Anticontractile Effect Research Articles

Effect of Resistance Training on NADPH Oxidase and Adiponectin in PVAT of OVX Rats

PURPOSE: Perivascular adipose tissue (PVAT) is a type of adipose tissue that surrounds vessels to provide anti-contractile effects. This study aimed to investigate the effect of resistance training on NADPH oxidase, adiponectin, and endothelial NOS (eNOS) expression in the abdominal aorta and PVAT of ovariectomized rats.METHODS: Sprague-Dawley rats at 20 weeks of age were divided into three groups: sham control (Sham, n=10), OVX-control (OVX_ Con, n=10), and OVX-resistance exercise (OVX_Rex, n=10). Resistance training was performed by climbing a ladder for 12 weeks. Western blotting was used to analyze target protein expression in the rat abdominal aorta and PVAT.RESULTS: NADPH oxidase (p67phox) expression was significantly higher in the OVX_Con group than in the sham group, but it was significantly decreased in the OVX_Rex group. The expression of adiponectin, AKT, and eNOS in both abdominal aorta and PVAT was significantly reduced in the OVX_Con group than in the Sham group, but it was improved in the OVX_Rex group.CONCLUSIONS:The results suggest that regular resistance training inhibits p67phox and increases adiponectin expression and phosphorylation of AKT and eNOS in abdominal aortic PVAT of ovariectomized rats.

Chronic cyclooxygenase-2 inhibition prevents the worsening of hypertension and endothelial dysfunction induced by ouabain in resistance arteries of spontaneously hypertensive rats

AimPrevious studies raise cyclooxygenase (COX) activation as a possible mechanism involved in the pathophysiology of ouabain-induced hypertension. We hypothesized that inhibition of COX-2 activity might prevent ouabain-induced vascular dysfunction and worsening of hypertension in spontaneously hypertensive rats (SHR). MethodsSHR were exposed to ouabain or vehicle and treated or not with the selective COX-2 inhibitor nimesulide for 5 weeks. Systolic blood pressure was measured by plethysmography. Vascular reactivity by wire myograph and protein expression by Western-blot were assessed in mesenteric resistance arteries (MRA) of groups. Thromboxane A2 (TXA2) production by ELISA was evaluated in MRA supernatants of groups. ResultsNoradrenaline-induced maximal contraction (Emax) was greater in MRA from SHR receiving ouabain than those of vehicle group. In situ inhibition of COX-2, TXA2 synthase, or TP receptor reduced the Emax to noradrenaline in MRA of ouabain to vehicle levels. TXA2 production was higher in ouabain than in vehicle group. Ouabain enhanced expression of cytoplasmic tyrosine kinase Src (c-Src)/ERK1/2/COX-2/TXA2 synthase/TP receptor in SHR MRA, but did not change NFkB/iKB ratio. Anticontractile effect of nitric oxide (NO) was smaller in MRA from ouabain- than vehicle-treated SHR, as well as eNOS and nNOS expression. Nimesulide co-treatment prevented the ouabain-induced worsening of hypertension and noradrenaline MRA hypercontractility in SHR. ConclusionOuabain worsen hypertension and induce MRA hypercontractility in SHR associated with upregulated c-Src/ERK1/2/COX-2/TXA2 synthase/TXA2/TP receptor axis. These effects were prevented by COX-2 inhibition.

