Fig. 1.

2,4,6-trinitro-benzene sulfonic acid (TNBS) induces intestinal inflammation in zebrafish larvae. (A) Experimental outline. Tg(lyz:DsRed2, cldn15la:GFP) zebrafish larvae were exposed to TNBS (50 µg/ml) or dextran sodium sulphate (DSS) (0.5%) from 72 hours post-fertilization (hpf) until 120 hpf. (B) Confocal microscopy images of DSS, TNBS and untreated (UT) Tg(lyz:DsRed2, cldn15la:GFP) larvae at 5× magnification at 120 hpf. Green fluorescence marks intestinal epithelial cells. Red fluorescence marks neutrophils. Scale bars: 100 µm. (C,D) Quantification of DsRed2⁺ cells in the intestine (C) and mean GFP⁺ intensity (sum of pixel intensities per number of pixels) (D). n=5, one experiment. Each data point represents one 120 hpf zebrafish larva. (E) Violin plots showing the relative expression of proinflammatory cytokines il1b, tnfa, il17a/f3 and il22 analyzed by qPCR in whole larvae at 120 hpf following exposure to TNBS (70 µg/ml). n=24-25, nine experiments. Data show transcript levels as arbitrary units (A.U.) with respect to eef1a1l1 (indicated as ef1a). Each dot represents a pool of ten zebrafish larvae. The black line represents the median. N.S., not significant; *P<0.05, **P<0.01, ***P<0.001. One-way ANOVA with Fisher's LSD test was used in C; unpaired Student's t-test was used in D and E.