Cellular and molecular mechanisms of statins: an update on pleiotropic effects

Simvastatin prevents and reverses chronic pulmonary hypertension in newborn rats via pleiotropic inhibition of RhoA signaling

Chronic neonatal pulmonary hypertension (PHT) frequently results in early death. Systemically administered Rho-kinase (ROCK) inhibitors prevent and reverse chronic PHT in neonatal rats, but at the cost of severe adverse effects, including systemic hypotension and growth restriction. Simvastatin has pleiotropic inhibitory effects on isoprenoid intermediates that may limit activity of RhoA, which signals upstream of ROCK. We therefore hypothesized that statin treatment would safely limit pulmonary vascular RhoA activity and prevent and reverse experimental chronic neonatal PHT via downstream inhibitory effects on pathological ROCK activity. Sprague-Dawley rats in normoxia (room air) or moderate normobaric hypoxia (13% O2) received simvastatin (2 mg·kg−1·day−1 ip) or vehicle from postnatal days 1–14 (prevention protocol) or from days 14–21 (rescue protocol). Chronic hypoxia increased RhoA and ROCK activity in lung tissue. Simvastatin reduced lung content of the isoprenoid intermediate farnesyl pyrophosphate and decreased RhoA/ROCK signaling in the hypoxia-exposed lung. Preventive or rescue treatment of chronic hypoxia-exposed animals with simvastatin decreased pulmonary vascular resistance, right ventricular hypertrophy, and pulmonary arterial remodeling. Preventive simvastatin treatment improved weight gain, did not lower systemic blood pressure, and did not cause apparent toxic effects on skeletal muscle, liver or brain. Rescue therapy with simvastatin improved exercise capacity. We conclude that simvastatin limits RhoA/ROCK activity in the chronic hypoxia-exposed lung, thus preventing or ameliorating hemodynamic and structural markers of chronic PHT and improving long-term outcome, without causing adverse effects.

Pre-treatment with simvastatin prevents the induction of diet-induced atherosclerosis in a rabbit model

The aim of the present study was to investigate the potential antiatherosclerotic activities of simvastatin in rabbits. Twenty-two, male, New Zealand rabbits were divided into the following groups: Control group (group C); cholesterol group (group A), in which the rabbits were fed a commercial rabbit chow supplemented with 0.5% w/w cholesterol for 8 weeks and then fed with normal chow for an additional 8 weeks; and a treatment group (group B), in which the rabbits initially received standard commercial rabbit chow along with being administered simvastatin for 8 weeks, following which they consumed a high-cholesterol diet for a further 8 weeks. The rabbits pre-treated with simvastatin presented significantly lower serum cholesterol and low-density lipoprotein cholesterol levels when compared with the non simvastatin-treated cholesterol-fed animals. Furthermore, none of the rabbits in the simvastatin group presented with atherosclerotic lesions in the aorta. Thus, simvastatin was demonstrated to exhibit preventive properties against the formation of atherosclerosis in the atherosclerosis model in the current study, predominantly via its hypolipidemic activity.

A non-hypocholesterolemic atorvastatin treatment improves vessel elasticity by acting on elastin composition in WHHL rabbits

BACKGROUND AND AIMS

Statins are prescribed for their preventative effects within atherosclerosis development. To our knowledge, no study focusing on very low-dose (non-hypolipidemic effect) and long-term atorvastatin treatment in vivo was available. Our aim was to assess the effect of such atorvastatin treatment on the mechanical and functional characteristics of arteries in the context of primary prevention.

METHODS

An atorvastatin treatment (2.5 mg/kg/day) was tested against controls on 34 male 3 to 12 month-old WHHL rabbits. No effect on total cholesterol, triglycerides, HDL or LDL was observed. The arterial stiffness was evaluated on vigil animals by pulse wave velocity (PWV) measurement. Then, in vitro measurements were made to evaluate (1) the endothelial and vascular smooth muscle function, (2) the elasticity of the arterial wall and (3) the composition in collagen and elastin in the aorta.

RESULTS

The PWV increasing observed with age in control group was canceled by treatment, creating a significance difference between groups at 12 months (5.17 ± 0.50 vs 2.14 ± 0.34 m s(-1) in control and treated groups respectively). Vasoreactivity modifications can't explain this result but maintain of elasticity with treatment in large arteries was confirm by a static tensile test. A first possible explanation is the change of wall composition with treatment, validated by the percentage of elastin at 12 months, 4.4% lower in the control group compared to the treated group (p < 0.05).

CONCLUSIONS

This study shows that a non-hypocholesterolemic statin treatment could improve vessel elasticity in the atherosclerotic WHHL model. The great novelty of this work is the vessel wall composition changing associated. This first approach in animal opens the reflection on the use of these low doses in humans. This could be interesting in the context of arterial stiffening with aging, non-hyperlipidemic atherosclerosis or with cholesterol reduce by another therapy or lifestyle modification.

