Comparative effects of azelnidipine and amlodipine on myocardial function and mortality after ischemia/reperfusion in dogs.

Effects of azelnidipine were examined and compared with those of amlodipine on stunned myocardium in dogs. The left anterior descending (LAD) coronary artery was ligated for 20 min and subsequently released for 60 min. A vehicle, azelnidipine (0.3 mg/kg), or amlodipine (0.3 or 1 mg/kg) was injected intravenously 20 min before LAD ligation. The heart rate increased after a depressor response in the presence of amlodipine, while it decreased despite a decrease in arterial pressures in the presence of azelnidipine. After reperfusion, the coronary flow (CF) significantly increased in the presence of azelnidipine, but did not change with amlodipine after reperfusion. A positive inotropic effect was observed after treatment with both calcium antagonists. Ischemia significantly decreased the percentage of segment shortening (%SS) in all groups. Treatment with both calcium antagonists significantly increased %SS after reperfusion, although high-energy phosphate levels did not improve in the presence of calcium antagonists 60 min after reperfusion. Mortality with azelnidipine was significantly lower than that with 0.3 mg/kg amlodipine immediately after reperfusion. In conclusion, improvement in myocardial stunning after pretreatment with azelnidipine is associated with an increase in CF after reperfusion. The negative chronotropic action may have contributed to decreased mortality due to reperfusion arrhythmias. Azelnidipine is more beneficial than amlodipine and may provide an additional advantage to patients with angina and hypertension.

Cardiac mast cell-derived renin promotes local angiotensin formation, norepinephrine release, and arrhythmias in ischemia/reperfusion.

Having identified renin in cardiac mast cells, we assessed whether its release leads to cardiac dysfunction. In Langendorff-perfused guinea pig hearts, mast cell degranulation with compound 48/80 released Ang I-forming activity. This activity was blocked by the selective renin inhibitor BILA2157, indicating that renin was responsible for Ang I formation. Local generation of cardiac Ang II from mast cell-derived renin also elicited norepinephrine release from isolated sympathetic nerve terminals. This action was mediated by Ang II-type 1 (AT1) receptors. In 2 models of ischemia/reperfusion using Langendorff-perfused guinea pig and mouse hearts, a significant coronary spillover of renin and norepinephrine was observed. In both models, this was accompanied by ventricular fibrillation. Mast cell stabilization with cromolyn or lodoxamide markedly reduced active renin overflow and attenuated both norepinephrine release and arrhythmias. Similar cardioprotection was observed in guinea pig hearts treated with BILA2157 or the AT1 receptor antagonist EXP3174. Renin overflow and arrhythmias in ischemia/reperfusion were much less prominent in hearts of mast cell-deficient mice than in control hearts. Thus, mast cell-derived renin is pivotal for activating a cardiac renin-angiotensin system leading to excessive norepinephrine release in ischemia/reperfusion. Mast cell-derived renin may be a useful therapeutic target for hyperadrenergic dysfunctions, such as arrhythmias, sudden cardiac death, myocardial ischemia, and congestive heart failure.

[Effect of the brand and generic medicine of pravastatin on dyslipidemia in rabbits fed a high cholesterol diet].

Mevalotin containing pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, is the brand medicine and well known to be effective for patients with dyslipidemia. Now, more than 20 generic pravastatins are available for clinical therapy. We compared pharmaceutical property of Mevan,a generic pravastatin, with that of Mevalotin.According to the definition of the Japanese Pharmacopoeia, Mevalotin 10 mg tablets were uniform in pravastatin content, whereas 5 mg tablets were rather variable. Variation in pravastatin content of Mevan 5 mg tablets was the same as Mevalotin 5 mg, whereas that of 10 mg tablets was very variable. The plasma concentration of pravastatin in the normal rabbits continuously increased until 180 min after oral administration of 30 mg Mevan, whereas it increased in a biphasic pattern after 30 mg Mevalotin.All rabbits were fed 0.2% cholesterol diet throughout the experiment. After 8 weeks, oral administration of either Mevalotin or Mevan was started at the dose of 30 mg pravastatin/day for 16 weeks. After a transient increase for a few weeks, the plasma levels of total- and LDL-cholesterol gradually decreased in Mevalotingroup, whereas these levels did not significantly changed in Mevan group within 16 weeks. The level of HDL-cholesterol in Mevan group tended to increase but not in Mevalotin group. The triglyceride level in Mevan group changed as well as that in Mevalotin group until 10 weeks after administration, and then gradually increased. The present results suggest that pharmaceutical properties of Mevan are not always identical with those of Mevalotin.

