Purines and the Health of Retinal Ganglion Cells

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DESCRIPTION (provided by applicant): Glaucoma is a major cause of blindness worldwide and is characterized by a series of pathological changes to optic nerve head astrocytes and retinal ganglion cells that eventually lead to vision loss. While the biggest risk factor for cell injury is elevated intraocular pressure (IOP), proinflammatory cytokines also contribute to the chronic disease. The mechanisms connecting physical strain to the cytokine response are unclear, however. This proposal is based upon the novel hypothesis that extracellular ATP links mechanical strain to the enhanced cytokine response in glaucoma. In particular, the mechanosensitive release of ATP through pannexin channels on optic nerve astrocytes can autostimulate adjacent P2X7 receptors, upregulating cytokine expression on a molecular level and activating cytokine release through both the inflammasome and classic release pathways. Using in vivo models of elevated IOP and in vitro models of cell stretch, we will demonstrate the mechanisms linking strain and inflammation and identify points of intervention. Aim 1 will confirm the involvement of cytokines IL-1� and IL-6 in models of chronic and acute glaucoma. The time course of cytokine activation will be determined and the relative contribution of proinflammatory signals in older animals will be assessed. The contribution of pannexin and P2X7 channels will be explored on a molecular level with knockout mice, and on a pharmacological level with channel blockers; the ability of antagonists to reduce inflammasome activation may identify new treatments. In Aim 2, the mechanisms connecting mechanical strain, ATP and cytokines will be confirmed in optic nerve head astrocytes while the effects of inflammasome product IL-1� on retinal ganglion cell health will be determined. In summary, this proposal will demonstrate that purinergic signaling links elevated IOP with the enhanced inflammatory response in astrocytes and pathology in retinal ganglion cells. This novel approach will advance our understanding of the disease on a mechanistic level while identifying possible new targets for intervention.