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

Molecular mechanism and potential role of mitophagy in acute pancreatitis

Acute pancreatitis (AP) is a multifaceted inflammatory disorder stemming from the aberrant activation of trypsin within the pancreas. Despite the contribution of various factors to the pathogenesis of AP, such as trypsin activation, dysregulated increases in cytosolic Ca2+ levels, inflammatory cascade activation, and mitochondrial dysfunction, the precise molecular mechanisms underlying the disease are still not fully understood. Mitophagy, a cellular process that preserves mitochondrial homeostasis under stress, has emerged as a pivotal player in the context of AP. Research suggests that augmenting mitophagy can mitigate pancreatic injury by clearing away malfunctioning mitochondria. Elucidating the role of mitophagy in AP may pave the way for novel therapeutic strategies. This review article aims to synthesize the current research findings on mitophagy in AP and underscore its significance in the clinical management of the disorder.

Renalase peptides reduce pancreatitis severity in mice

Acute pancreatitis, an acute inflammatory injury of the pancreas, lacks a specific treatment. The circulatory protein renalase is produced by the kidney and other tissues and has potent anti-inflammatory and prosurvival properties. Recombinant renalase can reduce the severity of mild cerulein pancreatitis; the activity is contained in a conserved 20 aa renalase site (RP220). Here, we investigated the therapeutic effects of renalase on pancreatitis using two clinically relevant models of acute pancreatitis. The ability of peptides containing the RP220 site to reduce injury in a 1-day post-endoscopic retrograde cholangiopancreatography (ERCP) and a 2-day severe cerulein induced in mice was examined. The initial dose of renalase peptides was given either prophylactically (before) or therapeutically (after) the initiation of the disease. Samples were collected to determine early pancreatitis responses (tissue edema, plasma amylase, active zymogens) and later histologic tissue injury and inflammatory changes. In both preclinical models, renalase peptides significantly reduced histologic damage associated with pancreatitis, especially inflammation, necrosis, and overall injury. Quantifying inflammation using specific immunohistochemical markers demonstrated that renalase peptides significantly reduced overall bone marrow-derived inflammation and neutrophils and macrophage populations in both models. In the severe cerulein model, administering a renalase peptide with or without pretreatment significantly reduced injury. Pancreatitis and renalase peptide effects appeared to be the same in female and male mice. These studies suggest renalase peptides that retain the anti-inflammatory and prosurvival properties of recombinant renalase can reduce the severity of acute pancreatitis and might be attractive candidates for therapeutic development.NEW & NOTEWORTHY Renalase is a secretory protein. The prosurvival and anti-inflammatory effects of the whole molecule are contained in a 20 aa renalase site (RP220). Systemic treatment with peptides containing this renalase site reduced the severity of post-endoscopic retrograde cholangiopancreatography (ERCP) and severe cerulein pancreatitis in mouse models.

Combination of the CRAC Channel Inhibitor CM4620 and Galactose as a Potential Therapy for Acute Pancreatitis

Acute pancreatitis (AP) is a life-threatening inflammatory disease with no specific therapy. Excessive cytoplasmic Ca2+ elevation and intracellular ATP depletion are responsible for the initiation of AP. Inhibition of Ca2+ release-activated Ca2+ (CRAC) channels has been proposed as a potential treatment, and currently, a novel selective CRAC channel inhibitor CM4620 (Auxora, CalciMedica) is in Phase 2b human trials. While CM4620 is on track to become the first effective treatment for AP, it does not produce complete protection in animal models. Recently, an alternative approach has suggested reducing ATP depletion with a natural carbohydrate galactose. Here, we have investigated the possibility of using the smallest effective concentration of CM4620 in combination with galactose. Protective effects of CM4620, in the range of 1-100 n m, have been studied against necrosis induced by bile acids, palmitoleic acid, or l-asparaginase. CM4620 markedly protected against necrosis induced by bile acids or asparaginase starting from 50 n m and palmitoleic acid starting from 1 n m. Combining CM4620 and galactose (1 m m) significantly reduced the extent of necrosis to near-control levels. In the palmitoleic acid-alcohol-induced experimental mouse model of AP, CM4620 at a concentration of 0.1 mg/kg alone significantly reduced edema, necrosis, inflammation, and the total histopathological score. A combination of 0.1 mg/kg CM4620 with galactose (100 m m) significantly reduced further necrosis, inflammation, and histopathological score. Our data show that CM4620 can be used at much lower concentrations than reported previously, reducing potential side effects. The novel combination of CM4620 with galactose synergistically targets complementary pathological mechanisms of AP.

