Ramipril protects the endothelium from high glucose-induced dysfunction through CaMKKß/AMPK and heme oxygenase-1 activation.

This study aims to investigate the effects of ramipril (RPL) on endothelial dysfunction associated with diabetes mellitus using cultured human aortic endothelial cells (HAECs) and a type 2 diabetic animal model. The effect of RPL on vasodilatory function in fat-fed, streptozotocin-treated rats was assessed. RPL treatment of 8 weeks alleviated insulin resistance and inhibited the decrease in endothelium-dependent vasodilation in diabetic rats. RPL treatment also reduced serum advanced glycation end products (AGE) concentration and rat aorta reactive oxygen species formation and increased aorta endothelium heme oxygenase-1 (HO-1) expression. Exposure of HAECs to high concentrations of glucose induced prolonged oxidative stress, apoptosis, and accumulation of AGEs. These effects were abolished by incubation of ramiprilat (RPT), the active metabolite of RPL. However, treatment of HAECs with STO-609, a CaMKKß (Ca(2+)/calmodulin-dependent protein kinase kinase-ß) inhibitor; compound C, an AMPK (AMP-activated protein kinase) inhibitor; and Zn(II)PPIX, a selective HO-1 inhibitor, blocked these beneficial effects of RPT. In addition, RPT increased nuclear factor erythroid 2-related factor-2 (Nrf-2) nuclear translocation and activation in a CaMKKß/AMPK pathway-dependent manner, leading to increased expression of the Nrf-2-regulated antioxidant enzyme, HO-1. The inhibition of CaMKKß or AMPK by pharmaceutical approach ablated RPT-induced HO-1 expression. Taken together, RPL ameliorates insulin resistance and endothelial dysfunction in diabetes via reducing oxidative stress. These effects are mediated by RPL activation of CaMKK-ß, which in turn activates the AMPK-Nrf-2-HO-1 pathway for enhanced endothelial function.

NO modulates myocardial O2 consumption in the nonhuman primate: an additional mechanism of action of amlodipine.

Recent evidence from our laboratory and others suggests that nitric oxide (NO) is a modulator of in vivo and in vitro oxygen consumption in the murine and canine heart. Therefore, the goal of our study was twofold: to determine whether NO modulates myocardial oxygen consumption in the nonhuman primate heart in vitro and to evaluate whether the seemingly cardioprotective actions of amlodipine may involve an NO-mediated mechanism. Using a Clark-type O2 electrode, we measured oxygen consumption in cynomologous monkey heart at baseline and after increasing doses of S-nitroso-N-acetylpenicillamine (SNAP; 10(-7)-10(-4) M), bradykinin (10(-7)-10(-4) M), ramiprilat (10(-7)-10(-4) M), and amlodipine (10(-7)-10(-5) M). SNAP (-38 +/- 5.8%), bradykinin (-19 +/- 3.9%), ramiprilat (-28 +/- 2.3%), and amlodipine (-23 +/- 4.5%) each caused significant (P < 0.05) reductions in myocardial oxygen consumption at their highest dose. Preincubation of tissue with nitro-L-arginine methyl ester (10(-4) M) blunted the effects of bradykinin (-5.4 +/- 3.2%), ramiprilat (-4.8 +/- 5.0%), and amlodipine (-5.3 +/- 5.0%) but had no effect on the tissue response to SNAP (-38 +/- 5.8%). Our results indicate that NO can reduce oxygen consumption in the primate myocardium in vitro, and they support a role for the calcium-channel blocker amlodipine as a modulator of myocardial oxygen consumption via a kinin-NO mediated mechanism.

Influence of age and dietary sodium on the cardiovascular and renal effects of ramipril in spontaneously hypertensive rats.

