Myeloperoxidase Gene Deletion Causes Drastic Microbiome Shifts in Mice and Does Not Mitigate Dextran Sodium Sulphate-Induced Colitis.

Neutrophil-myeloperoxidase (MPO) is a heme-containing peroxidase which produces excess amounts of hypochlorous acid during inflammation. While pharmacological MPO inhibition mitigates all indices of experimental colitis, no studies have corroborated the role of MPO using knockout (KO) models. Therefore, we investigated MPO deficient mice in a murine model of colitis. Wild type (Wt) and MPO-deficient mice were treated with dextran sodium sulphate (DSS) in a chronic model of experimental colitis with three acute cycles of DSS-induced colitis over 63 days, emulating IBD relapse and remission cycles. Mice were immunologically profiled at the gut muscoa and the faecal microbiome was assessed via 16S rRNA amplicon sequencing. Contrary to previous pharmacological antagonist studies targeting MPO, MPO-deficient mice showed no protection from experimental colitis during cyclical DSS-challenge. We are the first to report drastic faecal microbiota shifts in MPO-deficient mice, showing a significantly different microbiome profile on Day 1 of treatment, with a similar shift and distinction on Day 29 (half-way point), via qualitative and quantitative descriptions of phylogenetic distances. Herein, we provide the first evidence of substantial microbiome shifts in MPO-deficiency, which may influence disease progression. Our findings have significant implications for the utility of MPO-KO mice in investigating disease models.

Physiological Benefits of Novel Selenium Delivery via Nanoparticles.

Dietary selenium (Se) intake within the physiological range is critical to maintain various biological functions, including antioxidant defence, redox homeostasis, growth, reproduction, immunity, and thyroid hormone production. Chemical forms of dietary Se are diverse, including organic Se (selenomethionine, selenocysteine, and selenium-methyl-selenocysteine) and inorganic Se (selenate and selenite). Previous studies have largely investigated and compared the health impacts of dietary Se on agricultural stock and humans, where dietary Se has shown various benefits, including enhanced growth performance, immune functions, and nutritional quality of meats, with reduced oxidative stress and inflammation, and finally enhanced thyroid health and fertility in humans. The emergence of nanoparticles presents a novel and innovative technology. Notably, Se in the form of nanoparticles (SeNPs) has lower toxicity, higher bioavailability, lower excretion in animals, and is linked to more powerful and superior biological activities (at a comparable Se dose) than traditional chemical forms of dietary Se. As a result, the development of tailored SeNPs for their use in intensive agriculture and as candidate for therapeutic drugs for human pathologies is now being actively explored. This review highlights the biological impacts of SeNPs on growth and reproductive performances, their role in modulating heat and oxidative stress and inflammation and the varying modes of synthesis of SeNPs.

Role for Selenium in Metabolic Homeostasis and Human Reproduction.

Selenium (Se) is a micronutrient essential for life. Dietary intake of Se within the physiological range is critical for human health and reproductive functions. Selenium levels outside the recommended range have been implicated in infertility and variety of other human diseases. However, presently it is not clear how different dietary Se sources are processed in our bodies, and in which form or how much dietary Se is optimum to maintain metabolic homeostasis and boost reproductive health. This uncertainty leads to imprecision in published dietary guidelines and advice for human daily intake of Se and in some cases generating controversies and even adverse outcomes including mortality. The chief aim for this review is to describe the sources of organic and inorganic Se, the metabolic pathways of selenoproteins synthesis, and the critical role of selenprotenis in the thyroid gland homeostasis and reproductive/fertility functions. Controversies on the use of Se in clinical practice and future directions to address these challenges are also described and discussed herein.

Acute simvastatin inhibits K ATP channels of porcine coronary artery myocytes.

