Vascular Effects of Antihypertensive Drug Therapy

Maintenance over Time of the Effect Produced by Esmolol on the Structure and Function of Coronary Arteries in Hypertensive Heart Diseases

We previously observed that esmolol treatment for 48 h reduced vascular lesions in spontaneously hypertensive rats (SHRs). Therefore, we investigated whether this beneficial effect is persistent after withdrawal. Fourteen-month-old SHRs (SHR-Es) were treated with esmolol (300 μg/kg/min) or a vehicle for 48 h. Two separate groups were also given identical treatment, but they were then monitored for a further 1 week and 1 month after drug withdrawal. We analyzed the geometry and composition of the coronary artery, vascular reactivity and plasma redox status. Esmolol significantly decreased wall thickness (medial layer thickness and cell count), external diameter and cross-sectional area of the artery, and this effect persisted 1 month after drug withdrawal. Esmolol significantly improved endothelium-dependent relaxation by ACh (10⁻⁹–10⁻⁴ mol/L); this effect persisted 1 week (10⁻⁹–10⁻⁴ mol/L) and 1 month (10⁻⁶–10⁻⁴ mol/L) after withdrawal. Esmolol reduced the contraction induced by 5-HT (3 × 10⁻⁸–3 × 10⁻⁵ mol/L), and this effect persisted 1 week after withdrawal (10⁻⁶–3 × 10⁻⁵ mol/L). Esmolol increased nitrates and reduced glutathione, and it decreased malondialdehyde and carbonyls; this enhancement was maintained 1 month after withdrawal. This study shows that the effect of esmolol on coronary remodeling is persistent after treatment withdrawal in SHRs, and the improvement in plasma oxidative status can be implicated in this effect.

Impact of a Multichannel Blocker in Attenuating Intramyocardial Artery Remodeling in Hypertensive Rats through Increased Nitric Oxide Bioavailability

Dronedarone is recommended for the treatment of atrial fibrillation. However, we do not know its effect on vascular remodeling. This study was designed to assess whether dronedarone has the potential to improve the intramyocardial artery remodeling induced by chronic hypertension. Ten-month-old male spontaneously hypertensive rats (SHR) were randomly assigned to receive dronedarone (100 mg/kg) or vehicle. Age-matched male Wistar-Kyoto rats served as controls. After 14 days of treatment, we studied the structure (geometry and fibrosis) of the intramyocardial artery using histological analysis. Nitric oxide (NO) in plasma was analyzed. In the untreated SHR, we observed a significant increase in external diameter, lumen diameter, wall width, cross-sectional area, and collagen volume density, as was expected in the experimental model. Dronedarone induced a significant decrease in wall width, cross-sectional area, and collagen volume density in SHR-D in comparison with untreated SHR. The values obtained in SHR-D were similar in the WKY control group. We found significantly higher NO levels in plasma in SHR-D than in untreated SHR. Dronedarone improves the intramyocardial artery remodeling induced by chronic hypertension in SHR through increased nitric oxide bioavailability.

Vascular Aging and Disease of the Small Vessels

Cardiovascular events are the consequence of vascular damage at both the macro and microcirculatory level. The relationship between large stiffening artery and microvascular disease may be bidirectional, since wave reflection from microvascular sites could increase systolic blood pressure and pulse pressure, while transmission of increased arterial pulsatility to microvessels could represent a mechanism of damage. Hypertension and aging share similar mechanisms of vascular dysfunction. In fact, vascular remodelling, endothelial dysfunction and vascular stiffness are common features in hypertension and aging. Structural and functional changes in small arteries occur during normal and accelerated aging, possibly triggered by hypertension. A cross-talk may be present between large and small artery changes, interacting with pressure wave transmission and reflection, exaggerating cardiac, brain and kidney damage, and finally leading to cardiovascular and renal complications.

The protective effect of dronedarone on the structure and mechanical properties of the aorta in hypertensive rats by decreasing the concentration of symmetric dimethylarginine (SDMA)

BACKGROUND AND AIMS

Dronedarone is a new multichannel-blocking antiarrhythmic for the treatment of patients with atrial fibrillation. Our group has demonstrated that dronedarone produces regression of cardiac remodeling; however, its effect on the remodeling of the elastic arteries has not yet been reported. We aim to assess the effects of dronedarone on the regression of thoracic aortic remodeling in spontaneously hypertensive rats (SHRs).

