Human pancreatic acinar cells lack functional responses to cholecystokinin and gastrin

Albumin promoter-driven FlpO expression induces efficient genetic recombination in mouse liver

Tissue-specific gene manipulations are widely used in genetically engineered mouse models. A single recombinase system, such as the one using Alb-Cre, has been commonly used for liver-specific genetic manipulations. However, most diseases are complex, involving multiple genetic changes and various cell types. A dual recombinase system is required for conditionally modifying different genes sequentially in the same cell or inducing genetic changes in different cell types within the same organism. A FlpO cDNA was inserted between the last exon and 3'-UTR of the mouse albumin gene in a bacterial artificial chromosome (BAC-Alb-FlpO). The founders were crossed with various reporter mice to examine the efficiency of recombination. Liver cancer tumorigenesis was investigated by crossing the FlpO mice with FSF-KrasG12D mice and p53frt mice (KPF mice). BAC-Alb-FlpO mice exhibited highly efficient recombination capability in both hepatocytes and intrahepatic cholangiocytes. No recombination was observed in the duodenum and pancreatic cells. BAC-Alb-FlpO-mediated liver-specific expression of mutant KrasG12D and conditional deletion of p53 gene caused the development of liver cancer. Remarkably, liver cancer in these KPF mice manifested a distinctive mixed hepatocellular carcinoma and cholangiocarcinoma phenotype. A highly efficient and liver-specific BAC-Alb-FlpO mouse model was developed. In combination with other Cre lines, different genes can be manipulated sequentially in the same cell, or distinct genetic changes can be induced in different cell types of the same organism.NEW & NOTEWORTHY A liver-specific Alb-FlpO mouse line was generated. By coupling it with other existing CreERT or Cre lines, the dual recombinase approach can enable sequential gene modifications within the same cell or across various cell types in an organism for liver research through temporal and spatial gene manipulations.

Factors Affecting the Circulating Levels of Oxyntomodulin in Health and After Acute Pancreatitis

OBJECTIVES

To investigate the factors associated with the circulating levels of oxyntomodulin in healthy individuals and individuals after an episode of acute pancreatitis (AP).

METHODS

Blood samples were collected from all participants after an overnight fast and analyzed for 28 biomarkers. Participants also underwent comprehensive body composition analysis on a 3-T magnetic resonance imaging scanner. Regression analyses were done to investigate the associations between oxyntomodulin and the studied factors.

RESULTS

The study included 105 individuals who had a primary diagnosis of AP and 58 healthy individuals. Peptide YY (B coefficient, 0.094; 95% confidence interval [95% CI], 0.164-0.123), pancreatic polypeptide (0.048; 95% CI, 0.030-0.066), and leptin (0.394; 95% CI, 0.128-0.661) had significant associations with oxyntomodulin in healthy individuals. Peptide YY was the most prominent factor associated with oxyntomodulin, explaining 60% of its variance in health. Cholecystokinin (0.014; 95% CI, 0.010-0.018), amylin (-0.107; 95% CI, -0.192 to -0.021), and glycated hemoglobin (-0.761; 95% CI, -1.249 to -0.273) had significant associations with oxyntomodulin in individuals after AP. Cholecystokinin was the most prominent factor associated with oxyntomodulin, explaining 44% of its variance after AP.

CONCLUSIONS

Factors affecting the circulating levels of oxyntomodulin are different in health and after AP. These insights will enable the determination of populations that benefit from oxyntomodulin therapeutics in the future.

Multiple roles for cholinergic signaling in pancreatic diseases

Cholinergic nerves are widely distributed throughout the human body and participate in various physiological activities, including sensory, motor, and visceral activities, through cholinergic signaling. Cholinergic signaling plays an important role in pancreatic exocrine secretion. A large number of studies have found that cholinergic signaling overstimulates pancreatic acinar cells through muscarinic receptors, participates in the onset of pancreatic diseases such as acute pancreatitis and chronic pancreatitis, and can also inhibit the progression of pancreatic cancer. However, cholinergic signaling plays a role in reducing pain and inflammation through nicotinic receptors, but enhances the proliferation and invasion of pancreatic tumor cells. This review focuses on the progression of cholinergic signaling and pancreatic diseases in recent years and reveals the role of cholinergic signaling in pancreatic diseases.

Pancreas-specific CHRM3 activation causes pancreatitis in mice

Hyperstimulation of the cholecystokinin 1 receptor (CCK1R), a G protein-coupled receptor (GPCR), in pancreatic acinar cells is commonly used to induce pancreatitis in rodents. Human pancreatic acinar cells lack CCK1R but express cholinergic receptor muscarinic 3 (M3R), another GPCR. To test whether M3R activation is involved in pancreatitis, a mutant M3R was conditionally expressed in pancreatic acinar cells in mice. This mutant receptor loses responsiveness to its native ligand, acetylcholine, but can be activated by an inert small molecule, clozapine-N-oxide (CNO). Intracellular calcium and amylase were elicited by CNO in pancreatic acinar cells isolated from mutant M3R mice but not WT mice. Similarly, acute pancreatitis (AP) could be induced by a single injection of CNO in the transgenic mice but not WT mice. Compared with the cerulein-induced AP, CNO caused more widespread acinar cell death and inflammation. Furthermore, chronic pancreatitis developed at 4 weeks after 3 episodes of CNO-induced AP. In contrast, in mice with 3 recurrent episodes of cerulein-included AP, pancreas histology was restored in 4 weeks. Furthermore, the M3R antagonist ameliorated the severity of cerulein-induced AP in WT mice. We conclude that M3R activation can cause the pathogenesis of pancreatitis. This model may provide an alternative approach for pancreatitis research.

Pancreatic cancer cachexia: three dimensions of a complex syndrome

Cancer cachexia is a multifactorial syndrome that is characterised by a loss of skeletal muscle mass, is commonly associated with adipose tissue wasting and malaise, and responds poorly to therapeutic interventions. Although cachexia can affect patients who are severely ill with various malignant or non-malignant conditions, it is particularly common among patients with pancreatic cancer. Pancreatic cancer often leads to the development of cachexia through a combination of distinct factors, which, together, explain its high prevalence and clinical importance in this disease: systemic factors, including metabolic changes and pathogenic signals related to the tumour biology of pancreatic adenocarcinoma; factors resulting from the disruption of the digestive and endocrine functions of the pancreas; and factors related to the close anatomical and functional connection of the pancreas with the gut. In this review, we conceptualise the various insights into the mechanisms underlying pancreatic cancer cachexia according to these three dimensions to expose its particular complexity and the challenges that face clinicians in trying to devise therapeutic interventions.

The roles of calcium and ATP in the physiology and pathology of the exocrine pancreas

This review deals with the roles of calcium ions and ATP in the control of the normal functions of the different cell types in the exocrine pancreas as well as the roles of these molecules in the pathophysiology of acute pancreatitis. Repetitive rises in the local cytosolic calcium ion concentration in the apical part of the acinar cells not only activate exocytosis but also, via an increase in the intramitochondrial calcium ion concentration, stimulate the ATP formation that is needed to fuel the energy-requiring secretion process. However, intracellular calcium overload, resulting in a global sustained elevation of the cytosolic calcium ion concentration, has the opposite effect of decreasing mitochondrial ATP production, and this initiates processes that lead to necrosis. In the last few years it has become possible to image calcium signaling events simultaneously in acinar, stellate, and immune cells in intact lobules of the exocrine pancreas. This has disclosed processes by which these cells interact with each other, particularly in relation to the initiation and development of acute pancreatitis. By unraveling the molecular mechanisms underlying this disease, several promising therapeutic intervention sites have been identified. This provides hope that we may soon be able to effectively treat this often fatal disease.

Benefits of Sustained Upregulated Unimolecular GLP-1 and CCK Receptor Signalling in Obesity-Diabetes

Combined activation of GLP-1 and CCK1 receptors has potential to synergistically augment the appetite-suppressive and glucose homeostatic actions of the individual parent peptides. In the current study, pancreatic beta-cell benefits of combined GLP-1 and CCK1 receptor upregulation were established, before characterising bioactivity and antidiabetic efficacy of an acylated dual-acting GLP-1/CCK hybrid peptide, namely [Lys¹²Pal]Ex-4/CCK. Both exendin-4 and CCK exhibited (p<0.001) proliferative and anti-apoptotic effects in BRIN BD11 beta-cells. Proliferative benefits were significantly (p<0.01) augmented by combined peptide treatment when compared to either parent peptide alone. These effects were linked to increases (p<0.001) in GLUT2 and glucokinase beta-cell gene expression, with decreased (p<0.05-p<0.001) expression of NFκB and BAX. [Lys¹²Pal]Ex-4/CCK exhibited prominent insulinotropic actions in vitro, coupled with beneficial (p<0.001) satiety and glucose homeostatic effects in the mice, with bioactivity evident 24 h after administration. Following twice daily injection of [Lys¹²Pal]Ex-4/CCK for 28 days in diabetic high fat fed (HFF) mice with streptozotocin (STZ)-induced compromised beta-cells, there were clear reductions (p<0.05-p<0.001) in energy intake and body weight. Circulating glucose was returned to lean control concentrations, with associated increases (p<0.001) in plasma and pancreatic insulin levels. Glucose tolerance and insulin secretory responsiveness were significantly (p<0.05-p<0.001) improved by hybrid peptide therapy. In keeping with this, evaluation of pancreatic histology revealed restoration of normal islet alpha- to beta-cell ratios and reduction (p<0.01) in centralised islet glucagon staining. Improvements in pancreatic islet morphology were associated with increased (p<0.05) proliferation and reduced (p<0.001) apoptosis of beta-cells. Together, these data highlight the effectiveness of sustained dual GLP-1 and CCK1 receptor activation by [Lys¹²Pal]Ex-4/CCK for the treatment of obesity-related diabetes.

Experimental Acute Pancreatitis Models: History, Current Status, and Role in Translational Research

Acute pancreatitis is a potentially severe inflammatory disease that may be associated with a substantial morbidity and mortality. Currently there is no specific treatment for the disease, which indicates an ongoing demand for research into its pathogenesis and development of new therapeutic strategies. Due to the unpredictable course of acute pancreatitis and relatively concealed anatomical site in the retro-peritoneum, research on the human pancreas remains challenging. As a result, for over the last 100 years studies on the pathogenesis of this disease have heavily relied on animal models. This review aims to summarize different animal models of acute pancreatitis from the past to present and discuss their main characteristics and applications. It identifies key studies that have enhanced our current understanding of the pathogenesis of acute pancreatitis and highlights the instrumental role of animal models in translational research for developing novel therapies.

Cholecystokinin-1 receptor agonist induced pathological findings in the exocrine pancreas of non-human primates

BACKGROUND AND AIMS

Cholecystokinin (CCK) may potentially be used to treat obesity. However, it is well-known to induce acute pancreatitis and pancreas neoplasia in rodents, but not in primates. Here we report the nonclinical safety profile of a long-acting CCK-1 receptor (CCK-1R) agonist, NN9056, in rats and monkeys to support a First-in-Man clinical trial with NN9056.

METHODS

Thirteen-week toxicological studies were conducted in rats and non-human primates followed by histopathological evaluation of affected tissues. NN9056 was characterised in vitro, and CCK-1R expression was assessed by in situ hybridization in cynomolgus monkey and human pancreas tissues.

RESULTS

Affinity and potency of NN9056 was comparable to native sulphated CCK-8 (CCK-8) across species on the CCK-1R while it had no effect on the CCK-2 receptor (CCK-2R). In situ hybridization demonstrated abundant expression of CCK-1Rs in the exocrine pancreas of the rat. In contrast, it was only discreetly expressed on pancreatic acinar cells in the periphery of scattered lobules in monkeys. A similar expression pattern was observed in human pancreas. 13-weeks daily dosing with NN9056 produced the expected pancreatic pathological findings in rats. In monkeys, NN9056 increased pancreas weight and induced histopathological changes despite the low expression level of CCK-1Rs.

CONCLUSION

Surprisingly, chronic CCK-1R activation constitutes a risk for pancreatitis and trophic actions on the exocrine pancreas in monkeys. Since similar CCK-1R expression patterns were found in pancreas of monkeys and humans this risk is likely translatable to humans and clinical development of NN9056 was therefore halted.

Differential Cell Susceptibilities to KrasG12D in the Setting of Obstructive Chronic Pancreatitis

BACKGROUND & AIMS

Activating mutation of the KRAS gene is common in some cancers, such as pancreatic cancer, but rare in other cancers. Chronic pancreatitis is a predisposing condition for pancreatic ductal adenocarcinoma (PDAC), but how it synergizes with KRAS mutation is not known.

METHODS

We used a mouse model to express an activating mutation of Kras in conjunction with obstruction of the main pancreatic duct to recapitulate a common etiology of human chronic pancreatitis. Because the cell of origin of PDAC is not clear, Kras mutation was introduced into either duct cells or acinar cells.

RESULTS

Although KrasG12D expression in both cell types was protective against damage-associated cell death, chronic pancreatitis induced p53, p21, and growth arrest only in acinar-derived cells. Mutant duct cells did not elevate p53 or p21 expression and exhibited increased proliferation driving the appearance of PDAC over time.

CONCLUSIONS

One mechanism by which tissues may be susceptible or resistant to KRASG12D-initiated tumorigenesis is whether they undergo a p53-mediated damage response. In summary, we have uncovered a mechanism by which inflammation and intrinsic cellular programming synergize for the development of PDAC.

Long-acting CCK analogue NN9056 lowers food intake and body weight in obese Göttingen Minipigs

Background/Objectives

Cholecystokinin (CCK) is a regulator of appetite and energy intake in man. The aim of this study was to determine the effect of NN9056, a long-acting CCK-1 receptor-selective CCK analogue, on food intake and body weight (BW) in obese Göttingen Minipigs.