BACKGROUND: Statins (3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors) consumption provides beneficial effects on cardiovascular systems. However, effects of statins on vascular KATP channel gatings are unknown. METHODS: Pig left anterior descending coronary artery and human left internal mammary artery were isolated and endothelium-denuded for tension measurements and Western immunoblots. Enzymatically-dissociated/cultured arterial myocytes were used for patch-clamp electrophysiological studies and for [Ca(2+)]i, [ATP]i and [glucose]o uptake measurements. RESULTS: The cromakalim (10 nM to 10 µM)- and pinacidil (10 nM to 10 µM)-induced concentration-dependent relaxation of porcine coronary artery was inhibited by simvastatin (3 and 10 µM). Simvastatin (1, 3 and 10 µM) suppressed (in okadaic acid (10 nM)-sensitive manner) cromakalim (10 µM)- and pinacidil (10 µM)-mediated opening of whole-cell KATP channels of arterial myocytes. Simvastatin (10 µM) and AICAR (1 mM) elicited a time-dependent, compound C (1 µM)-sensitive [(3)H]-2-deoxy-glucose uptake and an increase in [ATP]i levels. A time (2-30 min)- and concentration (0.1-10 µM)-dependent increase by simvastatin of p-AMPKα-Thr(172) and p-PP2A-Tyr(307) expression was observed. The enhanced p-AMPKα-Thr(172) expression was inhibited by compound C, ryanodine (100 µM) and KN93 (10 µM). Simvastatin-induced p-PP2A-Tyr(307) expression was suppressed by okadaic acid, compound C, ryanodine, KN93, phloridzin (1 mM), ouabain (10 µM), and in [glucose]o-free or [Na(+)]o-free conditions. CONCLUSIONS: Simvastatin causes ryanodine-sensitive Ca(2+) release which is important for AMPKα-Thr(172) phosphorylation via Ca(2+)/CaMK II. AMPKα-Thr(172) phosphorylation causes [glucose]o uptake (and an [ATP]i increase), closure of KATP channels, and phosphorylation of AMPKα-Thr(172) and PP2A-Tyr(307) resulted. Phosphorylation of PP2A-Tyr(307) occurs at a site downstream of AMPKα-Thr(172) phosphorylation.

Mitochondrial monoamine oxidase-A-mediated hydrogen peroxide generation enhances 5-hydroxytryptamine-induced contraction of rat basilar artery.

BACKGROUND AND PURPOSE: We evaluated the role(s) of monoamine oxidase (MAO)-mediated H2O2 generation on 5-hydroxytryptamine (5-HT)-induced tension development of isolated basilar artery of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. EXPERIMENTAL APPROACH: Basilar artery (endothelium-denuded) was isolated for tension measurement and Western blots. Enzymically dissociated single myocytes from basilar arteries were used for patch-clamp electrophysiological and confocal microscopic studies. KEY RESULTS: Under resting tension, 5-HT elicited a concentration-dependent tension development with a greater sensitivity (with unchanged maximum tension development) in SHR compared with WKY (EC(50) : 28.4 ± 4.1 nM vs. 98.2 ± 9.4 nM). The exaggerated component of 5-HT-induced tension development in SHR was eradicated by polyethylene glycol-catalase, clorgyline and citalopram whereas exogenously applied H2O2 enhanced the 5-HT-elicited tension development in WKY. A greater protein expression of MAO-A was detected in basilar arteries from SHR than in those from WKY. In single myocytes and the entire basilar artery, 5-HT generated (clorgyline-sensitive) a greater amount of H2O2 in SHR compared with WKY. Whole-cell iberiotoxin-sensitive Ca(2+) -activated K(+) (BK(Ca) ) amplitude measured in myocytes of SHR was approximately threefold greater than that in WKY (at +60 mV: 7.61 ± 0.89 pA·pF(-1) vs. 2.61 ± 0.66 pA·pF(-1) ). In SHR myocytes, 5-HT caused a greater inhibition (clorgyline-, polyethylene glycol-catalase- and reduced glutathione-sensitive) of BK(Ca) amplitude than in those from WKY. CONCLUSIONS AND IMPLICATIONS: 5-HT caused an increased generation of mitochondrial H2O2 via MAO-A-mediated 5-HT metabolism, which caused a greater inhibition of BK(Ca) gating in basilar artery myocytes, leading to exaggerated basilar artery tension development in SHR.

Evaluation of anti-oxidant capacity of root of Scutellaria baicalensis Georgi, in comparison with roots of Polygonum multiflorum Thunb and Panax ginseng CA Meyer.

In Chinese communities, regular consumption of Chinese-medicated diets (CMD) (usually in the form of soup) is a traditional practice to promote health and prevent disease development. The overall improvement of health conditions is believed to be correlated with the anti-oxidant potentials of these herbs. Huangqin, roots of Scutellaria baicalensis Georgi (Lamiaceae), is one of the herbs commonly used in CMD. In this study, the anti-oxidant capacities of Huangqin extracts (water, ethanol and ether extracts) were evaluated and compared to commonly used CMD herbs, Heshouwu, roots of Polygonum multiflorum Thunb (Polygonaceae) and Renshen (or Ginseng), roots of Panax ginseng CA Meyer (Araliaceae). The anti-oxidant capacities were measured by using both cell-free assay [ferric reducing/anti-oxidant power (FRAP)] and biological methods [2,2'-azobis-(2-amidinopropane) (AAPH)-induced haemolysis assay and H(2)O(2)-induced cell damage on H9C2 cells]. Additionally, the total phenolic content was measured using Folin-Ciocalteu methods. Water extract of Huangqin has the highest anti-oxidant activities compared to the ethanol and ether extracts. A positive relationship between the anti-oxidant effects and total phenolic contents of extracts was demonstrated. This shows that Huangqin could be an effective dietary anti-oxidant that can be consumed regularly as a functional food for the prevention of oxidant/free radical-related diseases.

