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 f ollowing 2 enzymes involved in prostanoid synthesis: cyclooxygenase and pro stacyclin synthase, The present work focused on investigating the expressio n of prostaglandin (PG) E synthase (PGES) in vascular cells. After incubati on of vascular smooth muscle cells (SMCs) and human umbilical vein endothel ial cells (HUVECs) with [C-14]arachidonic acid, the profile of prostanoid s ynthesis was assessed by HPLC, Untransformed PGH, released by the cells was evaluated as the difference in the formation of PGF(2 alpha) in the incuba tions performed in the presence and in the absence of SnCl2. Resting SMCs a nd SMCs stimulated with phorbol 12-myristate 13-acetate (PMA), lipopolysacc haride (LPS), interleukin (IL)-1 beta, and tumor necrosis factor (TNF)-alph a formed PGE(2) and PGI(2) (evaluated as 6-oxo-PGF(1 alpha)), and in the pr esence of SnCl2 only a small amount of PGE(2) was deviated toward PGF(2 alp ha). In contrast, resting and stimulated HUVECs produced PGI(2), PGE(2), PG F(2 alpha), and PGD(2), and SnCl2 completely diverted PGE(2) and PGD(2) tow ard PGF(2 alpha). Reverse transcriptase-polymerase chain reaction analysis shows that mRNA encoding for PGES was not present in HUVECs and in endothel ial cells from saphenous vein. Nevertheless, PGES was expressed in SMCs and induced by IL-1 beta and TNF-alpha, and by PMA and LPS, although to a less er extent. Whereas SMC stimulation led to an increase in the synthesis of P GE(2) and PGI(2) but not of untransformed PGH(2), stimulation of endothelia l cells resulted in an enhanced release of the vasoconstricting prostanoid PGH(2).