Pre-eclampsia and cytokine induced oxidative stress

Analysis of the evolution of placental oxidative stress research from a bibliometric perspective

Background

Research on placental oxidative stress is pivotal for comprehending pregnancy-related physiological changes and disease mechanisms. Despite recent advancements, a comprehensive review of current status, hotspots, and trends remains challenging. This bibliometric study systematically analyzes the evolution of placental oxidative stress research, offering a reference for future studies.

Objective

To conduct a comprehensive bibliometric analysis of the literature on placental oxidative stress to identify research hotspots, trends, and key contributors, thereby providing guidance for future research.

Methods

Relevant data were retrieved from the Web of Science Core Collection database and analyzed using VOSviewer, CiteSpace, and the bibliometrix package. An in-depth analysis of 4,796 publications was conducted, focusing on publication year, country/region, institution, author, journal, references, and keywords. Data collection concluded on 29 April 2024.

Results

A total of 4,796 papers were retrieved from 1,173 journals, authored by 18,835 researchers from 4,257 institutions across 103 countries/regions. From 1991 to 2023, annual publications on placental oxidative stress increased from 7 to 359. The United States (1,222 publications, 64,158 citations), the University of Cambridge (125 publications, 13,562 citations), and Graham J. Burton (73 publications, 11,182 citations) were the most productive country, institution, and author, respectively. The journal Placenta had the highest number of publications (329) and citations (17,152), followed by the International Journal of Molecular Sciences (122 publications). The most frequent keywords were "oxidative stress," "expression," "pregnancy," "preeclampsia," and "lipid peroxidation." Emerging high-frequency keywords included "gestational diabetes mellitus," "health," "autophagy," "pathophysiology," "infection," "preterm birth," "stem cell," and "inflammation."

Conclusion

Over the past 3 decades, research has concentrated on oxidative stress processes, antioxidant mechanisms, pregnancy-related diseases, and gene expression regulation. Current research frontiers involve exploring pathophysiology and mechanisms, assessing emerging risk factors and environmental impacts, advancing cell biology and stem cell research, and understanding the complex interactions of inflammation and immune regulation. These studies elucidate the mechanisms of placental oxidative stress, offering essential scientific evidence for future intervention strategies, therapeutic approaches, and public health policies.

Paradoxes: Cholesterol and Hypoxia in Preeclampsia

Preeclampsia, a hypertensive disease of pregnancy of unknown etiology, is intensely studied as a model of cardiovascular disease (CVD) not only due to multiple shared pathologic elements but also because changes that develop over decades in CVD appear and resolve within days in preeclampsia. Those affected by preeclampsia and their offspring experience increased lifetime risks of CVD. At the systemic level, preeclampsia is characterized by increased cellular, membrane, and blood levels of cholesterol; however, cholesterol-dependent signaling, such as canonical Wnt/βcatenin, Hedgehog, and endothelial nitric oxide synthase, is downregulated indicating a cholesterol deficit with the upregulation of cholesterol synthesis and efflux. Hypoxia-related signaling in preeclampsia also appears to be paradoxical with increased Hypoxia-Inducible Factors in the placenta but measurably increased oxygen in maternal blood in placental villous spaces. This review addresses the molecular mechanisms by which excessive systemic cholesterol and deficient cholesterol-dependent signaling may arise from the effects of dietary lipid variance and environmental membrane modifiers causing the cellular hypoxia that characterizes preeclampsia.

Pentoxifylline as a therapeutic option for pre-eclampsia: a study on its placental effects

BACKGROUND AND PURPOSE

Recently pentoxifylline, a non-selective phosphodiesterase inhibitor and adenosine receptor antagonist, has attracted much interest for the treatment of the increased vascular resistance and endothelial dysfunction in pre-eclampsia. We therefore investigated the placental transfer, vascular effects and anti-inflammatory actions of pentoxifylline in healthy and pre-eclamptic human placentas.

EXPERIMENTAL APPROACH

The placental transfer and metabolism of pentoxifylline were studied using ex vivo placenta perfusion experiments. In wire myography experiments with chorionic plate arteries, pentoxifyllines vasodilator properties were investigated, focusing on the cGMP and cAMP pathways and adenosine receptors. Its effects on inflammatory factors were also studied in placental explants.

KEY RESULTS

Pentoxifylline transferred from the maternal to foetal circulation, reaching identical concentrations. The placenta metabolized pentoxifylline into its active metabolite lisofylline (M1), which was released into both circulations. In healthy placentas, pentoxifylline potentiated cAMP- and cGMP-induced vasodilation, as well as causing vasodilation by adenosine A₁ antagonism and via NO synthase and PKG. Pentoxifylline also reduced inflammatory factors secretion. In pre-eclamptic placentas, we observed that its vasodilator capacity was preserved, however not via NO-PKG but likely through adenosine signalling. Pentoxifylline neither potentiated vasodilation through cAMP and cGMP, nor suppressed the release of inflammatory factors from these placentas.

CONCLUSION AND IMPLICATIONS

Pentoxifylline is transferred across and metabolized by the placenta. Its beneficial effects on the NO pathway and inflammation are not retained in pre-eclampsia, limiting its application in this disease, although it could be useful for other placenta-related disorders. Future studies might focus on selective A₁ receptor antagonists as a new treatment for pre-eclampsia.

Long-Term Consequences of Placental Vascular Pathology on the Maternal and Offspring Cardiovascular Systems

Over the last thirty years, evidence has been accumulating that Hypertensive Disorders of Pregnancy (HDP) and, specifically, Preeclampsia (PE) produce not only long-term effects on the pregnant woman, but have also lasting consequences for the fetus. At the core of these consequences is the phenomenon known as defective deep placentation, being present in virtually every major obstetrical syndrome. The profound placental vascular lesions characteristic of this pathology can induce long-term adverse consequences for the pregnant woman's entire arterial system. In addition, placental growth restriction and function can, in turn, cause a decreased blood supply to the fetus, with long-lasting effects. Women with a history of HDP have an increased risk of Cardiovascular Diseases (CVD) compared with women with normal pregnancies. Specifically, these subjects are at a future higher risk of: Hypertension; Coronary artery disease; Heart failure; Peripheral vascular disease; Cerebrovascular accidents (Stroke); CVD-related mortality. Vascular pathology in pregnancy and CVD may share a common etiology and may have common risk factors, which are unmasked by the "stress" of pregnancy. It is also possible that the future occurrence of a CVD may be the consequence of endothelial dysfunction generated by pregnancy-induced hypertension that persists after delivery. Although biochemical and biophysical markers of PE abound, information on markers for a comparative evaluation in the various groups is still lacking. Long-term consequences for the fetus are an integral part of the theory of a fetal origin of a number of adult diseases, known as the Barker hypothesis. Indeed, intrauterine malnutrition and fetal growth restriction represent significant risk factors for the development of chronic hypertension, diabetes, stroke and death from coronary artery disease in adults. Other factors will also influence the development later in life of hypertension, coronary and myocardial disease; they include parental genetic disposition, epigenetic modifications, endothelial dysfunction, concurrent intrauterine exposures, and the lifestyle of the affected individual.

