Olive Leaf Extract Improves the Atherogenic Lipid Profile in Rats Fed a High Cholesterol Diet.

Coronary heart disease because of atherosclerosis is still the most common cause of mortality. Elevated levels of low-density lipoprotein and total cholesterol are major risk factors for atherosclerotic cardiovascular disease. The aim of this study was to evaluate the effects of the olive leaf extract on serum lipid profile, early changes of atherosclerosis and endothelium-dependent relaxations in cholesterol-fed rats. For this purpose, rats were fed by 2% cholesterol-enriched or standard chow for 8 weeks. Some rats in each group were also fed orally by olive leaf extract at doses of 50 or 100 mg/kg/day. Atorvastatin at dose of 20 mg/kg of body weight daily was also given as positive control. After 8 weeks, lipid profiles of rat serums were analyzed. Antioxidant enzyme activities (superoxide dismutase and glutathione peroxidase) and degree of lipid peroxidation (malondialdehyde levels) were also measured in the hearts isolated from rats. In addition, expression of adhesion molecules and endothelium-dependent relaxations of isolated thoracic aortas of rats were evaluated. Total cholesterol and LDL-cholesterol levels were found to be increased in cholesterol-fed rats, and both doses of olive leaf extract and atorvastatin significantly decreased those levels. In conclusion, because the olive leaf extract attenuates the increased cholesterol levels, it may have beneficial effects on atherosclerosis.

Vasodilator effects of cromakalim and HA 1077 in diabetic rat aorta.

BACKGROUND: Impairment of the vasorelaxant responses have been reported in diabetes mellitus. In this study, the roles of the K(ATP) channel and rho kinase pathway were evaluated by using the K(ATP) channel opener cromakalim and Rho-kinase inhibitor HA 1077 in diabetic rat aorta. METHODS: Adult male Wistar rats weighing (250-300 g) were divided into diabetic and control groups. Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ, 55 mg/kg/i.p). RESULTS: Vasodilator responses induced by cromakalim (10(-7) to 10(-3M)) and HA 1077 (10(-6) to 10(-4M)) were significantly less in diabetic rings compared with control rings (p <0.01). The decrease in the relaxant effect of cromakalim was more in endothelium-denuded rings compared to the endothelium-intact rings (p <0.05). There were no significant differences between endothelium intact and non-intact rings in the presence of HA 1077. When two drugs were administered together, relaxation was significantly less than with seperate administration of each drug in the diabetic group (p <0.01). Pre-treatment with N omega-nitro-L-arginine methylester (L-NAME) (10(-6) to 10(-4 M)), an NO synthase inhibitor, significantly decreased the relaxant response to cromakalime and HA 1077 in both the control and diabetic groups (p <0.05). CONCLUSIONS: These results suggest that the impaired relaxant effects were further decreased depending on K(ATP) channel activity but the effects of Rho-kinase enzyme inhibitors on relaxation responses were not significantly changed in diabetes mellitus.

Levosimendan attenuates reperfusion injury in an isolated perfused rat heart model.

OBJECTIVES: The aim of this study was to investigate the effect of levosimendan on apoptosis and infarct size when administered before ischemia in an isolated rat heart model. DESIGN: An in vitro experimental study. SETTING: Animal laboratory. PARTICIPANTS: Isolated perfused rat heart preparation (n = 22). INTERVENTIONS: Perfusion with Krebs-Henseleit solution was performed for 30 minutes and then 0.1 micromol/L of levosimendan was added to the perfusion fluid for 10 minutes before global ischemia; the control hearts received no levosimendan. Hearts underwent global ischemia for 30 minutes and then were reperfused for 30 minutes before specimens were obtained for testing. MEASUREMENTS AND MAIN RESULTS: Infarct sizes were measured at the end of the reperfusion period and expressed as a percentage of the area at risk. Myocardial apoptosis was detected by using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) method. Bcl-2 expression was determined to detect antiapoptotic activity. Infarct size was significantly less in the levosimendan group (26% +/- 3% v 40% +/- 4%, respectively; p = 0.009). Levosimendan significantly reduced the proportion of TUNEL-positive cardiomyocytes (3 +/- 1 v 20 +/- 4, respectively; p < 0.001) and increased Bcl-2 expression compared with control hearts (44% +/- 3% v 31% +/- 3%, respectively; p = 0.01). Recovery of left ventricular-developed pressure 30 minutes after reperfusion in ischemic hearts pretreated with levosimendan was significantly better than that of placebo-treated hearts (53% +/- 3% v 38% +/- 3% of baseline, respectively; p = 0.004). CONCLUSIONS: Levosimendan has a cardioprotective effect when administered before ischemia in ischemia-reperfusion injury. This effect may be useful in elective cardiac surgery for protecting myocytes from ischemia-reperfusion-induced apoptosis.

