Antioxidant gene expression in preeclamptic placentae: a preliminary investigation.

Oxidative stress has been implicated in the pathogenesis of preeclampsia. This study measured the relative mRNA expression of antioxidant proteins glutathione peroxidase 1 and 4, glutathione reductase, thioredoxin 1 and 2, thioredoxin reductase 1, thioredoxin peroxidase 3 and superoxide dismutase 1 and 2 in preeclamptic and non-preeclamptic placentae. Quantitative real-time PCR was conducted on placental mRNA isolated from preeclamptic and control patients. Cycle threshold numbers and fold differences were calculated as a measure of linear product amplification and used for comparison. The mRNA expression of glutathione reductase was significantly reduced (fold difference 0.41, p<0.05) in preeclamptic placenta when compared to controls while the expression of thioredoxin peroxidase 3 was significantly increased (fold difference 3.25, p<0.001) in the preeclamptic placentae. No significant difference in expression was observed for glutathione peroxidase 1 and 4, thioredoxin 1 and 2, thioredoxin reductase 1 and superoxide dismutase 1 and 2. These results suggest that it is the abnormal oxidative insult associated with preeclampsia not mRNA expression of antioxidant proteins that may be responsible for reduced antioxidant enzyme activity in preeclamptic placentae.

Chronic hypoxia in vivo reduces placental oxidative stress.

Decreased placental oxygenation and increased oxidative stress are implicated in the development of preeclampsia. Oxidative stress arises from imbalance between pro-versus anti-oxidants and can lead to biological oxidation and apoptosis. Because pregnant women living at high altitude (3100 m, HA) have lowered arterial PO2 and an increased incidence of preeclampsia, we hypothesized that HA placentas would have decreased anti-oxidant enzyme activity, increased oxidative stress (lipid peroxidation, protein oxidation and nitration) and greater trophoblast apoptosis than low-altitude (LA) placentas. We measured enzymatic activities, lipid and protein oxidation and co-factor concentrations by spectrophotometric techniques and ELISA in 12 LA and 18 HA placentas. Immunohistochemistry (IHC) was used to evaluate nitrated proteins and specific markers of apoptosis (activated caspase 3 and M30). Superoxide dismutase activity was marginally lower (p=0.05), while glutathione peroxidase activity (p<0.05), thioredoxin concentrations (p<0.005) and thioredoxin reductase activity p<0.01 were all reduced in HA placentas. Decreased anti-oxidant activity was not associated with increased oxidative stress: lipid peroxide content and protein carbonyl formation were lower at HA (p<0.01). We found greater nitrotyrosine residues in the syncytiotrophoblast at 3100 m (p<0.05), but apoptosis did not differ between altitudes. Our data suggest that hypoxia does not increase placental oxidative stress in vivo. Nitrative stress may be a consequence of hypoxia but does not appear to contribute to increased apoptosis. Lowered placental concentrations of anti-oxidants may contribute to the susceptibility of women living at HA to the development of preeclampsia, but are unlikely to be etiological.

The association between third trimester multivitamin/mineral supplements and gestational length in uncomplicated pregnancies.

BACKGROUND: Widespread use of maternal micronutrient supplements have been correlated to gestational length and outcome in women predisposed to pre-eclampsia and preterm birth. However, research is yet to be conducted examining the influence of micronutrient supplements on outcomes at term in uncomplicated pregnancies. AIM: To analyse the relationship between third trimester micronutrient supplementation and gestation length at birth, demographics and maternal birthing outcomes in well women at term in a South East Queensland representative population. METHODS: This research retrospectively analysed existing data pertaining to 427 uncomplicated, pregnancies birthing at the Gold Coast and Logan Hospitals using information gathered through the Environments for Healthy Living Study and Queensland perinatal data collection. Data were analysed using SPSS v20 by Chi square, ANOVA and regression analysis. FINDINGS: Women in the third trimester taking individual zinc, folic acid or iron supplements in combination with a multivitamin were twice as likely to birth beyond 41 completed weeks (AOR 2.054, 95% CI 1.310-7.383, p=0.038) then those who did not take any supplement when controlled for established confounders. Non supplement users were found to experience a lower rate of post dates labour and requirements for induction (AOR 0.483, 95% CI 0.278-0.840, p=0.01). CONCLUSION: Length of gestation demonstrates significant associations with micronutrient supplementation practices. Well women consuming third trimester individual micronutrient supplements in addition to multivitamins experienced a longer gestation at term compared to women taking no micronutrients, increasing their risk for postdates induction of labour.

