Attenuated cerulein-induced pancreatitis in nuclear factor-kappaB-deficient mice

Pancreatic Ubap2 deletion regulates glucose tolerance, inflammation, and protection from cerulein-induced pancreatitis

Ubiquitin-binding associated protein 2 (UBAP2) is reported to promote macropinocytosis and pancreatic adenocarcinoma (PDAC) growth, however, its role in normal pancreatic function remains unknown. We addressed this knowledge gap by generating UBAP2 knockout (U2KO) mice under a pancreas-specific Cre recombinase (Pdx1-Cre). Pancreatic architecture remained intact in U2KO animals, but they demonstrated slight glucose intolerance compared to controls. Upon cerulein challenge to induce pancreatitis, U2KO animals had reduced levels of several pancreatitis-relevant cytokines, amylase and lipase in the serum, reduced tissue damage, and lessened neutrophil infiltration into the pancreatic tissue. Mechanistically, cerulein-challenged U2KO animals revealed reduced NF-κB activation compared to controls. In vitro promoter binding studies confirmed the reduction of NF-κB binding to its target molecules supporting UBAP2 as a new regulator of inflammation in pancreatitis and may be exploited as a therapeutic target in future to inhibit pancreatitis.

New insights into the etiology, risk factors, and pathogenesis of pancreatitis in dogs: Potential impacts on clinical practice

While most cases of pancreatitis in dogs are thought to be idiopathic, potential risk factors are identified. In this article we provide a state‐of‐the‐art overview of suspected risk factors for pancreatitis in dogs, allowing for improved awareness and detection of potential dog‐specific risk factors, which might guide the development of disease prevention strategies. Additionally, we review important advances in our understanding of the pathophysiology of pancreatitis and potential areas for therapeutic manipulation based thereof. The outcome of pathophysiologic mechanisms and the development of clinical disease is dependent on the balance between stressors and protective mechanisms, which can be evaluated using the critical threshold theory.

NF-κB and Pancreatic Cancer; Chapter and Verse

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the world's most lethal cancers. An increase in occurrence, coupled with, presently limited treatment options, necessitates the pursuit of new therapeutic approaches. Many human cancers, including PDAC are initiated by unresolved inflammation. The transcription factor NF-κB coordinates many signals that drive cellular activation and proliferation during immunity but also those involved in inflammation and autophagy which may instigate tumorigenesis. It is not surprising therefore, that activation of canonical and non-canonical NF-κB pathways is increasingly recognized as an important driver of pancreatic injury, progression to tumorigenesis and drug resistance. Paradoxically, NF-κB dysregulation has also been shown to inhibit pancreatic inflammation and pancreatic cancer, depending on the context. A pro-oncogenic or pro-suppressive role for individual components of the NF-κB pathway appears to be cell type, microenvironment and even stage dependent. This review provides an outline of NF-κB signaling, focusing on the role of the various NF-κB family members in the evolving inflammatory PDAC microenvironment. Finally, we discuss pharmacological control of NF-κB to curb inflammation, focussing on novel anti-cancer agents which reinstate the process of cancer cell death, the Smac mimetics and their pre-clinical and early clinical trials.

Betulinic Acid Ameliorates the Severity of Acute Pancreatitis via Inhibition of the NF-κB Signaling Pathway in Mice

Acute pancreatitis (AP) is an inflammatory disorder, involving acinar cell death and the release of inflammatory cytokines. Currently, there are limited effective therapeutic agents for AP. Betulinic acid (BA) is a pentacyclic triterpenoid extracted from Betula platyphylla that has been shown to have anti-inflammatory effects. In this study, we aimed to investigate the effects of BA on AP and elucidate the potential underlying mechanisms. AP was induced in mice through six intraperitoneal injections of cerulein. After the last cerulein injection, the mice were sacrificed. Our results revealed that pre- and post-treatment with BA significantly reduced the severity of pancreatitis, as evidenced by a decrease in histological damage in the pancreas and lung, serum amylase and lipase activity and pancreatic myeloperoxidase activity. Furthermore, BA pretreatment reduced proinflammatory cytokine production, augmentation of chemokines, and infiltration of macrophages and neutrophils in the pancreas of AP mice. In addition, mice that were pretreated with BA showed a reduction in Iκ-Bα degradation and nuclear factor-kappa B (NF-κB) binding activity in the pancreas. Moreover, BA reduced the production of proinflammatory cytokines and NF-κB activation in pancreatic acinar cells (PACs). These findings suggest that BA may have prophylactic and therapeutic effects on AP via inhibition of the NF-κB signaling pathway.

LncRNA MEG3 Participates in Caerulein-Induced Inflammatory Injury in Human Pancreatic Cells via Regulating miR-195-5p/FGFR2 Axis and Inactivating NF-κB Pathway

Acute pancreatitis (AP) is a dysfunctional pancreas disease marked by severe inflammation. Long non-coding RNAs (lncRNAs) involving in the regulation of inflammatory responses have been frequently mentioned. The purpose of this study was to ensure the function and action mode of lncRNA maternally expressed gene 3 (MEG3) in caerulein-induced AP cell model. HPDE cells were treated with caerulein to establish an AP model in vitro. The expression of MEG3, miR-195-5p, and fibroblast growth factor receptor 2 (FGFR2) was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation and apoptosis were detected by 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometry assay, respectively. The expression of CyclinD1, B cell lymphoma/leukemia-2 (Bcl-2), Bcl-2-associated X protein (Bax), FGFR2, P65, phosphorylated P65 (p-P65), alpha inhibitor of nuclear factor kappa beta (NF-κB) (IκB-α), and phosphorylated IκB-α (p-IκB-α) at the protein level was quantified by western blot. The concentrations of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) were monitored by enzyme-linked immunosorbent assay (ELISA). The targeted relationship between miR-195-5p and MEG3 or FGFR2 was forecasted by the online software starBase v2.0 and verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. As a result, the expression of MEG3 and FGFR2 was decreased in caerulein-induced HPDE cells, while the expression of miR-195-5p was increased. MEG3 overexpression inhibited cell apoptosis and inflammatory responses that were induced by caerulein. Mechanically, miR-195-5p was targeted by MEG3 and abolished the effects of MEG3 overexpression. FGFR2 was a target of miR-195-5p, and MEG3 regulated the expression of FGFR2 by sponging miR-195-5p. FGFR2 overexpression abolished miR-195-5p enrichment-aggravated inflammatory injuries. Moreover, the NF-κB signaling pathway was involved in the MEG3/miR-195-5p/FGFR2 axis. Collectively, MEG3 participates in caerulein-induced inflammatory injuries by targeting the miR-195-5p/FGFR2 regulatory axis via mediating the NF-κB pathway in HPDE cells.

8α-Hydroxypinoresinol isolated from Nardostachys jatamansi ameliorates cerulein-induced acute pancreatitis through inhibition of NF-κB activation

Acute pancreatitis (AP) is a severe inflammatory condition of the pancreas, with no specific treatment available. We have previously reported that Nardostachys jatamansi (NJ) ameliorates cerulein-induced AP. However, the specific compound responsible for this inhibitory effect has not been identified. Therefore, in the present study, we focused on a single compound, 8α-hydroxypinoresinol (HP), from NJ. The aim of this study was to determine the effect of HP on the development of pancreatitis in mice and to explore the underlying mechanism(s). AP was induced by the injection of cerulein (50 μg/kg/h) for 6 h. HP (0.5, 5 or 10 mg/kg, i.p.) was administered 1 h prior to and 1, 3 or 5 h after the first cerulein injection, with vehicle- and DMSO-treated groups as controls. Blood samples were collected to determine serum levels of amylase, lipase, and cytokines. The pancreas was removed for morphological examination, myeloperoxidase (MPO) assays, cytokine assays, and assessment of nuclear factor (NF)-κB activation. The lungs were removed for morphological examination and MPO assays. Administration of HP dramatically improved pancreatic damage and pancreatitis-associated lung damage and also reduced amylase and lipase activities in serum. Moreover, administration of HP reduced the production of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in the pancreas and serum during AP. In addition, the administration of HP inhibited degradation of inhibitory κ-Bα (Iκ-Bα), NF-κB p65 translocation into nucleus and NF-κB binding activity in the pancreas. Our results suggest that HP exerted therapeutic effects on pancreatitis and these beneficial effects may be due to the inhibition of NF-κB activation.

