Aquaporin expression in blood-retinal barrier cells during experimental autoimmune uveitis

摘要

Purpose: Blood-retinal barrier (BRB)breakdown and retinal edema are major complications of autoimmuneuveitis and could be related to deregulation of aquaporin (AQP)expression. We have therefore evaluated the expression of AQP1 and AQP4on BRB cells during experimental autoimmune uveitis (EAU) in mice. Methods: C57Bl6 mice were immunized withinterphotoreceptor retinoid-binding protein (IRBP) peptide 1–16. Thedisease was graded clinically, and double immunolabeling using glialfibrillary acidic protein (GFAP; a marker of disease activity) and AQP1or AQP4 antibodies was performed at day 28. AQP1 expression was alsoinvestigated in mouse retinal pigment epithelium (RPE) cells (B6-RPE07cell line) by reverse transcriptase PCR and western blot under basaland tumor necrosis factor α (TNF-α)-stimulated conditions. Results: In both normal and EAU retina,AQP1 and AQP4 expression were restricted to the photoreceptor layer andto the Müller cells, respectively. Retinal endothelial cells neverexpressed AQP1. In vasculitis and intraretinal inflammatoryinfiltrates, decreased AQP1 expression was observed due to the loss ofphotoreceptors and the characteristic radial labeling of AQP4 was lost.On the other hand, no AQP4 expression was detected in RPE cells. AQP1was strongly expressed by choroidal endothelial cells, renderingdifficult the evaluation of AQP1 expression by RPE cells in vivo. Nomajor differences were found between EAU and controls at this level.Interestingly, B6-RPE07 cells expressed AQP1 in vitro, and TNF-αdownregulated AQP1 protein expression in those cells. Conclusions: Changes in retinalexpression of AQP1 and AQP4 during EAU were primarily due toinflammatory lesions, contrasting with major modulation of AQPexpression in BRB detected in other models of BRB breakdown. However,our data showed that TNF-α treatment strongly modulates AQP1 expressionin B6-RPE07 cells in vitro.