Inflammatory Biomarkers Interleukin 1 Beta (IL-1β) and Tumour Necrosis Factor Alpha (TNF-α) Are Differentially Elevated in Tobacco Smoke Associated COPD and Biomass Smoke Associated COPD

Chronic obstructive pulmonary disease (COPD), the leading cause of mortality and morbidity worldwide, is characterized by abnormal activation of inflammatory cells. The increased pro-inflammatory cytokines, such as tumour necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), further amplify the inflammation. We evaluated the dose response relationship of IL-1β and TNF-α levels and severity of airflow limitation, and differential responses in IL-1β and TNF-α between biomass COPD (BMS-COPD) and tobacco smoke COPD (TS-COPD) using a case control design in 160 subjects. Patients with COPD had higher serum levels of both IL-1β and TNF-α compared to healthy controls. A large difference in TNF-α was observed between TS-COPD and BMS-COPD, where TS-COPD patients had much higher levels. Serum IL-1β levels were higher in BMS-COPD. Levels of IL-1β correlated better with severity of airflow limitation than TNF-α levels. Both TNF-α and IL-1β levels had a negative linear relationship with Forced Expiratory Volume in 1st second (FEV1) and six-minute walk distance. The correlations were stronger with FEV1 than six-minute walk distance. The correlations of TNF-α and IL-1β with St George Respiratory Questionnaire (SGRQ) scores and body mass index (BMI) were not significant. In conclusion, the levels of pro-inflammatory cytokines TNF-α and IL-1β are differently elevated in TS-COPD and BMS-COPD, respectively.