Flavonone treatment reverses airway inflammation and remodelling in an asthma murine model

Abstract

Background and purpose: Asthma is an inflammatory disease that involves airway hyperresponsiveness and remodelling. Flavonoids have been associated to anti-inflammatory and antioxidant activities and may represent a potential therapeutic treatment of asthma. Our aim was to evaluate the effects of the sakuranetin treatment in several aspects of experimental asthma model in mice.

Experimental approach: Male BALB/c mice received ovalbumin (i.p.) on days 0 and 14, and were challenged with aerolized ovalbumin 1% on days 24, 26 and 28. Ovalbumin-sensitized animals received vehicle (saline and dimethyl sulfoxide, DMSO), sakuranetin (20 mg kg(-1) per mice) or dexamethasone (5 mg kg(-1) per mice) daily beginning from 24th to 29th day. Control group received saline inhalation and nasal drop vehicle. On day 29, we determined the airway hyperresponsiveness, inflammation and remodelling as well as specific IgE antibody. RANTES, IL-5, IL-4, Eotaxin, IL-10, TNF-α, IFN-γ and GMC-SF content in lung homogenate was performed by Bioplex assay, and 8-isoprostane and NF-kB activations were visualized in inflammatory cells by immunohistochemistry.

Key results: We have demonstrated that sakuranetin treatment attenuated airway hyperresponsiveness, inflammation and remodelling; and these effects could be attributed to Th2 pro-inflammatory cytokines and oxidative stress reduction as well as control of NF-kB activation.

Conclusions and implications: These results highlighted the importance of counteracting oxidative stress by flavonoids in this asthma model and suggest sakuranetin as a potential candidate for studies of treatment of asthma.

Figure 1

OVA-specific IgE antibodies titre measured by PCA technique. Data are presented as mean ± SE. OVA group: sensitized and treated with vehicle; OVA + SK group: sensitized and treated with sakuranetin; OVA + DX: sensitized and treated with dexamethasone. Note that both sakuranetin and dexamethasone treatments reduced the OVA-specific IgE antibodies in sensitized animals. *P < 0.001 compared with OVA.

Figure 2

Lung mechanics. (A) Respiratory system resistance (Rrs). (B) Percentage of maximal responses related to baseline of Rrs. (C) Respiratory system elastance (Ers). (D) Percentage of maximal responses related to baseline of Ers. Control group: non-sensitized and non-treated; OVA group: sensitized and vehicle treated; OVA + SK: sensitized and sakuranetin treated; OVA + DX group: sensitized and dexamethasone treated. All results are presented as mean ± SE. *P < 0.05 compared with other groups (Control, OVA + SK and OVA + DX); ^#P < 0.05 compared with Control only.

Figure 3

Lung mechanics. (A) Airway resistance (Raw). (B) Percentage of maximal responses related to baseline of Raw. (C) Tissue resistance (Gtis). (D) Percentage of maximal responses related to baseline of Gtis. (E) Tissue elastance (Htis). (F) Percentage of maximal responses related to baseline of Htis. Control group: non-sensitized and non-treated; OVA group: sensitized and vehicle treated; OVA + SK: sensitized and sakuranetin treated; OVA + DX group: sensitized and dexamethasone treated. All results are presented as mean ± SE. *P < 0.05 compared with other groups (Control, OVA + FL and OVA + DX).

Figure 4

Eosinophilic inflammation. Control group: non-sensitized and non-treated; OVA group: sensitized and vehicle treated; OVA + SK: sensitized and sakuranetin treated; OVA + DX group: sensitized and dexamethasone treated. All results are presented as mean ± SE. *P < 0.05 compared with control; **P < 0.05 compared with OVA.

Figure 5

Airway remodelling. Control group: non-sensitized and non-treated; OVA group: sensitized and vehicle treated; OVA + SK: sensitized and sakuranetin treated; OVA + DX group: sensitized and dexamethasone treated. All results are presented as mean ± SE. *P < 0.05 compared with control; **P < 0.05 compared with OVA. (B–E) Representative photomicrographs of airways stained with Picro Sirius for collagen fibres detection from animal of Control, OVA, OVA + SK and OVA + DX groups respectively.

Figure 6

Oxidative stress and NF-kB activation. Control group: non-sensitized and non-treated; OVA group: sensitized and vehicle treated; OVA + SK: sensitized and sakuranetin treated; OVA + DX group: sensitized and dexamethasone treated. All results are presented as mean ± SE. *P < 0.05 compared with control; **P < 0.05 compared with OVA; ^#P < 0.05 compared with OVA-SK.

Figure 7

Representative photomicrographs of airways stained with LUNA to eosinophil detection (A–D), with Picro Sirius (E–H) and with antibody against 8-iso-PGF-2α (I–L) from animal of Control, OVA, OVA + SK and OVA + DX groups (1st to 4st column respectively). It is clearly that OVA group presented more eosinophils, an intense collagen deposition and increase of 8-iso-PGF-2α positive area around airways. Both sakuranetin and dexamethasone treatments attenuated these responses in airways as shown in panels C, D, G, H, K and L. Control group: non-sensitized and non-treated; OVA group: sensitized and vehicle treated; OVA + SK: sensitized and sakuranetin treated; OVA + DX group: sensitized and dexamethasone treated.