METHOD

Ten-month-old male SHRs were randomly assigned to an intervention group (SHR-D), where the animals received dronedarone treatment (100 mg/kg), to a control group (SHR) where rats were given vehicle, or to a group (SHR-A) where they were given amiodarone. A fourth group of normotensive control rats (Wistar-Kyoto rats, WKY) was also added. After two weeks of treatment, we studied the structure, the elastic fiber content of the thoracic aorta using histological techniques and confocal microscopy, and the vascular mechanical properties using an organ bath and isometric tension analysis. A mass spectrometric determination of symmetric dimethylarginine (SDMA) concentrations was performed.

RESULTS

SHR group developed the classic remodeling expected from the experimental model: outward hypertrophic remodeling, increased elastic fiber content and wall stiffness. However, the SHR-D group showed statistically significantly lower values for aortic tunica media thickness, wall to lumen ratio, external diameter, cross-sectional area, volume density of the elastic fibers, wall stiffness, and aortic SDMA concentration when compared to the SHR group. These parameters were similar in the SHR and SHR-A groups. Interestingly, the values for tunica media thickness, volume density of the elastic fibers, wall stiffness, and SDMA concentration obtained from the SHR-D group were similar to those measured in the WKY group.

CONCLUSION

These results suggest that dronedarone improves the structure and passive mechanical properties of the thoracic aorta in hypertensive rats, and that this protective effect could be associated with a reduction in the concentration of aortic SDMA.

Dronedarone induces regression of coronary artery remodeling related to better global antioxidant status

Our group previously demonstrated that dronedarone induces regression of left ventricular hypertrophy in spontaneously hypertensive rats (SHRs). We assessed changes in vascular remodeling and oxidative stress following short-term use of this agent. The coronary artery was isolated from 10-month-old male SHRs treated with 100 mg kg^-1 dronedarone once daily for 14 days (SHR-D group), and age-matched untreated SHRs were used as hypertensive controls. We analyzed the geometry and composition of the artery and constructed dose-response curves for acetylcholine and serotonin (5-HT). We calculated a global score (OXY-SCORE) from plasma biomarkers of oxidative status: carbonyl levels, thiol levels, reduced glutathione levels, total antioxidant capacity, and superoxide anion scavenging activity. Finally, we analyzed asymmetric dimethylarginine (ADMA) concentrations in plasma. Dronedarone significantly decreased wall thickness (medial and adventitial layer thickness and cell count) and the cross-sectional area of the artery. Dronedarone significantly improved endothelium-dependent relaxation and reduced the contraction induced by 5-HT. The OXY-SCORE was negative in the SHR model group (suggesting an enhanced oxidative status) and was positive in the SHR-D group (suggesting enhanced antioxidant defense). Dronedarone significantly decreased the concentrations of ADMA. We conclude that dronedarone improves coronary artery remodeling in SHRs. The better global antioxidant status after treatment with dronedarone and decreased plasma ADMA levels could contribute to the cardiovascular protective effect of dronedarone.

Hemodynamic Consequences of Changes in Microvascular Structure

In hypertension, an increased media-to-lumen ratio of small resistance arteries might play an important role in the increase of vascular resistance, and may also be an adaptive response to the increased hemodynamic load. The presence of morphological alteration in the microvasculature may be associated to an impaired tissue perfusion and/or to the development of target organ damage. Structural alterations in the microcirculation might represent a predictor of the onset of cardio-cerebrovascular events and hypertension complications. A cross-talk between the small and large artery may exaggerate arterial damage, following a vicious circle. Therefore, in the present review, possible hemodynamic consequences of the presence of microvascular structural alterations will be considered, in terms of their time of onset, role in the development and/or maintenance of high blood pressure values, and interrelationships with structural/mechanical alterations of large conductance arteries.

Early regression of coronary artery remodeling with esmolol and DDAH/ADMA pathway in hypertensive rats

