Tumor necrosis factor receptor 2 as a possible marker of COPD in smokers and ex-smokers

Abstract

Introduction

Oxidative stress and systemic inflammation are higher in smokers and patients with COPD; however, markers that may help differentiate between smokers and patients with COPD have not yet been identified. We hypothesized that tumor necrosis factor-alpha receptor (TNFR) and soluble form of the receptor for advanced glycation end products (sRAGE) can be indicators of COPD in asymptomatic patients.

Patients and methods

We evaluated 32 smokers (smoking history >10 pack-years), 32 patients with mild/moderate COPD (smokers and ex-smokers), and 32 never smokers. Concentrations of C-reactive protein (CRP), interleukin (IL)-6, TNFR1 and TNFR2, advanced glycation end products (AGEs), and the sRAGE were measured in serum.

Results

There were higher CRP and AGEs concentrations in smokers and in patients with COPD ( P<0.001 and P=0.01, respectively) compared to controls, without statistical difference between smokers and patients with COPD. Concentrations of sRAGE, IL-6, and TNFR1 did not differ between study groups. TNFR2 was significantly higher in patients with COPD than in smokers ( P=0.004) and controls ( P=0.004), and the presence of COPD ( P=0.02) and CRP ( P=0.001) showed a positive association with TNFR2. Positive associations for smoking ( P=0.04), CRP ( P=0.03), and IL-6 ( P=0.03) with AGEs were also found. The interaction variable (smoking × COPD) showed a positive association with IL-6.

Conclusion

Our data suggest that TNFR2 may be a possible marker of COPD in asymptomatic smokers and ex-smokers. Although smokers and patients with early COPD presented other increased systemic inflammation markers (eg, CRP) and oxidative stress (measured by AGEs), they did not differentiate smokers from COPD.