The Role of Pannexin1 in Ischemic Injury of Retinal Ganglion Cells

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DESCRIPTION (provided by applicant): Our long-term goal is to prevent neuronal loss and functional deficits in retinal ischemia. Pursuant to our objective, we have identified a new, scantily explored membrane channel protein pannexin1 (Panx1), as a promising source for discovering new therapies. We established that Panx1 function as a molecular mediator of ischemic neuronal injury, and genetic ablation of this channel protects retinal ganglion cells from ischemic damage. Our central hypothesis states that Panx1 serves as a critical "convergence hub" for external stressors. Our proposed studies will compare relative contribution of distinct toxicity mechanisms mediated by Panx1 and identify which stimuli or their combinations trigger pathological opening of this channel in vulnerable retinal ganglion cells in ischemia. Specific Aims are designed to: 1) analyze toxicity pathways triggered by the Panx1 channel opening for their relative contribution toxicity to RGC injury~ 2) Compare protective effects of partial inhibition vs. full blockade or ablation of Panx1 channel in vivo in experimental retinal ischemia-reperfusion model. We will focus on both neuronal survival and preservation of retinal functionality following ischemia. Significance. Protecting retinal neurons from ischemic injury is essential for a comprehensive therapeutic strategy. The understanding of the Panx1-mediated toxicity pathways and their contribution to neuronal injury will permanently alter both conceptual and therapeutic approaches to retinal and brain ischemia. We will use the expertise developed and the unique tools designed for this proposal to evaluate the feasibility of Panx1 blockade for suppressing or preventing the vision loss in transient ischemia, an important clinical problem and the NIH NEI research objective. PUBLIC HEALTH RELEVANCE: Our long-term goal is to prevent neuronal loss and functional deficits in retinal ischemia. We have identified a new, previously unexplored molecular mediator of ischemic neuronal injury, a channel protein pannexin1 (Panx1). Based on our main finding demonstrating that the Panx1 gene ablation suppresses neuronal loss in ischemia-reperfusion, we hypothesize that in ischemia Panx1 function as a molecular mediator of neuronal injury. Our central hypothesis states that Panx1, through opening of a large membrane pore, facilitates ischemic injury and oxidative stress to the retina. We seek to reveal cause-and-effect relationship between Panx1 and the activation of distinct toxicity pathways in ischemia. We have developed a unique Panx1 conditional knockout mouse and novel Panx1-specific patch clamp protocol to reach the objectives of this proposal. The major outcomes of this study include the new knowledge on the Panx1-mediated toxicity pathways and their contribution to neuronal injury. We will also test a therapeutic potential of Panx1 blockade in alleviating retinal ischemic injury using animal model of ischemia-reperfusion.