HMG-CoA reductase inhibitor augments the serum total cholesterol-lowering effect of human adipose tissue-derived multilineage progenitor cells in hyperlipidemic homozygous Watanabe rabbits

Familial hypercholesterolemia (FH) is an autosomal codominant disease characterized by high concentrations of proatherogenic lipoproteins secondary to deficiency in low-density lipoprotein (LDL) receptor. We reported recently the use of in situ stem cell therapy of human adipose tissue-derived multilineage progenitor cells (hADMPCs) in lowering serum total cholesterol in the homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of homozygous FH. Here we demonstrate that pravastatin, an HMG-CoA reductase inhibitor, augmented the cholesterol-lowering effect of transplanted hADMPCs and enhanced LDL clearance in homozygous WHHL rabbit. The results suggest the potential beneficial effects of in situ stem cell therapy in concert with appropriately selected pharmaceutical agents, in regenerative medicine.     

HMG-CoA reductase inhibitor attenuates platelet adhesion in intestinal venules of hypercholesterolemic mice

Whereas the anti-inflammatory properties of statins have been extensively studied, less attention has been devoted to the antithrombogenic effects of these drugs. We evaluated the effect of short-term (18 h) treatment with pravastatin (1 mg/kg) on hypercholesterolemia-induced platelet-endothelial (P/E) cell adhesion in intestinal venules. Mice were placed on either a normal diet (ND) or cholesterol-enriched diet (HCD) for 2 wk. Wild-type mice fed a HCD exhibited significantly elevated blood serum cholesterol levels, which were unaltered by pravastatin treatment. ND or HCD platelets were isolated, fluorescently labeled, and administered to either ND or HCD recipients. Intravital videomicroscopy was used to quantify transient (saltation) and firm adhesion of platelets. HCD mice receiving platelets from either ND or HCD mice exhibited increased P/E cell interactions compared with ND mice receiving platelets from ND or HCD mice. P/E adhesion was dramatically reduced when platelets from donor mice, recipient mice, or both were treated with pravastatin. The protective effect of pravastatin in hypercholesterolemia-induced P/E cell adhesion was abolished in N(G)-nitro-l-arginine methyl ester-treated mice. These results indicate that 1). hypercholesterolemia-induced P/E cell adhesion is mediated by changes in the vascular wall rather than circulating platelets; 2). pravastatin treatment inhibits the prothrombogenic effects of hypercholesterolemia via an action on both endothelial cells and platelets; and 3). the protective effect of pravastatin is nitric oxide dependent.     

Atorvastatin, a potent HMG-CoA reductase inhibitor, is not antipyretic in rats

1. We investigated whether atorvastatin, a plasma cholesterol lowering and anti-inflammatory drug, attenuates lipopolysaccharide-induced fever in rats.

2. Sprague–Dawley rats, implanted with abdominal temperature-sensitive telemeters, were administered either lipopolysaccharide and placebo (n=7), lipopolysaccharide and atorvastatin (n=6), saline and placebo (n=8), or saline and atorvastatin (n=7).

3. Atorvastatin (100 mg kg⁻¹) was administered orally, as a suspension in a flavoured gelatine cube (placebo cubes contained no drug), 90 min before intraperitoneal injection of pyrogen (Salmonella typhosa lipopolysaccharide, 75 μg kg⁻¹) or sterile saline.

4. Atorvastatin did not disrupt normal thermoregulation. Atorvastatin also did not attenuate lipopolysaccharide-induced changes in body temperature and cage activity.

