Decreased plasma sRAGE levels in COPD: influence of oxygen therapy

Chronic obstructive pulmonary disease (COPD) is associated with systemic inflammation and oxidative stress. N(ε) -(carboxymethyl) lysine (CML), an advanced glycation end product (AGE) and the soluble decoy receptor, sRAGE, are exciting new molecules linked to oxidative stress and inflammation. Here the levels of plasma sRAGE and CML were determined and their variation in relation to lung function, external long-term oxygen therapy (LTOT) and plasma levels of inflammatory molecules in COPD evaluated.

Plasma sRAGE and CML levels were measured by ELISA in 146 patients with stable COPD and 81 healthy subjects, subgrouped from a larger case-control study and matched for age, gender and pack-years smoked.

Decreased levels of plasma sRAGE and no significant difference in levels of plasma CML were found in patients with COPD in comparison with controls. In the total group, plasma sRAGE was positively associated with FEV(1) and forced vital capacity and negatively with pack-years smoked. In patients receiving LTOT, levels of plasma sRAGE were lower compared with those without LTOT. Only in controls, a weak correlation was found between plasma sRAGE and CML. sRAGE did not correlate with measured inflammatory markers, whereas CML was negatively correlated with fibrinogen.

Plasma sRAGE levels are lower in patients with COPD compared with healthy control subjects, and even lower levels in patients receiving LTOT. Because sRAGE correlated with lung function only in the whole group, sRAGE can be considered a marker of COPD, but not of disease severity. A lack of clear association between sRAGE, CML and systemic inflammation is furthermore evident.