Bile acids induce Ca2+ release from both the endoplasmic reticulum and acidic intracellular calcium stores through activation of inositol trisphosphate receptors and ryanodine receptors

Cholic acid activation of GPBAR1 does not induce or exacerbate acute pancreatitis but promotes exocrine pancreatic secretion

Obstruction of bile ducts due to gallstones can lead to biliary acute pancreatitis (BAP). According to Perides et al., G protein-coupled bile acid receptor-1 (GPBAR1) mediates BAP. However, Zi's findings suggest that GPR39, rather than GPBAR1, mediates TLCAS-induced increases in cytosolic calcium and acinar cell necrosis, casting doubt on the role of GPBAR1 in BAP. Numerous G protein-coupled receptors on pancreatic acinar cells utilize Ca2+ and cyclic adenosine monophosphate (cAMP) as second messengers to manage pancreatic exocrine secretion, with significant cross-talk between these signals. The primary bile acid cholic acid (CA) and its conjugated forms are predominant in the human gallbladder. This study aimed to clarify the role and physiological significance of GPBAR1 by investigating the physiological and pathological effects of CA activation on GPBAR1 in pancreatic acinar cells. Isolated rat pancreatic acinar cells were treated with CA and CCK in vitro to observe the effect of CA-induced cAMP signaling on CCK-induced physiological and pathological calcium signaling. In vivo evaluations involved reverse biliopancreatic duct injections of 5 % sodium taurocholate (STC) or 5 % CA in rats. CA induced intracellular cAMP signaling in a concentration-dependent manner without increasing the intracellular Ca2+ concentration. CA did not independently cause calcium overload or enzyme activation, nor did it exacerbate calcium overload or enzyme activation from high-dose CCK. Reverse biliopancreatic duct injections of 5 % CA did not cause acute pancreatitis in the rats. Transcriptomic analysis revealed that 50 μM CA induced changes in gene expression related to protein synthesis in the endoplasmic reticulum and ribosomes. Furthermore, 50 μM CA accelerated the calcium waves and increased the enzyme secretion induced by CCK. GPBAR1 was found on the basolateral membrane in rat pancreatic tissue rather than near the apical region of acinar cells. GPBAR1 activation is not crucial for BAP activity but may play a role in bile acid regulation of pancreatic exocrine secretion, suggesting that GPBAR1 is a potential therapeutic target for pancreatic exocrine insufficiency.

Ca2+ signaling of pancreatic acinar cells in malignant hyperthermia susceptibility

BACKGROUND

Malignant hyperthermia susceptibility (MHS) and acute pancreatitis (AP) share a common cellular pathomechanism that is Ca2+-overload of the muscle fiber and the pancreatic acinar cell (PAC). In the muscle, gain-of-function mutations of the ryanodine receptor (RyR1) make the Ca2+-release mechanism hypersensitive to certain ligands, including Ca2+, volatile anaesthetics and succinylcholine, creating a medical emergency when the patient is exposed to these drugs. As RyR1 was shown to contribute to Ca2+-overload in PAC, we presumed that pancreata of MHS individuals are more prone to AP. Accordingly, a recent case study reported coincidence of MHS with recurrent AP, indicating a pathological link between the two diseases.

METHODS

We tested if MHS poses a risk for AP in mice carrying the Y522S MHS mutation. Fluorescent Ca2+ imaging was performed in PACs. Conventional histopathological analysis and plazma amylase measurement was performed using a cerulein-induced pancreatitis mouse model.

RESULTS

The intracellular Ca2+-signals of PACs from MHS mice were slightly bigger then in wild type when stimulated with 0.2 and 2 μM carbachol (cch) or with 1 and 5 mM bile acid (taurocholic acid). Store-operated-Ca2+-entry was also higher in PACs from MHS mice. Nevertheless, histopathological analysis and plasma amylase levels did not indicate more severe AP in MHS.

CONCLUSIONS

These results suggest that the Y522S RyR1 mutation alter the Ca2+-homeostasis in PACs, but not as much as to cause or aggravate AP.

Computational Model of Complex Calcium Dynamics: Store Operated Ca2+ Channels and Mitochondrial Associated Membranes in Pancreatic Acinar Cells

This proposed model explores the intricate Ca2+ dynamics within the pancreatic acinar cells (PACs) by emphasizing the role of store-operated Ca2+ entry (SOCE) and the mitochondrial-associated membranes (MAMs) in the secretory region (apical) of the PACs. Traditionally, Ca2+ releases from the endoplasmic reticulum (ER) via calcium-induced calcium release (CICR). It has been shown to be important in regulating functions such as secretion of digestive enzymes in PACs. However, this model posits that upon the depletion of Ca2+ in the ER, the signaling protein stromal interaction molecule (STIM1) is activated. Activated STIM1, then facilitates the opening of Orai channels, allowing Ca2+ influx through the store-operated calcium channels (SOCCs). The model highlights the complexity of the Ca2+ dynamics, and the importance of SOCE and MAMs in the PACs Ca2+ homeostasis. The numerical and bifurcation analysis illustrate how changes in agonist concentrations can lead to the diverse Ca2+ oscillation patterns, such as thin to broader oscillations, sinusoidal patterns, and baseline fluctuations, driven by the feedback mechanisms involving Ca2+ and inositol 1,4,5 trisphosphate (IP3). This understanding could have broader implications for cellular physiology and the development of therapies targeting Ca2+ signaling pathways.

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.

Pancreatitis in RYR1-related disorders

Mutations in RYR1 encoding the ryanodine receptor (RyR) skeletal muscle isoform (RyR1) are a common cause of inherited neuromuscular disorders. Despite its expression in a wide range of tissues, non-skeletal muscle manifestations associated with RYR1 mutations have only been rarely reported. Here, we report three patients with a diagnosis of Central Core Disease (CCD), King-Denborough Syndrome (KDS) and Malignant Hyperthermia Susceptibility (MHS), respectively, who in addition to their (putative) RYR1-related disorder also developed symptoms and signs of acute pancreatitis. In two patients, episodes were recurrent, with severe multisystem involvement and sequelae. RyR1-mediated calcium signalling plays an important role in normal pancreatic function but has also been critically implicated in the pathophysiology of acute pancreatitis, particularly in bile acid- and ethanol-induced forms. Findings from relevant animal models indicate that pancreatic damage in these conditions may be ameliorated through administration of the specific RyR1 antagonist dantrolene and other compounds modifying pancreatic metabolism including calcium signalling. These observations suggest that patients with RYR1 gain-of-function variants may be at increased risk of developing acute pancreatitis, a condition which should therefore be considered in the health surveillance of such individuals.

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

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

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

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

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

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

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.

Anti-inflammatory and anti-necrotic effects of lectins from Canavalia ensiformis and Canavalia brasiliensis in experimental acute pancreatitis

Lectins isolated from Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr) are promising molecules to prevent cell death. Acute pancreatitis, characterized by acinar cell necrosis and inflammation, presents significant morbidity and mortality. This study has investigated the effects of ConA and ConBr in experimental acute pancreatitis and pancreatic acinar cell death induced by bile acid. Pancreatitis was induced by retrograde pancreatic ductal injection of 3% sodium taurocholate (Na-TC) in male Swiss mice. ConA or ConBr (0.1, 1 or 10 mg/kg) were intravenously applied to mice 1 h and 12 h after induction. After 24 h, the severity of pancreatitis was evaluated by serum amylase and lipase, histopathological changes and myeloperoxidase assay. Pancreatic acinar cells were incubated with ConA (200 µg/ml) or ConBr (200 µg/ml) and taurolithocholic acid 3-sulfate (TLCS; 500 µM). Necrosis and changes in mitochondrial membrane potential (ΔѰm) were detected by fluorescence confocal microscopy. Treatment (post-insult) with ConA and ConBr decreased pancreatic damage caused by retrograde injection of Na-TC in mice, reducing pancreatic neutrophil infiltration, edema and necrosis. In addition, ConA and ConBr decreased pancreatic acinar cell necrosis and depolarization of ΔѰm caused by TLCS. The inhibition of necrosis was prevented by the lectin domain blockade. In conclusion, ConA and ConBr markedly inhibited in vitro and in vivo damage, effects partly dependent on the interaction with mannose residues on acinar cells. These data support the potential application of these proteins for treatment of acute pancreatitis.

