Levels of cathepsins S and H in pleural fluids of inflammatory and neoplastic origin.

Cathepsins S and H are present in immune cells and tissues and may play a role in the activation of an adoptive immune response. Our goal was to assess their protein levels in pleural fluids from 82 patients who underwent thoracentesis or thoracoscopy for therapeutic or diagnostic reasons and to relate them to an inflammatory, neoplastic or hemodynamic origin. Pleural effusions were also analyzed for a panel of 13 inflammatory or proliferative markers to test possible links to a nonspecific host reaction. Increased levels of cathepsin S were found in parainflammatory and cancer-related effusions compared to transudates. Cathepsin H levels were elevated only in parainflammatory effusions, whereas the levels in cancer-related effusions were comparable to transudates. Cathepsin S values significantly correlated with LDH, alpha-1-AT, VEGF, sICAM, sVCAM, MPO, uPA, MMP-9/TIMP-1, IL-8 and MCP-1, but not with CRP, IL-10 or cathepsin H. In contrast to cathepsin S, cathepsin H values did not correlate with markers of inflammation, indicating a specific role for cathepsin H in the pleural host response. In conclusion, the estimation of cathepsin S and cathepsin H may help to distinguish between effusions of different etiology.