Concerted cell and in vivo screen for pancreatic ductal adenocarcinoma (PDA) chemotherapeutics

PDA is a major cause of US cancer-related deaths. Oncogenic Kras presents in 90% of human PDAs. Kras mutations occur early in pre-neoplastic lesions but are insufficient to cause PDA. Other contributing factors early in disease progression include chronic pancreatitis, alterations in epigenetic regulators, and tumor suppressor gene mutation. GPCRs activate heterotrimeric G-proteins that stimulate intracellular calcium and oncogenic Kras signaling, thereby promoting pancreatitis and progression to PDA. By contrast, Rgs proteins inhibit Gi/q-coupled GPCRs to negatively regulate PDA progression. Rgs16::GFP is expressed in response to caerulein-induced acinar cell dedifferentiation, early neoplasia, and throughout PDA progression. In genetically engineered mouse models of PDA, Rgs16::GFP is useful for pre-clinical rapid in vivo validation of novel chemotherapeutics targeting early lesions in patients following successful resection or at high risk for progressing to PDA. Cultured primary PDA cells express Rgs16::GFP in response to cytotoxic drugs. A histone deacetylase inhibitor, TSA, stimulated Rgs16::GFP expression in PDA primary cells, potentiated gemcitabine and JQ1 cytotoxicity in cell culture, and Gem + TSA + JQ1 inhibited tumor initiation and progression in vivo. Here we establish the use of Rgs16::GFP expression for testing drug combinations in cell culture and validation of best candidates in our rapid in vivo screen.

Overcoming Adaptive Resistance to KRAS and MEK Inhibitors by Co-targeting mTORC1/2 Complexes in Pancreatic Cancer

Activating KRAS mutations are found in over 90% of pancreatic ductal adenocarcinomas (PDACs), yet KRAS has remained a difficult target to inhibit pharmacologically. Here, we demonstrate, using several human and mouse models of PDACs, rapid acquisition of tumor resistance in response to targeting KRAS or MEK, associated with integrin-linked kinase (ILK)-mediated increased phosphorylation of the mTORC2 component Rictor, and AKT. Although inhibition of mTORC1/2 results in a compensatory increase in ERK phosphorylation, combinatorial treatment of PDAC cells with either KRAS (G12C) or MEK inhibitors, together with mTORC1/2 inhibitors, results in synergistic cytotoxicity and cell death reflected by inhibition of pERK and pRictor/pAKT and of downstream regulators of protein synthesis and cell survival. Relative to single agents alone, this combination leads to durable inhibition of tumor growth and metastatic progression in vivo and increased survival. We have identified an effective combinatorial treatment strategy using clinically viable inhibitors, which can be applied to PDAC tumors with different KRAS mutations.

Immunotherapeutic strategies in pancreatic ductal adenocarcinoma (PDAC): current perspectives and future prospects

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest human malignancies with a dismal prognosis. During PDAC progression, the immune response is affected as cancer cells evade detection and elimination. Recently, there have been advances in the treatment of PDAC using immunotherapy, although a lot more work is yet to be done. In this review, we discuss these advances, challenges and potentials. We focus on existing and potential immune targets for PDAC, drugs used to target them, and some clinical trials conducted so far with them. Finally, novel targets in the tumour microenvironment such as stromal cells and other potential future areas to explore including bacterial therapy and the use of neoantigens in immunotherapy are highlighted.

Activated Ductal Proliferation Induced by N-Nitrosobis (2-oxopropyl)amine in Fat-infiltrated Pancreas of KK-Ay Mice

BACKGROUND/AIM

Our aim was to investigate whether tissue with fatty infiltration within the lobes of the pancreas (scattered FI) is sensitive to carcinogen-induced pancreatic ductal proliferation.

MATERIALS AND METHODS

Seven-week-old female C57BL/6J, C57BL/6J-Ay, KK-Ay, and ICR mice were subcutaneously treated with N-nitrosobis(2-oxopropyl) amine at a dose of 80 mg/kg body weight, and the differences in damage-induced cell proliferation and their biochemical data were compared 2 days after.

RESULTS

Scattered FI in the pancreas was obvious only in KK-Ay mice, which have high serum lipid, leptin and insulin levels, and cell proliferation both in pancreatic and common bile ducts was enhanced only in KK-Ay mice by the carcinogen treatment.

CONCLUSION

Scattered FI in the pancreas per se can be an important factor for carcinogenesis. The genetic background causing scattered FI of the pancreas should be further investigated.

Pancreatic Ductal Adenocarcinoma: Current and Evolving Therapies

Pancreatic ductal adenocarcinoma (PDAC), which constitutes 90% of pancreatic cancers, is the fourth leading cause of cancer-related deaths in the world. Due to the broad heterogeneity of genetic mutations and dense stromal environment, PDAC belongs to one of the most chemoresistant cancers. Most of the available treatments are palliative, with the objective of relieving disease-related symptoms and prolonging survival. Currently, available therapeutic options are surgery, radiation, chemotherapy, immunotherapy, and use of targeted drugs. However, thus far, therapies targeting cancer-associated molecular pathways have not given satisfactory results; this is due in part to the rapid upregulation of compensatory alternative pathways as well as dense desmoplastic reaction. In this review, we summarize currently available therapies and clinical trials, directed towards a plethora of pathways and components dysregulated during PDAC carcinogenesis. Emerging trends towards targeted therapies as the most promising approach will also be discussed.

Identification of pyrazolopyridazinones as PDEδ inhibitors

The prenyl-binding protein PDEδ is crucial for the plasma membrane localization of prenylated Ras. Recently, we have reported that the small-molecule Deltarasin binds to the prenyl-binding pocket of PDEδ, and impairs Ras enrichment at the plasma membrane, thereby affecting the proliferation of KRas-dependent human pancreatic ductal adenocarcinoma cell lines. Here, using structure-based compound design, we have now identified pyrazolopyridazinones as a novel, unrelated chemotype that binds to the prenyl-binding pocket of PDEδ with high affinity, thereby displacing prenylated Ras proteins in cells. Our results show that the new PDEδ inhibitor, named Deltazinone 1, is highly selective, exhibits less unspecific cytotoxicity than the previously reported Deltarasin and demonstrates a high correlation with the phenotypic effect of PDEδ knockdown in a set of human pancreatic cancer cell lines.

FRAX597, a PAK1 inhibitor, synergistically reduces pancreatic cancer growth when combined with gemcitabine

BACKGROUND

Pancreatic ductal adenocarcinoma remains one of the most lethal of all solid tumours. Treatment options are limited and gemcitabine-based chemotherapy remains the standard of care. Although growing evidence shows that p21-activated kinase 1 (PAK1) plays a crucial role in pancreatic cancer, its role has not been fully elucidated. This study aimed to characterise the expression and functional relevance of PAK1 in pancreatic cancer.

METHODS

PAK1 expression was measured in pancreatic cancer specimens by immunohistochemistry and in pancreatic cancer cell lines by western blotting. The effect of inhibition of PAK1 by either shRNA knock-down (KD), or by a selective inhibitor, FRAX597, alone or in combination with gemcitabine, on cell proliferation and migration/invasion was measured by thymidine uptake and Boyden chamber assays, respectively. The effect on tumour growth and survival was assessed in orthotopic murine models.

RESULTS

PAK1 was expressed in all human pancreatic cancer samples tested, an7d was upregulated in all pancreatic cancer cell lines tested. PAK1 KD inhibited pancreatic cancer cell growth and survival, and increased sensitivity to gemcitabine treatment. AKT activity and HIF1α expression were also inhibited. FRAX597 inhibited pancreatic cancer cell proliferation, survival, and migration/invasion. When combined with gemcitabine, FRAX597 synergistically inhibited pancreatic cancer proliferation in vitro and inhibited tumour growth in vivo.

CONCLUSIONS

These results implicate PAK1 as a regulator of pancreatic cancer cell growth and survival. Combination of a PAK1 inhibitor such as FRAX597 with cytotoxic chemotherapy deserves further study as a novel therapeutic approach to pancreatic cancer treatment.

