The role of endothelium in human hypertension

Targeting endothelial cells with golden spice curcumin: A promising therapy for cardiometabolic multimorbidity

Cardiometabolic multimorbidity (CMM) is an increasingly significant global public health concern. It encompasses the coexistence of multiple cardiometabolic diseases, including hypertension, stroke, heart disease, atherosclerosis, and T2DM. A crucial component to the development of CMM is the disruption of endothelial homeostasis. Therefore, therapies targeting endothelial cells through multi-targeted and multi-pathway approaches hold promise for preventing and treatment of CMM. Curcumin, a widely used dietary supplement derived from the golden spice Carcuma longa, has demonstrated remarkable potential in treatment of CMM through its interaction with endothelial cells. Numerous studies have identified various molecular targets of curcumin (such as NF-κB/PI3K/AKT, MAPK/NF-κB/IL-1β, HO-1, NOs, VEGF, ICAM-1 and ROS). These findings highlight the efficacy of curcumin as a therapeutic agent against CMM through the regulation of endothelial function. It is worth noting that there is a close relationship between the progression of CMM and endothelial damage, characterized by oxidative stress, inflammation, abnormal NO bioavailability and cell adhesion. This paper provides a comprehensive review of curcumin, including its availability, pharmacokinetics, pharmaceutics, and therapeutic application in treatment of CMM, as well as the challenges and future prospects for its clinical translation. In summary, curcumin shows promise as a potential treatment option for CMM, particularly due to its ability to target endothelial cells. It represents a novel and natural lead compound that may offer significant therapeutic benefits in the management of CMM.

Oxidative Stress, GTPCH1, and Endothelial Nitric Oxide Synthase Uncoupling in Hypertension

Significance: Hypertension has major health consequences, which is associated with endothelial dysfunction. Endothelial nitric oxide synthase (eNOS)-produced nitric oxide (NO) signaling in the vasculature plays an important role in maintaining vascular homeostasis. Considering the importance of NO system, this review aims to provide a brief overview of the biochemistry of members of NO signaling, including GTPCH1 [guanosine 5'-triphosphate (GTP) cyclohydrolase 1], tetrahydrobiopterin (BH4), and eNOS. Recent Advances: Being NO signaling activators and regulators of eNOS signaling, BH4 treatment is getting widespread attention either as potential therapeutic agents or as preventive agents. Recent clinical trials also support that BH4 treatment could be considered a promising therapeutic in hypertension. Critical Issues: Under conditions of BH4 depletion, eNOS-generated superoxides trigger pathological events. Abnormalities in NO availability and BH4 deficiency lead to disturbed redox regulation causing pathological events. This disturbed signaling influences the development of systemic hypertension as well as pulmonary hypertension. Future Directions: Considering the importance of BH4 and NO to improve the translational significance, it is essential to continue research on this field to manipulate BH4 to increase the efficacy for treating hypertension. Thus, this review also examines the current state of knowledge on the effects of eNOS activators on preclinical models and humans to utilize this information for potential therapy.

Isolation, purification and the anti-hypertensive effect of a novel angiotensin I-converting enzyme (ACE) inhibitory peptide from Ruditapes philippinarum fermented with Bacillus natto

A novel ACE inhibitory peptide (Val-Ile-Ser-Asp-Glu-Asp-Gly-Val-Thr-His) with a high anti-hypertensive effect isolated from Ruditapes philippinarum fermented with Bacillus natto.

Antihypertensive treatment differentially affects vascular sphingolipid biology in spontaneously hypertensive rats

Background

We have previously shown that essential hypertension in humans and spontaneously hypertensive rats (SHR), is associated with increased levels of ceramide and marked alterations in sphingolipid biology. Pharmacological elevation of ceramide in isolated carotid arteries of SHR leads to vasoconstriction via a calcium-independent phospholipase A₂, cyclooxygenase-1 and thromboxane synthase-dependent release of thromboxane A₂. This phenomenon is almost absent in vessels from normotensive Wistar Kyoto (WKY) rats. Here we investigated whether lowering of blood pressure can reverse elevated ceramide levels and reduce ceramide-mediated contractions in SHR.

Methods and Findings

For this purpose SHR were treated for 4 weeks with the angiotensin II type 1 receptor antagonist losartan or the vasodilator hydralazine. Both drugs decreased blood pressure equally (SBP untreated SHR: 191±7 mmHg, losartan: 125±5 mmHg and hydralazine: 113±14 mmHg). The blood pressure lowering was associated with a 20–25% reduction in vascular ceramide levels and improved endothelial function of isolated carotid arteries in both groups. Interestingly, losartan, but not hydralazine treatment, markedly reduced sphingomyelinase-induced contractions. While both drugs lowered cyclooxygenase-1 expression, only losartan and not hydralazine, reduced the endothelial expression of calcium-independent phospholipase A₂. The latter finding may explain the effect of losartan treatment on sphingomyelinase-induced vascular contraction.

Conclusion

In summary, this study corroborates the importance of sphingolipid biology in blood pressure control and specifically shows that blood pressure lowering reduces vascular ceramide levels in SHR and that losartan treatment, but not blood pressure lowering per se, reduces ceramide-mediated arterial contractions.

