Progressive improvement in the structure of resistance arteries of hypertensive patients after 2 years of treatment with an angiotensin I-converting enzyme inhibitor. Comparison with effects of a beta-blocker

Distinct transcriptomic profile of small arteries of hypertensive patients with chronic kidney disease identified miR-338-3p targeting GPX3 and PTPRS

OBJECTIVE

Hypertension is associated with vascular injury, which contributes to end-organ damage. MicroRNAs regulating mRNAs have been shown to play a role in vascular injury in hypertensive mice. We aimed to identify differentially expressed microRNAs and their mRNA targets in small arteries of hypertensive patients with/without chronic kidney disease (CKD) to shed light on the pathophysiological molecular mechanisms of vascular remodeling.

METHODS AND RESULTS

Normotensive individuals and hypertensive patients with/without CKD were recruited ( n  = 15-16 per group). Differentially expressed microRNAs and mRNAs were identified uniquely associated with hypertension (microRNAs: 10, mRNAs: 68) or CKD (microRNAs: 68, mRNAs: 395), and in both groups (microRNAs: 2, mRNAs: 32) with a P less than 0.05 and a fold change less than or greater than 1.3 in subcutaneous small arteries ( n  = 14-15). One of the top three differentially expressed microRNAs, miR-338-3p that was down-regulated in CKD, presented the best correlation between RNA sequencing and reverse transcription-quantitative PCR (RT-qPCR, R2  = 0.328, P  < 0.001). Profiling of human aortic vascular cells showed that miR-338-3p was mostly expressed in endothelial cells. Two of the selected top nine up-regulated miR-338-3p predicted targets, glutathione peroxidase 3 ( GPX3 ) and protein tyrosine phosphatase receptor type S ( PTPRS ), were validated with mimics by RT-qPCR in human aortic endothelial cells ( P  < 0.05) and by a luciferase assay in HEK293T cells ( P  < 0.05).

CONCLUSION

A distinct transcriptomic profile was observed in gluteal subcutaneous small arteries of hypertensive patients with CKD. Down-regulated miR-338-3p could contribute to GPX3 and PTPRS up-regulation via the canonical microRNA targeting machinery in hypertensive patients with CKD.

GRAPHICAL ABSTRACT

http://links.lww.com/HJH/C27.

Vascular Smooth Muscle Remodeling in Conductive and Resistance Arteries in Hypertension

Cardiovascular disease is a leading cause of death worldwide and accounts for >17.3 million deaths per year, with an estimated increase in incidence to 23.6 million by 2030. ¹ Cardiovascular death represents 31% of all global deaths ² -with stroke, heart attack, and ruptured aneurysms predominantly contributing to these high mortality rates. A key risk factor for cardiovascular disease is hypertension. Although treatment or reduction in hypertension can prevent the onset of cardiovascular events, existing therapies are only partially effective. A key pathological hallmark of hypertension is increased peripheral vascular resistance because of structural and functional changes in large (conductive) and small (resistance) arteries. In this review, we discuss the clinical implications of vascular remodeling, compare the differences between vascular smooth muscle cell remodeling in conductive and resistance arteries, discuss the genetic factors associated with vascular smooth muscle cell function in hypertensive patients, and provide a prospective assessment of current and future research and pharmacological targets for the treatment of hypertension.

Positive effects of aggressive vasodilator treatment of well-treated essential hypertensive patients

Increased systemic vascular resistance and coronary microvascular dysfunction are well-documented in essential hypertension (EH). We investigated the effect of additional vasodilating treatment on coronary and peripheral resistance circulation in EH patients with high systemic vascular resistance index (SVRI) despite well-treated blood pressure (BP). We enroled patients on stable antihypertensive treatment that were given intensified vasodilating therapy (ACE inhibitor, angiotensin II receptor blocker or calcium channel blocker). Before and following 6 months of intensified therapy, coronary resting and maximal artery flow were measured by transthoracic Doppler echocardiography to calculate coronary flow reserve (CFR) and minimum vascular resistance (C-R_min). Cardiac output was estimated by inert gas rebreathing to calculate SVRI. Maximal forearm blood flow was determined by venous occlusion plethysmography to calculate minimum vascular resistance (F-R_min). Patients were assigned into two groups: high-SVRI and low-SVRI subgroups, based on a median split at baseline. Following additional treatment SVRI decreased more in the high-SVRI group than in the low-SVRI group (14.4 vs -2.2%: P=0.003), despite similar baseline ambulatory BP (132/81 mm Hg) and BP reduction (6.5 and 4.6%: P=0.19). F-R_min remained unchanged (6.5 vs -2.0%: P=0.30), while C-R_min decreased by 22 and 24% (P=0.80) and CFR increased by 23 and 17% (P=0.16). Thus, intensified vasodilating therapy improved SVRI more in patients with high SVRI than in those with low SVRI. Regardless of SVRI status, the treatment improved cardiac but not forearm dilatation capacity. The substantial improvement of the hypertensive cardiac microvascular dysfunction was not related to the reduction in SVRI.

Prehypertension: Underlying pathology and therapeutic options

Prehypertension (PHTN) is a global major health risk that subjects individuals to double the risk of cardiovascular disease (CVD) independent of progression to overt hypertension. Its prevalence rate varies considerably from country to country ranging between 21.9% and 52%. Many hypotheses are proposed to explain the underlying pathophysiology of PHTN. The most notable of these implicate the renin-angiotensin system (RAS) and vascular endothelium. However, other processes that involve reactive oxygen species, the inflammatory cytokines, prostglandins and C-reactive protein as well as the autonomic and central nervous systems are also suggested. Drugs affecting RAS have been shown to produce beneficial effects in prehypertensives though such was not unequivocal. On the other hand, drugs such as β-adrenoceptor blocking agents were not shown to be useful. Leading clinical guidelines suggest using dietary and lifestyle modifications as a first line interventional strategy to curb the progress of PHTN; however, other clinically respected views call for using drugs. This review provides an overview of the potential pathophysiological processes associated with PHTN, abridges current intervention strategies and suggests investigating the value of using the "Polypill" in prehypertensive subjects to ascertain its potential in delaying (or preventing) CVD associated with raised blood pressure in the presence of other risk factors.

