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

Heme oxygenase/carbon monoxide system and development of the heart

Progressive differentiation controlled by intercellular signaling between pharyngeal mesoderm, foregut endoderm, and neural crest-derived mesenchyme is required for normal embryonic and fetal development. Gasotransmitters (criteria: 1) a small gas molecule; 2) freely permeable across membranes; 3) endogenously and enzymatically produced and its production regulated; 4) well-defined and specific functions at physiologically relevant concentrations; 5) functions can be mimicked by exogenously applied counterpart; and 6) cellular effects may or may not be second messenger-mediated, but should have specific cellular and molecular targets) are integral to gametogenesis and subsequent embryogenesis, fetal development, and normal heart maturation. Important for in utero development, the heme oxygenase/carbon monoxide system is expressed during gametogenesis, by the placenta, during embryonic development, and by the fetus. Complex sequences of biochemical pathways result in the progressive maturation of the human heart in utero. The resulting myocardial architecture, consisting of working myocardium, coronary arteries and veins, epicardium, valves and cardiac skeleton, endocardial lining, and cardiac conduction system, determines function. Oxygen metabolism in normal and maldeveloping hearts, which develop under reduced and fluctuating oxygen concentrations, is poorly understood. "Normal" hypoxia is critical for heart formation, but "abnormal" hypoxia in utero affects cardiogenesis. The heme oxygenase/carbon monoxide system is important for in utero cardiac development, and other factors also result in alterations of the heme oxygenase/carbon monoxide system during in utero cardiac development. This review will address the role of the heme oxygenase/carbon monoxide system during cardiac development in embryo and fetal development.

SWATH proteomics analysis of placental tissue with intrahepatic cholestasis of pregnancy

INTRODUCTION

Intrahepatic cholestasis of pregnancy (ICP) usually occurs in the second and third trimesters. The disease's etiology and diagnostic criteria are currently unknown. Based on a sequence window to obtain all theoretical fragment ions (SWATH) proteomic approach, this study sought to identify potential proteins in placental tissue that may be involved in the pathogenesis of ICP and adverse fetal pregnancy outcomes.

METHODS

The postpartum placental tissue of pregnant women with ICP were chosen as the case group (ICP group) (subdivided into mild ICP group (MICP group) and severe ICP group (SICP group)), and healthy pregnant women were chosen as the control group (CTR). The hematoxylin-eosin (HE) staining was used to observe the histologic changes of placenta. The SWATH analysis combined with liquid chromatography-tandem mass spectrometry (LC-MS) was used to screen the differentially expressed proteins (DEPs) in ICP and CTR groups, and bioinformatics analysis was used to find out the biological process of these differential proteins.

RESULTS

Proteomic studies showed there were 126 DEPs from pregnant women with ICP and healthy pregnant women. Most of the identified proteins were functionally related to humoral immune response, cell response to lipopolysaccharide, antioxidant activity and heme metabolism. A subsequent examination of placentas from patients with mild and severe ICP revealed 48 proteins that were differentially expressed. Through death domain receptors and fibrinogen complexes, these DEPs primarily regulate extrinsic apoptotic signaling pathways, blood coagulation, and fibrin clot formation. The differential expressions of HBD, HPX, PDE3A, and PRG4 were down-regulated by Western blot analysis, which was consistent with proteomics.

DISCUSSION

This preliminary study helps us to understand the changes in the placental proteome of ICP patients, and provides new insights into the pathophysiology of ICP.

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.

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).

Preeclampsia Emerging as a Risk Factor of Cardiovascular Disease in Women

The objective of this literature review was to explore the long-term cardiovascular effects of preeclampsia in women. The primary goal was to determine which organs were most commonly affected in this population. Although it was previously believed that preeclampsia is cured after the delivery of the fetus and the placenta current evidence supports an association between preeclampsia and cardiovascular disease later in life, many years after the manifestation of this hypertensive pregnancy related disorder. Therefore preeclampsia may be emerging as a novel cardiovascular risk factor for women, which requires long-term follow up.

Advances in biomarker development and potential application for preeclampsia based on pathogenesis

Preeclampsia (PE) is a pregnancy-specific complication that seriously threatens the health and safety of mothers and infants. The etiology of PE has not been fully elucidated, and no effective treatments are currently available. A pregnant woman with PE often has to make a tough choice on either endangering her own health to give a birth or being forced to terminate her pregnancy. It is recommended by the International Federation of Gynecology and Obstetrics that the combination of maternal high-risk factors and biomarkers could form a good strategy for predicting the risk of PE. Such a combination may also enable more effective monitoring and early clinical intervention in high-risk populations to reduce the risk of PE. Therefore, biomarkers validated by extensive clinical research may be formally applied for clinical PE risk prediction. In this review, we summarized data from clinical research on potential biomarkers and classified them according to the current four major hypotheses, namely placental or trophoblast ischemia and hypoxia, vascular endothelial injury, oxidative stress, and immune dysregulation. Additionally, we also discussed the underlying mechanisms by which these potential biomarkers may be involved in the pathogenesis of PE. Finally, we propose that multiple biomarkers reflecting different aspects of the disease pathogenesis should be used in combination to detect the high-risk PE population in support of clinically targeted intervention and prevention of PE. It is expected that tests made of more sensitive and reliable PE biomarkers based on the aforementioned major hypotheses could potentially improve the accuracy of PE prediction in the future.

