Showing papers in "Journal of Cardiovascular Pharmacology in 2000"

Sympathetic nervous system activation in essential hypertension, cardiac failure and psychosomatic heart disease.

Abstract: Regional sympathetic activity can be studied in humans using electrophysiological methods measuring sympathetic nerve firing rates and neurochemical techniques providing quantification of noradrenaline spillover to plasma from sympathetic nerves in individual organs. Essential hypertension: Such measurements in patients with essential hypertension disclose activation of the sympathetic outflows to skeletal muscle blood vessels, the heart and kidneys, particularly in younger patients. This sympathetic activation, in addition to underpinning the blood pressure elevation, most likely also contributes to left ventricular hypertrophy, and to the commonly associated metabolic abnormalities of insulin resistance and hyperlipidaemia. Antihypertensive drugs, such as moxonidine, which act primarily by inhibiting the sympathetic nervous system, should have additional clinical benefits beyond those attributable to blood pressure reduction, in protecting against hypertensive complications. Obesity-related hypertension: Understanding the neural pathophysiology of hypertension in the obese has been difficult. In normotensive obesity, renal sympathetic tone is doubled, but cardiac noradrenaline spillover (a measure of sympathetic activity in the heart) is only 50% of normal. In obesity-related hypertension, there is a comparable elevation of renal noradrenaline spillover, but without suppression of cardiac sympathetics (cardiac sympathetic activity being more than double that of normotensive obese and 25% higher than in healthy volunteers). Increased renal sympathetic activity in obesity may be a 'necessary' cause for the development of hypertension (and predisposes to hypertension development), but apparently is not a 'sufficient' cause. The discriminating feature of the obese who develop hypertension is the absence of the adaptive suppression of cardiac sympathetic tone seen in the normotensive obese. Heart failure: In cardiac failure, the sympathetic nerves of the heart are preferentially stimulated. Noradrenaline release from the failing heart at rest in untreated patients is increased as much as 50-fold, similar to the level seen in the healthy heart during near-maximal exercise. Activation of the cardiac sympathetic outflow provides adrenergic support to the failing myocardium, but at a cost of arrhythmia development and progressive myocardial deterioration. Psychosomatic heart disease: No more than 50% of clinical coronary heart disease is explicable in terms of classical cardiac risk factors. There is gathering evidence that psychological abnormalities, particularly depressive illness, anxiety states, including panic disorder and mental stress, are involved here, 'triggering' clinical cardiovascular events, and possibly also contributing to atherosclerosis development. The mechanisms of increased cardiac risk attributable to mental stress and psychiatric illness are not entirely clear, but activation of the sympathetic nervous system seems to be of prime importance.

Tetrahydrobiopterin improves endothelial function in patients with coronary artery disease.

Abstract: Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide synthase (NOS) and a scavenger of oxygen-derived free radicals. Decreased availability of BH4 leads, under in vitro conditions, to reduced nitric oxide (NO) production and increased superoxide formation. We studied the effect of exogenous BH4 on endothelial function of angiographically normal vessel segments in patients with coronary artery disease. Nineteen patients with coronary artery disease underwent quantitative coronary angiography with simultaneous coronary flow velocity measurements (Cardiometrics FloWire). Data were obtained in angiographically normal segments of the left coronary artery at baseline, after intracoronary (i.c.) administration of acetylcholine (Ach; 10(-4) M), after infusion of BH4 (10(-2) M), and after co-infusion of ACh and BH4. At the end of the study, 300 microg nitroglycerin (NTG) i.c. was administered to obtain maximal vasodilation. At each step, flow velocity was determined before and after 18 microg adenosine i.c. to assess coronary flow velocity reserve. In 15 patients, ACh induced coronary vasoconstriction of -18 +/- 3% (endothelial dysfunction; p < 0.0001 vs. baseline), and in four patients, vasodilation of +39 +/- 20%. In the 15 patients with endothelial dysfunction, BH4 alone did not influence vessel area but prevented vasoconstriction to ACh (+2 +/- 3%, NS, vs. baseline). Correspondingly, calculated volume flow showed the highest value after co-infusion of ACh and BH4. Coronary flow velocity reserve was comparable during the various infusion steps. BH4 prevents ACh-induced vasoconstriction of angiographically normal vessels in patients with coronary artery disease. Thus substitution of this cofactor of NOS may represent a new approach for the treatment of endothelial dysfunction.

Reproducibility of laser Doppler imaging of skin blood flow as a tool to assess endothelial function.

Abstract: Endothelial dysfunction might be an important and early event in the pathogenesis of major cardiovascular diseases Therefore, the evaluation of endothelial function in humans may be of great clinical relevance Usual methods for that purpose are either invasive and/or technically demanding In the dermal microcirculation, endothelial function may be assessed noninvasively from the laser Doppler measurement of increases in blood flow after either the transdermal application of acetylcholine by iontophoresis, or the release of transient arterial occlusion (reactive hyperemia) An endothelium-independent response may be provided by the iontophoresis of sodium nitroprusside This approach is notable for technical simplicity, but of uncertain reproducibility Sixteen young, healthy, nonsmoking males were examined in the fasting state Changes in skin blood flow were measured with a laser Doppler imager during the iontophoresis of acetylcholine and sodium nitroprusside, as well as during reactive hyperemia, on two different days, at each of two different sites on the volar face of the forearm Nonspecific effects related to the stimulation of terminal nerve fibers by the iontophoretic current were suppressed by prior surface anesthesia The iontophoresis of acetylcholine and sodium nitroprusside induced a seven- to eightfold increase in dermal blood flow The corresponding figure for peak reactive hyperemia was approximately fourfold The mean coefficients of variation of responses recorded on different days, on the same site, in the same individual were <10% for iontophoresis of acetylcholine and for peak reactive hyperemia, and between 10 and 20% for iontophoresis of sodium nitroprusside This day-to-day variation was significantly smaller than the site-to-site variation (p < 001 for all three responses) Endothelium-dependent and -independent responses of dermal blood flow evaluated with laser Doppler imaging are highly reproducible from day to day, at least in healthy nonsmoking young male subjects, and provided some simple precautions are observed, foremost among which is the strict standardization of the recording site These observations may have implications for the testing of endothelial function in clinical studies

