Expression of human cationic trypsinogen (PRSS1) in murine acinar cells promotes pancreatitis and apoptotic cell death

Abstract

Hereditary pancreatitis (HP) is an autosomal dominant disease that displays the features of both acute and chronic pancreatitis. Mutations in human cationic trypsinogen (PRSS1) are associated with HP and have provided some insight into the pathogenesis of pancreatitis, but mechanisms responsible for the initiation of pancreatitis have not been elucidated and the role of apoptosis and necrosis has been much debated. However, it has been generally accepted that trypsinogen, prematurely activated within the pancreatic acinar cell, has a major role in the initiation process. Functional studies of HP have been limited by the absence of an experimental system that authentically mimics disease development. We therefore developed a novel transgenic murine model system using wild-type (WT) human PRSS1 or two HP-associated mutants (R122H and N29I) to determine whether expression of human cationic trypsinogen in murine acinar cells promotes pancreatitis. The rat elastase promoter was used to target transgene expression to pancreatic acinar cells in three transgenic strains that were generated: Tg(Ela-PRSS1)NV, Tg(Ela-PRSS1*R122H)NV and Tg(Ela-PRSS1*N29I)NV. Mice were analysed histologically, immunohistochemically and biochemically. We found that transgene expression is restricted to pancreatic acinar cells and transgenic PRSS1 proteins are targeted to the pancreatic secretory pathway. Animals from all transgenic strains developed pancreatitis characterised by acinar cell vacuolisation, inflammatory infiltrates and fibrosis. Transgenic animals also developed more severe pancreatitis upon treatment with low-dose cerulein than controls, displaying significantly higher scores for oedema, inflammation and overall histopathology. Expression of PRSS1, WT or mutant, in acinar cells increased apoptosis in pancreatic tissues and isolated acinar cells. Moreover, studies of isolated acinar cells demonstrated that transgene expression promotes apoptosis rather than necrosis. We therefore conclude that expression of WT or mutant human PRSS1 in murine acinar cells induces apoptosis and is sufficient to promote spontaneous pancreatitis, which is enhanced in response to cellular insult.

Cathepsin B Activity Initiates Apoptosis via Digestive Protease Activation in Pancreatic Acinar Cells and Experimental Pancreatitis

“…On the other hand, increasing CTSB activity redistributed to the secretory pathway, despite increasing trypsinogen activation, does not increase the severity of pancreatitis or lead to spontaneous pancreatitis (28). Overexpression of trypsin(ogen), including but not restricted to hereditary pancreatitis-relevant mutant trypsinogen isoforms, leads to pancreatic injury or more severe pancreatitis (37,50), but the deletion of other trypsinogen isoforms does not have the expected opposite effect of reducing disease severity (27). Although our experiments do not exclude CTSB effects in nonacinar cells or extrapancreatic effects of CTSB-induced trypsin activation (38), our data regarding the role of CTSB activation inside the vesicular compartment of acinar cells are quite unequivocal.…”

CHETAH: a selective, hierarchical cell type identification method for single-cell RNA sequencing

“…These cell type-specific markers again exhibit a gradient of decreasing ductal and increasing acinar expression. Among the negatively correlating genes are acinar markers like CPA1, PRSS1 and CTRC 44,45 and among the positively correlating genes are pancreas duct cell markers like KRT7 and KRT19 46 . A similar gradient in the expressions of genes having unusually large loadings in the first principal component of their ductal cell population has been reported previously 17 .…”

Genetically inducedvs.classical animal models of chronic pancreatitis: a critical comparison

“…Caeruleintreatment in these mice led to only a slight increase in severity compared with that in the control group (72). Athwal et al (73) repeated the model a few years later, generating, among others, a transgenic strain containing the human PRSS1 mutant R122H. Although only 10% of the transgenic mice developed CP spontaneously, all of them showed susceptibility to intraperitoneal lowdose treatment with caerulein, leading to more-severe pancreatitis (73).…”

“…Athwal et al (73) repeated the model a few years later, generating, among others, a transgenic strain containing the human PRSS1 mutant R122H. Although only 10% of the transgenic mice developed CP spontaneously, all of them showed susceptibility to intraperitoneal lowdose treatment with caerulein, leading to more-severe pancreatitis (73). Interestingly, pancreatitis also developed spontaneously in transgenic mice possessing not-mutant human PRSS1, which the investigators assumed to be because of an imbalance in murine trypsinogen regulation (73).…”

“…Although only 10% of the transgenic mice developed CP spontaneously, all of them showed susceptibility to intraperitoneal lowdose treatment with caerulein, leading to more-severe pancreatitis (73). Interestingly, pancreatitis also developed spontaneously in transgenic mice possessing not-mutant human PRSS1, which the investigators assumed to be because of an imbalance in murine trypsinogen regulation (73). Here, it is unclear whether the transgenic mice with mutant human R122H really exhibit pancreatitis because of the mutation or whether the human PRSS1 itself has a toxic effect on the murine pancreas (74).…”