Figure 4

STAT1 is central to IFNγ-stimulated T84 epithelial responses. (a) siRNA against STAT1 reduces STAT1 synthesis and consequently IFNγ (10 ng/ml) of IRF-1 protein and also (b) blocks IFNγ-induced increases in HRP translocation (measured 48 h post-treatment), but not the drop in TER. (c) Data are presented as mean±s.d.; n=3 monolayers/treatment/experiment, representative of two experiments; ^*P<0.05 compared with scrambled siRNA control (Cont siRNA) and ^#P<0.05 compared with control and matched baseline data. (d) STAT1 siRNA reduced IFNγ-induced phosphorylation of STAT5 as revealed by immunoblotting (siRNA transfection of T84 was conducted 48 h before stimulation). (e, f) The general JAK kinase inhibition (10 μM) reduces IFNγ-induced phosphorylation of STAT1 and STAT5 (PP1 does not) and also significantly reduces the increased transepithelial flux of HRP (mean±s.d.; n=3 monolayers/treatment/experiment, representative of four experiments; ^*P<0.05 compared with control unstimulated (Unstim) monolayers).