Generation and functional significance of CXC chemokines for neutrophil-induced liver injury during endotoxemia.

The hypothesis that the neutrophil chemoattractant CXC chemokines KC and macrophage inflammatory protein-2 (MIP-2) are involved in neutrophil transmigration and liver injury was tested in C3Heb/FeJ mice treated with galactosamine (Gal, 700 mg/kg), endotoxin (ET, 100 microg/kg), or Gal + ET (Gal/ET). Hepatic KC and MIP-2 mRNA levels and plasma CXC chemokine concentrations were dramatically increased 1.5 h after Gal/ET or ET alone and gradually declined up to 7 h. Murine recombinant cytokines (TNF-alpha, IL-1 alpha, and IL-1 beta), but not Gal/ET, induced CXC chemokine formation in the ET-resistant C3H/HeJ strain. To assess the functional importance of KC and MIP-2, C3Heb/FeJ mice were treated with Gal/ET and control IgG or a combination of anti-KC and anti-MIP-2 antibodies. Anti-CXC chemokine antibodies did not attenuate hepatocellular apoptosis, sinusoidal neutrophil sequestration and extravasation, or liver injury at 7 h. Furthermore, there was no difference in liver injury between BALB/cJ wild-type and CXC receptor-2 gene knockout (CXCR2-/-) mice treated with Gal/ET. The higher neutrophil count in livers of CXCR2-/- than in wild-type mice after Gal/ET was caused by the elevated number of neutrophils located in sinusoids of untreated CXCR2-/- animals. The pancaspase inhibitor Z-Val-Ala-Asp-fluoromethylketone eliminated Gal/ET-induced apoptosis and neutrophil extravasation and injury but not CXC chemokine formation. Thus Gal/ET induced massive, cytokine-dependent CXC chemokine formation in the liver. However, neutrophil extravasation and injury occurred in response to apoptotic cell injury at 6-7 h and was independent of CXC chemokine formation.