Anji white tea relaxes precontracted arteries, represses voltage-gated Ca2+ channels and voltage-gated K+ channels in the arterial smooth muscle cells: Comparison with green tea main component (-)-epigallocatechin gallate

ETHNOPHARMACOLOGICAL RELEVANCE

Tea (Camellia sinensis) is a favorite drink worldwide. Tea extracts and green tea main component (-)-epigallocatechin gallate (EGCG) are recommended for various vascular diseases. Anji white tea is a very popular green tea. Its vascular effect profile, the mechanisms, and the contribution of EGCG to its integrated effect need elucidation.

AIM

To characterize the vasomotion effects of Anji white tea and EGCG, and to explore possible involvement of voltage-gated Ca2+ channels (VGCCs) and voltage-gated K+ (Kv) channels in their vasomotion effects.

MATERIALS AND METHODS

Anji white tea water soaking solution (AJWT) was prepared as daily tea-making process and concentrated to a concentration amounting to 200 mg/ml of dry tea leaves. The tension of rat arteries including aorta, coronary artery (RCA), cerebral basilar artery (CBA), intrarenal artery (IRA), intrapulmonary artery (IPA) and mesenteric artery (MA) was recorded with myographs. In arterial smooth muscle cells (ASMCs) freshly isolated from RCA, the levels of intracellular Ca2+ were measured with Ca2+-sensitive fluorescent probe fluo 4-AM, and Kv currents were recorded with patch clamp. The expressions of VGCCs and Kv channels were assayed with RT-qPCR and immunofluorescence staining.

RESULTS

At 0.4-12.8 mg/ml of dry tea leaves, AJWT profoundly relaxed all tested arteries precontracted with various vasoconstrictors about half with a small transient potentiation on the precontractions before the relaxation. KCl-induced precontraction was less sensitive than precontractions induced by phenylephrine (PE), U46619 and serotonin (5-HT). IPA was less sensitive to the relaxation compared with other arteries. AJWT pretreatment for 1 h, 24 h and 72 h time-dependently inhibited the contractile responses of RCAs. In sharp contrast, at equivalent concentrations according to its content in AJWT, EGCG intensified the precontractions in most small arteries, except that it induced relaxation in PE-precontracted aorta and MA, U46619-precontracted aorta and CBA. EGCG pretreatment for 1 h and 24 h did not significantly affect RCA contractile responses. In RCA ASMCs, AJWT reduced, while EGCG enhanced, intracellular Ca2+ elevation induced by depolarization which activates VGCCs. Patch clamp study showed that both AJWT and EGCG reduced Kv currents. RT-qPCR and immunofluorescence staining demonstrated that both AJWT and EGCG reduced the expressions of VGCCs and Kv channels.

CONCLUSION

AJWT, but not EGCG, consistently induces vasorelaxation. The vasomotion effects of either AJWT or EGCG vary with arterial beds and vasoconstrictors. Modulation of VGCCs, but not Kv channels, contributes to AJWT-induced vasorelaxation. It is suggested that Anji white tea water extract instead of EGCG may be a promising food supplement for vasospastic diseases.

Covered versus bare-metal stenting of the mesenteric arteries in patients with chronic mesenteric ischaemia (CoBaGI): a multicentre, patient-blinded and investigator-blinded, randomised controlled trial

BACKGROUND

Mesenteric artery stenting with a bare-metal stent is the current treatment for atherosclerotic chronic mesenteric ischaemia. Long-term patency of bare-metal stents is unsatisfactory due to in-stent intimal hyperplasia. Use of covered stents might improve long-term patency. We aimed to compare the patency of covered stents and bare-metal stents in patients with chronic mesenteric ischaemia.

METHODS

We conducted a multicentre, patient-blinded and investigator-blinded, randomised controlled trial including patients with chronic mesenteric ischaemia undergoing mesenteric artery stenting. Six centres in the Netherlands participated in this study, including two national chronic mesenteric ischaemia expert centres. Patients aged 18 years or older were eligible for inclusion when an endovascular mesenteric artery revascularisation was scheduled and a consensus diagnosis of chronic mesenteric ischaemia was made by a multidisciplinary team of gastroenterologists, interventional radiologists, and vascular surgeons. Exclusion criteria were stenosis length of 25 mm or greater, stenosis caused by median arcuate ligament syndrome or vasculitis, contraindication for CT angiography, or previous target vessel revascularisation. Digital 1:1 block randomisation with block sizes of four or six and stratification by inclusion centre was used to allocate patients to undergo stenting with bare-metal stents or covered stents at the start of the procedure. Patients, physicians performing follow-up, investigators, and radiologists were masked to treatment allocation. Interventionalists performing the procedure were not masked. The primary study outcome was the primary patency of covered stents and bare-metal stents at 24 months of follow-up, evaluated in the modified intention-to-treat population, in which stents with missing data for the outcome were excluded. Loss of primary patency was defined as the performance of a re-intervention to preserve patency, or 75% or greater luminal surface area reduction of the target vessel. CT angiography was performed at 6 months, 12 months, and 24 months post intervention to assess patency. The study is registered with ClinicalTrials.gov (NCT02428582) and is complete.

