| Summary: | <p>Abstract</p> <p>Background</p> <p>Endothelin-1 (ET-1) is a proinflammatory mediator and elevated in the regions of several brain injury and inflammatory diseases. The deleterious effects of ET-1 on endothelial cells may aggravate brain inflammation mediated through the regulation of cyclooxygenase-2 (COX-2)/prostaglandin E<sub>2</sub> (PGE<sub>2</sub>) system in various cell types. However, the signaling mechanisms underlying ET-1-induced COX-2 expression in brain microvascular endothelial cells remain unclear. Herein we investigated the effects of ET-1 in COX-2 regulation in mouse brain microvascular endothelial (bEnd.3) cells.</p> <p>Results</p> <p>The data obtained with Western blotting, RT-PCR, and immunofluorescent staining analyses showed that ET-1-induced COX-2 expression was mediated through an ET<sub>B</sub>-dependent transcriptional activation. Engagement of G<sub>i</sub>- and G<sub>q</sub>-protein-coupled ET<sub>B</sub> receptors by ET-1 led to phosphorylation of ERK1/2, p38 MAPK, and JNK1/2 and then activated transcription factor NF-κB. Moreover, the data of chromatin immunoprecipitation (ChIP) and promoter reporter assay demonstrated that the activated NF-κB was translocated into nucleus and bound to its corresponding binding sites in COX-2 promoter, thereby turning on COX-2 gene transcription. Finally, up-regulation of COX-2 by ET-1 promoted PGE<sub>2</sub> release in these cells.</p> <p>Conclusions</p> <p>These results suggested that in mouse bEnd.3 cells, activation of NF-κB by ET<sub>B</sub>-dependent MAPK cascades is essential for ET-1-induced up-regulation of COX-2/PGE<sub>2</sub> system. Understanding the mechanisms of COX-2 expression and PGE<sub>2</sub> release regulated by ET-1/ET<sub>B</sub> system on brain microvascular endothelial cells may provide rationally therapeutic interventions for brain injury or inflammatory diseases.</p>
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