A computational insight into the molecular interactions of chlorpyrifos and its degradation products with the human progesterone receptor leading to endocrine disruption

Chlorpyrifos (CPF) is a widely used pesticide effective against a large number of target pests, which is used by farmers to protect food crops. Based on earlier epidemiologic reports, which indicate that CPF might interfere with the progesterone signaling pathway and can affect conception, the present study was undertaken to evaluate the binding interaction of CPF with the human progesterone receptor (hPR). Progesterone is one of the important hormones of the reproductive system and through its receptor, PR, the progesterone signaling pathway regulates important reproductive functions including reproductive cyclicity and initiation and continuation of pregnancy. The binding interactions of four major degradation products of CPF, viz. chlorpyrifos-oxon (CPYO), des-ethyl chlorpyrifos (DEC), 3,5,6-trichloro-2-methoxypyridine (TMP), 3,5,6-trichloro-2-pyridinol (TCP), were also studied to evaluate the possibility of endocrine disruption caused by these metabolites. Docking studies revealed that CPF, CPYO, and DEC were able to involve important interacting amino acid residues of the hPR during molecular interactions and are capable of competing with progesterone. Thus, CPF and its degradation products can act as potential xenoligands for the hPR and can disrupt normal progesterone signaling pathway.