Microbial regulation of the keratinocyte AHR

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PROJECT SUMMARY The complexity of microbial communities inhabiting the healthy human skin have been illuminated in recent years, as well as signatures associated with inflammatory skin diseases such as atopic dermatitis. However, the molecular and biochemical mechanisms that mediate microbial symbiosis with the skin are not well understood. We recently found that homeostatic skin barrier function, epidermal differentiation, and recovery from injury are dependent on the microbiota in mice. These effects were mediated by the keratinocyte aryl hydrocarbon receptor (AHR). The AHR is a ligand-dependent xenobiotic receptor of foreign/toxic substances that is also known to regulate epidermal differentiation, tight junction/adhesion, and antimicrobial innate immune responses. The objective of this project is to identify and characterize microbial ligands of the AHR, and to test their utility in treating skin barrier dysfunction and infection. Epidermal barrier dysfunction is a key feature of atopic dermatitis, a common skin disorder characterized by chronic and relapsing, itchy, inflamed, skin lesions and dysbiotic microbiota. To test the hypothesis that commensal bacteria mediate AHR signaling to promote skin barrier integrity and defense, we propose three aims. 1) Define microbial mechanisms of keratinocyte AHR regulation that promote barrier repair; 2) Establish pharmacodynamic actions of microbial AHR ligands to promote skin barrier function and antimicrobial defense; and 3) Evaluate microbial AHR ligands in treatment of epidermal barrier dysfunction and S. aureus infection in murine models. Findings from these studies will provide novel, accessible targets to promote skin barrier function and repair, while advancing fundamental understanding of cutaneous host-microbiota interactions.