Proton Pump Inhibitors Inhibit Pancreatic Secretion: Role of Gastric and Non-Gastric H+/K+-ATPases

The mechanism by which pancreas secretes high HCO₃^- has not been fully resolved. This alkaline secretion, formed in pancreatic ducts, can be achieved by transporting HCO₃^- from serosa to mucosa or by moving H⁺ in the opposite direction. The aim of the present study was to determine whether H⁺/K⁺-ATPases are expressed and functional in human pancreatic ducts and whether proton pump inhibitors (PPIs) have effect on those. Here we show that the gastric HKα1 and HKβ subunits (ATP4A; ATP4B) and non-gastric HKα2 subunits (ATP12A) of H⁺/K⁺-ATPases are expressed in human pancreatic cells. Pumps have similar localizations in duct cell monolayers (Capan-1) and human pancreas, and notably the gastric pumps are localized on the luminal membranes. In Capan-1 cells, PPIs inhibited recovery of intracellular pH from acidosis. Furthermore, in rats treated with PPIs, pancreatic secretion was inhibited but concentrations of major ions in secretion follow similar excretory curves in control and PPI treated animals. In addition to HCO₃^-, pancreas also secretes K⁺. In conclusion, this study calls for a revision of the basic model for HCO₃^- secretion. We propose that proton transport is driving secretion, and that in addition it may provide a protective pH buffer zone and K⁺ recirculation. Furthermore, it seems relevant to re-evaluate whether PPIs should be used in treatment therapies where pancreatic functions are already compromised.

Apoptotic pathway induced by diallyl trisulfide in pancreatic cancer cells

AIM: To investigate the effects of diallyl trisulfide (DATS), a garlic-derived organosulfur compound, in pancreatic cancer cells.

METHODS: Human pancreatic cancer cells with wild-type p53 gene (Capan-2) and normal pancreatic epithelial cells (H6C7) were cultured in RPMI1640. DATS was prepared at a concentration of 100 μmol/L. Cell viability was determined via the methyl thiazolyl tetrazolium assay. Apoptotic cells were detected by TUNEL assay. Cell cycle analysis was performed using flow cytometry. Protein expression was determined by Western blot. Bax and Bcl-2 expression was detected by immunofluorescence. Apoptosis genes and cell cycle were assessed by quantitative real-time polymerase chain reaction.

RESULTS: DATS suppressed the viability of cultured human pancreatic cancer cells (Capan-2) by increasing the proportion of cells in the G2/M phase and induced apoptotic cell death. Western blot analysis indicated that DATS enhanced the expression of Fas, p21, p53 and cyclin B1, but downregulated the expression of Akt, cyclin D1, MDM2 and Bcl-2. DATS induced cell cycle inhibition which was correlated with elevated levels of cyclin B1 and p21, and reduced levels of cyclin D1 in Capan-2 cells and H6C7 cells. DATS-induced apoptosis was markedly elevated in Capan-2 cells compared with H6C7 cells, and this was correlated with elevated levels of cyclin B1 and p53, and reduced levels of Bcl-2. DATS-induced apoptosis was correlated with down-regulation of Bcl-2, Akt and cyclin D1 protein levels, and up-regulation of Bax, Fas, p53 and cyclin B protein levels in Capan-2 cells.

CONCLUSION: DATS induces apoptosis of pancreatic cancer cells (Capan-2) and non-tumorigenic pancreatic ductal epithelial cells (H6C7).

Proposal for generating new beta cells in a muted immune environment for type 1 diabetes

BACKGROUND

Over the past decade, many immune tolerance agents have shown promise in the non-obese diabetic mouse model for prevention and reversal of type 1 diabetes but have not been successful in clinical trials among recently diagnosed type 1 patients. The trials from decades ago using Cyclosporine A in significantly lower dosages than used for organ transplantation and in similar dosages that have increased T regulatory cell populations in conditions such as atopic dermatitis, demonstrated very high initial insulin-free remission rates when administered immediately after diagnosis. Over time, all newly diagnosed type 1 patients given Cyclosporine A required insulin. Human trials with immune tolerance agents suggest that in addition to an immune tolerance agent, a beta cell regeneration agent may also be necessary to induce long-lasting remission among patients with recent onset type 1 diabetes.

METHODS

A randomized, double-blind prospective trial among recent onset type 1 diabetes patients has been designed using Cyclosporine A and a proton-pump inhibitor, which increases gastrin levels and has been shown to work through the Reg receptor to transform pancreatic duct cells into islets.

Activin A, exendin-4, and glucose stimulate differentiation of human pancreatic ductal cells

Islet transplantation is one treatment option for diabetes mellitus. However, novel sources of pancreatic islets or insulin-producing cells are required because the amount of donor tissue available is severely limited. Pancreatic ductal cells are an alternative source of β-cells because they have the potential to differentiate into insulin-producing cells. We investigated whether treatment of human pancreatic ductal cells with activin A (ActA) and exendin-4 (EX-4) stimulated transdifferentiation of the cells, both in vitro and in vivo. We treated human pancreatic ductal cells with ActA and EX-4 in high-glucose media to induce differentiation into insulin-producing cells and transplanted the cells into streptozotocin-induced diabetic nude mice. Co-treatment of mice with ActA and EX-4 promoted cell proliferation, induced expression of pancreatic β-cell-specific markers, and caused glucose-induced insulin secretion compared with the ActA or EX-4 mono-treatment groups respectively. When pancreatic ductal cells treated with ActA and EX-4 in high-glucose media were transplanted into diabetic nude mice, their blood glucose levels normalized and insulin was detected in the graft. These findings suggest that pancreatic ductal cells have a potential to replace pancreatic islets for the treatment of diabetes mellitus when the ductal cells are co-treated with ActA, EX-4, and glucose to promote their differentiation into functional insulin-producing cells.

Akt kinase mediates the prosurvival effect of smoking compounds in pancreatic ductal cells

OBJECTIVES

Cigarette smoking is a major risk factor for pancreatic cancer (PaCa). However, the mechanisms of smoking-induced PaCa remain unknown. Here we investigated the effect of smoking compounds on cell death pathways in pancreatic ductal cells, precursors of PaCa.

METHODS

Human pancreatic ductal cells (HPDE6-c7) were cultured with cigarette smoke extract (CSE) or smoking compound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Apoptosis and autophagy were assessed by DNA fragmentation and immunofluorescence, respectively.

RESULTS

Exposure to CSE or NNK decreased DNA fragmentation and up-regulated BclXL. Akt kinase was activated by smoking compounds through reactive oxygen species-dependent mechanism. Specifically, Akt activation was prevented by inhibition of nicotinamide adenine dinucleotide oxidase. Molecular or pharmacologic inhibitions of Akt prevented the antiapoptotic effect of smoking compounds. Smoking compounds stimulated rapid (1 hour) and transient activation of 5'-adenosine monophosphate-activated protein kinase and formation of autophagic vacuoles, indicating stimulation of autophagy. Repeated exposure to CSE/NNK (48 hours or longer) abolished the early activation of autophagic markers. Inhibition of Akt prevented the antiautophagic effect of long exposure to smoking compounds, indicating that smoking-induced late activation of Akt prevents autophagy.

CONCLUSIONS

Long exposure of pancreatic ductal cells to smoking compounds inhibited apoptosis and autophagy. The results revealed a central role for Akt kinase in mediating key procarcinogenic effects of smoking compounds.

Chronic GLP-1 receptor activation by exendin-4 induces expansion of pancreatic duct glands in rats and accelerates formation of dysplastic lesions and chronic pancreatitis in the Kras(G12D) mouse model

Pancreatic duct glands (PDGs) have been hypothesized to give rise to pancreatic intraepithelial neoplasia (PanIN). Treatment with the glucagon-like peptide (GLP)-1 analog, exendin-4, for 12 weeks induced the expansion of PDGs with mucinous metaplasia and columnar cell atypia resembling low-grade PanIN in rats. In the pancreata of Pdx1-Cre; LSL-Kras(G12D) mice, exendin-4 led to acceleration of the disruption of exocrine architecture and chronic pancreatitis with mucinous metaplasia and increased formation of murine PanIN lesions. PDGs and PanIN lesions in rodent and human pancreata express the GLP-1 receptor. Exendin-4 induced proproliferative signaling pathways in human pancreatic duct cells, cAMP-protein kinase A and mitogen-activated protein kinase phosphorylation of cAMP-responsive element-binding protein, and increased cyclin D1 expression. These GLP-1 effects were more pronounced in the presence of an activating mutation of Kras and were inhibited by metformin. These data reveal that GLP-1 mimetic therapy may induce focal proliferation in the exocrine pancreas and, in the context of exocrine dysplasia, may accelerate formation of neoplastic PanIN lesions and exacerbate chronic pancreatitis.

