Specific pancreatic enzymes activate macrophages to produce tumor necrosis factor-alpha: role of nuclear factor kappa B and inhibitory kappa B proteins

Exosomes Derived From Cerulein-Stimulated Pancreatic Acinar Cells Mediate Peritoneal Macrophage M1 Polarization and Pyroptosis via an miR-24-3p/MARCH3/NLRP3 Axis in Acute Pancreatitis

OBJECTIVES

Acute pancreatitis (AP) has a high incidence of hospitalizations, morbidity, and mortality worldwide. A growing number of studies on AP pathogenesis are based on cerulein-induced experimental model, which simulates human AP in vivo. It has been demonstrated that both pancreatic acinar cells and peritoneal macrophages are involved in pancreatic inflammation and damage. However, their connection has not been well understood.

METHODS

A cerulein-induced AP model was established on the pancreatic acinar cell line AR42J. Rat macrophages were isolated from the peritoneal cavity. The effects of cerulein-induced pancreatic exosomes on the peritoneal macrophage and pancreas in vivo and in vitro were examined. The underlying molecular mechanism was investigated by exploring the regulatory role of downstream molecules.

RESULTS

We found that exosomes derived from cerulein-treated AR42J cells induced rat peritoneal macrophage M1 polarization and pyroptosis. miR-24-3p was upregulated in cerulein-stimulated exosomes, whereas the miR-24-3p inhibitor counteracted the effect of pancreatic exosomes on peritoneal macrophage M1 polarization and pyroptosis. Furthermore, miR-24-3p inhibited March3 expression, whereas MARCH3 mediated NLRP3 ubiquitination in rat peritoneal macrophages, which, in turn, contributed to the apoptosis, reactive oxygen species production, and inflammation in AR42J cells.

CONCLUSIONS

Exosomes derived from cerulein-stimulated pancreatic acinar cells mediate peritoneal macrophage M1 polarization and pyroptosis via an miR-24-3p/MARCH3/NLRP3 axis in AP.

The Role of Pancreatic Infiltrating Innate Immune Cells in Acute Pancreatitis

Acute pancreatitis (AP) is a leading cause of gastrointestinal-related hospital admissions with significant morbidity and mortality. Although the underlying pathophysiology of AP is rather complex, which greatly limits the treatment options, more and more studies have revealed that infiltrating immune cells play a critical role in the pathogenesis of AP and determine disease severity. Thus, immunomodulatory therapy targeting immune cells and related inflammatory mediators is expected to be a novel treatment modality for AP which may improve the prognosis of patients. Cells of the innate immune system, including macrophages, neutrophils, dendritic cells, and mast cells, represent the majority of infiltrating cells during AP. In this review, an overview of different populations of innate immune cells and their role during AP will be discussed, with a special focus on neutrophils and macrophages.

The Role of TLR-4 and Galectin-3 Interaction in Acute Pancreatitis

Toll-like receptor-4 (TLR-4) is a member of evolutionarily conserved type I transmembrane proteins that can initiate sterile inflammatory cascade in the pancreas. Expression of TLR-4 is up-regulated in pancreatic tissue, as well as, on peripheral blood innate immune cells in human and experimental models of acute pancreatitis. TLR-4 plays important pro-inflammatory roles during development of acute pancreatitis: it recognize alarmins released from injured acinar cells and promotes activation and infiltration of innate immune cells after the premature and intraacinar activation of tripsinogen. Galectin-3 is β-galactoside-binding lectin that plays pro-inflammatory roles in a variety autoimmune diseases, acute bacterial infections and during tumorigenesis. It is reported that Galectin-3 is alarmin in experimental models of neuroinflammation and binds to TLR-4 promoting the pro-inflammatory phenotype of microglia. Also, in experimental model of acute pancreatitis Galectin-3 is colocalized with TLR-4 on innate inflammatory cells resulted in enhanced production of inflammatory cytokines, TNF-α and IL-1β, increased infiltration of pro-inflammatory N1 neutrophils, macrophages and dendritic cells and increased damage of pancreatic tissue. This review paper discusses the role of TLR-4/Gal-3 axis in the pathogenesis of acute pancreatitis.

Human primary neutrophil mRNA does not contaminate human resolving macrophage mRNA after efferocytosis

The ingestion of apoptotic corpses by macrophages, a process called efferocytosis, is a crucial step in inflammation resolution, since it alters macrophage phenotype toward a pro-resolving profile to foil inflammation and to favor tissue repair. Up to now, the resolving macrophages remain poorly characterized, especially in humans. Global investigations, like RNA sequencing, would be very helpful to unravel some features of these elusive cells. Nonetheless, these inquiries may be challenging in a single-species model, since the fate of ingested mRNA remains unknown and may hinder any subsequent mRNA investigations in the phagocyte. A full human model consisting of primary human neutrophil and primary human monocyte-derived macrophage co-culture was set up several decades ago to mimic in vitro the efferocytosis process. However, to our knowledge, this model has not been characterized as a suitable model to perform global mRNA investigations. Indeed, the extent of ingested neutrophil mRNA contamination has not been assessed in resolving macrophages. This work answers to this crucial question. Indeed, based on the protocols presented in this article, we demonstrate that neutrophil mRNA is severely degraded and is not able to cross-contaminate resolving macrophage mRNA, contrary to apoptotic human peripheral blood derived mononuclear cell (PBMC) or apoptotic leukemic Jurkat cell mRNA. Moreover, this allogenic co-culture system does not favor neither neutrophil activation nor macrophage pro-inflammatory cytokine release. Collectively, we highlight that this model of primary human neutrophil and primary human monocyte-derived macrophage co-culture is the best model for mRNA investigations in human resolving macrophages to help improving our knowledge on these crucial cells.

