Statins in the 21st century: end of the simple story?

Pamidronate: A model compound of the pharmacology of nitrogen-containing bisphosphonates; A Leiden historical perspective

Pamidronate [3-amino-1-hydroxypropylidene-1,1-bisphosphonate (APD)] was the first nitrogen-containing bisphosphonate (N-BP) investigated in clinical studies. In contrast to other clinically used bisphosphonates, pamidronate was discovered and its properties were initially studied in an Academic Institution. On the occasion of the 50th Anniversary of the first publications on the biological effects of bisphosphonates, I review in this article the contribution of Leiden investigators to the development of pamidronate that led to the recognition of the significance of the Nitrogen atom in the side chain of bisphosphonates for their action on bone resorption and to the formulation of principles for the use of N-BPs in the management of patients with different skeletal disorders.

Monocyte-mediated drug delivery systems for the treatment of cardiovascular diseases

Major advances have been achieved in understanding the mechanisms and risk factors leading to cardiovascular disorders and consequently developing new therapies. A strong inflammatory response occurs with a substantial recruitment of innate immunity cells in atherosclerosis, myocardial infarction, and restenosis. Monocytes and macrophages are key players in the healing process that ensues following injury. In the inflamed arterial wall, monocytes, and monocyte-derived macrophages have specific functions in the initiation and resolution of inflammation, principally through phagocytosis, and the release of inflammatory cytokines and reactive oxygen species. In this review, we will focus on delivery systems, mainly nanoparticles, for modulating circulating monocytes/monocyte-derived macrophages. We review the different strategies of depletion or modulation of circulating monocytes and monocyte subtypes, using polymeric nanoparticles and liposomes for the therapy of myocardial infarction and restenosis. We will further discuss the strategies of exploiting circulating monocytes for biological targeting of nanocarrier-based drug delivery systems for therapeutic and diagnostic applications.

Liposome technology for cardiovascular disease treatment and diagnosis

INTRODUCTION

Over the past several decades, liposomes have been used in a variety of applications, from delivery vehicles to cell membrane models. In terms of pharmaceutical use, they can offer control over the release of active agents encapsulated into their lipid bilayer or aqueous core, while providing protection from degradation in the body. In addition, liposomes are versatile carriers, because targeting moieties can be conjugated on the surface to enhance delivery efficiency. It is for these reasons that liposomes have been applied as carriers for a multitude of drugs and genetic material, and as contrast agents, aimed to treat and diagnose cardiovascular diseases.

AREAS COVERED

This review details advancements in liposome technology used in the field of cardiovascular medicine. In particular, the application of liposomes to cardiovascular disease treatment and diagnosis, with a focus on delivering drugs, genetic material and improving cardiovascular imaging, will be explored. Advances in targeting liposomes to the vasculature will also be detailed.

EXPERT OPINION

Liposomes may provide the means to deliver drugs and other pharmaceutical agents for cardiovascular applications; however, there is still a vast amount of research and clinical trials that must be performed before a formulation is brought to market. Advancements in targeting abilities within the body, as well as the introduction of theranostic liposomes, capable of both delivering treating and imaging cardiac diseases, may be expected in the future of this burgeoning field.

Liposomal simvastatin attenuates neointimal hyperplasia in rats

Monocytes, macrophages, and inflammation play a key role in the process of neointimal proliferation and restenosis. The present study evaluated whether systemic and transient depletion of monocytes could be obtained by a single intravenous (IV) injection of simvastatin liposomes, for the inhibition of neointima formation. Balloon-injured carotid artery rats (n = 30) were randomly assigned to treatment groups of free simvastatin, simvastatin in liposomes (3 mg/kg), and saline (control). Stenosis and neointima to media ratio (N/M) were determined 14 days following single IV injection at the time of injury by morphometric analysis. Depletion of circulating monocytes was determined by flow cytometry analyzes of blood specimens. Inhibition of RAW264.7, J774, and THP-1 proliferation by simvastatin-loaded liposomes and free simvastatin was determined by the 3-(4, 5-dimethylthiazolyl-2)-2, 5- diphenyltetrazolium bromide assay. Simvastatin liposomes were successfully formulated and were found to be 1.5-2 times more potent than the free drug in suppressing the proliferation of monocytes/macrophages in cell cultures of RAW 264.7, J774, and THP-1. IV injection of liposomal simvastatin to carotid-injured rats (3 mg/kg, n = 4) resulted in a transient depletion of circulating monocytes, significantly more prolonged than that observed following treatment with free simvastatin. Administration to balloon-injured rats suppressed neointimal growth. N/M at 14 days was 1.56 +/- 0.16 and 0.90 +/- 0.12, control and simvastatin liposomes, respectively. One single systemic administration of liposomal simvastatin at the time of injury significantly suppresses neointimal formation in the rat model of restenosis, mediated via a partial and transient depletion of circulating monocytes.

Farnesyl diphosphate synthase is involved in the resistance to zoledronic acid of osteosarcoma cells

We recently demonstrated original anti-tumor effects of zoledronic acid (Zol) on osteosarcoma cell lines independently of their p53 and Rb status. The present study investigated the potential Zol-resistance acquired by osteosarcoma cells after prolonged treatment. After 12 weeks of culture in the presence of 1 μm Zol, the effects of high doses of Zol (10–100 μm) were compared between the untreated rat (OSRGA, ROS) and human (MG63, SAOS2) osteosarcoma cells and Zol-pretreated cells in terms of cell proliferation, cell cycle analysis, migration assay and cytoskeleton organization. Long-term treatment with 1 μm Zol reduced the sensitivity of osteosarcoma cells to high concentrations of Zol. Furthermore, the Zol-resistant cells were sensitive to conventional anti-cancer agents demonstrating that this resistance process is independent of the multidrug resistance phenotype. However, as similar experiments performed in the presence of clodronate and pamidronate evidenced that this drug resistance was restricted to the nitrogen-containing bisphosphonates, we then hypothesized that this resistance could be associated with a differential expression of farnesyl diphos-phate synthase (FPPS) also observed in human osteosarcoma samples. The transfection of Zol-resistant cells with FPPS siRNA strongly increased their sensitivity to Zol. This study demonstrates for the first time the induction of metabolic resistance after prolonged Zol treatment of osteosarcoma cells confirming the therapeutic potential of Zol for the treatment of bone malignant pathologies, but points out the importance of the treatment regimen may be important in terms of duration and dose to avoid the development of drug metabolic resistance.

Simvastatin inhibits TNFα-induced invasion of human cardiac myofibroblasts via both MMP-9-dependent and -independent mechanisms

Statins can reduce adverse myocardial remodeling independently of their cholesterol-lowering ability. We have previously reported that simvastatin inhibits tumor necrosis factor-alpha (TNFalpha)-induced cardiac myofibroblast invasion and MMP-9 secretion, key events in this remodeling process. The aim of the present study was to investigate the mechanisms underlying this effect. Selective MMP-9 gene silencing with siRNA oligonucleotides revealed that myofibroblast invasion through a Matrigel barrier (Boyden chamber assay) was MMP-9-dependent. In contrast, cell migration (in the absence of Matrigel) was MMP-9-independent. Simvastatin, a commonly prescribed statin, inhibited both invasion and migration of myofibroblasts and disrupted the actin cytoskeleton as determined by confocal microscopy of rhodamine-phalloidin staining. All these effects of simvastatin were mimicked by the Rho-kinase inhibitor Y27632. TNFalpha activated the ERK-1/2, p38 MAPK, PI-3-kinase and NF-kappaB pathways but not the JNK pathway, as determined by immunoblotting with phospho-specific antibodies. Quantitative RT-PCR revealed that TNFalpha-induced MMP-9 mRNA expression was substantially reduced by pharmacological inhibitors of the ERK-1/2, PI-3-kinase and NF-kappaB pathways. However, none of the signal transduction pathways studied was influenced by simvastatin treatment. Moreover, despite reducing MMP-9 secretion, simvastatin had no effect on MMP-9 promoter activity (luciferase reporter assay) and actually increased MMP-9 mRNA levels. In summary, simvastatin reduces TNFalpha-induced invasion of human cardiac myofibroblasts through two distinct mechanisms: (i) by attenuating cell migration via Rho-kinase inhibition and subsequent cytoskeletal disruption, and (ii) by decreasing MMP-9 secretion via a post-transcriptional mechanism.

