduction in cardiovascular events.Other cholesterol-lowering interventions are available, such as diet, exercise and the use of other hypolipidemic agents, but the use of statins is the only such intervention known to reduce cardiovascular risk in people with low and high blood cholesterol levels.^4–7 Thus, statins are now primarily indicated for the reduction of cardiovascular risk instead of being used mainly for the management of hypercholesterolemia.⁸With this broadening indication for use, expenditures on statins have increased and represent about 13% of total expenditures by provincial formularies in Canada.⁹ The absolute number of people at low cardiovascular risk who are taking statins has increased substantially over the last decade, driven by the large number of low-risk people in the general population.¹⁰ In addition, statins that are more effective in lowering low-density lipoprotein (LDL) cholesterol levels have become available.^3,11 These high-potency statins (atorvastatin and rosuvastatin) are substantially more expensive than low-potency statins available as generics (pravastatin, simvastatin, fluvastatin and lovastatin), although atorvastatin has recently become available as a generic in Canada.¹² Increasing costs and concerns over the absolute benefit of statins in people at low cardiovascular risk has raised concerns about the cost-effectiveness of statins in this group.We performed an incremental cost-utility analysis comparing low- and high-potency statins with no statins in patients at low cardiovascular risk in a Canadian setting. We used findings from our group’s recent systematic review of the efficacy of statins for primary prevention in low-risk people¹³ as well as observational data from a large provincial registry of patients documenting existing statin use. Our objective was to determine which strategy represents the best use of health care resources for the publicly funded health care system, and what investment would be required to fund statins.     

Statins interfere with the attachment of S. cerevisiae mtDNA to the inner mitochondrial membrane

Abstract

The 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme of the mevalonate pathway for the synthesis of cholesterol in mammals (ergosterol in fungi), is inhibited by statins, a class of cholesterol lowering drugs. Indeed, statins are in a wide medical use, yet statins treatment could induce side effects as hepatotoxicity and myopathy in patients. We used Saccharomyces cerevisiae as a model to investigate the effects of statins on mitochondria. We demonstrate that statins are active in S.cerevisiae by lowering the ergosterol content in cells and interfering with the attachment of mitochondrial DNA to the inner mitochondrial membrane. Experiments on murine myoblasts confirmed these results in mammals. We propose that the instability of mitochondrial DNA is an early indirect target of statins.     

Statins downregulate myeloperoxidase gene expression in macrophages

Statins, inhibitors of HMG-CoA reductase, have pleiotropic benefits independent of cholesterol levels, including anti-oxidant and anti-inflammatory effects. Here, we investigate the effect of statins on myeloperoxidase (MPO) expression. MPO, expressed in foam cell macrophages, was recently shown to oxidize the ApoA-1 component of HDL, impairing ABCA-1 mediated cholesterol efflux. High levels of serum MPO correlate with increased risk of CAD events. Findings here show that statins strongly inhibit MPO mRNA expression in human and murine monocyte-macrophages. Suppression was reversed by downstream intermediates of HMG-CoA reductase, mevalonate, and geranylgeranylpyrophosphate, but not farnesylpyrophosphate. An inhibitor of geranylgeranyltransferase, GGTI-286, mimics the effects of statins, indicating geranylgeranylation is key to MPO expression. Reduction of MPO mRNA levels was observed in vivo in leukocytes from statin-fed mice, correlating with reductions in MPO protein and enzyme activity. These findings suggest that the pleiotropic protections afforded by statins may be due in part to suppression of MPO expression.     

Impact of HMG-CoA reductase inhibition on oxidant-induced injury in human retinal pigment epithelium cells

In addition to cholesterol-lowering effect, HMG-CoA reductase inhibition by statins has been shown to have protective effect in many cells type. The loss of vision in retinal degeneration disease associates with oxidative stress and apoptosis in retinal pigment epithelium (RPE) cell. This study was designed to examine the effect of statins on oxidant-induced damage in human RPE cells. Cultured human ARPE-19 (ARPE) cells were challenged with hydrogen peroxide (H(2) O(2) ) plus tumor necrosis factor alpha (TNFα) in the presence or absence of statins or various stress signaling inhibitors, including anti-oxidants N-acetyl cysteine (NAC), the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium (DPI), and the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580. Apoptosis was evaluated by TUNEL analysis and cell viability was determined by MTT assay. Reactive oxygen species (ROS) were detected by 2',7'-dichlorodihydrofluorescein diacetate (H(2) DCFH-DA). Expression of p-p38 MAPK protein was measured by Western blot analysis. Our findings indicate that statins treatment significantly suppressed oxidant-induced ROS accumulation and RPE apoptosis. Statins increased cell viability in a dose-dependent manner. In addition, statins treatment prevented the activation of NADPH oxidase and p38 MAPK signaling induced by oxidative stress. These results suggest that statins protects ARPE cells from oxidative stress via an NADPH oxidase and/or p38 MAPK-dependent mechanisms, which may contribute to statins-induced beneficial effects on RPE function.     

Statin therapy in the elderly

PURPOSE OF REVIEW: The clinical efficacy and safety of statin therapy have been well established from a series of large-scale, randomized controlled trials. These trials, however, have predominantly recruited patients under the age of 70 years. As a consequence, the use of statins in older patients has remained controversial. RECENT FINDINGS: The results of the first trial to look exclusively at the elderly--the Prospective Study of Pravastatin in the Elderly at Risk--have added enormously to our understanding of the use of statins in the elderly. These findings, together with those from the large elderly cohort within the Heart Protection Study and the smaller elderly subgroups within the other major statin trials, have forced us to re-evaluate any systematic exclusion of elderly patients from statin therapy. SUMMARY: The collective evidence now strongly supports the use of statins in the at-risk elderly population.     

