Nakai Attenuates Allergic Airway Inflammation via Suppression of NF-κB and Enhancement of Nrf2/HO-1 Signaling.

Nakai (Scrophulariaceae) is a medicinal herb that grows in Korea and which has been widely used to treat fever, edema, neuritis and laryngitis. Hence, we evaluated the anti-inflammatory and antioxidant effects of the ethanol extract (SKE) of Nakai in an ovalbumin (OVA)-induced mouse model. We injected 20 μg of OVA with 2 mg of aluminum on day 0 and day 14 to induce allergic airway inflammation in six-week-old BALB/c mice, and mice were challenged with 1% OVA by nebulization for 1 h on days 21, 22, and 23. SKE was orally administered at 20 mg/kg and 40 mg/kg from day 18 to 23, and its effects were compared with those of montelukast treatment. SKE significantly reduced proinflammatory cytokines, inflammatory cell counts, immunoglobulin-E, and airway hyperresponsiveness during the OVA-induced allergic airway inflammation model; it also reduced airway inflammation and mucus production. In addition, SKE reduced the OVA-induced nuclear factor kappa B (NF-κB) phosphorylation in lung tissues while enhancing nuclear factor erythroid-derived 2-related factor (Nrf-2) and heme oxygenase-1 (HO-1) expression. In conclusion, SKE showed the protective effects on OVA-induced allergic airway inflammation via the suppression of NF-κB phosphorylation and the enhancement of the Nrf2/HO-1 signaling pathway. These results indicate that SKE is a potential therapeutic agent for allergic airway inflammation.