New mechanism underlying IL-31-induced atopic dermatitis

Background T H 2 cell–released IL-31 is a critical mediator in patients with atopic dermatitis (AD), a prevalent and debilitating chronic skin disorder. Brain-derived natriuretic peptide (BNP) has been described as a central itch mediator. The importance of BNP in peripheral (skin-derived) itch and its functional link to IL-31 within the neuroimmune axis of the skin is unknown. Objective We sought to investigate the function of BNP in the peripheral sensory system and skin in IL-31–induced itch and neuroepidermal communication in patients with AD. Methods Ca 2+ imaging, immunohistochemistry, quantitative real-time PCR, RNA sequencing, knockdown, cytokine/phosphokinase arrays, enzyme immune assay, and pharmacologic inhibition were performed to examine the cellular basis of the IL-31–stimulated, BNP-related itch signaling in dorsal root ganglionic neurons (DRGs) and skin cells, transgenic AD-like mouse models, and human skin of patients with AD and healthy subjects. Results In human DRGs we confirmed expression and co-occurrence of oncostatin M receptor β subunit and IL-31 receptor A in a small subset of the neuronal population. Furthermore, IL-31 activated approximately 50% of endothelin-1–responsive neurons, and half of the latter also responded to histamine. In murine DRGs IL-31 upregulated Nppb and induced soluble N-ethylmaleimide–sensitive factor activating protein receptor–dependent BNP release. In Grhl3PAR2 /+ mice house dust mite–induced severe AD-like dermatitis was associated with Nppb upregulation. Lesional IL-31 transgenic mice also exhibited increased Nppb transcripts in DRGs and the skin; accordingly, skin BNP receptor levels were increased. Importantly, expression of BNP and its receptor were increased in the skin of patients with AD. In human skin cells BNP stimulated a proinflammatory and itch-promoting phenotype. Conclusion For the first time, our findings show that BNP is implicated in AD and that IL-31 regulates BNP in both DRGs and the skin. IL-31 enhances BNP release and synthesis and orchestrates cytokine and chemokine release from skin cells, thereby coordinating the signaling pathways involved in itch. Inhibiting peripheral BNP function might be a novel therapeutic strategy for AD and pruritic conditions.