Neutrophil extracellular DNA traps promote neutophils migration and activation by TLR9 signalling in type 2 autoimmune pancreatitis

Neutrophil infiltration around the pancreatic ducts has been found to be associated with type 2 autoimmune pancreatitis (AIP). However, the functional role and clinical importance of neutrophils migration on the progress of pancreatitis is not fully understood. Here, we found that neutrophil extracellular traps (NETs) are abundant around the pancreatic duct in type 2 AIP patients. Moreover, we observed the expression of TLR9 is higher in pancreatic ductal epithelial Cells (HPDEC) in type 2 AIP patients than in other pancreatic diseases. TLR9 acts as a NET-DNA receptor on HPDEC that senses extracellular DNA and subsequently activates the NF-?B pathway to attract neutrophils motility and induce NETs formation. In addition, the TLR9 antagonist hydroxychloroquine (HCQ) can effectively inhibit the activation of inflammatory pathways, reduce the migration of neutrophils and block the positive feedback mechanism, which can be used as a potential target drug for the clinical treatment of type 2 AIP. Overall design: To determine the effect of upregulated TLR9 in the pathogenesis of type 2 AIP, we generated TLR9-overexpressing HPDEC stably expressing YFP-tagged TLR9 (WT and TLR9) and performed transcriptome-wide RNA sequencing (RNA-seq) after NETs treatment (Ctrl and NETs).