Reduction of resistance artery stiffness by treatment with the AT(1)-receptor antagonist losartan in essential hypertension

Single nucleotide polymorphism (SNP) rs4291 of the angiotensin-converting enzyme (ACE) gene is associated with the response to losartan treatment in hypertensive patients

Arterial hypertension is characterized by systolic pressure ≥ 140 mmHg and/or diastolic pressure ≥ 90 mmHg and its treatment consists of the use of antihypertensive drugs, as losartan and hydrochlorothiazide. Blood pressure is regulated by angiotensin-converting enzyme (ACE) and polymorphisms in the ACE gene are associated to a greater predisposition to hypertension and response to treatment. The aim of this study was to evaluate the association of genetic polymorphisms of ACE rs4363, rs4291 and rs4335 and the response to antihypertensive drugs in hypertensive patients from Ouro Preto/MG, Brazil. A case-control study was carried out with 87 hypertensive patients being treated with losartan and 75 with hydrochlorothiazide, who answered a questionnaire and had blood samples collected. Biochemical analyzes were performed on serum using UV/Vis spectrophotometry and identification of ACE variants rs4363, rs4291 and rs4335 was performed by real-time PCR using the TaqMan® system. Univariate logistic regression test was performed to compare categorical data in STATA 13.0 software. The results showed that there was an influence of ACE polymorphisms on the response to losartan, demonstrating that AT or TT genotypes of rs4291 were more frequent in the group of controlled AH (54.9%), indicating that these individuals are 2.8 times more likely to of being controlled AH (95% CI 1.12-6.80, p. =0.026) compared to those with AA genotype. In contrast, no influence of ACE polymorphisms on the response to hydrochlorothiazide was observed. In conclusion, the presence of the T allele of the rs4291 variant was associated to controled blood pressure when losartan was used as an antihypertensive agent. These results show the importance of pharmacogenetic studies to detect genetic characteristics, enabling therapeutic individuality and reducing costs for the healthcare system.

New Dawn for Atherosclerosis: Vascular Endothelial Cell Senescence and Death

Endothelial cells (ECs) form the inner linings of blood vessels, and are directly exposed to endogenous hazard signals and metabolites in the circulatory system. The senescence and death of ECs are not only adverse outcomes, but also causal contributors to endothelial dysfunction, an early risk marker of atherosclerosis. The pathophysiological process of EC senescence involves both structural and functional changes and has been linked to various factors, including oxidative stress, dysregulated cell cycle, hyperuricemia, vascular inflammation, and aberrant metabolite sensing and signaling. Multiple forms of EC death have been documented in atherosclerosis, including autophagic cell death, apoptosis, pyroptosis, NETosis, necroptosis, and ferroptosis. Despite this, the molecular mechanisms underlying EC senescence or death in atherogenesis are not fully understood. To provide a comprehensive update on the subject, this review examines the historic and latest findings on the molecular mechanisms and functional alterations associated with EC senescence and death in different stages of atherosclerosis.

Effects of Long-Term Intervention with Losartan, Aspirin and Atorvastatin on Vascular Remodeling in Juvenile Spontaneously Hypertensive Rats

Hypertension in adolescents is associated with adverse cardiac and vascular events. In addition to lowering blood pressure, it is not clear whether pharmacological therapy in early life can improve vascular remodeling. This study aimed to evaluate the effects of long-term administration of losartan, aspirin, and atorvastatin on vascular remodeling in juvenile spontaneously hypertensive rats (SHRs). Losartan, aspirin, and atorvastatin were administered via gavage at doses of 20, 10, and 10 mg/kg/day, respectively, on SHRs aged 6-22 weeks. Paraffin sections of the blood vessels were stained with hematoxylin-eosin (H&E) and Sirius Red to evaluate the changes in the vascular structure and the accumulation of different types of collagen. The plasma levels of renin, angiotensin II (Ang II), aldosterone (ALD), endothelin-1 (ET-1), interleukin-6 (IL-6), and neutrophil elastase (NE) were determined using ELISA kits. After the 16-week treatment with losartan, aspirin, and atorvastatin, the wall thickness of the thoracic aorta and carotid artery decreased. The integrity of the elastic fibers in the tunica media was maintained in an orderly manner, and collagen deposition in the adventitia was retarded. The plasma levels of renin, ALD, ET-1, IL-6, and NE in the SHRs also decreased. These findings suggest that losartan, aspirin, and atorvastatin could improve vascular remodeling beyond their antihypertensive, anti-inflammatory, and lipid-lowering effects. Many aspects of the protection provided by pharmacological therapy are important for the prevention of cardiovascular diseases in adults and older adults.

Arteriosclerosis and Atherosclerosis Assessment in Clinical Practice: Methods and Significance

Alongside cancer, cardiovascular disease (CVD) exhibits the highest rates of morbidity and mortality globally, in western society as well as in Asian countries. Aging is a serious problem for the Asian population as progression toward a super-aged society is moving at a remarkably high rate. This increased rate of aging leads to increased CVD risk and, consequently, high CVD incidence. However, aging is not the only deleterious factor of vascular problems; hypertension, hypercholesterolemia, diabetes mellitus, and kidney disease may induce atherosclerosis and arteriosclerosis (i.e., arterial stiffening), and the progression of these diseases ultimately leads to cardiovascular, cerebrovascular, chronic kidney, or peripheral artery disease. Despite the existence of several guidelines on the treatment of risk factors such as hypertension and CVD, there is still an ongoing debate regarding the clinical need for assessment of arteriosclerosis and atherosclerosis, which act as a bridge between cardiovascular risk factors and CVD. In other words, although arteriosclerosis and atherosclerosis are essential to our understanding of vascular diseases, the need for additional tests beyond the conventional diagnosis method remains disputed. This is presumably due to insufficient discussion on how to apply such tests in clinical practice. This study aimed to fill this gap.