Anti‐contractile activity of SIRT1 in the perivascular adipose tissue

Background ˗ Perivascular adipose tissue (PVAT) reduces the contraction of blood vessel at least in part by secreting transferable relaxing factors. Nevertheless, the molecular mechanisms underlying PVAT-mediated anti-contractile activity remain uncharacterized. The present study examined the role of SIRT1, a longevity regulator, in modulating the anti-contractile effects of PVAT. Methods and Results ˗ Mesenteric arteries with or without the attached PVAT were isolated from wild type animals (WT), or mice with selective overexpression of human SIRT1 in adipose tissues (Adipo-SIRT1). Wire myography was performed to examine phenylephrine-induced arterial contractions. PVAT derived from Adipo-SIRT1 exhibited dose- and time-dependent anti-contractile activity, which was not affected by feeding the animals with high fat diet. Molecular analyses revealed that overexpression of SIRT1 decreased the expression of Triadin, an important component of the calcium-releasing ryanodine receptor (RyR) channels. Treatment with dantrolene sodium, an inhibitor of RyR, increased the anti-contractile activity of PVAT derived from WT. Mechanistically, SIRT1-triggered mitochondrial hormesis via modulating the calcium flux from endoplasmic reticulum. The increased production of mitochondrial reactive oxygen species (mtROS) was critically involved in SIRT1-mediated anti-contractile activity of PVAT. The beneficial function of SIRT1 in PVAT was abolished in transgenic mice with selective overexpression of Triadin in adipose tissues (Adipo-TRDN). Conclusions ˗Increased SIRT1 expression in PVAT promotes vascular anti-contraction at least partly through down regulation of Triadin-mediated calcium signaling.

ROLE OF INHIBITION OF CGMP-DEPENDENT PROTEIN KINASE (PKG) SIGNALLING ON ANTICONTRACTILE FUNCTION OF PERIVASCULAR ADIPOSE TISSUE

Objective: Perivascular adipose tissue (PVAT) has an anticontractile effect.This capacity is lost in obesity (Circulation 2009) through adipocyte hypertrophy, leading to hypoxia, inflammation and oxidative stress. It has been previously demonstrated that cGMP-dependent protein kinase (PKG) plays a key role in regulating normal PVAT function (Cardiovasc Res. 2014). Aim of the study was to investigate functional responses of small resistance arteries with and without PVAT in normotensive subjects and obese patients, testing the effects of DT-2,(a peptidic highly selective inhibitor of PKG) on contractile response Design and method: We have investigated 9 normotensive severely obese patients (Obese) and 6 hypertensive severely obese patients (Obese-Hyper) undergoing bariatric surgery, as well as 7 normotensive lean subjects (CTRL) undergoing an election surgical intervention.No sign of local or systemic inflammation was present in any subject or patient. Subcutaneous small resistance arteries were dissected and mounted on a wire myograph. A concentration-response curve to noradrenaline (NA, from 10–9 to 10–5Mol/l) was evaluated in vessels with intact prerivascular fat tissue (WF)and in vessels in which perivascular fat tissue was removed (NoF). Concentration response to NA was repeated in small arteries WF and NoF in the presence of DT-2 (125 nM) in both normoxic and hypoxic (95% N2/5%CO2 for 30’)conditions Results: In normoxic conditions the presence of PVAT reduced contractile response to NA in small arteries from CTRL (ANOVA p = 0.04 vs. NoF). The anticontractile effect of PVAT completely disappeared in Obese and Obese-Hyper patients. In CTRL preincubation with DT-2 lead to increase contractile responses to NA in arteries WF (ANOVA p = 0,04 WF+DT-2 vs WF). This effect was more evident during hypoxic conditions after incubation with DT-2 in all groups. No significant effect was observed on contractile response to NA in arteries WF and NoF from Obese and Obese-Hyper patients after incubation of DT-2, in normoxic conditions Conclusions: The anticontractile effect of PVAT is present in normotensive subjects and it is lost after inhibition of PKG signalling. The absence of effect after preincubation of DT-2 on arteries WF from Obese and Obese-Hyper patients suggests a dysregulation of PKG signalling pathways in these groups, which seems essential for its downstream dilator function in small resistance arteries

