Acute interstitial pancreatitis in the rat induced by excessive doses of a pancreatic secretagogue

Berberine inhibits inflammatory mediators and attenuates acute pancreatitis through deactivation of JNK signaling pathways

Acute pancreatitis (AP) is a life-threatening disease. Berberine (BBR), a well-known plant alkaloid, is reported to have anti-inflammatory activity in many diseases. However, the effects of BBR on AP have not been clearly elucidated. Therefore, the present study aimed to investigate the effects of BBR on cerulein-induced AP in mice. AP was induced by either cerulein or l-arginine. In the BBR treated group, BBR was administered intraperitoneally 1h before the first cerulein or l-arginine injection. Blood samples were obtained to determine serum amylase and lipase activities and nitric oxide production. The pancreas and lung were rapidly removed for examination of histologic changes, myeloperoxidase (MPO) activity, and real-time reverse transcription-polymerase chain reaction. Furthermore, the regulating mechanisms of BBR were evaluated. Treatment of mice with BBR reduced pancreatic injury and activities of amylase, lipase, and pancreatitis-associated lung injury, as well as inhibited several inflammatory parameters such as the expression of pro-inflammatory cytokines and inducible nitric oxide synthesis (iNOS). Furthermore, BBR administration significantly inhibited c-Jun N-terminal kinase (JNK) activation in the cerulein-induced AP. Deactivation of JNK resulted in amelioration of pancreatitis and the inhibition of inflammatory mediators. These results suggest that BBR exerts anti-inflammatory effects on AP via JNK deactivation on mild and severe acute pancreatitis model, and could be a beneficial target in the management of AP.

Pathophysiological mechanisms in acute pancreatitis: Current understanding

The precise mechanisms involved in the pathophysiology of acute pancreatitis (AP) are still far from clear. Several earlier studies have focused mainly on pancreatic enzyme activation as the key intracellular perturbation in the pancreatic acinar cells. For decades, the trypsin-centered hypothesis has remained the focus of the intra-acinar events in acute pancreatitis. Recent advances in basic science research have lead to the better understanding of various other mechanisms such as oxidative and endoplasmic stress, impaired autophagy, mitochondrial dysfunction, etc. in causing acinar cell injury. Despite all efforts, the clinical outcome of patients with AP has not changed significantly over the years. This suggests that the knowledge of the critical molecular pathways in the pathophysiology of AP is still limited. The mechanisms through which the acinar cell injury leads to local and systemic inflammation are not well understood. The role of inflammatory markers and immune system activation is an area of much relevance from the point of view of finding a target for therapeutic intervention. Some data are available from experimental animal models but not much is known in human pancreatitis. This review intends to highlight the current understanding in this area.

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.

The Role of Gastrin and CCK Receptors in Pancreatic Cancer and other Malignancies

The gastrointestinal (GI) peptide gastrin is an important regulator of the release of gastric acid from the stomach parietal cells and it also plays an important role in growth of the gastrointestinal tract. It has become apparent that gastrin and its related peptide cholecystokinin (CCK) are also significantly involved with growth of GI cancers as well as other malignancies through activation of the cholecystokinin-B (CCK-B) receptor. Of interest, gastrin is expressed in the embryologic pancreas but not in the adult pancreas; however, gastrin becomes re-expressed in pancreatic cancer where it stimulates growth of this malignancy by an autocrine mechanism. Strategies to down-regulate gastrin or interfere with its interface with the CCK receptor with selective antibodies or receptor antagonists hold promise for the treatment of pancreatic cancer and other gastrin--responsive tumors.

Involvement of Membrane Blebbing in Immunological Disorders and Cancer

Cellular blebbing is a unique form of dynamic protrusion emanating from the plasma membrane which can be either apoptotic or nonapoptotic in nature. Blebs have been observed in a wide variety of cell types and in response to multiple mechanical and chemical stimuli. They have been linked to various physiological and pathological processes including tumor motility and invasion, as well as to various immunological disorders. They can form and retract extremely rapidly in seconds or minutes, or slowly over hours or days. This review focuses on recent evidence regarding the role of blebbing in cell locomotion with particular emphasis on its role in tumor metastasis, indicating the role of specific causative molecules. The phenomenon of blebbing has been observed in endocrine-resistant breast cancer cells in response to brief exposure to extracellular alkaline pH, which leads to enhanced invasive capacity. Genetic or pharmacological targeting of cellular blebs could serve as a potential therapeutic option to control tumor metastasis.

Tempol, a Membrane-Permeable Radical Scavenger, Exhibits Anti-Inflammatory and Cardioprotective Effects in the Cerulein-Induced Pancreatitis Rat Model

To date, it remains unclear whether mild form of acute pancreatitis (AP) may cause myocardial damage which may be asymptomatic for a long time. Pathogenesis of AP-related cardiac injury may be attributed in part to ROS/RNS overproduction. The aim of the present study was to evaluate the oxidative stress changes in both the pancreas and the heart and to estimate the protective effects of 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (tempol) at the early phase of AP. Cerulein-induced AP led to the development of acute edematous pancreatitis with a significant decrease in the level of sulfhydryl (–SH) groups (oxidation marker) both in heart and in pancreatic tissues as well as a substantial increase in plasma creatine kinase isoenzyme (CK-MB) activity (marker of the heart muscle lesion) which confirmed the role of oxidative stress in the pathogenesis of cardiac damage. The tempol treatment significantly reduced the intensity of inflammation and oxidative damage and decreased the morphological evidence of pancreas injury at early AP stages. Moreover, it markedly attenuated AP-induced cardiac damage revealed by normalization of the –SH group levels and CK-MB activity. On the basis of these studies, it is possible to conclude that tempol has a profound protective effect against cardiac and pancreatic damage induced by AP.

Effect of endogenous cholecystokinin on the course of acute pancreatitis in rats

AIM: To examine the effects of pancreatic rest, stimulation and rest/stimulation on the natural course of recovery after acute pancreatitis.

METHODS: Acute hemorrhagic pancreatitis (AP) was induced in male rats by intraductal infusion of 40 μL/100 g body weight of 3% sodium taurocholate. All rats took food ad libitum. At 24 h after induction of AP, rats were divided into four groups: control (AP-C), pancreas rest (AP-R), stimulation (AP-S), and rest/stimulation (AP-R/S). Rats in the AP-C, AP-R and AP-S groups received oral administration of 2 mL/kg body weight saline, cholecystokinin (CCK)-1 receptor antagonist, and endogenous CCK release stimulant, respectively, twice daily for 10 d, while those in the AP-R/S group received twice daily CCK-1 receptor antagonist for the first 5 d followed by twice daily CCK release stimulant for 5 d. Rats without any treatment were used as control group (Control). Biochemical and histological changes in the pancreas, and secretory function were evaluated on day 12 at 24 h after the last treatment.

RESULTS: Feeding ad libitum (AP-C) delayed biochemical, histological and functional recovery from AP. In AP-C rats, bombesin-stimulated pancreatic secretory function and HOMA-β-cell score were significantly lower than those in other groups of rats. In AP-R rats, protein per DNA ratio and pancreatic exocrine secretory function were significantly low compared with those in Control rats. In AP-S and AP-R/S rats, the above parameters recovered to the Control levels. Bombesin-stimulated pancreatic exocrine response in AP-R/S rats was higher than in AP-S rats and almost returned to control levels. In the pancreas of AP-C rats, destruction of pancreatic acini, marked infiltration of inflammatory cells, and strong expression of α-smooth muscle actin, tumor necrosis factor-α and interleukin-1β were seen. Pancreatic rest reversed these histological alterations, but not atrophy of pancreatic acini and mild infiltration of inflammatory cells. In AP-S and AP-R/S rats, the pancreas showed almost normal architecture.

