GNA11 differentially mediates fibroblast growth factor 2- and vascular endothelial growth factor A-induced cellular responses in human fetoplacental endothelial cells

Differential Distribution of Tryptophan-Metabolites in Fetal and Maternal Circulations During Normotensive and Preeclamptic Pregnancies

Preeclampsia (PE) is a hypertensive pregnancy, which is a leading cause of maternal and fetal morbidity and mortality during pregnancy. L-Tryptophan (Trp) is an essential amino acid, which can be metabolized into various biologically active metabolites. However, the levels of many circulating Trp-metabolites in human normotensive pregnancies (NT) and PE are undetermined. This study quantified the levels of Trp-metabolites in maternal and umbilical vein sera from women with NT and PE. Paired maternal and umbilical blood samples were collected from singleton pregnant patients. Twenty-five Trp-metabolites were measured in serum samples using liquid chromatography with tandem mass spectrometry. The effects of L-kynurenine (Kyn) and indole-3-lactic acid (ILA), on function of human umbilical vein endothelial cells (HUVECs), were also determined. Twenty Trp-metabolites were detected. The levels of 9 Trp-metabolites including Kyn and ILA were higher (P < 0.05) in umbilical vein than maternal serum, whereas 2 (5-hydroxy-L-tryptophan and serotonin) were lower (P < 0.05) in umbilical vein compared to maternal serum. PE significantly (P < 0.05) elevated ILA levels in maternal and umbilical vein sera. Kyn dose-dependently decreased (P < 0.05) cell viability. Kyn and ILA dose- and time-dependently (P < 0.05) increased monolayer integrity in HUVECs. These data suggest that these Trp-metabolites are important in regulating endothelial function during pregnancy, and the elevated ILA in PE may antagonize increased endothelial permeability occurring in PE.

Roles of aryl hydrocarbon receptor in endothelial angiogenic responses†

Aryl hydrocarbon receptor (AhR) is a transcription factor, which can be activated by a plethora of structure-diverse ligands. Historically, AhR is known for its involvements in regulation of metabolism of xenobiotics. However, normal physiological roles of AhR have been defined in other essential biological processes, including vascular growth and function, reproduction, and immunoresponses. In contrast, aberrant expression and activation of the AhR signaling pathway occur in a variety of human diseases, many of which (e.g., preeclampsia, atherosclerosis, and hypertension) could be associated with endothelial dysfunction. Indeed, emerging evidence has shown that either exogenous or endogenous AhR ligands can induce endothelial dysfunction in either an AhR-dependent or AhR-independent manner, possibly reliant on the blood vessel origin (artery and vein) of endothelial cells. Given that the AhR signaling pathway has broad impacts on endothelial and cardiovascular function, AhR ligands, AhR, and their downstream genes could be considered novel therapeutic targets for those endothelial-related diseases. This review will discuss the current knowledge of AhR's mediation on endothelial function and potential mechanisms underlying these actions with a focus on placental endothelial cells.

Role of oxygen in fetoplacental endothelial responses: hypoxia, physiological normoxia, or hyperoxia?

During pregnancy, placental vascular growth, which is essential for supporting the rapidly growing fetus, is associated with marked elevations in blood flow. These vascular changes take place under chronic physiological low O₂ (less than 2-8% O₂ in human; chronic physiological normoxia, CPN) throughout pregnancy. O₂ level below CPN pertinent to the placenta results in placental hypoxia. Such hypoxia can cause severe endothelial dysfunction, which is associated with adverse pregnancy outcomes (e.g., preeclampsia) and high risk of adult-onset cardiovascular diseases in children born to these pregnancy complications. However, our current knowledge about the mechanisms underlying fetoplacental endothelial function is derived primarily from cell models established under atmospheric O₂ (~21% O₂ at sea level, hyperoxia). Recent evidence has shown that fetoplacental endothelial cells cultured under CPN have distinct gene expression profiles and cellular responses compared with cells cultured under chronic hyperoxia. These data indicate the critical roles of CPN in programming fetal endothelial function and prompt us to re-examine the mechanisms governing fetoplacental endothelial function under CPN. Better understanding these mechanisms will facilitate us to develop preventive and therapeutic strategies for endothelial dysfunction-associated diseases (e.g., preeclampsia). This review will provide a brief summary on the impacts of CPN on endothelial function and its underlying mechanisms with a focus on fetoplacental endothelial cells.

