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. Oxidative stress plays an important role in the pathophysiology of preeclampsia, resulting from defective trophoblast invasion, reductions in placental perfusion and hence producing reactive oxygen species (ROS). In this study we used inhibitors of the mitochondrial respiratory chain to induce oxidative stress and studied the effect that selenium supplementation had on trophoblast viability.
Methods:
Trophoblast cells (BeWo, JEG-3 and Swan-71) were treated with Na Selenite (100nM) or Selenomethionine (500nM) 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. The Resazurin end point assay was used to measure the cellular viability. Cells were also treated with 240µM Antimycin C post selenium supplementation to generate oxidative stress. ROS production was quantified through Dichlorofluorescein (DCF) assay.
Results:
Selenium supplementation effectively up regulated the expression and activity of GPx and ThRed. There was a dose dependent decrease in the cellular activity in BeWo, JEG3 and Swan71 when treated with increasing concentrations of Antimycin or Rotenone. For Antimycin concentrations of 320µM and 160µM, applied for 4 hours, resulted in a significant decrease in cellular activity whereas Rotenone concentrations of 400 nM and 200 nM also showed a significant decrease. Prior incubation with Na Selenite or Selenomethionine was able to protect trophoblast cells from oxidative stress.
Treatment with 240µM Antimycin generated a maximal ROS response which could be lessened with supplementation with 800nM, 1000nM, and 1200nM Na Se or 1400nM and 1600nM SeMet.
Discussion:
These data suggest that selenoproteins such as GPx and ThxRed have an important role in protecting trophoblast mitochondria from oxidative stress. Excessive oxidative stress will result in tissue turnover and release of cellular components. This emphasises the importance of maintaining an adequate selenium supply during pregnancy and especially in pregnancies complicated by conditions such as preeclampsia.