Presence Of Perivascular Adipose Tissue Research Articles

The Vascular Function of Resistance Arteries Depends on NADPH Oxidase 4 and Is Exacerbated by Perivascular Adipose Tissue.

The NADPH oxidase NOX4 that releases H2O2 can mediate vasoprotective mechanisms under pathophysiological conditions in conductive arteries. However, the role of NOX4 in resistance arteries and in perivascular adipose tissue is not well understood. We hypothesized that NOX4 is of functional importance in resistance arteries and perivascular adipose tissue under dyslipidemia conditions. We detected elevated NOX4 expression in murine and human vessels under dyslipidemia. Diminishing Nox4 under these conditions led to endothelial dysfunction in resistance arteries. The mesenteric arteries of Nox4-/-/Ldlr-/- mice revealed decreased eNos mRNA expression. Inhibition of eNOS in those vessels did not affect vascular function, while in Ldlr-/- mice endothelial function was significantly altered. Anticontractile properties of perivascular adipose tissue at resistance arteries were diminished in Nox4-/-/Ldlr-/- compared with Ldlr-/- mice. In addition, the presence of perivascular adipose tissue further worsened endothelial dysfunction in mesenteric arteries under dyslipidemia conditions. Perivascular adipose tissue from mesenteric arteries revealed a higher expression of markers of white adipocytes compared to markers of beige/brown adipocytes. Among those white adipocyte markers, leptin was significantly less expressed in perivascular adipose tissue from Nox4-/-/Ldlr-/- mice compared with Ldlr-/- mice. Furthermore, in human perivascular adipose tissue with a profound pattern of white adipocyte marker genes, we detected a correlation of NOX4 and LEP expression. In addition, incubating arterial vessels with leptin induced nitrite release, indicating increased eNOS activity. In humans, a higher expression of leptin in perivascular adipose tissue correlated with eNOS expression in the corresponding left internal mammary artery. In conclusion, vascular function of resistance arteries was dependent on Nox4-derived H2O2, especially under dyslipidemia conditions. Perivascular adipose tissue of the mesenteric arteries with white adipose tissue characteristics further aggravated endothelial function through reduced leptin-eNOS signaling.

The anatomical feasibility of anterior intra- and extra-bifurcation approaches to L5-S1: an anatomic study based on lumbar MRI

BACKGROUND CONTEXTThe anterior approach at L5-S1 has many advantages, however, vascular complications are challenging for spinal surgeons who may not be familiar with the variability of vascular anatomy. There are three different anterior approaches (intra-bifurcation approach and extra-bifurcation: left-, and right-sided prepsoas approaches) described in previous studies to respond to the variability of anterior vascular anatomy for reduction in vascular injury, while no guidance for the choice of approach preoperatively. PURPOSETo analyze the anatomical feasibility of three anterior approaches to access the L5-S1 disc space according to a practical framework. STUDY DESIGNRetrospective study. PATIENT SAMPLELumbar magnetic resonance imaging (MRI) from patients who visited our outpatient clinic were reviewed, with 150 cases meeting the inclusion criteria. OUTCOME MEASURESThe following radiographic parameters were measured on axial T2-weighted MRI at the lower endplate of L5 and the upper endplate of S1: width of the vascular corridor, position of the left and right common iliac vein (CIV), and presence of perivascular adipose tissue (PAT). Moreover, we designed a safe line to evaluate the feasibility of left- and right-sided prepsoas approaches. Cases of lumbosacral transitional vertebrae were identified. METHODSThe feasibility of the intra-bifurcation approach was determined by the width of the vascular corridor, presence of PAT, and the position of the CIV. The feasibility of the prepsoas approach was determined by the relative position of the CIV to the safe line, presence of PAT, and the intersection point of the CIV and vertebral body. RESULTSSixty-eight percent, 64.7%, and 75.3% cases allowed the intra-bifurcation, left-, and right-sided prepsoas approach to L5-S1, respectively. The cases in this study had at least one of three anterior approaches to access L5-S1 disc space, and 74% of cases had more than one anatomical feasibility of anterior approach. The right-sided prepsoas approach was feasible in the majority of cases because of the vertical course of the right CIV with a significantly higher proportion of presence of PAT. Patients with lumbosacral transitional vertebrae (24 cases) may prefer the prepsoas approaches, and only six cases (25.0%) were determined to be feasible for the intra-bifurcation approach. CONCLUSIONSOur study proposes a practical framework to determine whether the three different anterior approaches are feasible access at L5-S1. According to the framework, all cases had the anatomical feasibility of using an anterior approach to access L5-S1, and three-fourths of cases had a replaceable anterior approach when encountering intraoperative difficulties.

Role of Perivascular Adipose Tissue in Aorta Reactivity from Obese and Hyperglycemic CD-1 Mice: New Insights into Perivascular Adipose Tissue.