Drug-Related Orthostatic Hypotension: Beyond Anti-Hypertensive Medications

Orthostatic hypotension (OH) is an abnormal blood pressure response to standing, which is associated with an increased risk of adverse outcomes such as syncope, falls, cognitive impairment, and mortality. Medical therapy is one the most common causes of OH, since numerous cardiovascular and psychoactive medications may interfere with the blood pressure response to standing, leading to drug-related OH. Additionally, hypotensive medications frequently overlap with other OH risk factors (e.g., advanced age, neurogenic autonomic dysfunction, and comorbidities), thus increasing the risk of symptoms and complications. Consequently, a medication review is recommended as a first-line approach in the diagnostic and therapeutic work-up of OH, with a view to minimizing the risk of drug-related orthostatic blood pressure impairment. If symptoms persist after the review of hypotensive medications, despite adherence to non-pharmacological interventions, specific drug treatment for OH can be considered. In this narrative review we present an overview of drugs acting on the cardiovascular and central nervous system that may potentially impair the orthostatic blood pressure response and we provide practical suggestions that may be helpful to guide medical therapy optimization in patients with OH. In addition, we summarize the available strategies for drug treatment of OH in patients with persistent symptoms despite non-pharmacological interventions.

Brain Angiotensin Type-1 and Type-2 Receptors in Physiological and Hypertensive Conditions: Focus on Neuroinflammation

PURPOSE OF REVIEW

To review recent data that suggest opposing effects of brain angiotensin type-1 (AT1R) and type-2 (AT2R) receptors on blood pressure (BP). Here, we discuss recent studies that suggest pro-hypertensive and pro-inflammatory actions of AT1R and anti-hypertensive and anti-inflammatory actions of AT2R. Further, we propose mechanisms for the interplay between brain angiotensin receptors and neuroinflammation in hypertension.

RECENT FINDINGS

The renin-angiotensin system (RAS) plays an important role in regulating cardiovascular physiology. This includes brain AT1R and AT2R, both of which are expressed in or adjacent to brain regions that control BP. Activation of AT1R within those brain regions mediate increases in BP and cause neuroinflammation, which augments the BP increase in hypertension. The fact that AT1R and AT2R have opposing actions on BP suggests that AT1R and AT2R may have similar opposing actions on neuroinflammation. However, the mechanisms by which brain AT1R and AT2R mediate neuroinflammatory responses remain unclear. The interplay between brain angiotensin receptor subtypes and neuroinflammation exacerbates or protects against hypertension.

Effects of allisartan isoproxil on blood pressure and target organ injury in patients with mild to moderate essential hypertension

Evidence has shown that angiotensin II type 1 receptor antagonists have lower blood pressure and have target organ protective effects, but this is not the case for the drug allisartan isoproxil. The aim of this study was to evaluate the effects of allisartan isoproxil on blood pressure and target organ injury in patients with mild to moderate essential hypertension.In total, 80 essential hypertensive participants were randomly divided into an allisartan group and a nifedipine group (n = 40 per group), and their blood pressure was measured once per month for 6 months. A 2-dimensional echocardiogram was performed at baseline and at the end of the study. The serum levels of renal injury indexes, endothelial function markers, inflammatory factors, blood biochemical assays and urinary measurements were determined at baseline and at 6 months.At the end of the study, both systolic and diastolic blood pressure were significantly decreased in the allisartan group compared with baseline and showed the same antihypertensive effect as the nifedipine group. Meanwhile, the left ventricular remodeling, 24-hours levels of urinary microalbumin, endothelial dysfunction, and arterial stiffness were all significantly improved compared with that of the baseline and the nifedipine group (all P < .05).The present study showed that allisartan isoproxil had favorable blood pressure lowering and heart, renal, and endothelial protective effects in patients with mild to moderate essential hypertension.

Changes in extracellular matrix in subcutaneous small resistance arteries of patients with essential hypertension

BACKGROUND

In the development of hypertensive microvascular remodeling, a relevant role may be played by changes in extracellular matrix proteins. Aim of this study was the to evaluate some extracellular matrix components within the tunica media of subcutaneous small arteries in 9 normotensive subjects and 12 essential hypertensive patients, submitted to a biopsy of subcutaneous fat from the gluteal or the anterior abdominal region.

PATIENTS AND METHODS

Subcutaneous small resistance arteries were dissected and mounted on an isometric myograph, and the tunica media to internal lumen ratio was measured. In addition, fibronectin, laminin, transforming growth factor-beta-1 (TGF-β1) and emilin-1 contents within the tunica media were evaluated by immunofluorescence and relative immunomorphometrical analysis (immunopositivity % of area). The total collagen content and collagen subtypes within the tunica media were evaluated using both Sirius red staining (under polarized light) and immunofluorescence assay.

RESULTS

Normotensive controls had less total and type III collagen in respect with hypertensive patients. Fibronectin and TGF-β1 tunica media content was significantly greater in essential hypertensive patients, compared with normotensive controls, while laminin and emilin-1 tunica media content was lesser in essential hypertensive patients, compared with normotensive controls. A significant correlation was observed between fibronectin tunica media content and media to lumen ratio.

CONCLUSIONS

Our results indicate that, in small resistance arteries of patients with essential hypertension, a relevant fibrosis may be detected; fibronectin and TGF-β1 tunica media content is increased, while laminin and emilin-1 content is decreased; these changes might be involved in the development of small resistance artery remodeling in humans.

Oxidative Stress and Hypertensive Diseases

It has become clear that reactive oxygen species (ROS) contribute to the development of hypertension via myriad effects. ROS are essential for normal cell function; however, they mediate pathologic changes in the brain, the kidney, and blood vessels that contribute to the genesis of chronic hypertension. There is also emerging evidence that ROS contribute to immune activation in hypertension. This article discusses these events and how they coordinate to contribute to hypertension and its consequent end-organ damage.

Effect of aliskiren on vascular remodelling in small retinal circulation

BACKGROUND

In hypertension, changes in small arterial structure are characterized by an increased wall-to-lumen ratio (WLR). These adaptive processes are modulated by the rennin-angiotensin system. It is unclear whether direct renin inhibitors exert protective effects on small arteries in hypertensive patients.

