Bile acids induce pancreatic acinar cell injury and pancreatitis by activating calcineurin

A low-dose prebiotic fiber supplement reduces lipopolysaccharide-binding protein concentrations in a subgroup of young, healthy adults consuming low-fiber diets

Although the beneficial effects of fiber supplementation on overall health and the gut microbiome are well-known, it is not clear whether fiber supplementation can also alter the concentrations of lipopolysaccharide-binding protein (LBP), a marker of intestinal permeability. A secondary analysis of a previously conducted study was performed. In the randomized-order, placebo-controlled, double-blinded, cross-over study 20 healthy, young participants consuming a low-fiber diet at baseline were administered a daily dose of 12 g of prebiotic fiber compared with a placebo over a period of 4 weeks with a 4-week washout between arms. In this secondary analysis, we hypothesized that the fiber supplement would reduce LBP concentration. We further hypothesized that lecithin cholesterol acyltransferase activity, a measure of high-density lipoprotein functional capacity, would be altered. Fiber supplementation did not significantly alter LBP concentration or lecithin cholesterol acyltransferase activity in the overall cohort. However, in a subgroup of individuals with elevated baseline LBP concentrations, fiber supplementation significantly reduced LBP from 9.27 ± 3.52 to 7.02 ± 2.32 µg/mL (P = .003). Exploratory analyses found positive correlations between microbial genes involved in lipopolysaccharide synthesis and conversely negative correlations with genes involved in antibiotic synthesis and LBP. Positive correlations between LBP and multiple sulfated molecules including sulfated bile acids and perfluorooctanesulfonate, and ibuprofen metabolites were also found. These findings highlight multiple environmental and lifestyle factors such as exposure to industrial chemicals and medication intake, in addition to diet, which may influence the association between the gut microbiome and gut barrier function.

Integrated global and unique metabolic characteristics to reveal the intervention effect of Yiyi decoction on acute pancreatitis

Yiyi decoction is a Chinese herbal formula for the treatment of acute pancreatitis that has been used in clinical practice for decades. A previous study has suggested that resveratrol, emodin, rhein and their derivatives might be the potential pharmacodynamic components in Yiyi decoction, and researchers have proposed that resveratrol, emodin and rhein are candidate markers for quality control. The present study investigated the intervention effect of Yiyi decoction and its effective components on murine acute pancreatitis using metabolomic approach that integrated global and unique metabolic characteristics. First, serum metabolomics based on the platform of ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was performed to assess metabolic changes in experimental acute pancreatitis. Second, an in-depth analysis of bile acid metabolism was performed based on an in-house database. Finally, an integrated analysis of the intervention effect of Yiyi decoction and its effective components in response to these metabolic perturbations was performed. As a result, 39 potential biomarkers for the pathogenesis of acute pancreatitis, mainly phospholipids, fatty acids, bile acids and lipoylcarnitines, were screened and annotated. Integrated analysis revealed that the metabolic disorders in acute pancreatitis mice were reversed by Yiyi decoction primarily via regulating glycerophospholipid metabolism, bile acid biosynthesis, carnitine synthesis and fatty acid metabolism. Yiyi decoction components may effectively target the migratory metabolome. Histopathological and biochemical analyses suggested that Yiyi decoction maintained the gut barrier function and inhibited inflammatory cytokines, thus exert anti-acute pancreatitis effects. The present study utilized an approach that integrated global and unique metabolic characteristics to elucidate the underlying mechanisms of Chinese herbal formulas from a metabolomics perspective.

Discoveries of GPR39 as an evolutionarily conserved receptor for bile acids and of its involvement in biliary acute pancreatitis

Acute pancreatitis (AP) is one of the most common gastrointestinal diseases. Bile acids (BAs) were proposed to be a cause of AP nearly 170 years ago, though the underlying mechanisms remain unclear. Here, we report that two G protein-coupled receptors, GPR39 and GHSR, mediated cellular responses to BAs. Our results revealed GPR39 as an evolutionarily conserved receptor for BAs, particularly 3-O-sulfated lithocholic acids. In cultured cell lines, GPR39 is sufficient for BA-induced Ca2+ elevation. In pancreatic acinar cells, GPR39 mediated BA-induced Ca2+ elevation and necrosis. Furthermore, AP induced by BAs was significantly reduced in GPR39 knockout mice. Our findings provide in vitro and in vivo evidence demonstrating that GPR39 is necessary and sufficient to mediate BA signaling, highlighting its involvement in biliary AP pathogenesis, and suggesting it as a promising therapeutic target for biliary AP.

Mitochondrial dysfunction in the pathogenesis of acute pancreatitis

The mechanism of cell damage during acute pancreatitis (AP) has not been fully elucidated, and there is still a lack of specific or effective treatments. Increasing evidence has implicated mitochondrial dysfunction as a key event in the pathophysiology of AP. Mitochondrial dysfunction is closely related to calcium (Ca2+) overload, intracellular adenosine triphosphate depletion, mitochondrial permeability transition pore openings, loss of mitochondrial membrane potential, mitophagy damage and inflammatory responses. Mitochondrial dysfunction is an early triggering event in the initiation and development of AP, and this organelle damage may precede the release of inflammatory cytokines, intracellular trypsin activation and vacuole formation of pancreatic acinar cells. This review provides further insight into the role of mitochondria in both physiological and pathophysiological aspects of AP, aiming to improve our understanding of the underlying mechanism which may lead to the development of therapeutic and preventive strategies for AP.

Bile acid metabolomics identifies chenodeoxycholic acid as a therapeutic agent for pancreatic necrosis

Bile acids are altered and associated with prognosis in patients with acute pancreatitis (AP). Here, we conduct targeted metabolomic analyses to detect bile acids changes in patients during the acute (n = 326) and the recovery (n = 133) phases of AP, as well as in healthy controls (n = 60). Chenodeoxycholic acid (CDCA) decreases in the acute phase, increases in the recovery phase, and is associated with pancreatic necrosis. CDCA and its derivative obeticholic acid exhibit a protective effect against acinar cell injury in vitro and pancreatic necrosis in murine models, and RNA sequencing reveals that the oxidative phosphorylation pathway is mainly involved. Moreover, we find that overexpression of farnesoid X receptor (FXR, CDCA receptor) inhibits pancreatic necrosis, and interfering expression of FXR exhibits an opposite phenotype in mice. Our results possibly suggest that targeting CDCA is a potential strategy for the treatment of acinar cell necrosis in AP, but further verification is needed.

Novel Non-duct-to-Mucosa Pancreaticojejunostomy Reconstruction After Pancreaticoduodenectomy: Focus on the Occurrence of Post-pancreatectomy Hemorrhage and Intra-abdominal Abscess

BACKGROUND

Postoperative pancreatic fistulas (POPFs) are considered inevitable in some patients after pancreaticoduodenectomy (PD), and measures to minimize their clinical impact are needed. Postpancreatectomy hemorrhage (PPH) and intra-abdominal abscess (IAA) are the most severe POPF-related complications, and concomitant leakage of contaminated intestinal content is considered the main cause. An innovative method, modified non-duct-to-mucosa pancreaticojejunostomy (TPJ), was created to prevent concomitant leakage of intestinal content, and its effectiveness was compared between two periods.

METHODS

All PD patients undergoing pancreaticojejunostomy from 2012 to 2021 were included. The TPJ group consisted of 529 patients recruited from January 2018 to December 2021. A total of 535 patients receiving the conventional method (CPJ) from January 2012 to June 2017 were used as a control group. PPH and POPF were defined according to the International Study Group of Pancreatic Surgery definition, but only PPH grade C was included for analysis. An IAA was defined as a collection of postoperative fluid managed by CT-guided drainage with documental culture.

