Tension In Arteries Research Articles

Hydroxysafflor yellow A actives BKCa channels and inhibits L-type Ca channels to induce vascular relaxation

Hydroxy-safflor yellow A (HSYA) can exert a variety of effects upon the vascular system. However, the underlying mechanisms are not clear. The present study is to investigate its vasodilating effect and the mechanisms. Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were enrolled for studying effects of HSYA on blood pressure, vasodilation, intracellular Ca2+ transient and membrane ion channels. Vasodilation and intracellular Ca2+ transient were measured by using vasomotor assay and fluorescence imaging system, respectively. The effect of HSYA on the large conductance Ca2+ activated and voltage-gated potassium channel (BKCa channel) currents in rat mesentery artery and on L-type calcium channel (Ca-L) currents in HEK293cells expressed with Ca-L were investigated using patch clamp techniques. Blood pressure of SHR and WKY rats were concentration dependently reduced by HSYA with a larger effect of HSYA in SHR than that in WKY rats. The tension of mesenteric arteries induced by 3 μM phenylephrine was attenuated by HSYA (IC50 = 90.8 μΜ). Patch clamp study showed that HSYA could activate BKCa channels and suppress Ca-L channels in a concentration dependent manner. The results of calcium signaling assays indicated that HSYA could reduce the intracellular free Ca2+ level. These findings demonstrate that HSYA could activate BKCa channels and inhibit Ca-L channels and reduce intracellular free Ca2+ level, which are probably important for its vasodilatory effect.

Effect of NO inhalation on ECMO use rate and mortality in infants born at or near term with respiratory failure.

Background:The molecular studies showed that Nitric oxide (NO) is an essential factor which regulates pulmonary artery tension. However, the conclusions of existing clinical studies were inconsistent.Objective:This meta-analysis is aimed to determine whether the inhalation of NO could improve oxygenation and reduce rate of death and use of extracorporeal membrane oxygenation (ECMO).Methods:The strategies used to search PubMed, The Cochrane Central Register of Controlled trials in the Cochrane Library, Embase, Web of science, Clinical Trials Registry, and China Biology Medicine disc, from inception to February, 2018. The primary outcomes were death or use of ECMO, death before hospital discharge, use of ECMO before hospital discharge, change in PaO2 after treatment. We assess the risk of bias in each included study by Cochrane Handbook, and calculated typical estimates of RR, each with its 95% CI, and for continuous outcomes, WMD or a summary estimate for SMD, each with its 95% CI.Results:Nine randomized controlled trials (RCTs) with a total of 856 participants were included in this meta-analysis. This meta-analysis revealed that the experimental group had significantly lower death or use of ECMO (RR 0.66, 95% CI 0.57–0.77, I2 = 0%, P < .00001) and lower use of ECMO before hospital discharge (RR 0.89, 95% CI 0.50–0.71, I2 = 0%, P < .00001) compared to control group. And in the infants without diaphragmatic hernia, experimental group had significantly higher change in PaO2 after treatment (MD 50.40, 95% CI 32.14–68.66, P < .00001). The meta-analysis also showing a tendency to improve in the death before hospital discharge (RR 0.89, 95% CI 0.60–1.31, I2 = 0%, P = .55) and the change in PaO2 after treatment of the infants with diaphragmatic hernia (MD 6.70, 95% CI −2.32 to 15.72, P < .00001, P = .15), but no difference between experimental group and control group.Conclusion:We found that NO inhalation can improve oxygenation and reduce rate of death and use of ECMO in this meta-analysis. Therefore, we recommend the use of NO inhalation for infants born at or near term with respiratory failure.

