Calcium signalling in the acinar environment of the exocrine pancreas: physiology and pathophysiology

Pancreatic stellate cells: Key players in pancreatic health and diseases (Review)

As a pluripotent cell, activated pancreatic stellate cells (PSCs) can differentiate into various pancreatic parenchymal cells and participate in the secretion of extracellular matrix and the repair of pancreatic damage. Additionally, PSCs characteristics allow them to contribute to pancreatic inflammation and carcinogenesis. Moreover, a detailed study of the pathogenesis of activated PSCs in pancreatic disease can offer promise for the development of innovative therapeutic strategies and improved patient prognoses. Therefore, the present study review aimed to examine the involvement of activated PSCs in pancreatic diseases and elucidate the underlying mechanisms to provide a viable therapeutic strategy for the management of pancreas‑related diseases.

Fibroblast subtypes in pancreatic cancer and pancreatitis: from mechanisms to therapeutic strategies

Excessive fibrosis is a predominant feature of pancreatic stroma and plays a crucial role in the development and progression of pancreatic ductal adenocarcinoma (PDAC) and chronic pancreatitis (CP). Emerging evidence showed diversity and heterogeneity of fibroblasts play crucial and somewhat contradictory roles, the interactions between fibroblasts and pancreatic cells or infiltrating immune cells are of great importance during PDAC and CP progression, with some promising therapeutic strategies being tested. Therefore, in this review, we describe the classification of fibroblasts and their functions in PDAC and pancreatitis, the mechanisms by which fibroblasts mediate the development and progression of PDAC and CP through direct or indirect interaction between fibroblast and pancreatic parenchymal cells, or by remodeling the pancreatic immune microenvironment mediates the development and progression of PDAC and CP. Finally, we summarized the current therapeutic strategies and agents that directly target subtypes of fibroblasts or interfere with their essential functions.

Activation and Regulation of Pancreatic Stellate Cells in Chronic Pancreatic Fibrosis: A Potential Therapeutic Approach for Chronic Pancreatitis

In the complex progression of fibrosis in chronic pancreatitis, pancreatic stellate cells (PSCs) emerge as central figures. These cells, initially in a dormant state characterized by the storage of vitamin A lipid droplets within the chronic pancreatitis microenvironment, undergo a profound transformation into an activated state, typified by the secretion of an abundant extracellular matrix, including α-smooth muscle actin (α-SMA). This review delves into the myriad factors that trigger PSC activation within the context of chronic pancreatitis. These factors encompass alcohol, cigarette smoke, hyperglycemia, mechanical stress, acinar cell injury, and inflammatory cells, with a focus on elucidating their underlying mechanisms. Additionally, we explore the regulatory factors that play significant roles during PSC activation, such as TGF-β, CTGF, IL-10, PDGF, among others. The investigation into these regulatory factors and pathways involved in PSC activation holds promise in identifying potential therapeutic targets for ameliorating fibrosis in chronic pancreatitis. We provide a summary of recent research findings pertaining to the modulation of PSC activation, covering essential genes and innovative regulatory mediators designed to counteract PSC activation. We anticipate that this research will stimulate further insights into PSC activation and the mechanisms of pancreatic fibrosis, ultimately leading to the discovery of groundbreaking therapies targeting cellular and molecular responses within these processes.

The context-dependent role of the Na+/Ca2+-exchanger (NCX) in pancreatic stellate cell migration

