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.
Keywords: Airway inflammation; Allergic asthma; Notch; Protocatechuic acid; STAT6; Th2 response.