Engagement of alphavbeta3 integrin regulates proliferation and apoptosis of hepatic stellate cells.
Hepatic stellate cells are the major source of the extracellular matrix that accumulates in fibrotic liver. During progressive liver fibrosis, hepatic stellate cells proliferate, but during resolution of fibrosis there is extensive stellate cell apoptosis that coincides with degradation of the liver scar. We have examined the possibility that the fate of stellate cells is influenced by the extracellular matrix through the intermediary of alpha(v)beta(3) integrin. alpha(v)beta(3) integrin was expressed by activated, myofibroblastic rat and human stellate cells in culture. Antagonism of this integrin using neutralizing antibodies, echistatin, or small inhibitory RNA to silence alpha(v) subunit expression inhibited stellate cell proliferation and their expression of proliferating cell nuclear antigen and activated forms of p44 and p42 MAPK. These alpha(v)beta(3) antagonists also increased apoptosis of cultured stellate cells, and this was associated with an increase in the BAX/BCL-2 protein ratio, induction of nuclear DNA fragmentation, and activation of intracellular caspase-3. Expression of tissue inhibitor of metalloproteinases-1 by activated stellate cells was reduced by the alpha(v)beta(3) antagonists, while matrix metalloproteinase-9 synthesis was enhanced. Stellate cells incubated with active recombinant matrix metalloproteinase-9 showed enhanced apoptosis, while cells treated with a synthetic inhibitor of this protease showed increased survival. Our studies suggest that alpha(v)beta(3) integrin regulates the fate of hepatic stellate cells. Degradation of alpha(v)beta(3) ligands surrounding activated stellate cells during resolution of liver fibrosis might decrease alpha(v)beta(3) integrin ligation, suppressing stellate cell proliferation and inducing a fibrolytic, matrix metalloproteinase-secreting phenotype that may prime stellate cells for apoptosis.
Zhou
Xiaoying
X
Liver Research Group, University Division of Infection, Inflammation and Repair, Southampton General Hospital, United Kingdom.
Murphy
Frank R
FR
Gehdu
Nitu
N
Zhang
Junlong
J
Iredale
John P
JP
Benyon
R Christopher
RC
D000165:Acridine Orange / Q000494:pharmacology; D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005355:Fibrosis; D005456:Fluorescent Dyes / Q000494:pharmacology; D020868:Gene Silencing; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D016023:Integrins / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D008024:Ligands; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D018613:Microscopy, Confocal; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010641:Phenotype; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D019096:Vitronectin / Q000378:metabolism
D000199:Actins; D005456:Fluorescent Dyes; D039302:Integrin alphaVbeta3; D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D010455:Peptides; D018809:Proliferating Cell Nuclear Antigen; D034741:RNA, Small Interfering; D019715:Tissue Inhibitor of Metalloproteinase-1; D019096:Vitronectin; C057986:echistatin; D003094:Collagen; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D020780:Matrix Metalloproteinase 9; D000165:Acridine Orange