endothelin-1 and Neointima

Despite the exploration of a large number of disparate drugs in animal models and clinical trials, no pharmacological intervention, with the exception of aggressive lipid lowering therapy has reduced late vein graft failure in man. The importance of devising more effective strategies is exemplified by the enormous economic consequences of vein graft failure. Worldwide, there are currently more than 1,000,000 coronary artery bypass graft surgery (CABG) operations a year, the same number of patients undergoing infrainguinal bypass for vascular diseases of the lower limb. The pathophysiology of vein graft failure is complex, involving disparate factors that include adhesion of platelets and leukocytes, rheological forces, metalloproteinase expression, proliferation and migration of vascular smooth muscle cells, neointima formation, oxidative stress, hypoxia and neural re-organisation. Although this diverse etiology may seem to preclude any single drug type as being effective in mediating vein graft failure: one factor that is involved in every facet of vein graft pathobiology is endothelin-1 (ET-1). As such a single drug type (ET(A) antagonist) may prove to be the magic bullet in this scenario. Thus, in this review, we will consider the etiology of vein graft disease in relation to ET-1 and will then present an argument (with evidence) that specific ET(A) receptor antagonists constitute a potentially effective means of preventing vein graft failure.

Topics: Endothelin A Receptor Antagonists; Endothelin-1; Graft Occlusion, Vascular; Graft Rejection; Humans; Molecular Targeted Therapy; Neointima; Receptor, Endothelin A; Veins

Obesity is associated with elevated circulating leptin levels and hypothalamic leptin resistance. Leptin receptors (LepRs) are expressed on endothelial cells, and leptin promotes neointima formation in a receptor-dependent manner. Our aim was to examine the importance of endothelial LepR (End.LepR) signaling during vascular remodeling and to determine whether the cardiovascular consequences of obesity are because of hyperleptinemia or endothelial leptin resistance.. Mice with loxP-flanked LepR alleles were mated with mice expressing Cre recombinase controlled by the inducible endothelial receptor tyrosine kinase promoter. Obesity was induced with high-fat diet. Neointima formation was examined after chemical carotid artery injury. Morphometric quantification revealed significantly greater intimal hyperplasia, neointimal cellularity, and proliferation in End.LepR knockout mice, and similar findings were obtained in obese, hyperleptinemic End.LepR wild-type animals. Analysis of primary endothelial cells confirmed abrogated signal transducer and activator of transcription-3 phosphorylation in response to leptin in LepR knockout and obese LepR wild-type mice. Quantitative PCR, ELISA, and immunofluorescence analyses revealed increased expression and release of endothelin-1 in End.LepR-deficient and LepR-resistant cells, and ET receptor A/B antagonists abrogated their paracrine effects on murine aortic smooth muscle cell proliferation. Reduced expression of peroxisome proliferator-activated receptor-γ and increased nuclear activator protein-1 staining was observed in End.LepR-deficient and LepR-resistant cells, and peroxisome proliferator-activated receptor-γ antagonization increased endothelial endothelin-1 expression.. Our findings suggest that intact endothelial leptin signaling limits neointima formation and that obesity represents a state of endothelial leptin resistance. These observations and the identification of endothelin-1 as soluble mediator of the cardiovascular risk factor obesity may have relevant therapeutic implications.

Topics: Animals; Carotid Arteries; Carotid Artery Injuries; Cell Movement; Cell Proliferation; Cells, Cultured; Diet, High-Fat; Disease Models, Animal; Endothelial Cells; Endothelin-1; Female; Genotype; Integrases; Leptin; Male; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Neointima; Obesity; Paracrine Communication; Phenotype; Phosphorylation; PPAR gamma; Promoter Regions, Genetic; Receptor, TIE-2; Receptors, Endothelin; Receptors, Leptin; Signal Transduction; STAT3 Transcription Factor; Vascular Remodeling

The potent vasoconstrictor endothelin-1 (ET-1), acting on the endothelin-A (ETA) receptor, promotes intimal lesion formation following vascular injury. The endothelin-B (ETB) receptor, which mediates nitric oxide release and ET-1 clearance in endothelial cells, may moderate lesion formation, but this is less clear. We used selective ET receptor antagonists and cell-specific deletion to address the hypothesis that ETB receptors in the endothelium inhibit lesion formation following arterial injury.. Neointimal proliferation was induced by wire or ligation injury to the femoral artery in mice treated with selective ETA (ABT-627) and/or ETB antagonists (A192621). Measurement of lesion formation by optical projection tomography and histology indicated that ETA blockade reduced lesion burden in both models. Although ETB blockade had little effect on ligation injury-induced lesion formation, after wire injury, blockade of the ETB receptor increased lesion burden (184% of vehicle; P < 0.05) and reversed the protective effects of an ETA antagonist. Selective deletion of ETB receptors from the endothelium, however, had no effect on neointimal lesion size.. These results are consistent with ETB receptor activation playing an important role in limiting neointimal lesion formation following acute vascular injury, but indicate that this protective effect is not mediated by those ETB receptors expressed by endothelial cells. These data support the proposal that selective ETA antagonists may be preferable to mixed ETA/ETB antagonists for targeting the arterial response to injury.

Topics: Animals; Blood Pressure; Endothelin B Receptor Antagonists; Endothelin-1; Male; Mice; Mice, Inbred C57BL; Neointima; Pyrrolidines; Receptor, Endothelin A; Receptor, Endothelin B; Vascular System Injuries

The purpose of this study was to evaluate the involvement of endothelin (ET)(B) receptor-mediated action in the sex differences in balloon injury-induced neointimal formation using the spotting-lethal rat, which carries a naturally occurring deletion in its ET(B) receptor gene. Male and female ET(B)-deficient and wild-type rats underwent balloon injury of the carotid artery. In the wild-type rats, the neointima/media ratio was significantly lower in females than in males, but this sex difference was attenuated by ovariectomy and restored by treatment with 17β-estradiol (20 μg/kg/day). In the ET(B)-deficient rats, the neointima/media ratio of the male and female rats was markedly increased to the same level, and this increase was not affected by ovariectomy or 17β-estradiol treatment. Treatment with (+)-(5S,6R,7R)-2-butyl-7-[2-((2S)-2-carboxypropyl)-4-methoxyphenyl]-5-(3,4-methylenedioxyphenyl)cyclopenteno[1,2-b]pyridine-6-carboxylic acid (J-104132) (10 mg/kg/day), an ET(A)/ET(B) dual receptor antagonist, markedly decreased the neointima/media ratio of the male wild-type rats and the male and female ET(B)-deficient rats, but not the female wild-type rats. In addition, 2R-(4-propoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N-(2,6-diethylphenyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid (A-192621) (30 mg/kg/day), a selective ET(B) receptor antagonist, abolished the sex difference of balloon injury-induced neointimal formation. 2R-(4-methoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N,N-di(n-butyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid (ABT-627) (10 mg/kg/day), a selective ET(A) receptor antagonist, and J-104132 (10 mg/kg/day) markedly decreased the neointima/media ratio to the same extent in males but not intact females. These results indicate that the sex difference in balloon injury-induced neointimal formation was abolished by genetic ET(B) receptor deficiency or its pharmacological blockade. The lack of a vasoprotective effect of estrogen and the augmentation of ET(A) receptor-mediated action seem to be responsible for the abolition of sex differences in the ET(B) receptor-inhibited condition.

Topics: Animals; Catheterization; Endothelin-1; Estrogens; Female; Male; Neointima; Ovariectomy; Pyridines; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; RNA, Messenger; Sex Characteristics; Systole