CONCANAVALIN A-INDUCED LIVER-CELL DAMAGE - ACTIVATION OF INTRACELLULAR PATHWAYS TRIGGERED BY TUMOR-NECROSIS-FACTOR IN MICE

Background & Aims: Concanavalin A (con A) induces tumor necrosis facto r (TNF)-dependent hepatocyte apoptosis resembling immune-mediated fulm inant hepatic failure in humans. Intracellular pathways originating at the TNF receptor are either linked to apoptosis, nuclear factor (NF)- kappa B translocation, or Jun kinase (JNK) activation. The aim of this study was to study TNF-dependent pathways after con A injection in vi vo. Methods: Con A, con A plus anti-TNF, and control buffer were injec ted into BALB/c mice. Immunofluorescence, Western blot, Northern blot, gel shift, Erk, and JNK activity and DNA fragmentation experiments we re performed at different time points after injection. Results: DNA fr agmentation in hepatocytes was increased 4-24 hours after con A inject ion. JNK was activated maximally (> 20-fold) directly after con A inje ction, whereas binding and nuclear translocation of NF-kappa B was max imal after 4 hours. All pathways were blocked by anti-TNF. JNK activat ion was specific because related ERK 1 + 2 were not activated after co n A. High nuclear expression of c-Jun was already evident 1 hour after con A injection; however, in contrast to JNK, anti-TNF treatment did not block c-Jun nuclear expression and DNA binding. Conclusions: In th e con A model, activation of TNF-dependent pathways is associated with apoptosis of hepatocytes. Their modulation in vivo may have implicati ons to develop new therapeutic strategies to prevent apoptosis.