Inhibitors of cholesteryl ester transfer protein – a new approach to coronary artery disease

Despite the use of the statins to lower low-density lipoprotein-cholesterol, leading to major reductions in the mortality and morbidity that is associated with coronary artery disease, considerable mortality and morbidity remains. Increasing high-density lipoprotein (HDL)-cholesterol levels has been associated with reduced coronary artery disease mortality and morbidity in several studies. Inhibition of cholesteryl ester transfer protein (CETP) activity leads to increased HDL-cholesterol. In cholesterol-fed rabbits, antibodies against CETP increased HDL-cholesterol and decreased atherosclerotic lesions. In healthy subjects with mild dyslipidaemia, the CETP inhibitors JTT-705 and torcetrapib increased HDL-cholesterol and decreased low-density lipoprotein-cholesterol. Increasing HDL-cholesterol with CETP inhibitors is a new approach to dyslipidaemia that requires further investigation, especially in patients who have coronary artery disease.

Dibenzodioxocinones—A new class of CETP inhibitors

Derivatives of the natural product 11-hydroxy-3-[(S)-1-hydroxy-3-methylbutyl]-4-methoxy-9-methyl-5H,7H-dibenzo[b,g][1,5]dioxocin-5-one 1 were studied as novel CETP inhibitors. Compound 2 was identified from HTS as a micromolar inhibitor. The compound suffered from very low stability in plasma. Optimisation by partial synthesis started from 1 and led to low-nanomolar inhibitors with good stability in rat plasma.

Atorvastatin versus pravastatin: intensive versus moderate lipid lowering

With so many statins available for clinical use in coronary artery syndromes, there has been much discussion about which is the best. Two recent trials have compared the clinical outcomes of intensive lipid lowering with atorvastatin 80 mg/day and standard lowering with pravastatin 40 mg/day. In the Pravastatin or Atorvastatin Evaluation and Infection Therapy (PROVE IT) trial, patients with acute coronary artery syndromes were enrolled, and pravastatin lowered the low-density lipoprotein (LDL)-cholesterol to 2.46 mmol/l, whereas atorvastatin lowered it to 1.60 mmol/l. Associated with this, there was a lower rate of clinical events (myocardial infarction, revascularisation) over 2 years with atorvastatin than pravastatin (22.4 versus 26.3%, respectively). The Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) trial also enrolled patients requiring angiography, and pravastatin lowered the LDL-cholesterol to 2.84 mmol/l, whereas atorvastatin lowered the LDL-cholesterol to 2.04 mmol/l. In the REVERSAL trial, atheroma volume progressed with pravastatin by 2.7% whilst remaining stable in the atorvastatin group (-0.4%) over 18 months. Thus, atorvastatin 80 mg/day causes a greater reduction in LDL-cholesterol than pravastatin 40 mg/day, and this is associated with a reduced progression of atheroma and reduced clinical events. As a consequence of these findings, the National Cholesterol Education Programme and European guidelines for LDL-cholesterol levels should be lowered.

Raising high-density lipoprotein cholesterol with inhibitors of cholesteryl ester transfer protein – a new approach to coronary artery disease

Although the low-density lipoprotein (LDL) cholesterol-lowering statins reduce the mortality and morbidity associated with coronary artery disease, considerable mortality and morbidity remains. Increasing high-density lipoprotein (HDL) cholesterol reduces coronary artery disease mortality and morbidity. In healthy subjects with mild dyslipidaemia, treatment with JTT-705 decreased cholesteryl ester transfer protein (CETP) activity, increased HDL-cholesterol and decreased LDL-cholesterol. Similarly, another CETP inhibitor, torcetrapib 120 mg/day has recently been shown to increase HDL-cholesterol by 46%, decrease LDL-cholesterol by 8% and have no effect on triglycerides in subjects with HDL-cholesterol < 1 mmol/l. In subjects treated with atorvastatin to lower their LDL-cholesterol levels, torcetrapib further lowered LDL-cholesterol while increasing HDL-cholesterol. In conclusion, raising HDL-cholesterol with inhibitors of CETP is a new approach to coronary artery disease that requires further investigation, especially in patients with coronary artery disease.

