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 (Gs-protein inhibitor), Rp-cAMP (cAMP antagonist) and KT5720 (PKA inhibitor), suggesting that the effect of 14,15-EET was mediated through Gs protein-coupled receptors which were linked to the cAMP/PKA-dependent pathway. Pretreatments with MK886 (PPARα antagonist) and GW9662 (PPARγ antagonist) did not influence 14,15-EET-induced vasorelaxation. The vasorelaxant effect of 14,15-EET was inhibited by AH6809 (EP2 receptor antagonist), whereas SC19220 (EP1 receptor antagonist), L798106 (EP3 receptor antagonist) and GW627368X (EP4 receptor antagonist) had no effect. The effect of 14,15-EET and the mechanism involved was mimicked by prostaglandin E2 (an EP2 receptor agonist). The 14,15-EET-induced relaxation was slightly potentiated in the presence of indomethacin (cyclooxygenase inhibitor which block PGE2 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 EP2 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 EP2 receptors. This subsequently leads to activation of cAMP/PKA-dependent pathway in vascular smooth muscle cells

Consumption of dried fruit of Crataegus pinnatifida (hawthorn) suppresses high cholesterol diet-induced hypercholesterolemia in rats

The hypocholesterolemic and atheroscleroprotective potentials of dietary consumption of hawthorn (dried fruit of Crataegus pinnatifida, Shan Zha) were investigated by monitoring plasma lipid profiles and aortic relaxation in Sprague–Dawley rats fed with either normal diet, high-cholesterol diet (HCD) or HCD supplemented with hawthorn powder (2%, w/w) (4 weeks). In HCD-fed rats, an increased plasma total cholesterol and LDL-cholesterol with a decreased HDL-cholesterol was observed, and consumption of hawthorn markedly suppressed the elevated total cholesterol and LDL-lipoprotein levels plus an increased HDL-cholesterol level. The blunted acetylcholine-induced, endothelium-dependent relaxation of isolated aortas of HCD-fed rats was improved by hawthorn. The development of fatty liver, an increased nitric oxide synthase (NOS) activity and an elevated oxidative stress (as estimated by the attenuated levels of anti-oxidant enzymes) associated with HCD were attenuated by hawthorn. Thus, the results demonstrated that hawthorn consumption provides overall beneficial effects on reversing HCD associated detrimental changes

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

The effects of folic acid (5.7 and 71 μg/kg, 4 weeks) consumption on the β-adrenoceptors (β-ARs)–elicited lipolysis in vitro of the abdominal adipocytes of lean/control (+m/+db) and obese/diabetic (+db/+db) mice (female) were investigated. β-AR agonists (salbutamol, a β2-AR agonist; BRL 37344 and CGP 12177, β3-AR agonists; adrenaline, a β-AR agonist)–mediated lipolysis, β2-, and β3-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 β-AR agonists–triggered lipolysis was observed in +db/+db mice, and folic acid supplementation (71 μg/kg) resulted in an improvement of both the baseline and the β-ARs–mediated lipolysis. In controls, a lower β2-and β3-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 μg/kg), a reduction of β2-AR protein expression was observed compared to the respective controls. In +db/+db mice, folic acid (5.7 and 71 μg/kg) consumption caused a dose-dependent increase of β3-AR protein expression compared to controls. We demonstrate that lipolysis elicited by β-AR (β2- and β3-ARs) agonists was blunted in +db/+db mice. Folic acid consumption has significant modulatory effects on β-ARs protein expression and lipolysis

The Lignan-Rich Fraction from Sambucus williamsii Hance Exerts Bone Protective Effects via Altering Circulating Serotonin and Gut Microbiota in Rats

Our previous study revealed that the bone anabolic effects of the lignan-rich fraction (SWCA) from Sambucus williamsii Hance was involved in modulating the metabolism of tryptophan in vivo and inhibiting serotonin (5-HT) synthesis in vitro. This study aimed to determine how SWCA modulates bone metabolism via serotonin in vivo. The effects of SWCA were evaluated by using 4-month-old Sprague-Dawley (SD) ovariectomized rats. The serum levels of 5-HT and kynurenine, the protein expressions of tryptophan hydroxylase 1 (TPH-1) and TPH-2, the genes and proteins related to the 5-HT signaling pathway as well as gut microbiota composition were determined. SWCA treatment alleviated bone loss and decreased serum levels of serotonin, which was negatively related to bone mineral density (BMD) in rats. It suppressed the protein expression of TPH-1 in the colon, and reversed the gene and protein expressions of FOXO1 and ATF4 in the femur in OVX rats, while it did not affect the TPH-2 protein expression in the cortex. SWCA treatment escalated the relative abundance of Antinobacteria and modulated several genera relating to BMD. These findings verified that the bone protective effects of lignans were mediated by serotonin, and provided evidence that lignans might be a good source of TPH-1 inhibitors

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 (EC50: 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 Ca2+-activated K+ (BKCa) 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 BKCa 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 BKCa gating in basilar artery myocytes, leading to exaggerated basilar artery tension development in SHR

Folic acid consumption reduces resistin level and restores the 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 μg/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 μg/kg folic acid. Acetylcholine-induced relaxation (with and without folic acid treatment) was sensitive to NG-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 μg/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 (eNOSSer1177) and AktSer473, 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

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 (EC50: 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 Ca2+-activated K+ (BKCa) 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 BKCa 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 BKCa gating in basilar artery myocytes, leading to exaggerated basilar artery tension development in SHR