14,15-Epoxyeicosatrienoic acid induces vasorelaxation through the prostaglandin EP(2) receptors in rat mesenteric artery.

Epoxyeicosatrienoic acids (EETs) induce vasorelaxation, probably through G protein-coupled receptors. The identity of these receptors is unclear, but it has been reported that EETs may bind to peroxisome proliferator activated receptors (PPARs) and E-prostanoid (EP) receptors. Therefore, we studied whether PPARs or EP receptors were involved in 14,15-EET-induced vasorelaxation. Isometric tensions of rat mesenteric arteries were measured. The vasorelaxant effect of 14,15-EET was inhibited by NF449 (G(s)-protein inhibitor), Rp-cAMP (cAMP antagonist) and KT5720 (PKA inhibitor), suggesting that the effect of 14,15-EET was mediated through G(s) protein-coupled receptors which were linked to the cAMP/PKA-dependent pathway. Pretreatments with MK886 (PPAR(alpha) antagonist) and GW9662 (PPAR(gamma) antagonist) did not influence 14,15-EET-induced vasorelaxation. The vasorelaxant effect of 14,15-EET was inhibited by AH6809 (EP(2) receptor antagonist), whereas SC19220 (EP(1) receptor antagonist), L798106 (EP(3) receptor antagonist) and GW627368X (EP(4) receptor antagonist) had no effect. The effect of 14,15-EET and the mechanism involved was mimicked by prostaglandin E(2) (an EP(2) receptor agonist). The 14,15-EET-induced relaxation was slightly potentiated in the presence of indomethacin (cyclooxygenase inhibitor which block PGE(2) synthesis). Binding study showed that the amount of 14,15-EET bound to the cell membrane of rat mesenteric arterial smooth muscle cells was much higher than that bound to the nuclear membrane. The binding of 14,15-EET to the cell membrane was attenuated by AH6809 and siRNA against EP(2) receptors. In conclusion, our study has demonstrated that 14,15-EET exerts relaxant effects on rat mesenteric arteries, at least partly via the stimulation of EP(2) receptors. This subsequently leads to activation of cAMP/PKA-dependent pathway in vascular smooth muscle cells.

Endothelium-derived nitric oxide inhibits the relaxation of the porcine coronary artery to natriuretic peptides by desensitizing big conductance calcium-activated potassium channels of vascular smooth muscle.

The present experiments investigated whether endothelium-derived mediators modulate the effect of natriuretic peptides in porcine coronary arteries. Rings with and without endothelium were suspended in organ chambers for isometric tension recording. Concentration-relaxation curves to C-type natriuretic peptide (CNP) and atrial natriuretic peptide (ANP) were obtained during contractions to endothelin-1. Removal of the endothelium potentiated relaxations to both CNP and ANP. N(omega)-nitro-L-arginine methyl ester potentiated relaxations to natriuretic peptides only in arteries with endothelium. Sodium nitroprusside (SNP) inhibited the response to the natriuretic peptides only in the absence of the endothelium. In rings with endothelium, 1H-[1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one (ODQ) and 4H-8-bromo-1,2,4-oxadiazolo[3,4-d]benz[b][1,4]oxazin-1-one (NS2028) potentiated CNP-mediated relaxations. Iberiotoxin (IBTX) reduced the response only in rings without endothelium. Glybenclamide inhibited the relaxations in both the presence and absence of endothelium. CNP-induced relaxations were reduced by 8-bromoguanosine 3',5'-cGMP (8-bromo-cGMP) to the same extent in rings with and without endothelium. There was no significant difference between the increased cGMP content caused by CNP in porcine coronary arteries with or without endothelium. In patch-clamp studies in porcine coronary arterial smooth muscle cells, the natriuretic peptide-mediated enhancement of the IBTX-sensitive big conductance calcium-activated potassium channel (BK(Ca)) amplitude was reversed by SNP and 8-bromo-cGMP. These findings demonstrate that, in the porcine coronary artery, the opening of BK(Ca) and ATP-dependent potassium channels of the vascular smooth muscle contributes to CNP-mediated relaxations. Endothelium-derived and exogenous NO inhibit the direct relaxing effect of natriuretic peptides by desensitizing the response of the BK(Ca)s of the vascular smooth muscle to the generation of cGMP.

Folic acid consumption reduces resistin level and restores blunted acetylcholine-induced aortic relaxation in obese/diabetic mice.

