Phospholipase A2 activation by melittin causes amylase release from exocrine pancreas

1989 ◽  
Vol 67 (5) ◽  
pp. 411-416 ◽  
Author(s):  
Seymour Heisler
Keyword(s):  
Arachidonic Acid ◽  
Exocrine Pancreas ◽  
Phospholipase A ◽  
Pancreatic Acinar Cells ◽  
Secretory Process ◽  
Acid Oxidation ◽  
Amylase Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Amylase Release

Phospholipase A2-induced deacylation of membrane phospholipids is associated with changes in membrane fluidity. The importance of this reaction in the pancreatic amylase secretory process was tested using melittin, a phospholipase A2 stimulating peptide. Phospholipase A2 activity (using [3H]arachidonic acid release as an index) and amylase secretion were both increased in a time- and concentration-dependent manner by melittin. Phospholipids prelabelled with [3H]oleic acid or [14C]linoleic acid also released radioactive free fatty acids in response to melittin. Prostaglandin synthesis was not involved in the melittin response, since inhibitors of arachidonic acid oxidation (indomethacin, 5,8,11,14-eicosatetraynoic acid) did not alter the ability of melittin to release [3H]arachidonic acid or amylase. When melittin was co-applied with carbachol, cholecystokinin octapeptide, or vasoactive intestinal peptide, amylase secretion was additive. The effect of melittin on both fatty acid and amylase release was dependent on extracellular calcium, though melittin's effects were not dependent on the intracellular accumulation of second messengers such as calcium or cAMP. The data suggest that activation of phospholipase A2 by melittin results in the triggering of the secretory process in exocrine pancreas by a different mechanism than that for other pancreatic secretagogues.Key words: melittin, phospholipase A2, pancreatic acinar cells, amylase secretion.

Effect of short-chain fatty acids on the secretory response of the ovine exocrine pancreas

1983 ◽  
Vol 244 (3) ◽  
pp. G284-G290 ◽  
Author(s):  
E. Harada ◽  
S. Kato
Keyword(s):  
Fatty Acids ◽  
Exocrine Pancreas ◽  
Short Chain Fatty Acids ◽  
Secretory Response ◽  
Short Chain ◽  
Pancreatic Acinar Cells ◽  
Dependent Manner ◽  
Amylase Release ◽  
Amylase Output ◽  
Chain Fatty Acids

The secretory response of the exocrine pancreas to short-chain fatty acids has been studied in anesthetized sheep and in isolated lobules. Butyrate, propionate, and acetate stimulated pancreatic juice flow and protein and amylase output in the anesthetized sheep. The secretory response to butyrate was significantly greater than that of propionate or acetate. Rapid intravenous injection of butyrate (625 mumol/kg) caused a 13-fold rise in the juice flow, 26-fold in protein output, and 37-fold in amylase output above the basal levels within 5 min and declined to basal levels over a period of 30 min. Responses to butyrate (625 mumol/kg) were comparable with those obtained with 2 U/kg pancreozymin (Boots). Detectable responses were obtained with 15 mu/kg butyrate, 125 mumol/kg propionate, and 312.5 mumol/kg acetate. The secretory response to butyrate (625 mumol/kg) was not affected by pretreatment with atropine and hexamethonium. In the isolated lobule preparation, amylase release increased in response to butyrate in a concentration-dependent manner, reaching a maximal level at 1 mM and declining at 100 mM. It is concluded that short-chain fatty acids act directly on pancreatic acinar cells to stimulate secretion. The physiological implications of these findings are considered.

Activin A: negative regulator of amylase secretion and cell proliferation in rat pancreatic acinar AR42J cells

1994 ◽  
Vol 267 (2) ◽  
pp. G220-G226
Author(s):  
H. Yasuda ◽  
S. Tanaka ◽  
H. Ohnishi ◽  
H. Mashima ◽  
N. Ogushi ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Pancreatic Islet ◽  
Activin A ◽  
Negative Regulator ◽  
Pancreatic Acinar Cells ◽  
Amylase Secretion ◽  
Dependent Manner ◽  
Amylase Release ◽  
Ar42j Cells ◽  
Dose Dependent