Ultraviolet light-induced apoptotic death is impaired by the HMG-CoA reductase inhibitor lovastatin

HMG-CoA reductase inhibitors (i.e., statins) attenuate C-terminal isoprenylation of Rho GTPases, thereby inhibiting UV-C-induced activation of c-Jun-N-terminal kinases/stress-activated protein kinases (JNKs/SAPKs). Inhibition of UV-C-triggered JNK/SAPK activation by lovastatin is due to inhibition of Rac-SEK1/MKK4-mediated phosphorylation of JNKs/SAPKs at Thr183/Tyr185. UV-C-stimulated phosphorylation of p38 kinase (Thr180/Tyr182) is also impaired by lovastatin. Cell killing provoked by UV-C irradiation was significantly inhibited by lovastatin. This was paralleled by a reduced frequency of chromosomal aberrations, accelerated recovery from UV-C-induced transient replication blockage, inhibition of Chk1 kinase activation and impaired cyclinB1 expression. Furthermore, UV-C-induced activation of caspases and apoptotic death was largely reduced by lovastatin. Inhibition of JNK/SAPK by transient overexpression of dominant-negative JNK1/SAPK1 also conferred resistance to UV-C light and attenuated activation of caspase 3. Based on the data, we suggest that lovastatin-provoked resistance to UV-C light is due to the inhibition of UV-C-inducible Rac-SEK1/MKK4-JNK/SAPK-dependent signal mechanisms regulating cell cycle progression and activation of caspases and apoptotic death.     

Peptide design of a competitive inhibitor for HMG-CoA reductase based on statin structure

This study investigates a proposed design of a peptide sequence that is based on a bioactive conformation of statins that act as the competitive inhibitors of HMG-CoA for HMGR. To bridge these heterogeneous organic compounds, a conformational aspect relating to an analysis of the flexibility of the peptide molecules and their occupied volumes was applied to the peptide design. The design criterion was formulated in terms of a proximity parameter (Pr), reflecting the probability of an active peptide conformation to approximate the statin. Through a structure-functional analysis of previously synthesized peptides and statin molecules, nine peptides were selected for the peptide library. Comparing the calculated proximity parameters, four peptides (IAVE, YAVE, IVAE, and YVAE) from the library were selected and synthesized. In vitro assays elucidated the inhibition properties for HMGR that are exhibited by these peptides. Among all peptides, YVAE showed the highest ability to inhibit HMGR. A kinetic analysis revealed that this peptide is a competitive inhibitor of HMG-CoA with an equilibrium constant of inhibitor binding (K(i)) of 15.2 +/- 1.4 microM. The calculated coefficient correlation (R) between log (IC(50)) and the inverse value of proximity parameter (1/Pr) was found to be 0.99, indicating a high degree of correlation and efficacy of the given approach in the peptide sequence design.     

HMG-CoA reductase inhibitor cerivastatin inhibits interleukin-6 expression and secretion in human adipocytes.

Human adipose tissue is a main contributor to plasma levels of pro-inflammatory cytokine IL-6. How IL-6 expression is regulated in adipocytes remains unclear. In the current study, we investigated the effect of the HMG-CoA reductase inhibitor, cerivastatin, on the production of IL-6 from cultured human adipocytes. Cerivastatin reduced both IL-6 mRNA and secretion in a dose- and time-dependent manner. The inhibitory effect on IL-6 mRNA was prevented by the intermediates of the cholesterol synthesis pathway, mevalonate and geranyl-geranyl-phyrophosphate (GGPP) but not by farnesyl-pyrophosphate. This suggests the involvement of geranylgeranyl-modified intermediates in the effect of cerivastatin on IL-6. Moreover, cerivastatin induced an inactivation of the phosphorylation of the p65 subunit of NFkappaB which was prevented by GGPP. Our data suggest that cerivastatin exerts an anti-inflammatory effect by down-regulating IL-6 levels in adipocytes, which seems to be mediated by reduced production of GGPP and interference with the NFkappaB pathway.     

Design of a highly potent inhibitory peptide acting as a competitive inhibitor of HMG-CoA reductase

This study presents a design of a highly potent and competitive inhibitory peptide for 3-hydroxy-3-methylglutaryl CoA reductase (HMGR). HMGR is the major regulatory enzyme of cholesterol biosynthesis and the target enzyme of many investigations aimed at lowering the rate of cholesterol biosynthesis. In previous studies, the two hypocholesterolemic peptides (LPYP and IAVPGEVA) were isolated and identified from soy protein. Based on these peptide sequences, a number of peptides were designed previously by using the correlation between the conformational flexibility and bioactivity. The design method that was applied in previous studies was slightly modified for the purpose of the current research and 12 new peptides were designed and synthesized. Among all peptides, SFGYVAE showed the highest ability to inhibit HMGR. A kinetic analysis revealed that this peptide is a competitive inhibitor of HMG-CoA with an equilibrium constant of inhibitor binding (K _i) of 12?±?0.4?nM. This is an overall 14,500-fold increase in inhibitory activity compared to the first isolated LPYP peptide from soybeans. Conformational data support a conformation of the designed peptides close to the bioactive conformation of the previously synthesized active peptides.     