FINDINGS

Between April 6, 2015, and March 11, 2019, 158 eligible patients underwent mesenteric artery stenting procedures, of whom 94 patients (with 128 stents) provided consent and were included in the study. 47 patients (62 stents) were assigned to the covered stents group (median age 69·0 years [IQR 63·0-76·5], 28 [60%] female) and 47 patients (66 stents) were assigned to the bare-metal stents group (median age 70·0 years [63·5-76·5], 33 [70%] female). At 24 months, the primary patency of covered stents (42 [81%] of 52 stents) was superior to that of bare-metal stents (26 [49%] of 53; odds ratio [OR] 4·4 [95% CI 1·8-10·5]; p<0·0001). A procedure-related adverse event occurred in 17 (36%) of 47 patients in the covered stents group versus nine (19%) of 47 in the bare-metal stent group (OR 2·4 [95% CI 0·9-6·3]; p=0·065). Most adverse events were related to the access site, including haematoma (five [11%] in the covered stents group vs six [13%] in the bare-metal stents group), pseudoaneurysm (five [11%] vs two [4%]), radial artery thrombosis (one [2%] vs none), and intravascular closure device (none vs one [2%]). Six (13%) patients in the covered stent group versus one (2%) in the bare-metal stent group had procedure-related adverse events not related to the access site, including stent luxation (three [6%] vs none), major bleeding (two (4%) vs none), mesenteric artery perforation (one [2%] vs one [2%]), mesenteric artery dissection (one [2%] vs one [2%]), and death (one [2%] vs none).

INTERPRETATION

The findings of this trial support the use of covered stents for mesenteric artery stenting in patients with chronic mesenteric ischaemia.

FUNDING

Atrium Maquet Getinge Group.

Mesenteric artery smooth muscle cells from hypertensive rats have increased microtubule acetylation

The dynamic nature of the microtubule network is dependent in part by post-translational modifications (PTMs) - particularly through acetylation, which stabilizes the microtubule network. Whether PTMs of the microtubule network in vascular smooth muscle cells (VSMCs) contribute to the pathophysiology of hypertension is unknown. The aim of this study was to determine the acetylated state of the microtubule network in the mesenteric arteries of spontaneously hypertensive rats (SHR). Experiments were performed on male normotensive rats and SHR mesenteric arteries. Western blotting and mass spectrometry determined changes in tubulin acetylation. Wire myography was used to investigate the effect of tubacin on isoprenaline-mediated vasorelaxations. Isolated cells from normotensive rats were used for scanning ion conductance microscopy (SICM). Mass spectrometry and Western blotting showed that tubulin acetylation is increased in the mesenteric arteries of the SHR compared with normotensive rats. Tubacin enhanced the β-adrenoceptor-mediated vasodilatation by isoprenaline when the endothelium was intact, but attenuated relaxations when the endothelium was denuded or nitric oxide production was inhibited. By pre-treating vessels with colchicine to disrupt the microtubule network, we were able to confirm that the effects of tubacin were microtubule-dependent. Using SICM, we examined the cell surface Young's modulus of VSMCs, but found no difference in control, tubacin-treated, or taxol-treated cells. Acetylation of tubulin at Lys40 is elevated in mesenteric arteries from the SHR. Furthermore, this study shows that tubacin has an endothelial-dependent bimodal effect on isoprenaline-mediated vasorelaxation.

Nitric oxide, endothelium-derived hyperpolarizing factor, and smooth muscle-dependent mechanisms contribute to magnesium-dependent vascular relaxation in mouse arteries

AIM

Magnesium (Mg2+ ) is a vasorelaxant. The underlying physiological mechanisms driving this vasorelaxation remain unclear. Studies were designed to test the hypothesis that multiple signaling pathways including nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in endothelial cells as well as Ca2+ antagonization and TRPM7 channels in vascular smooth muscle cells mediate Mg2+ -dependent vessel relaxation.

METHODS

To uncover these mechanisms, force development was measured ex vivo in aorta rings from mice using isometric wire myography. Concentration responses to Mg2+ were studied in intact and endothelium-denuded aortas. Key findings were confirmed in second-order mesenteric resistance arteries perfused ex vivo using pressure myography. Effects of Mg2+ on NO formation were measured in Chinese Hamster Ovary (CHO) cells, isolated mesenteric vessels, and mouse urine.

RESULTS

Mg2+ caused a significant concentration-dependent relaxation of aorta rings. This relaxation was attenuated significantly in endothelium-denuded aortas. The endothelium-dependent portion was inhibited by NO and cGMP blockade but not by cyclooxygenase inhibition. Mg2+ stimulated local NO formation in CHO cells and isolated mesenteric vessels without changing urinary NOx levels. High extracellular Mg2+ augmented acetylcholine-induced relaxation. SKCa and IKCa channel blockers apamin and TRAM34 inhibited Mg2+ -dependent relaxation. The endothelium-independent relaxation in aorta rings was inhibited by high extracellular Ca2+ . Combined blockade of NO, SKCa , and IKCa channels significantly reduced Mg2+ -dependent dilatation in mesenteric resistance vessels.

