Perivascular adipose tissue (PVAT) dysfunction is associated with vascular damage in cardiometabolic diseases. Although heart failure (HF)-induced endothelial dysfunction is associated with renin–angiotensin system (RAS) activation, no data have correlated this syndrome with PVAT dysfunction. Thus, the aim of the present study was to investigate whether the hyperactivation of the RAS in PVAT participates in the vascular dysfunction observed in rats with HF after myocardial infarction surgery. Wire myograph studies were carried out in thoracic aorta rings in the presence and absence of PVAT. An anticontractile effect of PVAT was observed in the rings of the control rats in the presence (33%) or absence (11%) of endothelium. Moreover, this response was substantially reduced in animals with HF (5%), and acute type 1 angiotensin II receptor (AT1R) and type 2 angiotensin II receptor (AT2R) blockade restored the anticontractile effect of PVAT. In addition, the angiotensin-converting enzyme 1 (ACE1) activity (26%) and angiotensin II levels (51%), as well as the AT1R and AT2R gene expression, were enhanced in the PVAT of rats with HF. Associated with these alterations, HF-induced lower nitric oxide bioavailability, oxidative stress and whitening of the PVAT, which suggests changes in the secretory function of this tissue. The ACE1/angiotensin II/AT1R and AT2R axes are involved in thoracic aorta PVAT dysfunction in rats with HF. These results suggest PVAT as a target in the pathophysiology of vascular dysfunction in HF and provide new perspectives for the treatment of this syndrome.

Syncytiotrophoblast extracellular vesicles (STBEVs), released into the maternal circulation during pregnancy, have been shown to affect vascular function; however, the mechanism remains unknown. In rats, STBEVs were shown to reduce endothelium-mediated vasodilation via lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a multi-ligand scavenger receptor that has been associated with vascular dysfunction. Recently, LOX-1 was shown to interact with the angiotensin II type 1 receptor (AT-1). We hypothesized that, in pregnant mice, STBEVs would impair vascular function via LOX-1 and would specifically affect angiotensin II responses. Uterine arteries from pregnant control (C57BL/6) and LOX-1 knockout (LOX-1KO) mice were isolated on gestational day (GD) 18.5. Endothelium-dependent (methylcholine (MCh); ± N(G)-Nitro-L-arginine methyl ester to assess nitric oxide (NO) contribution), and -independent (sodium nitroprusside) vasodilation, and vasoconstriction (angiotensin II; ± AT-1 [candesartan] or angiotensin II type 2 receptor (AT-2) [PD123.319] receptor antagonists; high potassium salt solution) responses were assessed using wire myography. AT-1 and AT-2 expression was analyzed using fluorescence microscopy. Human umbilical vein endothelial cells (HUVECs) were stimulated with STBEVs ± LOX-1 blocking antibody, and superoxide and peroxynitrite production were analyzed. Although MCh-induced vasodilation was decreased ( P =0.0012), NO contribution to vasodilation was greater in LOX-1KO mice ( P =0.0055). STBEVs delayed angiotensin II tachyphylaxis in arteries from control but not LOX-1KO mice ( P <0.0001), while AT-1 and AT-2 expression was unchanged. STBEVs increased peroxynitrite production in HUVECs via LOX-1 ( P =0.0091). In summary, LOX-1 deletion altered endothelium-mediated vasodilation, suggesting that LOX-1 contributes to vascular adaptations in pregnancy. STBEVs increased angiotensin II responsiveness and oxidative stress levels via LOX-1, suggesting that increased LOX-1 expression/activation or STBEVs could adversely affect vascular function and contribute to vascular complications of pregnancy.

