Mechanism of constrictive vascular remodeling by homocysteine: role of PPAR

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Abstract
To test the hypothesis that homocysteine induces constrictive vascular remodeling by inactivating peroxisome proliferator-activated receptor (PPAR), aortic endothelial cells (ECs) and smooth muscle cells (SMCs) were isolated. Collagen gels were prepared, and ECs or SMCs (105) or SMCs + ECs (104) were incorporated into the gels. To characterize PPAR, agonists of PPAR-α [ciprofibrate (CF)] and PPAR-γ [15-deoxy-12,14-prostaglandin J2(PGJ2)] were used. To determine the role of disintegrin metalloproteinase (DMP), cardiac inhibitor of metalloproteinase (CIMP) was used in collagen gels. Gel diameter at 0 h was 14.1 ± 0.2 mm and was unchanged up to 24 h as measured by a digital micrometer. SMCs reduce gel diameter to 10.5 ± 0.4 mm at 24 h. Addition of homocysteine to SMCs reduces further the gel diameter to 8.0 ± 0.2 mm, suggesting that SMCs induce contraction and that the contraction is further enhanced by homocysteine. Addition of ECs and SMCs reduces gel diameter to 12.0 ± 0.3 mm, suggesting that ECs play a role in collagen contraction. Only PGJ2, not CF, inhibits SMC contraction. However, both PGJ2and CF inhibit contraction of ECs and SMCs + ECs. Addition of anti-DMP blocks SMC- as well as homocysteine-mediated contraction. However, CIMP inhibits only homocysteine-mediated contraction. The results suggest that homocysteine may enhance vascular constrictive remodeling by inactivating PPAR-α and -γ in ECs and PPAR-γ in SMCs.

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