Preeclampsia and calcium adenosine triphosphatase activity of red blood cell ghosts

Biomarkers of oxidative stress and reproductive complications

Oxidative stress is the result of an imbalance between the formation of reactive oxygen species (ROS) and the levels of enzymatic and non-enzymatic antioxidants. The assessment of biological redox status is performed by the use of oxidative stress biomarkers. An oxidative stress biomarker is defined as any physical structure or process or chemical compound that can be assessed in a living being (in vivo) or in solid or fluid parts thereof (in vitro), the determination of which is a reproducible and reliable indicator of oxidative stress. The use of oxidative stress biomarkers allows early identification of the risk of developing diseases associated with this process and also opens up possibilities for new treatments. At the end of the last century, interest in oxidative stress biomarkers began to grow, due to evidence of the association between the generation of free radicals and various pathologies. Up to now, a significant number of studies have been carried out to identify and apply different oxidative stress biomarkers in clinical practice. Among the most important oxidative stress biomarkers, it can be mentioned the products of oxidative modifications of lipids, proteins, nucleic acids, and uric acid as well as the measurement of the total antioxidant capacity of fluids in the human body. In this review, we aim to present recent advances and current knowledge on the main biomarkers of oxidative stress, including the discovery of new biomarkers, with emphasis on the various reproductive complications associated with variations in oxidative stress levels.

Effect of Mg-Gluconate on the Osmotic Fragility of Red Blood Cells, Lipid Peroxidation, and Ca2+-ATPase (PMCA) Activity of Placental Homogenates and Red Blood Cell Ghosts From Salt-Loaded Pregnant Rats

Preeclampsia (PE) is a pregnancy-specific syndrome with multisystem involvement which leads to fetal, neonatal, and maternal morbidity and mortality. A model of salt-loaded pregnant rats has been previously studied, sharing several pathological characteristics of preeclamptic women. In this study, it was compared the effects of the treatment with an oral magnesium salt, magnesium gluconate (Mg-gluconate), on the osmotic fragility of red blood cells, lipid peroxidation, and PMCA activity of placental homogenates and red blood cell ghosts in salt-loaded pregnant rats. Mg-gluconate has a higher antioxidant capacity than MgSO₄ due to the presence of several hydroxyl groups in the two anions of this salt. Salt-loaded pregnant rats received 1.8% NaCl solution ad libitum as a beverage during the last week of pregnancy. On day 22nd of pregnancy, the rats were euthanized and red blood cells and placenta were obtained. Salt-loaded pregnant rats showed an increased level of lipid peroxidation and a lowered PMCA activity in placental and red blood cell ghosts, as well as an increased osmotic fragility of their red blood cells. The treatment of the salt-loaded pregnant rats with Mg-gluconate avoids the rise in the level of lipid peroxidation and the concomitant lowering of the PMCA activity of their red blood cell membranes, reaching values similar to those from control pregnant rats. Also, this treatment prevents the increase of the osmotic fragility of their red blood cells, keeping values similar to those from control pregnant rats. Mg-gluconate seems to be an important candidate for the replacement of the MgSO₄ treatment of preeclamptic women.

Evidence for the placenta-brain axis: multi-omic kernel aggregation predicts intellectual and social impairment in children born extremely preterm

BACKGROUND

Children born extremely preterm are at heightened risk for intellectual and social impairment, including Autism Spectrum Disorder (ASD). There is increasing evidence for a key role of the placenta in prenatal developmental programming, suggesting that the placenta may, in part, contribute to origins of neurodevelopmental outcomes.

METHODS

We examined associations between placental transcriptomic and epigenomic profiles and assessed their ability to predict intellectual and social impairment at age 10 years in 379 children from the Extremely Low Gestational Age Newborn (ELGAN) cohort. Assessment of intellectual ability (IQ) and social function was completed with the Differential Ability Scales-II and Social Responsiveness Scale (SRS), respectively. Examining IQ and SRS allows for studying ASD risk beyond the diagnostic criteria, as IQ and SRS are continuous measures strongly correlated with ASD. Genome-wide mRNA, CpG methylation and miRNA were assayeds with the Illumina Hiseq 2500, HTG EdgeSeq miRNA Whole Transcriptome Assay, and Illumina EPIC/850 K array, respectively. We conducted genome-wide differential analyses of placental mRNA, miRNA, and CpG methylation data. These molecular features were then integrated for a predictive analysis of IQ and SRS outcomes using kernel aggregation regression. We lastly examined associations between ASD and the multi-omic-predicted component of IQ and SRS.

