Scott F. Gallagher, Yanhua Peng, Jun Yang, Krista Haines, Kathryn Baksh, Heather Carpenter, P. K. Epling-Burnette, Michel M. Murr, University of South Florida, Tampa, FL

Background: Liver injury is a clinical prognostic indicator in acute pancreatitis. We previously demonstrated that Kupffer cell-derived FasL mediates liver injury during experimental acute pancreatitis. Aim: To determine the role of Fas/FasL in liver cell apoptosis during acute pancreatitis. Methods: Acute pancreatitis was induced in NIH, C57/C57 and knock-out mice for Fas and FasL (Fas-/- , FasL-/-) by CDE diet. Liver Fas, FasL, p38-MAPK, PARP, and Cytochrome C were determined by immunoblotting. Apoptosis was assessed by DNA fragmentation (ELISA) and TUNEL staining. Experiments were repeated in triplicates and gels were quantified by densitometry. Data are mean+/-SEM. Results: CDE-induced pancreatitis increased liver FasL(4280+/-580 vs. 733+/-336, p=0.01 pancreatitis vs. sham), Fas (2866+/-595 vs. 649+/-111, p=0.02 pancreatitis vs. sham), DNA fragmentation by 60% (p=0.03 pancreatitis vs. sham), TUNEL staining (40+/-2% vs. 14+/-1%, p<0.01 pancreatitis vs. sham) and upregulated cytochrome C (3600+/-177 vs. 1452+/-167, p<0.01 pancreatitis vs. sham) and PARP (7620+/-226 vs. 1215+/-17, p<0.01 pancreatitis vs. sham). In FasL-/- mice, the pancreatitis-induced upregulation of cytochrome C, PARP and p38-MAPK was significantly attenuated as compared to C57/C57 control mice. (Cytochrome C: 3514+/-53 vs. 6980+/-237; PARP: 3594+/-104 vs. 6393+/-591; p38-MAPK 1747+/-54 vs. 4894+/-388, all p<0.01; FasL-/- vs. C57). Similarly, the pancreatitis-induced upregulation of cytochrome C, PARP and p38-MAPK was attenuated in Fas-/- mice as compared to C57 mice (all p<0.01). In addition, pancreatitis-induced DNA fragmentation was reduced by 60% in Fas-/- and FasL-/- mice (p<0.01 vs. C57) Conclusions: Acute pancreatitis induces liver apoptosis and upregulates Fas/FasL and downstream apoptotic pathways. Pancreatitis-induced apoptosis was significantly reduced in Fas and FasL knock-out mice in addition to attenuation of cytochrome C, PARP and p38-MAPK, thereby suggesting a central role for Fas/FasL in liver injury during acute pancreatitis. The ability to manipulate interactions between Kupffer cell-derived FasL and hepatocytes may have important therapeutic implications.