Elisabet Vila

Role of Elastin in Spontaneously Hypertensive Rat Small Mesenteric Artery Remodelling

Chronic hypertension is associated with resistance artery remodelling and mechanical alterations. However, the contribution of elastin has not been thoroughly studied. Our objective was to evaluate the role of elastin in vascular remodelling of mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR). MRA segments from Wistar Kyoto rats (WKY) and SHR were pressurised under passive conditions at a range of physiological pressures with pressure myography. Confocal microscopy was used to determine differences in the quantity and organisation of elastin in intact pressure‐fixed arteries. To assess the contribution of elastin to MRA structure and mechanics, myograph‐mounted vessels were studied before and after elastase incubation. When compared with WKY, MRA from SHR showed: (1) a smaller lumen, (2) decreased distensibility at low pressures, (3) a leftward shift of the stress‐strain relationship, (4) redistribution of elastin within the internal elastic lamina (IEL) leading to smaller fenestrae but no change in fenestrae number or elastin amount. Elastase incubation (1) fragmented the structure of IEL in a concentration‐dependent fashion, (2) abolished all the structural and mechanical differences between strains, and (3) decreased distensibility at low pressures. The study shows the overriding role of elastin in determining vascular dimensions and mechanical properties in a resistance artery. In addition, it informs hypertensive remodelling. MRA remodelling and increased stiffness are accompanied by elastin restructuring within the IEL and elastin degradation reverses structural and mechanical alterations of SHR MRA. Differences in elastin organisation are, therefore, a central element in small artery remodelling in hypertension.

Assessing the (a)symmetry of concentration-effect curves: empirical versus mechanistic models

Modeling the shape of concentration-effect curves is of prime importance in pharmacology. Geometric descriptors characterizing these curves (the upper and lower asymptotes, the mid-point, the mid-point slope, and the point of inflection) are used for drug comparison or for assessing the change in agonist function after a system modification. The symmetry or asymmetry around the mid-point of a concentration-effect curve is a fundamental property that, regretfully, is often overlooked because, generally, models yielding exclusively symmetric curves are used. In the present review, empirical and mechanistic models are examined in their ability to fit experimental data. The geometric parameters of a survey of empirical models, the Hill equation, a logistic variant that we call the modified Hill equation, the Richards function, and the Gompertz model are determined. To analyze the relationship between asymmetry and mechanism, some examples from the ionic channel field, in an increasing degree of complexity, are used. It is shown that asymmetry arises from ionic channels with multiple binding sites that are partly occupied. The operational model of agonism is discussed both in its empirical general formulation and including the signal transduction mechanisms through G-protein-coupled receptors. It is shown that asymmetry results from systems where receptor distribution is allowed. Developed mathematical models are compared for describing experimental data on alpha-adrenoceptors. The existence or not of a relationship between the shape of the curves and receptor reserve is discussed.

New aspects of vascular remodelling: the involvement of all vascular cell types.

Conventionally, the architecture of arteries is based around the close‐packed smooth muscle cells and extracellular matrix. However, the adventitia and endothelium are now viewed as key players in vascular growth and repair. A new dynamic picture has emerged of blood vessels in a constant state of self‐maintenance. Recent work raises fundamental questions about the cellular heterogeneity of arteries and the time course and triggering of normal and pathological remodelling. A common denominator emerging in hypertensive remodelling is an early increase in adventitial cell density suggesting that adventitial cells drive remodelling and may initiate subsequent changes such as re‐arrangement of smooth muscle cells and extracellular matrix. The organization of vascular smooth muscle cells follows regular arrangements that can be modelled mathematically. In hypertension, new patterns can be quantified in these terms and give insights to how structure affects function. As with smooth muscle, little is known about the organization of the vascular endothelium, or its role in vascular remodelling. Current observations suggest that there may be a close relationship between the helical organization of smooth muscle cells and the underlying pattern of endothelial cells. The function of myoendothelial connections is a topic of great current interest and may relate to the structure of the internal elastic lamina through which the connections must pass. In hypertensive remodelling this must present an organizational challenge. The objective of this paper is to show how the functions of blood vessels depend on their architecture and a continuous interaction of different cell types and extracellular proteins.

