A novel model of severe gallstone pancreatitis: murine pancreatic duct ligation results in systemic inflammation and substantial mortality

Redefining Immune Dynamics in Acute Pancreatitis: The Protective Role of Galectin-3 Deletion and Treg Cell Enhancement

Acute pancreatitis (AP) is a complex inflammatory condition that can lead to systemic inflammatory responses and multiple organ dysfunction. This study investigates the role of Galectin-3 (Gal-3), a β-galactoside-binding lectin, in modulating acquired immune responses in AP. Acute pancreatitis was induced by ligation of the bile-pancreatic duct in wild-type and Galectin-3-deficient C57BL/6 mice. We determined the phenotypic and molecular features of inflammatory cells, serum concentrations of amylase, pancreatic trypsin activity, and pancreatic and lung pathology. Galectin-3 deficiency decreased the total number of CD3+CD49- T cells and CD4+ T helper cells, downregulated the production of inflammatory cytokine and IFN-γ, and increased the accumulation of IL-10-producing Foxp3+ T regulatory cells and regulatory CD4+ T cells in the pancreata of diseased animals. The deletion of Galectin-3 ameliorates acute pancreatitis characterized by lowering serum amylase concentration and pancreatic trypsin activity, and attenuating of the histopathology of the lung. These findings shed light on the role of Galectin-3 in acquired immune response in acute pancreatitis and identify Galectin-3 as an attractive target for investigation of the immunopathogenesis of disease and for consideration as a potential therapeutic target for patients with acute inflammatory disease of the pancreas.

Electroacupuncture Ameliorates Acute Pancreatitis: A Role for the Vagus Nerve-Mediated Cholinergic Anti-Inflammatory Pathway

Organ failure resulting from excessive inflammation is the leading cause of death in the early phase of acute pancreatitis (AP). The autonomic nervous system was reported to be involved in AP, and the vagus nerve could exert anti-inflammatory effects through α7 nicotinic acetylcholine receptor (α7nAChR) signaling. Acupuncture has been widely used in traditional Asian medicine, and recent studies suggested the inflammation modulating effect of electroacupuncture (EA) might be mediated by the autonomic nervous system. In this study, we aimed to investigate the effects of EA in AP animal models. Two independent AP mouse models were used, namely, caerulein hyperstimulation and pancreatic duct ligation. We found that EA at Zusanli acupoint increased vagus nerve activity, suppressed systemic inflammation, and alleviated the histopathological manifestations and leukocyte infiltrations of the pancreas. Induction of AP resulted in a remarkable decrease in the frequency of α7nAchR⁺ macrophages in the pancreas, while EA counteracted this phenomenon. The anti-inflammatory, pancreatic protective and upregulation of α7nAchR effects of EA were reduced in mice with vagotomy. Moreover, the therapeutic effects of EA were attenuated in mice treated with methyllycaconitine citrate, a selective α7nAChR antagonist. Taken together, EA could modulate inflammation, thereby exerting protective effects in AP. The mechanism may include activating the vagus nerve through the cholinergic anti-inflammatory pathway.

Vagus Nerve Stimulation Decreases Pancreatitis Severity in Mice

Background

Vagus nerve stimulation (VNS) is effective in reducing inflammation in various diseases, such as rheumatoid arthritis, colitis and acute kidney injury. The anti-inflammatory effect of vagus nerve in these diseases necessitates the interactions of neural activation and α7 nicotinic acetylcholine receptors (α7nAChRs) on splenic macrophages. In this study, we aimed to investigate the effect of VNS on severity in experimental acute pancreatitis (AP).

Methods

Two independent AP models were used, which induced in ICR mice with caerulein or pancreatic duct ligation (PDL). Thirty minutes after modeling, the left cervical carotid sheath containing the vagus nerve was electrically stimulated for 2 min. Plasma lipase and amylase activities, TNF-α levels and pancreas histologic damage were evaluated. In caerulein mice, the percentages of α7nAChR⁺ macrophage in pancreas and spleen were assessed by flow cytometry. Furthermore, splenectomy and adoptive transfer of VNS-conditioned α7nAChR splenocytes were performed in caerulein mice to evaluate the role of spleen in the protective effect of VNS.