Subjects/Methods

Tolerability of NN9056 and acute effects on food intake, pancreas histology, amylase and lipase levels were assessed in lean domestic pigs in doses up to 100 nmol/kg (n = 3–4). Subsequently, obese Göttingen Minipigs were treated subcutaneously (s.c.) once daily for 13 weeks with vehicle, NN9056 low dose (regulated from 5 to 2 nmol/kg) or NN9056 high dose (10 nmol/kg) (n = 7–8). Food intake was measured daily and BW twice weekly. At the end of the treatment period, an intravenous glucose tolerance test (IVGTT) and a 24-h exposure profile was obtained. Data are mean ± SD.

Results

The acute studies in domestic pigs showed significant and dose-dependent effect of NN9056 on food intake, acceptable tolerability and no histopathological signs of pancreatitis. Sub-chronic treatment in obese Göttingen Minipigs was also well tolerated and accumulated food intake was significantly lower in both treated groups compared to vehicle, with no significant difference between the dose levels of NN9056 (41.8 ± 12.6, 51.5 ± 13.8 and 86.5 ± 19.5 kg in high-dose, low-dose and vehicle groups, respectively, p = 0.012 and p < 0.0001 for low and high dose vs. vehicle, respectively). Accordingly, there was a weight loss in both treated groups vs. a weight gain in the vehicle group (−7.2 ± 4.6%, −2.3 ± 3.2% and 12.3 ± 3.9% in the high-dose, low-dose and vehicle groups, respectively, p < 0.0001 for both vs. vehicle). IVGTT data were not significantly different between groups.

Conclusion

NN9056, a long-acting CCK-1 receptor-selective CCK analogue, significantly reduced food intake and BW in obese Göttingen Minipigs after once daily s.c. dosing for 13 weeks.

The Orai Ca2+ channel inhibitor CM4620 targets both parenchymal and immune cells to reduce inflammation in experimental acute pancreatitis

KEY POINTS

This work confirms previous reports that CM4620, a small molecule inhibitor of Ca²⁺ entry via store operated Ca²⁺ entry (SOCE) channels formed by stromal interaction molecule 1 (STIM1)/Orai complexes, attenuates acinar cell pathology and acute pancreatitis in mouse experimental models. Here we report that intravenous administration of CM4620 reduces the severity of acute pancreatitis in the rat, a hitherto untested species. Using CM4620, we probe further the mechanisms whereby SOCE via STIM1/Orai complexes contributes to the disease in pancreatic acinar cells, supporting a role for endoplasmic reticulum stress/cell death pathways in these cells. Using CM4620, we show that SOCE via STIM1/Orai complexes promotes neutrophil oxidative burst and inflammatory gene expression during acute pancreatitis, including in immune cells which may be either circulating or invading the pancreas. Using CM4620, we show that SOCE via STIM1/Orai complexes promotes activation and fibroinflammatory gene expression within pancreatic stellate cells.

ABSTRACT

Key features of acute pancreatitis include excess cellular Ca²⁺ entry driven by Ca²⁺ depletion from the endoplasmic reticulum (ER) and subsequent activation of store-operated Ca²⁺ entry (SOCE) channels in the plasma membrane. In several cell types, including pancreatic acinar, stellate cells (PaSCs) and immune cells, SOCE is mediated via channels composed primarily of Orai1 and stromal interaction molecule 1 (STIM1). CM4620, a selective Orai1 inhibitor, prevents Ca²⁺ entry in acinar cells. This study investigates the effects of CM4620 in preventing or reducing acute pancreatitis features and severity. We tested the effects of CM4620 on SOCE, trypsinogen activation, acinar cell death, activation of NFAT and NF-κB, and inflammatory responses in ex vivo and in vivo rodent models of acute pancreatitis and human pancreatic acini. We also examined whether CM4620 inhibited cytokine release in immune cells, fibro-inflammatory responses in PaSCs, and oxidative burst in neutrophils, all cell types participating in pancreatitis. CM4620 administration to rats by i.v. infusion starting 30 min after induction of pancreatitis significantly diminished pancreatitis features including pancreatic oedema, acinar cell vacuolization, intrapancreatic trypsin activity, cell death signalling and acinar cell death. CM4620 also decreased myeloperoxidase activity and inflammatory cytokine expression in pancreas and lung tissues, fMLF peptide-induced oxidative burst in human neutrophils, and cytokine production in human peripheral blood mononuclear cells (PBMCs) and rodent PaSCs, indicating that Orai1/STIM1 channels participate in the inflammatory responses of these cell types during acute pancreatitis. These findings support pathological Ca²⁺ entry-mediated cell death and proinflammatory signalling as central mechanisms in acute pancreatitis pathobiology.

Cholecystokinin (CCK) Regulation of Pancreatic Acinar Cells: Physiological Actions and Signal Transduction Mechanisms

Pancreatic acinar cells synthesize and secrete about 20 digestive enzymes and ancillary proteins with the processes that match the supply of these enzymes to their need in digestion being regulated by a number of hormones (CCK, secretin and insulin), neurotransmitters (acetylcholine and VIP) and growth factors (EGF and IGF). Of these regulators, one of the most important and best studied is the gastrointestinal hormone, cholecystokinin (CCK). Furthermore, the acinar cell has become a model for seven transmembrane, heterotrimeric G protein coupled receptors to regulate multiple processes by distinct signal transduction cascades. In this review, we briefly describe the chemistry and physiology of CCK and then consider the major physiological effects of CCK on pancreatic acinar cells. The majority of the review is devoted to the physiologic signaling pathways activated by CCK receptors and heterotrimeric G proteins and the functions they affect. The pathways covered include the traditional second messenger pathways PLC-IP3-Ca²⁺ , DAG-PKC, and AC-cAMP-PKA/EPAC that primarily relate to secretion. Then there are the protein-protein interaction pathways Akt-mTOR-S6K, the three major MAPK pathways (ERK, JNK, and p38 MAPK), and Ca²⁺ -calcineurin-NFAT pathways that primarily regulate non-secretory processes including biosynthesis and growth, and several miscellaneous pathways that include the Rho family small G proteins, PKD, FAK, and Src that may regulate both secretory and nonsecretory processes but are not as well understood. © 2019 American Physiological Society. Compr Physiol 9:535-564, 2019.

Risk to human health related to the presence of perfluorooctane sulfonic acid and perfluorooctanoic acid in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in food. Regarding PFOS and PFOA occurrence, the final data set available for dietary exposure assessment contained a total of 20,019 analytical results (PFOS n = 10,191 and PFOA n = 9,828). There were large differences between upper and lower bound exposure due to analytical methods with insufficient sensitivity. The CONTAM Panel considered the lower bound estimates to be closer to true exposure levels. Important contributors to the lower bound mean chronic exposure were 'Fish and other seafood', 'Meat and meat products' and 'Eggs and egg products', for PFOS, and 'Milk and dairy products', 'Drinking water' and 'Fish and other seafood' for PFOA. PFOS and PFOA are readily absorbed in the gastrointestinal tract, excreted in urine and faeces, and do not undergo metabolism. Estimated human half-lives for PFOS and PFOA are about 5 years and 2-4 years, respectively. The derivation of a health-based guidance value was based on human epidemiological studies. For PFOS, the increase in serum total cholesterol in adults, and the decrease in antibody response at vaccination in children were identified as the critical effects. For PFOA, the increase in serum total cholesterol was the critical effect. Also reduced birth weight (for both compounds) and increased prevalence of high serum levels of the liver enzyme alanine aminotransferase (ALT) (for PFOA) were considered. After benchmark modelling of serum levels of PFOS and PFOA, and estimating the corresponding daily intakes, the CONTAM Panel established a tolerable weekly intake (TWI) of 13 ng/kg body weight (bw) per week for PFOS and 6 ng/kg bw per week for PFOA. For both compounds, exposure of a considerable proportion of the population exceeds the proposed TWIs.