Two to Tango: Dialogue between Adaptive and Innate Immunity in Type 1 Diabetes

Type 1 diabetes mellitus (T1DM) is a long-term and chronic autoimmune disorder, in which the immune system attacks the pancreatic β-cells. Both adaptive and innate immune systems are involved in T1DM development. Both B-cells and T-cells, including CD4 ⁺ and CD8 ⁺ T-cells, as well as other T-cell subsets, could affect onset of autoimmunity. Furthermore, cells involved in innate immunity, including the macrophages, dendritic cells, and natural killer (NK) cells, could also accelerate or decelerate T1DM development. In this review, the crosstalk and function of immune cells in the pathogenesis of T1DM, as well as the corresponding therapeutic interventions, are discussed.

Bidirectional Relationship Between Reduced Blood pH and Acute Pancreatitis: A Translational Study of Their Noxious Combination

Acute pancreatitis (AP) is often accompanied by alterations in the acid-base balance, but how blood pH influences the outcome of AP is largely unknown. We studied the association between blood pH and the outcome of AP with meta-analysis of clinical trials, and aimed to discover the causative relationship between blood pH and AP in animal models. PubMed, EMBASE, and Cochrane Controlled Trials Registry databases were searched from inception to January 2017. Human studies reporting systemic pH status and outcomes (mortality rate, severity scores, and length of hospital stay) of patient groups with AP were included in the analyses. We developed a new mouse model of chronic metabolic acidosis (MA) and induced mild or severe AP in the mice. Besides laboratory blood testing, the extent of pancreatic edema, necrosis, and leukocyte infiltration were assessed in tissue sections of the mice. Thirteen studies reported sufficient data in patient groups with AP (n = 2,311). Meta-analysis revealed markedly higher mortality, elevated severity scores, and longer hospital stay in AP patients with lower blood pH or base excess (P < 0.001 for all studied outcomes). Meta-regression analysis showed significant negative correlation between blood pH and mortality in severe AP. In our mouse model, pre-existing MA deteriorated the pancreatic damage in mild and severe AP and, vice versa, severe AP further decreased the blood pH of mice with MA. In conclusion, MA worsens the outcome of AP, while severe AP augments the decrease of blood pH. The discovery of this vicious metabolic cycle opens up new therapeutic possibilities in AP.

Targeting MicroRNA Function in Acute Pancreatitis

Acute pancreatitis (AP) is a common gastrointestinal disorder that featured by acute inflammatory responses leading to systemic inflammatory response syndrome (SIRS) or multiple organ failure. A worldwide increase in annual incidence has been observed during the past decade with high acute hospitalization and mortality. Lack of any specific treatment for AP, even to this day, is a reminder that there is much to be learned about the exact pathogenesis of AP. Fortunately, the discovery of microRNA (miRNA) has started an entirely new thought process regarding the molecular mechanism associated with the disease processes. Given the extensive effort made on miRNA research, certain types of miRNA have been identified across a variety of biological processes, including cell differentiation, apoptosis, metabolism, and inflammatory responses. Mutations in miRNA sequences or deregulation of miRNA expression may contribute to the alteration of a pivotal physiological function leading to AP. Designing miRNA-related tools for AP diagnosis and treatment presents a novel and potential research frontier. In this mini-review, we summarize the current knowledge of various miRNAs closely interacting with AP and the possible development of targeted miRNA therapies in this disease, which may benefit the development of potential disease biomarkers and novel treatment targets for future medical implications.

Pancreatic Acinar Cells Employ miRNAs as Mediators of Intercellular Communication to Participate in the Regulation of Pancreatitis-Associated Macrophage Activation

Macrophage activation plays an important role in the inflammatory response in acute pancreatitis. In the present study, the activation of AR42J pancreatic acinar cells was induced by taurolithocholate treatment. The results showed that the culture medium from the activated AR42J cells significantly enhanced NFκB activation in the macrophages compared to that without taurolithocholate treatment. Additionally, the precipitates obtained from ultracentrifugation of the culture media that were rich in exosomes were markedly more potent in activating macrophages compared with the supernatant fraction lacking exosomes. The results indicated that the mediators carried by the exosomes played important roles in macrophage activation. Exosomal miRNAs were extracted and examined using microarrays. A total of 115 differentially expressed miRNAs were identified, and 30 showed upregulated expression, while 85 displayed downregulated expression. Target genes of the differentially expressed miRNAs were predicted using TargetScan, MiRanda, and PicTar software programs. The putative target genes were subjected to KEGG functional analysis. The functions of the target genes were primarily enriched in MAPK pathways. Specifically, the target genes regulated macrophage activation through the TRAF6-TAB2-TAK1-NIK/IKK-NFκB pathway. As the mediators of signal transduction, miRNAs and their predicted target mRNAs regulate every step in the MAPK pathway.

Controversial role of toll-like receptors in acute pancreatitis

Acute pancreatitis (AP) is a common clinical condition with an incidence of about 300 or more patients per million annually. About 10%-15% of patients will develop severe acute pancreatitis (SAP) and of those, 10%-30% may die due to SAP-associated complications. Despite the improvements done in the diagnosis and management of AP, the mortality rate has not significantly declined during the last decades. Toll-like receptors (TLRs) are pattern-recognition receptors that seem to play a major role in the development of numerous diseases, which make these molecules attractive as potential therapeutic targets. TLRs are involved in the development of the systemic inflammatory response syndrome, a potentially lethal complication in SAP. In the present review, we explore the current knowledge about the role of different TLRs that have been described associated with AP. The main candidate for targeting seems to be TLR4, which recognizes numerous damage-associated molecular patterns related to AP. TLR2 has also been linked with AP, but there are only limited studies that exclusively studied its role in AP. There is also data suggesting that TLR9 may play a role in AP.