Bile acid- and ethanol-mediated activation of Orai1 damages pancreatic ductal secretion in acute pancreatitis

KEY POINTS

Sustained intracellular Ca²⁺ overload in pancreatic acinar and ductal cells is a hallmark of biliary and alcohol-induced acute pancreatitis, which leads to impaired ductal ion and fluid secretion. Orai1 is a plasma membrane Ca²⁺ channel that mediates extracellular Ca²⁺ influx upon endoplasmic reticulum Ca²⁺ depletion. Our results showed that Orai1 is expressed on the luminal plasma membrane of the ductal cells and selective Orai1 inhibition impaired Stim1-dependent extracellular Ca²⁺ influx evoked by bile acids or ethanol combined with non-oxidative ethanol metabolites. The prevention of sustained extracellular Ca²⁺ influx protected ductal cell secretory functions in in vitro models and maintained exocrine pancreatic secretion in in vivo AP models. Orai1 inhibition prevents the bile acid-, and alcohol-induced damage of the pancreatic ductal secretion and holds the potential of improving the outcome of acute pancreatitis.

ABSTRACT

Regardless of its etiology, sustained intracellular Ca²⁺ overload is a well-known hallmark of acute pancreatitis (AP). Toxic Ca²⁺ elevation induces pancreatic ductal cell damage characterized by impaired ion- and fluid secretion -essential to wash out the protein-rich fluid secreted by acinar cells while maintaining the alkaline intra-ductal pH under physiological conditions- and mitochondrial dysfunction. While prevention of ductal cell injury decreases the severity of AP, no specific drug target has yet been identified in the ductal cells. Although Orai1 -a store operated Ca²⁺ influx channel- is known to contribute to sustained Ca²⁺ overload in acinar cells, details concerning its expression and function in ductal cells are currently lacking. In this study, we demonstrate that functionally active Orai1 channels reside dominantly in the apical plasma membrane of pancreatic ductal cells. Selective CM5480-mediated Orai1 inhibition impairs Stim1-dependent extracellular Ca²⁺ influx evoked by bile acids or ethanol combined with non-oxidative ethanol metabolites. Furthermore, prevention of sustained extracellular Ca²⁺ influx protects ductal cell secretory function in vitro and decrease pancreatic ductal cell death. Finally, Orai1-inhibition partially restores and maintains proper exocrine pancreatic secretion in in vivo AP models. In conclusion, our results indicate that Orai1 inhibition prevents AP-related ductal cell function impairment and holds the potential of improving disease outcome. Abstract figure legend  This article is protected by copyright. All rights reserved.

Salidroside alleviates taurolithocholic acid 3-sulfate-induced AR42J cell injury

OBJECTIVES

To investigate the protective effects of Salidroside (Sal) on AP cell model induced by taurolithocholic acid 3-sulfate (TLC-S) as well as its underlying mechanism.

METHODS

AR42J cells were divided into normal group (N group), AP cell model group (Mod group), Sal treated alone group (S+N group) and Sal treated AP cell model group (S+Mod group). The cell viability was examined by CCK-8 assay. Secretion of lipase and trypsin by AR42J cells, quantified using commercial assay kits, was used as the markers of TLC-S-induced pancreatitis. The levels of TNF-α, IL-1β, IL-8, IL-6 and IL-10 in the cell supernatant were measured by ELISA. The effect of Sal on molecules in the NF-κB signaling pathway and autophagy was investigated by qRT-PCR and western blot.

RESULTS

The decreased cell viability in Mod group was increased by Sal (P < 0.01). The upheaved activities of lipase and trypsin in AP cell model were declined by Sal (P < 0.01). The levels of TNF-α, IL-1β, IL-8 and IL-6 in the cell supernatant, Beclin-1 and LC3-Ⅱ mRNA and protein, p-p65/p65 protein, which were increased in AP cell model, were decreased by Sal; and IL-10 in the cell supernatant, LAMP2 mRNA and protein, p-IκBα/IκBα protein which was declined in AP cell model, was increased by Sal (P < 0.05 or 0.01). There were no significant differences in all indexes between the N and S+N groups (P > 0.05).

CONCLUSIONS

Sal alleviated AR42J cells injury induced by TLC-S, inhibited the inflammatory responses and modulated the autophagy, mainly through inhibiting the NF-κB signaling pathway.

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.

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.

Nicotine stimulates ion transport via metabotropic β4 subunit containing nicotinic ACh receptors

Background and Purpose

Mucociliary clearance is an innate immune process of the airways, essential for removal of respiratory pathogens. It depends on ciliary beat and ion and fluid homeostasis of the epithelium. We have shown that nicotinic ACh receptors (nAChRs) activate ion transport in mouse tracheal epithelium. Yet the receptor subtypes and signalling pathways involved remained unknown.

Experimental Approach

Transepithelial short circuit currents (I_SC) of freshly isolated mouse tracheae were recorded using the Ussing chamber technique. Changes in [Ca²⁺]_i were studied on freshly dissociated mouse tracheal epithelial cells.

Key Results

Apical application of the nAChR agonist nicotine transiently increased I_SC. The nicotine effect was abolished by the nAChR antagonist mecamylamine. α‐Bungarotoxin (α7 antagonist) had no effect. The agonists epibatidine (α3β2, α4β2, α4β4 and α3β4) and A‐85380 (α4β2 and α3β4) increased I_SC. The antagonists dihydro‐β‐erythroidine (α4β2, α3β2, α4β4 and α3β4), α‐conotoxin MII (α3β2) and α‐conotoxin PnIA (α3β2) reduced the nicotine effect. Nicotine‐ and epibatidine‐induced currents were unaltered in β2^−/−mice, but in β4^−/− mice no increase was observed. In the presence of thapsigargin (endoplasmatic reticulum Ca²⁺‐ATPase inhibitor) or the ryanodine receptor antagonists JTV‐519 and dantrolene there was a reduction in the nicotine‐effect, indicating involvement of Ca²⁺ release from intracellular stores. Additionally, the PKA inhibitor H‐89 and the TMEM16A (Ca²⁺‐activated chloride channel) inhibitor T16Ainh‐A01 significantly reduced the nicotine‐effect.

Conclusion and Implications

α3β4 nAChRs are responsible for the nicotine‐induced current changes via Ca²⁺ release from intracellular stores, PKA and ryanodine receptor activation. These nAChRs might be possible targets to stimulate chloride transport via TMEM16A.

