Experimental Acute Pancreatitis Models: History, Current Status, and Role in Translational Research

Chaiqin chengqi decoction treatment mitigates hypertriglyceridemia-associated acute pancreatitis by modulating liver-mediated glycerophospholipid metabolism

BACKGROUND

The incidence of hypertriglyceridemia-associated acute pancreatitis (HTG-AP) is increasing globally and more so in China. The characteristics of liver-mediated metabolites and related key enzymes are rarely reported in HTG-AP. Chaiqin chengqi decoction (CQCQD) has been shown to protect against AP including HTG-AP in both patients and rodent models, but the underlying mechanisms in HTG-AP remain unexplored.

PURPOSE

To assess the characteristics of liver-mediated metabolism and the therapeutic mechanisms of CQCQD in HTG-AP.

METHODS

Male human apolipoprotein C3 transgenic (hApoC3-Tg; leading to HTG) mice or wild-type littermates received 7 intraperitoneal injections of cerulein (100 μg/kg) to establish HTG-AP and CER-AP, respectively. In HTG-AP, some mice received CQCQD (5.5 g/kg) gavage at 1, 5 or 9 h after disease induction. AP severity and related liver injury were determined by serological and histological parameters; and underlying mechanisms were identified by lipidomics and molecular biology. Molecular docking was used to identify key interactions between CQCQD compounds and metabolic enzymes, and subsequently validated in vitro in hepatocytes.

RESULTS

HTG-AP was associated with increased disease severity indices including augmented liver injury compared to CER-AP. CQCQD treatment reduced severity and liver injury of HTG-AP. Glycerophospholipid (GPL) metabolism was the most disturbed pathway in HTG-AP in comparison to HTG alone. In HTG-AP, the mRNA level of GPL enzymes involved in phosphocholine (PC) and phosphatidylethanolamine (PE) synthesis (Pcyt1a, Pcyt2, Pemt, and Lpcat) were markedly upregulated in the liver. Of the GPL metabolites, lysophosphatidylethanolamine LPE(16:0) in serum of HTG-AP was significantly elevated and positively correlated with the pancreas histopathology score (r = 0.65). In vitro, supernatant from Pcyt2-overexpressing hepatocytes co-incubated with LPE(16:0) or phospholipase A2 (a PC- and PE-hydrolyzing enzyme) alone induced pancreatic acinar cell death. CQCQD treatment downregulated PCYT1a and PCYT2 enzyme levels in the liver. Hesperidin and narirutin were identified top two CQCQD compounds with highest affinity docking to PCYT1a and PCYT2. Both hesperidin and narirutin reduced the level of some GPL metabolites in hepatocytes.

CONCLUSION

Liver-mediated GPL metabolism is excessively activated in HTG-AP with serum LPE(16:0) level correlating with disease severity. CQCQD reduces HTG-AP severity partially via modulating key enzymes in GPL metabolism pathway.

Heparan sulfate acts as an activator of the NLRP3 inflammasome promoting inflammatory response in the development of acute pancreatitis

BACKGROUND

Accumulating evidence has shown that the NOD-like receptor protein 3 (NLRP3) inflammasome plays a crucial role in the inflammatory cascades involved in the development of acute pancreatitis (AP). However, the specific agonist responsible for activating the NLRP3 inflammasome in this process has not yet been identified. The purpose of this study is to clarify whether heparan sulfate (HS) works as an NLRP3 inflammasome activator to evoke inflammatory cascades in the progression of AP.

METHODS

Two experimental mouse models of AP were utilized to investigate the pro-inflammatory activity of HS in the development of AP by measuring the secretion of inflammatory cytokines and the neutrophil infiltration in pancreatic tissue. The ability of HS to activate the NLRP3 inflammasome was evaluated both in vitro and in vivo. The nuclear factor kappa B (NF-κB)-mediated expression of NLRP3 inflammasome components in response to HS treatment was determined to decipher the role of HS in transcriptional priming of NLRP3 inflammasome. Furthermore, HS-triggered deubiquitination of NLRP3 was analyzed to reveal the promoting effect of HS on the NLRP3 inflammasome priming via a non-transcriptional pathway.

RESULTS

High plasma level of HS was observed with a positive correlation to that of inflammatory cytokines in AP mice. Administration of HS to mice resulted in an exacerbated inflammatory profile, while reducing HS production by an inhibitor of heparanase significantly attenuated inflammatory response. Pharmacological inhibition or genetic deletion of NLRP3 substantially suppressed the HS-stimulated elevation of IL-1β levels in AP mice. The in vitro data demonstrated that HS primarily serves as a priming signal for the activation of the NLRP3 inflammasome. HS possesses the ability to increase the transcriptional activity of NF-κB and TLR4/NF-κB-driven transcriptional pathway is employed for NLRP3 inflammasome priming. Moreover, HS-induced deubiquitination of NLRP3 is another pathway responsible for non-transcriptional priming of NLRP3 inflammasome.

