Journal of Biological Chemistry
Volume 287, Issue 9, 24 February 2012, Pages 6454-6468
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Neurobiology
Induction of COX-2 Enzyme and Down-regulation of COX-1 Expression by Lipopolysaccharide (LPS) Control Prostaglandin E2 Production in Astrocytes*

https://doi.org/10.1074/jbc.M111.327874Get rights and content
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Pathological conditions and pro-inflammatory stimuli in the brain induce cyclooxygenase-2 (COX-2), a key enzyme in arachidonic acid metabolism mediating the production of prostanoids that, among other actions, have strong vasoactive properties. Although low basal cerebral COX-2 expression has been reported, COX-2 is strongly induced by pro-inflammatory challenges, whereas COX-1 is constitutively expressed. However, the contribution of these enzymes in prostanoid formation varies depending on the stimuli and cell type. Astrocyte feet surround cerebral microvessels and release molecules that can trigger vascular responses. Here, we investigate the regulation of COX-2 induction and its role in prostanoid generation after a pro-inflammatory challenge with the bacterial lipopolysaccharide (LPS) in astroglia. Intracerebral administration of LPS in rodents induced strong COX-2 expression mainly in astroglia and microglia, whereas COX-1 expression was predominant in microglia and did not increase. In cultured astrocytes, LPS strongly induced COX-2 and microsomal prostaglandin-E2 (PGE2) synthase-1, mediated by the MyD88-dependent NFκB pathway and influenced by mitogen-activated protein kinase pathways. Studies in COX-deficient cells and using COX inhibitors demonstrated that COX-2 mediated the high production of PGE2 and, to a lesser extent, other prostanoids after LPS. In contrast, LPS down-regulated COX-1 in an MyD88-dependent fashion, and COX-1 deficiency increased PGE2 production after LPS. The results show that astrocytes respond to LPS by a COX-2-dependent production of prostanoids, mainly vasoactive PGE2, and suggest that the coordinated down-regulation of COX-1 facilitates PGE2 production after TLR-4 activation. These effects might induce cerebral blood flow responses to brain inflammation.

Astrocytes
Inflammation
Lipopolysaccharide (LPS)
Neuroinflammation
Prostaglandins
Signaling

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*

This work was supported in part by Spanish Ministry of Science and Innovation Grant SAF2008-04515 and by European Community FP7/2007-2013 Project, Agreement 201024.

This article contains supplemental Figs. 1–4.

1

Recipient of a Ph.D. fellowship from the Spanish Ministry of Science and Innovation.