TRPM2 channel-mediated cell death: An important mechanism linking oxidative stress-inducing pathological factors to associated pathological conditions

Oxidative stress resulting from the accumulation of high levels of reactive oxygen species is a salient feature of, and a well-recognised pathological factor for, diverse pathologies. One common mechanism for oxidative stress damage is via the disruption of intracellular ion homeostasis to induce cell death. TRPM2 is a non-selective Ca2+-permeable cation channel with a wide distribution throughout the body and is highly sensitive to activation by oxidative stress. Recent studies have collected abundant evidence to show its important role in mediating cell death induced by miscellaneous oxidative stress-inducing pathological factors, both endogenous and exogenous, including ischemia/reperfusion and the neurotoxicants amyloid-β peptides and MPTP/MPP+ that cause neuronal demise in the brain, myocardial ischemia/reperfusion, proinflammatory mediators that disrupt endothelial function, diabetogenic agent streptozotocin and diabetes risk factor free fatty acids that induce loss of pancreatic β-cells, bile acids that damage pancreatic acinar cells, renal ischemia/reperfusion and albuminuria that are detrimental to kidney cells, acetaminophen that triggers hepatocyte death, and nanoparticles that injure pericytes. Studies have also shed light on the signalling mechanisms by which these pathological factors activate the TRPM2 channel to alter intracellular ion homeostasis leading to aberrant initiation of various cell death pathways. TRPM2-mediated cell death thus emerges as an important mechanism in the pathogenesis of conditions including ischemic stroke, neurodegenerative diseases, cardiovascular diseases, diabetes, pancreatitis, chronic kidney disease, liver damage and neurovascular injury. These findings raise the exciting perspective of targeting the TRPM2 channel as a novel therapeutic strategy to treat such oxidative stress-associated diseases.

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.

The Effects of Inositol Metabolism in Pregnant Women on Offspring in the North and South of China

Background

Inositol is an essential nutrient for cell growth, survival and embryonic development. Myo-inositol is the predominant form in natural. To investigate the correlation between inositol metabolism and embryonic development, we assessed the metabolic characteristics of myo-inositol, phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂) and phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P₃) of pregnant women in the North China (Yangquan and Weihai) and South China (Nanchang and Haikou) China.

Material/Methods

All data were collected by face-to-face interview during pregnant women health visits using a questionnaire. Plasma levels of myo-inositol, PI(4,5)P₂ and PI(3,4,5)P₃ from 89 randomly collected pregnant women were detected by gas chromatography-mass spectrometry and enzyme linked immunosorbent assay.

Results

A total of 400 pregnant women were included in this survey. The plasma levels of myo-inositol and PI(4,5)P₂ in the North China group of pregnant women were significantly higher than that in the South China group (P<0.01). The birth weight of fetuses in the North China group was heavier than that in the South China group (P<0.01). The birth length of fetuses in Yangquan was the longest among the 4 cities (P<0.01). The incidence rate of birth defects was 3.05% in the North China group, and 0.0% in the South China group. In bivariate linear correlation analysis, the body weight correlated with myo-inositol (r=0.5044, P<0.0001), PI(4,5)P₂ (r=0.5950, P<0.0001) and PI(3,4,5)P₃ (r=0.4710, P<0.0001), the body length was correlated with PI(4,5)P₂ (r=0.3114, P=0.0035) and PI(3,4,5)P₃ (r=0.2638, P<0.0130).

Conclusions

The plasma levels of myo-inositol and PI(4,5)P₂ in pregnant women had significant difference between the North and the South of China, which might be correlated with fetal development and birth defects.

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.

Case Studies in Neuroscience: Lack of inhibitory synaptic plasticity in the substantia nigra pars reticulata of a patient with lithium-induced tremor

Tremor is a well-known side effect from many psychiatric medications, including lithium and dopamine antagonists. In patients whose psychiatric symptoms are stabilized and only respond to certain medications, deep brain stimulation may offer relief of the consequent motor complications. We report the case of an elderly male with disabling tremor related to lithium therapy for bipolar affective disorder, who was subsequently treated with deep brain stimulation. In this patient, we obtained recordings from the substantia nigra pars reticulata and performed a high-frequency stimulation protocol that robustly elicits long-term potentiation (LTP)-like changes in patients with Parkinson's disease. We hypothesized that in this patient, who did not have Parkinson's disease, the levels of inhibitory plasticity would be much greater. However, we found an unanticipated lack of plasticity in the patient with lithium-induced tremor, compared with two de novo control patients with Parkinson's disease. This patient was successfully treated with deep brain stimulation in the vicinity of the ventral oral posterior nucleus, an area of the thalamus that receives inputs from the basal ganglia. We postulate that the lithium-induced blockade of LTP may bring about motor complications such as tremor while simultaneously contributing to the therapeutic mechanism for treating the symptoms of psychiatric disorders such as bipolar affective disorder.NEW & NOTEWORTHY Use of a dual-microelectrode technique enabled us to compare long-term potentiation (LTP)-like changes in a patient with lithium-induced tremor to that of patients with Parkinson's disease. This study corroborated the findings in rodent brain slices that chronic lithium treatment may block LTP. Whereas a deficit in LTP may underlie the therapeutic mechanism for treating psychiatric disorders such as bipolar affective disorder, it may simultaneously contribute to consequent appearance of tremor.

miR‑92a‑3p regulates trypsinogen activation via Egr1 in AR42J cells

Acute pancreatitis (AP) exhibits high morbidity and mortality rates. The onset of AP is characterized by early trypsinogen activation. The present study aimed to investigate the expression of microRNA (miR)-92a-3p and early growth response protein 1 (Egr1), and the effect of miR-92a-3p on trypsinogen activation in the pancreatic exocrine cell line AR42J. mRNA and miRNA microarrays were used to identify differentially expressed mRNAs and miRNAs in AR42J cells. A miRNA-mRNA network was constructed using bioinformatics software, and Egr1 and its regulated miRNA subnetworks were identified by reviewing previous literature. The results suggested that miR-92a-3p could bind to Egr1 3′untranslated region sequence. Subsequently, miR-92a-3p mimic and inhibitor were used to transfect AR42J cells. Following transfection, reverse transcription-quantitative PCR and western blotting were performed to detect Egr1 expression. Furthermore, AR42J cells were cotransfected with miR-92a-3p inhibitor and small interfering (si)-Egr1. The trypsinogen activation rate of AR42J cells was measured by flow cytometry. Microarrays and bioinformatics results indicated that Egr1 may be a target gene of miR-92a-3p. In addition, the present study suggested that miR-92a-3p downregulated Egr1 in vitro and that miR-92a-3p and Egr1 expression was associated with trypsinogen activation. Furthermore, miR-92a-3p inhibitor reversed the effect of si-Egr1 on trypsinogen activation. In conclusion, miR-92a-3p may negatively regulate the activation of trypsinogen in AR42J cells via Egr1.

Effect of Docosahexaenoic Acid on Ca2+ Signaling Pathways in Cerulein-Treated Pancreatic Acinar Cells, Determined by RNA-Sequencing Analysis

Intracellular Ca²⁺ homeostasis is commonly disrupted in acute pancreatitis. Sustained Ca²⁺ release from internal stores in pancreatic acinar cells (PACs), mediated by inositol triphosphate receptor (IP3R) and the ryanodine receptor (RyR), plays a key role in the initiation and propagation of acute pancreatitis. Pancreatitis induced by cerulein, an analogue of cholecystokinin, causes premature activation of digestive enzymes and enhanced accumulation of cytokines and Ca²⁺ in the pancreas and, as such, it is a good model of acute pancreatitis. High concentrations of the omega-3 fatty acid docosahexaenoic acid (DHA) inhibit inflammatory signaling pathways and cytokine expression in PACs treated with cerulein. In the present study, we determined the effect of DHA on key regulators of Ca²⁺ signaling in cerulein-treated pancreatic acinar AR42 J cells. The results of RNA-Sequencing (RNA-Seq) analysis showed that cerulein up-regulates the expression of IP3R1 and RyR2 genes, and that pretreatment with DHA blocks these effects. The results of real-time PCR confirmed that DHA inhibits cerulein-induced IP3R1 and RyR2 gene expression, and demonstrated that DHA pre-treatment decreases the expression of the Relb gene, which encodes a component of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcriptional activator complex, and the c-fos gene, which encodes a component of activator protein-1 (AP-1) transcriptional activator complex. Taken together, DHA inhibits mRNA expression of IP3R1, RyR2, Relb, and c-fos, which is related to Ca²⁺ network in cerulein-stimulated PACs.