RESULTS

Genes with important roles in neurodevelopment and placental tissue organization were associated with intellectual and social impairment. Kernel aggregations of placental multi-omics strongly predicted intellectual and social function, explaining approximately 8% and 12% of variance in SRS and IQ scores via cross-validation, respectively. Predicted in-sample SRS and IQ showed significant positive and negative associations with ASD case-control status.

LIMITATIONS

The ELGAN cohort comprises children born pre-term, and generalization may be affected by unmeasured confounders associated with low gestational age. We conducted external validation of predictive models, though the sample size (N = 49) and the scope of the available out-sample placental dataset are limited. Further validation of the models is merited.

CONCLUSIONS

Aggregating information from biomarkers within and among molecular data types improves prediction of complex traits like social and intellectual ability in children born extremely preterm, suggesting that traits within the placenta-brain axis may be omnigenic.

The Plasma Membrane Calcium ATPases and Their Role as Major New Players in Human Disease

The Ca²⁺ extrusion function of the four mammalian isoforms of the plasma membrane calcium ATPases (PMCAs) is well established. There is also ever-increasing detail known of their roles in global and local Ca²⁺ homeostasis and intracellular Ca²⁺ signaling in a wide variety of cell types and tissues. It is becoming clear that the spatiotemporal patterns of expression of the PMCAs and the fact that their abundances and relative expression levels vary from cell type to cell type both reflect and impact on their specific functions in these cells. Over recent years it has become increasingly apparent that these genes have potentially significant roles in human health and disease, with PMCAs1-4 being associated with cardiovascular diseases, deafness, autism, ataxia, adenoma, and malarial resistance. This review will bring together evidence of the variety of tissue-specific functions of PMCAs and will highlight the roles these genes play in regulating normal physiological functions and the considerable impact the genes have on human disease.

Osmotic fragility of red blood cells, lipid peroxidation and Ca²⁺-ATPase activity of placental homogenates and red blood cell ghosts in salt-loaded pregnant rats

OBJECTIVE

To evaluate the osmotic fragility of red blood cells and the level of lipid peroxidation, the Ca(2+)-ATPase activity of red cell ghosts and placental homogenates from salt-loaded pregnant rats.

METHODS

Salt-loaded pregnant rats received 1.8% NaCl solution ad libitum as a beverage for seven days, starting on 15th day of pregnancy. Then, it was evaluated the level of lipid peroxidation and the Ca(2+)-ATPase activity of placental homogenates and red blood cell ghosts from control and experimental rats. Furthermore, the osmotic fragility of the red blood cells was evaluated by measuring the lysis of these cells when incubated with a NaCl solution with different osmolarities.

RESULTS

It was found that placental homogenates and red blood cell ghosts from experimental pregnant rats showed an increased level of lipid peroxidation and a lowered Ca(2+)-ATPase activity, as compared to control pregnant rats. They also presented an increased osmotic fragility of their red blood cells.

CONCLUSIONS

Salt-loaded pregnant rats showed, similar to preeclamptic women, an increased level of lipid peroxidation and a lowered Ca(2+)-ATPase activity in placental and red blood cells membranes, as well as an increased osmotic fragility of the red blood cells.

Na⁺, K⁺-ATPase and Ca²⁺-ATPase activities in basal and microvillous syncytiotrophoblast membranes from preeclamptic human term placenta

OBJECTIVE

The aim of this study is to evaluate the effect of preeclampsia on the level of lipid peroxidation, activity and expression of both plasma membrane Ca(2+)- and Na(+), K(+)-ATPases in syncytiotrophoblast.