The effect of exogenous apelin on the secretion of pancreatic juice in anaesthetized rats

Apelin is known to stimulate cholecystokinin (CCK) and inhibit insulin release, however the mechanisms on pancreatic secretion remain unclear. The present study aimed to determine the expression of apelin and apelin receptor in the pancreas by immunofluorescence studies and the effect of exogenous apelin on the secretion of pancreatic juice in anesthetized rats. Pancreatic-biliary juice (P-BJ) was collected from Wistar rats treated with apelin (10, 20 and 50 nmol/kg b.w., boluses given every 30 min intravenously or intraduodenaly). The same apelin doses were administered to rats subjected to intraduodenal tarazapide, capsaicin or vagotomy. Pancreatic blood flow was measured by a laser doppler flowmeter. Direct effects of apelin were tested on dispersed acinar cells. Apelin receptor was expressed on acinar cells, pancreatic duct and islets cells, whereas apelin in pancreatic acini, but not in the islets. Intravenous apelin decreased P-BJ volume, protein and trypsin outputs in a dose-dependent manner. In contrast, intraduodenal apelin stimulated P-BJ secretion. Pharmacological block of mucosal CCK(1) receptor by tarazepide, vagotomy and capsaicin pretreatment abolished the effects of intravenous and intraduodenal apelin on P-BJ volume, protein and tryspin outputs. Apelin decreased the pancreatic blood flow. Apelin at 10(-6) M increased the release of amylase from non-stimulated and CCK-8-stimulated acinar cells. In conclusion, apelin can affect the exocrine pancreas through a complex mechanism involving local blood flow regulation and is driven by vagal nerves.

Islet neogenesis-associated protein-related pentadecapeptide enhances the differentiation of islet-like clusters from human pancreatic duct cells

The differentiation of pancreatic ductal epithelial cells into beta-cells has been considered as an alternative method for increasing the number of islets for transplantation. Critical factors have been introduced into the in vitro differentiation protocol for pancreatic duct cells in order to enhance the production of beta-cells. Islet neogenesis-associated protein (INGAP) is an initiator of islet neogenesis and the peptide sequence 104-118 of INGAP has been shown to stimulate an increase in beta-cell mass in animals and also found in human pathological states involving islet neogenesis. To establish a novel method for the differentiation of beta-cells from human pancreatic duct cells with INGAP-related pentadecapeptide (INGAP-PP), the pancreatic duct cells were isolated, purified and expanded in vitro and differentiated using a four-step protocol that included nicotinamide, exendin-4, transforming growth factor beta(1) and INGAP-PP/Scrambled peptide (Scrambled-P). The production of islet-like clusters (ILCs) in the INGAP-PP group was significantly higher than that in the Scrambled-P control group after differentiation from an equal number of duct cells. The duct cells showed positive staining and expression for cytokeratin 19, pancreatic duodenal homeobox-1, nestin, and were negative for insulin and glucagon, as detected by both immunofluorescence and RT-PCR. Following differentiation the cells became insulin and glucagon positive. In addition, the ILCs from the INGAP-PP group secreted higher levels of insulin and C-peptide than the Scrambled-P group under a high glucose challenge. We conclude that INGAP peptide enhances the in vitro differentiation of pancreatic duct cells into islet-like clusters.

Effects of bile acids on pancreatic ductal bicarbonate secretion in guinea pig

BACKGROUND AND AIMS

Acute pancreatitis is associated with significant morbidity and mortality. Bile reflux into the pancreas is a common cause of acute pancreatitis and, although the bile can reach both acinar and ductal cells, most research to date has focused on the acinar cells. The aim of the present study was to investigate the effects of bile acids on HCO(3)(-) secretion from the ductal epithelium.

METHODS

Isolated guinea pig intralobular/interlobular pancreatic ducts were microperfused and the effects of unconjugated chenodeoxycholate (CDC) and conjugated glycochenodeoxycholate (GCDC) on intracellular calcium concentration ([Ca(2+)](i)) and pH (pH(i)) were measured using fluorescent dyes. Changes of pH(i) were used to calculate the rates of acid/base transport across the duct cell membranes.

RESULTS

Luminal administration of a low dose of CDC (0.1 mM) stimulated ductal HCO(3)(-) secretion, which was blocked by luminal H(2)DIDS (dihydro-4,4'-diisothiocyanostilbene-2,2'-disulfonic acid). In contrast, both luminal and basolateral administration of a high dose of CDC (1 mM) strongly inhibited HCO(3)(-) secretion. Both CDC and GCDC elevated [Ca(2+)](i), and this effect was blocked by BAPTA-AM (1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid), caffeine, xestospongin C and the phospholipase C inhibitor U73122. BAPTA-AM also inhibited the stimulatory effect of low doses of CDC on HCO(3)(-) secretion, but did not modulate the inhibitory effect of high doses of CDC.

CONCLUSIONS

It is concluded that the HCO(3)(-) secretion stimulated by low concentrations of bile acids acts to protect the pancreas against toxic bile, whereas inhibition of HCO(3)(-) secretion by high concentrations of bile acids may contribute to the progression of acute pancreatitis.

Stress-associated hormone, norepinephrine, increases proliferation and IL-6 levels of human pancreatic duct epithelial cells and can be inhibited by the dietary agent, sulforaphane

In current literature there is evidence that psychological factors can affect the incidence and progression of some cancers. Data obtained from animal models support the hypothesis that stress can be a cofactor. The underlying mechanisms for the association between psychological factors and pancreatic cancer are very poorly understood. In this study, we examined the possible growth promoting effects of the stress-associated hormone, norepinephrine, on immortalized human pancreatic duct epithelial cells. Our results suggest that norepinephrine can increase cell proliferation of human pancreatic duct epithelial cells. We also evaluated the ability of norepinephrine to induce interleukin-6 (IL-6), interleukin-10 (IL-10), and vascular endothelial growth factor (VEGF). All of which may promote oncogenesis of immortalized human pancreatic duct epithelial cells. We found that norepinephrine can increase the IL-6 and VEGF but not IL-10 levels secreted by human pancreatic duct epithelial cells. Since norepinephrine can increase cell proliferation of human pancreatic duct epithelial cells, we performed further testing to see if dietary agents, sulforaphane and resveratrol, can inhibit norepinephrine-mediated increases in cell proliferation in human pancreatic duct epithelial cells. Interestingly, our results demonstrated that sulforaphane but not resveratrol inhibits norepinephrine-mediated increases in cell viability in human pancreatic duct epithelial cells. Furthermore, sulforaphane also inhibits norepinephrine-mediated increase of the IL-6 levels but not VEGF levels. Our study is the first to demonstrate that stress-associated hormone, norepinephrine, can increase the cell proliferation and IL-6 levels of human pancreatic duct epithelial cells, which can be inhibited by sulforaphane, a chemopreventive agent and a natural compound from the Cruciferous vegetables.

The effects of contrast agent and intraductal pressure changes on the development of pancreatitis in an ERCP model in rats

OBJECTIVE

Although there are various experimental pancreatic models in animals, only a few studies have evaluated how intraductal pressure and contrast agent affect the development of pancreatitis after endoscopic retrograde cholangiopancreatograpy (ERCP).

MATERIALS AND METHODS

The rats were randomly divided into seven groups (n = 8/group). The rats in all groups underwent laparotomy and their biliopancreatic ducts were cannulated transduodenally using a 24G catheter. In the control group, group 1, the biliopancreatic ducts of the rats were not infused with any fluid. The biliopancreatic ducts of the rats in groups 2, 3, and 4 were infused with 0.5 ml isotonic NaCl solution at 10, 2, and 50 mmHg, respectively. Groups 5, 6, and 7 were given 0.5 ml of 50% diluted contrast agent at 10, 25, and 50 mmHg, respectively. The serum amylase, aspartate aminotransferase (AST), lactic dehydrogenase (LDH), and C-reactive protein (CRP) were measured 24 h after the procedure. Pancreatic tissue was also evaluated histopathologically.

RESULTS

Pancreatitis due to the contrast agent was noted when comparing the low pressure isotonic NaCl group and the low pressure contrast group (p < 0.05). Based on serum amylase and CRP values, there was a positive correlation between the severity and frequency of acute pancreatitis and pressure (p < 0.01). AST and LDH levels increased in all of the groups that underwent the procedure; however, no correlation was detected with increasing pressure or with the use of contrast agent (p > 0.05). Both pancreatic edema and the inflammatory cell infiltration score were elevated in isotonic NaCl and contrast group (p < 0.05); however, necrosis was not significantly changed (p > 0.05).

CONCLUSION

The results of this study suggest that the main mechanism for preventing pancreatitis after ERCP is to minimize trauma to the pancreatic canal, to cannulate the pancreas only when it is necessary, and to give contrast agent under low pressure when it is needed.

Effects of activin A on pancreatic ductal cells in streptozotocin-induced diabetic rats

BACKGROUND

The shortage of islets for transplantation has led to find alternative insulin producing cells. Pancreatic progenitor cells in the duct have the potential to grow and differentiate into endocrine cells. In this study, we examined whether activin A can promote the expansion and/or differentiation of ductal cells into insulin-producing cells.

