Changes of zymophagy during cell model of caerulein-induced experimental acute pancreatitis

Abstract

Objective To observe the changes of zymophagy during experimental acute pancreatitis (AP) induced by caerulein.Methods Pancreatic acinar cell line AR42J cells were cultured in 6-well plates till 90％ confluent and then divided into AP group and control group.Caerulein (1 × 10-8 mol/L) was added into AP group to establish AP cell model,and 1640 cell culture medium was added into control group.After caerulein treated for one,four,six,eight,12 and 24 hours,cells and cell culture supernatant were collected.The levels of cytokine interleukin (IL)-1,tumor necrosis factor (TNF)α,trypsinogen activation (TAP) and amylase were measured with enzyme-linked immunosorbent assay (ELISA) method.The expression of LC3 and Beclin1 at mRNA of each group were detected by reverse transcription-polymerase chain reaction (RT-PCR).The LC3B protein level of each group were detected by Western blotting.The changes of autophagosome and zymophagosome were observed by transmission electron microscopy.The difference between AP group and control group was analyzed by analysis of variance.Results The level of IL-1,TNFα,amylase and TAP in cell culture supernatant of control group was (18.83±7.10) pg/mL,(14.20±3.79) pg/mL,(10.03±2.85) U/L and (39.48±8.62) pg/mL,respectively.Those of AP group significantly increased at first hour ((62.13±11.25) pg/mL,F=3.32,P＜0.01 ; (30.98±7.11) pg/mL,F=3.05,P＜0.05; (25.06±6.82) U/L,F=2.90,P＜0.05 and (128.51± 18.30) pg/mL),F=2.62,P＜0.01,at fourth or sixth hour reached peak (IL-1 at fourth hour:(71.96± 15.82) pg/mL,F=7.25,P＜0.01;TNFα at sixth hour:(39.92±8.94) pg/mL,F=4.93,P＜0.05; amylase at fourth hour:(28.83 ± 8.31) U/L,F=2.06,P＜0.05; TAP at fourth hour:(146.29± 29.36) pg/mL,F=0.14,P＜0.01) and then gradually decreased.At fourth and sixth hour,the expression of LC3 at mRNA level in AP group was 3.18±0.82,1.71±0.14,respectively,while the expression of Beclin-1 rnRNA at first,fourth hour was 2.44±0.34 and 4.13±0.30,all of them were significantly increased compared with those of control group (0.21±0.04 and 0.30±0.08,LC3 mRNA F=0.79、0.06; Beclin mRNA F=2.31、0.36,all P＜ 0.05).There were no significant differences at other time points.The numbers of autophagosome and zymophagosome of AP group were significantly higher than those of control group under transmission electron microscopy.Conclusion Zymophagy occurred during AP cell model induced by caerulein,which suggested that zymophagy might involve in the mechanism of AP. Key words: Acute pancreatitis; Autophagy; Trypsinogen