Vasodilator Pathways Research Articles

Correction to: Cyclooxygenase-2 Selectively Controls Renal Blood Flow Through a Novel PPARβ/δ-Dependent Vasodilator Pathway.

HomeHypertensionVol. 71, No. 3Correction to: Cyclooxygenase-2 Selectively Controls Renal Blood Flow Through a Novel PPARβ/δ-Dependent Vasodilator Pathway Free AccessCorrectionPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessCorrectionPDF/EPUBCorrection to: Cyclooxygenase-2 Selectively Controls Renal Blood Flow Through a Novel PPARβ/δ-Dependent Vasodilator Pathway Originally published1 Mar 2018https://doi.org/10.1161/HYP.0000000000000070Hypertension. 2018;71:e10This article corrects the followingCyclooxygenase-2 Selectively Controls Renal Blood Flow Through a Novel PPARβ/δ-Dependent Vasodilator PathwayIn the article by Kirkby et al, “Cyclooxygenase-2 Selectively Controls Renal Blood Flow Through a Novel PPARβ/δ-Dependent Vasodilator Pathway,” which published online on January 2, 2018, and appeared in the February 2018 issue of the journal (Hypertension. 2018;71:297–305. DOI: 10.1161/HYPERTENSIONAHA.117.09906), corrections are needed.In the byline, the author name “Wang Xiaomeng” is set in reverse, and should read “Xiaomeng Wang.” The author byline is corrected to read, “Nicholas S. Kirkby, Walkyria Sampaio, Gisele Etelvino, Daniele T. Alves, Katie L. Anders, Rafael Temponi, Fisnik Shala, Anitha S. Nair, Blerina Ahmetaj-Shala, Jing Jiao, Harvey R. Herschman, Xiaomeng Wang, Walter Wahli, Robson A. Santos, Jane A. Mitchell.” The order of author initials is also corrected in affiliations, to read “Vascular Biology Laboratory, Lee Kong Chian School of Medicine (X.W.) and Lee Kong Chian School of Medicine (W.W), Nanyang Technological University, Singapore, Singapore; Institute of Molecular and Cell Biology, Proteos, Agency for Science Technology and Research, Singapore, Singapore (X.W.); Department of Cell Biology, Institute of Ophthalmology, University College London, United Kingdom (X.W.); Singapore Eye Research Institute (X.W.);” In Sources of Funding, the author name is corrected to read, “a grant from the Singapore Ministry of Education under its Singapore Ministry of Education Academic Research Fund Tier 2 (to X. Wang and W. Wahli, MOE2014-T2-1–036), and Start-Up grants from the Lee Kong Chian School of Medicine, Nanyang Technological University (to X. Wang and W. Wahli).”The authors apologize for the error. These corrections have been made to the current online version of the article, which is available at http://hyper.ahajournals.org/content/71/2/297. Previous Back to top Next FiguresReferencesRelatedDetailsCited By Bindu S, Mazumder S and Bandyopadhyay U (2020) Non-steroidal anti-inflammatory drugs (NSAIDs) and organ damage: A current perspective, Biochemical Pharmacology, 10.1016/j.bcp.2020.114147, 180, (114147), Online publication date: 1-Oct-2020. Related articlesCyclooxygenase-2 Selectively Controls Renal Blood Flow Through a Novel PPARβ/δ-Dependent Vasodilator PathwayNicholas S. Kirkby, et al. Hypertension. 2018;71:297-305 March 2018Vol 71, Issue 3 Advertisement Article InformationMetrics © 2018 American Heart Association, Inc.https://doi.org/10.1161/HYP.0000000000000070PMID: 29440288 Originally publishedMarch 1, 2018 PDF download Advertisement

Characterisation of the vasodilation effects of DHA and EPA, n-3 PUFAs (fish oils), in rat aorta and mesenteric resistance arteries.

