bq-123 and Hyperplasia

Urinary bladder hypertrophy and hyperplasia is a common feature of bladder outlet obstruction (BOO). The urinary bladder is known to synthesize endothelin-1 (ET-1). ET-1 is a potent vasoconstrictor peptide with mitogenic properties. Using an animal model of partial BOO we investigated the potential role of ET-1 and its receptor subtypes [endothelin-A and -B (ET(A) and ET(B))] in bladder vascular smooth muscle cells (SMC) proliferation. In the presence of 3-week-old BOO serum, ET(A) and ET(B) antagonists significantly (p = 0.008) inhibited detrusor and bladder neck SMC proliferation. Cell counts were significantly reduced from the detrusor (p = 0.03, p = 0.01 with ET(A) and ET(B) antagonists, respectively) and bladder neck (p = 0.01 for both ET(A) and ET(B) antagonists). These results suggest that ET-1 antagonists may prevent SMC hyperplasia associated with partial BOO.

Topics: Animals; Bromodeoxyuridine; Endothelin-1; Hyperplasia; Male; Oligopeptides; Peptides, Cyclic; Piperidines; Rabbits; Urinary Bladder; Urinary Bladder Neck Obstruction

Although a number of pharmacologic agents have been shown to reduce intimal hyperplasia in animal models of restenosis, to date no systemic agent has conclusively been shown to be effective in humans. Recently, considerable attention has been directed towards endothelin (ET), a potent vasoconstrictor and a powerful mitogen for vascular smooth muscle cells, as a mediator of intimal hyperplasia. Endothelin-1 has been shown to be mitogenic for human saphenous vein smooth muscle cells, and expression also is elevated in human vein graft stenosis. The aim of this study was the investigation of whether ET receptor antagonists can attenuate neointima formation in a laboratory model of vein graft intimal hyperplasia and the determination of whether the effects are mediated by a specific ET receptor subtype.. We used an organ culture of human saphenous vein, a well-validated model of vein graft intimal hyperplasia. Paired segments of human long saphenous vein were cultured with and without the following antagonists: bosentan, a nonselective ET receptor antagonist; BQ 123, a specific endothelin-A antagonist; or BQ 788, a specific endothelin-B (ETB) antagonist. After 14 days in the culture, the segments were fixed and processed and the sections were immunostained to facilitate the measurements of neointimal thickness with a computerized image analysis system.. The nonselective antagonist bosentan and the ETB selective antagonist BQ 788 significantly reduced neointima formation by 70% (P = .001) and 50% (P = .03), respectively, but the ETA antagonist BQ 123 had no significant effect on the reduction of neointima formation (P = 1.0).. The results of this study imply an important role for ET as a mediator of human vein graft intimal hyperplasia and imply further that a specific ETB antagonist may have a therapeutic potential for the prevention of vein graft stenosis.

Topics: Bosentan; Endothelin Receptor Antagonists; Humans; Hyperplasia; Oligopeptides; Organ Culture Techniques; Peptides, Cyclic; Piperidines; Receptor, Endothelin B; Receptors, Endothelin; Saphenous Vein; Sulfonamides; Tunica Intima

We investigated which subtypes of endothelin-1 (ET-1) receptors are involved in the pathogenesis of angioplasty-induced lesion formation in the rabbit carotid artery. Four weeks after removing endothelial cells (EC), we noted a marked intimal hyperplasia. The Bmax values for [125I]ET-1 and [125I]IRL1620 (an agonist for the ETB receptors) bindings were greater in the hyperplastic artery, without changes in Kd values. [125I]ET-1 binding was completely inhibited by unlabeled ET-1 and Ro 46-2005, a mixed-type antagonist for the ETA and ETB receptors, but partially by BQ123, a selective antagonist for ETA receptors, and IRL1620. The [125I]ET-1 binding sites not inhibited with BQ123 were significantly increased in the hyperplastic artery. The binding study suggested the presence of non-ETA/non-ETB receptors. The rank order of the increasing ratio in the density of receptors was ETB > putative non-ETA/non-ETB > total ET-1 receptors > ETA. The histochemical experiments with biotinylated ET-1 at lysine-9 side chain alone or in combination with unlabeled ET-1, BQ123, Ro 46-2005, or IRL1620, showed the ETA receptors to be localized mainly in the media, whereas the ETB receptors localized mainly in the neointima. These results suggest that the increased ET-1 receptors, especially ETB and/or putative non-ETA/non-ETB, are closely related to the occurrence of the intimal hyperplasia after endothelial removal.

Topics: Analysis of Variance; Angioplasty; Angioplasty, Balloon; Animals; Binding, Competitive; Carotid Arteries; Endothelins; Hyperplasia; Male; Microscopy, Electron, Scanning; Muscle, Smooth, Vascular; Peptide Fragments; Peptides, Cyclic; Pyrimidines; Rabbits; Radioligand Assay; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Sulfonamides