RESULTS

There were no significant differences in the rate of POPF between the two groups (46.0% vs. 44.8%; p = 0.700). Furthermore, the percentages of bile in the drainage fluid in the TPJ and CPJ groups were 2.3% and 9.2%, respectively (p < 0.001). Lower proportions of PPH (0.9% vs. 6.5%; p < 0.001) and IAA (5.7% vs. 10.8%; p < 0.001) were observed for TPJ than for CPJ. On adjusted models, TPJ was significantly associated with a lower rate of PPH (odds ratio [OR] 0.132, 95% confidence interval [CI] 0.051-0.343; p < 0.001) and IAA (OR 0.514, 95% CI 0.349-0.758; p = 0.001) than CPJ.

CONCLUSIONS

TPJ is feasible to be performed and is associated with a similar rate of POPF but a lower percentage of concomitant bile in the drainage fluid and subsequent rates of PPH and IAA than CPJ.

Systemic Bile Acids Affect the Severity of Acute Pancreatitis in Mice Depending on Their Hydrophobicity and the Disease Pathogenesis

Acute pancreatitis (AP) is a major, globally increasing gastrointestinal disease and a biliary origin is the most common cause. However, the effects of bile acids (BAs), given systemically, on the pancreas and on disease severity remains elusive. In this study, we have investigated the roles of different circulating BAs in animal models for AP to elucidate their impact on disease severity and the underlying pathomechanisms. BAs were incubated on isolated acini and AP was induced through repetitive injections of caerulein or L-arginine; pancreatic duct ligation (PDL); or combined biliopancreatic duct ligation (BPDL). Disease severity was assessed using biochemical and histological parameters. Serum cholecystokinin (CCK) concentrations were determined via enzyme immunoassay. The binding of the CCK1 receptor was measured using fluorescence-labeled CCK. In isolated acini, hydrophobic BAs mitigated the damaging effects of CCK. The same BAs further enhanced pancreatitis in L-arginine- and PDL-based pancreatitis, whereas they ameliorated pancreatic damage in the caerulein and BPDL models. Mechanistically, the binding affinity of the CCK1 receptor was significantly reduced by hydrophobic BAs. The hydrophobicity of BAs and the involvement of CCK seem to be relevant in the course of AP. Systemic BAs may affect the severity of AP by interfering with the CCK1 receptor.

Calcium, mitochondria and the initiation of acute pancreatitis

Acute pancreatitis is characterized by necrosis of its parenchymal cells and influx and activation of inflammatory cells that further promote injury and necrosis. This review is intended to discuss the central role of disorders of calcium metabolism and mitochondrial dysfunction in the mechanism of pancreatitis development. The disorders are placed in context of calcium and mitochondria in physiologic function of the pancreas. Moreover, we discuss potential therapeutics for preventing pathologic calcium signals that injure mitochondria and interventions that promote the removal of injured mitochondria and regenerate new and heathy populations of mitochondria.

Rectal INdomethacin, oral TacROlimus, or their combination for the prevention of post-ERCP pancreatitis (INTRO Trial): Protocol for a randomized, controlled, double-blinded trial

BACKGROUND

Acute pancreatitis remains the most common and morbid complication of endoscopic retrograde cholangiopancreatography (ERCP). The use of rectal indomethacin and pancreatic duct stenting has been shown to reduce the incidence and severity of post-ERCP pancreatitis (PEP), but these interventions have limitations. Recent clinical and translational evidence suggests a role for calcineurin inhibitors in the prevention of pancreatitis, with multiple retrospective case series showing a reduction in PEP rates in tacrolimus users.

METHODS

The INTRO trial is a multicenter, international, randomized, double-blinded, controlled trial. A total of 4,874 patients undergoing ERCP will be randomized to receive either oral tacrolimus (5 mg) or oral placebo 1-2 h before ERCP, and followed for 30 days post-procedure. Blood and pancreatic aspirate samples will also be collected in a subset of patients to quantify tacrolimus levels. The primary outcome of the study is the incidence of PEP. Secondary endpoints include the severity of PEP, ERCP-related complications, adverse drug events, length of hospital stay, cost-effectiveness, and the pharmacokinetics, pharmacodynamics, and pharmacogenomics of tacrolimus immune modulation in the pancreas.

CONCLUSIONS

The INTRO trial will assess the role of calcineurin inhibitors in PEP prophylaxis and develop a foundation for the clinical optimization of this therapeutic strategy from a pharmacologic and economic standpoint. With this clinical trial, we hope to demonstrate a novel approach to PEP prophylaxis using a widely available and well-characterized class of drugs.

TRIAL REGISTRATION

NCT05252754, registered on February 14, 2022.

A review of the rationale for the testing of the calcineurin inhibitor tacrolimus for post-ERCP pancreatitis prevention

Endoscopic retrograde cholangiopancreatography (ERCP) is commonly performed for the management of pancreaticobiliary disorders. The most troublesome ERCP-associated adverse event is post-ERCP pancreatitis (PEP), which occurs in up to 15% of all patients undergoing ERCP. A substantial body of preclinical data support a mechanistic rationale for calcineurin inhibitors in preventing PEP. The findings are coupled with recent clinical data suggesting lower rates of PEP in patients who concurrently use the calcineurin inhibitor tacrolimus (e.g., solid organ transplant recipients). In this review, we will firstly summarize data in support of testing the use of tacrolimus for PEP prophylaxis, either in combination with rectal indomethacin or by itself. Secondly, we propose that administering tacrolimus through the rectal route could be favorable for PEP prophylaxis over other routes of administration.

Autophagy, Acute Pancreatitis and the Metamorphoses of a Trypsinogen-Activating Organelle

Recent studies have highlighted the importance of autophagy and particularly non-canonical autophagy in the development and progression of acute pancreatitis (a frequent disease with considerable morbidity and significant mortality). An important early event in the development of acute pancreatitis is the intrapancreatic activation of trypsinogen, (i.e., formation of trypsin) leading to the autodigestion of the organ. Another prominent phenomenon associated with the initiation of this disease is vacuolisation and specifically the formation of giant endocytic vacuoles in pancreatic acinar cells. These organelles develop in acinar cells exposed to several inducers of acute pancreatitis (including taurolithocholic acid and high concentrations of secretagogues cholecystokinin and acetylcholine). Notably, early trypsinogen activation occurs in the endocytic vacuoles. These trypsinogen-activating organelles undergo activation, long-distance trafficking, and non-canonical autophagy. In this review, we will discuss the role of autophagy in acute pancreatitis and particularly focus on the recently discovered LAP-like non-canonical autophagy (LNCA) of endocytic vacuoles.

Qingyi decoction attenuates intestinal epithelial cell injury via the calcineurin/nuclear factor of activated T-cells pathway

BACKGROUND

Recent studies have demonstrated that dysfunction of the intestinal barrier is a significant contributing factor to the development of severe acute pancreatitis (SAP). A stable intestinal mucosa barrier functions as a major anatomic and functional barrier, owing to the balance between intestinal epithelial cell (IEC) proliferation and apoptosis. There is some evidence that calcium overload may trigger IEC apoptosis and that calcineurin (CaN)/nuclear factor of activated T-cells (NFAT) signaling might play an important role in calcium-mediated apoptosis.

AIM

To investigate the potential mechanisms underlying the therapeutic effect of Qingyi decoction (QYD) in SAP.

METHODS

A rat model of SAP was created via retrograde infusion of sodium deoxycholate. Serum levels of amylase, tumor necrosis factor (TNF-α), interleukin (IL)-6, D-lactic acid, and diamine oxidase (DAO); histological changes; and apoptosis of IECs were examined in rats with or without QYD treatment. The expression of the two subunits of CaN and NFAT in intestinal tissue was measured via quantitative real-time polymerase chain reaction and western blotting. For in vitro studies, Caco-2 cells were treated with lipopolysaccharide (LPS) and QYD serum, and then cell viability and intracellular calcium levels were detected.