Background and purposeIncreasing evidence suggests that the omega-3 polyunsaturated acids (n-3 PUFA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), are beneficial to cardiovascular health, promoting relaxation of vascular smooth muscle cells and vasodilation. Numerous studies have attempted to study these responses, but to date there has not been a systematic characterisation of both DHA and EPA mediated vasodilation in conduit and resistance arteries. Therefore, we aimed to fully characterise the n-3 PUFA-induced vasodilation pathways in rat aorta and mesenteric artery.MethodsWire myography was used to measure the vasomotor responses of freshly dissected rat mesenteric artery and aorta. Arteries were pre-constricted with U46619 and cumulative concentrations of either DHA or EPA (10 nM-30 μM) were added. The mechanisms by which n-3 PUFA relaxed arteries were investigated using inhibitors of vasodilator pathways, which include: nitric oxide synthase (NOS; L-NAME), cycloxygenase (COX; indomethacin), cytochrome P450 epoxygenase (CYP450; clotrimazole); and calcium-activated potassium channels (KCa), SKCa (apamin), IKCa (TRAM-34) and BKCa (paxilline).ResultsBoth DHA- and EPA-induced relaxations were partially inhibited following endothelium removal in rat mesenteric arteries. Similarly, in aorta EPA-induced relaxation was partially suppressed due to endothelium removal. CYP450 also contributed to EPA-induced relaxation in mesenteric artery. Inhibition of IKCa partially attenuated DHA-induced relaxation in aorta and mesenteric artery along with EPA-induced relaxation in mesenteric artery. Furthermore, this inhibition of DHA- and EPA-induced relaxation was increased following the additional blockade of BKCa in these arteries.ConclusionsThis study provides evidence of heterogeneity in the vasodilation mechanisms of DHA and EPA in different vascular beds. Our data also demonstrates that endothelium removal has little effect on relaxations produced by either PUFA. We demonstrate IKCa and BKCa are involved in DHA-induced relaxation in rat aorta and mesenteric artery; and EPA-induced relaxation in rat mesenteric artery only. CYP450 derived metabolites of EPA may also be involved in BKCa dependent relaxation. To our knowledge this is the first study indicating the involvement of IKCa in n-3 PUFA mediated relaxation.

Cyclooxygenase-2 Selectively Controls Renal Blood Flow Through a Novel PPARβ/δ-Dependent Vasodilator Pathway.

Cyclooxygenase-2 (COX-2) is an inducible enzyme expressed in inflammation and cancer targeted by nonsteroidal anti-inflammatory drugs. COX-2 is also expressed constitutively in discreet locations where its inhibition drives gastrointestinal and cardiovascular/renal side effects. Constitutive COX-2 expression in the kidney regulates renal function and blood flow; however, the global relevance of the kidney versus other tissues to COX-2-dependent blood flow regulation is not known. Here, we used a microsphere deposition technique and pharmacological COX-2 inhibition to map the contribution of COX-2 to regional blood flow in mice and compared this to COX-2 expression patterns using luciferase reporter mice. Across all tissues studied, COX-2 inhibition altered blood flow predominantly in the kidney, with some effects also seen in the spleen, adipose, and testes. Of these sites, only the kidney displayed appreciable local COX-2 expression. As the main site where COX-2 regulates blood flow, we next analyzed the pathways involved in kidney vascular responses using a novel technique of video imaging small arteries in living tissue slices. We found that the protective effect of COX-2 on renal vascular function was associated with prostacyclin signaling through PPARβ/δ (peroxisome proliferator-activated receptor-β/δ). These data demonstrate the kidney as the principle site in the body where local COX-2 controls blood flow and identifies a previously unreported PPARβ/δ-mediated renal vasodilator pathway as the mechanism. These findings have direct relevance to the renal and cardiovascular side effects of drugs that inhibit COX-2, as well as the potential of the COX-2/prostacyclin/PPARβ/δ axis as a therapeutic target in renal disease.

