Oxidized and Free Whole Blood Thiols in Preeclampsia

In Brief Objective To measure levels of oxidized and free thiols in whole blood of normotensive pregnant and preeclamptic women and evaluate the role of oxidative stress. Methods We measured whole blood oxidized and free levels of cysteine, homocysteine, cysteinylglycine, and glutathione by high performance liquid chromatography in women with normotensive pregnancies (n = 50), preeclampsia (n = 29), and preeclampsia complicated by the hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome (n = 16). Results Oxidized and free levels (median range, μmol/L) of cysteine and homocysteine were higher in women with preeclampsia than normotensive pregnancies (45 27–81 versus 29 9–91, P < .001, and 98 57–193 versus 69 33–215, P < .001; 0.8 0.2–4.4 versus 0.4 0.01–1.6, P < .001, and 2.1 0.7–9.4 versus 1.2 0.2–21.2, P < .01; respectively). The ratios of free to oxidized cysteine, homocysteine, and cysteinylglycine were lower in preeclampsia than normotensive pregnancy (2.2 1.3–3.0 versus 2.4 1.7–4.3, P < .001; 2.3 0.5–5.4 versus 2.9 1.1–24, P < .001; 4.1 2.3–11.6 versus 5.4 2.6–24.3, P < .02, respectively), indicating a shift in favor of the oxidized form of those thiols. In HELLP syndrome, levels of oxidized and free cysteine and levels of oxidized homocysteine were higher than normal (44 33–63 versus 29 9–91, P < .001, and 102 82–133 versus 69 33–215, P < .001; 1.0 0.3–2.9 versus 0.4 0.01–1.6, P < .001, respectively). No significant differences were found in oxidized glutathione levels in women with preeclampsia (22 5–49 versus 17 2–60, P = .06) or free levels in preeclamptic women with HELLP syndrome (757 624–993 versus 842 539–1516, P = .09) as compared with normotensive pregnant women. The ratios of free to oxidized cysteinylglycine and glutathione were higher in women with HELLP syndrome than in those with preeclampsia (5.4 3.3–12.7 versus 4.1 2.3–11.6, P = .02, and 56 28–124 versus 45 16–166, P = .02, respectively). Conclusion Significantly lower ratios of free to oxidized cysteine, homocysteine, and cysteinylglycine in preeclampsia might indicate oxidative stress. Low whole blood ratios of free and oxidized thiol levels for cysteine, homocysteine, and cysteinylglycine in preeclampsia reflect oxidative stress.