Roles of mitochondria-generated reactive oxygen species on X-ray-induced apoptosis in a human hepatocellular carcinoma cell line, HLE.
HLE, a human hepatocellular carcinoma cell line was transiently transfected with normal human MnSOD and MnSOD without a mitochondrial targeting signal (MTS). Mitochondrial reactive oxygen species (ROS), lipid peroxidation and apoptosis were examined as a function of time following 18.8 Gy X-ray irradiation. Our results showed that the level of mitochondrial ROS increased and reached a maximum level 2 hours after X-ray irradiation. Authentic MnSOD, but not MnSOD lacking MTS, protected against mitochondrial ROS, lipid peroxidation and apoptosis. In addition, the levels of mitochondrial ROS were consistently found to always correlate with the levels of authentic MnSOD in mitochondria. These results suggest that only when MnSOD is located in mitochondria is it efficient in protecting against cellular injuries by X-ray irradiation and that mitochondria are the critical sites of X-ray-induced cellular oxidative injuries.
Department of Oncology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
Hiroko P
HP
Indo
Osamu
O
Inanami
Tomoko
T
Koumura
Shigeaki
S
Suenaga
Hsiu-Chuan
HC
Yen
Shizuko
S
Kakinuma
Ken-Ichiro
K
Matsumoto
Ikuo
I
Nakanishi
William
W
St Clair
Daret K
DK
St Clair
Hirofumi
H
Matsui
Richard
R
Cornette
Oleg
O
Gusev
Takashi
T
Okuda
Yasuhito
Y
Nakagawa
Toshihiko
T
Ozawa
Hideyuki J
HJ
Majima
D017209:Apoptosis / Q000528:radiation effects*; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D005456:Fluorescent Dyes; D022781:Hepatocytes / Q000201:enzymology / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D015227:Lipid Peroxidation / Q000528:radiation effects; D008113:Liver Neoplasms; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000201:enzymology / Q000473:pathology / Q000528:radiation effects*; D021382:Protein Sorting Signals; D017382:Reactive Oxygen Species / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014965:X-Rays
D005456:Fluorescent Dyes; D021382:Protein Sorting Signals; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase