Abstract
Purpose: :
Leukocytes require adhesion molecules such as ICAM-1 to migrate across the blood-retinal-barrier. Depletion of ICAM-1 severely influences leukostasis and transmigration of leukocytes. Here we investigated the permeability of the blood-retinal-barrier in C57/Bl6 and ICAM-1 deficient mice with and without systemic LPS injection.
Methods: :
To experimentally induce uveitis the mice received a footpad injection of 25 mg/kg body weight lipopolysaccharide (LPS) from Salmonella typhimurium in phosphate-buffered saline (PBS) or PBS alone. 24h after LPS injection, animals were transcardialy perfused with fluorescent dyes of different molecular sizes. The dyes used were a rhodamine labeled lectin (concanavalin A, 104kDa), a fluorescein isothiocyanate labeled dextran (4kDa) and bisbenzimide (0,5kDa). After perfusion the eyes were enucleated and retinal flatmount preparation was conducted. Using a fluorescent microscope the retinal vessels was examined for leakage of the fluorescent dyes.
Results: :
C57/Bl6 and ICAM-1 deficient mice without LPS injection showed no leakage of the dextran. Bisbenzimide stained the nuclei and the lectin stained the luminal site of the blood vessel endothelial cells. 24h after LPS injection there was leakage of dextran and bisbenzimide out of the vessels in both strains. The lectin showed no leakage into the surrounding tissue.
Conclusions: :
There seems to be no need for leukocyte migration across the blood-retinal-barrier to induce permeability for certain fluorescent dyes.After LPS treatment molecules up to 4kDa can leak out of the vessels in the two mice strains used. Molecules bigger than 100kDa are not able to penetrate the blood-retinal-barrier. But it has to be considered that tight junctions are size and charge selective, so not every molecule of the same sizes used here will show the same effects.
Keywords: inflammation • uveitis-clinical/animal model