CONCLUSIONS

Our current work has unveiled HS as a new activator of the NLRP3 inflammasome responsible for the secondary inflammatory cascades during the development of AP, highlighting the HS-NLRP3 pathway as a potential target for future preventive and therapeutic approaches of AP.

Antioxidative effect of astragalosides on acute pancreatitis in mice

Introduction

The research examined the antioxidative impact of astragalosides (AST) on experimental acute pancreatitis (AP) in mice. This study aims to assess the correlation between varying doses of astragalosides and superoxide dismutase (SOD) activity in an acute pancreatitis mouse model. By examining the interplay between astragaloside's protective effects and its antioxidant properties, we aim to deepen our understanding of its therapeutic potential in acute pancreatitis.

Methods

The AP model in mice was induced by retrograde injection of sodium deoxycholate into the biliary and pancreatic ducts. Serum amylase activity was monitored at various time points following induction. Furthermore, 24 hours post-induction, levels of serum nitric oxide (NO), superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content in pancreatic tissue were assessed.

Results

The findings of this study illustrated that AST, while exhibiting a protective effect in experimental AP, could effectively lower the elevated serum NO levels, reduce MDA production, and enhance SOD activity in model mice. AST notably reduced MDA levels in the pancreatic tissue of AP mice, underscoring its ability to inhibit membrane peroxidation induced by oxygen free radicals. Furthermore, AST was observed to elevate SOD activity in scavenging oxygen free radicals in pancreatic tissue.

Conclusion

These findings suggest that AST enhances recovery in an experimental acute pancreatitis mouse model by exerting antioxidative effects.

Cannabidiol Mitigates Lipopolysaccharide-Induced Pancreatic Pathology: A Promising Therapeutic Strategy

Background: Lipopolysaccharides (LPSs) are a component of certain types of bacteria and can induce an inflammatory response in the body, including in the pancreas. Cannabidiol (CBD), a nonpsychoactive compound found in cannabis, has been shown to have anti-inflammatory effects and may offer potential therapeutic benefits for conditions involving inflammation and damage. The aim of this study was to investigate any potential preventative effects of CBD on experimental LPS-induced pancreatic pathology in rats. Materials and Methods: Thirty-two rats were randomly divided into four groups as control, LPS (5 mg/kg, intraperitoneally [i.p.]), LPS+CBD, and CBD (5 mg/kg, i.p.) groups. Six hours after administering LPS, the rats were euthanized, and blood and pancreatic tissue samples were taken for biochemical, polymerase chain reaction (PCR), histopathological, and immunohistochemical examinations. Results: The results indicated that LPS decreased serum glucose levels and increased lipase levels. It also caused severe hyperemia, increased vacuolization in endocrine cells, edema, and slight inflammatory cell infiltrations at the histopathological examination. Insulin and amylin expressions decreased during immunohistochemical analyses. At the PCR analysis, Silent Information Regulator 2 homolog 1 and peroxisome proliferator-activated receptor gamma coactivator-1 alpha expressions decreased and tumor protein p53 expressions increased in the LPS group. CBD improved the biochemical, PCR, histopathological, and immunohistochemical results. Conclusions: The findings of the current investigation demonstrated that LPS damages both the endocrine and exocrine pancreas. However, CBD demonstrated marked ameliorative effects in the pancreas in LPS induced rat model pancreatitis.

Activin A signaling stimulates neutrophil activation and macrophage migration in pancreatitis

Acute Pancreatitis (AP) is associated with high mortality and current treatment options are limited to supportive care. We found that blockade of activin A (activin) in mice improves outcomes in two murine models of AP. To test the hypothesis that activin is produced early in response to pancreatitis and is maintained throughout disease progression to stimulate immune cells, we first performed digital spatial profiling (DSP) of human chronic pancreatitis (CP) patient tissue. Then, transwell migration assays using RAW264.7 mouse macrophages and qPCR analysis of "neutrophil-like" HL-60 cells were used for functional correlation. Immunofluorescence and western blots on cerulein-induced pancreatitis samples from pancreatic acinar cell-specific Kras knock-in (Ptf1aCreER™; LSL-KrasG12D) and functional WT Ptf1aCreER™ mouse lines mimicking AP and CP to allow for in vivo confirmation. Our data suggest activin promotes neutrophil and macrophage activation both in situ and in vitro, while pancreatic activin production is increased as early as 1 h in response to pancreatitis and is maintained throughout CP in vivo. Taken together, activin is produced early in response to pancreatitis and is maintained throughout disease progression to promote neutrophil and macrophage activation.

