Melatonin as a principal component of red light therapy.

Melatonin is well recognized for its role as a potent antioxidant and is directly implicated in the free radical theory of aging [1] [Reiter RJ, Pablos MI, Agapito TT, Guerrero JM. Melatonin in the context of the free radical theory of aging. Ann N Y Acad Sci 1996;786:362-78]. Moreover, melatonin has been shown to retard age-related increases in lipid peroxidation and oxidative damage [2] [Okatani Y, Wakatsuki A, Reiter RJ. Melatonin protects hepatic mitochondrial respiratory chain activity in senescence-accelerated mice. J Pineal Res 2002;32:143-8] and to act directly upon the immune system [3] [Poon AM, Liu ZM, Pang CS, Brown GM, Pang SF. Evidence for a direct action of melatonin on the immune system. Biol Signals 1994;3:107-17]. This report focuses on characterizing documented functions of melatonin in the context of red light therapy and proposes that melatonin is a potential mediator of red light's therapeutic effects, a hypothesis that is as yet untested. Red light therapy (670 nm, 4J/cm(2)) has been shown to restore glutathione redox balance upon toxicological insult and enhance both cytochrome c oxidase and energy production, all of which may be affected by melatonin. The red light treatment has also been successfully implemented in the clinical setting for its effectiveness in reducing both the number of incidences and severity of oral mucositis resulting in part from the chemotherapy and/or radiation administered prior to bone marrow transplants. Moreover, red light therapy improves wound healing and is being further tested for its ability to ameliorate toxicant-induced retinal and visual cortical neuron damage. Researchers in the growing field of light therapy may be in a position to draw from and collaborate with melatonin researchers to better characterize this alternative treatment.