Bile acids induce necrosis in pancreatic stellate cells dependent on calcium entry and sodium-driven bile uptake

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.

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.

Bile Acids and Microbiota Interplay in Pancreatic Cancer

Evidence suggests the involvement of the microbiota, including oral, intra-tumoral and gut, in pancreatic cancer progression and response to therapy. The gut microbiota modulates the bile acid pool and is associated with maintaining host physiology. Studies have shown that the bile acid/gut microbiota axis is dysregulated in pancreatic cancer. Bile acid receptor expression and bile acid levels are dysregulated in pancreatic cancer as well. Studies have also shown that bile acids can cause pancreatic cell injury and facilitate cancer cell proliferation. The microbiota and its metabolites, including bile acids, are also altered in other conditions considered risk factors for pancreatic cancer development and can alter responses to chemotherapeutic treatments, thus affecting patient outcomes. Altogether, these findings suggest that the gut microbial and/or bile acid profiles could also serve as biomarkers for pancreatic cancer detection. This review will discuss the current knowledge on the interaction between gut microbiota interaction and bile acid metabolism in pancreatic cancer.

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.

Changes in Pancreatic Senescence Mediate Pancreatic Diseases

In recent years, there has been a significant increase in age-related diseases due to the improvement in life expectancy worldwide. The pancreas undergoes various morphological and pathological changes with aging, such as pancreatic atrophy, fatty degeneration, fibrosis, inflammatory cell infiltration, and exocrine pancreatic metaplasia. Meanwhile, these may predispose the individuals to aging-related diseases, such as diabetes, dyspepsia, pancreatic ductal adenocarcinoma, and pancreatitis, as the endocrine and exocrine functions of the pancreas are significantly affected by aging. Pancreatic senescence is associated with various underlying factors including genetic damage, DNA methylation, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, and inflammation. This paper reviews the alternations of morphologies and functions in the aging pancreas, especially β-cells, closely related to insulin secretion. Finally, we summarize the mechanisms of pancreatic senescence to provide potential targets for treating pancreatic aging-related diseases.

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.

The association between parenteral nutrition and pancreatic injury in adult patients: a retrospective observational study

BACKGROUND AND OBJECTIVE

Patients on parenteral nutrition (PN) are at high risk of both liver and pancreatic injury. More efforts were focused on liver, however, limited data is available to evaluate the effects of PN on pancreas. Thus, we performed a retrospective observational study to evaluate the association between PN and pancreatic injury in Chinese adult patients.

METHODS

Adult patients (18-80 years), who received PN for a week or longer, and with repeated measurements of pancreatic enzymes, were included in the analysis. Pancreatic injury was confirmed by serum level of pancreatic amylase (P-AMYwas 53 U/L or higher) or lipase (LP was 63 U/L or higher), which were evaluated at baseline and following every week during PN duration. Age, sex, body weight, height, diagnosis of diseases, history of diseases, surgery, white blood cell, c-reactive protein, liver and renal function, fasting blood glucose, lipid profile, and daily energy supplied by PN and enteral nutrition were abstracted from medical records.

RESULTS

A total number of 190 adult patients (125 men, 65 women) were included in the study. The average age and BMI were 61.8 ± 13.0 years and 21.7±3.3 kg/m², while medium serum level of P-AMY and LP were 29.0 U/L (quartile range: 18.0, 47.0) and 33.0 U/L (quartile range: 19.0, 58.0), respectively at baseline. The median duration of PN was 15 days (quartile range: 11.0, 21.0). The prevalence of pancreatic injury was 42.1% (80/190) while it was 28.4% (54/190), 43.3% (77/178), 47.8% (44/92) after one-, two-, and three-week or longer PN adminstration. The proportion of daily energy supplement by PN (OR = 3.77, 95%CI: 1.87, 7.61) and history of infection were positively (OR = 3.00, 95%CI: 1.23, 7.36), while disease history for diabetes mellitus (OR = 0.38, 95%CI: 0.15, 0.98) and cancer (OR = 0.46, 95%CI: 0.23, 0.95), were negetively associated with pancreatic injury. Total bile acids were associated with the increment of P-AMY (beta = 0.98, 95%CI: 0.39, 1.56) and LP (beta = 2.55, 95%CI: 0.98, 4.12) by multi-variate linear regression.

