Augmented PLA2Activity in Pre-eclamptic Decidual Tissue—A Key Player in the Pathophysiology of ‘Acute Atherosis’ in Pre-eclampsia?

Atherosis of Trophoblast Type

CONTEXT.—

There are 3 types of decidual vasculopathy, namely, acute atherosis, fibrinoid medial necrosis, and mural arterial hypertrophy. Persistence of vascular trophoblasts is also known to be related to maternal vascular malperfusion, but detailed study is lacking.

OBJECTIVE.—

To define atherosis of trophoblast type and distinguish it from atherosis of macrophage type with clinical significance.

DESIGN.—

A total of 1322 placentas from 2021 were collected with clinical, neonatal, and placental information, and routine placental pathology examination was performed. Decidual vasculopathy was classified on the basis of the new classification scheme including atherosis of macrophage type, atherosis of trophoblast type, fibrinoid medial necrosis, mural arterial hypertrophy, and mixed-type vasculopathy. The significance of these morphologic changes was examined on the basis of clinical, neonatal, and placental pathology features.

RESULTS.—

Decidual vasculopathy is classified as classic type, mural hypertrophy, and mixed type. Classic-type vasculopathy is further separated as atherosis and fibrinoid medial necrosis. Atherosis is defined as atherosis of macrophage type and atherosis of trophoblast type. Each category of decidual vasculopathy was evaluated in association with maternal, neonatal, and placental pathologic findings. Atherosis of macrophage type and mixed-type vasculopathy showed statistically significant association with preeclampsia/pregnancy-induced hypertension (PIH), low birth weight, and low placental weight. Atherosis of trophoblast type was associated with lower placental weight but not with other specific clinical features. Neonates of female sex were associated with mural arterial hypertrophy.

CONCLUSIONS.—

Atherosis of trophoblast type is a distinct pathologic feature in late pregnancy, and it is associated with lower placental weight. New classification of decidual vasculopathy helps with better stratification and categorization of placental maternal vascular abnormalities of late pregnancy.

Failure of physiological transformation and spiral artery atherosis: their roles in preeclampsia

Physiological transformation with remodeling of the uteroplacental spiral arteries is key to a successful placentation and normal placental function. It is an intricate process that involves, but is not restricted to, complex interactions between maternal decidual immune cells and invasive trophoblasts in the uterine wall. In normal pregnancy, the smooth muscle cells of the arterial tunica media of uteroplacental spiral arteries are replaced by invading trophoblasts and fibrinoid, and the arterial diameter increases 5- to 10-fold. Poor remodeling of the uteroplacental spiral arteries is linked to early-onset preeclampsia and several other major obstetrical syndromes, including fetal growth restriction, placental abruption, and spontaneous preterm premature rupture of membranes. Extravillous endoglandular and endovenous trophoblast invasions have recently been put forth as potential contributors to these syndromes as well. The well-acknowledged disturbed extravillous invasion of maternal spiral arteries in preeclampsia is summarized, as are briefly novel concepts of disturbed extravillous endoglandular and endovenous trophoblast invasions. Acute atherosis is a foam cell lesion of the uteroplacental spiral arteries associated with poor remodeling. It shares some morphologic features with early stages of atherosclerosis, but several molecular differences between these lesions have also recently been revealed. Acute atherosis is most prevalent at the maternal-fetal interface, at the tip of the spiral arteries. The localization of acute atherosis downstream of poorly remodeled arteries suggests that alterations in blood flow may trigger inflammation and foam cell development. Acute atherosis within the decidua basalis is not, however, confined to unremodeled areas of spiral arteries or to hypertensive disorders of pregnancy and may even be present in some clinically uneventful pregnancies. Given that foam cells of atherosclerotic lesions are known to arise from smooth muscle cells or macrophages activated by multiple types of inflammatory stimulation, we have proposed that multiple forms of decidual vascular inflammation may cause acute atherosis, with or without poor remodeling and/or preeclampsia. Furthermore, we propose that acute atherosis may develop at different gestational ages, depending on the type and degree of the inflammatory insult. This review summarizes the current knowledge of spiral artery remodeling defects and acute atherosis in preeclampsia. Some controversies will be presented, including endovascular and interstitial trophoblast invasion depths, the concept of 2-stage trophoblast invasion, and whether the replacement of maternal spiral artery endothelium by fetal endovascular trophoblasts is permanent. We will discuss the role of acute atherosis in the pathophysiology of preeclampsia and short- and long-term health correlates. Finally, we suggest future opportunities for research on this intriguing uteroplacental interface between the mother and fetus.

