PROTECT Trainee (Project 2) Lauren Tetz successfully defended her thesis on April 16, 2012. Our congratulations to the newly-minted Dr. Tetz! Read more about her thesis topic below.
MONO-2-ETHYLHEXYL PHTHALATE STIMULATES CELLULAR RESPONSES RELEVANT TO PARTURITION
ABSTRACT: Diethylhexyl phthalate (DEHP) is an environmental pollutant used universally as a plasticizer in polyvinyl consumer products. Exposure to DEHP increases risk of adverse pregnancy outcomes in humans, including decreased gestation length, preterm birth, low birth weight, and early pregnancy loss. Moreover, monoethylhexyl phthalate (MEHP), the active metabolite of DEHP, increases oxidative stress and activates innate immune responses in vitro. Although MEHP activates these responses in other cells and tissues, this has not been investigated in gestational tissues and cells. Because oxidative stress and innate immune activation are linked to the pathogenesis of preterm birth, we investigated MEHP stimulated oxidative stress and innate immune responses in human gestational cells and tissues as mechanisms by which MEHP exposure may contribute to preterm birth. To identify whether MEHP exposure may contribute to oxidative stress in the gestational compartment, we treated human placental cells (HTR-8/SVneo) with MEHP and measured reactive oxygen species (ROS) generation using the dichlorofluorescein (DCF) assay, oxidized thymine (oT) with mass-spectrometry, redox-sensitive gene expression with RT-PCR, and activation of caspase 3/7 using a luminescent assay. We found that MEHP modified redox-sensitive gene expression and increased ROS generation, oxidative DNA damage, and apoptosis. Notably, MEHP significantly induced mRNA expression of PTGS2, the gene for COX-2, an enzyme important for prostaglandin synthesis. To assess whether MEHP stimulates innate immune responses in the gestational compartment, we treated human primary placental macrophages, primary decidual macrophages, gestational membrane explants, and HTR-8/SVneo cells with MEHP and measured prostaglandin and cytokine release using enzyme-linked immunosorbent assays (ELISA). Our results demonstrate that MEHP treatment significantly increased total prostaglandin, PGF2?, and PGE2 release in human primary placental macrophage Hofbauer cells. MEHP treatment showed no effect on pro-inflammatory cytokine release. The results from the present study are consistent with the hypothesis that MEHP stimulates oxidative stress and prostaglandin responses in gestational tissues and cells. The findings from the current study warrant future epidemiological studies of oxidative stress and prostaglandin synthesis as mechanisms by which MEHP may contribute to preterm birth and other adverse pregnancy outcomes.