OCaR1 endows exocytic vesicles with autoregulatory competence by preventing uncontrolled Ca2+ release, exocytosis, and pancreatic tissue damage

Regulated exocytosis is initiated by increased Ca2+ concentrations in close spatial proximity to secretory granules, which is effectively prevented when the cell is at rest. Here we showed that exocytosis of zymogen granules in acinar cells was driven by Ca2+ directly released from acidic Ca2+ stores including secretory granules through NAADP-activated two-pore channels (TPCs). We identified OCaR1 (encoded by Tmem63a) as an organellar Ca2+ regulator protein integral to the membrane of secretory granules that controlled Ca2+ release via inhibition of TPC1 and TPC2 currents. Deletion of OCaR1 led to extensive Ca2+ release from NAADP-responsive granules under basal conditions as well as upon stimulation of GPCR receptors. Moreover, OCaR1 deletion exacerbated the disease phenotype in murine models of severe and chronic pancreatitis. Our findings showed OCaR1 as a gatekeeper of Ca2+ release that endows NAADP-sensitive secretory granules with an autoregulatory mechanism preventing uncontrolled exocytosis and pancreatic tissue damage.

Alcohol Promotes Lipogenesis in Sebocytes-Implications for Acne

The oral consumption of alcohol (ethanol) has a long tradition in humans and is an integral part of many cultures. The causal relationship between ethanol consumption and numerous diseases is well known. In addition to the well-described harmful effects on the liver and pancreas, there is also evidence that ethanol abuse triggers pathological skin conditions, including acne. In the present study, we addressed this issue by investigating the effect of ethanol on the energy metabolism in human SZ95 sebocytes, with particular focus on qualitative and quantitative lipogenesis. It was found that ethanol is a strong trigger for lipogenesis, with moderate effects on cell proliferation and toxicity. We identified the non-oxidative metabolism of ethanol, which produced fatty acid ethyl esters (FAEEs), as relevant for the lipogenic effect-the oxidative metabolism of ethanol does not contribute to lipogenesis. Correspondingly, using the Seahorse extracellular flux analyzer, we found an inhibition of the mitochondrial oxygen consumption rate as a measure of mitochondrial ATP production by ethanol. The ATP production rate from glycolysis was not affected. These data corroborate that ethanol-induced lipogenesis is independent from oxygen. In sum, our results give a causal explanation for the prevalence of acne in heavy drinkers, confirming that alcoholism should be considered as a systemic disease. Moreover, the identification of key factors driving ethanol-dependent lipogenesis may also be relevant in the treatment of acne vulgaris.

AAV-mediated hepatic LPL expression ameliorates severe hypertriglyceridemia and acute pancreatitis in Gpihbp1 deficient mice and rats

GPIHBP1 plays an important role in the hydrolysis of triglyceride (TG) lipoproteins by lipoprotein lipases (LPLs). However, Gpihbp1 knockout mice did not develop hypertriglyceridemia (HTG) during the suckling period but developed severe HTG after weaning on a chow diet. It has been postulated that LPL expression in the liver of suckling mice may be involved. To determine whether hepatic LPL expression could correct severe HTG in Gpihbp1 deficiency, liver-targeted LPL expression was achieved via intravenous administration of the adeno-associated virus (AAV)-human LPL gene, and the effects of AAV-LPL on HTG and HTG-related acute pancreatitis (HTG-AP) were observed. Suckling Gpihbp1-/- mice with high hepatic LPL expression did not develop HTG, whereas Gpihbp1-/- rat pups without hepatic LPL expression developed severe HTG. AAV-mediated liver-targeted LPL expression dose-dependently decreased plasma TG levels in Gpihbp1-/- mice and rats, increased post-heparin plasma LPL mass and activity, decreased mortality in Gpihbp1-/- rat pups, and reduced the susceptibility and severity of both Gpihbp1-/- animals to HTG-AP. However, the muscle expression of AAV-LPL had no significant effect on HTG. Targeted expression of LPL in the liver showed no obvious adverse reactions. Thus, liver-targeted LPL expression may be a new therapeutic approach for HTG-AP caused by GPIHBP1 deficiency.

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.

Fine tuning calcium dynamics by inhibition of Store-operated Calcium Entry as a novel therapeutic approach for the treatment of chronic pancreatitis

Chronic pancreatitis (CP) is a complex inflammatory disorder characterized by progressive fibrosis, leading to pancreatic dysfunction, reduced quality of life and an elevated pancreatic cancer risk. Current therapeutic options for CP are restricted to symptomatic treatment. Using ex vivo and in vivo preclinical disease models, Szabó et al. now explored for the first time the involvement of Store-operated Ca2+ entry (SOCE) in the progression of CP and propose that a selective pharmacological inhibition of the SOCE signaling component Orai1 might serve as specific treatment option for CP[1,2].