Immediate hypersensitivity elicits renin release from cardiac mast cells.

BACKGROUND: We recently reported that murine and cavian heart mast cells are a unique extrarenal source of renin. Ischemia/reperfusion releases this renin leading to local angiotensin formation and norepinephrine release. As mast cells are a primary target of hypersensitivity, we assessed whether anaphylactic mast cell degranulation also results in renin and norepinephrine release. METHODS: Hearts isolated from presensitized guinea pigs were challenged with antigen. RESULTS: Cardiac anaphylaxis was characterized by mast cell degranulation, evidenced by beta-hexosaminidase release and associated with renin and norepinephrine release. Mast cell stabilization with cromolyn or lodoxamide markedly attenuated the release of beta-hexosaminidase, renin and norepinephrine. Renin inhibition with BILA2157 did not affect mast cell degranulation, but attenuated norepinephrine release. CONCLUSIONS: Our findings disclose that immediate-type hypersensitivity elicits renin release from mast cells, activating a local renin-angiotensin system, thereby promoting norepinephrine release. As renin is stored in human heart mast cells, allergic reactions could initiate renin release, leading to local angiotensin formation and hyperadrenergic dysfunction.

Improvement of stunned myocardium in dogs with olmesartan, an angiotensin II type 1 receptor antagonist, is independent of type 2 receptors.

Olmesartan is a selective angiotensin II type 1 receptor (AT1) antagonist. In pentobarbital-anesthetized open-chest dogs, ischemia/reperfusion was induced by ligating the left anterior descending coronary artery for 20 min and releasing it for 60 min, respectively. The myocardial contraction in the ischemic area decreased and returned towards its pre-ischemic level during reperfusion but incompletely. Olmesartan improved the recovery of myocardial contraction during reperfusion associated with restoration of myocardial ATP. Angiotensin II repelled by AT1 receptors occupied by olmesartan can reach and stimulate the angiotensin II type 2 (AT2) receptors, resulting in some beneficial effects on the ischemic myocardium. In fact, AT2 receptor mRNA was found in the adult dog myocardium. In addition, the plasma level of angiotensin II was significantly increased by olmesartan. PD123319, a selective AT2 receptor antagonist, however, did not modify the effect of olmesartan on the cardiac contraction. The hypertensive response to exogenous angiotensin II was completely inhibited by olmesartan, whereas PD123319 did not abolish the effect of olmesartan. In conclusion, olmesartan protects the ischemic/reperfused heart against ischemic injury through inhibition of AT1 receptors but not indirect activation of AT2 receptors.

NO-1886 (ibrolipim), a lipoprotein lipase-promoting agent, accelerates the expression of UCP3 messenger RNA and ameliorates obesity in ovariectomized rats.

The synthetic compound NO-1886 (ibrolipim, [4-(4-bromo-2-cyano-phenylcarbamoyl)-benzyl]-phosphonic acid diethyl ester, CAS 133208-93-2) is a lipoprotein lipase (LPL)-promoting agent that decreases plasma triglycerides, increases high-density lipoprotein cholesterol levels, and prevents fat accumulation in high fat-fed rats. However, the effect of NO-1886 on body weight, fat accumulation, and energy expenditure in ovariectomized (OVX) rats is not clear. The primary aim of this study was to ascertain whether NO-1886 ameliorated obesity in OVX rats and to examine the effects on fatty acid oxidation-related enzymes. NO-1886 decreased accumulation of visceral fat and suppressed the increase in body weight resulting from the ovariectomy. NO-1886 decreased the respiratory quotient and increased expression of the fatty acid translocase messenger RNA (mRNA) in the liver, soleus muscle, and mesenteric fat. NO-1886 also increased the expression of fatty acid-binding protein mRNA in the liver and soleus muscle and the expression of the uncoupling protein 3 (UCP3) mRNA in the heart, soleus muscle, and mesenteric fat, but not in the brown adipose tissue. Furthermore, NO-1886 did not affect UCP1 and UCP2 in brown adipose tissue. Therefore, amelioration of obesity by NO-1886 in OVX rats is possibly because of an the increased expression of fatty acid oxidation-related enzymes and UCP3, both of which are related to fatty acid transfer and fat use. Our study indicates that the LPL-promoting agent NO-1886 may be potentially beneficial in the treatment of obesity and obesity-linked health problems in postmenopausal women.

