Mitochondrial signal lacking manganese superoxide dismutase failed to prevent cell death by reoxygenation following hypoxia in a human pancreatic cancer cell line, KP4.
One of the major characteristics of tumor is the presence of a hypoxic cell population, which is caused by abnormal distribution of blood vessels. Manganese superoxide dismutase (MnSOD) is a nuclear-encoded mitochondrial enzyme, which scavenges superoxide generated from the electron-transport chain in mitochondria. We examined whether MnSOD protects against hypoxia/reoxygenation (H/R)-induced oxidative stress using a human pancreas carcinoma-originated cell line, KP4. We also examined whether MnSOD is necessarily present in mitochondria to have a function. Normal human MnSOD and MnSOD without a mitochondrial targeting signal were transfected to KP4 cells, and reactive oxygen species, nitric oxide, lipid peroxidation, and apoptosis were examined as a function of time in air following 1 day of hypoxia as a H/R model. Our results showed H/R caused no increase in nitric oxide, but resulted in increases in reactive oxygen species, 4-hydroxy-2-nonenal protein adducts, and apoptosis. Authentic MnSOD protected against these processes and cell death, but MnSOD lacking a mitochondrial targeting signal could not. These results suggest that only when MnSOD is located in mitochondria is it efficient in protecting against cellular injuries by H/R, and they also indicate that mitochondria are primary sites of H/R-induced cellular oxidative injuries.
Hirai
Futoshi
F
First Department of Medicine, Chiba University, School of Medicine, Chiba 260-0856, Japan.
Motoori
Shigeatsu
S
Kakinuma
Shizuko
S
Tomita
Kazuo
K
Indo
Hiroko P
HP
Kato
Hirotoshi
H
Yamaguchi
Taketo
T
Yen
Hsiu-Chuan
HC
St  Clair
Daret K
DK
Nagano
Tetsuo
T
Ozawa
Toshihiko
T
Saisho
Hiromitsu
H
Majima
Hideyuki J
HJ
D000447:Aldehydes / Q000737:chemistry; D017209:Apoptosis; D016923:Cell Death; D045744:Cell Line, Tumor; D018736:DNA Adducts; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D006801:Humans; D000860:Hypoxia; D015227:Lipid Peroxidation; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology*; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014162:Transfection
D000447:Aldehydes; D018736:DNA Adducts; D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D013482:Superoxide Dismutase; C027576:4-hydroxy-2-nonenal; D010100:Oxygen