The Effects Of Montelukast On Eosinophilic Gastroenteritis In A Mouse Model

ObjectiveClinical study so far has demonstrated that montelukast, an oral leukotriene receptor antagonist, might be considered in patients with Eosinophilic gastroenteritis (EG). The aim of this study was to evaluate the effect of cysLTl receptor antagonist montelukast on oral ovalbumin (OVA) allergen induced EG inflammation in mice and to suggest some mechanisms underlying this effect.Methods50female BALB/c mice were randomly divided into two experimental groups: normal control group (n=10), OVA treatment group (n=40).The OVA treatment group was sensitized intraperitoneally on day1(50μg of OVA adsorbed to1mg of aluminum hydroxide adjuvant) and day15(50μg OVA) and challenged intragastrically on three occasions with ovalbumin on days20,22and24(50mg OVA) to induce gastro-intestinal eosinophilic inflammation. The control group was sensitized and challenged with Phosphate buffer saline (PBS) instead of OVA. Gastrointestinal symptoms were observed after challenged intragastrically with OVA and blood samples were collected from different groups of mice for blood eosinophil quantitation and serum IgE level testing. Ten mouse were randomly sacrificed (2mice in the normal control group and8mice in OVA treatment group) for histological analysis of stomach and jejunum, to validate the model successful. Then OVA treatment group were randomly divided into model group, montelukast group (MK group), prednisone group, MK and prednisone combination group.There were8mice in each group. The drug treatment groups were administered with prednisone (3mg/kg) and montelukast (1.5mg/kg) once daily from d26to d39. On day40, blood samples were collected from different groups of mice for blood eosinophil quantitation. At the end of experiment, mice were sacrificed. The levels of blood IgE, LTD4were determined by ELISA. A part of jejunal tissue was homogenized for ELISA analysis [eotaxin-1and inter-leukin-5(IL-5)]. Their gastrointestinal tract processed for histopathology using a light microscope and an image analysis system.Another portion of jejunal tissue was fixed with4%paraformaldehyde for major basic protein (MBP) immunohistochemistry.Expression level of cysteinyl leukotriene receptors-1(CysLTRl) mRNA in gastrointestinal tissues was determined by quantitative PCR.Results1. Clinical symptomsMice in normal control group hair luster, spirit was good, the activity was normal. After stimulate gastrointestinal allergy, mice in OVA treatment group of decreased activity and had poor spirit, piloerection, diarrhea symptoms. Given drug treatment2weeks, the symptoms in mice were improved compared with model group. All drug treatment groups had no significant difference.2. Body weightThe body weights of OVA-challenged mice were statistically lower than that in normal control group (20.65±0.78g vs21.25±0.88g,p<0.05), but this adverse effect was blocked by treatment with montelukast or prednisone. Body weights in MK and prednisone combination group, MK group and prednisone group were statistically higher than that in model group (20.91±0.83g#,21.30±1.16g##,21.31±1.00g##vs19.69±0.91g,#P<0.05,##P<0.01). There were no significant differences among the three drug treatment groups (P>0.05).3. Blood eosinophil quantitationThe level of blood eosinophil in OVA-challenged mice was significantly increased compared with normal control mice [12.00±2.82(×109/L) vs6.45±1.92(×109/L),P<0.01]. However, continuous treatment with montelukast or prednisone could significantly improve this parameter. The level of blood eosinophil in MK and prednisone combination group, MK group and prednisone was statistically lower than that in model group [(14.38±4.14(×109/L)##、16.38±2.67(×109/L)#、13.88±3.80##(×109/L) vs21.13±4.88(×109/L),#P<0.05,##P<0.01]. There were no significant differences among the three drug treatment groups (P>0.05).4. Histological analysis of stomach and jejunumIn normal control mice, the gastrointestinal mucosa layer is integrity. There were no gastric ulcer focus, hyperemia and edema. On histopathological examination, stomach tissues from OVA-challenged mice showed wide spread structure disorder, thinning, fracture and diffused cloudy swelling as compared with normal control group. Infiltration of the submucosa, muscularis propria, and subserosal connective tissue by eosinophils were all abnormal in these animals. In addition, mucosal