Microsomal prostaglandin E synthase-1 and cyclooxygenase-2 are both required for ischaemic excitotoxicity.
OBJECTIVE
Although both microsomal prostaglandin E synthase (mPGES)-1 and cyclooxygenase (COX)-2 are critical factors in stroke injury, but the interactions between these enzymes in the ischaemic brain is still obscure. This study examines the hypothesis that mPGES-1 activity is required for COX-2 to cause neuronal damage in ischaemic injury.


METHODS
We used a glutamate-induced excitotoxicity model in cultures of rat or mouse hippocampal slices and a mouse middle cerebral artery occlusion-reperfusion model in vivo. The effect of a COX-2 inhibitor on neuronal damage in mPGES-1 knockout (KO) mice was compared with that in wild-type (WT) mice.


RESULTS
In rat hippocampal slices, glutamate-induced excitotoxicity, as well as prostaglandin (PG) E(2) production and PGES activation, was significantly attenuated by either MK-886 or NS-398, inhibitors of mPGES-1 and COX-2 respectively; however, co-application of these inhibitors had neither an additive nor a synergistic effect. The protective effect of NS-398 on the excitotoxicity observed in WT slices was completely abolished in mPGES-1 KO slices, which showed less excitotoxicity than WT slices. In the transient focal ischaemia model, mPGES-1 and COX-2 were co-localized in the infarct region of the cortex. Injection of NS-398 reduced not only ischaemic PGE(2) production, but also ischaemic injuries in WT mice, but not in mPGES-1 KO mice, which showed less dysfunction than WT mice.


CONCLUSIONS
Microsomal prostaglandin E synthase-1 and COX-2 are co-induced by excess glutamate in ischaemic brain. These enzymes are co-localized and act together to exacerbate stroke injury, by excessive PGE(2) production.
Ikeda-Matsuo
Y
Y
Kitasato University, Tokyo, Japan. matsuoy@pharm.kitasato-u.ac.jp
Hirayama
Y
Y
Ota
A
A
Uematsu
S
S
Akira
S
S
Sasaki
Y
Y
D000818:Animals; D002545:Brain Ischemia / Q000201:enzymology / Q000503:physiopathology*; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D019746:Intramolecular Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008861:Microsomes / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000473:pathology; D000071876:Prostaglandin-E Synthases; D051381:Rats; D015427:Reperfusion Injury / Q000201:enzymology / Q000503:physiopathology*; D020521:Stroke / Q000201:enzymology / Q000503:physiopathology
D052246:Cyclooxygenase 2 Inhibitors; D018698:Glutamic Acid; D051546:Cyclooxygenase 2; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases; C000605865:Ptges protein, mouse; D015232:Dinoprostone