MyD88 mediates the pathogenesis of dermatitis in SHARPIN-deficient mice by regulating TNF production on the skin

Abstract

Abstract Mice deficient in SHANK-associated RH domain–interacting protein (SHARPIN), a component of the linear ubiquitin chain assembly complex (LUBAC), develop a spontaneous inflammatory disorder with pathologic hallmarks similar to atopic dermatitis and psoriasis in humans. Previous studies identified the crucial role of components of the TNF and IL-1 signaling pathways in the progression of disease in SHARPIN-deficient mice. However, an innate adaptor or sensor that relates to the disease progression has remained unknown. In this study, we found that the genetic ablation of myeloid differentiation primary response 88 (MyD88) completely rescued skin inflammation in SHARPIN-deficient (Sharpincpdm) mice. Systemic inflammation and immune cell dysregulation were also rescued. Fibroblasts derived from SharpincpdmMyd88−⁄− micefailed to provide protection against TNF-induced cell death. SharpincpdmMyd88−⁄− mice had reduced TNF production in their skin. Furthermore, depletion of the microbiota through the oral administration of antibiotics partially rescued both the skin inflammation and systemic inflammation, demonstrating a role for the gut microbiota in SHARPIN-deficient mice. Our findings suggest a detrimental role for the innate immune adaptor MyD88 in instigating skin inflammation in Sharpincpdm mice.