Background: Moderate alcohol consumption reduces the risk for coronary heart disease. This cardioprotection may be due to ethanol enhancement of fibrinolysis. Fibrinolysis involves the interaction of plasminogen activators (PAs) and the plasminogen activator inhibitor type-1 (PAI-1). Factor(s) that decrease endothelial cell (EC) PAI-1 expression increase fibrinolysis and may decrease the risk for cardiovascular disease.
Methods: Five promoter deletion fragments were generated from a 1.1-kb PAI-1 promoter fragment and ligated to a luciferase reporter gene. Cultured human umbilical vein endothelial cells (HUVECs) were transiently transfected with these PAI-1 deletion constructs. A 251-base pair (bp) fragment of the PAI-1 promoter, positions -800 to -549, was cloned upstream of a heterologous promoter/enhancer. ECs luciferase activity was measured in the absence/presence of 20 mM ethanol. Electrophoresis mobility shift assays were performed with nuclear extracts from untreated and ethanol-treated ECs using this 251-bp fragment.
Results: Deletion analysis showed a region between position -800 and -549 mediated ethanol repression of luciferase activity. This 251-bp promoter fragment also repressed the activity of a heterologous promoter/enhancer in the presence of ethanol. Using the labeled 251-bp fragment, nuclear extracts from ethanol-treated ECs contained two inducible bands and one enhanced band. Non-ethanol treated nuclear extracts also contained a band that was not observed in ethanol-treated samples. Competition using 100-fold molar excess of unlabeled probe abolished these four bands.
Conclusions: Repression of PAI-I gene transcription in cultured HUVECs exposed to ethanol may involve the interaction of several transcription factors with binding sites localized between positions -800 and -549 of the PAI-1 gene promoter.