Background: Perivascular adipose tissue (PVAT) plays an essential role in cardiovascular homeostasis. However, during obesity and diabetes, its role in vascular tone regulation is unclear. This study aimed to evaluate the function of the PVAT on aorta reactivity in the lean and cafeteria (CAF) diet-induced obese-hyperglycemic mice model. Methods: Aorta reactivity to phenylephrine, KCl, and acetylcholine was analyzed in lean (n = 6) and obese mice (n = 6). Also, nitric oxide (NO-) and cyclooxygenase participation, in the presence (n = 6) and absence (n = 6) of PVAT, were examined in the aortas. Results: After a CAF diet for 19 weeks, obese mice showed increased body weight, glucose intolerance, and hypercholesterolemia concerning lean mice. Vascular reactivity to phenylephrine was reduced significantly in the aorta of obese mice. In contrast, the contraction produced by KCl (80 mM) was increased in the aorta of obese mice independent of PVAT. Acetylcholine-induced vasorelaxation diminished in the aortas of obese mice in the presence of PVAT. Nonselective inhibition of cyclooxygenases likely shows that PVAT and endothelium release vasorelaxant prostanoids. Conclusions: The results suggest that PVAT modulates aorta reactivity by releasing NO-, decreasing the α1-adrenergic response to phenylephrine, and probably releasing vasorelaxant prostanoids. The data suggest that PVAT regulates the vascular smooth muscle and endothelial function in a CAF diet-induced obese-hyperglycemic mice model.

Contribution of RAS, ROS and COX-1-derived prostanoids to the contractile profile of perivascular adipose tissue in cafeteria diet-induced obesity

AimsObesity can lead to the loss of the anticontractile properties of perivascular adipose tissue (PVAT). Given that cafeteria (CAF) diet reflects the variety of highly calorie and easily accessible foods in Western societies, contributing to obesity and metabolic disorders, we sought to investigate the impact of CAF diet on PVAT vasoactive profile and the involvement of renin-angiotensin system, oxidative stress, and cyclooxygenase pathway. Main methodsMale Balb/c mice received standard or CAF diet for 4 weeks. Oral glucose tolerance and insulin sensitivity tests were performed, and fasting serum glucose, cholesterol and triglyceride parameters were determined. Vascular reactivity, fluorescence and immunofluorescence analyzes were carried out in intact thoracic aorta in the presence or absence of PVAT. Key findingsCAF diet was effective in inducing obesity and metabolic disorders, as demonstrated by increased body weight gain and adiposity index, hyperlipidemia, hyperglycemia, glucose intolerance and insulin insensitivity. Importantly, CAF diet led to a significant decrease in aortic contractility which was restored in the presence of PVAT, exhibiting therefore a contractile profile. The contractile effect of PVAT was associated with the activation of AT1 receptor, reactive oxygen species, cyclooxygenase-1, thromboxane A2 and prostaglandin E2 receptors. SignificanceThese findings suggest that the contractile profile of PVAT involving the renin-angiotensin system activation, reactive oxygen species and cyclooxygenase-1 metabolites may be a protective compensatory adaptive response during early stage of CAF diet-induced obesity as an attempt to restore the impaired vascular contraction observed in the absence of PVAT, contributing to the maintenance of vascular tone.

Modulation of Vasomotor Function by Perivascular Adipose Tissue of Renal Artery Depends on Severity of Arterial Dysfunction to Nitric Oxide and Severity of Metabolic Parameters.

Perivascular adipose tissue (PVAT) enhances vascular relaxation of mesenteric arteries in SHRSP.Z-Leprfa/IzmDmcr rats (SPZF), a metabolic syndrome model. We investigated and compared the effects of PVAT on the renal artery in SPZF with those on SHR/NDmcr-cp rats (CP). Renal arteries with and without PVAT were isolated from 23-week-old SPZF and CP. The effects of PVAT on acetylcholine- and nitroprusside-induced relaxation were examined using bioassays with phenylephrine-contracted arterial rings. Acetylcholine-induced relaxations without PVAT in SPZF and CP were 0.7- and 0.5-times lower in females than in males, respectively. In the presence of PVAT, acetylcholine-induced relaxations increased 1.4- and 2-times in male and female CP, respectively, but did not differ in SPZF. Nitroprusside-induced relaxation with and without PVAT was 0.7-times lower in female than in male SPZF but did not differ in CP. Angiotensin-II type-1 receptor (AT1R)/AT1R-associated protein mRNA ratios were lower in CP than in the SPZF and negatively correlated with the difference in arterial relaxation with and without PVAT. The effects of renal artery PVAT differed between the SPZF and CP groups. Higher levels of enhanced AT1R activity in SPZF PVAT may drive these differences by impairing the vascular smooth muscle responses to nitric oxide.

Does Dietary Methionine Alter Perivascular Adipose Tissue Function?