TNF-alpha-dependent regulation of acute pancreatitis severity by Ly-6C(hi) monocytes in mice

The roles of monocytes/macrophages and their mechanisms of action in the regulation of pancreatitis are poorly understood. To address these issues, we have employed genetically altered mouse strains that either express the human diphtheria toxin receptor (DTR) coupled to the CD11b promoter or have global deletion of TNF-α. Targeted, conditional depletion of monocytes/macrophages was achieved by administration of diphtheria toxin (DT) to CD11b-DTR mice. We show that in the absence of DT administration, pancreatitis is associated with an increase in pancreatic content of Ly-6C(hi) monocytes/macrophages but that this response is prevented by prior administration of DT to CD11b-DTR mice. DT administration also reduces pancreatic edema and acinar cell injury/necrosis in two dissimilar experimental models of acute pancreatitis (a secretagogue-induced model and a model elicited by retrograde pancreatic duct infusion of sodium taurocholate). In the secretagogue-elicited model, the DT-induced decrease in pancreatitis severity is reversed by adoptive transfer of purified Ly-6C(hi) monocytes harvested from non-DT-treated CD11b-DTR mice or by the transfer of purified Ly-6C(hi) monocytes harvested from TNF-α(+/+) donor mice, but it is not reversed by the transfer of Ly-6C(hi) monocytes harvested from TNF-α(-/-) donors. Our studies indicate that the Ly-6C(hi) monocyte subset regulates the severity of pancreatitis by promoting pancreatic edema and acinar cell injury/necrosis and that this phenomenon is dependent upon the expression of TNF-α by those cells. They suggest that therapies targeting Ly-6C(hi) monocytes and/or TNF-α expression by Ly-6C(hi) monocytes might prove beneficial in the prevention or treatment of acute pancreatitis.

Role of macrophages in the progression of acute pancreatitis

In addition to pancreatic cells, other inflammatory cell populations contribute to the generation of inflammatory mediators during acute pancreatitis. In particular, macrophages could be activated by mediators released during pancreatitis by a damaged pancreas. It has been reported that peritoneal macrophages, alveolar macrophages and Kupffer cells become activated in different stages of severe acute pancreatitis. However, macrophages display remarkable plasticity and can change their physiology in response to environmental cues. Depending on their microenvironmental stimulation, macrophages could follow different activation pathways resulting in marked phenotypic heterogeneity. This ability has made these cells interesting therapeutical targets and several approaches have been assayed to modulate the progression of inflammatory response secondary to acute pancreatitis. However, despite the recent advances in the modulation of macrophage function in vivo, the therapeutical applications of these strategies require a better understanding of the regulation of gene expression in these cells.

Use of gene expression profiles in cells of peripheral blood to identify new molecular markers of acute pancreatitis

HYPOTHESIS

Blood leukocytes play a major role in mediating local and systemic inflammation during acute pancreatitis. We hypothesize that peripheral blood mononuclear cells (PBMCs) in circulation exhibit unique changes in gene expression and could provide a "reporter" function that reflects the inflammatory response in the pancreas with acute pancreatitis.

DESIGN

To determine specific changes in blood leukocytes during acute pancreatitis, we studied the gene transcription profile in PBMCs in a rat model of experimental pancreatitis (sodium taurocholate). Normal rats, saline controls, and a model of septic shock were used as a controls. Complementary RNA obtained from PBMCs of each group (n = 3 in each group) were applied to Affymetrix rat genome DNA GeneChip arrays. Main Outcome Measure Changes in gene expression.

RESULTS

From the 8799 rat genes analyzed, 140 genes showed unique significant changes in their expression in PBMCs during the acute phase of pancreatitis, but not in sepsis. Among the 140 genes, 57 were up-regulated, while 69 were down-regulated. Platelet-derived growth factor receptor, prostaglandin E(2) receptor, and phospholipase D(1) were among the top up-regulated genes. Others included genes involved in G protein-coupled receptor and transforming growth factor beta-mediated signaling pathways, while genes associated with apoptosis, glucocorticoid receptors, and even the cholecystokinin receptor were down-regulated.

CONCLUSIONS

Microarray analysis in transcriptional profiling of PBMCs showed that genes that are uniquely related to molecular and pancreatic function display differential expression in acute pancreatitis. Profiling genes obtained from an easily accessible source during severe pancreatitis may identify surrogate markers for disease severity.

Up-regulation of Toll-like receptor 4 was suppressed by emodin and baicalin in the setting of acute pancreatitis

Acute pancreatitis (AP) activates the systemic inflammatory response and is potentially lethal. Recent studies demonstrated that pancreatic enzymes could induce cytokine expression via Toll-like receptor 4 (TLR4) signal pathway, indicating a possible role of TLR4 in local pancreatic injury and systemic inflammatory response. Emodin, an anthraquinone derivative from Radix et Rhizoma Rhei, and baicalin, a flavone from Scutellaria baicalensis Georgi, both have been reported to possess anti-inflammatory activities. In present study, we investigated the combined effect of emodin and baicalin on pancreatic damage and pancreatitis associated lung injury, as well as tissue TLR4 expression in the setting of AP. The results showed that combination of emodin and baicalin significantly reduced serum amylase, tumor necrosis factor-alpha and interleukin-6, attenuated pancreatic and pulmonary damage, also suppressed TLR4 expression in pancreas and lung. It could be speculated that amelioration of pancreatic and pulmonary damage by emodin and baicalin might contribute, in part at least, to the suppression of TLR4 expression. The present study provides beneficial evidence as to simultaneous treatment for AP, and also suggests an important role of TLR4 in pathophysiology of AP.

Protein kinase C-zeta is critical in pancreatitis-induced apoptosis of Kupffer cells

Protein kinase C-zeta (PKC-zeta) regulates cell death via NF-kappaB; therefore, we tested the hypothesis that PKC-zeta plays a critical role in pancreatitis-induced Kupffer cell apoptosis. Acute pancreatitis was induced in rats by cerulein injection 24 h later, livers were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, and apoptosis was assessed with Caspase-3 and DNA fragmentation. Kupffer cells from unoperated rats were infected with a PKC-zeta domain-negative adenovirus (AdPKCzeta-DN) to inhibit PKC-zeta, or transfected with pCMVPKC-zeta to overexpress PKC-zeta, and then stimulated with pancreatic elastase; cellular extracts were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation. Cerulein-induced pancreatitis upregulated PKC-zeta protein and activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3 and increased DNA fragmentation in rat livers (all p < 0.001 vs control). AdPKCzeta-DN abolished elastase-induced upregulation of PKC-zeta activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3 and DNA fragmentation (all p < 0.001 vs infection control), whereas overexpression of PKC-zeta augmented elastase-induced upregulation of IKKbeta, IKKgamma, Fas/FasL, Caspase-3 and DNA fragmentation (p < 0.001 vs control). PKC-zeta plays a critical role in pancreatitis-induced Kupffer cell apoptosis via NF-kappaB and Fas/FasL. The ability of Kupffer cells to autoregulate their stress response by upregulating their death receptor/ligand and key proapoptotic cell signaling systems warrants further investigation.

