12/15-lipoxygenase regulates intercellular adhesion molecule-1 expression and monocyte adhesion to endothelium through activation of RhoA and nuclear factor-kappaB.

12/15-lipoxygenase (12/15-LO) activity leads to the production of the proinflammatory eicosanoids 12-S-hydroxyeicosatetraenoic acid (12SHETE) and 13-S-hydroxyoctadecadienoic acid. We have previously shown a 3.5-fold increase in endothelial intercellular adhesion molecule (ICAM)-1 expression in mice overexpressing the 12/15-LO gene. We examined whether 12/15-LO activity regulated endothelial ICAM-1 expression. Freshly isolated aortic endothelial cells (EC) from 12/15-LO transgenic mice had significantly greater nuclear factor-kappaB (NF-kappaB) activation and ICAM mRNA expression compared with C57BL/6J control. 12/15-LO transgenic EC showed elevated RhoA activity, and inhibition of RhoA using either C3 toxin or the Rho-kinase inhibitor Y-27632 blocked NF-kappaB activation, ICAM-1 induction, and monocyte adhesion. Furthermore, we show that 12SHETE activates protein kinase Calpha, which forms a complex with active RhoA and is required for NF-kappaB-dependent ICAM expression in response to 12SHETE. The 12/15-LO pathway stimulates ICAM-1 expression through the RhoA/protein kinase Calpha-dependent activation of NF-kappaB. These findings identify a major signaling pathway in EC through which 12/15-LO contributes to vascular inflammation and atherosclerosis.