Human vascular smooth muscle cells but not endothelial cells express prostaglandin E synthase

Abstract

In a previous work, we postulated that endothelial cells possess only the following 2 enzymes involved in prostanoid synthesis: cyclooxygenase and prostacyclin synthase. The present work focused on investigating the expression of prostaglandin (PG) E synthase (PGES) in vascular cells. After incubation of vascular smooth muscle cells (SMCs) and human umbilical vein endothelial cells (HUVECs) with [14C]arachidonic acid, the profile of prostanoid synthesis was assessed by HPLC. Untransformed PGH2 released by the cells was evaluated as the difference in the formation of PGF(2α) in the incubations performed in the presence and in the absence of SnCl2. Resting SMCs and SMCs stimulated with phorbol 12-myristate 13-acetate (PMA), lipopolysaccharide (LPS), interleukin (IL)-1β, and tumor necrosis factor (TNF)-α formed PGE2 and PGI2 (evaluated as 6-oxo-PGF(1α)), and in the presence of SnCl2 only a small amount of PGE2 was deviated towed PGF(2α). In contrast, resting and stimulated HUVECs produced PGI2, PGE2, PGF(2α), and PGD2, and SnCl2 completely diverted PGE2 and PGD2 towed PGF(2α). Reverse transcriptase-polymerase chain reaction analysis shows that mRNA encoding for PGES was not present in HUVECs and in endothelial cells from saphenous vein. Nevertheless, PGES was expressed in SMCs and induced by IL-1β and TNF-α, and by PMA and LPS, although to a lesser extent. Whereas SMC stimulation led to an increase in the synthesis of PGE2 and PGI2 but not of untransformed PGH2, stimulation of endothelial cells resulted in an enchanced release of the vasoconstricting prostanoid PGH2.