Parenchymal cell apoptosis as a signal for sinusoidal sequestration and transendothelial migration of neutrophils in murine models of endotoxin and fas-antibody-induced liver injury

Abstract

Endotoxin (ET) induces neutrophil sequestration in hepatic sinusoids, the activation of proinflammatory transcription factors (nuclear factor κB [NF-κB]) with up-regulation of adhesion molecules on sinusoidal endothelial cells and hepatocytes. However, if galactosamine (Gal) is co-administered with ET, neutrophils transmigrate and attack parenchymal cells. This suggests that a signal from parenchymal cells triggers neutrophil transmigration. In this study, we tested the hypothesis that parenchymal cell apoptosis may induce neutrophil transendothelial migration in the Gal/ET model. Treatment of C3Heb/FeJ mice with 700 mg/kg Gal and 100 μg/kg ET induced tumor necrosis factor α (TNF-α) formation (13.25 ± 0.75 ng/mL) and hepatic NF-κB activation at 90 minutes; the generation of the C-X-C chemokine KC (2.86 ± 0.30 ng/mL at 5 hours); sinusoidal neutrophil sequestration (380 ± 21 polymorphonuclear leukocytes/50 high-power fields) and apoptosis (925% ± 29% increase of DNA fragmentation; and a 45-fold increase of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells) at 6 hours, followed by transmigration of neutrophils and development of substantial necrosis (38% ± 3% of hepatocytes; alanine transaminase [ALT]: 1,500 ± 300 U/L) at 7 hours. Administration of uridine (1,000 mg/kg) did not reduce plasma levels of TNF-α and KC, NF-κB activation, or polymorphonuclear leukocyte sequestration, but attenuated apoptosis by 90% to 94%. In these livers, neutrophils did not transmigrate and liver injury was prevented (necrosis: in vivo. However, apoptosis per se does not cause neutrophil sequestration in the liver vasculature.