Oxidative stress and endothelial dysfunction in hypertension

Systemic arterial hypertension is a highly prevalent cardiovascular risk factor that causes significant morbidity and mortality, and is becoming an increasingly common health problem because of the increasing longevity and prevalence of predisposing factors such as sedentary lifestyle, obesity and nutritional habits. Further complicating the impact of this disease, mild and moderate hypertension are usually asymptomatic, and their presence (and the subsequent increase in cardiovascular risk) is often unrecognized. The pathophysiology of hypertension involves a complex interaction of multiple vascular effectors including the activation of the sympathetic nervous system, of the renin-angiotensin-aldosterone system and of the inflammatory mediators. Subsequent vasoconstriction and inflammation ensue, leading to vessel wall remodeling and, finally, to the formation of atherosclerotic lesions as the hallmark of advanced disease. Oxidative stress and endothelial dysfunction are consistently observed in hypertensive subjects, but emerging evidence suggests that they also have a causal role in the molecular processes leading to hypertension. Reactive oxygen species (ROS) may directly alter vascular function or cause changes in vascular tone by several mechanisms including altered nitric oxide (NO) bioavailability or signaling. ROS-producing enzymes involved in the increased vascular oxidative stress observed during hypertension include the NADPH oxidase, xanthine oxidase, the mitochondrial respiratory chain and an uncoupled endothelial NO synthase. In the current review, we will summarize our current understanding of the molecular mechanisms in the development of hypertension with an emphasis on oxidative stress and endothelial dysfunction.

Epigallocatechin gallate elicits contractions of the isolated aorta of the aged spontaneously hypertensive rat

The present study examined the effect of the green tea catechin epigallocatechin gallate (EGCG) on endothelium-dependent responses in the aorta of 36-week-old spontaneously hypertensive rats (SHR). Isometric tension was measured in isolated aortic rings. The release of prostanoid end products was determined using enzyme immunoassay kits and the intracellular reactive oxygen species (ROS) concentration using confocal microscopy. EGCG did not improve endothelium-dependent relaxations evoked by acetylcholine, except in the presence of indomethacin. EGCG did not inhibit endothelium-dependent contractions induced by acetylcholine or ATP. At 10(-6) M and higher concentrations, EGCG caused increases in tension in the SHR aorta. The EGCG-induced contractions were accompanied by an increased production of ROS. The amount of prostanoid end products was increased significantly by EGCG, indicating that their production followed the activation of cyclooxygenase (COX). These prostanoids in turn stimulated thromboxane-prostanoid (TP) receptors and caused contractions. EGCG induced significantly smaller contractions in aortae of normotensive Wistar-Kyoto rats (WKY), accompanied with a lower production of ROS and a lesser release of prostanoids. These observations suggest that EGCG-induced contractions occur more readily in blood vessels of hypertensive than normotensive animals. The present findings indicate that the increased oxidative stress in the ageing hypertensive animals contributes to the loss of the beneficial effects and the enhancement of the adverse effects of EGCG.

Nebivolol in high-risk, obese African Americans with stage 1 hypertension: effects on blood pressure, vascular compliance, and endothelial function

The authors sought to determine whether nebivolol treatment results in changes in blood pressure (BP), nitric oxide bioavailability, and vascular function in obese African Americans with recently diagnosed stage 1 hypertension. Forty-three obese, hypertensive African Americans (mean BP: systolic, 148.8+/-14.3 mm Hg; diastolic, 90.4+/-8.2 mm Hg) were treated with nebivolol (5-10 mg/d) for 8 weeks. Primary outcomes were change in systolic and diastolic BP and efficacy in reaching normotensive BP. Mean systolic BP decreased by 9.2+/-14 mm Hg (P<.005) and diastolic BP decreased 6.8+/-9 mm Hg (P<.005) with 8 weeks of therapy. Significant improvements were seen in arterial compliance with nebivolol treatment as measured by aortic augmentation index (P<.005) and time to wave reflection (P=.013). Nebivolol treatment improved endothelial function as measured by flow-mediated dilation (P<.005). Levels of erythrocyte cellular superoxide dismutase increased with nebivolol, indirectly suggesting increased bioavailability of nitric oxide (P<.005). Monotherapy with nebivolol in obese, hypertensive African Americans results in significant systolic and diastolic BP reduction by mechanisms that include improved vascular function and compliance.

Endothelium-dependent contractions and endothelial dysfunction in human hypertension

The endothelium is a crucial regulator of vascular physiology, producing in healthy conditions several substances with a potent antiatherosclerotic properties. Accordingly, the presence of endothelial dysfunction is associated with subclinical atherosclerosis and with an increased future risk of cardiovascular events. A large body of evidence supports the fundamental role of nitric oxide (NO) as the main endothelium-derived relaxing factor. However, in the presence of pathological conditions, such as hypertension, endothelial cells, in response to a number of agents and physical stimuli, become also a source of endothelium-derived contracting factors (EDCFs), including endothelins and angiotensin II and particularly cyclooxygenase-derived prostanoids and superoxide anions. These latter were at first identified as responsible for impaired endothelium-dependent vasodilation in patients with essential hypertension. However, cyclooxygenase-dependent EDCFs production is characteristic of the aging process, and essential hypertension seems to only anticipate the phenomenon. It is worth noting that both in aging and hypertension EDCF production is associated with a parallel decrease in NO availability, suggesting that this substance could be oxygen free radicals themselves. Accordingly, in hypertension both indomethacin, a cyclooxygenase inhibitor, and vitamin C, an antioxidant, increase the vasodilation to acetylcholine by restoring NO availability. In conclusion, hypertension is characterized by a decline in endothelial function, associated with a progressive decrease in NO bioavailability and increase in the production of EDCF. The mechanisms that regulate the balance between NO and EDCF, and the processes transforming the endothelium from a protective organ to a source of vasoconstrictor, proaggregatory and promitogenic mediators remain to be determined.

