Interleukin-4-Mediated NLRP3 Inflammasome Activation in Microglia Contributes to Allergic Rhinitis via Central Sensitization

Background: The hypersensitive state of the central nervous system, commonly known as central sensitization, presumably drives allergic rhinitis (AR) pathogenesis. However, the involvement of central sensitization in AR and its related mechanisms have rarely been studied. Methods: An AR mouse model was induced via ovalbumin treatment. Activation of trigeminal nucleus caudalis (TNC) neurons was assessed by electrophysiological recordings and immunofluorescence staining. The role of TNC neurons in AR was investigated by selectively manipulating them through chemogenetics. The contribution of microglial neuroinflammation to central sensitization and AR was assessed by pharmacologically inhibiting microglial activation. The mechanism of central sensitization in AR was further determined using a microglia-neuron co-culture system. The role of interleukin (IL)-4 in neuroinflammation in AR was explored using in vivo and in vitro methods. Results: The intrinsic neuronal excitability and molecular markers of central sensitization were increased within the TNC of AR mice. Chemogenetic inhibition of TNC neurons ameliorated nasal symptoms, histological changes, autonomic dysfunction, and immune imbalance in AR mice. Moreover, AR mice exhibited an increased number of pro-inflammatory microglia, activation of the NOD-like Receptor protein 3 (NLRP3) inflammasome, and enhanced IL-1β production in the TNC. Pharmacological inhibition of microglial activation reduced central sensitization in AR mice and was accompanied by remission of AR. Transcriptomics analysis revealed the inflammatory-prone characteristics of IL-4-treated microglia. IL-4 exposure enhanced lipopolysaccharide-stimulated NLRP3 inflammasome activation in microglia. Intracerebral injection of IL-4 neutralizing antibodies ameliorates neuroinflammation and central sensitization in AR mice and was accompanied by remission of AR. Conclusions: This research uncovers a previously unidentified mechanism wherein microglial neuroinflammation-induced central sensitization in the TNC contributes to AR, providing a new promising approach for the treatment of AR. IL-4 induces noncanonical pro-inflammatory-prone microglia and participates in microglial NLRP3 inflammasome activation in AR.