Intravenous injection of cycloheximide induces apoptosis and up-regulates p53 and Fas receptor expression in the rat liver in vivo.

A single administration of protein synthesis inhibitor, cycloheximide (CHX) induces apoptosis of hepatocytes in vivo. We investigated the underlying mechanisms of this phenomenon and the role of p53 and Fas receptor using terminal dUTP nick end labeling (TUNEL), quantitative reverse transcription polymerase chain reaction and immunohistochemistry. Rat liver tissue specimens were obtained at different time intervals after injection of CHX. The proportion of TUNEL-positive apoptotic hepatocytes increased with time and reached a plateau at 2.5h after the injection. The p53 and Fas receptor mRNAs and the proportion of immunoreactive p53-positive and Fas receptor-positive hepatocytes increased markedly with time from 1h after the administration. Since the time course of increased proportion of apoptotic hepatocytes does not parallel that of p53- or Fas receptor-positive hepatocytes and apoptotic hepatocytes appeared prior to up-regulation of p53 and Fas receptor expression, it is likely that the enhanced expression of p53 and Fas receptor is not involved directly in CHX-induced apoptosis of hepatocytes in vivo. Rats injected with a single intravenous dose of CHX, however, provide a simple and useful model for investigating the apoptotic machinery and the molecular mechanism of transcriptional up-regulation of p53 and Fas receptor in hepatocytes.