Fig 1: In DSS-induced conventionally housed mice, IL-37 impairs epithelial tight functions integrity, promotes epithelial cell apoptosis, and suppresses NF-κB-mediated antibacterial gene expression in the colonic epithelium. Conventionally housed WT and IL-37tg mice were administered 1.5% DSS for eight days. Colon tissues and colonic epithelial cells were extracted on day 9. (A) There were representative images of immunohistochemical staining in colonic tissues with antibodies against Claudin1 and Occludin at day eight (Scale bars = 400 μm). Green: positive staining of Claudin1 (left panel), Occludin (right panel), and IgG control (upper right corner); Blue: positive staining of DAPI. IgG control is (B) Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining assay of the colonic epithelium (Scale bars = 100 μm). (C) qRT-PCR analysis of Il-1β and Ifn-γ mRNA expression in colonic intestinal epithelial cells (n = 8 each group). (D) Western blot analysis (left panels) and quantification (right panels) of p65, P-p65, p38, P-p38, c-Fos, and P-c-Fos levels in intestinal epithelial cells from conventionally housed WT and IL-37tg mice normalized to β-actin (n = 4 each group). Data are expressed as mean ± SEM. ** p < 0.01; *** p < 0.001, ns = no significant difference by unpaired two-tailed Student's t-test with Welch's correction.