Activation of the TGR5/cAMP/PKA/CREB axis in cholangiocytes mediates epithelial-mesenchymal transition and fibrosis in hepatolithiasis

BACKGROUND: The molecular mechanisms linking bile acid signaling to biliary fibrosis in hepatolithiasis are unclear. We investigated the role of the bile acid receptor TGR5 in driving fibrotic progression. METHODS: We employed an integrated strategy. TGR5 expression was assessed in human hepatolithiasis tissues and bioinformatics databases. A hepatolithiasis mouse model was compared with TGR5-knockout (TGR5-/-) mice, analyzing lipid metabolism, cholesterol transport, and fibrosis markers via ELISA, qPCR, and immunohistochemistry. In vitro, human intrahepatic biliary epithelial cells (HIBECs) were treated with bile acids, TGR5 agonists/inhibitors, and cAMP modulators. We assessed the cAMP/PKA/CREB pathway, epithelial-mesenchymal transition (EMT), and fibrosis. RESULTS: TGR5 was significantly overexpressed in hepatolithiasis tissues. Genetic deletion of TGR5 in mice alleviated metabolic disturbances and markedly reduced fibrosis markers (TGF-β1, α-SMA, Collagen I). In cholangiocytes, TGR5 activation stimulated the cAMP/PKA/CREB signaling cascade, promoting EMT and fibrosis. These pro-fibrotic effects were reversed by inhibiting TGR5 or cAMP. Mechanistically, TGR5-driven cAMP signaling induced CREB phosphorylation, leading to upregulated TGF-β1 expression, which sustains the fibrotic phenotype. CONCLUSION: This study defines a critical pathogenic axis in hepatolithiasis, whereby TGR5 activation in cholangiocytes triggers cAMP/PKA/CREB signaling to promote EMT and biliary fibrosis via TGF-β1. Our findings directly implicate TGR5 as a central therapeutic target for mitigating fibrosis in this disease.