CONCLUSION: The favorable treatment strategy for AP is to keep the pancreas at rest during an early stage followed by pancreatic stimulation by promoting endogenous CCK release.

Dynamic imaging of pancreatic nuclear factor κB (NF-κB) activation in live mice using adeno-associated virus (AAV) infusion and bioluminescence

Nuclear factor κB (NF-κB) is an important signaling molecule that plays a critical role in the development of acute pancreatitis. Current methods for examining NF-κB activation involve infection of an adenoviral NF-κB-luciferase reporter into cell lines or electrophoretic mobility shift assay of lysate. The use of adeno-associated viruses (AAVs) has proven to be an effective method of transfecting whole organs in live animals. We examined whether intrapancreatic duct infusion of AAV containing an NF-κB-luciferase reporter (AAV-NF-κB-luciferase) can reliably measure pancreatic NF-κB activation. We confirmed the infectivity of the AAV-NF-κB-luciferase reporter in HEK293 cells using a traditional luciferase readout. Mice were infused with AAV-NF-κB-luciferase 5 weeks before induction of pancreatitis (caerulein, 50 μg/kg). Unlike transgenic mice that globally express NF-κB-luciferase, AAV-infused mice showed a 15-fold increase in pancreas-specific NF-κB bioluminescence following 12 h of caerulein compared with baseline luminescence (p < 0.05). The specificity of the NF-κB-luciferase signal to the pancreas was confirmed by isolating the pancreas and adjacent organs and observing a predominant bioluminescent signal in the pancreas compared with liver, spleen, and stomach. A complementary mouse model of post-ERCP-pancreatitis also induced pancreatic NF-κB signals. Taken together these data provide the first demonstration that NF-κB activation can be examined in a live, dynamic fashion during pancreatic inflammation. We believe this technique offers a valuable tool to study real-time activation of NF-κB in vivo.

Distribution of cholecystokinin-B receptor genotype between patients with pancreatic cancer and controls and its impact on survival

OBJECTIVE

Cholecystokinin (CCK) and gastrin stimulate growth of pancreatic cancer through the CCK-B receptor (CCK-BR). A splice variant of the CCK-BR that results from a single nucleotide polymorphism (SNP) has been identified. Because the splice variant receptor has an extended third intracellular loop, an area involved in cell signaling and growth, we hypothesized that this genetic variant could contribute to the poor prognosis and short survival of this malignancy.

METHODS

DNA from 931 patients with pancreatic cancer was evaluated for the SNP (C > A; rs1800843) in the CCK-BR gene. For statistical analysis, the Fisher exact test was used to compare the genotype and allele frequency between the cancer cohort and normal controls and the dependence of genotype on factors, such as stage of disease and age, was analyzed using Cox proportional hazards models.

RESULTS

Compared to the normal cohort, the frequency of the A-allele in pancreatic cancer subjects was increased (P = 0.01123; odds ratio, 2.283). Even after adjustment for stage of disease, survival of subjects with the minor allele was significantly shorter than those with the wild-genotype (hazard ratio, 1.83; P = 3.11 × 10(-11)).

CONCLUSIONS

The CCK-BR SNP predicts survival and should be studied as a candidate genetic biomarker for those at risk of pancreatic cancer.

Apigenin inhibits pancreatic stellate cell activity in pancreatitis

BACKGROUND

Chronic pancreatitis (CP) is characterized by recurrent pancreatic injury, resulting in inflammation, necrosis, and fibrosis. There are currently no drugs limiting pancreatic fibrosis associated with CP, and there is a definite need to fill this void in patient care.

MATERIALS AND METHODS

Pancreatitis was induced in C57/BL6 mice using supraphysiologic doses of cerulein, and apigenin treatment (once daily, 50 μg per mouse by oral gavage) was initiated 1 wk into the recurrent acute pancreatitis (RAP) protocol. Pancreata were harvested after 4 wk of RAP. Immunostaining with fibronectin antibody was used to quantify the extent of pancreatic fibrosis. To assess how apigenin may decrease organ fibrosis, we evaluated the effect of apigenin on the proliferation and apoptosis of human pancreatic stellate cells (PSCs) in vitro. Finally, we assessed apigenin's effect on the gene expression in PSCs stimulated with parathyroid hormone-related protein, a profibrotic and proinflammatory mediator of pancreatitis, using reverse transcription-polymerase chain reaction.

RESULTS

After 4 wk of RAP, apigenin significantly reduced the fibrotic response to injury while preserving acinar units. Apigenin inhibited viability and induced apoptosis of PSCs in a time- and dose-dependent manner. Finally, apigenin reduced parathyroid hormone-related protein-stimulated increases in the PSC messenger RNA expression levels of extracellular matrix proteins collagen 1A1 and fibronectin, proliferating cell nuclear antigen, transforming growth factor-beta, and interleukin-6.

CONCLUSIONS

These in vivo and in vitro studies provide novel insights regarding apigenin's mechanism(s) of action in reducing the severity of RAP. Additional preclinical testing of apigenin analogs is warranted to develop a therapeutic agent for patients at risk for CP.

Trimetazidine significantly reduces cerulein-induced pancreatic apoptosis

OBJECTIVE

Acute pancreatitis continues to be associated with significant rates of mortality and morbidity, and therapeutic options are still very limited. We aimed to investigate the efficacy of trimetazidine on cerulein-induced pancreatic apoptosis and histopathological and biochemistrical consequences of acute pancreatitis.

METHODS

Thirty-two Wistar albino rats were randomized into four groups (group 1: control group; group 2: acute pancreatitis group; group 3: acute pancreatitis and trimetazidine treatment group; group 4: placebo group). Acute edematous pancreatitis was induced by subcutaneous cerulein injection (20 μg/kg) four times at one-hour intervals. Trimetazidine was prepared in suspension form. In group 3, after gas anesthesia, trimetazidine was administrated to rats via a catheter. Serum interleukin (IL)-1β, tumor necrosis factor (TNF)-α, amylase, lipase and leukocyte levels, pancreatic apoptotic status and pancreatic Schoenberg scores were determined for all groups. Results are given as the mean ± SD. A value of P<0.05 was accepted as statistically significant. SPSS for Windows v15.0 was used for statistical analyses.

RESULTS

In the acute pancreatitis group IL-1β, amylase, lipase and leukocyte levels were elevated and pancreatic histopathological evaluation revealed a diagnosis of acute pancreatitis IL-1β amylase and lipase levels and pancreatic inflammation were decreased significantly in the trimetazidine group (P<0.01). White blood cell counts and TNF-α concentrations for the trimetazidine group and the acute pancreatitis group were not significantly different. Trimetazidine significantly reduced apoptosis in pancreatic tissues and Schoenberg scores were also significantly reduced (P<0.05).

CONCLUSION

In this study, we showed that trimetazidine treatment significantly decreases the levels of IL-1β, amylase and lipase reduces pancreatic apoptosis and ameliorates the histopathological findings of cerulein-induced acute pancreatitis. Trimetazidine could be a new therapeutic option in the early treatment of acute pancreatitis.

Synergistic metabolic benefits of an exenatide analogue and cholecystokinin in diet-induced obese and leptin-deficient rodents

AIM

To test the impact of cholecystokinin (CCK) plus either amylin or a glucagon-like peptide-1 receptor (GLP-1R) agonist on metabolic variables in diet-induced obese (DIO) rodents.

METHODS

A stabilized acetylated version of CCK-8 (Ac-Y*-CCK-8), selective CCK1 receptor (CCK1R) or CCK2 receptor (CCK2R) agonists, amylin or the GLP-1R agonist and exenatide analogue AC3174 were administered in select combinations via continuous subcutaneous infusion to DIO rats for 14 days, or Lep(ob) /Lep(ob) mice for 28 days, and metabolic variables were assessed.