Vascular dysfunction is a hallmark of hypertension and the strongest risk factor to date for coronary artery disease. As Y chromosome lineage has emerged as one of the strongest genetic predictors of cardiovascular disease risk to date, we investigated if Y chromosome lineage modulated this important facet in the stroke-prone spontaneously hypertensive rat (SHRSP) using consomic strains. Here, we show that vascular dysfunction in the SHRSP is attributable to differential cyclooxygenase (COX) activity with nitric oxide (NO) levels playing a less significant role. Measurement of prostacyclin, the most abundant product of COX in the vasculature, confirmed the augmented COX activity in the SHRSP aorta. This was accompanied by functional impairment of the vasodilatory prostacyclin (IP) receptor, while inhibition of the thromboxane (TP) receptor significantly ameliorated vascular dysfunction in the SHRSP, suggesting this is the downstream target responsible for constrictor prostanoid activity. Importantly, Y chromosome lineage was shown to modulate vascular function in the SHRSP through influencing COX activity, prostacyclin levels and IP dysfunction. Vascular dysfunction in the renal and intrarenal arteries was also found to be prostanoid and Y chromosome dependent. Interestingly, despite no apparent differences in agonist-stimulated NO levels, basal NO levels were compromised in the SHRSP aorta, which was also Y chromosome dependent. Thus, in contrast with the widely held view that COX inhibition is deleterious for the vasculature due to inhibition of the vasodilator prostacyclin, we show that COX inhibition abolishes vascular dysfunction in three distinct vascular beds, with IP dysfunction likely being a key mechanism underlying this effect. We also delineate a novel role for Y chromosome lineage in regulating vascular function through modulation of COX and basal NO levels.

Obesity is associated with increased cardiovascular morbidity and mortality in part due to vascular abnormalities such as endothelial dysfunction and arterial stiffening. The hypertension and other health complications that arise from these vascular defects increase the risk of heart diseases and stroke. Prooxidant and proinflammatory signaling pathways as well as adipocyte-derived factors have emerged as critical mediators of obesity-associated vascular abnormalities. Designing treatments aimed specifically at improving the vascular dysfunction caused by obesity may provide an effective therapeutic approach to prevent the cardiovascular sequelae associated with excessive adiposity. In this review, we discuss the recent evidence supporting the role of oxidative stress and cytokines and inflammatory signals within the vasculature as well as the impact of the surrounding perivascular adipose tissue (PVAT) on the regulation of vascular function and arterial stiffening in obesity. In particular, we focus on the highly plastic nature of the vasculature in response to altered oxidant and inflammatory signaling and highlight how weight management can be an effective therapeutic approach to reduce the oxidative stress and inflammatory signaling and improve vascular function.

The maternal adaptation to pregnancy includes hyperlipidaemia, oxidative stress and chronic inflammation. In non-pregnant individuals, these processes are usually associated with poor vascular function. However, maternal vascular function is enhanced in pregnancy. It is not understood how this is achieved in the face of the adverse metabolic and inflammatory environment. Research into cardiovascular disease demonstrates that plasma HDL (high-density lipoprotein), by merit of its functionality rather than its plasma concentration, exerts protective effects on the vascular endothelium. HDL has vasodilatory, antioxidant, anti-thrombotic and anti-inflammatory effects, and can protect against endothelial cell damage. In pregnancy, the plasma HDL concentration starts to rise at 10 weeks of gestation, peaking at 20 weeks. The initial rise in plasma HDL occurs around the time of the establishment of the feto-placental circulation, a time when the trophoblast plugs in the maternal spiral arteries are released, generating oxidative stress. Thus there is the intriguing possibility that new HDL of improved function is synthesized around the time of the establishment of the feto-placental circulation. In obese pregnancy and, to a greater extent, in pre-eclampsia, plasma HDL levels are significantly decreased and maternal vascular function is reduced. Wire myography studies have shown an association between the plasma content of apolipoprotein AI, the major protein constituent of HDL, and blood vessel relaxation. These observations lead us to hypothesize that HDL concentration, and function, increases in pregnancy in order to protect the maternal vascular endothelium and that in pre-eclampsia this fails to occur.

