Magnus Centlow

Increased levels of cell-free hemoglobin, oxidation markers, and the antioxidative heme scavenger alpha(1)-microglobulin in preeclampsia.

Preeclampsia is a major cause of morbidity and mortality during pregnancy. To date, the pathogenesis of the disease is not fully understood. Recent studies show that preeclampsia is associated with overexpression of the hemoglobin genes alpha2 and gamma and accumulation of the protein in the vascular lumen of the placenta. Hypothesizing that cell-free hemoglobin leaks from the placenta into the maternal circulation and contributes to the endothelial damage and symptoms by inducing oxidative stress, we analyzed fetal and adult hemoglobin (HbF, HbA), haptoglobin, oxidation markers, and the heme scavenger and antioxidant alpha(1)-microglobulin in plasma, urine, and placenta in preeclamptic women (n=28) and women with normal pregnancy (n=27). The mean plasma concentrations of HbF, HbA, protein carbonyl groups, membrane peroxidation capacity, and alpha(1)-microglobulin were significantly increased in preeclamptic women. The levels of total plasma Hb correlated strongly with the systolic blood pressure. The plasma haptoglobin concentrations of women with preeclampsia were significantly depressed. Increased amounts of alpha(1)-microglobulin mRNA and protein were found in placenta from preeclamptic women, and the levels of plasma and placenta alpha(1)-microglobulin correlated with the plasma Hb concentrations. The heme-degrading form t-alpha(1)-microglobulin was significantly increased in urine in preeclampsia. These results support the idea that hemoglobin-induced oxidative stress is a pathogenic factor in preeclampsia.

Placental expression profiling in preeclampsia: local overproduction of hemoglobin may drive pathological changes.

OBJECTIVE To create a library enriched in cDNAs from preeclamptic placentas to print onto microarrays for placental profiling of preeclampsia (PE) and high risk pregnancies. DESIGN Prospective study. SETTING University womens clinic and academic research laboratory. PATIENT(S) Ten patients with PE, 5 with PE and bilateral notching, 5 with bilateral notching without PE, and 15 normotensive patients were recruited. INTERVENTION(S) Placenta and placenta bed biopsies were collected after delivery. MAIN OUTCOME MEASURE(S) Subtracted libraries of PE transcripts were produced, and cDNAs from these libraries were used to make PE-specific cDNA arrays. Results were verified quantitatively using real-time polymerase chain reaction (PCR) and histologically using in situ hybridization and immunohistochemistry. RESULT(S) Thirty genes were significantly altered in at least one group comparison. Differences in two candidate genes were confirmed using quantitative real-time PCR. Hemoglobin alpha2 and gamma transcripts were significantly overexpressed in the PE placenta. Scattered cells in the placenta and placental blood vessels were shown to express genes encoding these hemoglobin chains. CONCLUSION(S) We demonstrate increased hemoglobin production in the PE placenta. The hemoglobin may be released into the placenta blood vessel lumen. Free heme and hemoglobin are potent toxins that cause endothelial damage and inflammation.

Perfusion of human placenta with hemoglobin introduces preeclampsia-like injuries that are prevented by α1-microglobulin

BACKGROUND Preeclamptic women have increased plasma levels of free fetal hemoglobin (HbF), increased gene expression of placental HbF and accumulation of free HbF in the placental vascular lumen. Free hemoglobin (Hb) is pro-inflammatory, and causes oxidative stress and tissue damage. METHODOLOGY To show the impact of free Hb in PE, we used the dual ex vivo placental perfusion model. Placentas were perfused with Hb and investigated for physical parameters, Hb leakage, gene expression and morphology. The protective effects of α(1)-microglobulin (A1M), a heme- and radical-scavenger and antioxidant, was investigated. RESULTS Hb-addition into the fetal circulation led to a significant increase of the perfusion pressure and the feto-maternal leakage of free Hb. Morphological damages similar to the PE placentas were observed. Gene array showed up-regulation of genes related to immune response, apoptosis, and oxidative stress. Simultaneous addition of A1M to the maternal circulation inhibited the Hb leakage, morphological damage and gene up-regulation. Furthermore, perfusion with Hb and A1M induced a significant up-regulation of extracellular matrix genes. SIGNIFICANCE The ex vivo Hb-perfusion of human placenta resulted in physiological and morphological changes and a gene expression profile similar to what is observed in PE placentas. These results underline the potentially important role of free Hb in PE etiology. The damaging effects were counteracted by A1M, suggesting a role of this protein as a new potential PE therapeutic agent.

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

OBJECTIVE The aim of this study was to evaluate fetal hemoglobin (HbF) and α(1)-microglobulin (A1M) in maternal serum as first-trimester biomarkers for preeclampsia (PE). STUDY DESIGN The design was a case-control study. We included 96 patients in the first trimester of pregnancy (60 with PE and 36 controls). Venous serum samples were analyzed for HbF and total hemoglobin (Hb) by enzyme-linked immunosorbent assay and for A1M by radioimmunoassay. Sensitivity and specificity was calculated by logistic regression and receiver operating characteristic curve analysis. RESULTS The HbF/Hb ratio and A1M concentration were significantly elevated in serum from women with subsequent development of PE (P < .0001). The optimal sensitivity and specificity was obtained using the biomarkers in combination; 69% sensitivity for a 5% screen positive rate and 90% sensitivity for a 23% screen positive rate. CONCLUSION The study suggests that HbF/Hb ratio in combination with A1M is predictive biomarkers for PE.