Effects of diabetes and hypertension on structure and distensibilty of human small coronary arteries

OBJECTIVES

Previous studies have demonstrated that hypertension and diabetes induce significant structural remodelling of resistance arteries from various vascular beds. The hypothesis of this study is that structural alterations of small coronary arteries may occur during hypertension and diabetes. This study is the first to compare human coronary small resistance artery structure from normotensive and hypertensive patients, with and without diabetes undergoing coronary arterial bypass graft surgery.

METHODS

Small arteries were dissected from the atrial appendage removed from nondiabetic normotensive patients, nondiabetic hypertension and diabetic normotensive patients and hypertensive diabetic patients. Arteries were mounted in a pressure myograph and lumen diameter and wall thickness were measured across the pressure range of 3-100 mmHg to assess vessel structure and distensibility.

RESULTS

There were no significant differences in the lumen diameter, wall thickness, wall-to-lumen ratio and cross-sectional area of arteries in all groups. Arteries from nondiabetic patients with hypertension demonstrated decreased distensibility compared with nondiabetic normotensive patients. There is no difference in distensibility between vessels from diabetic hypertensive patients and either diabetic or nondiabetic normotensive patients.

CONCLUSION

Neither diabetes nor hypertension appears to have influenced arterial structure which may indicate that successful treatment of hypertension is associated with normal vascular structure in coronary small arteries.

The effect of selective antihypertensive drugs on the vascular remodeling-associated hypertension: insights from a profilin1 transgenic mouse model

Hypertension represents a major risk factor for cardiovascular diseases. We have developed a novel transgenic mouse model by overexpressing the cDNA of human profilin1 in the blood vessels of transgenic mice, which led to vascular hypertrophy and hypertension. We assessed the effects of losartan, amlodipine, or atenolol on vascular hypertrophy-associated hypertension, by treating the profilin1 transgenic mice for 4 weeks. Our myograph results showed improvement in the contraction response toward phenylephrine and in the relaxation response toward acetylcholine and sodium nitrite in losartan- and amlodipine-treated profilin1 mice. Western blot analyses using mesenteric arteries of losartan- and amlodipine-treated profilin1 mice showed significant decreases in their signaling, respectively, as follows: the expression of α1 integrin (104% and 93%) and β1 integrin (116% and 109%); p-ERK1/2 (149% and 130%) and p-JNK (171% and 137%); the phospho-myosin light chain 20 (117% and 150%); and the ROCKII expression (125% and 180%). Conversely, there were significant increases in the endothelial nitric oxide synthase expression (82% and 80%) and activation (p-endothelial nitric oxide synthase) (78% and 76%). On the other hand, atenolol-treated profilin1 mice showed no significant change in all measured parameters. In conclusion, the profilin1 gene may represent a new therapeutic target in the treatment of vascular hypertrophy-associated hypertension.

Resveratrol and small artery compliance and remodeling in the spontaneously hypertensive rat

BACKGROUND

Small arteries from the spontaneously hypertensive rat (SHR) exhibit abnormal stiffness and geometry. This study investigated the effects of resveratrol, a polyphenol found in foods such as red grapes, on small arteries in SHR.

METHODS

Wistar-Kyoto (WKY) rats and SHR were treated with resveratrol (2.5 mg/kg/day) for 10 weeks. Mesenteric small artery segments (third-order branches) were mounted in a pressure myograph, and vascular geometry and mechanical properties were calculated from lumen and media dimensions measured at incremental intraluminal pressures. Systolic blood pressure was measured by tail-cuff plethysmography.

RESULTS

Increased compliance and reduced wall component stiffness were observed in SHR arteries vs. WKY arteries. Though resveratrol did not prevent lowering of wall component stiffness, it did attenuate, at least in part, the increased compliance of SHR arteries. In contrast, resveratrol increased compliance and reduced wall component stiffness in WKY arteries. SHR arteries exhibited remodeling that consisted of narrowed lumens, thickened media widths, and augmented media-to-lumen ratios. Resveratrol partially attenuated the remodeling process and also abolished exaggerated ERK signaling and expression of proliferating cell nuclear antigen (a marker of proliferation) in SHR arteries. The latter effects might be related to the ability of resveratrol to alleviate oxidative stress in SHR and enhance protein kinase G (PKG) activity. Elevated blood pressure in 20-week-old SHR was unaffected by resveratrol.

CONCLUSIONS

The ability of resveratrol to limit the increase in compliance of SHR arteries is likely related to inhibitory effects on remodeling and pro-growth ERK signaling rather than blood pressure or arterial wall component stiffness.

