Effects of 4-hydroxy-2-nonenal, a marker of oxidative stress, on the cyclooxygenase-2 of human placenta in chorioamnionitis

Chorioamnionitis (CAM) is one of the causes of preterm labour. A recent study has indicated that NADPH oxidase, a reactive oxygen species (ROS)-producing enzyme, is activated in CAM. CAM is thought to be closely associated with oxidative stress. We have hypothesized that oxidative stress in CAM may induce preterm labour. The purpose of this study is to examine the effect of 4-hydroxy-2-nonenal (HNE), which is a marker of oxidative stress, on human placenta during preterm labour. We initially examined the HNE-modified proteins in human placentas by immunoblotting and immunohistochemistry using anti-HNE antibody. To examine the effect of HNE on human placenta, we stimulated human placental tissue with HNE. The expressions of cyclooxygenase-2 (COX-2) mRNA and protein were observed by RT-PCR and western blot analysis respectively. Furthermore, we measured the peroxidase activity of COX-2 by COX activity assay kit. Prostaglandin E(2) (PGE(2)) in the supernatants of placental tissue was also determined by enzyme-linked immunosorbent assay. Immunoblotting and immunohistochemistry showed that the levels of HNE-modified proteins were increased in the placentas with CAM, compared to the normal placenta. HNE induced the expression of COX-2 mRNA, protein and activity in the placental tissue culture stimulated with HNE. In addition, PGE(2) was also released into the medium in a time-dependent fashion. These findings suggest that HNE-modified proteins, which were increased in the placenta with CAM, play an important role in preterm labour.