The purpose of this study is to explain the aberrant, elevated neuronal expression of two specific proinflammatory markers, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), in Alzheimer's Disease brains. Although increased expression of these proteins in AD is attributed to an """"""""inflammatory"""""""" process occurring in the brain, neither the stimuli nor the consequences of this are known. Answering these questions will provide insight into the unknown mechanism of AD progression and ultimately help identify molecular targets for therapeutic neuroprotection. Previous studies demonstrate that neurotoxic beta-amyloid (Abeta) fibrils stimulate calcium influx in neurons. Elevated intracellular calcium is a potent stimulus for increased COX-2 expression in neurons. The proinflammatory cytokine, TNFalpha, is a well-described stimulus for increased iNOS expression in many cell types and is neuroprotective against Abeta fibrils. Preliminary data demonstrates that toxic Abeta fibril stimulation increases neuronal COX-2 expression in mouse cortical neuron cultures. Neuroprotective TNFa stimulation increases neuronal iNOS expression. These data suggest the hypotheses that COX-2 activity is required for Abeta-dependent toxicity in AD and iNOS activity is required for TNFa-dependent neuroprotection from Abeta fibrils. The following specific aims will address this hypothesis: 1) Quantitate the increase in COX-2 mRNA and/or protein level following toxic Abeta peptide stimulation of primary mouse cortical neuron cultures and determine whether COX-2 activity is required for the Abeta toxicity. Specific inhibitors of COX-2 activity will be tested for their ability to attenuate neuron death in the presence of Abeta fibrils. 2) Quantitate the increase in iNOS mRNA and/or protein level during TNFa-mediated neuroprotection from Abeta toxicity in cortical neuron cultures. Specific inhibitors of iNOS activity will be used to determine whether iNOS activity is required for the TNFalpha-dependent protection from AB fibrils.