CONCLUSIONS

In mouse conductance and resistance arteries Mg2+ -induced relaxation is contributed by endothelial NO formation, EDHF pathways, antagonism of Ca2+ in smooth muscle cells, and additional unidentified mechanisms.

Role of thrombospondin-1 in high-salt-induced mesenteric artery endothelial impairment in rats

The matrix glycoprotein thrombospondin-1 (THBS1) modulates nitric oxide (NO) signaling in endothelial cells. A high-salt diet induces deficiencies of NO production and bioavailability, thereby leading to endothelial dysfunction. In this study we investigated the changes of THBS1 expression and its pathological role in the dysfunction of mesenteric artery endothelial cells (MAECs) induced by a high-salt diet. Wild-type rats, and wild-type and Thbs1-/- mice were fed chow containing 8% w/w NaCl for 4 weeks. We showed that a high salt diet significantly increased THBS1 expression and secretion in plasma and MAECs, and damaged endothelium-dependent vasodilation of mesenteric resistance arteries in wild-type animals, but not in Thbs1-/- mice. In rat MAECs, we demonstrated that a high salt environment (10-40 mM) dose-dependently increased THBS1 expression accompanied by suppressed endothelial nitric oxide synthase (eNOS) and phospho-eNOS S1177 production as well as NO release. Blockade of transforming growth factor-β1 (TGF-β1) activity by a TGF-β1 inhibitor SB 431542 reversed THBS1 up-regulation, rescued the eNOS decrease, enhanced phospho-eNOS S1177 expression, and inhibited Smad4 translocation to the nucleus. By conducting dual-luciferase reporter experiments in HEK293T cells, we demonstrated that Smad4, a transcription promoter, upregulated Thbs1 transcription. We conclude that THBS1 contributes to endothelial dysfunction in a high-salt environment and may be a potential target for treatment of high-salt-induced endothelium dysfunction.

Histamine H2-receptor antagonism improves conduit artery endothelial function and reduces plasma aldosterone level without lowering arterial blood pressure in angiotensin II-hypertensive mice

Aldosterone through the mineralocorticoid receptor MR has detrimental effects on cardiovascular disease. It reduces the bioavailability of nitric oxide and impairs endothelium-dependent vasodilatation. In resistance arteries, aldosterone impairs the sensitivity of vascular smooth muscle cells to nitric oxide by promoting the local secretion of histamine which activates H2 receptors. The present experiments tested in vivo and ex vivo the hypothesis that systemic H2-receptor antagonism reduces arterial blood pressure and improves vasodilatation in angiotensin II-induced chronic hypertension. Hypertension was induced by intravenous infusion of angiotensin II (60 ng kg-1 min-1) in conscious, unrestrained mice infused concomitantly with the H2-receptor antagonist ranitidine (27.8 µg kg-1 min-1) or vehicle for 24 days. Heart rate and arterial blood pressure were recorded by indwelling arterial catheter. Resistance (mesenteric) and conductance (aortae) arteries were harvested for perfusion myography and isometric tension recordings by wire myography, respectively. Plasma was analyzed for aldosterone concentration. ANGII infusion resulted in elevated arterial blood pressure and while in vivo treatment with ranitidine reduced plasma aldosterone concentration, it did not reduce blood pressure. Ranitidine improved ex vivo endothelial function (acetylcholine 10-9 to 10-6 mol L-1) in mesenteric resistance arteries. This was abolished by ex vivo treatment with aldosterone (10-9 mol L-1, 1 h). In aortic segments, in vivo ranitidine treatment impaired relaxation. Activation of histamine H2 receptors promotes aldosterone secretion, does not affect arterial blood pressure, and protects endothelial function in conduit arteries but promotes endothelial dysfunction in resistance arteries during angiotensin II-mediated hypertension. Aldosterone contributes little to angiotensin II-induced hypertension in mice.

Testosterone modulates vasodilation in mesenteric arteries of hypertensive rats

AIMS

To evaluate the effects of testosterone on endothelium-dependent vasodilation and oxidative stress in mesenteric resistance arteries.

MAIN METHODS

Spontaneously hypertensive rats (SHR), aged 8 to 10 weeks, were divided into four groups: intact (SHAM), intact treated with testosterone (TTO; 3 mg/kg/day) via subcutaneous route (s.c.), intact treated with testosterone and anastrozole [aromatase enzyme inhibitor (TTO + ANA; 0.1 mg/kg/day, s.c.)] and intact treated with testosterone and finasteride [5 α-reductase enzyme inhibitor (TTO + FIN; 5 mg/kg/day, s.c.)] for four weeks. Concentration-response curves to acetylcholine (ACh, 0.1 nmol/L - 10 μmol/L) were obtained in mesenteric resistance arteries previously contracted with phenylephrine (PE, 3 μmol/L), before and after the use of selective inhibitors. Reactive oxygen species (ROS) levels were assessed in the vessels and the endothelium analyzed by scanning electron microscopy.

KEY FINDINGS

TTO group showed a lower participation of nitric oxide (NO), increased oxidative stress, and participation of prostanoids and endothelium-dependent hyperpolarization (EDH), possibly to maintain the vasodilator response. Lower participation of NO and prostanoids, combined to an increased participation of EDH, were observed in the TTO + ANA group, in addition to higher levels of ROS and altered endothelial morphology. The vasodilation to ACh was impaired in TTO + FIN, along increased participation of NO, reduction of prostanoids, and greater EDH-dependent vasodilation.