Direct demonstration of β1‐ and evidence against β2‐ and β3‐adrenoceptors, in smooth muscle cells of rat small mesenteric arteries

Recent evidence supports additional subtypes of vasodilator β‐adrenoceptor (β‐AR) besides the ‘classical’ β2. The aim of this study was to investigate the distribution of β‐ARs in the wall of rat mesenteric resistance artery (MRA), to establish the relative roles of β‐ARs in smooth muscle and other cell types in mediating vasodilatation and to analyse this in relation to the functional pharmacology. We first examined the vasodilator β‐AR subtype using ‘subtype‐selective’ agonists against the, commonly employed, phenylephrine‐induced tone. Concentration‐related relaxation was produced by isoprenaline (pEC50: 7.70±0.1) (β1 and β2). Salbutamol (β2), BRL 37344 (β3) and CGP 12177 (atypical β) caused relaxation but were 144, 100 and 263 times less potent than isoprenaline; the ‘β3‐adrenoceptor agonist’ CL 316243 was ineffective. In arteries precontracted with 5‐HT or U 46619, isoprenaline produced concentration‐related relaxation but salbutamol, BRL 37344, CGP 12177 and CL 316243 did not. SR 59230A, CGP 12177 and BRL 37344 caused a parallel rightward shift in the concentration–response curve to phenylephrine indicating competitive α1‐AR antagonism, explaining the false‐positive ‘vasodilator’ action against phenylephrine‐induced tone. Endothelial denudation but not L‐NAME slightly attenuated isoprenaline‐mediated vasodilatation in phenylephrine and U 46619 precontracted MRA. The β‐AR fluorescent ligand BODIPY TMR‐CGP 12177 behaved as an irreversible β1‐AR antagonist in MRA and bound to the surface and inside vascular smooth muscle cells in intact vascular wall. β‐ARs in smooth muscle cells were observed in a perinuclear location, consistent with the location of Golgi and endoplasmic reticulum. Binding of BODIPY TMR‐CGP 12177 was inhibited by BAAM (1 μM) in all three vascular tunics, confirming the presence of β‐ARs in adventitia, media and intima. Binding in adventitia was observed in both neuronal and non‐neuronal cell types. Lack of co‐localisation with a fluorescent ligand for α‐ARs confirms the selectivity of BODIPY TMR‐CGP 12177 for β‐ARs over α‐ARs. Our results support the presence of functional vasodilator β1‐ARs and show that they are mainly located in smooth muscle cells. Furthermore, we have demonstrated, for the first time, the usefulness of BODIPY TMR‐CGP 12177 for identifying β‐AR distribution in the ‘living’ vascular wall.

Uric Acid Therapy Improves Clinical Outcome in Women With Acute Ischemic Stroke

Background and Purpose— It is unknown whether women and men with acute ischemic stroke respond similar to an antioxidant regimen administered in combination with thrombolysis. Here, we investigated the independent effect of sex on the response to uric acid (UA) therapy in patients with acute stroke treated with alteplase. Methods— In the Efficacy Study of Combined Treatment With Uric Acid and rtPA in Acute Ischemic Stroke (URICO-ICTUS) trial, 206 women and 205 men were randomized to UA 1000 mg or placebo. In this reanalysis of the trial, the primary outcome was the rate of excellent outcome at 90 days (modified Rankin Scale, 0–1, or 2, if premorbid score of 2) in women and men using regression models adjusted for confounders associated with sex. The interaction of UA levels by treatment on infarct growth was assessed in selected patients. Results— Excellent outcome occurred in 47 of 111 (42%) women treated with UA, and 28 of 95 (29%) treated with placebo, and in 36 of 100 (36%) men treated with UA and 38 of 105 (34%) treated with placebo. Treatment and sex interacted significantly with excellent outcome (P=0.045). Thus, UA therapy doubled the effect of placebo to attain an excellent outcome in women (odd ratio [95% confidence interval], 2.088 [1.050–4.150]; P=0.036), but not in men (odd ratio [95% confidence interval], 0.999 [0.516–1.934]; P=0.997). The interactions between treatment and serum UA levels (P<0.001) or allantoin/UA ratio (P<0.001) on infarct growth were significant only in women. Conclusions— In women with acute ischemic stroke treated with alteplase, the administration of UA reduced infarct growth in selected patients and was better than placebo to reach excellent outcome. Clinical Trial Registration— URL: https://clinicaltrials.gov. Unique identifier: NCT00860366.