Copper and ceruloplasmin levels are closely related to the severity of preeclampsia

Objective: The aim of this study was to investigate the maternal serum concentrations of copper (Cu) and ceruloplasmin (CP) in patients with mild preeclampsia, severe preeclampsia, hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome, and to determine their association with the severity of the disease.Methods: This study was carried out at the largest tertiary care health center in the southeast region in Turkey and Department of Obstetrics and Gynecology, Dicle University Hospital. A total of 179 pregnant women, including 58 healthy pregnant women and 71 mild preeclampsia, 26 severe preeclampsia, and 24 HELLP syndrome cases classified according to the American College of Obstetricians and Gynecologists' 2013 guidelines were included in this prospective study. Blood samples were taken from all the pregnant women to evaluate the serum Cu and CP levels. The Cu level was determined via atomic absorption/emission spectroscopy, while the serum CP level was assessed with a nephelometric assay using an automatic image analyzer. Spearman's rank correlation tests were used to determine the correlations between the serum levels of the antioxidative markers and the preeclampsia severity.Results: The mean ± SD of the Cu was 81.2 ± 11.84 µg/dl in the mild preeclampsia cases and 160.2 ± 20.89 µg/dl in the severe preeclampsia cases (p < .001). The mean ± SD of the CP was 33.0 ± 4.81 mg/dl in the mild preeclampsia cases and 65.3 ± 9.17 mg/dl in the severe preeclampsia cases (p < .001). The Cu and CP levels were significantly higher in the patients with HELLP syndrome, which is an advanced and more severe form of severe preeclampsia, than in the mild and severe preeclampsia patients (p < .001 and p < .001, respectively). Therefore, the serum Cu and CP levels were correlated with the severity of preeclampsia (r = 859, p < .001 and r = 786, p < .001, respectively). In addition, there was a positive correlation between the serum Cu and CP levels and the systolic and diastolic blood pressure values and aspartate amino transferase levels (AST), and a negative correlation between the serum Cu and CP levels and the platelet count.Conclusion: This was the first study in which the ceruloplasmin and Cu levels were investigated in HELLP syndrome patients. When considering the results obtained in the present study, there were significant relationships between the Cu, CP levels which are the markers of oxidative stress and the preeclampsia severity.

Biochemical markers of placental dysfunction in assisted conception

A possible mechanism for poor perinatal outcomes in singleton pregnancies conceived following assisted reproductive technologies (ART) and those conceived naturally following a period of infertility (>12 months) is thought to be placental dysfunction. This was investigated by measuring plasma concentrations of biochemical markers: (i) soluble fms-like tyrosine kinase1 (sFlt1); (ii) placental growth factor (PlGF); (iii) leptin; and (iv) plasminogen activator inhibitor 2 (PAI-2), serially at four antenatal time points. Baseline concentrations of each marker after delivery were also measured. The control group was naturally conceived singleton pregnancies with no history of infertility. Non-smoking, age-matched nulliparous women with no significant medical history were recruited to all groups. The ART group had significantly lower mean plasma concentrations of PlGF at all antenatal time points compared to the control group (p < 0.001). The subfertility (SF) group had significantly higher mean serum concentrations of leptin than the other groups at all time points (p < 0.001), even after correction for body mass index. There were no significant differences in sFlt1 and PAI-2 concentrations between the groups. Low plasma PlGF concentrations in the ART group might suggest abnormal placentation and/or abnormal function in ART pregnancies with relevance to pathogenesis of pregnancy complications in these women.

Hypothesis: Pentoxifylline explores new horizons in treatment of preeclampsia

Preeclampsia, the leading cause of maternal morbidity and perinatal mortality, initiates as inappropriate immune response to trophoblastic invasion impairs placentation and placental circulation. A poorly perfused placenta generates superoxide anions as well as anti-angiogenic factors and this series of events result in impairment of endothelial function, followed by maternal morbidities such as hypertension, kidney injury and proteinuria. Renal loss of anti-coagulant proteins and subsequent hyper-coagulable state along with endothelial dysfunction accelerates progression of the disease toward eclampsia. Since Pentoxifylline, a methyl-xanthine derivative known for enhancement of vascular endothelial function, down-regulation of many inflammatory cytokines increased during preeclampsia, improvement of placental circulation, reduction of ischemia-reperfusion injury, enhancement of vasodilatation and endothelial function, ameliorating proteinuria, inhibition of platelet aggregation and decreasing risk of preterm labor, which are all amongst morbidities of preeclampsia, here it is hypothesized that Pentoxifylline prevents development of preeclampsia and/or decelerate progression of the disease.

Severe preeclampsia: association of genes polymorphisms and maternal cytokines production in Brazilian population

INTRODUCTION

Preeclampsia (PE) is a multi-system disorder of pregnancy characterized by hypertension and proteinuria. Healthy pregnancy is associated with a controlled inflammatory process, which is exacerbated in PE in response to excessive placental stimuli. Gene expression levels can affect inflammation and immune regulation. It is known that differences in cytokine allele frequencies amongst populations may contribute to difference in the incidence of several diseases.

OBJECTIVE

The aim of this study was to investigate the frequency of TNF-α, IL-6, IFN-γ and IL-10 genes polymorphisms and their relationship with the cytokines plasma levels in PE.

METHODS

A total of 281 women were included in this study; 116 with severe PE, 107 normotensive pregnant and 58 non-pregnant women. Cytokine genotyping was carried out by the polymerase chain reaction. The analyzed polymorphisms were: TNF-α (-308 G→A), IL-10 (-1082 G→A), IL-6 (-174 G→C), and IFN-γ (+874 A→T). Cytokine plasma levels were measured by Cytometric Bead Array method.

RESULTS

A higher frequency of the IFN-γ (+874) T/T genotype in severe PE comparing to normotensive pregnant women was found (P<0.001). TNF-α, IL-6 and IFN-γ plasma levels were higher in PE women compared to non-pregnant women (P<0.001; P<0.001; P=0.004). IL-6 and IFN-γ levels were also higher in PE women compared to normotensive pregnant (P<0.001; P=0.010). IL-10 levels were higher in normotensive pregnant women compared to PE (P<0.001). IFN-γ and IL-6 genes polymorphisms influenced the genic expression in PE and normotensive pregnant women, respectively.

CONCLUSIONS

These results suggest that IFN-γ seems to play a role in PE occurrence.

A review of the mechanism for poor placentation in early-onset preeclampsia: the role of autophagy in trophoblast invasion and vascular remodeling

Shallow trophoblast invasion and impaired vascular remodeling of spiral arteries have been recognized in early-onset preeclampsia. Placentation and vascular remodeling are multistep processes, and hypoxia, placental oxidative stress, excessive or atypical maternal immune response to trophoblasts, exaggerated inflammation, and increased production of anti-angiogenic factors such as the soluble form of the vascular endothelial growth factor (VEGF) receptor (sFlt-1) and soluble endoglin (sENG) may play a role in poor placentation in preeclampsia. Recent findings suggest that autophagy plays an important role in extravillous trophoblast (EVT) invasion and vascular remodeling under hypoxia, and sENG inhibits EVT invasion and vascular remodeling by the inhibition of autophagy under hypoxic conditions. In this review, we discuss the relationship between inadequate autophagy and poor placentation in preeclampsia.

