Expression and functional analysis of endothelial nitric oxide synthase (eNOS) in human placenta

Abstract

We have investigated the expression and localization of endothelium-derived nitric oxide synthase (eNOS) and the effect of eNOS on placental human chorionic gonadotrophin (HCG) release. eNOS mRNA was found to be expressed in all tissues, with its expression significantly (P < 0.05) increased across gestation. Compared to normal term gestation, placentae from term pregnancies with fetal retardation, or maternal diabetes, but not with maternal hypertension, displayed significantly more (P < 0.05) eNOS mRNA. By immunocytochemistry, we found staining for eNOS in both the cyto-and syncytiotrophoblasts of first trimester and a loss of cytotrophoblast eNOS staining in term placentae, while syncytiotrophoblasts at term were strongly eNOS positive. Additional staining was found in endothelium surrounding the vascular tree. HCG was found to colocalize with eNOS in trophoblasts, but not in endothelia. When placental explants were perifused, exposure to the NOS substrate, the NO donor, l-arginine and trinitroglycerol evoked a prompt, albeit transient, increase of HCG release. The NOS inhibitor delayed, but did not block arginine-induced HCG release. Thus, eNOS is expressed in the human placenta at increasing levels during gestation with further increases during some pathological conditions. A role for NO in the acute endocrine modulation of the placenta is suggested by the colocalization of eNOS with HCG in human trophoblasts and the prompt secretion of HCG in response to agents which increase NO concentrations.

The feto-placental endothelium in pregnancy pathologies

“…This enables the production of higher levels of the vasodilator nitric oxide (NO). This hypothesis is further supported by the finding that placental eNOS expression in elevated in diabetes [24]. GDM is associated with an altered response to vasorelaxing agents [25,26] of feto-placental and umbilical vessels, which furthermore supports the finding of changes in vascular tone.…”

Preserved placental oxygenation and development during severe systemic hypoxia

“…Indeed, it was recently shown that the eNOS promoter contains a hypoxia response element and thus might be a HIF target gene (11). Expression of iNOS and eNOS has been observed in human and murine placenta (10,41,45). Thus hypoxic upregulation of placental NOS expression may result in NO-mediated vasodilation, thereby increasing placental blood flow and reconstituting oxygen supply to the placenta.…”

Genotype-specific Influence on Nitric Oxide Synthase Gene Expression, Protein Concentrations, and Enzyme Activity in Cultured Human Endothelial Cells

“…Cultured cells were trypsinized and washed twice in phosphate-buffered saline (PBS; Dulbecco), and total RNA was extracted by a single-step method with a Qiagen RNeasy Total RNA extraction reagent set (Qiagen), according to the manufacturer's instructions. measurement of ecNOS mRNA ecNOS mRNA concentrations were analyzed by reverse transcription-PCR (RT-PCR), as described previously, with minor modifications (19 ). Briefly, 1 g of total RNA was reverse-transcribed for 1 h at 37°C in a 20-L volume with use of oligo(dT) primer.…”