ABSTRACT: Thromboxane A2 receptor (TPr) has been reported to trigger vascular inflammation. Nuclear factor ? B (NF-?B) is a known transcription factor. The aims of the present study were to determine the contributions of NF-?B activation to TPr-triggered vascular inflammation and elucidate the mechanism(s) underlying TPr activation of NF-?B.The effects of TPr activators, [1S-[1 alpha,2 alpha(Z),3beta(1E,3S*), 4 alpha]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (I-BOP) and U46619, on NF-?B activation, phosphorylation of rhoA/rho-associated kinases and liver kinase B1, cell adhesion and migration, proliferation, and endothelium-dependent vasorelaxation were assayed in cultured human umbilical vein endothelial cells, human monocytes, or isolated mouse aortas. Exposure of human umbilical vein endothelial cells to TPr agonists I-BOP and U46619 induced dose-dependent and time-dependent phosphorylation of inhibitor of ?B ? in parallel with aberrant expression of inflammatory markers cyclooxygenase-2, inducible nitric oxide synthase, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1. Inhibition of NF-?B by pharmacological or genetic means abolished TPr-triggered expression of inflammatory markers. Consistently, exposure of human umbilical vein endothelial cells to either I-BOP or U46619 significantly increased phosphorylation of inhibitor of ?B ?, I kappaB kinase, rhoA, rho-associated kinases, and liver kinase B1. Pretreatment of human umbilical vein endothelial cells with the TPr antagonist SQ29548 or rho-associated kinases inhibitor Y27632 or silencing of the LKB1 blocked TPr-enhanced phosphorylation of inhibitor of ?B ? and its upstream kinase, I kappaB kinase. Finally, exposure of isolated mouse aortas to either U46619 or I-BOP enhanced NF-?B activation and vascular inflammation in parallel with reduced endothelium-dependent relaxation in intact vessels.TPr stimulation instigates aberrant inflammation and endothelial dysfunction via rho-associated kinases/liver kinase B1/I kappaB kinase-dependent NF-?B activation in vascular endothelial cells.
