Curcumin alleviates experimental colitis via a potential mechanism involving memory B cells and Bcl-6-Syk-BLNK signaling

Figure 1 Drugs and protocols used in the study. A: Molecular structural formula of curcumin (Cur); B: Cur used in the experiment; C: Colitis induction and Cur administration. The experiment lasted for 22 d, including 3 d of adaptive feeding, 0-7 d of treatment with 3% DSS treatment with drinking water, and 7 d of free drinking water. Animals were divided into four groups: Control (n = 10), DSS (n = 10), DSS + Cur (100 mg/kg/d, n = 10), and Ctrl + Cur (100 mg/kg/d, n = 10) groups.

Figure 2 Therapeutic evaluation of curcumin on DSS-induced experimental colitis. A: Body weight of mice from days 0-22; B: Weight change of rate in mice from days 1-22; C: OB scores of mice in the four groups from days 1-22; D: DAI scores of mice in the four groups from days 1-22; E: Gross changes in colonic length; F: Colonic length of mice on day 22 in the four groups; G: Colonic weight; H: Body weight; I: Colonic weight index; J: Colonic weight/colonic length; K: Spleen weight; L: Spleen weight/body weight; M: Histological appearance of colons from individual groups of mice (hematoxylin and eosin staining, magnification 50 ×, scale bar = 100 μm); N: Pathological injury score. Data are presented as the mean ± SE (n = 8-10). ^aP < 0.05, ^bP < 0.01 vs Control group; ^cP < 0.05, ^dP < 0.01 vs DSS group.

Figure 3 Curcumin effectively regulates inflammatory cytokine expression. A: Concentration of IL-10 in colonic tissue; B: Concentration of IL-35 in colonic tissue; C: Concentration of IL-6 in colonic tissue; D: Concentration of IL-17A in colonic tissue; E: Concentration of IL-1β in colonic tissue; F: Concentration of TNF-α in colonic tissue. Data are presented as the mean ± SE (n = 8-10). ^aP < 0.05, ^bP < 0.01 vs Control group; ^cP < 0.05, ^dP < 0.01 vs DSS group.

Figure 4 Curcumin regulates differentiation of memory B cells in DSS-induced ulcerative colitis mice. A: Representative flow cytometry profile of peripheral blood mononuclear cells (PBMC); B: Representative flow cytometry profile of CD19⁺ cells in peripheral blood; C: Representative flow cytometry profile of CD19⁺ CD27⁺ cells in peripheral blood; D: Bar chart of CD19⁺ CD2 ⁺ memory B cells. Data are presented as the mean ± SE (n = 8-10). ^aP < 0.05, ^bP < 0.01 vs Control group; ^cP < 0.05, ^dP < 0.01 vs DSS group.

Figure 5 Curcumin regulates differentiation of memory B cells in DSS-induced ulcerative colitis mice. A: Representative flow cytometry profile of CD19⁺ CD27⁺ IgG⁺ cells in peripheral blood; B: Bar chart of CD19⁺ CD27⁺ IgG⁺ cells; C: Representative flow cytometry profile of CD19⁺ CD27⁺ IgM⁺ cells in peripheral blood; D: Bar chart of CD19⁺ CD27⁺ IgM⁺ cells; E: Representative flow cytometry profile of CD19⁺ CD27⁺ IgA⁺ cells in peripheral blood; F: Bar chart of CD19⁺ CD27⁺ IgA⁺ cells. Data are presented as the mean ± SE (n = 8-10). ^aP < 0.05, ^bP < 0.01 vs Control group; ^cP < 0.05, ^dP < 0.01 vs DSS group.

Figure 6 Curcumin regulates differentiation of memory B cells in DSS-induced ulcerative colitis mice. A: Representative flow cytometry profile of CD19⁺ CD27⁺ FCRL5⁺ cells in peripheral blood; B: Bar chart of CD19⁺ CD27⁺ FCRL5⁺ cells; C: Representative flow cytometry profile of CD19⁺ CD27⁺ CD103⁺ cells in peripheral blood; D: Bar chart of CD19⁺ CD27⁺ CD103⁺ cell; E: Representative flow cytometry profile of CD19⁺ CD27⁺ IL-10⁺ cells in peripheral blood; F: Bar chart of CD19⁺ CD27⁺ IL-10⁺ cells; G: Representative flow cytometry profile of CD19⁺ CD27⁺ FasL⁺ cells in peripheral blood; H: Bar chart of CD19⁺ CD27⁺ FasL⁺ cells. Data are presented as the mean ± SE (n = 8-10). ^aP < 0.05, ^bP < 0.01 vs Control group; ^cP < 0.05, ^dP < 0.01 vs DSS group.

Figure 7 Curcumin regulates differentiation of memory B cells in DSS-induced ulcerative colitis mice. A: Representative flow cytometry profile of CD19⁺ CD27⁺ PD-1⁺ cells in peripheral blood; B: Bar chart of CD19⁺ CD27⁺ PD-1⁺ cells; C: Representative flow cytometry profile of CD19⁺ CD27⁺ CD38⁺ cells in peripheral blood; D: Bar chart of CD19⁺ CD27⁺ CD38⁺ cells; E: Representative flow cytometry profile of CD19⁺ CD27⁺ CXCR3⁺ cells in peripheral blood; F: Bar chart of CD19⁺ CD27⁺ CXCR3⁺ cells; G: Representative flow cytometry profile of CD19⁺ CD27⁺ Tim-3⁺ cells in peripheral blood; H: Bar chart of CD19⁺ CD27⁺ Tim-3⁺ cells. Data are presented as the mean ± SE (n = 8-10). ^aP < 0.05, ^bP < 0.01 vs Control group; ^cP < 0.05, ^dP < 0.01 vs DSS group.

Figure 8 Curcumin regulates expression of memory B cell-related proteins in DSS-induced ulcerative colitis mice. A: Expression of Bcl-6, BLNK, p-BLNK, CIN85, Syk, and p-Syk in colon tissues as revealed by Western blot analysis. GAPDH served as the internal reference; B-G: Quantitative evaluation of (B) Bcl-6, (C) BLNK, (D) p-BLNK, (E) CIN85, (F) Syk, and (G) p-Syk. Data are presented as the mean ± SE (n = 8-10). ^aP < 0.05, ^bP < 0.01 vs Control group; ^cP < 0.05, ^dP < 0.01 vs DSS group.