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.

Potential Protein Biomarkers for Preeclampsia

To date, the etiology of preeclampsia (PE) has not been clarified and the specific treatment is lacking; hence, early prediction and prevention are very important. Thus, a large number of biomarkers that may be associated with PE have been identified based on proteomics to provide a reference for the prediction of PE and for the understanding of the pathological mechanisms of this disease. This article briefly summarizes the application of proteomics in PE and the potential protein biomarkers to provide a reference for other researchers.

Hypertension and Reproduction

PURPOSE OF REVIEW

Many aspects of reproduction have been associated with increased blood pressure and impaired glucose metabolism that reveals a subsequent increased risk of cardiovascular disease. The aim of this review is to assess reproductive life factors associated with an increased risk of hypertension and cardiovascular disease, e.g., early life programming, sexual, and reproductive health in men and women.

RECENT FINDINGS

Impaired fetal growth, with low birth weight adjusted for gestational age, has been found associated with hypertension in adulthood. Erectile dysfunction, currently considered an early diagnostic marker of cardiovascular disease preceding the manifestation of coronary artery disease by several years, frequently coexisting with hypertension, could also be exacerbated by some antihypertensive drugs. Male hypogonadism or subfertility are associated with increased cardiovascular risk. Hypertensive disorders in pregnancy including preeclampsia represent a major cause of maternal, fetal and neonatal morbidity, and mortality. The risk of developing preeclampsia can be substantially reduced in women at its high or moderate risk with a low dose of acetylsalicylic acid initiated from 12 weeks of gestation. An increased risk of hypertension in women following invasive-assisted reproductive technologies has been newly observed. Blood pressure elevation has been noticed following contraceptive pill use, around the menopause and in postmenopausal age. Furthermore, drug treatment of hypertension has to be considered as a factor with a potential impact on reproduction (e.g., due to teratogenic drug effects). In summary, a deeper understanding of reproductive life effects on hypertension and metabolic abnormalities may improve prediction of future cardiovascular disease.

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.

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.

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.

Integrated Systems Biology Approach Identifies Novel Maternal and Placental Pathways of Preeclampsia

Preeclampsia is a disease of the mother, fetus, and placenta, and the gaps in our understanding of the complex interactions among their respective disease pathways preclude successful treatment and prevention. The placenta has a key role in the pathogenesis of the terminal pathway characterized by exaggerated maternal systemic inflammation, generalized endothelial damage, hypertension, and proteinuria. This sine qua non of preeclampsia may be triggered by distinct underlying mechanisms that occur at early stages of pregnancy and induce different phenotypes. To gain insights into these molecular pathways, we employed a systems biology approach and integrated different "omics," clinical, placental, and functional data from patients with distinct phenotypes of preeclampsia. First trimester maternal blood proteomics uncovered an altered abundance of proteins of the renin-angiotensin and immune systems, complement, and coagulation cascades in patients with term or preterm preeclampsia. Moreover, first trimester maternal blood from preterm preeclamptic patients in vitro dysregulated trophoblastic gene expression. Placental transcriptomics of women with preterm preeclampsia identified distinct gene modules associated with maternal or fetal disease. Placental "virtual" liquid biopsy showed that the dysregulation of these disease gene modules originates during the first trimester. In vitro experiments on hub transcription factors of these gene modules demonstrated that DNA hypermethylation in the regulatory region of ZNF554 leads to gene down-regulation and impaired trophoblast invasion, while BCL6 and ARNT2 up-regulation sensitizes the trophoblast to ischemia, hallmarks of preterm preeclampsia. In summary, our data suggest that there are distinct maternal and placental disease pathways, and their interaction influences the clinical presentation of preeclampsia. The activation of maternal disease pathways can be detected in all phenotypes of preeclampsia earlier and upstream of placental dysfunction, not only downstream as described before, and distinct placental disease pathways are superimposed on these maternal pathways. This is a paradigm shift, which, in agreement with epidemiological studies, warrants for the central pathologic role of preexisting maternal diseases or perturbed maternal-fetal-placental immune interactions in preeclampsia. The description of these novel pathways in the "molecular phase" of preeclampsia and the identification of their hub molecules may enable timely molecular characterization of patients with distinct preeclampsia phenotypes.