Comprehensive review on the pathogenesis of hypertriglyceridaemia-associated acute pancreatitis

It is well known, that the inflammatory process that characterizes acute pancreatitis (AP) can lead to both pancreatic damage and systemic inflammatory response syndrome (SIRS). During the last 20 years, there has been a growing incidence of episodes of acute pancreatitis associated with hypertriglyceridaemia (HTAP). This review provides an overview of triglyceride metabolism and the potential mechanisms that may contribute to developing or exacerbating HTAP. The article comprehensively discusses the various pathological roles of free fatty acid, inflammatory response mechanisms, the involvement of microcirculation, serum calcium overload, oxidative stress and the endoplasmic reticulum, genetic polymorphism, and gut microbiota, which are known to trigger or escalate this condition. Future perspectives on HTAP appear promising, with ongoing research focused on developing more specific and effective treatment strategies.

Prospect of Mesenchymal Stem-Cell-Conditioned Medium in the Treatment of Acute Pancreatitis: A Systematic Review

Mesenchymal stem cells (MSCs) have demonstrated potential in both clinical and pre-clinical research for mitigating tissue damage and inflammation associated with acute pancreatitis (AP) via paracrine mechanisms. Hence, there has been a recent surge of interest among researchers in utilizing MSC cultured medium (CM) and its components for the treatment of AP, which is recognized as the primary cause of hospitalization for gastrointestinal disorders globally. A systematic review was conducted by searching the MEDLINE, EMBASE, and Web of Science databases. Studies that involve the administration of MSC-CM, extracellular vesicles/microvesicles (EVs/MVs), or exosomes to AP animal models are included. A total of six research studies, including eight experiments, were identified as relevant. The findings of this study provide evidence in favor of a beneficial impact of MSC-CM on both clinical and immunological outcomes. Nevertheless, prior to clinical trials, large animal models should be used and prolonged observation periods conducted in pre-clinical research. Challenges arise due to the lack of standardization and consensus on isolation processes, quantifications, and purity testing, making it difficult to compare reports and conduct meta-analyses in MSC-CM-based therapies.

AKBA alleviates experimental pancreatitis by inhibiting oxidative stress in Macrophages through the Nrf2/HO-1 pathway

BACKGROUND

Acute pancreatitis (AP) is an inflammatory condition of the pancreas characterized by oxidative stress and inflammation in its pathophysiology. Acetyl-11-keto-β-boswellic acid (AKBA) is an active triterpenoid with antioxidant activity. This article seeks to assess the impact of AKBA on AP and investigate its underlying mechanisms.

METHODS

AP was induced in wild-type, Lyz2+/cre Nrf2fl/fl mice and Pdx1+/cre Nrf2fl/fl mice by caerulein. Serum amylase and lipase levels, along with histological grading, were utilized to evaluate the severity of AP. Murine bone marrow-derived macrophages (BMDMs) were isolated, cultured, and polarized to the M1 subtype. Flow cytometry and ELISA were utilized to identify the macrophage phenotype. Alterations in oxidative stress damage and intracellular ROS were observed. Nrf2/HO-1 signaling pathways were also evaluated.

RESULTS

In a caerulein-induced mouse model of AP, treatment with AKBA reduced blood amylase and lipase activity and ameliorated pancreatic tissue histological and pathological features. Furthermore, AKBA significantly mitigated oxidative stress-induced damage and induced the expression of Nrf2 and HO-1 protein. Additionally, by using conditional knockout mice (Lyz2+/cre Nrf2fl/fl and Pdx1+/cre Nrf2fl/fl mice), we verified that Nrf2 primarily functions in macrophages rather than acinar cells. In vitro, AKBA inhibits pro-inflammatory M1-subtype macrophage polarization and reduces ROS generation through Nrf2/HO-1 oxidative stress pathway. Moreover, the protective effects of AKBA against AP were abolished in myeloid-specific Nrf2-deficient mice and BMDMs. Molecular docking results revealed interactions between AKBA and Nrf2.

CONCLUSION

Our results confirm that AKBA exerts protective effects against AP in mice by inhibiting oxidative stress in macrophages through the Nrf2/HO-1 Pathway.

Extracellular SQSTM1 exacerbates acute pancreatitis by activating autophagy-dependent ferroptosis

ABBREVIATIONS

5-HETE, 5-hydroxyeicosatetraenoic acid; ACSL4, acyl-CoA synthetase long chain family member 4; AP, acute pancreatitis; ATG, autophagy related; AGER, advanced glycosylation end-product specific receptor; DAMPs, danger/damage-associated molecular patterns; FTH1, ferritin heavy chain 1; GPX4, glutathione peroxidase 4; IL, interleukin; INSR, insulin receptor; MAP1LC3B, microtubule associated protein 1 light chain 3 beta; MDA, malondialdehyde; MPO, myeloperoxidase; PRRs, pattern recognition receptors; PUFA, polyunsaturated fatty acid; RNAi, RNA interference; SQSTM1, sequestosome 1; TNF, tumor necrosis factor; TLR, toll like receptor.