The role of lipoic acid in prevention of nitroglycerin tolerance

Besides other organic nitrates, nitroglycerin (glyceryl trinitrate; GTN) has been used to treat acute heart failure particularly due to ischemic heart disease. However, one of serious clinical problems of the GTN therapy, particularly a long-standing medication, is hemodynamic tolerance to GTN, manifested by the decreased therapeutic efficacy of the drug. The most recent studies have suggested that mitochondrial lipoate/dihydrolipoate system-dependent aldehyde dehydrogenase-2 plays a key role in nitric oxide release from GTN. The aldehyde dehydrogenase-2 performs three enzymatic activities of dehydrogenase, esterase and reductase. The reductase activity is responsible for bioactivation of organic nitrates, such as GTN yielding nitrite and dinitrate (1,2-GDN/1,3-GDN, approximately 8:1). In view of a large contribution of dihydrolipoic acid to stabilization and regeneration of thiol groups, necessary for the reductase activity of aldehyde dehydrogenase-2, we conducted studies aimed to determine whether lipoic acid administration to rats is able to prevent GTN tolerance. The studies were conducted on 4 groups of animals: control saline-treated, model GTN-tolerant, GTN + lipoic acid-treated, lipoic acid alone-administered groups. On the 9th day of experiment animals were given i.v. therapeutic dose of GTN. We measured in all animals systolic and diastolic blood pressure before injection of therapeutic dose of GTN into the cadual vein and during 20 min thereafter. Levels of nitric oxide and reactive oxygen species and activities of glutathione peroxidase and superoxide dismutase were assayed in the aorta, plasma and heart of all animals. In addition, levels of malondialdehyde, and non-protein thiols, and activities of glutathione S-transferase and gamma-glutamyl transpeptidase were evaluated in the heart and plasma. The obtained results indicate that treatment of rats with a combination of lipoic acid and GTN can efficiently counteract GTN tolerance.

Reduction of NO- and EDHF-mediated vasodilatation in hypertension: role of asymmetric dimethylarginine

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase (NOS), and endothelial dysfunction is related to the elevation of ADMA level in hypertension. Besides the NO-mediated pathway, the endothelium-derived hyperpolarizing factor (EDHF)-mediated pathway is involved in endothelial dysfunction. The aims of the present study were to evaluate the changes of endothelium-dependent dilatation of arteries in hypertension and the role of ADMA in NO- and EDHF-mediated vasodilatation. The great omental arteries were isolated from essential hypertensive and normotensive patients, and mesenteric arteries were isolated from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. NO-, EDHF-, and prostaglandin (PGI(2))-mediated endothelium-dependent vasodilatation were measured, and plasma concentrations of ADMA were determined in rats. Cultured endothelial cells were treated with ADMA (1-10 microM) for 48 h, and the mRNA and protein level of small-conductance Ca(2+)-activated K(+) channel 3 (SK3), which has been thought to be a key mediator of EDHF, was determined. Both NO- and EDHF-mediated endothelium-dependent responses were decreased in the great omental arteries of hypertensive patients and mesenteric arteries of SHR. Plasma levels of ADMA were significantly increased in SHR. In cultured endothelial cells, the expressions of SK3 mRNA and protein were concentration-dependently down-regulated in the presence of ADMA. The present study suggests that the inhibitory effect of ADMA on endothelial function not only involves NO-mediated endothelium-dependent vasodilatation but also the EDHF-mediated pathways in hypertensive animals and humans, and that ADMA can down-regulate the expression of SK3 channels in endothelial cells.

Clinical pharmacology and therapeutic use of antioxidant vitamins

The clinical use of antioxidants has gained considerable interest during the last decade. It was suggested from epidemiological studies that diets high in fruits and vegetables might help decrease the risk of cardiovascular disease. Therefore, supplements of vitamins C and E were applied through protocols aimed to prevent diseases such as atherosclerosis, preeclampsia or hypertension, thought to be mediated by oxidative stress. Despite the biological properties of these vitamins could account for an effective protection, as shown by several clinical and experimental studies, their efficacy remains controversial in the light of some recent clinical trials and meta-analyses. However, the methodology of these studies, criteria for selection of patients, the uncertain extent of progression of the disease when initiating supplementation, the lack of mechanistic studies containing basic scientific aspects, such as the bioavailability, pharmacokinetic properties, and the nature of the antioxidant sources of vitamins, could account for the inconsistency of the various clinical trials and meta-analyses assessing the efficacy of these vitamins to prevent human diseases. This review presents a survey of the clinical use of antioxidant vitamins E and C, proposing study models based on the biological effects of these compounds likely to counteract the pathophysiological mechanisms able to explain the structural and functional organ damage.

Chronic treatment with long-acting nifedipine reduces vasoconstriction to endothelin-1 in essential hypertension

Essential hypertension is associated with enhanced biological activity of endothelin-1 (ET-1) and impaired endothelium-dependent vasodilatation. Dihydropyridine calcium antagonists have antioxidant activity in vitro, and they improve endothelial function in vivo. We tested whether calcium antagonists also influence the biological activity of ET-1 in essential hypertensive (EH) patients in the presence and absence of hypercholesterolemia. In 9 healthy subjects (normotensive [NT] subjects, age: 48.3+/-7.6 years; blood pressure: 118+/-8.6/69+/-5.4 mm Hg) and 21 EH subjects (age: 50.0+/-7.8 years; blood pressure: 164.4+/-5.4/103.8+/-4.4 mm Hg), we studied forearm blood flow and its modification induced by intrabrachial administration of ET-1, phenylephrine, acetylcholine, and sodium nitroprusside at baseline and after 24 weeks of treatment with a nifedipine gastrointestinal therapeutic system (30 to 60 mg per day). At baseline, the first dose of ET-1 (0.5 microg/100 mL of forearm tissue per minute) caused a slight vasodilatation in NT but not in EH subjects, whereas the following higher doses caused a comparable dose-dependent vasoconstriction in EH and NT subjects. The effect of acetylcholine was significantly reduced in EH as compared with NT subjects. In contrast, sodium nitroprusside and phenylephrine had similar effects in NT and EH subjects. After chronic treatment with the nifedipine gastrointestinal therapeutic system, the vasoconstrictor effect induced by both ET-1 and phenylephrine was significantly blunted, whereas the response to acetylcholine was significantly increased and the vasodilation to sodium nitroprusside unchanged. Hypercholesterolemic EH subjects showed a further reduced response to acetylcholine compared with normocholesterolemic EH subjects, and the nifedipine gastrointestinal therapeutic system restored the vasodilation to acetylcholine in this subgroup. In conclusion, in EH subjects, chronic treatment with a long-acting dihydropyridine calcium antagonist not only exhibits a blood pressure-lowering effect but also reduces ET-1-induced vasoconstriction and improves endothelium-dependent vasodilation. Those vasculoprotective effects may importantly contribute to a reduction in major clinical events seen during treatment with these compounds.

