A novel role for myeloid endothelin-B receptors in hypertension

Abstract

Aims Hypertension is common. Recent data suggest that macrophages (M/) contribute to, and protect from, hypertension. Endothelin-1 (ET-1) is the most potent endogenous vasoconstrictor with additional pro-inflammatory properties. We investigated the role of the ET system in experimental and clinical hypertension by modifying M/ number and phenotype. Methods and results In vitro, M/ ET receptor function was explored using pharmacological, gene silencing, and knockout approaches. Using the CD11b-DTR mouse and novel mice with myeloid cell-specific endothelin-B (ETB) receptor deficiency (LysMETB-/-), we explored the effects of modifying M/ number and phenotype on the hypertensive effects of ET-1, angiotensin II (ANG II), a model that is ET-1 dependent, and salt. In patients with small vessel vasculitis, the impacts of M/ depleting and non-depleting therapies on blood pressure (BP) and endothelial function were examined. Mouse and human M/ expressed both endothelin-A and ETB receptors and displayed chemokinesis to ET-1. However, stimulation of M/ with exogenous ET-1 did not polarize M/ phenotype. Interestingly, both mouse and human M/ cleared ET-1 through ETB receptor mediated, and dynamin-dependent, endocytosis. M/ depletion resulted in an augmented chronic hypertensive response to both ET-1 and salt. LysMETB-/- mice displayed an exaggerated hypertensive response to both ET-1 and ANG II. Finally, in patients who received M/ depleting immuno-therapy BP was higher and endothelial function worse than in those receiving non-depleting therapies. Conclusion M/ and ET-1 may play an important role in BP control and potentially have a critical role as a therapeutic target in hypertension.