CONCLUSION

PN was associated with pancreatic injury, as demonstrated by the increase of both serum P-AMY and LP.

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.

TRPM7 Modulates Human Pancreatic Stellate Cell Activation

Pancreatic diseases, such as pancreatitis or pancreatic ductal adenocarcinoma, are characterized by the presence of activated pancreatic stellate cells (PSCs). These cells represent key actors in the tumor stroma, as they actively participate in disease development and progression: reprograming these PSCs into a quiescent phenotype has even been proposed as a promising strategy for restoring the hallmarks of a healthy pancreas. Since TRPM7 channels have been shown to regulate hepatic stellate cells proliferation and survival, we aimed to study the role of these magnesium channels in PSC activation and proliferation. PS-1 cells (isolated from a healthy pancreas) were used as a model of healthy PSCs: quiescence or activation were induced using all-trans retinoic acid or conditioned media of pancreatic cancer cells, respectively. The role of TRPM7 was studied by RNA silencing or by pharmacological inhibition. TRPM7 expression was found to be correlated with the activation status of PS-1 cells. TRPM7 expression was able to regulate proliferation through modulation of cell cycle regulators and most importantly p53, via the PI3K/Akt pathway, in a magnesium-dependent manner. Finally, the analysis of TCGA database showed the overexpression of TRPM7 in cancer-associated fibroblasts. Taken together, we provide strong evidences that TRPM7 can be considered as a marker of activated PSCs.

Association of Chronic Hepatitis B Infection and Antiviral Treatment With the Development of the Extrahepatic Malignancies: A Nationwide Cohort Study

PURPOSE

Epidemiologic studies suggest that chronic hepatitis B (CHB) is a risk factor for various primary extrahepatic malignancies. Our aim was to evaluate the associations of CHB and nucleos(t)ide analog (NA) treatment with the risk of the development of extrahepatic malignancies.

PATIENTS AND METHODS

We conducted an 18-month landmark analysis using nationwide claims data from the National Health Insurance Service of South Korea. Patients newly diagnosed with CHB in 2012-2014 (n = 90,944) and matched-controls (n = 685,436) were included. Patients with CHB were further classified as the NA-treated (CHB+/NA+, n = 6,539) or the NA-untreated (CHB+/NA-, n = 84,405) group. Inverse probability of treatment weighting analysis was applied to balance the treatment groups. Time-varying Cox analysis was performed to evaluate time-varying effect of NA treatment. The primary outcome was the development of any primary extrahepatic malignancy. Development of intrahepatic malignancy and death were considered as competing events.

RESULTS

During the study period (median = 47.4 months), 30,413 patients (3.9%) developed any extrahepatic malignancy. The CHB+/NA- group had a higher overall risk of extrahepatic malignancy than the CHB+/NA+ group (adjusted subdistribution hazard ratio [aSHR] = 1.28; 95% CI, 1.12 to 1.45; P < .001) or controls (aSHR = 1.22; 95% CI, 1.18 to 1.26; P < .001). There was no difference in the risk of extrahepatic malignancy between the CHB+/NA+ group and the controls (CHB+/NA+ v control: aSHR = 0.96; 95% CI, 0.84 to 1.08; P = .48). In time-varying Cox analysis, the CHB+/NA- patients were associated with a higher risk of extrahepatic malignancy than the CHB+/NA+ patients (aSHR = 1.37; 95% CI, 1.23 to 1.52; P < .001).

CONCLUSION

Patients with CHB have an elevated risk of developing primary extrahepatic malignancy. Long-term NA treatment was associated with a lower risk of extrahepatic malignancy development among patients with CHB.

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.

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.

