Fetal hemoglobin and α1-microglobulin as first- and early second-trimester predictive biomarkers for preeclampsia

Prediction of pre-eclampsia

Pre-eclampsia is a leading cause of neonatal and maternal mortality and morbidity that complicates approximately 2-8% of all pregnancies worldwide. The precise cause of pre-eclampsia is not completely understood, with several environmental, genetic, and maternal factors involved in its pathogenesis and pathophysiology. An accurate predictor of pre-eclampsia will facilitate early recognition, close surveillance according to the individual risk and early intervention, and reduce the negative consequences of the disorder. Current evidence shows that no single test predicts pre-eclampsia with sufficient accuracy to be clinically useful. A combination of markers into multiparametric models may provide a more useful and feasible predictive tool for pre-eclampsia screening in the routine care setting than a test of either component alone. This review presents a summary of the current advances on prediction of pre-eclampsia, highlighting their performance and applicability. Key priorities when conducting research on predicting pre-eclampsia are also analyzed.

The roles of free iron, heme, haemoglobin, and the scavenger proteins haemopexin and alpha-1-microglobulin in preeclampsia and fetal growth restriction

BACKGROUND

Preeclampsia (PE) is a complex pregnancy syndrome characterised by maternal hypertension and organ damage after 20 weeks of gestation and is associated with an increased risk of cardiovascular disease later in life. Extracellular haemoglobin (Hb) and its metabolites heme and iron are highly toxic molecules and several defence mechanisms have evolved to protect the tissue.

OBJECTIVES

We will discuss the roles of free iron, heme, Hb, and the scavenger proteins haemopexin and alpha-1-microglobulin in pregnancies complicated by PE and fetal growth restriction (FGR).

CONCLUSION

In PE, oxidative stress causes syncytiotrophoblast (STB) stress and increased shedding of placental STB-derived extracellular vesicles (STBEV). The level in maternal circulation correlates with the severity of hypertension and supports the involvement of STBEVs in causing maternal symptoms in PE. In PE and FGR, iron homeostasis is changed, and iron levels significantly correlate with the severity of the disease. The normal increase in plasma volume taking place during pregnancy is less for PE and FGR and therefore have a different impact on, for example, iron concentration, compared to normal pregnancy. Excess iron promotes ferroptosis is suggested to play a role in trophoblast stress and lipotoxicity. Non-erythroid α-globin regulates vasodilation through the endothelial nitric oxide synthase pathway, and hypoxia-induced α-globin expression in STBs in PE placentas is suggested to contribute to hypertension in PE. Underlying placental pathology in PE with and without FGR might be amplified by iron and heme overload causing oxidative stress and ferroptosis. As the placenta becomes stressed, the release of STBEVs increases and affects the maternal vasculature.

Hypoxia-Induced Alpha-Globin Expression in Syncytiotrophoblasts Mimics the Pattern Observed in Preeclamptic Placentas

Preeclampsia (PE) is a pregnancy disorder associated with placental dysfunction and elevated fetal hemoglobin (HbF). Early in pregnancy the placenta harbors hematopoietic stem and progenitor cells (HSPCs) and is an extramedullary source of erythropoiesis. However, globin expression is not unique to erythroid cells and can be triggered by hypoxia. To investigate the role of the placenta in increasing globin levels previously reported in PE, flow cytometry, histological and immunostaining and in situ analyses were used on placenta samples and ex vivo explant cultures. Our results indicated that in PE pregnancies, placental HSPC homing and erythropoiesis were not affected. Non-erythroid alpha-globin mRNA and protein, but not gamma-globin, were detected in syncytiotrophoblasts and stroma of PE placenta samples. Similarly, alpha-globin protein and mRNA were upregulated in normal placenta explants cultured in hypoxia. The upregulation was independent of HIF1 and NRF2, the two main candidates of globin transcription in non-erythroid cells. Our study is the first to demonstrate alpha-globin mRNA expression in syncytiotrophoblasts in PE, induced by hypoxia. However, gamma-globin was only expressed in erythrocytes. We conclude that alpha-globin, but not HbF, is expressed in placental syncytiotrophoblasts in PE and may contribute to the pathology of the disease.

Structure, Functions, and Physiological Roles of the Lipocalin α1-Microglobulin (A1M)

α₁-microglobulin (A1M) is found in all vertebrates including humans. A1M was, together with retinol-binding protein and β-lactoglobulin, one of the three original lipocalins when the family first was proposed in 1985. A1M is described as an antioxidant and tissue cleaning protein with reductase, heme- and radical-binding activities. These biochemical properties are driven by a strongly electronegative surface-exposed thiol group, C34, on loop 1 of the open end of the lipocalin barrel. A1M has been shown to have protective effects in vitro and in vivo in cell-, organ-, and animal models of oxidative stress-related medical conditions. The gene coding for A1M is unique among lipocalins since it is flanked downstream by four exons coding for another non-lipocalin protein, bikunin, and is consequently named α₁-microglobulin-bikunin precursor gene (AMBP). The precursor is cleaved in the Golgi, and A1M and bikunin are secreted from the cell separately. Recent publications have suggested novel physiological roles of A1M in regulation of endoplasmic reticulum activities and erythrocyte homeostasis. This review summarizes the present knowledge of the structure and functions of the lipocalin A1M and presents a current model of its biological role(s).

Knockout of the radical scavenger α1-microglobulin in mice results in defective bikunin synthesis, endoplasmic reticulum stress and increased body weight

α₁-microglobulin (A1M) is a ubiquitous protein with reductase and radical- and heme-binding properties. The protein is mainly expressed in the liver and encoded by the α₁-microglobulin-bikunin precursor (AMBP) gene together with the plasma proteinase inhibitor bikunin. The AMBP polypeptide is translated, glycosylated and the C-terminal bikunin part linked via a chondroitin sulfate glycosaminoglycan chain to one or two heavy chains in the endoplasmic reticulum (ER) and Golgi compartments. After proteolytic cleavage, the A1M protein and complexed bikunin parts are secreted separately. The complete physiological role of A1M, and the reason for the co-synthesis with bikunin, are both still unknown. The aim of this work was to develop an A1M knockout (A1M-KO) mouse model lacking expression of A1M, but with a preserved bikunin expression, and to study the phenotypic traits in these mice, with a focus on hepatic endoplasmic reticulum (ER) function. The bikunin expression was increased in the A1M-KO mouse livers, while the bikunin levels in plasma were decreased, indicating a defective biosynthesis of bikunin. The A1M-KO livers also showed an increased expression of transducers of the unfolded protein response (UPR), indicating an increased ER-stress in the livers. At twelve months of age, the A1M-KO mice also displayed an increased body weight, and an increased liver weight and lipid accumulation. Moreover, the KO mice showed an increased expression of endogenous antioxidants in the liver, but not in the kidneys. Together, these results suggest a physiological role of A1M as a regulator of the intracellular redox environment and more specifically the ER folding and posttranslational modification processes, particularly in the liver.

