sincalide and Carcinoma--Acinar-Cell

Pancreatic secretion can be influenced by cholecystokinin (CCK) either directly via actions on acinar cells or indirectly via actions on nerves. The presence and functional roles of CCK receptors on human pancreatic acinar cells remains unclear. In the current study human pancreatic acini were isolated and then treated with CCK-8, gastrin and/or carbachol. Functional parameters were measured including intracellular [Ca2+] and amylase secretion. It was observed that human acini did not respond to CCK agonists but did respond to carbachol with robust increases in functional parameters. Adenoviral-mediated gene transfer of CCK1 or CCK2 receptors to the human cells resulted in cell responses to CCK agonists. In order to determine the reason for the lack of responsiveness of the human acini, expression of receptor mRNAs was determined using quantitative RT-PCR and localized by in situ hybridization. mRNA levels for CCK1 receptors were approximately 30 times lower than those of CCK2 receptors, which were approximately 10 times lower than those of m3 Ach receptors as measured by quantitative PCR. Neither CCK1 nor CCK2 receptors were localized in adult human pancreas by in situ hybridization. These results indicate that human pancreatic acinar cells do not respond directly to CCK receptor activation and this is likely due to an insufficient level of receptor expression.

Topics: Amylases; Carcinoma, Acinar Cell; Cholecystokinin; Gastrins; Gene Expression Regulation, Neoplastic; Humans; In Situ Hybridization; Pancreatic Neoplasms; Receptors, Cholecystokinin; Reverse Transcriptase Polymerase Chain Reaction; Sincalide

The aim of the present study was to investigate the possible interaction between intracellular Ca(2+) and nitric oxide (NO) in rat pancreatic acinar cells, especially intracellular signaling events. (1) Nitric oxide donors SNP (0.1-100 μM) and NOR-3 (50-400 μM) induced Ca(2+) oscillations in fluo-4-loaded acini, that appeared to be analogous to what we usually observe in acini stimulated with physiological secretagogues such as CCK-8 and this oscillations were abolished in the presence of carboxy-PTIO. (2) The NO donors-evoked Ca(2+) oscillations were not abolished even in the absence of extracellular Ca(2+) but totally disappeared when cells were pretreated with thapsigargin, a sarcoplasmic-endoplasmic reticulum Ca(2+) ATPase (SERCA) inhibitor. (3) Inhibition of guanylate cyclase with 1 H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (ODQ) attenuated Ca(2+) oscillations evoked by SNP in the absence of extracellular Ca(2+). (4) Inhibitors of phospholipase C activity, U73122 and the IP(3)R blocker xestospongin C, both abolished the SNP-induced Ca(2+) response. (5) Furthermore, we found that both CCK-8 and carbachol (CCh) induced NO production in DAF-2-loaded acinar cells and that an inhibitor of NO synthase, N(G)-monomethyl-l-arginine (L-NMMA), significantly reduced CCK-8-induced Ca(2+) oscillation. These results indicate that NO mobilizes Ca(2+) from internal stores through activation of guanylate cyclase and resultant cGMP production. In addition, PLC activation of IP(3) production is also suggested to be involved in Ca(2+) mobilization via IP(3) receptors. This suggests the presence of cross-talk between Ca(2+) and NO in pancreatic acini and this cascade may, at least partially, participate in physiological secretagogue-evoked Ca(2+) dynamics in pancreatic acinar cells.