Metabolomic-based clinical studies and murine models for acute pancreatitis disease: A review

Acute pancreatitis (AP) is one of the most common gastroenterological disorders requiring hospitalization and is associated with substantial morbidity and mortality. Metabolomics nowadays not only help us to understand cellular metabolism to a degree that was not previously obtainable, but also to reveal the importance of the metabolites in physiological control, disease onset and development. An in-depth understanding of metabolic phenotyping would be therefore crucial for accurate diagnosis, prognosis and precise treatment of AP. In this review, we summarized and addressed the metabolomics design and workflow in AP studies, as well as the results and analysis of the in-depth of research. Based on the metabolic profiling work in both clinical populations and experimental AP models, we described the metabolites with potential utility as biomarkers and the correlation between the altered metabolites and AP status. Moreover, the disturbed metabolic pathways correlated with biological function were discussed in the end. A practical understanding of current and emerging metabolomic approaches applicable to AP and use of the metabolite information presented will aid in designing robust metabolomics and biological experiments that result in identification of unique biomarkers and mechanisms, and ultimately enhanced clinical decision-making.

Role of Bile Acids and Bile Salts in Acute Pancreatitis: From the Experimental to Clinical Studies

ABSTRACT

Acute pancreatitis (AP) is one of the most common gastroenterological disorders leading to hospitalization. It has long been debated whether biliary AP, about 30% to 50% of all cases, is induced by bile acids (BAs) when they reach the pancreas via reflux or via the systemic blood circulation.Besides their classical function in digestion, BAs have become an attractive research target because of their recently discovered property as signaling molecules. The underlying mechanisms of BAs have been investigated in various studies. Bile acids are internalized into acinar cells through specific G-protein-coupled BA receptor 1 and various transporters. They can further act via different receptors: the farnesoid X, ryanodine, and inositol triphosphate receptor. Bile acids induce a sustained Ca2+ influx from the endoplasmic reticulum and release of Ca2+ from acidic stores into the cytosol of acinar cells. The overload of intracellular Ca2+ results in mitochondrial depolarization and subsequent acinar cell necrosis. In addition, BAs have a biphasic effect on pancreatic ductal cells. A more detailed characterization of the mechanisms through which BAs contribute to the disease pathogenesis and severity will greatly improve our understanding of the underlying pathophysiology and may allow for the development of therapeutic and preventive strategies for gallstone-inducedAP.

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.

Signaling in the Physiology and Pathophysiology of Pancreatic Stellate Cells - a Brief Review of Recent Advances

The interest in pancreatic stellate cells (PSCs) has been steadily growing over the past two decades due mainly to the central role these cells have in the desmoplastic reaction associated with diseases of the pancreas, such as pancreatitis or pancreatic cancer. In recent years, the scientific community has devoted substantial efforts to understanding the signaling pathways that govern PSC activation and interactions with neoplastic cells. This mini review aims to summarize some very recent findings on signaling in PSCs and highlight their impact to the field.

Molecular Mechanism of Pancreatic Stellate Cells Activation in Chronic Pancreatitis and Pancreatic Cancer

Activated pancreatic stellate cells (PSCs) are the main effector cells in the process of fibrosis, a major pathological feature in pancreatic diseases that including chronic pancreatitis and pancreatic cancer. During tumorigenesis, quiescent PSCs change into an active myofibroblast-like phenotype which could create a favorable tumor microenvironment and facilitate cancer progression by increasing proliferation, invasiveness and inducing treatment resistance of pancreatic cancer cells. Many cellular signals are revealed contributing to the activation of PSCs, such as transforming growth factor-β, platelet derived growth factor, mitogen-activated protein kinase (MAPK), Smads, nuclear factor-κB (NF-κB) pathways and so on. Therefore, investigating the role of these factors and signaling pathways in PSCs activation will promote the development of PSCs-specific therapeutic strategies that may provide novel options for pancreatic cancer therapy. In this review, we systematically summarize the current knowledge about PSCs activation-associated stimulating factors and signaling pathways and hope to provide new strategies for the treatment of pancreatic diseases.

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.