Acute Atherosis Lesions at the Fetal-Maternal Border: Current Knowledge and Implications for Maternal Cardiovascular Health

Decidua basalis, the endometrium of pregnancy, is an important interface between maternal and fetal tissues, made up of both maternal and fetal cells. Acute atherosis is a uteroplacental spiral artery lesion. These patchy arterial wall lesions containing foam cells are predominantly found in the decidua basalis, at the tips of the maternal arteries, where they feed into the placental intervillous space. Acute atherosis is prevalent in preeclampsia and other obstetric syndromes such as fetal growth restriction. Causal factors and effects of acute atherosis remain uncertain. This is in part because decidua basalis is challenging to sample systematically and in large amounts following delivery. We summarize our decidua basalis vacuum suction method, which facilitates tissue-based studies of acute atherosis. We also describe our evidence-based research definition of acute atherosis. Here, we comprehensively review the existing literature on acute atherosis, its underlying mechanisms and possible short- and long-term effects. We propose that multiple pathways leading to decidual vascular inflammation may promote acute atherosis formation, with or without poor spiral artery remodeling and/or preeclampsia. These include maternal alloreactivity, ischemia-reperfusion injury, preexisting systemic inflammation, and microbial infection. The concept of acute atherosis as an inflammatory lesion is not novel. The lesions themselves have an inflammatory phenotype and resemble other arterial lesions of more extensively studied etiology. We discuss findings of concurrently dysregulated proteins involved in immune regulation and cardiovascular function in women with acute atherosis. We also propose a novel hypothesis linking cellular fetal microchimerism, which is prevalent in women with preeclampsia, with acute atherosis in pregnancy and future cardiovascular and neurovascular disease. Finally, women with a history of preeclampsia have an increased risk of premature cardiovascular disease. We review whether presence of acute atherosis may identify women at especially high risk for premature cardiovascular disease.

Pathogenesis of uteroplacental acute atherosis: An update on current research

Uteroplacental acute atherosis is a type of arterial vascular disease that affects the placenta during pregnancy and predominates in the maternal spiral arteries in the decidua basalis layer of the pregnant uterus. This condition is characterized by fibrin-like necrosis of the blood vessel walls, the accumulation of macrophages containing fat (foam cells), and the infiltration of macrophages around blood vessels. Uteroplacental acute atherosis is rare in normal pregnancy but occurs more frequently in patients with pregnancy complications, including preeclampsia, spontaneous preterm labor, preterm prelabor rupture of membranes, mid-trimester spontaneous abortion, fetal death, and small-for-gestational age. It is believed that the mechanisms underlying the development of uteroplacental acute atherosis are related to the incomplete physiological transformation of spiral arteries, placental inflammation, abnormal lipid metabolism, and oxidative stress. In this review, we describe the pathogenesis of uteroplacental acute atherosis to provide reference guidelines for the future prevention and treatment of uteroplacental acute atherosclerotic disease.