METHODS

In this double-blind, randomized, placebo-controlled study (http://www.clinicaltrials.gov: NCT01318395), 114 patients with primary hypertension were randomized to additional therapy with either placebo or aliskiren 300 mg for 8 weeks after 4 weeks of standardized open-label treatment with valsartan 320 mg (run-in phase). Parameter of arteriolar remodelling was WLR of retinal arterioles (80 - 140 μm) assessed noninvasively and in vivo by scanning laser Doppler flowmetry (Heidelberg Engineering, Germany). In addition, pulse wave analysis (SphygmoCor, AtCor Medical, Australia) and pulse pressure (PP) amplification were determined.

RESULTS

In the whole study population, no clear effect of additional therapy with aliskiren on vascular parameters was documented. When analyses were restricted to patients with vascular remodelling, defined by a median of WLR more than 0.3326 (n = 57), WLR was reduced after 8 weeks by the treatment with aliskiren compared with placebo (-0.044 ± 0.07 versus 0.0043 ± 0.07, P = 0.015). Consistently, after 8 weeks of on-top treatment with aliskiren, there was an improvement of PP amplification compared with placebo (0.025 ± 0.07 versus -0.034 ± 0.08, P = 0.013), indicative of less stiff arteries in the peripheral circulation.

CONCLUSION

Thus, our data indicate that treatment with aliskiren, given on top of valsartan therapy, improves altered vascular remodelling in hypertensive patients.

Angiotensin receptor blockers (ARB) outperform angiotensin-converting enzyme (ACE) inhibitors on ischemic stroke prevention in patients with hypertension and diabetes - A real-world population study in Taiwan

BACKGROUND

Combination therapy with angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARB) has been stressed for its comprehensive blocking of the renin-angiotensin-aldosterone system, but the evidence for their respective safety and efficacy, in particular with stroke prevention, is still insufficient in population-based follow-up studies in the real world.

METHODS

Using Taiwan's National Health Insurance claims data, we identified 5445 subjects aged 18years and older who had newly diagnosed hypertension in 1997-2010, from them diagnosed type 2 diabetes later. Among them, 2161 patients took ACEI, 1703 patients took ARB, 165 patients took both ACEI and ARB, and 1416 patients had neither.

RESULTS

During the follow-up period, the stroke incidence density was the lowest (23.02 per 1000person-years) in ARB group, followed by the group with neither medication, the ACEI group, and ARB/ACEI combination group (24.06, 30.23, and 37.86 per 1000person-years, respectively). Compared with patients taking neither medication, the adjusted hazard ratios (HRs) were 1.27 (95% CI 1.02-1.58) for ACEI group, 0.95 (95% CI 0.74-1.22) for ARB group, and 1.56 (95% CI 0.99-2.47) for ARB/ACEI combined group. Greater reduction in risk of stroke was observed in patients with high dose ARB (adjusted HR=0·42, 95% CI 0·24-0·75).

CONCLUSION

Our findings support the practice that ARBs could be used, from the perspective of stroke prevention, as a first-line antihypertensive drug for patients with both hypertension and diabetes. The group with ARB regimen reduces 26% of stroke in contrast to the group with ACEI regimen.

Effects of different types of antihypertensive agents on arterial stiffness: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

This system review and meta-analysis was conducted to systematically review and analyze the clinical benefits of different antihypertensive agents in improving arterial stiffness in hypertensive patients.

METHODS

PubMed database was searched for randomized controlled trials (RCTs) evaluating the effects of angiotensin receptor blockers (ARB) or other types of antihypertensive agents on pulse wave velocity (PWV). The main indicators were the improvements of PWV and augmentation index (AI) before and after randomized treatments with antihypertensive agents. For the studies that only provided the mean and standard deviation of the indicators before and after randomization, the standardized mean difference (SMD) method was directly applied to combine the mean and standard deviation of various indicators after the treatment. For the studies provided the mean and standard deviation of the changes of the indicators, the weighted mean difference (MD) method was applied to combine the mean and standard deviation of the therapeutic effect.

RESULTS

Ten RCT studies were included and the sample sizes range from 40 to 201 (total: 938). Four studies provided the changes of PWV before and after randomization, the pooled analysis showed that the changes of PWV in ARB group were not significantly higher than other antihypertensive agents [MD: 125.76, 95% confidence interval (CI): -78.70 to 330.23, P=0.23]; 4 studies provided the PWV values before and after randomization, the PWV values in ARB group were not significantly superior (SMD: 0.04, 95% CI: -0.16 to 0.24, P=0.71). Three studies provided the changes of AI before and after randomization, the ability of ARB to lower the level of the AI was superior to other antihypertensive agents (MD: 8.94, 95% CI: 2.18-5.71, P=0.01); 2 studies provided the AI value after randomization, the abilities of ARB and other anti-hypertensive agents to improve the AI were similar (SMD: 0.03, 95% CI: -1.20 to 1.26, P=0.06).

CONCLUSIONS

The effect of ARB on the improvement of the PWV level is not superior to other types of antihypertensive agents, but ARB is superior to other types of antihypertensive agents for improving the AI level. Overall, to improve of arterial stiffness, ARB maybe is superior to other antihypertensive agents.

Angiotensin-(1-7) prevents angiotensin II-induced fibrosis in cremaster microvessels

OBJECTIVE

The effect of the heptapeptide hormone Ang-(1-7) on microvascular fibrosis in rats with Ang II-induced hypertension was investigated, since vascular fibrosis/remodeling plays a prominent role in hypertension-induced end-organ damage and Ang-(1-7) inhibits vascular growth and fibrosis.

METHODS

Fibrosis of cremaster microvessels was studied in male Lewis rats infused with Ang II and/or Ang-(1-7).