The role of mitochondrial damage-associated molecular patterns in acute pancreatitis

Acute pancreatitis (AP) is one of the most common gastrointestinal tract diseases with significant morbidity and mortality. Current treatments remain unspecific and supportive due to the severity and clinical course of AP, which can fluctuate rapidly and unpredictably. Mitochondria, cellular power plant to produce energy, are involved in a variety of physiological or pathological activities in human body. There is a growing evidence indicating that mitochondria damage-associated molecular patterns (mtDAMPs) play an important role in pathogenesis and progression of AP. With the pro-inflammatory properties, released mtDAMPs may damage pancreatic cells by binding with receptors, activating downstream molecules and releasing inflammatory factors. This review focuses on the possible interaction between AP and mtDAMPs, which include cytochrome c (Cyt c), mitochondrial transcription factor A (TFAM), mitochondrial DNA (mtDNA), cardiolipin (CL), adenosine triphosphate (ATP) and succinate, with focus on experimental research and potential therapeutic targets in clinical practice. Preventing or diminishing the release of mtDAMPs or targeting the mtDAMPs receptors might have a role in AP progression.

The Role of the Gut Microbiome in the Development of Acute Pancreatitis

With the explosion research on the gut microbiome in the recent years, much insight has been accumulated in comprehending the crosstalk between the gut microbiota community and host health. Acute pancreatitis (AP) is one of the gastrointestinal diseases associated with significant morbidity and subsequent mortality. Studies have elucidated that gut microbiota are engaged in the pathological process of AP. Herein, we summarize the major roles of the gut microbiome in the development of AP. We then portray the association between dysbiosis of the gut microbiota and the severity of AP. Finally, we illustrate the promises and challenges that arise when seeking to incorporate the microbiome in acute pancreatitis treatment.

Molecular mechanisms of pain in acute pancreatitis: recent basic research advances and therapeutic implications

Although severe abdominal pain is the main symptom of acute pancreatitis, its mechanisms are poorly understood. An emerging body of literature evidence indicates that neurogenic inflammation might play a major role in modulating the perception of pain from the pancreas. Neurogenic inflammation is the result of a crosstalk between injured pancreatic tissue and activated neurons, which leads to an auto-amplification loop between inflammation and pain during the progression of acute pancreatitis. In this review, we summarize recent findings on the role of neuropeptides, ion channels, and the endocannabinoid system in acute pancreatitis-related pain. We also highlight potential therapeutic strategies that could be applied for managing severe pain in this disease.

Neutrophil-specific ORAI1 Calcium Channel Inhibition Reduces Pancreatitis-associated Acute Lung Injury

Acute pancreatitis is initiated within pancreatic exocrine cells and sustained by dysregulated systemic inflammatory responses mediated by neutrophils. Store-operated Ca2+ entry (SOCE) through ORAI1 channels in pancreatic acinar cells triggers acute pancreatitis, and ORAI1 inhibitors ameliorate experimental acute pancreatitis, but the role of ORAI1 in pancreatitis-associated acute lung injury has not been determined. Here, we showed mice with pancreas-specific deletion of Orai1 (Orai1ΔPdx1, ∼70% reduction in the expression of Orai1) are protected against pancreatic tissue damage and immune cell infiltration, but not pancreatitis-associated acute lung injury, suggesting the involvement of unknown cells that may cause such injury through SOCE via ORAI1. Genetic (Orai1ΔMRP8) or pharmacological inhibition of ORAI1 in murine and human neutrophils decreased Ca2+ influx and impaired chemotaxis, reactive oxygen species production, and neutrophil extracellular trap formation. Unlike pancreas-specific Orai1 deletion, mice with neutrophil-specific deletion of Orai1 (Orai1ΔMRP8) were protected against pancreatitis- and sepsis-associated lung cytokine release and injury, but not pancreatic injury in experimental acute pancreatitis. These results define critical differences between contributions from different cell types to either pancreatic or systemic organ injury in acute pancreatitis. Our findings suggest that any therapy for acute pancreatitis that targets multiple rather than single cell types is more likely to be effective.

Human pancreatic ductal organoids with controlled polarity provide a novel ex vivo tool to study epithelial cell physiology

Epithelial ion and fluid secretion determine the physiological functions of a broad range of organs, such as the lung, liver, or pancreas. The molecular mechanism of pancreatic ion secretion is challenging to investigate due to the limited access to functional human ductal epithelia. Patient-derived organoids may overcome these limitations, however direct accessibility of the apical membrane is not solved. In addition, due to the vectorial transport of ions and fluid the intraluminal pressure in the organoids is elevated, which may hinder the study of physiological processes. To overcome these, we developed an advanced culturing method for human pancreatic organoids based on the removal of the extracellular matrix that induced an apical-to-basal polarity switch also leading to reversed localization of proteins with polarized expression. The cells in the apical-out organoids had a cuboidal shape, whereas their resting intracellular Ca²⁺ concentration was more consistent compared to the cells in the apical-in organoids. Using this advanced model, we demonstrated the expression and function of two novel ion channels, the Ca²⁺ activated Cl^- channel Anoctamin 1 (ANO1) and the epithelial Na⁺ channel (ENaC), which were not considered in ductal cells yet. Finally, we showed that the available functional assays, such as forskolin-induced swelling, or intracellular Cl^- measurement have improved dynamic range when performed with apical-out organoids. Taken together our data suggest that polarity-switched human pancreatic ductal organoids are suitable models to expand our toolset in basic and translational research.

