Protective effect of Gloeostereum incarnatum on ulcerative colitis via modulation of Nrf2/NF‑κB signaling in C57BL/6 mice

Abstract

Chronic non‑specific inflammatory cell infiltration of the colon is generally considered to be the cause of ulcerative colitis (UC). Gloeostereum incarnatum (GI), a fungus rich in amino acids and fatty acids, exhibits a variety of biological functions. In the present study, GI was identified to contain 15 fatty acids, 17 amino acids and 11 metallic elements. The protective effect of GI against UC was investigated in C57BL/6 mice with UC induced by free drinking 3.5% dextran sulfate sodium (DSS). After a 21‑day oral administration, GI prevented weight loss, enhancement of the disease activity index and colonic pathological alterations in mice with UC. GI reduced the levels of pro‑inflammatory factors including interleukin (IL)‑1β, IL‑2, IL‑6 and IL‑12, tumor necrosis factor α and ‑β, interferon α and ‑γ, and pro‑oxidative factors including reactive oxygen species and nitric oxide. In addition, it enhanced the levels of immunological factors including immunoglobulin (Ig)A, IgM and IgG, and antioxidative factors including superoxide dismutase and catalase in the serum and/or colon tissues. GI enhanced the expression levels of nuclear factor erythroid 2‑related factor 2 (Nrf2) and its downstream proteins and suppressed the phosphorylation of NF‑κB signaling in colon tissues. Together, GI was shown to alleviate the physiological and pathological state of DSS‑induced UC in mice via its antioxidant and anti‑inflammatory functions, which may be associated with its modulation of the activation of Nrf2/NF‑κB signaling.

Figure 1.

GI regulates the physiology and pathology of UC mice. The mice were continuously exposed to DSS (3.5% DSS dissolved in D.D. water) for 28 days, SASP (0.6 g/kg of SASP dissolved in D.D. water) and GI (1.0, 2.0 and 4.0 g/kg of GI suspended in D.D. water) were administered from the 7th day. (A) GI reduced the DAI index of UC mice and (B) ameliorated the shortening of colon length. Hematoxylin and eosin staining of (C) colon (scale bar, 100 µm; magnification, ×40), (D) colon, (E) spleen, (F) liver and (G) kidney tissues (scale bar, 100 µm; magnification, ×400) from C57BL/6 mice. ^###P<0.001 vs. control mice; *P<0.05, **P<0.01 and ***P<0.001 vs. DSS-induced UC mice. GI, Gloeostereum incarnatum; UC, ulcerative colitis; DSS, dextran sulfate sodium; D.D., double distilled; SASP, sulfasalazine; DAI, disease activity index.

Figure 2.

GI increases the levels of immune factors in serum and colon tissues of mice with UC. GI raised the levels of (A) IgA, (B) IgM and (C) IgG in serum and colon tissues. ^#P<0.05, ^##P<0.01 and ^###P<0.001 vs. control mice; *P<0.05, **P<0.01 and ***P<0.001 vs. DSS-induced UC mice. GI, Gloeostereum incarnatum; UC, ulcerative colitis; DSS, dextran sulfate sodium.

Figure 3.

GI demonstrates antioxidant and anti-inflammatory functions via modulation the activation of Nrf2/NF-κB signaling. GI enhanced the expression levels of Nrf2, CAT, HO-1, SOD-1 and SOD-2, and reduced the phosphorylation level of NF-κB, IKKα+β and IκBα. The quantitative expression of each protein was normalized using GAPDH. ^##P<0.01 and ^###P<0.001 vs. control mice; *P<0.05, **P<0.01 and ***P<0.001 vs. DSS-induced UC mice. GI, Gloeostereum incarnatum; SASP, sulfasalazine; P-, phosphorylated; T-, total; Nrf2, nuclear factor erythroid 2-related factor 2; CAT, catalase; HO-1, heme oxygenase-1; SOD, superoxide dismutase; IKK, inhibitor of NF-κB kinase; IκB, inhibitor of NF-κB; DSS, dextran sulfate sodium; CTRL, control.