Gene Expression Pattern and Regulatory Network of α-Toxin Treatment in Bombyx mori

Bacillus bombyseptieus is a pathogen of Bombyx mori; it can cause bacterial septicemia in silkworm. One of the components of the parasporal crystal toxin of B. bombyseptieus, α-toxin, plays an important role in the process of infection in silkworm. In this study, we investigated the immune response of silkworm induced by α-toxin by using RNA-seq. We compared the changes in gene expression in the midgut, fatbody, and hemocytes of silkworm and in the B. mori embryonic cell line (BmE) after treatment with α-toxin and identified 952 differentially expressed genes and 353 differentially expressed long noncoding RNAs (lncRNAs). These regulated genes in different tissues were found to be enriched in different pathways. The upregulated genes in the midgut were mainly involved in peptidoglycan catabolic process and tyrosine kinase signaling pathway, whereas the downregulated genes were mainly involved in chitin metabolic pathways. The upregulated genes in fatbody were also involved in peptidoglycan catabolic process, but they were for a different peptidoglycan subtype. Further, genes encoding cecropins were enriched in the fatbody. The downregulated genes were mainly involved in the metabolic pathways of fundamental substances such as cellular protein metabolic process and nucleobase-containing compound metabolic process. These results suggest that α-toxin can induce various immune responses in silkworm, and further studies are warranted to understand the mechanism of α-toxin action in silkworm. Further, lncRNAs and differentially expressed genes were correlated using coexpression network analysis. Our findings revealed potential candidate genes and lncRNAs that might play important physiological functions in the immune response to α-toxins in silkworm.

Proteomic Analysis of Cyclic Ketamine Compounds Ability to Induce Neural Differentiation in Human Adult Mesenchymal Stem Cells

Neural regeneration is of great interest due to its potential to treat traumatic brain injuries and diseases that impact quality of life. Growth factor mediated differentiation can take up to several weeks to months to produce the cell of interest whereas chemical stimulation may be as minimal as a few hours. The smaller time scale is of great clinical relevance. Adipose derived stem cells (ADSCs) were treated for up to 24 h with a novel differentiation media containing the cyclic ketamine compounds to direct neurogenic induction. The extent of differentiation was investigated by proteome changes occurring during the process. The treatments indicated the ADSCs responded favorably to the neurogenic induction media by presenting a number of morphological cues of neuronal phenotype previously seen and a higher cell population post induction compared to previous studies. Furthermore, approximately 3500 proteins were analyzed and identified by mass spectrometric iTRAQ analyses. The bioinformatics analyses revealed hundreds of proteins whose expression level changes were statistically significant and biologically relevant to neurogenesis and annotated as being involved in neurogenic development. Complementing this, the Bioplex cytokine assay profiles present evidence of decreased panel of stress response cytokines and a relative increase in those involved in neurogenesis.

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.

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.

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.

BH4 domain peptides derived from Bcl-2/Bcl-XL as novel tools against acute pancreatitis

Biliary acute pancreatitis (AP) is a serious condition, which currently has no specific treatment. Taurolithocholic acid 3-sulfate (TLC-S) is one of the most potent bile acids causing cytosolic Ca2+ overload in pancreatic acinar cells (PACs), which results in premature activation of digestive enzymes and necrosis, hallmarks of AP. The inositol 1,4,5-trisphosphate receptor (IP3R) and the ryanodine receptor (RyR) play major roles in intracellular Ca2+ signaling. Inhibition of these endoplasmic reticulum-located channels suppresses TLC-S-induced Ca2+ release and necrosis, decreasing the severity of AP. Anti-apoptotic B-cell lymphoma (Bcl)-2-family members, such as Bcl-2 and Bcl-XL, have emerged as important modulators of IP3Rs and RyRs. These proteins contain four Bcl-2 homology (BH) domains of which the N-terminal BH4 domain exerts critical roles in regulating intracellular Ca2+ release channels. The BH4 domain of Bcl-2, but not of Bcl-XL, binds to and inhibits IP3Rs, whereas both BH4 domains inhibit RyRs. Although clear cytoprotective effects have been reported for these BH4 domains, it remains unclear whether they are capable of inhibiting pathological Ca2+-overload, associated with AP. Here we demonstrate in PACs that the BH4 domains of Bcl-2 and Bcl-XL inhibit RyR activity in response to the physiological agonist cholecystokinin. In addition, these BH4 domains inhibit pathophysiological TLC-S-induced Ca2+ overload in PACs via RyR inhibition, which in turn protects these cells from TLC-S-induced necrosis. This study shows for the first time the therapeutic potential of BH4 domain function by inhibiting pathological RyR-mediated Ca2+ release and necrosis, events that trigger AP.

miR-352 participates in the regulation of trypsinogen activation in pancreatic acinar cells by influencing the function of autophagic lysosomes

This study was performed to screen miRNAs and mRNAs that are differentially expressed during trypsinogen activation in acute pancreatitis and to verify their role in the process of trypsinogen activation. The function enrichment analysis showed that the functions of miR-352 and its regulatory targets lysosome-associated membrane protein 2 (LAMP2) and cathepsin L1 (CTSL1) were lysosome related. The results of the verification experiment showed that in the TLC-S-treated AR42J (pancreatic cell line) cells, miR-352 expression increased, expression levels of LAMP2 and CTSL1 were significantly reduced, trypsinogen activation was increased, and the autophagy pathway was blocked. In the miR-352 mimic-transfected cells, miR-352 expression increased, expression levels of LAMP2 and CTSL1 were significantly reduced, trypsinogen activation was increased, intracellular lysosomal pH increased, cathepsins L activity decreased and the amount of autophagolysosomes increased. In the miR-352 inhibitor-transfected cells, miR-352 expression was reduced, expression levels of LAMP2 and CTSL1 were significantly increased, trypsinogen activation was decreased, intracellular lysosomal pH decreased, cathepsins L activity increased and the amount of autophagolysosomes decreased. In the process of taurolithocholic acid 3-sulfate (TLC-S) induced trypsinogen activation, overexpression of miR-352 could down-regulate LAMP2 and CTSL1, resulting in the dysfunction of autophagic lysosome. Thus, the autophagy pathway was blocked, and trypsinogen activation was enhanced.

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.