SIGNIFICANCE

Testosterone contributes to endothelial vasodilation by enhancing EDH through an increased participation of epoxyeicosatrienoic acids. While the decrease in NO appears to involve the participation of dihydrotestosterone, 17 β-estradiol seems to stimulate the action of the NO pathway and prostanoids.

Differences in vasomotor function of mesenteric arteries between Ossabaw minipigs with predisposition to metabolic syndrome and Göttingen minipigs

Metabolic syndrome predisposes and contributes to the development and progression of atherosclerosis. The minipig strain "Ossabaw" is characterized by a predisposition to develop metabolic syndrome. We compared vasomotor function in Ossabaw minipigs before they developed their diseased phenotype to that of Göttingen minipigs without such genetic predisposition. Mesenteric arteries of adult Ossabaw and Göttingen minipigs were dissected postmortem and mounted on a myograph for isometric force measurements. Maximal vasoconstriction to potassium chloride (KClmax) was induced. Cumulative concentration-response curves were determined in response to norepinephrine. Endothelium-dependent (with carbachol) and endothelium-independent (with nitroprusside) vasodilation were analyzed after preconstriction by norepinephrine. In a bioinformatic analysis, variants/altered base pairs within genes associated with cardiovascular disease were analyzed. KClmax was similar between the minipig strains (15.6 ± 6.7 vs. 14.1 ± 3.4 ΔmN). Vasoconstriction in response to norepinephrine was more pronounced in Ossabaw than in Göttingen minipigs (increase of force to 143 ± 48 vs. 108 ± 38% of KClmax). Endothelium-dependent and endothelium-independent vasodilation were less pronounced in Ossabaw than in Göttingen minipigs (decrease of force to 46.4 ± 29.6 vs. 16.0 ± 18.4% and to 36.7 ± 25.2 vs. 2.3 ± 3.7% of norepinephrine-induced preconstriction). Vasomotor function was not different between the sexes. More altered base pairs/variants were identified in Ossabaw than in Göttingen minipigs for the exon encoding adrenoceptor-α1A. Vasomotor function in lean Ossabaw minipigs is shifted toward vasoconstriction and away from vasodilation in comparison with Göttingen minipigs, suggesting a genetic predisposition for vascular dysfunction and atherosclerosis in Ossabaw minipigs. Thus, Ossabaw minipigs may be a better model for human cardiovascular disease than Göttingen minipigs.NEW & NOTEWORTHY Animal models with a predisposition to metabolic syndrome and atherosclerosis are attracting growing interest for translational research, as they may better mimic the variability of patients with cardiovascular disease. In Ossabaw minipigs, with a polygenic predisposition to metabolic syndrome, but without the diseased phenotype, vasoconstriction is more and vasodilation is less pronounced in mesenteric arteries than in Göttingen minipigs. Ossabaw minipigs may be a more suitable model of human cardiovascular disease.

Gestational intermittent hypoxia induces endothelial dysfunction and hypertension in pregnant rats: role of endothelin type B receptor†

Obstructive sleep apnea is a recognized risk factor for gestational hypertension, yet the exact mechanism behind this association remains unclear. Here, we tested the hypothesis that intermittent hypoxia, a hallmark of obstructive sleep apnea, induces gestational hypertension through perturbed endothelin-1 signaling. Pregnant Sprague-Dawley rats were subjected to normoxia (control), mild intermittent hypoxia (10.5% O2), or severe intermittent hypoxia (6.5% O2) from gestational days 10-21. Blood pressure was monitored. Plasma was collected and mesenteric arteries were isolated for myograph and protein analyses. The mild and severe intermittent hypoxia groups demonstrated elevated blood pressure, reduced plasma nitrate/nitrite, and unchanged endothelin-1 levels compared to the control group. Western blot analysis revealed decreased expression of endothelin type B receptor and phosphorylated endothelial nitric oxide synthase, while the levels of endothelin type A receptor and total endothelial nitric oxide synthase remained unchanged following intermittent hypoxia exposure. The contractile responses to potassium chloride, phenylephrine, and endothelin-1 were unaffected in endothelium-denuded arteries from mild and severe intermittent hypoxia rats. However, mild and severe intermittent hypoxia rats exhibited impaired endothelium-dependent vasorelaxation responses to endothelin type B receptor agonist IRL-1620 and acetylcholine compared to controls. Endothelium denudation abolished IRL-1620-induced vasorelaxation, supporting the involvement of endothelium in endothelin type B receptor-mediated relaxation. Treatment with IRL-1620 during intermittent hypoxia exposure significantly attenuated intermittent hypoxia-induced hypertension in pregnant rats. This was associated with elevated circulating nitrate/nitrite levels, enhanced endothelin type B receptor expression, increased endothelial nitric oxide synthase activation, and improved vasodilation responses. Our data suggested that intermittent hypoxia exposure during gestation increases blood pressure in pregnant rats by suppressing endothelin type B receptor-mediated signaling, providing a molecular mechanism linking intermittent hypoxia and gestational hypertension.

