The aim of this study was to assess the expression of several
metalloproteinases (
MMPs) and tissue inhibitors of
metalloproteinases (TIMPs) in exudative
pleural effusions, and their relationship with inflammatory and fibrinolytic mediators in parapneumonic effusions. The study included 51 parapneumonic effusions (30
empyema or complicated parapneumonic, 21 noncomplicated parapneumonic), 28 tuberculous, 30 malignant and 30 transudates. Inflammatory markers (tumour
necrosis factor-alpha,
interleukin-8, polymorphonuclear
elastase), fibrinolytic system variables (
tissue plasminogen activator (PA),
urokinase PA (
u-PA),
plasminogen activation inhibitor (PAI)-1, PAI-2), and several
MMPs (MMP-1, MMP-2, MMP-8, MMP-9) and TIMPs (TIMP-1, TIMP-2) were determined by ELISA in plasma and pleural fluid. Elevated MMP-2 and
TIMP-1 concentrations were observed in all the pleural fluid samples studied. The group of
empyema or complicated parapneumonic effusions showed higher MMP-1, MMP-8 and MMP-9 concentrations than the remaining exudates. There was no correlation between
MMP and TIMP levels in plasma and pleural fluid in this group of effusions. In parapneumonic effusions, MMP-1, MMP-8 and MMP-9 showed a positive correlation with the inflammatory markers and with
u-PA and
PAI-1. Moreover, there was a relationship between MMP-8 concentration in pleural fluid and pleural thickening at the end of treatment. In conclusion, elevated metalloproteinase-1, -8 and -9 expression was found in parapneumonic
pleural effusions. These
metalloproteinases could be implicated in the local inflammatory response existing in this group of effusions.