METHODS

Pancreatic ductal cells were treated with activin A for differentiation into endocrine cells, and transplanted into the renal subcapsular space of streptozotocin (STZ)-induced diabetic rats. The identity of the endocrine cells was confirmed by immunostaining and analysis of the expression of transcription factors and endocrine genes by reverse-transcriptase polymerase chain reaction.

RESULTS

Activin A treatment significantly increased the DNA synthesis and the expression of insulin I, insulin II, PDX-1, Nkx 6.1, Glut-2, Pax-4, Pax-6, and Ngn-3. De novo synthesis of insulin in activin A-treated ductal cells was observed by the immunocytochemical detection of C-peptide and the differentiated ductal cells secreted significantly increased amount of insulin compared to nontreated ductal cells in response to glucose stimulation. When activin A-treated ductal cells were transplanted on STZ-induced diabetic rats, blood glucose levels were normalized and the removal of the transplanted kidney resulted in return to hyperglycemia.

CONCLUSIONS

The pancreatic ductal cells could be efficiently differentiated into insulin secreting cells by activin A treatment in vitro and normalize hyperglycemia in vivo.

Cigarette smoke components inhibited intercellular communication and differentiation in human pancreatic ductal epithelial cells

Smoking is a well-documented risk factor for the development of pancreatic adenocarcinoma. Although the most abundant polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke are methylated anthracenes and phenanthrenes, the epigenetic toxicity of these compounds has not been extensively studied. We previously showed that methylanthracenes, which possess a bay-like structure, affect epigenetic events such as an induced release of arachidonic acid, inhibition of gap junctional intercellular communication (GJIC) and induction of mitogen-activated protein kinases in a pluripotent rat liver epithelial stem cell line. Anthracenes with no bay-like structures were inactive. These biological effects are all molecular events associated with the promotional phase of cancer. A human immortalized, nontumorigenic pancreatic ductal epithelial cell line, H6c7, was examined to study the epigenetic toxicity of PAHs related to pancreatic cancer by using scrape-loading dye transfer, immunostaining, RT-PCR and telomerase assay methods. H6c7 cells were GJIC-incompetent and exhibited high telomerase activity when grown in growth factor and hormone-supplemented medium. In the presence of the cAMP elevating drugs (forskolin and IBMX) the cells became GJIC competent and expressed connexins. Telomerase activity was also decreased by cAMP elevating drug treatment. After induction of cAMP, 1-methylanthracene with bay-like structures inhibited GJIC, whereas the 2-methylanthracene lacking a bay-like structure had no effect on GJIC. Telomerase activity remained high in 1-methylanthracene treatment but not with 2-methylanthracene. These results indicate that a prominent component of cigarette smoke, namely methylanthracenes with distinct structural configurations, could be a potential etiological agent contributing to the epigenetic events of pancreatic cancer.

Acinar plasticity: development of a novel in vitro model to study human acinar-to-duct-to-islet differentiation

OBJECTIVES

The plasticity of pancreatic tissue is demonstrated in many pancreatic diseases. It has previously been shown that pancreatic islet-to-duct transformation and acinoductal metaplasia have been associated with both pancreatic regeneration and adenocarcinoma in various in vivo and in vitro settings. Understanding this inherent morphogenetic plasticity of the adult pancreas could lead to new therapeutic approaches to pancreatic disease.

METHODS

Cadaveric human pancreases (n = 7) were digested, and purified acinar tissue, which was approximately 85% immunoreactive for amylase and approximately 15% immunoreactive for CK-19, was embedded in a type 1 collagen matrix and cultured in a differentiation medium (DM) consisting of Dulbecco modified Eagle/F12 medium supplemented with cholera toxin (100 ng/mL), epidermal growth factor (10 ng/mL), and insulin (24 mU/mL) for 8 days. After this initial period, the resulting tissues were cultured in DM without cholera toxin, supplemented with gastrin (50 nmol/L) and hepatocyte growth factor (HGF; 10 ng/mL), with islet neogenesis-associated protein (INGAP; 167 nmol/L) or with gastrin + HGF + INGAP for 6 days. Tissue samples were then analyzed for amylase, cytokeratin 19, pancreas duodenum homeobox 1, and endocrine hormone immunoreactivity as well as dithizione positivity.

RESULTS

After 8 days of culture, approximately 90% of acini transformed into ductlike structures. This acinoductal transformation was characterized by a complete absence of amylase staining, with virtually all cells CK-19 immunoreactive. Addition of INGAP led to an approximately 18-fold increase in pancreas duodenum homeobox 1 immunoreactivity, although without an observed increase in insulin production as measured by dithizone positivity. However, when acinar-derived ductlike structures were cultured with gastrin + HGF + INGAP, the total incidence of dithizone-positive structures increased approximately 6-fold (10.9 +/- 2.9% vs 1.7 +/- 0.4%, P = 0.037). Treatment with gastrin + HGF alone led to no significant change in any of the measured parameters.

CONCLUSIONS

We have developed a novel in vitro model of adult human acinoductal metaplasia that will aid not only in developing new methods of expanding beta-cell mass but also provide insights into pancreatic carcinogenesis.

Effects of immunosuppressive drugs on in vitro neogenesis of human islets: mycophenolate mofetil inhibits the proliferation of ductal cells

Assuming that neogenesis contributes to long-term function of islet grafts, it is important to study the effects of immunosuppressive drugs on precursor cell proliferation and differentiation. We examined the effects of low-dose immunosuppressive drugs on these processes in vitro. Immunosuppressive drugs, including sirolimus, tacrolimus, mycophenolate mofetil (MMF), daclizumab and their combinations were tested in parallel culture wells through either the expansion phase (5-7 days) or the entire culture period (4-5 weeks). MMF, alone or in combination with sirolimus or tacrolimus, severely hampered duct-cell proliferation by 8-fold during the expansion period, and significantly reduced the total DNA content by about 40% after 5-week culture. After 4-5 week exposure to different drugs, only sirolimus and daclizumab showed no adverse effects on insulin content, whereas significant reductions of 30-60% in insulin content were seen in all other experimental groups. Only tacrolimus decreased the insulin content per DNA, as well as the proportion of insulin-positive cells. In conclusion, MMF has a potent inhibitory effect on neogenesis primarily through an antiproliferative effect on the precursors, whereas tacrolimus mainly affects beta-cell differentiation. Sirolimus and daclizumab have no adverse effects on these parameters. The immunosuppressive protocol may be an important determinant of long-term clinical islet graft function.

Vectorial bicarbonate transport by Capan-1 cells: a model for human pancreatic ductal secretion

Human pancreatic ducts secrete a bicarbonate-rich fluid but our knowledge of the secretory process is based mainly on studies of animal models. Our aim was to determine whether the HCO(3)(-) transport mechanisms in a human ductal cell line are similar to those previously identified in guinea-pig pancreatic ducts. Intracellular pH was measured by microfluorometry in Capan-1 cell monolayers grown on permeable filters and loaded with BCECF. Epithelial polarization was assessed by immunolocalization of occludin. Expression of mRNA for key electrolyte transporters and receptors was evaluated by RT-PCR. Capan-1 cells grown on permeable supports formed confluent, polarized monolayers with well developed tight junctions. The recovery of pH(i) from an acid load, induced by a short NH(4)(+) pulse, was mediated by Na(+)-dependent transporters located exclusively at the basolateral membrane. One was independent of HCO(3)(-) and blocked by EIPA (probably NHE1) while the other was HCO(3)(-)-dependent and blocked by H(2)DIDS (probably pNBC1). Changes in pH(i) following blockade of basolateral HCO(3)(-) accumulation confirmed that the cells achieve vectorial HCO(3)(-) secretion. Dose-dependent increases in HCO(3)(-) secretion were observed in response to stimulation of both secretin and VPAC receptors. ATP and UTP applied to the apical membrane stimulated HCO(3)(-) secretion but were inhibitory when applied to the basolateral membrane. HCO(3)(-) secretion in guinea-pig ducts and Capan-1 cell monolayers share many common features, suggesting that the latter is an excellent model for studies of human pancreatic HCO(3)(-) secretion.

