Increased expression of hypoxia-inducible factor-1alpha, p48, and the Notch signaling cascade during acute pancreatitis in mice

Integrating multi-omics data to analyze the potential pathogenic mechanism of CTSH gene involved in type 1 diabetes in the exocrine pancreas

Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of insulin-producing pancreatic islet beta cells. Despite significant advancements, the precise pathogenesis of the disease remains unknown. This work integrated data from expression quantitative trait locus (eQTL) studies with Genome wide association study (GWAS) summary data of T1D and single-cell transcriptome data to investigate the potential pathogenic mechanisms of the CTSH gene involved in T1D in exocrine pancreas. Using the summary data-based Mendelian randomization (SMR) approach, we obtained four potential causative genes associated with T1D: BTN3A2, PGAP3, SMARCE1 and CTSH. To further investigate these genes'roles in T1D development, we validated them using a scRNA-seq dataset from pancreatic tissues of both T1D patients and healthy controls. The analysis showed a significantly high expression of the CTSH gene in T1D acinar cells, whereas the other three genes showed no significant changes in the scRNA-seq data. Moreover, single-cell WGCNA analysis revealed the strongest positive correlation between the module containing CTSH and T1D. In addition, we found cellular ligand-receptor interactions between the acinar cells and different cell types, especially ductal cells. Finally, based on functional enrichment analysis, we hypothesized that the CTSH gene in the exocrine pancreas enhances the antiviral response, leading to the overexpression of pro-inflammatory cytokines and the development of an inflammatory microenvironment. This process promotes β cells injury and ultimately the development of T1D. Our findings offer insights into the underlying pathogenic mechanisms of T1D.

β Cell and Autophagy: What Do We Know?

Pancreatic β cells are central to glycemic regulation through insulin production. Studies show autophagy as an essential process in β cell function and fate. