Direct Vasorelaxant Research Articles

LC-MS Fingerprinting Development for Standardized Precipitate from Agastache mexicana, Which Induces Antihypertensive Effect through NO Production and Calcium Channel Blockade.

The aim of this work was to evaluate the vasorelaxant and antihypertensive effects of a standardized precipitate of the hydroalcoholic extract from Agastache mexicana (PPAm), comprising ursolic acid, oleanolic acid, acacetin, luteolin and tilianin, among others. In the ex vivo experiments, preincubation with L-NAME (nonspecific inhibitor of nitric oxide synthases) reduced the relaxation induced by PPAm; nevertheless, preincubation with indomethacin (nonspecific inhibitor of cyclooxygenases) did not generate any change in the vasorelaxation, and an opposed effect was observed to the contraction generated by CaCl2 addition. Oral administration of 100 mg/kg of PPAm induced a significant acute decrease in diastolic (DBP) and systolic (SBP) blood pressure in spontaneously hypertensive rats, without changes in heart rate. Additionally, PPAm showed a sustained antihypertensive subacute effect on both DBP and SBP for 10 days compared to the control group. On the other hand, human umbilical vein cells treated with 10 µg/mL of PPAm showed a significant reduction (p < 0.05) in intracellular adhesion molecule-1, compared to the control, but not on vascular cell adhesion molecule-1. In conclusion, PPAm induces a significant antihypertensive effect in acute- and subacute-period treatments, due to its direct vasorelaxant action on rat aortic rings through NO production and Ca2+ channel blockade.

Dapagliflozin prevents oxidative stress-induced endothelial dysfunction via sirtuin 1 activation

Recent studies have demonstrated that dapagliflozin, a sodium-glucose cotransporter type 2 (SGLT2) inhibitor, prevents endothelial dysfunction; however, direct effects of dapagliflozin on the endothelium under oxidative stress and the underlying mechanism of action are not completely understood. This study aimed to define the role and related mechanisms of dapagliflozin in hydrogen peroxide (H2O2)-induced endothelial dysfunction. The endothelium-dependent vasorelaxation effect of dapagliflozin was assessed in an organ bath study. Endothelial dysfunction was assessed using protein expression level and phosphorylation of endothelial nitric oxide synthase (eNOS), nitric oxide (NO), reactive oxygen species (ROS), senescence-associated beta-galactosidase (SA-β-gal) activity, and senescence marker proteins (p21, p53). Co-immunoprecipitation and protein acetylation were performed to detect protein interactions. Dapagliflozin exerted a direct vasorelaxant effect in the aortic rings of C57BL/6 J mice. Furthermore, there was a significant improvement in endothelium-dependent vasorelaxation in dapagliflozin-treated diabetic mice compared to vehicle controls. Moreover, intracellular ROS levels and ONOO- levels, increased by H2O2, were reduced by dapagliflozin. Importantly, dapagliflozin inhibited H2O2-induced senescence in the human umbilical vein endothelial cells (HUVECs), as indicated by reduced SA‐β‐gal, p21, and p53. Mechanistically, dapagliflozin reversed the H2O2-mediated inhibition of eNOS serine phosphorylation and sirtuin 1 (SIRT1) expression in endothelial cells. In particular, SIRT1-mediated eNOS deacetylation is reportedly involved in dapagliflozin-enhanced eNOS activity. These findings indicate that dapagliflozin ameliorates endothelial dysfunction by restoring eNOS activity, restoring NO bioavailability, and reducing ROS generation via SIRT1 activation in oxidative stress-stimulated endothelial cells.

Impact of Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors on Arterial Stiffness and Vascular Aging-What Do We Know So Far? (A Narrative Review).

Vascular aging, early vascular aging or supernormal vascular aging are concepts used for estimating the cardiovascular risk at a certain age. From the famous line of Thomas Sydenham that “a man is as old as his arteries” to the present day, clinical studies in the field of molecular biology of the vasculature have demonstrated the active role of vascular endothelium in the onset of cardiovascular diseases. Arterial stiffness is an important cardiovascular risk factor associated with the occurrence of cardiovascular events and a high risk of morbidity and mortality, especially in the presence of diabetes. Sodium–glucose cotransporter 2 inhibitors decrease arterial stiffness and vascular resistance by decreasing endothelial cell activation, stimulating direct vasorelaxation and ameliorating endothelial dysfunction or expression of pro-atherogenic cells and molecules.