Chapter 12 - Cutaneous active vasodilation as a heat loss thermoeffector

Human skin is the interface between the human body and the environment. As such, human temperature regulation relies largely on cutaneous vasomotor and sudomotor adjustments to appropriately thermoregulate. In particular, changes in skin blood flow can increase or decrease the convective heat transfer from internal tissues to the periphery where it can increase or prevent heat loss to the environment. Thermoregulatory control of the cutaneous vasculature is largely due to cutaneous sympathetic nerves. Sympathetic adrenergic nerves mediate vasoconstriction of the skin, similar to other vascular beds, whereas active vasodilator nerves in nonglabrous skin respond to changes in internal and peripheral temperatures and can profoundly increase skin blood flow. Activation of these vasodilator nerves is known as cutaneous active vasodilation and has been the subject of much recent research. This research has uncovered a highly complex system that involves the activation of multiple receptors and vasodilator pathways in a synergistic and sometimes redundant manner. This complexity and redundancy has left our understanding of cutaneous active vasodilation incomplete; however, the employment of new techniques and use of new pharmacologic agents have introduced many new insights into cutaneous active vasodilation.

Transcutaneous Carbon Dioxide Treatment Is Capable of Reducing Peripheral Vascular Resistance in Hypertensive Patients.

We aimed to investigate the effects of a single carbon dioxide (CO2) treatment on arterial stiffness by monitoring the changes of aortic pulse-wave velocity (PWV) and aortic augmentation index (AIXao), which are indicators of arterial stiffness. PWV and AIXao were measured by an invasively validated oscillometric device. The measurements of stiffness parameters were performed before the CO2 treatment, and at 1, 4 and 8 h after the first treatment. Thirty-one patients were included. No significant changes were found in PWV. AIXao decreased significantly 1 h and 4 h after CO2 treatment compared to baseline values (p=0.034 and p<0.001). AIXao increased 8 h after the CO2 treatment, but remained significantly lower than baseline AIXao values (p=0.016). CO2 treatment is capable of reducing peripheral vascular resistance. We hypothesize that CO2 is not only a temporal vasodilator but is also capable of activating vasodilation pathways.

Physical Exercise and ACE2-Angiotensin-(1-7)-Mas Receptor Axis of the Renin Angiotensin System.

Many physiological responses of the Renin Angiotensin System (RAS) are associated with two opposite pathways: (1) a classical one formed by angiotensin-converting enzyme (ACE), Angiotensin II (Ang II) and Angiotensin type 1 (AT1) receptor, which is associated to vasoconstriction, cell proliferation, organ hypertrophy, sodium retention and aldosterone release and (2) a counter-regulatory or vasodilator pathway comprising angiotensin-converting enzyme 2 (ACE2), Angiotensin-(1-7) [Ang-(1-7)] and Mas receptor, which is involved in vasodilation, antiproliferation, anti-hypertrophy, cardioprotective and renoprotective actions. This review aimed to bring up-to-date on the interactions between physical exercise and the vasodilator axis of the RAS (ACE2-Ang-(1-7)-Mas receptor axis). We also investigated the relation of acute and chronic exercise with blood pressure regulation and components of the vasodilator axis of the RAS. We searched studies with animal models and humans in PUBMED, LILACS and IBECS. Experimental studies showed that physical training can stimulate ACE2-Ang-(1-7)-Mas receptor axis in parallel with the inhibition of ACE-Ang II-AT1 receptor pathway. However, up to now, the interaction between the counter-regulatory RAS axis and physical training is not investigated in humans. The activation of ACE2-Ang-(1-7)-Mas receptor axis may have a role in the beneficial effects of physical training in experimental models. Further studies with humans are necessary.

No Sex Differences in Muscle O2 Delivery-to-Utilization Matching Before or During Contractions in Rats