Oxidative stress [increased bioavailability of reactive oxygen species (ROS)] plays a role in the endothelial dysfunction and vascular inflammation, which underlie vascular damage in diabetes. Statins are cholesterol-lowering drugs that are vasoprotective in diabetes through unknown mechanisms. We tested the hypothesis that atorvastatin decreases NADPH oxidase (Nox)-derived ROS generation and associated vascular injury in diabetes. Lepr db /Lepr db (db/db) mice, a model of Type 2 diabetes and control Lepr db /Lepr + (db/+) mice were administered atorvastatin (10 mg/kg per day, 2 weeks). Atorvastatin improved glucose tolerance in db/db mice. Systemic and vascular oxidative stress in db/db mice, characterized by increased plasma TBARS (thiobarbituric acid-reactive substances) levels and exaggerated vascular Nox-derived ROS generation respectively, were inhibited by atorvastatin. Cytosol-to-membrane translocation of the Nox regulatory subunit p47 phox and the small GTPase Rac1/2 was increased in vessels from db/db mice compared with db/+ mice, an effect blunted by atorvastatin. The increase in vascular Nox1/2/4 expression and increased phosphorylation of redox-sensitive mitogen-activated protein kinases (MAPKs) was abrogated by atorvastatin in db/db mice. Pro-inflammatory signalling (decreased IκB-α and increased NF-κB p50 expression, increased NF-κB p65 phosphorylation) and associated vascular inflammation [vascular cell adhesion molecule-1 (VCAM-1) expression and vascular monocyte adhesion], which were increased in aortas of db/db mice, were blunted by atorvastatin. Impaired acetylcholine (Ach)- and insulin (INS)-induced vasorelaxation in db/db mice was normalized by atorvastatin. Our results demonstrate that, in diabetic mice, atorvastatin decreases vascular oxidative stress and inflammation and ameliorates vascular injury through processes involving decreased activation of Rac1/2 and Nox. These findings elucidate redox-sensitive and Rac1/2-dependent mechanisms whereby statins protect against vascular injury in diabetes.

20-HETE (20-hydroxyeicosatetraenoic acid), a vasoconstrictor metabolite of arachidonic acid formed through the action of CYP4A (cytochrome P450-4A) in vascular smooth muscle cells, has been implicated in the development of hypertension and vascular dysfunction. There have been a number of reports in human subjects demonstrating an association between elevated urinary excretion of 20-HETE and hypertension, as well as increased 20-HETE production and vascular dysfunction. The Dahl SS (salt-sensitive) rat is a genetic model of salt-sensitive hypertension that exhibits vascular dysfunction, even when maintained on a normal-salt diet and before the development of hypertension. This mini-review highlights our current research on the role of CYP4A and 20-HETE in the vascular dysfunction of the Dahl SS rat. In our studies, the SS rat is compared with the consomic SS-5 BN rat, having chromosome 5 from the salt-resistant Brown Norway rat (carrying all CYP4A genes) introgressed on to the SS genetic background. Our laboratory has demonstrated restoration of normal vascular function in the SS rat with inhibition of the CYP4A/20-HETE pathway, suggesting a direct role for this pathway in the vascular dysfunction in this animal model. Our studies have also shown that the SS rat has an up-regulated CYP4A/20-HETE pathway within their cerebral vasculature compared with the SS-5 BN consomic rat, which causes endothelial dysfunction through the production of ROS (reactive oxygen species). Our data shows that ROS influences the expression of the CYP4A/20-HETE pathway in the SS rat in a feed-forward mechanism whereby elevated ROS stimulates production of 20-HETE. The presence of this vicious cycle offers a possible explanation for the spiralling effects of elevated 20-HETE on the development of vascular dysfunction in this animal model.

Pre-eclampsia is increasingly recognized as more than an isolated disease of pregnancy. Women who have had a pregnancy complicated by pre-eclampsia have a 4-fold increased risk of later cardiovascular disease. Intriguingly, the offspring of affected pregnancies also have an increased risk of higher blood pressure and almost double the risk of stroke in later life. Experimental approaches to identify the key features of pre-eclampsia responsible for this programming of offspring cardiovascular health, or the key biological pathways modified in the offspring, have the potential to highlight novel targets for early primary prevention strategies. As pre-eclampsia occurs in 2–5% of all pregnancies, the findings are relevant to the current healthcare of up to 3 million people in the U.K. and 15 million people in the U.S.A. In the present paper, we review the current literature that concerns potential mechanisms for adverse cardiovascular programming in offspring exposed to pre-eclampsia, considering two major areas of investigation: first, experimental models that mimic features of the in utero environment characteristic of pre-eclampsia, and secondly, how, in humans, offspring cardiovascular phenotype is altered after exposure to pre-eclampsia. We compare and contrast the findings from these two bodies of work to develop insights into the likely key pathways of relevance. The present review and analysis highlights the pivotal role of long-term changes in vascular function and identifies areas of growing interest, specifically, response to hypoxia, immune modification, epigenetics and the anti-angiogenic in utero milieu.