Carbon monoxide releasing molecule‑2 (CORM‑2)‑liberated CO ameliorates acute pancreatitis

The purpose of the present study was to investigate the effect of carbon monoxide (CO) released from CO‑releasing molecule 2 (CORM‑2) on mice with acute pancreatitis (AP). To perform the investigation, a mouse AP model was established using caerulein. The mice were treated with or without CORM‑2. The survival rate of the mice in the different groups was analyzed, and serum amylase and lipase levels were measured to assess the degree of pancreatic injury. The severity of AP was also evaluated by histological examination, and histopathological scoring of the pancreatic damage was performed. Pancreatic cell apoptosis was analyzed using a terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labelling assay. The function of the lung and liver was also assessed in the present study. Furthermore, the role of CORM‑2 on oxidative stress, intercellular adhesion molecule 1 (ICAM‑1) and vascular cell adhesion molecule 1 (VCAM‑1) expression, pro‑inflammatory cytokine production, and nuclear factor (NF)‑κB activation in the pancreas of AP mice was determined. The results demonstrated that CORM‑2 reduced the mortality, pancreatic damage, and lung and liver injury of AP mice. CORM‑2 administration also reduced systemic and localized inflammatory cell factors. Furthermore, treatment with CORM‑2 inhibited the expression of ICAM‑1 and VCAM‑1, and the activation of NF‑κB and phosphorylated inhibitor of NF‑κB subunit α, in the pancreas of AP mice. These results indicated that CO released from CORM‑2 exerted protective effects on AP mice, and the beneficial effects were likely due to inhibition of NF‑κB pathway activation.

Sustained bile drainage decreases the organs injuries via inflammation-associated factors modulation in a severe acute pancreatitis rat model

The timely and effective treatment for severe acute pancreatitis (SAP) is favorable to prognosis. Decompression of the bile duct might be a feasible way to decrease the progression of SAP. The present study investigated the effects of sustained bile external drainage on organs injury caused by SAP in Sprague-Dawley (SD) rats and the mechanisms involved. A total of 72 female SD rats weighting 190-230 g were randomly divided into four groups (n=18): Sham operation group (SOG), SOG + bile drainage group (BDG), SAP group, and SAP + BDG. Sodium taurocholate solution (4%; 1 mg/kg body weight) was used to set up SAP model via injection of retrograde puncture of biliopancreatic duct through the duodenum. A cannula was inserted into the bile duct and fixed externally to establish BDG model. At each time points (t=3, 6, 12; n=6), tissues from the liver, lung, and pancreas, and blood samples were collected. Serum amylase (AMY) was analyzed in all the samples. The levels of tumor necrosis factor-α (TNF-α), heme oxygenase-1 (HO-1), interleukin-10 (IL-10) and high mobility group box 1 (HMGB1) were detected by ELISA. Hematoxylin-eosin staining was performed to observe the histopathological changes, and nuclear transcription factor (NF)-κB-p65 levels in the pancreas were analyzed by western blotting. The data indicated that BDG alleviated the SAP progression and multiple organs injuries. Meanwhile, the histopathological changes of the pancreas, liver, and lungs were improved by BDG. BDG decreased the pathological scores of pancreas significantly (P<0.05). The levels of AMY, TNF-α, HMGB1, and NF-κB-p65 were significantly downregulated by BDG (P<0.05), while the level of HO-1 was upregulated and IL-10 was unchanged. In summary, BDG may attenuate the multiple organs injuries caused by SAP via downregulation of TNF-α, HMGB1, NF-κB-p65 and upregulation of HO-1.

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.

Carbon monoxide releasing molecule‑2 (CORM‑2)‑liberated CO ameliorates acute pancreatitis

The purpose of the present study was to investigate the effect of carbon monoxide (CO) released from CO-releasing molecule 2 (CORM-2) on mice with acute pancreatitis (AP). To perform the investigation, a mouse AP model was established using caerulein. The mice were treated with or without CORM-2. The survival rate of the mice in the different groups was analyzed, and serum amylase and lipase levels were measured to assess the degree of pancreatic injury. The severity of AP was also evaluated by histological examination, and histopathological scoring of the pancreatic damage was performed. Pancreatic cell apoptosis was analyzed using a terminal deoxynucleotidyl-transferase-mediated dUTP nick end labelling assay. The function of the lung and liver was also assessed in the present study. Furthermore, the role of CORM-2 on oxidative stress, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) expression, pro-inflammatory cytokine production, and nuclear factor (NF)-κB activation in the pancreas of AP mice was determined. The results demonstrated that CORM-2 reduced the mortality, pancreatic damage, and lung and liver injury of AP mice. CORM-2 administration also reduced systemic and localized inflammatory cell factors. Furthermore, treatment with CORM-2 inhibited the expression of ICAM-1 and VCAM-1, and the activation of NF-κB and phosphorylated inhibitor of NF-κB subunit α, in the pancreas of AP mice. These results indicated that CO released from CORM-2 exerted protective effects on AP mice, and the beneficial effects were likely due to inhibition of NF-κB pathway activation.

Chemerin alleviates acute pancreatitis in the rat thorough modulation of NF-κB signal

OBJECTIVE

Chemerin, an adipokine, works as the chemoattractant for the immune cells. The role of chemerin in the inflammatory reaction is controversial. Chemerin has been shown to aggravate the inflammatory response, but other studies demonstrated its anti-inflammatory influence. This study assessed the effects of chemerin on acute pancreatitis (AP) in vivo and in vitro.

METHODS

For in vivo experiments male Wistar rats were used. For in vitro study rat pancreatic AR42J cells were employed. Chemerin (1, 5 or 10 μg/kg) was given to the rats prior to the induction of AP by subcutaneous caerulein infusion (25 μg/kg). For in vitro studies cells were subjected to caerulein (10 nM) with or without chemerin (100 nM). Serum amylase activity was measured by enzymatic method, serum TNFα concentration - by ELISA kit. Western-blot was used to examine cellular proteins.

RESULTS

AP was confirmed by histological examination. Chemerin given to AP rats decreased histological manifestations of AP, reduced serum amylase activity and TNFα concentration. In AR42J cells subjected to caerulein with addition of chemerin signal for TNFα was reduced comparing to the cultures treated with caerulein alone. Analysis of the dynamics of nuclear translocation for p50, p65 and Bcl-3 points out to NF-κB attenuation as a mechanism of observed anti-inflammatory action of chemerin.

CONCLUSION

Chemerin significantly alleviated severity of AP in the rat, this is possibly due to the inhibition of pro-inflammatory signaling in the pancreatic cells.

RCAN1 is a marker of oxidative stress, induced in acute pancreatitis

BACKGROUND

To date, there still is a lack of specific acute pancreatitis markers and specifically an early marker that can reliably predict disease severity. The inflammatory response in acute pancreatitis is mediated in part through oxidative stress and calcineurin-NFAT (Nuclear Factor of Activated T-cells) signaling, which is inducing its own negative regulator, regulator of calcineurin 1 (RCAN1). Caerulein induction is a commonly used in vivo model of experimental acute pancreatitis. Caerulein induces CN-NFAT signaling, reactive oxygen species and inflammation.

METHODS

To screen for potential markers of acute pancreatitis, we used the caerulein model of experimental acute pancreatitis (AP) in C57Bl/6 J mice. Pancreata from treated and control mice were used for expression profiling. Promising gene candidates were validated in cell culture experiments using primary murine acinar cells and rat AR42J cells. These candidates were then further tested for their usefulness as biomarkers in mouse and human plasma.

RESULTS

We identified a number of novel genes, including Regulator of calcineurin 1 (Rcan1) and Sestrin 2 (Sesn2) and demonstrated that they are induced by oxidative stress, by stimulation with H₂O₂ and by inhibiting caerulein stimulated expression with the antioxidant N-acetylcysteine. We found Rcan1 protein to be significantly elevated in AP-induced mouse plasma as well as in plasma from AP patients.