Simvastatin inhibits MMP‐9 secretion from human saphenous vein smooth muscle cells by inhibiting the RhoA/ROCK pathway and reducing MMP‐9 mRNA levels

Increased matrix metalloproteinase-9 (MMP-9) expression is associated with intimal hyperplasia in saphenous vein (SV) bypass grafts. Recent evidence suggests that HMG-CoA reductase inhibitors (statins) can prevent the progression of vein graft failure. Here we investigated whether statins inhibited MMP-9 secretion from cultured human SV smooth muscle cells (SMC) and examined the underlying mechanisms. SV-SMC from different patients were exposed to phorbol ester (TPA) or PDGF-BB plus interleukin-1alpha (IL-1). MMP-9 secretion and mRNA expression were analyzed using gelatin zymography and RT-PCR, respectively. Specific signal transduction pathways were investigated by immunoblotting and pharmacological inhibition. Simvastatin reduced TPA- and PDGF/IL-1-induced MMP-9 secretion and mRNA levels, effects reversed by geranylgeranyl pyrophosphate and mimicked by inhibiting Rho geranylgeranylation or Rho-kinase (ROCK). MMP-9 secretion induced by PDGF/IL-1 was mediated via the ERK, p38 MAPK, and NFkappaB pathways, whereas that induced by TPA was mediated specifically via the ERK pathway. Simvastatin failed to inhibit activation of these signaling pathways. Moreover, simvastatin did not affect MMP-9 mRNA stability. Together these data suggest that simvastatin reduces MMP-9 secretion from human SV-SMC by inhibiting the RhoA/ROCK pathway and decreasing MMP-9 mRNA levels independently of effects on signaling pathways required for MMP-9 gene expression.

Collision-induced dissociation of the negative ions of simvastatin hydroxy acid and related species

Simvastatin hydroxy acid (1) is a well-known, potent HMG-CoA reductase inhibitor for the treatment of hypercholesterolemia. Its lactone, simvastatin (commercial name Zocor) (a prodrug of 1), has been widely prescribed in the USA and throughout the world. In this work, collision-induced dissociation (CID) of the negative ion of 1 (m/z 435), a carboxylic anion, was analyzed in detail. The major fragmentation pathway of this ion is a novel de-esterification to form the negative product ions at m/z 319 and 115. The ion at m/z 319 undergoes further collision-induced rearrangements to form the negative ions at m/z 215, 159 and 85. Possible mechanisms of the de-esterification are discussed in terms of both charge-initiated and charge-remote fragmentations. The de-esterification of the negative ion of 1 and the rearrangements of the ion at m/z 319 are rationalized by charge transfer and negative-charge initiated fragmentation. This study deepens our understanding of collision-induced fragmentations of carboxylic anions with multi-functional groups. A comparison of the CID data for the negative ions of 1 and 5 (a major oxidation degradate of 1) indicates that the analysis of the CID data for 1 can serve as a basis for identification of oxidation degradation products or metabolites of 1. The analysis of the CID data for the negative ion of 1 also reveals the fundamental characteristics of the CID data for the negative ions of other statin hydroxy acids such as lovastatin (3) and pravastatin (4).

Statin effects on cholesterol micro-domains in brain plasma membranes

Recent epidemiological studies revealed inhibitors of the hydroxymethylglutaryl-coenzyme A reductase, so-called statins, to be effective in lowering the prevalence of Alzheimer's disease (AD). In vitro, statins strongly reduced the cellular amyloid beta-protein load by modulating the processing of the amyloid beta precursor protein. Both observations are probably linked to cellular cholesterol homeostasis in brain. So far, little is known about brain effects of statins. Recently, we could demonstrate that treatment of mice with the lipophilic compound lovastatin resulted in a discrete reduction of brain membrane cholesterol levels. To follow up these findings, we subsequently carried out a further in vivo study including lovastatin and simvastatin as lipophilic agents, as well as pravastatin as a hydrophilic compound, focussing on their efficiency to affect subcellular membrane cholesterol pools in synaptosomal plasma membranes of mice. In contrast to the hydrophilic pravastatin, the lipophilic lovastatin and simvastatin strongly reduced the levels of free cholesterol in SPM. Interestingly, lovastatin and pravastatin but not simvastatin significantly reduced cholesterol levels in the exofacial membrane leaflet. These changes were accompanied by modified membrane bulk fluidity. All three statins reduced the expression of the raft marker protein flotillin. Alterations in transbilayer cholesterol distribution have been suggested as the underlying mechanism that forces amyloidogenic processing of APP in AD. Thus, our data give some first insight in the mode of action of statins to reduce the prevalence of AD in clinical trials.