Abstract
Photobiomodulation, by utilizing low-power light in the visible and near-infrared spectra to trigger biological responses in cells and tissues, has been considered as a possible therapeutic strategy for Alzheimer’s disease (AD), while its specific mechanisms have remained elusive. Here, we demonstrate that cognitive and memory impairment in an AD mouse model can be ameliorated by 1070-nm light via reducing cerebral β-amyloid (Aβ) burden, the hallmark of AD. The glial cells, including microglia and astrocytes, play important roles in Aβ clearance. Our results show that 1070-nm light pulsed at 10 Hz triggers microglia rather than astrocyte responses in AD mice. The 1070-nm light-induced microglia responses with alteration in morphology and increased colocalization with Aβ are sufficient to reduce Aβ load in AD mice. Moreover, 1070-nm light pulsed at 10 Hz can reduce perivascular microglia and promote angiogenesis to further enhance Aβ clearance. Our study confirms the important roles of microglia and cerebral vessels in the use of 1070-nm light for the treatment of AD mice and provides a framework for developing a novel therapeutic approach for AD.
Highlights
Photobiomodulation (PBM), known as low-level light therapy, is a promising therapeutic approach and has been applied to various diseases as an alternative intervention[1,2,3,4,5]
We studied the biological responses of microglia and astrocytes triggered by 1070-nm light and its effects on Aβ clearance and cognitive abilities
Our results showed that 1070-nm light pulsed at 10 Hz activated microglia rather than astrocytes to promote the degradation of Aβ
Summary
PS1 mice treatments A 1070-nm light irradiation apparatus was developed for non-invasive treatment of APP/PS1 double transgenic mice (Fig. 1a). No differences were found in the transmittance between different light pulse frequencies These results showed that approximately 8% of the 1070-nm light incident power penetrated through the scalp and 4.3% of that power penetrated through the scalp and skull combined. For 12M mice, the discrimination index decreased significantly in the APP/PS1 mice without irradiation (AD group) compared with the wild-type (WT) mice, and this was successfully rescued by administration of 1070-nm light pulsed at 10 Hz (Fig. 1c). The average velocity and total distance traveled did not differ significantly (Fig. 1d, e) among groups during the NOR test, which indicated that the higher discrimination index was not due to general differences in activities.
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