The Role of α1-Microglobulin (A1M) in Erythropoiesis and Erythrocyte Homeostasis-Therapeutic Opportunities in Hemolytic Conditions

α₁-microglobulin (A1M) is a small protein present in vertebrates including humans. It has several physiologically relevant properties, including binding of heme and radicals as well as enzymatic reduction, that are used in the protection of cells and tissue. Research has revealed that A1M can ameliorate heme and ROS-induced injuries in cell cultures, organs, explants and animal models. Recently, it was shown that A1M could reduce hemolysis in vitro, observed with several different types of insults and sources of RBCs. In addition, in a recently published study, it was observed that mice lacking A1M (A1M-KO) developed a macrocytic anemia phenotype. Altogether, this suggests that A1M may have a role in RBC development, stability and turnover. This opens up the possibility of utilizing A1M for therapeutic purposes in pathological conditions involving erythropoietic and hemolytic abnormalities. Here, we provide an overview of A1M and its potential therapeutic effect in the context of the following erythropoietic and hemolytic conditions: Diamond-Blackfan anemia (DBA), 5q-minus myelodysplastic syndrome (5q-MDS), blood transfusions (including storage), intraventricular hemorrhage (IVH), preeclampsia (PE) and atherosclerosis.

Hemopexin and α1-microglobulin heme scavengers with differential involvement in preeclampsia and fetal growth restriction

Hemopexin and α1-microglobulin act as scavengers to eliminate free heme-groups responsible for hemoglobin-induced oxidative stress. The present study evaluated maternal and fetal plasma concentrations of these scavengers in the different phenotypes of placenta-mediated disorders. Singleton pregnancies with normotensive fetal growth restriction [FGR] (n = 47), preeclampsia without FGR (n = 45) and preeclampsia with FGR (n = 51) were included prospectively as well as uncomplicated pregnancies (n = 49). Samples were collected at delivery and ELISA analysis was applied to measure the hemopexin and α1-microglobulin concentrations. In maternal blood in preeclampsia with and without FGR, hemopexin was significantly lower (p = 0.003 and p<0.001, respectively) and α1-microglobulin was significantly higher (p<0.001 in both) whereas no difference existed in normotensive FGR mothers compared to controls. In contrast, in fetal blood in growth restricted fetuses with and without preeclampsia, both hemopexin and α1-microglobulin were significantly lower (p<0.001 and p = 0.001 for hemopexin, p = 0.016 and p = 0.013 for α1-microglobulin, respectively) with no difference in fetuses from preeclampsia without FGR in comparison to controls. Thus, hemopexin and α1-microglobulin present significantly altered concentrations in maternal blood in the maternal disease -preeclampsia- and in cord blood in the fetal disease -FGR-, which supports their differential role in placenta-mediated disorders in accordance with the clinical presentation of these disorders.

α1-Microglobulin Binds Illuminated Flavins and Has a Protective Effect Against Sublethal Riboflavin-Induced Damage in Retinal Epithelial Cells

Riboflavin (vitamin B2) is an important constituent of the prosthetic groups flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), which are utilized as electron-carriers in energy metabolism. Excitation by UV-light leads to the generation of riboflavin radicals and reactive oxygen species (ROS), which can oxidize a wide range of biomolecules. The human protein α₁-microglobulin (A1M) is a reductase and a radical scavenger, which can protect cells and matrix against oxidative damage. Here, we provide evidence of a molecular interaction between illuminated riboflavin and A1M, similar to the radical scavenging reactions previously seen between A1M and other organic radicals. Binding between riboflavin and A1M was demonstrated by gel migration shift, UV-absorbance and fluorescence spectrum analysis. The reaction between A1M and UV-light illuminated riboflavin involved covalent modification of A1M and proteolytic release of an N-terminal part of the protein. Furthermore, A1M also inhibited the ROS-induced photoreduction reaction of riboflavin, in a reaction involving the free thiol group in position C34. Finally, the results show a protective effect of A1M, analyzed by gene expression rates of stress genes, against sublethal damage in retinal epithelial cells in culture. Together, our results suggest a new role of A1M as a scavenger of riboflavin radicals and ROS produced during illumination of riboflavin.

The role of hemoglobin degradation pathway in preeclampsia: A systematic review and meta-analysis

INTRODUCTION

Overproduction of fetal hemoglobin by the placenta leading to increased consumption of endogenous heme scavenging proteins has been recently implicated as a novel pathway in the pathogenesis of preeclampsia. The aim of the present systematic review was to evaluate maternal serum levels of fetal hemoglobin, haptoglobin, heme oxygenase-1, hemopexin and α1-microglobulin, as well as haptoglobin phenotypes among preeclamptic and healthy pregnant women and assess their predictive role in the disease.

METHODS

Medline, Scopus, CENTRAL, Clinicaltrials.gov and Google Scholar databases were systematically searched from inception. All studies comparing levels of fetal hemoglobin or heme scavengers among preeclamptic and healthy pregnant controls were deemed eligible.

RESULTS

Twenty-three studies were included, with a total number of 7461 pregnant women. Quantitative synthesis was not conducted for the comparison of serum levels due to high heterogeneity. Current evidence suggests that preeclampsia is associated with increased levels of fetal hemoglobin and α1-microglobulin, as well as with lower levels of serum hemopexin. Data regarding serum haptoglobin and heme oxygenase-1 were conflicting, as the available evidence did not unanimously suggest a significant change of their levels in the disease. Network meta-analysis indicated no significant association for any of the haptoglobin phenotypes with preeclampsia development.

DISCUSSION

The present review suggests that preeclampsia may be associated with increased fetal hemoglobin and α1-microglobulin and decreased hemopexin levels, although inter-study heterogeneity was high. Future large-scale studies are needed to fully elucidate the predictive efficacy of these markers by introducing cut-off values and defining the optimal gestational age for sampling.

Longitudinal changes in plasma hemopexin and alpha-1-microglobulin concentrations in women with and without clinical risk factors for pre-eclampsia

Recent studies have shown increased concentration of fetal hemoglobin (HbF) in pre-eclamptic women. Plasma hemopexin (Hpx) and alpha-1-microglobulin (A1M) are hemoglobin scavenger proteins that protect against toxic effects of free heme released in the hemoglobin degradation process. We used an enzyme-linked immunosorbent assay to analyze maternal plasma Hpx and A1M concentrations at 12–14, 18–20 and 26–28 weeks of gestation in three groups: 1) 51 women with a low risk for pre-eclampsia (LRW), 2) 49 women with a high risk for pre-eclampsia (PE) who did not develop PE (HRW) and 3) 42 women with a high risk for PE who developed PE (HRPE). The study had three aims: 1) to investigate whether longitudinal differences exist between study groups, 2) to examine if Hpx and A1M concentrations develop differently in pre-eclamptic women with small for gestational age (SGA) fetuses vs. pre-eclamptic women with appropriate for gestational age fetuses, and 3) to examine if longitudinal Hpx and A1M profiles differ by PE subtype (early-onset vs. late-onset and severe vs. non-severe PE). Repeated measures analysis of variance was used to analyze differences in Hpx and A1M concentrations between the groups. We found that the differences in longitudinal plasma Hpx and A1M concentrations in HRW compared to HRPE and to LRW may be associated with reduced risk of PE regardless of clinical risk factors. In women who developed PE, a high A1M concentration from midgestation to late second trimester was associated with SGA. There were no differences in longitudinal Hpx and A1M concentrations from first to late second trimester in high-risk women who developed early-onset or. late-onset PE or in women who developed severe or. non-severe PE.

