Regulation of ionizing radiation-induced apoptosis by mitochondrial NADP+-dependent isocitrate dehydrogenase.
Ionizing radiation induces the production of reactive oxygen species, which play an important causative role in apoptotic cell death. By supplying NADPH for antioxidant systems, we recently demonstrated that the control of mitochondrial redox balance and the cellular defense against oxidative damage are some of the primary functions of mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDPm). In this study, we demonstrate that modulation of IDPm activity in U937 cells regulates ionizing radiation-induced apoptosis. When we examined the regulatory role of IDPm against ionizing radiation-induced apoptosis in U937 cells transfected with the cDNA for mouse IDPm in sense and antisense orientations, a clear inverse relationship was observed between the amount of IDPm expressed in target cells and their susceptibility to apoptosis. Upon exposure to 2 gray gamma-irradiation, there was a distinct difference between the IDPm transfectant cells in regard to the morphological evidence of apoptosis, DNA fragmentation, cellular redox status, oxidative damage to cells, mitochondrial function, and the modulation of apoptotic marker proteins. In addition, transfection of HeLa cells with an IDPm small interfering RNA decreased the activity of IDPm, enhancing the susceptibility of radiation-induced apoptosis. Taken together, these results indicate that IDPm may play an important role in regulating the apoptosis induced by ionizing radiation, and the effect of IDPm small interfering RNA on HeLa cells offers the possibility of developing a modifier of radiation therapy.
Lee
Jin Hyup
JH
School of Life Sciences and Biotechnology, College of Natural Sciences, Kyungpook National University, Taegu 702-701, Korea.
Kim
Sung Youl
SY
Kil
In Sup
IS
Park
Jeen-Woo
JW
D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects*; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000235:genetics; D053938:DNA Fragmentation / Q000528:radiation effects*; D016373:DNA, Antisense / Q000235:genetics; D005720:Gamma Rays; D006367:HeLa Cells; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics; D024101:Mitochondrial Proteins / Q000096:biosynthesis* / Q000235:genetics; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction / Q000528:radiation effects; D018384:Oxidative Stress / Q000235:genetics / Q000528:radiation effects; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection; D020298:U937 Cells
D000975:Antioxidants; D051017:Apoptosis Regulatory Proteins; D016373:DNA, Antisense; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; D009249:NADP; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+)