Experimental Studies On The Relationship Between Peroxisome Proliferator-activated Receptorγ (PPAR-γ) And Bronchial Asthma

Introduction and ObjectiveAsthma is a chronic IFNlammatory disorder of the airways in which many cell types play a role. Eosinophil response appears to be a critical feature in asthma. Eosinophils play an effector role by release of proIFNlammatory mediators, cytotoxic mediators, and cytokines, resulting in vascular leakage, hypersecretion of mucus, smooth muscle contraction, epithelial shedding, and bronchial hyperresponsiveness. These cells are also involved in the regulation of the airways IFNlammation and in the initiation of the remodeling process by the release of cytokines and growth factors.Thiazolidinediones, such as rosiglitazone, are high-affinity ligands for peroxisome proliferator-activated receptorγ(PPARγ), a transcription factor of the nuclear hormone receptor superfamily, and are used as insulin-sensitizing drugs in type II diabetes mellitus. PPARγis originally known to regulate adipocyte differentiation and lipid metabolism. However, accumulating evidence indicates that PPARγaffects cell cycle, differentiation, and apoptosis. In addition, PPARγis also associated with anti-IFNlammatory responses.PPARγactivation down-regulates synthesis and release of immunomodulatory cytokines from various cell types. Some evidence indicates that PPARγmay be involved in airway IFNlammation and remodeling in patients with asthma.We have used a mouse model for asthma to determine the effect of PPARγagonists, rosiglitazone and PPARγon allergen-induced bronchial IFNlammation.In this experiment we investigate the expression of PPARγin asthmatic mouse airway and its sence .the effect of PPARγand its agonist Rosiglitazone on airway IFNlammation in mice .to know the effect of BUD on the expression of PPAR in airway IFNlammation and whether Rosiglitazone can inhence the Anti-IFNlammatory effect of BUD.Methods50 female BALB/c mice, 8-10 weeks of age, were divided into 5 groups: matched Rosiglitazone treatment group(A),Rosiglitazone+ BUD treatment group (B). BUD treatment group (C), asthma group (D), and control group (E). Mice were sensitized on days 1 and 14 by intraperitoneal injection of 20μg ovalbumin emulsified in 1 mg of aluminum hydroxide in a total volume of 200μl. on days 21-27, after the initial sensitization, the mice were challenged for 30 min with an aerosol of 3% (w/v) OVA in saline (or with saline as a control) using an ultrasonic nebulizer Rosiglitazone dissolved in distilled water was administered in group A and B 7 times by oral gavage at 24 h intervals on days 19-25, beginning 2 days before the first challenge.Serumal levels of IL-4 and IFN-γwere quantified by enzyme immunoassays according to the manufacturer.s protocol.In group Band C, BUD was administrated by airway 30min before challenge once for 30min every 24 hours. To count the EOS in the BALF to observe the lung tissue with microscope.To detect the serum level of IL-4 and IFN-γand detect PPARγmRNA, IFN-γmRNA, IL-13mRNA in the lung by ELISA. pathological section of lung was stained by immunohistochemistry and calculated positive cells. Results1. Effect of rosiglitazone on numbers of eosinophils in BAL fluids Numbers of eosinophils were increased significantly after OVA inhalation compared with levels after saline inhalation. The increased numbers of eosinophils in BAL fluids after OVA inhalation were significantly reduced by the administration of rosiglitazone. EOS of Group D is significant ly higher than others.GroupAand Bwas lower than D, however, A was still higher than C, that is, rosiglitazone can reduce EOS, but isnot as good as BUD.2. Effect of rosiglitazone on pathological changes of OVA-induced asthmaHistologic analyses revealed typical pathologic features of asthma in the mice in group D.Numerous IFNlammatory cells, including eosinophils, IFNiltrated around the bronchioles, and mucus and debris had accumulated in the lumen of bronchioles compared with the control. Mice in group A and B,which were treated with rosiglitazone showed marked reductions in the IFNiltration of IFNlammatory cells in the peribronchiolar region, in the number of IFNlammatory cells, and in the amount of debris in the airway lumen.The scores of total lung IFNlammation were increased significantly after OVA inhalation compared with scores after saline inhalation. The increased lung IFNlammation after OVA inhalation were significantly decreased by the administration of rosiglitazone. These results suggest that rosiglitazone inhibit antigen-induced IFNlammation in the lungs, including the IFNlux of eosinophils.Score of IFNlammatory cell in lung showed that D is the highest ,E is lowest, C is lower than A .so rosiglitazone can reduce the IFNlammation of EOS, but is not as good as BUD.3. Effect of rosiglitazone on level of IL-4 and IFN-γin serum.level of IL-4 in serum. Increased after chanllenge, with the descreasing of IFN-γ. IL-4 level of A and B reduced but still higher than C, and the increasing of IFN-γis still lower than C.so rosiglitazone can reduce the increasing IL-4 and increase the reducing IFN-γas BUD, but is less than the latter. Rosiglitazone only is less than BUD, however, using Rosiglitazone and BUD together is better than the latter .Perhaps There is some synergistic effect.4. Effect of rosiglitazone on level of PPAR-γmRNA expressing and positive cells in immunohistochemistry.After OVA inhalation, the PPARγexpressing increased and even further after Rosiglitazone administrated.The PPARγmRNA expressing level of D is higher than E ,and A and Bis even higher than D,C and E. C is lower than D .PPAR-γpositive cells in immunohistochemistry of D is more than E .A and B is more than D,C and E . C is less than D .5. Effect of rosiglitazone on level of IL-13 mRNA and IFN-γmRNA expressingLevel of IL-13 mRNA expressing in A, B, Cand E is lower than D. A is higher than B and C .So rosiglitazone can reduce the increasing expressing of IL-13mRNA, that is, may have the role of anti-IFNlammatory ,but is not as good as BUD.expressing level of IFN-γmRNA in E is higher than others. The serum level of IFN-γin A, B and C is higher than D. B is the highest and A is the lowest of the three. It seems that rosiglitazone can raise the reducing expressing level of IFN-γmRNA. mroeover, it is not as good as BUD, but it is better than BUD when together with the latter .So, Perhaps There is some synergistic effect.with rosiglitazone and BUD . Conclusion.1. PPARγperhaps has some anti-IFNlammatory role in asthma airway IFNlammation.2. The increasing expressing level of PPARγmRNA in asthma mice may be some protective reaction. The expressing level of PPARγmRNA in asthma mice lung is even higher after the administration of rosiglitazone.3. BUD can reduce the expressing level of PPARγmRNA in asthma mice lung.4. Administration of rosiglitazone can reduce the level of IL-4 and increase the level of IFN-γ.Rosiglitazone may make an anti-IFNlammatory role by interfering the Th2 pathway.5. Rosiglitazone can reduce the airway IFNlammation in asthma mice, but it is not as good as BUD.6. There is some synergistic effect .with rosiglitazone and BUD.7. Rosiglitazone may be ancillary drug of glucocorticosteroid in treating asthma.