Hydroxychloroquine Mitigates the Production of 8-Isoprostane and Improves Vascular Dysfunction: Implications for Treating Preeclampsia

In preeclampsia, widespread maternal endothelial dysfunction is often secondary to excessive generation of placental-derived anti-angiogenic factors, including soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), along with proinflammatory cytokines such as tumour necrosis factor-α (TNF-α) and activin A, understanding of which offers potential opportunities for the development of novel therapies. The antimalarial hydroxychloroquine is an anti-inflammatory drug improving endothelial homeostasis in lupus. It has not been explored as to whether it can improve placental and endothelial function in preeclampsia. In this in vitro study, term placental explants were used to assess the effects of hydroxychloroquine on placental production of sFlt-1, sEng, TNF-α, activin A, and 8-isoprostane after exposure to hypoxic injury or oxidative stress. Similarly, human umbilical vein endothelial cells (HUVECs) were used to assess the effects of hydroxychloroquine on in vitro markers of endothelial dysfunction. Hydroxychloroquine had no effect on the release of sFlt-1, sEng, TNF-α, activin A, or 8-isoprostane from placental explants exposed to hypoxic injury or oxidative stress. However, hydroxychloroquine mitigated TNF-α-induced HUVEC production of 8-isoprostane and Nicotinanamide adenine dinucleotide phosphate (NADPH) oxidase expression. Hydroxychloroquine also mitigated TNF-α and preeclamptic serum-induced HUVEC monolayer permeability and rescued the loss of zona occludens protein zona occludens 1 (ZO-1). Although hydroxychloroquine had no apparent effects on trophoblast function, it may be a useful endothelial protectant in women presenting with preeclampsia.

The immunophenotype of decidual macrophages in acute atherosis

PROBLEM

Acute atherosis is a uteroplacental arterial lesion that is associated with pregnancy complications such as preeclampsia and preterm birth, the latter being the leading cause of perinatal morbidity and mortality worldwide. However, the immunobiology of acute atherosis is poorly understood.

METHOD OF STUDY

Placental basal plate samples were collected from women who delivered with (n = 11) and without (n = 31) decidua basalis lesions of acute atherosis. Multicolor flow cytometry was used to quantify M1- and M2-like macrophage subsets and the expression of iNOS and IL-12 by decidual macrophages. Multiplex fluorescence staining and phenoptics were performed to localize M1-, MOX-, and Mhem-like macrophages in the decidual basalis.

RESULTS

Macrophages displayed diverse phenotypes in the decidua basalis with acute atherosis. M2-like macrophages were the most abundant subset in the decidua; yet, this macrophage subset did not change with the presence of acute atherosis. Decidual M1-like macrophages were increased in acute atherosis, and such macrophages displayed a pro-inflammatory phenotype, as indicated by the expression of iNOS and IL-12. Decidual M1-like pro-inflammatory macrophages were localized near both transformed and non-transformed vessels in the decidua basalis with acute atherosis. MOX and Mhem macrophages were also identified near transformed vessels in the decidua basalis with acute atherosis. Finally, monocyte-like cells were present on the vessel wall of non-transformed decidual vessels, indicating a possible intravascular source for macrophages in acute atherosis.

CONCLUSION

Decidual macrophages display different phenotypes, namely M1-like, M2-like, MOX, and Mhem subsets. Yet, pro-inflammatory macrophages are enriched in the decidua basalis with acute atherosis. These findings provide a molecular foundation for future mechanistic inquiries about the role of pro-inflammatory macrophages in the pathogenesis of acute atherosis.

Inhibitory Effect of the Punica granatum Fruit Extract on Angiotensin-II Type I Receptor and Thromboxane B2 in Endothelial Cells Induced by Plasma from Preeclamptic Patients

