Unveiling the interplay between hepatocyte SATB1 and innate immunity in autoimmune hepatitis

Investigating the function of SATB1 in hepatocytes is essential for developing therapeutic strategies for autoimmune hepatitis (AIH). Although SATB1 has been extensively studied in immune cells, its specific activity in hepatocytes within the context of AIH remains unclear.

SATB1 expression in AIH hepatocytes was assessed by qRT-PCR, Western blotting, flow cytometry, and immunohistochemistry. In vivo modulation used RNA interference viruses and overexpression plasmids. SATB1's proinflammatory effects were analyzed with protein microarray, immunohistochemistry, and flow cytometry. Chemotactic effects on RAW264.7 macrophages were tested in vitro, with mechanisms explored by dual-luciferase assays and CUT&RUN qPCR. Liver injury was evaluated by histopathology and serum biochemistry.

SATB1 was significantly upregulated in hepatocytes of AIH patients and models, showing a stronger increase in hepatocytes than in CD45⁺ cells, and positively correlated with liver injury severity. In vivo RNAi-mediated SATB1 inhibition reduced liver inflammation, while SATB1 overexpression aggravated AIH progression. Both interference and overexpression experiments confirmed that SATB1 promotes liver injury by facilitating the infiltration of proinflammatory (Ly6C^high) macrophage. In vitro, supernatant from SATB1-overexpressing hepatocytes enriched chemokine signaling pathways, leading to increased CCL2 expression and release, which attracted macrophages and drove their proinflammatory polarization. Mechanistically, SATB1 promoted CCL2 transcription by binding to its DNA and recruiting p300/CBP.

This study reveals that SATB1 is upregulated in hepatocytes in AIH. Elevated SATB1 levels in liver cells contribute to autoimmune hepatitis by increasing CCL2 expression, promoting the recruitment of inflammatory monocyte-derived macrophage, and reshaping the composition of the liver immune microenvironment.