RESULTS

Retrograde infusion of sodium deoxycholate increased the severity of pancreatic and intestinal pathology and the levels of serum amylase, TNF-α, and IL-6. Both the indicators of intestinal mucosa damage (D-lactic acid and DAO) and the levels of IEC apoptosis were elevated in the SAP group. QYD treatment reduced the serum levels of amylase, TNF-α, IL-6, D-lactic acid, and DAO and attenuated the histological findings. IEC apoptosis associated with SAP was ameliorated under QYD treatment. In addition, the protein expression levels of the two subunits of CaN were remarkably elevated in the SAP group, and the NFATc3 gene was significantly upregulated at both the transcript and protein levels in the SAP group compared with the control group. QYD significantly restrained CaN and NFATc3 gene expression in the intestine, which was upregulated in the SAP group. Furthermore, QYD serum significantly decreased the LPS-induced elevation in intracellular free Ca²⁺ levels and inhibited cell death.

CONCLUSION

QYD can exert protective effects against intestinal mucosa damage caused by SAP and the protective effects are mediated, at least partially, by restraining IEC apoptosis via the CaN/NFATc3 pathway.

Mechanism of Bile Acid-Induced Programmed Cell Death and Drug Discovery against Cancer: A Review

Bile acids are major signaling molecules that play a significant role as emulsifiers in the digestion and absorption of dietary lipids. Bile acids are amphiphilic molecules produced by the reaction of enzymes with cholesterol as a substrate, and they are the primary metabolites of cholesterol in the body. Bile acids were initially considered as tumor promoters, but many studies have deemed them to be tumor suppressors. The tumor-suppressive effect of bile acids is associated with programmed cell death. Moreover, based on this fact, several synthetic bile acid derivatives have also been used to induce programmed cell death in several types of human cancers. This review comprehensively summarizes the literature related to bile acid-induced programmed cell death, such as apoptosis, autophagy, and necroptosis, and the status of drug development using synthetic bile acid derivatives against human cancers. We hope that this review will provide a reference for the future research and development of drugs against cancer.

Bicarbonate Transport in Cystic Fibrosis and Pancreatitis

CFTR, the cystic fibrosis (CF) gene-encoded epithelial anion channel, has a prominent role in driving chloride, bicarbonate and fluid secretion in the ductal cells of the exocrine pancreas. Whereas severe mutations in CFTR cause fibrosis of the pancreas in utero, CFTR mutants with residual function, or CFTR variants with a normal chloride but defective bicarbonate permeability (CFTR^BD), are associated with an enhanced risk of pancreatitis. Recent studies indicate that CFTR function is not only compromised in genetic but also in selected patients with an acquired form of pancreatitis induced by alcohol, bile salts or smoking. In this review, we summarize recent insights into the mechanism and regulation of CFTR-mediated and modulated bicarbonate secretion in the pancreatic duct, including the role of the osmotic stress/chloride sensor WNK1 and the scaffolding protein IRBIT, and current knowledge about the role of CFTR in genetic and acquired forms of pancreatitis. Furthermore, we discuss the perspectives for CFTR modulator therapy in the treatment of exocrine pancreatic insufficiency and pancreatitis and introduce pancreatic organoids as a promising model system to study CFTR function in the human pancreas, its role in the pathology of pancreatitis and its sensitivity to CFTR modulators on a personalized basis.

Role of lysosomes in physiological activities, diseases, and therapy

Long known as digestive organelles, lysosomes have now emerged as multifaceted centers responsible for degradation, nutrient sensing, and immunity. Growing evidence also implicates role of lysosome-related mechanisms in pathologic process. In this review, we discuss physiological function of lysosomes and, more importantly, how the homeostasis of lysosomes is disrupted in several diseases, including atherosclerosis, neurodegenerative diseases, autoimmune disorders, pancreatitis, lysosomal storage disorders, and malignant tumors. In atherosclerosis and Gaucher disease, dysfunction of lysosomes changes cytokine secretion from macrophages, partially through inflammasome activation. In neurodegenerative diseases, defect autophagy facilitates accumulation of toxic protein and dysfunctional organelles leading to neuron death. Lysosomal dysfunction has been demonstrated in pathology of pancreatitis. Abnormal autophagy activation or inhibition has been revealed in autoimmune disorders. In tumor microenvironment, malignant phenotypes, including tumorigenesis, growth regulation, invasion, drug resistance, and radiotherapy resistance, of tumor cells and behaviors of tumor-associated macrophages, fibroblasts, dendritic cells, and T cells are also mediated by lysosomes. Based on these findings, a series of therapeutic methods targeting lysosomal proteins and processes have been developed from bench to bedside. In a word, present researches corroborate lysosomes to be pivotal organelles for understanding pathology of atherosclerosis, neurodegenerative diseases, autoimmune disorders, pancreatitis, and lysosomal storage disorders, and malignant tumors and developing novel therapeutic strategies.

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.

ACVIM consensus statement on pancreatitis in cats

Background

Pancreatitis in cats, although commonly diagnosed, still presents many diagnostic and management challenges.

Objective

To summarize the current literature as it relates to etiology, pathogenesis, diagnosis, and management of pancreatitis in cats and to arrive at clinically relevant suggestions for veterinary clinicians that are based on evidence, and where such evidence is lacking, based on consensus of experts in the field.

Animals

None.

Methods

A panel of 8 experts in the field (5 internists, 1 radiologist, 1 clinical pathologist, and 1 anatomic pathologist), with support from a librarian, was formed to assess and summarize evidence in the peer reviewed literature and complement it with consensus clinical recommendations.

Results

There was little literature on the etiology and pathogenesis of spontaneous pancreatitis in cats, but there was much in the literature about the disease in humans, along with some experimental evidence in cats and nonfeline species. Most evidence was in the area of diagnosis of pancreatitis in cats, which was summarized carefully. In contrast, there was little evidence on the management of pancreatitis in cats.

Conclusions and Clinical Importance

Pancreatitis is amenable to antemortem diagnosis by integrating all clinical and diagnostic information available, and recognizing that acute pancreatitis is far easier to diagnose than chronic pancreatitis. Although both forms of pancreatitis can be managed successfully in many cats, management measures are far less clearly defined for chronic pancreatitis.

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.

The Protective Effects of Calcineurin on Pancreatitis in Mice Depend on the Cellular Source

BACKGROUND & AIMS

Calcineurin is a ubiquitously expressed central Ca2+-responsive signaling molecule that mediates acute pancreatitis, but little is known about its effects. We compared the effects of calcineurin expression by hematopoietic cells vs pancreas in mouse models of pancreatitis and pancreatitis-associated lung inflammation.

METHODS

We performed studies with mice with hematopoietic-specific or pancreas-specific deletion of protein phosphatase 3, regulatory subunit B, alpha isoform (PPP3R1, also called CNB1), in mice with deletion of CNB1 (Cnb1UBC△/△) and in the corresponding controls for each deletion of CNB1. Acute pancreatitis was induced in mice by administration of caerulein or high-pressure infusion of radiocontrast into biliopancreatic ducts; some mice were also given intraductal infusions of an adeno-associated virus vector that expressed nuclear factor of activated T -cells (NFAT)-luciferase into pancreas. Pancreas, bone marrow, liver, kidney, heart, and lung were collected and analyzed by histopathology, immunohistochemistry, and immunoblots; levels of cytokines were measured in serum. Mouse and human primary pancreatic acinar cells were transfected with a vector that expressed NFAT-luciferase and incubated with an agent that blocks interaction of NFAT with calcineurin; cells were analyzed by immunofluorescence. Calcineurin-mediated neutrophil chemotaxis and reactive oxygen species production were measured in neutrophils from mice.