This study aims to evaluate whether the Punica granatum fruit extract modulates the Angiotensin-II Type I receptor (AT1-R) and thromboxane B2 level in endothelial cells induced by plasma from preeclamptic patients. Endothelial cells were obtained from human umbilical vascular endothelial cells. At confluence, endothelial cells were divided into five groups, which included endothelial cells exposed to 2% plasma from normal pregnancy (NP), endothelial cells exposed to 2% plasma from preeclamptic patients (PP), and endothelial cells exposed to PP in the presence of ethanolic extract of Punica granatum (PP + PG) at the following three doses: 14; 28; and 56 ppm. The expression of AT1-R was observed by immunohistochemistry technique, and thromboxane B2 level was done by immunoassay technique. Plasma from PP significantly increased AT1-R expression and thromboxane B2 levels compared to cells treated by normal pregnancy plasma. The increasing of AT1-R expression significantly (P < 0.05) attenuated by high dose treatments of Punica granatum extract. Moreover, the increasing of thromboxane B2 levels significantly (P < 0.05) attenuated by lowest dose treatments of Punica granatum extract. We further concluded that Punica granatum fruit protects and inhibits the sensitivity of endothelial cells to plasma from preeclamptic patients due to inhibition of AT1-R expression (56 ppm) and reduced thromboxane B2 levels (14 ppm).

A transcriptional profile of the decidua in preeclampsia

OBJECTIVE

We sought to obtain insight into possible mechanisms underlying preeclampsia using genomewide transcriptional profiling in decidua basalis.

STUDY DESIGN

Genomewide transcriptional profiling was performed on decidua basalis tissue from preeclamptic (n = 37) and normal (n = 58) pregnancies. Differentially expressed genes were identified and merged into canonical pathways and networks.

RESULTS

Of the 26,504 expressed transcripts detected, 455 were differentially expressed (P < .05; false discovery rate, P < .1). Both novel (ARL5B, SLITRK4) and previously reported preeclampsia-associated (PLA2G7, HMOX1) genes were identified. Pathway analysis revealed that tryptophan metabolism, endoplasmic reticulum stress, linoleic acid metabolism, notch signaling, fatty acid metabolism, arachidonic acid metabolism, and NRF2-mediated oxidative stress response were overrepresented canonical pathways.

CONCLUSION

In the present study single genes, canonical pathways, and gene-gene networks that are likely to play an important role in the pathogenesis of preeclampsia have been identified. Future functional studies are needed to accomplish a greater understanding of the mechanisms involved.

Isoprostanes 8-iPF2alpha-III: risk markers of premature rupture of fetal membranes?

AIMS

Isoprostanes may serve as sensitive and specific markers of in vivo oxidative stress intensity. We wanted to determine, whether or not isoprostane concentration may be considered as a risk marker of premature rupture of fetal membranes (PROM).

METHODS

On the basis of the presence of PROM and gestational maturity, a total of 128 patients were divided into: (1) preterm PROM (pPROM) group; (2) PROM at term group; (3) control preterm (C1) group and (4) control at term (C2) group. The concentrations of 8-iPF(2alpha)-III were determined using the enzyme-linked immunosorbent assay method.

RESULTS

The mean free isoprostane concentrations, examined in amniotic fluid and maternal plasma in the PROM at term patients were significantly higher than in C2 individuals (p < 0.01). The mean concentrations of free 8-iPF(2alpha)-III measured in blood plasma from women in the C1 group were significantly lower than in patients from the pPROM, PROM at term and C2 groups (p < 0.001, p < 0.00001 and p < 0.00001, respectively).

CONCLUSION

The measurement of free isoprostane concentration in maternal plasma and amniotic fluid may be considered as a laboratory marker of a PROM-risk pregnancy.

Predominant basal directional release of thromboxane, but not prostacyclin, by placental trophoblasts from normal and preeclamptic pregnancies

OBJECTIVE

To investigate apical and basal releases of thromboxane (TX) and prostacyclin (PGI2) by trophoblasts (TCs) from normal and preeclamptic (PE) placentas.