Serum Cholesterol and Ceruloplasmin Levels in Second Trimester can Predict Development of Pre-eclampsia

Background:

Pre-eclampsia is one of the leading causes of high rates of maternal and perinatal mortality and morbidity. Pathophysiology of pre-eclampsia is still obscure. Currently, there are no screening tests for pre-eclampsia that are reliable, valid, and economical. Parameters of oxidative stress could be early markers of endothelial dysfunction that predates clinical pre-eclampsia.

Aim:

This study was to study ceruloplasmin in nulliparous women as marker of oxidative stress and lipid profile to evaluate their value in prediction of pre-eclampsia.

Materials and Methods:

Prospective observational study. 306 nulliparous women had their serum lipid profile and ceruloplasmin levels measured at 14-16 weeks period of gestation as sample 1 and at 18-20 weeks as sample 2. All cases were followed up till the end of pregnancy for development of pre-eclampsia.

Results:

There was no statistically significant difference between the normals and pre-eclampsia cases at 14-16 week for all the oxidative stress parameters (P > 0.05), but at 18-20 week, there was statistically significant difference between the normals and pre-eclampsia cases in cholesterol and ceruloplasmin parameters (P < 0.05).

Conclusion:

Cholesterol and ceruloplasmin levels in second trimester (18-20 weeks) can predict the development of pre-eclampsia.

Assessment of placental oxidative stress in pre-eclampsia

OBJECTIVE

To study oxidative stress in placental tissue as well as in serum in pre-eclamptic women.

METHODS

Fifty pre-eclamptic cases and fifty normal pregnant women were selected in the study. Thio barbituric acid reacting substances (TBARS) was measured as oxidative stress marker and superoxide dismutase (SOD) and GSH (reduced glutathione) were measured for assessment of antioxidant status in placental tissue extract and serum.

RESULTS

TBARS and SOD activity were increased significantly (P < 0.001) in both placental homogenate and serum in pre-eclamptic women. Level of GSH was not altered much.

CONCLUSION

Placental oxidative stress can be assessed by measuring serum oxidative stress markers and this may help in prevention of further progress of this condition.

Analysis of the original causes of placental oxidative stress in normal pregnancy and pre-eclampsia: a hypothesis

Pre-eclampsia (PE) and eclampsia remain enigmatic despite intensive research. Growing evidence suggests that placental oxidative stress (OS) is involved in the etiopathogenesis of pre-eclampsia. Reduced perfusion as a result of abnormal placentation was proposed to be responsible for placental OS in PE. However, placental OS was also observed in normal pregnancy. The exact differences and correlation of placental OS in PE and normal pregnancy remain elusive. In this review, we attempted to link both normal pregnancy and PE on the causes of placental OS and proposed a hypothesis that placental OS in normal pregnancy, plus the exploration of other placental and/or maternal factors, could provide a novel explanation of that in PE. We concluded that pregnancy, placental abnormality and preexisting maternal constitutional conditions are three principle factors that could contribute to placental OS in PE. The specific causes in each clinical case could be heterogeneous, which requires individual analysis.

Measurement of the placental total antioxidant status in preeclamptic women using a novel automated method

AIM

We aimed to measure the levels of total antioxidant status (TAS) in placental samples from preeclamptic pregnant women and evaluate the relation of placental TAS, total oxidant status (TOS) and oxidative stress index (OSI) with fetomaternal compartments using the more recently designated Erel method.

MATERIAL AND METHODS

Thirty four preeclamptic and 27 normotensive pregnant women were enrolled in this prospective controlled study. Subjects were selected from women attending the Obstetrics and Gynecology Department of Gaziantep University. TAS, TOS, OSI were measured from placental, maternal and cord blood samples using a novel automated method. Statistical analyses were performed with SPSS for Windows version 13.0 (SPSS Inc., Chicago, IL, USA).

RESULTS

The TAS level of the placenta was evaluated as significantly lower (P<0.001) in preeclamptic women compared to normotensive women. In preeclamptic pregnancies, while the placental TAS level was not correlated with placental TOS level, the TAS levels of maternal plasma (P<0.001; r=0.584) and cord plasma (P<0.005; r=0.529) were significantly correlated with the TOS level of the placenta.

CONCLUSION

Our results support the concept that placental defective response to an oxidant stimulus plays a central role in the etiopathogenesis of preeclampsia by using the novel automated Erel method.

Association of tumor necrosis factor-alpha and interleukin-10 gene polymorphisms in Iranian patients with pre-eclampsia

PROBLEM

Considering that certain cytokines may change during pre-eclampsia (PE), because of functional polymorphisms in their genes, our purpose was to determine the association between tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) gene polymorphisms and development of PE.

METHOD OF STUDY

The genetic polymorphisms of TNF-alpha and IL-10 was studied by polymerase chain reaction-sequence specific primers in the DNA of peripheral blood cell from 160 patients with PE and 100 healthy pregnant women.

RESULTS

We found a significant difference between TNF-alpha A allele (-308) and G allele (-238) in PE patients compared with those of the control groups. A significantly higher C/C genotype frequency of IL-10 (-592 and -819) was observed in the PE patients than in the control groups. In addition, the frequencies of three common IL-10 haplotypes (GCC, ACC, and ATA) did not show any significant difference between the study groups.

CONCLUSION

These findings would support the concept of contribution of TNF-alpha and IL-10 gene polymorphisms in the pathogenesis of PE in our population.

The role of antioxidant vitamins in hypertensive disorders of pregnancy

Preeclampsia (PE) is an important and a leading cause of both maternal morbidity and adverse perinatal outcomes. Despite progress in perinatal medicine for patients with an established diagnosis of PE, a therapeutic approach other than termination of pregnancy was unsuccessful. Women predisposed to PE begin pregnancy with a certain degree of endothelial dysfunction, a lesion that precedes shallow placentation. The proposed sequence of events comprises endothelial dysfunction, defective trophoblast invasion, and consequential impaired placental perfusion, immune maladaptation and inflammation. The possible link between these could be oxidative stress by excessive production of reactive oxygen species coupled with inadequate or overwhelmed antioxidant defense mechanisms. These defense mechanisms, involving antioxidant vitamins and enzyme systems, may restrain the extent of damage caused by oxidative stress. Markers of oxidative stress in women with established PE were confirmed. Accordingly, these findings support an expected beneficial effect of antioxidant therapy in the prevention of PE and other pregnancy-related disorders. Numerous studies have been carried out in order to investigate this possible and simple prophylactic and/or therapeutic approach in prevention of oxidative stress and eventual reduction of PE and its perinatal complications. In this review the role of vitamin antioxidants in prevention and treatment of PE is discussed. Despite the logic behind using antioxidant vitamins, the data, thus far, are at best conflicting.