Effects of n-3 polyunsaturated fatty acid on store-operated calcium channels in coronary artery smooth muscle cells derived from diabetic rat

Objective: To investigate the impact of n-3 polyunsaturated fatty acid (n-3 PUFA) on function and expression of store-operated calcium channels (SOCC) in coronary artery smooth muscle cells (SMC) derived from diabetic rat. Methods: A total of 180 healthy male Sprague-Dawley (SD) rats were randomly divided into normal group (N, n=45), placebo-treated diabetic group (D, n=45), lose dose n-3 PUFA treated diabetic group (DL, n=45) and high dose n-3 PUFAs treated diabetic group (DH, n=45). Streptozotocin-induced diabetic rat animal model was established by two consecutive intraperitoneal injections. After modeling, rats in group DL and DH were treated with 10 mg·kg(-1)·d(-1) and 50 mg·kg(-1)·d(-1) n-3 PUFAs respectively per gavage for eight weeks. After eight weeks, rat coronary artery SMC was isolated by enzyme digestion. Changes of cytosolic calcium concentration in coronary artery SMC were examined by calcium fluorescence imaging technique, coronary artery tension was detected by myograph system, and protein expressions of SOCC on coronary artery SMC were measured by Western blot. Results: SOCC induced ΔF340/F380 of group N, D, DL and DH were 0.425±0.023, 0.838±0.037, 0.342±0.052 and 0.364±0.045 respectively, which was significantly lower in group N, DL, DH than in group D (P<0.05). SOCC induced changes of tensions were 0.94±0.09, 1.95±0.18, 1.35±0.24 and 1.01±0.18 in the group N, D, DL and DH, respectively, which was significantly lower in group N and DH than in group D (P<0.05). Protein expressions of STIM1, Orai1 and TRPC1 were significantly higher in diabetic rat coronary SMC than in group N (P<0.05). STIM1 protein expressions were significantly lower in group DL and DH than in group D, and Orai1 and TRPC1 protein expressions were similar among group. Conclusions: Coronary artery tension, cytosolic calcium concentration and protein expressions of SOCC are higher in diabetic rat coronary artery SMC when compared with normal rats. n-3 PUFA intervention could downregulate the protein expression of SOCC, reduce cytosolic calcium concentration and coronary artery tension, and is protective to the diabetic injury in coronary artery.

Placental effects and transfer of sildenafil in healthy and preeclamptic conditions.

BackgroundThe phosphodiesterase-5 inhibitor (PDE5) sildenafil has emerged as a promising treatment for preeclampsia (PE). However, a sildenafil trial was recently halted due to lack of effect and increased neonatal morbidity.MethodsEx vivo dual-sided perfusion of an isolated cotyledon and wire-myography on chorionic plate arteries were performed to study the effects of sildenafil and the non-selective PDE inhibitor vinpocetine on the response to the NO donor sodium nitroprusside (SNP) under healthy and PE conditions. Ex vivo perfusion was also used to study placental transfer of sildenafil in 6 healthy and 2 PE placentas. Furthermore, placental mRNA and protein levels of eNOS, iNOS, PDE5 and PDE1 were quantified.FindingsSildenafil and vinpocetine significantly enhanced SNP responses in chorionic plate arteries of healthy, but not PE placentas. Only sildenafil acutely decreased baseline tension in arteries of both healthy and PE placentas. At steady state, the foetal-to-maternal transfer ratio of sildenafil was 0·37 ± 0·03 in healthy placentas versus 0·66 and 0·47 in the 2 PE placentas. mRNA and protein levels of PDE5, eNOS and iNOS were comparable in both groups, while PDE1 levels were lower in PE.InterpretationThe absence of sildenafil-induced NO potentiation in arteries of PE placentas, combined with the non-PDE-mediated effects of sildenafil and the lack of PDE5 upregulation in PE, argue against sildenafil as the preferred drug of use in PE. Moreover, increased placental transfer of sildenafil in PE might underlie the neonatal morbidity in the STRIDER trial.FundThis study was funded by an mRACE Erasmus MC grant.

Decreased vasodilatory effect of Tanshinone ⅡA Sodium Sulfonate on mesenteric artery in hypertension

