Effects of resolvin D1 on the autophagy in acute pancreatitis in mice

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Objective To investigate the effects of resolvin D1 on autophagy in the prevention of acute pancreatitis (AP) in mice. Methods Thirty C57BL/6 mice were divided into control group, AP group and resolvin D1 group. AP model was established by intraperitoneal injection of cerulein at 50 μg·kg-1·h-1. Resolvin D1 was intraperitoneally given at 50 μg/kg one hour before and four hours after modeling. The mice of control group were intraperitoneally injected the same volume of 0.9% sodium chloride solution. The serum levels of amylase and lipase were measured by colorimetric method. The pathological injury of the lung and pancreatitis were observed under optical microscope. Autophagic vacuoles in acinar cells of pancreas of mice were evaluated by transmission electron microscope. And the expressions of autophagy related markers Beclin-1, p62 and LC3-Ⅱ at the mRNA and protein levels in pancreas of mice were detected by real time quantitative polymerase chain reaction (RT-qPCR) and Western blotting method. One-way analysis of variance and SNK-q were performed for statistical analysis. Results There were statistically significant differences in serum amylase and lipase levels between control group, AP group and resolvin D1 group (F=62.99 and 149.69, both P<0.01). The serum amylase and lipase levels of mice in resolvin D1 group were lower than those of AP group ((525.08±41.12) U/L vs. (752.62±42.03) U/L, (758.24±134.77) U/L vs. (1 201.06±112.53) U/L), and the differences were both statistically significant (both SNK-q test and P<0.01). In addition, there were statistically significant differences in the ratio of the pancreas and lung wet mass to body mass between control group, AP group and resolvin D1 group (F=11.36 and 18.51, both P<0.05). Pathological injury scores of pancreas and lung of resolvin D1 group were both lower than those of AP group (3.3±0.6 vs. 5.6±0.6, 5.4±0.5 vs. 8.8±0.4), and the differences were statistically significant (both SNK-q test and P<0.05). The results of transmission electron microscopy observation revealed that the number of autophagic vacuole of resolvin D1 group was less than that of AP group, and the size was smaller. Moreover, there were statistically significant differences in Beclin-1, p62 and LC3-Ⅱ mRNA between control group, AP group and resolvin D1 group (F=270.95, 151.83 and 124.77, all P<0.05). The relative expression mRNA levels of Beclin-1, p62 and LC3-Ⅱ of resolvin D1 group were 1.59±0.12, 2.75±0.27 and 1.34±0.14, respectively, which were lower than those of AP group (2.68±0.13, 3.32±0.30 and 3.37±0.26, respectively), and the differences were statistically significant (all SNK-q test and P<0.05). There were statistically significant differences in the expressions of Beclin-1, p62 and LC3-Ⅱat the protein level between control group, AP group and resolvin D1 group (F=116.63, 384.40 and 192.45, all P<0.05). The expressions of Beclin-1, p62 and LC3-Ⅱ at protein level of resolvin D1 group were 0.98±0.03, 0.57±0.04 and 0.31±0.03, respectively, which were lower than those of AP group (1.34±0.07, 1.02±0.03 and 0.48±0.04, respectively), and the differences were statistically significant (all SNK-q test and P<0.05). Conclusion Resolvin D1 ameliorates the severity of AP by attenuating the impaired autophagy and restoring autophagic flux in AP mice. Key words: Autophagy; Acute pancreatitis; Resolvin D1; Mice