Targeting Pancreatic Stellate Cells in Cancer

Pancreatic stellate cells (PSCs) are the major contributor to the aggressive, metastatic, and resilient nature of pancreatic ductal adenocarcinoma (PDAC), which has a poor prognosis with a 5-year survival rate of 8%. PSCs constitute more than 50% of the tumor stroma in PDAC, where they induce extensive desmoplasia by secreting abundant extracellular matrix (ECM) proteins. In addition, they establish dynamic crosstalk with cancer cells and other stromal cells, which collectively supports tumor progression via various inter- and intracellular pathways. These cellular interactions and associated pathways may reveal novel therapeutic opportunities against this unmet clinical problem. In this review article, we discuss the role of PSCs in inducing tumor progression, their crosstalk with other cells, and therapeutic strategies to target PSCs.

Guts and Gall: Bile Acids in Regulation of Intestinal Epithelial Function in Health and Disease

Epithelial cells line the entire surface of the gastrointestinal tract and its accessory organs where they primarily function in transporting digestive enzymes, nutrients, electrolytes, and fluid to and from the luminal contents. At the same time, epithelial cells are responsible for forming a physical and biochemical barrier that prevents the entry into the body of harmful agents, such as bacteria and their toxins. Dysregulation of epithelial transport and barrier function is associated with the pathogenesis of a number of conditions throughout the intestine, such as inflammatory bowel disease, chronic diarrhea, pancreatitis, reflux esophagitis, and cancer. Driven by discovery of specific receptors on intestinal epithelial cells, new insights into mechanisms that control their synthesis and enterohepatic circulation, and a growing appreciation of their roles as bioactive bacterial metabolites, bile acids are currently receiving a great deal of interest as critical regulators of epithelial function in health and disease. This review aims to summarize recent advances in this field and to highlight how bile acids are now emerging as exciting new targets for disease intervention.

Etiology, pathogenesis, diagnosis and treatment of bile reflux gastritis

Bile reflux gastritis is a common disease of the digestive system, whose clinical characteristics are abdominal pain, abdominal distention and nausea and vomiting, affecting the quality of life of patients seriously. However, the etiology and pathogenesis of bile reflux gastritis are still unclear, which may be related to gastrointestinal surgery, gallbladder disease, Helicobacter pylori infection, psychological factors, etc. There are many diagnostic methods, but a consensus on diagnosis is still lacking. Most of the current treatments are symptomatic treatments, but the overall efficacy is poor. This article reviews the etiology, pathogenesis, diagnosis and treatment of bile reflux gastritis, with an aim to provide a reference for further research of this disease.

ABT-199 (Venetoclax), a BH3-mimetic Bcl-2 inhibitor, does not cause Ca2+ -signalling dysregulation or toxicity in pancreatic acinar cells

BACKGROUND AND PURPOSE

Many cancer cells depend on anti-apoptotic B-cell lymphoma 2 (Bcl-2) proteins for their survival. Bcl-2 antagonism through Bcl-2 homology 3 (BH3) mimetics has emerged as a novel anti-cancer therapy. ABT-199 (Venetoclax), a recently developed BH3 mimetic that selectively inhibits Bcl-2, was introduced into the clinic for treatment of relapsed chronic lymphocytic leukaemia. Early generations of Bcl-2 inhibitors evoked sustained Ca²⁺ responses in pancreatic acinar cells (PACs) inducing cell death. Therefore, BH3 mimetics could potentially be toxic for the pancreas when used to treat cancer. Although ABT-199 was shown to kill Bcl-2-dependent cancer cells without affecting intracellular Ca²⁺ signalling, its effects on PACs have not yet been determined. Hence, it is essential and timely to assess whether this recently approved anti-leukaemic drug might potentially have pancreatotoxic effects.

EXPERIMENTAL APPROACH

Single-cell Ca²⁺ measurements and cell death analysis were performed on isolated mouse PACs.

KEY RESULTS

Inhibition of Bcl-2 via ABT-199 did not elicit intracellular Ca²⁺ signalling on its own or potentiate Ca²⁺ signalling induced by physiological/pathophysiological stimuli in PACs. Although ABT-199 did not affect cell death in PACs, under conditions that killed ABT-199-sensitive cancer cells, cytosolic Ca²⁺ extrusion was slightly enhanced in the presence of ABT-199. In contrast, inhibition of Bcl-xL potentiated pathophysiological Ca²⁺ responses in PACs, without exacerbating cell death.