Tanshinone ⅡA Sodium Sulfonate (DS-201), a derivative of traditional Chinese medicinal herb Danshen, has been clinically used for various cardiovascular diseases. Previous studies showed that DS-201 induced vascular relaxation partly due to the activation of the large conductance Ca2+-activated potassium (BKCa) channels. However, the efficacy of DS-201 on the resistant vessels in hypertension remains unknown. Mesentery arteries obtained from spontaneously hypertensive rats (SHR) and hypertension patients were used in this study. The endothelium-denuded mesenteric arteries were prepared to measure the artery tension and evaluate the vasodilatory effect of DS-201. The results showed that DS-201 had a vasodilatory effect on the mesenteric artery rings pre-contracted with either phenylephrine (PE) or thromboxane mimetic U46619 in a concentration-dependent manner. However, the vasodilatory effect of DS-201 significantly decreased in hypertension than in control arteries due to a decrease in protein level of BKCa β1subunit. A BKCa channel blocker IbTX (200 nM) significantly inhibited the relaxant effect of DS-201 on non-hypertensive arteries, whereas the BKCa channel specific agonist NS1619 rescued the vasodilating effects of DS-201 on hypertensive vessels. These results indicate that the vasodilating effect of DS-201 is BKCa-dependent. This study demonstrated that DS-201 alone may not be effective for treating hypertension, but it may be considered as therapy combined with BKCa-agonists or methods rescuing BKCa functions.

Effects of vasopressin during a pulmonary hypertensive crisis induced by acute hypoxia in a rat model of pulmonary hypertension

BackgroundA pulmonary hypertensive crisis (PHC) can be a life-threatening condition. We established a PHC model by exposing rats with monocrotaline (MCT)-induced pulmonary hypertension to acute hypoxia, and investigated the effects of vasopressin, phenylephrine, and norepinephrine on the PHC. MethodsFour weeks after MCT 60 mg kg−1 administration i.v., right ventricular systolic pressure (RVSP), systolic BP (SBP), mean BP (MBP), cardiac index (CI), and pulmonary vascular resistance index (PVRI) were measured. PHC defined as an RVSP exceeding or equal to SBP was induced by changing the fraction of inspiratory oxygen to 0.1. Rats were subsequently treated by vasopressin, phenylephrine, or norepinephrine, followed by assessment of systemic haemodynamics, isometric tension of femoral and pulmonary arteries, cardiac function, blood gas composition, and survival. ResultsPHC was associated with increased RV dilatation and paradoxical septal motion. Vasopressin increased MBP [mean (standard error)] from 52.6 (3.8) to 125.0 (8.9) mm Hg and CI from 25.4 (2.3) to 40.6 (1.8) ml min−1 100 g−1 while decreasing PVRI. Vasopressin also improved RV dilatation, oxygenation, and survival in PHC. In contrast, phenylephrine increased MBP from 54.8 (2.3) to 96.8 (3.2) mm Hg without improving cardiac pump function. Norepinephrine did not alter MBP. Vasopressin contracted femoral but not pulmonary arteries, whereas phenylephrine contracted both arterial beds. Hence, improvements with vasopressin in PHC might be associated with decreased PVRI and selective systemic vasoconstriction. ConclusionsIn this rat model of a PHC, vasopressin, but not phenylephrine or norepinephrine, resulted in better haemodynamic and vascular recovery.

NO donors induce vascular relaxation by different cellular mechanisms in hypertensive and normotensive rats

PurposeThis study investigated the intracellular mechanisms involved in the vasodilatation induced by the classic NO donor SNP and the non-classic NO donor cis-[Ru(bpy)2(py)(NO2)](PF6) (or RuBPY) in mesenteric resistance arteries obtained from renal hypertensive (2K-1C) and normotensive (2K) rats. MethodsOn the basis of fluorimetric assays in cultured vascular smooth muscle cells (VSMCs) isolated from 2K-1C and 2K rats, we measured NO release from SNP and RuBPY, cytosolic Ca2+ concentration ([Ca2+]c), and reactive oxygen species (ROS) with the selective probes DAF-2DA, Fluo-3AM and the more selective probe for peroxynitrite (7-CBA), respectively. We determined isometric tension in mesenteric arteries to assess SNP- and RuBPY-induced relaxation. ResultsSNP and RuBPY released NO in comparable amounts in cultured aortic VSMCs from hypertensive 2K-1C and normotensive 2K rats. The NO0 scavenger hydroxocobalamin blunted NO release. Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) inhibition with thapsigargin reduced [Ca2+]c in normotensive 2K rat VSMCs only. ROS amounts were greater in hypertensive 2K-1C than in normotensive 2K rat VSMCs, but neither SNP nor RuBPY altered ROS concentrations in any of the groups. SNP and RuBPY induced similar relaxation in hypertensive 2K-1C and normotensive 2K rat mesenteric resistance arteries. The SNP and RuBPY-induced relaxation involves sGC and PKG activation. On the other hand, SNP but not RuBPY activates K+ channels. Interestingly, SERCA inhibition reduces SNP induced relaxation only in normotensive 2K rat mesenteric arteries whereas RuBPY-induced relaxation does not involve SERCA activation in both normotensive and hypertensive arteries. ConclusionOur results indicate that SNP and RuBPY-induced mesenteric resistance artery relaxation involves NO/sGC/cGMP/PKG pathway activation. K+ channels and SERCA activation is required to SNP but not for RuBPY-induced relaxation. Moreover, SERCA seems to be impaired in hypertensive 2K-1C rat mesenteric resistance arteries although it does not impact SNP- or RuBPY-induced relaxation.

Simultaneous Measurements of Tension and Free H2S in Mesenteric Arteries.

Hydrogen sulfide (H2S), in addition to nitric oxide and carbon monoxide, is the third gasotransmitter and known to cause relaxation in peripheral arteries. Here we describe a method that allows simultaneous measurement of contractility in arteries mounted in an isometric wire myograph and the concentration of free H2S in the lumen of the artery as well as in the organ bath. This method can be used to directly correlate how much free H2S is needed to cause relaxation, which previously has been difficult to answer as H2S can be found in many different forms.

G-Protein-gated Inwardly-Rectifying K+ Channels and Large-conductance Calcium-Activated K+ Channels Are Involved in C-Type Natriuretic Peptide-Mediated Vasodilation in Human Arteries.

C-type natriuretic peptide (CNP) hyperpolarizes and relaxes the smooth muscle of blood vessels. We investigated whether G-protein-gated inwardly-rectifying K+ channels (GIRK) and large-conductance calcium-activated K+ channels (BKCa channels) were involved in CNP-evoked vasodilatation in human arteries. Isometric tension in human gastroepiploic arteries was measured using a wire myograph. Ion channel currents were recorded by the whole-cell patch-clamp technique. The concentration-dependent vasodilation induced by CNP was reduced significantly after inhibition of GIRK channels (by tertiapin-Q) or of BKCa channel (by paxilline). Immunochemical experiments showed that GIRK3 and GIRK4 subunits were expressed in human arteries. CNP also strongly increased the current density of GIRK and BKCa channels in human arterial smooth muscles. This suggested that the GIRK channel was functionally expressed in smooth muscle and vasodilation action was produced by CNP partly by opening the GIRK and BKCa channels in the human artery.

A13081 Effects of losartan on myocardial remodeling and coronary artery tension in HFHSs rats

A13081 Effects of losartan on myocardial remodeling and coronary artery tension in HFHSs rats

Renal Denervation Sensitizes Renal Resistance Arteries to L‐type Ca2+ Channel Activation

