Objective: Matrix metalloproteinases (MMPs) seem to play a prominent role in atherogenesis. Extracellular MMP inducer (EMMPRIN), a cell surface glycoprotein which stimulates MMP synthesis, has recently been detected in human atheroma. We have investigated the influence of oxidized low-density lipoproteins (oxLDLs) on EMMPRIN expression in human coronary artery smooth muscle cells (HCA-SMCs).
Methods and results: OxLDL induced a significant increase of EMMPRIN release into HCA-SMC supernatants and a concomitant decrease of cell-associated EMMPRIN. These effects were antagonized by antioxidants as well as by EDTA and the MMP inhibitor GM6001. Western blot analysis demonstrated that MMP-1 and MMP-2 induce the cleavage of the extracellular domain from cell-associated EMMPRIN. MMP-1 and MMP-2 synthesis was upregulated by oxLDL, and, in addition, we have shown that soluble EMMPRIN, isolated from macrophage supernatants, increased MMP-1 and MMP-2 synthesis in HCA-SMC.
Conclusions: Our data suggest that oxLDLs stimulate the release of soluble EMMPRIN, at least in part, by MMP-dependent shedding from the cell surface. Additionally, oxLDLs might induce a circular upregulation of matrix degradation because, in turn, soluble EMMPRIN stimulates MMP synthesis in HCA-SMC.