Regulation of Neuroprotective Lipid Sgnals by Spatially Distinct NMDA Receptors

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DESCRIPTION (provided by applicant): The proposed research is part of a long-term effort to understand how lipid signaling mechanisms determine the fate of brain cells affected by diseases which exhibit excitotoxic cell death. Stimulation of synaptic NMDA receptors promotes neuronal survival, while stimulation of extrasynaptic NMDA receptors leads to dominant, pro-death signaling. However, the molecular pathways that determine these two outcomes are not fully understood. Two largely non-overlapping gene expression programs mediating cell survival and cell death, respectively, are induced by signaling from these spatially distinct NMDA receptor subpopulations. Neuroprotection D1 (NPD1) is a stereospecific lipid mediator derived from docosahexaenoic acid (DMA) that activates a pro-survival gene expression program in human brain and retinal cells. Does NPD1 mediate pro- survival signals from synaptic NMDA receptors? Control of NPD1 bioavailability by synaptic and extrasynaptic NMDA receptors will be investigated using primary hippocampal cell cultures. Experiments will focus on NPD1 pool size regulation by brain-derived neurotrophic factor (BDNF), which is a mediator of pro- survival signaling from synaptic NMDA receptors and a known agonist of NPD1 synthesis. Experiments will employ techniques from cell and molecular biology and biochemistry, HPLC-ESI tandem mass spectrometry-based lipidomic analysis, and the use of 15-lipoxygenase-1 (15-LOX-1) deficient mice, which are incapable of NPD1 synthesis. The results of the proposed studies will demonstrate that pro-survival signaling from the synaptic NMDA receptor is mediated through enhancement of the NPD1 pool size via increased expression of BDNF. Additionally, 15-LOX-1 deficient neuronal cultures will be shown to be significantly more vulnerable to excitotoxic injury than wild type cultures, and NPD1 will be shown to attenuate excitotoxic injury in vitro and in vivo. PUBLIC HEALTH RELEVANCE: Stroke, epilepsy, and neurodegenerative diseases such as Alzheimer's Disease, which share calcium toxicity as a common pathological feature, represent tremendous health care burdens on society and touch countless lives globally. Understanding the balance of molecular level processes leading to cell death or survival is critical to improving patient outcomes in these diseases, and neuroprotective signaling of DMA-derived lipid messengers is a new and important horizon on the biomedical research landscape.