Steatotic liver disease induced by TCPOBOP-activated hepatic constitutive androstane receptor: Primary and secondary gene responses with links to disease progression

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Abstract
Constitutive Androstane Receptor (CAR, Nr1i3 ), a liver nuclear receptor and xenobiotic sensor, induces drug, steroid and lipid metabolizing enzymes, stimulates liver hypertrophy and hyperplasia, and ultimately, hepatocellular carcinogenesis. The mechanisms linking early CAR responses to subsequent disease development are poorly understood. Here we show that exposure of CD-1 mice to TCPOBOP, a halogenated xenochemical and selective CAR agonist ligand, induces pericentral steatosis marked by hepatic accumulation of cholesterol and neutral lipid, and elevated circulating alanine aminotransferase levels, indicating hepatocyte damage. TCPOBOP-induced steatosis was weaker in the pericentral region but stronger in the periportal region in females compared to males. Early (1-day) TCPOBOP transcriptional responses were enriched for CAR-bound primary response genes, and for lipid and xenobiotic metabolism and oxidative stress protection pathways; late (2-wk) TCPOBOP responses included many CAR binding-independent secondary response genes, with enrichment for immune response, macrophage activation, and cytokine and reactive oxygen species production. Late upstream regulators specific to TCPOBOP-exposed male liver were linked to pro-inflammatory responses and hepatocellular carcinoma progression. TCPOBOP administered weekly to male mice using a high corn oil vehicle activated carbohydrate-responsive transcription factor (MLXIPL)-regulated target genes, dysregulated mitochondrial respiratory and translation regulatory pathways, and induced more advanced liver pathology. Thus, TCPOBOP exposure recapitulates histological and gene expression changes characteristic of emerging steatotic liver disease, including secondary expression changes in liver non-parenchymal cells indicative of transition to a more advanced disease state. Upstream regulators of both the early and late TCPOBOP gene responses include novel biomarkers for foreign chemical-induced metabolic dysfunction-associated steatotic liver disease.
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