benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and Liver-Diseases

The mode of cell death after acetaminophen (AAP) overdose is controversially discussed. A recent study reported a protective effect of the pancaspase inhibitor Z-VAD-fmk against AAP toxicity in vivo but the mechanism of protection remained unclear. Therefore, the objective of this investigation was to assess if Z-VAD-fmk or the low doses of dimethyl sulfoxide (DMSO) used as solvent were responsible for the protection. Treatment with 10 mg/kg Z-VAD-fmk or diluted DMSO (0.25 ml/kg) for 15 min before but not 2.5 h after AAP prevented the oxidant stress (hepatic glutathione disulfide content; nitrotyrosine staining), DNA fragmentation (anti-histone ELISA, TUNEL assay) and liver injury (plasma ALT activities) at 6 h after administration of 300 mg/kg AAP. Even a lower dose (0.1 ml/kg) of DMSO was partially effective. DMSO pretreatment also attenuated the initial decline in hepatic glutathione levels. On the other hand, 10 microM Z-VAD-fmk was unable to prevent AAP-induced cell death in primary cultured mouse hepatocytes. We conclude that Z-VAD-fmk does not protect against AAP-induced liver injury and, therefore, caspases are not involved in the mechanism of AAP-induced liver injury. In contrast, the protection in vivo is caused by the diluted DMSO, which is used to solubilize the inhibitor Z-VAD-fmk. The results emphasize that even very low doses of DMSO, which are generally necessary to dissolve water-insoluble inhibitors, can have a profound impact on the toxicity of drugs and chemicals when metabolic activation is a critical aspect of the mechanism of cell injury.

Topics: Acetaminophen; Amino Acid Chloromethyl Ketones; Analgesics, Non-Narcotic; Animals; Caspase Inhibitors; Caspases; Chemical and Drug Induced Liver Injury; Cysteine Proteinase Inhibitors; Dimethyl Sulfoxide; Dose-Response Relationship, Drug; Liver Diseases; Male; Mice; Mice, Inbred Strains; Solvents

The chronological expression (over 24 h) of two adhesion molecules [intercellular adhesion molecule-1 (ICAM-1) and CD11b/CD18 (Mac-1)] and the extent of liver damage, including injury to sinusoidal endothelial cells (SECs) and hepatocyte apoptosis, were investigated under two conditions of rat liver ischemia-reperfusion (I/R) injury: reversible (30 min) and fatal I/R (60 min). The chronological profiles of upregulation of ICAM-1 on hepatocytes and Mac-1 showed changes in parallel with the other liver damage parameters, and the extent of upregulation and various parameters of liver injury were more advanced in the 60-min I/R group. Paradoxically, the degree of ICAM-1 upregulation of SECs decreased significantly in the 60-min I/R group vs. the 30-min I/R group. Repression of hepatocyte apoptosis by administration of the caspase inhibitor ZVAD-fmk resulted in attenuation of neutrophil infiltration and liver injury. These findings indicate that 1) neutrophil infiltration is involved in the development of liver I/R injury; 2) interaction between ICAM-1 on SECs and Mac-1 on neutrophils is not an essential step for neutrophil transmigration through the endothelial layer because SECs, specifically, were impaired in the early stages of liver I/R injury; 3) the role of ICAM-1 and Mac-1 is to adhere neutrophils firmly to hepatocytes and activate neutrophils; and 4) excessive parenchymal apoptosis may be the signal for the neutrophil-induced inflammatory and necrotic reaction.

Topics: Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Caspase Inhibitors; CD18 Antigens; Cell Nucleus; Cysteine Proteinase Inhibitors; DNA Fragmentation; Intercellular Adhesion Molecule-1; Kinetics; Liver Diseases; Macrophage-1 Antigen; Male; Necrosis; Neutrophil Infiltration; Rats; Rats, Wistar; Reperfusion Injury; Survival Rate

IL-18, produced as a biologically inactive precursor, is processed by caspase-1 in LPS-activated macrophages. Here, we investigated caspase-1-independent processing of IL-18 in Fas ligand (FasL)-stimulated macrophages and its involvement in liver injury. Administration of Propionibacterium acnes (P. acnes) upregulated functional Fas expression on macrophages in an IFNgamma-dependent manner, and these macrophages became competent to secrete mature IL-18 upon stimulation with FasL. This was also the case for caspase-1-deficient mice. Administration of recombinant soluble FasL (rFasL) after P. acnes priming induced comparable elevation of serum IL-18 in parallel with elevated serum liver enzyme levels. However, liver injury was not induced in IL-18-deficient mice after rFasL administration. These results indicate a caspase-1-independent pathway of IL-18 secretion from FasL-stimulated macrophages and its critical involvement in FasL-induced liver injury.

Topics: Amino Acid Chloromethyl Ketones; Animals; Caspase 1; Caspase Inhibitors; Cells, Cultured; Cysteine Proteinase Inhibitors; Fas Ligand Protein; fas Receptor; Female; Humans; Interleukin-18; Liver Diseases; Macrophages; Male; Membrane Glycoproteins; Mice; Mice, Inbred C57BL; Mice, Knockout; Recombinant Proteins; Solubility