Relaxation to flavones and flavonols in rat isolated thoracic aorta: mechanism of action and structure-activity relationships.

Abstract: The mechanism of the relaxant action and the structure-activity relation of flavonols (fisetin, quercetin, and 3,3',4'-trihydroxyflavone) and flavones (apigenin, chrysin, and luteolin) were examined in rat isolated thoracic aorta. The control responses to flavonols and flavones were compared with responses observed after the removal of the endothelium or in the presence of the L-type Ca2+ channel blocker, nifedipine (10(-7) M). The effects of flavonoids on contraction caused by the influx of extracellular Ca2+ and agonist-induced release of intracellular Ca2+ also were investigated. The flavones exhibited endothelium-independent vasorelaxation, whereas the removal of the endothelium significantly decreased the sensitivity of the relaxant responses to the flavonols without affecting the maximal relaxation. In the presence of nifedipine, the responses to apigenin, luteolin, and quercetin were significantly inhibited, but relaxation to chrysin, fisetin, and 3,3',4'-trihydroxyflavone was unaffected. All flavonols and flavones caused concentration-dependent inhibition of the contractile responses to exogenous application of Ca2+ and the release of intracellular Ca2+ stimulated by phenylephrine. Of the six flavonoids examined, 3,3',4'-trihydroxyflavone was the most potent when causing vasorelaxation or inhibition of contraction caused by the influx or release of Ca2+. In conclusion, these studies provide evidence that the hydroxyl substitution in the carbon 3 position that characterizes the flavonols is important in stimulating endothelium-dependent vasorelaxation, and the absence of hydroxyl substitution on the A phenolic ring enhances the relaxant action.

Inhibition of the Cardiac p38-mapk Pathway by Sb203580 Delays Ischemic Cell Death

Abstract: We report that SB203580 (SB), a specific inhibitor of p38-MAPK, protects pig myocardium against ischemic injury in an in vivo model. SB was applied by local infusion into the subsequently ischemic myocardium for 60 min before a 60-min period of coronary occlusion followed by 60-min reperfusion (index ischemia). Infarct size was reduced from a control value of 69.3 +/- 2.7% to 36.8 +/- 3.7%. When SB was infused systemically for 10 min before index ischemia, infarct size was reduced to 36.1 +/- 5.6%. We measured the content of phosphorylated p38-MAPK after systemic infusion of SB and Krebs-Henseleit buffer (KHB; negative control) and during the subsequent ischemic period using an antibody that reacts specifically with dual-phosphorylated p38-MAPK (Thr180/ Tyr182). Ischemia with and without SB significantly increased phospho-p38-MAPK, with a maximum reached at 20 min but was less at 30 and 45 min under the influence of the inhibitor. The systemic infusion of SB for 10 min before index ischemia did not significantly change the p38-MAPK activities (compared with vehicle, studied by in-gel phosphorylation) < or =20 min of ischemia, but activities were reduced at 30 and 45 min. Measurements of p38-MAPK activities in situations in which SB was present during in-gel phosphorylation showed significant inhibition of p38-MAPK activities. The systemic infusion of SB significantly inhibited the ischemia-induced phosphorylation of nuclear activating transcription factor 2 (ATF-2). Using a specific ATF-2 antibody, we did not observe significant changes in ATF-2 abundance when nuclear fractions from untreated, KHB-, and SB-treated tissues were compared. We investigated also the effect of local and systemic infusion of SB on the cardioprotection induced by ischemic preconditioning (IP). The infusions (local or systemic) of SB before and during the IP protocol did not influence the infarct size reduction mediated by IP. The observed protection of the myocardium against ischemic damage by SB points to the negative role of the p38-MAPK pathway during ischemia.

Use of statins and blood pressure control in treated hypertensive patients with hypercholesterolemia.

Abstract: High serum cholesterol has been frequently reported in patients with arterial hypertension in whom it might influence the blood pressure control. The aim of this study was to compare the extent of blood pressure changes in 41 patients with hypertension and hypercholesterolemia, taking antihypertensive drugs and treated for 3 months with statins (HC-S; pravastatin or simvastatin) and compared with matched controls with high (HC-D; 44) or normal serum cholesterol (NC-D; 45) undergoing antihypertensive treatment combined with dietary treatment alone. After 3 months of follow-up, a greater reduction of systolic (SBP) and diastolic (DBP) blood pressure values was observed in HC-S patients (ASBP/DBP, -11.3 +/-3/-10.6 +/- 2%) when compared with both HC-D (deltaSBP/DBP, -6.6 +/- 2/-6.1 +/- 2%; p < 0.05) and NC-D (deltaSBP/DBP, -6.9 +/- 2/-6.8 +/- 1.5%; p < 0.05). In statin-treated patients, a slight linear relation has been found between the percentage changes in DBP and those in plasma total cholesterol (R = 0.37, p = 0.043), whereas no relation was found with SBP changes (R =0.11; p = 0.35). In conclusion, the results of this study demonstrate that the use of statins in combination with antihypertensive drugs can improve blood pressure control in patients with uncontrolled hypertension and high serum cholesterol levels. The additional blood pressure reduction observed in patients treated with statins is clinically relevant and only partially related to the lipid-lowering effect.