Vascular Aging: Facts and Factors

“Man is as old as his arteries.” This old aphorism has been widely confirmed by epidemiological and observational studies establishing that cardiovascular diseases can be age-related in terms of their onset and progression. Besides, with aging come a number of physiological and morphological changes that alters cardiovascular function and lead to subsequently increased risk of cardiovascular disease, even in health asymptomatic individuals. Even though different adaptive mechanisms to protect blood vessels against mild stress have been described, the aging process induces a progressive failure of protective mechanisms, leading to vascular changes. The outcomes of the aging-related modifications are the impairment of homeostasis of the irrigated organs and resultant target organ damage. The increasing mean age of the population in industrialized countries has turned out to be an economic and public health problem, as the increase in life expectancy goes in parallel with high incidence of several pathological conditions, despite unprecedented advances in prevention, diagnostics, and treatment. Of all aging-related illness, cardiovascular diseases remain the leading cause of morbidity and mortality in the elderly, and thus it is imperative to understand the mechanism underlying cardiovascular senescence. This Research Topic presents a forum of comprehensive reviews on distinct aspects of the pathophysiology of vascular aging to provide insights into the causes and consequences of this complex process and attempts to propose new therapeutic strategies for the management of vascular senescence. Such as the idea proposed by Ming et al. (2012) and discussed by Cau and Tostes (2012), which suggests that targeting mTORC1-S6K1 signaling could be a promising therapeutic modality to retard the aging process and treat cardiovascular disease in the elderly. Vascular aging could be simply described as a consequence of natural physical stress and fatigue that could account for the major physical changes seen in elderly: dilation (after fracture of load-bearing material) and stiffening (by transfer of stress to the more rigid collagenous component of the arterial wall). Although aging-associated changes on vascular functioning are considered a set up for cardiovascular disease, modifications on cardiac, and central function could slow down or accelerate this set point. Therefore, it is crucial to understand how aging and other pathophysiological states affect the interaction between the heart and arterial network. The article by Wojciechowska et al. (2012) provides information on the changes with age in central and peripheral systolic blood pressure, based on data collected from randomly recruited European and Chinese subjects supporting a vicious circle between age-related stiffness, increasing systolic blood pressure, and cardiovascular complications. Chantler and Lakatta (2012) elegantly describe the concept of arterial ventricular coupling and provide valuable information on how aging, in the absence and presence of cardiovascular disease, affects the coupling both at rest and during exercise, and its pathophysiological consequences. In addition, vascular aging has been largely associated with senescence of the vascular endothelium. El Assar et al. (2012) present a wide overview of the mechanisms that participate on endothelial dysfunction that accompanies vascular aging, analyzing the synergisms, and interactions between them, some of the cellular mechanisms related to endothelial senescence as well as the prevention or reversion of those mechanisms that produce endothelial dysfunction. Cau et al. (2012) based on evidence from experimental models review the contribution of NO synthase (NOS) isoform alterations on aging-associated vascular dysfunctions, addressing the potential prevention by some drugs that modulate the expression/activity of NOS. Finally, Blanco and Bernabeu (2012) summarize data supporting the link between the splicing factor SRSF1 and endothelial cell senescence and suggest the existence of a common genetic program involving alternative splicing of a cluster of genes, which contributes to a senescent environment in the vessels. Nonetheless, aging-associated damage to the endothelium may not simply be a consequence of the endothelial cell malfunctioning, but also as a result of impaired maintenance repair systems by endothelial progenitor cell (EPC). As discussed by Williamson et al. (2012), a deterioration of endogenous EPC function with age may culminate in a decreased capacity for neovascularization and/or reduced re-endothelialization of vascular lesions, facilitating the development, progression, and clinical sequelae of cardiovascular disease. Growing evidence show that the progress of vascular aging in women follows a different chronology than in men. The gender-associated difference in the pathophysiology of cardiovascular disease has generated heated discussion, although a general consensus has validated a role of sex hormones in the modulation of vascular function and dysfunction. This research topic covers two fronts in this field: Novella et al. (2012) review clinical and experimental data to clarify how menopause and aging contribute jointly to vascular senescence and how estrogen modulates vascular response at different ages; Lopes et al. (2012) discuss the conflicting information on the role of testosterone to the regulation of vascular function in elder men and women. Last but not least, as suggested by Gragasin et al. (2012) the elderly is more frequently represented in common medical procedures and surgeries. Thus, understanding the circulatory changes that accompany the aging process is therefore becoming increasingly timely and relevant. These authors discuss aspects of vascular control in aging that are particularly relevant in the maintenance of intraoperative hemodynamic stability reviewing the effect of certain notable anesthetic agents with respect to the aging vasculature. Given the growing clinical relevance of the subject, we are pleased that our Research Topic has brought together basic and clinical scientists to spotlight on one of the greatest enemies of elder population: i.e., the vascular senescence. We hope that this Research Topic also place a special call on the need of studies to establish treatments and procedures to reduce the detrimental effects of vascular aging. It has been a great pleasure to be involved in this Research Topic and we would like to thank all of the authors, reviewers, and Frontiers staff for helping to make this Research Topic possible.