CONCLUSION

We demonstrated that Rcan1 is regulated by oxidative stress and identified RCAN1 as a potential diagnostic marker of AP.

Epithelial NEMO/IKKγ limits fibrosis and promotes regeneration during pancreatitis

OBJECTIVE

Inhibitory κB kinase (IKK)/nuclear factor κB (NF-κB) signalling has been implicated in the pathogenesis of pancreatitis, but its precise function has remained controversial. Here, we analyse the contribution of IKK/NF-κB signalling in epithelial cells to the pathogenesis of pancreatitis by targeting the IKK subunit NF-κB essential modulator (NEMO) (IKKγ), which is essential for canonical NF-κB activation.

DESIGN

Mice with a targeted deletion of NEMO in the pancreas were subjected to caerulein pancreatitis. Pancreata were examined at several time points and analysed for inflammation, fibrosis, cell death, cell proliferation, as well as cellular differentiation. Human samples were used to corroborate findings established in mice.

RESULTS

In acute pancreatitis, NEMO deletion in the pancreatic parenchyma resulted in minor changes during the early phase but led to the persistence of inflammatory and fibrotic foci in the recovery phase. In chronic pancreatitis, NEMO deletion aggravated inflammation and fibrosis, inhibited compensatory acinar cell proliferation, and enhanced acinar atrophy and acinar-ductal metaplasia. Gene expression analysis revealed sustained activation of profibrogenic genes and the CXCL12/CXCR4 axis in the absence of epithelial NEMO. In human chronic pancreatitis samples, the CXCL12/CXCR4 axis was activated as well, with CXCR4 expression correlating with the degree of fibrosis. The aggravating effects of NEMO deletion were attenuated by the administration of the CXCR4 antagonist AMD3100.

CONCLUSIONS

Our results suggest that NEMO in epithelial cells exerts a protective effect during pancreatitis by limiting inflammation and fibrosis and improving acinar cell regeneration. The CXCL12/CXCR4 axis is an important mediator of that effect and may also be of importance in human chronic pancreatitis.

Protective effects of tropisetron on cerulein-induced acute pancreatitis in mice

Acute pancreatitis (AP) causes morbidity and mortality. The aim of the present study was to investigate the protective effect of tropisetron against AP induced by cerulein. Cerulein (50μg/kg, 5 doses) was used to induce AP in mice. Six hours after final cerulein injection, animals were decapitated. Hepatic/pancreatic enzymes in the serum, pancreatic content of malondialdehyde (MDA), pro-inflammatory cytokines and myeloperoxidase (MPO) activity were measured. Tropisetron significantly attenuated pancreatic injury markers and decreased the amount of elevated serum amylase, lipase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), MPO activities and pro-inflammatory cytokines levels caused by AP in mice. Tropisetron didn't affect the pancreatic levels of MDA. Our results suggest that tropisetron could attenuate cerulein-induced AP by combating inflammatory signaling. Further clinical studies are needed to confirm its efficacy in patients with AP.

A small molecule inhibitor of NFκB blocks ER stress and the NLRP3 inflammasome and prevents progression of pancreatitis

BACKGROUND

The underlying molecular mechanism that leads to development of chronic pancreatitis remains elusive. The aim of this study is to understand the downstream inflammatory signaling involved in progression of chronic pancreatitis, and to use withaferin A (WA), a small molecule inhibitor of nuclear factor κB (NFκB), to prevent progression of chronic pancreatitis.

METHODS

Two different protocols were used to induce pancreatitis in mice: standard and stringent administration of cerulein. The severity of pancreatitis was assessed by means of pancreatic histology and serum amylase levels. Immunohistochemistry and flow-cytometric analysis was performed to visualize immune cell infiltration into the pancreas. Real-time PCR and Western blot were used to analyze the downstream signaling mechanism involved in the development of chronic pancreatitis.

RESULTS

The severity of cerulein-induced pancreatitis was reduced significantly by WA, used as either preventive or curative treatment. Immune cell infiltration into the pancreas and acinar cell death were efficiently reduced by WA treatment. Expression of proinflammatory and proapoptotic genes regulated by NFκB activation was increased by cerulein treatment, and WA suppressed these genes significantly. Sustained endoplasmic reticulum stress activation by cerulein administration was reduced. NLRP3 inflammasome activation in cerulein-induced pancreatitis was identified, and this was also potently blocked by WA. The human pancreatitis tissue gene signature correlated with the mouse model.

CONCLUSIONS

Our data provide evidence for the role of NFκB in the pathogenesis of chronic pancreatitis, and strongly suggest that WA could be used as a potential therapeutic drug to alleviate some forms of chronic pancreatitis.

Immunopathogenesis of pancreatitis

The conventional view of the pathogenesis of acute and chronic pancreatitis is that it is due to a genetic- or environment-based abnormality of intracellular acinar trypsinogen activation and thus to the induction of acinar cell injury that, in turn, sets in motion an intra-pancreatic inflammatory process. More recent studies, reviewed here, present strong evidence that while such trypsinogen activation is likely a necessary first step in the inflammatory cascade underlying pancreatitis, sustained pancreatic inflammation is dependent on damage-associated molecular patterns-mediated cytokine activation causing the translocation of commensal (gut) organisms into the circulation and their induction of innate immune responses in acinar cells. Quite unexpectedly, these recent studies reveal that the innate responses involve activation of responses by an innate factor, nucleotide-binding oligomerization domain 1 (NOD1), and that such NOD1 responses have a critical role in the activation/production of nuclear factor-kappa B and type I interferon. In addition, they reveal that chronic inflammation and its accompanying fibrosis are dependent on the generation of IL-33 by injured acinar cells and its downstream induction of T cells producing IL-13. These recent studies thus establish that pancreatitis is quite a unique form of inflammation and one susceptible to newer, more innovative therapy.

Apelin Regulates Nuclear Factor-κB's Involvement in the Inflammatory Response of Pancreatitis

OBJECTIVES

Inflammation plays a key role in pancreatitis. Earlier studies from our laboratory showed that experimental pancreatitis activated the pancreatic apelin-APJ axis robustly in mice. Apelin signaling reduced neutrophil invasion and the activation of pancreatic nuclear factor (NF)-κB in mice with experimental pancreatitis.

METHODS

The aim of this study was to assess whether apelin-induced inhibition of pancreatic NF-κB activation was linked mechanistically to apelin's inhibition of pancreatic inflammatory mediator up-regulation in mice with cerulein-induced chronic pancreatitis (CP). Whether apelin's inhibitory effects were associated with the inhibition of NF-κB binding to the promoter region of IL-1β was examined. The effects of apelin exposure on pancreatic IκB degradation/replenishment and membrane levels of phosphorylated protein kinase C were measured.

RESULTS

Results demonstrated that apelin inhibited the up-regulation of pancreatic tumor necrosis factor α, macrophage inflammatory protein-1 α/β, and IL-1β expression significantly in mice with CP. Chromatin immunoprecipitation assay findings showed that apelin inhibited NF-κB binding to a putative NF-κB binding site in the IL-1β promoter. Apelin exposure reduced the pancreatic membrane levels of phosphorylated protein kinase C-δ and enhanced the replenishment of pancreatic IκB proteins.

CONCLUSIONS

Together, these findings indicated that the inhibition of NF-κB activation by apelin was a mechanism behind the reduced pancreatic levels of inflammatory mediators in CP mice exposed to apelin.