Activin A, a member of the transforming growth factor-beta supergene family, exists in secretory granules of non-B-cells of rat pancreatic islet (H. Yasuda, K. Inoue, H. Shibata, T. Takeuchi, Y. Eto, Y. Hasegawa, N. Sekine, Y. Totsuka, T. Mine, E. Ogata, and I. Kojima. Endocrinology 133: 624-630, 1993). Because functions of exocrine pancreas are influenced by hormones in pancreatic islet, it is possible that activin A affects the function of pancreatic acinar cells. To examine this possibility, we studied the effects of activin A on amylase secretion and DNA synthesis in AR42J cells. In these cells, dexamethasone (Dx) induces increases in secretory organelles and secretion of amylase (C. D. Logsdon, J. Moessner, J. A. Williams, and I. D. Goldfine. J. Cell Biol. 100: 1200-1208 1985). Activin A did not change the rate of amylase release by itself nor affect the cholecystokinin-stimulated amylase release from Dx-treated differentiated AR42J cells. However, when activin A was added together with Dx, activin A inhibited Dx-induced increase in amylase content in a dose-dependent manner. In the presence of 1 nM activin A, the effect of Dx was abolished. In the absence of Dx, amylase content of the cells was also reduced by activin A in a dose-dependent manner. The maximum inhibitory effect was obtained by 10 nM activin A, and at this concentration amylase content became undetectable. In addition, activin A potently inhibited DNA synthesis as assessed by [3H]thymidine incorporation.(ABSTRACT TRUNCATED AT 250 WORDS)

Forskolin potentiates calcium-dependent amylase secretion from rat pancreatic acinar cells

1983 ◽  
Vol 61 (10) ◽  
pp. 1168-1176 ◽  
Author(s):  
Seymour Heisler
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Acinar Cells ◽  
Secretory Response ◽  
Pancreatic Acinar Cells ◽  
Secretory Process ◽  
Amylase Secretion ◽  
Primary Role ◽  
Amylase Release ◽  
Calcium Dependent

The cellular and molecular effects of forskolin, a direct, nonhormonal activator of adenylate cyclase, were assessed on the enzyme secretory process in dispersed rat pancreatic acinar cells. Forskolin stimulated adenylate cyclase activity in the absence of guanyl nucleotide. It promoted a rapid and marked increase in cellular accumulation of cyclic AMP alone or in combination with vasoactive intestinal peptide (VIP) but was itself a weak pancreatic agonist and did not increase the secretory response to VIP or other cyclic AMP dependent agonists. Somatostatin was a partial antagonist of forskolin stimulated cyclic AMP synthesis and forskolin plus cholecystokinin-octapeptide (CCK-OP) induced amylase release. Forskolin potentiated amylase secretion in response to calcium-dependent agonists such as CCK-OP, carbachol and A-23187, but did not affect the ability of CCK-OP and (or) carbachol to mobilize 45Ca from isotope preloaded cells; forskolin alone did not stimulate 45Ca release. In calcium-poor media, the secretory response to forskolin and CCK-OP was reduced in a both absolute and relative manner. The data suggests that calcium plays the primary role as intracellular mediator of enzyme secretion and that the role of cyclic AMP may be to modulate the efficiency of calcium utilization.

Pilocarpine and carbachol exhibit markedly different patterns of Ca2+ signaling in rat pancreatic acinar cells

1993 ◽  
Vol 264 (4) ◽  
pp. G786-G791 ◽  
Author(s):  
D. I. Yule ◽  
T. E. Essington ◽  
J. A. Williams
Keyword(s):  
Partial Agonist ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Muscarinic Agonist ◽  
Dependent Manner ◽  
Maximal Concentration ◽  
Concentration Dependent Manner ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Pi Hydrolysis

The effects of the partial muscarinic agonist pilocarpine on physiological responses were investigated in rat pancreatic acinar cells and compared with carbachol, a full muscarinic agonist, together with previous results using JMV-180, a partial agonist of CCK-A receptors. Pilocarpine was found to stimulate amylase release from isolated pancreatic acini in a concentration-dependent manner. At a maximal concentration (10 microM), pilocarpine was only capable of stimulating 63% of the secretion stimulated by a maximal concentration of carbachol. Moreover pilocarpine did not induce a decrease in secretion at supramaximal concentrations as does carbachol. In acini loaded with fura-2, superfusion of pilocarpine resulted exclusively in generation of intracellular Ca2+ concentration ([Ca2+]i) oscillations at all concentrations tested (0.3 microM-1 mM), in marked contrast to high concentrations of full agonists, which result in a biphasic sustained increase in [Ca2+]i. In common with low concentrations of other secretagogues that stimulate [Ca2+]i oscillations, pilocarpine at all concentrations was only able to stimulate a very small increase in phosphoinositide (PI) hydrolysis. In acini previously incubated with [3H]inositol, pilocarpine was shown to stimulate PI hydrolysis 27% above basal, compared with 872% for carbachol. To ascertain if this small degree of PI hydrolysis seen with pilocarpine is responsible for the generation of [Ca2+]i oscillations, an inhibitor of phospholipase C-linked processes, U-73122, which has been shown to inhibit Ca2+ oscillations induced by carbachol and CCK but not JMV-180 was tested. This agent rapidly inhibited pilocarpine-stimulated oscillations, indicating that in contrast to JMV-180, oscillations induced by pilocarpine are the result of PI hydrolysis.

