Gastroenterology

Gastroenterology

Volume 138, Issue 2, February 2010, Pages 715-725
Gastroenterology

Basic—Liver, Pancreas, and Biliary Tract
Biliary Acute Pancreatitis in Mice is Mediated by the G-Protein−Coupled Cell Surface Bile Acid Receptor Gpbar1

https://doi.org/10.1053/j.gastro.2009.10.052Get rights and content

Background & Aims

The mechanisms by which reflux of bile acids into the pancreas induces pancreatitis are unknown. We reasoned that key events responsible for this phenomenon might be mediated by Gpbar1, a recently identified and widely expressed G-protein−coupled, cell surface bile acid receptor.

Methods

Acute pancreatitis was induced in wild-type and Gpbar1−/− mice by either retrograde ductal infusion of taurolithocholic acid-3-sulfate (TLCS) or supramaximal secretagogue stimulation with caerulein. In vitro experiments were performed in which acini obtained from wild-type and Gpbar1−/− mice were exposed to either submicellar concentrations of TLCS (200−500 μM) or a supramaximally stimulating concentration of caerulein (10 nM).

Results

Gpbar1 is expressed at the apical pole of acinar cells and its genetic deletion is associated with reduced hyperamylasemia, edema, inflammation, and acinar cell injury in TLCS-induced, but not caerulein-induced, pancreatitis. In vitro, genetic deletion of Gpbar1 is associated with markedly reduced generation of pathological calcium transients, intracellular activation of digestive zymogens, and cell injury when these responses are induced by exposure to TLCS, but not when they are induced by exposure to caerulein.

Conclusions

Gpbar1 may play a critical role in the evolution of bile-acid−induced pancreatitis by coupling exposure to bile acids with generation of pathological intracellular calcium transients, intra-acinar cell zymogen activation, and acinar cell injury. Acute biliary pancreatitis may be a “receptor-mediated” disease and interventions that interfere with Gpbar1 function might prove beneficial in the treatment and/or prevention of biliary acute pancreatitis.

Section snippets

Materials and Methods

All experiments conformed to protocols approved by the Tufts Medical Center Animal Care and Use Committee. Most reagents, including tetrodotoxin, caerulein TLCS, and Na-taurocholate were purchased from Sigma (St Louis, MO). Fura 2/AM and 1,2-bis(2-aminophenoxy)ethane-N,N,N,N'-tetraacetic acid (BAPTA), were from Molecular Probes (Eugene, OR). Substrates for measuring trypsin and chymotrypsin activity were from Peptides International (Louisville, KY) and substrates for lactate dehydrogenase (LDH)

Bile Acid Receptor Gpbar1 is Expressed in the Pancreas

Gpbar1 expression in the pancreas of wild-type mice can be demonstrated by reverse transcriptase polymerase chain reaction (Figure 1) and it is lost following genetic deletion of Gpbar1. Immunofluorescence microscopy with a Leica TCS SP2 confocal microscope (Figure 1) indicates that most of the anti-Gpbar1 staining is localized to the region very near, but not identical, to the location of f-actin at the acinar cell apical pole. Positive Gpbar1 stain was also seen in gallbladder of wild-type

Discussion

Recent reports have indicated that, in addition to playing an essential role in dietary lipid absorption and cholesterol metabolism, bile acids can also act as signaling molecules. In this capacity, after being taken up by target cells, bile acids can regulate the expression of bile acid transporters by activating nuclear hormone receptors such as the farnesoid X receptor and the pregnane X receptor25, 26, 27 and they can directly activate mitogen-activated protein kinase pathways.28, 29

Acknowledgments

The authors are grateful to Dr Lovy–Wheeler for help with confocal microscopy.

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported by National Institutes of Health grant RO-1 31396 from National Institute of Diabetes, Digestive and Kidney Diseases (M.L.S.), P30-NS047423 and by a fellowship from Sigrid Jusélius Foundation, Finland (J.M.L.).

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