Interleukin-10 does not contribute to the anti-contractile nature of PVAT in health

Perivascular adipose tissue (PVAT) is protective and reduces contraction of blood vessels in health. PVAT is composed of adipocytes, multiple types of immune cells and stromal cells. Interleukin (IL)-10, an anti-inflammatory cytokine usually produced by T cells, B cells and macrophages, was identified as one of the highly expressed (mRNA) cytokines in the mesenteric PVAT of healthy rats. One report suggested that exogenous IL-10 causes relaxation of mouse mesenteric arteries, also suggesting that IL-10 maybe a potential anti-contractile factor. Hence, we hypothesized that PVAT-derived IL-10 causes vasorelaxation and/or reduces vasoconstriction, thus contributing to the anti-contractile nature of PVAT in health. Mesenteric arteries from rats and mice expressed the receptor for IL-10 (in tunica intima and media) as determined by immunohistochemistry. Mesenteric resistance arteries for rats and superior mesenteric artery for mice were used for isometric contractility studies. Increasing concentrations [0.4–100 ng/mL] of recombinant rat/mouse (rr/mr) IL-10 or vehicle was directly added to half-maximally constricted (phenylephrine, PE) vessels (without PVAT, with endothelium). IL-10 did not cause a direct vasorelaxation. Further, the ability of rrIL-10 to cause a rightward or downward shift of a vasoconstriction-response curve was tested in the rat. The vessels were incubated with rrIL-10 [100 ng/mL or 10 ng/mL] or vehicle for 1.5 h in the tissue bath followed by a cumulative PE [10−8–10−4 M] or U46619 [10−10–10−5 M] response curve. The maximal contractions and EC50 values were similar in IL-10 incubated vessels vs vehicle. Thus, acute exposure of exogenous IL-10 did not reduce local vasoconstriction. To further test if endogenous IL-10 from PVAT was anti-contractile, superior mesenteric arteries from IL-10 WT and KO mice, with and without PVAT, were subjected to increasing concentrations of PE. The anti-contractile nature of PVAT was preserved with both short-term and prolonged depletion (using younger and older mice, respectively) of endogenous IL-10 in males and females. Contrary to our hypothesis, PVAT-derived IL-10 neither caused vasorelaxation nor reduced local vasoconstriction directly/indirectly. Therefore, IL-10 does not contribute to the anti-contractile nature of PVAT in healthy rodents.

Detection of silent cerebral microcirculatory abnormalities in patients with manifest ischemic coronary disease: a perfusion brain MRI study combined with dipyridamole stress

Objectives Intravenous dipyridamole (DP) can induce transient perfusion abnormalities in the heart but also the brain indicated by brain SPECT. L-arginine can regulate the vascular tone via nitric oxide (NO). Therefore, we examined cerebral blood volume (CBV) by perfusion MRI and L-arginine level before and after DP stress in patients, who developed transient neurological signs, and compared these to unaffected patients. Design A total of nine patients with ischemic coronary disease after myocardial perfusion scintigraphy were selected for this prospective pilot study. Four had DP-induced transient mild neurologic signs during myocardial perfusion scintigraphy, while five had no neurological signs. By using perfusion MRI in both groups in a second stage, we examined CBV in identical areas of the two hemispheres before and during DP stress. Besides, pre-and post-stress L-arginine serum levels were also analyzed by high-performance liquid chromatography. Trial registration: NCT03688815. Results CBV in the sensory-motor area at baseline was significantly higher in patients with DP-induced transient neurological signs compared to patients without signs (p = 0.028). Intravenous DP normalized the higher perfusion by decreasing CBV, and also increased serum L-arginine level (p = 0.001). Conclusions Intravenous DP changed the CBV accompanied by a systemic elevation of L-arginine: this indicates a direct vasorelaxing effect on brain vessels, and an indirect vasodilator effect through L-arginine release presumably via NO. In areas with decreased CBV before DP, such double effects caused transient neurological symptoms presumably due to steal phenomenon. Therefore, intravenous DP may have a potential to identify patients with high risk for cerebral ischemia.