Role of tumor necrosis factor-alpha in acute pancreatitis: from biological basis to clinical evidence

Tumor necrosis factor (TNF)-alpha is a pleiotropic cytokine that exerts host-damaging effects in different autoimmune and inflammatory diseases. It is a key regulator of other proinflammatory cytokines and of leukocyte adhesion molecules, and it is a priming activator of immune cells. In recent years, several research lines-mostly derived from animal models and in vitro studies-suggested that TNF-alpha plays a pivotal role in the pathogenesis of acute pancreatitis. In particular, it contributes to the systemic progression of the inflammatory response and to the end-organ dysfunction often observed in severe disease. Current clinical applications of TNF-alpha in acute pancreatitis include the assessment of blood concentrations to predict disease severity and to identify individuals prone to develop complications such as multiple organ failure and septic shock. However, TNF-alpha is rapidly cleared from the bloodstream, and sensitivity and overall accuracy of its measurement seem strictly time dependent, thereby being of potential prognostic value only in the first days after the onset of the disease. In parallel, TNF-alpha has been evaluated as a novel pharmacologic target for treating pancreatitis. Although promising results have been observed in the laboratory, transition to clinical practice seems problematic, in particular, in the light of divergent results obtained in sepsis trials. Therefore, in future clinical trials pertaining to TNF-alpha neutralization in acute pancreatitis, timing of intervention should be related to changes in TNF-alpha serum levels, and inclusion and exclusion criteria should be accurately selected to better define the population most likely to benefit.

Immune status and inflammatory response differ locally and systemically in severe acute pancreatitis

OBJECTIVE

Acute pancreatitis (AP) is an inflammatory disorder that develops a complex cascade of immunological events. The local and systemic immune status and inflammatory response might contribute to the understanding of underlying pathophysiological mechanisms and potential treatment.

MATERIAL AND METHODS

Severe AP was induced by intraductal perfusion of 5% sodium taurodeoxycholate in rats. mRNA expression of cytokines and chemokines was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and NF-kappaB activation was assessed by electrophoretic mobility shift assay in fresh pancreatic acini and circulating monocytes 1, 3, 6 or 9 h after sham operation, induction of AP or N-acetylcysteine (NAC) pretreatment. Flow cytometry was performed on cells obtained from the peripheral blood.

RESULTS

An inverse relationship in pancreatic and circulating monocytic NF-kappaB activation was detected 6 and 9 h after induction of AP. NAC further suppressed monocytic NF-kappaB activation induced by AP as seen 9 h after induction of AP. A marked constitutive increase in the expression of IL-6, CINC and MCP-1 was seen in pancreatic acini, whereas no change in mRNA expression of inflammatory mediators was observed in circulating monocytes 6 h after induction of AP. Flow cytometry further confirmed the altered function of circulating monocytes.

CONCLUSIONS

The different immune status and inflammatory response in the pancreas and circulating monocytes improve the understanding of the mechanisms by which systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS) develop in severe AP. A potential therapeutic approach could be to restore the functional capacity of the immune system in AP. The use of an NF-kappaB inhibitor, preferentially reaching the local inflammatory foci, could be a potential future way of intervention.

Neutral Endopeptidase Determines the Severity of Pancreatitis-Associated Lung Injury1

BACKGROUND

Neutral endopeptidase (NEP) is a cell-surface metalloprotease that degrades proinflammatory peptides such as substance P, neurokinin A, and bradykinin. Inhibition of NEP exacerbates both experimental pancreatitis and the associated lung injury. It is unclear if worsened lung injury is the indirect result of more severe pancreatitis or if it is a direct effect of NEP inhibition in the lung.

MATERIALS AND METHODS

We used a model of pancreatitis-associated lung injury (PALI) to test the hypothesis that antagonism or genetic deletion of NEP augments PALI inflammation and pulmonary damage irregardless of the degree of pancreatitic inflammation.

RESULTS

In NEP(+/+) mice, intraperitoneal injection of porcine pancreatic elastase (elastase, 0.085 U/g at t = 0 h and t = 1 h) caused a 7-fold increase in lung myeloperoxidase (MPO) activity and marked pulmonary edema, neutrophil infiltration, and hemorrhage at 4 h as compared to control animals. The pattern of lung injury induced by elastase mimicked that observed among a separate group of animals with PALI induced by cerulein but was not associated with pancreatitis. Both NEP(-/-) mice and NEP(+/+) mice pretreated with the NEP antagonist phosphoramidon (10 mg/kg s.c.) had significant elevations of lung MPO and worsened lung histology compared to NEP(+/+) mice given elastase alone. Antagonism of either the vanilloid receptor transient receptor vanilloid 1 or the substance P receptor NK1-R had no effect on elastase-mediated lung injury in NEP-deficient mice.

CONCLUSIONS

NEP is an inhibitor of pancreatic elastase-induced lung injury, presumably via degradation of proinflammatory mediators.

Compartmentalization of the protease-antiprotease balance in early severe acute pancreatitis

OBJECTIVE

To assess the balance between trypsin and protease inhibitors simultaneously in the systemic circulation and in the thoracic lymph and peritoneal exudate.

