8-OH-DPAT protects against the loss of tight junctions caused by mitochondrial oxidative stress. (A-D) ARPE-19 cells were grown overnight in low serum medium. They were then treated with paraquat (300 μM), or 8-OH-DPAT (20 μM), or a combination of the two for 48 hours, or left untreated. Cells were fixed, stained with hematoxylin and eosin, and imaged by light microscopy at an original magnification of 20×. (E-H) ARPE-19 cells were grown for five weeks in low serum medium until a change to cuboidal shape was noticeable. They were then treated with paraquat (300 μM), or 8-OH-DPAT (20 μM), or a combination of the two for 48 hr, or left untreated. Cells were then permeabilized by treatment with non-ionic detergent and incubated with an antibody to ZO-1, followed by treatment with a Cy3 conjugated secondary antibody. Cells were visualized by fluorescence microscopy. A & E: cells in medium only; B & F: 300 μM paraquat; C & G: 300 μM paraquat plus 20 μM 8-OH-DPAT; D & H: 20 μM 8-OH-DPAT only.