Follistatin-like 1 protects endothelial function in the spontaneously hypertensive rat by inhibition of endoplasmic reticulum stress through AMPK-dependent mechanism

OBJECTIVE

Endothelial dysfunction is a critical initiating factor in the development of hypertension and related complications. Follistatin-like 1 (FSTL1) can promote endothelial cell function and stimulates revascularization in response to ischemic insult. However, it is unclear whether FSTL1 has an effect on ameliorating endothelial dysfunction in spontaneously hypertensive rats (SHRs).

METHODS

Wistar Kyoto (WKY) and SHRs were treated with a tail vein injection of vehicle (1 mL/day) or recombinant FSTL1 (100 μg/kg body weight/day) for 4 weeks. Blood pressure was measured by tail-cuff plethysmograph, and vascular reactivity in mesenteric arteries was measured using wire myography.

RESULTS

We found that treatment with FSTL1 reversed impaired endothelium-dependent relaxation (EDR) in mesenteric arteries and lowered blood pressure of SHRs. Decreased AMP-activated protein kinase (AMPK) phosphorylation, elevated endoplasmic reticulum (ER) stress markers, increased reactive oxygen species (ROS), and reduction of nitric oxide (NO) production in mesenteric arteries of SHRs were also reversed by FSTL1 treatment. Ex vivo treatment with FSTL1 improved the impaired EDR in mesenteric arteries from SHRs and reversed tunicamycin (ER stress inducer)-induced ER stress and the impairment of EDR in mesenteric arteries from WKY rats. The effects of FSTL1 were abolished by cotreatment of compound C (AMPK inhibitor).

CONCLUSIONS

These results suggest that FSTL1 prevents endothelial dysfunction in mesenteric arteries of SHRs through inhibiting ER stress and ROS and increasing NO production via activation of AMPK signaling.

Acute, pro-contractile effects of prorenin on rat mesenteric arteries

Prorenin and the prorenin receptor ((P)RR) are important, yet controversial, members of the renin-angiotensin-aldosterone system. The ((P)RR) is expressed throughout the body, including the vasculature, however, the direct effect of prorenin on arterial contractility is yet to be determined. Within rat mesenteric arteries, immunostaining and proximity ligation assays were used to determine the interacting partners of (P)RR in freshly isolated vascular smooth muscle cells (VSMCs). Wire myography examined the functional effect of prorenin. Simultaneous changes in [Ca2+ ]i and force were recorded in arteries loaded with Fura-2AM. Spontaneously transient outward currents were recorded via perforated whole-cell patch-clamp configuration in freshly isolated VSMCs. We found that the (P)RR is located within a distance of less than 40 nm from the V-ATPase, caveolin-1, ryanodine receptors, and large conductance Ca2+ -activated K+ channels (BKCa ) in VSMCs. [Ca2+ ]i imaging and isometric tension recordings indicate that 1 nM prorenin enhanced α1-adrenoreceptor-mediated contraction, associated with an increased number of Ca2+ waves, independent of voltage-gated Ca2+ channels activation. Incubation of VSMCs with 1 nM prorenin decreased the amplitude and frequency of spontaneously transient outward currents and attenuated BKCa -mediated relaxation. Inhibition of the V-ATPase with 100 nM bafilomycin prevented prorenin-mediated inhibition of BKCa -derived relaxation. Renin (1 nM) had no effect on BKCa -mediated relaxation. In conclusion, prorenin enhances arterial contractility by inhibition of BKCa and increasing intracellular Ca2+ release. It is likely that this effect is mediated through a local shift in pH upon activation of the (P)RR and stimulation of the V-ATPase.

Impaired vascular β-adrenergic relaxation in spontaneously hypertensive rats: The differences between conduit and resistance arteries

It was suggested that impaired β-adrenergic relaxation in spontaneously hypertensive rats (SHR) might contribute to their high blood pressure (BP). Our study was focused on isoprenaline-induced dilatation of conduit femoral or resistance mesenteric arteries and on isoprenaline-induced BP reduction in SHR and Wistar-Kyoto rats (WKY). We confirmed decreased β-adrenergic relaxation of SHR femoral arteries due to the absence of its endothelium-independent component, whereas endothelium-dependent component of β-adrenergic smooth muscle relaxation was similar in both strains. Conversely, isoprenaline-induced relaxation of resistance mesenteric arteries was similar in both strains and this was true for endothelium-dependent and endothelium-independent components. We observed moderately reduced sensitivity of SHR mesenteric arteries to salmeterol (β2-adrenergic agonist) and this strain difference disappeared after endothelium removal. However, there was no difference in mesenteric arteries relaxation by dobutamine (β1-adrenergic agonist) which was independent of endothelium. The increasing isoprenaline doses elicited similar BP decrease in both rat strains, although BP sensitivity to isoprenaline was slightly decreased in SHR. The blockade of cyclooxygenase (indomethacin) and NO synthase (L-NAME) further reduced BP sensitivity to isoprenaline in SHR. On the other hand, salmeterol elicited similar BP decrease in both strains and the blockade of cyclooxygenase and NO synthase increased BP sensitivity to salmeterol in SHR as compared to WKY. In conclusion, attenuated β-adrenergic vasodilatation of conduit arteries of SHR but similar β-adrenergic relaxation of resistance mesenteric arteries from WKY and SHR and their similar BP response to β-adrenergic agonists do not support major role of altered β-adrenergic vasodilatation for high BP in genetic hypertension.