METHODS

Twenty patients with early severe acute pancreatitis were studied. Enzymatically active and immunoreactive trypsin in conjunction with its major inhibitors were measured in the 3 compartments at the onset of end-organ failure(s). The molecular forms of trypsin were determined in the lymph and ascites by gel filtration chromatography to separate trypsinogen and free-and inhibitor-bound trypsin.

RESULTS

Both enzymatically active trypsin and immunoreactive trypsin levels were highest in ascites and lymph compared with the systemic circulation. Intracompartmental alpha1- protease inhibitor gradient moved in the opposite direction, whereas alpha2 macroglobulin concentration was highest in ascites and lowest in the lymph. Although most of the enzymatically and immunoreactive material in ascites and lymph consisted of trypsin complexed with alpha2 macroglobulin and trypsinogen, respectively, free active trypsin was detected in more than 80% of the samples.

CONCLUSIONS

In patients with early severe acute pancreatitis, there is a significant trypsinogen activation resulting in protease-antiprotease imbalance and thereby free enzymatically active trypsin in the 2 body fluid compartments in close vicinity to the inflammatory process. This may be involved in the pathophysiology of local and distant tissue damage.

Questioning Current Concepts in Acute Pancreatitis: Endotoxin Contamination of Porcine Pancreatic Elastase Is Responsible for Experimental Pancreatitis-Associated Distant Organ Failure

The systemic inflammatory response syndrome is responsible for pancreatitis-associated mortality. Recent in vitro and in vivo studies have suggested that pancreatic elastase is one missing link between the localized inflammatory process in the pancreas and distant organ dysfunction and failure. It has been shown that pancreatic elastase activates transcription factors, including NF-kappaB, and induces TNF-alpha secretion in myeloid cells via TLRs. In this study we demonstrate that a highly purified low endotoxin pancreatic elastase preparation (El-UP) failed both to activate NF-kappaB and to induce TNF-alpha release in RAW 264.7 cells and bone marrow-derived macrophages. In contrast, a less purified elastase preparation (El-IV) caused activation of NF-kappaB and was able to induce TNF-alpha release at very low concentrations. These effects were sensitive to pretreatment of the cells with polymyxin B and were resistant to heat inactivation. Endotoxin activity as determined by the Limulus amebocyte lysate assay was >3 orders of magnitude lower in the low endotoxin elastase preparation (El-UP) compared with less purified elastase preparations (El-IV). In contrast to contaminated elastase or LPS, elastase free of contamination (El-UP) failed to induce elevated serum TNF-alpha levels or pulmonary neutrophil infiltration after i.p. application in mice and did not induce lethality when coinjected with d-galactosamine. Failure of low endotoxin elastase (El-UP) to induce proinflammatory effects in vivo and in vitro was not due to functional inactivity of the elastase preparation, as determined by elastase activity assay. These results question current concepts of direct proinflammatory effects attributed to pancreatic elastase.

Severe acute pancreatitis: case-oriented discussion of interdisciplinary management

The clinical course of an episode of acute pancreatitis varies from a mild, transitory illness to a severe often necrotizing form with distant organ failure and a mortality rate of 20-40%. Patients with severe pancreatitis, representing about 15-20% of all patients with acute pancreatitis, need to be identified as early as possible after onset of symptoms allowing starting intensive care treatment early in the disease process. An episode of severe acute pancreatitis progresses in two phases. The first 10-14 days are characterized by a systemic inflammatory response syndrome maintained by the release of various inflammatory mediators. The second phase, beginning about 10-14 days after the onset of the disease is dominated by sepsis-related morbidity due to infected peripancreatic and pancreatic necrosis. This state is associated with septic multiple organ systemic failure. The importance of infection on the outcome of necrotizing pancreatitis has been clearly delineated and the pre-emptive use of broad-spectrum antibiotics that achieve effective tissue concentrations is considered standard management of patients with severe necrotizing pancreatitis, especially if associated with organ failure or extended necrosis. Patients with infected necrosis should undergo a surgical intervention. The standard open technique consisting of an organ preserving necrosectomy followed by a postoperative concept of lavage and/or drainage to evacuate necrotic debris occurring during the further course has recently been challenged by various minimally invasive approaches.

A nuclear import inhibitory peptide ameliorates the severity of cholecystokinin-induced acute pancreatitis

AIM: To assess the effect of our novel cell-permeable nuclear factor-kappaB (NF-κB) inhibitor peptide PN50 in an experimental model of acute pancreatitis. PN50 was produced by conjugating the cell-penetrating penetratin peptide with the nuclear localization signal of the NF-κB p50 subunit.

METHODS: Pancreatitis was induced in male Wistar rats by administering 2×100 μg/kg body weight of cholecystokinin-octapeptide (CCK) intraperitoneally (IP) at an interval of 1 h. PN50-treated animals received 1 mg/kg of PN50 IP 30 min before or after the CCK injections. The animals were sacrificed 4 h after the first injection of CCK.

RESULTS: All the examined laboratory (the pancreatic weight/body weight ratio, serum amylase activity, pancreatic levels of TNF-α and IL-6, degree of lipid peroxidation, reduced glutathione levels, NF-κB binding activity, pancreatic and lung myeloperoxidase activity) and morphological parameters of the disease were improved before and after treatment with the PN50 peptide. According to the histological findings, PN50 protected the animals against acute pancreatitis by favoring the induction of apoptotic, as opposed to necrotic acinar cell death associated with severe acute pancreatitis.

CONCLUSION: Our study implies that reversible inhibitors of stress-responsive transcription factors like NF-κB might be clinically useful for the suppression of the severity of acute pancreatitis.