RESULTS

Ang II elevated systolic blood pressure by approximately 40 mmHg, while blood pressure was not changed by Ang-(1-7). Ang II increased perivascular fibrosis surrounding 20-50 μm arterioles as well as interstitial fibrosis; coadministration of Ang-(1-7) prevented the increases in fibrosis. The fibrotic factor CTGF and phospho-Smad 2/3, which upregulates CTGF, were increased by Ang II; this effect was prevented by coadministration of Ang-(1-7). Although TGF-β phosphorylates Smad 2/3, TGF-β was no different among treatment groups. In contrast, Ang II increased the MAP kinase phospho-ERK1/2, which also phosphorylates Smad; p-ERK was reduced by Ang-(1-7). Ang-(1-7), in the presence or absence of Ang II, upregulated the MAP kinase phosphatase DUSP1.

CONCLUSIONS

These results suggest that Ang-(1-7) increases DUSP1 to reduce MAP kinase/Smad/CTGF signaling and decrease fibrosis in resistance arterioles, to attenuate end-organ damage associated with chronic hypertension.

Interactions between macro- and micro-circulation: are they relevant?

Macrovasculature, microvasculature, and the heart are the main determinants of the structure and function of the circulatory system. Due to viscoelastic properties of large arteries, the pulsatile pressure and flow that result from intermittent ventricular ejection are smoothed out, so that microvasculature mediates steadily the delivery of nutrients and oxygen to tissues. The disruption of this function, which occurs when microvascular structure develops, mainly in response to hypertension, leads to end-organ damage. Microvascular structure is not only the site of vascular resistance but probably also the origin of most of the wave reflections generating increased central systolic blood pressure in the elderly. Many data of the literature suggest that hypertension-related damage to the micro and macrovascular system may be corrected by pharmacological agents. Among them, β-blocking agents and diuretics have a negligible effect on microvascular structure, while renin-angiotensin system antagonists and calcium entry blockers have favorable actions, improving large artery mechanics and possibly reducing central wave reflections. Central pulse pressure, indicative of changes in large conduit arteries is an independent determinant of vascular remodelling in small resistance arteries and might represent a main target of antihypertensive treatment.

Managing cardiovascular risk in overweight children and adolescents

The scientific, medical, and lay communities are currently confronted with a serious medical and public health problem related to the marked non-remitting worldwide epidemic of obesity. This ever-increasing prevalence of obesity is accompanied by a host of inherently associated co-morbidities. As a result, obesity is fast becoming the major cause of premature death in the developed world. As pediatric and adult cardiologists, we have seen a dramatic increase in office referrals of overweight and obese children and adolescents, who already have obesity-related degenerative disease processes such as hypertension, dyslipidemia, the metabolic syndrome, and type 2 diabetes mellitus, as well as manifestations of early preclinical atherosclerotic cardiovascular disease, not previously observed in this age group. This article presents a review of the literature and recent scientific statements and recommendations issued by the American Heart Association (AHA) and the American Academy of Pediatrics (AAP) regarding the metabolic abnormalities associated with obesity, including newer identification and treatment strategies for obesity, dyslipidemia, and early subclinical coronary artery disease seen in high-risk children and adolescents.

Circulating endothelial progenitor cells, microvascular density and fibrosis in obesity before and after bariatric surgery

It is not known whether, in obesity, the capillary density or the number of circulating endothelial progenitor cells (EPCs) are reduced, or whether fibrosis of small vessels is also present. In addition, possible effects of weight reduction on these parameters have never been evaluated. Therefore, we investigated EPCs and capillary density in 25 patients with severe obesity, all submitted to bariatric surgery, and in 18 normotensive lean subjects and 12 hypertensive lean patients as controls. All patients underwent a biopsy of subcutaneous fat during bariatric surgery. In five patients, a second biopsy was obtained after consistent weight loss, about 1 year later, during a surgical intervention for abdominoplasty. EPCs and capillary density were reduced in obesity, and EPCs were significantly increased after weight reduction. Vascular collagen content was clearly increased in obese patients. No significant difference in vascular collagen was observed between normotensive obese patients and hypertensive obese patients. After pronounced weight reduction, collagen content was nearly normalized. No difference in stress-strain relation was observed among groups or before and after weight loss. In conclusion, our data suggest that microvascular rarefaction occurs in obesity. EPCs were significantly reduced in obese patients. Pronounced weight loss induced by bariatric surgery seems to induce a significant improvement of EPC number, but not of capillary rarefaction. A pronounced fibrosis of subcutaneous small resistance arteries is present in obese patients, regardless of the presence of increased blood pressure values. Consistent weight loss induced by bariatric surgery may induce an almost complete regression of microvascular fibrosis.

Angiotensin II type 1A receptors in vascular smooth muscle cells do not influence aortic remodeling in hypertension

Vascular injury and remodeling are common pathological sequelae of hypertension. Previous studies have suggested that the renin-angiotensin system acting through the type 1 angiotensin II (AT(1)) receptor promotes vascular pathology in hypertension. To study the role of AT(1) receptors in this process, we generated mice with cell-specific deletion of AT(1) receptors in vascular smooth muscle cells using Cre/Loxp technology. We crossed the SM22α-Cre transgenic mouse line expressing Cre recombinase in smooth muscle cells with a mouse line bearing a conditional allele of the Agtr1a gene (Agtr1a (flox)), encoding the major murine AT(1) receptor isoform (AT(1A)). In SM22α-Cre(+)Agtr1a (flox/flox) (SMKO) mice, AT(1A) receptors were efficiently deleted from vascular smooth muscle cells in larger vessels but not from resistance vessels such as preglomerular arterioles. Thus, vasoconstrictor responses to angiotensin II were preserved in SMKO mice. To induce hypertensive vascular remodeling, mice were continuously infused with angiotensin II for 4 weeks. During infusion of angiotensin II, blood pressures increased significantly and to a similar extent in SMKO and control mice. In control mice, there was evidence of vascular oxidative stress indicated by enhanced nitrated tyrosine residues in segments of aorta; this was significantly attenuated in SMKO mice. Despite these differences in oxidative stress, the extent of aortic medial expansion induced by angiotensin II infusion was virtually identical in both groups. Thus, vascular AT(1A) receptors promote oxidative stress in the aortic wall but are not required for remodeling in angiotensin II-dependent hypertension.