Effect of Slc26a6 deletion on apical Cl-/HCO3- exchanger activity and cAMP-stimulated bicarbonate secretion in pancreatic duct

The role of Slc26a6 (PAT1) on apical Cl-/HCO3- exchange and bicarbonate secretion in pancreatic duct cells was investigated using Slc26a6 null and wild-type (WT) mice. Apical Cl-/HCO3- exchange activity was measured with the pH-sensitive dye BCECF in microperfused interlobular ducts. The HCO3(-)-influx mode of apical [Cl-]i/[HCO3-]o exchange (where brackets denote concentration and subscripts i and o denote intra- and extracellular, respectively) was dramatically upregulated in Slc26a6 null mice (P < 0.01 vs. WT), whereas the HCO3(-)-efflux mode of apical [Cl-]o/[HCO3-]i exchange was decreased in Slc26a6 null mice (P < 0.05 vs. WT), suggesting the unidirectionality of the Slc26a6-mediated HCO3- transport. Fluid secretory rate in interlobular ducts were comparable in WT and Slc26a6 null mice (P > 0.05). In addition, when pancreatic juice was collected from whole animal in basal and secretin-stimulated conditions, neither juice volume nor its pH showed differences between WT and Slc26a6 null mice. Semiquantitative RT-PCR demonstrated more than fivefold upregulation in Slc26a3 (DRA) expression in Slc26a6 knockout pancreas. In conclusion, these results point to the role of Slc26a6 in HCO3- efflux at the apical membrane and also suggest the presence of a robust Slc26a3 compensatory upregulation, which can replace the function of Slc26a6 in pancreatic ducts.

Low concentrations of beta-carotene stimulate the proliferation of human pancreatic duct epithelial cells in a PKA-dependent manner

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is among the most common causes of cancer death. Preclinical and clinical studies on the preventive effects of beta-carotene or other retinoids have used dietary supplements that yielded high systemic concentrations (1-50 microM). While some of the preclinical data suggested cancer preventive effects of these agents, they have disappointed in clinical investigations.

MATERIALS AND METHODS

The effects of low concentrations (10 fM-200 nM)of beta-carotene on the proliferation, intracellular cAMP levels, PKA activation status and phosphorylation of EGFR-specific tyrosine kinases and ERK1/2 in immortalized human pancreatic duct epithelial cells was investigated.

RESULTS

Our data show significant concentration-dependent and PKA-dependent stimulation of all measured endpoints. Similar responses were achieved with forskolin. Our data indicate that low concentrations of beta-carotene stimulate the proliferation of the putative origin of PDAC, pancreatic duct epithelial cells via cAMP and PKA-dependent transactivation of the EGFR pathway. This could potentially have promoting effects on the development of PDAC.

The impact of the mTOR inhibitor sirolimus on the proliferation and function of pancreatic islets and ductal cells

AIMS/HYPOTHESIS

The Edmonton Protocol for islet transplantation has provided hope for type 1 diabetic patients. However, this protocol requires lifelong immunosuppression, specifically sirolimus, a cellular antiproliferate. The effect of sirolimus on human pancreatic ductal cells (HDCs) is not known. This may be important since HDCs are believed to be islet precursors. Since neonatal porcine islets (NPIs), which contain many ductal precursor cells, could be a potential clinical source of islets, we also tested the effects of sirolimus on this tissue.

METHODS

HDCs (n=4), NPIs (n=9) and human islets (n=5) were cultured with and without sirolimus (20 ng/ml) for 6 days.

RESULTS

HDCs and NPIs cultured with sirolimus showed a 50 and 28% decrease, respectively, in cell number relative to control (p<0.05). Control cultures expanded 1.65- and 2.44-fold relative to time 0. Decreases in cell number of sirolimus-treated HDCs were not due to apoptosis as measured by TUNEL staining. No functional effects on human islets or NPIs were observed following static incubation with high glucose. Treatment of syngeneically transplanted and naïve BALC/c mice with sirolimus resulted in altered OGTT profiles with prolonged elevation of hyperglycaemia and weight gain. There was no difference in graft and organ insulin content between treatment groups.

CONCLUSIONS/INTERPRETATION

Our results indicate that sirolimus decreases ductal cell numbers in culture and alters glucose-stimulated insulin secretion in vivo. The administration of sirolimus to islet transplant recipients is likely to impair graft function as a result of decreasing ductal neogenesis and induction of insulin resistance.

Ethanol and the tobacco-specific carcinogen, NNK, contribute to signaling in immortalized human pancreatic duct epithelial cells

OBJECTIVES

Smoking is a well-documented risk factor for pancreatic cancer. The tobacco-specific nitrosamine, NNK (4-[methylnitrosamino]-1-[3-pyridyl]-1-butanone), significantly induces pancreatic ductal adenocarcinomas in laboratory rodents. Recent observations suggest that ethanol enhances the tumorigenic effects of smoking. Ethanol consumption is associated with the development of chronic pancreatitis, also considered a predisposing factor for pancreatic ductal adenocarcinoma. Because the precise role of ethanol in pancreatic carcinogenesis is not known, this study sought to elucidate the cumulative effects of ethanol and NNK on particular signal transduction pathways that might play a role in cell proliferation in immortalized human pancreatic duct epithelial cells.

METHODS

The HPDE6-c7 cells are developed from pancreatic duct epithelial cells, which are the putative cells of origin of pancreatic ductal adenocarcinoma. Cell proliferation assays, Western blot, and cyclic adenosine monophosphate assays were used to demonstrate the effects of ethanol and NNK treatments on these cells.

RESULTS

Ethanol cotreatments enhanced the NNK-induced proliferation of these cells. This response was inhibited by the adenylyl cyclase, protein kinase A, mitogen-activated protein kinase (p42/p44), and epidermal growth factor receptor-specific tyrosine kinase inhibitors. Cotreatments of NNK and ethanol also increased cyclic adenosine monophosphate accumulation, cAMP response element-binding family of proteins and mitogen-activated protein kinase phosphorylation, and protein kinase A activation.

CONCLUSIONS

These findings suggest a potential role for these pathways contributing to the development of smoking- and alcohol-related pancreatic carcinogenesis.

Protein kinase C modulates the pulmonary inflammatory response in acute pancreatitis

The present study aims at evaluating the role of protein kinase C (PKC) in the development of acute lung injury, production of inflammatory mediators and expression of adhesion molecules on leukocytes after induction of acute pancreatitis (AP). AP was induced by the intraductal infusion of 5% sodium taurodeoxycholate in the rat. The animals had the PKC inhibitor polymyxin B administered intraperitoneally 30min prior to induction of AP. Levels of protein content, protease activity, cytokines and chemokines in bronchoalveolar lavage fluid (BALF) were assessed 1 and 6h after AP induction. Adhesion molecule expression on leukocytes were measured by flowcytometry. Pretreatment with polymyxin B prevented against acute pancreatitis-induced lung injury and the otherwise occurring increases in TNF-alpha, IL-1beta, MCP-1 and IL-10, as well as against the decreases in IL-2, IFNgamma and TIMP-1, decreased protease activity and down-regulation of CD31, CD54 and CD62L on recruited neutrophils and macrophages in BALF. The results indicate that the leukocyte response in acute pancreatitis vary depending on leukocyte subpopulation. It seems that activation of the PKC signalling pathway may play an important role in pancreatitis-associated lung injury.

Characterization of H+ and HCO3- transporters in CFPAC-1 human pancreatic duct cells

AIM: To characterize H⁺ and HCO₃^- transporters in polarized CFPAC-1 human pancreatic duct cells, which were derived from a cystic fibrosis patient with the ΔF508 CFTR mutation.

METHODS: CFPAC-1 cells were seeded at high density onto permeable supports and grown to confluence. The cells were loaded with the pH-sensitive fluorescent dye BCECF, and mounted into a perfusion chamber, which allowed the simultaneous perfusion of the basolateral and apical membranes. Transmembrane base flux was calculated from the changes in intracellular pH and the buffering capacity of the cells.

RESULTS: Our results showed differential permeability to HCO₃^-/CO₂ at the apical and basolateral membranes of CFPAC-1 cells. Na⁺/HCO₃^- co-transporters (NBCs) and Cl^-/HCO₃^- exchangers (AEs) were present on the basolateral membrane, and Na⁺/H⁺ exchangers (NHEs) on both the apical and basolateral membranes of the cells. Basolateral HCO₃^- uptake was sensitive to variations of extracellular K⁺ concentration, the membrane permeable carbonic anhydrase (CA) inhibitors acetazolamide (100 µmol/L) and ethoxyzolamide (100 µmol/L), and was partially inhibited by H₂-DIDS (600 µmol/L). The membrane-impermeable CA inhibitor 1-N-(4-sulfamoylphenylethyl)-2,4,6-trimethylpyridine perchlorate did not have any effect on HCO₃^- uptake. The basolateral AE had a much higher activity than that in the apical membrane, whereas there was no such difference with the NHE under resting conditions. Also, 10 µmol/L forskolin did not significantly influence Cl^-/HCO₃^- exchange on the apical and basolateral membranes. The administration of 250 µmol/L H₂-DIDS significantly inhibited the basolateral AE. Amiloride (300 µmol/L) completely inhibited NHEs on both membranes of the cells. RT-PCR revealed the expression of pNBC1, AE2, and NHE1 mRNA.