Folic acid supplementation provides beneficial effects on endothelial functions in patients with hyperhomocysteinemia. However, its effects on vascular functions under diabetic conditions are largely unknown. Therefore, the effect(s) of folic acid (5.7 and 71 microg/kg/day for 4 weeks) on aortic relaxation was investigated using obese/diabetic (+db/+db) mice and lean littermate (+db/+m) mice. Acetylcholine-induced relaxation in +db/+db mice was less than that observed in +db/+m mice. The reduced relaxation in +db/+db mice was restored by consumption of 71 microg/kg folic acid. Acetylcholine-induced relaxation (with and without folic acid treatment) was sensitive to N(G)-nitro-L-arginine methyl ester, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one, geldanamycin and triciribine. In addition, acetylcholine-induced relaxation was attenuated by resistin. The plasma level of resistin in +db/+db mice was sevenfold higher than that measured in +db/+m mice, and the elevated plasma level of resistin in +db/+db mice was reduced by 25% after treatment with 71 microg/kg folic acid. Folic acid slightly increased the ratio of reduced glutathione to oxidized glutathione in +db/+db mice. Moreover, folic acid caused a reduction in PTEN (phosphatase and tensin homolog deleted on chromosome 10) expression, an increase in the phosphorylation of endothelial nitric oxide synthase (eNOS(Ser1177)) and Akt(Ser473), and an enhanced interaction of heat shock protein 90 (HSP90) with eNOS in both strains, with greater magnitude observed in +db/+db mice. In conclusion, folic acid consumption improved blunted acetylcholine-induced relaxation in +db/+db mice. The mechanism may be, at least partly, attributed to enhancement of PI3K/HSP90/eNOS/Akt cascade, reduction in plasma resistin level, down-regulation of PTEN and slight modification of oxidative state.

Formononetin, an isoflavone, relaxes rat isolated aorta through endothelium-dependent and endothelium-independent pathways.

We evaluated the vasorelaxation effects of formononetin, an isoflavone/phytoestrogen found abundantly in Astragalus mongholicus Bunge, on rat isolated aorta and the underlying mechanisms involved. Cumulative administration of formononetin, genistein, daidzein and biochanin A relaxed phenylephrine-preconstricted aorta. Formononetin and biochanin A caused a similar magnitude of relaxation whereas daidzein was least potent. Mechanical removal of endothelium, L-NAME (100 microM) and methylene blue (10 microM) suppressed formononetin-induced relaxation. Formononetin increased endothelial nitric oxide (NO) synthase (eNOS), but not inducible NO synthase, activity with an up-regulation of eNOS mRNA and p-eNOS(Ser1177) protein expression. In endothelium-denuded preparations, formononetin-induced vasorelaxation was significantly reduced by glibenclamide (3 microM) and iberiotoxin (100 nM), and a combination of glibenclamide (3 microM) plus iberiotoxin (100 nM) abolished the relaxation. In contrast, formononetin-elicited endothelium-independent relaxation was not altered by ICI 182,780 (10 microM, an estrogen receptor (ER alpha/ER beta) antagonist) or mifepristone (10 microM, a progesterone receptor antagonist). In single aortic smooth muscle cells, formononetin caused opening of iberiotoxin-sensitive Ca(2+)-activated K(+) (BK(Ca)) channels and glibenclamide-sensitive adenosine triphosphate (ATP)-dependent K(+) (K(ATP)) channels. Thus, our results suggest that formononetin caused vascular relaxation via endothelium/NO-dependent mechanism and endothelium-independent mechanism which involves the activation of BK(Ca) and K(ATP) channels.

Folic acid supplementation modifies beta-adrenoceptor-mediated in vitro lipolysis of obese/diabetic (+db/+db) mice.

The effects of folic acid (5.7 and 71 microg/kg, 4 weeks) consumption on the beta-adrenoceptors (beta-ARs)-elicited lipolysis in vitro of the abdominal adipocytes of lean/control (+m/+db) and obese/diabetic (+db/+db) mice (female) were investigated. beta-AR agonists (salbutamol, a beta(2)-AR agonist; BRL 37344 and CGP 12177, beta(3)-AR agonists; adrenaline, a beta-AR agonist)-mediated lipolysis, beta(2)-, and beta(3)-ARs protein expression of the adipose tissues after folic acid consumption were evaluated. Our results demonstrate that a smaller magnitude of the basal (spontaneous) and the beta-AR agonists-triggered lipolysis was observed in +db/+db mice, and folic acid supplementation (71 microg/kg) resulted in an improvement of both the baseline and the beta-ARs-mediated lipolysis. In controls, a lower beta(2)-and beta(3)-ARs protein expression of the adipose tissues was detected in +db/+db mice, compared to +m/+db mice. In both strains fed with folic acid (71 microg/kg), a reduction of beta(2)-AR protein expression was observed compared to the respective controls. In +db/+db mice, folic acid (5.7 and 71 microg/kg) consumption caused a dose-dependent increase of beta(3)-AR protein expression compared to controls. We demonstrate that lipolysis elicited by beta-AR (beta(2)- and beta(3)-ARs) agonists was blunted in +db/+db mice. Folic acid consumption has significant modulatory effects on beta-ARs protein expression and lipolysis.

