title: In vivo detection of free radicals using molecular MRI and immuno-spin trapping in a mouse model for amyotrophic lateral sclerosis.
abstract: Free radicals associated with oxidative stress play a major role in amyotrophic lateral sclerosis (ALS). By combining immuno-spin trapping and molecular magnetic resonance imaging, in vivo trapped radical adducts were detected in the spinal cords of SOD1(G93A)-transgenic (Tg) mice, a model for ALS. For this study, the nitrone spin trap DMPO (5,5-dimethyl-1-pyrroline N-oxide) was administered (ip) over 5 days before administration (iv) of an anti-DMPO probe (anti-DMPO antibody covalently bound to an albumin-gadolinium-diethylenetriamine pentaacetic acid-biotin MRI contrast agent) to trap free radicals. MRI was used to detect the presence of the anti-DMPO radical adducts by a significant sustained increase in MR signal intensities (p < 0.05) or anti-DMPO probe concentrations measured from T₁ relaxations (p < 0.01). The biotin moiety of the anti-DMPO probe was targeted with fluorescence-labeled streptavidin to locate the probe in excised tissues. Negative controls included either Tg ALS mice initially administered saline rather than DMPO followed by the anti-DMPO probe or non-Tg mice initially administered DMPO and then the anti-DMPO probe. The anti-DMPO probe was found to bind to neurons via colocalization fluorescence microscopy. DMPO adducts were also confirmed in diseased/nondiseased tissues from animals administered DMPO. Apparent diffusion coefficients from diffusion-weighted images of spinal cords from Tg mice were significantly elevated (p < 0.001) compared to wild-type controls. This is the first report regarding the detection of in vivo trapped radical adducts in an ALS model. This novel, noninvasive, in vivo diagnostic method can be applied to investigate the involvement of free radical mechanisms in ALS rodent models.
authors.affiliation: Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA. Rheal-Towner@omrf.org
authors.forename: Rheal A
authors.initials: RA
authors.lastname: Towner
authors.forename: Nataliya
authors.initials: N
authors.lastname: Smith
authors.forename: Debra
authors.initials: D
authors.lastname: Saunders
authors.forename: Florea
authors.initials: F
authors.lastname: Lupu
authors.forename: Robert
authors.initials: R
authors.lastname: Silasi-Mansat
authors.forename: Melinda
authors.initials: M
authors.lastname: West
authors.forename: Dario C
authors.initials: DC
authors.lastname: Ramirez
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Gomez-Mejiba
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Bonini
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Mason
authors.forename: Marilyn
authors.initials: M
authors.lastname: Ehrenshaft
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hensley
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D003497:Cyclic N-Oxides / Q000008:administration & dosage; D004195:Disease Models, Animal; D005609:Free Radicals / Q000302:isolation & purification*; D006801:Humans; D008279:Magnetic Resonance Imaging; D051379:Mice; D008822:Mice, Transgenic; D011859:Radiography; D019097:Spin Trapping; D013482:Superoxide Dismutase / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D000072105:Superoxide Dismutase-1
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; C000606290:SOD1 protein, human; C017245:5,5-dimethyl-1-pyrroline-1-oxide; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1
keywords: 5,5-dimethyl-1-pyrroline-N-oxide; ADC; ALS; Ab; Amyotrophic lateral sclerosis; Anti-DMPO probe.; BBB; DMPO; DWI; ESR; Free radicals; Gd-DTPA; Gd-DTPA–albumin–anti-DMPO–biotin probe; IST; Immuno-spin trapping; In vivo; Molecular magnetic resonance imaging; RNS; ROS; SOD1; T(1); TE; TR; amyotrophic lateral sclerosis; antibody; apparent diffusion coefficient; blood–brain barrier; diffusion-weighted imaging; echo time; electron spin resonance; gadolinium diethylenetriamine pentaacetic acid; immuno-spin trapping; longitudinal relaxation constant; mMRI; molecular magnetic resonance imaging; reactive nitrogen species; reactive oxygen species; repetition time; superoxide dismutase 1