Circulatory therapeutics: use of antihypertensive agents and their effects on the vasculature

This review addresses the use of the different antihypertensive agents currently available and some in development, and their effects on the vasculature. The different classes of agents used in the treatment of hypertension, and the results of recent large clinical trials, dosing protocols and adverse effects are first briefly summarized. The consequences on blood vessels of the use of antihypertensive drugs and the differential effects on the biology of large and small arteries resulting in modulation of vascular remodelling and dysfunction in hypertensive patients are then described. Large elastic conduit arteries exhibit outward hypertrophic remodelling and increased stiffness, which contributes to raise systolic blood pressure and afterload on the heart. Small resistance arteries undergo eutrophic or hypertrophic inward remodelling, and impair tissue perfusion. By these mechanisms both large and small arteries may contribute to trigger cardiovascular events. Some antihypertensive agents correct these changes, which could contribute to improved outcome. The mechanisms that at the level of the vascular wall lead to remodelling and can be beneficially affected by antihypertensive agents will also be addressed. These include vasoconstriction, growth and inflammation. The molecular pathways contributing to growth and inflammation will be summarily described. Further identification of these signalling pathways should allow identification of novel targets leading to development of new and improved medications for the treatment of hypertension and cardiovascular disease.

Improving vascular function in hypertension: potential benefits of combination therapy with amlodipine and renin-angiotensin-aldosterone system blockers

Hypertension is characterized by endothelial dysfunction and increased risk for adverse cardiovascular outcomes. In addition to lowering blood pressure, the calcium-channel blocker amlodipine and blockers of the renin-angiotensin-aldosterone system (angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers) may further reduce cardiovascular risk by improving endothelial function when used alone or in combination. In fact, the beneficial effects of the combination of amlodipine and a renin-angiotensin-aldosterone system blocker on endothelial function have been found to be greater than the effect of either drug alone, likely due to additive effects on nitric oxide activity. This review summarizes the observed effects of these agents on endothelial function and the complementary mechanisms by which they act, thus providing rationale (beyond blood pressure benefits) for their use in combination.

Combining RAAS and calcium channel blockade: ACCOMPLISH in perspective

The Avoiding Cardiovascular events through COMbination therapy in Patients LIving with Systolic Hypertension (ACCOMPLISH) trial was the first trial to compare the cardiovascular outcomes of initial fixed-dose combination angiotensin-converting enzyme inhibitor (ACEI)/calcium channel blocker (CCB) and ACEI/diuretic therapy in patients with hypertension and high risk of cardiovascular events. The initial combination therapy was effective in this population, with ACEI/CCB therapy providing the greatest benefit (reduction in risk of cardiovascular events). Whether or not the findings of ACCOMPLISH can be applied to other renin-angiotensin-aldosterone system (RAAS) inhibitor/CCB combinations, such as angiotensin receptor blocker (ARB)/CCB combinations, has yet to be investigated. The present report reviews the results of ACCOMPLISH, data from trials comparing ARB and ACEI therapies, and findings from studies of ARB/CCB combination therapy that support the use and further study of combination therapy with RAAS inhibitors and CCBs.

Angiotensin-converting enzyme and vascular remodeling

Vascular remodeling is the result of a close interplay of changes in vascular tone and structure. In this review, the role of angiotension-converting enzyme (ACE) and the impact of ACE inhibition on vascular remodeling processes during vascular injury and restenosis, hypertension, atherosclerosis, and aneurysm formation are discussed. The role of ACE and angiotensin II (Ang II) in neointimal thickening has been firmly established by animal studies and is mediated by Ang II type 1 (AT(1)) receptor signaling events via monocyte chemoattractant protein-1 and NAD(P)H oxidase. ACE and Ang II are involved in the remodeling of large and resistance arteries during hypertension; here, cell proliferation and matrix remodeling are also regulated by signaling events downstream of the AT(1) receptor. In atherosclerosis, Ang II is involved in the inflammatory and tissue response, mediated by various signaling pathways downstream of the AT(1) receptor. Although ACE inhibition has been shown to inhibit atherosclerotic processes in experimental animal models, results of large clinical trials with ACE inhibitors were not conclusive. Remodeling of vessel dimensions and structure during aneurysm formation is counteracted by ACE inhibition. Here, a direct effect of ACE inhibitors on matrix metalloproteinase activity has to be considered as part of the working mechanism. The role of ACE2 in vascular remodeling has yet to be established; however, ACE2 has been shown to be associated with vascular changes in hypertension and atherosclerosis.

Should the results of TROPHY affect the JNC 7 definition of prehypertension?

In the Trial of Preventing Hypertension (TROPHY), volunteers with "high normal blood pressure" were randomized to 4 years of placebo (n = 381) or 2 years of 16 mg/d of candesartan (n = 391) followed by 2 years of placebo. At 2 years, there was a 26.8% absolute and a 66.3% relative risk reduction (P < 0.0001) of hypertension in the candesartan group. At study end, the former candesartan group had a 9.8% absolute and a 15.6% relative risk reduction (P < 0.007) of hypertension. The treatment was well tolerated. The Seventh Joint National Committee (JNC 7) changed the nomenclature from "high normal blood pressure" to "prehypertension" and widened the range to 120 to 139 and/or 80 to 89 mm Hg. Our results support the term "prehypertension" only for the 130 to 139 and/or 85 to 89 mm Hg group; in 4 years two thirds of the placebo group developed hypertension. We suggest stratifying the JNC classification into "prehypertension" (130-139 and/or 85-89 mm Hg) and "high normal blood pressure" (120-129 and/or 80-84 mm Hg). By the present JNC definition, only one quarter of adult men have normal blood pressure. Removing the disease label from another 28% would appropriately focus attention on high-risk prehypertension.

Small artery stucture adapts to vasodilatation rather than to blood pressure during antihypertensive treatment

OBJECTIVE

Correction of the abnormal structure of resistance arteries in essential hypertension may be an important treatment goal in addition to blood pressure (BP) reduction. We investigated how this may be achieved in a prospective clinical study.