Preeclampsia is Associated with Sex-Specific Transcriptional and Proteomic Changes in Fetal Erythroid Cells

Preeclampsia (PE) has been associated with placental dysfunction, resulting in fetal hypoxia, accelerated erythropoiesis, and increased erythroblast count in the umbilical cord blood (UCB). Although the detailed effects remain unknown, placental dysfunction can also cause inflammation, nutritional, and oxidative stress in the fetus that can affect erythropoiesis. Here, we compared the expression of surface adhesion molecules and the erythroid differentiation capacity of UCB hematopoietic stem/progenitor cells (HSPCs), UCB erythroid profiles along with the transcriptome and proteome of these cells between male and female fetuses from PE and normotensive pregnancies. While no significant differences were observed in UCB HSPC migration/homing and in vitro erythroid colony differentiation, the UCB HSPC transcriptome and the proteomic profile of the in vitro differentiated erythroid cells differed between PE vs. normotensive samples. Accordingly, despite the absence of significant differences in the UCB erythroid populations in male or female fetuses from PE or normotensive pregnancies, transcriptional changes were observed during erythropoiesis, particularly affecting male fetuses. Pathway analysis suggested deregulation in the mammalian target of rapamycin complex 1/AMP-activated protein kinase (mTORC1/AMPK) signaling pathways controlling cell cycle, differentiation, and protein synthesis. These results associate PE with transcriptional and proteomic changes in fetal HSPCs and erythroid cells that may underlie the higher erythroblast count in the UCB in PE.

Plasma Heme Scavengers Alpha-1-Microglobulin and Hemopexin as Biomarkers in High-Risk Pregnancies

Women with established preeclampsia (PE) have increased plasma concentration of free fetal hemoglobin. We measured two hemoglobin scavenger system proteins, hemopexin (Hpx) and alpha-1-microglobulin (A1M) in maternal plasma using enzyme-linked immunosorbent assay during the late second trimester of pregnancy in women with high and low risk of developing PE. In total 142 women were included in nested case-control study: 42 women diagnosed with PE and 100 controls (49 randomly selected high-risk and 51 low-risk controls). The concentration of plasma A1M in high-risk controls was higher compared to low-risk controls. Women with severe PE had higher plasma A1M levels compared to women with non-severe PE. In conclusion, the concentration of plasma A1M is increased in the late second trimester in high-risk controls, suggesting activation of endogenous protective system against oxidative stress.

rA1M-035, a Physicochemically Improved Human Recombinant α1-Microglobulin, Has Therapeutic Effects in Rhabdomyolysis-Induced Acute Kidney Injury

AIMS

Human α₁-microglobulin (A1M) is an endogenous reductase and radical- and heme-binding protein with physiological antioxidant protective functions. Recombinant human A1M (rA1M) has been shown to have therapeutic properties in animal models of preeclampsia, a pregnancy disease associated with oxidative stress. Recombinant A1M, however, lacks glycosylation, and shows lower solubility and stability than A1M purified from human plasma. The aims of this work were to (i) use site-directed mutagenesis to improve the physicochemical properties of rA1M, (ii) demonstrate that the physicochemically improved rA1M displays full in vitro cell protective effects as recombinant wild-type A1M (rA1M-wt), and (iii) show its therapeutic potential in vivo against acute kidney injury (AKI), another disease associated with oxidative stress.

RESULTS

A novel recombinant A1M-variant (rA1M-035) with three amino acid substitutions was constructed, successfully expressed, and purified. rA1M-035 had improved solubility and stability compared with rA1M-wt, and showed intact in vitro heme-binding, reductase, antioxidation, and cell protective activities. Both rA1M-035 and rA1M-wt showed, for the first time, potential in vivo protective effects on kidneys using a mouse rhabdomyolysis glycerol injection model of AKI.

INNOVATION

A novel recombinant A1M-variant, rA1M-035, was engineered. This protein showed improved solubility and stability compared with rA1M-wt, full in vitro functional activity, and potential protection against AKI in an in vivo rhabdomyolysis mouse model.

CONCLUSION

The new rA1M-035 is a better drug candidate than rA1M-wt for treatment of AKI and preeclampsia in human patients.

Targeting the vascular dysfunction: Potential treatments for preeclampsia

Preeclampsia is a pregnancy-specific disorder, primarily characterized by new-onset hypertension in combination with a variety of other maternal or fetal signs. The pathophysiological mechanisms underlying the disease are still not entirely clear. Systemic maternal vascular dysfunction underlies the clinical features of preeclampsia. It is a result of oxidative stress and the actions of excessive anti-angiogenic factors, such as soluble fms-like tyrosine kinase, soluble endoglin, and activin A, released by a dysfunctional placenta. The vascular dysfunction then leads to impaired regulation and secretion of relaxation factors and an increase in sensitivity/production of constrictors. This results in a more constricted vasculature rather than the relaxed vasodilated state associated with normal pregnancy. Currently, the only effective "treatment" for preeclampsia is delivery of the placenta and therefore the baby. Often, this means a preterm delivery to save the life of the mother, with all the attendant risks and burdens associated with fetal prematurity. To lessen this burden, there is a pressing need for more effective treatments that target the maternal vascular dysfunction that underlies the hypertension. This review details the vascular effects of key drugs undergoing clinical assessment as potential treatments for women with preeclampsia.

α1-Microglobulin Protects Against Bleeding-Induced Oxidative Damage in Knee Arthropathies

Knee injury increases the risk of developing knee osteoarthritis (OA). Recent evidence suggests involvement of oxidative stress induced by inflammation and bleeding in the joint. This study investigates the role in this process of α₁-microglobulin (A1M), a plasma and tissue antioxidant protein with reducing function, and heme- and radical-binding properties. We studied matched knee synovial fluid (sf) and serum (s) samples from 122 subjects (mean age 40 years, 31% females): 10 were knee healthy references, 13 had acute inflammatory arthritis (AIA), 79 knee injury 0–10 years prior to sampling, and 20 knee OA. Using immunoassays, we measured sf-A1M and s-A1M, sf-hemoglobin (sf-Hb), sf-total free heme (sf-Heme), and sf-carbonyl groups (sf-Carbonyl). We explored associations by partial correlation, or linear regression models with adjustments for age, sex and diagnosis, and evaluated diagnostic capacity by area under the receiver operator characteristics curve (AUC). The AIA group had 1.2- to 1.7-fold higher sf-A1M and s-A1M concentrations compared to the other diagnostic groups; other biomarkers showed no between-group differences. sf-A1M and s-A1M were with AUC of 0.76 and 0.78, respectively, diagnostic for AIA. In the injury group, the amount of bleeding in the joint was inversely correlated to time after injury when measured as sf-Heme (r = -0.41, p < 0.001), but not when measured as sf-Hb (r = -0.19, p = 0.098). A similar inverse association with time after injury was noted for sf-A1M (r = -0.30, p = 0.007), but not for s-A1M and sf-Carbonyl. Linear regression models showed that sf-Heme was more strongly associated with sf-A1M and sf-Carbonyl than sf-Hb. Independent of diagnosis, sf-Heme explained 5.7% of the variability in sf-A1M and 3.0% in the variability in sf-Carbonyl, but appeared unrelated to s-A1M. High sf-A1M and low sf-Heme or sf-Hb were independently associated with low sf-Carbonyl. In conclusion, our results demonstrate that independent of disease, Hb and heme within a knee joint correlates with an increased sf-A1M concentration that appears to be protective of oxidative damage, i.e., a reduction in carbonyl groups. High concentrations of A1M in synovial fluid and serum was further diagnostic for AIA.