Perivascular adipose tissue (PVAT) is an adipose depot surrounding blood vessels and is a paracrine regulator of vascular tone. Obesity is associated with the loss of PVAT‐mediated anti‐contractile properties, thus contributing to obesity‐associated hypertension. Hydrogen sulfide (H2S) is a gaseous signaling molecule that is produced in the vasculature and is important for regulating vascular tone. In PVAT, cystathionine gamma lyase (Cse) is the primary source of H2S which acts as an important adipose‐derived relaxing factor. Dietary methionine restriction recapitulates many of the metabolic effects of caloric restriction and leads to preferential expression of activating transcription factor 4 (ATF4) which facilitates Cse transcription. We hypothesized that dietary methionine restriction will prevent high fat diet‐induced loss of PVAT anti‐contractile properties, through activation of the integrated stress response (ISR) and increased ATF4‐mediated transcription of Cse. Male Wistar rats were fed either a control (C, 10% calories from fat) or a high fat diet (HFD) (H, 60% calories from fat) that was either methionine replete (R, 0.86% methionine) or methionine depleted (D, 0.12% methionine) for 12 weeks such that there were four groups: CR, CD, HR, and HD. Dietary methionine restriction prevented body weight gain, while rats fed a methionine replete diet gained weight over the 12 week feeding period. There was no difference in weight gain between control or HFD fed rats. Arterial blood pressure, measured in conscious rats using tail cuff plethysmography, was not different between the four groups over the 12 week feeding period. After 12 weeks on diets, arterial contractility was assessed using wire myography in 2nd order mesenteric arteries (MAs) with and without attached PVAT. In our hands, the presence of PVAT was associated with reduced contraction to norepinephrine (NE, 10 µM) and greater relaxation to acetylcholine (ACh,10 µM) in MAs from all groups, and HFD was not associated with a loss of PVAT anti‐contractile properties. In the presence of PVAT, dietary methionine restriction increased relaxation to ACh in NE‐precontracted MAs, while HFD had no effect on ACh‐induced relaxation. In conclusion, in male Wistar rats, while HFD had no effect on weight gain, blood pressure, or PVAT modulation of MA contractility, dietary methionine restriction for 12 weeks had profound effects on body weight gain, no effect on arterial blood pressure, and a small effect on MA ACh‐induced relaxation in the presence of PVAT. Future studies include examining gene and protein expression of Cse and other ATF4 responsive genes using real time qPCR, Western blot analysis, and immunohistochemical staining of arterial cross‐sections. These studies will provide further insights into dietary interventions to minimize the cardiovascular co‐morbidities associated with obesity.

The Vasoactive Effect of Perivascular Adipose Tissue and Hydrogen Sulfide in Thoracic Aortas of Normotensive and Spontaneously Hypertensive Rats.

The objective of this study was to investigate the vasoregulatory role of perivascular adipose tissue (PVAT) and its mutual interaction with endogenous and exogenous H2S in the thoracic aorta (TA) of adult normotensive Wistar rats and spontaneously hypertensive rats (SHRs). In SHRs, hypertension was associated with cardiac hypertrophy and increased contractility. Regardless of the strain, PVAT revealed an anticontractile effect; however, PVAT worsened endothelial-dependent vasorelaxation. Since H2S produced by both the vascular wall and PVAT had a pro-contractile effect in SHRs, H2S decreased the sensitivity of adrenergic receptors to noradrenaline in Wistar rats. While H2S had no contribution to endothelium-dependent relaxation in Wistar rats, in SHRs, H2S produced by the vascular wall had a pro-relaxant effect. We observed a larger vasorelaxation induced by exogenous H2S donor in SHRs than in Wistar rats. Additionally, in the presence of PVAT, this effect was potentiated. We demonstrated that PVAT of the TA aggravated endothelial function in SHRs. However, H2S produced by the TA vascular wall had a pro-relaxation effect, and PVAT revealed anti-contractile activity mediated by the release of an unknown factor and potentiated the vasorelaxation induced by exogenous H2S. All these actions could represent a form of compensatory mechanism to balance impaired vascular tone regulation.

Identification of Piezo1 channels in perivascular adipose tissue (PVAT) and their potential role in vascular function

The vasculature constantly experiences distension/pressure exerted by blood flow and responds to maintain homeostasis. We hypothesized that activation of the stretch sensitive, non-selective cation channel Piezo1 would directly increase vascular contraction in a way that might be modified by perivascular adipose tissue (PVAT). The presence and function of Piezo1 was investigated by RT-PCR, immunohistochemistry, and isolated tissue bath contractility. Superior and mesenteric resistance arteries, aortae, and their PVATs from male Sprague Dawley rats were used. Piezo1 mRNA was detected in aortic vessels, aortic PVAT, mesenteric vessels, and mesenteric PVAT. Both adipocytes and stromal vascular fraction of mesenteric PVAT expressed Piezo1 mRNA. In PVAT, expression of Piezo1 mRNA was greater in magnitude than that of Piezo2, transient receptor potential cation channel, subfamily V, member 4 (TRPV4), anoctamin 1, calcium activated chloride channel (TMEM16), and Pannexin1 (Panx1). Piezo1 protein was present in endothelium and PVAT of rat aortic and in PVAT of mesenteric artery. The Piezo1 agonists Yoda1 and Jedi2 (1 nM - 10 µM) did not stimulate aortic contraction [max < 10% phenylephrine (PE) 10 µM contraction] or relaxation in tissues + or -PVAT. Depolarizing the aorta by modestly elevated extracellular K+ did not unmask aortic contraction to Yoda1 (max <10% PE 10 µM contraction). Finally, the Piezo1 antagonist Dooku1 did not modify PE-induced aorta contraction + or -PVAT. Surprisingly, Dooku1 directly caused aortic contraction in the absence (Dooku1 =26 ± 11; Vehicle = 11 ± 11%PE contraction) but not in the presence of PVAT (Dooku1 = 2 ± 1; Vehicle = 8 ± 5% PE contraction). Thus, Piezo1 is present and functional in the isolated rat aorta but does not serve direct vascular contraction with or without PVAT. We reaffirmed the isolated mouse aorta relaxation to Yoda1, indicating a species difference in Piezo1 activity between mouse and rat.

