47.4 Discussion

CEP protein modifications are generated by the reaction of an oxidation fragment derived uniquely from DHA-containing phospholipids, namely with 4-hydroxy-7- oxohept-5-enoic acid, with primary amino groups (e.g., protein -lysyl NH2) (Gu et al. 2003a, b). DHA is highly oxidizable owing to its six double bond structure and furthermore, is abundant in retinal photoreceptor outer segments (Fliesler and Anderson 1983). The high oxygen tension and light in the retina provides a permissive environment for the production of oxidative post-translational modifications. Previously we found that rodents exposed to intense light accumulate elevated CEP adducts in the retina and elevated CEP adducts and autoantibodies in plasma (Gu et al. 2004; Renganathan et al. 2003). Other oxidative protein modifications accumulate in AMD ocular tissues, including for example, advanced glycation end products in the choriocapillaris, Bruch’s membrane and CNV membranes (Handa et al. 1999; Ishibashi et al. 1998), and in RPE lipofuscin granules, nitrotyrosine, iso[4]levuglandin E2-adducts and CEP (Ng et al. 2008).

This study shows that plasma CEP biomarker levels, in combination with genomic markers, can discriminate between AMD and control patients with up to80% accuracy and together proteomic and genomic biomarkers offer a potential early warning system for predicting AMD susceptibility. CEP biomarkers may also have utility in monitoring the efficacy of AMD therapeutics as CEP autoantibody titers appear to increase in direct proportion to the severity of RPE lesions in a mouse model of dry AMD (Hollyfield et al. 2008).

Acknowledgments This work was supported in part by US National Institute of Health grants EY015638, EY014239, GM21249, EY016072, BRTT 05–29 from the State of Ohio, a Foundation Fighting Blindness Center Grant, a Research to Prevent Blindness (RPB) Center Grant, a RPB Senior Investigator Award to JWC, a Steinbach Award to JWC, the VA Medical Research Service and the Cleveland Clinic Foundation. We thank Drs Joe G Hollyfield and Bela Anand-Apte for valuable discussions. The Clinical Genomic and Proteomic AMD Study Group was composed of the following individuals: David Barnhart OD1, William J Dupps MD1, Froncie A Gutman MD1, Peter K Kaiser MD1, Hilel Lewis MD1,5, Richard E Gans MD1,5, Bennie H Jeng MD1, Gregory S Kosmorsky DO1, Ronald R Krueger MD1,5, Ann Laurenzi OD1, Roger HS Langston, MD1,

Edward J Rockwood MD1,5, William E Sax MD1, Andrew P Schachat MD1, Jonathan E Sears MD1,5, Rishi Singh MD1, Scott D Smith MD1,5, Mindy Toabe OD1, Elias I Traboulsi MD1,5,

Nadia Waheed MD1, Steven E Wilson MD1,5, and Stacia S. Yaniglos OD4,6, Elisa Bala MD1,4, Sonya Bamba MD1, Sue Crowe BS1, Patrice Nerone RN1, Tiffany Ruez RN1, and Ellen Simpson RN1. JWC is a consultant for Alcon Research Ltd and Allergan, Inc. and has received funding for this research from Merck & Co and Johnson and Johnson. JWC and RGS each have a license for CEP as an inventor with Frantz Biomarkers, LLC.

References

Age-Related Eye Disease Study Group (2001) A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamine C and E, beta carotene, and zinc for age-related macular degeneration and vision loss. Arch Ophthalmol 119:1417–1436

Crabb JW, Miyagi M, Gu X et al (2002) Drusen proteome analysis: an approach to the etiology of age-related macular degeneration. Proc Natl Acad Sci U S A 99:14682–14687

Dewan A, Liu M, Hartman S et al (2006) HTRA1 promoter polymorphism in wet age-related macular degeneration. Science 314:989–992

Ebrahem Q, Renganathan K, Sears J et al (2006) Carboxyethylpyrrole oxidative protein modifications stimulate neovascularization: implications for age-related macular degeneration. Proc Natl Acad Sci U S A 103:13480–13484

Edwards AO, Ritter R 3rd, Abel KJ et al (2005) Complement factor H polymorphism and agerelated macular degeneration. Science 308:421–424

Fliesler SJ, Anderson RE (1983) Chemistry and metabolism of lipids in the vertebrate retina. Prog Lipid Res 22:79–131

Fritsche LG, Loenhardt T, Janssen A et al (2008) Age-related macular degeneration is associated with an unstable ARMS2 (LOC387715) mRNA. Nat Genet 40:892–896

Gu X, Meer SG, Miyagi M et al (2003a) Carboxyethylpyrrole protein adducts and autoantibodies, biomarkers for age-related macular degeneration. J Biol Chem 278:42027–42035

Gu J, Pauer GJT, Yue X et al (2009) Assessing susceptibility to age-related macular degeneration with proteomic and genomic biomarkers. Mol Cell Proteomics PMID: 19202148