METHODS

Plethysmography was used to measure forearm resting vascular resistance (Rrest) and minimum vascular resistance (Rmin) as a measure of vascular structure. Two different groups of patients with essential hypertension were examined at baseline and after 6 months of antihypertensive treatment. In group A, 21 patients with never-treated essential hypertension were treated by their general practitioners using a variety of drugs to allow an assessment of the drug-independent effects. In group B, 28 beta-blocker-treated patients were shifted to angiotensin II receptor blocker treatment (eprosartan) to allow vasodilatation with no change in BP.

RESULTS

In group A, mean ambulatory blood pressure (ABP) fell from 119 +/- 2 (SE) to 103 +/- 2 mmHg (P < 0.01), whereas mean ABP was unchanged in group B (100 +/- 1 to 99 +/- 1 mmHg, P = NS). Both groups showed similar reductions in Rrest (-33.4 and -28.5%, respectively) and in Rmin (-15.4 and -15.6%, respectively). There was a strong correlation between changes in Rrest and Rmin within both groups (r = 0.57, P < 0.01 and r = 0.68, P < 0.0001, respectively), whereas the change in BP in group A was not correlated to the change in Rmin (r = -0.03).

CONCLUSION

The correction of forearm resistance artery structure during antihypertensive treatment depends on the vasodilatation achieved rather than BP reduction.

Effect of losartan, compared with atenolol, on endothelial function and oxidative stress in patients with type 2 diabetes and hypertension

OBJECTIVE

It has been shown that angiotensin-converting enzyme inhibition or angiotensin receptor blockade may improve endothelial dysfunction, an early manifestation of atherosclerosis, in patients with diabetes. Whether this protective effect is mediated through blood pressure-lowering effects or other specific mechanisms such as a reduction in oxidative stress is not clear. We investigated the influence of losartan, compared with atenolol, on endothelial function and oxidative stress in patients with type 2 diabetes and hypertension.

METHODS

Thirteen patients were included in this randomized, double-blind, crossover study; they received losartan 50 mg twice daily for 4 weeks followed by atenolol 50 mg twice daily or vice versa. Concomitant medication with renin-angiotensin blocking agents or beta-blockers was withdrawn, whereas other medication remained unchanged. At baseline and after each treatment period, flow-mediated dilation of the brachial artery and oxidative stress were measured in serum samples.

RESULTS

Flow-mediated dilation was increased significantly after 4 weeks' treatment with losartan (3.4 +/- 0.44%) compared with atenolol (2.58 +/- 0.42%; P = 0.01). 8-Isoprostanes, a marker of oxidative stress, were significantly reduced in the losartan group compared with baseline (0.039 +/- 0.007 versus 0.067 +/- 0.006 ng/ml; P = 0.01), but did not differ from baseline with atenolol. Glucose, hemoglobin A1c, highly sensitive C-reactive protein, lipids and systolic blood pressure remained unaltered, whereas diastolic blood pressure tended to be lower in the atenolol group.

CONCLUSIONS

This study demonstrates that losartan significantly improved endothelial function in type 2 diabetes patients with hypertension compared with atenolol. This must be independent of the blood pressure-lowering effect of losartan and is probably caused by an antioxidative effect of the angiotensin receptor blocker.

The vascular endothelium in hypertension

The vascular endothelium plays a fundamental role in the basal and dynamic regulation of the circulation. Thus, it has a crucial role in the pathogenesis of hypertension. A spectrum of vasoactive substances is synthesised in the endothelium; of these, nitric oxide (NO), prostacyclin (PGI2) and endothelin (ET)-1 are the most important. There is a continuous basal release of NO determining the tone of peripheral blood vessels. Systemic inhibition of NO synthesis or scavenging of NO through oxidative stress causes an increase in arterial blood pressure. Also, the renin-angiotensin-aldosterone system has a major role in hypertension as it has a direct vasoconstrictor effect and important interactions with oxygen free radicals and NO. Prostacyclin, in contrast to NO, does not contribute to the maintenance of basal vascular tone of conduit arteries, but its effect on platelets is most important. ET acts as the natural counterpart to endothelium-derived NO and has an arterial blood pressure-raising effect in man. Anti-hypertensive therapy lowers blood pressure and may influence these different mediators, thus influencing endothelial function. In summary, due to its position between the blood pressure and smooth muscle cells responsible for peripheral resistance, the endothelium is thought to be both victim and offender in arterial hypertension. The delicate balance of endothelium-derived factors is disturbed in hypertension. Specific anti-hypertensive and anti-oxidant treatment is able to restore this balance.

Losartan improves resistance artery lesions and prevents CTGF and TGF-beta production in mild hypertensive patients

Although structural and functional changes of resistance arteries have been proposed to participate in arterial hypertension (HTA) outcome, not all therapies may correct these alterations, even if they normalize the blood pressure (BP). The aim of this study was to investigate the mechanisms of the protection afforded by the angiotensin receptor antagonist losartan in resistance arteries from patients with essential HTA. In all, 22 untreated hypertensive patients were randomized to receive losartan or amlodipine for 1 year and the morphological characteristics of resistance vessels from subcutaneous biopsies were evaluated. Protein expression of connective tissue growth factor (CTGF), transforming growth factor beta (TGF-beta), and collagens III and IV was detected by immunohistochemistry. In comparison with normotensive subjects, resistance arteries from hypertensive patients showed a significant media:lumen (M/L) ratio increment and a higher protein expression of CTGF, TGF-beta, and collagens. After 1 year of treatment, both losartan and amlodipine similarly controlled BP. However, M/L only decreased in patients under losartan treatment, whereas in the amlodipine-treated group this ratio continued to increase significantly. The administration of losartan prevented significant increments in CTGF, TGF-beta, and collagens in resistance arteries. By contrast, amlodipine-treated patients showed a higher vascular CTGF, TGF-beta, and collagen IV staining than before treatment. Our results show that the administration of losartan, but not amlodipine, to hypertensive patients improves structural abnormalities and prevents the production of CTGF and TGF-beta in small arteries, despite similar BP lowering. These data may explain the molecular mechanisms of the better vascular protection afforded by drugs interfering with the renin-angiotensin system.