Repetitive Cerulein-Induced Chronic Pancreatitis in Growing Pigs-A Pilot Study

Chronic pancreatitis (CP) is an irreversible and progressive inflammatory disease. Knowledge on the development and progression of CP is limited. The goal of the study was to define the serum profile of pro-inflammatory cytokines and the cell antioxidant defense system (superoxidase dismutase-SOD, and reduced glutathione-GSH) over time in a cerulein-induced CP model and explore the impact of these changes on selected cytokines in the intestinal mucosa and pancreatic tissue, as well as on selected serum biochemical parameters. The mRNA expression of CLDN1 and CDH1 genes, and levels of Claudin-1 and E-cadherin, proteins of gut barrier, in the intestinal mucosa were determined via western blot analysis. The study showed moderate pathomorphological changes in the pigs' pancreas 43 days after the last cerulein injection. Blood serum levels of interleukin (IL)-1-beta, IL-6, tumor necrosis factor alpha (TNF-alpha), C-reactive protein (CRP), lactate dehydrogenase (LDH), gamma-glutamyl transpeptidase (GGTP), SOD and GSH were increased following cerulein injections. IL-1-beta, IL-6, TNF-alpha and GSH were also increased in jejunal mucosa and pancreatic tissue. In duodenum, decreased mRNA expression of CDH1 and level of E-cadherin and increased D-lactate, an indicator of leaky gut, indicating an inflammatory state, were observed. Based on the current results, we can conclude that repetitive cerulein injections in growing pigs not only led to CP over time, but also induced inflammation in the intestine. As a result of the inflammation, the intestinal barrier was impaired.

Acute pancreatitis induces a transient hypercoagulable state in murine models

BACKGROUND/OBJECTIVES

Although understudied, risk of venous thromboembolism (VTE) appears to be increased during acute pancreatitis (AP). We aimed to further characterize a hypercoagulable state associated with AP utilizing thromboelastography (TEG), a readily available, point of care test.

METHODS

AP was induced in C57/Bl6 mice using l-arginine and caerulein. TEG was performed with citrated native samples. The maximum amplitude (MA) and coagulation index (CI), a composite marker of coagulability, were evaluated. Platelet aggregation was assessed using whole blood collagen-activated platelet impedance aggregometry. Circulating tissue factor (TF), the initiator of extrinsic coagulation, was measured with ELISA. A VTE model using IVC ligation followed by measurement of clot size and weight was evaluated. After IRB approval and consent, blood samples from patients hospitalized with a diagnosis of AP were evaluated by TEG.

RESULTS

Mice with AP displayed a significant increase in MA and CI, consistent with hypercoagulability. Hypercoagulability peaked at 24 h after induction of pancreatitis, then returned to baseline by 72 h. AP resulted in significantly increased platelet aggregation and elevated circulating TF. Increased clot formation with AP was observed in an in vivo model of deep vein thrombosis. In a proof of concept, correlative study, over two thirds of patients with AP demonstrated an elevated MA and CI compared to the normal range, consistent with hypercoagulability.

CONCLUSIONS

Murine acute pancreatitis results in a transient hypercoagulable state that can be assessed by TEG. Correlative evidence for hypercoagulability was also demonstrated in human pancreatitis. Further study to correlate coagulation measures to incidence of VTE in AP is warranted.

Hemorheological and Microcirculatory Relations of Acute Pancreatitis

Acute pancreatitis still means a serious challenge in clinical practice. Its pathomechanism is complex and has yet to be fully elucidated. Rheological properties of blood play an important role in tissue perfusion and show non-specific changes in acute pancreatitis. An increase in blood and plasma viscosity, impairment of red blood cell deformability, and enhanced red blood cell aggregation caused by metabolic, inflammatory, free radical-related changes and mechanical stress contribute to the deterioration of the blood flow in the large vessels and also in the microcirculation. Revealing the significance of these changes in acute pancreatitis may better explain the pathogenesis and optimize the therapy. In this review, we give an overview of the role of impaired microcirculation by changes in hemorheological properties in acute pancreatitis.

Circulating monocytes in acute pancreatitis

Acute pancreatitis is a common gastrointestinal disease characterized by inflammation of the exocrine pancreas and manifesting itself through acute onset of abdominal pain. It is frequently associated with organ failure, pancreatic necrosis, and death. Mounting evidence describes monocytes - phagocytic, antigen presenting, and regulatory cells of the innate immune system - as key contributors and regulators of the inflammatory response and subsequent organ failure in acute pancreatitis. This review highlights the recent advances of dynamic change of numbers, phenotypes, and functions of circulating monocytes as well as their underling regulatory mechanisms with a special focus on the role of lipid modulation during acute pancreatitis.