RESULTS

Combined administration of Ac-Y*-CCK-8 with either amylin or AC3174 induced greater than additive weight loss in DIO rats, with the overall magnitude of effect being greater with AC3174 + Ac-Y*-CCK-8 treatment. Co-infusion of AC3174 with a specific CCK1R agonist, but not a CCK2R agonist, recapitulated the weight loss mediated by AC3174 + Ac-Y*-CCK-8 in DIO rats, suggesting that synergy is mediated by CCK1R activation. In a 4 × 4 full-factorial response surface methodology study in DIO rats, a synergistic interaction between AC3174 and the CCK1R-selective agonist on body weight and food intake was noted. Co-administration of AC3174 and the CCK1R-selective agonist to obese diabetic Lep(ob) /Lep(ob) mice elicited a significantly greater reduction in percentage of glycated haemoglobin and food intake relative to the sum effects of monotherapy groups.

CONCLUSIONS

The anti-obesity and antidiabetic potential of combined GLP-1R and CCK1R agonism is an approach that warrants further investigation.

Evidence for a role of mitogen-activated protein kinases in the treatment of experimental acute pancreatitis

Acute pancreatitis (AP) is an inflammatory disease characterized by acute inflammation and necrosis of the pancreatic parenchyma. AP is often associated with organ failure, sepsis, and high mortality. The pathogenesis of AP is still not well understood. In recent years several papers have highlighted the cellular and molecular events of acute pancreatitis. Pancreatitis is initiated by activation of digestive enzymes within the acinar cells that are involved in autodigestion of the gland, followed by a massive infiltration of neutrophils and macrophages and release of inflammatory mediators, responsible for the local and systemic inflammatory response. The hallmark of AP is parenchymal cell necrosis that represents the cause of the high morbidity and mortality, so that new potential therapeutic approaches are indispensable for the treatment of patients at high risk of complications. However, not all factors that determine the onset and course of the disease have been explained. Aim of this article is to review the role of mitogen-activated protein kinases in pathogenesis of acute pancreatitis.

Cholecystokinin receptor antagonist halts progression of pancreatic cancer precursor lesions and fibrosis in mice

OBJECTIVES

Exogenous administration of cholecystokinin (CCK) induces hypertrophy and hyperplasia of the pancreas with an increase in DNA content. We hypothesized that endogenous CCK is involved in the malignant progression of pancreatic intraepithelial neoplasia (PanIN) lesions and the fibrosis associated with pancreatic cancer.

METHODS

The presence of CCK receptors in early PanIN lesions was examined by immunohistochemistry in mouse and human pancreas. Pdx1-Cre/LSL-Kras transgenic mice were randomized to receive either untreated drinking water or water supplemented with a CCK receptor antagonist (proglumide, 0.1 mg/mL). Pancreas from the mice were removed and examined histologically for number and grade of PanINs after 1, 2, or 4 months of antagonist therapy.

RESULTS

Both CCK-A and CCK-B receptors were identified in early stage PanINs from mouse and human pancreas. The grade of PanIN lesions was reversed, and progression to advanced lesions arrested in mice treated with proglumide compared with the controls (P = 0.004). Furthermore, pancreatic fibrosis was significantly reduced in antagonist-treated animals compared with vehicle (P < 0.001).

CONCLUSIONS

These findings demonstrate that endogenous CCK is in part responsible for the development and progression of pancreatic cancer. The use of CCK receptor antagonists may have a role in cancer prophylaxis in high-risk subjects and may reduce fibrosis in the microenvironment.

Application of caerulein and lipopolysaccharides in creating mouse models of mild or severe acute pancreatitis

AIM: To establish typical mouse models of mild or severe acute pancreatitis induced with caerulein (CAE) and/or lipopolysaccharides (LPS).

METHODS: Fifty healthy adult male C57 mice were randomly divided into five groups (with 10 mice in each group): a control group (CON group), the caerulein 7 group (CAE 7 group), a caerulein 7 plus LPS group (CAE 7 + LPS group), a caerulein 13 group (CAE 13 group), and a caerulein 13 plus LPS group (CAE 13 + LPS group). All the animals were killed three hours after the last intraperitoneal injection. The pancreas was carefully removed for microscopic examination and further observed under a transmission electron microscope (TEM). Serum amylase and lipase concentrations were assayed.

RESULTS: Enzyme levels and pathological score in all the experimental groups were significantly higher than those in the CON group (amylase lowest CAE 7 group: 27020 U/dL ± 3443 U/dL vs CON group: 2696 U/dL ± 400 U/dL, P < 0.01; lipase content lowest CAE 7 group: 1379 U/L ± 283 U/L vs CON group: 33 U/L ± 13 U/L, P < 0.01; pathological score lowest CAE 7 group: 5.8 ± 0.9 vs CON group: 0.1 ± 0.3, P < 0.01). Compared with the CAE 7 group, the enzyme levels and pathological score in the CAE 13 + LPS group increased more significantly (CAE 13 + LPS group amylase: 46969 U/dL ± 11852 U/dL vs CAE 7 group amylase: 27020 U/dL ± 3443 U/dL, P < 0.01; CAE13 + LPS group lipase: 1962 U/dL ± 496 U/dL vs CAE 7 group lipase: 1379 U/dL ± 283 U/dL, P < 0.05; CAE13 + LPS group pathological score : 11.1 ± 1.1 vs CAE 7 group pathological score : 5.8 ± 0.9, P < 0.05). The grade of pathological changes in the CAE 13 + LPS group was significantly higher than that in the CAE 13 group (CAE 13 + LPS group: 11.1 ± 1.1 vs CAE 13 group: 10.1 ± 0.99, P < 0.05). The ultrastructure of acinar cells was damaged in the CAE 7 group, and the rough endoplasmic reticulum and mitochondria were markedly swollen. However, in the CAE 13 + LPS group, the acinar cells were seriously damaged.

CONCLUSION: Caerulein alone by intraperitoneal injection 7 times can be used to prepare a typical model of acute edematous pancreatitis, and caerulein by intraperitoneal injection 13 times plus LPS at the last time can be used to produce typical acute necrotizing pancreatitis.

Pancreatic stellate cells and CX3CR1: occurrence in normal pancreas and acute and chronic pancreatitis and effect of their activation by a CX3CR1 agonist

OBJECTIVES

Numerous studies suggest important roles of the chemokine, fractalkine (CX3CL1), in acute/chronic pancreatitis; however, the possible mechanisms of the effects are unclear. Pancreatic stellate cells (PSCs) can play important roles in pancreatitis, secreting inflammatory cytokines/chemokines, as well as proliferation. Therefore, we investigated CX3CL1 receptor (CX3CR1) occurrence in normal pancreas and pancreatitis (acute/chronic) tissues and the effects of CX3CL1 on activated PSCs.

METHODS

CX3CR1 expression/localization in normal pancreas and pancreatitis (acute/chronic) tissues was evaluated with immunohistochemical analysis. CX3CR1 expression and effects of CX3CL1 on activated PSCs were examined with real-time polymerase chain reaction, BrdU (5-bromo-2-deoxyuridine) assays, and Western blotting.

RESULTS

In normal pancreas, acinar cells expressed CX3CR1 within granule-like formations in the cytoplasm, whereas in acute/chronic pancreatitis, acinar, ductal, and activated PSCs expressed CX3CR1 on cell membranes. With activation of normal PSCs, CX3CR1 is increased. CX3CL1 activated multiple signaling cascades in PSCs. CX3CL1 did not induce inflammatory genes expression in activated PSCs, but induced proliferation.

CONCLUSIONS

CX3CR1s are expressed in normal pancreas. Expression is increased in acute/chronic pancreatitis, and the CX3CR1s are activated. CX3CL1 induces proliferation of activated PSCs without increasing release of inflammatory mediators. These results suggest that CX3CR1 activation of PSCs could be important in their effects in pancreatitis, especially to PSC proliferation in pancreatitis where CX3CL1 levels are elevated.