Enhanced G-protein coupled receptors-mediated contraction and reduced endothelium-dependent relaxation in hypertension

The present study was designed to demonstrate a hypothesis that some G-protein coupled receptors are up-regulated and a dysfunction of endothelium occurs in hypertension. The arteries from hypertensive patients and spontaneously hypertensive rats (SHR) were tested. An in vitro myograph system was used to obtain concentration-contraction curves mediated by endothelin ET(A), endothelin ET(B), 5-hydroxytryptamine 2A (5-HT2A)-receptors and alpha1-adrenoceptors in the arterial segments. In hypertensive patients, the maximum contractions (Emax) induced by endothelin ET(B), endothelin ET(A) and 5-HT receptors were significantly increased with elevated pEC50 values, while a significantly leftward shift of alpha1-adrenoceptor-mediated contraction was seen. Similar results were obtained in SHR. Specific antagonists for 5-HT2A receptors or alpha1-adrenoceptors rightward shifted the concentration-contractile curves induced by 5-HT or noradrenaline, while the Emax were not significantly altered, suggesting that the contractions were mediated by 5-HT2A receptors and alpha1-adrenoceptors, respectively. Endothelium-dependent maximum relaxation (Rmax) in the arterial segments induced by acetylcholine was significantly decreased in both hypertensive patients and SHR. In addition, nitric oxide- and endothelium-derived hyperpolarizing factor-mediated dilatations were decreased significantly and the arterial endothelial cells were in part lost in SHR. In conclusion, endothelin ET(B), endothelin ET(A), 5-HT2A receptor- and alpha-adrenoceptor-mediated contractions were increased in hypertension, while the endothelium and its functions were damaged.

Insulin Resistance, Inflammation, and Blood Pressure Determine Vascular Dysfunction in CKD

BACKGROUND

Conventional cardiovascular risk equations underestimate the risk for cardiovascular disease (CVD) in patients with chronic kidney disease (CKD), implying a role for novel risk factors. Our aim was to compare vascular function and arterial compliance, known markers of CVD, between patients with CKD and healthy controls and examine their association with traditional and novel CVD risk factors.

METHODS

Vascular function was determined by using high-resolution ultrasonography to measure brachial artery endothelial-dependent flow-mediated dilatation (FMD) and endothelial-independent glyceryl trinitrate (GTN)-mediated dilatation. Arterial compliance was measured by using pulse contour analysis to generate large-artery (C1) and small-artery (C2) compliance. We also examined the relationship between vascular function, arterial compliance and blood pressure, lipid and lipoprotein levels, insulin resistance, inflammation, oxidative stress, and calcium and phosphate levels in 105 patients with CKD and 40 healthy controls.

RESULTS

Vascular function and arterial compliance were significantly impaired in patients with CKD compared with healthy controls: mean FMD, 3.8% +/- 0.3% (SE) versus 5.7% +/- 0.6%; GTN-mediated dilatation, 15.7% +/- 0.9% versus 19.6% +/- 1.0%; C1, geometric mean, 12.1 mL/mm Hg; 95% confidence interval (CI), 11.2 to 13.1 versus 15.1 mL/mm Hg; 95% CI, 13.7 to 16.5; and C2, 3.8 mL/mm Hg; 95% CI, 3.4 to 4.3 versus 5.0 mL/mm Hg; 95% CI, 4.2 to 6.0; all P < 0.05. Patients with CKD had greater waist-hip ratios, systolic blood pressures (SBPs), pulse pressures, triglyceride levels, oxidized low-density lipoprotein levels, high-sensitivity interleukin 6 levels, and Homeostasis Model Assessment (HOMA) scores (all P < 0.05) and lower high-density lipoprotein levels (P < 0.001). In patients with CKD, HOMA score and SBP were associated negatively with FMD (model R(2) = 0.28; P < 0.001), and SBP and waist-hip ratio were associated negatively with GTN-mediated dilatation (model R(2) = 0.25; P < 0.001). Pulse pressure was associated negatively with C1 (R(2) = 0.37; P < 0.001), and pulse pressure and high-sensitivity interleukin 6 level were associated negatively with C2 (model R(2) = 0.36; P < 0.001).

CONCLUSION

Insulin resistance, inflammation, systolic hypertension, and increased pulse pressure, but not dyslipidemia, were associated with vascular dysfunction and may be targets for future interventional strategies to reduce CVD risk in patients with CKD.

