Abstract 74: Endothelial PPARγ Protects Against Vascular Thrombosis by Downregulating P-Selectin-Mediated Leukocyte-Endothelial Interactions
Background and Hypothesis: Tissue-specific effects of peroxisome proliferator-activated receptor-gamma (PPARγ) on vascular thrombosis are not well understood. Using a novel murine model of selective interference with endothelial PPARγ, we tested the hypothesis that endothelial PPARγ protects against vascular thrombosis.
Methods: Transgenic mice expressing a dominant negative PPARγ mutant (E-V290M) selectively in endothelium were compared with non-transgenic (non-Tg) littermates. Susceptibility to occlusive thrombosis of the carotid artery was assessed following chemical (7% FeCl3) or photochemical (rose bengal and green laser) injury. Leukocyte rolling on mesenteric venules was measured by intravital microscopy. P-selectin mRNA levels were assayed by real-time PCR and P-selectin protein levels were measured by ELISA and flow cytometry. To assess the role of P-selectin and leukocytes in thrombosis, P-selectin blocking antibodies or leukocyte-depleting antibodies were infused before carotid artery injury.
Results: The time to occlusion of the carotid artery was significantly shortened in E-V290M mice compared with non-Tg mice after either chemical (5.1±0.2 vs. 10.1±3.3 vs. minutes; P=0.01) or photochemical injury (48±9 vs. 74±9 minutes; P=0.04). Both plasma P-selectin levels and P-selection mRNA levels in the carotid artery were significantly higher in E-V290M mice than in non-Tg mice (P<0.05), but no differences in platelet surface P-selectin were observed. Increased functional endothelial P-selectin activity was demonstrated by enhanced leukocyte rolling on mesenteric venules in E-V290M mice compared with non-Tg mice (53±8 vs. 25±7 per minute; P=0.025). The shortened occlusion times in E-V290M mice were reversed by P-selectin blocking antibodies or leukocyte-depleting antibodies (P=0.04, and P=0.02 respectively). Gene set enrichment analysis of a gene expression microarray demonstrated significant upregulation of NF-kB target genes, including P-selectin, in endothelial cells from E-V290M mice (P<0.001).
Conclusions: We conclude that endothelial PPARγ protects from thrombosis through a mechanism that involves downregulation of NF-kB-mediated P-selectin expression and leukocyte-endothelial interactions.
- © 2012 by American Heart Association, Inc.