Endothelin-Dependent Vasoconstriction in Human Uterine Artery: Application to Preeclampsia

BACKGROUND: Reduced uteroplacental perfusion, the initiating event in preeclampsia, is associated with enhanced endothelin-1 (ET-1) production which feeds the vasoconstriction of uterine artery. Whether the treatments of preeclampsia were effective on ET-1 induced contraction and could reverse placental ischemia is the question addressed in this study. We investigated the effect of antihypertensive drugs used in preeclampsia and of ET receptor antagonists on the contractile response to ET-1 on human uterine arteries. METHODOLOGY/PRINCIPAL FINDINGS: Experiments were performed, ex vivo, on human uterine artery samples obtained after hysterectomy. We studied variations in isometric tension of arterial rings in response to the vasoconstrictor ET-1 and evaluated the effects of various vasodilators and ET-receptor antagonists on this response. Among antihypertensive drugs, only dihydropyridines were effective in blocking and reversing the ET-1 contractile response. Their efficiency, independent of the concentration of ET-1, was only partial. Hydralazine, alpha-methyldopa and labetalol had no effect on ET-1 induced contraction which is mediated by both ET(A) and ET(B) receptors in uterine artery. ET receptors antagonists, BQ-123 and BQ-788, slightly reduced the amplitude of the response to ET-1. Combination of both antagonists was more efficient, but it was not possible to reverse the maximal ET-1-induced contraction with antagonists used alone or in combination. CONCLUSION: Pharmacological drugs currently used in the context of preeclampsia, do not reverse ET-1 induced contraction. Only dihydropyridines, which partially relax uterine artery previously contracted with ET-1, might offer interesting perspectives to improve placental perfusion

Human antimicrobial peptide LL-37 is present in atherosclerotic plaques and induces death of vascular smooth muscle cells: a laboratory study

BACKGROUND: Death of smooth muscle cells in the atherosclerotic plaques makes the plaques more prone to rupture, which can initiate an acute ischemic event. The development of atherosclerosis includes the migration of immune cells e.g. monocytes/macrophages and T lymphocytes into the lesions. Immune cells can release antimicrobial peptides. One of these, human cathelicidin antimicrobial peptide hCAP-18, is cleaved by proteinase 3 generating a 4.5 kDa C-terminal fragment named LL-37, which has been shown to be cytotoxic. The aim of the study was to explore a potential role of LL-37 in the pathophysiology of atherosclerosis. METHODS: We investigated the presence of LL-37 in human atherosclerotic lesions obtained at autopsy using immunohistochemistry. The direct effects of LL-37 on cultured vascular smooth muscle cells and isolated neutrophil granulocytes were investigated with morphological, biochemical and flow cytometry analysis. RESULTS: The neointima of atherosclerotic plaques was found to contain LL-37-like immunoreactivity, mainly in macrophages. In cultured smooth muscle cells, LL-37 at 30 μg/ml caused cell shrinkage, membrane blebbing, nuclear condensation, DNA fragmentation and an increase in caspase-3 activity as studied by microscopy, ELISA and enzyme activity assay, respectively. Flow cytometry demonstrated that LL-37 in a subset of the cells caused a small but rapidly developing increase in membrane permeability to propidium iodide, followed by a gradual development of FITC-annexin V binding. Another cell population stained heavily with both propidium iodide and FITC-annexin V. Neutrophil granulocytes were resistant to these effects of LL-37. CONCLUSION: This study shows that LL-37 is present in atherosclerotic lesions and that it induces death of vascular smooth muscle cells. In a subset of cells, the changes indicate the development of apoptosis triggered by an initial mild perturbation of plasma membrane integrity. The findings suggest a role for LL-37 as a mediator of immune cell-induced death of vascular smooth muscle cells in atherosclerosis

Effect of propofol on isolated human omental arteries and veins

To elucidate the effect and mode of action of propofol on human vascular smooth muscle tension, we have investigated the effect of propofol alone and the effect of propofol on contractions induced by U46619, KCl and caffeine on isolated human omental vessels. Propofol 10(-3) mol litre-1 induced contractions in both arteries and veins attenuated the contraction elicited by U46619, KCl and caffeine in a concentration-dependent manner. The threshold concentrations for the effect of propofol in the artery were: 10(-5) mol litre-1 (U46619, caffeine) and 10(-4) mol litre-1 (KCl); and in the vein, 10(-5) mol litre-1 (U46619) and 10(-4) mol litre-1 (KCl, caffeine). We conclude that propofol at lower concentrations appeared to primarily attenuate contraction involving release of cellularly sequestered calcium. At higher concentrations (> 10(-4.5) mol litre-1), propofol appeared to affect contraction involving extracellular or intracellular calcium fluxes similarly

Effects of propofol on substance P-induced relaxation in isolated human omental arteries and veins

