Effects of rosmarinic acid on the inflammatory response in allergic rhinitis rat models after PM2.5 exposure

BACKGROUND: Studies have shown the promising prospects of rosmarinic acid (RosA) for the prevention and treatment of allergic diseases. OBJECTIVE: The aim of this study was to investigate the effects of RosA on inflammatory reaction in rat models of allergic rhinitis (AR) after PM2.5 exposure. METHODS: Allergic rhinitis rat models were established by ovalbumin sensitization, and PM2.5 was applied at a concentration of 1000 μg/m(3), 3 h a day for 30 consecutive days. RosA was administered via intraperitoneal injection (20 mg/kg/d) for seven consecutive days. Allergic nasal symptoms were recorded. The expressions of interleukin (IL)‐4, IL‐13, interferon (INF)‐γ, and OVA‐sIgE were determined by ELISA. Histopathological changes in nasal mucosa were observed by HE staining. mRNA expressions of T‐bet and GATA‐3 in nasal mucosa were detected by RT‐PCR. NF‐κBp65 in cell nuclei and IκBα in cytoplasm were analyzed by Western blot. RESULTS: PM2.5 exposure worsened allergic nasal symptoms in AR rats, while RosA ameliorated these symptoms. Histopathologically, AR rats exhibited disorganized nasal mucosal epithelium, cell exfoliation, eosinophilic infiltration of lamina propria, gland swelling, and submucosal vascular congestion, which were aggravated by PM2.5 exposure and alleviated by RosA. RosA decreased the expressions of IL‐4, IL‐13, and increased the level of IFN‐γ in PM2.5‐exposed AR rats. After RosA intervention, the expressions of GATA‐3 mRNA and NF‐κBp65 in PM2.5‐exposed AR rats were significantly reduced, while those of T‐bet mRNA and IκBα were markedly increased. CONCLUSION: Rosmarinic acid may alleviate symptoms of AR rat models exposed to PM2.5 through the modulation of the NF‐κB pathway and Th1/Th2 balance.