scholarly journals Inhibitory effect of high leucine concentration on α-amylase secretion by pancreatic acinar cells: possible key factor of proteasome

2018 ◽  
Vol 38 (6) ◽  
Author(s):  
Long Guo ◽  
Baolong Liu ◽  
Chen Zheng ◽  
Hanxun Bai ◽  
Hao Ren ◽  
...  
Keyword(s):  
Amylase Activity ◽  
Acinar Cells ◽  
Inhibitory Effect ◽  
Proteasome Activity ◽  
Pancreatic Acinar Cells ◽  
Amylase Secretion ◽  
High Concentration ◽  
Amylase Release ◽  
Cholecystokinin Receptor ◽  
Key Factor

The present study aimed to investigate whether leucine affects the pancreatic exocrine by controlling the antisecretory factor (AF) and cholecystokinin receptor (CCKR) expression as well as the proteasome activity in pancreatic acinar cells of dairy calves. The pancreatic acinar cells were isolated from newborn Holstein bull calves and cultured using the Dulbecco’s modified Eagle’s medium/nutrient mixture F12 Ham’s liquid (DMEM/F12). There were six treatments of leucine dosage including 0 (control), 0.23, 0.45, 1.35, 4.05, and 12.15 mM, respectively. After culture for 3 h, the samples were collected for subsequent analysis. As the leucine concentration increased from 0 to 1.35 mM, the α-amylase activity in media decreased significantly (P<0.05), while further increase in leucine concentration did not show any decrease in α-amylase activity. Addition of leucine inhibited (P<0.05) the expression of AF and CCKR, and decreased the activity of proteasome (P<0.05) by 76%, 63%, 24%, 7%, and 9%, respectively. Correlation analysis results showed α-amylase secretion was negatively correlated with leucine concentration (P<0.01), and positively correlated with proteasome activity (P<0.01) and the expression of CCK1R (P<0.01) and AF (P<0.05). The biggest regression coefficient was showed between α-amylase activity and proteasome (0.7699, P<0.001). After inhibition of proteasome by MG-132, low dosage leucine decreased (P<0.05) the activity of proteasome and α-amylase, as well as the expression of CCK1R. In conclusion, we demonstrated that the high-concentration leucine induced decrease in α-amylase release was mainly by decreasing proteasome activity.

Regulation of CCK-induced amylase release by PKC-δ in rat pancreatic acinar cells

2004 ◽  
Vol 287 (4) ◽  
pp. G764-G771 ◽  
Author(s):  
Chenwei Li ◽  
Xuequn Chen ◽  
John A. Williams
Keyword(s):  
Acinar Cells ◽  
Adenoviral Vectors ◽  
Dominant Negative ◽  
Pancreatic Acinar Cells ◽  
Amylase Secretion ◽  
Wild Type ◽  
Amylase Release ◽  
Pkc Isoforms ◽  
Chemical Inhibitors ◽  
Dominant Negative Variant

PKC is known to be activated by pancreatic secretagogues such as CCK and carbachol and to participate along with calcium in amylase release. Four PKC isoforms, α, δ, ε, and ζ, have been identified in acinar cells, but which isoforms participate in amylase release are unknown. To identify the responsible isoforms, we used translocation assays, chemical inhibitors, and overexpression of individual isoforms and their dominant-negative variants by means of adenoviral vectors. CCK stimulation caused translocation of PKC-α, -δ, and -ε, but not -ζ from soluble to membrane fraction. CCK-induced amylase release was inhibited ∼30% by GF109203X, a broad spectrum PKC inhibitor, and by rottlerin, a PKC-δ inhibitor, but not by Gö6976, a PKC-α inhibitor, at concentrations from 1 to 5 μM. Neither overexpression of wild-type or dominant-negative PKC-α affected CCK-induced amylase release. Overexpression of PKC-δ and -ε enhanced amylase release, whereas only dominant-negative PKC-δ inhibited amylase release by 25%. PKC-δ overexpression increased amylase release at all concentrations of CCK, but dominant-negative PKC-δ only inhibited the maximal concentration; both similarly affected carbachol and JMV-180-induced amylase release. Overexpression of both PKC-δ and its dominant-negative variant affected the late but not the early phase of amylase release. GF109203X totally blocked the enhancement of amylase release by PKC-δ but had no further effect in the presence of dominant-negative PKC-δ. These results indicate that PKC-δ is the PKC isoform involved with amylase secretion.