Pancreatic stellate cells (PSCs) that can co-metastasize with cancer cells shape the tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC) by producing an excessive amount of extracellular matrix. This leads to a TME characterized by increased tissue pressure, hypoxia, and acidity. Moreover, cells within the tumor secrete growth factors. The stimuli of the TME trigger Ca2+ signaling and cellular Na+ loading. The Na+/Ca2+ exchanger (NCX) connects the cellular Ca2+ and Na+ homeostasis. The NCX is an electrogenic transporter, which shuffles 1 Ca2+ against 3 Na+ ions over the plasma membrane in a forward or reverse mode. Here, we studied how the impact of NCX activity on PSC migration is modulated by cues from the TME. NCX expression was revealed with qPCR and Western blot. [Ca2+]i, [Na+]i, and the cell membrane potential were determined with the fluorescent indicators Fura-2, Asante NaTRIUM Green-2, and DiBAC4(3), respectively. PSC migration was quantified with live-cell imaging. To mimic the TME, PSCs were exposed to hypoxia, pressure, acidic pH (pH 6.6), and PDGF. NCX-dependent signaling was determined with Western blot analyses. PSCs express NCX1.3 and NCX1.9. [Ca2+]i, [Na+]i, and the cell membrane potential are 94.4 nmol/l, 7.4 mmol/l, and - 39.8 mV, respectively. Thus, NCX1 usually operates in the forward (Ca2+ export) mode. NCX1 plays a differential role in translating cues from the TME into an altered migratory behavior. When NCX1 is operating in the forward mode, its inhibition accelerates PSC migration. Thus, NCX1-mediated extrusion of Ca2+ contributes to a slow mode of migration of PSCs.

The role of Ca2+ signalling in the pathology of exocrine pancreas

Exocrine pancreas has been the field of many successful studies in pancreatic physiology and pathology. However, related disease - acute pancreatitis (AP) is still takes it toll with more than 100,000 related deaths worldwide per year. In spite of significant scientific progress and several human trials currently running for AP, there is still no specific treatment in the clinic. Studies of the mechanism of initiation of AP have identified two crucial conditions: sustained elevations of cytoplasmic calcium concentration (Ca2+ plateau) and significantly reduced intracellular energy (ATP depletion). These hallmarks are interdependent, i.e., Ca2+ plateau increase energy demand for its clearance while energy production is greatly affected by the pathology. Result of long standing Ca2+ plateau is destabilisation of the secretory granules and premature activation of the digestive enzymes leading to necrotic cell death. Main attempts so far to break the vicious circle of cell death have been concentrated on reduction of Ca2+ overload or reduction of ATP depletion. This review will summarise these approaches, including recent developments of potential therapies for AP.

The 2022 George E Palade Medal Lecture: Toxic Ca2+ signals in acinar, stellate and endogenous immune cells are important drivers of acute pancreatitis

In this account of the 2022 Palade Medal Lecture, an attempt is made to explain, as simply as possible, the most essential features of normal physiological control of pancreatic enzyme secretion, as they have emerged from more than 50 years of experimental work. On that basis, further studies on the mechanism by which acute pancreatitis is initiated are then described. Calcium ion signaling is crucially important for both the normal physiology of secretion control as well as for the development of acute pancreatitis. Although acinar cell processes have, rightly, been central to our understanding of pancreatic physiology and pathophysiology, attention is here drawn to the additional critical influence of calcium signaling events in stellate and immune cells in the acinar environment. These signals contribute significantly to the crucially important inflammatory response in acute pancreatitis.

Watching Living Cells in Action in the Exocrine Pancreas: The Palade Prize Lecture

George Palade's pioneering electron microscopical studies of the pancreatic acinar cell revealed the intracellular secretory pathway from the rough endoplasmic reticulum at the base of the cell to the zymogen granules in the apical region. Palade also described for the first time the final stage of exocytotic enzyme secretion into the acinar lumen. The contemporary studies of the mechanism by which secretion is acutely controlled, and how the pancreas is destroyed in the disease acute pancreatitis, rely on monitoring molecular events in the various identified pancreatic cell types in the living pancreas. These studies have been carried out with the help of high-resolution fluorescence recordings, often in conjunction with patch clamp current measurements. In such studies we have gained much detailed information about the regulatory events in the exocrine pancreas in health as well as disease, and new therapeutic opportunities have been revealed.