Pathophysiological basis for the prophylaxis of preeclampsia through early supplementation with antioxidant vitamins

Preeclampsia (PE) is a multisystem disorder that remains a major cause of maternal and foetal morbidity and death. To date, no treatment has been found that prevents the development of the disease. Endothelial dysfunction is considered to underlie its clinical manifestations, such as maternal hypertension, proteinuria, and edema; however, the precise biochemical pathways involved remain unclear. A current hypothesis invokes the occurrence of oxidative stress as pathogenically important, as suggested by the fact that in PE, the placental and circulating levels of lipid peroxidation products (F2-isoprostanes and malondialdehyde [MDA]) are increased and endothelial cells are activated. A potential mechanism for endothelial dysfunction may occur via nuclear transcription factor kappa B (NF-kappaB) activation by oxidative stress. Alternatively, the idea that the antiangiogenic placental soluble fms-like tyrosine kinase 1 factor (sFlt1) is involved in the pathogenesis of this disease is just emerging; however, other pathophysiological events seem to precede its increased production. This review is focused on evidence providing a pathophysiological basis for the beneficial effect of early antioxidant therapy in the prevention of PE, mainly supported by the biological effects of vitamins C and E.

Effect of Prior Statin Use on Functional Outcome and Delayed Vasospasm after Acute Aneurysmal Subarachnoid Hemorrhage: A Matched Controlled Cohort Study

OBJECTIVE

Hydroxymethylglutaryl coenzyme A reductase inhibitors (statins), which exhibit beneficial cerebrovascular effects by modulating inflammation and nitric oxide production, have not been evaluated in acute aneurysmal subarachnoid hemorrhage (SAH) patients. The effect of prior statin use on 14-day functional outcome and on prevention of vasospasm-induced delayed cerebral ischemia (DCI) or stroke during hospitalization was analyzed.

METHODS

We conducted a 1:2 matched (age, admission Hunt and Hess grade, vascular disease/risk history) cohort study of 20 SAH patients on statins and 40 SAH controls. The primary outcome was functional outcome at 14 days (Modified Lawton Physical Self-Maintenance Scale and Barthel Index scale scores). Secondary outcomes were 14-day mortality, Modified Rankin Scale score, DCI, DCI supported by angiography/transcranial Doppler [TCD], cerebral infarctions of any type, and TCD highest mean velocity elevation.

RESULTS

Statin users demonstrated a significant protective effect on 14-day Barthel Index scale and Modified Lawton Physical Self-Maintenance Scale scores (77 +/- 10 versus 39 +/- 8, P = 0.003; 12 +/- 7 versus 19 +/- 9, P = 0.03, respectively). Moreover, statin users demonstrated a significantly lower incidence of DCI and DCI supported by angiography/TCD (10% versus 43%, P = 0.02; 5% versus 35%, P = 0.01, respectively), cerebral infarctions of any type (25% versus 63%, P = 0.01), and baseline-to-final TCD highest mean velocity change of 50 cm/s or greater (18% versus 51%, P = 0.03).

CONCLUSION

SAH statin users demonstrated significant improvement in 14-day functional outcome, a significantly lower incidence of DCI and cerebral infarctions of any type, as well as prevention of TCD highest mean velocity elevation. However, we did not find a significant statin impact on mortality or global outcome (Modified Rankin Scale) in this small sample. This study provides clinical evidence for the potential therapeutic benefit of statins after acute SAH.

Ouabain-induced hypertension alters the participation of endothelial factors in alpha-adrenergic responses differently in rat resistance and conductance mesenteric arteries

1. This study compares the role of endothelial factors in alpha-adrenoceptor contractile responses in mesenteric resistance (MRA) and superior (SMA) mesenteric arteries from ouabain-treated (8.0 microg day(-1), 5 weeks) and untreated rats. The role of the renin-angiotensin system was also evaluated. 2. Ouabain treatment increased systolic blood pressure. In addition, ouabain reduced the phenylephrine response in SMA but did not alter noradrenaline responses in MRA. 3. Endothelium removal or the nitric oxide synthase (NOS) inhibitor (l-NAME, 100 microm) increased the responses to alpha-adrenergic agonists in both vessels. After ouabain treatment, both endothelial modulation and the l-NAME effect were increased in SMA, while only the l-NAME effect was increased in MRA. Endothelial NOS expression remained unaltered after ouabain treatment. 4. Indomethacin (10 microm) similarly reduced the noradrenaline contraction in MRA from both groups; in contrast, in SMA, indomethacin only reduced phenylephrine-induced contractions in segments from untreated rats. Co-incubation of l-NAME and indomethacin leftward shifted the concentration-response curves for noradrenaline more in MRA from ouabain-treated rats; tetraethylammonium (2 mm) shifted the noradrenaline curves further leftward only in MRA from untreated rats. 5.Losartan treatment prevents the development of hypertension but not all vascular changes observed after ouabain treatment. 6. In conclusion, a rise in endothelial NO and impaired prostanoid participation might explain the reduction in phenylephrine-induced contraction in SMA after ouabain treatment. An increase in the modulatory effect of endothelial NO and impairment of endothelium-dependent hyperpolarizing factor effect might explain why the ouabain treatment had no effect on noradrenaline responses in MRA.

Non-invasive assessment of microvascular endothelial function by laser Doppler flowmetry in patients with essential hypertension

The aim of the study was to investigate the endothelium-dependent vasodilation in the forearm skin using two non-invasive laser Doppler applications in patients with essential hypertension (EHT) and in normotensive (NT) control subjects. The effect of two consecutive doses of acetylcholine (ACh) and that of sodium nitroprusside (SNP) on the skin microcirculation, and thereafter the postocclusive reactive hyperaemic (PORH) response, were measured in 25 patients with essential hypertension and also in 25 control normotensive healthy subjects. The plasma von Willebrand factor (vWF) level and activity were also determined. The average peakflow in PORH was 287 +/- 31.5% (x +/- S.E.M.) in EHT and 410.28 +/- 35.08% in NT (P < 0.01). The average hyperaemic response to the two doses of ACh-iontophoresis was 206.36 +/- 33.97 and 568.76 +/- 54.23% in EHT and 444.24 +/- 80.28 and 804.12 +/- 93.07% in NT (P < 0.01, 0.05). The response to SNP was similar in the two groups. The vWF levels were 122.5 +/- 13.2 and 89.6 +/- 8.1% (P = 0.0595, NS), the activities were 80.8 +/- 5.5 and 68.9 +/- 6.1% (P = 0.157, NS) in EHT and in NT, respectively. These results demonstrate that essential hypertension is associated with endothelial dysfunction in the skin microcirculation of the forearm.

Oxidative stress in juvenile essential hypertension

OBJECTIVE

Oxidative stress, an antioxidant/pro-oxidant imbalance, in patients with juvenile essential hypertension was measured via several biochemical parameters. As the blood pressure is associated with the body mass index (BMI), results were compared with those on BMI-matched controls.

DESIGN AND SETTING

A prospective observational study at a university teaching hospital.

PATIENTS

Children and adolescents with essential hypertension (mean standard deviation: age 14.4 +/- 3.1 years, BMI 25.0 +/- 6.9 kg/m(2), n = 52) before any treatment, and controls with a similar BMI distribution (age 14.3 +/- 4.3 years, BMI 24.4 +/- 6.6 kg/m(2), n = 48).

METHODS

Measurements were made of the plasma levels of (1) nitrites + nitrates, an indirect measure of available nitric oxide; (2) lipid peroxidation end-products, as malondialdehydes and free thiols; and (3) the redox status of the red blood cell glutathione, as a new oxidative stress parameter.

RESULTS

There were decreased plasma levels of nitrates and increased levels of lipid peroxidation end-products in the hypertensive patients, resulting in a consistent increase in the plasma lipid peroxidation/nitric oxide ratio as compared with the controls with the same BMI (P <0.01). This ratio additionally correlated directly with both the systolic and diastolic blood pressures for the overall patient population (P <0.001). A significant glutathione depletion in the red blood cells resulted in an elevated ratio of oxidized/reduced forms with a reduced antioxidant protective capacity in the hypertensive patients versus the BMI-matched controls (P <0.001).

CONCLUSIONS

The presence of systemic oxidative stress was proven in hypertensive children and adolescents, irrespective of their BMI.

Vasopeptidase inhibition and endothelial function in hypertension

Vasopeptidase inhibitors are a new class of drugs capable of inhibiting both angiotensin-converting enzyme and neutral endopeptidase 24.11. This involves simultaneous inhibition with a single molecule of two key enzymes, ACE and NEP, which are both involved in the regulation of cardiovascular homeostasis in many ways. This includes metabolism of several vasoactive peptides and their clearance from the circulation, therefore contributing to neurohumoral modulation, which might have therapeutic advantages in the prevention of endothelial dysfunction in hypertension.

Endothelial dysfunction in hypertension

The endothelium can greatly influence vascular tone and structure. The main endothelium-derived factor is nitric oxide (NO), which is not only a potent vasodilator but also inhibits platelet aggregation, smooth muscle cell proliferation, monocyte adhesion and adhesion molecule expression, thus protecting the vessel wall against the development of atherosclerosis and thrombosis. In human hypertension, endothelial dysfunction has been documented in peripheral and coronary macro- and microcirculation and in renal circulation. The mechanism responsible for endothelial alteration in essential hypertensive patients appears to be the activation of an alternative pathway involving cyclooxygenase, which reduces NO availability through production of oxidative stress. In the presence of impaired NO availability a hyperpolarizing factor seems to act as a compensatory pathway to sustain endothelium-dependent relaxation. This compensatory pathway can be further depressed by the simultaneous presence of essential hypertension and hyperhomocysteinaemia, another cardiovascular risk factor causing endothelial dysfunction. Finally, reduced NO availability can increase the biological activity of endothelin-1 because, while in healthy conditions the vasoconstrictor effect of endothelin-1 is partially blunted by endothelial ETB-receptor mediated NO production, in essential hypertensive patients this protective mechanism is lacking on account of impaired NO availability. This alteration in the NO pathway could be the main mechanism through which a dysfunctional endothelium could be a promoter of atherosclerosis and thrombosis and therefore lead to cardiovascular events in essential hypertensive patients.

The return of increased blood pressure after discontinuation of antihypertensive treatment is associated with an impaired post-ischemic skin blood flow response

OBJECTIVE

To assess the post-ischemic skin blood flow response after withdrawal of antihypertensive therapy in hypertensive patients with normal blood pressure during treatment.

DESIGN AND METHODS

Twenty hypertensive patients (group A) with a normal clinic blood pressure (<140/ 90 mmHg) receiving antihypertensive treatment (any monotherapy; one pill per day for at least 6 months) had their treatment discontinued. Before medication withdrawal and 2, 4, 12 and 24 weeks thereafter, the following measurements were made: clinic blood pressure, home blood pressure (three times per week, morning and evening) and skin blood flow response to a 5 min forearm arterial occlusion (using laser Doppler flowmetry). The patients were asked to perform an ambulatory blood pressure recording at any time if home blood pressure was > or =160/95 mmHg on two consecutive days, and treatment was initiated again, after determination of the skin hyperemic response, if daytime ambulatory blood pressure was > or =140/90 mmHg. The same studies were performed in 20 additional hypertensive individuals in whom antihypertensive treatment was not withdrawn (group B). The allocation of patients to groups A and B was random.

RESULTS

The data fom 18 patients in group A who adhered strictly to the procedure were available for analysis. Seven of them had to start treatment again within the first 4 weeks of follow-up; four additional patients started treatment again during the next 8 weeks (group A1). The seven other patients remained untreated (group A2). The skin hyperemic response decreased significantly in patients in group A1 and returned to baseline values at the end of the study, when there were again receiving antihypertensive treatment. In patients in group A2 a significant attenuation of the hyperemic response was also observed. This impaired response was present even at the end of the 6 month follow-up, at which time the patients were still untreated but exhibited a significantly greater blood pressure than before drug discontinuation. The hyperemic response of patients who did not stop treatment (group B) did not change during the course of the study.

