Production of MMPs in human cerebral endothelial cells and their role in shedding adhesion molecules

Matrix metalloproteinases (MMPs) are Zn2+-endopeptidases that seem to play an important role in chronic inflammatory diseases of the central nervous s ystem by disrupting the blood-brain barrier (BBB) and mediating the destruc tion of myelin components. We therefore investigated the influence of the p ro-inflammatory cytokine TNF-alpha on the expression and activation of seve ral MMPs in human cerebral endothelial cells (HCEC). HCEC constitutively ex press MMP-2 and MMP-3 mRNA, but only MMP-3 is upregulated on mRNA and prote in level after TNF-alpha stimulation. MMP-9 and MMP-12 mRNA could only be d etected under inflammatory conditions. Furthermore, MMPs are involved in sh edding of cell surface molecules. We therefore investigated the influence o f MMPs on the release of soluble adhesion molecules using marimastat, a spe cific broad-spectrum MMP inhibitor and other protease inhibitors like aprot inin or leupeptin. Only marimastat inhibited the TNF-alpha mediated release of sVCAM-1 in the supernatants of HCEC. Western blot results of culture su pernatants supported the time dependent release of the complete extracellul ar portion of the VCAM-1 molecule. These data suggest that MMPs produced by HCEC are actively involved in the shedding of soluble adhesion molecules a t the BBB.