Mallory body formation by ethanol feeding in drug-primed mice

Drug-primed mice, created by a 5-month feeding of diethyl-1,4-dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylate (DDC), followed by a 1-month withdrawal, were refed ethanol or isocaloric dextrose (control) diets intragastrically for 7 days. The formation of Mallory bodies (MBs) was monitored by immunofluorescence and immunoperoxidase microscopy using antibodies to cytokeratin and ubiquitin, and also by electron microscopy. The changes in cytokeratin 55 (CK55), ubiquitin conjugate, nuclear factor kappaB (NFkappaB) p65, NFkappaB p50, inhibitor kappaB alpha, c-myc, tumor necrosis factor alpha, and cytochrome P450 2E1 (CYP2E1) contents were determined by Western blotting using appropriate antibodies. The messenger RNA (mRNA) for CYP2E1, cytokeratin, ubiquitin, hepatocyte growth factor activator, and tissue transglutaminase was quantitated. MBs were present at 5 to 7 days' postfeeding with ethanol, but not with dextrose. They developed in clusters of "empty hepatocytes," where the cytokeratin antibody failed to recognize the typical filament structures seen in normal hepatocytes. MBs were larger and more numerous in the subcapsular region. Northern blots showed that CK55 mRNA was decreased by the ethanol treatment, but protein levels were increased, suggesting a decreased turnover of the cytokeratin. Likewise, the increase in CYP2E1 protein in the face of a lack of an increase in mRNA for CYP2E1 could be explained by a decreased turnover of this cytochrome. This is the first report of MB formation induced by ethanol ingestion in an experimental model.