Kumi Satoh

All hydrophobic HMG-CoA reductase inhibitors induce apoptotic death in rat pulmonary vein endothelial cells

3-Hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors (statins) are effective in patients with hypercholesterolemia to reduce risk of cardiovascular diseases, because of not only their lowering cholesterol effects but also their pleiotropic effects, such as improvement of endothelial cell dysfunction. On the other hand, statins prevent cell proliferation of various cells, including endothelial cells. We examined effects of all statins available at present on the viability of cultured rat pulmonary vein endothelial cells. Lovastatin, simvastatin, atorvastatin, fluvastatin and cerivastatin, which are hydrophobic statins, markedly reduced cell viability associated with DNA fragmentation, DNA laddering and activation of caspase-3, suggesting apoptotic cell death. Pravastatin, which is a hydrophilic statin, however, did not induce cell apoptosis. Apoptosis induced by hydrophobic statins was associated with activation of apoptosis-related intracellular signal transduction systems; attenuation of localization of RhoA to the membrane, induction of Rac1, and increase in phosphorylation of c-Jun N-terminal kinase and c-Jun. Endothelial cell apoptosis is underlying the improvement of the endothelial dysfunction with hydrophobic statins.

Effects of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on mitochondrial respiration in ischaemic dog hearts.

1 Effects of 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase inhibitors, pravastatin and simvastatin, on the myocardial level of coenzyme Q10, and on mitochrondrial respiration were examined in dogs 2 Either vehicle (control), pravastatin (4 mg kg−1day−1), or simvastatin (2 mg kg−1day−1) was administered orally for 3 weeks. First, the myocardial tissue level of coenzyme Q10 was determined in the 3 groups. Second, ischaemia was induced by ligating the left anterior descending coronary artery (LAD) in anaesthetized open chest dogs, pretreated with the inhibitors. After 30 min of ischaemia, nonischaemic and ischaemic myocardium were removed from the left circumflex and LAD regions, respectively, and immediately used for isolation of mitochondria. The mitochondrial respiration was determined by polarography, with glutamate and succinate used as substrates 3 Simvastatin significantly decreased the myocardial level of coenzyme Q10, but pravastatin did not 4 Ischaemia decreased the mitochondrial respiratory control index (RCI) in both groups. Significant differences in RCI between nonischaemic and ischaemic myocardium were observed in the control and simvastatin‐treated groups 5 Only in the simvastatin‐treated group did ischaemia significantly decrease the ADP/O ratio, determined with succinate 6 The present results indicate that simvastatin but not pravastatin may cause worsening of the myocardial mitochondrial respiration during ischaemia, probably because of reduction of the myocardial coenzyme Q10 level.

Disparity between angiographic regression and clinical event rates with hydrophobic statins

Statins are effective at lowering blood cholesterol concentration, and are given to patients with hypercholesterolaemia or hyperlipidaemia. Reduction of cholesterol concentration in serum can delay, or even regress, atherosclerotic lesions, leading to diminution of risk of cardiovascular disease. Results of studies have shown that the beneficial effects of statins depend not only on lowering cholesterol but also on many other factors. Production of mevalonic acid, a precursor of various essential substances for cell function (figure), is inhibited by hydrophobic statins. Thus these drugs might cause unexpected adverse effects in various tissues including the heart.

Lipophilic Hmg-coa Reductase Inhibitors Increase Myocardial Stunning in Dogs

Pretreatment of dogs with simvastatin, a lipophilic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, increases myocardial contractile dysfunction during reperfusion after ischemia (stunning), with reduction of tissue adenosine triphosphate (ATP). This was thought to be a consequence of prevention of ubiquinone biosynthesis by the lipophilic inhibitor in the myocardial cell. We examined whether other lipophilic HMG-CoA reductase inhibitors also influence myocardial stunning in dogs. Vehicle, atorvastatin (2 mg/ kg/day), fluvastatin (4 mg/kg/day), or cerivastatin (40 microg/kg/ day) was orally administered for 3 weeks. Hydrophilic pravastatin (4 mg/kg/day) also was given. After 3 weeks, pentobarbital-anesthetized dogs were subjected to 15-min left anterior descending coronary artery occlusion followed by 2-h reperfusion. Myocardial segment function was determined by sonomicrometry. Tissue levels of ATP were determined in 2-h reperfused hearts. All inhibitors significantly decreased serum cholesterol level. The three lipophilic inhibitors resulted in a worsening of segment function in the reperfused myocardium, as compared with the vehicle group. The levels of ATP in the atorvastatin, fluvastatin, and cerivastatin groups were significantly lower than that in the vehicle group. These results confirm that lipophilic HMG-CoA reductase inhibitors enhance myocardial stunning in association with ATP reduction after ischemia and reperfusion.

