Mechanism of Constrictive Vascular Remodeling by Homocyst(e)ine: A Role of Peroxisome Proliferator Activated Receptor

Short title: Disintegrin metalloproteinase and collagen gel contraction ABSTRACT To test the hypothesis that homocysteine induces constrictive vascular remodeling by promoting collagen contraction and by inactivating peroxisome proliferator activated receptor (PPAR), human aortic endothelial and smooth muscle cells (SMC) were isolated and characterized by positive labeling for van Willebrand factor VIII and α-smooth muscle actin, respectively. Collagen gels were prepared and endothelial or SMC (10 5) or SMC+endothelial cells (10 4) were incorporated into the gels. The gel diameter was measured by a digital micrometer at 24 h of culture. To characterize PPAR, agonist of PPARα (ciprofibrate, CF) and PPARγ (15-deoxy-_ 12, 14 prostaglandin J2, PGJ2) were added to the gels. To determine the role of disintegrin metalloproteinase (DMP) in collagen gel contraction, an anti-DMP antibody and cardiac inhibitor of metalloproteinase (CIMP) were used in collagen gels. The collagen gel diameter at 0 h was 14.1+0.2 mm and was unchanged upto 24 h. The SMC reduces collagen gel diameter to 10.5+0.4 mm at 24h. The addition of homocysteine to SMC increases further contraction by reducing the diameter to 8.0+0.2 mm. These results suggested that SMC induces collagen gel contraction and the contraction was further enhanced by homocysteine. The addition of endothelial cells and SMC reduces the gel diameter to 12.0+0.3 mm, suggesting that the endothelial cells ameliorate the SMC-mediated collagen gel contraction. Only PGJ2, not CF, inhibits SMC contraction. However, both PGJ2 and CF inhibit contraction of endothelial cells, and SMC+endothelial cells. The addition of anti-DMP blocks the SMC as well as homocysteine-mediated collagen gel contraction. However, CIMP inhibits only the homocysteine-mediated collagen gel contraction and not the contraction induced by SMC alone. The results may suggest that homocysteine enhances vascular constrictive remodeling by promoting collagen gel contraction and by inactivating PPARα and γ in endothelial cell and PPARγ in smooth muscle cells.