Our preclinical study demonstrated that esmolol produces early regression of left ventricular hypertrophy in arterial hypertension. The aim of this study was to assess the effects of short-term esmolol therapy on the regression of left anterior descending artery remodeling in spontaneously hypertensive rats (SHRs), and to determine whether the asymmetric dimethylarginine (ADMA)/dimethylarginine dimethylaminohydrolase (DDAH) pathway, a regulator of nitric oxide (NO) bioavailability, accounted for this regression. Fourteen-month-old male SHRs were treated intravenously with vehicle (SHR, n=15) or esmolol (SHR-E, n=20) (300 μg kg^-1 min^-1). Age-matched, vehicle-treated male Wistar-Kyoto rats (WKY, n=15) served as controls. SHRs were also treated with nitroglycerin (SHR-N, n=5). After 48 h, the left anterior descending artery structure and morphology were assessed, and dose-response curves for 5-hydroxytryptamine (5-HT, 10^-9-3 × 10^-5 mol l^-1) were constructed. ADMA concentrations in plasma and left ventricle and DDAH activity in tissue were analyzed. Wall thickness and cross-sectional area were significantly lower after treatment with esmolol in SHR-E than in SHR. Media thickness and smooth muscle cell count were lower in SHR-E than in SHR. Esmolol induced a significant reduction in adventitial cell count in SHR-E. The area under the concentration-response curves was significantly higher in SHR than in SHR-E, as were the esmolol normalized coronary artery contracting responses to 5-HT. We found significantly lower ADMA levels and significantly higher DDAH activity in the ventricle in SHR-E than in SHR. The protective effect of esmolol on the regression of left anterior descending artery remodeling may be related to the reduction in ADMA levels.

No effect of multivitamin supplementation on central blood pressure in healthy older people: A randomized controlled trial

BACKGROUND AND AIMS

Central blood pressure rises with age, which increases cardiovascular risk. There is some evidence that nutritional supplements may be useful to reduce central blood pressures in older people, but no studies have investigated the effects of multivitamin supplements for this purpose. This randomized, double-blind, placebo-controlled study investigated the effects of 16-weeks supplementation with gender-specific multivitamin and herbal supplements.

METHOD

Participants were healthy individuals, free from heart disease, and included 160 females aged ≥ 50 and 79 males aged 50-65 years. Analyses of co-variance, correcting for baseline cardiovascular assessments, were used to determine the effects of supplementation on central cardiovascular measures including augmentation index, augmentation pressure and pulse pressure. Significance was set at p = 0.016.

RESULTS

No effects of multivitamin supplementation were observed in either males or females (respectively) for central augmentation index (p = 0.841; p = 0.296), central augmentation pressure (p = 0.794; p = 0.442), and central pulse pressure (p = 0.078; p = 0.304). Similarly, there was no treatment effect observed for brachial systolic, diastolic or pulse pressures.

CONCLUSION

Four months multivitamin supplementation does not appear to exert any benefit to measures of central blood pressure in healthy older people.

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.

Short-term esmolol improves coronary artery remodeling in spontaneously hypertensive rats through increased nitric oxide bioavailability and superoxide dismutase activity

The aim of this study was to assess the effects of short-term esmolol therapy on coronary artery structure and function and plasma oxidative stress in spontaneously hypertensive rats (SHR). For this purpose, 14-month-old male SHR were treated for 48 hours with esmolol (SHR-E, 300 μg/kg/min). Age-matched untreated male SHR and Wistar Kyoto rats (WKY) were used as hypertensive and normotensive controls, respectively. At the end of intervention we performed a histological study to analyze coronary artery wall width (WW), wall-to-lumen ratio (W/L), and media cross-sectional area (MCSA). Dose-response curves for acetylcholine (ACh) and sodium nitroprusside were constructed. We also assessed several plasma oxidative stress biomarkers, namely, superoxide scavenging activity (SOSA), nitrites, and total antioxidant capacity (TAC). We observed a significant reduction in WW (P < 0.001), W/L (P < 0.05), and MCSA (P < 0.01) and improved endothelium-dependent relaxation (AUC_SHR-E = 201.2 ± 33 versus AUC_SHR = 97.5 ± 21, P < 0.05) in SHR-E compared with untreated SHR; no differences were observed for WW, MCSA, and endothelium-dependent relaxation by ACh at higher concentrations (10⁻⁶ to 10⁻⁴ mol/l) for SHR-E with respect to WKY. SOSA (P < 0.001) and nitrite (P < 0.01) values were significantly higher in SHR-E than in untreated SHR; however, TAC did not increase after treatment with esmolol. Esmolol improves early coronary artery remodeling in SHR.