METHODS

The level of lipid peroxidation was estimated by measuring TBARS. ATPase activities were quantified by a colorimetric method measuring the amount of inorganic phosphate during the assay. Expression of Ca(2+)- and Na(+), K(+)-ATPases in syncytiotrophoblast plasma membranes and term placenta tissue sections was investigated using Western blot and immunohistochemistry, respectively.

RESULTS

Our results show a higher level of lipid peroxidation of syncytiotrophoblast plasma membranes from preeclamptic, as compared to uncomplicated pregnant women. Preeclampsia also significantly reduced the activity of Ca(2+)- and Na(+), K(+)-ATPases; however, expression of both ATPases was unaffected.

CONCLUSION

Our findings suggest that the reduction of Ca(2+)- and Na(+), K(+)-ATPase activities during preeclampsia could be at least partially due to an increased level of lipid peroxidation of the syncytiotrophoblast plasma membranes.

Effect of hypoxia on the calcium and magnesium content, lipid peroxidation level, and Ca²⁺-ATPase activity of syncytiotrophoblast plasma membranes from placental explants

In the current study the possible relationship between the Ca²⁺/Mg²⁺ ratio of human syncytiotrophoblast plasma membranes and their lipid peroxidation and Ca²⁺-ATPase activity was determined. Syncytiotrophoblast plasma membranes of placental explants cultured under hypoxia increased their lipid peroxidation and Ca²⁺ content, diminished their Ca²⁺-ATPase activity, and kept their Mg²⁺ content unchanged. Membranes preincubated with different concentrations of Ca²⁺ increased their Ca²⁺ content without changes in their Mg²⁺ content. There is a direct relationship between Ca²⁺ content and lipid peroxidation of the membranes, as well as an inverse relationship between their Ca²⁺ content and Ca²⁺-ATPase activity. On the contrary, preincubation of membranes with different concentrations of Mg²⁺ showed a higher Mg²⁺ content without changing their lipid peroxidation and Ca²⁺-ATPase activity. Explants cultured under hypoxia in the presence of 4 mM MgSO₄ showed similar values of lipid peroxidation and Ca²⁺-ATPase activity of their membranes compared to those of explants cultured under normoxia. Increased Ca²⁺ content of the membranes by interacting with negatively charged phospholipids could result in destabilizing effects of the membrane structure, exposing hydrocarbon chains of fatty acids to the action of free radicals. Mg²⁺ might exert a stabilizing effect of the membranes, avoiding their exposure to free radicals.

The common single-nucleotide polymorphism rs2681472 is associated with early-onset preeclampsia in Northern Han Chinese women

Preeclampsia, characterized by hypertension and proteinuria, remains a leading cause of maternal morbidity and mortality. Recently, a genome-wide association study (GWAS) identified the single-nucleotide polymorphism, rs2681472, as a new hypertension susceptibility genetic variant. The purpose of this study was to evaluate the association between preeclampsia and rs268172 in a Northern Han Chinese population. We genotyped 1218 unrelated Northern Han Chinese women, including 515 patients with preeclampsia and 703 healthy controls. No significant differences were detected in the allele frequencies between patients and controls (P = .23). When patients were divided into early-onset and late-onset preeclampsia according to gestational age of disease onset, the allele frequencies significantly differed between controls and patients with early-onset preeclampsia (P = .02). Genotype frequencies also were significantly different between controls and patients early-onset preeclampsia when data were analyzed under additive (P = .03) and dominant (P = .009) models. We replicated this association in an independent Northern Han Chinese population and observed a significant difference in the allele frequencies between patients with early-onset preeclampsia and controls (P = .011). We report that rs2681472 is associated with early-onset preeclampsia in Northern Han Chinese women.