We have shown that a depolarized vascular smooth muscle cell (VSMC) membrane potential sensitizes renal resistance arteries of sympathectomized rats to L‐type Ca2+‐channel activation. We tested if local renal denervation induces a similar alteration. Further, we investigated the contribution of ATP‐dependent potassium (KATP) channels for the regulation of renal resistance artery tone and tested if a depolarized VSMC membrane potential contributes to the increase in renal arterial norepinephrine (NE) sensitivity that develops after sympathectomy and renal denervation.Renal resistance arteries were obtained from rats that underwent neonatal sympathectomy, local renal denervation or respective sham‐treatments. In addition, interlobular and distal arcuate arteries were dissected from human kidney samples. Vessels were investigated by small vessel myography. Cumulative concentration‐response curves (CRCs) were obtained for the L‐type Ca2+ channel activator S‐(−)‐BayK8644 and NE in the absence or presence of glibenclamide (KATP channel blocker) and levcromakalim (KATP channel activator).Maximum S‐(−)‐BayK8644‐induced wall tension was 70% of maximum K+‐induced wall tension in arteries from sympathectomized and renal denervated rats vs. 30% of maximum K+‐induced wall tension in controls (p &lt; 0.05). In human intrarenal arteries maximum S‐(−)‐BayK8644‐induced tension was 100% of K+‐induced tension. Levcromakalim (1 μM) abolished S‐(−)‐BayK8644 induced vasoconstrictions in rat and human arteries. Compared to respective controls, arteries from sympathectomized and renal denervated rats showed a leftward shift of the NE CRCs. Glibenclamide did not affect basal and NE‐induced wall tension in rat and human renal resistance arteries. Levcromakalim induced similar rightward shifts of the NE CRCs in vessels from sympathectomized, renal denervated and sham‐treated rats (DlogEC50 −0.58 – −0.27 M) and significantly blunted NE‐induced vasoconstrictions in human renal resistance arteries.L‐type Ca2+ channel activation is facilitated in renal resistance arteries of locally denervated kidneys suggesting that VSMC membrane potential is depolarized compared to VSMC from innervated kidneys. KATP channels are functional in rat and human renal resistance arteries. They play a minor role for the maintenance of basal tone but may mediate agonist‐induced vasodilation. The data further suggest that VSMC membrane potential depolarization does not significantly contribute to sympathectomy‐ and denervation‐induced NE supersensitivity in renal resistance arteries.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Protective cerebrovascular effects of hydroxysafflor yellow A (HSYA) on ischemic stroke

The purpose of the present work was designed to explore protective cerebrovascular effects of hydroxysafflor yellow A (HSYA), and provide preclinical efficacy and mechanism data for its possible application in patients with cerebral ischemia. The protective effect of HSYA on ischemic stroke was evaluated by infarct sizes and neurological scores in Sprague-Dawley (SD) rats with middle cerebral artery occlusion (MCAO). Cerebrovascular permeability was detected by Evans blue dye leakage in MCAO rats. Cerebral blood flow, as well as blood pressure and heart rate were monitored using flow probes in Beagle dogs. Basilar artery tension isolated from Beagle dogs was evaluated with an MPA 2000 data-acquisition system. Coagulation-related function was also judged, including rabbit platelet aggregation by adenosine diphosphate (ADP) and platelet-aggregating factor (PAF), rabbit blood viscosity by a blood viscometer, and thrombus formation by rat arterial-venous shunts. Results showed that HSYA treatment significantly decreased the infarct sizes, neurological scores and cerebrovascular permeability in rats with MCAO. However, cerebral blood flow, blood pressure and heart rate were not affected by HSYA. In vitro, HSYA had a strong effect on cerebrovascular vasodilatation, and significantly decreased platelet aggregation, blood viscosity, and thrombogenesis. Besides well-known anti-coagulation effects, HSYA protects against ischemic stroke by dilating cerebral vessels and improving cerebrovascular permeability.

Regulation of Coronary Arterial Large Conductance Ca2+-Activated K+ Channel Protein Expression and Function by n-3 Polyunsaturated Fatty Acids in Diabetic Rats

Aim: The objective of this study was to examine the effects of n-3 polyunsaturated fatty acids (n-3 PUFAs) on coronary arterial large conductance Ca²⁺-activated K⁺ (BK) channel function in coronary smooth muscle cells (SMCs) of streptozotocin-induced diabetic rats. Methods: The effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on coronary BK channel open probabilities were determined using the patch clamp technique. The mRNA and protein expressions of BK channel subunits were measured using qRT-PCR and Western blots. The coronary artery tension and coronary SMC Ca²⁺ concentrations were measured using a myograph system and fluorescence Ca²⁺ indicator. Results: Compared to nondiabetic control rats, the BK channel function was impaired with a reduced response to EPA and DHA in freshly isolated SMCs of diabetic rats. Oral administration of n-3 PUFAs had no effects on protein expressions of BK channel subunits in nondiabetic rats, but significantly enhanced those of BK-β₁ in diabetic rats without altering BK-α protein levels. Moreover, coronary ring tension induced by iberiotoxin (a specific BK channel blocker) was increased and cytosolic Ca²⁺ concentrations in coronary SMCs were decreased in diabetic rats, but no changes were found in nondiabetic rats. Conclusions: n-3 PUFAs protect the coronary BK channel function and coronary vasoreactivity in diabetic rats as a result of not only increasing BK-β₁ protein expressions, but also decreasing coronary artery tension and coronary smooth muscle cytosolic Ca²⁺ concentrations.

