Integrin alphavbeta6 is a marker of the progression of biliary and portal liver fibrosis and a novel target for antifibrotic therapies.
OBJECTIVE
The integrin alphavbeta6 promotes proliferation of specialized epithelia and acts as a receptor for the activation of latent TGFbeta1. We studied alphavbeta6 expression in experimental and human liver fibrosis and the potential of its pharmacological inhibition for treatment of hepatic fibrosis.


METHODS
alphavbeta6 expression was studied by quantitative PCR and immunohistochemistry in rats with cirrhosis due to bile duct ligation (BDL), administration of thioacetamide (TAA), in Mdr2(Abcb4)(-/-) mice with spontaneous biliary fibrosis, and in livers of patients with chronic hepatitis C (n=79) and end-stage liver disease due to various etiologies (n=18). The effect of a selective alphavbeta6 inhibitor was evaluated in Mdr2(Abcb4)(-/-) mice with ongoing fibrogenesis.


RESULTS
Integrin beta6 mRNA increased with fibrosis stage in hepatitis C and was upregulated between 25- and 100-fold in TAA- and BDL-induced cirrhosis, in Mdr2(Abcb4)(-/-) mice and in human end-stage liver disease. alphavbeta6 protein was absent in normal livers and expressed de novo on (activated) bile duct epithelia and transitional hepatocytes. A single dose of the alphavbeta6 inhibitor injected into Mdr2(Abcb4)(-/-) mice significantly induced profibrolytic matrix metalloproteinases (MMP)-8 and -9 after 3 h, with a corresponding increase in extracellular matrix-degrading activities. In parallel profibrogenic transcripts (procollagen alpha1(I), TGFbeta2, and MMP-2) showed a trend of downregulation.


CONCLUSIONS
(1) Integrin alphavbeta6 is induced de novo in rodent and human liver fibrosis, where it is expressed on activated bile duct epithelia and (transitional) hepatocytes during fibrosis progression. (2) In vivo a single dose of a small molecule alphavbeta6 inhibitor induced antifibrogenic and profibrolytic genes and activities, suggesting alphavbeta6 is a unique target for treatment of liver fibrosis.
Popov
Yury
Y
Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
Patsenker
Eleonora
E
Stickel
Felix
F
Zaks
Jessica
J
Bhaskar
K Ramakrishnan
KR
Niedobitek
Gerald
G
Kolb
Armin
A
Friess
Helmut
H
Schuppan
Detlef
D
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism; D000328:Adult; D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism*; D001652:Bile Ducts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015415:Biomarkers / Q000378:metabolism; D001706:Biopsy; D004195:Disease Models, Animal; D018450:Disease Progression; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005260:Female; D019698:Hepatitis C, Chronic / Q000378:metabolism / Q000473:pathology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008103:Liver Cirrhosis / Q000188:drug therapy* / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D011725:Pyridines / Q000494:pharmacology / Q000627:therapeutic use; D051381:Rats; D017208:Rats, Wistar; D000097202:ATP-Binding Cassette Sub-Family B Member 4
D018435:ATP Binding Cassette Transporter, Subfamily B; D000951:Antigens, Neoplasm; D015415:Biomarkers; D016023:Integrins; D011725:Pyridines; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C529593:EMD 527040; C073878:integrin alphavbeta6