Fig. 4

TRAIL does not enhance cell apoptosis in the inflamed colon of mice with DSS-induced colitis. a In the group with DSS-induced colitis, C57BL/6 mice were fed 2.5% DSS in sterilized drinking water for 5 days (days 0–5), followed by 2 days of normal water (days 6 and 7) and treated with either vehicle (200 μl/mouse/day, i.p.) or the TRAIL (50 μg/mouse/day, i.p.) from day 0. Control mice were given normal drinking water only. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining of the distal colon tissue from each group was carried out on day 3 and day 7. Positive controls were colon tissue slides from control mice pretreated with DNase I before TUNEL staining. TUNEL⁺ cells (arrow) indicate apoptotic cells. b C57BL/6 mice were fed 2.5% DSS in sterilized drinking water for 5 days (days 0–5), followed by 2 days of normal water (days 6 and 7). On day 7, colon tissues were collected and primary CD4⁺ T cells, CD8⁺ T cells, CD11c⁺ dendritic cells, and colonic epithelial cells from colon tissues were isolated, cultured in a 96-well plate (10⁴ cells per well), and treated with various concentrations of TRAIL for 24 h. The L292 cells were cultured and treated with TRAIL in the same manner. Cell lysates were collected and quantified using apoptotic ELISAs. Data are presented as the mean ± SD of triplicate samples. *p < 0.05, **p < 0.01 by Student’s t test, compared to the L929 cells without TRAIL treatment. Data are representative of three independent experiments