Involvement of NADPH oxidase in oxidized LDL-induced upregulation of heat shock factor-1 and plasminogen activator inhibitor-1 in vascular endothelial cells

Plasminogen activator inhibitor-1 (PAI-1) is implicated in thrombogenesis, inflammation, and extracellular matrix remodeling. Previous studies indicated that oxidized low-density lipoprotein (LDL) stimulated the generation of PAI-1 in vascular endothelial cells (EC). The present study demonstrated that LDL oxidized by copper, iron, or 3-morpholinosydnonimine increased the expression of NADPH oxidase (NOX) 2, PAI-1, and heat shock factor-1 (HSF1) in human umbilical vein EC or coronary artery EC compared with LDL or vehicle. Diphenyleneiodonium, a NOX inhibitor, prevented the increases of the expression of HSF1 and PAI-1 in EC induced by oxidized LDLs. Small-interference RNA (siRNA) for [p22.sup.phox], an essential subunit of NOX, prevented oxidized LDL-induced expression of NOX2, HSF1, and PAI-1 in EC. HSF1 siRNA inhibited oxidized LDL-induced expression of PAI-1 and HSF1, but not NOX2, in EC. The binding of HSF1 to PAI-1 promoter and the activity of PAI-1 promoter in EC were enhanced by oxidized LDL. Butylated hydroxytulene, a potent antioxidant, inhibited oxidized LDL-induced release of hydrogen peroxide ([H.sub.2][O.sub.2]) and the expression of NOX2, HSF1, and PAI-1 in EC. Treatment with [H.sub.2][O.sub.2] increased the abundance of NOX2, HSF1, and PAI-1 in EC. The results of the present study indicate that oxidized LDL-induced expression of NOX may lead to the elevated release of reactive oxygen species, the activation of HSF1, and the enhancement of the transcription of PAI-1 gene in cultured vascular EC. reduced nicotinamide adenine dinucleotide phosphatase; oxidized low-density lipoprotein