Study On The Mechanisms Underlying The Action Of Curcumin On Mouse Model Of Allergic Rhinitis

Objective:Curcumin is widely employed in the treatment of a wide variety of allergic diseases, however, the mechanisms underlying its action on allergic rhinitis (AR) are still not clear. Therefore, the aim of this subject was designed to investigate the mechanism underlying therapeutic effects of curcumin on AR via establishment of the ovalbumin-induced mice model of AR, so as to offer the theoretical basis for the treatment of AR.Methods:Initially, a mouse model of allergic rhinitis was set up intra-peritoneal injection of movalbumin (OVA) and, subsequently, the mice were subjected to the intranasal intervention with curcumin. In this work, the mice were divided into four groups. As OVA-induced allergic rhinitis model was established, mice were randomized to three groups (Group A, B, and C) and the normal mice were taken as a control group. The mice in the three experimental groups were received the following agents by gavage and administered daily for 3 days:(A) normal saline, (B) curcumin (100 mg/kg), (C) curcumin (200 mg/kg), respectively. After the final intranasal allergen challenge with OVA, the frequencies of sneezing and nose scratching were counted for 20 minutes to evaluate early allergic responses. Hematoxylin and Eosin (HE) staining was used to assess the histological changes of nasal mucosa in response to curcumin. ELISA, Western Blot, and immunohistochemistry were employed to estimate the impact of curcumin on inflammatory mediators and cytokines so as to explore the mechanism by which curcumin exerts its inhibitory effects on AR. Lastly, data were presented as mean ± SD and each experiment repeated at least three times. The statistical significance of the difference between the values of control and treatment groups was determined by either Student t test or Prism version 5 (GraphPad Software, Inc.). Values of p<0.05 were considered statistically significant.Results:1. Effect of Curcumin on the nasal symptoms and histological injury of nasal mucosa in OVA-sensitized miceThree days after the OVA sensitization, the number of sneezing and nasal rubbing of mice in three groups were counted for 20 min. The symptoms of allergic rhinitis were compared to non-sensitized BALB/c mice. At doses of 100 and 200 mg/kg, curcumin significantly decreased the number of sneezing. Similar results were obtained with nasal rubbing in BALB/c mice model. Histological analysis of the nasal mucosa obtained from the OVA group revealed grossly typical pathologic features of AR in the submucosa which was infiltrated with numerous inflammatory cells. There were significant differences in the gross appearance of cross sections between curcumin-treated mice and control mice. At doses of 1009 mg/kg and 200 mg/kg, curcumin protected the nasal mucosa against damages and greatly reduced infiltration of eosinophils. Those data suggest that curcumin could prevent the allergic rhinitis symptoms.2. Effect of Curcumin on serological markers in OVA-sensitized miceThe effect of curcumin on allergic responses in vivo, the levels of histamine, OVA-specific IgE, TNF-? and Src kinases Fyn, Lyn and Syk were measured by ELISA of the serum of OVA-sensitized mice. The results showed that the administration of curcumin at doses of 100 and 200 mg/kg significantly decreased histamine levels in the serum of OVA-sensitized mice compared to untreated OVA-sensitized mice. In addition, OVA-specific IgE level was also significantly reduced by curcumin administration. Moreover, the level of the inflammatory cytokine TNF-a was significantly decreased in the curcumin-treated group. Furthermore, the kinase activity Src kinasesof Fyn, Lyn and Syk were also significantly decreased in the curcumin-treated group (Fig.2D-F). These results indicated that curcumin might have anti-allergic activity via suppression of allergic mediator production.3. Effect of curcumin on histamine and cytokine release from mast cellsOVA-induced histamine and cytokine release in HMC-1 cells were measured by ELISA. Curcumin significantly decreased the OVA-induced histamine levels in the cells. PMA-induced release of TNF-a, IL-1?, IL-6 and IL-8 from the mast cells was significantly decreased by curcumin. These results indicated that curcumin has anti-inflammatory effects on mast cells by inhibiting the production of inflammatory cytokines related to allergic reactions.4. Effect of curcumin on MAPK/NF-?B pathways in mast cellsThe signaling pathways of the MAPK molecules and NF-?B, a transcription factor, are important in the control of the synthesis and release of inflammatory mediators by activated mast cells during allergic inflammation. Therefore, to examine the effect of curcumin on signaling pathways in mast cells, the phosphorylation of three MAPK molecules ERK1/2, p38 MAPK, JNK and NF-?B p65 subunit were analyzed by Western blot analysis. Results showed that PMA stimulation rapidly induced the phosphorylation of ERK 1/2, p38 MAPK and JNK in the mast cells. In addition, curcumin significantly suppressed PMA-induced phosphorylation of ERK, p38 and JNK MAPKs. The non-phosphorylated levels of the MAPK molecules remained the same.Moreover, curcumin attenuated the PMA-induced phosphorylation of I?-Ba in cytosol and the nuclear translocation of NF-?B p65 in the mast cells. These findings indicate the potential role of MAPK/NF-?B pathways in the suppression of inflammatory mediators by curcumin in mast cell-mediated allergic inflammation.Conclusions:1. Curcumin is able to improve rhinitis symptoms and to protect nasal mucosa from the injury2. Curcumin exerts its anti-allergic effect via inhibiting the release of allergic mediators in OVA-induced allergic rhinitis mice.3. Curcumin exerts its anti-inflammatory effects by suppressing the production of inflammatory cytokines.4. Curcumin exerts anti-inflammatory and anti-oxidant activity at least in part via the MAPK/NF-?B pathways.