edema, focal necrosis and infiltration by eosinophils into lamina propria as well as muscularis propria were also obvious in OVA-challenged mice jejunum. After treated with montelukast or prednisone, gastrointestinal tissues became typical of normal structure or mild architectural damage.5. Expression of MBP in intestinalMBP expression was increased in OVA-challenged mice when compared to control group. However, continues treatment with montelukast or prednisone significantly reversed this pathological change.6. The level of IgE in serumThe level of IgE in OVA-challenged mice was significantly higher than that in normal control group (249.90±28.66ng/ml vs174.24±17.09ng/ml, p<0.01). However, administration of montelukast or prednisone to oral OVA-challenged mice significantly reduced these levels. The levels of IgE in MK and prednisone combination group, MK group and prednisone were statistically lower than those in model group (220.78±21.02ng/ml#,214.36±19.66ng/ml##,202.68±16.97ng/ml##vs243.17±17.48ng/ml,#P<0.05,##P<0.01). There were no significant differences among the three drug treatment groups (P>0.05).7. The level of LTD4in serumThe level of LTD4in OVA-challenged mice was significantly higher than that in normal control (174.73±19.55ng/ml vs109.38±14.90ng/ml, P<0.01). Administration of montelukast to oral OVA-challenged mice significantly reduced these levels (126.39±35.93ng/ml,131.23±29.68ng/ml vs174.73±19.55ng/ml, p<0.01).However, administration of prednisone to oral OVA-challenged mice could not reduce these levels (159.31±45.13ng/ml vs174.73±19.55ng/ml,p>0.05).8. The expression of CysLTRl mRNA in intestinal tissuesAfter drug treatment, the expression level of CysLTR1mRNA in intestinal tissues of model group and normal group, there were significant differences (2.21±0.22vs1.16±0.36, P<0.05). MK and prednisone combination group,MK treated group compared with model group, there were significant differences (1.71±0.54#、1.63±0.33##vs2.21±0.22,#P<0.05,##P<0.01). Prednisone group and model group, there was no significant difference (2.01±0.26vs2.21±0.22, P>0.05). There were no significant difference among the three drug treatment groups (P>0.05).9. The content of IL-5in intestinal tissueRepetitive OVA challenge in mice induced a significant increase in the contents of IL-5when compared with non-OVA-challenged animals (162.59±17.93ng/g vs103.90±12.48ng/g, p<0.01). However, chronic continuous treatment with montelukast or prednisone could significantly improved these parameters compared with model group (127.29±30.96ng/g##,136.20±25.50ng/g#,113.57±34.26ng/g##vs162.59±17.93ng/g,#P<0.05,##P<0.01). There were no significant differences among the three drug treatment groups (P>0.05).10. The eotaxin-1content of intestinal tissueThe contents of eotaxin-1were increased significantly in OVA-challenged mice when compared with non-OVA-challenged animals (468.92±59.97ng/g vs291.77±50.77ng/g, p<0.01). Administration of montelukast to oral OVA-challenged mice significantly reduced these contents. MK and prednisone combination group, MK treated group compared with model group, there were significant differences (364.19±75.81ng/g,394.99±30.00ng/g vs468.92±59.97ng/g,p<0.01). However, administration of prednisone to oral OVA-challenged mice could not reduce these contents (424.77±53.77ng/g vs468.92±59.97ng/g, P>0.05). There were no significant differences among the three drug treatment groups (P>0.05).Conclusion1. Treatment with montelukast can improve clinical symptoms, decrease peripheral blood EOS and repair of gastrointestinal tissue damage in a mouse model of EG. This therapy is effect. The efficacy of montelukast as similar as prednisone.2. The level of serum LTD4and the expression of CysLTR1mRNA in jejunal tissue are significantly higher in a mouse model of EG. It may indicate that the leukotrienes play important role in the pathogenesis of EG mice.3. Montelukast can reduce inflammation and promote the recovery of gastrointestinal function by combined with CysLTR1and decrease of EOS.IgE and LTD4levels. It can attenuate intestinal IL-5and eotaxin-1contents in a mouse model of EG. Furthermore, these activities appeared to be mediated by inhibiting the expression of MBP and thus regulating the inflammation response.In conclusion, montelukast can reduce the inflammatory response in a mouse model by inhibiting EOS, IgE, LTD4, IL-5and Eotaxin-1pathway. Its efficacy is as well as prednisone.