The Role And Regulation Mechanism Of Autophagy Pathway For The Later Recovery Of Acute Pancreatitis

Objective:Autophagy is often referred to as a double-edged sword, either leading to cellular injury or protective effect in different conditions. Recently, the pathogenetic role of autophagy in the early onset of acute pancreatitis(AP) has been identified. however, the major cases of AP present in a self-limited form, which tend to be self-recovery in the later phase. So, there is a problem that whether autophagy can be a protective mechanism underlying the self-recovery phenomenon of AP. In order to answer this question, in this study, we will establish a self-limited AP model. On this base, we focuses on the alterations of status of autophagy flux, study the significance behind, and determine the underlying mechanisms.Methods:Self-limited AP was induced in rat by 3% sodium taurocholate injection in the pancreaticobiliary duct. Serum amylase activity assay, histological examination, and cell death detection(TUNEL assay) were used to assess the time course of AP severity.Meanwhile, the expression of autophagy related proteins such as LC3-II、p62and Lamp-2determined by Western-blot and(or) Immunohistochemistry were used to evaluate the status of autophagy flux. S6 RP phosphorylation was detected to determine the time course of m TOR activation. Rapamycin was administered to block m TOR activity. AP severity and the expression of LC3-II, p62, Lamp-2 and phosphorylated S6 RP were also determined after rapamycin administration.Results:1. After AP induction, serum amylase levels increased at 6 h to a peak at 12 h, started to decrease at 12 h but still maintained a high level, and then significantly decreased at 36 and 48 h; pancreatic pathological scores and acinar cell necrosis levels all gradually increased from 6 h to 24 h, but then significantly reduced at 36 and 48 h.2. After establishing the AP model, Lamp-2 expression evidently decreased at 6 h andcontinued to decrease to almost lost at 12 and 24 h, but was significantly upregulated at 36 and 48 h; expression of LC3-II and p62 gradually increased from 6 h to 24 h, but markedly declined from 36 h to 48 h; S6 RP phosphorylation exhibited a transient increase at 6 h and then depleted at 12 h–24 h, but again markedly increased at 36 h and 48 h.3. Compared with solvent control, rapamycin treatment inhibited m TOR activation of pancreas at 36 and 48 h after AP induction;meanwhile, rapamycin treatment resulted in the significant exacerbation of pancreatic pathological scores, acinar cell necrosis and LC3-II and p62 levels. Lamp-2 expression was inhibited after rapamycin administration.Conclusions:1. AP induced on rats by 3% sodium taurocholate injection into the pancreaticobiliary duct presents in a self-limited form, in which pancreatic injury tends to self-restore in the later phase, although it is initiated and aggravated in the early onset.2. On our model, the improvement of autophagy flux may serve as a protective mechanism underlying the later recovery of pancreatic injury in AP.3. The later activation of m TOR participates in the improvement of autophagy flux and the later recovery of pancreatic injury in AP.