Chronic inflammation, a major contributor to neurodegeneration in AD, occurs when glial cells (i.e.,astrocytes and microglia) undergo prolonged activation in response to oxidative stress. Oxidative stress andneurotoxic oligomeric p-amyloid (Ap) peptide production in AD brain can increase extracellular levels ofcytokines and nucleotides that activate receptors in glial cells to stimulate intracellular signaling pathwaysand promote reactive gliosis, an underlying cause of neuroinflammation. Chronic inflammation can beexacerbated by the infiltration of blood monocytes across the endothelium of cerebral microvessels thatmaintain the blood-brain barrier. Our research has shown that a G protein-coupled P2Y2 nucleotide receptor(P2Y2R) expressed in astrocytes and vascular cells is activated by the extracellular nucleotides ATP andDTP to induce responses characteristic of reactive gliosis and vascular inflammation. The P2Y2R isdistinguished among G protein-coupled receptors in its ability to interact directly with integrins (e.g., avPa/ps)and growth factor receptors to transactivate their signal transduction pathways. Proposed studies will test the hypothesis that chronic inflammation caused by oxidative stress andoligomeric Ap production in AD brain is mediated by P2Y2Rs for cytokine-like nucleotides in astrocytes andcerebromicrovessels through transactivation of integrins and growth factor receptors. P2Y2Rs also activatea-secretase to promote neuroprotective APP processing by distinct pathways from inflammation, suggestingthat this divergence in P2Y2R signaling can be exploited to retard the development of AD. Studies willevaluate three specific aims.
Aim 1 will elucidate pro-inflammatory pathways coupled to P2Y2Rs andATPrelease and the effects of oxidative stress and oligomeric Ap42 in primary astrocytes from TgCRNDS micethat harbor the Swedish (K670M/N671L) and Indiana (V717F) mutations in APP, an accepted animal modelof AD, as compared to C57/BL6 (wild type), P2Y2R'/', and TgCRNDS x P2Y2R~'~ mice. Studies also willdetermine mechanisms of transcriptional regulation of the P2Y2R.
Aim 2 will determine whether expressionof P2Y2Rs, and markers of inflammation and the AD phenotype are up-regulated in astrocytes, neurons andmicrovessels isolated from brain sections of TgCRNDS mice as compared to C57/BL6, P2Y2R'/', andTgCRNDS x P2Y2R~'~mice, and quantify ATP release in brain sections.
Aim 3 will determine mechanismsunderlying P2Y2R-mediated APP processing in NT-2 cells expressing the Swedish and Indiana doublemutant of APP, an in vitro neuronal cell model for AD, and in primary neurons. Together, these studies willprovide conclusive evidence to support a role for P2Y2Rs in the pathophysiology of AD, and define novelpathways activated by nucleotides that will lead to better treatments for this debilitating disease.
Showing the most recent 10 out of 113 publications