Pre-menopausal women express a reduced arterial blood pressure and risk of cardiovascular disease relative to age-matched men. The mechanism for these outcomes purportedly relate to elevated estrogen levels increasing endothelial nitric oxide (NO) synthase activity and NO-mediated vasorelaxation. PURPOSE: Based on the role that NO plays in the relationship between O2 delivery and utilization, we tested the hypothesis that females would show a fundamentally higher O2 delivery/utilization ratio; especially during muscle contractions, compared to males. METHODS: To test this hypothesis, the spinotrapezius muscle of Sprague Dawley rats (14 total; female = 7, male = 7) was surgically exposed and electrically stimulated at 1 Hz. Oxyphor G4 was injected into the muscle and phosphorescence quenching employed to determine the temporal profile of muscle interstitial space O2 partial pressure (PintO2, determined by O2 delivery/utilization ratio). This was performed under three conditions: control (CON), 300 μM sodium nitroprusside (SNP; NO donor) superfusion, and 1.5 mM L-arginine methyl ester (L-NAME; NOS blockade) superfusion. RESULTS: No differences were found for baseline PintO2 (CON: 21 ± 1 vs 17 ± 2; SNP: 40 ± 3 vs 36 ± 3; L-NAME: 16 ± 2 vs 14 ± 2 mmHg (all p > 0.05)); nor ΔPintO2 during contractions (CON: 13 ± 1 vs 12 ± 2; SNP 20 ± 2 vs 18 ± 2; L-NAME: 11 ± 1 vs 9 ± 1 mmHg (all p > 0.05)) between males and females, respectively. The kinetics response (mean response time) to contractions did not differ in any condition (CON: 17 ± 2 vs 16 ± 3; SNP: 21 ± 2 vs 28 ± 5; L-NAME: 15 ± 2 vs 14 ± 1 seconds (all p > 0.05)) between males and females, respectively. DISCUSSION: In direct contrast to our hypothesis, no sex differences were evident at rest or during contractions under any condition. Therefore, at rest and during muscle contractions, the effect of estrogen on NO bioavailability and vascular control are either insignificant or redundant to other vasodilatory pathways.

Dysregulation of Vasodilatory Pathways is a Contributory Factor to Acute Chest Syndrome

Acute chest syndrome (ACS), the second most common cause of hospitalization for sickle cell disease (SCD) patients and cause for 25% of premature death cases, remains a therapeutic challenge due to the unknown nature of the syndrome's development. SCD patients exhibit a baseline leukocytosis, or pro‐inflammatory state, that increases their risk of developing ACS. Red blood cells (RBC) of SCD patients induce injury to the lung microvasculature resulting in the release of clotting factors and inflammatory mediators. Our hypothesis is that these mediators sustain pulmonary endothelial injury and RBC adhesion to the vessel wall resulting in pulmonary vascular occlusion and ultimately ACS.ObjectiveTo investigate a mechanism by which RBCs stimulate production and release of inflammatory cytokines and proteins in SCD.MethodsStudies were conducted on human pulmonary microvascular endothelial cells (HPMEC) with and without overlay with RBCs or neutrophils of SCD patients in the steady state. Inflammatory mediators were measured by ELISA or Western blotting. Data were analyzed statistically at p&lt;0.05.ResultsHPMEC cultured with RBCs from SCD patients released 40% more leukotriene C4 and 6‐fold more 11β‐PGF2α and more TxA2 than controls. Release of prostacyclin by SCD RBC blood was not different from control.ConclusionsSickle cell mutation‐bearing erythrocytes cause release of inflammatory mediators that activate vasoconstrictive pathways in HPMEC and down‐regulate vasodilatory pathways. This condition may eventually overwhelm the ability of the HPMEC to secrete vasodilators. A closer look at the interaction of these mediators and microvascular endothelium may reveal genetic polymorphisms and provide a potential for therapeutic targeting with gene silencing technology.Support or Funding InformationAMA Foundation

Molecular imaging with engineered physiology.

In vivo imaging techniques are powerful tools for evaluating biological systems. Relating image signals to precise molecular phenomena can be challenging, however, due to limitations of the existing optical, magnetic and radioactive imaging probe mechanisms. Here we demonstrate a concept for molecular imaging which bypasses the need for conventional imaging agents by perturbing the endogenous multimodal contrast provided by the vasculature. Variants of the calcitonin gene-related peptide artificially activate vasodilation pathways in rat brain and induce contrast changes that are readily measured by optical and magnetic resonance imaging. CGRP-based agents induce effects at nanomolar concentrations in deep tissue and can be engineered into switchable analyte-dependent forms and genetically encoded reporters suitable for molecular imaging or cell tracking. Such artificially engineered physiological changes, therefore, provide a highly versatile means for sensitive analysis of molecular events in living organisms.