Preeclampsia and the challenge of early prediction: reality or utopia? State of art and critical review of literature

Purpose: The challenge to obtain improved predictive tools, able to identify women destined to develop preeclampsia (PE), is raising the interest of researchers for the attractive chance to allow for timely initiation of prophylactic therapy, appropriate antenatal surveillance, and better-targeted research into preventive interventions. We aimed to gather all the evidence reported up to now in scientific literature relating to all prediction tests for PE.Materials and methods: We searched articles on conventional literature platforms from January 1952 to August 2016, using the terms "preeclampsia," "gestational preeclampsia," and "gestational hypertensive disorders" combined with "predictive test" and "risk assessment." Abstracts/titles identified by the search were screened by three investigators.Results: The search identified 203 citations, of which 154 potentially relevant after the initial evaluation. Among these studies, 20 full articles were excluded, therefore, 134 primary studies met the criteria for inclusion and were analyzed.Conclusions: Current evidence suggests that a combination of several features may provide the best predictive accuracy for the identification of PE. Large-scale, multicenter, multiethnic, prospective trials are required to propose an ideal combination of markers for routine screening.

Clinical Presentation of Preeclampsia and the Diagnostic Value of Proteins and Their Methylation Products as Biomarkers in Pregnant Women with Preeclampsia and Their Newborns

Preeclampsia (PE) is a disorder which affects 1-10% of pregnant women worldwide. It is characterised by hypertension and proteinuria in the later stages of gestation and can lead to maternal and perinatal morbidity and mortality. Other than the delivery of the foetus and the removal of the placenta, to date there are no therapeutic approaches to treat or prevent PE. It is thus only possible to reduce PE-related mortality through early detection, careful monitoring, and treatment of the symptoms. For these reasons the search for noninvasive, blood-borne, or urinary biochemical markers that could be used for the screening, presymptomatic diagnosis, and prediction of the development of PE is of great urgency. So far, a number of biomarkers have been proposed for predicting PE, based on pathophysiological observations, but these have mostly proven to be unreliable and inconsistent between different studies. The clinical presentation of PE and data gathered for the biochemical markers placental growth factor (PlGF), soluble Feline McDonough Sarcoma- (fms-) like tyrosine kinase-1 (sFlt-1), asymmetric dimethylarginine (ADMA), and methyl-lysine is being reviewed with the aim of providing both a clinical and biochemical understanding of how these biomarkers might assist in the diagnosis of PE or indicate its severity.

The hemoglobin degradation pathway in patients with preeclampsia - Fetal hemoglobin, heme, heme oxygenase-1 and hemopexin - Potential diagnostic biomarkers?

OBJECTIVE

The aim of this study was to investigate how maternal cell-free fetal hemoglobin and heme impact the scavenger enzyme systems Hemopexin and Heme Oxygenase-1 in patients with preeclampsia (PE). The secondary aims were to evaluate these proteins as biomarkers for severity of the clinical manifestation i.e. hypertension, in early- and late onset PE.

MATERIAL AND METHODS

Plasma samples taken within the last 24 h before delivery from 135 patients were analyzed, 89 PE and 46 normal pregnancies. All samples were analyzed for cell-free fetal hemoglobin (HbF), heme, hemopexin enzymatic activity (Hx activity), hemopexin concentration (Hx), and heme oxygenase 1 concentration (HO-1). Logistic regression analysis with ROC-curve analysis was performed to evaluate the possible use as biomarkers for preeclampsia.

RESULTS

There were significantly higher levels of HbF (p = 0.01) and heme (0.01) but significantly lower Hx activity (p = 0.02), Hx (p < 0.0001) and HO-1 (p = 0.03) in PE plasma as compared to plasma of normal pregnancies. The Hx activity was significantly inversely correlated (p = 0.04) to the diastolic blood pressure. The HO-1 concentration was significantly inversely correlated to both the systolic and diastolic blood pressure (p = 0.01 and p = 0.003). ROC-curve analysis showed a combined detection rate for these biomarkers of 84% at 10% false positive rate.

CONCLUSIONS

Increased maternal plasma levels of heme and HbF in PE are associated with decreased HO-1 and hemopexin protein levels as well as reduced hemopexin activity. By measuring the consumption of the scavenger protein Hx, and the proteins in the Hb degradation system, clinical information about the dynamics of the disease can be obtained.

New Models of Pregnancy-Associated Hypertension

Pregnancy-associated hypertensive disorders are leading causes of maternal and fetal mortality. These include: pre-pregnancy hypertension that persists throughout gestation (chronic/preexisting hypertension), de novo hypertension that is diagnosed after 20 weeks of gestation and resolves after birth (gestational hypertension), de novo hypertension that is diagnosed after 20 weeks of gestation with or without proteinuria and end-organ damage (preeclampsia and eclampsia), and chronic hypertension with superimposed preeclampsia during gestation. Preeclampsia is the most severe form of these disorders. Animal models have been developed by employing surgical, genetic, and pharmacological approaches in order to recapitulate the maternal symptoms of preeclampsia and other hypertensive disorders of pregnancy. The scope of this brief review is to present an up-to-date synthesis of our knowledge of experimental models of pregnancy-associated hypertensive disorders. Novel models, defined in this review as characterized within the last 5 years, will be described and critically discussed. In this review, we will also discuss established experimental models of pregnancy-associated hypertensive disorders in the context of their contribution to new advances in our knowledge about the pathophysiology of these disorders and potential therapeutics. Emphasis will be placed on animal models of preeclampsia; however, models of other hypertensive disorders in pregnancy will also be reviewed.

Urinary Extracellular Vesicles of Podocyte Origin and Renal Injury in Preeclampsia

Renal histologic expression of the podocyte-specific protein, nephrin, but not podocin, is reduced in preeclamptic compared with normotensive pregnancies. We hypothesized that renal expression of podocyte-specific proteins would be reflected in urinary extracellular vesicles (EVs) of podocyte origin and accompanied by increased urinary soluble nephrin levels (nephrinuria) in preeclampsia. We further postulated that podocyte injury and attendant formation of EVs are related mechanistically to cellfree fetal hemoglobin (HbF) in maternal plasma. Our study population included preeclamptic (n=49) and normotensive (n=42) pregnant women recruited at delivery. Plasma measurements included HbF concentrations and concentrations of the endogenous chelators haptoglobin, hemopexin, and α_1- microglobulin. We assessed concentrations of urinary EVs containing immunologically detectable podocyte-specific proteins by digital flow cytometry and measured nephrinuria by ELISA. The mechanistic role of HbF in podocyte injury was studied in pregnant rabbits. Compared with urine from women with normotensive pregnancies, urine from women with preeclamptic pregnancies contained a high ratio of podocin-positive to nephrin-positive urinary EVs (podocin⁺ EVs-to-nephrin⁺ EVs ratio) and increased nephrinuria, both of which correlated with proteinuria. Plasma levels of hemopexin, which were decreased in women with preeclampsia, negatively correlated with proteinuria, urinary podocin⁺ EVs-to-nephrin⁺ EVs ratio, and nephrinuria. Administration of HbF to pregnant rabbits increased the number of urinary EVs of podocyte origin. These findings provide evidence that urinary EVs are reflective of preeclampsia-related altered podocyte protein expression. Furthermore, renal injury in preeclampsia associated with an elevated urinary podocin⁺ EVs-to-nephrin⁺ EVs ratio and may be mediated by prolonged exposure to cellfree HbF.