Contribution of RhoA kinase and protein kinase C to weak relaxant effect of pinacidil on carbachol-induced contractions in sensitized guinea-pig trachealis.

The exact mechanisms underlying the weak bronchodilator effect of K(ATP) channel openers on cholinergic stimulations is unknown. The present study was designed to examine the relaxant efect of pinacidil in guinea-pig trachea stimulated with carbachol by the presence of calcium sensitizer inhibitors; HA 1077, a rhoA kinase inhibitor, and chelerythrine, a protein kinase C inhibitor. Adenosine (10 microM) was used as other contractile agent for comparison. Tracheal tissues were isolated from ovalbumin sensitized guineapigs and changes in tension were recorded isometrically. Pinacidil (1-100 muM, cumulatively) and HA 1077 (0.01-30 microM, cumulatively) produced concentration-dependent relaxations in unstimulated tisues. The relaxant response to pinacidil decreased in carbachol contracted tissues, but increased in adenosine-stimulated tissues. Pretreatment of the tissues with HA 1077 (0.1 microM) and chelerythrine (10 microM) increased the pinacidil-induced relaxations by approximately %100 and %40, respectively. Glibenclamide, a KATP channel blocker, partially antagonized the pinacidil response in contracted tissues. Glibenclamide also inhibited the carbachol and adenosine induced contractions. These results suggest that diminish effect of pinacidil may have related to the enhanced calcium sensitization by cholinergic stimulation. Rho kinase inhibitors appear more effective than PKC inhibitors to achieve of this failure.

The role of ATP sensitive K+ channels and of nitric oxide synthase on myocardial ischemia/reperfusion-induced apoptosis.

During ischemia, ATP-sensitive K+ channels (KATP channels) open, and this triggers necrotic processes and apoptosis. In this study, we investigated whether selective sarcoplasmic and mitochondrial KATP channel blockers affected myocardial apoptosis and nitric oxide synthase (NOS) activity in a rat model of myocardial ischemia/reperfusion in vitro. Isolated rat hearts were subjected to 30 min of coronary artery occlusion followed by 30 min of reperfusion. A selective sarcKATP channel blocker, HMR1098 and a selective mitoKATP channel blocker, 5-hydroxydecanoate, were added to the perfusion fluid 10 min before occlusion. Myocardial apoptosis was detected immunohistochemically using the TUNEL method. Myocardial inducible NOS (iNOS) and endothelial NOS (eNOS) were determined immunohistochemically. In control hearts, apoptosis induction was associated with a greater immunoreactivity of iNOS than eNOS. Treatment with HMR1098, at a concentration of 3 micromol/l, significantly reduced the TUNEL-positive cardiomyocytes and this was associated with decreased iNOS and increased eNOS immunoreactivity. When this drug was administered at a higher concentration, at 30 micromol/l, a more marked reduction in apoptosis was observed but, in contrast to the effects observed at the lower drug concentration, eNOS immunoreactivity was almost completely abolished while iNOS was strong. Moreover, ischemia-induced cardiac dysfunction (e.g. contractile force and recovery of coronary flow) was increased by the higher concentration of HMR 1098. In hearts treated with 5-hydroxydecanoate, myocyte apoptosis was slightly reduced, and this was associated with an almost equal increase in both iNOS and eNOS immunoreactivity. These findings suggest that iNOS appears to be more important than eNOS in the reduction of apoptosis. However, the further inhibition of apoptosis by the higher concentration of HMR 1098 was associated with poorer cardiac function.