Inhibition of the renin angiotensin system: implications for the endothelium

The endothelium is critically involved in modulating vascular tone through the release of vasodilator (mainly nitric oxide; NO) and vasoconstrictor agents. Under normal conditions the endothelium induces NO-mediated vasodilation, and opposes cell adhesion and thrombosis. Angiotensin II-induced generation of reactive oxygen species plays a key role in the pathophysiology of endothelial dysfunction by reducing NO bioavailability. Endothelial dysfunction is associated with several pathologic conditions, including hypertension and diabetes, and is characterized by altered vascular tone, inflammation, and thrombosis in the vascular wall. Inhibition of the renin-angiotensin-aldosterone system has induced beneficial effects on endothelial function in animals and humans. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and mineralocorticoid receptor antagonists have improved endothelial function in hypertension and diabetes, slowed the progression of atherosclerosis, and reduced the risk associated with cardiovascular disease.

Angiotensin Receptor Blocker Added to Previous Antihypertensive Agents on Arteries of Diabetic Hypertensive Patients

Lowering elevated blood pressure (BP) in diabetic hypertensive individuals decreases cardiovascular events. We questioned whether remodeling of resistance arteries from hypertensive diabetic patients would improve after 1 year of tight BP control with addition of either the angiotensin receptor blocker (ARB) valsartan or the β-blocker (BB) atenolol to previous therapy, which included angiotensin-converting enzyme inhibitors (ACEIs) and/or calcium channel blockers. Twenty-eight hypertensive type 2 diabetic patients treated with oral hypoglycemic and antihypertensive agents (not receiving ARBs or BBs) were randomly assigned to double-blind treatment for 1 year with valsartan (80 to 160 mg) or atenolol (50 to 100 mg) daily, added to previous therapy. Resistance arteries dissected from gluteal subcutaneous tissues were assessed on a pressurized myograph. After 1 year of treatment, systolic and diastolic BP and glycemia were equally well controlled in the valsartan and atenolol groups. Endothelium-dependent and independent relaxation did not change in the treated groups. After 1 year of treatment, resistance artery media:lumen ratio decreased in the valsartan group (7.9±0.5% after versus 9.8±0.6% before; P <0.05) but not in the atenolol-treated group (9.9±0.9% versus 10.6±1%; P value not significant). Artery walls from atenolol-treated patients became stiffer, with no change in the valsartan-treated patients. In conclusion, similar intensive BP control for 1 year with valsartan was associated with improved structure of resistance arteries in diabetic hypertensive patients, whereas vessels from atenolol-treated patients exhibited unchanged remodeling and a stiffer wall. The addition of ARBs but not BBs to antihypertensive medications that may include angiotensin-converting enzyme inhibitors and/or calcium channel blockers results in an improvement in resistance artery remodeling in diabetic hypertensive patients.

Feasibility of treating prehypertension with an angiotensin-receptor blocker

BACKGROUND

Prehypertension is considered a precursor of stage 1 hypertension and a predictor of excessive cardiovascular risk. We investigated whether pharmacologic treatment of prehypertension prevents or postpones stage 1 hypertension.

METHODS

Participants with repeated measurements of systolic pressure of 130 to 139 mm Hg and diastolic pressure of 89 mm Hg or lower, or systolic pressure of 139 mm Hg or lower and diastolic pressure of 85 to 89 mm Hg, were randomly assigned to receive two years of candesartan (Atacand, AstraZeneca) or placebo, followed by two years of placebo for all. When a participant reached the study end point of stage 1 hypertension, treatment with antihypertensive agents was initiated. Both the candesartan group and the placebo group were instructed to make changes in lifestyle to reduce blood pressure throughout the trial.

RESULTS

A total of 409 participants were randomly assigned to candesartan, and 400 to placebo. Data on 772 participants (391 in the candesartan group and 381 in the placebo group; mean age, 48.5 years; 59.6 percent men) were available for analysis. During the first two years, hypertension developed in 154 participants in the placebo group and 53 of those in the candesartan group (relative risk reduction, 66.3 percent; P<0.001). After four years, hypertension had developed in 240 participants in the placebo group and 208 of those in the candesartan group (relative risk reduction, 15.6 percent; P<0.007). Serious adverse events occurred in 3.5 percent of the participants assigned to candesartan and 5.9 percent of those receiving placebo.

CONCLUSIONS

Over a period of four years, stage 1 hypertension developed in nearly two thirds of patients with untreated prehypertension (the placebo group). Treatment of prehypertension with candesartan appeared to be well tolerated and reduced the risk of incident hypertension during the study period. Thus, treatment of prehypertension appears to be feasible. (ClinicalTrials.gov number, NCT00227318.).

Small artery remodeling in hypertension and diabetes

The development of structural changes in the systemic vasculature is the end result of established hypertension. In essential hypertension, small artery smooth muscle cells are restructured around a smaller lumen, and there is no net growth of the vascular wall, whereas in some secondary forms of hypertension and in non-insulin-dependent diabetes mellitus, a hypertrophic remodeling may be detected. Indices of small resistance artery structure, such as the tunica media to internal lumen ratio, may have a strong prognostic significance in hypertensive patients. Various antihypertensive drugs seem to have different effects on vascular structure. A complete normalization of small resistance artery structure was demonstrated in hypertensive patients, after prolonged and effective therapy with angiotensin-converting enzyme inhibitors, angiotensin II-receptor blockers, and calcium antagonists. Few data are available in diabetic hypertensive patients; however, blockade of the renin-angiotensin system seems to be effective in this regard.