Inhibition of the ER-kinase cascade by PD98059 and UO126 counteracts ischemic preconditioning in pig myocardium.

Abstract: Summary:Our previous studies suggested a protective role of the extracellular signal-regulated kinases (ERKs) cascade in ischemic preconditioning (IP) in the porcine heart. To test this hypothesis further, we studied the influence of the novel specific inhibitors of mitogen-activated protein kinase

Insulin resistance in chronic heart failure.

Abstract: Insulin resistance is an important risk factor for the development of hypertension, atherosclerotic heart disease, left ventricular hypertrophy and dysfunction, and heart failure. It reflects a disturbance of glucose metabolism and potentially worsens metabolic efficiency of both skeletal muscle and cardiac muscle. The exact mechanisms of insulin resistance are not known, but the finding of significant insulin resistance occurring as a consequence of heart failure raises interesting possibilities as to its pathogenesis. While sympathetic nervous system overactivity can acutely reduce insulin sensitivity, it is not clear to what extent, in stable optimally treated chronic heart failure (CHF), the neurohormonal overactivity of this syndrome is the major cause of insulin resistance. Other potential mechanisms include the loss of skeletal muscle bulk, impaired endothelial function and reduced skeletal muscle blood flow, and a possible direct action of proinflammatory cytokines such as tumour necrosis factor-alpha. The consequences of insulin resistance in heart failure are not known, but the severity of the abnormality appears to parallel symptomatics and exercise limitation in this condition, and, in particular, be related to the impairment of gross skeletal muscle function. While specific therapies to correct insulin resistance in CHF have not been evaluated, there are several exciting possibilities on the horizon. Several nonpharmacological therapies have been shown to increase insulin sensitivity in patients with normal left ventricular function, and if these benefits could be duplicated in CHF, they may offer symptomatic benefit. These include weight reduction in the obese, regular exercise training and the use of dietary manipulation such as low-fat, high-fibre diets. Drug treatments with positive effects on insulin sensitivity include some angiotensin converting enzyme-inhibitors as well as newer drug groups, such as the glitazones and moxonidine, a centrally active agent with effects on the recently described imidazoline I-1 receptor that inhibits central sympathetic tone. The role of these agents in reversing the insulin resistance of chronic heart failure warrants further investigation.

Myocardial Protection with Red Wine Extract

Abstract: Cardioprotective action of red wine was studied by preperfusing isolated rat hearts with ethanol-free red wine extract for 15 min before subjecting them to 30 min of global ischemia followed by 2 h of reperfusion. Four other group of rats were studied under identical conditions, of which one served as control; one was treated with 10 microM trans-resveratrol (RVT), one of the major antioxidants found in red wines; another, with 0.07% ethanol; and another, with 0.07% ethanol plus 10 microM RVT. The results of our study demonstrated that both red wine extract and RVT were equally cardioprotective, as evidenced by their abilities to improve postischemic ventricular functions including developed pressure and aortic flow. Developed pressure values at 60 min after reperfusion were 81.8 +/- 1.2 and 68.8 +/- 4.1 mm Hg for the red wine extract and RVT groups, respectively, versus 49.7 +/- 2.7 mm Hg for the control group. These compounds also reduced myocardial infarct size compared with the control hearts (20.1 +/- 0.5% and 10.5 +/- 0.3% for red wine extract and RVT groups, respectively, vs. 29.9 +/- 3.1% for the control group). The ethanol-treated group displayed slightly better functional recovery, which deteriorated sharply toward the end of the reperfusion period, and the extent of infarction was comparable to that of the control group (31.5 +/- 0.9%). In the ethanol plus RVT group, postischemic contractile function was significantly better than control, and infarct size also was reduced to 20.9 +/- 0.7%. The amount of malonaldehyde formation in the postischemic myocardium was reduced by red wine extract and RVT, indicating a reduction of oxidative stress developed in the ischemic reperfused myocardium. In vitro studies revealed that red wine extract is a potent antioxidant as evidenced by its ability to scavenge peroxyl radical in vitro. Taken together, the results of our study indicate that red wines are cardioprotective by their ability to function as an in vivo antioxidant.

Nitrotyrosine causes selective Vascular endothelial dysfunction and DNA damage

Abstract: Summary:Vascular endothelial dysfunction is recognized as a contributor to a wide array of cardiovascular disease states, but the initiating events involved are incompletely defined. Elevated plasma levels of free 3-nitro-L-tyrosine (3NT, biomarker of peroxynitrite formation) have been measured in s

Short-term atorvastatin treatment improves endothelial function in hypercholesterolemic women.

Abstract: Summary:Endothelial dysfunction represents the earliest stage of atherosclerosis and is usually present in hypercholesterolemia. Treatment with statins has been shown to normalize endothelial function in middle-aged men with hypercholesterolemia. We evaluated the effect over time of atorvastatin on

Reactive oxygen species induce proliferation of bovine aortic endothelial cells.