Influences of pravastatin and simvastatin, HMG-CoA reductase inhibitors, on myocardial stunning in dogs.

Summary: We examined the effects of pravastatin and simvastatin, HMG-CoA reductase inhibitors, on stunned myocardium in vivo. Pravastatin and simvastatin were given orally 2 mg/kg for 3 weeks. After 3 weeks of administration, pentobarbital-anesthetized dogs were subjected to 15-min left anterior descending (LAD) coronary artery occlusion followed by 2-h reperfusion. Myocairdial segment function was determined by sonomicrometry. The tissue energy and carbohydrate metabolites were determined in the 2-h-reperfused hearts. Administration of pravastatin and simvastatin for 3 weeks decreased serum cholesterol level and blood pressure (BP). Simvastatin resulted in a worsening of segment shortening in the reperfused myocardium as compared with control and pravastatin groups. The level of ATP in the simvastatin group was significantly lower as compared with that in the control group. The other metabolite levels were not significantly altered by either pravastatin or simvastatin. These results suggest that simvastatin enhances stunning of the myocardium in association with ATP reduction after reperfusion subsequent to ischemia

Effects of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on mitochondrial respiration in ischemic rat hearts

The aim of the present study was to examine the effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors on mitochondrial respiration in ischemic rat hearts, and to compare the effects between water-soluble pravastatin and lipid-soluble simvastatin. Either vehicle (0.5% carboxymethyl cellulose), pravastatin (2 or 4 mg/kg per day), or simvastatin (1 or 2 mg/kg per day) was orally administered for 3 weeks. Ischemia was induced by ligating the aorta for 60 min in anesthetized open chest rats under artificial respiration. The hearts were removed, mitochondria were isolated, and the respiration was determined by polarography using glutamate and succinate as substrates. When succinate was used as a substrate, the ADP-stimulated respiration (QO3) and ATP production per unit oxygen (ADP/O ratio) were decreased by ischemia. The decreases in QO3 and ADP/O ratio in the pravastatin- and simvastatin-treated groups appeared to be more prominent than those in the vehicle-treated group. This was especially true in the simvastatin-treated group. The ADP-limited respiration (QO4) with succinate in the vehicle-treated heart was slightly increased by ischemia, while that in the pravastatin- or simvastatin-treated hearts was decreased. In conclusion, HMG-CoA reductase inhibitors may result in worsening of myocardial mitochondrial respiration during ischemia.

Influence of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on mitochondrial respiration in rat liver during ischemia.

Effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, pravastatin and simvastatin, on mitochondrial respiration in ischemic rat liver were examined. Either vehicle, pravastatin (2 or 4 mg/kg per day), or simvastatin (1 or 2 mg/kg per day) was orally administered for 3 weeks. Liver ischemia was induced by cessation of the systemic circulation for 60 min. Liver mitochondria were isolated and the respiration was determined by polarography using glutamate and succinate as substrates. In the vehicle-treated group, ischemia drcreased ZO3, respiratory control index (RCI: QO3/QO4), and ADP/O ratio. Pretreatments with pravastatin and simvastatin enhanced the decreases in QO3 measured with either glutamate or succinate, and in ADP/O ratio measured with succinate. Because of decreasing QO4, HMG-CoA reductase inhibitors did not modify the changes in RCI due to ischemia. There were no significant differences in respiratory indices between pravastatin- and simvastatin-treated groups. In conclusion, HMG-CoA reductase inhibitors may enhance respiratory impairment of liver mitochondria under pathophysiological conditions, such as ischemia.

