Interferon-gamma induces reactive oxygen species and endoplasmic reticulum stress at the hepatic apoptosis.
Interferon-gamma (IFN-gamma) induces cell-cycle arrest and p53-independent apoptosis in primary cultured hepatocytes. However, the detailed mechanism, including regulating molecules, is still unclear. In this study, we found that IFN-gamma induced generation of reactive oxygen species (ROS) in primary hepatocytes and that pyrrolidinedithiocarbamate (PDTC), an anti-oxidant reagent, completely suppressed IFN-gamma-induced hepatic apoptosis. PDTC blocked apoptosis downstream from IRF-1 and upstream from caspase activation, suggesting that the generation of ROS occurred between these stages. However, IFN-gamma also induced the generation of ROS in IRF-1-deficient hepatocytes, cells insensitive to IFN-gamma-induced apoptosis. Moreover, a general cyclooxygenase (COX) inhibitor, indomethacin (but not the cyclooxygenase 2-specific inhibitor, NS-398) also inhibited the apoptosis without blocking the generation of ROS. Both PDTC and indomethacin also blocked IFN-gamma-induced release of cytochrome c from mitochondria. These results suggest that ROS are not the only or sufficient mediators of IFN-gamma-induced hepatic apoptosis. In contrast, we also found that IFN-gamma induced endoplasmic reticulum (ER) stress proteins, CHOP/GADD153 and caspase 12, in wild-type primary hepatocytes, but induced only caspase 12 and not CHOP/GADD153 protein in IRF-1-deficient hepatocytes. These results suggest that IFN-gamma induces ER stress in primary hepatocytes. Both the ROS and ER stress induced by IFN-gamma may be complementary mediators that induce apoptosis in primary hepatocytes.
Watanabe
Yoshifumi
Y
Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama 226-8501, Japan. Yoshifumi_Watanabe@nts.toray.co.jp
Suzuki
Osamu
O
Haruyama
Takahiro
T
Akaike
Toshihiro
T
D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D004721:Endoplasmic Reticulum / Q000187:drug effects*; D007213:Indomethacin / Q000494:pharmacology; D007371:Interferon-gamma / Q000502:physiology*; D008099:Liver / Q000166:cytology* / Q000187:drug effects; D011759:Pyrrolidines / Q000494:pharmacology; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013859:Thiocarbamates / Q000494:pharmacology
D017931:DNA Primers; D011759:Pyrrolidines; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D013859:Thiocarbamates; C020972:pyrrolidine dithiocarbamic acid; D007371:Interferon-gamma; D007213:Indomethacin