Qian Li

Department of Oncology, The First Affiliated Hospital with Nanjing Medical University

Objective:The incidence of colorectal cancer ranked the third in men and the second in women. High aggressiveness of colorectal cancer makes it prone to relapse or metastasis. CPT-11 is one of the main drugs treated for advanced colorectal cancer. Despite its good efficacy, the side effects seriously affect the quality of the life of patients and the follow-up treatment during decades of clinical application. Delayed diarrhea, a does limiting toxicity, usually happens after 24 hours of treatment and the rate of occurrence is up to 90% (nearly 50% in China). If this symptom is failed to be recognized and adequately treated, it will be life-threatening. However, the real molecular mechanism of delayed diarrhea is still poorly understood. In this study, we had discovered that CPT-11 promoted macrophages infiltration into intestinal tissues and activated the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome, inducing a robust IL-1β response and causing colonic inflammation which was similar to DSS induced experimental colitis. Moreover, CPT-11 plus LPS triggerd mouse bone marrow-derived macrophages (BMDMs) and human acute monocytic leukemia cells (THP-1 cell) staying in a highly activated status, showing increased caspase-1 activity, releasing great amounts of IL-1β and IL-18. Subsequent results showed andrographolide, a drug has been reported that it could induce macrophage autophagy and inhibit NLRP3 inflammasome activation, could improve colitis induced by CPT-11 in vitro and in vivo. This indicated that inhibition of NLRP3 inflammasome activation may be an effective strategy for CPT-11 induced delayed diarrhea. Our findings provide a basis for developing novel strategies that improve clinical implications of CPT-11. Method: 1. Assessed the degreed of lesions of intestines in CPT-11 induced colitis mouse model; 2. Examined inflammatory cytokines expression in colonic tissues of CPT-11-induced experimental colitis model; 3. Detected NLRP3 inflammasome activation and macrophage infiltration in intestinal tissues; 4. Assessed the expression of NLRP3 associated factors (cleaved caspase 1, IL-1β, IL-18) in mouse BMDMs and THP-1 cell. Result: 1. CPT-11 could induce experimental colitis, promote macrophages infiltration in intestinal tissues, elevate proinflammatory cytokines expression, decrease immunosuppressive cytokines expression, increase intestinal permeability and cause mucosal injury in mice; 2. CPT-11 could activate NLRP3 inflammasome in macrophages infiltrated in intestinal tissues; 3. CPT-11 could activate NLRP3 inflammasome in mouse BMDMs and THP-1 cell; 4. Andrographolide could suppress NLRP3 inflammasome activation induced by CPT-11. Conclusion: In this study, CPT-11 successfully induced experimental colitis which was similar to DSS induced colitis. The results indicated that CPT-11 could activate NLRP3 inflammasome in macrophages, releasing great amounts of proinflammatory cytokines such as IL-1β and IL-18. This may contribute to delayed diarrhea caused by chemotherapy. Our study discovered a new mechanism of CPT-11 induced delayed diarrhea and provide a new method to prevent and treat with this side effect in clinical application.

Key Words: Irinotecan  NLRP3 inflammasome  delayed diarrhea