Syncytiotrophoblast derived extracellular vesicles transfer functional placental miRNAs to primary human endothelial cells

During the pregnancy associated syndrome preeclampsia (PE), there is increased release of placental syncytiotrophoblast extracellular vesicles (STBEVs) and free foetal haemoglobin (HbF) into the maternal circulation. In the present study we investigated the uptake of normal and PE STBEVs by primary human coronary artery endothelial cells (HCAEC) and the effects of free HbF on this uptake. Our results show internalization of STBEVs into primary HCAEC, and transfer of placenta specific miRNAs from STBEVs into the endoplasmic reticulum and mitochondria of these recipient cells. Further, the transferred miRNAs were functional, causing a down regulation of specific target genes, including the PE associated gene fms related tyrosine kinase 1 (FLT1). When co-treating normal STBEVs with HbF, the miRNA deposition is altered from the mitochondria to the ER and the cell membrane becomes ruffled, as was also seen with PE STBEVs. These findings suggest that STBEVs may cause endothelial damage and contribute to the endothelial dysfunction typical for PE. The miRNA mediated effects on gene expression may contribute to the oxidative and endoplasmic reticulum stress described in PE, as well as endothelial reprogramming that may underlay the increased risk of cardiovascular disease reported for women with PE later in life.

Fetal hemoglobin in umbilical cord blood in preeclamptic and normotensive pregnancies: A cross-sectional comparative study

Preeclampsia (PE) is associated with increased fetal hemoglobin (HbF) in the maternal circulation but its source is unknown. To investigate whether excessive HbF is produced in the placenta or the fetus, the concentration of HbF (cHbF) in the arterial and venous umbilical cord blood (UCB) was compared in 15825 normotensive and 444 PE pregnancies. The effect of fetal gender on cHbF was also evaluated in both groups. Arterial and venous UCB sampled immediately after birth at 36-42 weeks of gestation were analyzed for total Hb concentration (ctHb) (g/L) and HbF% using a Radiometer blood gas analyzer. Non-parametric tests were used for statistical comparison and P values < 0.05 were considered significant. Our results indicated higher cHbF in venous compared to arterial UCB in both normotensive (118.90 vs 117.30) and PE (126.75 vs 120.12) groups. In PE compared to normotensive pregnancies, a significant increase was observed in arterial and venous ctHb (171.00 vs 166.00 and 168.00 vs 163.00, respectively) while cHbF was only significantly increased in venous UCB (126.75 vs 118.90). The pattern was similar in both genders. These results indicate a substantial placental contribution to HbF levels in UCB, which increases in PE and is independent of fetal gender, suggesting the elevated cHbF evident in PE results from placental dysfunction.

Elevated levels of protein AMBP in cerebrospinal fluid of women with preeclampsia compared to normotensive pregnant women

PURPOSE

To investigate the cerebrospinal fluid (CSF) proteome of patients with preeclampsia (PE) and normotensive pregnant women, in order to provide a better understanding of brain involvement in PE.

EXPERIMENTAL DESIGN

Ninety-eight CSF samples (43 women with PE and 55 normotensive controls) were analyzed by LC-MS/MS proteome profiling. CSF was obtained during the spinal puncture before caesarean delivery.

RESULTS

Eight proteins were higher abundant and 17 proteins were lower abundant in patients with PE. The most significantly differentially abundant protein was protein AMBP (alpha-1-microglobulin/bikunin precursor). This finding was validated by performing an ELISA experiment (p = 0.002).

CONCLUSIONS AND CLINICAL RELEVANCE

The current study showed a clear difference between the protein profiles of CSF from patients with PE and normotensive pregnant women. Protein AMBP is a precursor of a heme-binding protein that counteracts the damaging effects of free hemoglobin, which may be related to the presence of free hemoglobin in CSF. Protein levels showed correlations with clinical symptoms during pregnancy and postpartum. To our knowledge, this is the first LC-MS/MS proteome profiling study on a unique set of CSF samples from (severe) preeclamptic patients and normotensive pregnant women.

Nested case-control study reveals increased levels of urinary proteins from human kidney toxicity panels in women predicted to develop preeclampsia

PURPOSE

The aim of this study was to evaluate the usefulness of urine concentrations of 12 proteins as a risk parameter for developing preeclampsia (PE).

METHODS

A nested case-control study was designed to determine protein concentrations in urine from women predicted to develop PE (WPD-PE) and normotensive pregnancies (controls). Protein profiles were determined at 12, 16 and 20 gestational weeks (GW) using the Bio-Plex Pro human kidney toxicity Panel 1 and Panel 2 (Bio-Rad). Receiver operating characteristic (ROC) curve analyses were performed. Correlations between proteins and clinical parameters at the time of PE diagnosis were also assessed.

RESULTS

Significant differences were observed in urine cystatin C (Cys C) levels at 16 and 20 GW and clusterin at 20 GW between WPD-PE and controls (P < 0.05). ROC analysis revealed that Cys C at 16 GW had the highest area under the ROC curve (0.758). At 16 GW, patients with urine Cys C levels above 73.7 ng/mL had eightfold increased odds for developing PE (odds ratio 7.92; 95 % CI 1.3-47.5; P = 0.027). A positive correlation was found between urinary Cys C (at 16 and 20 GW) and leukocyte counts, total proteins, aspartate aminotransferase, alanine aminotransferase, bilirubin and lactate dehydrogenase at the time of PE diagnosis (P value < 0.05).

CONCLUSIONS

Urinary Cys C and clusterin showed predictive value for PE development in our cohort. Further studies are needed to validate their use as predictive biomarkers for PE and/or their participation in PE pathogenesis.

Fetal hemoglobin, α1-microglobulin and hemopexin are potential predictive first trimester biomarkers for preeclampsia

OBJECTIVE

Overproduction of cell-free fetal hemoglobin (HbF) in the preeclamptic placenta has been recently implicated as a new etiological factor of preeclampsia. In this study, maternal serum levels of HbF and the endogenous hemoglobin/heme scavenging systems were evaluated as predictive biomarkers for preeclampsia in combination with uterine artery Doppler ultrasound.

STUDY DESIGN

Case-control study including 433 women in early pregnancy (mean 13.7weeks of gestation) of which 86 subsequently developed preeclampsia. The serum concentrations of HbF, total cell-free hemoglobin, hemopexin, haptoglobin and α1-microglobulin were measured in maternal serum. All patients were examined with uterine artery Doppler ultrasound. Logistic regression models were developed, which included the biomarkers, ultrasound indices, and maternal risk factors.

RESULTS

There were significantly higher serum concentrations of HbF and α1-microglobulin and significantly lower serum concentrations of hemopexin in patients who later developed preeclampsia. The uterine artery Doppler ultrasound results showed significantly higher pulsatility index values in the preeclampsia group. The optimal prediction model was obtained by combining HbF, α1-microglobulin and hemopexin in combination with the maternal characteristics parity, diabetes and pre-pregnancy hypertension. The optimal sensitivity for all preeclampsia was 60% at 95% specificity.

CONCLUSIONS

Overproduction of placentally derived HbF and depletion of hemoglobin/heme scavenging mechanisms are involved in the pathogenesis of preeclampsia. The combination of HbF and α1-microglobulin and/or hemopexin may serve as a prediction model for preeclampsia in combination with maternal risk factors and/or uterine artery Doppler ultrasound.

Inventory of Novel Animal Models Addressing Etiology of Preeclampsia in the Development of New Therapeutic/Intervention Opportunities

Preeclampsia is a pregnancy-related disease afflicting 3-7% of pregnancies worldwide and leads to maternal and infant morbidity and mortality. The disease is of placental origin and is commonly described as a disease of two stages. A variety of preeclampsia animal models have been proposed, but all of them have limitations in fully recapitulating the human disease. Based on the research question at hand, different or multiple models might be suitable. Multiple animal models in combination with in vitro or ex vivo studies on human placenta together offer a synergistic platform to further our understanding of the etiology of preeclampsia and potential therapeutic interventions. The described animal models of preeclampsia divide into four categories (i) spontaneous, (ii) surgically induced, (iii) pharmacologically/substance induced, and (iv) transgenic. This review aims at providing an inventory of novel models addressing etiology of the disease and or therapeutic/intervention opportunities.

