Lymphotoxin-beta receptor signaling regulates hepatic stellate cell function and wound healing in a murine model of chronic liver injury.
Lymphotoxin-beta (LTbeta) is a proinflammatory cytokine and a member of the tumor necrosis factor (TNF) superfamily known for its role in mediating lymph node development and homeostasis. Our recent studies suggest a role for LTbeta in mediating the pathogenesis of human chronic liver disease. We hypothesize that LTbeta co-ordinates the wound healing response in liver injury via direct effects on hepatic stellate cells. This study used the choline-deficient, ethionine-supplemented (CDE) dietary model of chronic liver injury, which induces inflammation, liver progenitor cell proliferation, and portal fibrosis, to assess (1) the cellular expression of LTbeta, and (2) the role of LTbeta receptor (LTbetaR) in mediating wound healing, in LTbetaR(-/-) versus wild-type mice. In addition, primary isolates of hepatic stellate cells were treated with LTbetaR-ligands LTbeta and LTbeta-related inducible ligand competing for glycoprotein D binding to herpesvirus entry mediator on T cells (LIGHT), and mediators of hepatic stellate cell function and fibrogenesis were assessed. LTbeta was localized to progenitor cells immediately adjacent to activated hepatic stellate cells in the periportal region of the liver in wild-type mice fed the CDE diet. LTbetaR(-/-) mice fed the CDE diet showed significantly reduced fibrosis and a dysregulated immune response. LTbetaR was demonstrated on isolated hepatic stellate cells, which when stimulated by LTbeta and LIGHT, activated the nuclear factor kappa B (NF-kappaB) signaling pathway. Neither LTbeta nor LIGHT had any effect on alpha-smooth muscle actin, tissue inhibitor of metalloproteinase 1, transforming growth factor beta, or procollagen alpha(1)(I) expression; however, leukocyte recruitment-associated factors intercellular adhesion molecule 1 and regulated upon activation T cells expressed and secreted (RANTES) were markedly up-regulated. RANTES caused the chemotaxis of a liver progenitor cell line expressing CCR5.


CONCLUSIONS
This study suggests that LTbetaR on hepatic stellate cells may be involved in paracrine signaling with nearby LTbeta-expressing liver progenitor cells mediating recruitment of progenitor cells, hepatic stellate cells, and leukocytes required for wound healing and regeneration during chronic liver injury.
Ruddell
Richard G
RG
Hepatic Fibrosis Group, The University of Queensland, Brisbane, Australia.
Knight
Belinda
B
Tirnitz-Parker
Janina E E
JE
Akhurst
Barbara
B
Summerville
Lesa
L
Subramaniam
V Nathan
VN
Olynyk
John K
JK
Ramm
Grant A
GA
D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D002796:Choline Deficiency / Q000503:physiopathology; D024042:Collagen Type I / Q000096:biosynthesis; D004195:Disease Models, Animal; D005001:Ethionine / Q000502:physiology; D055166:Hepatic Stellate Cells / Q000502:physiology*; D008099:Liver / Q000293:injuries*; D008115:Liver Regeneration / Q000502:physiology; D053361:Lymphotoxin alpha1, beta2 Heterotrimer / Q000096:biosynthesis / Q000502:physiology*; D053259:Lymphotoxin beta Receptor / Q000502:physiology*; D008297:Male; D051379:Mice; D051381:Rats; D014945:Wound Healing / Q000502:physiology*
D024042:Collagen Type I; D053361:Lymphotoxin alpha1, beta2 Heterotrimer; D053259:Lymphotoxin beta Receptor; D005001:Ethionine