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

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 [(14)C]arachidonic acid, the profile of prostanoid synthesis was assessed by HPLC. Untransformed PGH(2) released by the cells was evaluated as the difference in the formation of PGF(2alpha) in the incubations performed in the presence and in the absence of SnCl(2). Resting SMCs and SMCs stimulated with phorbol 12-myristate 13-acetate (PMA), lipopolysaccharide (LPS), interleukin (IL)-1beta, and tumor necrosis factor (TNF)-alpha formed PGE(2) and PGI(2) (evaluated as 6-oxo-PGF(1alpha)), and in the presence of SnCl(2) only a small amount of PGE(2) was deviated toward PGF(2alpha). In contrast, resting and stimulated HUVECs produced PGI(2), PGE(2), PGF(2alpha), and PGD(2), and SnCl(2) completely diverted PGE(2) and PGD(2) toward PGF(2alpha). 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-1beta and TNF-alpha, and by PMA and LPS, although to a lesser extent. Whereas SMC stimulation led to an increase in the synthesis of PGE(2) and PGI(2) but not of untransformed PGH(2), stimulation of endothelial cells resulted in an enhanced release of the vasoconstricting prostanoid PGH(2).