Effects of interferon alpha-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 ac companied by impaired renal function and capillary leak syndrome. To explor e 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-PK1 cells were cultured on microporous membranes. Transepithel ial 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 micr oscopy. 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/m l. Tyrphostin, an inhibitor of phosphotyrosine kinases, ameliorated the IFN alpha-induced decrease in TER. Increased expression of occludin and E-cadh erin was detected by Western blot analysis after IFN alpha treatment. Immun ofluorescence confocal microscopy revealed a broader staining of occludin a nd E-cadherin following IFN alpha treatment, with prominent staining at the basal cell pole in addition to localization at the junctional region. A ma rked increase in phosphotyrosine staining along the apico-lateral cell bord er was detected after IFN alpha treatment. Conclusions. These findings provide evidence that IFN alpha can directly af fect barrier function in renal epithelial cells. The mechanisms involve enh anced tyrosine phosphorylation and overexpression and possibly displacement or missorting of the junctional proteins occludin and E-cadherin.