Activation of pancreatic stellate cells attenuates intracellular Ca2+ signals due to downregulation of TRPA1 and protects against cell death induced by alcohol metabolites

Alcohol abuse, an increasing problem in developed societies, is one of the leading causes of acute and chronic pancreatitis. Alcoholic pancreatitis is often associated with fibrosis mediated by activated pancreatic stellate cells (PSCs). Alcohol toxicity predominantly depends on its non-oxidative metabolites, fatty acid ethyl esters, generated from ethanol and fatty acids. Although the role of non-oxidative alcohol metabolites and dysregulated Ca²⁺ signalling in enzyme-storing pancreatic acinar cells is well established as the core mechanism of pancreatitis, signals in PSCs that trigger fibrogenesis are less clear. Here, we investigate real-time Ca²⁺ signalling, changes in mitochondrial potential and cell death induced by ethanol metabolites in quiescent vs TGF-β-activated PSCs, compare the expression of Ca²⁺ channels and pumps between the two phenotypes and the consequences these differences have on the pathogenesis of alcoholic pancreatitis. The extent of PSC activation in the pancreatitis of different aetiologies has been investigated in three animal models. Unlike biliary pancreatitis, alcohol-induced pancreatitis results in the activation of PSCs throughout the entire tissue. Ethanol and palmitoleic acid (POA) or palmitoleic acid ethyl ester (POAEE) act directly on quiescent PSCs, inducing cytosolic Ca²⁺ overload, disrupting mitochondrial functions, and inducing cell death. However, activated PSCs acquire remarkable resistance against ethanol metabolites via enhanced Ca²⁺-handling capacity, predominantly due to the downregulation of the TRPA1 channel. Inhibition or knockdown of TRPA1 reduces EtOH/POA-induced cytosolic Ca²⁺ overload and protects quiescent PSCs from cell death, similarly to the activated phenotype. Our results lead us to review current dogmas on alcoholic pancreatitis. While acinar cells and quiescent PSCs are prone to cell death caused by ethanol metabolites, activated PSCs can withstand noxious signals and, despite ongoing inflammation, deposit extracellular matrix components. Modulation of Ca²⁺ signals in PSCs by TRPA1 agonists/antagonists could become a strategy to shift the balance of tissue PSCs towards quiescent cells, thus limiting pancreatic fibrosis.

Current Trends and Research Hotspots in Pancreatic Stellate Cells: A Bibliometric Study

Background

Pancreatic stellate cells (PSCs) play crucial roles in acute/chronic pancreatitis and pancreatic cancer. In this study, bibliometric analysis was used to quantitatively and qualitatively analyze the literature related to PSCs from 1998-2021 to summarize the current trends and research topics in this field.

Methods

Relevant literature data were downloaded from the Science Citation Index Expanded Web of Science Core Collection (WoSCC) on April 07, 2021, using Clarivate Analytics. Biblioshiny R packages, VOSviewer, Citespace, BICOMB, gCLUTO, and the Online Analysis Platform of Literature Metrology (http://bibliometric.com) were used to analyze the manually selected data.

Results

A total of 958 relevant studies published in 48 countries or regions were identified. The United States of America (USA) had the highest number of publications, followed by the People's Republic of China, Germany, and Japan. Tohoku University (Japan), the University of New South Wales (Australia), the University of Texas MD Anderson Cancer Center (USA), Technical University of Munich (Germany), and University of Rostock (Germany) were the top five institutions with most publications. Nine major clusters were generated using reference co-citation analysis. Keyword burst detection revealed that progression (2016-2021), microenvironment (2016-2021), and tumor microenvironment (2017-2021) were the current frontier keywords. Biclustering analysis identified five research hotspots in the field of PSCs during 1998-2021.

