RT Journal Article
SR Electronic
T1 Blocking mitochondrial alanine and pyruvate metabolism in hepatocytes worsens acetaminophen-induced liver injury in mice
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2022.06.14.495517
DO 10.1101/2022.06.14.495517
A1 Joel H. Vazquez
A1 Nicole K.H. Yiew
A1 Michael R. Martino
A1 Felicia D. Allard
A1 Eric U. Yee
A1 Sandra S. McCullough
A1 Laura P. James
A1 Brian N. Finck
A1 Mitchell R. McGill
YR 2022
UL http://biorxiv.org/content/early/2022/06/17/2022.06.14.495517.abstract
AB Background and Aims Acetaminophen (APAP) overdose causes mitochondrial damage and acute liver injury. Alanine and pyruvate are important substrates for the TCA cycle and increasing evidence points to a protective role for mitochondrial intermediary metabolism in APAP hepatotoxicity. We hypothesized that suppressing hepatic alanine and pyruvate metabolism by blocking alanine transaminase (ALT) and/or the mitochondrial pyruvate carrier (MPC) would impair mitochondrial metabolism in APAP toxicity and therefore exacerbate APAP-induced injury.Methods We treated wild-type mice with the ALT inhibitor β-chloro-l-alanine (BCLA) before a toxic dose of APAP (300 mg/kg) and measured liver injury (serum ALT and lactate dehydrogenase [LDH], histology) and other parameters. We also generated liver-specific ALT2 knockout (KO) mice, mitochondrial pyruvate carrier 2 (MPC) KO mice, and combined ALT2/MPC KO (CKO) mice, and compared injury, APAP-protein adducts, glutathione, c-Jun N-terminal kinase activation, Cyp2e1 expression, and serum metabolomics among genotypes.Results BCLA reduced hepatic ALT activity up to 65% but did not affect injury. ALT2 deletion also had no effect on APAP hepatotoxicity. Similarly, MPC deletion alone had no effect. However, combined ALT2 and MPC loss significantly worsened injury (p = 0.005 for LDH for WT vs. CKO; p = 0.07 for % necrosis), increased plasma pyruvate content (p = 0.032), altered the plasma abundance of several amino acids, and decreased basal hepatic glutathione (p = 0.053). Importantly, the exacerbation of injury in CKO mice was not associated with increased APAP-protein adducts.Conclusions The MPC and ALT systems are critical redundant mechanisms to conserve mitochondrial metabolism and limit APAP toxicity. ALT activity is more than a passive biomarker of injury in this context.Competing Interest StatementThis study was funded in part by a 2018 Pinnacle Research Award from the AASLD Foundation (MRM); the Arkansas Biosciences Institute (MRM), which is the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000; and the National Institutes of Health grants T32 GM106999 (JHV), R01 DK104735 (BNF), R01 DK117657 (BNF), UL1TR003107 (LPJ), and SB1DK079387 (LPJ). LPJ is the Chief Medical Officer of Acetaminophen Toxicity Diagnostics, LLC, which is developing methods for measurement of APAP-protein adducts; MRM consults for Acetaminophen Toxicity Diagnostics, LLC, and has received research funds from GlaxoSmithKline for unrelated projects; BNF is a shareholder and member of the scientific advisory board of Cirius Therapeutics, which is developing an MPC inhibitor for treating nonalcoholic steatohepatitis. The remaining authors declare that they have no conflicts of interest related to the content of this article.ALFacute liver failureALTalanine aminotransferaseAPAPacetaminophenCKOcombined ALT2/MPC knockoutJNKc-Jun N-terminal kinaseKOknockoutLDHlactate dehydrogenaseMPCmitochondrial pyruvate carrierNAPQIN-acetyl-p-benzoquinone imineP450cytochrome P450PDHpyruvate dehydrogenasePDK4pyruvate dehydrogenase kinase 4TCAtricarboxylic acid