Molecular mechanisms involved in pre-eclampsia through expressional regulation of endothelin-1

Gestational intermittent hypoxia induces endothelial dysfunction and hypertension in pregnant rats: role of endothelin type B receptor†

Obstructive sleep apnea is a recognized risk factor for gestational hypertension, yet the exact mechanism behind this association remains unclear. Here, we tested the hypothesis that intermittent hypoxia, a hallmark of obstructive sleep apnea, induces gestational hypertension through perturbed endothelin-1 signaling. Pregnant Sprague-Dawley rats were subjected to normoxia (control), mild intermittent hypoxia (10.5% O2), or severe intermittent hypoxia (6.5% O2) from gestational days 10-21. Blood pressure was monitored. Plasma was collected and mesenteric arteries were isolated for myograph and protein analyses. The mild and severe intermittent hypoxia groups demonstrated elevated blood pressure, reduced plasma nitrate/nitrite, and unchanged endothelin-1 levels compared to the control group. Western blot analysis revealed decreased expression of endothelin type B receptor and phosphorylated endothelial nitric oxide synthase, while the levels of endothelin type A receptor and total endothelial nitric oxide synthase remained unchanged following intermittent hypoxia exposure. The contractile responses to potassium chloride, phenylephrine, and endothelin-1 were unaffected in endothelium-denuded arteries from mild and severe intermittent hypoxia rats. However, mild and severe intermittent hypoxia rats exhibited impaired endothelium-dependent vasorelaxation responses to endothelin type B receptor agonist IRL-1620 and acetylcholine compared to controls. Endothelium denudation abolished IRL-1620-induced vasorelaxation, supporting the involvement of endothelium in endothelin type B receptor-mediated relaxation. Treatment with IRL-1620 during intermittent hypoxia exposure significantly attenuated intermittent hypoxia-induced hypertension in pregnant rats. This was associated with elevated circulating nitrate/nitrite levels, enhanced endothelin type B receptor expression, increased endothelial nitric oxide synthase activation, and improved vasodilation responses. Our data suggested that intermittent hypoxia exposure during gestation increases blood pressure in pregnant rats by suppressing endothelin type B receptor-mediated signaling, providing a molecular mechanism linking intermittent hypoxia and gestational hypertension.

Functional and Histological Changes in Umbilical Artery and Myometrium Isolated from IUGR Complicated Pregnancies

Objective: To investigate the relaxation responses mediated by L-type Ca2+ channels and big-conductance Ca2+-activated K+ (BKCa) channels and histological changes in the human umbilical artery (HUA) and myometrium smooth muscle isolated from pregnancies complicated with intrauterine growth restriction (IUGR).Methods: The muscle reactivity and the histology of the smooth muscle of the HUA and myometrium retrieved from 14 women with IUGR and 14 controls were investigated by the isolated tissue bath and immunohistochemical method.Results: In HUA, the maximum relaxation responses and pD2 values of nifedipine and NS11021 (BKCa channel opener) were significantly increased and significant histopathological changes are observed in the IUGR group.Conclusions: The pathogenesis of IUGR might be associated with the impairment in the functional responses of L-type Ca2+ channels and BKCa channels in HUA smooth muscle. The increased staining of myometrium and UC with HIF-1α in IUGR may indicate apoptosis, histological damage, and impaired fetal growth.

Preliminary evidence that blocking the uptake of placenta-derived preeclamptic extracellular vesicles protects the vascular endothelium and prevents vasoconstriction

Preeclampsia (PE) is a pregnancy syndrome characterized by hypertension and organ damage manifesting after 20 gestational weeks. The etiology is of multifactorial origin, where placental stress causes increased levels of placenta-derived extracellular vesicles (STBEVs) in the maternal circulation, shown to cause inflammation, endothelial activation, vasoconstriction, and anti-angiogenic activity. General endothelial dysfunction is believed to be initiated by endothelial insult during pregnancy that alters vascular function resulting in increased arterial stiffness, cardiac dysfunction, and increased risk of cardiovascular disease later in life. We compared the effect of normal and PE derived STBEVs in vitro on vascular contractility of human subcutaneous arteries using wire myography. Cellular structures of exposed vessels were investigated by transmission electron microscopy. We explored strategies to pharmacologically block the effects of the STBEVs on human vessels. The PE STBEVs caused significantly stronger angiotensin II-mediated contractions and extended structural damage to human subcutaneous arteries compared to normal STBEVs. These negative effects could be reduced by blocking vesicle uptake by endothelial cells, using chlorpromazine or specific antibodies towards the LOX-1 receptor. The therapeutic potential of blocking vesicle uptake should be further explored, to reduce the permanent damage caused on the vasculature during PE pregnancy to prevent future cardiovascular risk.