Murine Pre-Eclampsia Induced by Unspecific Activation of the Immune System Correlates with Alterations in the eNOS and AT1 Receptor Expression in the Kidneys and Placenta

It remains arguable if an animal model can be of use in pre-eclampsia (PE) studies, as it is clearly a human disease not observed spontaneously in other species. The aim of this study was to investigate whether PE-like signs in mice inoculated with activated Th1 cells were accompanied by abnormal expression of molecules related to the regulation of blood pressure, viz. nitric oxide synthase enzymes (eNOS and iNOS) and angiotensin (Ang) II receptors (AT1R and AT2R), in order to analyse the relevance of this model for human disease. In this model, C57/BL6-mated BALB/c females received lymphocytes crosslined with anti-CD3 and cultured with interleukin (IL)-2 and IL-12 to mimic PE pathology. Control mice received PBS. eNOS, iNOS and AT1R but not AT2R expression was augmented in the kidneys of PE-mice compared with control pregnant mice. The expression of eNOS but not of iNOS was augmented at the fetal-maternal interface of PE-mice as compared with the controls. NOSs regulate the synthesis of NO, a blood pressure and parturition mediator. As its expression is increased in PE patients, our data suggest that the Th1 cells-induced signs in this model are due to similar mechanisms as in humans. AT1R and AT2R mediate the effect of Ang II, and particularly the AT1R appears to be involved in the pathogenesis of human PE. The increased AT1R expression in the kidneys of PE-mice reinforces the theory that Th1 cells elicit a pathological situation closely resembling the human PE. All together, our data support the use of this animal model to study mechanisms underlying clinically overt PE.

Preeclampsia activates circulating immune cells with engagement of the NF-kappaB pathway

PROBLEM

Compelling evidence implicates peripheral immune activation in the pathophysiology of preeclampsia. Polymorphonuclear neutrophils appear to be the cells most strongly affected, with changes in expression of surface markers and release of granule enzymes. Here, we investigated activation in additional leukocyte populations among women with preeclampsia.

METHOD

We used flow cytometry to evaluate changes in leukocyte markers in preeclampsia compared with uncomplicated pregnancy. To gain insights into intracellular pathways involved in leukocyte activation, we monitored the NF-kappaB signal transduction pathway. Plasma levels of interleukin-6 (IL-6) were also studied as an additional indication of cellular activation.

RESULTS

Preeclampsia is associated with changes in L-selectin (CD62L) on neutrophils (P = 0.004), monocytes (P = 0.013), and T cells (P = 0.048) when compared with normal pregnancy. These changes include an increase in nuclear translocation of NF-kappaB and increased levels of IL-6 (P = 0.005).

CONCLUSIONS

These findings are consistent with the presence of a generalized phenomenon of immune activation in preeclampsia.

Placental-related diseases of pregnancy: Involvement of oxidative stress and implications in human evolution

Miscarriage and pre-eclampsia are the most common disorders of human pregnancy. Both are placental-related and exceptional in other mammalian species. Ultrasound imaging has enabled events during early pregnancy to be visualized in vivo for the first time. As a result, a new understanding of the early materno-fetal relationship has emerged and, with it, new insight into the pathogenesis of these disorders. Unifying the two is the concept of placental oxidative stress, with associated necrosis and apoptosis of the trophoblastic epithelium of the placental villous tree. In normal pregnancies, the earliest stages of development take place in a low oxygen (O2) environment. This physiological hypoxia of the early gestational sac protects the developing fetus against the deleterious and teratogenic effects of O2 free radicals (OFRs). In miscarriage, development of the placento-decidual interface is severely impaired leading to early and widespread onset of maternal blood flow and major oxidative degeneration. This mechanism is common to all miscarriages, with the time at which it occurs in the first trimester depending on the aetiology. In contrast, in pre-eclampsia the trophoblastic invasion is sufficient to allow early pregnancy phases of placentation but too shallow for complete transformation of the arterial utero-placental circulation, predisposing to a repetitive ischaemia-reperfusion (I/R) phenomenon. We suggest that pre-eclampsia is a three-stage disorder with the primary pathology being an excessive or atypical maternal immune response. This would impair the placentation process leading to chronic oxidative stress in the placenta and finally to diffuse maternal endothelial cell dysfunction.

Shared and disparate components of the pathophysiologies of fetal growth restriction and preeclampsia

Intrauterine growth restriction (IUGR) and preeclampsia differ in their association with maternal disease but share a similar placental pathology. Moreover, mothers who have had pregnancies complicated by preeclampsia or IUGR are at elevated later-life cardiovascular risk. Why, then, do some women develop IUGR and others develop preeclampsia? In this clinical opinion, based on a review of the literature, we hypothesize that both women experiencing preeclampsia and IUGR enter pregnancy with some degree of endothelial dysfunction, a lesion that predisposes to shallow placentation. In our opinion, preeclampsia develops when abnormal placentation, through the mediator of elevated circulating cytokines, interacts with maternal metabolic syndrome, comprised of adiposity, insulin resistance/hyperglycemia, hyperlipidemia, and coagulopathy. IUGR develops in the absence of antenatal metabolic syndrome. Among these women, the baby is affected by shallow placentation but the mother does not develop clinically apparent disease. This conceptualization provides a testable framework for future etiologic studies of preeclampsia and IUGR.

Pre-eclampsia is not associated with changes in the levels of regulatory T cells in peripheral blood

PROBLEM

The acceptance of the semi-allogeneic fetus within the maternal environment requires tolerance mechanisms not fully characterized yet. Normal pregnancy is known to be associated with a Th2 profile. Furthermore, regulatory T cells (Tregs) were proposed to regulate the Th2/Th1 balance at early stages of pregnancy. Treg may avoid the shift to a Th1 profile, thus preventing miscarriage. Accordingly, spontaneous abortion is characterized by a Th1 dominance and diminished levels of Treg. The major aim of the present work was to investigate if pre-eclampsia, a late immunological complication of pregnancy, is characterized by similar hallmarks.

METHOD OF STUDY

We measured the surface antigens CD4, CD25, CD8 and CTLA4 in peripheral blood from patients suffering from pre-eclampsia (n = 8) and age-matched patients undergoing normal pregnancies (n = 9) by four-color flow cytometry.

RESULTS

We were not able to find any significant differences in the levels of CD4(+), CD25(+), CD8(+), CTLA4, CD4(+)/CD25(+), CD4(+)/CD25(bright), CD4(+)/CTLA4, CD25(+)/CTLA4, CD4(+)/CD25(+)/CTLA4, CD8(+)/CD25(+), CD8(+)/CTLA4 or CD8(+)/CD25(+)/CTLA4 cell subsets.

CONCLUSIONS

Our data confirm comparable number of Tregs during pre-eclampsia and normal pregnancy in peripheral blood. Other regulatory mechanisms might be involved during late pregnancy.

Total peroxyl radical-trapping ability and anti-oxidant vitamins of the umbilical venous plasma and the placenta in pre-eclampsia

AIM

Our purpose was to investigate lipid peroxide levels, total peroxyl radical-trapping anti-oxidative parameter (TRAP) values, and anti-oxidant vitamin levels in umbilical venous plasma and placental tissues, and to evaluate their roles in the pathophysiology of pre-eclampsia.

METHODS

Samples of umbilical venous plasma and placental tissue homogenates were obtained from 23 normal and 18 pre-eclamptic women at between 33 and 40 weeks' gestation. The enzyme-linked immunosorbent assay method was used to assay alpha-tumor necrosis factor (TNF-alpha), and lipid peroxide levels were measured by thiobarbituric acid reaction. The TRAP values were measured using the modified Wayner's method. Ascorbic acid, retinol alpha-tocopherol and gamma-tocopherol were measured by high performance liquid chromatography.