Stimulus–secretion coupling in exocrine pancreas: possible role of calmodulin

1981 ◽  
Vol 59 (9) ◽  
pp. 994-1001 ◽  
Author(s):  
Seymour Heisler ◽  
Laurence Chauvelot ◽  
Diane Desjardins ◽  
Christiane Noel ◽  
Herman Lambert ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Pancreatic Enzyme ◽  
Antidepressant Drugs ◽  
Enzyme Secretion ◽  
Pancreatic Acinar Cells ◽  
Secretory Process ◽  
Amylase Secretion ◽  
Enzyme Release ◽  
Mediated Effects ◽  
Pancreatic Enzyme Secretion

Many calcium-mediated effects in mammalian cells may be activated by calcium-calmodulin stimulated enzymes. These effects are inhibited by various antidepressant drugs which bind to and inactivate calmodulin. In the current study, calmodulin was identified by affinity chromatography and gel electrophoresis in the cytoplasm of dispersed rat pancreatic acinar cells. Its role in enzyme secretion was assessed by evaluating the effects of various antidepressant drugs on the enzyme secretory process. Chlorpromazine, trifluoperazine, thioridazine, chlorprothixene and amitriptyline inhibited amylase secretion stimulated by carbacol, A-23187, and cholecystokinin-pancreozymin but not that elicitied by dibutyryl cyclic AMP secretin or vasoactive intestinal peptide (VIP). Haloperidol, sulpiride, phenobarbital, and ethanol were without effect on secretagogue-stimulated enzyme release. Only those agents which blocked secretion also inhibited 45Ca release stimulated by carbachol from isotope preloaded cells. The data suggest that calmodulin may have a functional role in pancreatic enzyme secretion.

CRHSP-24 phosphorylation is regulated by multiple signaling pathways in pancreatic acinar cells

2003 ◽  
Vol 285 (4) ◽  
pp. G726-G734 ◽  
Author(s):  
Claus Schäfer ◽  
Hanna Steffen ◽  
Karen J. Krzykowski ◽  
Burkhard Göke ◽  
Guy E. Groblewski
Keyword(s):  
Signaling Pathways ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Dependent Manner ◽  
Calyculin A ◽  
Concentration Dependent Manner ◽  
Pancreatic Acini ◽  
Heat Stable ◽  
Heat Stable Protein ◽  
Mrna Binding

Ca2+-regulated heat-stable protein of 24 kDa (CRHSP-24) is a serine phosphoprotein originally identified as a physiological substrate for the Ca2+-calmodulin regulated protein phosphatase calcineurin (PP2B). CRHSP-24 is a paralog of the brain-specific mRNA-binding protein PIPPin and was recently shown to interact with the STYX/dead phosphatase protein in developing spermatids (Wishart MJ and Dixon JE. Proc Natl Acad Sci USA 99: 2112–2117, 2002). Investigation of the effects of phorbol ester (12- o-tetradecanoylphorbol-13-acetate; TPA) and cAMP analogs in 32P-labeled pancreatic acini revealed that these agents acutely dephosphorylated CRHSP-24 by a Ca2+-independent mechanism. Indeed, cAMP- and TPA-mediated dephosphorylation of CRHSP-24 was fully inhibited by the PP1/PP2A inhibitor calyculin A, indicating that the protein is regulated by an additional phosphatase other than PP2B. Supporting this, CRHSP-24 dephosphorylation in response to the Ca2+-mobilizing hormone cholecystokinin was differentially inhibited by calyculin A and the PP2B-selective inhibitor cyclosporin A. Stimulation of acini with secretin, a secretagogue that signals through the cAMP pathway in acini, induced CRHSP-24 dephosphorylation in a concentration-dependent manner. Isoelectric focusing and immunoblotting indicated that elevated cellular Ca2+ dephosphorylated CRHSP-24 on at least three serine sites, whereas cAMP and TPA partially dephosphorylated the protein on at least two sites. The cAMP-mediated dephosphorylation of CRHSP-24 was inhibited by low concentrations of okadaic acid (10 nM) and fostriecin (1 μM), suggesting that CRHSP-24 is regulated by PP2A or PP4. Collectively, these data indicate that CRHSP-24 is regulated by diverse and physiologically relevant signaling pathways in acinar cells, including Ca2+, cAMP, and diacylglycerol.

scholarly journals Delayed treatment with fenofibrate protects against high-fat diet-induced kidney injury in mice: the possible role of AMPK autophagy

