Besides helping to maintain a reducing intracellular environment, the thioredoxin (Trx) system impacts bioenergetics and drug metabolism. We show that hepatocyte-specific disruption of Txnrd1, encoding Trx reductase-1 (TrxR1), causes a metabolic switch in which lipogenic genes are repressed and periportal hepatocytes become engorged with glycogen. These livers also overexpress machinery for biosynthesis of glutathione and conversion of glycogen into UDP-glucuronate; they stockpile glutathione-S-transferases and UDP-glucuronyl-transferases; and they overexpress xenobiotic exporters. This realigned metabolic profile suggested that the mutant hepatocytes might be preconditioned to more effectively detoxify certain xenobiotic challenges. Hepatocytes convert the pro-toxin acetaminophen (APAP, paracetamol) into cytotoxic N-acetyl-p-benzoquinone imine (NAPQI). APAP defenses include glucuronidation of APAP or glutathionylation of NAPQI, allowing removal by xenobiotic exporters. We found that NAPQI directly inactivates TrxR1, yet Txnrd1-null livers were resistant to APAP-induced hepatotoxicity. Txnrd1-null livers did not have more effective gene expression responses to APAP challenge; however, their constitutive metabolic state supported more robust GSH biosynthesis, glutathionylation, and glucuronidation systems. Following APAP challenge, this effectively sustained the GSH system and attenuated damage.
Keywords: 5,5′-dithiobis(2-nitrobenzoic acid); ALT; APAP; ATP-binding cassette subfamily C multidrug-resistance transporters; Abcc; Aox1; BSO; Bioenergetics; CYP; Cre; DTNB; DTT; Drug metabolism; EDTA; GSH; GSSG; GST; Gsr; H&E; KEGG; Kyoto Encyclopedia of Genes and Genomes; MS; N-acetyl-p-benzoquinone imine; N-acetylcysteine; NAC; NADPH-quinine oxidase; NAPQI; Nqo1; ROS; Redox biology; SDS; SDS-PAGE; SDS-polyacrylamide gel electrophoresis; SEM; SULT; Sec; Thioredoxin reductase; Trx; TrxR; Txnip; UGDH; UGT; acetaminophen (paracetamol); alanine transaminase; aldehyde oxidase-1; bacteriophage P1 cyclization recombinase; buthionine sulfoximine; cytochrome P450; dithiothreitol; ethylenediamine tetraacetic acid; glutathione reductase; glutathione-S-transferase; hematoxylin and eosin; kDa; kilo-Dalton; loxP; mass spectrometry; oxidized glutathione disulfide; p-APDG; p-APDGS; p-acetamidophenyl-β-D-glucronide; p-acetamidophenyl-β-D-glucronide sodium salt; reactive oxygen species; recognition sites for Cre; reduced glutathione; selenocysteine; sodium dodecyl sulfate; standard error of the mean; sulfotransferase; thioredoxin mRNA or protein; thioredoxin reducatse-1 gene; thioredoxin reductase mRNA or protein; thioredoxin-interacting protein; txnrd1; uridine diphosphate-glucose dehydrogenase; uridine diphosphate-glucuronate transferase.
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