The rise of genetically engineered mouse models of pancreatitis: A review of literature

Pancreatitis is increasingly recognized as not merely a local inflammation of the pancreas but also a disease with high frequency of systemic sequelae. Current understanding of the cellular mechanisms that trigger it and affect the development of sequelae are limited. Genetically engineered mouse models can be a useful tool to study the pathophysiology of pancreatitis. This article gives an overview of the genetically engineered mouse models that spontaneously develop pancreatitis and discusses those that most closely replicate different pancreatitis hallmarks observed in humans.

Human Pancreatic Acinar Cells: Proteomic Characterization, Physiologic Responses, and Organellar Disorders in ex Vivo Pancreatitis

Knowledge of the molecular mechanisms of acute pancreatitis is largely based on studies using rodents. To assess similar mechanisms in humans, we performed ex vivo pancreatitis studies in human acini isolated from cadaveric pancreata from organ donors. Because data on these human acinar preparations are sparse, we assessed their functional integrity and cellular and organellar morphology using light, fluorescence, and electron microscopy; and their proteome by liquid chromatography-tandem mass spectrometry. Acinar cell responses to the muscarinic agonist carbachol (CCh) and the bile acid taurolithocholic acid 3-sulfate were also analyzed. Proteomic analysis of acini from donors of diverse ethnicity showed similar profiles of digestive enzymes and proteins involved in translation, secretion, and endolysosomal function. Human acini preferentially expressed the muscarinic acetylcholine receptor M3 and maintained physiological responses to CCh for at least 20 hours. As in rodent acini, human acini exposed to toxic concentrations of CCh and taurolithocholic acid 3-sulfate responded with trypsinogen activation, decreased cell viability, organelle damage manifest by mitochondrial depolarization, disordered autophagy, and pathological endoplasmic reticulum stress. Human acini also secreted inflammatory mediators elevated in acute pancreatitis patients, including IL-6, tumor necrosis factor-α, IL-1β, chemokine (C-C motif) ligands 2 and 3, macrophage inhibitory factor, and chemokines mediating neutrophil and monocyte infiltration. In conclusion, human cadaveric pancreatic acini maintain physiological functions and have similar pathological responses and organellar disorders with pancreatitis-causing treatments as observed in rodent acini.

Ex vivo human pancreatic slice preparations offer a valuable model for studying pancreatic exocrine biology

A genuine understanding of human exocrine pancreas biology and pathobiology has been hampered by a lack of suitable preparations and reliance on rodent models employing dispersed acini preparations. We have developed an organotypic slice preparation of the normal portions of human pancreas obtained from cancer resections. The preparation was assessed for physiologic and pathologic responses to the cholinergic agonist carbachol (Cch) and cholecystokinin (CCK-8), including 1) amylase secretion, 2) exocytosis, 3) intracellular Ca²⁺ responses, 4) cytoplasmic autophagic vacuole formation, and 5) protease activation. Cch and CCK-8 both dose-dependently stimulated secretory responses from human pancreas slices similar to those previously observed in dispersed rodent acini. Confocal microscopy imaging showed that these responses were accounted for by efficient apical exocytosis at physiologic doses of both agonists and by apical blockade and redirection of exocytosis to the basolateral plasma membrane at supramaximal doses. The secretory responses and exocytotic events evoked by CCK-8 were mediated by CCK-A and not CCK-B receptors. Physiologic agonist doses evoked oscillatory Ca²⁺ increases across the acini. Supraphysiologic doses induced formation of cytoplasmic autophagic vacuoles and activation of proteases (trypsin, chymotrypsin). Maximal atropine pretreatment that completely blocked all the Cch-evoked responses did not affect any of the CCK-8-evoked responses, indicating that rather than acting on the nerves within the pancreas slice, CCK cellular actions directly affected human acinar cells. Human pancreas slices represent excellent preparations to examine pancreatic cell biology and pathobiology and could help screen for potential treatments for human pancreatitis.

Cholecystokinin-From Local Gut Hormone to Ubiquitous Messenger

Cholecystokinin (CCK) was discovered in 1928 in jejunal extracts as a gallbladder contraction factor. It was later shown to be member of a peptide family, which are all ligands for the CCK₁ and CCK₂ receptors. CCK peptides are known to be synthetized in small intestinal endocrine I-cells and cerebral neurons. But in addition, CCK is expressed in several endocrine glands (pituitary cells, thyroid C-cells, pancreatic islets, the adrenals, and the testes); in peripheral nerves; in cortical and medullary kidney cells; in cardial myocytes; and in cells of the immune system. CCK peptides stimulate pancreatic enzyme secretion and growth, gallbladder contraction, and gut motility, satiety and inhibit acid secretion from the stomach. Moreover, they are major neurotransmitters in the brain and the periphery. CCK peptides also stimulate calcitonin, insulin, and glucagon secretion, and they may act as natriuretic peptides in the kidneys. CCK peptides are derived from proCCK with a C-terminal bioactive YMGWMDFamide sequence, in which the Y-residue is partly O-sulfated. The plasma forms are CCK-58, -33, -22, and -8, whereas the small CCK-8 and -5 are potent neurotransmitters. Over the last decades, CCK expression has also been encountered in tumors (neuroendocrine tumors, cerebral astrocytomas, gliomas, acoustic neuromas, and specific pediatric tumors). Recently, a metastastic islet cell tumor was found to cause a specific CCKoma syndrome, suggesting that circulating CCK may be a useful tumor marker.

Animal models of gastrointestinal and liver diseases. Animal models of acute and chronic pancreatitis

Animal models of pancreatitis are useful for elucidating the pathogenesis of pancreatitis and developing and testing novel interventions. In this review, we aim to summarize the most commonly used animal models, overview their pathophysiology, and discuss their strengths and limitations. We will also briefly describe common animal study procedures and refer readers to more detailed protocols in the literature. Although animal models include pigs, dogs, opossums, and other animals, we will mainly focus on rodent models because of their popularity. Autoimmune pancreatitis and genetically engineered animal models will be reviewed elsewhere.

