Dysregulation of the Amniotic PPAR gamma Pathway by Phthalates: Modulation of the Anti-Inflammatory Activity of PPAR gamma in Human Fetal Membranes

Phthalates are reprotoxic pollutants that are omnipresent in the environment. Detectable in amniotic fluid, these compounds (with the most concentrated being mono-2-ethylhexyl phthalate (MEHP)) are in direct contact with fetal membranes (FMs). They can lead to the premature rupture of FMs by deregulating cellular and molecular pathways, such as, for example, the nuclear transcription factor peroxysome proliferator-activated receptor gamma (PPAR gamma) pathway. The objective was to study the impact of MEHP on the PPAR gamma pathway in FMs using amnion and choriodecidua across the three trimesters of pregnancy and the amniotic epithelial AV3 cell model by analyzing (i) PPAR gamma expression (mRNA and proteins) using RT-qPCR and Western blot assays; (ii) cytotoxicity and cell viability following MEHP treatment by lactate dehydrogenase (LDH) measurement and using Cell-counting Kit 8; and (iii) modulation by MEHP of PPAR gamma transcriptional activity (using a reporter gene assay) and PPAR gamma anti-inflammatory properties (by measuring IL6 and IL8 levels). PPAR gamma is expressed in the human amnion and choriodecidua during the three trimesters of pregnancy and in amniotic cells. In the AV3 cell line, MEHP is not cytotoxic and does not reduce cell viability, but it reduces PPAR gamma activity, here induced by a classical agonist without influencing its expression. MEHP also reduces PPAR gamma's anti-inflammatory properties. In conclusion, PPAR gamma signaling is dysregulated by MEHP; this paves the way for future explorations to highlight the hypothesis of phthalates as an amniotic PPAR gamma disruptor that can explain the premature rupture of FMs.