First trimester prediction of preeclampsia

Preeclampsia (PE) is a serious pregnancy-related condition that causes severe maternal and fetal morbidity and mortality. Within the recent years, there has been an increasing focus in predicting PE at the end of the first trimester of pregnancy. In this review, literature published between 2011 and 2015 was evaluated. In a total of six biomarker algorithms, for first and early second trimester, the prediction of preeclampsia is discussed. In addition, one randomized clinical trial was included. Several algorithms were based on placental biomarkers such as pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PLGF), and soluble FMS-like tyrosine kinase 1 (s-FLT-1). The algorithms containing these biomarkers showed a high prediction rate (PR) for early onset PE, ranging from 44 to 92 % at 5 % false positive rate (FPR). New biomarkers suggest an alternative model based on free HbF and the heme scavenger alpha-1-microglobulin (A1M) with a prediction rate of 69 % at an FPR of 5 %. Interestingly, this model performs well without uterine artery Doppler pulsatility index (UtAD-PI), which is an advantage particularly if the screening method were to be implemented in developing countries. The randomized clinical trial showed a clear reduction in early onset PE as well as reducing preterm PE if identified high-risk pregnancies were treated with low-dose aspirin. In conclusion, PE prediction is now possible through several prediction algorithms and prophylaxis is beneficial in high-risk cases.

Early Pregnancy Biomarkers in Pre-Eclampsia: A Systematic Review and Meta-Analysis

Pre-eclampsia (PE) complicates 2%–8% of all pregnancies and is an important cause of perinatal morbidity and mortality worldwide. In order to reduce these complications and to develop possible treatment modalities, it is important to identify women at risk of developing PE. The use of biomarkers in early pregnancy would allow appropriate stratification into high and low risk pregnancies for the purpose of defining surveillance in pregnancy and to administer interventions. We used formal methods for a systematic review and meta-analyses to assess the accuracy of all biomarkers that have been evaluated so far during the first and early second trimester of pregnancy to predict PE. We found low predictive values using individual biomarkers which included a disintegrin and metalloprotease 12 (ADAM-12), inhibin-A, pregnancy associated plasma protein A (PAPP-A), placental growth factor (PlGF) and placental protein 13 (PP-13). The pooled sensitivity of all single biomarkers was 0.40 (95% CI 0.39–0.41) at a false positive rate of 10%. The area under the Summary of Receiver Operating Characteristics Curve (SROC) was 0.786 (SE 0.02). When a combination model was used, the predictive value improved to an area under the SROC of 0.893 (SE 0.03). In conclusion, although there are multiple potential biomarkers for PE their efficacy has been inconsistent and comparisons are difficult because of heterogeneity between different studies. Therefore, there is an urgent need for high quality, large-scale multicentre research in biomarkers for PE so that the best predictive marker(s) can be identified in order to improve the management of women destined to develop PE.

The Human Endogenous Protection System against Cell-Free Hemoglobin and Heme Is Overwhelmed in Preeclampsia and Provides Potential Biomarkers and Clinical Indicators

Preeclampsia (PE) complicates 3-8% of all pregnancies and manifests clinically as hypertension and proteinuria in the second half of gestation. The pathogenesis of PE is not fully understood but recent studies have described the involvement of cell-free fetal hemoglobin (HbF). Hypothesizing that PE is associated with prolonged hemolysis we have studied the response of the cell-free Hb- and heme defense network. Thus, we have investigated the levels of cell-free HbF (both free, denoted HbF, and in complex with Hp, denoted Hp-HbF) as well as the major human endogenous Hb- and heme-scavenging systems: haptoglobin (Hp), hemopexin (Hpx), α1-microglobulin (A1M) and CD163 in plasma of PE women (n = 98) and women with normal pregnancies (n = 47) at term. A significant increase of the mean plasma HbF concentration was observed in women with PE. Plasma levels of Hp and Hpx were statistically significantly reduced, whereas the level of the extravascular heme- and radical scavenger A1M was significantly increased in plasma of women with PE. The Hpx levels significantly correlated with maternal blood pressure. Furthermore, HbF and the related scavenger proteins displayed a potential to be used as clinical biomarkers for more precise diagnosis of PE and are candidates as predictors of identifying pregnancies with increased risk of obstetrical complications. The results support that PE pathophysiology is associated with increased HbF-concentrations and an activation of the physiological Hb-heme defense systems.

Combined Screening for Early Detection of Pre-Eclampsia

Although the precise pathophysiology of pre-eclampsia remains unknown, this condition continues to be a major cause of maternal and fetal mortality. Early prediction of pre-eclampsia would allow for timely initiation of preventive therapy. A combination of biophysical and biochemical markers are superior to other tests for early prediction of the development of pre-eclampsia. Apart from the use of parameters in first-trimester aneuploidy screening, cell-free fetal DNA quantification is emerging as a promising marker for prediction of pre-eclampsia. This article reviews the current research of the most important strategies for prediction of pre-eclampsia, including the use of maternal risk factors, mean maternal arterial pressure, ultrasound parameters, and biomarkers.

The menagerie of human lipocalins: a natural protein scaffold for molecular recognition of physiological compounds

While immunoglobulins are well-known for their characteristic ability to bind macromolecular antigens (i.e., as antibodies during an immune response), the lipocalins constitute a family of proteins whose role is the complexation of small molecules for various physiological processes. In fact, a number of low-molecular-weight substances in multicellular organisms show poor solubility, are prone to chemical decomposition, or play a pathophysiological role and thus require specific binding proteins for transport through body fluids, storage, or sequestration. In many cases, lipocalins are involved in such tasks. Lipocalins are small, usually monomeric proteins with 150-180 residues and diameters of approximately 40 Å, adopting a compact fold that is dominated by a central eight-stranded up-and-down β-barrel. At the amino-terminal end, this core is flanked by a coiled polypeptide segment, while its carboxy-terminal end is followed by an α-helix that leans against the β-barrel as well as an amino acid stretch in a more-or-less extended conformation, which finally is fixed by a disulfide bond. Within the β-barrel, the antiparallel strands (designated A to H) are arranged in a (+1)7 topology and wind around a central axis in a right-handed manner such that part of strand A is hydrogen-bonded to strand H again. Whereas the lower region of the β-barrel is closed by short loops and densely packed hydrophobic side chains, including many aromatic residues, the upper end is usually open to solvent. There, four long loops, each connecting one pair of β-strands, together form the entrance to a cup-shaped cavity. Depending on the individual structure of a lipocalin, and especially on the lengths and amino acid sequences of its four loops, this pocket can accommodate chemical ligands of various sizes and shapes, including lipids, steroids, and other chemical hormones as well as secondary metabolites such as vitamins, cofactors, or odorants. While lipocalins are ubiquitous in all higher organisms, physiologically important members of this family have long been known in the human body, for example with the plasma retinol-binding protein that serves for the transport of vitamin A. This prototypic human lipocalin was the first for which a crystal structure was solved. Notably, several other lipocalins were discovered and assigned to this protein class before the term itself became familiar, which explains their diverse names in the scientific literature. To date, up to 15 distinct members of the lipocalin family have been characterized in humans, and during the last two decades the three-dimensional structures of a dozen major subtypes have been elucidated. This Account presents a comprehensive overview of the human lipocalins, revealing common structural principles but also deviations that explain individual functional features. Taking advantage of modern methods for combinatorial protein design, lipocalins have also been employed as scaffolds for the construction of artifical binding proteins with novel ligand specificities, so-called Anticalins, hence opening perspectives as a new class of biopharmaceuticals for medical therapy.