An Inflammatory Role for the Mammalian Carboxypeptidase Inhibitor Latexin: Relationship to Cystatins and the Tumor Suppressor TIG1

Latexin, the only known mammalian carboxypeptidase inhibitor, has no detectable sequence similarity with plant and parasite inhibitors, but it is related to a human putative tumor suppressor protein, TIG1. Latexin is expressed in the developing brain, and we find that it plays a role in inflammation, as it is expressed at high levels and is inducible in macrophages in concert with other protease inhibitors and potential protease targets. The crystal structure of mouse latexin, solved at 1.83 A resolution, shows no structural relationship with other carboxypeptidase inhibitors. Furthermore, despite a lack of detectable sequence duplication, the structure incorporates two topologically analogous domains related by pseudo two-fold symmetry. Surprisingly, these domains share a cystatin fold architecture found in proteins that inhibit cysteine proteases, suggesting an evolutionary and possibly functional relationship. The structure of the tumor suppressor protein TIG1 was modeled, revealing its putative membrane binding surface.

Proinflammatory effects of pancreatic elastase are mediated through TLR4 and NF-kappaB

Pancreatic elastase has been implicated in the pathophysiology of severe acute pancreatitis, characterized by systemic inflammatory response, distant organ failure, and high mortality. Here we show that pancreatic elastase activates transcription factors NF-kappaB, AP-1, and NFAT in human myeloid cells (U-937 and THP-1) in culture. Pancreatic elastase also induces TNF-alpha secretion and increased expression of CD11b in THP-1 cells which can be inhibited by neutralizing anti-Toll-like receptor 4 (TLR4) antibodies. NF-kappaB blocking agents (MG-132, PGA1) prevented elastase-induced TNF-alpha secretion from THP-1 cells. Our results suggest that pancreatic elastase-induced proinflammatory effects are mediated by TLR4 and NF-kappaB in human myeloid cells.

p8 improves pancreatic response to acute pancreatitis by enhancing the expression of the anti-inflammatory protein pancreatitis-associated protein I

p8 is a transcription cofactor whose expression is strongly and rapidly activated in pancreatic acinar cells during the acute phase of pancreatitis. A p8-deficient mouse strain was generated as a tool to investigate its function. Upon induction of acute pancreatitis, myeloperoxidase activity in pancreas and serum concentrations of amylase and lipase were much higher and pancreatic lesions more severe in p8-deficient mice than in wild-type, indicating that p8 expression decreased pancreatic sensitivity to pancreatitis induction. The protective mechanism might involve the pancreatitis-associated protein (PAP I), whose strong induction during pancreatitis is p8-dependent, because administration of anti-PAP I antibodies to rats increased pancreatic inflammation during pancreatitis. In addition, 100 ng/ml PAP I in the culture medium of macrophages prevented their activation by tumor necrosis factor alpha, strongly suggesting that PAP I was an anti-inflammatory factor. Finally, PAP I was able to inhibit NFkappaB activation by tumor necrosis factor alpha, in macrophages and in the AR42J pancreatic acinar cell line. In conclusion, p8 improves pancreatic resistance to inducers of acute pancreatitis by a mechanism implicating the expression of the anti-inflammatory protein PAP I.

Intercellular adhesion molecule-1 expression in pancreas graft and its signal transducer

AIM

To investigate the effect of neutrophil elastase inhibitor (ONO-5046) on expression of intercellular adhesion molecule-1 and transduction signal after pancreasduodenal transplantation in rats.

METHODS

ONO-5 046 was injected intravenously into experimental animal models. ICAM-1 mRNA transduction signals were detected in rat endothelial cells with regard to the effect of many reagents on expression of ICAM.

RESULTS

ICAM-1 mRNA level decreased in pancreatic grafts of experimental animals. ICAM-1 mRNA expression was increased in rat endothelial cells in vitro stimulated by NE, while that it could be inhibited by ONO-5046. Calcium ionophore enhenced ICAM-1 mRNA expression. In contrast, a phospholipase C inhibitor, calcium chelator and nuclear factor-kappa B inhibitor regulated down NE induction of ICAM-1 mRNA.

CONCLUSION

ICAM-1 expression stimulated by NE in pancreatic grafts may be associated with intracellular Ca²⁺ influx and a phospholipase C signal transduction.

Pancreatic elastase is proven to be a mannose-binding protein--implications for the systemic response to pancreatitis

BACKGROUND

Mannose-binding proteins (MBPs) have been isolated from serum, liver, lung, and kidney and are believed to play an important role in first-line host defense during acute phase inflammatory response. Because of the inflammatory nature of pancreatitis, we postulate that the pancreas produces endogenous MBP.

METHODS

Pancreatic juice, from both human and rat, was collected by pancreatic duct cannulation and subjected to mannose-Sepharose affinity chromatography to isolate pancreatic MBP (pMBP). Protein eluates from the mannose-Sepharose column were analyzed using reverse-phase high-performance liquid chromatography, sodium dodeclysulfate-polyacrylamide gel electrophoresis, and, subsequently, by N-terminal protein sequencing. Western blot analysis was used to identify the pMBP, and reverse transcriptionase-polymerase chain reaction was used to examine its mRNA expression. Complement lysis was measured using red blood cells coated with yeast mannan. Tumor necrosis factor (TNF)-alpha mRNA expression in macrophages was measured using RNase protection assay.

RESULTS

A 30-kd MBP was isolated from both human and rat pancreatic juice and a rat acinar cell line. Genetic analysis (using RT-PCR with known MBP primers) and protein analysis (using Western blot with a known anti-MBP antibody) suggest that the pMBP is different from any previously described MBP. Protein sequencing analysis of pMBP generated an N-terminus sequence of 12 residues, indicating that pMBP is human pancreatic elastase III. Western blot analysis using an anti-elastase antibody confirms that the pMBP is a pancreatic elastase. Exposure of macrophages to pancreatic elastase resulted in an increased mRNA level of TNF-alpha, a potent proinflammatory cytokine in acute-phase response. Addition of mannan to pancreatic elastase further upregulated the TNF-alpha response.

CONCLUSION

We isolated an MBP from the pancreas and identified it as pancreatic elastase. We characterized it as having properties different from that of any previously known MBP. We showed that pMBP or pancreatic elastase is involved in the activation of macrophages, and that this activation is potentiated by mannan. We postulate that the mannose-binding properties of pancreatic elastase identify this enzyme as a candidate catalyst for both pancreatic and systemic inflammation.

