Mechanisms of phototherapy of Alzheimer’s disease during sleep and wakefulness:the role of the meningeal lymphatics

With the increase in the aging population,the global number of people with Alzheimer’s disease(AD)progressively increased worldwide.The situation is aggravated by the fact that there is no the efective pharmacological therapy of AD.Photobiomodulation(PBM)is non-pharmacological approach that has shown very promising results in the therapy of AD in pilot clinical and animal studies.However,the mechanisms of therapeutic efects of PBM for AD are poorly understood.In this study on mice,we demonstrate that photodynamic efects of 5-aminolevulenic acid and laser 635 nm cause reduction of network of the meningeal lymphatic vessels(MLVs)leading to suppression of lymphatic removal of beta-amyloid(Aβ)from the right lateral ventricle and the hippocampus.Using the original protocol of PBM under electroencephalographic monitoring of wakefulness and sleep stages in non-anesthetized mice,we discover that the 7-day course of PBM during deep sleep vs.wakefulness provides better restoration of clearance of Aβfrom the ventricular system of the brain and the hippocampus.Our results shed light on the mechanism of PBM and show the stimulating efects of PBM on the brain lymphatic drainage that promotes transport of Aβvia the lymphatic pathway.The efects of PBM on the brain lymphatics in sleeping brain open a new niche in the study of restorative functions of sleep as well as it is an important informative platform for the development of innovative smart sleep technologies for the therapy of AD.