Inhibition of phosphatidylinositol 3-kinase inhibits intracellular zymogen activation but not enzyme secretion in pancreatic acinar cells

2006 ◽  
Vol 203 (3) ◽  
pp. S13
Author(s):  
L. Andy Chen ◽  
Hiroki Watanabe ◽  
B. Mark Evers
Keyword(s):  
Acinar Cells ◽  
Enzyme Secretion ◽  
Pancreatic Acinar Cells ◽  
Zymogen Activation ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

Phosphatidylinositol 3-kinase facilitates bile acid-induced Ca2+ responses in pancreatic acinar cells

2007 ◽  
Vol 292 (3) ◽  
pp. G875-G886 ◽  
Author(s):  
L. Fischer ◽  
A. S. Gukovskaya ◽  
J. M. Penninger ◽  
O. A. Mareninova ◽  
H. Friess ◽  
...  
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Phosphatidylinositol 3 Kinase ◽  
Pi3k Inhibitors ◽  
Trypsinogen Activation ◽  
Plasmic Reticulum ◽  
Intracellular Ca ◽  
Phosphatidylinositol 3

Bile acids are known to induce Ca2+ signals in pancreatic acinar cells. We have recently shown that phosphatidylinositol 3-kinase (PI3K) regulates changes in free cytosolic Ca2+ concentration ([Ca2+]i) elicited by CCK by inhibiting sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA). The present study sought to determine whether PI3K regulates bile acid-induced [Ca2+]i responses. In pancreatic acinar cells, pharmacological inhibition of PI3K with LY-294002 or wortmannin inhibited [Ca2+]i responses to taurolithocholic acid 3-sulfate (TLC-S) and taurochenodeoxycholate (TCDC). Furthermore, genetic deletion of the PI3K γ-isoform also decreased [Ca2+]i responses to bile acids. Depletion of CCK-sensitive intracellular Ca2+ pools or application of caffeine inhibited bile acid-induced [Ca2+]i signals, indicating that bile acids release Ca2+ from agonist-sensitive endoplasmic reticulum (ER) stores via an inositol ( 1 , 4 , 5 )-trisphosphate-dependent mechanism. PI3K inhibitors increased the amount of Ca2+ in intracellular stores during the exposure of acinar cells to bile acids, suggesting that PI3K negatively regulates SERCA-dependent Ca2+ reloading into the ER. Bile acids inhibited Ca2+ reloading into ER in permeabilized acinar cells. This effect was augmented by phosphatidylinositol ( 3 , 4 , 5 )-trisphosphate (PIP3), suggesting that both bile acids and PI3K act synergistically to inhibit SERCA. Furthermore, inhibition of PI3K by LY-294002 completely inhibited trypsinogen activation caused by the bile acid TLC-S. Our results indicate that PI3K and its product, PIP3, facilitate bile acid-induced [Ca2+]i responses in pancreatic acinar cells through inhibition of SERCA-dependent Ca2+ reloading into the ER and that bile acid-induced trypsinogen activation is mediated by PI3K. The findings have important implications for the mechanism of acute pancreatitis since [Ca2+]i increases and trypsinogen activation mediate key pathological processes in this disorder.

Phosphatidylinositol 3-kinase regulates Ca2+ signaling in pancreatic acinar cells through inhibition of sarco(endo)plasmic reticulum Ca2+-ATPase

2004 ◽  
Vol 287 (6) ◽  
pp. G1200-G1212 ◽  
Author(s):  
L. Fischer ◽  
A. S. Gukovskaya ◽  
S. H. Young ◽  
I. Gukovsky ◽  
A. Lugea ◽  
...  
Keyword(s):  
Kinase Inhibitors ◽  
Specific Inhibitor ◽  
Acinar Cells ◽  
Pi3 Kinase ◽  
Pancreatic Acinar Cells ◽  
Phosphatidylinositol 3 Kinase ◽  
Kinase Inhibition ◽  
Plasmic Reticulum ◽  
Genetic Deletion ◽  
Phosphatidylinositol 3