Results

VNS reduced plasma lipase and amylase activities, blunted the concentrations of TNF-α and protected against pancreas histologic damage in two AP models. Survival rates were improved in the PDL model after VNS. In caerulein AP mice, VNS increased the percentages of α7nAChR⁺ macrophages in pancreas and spleen. Adoptive transfer of VNS-treated α7nAChR splenocytes provided protection against pancreatitis in recipient mice. However, splenectomy did not abolish the protective effect of VNS.

Conclusions

VNS reduces disease severity and attenuates inflammation in AP mice. This effect is independent of spleen and is probably related to α7nAChR on macrophage.

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

Acute pancreatitis is a potentially severe inflammatory disease that may be associated with a substantial morbidity and mortality. Currently there is no specific treatment for the disease, which indicates an ongoing demand for research into its pathogenesis and development of new therapeutic strategies. Due to the unpredictable course of acute pancreatitis and relatively concealed anatomical site in the retro-peritoneum, research on the human pancreas remains challenging. As a result, for over the last 100 years studies on the pathogenesis of this disease have heavily relied on animal models. This review aims to summarize different animal models of acute pancreatitis from the past to present and discuss their main characteristics and applications. It identifies key studies that have enhanced our current understanding of the pathogenesis of acute pancreatitis and highlights the instrumental role of animal models in translational research for developing novel therapies.

Early Intra-Acinar Events in Pathogenesis of Pancreatitis

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

Deletion of Galectin-3 attenuates acute pancreatitis in mice by affecting activation of innate inflammatory cells

Acute pancreatitis is characterized by autodigestion of pancreatic cells followed by acute inflammation leading to pathology and death. In experimental acute pancreatitis, pancreatic acinar cells and infiltrating macrophages express Galectin-3 but its role in pathology of this disease is unknown. Therefore, we studied its role using Galectin-3 deficient mice. Deletion of Galectin-3 prolonged the survival of mice, led to attenuation of histopathology, and decreased infiltration of mononuclear cells and neutrophils that express TLR-4, in particular, pro-inflammatory N1 neutrophils. Galectin-3 and TLR-4 are also colocalized on infiltrating cells. Lack of Galectin-3 reduced expression of pro-inflammatory TNF-α and IL-1β in F4/80⁺ CD11c- and CD11c⁺ F4/80^- cells. Thus, deletion of Galectin-3 ameliorates acute pancreatitis by attenuating early influx of neutrophils and inflammatory mononuclear cells of innate immunity. These findings provide the basis to consider Galectin-3 as a therapeutic target in acute pancreatitis.

Protective Effects of Calcitonin Gene-Related Peptide-Mediated p38 Mitogen-Activated Protein Kinase Pathway on Severe Acute Pancreatitis in Rats

BACKGROUND

Calcitonin gene-related peptide (CGRP) has antioxidant and anti-inflammatory activities on the pathological damage of acute pancreatitis. However, its molecular mechanism on severe acute pancreatitis (SAP) remains unknown.

AIMS

To evaluate the influence of CGRP-mediated p38MAPK signaling pathway in rats with SAP.

METHODS

SD rats were randomly divided into Sham group, SAP group, CGRP group (SAP rats injected with CGRP), SB203580 group (rats injected with p38MAPK pathway inhibitor SB203580), and CGRP8-37 group (SAP rats injected with CGRP8-37). Serum amylase and lipase activities were determined. Histopathological observations were evaluated, and the expression of inflammatory cytokines and oxidative stress-related indexes were measured.