The Role of Perivascular Adipose Tissue in Early Changes in Arterial Function during High-Fat Diet and Its Combination with High-Fructose Intake in Rats

The aim of the current study was to evaluate the influence of a high-fat diet and its combination with high-fructose intake on young normotensive rats, with focus on the modulatory effect of perivascular adipose tissue (PVAT) on the reactivity of isolated arteries. Six-week-old Wistar–Kyoto rats were treated for 8 weeks with a control diet (10% fat), a high-fat diet (HFD; 45% fat), or a combination of the HFD with a 10% solution of fructose. Contractile and relaxant responses of isolated rat arteries, with preserved and removed PVAT for selected vasoactive stimuli, were recorded isometrically by a force displacement transducer. The results demonstrated that, in young rats, eight weeks of the HFD might lead to body fat accumulation and early excitation of the cardiovascular sympathetic nervous system, as shown by increased heart rate and enhanced arterial contractile responses induced by endogenous noradrenaline released from perivascular sympathetic nerves. The addition of high-fructose intake deteriorated this state by impairment of arterial relaxation and resulted in mild elevation of systolic blood pressure; however, the increase in arterial neurogenic contractions was not detected. The diet-induced alterations in isolated arteries were observed only in the presence of PVAT, indicating that this structure is important in initiation of early vascular changes during the development of metabolic syndrome.

Abstract P171: Comparison Of Modulation Of Renal Arterial Tone By Perivascular Adipose Tissue Between Two Animal Models Of Metabolic Syndrome

Sex differences have recently been noticed in the regulation of arterial tone by perivascular adipose tissue (PVAT). In SHRSP.Z- Lepr fa /IzmDmcr (SHRSP.ZF) rats, an animal model of metabolic syndrome (MetS), we demonstrated that mesenteric and renal PVAT in female rats consistently have an enhancing effect on vasodilation at 23 weeks, an age by which the effect of PVAT is impaired in the male rats. This could explain the sex differences in the prevalence of cardiovascular complications in patients with MetS. Therefore, we determined whether the sex difference in PVAT response also occurs in another animal model of MetS, SHR/NDmcr-cp (SHR-cp) rats.Renal arteries were isolated from male and female 23-week-old SHR-cp rats, and ring preparations with and without PVAT were made. After a stable contraction was obtained by phenylephrine administration, vasodilation in response to acetylcholine was examined using organ bath methods.Vasodilation in arteries without PVAT from female rats was smaller than that in arteries without PVAT from male rats, and presence of PVAT in arteries from female rats increased vasodilation to the same level as that observed in arteries without PVAT from male rats. Furthermore, renal PVAT in male rats was shown to have an enhancing effect on vasodilation.The present study did not identify sex differences in renal PVAT-mediated modulation in SHR-cp rats because the enhancing effects of PVAT did not disappear in male SHR-cp rats, in contrast to that observed in male SHRSP.ZF rats at the same age. The difference in PVAT response in male rats between two MetS models may be due to differences in the severity of MetS symptoms, especially blood pressure, between the models.

Perivascular adipose tissue and microvascular endothelial dysfunction in obese mice: Beneficial effects of aerobic exercise in adiponectin receptor (AdipoR1) and peNOSSer1177.

In the present study, we aim to investigate the effects of aerobic physical training on perivascular adipose tissue (PVAT)-induced microvascular dysfunction of the femoral artery in obese mice. Microvascular reactivity was evaluated in control sedentary (c-SD), obese sedentary (o-SD) and obese trained (o-TR) male mice (C57BL6/JUnib), in the absence (PVAT-) or the presence (PVAT+) of femoral artery PVAT. We also analyzed protein expression, vascular nitric oxide (NO) production and reactive oxygen species (ROS) generation in PVAT. The blood glucose, triglycerides and total cholesterol levels were increased in the o-SD group, when compared with the c-SD group. The maximal responses and the potency to acetylcholine (ACh) were decreased in PVAT+ compared with PVAT- rings in the o-SD group, accompanied by a decrease in vascular protein expression of peNOSSer1177 , Cu/Zn-SOD, leptin receptor (Ob-R) and adiponectin receptor (AdipoR1). The protein expression of leptin increased and that of adiponectin decreased in PVAT. Additionally, vascular NO production was reduced and ROS generation was enhanced in PVAT in the o-SD group. Aerobic exercise training was effective for normalizing ACh relaxation response, vascular NO production and ROS generation in the o-TR group. It partially re-established the vascular protein expression of peNOSSer1177 and the PVAT leptin; normalized the vascular Cu/Zn-SOD and AdipoR1 protein expressions. In obese sedentary mice, the presence of PVAT is involved in the process of microvascular dysfunction of the femoral artery in a pathway associated with increased inflammation and ROS generation. The aerobic exercise training normalized the vascular response, the NO production and/or bioavailability and oxidative stress, with improved vascular expressions of Cu/Zn-SOD, peNOSser1177 , and AdipoR1.