Effects of Berberine against Pancreatitis and Pancreatic Cancer

The pancreas is a glandular organ with endocrine and exocrine functions necessary for the maintenance of blood glucose homeostasis and secretion of digestive enzymes. Pancreatitis is characterized by inflammation of the pancreas leading to temporary or permanent pancreatic dysfunction. Inflammation and fibrosis caused by chronic pancreatitis exacerbate malignant transformation and significantly increase the risk of developing pancreatic cancer, the world's most aggressive cancer with a 5-year survival rate less than 10%. Berberine (BBR) is a naturally occurring plant-derived polyphenol present in a variety of herbal remedies used in traditional medicine to treat ulcers, infections, jaundice, and inflammation. The current review summarizes the existing in vitro and in vivo evidence on the effects of BBR against pancreatitis and pancreatic cancer with a focus on the signalling mechanisms underlying the effects of BBR.

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

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

MyD88 deficiency aggravates the severity of acute pancreatitis by promoting MyD88-independent TRIF pathway-mediated necrosis

Background

With uncontrolled inflammatory progression, acute pancreatitis (AP) can progress to severe acute pancreatitis (SAP). Inflammation and parenchymal cell death are key pathologic responses of AP. Toll-like receptor 4 (TLR4) plays a pro-inflammatory role in AP. Myeloid differentiation primary response protein 88 (MyD88) is the most essential utilized adaptor of TLR4, but its role in AP remains unclear. We investigated the potential role of MyD88 in the pathogenesis of AP.

Methods

An AP model was induced by administering either cerulein or L-arginine to wild-type or MyD88-deficient mice. Additionally, receptor-interacting protein kinase 1 (RIP1) inhibitor necrostatin-1 (Nec-1) was administered to the MyD88^-/- mice. The severity of AP was determined by measuring serum amylase and lipase activities, quantifying pancreatic myeloperoxidase (MPO) activity, and histological examination. The effects of MyD88 deletion on cell death and the inflammatory response were determined by measuring apoptosis, necrosis, and inflammatory cytokines. Western blot was used to assess the necrotic mediators, RIP1 and RIP3.

Results

The deletion of MyD88 resulted in more severe acute experimental pancreatitis as assessed by increased amylase and lipase activities, increased pancreatic MPO activity, a reduced anti-inflammatory response, reduced apoptosis, and increased necrosis. Additionally, Nec-1 treatment significantly reduced necrosis in the MyD88^-/- mice.

Conclusions

The deletion of MyD88 inhibited the TLR4/MyD88-dependent pathway mediated protective immune defense response and enhanced TLR4/MyD88-independent TRIF pathway-mediated pancreatic necrosis, which in turn aggravated the severity of AP. The critical role of MyD88 in immune defense response and cell death indicates that MyD88 represents a potential therapeutic target in the management of AP.

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

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

Transcriptomics and Network Pharmacology Reveal the Protective Effect of Chaiqin Chengqi Decoction on Obesity-Related Alcohol-Induced Acute Pancreatitis via Oxidative Stress and PI3K/Akt Signaling Pathway

Obesity-related acute pancreatitis (AP) is characterized by increasing prevalence worldwide and worse clinical outcomes compared to AP of other etiologies. Chaiqin chengqi decoction (CQCQD), a Chinese herbal formula, has long been used for the clinical management of AP but its therapeutic actions and the underlying mechanisms have not been fully elucidated. This study has investigated the pharmacological mechanisms of CQCQD in a novel mouse model of obesity-related alcohol-induced AP (OA-AP). The mouse OA-AP model was induced by a high-fat diet for 12 weeks and subsequently two intraperitoneal injections of ethanol, CQCQD was administered 2 h after the first injection of ethanol. The severity of OA-AP was assessed and correlated with changes in transcriptomic profiles and network pharmacology in the pancreatic and adipose tissues, and further docking analysis modeled the interactions between compounds of CQCQD and their key targets. The results showed that CQCQD significantly reduced pancreatic necrosis, alleviated systemic inflammation, and decreased the parameters associated with multi-organ dysfunction. Transcriptomics and network pharmacology analysis, as well as further experimental validation, have shown that CQCQD induced Nrf2/HO-1 antioxidant protein response and decreased Akt phosphorylation in the pancreatic and adipose tissues. In vitro, CQCQD protected freshly isolated pancreatic acinar cells from H₂O₂-elicited oxidative stress and necrotic cell death. The docking results of AKT1 and the active compounds related to AKT1 in CQCQD showed high binding affinity. In conclusion, CQCQD ameliorates the severity of OA-AP by activating of the antioxidant protein response and down-regulating of the PI3K/Akt signaling pathway in the pancreas and visceral adipose tissue.