Differential Gene Expression Analysis of Placentas with Increased Vascular Resistance and Pre-Eclampsia Using Whole-Genome Microarrays

Pre-eclampsia is a pregnancy complication characterized by hypertension and proteinuria. There are several factors associated with an increased risk of developing pre-eclampsia, one of which is increased uterine artery resistance, referred to as “notching”. However, some women do not progress into pre-eclampsia whereas others may have a higher risk of doing so. The placenta, central in pre-eclampsia pathology, may express genes associated with either protection or progression into pre-eclampsia. In order to search for genes associated with protection or progression, whole-genome profiling was performed. Placental tissue from 15 controls, 10 pre-eclamptic, 5 pre-eclampsia with notching, and 5 with notching only were analyzed using microarray and antibody microarrays to study some of the same gene product and functionally related ones. The microarray showed 148 genes to be significantly altered between the four groups. In the preeclamptic group compared to notch only, there was increased expression of genes related to chemotaxis and the NF-kappa B pathway and decreased expression of genes related to antigen processing and presentation, such as human leukocyte antigen B. Our results indicate that progression of pre-eclampsia from notching may involve the development of inflammation. Increased expression of antigen-presenting genes, as seen in the notch-only placenta, may prevent this inflammatory response and, thereby, protect the patient from developing pre-eclampsia.

Gene expression profiling of placentae from women with early- and late-onset pre-eclampsia: down-regulation of the angiogenesis-related genes ACVRL1 and EGFL7 in early-onset disease

The underlying mechanisms behind the obstetric condition pre-eclampsia (PE) are still unclear. Manifestation of PE is heterogeneous and it has therefore been proposed to be a syndrome with different causes rather than one disease with a specific aetiology. Recently, we showed differences in circulating angiogenic factors between two subgroups-early- and late-onset PE. To further elucidate the differences between the two, we investigated placental gene expression profiles. Whole genome microarray technology and bioinformatic analysis were used to evaluate gene expression profiles in placentae from early- (24-32 gestational weeks, n = 8) and late-onset (36-41 gestational weeks, n = 7) PE. The results were verified by using quantitative real-time (qRT)-PCR. We found significant differences in the expression of 196 genes in early- compared with late-onset PE, 45 of these genes showing a fold change above 2. Bioinformatic analysis revealed alterations in angiogenesis and regulation of cell motility. Two angiogenesis-associated transcripts (Egfl7 and Acvrl1) showed lower expression in early-onset PE versus late-onset PE (P = 0.037 and P = 0.003) and versus gestational age-matched controls (P = 0.007 and P = 0.011). We conclude that angiogenesis-associated genes are regulated in a different manner in the two subgroups, and that the gene expression profiles of early- and late-onset PE diverge, supporting the hypothesis of early- and late-onset PE being at least partly two separate entities.

Differential Proteome Analysis of the Preeclamptic Placenta Using Optimized Protein Extraction

The human placenta is a difficult tissue to work with using proteomic technology since it contains large amounts of lipids and glycogen. Both lipids and glycogen are known to interfere with the first step in the two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), the isoelectric focusing. In order to gain the best possible protein separation on 2D-PAGE, an optimized sample preparation protocol for placental proteins was developed. Two different buffers, urea/CHAPS and Hepes, were used for solubilization in combination with six different precipitation methods. The removal of glycogen from the samples by centrifugation was crucial for the final proteome maps. Solubilization with urea/CHAPS in combination with dichloromethane/methanol or acidified acetone proved to be the best precipitation procedures. When applied to clinical placenta samples apolipoprotein A1 was found to be accumulated in the preeclamptic placenta, where it may either have a nutritional effect or act as a modifier of signal transduction.

Tissue proteome profiling of preeclamptic placenta using recombinant antibody microarrays

Purpose: Preeclampsia (PE) is a severe, multi‐system pregnancy disorder of yet unknown cause, missing means of treatment, and our fundamental understanding of the disease is still impaired. The purpose of this discovery study was to define candidate placenta tissue protein biomarker signatures to further decipher the molecular features of PE.

Die in-vitro Perfusion der menschlichen Plazenta mit Eryhtrozyten und Xanthine Oxidase als in vitro Simulation von Praeeklampsie

BACKGROUND AND PURPOSE Preeclampsia is a major obstetric problem of unknown etiology. The fact that removal of the placenta is the only cure for preeclampsia, has led to the well-established hypothesis, that the placenta is central in the etiology. Gene profiling and proteomics studies have suggested oxidative stress caused by reperfusion and free oxygen radicals as a potential pathophysiological mechanism in preeclampsia. In this study, the dual placental perfusion model was used in order to evaluate the damaging effects of oxidative stress induced by xanthine/xanthine oxides and free hemoglobin. MATERIAL AND METHODS The dual placenta perfusion model is a well-established in vitro model for functional placental studies. Placentas were perfused with medium containing either xanthine/xanthine oxidase or erythrocytes as a source of free hemoglobin. Concentration of free hemoglobin in the medium was measured by means of ELISA. Whole genome microarray technique and bioinformatics were used to evaluate the gene expression profile in the two groups. RESULTS Substantial levels of free adult hemoglobin were detected in the perfusions. A total of 58 genes showed altered gene expression, the most altered were hemoglobin alpha, beta and gamma, tissue factor pathway inhibitor 2 and superoxide dismutase 2. Bioinformatics revealed that biological processes related to oxidative stress, anti-apoptosis and iron ion binding were significantly altered. CONCLUSIONS The results suggest that perfusion with xanthine/xanthine oxidase and free hemoglobin induce changes in gene expression similar to what has been described for the preeclamptic placenta.