Inhibitory effect of nonsteroidal anti-inflammatory drugs on adenosine transport in vascular smooth muscle cells.

It is generally accepted that the clinical efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) arises mainly from the inhibition of cyclooxygenase (COX). However, more evidence has suggested that certain pharmacological actions of NSAIDs may be mediated by COX-independent mechanisms. The present study investigated the effects of NSAIDs on adenosine uptake in human aortic smooth muscle cells (HASMCs). Among the NSAIDs tested (all at 100 microM), aspirin, ibuprofen and naproxen had no effect on [(3)H]adenosine uptake. Piroxicam inhibited [(3)H]adenosine uptake by 30%, while etodolac, indomethacin, ketoprofen, mefenamic acid and sulindac inhibited [(3)H]adenosine by 13-18%. Sulindac sulfide, an active metabolite of sulindac, inhibited [(3)H]adenosine uptake and [(3)H]nitrobenzylmercaptopurine ribonucleoside (NBMPR) binding of HASMCs with IC(50) values of 40.67+/-4.82 and 24.19+/-3.76 muM, respectively. Kinetic studies revealed that sulindac sulfide was a competitive inhibitor of adenosine uptake. Using the nucleoside-transporter-deficient PK15NTD cells that stably express equilibrative nucleoside transport (ENT) 1 and ENT2, it was found that the inhibitory effect of sulindac sulfide on ENT1 was greater than that on ENT2. Sulindac sulfide increased the extracellular adenosine level. In addition, it inhibited the proliferation of HASMCs and this anti-proliferative effect could be abolished by adenosine A(2B) receptor antagonist. Our results suggest that sulindac sulfide may exert pharmacological effects through the inhibition of adenosine uptake, which modulates the availability of adenosine in the vicinity of adenosine receptors.

Role of monoamine oxidases in the exaggerated 5-hydroxytryptamine-induced tension development of human isolated preeclamptic umbilical artery.

We investigated the role(s) of monoamine oxidases (MAOs) on the altered 5-hydroxytryptamine (5-HT, serotonin)-induced tension development of the isolated umbilical artery of preeclamptic pregnancy of Chinese women. An enhanced 5-HT-induced tension development of the umbilical artery of preeclamptic pregnancy was observed when compared with that of normal pregnancy. The enhanced component of 5-HT-induced tension development was eradicated by clorgyline (a MAO-A inhibitor). Blockade of eNOS (endothelial isoform nitric oxide synthase) (N(omega)-nitro-L-arginine methyl ester), 5-HT transporter (citalopram), 5-HT receptor subtypes (5HT2B, SB 204741; 5-HT2C, RS 102221; 5-HT7, SB 269970), and endothelium denudation of the umbilical artery of normal pregnancy mimicked the enhanced 5-HT-induced tension development as observed in the preeclamptic tissues. In contrast, no apparent changes in 5-HT-induced tension development of the umbilical artery of preeclamptic pregnancy were observed with the same pharmacological manipulations. A decreased protein expression levels of MAO-A and eNOS (no iNOS and MAO-B expression was detected) and no change in caveolin-1 and 5-HT transporter expression were demonstrated in the umbilical artery (endothelium intact) lysate of preeclamptic pregnancy, compared to that of the umbilical artery of normal pregnancy. Thus, in the umbilical artery of preeclamptic pregnancy, a decrease of MAO-A and eNOS protein expression levels are probably associated with, or responsible for, the exaggerated 5-HT-induced tension development.

Comparison of vascular relaxation, lipolysis and glucose uptake by peroxisome proliferator-activated receptor-gamma activation in +db/+m and +db/+db mice.

In this study, we determined the in vitro effect of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activation on the aortic relaxation, lipolysis and insulin-induced [(3)H]-glucose uptake of the abdominal (omental) adipocytes of the non-diabetic (+db/+m) and obese/diabetic (+db/+db) mice. The expression of PPAR-gamma (mRNA and protein) in aorta and adipose tissues was evaluated and compared. Cumulative application of ciglitazone, pioglitazone and troglitazone (PPAR-gamma agonists) caused a concentration-dependent aortic relaxation (sensitive to 2-chloro-5-nitro-N-phenylbenzamide (GW9662) (1 microM, a selective PPAR-gamma antagonist) and N(omega)-nitro-l-arginine methyl ester (l-NAME) (20 microM, a nitric oxide synthase inhibitor)) with a maximum relaxation of approximately 30% (3 microM) in +db/+m mice, whereas no relaxation was observed in +db/+db mice. All PPAR-gamma agonists examined did not alter the basal lipolysis of both species, but forskolin caused a concentration-dependent lipolysis, with a greater magnitude observed in +db/+m mice. Insulin (0.1 and 1 microM) caused an enhancement of [(3)H]-glucose uptake into adipocytes with a greater magnitude in +db/+m mice. In contrast, none of the PPAR-gamma agonists tested (0.1, 1 and 10 microM) altered the basal and the insulin (0.1 microM)-induced [(3)H]-glucose uptake into adipocytes of both species. In addition, there was no difference in PPAR-gamma expression (mRNA and protein) in the aorta and adipose tissues between the species. In conclusion, our results demonstrate that PPAR-gamma is present in the abdominal (omental) adipose tissue and thoracic aorta. An acute activation of PPAR-gamma produced a small ( approximately 30%) aortic relaxation (nitric oxide/endothelium-dependent) of +db/+m mice. However, all PPAR-gamma agonists examined have no acute effect on lipolysis and the insulin-induced glucose uptake into adipocytes of both +db/+m and +db/+db mice.