Topics: Animals; Calcium; Carcinoma, Acinar Cell; Estrenes; Inositol 1,4,5-Trisphosphate; Macrocyclic Compounds; Male; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Oxadiazoles; Oxazoles; Pancreatic Neoplasms; Phosphodiesterase Inhibitors; Pyrrolidinones; Quinoxalines; Rats; Rats, Wistar; Signal Transduction; Sincalide; Type C Phospholipases

To investigate the effects of increasing concentrations of cholecystokinin octapeptide (CCK-8) on a pancreatic acinar adenocarcinoma.. Growth of the tumour was estimated in vivo on rats bearing a subcutaneous pancreatic carcinoma, and in vitro on primary cultured tumour cells. CCK receptors were characterized by binding assays.. CCK-8, administered for 12 successive days, exerted a biphasic action on tumour growth: a dose-dependent stimulation with low doses (0.1 and 0.5 microg/kg) and inhibition with high doses (2 and 4 microg/ kg) as shown by respective increases and decreases in tumor volume, protein, RNA and amylase contents. In cell cultures, [3H]thymidine incorporation was dose-dependently increased with 10-(10) to 10(-8) M CCK-8 and inhibited with 10(-7) M. Both effects were completely suppressed by the CCK-receptor antagonists CR 1409 and L 364,718 (10(-4) M). Binding studies showed the overexpression of two classes of CCK-A receptors of low and high affinity when compared to the normal pancreas which was less sensitive to CCK-8.. CCK-8 exerts a biphasic growth response on the acinar pancreatic carcinoma, mediated by two classes of CCK-A receptors overexpressed in the tumour.

Topics: Animals; Azaserine; Carcinoma, Acinar Cell; Cell Division; Dose-Response Relationship, Drug; Iodine Radioisotopes; Pancreatic Neoplasms; Radioligand Assay; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; Sincalide; Tumor Cells, Cultured

It was recently found that cholecystokinin (CCK) activates mitogen-activated protein kinases (MAPK) in isolated rat pancreatic acini. The present study evaluates whether one or both types of CCK receptors are capable of MAPK activation in pancreatic AR42J acinar cells as well as CHO cells transfected with CCK-A or CCK-B receptors. CCK significantly increased p44 MAPK and p42 MAPK activities in AR42J cells. Minimal, half-maximal, and maximal responses were observed at 30 and 500 pM and 10 nM, respectively, after CCK-8 stimulation and at 100 pM and 1.5 and 30 nM, respectively, after gastrin stimulation. Glycine-extended gastrin had no effect at 100 nM and a small but significant effect at 1 microM. The CCK-B receptor antagonist L365,260 almost totally blocked MAPK activation in AR42J cells after stimulation with gastrin and glycine-extended gastrin and substantially reduced the activation of both kinases by CCK-8, while the CCK-A receptor antagonist L364,718 was much less effective. The CCK-A-selective agonist A71376, however, was an effective stimulant of MAPK activity. In an alternative approach, stably transfected CHO cells bearing either CCK-A or CCK-B receptors were stimulated with CCK-8. Each receptor induced a time-dependent increase in activity of both MAPKs by five- to sixfold in CCK-A- and CCK-B-bearing cells. In conclusion, both CCK-A and CCK-B receptors activate MAPK in AR42J cells and in transfected CHO cells.

Topics: Animals; Benzodiazepinones; Blotting, Western; Carcinoma, Acinar Cell; Cells, Cultured; CHO Cells; Cricetinae; Devazepide; Dose-Response Relationship, Drug; Gastrins; MAP Kinase Kinase Kinase 4; MAP Kinase Kinase Kinases; Oligopeptides; Pancreatic Neoplasms; Phenylurea Compounds; Protein Kinases; Rats; Receptor, Cholecystokinin A; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Reference Values; Sincalide; Transfection; Tumor Cells, Cultured