Sulforaphane Protects Pancreatic Acinar Cell Injury by Modulating Nrf2-Mediated Oxidative Stress and NLRP3 Inflammatory Pathway

Acute pancreatitis (AP) is characterized by early activation of intra-acinar proteases followed by acinar cell death and inflammation. Cellular oxidative stress is a key mechanism underlying these pathological events. Sulforaphane (SFN) is a natural organosulfur antioxidant with undescribed effects on AP. Here we investigated modulatory effects of SFN on cellular oxidation and inflammation in AP. AP was induced by cerulean hyperstimulation in BALB/c mice. Treatment group received a single dose of 5 mg/kg SFN for 3 consecutive days before AP. We found that SFN administration attenuated pancreatic injury as evidenced by serum amylase, pancreatic edema, and myeloperoxidase, as well as by histological examination. SFN administration reverted AP-associated dysregulation of oxidative stress markers including pancreatic malondialdehyde and redox enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx). In acinar cells, SFN treatment upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) expression and Nrf2-regulated redox genes including quinoneoxidoreductase-1, heme oxidase-1, SOD1, and GPx1. In addition, SFN selectively suppressed cerulein-induced activation of the nucleotide-binding domain leucine-rich repeat containing family, pyrin domain-containing 3 (NLRP3) inflammasome, in parallel with reduced nuclear factor- (NF-) κB activation and modulated NF-κB-responsive cytokine expression. Together, our data suggested that SFN modulates Nrf2-mediated oxidative stress and NLRP3/NF-κB inflammatory pathways in acinar cells, thereby protecting against AP.

NF-κB in acute pancreatitis: Mechanisms and therapeutic potential

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

Inhibition of pancreatic oxidative damage by stilbene derivative dihydro-resveratrol: implication for treatment of acute pancreatitis

Trans-resveratrol is a natural stilbenoid possessing multifarious pharmacological benefits; however, when orally consumed, it is rapidly metabolised by colonic microflora and converted to dihydro-resveratrol. Thus, this microbial metabolite is of great therapeutic relevance. In the present study, upon the oral administration of dihydro-resveratrol (10–50 mg/kg), the severity of acute pancreatitis in the cerulein-treated rats was significantly ameliorated as evidenced by decreased α-amylase activities in the plasma and lessened oedema formation in the pancreatic parenchyma. In addition, the generation of intracellular reactive oxidative products, including malondialdehyde and protein carbonyls, was accordingly reduced, so as the production of pro-inflammatory cytokines. While inhibiting the activities of NADPH oxidase and myeloperoxidase, the depletion of glutathione was considerably restored. Importantly, the attenuation of pancreatic oxidative damage by dihydro-resveratrol was associated with a down-regulation of the nuclear factor-kappaB and phosphatidylinositol 3′-kinase-serine/threonine kinase signalling pathways. Furthermore, we demonstrated that the solubility of dihydro-resveratrol was at least 5 times higher than trans-resveratrol whilst exhibiting a much lower cytotoxicity. Collectively, the current findings accentuate new mechanistic insight of dihydro-resveratrol in pancreatic oxidative damage, and advocate its therapeutic potential for the management of acute pancreatitis, particularly for patients unresponsive to trans-resveratrol due to the lack of proper microbial strains.

BCL3 Reduces the Sterile Inflammatory Response in Pancreatic and Biliary Tissues

BACKGROUND & AIMS

Under conditions of inflammation in the absence of micro-organisms (sterile inflammation), necrotic cells release damage-associated molecular patterns that bind to Toll-like receptors on immune cells to activate a signaling pathway that involves activation of IκB kinase and nuclear factor κB (NF-κB). Little is known about the mechanisms that control NF-κB activity during sterile inflammation. We analyzed the contribution of B-cell CLL/lymphoma 3 (BCL3), a transcription factor that associates with NF-κB, in control of sterile inflammation in the pancreas and biliary system of mice.

METHODS

Acute pancreatitis (AP) was induced in C57BL/6 (control) and Bcl3(-/-) mice by intraperitoneal injection of cerulein or pancreatic infusion of sodium taurocholate. We also studied Mdr2(-/-) mice, which develop spontaneous biliary inflammation, as well as Bcl3(-/-)Mdr2(-/-) mice. We performed immunohistochemical analyses of inflamed and noninflamed regions of pancreatic tissue from patients with AP or primary sclerosing cholangitis (PSC), as well as from mice. Immune cells were characterized by fluorescence-activated cell sorting analysis. Control or Bcl3(-/-) mice were irradiated, injected with bone marrow from Bcl3(-/-) or control mice, and AP was induced.

RESULTS

Pancreatic or biliary tissues from patients with AP or PSC had higher levels of BCL3 and phosphorylated RelA and IκBα in inflamed vs noninflamed regions. Levels of BCL3 were higher in pancreata from control mice given cerulein than from mice without AP, and were higher in biliary tissues from Mdr2(-/-) mice than from control mice. Bcl3(-/-) mice developed more severe AP after administration of cerulein or sodium taurocholate than control mice; pancreata from the Bcl3(-/-) mice with AP had greater numbers of macrophages, myeloid-derived suppressor cells, dendritic cells, and granulocytes than control mice with AP. Activation of NF-κB was significantly prolonged in Bcl3(-/-) mice with AP, compared with control mice with AP. Bcl3(-/-)Mdr2(-/-) mice developed more severe cholestasis and had increased markers of liver injury and increased proliferation of biliary epithelial cells and hepatocytes than Mdr2(-/-) mice. In experiments with bone marrow chimeras, expression of BCL3 by acinar cells, but not myeloid cells, was required for reduction of inflammation during development of AP. BCL3 inhibited ubiquitination and proteasome-mediated degradation of p50 homodimers, which prolonged binding of NF-κB heterodimers to DNA.

CONCLUSIONS

BCL3 is up-regulated in inflamed pancreatic or biliary tissues from mice and patients with AP or cholangitis. Its production appears to reduce the inflammatory response in these tissues via blocking ubiquitination and proteasome-mediated degradation of p50 homodimers.

Role of liver in modulating the release of inflammatory cytokines involved in lung and multiple organ dysfunction in severe acute pancreatitis

The objective of this study was to understand the role of liver in modulating remote organ dysfunction during severe acute pancreatitis (SAP). We used sodium taurocholate and endotoxin to induce SAP in the rats and confirmed the development of this condition by measuring serum and ascite levels of the biomarkers of liver and lung damage. Our results showed that expression of tumor necrosis factor (TNF)-α was up-regulated sequentially, first in the gut, then in the liver, and finally in lung. Moreover, the SAP-induced increase in the expressions of TNF-α and IL-6 occurring in gut, liver, and lung was directly related to the increase in time. However, in liver and lung, the transcriptional activity of NF-κB and expression of TNF-α at 4 and 8 h were not increased. The distribution sequence of the pro-inflammatory cytokines to various organs was determined by their detection in the blood from portal vein and inferior vena cava. Although liver received TNF-α during 0.5-8 h of the SAP induction, the release of this cytokine into vena cava was not increased in this period of time. In conclusion, our results suggest that the aggravation of SAP leading to development of MODS exhibited the gut-liver-lung cytokine axis. Furthermore, this study indicates that liver performs both protective and stimulatory activities in the modulation of pro-inflammatory cytokine generation and their distribution to remote organs, such as lungs.

Induction of chronic pancreatitis by pancreatic duct ligation activates BMP2, apelin, and PTHrP expression in mice

Chronic pancreatitis (CP) is a devastating disease with no treatments. Experimental models have been developed to reproduce the parenchyma and inflammatory responses typical of human CP. For the present study, one objective was to assess and compare the effects of pancreatic duct ligation (PDL) to those of repetitive cerulein (Cer)-induced CP in mice on pancreatic production of bone morphogenetic protein-2 (BMP2), apelin, and parathyroid hormone-related protein (PTHrP). A second objective was to determine the extent of cross talk among pancreatic BMP2, apelin, and PTHrP signaling systems. We focused on BMP2, apelin, and PTHrP since these factors regulate the inflammation-fibrosis cascade during pancreatitis. Findings showed that PDL- and Cer-induced CP resulted in significant elevations in expression and peptide/protein levels of pancreatic BMP2, apelin, and PTHrP. In vivo mouse and in vitro pancreatic cell culture experiments demonstrated that BMP2 stimulated pancreatic apelin expression whereas apelin expression was inhibited by PTHrP exposure. Apelin or BMP2 exposure inhibited PTHrP expression, and PTHrP stimulated upregulation of gremlin, an endogenous inhibitor of BMP2 activity. Transforming growth factor-β (TGF-β) stimulated PTHrP expression. Together, findings demonstrated that PDL- and Cer-induced CP resulted in increased production of the pancreatic BMP2, apelin, and PTHrP signaling systems and that significant cross talk occurred among pancreatic BMP2, apelin, and PTHrP. These results together with previous findings imply that these factors interact via a pancreatic network to regulate the inflammation-fibrosis cascade during CP. More importantly, this network communicated with TGF-β, a key effector of pancreatic pathophysiology. This novel network may be amenable to pharmacologic manipulations during CP in humans.

