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

Abstract

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 μM/ mg protein versus 5.33±4.03 μM/ 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 units/ 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.