Perivascular adipose tissue (PVAT)‐mediated buffering of vasoconstriction in placental ischemia‐induced hypertensive rats

Preeclampsia is a pregnancy-specific hypertensive disorder diagnosed along with systemic endothelial and vascular dysfunction. A novel regulator of vascular tone is the perivascular adipose tissue (PVAT) that surrounds most blood vessels and functions to blunt vasoconstriction. However, it is unknown whether PVAT becomes dysfunctional in preeclampsia. Preeclampsia arises from placental ischemia to elicit release of pro-vasoconstrictive factors into the maternal circulation. In this study, it was hypothesized that placental ischemic rats have attenuated PVAT-mediated buffering of vasoconstriction. Placental ischemia was induced on gestational day 14 in Sprague-Dawley rats by conducting the Reduced Uterine Perfusion Pressure (RUPP) protocol. Conscious blood pressure measurements (carotid catheter) and wire myography were conducted on day 19. Mean arterial blood pressure was significantly elevated (P<0.05) in RUPP (N=6, 117±3 mmHg) vs. Pregnant (N=6, 97±3 mmHg) rats. In aortas, the maximum response (as % increase in force from baseline tension) to KCl-induced depolarization was not affected (P>0.05) by RUPP or the presence of PVAT: Pregnant+PVAT (43±9%) vs. Pregnant-PVAT (42±5%) and RUPP+PVAT (42±%7) vs. RUPP-PVAT (48±7%). Furthermore, phenylephrine (Phe, alpha1-adrenergic receptor agonist)-induced vasoconstriction was similar (P>0.05) in Pregnant+PVAT (69±11%) vs. Pregnant-PVAT (70±12%) and RUPP+PVAT (38±12%) vs. RUPP-PVAT (34±9%), with the 2-way ANOVA detecting a main effect only for RUPP (P<0.05). It was then assessed whether the endothelium controls PVAT function whereby denuding the endothelium did not impact (P>0.05) any of the respective Phe responses in Pregnant+PVAT-Endo (60±12%), Pregnant-PVAT-Endo (72±11%), RUPP+PVAT-Endo (30±15%), or RUPP-PVAT-Endo (22±7%). In smaller, third-order mesenteric arteries, direct depolarization by KCl responses were similar (P>0.05) between Pregnant+PVAT (176±19%), Pregnant-PVAT (149±17%), RUPP+PVAT (148±30%), and RUPP-PVAT (167±27%). As for Phe, the 2-way ANOVA identified a main effect (P<0.05) only for PVAT to blunt Phe-induced vasoconstriction in Pregnant+PVAT (259±38%) vs. Pregnant-PVAT (337±26%) and RUPP+PVAT (176±39%) vs. RUPP-PVAT (379±47%), with no difference for the influence of PVAT between RUPP and Pregnant groups. Removal of the endothelium further attenuated Phe responses in the PVAT groups: Pregnant+PVAT-Endo (174±66%) and RUPP+PVAT-Endo (-3±3%) vs. their respective groups without PVAT: Pregnant-PVAT-Endo (379±39%) and RUPP-PVAT-Endo (339±167%). In fact, the degree of this attenuation to Phe-induced vasoconstriction was the greatest (P<0.05) in the RUPP+PVAT-Endo (-104±3%) group compared all other groups: RUPP-PVAT-Endo (19±59%), Pregnant+PVAT-Endo (10±11%), and Pregnant-PVAT-Endo (10±11%). In conclusion, as it was found that removal of the endothelium allows for enhanced PVAT blunting of vasoconstriction in RUPP rats, these data indicate that placental ischemia drives endothelial dysfunction to subsequently disrupt PVAT function in small arteries during pregnancy.

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.