To elucidate if an effect of propofol on endothelium-dependent relaxation could contribute to propofol-induced vasodilation, smooth muscle relaxation of isolated human omental artery and vein segments precontracted by endothelin-1 were measured. Substance P induced a concentration-dependent relaxation (mean +/- SEM) in both artery (63 +/-8.4% of precontraction, n = 9) and vein (60+/-11%, n = 7). The relaxation was enhanced by 10(-6) M propofol (artery, 72+/-9.5%, n = 9; vein, 81+/-12%, n = 7) but not affected by 10(-7), 10(-5) and 10(-4) M propofol. In the presence of Nomega-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor), 10(-6) M propofol still enhanced the substance P-induced relaxation in arteries but not veins, whereas 10(-4) M propofol inhibited the relaxation in both arteries (rightward shift of the concentration-response curve) and veins (28+/-7.5%, n = 8). In the presence of potassium chloride (to prevent hyperpolarization), the enhancement of substance P-induced relaxation by 10(-6) M propofol was abolished in both arteries and veins whereas 10(-5) and 10(-4) M propofol reduced the relaxation in arteries (38+/-13% at 10(-5) M, n = 6; 30+/-11% at 10(-4) M, n = 6) but not in veins. These results demonstrate that propofol, at lower, clinically relevant concentrations, promotes endothelium-dependent relaxation mediated via hyperpolarization in human omental arteries and via both nitric oxide and hyperpolarization in human omental veins

Endothelium-dependent relaxation by substance P in human isolated omental arteries and veins: relative contribution of prostanoids, nitric oxide and hyperpolarization

1. The objective of the present study was to investigate human omental arteries and veins with respect to: (i) the contractile effect of the thromboxane A(2) analogue U46619, (ii) endothelium-dependency and mediators of the relaxing effect of substance P (SP) and acetylcholine (ACh). 2. Changes in isometric tension in response to administration of U46619, SP and ACh were measured in human isolated omental arteries and veins with and without endothelium. To investigate the mechanism of action of SP, the SP-induced relaxation was measured in the presence of indomethacin (cyclo-oxygenase inhibitor), N(G)-monomethyl-L-arginine (L-NMMA, nitric oxide-synthase inhibitor), KCl (inhibitor of endothelium-dependent hyperpolarization), tetraethylammonium (TEA; non-selective inhibitor of K(+)-channels, with some preference for the high conductance Ca(2+)-activated K(+)-channel, BK(Ca)), glibenclamide (inhibitor of the ATP-sensitive K(+)-channel) and/or clotrimazole (inhibitor of the cytochrome P450-system and the intermediate conductance Ca(2+)-activated K(+)-channel, IK(Ca)). 3. U46619 contracted both the artery and the vein segments. Endothelium removal did not alter the contraction. 4. ACh caused neither contraction nor relaxation in artery and vein segments precontracted with U46619. 5. In both artery and vein segments precontracted with U46619, SP produced endothelium-dependent relaxation. The relaxation was unaffected by indomethacin, but was incompletely reduced by L-NMMA and KCl respectively. The L-NMMA-resistent relaxation was abolished in the presence of KCl. 6. TEA inhibited the SP-induced relaxation in artery and vein segments both in the presence and absence of L-NMMA and indomethacin, while glibenclamide and clotrimazole had no effect. 7. In conclusion, the SP-induced relaxation in human omental arteries and veins seems to be mediated via NO and endothelium-dependent hyperpolarization. K(ATP) and I(KCa) are probably not involved in the hyperpolarization, but activation of BK(Ca) may contribute to the hyperpolarization. Prostanoid synthesis and the cytochrome P450-system are probably not involved in the SP-induced relaxation in this area

Characteristics of contractile 5-HT receptors in isolated human omental arteries: presence of 5-HT1 and 5-HT2 receptors

5-Hydroxytryptamine (5-HT) has a variety of biological effects, e.g. it induces and modulates vascular smooth muscle activity. The effects are mainly mediated via a hetergenous group of 5-HT receptor subtypes. In order to elucidate the 5-HT receptor mechanisms in the human splanchnic circulation, in vitro studies were carried out on omental arteries obtained from patients undergoing abdominal surgery. Four 5-HT receptor agonists with different selectivity all induced concentration-dependent contraction (potency and order of potency indicated): 5-HT (non-selective; 6.12 +/- 0.14)=sumatriptan (5-HT1; 6.32 +/- 0.07) > alpha-methyl-5-HT (5-HT2; 5.41 +/- 0.05) > 2-methyl-5-HT (5-HT3; < or =4.46+/-0.05). The 5-HT1/5-HT2 receptor antagonist methiothepin antagonised the contraction induced by 5-HT, sumatriptan, alpha-methyl-5-HT and 2-methyl-5-HT. The 5-HT2 receptor antagonist ketanserin antagonised the contraction induced by 5-HT, alpha-methyl-5-HT and 2-methyl-5-HT. The 5-HT3 receptor antagonist tropisetron did not antagonise the contraction elicited by 2-methyl-5-HT. The results suggest that 5-HT-induced conataction in human omental arteries involves both 5-HT1 and 5-HT2, but maybe not 5-HT3-receptors