The helmet experiment in Parkinson’s disease: an observation of the mechanism of neuroprotection by near infra-red light

摘要

Summary: A puzzling feature of reports of near infrared light (NIr) treatment of soft tissue wounds is the lack oflaterality in the tissue response - it is typically bilateral after a unilateral exposure. This has led to the idea thatNIr has an ‘indirect’ effect on non-irradiated tissues, mediated by circulating ‘factors’. We have recentlyreported that NIr protects midbrain dopaminergic cells of mice from parkinsonian insult. In those studies, NIrwas directed to the head, on the assumption that it would penetrate the skull and brain to reach the midbrain; inpractice the whole dorsum of the mouse was irradiated. In this study, we applied NIr to the body only,preventing the radiation reaching the head with a ‘helmet’ of aluminium foil. NIr radiation of the body only waseffective in protecting these cells, although less protective than radiation of both body and head. The resultssuggest that the neuroprotective effect of NIr may be mediated at least partially by a systemic or indirect effect.The possibility of immune system involvement will be discussed.