Overexpression of the aryl hydrocarbon receptor nuclear translocator partially rescues fetoplacental angiogenesis in severe fetal growth restriction

Pregnancies complicated by severe fetal growth restriction with abnormal umbilical artery Doppler velocimetry (FGRadv) are at substantial risk for adverse perinatal and long-term outcomes. Impaired angiogenesis of the placental vasculature in these pregnancies results in a sparse, poorly branched vascular tree, which structurally contributes to the abnormally elevated fetoplacental vascular resistance that is clinically manifested by absent or reversed umbilical artery Doppler indices. Previous studies have shown that aryl hydrocarbon receptor nuclear translocator (ARNT) is a key mediator of proper placental angiogenesis, and within placental endothelial cells (ECs) from human FGRadv pregnancies, low expression of ARNT leads to decreased vascular endothelial growth factor A (VEGFA) expression and deficient tube formation. Thus, the aim of the present study was to determine the effect of VEGFA administration or ARNT overexpression on angiogenic potential of FGRadv ECs. ECs were isolated and cultured from FGRadv or gestational age-matched control placentas and subjected to either vehicle vs VEGFA treatment or transduction with adenoviral-CMV (ad-CMV) vs adenoviral-ARNT (ad-ARNT) constructs. They were then assessed via wound scratch and tube formation assays. We found that VEGFA administration nominally improved FGRadv EC migration (P<0.01) and tube formation (P<0.05). ARNT overexpression led to significantly enhanced ARNT expression in FGRadv ECs (P<0.01), to a level similar to control ECs. Despite this, FGRadv EC migration (P<0.05) and tube formation (P<0.05) were still only partially rescued. This suggests that although ARNT does play a role in fetoplacental EC migration, other factors in addition to ARNT are likely also important in placental angiogenesis.

Sexual Dimorphisms of Preeclampsia-Dysregulated Transcriptomic Profiles and Cell Function in Fetal Endothelial Cells

Preeclampsia impairs fetoplacental vascular function and increases risks of adult-onset cardiovascular disorders in children born to preeclamptic mothers, implicating that preeclampsia programs fetal vasculature in utero. However, the underlying mechanisms remain elusive. We hypothesize that preeclampsia alters fetal endothelial gene expression and disturbs cytokines- and growth factors-induced endothelial responses. RNA sequencing analysis was performed on unpassaged human umbilical vein endothelial cells (HUVECs) from normotensive and preeclamptic pregnancies. Functional assays for endothelial monolayer integrity, proliferation, and migration were conducted on passage 1 HUVECs from normotensive and preeclamptic pregnancies. Compared with normotensive cells, 926 and 172 genes were dysregulated in unpassaged female and male HUVECs from preeclamptic pregnancies, respectively. Many of these preeclampsia-dysregulated genes are associated with cardiovascular diseases (eg, heart failure) and endothelial function (eg, cell migration, calcium signaling, and endothelial nitric oxide synthase signaling). TNF (tumor necrosis factor)-α-, TGF (transforming growth factor)-β1-, FGF (fibroblast growth factor)-2-, and VEGFA (vascular endothelial growth factor A)-regulated gene networks were differentially disrupted in unpassaged female and male HUVECs from preeclamptic pregnancies. Moreover, preeclampsia decreased endothelial monolayer integrity in responses to TNF-α in both female and male HUVECs. Preeclampsia decreased TGF-β1-strengthened monolayer integrity in female HUVECs, whereas it enhanced FGF-2-strengthened monolayer integrity in male HUVECs. Preeclampsia promoted TNF-α-, TGF-β1-, and VEGFA-induced cell proliferation in female, but not in male HUVECs. Preeclampsia inhibited TNF-α-induced cell migration in female HUVECs, but had an opposite effect on male HUVECs. In conclusion, preeclampsia differentially dysregulates cardiovascular diseases- and endothelial function-associated genes/pathways in female and male fetal endothelial cells in association with the sexual dimorphisms of preeclampsia-dysregulated fetal endothelial function.

G Protein α Subunit 14 Mediates Fibroblast Growth Factor 2-Induced Cellular Responses in Human Endothelial Cells

During pregnancy, a tremendous increase in fetoplacental angiogenesis is associated with elevated blood flow. Aberrant fetoplacental vascular function may lead to pregnancy complications including pre-eclampsia. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are crucial regulators of fetoplacental endothelial function. G protein α subunit 14 (GNA14), a member of Gαq/11 subfamily is involved in mediating hypertensive diseases and tumor vascularization. However, little is known about roles of GNA14 in mediating the FGF2- and VEGFA-induced fetoplacental endothelial function. Using human umbilical vein endothelial cells (HUVECs) cultured under physiological chronic low oxygen (3% O₂ ) as a cell model, we show that transfecting cells with adenovirus carrying GNA14 complementary DNA (cDNA; Ad-GNA14) increases (p < 0.05) protein expression of GNA14. GNA14 overexpression blocks (p < 0.05) FGF2-stimulated endothelial migration, whereas it enhances (p < 0.05) endothelial monolayer integrity (maximum increase of ~35% over the control at 24 hr) in response to FGF2. In contrast, GNA14 overexpression does not significantly alter VEGFA-stimulated cell migration, VEGFA-weakened cell monolayer integrity, and intracellular Ca⁺⁺ mobilization in response to adenosine triphosphate (ATP), FGF2, and VEGFA. GNA14 overexpression does not alter either FGF2- or VEGFA-induced phosphorylation of ERK1/2. However, GNA14 overexpression time-dependently elevates (p < 0.05) phosphorylation of phospholipase C-β3 (PLCβ3) at S1105 in response to FGF2, but not VEGFA. These data suggest that GNA14 distinctively mediates fetoplacental endothelial cell migration and permeability in response to FGF2 and VEGFA, possibly in part by altering activation of PLCβ3 under physiological chronic low oxygen.