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Keywords:

Animals, Aorta, Cells, Cultured, Collagenases, Culture Media, Conditioned, Culture Media, Serum-Free, Embryo, Enzyme Activation, Enzyme Induction, Female, Fibroblasts, Gelatinases, Gene Targeting, Macrophages, Peritoneal, Male, Matrix Metalloproteinase 2, Matrix Metalloproteinase 9, Metalloendopeptidases, Mice, Mice, Inbred C57BL, Mice, Knockout, Muscle, Smooth, Vascular, Plasmin, Plasminogen, Plasminogen Activator Inhibitor 1, Skin, Tissue Plasminogen Activator, Urinary Plasminogen Activator, Science & Technology, Life Sciences & Biomedicine, Hematology, Peripheral Vascular Disease, Cardiovascular System & Cardiology, MATRIX METALLOPROTEINASE-3 STROMELYSIN, MUSCLE CELL-MIGRATION, ENZYMATIC-PROPERTIES, IV COLLAGENASE, ARTERIAL INJURY, DEFICIENT MICE, GENE-FUNCTION, ACTIVATION, PRECURSOR, INHIBITORS, Embryo, Mammalian, Fibrinolysin, Urokinase-Type Plasminogen Activator, 1102 Cardiorespiratory Medicine and Haematology, 1103 Clinical Sciences, Cardiovascular System & Hematology, 3201 Cardiovascular medicine and haematology, 3202 Clinical sciences

Abstract:

To investigate a potential physiological role of the plasminogen/plasmin system in activation of the matrix metalloproteinase (MMP) system, the distribution of latent and active MMP-2 (gelatinase A) or MMP-9 (gelatinase B) was monitored in aorta extracts and in serum-free conditioned cell culture medium obtained from wild-type (WT) mice and from mice with deficiency of tissue-type plasminogen activator (t-PA(-/-)), urokinase-type plasminogen activator (u-PA(-/-)), plasminogen activator inhibitor-1 (PAI-1(-/-)) or plasminogen (Plg(-/-)). In aorta extracts, the contribution of active MMP-2 to the total MMP-2 level ranged between 7 and 16% for the different genotypes, whereas active MMP-9 was not detected. The contribution of active 58 kDa MMP-2 to the total MMP-2 level (active plus latent) ranged between 14 and 29% (mean of 3 experiments) for fibroblasts of the different genotypes, and between 18 and 32% for smooth muscle cells, and was relatively constant in time (7-72 h). The contribution of active 83 kDa MMP-9 to the total MMP-9 level ranged between 15 and 29% for fibroblasts of the different genotypes and was relatively constant in time (24-72 h); corresponding values were 17 to 57% for smooth muscle cells, with the exception of Plg(-/-) smooth muscle cells which had undetectable levels of active MMP-9. Addition of plasmin(ogen) to the cell culture medium of fibroblasts did not significantly affect the distribution of active and latent MMP-2, but resulted in an approximately two-fold enhancement of the contribution of active MMP-9. In macrophages of Plg(-/-) mice, active MMP-9 was detected only when the cells were cultured in the presence of plasminogen. These data indicate that activation of proMMP-2 occurs independently of the physiological plasminogen activators and of plasmin(ogen) in all the cell types evaluated. Activation of proMMP-9 was enhanced in the presence of plasmin(ogen), but active MMP-9 was also detected in fibroblasts of Plg(-/-) mice, indicating that in vivo activation may occur via plasmin(ogen)-independent mechanisms.