The pathogenic role of the canonical Wnt pathway in age-related macular degeneration.
OBJECTIVE
The authors' previous studies showed that the Wnt signaling pathway is activated in the retinas and retinal pigment epithelia of animal models of age-related macular degeneration (AMD) and diabetic retinopathy (DR). The purpose of this study was to investigate the role of the canonical Wnt pathway in pathogenesis of these diseases.


METHODS
The Wnt pathway was activated using the Wnt3a-conditioned medium and adenovirus expressing a constitutively active mutant of beta-catenin (Ad-S37A) in ARPE19, a cell line derived from human RPE. Ad-S37A was injected into the vitreous of normal rats to activate the Wnt pathway in the retina. Accumulation of beta-catenin was determined by Western blot analysis, and its nuclear translocation was revealed by immunocytochemistry. Inflammatory factors were quantified by Western blot analysis and ELISA. Oxidative stress was determined by measuring intracellular reactive oxygen species (ROS) generation and nitrotyrosine levels.


RESULTS
The Wnt3a-conditioned medium and Ad-S37A both increased beta-catenin levels and its nuclear translocation in ARPE19 cells, suggesting activation of the canonical Wnt pathway. Activation of the Wnt pathway significantly upregulated the expression of VEGF, NF-kappaB, and TNF-alpha. Further, Ad-S37A induced ROS generation in a dose-dependent manner. Wnt3a also induced a twofold increase of ROS generation. Intravitreal injection of Ad-S37A upregulated the expression of VEGF, ICAM-1, NF-kappaB, and TNF-alpha and increased protein nitrotyrosine levels in the retinas of normal rats.


CONCLUSIONS
Activation of the canonical Wnt pathway is sufficient to induce retinal inflammation and oxidative stress and plays a pathogenic role in AMD and DR.
Zhou
Ti
T
Department of Biochemistry, Zhongshan Medical School, Sun Yat-sen University, Guangzhou, China.
Hu
Yang
Y
Chen
Ying
Y
Zhou
Kevin K
KK
Zhang
Bin
B
Gao
Guoquan
G
Ma
Jian-xing
JX
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000378:metabolism; D006801:Humans; D056965:Injections, Intraocular; D008268:Macular Degeneration / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D018384:Oxidative Stress / Q000502:physiology; D051381:Rats; D011914:Rats, Inbred BN; D017382:Reactive Oxygen Species / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000378:metabolism* / Q000473:pathology*; D012173:Retinitis / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology; D014822:Vitreous Body; D051153:Wnt Proteins / Q000378:metabolism*; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
C495270:CTNNB1 protein, human; D017077:Culture Media, Conditioned; D017382:Reactive Oxygen Species; C555510:WNT3A protein, human; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; D051176:beta Catenin; C002744:3-nitrotyrosine; D014443:Tyrosine