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Objective: To improve the apoptosis/necrosis In vitro model of ascites-induced acute pancreatitic (AP) acinar cells by using the co-culture system and mixed ascites technology for the first time. Furthermore, we compared this improved model with cerulein and cerulein+LPS models, and observed the effects of three models on acinar apoptotic/necrotic-related indicators., Methods: The In vitro cultured rat acinar cells AR42J were divided in four groups: control group (medium+PBS), cerulein group (medium+10 nmol/L cerulein), cerulein+LPS group (medium+10 nmol/L cerulein+10 mg/L LPS) and improved ascites group. In the improved ascites group, the ascites of sodium taurocholate-induced rat model was mixed and added into the co-culture system to stimulated In vitro cultured homogenous acinar cells. The co-culture system was set as follows: the chambers with the pore size of 1 μm were placed in the cultue plate, and the culture medium and mixed ascites were respectively added to the culture plate and the chamber at a ratio of 1:1. The acinar cells in each group were collected after 24 h stimulation. The apoptotic/necrotic rates, the expressions of apoptosis/necrosis related proteins [B-cell lymphoma protein 2 (Bcl-2), Bcl-2-associated X protein (Bax) and receptor interacting protein 1 (RIP1)], and the ultra-structure of acinar cells were detected by flow cytometry, Western blot and transmission electron microscopy (TEM)., Results: The acinar cells in the improved ascites model were mainly characterized by necrosis; compared with the other 3 groups, the apoptosis rate and necrosis rate were both up-regulated, RIP1 and BAX protein expression levels were up-regulated, and Bcl-2 protein was down-regulated. TEM results showed the organelle structure of acinar cells was destroyed, and the cell membrane was degraded in the improved ascites model. Compared with the control group, apoptosis rate of acinar cells in the cerulein and cerulein+LPS models were increased and necrosis rate were not changed. The expression of pro-apoptotic protein Bax was increased, while the expression level of RIP1 was not significantly increased. TEM results showed that in cerulein group and cerulein+LPS group, the chromatin of the cells was condensed into a mass, the cytoplasm was degraded and the cell membrane was intact, showing typical apoptosis characteristics., Conclusion: Compared with cerulein and cerulein +LPS models, which mainly focus on apoptosis of acinar cells and applied to mild acute pancreatitis study, the improved ascites model mainly focuses on the necrosis of acinar cells and is a good model for studying acinar cell necrosis and severe acute pancreatitis., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Science Edition).)

Acute pancreatitis (AP) is a potentially lethal disease characterized by inflammation and parenchymal cell death; also, the severity of AP correlates directly with necrosis and inversely with apoptosis. However, mechanisms of regulating cell death in AP remain unclear. The endoplasmic reticulum (ER) chaperone protein GRP78 has anti-apoptotic properties, in addition to modulating ER stress responses. This study used RNA interference (RNAi) approach to investigate the potential role of GRP78 in regulating apoptosis during AP. In vitro models of AP were successfully developed by treating AR42J cells with cerulein or cerulein plus lipoplysaccharide (LPS). There was more pancreatic inflammation and less apoptosis with the cerulein plus LPS treatment. Furthermore, knockdown of GRP78 expression markedly promoted apoptosis and reduced necrosis in pancreatic acinar cells. This was accomplished by enhancing the activation of caspases and inhibiting the activity of X-linked inhibitor of apoptosis protein (XIAP), as well as a receptor interacting protein kinase-1(RIPK1), which is a key mediator of necrosis. This attenuated the severity of pancreatic inflammation, especially after cerulein plus LPS treatment. In conclusion, these findings indicate that GRP78 plays an anti-apoptotic role in regulating the cell death response during AP. Therefore, GRP78 is a potential therapeutic target for AP.

Objective: To design and construct a lentiviral vector containing shRNA against rat glucose-regulated protein 78 gene (GRP78), and to establish rat pancreatic acinar cell line with stable knockdown of GRP78 expression., Methods: Constructed three plasmid expression vectors coding shRNA against GRP78, and converted them into lentiviral particles using three plasmid package systems. Then, AR42J cells were transduced with produced lentiviral particles. The green fluorescent protein (GFP) positive cells were selected by fluorescence-activated cell sorting (FACS), the GRP78 gene mRNA and protein expression were detected by real-time PCR and Western blot., Results: The DNA sequencing showed that the lentiviral vectors containing shRNA against GRP78 gene were constructed correctly. After the transduction, highly efficient transduction (> 85%) of lentivirus in AR42J cells was observed by fluorescent microscopy and FACS. Quantitative real-time PCR showed that GRP78 mRNA expression in AR42J cells was suppressed by LVshGRP78-1, LVshGRP78-2 and LVshGRP78-3 lentivirus about 69.4% +/- 1.42%, 74.7% +/- 1.69% and 86.6% +/- 1.73% as compared with that of the untreated cells (P < 0.05), while LV-Non Target had no significant effect on the GRP78 mRNA level (P > 0.05). Western blot showed that the suppressed effect of LVshGRP78 lentivirus on GRP78 protein was consistent with GRP78 mRNA., Conclusion: The results demonstrated that lentiviral vectors containing the shRNA against GRP78 gene were successfully constructed, which could stably knock down the GRP78 expression in AR42J cells. This study will provide a new cell model for further study of the role of GRP78 in the pathogenesis of acute pancreatitis.