α-Linolenic Acid Screened by Molecular Docking Attenuates Inflammation by Regulating Th1/Th2 Imbalance in Ovalbumin-Induced Mice of Allergic Rhinitis

Abstract

α-Linolenic acid (ALA) is a natural essential fatty acid widely found in plant seed oils and beans, which shows positive anti-inflammatory and antiallergic effects. In our previous study, ALA was proven to bind tightly to the seven protein targets closely associated with allergic rhinitis (AR) by molecular docking, which indicates that ALA may have a potential role in the treatment of AR. A mouse model of AR induced by ovalbumin (OVA) was adopted in this study to explore the therapeutical effect and potential mechanism of ALA in treating AR. Results demonstrated that ALA remarkably relieved the nasal symptoms, reduced the OVA-sIgE level in the serum, relieved the histopathological injuries, and downregulated the mRNA expression levels of IL-6 and IL-1β in the nasal mucosa. ALA also remarkably moderated the imbalance of Th1/Th2 cells, increased the mRNA expression levels of T-bet and STAT1, and reduced GATA3 and STAT6. ALA was proven to have a substantial therapeutic effect on mice with AR, and the underlying mechanism was likely to be the regulation of Th1/Th2 imbalance through the JAK/T-bet/STAT1 and JAK/GATA3/STAT6 pathways. This study provides a specific experimental basis for the clinical use and drug development of ALA in the treatment of AR.

Keywords: Th1/Th2 imbalance; allergic rhinitis; molecular docking; mouse model; α-Linolenic acid.

Figure 1

Molecular docking diagram of ALA with 5-LO, HRH1, CBG, mAChR M1, mAChR M3, PDE4 B, and PGD2. 5-LO, 5-lipoxygenase; HRH1, histamine H1 receptor; CBG, corticosteroid-binding globulin; mAChR M1, M1 muscarinic acetylcholine receptor; mAChR M3, M3 muscarinic acetylcholine receptor; PDE4B, phosphodiesterase 4B; PGD2, prostaglandin D2.

Figure 2

Effect of ALA on OVA-induced AR in mice. The numbers of sneezing (A) and rubbing actions (B) of mice were counted for 30 min immediately after the last intranasal challenge. (C) The level of OVA-sIgE in serum were measured by enzyme-linked immunosorbent assay (ELISA). The HE (D) and PAS (E) staining were used to observe the histopathological changes in nasal mucosa samples of mice. Between-group comparisons were performed using one-way ANOVA coupled with LSD t-test (equal variances assumed) or Tamhane’s T2 test (equal variances not assumed). Data are expressed as mean ± SD; n = 10; * p < 0.05, ** p < 0.01 versus AR model. Dex, dexamethasone; ALA-L, low dose of α-linolenic acid; ALA-H, high dose of α-linolenic acid.

Figure 3

Effect of ALA on the mRNA expression levels of IL-6 (A), IL-1β (B), IFN-γ (C), and IL-4 (D) in the nasal mucosa of AR mice. Between-group comparisons were performed using one-way ANOVA coupled with LSD t-test (equal variances assumed) or Tamhane’s T2 test (equal variances not assumed). Data are expressed as mean ± SD; n = 4; ** p < 0.01 versus AR model. Dex, dexamethasone; ALA-L, low dose of α-linolenic acid; ALA-H, high dose of α-linolenic acid.

Figure 4

Effect of ALA on the percentages of CD3⁺CD4⁺IFN-γ⁺ Th1 and CD3⁺CD4⁺IL-4⁺ Th2 cells in the spleen of AR mice. Representative dot plots of CD3⁺CD4⁺IFN-γ⁺ Th1 (in the upper left quadrant) and CD3⁺CD4⁺IL-4⁺ Th2 cells (in the lower right quadrant) (A), and the percentages of CD3⁺CD4⁺IFN-γ⁺ Th1 cells (B) and Th2 cells (C) in the SMCs separated from the spleen samples are analyzed via flow cytometry. Between-group comparisons were performed using one-way ANOVA coupled with LSD t-test (equal variances assumed) or Tamhane’s T2 test (equal variances not assumed). Data are expressed as mean ± SD; n = 3; * p < 0.05, ** p < 0.01 versus AR model. Dex, dexamethasone; ALA-L, low dose of α-linolenic acid; ALA-H, high dose of α-linolenic acid.

Figure 5

Effect of ALA on the mRNA expression levels of T-bet (A), GATA3 (B), STAT1 (C), and STAT6 (D) in the nasal mucosa in AR mice. Between-group comparisons were performed using one-way ANOVA coupled with LSD t-test (equal variances assumed) or Tamhane’s T2 test (equal variances not assumed). Data are expressed as mean ± SD; n = 4; * p < 0.05, ** p < 0.01 versus AR model. Dex, dexamethasone; ALA-L, low dose of α-linolenic acid; ALA-H, high dose of α-linolenic acid.

Figure 6

Flow chart of the OVA-induced AR model and ALA administration.