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

Abstract

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 180 μM MEHP increased ROS generation, oxidative DNA damage, and caspase 3/7 activity, and resulted in differential expression of redox-sensitive genes. Notably, 90 and 180 μM 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.

Associations of urinary 5-methyl-2′-deoxycytidine and 5-hydroxymethyl-2′-deoxycytidine with phthalate exposure and semen quality in 562 Chinese adult men

“…Previous research showed that phthalate exposure increased the production of reactive oxygen species (Rusyn et al, 2001). Therefore we speculate that the phthalate-induced oxidative stress caused apoptosis or DNA lesions (Tetz et al, 2013), resulting in high (Nagata et al, 2003;Zhu, 2009), and then the release of excessive products (5mdC and 5hmdC) into the urine. Previous studies suggest that phthalates are reproductive toxicants that may impair human semen quality (Duty et al, 2003;Hauser et al, 2006).…”

“…Several processes such as DNA damage and apoptosis may affect the metabolism of DNA and finally affect semen quality (Agarwal et al, 2003). In addition, phthalates have been proved to increase the production of reactive oxygen species (ROS), and consequently induce DNA lesions and apoptosis (Rusyn et al, 2001;Tetz et al, 2013). In conclusion, we hypothesized that phthalate-induced oxidative stress caused apoptosis or DNA lesions resulting in the release of excessive degradation products, 5mdC and 5hmdC, into urine.…”

Effect of environmental phthalate exposure on pregnancy duration and birth outcomes

“…As indicated by , different mechanisms can explain the relationship between phthalate exposure and a shortened pregnancy or preterm delivery [14,15]. First, phthalate exposure can cause impaired placentation early in pregnancy via induction of oxidative stress [39][40][41]. Increases in circulating maternal levels of reactive oxygen species can cause apoptosis and alter cytotrophoblast turnover rate in the developing placenta, leading to impaired placentation and in consequence preeclampsia or intrauterine growth restriction (IUGR), which are characteristics of a placental preterm birth [14,15].…”

Considerable exposure to the endocrine disrupting chemicals phthalates and bisphenol-A in intensive care unit (ICU) patients

“…These levels are proof of a high and continuous level of exposure throughout the period of biomonitoring in the ICU. This is of great concern because these high serum levels (BPA reached 1 μM, MEHP N 10 μM, and the other PMs are even up to 30 μM) match the concentrations that may induce effects in vitro: histamine release from mast cells (O'Brien et al, 2014), lipid accumulation (Grasselli et al, 2013), a decrease in the maturation of human oocytes (Machtinger et al, 2013), induction of cytokine production and modulation of T cell activation (Yamashita et al, 2005), oxidative DNA damage, and the production of intracellular reactive oxygen species in endothelial and other cells (Ban et al, 2014;Chen et al, 2011;Tetz et al, 2013;Yang et al, 2014). Although a plethora of deleterious effects has been found for BPA and PMs in animal and human studies in vivo, the extent to which these chemicals have a clinical effect in critically ill patients is unclear.…”