Chromatin breakdown by deoxyribonuclease1 promotes acetaminophen-induced liver necrosis: an ultrastructural and histochemical study on male CD-1 mice

We analyzed in male wild-type (WT) and Dnase1 knockout (KO) CD-1 mice after acetaminophen (APAP)-intoxication the hepatolobular distribution of APAP-adducts in relation to DNA-damage by terminal deoxyribonucleotidyl-transferase dUTP nick end-labeling (TUNEL), the ultrastructural alterations of hepatocellular morphology and the intracellular localization of Dnase1. Treatment of WT-mice with 600 mg/kg APAP led to extensive pericentral necrosis. Electron microscopy (EM) demonstrated vesiculation of the rough endoplasmatic reticulum and swelling of mitochondria. Pericentral WT-hepatocyte nuclei exhibited pyknosis, karyorrhexis and karyolysis. In contrast, livers from treated KO-mice exhibited almost normal light microscopical structure and EM revealed only mild signs of hepatocellular damage. In WT-mice several layers of pericentral hepatocytes displayed APAP-adduct formation and subsequent DNA-damage, whereas in KO-animals only few cells were affected. Serum aminotransferases rose similarly in both mouse strains up to 12 h, thereafter increased only in WT-mice. Immunogold-EM revealed the translocation of Dnase1 from the rER into the nuclei of treated WT-mice. In KO-mice, APAP-adduct formation was retarded and less extensive suggesting that detoxification of APAP must have been more effective in KO-mice possibly due to the lack of energy depletion otherwise caused by Dnase1-induced DNA-damage in WT-mice.