RESULTS

Levels of TNF-alpha in placental tissue homogenates of women with pre-eclampsia were significantly higher than those of women with normal pregnancy (21.4 +/- 3.39 v. 10.3 +/- 1.06 pg/mL, P < 0.05). Lipid peroxide levels in umbilical venous plasma and placental tissue homogenates of women with pre-eclampsia were significantly higher than those of women with normal pregnancy (10.3 +/- 1.1 v. 5.85 +/- 0.53, P < 0.01, 5.14 +/- 0.40 v. 3.99 +/- 0.33 nmol/mg protein, P < 0.05, respectively). The TRAP values in umbilical venous plasma and placental tissue homogenates of women with pre-eclampsia were significantly lower than those of women with normal pregnancy (0.39 +/- 0.02 v. 0.45 +/- 0.02, P < 0.05, 0.27 +/- 0.02 v. 0.34 +/- 0.03 mM, P < 0.05, respectively). Ascorbic acid levels in umbilical venous plasma and placental tissue homogenates of women with pre-eclampsia were significantly lower than those of women with normal pregnancy (325.4 +/- 50.4 v. 543 +/- 73.8, P < 0.05, 219.0 +/- 21.0 v. 333.3 +/- 32.6 nmol/mL, P < 0.05, respectively).

CONCLUSIONS

The above results suggest that increased oxidative stress in the placenta is involved in the pathophysiology of pre-eclampsia, and ascorbic acid may act as an important preventative factor in the development of pre-eclampsia.

Determination of Interleukin-6 and Tumor Necrosis Factor-alpha concentrations in Iranian-Khorasanian patients with preeclampsia

Background

Our objective was to determine the role of Interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-alpha), markers of immune activation and endothelial dysfunction, in patients with preeclampsia.

Methods

Twenty four women with preeclampsia and eighteen antepartum normotensive pregnant women were recruited as controls. Serum levels of IL-6 and TNF-alpha were measured by enzyme-linked immunosorbent assay. We used independent-samples t test to assess the differences in the concentration of cytokines in preeclamptic patients and control subjects.

Results

IL-6 levels [mean (S.D.)] were significantly higher in preeclamptic women [5.8 (4.85) pg/ml] compared to normal pregnant women [3.01 (2.45) pg/ml] (p = 0.02). There was no significant change in concentration of TNF-alpha in preeclamptic women [53.8 (30.0) pg/ml] compared to normal pregnant women [51.9 (33.8) pg/ml] (p > 0.1).

Conclusion

The results of this study show that IL-6 as a pro-inflammatory cytokine is present in higher concentration in women with preeclampsia. The study was undertaken in women with established preeclampsia and it is not possible to determine whether the increased concentration of IL-6 is a cause or consequence of the disease. Furthermore, these findings suggest that serum TNF-alpha level is not associated with preeclampsia.

Tumor Necrosis Factor-α in the Placenta is not Elevated in Pre-eclamptic Patients Despite its Elevation in Peripheral Blood

PROBLEM

Tumor necrosis factor-alpha (TNF-alpha) is present in human placental and uterine cells at the early and late stages of gestation and promotes the regulation of trophoblast growth and invasion. We evaluated whether TNF-alpha levels in the placenta and blood of pre-eclamptic women differed from those with normal pregnancies.

METHOD OF STUDY

The subjects were 39 pregnant women carrying single fetuses (21 normal-pregnant and 18 pre-eclamptic patients). Their average gestational age at entry was 38-39 weeks. Peripheral blood was collected before the onset of labor and separated serum was stored at -20 degrees C. A tissue segment of the placenta was cut and frozen in liquid nitrogen immediately after delivery at -80 degrees C. The frozen placental tissue was added to phosphate-buffered saline. The tissue was fully homogenized and centrifuged. Separated supernatant was stored at -80 degrees C. TNF-alpha levels in separated serum and TNF-alpha and total protein (TP) levels in separated supernatant were measured. The presence of TNF-alpha in the placenta was evaluated by immunohistochemistry in five pre-eclamptic and five normal-pregnant patients.

RESULTS

Serum TNF-alpha levels were higher in pre-eclampsia than in normal pregnancies. However, TNF-alpha/TP levels in the placenta did not differ significantly between the two groups. As for TNF-alpha immunostaining of trophoblastic cells in the placenta, it was weak in three and moderate in two of the normal pregnancies, while it was absent in two, weak in one, and moderate in two in the pre-eclampsia group.

CONCLUSIONS

We demonstrated no significant increase in TNF-alpha/TP levels in the placenta in pre-eclampsia despite a significant increase in serum TNF-alpha levels. There was no strong immunostaining for TNF-alpha detected by immunohistochemistry in the pre-eclampsia group. These findings suggest that TNF-alpha in the placenta is not a key cytokine to interfere with normal trophoblast invasion into the myometrium in pre-eclampsia, and that sources other than the placenta may contribute to the elevated levels of TNF-alpha found in the circulation of pre-eclamptic patients.

Th1/Th2 balance in preeclampsia

The syndrome of preeclampsia has previously been ascribed to generalized maternal endothelial dysfunction, poor placentation and excessive maternal inflammatory response. Recent reports suggest that preeclampsia is associated with a Th1 predominant profile and may be considered as a failure of the tolerance system allowing the second physiological trophoblastic invasion. In this review, we discuss that Th1 predominant immunity is closely related to inflammation, endothelial dysfunction and poor placentation.

Xanthine oxidase activation in mild gestational hypertension

OBJECTIVE

We hypothesized that activation of the xanthine oxidase (XO) enzyme system is a potential source of free radicals in pregnancy-induced hypertension (PIH).

METHODS

A prospective observational study was carried out on 16 pregnant women who met the criteria of gestational hypertension [rise in blood pressure (BP) of 30 mm Hg systolic or 15 mm Hg diastolic after 20 weeks gestation or BP>140/90 mm Hg if earlier pressure is unknown] without proteinuria or any signs of renal impairment. Fourteen women with a clinically normal pregnancy matched for maternal age, parity, and gestational age acted as pregnant controls. Nonpregnant control women were members of the laboratory staff ( n=15).

MAIN OUTCOME MEASURES

Concentrations of free sulfhydryl (SH) groups, purine catabolites, lipid peroxidation products in plasma, and blood carboxyhemoglobin levels were used to follow oxidative stress and potential hemolysis. A noninvasive measurement of functional XO activity was carried out (i.e., the urinary ratio of the two metabolites of caffeine was estimated).

RESULTS

A pronounced oxidative stress was demonstrated in plasma samples of patients with hypertension by the elevated concentrations of uric acid and lipid peroxidation products. A reduced level of free sulfhydryl groups and an increased concentration of hypoxanthine (HX) were shown in normotensive pregnant individuals. The XO activity index was substantially higher in overweight pregnant subjects with mild hypertension [0.849+/-0.096 ( p<0.01)] than in normotensive pregnant women or in age-matched nonpregnant subjects [0.596+/-0.105, 0.542+/-0.049 (means+/-SD), respectively].

CONCLUSIONS

Our study of mildly hypertensive pregnant subjects provides additional evidence of the putative role of XO activation as a source of free radicals in the early stage of endothelial dysfunction.