Pregnancy-associated plasma protein A (PAPP-A) and preeclampsia

Pregnancy-associated plasma protein A (PAPP-A) is a key regulator of insulin-like growth factor bioavailability essential for normal fetal development. In maternal blood, this protein increases with gestational age and then rapidly decreases after delivery. It is routinely used for Down syndrome screening in the first trimester of pregnancy, and its decrease compared to a normal pregnancy indicates an increased risk for both chromosomal anomalies and adverse pregnancy outcomes. It belongs to a group of biomarkers that predict later preeclampsia development, primarily early onset preeclampsia; however, it should be combined with a Doppler ultrasonography of the uterine artery (pulsatile index) and other biochemical and maternal factors to achieve a higher detection rate with an acceptable false positivity rate. Some studies have demonstrated an even more pronounced decrease of PAPP-A in the early second trimester of pregnancy in women who subsequently develop preeclampsia compared with women who do not develop preeclampsia. Conversely, during the last trimester of pregnancy, its concentration increases even more in patients with preeclampsia than in patients without. It is also detectable at very low levels in nonpregnant individuals, and a higher concentration indicates an adverse effect in patients with acute coronary syndromes or stable atherosclerotic disease and in patients with end-stage renal disease who are being treated with hemodialysis.

Predictive biomarkers of pre-eclampsia and effectiveness of preventative interventions for the disease

INTRODUCTION

Pre-eclampsia (PE) is one of the most common pregnancy complication characterized by placental and maternal vascular dysfunction. It affects about 3 - 8% of women during the second half of pregnancy and represents one of the major causes of neonatal morbidity and mortality. The etiology of PE largely remains unknown.

AREAS COVERED

PE is considered a syndrome with multisystem involvement, so the ideal predictive test for it should utilize a combination of many predictors. Measurement in early pregnancy of a variety of biophysical and biochemical markers implicated in the pathophysiology of PE associated with clinical risk factors has been proposed to predict the development of the syndrome, thereby mitigating an adverse outcome.

EXPERT OPINION

The identification of reliable indicators is a clinically relevant issue that could result in early therapeutic intervention and leading to the prevention of maternal and fetal injuries before the manifestation of clinical signs. Many factors complicate the prevention of PE cases. Most are attributed to unknown etiology, the low predictive value of current screening tests and the several presentations of the disease. Although preventative treatments have been studied extensively, an effective intervention to avoid the development of PE has not yet been discovered.

Syncytiotrophoblast vesicles show altered micro-RNA and haemoglobin content after ex-vivo perfusion of placentas with haemoglobin to mimic preeclampsia

Background

Cell-free foetal haemoglobin (HbF) has been shown to play a role in the pathology of preeclampsia (PE). In the present study, we aimed to further characterize the harmful effects of extracellular free haemoglobin (Hb) on the placenta. In particular, we investigated whether cell-free Hb affects the release of placental syncytiotrophoblast vesicles (STBMs) and their micro-RNA content.

Methods

The dual ex-vivo perfusion system was used to perfuse isolated cotyledons from human placenta, with medium alone (control) or supplemented with cell-free Hb. Perfusion medium from the maternal side of the placenta was collected at the end of all perfusion phases. The STBMs were isolated using ultra-centrifugation, at 10,000×g and 150,000×g (referred to as 10K and 150K STBMs). The STBMs were characterized using the nanoparticle tracking analysis, identification of surface markers and transmission electron microscopy. RNA was extracted and nine different micro-RNAs, related to hypoxia, PE and Hb synthesis, were selected for analysis by quantitative PCR.

Results

All micro-RNAs investigated were present in the STBMs. Mir-517a, mir-141 and mir-517b were down regulated after Hb perfusion in the 10K STBMs. Furthermore, Hb was shown to be carried by the STBMs.

Conclusion

This study showed that Hb perfusion can alter the micro-RNA content of released STBMs. Of particular interest is the alteration of two placenta specific micro-RNAs; mir-517a and mir-517b. We have also seen that STBMs may function as carriers of Hb into the maternal circulation.

A1M/α1-microglobulin protects from heme-induced placental and renal damage in a pregnant sheep model of preeclampsia

Preeclampsia (PE) is a serious pregnancy complication that manifests as hypertension and proteinuria after the 20(th) gestation week. Previously, fetal hemoglobin (HbF) has been identified as a plausible causative factor. Cell-free Hb and its degradation products are known to cause oxidative stress and tissue damage, typical of the PE placenta. A1M (α1-microglobulin) is an endogenous scavenger of radicals and heme. Here, the usefulness of A1M as a treatment for PE is investigated in the pregnant ewe PE model, in which starvation induces PE symptoms via hemolysis. Eleven ewes, in late pregnancy, were starved for 36 hours and then treated with A1M (n = 5) or placebo (n = 6) injections. After injections, the ewes were re-fed and observed for additional 72 hours. They were monitored for blood pressure, proteinuria, blood cell distribution and clinical and inflammation markers in plasma. Before termination, the utero-placental circulation was analyzed with Doppler velocimetry and the kidney glomerular function was analyzed by Ficoll sieving. At termination, blood, kidney and placenta samples were collected and analyzed for changes in gene expression and tissue structure. The starvation resulted in increased amounts of the hemolysis marker bilirubin in the blood, structural damages to the placenta and kidneys and an increased glomerular sieving coefficient indicating a defect filtration barrier. Treatment with A1M ameliorated these changes without signs of side-effects. In conclusion, A1M displayed positive therapeutic effects in the ewe starvation PE model, and was well tolerated. Therefore, we suggest A1M as a plausible treatment for PE in humans.

Extracellular fetal hemoglobin induces increases in glomerular permeability: inhibition with α1-microglobulin and tempol

Extracellular fetal hemoglobin (HbF) and adult hemoglobin (HbA) are proinflammatory and generate ROS. Increased plasma levels of extracellular HbF have recently been reported to occur in early preeclampsia. α1-Microglobulin (A1M) is a physiological heme-binding protein and radical scavenger that has been shown to counteract vascular permeability increases induced by HbA in the perfused placenta. The present study was performed to investigate whether HbF and HbA will increase glomerular permeability in vivo and to test whether A1M and tempol, a ROS scavenger, can prevent their effects. Anesthetized Wistar rats were continuously infused intravenously with either HbA, HbF, or cyano-inactivated HbF together with FITC-Ficoll-70/400, inulin, and (51)Cr-labeled EDTA for 2 h. Plasma samples and urine samples (left ureter) were taken repeatedly and analyzed by high-performance size exclusion chromatography to assess glomerular sieving coefficients for Ficoll of radius 10-80 Å. In separate experiments, A1M or tempol was given before and during Hb infusions. Extracellular HbF caused rapid, transient increases in glomerular permeability to large Ficoll molecules (50-80Å), contrary to the effects of HbA and cyano-inactivated HbF. For HbF, glomerular sieving coefficients for Ficoll of radius 60Å increased from 3.85 ± 0.85 × 10(-5) to 2.60 ± 0.96 × 10(-4) at 15 min, changes that were abrogated by tempol and reduced by A1M. In conclusion, our data demonstrate that extracellular HbF, infused systemically, can acutely increase glomerular permeability through inducing oxidative stress.

