BACKGROUNDGenetic factors are believed to play a role in the individual susceptibility to chronic obstructive pulmonary disease (COPD). A single nucleotide polymorphism (SNP) of tumour necrosis factor-alpha (TNF-alpha) has been reported but inconsistent results may arise from different populations and phenotypes of COPD. There are only a few published studies of interleukin-13 (IL-13) SNPs on COPD. The SNPs of TNF-alpha and IL-13 have not been studied in the Chinese population. This research was conducted to study the frequencies of IL-13 gene promoter 1055 (IL-13-1055) and TNF-alpha gene-308 polymorphisms in the patients with COPD and to investigate the effect of those genetic polymorphisms on COPD in the Chinese population.

METHODSA cohort of COPD patients and age matched controls were recruited from an inpatient hospital service in Beijing. Venous blood was obtained and genomic DNA was extracted from peripheral blood monocytes using standard method. Genomic DNA was used as a template for amplification by polymerase chain reaction (PCR) to determine the polymorphism at -1055 in the IL-13 gene promoter region. PCR restriction fragment length polymorphism (RFLP) was used to determine polymorphisms in the TNF-alpha gene-308 position. The products were investigated by sequence analysis also.

RESULTSOne hundred and eleven COPD patients and 97 controls were studied. Seventy-five cases were current smokers in COPD patients and 36 were current smokers in controls. The frequencies of TT genotype in the IL-13 gene promoter region were 11.7% (13/111) in the COPD group and 13.4% (13/97) in the controls (P = 0.713). However, the OR value of TT genotype was significantly increased to 6.4 (95% CI 1.62 - 25.39) in the smokers with COPD. TT genotype was also positively related to family history of COPD, OR = 7.7 (95% CI 1.37 - 43.80). The frequencies of A allele in the TNF-alpha gene were 5.9% in COPD and 3.1% in controls (P = 0.131). The OR value of A allele was 5.0 (95% CI 1.011 to 25.059) in smokers with COPD.

CONCLUSIONSThere is no significant difference in the frequencies of the TT genotype of IL-13-1055 or the A allele of the TNF-alpha between Han Chinese patients with COPD versus control. Thus, it does not appear that these SNPs are independent factors in COPD for Han nationality in Beijing. However, these SNPs may increase the risk of COPD among smokers.