Oxidized transthyretin in amniotic fluid as an early marker of preeclampsia

Preeclampsia is a pregnancy-specific hypertensive syndrome and a major cause of maternal and fetal morbidity and mortality. At the present time, no reliable screening tests to identify women at risk are available. We have compared the amniotic fluids (AF) proteomic maps of five preeclamptic patients with those of five controls. The analysis was carried out by two-dimensional electrophoresis followed by peptide mapping and tandem mass spectrometric analysis. Besides the implementation of the previously published AF proteomic maps, our results show that transthyretin (TTR), the protein responsible for transporting both the thyroid hormone tyroxine and the retinol binding protein, is present in the AF of both preeclamptic and control women as a mixture of dimeric and post-translationally modified monomeric forms. Although the nature of these forms is similar in both groups, the preeclamptic women showed a significant increase in the amount of monomeric proteins with respect to the control group. Since the TTR monomeric forms are the results of different oxidizing reactions, we hypothesize that the higher oxidative stress in preeclampsia is the major destabilizing factor of the TTR functional dimeric form in the preeclamptic women.