Abstract P061: Identification Of Piezo1 Channels In Perivascular Adipose Tissue (pvat) And Their Potential Role In Vascular Function

The vasculature constantly experiences distension/pressure exerted by the blood and responds accordingly to maintain homeostasis. Perivascular adipose tissue (PVAT) is gaining support as a formal blood vessel layer and also experiences these changes. We hypothesized that activation of the mechanotransducer Piezo1 directly increases vascular contraction in a way that might be modified by PVAT. The presence of Piezo1 was investigated at the mRNA level via PCR; protein via immunohistochemistry; and contractility via isolated tissue bath. Rat superior and mesenteric arteries, thoracic aortae, human mesenteric vessels and their PVATs were studied. Piezo1 mRNA (beta2 microglobulin calibrator) was expressed in the aortic vessel (2 -ΔC T =0.011); aortic PVAT (2 -ΔC T =0.0172); mesenteric vessel (2 -ΔC T =.00302), and mesenteric PVAT (2 -ΔC T =0.0219). Both adipocytes (2 -ΔC T =0.0249) and stromal vascular fraction (2 -ΔC T =0.0159) of mesenteric PVAT expressed Piezo1 mRNA. Piezo1 mRNA expression was greater in magnitude (one-way ANOVA) than that of the mechanotransducers Piezo2, TRPV4, TMEM16, and Panx1. Piezo1 protein was present in rat aortic PVAT, rat mesenteric (mes) artery, vein, and PVAT, as well as in human artery, vein, and PVAT. The Piezo1 agonists Yoda and Jedi (1 nM - 10 μM) did not stimulate rat aortic contraction [max &lt;10% phenylephrine (PE) 10 μM contraction] or relaxation independent from vehicle in tissues + or - PVAT (relaxation as % of half maximal PE contraction was: Veh-PVAT=45.3±7.0; Yoda-PVAT=46.7±25.6; Jedi-PVAT= 40.4±10.3; Veh+PVAT= 71.8±19.7; Jedi+PVAT=39.1±13.2; Yoda +PVAT=21.6±10.9). Slightly K+ depolarizing the aorta did not unmask contraction to Yoda. Finally, the Piezo1 antagonist Dooku [10 μM] did not shift the PE curve (-log EC50 values [M]: Veh-PVAT= 7.96±0.12; Dooku-PVAT=7.26±0.22, Veh+PVAT=7.29±0.08; Dooku+PVAT=6.96±0.07). Surprisingly, Dooku [10 μM] directly caused aortic contraction in the absence of PVAT (Dooku 27.2±11.7 vs vehicle 13.5±11.2 %PE contraction), but not in the presence of PVAT vs vehicle (Dooku 2.9±1.9 vs Vehicle 7.3±5.2% PE contraction). Thus, Piezo1 is present and functional in the isolated aorta, important knowledge given that this molecule may serve as a translator of vascular pressure.

Western Diet‐Induced Hypertension involves HMGB1/TLR4 Signaling in Perivascular Adipose Tissue of Female Rats

BackgroundOverconsumption of a Western Diet (WD), a high‐fat and high‐sugar diet, is a major factor implicated in rising obesity rates in the US. Perivascular adipose tissue (PVAT) possesses a vasculo‐protective role. In obesity, PVAT expands and becomes inflamed, contributing to vascular complications. High motility group box 1 (HMGB1), a cytokine, has been demonstrated to mediate vascular inflammation. Recent studies also suggest that PVAT plays a role in obesity‐related hypertension; however, the underlying mechanisms are still not well understood. We hypothesize that WD increases HMGB1 production in PVAT which in turn activates Toll‐like receptor 4 (TLR4) signaling in an autocrine/paracrine manner, resulting in hypertension.MethodsWe have established a model of WD‐induced hypertension in female rats. Adult female Wistar rats (n= 9) were randomized into two groups. Control Group (n= 4) received a regular chow diet (5% fat, 48.7% carbohydrates [3.2% sucrose], and 24.1% protein) and WD group (n= 5) received WD (40% fat, 43% carbohydrates [34% sucrose], and 17% protein) for 28 weeks. Metabolic parameters (body weight, body mass index (BMI), triglycerides, and non‐esterified free fatty acids [NEFA]) were assessed. Arterial blood pressure was measured via carotid catherization at the end of the experimental protocol. Thoracic aortas with PVAT were obtained for vascular studies and molecular assays. Vascular studies were performed using a wire myograph to assess vasodilatory responses.ResultsBody weight (358.9 ± 10.2 vs 270.1 ± 12.3g controls, p&lt;0.005) and BMI (0.68 ± 0.02 vs. 0.06 ± 0.03 g/cm2controls, p&lt;0.005) were increased in the WD group, confirming obesity. The WD group also demonstrated increased serum triglycerides (49.8 ± 4.7 vs. 14.3 ± 1.8mg/dL controls, p&lt;0.05) and NEFA (0.57 ± 0.02 vs. 0.79 ± 0.04 mM controls, p&lt;0.05). WD increased systolic blood pressure (144.04 ± 2.8 vs. 115.1 ± 3.9 mmHg controls, p&lt;0.001), diastolic blood pressure (108.3 ± 3.1 vs. 89.5 ± 4.3 mmHg controls, p&lt;0.01), and heart rate (386.1 ± 8.8 vs. 307.7 ± 40.3 bpm controls, p&lt;0.05). Impaired vasodilation in the WD group in comparison to controls was worsened in the presence of PVAT, suggesting dysfunctional PVAT. Histological analysis of PVAT revealed a switch from brown‐like adipose tissue to white‐like adipose tissue, along with a significant decrease in uncoupling protein 1 (UCP‐1) expression (1.5‐fold decreased, p&lt;0.05), a marker of thermogenesis. An oxidative/inflammatory state in the PVAT was confirmed by a 50% increase in reactive oxygen species levels (p&lt;0.01). Strikingly, the novelty of this study revealed increased HMGB1 expression (2.0‐fold increased, p&lt;0.05) along with increased TLR4 expression (2.5‐fold increased, p&lt;0.05) in the PVAT of the WD group.ConclusionOur findings suggest that upregulated HMGB1/TLR4 signaling in the PVAT may induce a local inflammatory response through an autocrine/paracrine manner in the vasculature, contributing to dysregulation of blood pressure in the context of obesity.Support or Funding InformationNIH