Effects of nebivolol on ischemia-induced metabolic changes in dog hearts

dl-Nebivolol has a &bgr;1-adrenergic blocking property and l-nebivolol has an endothelial-dependent vasodilating property, sp that a racemic mixture, &dgr;l-nebivolol, shows both properties. This study examined the effect of dl-nebivolol on ischemic myocardium in anesthetized open chest dogs. Ischemia was induced for 3 min by ligating the left anterior descending coronary artery 10 min after IV injection of vehicle, dl-nebivolol (0.03, 0.1, and 0.3 mg/kg), or d- or l-nebivolol (0.15 mg/kg). Ischemia significantly decreased the levels of ATP, creatine phosphate, and fructose-1,6-diphosphate and increased those of ADP, AMP, hexose monophosphates, and ratio of [lactate]/[pyruvate]. dl-Nebivolol at higher doses significantly attenuated some metabolic changes caused by ischemia. Although neither enantiomers significantly affected these ischemia-induced metabolic changes, d-nebivolol appeared to attenuate adenine nucleotide reduction due to ischemia. Pretreatment with Nw-nitro-l-arginine methyl ester did not abolish the restoration of ischemia-induced myocardial metabolic changes by dl-nebivolol. In conclusion, dl-nebivolol lessens ischemic derangement of myocardial metabolism, and the effects may be due mainly to its &bgr;-adrenergic blocking property but not to endothelium-dependent vasorelaxing property.

AMPK activation by prolonged stimulation with interleukin‐1β contributes to the promotion of GLUT4 translocation in skeletal muscle cells

Impaired insulin signaling in skeletal muscle cells causes insulin resistance associated with the onset of type 2 diabetes. Although interleukin (IL)‐1β has been considered to be implicated in the pathogenesis of type 2 diabetes, the action of prolonged stimulation with IL‐1β on the insulin signaling pathway in skeletal muscle cells remains poorly understood. In the current study, we investigated the effect of IL‐1β stimulation on insulin signal transduction from the insulin receptor (IR), resulting in glucose transporter 4 (GLUT4) translocation in skeletal muscle cells. In L6‐GLUT4myc cells, stimulation with IL‐1β for 24 h promoted GLUT4 translocation to the plasma membrane and increased glucose uptake in a concentration‐dependent manner, whereas short‐term stimulation with IL‐1 for up to 6 h did not affect that. In addition, stimulation with IL‐1β for 24 h further increased insulin‐stimulated GLUT4 translocation. Interestingly, stimulation with IL‐1β for 24 h did not cause any change in the phosphorylation of insulin signal molecules IR, insulin receptor substrate (IRS)‐1, Akt, and p21‐activated kinase (PAK1). Stimulation with IL‐1β for 24 h significantly increased AMP‐activated protein kinase (AMPK) phosphorylation and GLUT4 protein expression. Small interfering RNA (siRNA) targeting AMPK1/2 significantly inhibited IL‐1β‐stimulated GLUT4 translocation. These results suggest that prolonged stimulation with IL‐1β positively regulates GLUT4 translocation in skeletal muscle cells. IL‐1β may have a beneficial effect on maintaining glucose homeostasis in skeletal muscle cells in patients with type 2 diabetes. 

Effects of pimobendan and EGIS 9377, cardiotonic agents, and OG-VI, a nucleoside-nucleotide mixture, administered during reperfusion after ischemia on stunned myocardium in dogs.

BackgroundPimobendan is a so‐called calcium sensitizer that exerts a positive inotropic action. EGIS 9377 is synthesized as a calcium sensitizer. OG‐VI is a nucleoside–nucleotide mixture that ameliorates the myocardial dysfunction (myocardial stunning) after ischemia. ObjectiveTo determine whether administration of these agents after the onset of reperfusion after ischemia improves the condition of stunned myocardium. MethodsDogs anesthetized with pentobarbital were subjected to 20 min ligation of left anterior descending coronary artery and then 60 min reperfusion. The corresponding vehicle, 0.3 and 1 mg/kg pimobendan, or 1 and 3 mg/kg EGIS 9377 was injected intravenously 30 min after the onset of reperfusion. Saline solution or 1.2 μmol/kg per min OG‐VI was infused for 30 min, starting 30 min after the reperfusion. Shortening of myocardial segment was measured by sonomicrometry. The tissue levels of energy and carbohydrate metabolites in the 60 min‐reperfused hearts were determined. ResultsShortening of myocardial segments significantly decreased during ischemia, and returned toward preischemic level after reperfusion for all groups, although the contractile dysfunction still remained. Injections and infusion of pimobendan, EGIS 9377, and OG‐VI after the onset of reperfusion ameliorated the contractile dysfunction. Systemic vascular resistance was decreased by administrations of pimobendan and OG‐VI. The levels of high‐energy phosphates in 60 min‐reperfused heart were not changed by either treatment. ConclusionAdministration of pimobendan, EGIS 9377, and OG‐VI ameliorate the myocardial contractile dysfunction after ischemia even when these agents are administered after the onset of reperfusion. The increase in contractile function due to these agents did not worsen the myocardial energy balance.