Type 2 cytokines pleiotropically modulate sensory nerve architecture and neuroimmune interactions to mediate itch [Mouse ear pinnae]
Background: Anti-type 2 cytokine therapies represent promising interventions for chronic itch; however, their precise mechanisms in restoring nerve architecture and mitigating inflammation and pruritus remain incompletely understood. This study aimed to elucidate the mechanistic roles of IL-4, IL-13, and IL-31 in the pathophysiology of itch associated with type 2 inflammatory skin diseases. Methods: The effect of IL-4, IL-13, and/or IL-31 on neurite outgrowth and/or transcriptomic changes were analyzed in human and mouse dorsal root ganglion (DRG) neuronal cultures. Mouse ear pinnae were processed for histologic, transcriptomic, and proteomic analyses 4 days after intradermal injection of IL-4, IL-13, and/or IL-31. To evaluate functional correlations with neuronal responses, mice were subcutaneously challenged with IL-4, IL-13, and/or IL-31, and scratching behavior was monitored. Association between IL-4/IL-13–IL-4Ra axis and severity of atopic dermatitis (AD) was evaluated through correlative analyses of human DRG transcriptomic changes and AD transcriptomic datasets (GSE130588 and BioMap consortium). Results: IL-4 and IL-13 promote mouse and human DRG sensory neuron growth, with effects similar to or greater than IL-31. In mice, intradermal IL-4, IL-13, and IL-31 increased epidermal nerve growth; however, only IL-4 and IL-13 induced hyperplasia and immune cell recruitment. Multi-omic analyses revealed that IL-4 and IL-13 have a broader impact on neuroimmune interactions than IL-31. In a murine DRG neuron-eosinophil co-culture, IL-4Ra blockade reduced neurite growth. IL-13 and IL-31 elicited acute scratching, demonstrating their roles as direct pruritogens; IL-4 synergistically enhanced IL-13-induced itch, resulting in greater pruritic responses than IL-31. Additionally, a set of itch-associated genes upregulated by IL-4 and IL-13 and downregulated by dupilumab-mediated IL-4Ra blockade in human DRG neuronal cultures showed positive correlation with AD severity. Conclusions: These findings establish the IL-4/IL-13–IL-4Ra axis as a key regulator of inflammatory skin nerve innervation, neuroimmune interactions, barrier integrity, and itch response, highlighting its mechanistic role in modulating sensory neuronal function and shaping the inflammatory microenvironment that drives itch pathophysiology. Overall design: RNA-seq profiling of mouse ear pinnae with intradermal injection of IL-4, IL-13, IL-31, or PBS (n=5 per group)