Restoring Perivascular Adipose Tissue Function in Obesity Using Exercise

PurposePerivascular adipose tissue (PVAT) exerts an anti-contractile effect which is vital in regulating vascular tone. This effect is mediated via sympathetic nervous stimulation of PVAT by a mechanism which involves noradrenaline uptake through organic cation transporter 3 (OCT3) and β3-adrenoceptor-mediated adiponectin release. In obesity, autonomic dysfunction occurs, which may result in a loss of PVAT function and subsequent vascular disease. Accordingly, we have investigated abnormalities in obese PVAT, and the potential for exercise in restoring function.MethodsVascular contractility to electrical field stimulation (EFS) was assessed ex vivo in the presence of pharmacological tools in ±PVAT vessels from obese and exercised obese mice. Immunohistochemistry was used to detect changes in expression of β3-adrenoceptors, OCT3 and tumour necrosis factor-α (TNFα) in PVAT.ResultsHigh fat feeding induced hypertension, hyperglycaemia, and hyperinsulinaemia, which was reversed using exercise, independent of weight loss. Obesity induced a loss of the PVAT anti-contractile effect, which could not be restored via β3-adrenoceptor activation. Moreover, adiponectin no longer exerts vasodilation. Additionally, exercise reversed PVAT dysfunction in obesity by reducing inflammation of PVAT and increasing β3-adrenoceptor and OCT3 expression, which were downregulated in obesity. Furthermore, the vasodilator effects of adiponectin were restored.ConclusionLoss of neutrally mediated PVAT anti-contractile function in obesity will contribute to the development of hypertension and type II diabetes. Exercise training will restore function and treat the vascular complications of obesity.

NO, ROS, RAS, and PVAT: More Than a Soup of Letters.

Perivascular adipose tissue (PVAT) has recently entered in the realm of cardiovascular diseases as a putative target for intervention. Notwithstanding its relevance, there is still a long way before the role of PVAT in physiology and pathology is fully understood. The general idea that PVAT anti-contractile effect is beneficial and its pro-contractile effect is harmful is being questioned by several reports. The role of some PVAT important products or systems such as nitric oxide (NO), reactive oxygen species (ROS), and RAS may vary depending on the context, disease, place of production, etc., which adds doubts on how mediators of PVAT anti- and pro-contractile effects are called to action and their final result. This short review will address some points regarding NO, ROS, and RAS in the beneficial and harmful roles of PVAT.

The Vasoactive Role of Perivascular Adipose Tissue and the Sulfide Signaling Pathway in a Nonobese Model of Metabolic Syndrome.

The aim of this study was to evaluate the mutual relationship among perivascular adipose tissue (PVAT) and endogenous and exogenous H2S in vasoactive responses of isolated arteries from adult normotensive (Wistar) rats and hypertriglyceridemic (HTG) rats, which are a nonobese model of metabolic syndrome. In HTG rats, mild hypertension was associated with glucose intolerance, dyslipidemia, increased amount of retroperitoneal fat, increased arterial contractility, and endothelial dysfunction associated with arterial wall injury, which was accompanied by decreased nitric oxide (NO)-synthase activity, increased expression of H2S producing enzyme, and an altered oxidative state. In HTG, endogenous H2S participated in the inhibition of endothelium-dependent vasorelaxation regardless of PVAT presence; on the other hand, aortas with preserved PVAT revealed a stronger anticontractile effect mediated at least partially by H2S. Although we observed a higher vasorelaxation induced by exogenous H2S donor in HTG rats than in Wistar rats, intact PVAT subtilized this effect. We demonstrate that, in HTG rats, endogenous H2S could manifest a dual effect depending on the type of triggered signaling pathway. H2S within the arterial wall contributes to endothelial dysfunction. On the other hand, PVAT of HTG is endowed with compensatory vasoactive mechanisms, which include stronger anti-contractile action of H2S. Nevertheless, the possible negative impact of PVAT during hypertriglyceridemia on the activity of exogenous H2S donors needs to be taken into consideration.

High-Carbohydrate Diet Enhanced the Anticontractile Effect of Perivascular Adipose Tissue Through Activation of Renin-Angiotensin System