Endothelium-independent relaxation to raloxifene in porcine coronary artery.

Although the vascular action of raloxifene has been studied in several vascular beds, the underlying mechanisms are still incompletely understood. The role of endothelium in raloxifene-induced vascular responses was controversial. The present study was designed to examine endothelium-independent effects of raloxifene in isolated porcine left circumflex coronary arteries. Arterial rings were suspended in organ baths and changes in isometric tension were measured. The large-conductance Ca2+-activated K+(BK(Ca)) currents were recorded using a whole-cell patch-clamp technique. Treatment with raloxifene (1-10 micromol/l) reduced the contractions to 9,11-dideoxy-11alpha,9alpha-epoxy-methanoprostaglandin F2alpha (U46619), serotonin (5-HT), endothelin-1 in normal Krebs solution and to CaCl2 in a Ca2+-free, high K+-containing solution. In endothelin-1-contracted rings, raloxifene (0.3 to 50 micromol/l) caused relaxations which were comparable in rings with and without endothelium. The raloxifene-induced relaxation was reduced by putative K+ channel blockers, iberiotoxin and tetraethyl ammonium chloride (TEA+) in rings with and without endothelium, or by elevated extracellular K+ ions (30 mmol/l K+ and 60 mmol/l K+). 13-methyl-7-[9-(4,4,5,5,5-pentafluoropentylsulfinyl)nonyl]-7,8,9,11,12,13,14,15,16, 17-decahydro-6H-cyclopenta[a] phenanthrene-3,17-diol (ICI 182,780) did not affect raloxifene-induced relaxation. Raloxifene enhanced the outward BK(Ca) currents, which were sensitive to inhibition by iberiotoxin. In summary, the present study shows that raloxifene acutely relaxes porcine coronary arteries via an endothelium-independent mechanism without involving the ICI 182,780-sensitive estrogen receptors. Raloxifene mainly acts on the vascular smooth muscle cells to induce vasorelaxation by the inhibition of Ca2+ channels and the activation of BK(Ca) channels. The former mechanism appears to play a more significant role.

Modulation by homocysteine of the iberiotoxin-sensitive, Ca2+ -activated K+ channels of porcine coronary artery smooth muscle cells.

We evaluated the acute effect of homocysteine on the iberiotoxin-sensitive, Ca(2+)-activated K(+) (BK(Ca)) channels of the porcine coronary artery smooth muscle cells. NS 1619 (1 to 30 microM) caused a concentration-dependent enhancement of the BK(Ca) amplitude (recorded using the whole-cell, membrane-rupture configuration) only with an elevated [Ca(2+)](i) of approximately 444 nM, but not with [Ca(2+)](i) of approximately 100 nM. Homocysteine (30 microM) caused a small inhibition ( approximately 16%) of the BK(Ca) amplitude ([Ca(2+)](i)= approximately 444 nM), and a greater inhibition ( approximately 77%) was observed with 100 microM NADH present in the pipette solution. The inhibition persisted after washing. With NADPH (100 microM), a smaller magnitude of inhibition ( approximately 34%) of the BK(Ca) amplitude was recorded. The NS 1619-mediated enhancement of the BK(Ca) amplitude (with elevated [Ca(2+)](i) plus NADH in the pipette) was attenuated by homocysteine. The homocysteine-mediated inhibition of the BK(Ca) amplitude was suppressed by Tiron (10 mM) or diphenylene iodonium (30 nM), applied alone, but not by superoxide dismutase (500 U/ml) and catalase (500 U/ml). Generation of superoxide (O(2)(-)) of the smooth muscle cells (with NADH presence), measured using the lucigenin-enhanced chemiluminescence, was markedly increased by angiotensin II (100 nM) and homocysteine (30 microM). The chemiluminescence signal was sensitive to apocynin (300 microM) or Tiron, applied alone, but not to superoxide dismutase and catalase. In conclusion, our results demonstrate that acute homocysteine application inhibits the iberiotoxin-sensitive BK(Ca) channels (with elevated [Ca(2+)](i) and NADH present) which is probably caused by the NADH oxidase activation and the concomitant generation of intracellular superoxide.