Conclusion

In this study, a scientometric analysis of 958 original documents related to PSCs showed that the research topics of these studies are likely in the transition from acute/chronic pancreatitis to pancreatic cancer. The current research trends regarding PSCs are related to pancreatic cancer, such as tumor microenvironment. This study summarizes five research hotspots in the field of PSCs between 1998 and 2021 and thus may provide insights for future research.

SARS-CoV-2 S Protein Subunit 1 Elicits Ca2+ Influx - Dependent Ca2+ Signals in Pancreatic Stellate Cells and Macrophages In Situ

The S protein subunit 1 (S1) of SARS-CoV-2 is known to be responsible for the binding of the virus to host cell receptors, but the initial intracellular signalling steps following receptor activation of cells in the exocrine pancreas are unknown. Using an intact live mouse pancreatic lobule preparation, we observed that S1 elicited Ca²⁺ signals in stellate cells and macrophages, but not in the dominant acinar cells. The Ca²⁺ signals occurred mostly in the form of repetitive Ca²⁺ spikes. The probability of observing Ca²⁺ signals depended on the S1 concentration. The threshold was close to 70 nM, whereas at 600 nM, all cells responded. The SARS-Cov-2 nucleocapsid protein did not elicit any Ca²⁺ signals in any of the three cell types tested. The S1-induced Ca²⁺ signals in stellate cells started much faster (122 ± 37s) than those in macrophages (468 ± 68s). Furthermore, the interleukin-18 binding protein (IL-18BP) abolished the responses in macrophages without affecting the Ca²⁺ signals in stellate cells. The S1-elicited Ca²⁺ signals were completely dependent on the presence of external Ca²⁺ and were abolished by a selective inhibitor (CM4620) of Orai1 Ca²⁺ Release Activated Ca²⁺ channels. SARS-CoV-2 may contribute to acute pancreatitis, an often fatal inflammatory human disease. The S1-elicited Ca²⁺ signals we have observed in the pancreatic stellate cells and endogenous macrophages may play an important part in the development of the inflammatory process.

Saikosaponin D Attenuates Pancreatic Injury Through Suppressing the Apoptosis of Acinar Cell via Modulation of the MAPK Signaling Pathway

Chronic pancreatitis (CP) is a progressive fibro-inflammatory syndrome. The damage of acinar cells is the main cause of inflammation and the activation of pancreatic stellate cells (PSCs), which can thereby possibly further aggravate the apoptosis of more acinar cells. Saikosaponind (SSd), a major active ingredient derived from Chinese medicinal herb bupleurum falcatum, which exerted multiple pharmacological effects. However, it is not clear whether SSd protects pancreatic injury of CP via regulating the apoptosis of pancreatic acinar cells. This study systematically investigated the effect of SSd on pancreatic injury of CP in vivo and in vitro. The results revealed that SSd attenuate pancreatic damage, decrease the apoptosis and suppress the phosphorylation level of MAPK family proteins (JNK1/2, ERK1/2, and p38 MAPK) significantly in the pancreas of CP rats. In addition, SSd markedly reduced the apoptosis and inflammation of pancreatic acinar AR42J cells induced by cerulein, a drug induced CP, or Conditioned Medium from PSCs (PSCs-CM) or the combination of PSCs-CM and cerulein. Moreover, SSd significantly inhibited the activated phosphorylation of JNK1/2, ERK1/2, and p38 MAPK induced by cerulein or the combination of PSCs-CM and cerulein in AR42J cells. Furthermore, SSd treatment markedly decreased the protein levels of p-JNK and p-p38 MAPK caused by PSCs-CM alone. In conclusion, SSd ameliorated pancreatic injury, suppressed AR42J inflammation and apoptosis induced by cerulein, interrupted the effect of PSCs-CM on AR42J cells inflammation and apoptosis, possibly through MAPK pathway.