Zinc pyrithione induces endothelium-dependent hyperpolarization-mediated mesenteric vasorelaxation in healthy and colitic mice

BACKGROUND

Although Zinc pyrithione (ZPT) could lower blood pressure by inducing vasorelaxation, it is unclear if it is able to induce vasorelaxation of mesenteric arterioles in health and ulcerative colitis (UC) to exert anti-colitic action.

METHODS

The vasorelaxation of the second-order branch of the mesenteric artery from wide type (WT) mice, TRPV1-/-(KO) mice, and TRPV4-/-(KO) mice was determined using a Mulvany-style wire myograph. Calcium imaging and patch clamp were applied to analyze the actions of ZPT in human vascular endothelial cells. Mouse model of UC was used to evaluate the anti-colitic action of ZPT.

RESULTS

ZPT dose-dependently induced mesenteric vasorelaxation predominately through endothelium-dependent hyperpolarization (EDH), which could be attenuated by intracellular Zn2+ and Ca2+ chelators TPEN and BAPTA-AM. The ZPT/EDH-mediated vasorelaxation via TRPV1, TRPV4 and TRPA1 channels was verified by a combination of selective pharmacological inhibitors and TRPV1-KO and TRPV4-KO mice. Moreover. ZPT induced Ca2+ entry via vascular endothelial TRPV1/4 and TRPA1 channels and enhanced membrane non-selective currents through these channels. Notably, ZPT exerted anti-colitic effects by rescuing the impaired acetylcholine (ACh)-induced mesenteric vasorelaxation in colitic mice.

CONCLUSIONS

ZPT/Zn2+ induces EDH-mediated mesenteric vasorelaxation through activating endothelial multiple TRPV1/4 and TPPA1 channels in health, and rescues the impaired ACh-induced vasorelaxation to exert anti-colitic action. Our study may open a new avenue of potential vessel-specific targeted therapy for UC.

Endovascular treatment of systematic isolated mesenteric artery dissection with a patent false lumen: Bare stents alone versus stent-assisted coiling

OBJECTIVES

Bare stent treatment and bare stent-assisted coiling treatment have not been directly compared in symptomatic isolated superior mesenteric artery dissection with a patent false lumen. Thus, we compared the early and mid-term outcomes of bare stent treatment and bare stent-assisted coiling treatment to determine the most effective remedy for patients with this condition.

METHODS

Consecutive patients diagnosed with systematic isolated superior mesenteric artery dissection with a patent false lumen admitted to the study hospital between January 2016 and December 2021 were enrolled in this retrospective study. Their demographic data, clinical findings, treatment options, early outcomes, and follow-up results were analyzed.

RESULTS

A total of 85 patients (83 men) were included. 34.1% (n = 29) adopted bare stent treatment and 65.9% (n = 56) underwent bare stent-assisted coiling treatment. The symptoms were relieved in all patients (100%) with bare stent treatment and bare stent-assisted coiling treatment. There was no significant difference in the length of hospital stay between the two endovascular treatments (p = 0.354). The cumulative complete remodeling rate was 100% in bare stent-assisted coiling treatment vs. 70.4% in bare stent treatment (p < 0.0001). The prevalence of adverse events for abdominal pain recurrence (none in BST or bare stent-assisted coiling treatment), and formation of the aneurysm (two in bare stent treatment, and none in bare stent-assisted coiling treatment) showed no significant difference at follow-up.

CONCLUSION

Both bare stent treatment and bare stent-assisted coiling treatment for symptomatic isolated superior mesenteric artery dissection with a patent false lumen have the same satisfying early outcome. In the midterm follow-up, bare stent-assisted coiling treatment has the higher cumulative complete remodeling rate which could be prioritized to treat this condition.

Cl- induces endothelium-dependent mesenteric arteriolar vasorelaxation through the NKCC1/TRPV4/NCX axis

AIMS

Although absorbed NaCl increases intestinal blood flow to facilitate absorption and transportation, it is unclear if it can directly mediate mesenteric arterial relaxation. We aimed to investigate and test our hypothesis that Cl- induces mesenteric arterial vasorelaxation via endothelium-dependent hyperpolarization (EDH).

MAIN METHODS

We used wire myograph to study NaCl-induced vasorelaxation of mesenteric arteries isolated from mice. Cl-, Ca2+ and K+ imaging was performed in human vascular endothelial cells pre-treated with pharmacological agents.

