The role of protein-tyrosine phosphorylation and gelatinase production in the migration and proliferation of smooth muscle cells

Background: It has been reported that matrix metalloproteinase (MMP) was expressed in coronary arterial atherosclerotic lesions. However, not much is known about the relationship between the production of MMP and the progression of atherosclerosis. Purpose and method: To demonstrate the association between the protein-tyrosine phosphorylation (PTP) and the activation of extracellular MMP in the proliferation and migration of vascular smooth muscle cells (VSMCs), the effect of platelet-derived growth factor (PDGF) and vanadate (an inhibitor of protein-tyrosine phosphatase and an activator of certain protein-tyrosine kinases) on mitogenesis ([ 3 H]thymidine incorporation after 24 hours), migration, PTP (Western blot analysis using anti-phosphotyrosine antibodies), and production of MMP (gelatin zymography) was examined in cultured VSMCs. Results: Both vanadate (1–5 μmol/l) and PDGF (1–10 ng/ml) caused a dose-dependent increase in thymidine incorporation and migration and produced 72-kDa type IV gelatinase (MMP-2) in VSMCs. The combination of vanadate and PDGF resulted in a dose-dependent synergistic effect on thymidine incorporation and MMP-2 production. Western blot analysis revealed that PDGF caused an increase in PTP, extracellular signal-regulated kinases (ERK1, ERK2) and PDGF receptor in VSMCs. Vanadate given together with PDGF induced a marked increase in the intensity of tyrosine phosphorylation in these proteins. Tyrosine kinase inhibitors (genistein and herbimycin A) and a synthetic inhibitor of MMP (1,10-phenanthroline) and an anti-MMP-2 neutralizing antibody inhibited the mitogenic effect induced by vanadate and/or PDGF. Conclusions: The data suggest that the proliferation and migration of cultured VSMCs was closely related to the stimulation of MMP-2 production that was induced through activation of PTK.