Probiotic effects on skin health: the case of photoprotection as a model of gut-skin dialog

Abstract

The skin is the most external organ of our body, and it is constantly exposed to environmental challenges. In this way, ultraviolet radiation (UVr) contained within sunlight is one of the most important insults that our skin deals with. UVr deeply affects skin cells, promoting DNA damage, oxidative stress, and mitochondrial alterations, all of which lead to local inflammation after acute exposures and to skin carcinogenesis after chronic ones. Additionally, UVr can also alter our immune system, suppressing adaptive immune responses.

Probiotic microorganisms are very well known for their capacity to modulate the immune system, mainly at the gastrointestinal tract. However, orally administered probiotics also affect skin immunity. It has been demonstrated that different oral probiotic formulations may impact skin health. Whole microorganisms, as well as isolated molecules, have proven to be effective in skin photoprotection, avoiding detrimental effects of UVr on the skin. Some of these effects have been shown, such as a protection against UV-induced immunosuppression, carcinogenesis, loss of Langerhans cells, and other effects that will be summarized in the present chapter.

The mechanisms responsible for the translocation of the effects from the gut epithelium to the skin and its draining lymph nodes are still poorly understood, but some hypotheses will be set out here, considering the effects of probiotics on the gut-associated lymphoid tissue.