Calcium imaging in intact mouse acinar cells in acute pancreas tissue slices

The physiology and pathophysiology of the exocrine pancreas are in close connection to changes in intra-cellular Ca²⁺ concentration. Most of our knowledge is based on in vitro experiments on acinar cells or acini enzymatically isolated from their surroundings, which can alter their structure, physiology, and limit our understanding. Due to these limitations, the acute pancreas tissue slice technique was introduced almost two decades ago as a complementary approach to assess the morphology and physiology of both the endocrine and exocrine pancreas in a more conserved in situ setting. In this study, we extend previous work to functional multicellular calcium imaging on acinar cells in tissue slices. The viability and morphological characteristics of acinar cells within the tissue slice were assessed using the LIVE/DEAD assay, transmission electron microscopy, and immunofluorescence imaging. The main aim of our study was to characterize the responses of acinar cells to stimulation with acetylcholine and compare them with responses to cerulein in pancreatic tissue slices, with special emphasis on inter-cellular and inter-acinar heterogeneity and coupling. To this end, calcium imaging was performed employing confocal microscopy during stimulation with a wide range of acetylcholine concentrations and selected concentrations of cerulein. We show that various calcium oscillation parameters depend monotonically on the stimulus concentration and that the activity is rather well synchronized within acini, but not between acini. The acute pancreas tissue slice represents a viable and reliable experimental approach for the evaluation of both intra- and inter-cellular signaling characteristics of acinar cell calcium dynamics. It can be utilized to assess many cells simultaneously with a high spatiotemporal resolution, thus providing an efficient and high-yield platform for future studies of normal acinar cell biology, pathophysiology, and screening pharmacological substances.

A microRNA checkpoint for Ca2+ signaling and overload in acute pancreatitis

Acute pancreatitis (AP) is a common digestive disease without specific treatment, and its pathogenesis features multiple deleterious amplification loops dependent on translation, triggered by cytosolic Ca2+ ([Ca2+]i) overload; however, the underlying mechanisms in Ca2+ overload of AP remains incompletely understood. Here we show that microRNA-26a (miR-26a) inhibits pancreatic acinar cell (PAC) store-operated Ca2+ entry (SOCE) channel expression, Ca2+ overload, and AP. We find that major SOCE channels are post-transcriptionally induced in PACs during AP, whereas miR-26a expression is reduced in experimental and human AP and correlated with AP severity. Mechanistically, miR-26a simultaneously targets Trpc3 and Trpc6 SOCE channels and attenuates physiological oscillations and pathological elevations of [Ca2+]i in PACs. MiR-26a deficiency increases SOCE channel expression and [Ca2+]i overload, and significantly exacerbates AP. Conversely, global or PAC-specific overexpression of miR-26a in mice ameliorates pancreatic edema, neutrophil infiltration, acinar necrosis, and systemic inflammation, accompanied with remarkable improvements on pathological determinants related with [Ca2+]i overload. Moreover, pancreatic or systemic administration of an miR-26a mimic to mice significantly alleviates experimental AP. These findings reveal a previously unknown mechanism underlying AP pathogenesis, establish a critical role for miR-26a in Ca2+ signaling in the exocrine pancreas, and identify a potential target for the treatment of AP.

Ketogenesis acts as an endogenous protective programme to restrain inflammatory macrophage activation during acute pancreatitis

Background

Innate immunity and metabolites link to the pathogenesis and severity of acute pancreatitis (AP). However, liver metabolism and its role in immune response and AP progression remain elusive. We investigated the function of liver metabolism in the pathogenesis of AP.

Methods

Circulating ketone body β-hydroxybutyrate (βOHB) levels were determined in AP clinical cohorts and caerulein-induced AP (CER-AP) mouse models receiving seven (Cer*7) or twelve (Cer*12) injection regimens at hourly intervals. Liver transcriptomics and metabolomics were compared between CER-AP (Cer*7) and CER-AP (Cer*12). Inhibition of fatty acid β-oxidation (FAO)-ketogenesis, or supplementation of βOHB was performed in mouse models of AP. The effect and mechanism of βOHB were examined in vitro.

Findings

Elevated circulating βOHB was observed in patients with non-severe AP (SAP) but not SAP. These findings were replicated in CER-AP (Cer*7) and CER-AP (Cer*12), which manifested as limited and hyperactive immune responses, respectively. FAO-ketogenesis was activated in CER-AP (Cer*7), while impaired long-chain FAO and mitochondrial function were observed in the liver of CER-AP (Cer*12). Blockage of FAO-ketogenesis (Cpt1a antagonism or Hmgcs2 knockdown) worsened, while supplementation of βOHB or its precursor 1,3-butanediol alleviated the severity of CER-AP. Mechanistically, βOHB had a discernible effect on pancreatic acinar cell damage, instead, it greatly attenuated the activation of pancreatic and systemic proinflammatory macrophages via class I histone deacetylases.