Modulation of microRNA Expression in Subjects with Metabolic Syndrome and Decrease of Cholesterol Efflux from Macrophages via microRNA-33-Mediated Attenuation of ATP-Binding Cassette Transporter A1 Expression by Statins

Metabolic syndrome (MetS) is a complicated health problem that encompasses a variety of metabolic disorders. In this study, we analyzed the relationship between the major biochemical parameters associated with MetS and circulating levels of microRNA (miR)-33, miR-103, and miR-155. We found that miRNA-33 levels were positively correlated with levels of fasting blood glucose, glycosylated hemoglobin A1c, total cholesterol, LDL-cholesterol, and triacylglycerol, but negatively correlated with HDL-cholesterol levels. In the cellular study, miR-33 levels were increased in macrophages treated with high glucose and cholesterol-lowering drugs atorvastatin and pitavastatin. miR-33 has been reported to play an essential role in cholesterol homeostasis through ATP-binding cassette transporter A1 (ABCA1) regulation and reverse cholesterol transport. However, the molecular mechanism underlying the linkage between miR-33 and statin treatment remains unclear. In the present study, we investigated whether atorvastatin and pitavastatin exert their functions through the modulation of miR-33 and ABCA1-mediated cholesterol efflux from macrophages. The results showed that treatment of the statins up-regulated miR-33 expression, but down-regulated ABCA1 mRNA levels in RAW264.7 cells and bone marrow-derived macrophages. Statin-mediated ABCA1 regulation occurs at the post-transcriptional level through targeting of the 3′-UTR of the ABCA1 transcript by miR-33. Additionally, we found significant down-regulation of ABCA1 protein expression in macrophages treated with statins. Finally, we showed that high glucose and statin treatment significantly suppressed cholesterol efflux from macrophages. These findings have highlighted the complexity of statins, which may exert detrimental effects on metabolic abnormalities through regulation of miR-33 target genes.

The endothelium as the common denominator in malignant hypertension and thrombotic microangiopathy

The endothelium plays a pivotal role in vascular biology. The endothelium is the primary site of injury in thrombotic microangiopathies including malignant hypertension. Endothelial injury in thrombotic microangiopathies is the result of increased shear stress, toxins, and/or dysregulated complement activation. Endothelial injury can lead to microvascular thrombosis resulting in ischemia and organ dysfunction, the clinical hallmarks of thrombotic microangiopathies. Currently, available therapies target the underlying mechanisms that lead to endothelial injury in these conditions. Ongoing investigations aim at identifying drugs that protect the endothelium.

LDL-lipids from patients with hypercholesterolaemia and Alzheimer's disease are inflammatory to microvascular endothelial cells: mitigation by statin intervention

Elevated low-density lipoprotein (LDL) concentration in mid-life increases the risk of developing Alzheimer's disease (AD) in later life. Increased oxidized LDL (oxLDL) modification and nitration is observed during dementia and hypercholesterolaemia. We investigated the hypothesis that statin intervention in mid-life mitigates the inflammatory effects of oxLDL on the microvasculature. Human microvascular endothelial cells (HMVECs) were maintained in transwells to mimic the microvasculature and exposed to patient and control LDL. Blood was obtained from statin-naive, normo- and hyper-lipidaemic subjects, AD with vascular dementia (AD-plus) and AD subjects (n=10/group) at baseline. Only hyperlipidaemic subjects with normal cognitive function received 40 mg of simvastatin intervention/day for 3 months. Blood was re-analysed from normo- and hyper-lipidaemic subjects after 3 months. LDL isolated from statin-naive hyperlipidaemic, AD and AD-plus subjects was more oxidized (agarose gel electrophoretic mobility, protein carbonyl content and 8-isoprostane F2α) compared with control subjects. Statin intervention decreased protein carbonyls (2.5±0.4 compared with 3.95±0.2 nmol/mg; P<0.001) and 8-isoprostane F2α (30.4±4.0 pg/ml compared with 43.5±8.42 pg/ml; P<0.05). HMVEC treatment with LDL-lipids (LDL-L) from hyperlipidaemic, AD and AD-plus subjects impaired endothelial tight junction expression and decreased total glutathione levels (AD; 18.61±1.3, AD-plus; 16.5±0.7 nmol/mg of protein) compared with untreated cells (23.8±1.2 compared with nmol/mg of protein). Basolateral interleukin (IL)-6 secretion was increased by LDL-L from hyperlipidaemic (78.4±1.9 pg/ml), AD (63.2±5.9 pg/ml) and AD-plus (80.8±0.9 pg/ml) groups compared with healthy subject lipids (18.6±3.6 pg/ml). LDL-L isolated after statin intervention did not affect endothelial function. In summary, LDL-L from hypercholesterolaemic, AD and AD-plus patients are inflammatory to HMVECs. In vivo intervention with statins reduces the damaging effects of LDL-L on HMVECs.

Addressing Therapeutic Options for Ebola Virus Infection in Current and Future Outbreaks

Ebola virus can cause severe hemorrhagic disease with high fatality rates. Currently, no specific therapeutic agent or vaccine has been approved for treatment and prevention of Ebola virus infection of humans. Although the number of Ebola cases has fallen in the last few weeks, multiple outbreaks of Ebola virus infection and the likelihood of future exposure highlight the need for development and rapid evaluation of pre- and postexposure treatments. Here, we briefly review the existing and future options for anti-Ebola therapy, based on the data coming from rare clinical reports, studies on animals, and results from in vitro models. We also project the mechanistic hypotheses of several potential drugs against Ebola virus, including small-molecule-based drugs, which are under development and being tested in animal models or in vitro using various cell types. Our paper discusses strategies toward identifying and testing anti-Ebola virus properties of known and medically approved drugs, especially those that can limit the pathological inflammatory response in Ebola patients and thereby provide protection from mortality. We underline the importance of developing combinational therapy for better treatment outcomes for Ebola patients.