IL‐10 Neither Causes Direct Vasorelaxation Nor Reduces Vasoconstriction in Rat Mesenteric Resistance Arteries

Perivascular adipose tissue (PVAT) is the fat that surrounds most of the peripheral blood vessels in the body. PVAT is protective and reduces contraction of blood vessels in health. We discovered that in health, PVAT around the rat small mesenteric resistance vessels (MRPVAT) contained a community of immune cells including T cells, B cells, macrophages, NK cells, neutrophils and mast cells. Interleukin (IL)‐10‐‐an anti‐inflammatory cytokine usually produced by T cells, B cells and macrophages‐‐was identified as one of the highly expressed (mRNA) cytokines in MRPVAT. One report suggests that IL‐10 causes relaxation of mouse mesenteric arteries. Hence, we hypothesized that IL‐10 directly causes vasorelaxation and/or reduces vasoconstriction in healthy rats. Male Sprague Dawley rats (12–14 weeks age) were used. Mesenteric resistance arteries expressed the receptor for IL‐10 (tunica intima and media) as determined by immunohistochemistry. Isolated tissue bath and third order mesenteric resistance arteries (without PVAT and with intact endothelium) were used for isometric contractility studies. Increasing concentrations [0.4–100 ng/mL] of recombinant rat (rr) IL‐10 or vehicle was directly added to half‐maximally constricted (phenylephrine PE or thromboxane A2 agonist U46619) vessels. IL‐10 did not reduce contraction, suggesting it was not a direct vasorelaxant. Further, the ability of rrIL‐10 to cause a rightward or downward shift of a vasoconstrictant‐response curve was tested. The vessels were incubated with rrIL‐10 [100 ng/mL or 10 ng/mL] or vehicle for 1.5 hours in the tissue bath followed by a cumulative PE [10−9–10−5 M] or U46619 [10−10–10−5 M] response curve. The maximal contractions or EC50 values (shown in table ) were not statistically different in rrIL‐10 incubated vessels vs vehicle. Thus, acute exposure of exogenous IL‐10 neither caused direct vasorelaxation nor reduced vasoconstriction. Further studies with neutralizing antibody for IL‐10 to vessels ± PVAT will help determine if IL‐10 produced in the PVAT causes vasorelaxation and/or reduction in local vasoconstriction indirectly, thus contributing to the anti‐contractile nature of PVAT.Support or Funding InformationNIH HL70687 −Log EC50 ± SEM (n=6–10 arteries/3–5 rats/curve) Vehicle rrIL‐10 (100 ng/mL) PE curve 5.7± 0.05 5.6±0.05 U46619 curve 7.6±0.28 7.2±0.59 Vehicle rrIL‐10 (10 ng/mL) PE curve 5.7±0.03 5.6±0.04 U46619 curve 7.1±0.12 7.2±0.13

In Vitro Effects of Eicosapentaenoic and Docosahexaenoic Acid on the Vascular Tone of a Human Saphenous Vein: Influence of Precontractile Agents

Cardiovascular effects of omega-3 polyunsaturated fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been widely reported. However, there are limited studies concerning their effects on human blood vessels. Therefore, the aim of this study was to investigate the direct vascular effects of EPA and DHA on the human saphenous vein (SV) precontracted with either prostaglandin F2α (PGF2α), or thromboxane A2 analogue (U46619), or norepinephrine (NE). Moreover, we aimed to investigate the protein expression of free fatty acid receptor 4 (FFAR4) in human SV. Pretreatment of human SV rings with EPA and DHA (100μM, 30min) was tested on vascular reactivity induced by PGF2α (10 nM to 5 μM), NE (10 nM to 100 μM), and U46619 (1nM to 100 nM). In addition, direct relaxant effects of EPA/DHA (1-100μM) were tested in human SV rings precontracted by PGF2α, NE, and U46619. Furthermore, the involvement of potassium channels on their vascular effects was investigated in the presence of the nonselective K+ channel inhibitor tetraethylammonium chloride. Pretreatment with EPA and DHA resulted in a significant decrease in vascular reactivity induced by U46619 and PGF2α compared to NE. In the presence of TEA, the relaxant effects of EPA and DHA were significantly decreased in SV preparations precontracted by U46619 and PGF2α for DHA. Furthermore, FFAR-4 protein was expressed in tissue extracts of humanSV. Our study demonstrates that both EPA and DHA reduce the increased vascular tone elicited by contractile agents on the human SV and that the direct vasorelaxant effect is likely to involve potassium channels.