RESULTS

Mice with hematopoietic-specific deletion of CNB1 developed the same level of local pancreatic inflammation as control mice after administration of caerulein or infusion of radiocontrast into biliopancreatic ducts. Cnb1UBC△/△ mice or mice with pancreas-specific deletion of CNB1 developed less severe pancreatitis and reduced pancreatic inflammation after administration of caerulein or infusion of radiocontrast into biliopancreatic ducts compared with control mice. NFAT was activated in pancreas of Swiss Webster mice given caerulein or infusions of radiocontrast into biliopancreatic ducts. Blocking the interaction between calcineurin and NFAT did not reduce pancreatic acinar cell necrosis in response to caerulein or infusions of radiocontrast. Mice with hematopoietic-specific deletion of CNB1 (but not mice with pancreas-specific deletion of CNB1) had reduced infiltration of lung tissues by neutrophils. Neutrophil chemotaxis and production of reactive oxygen species were decreased after incubation with a calcineurin inhibitor.

CONCLUSIONS

Hematopoietic and neutrophil expression of calcineurin promotes pancreatitis-associated lung inflammation, whereas pancreatic calcineurin promotes local pancreatic inflammation. The findings indicate that the protective effects of blocking or deleting calcineurin on pancreatitis are mediated by the source of its expression. This information should be used in the development of strategies to inhibit calcineurin for the prevention of pancreatitis and pancreatitis-associated lung inflammation.

The Remedial Potential of Lycopene in Pancreatitis through Regulation of Autophagy

Autophagy is an evolutionarily conserved process that degrades damaged organelles and recycles macromolecules to support cell survival. However, in certain disease states, dysregulated autophagy can play an important role in cell death. In pancreatitis, the accumulation of autophagic vacuoles and damaged mitochondria and premature activation of trypsinogen are shown in pancreatic acinar cells (PACs), which are the hallmarks of impaired autophagy. Oxidative stress mediates inflammatory signaling and cytokine expression in PACs, and it also causes mitochondrial dysfunction and dysregulated autophagy. Thus, oxidative stress may be a mediator for autophagic impairment in pancreatitis. Lycopene is a natural pigment that contributes to the red color of fruits and vegetables. Due to its antioxidant activity, it inhibited oxidative stress-induced expression of cytokines in experimental models of acute pancreatitis. Lycopene reduces cell death through the activation of 5′-AMP-activated protein kinase-dependent autophagy in certain cells. Therefore, lycopene may ameliorate pancreatitis by preventing oxidative stress-induced impairment of autophagy and/or by directly activating autophagy in PACs.

Knockout of the Mitochondrial Calcium Uniporter Strongly Suppresses Stimulus-Metabolism Coupling in Pancreatic Acinar Cells but Does Not Reduce Severity of Experimental Acute Pancreatitis

Acute pancreatitis is a frequent disease that lacks specific drug treatment. Unravelling the molecular mechanisms of acute pancreatitis is essential for the development of new therapeutics. Several inducers of acute pancreatitis trigger sustained Ca²⁺ increases in the cytosol and mitochondria of pancreatic acinar cells. The mitochondrial calcium uniporter (MCU) mediates mitochondrial Ca²⁺ uptake that regulates bioenergetics and plays an important role in cell survival, damage and death. Aberrant Ca²⁺ signaling and mitochondrial damage in pancreatic acinar cells have been implicated in the initiation of acute pancreatitis. The primary aim of this study was to assess the involvement of the MCU in experimental acute pancreatitis. We found that pancreatic acinar cells from MCU^-/- mice display dramatically reduced mitochondrial Ca²⁺ uptake. This is consistent with the drastic changes of stimulus-metabolism coupling, manifested by the reduction of mitochondrial NADH/FAD⁺ responses to cholecystokinin and in the decrease of cholecystokinin-stimulated oxygen consumption. However, in three experimental models of acute pancreatitis (induced by caerulein, taurolithocholic acid 3-sulfate or palmitoleic acid plus ethanol), MCU knockout failed to reduce the biochemical and histological changes characterizing the severity of local and systemic damage. A possible explanation of this surprising finding is the redundancy of damaging mechanisms activated by the inducers of acute pancreatitis.

Intracellular Ca2+ Signalling in the Pathogenesis of Acute Pancreatitis: Recent Advances and Translational Perspectives

Intracellular Ca²⁺ signalling is a major signal transductional pathway in non-excitable cells, responsible for the regulation of a variety of physiological functions. In the secretory epithelial cells of the exocrine pancreas, such as acinar and ductal cells, intracellular Ca²⁺ elevation regulates digestive enzyme secretion in acini or fluid and ion secretion in ductal cells. Although Ca²⁺ is a uniquely versatile orchestrator of epithelial physiology, unregulated global elevation of the intracellular Ca²⁺ concentration is an early trigger for the development of acute pancreatitis (AP). Regardless of the aetiology, different forms of AP all exhibit sustained intracellular Ca²⁺ elevation as a common hallmark. The release of endoplasmic reticulum (ER) Ca²⁺ stores by toxins (such as bile acids or fatty acid ethyl esters (FAEEs)) or increased intrapancreatic pressure activates the influx of extracellular Ca²⁺ via the Orai1 Ca²⁺ channel, a process known as store-operated Ca²⁺ entry (SOCE). Intracellular Ca²⁺ overload can lead to premature activation of trypsinogen in pancreatic acinar cells and impaired fluid and HCO₃^- secretion in ductal cells. Increased and unbalanced reactive oxygen species (ROS) production caused by sustained Ca²⁺ elevation further contributes to cell dysfunction, leading to mitochondrial damage and cell death. Translational studies of AP identified several potential target molecules that can be modified to prevent intracellular Ca²⁺ overload. One of the most promising drugs, a selective inhibitor of the Orai1 channel that has been shown to inhibit extracellular Ca²⁺ influx and protect cells from injury, is currently being tested in clinical trials. In this review, we will summarise the recent advances in the field, with a special focus on the translational aspects of the basic findings.

Thermodynamic interference with bile acid demicelleization reduces systemic entry and injury during cholestasis

Bile acids (BA), with their large hydrophobic steroid nucleus and polar groups are amphipathic molecules. In bile, these exist as micelles above their critical micellar concentration (CMC). In blood at low concentrations, these exist as monomers, initiating cellular signals. This micellar to monomer transition may involve complex thermodynamic interactions between bile salts alone or with phospholipids, i.e. mixed micelles and the aqueous environment. We therefore went on to test if therapeutically relevant changes in temperature could influence micellar behavior of bile salts, and in turn whether this affected the biological responses in cells, and in vivo. Sodium taurocholate (STC) belongs to a major class of bile salts. STC has a CMC in the 5–8 mM range and its infusion into the pancreatic duct is commonly used to study pancreatitis. We thus studied micellar breakdown of STC using isothermal titration calorimetry (ITC), dynamic light scattering and cryogenic transmission electron microscopy. Under conditions relevant to the in vivo environment (pH 7.4, Na 0.15 M), ITC showed STC to have a U shaped reduction in micellar breakdown between 37 °C and 15 °C with a nadir at 25 °C approaching ≈90% inhibition. This temperature dependence paralleled pancreatic acinar injury induced by monomeric STC. Mixed micelles of STC and 1-palmitoyl, 2-oleyl phosphatidylcholine, a phospholipid present in high proportions in bile, behaved similarly, with ≈75% reduction in micellar breakdown at 25 °C compared to 37 °C. In vivo pancreatic cooling to 25 °C reduced the increase in circulating BAs after infusion of 120 mM (5%) STC into the pancreatic duct, and duct ligation. Lower BA levels were associated with improved cardiac function, reduced myocardial damage, shock, lung injury and improved survival independent of pancreatic injury. Thus micellar breakdown of bile salts is essential for their entry into the systemic circulation, and thermodynamic interference with this may reduce their systemic entry and consequent injury during cholestasis, such as from biliary pancreatitis.