Abstract: The effects of reactive oxygen species (ROS) on different cellular types are variable. In some conditions they can be harmful metabolites, but they can also act as intracellular messengers that are able to activate different transcription factors. Based on previous reports in which ROS were shown to stimulate the proliferation of mesenchymal cells, this study was carried out to assess this effect on bovine aortic endothelial cells (BAECs). When cells were incubated with glucose oxidase (GO), an enzyme that generates H2O2 continuously, a significant increase in BAEC proliferation was detected. BAEC proliferation was measured by the incorporation of [3H]-thymidine in the DNA of BAECs, and also by an increase in the number of cells. The effect observed with GO was maximal at 8-24 h. Catalase abolishes proliferation. We also tested the ability of GO to phosphorylate tyrosine residues in endothelial cell proteins. A significant increase in tyrosine phosphorylation was found, which might constitute the molecular basis for proliferative effect of GO. In conclusion, these results demonstrate the ability of H2O2 to stimulate BAEC proliferation at least under certain experimental conditions. We suggest a general activation of the cascade of tyrosine phosphorylation as one of the possible cellular mechanisms responsible for GO-induced BAEC proliferation.

Mechanisms and clinical implications of blood pressure variability

Abstract: Several studies have unequivocally shown that the target-organ damage associated with the hypertensive condition is more closely related to 24 h average blood pressure values than to clinic blood pressure. Blood pressure, however, is highly variable over the daytime and night-time period, and of major interest is whether average 24 h blood pressure values, as well as 24 h blood pressure variability, correlate with, and are possibly responsible for, the hypertension-related alterations of the target-organ structure and function. This paper will address this issue by discussing the main features of blood pressure variability in hypertension. It will also examine the mechanisms involved in this phenomenon, with particular emphasis on the pathogenetic role of sympathetic neural factors. The clinical relevance of blood pressure variability in promoting target-organ damage, as well as its therapeutic implications, will finally be highlighted.

Oculohypotensive effect of angiotensin-converting enzyme inhibitors in acute and chronic models of glaucoma.

Abstract: We have studied the effects of various angiotensin-converting enzyme (ACE) inhibitors on intraocular pressure (IOP) of rabbits with experimentally induced ocular hypertension and their mechanism of action. Acute ocular hypertension was induced by infusion of 5% glucose (15 ml/kg) through marginal ear vein, whereas chronic glaucoma was induced by injection of alpha-chymotrypsin into the posterior chamber of the eye. IOP was measured by tonometer. All ACE inhibitors were instilled topically in the eye in a sterile solution. The effect of ACE inhibitors also was studied on serum cholinesterase (true and pseudo) and the enzyme ACE in vitro. Enalaprilat, ramiprilat, and fosinopril produced a time-dependent decrease of IOP in both acute and chronic models of ocular hypertension in rabbits. The decrease in IOP was observed for >4 h, and the extent of decrease was comparable to that with both pilocarpine and betaxolol. Prodrugs enalapril and ramipril failed to produced any change in IOP. Losartan also produced a significant decrease in IOP in the chronic model of ocular hypertension in rabbits. All the three ACE inhibitors were found to inhibit ACE activity in aqueous humor. The enzyme cholinesterase was found to be inhibited by enalaprilat, ramiprilat, and fosinopril. However, atropine did not alter the IOP-lowering effect of enalaprilat in rabbits. Indomethacin pretreatment produced slight but significant inhibition of the IOP-lowering effect of enalaprilat in rabbits. Our data suggest that ACE inhibitors enalaprilat, ramiprilat, and fosinopril produce a significant ocular hypotensive effect in acute and chronic models of ocular hypertension in rabbits. Inhibition of ACE in aqueous humor, and in ocular tissues, resulting in reduced angiotensin II formation, could be one of the major mechanisms responsible for the IOP reduction by ACE inhibitors in rabbits.

Estrogen increases eNOS and NOx release in human coronary artery endothelium.

Abstract: Summary:Estrogen protects against the development of coronary heart disease in women. This study was designed to examine the direct effects of estrogen on nitric oxide release and endothelial nitric oxide synthase (eNOS) expression in cultured human coronary artery endothelial cells (HCAECs). NOx (n

Effect of perhexiline and oxfenicine on myocardial function and metabolism during low-flow ischemia/reperfusion in the isolated rat heart.

Abstract: Perhexiline is a potent prophylactic anti-anginal agent that has been shown to inhibit myocardial utilization of long-chain fatty acids and to inhibit the mitochondrial enzyme carnitine palmitoyltransferase (CPT)-1. We compared the hemodynamic and biochemical effects of perhexiline (0.5 and 2.0 microM) and of another CPT-1 inhibitor, oxfenicine (0.5 mM), in Langendorff-perfused rat hearts subjected to 60 min of low-flow ischemia (95% flow reduction) followed by 30 min of reperfusion. Both perhexiline (2 microM only) and oxfenicine attenuated (p < 0.003, p < 0.0002, respectively) increases in diastolic tension during ischemia, without significant effects on developed tension, or on cardiac function during reperfusion. Myocardial concentrations of long-chain acylcarnitines (LCAC), products of CPT-1 action, were decreased (p < 0.05) by oxfenicine, unaffected by 2 microM perhexiline, and increased slightly by 0.5 microM perhexiline. Perhexiline, but not the active metabolite of oxfenicine, also inhibited cardiac CPT-2 with similar IC50 and Emax, although lower Hill slope, compared with CPT-1. Oxfenicine, but not perhexiline, reduced concentrations of the endogenous CPT-1 inhibitor, malonyl-CoA. Perhexiline, but not oxfenicine, inhibited myocardial release of lactate during normal flow. We conclude that (a) perhexiline protects against diastolic dysfunction during ischemia in this model, independent of major changes in LCAC accumulation and (b) this may result from simultaneous effects of perhexiline on myocardial CPT-1 and CPT-2.

