Abstract
Regulation of αvβ3 and α5β1 integrin function plays a crucial role in atherosclerosis. Possible regulators of integrin–matrix interactions are integrin‐binding ADAMs (proteins with a disintegrin‐ and metalloproteinase‐domain), like ADAM‐15 and ADAM‐9. Molecular interactions between ADAM‐15, α5β1, and αvβ3 have been demonstrated. ADAM‐9 and ADAM‐15 were found to be interdependently regulated. This study, therefore, investigated whether the upregulation of integrins α5β1 and αvβ3 was correlated with the expression of integrin‐binding ADAMs in atherosclerotic processes. Human arterial and venous vascular smooth muscle cells (VSMCs) were incubated with PDGF over different time intervals up to a 3‐day culture period. mRNA concentrations, quantified by real‐time RT‐PCR and normalized to PBGD, of integrins αvβ3 and α5β1 were strongly increased after a 12‐h PDGF‐incubation in arterial and venous VSMC. ADAM‐15 and ADAM‐9 mRNA production showed a corresponding increase following integrin upregulation after a 24‐h incubation period. Western blot anaylsis revealed an increased protein expression of integrins and ADAMs in PDGF‐stimulated VSMC. Additionally, mRNA concentrations of atherosclerotic and normal human specimens were quantified by real‐time RT‐PCR. mRNA of ADAMs and integrins was significantly increased in atherosclerotic arteries compared to normal arteries. Immunohistochemistry of these specimens showed an increased expression and codistribution of both ADAMs and integrins in atherosclerosis. In conclusion, upregulation of ADAM‐15 and ADAM‐9 in atherosclerosis appears to follow an increase in α5β1 and αvβ3 integrins. Since α5β1 and αvβ3 are known to promote smooth muscle cell migration and proliferation, upregulation of ADAM‐15 and ADAM‐9 could balance integrin–matrix interactions and cell migration, thus modulating neointima progression. J. Cell. Biochem. 89: 808–823, 2003. © 2003 Wiley‐Liss, Inc.