Molecular mechanism investigation of cycloheximide-induced hepatocyte apoptosis in rat livers by morphological and microarray analysis.

Male F344 rats were intravenously treated with 6 mg/kg cycloheximide (CHX), and microarray analysis was conducted on their livers 1, 2 and 6h after the CHX treatment. The histopathological examination and serum chemistry results indicated a mild hepatic cell death 2 and 6h after the CHX treatment, respectively. Multi-focal hepatocellular necrosis with slight neutrophil infiltration was observed 6h after the CHX treatment. The TUNEL staining results showed that the number of apoptotic hepatocytes was the highest 2h after the CHX treatment. Dramatic increases in the mRNA levels of ATF3 and CHOP genes, both of which were reported to play roles in the ER stress-mediated apoptosis pathway, were observed from 1h after the CHX treatment. In addition, increase of GADD45, p21 and p53 mRNA levels also suggested a time course-related stimulation of hepatocellular apoptotic signals. These results suggest that the hepatocyte apoptosis induced by the CHX treatment is triggered by ER stress. The hepatic mRNA levels of proinflammatory genes, such as TNFalpha, IL-1alpha and beta, were also increased 1 and 2h after the CHX treatment, supposedly mediated by the activated Kupffer cells engulfing the apoptotic hepatocytes.