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.

Confinement of Triple-Enzyme-Involved Antioxidant Cascade in Two-Dimensional Nanostructure

Application of antioxidant enzymes in medical or industrial processes is limited due to their high sensitivity to environmental conditions. Incorporation of such enzymes in nanostructures provides a promising route to obtain highly efficient and robust biocatalytic system to scavenge reactive oxygen species (ROS). Here, this question was addressed by confinement of superoxide dismutase (SOD), horseradish peroxidase (HRP), and catalase (CAT) enzymes into nanostructures containing polyelectrolyte building blocks (alginate (Alg) and trimethyl chitosan (TMC)) and delaminated layered double hydroxide (dLDH) nanoparticle support. The nanocomposite possessed excellent structural and colloidal stability, while antioxidant tests revealed that the enzymes remained active upon immobilization and the developed composite greatly reduced intracellular oxidative stress in two-dimensional cell cultures. Moreover, it effectively prevented hydrogen peroxide-induced double stranded DNA breaks, which is a common consequence of oxidative stress. The results provide important tools to design complex nanostructures with multienzymatic antioxidant activities for ROS scavenging.

ORAI Calcium Channels: Regulation, Function, Pharmacology, and Therapeutic Targets

The changes in intracellular free calcium (Ca2+) levels are one of the most widely regulators of cell function; therefore, calcium as a universal intracellular mediator is involved in very important human diseases and disorders. In many cells, Ca2+ inflow is mediated by store-operated calcium channels, and it is recognized that the store-operated calcium entry (SOCE) is mediated by the two partners: the pore-forming proteins Orai (Orai1-3) and the calcium store sensor, stromal interaction molecule (STIM1-2). Importantly, the Orai/STIM channels are involved in crucial cell signalling processes such as growth factors, neurotransmitters, and cytokines via interaction with protein tyrosine kinase coupled receptors and G protein-coupled receptors. Therefore, in recent years, the issue of Orai/STIM channels as a drug target in human diseases has received considerable attention. This review summarizes and highlights our current knowledge of the Orai/STIM channels in human diseases and disorders, including immunodeficiency, myopathy, tubular aggregate, Stormorken syndrome, York platelet syndrome, cardiovascular and metabolic disorders, and cancers, as well as suggesting these channels as drug targets for pharmacological therapeutic intervention. Moreover, this work will also focus on the pharmacological modulators of Orai/STIM channel complexes. Together, our thoughtful of the biology and physiology of the Orai/STIM channels have grown remarkably during the past three decades, and the next important milestone in the field of store-operated calcium entry will be to identify potent and selective small molecules as a therapeutic agent with the purpose to target human diseases and disorders for patient benefit.

Thiopurines impair the apical plasma membrane expression of CFTR in pancreatic ductal cells via RAC1 inhibition

BACKGROUND AND AIMS

Thiopurine-induced acute pancreatitis (TIP) is one of the most common adverse events among inflammatory bowel disease patients treated with azathioprine (AZA), representing a significant clinical burden. Previous studies focused on immune-mediated processes, however, the exact pathomechanism of TIP is essentially unclear.

METHODS

To model TIP in vivo, we triggered cerulein-induced experimental pancreatitis in mice receiving a daily oral dose of 1.5 mg/kg AZA. Also, freshly isolated mouse pancreatic cells were exposed to AZA ex vivo, and acinar cell viability, ductal and acinar Ca²⁺ signaling, ductal Cl^- and HCO₃^- secretion, as well as cystic fibrosis transmembrane conductance regulator (CFTR) expression were assessed using microscopy techniques. Ras-related C3 botulinum toxin substrate (RAC1) activity was measured with a G-LISA assay. Super-resolution microscopy was used to determine protein colocalization.

RESULTS

We demonstrated that AZA treatment increases tissue damage in the early phase of cerulein-induced pancreatitis in vivo. Also, both per os and ex vivo AZA exposure impaired pancreatic fluid and ductal HCO₃^- and Cl^- secretion, but did not affect acinar cells. Furthermore, ex vivo AZA exposure also inhibited RAC1 activity in ductal cells leading to decreased co-localization of CFTR and the anchor protein ezrin, resulting in impaired plasma membrane localization of CFTR.

CONCLUSIONS

AZA impaired the ductal HCO₃^- and Cl^- secretion through the inhibition of RAC1 activity leading to diminished ezrin-CFTR interaction and disturbed apical plasma membrane expression of CFTR. We report a novel direct toxic effect of AZA on pancreatic ductal cells and suggest that the restoration of ductal function might help to prevent TIP in the future.