CONCLUSION: These data suggest that apart from the lack of CFTR and apical Cl^-/HCO₃^- exchanger activity, CFPAC-1 cells express similar H⁺ and HCO₃^- transporters to those observed in native animal tissue.

SLC26 transporters and the inhibitory control of pancreatic ductal bicarbonate secretion

SLC26 anion exchangers (probably SLC26A3 and SLC26A6) are expressed on the apical membrane of pancreatic duct cells and play a key role in HCO3- secretion; a process that is inhibited by the neuropeptide, substance P (SP). SP had no effect on basolateral HCO3- transporters in the duct cell or on CFTR Cl- channels, but inhibited a Cl- -dependent HCO3- efflux step on the apical membrane. In microperfused ducts, luminal H2DIDS (0.5mM) caused intracellular pH to alkalinize (consistent with inhibition of HCO3- efflux) and, like SP, inhibited HCO3- secretion. SP did not reduce HCO3- secretion further when H2DIDS was applied to the duct lumen, suggesting that SP and H2DIDS inhibit the same transporter on the apical membrane. As SLC26A6 is DIDS-sensitive, this isoform is the likely target for SP. The inhibitory effect of SP was mimicked by phorbol 12,13-dibutyrate (PDBu), an activator of protein kinase C (PKC). Moreover, bisindolylmaleimide, a blocker of PKC, relieved the inhibitory effect of both SP and PDBu on HCO3- secretion. Western blot analysis revealed that guinea pig pancreatic ducts express the alpha, beta1, delta, epsilon, eta, theta, zeta and mu isoforms o f PKC. We conclude that PKC is a negative regulator of SLC26 activity in pancreatic duct cells.

Safe management of the pancreatic remnant with prolamine duct occlusion after extended pancreaticoduodenectomy

BACKGROUND/AIMS

Occlusion of the pancreatic duct system has been used to prevent pancreatic leakage by abolishing pancreatic exocrine secretion in pancreatic surgery. However, ductal occlusion has not proved satisfactory for preventing pancreatic fistulas in pancreaticoduodenectomy (PD).

METHODOLOGY

Pancreatic duct occlusion with a watertight drainage system around the pancreatic stump was performed following extended PD in 17 patients with (n=12) or without (n=5) a dilated pancreatic duct.

RESULTS

Transient pancreatitis during the early postoperative period occurred in all patients with a nondilated pancreatic duct. No patient developed pancreatic fistula or any other serious complication in both groups.

CONCLUSIONS

Pancreatic duct occlusion may minimize the risk of pancreatic leakage in patients with a nondilated pancreatic duct and a normal pancreas as well as in those with a dilated, obstructed pancreatic duct without compromising the postoperative quality of life. This is a safe and reliable technique for managing the pancreatic remnant in patients undergoing extended PD for advanced pancreaticobiliary malignancy.

The tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone stimulates proliferation of immortalized human pancreatic duct epithelia through beta-adrenergic transactivation of EGF receptors

PURPOSE

Pancreatic ductal adenocarcinoma is an aggressive smoking-associated human cancer in both men and women. The nicotine-derived 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is thought to contribute to the development of these neoplasms in smokers through genotoxic effects. However, NNK has been recently identified as an agonist for both beta(1)- and beta(2)-adrenergic receptors. Binding of NNK to these receptors stimulates proliferation of pulmonary and pancreatic adenocarcinomas cells in vitro and in hamster models. The goal of this study was to elucidate the NNK effects on the signal transduction pathways downstream of both beta(1)- and beta(2)-adrenergic receptors in immortalized human pancreatic HPDE6-c7 cells.

METHODS

The HPDE6-c7 cells are developed from normal pancreatic duct epithelial cells which are the putative cells of origin of pancreatic ductal adenocarcinoma. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cell proliferation assays, Western blot and cyclic AMP assays were employed to demonstrate the effects of NNK and other beta(1)- and beta(2)-adrenergic agonists and antagonist treatments on these cells.

RESULTS

MTT cell proliferation assays demonstrated that NNK and the classic beta-adrenergic agonist, isoproterenol, increased cell proliferation in HPDE6-c7 cells. Western blot and cyclic AMP assays demonstrated that NNK treatments also resulted in: (1) transactivation of the epidermal growth factor receptor, EGFR, (2) an increase in intracellular cyclic AMP accumulation, and (3) phosphorylation of mitogen-activated protein kinase, Erk1/2. The proliferative response to NNK and isoproterenol were inhibited by the use of beta-blockers (propranolol), and the inhibitors of adenylyl cyclase (SQ 22536), EGFR-specific tyrosine kinase (AG 1478) and Erk (PD 98059).

CONCLUSION

These findings suggest that the NNK -mediated beta-adrenergic receptor transactivation of the EGFR and phosphorylation of Erk1/2 in immortalized human pancreatic duct epithelial cells as a novel mechanism might contribute to the development of tobacco-associated pancreatic carcinogenesis.

Quantification of pancreatic exocrine function with secretin-enhanced magnetic resonance cholangiopancreatography: normal values and short-term effects of pancreatic duct drainage procedures in chronic pancreatitis. Initial results

The aim of this study was to quantify pancreatic exocrine function in normal subjects and in patients with chronic pancreatitis (CP) before and after pancreatic duct drainage procedures (PDDP) with dynamic secretin-enhanced magnetic resonance (MR) cholangiopancreatography (S-MRCP). Pancreatic exocrine secretions [quantified by pancreatic flow output (PFO) and total excreted volume (TEV)] were quantified twice in ten healthy volunteers and before and after treatment in 20 CP patients (18 classified as severe, one as moderate, and one as mild according to the Cambridge classification). PFO and TEV were derived from a linear regression between MR-calculated volumes and time. In all subjects, pancreatic exocrine fluid volume initially increased linearly with time during secretin stimulation. In controls, the mean PFO and TEV were 6.8 ml/min and 97 ml; intra-individual deviations were 0.8 ml/min and 16 ml. In 10/20 patients with impaired exocrine secretions before treatment, a significant increase of PFO and TEV was observed after treatment (P<0.05); 3/20 patients presented post-procedural acute pancreatitis and a reduced PFO. The S-MRCP quantification method used in the present study is reproducible and provides normal values for PFO and TEV in the range of those obtained from previous published intubation studies. The initial results in CP patients have demonstrated non-invasively a significant short-term improvement of PFO and TEV after PDDP.

Combination therapy with epidermal growth factor and gastrin induces neogenesis of human islet {beta}-cells from pancreatic duct cells and an increase in functional {beta}-cell mass

Pancreatic islet transplantation is a viable treatment for type 1 diabetes, but is limited by human donor tissue availability. The combination of epidermal growth factor (EGF) and gastrin induces islet beta-cell neogenesis from pancreatic exocrine duct cells in rodents. In this study we investigated whether EGF and gastrin could expand the beta-cell mass in adult human isolated islets that contain duct as well as endocrine cells. Human islet cells were cultured for 4 wk in serum-free medium (control) or in medium with EGF (0.3 mug/ml), gastrin (1.0 mug/ml), or the combination of EGF and gastrin. beta-Cell numbers were increased in cultures with EGF plus gastrin (+118%) and with EGF (+81%), but not in cultures with gastrin (-3%) or control medium (-62%). After withdrawal of EGF and gastrin and an additional 4 wk in control medium, beta-cell numbers continued to increase only in cultures previously incubated with both EGF and gastrin (+232%). EGF plus gastrin also significantly increased cytokeratin 19-positive duct cells (+678%) in the cultures. Gastrin, alone or in combination with EGF, but not EGF alone, increased the expression of pancreatic and duodenal homeobox factor-1 as well as insulin and C peptide in the cytokeratin 19-positive duct cells. Also, EGF plus gastrin significantly increased beta-cells and insulin content in human islets implanted in immunodeficient nonobese diabetic-severe combined immune deficiency mice as well as insulin secretory responses of the human islet grafts to glucose challenge. In conclusion, combination therapy with EGF and gastrin increases beta-cell mass in adult human pancreatic islets in vitro and in vivo, and this appears to result from the induction of beta-cell neogenesis from pancreatic exocrine duct cells.

