Anti‑inflammatory effects of dihydromyricetin in a mouse model of asthma

Abstract

Dihydromyricetin (DHM) is a plant flavonoid and is the primary active ingredient isolated from the medicinal herb, Ampelopsis grossedentata. DHM has been shown to possess various pharmacological activities, including anti‑inflammatory effects. However, the possible role of DHM in asthma treatment remains to be elucidated. The present study aimed to investigate its anti‑inflammatory properties in mice with symptoms of allergic asthma. The C57BL/6 mice were sensitized and challenged with ovalbumin (OVA) to induce asthma. DHM or phosphate‑buffered saline treatment was administered 1 h prior to the OVA challenge. The levels of interleukin (IL)‑4, IL‑5 and IL‑13 in the bronchoalveolar lavage (BAL) fluid were measured by enzyme‑linked immunosorbent assay (ELISA), and OVA‑specific serum IgE and IgG1 levels were also determined by ELISA. Histopathological staining was performed to evaluate the infiltration of inflammatory cells into the BAL fluid, lung tissues and goblet cell hyperplasia. DHM treatment significantly reduced the total number of inflammatory cells, including eosinophils, neutrophils, lymphocytes and macrophages, in the BAL fluid. DHM also reduced the levels of IL‑4, IL‑5 and IL‑13 in the BAL fluid, and reduced the secretion of OVA‑specific IgE and IgG1 in the serum. The histological staining demonstrated that DHM treatment effectively suppressed the OVA‑induced inflammatory cells in the lung tissues and in the mucus hypersecreted by goblet cells in the airway. These results showed that DHM had a potent anti‑inflammatory effect in an OVA‑induced mouse model of asthma, offering potential as an anti‑inflammatory agent for the treatment of asthma.

Figure 1.

Effect of DHM on OVA-induced inflammatory cells counts in BAL fluid. (A) Chemical structure of DHM. (B) Recovered cells from BAL fluid were counted following Wright's staining. Data are expressed as the mean ± standard deviation (n=8), *P<0.05 and **P<0.01, vs. OVA. DHM, dihydromyricetin; OVA, ovalbumin; BAL, bronchoalveolar lavage.

Figure 2.

Effects of DHM on OVA-induced IgE and IgG1 in serum. Mouse serum was collected 24 h following the final OVA challenged and the levels of OVA-specific (A) IgE and (B) IgG1 in serum were determined using enzyme-linked immunosorbent assays. Data are expressed as the mean ± standard deviation (n=8), **P<0.01, vs. OVA. DHM, dihydromyricetin; OVA, ovalbumin; Dex, dexamethasone.

Figure 3.

Effects of DHM on cytokine levels in BAL fluid. BAL fluid was collected following the final OVA challenge, and the levels of (A) IL-4, (B) IL-5 and (C) IL-13 were analyzed using enzyme-linked immunosorbent assays. Data are expressed as the mean ± standard deviation (n=8), *P<0.05 and **P<0.01, vs. OVA. DHM, dihydromyricetin; OVA, ovalbumin; Dex, dexamethasone; IL, interleukin.

Figure 4.

Effect of DHM on the recruitment of inflammatory cells in lung tissue. Lung tissues were obtained from the mice following the final OVA challenge, and was fixed, embedded, cut into sections and stained with hematoxylin and eosin solution to detect the infiltration of inflammatory cells. (A) phosphate-buffered saline-challenged mice; (B) OVA-challenged mice; (C) asthmatic mice treated with dexamethasone (2 mg/kg); (D) asthmatic mice treated with DHM (10 mg/kg). Magnification, ×200. DHM, dihydromyricetin; OVA, ovalbumin.

Figure 5.

Effect of DHM on mucus production. Lung tissues were fixed, embedded, cut into section, and then stained with periodic acid-Schiff solution to identify mucus hypersecretion. (A) Phosphate-buffered saline-challenged mice; (B) ovalbumin-challenged mice; (C) asthmatic mice treated with dexamethasone (2 mg/kg); (D) asthmatic mice treated with DHM (10 mg/kg). Magnification, ×400. DHM, dihydromyricetin.

Figure 6.

Effect of DHM on AHR. AHR in the mice treated with increasing concentrations of methacholine (0–40 mg/ml) was measured using whole-body plethysmography 24 h following the final OVA challenge. Penh values are expressed as mean ± standard deviation (n=5). *P<0.05 and **P<0.01, vs. OVA. DHM, dihydromyricetin; OVA, ovalbumin; Dex, dexamethasone; AHR, airway hyperresponsiveness.