Animal Models of Gastrointestinal and Liver Diseases. The difficulty of animal modeling of pancreatic cancer for preclinical evaluation of therapeutics

Pancreatic ductal adenocarcinoma (PDAC) is relatively rare but extremely lethal. Standard cytotoxic therapeutics provide little benefit. To date, newer targeted therapeutics have also not been highly successful. Often novel therapeutics that have appeared to perform well in preclinical models have failed in the clinic. Many factors contribute to these failures, but the one most often attributed is the shortcomings of the preclinical models. A plethora of animal models now exist for PDAC, including cell line xenografts, patient-derived xenografts, a wide variety of genetic mouse models, and syngeneic xenografts. These models have generated a tremendous amount of information useful for the understanding of PDAC. Yet none seems to well predict clinical outcomes of new treatments. This review will discuss how genetic instability and cellular heterogeneity make this disease so difficult to model accurately. We will also discuss the strengths and weaknesses of many of the popular models. Ultimately we will argue that there is no perfect model and that the best approach to understanding clinical performance is the use of multiple preclinical models with an understanding of their salient features.

Role of Parathyroid Hormone-Related Protein Signaling in Chronic Pancreatitis

Chronic pancreatitis (CP), a progressive inflammatory disease where acini are destroyed and replaced by fibrous tissue, increases the risk for pancreatic cancer. Risk factors include alcohol, smoking, and obesity. The effects of these risk factors are exacerbated in patients with mutations in genes that predispose to CP. The different environmental and genetic factors produce the same clinical phenotype; once CP develops, disease course is the same regardless of etiology. Critical questions still need to be answered to understand what modifies predisposition to develop CP in persons exposed to risk factors. We postulate that risk factors modulate endogenous pathways, with parathyroid hormone-related protein (PTHrP) signaling being one such pathway. In support, PTHrP levels are elevated in mice treated with alcohol, and in mouse models of cerulein- and pancreatic duct ligation-induced CP. Disrupting the Pthrp gene in acinar cells exerts protective effects (decreased edema, histological damage, amylase and cytokine release, and fibrosis) in these CP models. PTHrP levels are elevated in human CP. Currently, CP care lacks specific pharmacological interventions. Targeting PTHrP signaling may present a novel therapeutic strategy that inhibits pancreatic inflammation and fibrosis, especially since the risk of developing pancreatic cancer is strongly associated with duration of chronic inflammation.

Acinar cell-specific knockout of the PTHrP gene decreases the proinflammatory and profibrotic responses in pancreatitis

Pancreatitis is a necroinflammatory disease with acute and chronic manifestations. Accumulated damage incurred during repeated bouts of acute pancreatitis (AP) can lead to chronic pancreatitis (CP). Pancreatic parathyroid hormone-related protein (PTHrP) levels are elevated in a mouse model of cerulein-induced AP. Here, we show elevated PTHrP levels in mouse models of pancreatitis induced by chronic cerulein administration and pancreatic duct ligation. Because acinar cells play a major role in the pathophysiology of pancreatitis, mice with acinar cell-specific targeted disruption of the Pthrp gene (PTHrP(Δacinar)) were generated to assess the role of acinar cell-secreted PTHrP in pancreatitis. These mice were generated using Cre-LoxP technology and the acinar cell-specific elastase promoter. PTHrP(Δacinar) exerted protective effects in cerulein and pancreatic duct ligation models, evident as decreased edema, histological damage, amylase secretion, pancreatic stellate cell (PSC) activation, and extracellular matrix deposition. Treating acinar cells in vitro with cerulein increased IL-6 expression and NF-κB activity; these effects were attenuated in PTHrP(Δacinar) cells, as were the cerulein- and carbachol-induced elevations in amylase secretion. The cerulein-induced upregulation of procollagen I expression was lost in PSCs from PTHrP(Δacinar) mice. PTHrP immunostaining was elevated in human CP sections. The cerulein-induced upregulation of IL-6 and ICAM-1 (human acinar cells) and procollagen I (human PSCs) was suppressed by pretreatment with the PTH1R antagonist, PTHrP (7-34). These findings establish PTHrP as a novel mediator of inflammation and fibrosis associated with CP. Acinar cell-secreted PTHrP modulates acinar cell function via its effects on proinflammatory cytokine release and functions via a paracrine pathway to activate PSCs.

A novel 2-step culture model for long-term in vitro maintenance of human pancreatic acinar cells

OBJECTIVES

Because of rapid loss of functional differentiation that regularly occurs in vitro, culture systems permitting long-term studies on pancreatic acinar cells pose a major technical challenge. We recently described a method for long-term cultivation of mouse acinar cells. Here, we introduce a novel 2-step culture system for human pancreatic acinar cells.

METHODS

The system involves 2 successive culture phases, which are as follows: primary organotypic culture of isolated acinar clusters under soft Matrigel (BD Biosciences, Bedford, Mass; range, 2-3 days) followed by dissociation and secondary monolayer culture of acinar cells (4 days). Basal and agonist-induced amylase secretion was used to assess the secretory capability.

RESULTS

Acinar clusters showed excellent morphology and stable basal amylase secretion throughout primary culture. Carbachol (0.1 mM/L) increased amylase secretion 1.4-fold (P = 0.021) versus basal in 3 independent 4-day secondary cultures. Despite the controversy about the presence and roles of cholecystokinin receptors in human acinar cells, one of them also responded to 0.1 and 10 nM/L concentrations of caerulein with 1.9- and 1.4-fold increases in the rate of amylase secretion, respectively.

CONCLUSIONS

Our technique allows cultured human acinar cells to maintain secretory differentiation for a minimum of 7 days. The technique provides novel prospects for in vitro modeling of the human exocrine pancreas.

Pathology review of proliferative lesions of the exocrine pancreas in two chronic feeding studies in rats with ammonium perfluorooctanoate

Two chronic dietary studies, conducted years apart, with ammonium perfluorooctanoate (APFO) in Sprague Dawley rats have been previously reported. Although both included male 300 ppm dietary dose groups, only the later study, conducted in 1990–1992 by Biegel et al., reported an increase in proliferative lesions (hyperplasia and adenoma) of the acinar pancreas. An assessment of the significance of the differences between both studies requires careful consideration of: the diagnostic criteria for proliferative acinar cell lesions of the rat pancreas (for example, the diagnosis of pancreatic acinar cell hyperplasia versus adenoma is based on the two-dimensional size of the lesion rather than distinct morphological differences); the basis for those criteria in light of their relevance to biological behavior; and the potential diagnostic variability between individual pathologists for difficult-to-classify lesions. A pathology peer review of male exocrine pancreatic tissues from the earlier study, conducted in 1981–1983 by Butenhoff et al., was undertaken. This review identified an increase in acinar cell hyperplasia but not adenoma or carcinoma in the earlier study. Both studies observed a proliferative response in the acinar pancreas which was more pronounced in the study by Biegel et al. Definitive reasons for the greater incidence of proliferative lesions in the later study were not identified, but some possible explanations are presented herein. The relevance of this finding to human risk assessment, in the face of differences in the biological behavior of human and rat pancreatic proliferative lesions and the proposed mechanism of formation of these lesions, are questionable.