Anatomical Feasibility of Right Oblique Approach for L5-S1 Oblique Lumbar Interbody Fusion

We compared left and right vascular anatomy at the L5-S1 disc space and validated the anatomical feasibility of the right oblique approach for L5-S1 oblique lumbar interbody fusion. Axial T2-weighted magnetic resonance imaging studies at the L5-S1 disc level were used to study 274 subjects (164 women and 110 men; average age, 62.97 years). The distance from the center of the L5-S1 disc to the medial wall of the left or right vessel was measured. Using the vessel position, 3 groups were established: medial, middle, and lateral. To describe the morphological configuration, the vessel type and the presence of perivascular adipose tissue (PVAT) around the vessels were identified on both sides. The vessels on the left L5-S1 disc space were located 12.47 mm from the midline and most subjects (209subjects; 76.3%) were included in the medial or middle group. On the right side, the vessels were located more laterally (16.93 mm; P= 0.000) and most subjects (248subjects; 90.5%) were in the middle or lateral group. On the left side, vessels were mostly veins (260 subjects; 94.9%) and 139 subjects (50.7%) had PVAT. On the right side, the vessels were mostly arteries (213 subjects; 77.7%) and 242 (88.3%) had PVAT. The vessels on the right side of the L5-S1 disc were located more laterally, and most vessels on the right side were arteries accompanying PVAT, which might minimize vessel manipulation. These results indicate that the right side of the L5-S1 disc could provide feasible access for oblique lumbar interbody fusion at L5-S1.

The role of perivascular adipose tissue and endogenous hydrogen sulfide in vasoactive responses of isolated mesenteric arteries in normotensive and spontaneously hypertensive rats.

Perivascular adipose tissue (PVAT) and hydrogen sulfide (H2S) play important roles in the modulation of vasoactive responses and can interfere with the ethiopathogenesis of essential hypertension. The aim of this study was to evaluate the mutual relationship between PVAT and H2S (endogenously produced, exogenous) in vasoactive responses of isolated mesenteric arteries (MA) in adult normotensive (Wistar) and spontaneously hypertensive rats (SHR). In SHR, hypertension was associated with cardiac hypertrophy and increased contractility; however, there were no differences in the amount of retroperitoneal fat between strains. PVAT revealed the anti-contractile effect on vasoconstriction induced by exogenous noradrenaline in both strains, but surprisingly, this effect was stronger in SHR. Concurrently; PVAT exhibited a pro-contractile effect on contractions to endogenous noradrenaline released from arterial sympathetic nerves in SHR, but not in Wistar rats. We confirmed the anti-contractile effect of H2S in both, the vascular wall and PVAT of Wistar rats because the pre-treatment with propargylglycine (PPG), an inhibitor of H2S producing enzyme, significantly increased the noradrenaline-induced contraction. In SHR, H2S in the vascular wall exhibited a pro-contractile effect that was eliminated by the presence of PVAT; however, the pre-treatment with PPG did not affect noradrenaline contraction farther. Nevertheless, unlike in Wistar rats, the presence of PVAT potentiated the vasorelaxant effect of exogenously applied H2S in SHR. Our results confirmed that PVAT of MA and endogenously produced H2S could manifest as pro-contractile or as anti-contractile. In SHR, unlike in Wistar rats, the pro-contractile effect of PVAT associated with the stimulation of perivascular nerves, and the pro-contractile effect of H2S in the arterial wall could represent pathologic features. On the other hand, PVAT of SHR is endowed with compensatory vasoactive mechanisms, which include stronger anti-contractile action of an unknown factor (other than H2S) and potentiation of the vasorelaxant effect of exogenous H2S.

