2010 — 2020 |
Sappington, Rebecca M |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Interleukin-6 and Retinal Ganglion Cell Degeneration in Glaucoma
DESCRIPTION (provided by applicant): Glaucoma is an age-related disease that blinds through the degeneration of retinal ganglion cells (RGCs) and their axons in the optic nerve. By 2020, 80 million people will suffer from the disease, making it the leading cause of irreversible blindness. While age is the leading risk factor, elevated intraocular pressure (IOP) remains the primary treatable factor. Elevated IOP challenges RGC survival directly, but also indirectly by affecting signals from other other cell types. Interleukin-6 is an inflammatory cytokine released by glial cells that we have shown can be neuroprotective for isolated RGCs under pressure (Sappington et al., 2006). However, the effectiveness of IL-6 as a potential therapeutic intervention for glaucoma is likely to depend upon age, IOP and the physiological state of the RGC. The purpose of this proposal is to determine the impact and therapeutic relevance of IL-6 for RGCs challenged by age and elevated IOP in vivo. Using two mouse models of glaucoma, we will determine whether glial cells are a primary source of IL-6 and how production of IL-6 relates to 1) receptivity of RGCs to IL-6 and 2) function and survival of RGCs. To determine directly the influence of the IL-6 pathway on RGC survival, we will manipulate expression or activity of IL-6 and its receptor IL-6R in both models. We will utilize the DBA/2 mouse, a chronic model of ocular hypertension, and an acute model we have developed that uses microbeads to occlude aqueous flow and elevate IOP. As a function of age and IOP in these models, we will quantify cell type-specific expression and localization of IL-6 and IL-6R. We will correlate these data with the decline of RGC function and progression of degeneration. For assessment of RGC degeneration, we will use morphometric techniques to quantify changes in RGC soma density in retina and changes in axon caliber and density in the optic nerve. To assess RGC function, we will quantify anterograde and retrograde axonal transport using active-uptake tracers and ionic activity using and manganese-enhanced magnetic resonance imaging. Data regarding IL-6 signaling and RGC pathology will serve to identify a therapeutic window(s) for manipulation of the IL-6 system in each model using loss and gain of function studies. For loss of function studies, we will utilize a commercially-available IL-6 knockout mouse and antibody therapy directed at neutralization of IL-6. For gain of function studies, we will utilize a commercially-available IL-6 overexpression mouse, recombinant IL-6 therapy and antibody therapy directed at activation of IL-6R. Completion of these aims will provide insight into many key components of IL-6 signaling in glaucoma: 1) the levels and pattern of IL-6 expression: 2) cell type-specific expression of IL-6 and IL6-R, and 3) how IL-6 signaling influences RGC survival and function during disease progression. PUBLIC HEALTH RELEVANCE: Glaucoma is the leading cause of irreversible blindness worldwide, involving the death of retinal ganglion cells (RGCs) and an association with elevated IOP. Elevated IOP challenges RGC survival directly, but also indirectly by affecting signals from other cells that could serve a protective role. We propose a series of studies to examine the potential of the inflammatory cytokine interleukin-6 as a therapeutic target to rescue RGCs in glaucoma.
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2016 — 2017 |
Li, Deyu (co-PI) [⬀] Sappington, Rebecca M Xu, Yaqiong |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Graphene Optoelectronic Probes For Mapping Electrical Activities in Retina
? DESCRIPTION: Retinal ganglion cell (RGC) degeneration in glaucoma is both a spatial and temporal progression of physiological dysfunction. Recent studies indicate that deficits in anterograde transport in RGC axons precede their physical loss and axon conductance is compromised during this early phase of degeneration. Interestingly, these functional deficits in axon physiology tend to occur in clusters of neighboring RGCs, suggesting that external cues in the immediate milieu may play a role in spatial spreading of functional deficits. Currently the physiological relevance of spatial aspects in the glaucomatous neurodegeneration process is poorly understood because traditional assays do not have the spatiotemporal resolution to probe groups of cells throughout an intact neurodegenerative tissue. The lack of effective assays to probe groups of cells in a spatiotemporally controlled manner, while maintaining their in vivo structural and chemical relationships poses a major challenge to our understanding of neurodegeneration in a variety of diseases. To address this issue, we are developing a versatile graphene-based microfluidic platform, which allows for recording and manipulating electrical activities of individual cells in a whole retinal tissue, long term ex vivo culture of retina in god health, multiple point-access to the retina for local stimulation through chemical factors, as well as high resolution confocal microscopy examination of the retina. A unique advantage of graphene is that its whole volume is exposed to the environment, which maximizes its sensitivity to local electrochemical potential change. For example, graphene transistors are capable of detecting individual gas molecules, due to its high surface to volume ratio and high electron mobility (100 to 1000 times higher than silicon). The high electron mobility also enables graphene transistors to operate at very high frequencies (up to 500 GHz), leading to high temporal resolution. Because of its strength and flexibility, graphene can adhere to cell membranes or tissue slices to achieve high electrical sensitivity. Furthermore, a single-layer of graphene transmits more than 97% of incident light, making it ideal to be used as transparent electrical devices that are compatible with optical imaging techniques. Recently, we have shown that scanning photocurrent microscopy can provide a local photoconductance map with a precision 10 times greater than the diffraction limit. As such, our unprecedented neurotechnology, a rare combination of graphene probes, scanning photocurrent microscopy, and a novel microfluidic platform, will enable new assays to study cell-cell interactions that regulate neurodegenerative disorders of retina.
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