Interferon alpha 2b increases paracellular permeability of renal proximal tubular LLC-PK1 cells via a mitogen activated protein kinase signaling pathway

The therapeutic administration of Interferon alpha 2b (IFN alpha) is often accompanied by impaired renal function, i.e. reduced glomerular filtration rate and sometimes a so-called "capillary leak syndrome". To clarify the me chanism behind the renal dysfunction, confluent monolayers of LLC-PK1 cells were used as a model system to analyze the effects of IFN alpha, on renal tubular epithelium. Examination of epithelial barrier function via measurem ent of transepithelial resistance (TER) revealed a dose dependent increase in paracellular permeability by IFN alpha treatment. The effect was reversi ble upon removal of IFN alpha at doses up to 5 x 10(3) U/mL. Apical or baso lateral application of IFN alpha yielded the same decrease in TER. Tyrphost in A25, an inhibitor of phosphotyrosine kinases, ameliorated the IFN alpha induced decrease of TER. In order to unravel intracellular signal transduct ion pathways that may mediate IFN alpha induced changes of epithelial barri er function, we inhibited IFN alpha signaling through a mitogen activated p rotein kinase pathway by the Mek1 inhibitor PD98059. The inhibitor could be shown to prevent IFN alpha induced decrease of transepithelial resistance. Inhibitors of the p38 mitogen activated protein kinase pathway did not aff ect IFN alpha mediated changes of epithelial barrier function, indicating a highly specific role for the Mek/Erk pathway. Activation of mitogen activa ted protein kinase pathways by epidermal growth factor or anisomycin could not, per se, imitate the effect of IFNa on the paracellular permeability of LLC-PK1 monolayers. These findings provide evidence that IFN alpha can aff ect barrier function in renal epithelial cells via activation of the Mek/Er k pathway.