Interpretation

Our findings reveal that hepatic ketogenesis is activated as an endogenous protective programme to restrain AP progression, indicating its potential therapeutic value.

Funding

This work was supported by the National Natural Science Foundation of China, Shanghai Youth Talent Support Programme, and Shanghai Municipal Education Commission-Gaofeng Clinical Medicine Grant.

Reduction in O-GlcNAcylation Mitigates the Severity of Inflammatory Response in Cerulein-Induced Acute Pancreatitis in a Mouse Model

Acute pancreatitis (AP) involves premature trypsinogen activation, which mediates a cascade of pro-inflammatory signaling that causes early stages of pancreatic injury. Activation of the transcription factor κB (NF-κB) and secretion of pro-inflammatory mediators are major events in AP. O-GlcNAc transferase (OGT), a stress-sensitive enzyme, was recently implicated to regulate NF-κB activation and inflammation in AP in vitro. This study aims to determine whether a pancreas-specific transgenic reduction in OGT in a mouse model affects the severity of AP in vivo. Mice with reduced pancreatic OGT (OGT^Panc+/-) at 8 weeks of age were randomized to cerulein, which induces pancreatitis, or saline injections. AP was confirmed by elevated amylase levels and on histological analysis. The histological scoring demonstrated that OGT^Panc+/- mice had decreased severity of AP. Additionally, serum lipase, LDH, and TNF-α in OGT^Panc+/- did not significantly increase in response to cerulein treatment as compared to controls, suggesting attenuated AP induction in this model. Our study reveals the effect of reducing pancreatic OGT levels on the severity of pancreatitis, warranting further investigation on the role of OGT in the pathology of AP.

Blood-brain barrier dysfunction in L-ornithine induced acute pancreatitis in rats and the direct effect of L-ornithine on cultured brain endothelial cells

BACKGROUND

In severe acute pancreatitis (AP) the CNS is affected manifesting in neurological symptoms. Earlier research from our laboratory showed blood-brain barrier (BBB) permeability elevation in a taurocholate-induced AP model. Here we aimed to further explore BBB changes in AP using a different, non-invasive in vivo model induced by L-ornithine. Our goal was also to identify whether L-ornithine, a cationic amino acid, has a direct effect on brain endothelial cells in vitro contributing to the observed BBB changes.

METHODS

AP was induced in rats by the intraperitoneal administration of L-ornithine-HCl. Vessel permeability and the gene expression of the primary transporter of L-ornithine, cationic amino acid transporter-1 (Cat-1) in the brain cortex, pancreas, liver and lung were determined. Ultrastructural changes were followed by transmission electron microscopy. The direct effect of L-ornithine was tested on primary rat brain endothelial cells and a triple co-culture model of the BBB. Viability and barrier integrity, including permeability and TEER, nitrogen monoxide (NO) and reactive oxygen species (ROS) production and NF-κB translocation were measured. Fluorescent staining for claudin-5, occludin, ZO-1, β-catenin, cell adhesion molecules Icam-1 and Vcam-1 and mitochondria was performed. Cell surface charge was measured by laser Doppler velocimetry.

RESULTS

In the L-ornithine-induced AP model vessel permeability for fluorescein and Cat-1 expression levels were elevated in the brain cortex and pancreas. On the ultrastructural level surface glycocalyx and mitochondrial damage, tight junction and basal membrane alterations, and glial edema were observed. L-ornithine decreased cell impedance and elevated the BBB model permeability in vitro. Discontinuity in the surface glycocalyx labeling and immunostaining of junctional proteins, cytoplasmic redistribution of ZO-1 and β-catenin, and elevation of Vcam-1 expression were measured. ROS production was increased and mitochondrial network was damaged without NF-κB, NO production or mitochondrial membrane potential alterations. Similar ultrastructural changes were seen in L-ornithine treated brain endothelial cells as in vivo. The basal negative zeta potential of brain endothelial cells became more positive after L-ornithine treatment.

CONCLUSION

We demonstrated BBB damage in the L-ornithine-induced rat AP model suggesting a general, AP model independent effect. L-ornithine induced oxidative stress, decreased barrier integrity and altered BBB morphology in a culture BBB model. These data suggest a direct effect of the cationic L-ornithine on brain endothelium. Endothelial surface glycocalyx injury was revealed both in vivo and in vitro, as an additional novel component of the BBB-related pathological changes in AP.

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

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