Interleukin-13 R130Q aggravates airway smooth-muscle phenotypic switching and promotes airway remodeling in severe asthma.

Introduction: Airway remodeling represents a key pathological feature of severe asthma. Although the interleukin-13 (IL-13) R130Q variant is associated with increased disease severity, its specific contribution to airway remodeling remains unclear. Methods: This study used an ovalbumin (OVA)-induced asthma model in which mice were sensitized intraperitoneally with OVA/alum and subsequently challenged intranasally with OVA; human IL-13 130R or IL-13 130Q was administered intranasally before each challenge. Primary human bronchial smooth muscle cells (hBSMCs) from a single healthy donor were treated with both variants to assess CCK-8-derived proliferative/metabolic activity, migration, acetylcholine (ACh)-induced intracellular calcium responses, and IL-4 and IL-5 concentrations in culture supernatants. JAK2 and STAT6 phosphorylation was evaluated separately as a downstream signaling readout. Structural modeling and independent triplicate 100-ns molecular dynamics simulations of the IL-13/IL-13 receptor alpha 2 (IL-13Rα2) complex were performed using GROMACS 2025.4 with the AMBER ff19SB force field, and molecular mechanics/generalized Born surface area analysis was used for relative comparison of binding free energies. Results: IL-13 130Q produced limited airway changes in mice without OVA sensitization, but exacerbated airway wall thickening, luminal narrowing, smooth-muscle expansion, and pulmonary inflammation in OVA-sensitized and intranasally challenged mice. In hBSMCs, IL-13 130Q induced greater CCK-8-derived proliferative/metabolic activity, migration, ACh-induced intracellular calcium responses, and IL-4 and IL-5 concentrations than IL-13 130R at 10 -100 ng/mL. Molecular dynamics analyses suggested the reduced binding stability of IL-13 130Q/IL-13Rα2 complex, as reflected by fewer interfacial hydrogen bonds, altered intermolecular contacts, and a less favorable relative binding free energy. Elevated JAK2/STAT6 phosphorylation indicated the amplification of downstream signaling, mechanistically tied to potential reduced decoy-receptor affinity. Conclusion: These preclinical data support a contextdependent potentiating function of IL13 130Q in airway smoothmuscle phenotypic modulation and airway remodeling. Further investigation may rationalize genotype-based stratification in the therapy of severe asthma.