Hydrogen peroxide selectively increases paracellular leak pathway permeability of renal epithelial cells

Increased paracellular solute flux is observed in several renal pathogenic processes characterized by oxidative stress. We undertook a study to examine the effect of H 2 O 2 treatment, as a model of oxidative stress, on paracellular permeability of two renal epithelial cell lines, LLC‐PK 1 and MDCK. Both the pore pathway (small ions; TransEpithelial Resistance (TER)) and leak pathway (large solutes; calcein flux) were monitored. MDCK monolayer calcein flux was much lower than LLC‐PK 1 monolayer calcein flux. In contrast, MDCK monolayer TER was about 2‐fold lower than LLC‐PK 1 monolayer TER. Sublethal H 2 O 2 produced a concentration‐dependent increase in calcein flux in both renal cell lines. In contrast, TER only decreased at H 2 O 2 concentrations that increased cell death. H 2 O 2 treatment did not produce a marked change in total contents of multiple tight junction proteins nor in their distributions between Triton X‐100‐soluble and –insoluble fractions, although treatment may have produced a modest decrease in Triton X‐100‐insoluble ZO‐2 content. Surprisingly, occludin overexpression impaired and occludin knockdown modestly enhanced the ability of H 2 O 2 to increase transepithelial calcein flux. H 2 O 2 treatment produced a transient activation of src Family Kinases (SFKs). SFK inhibitors, but not inactive analogs, attenuated the H 2 O 2 ‐induced increase in calcein flux. (Supported by institutional funds)