PROFILE OF PROSTAGLANDINS INDUCED BY ENDOTHELIN-1 IN HUMAN BRAIN CAPILLARY ENDOTHELIUM

The vasoactive peptide, endothelin-1(ET-1) has been implicated in the pathophysiology of various diseases. Recently, we have shown that human brain endothelial cells both secrete and express immunoreactive ET-1 high-affinity ET(A) receptors coupled to activation of phospholipase C (PLC). The present study demonstrates concentration-dependent stimulation of prostanoids [thromboxane B2 (TxB2), prostaglandin F2alpha (PGF2alpha), 6-keto prostaglandin F1alpha (6-keto PGF1alpha) prostaglandin E2 (PGE2), and prostaglandin D2 (PGD2)] Production by ET-1 in capillary endothelial cells derived from human brain (HBCEC). The increase in the vasoconstrictive prostanoids TxA2 and PGF2alpha temporally preceded that of the vasodilatory PGI2, PGE2 and PGD2, and was seen after 15 min of incubation with ET-1 (10 nM). Increased production of vasodilatory prostanoids was observed between 4-8 h of incubation, whereas normalization of both vasoconstrictive and vasodilatory prostaglandins occurred 24 h after addition of ET-1. Both ET-1-stimulated prostanoid and IP3 production were inhibited by BQ123, a specific antagonist of ET(A) receptors. ET-1-induced prostanoid secretion by HBCEC was also inhibited by dexamethasone (50 muM) and diminished by neomycin (50 muM) and verapamil (10 muM) but not by nifedipine. Phorbol myristate ester potentiated ET-1-stimulated prostanoid secretion, whereas it inhibited IP3 production. Data indicate that ET-1 activates phospholipase A2 (PLA2) and PLC in HBCEC by different intracellular mechanisms. The subsequently induced secretion of vasoactive prostanoids by HBCEC may contribute both qualitatively and temporally to the vasoactive actions of ET-1.