The perivascular adipose tissue (PVAT) is an active endocrine organ responsible for release several substances that influence on vascular tone. Increasing evidence suggest that hyperactivation of the local renin-angiotensin system (RAS) in the PVAT plays a pivotal role in the pathogenesis of cardiometabolic diseases. However, the local RAS contribution to the PVAT control of vascular tone during obesity is still not clear. Since the consumption of a high-carbohydrate diet (HC diet) contributes to obesity inducing a rapid and sustained increase in adiposity, so that the functional activity of PVAT could be modulated, we aimed to evaluate the effect of HC diet on the PVAT control of vascular tone and verify the involvement of RAS in this effect. For that, male Balb/c mice were fed standard or HC diet for 4 weeks. Vascular reactivity, histology, fluorescence, and immunofluorescence analysis were performed in intact thoracic aorta in the presence or absence of PVAT. The results showed that HC diet caused an increase in visceral adiposity and also in the PVAT area. Phenylephrine-induced vasoconstriction was significantly reduced in the HC group only in the presence of PVAT. The anticontractile effect of PVAT induced by HC diet was lost when aortic rings were previously incubated with angiotensin-converting enzyme inhibitor, Mas, and AT2 receptors antagonists, PI3K, nNOS, and iNOS inhibitors, hydrogen peroxide (H2O2) decomposing enzyme or non-selective potassium channels blocker. Immunofluorescence assays showed that both Mas and AT2 receptors as well as nNOS and iNOS isoforms were markedly expressed in the PVAT of the HC group. Furthermore, the PVAT from HC group also exhibited higher nitric oxide (NO) and hydrogen peroxide bioavailability. Taken together, these findings suggest that the anticontractile effect of PVAT induced by HC diet involves the signaling cascade triggered by the renin-angiotensin system through the activation of Mas and AT2 receptors, PI3K, nNOS, and iNOS, leading to increased production of nitric oxide and hydrogen peroxide, and subsequently opening of potassium channels. The contribution of PVAT during HC diet-induced obesity could be a compensatory adaptive characteristic in order to preserve the vascular function.

Melatonin reverses the loss of the anticontractile effect of perivascular adipose tissue in obese rats.

Perivascular adipose tissue (PVAT) undergoes functional changes in obesity. Increased oxidative stress is a central mechanism whereby obesity induces loss of the anticontractile effect of PVAT. Melatonin is an antioxidant that displays vasoprotective action in cardiovascular disease. Here, we sought to investigate whether melatonin would restore the anticontractile effect of periaortic PVAT in obesity. Male Wistar Hannover rats were treated for 10weeks with a high-calorie diet. Melatonin (5mg/kg/d, p.o., gavage) was administered for 2weeks. Functional findings showed that obesity-induced loss of the anticontractile effect of PVAT and treatment with melatonin reversed this response. Tiron [a scavenger of superoxide anion (O2 - )] restored the anticontractile effect of PVAT in aortas from obese rats, suggesting a role for reactive oxygen species (ROS) in such response. Decreased superoxide dismutase (SOD) activity and augmented levels of ROS were detected in periaortic PVAT from obese rats. These responses were accompanied by decreased levels of nitric oxide (NO) in PVAT. Treatment with melatonin restored SOD activity, decreased ROS levels, and increased NO bioavailability in PVAT from obese rats. Here, we first reported the beneficial effects of melatonin in periaortic PVAT in obesity. Melatonin reversed the adverse effects of obesity in PVAT that included overproduction of ROS, reduced SOD activity, and decreased bioavailability of NO. Therefore, PVAT may constitute an important target for the treatment of obesity-induced vascular dysfunction and melatonin emerges as a potential tool in the management of the vascular complications induced by obesity.

The Functional Availability of Arterial Kv7 Channels Is Suppressed Considerably by Large-Conductance Calcium-Activated Potassium Channels in 2- to 3-Month Old but Not in 10- to 15-Day Old Rats

BackgroundVoltage-gated potassium (Kv) channels, especially Kv7 channels, are major potassium channels identified in vascular smooth muscle cells with a great, albeit differential functional impact in various vessels. Vascular smooth muscle Kv7 channels always coexist with other K channels, in particular with BK channels. BK channels differ in the extent to which they influence vascular contractility. Whether this difference also causes the variability in the functional impact of Kv7 channels is unknown. Therefore, this study addressed the hypothesis that the functional impact of Kv7 channels depends on BK channels.Experimental ApproachExperiments were performed on young and adult rat gracilis and saphenous arteries using real-time PCR as well as pressure and wire myography.Key ResultsSeveral subfamily members of Kv7 (KCNQ) and BK channels were expressed in saphenous and gracilis arteries: the highest expression was observed for BKα, BKβ1 and KCNQ4. Arterial contractility was assessed with methoxamine-induced contractions and pressure-induced myogenic responses. In vessels of adult rats, inhibition of Kv7 channels or BK channels by XE991 or IBTX, respectively enhanced arterial contractility to a similar degree, whereas activation of Kv7 channels or BK channels by retigabine or NS19504, respectively reduced arterial contractility to a similar degree. Further, IBTX increased both the contractile effect of XE991 and the anticontractile effect of retigabine, whereas NS19504 reduced the effect of retigabine and impaired the effect of XE991. In vessels of young rats, inhibition of Kv7 channels by XE991 enhanced arterial contractility much stronger than inhibition of BK channels by IBTX, whereas activation of Kv7 by retigabine reduced arterial contractility to a greater extent than activation of BK channels by NS19504. Further, IBTX increased the anticontractile effect of retigabine but not the contractile effect of XE991, whereas NS19504 reduced the effect of retigabine and impaired the effect of XE991.ConclusionKv7 and BK channels are expressed in young and adult rat arteries and function as negative feedback modulators in the regulation of contractility of these arteries. Importantly, BK channels govern the extent of functional impact of Kv7 channels. This effect depends on the relationship between the functional activities of BK and Kv7 channels.