Endothelin and pulmonary hypertension.

Abstract: Biochemical and molecular biological evidence indicates that endothelin (ET)-1 and its receptors are selectively upregulated in the lung during exposure to hypoxia, while functional evidence indicates that ET-1 is a major mediator of hypoxia-induced pulmonary vasoconstriction and vascular remodeling. Hypoxia stimulates ET-1 gene transcription and peptide synthesis in cultured endothelial cells, and plasma ET-1 levels are increased in patients with primary pulmonary hypertension, and in humans exposed to high altitude, while immunoreactive ET-1 and ET-1 mRNA levels are increased in pulmonary artery endothelial cells of patients with primary pulmonary hypertension. Rats exposed to normobaric hypoxia exhibit increased pulmonary artery pressure, increased ET-1 peptide levels in plasma and lung, and selective increases in steady-state ET-1 and ET(A) and ET(B) receptor mRNA levels in lung but not in organs perfused by the systemic vasculature. The observations that both ET-1 and its major vascular smooth-muscle cell receptor are upregulated in response to hypoxia suggest that ET-1 may be a mediator of hypoxia-induced pulmonary hypertension. Moreover, hypoxic pulmonary vasoconstriction and vascular remodeling can be prevented and reversed by administration of either an ET(A)-selective or a combined ET(A) and ET(B) receptor antagonist. These findings support the hypothesis that endogenous ET-1 plays a major role in hypoxic pulmonary vasoconstriction/hypertension, right heart hypertrophy, and pulmonary vascular remodeling and suggest that ET-receptor blockers may be useful in the treatment and prevention of hypoxic pulmonary hypertension in humans.

Evidence that prostaglandins mediate the antihypertensive actions of angiotensin-(1-7) during chronic blockade of the renin-angiotensin system.

Abstract: Prostaglandins are known to participate in the antihypertensive actions of angiotensin-converting enzyme (ACE) inhibition and angiotensin type 1 (AT1)-receptor antagonism. Because angiotensin-(1-7) [Ang-(1-7)] is markedly elevated after prolonged ACE-inhibitor treatment, we determined whether the antihypertensive effects of Ang-(1-7) were mediated by release of prostaglandins. Male spontaneously hypertensive rats (SHRs, 10 weeks) were treated for 9 days with either lisinopril (20 mg/kg) or losartan (10 mg/kg) or a combination of both drugs. Rats were implanted with catheters in the carotid artery and jugular vein to record blood pressure and to infuse drug solutions, respectively. Neutralization of circulating Ang-(1-7) by monoclonal antibody resulted in a dose-dependent increase in blood pressure in SHRs treated with either lisinopril or losartan. Administration of CGS 24592 to block Ang-(1-7) formation also resulted in an increase in blood pressure that was comparable to antibody infusion. However, Ang-(1-7) blockade evoked a greater elevation in blood pressure in the lisinopril and lisinopril/losartan-treated rats in comparison to those treated with losartan alone. Acute treatment with the cyclooxygenase (COX) inhibitor indomethacin increased blood pressure to a similar extent to that of CGS 24592, as well as blocked the increase in pressure with the neprilysin inhibitor in the lisinopril/losartan group. In the losartan-treated animals, however, indomethacin increased blood pressure by a larger extent than that of the Ang-(1-7) antibody or CGS 24592, and CGS 24592 did not abolish the subsequent pressor response to indomethacin in these animals. In contrast to the antibody or neprilysin inhibitor, administration of the Ang-(1-7) antagonist D-[Ala7]-Ang-(1-7) increased blood pressure to a similar extent in lisinopril or losartan treatments. Moreover, D-[Ala7]-Ang-(1-7) increased blood pressure to a comparable extent as indomethacin and blocked any further increase with the COX inhibitor in the losartan-treated SHRs. High-resolution emulsion autoradiography revealed 125I-[Sarcosine1, Threonine8]-Ang II (Sarthran) binding in the mesenteric artery and thoracic aorta in the presence of both LOS and the AT2 antagonist PD123319. The non-AT1/non-AT2 Sarthran binding was displaced by Ang-(1-7), DALA, or Ang II. These studies suggest that vasodilatory eicosanoids mediate the antihypertensive effects of endogenous Ang-(1-7) in both LIS and LIS/LOS therapies. Furthermore, in the presence of AT1-receptor blockade, Ang II may interact with a DALA-sensitive site to promote eicosanoid release.

Selective antagonism of endothelin-A-receptors improves outcome in both head trauma and focal stroke in rat.

