20-Hydroxyeicosatetraenoic acid synthesis is increased in human neutrophils and platelets by angiotensin II and endothelin-1

Abstract

The cytochrome P-450 arachidonic acid metabolite 20-HETE is central to the regulation of vascular tone, renal function, and blood pressure and is synthesized in the rat kidney in response to angiotensin II (ANG II) and endothelin-1 (ET-1). There are very few studies examining the cellular synthesis of 20-HETE in humans. We aimed to measure human neutrophil and platelet 20-HETE levels under basal conditions and after ANG II, ET-1, and calcium ionophore (CaI). 20-HETE was measured in human platelets and neutrophils after saline (control), CaI (2.5 μg/ml), and ANG II or ET-1 (10 nmol/l-1 μmol/l) incubations. The effect of cells, which were preincubated with the ω-hydroxylase inhibitor N-hydroxy-N'-(4-butyl-2-methylphenyl) (HET0016, 10 nM), ANG II types 1 or 2 (AT(1) or AT(2)) receptor inhibition with irbesartan (1 μmol/l) or PD-123319 (1 μmol/l), or endothelin receptor subtypes A or B (ET(A) or ET(B)) receptor inhibition with BQ-123 or BQ-778 (100 nmol/l), was studied. Neutrophil and platelet content and release of 20-HETE was significantly increased by CaI and blocked by the ω-hydroxylase inhibitor HET0016. ANG II and ET-1 significantly increased neutrophil and platelet content and release of 20-HETE. ANG II increased 20-HETE via the AT(2) receptor. ET-1 increased 20-HETE through the ET(B) receptor in platelets and both the ET(A) and ET(B) receptors in neutrophils. These studies show that human platelets and neutrophils synthesize 20-HETE in response to ANG II and ET-1. 20-HETE synthesis in both cell types was predominantly mediated via the AT(2) and ET(B) receptors. Stimulation via these receptor pathways has generally been thought to be cardioprotective and requires further studies in clinical situations associated with low-grade inflammation or where ANG II and ET-1 are elevated to clarify the role of 20-HETE.