Renin-angiotensin system overactivation in perivascular adipose tissue contributes to vascular dysfunction in heart failure.

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.

Dysfunction of perivascular adipose tissue in mesenteric artery is restored by aerobic exercise in high-fat diet induced obesity.

This study investigated the function of perivascular adipose tissue (PVAT) on vascular contractility within resistant arteries in high-fat diet induced obese rats after long-term aerobic exercise. Male Sprague-Dawley rats were subjected to normal diet control group (N-CTRL), normal diet exercise group (N-EX), high-fat diet control group (H-CTRL), and high-fat diet exercise group (H-EX) (n=8 in each group). After intervention, adipose tissues morphology was observed. Vasomotor function of mesenteric arteries with or without PVAT were assessed; mesenteric PVAT isolated from each group were transferred to chambers bath with untreated vessels (without PVAT) to evaluate the independent effect. Isolated PVAT was further pre-treated with inhibitor of cystathionine-γ-lyase (CSE), a key hydrogen sulphide (H2 S) enzyme. Results showed that the size of lipid droplet around mesenteric arteries from H-EX was significantly reduced (P<.05); uncoupling protein1 (UCP1) in PVAT from H-EX was enhanced. In N-CTRL, N-EX, and H-EX, vessels without PVAT showed higher sensitivity to serotonin (5-HT) than that with intact PVAT. Vascular tension by 5-HT was significantly reduced in H-EX than H-CTRL (P<.05) in vessels with PVAT. Transferred PVAT from H-EX compared with H-CTRL significantly reduced vascular sensitivity to 5-HT (P<.05), and this effect was eliminated through inhibiting CSE. In summary, the anti-contractile effect of PVAT on resistance artery was impaired in obesity but restored by long-term aerobic exercise. The function of PVAT modified by obesity or by exercise has an independent influence on vascular reactivity, and PVAT derived H2 S may participate in this process.

Anticontractile Effect of Perivascular Adipose Tissue But Not of Endothelium Is Enhanced by Hydrogen Sulfide Stimulation in Hypertensive Pregnant Rat Aortae.

Perivascular adipose tissue (PVAT) modulates the vascular tone. Hydrogen sulfide (H2S) is synthetized by cystathionine gamma-lyase (CSE) in brown PVAT. Modulation of vascular contractility by H2S is, in part, adenosine triphosphate (ATP)-sensitive potassium channels dependent. However, the role of PVAT-derived H2S in hypertensive pregnancy (HTN-Preg) is unclear. Therefore, we aimed to examine the involvement of H2S in the anticontractile effect of PVAT in aortae from normotensive and hypertensive pregnant rats. To this end, phenylephrine-induced contractions in the presence and absence of PVAT and endothelium in aortae from normotensive pregnant (Norm-Preg) and HTN-Preg rats were investigated. Maternal blood pressure, fetal-placental parameters, angiogenesis-related biomarkers, and H2S levels were also assessed. We found that circulating H2S is elevated in hypertensive pregnancy associated with angiogenic imbalance, fetal and placental growth restrictions, which revealed that there is H2S pathway activation. Moreover, under stimulated H2S formation PVAT, but not endothelium, reduced phenylephrine-induced contractions in aortae from HTN-Preg rats. Also, H2S synthesis inhibitor abolished anticontractile effects of PVAT and endothelium. Furthermore, anticontractile effect of PVAT, but not of endothelium, was eliminated by ATP-sensitive potassium channels blocker. In accordance, increases in H2S levels in PVAT and placenta, but not in aortae without PVAT, were also observed. In conclusion, anticontractile effect of PVAT is lost, at least in part, in HTN-Preg aortae and PVAT effect is ATP-sensitive potassium channels dependent in normotensive and hypertensive pregnant rat aortae. PVAT but not endothelium is responsive to the H2S stimulation in hypertensive pregnant rat aortae, implying a key role for PVAT-derived H2S under endothelial dysfunction.

