Mechanisms for the induction of HNE- MDA- and AGE-adducts, RAGE and VEGF in retinal pigment epithelial cells

• Published in: Experimental eye research Vol. 80; no. 4; pp. 567 - 580
• Main Authors: Zhou, Jilin, Cai, Bolin, Jang, Young P., Pachydaki, Sophia, Schmidt, Ann Marie, Sparrow, Janet R.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2005
• Subjects: 4-hydroxynonenal, HNE; A2E; advanced glycation end products; age-related macular degeneration; Aldehydes - analysis; Aldehydes - metabolism; Cells, Cultured; Epithelial Cells - chemistry; Eye Proteins - analysis; Gene Expression; Glycation End Products, Advanced - metabolism; Growth Inhibitors - analysis; Growth Inhibitors - metabolism; Humans; Immunoblotting - methods; Immunohistochemistry - methods; Light; lipid peroxidation; Lipid Peroxidation - physiology; lipofuscin; Macular Degeneration - metabolism; Malondialdehyde - antagonists & inhibitors; Malondialdehyde - metabolism; malondialdhyde, MDA; Pigment Epithelium of Eye - chemistry; Pyridinium Compounds - metabolism; RAGE; Receptor for Advanced Glycation End Products; Receptors, Immunologic - analysis; Receptors, Immunologic - metabolism; retinal pigment epithelium; Retinoids - metabolism; Reverse Transcriptase Polymerase Chain Reaction - methods; RNA, Messenger - analysis; Up-Regulation - physiology; vascular endothelial growth factor; Vascular Endothelial Growth Factors - metabolism; A2E; vascular endothelial growth factor; lipofuscin; malondialdhyde, MDA; retinal pigment epithelium; 4-hydroxynonenal, HNE; RAGE; age-related macular degeneration; lipid peroxidation; advanced glycation end products
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1016/j.exer.2004.11.009

Pathological features of age-related macular degeneration such as the formation of extracellular deposits and neovascularization are frequently viewed as outcomes of compromising processes within retinal pigment epithelial cells, but the initiating circumstances are poorly understood. Here we tested the hypothesis that photooxidation events initiated by A2E, a blue light-excitable aging fluorophore of the retinal pigment epithelium, can set the stage for altered cellular signaling and changes in the expression of genes that can impact the extracellular milieu. Proteins modified by lipid peroxidation products (4-hydroxynonenal; malondialdhyde) and advanced glycation end products were detected at sites of blue light irradiation both in association with the cultured A2E-laden retinal pigment epithelial cells and within the fibronectin substrate on which the cells were grown. RAGE, the cell surface receptor that transduces the effects of advanced glycation end products, was also upregulated, and RAGE expression co-localized with the deposition of advanced glycation end products. Blue light triggered alterations in gene expression was also evidenced by elevations in both transcripts and protein for vascular endothelial growth factor, a potent angiogenic and permeability-enhancing factor. These findings indicate that cell associated and extracellular modification of proteins by lipid peroxidation products and advanced glycation end products together with increased expression of RAGE and vascular endothelial growth factor may be induced consequent to blue light illumination of A2E-burdened retinal pigment epithelial cells. Thus, photooxidative events that are not an immediate threat to retinal pigment epithelial cell viability may nevertheless elicit sustained perturbation that could ultimately alter neighboring tissues and impact retinal pigment epithelial cell function.