Sex and age discrepancy of HbA1c and fetal hemoglobin determined by HPLC in a large Chinese Han population

BACKGROUND

It is accepted that HbA1c is an effective indicator to evaluate glycemic control. Fetal hemoglobin (HbF) is seldom measured because traditional detection is inconvenient. In this regard, there may be an advantage in using HPLC autoanalysis of HbA1c as a surrogate method for HbF detection. The aim of the present study was to explore the distribution of HbA1c and HbF in a large Chinese Han population.

METHODS

In all, 70 553 blood samples were collected between January 2012 and June 2016. Study subjects were inpatients undergoing routine medical care and were divided into four groups based on age: Group A, 20-39 years; Group B, 40-59 years; Group C, 60-79 years; and Group D, ≥80 years. Blood HbA1c and HbF concentrations were measured by HPLC using a Tosho Bioscience (Tokyo, Japan) G8 analyzer.

RESULTS

There was a positive association between HbA1c and age, and a negative association between HbF and age. The concentration range of HbF was narrow and HbF concentrations were significantly higher in females than males, regardless of age (median 0.7% vs 0.6%, respectively; P < 0.0001). There was a low degree of correlation between HbF and HbA1c (r = 0.181, P < 0.0001). Although median HbA1c levels were higher in male than female subjects aged 20-59 years (5.5% vs 5.4%, respectively, in Group A; 5.9% vs 5.8%, respectively in Group B), in the 60-79 years group, HbA1c levels were lower in males than females (6.1% vs 6.2%, respectively; P < 0.0001).

CONCLUSIONS

The data suggest that sex and age should be considered in clinical interpretation of HbA1c.

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.

Plasma biomarkers for the identification of women at risk for early-onset preeclampsia

BACKGROUND

To identify potential biomarkers in the 1st trimester of pregnancy for the identification of women destined to develop early onset preeclampsia (EOPE).

METHODS

Blood samples were obtained from pregnant women at 11-13 weeks of gestation. Women were followed up until delivery. Five samples from EOPE complicated pregnancies and 5 from unaffected ones were analysed using 2-DE and MALDI-TOF-TOF MS/MS. The altered expression of selected proteins was verified by ELISA in an extended sample cohort.

RESULTS

Twelve proteins were differentially expressed in the plasma of women who subsequently developed EOPE as compared to controls. Alpha-1-antitrypsin (A1AT), CD5 antigen-like molecule (CD5L) Keratin, type I cytoskeletal 9 (K1C9), Myeloid cell nuclear differentiation antigen (MNDA), Transferrin (TRFE) and Vitamin D-binding protein (VTDB) were up-regulated with fold changes 3.14, 2.18, 1.53, 1.53, 4.26 3.38 respectively, whereas Alpha-2-HS-glycoprotein (FETUA), Beta-2-glycoprotein 1 (APOH), Complement factor B (CFAB), Haptoglobin (HPT), Vitronectin (VTNC) and Zinc-alpha-2-glycoprotein (ZA2G) were down-regulated with fold changes -0.38, -0.76, -0.24, -0.47, -0.23, and -0.50 respectively. The down-regulation of APOH, VTNC and HPT was verified using ELISA.

CONCLUSIONS

The differentially expressed proteins represent potential biomarkers for the early screening for EOPE. Follow-up experiments however are necessary for evaluation.

Fetal hemoglobin is much less prone to DNA cleavage compared to the adult protein

Hemoglobin (Hb) is well protected inside the red blood cells (RBCs). Upon hemolysis and when free in circulation, Hb can be involved in a range of radical generating reactions and may thereby attack several different biomolecules. In this study, we have examined the potential damaging effects of cell-free Hb on plasmid DNA (pDNA). Hb induced cleavage of supercoiled pDNA (sc pDNA) which was proportional to the concentration of Hb applied. Almost 70% of sc pDNA was converted to open circular or linear DNA using 10 µM of Hb in 12 h. Hb can be present in several different forms. The oxy (HbO₂) and met forms are most reactive, while the carboxy-protein shows only low hydrolytic activity. Hemoglobin A (HbA) could easily induce complete pDNA cleavage while fetal hemoglobin (HbF) was three-fold less reactive. By inserting, a redox active cysteine residue on the surface of the alpha chain of HbF by site-directed mutagenesis, the DNA cleavage reaction was enhanced by 82%. Reactive oxygen species were not directly involved in the reaction since addition of superoxide dismutase and catalase did not prevent pDNA cleavage. The reactivity of Hb with pDNA can rather be associated with the formation of protein based radicals.

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Hemoglobin induced plasmid DNA cleavage in the absence of hydrogen peroxide.

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Fetal hemoglobin was three-fold less reactive compared to the adult protein on plasmid DNA.

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Insertion of a cysteine residue in the alpha chain enhanced the DNA cleavage reaction by 82%.

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Protein based radicals are associated with the DNA cleavage activity of hemoglobin.