Drusen complement components C3a and C5a promote choroidal neovascularization

doi:10.1073/pnas.0408835103

Drusen complement components C3a and C5a promote choroidal neovascularization

*Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY 40536;
^‡Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109;
^§Department of Microbiology, University of Alabama, Birmingham, AL 35294;
^¶Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104;
^∥Department of Ophthalmology and Visual Science, Moran Eye Center and Program in Human Molecular Biology and Genetics, Eccles Institute of Human Genetics, University of Utah, Salt Lake City, UT 84132; and
**Department of Ophthalmology, Medical College of Georgia, Augusta, GA 30912

Edited by Jeremy Nathans, Johns Hopkins University School of Medicine, Baltimore, MD, and approved December 22, 2005
↵ ^†M.N., B.J.R., E.S., and J.Z.B. contributed equally to this work. (received for review November 29, 2004)

Abstract

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in industrialized nations, affecting 30–50 million people worldwide. The earliest clinical hallmark of AMD is the presence of drusen, extracellular deposits that accumulate beneath the retinal pigmented epithelium. Although drusen nearly always precede and increase the risk of choroidal neovascularization (CNV), the late vision-threatening stage of AMD, it is unknown whether drusen contribute to the development of CNV. Both in patients with AMD and in a recently described mouse model of AMD, early subretinal pigmented epithelium deposition of complement components C3 and C5 occurs, suggesting a contributing role for these inflammatory proteins in the development of AMD. Here we provide evidence that bioactive fragments of these complement components (C3a and C5a) are present in drusen of patients with AMD, and that C3a and C5a induce VEGF expression in vitro and in vivo. Further, we demonstrate that C3a and C5a are generated early in the course of laser-induced CNV, an accelerated model of neovascular AMD driven by VEGF and recruitment of leukocytes into the choroid. We also show that genetic ablation of receptors for C3a or C5a reduces VEGF expression, leukocyte recruitment, and CNV formation after laser injury, and that antibody-mediated neutralization of C3a or C5a or pharmacological blockade of their receptors also reduces CNV. Collectively, these findings establish a mechanistic basis for the clinical observation that drusen predispose to CNV, revealing a role for immunological phenomena in angiogenesis and providing therapeutic targets for AMD.

Footnotes

^††To whom correspondence should be addressed. E-mail: jamba2{at}uky.edu
Author contributions: B.K.A. and J.A. designed research; M.N., B.J.R., E.S., Y.C., J.Z.B., and J.A. performed research; J.V.S., S.R.B., J.D.L., Y.C., and K.Z. contributed new reagents/analytic tools; J.A. analyzed data; and B.J.R., S.R.B., J.D.L., B.K.A., and J.A. wrote the paper.
Conflict of interest statement: J.A. is listed on a patent application filed by the University of Kentucky describing these findings.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

Abbreviations:

AMD,

age-related macular degeneration;

CNV,

choroidal neovascularization;

C3/5,

complement components 3/5;

C3a/5a,

bioactive fragments of C3/5;

C3aR/5aR,

Cea/5a receptors;

RPE,

retinal pigmented epithelium.