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The mechanisms linking prothrombotic changes to endothelial dysfunction and accelerated atheroma formation have yet to be fully defined. Expression of TF (tissue factor) on the endothelium is potentially an initiating event as binding and activation of FVII (factor VII) can result in thrombosis. Although PAR2 (protease-activated receptor-2) is expressed on vascular endothelium, its precise physiological significance and mechanism of activation have yet to be defined. In the present study, we investigated whether PAR2 can be activated by FVIIa (activated FVII) and induce ET-1 (endothelin-1) synthesis. In bovine aortic endothelial cells pretreated with TNF (tumour necrosis factor-alpha) to increase TF expression, FVIIa stimulated ET-1 synthesis via activation of PAR2. Although FX (factor X) alone was inactive, this response was enhanced by using FVII and FX in combination. Inhibition of the proteolytic activity of FVIIa abolished the response. The PAR2 agonist peptide SLIGKV also enhanced ET-1 release on TNF-pretreated cells. The response to FVIIa was inhibited by a PAR2 antagonist peptide FSLLRY. Inhibition of the p38 MAPK (mitogen-activated protein kinase) reduced PAR2 expression and the ET-1 response. In summary, FVIIa can stimulate ET-1 synthesis in endothelial cells by activating PAR2, demonstrating a potential link between thrombotic processes and endothelial cell dysfunction.

Reduced endothelium-dependent vasodilator responses with increased synthesis of ET-1 (endothelin-1) are characteristics of endothelial dysfunction in heart failure and are predictive of mortality. Identification of treatments that correct these abnormalities may have particular benefit for patients who become refractory to current regimens. Hawthorn preparations have a long history in the treatment of heart failure. Therefore we tested their inhibitory effects on ET-1 synthesis by cultured endothelial cells. These actions were compared with that of GSE (grape seed extract), as the vasoactive components of both these herbal remedies are mainly oligomeric flavan-3-ols called procyanidins. This showed extracts of hawthorn and grape seed were equipotent as inhibitors of ET-1 synthesis. GSE also produced a potent endothelium-dependent vasodilator response on preparations of isolated aorta. Suppression of ET-1 synthesis at the same time as induction of endothelium-dependent vasodilation is a similar response to that triggered by laminar shear stress. Based on these results and previous findings, we hypothesize that through their pharmacological properties procyanidins stimulate a pseudo laminar shear stress response in endothelial cells, which helps restore endothelial function and underlies the benefit from treatment with hawthorn extract in heart failure.

Regular consumption of red wine reduces mortality from coronary heart disease. This observation has been attributed to the anti-thrombotic effects of ethanol and to the antioxidant properties of polyphenolic compounds present in red wine. Here we show that an extract of red wine polyphenols causes a concentration-dependent inhibition of endothelin-1 synthesis in cultured bovine aortic endothelial cells. This action was associated with modifications in phosphotyrosine staining, indicating that the active components of red wine cause specific modifications of tyrosine kinase signalling. Thus inhibition of endothelin-1 synthesis by red wine may reduce the development of atherosclerosis, and hence decrease coronary heart disease.

In this study, we investigated the production of endothelin 1 (ET-1) by a human microvascular endothelial cell line, HMEC-1, co-cultured with Plasmodium falciparum-parasitized red blood cells (pRBCs). The results indicate that hypoxia increased the basal level of ET-1 production by HMEC-1 cells after 24 or 48 h of treatment. However, the co-incubation of HMEC-1 cells with pRBCs, but not with uninfected RBCs, induced a dose-dependent decrease of both constitutive and hypoxia-induced ET-1 production. The inhibition was not due to a decrease in cell viability, as lactate dehydrogenase release remained constant. These results indicate that pRBCs are able to interfere with both the constitutive and stimulated ET-1 release from the microvascular endothelium, thus inducing local modifications of the vascular tone and of the inflammatory response. This could be of relevance in the pathogenesis of the most severe forms of P. falciparum infections, such as cerebral malaria or malaria during pregnancy.

Endothelin-1 (ET-1) and atrial natriuretic peptide (ANP) play important roles in the regulation of body fluid balance in congestive heart failure (CHF). Renal production of ET-1 increases in CHF and it is a significant independent predictor of sodium excretion. ANP inhibits the ET system through cGMP, a second messenger of ANP. However, in severe CHF, plasma cGMP levels reached a plateau despite the activation of ANP secretion. Thus, ANP does not seem to sufficiently oppose exaggerated ET-1 actions in severe CHF, partially due to the accelerated degradation of cGMP, through phosphodiesterase type 5 (PDE5). We examined the chronic effects of a PDE5 inhibitor, T-1032 (1 mg/kg per day, n=5), on renal function and renal production of ET-1 in dogs with CHF induced by rapid ventricular pacing (270 beats/min). Vehicle dogs were given a placebo (n=5) and normal dogs (n=5) served as normal controls without pacing. In this experimentally produced CHF, plasma levels of ET-1, ANP and cGMP were elevated and renal production of cGMP was increased compared with the normal group, associated with increases in renal expression of preproET-1 mRNA and the number of ET-1-positive cells in glomeruli. In the T-1032 group, systemic and renal production of cGMP were further increased compared with the vehicle group despite no significant difference in plasma ANP levels between the two groups. Subsequently, the agent significantly improved urine flow rate, sodium excretion rate and glomerular filtration rate (GFR) associated with reductions in renal expression of preproET-1 mRNA and the number of ET-1-positive cells compared with the vehicle group. Moreover, there was a significant negative correlation between the number of ET-1-positive cells and GFR (r=-0.802 and P<0.001 respectively). Our results indicate that chronic PDE5 inhibition ameliorates the antagonistic relationship between renal ANP and ET-1 through the cGMP pathway, subsequently preventing renal dysfunction during the progression of CHF.

