Localization of thioredoxin reductase and thioredoxin in normal human placenta and their protective effect against oxidative stress

Recent studies have indicated that oxidative stress is involved in the path ogenesis of pre-eclampsia. Oxidative stress damages systemic tissues, and p lacental damage may result in intrauterine growth retardation and fetal dis tress. Thus, this study attempted to elucidate the placental localization o f thioredoxin and thioredoxin reductase, substances that may reduce oxidati ve stress. Furthermore, it studied the defence mechanism of the thioredoxin -thioredoxin reductase system against oxidative stress in mitochondria of n ormal human placenta where reactive oxygen species are primarily produced. The examination of thioredoxin reductase activity in subcellular fractions of human placenta indicated that thioredoxin reductase was located not only in cytoplasm, but also in mitochondria. The existence of thioredoxin and t hioredoxin reductase in human placenta was confirmed immunologically using antibodies raised against thioredoxin and thioredoxin reductase. Thioredoxi n and thioredoxin reductase were localized histochemically in cytotrophobla sts, decidua, and stromal cells in the stem villi. The addition of exogenou s thioredoxin and thioredoxin reductase to fumarase in mitochondria of huma n placenta displayed a protective effect against oxidative stress. In concl usion, this study confirmed the intracellular localization and the tissue d istribution of thioredoxin and thioredoxin reductase in human placenta. Mor eover, the complete thioredoxin-thioredoxin reductase system in human place nta may protect the placenta from damage caused by oxidative stress. (C) 19 99 W. B. Saunders Company Ltd.