title: The impact of near-infrared light on dopaminergic cell survival in a transgenic mouse model of parkinsonism.
abstract: We have examined whether near-infrared light (NIr) treatment mitigates oxidative stress and increased expression of hyperphosphorylated tau in a tau transgenic mouse strain (K3) that has a progressive degeneration of dopaminergic cells in the substantia nigra pars compacta (SNc). The brains of wild-type (WT), untreated K3 and NIr-treated K3 mice, aged five months (thus after the onset of parkinsonian signs and neuropathology), were labelled immunohistochemically for the oxidative stress markers 4-hydroxynonenal (4-HNE) and 8-hydroxy-2'-deoxyguanosine (8-OHDG), hyperphosphorylated tau (using the AT8 antibody) and tyrosine hydroxylase (TH). The average intensity and area of 4-HNE, 8-OHDG and AT8 immunoreactivity were measured using the MetaMorph software and TH⁺ cell number was estimated using stereology. Our results showed immunoreactivity for 4-HNE, 8-OHDG and AT8 within the SNc was increased in K3 mice compared to WT, and that this increase was mitigated by NIr. Results further showed that TH⁺ cell number was lower in K3 mice than in WT, and that this loss was mitigated by NIr. In summary, NIr treatment reduced the oxidative stress caused by the tau transgene in the SNc of K3 mice and saved SNc cells from degeneration. Our results, when taken together with those in other models, strengthen the notion that NIr treatment saves dopaminergic cells in the parkinsonian condition.
authors.affiliation: Discipline of Physiology, University of Sydney, Australia; Bosch Institute, University of Sydney, Australia.
authors.forename: Sivaraman
authors.initials: S
authors.lastname: Purushothuman
authors.forename: Charith
authors.initials: C
authors.lastname: Nandasena
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Johnstone
authors.forename: Jonathan
authors.initials: J
authors.lastname: Stone
authors.forename: John
authors.initials: J
authors.lastname: Mitrofanis
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects*; D004195:Disease Models, Animal; D059290:Dopaminergic Neurons / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D007259:Infrared Rays; D028022:Low-Level Light Therapy; D051379:Mice; D008822:Mice, Transgenic; D018384:Oxidative Stress / Q000528:radiation effects; D020734:Parkinsonian Disorders / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation / Q000528:radiation effects; D016875:tau Proteins / Q000378:metabolism
chemical_list: D016875:tau Proteins
keywords: Hyperphosphorylated tau; K369I mice; Oxidative stress; Photobiomodulation; Substantia nigra; Tyrosine hydroxylase