Preeclampsia and expression of inducible nitric oxide synthase messenger RNA in umbilical vein endothelial cells

Objectives: Vasodilatory nitric oxide (NO) is evidently a factor in pregnancy physiology and perhaps also in preeclampsia. Human umbilical vein endothelial cells (HUVECs) express the calcium-dependent NO synthase (NOS), whereas the scanty data on the expression of the inducible isoform of NOS (iNOS) are discrepant. We have previously shown that HUVECs can express iNOS and now further characterize the regulation of iNOS induction in freshly isolated HUVECs in vitro. In addition, we study whether iNOS mRNA expression is induced in vivo in preeclampsia. Study Design: Freshly isolated HUVECs from normal pregnancies were treated with proinflammatory cytokines, and inducible NO production was detected by measurement of nitrate and nitrite accumulation in the media. The expression of iNOS mRNA in these cells was detected by the reverse transcriptase-polymerase chain reaction. In addition, HUVECs from preeclamptic (n = 9) and normal (n = 11) pregnancies were lyzed immediately after delivery and assayed for iNOS mRNA. Results: The cytokine treatment of HUVECs led to consistent expression of iNOS mRNA and NO synthesis. Dexamethasone blunted both the expression of iNOS mRNA and the production of NO, whereas NOS inhibitor N-G-methyl-L-arginine merely suppressed the release of NO. No iNOS mRNA could be detected under basal conditions in HUVECs from preeclamptic or control patients. Conclusions: HUVECs are able to express iNOS after cytokine-stimulation in vitro, but this pathway was not activated in preeclampsia.