Induction of heme oxygenase-1 attenuates lipopolysaccharide-induced cyclooxygenase-2 expression in mouse brain endothelial cells.

Abstract

BACKGROUND:

Prostaglandin E2 (PGE2), an arachidonic acid metabolite converted by cyclooxygenase-2 (COX-2), plays important roles in the regulation of endothelial functions in response to bacterial infection. The enzymatic activity of COX-2 can be down-regulated by heme oxygenase-1 (HO-1) induction. However, the mechanisms underlying HO-1 modulating COX-2 protein expression are not known.

OBJECTIVE:

The aim of the present study was to investigate whether the up-regulation of HO-1 regulates COX-2 expression induced by lipopolysaccharide (LPS), an endotoxin produced by Gram negative bacteria, in mouse brain endothelial cells (bEnd.3)

METHODS:

Cultured bEnd.3 cells were used to investigate LPS-induced COX-2 expression and PGE2 production. Cobalt protoporphyrin IX (CoPP, an HO-1 inducer), infection with a recombinant adenovirus carried with HO-1 gene (Adv-HO-1), or zinc protoporphyrin (ZnPP, an HO-1 inhibitor) was used to stimulate HO-1 induction or inhibit HO-1 activity. The expressions of COX-2 and HO-1 were evaluated by western blotting. PGE2 levels were detected by an enzyme-linked immunoassay. Hemoglobin (a chelator of carbon monoxide, CO, one of metabolites of HO-1) and CO-RM2 (a CO releasing molecule) were used to investigate the mechanisms of HO-1 regulating COX-2 expression.

RESULTS:

We found that LPS-induced COX-2 expression and PGE2 production were mediated through NF-κB (p65) via activation of Toll-like receptor 4 (TLR4). LPS-induced COX-2 expression was inhibited by HO-1 induction by pretreatment with CoPP or infection with Adv-HO-1. This inhibitory effect of HO-1 was reversed by pretreatment with either ZnPP or hemoglobin. Pretreatment with CO-RM2 also inhibited TLR4/MyD88 complex formation, NF-κB (p65) activation, COX-2 expression, and PGE2 production induced by LPS.

CONCLUSIONS:

We show here a novel inhibition of HO-1 on LPS-induced COX-2/PGE2 production in bEnd.3. Our results reinforce the emerging role of cerebral endothelium-derived HO-1 as a protector against cerebral vascular inflammation triggered by bacterial infection.

• Authors: Ruey-Horng Shih, Chuen-Mao Yang
• Journal: Journal of neuroinflammation (J Neuroinflammation) Vol. 7 Pg. 86 (Nov 30 2010) ISSN: 1742-2094 [Electronic] England
• PMID: 21118574 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Lipopolysaccharides
• NF-kappa B
• Heme Oxygenase-1
• Cyclooxygenase 2
• Dinoprostone

Topics

• Animals
• Cells, Cultured
• Cerebrovascular Circulation (drug effects, physiology)
• Cyclooxygenase 2 (genetics, metabolism)
• Dinoprostone (metabolism)
• Endothelial Cells (cytology, drug effects, enzymology)
• Endothelium, Vascular (cytology, drug effects)
• Heme Oxygenase-1 (genetics, metabolism)
• Humans
• Lipopolysaccharides (pharmacology)
• Mice
• NF-kappa B (metabolism)
• Up-Regulation