Effects Of Budesonide On Nitric Oxide Synthase And Endothelin In Mice With Allergic Asthma

Background: Asthma is a complex syndrome with many clinical phenotypes, but in all of these, airway hyperresponsiveness (AHR) associated with airway remodeling and inflammation are central processes. The pathological process is linked to chronic inflammation, which is responsible for airway hyperresponsiveness following the infilitration and accumulation of inflammatory cells and the remodeling of the airway. These cells, as well as mast cells and lung resident macrophages, release a series of mediators and cytokines that are responsible for induction and maintenance of the airway inflammation. Nitric oxide (NO) and endothelin (ET) seems to have an important role in asthma. It has been demonstrated that the plasma concentration of NO and ET-1 in asthmatic was significantly higher than the control subject. Moreover, the study noted there was a significant positive correlation between NO and ET-1[1]. Inhaled corticosteroids (ICS) are currently considered to be the most effective means of reducing airway inflammation, symptom, and morbidity in children with asthma[2]. But the exact mechanisms by which they work are not fully understood. The purpose of this study was to investigate the effects of budesonide (BUD) on nitric oxide synthase (NOS) and ET in serum, bronchoalveolar lavage fluid (BALF), and lungs of mice with asthma and to explore its molecular mechanism.Objective: Using mature asthmatic model of mouse, we observed the effects of BUD on NOS and ET in asthmatic mice and to explore its role on asthma.Methods: Thirty female BALB/c mice (6~8weeks old, 20~22g) were randomly divided into three groups:Asthmatic model group (A): Ten mice were sensitized by 0.2ml allergen solution (containing 0.01% OVA 0.1ml and imject alum 0.1ml) individually through intra- peritoneal injection on day 1, day 8 and day 15, seven days after sensitization, the mice were challenged with aerosolized 1%OVA solution for 30 minutes once daily on days 22 to 28.BUD therapy group (B): Ten mice were treated with inhalation of 0.2mg BUD aerosol for 30 minutes per day before inhaled OVA on days 22 to 28, and then managed just as group A.Normal control group (C): Ten mice were treated with normal saline instead of aerosolized OVA.BALF, peripheral blood (PB) and lung tissue were collected at 12 hours following the final allergen challenge respectively. The symptom was observed. The leukocytes and eosinophils were determined in BALF and lung homogenate. NOS and ET were measured with radioimmunoassay in serum, BALF and lung homoge- nate. To show the inflammation cells infiltration and mucus production, the histology of lung tissue was also observed.Results:1. The symptom and physical sign: After the antigen challenged, as compared with group C, the symptom and physical sign were obvious in group A. Allergen challenge also increased the respiratory frequency measured in group A when compared with group C. But there were no differences between group B and group C.2. The changes of the total number of leukocytes and the percent of eosinophils in BALF and lung homogenate after inhaled BUD :The number of inflammatory cells and the percentage of eosinophils (Eos%) in both BALF and lung homogenate in group A were significantly increased when compared with group C (P<0.01). BUD treatment significantly attenuated the increases in BALF and lung homogenate, respectively. But the scores were still remained differences from group C (P<0.05).3. The effects of BUD on the levels of TNOS,iNOS,cNOS and ET-1 in BALF, serum, and lung homogenate:Either the activity of TNOS,iNOS,cNOS or the levels of ET-1 was significantly increased in BALF, serum and lung homogenate in group A compared with group C, respectively. And obviously in the lung homogenate. A positive correlation was observed between iNOS and ET-1 in the serum, BALF and lung homogenate of group A (P<0.01). BUD treatment did have a significant effect on the activity of TNOS,iNOS,cNOS , there were no differences between gpoup B and group C. However, this same treatment significantly attenuated ET-1 increases in BALF, serum, and lung homogenate, respectively. But still have differences compared with group C(P<0.05). 4. The effects of BUD on the pathomorphology of lung tissues: Obviously infiltration of inflammatory cells and proliferation of goblet cells as well as enhancement of mucus and smooth muscle hyperplasia and remodeling could be seen in the lungs of asthmatic mice (group A). Treatment with BUD effectively reduced the above mentioned. No significantly difference was found between group B and C.Conclusions:1. The results of this study have identified NOS and ET as potentially important mediators play important role in the pathogenesis of asthma.2. The relationship between iNOS and ET was obviously positive correlativity. It shows there were synergistic effects between iNOS and ET, and they may aggravate the development of asthma.3. BUD can effectively decreased the airway inflammatory cells infiltration and the levels of NOS and ET in serum, BALF and lung tissues of mice with OVA sensitized/challenged asthma, the mechanism of the effects may be related to down-regulation the expression of them in lung tissues caused by BUD. But the suppression was imperfectly, and there were being a long time to control the airway inflammation if once it was indeed.