Calcineurin and Inflammatory Signaling Processes in Aging and AD

Alzheimer's disease (AD) is a devastating and irreversible neurological disease that progressively alters personality and behavior, and destroys cognitive function. With an annual price tag exceeding 100 billion dollars, AD is also one of the nation's most costly diseases. In recent years, anti-inflammatory agents have emerged as promising compounds for delaying the onset of AD symptoms. Yet, our understanding of the mechanisms underlying neuro-immune/inflammatory (im/inf) signaling in the brain remains incomplete. The Ca2+/calmodulin dependent protein phosphatase, calcineurin, plays a critical role in im/inf signaling cascades in lymphocytes and other cell types, but has received little consideration for a similar role in nervous tissue. In the past year, we found that calcineurin activation in neuron-glia co-cultures was sufficient for recapitulating several components of the im/inf response found consistently with aging and AD, including astrocyte activation and the induction of numerous im/inf-related gene cascades. We also observed a marked and selective upregulation of calcineurin in activated astrocytes surrounding amyloid deposits in AD model mice. The long-term goal of this project is to therefore test the hypothesis that calcineurin is a critical component for the activation of im/inf signaling processes associated with AD. The first two aims will test whether activation of calcineurin and/or the calcineurin-dependent transcription factor, NFAT is necessary for im/inf signaling in astrocytes. Biologically relevant inflammatory mediators will be delivered to astrocytespecific cultures in the presence or absence of potent calcineurin and NFAT inhibitors. The induction of imlinf markers will be assessed with Western blots, RT-PCR, and cytokine arrays. Potential Ca2+ sources for calcineurin activation in astrocytes will also be examined, along with the possibility that calcineurin amplifies its own activity by up-regulating these Ca2+ sources. Aim three will use cell fractionation, immunoprecipitation, Western blot, phosphatase activity assays, immunohistochemistry, and in situ hybridization to qualitatively and quantitatively assess changes in calcineurin signaling in AD brain specimens and/or in a rodent model of AD. Completion of these studies will greatly increase our knowledge of the role of calcineurin in neuroinflammation and AD, and may lead to the development of novel treatment strategies for this disease and other degenerative conditions where neuroinflammation is prominent.