|M.Sc Student||Khodalev Olga|
|Subject||The Effect of Death Pathway Inhibition on the Production and|
Activity of Matrix Metalloproteinase-2 (MMP-2)in
in Human Endothelial Cells
|Department||Department of Medicine||Supervisors||ASSOCIATE PROF. Nitza Lahat|
|DR. Sarah Shapiro|
|Full Thesis text|
MMP-2, a matrix metalloproteinase that degrades basal membranes and extracellular matrix components was shown to be essential for both endothelial cell (ECs) angiogenesis and their apoptotic death. MMP-2 pro-enzyme undergoes stepwise activation through interactions with membrane-type (MT)1-MMP leading to primary cleavage of MMP-2 to its intermediate-form and followed by cleavage to its fully active-form. Caspases and p38 MAP kinases (p38) are important pathways associated with apoptosis of ECs, however their inter-relationships and connections with MMP-2 and its activator are not clear.
Inhibitors of two major apoptotic pathways, caspases and p38 MAPK (p38) were used to evaluate the role of MMP-2 in angiogenic processes of cultured ECs as well as the reciprocal influences of MMP-2 on the apoptotic pathways. We found that the two apoptotic pathways differently influenced the viability, proliferation, migration, morphology and expression of the cytoskeletal molecule, focal adhesion kinase. The results suggest that p38 enhances MMP-2 synthesis, its intermediate and fully activated forms, partially via MT1-MMP activity. However, caspases enhance MMP-2 production and full activation, while reducing MT1-MMP and the intermediate-form of MMP-2. Thus the two apoptotic pathways differ in the mechanisms involving MMP-2 expression and activation.
The intermediate-form of MMP-2 supported survival and migration, while the fully active-form led to ECs death, and a pro-rich MMP-2 environment had protective survival effects, even in the presence of the fully active enzyme. Thus the microenvironmental ratio between the different MMP-2 forms determines ECs survival. The MMP-2 forms did not affect tubulogenesis, accentuating specific MMP-2 influences on distinct angiogenic steps.
Interactions between the apoptotic pathways were observed, as well as a regulatory loop between active MMP-2 and p38 but not between MMP-2 and caspases, suggesting that MMP-2 is downstream to caspases where it serves as an “exterminator” molecule. In summary, modification of caspases and p38 pathways, via changes in the concentration of the different forms of MMP-2 in the micro-milieu, affect survival and death processes in ECs.