Cytokines of the placenta and extra-placental membranes: roles and regulation during human pregnancy and parturition

Summary In an earlier, companion, review, we concluded that cytokines produced by the placenta and associated membranes are likely to be involved in control of the processes of implantation and placental development (Bowen et al., 2002). In this review, we discuss evidence that cytokines continue to be part of a paracrine/autocrine regulatory network in the placenta and membranes throughout the mid and late stages of gestation. Cytokines are involved in regulation of placental growth during these later stages of pregnancy and also function to protect the fetus from pathological organisms. The evidence, while not entirely consistent, suggests that production of certain cytokines within the extraplacental membranes is altered during normal term parturition, whereas in the villous placenta evidence of labour-associated changes is much more equivocal. Roles for cytokines have been postulated in many facets of parturition, including expulsion of the fetus by uterine contractions, membrane rupture, and dilation of the cervix. Imbalances and disruptions to the cytokine milieu have been implicated in a number of diseases of pregnancy involving abnormalities of both placental growth/establishment and initiation of parturition. Cytokine secretion induced by intrauterine infection is associated with increased occurrence or severity of some neonatal diseases. This wealth of data supports the view that cytokines are an integral part of a functional regulatory/communication network operating within the placental-maternal unit during normal gestation.

Endothelial junctional protein redistribution and increased monolayer permeability in human umbilical vein endothelial cells isolated during preeclampsia

OBJECTIVE

To examine monolayer permeability and junctional protein distribution and expression in endothelial cells isolated from women with preeclampsia and from women with normal pregnancies. We hypothesized that increased endothelial monolayer permeability in preeclampsia reflects altered monolayer barrier properties produced by disorganization of endothelial cell junction proteins.

STUDY DESIGN

Endothelial cells were isolated from umbilical veins from women with normal pregnancies (n = 9) and from women with preeclampsia (n = 9) immediately after delivery. In the first passage of endothelial cells, the permeability was determined by measurement of horseradish peroxidase passage through confluent cell monolayers grown on transwell filters, and the distribution and protein expression of vascular endothelial cadherin and occludin were evaluated by use of immunofluorescent staining of the proteins and Western blot analysis. The distribution of vascular endothelial cadherin was also evaluated in the second and third passage endothelial cells. Messenger ribonucleic acid expression of vascular endothelial cadherin and occludin were examined by reverse transcriptase polymerase chain reaction. Data were expressed as mean values (+/- SE) and were analyzed by use of an unpaired t test.

RESULTS

The relative monolayer permeability was significantly increased in the endothelial cells isolated from women with preeclampsia compared with those isolated from women with normal pregnancies (0.271 +/- 0.049 versus 0.086 +/- 0.031 for DeltaOD(470); P <.05). Vascular endothelial cadherin expression for normal endothelial cells showed a continuous staining of the junctional protein that surrounded cell borders. In comparison, vascular endothelial cadherin in endothelial cells from preeclamptic pregnancies exhibited disorganized staining and vascular endothelial cadherin fibrils were retracted, with gaps present at the cell borders. The expression of occludin showed a pattern similar to that of vascular endothelial cadherin in both normal and preeclamptic conditions. Western blot results for expression of vascular endothelial cadherin and occludin also showed decreased expression of junctional proteins. The altered endothelial cell junctional protein distribution and expression of vascular endothelial cadherin and occludin observed in the first passage of endothelial cells from preeclamptic pregnancies was restored to normal by the time cells reached the third passage in vitro. There was no statistical difference in mRNA expression for the vascular endothelial cadherin and occludin between normal endothelial cells and those from preeclamptic pregnancies.

CONCLUSION

In preeclampsia, increased endothelial cell monolayer permeability appears to reflect disorganized and diminished expression of endothelial cell junctional proteins. The latter response is mediated at the posttranscriptional level. These findings provide new insights about the cellular and molecular basis for altered endothelial cell integrity and barrier dysfunction that are associated with preeclampsia.

Predictive value of tumor necrosis factor alpha (TNF-alpha) in preeclampsia

OBJECTIVE

To assess the measurement of plasma tumor necrosis factor alpha (TNF-alpha) as a predictive test for the development of preeclampsia.

STUDY DESIGN

One-hundred and twenty pregnant women were included in this prospective longitudinal study. Maternal plasma TNF-alpha levels were measured in the first, second and third trimesters by immunosorbent assay (ELISA). Preeclamptic patients were determined prospectively. Preeclamptic and normotensive patients were compared to assess the predictive value of TNF-alpha in preeclampsia.

RESULTS

Ninety patients completed the study. Preeclampsia developed in 10 out of 90 patients (11.1%). Plasma TNF-alpha levels were higher in preeclamptic patients than normotensive women in the third trimester of pregnancy (P<0.05). No difference was found between groups in the first and second trimesters (P>0.05). With the use of the receiver operating characteristics (ROC) 10.13 pg/ml was found to be a cut-off value predictive for the development of preeclampsia in the third trimester, but cut-off values in the first and second trimesters could not be found. The specificity, sensitivity, positive and negative predictive values were 90, 78, 33 and 98%, respectively.

CONCLUSION

This study shows that plasma TNF-alpha levels are not useful as a specific marker for prediction of preeclampsia in the first and second trimesters. But determination of TNF-alpha may be useful for the prediction in the early third trimester.

Lack of association of severe preeclampsia with maternal and fetal mutant alleles for tumor necrosis factor alpha and lymphotoxin alpha genes and plasma tumor necrosis factor alpha levels

OBJECTIVE

The purpose of this study was to determine whether the increased frequency of mutant alleles of the gene for tumor necrosis factor alpha and elevated maternal and fetal plasma levels of tumor necrosis factor alpha were associated with severe preeclampsia.

STUDY DESIGN

We performed a prospective cross-sectional study involving 112 patients with severe preeclampsia matched for gestational age with 106 normotensive pregnant women. Deoxyribonucleic acid for restriction fragment length polymorphism analysis was extracted from maternal and fetal blood. Two mutations associated with the gene for tumor necrosis factor alpha were assayed by polymerase chain reaction. Polymerase chain reaction products were digested with the restriction enzyme Ncol and then fractionated by gel electrophoresis. Genotypic frequencies were calculated. Maternal and fetal plasma tumor necrosis factor alpha levels were assayed by the dual monoclonal antibody sandwich enzyme-linked immunosorbent assay technique. The chi2 test, the Fisher exact test, the Student t test, and the Mann-Whitney test were performed to calculate statistical significance.

RESULTS

The differences in the genotypic frequencies of the two loci were not significant in either maternal or fetal samples between control women and women with pregnancies complicated by severe preeclampsia. There was no statistical difference in median maternal plasma levels of tumor necrosis factor alpha between control subjects (0.0 pg/mL) and patients with severe preeclampsia (2.5 pg/mL; P =.36). Unexpectedly, fetal plasma tumor necrosis factor alpha levels were found to be significantly elevated in control women (18.4 pg/mL) relative to women with severe preeclampsia (9.1 pg/mL; P <.0001).

CONCLUSION

Neither the genotypic frequencies for tumor necrosis factor alpha mutant alleles nor maternal tumor necrosis factor alpha plasma levels were increased in patients with severe preeclampsia.