Role of the c-Jun N-terminal kinase signaling pathway in the activation of trypsinogen in rat pancreatic acinar cells

Bile acid causes trypsinogen activation in pancreatic acinar cells through a complex process. Additional research is required to further elucidate which signaling pathways affect trypsinogen activation when activated. the changes in the whole‑genome expression profile of AR42J cells under the effect of taurolithocholic acid 3‑sulfate (TLC‑S) were investigated. Furthermore, gene groups that may play a regulatory role were analyzed using the modular approach of biological networks. The aim of the present study was to improve our understanding of the changes in TLC‑S‑stimulated AR42J cells through a genetic functional modular analysis. whole‑genome expression profile chip arrays were applied to detect genes that were differentially expressed in pancreatic acinar AR42J cells treated with TLC‑S for 20 min. Based on the human protein reference database, a protein‑protein interaction network was obtained, which was then processed by CFinder software to derive 14 modules. Among these 14 modules, the gene ontology biological processes enrichment analysis identified two as modules of interest. Kyoto encyclopedia of genes and genomes map analysis revealed that MAP2K4, MAPK8 and FLNA are part of the c-Jun N-terminal kinase (JNK) pathway. The JNK signaling pathway is involved in regulating trypsinogen activation in rat pancreatic AR42J cells. Next, a regulatory network of seven kinase inhibitors was constructed. SP600125 is an ATP‑competitive, efficient, selective and reversible inhibitor of JNK. the results were verified by four sets of experiments and demonstrated that trypsinogen activation is mediated by the JNK signaling pathway in the pathogenesis of acute pancreatitis (AP). The present study provided a useful reference for better understanding the pathogenesis of AP and identifying new targets to regulate trypsinogen activation, in addition to providing valuable information for the treatment of AP.

Ca2+ toxicity and mitochondrial damage in acute pancreatitis: translational overview

Acute pancreatitis (AP) is a leading cause of hospitalization among non-malignant gastrointestinal disorders. The mortality of severe AP can reach 30-50%, which is most probably owing to the lack of specific treatment. Therefore, AP is a major healthcare problem, which urges researchers to identify novel drug targets. Studies from the last decades highlighted that the toxic cellular Ca(2+) overload and mitochondrial damage are key pathogenic steps in the disease development affecting both acinar and ductal cell functions. Moreover, recent observations showed that modifying the cellular Ca(2+) signalling might be beneficial in AP. The inhibition of Ca(2+) release from the endoplasmic reticulum or the activity of plasma membrane Ca(2+) influx channels decreased the severity of AP in experimental models. Similarly, inhibition of mitochondrial permeability transition pore (MPTP) opening also seems to improve the outcome of AP in in vivo animal models. At the moment MPTP blockers are under detailed clinical investigation to test whether interventions in MPTP openings and/or Ca(2+) homeostasis of the cells can be specific targets in prevention or treatment of cell damage in AP.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.

Ca2+ signalling underlying pancreatitis

In spite of significant scientific progress in recent years, acute pancreatitis (AP) is still a dangerous and in up to 5% of cases deadly disease with no specific cure. It is self-resolved in the majority of cases, but could result in chronic pancreatitis (CP) and increased risk of pancreatic cancer (PC). One of the early events in AP is premature activation of digestive pro-enzymes, including trypsinogen, inside pancreatic acinar cells (PACs) due to an excessive rise in the cytosolic Ca²⁺ concentration, which is the result of Ca²⁺ release from internal stores followed by Ca²⁺ entry through the store operated Ca²⁺ channels in the plasma membrane. The leading causes of AP are high alcohol intake and biliary disease with gallstones obstruction leading to bile reflux into the pancreatic duct. Recently attention in this area of research turned to another cause of AP - Asparaginase based drugs - which have been used quite successfully in treatments of childhood acute lymphoblastic leukaemia (ALL). Unfortunately, Asparaginase is implicated in triggering AP in 5-10% of cases as a side effect of the anti-cancer therapy. The main features of Asparaginase-elicited AP (AAP) were found to be remarkably similar to AP induced by alcohol metabolites and bile acids. Several potential therapeutic avenues in counteracting AAP have been suggested and could also be useful for dealing with AP induced by other causes. Another interesting development in this field includes recent research related to pancreatic stellate cells (PSCs) that are much less studied in their natural environment but nevertheless critically involved in AP, CP and PC. This review will attempt to evaluate developments, approaches and potential therapies for AP and discuss links to other relevant diseases.

Caffeine Inhibits Fluid Secretion by Interlobular Ducts From Guinea Pig Pancreas

OBJECTIVES

Caffeine is contained in coffee, tea, and numerous beverages and foods. We examined the direct effects of caffeine on the physiological function of pancreatic duct cells by using interlobular duct segments isolated from guinea pig pancreas.

METHODS

The rate of fluid secretion was continuously measured by monitoring the luminal volume of isolated duct segments. Changes in intracellular Ca concentration ([Ca]i) were estimated by microfluorometry in ducts loaded with Fura-2.

RESULTS

Both secretin-stimulated and acetylcholine (ACh)-stimulated fluid secretions were substantially and reversibly inhibited by relatively low concentrations of caffeine as low as 0.03 mM relevant to blood levels after ingestion of caffeine-containing beverages. Caffeine inhibited ACh-induced elevation of [Ca]i and secretin-induced fluctuation of [Ca]i. Caffeine abolished thapsigargin-induced intracellular Ca release but did not affect the entry of extracellular Ca. Caffeine (0.05 mM) abolished ethanol (1 mM)-induced fluid hypersecretion in secretin-stimulated pancreatic duct.

CONCLUSIONS

Low concentrations of caffeine directly inhibit pancreatic ductal fluid secretion stimulated by secretin or ACh and also ethanol-induced fluid hypersecretion. The inhibition by caffeine seems to be mediated by the blockade of intracellular Ca mobilization. Daily intake of caffeine may reduce the volume of pancreatic juice secretion.

Caffeine protects against experimental acute pancreatitis by inhibition of inositol 1,4,5-trisphosphate receptor-mediated Ca2+ release

OBJECTIVE

Caffeine reduces toxic Ca²⁺ signals in pancreatic acinar cells via inhibition of inositol 1,4,5-trisphosphate receptor (IP₃R)-mediated signalling, but effects of other xanthines have not been evaluated, nor effects of xanthines on experimental acute pancreatitis (AP). We have determined effects of caffeine and its xanthine metabolites on pancreatic acinar IP₃R-mediated Ca²⁺ signalling and experimental AP.

DESIGN

Isolated pancreatic acinar cells were exposed to secretagogues, uncaged IP₃ or toxins that induce AP and effects of xanthines, non-xanthine phosphodiesterase (PDE) inhibitors and cyclic adenosine monophosphate and cyclic guanosine monophosphate (cAMP/cGMP) determined. The intracellular cytosolic calcium concentration ([Ca²⁺]_C), mitochondrial depolarisation and necrosis were assessed by confocal microscopy. Effects of xanthines were evaluated in caerulein-induced AP (CER-AP), taurolithocholic acid 3-sulfate-induced AP (TLCS-AP) or palmitoleic acid plus ethanol-induced AP (fatty acid ethyl ester AP (FAEE-AP)). Serum xanthines were measured by liquid chromatography-mass spectrometry.

RESULTS

Caffeine, dimethylxanthines and non-xanthine PDE inhibitors blocked IP₃-mediated Ca²⁺ oscillations, while monomethylxanthines had little effect. Caffeine and dimethylxanthines inhibited uncaged IP₃-induced Ca²⁺ rises, toxin-induced Ca²⁺ release, mitochondrial depolarisation and necrotic cell death pathway activation; cAMP/cGMP did not inhibit toxin-induced Ca²⁺ rises. Caffeine significantly ameliorated CER-AP with most effect at 25 mg/kg (seven injections hourly); paraxanthine or theophylline did not. Caffeine at 25 mg/kg significantly ameliorated TLCS-AP and FAEE-AP. Mean total serum levels of dimethylxanthines and trimethylxanthines peaked at >2 mM with 25 mg/kg caffeine but at <100 µM with 25 mg/kg paraxanthine or theophylline.