2,3,7,8-Tetrachlorodibenzo-p-dioxin Induces Vascular Dysfunction That is Dependent on Perivascular Adipose and Cytochrome P4501A1 Expression.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is associated with hypertension in humans and animals, and studies suggest that cytochrome P4501A1 (Cyp1a1) induction and vascular dysfunction may contribute. We investigated the role of perivascular adipose tissue (PVAT) and Cyp1a1 in TCDD-induced vascular dysfunction. Cyp1a1 wild-type (WT) and knockout (KO) male mice were fed a dough pill containing 1,4-p-dioxane (TCDD vehicle control) on days 0 and 7, or 1000ng/kg TCDD on day 0 and 250ng/kg TCDD on day 7. mRNA expression of Cyp1a1 was assessed on days 3, 7, and 14, and of Cyp1b1, 1a2, angiotensinogen, and phosphodiesterase 5a on day 14. Dose-dependent vasoconstriction to a thromboxane A2 mimetic (U46619), and vasorelaxation to acetylcholine and a nitric oxide donor (S-nitroso-N-acetyl-DL-penicillamine, SNAP), were investigated in the aorta with and without PVAT. Cyp1a1 and 1a2 mRNA was induced in aorta of WT mice only with PVAT, and Cyp1a1 induction was sustained through day 14. TCDD significantly enhanced constriction to U46619 in WT mice and inhibited relaxation to both acetylcholine and SNAP, but only in the presence of PVAT. The effects of TCDD on U46619 constriction and SNAP relaxation were not observed in Cyp1a1 KO mice. Finally, in aorta + PVAT of WT mice TCDD significantly induced expression of angiotensinogen and phosphodiesterase 5a both of which could contribute to the TCDD-induced vascular dysfunction. These data establish PVAT as a TCDD target which is critically involved in mediating vascular dysfunction. TCDD enhances vasoconstriction via the thromboxane/prostanoid (TP) receptor and inhibits vasorelaxation via nitric oxide (NO) signaling. This TCDD-induced vascular dysfunction requires perivascular adipose (PVAT) and cytochrome P4501a1 (CYP1a1) induction.

Influence of Age on Anticontractile Effect of Perivascular Adipose Tissue in Normotensive and Hypertensive Rats.

Perivascular adipose tissue (PVAT) and its vasomodulatory effects play an important role in the physiology and pathophysiology of blood vessels. Alterations in PVAT associated with reduction in its anticontractile influence are proven to contribute to vascular dysfunction in hypertension. The aim of this study was to examine whether the changes in PVAT properties could participate in progression of vascular abnormalities in developing spontaneously hypertensive rats (SHR). Normotensive Wistar-Kyoto (WKY) rats and SHR, both in 5th and in 12th week of age, were used. Systolic blood pressure was similar between WKY rats and SHR in 5th week of age; however, in 12th week, it was significantly increased in SHR comparing to WKY rats. The amount of retroperitoneal fat was higher in WKY rats in both age groups, whereas body weight was higher in WKY rats only in 12th week, when compared to age-matched SHR. From isolated superior mesenteric arteries, two ring preparations were prepared for isometric tension recording, one with PVAT intact and other with PVAT removed. In WKY rats as well as in SHR, arterial contractile responses to noradrenaline, applied cumulatively on rings, were significantly inhibited in the presence of intact PVAT. In both age groups, anticontractile effect of PVAT was higher in WKY rats than in SHR. Neurogenic contractions, induced by electrical stimulation of perivascular sympathoadrenergic nerves, were significantly attenuated in the presence of PVAT in WKY mesenteric arteries from both age groups; however, in arteries from SHR, intact PVAT had no influence on this type of contractile responses. The results suggest that in SHR impairment of anticontractile effect of PVAT precedes hypertension and might contribute to its development.

The angiotensin II type 2 receptor promotes perivascular adipose tissue-dependent dilation in type 2 diabetic female mice and contraction in healthy mice

Diabetes mellitus is associated with severe cardiovascular disorders involving the renin-angiotensin system, mainly through angiotensin II type 1 receptor (AT1R) activation. Although the angiotensin type 2 receptor (AT2R) opposes the effects of AT1R, with vasodilator and anti-trophic properties, its role in diabetes remains debatable. However, AT2R expression level is activated by estrogens and is involved in adipose tissue maturation and in vasodilatation in type 1 diabetes. We investigated the role of AT2R in perivascular adipose tissue (PVAT)-dependent tone in the aorta in a model of type 2 diabetes in female mice with AT2R(AT2R+/+) or without(AT2R−/−). We used 3 month-old female AT2R+/+ and AT2R−/− mice fed a diabetogenic diet in order to induce type 2 diabetes after 4 months. Mice were intact or ovariectomized. Arteries were isolated for in vitro study of vascular reactivity and left with or without PVAT. In AT2R+/+ mice, in the presence of PVAT, phenylephrine-mediated contraction was increased, but PVAT did not affect endothelium dependent (acetylcholine) and independent (sodium nitroprusside)-relaxation. This effect of PVAT was abolished after ovariectomy. PVAT-dependent contraction was also absent in AT2R−/− mice. On the other hand, in type 2 diabetic mice, PVAT was associated with a reduced vasoconstriction and increased vasodilation. In these diabetic mice, PVAT-dependent relaxation was abolished in AT2R−/− mice whereas it was not affected by ovariectomy. Thus, PVAT, in diabetic female mice, opposes vasoconstriction through a mechanism involving AT2R. Therefore AT2R might represent a new therapeutic target in type 2 diabetes in females.