Endothelin-1 (ET-1) production is increased in hypertrophied hearts accompanied with fibrosis. ET-1 is a potent mitogen of fibroblasts and ET receptor antagonists are reported to inhibit the proliferation of fibroblasts and cardiac fibrosis. Peroxisome-proliferator-activated receptor alpha (PPAR alpha), one of the nuclear hormone receptors, suppresses activator protein-1 (AP-1), one of the nuclear transcription factors. Activation of PPAR alpha is reported to inhibit thrombin-induced ET-1 production by repressing the AP-1 signalling pathway in vascular endothelial cells. We investigated effects of the PPAR alpha activator fenofibrate (80 mg/kg per day, per os) on mRNA levels of ET-1, collagen type I and type III and histological features of myocardial fibrosis in hypertrophied rat hearts due to pressure-overload by abdominal aortic banding (AB). The treatment with fenofibrate or vehicle was started 7 days before the AB operation. Four days after the AB operation, fenofibrate treatment significantly reduced ET-1 mRNA expression compared with vehicle treatment in AB rat hearts. Collagen type I and type III mRNA expression, and interstitial and perivascular fibrosis were attenuated in the fenofibrate-treated AB rat group. Since the ET-1 gene has AP-1 response elements in the 5'-flanking region, it is suggested that myocardial fibrosis is effectively inhibited by fenofibrate through suppression of AP-1-mediated ET-1 gene augmentation in the pressure-overloaded heart caused by aortic banding in rats.

We have reported previously that the nitric oxide (NO) donor FK409 [(+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexanamide] improved renal dysfunction as well as renal lesions in rats with ischaemia/reperfusion injury. We also found that FK409 substantially reduced endothelin-1 (ET-1) production in cultured vascular endothelial cells (ECs). Nuclear factor kappa B (NF-kappa B) is known to play a key role in the development of ischaemic disorders through regulation of the expression of a variety of genes. In the present study, we examined the effects of FK409 on ET-1 production in cultured pig aortic ECs, and the possible involvement of NF-kappa B in the inhibitory effect of NO on ET-1 production. FK409 significantly attenuated basal and tumour necrosis factor-alpha (TNF-alpha)-induced preproET-1 mRNA expression in ECs. In addition, FK409 diminished basal and TNF-alpha-stimulated NF-kappa B activation in ECs. Pretreatment with N-benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal or BAY 11-7082, both of which are suppressors of NF-kappa B activation, effectively attenuated basal and TNF-alpha-induced ET-1 mRNA expression. These findings suggest that the suppression of NF-kappa B activation is at least partly involved in the FK409-induced inhibition of ET-1 production in ECs. We propose that NF-kappa B activation plays an important role in ET-1 production.

Using Na(+)/Ca(2+) exchanger (NCX1)-deficient mice, the pathophysiological role of Ca(2+) overload via the reverse mode of the Na(+)/Ca(2+) exchanger in ischaemia/reperfusion-induced renal injury was investigated. Since NCX1(-/-) homozygous mice die of heart failure before birth, we utilized NCX1(+/-) heterozygous mice. The ischaemia/reperfusion-induced renal dysfunction in heterozygous mice were significantly attenuated compared with cases in wild-type mice. Also, histological renal damage such as tubular necrosis and proteinaceous casts in tubuli in heterozygous mice were much less than that in wild-type mice. Ca(2+) deposition in necrotic tubular epithelium was observed more markedly in wild-type than in heterozygous mice. The increase in renal endothelin-1 (ET-1) content was significantly greater in wild-type than in heterozygous mice, and this reflected the difference in immunohistochemical ET-1 localization in necrotic tubular epithelium. We conclude that Ca(2+) overload via the reverse-mode of Na(+)/Ca(2+) exchange, followed by renal ET-1 overproduction, plays an important role in the pathogenesis of ischaemia/reperfusion-induced acute renal failure.