Calcium is a key mediator of hormone-induced enzyme secretion in pancreatic acinar cells. At the same time, abnormal Ca2+ responses are associated with pancreatitis. We have recently shown that inhibition of phosphatidylinositol 3-kinase (PI3-kinase) by LY-294002 and wortmannin, as well as genetic deletion of PI3-kinase-γ, regulates Ca2+ responses and the Ca2+-sensitive trypsinogen activation in pancreatic acinar cells. The present study sought to determine the mechanisms of PI3-kinase involvement in Ca2+ responses induced in these cells by CCK and carbachol. The PI3-kinase inhibitors inhibited both Ca2+ influx and mobilization from intracellular stores induced by stimulation of acini with physiological and pathological concentrations of CCK, as well as with carbachol. PI3-kinase inhibition facilitated the decay of cytosolic free Ca2+ concentration ([Ca2+]i) oscillations observed in individual acinar cells. The PI3-kinase inhibitors decreased neither CCK-induced inositol 1,4,5-trisphosphate [Ins( 1 , 4 , 5 )P3] production nor Ins( 1 , 4 , 5 )P3-induced Ca2+ mobilization, suggesting that the effect of PI3-kinase inhibition is not through Ins( 1 , 4 , 5 )P3 or Ins( 1 , 4 , 5 )P3 receptors. PI3-kinase inhibition did not affect Ca2+ mobilization induced by thapsigargin, a specific inhibitor of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA). Moreover, SERCA blockade with thapsigargin abolished the effects of pharmacological and genetic PI3-kinase inhibition on [Ca2+]i signals, suggesting SERCA as a downstream target of PI3-kinase. Both pharmacological PI3-kinase inhibition and genetic deletion of PI3-kinase-γ increased the amount of Ca2+ in intracellular stores during CCK stimulation. Finally, addition of the PI3-kinase product phosphatidylinositol 3,4,5-trisphosphate to permeabilized acini significantly attenuated Ca2+ reloading into the endoplasmic reticulum. The results indicate that PI3-kinase regulates Ca2+ signaling in pancreatic acinar cells through its inhibitory effect on SERCA.

Caerulein-induced intracellular pancreatic zymogen activation is dependent on calcineurin

2007 ◽  
Vol 292 (6) ◽  
pp. G1594-G1599 ◽  
Author(s):  
Sohail Z. Husain ◽  
Wayne M. Grant ◽  
Fred S. Gorelick ◽  
Michael H. Nathanson ◽  
Ahsan U. Shah
Keyword(s):  
Calcineurin Inhibitors ◽  
Acinar Cells ◽  
Enzyme Secretion ◽  
Pancreatic Acinar Cells ◽  
Amylase Secretion ◽  
Zymogen Activation ◽  
Inhibitory Peptide ◽  
Protein Phosphatase 2B ◽  
Chymotrypsin Activity ◽  
Downstream Effectors

Aberrant cytosolic Ca2+ flux in pancreatic acinar cells is critical to the pathological pancreatic zymogen activation observed in acute pancreatitis, but the downstream effectors are not known. In this study, we examined the role of Ca2+-activated protein phosphatase 2B (or calcineurin) in zymogen activation. Isolated pancreatic acinar cells were stimulated with supraphysiological caerulein (100 nM) with or without the calcineurin inhibitors FK506 or cell-permeable calcineurin inhibitory peptide (CiP). Chymotrypsin activity was measured as a marker of zymogen activation, and the percent amylase secretion was used as a measure of enzyme secretion. Cytosolic Ca2+ changes were recorded in acinar cells loaded with the intermediate Ca2+-affinity dye fluo-5F using a scanning confocal microscope. A 50% reduction in chymotrypsin activity was observed after pretreatment with 1 μM FK506 or 10 μM CiP. These pretreatments did not affect amylase secretion or the rise in cytosolic Ca2+ after caerulein stimulation. These findings suggest that calcineurin mediates caerulein-induced intra-acinar zymogen activation but not enzyme secretion or the initial caerulein-induced cytosolic Ca2+ signal.