CONCLUSIONS

Our findings show a decrease in the postischemic skin blood flow response after withdrawal of antihypertensive treatment in hypertensive patients. This impaired response may be due to the development of endothelial dysfunction, vascular remodeling, or both, and might contribute to the return of blood pressure to hypertensive values after withdrawal of antihypertensive therapy.

Vasopeptidase inhibition exhibits endothelial protection in salt-induced hypertension

Omapatrilat represents a new class of drugs capable of inhibiting both ACE and neutral endopeptidase 24.11, the so-called vasopeptidase inhibitors. It therefore contributes to neurohumoral modulation, which might improve endothelial function in cardiovascular diseases. This study investigated the effect of omapatrilat in comparison to the ACE inhibitor captopril on systolic blood pressure and endothelial function in salt-induced hypertension. Dahl salt-sensitive rats (n=6/group) on standard or salt-enriched (4% NaCl) chow were treated for 8 weeks with either omapatrilat (36+/-4 mg/kg per day), captopril (94+/-2 mg/kg per day), or placebo. Aortic rings were then isolated and suspended in organ chambers for isometric tension recording. Systolic blood pressure of salt-fed, placebo-treated animals increased to 196+/-6 mm Hg, which was prevented by omapatrilat (162+/-5 mm Hg, P<0.05) and captopril (164+/-7 mm Hg, P<0.05) to a comparable degree. In control rats, acetylcholine (10(-10) to 10(-5) mol/L) induced endothelium-dependent relaxation (97+/-4%), which was reduced by high-salt diet to 30+/-5% (P<0.005; n=6). Omapatrilat improved relaxation to a greater extent (86+/-5%) than did captopril (57+/-6%; P<0.05). eNOS protein expression and aortic nitrite/nitrate content were reduced in hypertensive rats and improved by both omapatrilat and captopril. Aortic endothelin-1 levels were increased in salt-fed animals and unaffected by omapatrilat or captopril. These data suggest that despite comparable blood pressure, omapatrilat is superior to captopril in improving endothelium-dependent relaxation in salt-sensitive hypertension.

Nitric oxide, peroxynitrite and cGMP in atherosclerosis-induced hypertension in rabbits: beneficial effects of cicletanine

We studied the effect of the furopyridine derivative antihypertensive drug, cicletanine, on blood pressure, vascular nitric oxide (NO) and cyclic guanosine 3':5'-monophosphate (cGMP) content in the aorta and the renal and carotid arteries, aortic superoxide production, and serum nitrotyrosine level in hypertensive/atherosclerotic rabbits. The effect of cicletanine was compared to that of furosemide. Rabbits were fed a normal or a cholesterol-enriched (1.5%) diet over 8 weeks. On the 8th week, the rabbits were treated per os with 2 x 50 mg/kg daily doses of cicletanine, furosemide, or vehicle for 5 days (n = 5-6 in each groups). The cholesterol diet increased mean arterial blood pressure (MABP) from 86 +/- 1 to 94 +/- 2 mm Hg (p < 0.05). Cicletanine decreased MABP in atherosclerotic rabbits to 85 +/- 1 mm Hg (p < 0.05), but it did not affect MABP in normal animals. Furosemide was without effect in both groups. In normal animals, NO content (assessed by electron spin resonance after in vivo spin trapping) in the aorta and the renal and carotid arteries was increased by cicletanine, and the drug increased cGMP in the renal artery as measured by radioimmunoassay. The cholesterol-enriched diet decreased both vascular NO and cGMP and increased aortic superoxide production assessed by lucigenin-enhanced chemiluminescence and serum nitrotyrosine determined by ELISA. In atherosclerotic animals, cicletanine increased NO and cGMP content in the aorta and the renal and carotid arteries and decreased aortic superoxide production and serum nitrotyrosine. Furosemide did not influence these parameters. We conclude that cicletanine lowers blood pressure in hypertensive/atherosclerotic rabbits. The antihypertensive effect of the drug in atherosclerosis may be based on its beneficial effects on the vascular NO-cGMP system and on the formation of reactive oxygen species.

ACE-inhibition modulates some endothelial functions in healthy subjects and in normotensive type 1 diabetic patients

BACKGROUND

The usefulness of treatment with an angiotensin-converting enzyme-inhibitor (ACE-inhibitor) in normotensive patients with type 1 diabetes is controversial. We investigated whether ACE-inhibition improves endothelial function in such patients and compared the responses to those in healthy subjects.

DESIGN

We studied 23 healthy volunteers (controls, aged 29.8 [SD 7.0] years) and 24 type 1 diabetic patients (aged 28.7 [9. 6] years; HbA1c 8.1 [1.2]%; diabetes duration 13.8 [2-30] years; blood pressure < 140/90 mm Hg; 7 with microalbuminuria) after 5 weeks of ACE-inhibition (quinapril, 10 mg day-1) and placebo in a randomized, double-blind cross-over design. Estimates of endothelial function obtained were by flow-mediated vasodilation and plasma levels of endothelium-derived proteins.

RESULTS

As estimated from the measurements on placebo, type 1 diabetic patients, as compared to the controls, had some impairment of endothelial function: plasma tissue-type plasminogen activator levels were lower (3.5 vs. 5.4 ng mL(-1), P<0.05), but there were no significant differences in brachial artery flow-mediated vasodilation or plasma levels of von Willebrand Factor, endothelin-1, plasminogen activator inhibitor-1, soluble E-selectin or vascular cell adhesion molecule-1. As compared to placebo, ACE-inhibition increased flow-mediated vasodilation in controls (by 3.84% points [95% CI, 0.66 - 7.02], P<0.05), but not in type 1 diabetic patients (0.82% points [95% CI, -2.72 - 4.36], P = 0.64; P = 0.08 vs. controls). On ACE-inhibition soluble E-selectin levels decreased both in controls (from 43.0 to 37.0 ng mL(-1), P<0.01) and in type 1 diabetic patients (from 41.0 to 39.0 ng mL(-1), P = 0.09). Other endothelial markers did not change during ACE-inhibition.

