Key result
Inhibition of furin-like proprotein convertases significantly reduced macrophage MT1-MMP-dependent activation of pro-MMP-2, highlighting them as potential targets in atherosclerosis.
Why the study?
Does inhibition of furin-like PCs reduce MT1-MMP-dependent activation of pro-MMP-2 in human macrophages?
Does inhibition of furin-like PCs reduce MT1-MMP-dependent activation of pro-MMP-2 in human macrophages?
Furin-like proprotein convertases are central regulators of the MT-MMP-MMP-2 proteolytic cascade in macrophages, suggesting they are potential therapeutic targets in atherosclerosis.
MT1-MMP activation in macrophages may influence plaque stability; hypothesis-generating and leaves open therapeutic targeting in atherosclerosis.
BACKGROUND: Accumulation of macrophages and their in situ expression of matrix metalloproteinases (MMPs) are important determinants of plaque stability. Activation of membrane-bound MT1-MMP, the major activator of pro-MMP-2, requires intracellular endoproteolytic cleavage of its precursor protein. This type of activation typically requires suitable furin-like proprotein convertases (PCs), specifically furin and PC5. The present study was done to investigate the function of MT1-MMP as well as furin-like PCs in mononuclear inflammatory cells. METHODS AND RESULTS: Macrophage differentiation of human monocytic THP-1 cells was accompanied by increased expression of furin, PC5, and MT1-MMP. Some pro-MMP-2 activation was found in macrophages, but pro-MMP-2 level or activation was not enhanced after stimulation with the proinflammatory mediators tumor necrosis factor-alpha or lipopolysaccharide. However, culturing of macrophages in conditioned medium from serum-starved vascular smooth muscle cells, which constitutively secrete pro-MMP-2, resulted in a strong pro-MMP-2 activation. Inhibition of furin-like PCs with the specific pharmacological inhibitor decanoyl-RVKR-chloromethylketone (dec-CMK) inhibited MT1-MMP activation in macrophages. Dec-CMK or furin-specific small interfering RNA significantly inhibited macrophage MT1-MMP-dependent activation of vascular smooth muscle cell-derived pro-MMP-2. Flow cytometry demonstrated that human circulating monocytes express furin and PC5, and MT1-MMP and immunohistochemistry revealed their colocalization in macrophages in advanced human atherosclerotic lesions. CONCLUSIONS: Furin-like PCs (furin and PC5) play a central role in a MT-MMP-MMP-2 proteolytic cascade, involving provision of macrophage MT1-MMP for the activation of pro-MMP-2 synthesized by other cells. Furin and PC5 are expressed in human peripheral blood mononuclear cells and colocalize with MT1-MMP in macrophages in the atherosclerotic plaque, supporting the hypothesis that they are potential targets in atherosclerosis.
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Stawowy et al. (2005) studied Atherosclerosis. Furin-like PC inhibition (dec-CMK or siRNA) was evaluated on MT1-MMP and pro-MMP-2 activation. Inhibition of furin-like proprotein convertases significantly reduced macrophage MT1-MMP-dependent activation of pro-MMP-2, highlighting them as potential targets in atherosclerosis.
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