Up-regulation of COX-2/PGE2 by endothelin-1 via MAPK-dependent NF-κB pathway in mouse brain microvascular endothelial cells

Chih-Chung Lin,Shin-Ei Cheng,Pei-Ling Chi,Chuen-Mao Yang,Hsi-Lung Hsieh,Ruey-Horng Shih

doi:10.1186/1478-811x-11-8

Abstract

BackgroundEndothelin-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 E2 (PGE2) 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.ResultsThe data obtained with Western blotting, RT-PCR, and immunofluorescent staining analyses showed that ET-1-induced COX-2 expression was mediated through an ETB-dependent transcriptional activation. Engagement of Gi- and Gq-protein-coupled ETB 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 PGE2 release in these cells.ConclusionsThese results suggested that in mouse bEnd.3 cells, activation of NF-κB by ETB-dependent MAPK cascades is essential for ET-1-induced up-regulation of COX-2/PGE2 system. Understanding the mechanisms of COX-2 expression and PGE2 release regulated by ET-1/ETB system on brain microvascular endothelial cells may provide rationally therapeutic interventions for brain injury or inflammatory diseases.

Highlights

Endothelin-1 (ET-1) is a proinflammatory mediator and elevated in the regions of several brain injury and inflammatory diseases
These findings suggested that ET-1 induces COX-2 expression at the transcriptional and translational levels, which is mediated through the ETB receptor-dependent activation of ERK1/2, p38 mitogen-activated protein kinases (MAPKs), JNK1/2, and NF-κB pathway, leading to prostaglandin E2 (PGE2) biosynthesis in mouse bEnd.3 cells
ET-1 induces COX-2 expression and PGE2 release in bEnd.3 cells To investigate the effect of ET-1 on COX-2/PGE2 system, bEnd.3 cells were incubated with various concentrations of ET-1 for the indicated time intervals

Summary

Introduction

Endothelin-1 (ET-1) is a proinflammatory mediator and elevated in the regions of several brain injury and inflammatory diseases. In the development of various vascular diseases, an early finding is dysfunction of the vascular endothelium that is closely related to clinical events in patients with atherosclerosis and hypertension [2,3] The vasoactive mediators such as endothelin (ET) could be produced by endothelial cells to maintain hemodynamic responses. It has been demonstrated that endothelial ET-1 induces cytokines or chemokines (e.g., interleukine-1 or interleukin-8) production and secretion by non-neuronal cells, including astrocytes and human brain-derived endothelial cells, which directly contributes to BBB breakdown during CNS inflammation [11,13]. These findings suggest that ET-1 might be involved in neuroinflammation. The detailed mechanisms responsible for ET-1 action are still limited

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