[Isolated systolic hypertension. An independent disease]

Hypertension can be classified based on certain criteria, such as severity, existence of specific end-organ damage, or the dominant blood pressure subphenotype so that isolated diastolic hypertension (IDH), mixed systolic-diastolic hypertension (SDH), and isolated systolic hypertensive (ISH) states can be defined. The FRAMINGHAM study was the first to demonstrate a continuous increase of systolic blood pressure with age and a peak of diastolic pressure between 55 and 65 years of age. This results not only in a high prevalence of hypertension of approximately 50-80% beyond the age of 60 but also in a disproportionately high increase in isolated systolic hypertension. ISH develops either as a new condition mostly from the group of primary high-normal blood pressure or secondly through burnout of existing systolic-diastolic hypertension with highly progressive vascular ageing.The pathophysiological background lies in remodeling processes in the macrovascular and microvascular compartments with stiffening of conduit and peripheral arterial vessels. In clinical practice these processes are easy to measure by determining pulse wave velocity (PWV), the augmentation index, and pulse pressure. These parameters are closely related to cardiovascular and cerebrovascular morbidity and mortality ISH is not only a hypertension subphenotype but often indicates significant organ damage or may even be considered to be a secondary form of hypertension characterized by remodeled and stiffened arterial vessel walls and this condition is difficult to treat. It appears therefore that ISH warrants special therapeutic strategies with a focus on antiproliferative, antistiffening, anti-atherosclerotic, and vasodilating actions. As a result of the available data from the results of treatment studies it appears that renin-angiotensin system (RAS) blockers and calcium channel blockers (CCBs) are the preferred drugs for treatment of this condition.

Aging and arterial stiffness

Arterial walls stiffen with age. The most consistent and well-reported changes are luminal enlargement with wall thickening and a reduction of elastic properties at the level of large elastic arteries. Longstanding arterial pulsation in the central artery causes elastin fiber fatigue and fracture. Increased vascular calcification and endothelial dysfunction are also characteristic of arterial aging. These changes lead to increased pulse wave velocity, especially along central elastic arteries, and increases in systolic blood pressure and pulse pressure. Vascular aging is accelerated by coexisting cardiovascular risk factors, such as hypertension, metabolic syndrome and diabetes. Vascular aging is an independent risk factor for cardiovascular disease, from atherosclerosis to target organ damage, including coronary artery disease, stroke and heart failure. Various strategies, especially controlling hypertension, show benefit in preventing, delaying or attenuating vascular aging.

Comparing angiotensin II receptor blockers on benefits beyond blood pressure

The renin-angiotensin-aldosterone system (RAAS) is one of the main regulators of blood pressure, renal hemodynamics, and volume homeostasis in normal physiology, and contributes to the development of renal and cardiovascular (CV) diseases. Therefore, pharmacologic blockade of RAAS constitutes an attractive strategy in preventing the progression of renal and CV diseases. This concept has been supported by clinical trials involving patients with hypertension, diabetic nephropathy, and heart failure, and those after myocardial infarction. The use of angiotensin II receptor blockers (ARBs) in clinical practice has increased over the last decade. Since their introduction in 1995, seven ARBs have been made available, with approved indications for hypertension and some with additional indications beyond blood pressure reduction. Considering that ARBs share a similar mechanism of action and exhibit similar tolerability profiles, it is assumed that a class effect exists and that they can be used interchangeably. However, pharmacologic and dosing differences exist among the various ARBs, and these differences can potentially influence their individual effectiveness. Understanding these differences has important implications when choosing an ARB for any particular condition in an individual patient, such as heart failure, stroke, and CV risk reduction (prevention of myocardial infarction). A review of the literature for existing randomized controlled trials across various ARBs clearly indicates differences within this class of agents. Ongoing clinical trials are evaluating the role of ARBs in the prevention and reduction of CV rates of morbidity and mortality in high-risk patients.

Role of extracellular matrix in vascular remodeling of hypertension

PURPOSE OF REVIEW

Arterial stiffness due to alterations in extracellular matrix is one of the mechanisms responsible for increased peripheral resistance in hypertension. Recent evidence points to arterial stiffness as an independent predictor of cardiovascular events. This review focuses on recent advances in the biology of extracellular matrix proteins involved in hypertension-associated vascular changes.

RECENT FINDINGS

The vascular extracellular matrix is a complex heterogeneous tissue comprising collagens, elastin, glycoproteins, and proteoglycans. These constituents not only provide mechanical integrity to the vessel wall but also possess a repertoire of insoluble ligands that induce cell signaling to control proliferation, migration, differentiation, and survival. It is now evident that it is not only the quantity but also the quality of the new synthesized extracellular matrix that determines changes in vascular stiffness in hypertension. Also, the control of cross-linking and the interactions between the extracellular matrix and vascular cells seem to be important.

SUMMARY

It is now evident that some of the currently used antihypertensive therapies can correct vascular stiffness and fibrosis. A better understanding of molecular mechanisms underlying alterations in extracellular matrix in hypertension will provide insights into novel therapies to reduce arterial stiffness and will identify new roles of established antihypertensive drugs.

Altered structure of small cerebral arteries in patients with essential hypertension

OBJECTIVE

Structural alterations in the microcirculation may be considered an important mechanism of organ damage. An increased media-to-lumen ratio of subcutaneous small resistance arteries has been demonstrated to predict the development of cardiocerebrovascular events in hypertensive patients. Alterations in the structure of small cerebral arteries have been demonstrated in animal models of experimental or genetic hypertension. However, no evaluation with reliable techniques has ever been performed in humans.

DESIGN AND METHODS

Twenty-eight participants were included in the present study: they were 13 hypertensive patients and 15 normotensive individuals. All participants underwent a neurosurgical intervention for benign or malign tumors. A small portion of morphologically normal cerebral tissue was excised from surgical samples and examined. Cerebral small resistance arteries (relaxed diameter around 200 mum) were dissected and mounted on an isometric and isobaric myograph, and the tunica media to internal lumen ratio was measured. In addition, cerebral cortical microvessel density (MVD) was also evaluated. The tissue was sectioned and stained for CD31, and MVD was measured with an automated image analyzer (percentage of area stained). Blood pressure values were evaluated, before surgical intervention, by standard sphygmomanometry.