The HMG-CoA reductase inhibitor simvastatin activates the protein kinase Akt and promotes angiogenesis in normocholesterolemic animals

Recent studies suggest that statins can function to protect the vasculature in a manner that is independent of their lipid-lowering activity. We show here that statins rapidly activate the protein kinase Akt/PKB in endothelial cells. Accordingly, simvastatin enhanced phosphorylation of the endogenous Akt substrate endothelial nitric oxide synthase (eNOS), inhibited apoptosis and accelerated vascular structure formation in vitro in an Akt-dependent manner. Similar to vascular endothelial growth factor (VEGF) treatment, both simvastatin administration and enhanced Akt signaling in the endothelium promoted angiogenesis in ischemic limbs of normocholesterolemic rabbits. Therefore, activation of Akt represents a mechanism that can account for some of the beneficial side effects of statins, including the promotion of new blood vessel growth.     

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.     

Activation of HMG-CoA reductase by microsomal phosphatase

HMG-CoA reductase activity can be modulated by a reversible phosphorylation-dephosphorylation with the phosphorylated form of the enzyme being inactive and the dephosphorylated form, active. Phosphatases from diverse sources, including cytosol, have been shown to dephosphorylate and activate HMG-CoA reductase. The present study demonstrates phosphatase activity capable of activating HMG-CoA reductase that is associated with purified microsomes. The incubation of microsomes at 37 degrees C for 40 min results in a twofold stimulation of HMG-CoA reductase activity, and this stimulation is blocked by sodium fluoride or phosphate. The ability of microsomes to increase HMG-CoA reductase activity occurs regardless of whether microsomes are prepared by ultracentrifugation or calcium precipitation. Additionally, phosphatases capable of activating HMG-CoA reductase are present in both the smooth and rough endoplasmic reticulum. Freeze-thawing does not prevent microsomes from activating HMG-CoA reductase but preincubation results in a significant decrease in the ability of microsomes to increase HMG-CoA reductase activity. Thus, the present study demonstrates that purified liver microsomes contain phosphatase activity capable of activating HMG-CoA reductase.     

Anti-lipid deposition effect of HMG-CoA reductase inhibitor, pitavastatin, in a rat model of hypertension and hypercholesterolemia

Since the rat is an atherosclerosis-resistant species, the study of atherosclerosis using rats is limited. The present study was undertaken to develop an atherosclerotic model in rats, to investigate the effect of nitric oxide (NO) inactivation and hyperlipidemia, and to evaluate the effect of pitavastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) inhibitor, on NO inactivation and on hyperlipidemia-induced changes in the cardiovascular system. Four-month-old male spontaneously hypertensive hyperlipidemic rats (SHHR) and Sprague-Dawley (SD) rats were used to study 1) the effect of the period of treatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 100 mg/L) on high fat diet (HFD)-treated SHHR and SD rats, and 2) the effect of pitavastatin (Pit, 0.3 mg/kg/day) on the changes in the aorta of L-NAME- and HFD-treated SHHR and SD rats. L-NAME administration for 1 month then HFD feeding for 2 months markedly increased the deposition of lipids and the thickness of the endothelium in SHHR. Continuous L-NAME treatment with HFD produced severe injury and stripped of endothelium in both strains. The plasma total cholesterol of L-NAME + HFD-treated and L-NAME + HFD + Pit-treated SHHR was significantly higher than that of control SHHR. Lipid deposition, however, was comparatively less in the aorta of L-NAME + HFD + Pit-treated SHHR. The concentration of cholesterol in the aorta of control SHHR was significantly lower than that in the aorta of L-NAME + HFD-treated SHHR, whereas that of L-NAME + HFD + Pit-treated SHHR was the same as that in control SHHR. These data indicated that Pit blocked lipid deposition in the aorta of L-NAME + HFD treated SHHR without changing plasma lipid profiles. In conclusion, NO inactivation and HFD induce lipid deposition in the endothelium, and the HMG-CoA reductase inhibitor blocks the deposition in SHHR.     