TRPM2-mediated extracellular Ca2+ entry promotes acinar cell necrosis in biliary acute pancreatitis

KEY POINTS

Acute biliary pancreatitis is a significant clinical challenge as currently no specific pharmaceutical treatment exists. Intracellular Ca²⁺ overload, increased reactive oxygen species (ROS) production, mitochondrial damage and intra-acinar digestive enzyme activation caused by bile acids are hallmarks of acute biliary pancreatitis. Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that has recently emerged as an important contributor to oxidative-stress-induced cellular Ca²⁺ overload across different diseases. We demonstrated that TRPM2 is expressed in the plasma membrane of mouse pancreatic acinar and ductal cells, which can be activated by increased oxidative stress induced by H₂ O₂ treatment and contributed to bile acid-induced extracellular Ca²⁺ influx in acinar cells, which promoted acinar cell necrosis in vitro and in vivo. These results suggest that the inhibition of TRPM2 may be a potential treatment option for biliary pancreatitis.

ABSTRACT

Acute biliary pancreatitis poses a significant clinical challenge as currently no specific pharmaceutical treatment exists. Disturbed intracellular Ca²⁺ signalling caused by bile acids is a hallmark of the disease, which induces increased reactive oxygen species (ROS) production, mitochondrial damage, intra-acinar digestive enzyme activation and cell death. Because of this mechanism of action, prevention of toxic cellular Ca²⁺ overload is a promising therapeutic target. Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that has recently emerged as an important contributor to oxidative-stress-induced cellular Ca²⁺ overload across different diseases. However, the expression and possible functions of TRPM2 in the exocrine pancreas remain unknown. Here we found that TRPM2 is expressed in the plasma membrane of mouse pancreatic acinar and ductal cells, which can be activated by increased oxidative stress induced by H₂ O₂ treatment. TRPM2 activity was found to contribute to bile acid-induced extracellular Ca²⁺ influx in acinar cells, but did not have the same effect in ductal cells. The generation of intracellular ROS in response to bile acids was remarkably higher in pancreatic acinar cells compared to isolated ducts, which can explain the difference between acinar and ductal cells. This activity promoted acinar cell necrosis in vitro independently from mitochondrial damage or mitochondrial fragmentation. In addition, bile-acid-induced experimental pancreatitis was less severe in TRPM2 knockout mice, whereas the lack of TRPM2 had no protective effect in cerulein-induced acute pancreatitis. Our results suggest that the inhibition of TRPM2 may be a potential treatment option for biliary pancreatitis.

Asparagine Synthetase Is Highly Expressed at Baseline in the Pancreas Through Heightened PERK Signaling

Asparaginase (ASNase) causes pancreatitis in approximately 10% of leukemia patients, and the mechanisms underlying this painful complication are not known. ASNase primarily depletes circulating asparagine, and the endogenously expressed enzyme, asparagine synthetase (ASNS), replenishes asparagine. ASNS was suggested previously to be highly expressed in the pancreas. In this study, we determined the expression pattern of ASNS in the pancreas and the mechanism for increased pancreatic ASNS abundance. Compared with other organs, ASNS was highly expressed in both the human and mouse pancreas, and, within the pancreas, ASNS was present primarily in the acinar cells. The high baseline pancreatic ASNS was associated with higher baseline activation of protein kinase R-like endoplasmic reticulum kinase (PERK) signaling in the pancreas, and inhibition of PERK in acinar cells lessened ASNS expression. ASNase exposure, but not the common pancreatitis triggers, uniquely up-regulated ASNS expression, indicating that the increase is mediated by nutrient stress. The up-regulation of acinar ASNS with ASNase exposure was owing to increased transcriptional rather than delayed degradation. Knockdown of ASNS in the 266-6 acinar cells provoked acinar cell injury and worsened ASNase-induced injury, whereas ASNS overexpression protected against ASNase-induced injury. In summary, ASNS is highly expressed in the pancreatic acinar cells through heightened basal activation of PERK, and ASNS appears to be crucial to maintaining acinar cell integrity. The implications are that ASNS is especially hardwired in the pancreas to protect against both baseline perturbations and nutrient deprivation stressors, such as during ASNase exposure.

Gut Microbiota-Derived Components and Metabolites in the Progression of Non-Alcoholic Fatty Liver Disease (NAFLD)

Human gut microbiota has been increasingly recognized as a pivotal determinant of non-alcoholic fatty liver disease (NAFLD). Apart from the changes in the composition of gut microbiota, the components and metabolites derived from intestinal microbiota have emerged as key factors in modulating the pathological process of NAFLD. Compelling evidences have revealed that gut microbiota generates a variety of bioactive substances that interact with the host liver cells through the portal vein. These substances include the components derived from bacteria such as lipopolysaccharides, peptidoglycan, DNA, and extracellular vesicles, as well as the metabolites ranging from short-chain fatty acids, indole and its derivatives, trimethylamine, secondary bile acids, to carotenoids and phenolic compounds. The mechanisms underlying the hepatic responses to the bioactive substances from gut bacteria have been associated with the regulation of glycolipid metabolism, immune signaling response, and redox homeostasis. Illuminating the interplay between the unique factors produced from gut microbiome and the liver will provide a novel therapeutical target for NAFLD. The current review highlights the recent advances on the mechanisms by which the key ingredients and metabolites from gut microbiota modulate the development and progression of NAFLD.

Hypoxia-Inducible Factor-1α Knockdown Plus Glutamine Supplementation Attenuates the Predominance of Necrosis over Apoptosis by Relieving Cellular Energy Stress in Acute Pancreatitis

The present study was conducted to investigate the effect and potential mechanism of hypoxia-inducible factor-1α (HIF-1α) genetic inhibition plus glutamine (Gln) supplementation on necrosis-apoptosis imbalance during acute pancreatitis (AP), with a specific focus on the regulations of intracellular energy metabolism status. Wistar rats and AR42J cells were used to establish AP models. When indicated, a HIF-1α knockdown with or without a Gln supplementation was administered. In vivo, local and systemic inflammatory injuries were assessed by serum cytokine measurement, H&E staining, and transmission electron microscope (TEM) observation of pancreatic tissue. In vitro, intracellular energy metabolism status was evaluated by measuring the intracellular adenosine triphosphate (ATP), lactic acid, and Ca²⁺ concentrations and the mitochondrial potential. In addition, changes in the apoptotic activity were analyzed using TUNEL staining in vivo and an apoptosis assay in vitro. HIF-1α knockdown alleviated AP-related inflammatory injury as indicated by the measurements of serum cytokines and examinations of TEM and H&E staining of pancreatic tissues. HIF-1α knockdown played an antioxidative role against AP-related injuries by preventing the increase in the intracellular Ca²⁺ concentration and the decrease in the mitochondrial membrane potential and subsequently by suppressing the glycolysis pathway and increasing energy anabolism in AR42J cells after AP induction. Apoptosis was significantly upregulated when HIF-1α was knocked down before AP induction due to an attenuation of the translocation of nuclear factor-kappa B to the nuclei. Furthermore, these merits of HIF-1α knockdown in the relief of the metabolic stress and upregulation of apoptosis were more significant when Gln was administered concomitantly. In conclusion, Gln-supplemented HIF-1α knockdown might be promising for the future management of AP by relieving the intracellular energy stress, thereby attenuating the predominance of necrosis over apoptosis.

Elevated intracellular trypsin exacerbates acute pancreatitis and chronic pancreatitis in mice

Intra-acinar trypsinogen activation occurs in the earliest stages of pancreatitis and is believed to play important roles in pancreatitis pathogenesis. However, the exact role of intra-acinar trypsin activity in pancreatitis remains elusive. Here, we aimed to examine the specific effects of intra-acinar trypsin activity on the development of pancreatitis using a transgenic mouse model. This transgenic mouse model allowed for the conditional expression of a mutant trypsinogen that can be activated specifically inside pancreatic acinar cells. We found that expression of this active mutated trypsin had no significant effect on triggering spontaneous pancreatitis. Instead, several protective compensatory mechanisms, including SPINK1 and heat shock proteins, were upregulated. Notably, these transgenic mice developed much more severe acute pancreatitis, compared with control mice, when challenged with caerulein. Elevated tissue edema, serum amylase, inflammatory cell infiltration and acinar cell apoptosis were dramatically associated with increased trypsin activity. Furthermore, chronic pathological changes were observed in the pancreas of all transgenic mice, including inflammatory cell infiltration, parenchymal atrophy and cell loss, fibrosis, and fatty replacement. These changes were not observed in control mice treated with caerulein. The alterations in pancreata from transgenic mice mimicked the histological changes common to human chronic pancreatitis. Taken together, we provided in vivo evidence that increased intra-acinar activation of trypsinogen plays an important role in the initiation and progression of both acute and chronic pancreatitis. NEW & NOTEWORTHY Trypsinogen is activated early in pancreatitis. However, the roles of trypsin in the development of pancreatitis have not been fully addressed. Using a genetic approach, we showed trypsin activity is critical for the severity of both acute and chronic pancreatitis.

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.

Drug Displacement Strategy for Treatment of Acute Liver Injury with Cyclodextrin-Liposome Nanoassembly

Biofunctional supramolecular assemblies that combine macrocyclic receptors and amphiphiles are potent drug delivery systems, but optimization and implementation challenges remain. We herein describe a cooperative drug displacement strategy exemplified by the use of cyclodextrin-liposome supramolecular nanoassemblies as a therapy for acute liver injury. The hepatoprotective drug silibinin was solubilized in phosphotyramine-modified β-cyclodextrin, and subsequent encapsulation of the silibinin-cyclodextrin complex in phosphatidylcholine liposomes gave uniformly sized and stable nanoassemblies that accumulated preferentially in the liver of mice. Enzymatic cleavage of the phosphate ester of the β-cyclodextrin resulted in rapid release of the encapsulated silibinin. Significantly, silibinin could be readily displaced by cytotoxic bile acids, thus leading to the removal of excess bile acids from the bodies of mice and the recovery of liver function. Our results demonstrate that cyclodextrin-based nanoassemblies with a dual role of solubilizing a drug and removing toxins constitute a promising therapy for hepatic injury.

Genetics, Cell Biology, and Pathophysiology of Pancreatitis

Since the discovery of the first trypsinogen mutation in families with hereditary pancreatitis, pancreatic genetics has made rapid progress. The identification of mutations in genes involved in the digestive protease-antiprotease pathway has lent additional support to the notion that pancreatitis is a disease of autodigestion. Clinical and experimental observations have provided compelling evidence that premature intrapancreatic activation of digestive proteases is critical in pancreatitis onset. However, disease course and severity are mostly governed by inflammatory cells that drive local and systemic immune responses. In this article, we review the genetics, cell biology, and immunology of pancreatitis with a focus on protease activation pathways and other early events.

Early Intra-Acinar Events in Pathogenesis of Pancreatitis

Premature activation of digestive enzymes in the pancreas has been linked to development of pancreatitis for more than a century. Recent development of novel models to study the role of pathologic enzyme activation has led to advances in our understanding of the mechanisms of pancreatic injury. Colocalization of zymogen and lysosomal fraction occurs early after pancreatitis-causing stimulus. Cathepsin B activates trypsinogen in these colocalized organelles. Active trypsin increases permeability of these organelles resulting in leakage of cathepsin B into the cytosol leading to acinar cell death. Although trypsin-mediated cell death leads to pancreatic injury in early stages of pancreatitis, multiple parallel mechanisms, including activation of inflammatory cascades, endoplasmic reticulum stress, autophagy, and mitochondrial dysfunction in the acinar cells are now recognized to be important in driving the profound systemic inflammatory response and extensive pancreatic injury seen in acute pancreatitis. Chymotrypsin, another acinar protease, has recently been shown be play critical role in clearance of pathologically activated trypsin protecting against pancreatic injury. Mutations in trypsin and other genes thought to be associated with pathologic enzyme activation (such as serine protease inhibitor 1) have been found in familial forms of pancreatitis. Sustained intra-acinar activation of nuclear factor κB pathway seems to be key pathogenic mechanism in chronic pancreatitis. Better understanding of these mechanisms will hopefully allow us to improve treatment strategies in acute and chronic pancreatitis.

Multimodal Transgastric Local Pancreatic Hypothermia Reduces Severity of Acute Pancreatitis in Rats and Increases Survival

BACKGROUND & AIMS

Acute pancreatitis (AP) of different etiologies is associated with the activation of different signaling pathways in pancreatic cells, posing challenges to the development of targeted therapies. We investigated whether local pancreatic hypothermia, without systemic hypothermia, could lessen the severity of AP induced by different methods in rats.

METHODS

A urethane balloon with 2 polyurethane tubes was placed inside the stomach of rats. AP was induced in Wistar rats by the administration of cerulein or glyceryl tri-linoleate (GTL). Then, cold water was infused into the balloon to cool the pancreas. Pancreatic temperatures were selected based on those found to decrease acinar cell injury. An un-perfused balloon was used as a control. Pancreatic and rectal temperatures were monitored, and an infrared lamp or heating pad was used to avoid generalized hypothermia. We collected blood, pancreas, kidney, and lung tissues and analyzed them by histology, immunofluorescence, immunoblot, cytokine and chemokine magnetic bead, and DNA damage assays. The effect of hypothermia on signaling pathways initiated by cerulein and GTL was studied in acinar cells.

RESULTS

Rats with pancreatic cooling developed less severe GTL-induced AP compared with rats that received the control balloon. In acinar cells, cooling decreased the lipolysis induced by GTL, increased the micellar form of its fatty acid, lowered the increase in cytosolic calcium, prevented the loss of mitochondrial membrane potential (by 70%-80%), and resulted in a 40%-50% decrease in the uptake of a fatty acid tracer. In rats with AP, cooling decreased pancreatic necrosis by 48%, decreased serum levels of cytokines and markers of cell damage, and decreased markers of lung and renal damage. Pancreatic cooling increased the proportions of rats surviving 6 hours after induction of AP (to 90%, from <10% of rats that received the control balloon). In rats with cerulein-induced AP, pancreatic cooling decreased pancreatic markers of apoptosis and inflammation.

CONCLUSIONS

In rats with AP, transgastric local pancreatic hypothermia decreases pancreatic necrosis, apoptosis, inflammation, and markers of pancreatitis severity and increases survival.

Research Progress on the Relationship Between Acute Pancreatitis and Calcium Overload in Acinar Cells

Acute pancreatitis is a human disease with multiple causes that leads to autodigestion of the pancreas. There is sufficient evidence to support the key role of sustained increase in cytosolic calcium concentrations in the early pathogenesis of the disease. To clarify the mechanism of maintaining calcium homeostasis in the cell and pathological processes caused by calcium overload would help to research directly targeted therapeutic agents. We will specifically review the following: intracellular calcium homeostasis and regulation, the occurrence of calcium overload in acinar cells, the role of calcium overload in the pathogenesis of AP, the treatment strategy proposed for calcium overload.

Transient High Pressure in Pancreatic Ducts Promotes Inflammation and Alters Tight Junctions via Calcineurin Signaling in Mice

BACKGROUND & AIMS

Pancreatitis after endoscopic retrograde cholangiopancreatography (PEP) is thought to be provoked by pancreatic ductal hypertension, via unknown mechanisms. We investigated the effects of hydrostatic pressures on the development of pancreatitis in mice.

