Pancreatic Acinar Cells-Derived Sphingosine-1-Phosphate Contributes To Fibrosis Of Chronic Pancreatitis Via Inducing Autophagy And Activation Of Pancreatic Stellate Cells

Background: Chronic pancreatitis is a disease characterized by acinar cell destruction and progressive fibrosis.The pathological characteristics of chronic pancreatitis include parenchyma destruction of the pancreas,acinar atrophy,inflammatory cell infiltration,fibrous tissue replacement,acinar duct metaplasia,and a decline of pancreatic secretion.Pancreatic fibrosis is the main pathological manifestation of chronic pancreatitis.The essence is increased synthesis and decreased degradation of collagen-based extracellular matrix,resulting in excessive extracellular matrix deposition.The formation of pancreatic fibrosis is a complex pathological process mediated by complex signal network pathways,centered on the activation of pancreatic stellate cells,involved in various cytokines and inflammatory mediators,and ultimately characterized by fibroblast proliferation and extracellular matrix deposition.Among them,the activation of pancreatic stellate cells is a key step in the pathogenesis of chronic pancreatitis fibrosis.However,the specific mechanism of pancreatic stellate cell activation has not been fully elucidated.Studies have shown that Sphingosine Kinase 1(SPHK1)/ Sphingosine 1-phosphate(S1P)signaling pathway plays an important role in fibrosis diseases.Including pulmonary fibrosis,liver fibrosis,kidney fibrosis,myocardial fibrosis,etc.In addition,our previous study also showed that SPHK1 has an obvious proinflammatory effect in acute pancreatitis,however,the relationship between SPHK1/S1 P pathway and chronic pancreatitis remains unknown.Objective: To investigate the mechanism of SPHK1/S1 P in a mouse fibrosis model of chronic pancreatitis.Methods: The mouse model of chronic pancreatitis was established by intraperitoneal injection of rainranin or surgical ligation of the pancreatic duct,and the expression level of the SPHK1/S1 P signaling pathway was evaluated.The role of SPHK1 in chronic pancreatitis was evaluated using mice with SPHK1 knockout gene.The activation of pancreatic stellate cells and the level of pancreatic fibrosis in chronic pancreatitis specimens were analyzed by immunohistochemistry and immunofluorescence.Mouse pancreatic primary acinar cells and primary stellate cells were extracted to establish the co-culture test of pancreatic acinar cells and pancreatic stellate cells in vitro.To evaluate the effects of the SPHK1/S1 P pathway and Sphingosine-1-Phosphate Receptor 2(S1PR2)on autophagy and activation of pancreatic stele cells.The activation levels of pancreatic stellate cells were evaluated by immunofluorescence,Transwell,Western Blot,and q RT-PCR.Finally,the pathogenesis of chronic pancreatitis was evaluated in mice treated with SPHK1 or S1PR2 inhibitors.Results: 1.Compared with the control group,SPHK1 expression and S1 P level in the peripheral blood of mice with chronic pancreatitis were significantly increased.2.Compared with the control group,SPHK1 knockout mice with chronic pancreatitis showed significantly reduced pancreatic fibrosis and stellate cell activation.3.Stimulated pancreatic acinar cell culture medium can significantly activate pancreatic stellate cells,but inhibition of SPHK1 expression in pancreatic acinar cells inhibited this activation.4.S1P secreted by pancreatic acinus cells specifically binds to S1PR2 in pancreatic stellate cells,and induces autophagy and activation of pancreatic stellate cells by regulating AMPK/m TOR pathway.5.Hypoxia caused by the pancreatic fibrosis environment can promote SPHK1 transcription by up-regulating HIF-1? and HIF-2? in pancreatic acinar cells.6.Injection of SPHK1 inhibitor PF-543 or S1PR2 inhibitor JTE-013 significantly reduced the degree of pancreatic fibrosis in mice with chronic pancreatitis.Conclusion: The activated SPHK1/S1 P signaling axis in pancreatic acinus cells induces autophagy and activation of pancreatic stellate cells by regulating S1PR2/AMPK/m TOR pathway,leading to the production and secretion of a large amount of extracellular matrix in pancreatic stellate cells,thus promoting the formation of fibrosis in chronic pancreatitis.In addition,the anoxic microenvironment may be involved in the interaction between pancreatic acinar cells and pancreatic stellate cells.