METHODS

TCs isolated from normal and PE placentas were incubated in cell culture inserts for 48h. Medium from the upper (apical) and the lower (basal) chambers were then collected separately and measured for TX and PGI2 by their stable metabolites of TXB2 and 6-keto PGF1alpha by ELISA. Apical and basal releases of TX and PGI were also examined with apical exposure of TCs to arachidonic acid (AA)+/-aspirin at different concentrations. Villous tissue expressions for PGI synthase, TX synthase and TX (TP) receptor were examined by immunohistochemistry.

RESULTS

(1) TXB2, but not 6-keto PGF1alpha, concentrations were significantly higher in the lower than in the upper chambers with both normal and PE TCs (p<0.01); (2) apical exposure of TCs to AA resulted in a significant increase in TX release towards both the upper and the lower chambers in normal TCs (p<0.01), but only a significant increase in the upper chamber in PE TCs (p<0.01); (3) aspirin could attenuate AA-induced TX release both in the upper and the lower chambers in normal, but not in PE, TCs (p<0.01), respectively; (4) there were no differences in 6-keto PGF1alpha productions both in normal and PE TCs treated with AA+/-aspirin; (5) intense staining of TX synthase and TP receptor was seen in syncytiotrophoblast layer, villous core vessels and stromal cells in preeclamptic placental tissue sections.

CONCLUSION

Predominant basal release of TX together with intense staining of TX synthase and TP receptor in trophoblasts, stromal cells and villous core vessels are found in placentas from PE. We speculate if predominant basal release of TX by TCs occurs in vivo as we found in our in vitro culture condition, basal released TX may play a significant role in increased placental vasoconstriction such as in PE.

Impact of atorvastatin treatment on platelet-activating factor acetylhydrolase and 15-F(2trans)-isoprostane in hypercholesterolaemic patients

AIMS

Isoprostanes are the product of free radical oxidation of arachidonic acid, whose hydrolysis from phospholipids is presumably catalysed by phospholipases A(2) (PLA(2)s) such as group IIA or V PLA(2)s, or group VII PLA(2)[platelet-activating factor acetylhydrolase (PAF-AH), lipoprotein-associated phospholipase]. Atorvastatin reduces concentrations of low-density lipoprotein (LDL), with which PAF-AH is associated, and PLA(2)s' protein concentrations. We investigated the effect of atorvastatin on PLA(2)s and PAF-AH activity and the urinary excretion of 15-F(2trans)-isoprostane (15-F(2t)-IsoP, 8-iso-PGF(2alpha), iPF(2alpha)-III).

METHODS

Twenty-four hypercholesterolaemic individuals naive to lipid-lowering therapy were randomized to atorvastatin 40 mg or placebo for 6 weeks. The 15-F(2t)-isoP urinary excretion (gas chromatography/mass spectrometry), PAF-AH and group IIA and V PLA(2) activities (photometry) were assessed at baseline and end-point.

RESULTS

At end-point, 15-F(2t)-isoP urinary excretion concentrations as well as PLA(2)s' activity were unchanged under atorvastatin (mean change 0.21 +/- 1.79 ng h(-1), 95% confidence interval -0.92, 1.35 and 0.33 +/- 0.94 nmol min(-1) ml(-1), -0.27, 0.93) and under placebo (mean change 0.69 +/- 1.69 ng h(-1), -0.52, 1.90 and 1.29 +/- 2.16 nmol min(-1) ml(-1), -0.25, 2.84). Atorvastatin treatment decreased total (P < 0.001) and LDL-cholesterol (P < 0.001) but had no effect on high-density lipoprotein. PAF-AH activity was lowered in the atorvastatin group (mean change - 5.27+/- 1.96 nmol min(-1) ml(-1), -6.51, -4.03, P < 0.001) but not in the placebo group (mean change 1.02 +/- 1.64 nmol min(-1) ml(-1), 0.15, 2.20), and the change in PAF-AH activity was correlated with that in total (P = 0.03) and LDL-cholesterol (P = 0.03).

