Asparagine protects pericentral hepatocytes during acute liver injury
Yu Sun, Hadrien Demagny, Adrien Faure, Francesca Pontanari, Antoine Jalil, Nadia Bresciani, Ece Yildiz, Melanie Korbelius, Alessia Perino, Kristina Schoonjans
Yu Sun, Hadrien Demagny, Adrien Faure, Francesca Pontanari, Antoine Jalil, Nadia Bresciani, Ece Yildiz, Melanie Korbelius, Alessia Perino, Kristina Schoonjans
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Research Article Hepatology Metabolism

Asparagine protects pericentral hepatocytes during acute liver injury

Abstract

The nonessential amino acid asparagine can only be synthesized de novo by the enzymatic activity of asparagine synthetase (ASNS). While ASNS and asparagine have been implicated in the response to numerous metabolic stressors in cultured cells, the in vivo relevance of this enzyme in stress-related pathways remains unexplored. Here, we found ASNS to be expressed in pericentral hepatocytes, a population of hepatic cells specialized in xenobiotic detoxification. ASNS expression was strongly enhanced in 2 models of acute liver injury: carbon tetrachloride (CCl4) and acetaminophen. We found that mice with hepatocyte-specific Asns deletion were more prone to pericentral liver damage than their control littermates after toxin exposure. This phenotype could be reverted by i.v. administration of asparagine. Unexpectedly, the stress-induced upregulation of ASNS involved an ATF4-independent, noncanonical pathway mediated by the nuclear receptor, liver receptor homolog 1 (LRH-1; NR5A2). Altogether, our data indicate that the induction of the asparagine-producing enzyme ASNS acts as an adaptive mechanism to constrain the necrotic wave that follows toxin administration and provide proof of concept that i.v. delivery of asparagine can dampen hepatotoxin-induced pericentral hepatocellular death.

Authors

Yu Sun, Hadrien Demagny, Adrien Faure, Francesca Pontanari, Antoine Jalil, Nadia Bresciani, Ece Yildiz, Melanie Korbelius, Alessia Perino, Kristina Schoonjans

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Figure 4

Asns is a direct LRH-1 targeted pericentral gene.

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Asns is a direct LRH-1 targeted pericentral gene. (A) Western blotting ...
(A) Western blotting analysis of total liver lysates from C57BL/6J mice collected at indicated time points after CCl4 treatment. (B) Heatmap showing the expression levels of Asns and known LRH-1 targets in publicly available data sets (GSE59305 and GSE59304). (C) mRNA and protein analyses of total cell lysates from livers of Lrh-1hep+/+ and Lrh-1hep–/– mice, or Lrh-1wt and Lrh-1K289R mice. n = 4 (Lrh-1hep+/+, Lrh-1wt, and Lrh-1K289R) and n = 5 (Lrh-1hep–/–). (D) Representative images of immunofluorescent staining for ASNS and GLUL in livers from the indicated genetically modified mouse lines. Scale bar: 100 μm. (E) Transcription factor binding site analysis of mouse Asns promoter sequence showed 1 ATF4 binding site and 4 predicted LRH-1 binding sites. Numbers indicate distance from transcription start site (TSS). (F) Binding of LRH-1 to the 4 Asns promoter sites assessed by ChIP analysis using genomic DNA from livers of Lrh-1hep+/+ and Lrh-1hep–/– mice treated with or without CCl4 for 24 hours. n = 4 animals for each group. Error bars denote SEM. Statistical analysis was performed by unpaired t test (C) and 2-way ANOVA followed by Bonferroni’s post-hoc test (F). *P < 0.05; **P < 0.01; ***P < 0.001.