METHODS

We performed studies with Swiss Webster mice, B6129 mice (controls), and B6129 mice with disruption of the protein phosphatase 3, catalytic subunit, βisoform gene (Cnab-/- mice). Acute pancreatitis was induced in mice by retrograde biliopancreatic ductal or intraductal infusion of saline with a constant hydrostatic pressure while the proximal common bile duct was clamped -these mice were used as a model of PEP. Some mice were given pancreatic infusions of adeno-associated virus 6-nuclear factor of activated T-cells-luciferase to monitor calcineurin activity or the calcineurin inhibitor FK506. Blood samples and pancreas were collected at 6 and 24 hours and analyzed by enzyme-linked immunosorbent assay, histology, immunohistochemistry, or fluorescence microscopy. Ca2+ signaling and mitochondrial permeability were measured in pancreatic acinar cells isolated 15 minutes after PEP induction. Ca2+-activated phosphatase calcineurin within the pancreas was tracked in vivo over 24 hours.

RESULTS

Intraductal pressures of up to 130 mm Hg were observed in the previously reported model of PEP; we found that application of hydrostatic pressures of 100 and 150 mm Hg for 10 minutes consistently induced pancreatitis. Pancreatic tissues had markers of inflammation (increased levels of interleukin [IL] 6, IL1B, and tumor necrosis factor), activation of signal transducer and activator of transcription 3, increased serum amylase and IL6, and loss of tight junction integrity. Transiently high pressures dysregulated Ca2+ processing (reduced Ca2+ oscillations and an increased peak plateau Ca2+ signal) and reduced the mitochondrial membrane potential. We observed activation of pancreatic calcineurin in the pancreas in mice. Cnab-/- mice, which lack the catalytic subunit of calcineurin, and mice given FK506 did not develop pressure-induced pancreatic inflammation, edema, or loss of tight junction integrity.

CONCLUSIONS

Transient high ductal pressure produces pancreatic inflammation and loss of tight junction integrity in a mouse model of PEP. These processes require calcineurin signaling. Calcineurin inhibitors might be used to prevent acute pancreatitis that results from obstruction.

RCAN1 is a marker of oxidative stress, induced in acute pancreatitis

BACKGROUND

To date, there still is a lack of specific acute pancreatitis markers and specifically an early marker that can reliably predict disease severity. The inflammatory response in acute pancreatitis is mediated in part through oxidative stress and calcineurin-NFAT (Nuclear Factor of Activated T-cells) signaling, which is inducing its own negative regulator, regulator of calcineurin 1 (RCAN1). Caerulein induction is a commonly used in vivo model of experimental acute pancreatitis. Caerulein induces CN-NFAT signaling, reactive oxygen species and inflammation.

METHODS

To screen for potential markers of acute pancreatitis, we used the caerulein model of experimental acute pancreatitis (AP) in C57Bl/6 J mice. Pancreata from treated and control mice were used for expression profiling. Promising gene candidates were validated in cell culture experiments using primary murine acinar cells and rat AR42J cells. These candidates were then further tested for their usefulness as biomarkers in mouse and human plasma.

RESULTS

We identified a number of novel genes, including Regulator of calcineurin 1 (Rcan1) and Sestrin 2 (Sesn2) and demonstrated that they are induced by oxidative stress, by stimulation with H₂O₂ and by inhibiting caerulein stimulated expression with the antioxidant N-acetylcysteine. We found Rcan1 protein to be significantly elevated in AP-induced mouse plasma as well as in plasma from AP patients.

CONCLUSION

We demonstrated that Rcan1 is regulated by oxidative stress and identified RCAN1 as a potential diagnostic marker of AP.

The Importance of Aquaporin 1 in Pancreatitis and Its Relation to the CFTR Cl- Channel

Aquaporins (AQPs) facilitate the transepithelial water flow involved in epithelial fluid secretion in numerous tissues; however, their function in the pancreas is less characterized. Acute pancreatitis (AP) is a serious disorder in which specific treatment is still not possible. Accumulating evidence indicate that decreased pancreatic ductal fluid secretion plays an essential role in AP; therefore, the aim of this study was to investigate the physiological and pathophysiological role of AQPs in the pancreas. Expression and localization of AQPs were investigated by real-time PCR and immunocytochemistry, whereas osmotic transmembrane water permeability was estimated by the dye dilution technique, in Capan-1 cells. The presence of AQP1 and CFTR in the mice and human pancreas were investigated by immunohistochemistry. Pancreatic ductal HCO₃^- and fluid secretion were studied on pancreatic ducts isolated from wild-type (WT) and AQP1 knock out (KO) mice using microfluorometry and videomicroscopy, respectively. In vivo pancreatic fluid secretion was estimated by magnetic resonance imaging. AP was induced by intraperitoneal injection of cerulein and disease severity was assessed by measuring biochemical and histological parameters. In the mice, the presence of AQP1 was detected throughout the whole plasma membrane of the ductal cells and its expression highly depends on the presence of CFTR Cl^- channel. In contrast, the expression of AQP1 is mainly localized to the apical membrane of ductal cells in the human pancreas. Bile acid treatment dose- and time-dependently decreased mRNA and protein expression of AQP1 and reduced expression of this channel was also demonstrated in patients suffering from acute and chronic pancreatitis. HCO₃^- and fluid secretion significantly decreased in AQP1 KO versus WT mice and the absence of AQP1 also worsened the severity of pancreatitis. Our results suggest that AQP1 plays an essential role in pancreatic ductal fluid and HCO₃^- secretion and decreased expression of the channel alters fluid secretion which probably contribute to increased susceptibility of the pancreas to inflammation.

Region-specific proteolysis differentially modulates type 2 and type 3 inositol 1,4,5-trisphosphate receptor activity in models of acute pancreatitis

Fine-tuning of the activity of inositol 1,4,5-trisphosphate receptors (IP₃R) by a diverse array of regulatory inputs results in intracellular Ca²⁺ signals with distinct characteristics. These events allow the activation of specific downstream effectors. We reported previously that region-specific proteolysis represents a novel regulatory event for type 1 IP₃R (R1). Specifically, caspase-fragmented R1 display a marked increase in single-channel open probability. More importantly, the distinct characteristics of the Ca²⁺ signals elicited via fragmented R1 can activate alternate downstream effectors. In this report, we expand these studies to investigate whether all IP₃R subtypes are regulated by proteolysis. We now show that type 2 and type 3 IP₃R (R2 and R3, respectively) are proteolytically cleaved in rodent models of acute pancreatitis. Surprisingly, fragmented IP₃R retained tetrameric architecture, remained embedded in endoplasmic reticulum membranes and were not functionally disabled. Proteolysis was associated with a marked attenuation of the frequency of Ca²⁺ signals in pancreatic lobules. Consistent with these data, expression of DNAs encoding complementary R2 and R3 peptides mimicking fragmented receptors at particular sites, resulted in a significant decrease in the frequency of agonist-stimulated Ca²⁺ oscillations. Further, proteolysis of R2 resulted in a marked decrease in single-channel open probability. Taken together, proteolytic fragmentation modulates R2 and R3 activity in a region-specific manner, and this event may contribute to the altered Ca²⁺ signals in pancreatic acinar cells during acute pancreatitis.

