Objective: Placental production of lipid peroxides is abnormally increased in preeclampsia. The reason for this is not known, but if placental antioxidant enzymes were deficient, lipid peroxides would increase unchecked. In this study, we measured 1) enzyme activities of superoxide dismutase (CuZn-SOD), catalase, and glutathione peroxidase (GSH-Px) and tissue levels of vitamin E, and 2) mRNA expression of CuZn-SOD, catalase, and GSH-Px in normal and preeclamptic placentas.
Methods: Placental tissues were obtained from normal (n = 16) preeclamptic (n = 12) pregnancies immediately after delivery. Tissue pieces were frozen in liquid nitrogen and stored at -80C until assayed. The enzyme activities of CuZn-SOD, catalase, and GSH-Px and the levels of vitamin E were determined by spectrophotometric assays. Messenger RNA expression of CuZn-SOD, catalase, and GSH-Px was determined by Northern blot analysis.
Results: The activities of CuZn-SOD and GSH-Px and the tissue levels of vitamin E were significantly lower in preeclamptic placentas than in normal placentas (CuZn-SOD: 1.13 +/- 0.49 versus 3.71 +/- 0.71 U/mg protein, P < .01; GSH-Px: 0.18 +/- 0.01 versus 0.26 +/- 0.02 U/mg, P < .01; vitamin E: 0.08 +/- 0.01 versus 0.18 +/- 0.01 microgram/mg, mean +/- standard error, P < .001), whereas the activity of catalase was significantly higher (93 +/- 3 versus 83 +/- 2 U/mg, P < .05). Relative mRNA expression of CuZn-SOD and GSH-Px was significantly lower in preeclamptic than normal placentas (P < 0.05), but there was no significant difference for catalase (P > .4).
Conclusions: 1) Activities of CuZn-SOD and GSH-Px and the tissue levels of vitamin E are significantly lower in preeclamptic than in normal placentas. 2) Activity of catalase is significantly higher in preeclamptic than in normal placentas. 3) Messenger RNA expression for CuZn-SOD and GSH-Px is lower in preeclamptic placentas. We speculate that decreased antioxidant activity may result in increased lipid peroxide levels in preeclamptic placentas.