Cytokine levels in midtrimester amniotic fluid in normal pregnancy and in the prediction of pre-eclampsia

Midtrimester amniotic fluid cytokines may reflect the function of the maternal immune system in the maternal-fetal interface and thus be predictive of pre-eclampsia. We determined the concentrations of interleukin (IL)-6, IL-8, IL-10, IL-11, IL-12, IL-15, tumour necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta in amniotic fluid at 14-16 weeks of gestation from women with normal pregnancies and from those who subsequently developed severe pre-eclampsia. The concentrations of the cytokines in amniotic fluid did not significantly differ between patients and normal controls. The median concentration of IL-6 was 950 pg/ml in normal pregnant women and 578 pg/ml in the patient group. The median concentration of IL-8 was 606 pg/ml in normal controls and 294 pg/ml in the patient group. The levels of IL-6, IL-8 and TGF-beta correlated positively with each other. TNF-alpha concentrations were low and similar in both groups. IL-10 and IL-12 were detected at very low levels in 37 and 7% of the samples, respectively. No difference was found in IL-15 concentrations between the groups. IL-11 was found only at low levels in both groups. Although none of the cytokines measured was predictive of pre-eclampsia, this study provides information of cytokines in amniotic fluid during the period when the spiral arteries are remodelled.

The effects of vascular endothelial growth factor on endothelial cells: a potential role in preeclampsia

OBJECTIVES

Preeclampsia is primarily a disorder of the maternal endothelium. An as yet unidentified circulating factor causes widespread alteration in endothelial function, and levels of vascular endothelial growth factor are elevated in preeclampsia. We hypothesized that vascular endothelial growth factor is involved in the alteration of endothelial function and set out to find further evidence for this contention.

STUDY DESIGN

Bovine microvascular endothelial cells (B-88) were cultured in vitro. These cultured cells were then stimulated with vascular endothelial growth factor and with plasma from women with preeclampsia in the presence and absence of anti-vascular endothelial growth factor antibody. Prostacyclin, nitric oxide, and lactate dehydrogenase levels were measured.

RESULTS

Vascular endothelial growth factor induced a significant concentration-dependent increase in prostacyclin production but not nitric oxide production. Cells stimulated with plasma from women with preeclampsia showed increases in production of both prostacyclin and nitric oxide. Vascular endothelial growth factor concentration in plasma was correlated with prostacyclin production by stimulated cells. The increase in prostacyclin production that usually followed the addition of plasma did not occur when anti-vascular endothelial growth factor antibody was present.

CONCLUSIONS

Vascular endothelial growth factor has the ability to alter endothelial cell function in a manner analogous to that of plasma from women with preeclampsia.

The immunology of preeclampsia

The immune maladaptation hypothesis of preeclampsia is concordant with cytokine-mediated oxidative stress, chronology of endothelial activation, lipid changes, adverse effect of changing partners, and the protective effect of sperm exposure. Genetic factors may involve underlying hereditary thrombophilic disorders and hyperhomocysteinemia, essential hypertension and/or obesity, or control of the Th1/Th2 balance and thus affect the maternal response against fetal antigens. Placental ischemia and increased syncytiotrophoblast deportation are probably end-stage disease phenomena.

Plasma tumor necrosis factor-alpha soluble receptor p55 (sTNFp55) concentrations in eclamptic, preeclamptic and normotensive pregnant Zimbabwean women

We sought to examine the relationship between excessive tumor necrosis factor-alpha (TNF-alpha) release (as measured by sTNFp55 plasma concentrations) and risk of eclampsia and preeclampsia, respectively, among sub-Saharan African women delivering at Harare Maternity Hospital, Zimbabwe. In total, 33 pregnant women with eclampsia, 138 women with preeclampsia and 185 normotensive women were included in a case-control study conducted during the period, June 1995 through April 1996. Postpartum plasma sTNFp55 was measured by enzyme linked immunosorbent assay. Women with eclampsia had significantly higher sTNFp55 than normotensive controls (1.87 vs 1.35 ng/ml, P<0.001). Similarly, women with preeclampsia had sTNFp55 concentrations higher than normotensive controls (1.69 vs 1.35 ng/ml, P < 0.001). The odds ratio for eclampsia was 5.00 (adjusted odds ratio (OR) 5.00, 95% confidence interval (CI) 1.20-20.92) among women in the highest quartile of the control sTNFp55 distribution compared with women in the lowest quartile. The corresponding odds ratio and 95% CI for preeclampsia was 2.37 (1.11-5.06). Postpartum plasma sTNFp55 concentrations are increased among Zimbabwean women with eclampsia and preeclampsia as compared with their normotensive counterparts. These findings are consistent with the hypothesized role of cytokines in mediating endothelial dysfunction and the pathogenesis of preeclampsia/eclampsia. Additional work is needed to identify modifiable risk factors for the excessive synthesis and release of TNF-alpha in pregnancy; and to assess whether measurements of sTNFp55 early in pregnancy may be used to identify women likely to benefit from anti-inflammatory therapy.

Etiology and pathogenesis of preeclampsia: current concepts

The etiology of preeclampsia is unknown. At present, 4 hypotheses are the subject of extensive investigation, as follows: (1) Placental ischemia-Increased trophoblast deportation, as a consequence of ischemia, may inflict endothelial cell dysfunction. (2) Very low-density lipoprotein versus toxicity-preventing activity-In compensation for increased energy demand during pregnancy, nonesterified fatty acids are mobilized. In women with low albumin concentrations, transporting extra nonesterified fatty acids from adipose tissues to the liver is likely to reduce albumin's antitoxic activity to a point at which very-low density lipoprotein toxicity is expressed. (3) Immune maladaptation-Interaction between decidual leukocytes and invading cytotrophoblast cells is essential for normal trophoblast invasion and development. Immune maladaptation may cause shallow invasion of spiral arteries by endovascular cytotrophoblast cells and endothelial cell dysfunction mediated by an increased decidual release of cytokines, proteolytic enzymes, and free radical species. (4) Genetic imprinting-Development of preeclampsia-eclampsia may be based on a single recessive gene or a dominant gene with incomplete penetrance. Penetrance may be dependent on fetal genotype. The possibility of genetic imprinting should be considered in future genetic investigations of preeclampsia.

Circulating levels of immunoreactive cytokines in women with preeclampsia

PROBLEM

Circulating inflammatory cytokines have been implicated in the pathogenesis of preeclampsia. To test this hypothesis, we measured plasma levels of immunoreactive tumor necrosis factor (TNF)-alpha and -beta, interleukin (IL)-1 alpha and -beta, and IL-6 and -10 in women with preeclampsia, in women with transient gestational hypertension, and throughout normal pregnancy.

METHOD OF STUDY

Enzyme-linked immunosorbent assays were used and subjected to extensive validation studies.

RESULTS

The median concentration of plasma TNF-alpha was increased by twofold in women with preeclampsia compared with that in normal third-trimester pregnancy (P < 0.001) and in women with gestational hypertension (P < 0.04). The median concentration of plasma IL-6 was increased by threefold in women with preeclampsia compared with that in normal third-trimester pregnancy (P < 0.001) and increased twofold compared with that in women with gestational hypertension (P < 0.1). There were no significant differences observed in the levels of plasma IL-1 beta and IL-10 between the preeclamptic and other subject groups. The level of IL-1 beta, but not the levels of IL-10, TNF-alpha, or IL-6, was significantly changed during normal pregnancy compared with the nonpregnant condition manifesting an overall decline (P < 0.04). TNF-beta and IL-1 alpha were not detected in any samples, possibly because of the low sensitivity of these particular immunoassays.

