Therapeutic effects of a combination of Chinese quince and Saururus chinensis extract on allergic airway inflammation in an ovalbumin-induced asthma mouse model

Abstract

Background: Allergic asthma involves chronic inflammation, airway remodeling, and hyperresponsiveness. Inhaled corticosteroids combined with long-acting β2 agonists are effective; however, some patients experience side effects, highlighting the need for safer natural alternatives suitable for long-term use. Chinese quince (Q) and Saururus chinensis (SC) are used to treat various diseases, including asthma and inflammation. Q and SC extracts contain bioactive compounds that help modulate airway inflammation. Therefore, combining the two may enhance their immunomodulatory effects. However, the effects of a Q/SC mixture on allergic asthma remain unclear. The aim of this study is to assess the therapeutic effectiveness of a Q/SC mixture in treating asthma.

Methods: The therapeutic efficacy of the Q/SC extract was evaluated in an ovalbumin (OVA)-induced allergic airway inflammation model. After euthanasia, we assessed cell counts, cytokine expression in the bronchoalveolar lavage fluid (BALF), blood immunoglobulin (Ig) E levels, inflammatory cell infiltration, mucus production in the lung tissue, and the expression of protein and cytokine.

Results: A high-concentration Q/SC extract significantly reduced total cell and eosinophil counts, cytokine expression in BALF, and serum IgE levels. Furthermore, it reduced the expression of type 2 cytokines (IL-4, IL-5, IL-13) and inducible nitric oxide synthase in lung tissue. The extract also attenuated inflammatory cell infiltration and mucus production while inhibiting the STAT6 signaling pathway.

Conclusion: A high concentration of Q/SC extract effectively alleviates allergic airway inflammation by reducing eosinophilic inflammation, type 2 cytokine secretion, and mucus hyperproduction. This suggests that it could be a potential remedy for managing allergic airway inflammation.

Keywords: Chinese quince; STAT6; Saururus chinensis; allergic asthma; inflammatory response; mucus production; ovalbumin; type 2 immune response.

Figure 1

Experimental schedule for the asthma mouse model and the effect of Chinese quince/Saururus chinensis (Q/SC) extract on inflammation in bronchoalveolar lavage fluid (BALF). (A) Experimental procedure for the allergic asthma model and administration of dexamethasone (DEX) and Q/SC extract. (B) BALF cells are plated on clean glass slides and stained with Diff-Quik. Scale bar = 50 μm. (C) Total and differential cell counts are conducted using a cell counter under light microscopy. Data are shown as the means ± SEMs. ^###p < 0.001 vs. the normal control group. ^***p < 0.001 and ^**p < 0.01 vs. the ovalbumin-challenged group. NC, normal control; OVA, ovalbumin; DEX, dexamethasone; Q, Chinese quince; SC, Saururus chinensis; BALF, bronchoalveolar lavage fluid.

Figure 2

Effects of Chinese quince/Saururus chinensis (Q/SC) extract on immunoglobulin E (IgE) production and immune cell infiltration in ovalbumin (OVA)-induced allergic asthma mice. (A) The paraffin-embedded lung sections were stained with hematoxylin and eosin. Scale bar = 200 μm. (B) Lung inflammatory scores are determined using histological analysis of lung tissues. (C) Serum IgE levels are detected using enzyme-linked immunosorbent assay. Data are displayed as the means ± SEMs. ^###p < 0.001 vs. normal control group. ^***p < 0.001 and ^**p < 0.01 vs. OVA-challenged group. NC, normal control; OVA, ovalbumin; IgE, immunoglobulin E.

Figure 3

Effects of Chinese quince/Saururus chinensis (Q/SC) extract on non-type 2 and type 2 inflammation and inducible nitric oxide synthase (iNOS) expression in ovalbumin (OVA)-induced allergic asthma. (A,B) Enzyme-linked immunosorbent assay (ELISA) is conducted to detect the levels of interleukin (IL)-4 and IL-13, as type 2 cytokine levels in bronchoalveolar lavage fluid (BALF). (C–F) ELISA is also conducted to measure the levels of interleukin (IL)-1β, Tumor necrosis factor (TNF)-α, and IL-17, as non-type 2 cytokines, and iNOS expression in lung homogenates. Data are displayed as the means ± SEMs. ^###p < 0.001, ^##p < 0.01, and ^#p < 0.05 vs. the normal control group. ^***p < 0.001, ^**p < 0.01, and ^*p < 0.05 vs. the OVA-challenged group. iNos, inducible nitric oxide synthase; OVA, ovalbumin; BALF, Bronchoalveolar lavage fluid; ELISA, Enzyme-linked immunosorbent assay.

Figure 4

Chinese quince/Saururus chinensis (Q/SC) extract suppresses mRNA expressions of type 2-related cytokines and inducible nitric oxide synthase (iNOS). (A–C) The mRNA levels of type 2 cytokines (interleukin (IL)-4, IL-5, and IL-13), (D–F) non-type 2 cytokines (IL-1β, TNF-α, and IL-17), and (G) iNOS in homogenates are assessed using reverse transcription quantitative polymerase chain reaction and are normalized to glyceraldehyde 3-phosphate dehydrogenase levels. Data are displayed as the means ±SEM. ^###p < 0.001 and ^#p < 0.05 vs. the normal control (NC) group. ^***p < 0.001, ^**p < 0.01, and ^*p < 0.05 vs. the ovalbumin-challenged group.

Figure 5

Effect of the Chinese quince/Saururus chinensis (Q/SC) extract on mucus production and the STAT6 signaling pathway in ovalbumin (OVA)-induced allergic asthma. (A) Periodic acid-Schiff staining is used to assess goblet cell hyperplasia in the epithelium. Scale bar = 100 μm. (B) Quantification of goblet cells in lung tissues. (C) The mRNA level of the mucus gene MUC5AC is quantified using reverse transcription quantitative polymerase chain reaction and is normalized to glyceraldehyde 3-phosphate dehydrogenase levels. (D) STAT6 phosphorylation is measured using western blot. The total forms of each protein are used as loading controls. Data are displayed as the means ± SEMs. ^###p < 0.001 vs. the normal control group. ^***p < 0.001, ^**p < 0.01, and ^*p < 0.05 vs. the OVA-challenged group.