Gu X, Renganathan K, Grimm C et al (2004) Rapid changes in retinal oxidative protein modifications induced by blue light. Invest Ophthalmol Vis Sci 45:E-abstract 3474

Gu X, Sun M, Gugiu B et al (2003b) Oxidatively truncated docosahexaenoate phospholipids: total synthesis, generation, and peptide adduction chemistry. J Org Chem 68:3749–3761

Hageman GS, Anderson DH, Johnson LV et al (2005) A common haplotype in the complement regulatory gene factor H (HF1/CFH) predisposes individuals to age-related macular degeneration. Proc Natl Acad Sci U S A 102:7227–7232

Haines JL, Hauser MA, Schmidt S et al (2005) Complement factor H variant increases the risk of age-related macular degeneration. Science 308:419–421

Handa JT, Verzijl N, Matsunaga H (1999) Increase in the advanced glycation end product pentosidine in Bruch’s membrane with age. Invest Ophthalmol Vis Sci 40:775–779

Hollyfield JG, Bonilha VL, Rayborn ME et al (2008) Oxidative damage-induced inflammation initiates age-related macular degeneration. Nat Med 14:194–198

Ishibashi T, Murata T, Hangai M et al (1998) Advanced glycation end products in age-related macular degeneration. Arch Ophthalmol 116:1629–1632

Jakobsdottir J, Conley YP, Weeks DE et al (2005) Susceptibility genes for age-related maculopathy on chromosome 10q26. Am J Hum Genet 77:389–407

Klein RJ, Zeiss C, Chew EY et al (2005) Complement factor H polymorphism in age-related macular degeneration. Science 308:385–389

Maller JB, Fagerness JA, Reynolds RC et al (2007) Variation in complement factor 3 is associated with risk of age-related macular degeneration. Nat Genet 39:1200–1201

Maller J, George S, Purcell S et al (2006) Common variation in three genes, including a noncoding variant in CFH, strongly influences risk of age-related macular degeneration. Nat Genet 38:1055–1059

Ng KP, Gugiu B, Renganathan K et al (2008) Retinal pigment epithelium lipofuscin proteomics. Mol Cell Proteomics 7:1397–1405

Renganathan K, Ebrahem Q, Vasanji A et al (2008) Carboxyethylpyrrole adducts, age-related macular degeneration and neovascularization. Adv Exp Med Biol 613:261–267

Renganathan K, Sun M, Darrow R et al (2003) Light induced protein modifications and lipid oxidation products in rat retina. Invest Ophthalmol Vis Sci 44:E-abstract 5129

Rivera A, Fisher SA, Fritsche LG et al (2005) Hypothetical LOC387715 is a second major susceptibility gene for age-related macular degeneration, contributing independently of complement factor H to disease risk. Hum Mol Genet 14:3227–3236

Yang Z, Camp NJ, Sun H (2006) A variant of the HTRA1 gene increases susceptibility to agerelated macular degeneration. Science 314:992–993

Yates JR, Sepp T, Matharu BK et al (2007) Complement C3 variant and the risk of age-related macular degeneration. N Engl J Med 357:553–561

Chapter 48

Impaired Intracellular Signaling May Allow Up-Regulation of CTGF-Synthesis and Secondary Peri-Retinal Fibrosis in Human Retinal Pigment Epithelial Cells from Patients with Age-Related Macular Degeneration

Piyush C. Kothary, Jaya Badhwar, Christina Weng, and Monte A. Del Monte

Abstract Age-related macular degeneration (AMD) is a major sight-threatening ocular disorder in the United States of America and the world, yet its etiology is not clearly understood, preventing the development of effective prevention or therapy. Connective tissue growth factor (CTGF) has been implicated in the pathological synthesis of peri-retinal fibrous tissue in patients with AMD. Very little is known about the mechanism of this interaction. In this study, the authors demonstrate that insulin like growth factor-1 (IGF-1) and glucose-stimulated CTGF production are not blocked by the MAP kinase pathway inhibitor, PD98059 in hRPE cells obtained from eyes of a patient with AMD in contrast to hRPE cells obtained from normal human eyes. This suggests that there may be abnormal CTGF synthesis regulation in AMD, which may play a role in fibrous peri-retinal membrane formation in patients with AMD-related proliferative vitreoretinopathy.

48.1 Introduction

The human retinal pigment endothelium (hRPE) is a single layer of cells located between the photoreceptors and Bruch’s membrane. It is mitotically inactive in adult eyes. However, in some pathological states, it undergoes mitosis, cell division, and metaplasia. Growth factors have been implicated in inducing pathological proliferation and migration of hRPE cells (Kothary et al. 2001).

M.A. Del Monte (B)

Department of Ophthalmology and Visual Sciences, University of Michigan/Kellogg Eye Center, Ann Arbor, MI, USA

e-mail: madm@umich.edu

Medicine and Biology 664, DOI 10.1007/978-1-4419-1399-9_48,C Springer Science+Business Media, LLC 2010