Stars and stripes in pancreatic cancer: role of stellate cells and stroma in cancer progression

Pancreatic cancer is a devastating disease with an unacceptably high mortality to incidence ratio. Traditional therapeutic approaches such as surgery in combination with chemo- or radiotherapy have had limited efficacy in improving the outcome of this disease. Up until just under a decade ago, the prominent desmoplastic reaction which is a characteristic of the majority of pancreatic ductal adenocarcinomas (PDAC) had been largely ignored. However, since the identification of the pancreatic stellate cell (PSC) as the key cell responsible for the production of the collagenous stroma in PDAC, increasing attention has been paid to the role of the stromal reaction in pancreatic cancer pathobiology. There is now compelling evidence that PSCs interact not only with cancer cells themselves, but with several other cell types in the stroma (endothelial cells, immune cells, and possibly neuronal cells) to promote cancer progression. This review summarizes current knowledge in the field about the influence of PSCs and the stromal microenvironment on cancer behavior and discusses novel therapeutic approaches which reflect an increasing awareness amongst clinicians and researchers that targeting cancer cells alone is no longer sufficient to improve patient outcome and that combinatorial treatments targeting the stroma as well as the cancer cells will be required to change the clinical course of this disease.

Cholecystokinin and pancreatic cancer: the chicken or the egg?

The gastrointestinal peptide cholecystokinin (CCK) causes the release of pancreatic digestive enzymes and growth of the normal pancreas. Exogenous CCK administration has been used in animal models to study pancreatitis and also as a promoter of carcinogen-induced or Kras-driven pancreatic cancer. Defining CCK receptors in normal human pancreas has been problematic because of its retroperitoneal location, high concentrations of pancreatic proteases, and endogenous RNase. Most studies indicate that the predominant receptor in human pancreas is the CCK-B type, and CCK-A is the predominant form in rodent pancreas. In pancreatic cancer cells and tumors, the role of CCK is better established because receptors are often overexpressed by these cancer cells and stimulation of such receptors promotes growth. Furthermore, in established cancer, endogenous production of CCK and/or gastrin occurs and their actions stimulate the synthesis of more receptors plus growth by an autocrine mechanism. Initially it was thought that the mechanism by which CCK served to potentiate carcinogenesis was by interplay with inflammation in the pancreatic microenvironment. But with the recent findings of CCK receptors on early PanIN (pancreatic intraepithelial neoplasia) lesions and on stellate cells, the question has been raised that perhaps CCK actions are not the result of cancer but an early driving promoter of cancer. This review will summarize what is known regarding CCK, its receptors, and pancreatic cancer, and also what is unknown and requires further investigation to determine which comes first, the chicken or the egg, "CCK or the cancer."

Overview of exocrine pancreatic pathobiology

Exocrine pancreas is a source of several enzymes that are essential for the digestive process. The exocrine pancreatic secretion is tightly regulated by the neuroendocrine system. The endocrine pancreas is tightly integrated anatomically and physiologically with the exocrine pancreas and modulates its function. Compound-induced pancreatitis is not a common event in toxicology or drug development, but it becomes a significant liability when encountered. Understanding the species-specific differences in physiology is essential to understand the underlying pathobiology of pancreatic disease in animal models and its relevance to human disease. This review will mainly focus on understanding the morphology and physiology of the pancreas, unique islet-exocrine interactions, and pancreatitis.

Species- and Dose-Specific Pancreatic Responses and Progression in Single- and Repeat-Dose Studies with GI181771X

Compound-induced pancreatic injury is a serious liability in preclinical toxicity studies. However, its relevance to humans should be cautiously evaluated because of interspecies variations. To highlight such variations, we evaluated the species- and dose-specific pancreatic responses and progression caused by GI181771X, a novel cholecystokinin 1 receptor agonist investigated by GlaxoSmithKline for the treatment of obesity. Acute (up to 2,000 mg/kg GI181771X, as single dose) and repeat-dose studies in mice and/or rats (0.25–250 mg/kg/day for 7 days to 26 weeks) showed wide-ranging morphological changes in the pancreas that were dose and duration dependent, including necrotizing pancreatitis, acinar cell hypertrophy/atrophy, zymogen degranulation, focal acinar cell hyperplasia, and interstitial inflammation. In contrast to rodents, pancreatic changes were not observed in cynomolgus monkeys given GI181771X (1–500 mg/kg/day with higher systemic exposure than rats) for up to 52 weeks. Similarly, no GI181771X treatment-associated abnormalities in pancreatic structure were noted in a 24-week clinical trial with obese patients (body mass index >30 or >27 kg/m2) as assessed by abdominal ultrasound or by magnetic resonance imaging. Mechanisms for interspecies variations in the pancreatic response to CCK among rodents, monkeys, and humans and their relevance to human risk are discussed.

Models of acute and chronic pancreatitis

Animal models of acute and chronic pancreatitis have been created to examine mechanisms of pathogenesis, test therapeutic interventions, and study the influence of inflammation on the development of pancreatic cancer. In vitro models can be used to study early stage, short-term processes that involve acinar cell responses. Rodent models reproducibly develop mild or severe disease. One of the most commonly used pancreatitis models is created by administration of supraphysiologic concentrations of caerulein, an ortholog of cholecystokinin. Induction of chronic pancreatitis with factors thought to have a role in human disease, such as combinations of lipopolysaccharide and chronic ethanol feeding, might be relevant to human disease. Models of autoimmune chronic pancreatitis have also been developed. Most models, particularly of chronic pancreatitis, require further characterization to determine which features of human disease they include.

Expression of cholecystokinin-1 receptor is correlated with proteinuria in human diabetic nephropathy

This study aimed to examine the expression of cholecystokinin-1 receptor (CCK-1R) in the kidneys of type 2 diabetic nephropathy (DN) and the correlation of CCK-1R mRNA and proteinuria. Localization of CCK-1R in kidney of diabetic patient with nephropathy was examined by immunohistochemistry and in situ hybridization. The glomeruli did not express CCK-1R in either control or diabetic nephropathic kidneys. However, the expressions of CCK-1R protein and mRNA in tubules were significantly increased in DN, which had no relationship with the severity of DN. Furthermore, there was a positive correlation between the percentage of cells positive for CCK-1R mRNA and the degree of proteinuria. Increased CCK-1R expression could be demonstrated in the tubules and the CCK-1R might be implicated in the development of proteinuria in human DN.

Pharmacological and genetic inhibition of calcineurin protects against carbachol-induced pathological zymogen activation and acinar cell injury

Acute pancreatitis is a major health burden for which there are currently no targeted therapies. Premature activation of digestive proenzymes, or zymogens, within the pancreatic acinar cell is an early and critical event in this disease. A high-amplitude, sustained rise in acinar cell Ca(2+) is required for zymogen activation. We previously showed in a cholecystokinin-induced pancreatitis model that a potential target of this aberrant Ca(2+) signaling is the Ca(2+)-activated phosphatase calcineurin (Cn). However, in this study, we examined the role of Cn on both zymogen activation and injury, in the clinically relevant condition of neurogenic stimulation (by giving the acetylcholine analog carbachol) using three different Cn inhibitors or Cn-deficient acinar cells. In freshly isolated mouse acinar cells, pretreatment with FK506, calcineurin inhibitory peptide (CiP), or cyclosporine (CsA) blocked intra-acinar zymogen activation (n = 3; P < 0.05). The Cn inhibitors also reduced leakage of lactate dehydrogenase (LDH) by 79%, 62%, and 63%, respectively (n = 3; P < 0.05). Of the various Cn isoforms, the β-isoform of the catalytic A subunit (CnAβ) was strongly expressed in mouse acinar cells. For this reason, we obtained acinar cells from CnAβ-deficient mice (CnAβ-/-) and observed an 84% and 50% reduction in trypsin and chymotrypsin activation, respectively, compared with wild-type controls (n = 3; P < 0.05). LDH release in the CnAβ-deficient cells was reduced by 50% (n = 2; P < 0.05). The CnAβ-deficient cells were also protected against zymogen activation and cell injury induced by the cholecystokinin analog caerulein. Importantly, amylase secretion was generally not affected by either the Cn inhibitors or Cn deficiency. These data provide both pharmacological and genetic evidence that implicates Cn in intra-acinar zymogen activation and cell injury during pancreatitis.

Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion

Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.

The CCK(-like) receptor in the animal kingdom: functions, evolution and structures

In this review, the cholecystokinin (CCK)(-like) receptors throughout the animal kingdom are compared on the level of physiological functions, evolutionary basis and molecular structure. In vertebrates, the CCK receptor is an important member of the G-protein coupled receptors as it is involved in the regulation of many physiological functions like satiety, gastrointestinal motility, gastric acid secretion, gall bladder contraction, pancreatic secretion, panic, anxiety and memory and learning processes. A homolog for this receptor is also found in nematodes and arthropods, called CK receptor and sulfakinin (SK) receptor, respectively. These receptors seem to have evolved from a common ancestor which is probably still closely related to the nematode CK receptor. The SK receptor is more closely related to the CCK receptor and seems to have similar functions. A molecular 3D-model for the CCK receptor type 1 has been built together with the docking of the natural ligands for the CCK and SK receptors in the CCK receptor type 1. These molecular models can help to study ligand-receptor interactions, that can in turn be useful in the development of new CCK(-like) receptor agonists and antagonists with beneficial health effects in humans or potential for pest control.

Pancreatic stellate cells produce acetylcholine and may play a role in pancreatic exocrine secretion

The pancreatic secretagogue cholecystokinin (CCK) is widely thought to stimulate enzyme secretion by acinar cells indirectly via activation of the vagus nerve. We postulate an alternative pathway for CCK-induced pancreatic secretion. We hypothesize that neurally related pancreatic stellate cells (PSCs; located in close proximity to the basolateral aspect of acinar cells) play a regulatory role in pancreatic secretion by serving as an intermediate target for CCK and secreting the neurotransmitter acetylcholine (ACh), which, in turn, stimulates acinar enzyme secretion. To determine whether PSCs (i) exhibit CCK-dependent ACh secretion and (ii) influence acinar enzyme secretion, primary cultures of human and rat PSCs were used. Immunoblotting and/or immunofluorescence was used to detect choline acetyltransferase (ACh synthesizing enzyme), vesicular ACh transporter (VAChT), synaptophysin, and CCK receptors 1 and 2. Synaptic-like vesicles in PSCs were identified by EM. ACh secretion by PSCs exposed to 20 pM CCK was measured by LC-MS/MS. Amylase secretion by acini [pretreated with and without the muscarinic receptor antagonist atropine (10 μM) and cocultured with PSCs] was measured by colorimetry. PSCs express ACh synthesizing enzyme, VAChT, synaptophysin, and CCK receptors; exhibit CCK-dependent ACh secretion; and stimulate amylase secretion by acini, which is blocked by atropine. In conclusion, PSCs express the essential elements for ACh synthesis and secretion. CCK stimulates ACh secretion by PSCs, which, in turn, induces amylase secretion by acini. Therefore, PSCs may represent a previously unrecognized intrapancreatic pathway regulating CCK-induced pancreatic exocrine secretion.

Derivation of a reference dose and drinking water equivalent level for 1,2,3-trichloropropane

In some US potable water supplies, 1,2,3-trichloropropane (TCP) has been present at ranges of non-detect to less than 100 ppb, resulting from past uses. In subchronic oral studies, TCP produced toxicity in kidneys, liver, and other tissues. TCP administered by corn oil gavage in chronic studies produced tumors at multiple sites in rats and mice; however, interpretation of these studies was impeded by substantial premature mortality. Drinking water equivalent levels (DWELs) were estimated for a lifetime of consumption by applying biologically-based safety/risk assessment approaches, including Monte Carlo techniques, and with consideration of kinetics and modes of action, to possibly replace default assumptions. Internationally recognized Frameworks for human relevance of animal data were employed to interpret the findings. Calculated were a reference dose (=39 microg/kg d) for non-cancer and Cancer Values (CV) (=10-14 microg/kg d) based on non-linear dose-response relationships for mutagenicity as a precursor of cancer. Lifetime Average Daily Intakes (LADI) are 3130 and 790-1120 microg/person-d for non-cancer and cancer, respectively. DWELs, estimated by applying a relative source contribution (RSC) of 50% to the LADIs, are 780 and 200-280 microg/L for non-cancer and cancer, respectively. These DWELs may inform establishment of formal/informal guidelines and standards to protect public health.

Control of somatostatin (SS) secretion by CCK-1 and CCK-2 receptors' occupation in RIN-14B cells, a rat pancreatic islet cell line

OBJECTIVES

This study evaluated the role played by cholecystokinin (CCK) receptors' occupation in the control of somatostatin (SS) secretion in RIN-14B cells.

METHODS

The presence of the CCK receptors 1 and 2 was confirmed by immunofluorescence, and SS secretion was evaluated by enzyme-linked immunosorbent assay.

RESULTS

By immunofluorescence, 95% of the cell population was composed of SS cells bearing both CCK-R subtypes with 5% of beta cells (data not shown). Cerulein (Cae), a CCK-1R agonist, and pentagastrin, a CCK-2R agonist, dose-dependently increased SS release, 3-fold at 1 mumol/L Cae, 2.5-fold at 10 mumol/L pentagastrin, with occupation of both CCKRs confirmed by L-364,178 and L-365,260 inhibition of CCK receptors 1 and 2. The occupation of high-affinity CCK-1R by Cae was confirmed on SS release with JMV-180, a high-affinity CCK-1R agonist, and absence of SS release inhibition at high Cae concentration occupying the low-affinity CCK-1R. These cells release more than 60% of their SS content by constitutive secretion, confirmed by cycloheximide and brefeldin inhibiting SS synthesis and intracellular trafficking, respectively.

CONCLUSIONS

Both CCKR subtypes occupy RIN-14B cells and initiate SS secretion through constitutive secretion controlled at SS synthesis level. Somatostatin secretion via the CCK-1R occupation mobilizes its high-affinity sites.

Control of pancreatic secretion in humans

Studies on the control of pancreatic secretion in humans of all ages have been a difficult task over the years because of patients' availability and ethic committee rules. Nevertheless, studies were performed and the objectives of this review are to summarize our knowledge on the development of secretory process in newborns, on the different phases of the pancreatic responses to a meal, on the pancreatic responses to the different components of the diet, on the mechanisms involved in the control of the pancreatic responses, and finally on the receptors involved in these controls.