Abstract: Increased levels of endothelin (ET) have been demonstrated in the ischemic brain, and ET receptor antagonism has been shown to improve outcome in cerebral ischemia. However, no previous work has been carried out evaluating the role of ET and its antagonism in brain trauma as compared to experimental stroke. In this study, we evaluated changes in brain ET levels following closed head injury (CHI) and the effects of SB 234551, an endothelin-A-(ETA) selective antagonist, and SB 209670, a mixed endothelin-A-and -B- (ET A /ET B ) antagonist, on outcome in CHI and focal stroke. Male Sabra rats were subjected to CHI (weight drop model). Male Sprague Dawley rats were subjected to focal stroke (intraluminal suture model). Motor function(s) were assessed and immunoreactive ET (irET) and the degree of cerebral edema were measured for 24 h after CHI. Brain swelling (edema), neurological deficits and forebrain infarct volumes were measured 24 h after focal stroke. Antagonists (total doses of 7.5, 15, 30 or 60 mg/kg) were administered intravenously for 6-24 h (beginning 15 min after injury). Control rats were infused with vehicle. CHI resulted in increased ET levels in the directly contused hemisphere at 12 and 24 h. In addition, SB 234551 significantly reduced neurological deficits (decreased 30%) and brain edema (decreased 40%) following CHI (p < 0.05 at 60 mg/kg dose). SB 209670 had no effects on CHI outcome. Focal stroke studies yielded similar results. SB 234551 reduced focal stroke-induced neurological deficits by 50%, brain swelling by 54% and the degree of infarction by 36% (p < 0.05 at 30 mg/kg). SB 209670 did not provide any neuroprotection in focal stroke. These data indicate that ET plays a significant role in the pathophysiology of CHI, and that selectively targeting ETA-receptors similarly in both CHI and stroke might be a therapeutic opportunity.

Sarpogrelate, a selective 5-HT2A serotonergic receptor antagonist, inhibits serotonin-induced coronary artery spasm in a porcine model.

Abstract: Serotonin is one of the most important vasoactive substances and has been implicated in the pathogenesis of coronary artery spasm and of acute coronary syndrome. We have recently demonstrated that local and long-term treatment with interleukin-1beta(IL-1beta) causes coronary arteriosclerotic changes and hyperconstrictive responses to serotonin in pigs in vivo. However, it remains to be examined which serotonergic (5-HT) receptor subtype mediates coronary spasm and whether alterations in serotonergic receptors are involved in the abnormality. In this study, we examined the inhibitory effect of sarpogrelate, a selective 5-HT2A serotonergic receptor antagonist, on the serotonin-induced coronary spasm as well as the possible alterations of serotonergic receptors in our porcine model. A segment of the porcine coronary artery was carefully dissected and aseptically wrapped with cotton mesh absorbing IL-1beta-bound microbeads from the adventitia. Two weeks after the procedure, angiographic study was performed, followed by binding assay for 5-HT1B and 5-HT2A serotonergic receptors and reverse transcription-polymerase chain reaction (RT-PCR) analysis for mRNA of those receptors. Angiographic study showed coronary vasospastic responses to serotonin at the IL-1beta-treated site. Sarpogrelate dose-dependently inhibited the serotonin-induced coronary spasm, but it did not affect the prostaglandin F2alpha-induced vasoconstriction. Radiolabeled receptor-binding assay showed that receptor affinity or receptor number of the 5-HT1B, or 5-HT2A receptors did not differ significantly between the spastic and the control sites. Furthermore, RT-PCR analysis showed that the expression of neither 5-HT2A nor 5-HT1B receptor mRNA was significantly altered at the spastic site. These results indicate that serotonin-induced coronary spasm is mediated primarily by 5-HT2A receptor in our porcine model, although the 5-HT2A receptor was not up-regulated, suggesting that alteration in the signal-transduction pathway for vascular smooth muscle contraction beyond the 5-HT2A receptor plays a primary role in the pathogenesis of coronary spasm in our porcine model.

Additive hypotensive effect of angiotensin-converting enzyme inhibition and angiotensin-receptor antagonism in essential hypertension.

Abstract: The study was designed to assess the antihypertensive effect of combined angiotensin-converting enzyme (ACE) inhibition and angiotensin II type 1 receptor (AT1) antagonism in patients with essential hypertension. Twenty patients with uncontrolled ambulatory diastolic blood pressure (BP) after 6 weeks of ACE inhibitor monotherapy (benazepril, 20 mg, o.d.) were randomized to receive double-blind valsartan, 80 mg, o.d. (AT1 antagonist) or matching placebo for 5 weeks while continuing to receive background benazepril. Then patients crossed over to the alternative regimen for a second 5-week period. The 24-h ambulatory BP was monitored on the final day of the benazepril monotherapy period and on the final day of each double-blind treatment period. Valsartan added to benazepril produced a significant antihypertensive effect with a benefit over placebo of 6.5 +/- 12.6/4.5 +/- 8.0 mm Hg (systolic/diastolic) for average awake ambulatory BP (p < 0.05), 7.1 +/- 9.4/5.6 +/- 6.5 mm Hg for asleep BP (p < 0.01), and 6.8 +/- 9.7/4.9 +/- 6.8 mm Hg for average 24-h ambulatory BP (p < 0.01). Pulse rate was unaffected. Plasma active renin was higher on the benazepril-valsartan combination compared with benazepril-placebo (p < 0.05). There was no change in routine biochemical variables when valsartan was added to benazepril. Six patients reported mild dizziness or fatigue (three also with placebo). These data suggest that in hypertensive patients uncontrolled with an ACE inhibitor, the addition of an AT1 antagonist provides a powerful and safe antihypertensive drug combination.