CONCLUSIONS

Caffeine and its dimethylxanthine metabolites reduced pathological IP₃R-mediated pancreatic acinar Ca²⁺ signals but only caffeine ameliorated experimental AP. Caffeine is a suitable starting point for medicinal chemistry.

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

KEY POINTS

Acute biliary pancreatitis is a sudden and severe condition initiated by bile reflux into the pancreas. Bile acids are known to induce Ca2+ signals and necrosis in isolated pancreatic acinar cells but the effects of bile acids on stellate cells are unexplored. Here we show that cholate and taurocholate elicit more dramatic Ca2+ signals and necrosis in stellate cells compared to the adjacent acinar cells in pancreatic lobules; whereas taurolithocholic acid 3-sulfate primarily affects acinar cells. Ca2+ signals and necrosis are strongly dependent on extracellular Ca2+ as well as Na+ ; and Na+ -dependent transport plays an important role in the overall bile acid uptake in pancreatic stellate cells. Bile acid-mediated pancreatic damage can be further escalated by bradykinin-induced signals in stellate cells and thus killing of stellate cells by bile acids might have important implications in acute biliary pancreatitis.

ABSTRACT

Acute biliary pancreatitis, caused by bile reflux into the pancreas, is a serious condition characterised by premature activation of digestive enzymes within acinar cells, followed by necrosis and inflammation. Bile acids are known to induce pathological Ca2+ signals and necrosis in acinar cells. However, bile acid-elicited signalling events in stellate cells remain unexplored. This is the first study to demonstrate the pathophysiological effects of bile acids on stellate cells in two experimental models: ex vivo (mouse pancreatic lobules) and in vitro (human cells). Sodium cholate and taurocholate induced cytosolic Ca2+ elevations in stellate cells, larger than those elicited simultaneously in the neighbouring acinar cells. In contrast, taurolithocholic acid 3-sulfate (TLC-S), known to induce Ca2+ oscillations in acinar cells, had only minor effects on stellate cells in lobules. The dependence of the Ca2+ signals on extracellular Na+ and the presence of sodium-taurocholate cotransporting polypeptide (NTCP) indicate a Na+ -dependent bile acid uptake mechanism in stellate cells. Bile acid treatment caused necrosis predominantly in stellate cells, which was abolished by removal of extracellular Ca2+ and significantly reduced in the absence of Na+ , showing that bile-dependent cell death was a downstream event of Ca2+ signals. Finally, combined application of TLC-S and the inflammatory mediator bradykinin caused more extensive necrosis in both stellate and acinar cells than TLC-S alone. Our findings shed new light on the mechanism by which bile acids promote pancreatic pathology. This involves not only signalling in acinar cells but also in stellate cells.

Mechanism of mitochondrial permeability transition pore induction and damage in the pancreas: inhibition prevents acute pancreatitis by protecting production of ATP

OBJECTIVE

Acute pancreatitis is caused by toxins that induce acinar cell calcium overload, zymogen activation, cytokine release and cell death, yet is without specific drug therapy. Mitochondrial dysfunction has been implicated but the mechanism not established.

DESIGN

We investigated the mechanism of induction and consequences of the mitochondrial permeability transition pore (MPTP) in the pancreas using cell biological methods including confocal microscopy, patch clamp technology and multiple clinically representative disease models. Effects of genetic and pharmacological inhibition of the MPTP were examined in isolated murine and human pancreatic acinar cells, and in hyperstimulation, bile acid, alcoholic and choline-deficient, ethionine-supplemented acute pancreatitis.

RESULTS

MPTP opening was mediated by toxin-induced inositol trisphosphate and ryanodine receptor calcium channel release, and resulted in diminished ATP production, leading to impaired calcium clearance, defective autophagy, zymogen activation, cytokine production, phosphoglycerate mutase 5 activation and necrosis, which was prevented by intracellular ATP supplementation. When MPTP opening was inhibited genetically or pharmacologically, all biochemical, immunological and histopathological responses of acute pancreatitis in all four models were reduced or abolished.

CONCLUSIONS

This work demonstrates the mechanism and consequences of MPTP opening to be fundamental to multiple forms of acute pancreatitis and validates the MPTP as a drug target for this disease.

Role of ion transporters in the bile acid-induced esophageal injury

Barrett's esophagus (BE) is considered to be the most severe complication of gastro-esophageal reflux disease (GERD), in which the prolonged, repetitive episodes of combined acidic and biliary reflux result in the replacement of the squamous esophageal lining by columnar epithelium. Therefore, the acid-extruding mechanisms of esophageal epithelial cells (EECs) may play an important role in the defense. Our aim was to identify the presence of acid/base transporters on EECs and to investigate the effect of bile acids on their expressions and functions. Human EEC lines (CP-A and CP-D) were acutely exposed to bile acid cocktail (BAC) and the changes in intracellular pH (pHi) and Ca(2+) concentration ([Ca(2+)]i) were measured by microfluorometry. mRNA and protein expression of ion transporters was investigated by RT-PCR, Western blot, and immunohistochemistry. We have identified the presence of a Na(+)/H(+) exchanger (NHE), Na(+)/HCO3 (-) cotransporter (NBC), and a Cl(-)-dependent HCO3 (-) secretory mechanism in CP-A and CP-D cells. Acute administration of BAC stimulated HCO3 (-) secretion in both cell lines and the NHE activity in CP-D cells by an inositol triphosphate-dependent calcium release. Chronic administration of BAC to EECs increased the expression of ion transporters compared with nontreated cells. A similar expression pattern was observed in biopsy samples from BE compared with normal epithelium. We have shown that acute administration of bile acids differently alters ion transport mechanisms of EECs, whereas chronic exposure to bile acids increases the expression of acid/base transporters. We speculate that these adaptive processes of EECs represent an important mucosal defense against the bile acid-induced epithelial injury.

NF-κB in acute pancreatitis: Mechanisms and therapeutic potential

The incidence of acute pancreatitis (AP) is increasing globally and mortality could be high among patients with organ failure and infected necrosis. The predominant factors responsible for the morbidity and mortality of AP are systemic inflammatory response syndrome and multiorgan dysfunction. Even though preclinical studies have shown antisecretory agents (somatostatin), antioxidants (S-adenosyl methionine [SAM], selenium), protease inhibitors, platelet activating factor inhibitor (Lexipafant), and anti-inflammatory immunomodulators (eg. prostaglandin E, indomethacin) to benefit AP in terms of reducing the severity and/or mortality, most of these agents have shown heterogeneous results in clinical studies. Several years of experimental studies have implicated nuclear factor-kappa B (NF-κB) activation as an early and central event in the progression of inflammation in AP. In this manuscript, we review the literature on the role of NF-κB in the pathogenesis of AP, its early intraacinar activation, and how it results in progression of the disease. We also discuss why anti-protease, antisecretory, and anti-inflammatory agents are unlikely to be effective in clinical acute pancreatitis. NF-κB, being a central molecule that links the initial acinar injury to systemic inflammation and perpetuate the inflammation, we propose that more studies be focussed towards targeted inhibition of NF-κB activity. Direct NF-κB inhibition strategies have already been attempted in patients with various cancers. So far, peroxisome proliferator activator receptor gamma (PPAR-γ) ligand, pyrrolidine dithiocarbamate (PDTC), proteasome inhibitor and calpain I inhibitor have been shown to have direct inhibitory effects on NF-κB activation in experimental AP.

