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Sunlight Benefits Multiple Sclerosis Independently of Vitamin D
Becklund BR, Severson KS, Vang SV, Deluca HF. UV radiation suppresses experimental autoimmune encephalomyelitis independent of vitamin D production. Proc Natl Acad Sci U S A. 2010 Mar 22. [Epub ahead of print]
Department of Biochemistry, University of Wisconsin, Madison, WI 53706.
Although the exact cause of multiple sclerosis (MS) is unknown, a number of genetic and environmental factors are thought to influence MS susceptibility. One potential environmental factor is sunlight and the subsequent production of vitamin D.
A number of studies have correlated decreased exposure to UV radiation (UVR) and low serum 25-hydroxyvitamin D(3) [25(OH)D(3)] levels with an increased risk for developing MS. Furthermore, both UVR and the active form of vitamin D, 1alpha,25-dihydroxyvitamin D(3), suppress disease in the experimental autoimmune encephalomyelitis (EAE) animal model of MS. These observations led to the hypothesis that UVR likely suppresses disease through the increased production of vitamin D.
However, UVR can suppress the immune system independent of vitamin D. Therefore, it is unclear whether UVR, vitamin D, or both are necessary for the putative decrease in MS susceptibility.
We have probed the ability of UVR to suppress disease in the EAE model of MS and assessed the effect of UVR on serum 25(OH)D(3) and calcium levels. Our results indicate that continuous treatment with UVR dramatically suppresses clinical signs of EAE. Interestingly, disease suppression occurs with only a modest, transient increase in serum 25(OH)D(3) levels.
Further analysis demonstrated that the levels of 25(OH)D(3) obtained upon UVR treatment were insufficient to suppress EAE independent of UVR treatment.
These results suggest that UVR is likely suppressing disease independent of vitamin D production, and that vitamin D supplementation alone may not replace the ability of sunlight to reduce MS susceptibility.
Mehta BK. New hypotheses on sunlight and the geographic variability of multiple sclerosis prevalence. J Neurol Sci. 2010 May 15;292(1-2):5-10. Epub 2010 Mar 1.
Department of Neurology, Jacobs Neurological Institute, State University of New York-Buffalo, 100 High Street, Buffalo, NY 14203, USA. bijal@yahoo.com
Multiple sclerosis is an autoimmune demyelinating disorder of the central nervous system. Its etiology continues to be elucidated.
The debate about the environmental impact on the disease etiology and progression has focused on sun light exposure in the recent past, but mainly as it applies to vitamin D and its derivatives.
This paper will discuss how sunlight stimulus may effect neuronal and microglial antigenic presentation based on sunlight-dependent neuronal activity, as well as how sunlight may alter the amount of vitamin A and melatonin levels during immune development in the central nervous system.
Changes in the number of antigens presented to lymphocytes by antigen-presenting cells for self-selective removal during immune development could therefore alter the number of circulating self-recognizing B and T-lymphocytes. This situation would increase susceptibility to a significantly greater number of self-antigens, and lead to autoimmune disorders such as multiple sclerosis.
Last updated 2 April 2010
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