title: Role of cytosolic NADP+-dependent isocitrate dehydrogenase in ischemia-reperfusion injury in mouse kidney.
abstract: Cytosolic NADP+-dependent isocitrate dehydrogenase (IDPc) synthesizes reduced NADP (NADPH), which is an essential cofactor for the generation of reduced glutathione (GSH), the most abundant and important antioxidant in mammalian cells. We investigated the role of IDPc in kidney ischemia-reperfusion (I/R) in mice. The activity and expression of IDPc were highest in the cortex, modest in the outer medulla, and lowest in the inner medulla. NADPH levels were greatest in the cortex. IDPc expression in the S1 and S2 segments of proximal tubules was higher than in the S3 segment, which is much more susceptible to I/R. IDPc protein was also highly expressed in the mitochondrion-rich intercalated cells of the collecting duct. IDPc activity was 10- to 30-fold higher than the activity of glucose-6-phosphate dehydrogenase, another producer of cytosolic NADPH, in various kidney regions. This study identifies that IDPc may be the primary source of NADPH in the kidney. I/R significantly reduced IDPc expression and activity and NADPH production and increased the ratio of oxidized glutathione to total glutathione [GSSG/(GSH+GSSG)], resulting in kidney dysfunction, tubular cell damage, and lipid peroxidation. In LLC-PK(1) cells, upregulation of IDPc by IDPc gene transfer protected the cells against hydrogen peroxide, enhancing NADPH production, inhibiting the increase of GSSG/(GSH+GSSG), and reducing lipid peroxidation. IDPc downregulation by small interference RNA treatment presented results contrasting with the upregulation. In conclusion, these results demonstrate that IDPc is expressed differentially along tubules in patterns that may contribute to differences in susceptibility to injury, is a major enzyme in cytosolic NADPH generation in kidney, and is downregulated with I/R.
authors.affiliation: Department of Anatomy and BK 21 Project, Kyungpook National University School of Medicine, Daegu, Republic of Korea.
authors.forename: Jinu
authors.initials: J
authors.lastname: Kim
authors.forename: Ki Young
authors.initials: KY
authors.lastname: Kim
authors.forename: Hee-Seong
authors.initials: HS
authors.lastname: Jang
authors.forename: Takumi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Ken
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Kosaku
authors.initials: K
authors.lastname: Nitta
authors.forename: Jeen-Woo
authors.initials: JW
authors.lastname: Park
authors.forename: Joseph V
authors.initials: JV
authors.lastname: Bonventre
authors.forename: Kwon Moo
authors.initials: KM
authors.lastname: Park
mesh_terms: D000818:Animals; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology; D015536:Down-Regulation; D004847:Epithelial Cells / Q000201:enzymology; D007521:Isocitrate Dehydrogenase / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology / Q000293:injuries*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009249:NADP / Q000378:metabolism; D018384:Oxidative Stress; D015427:Reperfusion Injury / Q000201:enzymology*; D013552:Swine; D015854:Up-Regulation; D019459:Urothelium / Q000201:enzymology
chemical_list: D009249:NADP; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+)