CONCLUSION AND IMPLICATIONS

Our results demonstrate that apart from having a modest effect on cytosolic Ca²⁺ extrusion, ABT-199 does not substantially alter intracellular Ca²⁺ homeostasis in normal PACs and should be safe for the pancreas during cancer treatment.

LINKED ARTICLES

This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

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

Key points

Ca²⁺ signalling in different cell types in exocrine pancreatic lobules was monitored simultaneously and signalling responses to various stimuli were directly compared.

Ca²⁺ signals evoked by K⁺‐induced depolarization were recorded from pancreatic nerve cells. Nerve cell stimulation evoked Ca²⁺ signals in acinar but not in stellate cells.

Stellate cells are not electrically excitable as they, like acinar cells, did not generate Ca²⁺ signals in response to membrane depolarization.

The responsiveness of the stellate cells to bradykinin was markedly reduced in experimental alcohol‐related acute pancreatitis, but they became sensitive to stimulation with trypsin.

Our results provide fresh evidence for an important role of stellate cells in acute pancreatitis. They seem to be a critical element in a vicious circle promoting necrotic acinar cell death. Initial trypsin release from a few dying acinar cells generates Ca²⁺ signals in the stellate cells, which then in turn damage more acinar cells causing further trypsin liberation.

Abstract

Physiological Ca²⁺ signals in pancreatic acinar cells control fluid and enzyme secretion, whereas excessive Ca²⁺ signals induced by pathological agents induce destructive processes leading to acute pancreatitis. Ca²⁺ signals in the peri‐acinar stellate cells may also play a role in the development of acute pancreatitis. In this study, we explored Ca²⁺ signalling in the different cell types in the acinar environment of the pancreatic tissue. We have, for the first time, recorded depolarization‐evoked Ca²⁺ signals in pancreatic nerves and shown that whereas acinar cells receive a functional cholinergic innervation, there is no evidence for functional innervation of the stellate cells. The stellate, like the acinar, cells are not electrically excitable as they do not generate Ca²⁺ signals in response to membrane depolarization. The principal agent evoking Ca²⁺ signals in the stellate cells is bradykinin, but in experimental alcohol‐related acute pancreatitis, these cells become much less responsive to bradykinin and then acquire sensitivity to trypsin. Our new findings have implications for our understanding of the development of acute pancreatitis and we propose a scheme in which Ca²⁺ signals in stellate cells provide an amplification loop promoting acinar cell death. Initial release of the proteases kallikrein and trypsin from dying acinar cells can, via bradykinin generation and protease‐activated receptors, induce Ca²⁺ signals in stellate cells which can then, possibly via nitric oxide generation, damage more acinar cells and thereby cause additional release of proteases, generating a vicious circle.

Ca²⁺ signalling in different cell types in exocrine pancreatic lobules was monitored simultaneously and signalling responses to various stimuli were directly compared.

Ca²⁺ signals evoked by K⁺‐induced depolarization were recorded from pancreatic nerve cells. Nerve cell stimulation evoked Ca²⁺ signals in acinar but not in stellate cells.

Stellate cells are not electrically excitable as they, like acinar cells, did not generate Ca²⁺ signals in response to membrane depolarization.

The responsiveness of the stellate cells to bradykinin was markedly reduced in experimental alcohol‐related acute pancreatitis, but they became sensitive to stimulation with trypsin.

Our results provide fresh evidence for an important role of stellate cells in acute pancreatitis. They seem to be a critical element in a vicious circle promoting necrotic acinar cell death. Initial trypsin release from a few dying acinar cells generates Ca²⁺ signals in the stellate cells, which then in turn damage more acinar cells causing further trypsin liberation.

Pancreatic stellate cells: what's new?

PURPOSE OF REVIEW

Pancreatic stellate cells (PSCs) play an integral role in the pathogenesis of pancreatitis and pancreatic cancer. With the developing knowledge of this important cell type, we are at the cusp of developing effective therapies for the above diseases based upon targeting the PSC and modulating its function.