Differential regulation of nitric oxide synthase function in aorta and tail artery from 5/6 nephrectomized rats

Chronic renal failure (CRF) is associated with hypertension and concomitant endothelial dysfunction, enhanced vasoconstriction, and nitric oxide synthase (NOS) dysfunction. Vascular function in patients is assessed in peripheral extremity arteries like the finger arteries, whereas animal studies often use the centrally located aorta. Therefore, we examined whether peripheral tail artery and aortic NOS function are differentially regulated by blood pressure in rats with CRF. Using wire myography, arterial function was assessed in 16-week-old Sprague-Dawley rats that were subjected to 5/6 nephrectomy (Nx; arterial ligation model) 8 weeks earlier or non-Nx (control) rats. In aortas from Nx rats, endothelial-dependent vasorelaxation response to acetylcholine (ACh) was blunted and there was enhancement of phenylephrine (PE)-mediated vasoconstriction. Inversely, tail arteries from Nx rats had no change in endothelial function and reduced response to PE. Studies where arterial segments were incubated with the nonspecific NOS inhibitor, L-NAME, showed that Nx reduced NOS function in the aorta but increased NOS function in tail artery for both ACh and PE responses. Furthermore, the observed alterations in NOS function in both aorta and tail artery were abolished when mean arterial blood pressure, as assessed by telemetry, was maintained at normal levels in the 5/6 Nx rats using triple therapy: hydralazine (30 mg/kg per day), hydrochlorothiazide (10 mg/kg per day), and reserpine (0.5 mg/kg per day). In conclusion, differential changes of NOS function in central versus peripheral arteries in CRF are dependent upon hypertension.

Activation of angiotensin II type 1 receptor-associated protein exerts an inhibitory effect on vascular hypertrophy and oxidative stress in angiotensin II-mediated hypertension

AIMS

Activation of tissue angiotensin II (Ang II) type 1 receptor (AT1R) plays an important role in the development of vascular remodelling. We have shown that the AT1R-associated protein (ATRAP/Agtrap), a specific binding protein of AT1R, functions as an endogenous inhibitor to prevent pathological activation of the tissue renin-angiotensin system. In this study, we investigated the effects of ATRAP on Ang II-induced vascular remodelling.

METHODS AND RESULTS

Transgenic (Tg) mice with a pattern of aortic vascular-dominant overexpression of ATRAP were obtained, and Ang II or vehicle was continuously infused into Tg and wild-type (Wt) mice via an osmotic minipump for 14 days. Although blood pressure of Ang II-infused Tg mice was comparable with that of Ang II-infused Wt mice, the Ang II-mediated development of aortic vascular hypertrophy was partially inhibited in Tg mice compared with Wt mice. In addition, Ang II-mediated up-regulation of vascular Nox4 and p22(phox), NADPH oxidase components, and 4-HNE, a marker of reactive oxygen species (ROS) generation, was significantly suppressed in Tg mice, with a concomitant inhibition of activation of aortic vascular p38MAPK and JNK by Ang II. This protection afforded by vascular ATRAP against Ang II-induced activation of NADPH oxidase is supported by in vitro experimental data using adenoviral transfer of recombinant ATRAP.

CONCLUSION

These results indicate that activation of aortic vascular ATRAP partially inhibits the Nox4/p22(phox)-ROS-p38MAPK/JNK pathway and pathological aortic hypertrophy provoked by Ang II-mediated hypertension, thereby suggesting ATRAP as a novel receptor-binding modulator of vascular pathophysiology.

Multivariate normal tissue complication probability modeling of gastrointestinal toxicity after external beam radiotherapy for localized prostate cancer

Background

The risk of radio-induced gastrointestinal (GI) complications is affected by several factors other than the dose to the rectum such as patient characteristics, hormonal or antihypertensive therapy, and acute rectal toxicity. Purpose of this work is to study clinical and dosimetric parameters impacting on late GI toxicity after prostate external beam radiotherapy (RT) and to establish multivariate normal tissue complication probability (NTCP) model for radiation-induced GI complications.

Methods

A total of 57 men who had undergone definitive RT for prostate cancer were evaluated for GI events classified using the RTOG/EORTC scoring system. Their median age was 73 years (range 53–85). The patients were assessed for GI toxicity before, during, and periodically after RT completion. Several clinical variables along with rectum dose-volume parameters (Vx) were collected and their correlation to GI toxicity was analyzed by Spearman’s rank correlation coefficient (Rs). Multivariate logistic regression method using resampling techniques was applied to select model order and parameters for NTCP modeling. Model performance was evaluated through the area under the receiver operating characteristic curve (AUC).

Results

At a median follow-up of 30 months, 37% (21/57) patients developed G1-2 acute GI events while 33% (19/57) were diagnosed with G1-2 late GI events. An NTCP model for late mild/moderate GI toxicity based on three variables including V65 (OR = 1.03), antihypertensive and/or anticoagulant (AH/AC) drugs (OR = 0.24), and acute GI toxicity (OR = 4.3) was selected as the most predictive model (Rs = 0.47, p < 0.001; AUC = 0.79). This three-variable model outperforms the logistic model based on V65 only (Rs = 0.28, p < 0.001; AUC = 0.69).