Mechanisms and time course of menthol-induced cutaneous vasodilation

Menthol is a vasoactive compound that is widely used in topical analgesic agents. Menthol induces cutaneous vasodilation, however the underlying mechanisms are unknown. Determining the rates of appearance and clearance of menthol in the skin is important for optimizing topical treatment formulation and dosing. The purpose of this study was to determine the mechanisms contributing to menthol-mediated cutaneous vasodilation and to establish a time course for menthol appearance/clearance in the skin. Ten young (23±1years, 5 males 5 females) subjects participated in two protocols. In study 1, four intradermal microdialysis fibers were perfused with increasing doses of menthol (0.1-500mM) and inhibitors for nitric oxide (NO), endothelium derived hyperpolarizing factors (EDHFs), and sensory nerves. Skin blood flow was measured with laser Doppler flowmetry and normalized to %CVCmax. In study 2, two intradermal microdialysis fibers were perfused with lactated Ringer's solution. 0.017mL·cm-2 of a 4% menthol gel was placed over each fiber. 5μL samples of dialysate from the microdialysis fibers were collected every 30min and analyzed for the presence of menthol with high performance gas chromatography/mass spectrometry. Skin blood flow (laser speckle contrast imaging) and subjective ratings of menthol sensation were simultaneously obtained with dialysate samples. In study 1, menthol induced cutaneous vasodilation at all doses ≥100mM (all p<0.05). However, inhibition of either NO, EDHFs, or sensory nerves fully inhibited menthol-mediated vasodilation (all p>0.05). In study 2, significant menthol was detected in dialysate 30min post menthol application (0.89ng, p=0.0002). Relative to baseline, cutaneous vasodilation was elevated from minutes 15-45 and ratings of menthol sensation were elevated from minute 5-60 post menthol application (all p<0.05). Menthol induces cutaneous vasodilation in the skin through multiple vasodilator pathways, including NO, EDHF, and sensory nerves. Topical menthol is detectable in the skin within 30min and is cleared by 60min. Skin blood flow and perceptual measures follow a similar time course as menthol appearance/clearance.

Vascular actions of relaxin: nitric oxide and beyond.

This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.

Acute eprosartan-induced intrarenal vasodilation in hypertensive humans is not influenced by dietary sodium intake or angiotensin II co-infusion.

Angiotensin II (Ang II) is thought to play an important role in the development of hypertension. Nevertheless, knowledge on the angiotensin II type-1-receptors (AT1Rs) in the hypertensive kidney and the influence of sodium intake and renin-angiotensin system activity on intrarenal AT1R blockade is scarce. To improve our understanding of renal AT1Rs in hypertensive patients, we studied the effects of acute, local administration of AT1R-blocker eprosartan in kidneys of patients with essential hypertension (off medication). In 73 hypertensive patients who were scheduled for diagnostic renal angiography, we measured renal blood flow (Xenon washout method) before and during intrarenal infusion of two incremental doses of eprosartan (3 and 10 μg/kg/min for 15 min per dose). We hypothesized that the vasodilatory effects of eprosartan would be enhanced by low sodium intake and would be reduced during Ang II co-infusion. Therefore, we allocated the patients to either a high or a low sodium diet and coinfused Ang II (1 ng/kg/min) in a subgroup. Eprosartan infusion resulted in intrarenal vasodilation in all groups. No differences in the magnitude of this effect were found between the groups. No correlation was found between 24-h urinary sodium excretion (a proxy for dietary sodium intake) and the effect of eprosartan. Eprosartan-induced vasodilation is not influenced by sodium intake and/or co-infusion of Ang II. These rather unexpected findings could be explained by differences between circulating and tissue Ang II levels, variations in AT1R expression, and/or stimulation of other vasodilatory pathways.

The influence of silica nanoparticles on small mesenteric arterial function.

