[Effects of methionine restriction on allergic airway inflammation]

Objective:To investigate the effects and underlying mechanisms of the methionine-restricted diet（MRD） on type 2 inflammatory airway diseases, and to provide experimental evidence for nutritional interventions in allergic diseases. Methods:Specific pathogen-free（SPF） C57BL/6J mice were used to establish house dust mite（HDM） -induced allergic rhinitis（AR） and ovalbumin（OVA） -induced asthma models. Mice were randomly assigned to either a MRD（0.12% methionine） group or a standard control diet（CD, 0.86% methionine） group. An additional group receiving MRD alone was included to assess its impact on the peripheral immune system. The in vivo effects of MRD were evaluated through histology（H&E staining）, q-PCR, and flow cytometry. In addition, in vitro Th2 cell differentiation assays were conducted under methionine restriction（MR）. Results:Compared to the CD group, MRD significantly alleviated nasal mucosal inflammation in the AR model and reduced lung inflammation in the asthma model, along with decreased levels of key type 2 inflammatory cytokines including IL-4, IL-5, IL-13 and so on）. Four weeks of MRD alone did not significantly alter peripheral immune homeostasis. The in vitro experiments further demonstrated that MR directly inhibited the differentiation of nave CD4⁺T cells into Th2 cells. Conclusion:MRD can suppress Th2 cell-driven allergic airway inflammation while maintaining overall immune homeostasis, offering a potential nutritional intervention strategy for allergic diseases.