Erucin exhibits vasorelaxing effects and antihypertensive activity by H2S‐releasing properties

Hydrogen sulfide (H2 S)-releasing agents are viewed as potential antihypertensive drugs. Recently, natural isothiocyanates emerged as original H2 S-donor agents. Among them, erucin, present in some edible cruciferous plants, shows suitable H2 S-releasing properties and features of "druggability." The aim of this work was to investigate the erucin-mediated release of H2 S inside vascular cells, its vasorelaxing effects, and activity on BP of normo and hypertensive animals. Intracellular H2 S-release and the hyperpolarizing effect of erucin were tested using fluorescent dye, in human aortic smooth muscle cells (HASMCs). Its direct vasorelaxing effect and ability to inhibit noradrenaline-induced vasoconstriction were evaluated on endothelium-intact or -denuded rat aortic rings. Its vasodilator properties were tested in coronary arteries using Langendorff-perfused rat hearts. Finally, erucin's antihypertensive activity was evaluated in vivo in normotensive and spontaneously hypertensive rats (SHRs) by recording systolic BP using the tail-cuff method. Erucin induced the release of H2 S inside HASMCs. Moreover, erucin hyperpolarized the membrane of HASMCs membrane in a concentration-dependent manner. It induced vasodilatation of rat aortic rings, in endothelium-denuded vessels. This effect was further improved by the presence of endothelial NO. When pre-incubated with rat aortic rings, erucin induced concentration-dependent inhibition of noradrenaline-induced vasoconstriction. Erucin did not affect basal coronary flow but restored the flow to normal in pre-contracted coronary vessels. Finally, in vivo, erucin decreased systolic BP in SHRs by about 25%, and restored the BP to values observed in normotensive rats. Erucin is an H2 S donor endowed with vasorelaxing and antihypertensive effects. This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

A11957 Irisin Lowers Blood Pressure by Improvement of Endothelial Dysfunction via AMPK-Akt-eNOS-NO Pathway in the Spontaneously Hypertensive Rat

Objectives: Exercise is a major nonpharmacological treatment for hypertension, but its underlying mechanisms are still not completely elucidated. Irisin, a polypeptide containing 112 amino acids, which is secreted mainly by skeletal muscle cells during exercise, exerts a protective role in metabolic diseases, such as diabetes and obesity. Due to the close relationship between irisin and metabolic diseases, we hypothesized that irisin may play a role in the regulation of blood pressure. Methods: Blood pressures of male WKY rats and SHRs were monitored via the carotid artery. The vascular response was checked by tension measurement of the artery rings. Protein expression was tested by immunoblot. Results: Our study found that the acute intravenous injection of irisin reduced blood pressure in SHRs but not WKY rats. Irisin, by itself, had no direct vasorelaxing effect in phenylephrine-pre-constricted mesenteric arteries from SHRs. However, irisin augmented the acetylcholine-induced vasorelaxation in mesenteric arteries from SHRs that could be reversed by Nω-nitro-L-arginine-methyl ester (L-NAME, 100 μM), indicating a role of NO in this action. Indeed, irisin increased NO production and phosphorylation of eNOS in endothelial cells. 5¢-AMP-activated protein kinase (AMPK) was involved in the vasorelaxing effect of irisin because compound C (20 μM), an AMPK inhibitor, blocked the irisin-mediated increase in phosphorylation of eNOS and Akt in endothelial cells and vasodilation in mesenteric arteries. Conclusion: We conclude that acute administration of irisin lowers blood pressure of SHRs by amelioration of endothelial dysfunction of the mesenteric artery via AMPK-Akt-eNOS-NO signaling pathway.

A novel S-nitrosocaptopril monohydrate for pulmonary arterial hypertension: H2O and –SNO intermolecular stabilization chemistry

S-nitrosocaptopril (CapNO) possesses dual capacities of both Captopril and an NO donor with enhanced efficacy and reduced side effects. CapNO crystals are difficult to make due to its unstable S-NO bond. Here, we report a novel stable S-nitrosocaptopril monohydrate (CapNO·H2O) that is stabilized by intermolecular five-membered structure, where one H of H2O forms a hydrogen bond with O- of the stable resonance zwitterion Cap–S+=N–O-, and the O in H2O forms the dipole-dipole interaction with S+ through two unpaired electrons. With the chelation and common ion effect, we synthesized and characterized CapNO·H2O that is stable at 4 °C for 180 days and thereafter without significant degradation. Compared to Captopril, CapNO showed direct vasorelaxation and beneficial effect on PAH rats, and could be self-assembled in rat stomach when Captopril and NaNO2 were given separately. This novel CapNO·H2O with low entropy paves an avenue for its clinical trials and commercialization.

