Acute pancreatitis is a common, life-threatening disorder of the pancreas. Abnormal acinar cell Ca2+ signals play a crucial role in initiating this disease. We have previously shown that abnormally elevated Ca2+ signals in the basal region are associated with pathologic intra-acinar protease activation, an early and critical event in the development of pancreatitis. This Ca2+ signal is mediated by an endoplasmic reticulum (ER) Ca2+ channel, the ryanodine receptor (RyR). In this proposal, we examine mechanisms that regulate this pathologic RyR Ca2+ release in the acinar cell. We have shown that increasing cAMP in acinar cells causes RyR phosphorylation, RyR Ca2+ release, and enhanced protease activation1, 2. In preliminary work, we demonstrate that alcohol, a leading cause of pancreatitis, triggers cAMP-mediated RyR phosphorylation as well as RyR Ca2+ release and enhanced protease activation. Therefore, we hypothesize that intra-acinar protease activation and pancreatitis, particularly that induced by alcohol exposure, are triggered by release of acinar cell Ca2+ from pathologically activated, phosphorylated RyRs. In this proposal, using a combination of novel genetic and pharmacologic tools, we will, in the presence or absence of alcohol, pursue the following Specific Aims: (1) Examine whether RyR phosphorylation causes RyR Ca2+ release in isolated acini (2) Study whether RyR phosphorylation and RyR Ca2+ release predispose to protease activation in isolated acini (3) Determine whether RyR phosphorylation and RyR Ca2+ release predispose to protease activation and pancreatitis in vivo. The effects of phosphorylation on RyR sites thought to mediate PKA-dependent RyR Ca2+ release will be directly tested using previously generated transgenic mice that harbor phospho-mimetic or phospho-resistant mutations in the RyR PKA phosphorylation site. It is anticipated that these studies on the role of the RyR in pathologic protease activation and pancreatitis will (1) lead to improved understanding of aberrant Ca2+ signaling in pancreatitis, (2) provide a novel link between alcohol and RyR Ca2+ release that may have broader implications for mechanisms contributing to alcohol's complications in multiple other organ systems, and (3) suggest treatment strategies that target the RyR in the pancreas.

Public Health Relevance

Acute pancreatitis is a life-threatening and painful disease of the pancreas that starts with auto-digestion by its own digestive enzymes. Alcoholic disease is a leading cause of this disease. Calcium signals within the pancreas are required for this pathologic digestion, and thus our studies are focused on understanding the role of abnormal release of calcium through a protein calcium channel called the ryanodine receptor in the development of auto-digestion and resultant pancreatitis, in particular vis-`-vis alcohol exposure.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK083327-06
Application #
8477183
Study Section
Clinical and Integrative Gastrointestinal Pathobiology Study Section (CIGP)
Program Officer
Serrano, Jose
Project Start
2009-06-01
Project End
2014-05-31
Budget Start
2013-06-01
Budget End
2014-05-31
Support Year
6
Fiscal Year
2013
Total Cost
$280,487
Indirect Cost
$95,347
Name
University of Pittsburgh
Department
Pediatrics
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
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Muili, Kamaldeen A; Jin, Shunqian; Orabi, Abrahim I et al. (2013) Pancreatic acinar cell nuclear factor *B activation because of bile acid exposure is dependent on calcineurin. J Biol Chem 288:21065-73
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Raizner, Aileen; Phatak, Uma Padhye; Baker, Kenneth et al. (2013) Acute necrotizing pancreatitis in children. J Pediatr 162:788-92
Muili, Kamaldeen A; Wang, Dong; Orabi, Abrahim I et al. (2013) Bile acids induce pancreatic acinar cell injury and pancreatitis by activating calcineurin. J Biol Chem 288:570-80

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