Experimental models of pancreatitis

Acute pancreatitis is an inflammatory disease characterized by interstitial edema, inflammatory cell infiltration, and acinar cell necrosis, depending on its severity. Regardless of the extent of tissue injury, acute pancreatitis is a completely reversible process with evident normal tissue architecture after recovery. Its pathogenic mechanism has been known to be closely related to intracellular digestive enzyme activation. In contrast to acute pancreatitis, chronic pancreatitis is characterized by irreversible tissue damage such as acinar cell atrophy and pancreatic fibrosis that results in exocrine and endocrine insufficiency. Recently, many studies of chronic pancreatitis have been prompted by the discovery of the pancreatic stellate cell, which has been identified and distinguished as the key effector cell of pancreatic fibrosis. However, investigations into the pathogenesis and treatment of pancreatitis face many obstacles because of its anatomical location and disparate clinical course. Due to these difficulties, most of our knowledge on pancreatitis is based on research conducted using experimental models of pancreatitis. In this review, several experimental models of pancreatitis will be discussed in terms of technique, advantages, and limitations.

Experimental models of pancreatitis

Acute pancreatitis is an inflammatory disease characterized by interstitial edema, inflammatory cell infiltration, and acinar cell necrosis, depending on its severity. Regardless of the extent of tissue injury, acute pancreatitis is a completely reversible process with evident normal tissue architecture after recovery. Its pathogenic mechanism has been known to be closely related to intracellular digestive enzyme activation. In contrast to acute pancreatitis, chronic pancreatitis is characterized by irreversible tissue damage such as acinar cell atrophy and pancreatic fibrosis that results in exocrine and endocrine insufficiency. Recently, many studies of chronic pancreatitis have been prompted by the discovery of the pancreatic stellate cell, which has been identified and distinguished as the key effector cell of pancreatic fibrosis. However, investigations into the pathogenesis and treatment of pancreatitis face many obstacles because of its anatomical location and disparate clinical course. Due to these difficulties, most of our knowledge on pancreatitis is based on research conducted using experimental models of pancreatitis. In this review, several experimental models of pancreatitis will be discussed in terms of technique, advantages, and limitations.

Acute pancreatitis: The stress factor

Acute pancreatitis is an inflammatory disorder of the pancreas that may cause life-threatening complications. Etiologies of pancreatitis vary, with gallstones accounting for the majority of all cases, followed by alcohol. Other causes of pancreatitis include trauma, ischemia, mechanical obstruction, infections, autoimmune, hereditary, and drugs. The main events occurring in the pancreatic acinar cell that initiate and propagate acute pancreatitis include inhibition of secretion, intracellular activation of proteases, and generation of inflammatory mediators. Small cytokines known as chemokines are released from damaged pancreatic cells and attract inflammatory cells, whose systemic action ultimately determined the severity of the disease. Indeed, severe forms of pancreatitis may result in systemic inflammatory response syndrome and multiorgan dysfunction syndrome, characterized by a progressive physiologic failure of several interdependent organ systems. Stress occurs when homeostasis is threatened, and stressors can include physical or mental forces, or combinations of both. Depending on the timing and duration, stress can result in beneficial or harmful consequences. While it is well established that a previous acute-short-term stress decreases the severity of experimentally-induced pancreatitis, the worsening effects of chronic stress on the exocrine pancreas have received relatively little attention. This review will focus on the influence of both prior acute-short-term and chronic stress in acute pancreatitis.

Experimental models of pancreatitis

Acute pancreatitis is an inflammatory disease characterized by interstitial edema, inflammatory cell infiltration, and acinar cell necrosis, depending on its severity. Regardless of the extent of tissue injury, acute pancreatitis is a completely reversible process with evident normal tissue architecture after recovery. Its pathogenic mechanism has been known to be closely related to intracellular digestive enzyme activation. In contrast to acute pancreatitis, chronic pancreatitis is characterized by irreversible tissue damage such as acinar cell atrophy and pancreatic fibrosis that results in exocrine and endocrine insufficiency. Recently, many studies of chronic pancreatitis have been prompted by the discovery of the pancreatic stellate cell, which has been identified and distinguished as the key effector cell of pancreatic fibrosis. However, investigations into the pathogenesis and treatment of pancreatitis face many obstacles because of its anatomical location and disparate clinical course. Due to these difficulties, most of our knowledge on pancreatitis is based on research conducted using experimental models of pancreatitis. In this review, several experimental models of pancreatitis will be discussed in terms of technique, advantages, and limitations.

Isoprenylcysteine carboxylmethyltransferase deficiency exacerbates KRAS-driven pancreatic neoplasia via Notch suppression

RAS is the most frequently mutated oncogene in human cancers. Despite decades of effort, anti-RAS therapies have remained elusive. Isoprenylcysteine carboxylmethyltransferase (ICMT) methylates RAS and other CaaX-containing proteins, but its potential as a target for cancer therapy has not been fully evaluated. We crossed a Pdx1-Cre;LSL-KrasG12D mouse, which is a model of pancreatic ductal adenocarcinoma (PDA), with a mouse harboring a floxed allele of Icmt. Surprisingly, we found that ICMT deficiency dramatically accelerated the development and progression of neoplasia. ICMT-deficient pancreatic ductal epithelial cells had a slight growth advantage and were resistant to premature senescence by a mechanism that involved suppression of cyclin-dependent kinase inhibitor 2A (p16INK4A) expression. ICMT deficiency precisely phenocopied Notch1 deficiency in the Pdx1-Cre;LSL-KrasG12D model by exacerbating pancreatic intraepithelial neoplasias, promoting facial papillomas, and derepressing Wnt signaling. Silencing ICMT in human osteosarcoma cells decreased Notch1 signaling in response to stimulation with cell-surface ligands. Additionally, targeted silencing of Ste14, the Drosophila homolog of Icmt, resulted in defects in wing development, consistent with Notch loss of function. Our data suggest that ICMT behaves like a tumor suppressor in PDA because it is required for Notch1 signaling.

Recent advances in the investigation of pancreatic inflammation induced by large doses of basic amino acids in rodents

It has been known for approximately 30 years that large doses of the semi-essential basic amino acid L-arginine induce severe pancreatic inflammation in rats. Recently, it has been demonstrated that L-arginine can also induce pancreatitis in mice. Moreover, other basic amino acids like L-ornithine and L-lysine can cause exocrine pancreatic damage without affecting the endocrine parenchyma and the ducts in rats. The utilization of these noninvasive severe basic amino acid-induced pancreatitis models is becoming increasingly popular and appreciated as these models nicely reproduce most laboratory and morphological features of human pancreatitis. Consequently, the investigation of basic amino acid-induced pancreatitis may offer us a better understanding of the pathogenesis and possible treatment options of the human disease.

