HGF regulates the activation of TGF-β1 in rat hepatocytes and hepatic stellate cells.
Hepatocyte growth factor (HGF) ameliorates experimental liver fibrosis through many mechanisms, including degradation of accumulated collagen and decreased expression of fibrotic genes. Investigating an upstream mechanism in which HGF could decrease many fibrotic effectors, we asked whether HGF regulates activation of the fibrotic cytokine transforming growth factor-beta 1 (TGF-β1). Specifically, we tested whether HGF decreases the levels of active TGF-β1, and whether such decrease depends on the predominantly hepatocyte-secreted protease plasmin, and whether it depends on the TGF-β1 activator thrombospondin-1 (TSP-1). With hepatocyte monocultures, we found HGF-induced hepatocyte proliferation did increase total levels of plasmin, while decreasing gene expression of fibrotic markers (PAI-1, TGF-β1, and TIMP-2). With in vitro models of fibrotic liver (HSC-T6 hepatic stellate cells, or co-cultures of HSC-T6 and hepatocytes), we found high levels of fibrosis-associated proteins such as TSP-1, active TGF-β1, and Collagen I. HGF treatment on these fibrotic cultures stimulated plasmin levels; increased TSP-1 protein cleavage; and decreased the levels of active TGF-β1 and Collagen I. When plasmin was blocked by the inhibitor aprotinin, HGF could no longer decrease TGF-β1 activation and Collagen I. Meanwhile, the TSP-1-specific peptide inhibitor, LSKL, reduced TGF-β1 to the same level as in the HGF-treated cultures; combining LSKL and HGF treatments caused no further decrease, suggesting that HGF affects the TSP-1 dependent pathway of TGF-β1 activation. Therefore, HGF can decrease TGF-β1 activation and TGF-β1-dependent fibrotic markers, by stimulating hepatocytes to produce plasmin, and by antagonizing TSP-1-dependent activation of TGF-β1.
NUS Graduate School for Integrative Sciences and Engineering, Singapore.
Balakrishnan Chakrapani
BC
Narmada
Ser-Mien
SM
Chia
Lisa
L
Tucker-Kellogg
Hanry
H
Yu
D000818:Animals; D007611:Aprotinin / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D024042:Collagen Type I / Q000032:analysis; D005341:Fibrinolysin / Q000032:analysis; D055166:Hepatic Stellate Cells / Q000187:drug effects / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology / Q000502:physiology*; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000188:drug therapy; D008297:Male; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D019700:Thrombospondin 1 / Q000032:analysis / Q000037:antagonists & inhibitors; D053773:Transforming Growth Factor beta1 / Q000096:biosynthesis*
D024042:Collagen Type I; C487834:Leu-Ser-Lys-Leu peptide; D010455:Peptides; D015842:Serine Proteinase Inhibitors; D019700:Thrombospondin 1; D053773:Transforming Growth Factor beta1; D017228:Hepatocyte Growth Factor; D007611:Aprotinin; D005341:Fibrinolysin