Glyburide Suppresses Inflammation-Related Colorectal Tumorigenesis Through Inhibition of NLRP3 Inflammasome

Abstract

Colorectal cancer represents one of the most serious complications of inflammatory bowel disease. The NLRP3 inflammasome plays a pivotal role in the onset and progression of inflammatory bowel disease and is also implicated in colorectal cancer. This study aimed to investigate whether NLRP3 deficiency or glyburide, a sulfonylurea used for diabetes management and known as an NLRP3 inhibitor, could suppress colitis and its related colorectal tumorigenesis. Mice were divided into three groups: a control group, a glyburide group, and an NLRP3-deficient group. We investigated acute colitis and inflammation-related tumor models using azoxymethane and dextran sodium sulfate. In the colitis model, the colonic inflammation grade was significantly increased in NLRP3-deficient mice but not in mice administered glyburide. In the colorectal carcinogenesis model, fewer colorectal tumors were observed in both NLRP3-deficient and glyburide-treated groups. Additionally, a reduction in the expression levels of inflammatory cytokine genes was detected in the colonic mucosa of the mice of these groups. These findings suggest that NLRP3 deficiency may exacerbate acute colitis, while pharmacological inhibition, as well as deficiency of NLRP3, suppresses colitis-related tumorigenesis, presumably due to the attenuation of chronic inflammation in the colorectum. Glyburide holds promise as a potential chemopreventive agent for colitis-related colorectal cancer.

Keywords: NLRP3; colorectal cancer; glyburide; inflammatory bowel disease.

Figure 1

Effects of glyburide or NLRP3 deficiency on colitis induced by DSS (experiment 1). (A) Chemical structure of glyburide. (B) Study protocol of DSS-induced colitis. (C) Body weight change in the experimental mice. Percentage of weight loss at the end of the study compared to the beginning. (D) Colon length measured from the ileocecal junction to the anal verge. (E) Representative photographs of colon sections stained with hematoxylin and eosin. Enlarged pictures of the section enclosed within the square in the upper panels are shown in the corresponding lower panels. Scale bars: 100 µm for upper panels and 50 µm for lower panels. (F) Inflammation scores. Data represent mean ± standard error. * p  <  0.05. CTRL, control (C57BL/6J) mice; DSS, dextran sodium sulfate; GLB, glyburide; KO, knockout.

Figure 2

Effect of GLB and NLRP3 deficiency on expression levels of inflammatory cytokines in the colon of a mouse colitis model. mRNA expression levels of Il1b, Il6, and Tnf in the colonic mucosa were measured by qRT-PCR with specific primers. Data represent mean ± standard error. * p  <  0.05. CTRL, control C57BL/6J mice; DSS, dextran sodium sulfate; GLB, glyburide; KO, knockout.

Figure 3

Effects of glyburide or NLRP3 deficiency on inflammation-related colon tumorigenesis induced by AOM/DSS (experiment 2). (A) Study protocol of a mouse AOM/DSS-induced CRC model. (B) Body weight change in the experimental mice. Percentage of weight gain at the end of the study compared to the beginning. (C) Blood glucose levels at the end of the experiment. (D) Representative macroscopic pictures of tumors in the colorectum of the experimental mice. (E) Representative pathological image of the colon tumor in each experimental group. Scale bars: 500 µm. (F) Number of tumors per mouse colon. Data represent mean ± standard error. * p  <  0.05. AOM, azoxymethane; CTRL, control C57BL/6J mice; DSS, dextran sodium sulfate; GLB, glyburide; KO, knockout.

Figure 4

Effects of GLB and NLRP3 deficiency on gene expressions in the colon of a mouse colon tumorigenesis model. mRNA expression levels of (A) Il1b, Il6, and Tnf, and of (B) Cyclind1, Ptgs2, and Tgfb in the colonic mucosa were measured by qRT-PCR with specific primers. Data represent mean ± standard error. * p  <  0.05. AOM, azoxymethane; CTRL, control C57BL/6J mice; DSS, dextran sodium sulfate; GLB, glyburide; KO, knockout.