Measurement of human leukocyte microsomal HMG-CoA reductase activity

Methods were developed for determination of microsomal HMG-CoA reductase activity from freshly isolated human lymphocytes, monocytes, and granulocytes or cultured human lymphoid cells. Reductase activity in monocytes is approximately twice that in lymphocytes or granulocytes. The activity in cultured cells is approximately 34-fold greater than that in freshly isolated cells. Assay conditions were such as to preclude formation of HMG-CoA cleavage products. Leukocyte reductase activity was inhibited by dichloroacetate, a noncompetitive inhibitor of rat liver reductase and a serum cholesterol-lowering agent in man. Measurement of microsomal reductase activity from freshly isolated leukocytes may prove useful in assessing in vivo regulation of cholesterol synthesis in man.     

HMG-CoA reductase inhibitor decreases small dense low-density lipoprotein and remnant-like particle cholesterol in patients with type-2 diabetes

Our studies have focused on the effect of injection of L-NAME and sodium nitroprussiate (SNP) on the salivary secretion, arterial blood pressure, sodium excretion and urinary volume induced by pilocarpine which was injected into the medial septal area (MSA). Rats were anesthetized with urethane (1.25 g/kg b. wt.) and a stainless steel cannula was implanted into their MSA. The amount of saliva secretion was studied over a five-minute period after injection of pilocarpine into MSA. Injection of pilocarpine (10, 20, 40, 80, 160 microg/microl) into MSA produced a dose-dependent increase in salivary secretion. L-NG-nitro arginine methyl-esther (L-NAME) (40 microg/microl), a nitric oxide (NO) synthase inhibitor, was injected into MSA prior to the injection of pilocarpine into MSA, producing an increase in salivary secretion due to the effect of pilocarpine. Sodium nitroprussiate (SNP) (30 microg/microl) was injected into MSA prior to the injection of pilocarpine into MSA attenuating the increase in salivary secretion induced by pilocarpine. Medial arterial pressure (MAP) increase after injections of pilocarpine into the MSA. L-NAME injected into the MSA prior to injection of pilocarpine into MSA increased the MAP. SNP injected into the MSA prior to pilocarpine attenuated the effect of pilocarpine on MAP. Pilocarpine (40 ug/ul) injected into the MAS induced an increase in sodium and urinary excretion. L-NAME injected prior to pilocarpine into the MSA increased the urinary sodium excretion and urinary volume induced by pilocarpine. SNP injected prior to pilocarpine into the MSA decreased the sodium excretion and urinary volume induced by pilocarpine. All these roles of pilocarpine depend on the release of nitric oxide into the MSA. We may also conclude that the MSA is involved with the cholinergic excitatory mechanism that induce salivary secretion, increase in MAP and increase in sodium excretion and urinary volume.     

Regulation of hepatic HMG-CoA reductase in vivo by reversible phosphorylation

The transbilayer distribution of aminophospholipids in trout intestinal brush-border membrane has been investigated using trinitrobenzene sulfonic acid (TNBS). In the middle intestine, phosphatidylethanolamine (PE) is symmetrically distributed between the two leaflets while 68% of the phosphatidylserine (PS) are located in the inner membrane leaflet. In the posterior intestine, 64% of the PE and 69% of the PS are located in the inner membrane leaflet. When asymmetrically distributed, the inner species of PE and PS have a higher content of 22:6(n-3) than the outer ones. This asymmetric distribution of docosahexaenoic acid in trout intestinal brush-border membrane might be related to the rod-like shape of the microvillus membrane and to its metabolism to hydroxylated derivatives.