To determine the influence of silica nanoparticles (SiNPs) on small arterial function; both ex vivo and in vivo. Mono-dispersed dye-encapsulated SiNPs (97.85 ± 2.26 nm) were fabricated and vasoconstrictor and vasodilator responses of mesenteric arteries assessed. We show that while exposure to SiNPs under static conditions, attenuated endothelial dependent dilator responses ex vivo, attenuation was only evident at lower agonist concentrations, when exposed under flow conditions or after intravenous administration in vivo. Pharmacological inhibition studies suggest that SiNPs may interfere with the endothelial dependent hyperpolarizing factor vasodilator pathway. The dosage dependent influence of SiNPs on arterial function will help identify strategies for their safe clinical administration.

Hypoxia and hyperoxia potentiate PAF receptor-mediated effects in newborn ovine pulmonary arterial smooth muscle cells: significance in oxygen therapy of PPHN.

Platelet‐activating factor (PAF) acting via its receptor (PAFR) is implicated in the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN). Effects of long‐term oxygen therapy on newborn lung are not well understood; therefore, we studied the effect of oxygen tension on ovine newborn pulmonary artery smooth muscle cells (NBPASMC). Our global hypothesis is that PPHN results from failure of newborn lamb pulmonary system to downregulate PAFR activity or to upregulate vasodilatory cyclic nucleotides (Cnucs) activity. NBPASMC from newborns 6–12 days old were studied in vitro at three different oxygen tensions (pO 2, [Torr]: hypoxia, <40; normoxia, 80–100; and hyperoxia, >100 Torr often clinically imposed upon newborns with PPHN). PAFR‐ and Cnucs mediated effects were determined. PAFR and PKA Cα mRNA expression as well as prostacyclin, thromboxane, cAMP production, and DNA synthesis was studied to assess PAFR‐mediated hypertrophy and/or hyperplasia. Hypoxia and hyperoxia increased specific PAFR binding. PAF treatment during hyperoxia increased PAFR gene, but decreased PKA‐Cα gene expression. Hypoxia and hyperoxia increased NBPASMC proliferation via PAFR signaling. Baseline prostacyclin level was ninefold greater than in fetal PASMC, whereas baseline thromboxane was sevenfold less suggesting greater postnatal cyclooxygenase activity in NBPASMC. PAF decreased, while forskolin and 8‐Br‐cAMP increased cAMP production. Decrease of PAFR effects by Cnucs indicates that normal newborn PA physiology favors vasodilator pathways to minimize PAF‐induced hypertrophy or hyperplasia. We speculate that failure of newborn lung to anchor downregulation of vasoconstrictors with upregulation of vasodilators leads to PPHN.

Temporal Changes in Skeletal Muscle Capillary Responses and Endothelial-Derived Vasodilators in Obesity-Related Insulin Resistance.

The inability of insulin to increase skeletal muscle capillary blood volume (CBV) reduces glucose uptake in insulin resistance (IR). We hypothesized that abnormalities in endothelial-derived vasodilator pathways are temporally associated with the development of IR and an impaired ability to increase skeletal muscle CBV. A comprehensive metabolic and vascular screening assessment was performed on 10 adult rhesus macaques at baseline and every 4–6 months for 2 years after starting a high-fat diet supplemented with fructose. Diet changes resulted in an 80% increase in truncal fat by 4 months. Hyperinsulinemia and decreased glucose utilization were observed from 4 to 18 months. At 24 months, pancreatic secretory function and the glucose utilization rate declined. CBV at rest and during an intravenous glucose tolerance test demonstrated a sustained increase from 4 to 18 months and then abruptly fell at 24 months. Nitric oxide bioavailability progressively decreased over 2 years. Conversely, endothelial-derived vasodilators progressively increased over 18 months and then abruptly decreased at 24 months in concert with the CBV. The increase in basal and glucose-mediated CBV early in IR may represent a compensatory response through endothelial-derived vasodilator pathways. The inability to sustain a vascular compensatory response limits glucose-mediated increases in CBV, which correlates with the severity of IR.