Loganin protects against pancreatitis by inhibiting NF-κB activation

Acute pancreatitis (AP) is an inflammatory disease of the pancreas, which, in its most severe form, is associated with multi-organ failure and death. Loganin, a major iridoid glycoside obtained from Corni fructus, has been shown to have anti-inflammatory and anti-shock effects. However, the effects of loganin on AP have not been determined. Pre-treatment of loganin reduced pancreatic damage and AP-associated lung injury and attenuated the severity of AP, as evidenced by (1) a reduction in several biochemical parameters (pancreatic weight to body weight ratio, myeloperoxidase activity, and level of amylase) and (2) production of pro-inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α. However, post-treatment of loganin failed to improve pancreatic damage and biochemical parameters of AP, but could inhibit the AP-induced elevation of IL-1β and TNF-α significantly. In addition, cerulein-induced activation of nuclear factor (NF)-κB was inhibited in the pancreas by administration of loganin. In conclusion, these results suggest that loganin exhibits an anti-inflammatory effect in cases of AP and its pulmonary complications through inhibition of NF-κB activation.

Role of Parathyroid Hormone-Related Protein Signaling in Chronic Pancreatitis

Chronic pancreatitis (CP), a progressive inflammatory disease where acini are destroyed and replaced by fibrous tissue, increases the risk for pancreatic cancer. Risk factors include alcohol, smoking, and obesity. The effects of these risk factors are exacerbated in patients with mutations in genes that predispose to CP. The different environmental and genetic factors produce the same clinical phenotype; once CP develops, disease course is the same regardless of etiology. Critical questions still need to be answered to understand what modifies predisposition to develop CP in persons exposed to risk factors. We postulate that risk factors modulate endogenous pathways, with parathyroid hormone-related protein (PTHrP) signaling being one such pathway. In support, PTHrP levels are elevated in mice treated with alcohol, and in mouse models of cerulein- and pancreatic duct ligation-induced CP. Disrupting the Pthrp gene in acinar cells exerts protective effects (decreased edema, histological damage, amylase and cytokine release, and fibrosis) in these CP models. PTHrP levels are elevated in human CP. Currently, CP care lacks specific pharmacological interventions. Targeting PTHrP signaling may present a novel therapeutic strategy that inhibits pancreatic inflammation and fibrosis, especially since the risk of developing pancreatic cancer is strongly associated with duration of chronic inflammation.

Redox signaling in acute pancreatitis

Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF-VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis.

Framework for interpretation of trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis

Early intracellular premature trypsinogen activation was interpreted as the key initiator of pancreatitis. When the balance in the homeostasis of trypsin and antitrypsin system is disequilibrated, elevated aggressive enzymes directly attack the pancreatic tissue, which leads to pancreatic destruction and inflammation. However, trypsin alone is not enough to cause complications in pancreatitis, which may play a crucial role in modulating signaling events in the initial phase of the disease. NFκB activation is the major inflammatory pathway involved in the occurrence and development of pancreatitis and it can be induced by intrapancreatic activation of trypsinogen. Synthesis of trypsinogen occurs in endoplasmic reticulum (ER), and ER stress is an important early acinar cell event. Components of ER stress response are known to be able to trigger cell death as well as NFκB signaling cascade. The strongest evidence supporting the trypsin-centered theory is that gene mutations, which lead to the generation of more trypsin, or reduce the activity of trypsin inhibitors or trypsin degradation, are associated with pancreatitis. Thus, trypsin-antitrypsin imbalance may be the first step leading to pancreatic autodigestion and inducing other pathways. Continued experimental studies are necessary to determine the specific relationships between trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis. In this article, we review the latest advances that contributed to the understanding of the basic mechanisms behind the occurrence and development of pancreatitis with a focus on the interpretation of trypsin-antitrypsin imbalance and their relationships with other inflammation pathways. We additionally highlight genetic predispositions to pancreatitis and possible mechanisms associated with them.

Role of phosphoinositide 3-kinase in the pathogenesis of acute pancreatitis

A large body of experimental and clinical data supports the notion that inflammation in acute pancreatitis has a crucial role in the pathogenesis of local and systemic damage and is a major determinant of clinical severity. Thus, research has recently focused on molecules that can regulate the inflammatory processes, such as phosphoinositide 3-kinases (PI3Ks), a family of lipid and protein kinases involved in intracellular signal transduction. Studies using genetic ablation or pharmacologic inhibitors of different PI3K isoforms, in particular the class I PI3Kδ and PI3Kγ, have contributed to a greater understanding of the roles of these kinases in the modulation of inflammatory and immune responses. Recent data suggest that PI3Ks are also involved in the pathogenesis of acute pancreatitis. Activation of the PI3K signaling pathway, and in particular of the class IB PI3Kγ isoform, has a significant role in those events which are necessary for the initiation of acute pancreatic injury, namely calcium signaling alteration, trypsinogen activation, and nuclear factor-κB transcription. Moreover, PI3Kγ is instrumental in modulating acinar cell apoptosis, and regulating local neutrophil infiltration and systemic inflammatory responses during the course of experimental acute pancreatitis. The availability of PI3K inhibitors selective for specific isoforms may provide new valuable therapeutic strategies to improve the clinical course of this disease. This article presents a brief summary of PI3K structure and function, and highlights recent advances that implicate PI3Ks in the pathogenesis of acute pancreatitis.

Intracellular Hmgb1 inhibits inflammatory nucleosome release and limits acute pancreatitis in mice

BACKGROUND & AIMS

High mobility group box 1 (HMGB1) is an abundant protein that regulates chromosome architecture and also functions as a damage-associated molecular pattern molecule. Little is known about its intracellular roles in response to tissue injury or during subsequent local and systemic inflammatory responses. We investigated the function of Hmgb1 in mice after induction of acute pancreatitis.

METHODS

We utilized a Cre/LoxP system to create mice with pancreas-specific disruption in Hmbg1 (Pdx1-Cre; HMGB1(flox/flox) mice). Acute pancreatitis was induced in these mice (HMGB1(flox/flox) mice served as controls) after injection of l-arginine or cerulein. Pancreatic tissues and acinar cells were collected and analyzed by histologic, immunoblot, and immunohistochemical analyses.

RESULTS

After injection of l-arginine or cerulein, Pdx1-Cre; HMGB1(flox/flox) mice developed acute pancreatitis more rapidly than controls, with increased mortality. Pancreatic tissues of these mice also had higher levels of serum amylase, acinar cell death, leukocyte infiltration, and interstitial edema than controls. Pancreatic tissues and acinar cells collected from the Pdx1-Cre; HMGB1(flox/flox) mice after l-arginine or cerulein injection demonstrated nuclear catastrophe with greater nucleosome release when compared with controls, along with increased phosphorylation/activation of RELA nuclear factor κB, degradation of inhibitor of κB, and phosphorylation of mitogen-activated protein kinase. Inhibitors of reactive oxygen species (N-acetyl-l-cysteine) blocked l-arginine-induced DNA damage, necrosis, apoptosis, release of nucleosomes, and activation of nuclear factor κB in pancreatic tissues and acinar cells from Pdx1-Cre; HMGB1(flox/flox) and control mice. Exogenous genomic DNA and recombinant histone H3 proteins significantly induced release of HMGB1 from mouse macrophages; administration of antibodies against H3 to mice reduced serum levels of HMGB1 and increased survival after l-arginine injection.