Dual effects of n-alcohols on fluid secretion from guinea pig pancreatic ducts

Ethanol strongly augments secretin-stimulated, but not acetylcholine (ACh)-stimulated, fluid secretion from pancreatic duct cells. To understand its mechanism of action, we examined the effect of short-chain n-alcohols on fluid secretion and intracellular Ca2+ concentration ([Ca2+]i) in guinea pig pancreatic ducts. Fluid secretion was measured by monitoring the luminal volume of isolated interlobular ducts. [Ca2+]i was estimated using fura-2 microfluorometry. Methanol and ethanol at 0.3–10 mM concentrations significantly augmented fluid secretion and induced a transient elevation of [Ca2+]i in secretin- or dibutyryl adenosine 3′,5′-cyclic monophosphate (DBcAMP)-stimulated ducts. However, they failed to affect fluid secretion and [Ca2+]i in unstimulated and ACh-stimulated ducts. In contrast, propanol and butanol at 0.3–10 mM concentrations significantly reduced fluid secretion and decreased [Ca2+]i in unstimulated ducts and in ducts stimulated with secretin, DBcAMP, or ACh. Both stimulatory and inhibitory effects of n-alcohols completely disappeared after their removal from the perfusate. Propanol and butanol inhibited the plateau phase, but not the initial peak, of [Ca2+]i response to ACh as well as the [Ca2+]i elevation induced by thapsigargin, suggesting that they inhibit Ca2+ influx. Removal of extracellular Ca2+ reduced [Ca2+]i in duct cells and completely abolished secretin-stimulated fluid secretion. In conclusion, there is a distinct cutoff point between ethanol (C2) and propanol (C3) in their effects on fluid secretion and [Ca2+]i in duct cells. Short-chain n-alcohols appear to affect pancreatic ductal fluid secretion by activating or inhibiting the plasma membrane Ca2+ channel.

Direct measurement of acid efflux from isolated guinea pig pancreatic ducts

OBJECTIVES

The current studies used the technique of microphysiometry to directly determine the effects of stimulators and inhibitors of pancreatic duct secretion on acid efflux from isolated pancreatic ducts.

METHODS

Main and interlobular ducts were isolated from guinea pig pancreata by collagenase digestion and manual selection. Segments were placed in the chambers of a microphysiometer, which uses a silicon chip-based, light-addressable potentiometric sensor to determine the proton concentration in the superfusing solution. Isolated ducts were superfused with a low buffer capacity Ringer's solution at 37 degrees C and the extracellular acidification rate (EAR) was determined by computer-directed protocols.

RESULTS

A survey of potential agonists demonstrated that both secretin and the cholinomimetic, carbachol, dramatically increased EAR, with EC50 of 3 nmol/L and 0.6 mumol/L, respectively. The changes in EAR induced by both secretagogues were rapid, peaking within 4-6 minutes, and then declining to a level below the peak but above basal EAR. The enhanced EAR was maintained for at least 30 minutes in the presence of either secretagogue. More modest increases in EAR were evoked by bombesin, substance P, and vasoactive intestinal peptide (VIP). Cholecystokinin and isoproterenol caused no significant change in pancreatic duct EAR. A combination of amiloride and bafilomycin A1, inhibitors, respectively, of Na/H exchange and of vacuolar type H-ATPase activity, caused a dramatic drop in EAR but did not fully inhibit the increase in EAR elicited by carbachol, suggesting that other mechanisms may contribute to agonist-stimulated EAR of pancreatic ducts.

CONCLUSIONS

Thus, the results support the use of microphysiometry as a tool to study pancreatic duct physiology and in particular a method to measure acid efflux from the serosal surface.

Morphogenetic plasticity of adult human pancreatic islets of Langerhans

The aim of this study was to investigate the phenotypic plasticity of pancreatic islets of Langerhans. Quiescent adult human islets were induced to undergo a phenotypic switch to highly proliferative duct-like structures in a process characterized by a loss of expression of islet-specific hormones and transcription factors as well as a temporally related rise in the expression of markers of both duct epithelial and progenitor cells. Short-term treatment of these primitive duct-like structures with the neogenic factor islet neogenesis-associated protein (INGAP104-118) induced their reconversion back to islet-like structures in a PI3-kinase-dependent manner. These neoislets resembled freshly isolated human islets with respect to the presence and topological arrangement of the four endocrine cell types, islet gene expression and hormone production, insulin content and glucose-responsive insulin secretion. Our results suggest that adult human islets possess a remarkable degree of morphogenetic plasticity. This novel observation may have important implications for understanding pancreatic carcinogenesis and islet neogenesis.

EGF-induced proliferation of adult human pancreatic duct cells is mediated by the MEK/ERK cascade

Human postnatal pancreatic duct cells are a potential source of new beta cells. Factors regulating proliferation of human pancreatic duct cells in vitro are unknown. In several other cell types, this process is influenced by ligands of the ErbB receptor family. The expression and functionality of the ErbB family members and their possible role in duct cell proliferation were determined. In cultured adult human pancreatic duct cells the different members of the ErbB family (ErbB1-4) were present at transcript and protein level. Stimulation of the duct cells with epidermal growth factor (EGF) and betacellulin results in Tyr-phosphorylation of ErbB1 and ErbB2, followed by activation of Shc, MEK1/2 and ERK1/2. Duct cells with activated ErbB signaling changed morphology and motility. EGF induced proliferation of a fraction of the duct cells and treatment with PD98059 prevented Ki67 expression in EGF-supplemented cells. When transduced with recombinant adenovirus expressing constitutively activated MEK1, duct cells proliferate and spread even in the absence of EGF. Importantly, the adult human duct cells retain their capacity to recapitulate ngn3-induced embryonic (neuro)endocrine differentiation after proliferation. Therefore, the present data support a possible role for human adult pancreatic duct cells, following expansion and transdifferentiation, as a source of insulin by transplantation to type I diabetes patients.

Protein kinase C mediates the inhibitory effect of substance P on HCO3- secretion from guinea pig pancreatic ducts

The inhibitory control of pancreatic ductal HCO(3)(-) secretion may be physiologically important in terms of limiting the hydrostatic pressure developed within the ducts and in terms of switching off pancreatic secretion after a meal. Substance P (SP) inhibits secretin-stimulated HCO(3)(-) secretion by modulating a Cl(-)-dependent HCO(3)(-) efflux step at the apical membrane of the duct cell (Hegyi P, Gray MA, and Argent BE. Am J Physiol Cell Physiol 285: C268-C276, 2003). In the present study, we have shown that SP is present in periductal nerves within the guinea pig pancreas, that PKC mediates the effect of SP, and that SP inhibits an anion exchanger on the luminal membrane of the duct cell. Secretin (10 nM) stimulated HCO(3)(-) secretion by sealed, nonperfused, ducts about threefold, and this effect was totally inhibited by SP (20 nM). Phorbol 12,13-dibutyrate (PDBu; 100 nM), an activator of PKC, reduced basal HCO(3)(-) secretion by approximately 40% and totally blocked secretin-stimulated secretion. In addition, bisindolylmaleimide I (1 nM to 1 microM), an inhibitor of PKC, relieved the inhibitory effect of SP on secretin-stimulated HCO(3)(-) secretion and also reversed the inhibitory effect of PDBu. Western blot analysis revealed that guinea pig pancreatic ducts express the alpha-, beta(I)-, delta-, epsilon-, eta-, theta-, zeta-, and mu-isoforms of PKC. In microperfused ducts, luminal H(2)DIDS (0.5 mM) caused intracellular pH to alkalinize and, like SP, inhibited basal and secretin-stimulated HCO(3)(-) secretion. SP did not inhibit secretion further when H(2)DIDS was present in the lumen, suggesting that SP and H(2)DIDS both inhibit the activity of an anion exchanger on the luminal membrane of the duct cell.

Mediastinal pancreatic pseudocyst caused by obstruction of the pancreatic duct was eliminated by bromhexine hydrochloride

A 49-year-old man, who had a 30-year history of drinking the equivalent of 80 g of ethanol per day, underwent a detailed medical examination for cough and dyspnea. Chest-abdominal computed tomography and endoscopic retrograde pancreatography led to the diagnosis of a mediastinal pancreatic pseudocyst resulting from obstruction of the pancreatic duct by a protein plug. The pseudocyst rapidly improved with conservative treatment with camostat mesilate, H2-receptor antagonist and digestive enzymes. Although the patient abstained from alcohol for approximately 6 months, he resumed drinking, leading to recurrent attacks of pancreatitis. Bromhexine hydrochloride was then administered for 6 months, with the expectation that it would have a mucolytic effect on the pancreatic juice, resulting in improvement in the clinical symptoms, pancreatic enzymes and pancreatic exocrine function, as well as elimination of the protein plug. Bromhexine hydrochloride may be a new therapy for pathological states, such as alcoholic chronic pancreatitis, in which there is increased viscosity of the pancreatic juice because of elevated protein concentration, leading to protein plug formation and temporary blockage of the pancreatic duct.

