Relocation of truncated bid plays an important role in suppression of tumor necrosis factor alpha induced apoptosis in hepatocytes isolated from transgenic mouse

BACKGROUND/AIMS: Tumor necrosis factor alpha (TNFalpha) induces apoptosis in murine hepatocytes pretreated with Actinomycin D (ActD) in vitro. This study sought to clarify the relationship between hepatic energy status and TNFalpha-induced hepatocyte apoptosis, using mice transgenic for creatine kinase (CK) expression. MATERIALS AND METHODS: Hepatocytes from CK transgenic mice were cultured with or without creatine (Cr). The concentrations of ATP and phosphocreatine (PCr) in hepatocytes were measured by high-pressure liquid chromatography. Sixteen hours after treatment with ActD and TNFalpha, we evaluated cell viability of these hepatocytes. We examined truncated Bid and cytochrome c by immunoblot analysis. RESULTS: Six hours after cell isolation, the concentration of PCr in CK transgenic hepatocytes cultured with Cr increased to 8.23 +/- 0.01 microg/mg protein, while that of hepatocytes cultured without Cr was lower than 0.1 microg/mg protein. In hepatocytes cultured without Cr, ActD and TNFalpha treatment induced massive cell death, while hepatocytes cultured with Cr maintained greater than 80% viability. In CK transgenic hepatocytes cultured with Cr, truncated Bid relocation to mitochondria was highly suppressed, compared to CK transgenic hepatocytes cultured without Cr. CONCLUSION: PCr accumulation may prevent TNFalpha-induced apoptosis in murine hepatocytes by suppression of truncated Bid targeting to mitochondria.