Association of trypsin-2 with activation of gelatinase B and collagenase-2 in human bronchoalveolar lavage fluid in vivo

BACKGROUND: Tissue injury mediated by matrix metalloproteinases (MMPs) is a hallmark of inflammatory lung diseases. Latent secreted proMMPs must be activated to be catalytically competent. AIM: Our aim was to analyse an involvement of the trypsin-2, trypsin-2-α1-proteinase inhibitor (PI) complex and tumour-associated trypsin inhibitor (TATI) in the in vivo activation of proMMP-8, -9 and -2. METHODS: Concentrations of trypsin-2, trypsin-Z-a,-PI complex and TAT1 in bronchoalveolar lavage fluid (BALF) were analysed by immunofluorometry. Molecular forms and expression of trypsin-2 and trypsin-2-α,-PI complex were identified by Western immunoblot and immunocyto-chemistry. Gelatinolytic and collagenolytic activities were measured by substrate-based activity assays. RESULTS: BALFs from 16 of 43 patients and BALFs from five of 15 healthy controls contained trypsin-2-a,-PI complex. TAT1 was found in all healthy control BALFs (median 0.12 μg/L, range 0.02-0.66 μg/L) whereas 8 of 43 BALFs from patients (median 0, range 0-0.64 μg/L, P = 0.0001) contained TATI. Patient BALFs showed significantly increased activation of MMP-9 and MMP-8 compared with healthy controls. The concentrations of trypsin-2-α,-PI complex correlated with the in vivo activation of MMP-9 and -8 (r = 0.68, P= 0.002 and r = 0.61, P = 0.008) but not with the activation of MMP-2 in BALFs.