Liver kinase b1 is required for thromboxane receptor-dependent nuclear factor-kB activation and inflammatory responses

Abstract

Objective-Thromboxane A2 receptor (TPr) has been reported to trigger vascular inflammation. Nuclear factor γ B (NF-kB) is a known transcription factor. The aims of the present study were to determine the contributions of NF-kB activation to TPr-triggered vascular inflammation and elucidate the mechanism(s) underlying TPr activation of NF-kB. Approach and Results-The effects of TPr activators, [1S-[1alpha,2alpha(Z),3beta(1E,3S), 4alpha]]-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-kB 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 kB a 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-kB 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 kB a, IkappaB 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 kB a and its upstream kinase, IkappaB kinase. Finally, exposure of isolated mouse aortas to either U46619 or I-BOP enhanced NF-kB activation and vascular inflammation in parallel with reduced endothelium-dependent relaxation in intact vessels. Conclusions-TPr stimulation instigates aberrant inflammation and endothelial dysfunction via rhoassociated kinases/liver kinase B1/IkappaB kinase-dependent NF-kB activation in vascular endothelial cells. © 2013 American Heart Association, Inc.