It is remarkable that photoreceptors and retinal pigment epithelial (RPE) cells remain unchanged for many decades in healthy eyes, despite the stress they undergo in their adverse environment. The long-range goal of this ongoing research is to explain this remarkable fact, to use this knowledge to understand what might go wrong in photoreceptor degenerations in terms of cell survival signaling, and to be able to contribute to the initiation of translational studies. Supported by this grant, we and our colleagues discovered the docosahexaenoic acid (DHA)-derived mediator, neuroprotectin D1 (NPD1), and found that it is anti-inflammatory and anti-apoptotic in the RPE and central nervous system. We have also found a stereoselective site of action and specific binding in RPE cells that suggest the presence of a specific high affinity receptor for NPD1. We also identified photoreceptor outer segment phagocytosis as an inducer of NPD1 in RPE cells that, in turn, is cytoprotective against damage. Moreover, A2E-mediated RPE cell apoptosis is inhibited by NPD1. We identified pigment epithelium derived factor (PEDF, a potent antiangiogenic growth factor) and other neurotrophins as NPD1-synthesis agonists, and defined synthesis and bioactivity of NPD1. This fundamental progress sets a foundation upon which we can delineate mechanisms of action of NPD1. Using RPE cell cultures, rhodopsin transgenic rats and the Ccl2/Cx3cr1-deficient mouse we will define counteracting inflammatory and apoptotic signaling, relevant to dry forms of age-related macular degeneration (AMD), retinitis pigmentosa (RP) and choroidal neovascularization (CNV), as in the wet form of AMD. Our central hypothesis is that NPD1 regulates RPE cell survival when homeostasis is disrupted. NPD1 down regulates inflammatory and pro-apoptotic signaling, as well as pathoangiogenesis while targeting specific cell survival events. We will use a combination of molecular, cell biological, animal models and mediator lipidomic approaches to accomplish the following specific aims:
Specific Aim 1 : To test the hypothesis that NPD1 induces RPE cell survival through upstream signaling by PI3K/Akt, and dephosphorylation of Bcl-xL by PP2A.
Specific Aim 2 : To test the hypothesis that NPD1 subsequently targets downstream signaling through the expression of Wnt5a gene network.
Specific Aim 3 : To test the prediction that NPD1 reduces inflammation and promotes cell survival through upstream (Aim 1) and downstream (Aim 2) signaling in animal models of retinal degenerations.
Specific Aim 4 : To test the hypothesis that NPD1 signaling ameliorates experimental retinal degeneration. Scientific Impact: Five years from today we will know the manner by which NPD1 signaling mechanisms regulate and preserve the integrity of photoreceptors and RPE cells, which will translate to new understandings regarding ocular health and retinal diseases. We will thus contribute to apply this knowledge to the prevention, repair or amelioration of retinal degenerative diseases.
The long-range goal for the future of this ongoing research project is to explain the remarkable fact that photoreceptors and retinal pigment epithelial (RPE) cells remain structurally and functionally unchanged for many decades in healthy eyes, despite the stress they undergo in their adverse environment, and to use this knowledge to understand what might go wrong in certain retinal diseases. Our central hypothesis is that neuroprotectin D1 (NPD1) regulates retinal pigment epithelial (RPE) cell survival when homeostasis is disrupted (e.g. enhanced oxidative stress conditions);that is, oxidative stress itself triggers NPD1 synthesis as well as pigment epithelial derived factor (PEDF) and other neurotrophins, and that NPD1 in turn down regulates inflammatory and pro-apoptotic signaling as well as pathoangiogenesis through targeting of specific cell survival events. The novel anti-inflammatory, anti-apoptotic and pro-homeostatic signaling regulated by neuroprotectin D1 (NPD1), as revealed by the proposed experiments, will provide new knowledge on the signaling mechanisms that regulate and preserve the integrity of photoreceptors and retinal pigment epithelial cells, which can lead to future therapies for the prevention, repair, or amelioration of retinal degenerative diseases.
Showing the most recent 10 out of 69 publications
