title: Geldanamycin analog 17-DMAG inhibits iNOS and caspases in gamma-irradiated human T cells.
abstract: Inducible nitric oxide synthase (iNOS) expression and NO production increase after radiation exposure. We showed previously that inhibiting iNOS expression prevents hemorrhage injury; we therefore investigated whether inhibiting iNOS expression also limits radiation injury. Human Jurkat T cells were exposed to gamma radiation (2, 4, 6 or 8 Gy), and cell lysates were collected for analysis at selected times afterward. Radiation exposure increased iNOS expression within 4 h postirradiation by increasing the levels of the iNOS transcription factors NF-kappaB and KLF6. By 24 h postirradiation cell viability was reduced. In these cells, NO production, lipid peroxidation, protein nitration, apoptosomes (formed by cytochrome c, caspase 9 and Apaf-1), and caspase 3 activity were significantly elevated, suggesting that the iNOS pathway had been activated. Treatment with the iNOS inhibitors 17-DMAG or L-NIL-6 24 h prior to irradiation limited these changes, as did treatment with iNOS siRNA to silence the iNOS gene. These results suggest radiation injury involves the iNOS pathway, and iNOS-mediated NO produced endogenously in the T cell alters overall T-cell function and results in apoptosis and cell lethality. Control of iNOS expression may represent a useful approach for protecting T cells from radiation injury.
authors.affiliation: Department of Radiation Biology, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20889-5603, USA. kiang@afrri.usuhs.mil
authors.forename: Juliann G
authors.initials: JG
authors.lastname: Kiang
authors.forename: Joan T
authors.initials: JT
authors.lastname: Smith
authors.forename: Neil G
authors.initials: NG
authors.lastname: Agravante
mesh_terms: D016227:Benzoquinones / Q000008:administration & dosage*; D020169:Caspases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D006801:Humans; D019169:Jurkat Cells; D047029:Lactams, Macrocyclic / Q000008:administration & dosage*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000187:drug effects / Q000502:physiology*; D011837:Radiation-Protective Agents / Q000008:administration & dosage; D013601:T-Lymphocytes / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects*
chemical_list: D016227:Benzoquinones; D047029:Lactams, Macrocyclic; D011837:Radiation-Protective Agents; C448659:17-(dimethylaminoethylamino)-17-demethoxygeldanamycin; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; D020169:Caspases; C001277:geldanamycin