Photoimmunology and Multiple Sclerosis

Abstract

The ultraviolet (UV) radiation contained in sunlight is a powerful immune suppressant. While exposure to UV is best known for its ability to cause skin cancer, it is also associated with protection against a range of autoimmune diseases, particularly multiple sclerosis (MS). Although the precise mechanism by which sunlight affords protection from MS remains to be determined, some have hypothesised that UV immunosuppression explains the "latitude-gradient effect" associated with MS. By stimulating the release of soluble factors in exposed skin, UV activates immune suppressive pathways that culminate in the induction of regulatory cells in distant tissues. Each and every one of the immune suppressive cells and molecules activated by UV exposure are potential targets for treating and preventing MS. A thorough understanding of the mechanisms involved is therefore required if we are to realise the therapeutic potential of photoimmunology.

Brain health: time matters in multiple sclerosis

“…It is most prevalent in North America, Europe, Australia, New Zealand (Multiple Sclerosis International Federation, 2013a), other countries with Caucasian populations (Multiple Sclerosis International Federation, 2013i) and Iran (Etemadifar et al, 2013). The causes of MS are unclear, but risk is partially determined by a complex interaction between genetic (Robertson et al, 1996;Carton et al, 1997;Willer et al, 2003;De Jager et al, 2009) and environmental (Martyn et al, 1993;Levin et al, 2005;Handunnetthi et al, 2010;Levin et al, 2010;Solomon and Whitham, 2010;Handel et al, 2011;Simpson et al, 2011;Torkildsen et al, 2012;Disanto et al, 2013;Berg-Hansen et al, 2014;Breuer et al, 2014;Fiddes et al, 2014;Spelman et al, 2014;Torkildsen et al, 2014;Marsh-Wakefield and Byrne, 2015) factors.…”

Environmental control of autoimmune inflammation in the central nervous system

“…dendritic cells, B and T cells, monocytes) and inflammatory mediators (e.g. IL-10, IL-13, IL-33) relevant to MS pathogenesis, which are most likely acting in concert to suppress pro-inflammatory activity while promoting anti-inflammatory effects 26 . In addition, the UVB-dependent generation of bioactive Vitamin D and its relevance for MS have been studied over decades, since high serum levels of Vitamin D correlate with low incidence and disease activity, thus representing both a mechanistic explanation for the latitude gradient as well as a druggable target for MS 27,28 .…”

Experimental autoimmune encephalomyelitis (EAE) up-regulates the mitochondrial activity and manganese superoxide dismutase (MnSOD) in the mouse renal cortex

“…For example, the gut could play a critical role in MS, because the impaired gut barrier leads to elevated translocation of MS-relevant microbiota across the intestinal barrier into circulation [ 1 ]. Moreover, UV exposure is associated with benefits against MS [ 2 ]. Skin increases release of soluble factors following UV exposure, leading to activation of immune suppressive pathways, protecting against the disease [ 2 ].…”

“…Moreover, UV exposure is associated with benefits against MS [ 2 ]. Skin increases release of soluble factors following UV exposure, leading to activation of immune suppressive pathways, protecting against the disease [ 2 ]. It has also been known that Na or high Na intake increases the production of pro-inflammatory cytokines and decreases the production of immune regulatory cytokines both in vitro and in vivo [ 3 – 7 ], and that high salt diets exacerbate EAE [ 4 , 5 ].…”