Role of NADP+-dependent isocitrate dehydrogenase (NADP+-ICDH) on cellular defence against oxidative injury by gamma-rays.
OBJECTIVE
To investigate the regulation of NADPH-producing isocitrate dehydrogenase (ICDH) in cytosol (IDPc) and mitochondria (IDPm) upon gamma-ray irradiation, and the roles of IDPc and IDPm in the protection against cellular damage induced by gamma-ray irradiation.


METHODS
Changes of IDPc and IDPm proteins upon gamma-ray irradiation to NIH3T3 cells were analysed by immunoblotting. To increase or decrease the expression of IDPc or IDPm, NIH3T3 cells were stably transfected with mouse IDPc or IDPm cDNA in either the sense or the antisense direction. The transfected cells with either increased or decreased IDPc or IDPm were exposed to gamma-rays, and the levels of reactive oxygen species generation, protein oxidation and lipid peroxidation were measured.


RESULTS
Both IDPc and IDPm activities were induced by gamma-ray in NIH3T3 cells. Cells with decreased expression of IDPc or IDPm had elevated reactive oxygen species generation, lipid peroxidation and protein oxidation. Conversely, overproduction of IDPc or IDPm protein partially protected the cells from oxidative damage induced by gamma-ray irradiation.


CONCLUSIONS
The protective role of IDPc and IDPm against gamma-ray-induced cellular damage can be attributed to elevated NADPH, reducing equivalents needed for recycling reduced glutathione in the cytosol and mitochondria. Thus, a primary biological function of the ICDHs may be production of NADPH, which is a prerequisite for some cellular defence systems against oxidative damage.
Lee
S H
SH
Department of Genetic Engineering, Kyungpook National University, Daegu 702-701, Korea.
Jo
S H
SH
Lee
S M
SM
Koh
H J
HJ
Song
H
H
Park
J W
JW
Lee
W H
WH
Huh
T L
TL
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D007521:Isocitrate Dehydrogenase / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000528:radiation effects; D051379:Mice; D041681:NIH 3T3 Cells; D010084:Oxidation-Reduction / Q000528:radiation effects; D018384:Oxidative Stress / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage; D017382:Reactive Oxygen Species / Q000378:metabolism*
D017382:Reactive Oxygen Species; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+)