KEY FINDINGS

The Cl- concentration-dependently induced vasorelaxation of mesenteric arteries likely through EDH. The Cl--induced vasorelaxation was attenuated in TRPV4 KO mice and inhibited by selective blockers of Na+-K+-2Cl- cotransporter 1 (NKCC1) (bumetanide, 10 μM), transient receptor potential vanilloid 4 (TRPV4) (RN-1734, 40 μM), and small conductance Ca2+-activated K+ channels (SKCa) (apamin, 3 μM)/ intermediate conductance Ca2+-activated K+ channels (IKCa) (TRAM-34, 10 μM) and myoendothelial gap junction (18α-glycyrrhetinic acid, 10 μM), but enhanced by a selective activator of IKCa/SKCa (SKA-31, 0.3 μM). Cl- decreased intracellular K+ concentrations in endothelial cells, which was reversed by apamin (200 nM) plus TRAM-34 (500 nM). Extracellular Cl- raised intracellular Cl- concentrations in endothelial cells, which was attenuated by bumetanide (10 μM). Finally, Cl- induced a transient Ca2+ signaling via TRPV4 in endothelial cells, which became sustained when the Ca2+ exit mode of Na+-Ca2+ exchanger (NCX) was blocked.

SIGNIFICANCE

Cl- induces a pure EDH-mediated vasorelaxation of mesenteric arteries through activation of endothelial NKCC1/TRPV4/NCX axis. We have provided a novel insight into the role of Cl--induced vasorelaxation via EDH mechanism.

Ezetimibe Induces Vasodilation in Rat Mesenteric Resistance Arteries through Inhibition of Extracellular Ca2+ Influx

Ezetimibe is a lipid-lowering agent that selectively inhibits cholesterol absorption by binding to the Niemann-Pick C1-like 1 (NPC1L1) protein. Although it is well known that administration of ezetimibe in hypercholesterolemia patients reduces the risk of cardiovascular events through attenuation of atherosclerosis, studies on the direct effect of ezetimibe on vascular function are not sufficient. The aim of the present study was to investigate the vascular effects of ezetimibe in rat mesenteric arteries. In the present study, 12-week-old male Sprague Dawley rats were used. After the rats were sacrificed, the second branches of the mesenteric arteries were isolated and cut into 2-3 mm segments and mounted in a multi-wire myography system to measure isometric tension. Ezetimibe reduced vasoconstriction induced by U46619 (500 nM) in endothelium-intact and endothelium-denuded arteries. Ezetimibe-induced vasodilation was not affected by the endothelial nitric oxide synthase (eNOS) inhibitor Nω-Nitro-L-arginine (L-NNA, 300 μM) or the non-selective potassium channel blocker, tetraethylammonium (TEA, 10 mM). Moreover, ezetimibe also completely blocked the contraction induced by an increase in external calcium concentration. Ezetimibe significantly reduced vascular contraction induced by L-type Ca2+ channel activator (Bay K 8644, 30 nM). Treatment with ezetimibe decreased the phosphorylation level of 20 kDa myosin light chain (MLC20) in vascular smooth muscle cells. In the present study, we found that ezetimibe has a significant vasodilatory effect in rat mesenteric resistance arteries. These results suggest that ezetimibe may have beneficial cardiovascular effects beyond its cholesterol-lowering properties.

Basal NAD(H) redox state permits hydrogen peroxide-induced mesenteric artery dilatation

Smooth muscle voltage-gated K+ (Kv) channels in resistance arteries control vascular tone and contribute to the coupling of blood flow with local metabolic activity. Members of the Kv1 family are expressed in vascular smooth muscle and are modulated upon physiological elevation of local metabolites, including the glycolytic end-product l-lactate and superoxide-derived hydrogen peroxide (H2 O2 ). Here, we show that l-lactate elicits vasodilatation of small-diameter mesenteric arteries in a mechanism that requires lactate dehydrogenase (LDH). Using the inside-out configuration of the patch clamp technique, we show that increases in NADH that reflect LDH-mediated conversion of l-lactate to pyruvate directly stimulate the activity of single Kv1 channels and significantly enhance the sensitivity of Kv1 activity to H2 O2 . Consistent with these findings, H2 O2 -evoked vasodilatation was significantly greater in the presence of 10 mM l-lactate relative to lactate-free conditions, yet was abolished in the presence of 10 mM pyruvate, which shifts the LDH reaction towards the generation of NAD+ . Moreover, the enhancement of H2 O2 -induced vasodilatation was abolished in arteries from double transgenic mice with selective overexpression of the intracellular Kvβ1.1 subunit in smooth muscle cells. Together, our results indicate that the Kvβ complex of native vascular Kv1 channels serves as a nodal effector for multiple redox signals to precisely control channel activity and vascular tone in the face of dynamic tissue-derived metabolic cues. KEY POINTS: Vasodilatation of mesenteric arteries by elevated external l-lactate requires its conversion by lactate dehydrogenase. Application of either NADH or H2 O2 potentiates single Kv channel currents in excised membrane patches from mesenteric artery smooth muscle cells. The binding of NADH enhances the stimulatory effects of H2 O2 on single Kv channel activity. The vasodilatory response to H2 O2 is differentially modified upon elevation of external l-lactate or pyruvate. The presence of l-lactate enhances the vasodilatory response to H2 O2 via the Kvβ subunit complex in smooth muscle.

Endothelium-dependent relaxation is impaired in Schlager hypertensive (BPH/2J) mice by region-specific mechanisms in conductance and resistance arteries

AIMS

Endothelial dysfunction and arterial stiffness are hallmarks of hypertension, and major risk factors for cardiovascular disease. BPH/2J (Schlager) mice are a genetic model of spontaneous hypertension, but little is known about the vascular pathophysiology of these mice and the region-specific differences between vascular beds. Therefore, this study compared the vascular function and structure of large conductance (aorta and femoral) and resistance (mesenteric) arteries of BPH/2J mice with their normotensive BPN/2J counterparts.