CONCLUSION

Elevated levels of TNF-alpha and IL-6 may contribute to the putative endothelial dysfunction of preeclampsia.

Elevated IL-6 in midtrimester amniotic fluid is involved with the onset of preeclampsia

PROBLEM

The primary defect of placental development in preeclampsia is speculated to occur at midtrimester gestation. Abnormal feto-maternal immune reactions have been considered as factors in such defective placentation.

METHOD OF STUDY

Midtrimester amniotic fluid specimens were retrospectively identified as coming from gestations that later had severe preeclampsia develop, gestations with normal outcomes, and gestations measured for cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL-1 beta, IL-6, and IL-8). The effect of each cytokine on thrombomodulin levels was tested in cultured trophoblast cells.

RESULTS

Among the measured cytokines, IL-6 and IL-8 were significantly elevated in the midtrimester amniotic fluid of the future preeclamptic group. Trophoblasts stimulated with TNF-alpha plus IL-6 had significantly decreased levels of cellular thrombomodulin compared to those without cytokine addition.

CONCLUSIONS

Elevated cytokines in midtrimester amniotic fluid suggest an abnormal fetomaternal immune response occurring before the clinical manifestation of preeclampsia. Cytokine-induced suppression of thrombomodulin in trophoblasts may be directly involved in the pathogenesis of preeclampsia.

Oxidation of erythrocyte glutathione by monocytes stimulated with interleukin-6. Analysis by 1H spin echo NMR

1H spin echo NMR was used to follow the release of reactive oxygen species (ROS) from human monocytes by monitoring erythrocyte glutathione status, which is sensitive to applied oxidative stress. This allowed the ability of the cytokine interleukin-6 (IL-6) to stimulate release of ROS from monocytes to be assessed in terms of oxidative damage to other cells, providing an estimation of its importance in vivo. It was found that incubation of monocytes with erythrocytes in the presence of IL-6 resulted in oxidation of the erythrocyte glutathione pool, indicating that oxidants are released in sufficient amounts to cause oxidative stress. High levels of IL-6 occurring in plasma of women with severe pre-eclampsia could therefore be responsible for depleted plasma antioxidants and haemolysis. The oxidation of erythrocyte glutathione was inhibited by the presence of the cyclooxygenase inhibitor indomethacin, suggesting that this may be of value in the treatment of oxidative pathologies.

Decreased first trimester uric acid production in future preeclamptic patients

The relationship between first trimester uric acid production and later development of pregnancy induced hypertensive disorders (PIHD) was investigated. An anti-oxidant role for uric acid has been mentioned. Since uric acid and fibronectin (PF) are both markers of preeclampsia, the relationship between these two substances was also studied. Controls (n = 72) and patients with PIHD (n = 120) were selected. Uric acid was measured in serum and 24-hours urine samples (uric acid excretion) and PF in blood plasma in 270 nulliparous women at 13 +/- 2 weeks of gestation. Uric acid excretion was significantly lower in the first trimester in a group of patients who later develop PIHD as compared to patients who remain normotensive (p < 0.05), especially when corrected for body weight (p < 0.01). Patients with elevated PF levels in the first trimester showed a significantly lower uric acid excretion than patients with normal PF levels (p < 0.05). The data show diminished uric acid production in patients who will likely develop preeclampsia suggesting an impaired anti-oxidant production in the first trimester. This observation fits well with the hypothesis that an imbalance between anti-oxidant and oxidants plays an important role in the pathogenesis of preeclampsia.

Evidence for an elevation in serum interleukin-2 and tumor necrosis factor-alpha levels before the clinical manifestations of preeclampsia

PROBLEM

The purpose of this study is to clarify whether the disruption of immune regulation occurs in early pregnancy before the clinical manifestations of preeclampsia.

METHOD OF STUDY

The serum concentrations of interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-alpha) were determined by using enzyme-linked immunoadsorbent assay (ELISA) in the first trimester of pregnancy in women who had preeclampsia develop after 28 weeks of pregnancy (preeclamptic group) and in women who completed pregnancy uneventfully (control group).

RESULTS

Serum concentrations of both IL-2 and TNF-alpha in the first trimester of the preeclamptic group were significantly higher than those of the control group.

CONCLUSIONS

That the perturbation of feto-maternal immune regulation may precede the clinical manifestations of preeclampsia, which may be of relevance in the development of preeclampsia, is suggested.

Placental cytokines and the pathogenesis of preeclampsia

The authors explore the hypothesis that tumor necrosis factor-alpha (TNF-alpha) and possibly other inflammatory cytokines are overproduced by the placenta in response to local ischemia/hypoxia contributing to increased plasma levels, and subsequent endothelial activation and dysfunction in the pregnancy disorder, preeclampsia. It is widely held that inadequate trophoblast invasion and physiologic remodeling of spiral arteries initiate placental ischemia/hypoxia in preeclampsia. Furthermore, focal areas of placental hypoxia have been implicated in the production of "toxic" factor(s) by the placenta, which circulate and cause maternal disease. Placental trophoblast cells and fetoplacental macrophages normally produce TNF-alpha and interleukin-1 (IL-1), which are capable of producing endothelial cell activation and dysfunction. Hypoxia has recently been reported to increase TNF-alpha and IL-1 production by term villous explants from the human placenta. Placental cells also express erythropoietin (EPO), which is the prototype molecule for transcriptional regulation by hypoxia in mammals. Interestingly, TNF-alpha and IL-1 have DNA sequence homologous or nearly homologous to the hypoxia-responsive enhancer element of the EPO gene, thus providing a potential, but as of yet, untested molecular link between placental hypoxia and stimulation of cytokine production. Inflammatory cytokines overproduced by the placenta in response to hypoxia may then lead to increased plasma levels and endothelial activation and dysfunction in preeclampsia. The purpose of this short review is to critically evaluate the hypothesis that placental cytokines contribute to the pathogenesis of preeclampsia. Of note, the etiology of the disease presumably related to deficient trophoblast invasion is beyond the scope of this work.

Endothelial dysfunction in preeclampsia. Part I: Primary prevention. Therapeutic perspectives

Endothelial dysfunction is the final common pathway in the pathogenesis of preeclampsia. Future therapeutic modalities aimed at preventing or treating preeclampsia should either reduce the extent of (or even prevent) endothelial cell dysfunction (primary prevention) or should reduce the consequences of endothelial cell dysfunction (secondary and tertiary prevention). Relevant potential and promising directions for further research will be discussed. Part I of this review concerns the primary prevention of preeclampsia. The etiology of preeclampsia is still unknown. The 4 hypotheses that are the most popular currently are the placental ischemia hypothesis, the immune maladaptation/spiral artery-decidual ¿toxin' hypothesis, the VLDL (very low density lipoproteins)/TxPA (toxicity preventing activity) hypothesis, and the genetic hypothesis. For the near future only the disturbed VLDL/TxPA balance and the imbalance between free radicals and scavengers appear to be amenable for clinical research purposes.