Protocatechuic acid supplement alleviates allergic airway inflammation by inhibiting the IL-4Rα–STAT6 and Jagged 1/Jagged2–Notch1/Notch2 pathways in allergic asthmatic mice

Objective and design To clarify the effects of dietary supplementation of protocatechuic acid (PCA) and in-depth mechanisms on allergic asthma in ovalbumin (OVA)-induced mice. Materials Female BALB/c mice were randomly divided into three groups ( n = 10 in each group): control group, OVA-induced allergic asthma group, and OVA plus PCA group. Treatment Dietary supplementation of PCA was achieved by adding 50 mg/kg PCA to AIN 93G diet for 25 days. Methods Peripheral blood cells, pulmonary inflammatory cell infiltration, the levels of IL-4, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF), the mRNA levels of Th2-related genes in the lungs, and the protein expressions of the IL-4Rα–STAT6 and the Jagged1/Jagged2–Notch1/Notch2 signaling pathways were measured. Results Significantly reduced inflammatory cells infiltration and mucosal hypersecretion in the lung tissues, repaired levels of interleukin IL-4, IL-5, and IL-13 in the BALF, and decreased mRNA expression of IL-4, IL-5, and GATA3 were observed in OVA plus PCA group. Moreover, PCA treatment down-regulated the protein levels of IL-4Rα–STAT6 and Jagged1/Jagged2–Notch1/Notch2 signaling pathways. Conclusions Dietary supplement of PCA alleviated allergic asthma partly through suppressing the IL-4Rα–STAT6 and Jagged1/Jagged2–Notch1/Notch2 signaling pathways in mice. Our study provided the theoretic basis of PCA used as functional food in preventing allergic asthma.