CONCLUSIONS

In 2 mouse models of acute pancreatitis, intracellular HMGB1 appeared to prevent nuclear catastrophe and release of inflammatory nucleosomes to block inflammation. These findings indicate a role for the innate immune response in tissue damage.

New insights into the pathogenesis of pancreatitis

PURPOSE OF REVIEW

In this article, we review important advances in our understanding of the mechanisms of pancreatitis.

RECENT FINDINGS

The relative contributions of intrapancreatic trypsinogen activation and nuclear factor kappa B (NFκB) activation, the two major early independent cellular events in pancreatitis, have been investigated using novel genetic models. Trypsinogen activation has traditionally held the spotlight for many decades as the central pathogenic event of pancreatitis. However, recent experimental evidence points to the role of trypsin activation in early acinar cell damage but not in the inflammatory response of acute pancreatitis, which was shown to be induced by NFκB activation. Further, chronic pancreatitis developed independently of trypsinogen activation in the caerulein model. Sustained NFκB activation, but not persistent intra-acinar expression of active trypsin, was shown to result in chronic pancreatitis. Calcineurin-NFAT (nuclear factor of activated T-cells) signaling was shown to mediate downstream effects of pathologic rise in intracellular calcium. Interleukin-6 was identified as a key cytokine mediating pancreatitis-associated lung injury.

SUMMARY

Recent advances challenge the long-believed trypsin-centered understanding of pancreatitis. It is becoming increasingly clear that activation of intense inflammatory signaling mechanisms in acinar cells is crucial to the pathogenesis of pancreatitis, which may explain the strong systemic inflammatory response in pancreatitis.

Inflammation, autophagy, and obesity: common features in the pathogenesis of pancreatitis and pancreatic cancer

Inflammation and autophagy are cellular defense mechanisms. When these processes are deregulated (deficient or overactivated) they produce pathologic effects, such as oxidative stress, metabolic impairments, and cell death. Unresolved inflammation and disrupted regulation of autophagy are common features of pancreatitis and pancreatic cancer. Furthermore, obesity, a risk factor for pancreatitis and pancreatic cancer, promotes inflammation and inhibits or deregulates autophagy, creating an environment that facilitates the induction and progression of pancreatic diseases. However, little is known about how inflammation, autophagy, and obesity interact to promote exocrine pancreatic disorders. We review the roles of inflammation and autophagy, and their deregulation by obesity, in pancreatic diseases. We discuss the connections among disordered pathways and important areas for future research.

Cerulein-induced chronic pancreatitis does not require intra-acinar activation of trypsinogen in mice

BACKGROUND & AIMS

Premature activation of trypsinogen activation can cause pancreatic injury and has been associated with chronic pancreatitis (CP). Mice that lack intra-acinar activation of trypsinogen, such as trypsinogen-7-null (T(-/-)) and cathepsin B-null (CB(-/-)) mice, have been used to study trypsin-independent processes of CP development. We compared histologic features and inflammatory responses of pancreatic tissues from these mice with those from wild-type mice after the development of CP.

METHODS

CP was induced in wild-type, T(-/-), and CB(-/-) mice by twice-weekly induction of acute pancreatitis for 10 weeks; acute pancreatitis was induced by hourly intraperitoneal injections of cerulein (50 μg/kg × 6). Pancreatic samples were collected and evaluated by histologic and immunohistochemical analyses. Normal human pancreas samples, obtained from the islet transplant program at the University of Minnesota, were used as controls and CP samples were obtained from surgical resections.

RESULTS

Compared with pancreatic tissues from wild-type mice, those from T(-/-) and CB(-/-) mice had similar levels of atrophy, histomorphologic features of CP, and chronic inflammation. All samples had comparable intra-acinar activation of nuclear factor (NF)-κB, a transcription factor that regulates the inflammatory response, immediately after injection of cerulein. Pancreatic tissue samples from patients with CP had increased activation of NF-κB (based on nuclear translocation of p65 in acinar cells) compared with controls.

CONCLUSIONS

Induction of CP in mice by cerulein injection does not require intra-acinar activation of trypsinogen. Pancreatic acinar cells of patients with CP have increased levels of NF-κB activation compared with controls; regulation of the inflammatory response by this transcription factor might be involved in the pathogenesis of CP.

Protective effects of edaravone on experimental chronic pancreatitis induced by dibutyltin dichloride in rats

BACKGROUND/AIMS

To investigate the effects of edaravone, a potent free radical scavenger, on dibutyltin dichloride (DBTC)-induced chronic pancreatitis (CP) and pancreatic fibrosis.

METHODS

Male Sprague-Dawley rats were randomly divided into four groups (n = 16 each): control, DBTC, DBTC + edaravone, and control + edaravone. Edaravone or normal saline at a daily dose of 6 mg/kg body weight was given intraperitoneally from day 5 to day 28 after DBTC administration. On days 14 and 28, the rats were evaluated morphologically and biochemically. The expression of cytokines in pancreas TGF-β, IL-6 and TNF<alpha> was detected using RT-PCR. The activation of nuclear factor (NF)-κB in pancreatic tissue was evaluated by immunostaining and western-blot for NF-κB p65. α-smooth muscle actin (α-SMA) expression was also evaluated by immunostaining and western-blot to investigate the activation of pancreatic stellate cells (PSCs).

RESULT

Edaravone treatment improved the rats' body weight (p < 0.01) and feed intake levels (p < 0.05), improved the histological scores and alleviated the fibrosis of pancreas samples (p < 0.05), as well as markedly increased superoxide dismutase (SOD) activity and decreased malondialdehyde (MDA) concentrations in pancreatic tissue (p < 0.01 for both). The expression of cytokines TGF-β, IL-6 and TNF<alpha> in pancreas of DBTC group was also down-regulated by edaravone after treatment. Edaravone inhibited the activation of NF-κB and PSCs and exhibited protective effects on pancreatic tissue damage in CP.

CONCLUSIONS

This antioxidant may be a promising therapeutic intervention for human CP.

Development of a rat model of severe acute pancreatitis-associated lung injury

AIM: To establish a rat model of severe acute pancreatitis (SAP)-associated lung injury (LI) by occluding the head of the pancreas.

METHODS: Two hundred and ten rats were randomly and equally divided into a control group, a sham-operated group, and a SAP-LI model group. Rats in each group was further divided into seven subgroups for testing at 0, 6, 12, 18, 24, 36, and 48 h (n = 10 for each). The SAP-LI model group underwent occlusion of the head of the pancreas with vessel forceps. The sham-operated group underwent a surgical procedure similar to the SAP-LI model group but the head of the pancreas was not occluded. The control group only underwent anesthetization for 3 h. Blood, pulmonary alveolar lavage fluid, lung tissue and pancreatic tissue samples were collected at various time points. The level of serum amylase, content of serum proteins, percentage of polymorphonuclear neutrophils, wet/dry weight ratio of lung tissue, and content of proteins in pulmonary alveolar lavage fluid were determined. Pathological changes in lung and pancreatic tissues were observed under a light microscope.

RESULTS: All rats were live in the experiment. The level of serum amylase (5052.1 U/L ± 114.9 U/L, P < 0.01) and the percentage of polymorphonuclear neutrophils (75.2% ± 5.8%, P < 0.05) reached the peak at 12 h, and the ratio of the content of proteins in pulmonary alveolar lavage fluid to the content of serum proteins reached the peak at 36 h in the SAP-LI model group (0.009021 ± 0.000107, P < 0.01). The wet/dry weight ratio of lung tissue, reaching the minimum at 36 h in the SAP-LI mold group (1.2001 ± 0.0443, P < 0.01), differed significantly between the SAP-LI group and the other two groups (both P < 0.05). Pancreatic tissue injury became worse with the prolongation of time. LI was most serious at 36 h. Serum amylase showed a correlation with the percentage of polymorphonuclear neutrophils and wet/dry weight ratio of lung tissue (r = 0.788,P < 0.01; r = 0.365, P = 0.002). The percentage of polymorphonuclear neutrophils showed a correlation with the wet/dry weight ratio of lung tissue (r = 0.348, P = 0.003). The wet/dry weight ratio of lung tissue showed a correlation with the ratio of the content of proteins in pulmonary alveolar lavage fluid to the content of serum proteins (r = -0.717, P < 0.01). The score of pancreatic tissue pathology showed a correlation with that of lung tissue pathology (r = 0.934, P < 0.01).