Dapagliflozin attenuates human vascular endothelial cell activation and induces vasorelaxation: A potential mechanism for inhibition of atherogenesis.

Sodium glucose transporter type 2 inhibitors may reduce cardiovascular events in type 2 diabetes. Our study aimed to determine the effect of the sodium glucose transporter type 2 inhibitor dapagliflozin on endothelial cell activation, vasoreactivity and atherogenesis using in vitro and in vivo models and identify associated molecular mechanisms. In vitro studies utilised human vascular endothelial cells stimulated with tumour necrosis factor α or hyperglycaemic conditions. In vivo studies were performed in C57Bl/6J mice to evaluate direct vasorelaxation responses evoked by acute dapagliflozin administration and acute vaso-protective effects of dapagliflozin on hyperglycaemia-induced endothelial dysfunction. Adult and aged Apolipoprotein E-deficient mice maintained on a high-fat diet were used to investigate endothelial-dependent vascular reactivity and atherogenesis. Dapagliflozin treatment (1.0 mg/kg/day) was administered for 4 weeks. In vitro studies demonstrated dapagliflozin-mediated attenuation of tumour necrosis factor α- and hyperglycaemia-induced increases in intercellular adhesion molecule-1, vascular cell adhesion molecule-1, plasminogen activator inhibitor type 1 and NFκB expression. Acute dapagliflozin administration dose-dependently induced endothelium-independent vasorelaxation. Chronic dapagliflozin treatment improved endothelial function and significantly reduced in vivo vascular adhesion molecule and phospho-IκB expression together with macrophage vessel wall infiltration. These observations identify a potential role for dapagliflozin in the attenuation of atherogenesis and identify anti-inflammatory molecular mechanisms associated with these effects.

Possible mechanisms involved in the vasorelaxant effect produced by clobenzorex in aortic segments of rats.

Clobenzorex is a metabolic precursor of amphetamine indicated for the treatment of obesity. Amphetamines have been involved with cardiovascular side effects such as hypertension and pulmonary arterial hypertension. The aim of the present study was to investigate whether the direct application of 10–9–10–5 M clobenzorex on isolated phenylephrine-precontracted rat aortic rings produces vascular effects, and if so, what mechanisms may be involved. Clobenzorex produced an immediate concentration-dependent vasorelaxant effect at the higher concentrations (10–7.5–10–5 M). The present outcome was not modified by 10–6 M atropine (an antagonist of muscarinic acetylcholine receptors), 3.1×10–7 M glibenclamide (an ATP-sensitive K+ channel blocker), 10–3 M 4-aminopyridine (4-AP; a voltage-activated K+ channel blocker), 10–5 M indomethacin (a prostaglandin synthesis inhibitor), 10–5 M clotrimazole (a cytochrome P450 inhibitor) or 10–5 M cycloheximide (a general protein synthesis inhibitor). Contrarily, the clobenzorex-induced vasorelaxation was significantly attenuated (P<0.05) by 10–5 M L-NAME (a direct inhibitor of nitric oxide synthase), 10–7 M ODQ (an inhibitor of nitric oxide-sensitive guanylyl cyclase), 10–6 M KT 5823 (an inhibitor of protein kinase G), 10–2 M TEA (a Ca2+-activated K+ channel blocker and non-specific voltage-activated K+ channel blocker) and 10–7 M apamin plus 10–7 M charybdotoxin (blockers of small- and large-conductance Ca2+-activated K+ channels, respectively), and was blocked by 8×10–2 M potassium (a high concentration) and removal of the vascular endothelium. These results suggest that the direct vasorelaxant effect by clobenzorex on phenylephrine-precontracted rat aortic rings involved stimulation of the NO/cGMP/PKG/Ca2+-activated K+ channel pathway.

Irisin Lowers Blood Pressure by Improvement of Endothelial Dysfunction via AMPK-Akt-eNOS-NO Pathway in the Spontaneously Hypertensive Rat.

