Cloning Angiotensin II (Ang) Responsive Genes in Vascular Smooth Muscle

And a vasoconstrictor hormone, has been implicated in the vascular changes associated with hypertension and atherosclerosis. We have used two approaches to elucidate molecular events regulated by Ang in VSMC. Using a “candidate” gene approach, we have found that Ang induces the expression of tissue factor (TF) mRNA and activity in cultured VSMC. A similar increase in TF mRNA and activity are induced in rat aortas after balloon injury. Ang also induces KC, a gene encoding a leukocyte chemoattractant. KC is also induced in experimental balloon injury models. Using differential screening of VSMC cDNA libraries, we have found that Ang induces mRNAs encoding the matrix proteins, thrombospondin, osteopontin (OPN), and lysyl oxidase (LO) and causes marked increases in OPN protein and LO activity in the culture medium. We have generated stable VSMC lines with decreased expression of OPN, which fail to migrate into 3D collagen gels. We have also isolated SM-20, a gene encoding a ≈2.8kB mRNA, corresponding to a ≈40 kD protein whose sequence in hot homologous to other proteins in the GenBank. SM-20 is induced within 30 min of treatment with Ang or PDGF. SM-20 antigen is found only in the VSMC of rat and human arterial media, and not in the adventitia or endothelium. High levels of SM-20 are also found in human atherosclerotic neointima. SM-20 may provide a novel VSMC-specific marker in the vessel wall. These results demonstrate that Ang induces in VSMC genes encoding matrix proteins, cytokines, and a procoagulant and may have profound effects on the growth, migratory, inflammatory, and thrombotic responses of VSMC.