Objective:To investigate the protective mechanism of topoisomerase I inhibitor on pancreatic acinar cells and lung during acute pancreatitis (AP) in mice.Methods:Eighteen Balb/C male mice were randomly divided into three groups using random number method: control group, AP group and CPT+ AP group. AP model was established by intraperitoneal injection of caerulein and lipopolysaccharide. CPT+ AP group received intraperitoneal injection of camptothecin (CPT, 50 mg/kg) before AP induction. Mice in control group were intraperitoneal injected with an equal volume of normal saline. The pathological examinations of pancreas and lung tissue were analyzed. The serum levels of amylase and lipase were detected by enzyme linked immunosorbent assay (ELISA) and the mRNA expression of IL-1 and IL-6 were analyzed by reverse transcription-polymerase chain reaction (RT-PCR); the infiltration of CD 45+ cells in pancreas and lung tissue as well as the expression of phosphorylated mixed lineage kinase domain-like protein(MLKL) in pancreas were detected by immunohistochemistry; the apoptosis index of pancreatic cells was analyzed by TUNEL assay. Results:The pathological scores of pancreas and lung tissue, serum levels of amylase and lipase in CPT+ AP group were [(2.30±0.31), (2.29±0.34), (1742.33±183.51)U/L and (46.90±2.17)U/L], which were significantly lower than those in AP group [(5.06±0.88), (3.40±0.09), (2385.33±383.10)U/L and (69.13±9.76)U/L]; the mRNA expression of IL-1 and IL-6 in pancreatic tissue were 95.79±48.11, 255.50±213.32, which were also remarkably lower than those in AP group (212.35±80.61, 1006.80±509.06); the infiltration of CD 45+ inflammatory cells in pancreas and lung were (14.25±5.32, 29.20±4.44)/high power field, which were notably lower than those in AP group (59.83±13.67, 58.25±5.91)/high power field; the apoptosis index of pancreatic cells was significantly higher than that in AP group [(3.64±1.16)% vs (1.92±0.29)%]; the histochemistry score of phosphorylated MLKL protein in pancreatic tissue was significantly lower than that in AP group (1.75±0.20 vs 4.53±1.28), and the differences were statistically significant (all P value <0.05). Conclusions:Topoisomerase I inhibitor could induce the apoptosis of pancreatic acinar cells and inhibit the death mode of necrotic pancreatic acinar cells during AP remodeling, thus reducing pancreatic local injury and AP-associated lung injury.