RESULTS

M/L was significantly greater and MVD significantly lower in hypertensive patients than that in normotensive individuals. No difference between groups in collagen content or mechanical properties of cerebral small arteries was observed.

CONCLUSION

Our results indicate that structural alterations of small cerebral vessels are present in hypertensive patients compared with normotensive individuals, similar to those previously observed in subcutaneous small arteries.

Angiotensin II, mitochondria, cytoskeletal, and extracellular matrix connections: an integrating viewpoint

Malfunctioning mitochondria strongly participate in the pathogenesis of cardiovascular damage associated with hypertension and other disease conditions. Eukaryotic cells move, assume their shape, resist mechanical stress, accommodate their internal constituents, and transmit signals by relying on the constant remodeling of cytoskeleton filaments. Mitochondrial ATP is needed to support cytoskeletal dynamics. Conversely, mitochondria need to interact with cytoskeletal elements to achieve normal motility, morphology, localization, and function. Extracellular matrix (ECM) quantity and quality influence cellular growth, differentiation, morphology, survival, and mobility. Mitochondria can sense ECM composition changes, and changes in mitochondrial functioning modify the ECM. Maladaptive ECM and cytoskeletal alterations occur in a number of cardiac conditions and in most types of glomerulosclerosis, leading to cardiovascular and renal fibrosis, respectively. Angiotensin II (ANG II), a vasoactive peptide and growth factor, stimulates cytosolic and mitochondrial oxidant production, eventually leading to mitochondrial dysfunction. Also, by inducing integrin/focal adhesion changes, ANG II regulates ECM and cytoskeletal composition and organization and, accordingly, contributes to the pathogenesis of cardiovascular remodeling. ANG II-initiated integrin signaling results in the release of transforming growth factor-β1 (TGF-β1), a cytokine that modifies ECM composition and structure, induces reorganization of the cytoskeleton, and modifies mitochondrial function. Therefore, it is possible to hypothesize that the depression of mitochondrial energy metabolism brought about by ANG II is preceded by ANG II-induced integrin signaling and the consequent derangement of the cytoskeletal filament network and/or ECM organization. ANG II-dependent TGF-β1 release is a potential link between ANG II, ECM, and cytoskeleton derangements and mitochondrial dysfunction. It is necessary to emphasize that the present hypothesis is among many other plausible explanations for ANG II-mediated mitochondrial dysfunction. A potential limitation of this proposal is that the results compiled here were obtained in different cells, tissues, and/or experimental models.

From mitochondria to disease: role of the renin-angiotensin system

Mitochondria are energy-producing organelles that conduct other key cellular tasks. Thus, mitochondrial damage may impair various aspects of tissue functioning. Mitochondria generate oxygen- and nitrogen-derived oxidants, being themselves major oxidation targets. Dysfunctional mitochondria seem to contribute to the pathophysiology of hypertension, cardiac failure, the metabolic syndrome, obesity, diabetes mellitus, renal disease, atherosclerosis, and aging. Mitochondrial proteins and metabolic intermediates participate in various cellular processes, apart from their well-known roles in energy metabolism. This emphasizes the participation of dysfunctional mitochondria in disease, notwithstanding that most evidences supporting this concept come from animal and cultured-cell studies. Mitochondrial oxidant production is altered by several factors related to vascular pathophysiology. Among these, angiotensin-II stimulates mitochondrial oxidant release leading to energy metabolism depression. By lowering mitochondrial oxidant production, angiotensin-II inhibition enhances energy production and protects mitochondrial structure. This seems to be one of the mechanisms underlying the benefits of angiotensin-II inhibition in hypertension, diabetes, and aging rodent models. If some of these findings can be reproduced in humans, they would provide a new perspective on the implications that RAS-blockade can offer as a therapeutic strategy. This review intends to present available information pointing to mitochondria as targets for therapeutic Ang-II blockade in human renal and CV 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.

Changes in extracellular matrix in subcutaneous small resistance arteries of patients with primary aldosteronism

CONTEXT AND OBJECTIVE

It has been previously demonstrated that aldosterone may possess a strong profibrotic action in vitro and in animal models of genetic or experimental hypertension. Our aim was to evaluate whether such a profibrotic action is present also in the human microcirculation.

DESIGN AND PATIENTS

We investigated 13 patients with primary aldosteronism, seven patients with essential hypertension, and 10 normotensive controls. All subjects were submitted to a biopsy of gluteal sc fat tissue. Small resistance arteries were dissected and mounted on an isometric myograph, and the tunica media to internal lumen ratio was measured.

MAIN OUTCOME MEASURES

The total collagen content within the tunica media was detected (Sirius red staining and image analysis), and collagen subtypes were evaluated using polarized light microscopy; under this condition thicker type I collagen fibers appear orange or red, whereas thinner type III collagen fibers are yellow or green.

RESULTS

Tunica media to internal lumen ratio was significantly increased in primary aldosteronism and in essential hypertension compared with normotensive controls. Clinic blood pressure values were similar in primary aldosteronism and in essential hypertension, and greater than in normotensive controls. Normotensive controls had less total and type III collagen (3.23 +/- 0.58 and 1.60 +/- 0.22%, respectively) in respect to the two hypertensive groups (P < 0.001). Total collagen and type III vascular collagen were significantly greater in primary aldosteronism (total collagen, 8.17 +/- 1.38%; type III collagen, 6.06 +/- 0.74%; P < 0.05) than in essential hypertension (total collagen, 6.84 +/- 1.15%; type III collagen, 5.25 +/- 0.80%).

CONCLUSIONS

Our results indicate that, in small resistance arteries of patients with primary aldosteronism, a pronounced fibrosis may be detected, even more evident than in blood-pressure-matched patients with essential hypertension.

