Ceruloplasmin/hephaestin knockout mice model morphologic and molecular features of AMD.
OBJECTIVE
Iron is an essential element in human metabolism but also is a potent generator of oxidative damage with levels that increase with age. Several studies suggest that iron accumulation may be a factor in age-related macular degeneration (AMD). In prior studies, both iron overload and features of AMD were identified in mice deficient in the ferroxidase ceruloplasmin (Cp) and its homologue hephaestin (Heph) (double knockout, DKO). In this study, the location and timing of iron accumulation, the rate and reproducibility of retinal degeneration, and the roles of oxidative stress and complement activation were determined.


METHODS
Morphologic analysis and histochemical iron detection by Perls' staining was performed on retina sections from DKO and control mice. Immunofluorescence and immunohistochemistry were performed with antibodies detecting activated complement factor C3, transferrin receptor, L-ferritin, and macrophages. Tissue iron levels were measured by atomic absorption spectrophotometry. Isoprostane F2alpha-VI, a specific marker of oxidative stress, was quantified in the tissue by gas chromatography/mass spectrometry.


RESULTS
DKOs exhibited highly reproducible age-dependent iron overload, which plateaued at 6 months of age, with subsequent progressive retinal degeneration continuing to at least 12 months. The degeneration shared some features of AMD, including RPE hypertrophy and hyperplasia, photoreceptor degeneration, subretinal neovascularization, RPE lipofuscin accumulation, oxidative stress, and complement activation.


CONCLUSIONS
DKOs have age-dependent iron accumulation followed by retinal degeneration modeling some of the morphologic and molecular features of AMD. Therefore, these mice are a good platform on which to test therapeutic agents for AMD, such as antioxidants, iron chelators, and antiangiogenic agents.
Hadziahmetovic
Majda
M
FM Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Dentchev
Tzvete
T
Song
Ying
Y
Haddad
Nadine
N
He
Xining
X
Hahn
Paul
P
Pratico
Domenico
D
Wen
Rong
R
Harris
Z Leah
ZL
Lambris
John D
JD
Beard
John
J
Dunaief
Joshua L
JL
D000818:Animals; D001052:Apoferritins / Q000378:metabolism; D002570:Ceruloplasmin / Q000502:physiology*; D002829:Choroid / Q000378:metabolism; D003167:Complement Activation; D003176:Complement C3 / Q000378:metabolism; D011415:Complement Factor B / Q000378:metabolism; D015237:Dinoprost / Q000031:analogs & derivatives / Q000378:metabolism; D004195:Disease Models, Animal; D008401:Gas Chromatography-Mass Spectrometry; D007501:Iron / Q000378:metabolism; D019190:Iron Overload / Q000378:metabolism / Q000473:pathology*; D008264:Macrophages / Q000473:pathology; D008268:Macular Degeneration / Q000378:metabolism / Q000473:pathology*; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018384:Oxidative Stress; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D011990:Receptors, Transferrin / Q000378:metabolism; D012160:Retina / Q000378:metabolism; D013054:Spectrophotometry, Atomic
C115626:8,12-iso-isoprostane F2alpha-VI; D003176:Complement C3; C117324:Heph protein, mouse; D008565:Membrane Proteins; D011990:Receptors, Transferrin; D001052:Apoferritins; D015237:Dinoprost; D007501:Iron; D002570:Ceruloplasmin; D011415:Complement Factor B