0093 : Endothelium masks increased sympathetic vasopressor activity in rats with metabolic syndrome

Despite sympathetic hyperactivation is considered as a key trigger of hypertension, in some obese or metabolic syndrome (MetS) subjects, such altered sympatho-vagal balance was not associated with changes in arterial blood pressure. Vascular endothelium is a potent modulator of adrenergic vascular tone, thus we aimed to determine, in a rat model of MetS, whether the endothelium and especially the classical vasodilatory eNOS-NO pathway could counteract the effect of increased sympathetic vasopressor action. After14 weeks of high fat high sucrose diet (HFS), HFS developed several features of MetS phenotype, such as increased body mass, abdominal fat accumulation, high LDL and triglycerides levels, higher fasting blood glucose and insulinemia, as well as impaired glucose and insulin tolerance compared with control rats (Ctrl) fed with standard diet. As assessed by catecholamine assay and heart rate variability analysis (HRV), HFS rats also presented increased sympathetic outflow but without consequences on skin microcirculation and arterial blood pressure. In HFS rats, vascular reactivity test revealed hyporeactivity to α1-adrenergic receptors (AR) stimulation with unchanged α 1DAR expression. This phenomenon was rather due to endothelial adaptation since endothelial removal or eNOS inhibition by L-NAME normalized adrenergic vasoconstriction in HFS rats. In addition, eNOS phosphorylation (activation site, ser1177) was increased by PE in HFS ones only. In line with this result, eNOS inhibition in-vivo also revealed higher blood pressure in HFS rats compared to Ctrl ones. In conclusion, tonic restrain of adrenergic vasopressor action by endothelium is increased in HFS rats which contribute to maintain their blood pressure in normal range. The author hereby declares no conflict of interest

Mechanism of vascular dysfunction due to circulating factors in women with pre-eclampsia.

Circulating factors have been proposed to play a major role in the pathophysiology of endothelial dysfunction in pre-eclampsia (PE), which is defined as new-onset hypertension with proteinuria after 20 weeks of gestation. However, the mechanisms leading to altered vascular reactivity remain unclear. We hypothesized that circulating factors lead to endothelial dysfunction by increasing oxidative stress and reducing nitric oxide (NO) and prostaglandin (PG) bioavailability. Pregnant rat uterine and mesenteric arteries were incubated overnight with 3% normotensive (NP) or PE plasma collected from women upon admission to hospital. Responses to methacholine (MCh) were obtained using wire myography to assess endothelial function pathways. Vascular superoxide level was measured via dihydroethidium staining and nitric oxide synthase (NOS) expression via Western blots. PE plasma significantly increased superoxide levels and impaired endothelial dysfunction in uterine arteries (Emax 79.9±5.6% compared with 44.9±6.3%, P=0.0004), which was restored in the presence of oxidant scavengers or PG synthesis inhibition. Uterine artery vasodilation was abolished in the presence of pan-NOS inhibitor (P<0.0001) in both NP- and PE-treated vessels, but inducible nitric oxide synthase (iNOS)-dependent vasodilation was present only in NP-treated arteries. Uterine arteries exposed to PE plasma exhibit an increased endothelial NOS expression and a decreased iNOS expression. PE plasma did not alter endothelial function in mesenteric arteries, suggesting that the effect of circulating factors was vascular-bed-specific. We have shown that circulating factors lead to endothelial dysfunction via altered oxidative stress and vasodilator pathways. The present study contributes to our understanding of the pathophysiology and finding a potential target for intervention in PE.

Fetal and postnatal ovine mesenteric vascular reactivity.

Intestinal circulation and mesenteric arterial (MA) reactivity may play a role in preparing the fetus for enteral nutrition. We hypothesized that MA vasoreactivity changes with gestation and vasodilator pathways predominate in the postnatal period. Small distal MA rings (0.5-mm diameter) were isolated from fetal (116-d, 128-d, 134-d, and 141-d gestation, term ~ 147 d) and postnatal lambs. Vasoreactivity was evaluated using vasoconstrictors (norepinephrine (NE) after pretreatment with propranolol and endothelin-1(ET-1)) and vasodilators (NO donors A23187 and s-nitrosopenicillamine (SNAP)). Protein and mRNA assays for receptors and enzymes (endothelin receptor A, alpha-adrenergic receptor 1A (ADRA1A), endothelial NO synthase (eNOS), soluble guanylyl cyclase (sGC), and phosphodiesterase5 (PDE5)) were performed in mesenteric arteries. MA constriction to NE and ET-1 peaked at 134 d. Relaxation to A23187 and SNAP was maximal after birth. Basal eNOS activity was low at 134 d. ADRA1A mRNA and protein increased significantly at 134 d and decreased postnatally. sGC and PDE5 protein increased from 134 to 141 d. Mesenteric vasoconstriction predominates in late-preterm gestation (134 d; the postconceptional age with the highest incidence of necrotizing enterocolitis (NEC)) followed by a conversion to vasodilatory influences near the time of full-term birth. Perturbations in this ontogenic mechanism, including preterm birth, may be a risk factor for NEC.