Important differences exist in the responses to photodynamic agents of normal and tumour-derived pancreatic acinar cells. In the present study amylase release has been used to assess the mechanisms by which the photodynamic drugs tetra- and disulphonated aluminium phthalocyanine (A1PcS4, A1PcS2) act on pancreatic cells via energy and calcium-dependent activation and transduction pathways. The photodynamic release of amylase was found to be energy dependent and inhibited by the chelation of free cytoplasmic calcium but not by the removal of extracellular calcium. In contrast to their effects on normal acinar cells, the photodynamic action of A1PcS4 and A1PcS2 was to inhibit amylase secretion from pancreatoma AR4-2J cells. Removal of extracellular calcium reversed this inhibitory effect on AR4-2J cells and produced a significant increase in amylase release, but chelation of free cytoplasmic calcium did not affect the inhibitory photodynamic action of the phthalocyanines on amylase release from the tumour cells. Overall, these results demonstrate further important distinctions between the photodynamic action of sulphonated aluminium phthalocyanines on normal versus tumour exocrine cells of the pancreas and indicate that calcium plays an important role in photodynamic drug action, since these agents affected intracellular calcium mobilisation at some distal point in the membrane signal transduction pathway for regulated secretion. Furthermore, the photodynamic inhibition of constitutive secretion in tumour cells may involve a calcium-dependent membrane target site or modulation of membrane calcium channels by activation of protein kinase C.

Topics: Amylases; Animals; Antimycin A; Bethanechol; Calcium; Carcinoma, Acinar Cell; Deoxyglucose; Egtazic Acid; Indoles; Male; Oligomycins; Organometallic Compounds; Pancreas; Pancreatic Neoplasms; Photochemotherapy; Radiation-Sensitizing Agents; Rats; Rats, Sprague-Dawley; Signal Transduction; Sincalide; Stimulation, Chemical; Tumor Cells, Cultured

Transgenic mice bearing the rat elastase I promoter - SV40 T-antigen (ELSV) fusion gene develop pancreatic acinar cell carcinomas by 3-6 months of age. In other animal models of pancreatic cancer, cholecystokinin (CCK) has been shown to be a tumor promoter. Therefore, we characterized CCK binding properties and CCK-A receptor mRNA expression in pancreatic carcinomas and dysplastic pancreata from the Tg(Ela-1, SV40E+Ela-1, neo)Bri19 strain of ELSV transgenic mice. To accomplish this, we utilized 125I-Bolton-Hunter-labeled-cholecystokinin octapeptide (125I-BH-CCK-8) binding studies, reverse transcription-polymerase chain reaction (RT-PCR), and Southern blot analysis to examine pancreatic carcinomas from 26-week-old male ELSV transgenic mice, dysplastic pancreata from 8-week-old male ELSV transgenic mice, and normal pancreas from 30-week-old nontransgenic male mice (SJL/J) and 8-week-old nontransgenic male mice (B6SJLF1/J). Optimal saturable CCK-8 binding was detected at pH 6.5, 22 degrees C. Competitive inhibition 125I-BH-CCK-8 binding assays performed on all four mouse pancreatic tissues showed that CCK-8 bound to two classes of CCK binding sites: a high affinity, lower capacity CCK binding site and a low affinity, higher capacity CCK binding site. RT-PCR and Southern blot analysis confirmed the 125I-BH-CCK-8 binding studies by demonstrating CCK-A receptor mRNA expression in the ELSV transgenic pancreatic carcinomas and dysplastic pancreas, as well as in normal nontransgenic mouse pancreas. In conclusion, pancreatic carcinomas and dysplastic pancreas from ELSV transgenic mice and normal nontransgenic mouse pancreas all bind 125I-BH-CCK-8 and express mRNA for the CCK-A receptor. In contrast to chemically-induced pancreatic tumors in the rat, ELSV transgenic mouse pancreatic tumors do not appear to significantly overexpress CCK-A receptors.

Topics: Animals; Antigens, Polyomavirus Transforming; Base Sequence; Binding, Competitive; Blotting, Southern; Carcinoma, Acinar Cell; Indicators and Reagents; Iodine Radioisotopes; Male; Mice; Mice, Transgenic; Molecular Sequence Data; Pancreas; Pancreatic Elastase; Pancreatic Neoplasms; Polymerase Chain Reaction; Promoter Regions, Genetic; Rats; Receptor, Cholecystokinin A; Receptors, Cholecystokinin; Recombinant Fusion Proteins; RNA, Messenger; Sincalide; Succinimides; Transcription, Genetic