Angiotensin II mediates acinar cell apoptosis during the development of rat pancreatic fibrosis by AT1R

OBJECTIVES

The mechanisms of pancreatic fibrosis were not fully elucidated. Apoptosis has been suggested to be involved in the progression of pancreatic fibrosis. It has been reported that the renin-angiotensin system (RAS) plays a crucial role in the formation of fibrosis, including in the kidney, heart, and liver. We recently reported that the angiotensin II type I receptor (AT1R) antagonist losartan has been able to alleviate the pancreatic fibrosis in the rat model, indicating angiotensin II participated in the progression of pancreatic fibrosis. In present study, the possible effects of angiotensin II-mediated apoptosis of pancreatic acinar cells were investigated in rat pancreatic fibrosis induced by trinitrobenzene sulfonic acid (TNBS) by AT1R, with special reference to the losartan administration.

METHODS

Male Sprague-Dawley rats (200-300 g) were randomly divided into a normal group, a control group, and a losartan-treatment group. Pancreatic fibrosis was induced by infusion of 2% TNBS into the pancreatic duct. Rats were treated with losartan (10 mg/kg) by gavage daily in the losartan-treatment group and the same volume of sterile distilled water was administered to the control group. All treatments started on the first day and ended 8 weeks after the operation. On day 3 and at weeks 1, 2, 3, 4, and 8, the histologic changes of the pancreas were examined by hematoxylin and eosin staining, and pancreatic acinar cell apoptosis was investigated by using electron microscopy and terminal deoxynucleotidyl transferase UTP nick end labeling (TUNEL), indicated by the apoptotic index (AI). Expressions of Bax, Bak, and Bcl-2 mRNA in the pancreas were detected by reverse transcriptase polymerase chain reaction (RT-PCR) on day 3 and at weeks 1, 2, 3, and 4.

RESULTS

Compared with the control group, losartan treatment significantly alleviated the histologic abnormalities, including infiltration of inflammatory cells and acinar cells atrophy. In the control group, a typical morphologic presentation of acinar cell apoptosis was seen either with electron microscopy or TUNEL staining. The AI was increased in pancreatic tissue. Meanwhile, Bax and Bak mRNA expression was increased, but Bcl-2 mRNA expression was decreased, as compared with the normal group. The administration of losartan resulted in inhibition of acinar cell apoptosis and down-regulation of Bax, Bak, and Bcl-2 mRNA expression. The Bax/Bcl-2 ratio was lower in losartan-treated rats than in control rats.

CONCLUSION

Losartan prevents apoptosis of pancreatic acinar cell by blocking AT1R during the development of pancreatic fibrosis. This action may be associated with its regulation of apoptosis-associated genes, such as Bax, Bak, and Bcl-2 mRNA. The results of present study suggest that angiotensin II probably mediates pancreatic acinar cell apoptosis during the course of pancreatic fibrosis.

Protease-activated receptor-2 regulates bicarbonate secretion by pancreatic duct cells in vitro

BACKGROUND

Pancreatic duct cells (PDCs) are responsible for bicarbonate production by the pancreas. The trypsin-sensitive protease-activated receptor (PAR-2), also known as the trypsin receptor, is highly expressed in the pancreatic duct system and has been shown to regulate PDC ion transport. The possible role of this receptor on bicarbonate secretion, the central function of duct cells, is unknown. We hypothesize that PAR-2 may regulate pancreatic bicarbonate secretion during times of inappropriate pancreatic enzyme activation.

METHODS

To study this hypothesis in vitro, explants of the bovine main pancreatic duct were isolated and maintained in primary culture. They were then mounted in Ussing chambers, and bicarbonate secretion was determined with an autoburette titration. The response to luminal or serosal trypsin (10 micromol/L) and the synthetic trypsin receptor activating peptide (TRAP) (30 micromol/L) on spontaneous and secretin-stimulated bicarbonate secretion (10 nmol/L) was examined.

RESULTS

Serosal trypsin had no effect. Both luminal trypsin and TRAP significantly reduced the spontaneous bicarbonate secretion observed at luminal pH 7.4 (2.8 +/- 0.2 - 0.4 +/- 0.1 micromol/hr/cm(2) and 4.0 +/- 1.2 - 1.6 +/- 0.4 micromol/hr/cm(2), respectively) in a reversible manner. Baseline bicarbonate secretion at luminal pH 8.0 was reduced by trypsin and TRAP, but the increase in response to secretin stimulation observed with controls was unaffected.

CONCLUSIONS

PAR-2 activation may be the mechanism by which pancreatic juice secretion is inhibited during pancreatitis. We suggest that pharmacologic activation of PAR-2 receptors could suppress pancreatic exocrine secretion and thus serve as a potential agent in the treatment and prevention of pancreatic fistulas.

In vitro cultivation of human fetal pancreatic ductal stem cells and their differentiation into insulin-producing cells

AIM: To isolate, culture and identify the human fetal pancreatic ductal stem cells in vitro, and to observe the potency of these multipotential cells differentiation into insulin-producing cells.

METHODS: The human fetal pancreas was digested by 1 g/L collagease type IV and then 2.5 g/L trypsin was used to isolate the pancreatic ductal stem cells, followed by culture in serum-free, glucose-free DMEM media with some additional chemical substrates in vitro (according to the different stage). The cells were induced by glucose-free (control), 5 mmol/L, 17.8 mmol/L and 25 mmol/L glucose, respectively. The cell types of differentiated cells were identified using immunocytochemical staining.

RESULTS: The shape of human fetal pancreatic ductal stem cells cultured in vitro was firstly fusiform in the first 2 wk, and became monolayer and cobblestone pattern after another 3 to 4 wk. After induced and differentiated by the glucose of different concentrations for another 1 to 2 wk, the cells formed the pancreatic islet-like structures. The identification and potency of these cells were then identified by using the pancreatic ductal stem cell marker, cytokeratin-19 (CK-19), pancreatic β cell marker, insulin and pancreatic α cell marker, glucagons with immunocytochemical staining. At the end of the second week, 95.2% of the cells were positive for CK-19 immunoreactivity. Up to 22.7% of the cells induced by glucose were positive for insulin immunoreactivity, and less than 3.8% of the cells were positive for glucagon immunoreactivity in pancreatic islet-like structures. The positive ratio of immunoreactive staining was dependent on the concentration of glucose, and it was observed that the 17.8 mmol/L glucose stimulated effectively to produce insulin- and glucagons-producing cells.

CONCLUSION: The human fetal pancreatic ductal stem cells are capable of proliferation in vitro. These cells have multidifferentiation potential and can be induced by glucose and differentiated into insulin-producing cells in vitro.

Basolateral anion transport mechanisms underlying fluid secretion by mouse, rat and guinea-pig pancreatic ducts

Fluid secretion by interlobular pancreatic ducts was determined by using video microscopy to measure the rate of swelling of isolated duct segments that had sealed following overnight culture. The aim was to compare the HCO(3)(-) requirement for secretin-evoked secretion in mouse, rat and guinea-pig pancreas. In mouse and rat ducts, fluid secretion could be evoked by 10 nm secretin and 5 microm forskolin in the absence of extracellular HCO(3)(-). In guinea-pig ducts, however, fluid secretion was totally dependent on HCO(3)(-). Forskolin-stimulated fluid secretion by mouse and rat ducts in the absence of HCO(3)(-) was dependent on extracellular Cl(-) and was completely inhibited by bumetanide (30 microm). It was therefore probably mediated by a basolateral Na(+)-K(+)-2Cl(-) cotransporter. In the presence of HCO(3)(-), forskolin-stimulated fluid secretion was reduced approximately 40% by bumetanide, approximately 50% by inhibitors of basolateral HCO(3)(-) uptake (3 microm EIPA and 500 microm H(2)DIDS), and was totally abolished by simultaneous application of all three inhibitors. We conclude that the driving force for secretin-evoked fluid secretion by mouse and rat ducts is provided by parallel basolateral mechanisms: Na(+)-H(+) exchange and Na(+)-HCO(3)(-) cotransport mediating HCO(3)(-) uptake, and Na(+)-K(+)-2Cl(-) cotransport mediating Cl(-) uptake. The absence or inactivity of the Cl(-) uptake pathway in the guinea-pig pancreatic ducts may help to account for the much higher concentrations of HCO(3)(-) secreted in this species.