The molecular mechanism that leads to age-related macular degeneration (AMD) is poorly understood. Gene expression profiling identified adrenomedullin (ADM) as a possible molecular target for the treatment of AMD and expression of ADM was upregulated in eyes with laser-induced choroidal neovascularization (CNV). In vivo experiments strongly indicated that ADM inhibits laser-induced CNV. In vitro tube formation assay demonstrated that neither ADM nor conditioned medium from the retinal pigment epithelial (RPE) cells, D407 cells, treated with ADM affected the capillary-formation of human umbilical vein endothelial cells. In contrast, in vitro macrophage migration assay clearly demonstrated that the conditioned medium of D407 inhibited macrophage migration. Furthermore, the expression of C-C motif chemokine 2 (CCL2) was significantly inhibited in D407 cells after ADM treatment. In vivo experiments using a laser-induced CNV model in ADM(+/-) mice demonstrated that CCL2 expression was upregulated in ADM(+/-) mice with concomitant increase in macrophage migration in the subretinal space. Additionally, the effect of ADM was abrogated in CCL2 knockout mice. These results suggest that administration of ADM inhibits macrophage migration in the subretinal space and leads to the suppression of laser-induced CNV in an animal model. The inhibition of macrophage migration occurred through the CCL2 from RPE. This study provides a novel potential therapeutic target for AMD which does not substantially disrupt VEGF-A signaling mediated vasculogenesis.
Copyright © 2012 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.