Abstract
In previous studies we found that neuronal overexpression of human cyclooxygenase (COX)-2 in transgenic mice potentiated excitotoxicity in vivo and in vitro. To clarify the molecular mechanisms involved in COX-2-mediated potentiation of excitotoxicity, we used cDNA microarray to identify candidate genes the expression of which is altered in the cerebral cortex of homozygous human hCOX-2 transgenic mice. We found that the mRNA expression of the cell cycle kinase (CDK) inhibitor-inhibitor kinase (INK) p18INK4, a specific inhibitor of CDK 4,6, which controls the activation of the retinoblastoma (Rb) tumor suppressor protein phosphorylation, was decreased in the brain of adult hCOX-2 homozygous transgenics. Conversely, chronic treatment of the hCOX-2 transgenics with the preferential COX-2 inhibitor nimesulide reversed the hCOX-2-mediated decrease of cortical p18INK4 mRNA expression in the brain. Further in vitro studies revealed that in primary cortico-hippocampal neurons derived from homozygous hCOX-2 transgenic mice, COX-2 overexpression accelerates glutamate-mediated apoptotic damage that is prevented by the CDK inhibitor flavoperidol. Moreover, treatment of wild-type primary cortico-hippocampal neuron cultures with the COX-2 preferential inhibitor nimesulide significantly attenuated glutamate-mediated apoptotic damage, which coincided with inhibition of glutamate-mediated pRb phosphorylation. These data indicate that hCOX-2 overexpression causes neuronal cell cycle deregulation in the brain and provides further rationale for targeting neuronal COX-2 in neuroprotective therapeutic research.
Footnotes
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The study was supported by National Institutes of Health (National Institute on Aging) Grant AG 14766 and in part by private funding from Helsinn Healthcare SA to G.M.P.
- Abbreviations:
- COX
- cyclooxygenase
- PGE2
- prostaglandin E2
- KA
- kainic acid
- hCOX
- human cyclooxygenase
- CDK
- cell cycle-dependent kinase
- INK
- inhibitor kinase
- Rb
- retinoblastoma
- bp
- base pair
- WT
- wild-type
- GAPDH
- glyceraldehyde phosphate dehydrogenase
- PBS
- phosphate-buffered saline
- DMSO
- dimethyl sulfoxide
- AD
- Alzheimer's disease
- CIP
- cycle-inhibitory protein
- KIP
- kinase-inhibitory protein
- Received October 8, 2001.
- Accepted January 9, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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