Evaluation of toxicological biomarkers in secreted proteins of HepG2 cells exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin and their expressions in the plasma of rats and incineration workers

Toxicological biomarkers of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) were investigated in proteins secreted by HepG2 cells and their expression levels were determined in the plasma of rats exposed to 2,3,7,8-TCDD and in the plasma of incineration workers exposed to dioxins. HepG2 cells were treated with various concentrations of 2,3,7,8-TCDD (0, 0.25, 0.5, 1, 2.5, 5, 10, 25 nM) for 24 or 48 h. MTT and Comet assays were performed to determine cytotoxicities and genotoxicities to select exposure concentrations for the proteomic analysis of proteins secreted by 2,3,7,8-TCDD-treated cells. In the proteomic analysis, dose- and time-dependent toxicological biomarkers were evaluated using two pI ranges (4-7 and 6-9) using a large gel 2-DE system. Fifteen secreted proteins were identified by a nano-LC-ESI-MS/MS and nano-ESI on a Q-TOF2 MS and the identities of eight secreted proteins including glyoxalase 1 (GLO 1), homogentisate dioxygenase (HGD), peroxiredoxin 1 (PRX 1), proteasome subunit beta type (PSMB) 5 and 6, UDP-glucose 6-dehydrogenase (UDP-GlcDH), hydroxyacyl-coenzyme A dehydrogenase (HADH) and serotransferrin (STF) were confirmed by western blotting. Of these, PSMB 5 and PRX 1 were also found in the plasma of rats exposed to 2,3,7,8-TCDD, whereas GLO 1, HGD, PSMB 6 and PRX 1 were found in the plasma of incineration workers exposed to dioxins.