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.

Possible mechanisms underlying statin-induced skeletal muscle toxicity in L6 fibroblasts and in rats.

3-Hydroxy-3-methylglutaryl CoA reductase inhibitors (statins) are safe and well-tolerated therapeutic drugs. However, they occasionally induce myotoxicity such as myopathy and rhabdomyolysis. Here, we investigated the mechanism of statin-induced myotoxicity in L6 fibroblasts and in rats in vivo. L6 fibroblasts were differentiated and then treated with pravastatin, simvastatin, or fluvastatin for 72 h. Hydrophobic simvastatin and fluvastatin decreased cell viability in a dose-dependent manner via apoptosis characterized by typical nuclear fragmentation and condensation and caspase-3 activation. Both hydrophobic statins transferred RhoA localization from the cell membrane to the cytosol. These changes induced by both hydrophobic statins were completely abolished by the co-application of geranylgeranylpyrophosphate (GGPP). Y27632, a Rho-kinase inhibitor, mimicked the hydrophobic statin-induced apoptosis. Hydrophilic pravastatin did not affect the viability of the cells. Fluvastatin was continuously infused (2.08 mg/kg at an infusion rate of 0.5 mL/h) into the right internal jugular vein of the rats in vivo for 72 h. Fluvastatin infusion significantly elevated the plasma CPK level and transferred RhoA localization in the skeletal muscle from the cell membrane to the cytosol. In conclusion, RhoA dysfunction due to loss of lipid modification with GGPP is involved in the mechanisms of statin-induced skeletal muscle toxicity.

Effects of rosuvastatin and pitavastatin on ischemia-induced myocardial stunning in dogs.

Incomplete recovery of myocardial contraction after reperfusion following brief ischemia is called the "stunning phenomenon" in an animal experiment. A hydrophilic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) does not affect this phenomenon, but lipophilic statins further reduce the contraction during reperfusion. The effects of novel hydrophilic rosuvastatin and lipophilic pitavastatin on myocardial stunning in dogs were examined. In a preliminary experiment in vitro, pitavastatin reduced L6 cell viability at 10(-6) M and higher, whereas rosuvastatin and pravastatin up to 10(-5) M did not show such effects. An empty capsule or a capsule filled with rosuvastatin (2 mg/kg per day) or pitavastatin (0.4 mg/kg per day) was orally administered to dogs. After 3 weeks, both statins lowered the serum cholesterol level to the same extent. Under pentobarbital anesthesia, dogs were subjected to 15-min ischemia followed by 120-min reperfusion. Ischemia arrested the myocardial contraction in the ischemic area, and reperfusion recovered it but incompletely, showing the stunning phenomenon. Rosuvastatin did not modify the stunning phenomenon, while pitavastatin further deteriorated the myocardial contraction during reperfusion.

Effects of minoxidil on ischemia-induced mechanical and metabolic dysfunction in dog myocardium.

Effects of minoxidil on ischemia-induced myocardial mechanical and metabolic dysfunction were examined in anesthetized open-chest dogs. A regional portion of the left ventricle was made ischemic for 20 min by ligating the left anterior descending coronary artery, and then reperfused for 120 min. Dimethylsulfoxide or minoxidil (0.3, or 1.0 mg/kg) was injected intravenously 10 min before ligation. Ischemia decreased regional myocardial contraction, and reperfusion recovered it but incompletely. Myocardial metabolic derangement was observed during ischemia, such as decreases in the myocardial levels of ATP and creatine phosphate. These metabolic changes caused by ischemia were restored by reperfusion. Minoxidil injection at 0.3 and 1.0 mg/kg significantly decreased blood pressures but increased coronary flow. Pretreatment with minoxidil significantly enhanced the recovery of myocardial contraction during reperfusion after ischemia. The levels of ATP and creatine phosphate in the ischemic myocardium were significantly preserved by minoxidil at 0.3 mg/kg. No significant effect of minoxidil on the metabolism was observed in the 120 min reperfused myocardium. In conclusion, minoxidil improved the mechanical dysfunction in the reperfused heart and the drug at low dose preserved high-energy phosphates during ischemia.