Contribution of glibenclamide-sensitive, ATP-dependent K+ channel activation to acetophenone analogues-mediated in vitro pulmonary artery relaxation of rat.

Compared to the currently available therapeutic drugs for peripheral vascular diseases, agents that are selective for relaxing pulmonary circulation are scarce. The present study was undertaken, using isometric tension change measurement and whole-cell patch-clamp electrophysiology methods, to evaluate the vascular relaxation effect and the underlying mechanisms involved of two naturally found alkaloids: paeonol (2-hydroxy-4-methoxy-acetophenone), acetovanillone (4-hydroxy-3-methoxy-acetophenone) and the non-substituted analogue acetophenone on pulmonary artery of Sprague-Dawley rats. Cumulative administration (3 microM-1 mM) of acetophenone analogues resulted in a concentration-dependent relaxation of phenylephrine (1 microM) pre-contracted pulmonary artery. A relative order of inhibitory potency, estimated by comparing the concentration at which a 50% relaxation of phenylephrine-induced contraction observed was: acetovanillone > paeonol > acetophenone. Endothelial denudation and inhibition of nitric oxide synthase (with 20 microM N(G)-nitro-L-arginine methyl-ester) only moderately suppressed (17.6 +/- 4.2%) acetovanillone- but not paeonol- or acetophenone-mediated maximum relaxation. Glibenclamide (3 microM, an ATP-sensitive K(+) (IK(ATP)) channel blocker) markedly attenuated all acetophenone analogues-mediated endothelium-independent relaxation. Neither cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL 12330A, 10 microM), iberiotoxin (300 nM), 4-aminopyridine (3 mM), (+/-)-propranolol (1 microM, a non-selective beta-adrenoceptor blocker) nor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (3 microM, a guanylate cyclase inhibitor) altered endothelium-independent relaxation. In electrophysiological experiments using single pulmonary artery smooth muscle cells, acetovanillone, paeonol, acetophenone and cromakalim activated glibenclamide-sensitive, IK(ATP) channels. In conclusion, our results demonstrate that acetophenone analogues caused pulmonary artery relaxation through opening of IK(ATP) channels. In addition, acetovanillone-mediated pulmonary artery relaxation is partly depended on nitric oxide released from endothelium.

Activation of iberiotoxin-sensitive, Ca2+-activated K+ channels of porcine isolated left anterior descending coronary artery by diosgenin.

The objective of this study was to determine the vasodilating effect of 3beta-hydroxy-5-spirostene (diosgenin), a phytoestrogen found in wild yams, using porcine resistance left anterior descending coronary artery. In 5-hydroxytryptamine (3 microM) pre-contracted preparation, diosgenin caused a concentration-dependent (0.01 to 1 microM), endothelium-independent relaxation, with a maximum relaxation of approximately 72% at 1 microM. No apparent effect was observed with 17beta-oestradiol and progesterone with concentrations < or =0.3 microM, and a relaxation of approximately 15% and approximately 23% caused by 17beta-oestradiol (1 microM) and progesterone (1 microM), respectively. Diosgenin-elicited relaxation was not altered by 7alpha,17beta-[9[(4,4,5,5,5-pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17-diol (ICI 182,780), mifepristone, (+)-bicuculline, cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL 12330A), glibenclamide and scavengers of reactive oxygen species. The iberiotoxin-sensitive, Ca2+-activated K+ (BK(Ca)) current of single vascular myocytes recorded, using patch-clamp techniques, was markedly enhanced by diosgenin, 17beta-oestradiol and progesterone. Application of (9S, 10R, 12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT 5823, 300 nM) eradicated the enhancement of BK(Ca) amplitude. Diosgenin, 17beta-oestradiol and progesterone did not affect whereas phloretin, biochanin A and zearalanone (1 microM each) significantly suppressed [Ca2+]o-induced contraction. In oestrogen competition essay using human breast cancer cell (MCF-7 cells), diosgenin (0.001 nM to 10 microM) did not interact with oestrogen receptor-alpha, and no displacement of [3H]17beta-oestradiol was observed. In oestrogen receptor alpha- and beta-fluorescence polarization competitor assay, diosgenin (100 microM) demonstrated a greater competition with the beta-isoform of oestrogen receptor. These results suggest that diosgenin caused an acute, endothelium-independent coronary artery relaxation via protein kinase G signalling cascade and an activation of BK(Ca) channel of arterial smooth muscle cells. The oestrogen receptor (alpha and beta-isoforms) and progesterone receptor are probably not involved.

An in vitro study of histamine on the pulmonary artery of the Wistar-Kyoto and spontaneously hypertensive rats.

