Submitted on February 3, 2009
Revised on May 29, 2009
Accepted on June 16, 2009
Preactivation of NKT cells with 
-GalCer protects against hepatic ischemia-reperfusion injury in mouse by a mechanism involving IL-13 and adenosine A2A receptor
Zongxian Cao1, Youzhong Yuan1, Geetha Jeyabalan, Qiang Du1, Allan Tsung2, David A. Geller3, and Timothy R. Billiar1*
1 University of Pittsburgh
2 University of Pittsburgh Medical Center
3 Yale University
* To whom correspondence should be addressed. E-mail: billiartr{at}upmc.edu.
Hepatic preconditioning has emerged as a promising strategy of activating natural pathways to augment tolerance to liver ischemia-reperfusion (IR) injury. Liver-resident natural killer T (NKT) cells play an important role in modulating the local immune and inflammatory responses. This work was aimed to investigate whether pre-activation of NKT cells could provide a beneficial "preconditioning" effect to ameliorate the subsequent hepatic IR injury. To selectively activate NKT cells, C57BL/6 mice were treated intraperitoneally with the glycolipid antigen 
-galactosylceramide (-GalCer) 1 h prior to hepatic ischemia. Significantly reduced liver IR injury was observed in mice pretreated with -GalCer, and this protective effect was specifically abrogated by a CD1d blocking antibody. Serum TNF-, IFN-
and IL-13 levels were markedly increased shortly after -GalCer injection. Pretreatment with a neutralizing antibody against TNF- or IFN- did not influence the protective effect of -GalCer preconditioning, whereas pre-administration of an IL-13 neutralizing antibody completely abolished the effect. Treatment with -GalCer also led to an increased expression of adenosine A2A receptor (A2AR) in the liver, and blockade of A2AR by SH58261 diminished -GalCer pretreatment-mediated attenuation of liver IR injury. In contrast, administration of the selective A2AR agonist CGS21680 reversed the counteracting effect of the IL-13 neutralizing antibody on -GalCer preconditioning. Additionally, -GalCer pretreatment was associated with a decreased neutrophil accumulation in the ischemic liver. These findings provide the first evidence that hepatic preconditioning by pre-activation of NKT cells with -GalCer protects the liver from IR injury via an IL-13 and adenosine A2AR dependent mechanism.