PSCs and GLP-1R: occurrence in normal pancreas, acute/chronic pancreatitis and effect of their activation by a GLP-1R agonist

There is increasing concern about the development of pancreatitis in patients with diabetes mellitus who received long-term glucagon-like peptide-1 (GLP-1) analog treatment. Its pathogenesis is unknown. The effects of GLP-1 agonists on pancreatic endocrine cells are well studied; however, there is little information on effects on other pancreatic tissues that might be involved in inflammatory processes. Pancreatic stellate cells (PSCs) can have an important role in pancreatitis, secreting various inflammatory cytokines/chemokines, as well as collagen. In this study, we investigated GLP-1R occurrence in normal pancreas, acute pancreatitis (AP)/chronic pancreatitis (CP), and the effects of GLP-1 analog on normal PSCs, their ability to stimulate inflammatory mediator secretion or proliferation. GLP-1 receptor (GLP-1R) expression/localization in normal pancreas and pancreatitis (AP/CP) tissues were evaluated with histological/immunohistochemical analysis. PSCs were isolated from male Wistar rats. GLP-1R expression and effects of GLP-1 analog on activated PSCs was examined with real-time PCR, MTS assays and western blotting. In normal pancreas, pancreatic β cells expressed GLP-1R, with only low expression in acinar cells, whereas in AP or CP, acinar cells, ductal cells and activated PSCs expressed GLP-1R. With activation of normal PSCs, GLP-1R is markedly increased, as is multiple other incretin-related receptors. The GLP-1 analog, liraglutide, did not induce inflammatory genes expression in activated PSCs, but induced proliferation. Liraglutide activated multiple signaling cascades in PSCs, and the extracellular signal-regulated kinase pathway mediated the PSCs proliferation. GLP-1Rs are expressed in normal pancreas and there is marked enhanced expression in AP/CP. GLP-1-agonist induced cell proliferation of activated PSCs without increasing release of inflammatory mediators. These results suggest chronic treatment with GLP-1R agonists could lead to proliferation/chronic activation of PSCs, which may lead to important effects in the pancreas.

A review of animal models of nonneoplastic pancreatic diseases

The nonneoplastic diseases of the human pancreas generally comprise the inflammatory and degenerative conditions that include acute and chronic pancreatitis, with cystic fibrosis being arguably one of the most important diseases that induce the condition. Both acute and chronic conditions vary in severity, but both can be life threatening; and because of this fact, the study of their progression, and their responsiveness to therapy, is largely conducted by indirect means using serum markers of damage and repair such as amylase and lipase activities that normally occur at very low levels in the circulation but can be significantly increased during inflammatory episodes. Progress in the understanding the pathogenesis of both conditions has therefore been largely due to time course studies in animal models of pancreatitis, and it is in this context that animal model development has been so significant. In general terms, the animal models can be divided into the invasive, surgical procedures, and those induced by the administration of chemical secretagogues that induce hypersecretion of the pancreatic enzymes. The former include ligation and/or cannulation of the biliopancreatic ducts with infusion of solutions of various kinds, or the formation of closed duodenal loops. Secretagogue administration includes administration of caerulein or l-arginine in various protocols. An additional model involves administration of dibutyltin dichloride, which induces a partial blockage of the pancreatic ducts to induce pancreatic disease through enzymic reflux into the gland. The models have been invaluable in generating testable hypotheses for the human diseases. These hypotheses for the production of cellular damage as the initiating events in the disease include (1) intracellular chemical activation, (2) pancreatic secretion reflux, (3) intracellular production of reactive oxygen species, and (4) intracellular production of free radicals.

Overview of the pancreatic toxicity and carcinogenesis session

The theme of the Society of Toxicologic Pathology Annual Symposium 2013 was "Toxicologic Pathology of the Digestive Tract and Pancreas." The last session focused on pancreatic toxicity and carcinogenesis. This overview highlights the various presentations in this session, focusing on pancreatic toxicologic pathology, responses of the pancreas to xenobiotics, and current understanding on pancreatic carcinogenesis. The objective of this symposium overview and the subsequent articles from this session is to enable the audience to develop a better appreciation for the pancreas as a target organ in toxicological studies.

Oxidative stress in acute pancreatitis: lost in translation?

Oxidative stress has been implicated in the pathogenesis of acute pancreatitis, a severe and debilitating inflammation of the pancreas that carries a significant mortality, and which imposes a considerable financial burden on the health system due to patient care. Although extensive efforts have been directed towards the elucidation of critical underlying mechanisms and the identification of novel therapeutic targets, the disease remains without a specific therapy. In experimental animal models of acute pancreatitis, increased oxidative stress and decreased antioxidant defences have been observed, changes also detected in patients clinically. However, despite the promise of studies evaluating the effects of antioxidants in these model systems, translation to the clinic has thus far been disappointing. This may reflect many factors involved in the design of both preclinical and clinical evaluations of antioxidant therapy, not least the fact that most experimental studies have focussed on pre-treatment rather than post-injury assessment. This review has examined evidence relating to the involvement of oxidative stress in the pathophysiology of acute pancreatitis, focussing on experimental models and the clinical experience, including the experimental techniques employed and potential of antioxidant therapy.

Models of acute and chronic pancreatitis

Animal models of acute and chronic pancreatitis have been created to examine mechanisms of pathogenesis, test therapeutic interventions, and study the influence of inflammation on the development of pancreatic cancer. In vitro models can be used to study early stage, short-term processes that involve acinar cell responses. Rodent models reproducibly develop mild or severe disease. One of the most commonly used pancreatitis models is created by administration of supraphysiologic concentrations of caerulein, an ortholog of cholecystokinin. Induction of chronic pancreatitis with factors thought to have a role in human disease, such as combinations of lipopolysaccharide and chronic ethanol feeding, might be relevant to human disease. Models of autoimmune chronic pancreatitis have also been developed. Most models, particularly of chronic pancreatitis, require further characterization to determine which features of human disease they include.

Inflexinol reduces severity of acute pancreatitis by inhibiting nuclear factor-κB activation in cerulein-induced pancreatitis

OBJECTIVES

To examine the effect of inflexinol on the development of acute pancreatitis (AP) and to investigate the mechanisms responsible for the protective effect against AP.

METHODS

Acute pancreatitis was induced in mice by intraperitoneal injection of cerulein. Inflexinol was administered intraperitoneally 4 times every 6 hours from 1 hour before the first cerulein injection. Serum amylase activity and histology of the pancreas were measured. Determination of pancreatic nuclear factor-κB (NF-κB) p65 expression was conducted by Western blotting and immunohistochemistry to investigate the mechanisms responsible for the inflexinol effects.

RESULTS

Serum amylase activity in the cerulein group was significantly higher than that in the control group (P < 0.05). Pancreatic histology revealed marked inflammatory changes in the cerulein group such as interstitial edema, vacuolization, necrosis, and infiltration of inflammatory cells; and Western blotting and immunohistochemistry showed marked NF-κB p65 expression. Treatment with inflexinol significantly attenuated the inflammatory changes in pancreatic histology at 24, 48, and 72 hours (P < 0.05). Pancreatic NF-κB p65 expression decreased significantly after inflexinol treatment (P < 0.05).

CONCLUSION

Inflexinol reduced the severity of cerulein-induced AP by inhibiting NF-κB activation.

Pharmacological inhibition of PAR2 with the pepducin P2pal-18S protects mice against acute experimental biliary pancreatitis

Pancreatic acinar cells express proteinase-activated receptor-2 (PAR2) that is activated by trypsin-like serine proteases and has been shown to exert model-specific effects on the severity of experimental pancreatitis, i.e., PAR2(-/-) mice are protected from experimental acute biliary pancreatitis but develop more severe secretagogue-induced pancreatitis. P2pal-18S is a novel pepducin lipopeptide that targets and inhibits PAR2. In studies monitoring PAR2-stimulated intracellular Ca(2+) concentration changes, we show that P2pal-18S is a full PAR2 inhibitor in acinar cells. Our in vivo studies show that P2pal-18S significantly reduces the severity of experimental biliary pancreatitis induced by retrograde intraductal bile acid infusion, which mimics injury induced by endoscopic retrograde cholangiopancreatography (ERCP). This reduction in pancreatitis severity is observed when the pepducin is given before or 2 h after bile acid infusion but not when it is given 5 h after bile acid infusion. Conversely, P2pal-18S increases the severity of secretagogue-induced pancreatitis. In vitro studies indicate that P2pal-18S protects acinar cells against bile acid-induced injury/death, but it does not alter bile acid-induced intracellular zymogen activation. These studies are the first to report the effects of an effective PAR2 pharmacological inhibitor on pancreatic acinar cells and on the severity of experimental pancreatitis. They raise the possibility that a pepducin such as P2pal-18S might prove useful in the clinical management of patients at risk for developing severe biliary pancreatitis such as occurs following ERCP.

