The long-term goal is to understand the fundamental basis of complement signaling in the eye, and how misregulation in this process leads to pathology, to ultimately aid in the development of therapeutic approaches for devastating blinding diseases. Age-related macular degeneration (AMD) occurs in two forms, dry and wet. Dry AMD is characterized by drusen, RPE damage, and photoreceptor cell loss. In some patients, the dry form can transition to wet AMD. Wet AMD, presents itself with chroidal neovascularization (CNV), leakage of these new vessels, and rapid photoreceptor loss. Recent genetic evidence has implicated variations in the complement inhibitor protein factor H (CFH), as well as in the genes for complement factor B (CFB), C2 and C3, as potential risk factors for the disease. A common environmental stressor in AMD is oxidative stress. Three pathways activate the complement system: the classical (CP), alternative (AP), and mannose- binding lectin pathway (LP);all three converge on the same down-stream cascade. Experiments from our own laboratory as well as others, using the laser-damage model of CNV, have suggested that AP signaling is required for CNV development;whereas conflicting evidence has been published in the involvement of the other pathways. AP activity was found to control the generation of the proangiogenic factor vascular endothelial growth factor (VEGF), required for triggering new vessel growth. Finally, we have shown that AP activation is involved in oxidative stress-mediated RPE dysfunction characterized by VEGF and MMP release from RPE monolayers. Oxidative stress was found to sensitize the RPE to complement attack by reducing the levels of membrane-bound endogenous complement inhibitors. For this proposal we will be guided by our overall hypothesis that pathologic activation of the AP has direct effects on the RPE, generating a permissive cellular environment for AMD pathology. This hypothesis will be tested in three aims, both in vivo as well as in RPE cultures (primary human and mouse RPE cells). Using mice in which different pathways of the complement cascade are disrupted and complement-depleted serum, we will examine the relative roles of complement activation mechanisms and determine whether AP activation is required or sufficient. To identify the source of AP proteins (i.e., liver or eye), tissue-specific transgenic mice are analyzed. Next, we will test whether complement activation is specific for CNV, or whether AMD pathologies related to oxidative stress in the Sod1-/- mouse require a hyperactive complement cascade for them to develop. Experiments will be performed to test whether VEGF is involved in mechanisms of complement-mediated injury. And finally, the hypothesis will be put to test in vivo. We will use complement inhibitor strategies using targeted inhibitors that block the complement cascade at different levels to interfere with CNV. Testing inhibitors will not only establish their therapeutic value, but in addition, elucidating their mechanisms in CNV mice will investigate the roles and contributions of the different complement components in CNV.

Public Health Relevance

Age-related macular degeneration (AMD) involves activation of the alternative pathway (AP) of complement and oxidative stress. We are investigating in both an animal model of AMD as well as in retinal pigment epithelial cells (RPE) monolayers how the pathologic activation of the AP, possibly facilitated by oxidative stress, causes direct cellular injury, triggers choroidal neovascularization (CNV), one of the hallmarks of wet AMD, and induces the RPE to secrete factors that promote AMD. Our current research suggests that complement inhibitors may be very effective therapeutic agents, as they target proximal events prior to inflammation and CNV.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY019320-02
Application #
8103872
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Shen, Grace L
Project Start
2010-07-01
Project End
2015-06-30
Budget Start
2011-07-01
Budget End
2012-06-30
Support Year
2
Fiscal Year
2011
Total Cost
$317,533
Indirect Cost
Name
Medical University of South Carolina
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
183710748
City
Charleston
State
SC
Country
United States
Zip Code
29425
Obert, Elisabeth; Strauss, Randy; Brandon, Carlene et al. (2017) Targeting the tight junction protein, zonula occludens-1, with the connexin43 mimetic peptide, ?CT1, reduces VEGF-dependent RPE pathophysiology. J Mol Med (Berl) 95:535-552
Beeson, Craig; Lindsey, Chris; Nasarre, Cecile et al. (2016) Small Molecules that Protect Mitochondrial Function from Metabolic Stress Decelerate Loss of Photoreceptor Cells in Murine Retinal Degeneration Models. Adv Exp Med Biol 854:449-54
Woodell, Alex; Jones, Bryan W; Williamson, Tucker et al. (2016) A Targeted Inhibitor of the Alternative Complement Pathway Accelerates Recovery From Smoke-Induced Ocular Injury. Invest Ophthalmol Vis Sci 57:1728-37
Holers, V Michael; Tomlinson, Stephen; Kulik, Liudmila et al. (2016) New therapeutic and diagnostic opportunities for injured tissue-specific targeting of complement inhibitors and imaging modalities. Semin Immunol 28:260-7
Smith, Amena W; Rohrer, Baerbel; Wheless, Lee et al. (2016) Calpain inhibition reduces structural and functional impairment of retinal ganglion cells in experimental optic neuritis. J Neurochem 139:270-284
Song, Delu; Wilson, Brooks; Zhao, Liangliang et al. (2016) Retinal Pre-Conditioning by CD59a Knockout Protects against Light-Induced Photoreceptor Degeneration. PLoS One 11:e0166348
Rohrer, Bärbel; Bandyopadhyay, Mausumi; Beeson, Craig (2016) Reduced Metabolic Capacity in Aged Primary Retinal Pigment Epithelium (RPE) is Correlated with Increased Susceptibility to Oxidative Stress. Adv Exp Med Biol 854:793-8
Coughlin, Beth; Schnabolk, Gloriane; Joseph, Kusumam et al. (2016) Connecting the innate and adaptive immune responses in mouse choroidal neovascularization via the anaphylatoxin C5a and ??T-cells. Sci Rep 6:23794
Genewsky, Andreas; Jost, Ingmar; Busch, Catharina et al. (2015) Activation of endogenously expressed ion channels by active complement in the retinal pigment epithelium. Pflugers Arch 467:2179-91
Leonard, Anthony P; Cameron, Robert B; Speiser, Jaime L et al. (2015) Quantitative analysis of mitochondrial morphology and membrane potential in living cells using high-content imaging, machine learning, and morphological binning. Biochim Biophys Acta 1853:348-60

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