Vascular and cellular calcium in normal and hypertensive pregnancy

Normal pregnancy is associated with significant hemodynamic changes in the cardiovascular system in order to meet the metabolic demands of mother and fetus. These changes include increased cardiac output, decreased vascular resistance, and vascular remodeling in the uterine and systemic circulation. Preeclampsia (PE) is a major complication of pregnancy characterized by proteinuria and hypertension. Several risk factors have been implicated in the pathogenesis of PE including genetic and dietary factors. Ca2+ is an essential dietary element and an important regulator of many cellular processes including vascular function. The importance of adequate dietary Ca2+ intake during pregnancy is supported by many studies. Pregnancy-associated changes in Ca2+ metabolism and plasma Ca2+ have been observed. During pregnancy, changes in intracellular free Ca2+ concentration ([Ca2+](i)) have been described in red blood cells, platelets and immune cells. Also, during pregnancy, an increase in [Ca2+](i) in endothelial cells (EC) stimulates the production of vasodilator substances such as nitric oxide and prostacyclin. Normal pregnancy is also associated with decreased vascular smooth muscle (VSM) [Ca2+](i) and possibly the Ca2+-sensitization pathways of VSM contraction including protein kinase C, Rho-kinase, and mitogen-activated protein kinase. Ca2+-dependent matrix metalloproteinases could also promote extracellular matrix degradation and vascular remodeling during pregnancy. Disruption in the balance between dietary, plasma and vascular cell Ca2+ may be responsible for some of the manifestation of PE including procoagulation, decreased vasodilation, and increased vasoconstriction and vascular resistance. The potential benefits of Ca2+ supplements during pregnancy, and the use of modulators of vascular Ca2+ to reduce the manifestations of PE in susceptible women remain an important area for experimental and clinical research.

Calcium‐ATPase Activity of Red Blood Cell Ghosts from Preeclamptic Women, Antepartum and Postpartum

OBJECTIVE

We determined the calcium activated adenosine triphosphatase (Ca-ATPase) activity and level of lipid peroxidation thiobarbituric acid-reactive substances (TBARS) of red blood cell ghosts in the antepartum and postpartum of normotensive and preeclamptic pregnant women.

METHODS

Samples of venous blood were obtained by venipuncture of nulliparous normotensive and preeclamptic pregnant women antepartum and two, four, six, and 20 weeks postpartum. The red blood cell ghosts were prepared and assayed for Ca-ATPase activity and TBARS.

MAIN OUTCOME MEASURE(S)

We expected to find a return to normal values of both Ca-ATPase activity and TBARS level of the red blood cell ghosts, modified in the preeclamptic pregnant women, during their puerperium.

RESULTS

The Ca-ATPase activity of red cell ghosts from preeclamptic women, antepartum, is lower than that of normotensive pregnant women. The ATPase activity returns to normal values during the first six weeks of postpartum. The level of TBARS of red cell ghosts from preeclamptic women follows a pattern that is inversely proportional to the one of the Ca-ATPase activity.

CONCLUSIONS

Preeclampsia produces a significant diminution of the Ca-ATPase activity and an increase in the levels of TBARS in the erythrocytes. As soon as all the symptoms of preeclampsia disappear in the postpartum, both Ca-ATPase activity and TBARS return to normal values.

Preeclampsia and Calcium‐ATPase Activity of Plasma Membranes from Human Myometrium and Placental Trophoblast

OBJECTIVE

We determined calcium-activated adenosine triphosphatase (Ca-ATPase) activity and thiobarbituric acid-reactive substances (TBARS) of plasma membranes from myometrium and placental trophoblast of normotensive and preeclamptic pregnant women.

METHODS

Samples of myometrium were obtained by uterine biopsies taken upon delivery by cesarean section from nulliparous normotensive and preeclamptic pregnant women. Placentas were obtained after full term vaginal delivery from either normotensive or preeclamptic women. Plasma membrane fractions were prepared from both myometrium and placenta and assayed for Ca-ATPase activity and TBARS.

MAIN OUTCOME MEASURE(S)

We expected to find a higher level of TBARS and, consequently, a lower activity of Ca-ATPase of the plasma membrane fractions obtained from both myometrium and placenta of preeclamptic women.

RESULTS

The Ca-ATPase activity of myometrium and placental trophoblast from preeclamptic women was about 50% lower than that from normotensive women, while the TBARS were higher.

CONCLUSIONS

A reduced Ca-ATPase activity, caused by an increased level of TBARS, may result in an increase in the cytosolic calcium concentration in the vascular smooth muscle cells of preeclamptic women and thus partially explain the high blood pressure developed by these patients.

