Modulation of copper zinc superoxide dismutase expression and activity with in vitro differentiation of human villous cytotrophoblasts

Due to the role of oxygen free radicals in trophoblast cell differentiation, we used the in vitro model of villous cytotrophoblast differentiation into the syncytiotrophoblast to investigate the modulation of the key antioxidant enzyme copper/zinc superoxide dismutase (SOD-1) in the human trophoblast during pregnancy. Cytotrophoblast cells were isolated from first-trimester and term placentae. SOD-1 mRNA levels were determined using real-time quantitative polymerase chain reaction, protein levels were determined by immunoblotting with a specific monoclonal antibody, and oxidoreductase activity was measured during syncytiotrophoblast formation in vitro. Interestingly, SOD-1 protein levels fell significantly (P<0.001) during syncytiotrophoblast formation but no corresponding change in enzyme activity was observed. This apparent discrepancy may be related to different amounts of SOD-1 co-factor in the two cell types. Indeed the level of copper was significantly higher (P<0.05) in syncytiotrophoblast as compared with cytotrophoblast. SOD-1 mRNA levels remained stable during cytotrophoblast differentiation. SOD-1 expression and activity were similar in cytotrophoblast cells isolated from first-trimester and term placentae, and in the differentiated syncytiotrophoblast in vitro. These results underline the need to determine SOD-1 protein expression and activity simultaneously in order to gain a better knowledge of its role in human trophoblast cell differentiation. (C) 2000 Harcourt Publishers Ltd.