HSPA5 Inhibitor Meliorate DSS-Induced Colitis through HSPA1A/CHIP

Abstract

Objective: Ulcerative colitis (UC) is closely related to immune response, in which Treg cells (Tregs) suppress the autoimmune response of effector T cells to maintain homeostasis. As a marker of endoplasmic reticulum stress (ERS), HSPA5 was highly expressed in the colon tissue of UC patients. This study is aimed at evaluating the therapeutic effect of HSPA5 inhibitor (HA15) on dextran sulfate sodium- (DSS-) induced ulcerative colitis in mice and explored the effect and related mechanism of HSPA5 inhibitor on the differentiation and function of Tregs.

Methods: Thirty-two C57BL/6 mice were randomly divided into four groups (8 mice per group): normal control group, DSS model group, HSPA5 inhibitor (HA15) group (intraperitoneal injection), and dexamethasone (DXM) group (intraperitoneal injection). Except for the blank control group, the other groups were induced with 3% DSS for 7 days and then given corresponding intervention therapy for 7 days.

Results: The disease activity index (DAI) score, colon length, histopathological changes, and scores of DSS-induced mice show that HA15 could significantly improve the degree of inflammation in ulcerative colitis. Moreover, HA15 can better inhibit the expression of HSPA5, HSPA1A, and CHIP in the colon and increase the level of FOXP3 mRNA. Finally, the content of Treg cells and the levels of IL-10 and TGF-β1 were significantly increased, and the levels of IL-6 were significantly reduced.

Conclusions: HA15 can improve the differentiation and function of Treg cells by inhibiting the HSPA1A/CHIP pathway, thereby improving ulcerative colitis. Therefore, inhibiting the expression of HSPA5 may serve as a new approach to treat ulcerative colitis.

Figure 1

Expressions of HSPA5 in colonic tissue and the effects of pharmacotherapies on DSS-induced colitis in mice. (a) The colonic protein levels of HSPA5 measured by Western blotting. (b) Representative protein levels of HSPA5/GAPDH. (c) Levels of HSPA5 mRNA in colonic tissue. Data are shown as means ± SD (n = 3). (d) The disease activity index (DAI) score of each group was monitored daily. (e) Typical colonic appearance of each group. (f) Colon length of each group. (g) Histological analysis (×50, ×200) about pathological changes of colonic tissue under a microscope. (h) Histological score of each group. Data are shown as means ± SD (n = 8). ^∗∗P < 0.01, ^∗∗∗P < 0.001, vs. DSS group.

Figure 2

The proportion of Treg cells in the spleen and MLNs and the levels of cytokines and transcription factors of Treg cell differentiation. (a) Flow cytometry pictures of Treg cells in the spleen and MLNs of mice. (b) The proportion of Treg cells in the spleen of mice in each group was statistically analyzed. (c) The proportion of Treg cells in MLNs of mice in each group was statistically analyzed. (d, e) The relative contents of TGF-β1mRNA and FOXP3 mRNA in colon tissue of mice in each group were measured by RT-PCR. (f–h) The levels of TGF-β1, IL-6, and IL-10 in colon tissues of mice in each group were measured by ELISA. Data are shown as means ± SD (n = 3). ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001, vs. DSS group.

Figure 3

Expressions of HSPA1A and CHIP in colonic tissue. (a) The colonic protein levels of HSPA1A and CHIP measured by Western blotting. (b) Representative protein levels of HSPA1A/GAPDH. (c) Levels of HSPA1A mRNA in colonic tissue. (d) Representative protein levels of CHIP/GAPDH. (e) Levels of CHIP mRNA in colonic tissue. Data are shown as means ± SD (n = 3). ^∗∗P < 0.01, ^∗∗∗P < 0.001, vs. DSS group.