Several studies have demonstrated that endothelin-1 (ET-1) plays an important pathophysiological role in ischaemic renal failure and drug-induced renal injury, such as cyclosporine A (CsA)- and tacrolimus-associated nephrotoxicity. This study aimed to investigate whether the new immunosuppressive drug mycophenolic acid (MPA), which in contrast with CsA and tacrolimus lacks nephrotoxic side effects, modulates ET-1 synthesis in endothelial cells and renal epithelial cells. ET-1 release by cultured human umbilical vein endothelial cells (HUVEC), human renal artery endothelial cells (RAEC) and rabbit proximal tubule cells was measured with a specific ELISA. ET-1 mRNA expression was investigated by reverse transcription-PCR. MPA (2.5-50 microg/ml) induced a significant decrease in ET-1 mRNA expression (minimum 51.8+/-3.8% of control; P<0.001) in HUVEC and RAEC. After a 48 h incubation with MPA (1-50 microg/ml), a significant decrease in ET-1 release per culture well (minimum 56.8+/-1.7%; P<0.001) and DNA content per culture well (minimum 58.7+/-1.9%; P<0.001) was observed with HUVEC and RAEC, whereas ET-1 release referred to the DNA content in the corresponding culture well did not differ significantly from controls. In rabbit proximal tubule cells, ET-1 release referred to the cell number in the corresponding culture well was also reduced after incubation with MPA (minimum 86.2+/-2.4%; P<0.05). This study provides evidence that, in contrast with CsA and tacrolimus, MPA does not stimulate ET-1 synthesis. The present results might explain the clinical observation that renal function often improves when CsA or tacrolimus is replaced by mycophenolate mofetil.

Endothelin-1 (ET-1) is present at high concentrations in ovarian cancer ascites and is overexpressed in primary and metastatic ovarian carcinomas. In these tumours the presence of ET-1 is associated with enhanced neovascularization and with vascular endothelial growth factor (VEGF) expression. In these tumour cells, ET-1 acts as an autocrine growth factor selectively through the receptor ET(A), which is predominantly expressed in tumour cells. Furthermore, ET-1 produced by ovarian tumour cells stimulates VEGF production and VEGF-mediated angiogenic effects through ET(A) binding. These results demonstrate that activation of the ET(A) in ovarian carcinoma cells promotes cell proliferation, neovascularization and invasion, which are the principal hallmarks of malignant transformation. The present study was designed to investigate the effects of the ET(A)-selective antagonist ABT-627 on the ET-1-induced mitogenic effect in both primary cultures (PMOV1 and PMOV2) and cell lines (OVCA 433 and HEY) of ovarian carcinoma. All tumour cells express the components of the ET-1 system and secrete ET-1. ET(A) blockade by ABT-627 inhibits ET-1-induced mitogenic effects. The ET(B) antagonist BQ-788 is ineffective although all cell lines express both ET(A) and ET(B) mRNAs. In conclusion, our results demonstrate that ABT-627 is capable of inhibiting the proliferative activity of ET-1, suggesting that this potent ET(A) antagonist may provide a novel approach to the multidisciplinary treatment of ovarian carcinoma.

In order to evaluate whether lipid abnormalities may contribute to endothelial dysfunction in pre-eclampsia, the present study examined the in vitro effects of very-low-density lipoprotein (VLDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL), isolated from women with pre-eclampsia and matched controls, on the endothelial synthesis of 6-oxo-prostaglandin F(1alpha) (6-oxo-PGF(1alpha); a metabolite of prostacyclin) and endothelin 1, and on the expression of nitric oxide synthase 3 (NOS3) mRNA. VLDL, LDL and HDL cholesterol were isolated from 20 pre-eclamptic and 20 age- and gestation-matched normal pregnant women. The lipoproteins (50 microgram/ml) and lipoprotein-free control plasma were incubated for 1, 3 and 6 h at 37 degrees C with a human umbilical endothelial cell line. The synthesis of 6-oxo-PGF(1alpha) and endothelin 1, and NOS3 mRNA expression, were measured at each time point. VLDL from pre-eclamptic women stimulated endothelial cell 6-oxo-PGF(1alpha) synthesis to a lesser extent than that from normal pregnant women (P<0.05). LDL from women with pre-eclampsia also stimulated 6-oxo-PGF(1alpha) synthesis to a lesser extent than LDL from normal pregnant women, but the effect was less sustained. The effect of HDL from women with pre-eclampsia on 6-oxo-PGF(1alpha) synthesis was similar to that of HDL from normal pregnant women. The pre-incubation levels of lipid peroxides in VLDL and LDL were not different between the normal pregnant and pre-eclamptic women, and cannot account for the decrease in 6-oxo-PGF(1alpha) synthesis. VLDL, LDL and HDL from women with pre-eclampsia did not affect endothelial cell synthesis of endothelin 1 or expression of NOS3 mRNA differently from lipoproteins from normal pregnant women. This study suggests that VLDL, and to a lesser extent LDL, from women with pre-eclampsia could potentially contribute to the reduced systemic 6-oxo-PGF(1alpha) synthesis observed in the pre-eclamptic syndrome.