Conclusions

We propose a logistic NTCP model for late GI toxicity considering not only rectal irradiation dose but also clinical patient-specific factors. Accordingly, the risk of G1-2 late GI increases as V65 increases, it is higher for patients experiencing previous acute toxicity and it is lower for patients who take AH/AC drugs. The developed NTCP model could represent a potentially useful tool to be used in prospective trial and for comparison among different RT techniques.

Biomechanical factors as triggers of vascular growth

Haemodynamic factors influence all forms of vascular growth (vasculogenesis, angiogenesis, arteriogenesis). Because of its prominent role in atherosclerosis, shear stress has gained particular attention, but other factors such as circumferential stretch are equally important to maintain the integrity and to (re)model the vascular network. While these haemodynamic forces are crucial determinants of the appearance and the structure of the vasculature, they are in turn subjected to structural changes in the blood vessels, such as an increased arterial stiffness in chronic arterial hypertension and ageing. This results in an interplay between the various forces (biomechanical forces) and the involved vascular elements. Although many molecular mediators of biomechanical forces still need to be identified, there is plenty of evidence for the causal role of these forces in vascular growth processes, which will be summarized in this review. In addition, we will discuss the effects of concomitant diseases and disorders on these processes by altering either the biomechanics or their transduction into biological signals. Particularly endothelial dysfunction, diabetes, hypercholesterolaemia, and age affect mechanosensing and -transduction of flow signals, thereby underpinning their influence on cardiovascular health. Finally, current approaches to modify biomechanical forces to therapeutically modulate vascular growth in humans will be described.

Plasticity of TRPV1-Expressing Sensory Neurons Mediating Autonomic Dysreflexia Following Spinal Cord Injury

Spinal cord injury (SCI) triggers profound changes in visceral and somatic targets of sensory neurons below the level of injury. Despite this, little is known about the influence of injury to the spinal cord on sensory ganglia. One of the defining characteristics of sensory neurons is the size of their cell body: for example, nociceptors are smaller in size than mechanoreceptors or proprioceptors. In these experiments, we first used a comprehensive immunohistochemical approach to characterize the size distribution of sensory neurons after high- and low-thoracic SCI. Male Wistar rats (300 g) received a spinal cord transection (T3 or T10) or sham-injury. At 30 days post-injury, dorsal root ganglia (DRGs) and spinal cords were harvested and analyzed immunohistochemically. In a wide survey of primary afferents, only those expressing the capsaicin receptor (TRPV1) exhibited somal hypertrophy after T3 SCI. Hypertrophy only occurred caudal to SCI and was pronounced in ganglia far distal to SCI (i.e., in L4-S1 DRGs). Injury-induced hypertrophy was accompanied by a small expansion of central territory in the lumbar spinal dorsal horn and by evidence of TRPV1 upregulation. Importantly, hypertrophy of TRPV1-positive neurons was modest after T10 SCI. Given the specific effects of T3 SCI on TRPV1-positive afferents, we hypothesized that these afferents contribute to autonomic dysreflexia (AD). Rats with T3 SCI received vehicle or capsaicin via intrathecal injection at 2 or 28 days post-SCI; at 30 days, AD was assessed by recording intra-arterial blood pressure during colo-rectal distension (CRD). In both groups of capsaicin-treated animals, the severity of AD was dramatically reduced. While AD is multi-factorial in origin, TRPV1-positive afferents are clearly involved in AD elicited by CRD. These findings implicate TRPV1-positive afferents in the initiation of AD and suggest that TRPV1 may be a therapeutic target for amelioration or prevention of AD after high SCI.

Arterial stiffness/elasticity in the contribution to progression of heart failure

Arterial stiffness/elasticity plays a major role in the pathogenesis of heart failure beyond arterial blood pressure. Arterial wave reflections are generated from the periphery of the vascular system, especially at the level of the small arteries. The pattern change of the arterial wave reflections can alter the ventricular-vascular coupling in a pathologic manner, leading to heart failure. Several noninvasive techniques are used to estimate arterial stiffness/elasticity. Small artery elasticity has important predictive value for the diagnosis of heart failure. The beneficial effect of some cardiovascular therapy on arterial stiffness/elasticity has potential to prevent or delay the progression of heart failure.