Effects of TCDD on gene expression in hepatocytes isolated from WT and PkmΔDRE mice.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) reprograms central carbon metabolism by switching pyruvate kinase expression from isoform M1 (Pkm1) to M2 (Pkm2) mediated by aryl hydrocarbon receptor (AhR) binding to a dioxin response element (DRE) located between exon 3 and 4 within the Pkm locus. To further investigate the consequences of Pkm isoform switching in TCDD elicited hepatotoxicity, we examined gene expression in primary hepatocytes isolated from mice with the Pkm locus DRE excised (PkmΔDRE). Wild-type and PkmΔDRE hepatocytes were treated with 10 nM TCDD for 2, 4, 8, 12, 24, 48, 72, 96 and 120 hours. Central carbon metabolite changes were also assessed in WT and PkmΔDRE mice treated with 30 µg/kg TCDD every 4 day for 28 days. While AHR target genes were comparably induced, some genes exhibited divergent expression patterns in PkmΔDREmice compared to wild-types following treatment with TCDD. Notably, antioxidant gene expression was delayed in PkmΔDRE hepatocytes. Metabolomic analysis also revealed differences in glycolytic, TCA cycle and pentose phosphate pathway metabolite levels in TCDD treated WT and PkmΔDRE liver extracts. In addition, amino acid metabolism and serine/glycine synthesis were also elevated, especially in PkmΔDRE. These findings indicate PKM2 induction affects the transcriptional and metabolic coordination of hepatic responses to TCDD.