Background & aims: Fibrosis in the liver is the main histological determinant of non-alcoholic steatohepatitis (NASH), a disease that parallels the worldwide surge in metabolic syndromes. Currently, there is no effective treatment for liver fibrosis. While Hippo/YAP (Yes-associated protein) signaling is essential for liver regeneration, its aberrant activation frequently leads to fibrosis and tumorigenesis. Unravelling "context-specific" contributions of YAP in liver repair might help selectively bypass fibrosis and preserve the pro-regenerative YAP function in hepatic diseases.
Methods: We used murine liver fibrosis and minipig NASH models, liver biopsies from cirrhotic patients, single-cell RNA sequencing (scRNA-Seq) and a G-protein-coupled receptor (GPCR) ligand screening system.
Results: YAP levels in macrophages are increased in the livers of humans and mice with liver fibrosis. The fibrogenic role of macrophage YAP was evidenced via boosting type I interferon and attenuating liver fibrosis in mice specifically lacking Yap1 in myeloid cells. scRNA-Seq further showed that defecting YAP pathway in macrophages diminished a fibrogenic vascular endothelial cell subset exhibiting pro-fibrotic molecular signatures such as CTGF and VCAM1 expression. To specifically target fibrogenic YAP in macrophages, we utilized a GPCR ligand screening system and identified a dopamine receptor D2 (DRD2) antagonist that selectively blocked YAP in macrophages but not hepatocytes. Genetic and pharmacological targeting of macrophage DRD2 attenuated liver fibrosis. In a large animal (minipig) NASH model recapitulating human pathology, DRD2 antagonist blocked fibrosis and restored hepatic architecture.
Conclusions: DRD2 antagonization selectively targets YAP-dependent fibrogenic crosstalk between macrophages and CTGF+VCAM1+ endothelial cells, promoting liver regeneration over fibrosis in both rodent and large animal models.
Lay summary: Fibrosis in the liver is one of the main histological determinants of non-alcoholic steatohepatitis (NASH), a disease paralleling a worldwide surge in metabolic syndromes. Our study demonstrates that myeloid-specific YAP deficiency attenuates liver fibrosis. Dopamine receptor D2 (DRD2) antagonization selectively blocks YAP in macrophages and thwarts liver fibrosis in both rodent and large animal models, showing the potential for the GPCR targeting-based NASH therapies.
Keywords: Hippo/YAP signaling; dopamine receptor D2; endothelial cell; intrahepatic macrophage; liver fibrosis; non-alcoholic steatohepatitis (NASH); type I interferon.
Copyright © 2021. Published by Elsevier B.V.