Underlying mechanisms preserving coronary basal tone and NO-mediated relaxation in obesity: Involvement of β1 subunit-mediated upregulation of BKCa channels

Background and aimsThe impact of obesity on vasomotor regulation of coronary arteries and its underlying mechanisms are not completely understood and, in particular, the role of BKCa channels in the NO-mediated coronary vasodilation in obesity remains to be elucidated. MethodsThe effects of selective blockade of BKCa channel was tested on nitric oxide (NO)-mediated vasodilator responses of coronary arteries from lean and obese Zucker rats (LZR and OZR, respectively) by means of simultaneous measurements of intracellular Ca2+ concentration ([Ca2+]i) by Fura-2 fluorescence and tension in endothelium-denuded coronary arteries mounted in microvascular myographs. BKCa channel subunits expression was measured by Western blot. ResultsThe selective BKCa channel blocker iberitoxin largely reduced the relaxations and decreases in [Ca2+]i induced by a NO donor in coronary arteries from OZR. Iberitoxin increased to a great extent both basal [Ca2+]i and tone in OZR. The agonist of the voltage-gated L-type calcium channels Bay K8644 induced an increase in [Ca2+]i and tone that was significantly smaller in arteries from OZR, which was restored to control levels in LZR after BKCa channel inhibition. Caffeine- and ryanodine-induced intracellular Ca2+ mobilization and BKCa channel β1 subunit expression were increased in arteries from OZR. ConclusionsThe present study suggests that an enhanced activity of VSM BKCa channels, associated with up-regulation of channel β1 subunit and with a higher intracellular Ca2+ mobilization, contributes to the preserved NO-mediated vasodilatation and basal tone of coronary arteries in obesity.

Differential inhibitory response to telcagepant on \u03b1CGRP induced vasorelaxation and intracellular Ca2+ levels in the perfused and non-perfused isolated rat middle cerebral artery

BackgroundCalcitonin gene-related peptide (CGRP) is one of the most potent endogenous vasodilators identified to date. The present study elucidates the differential interaction of CGRP, its receptor and the effect of the CGRP-receptor antagonist telcagepant on intracellular Ca2+ -levels and tension in rat middle cerebral arteries (MCA) by pressurized arteriography, FURA-2/wire myography and immunohistochemistry.MethodsA pressurized arteriograph system was used to evaluate changes in MCA tension when subjected to CGRP and/or telcagepant. Intracellular calcium levels were evaluated using a FURA-2/wire myograph system. Localization of the CGRP-receptor components was verified using immunohistochemistry.ResultsAbluminal but not luminal αCGRP (10-12-10-6 M) caused concentration-dependent vasorelaxation in rat MCA. Luminal telcagepant (10-6 M) failed to inhibit this relaxation, while abluminal telcagepant inhibited the relaxation (10-6 M). Using the FURA-2 method in combination with wire myography we observed that αCGRP reduced intracellular calcium levels and in parallel the vascular tone. Telcagepant (10-6 M) inhibited both vasorelaxation and drop in intracellular calcium levels. Both functional components of the CGRP receptor, CLR (calcitonin receptor-like receptor) and RAMP1 (receptor activity modifying peptide 1) were found in the smooth muscle cells but not in the endothelial cells of the cerebral vasculature.ConclusionsThis study thus demonstrates the relaxant effect of αCGRP on rat MCA. The vasorelaxation is associated with a simultaneous decrease in intracellular calcium levels. Telcagepant reduced relaxation and thwarted the reduction in intracellular calcium levels localized in the vascular smooth muscle cells. In addition, telcagepant may act as a non-competitive antagonist at concentrations greater than 10-8 M.

The differential effects of systemic vasoconstrictors on human pulmonary artery tension.

