| Asthma refers to a chronic airway inflammatory disease associated with many kinds of cells and inflammatory factors, which is characterized by variable airflow limitation, airway hyperresponsiveness, airway inflammation and increased inflammatory factor expression, airway remodeling and increased airway mucus hypersecretion. At present, there are many patients with refractory asthma, who are not sensitive to the conventional drugs for asthma, and they would eventually develop into severe asthma, which would lead to enormous economic burden on families and society. Therefore, it would be beneficial for the patients with refractory asthma to investigate molecular mechanisms of asthma and explore effective therapeutics, which would decrease improve the lung function of asthmatic patients and increase their survival rate.In the past, the primary pathogenesis of asthma was the imbalance of Th1/Th2paradigm, characterized by the over-responsiveness of Th2response.According to the epidemiological surveys, during the period of recent years, there is increasing number of atypical asthma. The scientists have carried out many scientific researches to it. With the discovery of some new Th cell cluster and the further study of their functions, the people tend to know more about the pathogenesis of asthma, which means that the mechanisms of asthma, as people knows, would be changed from the hypothesis of Thl/Th2imbalance to the immune disorder, which involved many Th cell populations such as Thl, Th2, Th9, Th17and Treg cells.Rapamycin (RAPA) is a white crystalline solid, and served as a lipophilic macrocylic lactone and immunosuppressant. At first, RAPA was studied as an antifungal with low-toxicity. In1977, it had been found RAPA had immunosuppressive effects. And with the further studies about it, we gradually got to know that RAPA can regulate T cells and other cells by inhibiting their process from G1to S. Since1989, RAPA has been used as treatment of drug trail for organ transplant rejection. During these recent ten years, there were some reports about that RAPA could regulate asthmatic airway inflammation. However, it is unclear that its roles in the prevention of anti allergic airway inflammation, and so on. Through establishing acute ovalbumin induced asthmatic model, we explore the effects of rapamycin on asthma and the related immune mechanisms.Objective:the aim of this study is to investigate the protective effects of rapamycin on asthma in mouse model, and explore the underlying regulatory mechanisms.Method:6-8week old C57BL/6mouse were given the new ID by their weight from small to large. By using the Random number table, the mouse was randomly divided into four groups of SHAM, SHAM+RAPA, OVA and OVA+RAPA. Group-SHAM:we provided the mouse of this group sensitization and challenge with PBS, and DMSO (i.p.,0.9ul DMSO/200ul PBS); Group-SHAM+RAPA:we sensitized the mouse by using PBS, and treatment of RAPA (i.p., lmg/kg), followed by PBS challenge; Group-OVA:we provided the mouse of this group sensitization and challenge with OVA, and DMSO (i.p.,0.9ul DMSO/200ul PBS); Group-OVA+RAPA: we sensitized the mouse by using OVA, and pre-treatment of RAPA (i.p.,1mg/kg)1hour before the OVA challenge. The mouse was sacrificed at the indicated time after the last OVA and PBS exposure. The BALF was harvested for counting the numbers of total cell and the classified cell as eosinophils, lymphcytes and neutrophils; the left lung lobes were removed for the pathological assay; we estimated the expression of some inflammatory factors and cytokine receptors in lung and spleen by Q-PCR, and we also examined the expression levels of cytokines of lung homogenate. What is more, the percentage of CD4+T cells, CD4+IL-17A+T cells and Treg cells were determined by using Flow Cytometry Assay.Results:An OVA-induced asthmatic mouse model was successfully established and confirmed by BALF cell counting, pathological assay and cytokine expression level. We gave the mouse systemic administration of rapamycin through intraperitoneal injection (i.p.)1hour before1%OVA challenge. Compared with group OVA, pre-treatment of RAPA significantly decreased the number of total BALF cells, eosinophils and lymphcytes (P<0.001) and the allergy induced neutrophilic infiltration was attenuated by RAPA (P<0.05). According to the pathological assay, the allergy exposure induced hyperplasia and hypertrophy of airway epithelium was alleviated (P<0.01), and production of mucus was decreased (P<0.001). Rapamycin also decreased the gene expression of Muc5AC at lung (P<0.05), down-regulated the expressions of inflammatory cytokines including IL-13, IL-17A, IL-25, and inflammatory cytokine receptor as IL-17RB. What is more, the percentage of both CD4+T cells and IL-17A-producing CD4+T cells were decreased (P<0.05) by RAPA, while the level of Treg was not significantly changed (P>0.05).Conclusion:Rapamycin pre-treatment has a protective effect on ovalbumin induced pulmonary inflammation. The underlying mechanisms may be due to down-regulate the expression of inflammatory cytokines and cytokine receptors, decrease inflammatory cell infiltration, inhibit the number and functions of IL-17A-producing cell, but not via regulating the number and functions of Treg cells. |
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