Gastroenterology

Gastroenterology

Volume 141, Issue 6, December 2011, Pages 2210-2217.e2
Gastroenterology

Original Research
Basic and Translational—Pancreas
Intra-acinar Trypsinogen Activation Mediates Early Stages of Pancreatic Injury but Not Inflammation in Mice With Acute Pancreatitis

https://doi.org/10.1053/j.gastro.2011.08.033Get rights and content

Background & Aims

The role of trypsinogen activation in the pathogenesis of acute pancreatitis (AP) has not been clearly established.

Methods

We generated and characterized mice lacking trypsinogen isoform 7 (T7) gene (T−/−). The effects of pathologic activation of trypsinogen were studied in these mice during induction of AP with cerulein. Acinar cell death, tissue damage, early intra-acinar activation of the transcription factor nuclear factor κB (NF-κB), and local and systemic inflammation were compared between T−/− and wild-type mice with AP.

Results

Deletion of T7 reduced the total trypsinogen content by 60% but did not affect physiologic function. T−/− mice lacked pathologic activation of trypsinogen, which occurs within acinar cells during early stages of AP progression. Absence of trypsinogen activation in T−/− mice led to near complete inhibition of acinar cell death in vitro and a 50% reduction in acinar necrosis during AP progression. However, T−/− mice had similar degrees of local and systemic inflammation during AP progression and comparable levels of intra-acinar NF-κB activation, which was previously shown to occur concurrently with trypsinogen activation during early stages of pancreatitis.

Conclusions

T7 is activated during pathogenesis of AP in mice. Intra-acinar trypsinogen activation leads to acinar death during early stages of pancreatitis, which accounts for 50% of the pancreatic damage in AP. However, progression of local and systemic inflammation in AP does not require trypsinogen activation. NF-κB is activated early in acinar cells, independently of trypsinogen activation, and might be responsible for progression of AP.

Section snippets

Materials and Methods

All experiments were performed according to protocols approved by the Institutional Animal Care and Use Committee of the University of Minnesota. AP was induced by intraperitoneal injections of cerulein at 50 μg  ·  kg−1  ·  h−1 given 10 times. Animals were killed 1 hour after the last injection or 30 minutes after the first injection for early time point experiments. For further experimental and methodological details, see Supplementary Materials and Methods.

Phenotype Characterization of T−/− Mice

We successfully deleted T7 gene in these novel knockout mice (T−/−). This was confirmed by absence of T7 gene transcript/messenger RNA (Figure 1A). Probing with antibody against trypsinogen showed (Figure 1B) 2 important results: (1) reduction of band intensity at 26 kilodaltons in T−/− mice (this band is known to correspond to trypsinogens based on previous studies on human and mouse32, 40, 41) and (2) absence of the peptide corresponding to the 17-kilodalton band in T−/− mice. Human cationic

Discussion

In this study, we report generation of novel knockout mice lacking T7 (mouse cationic trypsinogen) and have characterized its phenotype. Using this novel and simple yet rigorous tool, we show that T7 trypsinogen is the isoform that is involved in pathologic intra-acinar activation during AP and explore the role of this pathologic process. We establish that intracellular trypsinogen activation leads to acinar cell death during early pancreatitis and this process is responsible for half of

Acknowledgments

The authors thank Ashley Bekolay for superb technical help during this project and Dr Steve Jones of University of Massachusetts Medical School for generating the T7−/− mice.

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported in part by National Institutes of Health grants RO1 DK058694, RO1 DK 092145, and RO1 DK093047 (to A.K.S.).

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