Effects of interferon alpha-2b on barrier function and junctional complexes of renal proximal tubular LLC-PK1 cells.
BACKGROUND
Interferon alpha-2b (IFNalpha) treatment of diseases can be accompanied by impaired renal function and capillary leak syndrome. To explore potential mechanisms of IFNalpha-induced renal dysfunction, an in vitro cell culture model system was established to investigate the effects of IFNalpha on barrier function and junctional complexes.


METHODS
LLC-PK1 cells were cultured on microporous membranes. Transepithelial resistance (TER) was measured, and the dose- and time-dependent effects of IFNalpha were assessed. The expression patterns of junctional proteins were examined by Western blot analysis and by confocal immunofluorescence microscopy.


RESULTS
IFNalpha produced a dose- and time-dependent decrease in TER. The effect was reversible on removal of IFNalpha at doses up to 5 x 103 U/ml. Tyrphostin, an inhibitor of phosphotyrosine kinases, ameliorated the IFNalpha-induced decrease in TER. Increased expression of occludin and E-cadherin was detected by Western blot analysis after IFNalpha treatment. Immunofluorescence confocal microscopy revealed a broader staining of occludin and E-cadherin following IFNalpha 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 IFNalpha treatment.


CONCLUSIONS
These findings provide evidence that IFNalpha 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.
Lechner
J
J
Institute of Physiology, University of Innsburck, Austria.
Krall
M
M
Netzer
A
A
Radmayr
C
C
Ryan
M P
MP
Pfaller
W
W
D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D017097:Electric Impedance; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure; D018374:LLC-PK1 Cells; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011994:Recombinant Proteins; D013552:Swine; D019108:Tight Junctions / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure; D014443:Tyrosine / Q000378:metabolism; D062826:Zonula Occludens-1 Protein
D015820:Cadherins; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D008565:Membrane Proteins; D062793:Occludin; D010750:Phosphoproteins; D011994:Recombinant Proteins; D062826:Zonula Occludens-1 Protein; D014443:Tyrosine