The role of endothelin receptor antagonists in cardiovascular pharmacotherapy

Endothelin receptor type B counteracts tenascin-C-induced endothelin receptor type A-dependent focal adhesion and actin stress fiber disorganization

Tenascin-C, an extracellular matrix molecule of the tumor-specific microenvironment, counteracts the tumor cell proliferation-suppressing effect of fibronectin by blocking the integrin alpha(5)beta(1)/syndecan-4 complex. This causes cell rounding and stimulates tumor cell proliferation. Tenascin-C also stimulates endothelin receptor type A (EDNRA) expression. Here, we investigated whether signaling through endothelin receptors affects tenascin-C-induced cell rounding. We observed that endothelin receptor type B (EDNRB) activation inhibited cell rounding by tenascin-C and induced spreading by restoring expression and function of focal adhesion kinase (FAK), paxillin, RhoA, and tropomyosin-1 (TM1) via activation of epidermal growth factor receptor, phospholipase C, c-Jun NH(2)-terminal kinase, and the phosphatidylinositol 3-kinase pathway. In contrast to EDNRB, signaling through EDNRA induced cell rounding, which correlated with FAK inhibition and TM1 and RhoA protein destabilization in the presence of tenascin-C. This occurred in a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-dependent manner. Thus, tumorigenesis might be enhanced by tenascin-C involving EDNRA signaling. Inhibition of tenascin-C in combination with blocking both endothelin receptors could present a strategy for sensitization of cancer and endothelial cells toward anoikis.

Novel Benzo[1,4]diazepin-2-one Derivatives as Endothelin Receptor Antagonists

Since its discovery in 1988 by Yanagisawa et al., endothelin (ET), a potent vasoconstrictor, has been widely implicated in the pathophysiology of cardiovascular, cerebrovascular, and renal diseases. Many research groups have embarked on the discovery and development of ET receptor antagonists for the treatment of such diseases. While several compounds, e.g., ambrisentan 2, are in late clinical trials for various indications, one compound (bosentan, Tracleer) is being marketed to treat pulmonary arterial hypertension. Inspired by the structure of ambrisentan 2, we designed a novel class of ET receptor antagonists based on a 1,3,4,5-tetrahydro-1H-benzo[e][1,4]diazepin-2-one scaffold. Here, we report on the preparation as well as the in vitro and in vivo structure-activity relationships of these derivatives. Potent dual ET(A)/ET(B) receptor antagonists with affinities in the low nanomolar range have been identified. In addition, several compounds efficiently reduced arterial blood pressure after oral administration to Dahl salt sensitive rats. In this animal model, the efficacy of the benzo[e][1,4]diazepin-2-one derivative rac-39au was superior to that of racemic ambrisentan, rac-2.

Left but not right cardiac hypertrophy in atrial natriuretic peptide receptor-deficient mice is prevented by angiotensin type 1 receptor antagonist losartan

Mice with a genetic deletion of the atrial natriuretic peptide (ANP) receptor, guanylyl cyclase A (GC-A -/-), have chronic arterial hypertension and cardiac hypertrophy from the first day of life. To characterize the role of the angiotensin II and endothelin systems in the development of this cardiovascular phenotype, the effects of chronic treatment with either the angiotensin type I (AT1) receptor antagonist losartan or the endothelin A receptor antagonist BSF208075 were tested. Losartan almost completely reversed systemic arterial hypertension and left ventricular hypertrophy of GC-A -/- mice. This was accompanied by a marked regression of the left ventricular mRNA expression of cardiac hypertrophy markers such as ANP and brain natriuretic peptide and a significant reduction of left ventricular and pulmonary interstitial collagen accumulation. BSF208075 had no effect on any of these cardiovascular parameters. Intriguingly, GC-A -/- mice also showed a very marked right ventricular hypertrophy, which was not reversed by losartan or BSF208075 treatment. Analyses of components of the renin-angiotensin system (RAS) revealed an inhibition of renal and systemic RAS contrasting with increased local left ventricular angiotensin II levels in GC-A -/- mice. Collectively, the results suggest that RAS plays a more important role than the endothelin system in the pathogenesis of arterial hypertension as well as left ventricular hypertrophy and fibrosis in GC-A gene-disrupted mice.