Antihypertensive drugs and the sympathetic nervous system

Abstract: The sympathetic nervous system (SNS) plays an important role in the regulation of blood pressure homeostasis and cardiac function. Furthermore, the increased SNS activity is a predictor of mortality in patients with hypertension, coronary artery disease and congestive heart failure. Experimental data and a few clinical trials suggest that there are important interactions between the main pressor systems, i.e. the SNS, the renin-angiotensin system and the vascular endothelium with the strongest vasoconstrictor, endothelin. The main methods for the assessment of SNS activity are described. Cardiovascular drugs of different classes interfere differently with the SNS and the other pressor systems. Pure vasodilators including nitrates, alpha-blockers and dihydropyridine (DHP)-calcium channel blockers increase SNS activity. Finally, central sympatholytics and possibly phenylalkylamine-type calcium channel blockers reduce SNS activity. The effects of angiotensin-II receptor antagonists on SNS activity in humans is not clear; experimental data are discussed in this review. There are important interactions between the pressor systems under experimental conditions. Recent studies in humans suggest that an activation of the SNS with pure vasodilators in parallel increases plasma endothelin. It can be assumed that, in cardiovascular diseases with already enhanced SNS activity, drugs which do not increase SNS activity or even lower it are preferable. Whether this reflects in lower mortality needs to be investigated in intervention trials.

The endothelin family: an overview.

Abstract: Endothelin (ET) is a potent vasoconstrictive peptide initially found in the conditioned medium of cultured endothelial cells (1). It comprises 21 amino acid residues including four cysteine residues. The four cysteine residues form two intramolecular disulfide bonds. No amino acid sequence similar to that of ET had been previously reported. Furthermore its pharmacological action was unique. When it was injected intravenously into rats, a sustained and long-lasting pressor response was observed, suggesting a role of ET in maintenance of blood pressure or generation of hypertension. For these reasons many investigators were interested in this peptide. However, numerous reports following publication of the first paper detailing study of ET revealed that the mechanism for maintenance of blood pressure was not so simple. Apart from this problem, many pharmacological studies revealed that ET was active not only in the cardiovascular system but also in noncardiovascular systems. Those results stimulated further the worldwide interest in ET.

β-blockers of the third generation inhibit Endothelin-1 liberation, mRNA production and proliferation of human coronary smooth muscle and endothelial cells

Abstract: Endothelin-1 (ET-1) plays an important role in atherogenesis. The aim of the study reported here was to investigate the effects of the third generation β-blockers nebivolol and carvedilol on ET-1 liberation, preproendothelin-1 production and on proliferation of human coronary cells. Human coronary endothelial (HEC) and smooth muscle cells (HCSMC) were grown with carvedilol or nebivolol (10 -7 -10 -5 mol/l). Incubation for 1, 2 or 7 days resulted in an 80% concentration- and time-dependent reduction in HCSMC proliferation. β-blockers such as propranolol or metoprolol did not influence cell proliferation. Nebivolol (10 -7 mol/l) inhibited accelerated HCSMC proliferation in the presence of growth factors such as transforming growth factor-β1 or platelet-derived growth factor BB. During incubation with nebivolol or carvedilol ET-1 secretion decreased. For nebivolol this is a result of a reduction in preproendothelin-1 mRNA levels. β-blockers of the third generation that reduce the cell proliferation and ET-1 secretion may represent strategies with great promise for antiproliferative therapy of coronary heart disease.

FTY720 prevents development of experimental autoimmune myocarditis through reduction of circulating lymphocytes.

Abstract: Summary:FTY720 is a new immunosuppressant agent and selectively decreases the number of circulating lymphocytes. In this study, we compared the effects of FTY720 with those of tacrolimus on experimental autoimmune myocarditis (EAM) in rats. A significant decrease in circulating lymphocyte counts was

Roles of tyrosine kinase and protein kinase C in infarct size limitation by repetitive ischemic preconditioning in the rat.

Abstract: In this study, we examined the possibility that infarct-size limitation by repetitive preconditioning (PC) is achieved by activation of both protein kinase C (PKC) and tyrosine kinase. In addition, we assessed whether such kinase activation is triggered by angiotensin II type 1 (AT1) and alpha1-adrenergic receptors and whether sarcolemmal and mitochondrial adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels play roles as effectors of cardioprotection in the rat. Under pentobarbital anesthesia, myocardial infarction was induced by 20-min coronary occlusion and 3-h reperfusion in the rat. Infarct size was determined by tetrazolium and expressed as a percentage of area at risk (%IS/AR). PC with one cycle of 5-min ischemia/5-min reperfusion before 20-min ischemia significantly reduced %IS/AR from the control value of 49.4 +/- 2.0 to 35.4 +/- 2.8, and repetitive PC with two cycles of 5-min ischemia/5-min reperfusion further limited %IS/AR to 3.2 +/-0.9. Infarct-size limitation by single-cycle PC was completely abolished by a PKC inhibitor, staurosporine (100 microg/kg; %IS/ AR, 45.7 +/- 5.0). In contrast, the cardioprotection by repetitive PC was only partially blocked by staurosporine (%IS/AR, 19.8 +/- 2.4), another PKC inhibitor, polymyxin B (5 mg/kg; %IS/AR, 16.2 +/- 3.1), or a tyrosine kinase inhibitor, genistein (5 mg/kg; %IS/AR, 21.8 +/- 1.4). However, a combined injection of genistein and staurosporine additively inhibited protection of repetitive PC (%IS/AR, 36.4 +/- 1.7). Staurosporine, polymyxin B, or genistein alone did not modify %IS/AR in nonpreconditioned rat hearts. Infarct-size limitation by repetitive PC was not attenuated by pretreatment with a selective AT1-receptor blocker (CV11974, 10 mg/kg), prazosin (0.6 mg/kg; %IS/AR, 6.4 +/- 3.2 and 1.6 +/- 0.5, respectively). A selective blocker of mitochondrial K(ATP) channels, 5-hydroxydecanoate (3 mg/kg), completely abolished the cardioprotective effect (%IS/AR, 50.8 +/-3.5), but HMR1883 (3 mg/kg), a selective blocker of sarcolemmal K(ATP) channels, failed to inhibit the preconditioning effect (%IS/AR, 4.4 +/- 0.7). These findings suggest that repetition of PC provokes activation of both PKC and tyrosine kinase, leading to enhanced antiinfarct tolerance by opening of mitochondrial but not sarcolemmal K(ATP) channels. It is unlikely that activation of either AT1 or alpha1-adrenergic receptor alone is crucial to trigger preconditioning. Key Words: Tyrosine kinase-Genistein-Angiotensin II-alpha1-Adrenergic receptor-Sarcolemmal K(ATP) channel-Mitochondrial K(ATP) channel.