Increased anti-oxidant enzyme activity and biological oxidation in placentae of pregnancies complicated by maternal asthma.

Our previous work has demonstrated that alterations in placental function are associated with changes in fetal development in pregnancies complicated by asthma. The pathophysiology of asthma in adults and children and intrauterine growth restriction during pregnancy are associated with oxidative stress. Based on this information, we examined whether placental anti-oxidant pathways and markers of biological oxidation were altered in pregnancies complicated by asthma. Anti-oxidant enzyme activities of superoxide dismutase, glutathione peroxidase and thioredoxin reductase, thioredoxin concentrations, lipid and protein oxidation levels were measured in placentae of pregnancies complicated by asthma and compared to uncomplicated, non-asthmatic pregnancies. Placental tissue homogenates of pregnancies complicated by asthma demonstrated significantly increased levels of lipid peroxidation (25.7+/-1.8 micromol/mg protein versus 12.1+/-1.6 micromol/mg protein, P=0.008) and protein carbonyl concentrations (414.6+/-51.4 units/mg protein versus 222.3+/-32.6 units/mg protein, P=0.0032) when compared to non-asthmatic controls. The activities of the anti-oxidant proteins superoxide dismutase (2.17+/-0.09 units/mg protein versus 1.67+/-0.09 units/mg protein, P=0.014) and thioredoxin reductase (54.0+/-6.9 units/mg protein versus 28.7+/-6.0 units/mg protein, P=0.009) were significantly increased in the presence of maternal asthma. Placental thioredoxin levels (102.9+/-5.3 ng/mg protein versus 92.9+/-8.6 ng/mg protein, P=0.37) and glutathione peroxidase activity (27.3+/-2.2 mmol/min/mg protein versus 28.3+/-2.2 mmol/min/mg, P=0.83) were not significantly different in pregnancies complicated by asthma and non-asthmatic pregnancies. There was no effect of fetal sex, asthma severity or treatment for asthma on these pathways. Maternal asthma during pregnancy is associated with increased placental enzymatic anti-oxidant capacity and also increased protein oxidation suggesting there is a compensatory increase in anti-oxidant activity in response to increased oxidative stress.

Increased biological oxidation and reduced anti-oxidant enzyme activity in pre-eclamptic placentae.

Oxidative stress occurs when cellular levels of reactive oxygen species exceed anti-oxidant capabilities and has been implicated in the pathogenesis of pre-eclampsia. In this study we have examined the tissue levels of endogenous anti-oxidant proteins (superoxide dismutase, glutathione peroxidase, thioredoxin reductase and thioredoxin) and the level of lipid and protein oxidation in placental samples from normal and pre-eclamptic pregnancies. Pre-eclamptic tissue homogenates demonstrated significantly increased levels of lipid peroxidation (20.68 +/- 7.811 microM protein versus 5.33 +/- 4.03 microM/mg protein, P < 0.001) and a trended increase in protein carbonyl concentration (248.1 +/- 97.71 units/mg protein versus 209.7 +/- 82.6 U/mg protein) when compared to controls. The levels and activities of the anti-oxidant proteins superoxide dismutase (2.48 +/- 0.6 U/mg protein versus 2.02 +/- 0.51 U/mg protein, P <0.02), thioredoxin reductase (19.25 +/- 9.81 U/mg protein versus 13.02 +/- 5.66 U/mg protein,P = 0.02), thioredoxin (107.00 +/- 18.11 ng/mg protein versus 91.12 +/- 21.18 ng/mg protein, P = 0.02) and glutathione peroxidase (17.33 +/- 6.63 mmol/min/mg protein versus 11.50 +/- 3.11 mmol/min/mg, P < 0.02) were all found to be significantly reduced when comparing pre-eclamptic placental tissue homogenates to gestational age-matched control placentae from non-pre-eclamptic pregnancies. The results of this study demonstrate a decreased enzymatic anti-oxidant capacity and increased oxidation in placental tissue from pre-eclamptic women, which may contribute to the pathogenesis of this complex disorder.

