Sodium houttuyfonate plays a protective role in the asthmatic airway by alleviating the NLRP3-related pyroptosis and Th1/Th2 immune imbalance.

Background: Houttuynia cordata is an herbal compound that grows in China and exhibits anti-inflammatory, antiviral, and antioxidant properties. Additionally, pyroptosis is mediated by the activated NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome after stimulation by various inflammatory factors in asthma.

Objective: To investigate the effect of sodium houttuyfonate on NLRP3 inflammasome-related pyroptosis and Th1/Th2 immune imbalance in asthma.

Methods: Asthmatic mice model were made, sodium houttuyfonate was injected intraperitoneally to treat the asthmatic mice. Airway reactivity, cell classification and counting in the bronchoalveolar lavage fluid were measured. Hematoxylin-eosin and periodic acid-Schiff staining were used to analyze airway inflammation and mucus hypersecretion. Beas-2b cells were cultured, LPS, NLRP3 antagonist (Mcc950) and sodium houttuyfonate were used to intervene the Beas-2b cells, NLRP3, ASC, caspase-1, GSDMD, IL-1β, and IL-18 expression in the lung tissue and cells were analyzed using immunohistochemistry and western blot, while qRT- PCR was performed to analyze the mRNA contents in the pulmonary and the cells, respectively. Th1 and Th2 cytokines (IL-4 and IFN-γ) were detected with ELISA and the proportions of Th1 and Th2 in splenocyte were detected by flow cytometry.

Results: Airway reactivity decreased in sodium houttuyfonate group when compared with asthmatic group mice. In the BALF, the numbers of leukocytes, eosinophils, neutrophils, lymphocytes, and macrophages were significantly lower in sodium houttuyfonate group mice than in asthmatic group mice. The proportion of TH1/TH2 cells in spleen cells and IFN-γ /IL-4 in plasma increased in sodium houttuyfonate treatment group when compared with asthma group. Immunohistochemistry, western blot and RT-PCR showed that the expressions of NLRP3, ASC, caspase-1, GSDMD, IL-1β and IL-18 were decreased in the lung tissue of mice after treated with sodium houttuyfonate when compared with those in the asthma group. However, sodium houttuyfonate combined with dexamethasone induced a stronger effect on NLRP3-related pyroptosis and Th1/Th2 immune imbalance compared to sodium houttuyfonate or dexamethasone alone. Beas-2b cells were cultured in vitro, sodium houttuyfonate can alleviate LPS-induced ASC, casepase-1, GSDMD, IL-18 and IL-1β increasing, especially in SH (10 μg/ml) treated group, but the effect less than Mcc950.

Conclusions: Sodium houttuyfonate can alleviated NLRP3-related pyroptosis and Th1/Th2 immune imbalance to reduce asthma airway inflammation and airway reactivity.