Matrix metalloproteinases (MMPs) is a family of proteolytic
enzymes involved in remodeling of extracellular matrix. Although
proteolytic enzymes are produced by many cell types, mast cells
seem to be more important than other types in remodeling of
pulmonary arteries during hypoxia. Therefore, we tested in vitro
production of MMPs and serine proteases in four cell types (mast
cells, fibroblasts, vascular smooth muscle cells and endothelial
cells) cultivated for 48 h under normoxic or hypoxic (3 % O2)
conditions. MMP-13 was visualized by immunohistochemistry,
MMP-2 and MMP-9 were detected by zymography in cell lysates.
Enzymatic activities (MMPs, tryptase and chymase) were
estimated in the cultivation media. Hypoxia had a minimal effect
on total MMP activity in the cultivation media of all types of cells,
but immunofluorescence revealed higher intensity of MMP-13 in
the cells exposed to hypoxia except of fibroblasts. Tryptase
activity was three times higher and chymase activity twice higher
in mast cells cultivated in hypoxia than in those cultured in
normoxia. Among all cell types studied here, mast cells are the
most abundant source of proteolytic enzymes under normoxic
and hypoxic conditions. Moreover, in these cells hypoxia
increases the production of both specific serine proteases
tryptase and chymase, which can act as MMPs activators.