Developmental acceleration of bradykinin-dependent relaxation by prenatal chronic hypoxia impedes normal development after birth.

Bradykinin-induced activation of the pulmonary endothelium triggers nitric oxide production and other signals that cause vasorelaxation, including stimulation of large-conductance Ca(2+)-activated K(+) (BKCa) channels in myocytes that hyperpolarize the plasma membrane and decrease intracellular Ca(2+). Intrauterine chronic hypoxia (CH) may reduce vasorelaxation in the fetal-to-newborn transition and contribute to pulmonary hypertension of the newborn. Thus we examined the effects of maturation and CH on the role of BKCa channels during bradykinin-induced vasorelaxation by examining endothelial Ca(2+) signals, wire myography, and Western immunoblots on pulmonary arteries isolated from near-term fetal (∼ 140 days gestation) and newborn, 10- to 20-day-old, sheep that lived in normoxia at 700 m or in CH at high altitude (3,801 m) for >100 days. CH enhanced bradykinin-induced relaxation of fetal vessels but decreased relaxation in newborns. Endothelial Ca(2+) responses decreased with maturation but increased with CH. Bradykinin-dependent relaxation was sensitive to 100 μM nitro-L-arginine methyl ester or 10 μM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, supporting roles for endothelial nitric oxide synthase and soluble guanylate cyclase activation. Indomethacin blocked relaxation in CH vessels, suggesting upregulation of PLA2 pathways. BKCa channel inhibition with 1 mM tetraethylammonium reduced bradykinin-induced vasorelaxation in the normoxic newborn and fetal CH vessels. Maturation reduced whole cell BKCa channel α1-subunit expression but increased β1-subunit expression. These results suggest that CH amplifies the contribution of BKCa channels to bradykinin-induced vasorelaxation in fetal sheep but stunts further development of this vasodilatory pathway in newborns. This involves complex changes in multiple components of the bradykinin-signaling axes.

TRPM8 Channel Activation Induced by Monoterpenoid Rotundifolone Underlies Mesenteric Artery Relaxation

In this study, our aims were to investigate transient receptor potential melastatin-8 channels (TRPM8) involvement in rotundifolone induced relaxation in the mesenteric artery and to increase the understanding of the role of these thermosensitive TRP channels in vascular tissue. Thus, message and protein levels of TRPM8 were measured by semi-quantitative PCR and western blotting in superior mesenteric arteries from 12 week-old Spague-Dawley (SD) rats. Isometric tension recordings evaluated the relaxant response in mesenteric rings were also performed. Additionally, the intracellular Ca2+ changes in mesenteric artery myocytes were measured using confocal microscopy. Using PCR and western blotting, both TRPM8 channel mRNA and protein expression was measured in SD rat mesenteric artery. Rotundifolone and menthol induced relaxation in the isolated superior mesenteric artery from SD rats and improved the relaxant response induced by cool temperatures. Also, this monoterpene induced an increase in transient intracellular Ca2+. These responses were significantly attenuated by pretreatment with capsazepine or BCTC, both TRPM8 channels blockers. The response induced by rotundifolone was not significantly attenuated by ruthenium red, a non-selective TRP channels blocker, or following capsaicin-mediated desensitization of TRPV1. Our findings suggest that rotundifolone induces relaxation by activating TRPM8 channels in rat superior mesenteric artery, more selectively than menthol, the classic TRPM8 agonist, and TRPM8 channels participates in vasodilatory pathways in isolated rat mesenteric arteries.