Lipid Peroxidation and Ca-ATPase Activity of Basal Plasma Membranes of Syncytiotrophoblast from Normotensive Pregnant Women

BACKGROUND

The Ca-ATPase activity of the plasma membranes of several tissues of preeclamptic pregnant women is significantly reduced when compared with the values of normotensive pregnant women. This has been explained considering the raise in the level of lipid peroxidation of the plasma membranes with preeclampsia. In this work we studied the effect of lipid peroxidation of syncytiotrophoblast basal (fetal facing) plasma membranes from normotensive pregnant women, on their level of Ca-ATPase activity.

METHODS

The syncytiotrophoblast basal (fetal facing) plasma membranes from normotensive pregnant women were isolated and irradiated with ultraviolet (UV) light (254 nm). The membranes were then assayed for Ca-ATPase activity and lipid peroxidation by TBARS.

RESULTS

The UV irradiation raises the level of lipid peroxidation of the membranes, producing a concomitant inhibition of their Ca-ATPase activity. Presence of the antioxidant butylated hydroxytoluene during the UV irradiation of the membranes prevents increase in their level of lipid peroxidation and hence the inhibition of their Ca-ATPase activity.

CONCLUSION

These results give a strong support to the hypothesis that the lowered Ca-ATPase activity already described for plasma membranes of several tissues of preeclamptic women is the consequence of the increased level of lipid peroxidation shown by these membranes.

The plasma membrane Ca2+-ATPase protein from red blood cells is not modified in preeclampsia

Plasma membrane Ca2+-ATPase activity diminishes by about 50% in red blood cells during preeclampsia. We investigated whether the number of Ca2+-ATPase molecules is modified in red cell membranes from preeclamptic pregnant women by measuring the specific phosphorylated intermediate of this enzyme. Also, we isolated the Ca2+-ATPase protein from both normotensive and preeclamptic pregnant women and estimated its molecular weight, and its cross-reactions with specific polyclonal and monoclonal (5F10) antibodies against it. We measured the Ca2+-ATPase activity in a purified state and the effect of known modulators of this ATPase. It was found that the phosphorylated intermediate associated with PMCA is similar for red cell ghosts from normotensive and preeclamptic women, suggesting a similar number of ATPase molecules in these membranes. The molecular weight of the Ca2+-ATPase is around 140 kDa for both normotensive and preeclamptic membranes, and its cross-reactions with specific antibodies is similar, suggesting that the protein structure remains intact in preeclampsia. Calmodulin, ethanol, or both calmodulin plus ethanol, stimulated the Ca2+-ATPase activity to the same extent for both normotensive and preeclamptic preparations. Our results showed that the reduced Ca2+-ATPase activity of the red cell membranes from preeclamptic women is not associated with a defective enzyme, but rather with a high level of lipid peroxidation.

Effect of magnesium sulfate on the calcium-stimulated adenosine triphosphatase activity and lipid peroxidation of red blood cell membranes from preeclamptic women

The effect of the treatment with magnesium sulfate (MgSO(4)) on Ca-ATPase activity and level of lipid peroxidation of red blood cells from preeclamptic pregnant women was examined because it is known that these parameters are affected with preeclampsia. Red cell ghosts from 11 normotensive and 11 preeclamptic pregnant women, before and after treatment with MgSO(4), were assayed for Ca-ATPase activity and level of lipid peroxidation, determined as TBARS or conjugated dienes. It was found that the Ca-ATPase activity is significantly lower and the level of lipid peroxidation is significantly higher in the preeclamptic women with no treatment, as compared to normotensive pregnant women. Both parameters return to normal values after the MgSO(4) therapy. These results can be mimicked by in vitro preincubation with MgSO(4) of intact red blood cells from preeclamptic pregnant women, without any treatment. Our data indicate that MgSO(4) treatment of preeclamptic pregnant women modifies both the Ca-ATPase activity and the level of lipid peroxidation of their red blood cell membranes, reaching values similar to those of normotensive pregnant women. The diminution of the level of lipid peroxidation by MgSO(4), can account for the increase in Ca-ATPase activity.