Uric acid improves glucose‐driven oxidative stress in human ischemic stroke

A study was undertaken to test in a subgroup reanalysis of the URICO‐ICTUS trial whether uric acid is superior to placebo in improving the functional outcome in patients with acute stroke and hyperglycemia.

Influence of elastin on rat small artery mechanical properties

We have previously developed a method for estimating elastin content and organization in resistance arteries, where it is a minor component. The aim of the present study was to validate the method against a quantitative assay and to determine the relative importance of elastin content and organization for intrinsic elasticity of small arteries. Mesenteric third order branches (from 10‐day‐old, 1‐ and 6‐month‐old rats) and middle cerebral arteries (from 6‐month‐old rats) were pressurized. β‐Values were calculated from stress–strain relationships and used as indicators of intrinsic stiffness. The same pressure‐fixed arteries were used to estimate elastin content and organization in the internal elastic lamina with confocal microscopy. Collagen and elastin contents were determined by Picrosirius Red staining and radioimmunoassay for desmosine, respectively. Confocal and desmosine assays gave similar results: no difference in elastin content of mesenteric vessels from 1‐ and 6‐month‐old rats, and a significant reduction in cerebral compared to mesenteric arteries. For all parameters (elastin and collagen content, fenestrae area and internal elastic lamina thickness) the best correlation was found between β‐values and fenestrae size. These data suggest that in small arteries: (1) confocal microscopy can be used as a method for the simultaneous study of changes in elastin content and organization; and (2) elastin organization might be a key determinant of intrinsic elastic properties.

Mechanisms involved in the early increase of serotonin contraction evoked by endotoxin in rat middle cerebral arteries

The present study investigated the mechanisms involved in the increased 5‐hydroxytryptamine (5‐HT) vasoconstriction observed in rat middle cerebral arteries exposed in vitro to lipopolysaccharide (LPS, 10 μg ml−1) for 1–5 h. Functional, immunohistochemical and Western blot analysis and superoxide anion measurements by ethidium fluorescence were performed. LPS exposure increased 5‐HT (10 μM) vasoconstriction only during the first 4 h. In contrast to control tissue, indomethacin (10 μM), the COX‐2 inhibitor NS 398 (10 μM), the TXA2/PGH2 receptor antagonist SQ 29,548 (1 μM) and the TXA2 synthase inhibitor furegrelate (1 μM) reduced 5‐HT contraction of LPS‐treated arteries from hour one. The iNOS inhibitor aminoguanidine (0.1 mM) increased 5‐HT contraction from hour three of LPS incubation. The superoxide anion scavenger superoxide dismutase (SOD, 100 U ml−1) and the H2O2 scavenger catalase (1000 U ml−1), as well as the respective inhibitors of NAD(P)H oxidase and xanthine oxidase, apocynin (0.3 mM) and allopurinol (0.3 mM), reduced 5‐HT contraction after LPS incubation. LPS induced an increase in superoxide anion levels that was abolished by PEG‐SOD. Subthreshold concentrations of the TXA2 analogue U 46619, xanthine/xanthine oxidase and H2O2 potentiated, whereas those of sodium nitroprusside inhibited, the 5‐HT contraction. COX‐2 expression was increased at 1 and 5 h of LPS incubation, while that of iNOS, Cu/Zn‐SOD and Mn‐SOD was only increased after 5 h. All the three vascular layers expressed COX‐2 and Cu/Zn‐SOD. iNOS expression was detected in the endothelium and adventitia after LPS. In conclusion, increased production of TXA2 from COX‐2, superoxide anion and H2O2 enhanced vasoconstriction to 5‐HT during the first few hours of LPS exposure; iNOS and SOD expression counteracted that increase at 5 h. These changes can contribute to the disturbance of cerebral blood flow in endotoxic shock.

Different β-adrenoceptor subtypes coupling to cAMP or NO/cGMP pathways: implications in the relaxant response of rat conductance and resistance vessels

To analyse the relative contribution of β1‐, β2‐ and β3‐adrenoceptors (Adrb) to vasodilatation in conductance and resistance vessels, assessing the role of cAMP and/or NO/cGMP signalling pathways.