2017 ◽  
Vol 312 (2) ◽  
pp. F323-F334 ◽  
Author(s):  
Minji Sohn ◽  
Keumji Kim ◽  
Md Jamal Uddin ◽  
Gayoung Lee ◽  
Inah Hwang ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Kidney Injury ◽  
Acid Oxidation ◽  
Peroxisome Proliferator ◽  
Dependent Manner ◽  
High Fat ◽  
Concentration Dependent Manner ◽  
Delayed Treatment ◽  
Compound C

Fenofibrate activates not only peroxisome proliferator-activated receptor-α (PPARα) but also adenosine monophosphate-activated protein kinase (AMPK). AMPK-mediated cellular responses protect kidney from high-fat diet (HFD)-induced injury, and autophagy resulting from AMPK activation has been regarded as a stress-response mechanism. Thus the present study examined the role of AMPK and autophagy in the renotherapeutic effects of fenofibrate. C57BL/6J mice were divided into three groups: normal diet (ND), HFD, and HFD + fenofibrate (HFD + FF). Fenofibrate was administered 4 wk after the initiation of the HFD when renal injury was initiated. Mouse proximal tubule cells (mProx24) were used to clarify the role of AMPK. Feeding mice with HFD for 12 wk induced insulin resistance and kidney injury such as albuminuria, glomerulosclerosis, tubular injury, and inflammation, which were effectively inhibited by fenofibrate. In addition, fenofibrate treatment resulted in the activation of renal AMPK, upregulation of fatty acid oxidation (FAO) enzymes and antioxidants, and induction of autophagy in the HFD mice. In mProx24 cells, fenofibrate activated AMPK in a concentration-dependent manner, upregulated FAO enzymes and antioxidants, and induced autophagy, all of which were inhibited by treatment of compound C, an AMPK inhibitor. Fenofibrate-induced autophagy was also significantly blocked by AMPKα1 siRNA but not by PPARα siRNA. Collectively, these results demonstrate that delayed treatment with fenofibrate has a therapeutic effect on HFD-induced kidney injury, at least in part, through the activation of AMPK and induction of subsequent downstream effectors: autophagy, FAO enzymes, and antioxidants.

11,12-Epoxyeicosatrienoic Acid Attenuates Synthesis of Prostaglandin E2 in Rat Monocytes Stimulated with Lipopolysaccharide

2003 ◽  
Vol 228 (7) ◽  
pp. 786-794 ◽  
Author(s):  
Wieslaw Kozak ◽  
David M. Aronoff ◽  
Olivier Boutaud ◽  
Anna Kozak
Keyword(s):  
Cell Culture ◽  
Arachidonic Acid ◽  
Negative Feedback ◽  
Inhibitory Effect ◽  
Prostaglandin E ◽  
Dependent Manner ◽  
Epoxyeicosatrienoic Acid ◽  
Concentration Dependent Manner ◽  
Cox 2 ◽  
Cytochrome P 450

Cytochrome P-450 monooxygenase (epoxygenase)-derived arachidonic acid (AA) metabolites, including 11,12-epoxyeicosatrienoic acid (11,12-EET), possess anti-inflammatory and antipyretic properties. Prostaglandin E2 (PGE2), a cyclooxygenase (COX)-derived metabolite of AA, is a well-defined mediator of fever and inflammation. We have tested the hypothesis that 11,12-EET attenuates synthesis of PGE2 in monocytes, which are the cells that are indispensable for induction of fever and initiation of inflammation. Monocytes isolated from freshly collected rat blood were stimulated with lipopolysaccharide (LPS; 100 ng/2 × 105 cells) to induce COX-2 and stimulate generation of PGE2. SKF-525A, an inhibitor of epoxygenases, significantly augmented the lipopolysaccharide-provoked synthesis of PGE2 in cell culture in a concentration-dependent manner. It did not affect, however, elevation of the expression of COX-2 protein in monocytes stimulated with LPS. 11,12-EET also did not affect the induction of COX-2 in monocytes incubated with lipopolysaccharide. However, 11,12-EET suppressed, in a concentration-dependent fashion, the generation of PGE2 in incubates. Preincubation of a murine COX-2 preparation for 0–5 min with three concentrations of 11,12-EET (1, 5, and 10 μM) inhibited the oxygenation of [14C]-labeled AA by the enzyme. The inhibitory effect of 11,12-EET on COX-2 was time-and-concentration-dependent, suggesting a mechanism-based inhibition. Based on these data, we conclude that 11,12-EET suppresses generation of PGE2 in monocytes via modulating the activity of COX-2. These data support the hypothesis that epoxygenasederived AA metabolites constitute a negative feedback on the enhanced synthesis of prostaglandins upon inflammation.

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