Comparative effects of angiotensin II AT-1-type receptor antagonists in vitro on human platelet activation.

Abstract: Summary:A recent study has shown that losartan, an AT-1-receptor antagonist, interacts with thromboxane A2 (TxA2)/prostaglandin H2 (PGH2) receptors in human platelets. The aim of this study was to analyze the ability of different angiotensin II (Ang II) AT-1-receptor antagonists to inhibit TxA2-depe

Prevention of doxorubicin (adriamycin)-induced cardiomyopathy by simultaneous administration of angiotensin-converting enzyme inhibitor assessed by acoustic densitometry.

Abstract: The purpose of our study has to determine the myocardial protective effects of the angiotensin-converting enzyme (ACE) inhibitor temocapril (TEM, 7 mg/kg/day) simultaneously administered with doxorubicin (Adriamycin). Twenty male Sprague-Dawley rats were intraperitoneally administered a cumulative dose of 15 mg/kg of doxorubicin (each dose of 1.0 mg/kg x 15) for 3 weeks, and divided into TEM-untreated and -treated rats. Seven control rats were injected with saline intraperitoneally. Body weight, hemodynamics, and echocardiographic measurements including quantitative analysis of ultrasonic integrated backscatter (IB) were obtained for 12 weeks after treatment. Finally, rats were killed for histopathologic study. At 6 weeks, end-diastolic left ventricular diameter (LVD) and percentage fractional shortening (%FS) were similar in TEM-treated and TEM-untreated rats, but cyclic variation of IB (dB) significantly decreased in TEM-untreated rats (7.3 +/- 1.2; control rats, 9.7 +/- 0.9; p < 0.01). At 12 weeks, %FS decreased in TEM-untreated rats (26.1 +/- 6.1%: TEM-treated rats, 34.2 +/- 6.2; p < 0.05), and calibrated IB (dB) in TEM-untreated rats (15.5 +/- 0.5) increased as compared with that in TEM-treated rats (12.1 +/- 0.7; p < 0.01). Interstitial collagen accumulation increased in TEM-untreated rats and was inhibited in treated rats. Simultaneous administration of TEM with doxorubicin was beneficial in preventing doxorubicin-induced myocardial damage, and myocardial tissue characterization was useful for the early detection of myocardial damage and the assessment of therapy.

Effects of cerivastatin on human arterial smooth muscle cell proliferation and migration in transfilter cocultures.

Abstract: Summary: Statins competitively inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity reducing mevalonate synthesis. In this study, antiproliferative and antimigratory effects of the new compound cerivastatin were analyzed and compared with classic statins of the first and second generation using mono- and cocultures of human arterial smooth muscle (haSMC) and endothelial (haEC) cells. Effects on the mitotic index and mitochondrial activity of haEC and haSMC monocultures were tested using BrdU enzyme-linked immunosorbent assay (ELISA) and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) tests, respectively. In lactate dehydrogenase (LDH) assays, cytotoxicity of statins was studied. Transfilter cocultures were performed for 14 days to evaluate haSMC growth under the stimulatory effect of proliferating haEC, which release growth factors [e.g., platelet-derived growth factor (PDGF)]. The hydrophobic statins simvastatin, lovastatin, and atorvastatin significantly inhibited haSMC and haEC growth in monocultures at 0.5-50 μM. However, most potent effects were exerted by cerivastatin in 10- to 30-fold lower doses without any significant cytotoxicity. More important, cerivastatin showed also significant effects on haSMC proliferation and migration in transfilter cocultures at extremely low doses (IC50, 0.04-0.06 μM), even when applied exclusively to the endothelial side and in the presence of low-density lipoprotein (LDL). Addition of mevalonate abolished the effects of cerivastatin completely. Even in the presence of growth-stimulating haEC and LDL, cerivastatin was found to be the most potent inhibitor of haSMC proliferation and migration in doses that also can be reached in human serum after oral drug administration. The results support the concept that statins seems to influence additional cellular mechanisms beyond cholesterol reduction, which might also have a relevance for the prevention of restenosis.

Inhibitory effects of dronedarone on muscarinic K+ current in guinea pig atrial cells.

Abstract: Summary:Dronedarone (SR33589), an amiodarone-like non-iodinated antiarrhythmic agent, is undergoing clinical trials in atrial fibrillation. Because vagal activation plays a role in the pathophysiology of supraventricular arrhythmias, we have assessed the ability of dronedarone (0.01, 0.1, and 1 μM),