Macular Degeneration: Kaliappan S

Bora PS, Kaliappan S, Lyzogubov VV, Tytarenko RG, Thotakura S, Viswanathan T, Bora NS. · Department of Ophthalmology, Jones Eye Institute, Pat & Willard Walker Eye Research Center, 4301 West Markham, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. · FEBS Lett. · Pubmed #17466298 No free full text.

Abstract: The aim of this study was to investigate the role of adiponectin (APN) in a mouse model of laser induced choroidal neovascularization (CNV). We have shown by immunohistochemistry that the expression of APN, adiponectin receptor 1, adiponectin receptor 2 and T cadherin gradually increased from day 1 to day 7 post-laser in laser treated mice compared to controls. Recombinant APN (rAPN) was injected intraperitoneally (i.p., 25 microg/mouse) or intravitreally (2 microg/eye) in lasered mice. Another set of lasered mice received APN peptide via i.p. (75 microg/mouse) or intravitreal (30 microg/eye) route. Control mice received a similar treatment with PBS, control protein or control peptide after laser treatment. We found that in the i.p. and intravitreal injection of rAPN resulted in 78% and 68% inhibition respectively in the size of CNV complex compared to control mice. Similar results were observed when APN peptide was injected intravitreally or i.p. Treatment with rAPN or the peptide resulted in decreased levels of vascular endothelial growth factor. Thus, APN inhibited choroidal angiogenesis and may have therapeutic implications in the treatment of wet age related macular degeneration.

Tezel TH, Bodek E, Sönmez K, Kaliappan S, Kaplan HJ, Hu Z, Garen A. · Department of Ophthalmology & Visual Sciences, Kentucky Lions Eye Center, University of Louisville School of Medicine, Louisville, KY 40202, USA. · Ocul Immunol Inflamm. · Pubmed #17365800 No free full text.

Abstract: PURPOSE: ICON is a fusion protein composed of factor VII, the natural ligand for tissue factor, conjugated to the Fc domain of a human IgG1 immunoglobulin. It binds to the tissue factor expressed on neovascular endothelia and initiates a cytolytic immune attack that destroys the neovascular tissue. We previously showed that mouse factor VII-Fc chimeric antibody (mICON) dramatically decreases the frequency of choroidal neovascularization in a laser-induced choroidal neovascularization model in mice. Herein, we determined the safety and efficacy of mICON in destroying subretinal choroidal neovascularization in pig eyes. METHODS: mICON (150-1200 microg) was administered into the midvitreous cavity of the pig eye either before (on Day 0) or after (on Day 10) induction of choroidal neovascularization with laser photocoagulation. On Day 14, the incidence of choroidal neovascularization was determined using confocal microscopy. We also determined the binding specificity (% binding to choroidal neovascularization/% binding to non-choroidal neovascularization areas) of mICON to tissue factor expressed on endothelial cells of laser-induced choroidal neovascularization. RESULTS: We observed that mICON selectively destroyed choroidal neovascularization in a dose-dependent manner (r = -0.93; EDB50B = 571.3 microg). Obliteration of the choroidal neovascular complex was more prominent at doses > 300 microg (p < 0.05). No systemic or local complications (including retinal tear/detachment, inflammation, infection, cataract, or glaucoma) were observed. Binding specificities of hICON (2.2 +/- 0.2) and mICON (3.4 +/- 0.4) were significantly higher than that of anti-von Willebrand antibody (0.1 +/- 0.01, p < 0.001). CONCLUSIONS: Both hICON and mICON bound to the neovascular endothelia of choroidal neovascularization with greater specificity than anti-von Willebrand antibody. Furthermore, mICON can selectively obliterate already established choroidal neovascularization, which suggests that it may be useful for immunotherapy in patients with exudative (wet) macular degeneration.

Bora NS, Kaliappan S, Jha P, Xu Q, Sivasankar B, Harris CL, Morgan BP, Bora PS. · Department of Ophthalmology, Jones Eye Institute, Pat and Willard Walker Eye Research Center, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. · J Immunol. · Pubmed #17237428 links to  free full text

