Leukocyte diapedesis in vivo induces transient loss of tight junction protein at the blood-retina barrier.
OBJECTIVE
Although much is now understood about the molecular structure of tight junctions (TJs), little is known about the regulation of their function during neural inflammatory disease processes in vivo. The mechanisms by which leukocytes transmigrate the blood-retina barrier (BRB) without affecting endothelial permeability are controversial.


METHODS
Confocal immunofluorescence microscopy of ex vivo retinal wholemounts was used to study BRB integrity during leukocyte adhesion and migration during experimental autoimmune uveoretinitis (EAU). Western blot analysis was used to measure levels of TJ proteins in EAU retina and RPE and in normal retina or RPE cultured with cytokines or chemokines.


RESULTS
No evidence for discontinuity or other weakness of the endothelial or epithelial barrier at tricellular corners was observed, and maximum disruption of TJ protein expression was focused in retinal venules correlating with sites of leukocyte extravasation. Areas of maximum TJ protein loss in vivo also correlated with redistribution or loss of ensheathing astrocyte processes on venules but not adjacent capillaries or arterioles. Exposure of normal choroidal and retinal explants ex vivo to cytokines and chemokines alone did not downregulate total occludin-1 or claudin-3 TJ protein expression.


CONCLUSIONS
The data presented herein support an active role for leukocytes in TJ disruption and blood-retina barrier (BRB) breakdown during retinal inflammation and further implicate venule microenvironment as a key factor in leukocyte recruitment to retinal tissue in vivo.
Department of Ophthalmology, School of Medicine, University of Aberdeen, Aberdeen, Scotland, United Kingdom.
Heping
H
Xu
Rosemary
R
Dawson
Isabel J
IJ
Crane
Janet
J
Liversidge
D000818:Animals; D001327:Autoimmune Diseases / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D001813:Blood-Retinal Barrier / Q000502:physiology*; D015153:Blotting, Western; D062445:Claudin-1; D062465:Claudin-3; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism; D005136:Eye Proteins; D007962:Leukocytes / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D012171:Retinal Vessels / Q000378:metabolism; D012173:Retinitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D012177:Retinol-Binding Proteins; D019108:Tight Junctions / Q000378:metabolism*; D014605:Uveitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D062826:Zonula Occludens-1 Protein; D000099214:Retinol-Binding Proteins, Interstitial
D062445:Claudin-1; D062465:Claudin-3; D005136:Eye Proteins; D008565:Membrane Proteins; D062793:Occludin; D010750:Phosphoproteins; D012177:Retinol-Binding Proteins; D062826:Zonula Occludens-1 Protein; D000099214:Retinol-Binding Proteins, Interstitial; C568113:Cldn1 protein, mouse; C568123:Cldn3 protein, mouse; C568986:Ocln protein, mouse; C569043:Tjp1 protein, mouse