Immunohistochemical localization of alpha-tocopherol transfer protein and lipoperoxidation products in human first-trimester and term placenta

Objective

Pregnancy is described as a state of oxidative stress arising from the high metabolic turnover taking place during feto-placental development and little is known about the balance of oxidation and antioxidation in early human pregnancy. The aim of this study was to analyze placental expression of α-tocopherol transfer protein (α-TTP) as the major transport protein for the antioxidant α-tocopherol as well as the placental expression of two lipoperoxidation products, malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE) in early first-trimester and term human placenta.

Study design

Placental tissue was obtained from 10 pregnancy interruptions at 6–8 weeks gestational age and 10 samples were obtained from term pregnancies after routine cesarean section. The placental expression of α-TTP, MDA and HNE has been investigated with immunohistochemistry by the use of specific human α-TTP, MDA and HNE antibodies.

Results

While MDA and HNE showed similar expression in first-trimester and term placenta, α-TTP expression was less in first-trimester syncytiotrophoblast as compared to term. In first-trimester specimen, α-TTP showed major expression in extravillous trophoblast. In amniotic epithelial cells, a rising tendency in all three parameters investigated from immature to mature cells could be documented. No direct correlation between α-TTP, MDA and HNE expression was detected.

Conclusions

Our study shows the presence of α-TTP not only in term, but in first-trimester extravillous trophoblast, syncytiotrophoblast and amniotic epithelium. Furthermore, lipoperoxidation products MDA and HNE are also present in first-trimester and term placenta, documenting the presence of oxidative processes in the placenta from early on. It therefore seems possible that scavenging of reactive oxygen species (ROS) by α-tocopherol is already required in first-trimester human pregnancy, but the missing correlation to MDA and HNE expression leads to the speculation that α-TTP and its ligand α-tocopherol have functions beyond the antioxidative capacity of α-tocopherol in early pregnancy.