Modulation of Vascular Function by Perivascular Adipose Tissue: Sex Differences.

In addition to the endothelium, the perivascular adipose tissue (PVAT) has been described to be involved in the local modulation of vascular function by synthetizing and releasing vasoactive factors. Under physiological conditions, PVAT has anticontractile and anti-inflammatory effects. However, in the context of hypertension, obesity and type 2 diabetes, the PVAT pattern of anticontractile adipokines is altered, favoring oxidative stress, inflammation and, consequently, vascular dysfunction. Therefore, dysfunctional PVAT has become a target for therapeutic intervention in cardiometabolic diseases. An increasing number of studies have revealed sex differences in PVAT morphology and in the modulatory effects of PVAT on endothelial function and vascular tone. Moreover, distinct mechanisms underlying PVAT dysfunction may account for vascular abnormalities in males and females. Therefore, targeting sex-specific mechanisms of PVAT dysfunction in cardiovascular diseases is an evolving strategy for cardiovascular protection.

Anti-Contractile and Anti-Inflammatory Effects of Diacerein on Isolated Mouse Airways Smooth Muscle and Mouse Asthma Model.

Characterized by abnormal smooth muscle contractility and airway inflammation, asthma is one of the most common airway diseases worldwide. Diacerein is a well-known anti-inflammatory drug, widely used in osteoarthritis. In current study, the innovative usage of diacerein in anti-contractile and anti-inflammatory treatment of asthma was studied. In vitro experiments including tension measurement and patch-clamp technique and in vivo experiments including establishment of mice model and measurement of respiratory resistance were applied to explore the role of diacerein in asthma. It turned out that agonist-precontracted mouse airway smooth muscle could be relaxed by diacerein via intracellular and extracellular calcium mobilization which was mediated by switched voltage-dependent L-type Ca2+ channels, non-selective cation channels, large-conductance Ca2+-activated K+ channel, and Na+/Ca2+ exchangers. Furthermore, diacerein could relieve bronchospasm and control airway inflammation in asthmatic mice via reduction of several inflammatory factors. Our studies elucidated the potential therapeutic property of diacerein in asthma treatment and the possible underlying mechanism. It also confirmed that new uses for already-approved drugs could be an important form of innovation.

Perivascular adipose tissue phenotype and sepsis vascular dysfunction: Differential contribution of NO, ROS and beta 3-adrenergic receptor

AimsVascular dysfunction plays a key role in sepsis but the role of perivascular adipose tissue (PVAT) in this condition is relatively unknown. Main methodsSepsis was induced by cecal ligation and puncture (CLP). The responses of the aorta and superior mesenteric artery to norepinephrine in the presence or absence of PVAT were evaluated. Fluorescent probes measured the production of nitric oxide (NO) and reactive oxygen species (ROS). NO synthases (NOS) and β3-adrenoceptor expression were detected by immunofluorescence and S-nitrosylation by the biotin switch assay. Key findingsAorta and superior mesenteric arteries from septic animals with intact PVAT showed a worsened response to the vasoconstrictor compared to vessels without PVAT. PVAT from the aorta (APVAT) produced NO and ROS whereas PVAT from the superior mesenteric artery (MPVAT) produced only ROS. Septic APVAT exhibited a higher density of NOS-1 and NOS-3. S-nitrosylation was found in APVAT. Donor (PVAT obtained from normal or septic rats):Host (normal vessel without PVAT) experiments showed that L-NAME, ODQ and β3-adrenergic receptor antagonist blocked the septic APVAT anti-contractile effect. None of these compounds affected MPVAT; tempol, but not apocynin, blocked its anti-contractile effect. SignificancePVAT contributes to the anti-contractile effect in the aorta and mesenteric artery of septic rats through different pathways. β3-Adrenergic receptor and NO appear to be key mediators of this effect in APVAT, but not in MPVAT where ROS seem to be a relevant mediator. Therefore, PVAT is a relevant player of sepsis vascular dysfunction.

