Cytochrome P450 2E1 deficiency alters hepatic mitochondria and impairs liver organoid formation

Cytochrome P450 2E1 (CYP2E1) is a liver-expressed monooxygenase that metabolizes low molecular weight pollutants, drugs, and endogenous substrates such as fatty acids and ketones. Germline Cyp2e1 knockout (KO) mice were developed in the late 1990s and were initially reported to lack an overt phenotype. Subsequent studies showed that these mice are protected from liver injury caused by ethanol, high-fat diet, and chemical exposures. However, most prior work has focused on males. Here, we examined baseline effects of Cyp2e1 deletion in female and male mice.

Using Cyp2e1-KO (129/Sv-Cyp2e1^tm1Gonz/J, KO) and wild-type (WT; 129S1/SvImJ) mice, bulk liver mRNA sequencing revealed marked transcriptional changes in female KO liver compared with WT females, including enrichment of mitochondrial pathways. Follow-up studies confirmed that female KO livers exhibited impaired mitochondrial function and decreased mtDNA copy number relative to WT. These effects were less pronounced in males. To assess functional consequences of these mitochondrial alterations, primary liver cells were isolated and used to generate organoids. Cyp2e1 KO liver organoids showed impaired growth, with male KO organoids exhibiting slower growth and most female KO cells failing to form organoids. Histological analysis further revealed biliary and hepatocellular abnormalities in KO livers that were more prevalent and severe in females.

Complete loss of CYP2E1 has important phenotypic consequences in the liver, including striking female-biased abnormalities at baseline. These findings raise caution for therapeutic strategies aimed at broadly suppressing CYP2E1 activity and highlight the importance of incorporating sex as a biological variable in future studies.