The goal of the proposed studies is to further explore the mechanisms by which cyclooxygenase (COX)-2, an enzyme involved in inflammatory mechanisms as well as neuronal activities, may promote neurodegeneration in the brain of a mouse model of AD-type neuropathology. Using cDNA microarray high-throughput technique, we have being exploring changes in gene expression caused by over expressing human (h)COX-2 in neurons of APPswe/PSI-A246E/hCOX-2 triple transgenic mice, obtained by crossing APPswe/PSI-A246E with mice over expressing hCOX-2 in neuron. Genes that are differentially up- or down- regulated in the brain of APPswe/PSI-A246E or APPswe/PSI-A246E/ hCOX-2, relative to wild type (WT) control littermates (and which are not regulated in hCOX-2 single transgenics), were identified and organized into functional clusters based on similarities in biological functions. One cluster of genes whose expression was selectively influenced by hCOX-2 over expression in the brain of APPswe/PS I-A246E/hCOX-2, was found to correlate with variations in cell-cycle activity and Wingless/Int-I (Wnt) pathway function. The Wnt (the name is derived from mouse Int-I and drosophila wingless) signal transduction pathway is a large family of signaling molecules including e.g. Disheveled (Dvl), Glycogen synthase kinase (GSK-3beta), and beta-catenin among others, with well-established roles in regulating cell cycle, embryonic patterning, cell proliferation and cell determination. Based on the cDNA microarray evidence we continued exploring the potential role ofhCOX-2 on indexes of cell-cycle activity and Wnt signal transduction. We found that over expression of exogenous hCOX-2 in neuron of APPswe/PSI-A246E/hCOX-2 triple transgenics leads to >3 fold elevation in the number of S795-phosphorylated tumor suppressor (pRb) protein and active caspase 3 immunopositive neurons, which are indexes of cell-cycle-activity during response to Abeta1-42 mediated apoptotic death, confirming cDNA array evidence. This evidence was confirmed in in vitro studies showing that over expression of hCOX-2 in primary cortico-hippocampal neurons derived from hCOX-2 transgenics potentiates Abeta1-42 mediated apoptotic neuron death which could be attenuated prevented by treatment of cultures with the cell-cycle dependent kinase inhibitor (CDK) flavoperidol, suggesting that COX-2 may potentiate Abeta1-42 apoptotic neuron death through activation of cell-cycle. We continued exploring these mechanisms and found that the hCOX-2 mediated potentiation of A13 1-42 apoptotic death coincided with an inhibition of Y216 -GSK-3beta phosphorylation and intracellular redistribution of beta-catenin, which is an index of activation of the Wnt signal transduction pathway, as early as four hours after Abeta1-42 treatment. The proposed studies continuing the exploration of the mechanisms by which COX-2 may promote apoptotic neuron death in a model of AD type neuropathology will clarify the role of COX-2 in inflammatory neurodegeneration during Alzheimer's disease.
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