Serum levels of CD163 and TWEAK in patients with pulmonary arterial hypertension

Background: Inflammation may play a pivotal role in the pathogenesis of pulmonary arterial hypertension (PAH). We evaluated the concentrations of serum sTWEAK, its scavenger receptor sCD163 and sTWEAK/sCD163 ratio in patients with PAH.

Design: The study enrolled 26 stable patients with PAH confirmed by right heart catheterization and 24 healthy volunteers matched for age, sex and body weight. All patients underwent transthoracic echocardiography, cardiopulmonary exercise test, 6-min walk test, measurement of lung diffusing capacity for the carbon monoxide (DLCO) and venous blood tests. Concentrations of sTWEAK and sCD163 were determined using ELISA kits.

Results: The PAH patients were characterized by significantly higher median serum sCD163 levels (1072 vs 890ng/ml, p=0.04) together with lower serum sTWEAK concentrations (200 vs 278.1pg/ml, p=0.003) comparing to control subjects. sTWEAK/sCD163 ratio was therefore significantly lower in PAH group (0.18 vs 0.33, p=0.0005). No correlation was found between sTWEAK and sCD163 concentrations in both groups. We observed statistically significant inverse correlation between peak VO2 consumption and sCD163 concentrations (r=-0.52, p<0.05) and positive with sTWEAK/sCD163 ratio (r=0.45, p<0.05) in PAH group. Moreover, sTWEAK/sCD163 ratio positively correlated with % of predicted values of DLCO (r=0.42, p<0.05).

Conclusions: Patients with PAH present altered serum sTWEAK and sCD163 levels. The sTWEAK/sCD163 ratio appears to be a better indicator of the severity of PAH as compared to sTWEAK or sCD163 alone. The exact role of sCD163 or interaction between CD163 and sTWEAK in the initiation or progression of PAH as well as their potential prognostic significance remains to be established.