SUN-LB93 Mineralocorticoid Receptor Mediates Sex-Dependent Anticontractile Effect of Perivascular Adipose Tissue in Obese Mice

Obesity, a condition of excessive fat mass and subclinical inflammation, reached epidemic proportions with higher prevalence in women compared to men worldwide. Expansion of the perivascular adipose tissue (PVAT) is observed in obesity and clinical studies indicate a positive correlation between PVAT amount and body mass index. PVAT, a fat depot surrounding most of the vessels, modulates vascular function by releasing PVAT-derived factors such as adipokines that exert anticontractile effect in health individuals. Despite sexual dimorphism on PVAT morphology, it is still unknown whether or not there is sex differences in the PVAT modulating vascular function in the setting of obesity. Aldosterone-mineralocorticoid receptor (MR) signaling pathway has been demonstrated to be adipogenic and proinflammatory in classical fat depots and treatment with MR antagonists (A) might reverse vascular dysfunction and remodeling in obese models, especially in female sex. Therefore, we aimed to evaluate the anticontractile effect of PVAT in male and female obese mice and hypothesized that MR signaling would be involved in possible sex differences in PVAT dysfunction in obesity. Male and female C57Bl6/J mice were fed a chow or a high-fat diet (HFD, 60% energy from fat) for 20 weeks. At the last 4 weeks of HFD, female and male mice were treated with the MRA spironolactone (Spi, 100 mg/kg/day). HFD feeding significantly increased body weight and visceral adipose tissue, which was not modified by Spi treatment in both sexes. Resistance mesenteric arteries were isolated with or without PVAT and mounted in a wire myograph to evaluate vascular contractile responses. Lean male and female mice PVAT had an anticontractile effect in the response to phenylephrine that was greater in females than males. The anticontractile effect of PVAT was significantly impaired in obese females but not modified in males. HFD-induced dysfunctional PVAT was prevented by Spi treatment in females. Next, we evaluated the protein expression of aldosterone-synthase CYP11B2, serum and glucocorticoid-regulated kinase 1 (SGK1), and epithelial sodium channel subunits (ENaCs) in isolated mesenteric PVAT of lean and obese male and female mice. There was an increased expression of CYP11B2, SGK1 and ENaCs only in obese female PVAT. Protein expression of adiponectin, a major PVAT-released adipokine was also increased in female mesenteric PVAT. In conclusion, the findings suggest sexual dimorphism in PVAT function in health and in obesity. Although anticontractile role of PVAT was exacerbated in lean female mice, female sex was more susceptible to develop PVAT dysfunction in the setting of obesity which was prevented by MR blockade. HFD-induced PVAT dysfunction in females was associated with increased expression of SGK1 and ENaCs. Therefore, data suggest MR activation as a mechanism mediating sex differences in PVAT dysfunction.FAPESP, CAPES.

Chronic Iron Overload Restrains the Benefits of Aerobic Exercise to the Vasculature.

Physical exercise is a well-recognized effective non-pharmacological therapy for cardiovascular diseases. However, because iron is essential element in many physiological processes including hemoglobin and myoglobin synthesis, thereby playing a role on oxygen transport, many athletes use iron supplement to improve physical performance. Regarding this, iron overload is associated with oxidative stress and damage to various systems, including cardiovascular. Thus, we aimed to identify the vascular effects of aerobic exercise in a rat model of iron overload. Male Wistar rats were treated with 100mg/kg/day iron-dextran, i.p., 5days a week for 4weeks, and then underwent aerobic exercise protocol on a treadmill at moderate intensity, 60min/day, 5days a week for 8weeks. Exercise reduced vasoconstrictor response of isolated aortic rings by increasing participation of nitric oxide (NO) and reducing oxidative stress, but these benefits to the vasculature were not observed in rats previously subjected to iron overload. The reduced vasoconstriction in the exercised group was reversed by incubation with superoxide dismutase (SOD) inhibitor, suggesting that increased SOD activity by exercise was lost in iron overload rats. Iron overload groups increased serum levels of iron, transferrin saturation, and iron deposition in the liver, gastrocnemius muscle, and aorta, and the catalase was overexpressed in the aorta probably as a compensatory mechanism to the increased oxidative stress. In conclusion, despite the known beneficial effects of aerobic exercise on vasculature, our results indicate that previous iron overload impeded the anticontractile effect mediated by increased NO bioavailability and endogenous antioxidant response due to exercise protocol.

