ACTIVATED NEUTROPHILS FROM RAT INJURED ISOLATED HEPATOCYTES

BACKGROUND: Activated neutrophils (PMNs) release cytotoxic agents that can damage surrounding tissue. These studies were performed to determ ine whether activated PMNs from rat could injure isolated, rat hepatic parenchymal cells (HCs) in vitro. EXPERIMENTAL DESIGN: HCs were cocul tured with unstimulated rat PMNs or with PMNs activated with either f- met-leu-phe (FMLP) or phorbol myristate acetate (PMA), that stimulate predominantly degranulation or superoxide production, respectively. To xicity to HCs was evaluated from release of alanine aminotransferase i nto the medium. RESULTS: Alanine aminotransferase release was greater in HCs cocultured with FMLP- or PMA-stimulated PMNs compared with unst imulated PMNs. Toxicity was observed by 16 hours after stimulation of PMNs. To test the possible involvement of a soluble mediator released by activated PMNs, HCs were incubated with conditioned medium from PMN s. Compared with unstimulated PMNs, toxicity to HCs was greater in the presence of conditioned medium from FMLP-stimulated PMNs, but not con ditioned medium from PMA-activated PMNs. Reactive oxygen species do no t appear to be involved in the mechanism by which activated PMNs damag e HCs since superoxide dismutase, catalase, superoxide dismutase + cat alase, or desferrioxamine failed to prevent the injury. Furthermore, l ess superoxide anion was detected in PMA-stimulated PMNs when either H Cs or HC-conditioned medium was present. Proteolytic enzymes released by stimulated PMNs may play a role in HC damage since an inhibitor of proteases diminished injury due to PMNs activated by either FMLP or PM A. CONCLUSIONS: These results indicate that activated, rat PMNs damage HCs in culture. The data suggest that reactive oxygen species are not involved in the mechanism, but that release of proteolytic enzymes ma y play a role in the toxic response.