AngII (angiotensin II) may contribute to cardiovascular risk in obesity via adverse effects on insulin sensitivity and endothelial function. In the present study, we examined the effects of ARB (angiotensin receptor blocker) therapy (losartan, 100 mg/day) on insulin sensitivity and endothelial function in 53 subjects with stage I hypertension, abdominal obesity and impaired fasting glucose. The study design was a randomized double-blinded parallel design placebo-controlled multi-centre trial of 8 weeks duration. We used the hyperinsulinaemic–euglycaemic clamp technique to measure insulin sensitivity (expressed as the ‘ M / I ’ value) and RH-PAT (reactive hyperaemia-peripheral arterial tonometry) to measure endothelial function. Additional measures included HOMA (homoeostasis model assessment)-B, an index of pancreatic β-cell function, and markers of inflammation [e.g. CRP (C-reactive protein)] and oxidative stress (e.g. F 2 -isoprostanes). ARB therapy did not alter insulin sensitivity [5.2 (2.7) pre-treatment and 4.6 (1.6) post-treatment] compared with placebo therapy [6.1 (2.9) pre-treatment and 5.3 (2.7) post-treatment; P value not significant], but did improve the HOMA-B compared with placebo therapy ( P =0.05). ARB therapy also did not change endothelial function [RH-PAT, 2.15 (0.7) pre-treatment and 2.11 (0.7) post-treatment] compared with placebo therapy [RH-PAT, 1.81 (0.5) pre-treatment and 1.76 (0.7) post-treatment; P value not significant]. Markers of inflammation and oxidative stress were not significantly changed by ARB therapy. In conclusion, ARB therapy did not alter peripheral insulin sensitivity or endothelial function in this cohort of patients with essential hypertension, abdominal obesity and impaired fasting glucose, but did improve pancreatic β-cell function.

Abnormal glucocorticoid metabolism contributes to vascular dysfunction and cardiovascular disease. Cortisol activation of vascular mineralocorticoid and glucocorticoid receptors is regulated by two types of 11β-HSD (11-β hydroxysteroid dehydrogenase), namely 11β-HSD2 and 11β-HSD1 (type 2 and type 1 11β-HSD respectively). We hypothesized that inhibition of 11β-HSD would attenuate vascular function in healthy humans. A total of 15 healthy subjects were treated with the selective 11β-HSD inhibitor GA (glycyrrhetinic acid) or matching placebo in a randomized double-blinded cross-over trial. 11β-HSD activity was assessed by the urinary cortisol/cortisone ratio, and vascular function was measured using strain-gauge plethysmography. Endothelial function was measured through incremental brachial artery administration of methacholine (0.3–10 μg/min) and vascular smooth muscle function with incremental verapamil (10–300 μg/min). GA increased the 24-h urinary cortisol/cortisone ratio compared with placebo ( P =0.008). GA tended to reduce the FBF (forearm blood flow) response to methacholine ( P =0.09) and significantly reduced the FBF response to verapamil compared with placebo ( P =0.04). MAP (mean arterial pressure) did not differ between the study conditions. 11β-HSD inhibition attenuated vascular smooth muscle vasodilatory function in healthy humans. Disturbances in cortisol activity resulting from 11β-HSD inactivation is therefore a second plausible mechanism for mineralocorticoid-mediated hypertension in humans.

