Effect of 710-nm Visible Light Irradiation on Neuroprotection and Immune Function after Stroke

Abstract

Objective: The phototherapeutic effects of low level infrared laser irradiation (808 nm) on brain neuronal cell protection after stroke have been presented recently. We previously reported that 710-nm wavelength visible light (VIS) increases total lymphocyte counts in vivo, especially CD4⁺ T lymphocytes. In this study, we investigated the effects of 710-nm VIS irradiation on neuronal protection and recovery correlating with cellular immunity in stroke rats. Methods: Rats were subjected to 90-min middle cerebral artery occlusion (MCAO) followed by reperfusion and were divided into two groups: irradiation and no irradiation. The irradiation group had been exposed to 710-nm VIS for 3 weeks after MCAO establishment or sham operation. The helper T cell (CD4⁺) count in the whole blood and infarct volume were measured. Messenger RNA expression levels of IL-4 and IL-10 in peripheral blood mononuclear cells were measured, a histologic study including microglia activation and regulatory T (Treg) cell markers, neurological severity scoring and a parallel bar walking test were all performed. Results: CD4⁺ cell count was reduced after MCAO but was significantly increased by 710-nm VIS irradiation. The infarct sizes were decreased in the MCAO + irradiation group compared with the MCAO control group. IL-10 mRNA expression and the immunoreactivity of Treg cells were increased in the MCAO + irradiation group compared with the MCAO control group. Increased microglia activation after MCAO was reduced by 710-nm VIS irradiation. The irradiation group also showed improved neurological severity score levels and step fault scores after MCAO. Conclusions: Our data suggest that 710-nm VIS irradiation may activate cellular immunity, reduce brain infarction and ultimately induce functional recovery in a stroke animal model.

Low‐level light emitting diode (LED) therapy suppresses inflammasome‐mediated brain damage in experimental ischemic stroke

“…It has been reported that near‐infrared light therapy decreases depression in human subjects and improves locomotor activity in rats with traumatic brain injury and mice with Parkinson's disease . Moreover, low‐level light therapy using near‐infrared has reduced ischemic brain damage in experimentally induced stroke in rabbits , and showed neuroprotection effect in experimental stroke of rats . It was previously reported that low‐level light therapy is also effective in a pre‐conditioning mode on pain, heart attack, wound healing, central nervous system and so on .…”

“…Transcranial near‐infrared light therapy was shown to reduce ischemic brain damage in rabbit acute ischemic stroke . Light therapy (710 nm) showed neuroprotection in rat experimental stroke models , and has shown clinical promise when tissue regeneration and prevention of tissue damage are required . Furthermore, low‐level laser light (800 nm) improves cognitive deficits and modulates neuroinflammation after traumatic brain injury , and low‐level laser therapy (632.8 nm) suppresses microglia activation in BV2 microglial cells .…”

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Regulatory T Cell in Stroke: A New Paradigm for Immune Regulation

“…Furthermore, it has been reported that FoxP3 + CD25 + CD4 + Tregs may be a facilitator for Cocaine-and-amphetamine-regulated-transcript- (CART-) mediated neuroprotection after stroke [91]. In an MCAO model, 710 nm wavelength visible light irradiation reduced brain infarction and enhanced functional recovery, perhaps by altering cellular immunity, including increasing the number of CD25 + CD4 + Tregs and decreasing microglia activation in the ischemic core and the peri-infarct region [92]. Moreover, intravenous albumin administration reduced Toll-like receptor 4 expression but significantly increased FoxP3 + CD25 + CD4 + Tregs expression levels and elevated IL-10 and TGF- β 1 production, eventually conferring neuroprotective effects during postischemic stroke treatment [93].…”