Photobiomodulation with IR1072nm in the murine CNS:
in vitro and in vivo studies

Abstract

Photobiomodulation refers to low-intensity light therapy (LILT) in the far-red to near-infrared (IR) region of the spectrum (630-1000nm). A peak wavelength, 1072nm (IR1072), in the IR transmission spectrum has been previously shown to have protective effects against UVA toxicity in human lymphocytes and beneficial effects on working memory in IR-treated 12 month old CD-1 mice. The aim of this investigation was to establish the beneficial effects of IR1072 in the murine mammalian CNS utilising a range of in vivo and in vitro model systems. Acute treatment of primary rat neuronal cultures with IR1072 endowed an insult severity-dependent protective effect; the less severe the insult the more profound the protection. An age-dependent (3 month to 12 month) reduction in brain derived neurotrophic factor (BDNF) and heat shock protein HSP27, and HSP40 and HSP90 was observed in both CD-1 and TASTPM Alzheimer disease mice, which may underlie the severe learning deficits seen in these mice. Acute whole body treatments of CD-1 mice in vivo comprising ten consecutive daily 6 minute sessions of IR1072 elicited increased mitochondrial complex II enzyme activity. Long-term chronic in vivo IR1072 treatments in CD-1 mice, consisting of biweekly 6 minutes sessions spanning a 5 month period, increased expression of selective HSPs, notably HSP27 in cortical and hippocampal regions. Following chronic IR1072 treatment, a profound reduction of AMPA receptor binding sites in CD-1 mice, and reduced total Aβ1-42 expression and small amyloid plaque counts (in cortex and dentate gyrus) in TASTPM mice, was observed. Overall, this thesis reveals new mechanisms of photobiomodulation with IR1072 which involves restoring cellular homeostasis for optimal functional operation of a neuron.