Postural Blood Pressure Changes and Orthostatic Hypotension in the Elderly Patient

With age our ability to maintain haemodynamic homeostasis during position changes becomes less effective. This predisposes elderly patients to significant changes in blood pressure upon standing and orthostatic hypotension (OH). The prevalence of OH varies according to the population being studied. A range of between 5% and 60% has been reported with the lower rate in elderly individuals living in the community and higher rates in those living in an institution or in the acute-care setting. Multiple factors have been linked to OH including age, bed rest, low body mass index and medications. Although antihypertensive medications can theoretically, as a group, worsen OH, the majority of cross-sectional studies have found no association. In addition, prospective randomised trials have demonstrated an improvement in postural blood pressure (PBP) changes with antihypertensive medications. When considering the individual classes, peripheral vasodilators, specifically alpha-adrenoceptor antagonists and nondihydropyridine calcium channel antagonists, can exacerbate PBP changes and lead to OH. ACE inhibitors, angiotensin-receptor antagonists and beta-adrenoceptor antagonists with intrinsic sympathomimetic activity are less likely to worsen OH. Careful management of electrolyte disturbance can decrease the risk of developing OH with diuretic use. With the aging population, this problem will be encountered by the clinicians at a much higher rate. A detailed patient history, an accurate orthostatic blood pressure measurement and careful evaluation of the autonomic nervous system can provide clinical guidance for management of OH. In hypertensive individuals with no pre-treatment OH, the use of antihypertensive medication can be safe and lead to a low risk of developing OH. In individuals with pre-treatment OH or who develop OH while on antihypertensive medications avoidance of the classes that may exacerbate OH and a judicious use of antihypertensive classes that may improve PBP changes may be safe and adequate treatment.

Concerted action of the renin-angiotensin system, mitochondria, and antioxidant defenses in aging

Angiotensin-converting enzyme inhibitors (ACEi) and AT-1 receptor blockers (ARB) are two types of drugs that inhibit the renin-angiotensin system (RAS), and can attenuate the progression to cardiac and/or renal functional impairment, secondary to diverse pathologies. Some of the beneficial effects of ACEi and ARB occur independently of the ability of these drugs to reduce arterial blood pressure. Both, in animals, and in humans, we observed an enhancement of antioxidant defenses that occurred after treatment with ACEi. Based on these results, we postulate that some of the beneficial health effects associated to RAS inhibition can be ascribed to the prevention of oxidant-mediated damage. Furthermore, considering that: (i). RAS inhibition attenuates certain age-associated degenerative changes; (ii). aging was postulated to result from the accumulation of oxidant-mediated damage; and (iii). mitochondria are a major source of oxidants, we studied potential associations among RAS inhibition, mitochondrial function and production of oxidants and nitric oxide, and aging. The results obtained suggest, that RAS inhibitors, i.e. enalapril and losartan, can protect against the effects of aging by attenuating oxidant damage to mitochondria, and in consequence, they preserve mitochondrial function. The mechanism(s) explaining such attenuation of oxidant damage can relay on a reduction of the ANG-II-dependent generation of superoxide and/or an increased detoxification of reactive nitrogen and oxygen species by recomposition of antioxidant defense levels.

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.

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.

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.

Comparative antihypertensive efficacy of olmesartan: comparison with other angiotensin II receptor antagonists

Hypertension is a major risk factor for cardiovascular morbidity and mortality. Effective control of elevated blood pressure (BP) has been shown to reduce this risk. Early studies of risk reduction assumed that the mechanism by which BP was lowered had little impact on the benefit obtained. Recent evidence, however, suggests that agents that inhibit the renin-angiotensin system may be particularly beneficial. The results of the recent Heart Outcomes Prevention Evaluation (HOPE) trial suggest that angiotensin-converting enzyme (ACE) inhibitors have a greater impact on cardiovascular morbidity and mortality than would be anticipated from their antihypertensive effects alone. Angiotensin receptor blockers, the other major class of antihypertensive drugs that inhibit the renin-angiotensin system, have not been widely tested in outcomes trials, but early results suggest that they are beneficial for controlling target organ damage that is related to hypertension. Furthermore, unlike ACE inhibitors, these agents have a side-effect profile that is similar to that of placebo. Based on their efficacy in controlling hypertension and their wider health benefits, together with minimal side effects, angiotensin II (A II) receptor blockers should be considered as first-line agents for the treatment of hypertension, particularly in patients with other cardiovascular risk factors. Preliminary evidence suggests that olmesartan, an A II receptor blocker currently being evaluated for approval for clinical use, may provide antihypertensive efficacy that is superior to other members of the class.

Effects of antihypertensive drugs on vascular remodeling: do they predict outcome in response to antihypertensive therapy?

Remodeling of large and small arteries in hypertension contributes to elevation of blood pressure, and may participate in the complications of hypertension. Large arteries exhibit increased lumen size, thickened media with increased collagen deposition, and decreased compliance, which contributes to raised systolic blood pressure and pulse pressure. In small (resistance) arteries smooth muscle cells are restructured around a smaller lumen, without true hypertrophy, particularly in milder forms of hypertension, whereas in severe forms and in secondary hypertension hypertrophic remodeling has been reported. Endothelial dysfunction occurs in many patients, with prevalence similar to that of left ventricular hypertrophy. Treatment with angiotensin-converting enzyme inhibitors, angiotensin receptor subtype 1 antagonists and long-acting calcium channel blockers has corrected changes in large and small arteries in hypertensive patients. Treatment with beta-blockers did not modify either structure or function of small arteries. Improved outcomes were reported in clinical trials with drugs that exert vascular protective effects, such as angiotensin-converting enzyme inhibitors and angiotensin receptor subtype 1 antagonists, as well as with those that do not appear to improve vascular structure or function. Recent trials suggest that these different drugs may provide similar benefits essentially through blood pressure lowering, although some minor differences between drugs have been noted. For example, the alpha-blocker doxasozin has been associated with worse outcomes (heart failure) than have diuretics. That hard end-point clinical trials have not demonstrated any advantages of agents with vasculoprotective properties may relate in part to the relatively short duration of some of these multicenter trials (3-5 years). Another contributing factor may be the low number of events with each drug class in the longer trials. Thus, current evidence does not support the rational expectation that vasculoprotective antihypertensive agents will be associated with better outcomes in hypertensive patients, possibly because of limitations of these trials.

