Osteoprotegerin/sRANKL Signaling System in Pulmonary Sarcoidosis: A Bronchoalveolar Lavage Study

Osteoprotegerin (OPG), a soluble tumor necrosis factor receptor family molecule, protects endothelial cells from apoptosis in vitro and promotes neovascularization in vivo. Angiogenesis may be crucial for the course and outcome of sarcoidosis. In this study, we evaluated the clinical usefulness of OPG and its ligand, a soluble receptor activator of nuclear factor-kappaB (sRANKL), in bronchoalveolar lavage fluid (BALF) in patients with sarcoidosis (BBS, Besniera-Boeck-Schaumann disease). We studied 22 BBS patients and 15 healthy volunteers as a control group. The levels of OPG, sRANKL, and interleukin-18 (IL-18) were measured by the Elisa method. The BALF levels of sRANKL and IL-18 were higher in the BBS patients compared with controls [sRANKL: 2.12 (0.82-10.23) vs. 1.12 (0.79-4.39) pmol/l, p = 0.03; IL-18: 34.29 (12.50-133.70) vs. 13.05 (12.43-25.88) pg/ml, p = 0.001]. There were no significant differences between the concentration of OPG in the BBS patients and healthy controls [0.22 (0.14-0.81) vs. 0.23 (0.14-0.75) pmol/l]. In the BBS patients we found correlations between sRANKL and IL-18 in BALF (r = 0.742, p = 0.0001) and between OPG and lung diffusing capacity for carbon monoxide (DLCO) (r = -0.528, p = 0.029). Receiver-operating characteristic (ROC) curve was applied to find the cut-off for the BALF level of sRANKL (BBS vs. healthy: 1.32 pmol/l). We conclude that OPG and sRANKL may have usefulness in clinical evaluation of BBS patients.