RECENT FINDINGS

The major themes of the recent PSC literature include: PSC interactions with the extracellular matrix and other stromal components; intracellular calcium physiology as drivers of mechanical interactions and necrosis; the relationship between proinflammatory, protumoural, angiogenic, and metabolic pathways in pancreatic necrosis, fibrosis, and carcinogenesis; and targeting of the stroma for antitumoural and antifibrotic effects.

SUMMARY

Traditionally, there have been few treatment options for pancreatitis and pancreatic cancer. The elucidation of the wide-ranging functions of PSCs provide an opportunity for treatments based on stromal reprogramming.

TRPC6 channels modulate the response of pancreatic stellate cells to hypoxia

Pancreatic cancer is characterized by a massive fibrosis (desmoplasia), which is primarily caused by activated pancreatic stellate cells (PSCs). This leads to a hypoxic tumor microenvironment further reinforcing the activation of PSCs by stimulating their secretion of growth factors and chemokines. Since many of them elicit their effects via G-protein-coupled receptors (GPCRs), we tested whether TRPC6 channels, effector proteins of many G-protein-coupled receptor pathways, are required for the hypoxic activation of PSCs. Thus far, the function of ion channels in PSCs is virtually unexplored. qPCR revealed TRPC6 channels to be one of the most abundant TRPC channels in primary cultures of murine PSCs. TRPC6 channel function was assessed by comparing PSCs from TRPC6^-/- mice and wildtype (wt) littermates. Cell migration, Ca²⁺ signaling, and cytokine secretion were analyzed as readout for PSC activation. Hypoxia was induced by incubating PSCs for 24 h in 1% O₂ or chemically with dimethyloxalylglycine (DMOG). PSCs migrate faster in response to hypoxia. Due to reduced autocrine stimulation, TRPC6^-/- PSCs fail to increase their rate of migration to the same level as wt PSCs under hypoxic conditions. This defect could not be overcome by the stimulation with platelet-derived growth factor. In line with these results, calcium influx is increased in wt but not TRPC6^-/- PSCs under hypoxia. We conclude that TRPC6 channels of PSCs are major effector proteins in an autocrine stimulation pathway triggered by hypoxia.

Inhibition of Jak/STAT signaling reduces the activation of pancreatic stellate cells in vitro and limits caerulein-induced chronic pancreatitis in vivo

Chronic pancreatitis (CP) is a fibro-inflammatory disease leading to pain, maldigestion, and pancreatic insufficiency. No therapeutic options exist due to a limited understanding of the biology of CP pathology. Recent findings implicate pancreatic stellate cells (PSC) as prominent mediators of inflammatory and fibrotic processes during CP. Here, we utilized primary and immortalized PSC obtained from mice and patients with CP or pancreatic cancer to examine the effect of Jak/STAT and MAPK pathway inhibition in vitro. The well-characterized caerulein model of CP was used to assess the therapeutic efficacy of Jak1/2 inhibition in vivo. Treatment of cultured PSC with the Jak1/2 inhibitor ruxolitinib reduced STAT3 phosphorylation, cell proliferation, and expression of alpha-smooth muscle actin (α-SMA), a marker of PSC activation. Treatment with the MAPK inhibitor, MEK162, had less consistent effects on PSC proliferation and no impact on activation. In the caerulein-induced murine model of CP, administration of ruxolitinib for one week significantly reduced biomarkers of inflammation and fibrosis. These data suggest that the Jak/STAT pathway plays a prominent role in PSC proliferation and activation. In vivo treatment with the Jak1/2 inhibitor ruxolitinib reduced the severity of experimental CP, suggesting that targeting Jak/STAT signaling may represent a promising therapeutic strategy for CP.

Biology of pancreatic stellate cells-more than just pancreatic cancer

Pancreatic stellate cells, normally quiescent, are capable of remarkable transition into their activated myofibroblast-like phenotype. It is now commonly accepted that these cells play a pivotal role in the desmoplastic reaction present in severe pancreatic disorders. In recent years, enormous scientific effort has been devoted to understanding their roles in pancreatic cancer, which continues to remain one of the most deadly diseases. Therefore, it is not surprising that considerably less attention has been given to studying physiological functions of pancreatic stellate cells. Here, we review recent advances not only in the field of pancreatic stellate cell pathophysiology but also emphasise their roles in physiological processes.

