Atopic dermatitis (AD) is a common inflammatory skin disease with increased colonization by pathogenic Staphylococcus aureus, which has been linked to production of abnormal levels of antimicrobial peptides (AMPs) in AD skin. Ultraviolet radiation (UVR) phototherapy is a widely used treatment for AD. We hypothesize that the efficacy of phototherapy in AD patients depends on the ability of UVR to (re)induce the expression of AMPs from host skin and normalize dysbiotic S. aureus colonization. To test this hypothesis, we developed a new mouse model of AD by treating the skin with calcipotriol (MC903) and an S. aureus clinical isolate. The mice were exposed to UVR, and inflammation was quantified by skin swelling each day throughout the protocol. In vitro experiments were performed by exposing S. aureus to varying doses of UVR to investigate the direct effects. Finally, skin biopsies obtained from mice were exposed to UV radiation ex-vivo and the secretome was collected, which was then cultured with S. aureus and its growth was monitored. Significant reduction in inflammation linked to increased expression of various AMPs (defensins, S100s) and reduced levels of S. aureus were observed after UV treatment. In vitro experiments showed that UVR exposure directly affected S. aureus growth in a dose- and density-dependent manner. Finally, secretome obtained from UV-irradiated ex-vivo skin contained AMPs (defensins, S100s) that significantly reduced S. aureus growth in vitro. Taken together, our study demonstrates that UV irradiation can reduce S. aureus associated AD-like inflammation by directly impacting the S. aureus growth and in directly by inducing the expression of AMPs. These results open avenues for the development of new therapeutic strategies using antimicrobials to treat AD.

ESDR378 - Ultraviolet radiation-induced antimicrobials neutralize S. aureus and reduce atopic dermatitis-associated inflammation

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.