In vivo imaging with fluorescent smart probes to assess treatment strategies for acute pancreatitis

BACKGROUND AND AIMS

Endoprotease activation is a key step in acute pancreatitis and early inhibition of these enzymes may protect from organ damage. In vivo models commonly used to evaluate protease inhibitors require animal sacrifice and therefore limit the assessment of dynamic processes. Here, we established a non-invasive fluorescence imaging-based biomarker assay to assess real-time protease inhibition and disease progression in a preclinical model of experimental pancreatitis.

METHODS

Edema development and trypsin activation were imaged in a rat caerulein-injection pancreatitis model. A fluorescent "smart" probe, selectively activated by trypsin, was synthesized by labeling with Cy5.5 of a pegylated poly-L-lysine copolymer. Following injection of the probe, trypsin activation was monitored in the presence or absence of inhibitors by in vivo and ex vivo imaging.

RESULTS

We established the trypsin-selectivity of the fluorescent probe in vitro using a panel of endopeptidases and specific inhibitor. In vivo, the probe accumulated in the liver and a region attributed to the pancreas by necropsy. A dose dependent decrease of total pancreatic fluorescence signal occurred upon administration of known trypsin inhibitors. The fluorescence-based method was a better predictor of trypsin inhibition than pancreatic to body weight ratio.

CONCLUSIONS

We established a fluorescence imaging assay to access trypsin inhibition in real-time in vivo. This method is more sensitive and dynamic than classic tissue sample readouts and could be applied to preclinically optimize trypsin inhibitors towards intrapancreatic target inhibition.

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.

The role of calcium in acute pancreatitis

Until recently, it was unclear whether calcium is more than a bystander in the development of acute pancreatitis. Now important evidence has been accumulated supporting a pivotal role of intracellular levels of calcium in the early pathogenesis of the disease. A sustained increase of cytosolic calcium concentrations, as observed in various models of acute pancreatitis, was identified as sabotaging crucial cellular defense mechanisms and initiating premature trypsinogen activation. These processes lead the acinar cell to necrosis, with spillage of activated proteases into the interstitial space, affecting surrounding acinar cells and initiating a vicious circle that ends in macroscopic acute pancreatitis and systemic inflammatory response syndrome. Comprehensive knowledge of the pathobiology of cytosolic calcium in the pancreatic acinar cell is leading to the understanding of coherent molecular pathways of early events in the pathogenesis of acute pancreatitis and is opening horizons for research into directly targeted therapeutic agents.

Animal models for investigating chronic pancreatitis

Chronic pancreatitis is defined as a continuous or recurrent inflammatory disease of the pancreas characterized by progressive and irreversible morphological changes. It typically causes pain and permanent impairment of pancreatic function. In chronic pancreatitis areas of focal necrosis are followed by perilobular and intralobular fibrosis of the parenchyma, by stone formation in the pancreatic duct, calcifications in the parenchyma as well as the formation of pseudocysts. Late in the course of the disease a progressive loss of endocrine and exocrine function occurs. Despite advances in understanding the pathogenesis no causal treatment for chronic pancreatitis is presently available. Thus, there is a need for well characterized animal models for further investigations that allow translation to the human situation. This review summarizes existing experimental models and distinguishes them according to the type of pathological stimulus used for induction of pancreatitis. There is a special focus on pancreatic duct ligation, repetitive overstimulation with caerulein and chronic alcohol feeding. Secondly, attention is drawn to genetic models that have recently been generated and which mimic features of chronic pancreatitis in man. Each technique will be supplemented with data on the pathophysiological background of the model and their limitations will be discussed.

A novel animal model for studying pancreatic regeneration by employing photochemical reaction

PURPOSE

We present photochemical-induced pancreatic necrosis (PIPN) as a novel induction method for studying pancreatic regeneration in an animal model.

METHODS

Photosensitive Rose Bengal was injected through the femoral vein in rats, followed by illumination of the surface of the pancreas with a cool halogen light for a period of 20 min. At 3, 6, and 24 h, and 7, 10, 14, and 20 days, experimental animals were sacrificed; all the animals received intravenous injection with 5-bromo-2-deoxyuridine (BrdU) 1 h prior to sacrifice.

RESULTS

At 3-6 h of induction of PIPN, pancreatic necrosis was superficially observed in the illuminated field. At 24 h, there was a slight increase in the depth and width of the lesion along with appearance of vascular congestion and thrombosis in the lesion. On days 7-10, the area of illumination was totally replaced by necrotic pancreatic tissue, inflammatory cell infiltrates, and newly appearing cellular components, including mesenchymal and epithelial cells, which formed tubular complexes. On day 14, clusters of tubular complexes intermingled with acinar cells, which were proven as newly formed acinar tissue by BrdU staining. On day 20, all the lesions had returned to a normal state of pancreatic tissue.

CONCLUSION

This study demonstrates the potential of PIPN as a valuable method for production of an animal model for studying healing processes or regeneration of pancreatic tissue after injury.

Characterization of dsRNA-induced pancreatitis model reveals the regulatory role of IFN regulatory factor 2 (Irf2) in trypsinogen5 gene transcription

Mice deficient for interferon regulatory factor (Irf)2 (Irf2(-/-) mice) exhibit immunological abnormalities and cannot survive lymphocytic choriomeningitis virus infection. The pancreas of these animals is highly inflamed, a phenotype replicated by treatment with poly(I:C), a synthetic double-stranded RNA. Trypsinogen5 mRNA was constitutively up-regulated about 1,000-fold in Irf2(-/-) mice compared with controls as assessed by quantitative RT-PCR. Further knockout of IFNα/β receptor 1(Ifnar1) abolished poly(I:C)-induced pancreatitis but had no effect on the constitutive up-regulation of trypsinogen5 gene, indicating crucial type I IFN signaling to elicit the inflammation. Analysis of Ifnar1(-/-) mice confirmed type I IFN-dependent transcriptional activation of dsRNA-sensing pattern recognition receptor genes MDA5, RIG-I, and TLR3, which induced poly(I:C)-dependent cell death in acinar cells in the absence of IRF2. We speculate that Trypsin5, the trypsinogen5 gene product, leaking from dead acinar cells triggers a chain reaction leading to lethal pancreatitis in Irf2(-/-) mice because it is resistant to a major endogenous trypsin inhibitor, Spink3.

Phenotypic changes in mouse pancreatic stellate cell Ca2+ signaling events following activation in culture and in a disease model of pancreatitis

The specific characteristics of intracellular Ca 2+ signaling and the downstream consequences of these events were investigated in mouse pancreatic stellate cells (PSC) in culture and in situ using multiphoton microscopy in pancreatic lobules. PSC undergo a phenotypic transformation from a quiescent state to a myofibroblast-like phenotype in culture. This is believed to parallel the induction of an activated state observed in pancreatic disease such as chronic pancreatitis and pancreatic cancer. By day 7 in culture, the complement of cell surface receptors coupled to intracellular Ca 2+ signaling was shown to be markedly altered. Specifically, protease-activated receptors (PAR) 1 and 2, responsive to thrombin and trypsin, respectively, and platelet-derived growth factor (PDGF) receptors were expressed only in activated PSC (aPSC). PAR-1, ATP, and PDGF receptor activation resulted in prominent nuclear Ca 2+ signals. Nuclear Ca 2+ signals and aPSC proliferation were abolished by expression of parvalbumin targeted to the nucleus. In pancreatic lobules, PSC responded to agonists consistent with the presence of only quiescent PSC. aPSC were observed following induction of experimental pancreatitis. In contrast, in a mouse model of pancreatic disease harboring elevated K-Ras activity in acinar cells, aPSC were present under control conditions and their number greatly increased following induction of pancreatitis. These data are consistent with nuclear Ca 2+ signaling generated by agents such as trypsin and thrombin, likely present in the pancreas in disease states, resulting in proliferation of "primed" aPSC to contribute to the severity of pancreatic disease.