Selenium supplementation protects trophoblast cells from mitochondrial oxidative stress.

INTRODUCTION: Oxidative stress plays an important role in the pathogenesis of preeclampsia, a placental disorder affecting approximately 7% of pregnancies. Trophoblast cells are susceptible to oxidative stress which causes increased cell death and placental turnover. In this study, inhibitors of the mitochondrial respiratory chain were utilised to induce oxidative stress and the effect that selenium supplementation had on trophoblast viability was investigated. METHODS: Trophoblast cells (BeWo, JEG-3 and Swan-71) were treated with Na Selenite (100 nM) or Selenomethionine (500 nM) to increase the biological activity of antioxidants Glutathione Peroxidase and Thioredoxin Reductase. The cells were then oxidatively stressed with the addition of increasing doses of Antimycin C and Rotenone and the Resazurin end point assay was used to assess cellular activity. RESULTS: There was a significant dose dependent decrease in the cellular activity in BeWo, JEG-3 and Swan-71 when treated for 4 h with increasing concentrations of Antimycin (40-320 µM) and Rotenone (100-800 nM). Prior incubation with Na Selenite and Selenomethionine was able to protect trophoblast cells from oxidative stress at Rotenone concentrations of 200 and 400 nM (P < 0.001) and Antimycin concentrations of 80-240 µM (P < 0.001). DISCUSSION: These data suggest that selenoproteins such as Glutathione Peroxidase and Thioredoxin Reductase have an important role in protecting trophoblast mitochondria from oxidative stress. CONCLUSIONS: This study emphasises the importance of maintaining an adequate selenium supply during pregnancy and especially in pregnancies complicated by conditions such as preeclampsia.

Selenium supplementation protects trophoblast cells from oxidative stress.

Oxidative stress is a key feature in the pathogenesis of pre-eclampsia and antioxidants have been proposed as a potential therapy in the treatment of this important complication of pregnancy. In this report selenium supplementation was used to up-regulate the antioxidant enzymes glutathione peroxidase and thioredoxin reductase and the protective effect that this had on cellular metabolism during oxidative stress was examined. Bewo and Jeg-3 trophoblast cells were supplemented with organic and inorganic forms of selenium and 3 forms of peroxide in a range of doses were utilised to generate oxidative stress. Thioredoxin reductase and glutathione peroxidase activity were maximally expressed after supplementation with 100 nM NaSe and 500 nM SeMethionine. Application of H2O2 in the range of 200-400 µM for 24h resulted in significant (p<0.001) inhibition of cellular activity, an effect negated by Se supplementation. Tert-butyl H2O2 and cumene H2O2 concentrations between 30 and 50 uM similarly inhibited cellular activity and this could be significantly (p<0.001) reversed by Se supplementation. Auranofin, a specific inhibitor of thioredoxin reductase and glutathione peroxidase was used to prove that the protective effect generated by Se supplementation was due to up regulation of these enzymes. These studies provide direct evidence that selenium supplementation can up-regulate endogenous antioxidant systems and protects trophoblast cells from oxidative stress. This may inform the development of future therapies for pre-eclampsia and emphasises the importance of selenium adequacy during pregnancy.

Selenium and preeclampsia: A global perspective.

