Purpose: To examine the effects of interleukin (IL)-1beta on the resistance and permeability of the tight junctions of cultured retinal pigment epithelial cells.
Methods: A human RPE cell line (ARPE-19) cultured on microporous filter-supports was used. IL-1beta and monoclonal anti-IL-1beta antibody-treated IL-1beta (mAbIL-1beta) were added to the standard culture medium. Transepithelial resistance (TER) of confluent RPE cells was measured by epithelial voltmeter. The permeability of the RPE cells to sodium fluorescein, horseradish peroxidase, and inulin was measured. The expression of the occludin and claudin was determined by real-time polymerase chain reaction (PCR), immunohistochemistry, and Western blot analysis.
Results: A significantly greater decrease of TER occurred in IL-1beta-supplemented medium than in standard medium plus mAbIL-1beta after several days of stimulation. A significantly greater increase of sodium fluorescein, horseradish peroxidase, and inulin permeability occurred in IL-1beta-supplemented medium than in standard medium. The expression of the occludin gene and some types of claudin genes was observed. The expression of occludin was downregulated and that of claudin-1 upregulated more in IL-1beta-supplemented medium than in standard medium by real-time PCR, immunohistochemistry, and Western blot analysis.
Conclusions: The tight junctions of ARPE-19 cells are altered by IL-1beta supplementation either directly or through other factors activated by IL-1beta. The downregulation of occludin and upregulation of claudin-1 may have participated in the dysfunction of the RPE tight junctions in these in vitro experiments.