Pre-Eclampsia: From Etiology and Molecular Mechanisms to Clinical Tools-A Review of the Literature

Pre-eclampsia is a severe pregnancy-related complication that manifests as a syndrome with multisystem involvement and damage. It has significantly grown in frequency during the past 30 years and could be considered as one of the major causes of maternal and fetal morbidity and mortality. However, the specific etiology and molecular mechanisms of pre-eclampsia are still poorly known and could have a variety of causes, such as altered angiogenesis, inflammations, maternal infections, obesity, metabolic disorders, gestational diabetes, and autoimmune diseases. Perhaps the most promising area under investigation is the imbalance of maternal angiogenic factors and its effects on vascular function, though studies in placental oxidative stress and maternal immune response have demonstrated intriguing findings. However, to determine the relative importance of each cause and the impact of actions aiming to significantly reduce the incidence of this illness, more research is needed. Moreover, it is necessary to better understand the etiologies of each subtype of pre-eclampsia as well as the pathophysiology of other major obstetrical syndromes to identify a clinical tool able to recognize patients at risk of pre-eclampsia early.

Comparison of relaxant effects of nifedipine and NS11021 on isolated umbilical arteries of healthy and preeclamptic pregnant women

OBJECTIVES

Potassium (K⁺) channel openers and calcium (Ca²⁺) channel blockers are currently used to treat acute severe hypertension in pregnancy. We aimed to investigate the vasorelaxant effect of NS11021, a potent and specific big-conductance Ca²⁺-activated K⁺ (BKCa) channel activator, and to compare it with the vasorelaxant effect of nifedipine on human umbilical arteries (HUAs) isolated from healthy and preeclamptic pregnants.

STUDY DESIGN

A total of 29 HUAs were isolated immediately after delivery from 14 healthy and 15 preeclamptic pregnant with severe features. The concentration-dependent relaxation responses were obtained to nifedipine and NS11021 on HUAs precontracted with endothelin-1 (ET-1) (10^-8 M) in an isolated tissue bath.

RESULTS

Both nifedipine and NS11021 caused concentration-dependent relaxation responses in HUAs from healthy and preeclamptic pregnants. While the maximum responses (Emax) and pD₂ values of nifedipine did not change significantly in both groups, the Emax and pD₂ values of NS11021 were significantly decreased in the preeclampsia group (Emax ± SEM; %75.57 ± 4.53 and %43.75 ± 14.00 and pD₂ ± SEM; 6.92 ± 0.26 and 5.24 ± 0.53 respectively, p < 0.05). In addition, the pD₂ value of NS11021 was not significantly different from that of nifedipine in the control group, but decreased significantly in the preeclampsia group (pD₂ ± SEM 7.1 ± 0.41 and 5.2 ± 0.53, p < 0.05, respectively).

CONCLUSIONS

Efficacy and potency of NS11021 decreased in HUAs from preeclamptic pregnants. Also, NS11021 is less potent than nifedipine in the preeclampsia group. BKCa channels may have a role in the pathogenesis of preeclampsia, however, further experimental studies are needed to elucidate that.

Role of microRNAs in trophoblast invasion and spiral artery remodeling: Implications for preeclampsia

It is now well-established that microRNAs (miRNAs) are important regulators of gene expression. The role of miRNAs in placental development and trophoblast function is constantly expanding. Trophoblast invasion and their ability to remodel uterine spiral arteries are essential for proper placental development and successful pregnancy outcome. Many miRNAs are reported to be dysregulated in pregnancy complications, especially preeclampsia and they exert various regulatory effects on trophoblasts. In this review, we provide a brief overview of miRNA biogenesis and their mechanism of action, as well as of trophoblasts differentiation, invasion and spiral artery remodeling. We then discuss the role of miRNAs in trophoblasts invasion and spiral artery remodeling, focusing on miRNAs that have been thoroughly investigated, especially using multiple model systems. We also discuss the potential role of miRNAs in the pathogenesis of preeclampsia.