Angiopoietin-2 levels are elevated in exudatative pleural effusions

Objective: To examine the pleural fluid (PF) and serum levels of angiopoietin (Ang)-1, Ang-2, and vascular endothelial growth factor (VEGF) in patients with pleural effusions (PEs). Methods: One hundred fifteen patients, 16 with transudative PEs due to heart failure and 99 with exudative PEs (malignant, 40; parapneumonic, 24; tuberculous, 13; miscellaneous etiologies, 22) were included in the study. PF and serum levels of the growth Factors were measured using enzyme-linked immunosorbent assay. Results: PF Ang-2 and VEGF levels but not Ang-1 levels were higher (p < 0.001) in exudates than in transudates. PF Ang-2 levels were higher in tuberculous PEs than in PEs of any other etiology and were lower in heart failure PEs than in PEs of any other etiology. The highest PF VEGF levels were observed in patients with malignant and parapneumonic PEs. The lowest PF VEGF levels were observed in patients with transudates. In PEs, Ang-2 levels correlate with VEGF levels (p < 0.001), RBC count (p = 0.002), nucleated cell count (p < 0.001), total protein levels (p < 0.001), and lactate dehydrogenase levels (p < 0.001). PF Ang-1 levels were lower than serum Ang-1 levels both in patients with exudates (p < 0.001) and in those with transudates (p = 0.001). PF Ang-2 levels were higher than serum Ang-2 levels both in patients with exudates (p < 0.001) and in those with transudates (p = 0.045). PF VEGF levels were higher than serum VEGF levels in patients with malignant PEs (p < 0.001) and parapneumonic PEs (p = 0.003), but lower than serum VEGF levels in heart failure PEs (p < 0.001). In patients with tuberculous PEs and exudative PEs of miscellaneous etiology, PF and serum VEGF levels did not differ significantly. Conclusion: Ang-2 levels but not Ang-1 levels are elevated in exudative PEs, and they correlate with levels of VEGF and markers of pleural inflammation. It is thus possible that Ang-2 along with VEGF participate in pleural inflammation and the pathogenesis of exudative PEs.