Interleukin-6 serum level and -597 A/G gene polymorphism in moderate and severe chronic obstructive pulmonary disease

Abstract

Inflammation is a major pathogenic pathway in pulmonary chronic obstructive disease (COPD). Interleukin-6 (IL-6) mediates the local and systemic immune response. The aim consisted in investigating the relationship between IL-6 serum levels and IL-6 -597A/G gene polymorphism (rs1800797) with COPD. Serum levels of IL-6 were determined using an enzyme-linked immune-sorbent assay, in 120 participants (60 COPD patients and 60 healthy subjects), from Transylvanian region. The IL-6 -597A/G gene polymorphism was investigated by high molecular weight genomic DNA extracted from the peripheral blood leukocytes, and subsequently analyzed by the Polymerase Chain Reaction Restriction Fragment Length Polymorphism (PCR-RFLP) technique. Smoking history, the severity of the disease, expressed by the GOLD stages, and arterial blood partial pressure of oxygen (PaO 2 ) levels were also investigated. COPD patients had significantly elevated blood levels of IL-6 when compared to the control group ( p < 0.05). The frequencies of AA, AG, and GG genotypes were 61.6%, 26.6%, and 11.6% in the COPD cases and 70%, 23.3%, and 6.7% in healthy subjects, respectively. There were no statistically significant differences in IL-6 rs1800797 genotypes and allele frequencies between cases and controls ( χ 2 = 0.54, OR = 1.29 and χ 2 = 0.21, OR = 1.48, respectively). Higher serum levels of IL-6 were found in the GG genotype subgroup in COPD patients. IL 6 levels are higher in COPD patients, where positively correlate with pack-year index, but not with clinical features. Although COPD patients did not have statistically different rs1800797 allele distribution compared to healthy subjects, the GG genotype is associated with higher IL6 serum levels.