The cyclooxygenase site, but not the peroxidase site of cyclooxygenase-2 is required for neurotoxicity in hypoxic and ischemic injury.
Cyclooxygenase-2 (COX-2) activity has been implicated in the pathogenesis of ischemic injury, but the exact mechanisms responsible for its toxicity remain unclear. Infection of primary neurons with an adenovirus expressing wild type (WT) COX-2 increased the susceptibility of neurons to hypoxia. Infection with an adenoviral vector expressing COX-2 with a mutation at the cyclooxygenase site did not increase susceptibility to hypoxia, whereas over-expression of COX-2 with a mutation in the peroxidase site produced similar susceptibility to hypoxia as WT COX-2. Primary neuronal cultures obtained from transgenic mice bearing a mutation in the COX-2 cylooxygenase site were protected from hypoxia. Mice with a mutation in the cyclooxygenase site had smaller infarctions 24 h after 70 min of middle cerebral artery occlusion than WT control mice. COX-2 activity had no effect on the formation of protein carbonyls. Ascorbate radicals were detected by electron paramagnetic resonance as a product of recombinant COX-2 activity and were blocked by COX-2 inhibitors. Similarly, formation of ascorbate radicals was inhibited in the presence of COX-2 inhibitors and in homogenates obtained from COX-2 null mice. Taken together, these results indicate that the cyclooxygenase activity of COX-2 is necessary to exacerbate neuronal hypoxia/ischemia injury rather than the peroxidase activity of the enzyme.
Li
Wenjin
W
Geriatric Research Educational and Clinical Center, VA Pittsburgh Healthcare System, University of Pittsburgh, Pittsburgh, Pennsylvania 15205, USA.
Wu
Shasha
S
Ahmad
Muzamil
M
Jiang
Jianfei
J
Liu
Hao
H
Nagayama
Tetsuya
T
Rose
Marie E
ME
Tyurin
Vladimir A
VA
Tyurina
Yulia Y
YY
Borisenko
Grigory G
GG
Belikova
Natalia
N
Chen
Jun
J
Kagan
Valerian E
VE
Graham
Steven H
SH
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D020520:Brain Infarction / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology; D020134:Catalytic Domain / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology; D051379:Mice; D008822:Mice, Transgenic; D009410:Nerve Degeneration / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology; D018384:Oxidative Stress / Q000502:physiology; D009195:Peroxidase / Q000378:metabolism; D044262:Prostaglandin H2 / Q000096:biosynthesis; D051381:Rats
D052246:Cyclooxygenase 2 Inhibitors; D005609:Free Radicals; D016718:Arachidonic Acid; D044262:Prostaglandin H2; D009195:Peroxidase; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D001205:Ascorbic Acid