Acute pulmonary hypertension following cardiac surgery can have a significant effect on postoperative morbidity and mortality. However, limited data are available on the efficacy and potency of clinically used systemic vasopressors on the pulmonary vasculature. The aim of this study was to use human pulmonary artery to characterize the pharmacological effects of clinically used vasopressors on the human pulmonary vasculature. Fifty-seven pulmonary artery rings of internal diameter 2-4 mm and 2 mm long, mounted in a multiwire myograph system, were used to measure changes in isometric tension. We constructed concentration response curves by cumulative addition to the myograph chambers of KCl, noradrenaline (NA), adrenaline (AD), vasopressin, endothelin-1 (ET-1) and prostaglandin F2a (PGF2a). AD, NA, ET-1, PGF2a and KCl caused dose-dependent vasoconstriction in the pulmonary artery samples (EC50 246 nM [95% confidence interval, CI, 153-394 nM], 150 nM [95% CI 51-447 nM], 1.46 nM [95% CI 0.69-3.1 nM], 6.35 µM [95% CI 3.58-11.2 µM] and 17.24 mM [95% CI 12.43-24.07 mM], respectively), whereas vasopressin had no significant effect. The order of efficacy was KCl = PGF2a > AD > NA > ET-1 and the order of potency was ET-1 T-AD = NA > PGF2a > KCl. This study demonstrated the efficacy and potency of clinically used vasopressors and endogenous vasopressors on human pulmonary vascular tone. PGF2a and KCl equally caused maximal amounts of constriction, whereas ET-1 had less effect and vasopressin had no effect. These effects may need to be taken into account in the clinical setting because they might result in the development of pulmonary hypertension.

Mitochondrial Fission Inhibitors Suppress Endothelin-1-Induced Artery Constriction

Background/Aims: Endothelin-1 is implicated in the pathogenesis of hypertension, but the underlying mechanisms remained elusive. Our previous study found that inhibition of mitochondrial fission of smooth muscle cells suppressed phenylephrine- and high K⁺-induced artery constriction. Here, we studied the effects of mitochondrial fission inhibitors on endothelin-1-induced vasoconstriction. Methods: The tension of rat mesenteric arteries and thoracic aorta was measured by using a multi-wire myograph system. Mitochondrial morphology of aortic smooth muscle cells was observed by using transmission electron microscopy. Results: Dynamin-related protein-1 selective inhibitor mdivi-1 relaxed endothelin-1-induced constriction, and mdivi-1 pre-treatment prevented endothelin-1-induced constriction of rat mesenteric arteries with intact and denuded endothelium. Mdivi-1 had a similar inhibitory effect on rat thoracic aorta. Another mitochondrial fission inhibitor dynasore showed similar effects as mdivi-1 in rat mesenteric arteries. Mdivi-1 inhibited endothelin-1-induced increase of mitochondrial fission in smooth muscle cells of rat aorta. Rho-associated protein kinase inhibitor Y-27632 which relaxed endothelin-1-induced vasoconstriction inhibited endothelin-1-induced mitochondrial fission in smooth muscle cells of rat aorta. Conclusion: Endothelin-1 increases mitochondrial fission in vascular smooth muscle cells, and mitochondrial fission inhibitors suppress endothelin-1-induced vasoconstriction.

Farnesoid X receptor activation regulates vascular tension of rat mesenteric resistance arteries

The peripheral vascular resistance is a critical determinant of blood pressure. The farnesoid X receptor (FXR) in the vasculature have been shown to regulate vascular tension of large vessels. In present work, we investigated whether FXR activation regulates vascular tension of rat mesenteric resistance arteries (MRA). We detected the protein abundances of Ang II type 1/2 receptor (AT1R, AT2R) and bradykinin type 1/2 receptor (B1R, B2R) following FXR stimulation. The endothelial/inducible NO synthase (eNOS/iNOS)/NO and cyclooxygenase (COX)/ thromboxane A2 (TXA2), and the vascular tone were also investigated following FXR activation with presence or absence of AT2R-B2R blockade. We found that the FXR ligands GW4064 and INT-747 increased the protein abundance of AT2R and B1/B2R. AT2R blockade with PD123319 reversed the effects of FXR agonists on levels of B2R but not B1R in MRAECs. Moreover, GW4064 and INT-747 upregulated the expression of eNOS and enhanced NOS activity, enhanced vasodilation, attenuated vasoconstriction and myogenic tone respectively, which were partially reversed by AT2R -B2R blockade. However, there were no significant effects of FXR-AT2R-B2R activation on COX1/2-TXA2 in MRAECs. The present study suggested that FXR-AT2R -B2R pathway activation regulated vascular tension of rat MRA through eNOS-NO but not COX-TXA2 pathway in physiological conditions.