scholarly journals Pancreatogenic Diabetes: Triggering Effects of Alcohol and HIV

Biology ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 108
Author(s):  
Moses New-Aaron ◽  
Murali Ganesan ◽  
Raghubendra Singh Dagur ◽  
Kusum K. Kharbanda ◽  
Larisa Y. Poluektova ◽  
...  
Keyword(s):  
Multiorgan Failure ◽  
Acinar Cells ◽  
Pancreatic Stellate Cells ◽  
Pancreatic Acinar Cells ◽  
Alcoholic Pancreatitis ◽  
People Living With Hiv ◽  
Zymogen Activation ◽  
Pancreatogenic Diabetes ◽  
Hiv Entry ◽  
Living With Hiv

Multiorgan failure may not be completely resolved among people living with HIV despite HAART use. Although the chances of organ dysfunction may be relatively low, alcohol may potentiate HIV-induced toxic effects in the organs of alcohol-abusing, HIV-infected individuals. The pancreas is one of the most implicated organs, which is manifested as diabetes mellitus or pancreatic cancer. Both alcohol and HIV may trigger pancreatitis, but the combined effects have not been explored. The aim of this review is to explore the literature for understanding the mechanisms of HIV and alcohol-induced pancreatotoxicity. We found that while premature alcohol-inducing zymogen activation is a known trigger of alcoholic pancreatitis, HIV entry through C-C chemokine receptor type 5 (CCR5) into pancreatic acinar cells may also contribute to pancreatitis in people living with HIV (PLWH). HIV proteins induce oxidative and ER stresses, causing necrosis. Furthermore, infiltrative immune cells induce necrosis on HIV-containing acinar cells. When necrotic products interact with pancreatic stellate cells, they become activated, leading to the release of both inflammatory and profibrotic cytokines and resulting in pancreatitis. Effective therapeutic strategies should block CCR5 and ameliorate alcohol’s effects on acinar cells.

scholarly journals Absence of the neutrophil serine protease cathepsin G decreases neutrophil granulocyte infiltration but does not change the severity of acute pancreatitis

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ali A. Aghdassi ◽  
Daniel S. John ◽  
Matthias Sendler ◽  
Christian Storck ◽  
Cindy van den Brandt ◽  
...  
Keyword(s):  
Acute Pancreatitis ◽  
Serine Protease ◽  
Acinar Cells ◽  
Neutrophil Infiltration ◽  
Cathepsin G ◽  
Pancreatic Acinar Cells ◽  
Neutrophil Granulocyte ◽  
Zymogen Activation ◽  
Trypsinogen Activation ◽  
Extracellular Matrix Components

AbstractAcute pancreatitis is characterized by an early intracellular protease activation and invasion of leukocytes into the pancreas. Cathepsins constitute a large group of lysosomal enzymes, that have been shown to modulate trypsinogen activation and neutrophil infiltration. Cathepsin G (CTSG) is a neutrophil serine protease of the chymotrypsin C family known to degrade extracellular matrix components and to have regulatory functions in inflammatory disorders. The aim of this study was to investigate the role of CTSG in pancreatitis. Isolated acinar cells were exposed to recombinant CTSG and supramaximal cholezystokinin stimulation. In CTSG−/− mice and corresponding controls acute experimental pancreatitis was induced by serial caerulein injections. Severity was assessed by histology, serum enzyme levels and zymogen activation. Neutrophil infiltration was quantified by chloro-acetate ersterase staining and myeloperoxidase measurement. CTSG was expessed in inflammatory cells but not in pancreatic acinar cells. CTSG had no effect on intra-acinar-cell trypsinogen activation. In CTSG−/− mice a transient decrease of neutrophil infiltration into the pancreas and lungs was found during acute pancreatitis while the disease severity remained largely unchanged. CTSG is involved in pancreatic neutrophil infiltration during pancreatitis, albeit to a lesser degree than the related neutrophil (PMN) elastase. Its absence therefore leaves pancreatitis severity essentially unaffected.

