Mono-2-ethylhexyl phthalate induces oxidative stress responses in human placental cells in vitro.

Di-2-ethylhexyl phthalate (DEHP) is an environmental contaminant commonly used as a plasticizer in polyvinyl chloride products. Exposure to DEHP has been linked to adverse pregnancy outcomes in humans including preterm birth, low birth-weight, and pregnancy loss. Although oxidative stress is linked to the pathology of adverse pregnancy outcomes, effects of DEHP metabolites, including the active metabolite, mono-2-ethylhexyl phthalate (MEHP), on oxidative stress responses in placental cells have not been previously evaluated. The objective of the current study is to identify MEHP-stimulated oxidative stress responses in human placental cells. We treated a human placental cell line, HTR-8/SVneo, with MEHP and then measured reactive oxygen species (ROS) generation using the dichlorofluorescein assay, oxidized thymine with mass-spectrometry, redox-sensitive gene expression with qRT-PCR, and apoptosis using a luminescence assay for caspase 3/7 activity. Treatment of HTR-8 cells with 180µM MEHP increased ROS generation, oxidative DNA damage, and caspase 3/7 activity, and resulted in differential expression of redox-sensitive genes. Notably, 90 and 180µM MEHP significantly induced mRNA expression of prostaglandin-endoperoxide synthase 2 (PTGS2), an enzyme important for synthesis of prostaglandins implicated in initiation of labor. The results from the present study are the first to demonstrate that MEHP stimulates oxidative stress responses in placental cells. Furthermore, the MEHP concentrations used were within an order of magnitude of the highest concentrations measured previously in human umbilical cord or maternal serum. The findings from the current study warrant future mechanistic studies of oxidative stress, apoptosis, and prostaglandins as molecular mediators of DEHP/MEHP-associated adverse pregnancy outcomes.

Implementing CUREs with Cookbook-Style Laboratory Exercises in In-Person, Online, and Hybrid Formats.

Course-based undergraduate research experiences (CUREs) provide students with ample opportunity to engage in the scientific process and are increasingly replacing more traditional cookbook-style laboratory exercises in the undergraduate biology curriculum. The COVID-19 pandemic has highlighted the difficulty of implementing these projects during times of crisis. The quick transition to online learning during the pandemic afforded us a unique opportunity to develop an alternative version of our CURE for the online environment and to compare the efficacy of our CURE on learning gains in online versus in-person learning situations. Compared with a previous semester, our data suggest no significant differences in learning gains between students who participated in a hands-on CURE and an online CURE. Taken together the data suggests an avenue for CURE implementation even while teaching in online or hybrid formats. We discuss strategies that made the CURE successful in the online format and offer suggestions for how to adapt such activities for online or hybrid courses.

Tert-Butyl Hydroperoxide Stimulated Apoptosis Independent of Prostaglandin E2 and IL-6 in the HTR-8/SVneo Human Placental Cell Line.

Significant gaps exist in our knowledge of how cellular redox status, sometimes referred to as oxidative stress, impacts placental trophoblasts. The present study used tert-butyl hydroperoxide (TBHP) as a known generator of reactive oxygen species (ROS) in the extravillous trophoblast cell line HTR-8/SVneo to examine the role of cellular redox disruption of prostaglandin E2 (PGE2) and the cytokine IL-6 in cell death. Cells were exposed to 0, 12.5, 25, or 50 µM TBHP for 4, 8, and 24 h to ascertain effects on cell viability, caspase 3/7 activity, PGE2 release, PTGS2 mRNA expression, and IL-6 release. Experiments with inhibitors included the cyclooxygenase inhibitor indomethacin, mitogen-activated protein kinase inhibitors (PD169316, U0126, or SP600125), or treatments to counter expected consequences of TBHP-stimulated generation of ROS (deferoxamine [DFO], butylated hydroxyanisole [BHA], and N,N'-diphenyl-1,4-phenylenediamine [DPPD]) using 24-h exposure to 50 µM TBHP. Cell viability, measured by ATP content, decreased 24% relative to controls with a 24-h exposure to 50 µM TBHP, but not at lower TBHP concentrations nor at earlier time points. Exposure to 50 µM TBHP increased caspase 3/7 activity, an indicator of apoptosis, after 8 and 24 h. Antioxidant treatment markedly reduced TBHP-stimulated caspase 3/7 activity, PGE2 release, and IL-6 release. TBHP-stimulated IL-6 release was blocked by PD169316 but unaltered by indomethacin. These data suggest that TBHP-stimulated IL-6 release and caspase 3/7 activation were independent of PGE2 yet were interrupted by treatments with known antioxidant properties, providing new insight into relationships between PGE2, IL-6, and apoptosis under conditions of chemically induced cellular oxidation.