BackgroundExercise is a major nonpharmacological treatment for hypertension, but its underlying mechanisms are still not completely elucidated. Irisin, a polypeptide containing 112 amino acids, which is secreted mainly by skeletal muscle cells during exercise, exerts a protective role in metabolic diseases, such as diabetes mellitus and obesity. Because of the close relationship between irisin and metabolic diseases, we hypothesized that irisin may play a role in the regulation of blood pressure.Methods and ResultsBlood pressures of male Wistar‐Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) were monitored through the carotid artery. Our study found that acute intravenous injection of irisin reduced blood pressure in SHRs, but not WKY rats. Irisin, by itself, had no direct vasorelaxing effect in phenylephrine‐preconstricted mesenteric arteries from SHRs. However, irisin augmented the acetylcholine‐induced vasorelaxation in mesenteric arteries from SHRs that could be reversed by Nω‐nitro‐l‐arginine‐methyl ester (L‐NAME; 100 μmol/L), indicating a role of nitric oxide (NO) in this action. Indeed, irisin increased NO production and phosphorylation of endothelial nirtic oxide synthase (eNOS) in endothelial cells. 5′‐AMP‐activated protein kinase (AMPK) was involved in the vasorelaxing effect of irisin because compound C (20 μmol/L), an AMPK inhibitor, blocked the irisin‐mediated increase in phosphorylation of eNOS and protein kinase B (Akt) in endothelial cells and vasodilation in mesenteric arteries.ConclusionsWe conclude that acute administration of irisin lowers blood pressure of SHRs by amelioration of endothelial dysfunction of the mesenteric artery through the AMPK‐Akt‐eNOS‐NO signaling pathway.

6-Gingerol alleviates exaggerated vasoconstriction in diabetic rat aorta through direct vasodilation and nitric oxide generation.

The aim of the present study is to investigate the effect and potential mechanism of action of 6-gingerol on alterations of vascular reactivity in the isolated aorta from diabetic rats. Male Wistar rats were divided into two experimental groups, control and diabetics. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg kg−1), and the rats were left for 10 weeks to develop vascular complications. The effect of in vitro incubation with 6-gingerol (0.3–3 μM) on the vasoconstrictor response of the isolated diabetic aortae to phenylephrine and the vasodilator response to acetylcholine was examined. Effect of 6-gingerol was also examined on aortae incubated with methylglyoxal as an advanced glycation end product (AGE). To investigate the mechanism of action of 6-gingerol, the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester hydrochloride (100 μM), guanylate cyclase inhibitor methylene blue (5 μM), calcium-activated potassium channel blocker tetraethylammonium chloride (10 mM), and cyclooxygenase inhibitor indomethacin (5 μM) were added 30 minutes before assessing the direct vasorelaxant effect of 6-gingerol. Moreover, in vitro effects of 6-gingerol on NO release and the effect of 6-gingerol on AGE production were examined. Results showed that incubation of aortae with 6-gingerol (0.3–10 μM) alleviated the exaggerated vasoconstriction of diabetic aortae to phenylephrine in a concentration-dependent manner with no significant effect on the impaired relaxatory response to acetylcholine. Similar results were seen in the aortae exposed to methylglyoxal. In addition, 6-gingerol induced a direct vasodilation effect that was significantly inhibited by Nω-nitro-l-arginine methyl ester hydrochloride and methylene blue. Furthermore, 6-gingerol stimulated aortic NO generation but had no effect on AGE formation. In conclusion, 6-gingerol ameliorates enhanced vascular contraction in diabetic aortae, which may be partially attributed to its ability to increase the production of NO and stimulation of cyclic guanosine monophosphate.

Berberine via suppression of transient receptor potential vanilloid 4 channel improves vascular stiffness in mice.

Berberine, as an alkaloid found in many Chinese herbs, improves vascular functions in patients with cardiovascular diseases. We determined the effects of berberine in hypertension and vascular ageing, and elucidated the underlying mechanisms. In isolated aortas, berberine dose-dependently elicited aortic relaxation. In cultured cells, berberine induced the relaxation of vascular smooth muscle cells (VSMCs). Overexpression of transient receptor potential vanilloid 4 (TRPV4) channel by genetic approaches abolished the berberine-induced reduction in intracellular Ca2+ concentration in VSMCs and attenuated berberine-elicited vessel dilation in mice aortas. In deoxycorticosterone acetate (DOCA)-induced hypertensive model, treatment of mice with berberine or RN-1734, a pharmacological inhibitor of TRPV4, significantly decreased systemic blood pressure (BP) in control mice or mice infected with an adenovirus vector. However, berberine-induced effects of lowering BP were reversed by overexpressing TRPV4 in mice by infecting with adenovirus. Furthermore, long-term administration of berberine decreased mean BP and pulse BP, increased artery response to vasodilator and reduced vascular collagen content in aged mice deficient in apolipoprotein E (Apoe-KO), but not in Apoe-KO old mice with lentivirus-mediated overexpression of TRPV4 channel. In conclusion, berberine induces direct vasorelaxation to lower BP and reduces vascular stiffness in aged mice through suppression of TRPV4.