Predictive factors for preeclampsia in pregnant women: a Receiver Operation Character approach

INTRODUCTION

Preeclampsia is a major cause of maternal and prenatal mortality and morbidity worldwide. There are some risk factors that are of great value for prediction of preeclampsia by which the practitioners can counsel women regarding this disease. The aim of this study was to analyze the role of such risk factors as the predictors associated with preeclampsia among Iranian women using logistic regression.

MATERIAL AND METHODS

The role of some risk factors such as demographic, anthropometric, medical and obstetrics variables in preeclampsia among 610 women attending the obstetric ward of Mustafa hospital in Ilam in the west of Iran was analyzed from May to September 2010. All the pregnant women referred to this hospital participated in the study except those cases that had abortion. Unvaried and Multiple logistic regression analyses were used to find the predictive factors behind preeclampsia. Standard errors of area compute using nonparametric methods. A p-value of 0.05 was considered statistically significant.

RESULTS

Prevalence of preeclampsia was 9.5% (95% CI 7.4-11.6%). Predictive model build using history of preeclampsia, history of hypertension, and history of infertility. Area Under the Receiver Operation Character (AUROC) was estimated 0.67 (95% CI 0.59-0.67, p < 0.01) that showed that using the model is much better than having a guess.

CONCLUSIONS

The odd of preeclampsia increased in women with a history of preeclampsia, hypertension and infertility. Recognition of these predictor factors would improve the ability to diagnose and monitor women likely to develop preeclampsia before the onset of disease for timely interventions.

Decreased levels of folate receptor-β and reduced numbers of fetal macrophages (Hofbauer cells) in placentas from pregnancies with severe pre-eclampsia

PROBLEM

Pre-eclampsia (PE), a pregnancy complication of unknown etiology, is a major cause of maternal and fetal mortality and morbidity. Previous studies have described placental genes that are up-regulated in expression in PE, but few studies have addressed placental gene suppression in this syndrome.

METHOD OF STUDY

Gene profiling and quantitative reverse transcription PCR (qRTPCR) analyses were used to identify genes down-regulated in placentas from women with severe preterm PE compared with gestational age-matched normotensive controls with spontaneous preterm birth (sPTB). Western blotting and immunohistochemistry were used to evaluate levels and patterns of cell type-specific protein expression in PE and sPTB group placentas.

RESULTS

Levels of macrophage marker [folate receptor (FR)-β, CD163, and CD68] mRNA and FR-β protein were significantly down-regulated in PE group placentas compared with the sPTB group. Numbers of Hofbauer cells (HBCs, fetal macrophages) and FR-β protein in these cells were reduced in PE group placentas.

CONCLUSION

Severe PE is associated with decreased placental expression of FR-β and a reduction in the number of HBCs. Reduced placental macrophage function is likely to play a key role in the pathophysiology of PE.

Glucocorticoids enhance CD163 expression in placental Hofbauer cells

Periplacental levels of glucocorticoid (GC) peak at parturition, and synthetic GC is administered to women at risk for preterm delivery. However, little is known concerning cell-type-specific effects of GC in placenta. Hofbauer cells (HBCs) are fetal macrophages that are located adjacent to fetal capillaries in placenta. The goal of the current study was to determine whether GC treatment altered HBC gene expression and function. Western blotting and flow cytometry revealed CD163 and folate receptor-β (FR-β), markers of antiinflammatory M2 macrophages, were specifically expressed by primary cultures of HBCs immunopurified from human term placentas. GC receptor mRNA and protein levels were higher in HBCs compared with placental fibroblasts. Treatment of HBCs with cortisol or dexamethasone (DEX) markedly and specifically enhanced CD163 protein and mRNA levels, whereas expression of FR-β and CD68 were largely unresponsive to GC treatment. DEX treatment also increased hemoglobin uptake by HBCs, evidence of enhanced HBC function. The level of CD163 mRNA, but not FR-β or CD68 mRNA, was stimulated in placental explant cultures by DEX treatment, and increased CD163/FR-β and CD163/CD68 mRNA ratios sensitively reflected the response to GC. Maternal GC administration was associated with increased CD163/FR-β and CD163/CD68 mRNA ratios in placentas from women with spontaneous preterm birth. In conclusion, in vitro studies indicated that GC treatment specifically up-regulated CD163 expression in HBCs and enhanced HBC function. In addition, the observed alterations in patterns of expression of macrophage marker genes associated with maternal GC administration suggest that HBCs are in vivo targets of GC action.

Pathological conditions involving extracellular hemoglobin: molecular mechanisms, clinical significance, and novel therapeutic opportunities for α(1)-microglobulin

Hemoglobin (Hb) is the major oxygen (O(2))-carrying system of the blood but has many potentially dangerous side effects due to oxidation and reduction reactions of the heme-bound iron and O(2). Extracellular Hb, resulting from hemolysis or exogenous infusion, is shown to be an important pathogenic factor in a growing number of diseases. This review briefly outlines the oxidative/reductive toxic reactions of Hb and its metabolites. It also describes physiological protection mechanisms that have evolved against extracellular Hb, with a focus on the most recently discovered: the heme- and radical-binding protein α(1)-microglobulin (A1M). This protein is found in all vertebrates, including man, and operates by rapidly clearing cytosols and extravascular fluids of heme groups and free radicals released from Hb. Five groups of pathological conditions with high concentrations of extracellular Hb are described: hemolytic anemias and transfusion reactions, the pregnancy complication pre-eclampsia, cerebral intraventricular hemorrhage of premature infants, chronic inflammatory leg ulcers, and infusion of Hb-based O(2) carriers as blood substitutes. Finally, possible treatments of these conditions are discussed, giving a special attention to the described protective effects of A1M.

The crystal structure of human α1-microglobulin reveals a potential haem-binding site

We describe the 2.3 Å (1 Å=0.1 nm) X-ray structure of α1m (α1-microglobulin), an abundant protein in human blood plasma, which reveals the β-barrel fold typical for lipocalins with a deep pocket lined by four loops at its open rim. Loop #1 harbours the residue Cys34 which is responsible for covalent cross-linking with plasma IgA. A single disulfide bond between Cys72 and Cys169 connects the C-terminal segment to the β-barrel, as in many other lipocalins. The exposed imidazole side chains of His122 and His123 in loop #4 give rise to a double Ni2+-binding site together with a crystallographic neighbour. The closest structural relatives of α1m are the complement protein component C8γ, the L-prostaglandin D synthase and lipocalin 15, three other structurally characterized members of the lipocalin family in humans that have only distant sequence similarity. In contrast with these, α1m is initially expressed as a bifunctional fusion protein with the protease inhibitor bikunin. Neither the electron density nor ESI–MS (electrospray ionization MS) provide evidence for a chromophore bound to the recombinant α1m, also known as ‘yellow/brown lipocalin’. However, the three side chains of Lys92, Lys118 and Lys130 that were reported to be involved in covalent chromophore binding appear to be freely accessible to ligands accommodated in the hydrophobic pocket. A structural feature similar to the well-known Cys–Pro haem-binding motif indicates the presence of a haem-binding site within the loop region of α1m, which explains previous biochemical findings and supports a physiological role in haem scavenging, as well as redox-mediated detoxification.