TLR9 and the NLRP3 inflammasome link acinar cell death with inflammation in acute pancreatitis

BACKGROUND & AIMS

Acute pancreatitis is characterized by early activation of intracellular proteases followed by acinar cell death and inflammation. Activation of damage-associated molecular pattern (DAMP) receptors and a cytosolic complex termed the inflammasome initiate forms of inflammation. In this study, we examined whether DAMP-receptors and the inflammasome provide the link between cell death and the initiation of inflammation in pancreatitis.

METHODS

Acute pancreatitis was induced by caerulein stimulation in wild-type mice and mice deficient in components of the inflammasome (apoptosis-associated speck-like protein containing a caspase recruitment domain [ASC], NLRP3, caspase-1), Toll-like receptor 9 (TLR9), or the purinergic receptor P2X(7). Resident and infiltrating immune cell populations and pro-interleukin-1β expression were characterized in control and caerulein-treated adult murine pancreas. TLR9 expression was quantified in pancreatic cell populations. Additionally, wild-type mice were pretreated with a TLR9 antagonist before induction of acute pancreatitis by caerulein or retrograde bile duct infusion of taurolithocholic acid 3-sulfate.

RESULTS

Caspase-1, ASC, and NLRP3 were required for inflammation in acute pancreatitis. Genetic deletion of Tlr9 reduced pancreatic edema, inflammation, and pro-IL-1β expression in pancreatitis. TLR9 was expressed in resident immune cells of the pancreas, which are predominantly macrophages. Pretreatment with the TLR9 antagonist IRS954 reduced pancreatic edema, inflammatory infiltrate, and apoptosis. Pretreatment with IRS954 reduced pancreatic necrosis and lung inflammation in taurolithocholic acid 3-sulfate-induced acute pancreatitis.

CONCLUSIONS

Components of the inflammasome, ASC, caspase-1, and NLRP3, are required for the development of inflammation in acute pancreatitis. TLR9 and P2X(7) are important DAMP receptors upstream of inflammasome activation, and their antagonism could provide a new therapeutic strategy for treating acute pancreatitis.

Akt pathway is required for oestrogen-mediated attenuation of lung injury in a rodent model of cerulein-induced acute pancreatitis

BACKGROUND

The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) is known to be an endogenous negative feedback or compensatory mechanism that serves to limit pro-inflammatory and chemotactic events in response to injury. The aim of this study is to elucidate whether Akt plays any role in 17β-estradiol (E2)-mediated attenuation of lung injury after acute pancreatitis (AP).

MATERIALS AND METHODS

Male Sprague-Dawley rats underwent cerulein-induced AP. Rats were treated with vehicle (cyclodextrin), E2 (1 mg/kg body weight [BW]), or E2 plus PI3K/Akt inhibitor Wortmannin (100 μg/kg BW) 1h after the onset of AP. At 8 h after sham operation or AP, various parameters were measured.

RESULTS

AP led to a significant decrease in lung Akt phosphorylation, which was associated with increased lung tissue myeloperoxidase (MPO) activity, wet-to-dry weight ratios, interleukin (IL)-6, tumor necrosis factor (TNF)-α, cytokine-induced neutrophil chemoattractant (CINC)-1, and CINC-3 levels. Administration of E2 after AP restored the AP-induced decrease in Akt phosphorylation and attenuated the increase in lung injury markers (MPO activity and wet-to dry weight ratios) and pro-inflammatory mediator production. The effects of E2 on the lung were abolished by co-administration of Wortmannin.

CONCLUSIONS

These results collectively suggest evidences that the Akt pathway seems to be required for E2-mediated protection of lung injury after 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.

Changes in the morphology and lability of lysosomal subpopulations in caerulein-induced acute pancreatitis

BACKGROUND AND AIMS

Lysosomes play an important role in acute pancreatitis (AP). Here we developed a method for the isolation of lysosome subpopulations from rat pancreas and assessed the stability of lysosomal membranes.

METHODS

AP was induced by four subcutaneous injections of 20 μg caerulein/kg body weight at hourly intervals. The animals were killed 9h after the first injection. Marker enzymes [N-acetyl-β-D-glucosaminidase (NAG), cathepsin B and succinate dehydrogenase (SDH)] were assayed in subcellular fractions from control pancreas and in pancreatitis. Lysosomal subpopulations were separated by Percoll density gradient centrifugation and observed by electron microscopy. NAG molecular forms were determined by DEAE-cellulose chromatography.

RESULTS

AP was associated with: (i) increases in the specific activity of lysosomal enzymes in the soluble fraction, (ii) changes in the size and alterations in the morphology of the organelles from the lysosomal subpopulations, (iii) the appearance of large vacuoles in the primary and secondary lysosome subpopulations, (iv) the increase in the amount of the NAG form associated with the pancreatic lysosomal membrane as well as its release towards the soluble fraction.

CONCLUSIONS

Lysosome subpopulations are separated by a combination of differential and Percoll density gradient centrifugations. Primary lysosome membrane stability decreases in AP.

Chronic stress sensitizes rats to pancreatitis induced by cerulein: Role of TNF-α

AIM: To investigate chronic stress as a susceptibility factor for developing pancreatitis, as well as tumor necrosis factor-α (TNF-α) as a putative sensitizer.

METHODS: Rat pancreatic acini were used to analyze the influence of TNF-α on submaximal (50 pmol/L) cholecystokinin (CCK) stimulation. Chronic restraint (4 h every day for 21 d) was used to evaluate the effects of submaximal (0.2 μg/kg per hour) cerulein stimulation on chronically stressed rats.

RESULTS: In vitro exposure of pancreatic acini to TNF-α disorganized the actin cytoskeleton. This was further increased by TNF-α/CCK treatment, which additionally reduced amylase secretion, and increased trypsin and nuclear factor-κB activities in a protein-kinase-C δ and ε-dependent manner. TNF-α/CCK also enhanced caspases’ activity and lactate dehydrogenase release, induced ATP loss, and augmented the ADP/ATP ratio. In vivo, rats under chronic restraint exhibited elevated serum and pancreatic TNF-α levels. Serum, pancreatic, and lung inflammatory parameters, as well as caspases’activity in pancreatic and lung tissue, were substantially enhanced in stressed/cerulein-treated rats, which also experienced tissues’ ATP loss and greater ADP/ATP ratios. Histological examination revealed that stressed/cerulein-treated animals developed abundant pancreatic and lung edema, hemorrhage and leukocyte infiltrate, and pancreatic necrosis. Pancreatitis severity was greatly decreased by treating animals with an anti-TNF-α-antibody, which diminished all inflammatory parameters, histopathological scores, and apoptotic/necrotic markers in stressed/cerulein-treated rats.

CONCLUSION: In rats, chronic stress increases susceptibility for developing pancreatitis, which involves TNF-α sensitization of pancreatic acinar cells to undergo injury by physiological cerulein stimulation.

Molecular characterization of the endoplasmic reticulum: insights from proteomic studies

The endoplasmic reticulum (ER) is a multifunctional intracellular organelle responsible for the synthesis, processing and trafficking of a wide variety of proteins essential for cell growth and survival. Therefore, comprehensive characterization of the ER proteome is of great importance to the understanding of its functions and has been actively pursued in the past decade by scientists in the proteomics field. This review summarizes major proteomic studies published in the past decade that focused on the ER proteome. We evaluate the data sets obtained from two different organs, liver and pancreas each of which contains a primary cell type (hepatocyte and acinar cell) with specialized functions. We also discuss how the nature of the proteins uncovered is related to the methods of organelle purification, organelle purity and the techniques used for protein separation prior to MS. In addition, this review also puts emphasis on the biological insights gained from these studies regarding the molecular functions of the ER including protein synthesis and translocation, protein folding and quality control, ER-associated degradation and ER stress, ER export and membrane trafficking, calcium homeostasis and detoxification and drug metabolism.