Systemic hypotensive effects of testosterone are androgen structure-specific and neuronal nitric oxide synthase-dependent.

Testosterone (TES) and other androgens exert a direct vasorelaxing action on the vasculature in vitro that is structurally specific and independent of cytosolic androgen receptor (AR). The effects of intravenous androgen infusions on mean arterial blood pressure (BP) and heart rate (HR) were determined in conscious, unrestrained, chronically catheterized, ganglionically blocked (hexamethonium, HEX; 30 mg/kg ip) male Sprague-Dawley (SD) and testicular-feminized male (Tfm; AR-deficient) rats, 16-20 wk of age. BP and HR were recorded at baseline and with increasing doses of androgens (0.375-6.00 μmol·kg(-1)·min(-1) iv; 10 min/dose). Data are expressed as means ± SE (n = 5-8 rats/group). In SD rats, baseline BP and HR averaged 103 ± 4 mmHg and 353 ± 12 beats/min (bpm). TES produced a dose-dependent reduction in BP to a low of 87 ± 4 mmHg (Δ16%), while HR was unchanged (354 ± 14 bpm). Neither BP (109 ± 3 mmHg) nor HR (395 ± 13 bpm) were altered by vehicle (10% EtOH in 0.9% saline; 0.15 ml·kg(-1)·min(-1), iv). In Tfm, TES produced a similar reduction in BP (99 ± 3 to 86 ± 3 mmHg, Δ13%); HR was unchanged (369 ± 18 bpm). In SD, 5β-dihydrotestosterone (genomically inactive metabolite) produced a greater reduction in BP than TES (102 ± 2 to 79 ± 2 mmHg, Δ23%); HR was unchanged (361 ± 9). A 20-μg iv bolus of sodium nitroprusside in both SD and Tfm rats reduced BP 30-40 mmHg, while HR was unchanged, confirming blockade by HEX. Pretreatment of SD rats with neuronal nitric oxide synthase (nNOS) inhibitor (S-methyl-thiocitrulline, SMTC; 20 μg·kg(-1)·min(-1) × 30 min) abolished the hypotensive effects of TES infusion on BP (104 ± 2 vs. 101 ± 2 mmHg) and HR (326 ± 11 vs. 324 ± 8 bpm). These data suggest the systemic hypotensive effect of TES and other androgens involves a direct vasodilatory action on the peripheral vasculature which, like the effect observed in isolated arteries, is structurally specific and AR-independent, and involves activation of nNOS.

Effects of Resveratrol on Contractions of the Rat Tail Artery

In 2000, Naderali et. al. reported in Clinical Science (98:537-43) that resveratrol's direct vasorelaxant effect in vitro (on either adrenergic receptor-induced or high potassium-induced vascular smooth muscle contractions) was significantly greater in ring segments cut from mesenteric resistance arteries than from the main uterine conductance artery of female guinea pigs. Since then this important difference has not been confirmed in any other resistance versus conductance arterial tissues, and isolated from the same vasculature perfusing the same organ rather than different vessels perfusing different organs. The most distal and most proximal portions of the notably long ventral tail artery of the laboratory rat are commonly known for their unique structural and functional similarities to other resistance and conductance arteries (respectively) found throughout the rest of the body. Accordingly, we tested for relaxant effects of resveratrol in vitro in adrenergically pre-contracted rings cut from short segments of the distal and proximal portions of the tail artery from male rats. Its half-maximally effective concentration values were essentially identical (25±3 versus 27±3 micromolar) in distal versus proximal segments; results which do not confirm a greater relaxant effect of resveratrol in resistance versus conductance arterial tissues. Therefore, what Naderali et. al. previously observed may have been due to some other property that differed between their mesenteric and uterine arterial preparations. Support: MWU Master's Program.