Dual Mode of Action of Acetylcholine on Cytosolic Calcium Oscillations in Pancreatic Beta and Acinar Cells In Situ

Cholinergic innervation in the pancreas controls both the release of digestive enzymes to support the intestinal digestion and absorption, as well as insulin release to promote nutrient use in the cells of the body. The effects of muscarinic receptor stimulation are described in detail for endocrine beta cells and exocrine acinar cells separately. Here we describe morphological and functional criteria to separate these two cell types in situ in tissue slices and simultaneously measure their response to ACh stimulation on cytosolic Ca2+ oscillations [Ca2+]c in stimulatory glucose conditions. Our results show that both cell types respond to glucose directly in the concentration range compatible with the glucose transporters they express. The physiological ACh concentration increases the frequency of glucose stimulated [Ca2+]c oscillations in both cell types and synchronizes [Ca2+]c oscillations in acinar cells. The supraphysiological ACh concentration further increases the oscillation frequency on the level of individual beta cells, inhibits the synchronization between these cells, and abolishes oscillatory activity in acinar cells. We discuss possible mechanisms leading to the observed phenomena.

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.

Pancreatitis initiated pancreatic ductal adenocarcinoma: Pathophysiology explaining clinical evidence

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant lethal disease due to its asymptomatic at its early lesion of the disease and drug resistance. Target therapy associated with molecular pathways so far seems not to produce reasonable outcomes. Understanding of the molecular mechanisms underlying inflammation-initiated tumorigenesis may be helpful for development of an effective therapy of the disease. A line of studies showed that pancreatic tumorigenesis was resulted from pancreatitis, which was caused synergistically by various pancreatic cells. This review focuses on those players and their possible clinic implications, such as exocrine acinar cells, ductal cells, and various stromal cells, including pancreatic stellate cells (PSCs), macrophages, lymphocytes, neutrophils, mast cells, adipocytes and endothelial cells, working together with each other in an inflammation-mediated microenvironment governed by a myriad of cellular signaling networks towards PDAC.

Auxora for the Treatment of Patients With Acute Pancreatitis and Accompanying Systemic Inflammatory Response Syndrome: Clinical Development of a Calcium Release-Activated Calcium Channel Inhibitor

OBJECTIVES

To assess the safety of Auxora in patients with acute pancreatitis (AP), systemic inflammatory response syndrome (SIRS), and hypoxemia, and identify efficacy endpoints to prospectively test in future studies.

METHODS

This phase 2, open-label, dose-response study randomized patients with AP, accompanying SIRS, and hypoxemia (n = 21) to receive low-dose or high-dose Auxora plus standard of care (SOC) or SOC alone. All patients received pancreatic contrast-enhanced computed tomography scans at screenings, day 5/discharge, and as clinically required 90 days postrandomization; scans were blinded and centrally read to determine AP severity using computed tomography severity index. Solid food tolerance was assessed at every meal and SIRS every 12 hours.

RESULTS

The number of patients experiencing serious adverse events was not increased with Auxora versus SOC alone. Three (36.5%) patients with moderate AP receiving low-dose Auxora improved to mild AP; no computed tomography severity index improvements were observed with SOC. By study end, patients receiving Auxora better tolerated solid foods, had less persistent SIRS, and had reduced hospitalization versus SOC.

CONCLUSIONS

The favorable safety profile and patient outcomes suggest Auxora may be an appropriate early treatment for patients with AP and SIRS. Clinical development will continue in a randomized, controlled, blinded, dose-ranging study.

Critical thresholds: key to unlocking the door to the prevention and specific treatments for acute pancreatitis

Acute pancreatitis (AP), an acute inflammatory disorder of the exocrine pancreas, is one of the most common gastrointestinal diseases encountered in emergency departments with no specific treatments. Laboratory-based research has formed the cornerstone of endeavours to decipher the pathophysiology of AP, because of the limitations of such study in human beings. While this has provided us with substantial understanding, we cannot answer several pressing questions. These are: (a) Why is it that only a minority of individuals with gallstones, or who drink alcohol excessively, or are exposed to other causative factors develop AP? (b) Why do only some develop more severe manifestations of AP with necrosis and/or organ failure? (c) Why have we been unable to find an effective therapeutic for AP? This manuscript provides a state-of-the-art review of our current understanding of the pathophysiology of AP providing insights into the unanswered clinical questions. We describe multiple protective factors operating in most people, and multiple stressors that in a minority induce AP, independently or together, via amplification loops. We present testable hypotheses aimed at halting progression of severity for the development of effective treatments for this common unpredictable disease.

