CXC chemokine ligand 4 (Cxcl4) is a platelet-derived mediator of experimental liver fibrosis.
Liver fibrosis is a major cause of morbidity and mortality worldwide. Platelets are involved in liver damage, but the underlying molecular mechanisms remain elusive. Here, we investigate the platelet-derived chemokine (C-X-C motif) ligand 4 (CXCL4) as a molecular mediator of fibrotic liver damage. Serum concentrations and intrahepatic messenger RNA of CXCL4 were measured in patients with chronic liver diseases and mice after toxic liver injury. Platelet aggregation in early fibrosis was determined by electron microscopy in patients and by immunohistochemistry in mice. Cxcl4(-/-) and wild-type mice were subjected to two models of chronic liver injury (CCl(4) and thioacetamide). The fibrotic phenotype was analyzed by histological, biochemical, and molecular analyses. Intrahepatic infiltration of immune cells was investigated by fluorescence-activated cell sorting, and stellate cells were stimulated with recombinant Cxcl4 in vitro. The results showed that patients with advanced hepatitis C virus-induced fibrosis or nonalcoholic steatohepatitis had increased serum levels and intrahepatic CXCL4 messenger RNA concentrations. Platelets were found directly adjacent to collagen fibrils. The CCl(4) and thioacetamide treatment led to an increase of hepatic Cxcl4 levels, platelet activation, and aggregation in early fibrosis in mice. Accordingly, genetic deletion of Cxcl4 in mice significantly reduced histological and biochemical liver damage in vivo, which was accompanied by changes in the expression of fibrosis-related genes (Timp-1 [tissue inhibitor of matrix metalloproteinase 1], Mmp9 [matrix metalloproteinase 9], Tgf-beta [transforming growth factor beta], IL10 [interleukin 10]). Functionally, Cxcl4(-/-) mice showed a strongly decreased infiltration of neutrophils (Ly6G) and CD8(+) T cells into the liver. In vitro, recombinant murine Cxcl4 stimulated the proliferation, chemotaxis, and chemokine expression of hepatic stellate cells.


CONCLUSIONS
The results underscore an important role of platelets in chronic liver damage and imply a new target for antifibrotic therapies.
Zaldivar
Mirko Moreno
MM
Department of Medicine III, University Hospital Aachen, Aachen, Germany.
Pauels
Katrin
K
von Hundelshausen
Philipp
P
Berres
Marie-Luise
ML
Schmitz
Petra
P
Bornemann
Jörg
J
Kowalska
M Anna
MA
Gassler
Nikolaus
N
Streetz
Konrad L
KL
Weiskirchen
Ralf
R
Trautwein
Christian
C
Weber
Christian
C
Wasmuth
Hermann E
HE
D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D002251:Carbon Tetrachloride / Q000633:toxicity; D002633:Chemotaxis; D055166:Hepatic Stellate Cells / Q000502:physiology; D006526:Hepatitis C / Q000150:complications; D006801:Humans; D008106:Liver Cirrhosis, Experimental / Q000209:etiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D020556:Neutrophil Infiltration; D015539:Platelet Activation; D010978:Platelet Factor 4 / Q000097:blood / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis
D012333:RNA, Messenger; D010978:Platelet Factor 4; D002251:Carbon Tetrachloride