title: Indirect application of near infrared light induces neuroprotection in a mouse model of parkinsonism - an abscopal neuroprotective effect.
abstract: We have previously shown near infrared light (NIr), directed transcranially, mitigates the loss of dopaminergic cells in MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-treated mice, a model of parkinsonism. These findings complement others suggesting NIr treatment protects against damage from various insults. However one puzzling feature of NIr treatment is that unilateral exposure can lead to a bilateral healing response, suggesting NIr may have 'indirect' protective effects. We investigated whether remote NIr treatment is neuroprotective by administering different MPTP doses (50-, 75-, 100-mg/kg) to mice and treating with 670-nm light directed specifically at either the head or body. Our results show that, despite no direct irradiation of the damaged tissue, remote NIr treatment produces a significant rescue of tyrosine hydroxylase-positive cells in the substantia nigra pars compacta at the milder MPTP dose of 50-mg/kg (∼30% increase vs sham-treated MPTP mice, p<0.05). However this protection did not appear as robust as that achieved by direct irradiation of the head (∼50% increase vs sham-treated MPTP mice, p<0.001). There was no quantifiable protective effect of NIr at higher MPTP doses, irrespective of the delivery mode. Astrocyte and microglia cell numbers in substantia nigra pars compacta were not influenced by either mode of NIr treatment. In summary, the findings suggest that treatment of a remote tissue with NIr is sufficient to induce protection of the brain, reminiscent of the 'abscopal effect' sometimes observed in radiation treatment of metastatic cancer. This discovery has implications for the clinical translation of light-based therapies, providing an improved mode of delivery over transcranial irradiation.
authors.affiliation: Bosch Institute, University of Sydney, Australia; Discipline of Physiology, University of Sydney, Australia. Electronic address: Daniel.Johnstone@sydney.edu.au.
authors.forename: D M
authors.initials: DM
authors.lastname: Johnstone
authors.affiliation: Discipline of Anatomy & Histology, University of Sydney, Australia.
authors.forename: N
authors.initials: N
authors.lastname: el Massri
authors.affiliation: CEA, LETI, 38054 Grenoble, France.
authors.forename: C
authors.initials: C
authors.lastname: Moro
authors.affiliation: Bosch Institute, University of Sydney, Australia; Discipline of Physiology, University of Sydney, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Spana
authors.affiliation: Bosch Mass Spectrometry Facility, Bosch Institute, University of Sydney, Australia.
authors.forename: X S
authors.initials: XS
authors.lastname: Wang
authors.affiliation: CEA, LETI, 38054 Grenoble, France.
authors.forename: N
authors.initials: N
authors.lastname: Torres
authors.affiliation: CEA, LETI, 38054 Grenoble, France.
authors.forename: C
authors.initials: C
authors.lastname: Chabrol
authors.affiliation: CEA, LETI, 38054 Grenoble, France.
authors.forename: X
authors.initials: X
authors.lastname: De Jaeger
authors.affiliation: CEA, LETI, 38054 Grenoble, France.
authors.forename: F
authors.initials: F
authors.lastname: Reinhart
authors.affiliation: Bosch Institute, University of Sydney, Australia; Discipline of Physiology, University of Sydney, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Purushothuman
authors.affiliation: CEA, LETI, 38054 Grenoble, France.
authors.forename: A-L
authors.initials: AL
authors.lastname: Benabid
authors.affiliation: Bosch Institute, University of Sydney, Australia; Discipline of Physiology, University of Sydney, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Stone
authors.affiliation: Bosch Institute, University of Sydney, Australia; Discipline of Anatomy & Histology, University of Sydney, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Mitrofanis
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D002452:Cell Count; D004195:Disease Models, Animal; D028022:Low-Level Light Therapy; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D017628:Microglia / Q000378:metabolism*; D018696:Neuroprotective Agents; D020734:Parkinsonian Disorders / Q000378:metabolism / Q000628:therapy*; D065842:Pars Compacta / Q000378:metabolism*; D010789:Phototherapy; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D018696:Neuroprotective Agents; D014446:Tyrosine 3-Monooxygenase
keywords: MPTP; Parkinson’s disease; mouse model; near infrared light; neuroprotection