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.

Calcium Signaling in Pancreatic Immune Cells In situ

Immune cells were identified in intact live mouse pancreatic lobules and their Ca²⁺ signals, evoked by various agents, characterized and compared with the simultaneously recorded Ca²⁺ signals in neighboring acinar and stellate cells. Immunochemistry in the live lobules indicated that the pancreatic immune cells most likely are macrophages. In the normal pancreas the density of these cells is very low, but induction of acute pancreatitis (AP), by a combination of ethanol and fatty acids, markedly increased the number of the immune cells. The principal agent eliciting Ca²⁺ signals in the pancreatic immune cells was ATP, but these cells also frequently produced Ca²⁺ signals in response to acetylcholine and to high concentrations of bradykinin. Pharmacological studies, using specific purinergic agonists and antagonists, indicated that the ATP-elicited Ca²⁺ signals were mediated by both P2Y1 and P2Y13 receptors. The pancreatic immune cells were not electrically excitable and the Ca²⁺ signals generated by ATP were primarily due to release of Ca²⁺ from internal stores followed by store-operated Ca²⁺ entry through Ca²⁺ release-activated Ca²⁺ channels. The ATP-induced intracellular Ca²⁺ liberation was dependent on both IP₃ generation and IP₃ receptors. We propose that the ATP-elicited Ca²⁺ signal generation in the pancreatic immune cells is likely to play an important role in the severe inflammatory response to the primary injury of the acinar cells that occurs in AP.

Severe acute pancreatitis: surgical indications and treatment

Background

Acute pancreatitis (AP) is defined as an acute inflammatory attack of the pancreas of sudden onset. Around 25% of patients have either moderately severe or severe disease with a mortality rate of 15–20%.

Purpose

The aim of this article was to summarize the advances being made in the understanding of this disease and the important role of surgery.

Results and conclusions

An accurate diagnosis should be made a soon as possible, initiating resuscitation with large volume intravenous fluids and oxygen by mask. Predicted severe disease will require intensive monitoring. Most deaths within the first week are due to multi-organ failure; thus, these patients will require intensive therapy unit management. During the second phase of the disease, death is due to local complications arising from the pancreatic inflammation, requiring accurate identification to determine the correct form of treatment. Acute peripancreatic fluid collections arise < 4 weeks after onset of interstitial edematous pancreatitis, not requiring any treatment. Most pancreatic pseudocysts arise > 4 weeks and largely resolve on conservative management. Necrotizing pancreatitis causing acute necrotic collections and later walled-off necrosis will require treatment if symptomatic or infected. Initial endoscopic transgastric or percutaneous drainage will resolve less serious collections but necrosectomy using minimally invasive approaches will be needed for more serious collections. To prevent recurrent attacks of AP, causative factors need to be removed where possible such as cholecystectomy and cessation of alcohol. Future progress requires improved management of multi-organ failure and more effective minimally invasive techniques for the removal of necrosis.

