Purpose: The aim of this study was to investigate the relationship between changes in IL-1β expression and intestinal apoptosis after chemotherapy. And we further determine whether interleukin-1 receptor antagonist (IL-1Ra) reduces apoptosis in vivo after 5-fluorouracil (5-FU) chemotherapy in the small intestine.
Methods: Intestinal mucositis was induced in mice by intraperitoneal injection of a single dose of 5-FU (200 mg/kg). IL-1Ra (1 mg/kg) was injected subcutaneously twice daily after 5-FU injection. 5-FU-induced intestinal apoptosis was detected by TUNEL assay. The expression of IL-1β induced by 5-FU in local intestinal tissue was examined by RT-PCR and immunohistochemistry. Assessment of 5-FU-induced mucositis (histology, diarrhea scores, bowel weight) was performed. The apoptosis-related proteins were investigated by western blotting analysis. The proliferation of intestine was examined by immunohistological staining of PCNA. Viability of IEC-6 cells was determined using the CCK-8 assay. The apoptosis of IEC-6 cells was examined by Hoechst 33342 staining.
Results: The variation of IL-1β expression induced by 5-FU was in accordance with the changes in intestinal apoptosis. Administration of IL-1Ra could block the destructive effect of IL-1β and reduce apoptosis in the small intestinal crypt after chemotherapy. The protection against apoptosis was in accordance with the reduction of the up-regulation of Bax and caspase 3 and the elimination of the down-regulation of Bcl-2 and Bcl-xL. Moreover, IL-1Ra attenuated the severity of intestinal mucositis induced by 5-FU and enhanced intestinal crypt proliferation. In vitro experiments showed that IL-1Ra suppressed apoptosis and increased cell viability in enterocyte IEC-6 cells treated with 5-FU. Additionally, IL-1Ra did not affect the chemotherapeutic effect of 5-FU in tumor CT-26 xenograft mice.
Conclusions: Our studies elucidate that IL-1β is quite possibly involved in and mediated the course of intestinal apoptosis after 5-FU chemotherapy. Administered with IL-1Ra protects mice against intestinal apoptosis induced by 5-FU, relieves mucosal impairment of the small intestine, and facilitates the recovery of the intestinal mucosa. IL-1Ra treatment offers a novel promising strategy for the prevention and cure of chemotherapy-induced intestinal mucositis in clinical practice.