CONCLUSION: A new rat model of SAP-associated LI has been successfully developed by occluding the head of the pancreas, providing an ideal model for studying the pathogenesis and treatment of this condition. LI was most serious at 36 h, which is the optimal time point for inducing SAP-associated LI.

Nuclear factor-κB in pancreatitis: Jack-of-all-trades, but which one is more important?

See “Deletion of IκBα activates RelA to reduce acute pancreatitis in mice through up-regulation of Spi2A,” by Neuhöfer P, Liang S, Einwächter H, et al, on page 192; and “Activation of nuclear factor-κB in acinar cells increases the severity of pancreatitis in mice,” by Huang H, Liu Y, Daniluk J, et al, on page 202.

Pathogenic mechanisms of acute pancreatitis

PURPOSE OF REVIEW

In this article, recent advances in the pathogenesis of acute pancreatitis have been reviewed.

RECENT FINDINGS

Pathologic intra-acinar trypsinogen activation had been hypothesized to be the central mechanism of pancreatitis for over a century. This hypothesis could be explored for the first time with the development of a novel mouse model lacking pathologic intra-acinar trypsinogen activation. It became clear that intra-acinar trypsinogen activation contributes to early acinar injury, but local and systemic inflammation progress independently during pancreatitis. Early intra-acinar nuclear factor kappa B (NFκB) activation, which occurs parallel to but independent of trypsinogen activation, may be crucial in pancreatitis. Although the mechanism of NFκB and trypsinogen activation is not entirely clear, further insights have been made into key pathogenic cellular events such as calcium signaling, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, autophagy and impaired trafficking, and lysosomal and secretory responses. Cellular intrinsic damage-sensing mechanisms that lead to activation of the inflammatory response aimed at repair, but lead to disease when overwhelmed, are beginning to be understood.

SUMMARY

New findings necessitate a paradigm shift in our understanding of acute pancreatitis. Intra-acinar trypsinogen activation leads to early pancreatic injury, but the inflammatory response of acute pancreatitis develops independently, driven by early activation of inflammatory pathways.

Redox signaling and histone acetylation in acute pancreatitis

Histone acetylation via CBP/p300 coordinates the expression of proinflammatory cytokines in the activation phase of inflammation, particularly through mitogen-activated protein kinases (MAPKs), nuclear factor-κB (NF-κB), and signal transducers and activators of transcription (STAT) pathways. In contrast, histone deacetylases (HDACs) and protein phosphatases are mainly involved in the attenuation phase of inflammation. The role of reactive oxygen species (ROS) in the inflammatory cascade is much more important than expected. Mitochondrial ROS act as signal-transducing molecules that trigger proinflammatory cytokine production via inflammasome-independent and inflammasome-dependent pathways. The major source of ROS in acute inflammation seems to be NADPH oxidases, whereas NF-κB, protein phosphatases, and HDACs are the major targets of ROS and redox signaling in this process. There is a cross-talk between oxidative stress and proinflammatory cytokines through serine/threonine protein phosphatases, tyrosine protein phosphatases, and MAPKs that greatly contributes to amplification of the uncontrolled inflammatory cascade and tissue injury in acute pancreatitis. Chromatin remodeling during induction of proinflammatory genes would depend primarily on phosphorylation of transcription factors and their binding to gene promoters together with recruitment of histone acetyltransferases. PP2A should be considered a key modulator of the inflammatory cascade in acute pancreatitis through the ERK/NF-κB pathway and histone acetylation.

Intra-acinar trypsinogen activation mediates early stages of pancreatic injury but not inflammation in mice with acute pancreatitis

BACKGROUND & AIMS

The role of trypsinogen activation in the pathogenesis of acute pancreatitis (AP) has not been clearly established.

METHODS

We generated and characterized mice lacking trypsinogen isoform 7 (T7) gene (T(-/-)). The effects of pathologic activation of trypsinogen were studied in these mice during induction of AP with cerulein. Acinar cell death, tissue damage, early intra-acinar activation of the transcription factor nuclear factor κB (NF-κB), and local and systemic inflammation were compared between T(-/-) and wild-type mice with AP.

RESULTS

Deletion of T7 reduced the total trypsinogen content by 60% but did not affect physiologic function. T(-/-) mice lacked pathologic activation of trypsinogen, which occurs within acinar cells during early stages of AP progression. Absence of trypsinogen activation in T(-/-) mice led to near complete inhibition of acinar cell death in vitro and a 50% reduction in acinar necrosis during AP progression. However, T(-/-) mice had similar degrees of local and systemic inflammation during AP progression and comparable levels of intra-acinar NF-κB activation, which was previously shown to occur concurrently with trypsinogen activation during early stages of pancreatitis.

CONCLUSIONS

T7 is activated during pathogenesis of AP in mice. Intra-acinar trypsinogen activation leads to acinar death during early stages of pancreatitis, which accounts for 50% of the pancreatic damage in AP. However, progression of local and systemic inflammation in AP does not require trypsinogen activation. NF-κB is activated early in acinar cells, independently of trypsinogen activation, and might be responsible for progression of AP.

α-Tocopherol treatment ameliorates chronic pancreatitis in an experimental rat model induced by trinitrobenzene sulfonic acid

OBJECTIVE

To investigate the effects of α-tocopherol on pancreatic fibrosis and survival in rats with experimental chronic pancreatitis induced by trinitrobenzene sulfonic acid (TNBS).

METHODS

Chronic pancreatitis was induced in male Sprague-Dawley rats by infusion of TNBS into the pancreatic duct. α-Tocopherol (300, 600 or 900 mg/kg) was orally administered to rats with experimental pancreatitis (treatment group) daily for 4 weeks. The relative pancreatic weight, pancreatic pseudocyst and death rate were observed. Paraffin-embedded tissue samples were sliced, stained by hematoxylin-eosin and histopathologically examined.

RESULTS

α-Tocopherol administration significantly ameliorated the pancreatic weight loss induced by TNBS in chronic pancreatitis rats compared to the control group. There were pancreatic pseudocysts in 69% of the α-tocopherol group, and in 100% of the control group. α-Tocopherol administration led to a significant increase of the survival rate. The histopathologic scores were higher in the control group than in the α-tocopherol group. Subgroup analysis of histopathologic scores revealed that a high dose of α-tocopherol results in less pancreatic injuries.

CONCLUSION

α-Tocopherol treatment elevates survival rate, extenuates fibrosis and increases relative pancreatic weight in the chronic pancreatitis model. α-Tocopherol therapy in chronic pancreatitis is now required to confirm these findings and establish the role of this treatment in the management of this disabling condition. and IAP.

Flavocoxid, a dual inhibitor of cyclooxygenase-2 and 5-lipoxygenase, reduces pancreatic damage in an experimental model of acute pancreatitis

BACKGROUND AND PURPOSE

Acute pancreatitis is an autodigestive process resulting in acute inflammation of the pancreas. Accumulating evidence indicates the essential contribution of cyclooxygenase (COX)-2 and 5-lipoxygenase (5-LOX) to acute pancreatitis. We studied the effects of flavocoxid, a plant-derived dual inhibitor of COX-2 and 5-LOX, in a model of caerulein (CER)-induced acute pancreatitis.

EXPERIMENTAL APPROACH

Rats were given CER (80 µg·kg⁻¹ for each of four injections at hourly intervals) or vehicle (Sham-CER). Animals were then randomized to receive flavocoxid (20 mg·kg⁻¹ i.p.) or vehicle, 30 min after the first CER injection. Two hours after the last CER injection, we evaluated damage to the pancreas by histological methods; serum levels of amylase, lipase, leukotriene (LT)B₄ and prostaglandin (PG)E₂ ; pancreatic expression of COX-2 and 5-LOX and tumour necrosis factor-α (TNF-α) gene expression by real-time polymerase chain reaction.

