Four SNPs and Systemic Level of FOXP3 in Smokers and Patients with Chronic Obstructive Pulmonary Disease

Forkhead box P3 (FOXP3) is the essential transcription factor for the function of regulatory T-cell (Treg). However, the gene mutation of FOXP3 in patients with chronic obstructive pulmonary disease (COPD) at different stages has not been reported. We aim to investigate four single nucleotide polymorphisms (SNPs) and the mRNA expression of FOXP3 in smokers with normal lung function and smokers with COPD at different stages. FOXP3 mRNA expression and SNPs in FOXP3 were assessed in nonsmokers with normal lung function (N), smokers with normal lung function (S), smokers with COPD in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 or 2 grade (COPD 1-2), and smokers with COPD in GOLD 3 or 4 grade (COPD 3-4). In peripheral blood sample, FOXP3 mRNA was assessed using real-time quantitative PCR and SNPs were analyzed by TaqMan PCR. FOXP3 mRNA level in peripheral blood sample was decreased when COPD was aggravated. The frequency of FOXP3 rs5902434 genotype del/del and allele del are lower in COPD 1-2 and COPD 3-4 than that in N or S. The rs5902434 genotype del/del and allele del were, respectively, associated with decreased risk of COPD and lung function decline. The rs5902434 genotypic distribution was correlated with FOXP3 mRNA level. In conclusion, both FOXP3 rs5902434 genotypes and alleles were differently distributed in COPD patients and smokers with normal lung function. The distribution of del/del genotype was associated with systemic expression of FOXP3 mRNA. More research is needed to explore the role of FOXP3 gene polymorphism in immunoinflammation of COPD.