The Research Of ADAM33 Gene In Bronchial Asthma

BackgroundAsthma as anallergic disease has rapidly become an important public health problem. Asthma is a very common chronic disease involving genetic and environmental factors and it has a high heritability, involing many genes have been identified in its pathogenesis. Some studies have shown that a number of genes and their polymorphisms contribute to asthma occurrence and/or severity. Asthma can be said to be a complex genetic disease in which there are multiple genetic effects interacting with the environment to modify susceptibility and severity of this disease. A disintegrin and metalloproteinase 33 (ADAM33), a novel member of the ADAM family, has been one of the most exciting candidate genes for asthma since its first association with the disease in Caucasian population. Recently, Studies on the association of ADAM33 gene polymorphisms with risk of asthma are controversial; some found a positive association, whereas in others such association is negative. We therefore focused on testing the hypothesis that either SNPs of the ADAM33 gene may be associated with asthma risk in Shandong han population, we selected four polymorphic sites (F+1, S2, T2, and V4) for genotyping. Through the research of the association of ADAM33 gene polymorphisms with asthma, we hope to improve our knowledge about ADAM33 gene and further understand the pathogenesis of asthma. Early screening can help early intervention in asthma, and then reduce the occurrence of asthma and guide the corresponding therapy.ADAM33 has been shown to be expressed in lung fibroblasts and bronchial smooth muscle and the protein has been detected in lung tissue, smooth muscle cells and fibroblasts, playing a major role in airway remodeling. It' s not long since ADAM33 gene was found, so few studies were related about ADAM33. It remain unclear the relationship between the ADAM33 expression and functional changes with airway remodeling in asthma. In present study, we researched ADAM33 expression and the airway remodeling in mouse model of chronic asthma induced by ovalbumin sensitisation. The effect of inhaled budesonide intervention on airway remodeling and ADAM33 expression compared with systemic dexamethasone treatment was described. We hope to clarify its role in the mechanism and evaluate its relationship with airway remodeling and the value of early intervention with budesonide. The research contents were divided into two parts as below.Part I:Association of ADAM33 gene polymorphisms with asthma in Shandong populationOBJECTIVEThe aim of this study was to evaluate the potential relationship between polymorphisms of ADAM33 and asthma in a Han population in SHANDONG province of China.METHODSA case-control study was conducted in Han population of SHANDONG province of China. A total of 126 asthma patients and a control group of 121 healthy volunteers were recruited for this study. Four polymorphic sites (F+1, S2, T2, and V4) were selected for genotyping. Genotypes were determined by the Allele-Specific Polymerase chain reaction (AS-PCR) with Fluorescence Melting Curves and DNA sequencing method. All statistical analyses were carried out using the SPSS13.0 statistical software package. Analysis of variance, t test and chi-square test were used for statistics.RESULTSDeviations from Hardy-Weinberg equilibrium were not observed in the asthma or control group for any polymorphisms (P>0.05). The genotype and allele frequencies were compared between the two groups. Statistically significant differences in the distributions of the S2 site between patients and controls were observed. The G allele of the SNP S2 was significantly more common in the asthma group than in the control group (x2=5.122 P=0.02<0.05). This result suggested that the SNP S2 in the exon 19 of ADAM33 gene was significantly associated with asthma in Han population of SHANDONG province of China. There was an increased risk for asthma associated with a G allele (odds ratio= 1.59; 95% confidence interval 1.06-2.38). But no significant differences were found with asthma severity (x2=0.335, P=0.855> 0.05) and lung function decrease. As to the F+1, T2 and V4 polymorphism, there were no difference in genotype distribution between asthmatics and the control group (x2=1.638 P =0.44>0.05; x2=1.050 P=0.59>0.05; and x2=0.369 P=0.83>0.05, respectively).CONCLUSIONThese preliminary results suggest an association between ADAM33 polymorphisms S2 C/G and asthma in Han population in SHANDONG province of China. But no association were found between ADAM33 polymorphisms S2 and asthma severity or lung function decrease. The SNPs (F+1 C/T, T2 G/A, and V4 C/G) of the ADAM33 gene may be the causal variants in asthma disease, but the strength of this evidence is limited by our small sample size.PartⅡ:The research of the expression of Adam33 gene and the effects of Budesonide in the ovalbumin sensitized and challenged miceOBJECTIVETo observe the changes of airway inflammation and remodeling in a murine model of chronic asthma and effects of Budesonide(BUD) on it.METHODS Twenty-four BALB/c mice were divided into 4 groups(6 in each group) including group A [ovalbumin(OVA) sensitized/challenged mice], group B (saline sensitized/challenged mice), group C(OVA sensitized/challenged mice treated by deximesone)and group D(OVA sensitized/challenged mice treated by BUD). Bronchial alveolar lavage fluid was performed and cell differential was examined by Wright-Giemsa staining; Pathological slides were prepared stained with hematoxylin-eosin and Masson's Trichrome. The total bronchial wall area (WAt/Pbm) and the bronchial smooth muscle area (WAm/Pbm) were measured by using image analysis system. The levels of IL-4,IL-5,IFN-γand TGF-β1 in sera were tested by enzyme linked immunosorbent assay(ELISA). Allele-Specific Polymerase chain reaction (AS-PCR) was used to determine the expression of ADAM33 gene.RESULTSIn group A the total cell count and the percentage of eosinophils in BALF were markedly elevated as compared with group B (P<0.05). Levels of IL-4, IL-5 and TGF-β1 in group A were increased and IFN-γdecreased significantly compared with those in group B(P<0.05), that of C and D group different statistically significant than A and B group (P<0.05).There was no difference between group C and D(P>0.05). Pathology examination on mice airway epithelial tissue in group A showed the increased thickness of airway smooth muscle and Collagen deposition than in group B(P<0.05), while that in group C and D reduced obviously than group A (P<0.05). Compared with that in B group, WAt/Pbm and WAm/Pbm of group A increased significantly (P<0.05), while that of C and D group both reduced statistically significant than A group(P<0.05). There was no difference between group C and D(P>0.05). There was a significantly increase of ADAM33 mRNA expression level in group A than in group B (P<0.05), and it was much lower in group C and D than in group A (P<0.05). No significant differences were found in group C with group D(P>0.05). There was a significant positive correlation of ADAM33 mRNA expression with serum TGF-β1 (r=0.919, P<0.05), but no significant correlation with IL-4,INF-γor IL-5 (r=0.589,-0.116 and 0.443, P>0.05)。CONCLUSIONAirway remodeling could occur in the chronic asthma. The effect of Early intervention with BUD might partially inhibits its process via lower expression of ADAM33 in chronic asthma.