Pancreatic stellate cells exhibit adaptation to oxidative stress evoked by hypoxia

BACKGROUND INFORMATION

Pancreatic stellate cells play a key role in the fibrosis that develops in diseases such as pancreatic cancer. In the growing tumour, a hypoxia condition develops under which cancer cells are able to proliferate. The growth of fibrotic tissue contributes to hypoxia. In this study, the effect of hypoxia (1% O₂ ) on pancreatic stellate cells physiology was investigated. Changes in intracellular free-Ca²⁺ concentration, mitochondrial free-Ca²⁺ concentration and mitochondrial membrane potential were studied by fluorescence techniques. The status of enzymes responsible for the cellular oxidative state was analyzed by quantitative reverse transcription-polymerase chain reaction, high-performance liquid chromatography, spectrophotometric and fluorimetric methods and by Western blotting analysis. Cell viability and proliferation were studied by crystal violet test, 5-bromo-2-deoxyuridine cell proliferation test and Western blotting analysis. Finally, cell migration was studied employing the wound healing assay.

RESULTS

Hypoxia induced an increase in intracellular and mitochondrial free-Ca²⁺ concentration, whereas mitochondrial membrane potential was decreased. An increase in mitochondrial reactive oxygen species production was observed. Additionally, an increase in the oxidation of proteins and lipids was detected. Moreover, cellular total antioxidant capacity was decreased. Increases in the expression of superoxide dismutase 1 and 2 were observed and superoxide dismutase activity was augmented. Hypoxia evoked a decrease in the oxidized/reduced glutathione ratio. An increase in the phosphorylation of nuclear factor erythroid 2-related factor and in expression of the antioxidant enzymes catalytic subunit of glutamate-cysteine ligase, catalase, NAD(P)H-quinone oxidoreductase 1 and heme oxygenase-1 were detected. The expression of cyclin A was decreased, whereas expression of cyclin D and the content of 5-bromo-2-deoxyuridine were increased. This was accompanied by an increase in cell viability. The phosphorylation state of c-Jun NH₂ -terminal kinase was increased, whereas that of p44/42 and p38 was decreased. Finally, cells subjected to hypoxia maintained migration ability.

CONCLUSIONS AND SIGNIFICANCE

Hypoxia creates pro-oxidant conditions in pancreatic stellate cells to which cells adapt and leads to increased viability and proliferation.

Evaluation and Management of Suspected Early Chronic Pancreatitis (ECP)

PURPOSE OF REVIEW

Chronic pancreatitis in the advanced stages leads to significant health care utilization because of the associated complications. Early-stage diagnosis could prevent the development of these complications by appropriate management. In this article, we reviewed the recent evidence pertaining to the diagnosis and management of early chronic pancreatitis (ECP).

RECENT FINDINGS

The working group for the International Consensus Guidelines for Chronic Pancreatitis has published consensus-based statements to streamline the diagnosis of ECP. There is no international consensus on the definition and diagnosis of ECP. The Revised Japanese Diagnostic Criteria for ECP based on clinical features and endoscopic ultrasound findings have been proposed. Large prospective cohort studies are needed to develop and validate internationally acceptable diagnostic criteria. ECP is recognized as a distinct stage in the development and progression of CP. Consensus-based definitions and diagnostic criteria need to be developed.

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.

CRAC channels in secretory epithelial cell function and disease

The receptor-evoked Ca²⁺ signal in secretory epithelia mediate many cellular functions essential for cell survival and their most fundamental functions of secretory granules exocytosis and fluid and electrolyte secretion. Ca²⁺ influx is a key component of the receptor-evoked Ca²⁺ signal in secretory cell and is mediated by both TRPC and the STIM1-activated Orai1 channels that mediates the Ca²⁺ release-activated current (CRAC) I_crac. The core components of the receptor-evoked Ca²⁺ signal are assembled at the ER/PM junctions where exchange of materials between the plasma membrane and internal organelles take place, including transfer of lipids and Ca²⁺. The Ca²⁺ signal generated at the confined space of the ER/PM junctions is necessary for activation of the Ca²⁺-regulated proteins and ion channels that mediate exocytosis with high fidelity and tight control. In this review we discuss the general properties of Ca²⁺ signaling, PI(4,5)P₂ and other lipids at the ER/PM junctions with regard to secretory cells function and disease caused by uncontrolled Ca²⁺ influx.