SOCE induced calcium overload regulates autophagy in acute pancreatitis via calcineurin activation

Acute pancreatitis (AP) is an acute inflammatory process of the pancreas that is characterized by inflammation, edema, vacuolization and necrosis, which has significant morbidity and lethality. The pathogenesis of AP has not been established completely. An early and critical feature of AP is the aberrant signaling of Calcium (Ca2+) within the pancreatic acinar cell, termed Ca2+ overload. Store-operated Ca2+ (SOC) channels are the principal Ca2+ influx channels that contribute to Ca2+ overload in pancreatic acinar cells. Store-operated Ca2+ entry (SOCE) has been proved to be a key pathogenic step in AP development that leads to trypsin activation, inflammation and vacuolization. However, the molecular mechanisms are still poorly understood. By establishing Ca2+ overload model and mouse AP model using caerulein, we found that caerulein triggered SOCE via inducing interaction between STIM1 and Orai1, which activated calcineurin (CaN); CaN activated the nuclear factor of activated T cells (NFAT) and transcription factor EB (TFEB), thus promoting the transcriptional activation of multiple chemokines genes and autophagy-associated genes respectively. To the best of our knowledge, this is the first evidence showing that SOCE activates TFEB via CaN activation, which may have noticeable longer-term effects on autophagy and vacuolization in AP development. Our findings reveal the role for SOCE/CaN in AP development and provide potential targets for AP treatment.

Nitric oxide signals are interlinked with calcium signals in normal pancreatic stellate cells upon oxidative stress and inflammation

The mammalian diffuse stellate cell system comprises retinoid-storing cells capable of remarkable transformations from a quiescent to an activated myofibroblast-like phenotype. Activated pancreatic stellate cells (PSCs) attract attention owing to the pivotal role they play in development of tissue fibrosis in chronic pancreatitis and pancreatic cancer. However, little is known about the actual role of PSCs in the normal pancreas. These enigmatic cells have recently been shown to respond to physiological stimuli in a manner that is markedly different from their neighbouring pancreatic acinar cells (PACs). Here, we demonstrate the capacity of PSCs to generate nitric oxide (NO), a free radical messenger mediating, for example, inflammation and vasodilatation. We show that production of cytosolic NO in PSCs is unambiguously related to cytosolic Ca²⁺ signals. Only stimuli that evoke Ca²⁺ signals in the PSCs elicit consequent NO generation. We provide fresh evidence for the striking difference between signalling pathways in PSCs and adjacent PACs, because PSCs, in contrast to PACs, generate substantial Ca²⁺-mediated and NOS-dependent NO signals. We also show that inhibition of NO generation protects both PSCs and PACs from necrosis. Our results highlight the interplay between Ca²⁺ and NO signalling pathways in cell–cell communication, and also identify a potential therapeutic target for anti-inflammatory therapies.

Acinar injury and early cytokine response in human acute biliary pancreatitis

Clinical acute pancreatitis (AP) is marked by an early phase of systemic inflammatory response syndrome (SIRS) with multiorgan dysfunction (MODS), and a late phase characterized by sepsis with MODS. However, the mechanisms of acinar injury in human AP and the associated systemic inflammation are not clearly understood. This study, for the first time, evaluated the early interactions of bile acid induced human pancreatic acinar injury and the resulting cytokine response. We exposed freshly procured resected human pancreata to taurolithocolic acid (TLCS) and evaluated for acinar injury, cytokine release and interaction with peripheral blood mononuclear cells (PBMCs). We observed autophagy in acinar cells in response to TLCS exposure. There was also time-dependent release of IL-6, IL-8 and TNF-α from the injured acini that resulted in activation of PBMCs. We also observed that cytokines secreted by activated PBMCs resulted in acinar cell apoptosis and further cytokine release from them. Our data suggests that the earliest immune response in human AP originates within the acinar cell itself, which subsequently activates circulating PBMCs leading to SIRS. These findings need further detailed evaluation so that specific therapeutic targets to curb SIRS and resulting early adverse outcomes could be identified and tested.

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.

The bile acid receptor FXR attenuates acinar cell autophagy in chronic pancreatitis

The functional relationship between bile acid (BA) and autophagy has not been evaluated in the context of pancreatitis. Here we investigated whether BA and their nuclear farnesoid X receptor (FXR) modulate autophagy and the development of pancreatitis. FXR expression, autophagy, apoptosis and necroptosis were determined in human chronic pancreatitis (CP) tissue in vivo and in pancreatic cells lines in vitro by means of real-time PCR, immunoblots and immunofluorescence. Pancreatic cell lines exposed to the most abundant BAs glycochenodeoxycholate (GCDC) and taurocholic acid (TCA) increased the expression of nuclear FXR and diminished that of the essential autophagy-related protein ATG7. BA was also elevated in pancreatic tissues from CP patients, correlating with elevated FXR and curtailed ATG7 expression with locally reduced autophagic activity. This was accompanied by an increased manifestation of CP hallmarks including apoptosis, necroptosis, inflammation and fibrosis. The present results suggest a cascade of events in which local accumulation of BA signals via FXR to suppress autophagy in pancreatic acinar cells, thereby unleashing acinar cell apoptosis and necroptosis. Thus, BA may cause CP by suppressing autophagy and exacerbating acinar cell apoptosis and necroptosis.

Role of hyperlipidimia in pathogenesis of acute pancreatitis

Recently, many studies have focused on the relationship between hyperlipidemia (HL) and acute pancreatitis (AP). HL is a significant cause of AP, but it may also be secondary to AP. Hypertriglyceridemia (HTG) and hypercholesterolemia (HTC) are two types of HL. It is generally believed that HTG may induce AP and AP could increase the incidence of HTG. However, the relationship between HTC and AP has not yet confirmed. The diagnosis of hyperlipidemic acute pancreatitis (HLAP) needs not only the evidence of AP, but also an elevated level of serum lipids. Nevertheless, there still exist some divergent opinions regarding the level of serum lipids. Since the diagnosis of HLAP is critical for the therapy and prognosis, the lack of unified diagnostic criteria poses a great challenge for clinicians.

Phenolic compounds isolated from Dioscorea zingiberensis protect against pancreatic acinar cells necrosis induced by sodium taurocholate

One new bibenzyl (1) and one new phenanthrene (2), together with two known bibenzyls (3-4) and four known diarylheptanoids (5-8) were isolated from the rhizomes of Dioscorea zingiberensis. The structures of 1-2 were elucidated by spectroscopic methods including 1D and 2D NMR. Phenols 1-8 were evaluated for their anti-pancreatitic activities on sodium taurocholate (NaT)-induced pancreatic acinars necrosis. Notably, 0.5mM of compound 6 exhibited comparable inhibitory effect with 5mM of caffeine. Furthermore, compound 6 prevented the ATP depletion and excessive ROS production which could be also involved in mitochondria-mediated injuries in acute pancreatitis. As a result, compound 6 has been demonstrated to be a potential candidate for mediating mitochondrial dysfunction to prevent pancreatic necrosis. This study is also the first report on the isolation of bibenzyls and diarylheptanoids from this plant.

Comprehensive analysis of microRNA signature of mouse pancreatic acini: overexpression of miR-21-3p in acute pancreatitis

In the current study, we have characterized the global miRNA expression profile in mouse pancreatic acinar cells and during acute pancreatitis using next-generation RNA sequencing. We identified 324 known and six novel miRNAs that are expressed in mouse pancreatic acinar cells. In the basal state, miR-148a-3p, miR-375-3p, miR-217-5p, and miR-200a-3p were among the most abundantly expressed, whereas miR-24-5p and miR-421-3p were the least abundant. Treatment of acinar cells with caerulein (100 nM) and taurolithocholic acid 3-sulfate [TLC-S (250 μM)] induced numerous changes in miRNA expression profile. In particular, we found significant overexpression of miR-21-3p in acini treated with caerulein and TLC-S. We further looked at the expression of miR-21-3p in caerulein, l-arginine, and caerulein + LPS-induced acute pancreatitis mouse models and found 12-, 21-, and 50-fold increased expression in the pancreas, respectively. In summary, this is the first comprehensive analysis of global miRNA expression profile of mouse pancreatic acinar cells in normal and disease conditions. Our analysis shows that miR-21-3p expression level correlates with the severity of the disease.