The Influence of Perivascular Adipose Tissue on Vascular Function in a Rabbit Model

The recent acknowledgment of the paracrine role of perivascular adipose tissue (PVAT) in vascular modulation has been supported by many studies investigating major arteries in several animal models and humans. The influence of PVAT on the functional activity of the vascular bed has been a matter of debate, whether it is an anticontractile effect with protective roles or a pro-contractile effect, investigations are underway to address this obscurity. In this investigation, we have studied the effects of vasoconstrictors, phenylephrine and noradrenaline, and vasorelaxants, carbachol and s-nitroso-n- acetylpenicillamine (SNAP), on subclavian and iliac rings with and without PVAT attached; and concentration-response curves were constructed accordingly. Levels of nitric oxide (NO) generated due to activation of the enzyme adenosine monophosphate-activated protein kinase (AMPK) by 5-Aminoimi- dazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) were measured in sub- clavian and iliac PVAT conditioned media. Additionally, Haematoxylin and Eosin staining was performed to analyze and compare the histological characteristics of both arteries. Subclavian and iliac rings with PVAT attached showed stronger contraction to phenylephrine and noradrenaline than that of rings without PVAT attached. At the same time, relaxation tests reported lower relaxation percentages in subclavian and iliac rings with PVAT attached compared to rings without PVAT attached in response to carbachol and SNAP. PVAT treated with AICAR generated higher levels of NO compared to levels of untreated PVAT. Conclusions drawn were the pro-contractile effects demonstrated by the PVAT especially in high concentrations of drugs used. In addition, histology analysis revealed characteristics of white adipose tissue in both PVATs.

Increased inflammation, oxidative stress and a reduction in antioxidant defense enzymes in perivascular adipose tissue contribute to vascular dysfunction in type 2 diabetes

BackgroundPerivascular adipose tissue (PVAT) surrounds most large blood vessels and plays an important role in vascular homeostasis. The present study was conducted to investigate the contribution of PVAT to vascular dysfunction in a rat model of type 2 diabetes. Material and methodsSeveral in vivo parameters such as lipid profile (total cholesterol and triglyceride systemic levels), fasting glucose levels, glucose tolerance and insulin sensitivity (through glucose and insulin tolerance tests, respectively) were determined in Goto-Kakizaki (GK) diabetic rats and compared with control Wistar rats. At the vascular level, endothelial dependent and independent relaxation and contraction studies were performed in aortic rings in the absence (PVAT−) or in the presence (PVAT+) of thoracic PVAT. We also evaluated vascular oxidative stress and performed western blots, PCR and immunohistochemistry analysis of cytokines and various enzymes in PVAT. ResultsEndothelium-dependent relaxation to acetylcholine, assessed by wire myography, was impaired in GK rats and improved by the antioxidant TEMPOL and by the TLR4 inhibitor, CLI-095 suggesting an increase in oxidative stress and inflammation. In addition, vascular superoxide and peroxynitrite production was increased in the vascular wall of diabetic rats, accompanied by reduced nitric oxide bioavailability. The presence of PVAT had an anticontractile effect in response to phenylephrine in Wistar rats that was lost in GK rats. Western blot and immunohistochemistry analysis revealed that PVAT phenotype shifts, under diabetic conditions, towards a proinflammatory (with increment in CRP, CCL2, CD36), pro-oxidant (increased levels of aldose reductase, and reduced levels of antioxidant deference enzymes) and vasoconstriction state. ConclusionOur data suggest that this rat model of type 2 diabetes is associated with perivascular adipose dysfunction that contributes to oxidative stress, inflammation and endothelial dysfunction.