CONCLUSION

Our results show a lowering effect of atorvastatin on PAF-AH activity associated with its lipid-lowering effect and exclude a key role of PAF-AH in the liberation of 15-F(2t)-isoP from phospholipids.

Augmented oxidative stress as well as antioxidant capacity in maternal circulation in preeclampsia

OBJECTIVES

Isoprostanes are stable markers of oxidative stress. We wanted to assess maternal circulating levels of total 8-isoprostane and indices of antioxidant capacity in preeclampsia compared to uneventful pregnancies.

STUDY DESIGN

Total 8-isoprostane concentrations, FRAP (ferric reducing ability of plasma), Vitamin E and d-ROM (diacron reactive oxygen metabolites) were measured in maternal venous blood samples from preeclamptic (n=21) and uncomplicated (n=38) pregnancies at cesarean section.

RESULTS

Median total 8-isoprostane concentration was elevated in preeclampsia compared to uncomplicated pregnancies (354 and 218 pg/mL, P=0.02). Median FRAP level was also elevated in preeclampsia compared to uncomplicated pregnancies, but to a lesser degree than 8-isoprostane. A positive correlation between 8-isoprostane and previously analyzed placenta-derived sFlt1 (soluble fms-like tyrosine kinase 1) levels in the maternal circulation was found in preeclampsia.

CONCLUSION

We found a relative more increase for the oxidative stress marker (8-isoprostane) than for the antioxidant capacity (FRAP) in preeclampsia compared to uneventful pregnancies.

Increased phospholipase A2 and thromboxane but not prostacyclin production by placental trophoblast cells from normal and preeclamptic pregnancies cultured under hypoxia condition

In this study we determined whether hypoxia could promote vasoactivator thromboxane (TX) and prostacyclin (PGI2) as well as phospholipase A2 (PLA2) production by placental trophoblast cells (TCs) from normal and preeclamptic (PE) pregnancies. Placentas were obtained immediately after delivery from normal (n=9) and preeclamptic (n=9) pregnancies. TCs were isolated by dispase digestion of villous tissue and purified by Percoll gradient centrifugation. TCs (5x10(6) cells/well) were cultured with Dulbecco's Modified Eagles Medium (DMEM) under hypoxia condition (2% O2/5% CO2/93% N2) for 48 h. TCs cultured under normoxia condition (5% CO2/air) were used as control. Culture medium was collected at the end of incubation. Productions for TX, PGI2 and PLA2 were measured by ACE competitive enzyme immunoassay (EIA). Comparisons were made using the Mann-Whitney U test or paired t-test and the data are expressed as mean+/-SE (pg/microg cellular protein). Significance was set at a p-value of <0.05. We found: (1) PE-TCs produced more TXB2 and PLA2 than normal-TCs under normoxia conditions, TXB2: 4.33+/-1.03 vs. 1.84+/-0.29 pg/microg protein, p<0.05; PLA2: 0.38+/-0.08 vs. 0.21+/-0.03 pg/microg protein, p<0.05, respectively. (2) Hypoxia promoted both PE- and normal-TCs to generate more TXB2 and PLA2, TXB2: 6.36+/-1.72 vs. 3.05+/-0.45 pg/microg; PLA2: 0.52+/-0.10 vs. 0.30+/-0.04 pg/microg, respectively. (3) No change in 6-keto PGF1alpha production was observed for normal-TCs or PE-TCs when compared under normoxia vs. hypoxia condition, normal-TCs: 0.20+/-0.05 vs. 0.21+/-0.05 pg/microg; PE-TCs: 0.38+/-0.05 vs. 0.36+/-0.04 pg/microg, respectively. We concluded that hypoxia promotes both PLA2 and TX, but not PGI2, production by placental trophoblast cells cultured under hypoxia condition. These results suggest that increased PLA2 release may alter the arachidonic acid cascade and promote TX synthesis. Relative hypoxia could contribute to the increase in TX production and result in vasoconstriction in placental vasculature in preeclampsia.