Systemic nf-kappaB activation in a transgenic mouse model of acute pancreatitis

BACKGROUND

Transcription factor NF-kappaB has been implicated in numerous human inflammatory diseases. Acute pancreatitis can result in remote tissue injury, but the involved mechanisms are unknown. This study evaluates the role of systemic NF-kappaB activation in the pathogenesis of lung inflammation in a transgenic pancreatitis model.

MATERIALS AND METHODS

Using transgenic mice expressing photinus luciferase controlled by an NF-kappaB-dependent promoter, luciferase activity was measured in pancreas, liver, and lung tissues as a surrogate marker of NF-kappaB activity. Luciferase activity was measured by in vivo bioluminescence and correlated to an in vitro luciferase assay of organ homogenates. Following measurement of luciferase activity in uninjured animals, these animals were fed a choline-deficient, ethionine supplemented diet for 48 h to induce pancreatitis, and luciferase activity was then measured at 48, 60, 72, and 96 h. Lung inflammation was determined by total nucleated cell counts in bronchoalveolar lavage (BAL) fluid.

RESULTS

Bioluminescence detected increased luciferase activity over the upper abdominal region at 48 and 60 h (P < 0.05), and over the thorax at 60 and 72 h (P < 0.05). Luciferase assays showed significantly increased luciferase activity in both liver and lung tissue at 48 (liver = P < 0.005, lung = P < 0.05) and 60 h (liver = P < 0.05, lung = P < 0.05) compared to activity in uninjured controls. Total nucleated cell counts in BAL fluid were significantly increased at 72 h (P < 0.05) compared with controls.

CONCLUSION

In this model, NF-kappaB binding activity is increased in the liver and lung. These data suggest that the liver modulates pancreatitis-induced systemic inflammatory response syndrome (SIRS) and suggest strategies to reduce multisystem injury.

Macrophage migration inhibitory factor is a critical mediator of severe acute pancreatitis

BACKGROUND & AIMS

Macrophage migration inhibitory factor (MIF), originally described as an inhibitor of the random migration of macrophages, has been shown recently to be involved in the pathogenesis of several inflammatory diseases such as sepsis. The aim of this study was to clarify the role of MIF in acute pancreatitis (AP).

METHODS

Hemorrhagic necrotizing pancreatitis and edematous pancreatitis were induced by the injection of taurocholic acid (TCA pancreatitis) and cerulein (cerulein pancreatitis), respectively, on male Wistar rats. MIF levels in ascitic fluids, serum, and the organs were determined. The effects of anti-MIF antibody were examined on the prognosis of rats with TCA pancreatitis and of female CD-1 mice with choline-deficient, ethionine-supplemented, diet-induced model of severe AP. In addition, serum MIF levels in AP patients and in healthy controls were measured.

RESULTS

Serum and ascitic MIF levels in TCA pancreatitis were increased rapidly and decreased gradually thereafter. Ascitic MIF levels were also increased in cerulein pancreatitis, but to a lesser degree. MIF level was increased in the lung in TCA pancreatitis, but not in the pancreas and the liver. Prophylactic (1 hour before and immediately after induction) administration of anti-MIF antibody significantly improved the survival rate of rats with TCA pancreatitis. The survival rate of mice with severe AP was also improved significantly by the antibody treatment. Serum MIF levels were higher in severe AP patients than mild AP patients and healthy controls.

CONCLUSIONS

These results suggest a role of MIF in the pathogenesis of severe AP.

Molecular cloning and characterization of chymopasin, a novel serine protease from rat pancreas

INTRODUCTION

Pancreas secretes many enzymes for food digestion into the pancreatic juice. We cloned a novel serine protease, chymopasin, from rat pancreas.

AIMS

To know the localization of this enzyme in the pancreas and to analyze the enzymatic characteristics.

METHODOLOGY

We cloned chymopasin cDNA using 3' and 5' RACEs. Northern blot and in situ hybridization were used to study the expression of this enzyme. Recombinant chymopasin protein produced by was analyzed by Western blot using specific antibody, and its enzymatic characteristics were examined using commercially available synthetic substrates, fibrin and gelatin.

RESULTS

The open reading frame of rat chymopasin consisted of 792 bp encoding 264 amino acid residues. The deduced amino acid sequence contained the essential catalytic triad characteristic of the serine protease family. There was no putative N-glycosylation site. The amino acid sequence of rat chymopasin showed 54.5% identity to rat chymotrypsin B. Northern blot analysis showed that the transcript was strongly expressed in the pancreas. In situ hybridization with digoxigenin-labeled cRNA probe showed that the positive signals were observed in the acinar cells, but not in the islet or duct cells. Chymopasin protein was detected in the pancreas homogenate and bile-pancreatic juice. Further, cerulein stimulated the secretion of rat chymopasin into bile-pancreatic juice.

CONCLUSION

These results suggested that rat chymopasin might be a digestive enzyme secreted from the acinar cells. From the enzyme assay using synthetic substrates, the purified recombinant chymopasin expressed in showed chymotrypsin-like activity. In addition, rat recombinant chymopasin showed fibrinolytic and gelatinolytic activities. These results suggested a role in the pathogenesis of pancreatic damage.

Selective inhibition of NF-kappaB attenuates the severity of cerulein-induced acute pancreatitis

BACKGROUND

Acute pancreatitis (AP) is associated with increased cytokine production, which can ultimately produce deleterious local and systemic effects. The transcription factor NF-kappaB is activated by degradation of its inhibitory factor, IkappaB, and can stimulate various cytokines. The purpose of this study was to determine whether the inhibition of NF-kappaB binding activity with a novel peptide that binds to the NF-kappaB essential modifier binding domain (NBD) could attenuate the severity of AP.

