Plasmacytoid dendritic cell-derived IFN-α promotes murine liver ischemia/reperfusion injury by induction of hepatocyte IRF-1.
Plasmacytoid dendritic cells (pDC) constitute the body's principal source of type I interferon (IFN) and are comparatively abundant in the liver. Among various cytokines implicated in liver ischemia and reperfusion (I/R) injury, type I IFNs have been described recently as playing an essential role in its pathogenesis. Moreover, type I IFNs have been shown to up-regulate hepatocyte expression of IFN regulatory factor 1 (IRF-1), a key transcription factor that regulates apoptosis and induces liver damage after I/R. Our aim was to ascertain the capacity of IFN-α released by liver pDC to induce liver damage through hepatic IRF-1 up-regulation after I/R injury. Our findings show that liver pDC mature and produce IFN-α in response to liver I/R. Liver pDC isolated after I/R induced elevated levels of IRF-1 production by hepatocytes compared with liver pDC isolated from sham-operated mice. Notably, hepatic IRF-1 expression was reduced significantly by neutralizing IFN-α. In vivo, IFN-α neutralization protected the liver from I/R injury by reducing hepatocyte apoptosis. This was associated with impaired expression of IRF-1 and proapoptotic molecules such as Fas ligand, its receptor (Fas) and death receptor 5, which are regulated by IRF-1. Furthermore, pDC-depleted mice failed to up-regulate hepatic IFN-α and displayed less liver injury associated with reduced levels of hepatic interleukin (IL)-6, tumor necrosis factor-α, and hepatocyte apoptosis after I/R compared with controls.


CONCLUSIONS
these data support the hypothesis that IFN-α derived from liver pDC plays a key role in the pathogenesis of liver I/R injury by enhancing apoptosis as a consequence of induction of hepatocyte IRF-1 expression.
Thomas E. Starzl Transplantation Institute, Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA.
Antonino
A
Castellaneta
Osamu
O
Yoshida
Shoko
S
Kimura
Shinichiro
S
Yokota
David A
DA
Geller
Noriko
N
Murase
Angus W
AW
Thomson
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism; D004195:Disease Models, Animal; D022781:Hepatocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D050856:Interferon Regulatory Factor-1 / Q000276:immunology* / Q000378:metabolism; D016898:Interferon-alpha / Q000276:immunology* / Q000378:metabolism; D015850:Interleukin-6 / Q000276:immunology / Q000378:metabolism; D008107:Liver Diseases / Q000276:immunology* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015427:Reperfusion Injury / Q000276:immunology* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism; D015854:Up-Regulation / Q000276:immunology
C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D016898:Interferon-alpha; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; C577686:interleukin-6, mouse