Dantrolene mitigates caerulein-induced pancreatitis in vivo in mice

Acute pancreatitis is a painful, inflammatory disorder for which adequate treatments are lacking. An early, critical step in its development is the aberrant signaling of Ca(2+) within the pancreatic acinar cell. This Ca(2+) release is modulated by the intracellular Ca(2+) channel the ryanodine receptor (RYR). We have previously shown that RYR inhibition reduces pathological intra-acinar protease activation, an early marker of pancreatitis. In this study, we examined whether pretreatment with the RYR inhibitor dantrolene attenuates the severity of caerulein-induced pancreatitis in mice. Immunofluorescent labeling for RYR from mouse pancreatic sections showed localization to the basolateral region of the acinar cell. After 1 h of caerulein hyperstimulation in vivo, dantrolene 1) reduced pancreatic trypsin activity by 59% (P < 0.05) and 2) mitigated early ultrastructural derangements within the acinar cell. Eight hours after pancreatitis induction, dantrolene reduced pancreatic trypsin activity and serum amylase by 61 and 32%, respectively (P < 0.05). At this later time point, overall histological severity of pancreatitis was reduced by 63% with dantrolene pretreatment (P < 0.05). TUNEL-positive cells were reduced by 58% (P < 0.05). These data suggest that the RYR plays an important role in mediating early acinar cell events during in vivo pancreatitis and contributes to disease severity. Blockade of Ca(2+) signals and particularly RYR-Ca(2+) may be useful as prophylactic treatment for this disease in high-risk settings for pancreatitis.

Damage of the interstitial cells of Cajal and myenteric neurons causing ileus in acute necrotizing pancreatitis rats

BACKGROUND

Small intestinal motility is impaired in acute necrotizing pancreatitis (ANP). The present study was designed to detect the impairment in small intestinal motility and to assess the role of interstitial cells of Cajal (ICC), myenteric neurons and the associated mechanism in the pathogenesis of ileus during experimentally induced acute pancreatitis.

METHODS

ANP was induced by intraperitoneal injections of 30% L-ornithine at a dose of 3 g/kg at hourly intervals. The alterations of small intestine electrical activity--migrating myoelectric complexes (MMCs), and slow waves--were measured 24 hr after ANP induction. The spontaneous mechanical activity and the contractile response to ACh, KCl, tetrodotoxin (TTX) and the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine (L-NNA) were evaluated by organ bath technique, and the morphologic alterations of the network of ICC, myenteric neurons and neuronal nitric oxide synthase (nNOS) immunoreactive cells were evaluated using the markers of c-Kit, PGP9.5, and nNOS, respectively. To demonstrate the deficiencies in enteric neuronal origin, we also measured nNOS expression in the muscular layer of ileum.

RESULTS

L-ornithine-induced necrotizing pancreatitis manifests with multiple symptoms, including decreased amplitude of spontaneous contractions in small intestinal smooth muscle, declined contractile response to ACh, TTX, and L-NNA in vitro, disrupted MMC cycle length, decreased dominant frequency and dominant power of slow waves in vivo. Furthermore, the morphologic studies demonstrated the damage of ICC (ANP group versus control; P = .000), myenteric neurons (ANP group versus control; P = .001) and nNOS immunoreactive neurons (ANP group versus control; P = .000). We also observed a substantial loss in the expression of nNOS protein in muscular layer of the small intestine (ANP group versus control; P = .032).

CONCLUSION

Our results suggest that the pathogenesis of the small intestinal paralysis in ANP may be related to the deficiencies in ICC and nNOS neurons.

Pancreas-specific ablation of beta1 integrin induces tissue degeneration by disrupting acinar cell polarity

BACKGROUND & AIMS

Integrin contact with basement membrane is a major determinant of epithelial cell polarity. beta1 integrin heterodimers are the primary receptors for basement membrane in pancreatic acinar cells, which function to synthesize and directionally secrete digestive enzymes into a central lumen. Aberrant acinar secretion and exposure of the parenchyma to digestive enzyme activity lead to organ damage and pancreatitis.

METHODS

beta1 integrin conditional knockout mice were crossed to Ptf1a-Cre mice to ablate beta1 integrin in the pancreas. Histopathology of aged and cerulein-treated mice were assessed by histology and immunocytochemistry. Directional secretion was determined in vitro by FM1-43 loading with cerulein stimulation.

RESULTS

Pancreas-specific ablation of beta1 integrin led to progressive organ degeneration, associated with focal acinar cell necrosis and ductal metaplasia along with widespread inflammation and collagen deposition. beta1 Integrin-null pancreata were highly susceptible to cerulein-induced acute pancreatitis, displaying an enhanced level of damage with no loss in regeneration. Degenerating beta1 integrin-null pancreata were marked by disruption of acinar cell polarity. Protein kinase C epsilon, normally localized apically, was found in the cytoplasm where it can lead to intracellular digestive enzyme activation. beta1 Integrin-null acinar cells displayed indiscriminate secretion to all membrane surfaces, consistent with an observed loss of basolateral membrane localization of Munc18c, which normally prevents basal secretion of digestive enzymes.

CONCLUSIONS

Ablation of beta1 integrin induces organ atrophy by disrupting acinar cell polarity and exposing the pancreatic parenchyma to digestive enzymes.

Quantitative organellar proteomics analysis of rough endoplasmic reticulum from normal and acute pancreatitis rat pancreas

The rough endoplasmic reticulum (RER) is a central organelle for synthesizing and processing digestive enzymes and alteration of ER functions may participate in the pathogenesis of acute pancreatitis (AP). To comprehensively characterize the normal and diseased RER subproteome, this study quantitatively compared the protein compositions of pancreatic RER between normal and AP animals using isobaric tags (iTRAQ) and 2D LC-MALDI-MS/MS. A total of 469 unique proteins were revealed from four independent experiments using two different AP models. These proteins belong to a large number of functional categories including ribosomal proteins, translocon subunits, chaperones, secretory proteins, and glyco- and lipid-processing enzymes. A total of 37 RER proteins (25 unique in arginine-induced, 6 unique in caerulein-induced and 6 common in both models of AP) showed significant changes during AP including translational regulators and digestive enzymes, whereas only mild changes were found in some ER chaperones. The six proteins common to both AP models included a decrease in pancreatic triacylglycerol lipase precursor, Erp27, and prolyl 4-hydroxylase beta polypeptide as well as a dramatic increase in fibrinogen alpha, beta and gamma chains. These results suggest that the early stages of AP involve changes of multiple RER proteins that may affect the synthesis and processing of digestive enzymes.

Epithelial progenitor 1, a novel factor associated with epithelial cell growth and differentiation

The growth and renewal of epithelial tissue is a highly orchestrated and tightly regulated process occurring in different tissue types under a variety of circumstances. We have been studying the process of pancreatic regeneration in mice. We have identified a cell surface protein, named EP1, which is expressed on the duct epithelium during pancreatic regeneration. Whereas it is not detected in the pancreas of normal mice, it is found in the intestinal epithelium of normal adult mice, as well as during pancreatic repair following cerulein-induced destruction of the acinar tissue. The distinctive situations in which EP1 is expressed, all of which share in common epithelial cell growth in the gastrointestinal tract, suggest that EP1 is involved in the growth and renewal of epithelial tissues in both the intestine and the pancreas.