Activation of the auricular vagus nerve reflex suppresses airway inflammation.

Abstract

The vagus nerve regulates inflammation via sensory-motor arcs. While vagal sensory neurons relay signals from within the body (interoception), whether external inputs can regulate visceral neuroimmune responses (exteroception) remains poorly understood. We unveiled a skin-lung reflex by which sensory neurons from the auricular skin suppressed Alternaria alternata-induced allergic airway inflammation. Viral and chemical neural tracing revealed distinct sensory projections from the vagal ganglia to the auricular skin. Pharmacologic, chemogenetic, and optogenetic activation of auricular transient receptor potential vanilloid 1 (TRPV1)⁺ afferents attenuated type 2 allergic lung inflammation, including group 2 innate lymphoid cell, eosinophil, and type 2 cytokine responses in the airway. Conversely, silencing of these sensory neurons via the skin exacerbated lung inflammation, and immunosuppression of airway inflammation was dependent on the neuropeptide calcitonin gene-related peptide (CGRP)β. These findings reveal an evolutionarily conserved somato-visceral reflex by which exteroceptive inputs impact visceral inflammation. Thus, transcutaneous neuromodulation may represent a therapeutic strategy to treat visceral inflammation.