Association between risk of myopathy and cholesterol-lowering effect: a comparison of all statins

In the present study, we examined the mechanisms underlying the cytotoxicity of pitavastatin, a new statin, and we compared the in vitro potencies of muscle cytotoxicity using a prototypic embryonal rhabdomyosarcoma cell line (RD cells), a typical side effect of statins and compared the cholesterol-lowering effects of statins using Hep G2 hepatoma cells. Pitavastatin reduced the number of viable cells and caused caspase-9 and -3/7 activation in a time- and concentration-dependent manner. The comparison of cytotoxities of statins showed that statins significantly reduced cell viability and markedly enhanced activity of caspase-3/7 in concentration-dependent manner. On the other hand, the effects of hydrophilic statins, pravastatin, rosuvastatin were very weak. The rank order of cytotoxicity was cerivastatin > simvastatin acid> fluvastatin > atorvastatin > lovastatin acid > pitavastatin > rosuvastatin, pravastatin. Statin-induced cytotoxicity is associated with these partition coefficients. On the other hand, the cholesterol-lowering effect of statins did not correlate with these partition coefficients and cytotoxicity. Thus, it is necessary to consider the association between risk of myopathy and cholesterol-lowering effect of a statin for precise use of statins.     

Statins and Neuroprotection: Basic Pharmacology Needed

Statins are attracting great interest albeit with some controversy in treating certain neurodegenerative diseases such as Alzheimer disease, Parkinson disease, multiple sclerosis, ischemic stroke, and traumatic brain injury. Support for the use of statins has come from human studies and animal and cell models. Despite the intense level of interest, there is a deficiency in information on the basic pharmacokinetics and pharmacodynamics of statins in the brain. The purpose of this focused review is to examine what is known and the gaps in our knowledge on detectability of statin lactones and acids in the brain, membrane partitioning and active transport of statins across the blood–brain barrier, and statin effects on brain isoprenoid levels. Statins may be efficacious in treating certain neurodegenerative diseases. Having basic information on statin pharmacokinetics and pharmacodynamics in the brain would provide insight into specific drug targets and also provide the rationale for optimizing statins in terms of enhancing brain influx and inhibiting efflux.     

Statins modulate the levels of osteoprotegerin/receptor activator of NFkappaB ligand mRNA in mouse bone-cell cultures.

Statins stimulate bone formation partly by inducing osteoblast differentiation, although there is controversy about the effects of statins on bone mineral density and fracture risk. Several studies have revealed that statins suppress bone resorption. However, the mechanism by which statins inhibit bone resorption is still unclear. The present study was performed to clarify the effects of statins on osteoclast formation as well as the levels of osteoprotegerin (OPG) and receptor activator of NFkappaB ligand (RANKL) mRNA in mouse bone-cell cultures by semiquantitative RT-PCR. 10(-8) M 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] significantly stimulated osteoclast formation and 10(-6) M statins (mevastatin and simvastatin) significantly antagonized osteoclast formation stimulated by 1,25(OH)2D3 in mouse bone-cell cultures, including both osteoblasts and osteoclasts. 10(-6) M mevastatin and simvastatin increased the level of OPG mRNA in mouse bone-cell cultures. On the other hand, 10(-6) M mevastatin and simvastatin inhibited the level of RANKL mRNA in these cultures. In conclusion, the present study demonstrates that statins inhibit osteoclast formation in mouse bone-cell cultures. Moreover, statins also increased and decreased the levels of OPG and RANKL mRNA expression in these cultures, respectively. The modulation of OPG/RANKL may be involved in the inhibition of osteoclast formation by statins.     

Statin diabetogenicity: guidance for clinicians

Type 2 diabetes (T2D) is a strong, independent risk factor for cardiovascular (CV) and cerebrovascular outcomes. Meta-analysis of five randomised clinical trials (n = 33,040) showed that, although intensive versus standard glycaemic control significantly reduced CV events in people with T2D, the reduction was less than that achieved with lipid-lowering or antihypertensive treatment. Furthermore, fasting plasma glucose (FPG) concentrations were a modest predictor for CV risk in people without T2D. Thus, although effective glycaemic control is important for the prevention/management of T2D, other risk factors must be addressed to effectively reduce CV risk. Reducing low-density lipoprotein-cholesterol levels using statins significantly reduces CV risk in people with and without T2D. Although statins are generally safe and well tolerated, conflicting data exist regarding the diabetogenic effects of some statins. Based on recent clinical trial data, the US Food and Drug Administration have changed the labelling of all statins to include ‘an effect of statins on incident diabetes and increases in haemoglobin A1c and/or FPG’. However, the literature suggests that the beneficial effects of most statins on CV risk continue to outweigh their diabetogenic risks and that statins should remain as first-line therapy for the majority of people with dyslipidaemia and metabolic syndrome or T2D. Mechanisms explaining the potentially higher incidence of T2D with statin therapy have not been confirmed. However, independent predictors for statin-associated T2D appear to include elevated levels of baseline FPG, BMI, blood pressure and fasting triglycerides. Moreover, although some statins (for example, atorvastatin) are associated with increased haemoglobin A1c levels in patients receiving intensive but not moderate therapy, other statins (for example, pitavastatin) have demonstrated neutral or favourable effects on glucose control in patients with and without T2D or metabolic syndrome. The potential diabetogenic effects of statins may therefore differ between drugs. In conclusion, conflicting data exist regarding the diabetogenic effects of statins. Further studies are required to understand whether all statins have the same effect and whether some patient groups are at higher risk than others. Meanwhile, results suggest that the net CV benefit favours the use of statin therapy in patients with dyslipidaemia, irrespective of T2D risk.