Fig. 5

Phosphorylation and dephosphorylation regulates tight junction integrity. Panel a. Pre-treating NHBE cells with 15 or 30 μM AG82, a protein tyrosine kinase inhibitor, blocks the decrease in resistance associated with H₂O₂ exposure (mean ± s.e.m., n = 7 cultures from 6 lung donors each concentration, * = p < 0.05 compared to H₂O₂ alone). Panel b. Pretreatment of cultures with AG82 (15 μM) and H₂O₂ was not different from control untreated cultures: no increase in permeability seen (n = 3 cultures from 3 lungs). Panel c. The phosphatase inhibitor phenylarsine oxide decreased the resistance in NHBE cultures in a concentration dependent fashion (2.5–25 μM), similar to H₂O₂ (n = 4 cultures from 4 lung donors, * = p < 0.05 compared to no H₂O₂ control). Panel d. Mannitol flux experiments also showed an increase in permeability induced by phosphatase inhibition (25 μM phenylarsine oxide, n = 3 cultures from 3 lungs, * = p < 0.05)