Ultraviolet Irradiation of Skin Alters the Faecal Microbiome Independently of Vitamin D in Mice

Abstract

Reduced sunlight exposure has been associated with an increased incidence of Crohn’s disease and ulcerative colitis. The effect of ultraviolet radiation (UVR) on the faecal microbiome and susceptibility to colitis has not been explored. C57Bl/6 female mice were fed three different vitamin D-containing diets for 24 days before half of the mice in each group were UV-irradiated (1 kJ/m2) for each of four days, followed by twice-weekly irradiation of shaved dorsal skin for 35 days. Faecal DNA was extracted and high-throughput sequencing of the 16S RNA gene performed. UV irradiation of skin was associated with a significant change in the beta-diversity of faeces compared to nonirradiated mice, independently of vitamin D. Specifically, members of phylum Firmicutes, including Coprococcus, were enriched, whereas members of phylum Bacteroidetes, such as Bacteroidales, were depleted. Expression of colonic CYP27B1 increased by four-fold and IL1β decreased by five-fold, suggesting a UVR-induced anti-inflammatory effect. UV-irradiated mice, however, were not protected against colitis induced by dextran sodium sulfate (DSS), although distinct faecal microbiome differences were documented post-DSS between UV-irradiated and nonirradiated mice. Thus, skin exposure to UVR alters the faecal microbiome, and further investigations to explore the implications of this in health and disease are warranted.

Effects of B-Wave Ultraviolet Supplementation Using Light-Emitting Diodes on Caged Laying Hens during the Later Phase of the Laying Cycle

“…Because leg skin becoming thick during the later phase of the laying cycle might block most of the UV rays, we hypothesized that the intensity of the UVB-LED lamp may also be a major factor. UV (250-360 nm) was an effective method of acquiring vitamin D [34]. However, the results show that the serum 1,25(OH) 2 D 3 content was not affected by UVB exposure.…”

The Role of Vitamin D in the Pathogenesis of Inflammatory Bowel Disease

“…It is known that the disruption in the balance between regulatory and proinflammatory pathways of the immune system, as well as a compromise in the epithelial barrier integrity, is the basis for the pathogenesis of IBD, thus underlying the importance and the potential role of vitamin D in this disorder. Vitamin D exerts other important effects on intestinal microbiome [34,35], and further research is needed to better elucidate this issue.…”

“…Alterations of the fecal microbiome may be another mechanism through which vitamin D influences the risk of developing IBD, as shown by preliminary studies in rat models [34]. In a small interventional study, Schäffler et al found that, in contrast to healthy controls, the administration of vitamin D to patients with CD was associated with changes in bacterial intestinal flora, which are particularly evident after one week: the typical bacteria shifted from Betaproteobacteria to Bacteroidetes [35].…”

Temperature as a modulator of the gut microbiome: what are the implications and opportunities for thermal medicine?

“…This points out that there is likely a time-of-day effect when sampling the microbiome [55]. Different types of light exposure can have an effect; mice exposed to UV irradiation showed a skewing of the microbiome towards increased Firmicutes: Bacteroidetes ratio [56]. Furthermore, Circadian disruption can alter the gut microbiome [57] and sensitivity to antitumor therapies [58].…”