Effects of interferon α-2b on barrier function and junctional complexes of renal proximal tubular LLC-PK1 cells

Background. Interferon alpha-2b (IFN alpha) treatment of diseases can be accompanied by impaired renal function and capillary leak syndrome. To explore potential mechanisms of IFN alpha-induced renal dysfunction, an in vitro cell culture model system was established to investigate the effects of IFN alpha on barrier function and junctional complexes. Methods. LLC-PK(1) cells were cultured on microporous membranes. Transepithelial resistance (TER) was measured, and the dose- and time-dependent effects of IFNa were assessed. The expression patterns of junctional proteins were examined by Western blot analysis and by confocal immuno-fluorescence microscopy. Results. IFN alpha produced a dose- and time-dependent decrease in TER. The effect was reversible on removal of IFN alpha at doses up to 5 x 10(3) U/ml. Tyrphostin, an inhibitor of phosphotyrosine kinases, ameliorated the IFN alpha-induced decrease in TER. Increased expression of occludin and E-cadherin was detected by Western blot analysis after IFN alpha treatment. Immunofluorescence confocal microscopy revealed a broader staining of occludin and E-cadherin following IFN alpha treatment, with prominent staining at the basal cell pole in addition to localization at the junctional region. A marked increase in phosphotyrosine staining along the apico-lateral cell border was detected after IFN alpha treatment. Conclusions. These findings provide evidence that IFN alpha can directly affect barrier function in renal epithelial cells. The mechanisms involve enhanced tyrosine phosphorylation and overexpression and possibly displacement or missorting of the junctional proteins occludin and E-cadherin.