The Neural Mechanism of Respiratory Allergies and Infections

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Abstract Allergic rhinitis is the most common mucosal allergy. Its cardinal symptoms include excessive sneezing and rhinorrhea, which severely impact our life quality and productivity. Although antihistamines effectively relieved sneezing induced by intermittent mild allergic rhinitis, they are ineffective against persistent moderate/severe allergic rhinitis. The development of new drugs for alleviating allergic sneezing is hindered by a lack of information about the principal nasal sensory neurons that mediate sneezing and their interactions with immune cells. In this proposal, we hypothesize that a highly restricted population of nasal sensory neurons defined by the expression of MrgprC11 detect mast cell mediators in allergic rhinitis and trigger the sneezing reflex. In Aim 1, we will characterize the innervation pattern of MrgprC11-expressing fibers in the nasal mucosa and examine their pathological changes under allergic rhinitis using genetic labeling and axonal tracing approaches. Furthermore, we will determine their physiological responses to a variety of sneeze-inducing molecules using a novel ex vivo calcium-imaging tool. These studies will provide important information on the initial detection of nasal irritants and transduction of sneezing signals. In Aim 2, we will define the role of MrgprC11+ fibers in acute sneezing. We will determine whether ablation of MrgprC11+ neurons attenuates sneezing responses to a variety of nasal irritants and whether selective activation of MrgprC11+ sensory fibers in the nasal mucosa evokes sneezing. These studies will establish whether MrgprC11+ sensory fibers are required for sneezing induced by different sensory stimuli. In Aim 3, we will investigate the neuro-immune interactions between MrgprC11+ nasal sensory fibers and mast cells in allergic rhinitis. We will test whether degranulated mast cells activate MrgprC11+ nasal sensory fibers to induce sneezing in allergic rhinitis. Furthermore, we will determine whether pharmacological silencing of MrgprC11+ sensory fibers is a feasible therapeutic strategy to control sneezing associated with allergic rhinitis. These studies will not only advance our understanding of the neuro-immune interactions that trigger sneezing, but also provide a novel neuronal target for controlling nasal allergic symptoms.