TRP (transient receptor potential) channels play important roles in the regulation of normal and pathological cellular function. In the vasculature, TRP channels are present both in ECs (endothelial cells) and vascular SMCs (smooth muscle cells) and contribute to vasomotor control mechanisms in most vascular beds. Vascular TRP channels are activated by various stimuli, such as mechanical perturbation, receptor activation and dietary molecules. Some of the specific roles of these channels in normal and impaired vascular function have emerged in recent years and include participation in vascular signalling processes, such as neurotransmission, hormonal signalling, NO production, myogenic tone and autoregulation of blood flow, thermoregulation, responses to oxidative stress and cellular proliferative activity. Current research is aimed at understanding the interactions of TRP channels with other vascular proteins and signalling mechanisms. These studies should reveal new targets for pharmacological therapy of vascular diseases, such as hypertension, ischaemia and vasospasm, and vascular proliferative states.

Inactivity is associated with endothelial dysfunction and the development of cardiovascular disease. Exercise training has a favourable effect in the management of hypertension, heart failure and ischaemic heart disease. These beneficial effects are probably mediated through improvements of vascular function and, in this issue of Clinical Science , Hägg and co-authors propose a coronary artery effect. The use of a Doppler technique for non-invasive assessment of coronary flow reserve in a small animal model is an exciting aspect of this study. If feasible in the hands of other investigators, the availability of sequential coronary flow measurements in animal models may help improve our understanding of the mechanisms of disorders of the coronary circulation.

Vascular integrity in the healthy endothelium is maintained through the release of a variety of paracrine factors such as NO (nitric oxide). Endothelial dysfunction, characterized by reduced NO bioavailability, is associated with obesity, insulin resistance and Type II diabetes. Insulin has been demonstrated to have direct effects on the endothelium to increase NO bioavailability. Therefore altered insulin signalling in the endothelium represents a candidate mechanism underlying the association between insulin resistance and endothelial dysfunction. In recent years, it has become apparent that insulin sensitivity is regulated by the adipocytokines, a group of bioactive proteins secreted by adipose tissue. Secretion of adipocytokines is altered in obese individuals and there is increasing evidence that the adipocytokines have direct effects on the vascular endothelium. A number of current antidiabetic strategies have been demonstrated to have beneficial effects on endothelial function and to alter adipocytokine concentrations in addition to their effects on glucose homoeostasis. In this review we will explore the notion that the association between insulin resistance and endothelial dysfunction is accounted for by adipocytokine action on the endothelium. In addition, we examine the effects of weight loss, exercise and antidiabetic drugs on adipocytokine availability and endothelial function.

Elevated blood levels of Hcy (homocysteine) are associated with endothelial dysfunction in the systemic and coronary arterial beds. We wished to know if similar changes could be detected in the pulmonary circulation, using non-invasive tests. We studied ten normal young men aged 23–31 years, in whom acute hyperhomocysteinaemia was induced by oral ingestion of methionine. Cardiopulmonary exercise testing [including measurement of exhaled breath NO (nitric oxide)] was performed on two occasions, with and without methionine loading. In addition, blood samples for vWf (von Willebrand factor) and factor VIIIc were taken as markers of endothelial function. After oral methionine, plasma Hcy increased from 11.8±3.1 to 31.2±10.3 µmol/l (values are means±S.D.; P <0.0001), whereas there was no increase after placebo. After exercise there was an increase in V NO (NO production) and circulating plasma levels of vWf and factor VIIIc, but these were similar in the two tests. Exercise time, HR (heart rate) and BP (blood pressure) responses and P V O 2 (peak achieved O 2 uptake) were also similar in the two tests. V E (expiratory minute ventilation)/ V CO 2 (CO 2 production) was similar in the two groups at rest (methionine, 31.9±3.9; placebo, 30.5±3.9; P =0.11), but increased during exercise after methionine (at peak, 32.2±4.6 compared with 29.9±2.8; P =0.016). P ETCO 2 (end-tidal partial pressure of CO 2 ) was also similar in the two groups at rest (35.1±2.9 compared with 36.8±3.2; P =0.11), but decreased throughout the methionine test (peak 34.1±4.4 compared with 36.7±3.5; P =0.006). V E vs V CO 2 slope also increased in the methionine test (25.2±2.4 compared with 22.8±2.3; P =0.003). In conclusion, small, but consistent and significant, changes in respiratory gas exchange were seen after methionine loading, compatible with a V / Q (ventilation/perfusion) mismatch due to pulmonary vascular endothelial dysfunction.