STUDY DESIGN

AP was induced in Swiss Webster mice by hourly injections of the cholecystokinin analogue cerulein (50 microg/kg). Mice were injected with either the wild-type or control (mutated) NBD peptide at the time of the first cerulein injection; they were then sacrificed over a time course, and pancreata and lungs were harvested for histologic analysis and scoring. Myeloperoxidase activity was measured to assess neutrophil sequestration as an indicator of inflammation. NF-kappaB binding activity and steady-state levels of IkappaB and NF-kappaB subunits were determined by gel shift and Western blot, respectively.

RESULTS

AP resulted in increased NF-kappaB DNA-binding activity and decreased steady-state levels of IkappaB. Treatment with NBD peptide decreased inflammation in the pancreas, decreased hemorrhage in the lungs, and decreased myeloperoxidase activity in both pancreas and lung.

CONCLUSIONS

The marked induction of NF-kappaB binding activity suggests a role for this transcription factor in the early inflammatory changes associated with AP. Treatment with the NBD peptide attenuated the severity of injury associated with AP. Novel compounds that selectively target NF-kappaB may prove to be useful treatment of AP and AP-associated lung injury.

Recombinant human neutral endopeptidase ameliorates pancreatic elastase-induced lung injury

BACKGROUND

Genetic deletion of neutral endopeptidase (NEP), a cell-surface metalloprotease that degrades proinflammatory peptides, exacerbates lung injury induced by pancreatic elastase in a model of pancreatitis-associated lung injury. We tested 3 hypotheses: (1) genetic deletion of NEP prolongs lung recovery after elastase injections; (2) elastase-mediated lung injury is associated with down-regulation of NEP; and (3) pretreatment of NEP (-/-) and (+/+) animals with recombinant human NEP (rhNEP) reduces pulmonary damage in this model.

METHODS

NEP (+/+) or (-/-) mice were injected with pancreatic elastase (0.085 U/g/dose intraperitoneally) or saline carrier at t = 0 hours and t = 1 hour. Some mice were pretreated with rhNEP (3 mg/kg intraperitoneally). Serum elastase, lung histologic score, myeloperoxidase, and NEP activities were measured at 4, 8, or 12 hours.

RESULTS

NEP (-/-) mice had worse pulmonary inflammation at 4 and 8 hours versus (+/+) mice. Lung NEP activity was similar in elastase-treated and control (+/+) animals. Pretreatment with rhNEP reduced myeloperoxidase and improved histology at 4 hours in NEP (-/-) and (+/+) mice.

CONCLUSIONS

Pancreatic elastase induces lung injury that is worse and prolonged in NEP (-/-) mice. Pretreatment with rhNEP ameliorates this injury. Thus, upregulation of NEP is a potential therapeutic approach for pancreatitis-associated lung injury.

Pancreatic elastase induces liver injury by activating cytokine production within Kupffer cells via nuclear factor-Kappa B

Liver injury is a manifestation of the systemic inflammatory response during acute pancreatitis. We have demonstrated that elastase induces macrophage tumor necrosis factor (TNF) production in distant organs, thus mimicking pancreatitis-associated organ injury. The aim of this study was to determine the mechanism by which elastase induces hepatic cytokine production. Rat livers (n = 40) were perfused with elastase +/- gadolinium (Gd) to inhibit Kupffer cells. Liver parenchymal enzymes and TNF were measured in the effluent. In vitro, rat hepatocytes or Kupffer cells were treated with elastase (1 U/ml) +/- Gd (0.5 mg/ml) or pyrrolidine dithiocarbamate (PDTC; 0.5 mg/ml). TNF protein, TNF messenger RNA, and NF-kappa B activation were determined. In vivo, Gd blunted the elastase-induced TNF production and decreased AST, ALT, LDH, and nonviable cells (propidium iodide) (P < or= 0.03 vs. elastase). In vitro, elastase induced TNF production from Kupffer cells (P < 0.001 vs. control) but not from hepatocytes. Gd or PDTC significantly attenuated the elastase-induced TNF production (P < 0.001). Elastase-induced overexpression of TNF messengerRNA and activation of NF-kappa B was attenuated by Gd. Pancreatic elastase induces a pattern of liver injury similar to that seen during acute pancreatitis by activating cytokine production and gene expression within Kupffer cells via NF-kappa B. Gd exhibits a protective effect against elastase-induced liver injury by inhibiting activation of NF-kappa B.

Differential Effects of Apoptotic Versus Lysed Cells on Macrophage Production of Cytokines: Role of Proteases

Granulocytes undergoing apoptosis are recognized and removed by phagocytes before their lysis. The release of their formidable arsenal of proteases and other toxic intracellular contents into tissues can create significant damage, prolonging the inflammatory response. Binding and/or uptake of apoptotic cells by macrophages inhibits release of proinflammatory cytokines by mechanisms that involve anti-inflammatory mediators, including TGF-beta. To model the direct effects of necrotic cells on macrophage cytokine production, we added lysed or apoptotic neutrophils and lymphocytes to mouse and human macrophages in the absence of serum to avoid complement activation. The results confirmed the ability of lysed neutrophils, but not lymphocytes, to significantly stimulate production of macrophage-inflammatory protein 2 or IL-8, TNF-alpha, and IL-10. Concomitantly, induction of TGF-beta1 by lysed neutrophils was significantly lower than that observed for apoptotic cells. The addition of selected serine protease inhibitors and anti-human elastase Ab markedly reduced the proinflammatory effects, the lysed neutrophils then behaving as an anti-inflammatory stimulus similar to intact apoptotic cells. Separation of lysed neutrophils into membrane and soluble fractions showed that the neutrophil membranes behaved like apoptotic cells. Thus, the cytokine response seen when macrophages were exposed to lysed neutrophils was largely due to liberated proteases. Therefore, we suggest that anti-inflammatory signals can be given by PtdSer-containing cell membranes, whether from early apoptotic, late apoptotic, or lysed cells, but can be overcome by proteases liberated during lysis. Therefore, the outcome of an inflammatory reaction and the potential immunogenicity of Ags within the damaged cell will be determined by which signals predominate.