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Neuroscience. 2014 Aug 22;274:93-101. doi: 10.1016/j.neuroscience.2014.05.023. Epub 2014 May 21.

Indirect application of near infrared light induces neuroprotection in a mouse model of parkinsonism - an abscopal neuroprotective effect.

Author information

1
Bosch Institute, University of Sydney, Australia; Discipline of Physiology, University of Sydney, Australia. Electronic address: Daniel.Johnstone@sydney.edu.au.
2
Discipline of Anatomy & Histology, University of Sydney, Australia.
3
CEA, LETI, 38054 Grenoble, France.
4
Bosch Institute, University of Sydney, Australia; Discipline of Physiology, University of Sydney, Australia.
5
Bosch Mass Spectrometry Facility, Bosch Institute, University of Sydney, Australia.
6
Bosch Institute, University of Sydney, Australia; Discipline of Anatomy & Histology, University of Sydney, Australia.

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.

KEYWORDS:

MPTP; Parkinson’s disease; mouse model; near infrared light; neuroprotection

[Indexed for MEDLINE]

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