Nitric Oxide Inhibits Hetero-adhesion of Cancer Cells to Endothelial Cells: Restraining Circulating Tumor Cells from Initiating Metastatic Cascade

Adhesion of circulating tumor cells (CTCs) to vascular endothelial bed becomes a crucial starting point in metastatic cascade. We hypothesized that nitric oxide (NO) may prevent cancer metastasis from happening by its direct vasodilation and inhibition of cell adhesion molecules (CAMs). Here we show that S-nitrosocaptopril (CAP-NO, a typical NO donor) produced direct vasorelaxation that can be antagonized by typical NO scavenger hemoglobin and guanylate cyclase inhibitor. Cytokines significantly stimulated production of typical CAMs by the highly-purified human umbilical vein endothelial cells (HUVECs). CAP-NO inhibited expression of the stimulated CAMs (particularly VCAM-1) and the resultant hetero-adhesion of human colorectal cancer cells HT-29 to the HUVECs in a concentration-dependent manner. The same concentration of CAP-NO, however, did not significantly affect cell viability, cell cycle and mitochondrial membrane potential of HT-29, thus excluding the possibility that inhibition of the hetero-adhesion was caused by cytotoxicity by CAP-NO on HT-29. Hemoglobin reversed the inhibition of CAP-NO on both the hetero-adhesion between HT-29 and HUVECs and VCAM-1 expression. These data demonstrate that CAP-NO, by directly releasing NO, produces vasorelaxation and interferes with hetero-adhesion of cancer cells to vascular endothelium via down-regulating expression of CAMs. The study highlights the importance of NO in cancer metastatic prevention.

Antihypertensive and vasorelaxant effects of dihydrospinochalcone-A isolated from Lonchocarpus xuul Lundell by NO production: Computational and ex vivo approaches

Current work was conducted to evaluate the vasorelaxant effect of dihydrospinochalcone-A (1) and isocordoin (2), compounds type chalcone isolated from Lonchocarpus xuul, an endemic tree of the Yucatan Peninsula, Mexico. Compounds 1 and 2 were found to induce significant relaxant effect in a concentration-dependent manner on aortic rat rings pre-contracted with noradrenaline (NA, 0.1μM). Compound 1 was the most active and its effect was endothelium-dependent (Emax=79.67% and EC50=21.46μM with endothelium and Emax=23.58% and EC50=91.8μM without endothelium, respectively). The functional mechanism of action for 1 was elucidated. Pre-incubation with l-NAME (unspecific nitric oxide synthase inhibitor), indomethacin (unspecific COX inhibitor), ODQ (soluble guanylyl cyclase inhibitor), atropine (cholinergic receptor antagonist), TEA (unspecific potassium channel blocker) reduced relaxations induced by 1. Oral administration of 50mg/kg of compound 1 exhibited significant decrease in diastolic and systolic blood pressure in SHR rats. The heart rate was not modified. Compound 1 was docked with a crystal structure of eNOS. Dihydrospinochalcone-A showed calculated affinity with eNOS in the C1 binding pockets, near the catalytic site; Trp449, Trp447 and His373 through aromatic and π–π interactions, also His463 and Arg367 are the residues that make hydrogen bonds with the carbonyl and hydroxyl groups.In conclusion, dihydrospinochalcone-A induces a significant antihypertensive effect due to its direct vasorelaxant action on rat aorta rings, through NO/sCG/PKG pathway and potassium channel opening.

Comparison of the Intrinsic Vasorelaxant and Inotropic Effects of the Antiarrhythmic Agents Vernakalant and Flecainide in Human Isolated Vascular and Cardiac Tissues

This study explored the intrinsic vasorelaxant and inotropic effects of the mixed potassium and sodium channel blocker atrial antiarrhythmic vernakalant and the class IC antiarrhythmic agent flecainide in human isolated subcutaneous resistance artery and in ventricular trabecular muscle preparations. At test concentrations encompassing free plasma concentrations associated with clinical efficacy for conversion of atrial fibrillation, vernakalant (1-10 μM) displayed no significant direct effects on human resistance artery tone or ventricular contractility. In contrast, tested at equimolar concentrations, flecainide significantly reduced peak isometric contractile force (10 μM) and maximal rates of force development and decline (3 and 10 μM) in the human ventricular muscle preparation while displaying no significant effect on human resistance artery tone. The lack of effects of vernakalant on human resistance artery tone and ventricular muscle contractile function suggests that direct vasorelaxant and inotropic effects do not underlie the rare hypotensive events observed clinically with vernakalant, raising the possibility that secondary (eg, reflex) effects may mediate these events. The demonstration of negative inotropic effects with flecainide in the human ventricular muscle preparations in the absence of an effect on resistance artery tone suggests that the hemodynamic effects of flecainide observed clinically result primarily from direct negative inotropic effects.