Interleukin 1beta induces functional prostaglandin E synthase in cultured human umbilical vein endothelial cells.

Prostaglandin endoperoxide H 2 (PGH 2 ) is generated from arachidonic acid by either constitutive (COX-1) or inducible (COX-2) cyclooxygenases. In arterial wall PGH 2 is converted by PGI 2 synthase (PGI-S) to prostacyclin (PGI 2 ), and in platelets by thromboxane synthase (TX-S) to thromboxane (TXA 2 ). Other prostanoids as PGD 2 , PGF 2 α or PGE 2 were believed to arise non-enzymatically from PGH 2 . Only recently, human prostaglandin E synthase (PGE-S) has been identified and cloned as a membrane bound, microsomal, glutathione-dependent inducible enzyme. Here we demonstrated that interleukin 1β (1L-1β) is an inducer of COX-2 and PGE-S in human umbilical vein endothelial cells (HUVEC). Functional expression of PGE-S was measured at the level of specific mRNA by semi-quantitative RT-PCR, PGE-S protein was detected by Western blot in HUVEC, while PGE 2 was measured by immunoassay in the supernatant. Actinomycin D, a classical transcription inhibitor, was used to prove that indeed IL-1β induced the functional PGE-S enzyme. PGE 2 generation in HUVEC was inhibited by indomethacin, acetamoniphen and dexamethasone. In conclusion, we found that in cultured endothelial cells IL-1β induced as evidenced by the appearance of its transcript and its functional enzyme. The induction of endothelial PGE-S and COX-2 appeared to be and their transcripts were induced as fast as one might expect from immediate early genes. It means that IL-1β-triggered-PGE 2 biosynthesis in endothelial cells is probably regulated by induction of both COX-2 and PGE-S. This is way we hypothesise the existence of at least two distinct pools of COX-2: the first selectively coupled to PGE-S and the second one that is coupled to PGI-S yielding the main endothelial product - PGI 2 .