IL-33 Aggravates DSS-Induced Acute Colitis in Mouse Colon Lamina Propria by Enhancing Th2 Cell Responses

Abstract

Interleukin- (IL-) 33, a member of the IL-1 cytokine family, is an important modulator of the immune system associated with several immune-mediated diseases. IL-33 was expressed in high level on epithelial cells of intestinal tract. It suggested that IL-33 plays a potential role in inflammatory bowel diseases (IBD). We investigated the role of interleukin- (IL-) 33 in dextran sulphate sodium- (DSS-) induced acute colitis in mice using recombinant mouse IL-33 protein (rIL-33). We found that DSS-induced acute colitis was aggravated by rIL-33 treatment. rIL-33-treated DSS mice showed markedly reduced levels of interferon- (IFN-)γ and IL-17A in their colon lamina propria lymphocytes (LPL), but the levels of Th2 cytokines, such as IL-5 and IL-13, in these cells were significantly increased, compared to DSS mice treated with PBS. Our results suggested that IL-33 stimulated CD4(+)T cells and caused the cell to adopt a Th2-type response but at the same time suppressed Th17 and Th1 cell responses. Therefore, IL-33 may be involved in pathogenesis of DSS-induced acute colitis by promoting Th2 cell response in intestinal mucosa of mice. Modulation of IL-33/ST2 signaling by monoclonal antibody (mAb) could be a novel biological therapy in DSS-induced acute colitis.

Figure 1

Administration of rIL-33 results in exacerbation of DSS-induced acute colitis. (a) Weight loss, survival rate, and disease activity index; (b) histological score (original magnification, ×200); (c) macroscopic changes and colon length. Data indicate mean ± SD of 8 mice of each group obtained from a representative of three independent experiments (n = 8 per group). ^∗ P < 0.05, ^∗∗ P < 0.01, and ^# P < 0.0001.

Figure 2

Flow cytometry analysis of the populations of LPL in the colon in rIL-33- and PBS-treated mice with or without acute colitis. ((a), (c)) The percentage of neutrophil, macrophage, CD4⁺, CD4⁺CD44⁺, CD4⁺CD25⁺, B220⁺CD25⁺, γδT cell, and NK and NKT cell in LP in the colon of rIL-33- and PBS-treated mice with or without acute colitis; ((b), (d)) the absolute number of LPL in the colon of rIL-33- and PBS-treated mice with or without acute colitis. Data indicating mean ± SD obtained from a representative of three independent experiments were valued by a Student's t-test (n = 3 per group). ^∗ P < 0.05; ^∗∗ P < 0.01.

Figure 3

Cytokine-producing T cells in the LPL of colon in rIL-33- and PBS-treated mice with or without DSS-induced acute colitis. ((a), (c)) The percent of CD4⁺IFN-γ ⁺ or CD4⁺IL-17A⁺ T-LPL in the LPL of colon in rIL-33- and PBS-treated mice with or without DSS-induced acute colitis. ((b), (d)) The absolute number of CD4⁺IFN-γ ⁺ or CD4⁺IL-17A⁺ T-LPL in the LPL of colon in rIL-33- and PBS-treated mice with or without DSS-induced acute colitis. Data indicating mean ± SD obtained from a representative of three independent experiments were valued by a Student's t-test (n = 4 per group). ^∗ P < 0.05; ^∗∗ P < 0.01.

Figure 4

ELISA analysis of cytokine production in LP of colon in rIL-33- and PBS-treated mice with or without DSS-induced acute colitis. The level of IFN-γ, IL-17A, IL-4, IL-5, IL-13, or IL-10 production in the culture supernatants of LPL of colon was analyzed by ELISA with or without anti-CD28/anti-CD3 mAbs stimulations. Data indicating mean ± SD obtained from a representative of three independent experiments were valued by a Student's t-test (n = 4 per group). ^∗ P < 0.05; ^∗∗ P < 0.01; ^∗∗∗ P < 0.001.

Figure 5

Total mRNA was extracted from colonic tissues to analyze the expression of IL-4, IL-5, IL-13, IFN-γ, IL-17A, IL-10, Foxp3, T-bet, GATA-3, and RORγt by real-time PCR. Data indicating mean ± SD obtained from a representative of three independent experiments were valued by a Student's t-test (n = 5 per group). ^∗ P < 0.05; ^∗∗ P < 0.01; ^∗∗∗ P < 0.001.