Anti-allergic rhinitis activity of α-lipoic acid via balancing Th17/Treg expression and enhancing Nrf2/HO-1 pathway signaling.

An ovalbumin (OVA)-induced allergic rhinitis (AR) mouse model was established to investigate whether α-Lipoic acid (LA) has a protective effect against upper respiratory tract inflammation. BALB/c mice were sensitized by intraperitoneal injection and challenged by intranasal application of OVA. Mice were orally administered various doses of LA once daily (2, 10, 50 mg/kg) and dexamethasone (Dex; 2.5 mg/kg) 1 h before OVA challenge. Allergic nasal symptoms, levels of OVA-specific immunoglobulins, cytokines, and transcription factors were measured. Nasal and lung histopathology were evaluated. LA administration significantly alleviated the nasal symptoms such as rubbing and sneezing, markedly reduced both serum OVA-specific IgE and IgG1 levels. The LA treatment group showed markedly up-regulated levels of the Treg cytokine IL-10 and Treg transcription factor Foxp3. In contrast, it showed down-regulated levels of the Th17 cytokine IL-17 and the Th17 transcription factor STAT3, and RORγ. LA greatly enhanced the nuclear factor erythroid-derived 2/heme oxygenase 1 (Nrf2/HO-1) pathway signaling and inhibited the activation of NF-κB/IκB, markedly suppressed the levels of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, IL-8 and chemokine COX-2. The histologic alterations of nasal and lung tissues of AR mice were effectively ameliorated by LA. Based on these results, we suggest that LA could be a potential therapeutic agent in OVA-induced AR by virtue of its role in controlling the Th17/Treg balance and enhancing Nrf2/HO-1 pathway signaling.