Messenger role of calcium in function of pancreatic acinar cells

1980 ◽  
Vol 239 (5) ◽  
pp. G335-G347
Author(s):  
I. Schulz
Keyword(s):  
Plasma Membrane ◽  
Acinar Cells ◽  
Enzyme Secretion ◽  
Pancreatic Acinar Cells ◽  
Free Calcium ◽  
Plasma Membrane Permeability ◽  
Cyclic Monophosphate ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
Group D

Enzyme secretion from the exocrine pancreas is elicited by a) cholinergic stimulants, b) hormones belonging to the family of pancreozymin, c) some amphibian peptides such as bombesin, eledoisin, and physalaemin, and d) secretin and vasoactive intestinal polypeptide. Whereas the mechanism of the group d hormones in stimulating enzyme secretion involves adenosine 3',5'-cyclic monophosphate, the others seem to use a common pathway involving Ca2+ as intracellular messenger and probably guanosine 3',5'-cyclic monophosphate as modulator of their action. Their effects can be ascribed to two processes. One pathway involves release of Ca2+ from an intracellular store that is most likely located in the plasma membrane. This phase is independent of extracellular Ca2+ and leads to a rise of guanosine 3',5'-cyclic monophosphate. The other pathway is characterized by an increased permeability of the plasma membrane for Ca2+ and is necessary for sustained secretion. Both pathways lead to an increase cytosolic-free Ca2+ concentration. Ca2+ is either directly involved in fusion of zymogen granules with the luminal cell membrane or triggers events that lead to exocytosis. Furthermore, augmented cytosolic-free calcium concentration a) increased the plasma membrane permeability for Na+, Cl-, and K+, which leads to depolarization of the cell, and b) induces uncoupling of neighboring acinar cells.

scholarly journals Pharmacological inhibition of PAR2 with the pepducin P2pal-18S protects mice against acute experimental biliary pancreatitis

2013 ◽  
Vol 304 (5) ◽  
pp. G516-G526 ◽  
Author(s):  
E. S. Michael ◽  
A. Kuliopulos ◽  
L. Covic ◽  
M. L. Steer ◽  
G. Perides
Keyword(s):  
Bile Acid ◽  
Acinar Cells ◽  
Experimental Pancreatitis ◽  
In Vivo Studies ◽  
Pancreatic Acinar Cells ◽  
Biliary Pancreatitis ◽  
Zymogen Activation ◽  
Injury Death ◽  
Acid Infusion ◽  
Concentration Changes

Pancreatic acinar cells express proteinase-activated receptor-2 (PAR2) that is activated by trypsin-like serine proteases and has been shown to exert model-specific effects on the severity of experimental pancreatitis, i.e., PAR2−/− mice are protected from experimental acute biliary pancreatitis but develop more severe secretagogue-induced pancreatitis. P2pal-18S is a novel pepducin lipopeptide that targets and inhibits PAR2. In studies monitoring PAR2-stimulated intracellular Ca2+ concentration changes, we show that P2pal-18S is a full PAR2 inhibitor in acinar cells. Our in vivo studies show that P2pal-18S significantly reduces the severity of experimental biliary pancreatitis induced by retrograde intraductal bile acid infusion, which mimics injury induced by endoscopic retrograde cholangiopancreatography (ERCP). This reduction in pancreatitis severity is observed when the pepducin is given before or 2 h after bile acid infusion but not when it is given 5 h after bile acid infusion. Conversely, P2pal-18S increases the severity of secretagogue-induced pancreatitis. In vitro studies indicate that P2pal-18S protects acinar cells against bile acid-induced injury/death, but it does not alter bile acid-induced intracellular zymogen activation. These studies are the first to report the effects of an effective PAR2 pharmacological inhibitor on pancreatic acinar cells and on the severity of experimental pancreatitis. They raise the possibility that a pepducin such as P2pal-18S might prove useful in the clinical management of patients at risk for developing severe biliary pancreatitis such as occurs following ERCP.

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