Small Molecule Inhibitors of Cyclophilin D To Protect Mitochondrial Function as a Potential Treatment for Acute Pancreatitis

Opening of the mitochondrial permeability transition pore (MPTP) causes mitochondrial dysfunction and necrosis in acute pancreatitis (AP), a condition without specific drug treatment. Cyclophilin D (CypD) is a mitochondrial matrix peptidyl-prolyl isomerase that regulates the MPTP and is a drug target for AP. We have synthesized urea-based small molecule inhibitors of cyclophilins and tested them against CypD using binding and isomerase activity assays. Thermodynamic profiles of the CypD/inhibitor interactions were determined by isothermal titration calorimetry. Seven new high-resolution crystal structures of CypD-inhibitor complexes were obtained to guide compound optimization. Compounds 4, 13, 14, and 19 were tested in freshly isolated murine pancreatic acinar cells (PACs) to determine inhibition of toxin-induced loss of mitochondrial membrane potential (ΔΨm) and necrotic cell death pathway activation. Compound 19 was found to have a Kd of 410 nM and a favorable thermodynamic profile, and it showed significant protection of ΔΨm and reduced necrosis of murine as well as human PACs. Compound 19 holds significant promise for future lead optimization.

A novel, protective role of ursodeoxycholate in bile-induced pancreatic ductal injury

We have previously shown that chenodeoxycholic acid (CDCA) strongly inhibits pancreatic ductal HCO3 (-) secretion through the destruction of mitochondrial function, which may have significance in the pathomechanism of acute pancreatitis (AP). Ursodeoxycholic acid (UDCA) is known to protect the mitochondria against hydrophobic bile acids and has an ameliorating effect on cell death. Therefore, our aim was to investigate the effect of UDCA pretreatment on CDCA-induced pancreatic ductal injury. Guinea pig intrainterlobular pancreatic ducts were isolated by collagenase digestion. Ducts were treated with UDCA for 5 and 24 h, and the effect of CDCA on intracellular Ca(2+) concentration ([Ca(2+)]i), intracellular pH (pHi), morphological and functional changes of mitochondria, and the rate of apoptosis were investigated. AP was induced in rat by retrograde intraductal injection of CDCA (0.5%), and the disease severity of pancreatitis was assessed by measuring standard laboratory and histological parameters. Twenty-four-hour pretreatment of pancreatic ducts with 0.5 mM UDCA significantly reduced the rate of ATP depletion, mitochondrial injury, and cell death induced by 1 mM CDCA and completely prevented the inhibitory effect of CDCA on acid-base transporters. UDCA pretreatment had no effect on CDCA-induced Ca(2+) signaling. Oral administration of UDCA (250 mg/kg) markedly reduced the severity of CDCA-induced AP. Our results clearly demonstrate that UDCA 1) suppresses the CDCA-induced pancreatic ductal injury by reducing apoptosis and mitochondrial damage and 2) reduces the severity of CDCA-induced AP. The protective effect of UDCA against hydrophobic bile acids may represent a novel therapeutic target in the treatment of biliary AP.

Development Rapid Analytical Methods for Inositol as a Trace Component by HPLC and LC-MS/MS in Infant Formula

A rapid and simple analytical method, using liquid chromatography tandem mass spectrometry (LC-MS/MS), was developed to detect myo-inositol (MI) in infant formulas. For protein removal: acid hydrolysis and lipid removal through organic solvent extraction. The operating conditions for instrumental analysis were determined based on previously reported analogous methods that used LC-MS/MS. Quantitative analysis was used for the detection limit test, infant formula recovery test, and standard reference material (SRM) 1849a to verify the validity of our LC-MS/MS analytical method, which was developed to quantify MI. For validation, the results of our method were compared with the results of quantitative analyses of certified values. The test results showed that the limit of detection was 0.05 mg/L, the limit of quantitation was 0.17 mg/L, and the method detection limit was 17 mg/kg. The recovery test exhibited a recovery between 98.07-98.43% and a relative standard deviation between 1.93-2.74%. Therefore, the result values were good. Additionally, SRM 1849a was measured to have an MI content of 401.84 mg/kg and recovery of 98.25%, which is comparable to the median certified value of 409 mg/kg. From the aforementioned results, we judged that the instrumental analysis conditions and preparation method used in this study were valid. The rapid analytical method developed herein could be implemented in many laboratories that seek to save time and labor.

Ca(2+) signals mediated by bradykinin type 2 receptors in normal pancreatic stellate cells can be inhibited by specific Ca(2+) channel blockade

KEY POINTS

Bradykinin may play a role in the autodigestive disease acute pancreatitis, but little is known about its pancreatic actions. In this study, we have investigated bradykinin-elicited Ca(2+) signal generation in normal mouse pancreatic lobules. We found complete separation of Ca(2+) signalling between pancreatic acinar (PACs) and stellate cells (PSCs). Pathophysiologically relevant bradykinin concentrations consistently evoked Ca(2+) signals, via B2 receptors, in PSCs but never in neighbouring PACs, whereas cholecystokinin, consistently evoking Ca(2+) signals in PACs, never elicited Ca(2+) signals in PSCs. The bradykinin-elicited Ca(2+) signals were due to initial Ca(2+) release from inositol trisphosphate-sensitive stores followed by Ca(2+) entry through Ca(2+) release-activated channels (CRACs). The Ca(2+) entry phase was effectively inhibited by a CRAC blocker. B2 receptor blockade reduced the extent of PAC necrosis evoked by pancreatitis-promoting agents and we therefore conclude that bradykinin plays a role in acute pancreatitis via specific actions on PSCs.

ABSTRACT

Normal pancreatic stellate cells (PSCs) are regarded as quiescent, only to become activated in chronic pancreatitis and pancreatic cancer. However, we now report that these cells in their normal microenvironment are far from quiescent, but are capable of generating substantial Ca(2+) signals. We have compared Ca(2+) signalling in PSCs and their better studied neighbouring acinar cells (PACs) and found complete separation of Ca(2+) signalling in even closely neighbouring PACs and PSCs. Bradykinin (BK), at concentrations corresponding to the slightly elevated plasma BK levels that have been shown to occur in the auto-digestive disease acute pancreatitis in vivo, consistently elicited substantial Ca(2+) signals in PSCs, but never in neighbouring PACs, whereas the physiological PAC stimulant cholecystokinin failed to evoke Ca(2+) signals in PSCs. The BK-induced Ca(2+) signals were mediated by B2 receptors and B2 receptor blockade protected against PAC necrosis evoked by agents causing acute pancreatitis. The initial Ca(2+) rise in PSCs was due to inositol trisphosphate receptor-mediated release from internal stores, whereas the sustained phase depended on external Ca(2+) entry through Ca(2+) release-activated Ca(2+) (CRAC) channels. CRAC channel inhibitors, which have been shown to protect PACs against damage caused by agents inducing pancreatitis, therefore also inhibit Ca(2+) signal generation in PSCs and this may be helpful in treating acute pancreatitis.