Effect of treatment with candesartan or enalapril on subcutaneous small artery structure in hypertensive patients with noninsulin-dependent diabetes mellitus

Structural alterations of subcutaneous small resistance arteries are associated with a worse clinical prognosis in hypertension and noninsulin-dependent diabetes mellitus (NIDDM). However, no data are presently available about the effects of antihypertensive therapy on vascular structure in hypertensive patients with NIDDM. Therefore, we have investigated the effect of an angiotensin-converting enzyme inhibitor, enalapril, and a highly selective angiotensin receptor blocker, candesartan cilexetil, on indices of subcutaneous small resistance artery structure in 15 patients with mild hypertension and NIDDM. Eight patients were treated with candesartan (8 to 16 mg per day) and 7 with enalapril (10 to 20 mg per day) for 1 year. Each patient underwent a biopsy of the subcutaneous fat from the gluteal region at baseline and after 1 year of treatment. Small arteries were dissected and mounted on a micromyograph and the media-to-internal lumen ratio was evaluated; moreover, endothelium-dependent vasodilation to acetylcholine was assessed. A similar blood pressure-lowering effect and a similar reduction of the media-to-lumen ratio of small arteries was observed with the 2 drugs. Vascular collagen content was reduced and metalloproteinase-9 was increased by candesartan, but not by enalapril. Changes of circulating indices of collagen turnover and circulating matrix metalloproteinase paralleled those of vascular collagen. The 2 drugs equally improved endothelial function. In conclusion, antihypertensive treatment with drugs that inhibit the renin-angiotensin-aldosterone system activity is able to correct, at least in part, alterations in small resistance artery structure in hypertensive patients with NIDDM. Candesartan may be more effective than enalapril in reducing collagen content in the vasculature.

Antihypertensive medications for risk reduction of first and recurrent ischemic stroke

It is increasingly clear that even a small reduction in blood pressure results in a substantial risk reduction of vascular events including ischemic stroke. Recently, several comparative prospective trials of angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers have demonstrated that, for equivalent reductions in blood pressure, these drugs may confer a greater effect on the prevention of primary and recurrent ischemic stroke compared with other antihypertensive medications. Given this information from prospective randomized trials, it appears that this class of drugs should be the first-line treatment for hypertension in patients at risk of a first or recurrent ischemic stroke. This review will critically assess the scientific basis and rationale of the use of angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers in primary and secondary stroke prevention.

Protein Kinase C in Cardiac Disease and as a Potential Therapeutic Target

Protein kinase C (PKC) is a member of a large family of serine/threonine kinases that plays an integral role in many of the signaling cascades that govern cellular behavior. As such, it is intricately involved in the processes that mediate disease pathogenesis. Strategies that serve to alter PKC function may prove to be useful in the treatment of numerous disease states. This article reviews the various roles PKC may play in cardiovascular disease, specifically with regard to ischemic heart disease, cardiac hypertrophy, heart failure, hypertension, and atherosclerosis, and suggests the potential for developing therapeutic approaches that can target PKC activity.

Atenolol in hypertension: is it a wise choice?

BACKGROUND

Atenolol is one of the most widely used beta blockers clinically, and has often been used as a reference drug in randomised controlled trials of hypertension. However, questions have been raised about atenolol as the best reference drug for comparisons with other antihypertensives. Thus, our aim was to systematically review the effect of atenolol on cardiovascular morbidity and mortality in hypertensive patients.

METHODS

Reports were identified through searches of The Cochrane Library, MEDLINE, relevant textbooks, and by personal communication with established researchers in hypertension. Randomised controlled trials that assessed the effect of atenolol on cardiovascular morbidity or mortality in patients with primary hypertension were included.

FINDINGS

We identified four studies that compared atenolol with placebo or no treatment, and five that compared atenolol with other antihypertensive drugs. Despite major differences in blood pressure lowering, there were no outcome differences between atenolol and placebo in the four studies, comprising 6825 patients, who were followed up for a mean of 4.6 years on all-cause mortality (relative risk 1.01 [95% CI 0.89-1.15]), cardiovascular mortality (0.99 [0.83-1.18]), or myocardial infarction (0.99 [0.83-1.19]). The risk of stroke, however, tended to be lower in the atenolol than in the placebo group (0.85 [0.72-1.01]). When atenolol was compared with other antihypertensives, there were no major differences in blood pressure lowering between the treatment arms. Our meta-analysis showed a significantly higher mortality (1.13 [1.02-1.25]) with atenolol treatment than with other active treatment, in the five studies comprising 17671 patients who were followed up for a mean of 4.6 years. Moreover, cardiovascular mortality also tended to be higher with atenolol treatment than with other antihypertensive treatment. Stroke was also more frequent with atenolol treatment.

INTERPRETATION

Our results cast doubts on atenolol as a suitable drug for hypertensive patients. Moreover, they challenge the use of atenolol as a reference drug in outcome trials in hypertension.