Phenylephrine Decreases Vascular Tension in Goat Arteries in Specific Circumstances.

Phenylephrine (PE) causes vasoconstriction through alpha adrenergic receptors. PE-induced vasodilatation has also been reported earlier in pre-constricted vessels. Here we demonstrate in spiral strips of goat arteries that addition of PE can decrease tone even from base-line levels (i.e. not pre-constricted) and show that this process requires nitric oxide (NO) and alpha adrenergic stimulation, but is cGMP-independent. Under control conditions, PE caused vasoconstriction, but under conditions where NO levels are higher, as with L-Arginine or sodium nitroprusside, PE decreased vessel tension. L-Arginine/PE combination was not able to decrease tension when alpha adrenoceptors were blocked with Phentolamine or endothelial nitric oxide synthase (eNOS) was blocked with Nω-Nitro-L-arginine (L-NNA). Propranolol, a beta blocker, was unable to prevent the reduction in tension by the L-Arginine/PE combination. Adrenaline and noradrenaline (and not isoproterenol) also reduced vessel tension in the presence of L-Arginine. Even when NO levels were not enhanced, relieving NO from having to stimulate the enzyme soluble guanylyl cyclase (sGC) (either by using sGC blockers, namely ODQ or methylene blue, or by enhancing cGMP levels (with sildenafil) which by negative feedback probably inhibits sGC) led to PE-induced reduction of vascular tension. PMA—phorbol myristate acetate—an agonist which stimulates Protein Kinase C was able to prevent the ability of PE to reduce vascular tension in a high NO environment. Our conclusion is that PE reduces vascular tension through alpha adrenoceptors if there is excess NO availability to activate a putative pathway. Though the reduction of vessel tone by PE is dependent on NO, it is independent of cGMP. Prior treatment with PMA or PE itself can prevent further PE-induced reduction of tension in a high NO environment. The results here suggest, counter-intuitively, that alpha blockers may be of help in the treatment of septic shock where nitric oxide levels are high.

15-oxo-ETE-induced internal carotid artery constriction in hypoxic rats is mediated by potassium channels.

Our own study as well as others have previously reported that hypoxia activates 15-lipoxygenase (15-LO) in the brain, causing a series of chain reactions, which exacerbates ischemic stroke. 15-hydroxyeicosatetraenoic acid (15-HETE) and 15-oxo-eicosatetraenoic acid (15-oxo-ETE/15-KETE) are 15-LO-specific metabolites of arachidonic acid (AA). 15-HETE was found to be rapidly converted into 15-oxo-ETE by 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in some circumstances. We have demonstrated that 15-HETE promotes cerebral vasoconstriction during hypoxia. However, the effect of 15-oxo-ETE upon the contraction of cerebral vasculature remains unclear. To investigate this effect and to clarify the underlying mechanism, we performed immunohistochemistry and Western blot to test the expression of 15-PGDH in rat cerebral tissue, examined internal carotid artery (ICA) tension in isolated rat ICA rings. Western blot and reverse transcription polymerase chain reaction (RT-PCR) were used to analyze the expression of voltage-gated potassium (Kv) channels (Kv2.1, Kv1.5, and Kv1.1) in cultured cerebral arterial smooth muscle cells (CASMCs). The results showed that the levels of 15-PGDH expression were drastically elevated in the cerebral of rats with hypoxia, and 15-oxo-ETE enhanced ICA contraction in a dose-dependent manner. This effect was more significant in the hypoxic rats than in the normoxic rats. We also found that 15-oxo-ETE significantly attenuated the expression of Kv2.1 and Kv1.5, but not Kv1.1. In conclusion, these results suggest that 15-oxo-ETE leads to the contraction of the ICA, especially under hypoxic conditions and that specific Kv channels may play an important role in 15-oxo-ETE-induced ICA constriction.