IL-1Ra selectively protects intestinal crypt epithelial cells, but not tumor cells, from chemotoxicity via p53-mediated upregulation of p21(WAF1) and p27(KIP1.).

Chemotherapy-induced intestinal mucositis (CIM) is a major dose-limiting side effect, resulting from the nonspecific cytoablative actions of chemoagents, including 5-fluorouracil (5-FU) and irinotecan (CPT-11). Preventive strategies are urgently needed for the predictable CIM. Previously, we have demonstrated an important role of recombinant human interleukin-1 receptor antagonist (rhIL-1Ra) in the prevention of cyclophosphamide-induced mucositis in mice. In this study, the preventive role of rhIL-1Ra was further evaluated in 5-FU- and CPT-11-induced mucositis mouse models. rhIL-1Ra pretreatment reduced the incidence, severity, and duration of chemotherapy-induced diarrhea, through attenuating crypt apoptosis and improving crypt survival in wild-type mice, but not in IL-1RI(-/-), p53(-/-), and p21(-/-) mice. Further studies demonstrated that rhIL-1Ra promoted the cell cycle arrest of intestinal crypt epithelia (ICE) through elevating the cellular level of p21(WAF1) and p27(KIP1), which was abolished in IL-1RI(-/-) and p53(-/-) mice, and in p21(WAF1) and p27(KIP1) silenced IEC-6 cells. Importantly, the tumor growth and sensitivity to chemotherapy were not affected by rhIL-1Ra in cultures of tumor cell lines and in a syngeneic tumor-transplantation mouse model. The present study demonstrated that rhIL-1Ra effectively and specifically protected ICE from chemotoxicity through reversible reduction of the basal level of IL-1 signaling to promote normal cell cycle arrest, but not tumor cells. Our findings support the clinical development of rhIL-1Ra in the prevention of CIM.