Pathogenesis of structural vascular changes in hypertension

The pathogenic role of angiotensin II (ANG II), dietary sodium chloride, sympathetic activation, obesity and aldosterone in the development of structural vascular changes (SVCs) in hypertension is considered from three perspectives (criteria): their utility in predicting hypertension and its complications (predictability); the effect of their inhibition or removal on the reversal of SVCs (reversibility); and their ability to induce SVCs in experimental animals (reproducibility). Only ANG II meets all three criteria. Importantly, ANG II increases preglomerular vascular resistance by inducing structural changes in renal cortical resistance arteries and arterioles. High salt intake, by dilating and thereby stiffening some arteries, may play a role in the development of systolic hypertension with aging, but does not produce structural changes in renal cortical resistance vessels. While high circulating levels of norepinephrine are associated with SVCs, the experimental evidence for the role of sympathetic nerve stimulation in the development of SVCs is inconclusive. Obesity is associated with hypertension, but is not known to be associated with SVCs. Salt-loading is required for aldosterone to produce SVCs, but vascular pathology in this experimental model differs from that in benign essential hypertension. The findings of this review indicate that SVCs in extra-renal sites by themselves do not lead to hypertension; structural changes in renal cortical arteries and arterioles that increase preglomerular vascular resistance are needed. Progressive trophic stimulation of preglomerular resistance vessels by itself may lead to hypertension. ANG II is prime candidate for such stimulus.

beta-Blockers in hypertension: is carvedilol different?

Most studies assessing the effects of beta-blockers were carried out with traditional, beta(1)-selective beta-blockers, such as metoprolol and atenolol. Pathophysiologic and pharmacologic studies have documented that not all beta-blockers are created equal. In particular, the pharmacologic and clinical profiles of the newer, vasodilating beta-blockers, such as carvedilol, have been shown to differ from those of the traditional beta-blockers. These differences, although relevant in the younger patient with hypertension, are particularly important in elderly patients in whom traditional beta-blockers may not be as effective or as well tolerated as the newer vasodilating agents.

Persistent Remodeling of Resistance Arteries in Type 2 Diabetic Patients on Antihypertensive Treatment

We hypothesized that resistance arteries from diabetic patients with controlled hypertension have less remodeling than vessels from untreated hypertensive subjects. Eight normotensive subjects (aged 44±3 years, 3 men; values are mean±SEM), 19 untreated hypertensive subjects (46±2 years, 9 men), and 23 hypertensive subjects with type 2 diabetes mellitus under antihypertensive treatment (58±1 years, 15 men) were studied. Resistance arteries dissected from gluteal subcutaneous tissue were assessed on a pressurized myograph. Most diabetic patients (70%) were being treated with angiotensin-converting enzyme inhibitors. Although systolic blood pressure was still above the normotensive range in these patients (144±2 versus 150±3 mm Hg in hypertensive and 114±4 mm Hg in normotensive subjects), diastolic blood pressure was well controlled (83±2 mm Hg) and significantly lower compared with that in untreated hypertensives (100±1 mm Hg; P <0.001) but higher than in normotensives (76±3 mm Hg; P <0.05). Thus, pulse pressure was higher in diabetic patients ( P <0.05). The media-to-lumen ratio of resistance arteries was greater in hypertensives (0.083±0.002) compared with normotensive controls (0.059±0.003; P <0.05) and was even higher in diabetic hypertensive subjects (0.105±0.004; P <0.001 versus normotensive controls). The medial cross-sectional area was greater in diabetic and hypertensive patients compared with normotensive controls ( P <0.001). Acetylcholine-induced relaxation was impaired in vessels from hypertensive patients and from patients with both diabetes mellitus and hypertension ( P <0.05 versus normotensive controls), whereas endothelium-independent vasorelaxation was similar in all groups. Despite effective antihypertensive treatment, resistance arteries from hypertensive diabetic patients showed marked remodeling, greater than that of vessels from untreated, nondiabetic, hypertensive subjects, in agreement with the high cardiovascular risk of subjects suffering from both diabetes and hypertension.

Long-term treatment with nebivolol improves arterial reactivity and reduces ventricular hypertrophy in spontaneously hypertensive rats

The aim of this study was to assess the effects of long-term nebivolol therapy on high blood pressure, impaired endothelial function in aorta, and damage observed in heart and conductance arteries in spontaneously hypertensive rats (SHR). For this purpose, SHR were treated for 9 weeks with nebivolol (8 mg/kg per day). Untreated SHR and Wistar Kyoto rats were used as hypertensive and normotensive controls, respectively. The left ventricle/body weight ratio was used as an index of cardiac hypertrophy, and to evaluate vascular function, responses induced by potassium chloride, noradrenaline, acetylcholine, and sodium nitroprusside were tested on aortic rings. Aortic morphometry and fibrosis were determined in parallel by a quantitative technique. Systolic blood pressure, measured by the tail-cuff method, was lower in treated SHR than in the untreated group (194 +/- 3 versus 150 +/- 4 mm Hg). The cardiac hypertrophy index was significantly reduced by the treatment. In aortic rings, treatment with nebivolol significantly reduced the maximal response to both KCl and NA in SHR. In vessels precontracted with phenylephrine relaxant, activity due to acetylcholine was higher in normotensive rats than in SHR and the treatment significantly improved this response. The effect of sodium nitroprusside on aortic rings was similar in all groups. Medial thickness and collagen content were significantly reduced in comparison with SHR. In conclusion, the chronic antihypertensive effect of nebivolol in SHR was accompanied by an improvement in vascular structure and function and in the cardiac hypertrophy index.

Effect of antihypertensive treatment on small artery remodeling in hypertension

Blood vessels are remodeled in hypertension both structurally and functionally. The changes that occur in their structure, mechanical properties, and function contribute to blood pressure elevation and to complications of hypertension. We studied the remodeling of small arteries in experimental animals and humans. Smooth muscle cells of small arteries are restructured around a smaller lumen, with significant remodeling of the extracellular matrix and collagen and fibronectin deposition. Interestingly, there is no evidence of net growth of the vascular wall (which results in so-called eutrophic remodeling), particularly in the milder forms of human essential hypertension. Hypertrophic remodeling and increased small artery stiffness may be found in more severe forms of hypertension. Almost all hypertensive patients have vascular structural remodeling. However, only some exhibit endothelial dysfunction. This is particularly true in mild hypertension, in which endothelial dysfunction is less common. A 1-year treatment of hypertensive patients with angiotensin converting enzyme inhibitors, angiotensin AT1 receptor antagonists, and long acting calcium channel blockers corrected small artery structure and, to variable degrees depending on the agents used, impaired endothelial function. In contrast, beta blockers did not improve structure, function, or mechanics of vessels. When beta-blocker-treated patients were switched to an AT1 receptor antagonist, small artery structure and impaired endothelial function were corrected. The vascular protective action of some antihypertensive agents may contribute to improve outcome for hypertensive patients, although this is presently unproven.

