Competitive Binding of CREB and ATF2 to cAMP/ATF Responsive Element Regulates eNOS Gene Expression in Endothelial Cells

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Abstract

Objective—

Expression of endothelial nitric oxide synthase (eNOS) is a critical determinant for vascular homeostasis. We examined the effects of Beraprost sodium (BPS), a stable analogue of prostacyclin, on the eNOS gene expression in the presence of inflammatory cytokine interleukin (IL)-1β in cultured endothelial cells.

Method and Results—

Exposure of human and bovine endothelial cells to IL-1β decreased eNOS expression. Western blot analysis using phospho-specific antibodies showed that IL-1β stimulated p38 MAP kinase and phosphorylated ATF2. BPS inhibited these effects via protein kinase A (PKA)/cAMP-responsive element binding protein (CREB) activation. Transfection assays using site-specific mutation constructs showed that CRE/ATF elements located at −733 and −603 within the human eNOS promoter are necessary for full IL-1β responsiveness. BPS attenuated the IL-1β–mediated decrease in eNOS promoter activity and the expression of eNOS gene through PKA pathway. Electrophoretic gel mobility shift assays showed that IL-1β increased the binding of phosphorylated ATF2 to CRE/ATF. On treatment with BPS, phosphorylated CREB predominantly bound to CRE/ATF.

Conclusions—

These results indicate that IL-1β and BPS antagonistically regulates the eNOS expression through the activation of p38 and PKA, respectively. Furthermore, the ability to bind both CREB and ATF2 implicates the CRE/ATF sequence as a potential target for multiple signaling pathways in the regulation of the eNOS gene transcription.

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