Small artery remodeling in hypertension: can it be corrected?

Vascular structure, function, and mechanics are altered in hypertension, which contributes to an important degree to complications of elevated blood pressure. Vascular hypertrophy with collagen deposition and increased stiffness is found in large arteries, whereas in small arteries, smooth muscle cells are restructured around a smaller lumen, and there is no net growth of the vascular wall, particularly in milder forms of hypertension. Hypertrophic remodeling and increased small artery stiffness may be found in more severe hypertension. Endothelial dysfunction occurs in large or smaller vessels in a variable percentage of patients, particularly in presence of other risk factors such as diabetes, smoking, dyslipidemia, and advanced atherosclerosis. In clinical trials, 1-year treatment with angiotensin-converting enzyme inhibitors, angiotensin AT1 receptor antagonists, and long-acting calcium channel blockers corrected small artery structure and endothelial dysfunction in hypertensive patients, whereas beta-adrenergic receptor blockers did not. Improved outcomes in hypertensive patients demonstrated in recent trials with some but not others of these agents could be a consequence, at least in part, of vascular protection offered by some antihypertensive agents.

Small artery remodeling is the most prevalent (earliest?) form of target organ damage in mild essential hypertension

BACKGROUND

The heart and blood vessels are exposed to elevated blood pressure (BP) in hypertensive patients, but their changes in response to BP or non-hemodynamic stimuli may be different, and occur with different time-courses. To evaluate this, we studied the prevalence of structural and functional alterations of resistance arteries and cardiac hypertrophy in patients with mild essential hypertension.

METHODS

Resistance arteries were dissected from gluteal subcutaneous tissue from 38 hypertensive patients (47 +/- 1 years; 71% male; BP 148 +/- 2/99 +/- mmHg), studied on a pressurized myograph, and compared to those from 10 normotensives (44 +/- 3 years; 40% male; BP 113 +/- 4/76 +/- 2 mmHg).

RESULTS

The prevalence of abnormal structure (media-to-lumen ratio, M/L) and impaired endothelial function (maximal acetylcholine response) was 97 and 58% (abnormal was defined as greater than mean + 1 SD of normotensives), or 63 and 34% (abnormal defined as greater than mean +/- 2SD). Thirty four percent of hypertensive patients exhibited left ventricular hypertrophy by echocardiography. When grouped into tertiles according to increasing ambulatory systolic BP (SBP), the highest BP tertile showed increased M/L (P< 0.01) and left ventricular mass index (LVMI, P < 0.05) and marginally decreased endothelial function (P= 0.07). LVMI was greatest in the tertile of patients with highest M/L (P< 0.05). Endothelial function was decreased in the tertile with greatest vascular stiffness (P< 0.01). By multivariate analysis, M/L correlated with ambulatory SBP (beta = 0.40, P= 0.02), and LVMI correlated with ambulatory SBP (beta = 0.41, P = 0.001) and body mass index (beta = 0.30, P< 0.05). Female sex influenced endothelial function negatively (beta = -0.63, P< 0.01).

CONCLUSION

Structural alterations of resistance arteries were demonstrated in most hypertensive patients, followed by endothelial dysfunction and cardiac hypertrophy in a smaller number of hypertensives. Small artery structural remodeling may precede most clinically relevant manifestations of target organ damage in mild essential hypertension.

Structure and mechanical properties of resistance arteries in hypertension: role of adhesion molecules and extracellular matrix determinants

Abnormalities of resistance arteries may play a role in the pathogenesis and pathophysiology of hypertension in experimental animals and humans. Vessels that, when relaxed, measure <400 microm in lumen diameter act as the major site of vascular resistance and include a network of small arteries (lumen approximately 100 to 400 microm) and arterioles (<100 microm). Because increased peripheral resistance is generated by a narrowed lumen diameter, significant effort has been focused on determining the mechanisms that reduce lumen size. Three important vascular components are clearly involved, including alterations of vascular structure, mechanics (stiffness), and function. Structural abnormalities comprise a reduced lumen diameter and thickening of the vascular media, resulting in an increased media-lumen ratio. Changes in the mechanical properties of an artery, particularly increased stiffness, may also result in a reduced lumen diameter. These vascular abnormalities may be caused or influenced by the expression and/or topographic localization of extracellular matrix components, such as collagen and elastin, and by changes in cell-extracellular fibrillar attachment sites, such as adhesion molecules like integrins. This article discusses the abnormalities of resistance arteries in hypertension and reviews the evidence suggesting an important role for adhesive and extracellular matrix determinants.

Effects of antihypertensive therapy on hypertensive vascular disease

Hypertension is associated with alterations in the structure, function, and mechanical properties of large and small arteries. Changes in the endothelium, smooth muscle cell, extracellular matrix, and possibly the adventitia, contribute to complications of hypertension. In large arteries, vascular hypertrophy is found, often with increased stiffness of media components. In small arteries, particularly in mild hypertension, rearrangement of smooth muscle cells around a smaller lumen without changes in media volume (eutrophic remodeling) occurs; in more severe hypertension, hypertrophic remodeling with increased vascular stiffness can be found. Vascular remodeling is accompanied by an increase in the extracellular matrix, particularly collagen deposition. Recent studies have demonstrated that vascular remodeling and endothelial dysfunction of small and large vessels may be normalized by treatment with some antihypertensive agents (angiotensin converting enzyme inhibitors, angiotensin AT(1) receptor antagonists, and long-acting calcium channel blockers). Angiotensin converting enzyme inhibitors have now been shown to improve outcomes in hypertensive patients, an effect that may in part be related to the vascular protective effects reviewed here.