MAIN METHODS

Blood pressure was measured in BPH/2J and BPN/3J mice via pre-implanted radiotelemetry probes. At endpoint, vascular function and passive mechanical wall properties were assessed using wire and pressure myography, qPCR and histology.

KEY FINDINGS

Mean arterial blood pressure was elevated in BPH/2J mice compared to BPN/3J controls. Endothelium-dependent relaxation to acetylcholine was attenuated in both the aorta and mesenteric arteries of BPH/2J mice, but through different mechanisms. In the aorta, hypertension reduced the contribution of prostanoids. Conversely, in the mesenteric arteries, hypertension reduced the contribution of both nitric oxide and endothelium-dependent hyperpolarization. Hypertension reduced volume compliance in both femoral and mesenteric arteries, but hypertrophic inward remodelling was only observed in the mesenteric arteries of BPH/2J mice.

SIGNIFICANCE

This is the first comprehensive investigation of vascular function and structural remodelling in BPH/2J mice. Overall, hypertensive BPH/2J mice exhibited endothelial dysfunction and adverse vascular remodelling in the macro- and microvasculature, underpinned by distinct region-specific mechanisms. This highlights BPH/2J mice as a highly suitable model for evaluating novel therapeutics to treat hypertension-associated vascular dysfunction.

The pig is a better model than the rabbit or rat for studying the pathophysiology of human mesenteric arteries

AIMS

Animal models are essential to investigate cardiovascular pathophysiology and pharmacology, but phylogenetic diversity makes it necessary to identify the model with vasculature most similar to that of humans.

METHODS AND RESULTS

In this study, we compared the mesenteric arteries of humans, pigs, rabbits and rats in terms of the i) evolutionary changes in the amino acid sequences of α₁ and β2 adrenoceptors; M₁, M₂, and M₃ muscarinic receptors; and bradykinin (BKR) and thromboxane-prostanoid (TP) receptors, through bioinformatics tools; ii) expression of α₁, β₂, M1, M3 and TP receptors in each tunica, as assessed by immunofluorescence; and iii) reactivity to receptor-dependent and independent contractile agonists and relaxants, by performing organ bath assays. Phylogenetically, pigs showed the highest degree of evolutionary closeness to humans for all receptors, and with the exception of BKR, rabbits presented the greatest evolutionary difference compared to humans, pigs and rats. The expression of the measured receptors in the three vascular tunica in pigs was most similar to that in humans. Using a one-way ANOVA to determine the differences in vascular reactivity, we found that the reactivity of pigs was the most similar to that of humans in terms of sensitivity (pD2) and maximum effect of vascular reactivity (Emax) to KCl, phenylephrine, isoproterenol and carbachol.

CONCLUSIONS

The pig is a better vascular model than the rabbit or rat to extrapolate results to human mesenteric arteries. Comparative vascular studies have implications for understanding the evolutionary history of different species.

TRANSLATIONAL PERSPECTIVE

The presented findings are useful for identifying an animal model with a vasculature that is similar to that of humans. This information is important to extrapolate, with greater precision, the findings in arterial pathophysiology or pharmacology from animal models to the healthy or diseased human being.

Ethanol consumption favors pro-contractile phenotype of perivascular adipose tissue: A role for interleukin-6

Perivascular adipose tissue (PVAT) exerts anticontractile effect, but under non-physiological conditions it may contribute to vascular dysfunction by releasing pro-inflammatory cytokines. Since PVAT is an important source of interleukin (IL)-6, we evaluated whether this cytokine would contribute to ethanol-induced vascular dysfunction. With this purpose, male C57BL/6 wild-type (WT) or IL-6-deficient mice (IL-6^-/-) were treated with ethanol for 12 weeks. Increased blood pressure was evidenced after 4 and 6 weeks of treatment with ethanol in WT and IL-6^-/- mice, respectively. In WT mice, ethanol increased plasma and PVAT levels of IL-6. Ethanol favoured pro-contractile phenotype of PVAT in mesenteric arteries from WT, but not IL-6-deficient mice. Functional studies showed that tiron [(a scavenger of superoxide (O₂^-)] reversed the pro-contractile effect of PVAT in mesenteric arteries from ethanol-treated mice. Ethanol increased the levels of O₂^- in PVAT from WT mice. Ethanol-induced increase in O₂^- generation was higher in arteries with PVAT from WT mice when compared to IL-6-deficient mice. Treatment with ethanol augmented myeloperoxidase activity in the mesenteric arterial bed (MAB; with or without PVAT) from WT, but not IL-6-deficient mice. In conclusion, IL-6 contributes to the pro-contractile effect of PVAT by a mechanism that involves increase in ROS generation. Additionally, IL-6 mediates intravascular recruitment of neutrophils in response to ethanol and plays a role in the early stages of ethanol-induced hypertension. Collectively, our findings provide novel evidence for a role of IL-6 in the vascular dysfunction induced by ethanol.