Preeclampsia is a complex multisystem disorder of pregnancy where oxidative stress plays an important aetiological role. The role of selenium in the synthesis of endogenous antioxidants is well documented, and a significant reduction in selenium has been reported in preeclamptic women. The objective of this study was to map global selenium status and preeclampsia incidence. This study identified peer reviewed journal articles reporting national preeclampsia incidence (%) and matched these with reported values of selenium intake and plasma/serum selenium concentrations (µg/L). Matched data were obtained for 45 regions, reporting 6456,570 births, spanning Europe, Asia, Australasia, Africa, North and South America. Increasing plasma selenium concentration was found to be correlated with a reduction in preeclampsia incidence (Pearson's r=-0.604, P<0.0001). Countries with a reported serum/plasma selenium level of ⩾95µg/L were considered selenium sufficient and a significant reduction in preeclampsia incidence for countries above this value (P=0.0007) was noted. Significant reductions in preeclampsia incidence were found to coincide with increases in plasma/serum selenium concentration in the New Zealand (P=0.0003) and Finland (0.0028) populations following Government intervention. This study supports the hypothesis that selenium supplementation may be beneficial in reducing oxidative stress in women at risk of preeclampsia.

The serum concentration of estradiol after embryo transfer and the decline from preovulatory levels may influence the success of IVF treatment.

AIM: To establish the influence that serum estradiol concentrations prior to oocyte retrieval and 3 days after embryo transfer have on the establishment of in vitro fertilization (IVF) pregnancy. METHOD: Preovulatory (day-0) and luteal-phase (day-6) estradiol concentrations were retrospectively analyzed in 310 infertile patients, undertaking 1st-cycle conventional IVF or intracytoplasmic sperm injection. RESULTS: The IVF treatment success is significantly reduced in patients with an estradiol level <600 pg/ml and also when a rapid decline in luteal-phase estradiol concentrations from preovulatory concentrations (day 0:day 6 ratio) was exhibited. CONCLUSION: A day 0:day 6 estradiol ratio >5 and a serum estradiol concentration <600 pg/ml may adversely impact on the establishment of pregnancy in IVF.

Selenium deficiency as a model of experimental pre-eclampsia in rats.

Epidemiological studies and in vitro analysis demonstrate correlations between selenium status and human pre-eclampsia (PET). Selenium is an essential component in the anti-oxidant proteins glutathione peroxidase and thioredoxin reductase, which are produced in lower amounts in pre-eclamptic placenta. This study examined the effect of modulating dietary selenium content in pregnant rats. Rats were fed diets containing no selenium, 239 microg/kg selenium or 1000 microg/kg selenium, four weeks prior to and following conception. Significant pregnancy-specific increases in systolic blood pressure (116.4 +/- 5.2 mmHg vs 108 +/- 6.8 mmHg vs 111.4 +/- 4.7 mmHg) and proteinuria (9.68 +/- 2.12 microg/ml vs 5.93 +/- 1.59 microg/ml vs 4.43 +/- 0.96 microg/ml) were demonstrated in animals fed a selenium free-diet when compared with normal or high selenium diets. Placental weight and pup number were not affected by selenium deprivation, however a significant decrease in the pup weight was evident. Selenium deprivation caused dose-dependent decreases in liver glutathione peroxidase (28.55 +/- 3.82 mmoles/min/mg vs 34.68 +/- 8.64 mmoles/min/mg) and thioredoxin reductase (2.37 +/- 1.25 U/mg vs 6.68 +/- 1.82 U/mg) activity, whereas superoxide dismutase activity remained constant. Placental activity of these enzymes also decreased leading to oxidative stress as measured by increased lipid peroxides (17.92 +/- 1.78 micromoles/mg vs 8.30 +/- 5.52 micromoles/mg) and protein carbonyls in tissue extracts from selenium-free animals. These results suggest that selenium deficiency in pregnant rats leads to symptoms similar to those seen in human PET and may provide an experimental model for studying this complex disease.