Abstract
Identification of toxic components of complex mixtures is a challenge. Here, oil sands process-affected water (OSPW) was used as a case study to identify those toxic components with a known protein target. Organic chemicals in OSPW exhibited dose-dependent activation of peroxisome proliferator-activated receptor gamma (PPAR gamma) at concentrations less than those currently in the environment (0.025X equivalent of full-strength OSPW), by use of a luciferase reporter gene assay. Activation of PPAR gamma-mediated adipogenesis by OSPW was confirmed in 3T3L1 preadipocytes, as evidenced by accumulation of lipids and up regulation of AP2, LPL, and PPAR gamma gene expression after exposure to polar fractions of OSPW. Unexpectedly, the nonpolar fractions of OSPW inhibited differentiation of preadipocytes via activation of the Writ signaling pathway. Organic chemicals in OSPW that were ligands of PAPR gamma were identified by use of a pull-down system combined with untargeted chemical analysis (PUCA), with a recombinant PPAR gamma protein. Thirty ligands of PPAR gamma were identified by use of the PUCA assay. High resolution MS1 and MS2 spectra were combined to predict the formulas or structures of a subset of ligands, and polyoxygenated or heteroatomic chemicals, especially hydroxylated carboxylic/sulfonic acids. were the major ligands of PPAR gamma.