HIVEP1 aggravates NASH by reprogramming polyamine metabolism in T _H 17 cells

Nonalcoholic steatohepatitis (NASH) is a chronic, inflammatory form of nonalcoholic fatty liver disease (NAFLD) that frequently progresses to cirrhosis and hepatocellular carcinoma (HCC). However, the role of various immune cells in switching from NAFLD to NASH remains elusive. Here, we took an unbiased single-cell assay for transposase accessible chromatin sequencing (scATAC-seq) approach to investigate the cellular composition, gene expression profiling, and causative roles of immune cells in NASH development. T helper 17 (T_H17) cells were identified as the most abundant subpopulation of immune cells in mouse livers with NASH. Further analysis of scATAC-seq data and single-cell RNA sequencing (scRNA-seq) data from the GEO database showed that human immunodeficiency virus type I enhancer binding protein 1 (HIVEP1) is a critical transcription factor (TF) regulating T_H17 cell differentiation and cytokine production. Specific knockout of <i>Hivep1</i> in IL-17A⁺ and CD4⁺ T cells in mice showed impairment of T_H17 cell differentiation and alleviation of NASH development. Mechanistically, HIVEP1 transcriptionally regulated ornithine decarboxylase 1 (ODC1), the rate-limiting enzyme of polyamine metabolism, to modulate T_H17 cell differentiation and cytokine production. Consequently, pharmacological inhibition of ODC1 decreased cytokine production, alleviated inflammation, and prevented the NAFLD-to-NASH transition. Together, our findings elucidate the role of polyamine metabolism in T_H17 cell-mediated NASH development and identify potential therapeutic targets for the effective treatment of NASH.