RESULTS

Compared with Sham group, SAP rats were increased in the activities of serum amylase and lipase, the pathologic assessment of pancreatic tissue, the levels of TNF-α, IL-1β, IL-6, and IL-8, the content of MDA and MPO, and the expressions of CGRP, and p-p38MAPK protein, but they were decreased in SOD activity and GSH content. The above alterations were aggravated in the CGRP8-37 group when compared with SAP group. Besides, in comparison with SAP group, rats in the CGRP and SB203580 groups presented a reduction in the activities of serum amylase and lipase, the levels of inflammatory cytokines, the content of MDA and MPO, and the expressions of p-p38MAPK protein, while showed an elevation in SOD activity and GSH content.

CONCLUSION

Pretreatment with CGRP alleviated oxidative stress and inflammatory response of SAP rats possibly by suppressing the activity of p38MAPK pathway, and thereby postponing the disease progression.

Gamma-enolase predicts lung damage in severe acute pancreatitis-induced acute lung injury

Severe acute pancreatitis (SAP) associated acute lung injury (ALI) accounts for about 70% mortality of SAP patients. However, there are no precise biomarkers for the disease currently. Herein, we evaluated the potential of gamma-enolase (ENO2), against its universal isoform alpha-enolase (ENO1), as a marker of SAP-ALI in a rat model. Firstly, 16 male Sprague-Dawley rats were randomly divided into two groups, Sham (n = 8) and SAP-ALI (n = 8), for pancreatitis induction. Ultra-structure examination by electron microscopy and HE staining were used for lung injury assessment. Lung tissue expressions of alpha-enolase and gamma-enolase were evaluated by qRT-PCR and immunohistochemistry. In a prospective validation experiment, 28 rats were used: sham (n = 8), SAP-ALI at 3 h (3 h, n = 10), and SAP-ALI at 24 h (24 h, n = 10). Lung tissue damage, tissue expression and circulating alpha-enolase and gamma-enolase levels were evaluated. Elevated serum levels of α-amylase and TNF-α were observed in SAP rats but not in sham-operated rats. Histological examination of pancreatic and lung tissues indicated marked damage in SAP rats. While alpha-enolase was universally expressed, gamma-enolase was expressed only in damaged lung tissues. Gamma-enolase was detected in lung tissues, BALF, and serum as early as 3 h post-surgery when physical pathological damage was not apparent. Unlike alpha-enolase, secreted and/or circulating gamma-enolase level progressively increased, especially in serum, as lung damage progressed. Thus, gamma-enolase may signal and correlate lung tissue damage well before obvious physical pathological tissue damage and might be a candidate diagnostic and/or prognostic marker.

Accelerating the Drug Delivery Pipeline for Acute and Chronic Pancreatitis-Knowledge Gaps and Research Opportunities: Overview Summary of a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

A workshop was sponsored by the Division of Digestive Diseases and Nutrition, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, on July 25, 2018, in Pittsburgh, Penn. The workshop was designed to bring together a multidisciplinary group of experts to accelerate the development of therapeutics for clinical application in inflammatory diseases of the exocrine pancreas. Three separate working groups (acute pancreatitis, recurrent acute pancreatitis, and chronic pancreatitis) were formed to address the needs, gaps, and opportunities. The working groups included patients with pancreatic diseases, pharmaceutical company leaders, basic scientists, clinical researchers, and representatives from the US Food and Drug Administration to assist with regulatory considerations and to identify the unmet needs, research targets, and opportunities to provide direction for successful development of therapeutic agents in these diseases. This article represents the summary of the overview presentations at the National Institute of Diabetes and Digestive and Kidney Diseases workshop including an ongoing drug trial in acute pancreatitis; a successful drug development network developed by the Cystic Fibrosis Foundation; and considerations for subject selection in drug trials, incorporating Food and Drug Administration guidelines on clinical trial design and clinical outcome measures. The summaries of each working group follow separately in accompanying articles.