Gastrin, cholecystokinin and gastrointestinal tract functions in mammals

The aim of the present review is to synthesise and summarise our recent knowledge on the involvement of cholecystokinin (CCK) and gastrin peptides and their receptors in the control of digestive functions and more generally their role in the field of nutrition in mammals. First, we examined the release of these peptides from the gut, focusing on their molecular forms, the factors regulating their release and the signalling pathways mediating their effects. Second, general physiological effects of CCK and gastrin peptides are described with regard to their specific receptors and the role of CCK on vagal mucosal afferent nerve activities. Local effects of CCK and gastrin in the gut are also reported, including gut development, gastrointestinal motility and control of pancreatic functions through vagal afferent pathways, including NO. Third, some examples of the intervention of the CCK and gastrin peptides are exposed in diseases, taking into account intervention of the classical receptor subtypes (CCK1 and CCK2 receptors) and their heterodimerisation as well as CCK-C receptor subtype. Finally, applications and future challenges are suggested in the nutritional field (performances) and in therapy with regards to the molecular forms or in relation with the type of receptor as well as new techniques to be utilised in detection or in therapy of disease. In conclusion, the present review underlines recent developments in this field: CCK and gastrin peptides and their receptors are the key factor of nutritional aspects; a better understanding of the mechanisms involved may increase the efficiency of the nutritional functions and the treatment of abnormalities under pathological conditions.

Cholecystokinin-58 and cholecystokinin-8 exhibit similar actions on calcium signaling, zymogen secretion, and cell fate in murine pancreatic acinar cells

The gastrointestinal hormone CCK exists in various molecular forms, with differences in bioactivity between the well-characterized CCK-8 and larger CCK-58 previously reported. We have compared the effects of these peptides on cytosolic calcium concentration ([Ca(2+)](c)), mitochondrial metabolism, enzyme secretion, and cell fate in murine isolated pancreatic acinar cells using fluorescence confocal microscopy and patch-clamp electrophysiology. CCK-58 (1-10 pM) induced transient, oscillatory increases of [Ca(2+)](c), which showed apical to basolateral progression and were associated with a rise of mitochondrial NAD(P)H. CCK-58 (10 pM) induced zymogen exocytosis in isolated cells and amylase secretion from isolated cells and whole tissues. Hyperstimulation with supraphysiological CCK-58 (5 nM) induced a single large increase of [Ca(2+)](c) that declined to a plateau, which remained above the basal level 20 min after application and was dependent on external Ca(2+) entry. In cells dispersed from the same tissues, CCK-8 induced similar patterns of responses to those of CCK-58, with oscillatory increases of [Ca(2+)](c) at lower (pM) concentrations and sustained responses at 5 nM. CCK-58 and CCK-8 exhibited similar profiles of action on cell death, with increases in necrosis at high CCK-58 and CCK-8 (10 nM) that were not significantly different between peptides. The present experiments indicate that CCK-8 and CCK-58 have essentially identical actions on the acinar cell at high and low agonist concentrations, suggesting an action via the same receptor and that the differences observed in an intact rat model may result from indirect effects of the peptides. Our data strengthen the argument that CCK-58 is an important physiological form of this gastrointestinal hormone.

Therapeutic potential for novel drugs targeting the type 1 cholecystokinin receptor

Cholecystokinin (CCK) is a physiologically important gastrointestinal and neuronal peptide hormone, with roles in stimulating gallbladder contraction, pancreatic secretion, gastrointestinal motility and satiety. CCK exerts its effects via interactions with two structurally related class I guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs), the CCK(1) receptor and the CCK(2) receptor. Here, we focus on the CCK(1) receptor, with particular relevance to the broad spectrum of signalling initiated by activation with the natural full agonist peptide ligand, CCK. Distinct ligand-binding pockets have been defined for the natural peptide ligand and for some non-peptidyl small molecule ligands. While many CCK(1) receptor ligands have been developed and have had their pharmacology well described, their clinical potential has not yet been fully explored. The case is built for the potential importance of developing more selective partial agonists and allosteric modulators of this receptor that could have important roles in the treatment of common clinical syndromes.

Ras activity levels control the development of pancreatic diseases

BACKGROUND & AIMS

Differentiated pancreatic acinar cells expressing endogenous levels of mutant K-Ras do not spontaneously develop pancreatic ductal adenocarcinoma (PDAC). However, we hypothesized that acinar cells would develop PDAC in the presence of Ras activity levels mimicking those of human tumor cells.

METHODS

We measured Ras activity in PDAC cells from mice and humans using a Raf pull-down assay. We compared the effects of acinar cell expression of mutant K-Ras at endogenous and elevated levels on Ras activity and on the development of PDAC.

RESULTS

Ras activity was greatly elevated in PDAC cells compared with nontransformed cells expressing endogenous levels of mutant K-Ras. Expression of endogenous levels of mutant K-Ras in differentiated acinar cells resulted in moderately elevated Ras activity and in sparse murine pancreatic intraepithelial neoplasias (mPanINs) that did not spontaneously advance to PDAC unless the tumor suppressor p53 was simultaneously deleted. In contrast, expression of mutant K-Ras at higher levels generated Ras activity equal to that in PDAC. High Ras activity mimicking levels in PDAC led to acinar cell senescence and generated inflammation and fibrosis resembling the histologic features of chronic pancreatitis. With higher Ras activity in acinar cells, abundant mPanINs formed and spontaneously progressed to both cystic papillary carcinoma and metastatic PDAC.

CONCLUSIONS

There is an important relationship between Ras activity levels and the progression of PDAC. Sufficient Ras activity in pancreatic acinar induces several important pancreatic disease manifestations not previously reported and supports a potential direct linkage between chronic pancreatitis, cystic papillary carcinoma, and PDAC.

Intracellular trypsin induces pancreatic acinar cell death but not NF-kappaB activation

Premature intracellular activation of the digestive enzyme trypsinogen is considered to be the initiating event in pancreatitis. However, the direct consequences of intracellular trypsin activity have not previously been examined. In the current study, a mutant trypsinogen (paired basic amino acid cleaving enzyme (PACE)-trypsinogen), which is activated intracellularly by the endogenous protease PACE, was developed. This new construct allowed for the first time direct examination of the effects of intracellular trypsin on pancreatic acinar cells. We found that PACE-trypsinogen was expressed in the secretory pathway and was activated within acinar cells. Expression of PACE-trypsinogen induced apoptosis of HEK293 cells and pancreatic acinar cells, as indicated by histology, DNA laddering, PARP cleavage, and caspase-3 activation. Cell death was blocked by the trypsin inhibitor Pefabloc but not by the pancaspase inhibitor benzyloxycarbonyl-VAD, indicating that caspase-independent pathways were also involved. However, intracellular trypsin had no significant effect on the activity of the proinflammatory transcription factor NF-kappaB. In contrast, extracellular trypsin caused cell damage and dramatically increased NF-kappaB activity. These data indicate that localization of active trypsin determines its effects on pancreatic acinar cells. This new model will greatly improve our understanding of the role of active trypsin in pancreatitis and its associated inflammatory response.