Bile acids inhibit Na⁺/H⁺ exchanger and Cl⁻/HCO₃⁻ exchanger activities via cellular energy breakdown and Ca²⁺ overload in human colonic crypts

Bile acids play important physiological role in the solubilisation and absorption of dietary lipids. However, under pathophysiological conditions, such as short bowel syndrome, they can reach the colon in high concentrations inducing diarrhoea. In this study, our aim was to characterise the cellular pathomechanism of bile-induced diarrhoea using human samples. Colonic crypts were isolated from biopsies of patients (controls with negative colonoscopic findings) and of cholecystectomised/ileum-resected patients with or without diarrhoea. In vitro measurement of the transporter activities revealed impaired Na⁺/H⁺ exchanger (NHE) and Cl⁻/HCO₃⁻ exchanger (CBE) activities in cholecystectomised/ileum-resected patients suffering from diarrhoea, compared to control patients. Acute treatment of colonic crypts with 0.3 mM chenodeoxycholate caused dose-dependent intracellular acidosis; moreover, the activities of acid/base transporters (NHE and CBE) were strongly impaired. This concentration of chenodeoxycholate did not cause morphological changes in colonic epithelial cells, although significantly reduced the intracellular ATP level, decreased mitochondrial transmembrane potential and caused sustained intracellular Ca²⁺ elevation. We also showed that chenodeoxycholate induced Ca²⁺ release from the endoplasmic reticulum and extracellular Ca²⁺ influx contributing to the Ca²⁺ elevation. Importantly, our results suggest that the chenodeoxycholate-induced inhibition of NHE activities was ATP-dependent, whereas the inhibition of CBE activity was mediated by the sustained Ca²⁺ elevation. We suggest that bile acids inhibit the function of ion transporters via cellular energy breakdown and Ca²⁺ overload in human colonic epithelial cells, which can reduce fluid and electrolyte absorption in the colon and promote the development of diarrhea.

Breakdown of bioenergetics evoked by mitochondrial damage in acute pancreatitis: Mechanisms and consequences

Acute pancreatitis is a severe inflammatory disease with unacceptably high mortality and without specific therapy. Clinical studies revealed that energy supplementation of patients via enteral feeding decreases systemic infections, multi-organ failure and mortality. These clinical observations have been supported by in vitro and in vivo experimental studies which showed that the most common pancreatitis inducing factors, such as bile acids, ethanol and non-oxidative ethanol metabolites induce intracellular ATP depletion and mitochondrial damage both in pancreatic acinar and ductal cells. Notably, the in vitro supplementation of ATP prevented the cellular damage and restored cell functions in both cell types. These observations suggest that either prevention of mitochondrial damage or restoration of intracellular ATP level might provide therapeutical benefits.

Bile acid effects are mediated by ATP release and purinergic signalling in exocrine pancreatic cells

Background

In many cells, bile acids (BAs) have a multitude of effects, some of which may be mediated by specific receptors such the TGR5 or FXR receptors. In pancreas systemic BAs, as well as intra-ductal BAs from bile reflux, can affect pancreatic secretion. Extracellular ATP and purinergic signalling are other important regulators of similar secretory mechanisms in pancreas. The aim of our study was to elucidate whether there is interplay between ATP and BA signalling.

Results

Here we show that CDCA (chenodeoxycholic acid) caused fast and concentration-dependent ATP release from acini (AR42J) and duct cells (Capan-1). Taurine and glycine conjugated forms of CDCA had smaller effects on ATP release in Capan-1 cells. In duct monolayers, CDCA stimulated ATP release mainly from the luminal membrane; the releasing mechanisms involved both vesicular and non-vesicular secretion pathways. Duct cells were not depleted of intracellular ATP with CDCA, but acinar cells lost some ATP, as detected by several methods including ATP sensor AT1.03^YEMK. In duct cells, CDCA caused reversible increase in the intracellular Ca²⁺ concentration [Ca^{2 +}]_i, which could be significantly inhibited by antagonists of purinergic receptors. The TGR5 receptor, expressed on the luminal side of pancreatic ducts, was not involved in ATP release and Ca²⁺ signals, but could stimulate Na⁺/Ca²⁺ exchange in some conditions.

Conclusions

CDCA evokes significant ATP release that can stimulate purinergic receptors, which in turn increase [Ca²⁺]_i. The TGR5 receptor is not involved in these processes but can play a protective role at high intracellular Ca²⁺ conditions. We propose that purinergic signalling could be taken into consideration in other cells/organs, and thereby potentially explain some of the multifaceted effects of BAs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-015-0107-9) contains supplementary material, which is available to authorized users.

Modulation of Hepatic Protein Kinase Cβ Expression in Metabolic Adaptation to a Lithogenic Diet

BACKGROUND & AIMS

Dietary factors are likely an important determinant of gallstone development, and difficulty in adapting to lithogenic diets may predispose individuals to gallstone formation. Identification of the critical early diet-dependent metabolic markers of adaptability is urgently needed to prevent gallstone development. We focus on the interaction between diet and genes, and the resulting potential to influence gallstone risk by dietary modification.

METHODS

Expression levels of hepatic protein kinase C (PKC) isoforms were determined in lithogenic diet-fed mice, and the relationship of hepatic cholesterol content and PKCβ expression and the effect of hepatic PKCβ overexpression on intracellular signaling pathways were analyzed.

RESULTS

Lithogenic diet feeding resulted in a striking induction of hepatic PKCβ and PKCδ mRNA and protein levels, which preceded the appearance of biliary cholesterol crystals. Unlike PKCβ deficiency, global PKCδ deficiency did not influence lithogenic diet-induced gallstone formation. Interestingly, a deficiency of apolipoprotein E abrogated the diet-induced hepatic PKCβ expression, whereas a deficiency of liver X receptor-α further potentiated the induction, suggesting a potential link between the degree of hepatic PKCβ induction and the intracellular cholesterol content. Furthermore, our results suggest that PKCβ is a physiologic repressor of ileum basal fibroblast growth factor 15 (FGF15) expression and activity of hepatic proto-oncogene serine/threonine-protein kinase Raf-1/mitogen-activated protein (MAP) kinase kinase/extracellular signal-regulated kinases 1/2 (Raf-1/MEK/ERK1/2) cascade proteins, and the complex interactions between these pathways may determine the degree of hepatic ERK1/2 activation, a potent suppressor of cholesterol 7α-hydroxylase and sterol 12α-hydroxylase expression. We found that PKCβ regulated Raf-1 activity by modulating the inhibitory Raf-1^Ser259 phosphorylation.

CONCLUSIONS

Our results demonstrate a novel interaction between the hepatic PKCβ/Raf-1 regulatory axis and ileum PKCβ/FGF15/ERK axis, which could modulate the bile lithogenecity of dietary lipids. The data presented are consistent with a two-pronged mechanism by which intestine and liver PKCβ signaling converges on the liver ERK1/2 pathway to control the hepatic adaptive response to a lithogenic diet. Elucidating the impact and the underlying mechanism(s) of PKCβ action could help us understand how different types of dietary fat modify the risk of gallstone formation, information that could help to identify novel targets for therapeutic approaches to combat this disease.

A primer of NAADP-mediated Ca(2+) signalling: From sea urchin eggs to mammalian cells

Since the discovery of the Ca(2+) mobilizing effects of the pyridine nucleotide metabolite, nicotinic acid adenine dinucleotide phosphate (NAADP), this molecule has been demonstrated to function as a Ca(2+) mobilizing intracellular messenger in a wide range of cell types. In this review, I will briefly summarize the distinct principles behind NAADP-mediated Ca(2+) signalling before going on to outline the role of this messenger in the physiology of specific cell types. Central to the discussion here is the finding that NAADP principally mobilizes Ca(2+) from acidic organelles such as lysosomes and it is this property that allows NAADP to play a unique role in intracellular Ca(2+) signalling. Lysosomes and related organelles are small Ca(2+) stores but importantly may also initiate a two-way dialogue with other Ca(2+) storage organelles to amplify Ca(2+) release, and may be strategically localized to influence localized Ca(2+) signalling microdomains. The study of NAADP signalling has created a new and fruitful focus on the lysosome and endolysosomal system as major players in calcium signalling and pathophysiology.