Abstract: We have shown that membrane attack complex (MAC) formation via the activation of the alternative pathway plays a central role in the laser-induced choroidal neovascularization (CNV). This study was undertaken to understand the role of a complement regulatory protein, CD59, which controls MAC assembly and function, in this model. CNV was induced by laser photocoagulation in C57BL/6 and Cd59a(-/-) mice using an argon laser. Animals from each group were sacrificed on day 1, 3, 5, and 7 postlaser. Retinal pigment epithelium-choroid-scleral tissue was examined to determine the incidence and size of CNV complex, and semiquantitative RT-PCR and Western blot analysis for CD59a was studied. Recombinant soluble mouse CD59a-IgG2a fusion (rsCD59a-Fc) protein was injected via i.p. or intravitreal routes 24 h before laser. Our results demonstrated that CD59a (both mRNA and protein) was down-regulated during laser-induced CNV. Cd59a(-/-) mice developed CNV complex early in the disease process. Increased MAC deposition was also observed in these Cd59a(-/-) mice. Administration of rsCD59a-Fc inhibited the development of CNV complex in the mouse model by blocking MAC formation and also inhibited expression of angiogenic growth factors. These data provide strong evidence that CD59a plays a crucial role in regulating complement activation and MAC formation essential for the release of growth factors that drive the development of laser-induced CNV in mice. Thus, our results suggest that the inhibition of complement by soluble CD59 may provide a novel therapeutic alternative to current treatment.

Bora PS, Kaliappan S, Xu Q, Kumar S, Wang Y, Kaplan HJ, Bora NS. · Department of Ophthalmology and Visual Science, Kentucky Lions Eye Center, University of Louisville, KY, USA. · FEBS J. · Pubmed #16689928 No free full text.

Abstract: One of the pathologic complications of exudative (i.e. wet-type) age-related macular degeneration (AMD) is choroidal neovascularization (CNV). The aim of this study was to investigate whether chronic and heavy alcohol consumption influenced the development of CNV in a rat model. The oxidative metabolism of alcohol is minimal or absent in the eye, so that ethanol is metabolized via a nonoxidative pathway to form fatty acid ethyl esters (FAEE). Fatty acid ethyl ester synthase (FAEES) was purified from the choroid of Brown Norway (BN) rats. The purified protein was 60 kDa in size and the antibody raised against this protein showed a single band on western blot. BN rats on a regular diet were fed alcohol for 10 weeks. Control rats were fed water with a regular diet and pair-fed control rats were fed regular diet, water and glucose. We found that FAEES activity was increased 4.0-fold in the choroid of alcohol-treated rats compared with controls. The amount of ethyl esters produced in the choroid of 10 week alcohol-fed rats was 7.4-fold more than rats fed alcohol for 1 week. The increased accumulation of ethyl esters was associated with a 3.0-fold increased expression of cyclin E and cyclin E/CDK2; however, the level of the cyclin kinase inhibitor, p27Kip, did not change. The increased accumulation of ethyl esters was also associated with 3.0-fold decreased expression of APN in the choroid. We also found that the size of CNV increased by 28% in alcohol-fed rats. Thus, our study showed that chronic, heavy alcohol intake was associated with both an increased accumulation of ethyl esters in the choroid and an exacerbation of the CNV induced by laser treatment. These results may provide insight into the link between heavy alcohol consumption and exudative AMD.

Bora PS, Sohn JH, Cruz JM, Jha P, Nishihori H, Wang Y, Kaliappan S, Kaplan HJ, Bora NS. · Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Center, University of Louisville, 301E Muhammad Ali Boulevard, Louisville, KY 40202, USA. · J Immunol. · Pubmed #15611275 links to  free full text

Abstract: Choroidal neovascularization (CNV), or choroidal angiogenesis, is the hallmark of age-related macular degeneration and a leading cause of visual loss after age 55. The pathogenesis of new choroidal vessel formation is poorly understood. Although inflammation has been implicated in the development of CNV, the role of complement in CNV has not been explored experimentally. A reliable way to produce CNV in animals is to rupture Bruch's membrane with laser photocoagulation. A murine model of laser-induced CNV in C57BL/6 mice revealed the deposition of C3 and membrane attack complex (MAC) in the neovascular complex. CNV was inhibited by complement depletion using cobra venom factor and did not develop in C3(-/-) mice. Anti-murine C6 Abs in C57BL/6 mice inhibited MAC formation and also resulted in the inhibition of CNV. Vascular endothelial growth factor, TGF-beta2, and beta-fibroblast growth factor were elevated in C57BL/6 mice after laser-induced CNV; complement depletion resulted in a marked reduction in the level of these angiogenic factors. Thus, activation of complement, specifically the formation of MAC, is essential for the development of laser- induced choroidal angiogenesis in mice. It is possible that a similar mechanism may be involved in the pathophysiology of other angiogenesis essential diseases.