Lipopolysaccharide (LPS) activated transforming growth factor-β–activating kinase (TAK)-1 in vivo, and TAK-1 inhibition prevented the LPS-induced increase in mouse intestinal epithelial tight junction permeability. A: LPS i.p. injections (0.1 mg/kg body weight) in mice caused activation of TAK-1 (phopshoTAK-1) expression by day 3. Densitometry of phosphoTAK-1 protein levels. B: Confocal immunofluorescence showed increase in phopshoTAK-1 expression (green) (arrowheads) (nucleus, blue) in the intestines (enterocytes) of mice treated with LPS (0.1 mg/kg body weight). C: Pretreatment with TAK-1 inhibitor (Inh), oxozeaenol (5 mg/kg body weight), prevented the LPS-induced increase in 10K dextran flux. Oxozeaenol was dissolved in dimethyl sulfoxide and injected intraperitoneally, 1 hour before LPS injection. n = 3 experiments (A and B). ∗∗P < 0.01, ∗∗∗P < 0.001 versus control; †††P < 0.001 versus LPS. Scale bars = 5 μm. C, control.