ACTIVATION OF HUMAN UMBILICAL VEIN ENDOTHELIAL-CELL PROGELATINASE-A BY PHORBOL-MYRISTATE ACETATE - A PROTEIN-KINASE-C-DEPENDENT MECHANISM INVOLVING A MEMBRANE-TYPE MATRIX METALLOPROTEINASE

Matrix metalloproteinases play an important role in tumor invasion, an giogenesis and inflammatory tissue destruction. The 72-kd gelatinase A is the most widely distributed. Along with the 92-kd gelatinase B, it plays an important role in basement membrane turnover. Gelatinase A i s secreted as progelatinase A and, when activated, can cause extracell ular matrix destruction. The physiologic mechanism of this activation is not well understood. Based on the importance of endothelial cells i n inflammation and cancer, we sought in this study to systematically s tudy the PMA-induced activation of endothelial cell progelatinase A. U sing HUVEC, we demonstrated that PMA-induced activation of progelatina se A in these vascular endothelial cells (a) was protein kinase C-depe ndent as it was blocked by H-7; (b) occurred through cell-mediated eve nts as PMA was unable to activate progelatinase A in a cell-free syste m and that low dose tissue inhibitor of metalloproteinases-2, but not tissue inhibitor of metalloproteinases-1, totally inhibited PMA-induce d activation; (c) was accompanied by an increase in the membrane-type matrix metalloproteinase (MT-MMP). We also found that the combination of PMA and the cytokine tumor necrosis factor-alpha increased HUVEC se cretion and activation of gelatinase B. In conclusion, our data show t hat PMA activation of vascular endothelial cell progelatinase A is a c ell membrane event that is at least partially mediated through a PKC-d ependent mechanism and is accompanied by an increase synthesis of MT-M MP. These data suggest a role for MT-MMP in the activation of progelat inase A in vascular endothelial cells.