EXPRESSION OF MESSENGER-RNA FOR PHOSPHOLIPASE A(2), CYCLOOXYGENASES, AND LIPOXYGENASES IN CULTURED HUMAN UMBILICAL VASCULAR ENDOTHELIAL ANDSMOOTH-MUSCLE CELLS AND IN BIOPSIES FROM UMBILICAL ARTERIES AND VEINS

Arachidonic acid (AA) is released by phospholipase A(2) (PLA(2)) and t hen converted into vasoactive and inflammatory eicosanoids by cyclooxy genases (COX) and lipoxygenases (LOX). These eicosanoids are important paracrine regulators of vascular permeability, blood flow, local pro- and anticoagulant activity and they play a major role in the local in flammatory response. We have investigated the presence of mRNAs for PL A(2) and for isoforms of COX and LOX in both human endothelial cells ( EC) and in human smooth muscle cells (SMC) in culture and in vascular biopsies of human umbilical veins (HUVB) and arteries (HUAB) by using the reversed transcription-polymerase chain reaction (RT-PCR) techniqu e. Results show detectable levels of PLA(2) type IV (cPLA(2)) in cultu red EC and SMC and in vascular wall biopsies from HUAB and HUVB. The c ultured EC and SMC demonstrate higher levels of both COX-1 and COX-2 w ith PCR analyses than do vascular wall biopsies from HUAB and HUVB. Th is indicates a difference in the native expression of COX-1 and COX-2 in cultures of EC and SMC compared to that in biopsies from intact ves sel walls. The EC and SMC in culture do not express mRNA for 5-LOX, th at was, however, expressed in the vascular wall biopsies. This speaks in favour of a constitutive, i.e, in vivo expression of 5-LOX in SMC i n the vascular wall of both umbilical vein and arteries. Thus results from in vitro studies of constitutive COX and LOX expression in EC and vascular SMC in culture cannot simply be extrapolated to represent in vivo conditions.