The p53 signaling pathway may be important for the pathogenesis of emphysematous changes in the lungs of smokers. Polymorphism of p53 at codon 72 is known to affect apoptotic effector proteins, and the polymorphism of mouse double minute 2 homolog (MDM2) SNP309 is known to increase MDM2 expression. The aim of this study was to assess polymorphisms of the p53 and MDM2 genes in smokers and confirm the role of SNPs in these genes in the pathogenesis of pulmonary emphysema.
365 patients with a smoking history were included in this study, and the polymorphisms of p53 and MDM2 genes were identified. The degree of pulmonary emphysema was determined by computed tomography scanning. SNPs, MDM2 mRNA and p53 protein levels were assessed in human lung tissues from smokers. Plasmids encoding p53 and MDM2 SNPs were used to transfect human lung fibroblasts (HLFs) with or without cigarette smoke extract (CSE), and effect on cell proliferation and MDM2 promoter activity were measured.
The polymorphisms of p53 and MDM2 genes were associated with emphysematous changes in the lung, and were also associated with p53 protein and MDM2 mRNA expression in the lung tissue samples. Transfection with a p53 gene-coding plasmid regulated HLFs proliferation, and the analysis of P2 promoter activity in MDM2 SNP309-coding HLFs showed the promoter activity was altered by CSE.
Our data demonstrate that p53 and MDM2 gene polymorphisms are associated with apoptotic signaling and smoking-related emphysematous changes in the lungs from smokers.