Why beta-blockers are not cardioprotective in elderly patients with hypertension

Despite the fact that beta-blockers have been used for the treatment of hypertension for more than 30 years, no study has shown that their use reduces morbidity and mortality in the elderly. To the contrary, the British Medical Research Council trial in the elderly documented that although blood pressure was lowered effectively and significantly by atenolol, morbidity and mortality in the beta-blocker group did not differ from that of the placebo group. Not only was beta-blocker monotherapy not effective, but patients who received the combination of beta-blockers and diuretics fared consistently worse than those on diuretics alone. beta-blockers are less effective than diuretics in lowering blood pressure, and are poorly tolerated in the elderly. The reason for their inefficacy in the elderly may be related to their inherent unfavorable effect on systemic hemodynamics and pathophysiologic findings in the arterial tree, heart, kidneys, brain, and on the metabolism of lipids and carbohydrates. Decreased beta-adrenergic responsiveness with age and comorbid conditions makes beta-blockers unattractive. Thus, they should not be considered appropriate for first-line therapy of uncomplicated hypertension in the geriatric population.

Vascular and cardiac benefits of angiotensin receptor blockers

Angiotensin II not only is a vasoconstrictor, but it also affects cell growth and apoptosis, inflammation, fibrosis, and coagulation. Blockade of the renin-angiotensin system, either with inhibitors of the generation of angiotensin (angiotensin-converting enzyme [ACE] inhibitors) or with blockers of angiotensin receptors, reduces blood pressure and inhibits other pathophysiological actions. These other effects provide benefits in coronary heart disease, heart failure, diabetic nephropathy, and stroke beyond blood pressure reduction. These benefits were first demonstrated with ACE inhibitors. However, the mechanism of action of angiotensin receptor blockers, which block angiotensin II stimulation at the angiotensin type 1 receptor but not at the type 2 receptor, may have advantages, particularly for endothelial dysfunction and vascular remodeling, as well as cardiac and renal protection. Recent multicenter trials suggest that ACE inhibitors and angiotensin receptor blockers may reduce morbidity and mortality associated with cardiovascular and renal disease beyond blood pressure reduction. Several studies with different angiotensin receptor blockers, including comparisons with ACE inhibitors, are under way, and should provide further guidance for their clinical use.

Vascular remodeling during healing after myocardial infarction in the dog model: effects of reperfusion, amlodipine and enalapril

OBJECTIVES

We sought to determine whether reperfusion and the calcium channel blocker amlodipine or the angiotensin-converting enzyme inhibitor enalapril, during healing over six weeks after myocardial infarction (MI), limit structural vascular remodeling in the noninfarct zone (NIZ).

BACKGROUND

The effect of reperfusion and amlodipine or enalapril on structural vascular remodeling during healing of MI has not been determined.

METHODS

We randomly assigned 54 dogs to reperfused or nonreperfused MI, followed by twice-daily doses of oral placebo, amlodipine (5 mg) or enalapril (5 mg) for six weeks and three days off treatment, or to three matching sham groups. We measured in vivo hemodynamic data and left ventricular (LV) function and remodeling (by echocardiography) over the six weeks, as well as ex vivo structural vascular, ventricular and collagen remodeling in the hearts after six weeks.

RESULTS

Compared with placebo and sham groups, both amlodipine and enalapril with or without reperfusion produced LV unloading and limited structural LV remodeling and dysfunction over six weeks in vivo, and also decreased the NIZ resistance vessel media/lumen area ratio at six weeks ex vivo. In addition, amlodipine, but not enalapril, preserved infarct scar collagen and increased the border zone collagen volume fraction and perivascular fibrosis, as well as NIZ resistance vessel media thickness. Enalapril, but not amlodipine, decreased transforming growth factor-beta in the border zone and NIZ.

CONCLUSIONS

The results indicate that therapy with amlodipine and enalapril during healing after reperfused MI limits structural vascular remodeling in the NIZ, probably by different mechanisms.

Vascular signaling pathways in the metabolic syndrome

There are several potential cellular and molecular pathways whereby cardiovascular risk factors act through very specific signal transduction pathways in the formation of atherosclerosis, as seen often in the metabolic syndrome. Many examples point to multiple postreceptor defects in the insulin signaling pathway in vascular tissue, however, there are differences in the insulin receptor pathway in vascular tissue compared with skeletal muscle or fat. In addition to insulin receptors, insulin may affect atherosclerotic changes in the vascular cells via stimulation of insulin-like growth factor-1 receptors and their signaling pathway. Insulin also causes activation of the vascular renin-angiotensin system in both vascular smooth muscle cells and endothelial cells. Insulin-activated tissue renin-angiotensin system leads to increased cell growth and contributes to the cause of atherosclerosis. The fact that agents that inhibit the renin-angiotensin system also block insulin-mediated renin-angiotensin system expression and cell growth reinforces the potential implication of a vascular insulin-renin-angiotensin system pathway. Finally, novel substances such as the adipokines, factors produced from fat cells, reveal new risk factors in the metabolic syndrome and offer further evidence for a link between insulin resistance and accelerated atherosclerosis.