KEY RESULTS

Caerulein induced inflammatory changes in the pancreas and raised values of the other variables measured. In CER-treated animals, but not in those given saline, flavocoxid inhibited COX-2 and 5-LOX expression, reduced serum levels of lipase and amylase and the degree of pancreatic oedema. Treatment with flavocoxid blunted the increased pancreatic TNF-α mRNA expression, serum leukotriene B₄ and prostaglandin E₂ levels, and protected against histological damage in terms of vacuolization and leukocyte infiltration.

CONCLUSIONS AND IMPLICATIONS

Our results confirm the key role of both COX-2 and 5-LOX in the inflammatory response to acute pancreatitis. Flavocoxid may provide a potential therapeutic approach to the treatment of patients at high risk of developing this life-threatening condition.

Alteration and role of heat shock proteins in acute pancreatitis

Many etiological factors are involved in the pathogenesis of acute pancreatitis. The pathogenesis of acute pancreatitis has been attributed to such causes as trypsin autodigestion, pancreatic microcirculation malfunction, the calcium overload in pancreatic acinar cells, oxygen free radical injury, cytokine injury, and has been treated in detail in numerous reviews. More recently, heat shock proteins (HSP), particularly heat shock protein 60 (HSP60), have receive increasing attention as another possible factor in the pathogenesis and development of acute pancreatitis. This brief review aims to: (i) outline our current understanding of HSP and their role in pancreatitis; (ii) discuss the available evidences that suggest HSP's interplay between pancreas tissues and etiological agents; (iii) delineate the functional mechanisms of HSP proposed by different research groups, and offer new thinking in preventing and treating acute pancreatitis in general.

High-dose naproxen aggravates pancreatic fibrosis in a rat model of chronic pancreatitis

OBJECTIVES

: Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely prescribed for the treatment of pain in chronic pancreatitis (CP). This study aimed to investigate the effect of NSAIDs on the inflammation and fibrosis progression in trinitrobenzene sulfonic acid-induced CP rats.

METHODS

Chronic pancreatitis was induced by trinitrobenzene sulfonic acid infusion into rat pancreatic ducts. Naproxen treatment (20 and 40 mg/kg per os [PO] and intraperitoneally) started 2 weeks after the induction of CP for 3 weeks. Histological analysis of the pancreas, Van Gieson staining, and contents of hydroxyproline were used to evaluate pancreatic damage and fibrosis. Furthermore, the effect of naproxen on nociceptive reflective behaviors and serum tumor necrosis factor alpha concentration were studied, and immunohistochemical analysis of alpha-smooth muscle actin in the pancreas was performed.

RESULTS

Pancreatic collagen content and alpha-smooth muscle actin expression were higher in the CP group treated with high-dose (40 mg/kg PO) naproxen (P < 0.05). High-dose naproxen administered orally aggravated pancreatic fibrosis and inflammation (P < 0.05). Instead of playing an analgesic role, high-dose naproxen decreased the thermal withdrawal latencies in CP rats (P < 0.05).

CONCLUSIONS

High-dose naproxen treatment (40 mg/kg PO) aggravated pancreatic fibrosis in CP rats and played an algogenic role that suggests the potential risk of long-term use of NSAIDs as analgesic in clinical practice with CP.

TRAF6 as the key adaptor of TLR4 signaling pathway is involved in acute pancreatitis

OBJECTIVES

To study the potential role of tumor necrosis factor receptor-associated factor 6 (TRAF6) as the key adaptor of the toll-like receptor 4 (TLR4) signaling pathway in acute pancreatitis (AP) in mice.

METHODS

Acute pancreatitis was induced by 7 intraperitoneal injections of cerulein in TLR4-deficient (TLR4-Def) and TLR4 wild-type (TLR4-WT) mice. Inflammatory severity was scored and evaluated based on pathological study. TRAF6 expression was determined by reverse transcriptase polymerase chain reaction, Western blot, and immunohistochemistry.

RESULTS

Acute pancreatitis was successfully induced in both mice strains, but the inflammatory progression was different. In TLR4-Def mice, pancreatic inflammation was blunt and mild first, then became increasingly intensive and peaked at the later stage, whereas in the TLR4-WT mice, the response was fast initiated and peaked at the early stage of AP, then alleviated gradually. TRAF6 expression in TLR4-Def mice was significantly higher than that in the TLR4-WT mice. Immunohistochemistry located TRAF6 expressed mainly in the pancreatic acinar cells.

CONCLUSIONS

The TLR4-TRAF6 signaling pathway is critically involved in AP. Other signaling pathways beyond TLR4 may participate in the pancreatic inflammatory process via TRAF6. As a convergence point of the TLR4-dependent and the TLR4-independent signaling pathways, TRAF6 plays an important role in AP.

Leflunomide: is a new oral agent in treatment of acute pancreatitis?

OBJECTIVES

Nuclear factor-kappaB (NF-kappaB) is a potent mediator in several steps of acute pancreatitis. Leflunomide is a novel immunomodulating drug that is also a potent inhibitor of NF-kappaB activation. The aim of this study was to investigate the effects of leflunomide pretreatment in severe necrotizing pancreatitis in rats.

METHODS

Fifty rats were randomly divided into 5 groups. Severe necrotizing pancreatitis was induced by retrograde injection of 3% sodium taurocholate into the common biliopancreatic duct. Leflunomide (10 mg/kg) was given intragastrically for 2 doses before the experiment. Serum amylase activity, pancreatic histopathologic condition, malondialdehyde level, myeloperoxidase enzyme activity, nitric oxide level, and pulmonary changes were assessed.

RESULTS

Leflunomide pretreatment significantly ameliorated pancreatic hemorrhage, edema, and neutrophil infiltration and decreased histopathological score compared with the untreated severe necrotizing pancreatitis group (pathological score [mean +/- SEM]: 6.70 +/- 1.19 vs 12.36 +/- 1.08 in the leflunomide treated and untreated groups, respectively, P < 0.01). Pulmonary changes was decreased in the leflunomide treated group (3.90 +/- 0.45 vs 4.75 +/- 0.25, respectively). Change in pulmonary alveolar distention was significant. Although serum amylase levels also decreased, the difference was not significant (5922 +/- 3290 vs 15547 +/- 5090 U/mL).

CONCLUSIONS

Leflunomide is a beneficial agent in the severe form of acute pancreatitis in rats and should be considered as a potential agent for treatment of acute pancreatitis.

Down-regulation of tumor necrosis factor-associated factor 6 is associated with progression of acute pancreatitis complicating lung injury in mice

Acute lung injury is one of the critical complications of acute pancreatitis (AP). Tumor necrosis factor-associated factor 6 (TRAF6) is a key adaptor that regulates various inflammatory signaling pathways, including those mediated by Toll-like receptors (TLRs). This study was performed to investigate the potential role of TRAF6 in the pathogenesis of AP and pancreatitis-associated acute lung injury using a mouse model of caerulein-induced AP (CAP). CAP was induced by intraperitoneal injection of caerulein hourly for 7 times (50 microg/kg), and control mice were treated with saline of the same volume. Typical pancreatic and lung inflammation was observed in the early stage (1 h) of CAP, as judged by morphological changes. Likewise, in CAP mice, the pancreatic myeloperoxidase activity and serum levels of interleukin-6 and interleukin-10 were significantly increased after 2 h, peaked at 4h, and then decreased by 24 h. The expression of TRAF6 was then studied by real time-PCR, immunohistochemistry, and Western blot analysis. Compared with control group, TRAF6 mRNA level was decreased in CAP group within the first 12 h, and then significantly increased after 24 h, which was in accordance with the protein level detected by Western blot analysis and immunohistochemistry. Moreover, TRAF6 protein was expressed in both pancreatic acinar cells and lung bronchial epithelial cells. In conclusion, the down-regulation of TRAF6 was associated with increased inflammatory severity in the pancreas and lung, suggesting that TRAF6 is involved in the anti-inflammatory process during AP. TRAF6 may be a potential molecular target for treating AP.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.