The vascular response to most neurotransmitters of different vascular beds is altered under hypertensive condition. The modulatory effect of genetic pulmonary arterial hypertension on histamine responses is not known. The present study was undertaken to evaluate the modulatory effect of enzymatic degradation (via histamine N-methyl-transferase and diamine oxidase) on the vascular response of histamine, and the subtype(s) of histamine receptor present in the pulmonary artery (first branch, O.D. approximately 800 microm) of the normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) (male, 22-26 weeks old). In phenylephrine (1 microM) pre-contracted preparations, histamine and 6-[2-(4-imidazolyl)ethylamino]-N-(4-trifluoromethylphenyl) heptanecarboxamide (HTMT, a histamine H(1) receptor agonist) elicited a concentration-dependent relaxation, with a smaller magnitude recorded in SHR. Application of 10 microM S-[4-(N,N-dimethylamino)-butyl]isothiourea (SKF 91488, a selective histamine N-methyl-transferase inhibitor), but not aminoguanidine (100 microM, a diamine oxidase inhibitor), significantly attenuated histamine-induced relaxation. Clobenpropit (1 nM, a potent histamine H(3) receptor antagonist) "antagonised" the suppressive effect of SKF 91488 and histamine-evoked relaxation was restored. Endothelial denudation reduced histamine- and abolished HTMT-elicited relaxation. Dimaprit (a histamine H(2) receptor agonist) caused an endothelium-independent, cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL 12330A, 10 microM, an adenylate cyclase inhibitor)-sensitive, concentration-dependent relaxation, with a similar magnitude in both strains of rat. Histamine-evoked relaxation was reversed into a further contraction (clobenpropit (10 nM)-sensitive) (with a greater magnitude occurred in the WKY rat) after blocking the histamine H(1) and H(2) receptors with diphenhydramine plus cimetidine (30 microM each). A similar further contraction (clobenpropit-sensitive) was observed with imetit (a histamine H(3)/H(4) receptor agonist) (> or =3 microM). Under resting tension, imetit (> or =0.3 microM) caused a clobenpropit (10 nM)- and prazosin (1 microM)-sensitive, concentration-dependent contraction, with a greater contraction in the WKY rats. Our results suggest that inhibition of histamine catabolism using SKF 91488 (histamine N-methyl-transferase inhibitor) resulted in a reduction of histamine-mediated relaxation that was due to the activation of the clobenpropit-sensitive, histamine H(3)/H(4) receptor and the release of catecholamine. In addition, activation of histamine H(1) and H(2) receptors resulted in relaxation whereas histamine H(3)/H(4) receptor activation by imetit yielded a prazosin-sensitive contraction of the pulmonary artery.

Mechanisms responsible for the in vitro relaxation of ligustrazine on porcine left anterior descending coronary artery.

In this study, we have evaluated the underlying mechanisms responsible for the relaxation response of ligustrazine (2,3,5,6-tetra-methyl-pyrazine; 2,3,5,6-MP) and its structural analogues (2-methyl-pyrazine (2-MP); ethyl-pyrazine (EP); 2,3-di-methyl-pyrazine (2,3-MP); 2,5-di-methyl-pyrazine (2,5-MP); 2,6-di-methyl-pyrazine (2,6-MP) and 2,3,5-tri-methyl-pyrazine (2,3,5-MP)) in porcine left anterior descending coronary artery (tertiary branch, O.D. 2,3,5-MP>EP>2,5-MP>/=2,6-MP>/=2,3-MP>2-MP. Besides, salbutamol and forskolin caused an endothelium-independent relaxation. The relaxation response of ligustrazine, salbutamol and forskolin was blunted in the presence of cis-N-(2-phenylcyclopentyl) azacyclotridec-1-en-2-amine (MDL 12330A) (10 microM, an adenylate cyclase inhibitor) and N-[2-((bromocinnamyl)amino)ethyl]-5-isoquinoline-sulphonamide (H-89, a protein kinase A inhibitor, 3 microM). Patch-clamp, whole-cell electrophysiological studies using single smooth muscle cells of the left anterior descending coronary artery revealed that ligustrazine (300 microM), salbutamol (30 microM) and forskolin (1 microM) inhibited the nifedipine-sensitive L-type Ca(2+) channels, and the inhibitory effect was eradicated by MDL 12330A (10 microM) and H-89 (1 microM). However, neither the Ca(2+)-dependent K(+) channel nor the ATP-dependent K(+) channel was modified by ligustrazine (300 microM). In conclusion, our results indicate that ligustrazine-mediated left anterior descending coronary artery relaxation is due to the activation of adenylate cyclase/protein kinase A cascade and the subsequent inhibition of nifedipine-sensitive, voltage-dependent L-type Ca(2+) channels. However, opening of K(+) channels seems to play no role in mediating the relaxation effect of ligustrazine.