Aquaporin expression in blood-retinal barrier cells during experimental autoimmune uveitis.
OBJECTIVE
Blood-retinal barrier (BRB) breakdown and retinal edema are major complications of autoimmune uveitis and could be related to deregulation of aquaporin (AQP) expression. We have therefore evaluated the expression of AQP1 and AQP4 on BRB cells during experimental autoimmune uveitis (EAU) in mice.


METHODS
C57Bl6 mice were immunized with interphotoreceptor retinoid-binding protein (IRBP) peptide 1-16. The disease was graded clinically, and double immunolabeling using glial fibrillary acidic protein (GFAP; a marker of disease activity) and AQP1 or AQP4 antibodies was performed at day 28. AQP1 expression was also investigated in mouse retinal pigment epithelium (RPE) cells (B6-RPE07 cell line) by reverse transcriptase PCR and western blot under basal and tumor necrosis factor alpha (TNF-alpha)-stimulated conditions.


RESULTS
In both normal and EAU retina, AQP1 and AQP4 expression were restricted to the photoreceptor layer and to the Müller cells, respectively. Retinal endothelial cells never expressed AQP1. In vasculitis and intraretinal inflammatory infiltrates, decreased AQP1 expression was observed due to the loss of photoreceptors and the characteristic radial labeling of AQP4 was lost. On the other hand, no AQP4 expression was detected in RPE cells. AQP1 was strongly expressed by choroidal endothelial cells, rendering difficult the evaluation of AQP1 expression by RPE cells in vivo. No major differences were found between EAU and controls at this level. Interestingly, B6-RPE07 cells expressed AQP1 in vitro, and TNF-alpha downregulated AQP1 protein expression in those cells.


CONCLUSIONS
Changes in retinal expression of AQP1 and AQP4 during EAU were primarily due to inflammatory lesions, contrasting with major modulation of AQP expression in BRB detected in other models of BRB breakdown. However, our data showed that TNF-alpha treatment strongly modulates AQP1 expression in B6-RPE07 cells in vitro.
Motulsky
Elie
E
Laboratory of Biological Chemistry and Nutrition, Université Libre de Bruxelles, Brussels, Belgium.
Koch
Philippe
P
Janssens
Sarah
S
Liénart
Maité
M
Vanbellinghen
Anne-Marie
AM
Bolaky
Nargis
N
Chan
Chi-Chao
CC
Caspers
Laure
L
Martin-Martinez
Maria-Dolores
MD
Xu
Heping
H
Delporte
Christine
C
Willermain
François
F
D000818:Animals; D051398:Aquaporin 1 / Q000235:genetics / Q000378:metabolism*; D051401:Aquaporin 4 / Q000378:metabolism*; D001813:Blood-Retinal Barrier / Q000378:metabolism* / Q000473:pathology*; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D010857:Pigment Epithelium of Eye / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014605:Uveitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology*
C496021:Aqp1 protein, mouse; C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D005904:Glial Fibrillary Acidic Protein; D012333:RNA, Messenger; D051398:Aquaporin 1
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