Lipid peroxidation and active calcium transport in inside–out vesicles of red blood cells from preeclamptic women

We previously reported that in preeclampsia Ca-ATPase activity diminishes about 50% in red blood cells, myometrium and syncitiotrophoblast plasma membranes. In this work, we measured the active Ca++ uptake by inside-out vesicles of human red blood cells from preeclamptic and normotensive pregnant women. Active calcium uptake by the vesicles was diminished by 49+/-3% in the preeclamptic women as compared to the gestational controls ( 8.06 +/- 0.11 nmol Ca++/mg protein min, gestational controls; 4.08 +/- 0.1 nmol Ca++/mg protein min, preeclamptics). This lowered calcium uptake correlates well with the lowered Ca-ATPase activity found in the red blood cells ghosts of the preeclamptic women (17.05 +/- 0.96 nmol Pi/mg protein min, gestational controls; 8.85 +/- 0.45 nmol Pi/mg protein min, preeclamptics). The reduced calcium uptake and Ca-ATPase activity of the red cell membranes both appear to be associated with a high level of lipid peroxidation. Thus there is a diminution in the active transport of calcium in the red blood cells of preeclamptic women. If this also occurs in other cell types of the preclamptic women, it could result in an increase in their cytosolic calcium concentration which might be responsible, in part, for some of the symptoms of this disease.

Calcium metabolism in pre-eclampsia

OBJECTIVES

To study calcium metabolism in pre-eclampsia and normotensive gravid women.

METHOD

Ten milliliters of heparinized blood samples and 24-h urine samples were collected from 50 pre-eclamptic and 50 normotensive primigravidae. Blood samples were studied for calcium uptake, intracellular calcium level and calcium-dependent adenosine triphosphatase activity of red blood cell ghost. Urinary calcium excretion was estimated from the 24-h urine samples. These values were compared in the two groups.

RESULTS

The mean gestational age at recruitment was similar in both the groups. The mean maternal age was 24.28 +/- 2.41 years in pre-eclamptic and 23.48 +/- 4.16 years in normotensive women. In pre-eclampsia 24-h urinary calcium excretion (71.20 +/- 22.95 mg/day) and calcium-dependent ATPase activity (10.78 +/- 2.40 nmol/Pi/mg protein/min) was significantly lower compared to normotensive primigravidae (calcium excretion = 189.24 +/- 57.06 mg/day; Ca2+-dependent ATPase = 12.64 +/- 2.42 nmolPi/mg /protein per min; P < 0.001). Intracellular calcium levels and calcium uptake at 10 min by red blood cells were significantly higher in pre-eclampsia (P < 0.05). Calcium uptake by red blood cells at 20 and 30 min was similar in both groups.

CONCLUSION

Pre-eclampsia is associated with increased levels of intracellular calcium, decreased calcium-dependent ATPase activity of erythrocytes and hypocalciuria.

Preeclampsia, lipid peroxidation, and calcium adenosine triphosphatase activity of red blood cell ghosts

OBJECTIVE

We evaluated the effect of lipid peroxidation on the calcium adenosine triphosphatase activity of red blood cell ghosts from normotensive pregnant women and compared it with the adenosine triphosphatase activity and lipid peroxidation in preeclampsia.

STUDY DESIGN

Ten nulliparous normotensive and 10 nulliparous preeclamptic pregnant women (38 to 39 weeks of gestation) were used as blood donors. Preeclampsia was diagnosed on the basis of blood pressure (>140/90 mm Hg) and proteinuria (>0.5 gm of urinary protein per day). Red blood cell ghosts were prepared for both groups and used for calcium adenosine triphosphatase activity and lipid peroxidation determinations. Control ghosts (normotensive) were irradiated with ultraviolet light for different lengths of time.

RESULTS

Calcium adenosine triphosphatase activity of red blood cell ghosts from normotensive women is sensitive to lipid peroxidation. The lipid peroxidation of red blood cell ghosts from preeclamptic women is higher than that from normotensive women.

CONCLUSION

The diminution of the calcium adenosine triphosphatase activity with preeclampsia could be explained by the sensitivity of this adenosine triphosphatase to lipid peroxidation.