BH3 mimetic-elicited Ca2+ signals in pancreatic acinar cells are dependent on Bax and can be reduced by Ca2+-like peptides

BH3 mimetics are small-molecule inhibitors of B-cell lymphoma-2 (Bcl-2) and Bcl-xL, which disrupt the heterodimerisation of anti- and pro-apoptotic Bcl-2 family members sensitising cells to apoptotic death. These compounds have been developed as anti-cancer agents to counteract increased levels of Bcl-2 proteins often present in cancer cells. Application of a chemotherapeutic drug supported with a BH3 mimetic has the potential to overcome drug resistance in cancers overexpressing anti-apoptotic Bcl-2 proteins and thus increase the success rate of the treatment. We have previously shown that the BH3 mimetics, BH3I-2' and HA14-1, induce Ca²⁺ release from intracellular stores followed by a sustained elevation of the cytosolic Ca²⁺ concentration. Here we demonstrate that loss of Bax, but not Bcl-2 or Bak, inhibits this sustained Ca²⁺ elevation. What is more, in the absence of Bax, thapsigargin-elicited responses were decreased; and in two-photon-permeabilised bax^-/- cells, Ca²⁺ loss from the ER was reduced compared to WT cells. The Ca²⁺-like peptides, CALP-1 and CALP-3, which activate EF hand motifs of Ca²⁺-binding proteins, significantly reduced excessive Ca²⁺ signals and necrosis caused by two BH3 mimetics: BH3I-2' and gossypol. In the presence of CALP-1, cell death was shifted from necrotic towards apoptotic, whereas CALP-3 increased the proportion of live cells. Importantly, neither of the CALPs markedly affected physiological Ca²⁺ signals elicited by ACh, or cholecystokinin. In conclusion, the reduction in passive ER Ca²⁺ leak in bax^-/- cells as well as the fact that BH3 mimetics trigger substantial Ca²⁺ signals by liberating Bax, indicate that Bax may regulate Ca²⁺ leak channels in the ER. This study also demonstrates proof-of-principle that pre-activation of EF hand Ca²⁺-binding sites by CALPs can be used to ameliorate excessive Ca²⁺ signals caused by BH3 mimetics and shift necrotic death towards apoptosis.

One compound of saponins from Disocorea zingiberensis protected against experimental acute pancreatitis by preventing mitochondria-mediated necrosis

Acute pancreatitis (AP) is a painful inflammatory disorder of the exocrine pancreas, ranking as the most common gastrointestinal reasons for hospitalization with no specific therapy currently. Diosgenyl saponins extracted from natural products and diosgenin or its derivatives have been shown to exert anti-inflammatory effects in various diseases. However, the therapeutic effects of diosgenyl saponins from Dioscorea zingiberensis C. H. Wright in AP have not yet been determined. Five compounds were extracted and screened for taurocholate-induced necrosis in mouse pancreatic acinar cells. Particularly, 26-O-β-d-glucopyranosyl-3β, 22α, 26-trihydroxy-25(R)-furosta-5-en-3-O-[α-L-rhamnopyranosyl-(1 → 4)]-β-d-glucopyranoside (compound 1) exhibited the best protective effects with no toxicity observed. Next, we showed compound 1 concentration-dependently inhibited necrotic cell death pathway activation and 2.5 mM compound 1 also prevented the loss of mitochondrial membrane potential, adenosine triphosphate production, and reactive oxygen species generation in mouse pancreatic acinar cells. Finally, we showed compound 1 protected against three clinically representative murine models of AP and significantly improved pancreatitis-associated acute lung injury. These data provide in vitro and in vivo evidence that one compound of diosgenyl saponins can be potential treatment for AP. This study suggests natural saponins may serve as fruitful sources for exploring/identifying potential therapies for inflammatory diseases.