Accelerating the Drug Delivery Pipeline for Acute and Chronic Pancreatitis: Summary of the Working Group on Drug Development and Trials in Acute Pancreatitis at the National Institute of Diabetes and Digestive and Kidney Diseases Workshop

A workshop was sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases to focus on research gaps and opportunities on drug development for pancreatitis. This conference was held on July 25, 2018, and structured into 3 working groups (WG): acute pancreatitis (AP) WG, recurrent AP WG, and chronic pancreatitis WG. This article reports the outcome of the work accomplished by the AP WG to provide the natural history, epidemiology, and current management of AP; inform about the role of preclinical models in therapy selection; and discuss clinical trial designs with clinical and patient-reported outcomes to test new therapies.

Translational Insights Into Peroxisome Proliferator-Activated Receptors in Experimental Acute Pancreatitis

Acute pancreatitis (AP) is an inflammatory disorder of the exocrine pancreas frequently associated with metabolic causes, contributing factors, or consequences, including hypertriglyceridemia, obesity, and disorders of intermediary metabolism, respectively. To date, there is no specific therapy for this disease. Future optimal therapy should correct both inflammatory and metabolic components of the disease. Peroxisome proliferator-activated receptors (PPARs) are lipid-sensing nuclear receptors that control inflammatory and metabolic pathways via ligand-dependent and ligand-independent mechanisms. There are 3 known subtypes, PPAR-α, PPAR-β/δ, and PPAR-γ, which are differentially expressed in various tissues. The PPARs interact closely with other transcription factors such as nuclear factor κB and signal tranducers and activators of transcription that have pivotal roles in the pathobiology of AP. In this comprehensive review, we summarize the role of PPARs in AP, highlighting important in vitro and in vivo experimental findings. Finally, we propose future research directions as well as potential translational use of PPAR agonists in the treatment of AP.

The novel cytokine interleukin-33 activates acinar cell proinflammatory pathways and induces acute pancreatic inflammation in mice

Background

Acute pancreatitis is potentially fatal but treatment options are limited as disease pathogenesis is poorly understood. IL-33, a novel IL-1 cytokine family member, plays a role in various inflammatory conditions but its role in acute pancreatitis is not well understood. Specifically, whether pancreatic acinar cells produce IL-33 when stressed or respond to IL-33 stimulation, and whether IL-33 exacerbates acute pancreatic inflammation is unknown.

Methods/Results

In duct ligation-induced acute pancreatitis in mice and rats, we found that (a) IL-33 concentration was increased in the pancreas; (b) mast cells, which secrete and also respond to IL-33, showed degranulation in the pancreas and lung; (c) plasma histamine and pancreatic substance P concentrations were increased; and (d) pancreatic and pulmonary proinflammatory cytokine concentrations were increased. In isolated mouse pancreatic acinar cells, TNF-α stimulation increased IL-33 release while IL-33 stimulation increased proinflammatory cytokine release, both involving the ERK MAP kinase pathway; the flavonoid luteolin inhibited IL-33-stimulated IL-6 and CCL2/MCP-1 release. In mice without duct ligation, exogenous IL-33 administration induced pancreatic inflammation without mast cell degranulation or jejunal inflammation; pancreatic changes included multifocal edema and perivascular infiltration by neutrophils and some macrophages. ERK MAP kinase (but not p38 or JNK) and NF-kB subunit p65 were activated in the pancreas of mice receiving exogenous IL-33, and acinar cells isolated from the pancreas of these mice showed increased spontaneous cytokine release (IL-6, CXCL2/MIP-2α). Also, IL-33 activated ERK in human pancreatic tissue.

Significance

As exogenous IL-33 does not induce jejunal inflammation in the same mice in which it induces pancreatic inflammation, we have discovered a potential role for an IL-33/acinar cell axis in the recruitment of neutrophils and macrophages and the exacerbation of acute pancreatic inflammation.

Conclusion

IL-33 is induced in acute pancreatitis, activates acinar cell proinflammatory pathways and exacerbates acute pancreatic inflammation.