CONCLUSION

Normotensive type 1 diabetic patients with normoalbuminara or microalbuminuria have mild endothelial dysfunction. Short-term ACE-inhibition improves endothelial function as reflected by a decreased sE-selectin in healthy subjects and in normotensive type 1 diabetic patients. In healthy subjects, ACE-inhibition increases flow-mediated vasodilation. In contrast, in type 1 diabetic patients, ACE-inhibition does not affect flow-mediated vasodilation.

The roles of platelet function, thromboxane, blood lipids and nitric oxide in hypertension of children and adolescents

The roles of platelet function, plasma lipids and nitric oxide (NO) were studied in adolescent patients with essential hypertension (JEHT group), with chronic renal failure (CRF) associated with hypertension (CRFH group), and CRF patients with normal blood pressure (CRF group), as compared with normal controls (cont. group). Platelet aggregation and the thromboxane B(2)(TxB(2)) level were significantly higher in the JEHT and CRFH groups as compared with the cont. group, whereas they were significantly lower in the CRF group. On the other hand, the platelet cAMP level was significantly lower in the JEHT and CRFH groups than in the cont. group. The plasma NO level was significantly higher only in the JEHT as compared with the cont. group (120 +/- 39 and 89 +/- 21 microM, respectively). The plasma total cholesterol, triglyceride and LDL cholesterol concentrations were normal in the JEHT group, but high in the CRF and CRFH group, the HDL cholesterol level was lower in the CRF and CRFH groups as compared with the cont. and JEHT groups. There was a positive correlation between the platelet aggregation and the TxB(2)level and between the BP and the platelet aggregation. In conclusion, hyperlipidaemia is commonly present in uraemia with haemodialysis, but is not specific for hypertension in children, while an increased platelet function is frequently associated with hypertension. The increased NO level might play a compensatory role in JEHT.

Antihypertensive drugs and reversing of endothelial dysfunction in hypertension

Essential hypertension is associated with impaired endothelium-dependent vasodilation and is caused mainly by production of oxygen free radicals that can destroy nitric oxide (NO), impairing its beneficial and protective effects on the vessel wall. Antihypertensive drugs can improve or restore endothelium-dependent vasodilation depending on their ability to counteract the mechanisms that impair endothelial function. Although treatment with atenolol gives negative results in peripheral subcutaneous and muscle microcirculation, acute nebivolol exerts a modest vasodilating effect in the forearm circulation. Whether this compound can activate NO production in essential hypertensive patients is controversial. Calcium entry blockers, particularly the dihydropyridine-like drugs, can reverse impaired endothelium-dependent vasodilation in different vascular districts, including the subcutaneous, epicardial, and peripheral arteries and forearm circulation. In the forearm circulation, nifedipine and lacidipine can improve endothelial dysfunction by restoring NO availability. Angiotensin-converting enzyme (ACE) inhibitors, however, seem to improve endothelial function in subcutaneous, epicardial, and renal circulation, but are ineffective in potentiating the blunted response to acetylcholine in the forearm of patients with essential hypertension. Finally, recent evidence suggests angiotensin II receptor antagonists can restore endothelium-dependent vasodilation to acetylcholine in subcutaneous, but not in the forearm muscle, microcirculation. However, treatment with an angiotensin II receptor antagonist can improve basal NO release and decrease the vasoconstrictor effect of endogenous endothelin-1.

Angiotensin II (ATII)-inducible platelet-derived growth factor A-chain gene expression is p42/44 extracellular signal-regulated kinase-1/2 and Egr-1-dependent and mediated via the ATII type 1 but not type 2 receptor. Induction by ATII antagonized by nitric oxide

Angiotensin II (ATII) and platelet-derived growth factor (PDGF) are two vasoconstrictors implicated in the maintenance of normal vascular homeostasis. PDGF A-chain levels increase in cultured vascular smooth muscle cells (SMCs) exposed to ATII. The molecular mechanisms underlying this induction are not known. We used transient transfection analysis to show that ATII can increase reporter gene activity driven by fragments of the PDGF-A promoter bearing recognition elements for the transcription factor, Egr-1. Nuclear run-off experiments indicate that ATII induces Egr-1 expression at the level of transcription. Gel shift and supershift studies show that Egr-1 protein accumulates in the nuclei of SMCs exposed to ATII and binds to the proximal region of the PDGF-A promoter in a specific, time-dependent manner. ATII induced extracellular-signal regulated kinase (p42/44 ERK) activity as did phorbol 12-myristate 13-acetate. The specific MEK1/2 inhibitor, PD98059, suppressed both PDGF-A and Egr-1 endogenous and promoter-dependent expression inducible by ATII. The ATII type 1 receptor (AT1) antagonist, Losartan, inhibited ATII-induction of p42/44 ERK, as well as Egr-1 and PDGF-A, whereas neither PD123319, an AT2 receptor antagonist, nor wortmannin, an inhibitor of phosphatidylinositol 3-kinase and c-Jun N-terminal kinase, had any effect. ATII-induction of Egr-1 and PDGF-A was blocked by SIN-1, a NO donor. In addition, this pathway was blocked by overexpression of NO synthase. Collectively, these findings demonstrate that ATII activation of the PDGF-A promoter is mediated via the MEK/ERK/Egr-1 pathway and AT1 receptor and that this process is antagonized by NO.