BACKGROUND AND PURPOSE:
Hepatic stellate cells (HSCs) are liver-specific pericytes regulating angiogenesis during liver fibrosis. We aimed to elucidate the mechanisms by which hedgehog signaling regulated HSC angiogenic properties and to validate the therapeutic implications.
EXPERIMENTAL APPROACH:
Rats and mice were intoxicated with carbon tetrachloride for in vivo evaluation of hepatic angiogenesis and fibrotic injury. Diversified molecular approaches including real-time PCR, Western blot, luciferase reporter assay, chromatin immunoprecipitation, electrophoretic mobility shift assay, and co-immunoprecipitation were used to investigate the underlying mechanisms in vitro.
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BACKGROUND AND PURPOSE:
Hepatic stellate cells (HSCs) are liver-specific pericytes regulating angiogenesis during liver fibrosis. We aimed to elucidate the mechanisms by which hedgehog signaling regulated HSC angiogenic properties and to validate the therapeutic implications.
EXPERIMENTAL APPROACH:
Rats and mice were intoxicated with carbon tetrachloride for in vivo evaluation of hepatic angiogenesis and fibrotic injury. Diversified molecular approaches including real-time PCR, Western blot, luciferase reporter assay, chromatin immunoprecipitation, electrophoretic mobility shift assay, and co-immunoprecipitation were used to investigate the underlying mechanisms in vitro.
KEY RESULTS:
Angiogenesis was concomitant with upregulation of Smoothened (SMO) and hypoxia inducible factor-1α (HIF-1α) in rat fibrotic liver. SMO inhibitor cyclopamine and Gli1 inhibitor GANT-58 reduced the expression of vascular endothelial growth factor (VEGF) and angiopoietin 1 in HSCs, and repressed HSC tubulogenesis capacity. HIF-1α inhibitor PX-478 suppressed HSC angiogenic behaviors, and inhibition of hedgehog decreased HIF-1α expression. Furthermore, heat shock protein 90 (HSP90) was characterized as a direct target gene of canonical hedgehog signaling in HSCs. HSP90 inhibitor 17-AAG reduced HSP90 binding to HIF-1α, downregulated HIF-1α protein abundance, and repressed HIF-1α binding to DNA. 17-AAG also abolished SAG (a SMO agonist)-enhanced HSC angiogenic properties. Finally, the natural compound ligustrazine was found to inhibit canonical hedgehog signaling leading to suppressed angiogenic properties of HSCs in vitro, and ameliorated liver fibrosis and sinusoidal angiogenesis in mice.
CONCLUSION AND IMPLICATIONS:
We uncovered a novel mechanism by which canonical hedgehog governed HSC-mediated liver angiogenesis. Selective inhibition of HSC hedgehog signaling could be a promising therapeutic approach for hepatic fibrosis. This article is protected by copyright. All rights reserved.