The aim of the present study was to investigate the influence of age and an increased intake of dietary sodium on the cardiovascular and renal effects of the angiotensin converting enzyme inhibitor, ramipril. Male spontaneously hypertensive rats (SHR) aged 10 and 60 weeks received either control or a high level of sodium (0.3% vs. 2.6% Na) and ramipril (2 mg/kg/day) mixed in the chow for 6 weeks. Blood pressure was measured weekly by tail-cuff method. Arterial functions were determined by measuring vascular contractile and relaxation responses of mesenteric arterial rings in vitro at the end of the study. An age-related increase in systolic blood pressure, left ventricular (LVH) and renal hypertrophy (RH) as well as proteinuria were found in SHR. The vascular relaxation to nitroprusside was impaired in aged SHR. The high sodium intake accelerated the development of hypertension only in young SHR but increased LVH and RH in both age groups. Ramipril effectively lowered blood pressure in both age groups, but decreased the LVH significantly only in young rats. Ramipril markedly improved the vascular relaxation to acetylcholine and nitroprusside only in young rats. The vascular contractile responses to noradrenaline and potassium chloride were not affected by age, sodium intake or ramipril treatment. The high sodium intake markedly attenuated the cardiovascular effects of ramipril. The high-sodium diet enhanced the urinary excretion of cyclic GMP in both age groups, while it increased urinary excretion of protein in young SHR only. In conclusion, the cardiovascular effects of ramipril were impaired with advanced age even in the presence of a control intake of sodium. A high sodium intake attenuated or even abolished the cardiovascular effects of ramipril in both young and aged SHR.

Inhibition of nitric oxide synthase prevents myocardial protection by ramiprilat.

The objective of this investigation was to determine the role of nitric oxide synthase in the action of the angiotensin-converting enzyme inhibitor, ramiprilat, to reduce myocardial ischemia/reperfusion injury. Ramiprilat, the nitric oxide synthase inhibitor NG-nitro-L-NAME (L-NAME), ramiprilat plus L-NAME, or saline (n = 8 each group), were administered i.v. in intact animal preparations of experimentally induced acute myocardial ischemia. Anesthetized, open-chest rabbits were instrumented for measurement of systemic hemodynamics and left ventricular pressure from which left ventricular +dP/dtmax was derived. Animals were subjected to 30 min of left main coronary artery occlusion (marginal branch) followed by 2 hr of reperfusion. Ramiprilat (50 micrograms/kg) or saline was administered 5 min before reperfusion, and those rabbits receiving L-NAME (100 micrograms/kg/min) were pretreated starting 30 min before occlusion throughout the remainder of the experiment. After reperfusion, myocardial infarct size (IS) was determined via tetrazolium staining and expressed as a percentage of area at risk (AR). IS/AR% was significantly reduced in rabbits administered ramiprilat (19 +/- 3%) compared to those receiving saline (39 +/- 2%), ramiprilat plus L-NAME (43 +/- 4%) or L-NAME alone (43 +/- 2%; mean +/- S.E.M.; P < .05). AR as a percent of total left ventricular mass was not different between any of the four treatment groups. Systemic hemodynamic effects were not significantly different between groups. The results indicate that the effect of ramiprilat to reduce infarct size is abolished by pretreatment with L-NAME.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of myocardial infarct size in rabbits by ramiprilat: reversal by the bradykinin antagonist HOE 140.

We wished to determine, using a novel specific antagonist of BK2, HOE 140, (a) if the angiotensin-converting enzyme (ACE) inhibitor, ramiprilat, reduces myocardial infarct size in a well-established animal model of ischemia/reperfusion with minimal coronary collateralization, and (b) if the reduction in myocardial infarct size occurred through a bradykinin-dependent mechanism Saline vehicle, ramiprilat, HOE 140, or ramiprilat plus HOE 140 (n = 6 each group), was administered intravenously (i.v.) in intact animal preparations of experimentally induced acute myocardial ischemia. Anesthetized, open-chest rabbits were instrumented for measurement of systemic hemodynamics and left ventricular pressure (LVP), from which LV + dP/dtmax was derived. Animals were subjected to 30-min left main coronary artery occlusion (marginal branch) followed by 2-h reperfusion. Ramiprilat (50 micrograms/kg) or saline was administered before reperfusion, and rabbits receiving HOE 140 were pretreated before occlusion (1 microgram/kg). In separate duration of action experiments (n = 6 each group), the above doses of ramiprilat or HOE 140 had significant vascular antagonism of sufficient duration against serial challenge with angiotensin I (AI) or bradykinin, respectively. After reperfusion, myocardial infarct size (IS) was determined by tetrazolium staining and expressed as a percentage of area at risk (AR). IS/AR% was significantly reduced in rabbits that received ramiprilat (20 +/- 6%, p < 0.05) as compared with those that received saline (41 +/- 6%), ramiprilat plus HOE 140 (47 +/- 2%), or HOE 140 alone (43 +/- 4%, mean +/- SEM). AR as a percentage of total LV mass was not different between any of the four treatment groups. Tachycardia was observed during early reperfusion in each group treated with ramiprilat.(ABSTRACT TRUNCATED AT 250 WORDS)