Luteolin ameliorates inflammation and Th1/Th2 imbalance via regulating the TLR4/NF-κB pathway in allergic rhinitis rats

Abstract

Objective

Luteolin has an anti-allergic effect but its mechanism is not clear. This study attempted to determine the mechanisms of luteolin in rhinitis.

Methods

Allergic rhinitis rat model was established by ovalbumin (OVA) stimulation. Then, the rats were treated with normal saline, luteolin, or lipopolysaccharide (LPS) for 14 days. Nasal symptoms were scored; the histopathological changes of nasal mucosa were detected by hematoxylin–eosin staining. Serum levels of Th1 type cytokines (IFN-γ, IL-2), Th2 type cytokines (IL-4, IL-5, IL-13), and OVA-specific IgE (sIgE) were determined by ELISA. The expressions of Toll-like receptor 4 (TLR4) and p65 in nasal mucosa were detected by Western blot or immunohistochemistry.

Results

Luteolin decreased symptom scores, specifically, the scores in control group, model group, model + 0.1 mg/kg luteolin, model + 1 mg/kg luteolin, and model + 10 mg/kg luteolin groups were 0.63 ± 0.52, 7.88 ± 0.83, 1.38 ± 0.52, 2.75 ± 0.46, and 5.00 ± 0.53, respectively. Luteolin ameliorated nasal mucosa inflammation by promoting the down-regulated levels of Th1 type cytokines, and suppressing the up-regulated levels of Th2 type cytokines, OVE-sIgE, TLR4, and p65. LPS further increased symptom scores, aggravated nasal mucosa inflammation, improved the unbalance of Th1/Th2 type cytokines, and lowered the expressions of OVE-sIgE, TLR4, and p65. Moreover, LPS reversed the effect of luteolin on allergic rhinitis rats.

Conclusion

Luteolin ameliorated inflammation and Th1/Th2 imbalance via regulating the TLR4/NF-κB pathway in allergic rhinitis rats. This study provided novel evidence that luteolin could be used as a candidate drug in allergic rhinitis treatment.

Keywords:

• Th1/Th2 cytokines
• lipopolysaccharide
• ovalbumin
• luteolin
• allergic rhinitis

Author contributions

Substantial contributions to conception and design: Jinhui Dong.

Data acquisition, data analysis and interpretation: Ou Xu, Jianxing Wang, Chunguang Shan, Xiumin Ren.

Drafting the article or critically revising it for important intellectual content: Jinhui Dong.

Final approval of the version to be published: Jinhui Dong, Ou Xu, Jianxing Wang, Chunguang Shan, Xiumin Ren.

Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of the work are appropriately investigated and resolved: Jinhui Dong, Ou Xu, Jianxing Wang, Chunguang Shan, Xiumin Ren.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The analyzed data sets generated during the study are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by Effect of Immunotherapy on IL-17, IL-35 and Treg/Th17 Cell Balance in Patients with Allergic Rhinitis [20170118].