Enrichment of murine CD68+ CCR2+ and CD68+ CD206+ lung macrophages in acute pancreatitis-associated acute lung injury

Acute lung injury (ALI) is an important cause of mortality in critically ill patients. Acute pancreatitis (AP) is one of the risk factors for developing this syndrome. Among the inflammatory cells, macrophages have a key role in determining the severity of the acute lung injury. In the lungs, macrophages constitute a heterogeneous cell population distributed in different compartments. Changes in not only the macrophage count, but also in their phenotype have been seen during the course of lung injury. A murine ductal ligation model of acute pancreatitis showed substantial morphological changes in the pancreas and lungs. Immunohistochemistry showed neutrophil recruitment into both organs after 9 hours and later on. F4/80(+) cells in the pancreas increased in the ligated animals, though there was not a significant difference in their number in the lungs as compared to sham operated animals. Flow cytometry analysis of lung macrophages demonstrated an enrichment of F4/80(-) CD68(+)CCR2(+) and F4/80(-) CD68(+)CD206(+) lung macrophages in ligated animals (AP) as compared to the sham operated group. The level of interleukin-6 in plasma increased 3 hours after ligation compared to the sham operated group, as a first indicator of a systemic inflammatory response.This study suggests a role for F4/80(-) CD68(+) macrophages in the pathogenesis of acute lung injury in acute pancreatitis. Studying lung macrophages for different phenotypic markers, their polarization, activation and recruitment, in the context of acute lung injury, is a novel area to potentially identify interventions which may improve the outcome of acute lung injury.

Sterile inflammatory response in acute pancreatitis

The initial injury in acute pancreatitis is characteristically sterile and results in acinar cells necrosis. Intracellular contents released from damaged cells into the extracellular space serve as damage-associated molecular patterns (DAMPs) that trigger inflammation. There is increasing evidence that this sterile inflammatory response mediated through DAMPs released from necrotic acinar cells is a key determinant of further pancreatic injury, remote organ injury, and disease resolution in experimental models. A number of DAMPS, including high-mobility group box protein 1, DNA, adenosine triphosphate and heat shock protein 70, have been shown to have a role in experimental pancreatitis. Many of these DAMPs are also detectable in the human pancreatitis. Genetic deletion and pharmacologic antagonism demonstrate that specific DAMP receptors, including Toll-like receptor (TLR) 4, TLR9, and P2X7, are also required for inflammation in experimental acute pancreatitis. Downstream DAMP-sensing components include nod-like receptor protein 3, caspase 1, interleukin-1β (IL-1), IL-18, and IL-1 receptor, and also are required for full experimental pancreatitis. These DAMP-mediated pathways provide novel therapeutic targets using antagonists of TLRs and other receptors.

Systemic inflammation with multiorgan dysfunction is the cause of death in murine ligation-induced acute pancreatitis

BACKGROUND

We have previously shown that distal pancreatic duct ligation-induced acute pancreatitis in mice is associated with substantial mortality.

METHODS

We examined the cause of death in duct ligation-induced acute pancreatitis in mice by serial examination of multiple parameters in three experimental groups: distal pancreatic duct ligation (PD), bile duct ligation alone (BD), and sham operation (S).

RESULTS

BD and S had no mortality, while PD had 94% mortality with most deaths between days 2 and 4. Characteristics of mice with acute pancreatitis included (ANOVA; p < 0.05): extracellular regulated kinase activation in the pancreas and lung; pancreatic neutrophil infiltration and acinar cell necrosis maximal on day 2; increased plasma cytokine and aspartate aminotransferase levels and bronchoalveolar lavage fluid neutrophil count and cytokine levels, peaked on day 3; hypotension and bradycardia were worst on day 4; pulmonary neutrophil infiltration and plasma creatinine level peaked on day 4. Liver injury evidenced by raised aspartate serum transaminase after hepatic obstruction was exacerbated by PD.

CONCLUSIONS

Systemic inflammation with multiorgan dysfunction causes death in pancreatic duct ligation-induced acute pancreatitis in mice. This experimental model is a suitable experimental analogy of "early severe gallstone pancreatitis" to investigate disease pathogenesis and to evaluate novel therapeutic strategies.