Mono-2-ethylhexyl phthalate inhibits human extravillous trophoblast invasion via the PPARγ pathway

Concerns over the adverse reproductive outcomes in human have been raised, more evidence including the underlying mechanism are required. Since extravillous trophoblast (EVT) invasion is an important physiological step during early development, the effects of mono-2-ethylhexyl phthalate (MEHP), the bioactive metabolite of DEHP, on EVT invasion were investigated using Matrigel-coated transwell chambers and cell line HTR-8/SVneo. In the transwell-based invasive assay, MEHP exposure inhibited EVT invasion as judged by decreased invasion index. Further analysis showed that MEHP exposure significantly inhibited the activity of matrix metalloproteinase-9 (MMP-9), which is an important positive regulator of EVT invasion. Meanwhile, the protein levels of tissue inhibitor matrix metalloproteinase-1 (TIMP-1), one key negative regulator of EVT invasion, were upregulated by MEHP treatment. Finally, inactivation of PPARγ pathway by either PPARγ inhibitors or PPARγ shRNA knockdown rescued the MEHP-induced inhibited invasion of HTR-8/SVneo cells, which is accompanied by the recovery of inhibited MMP-9 expression. The present study provides the evidence that MEHP exposure inhibits trophoblast invasion via PPARγ at concentrations comparable to those found in humans, which provides an insight in understanding the mechanisms of DEHP-associated early pregnancy loss.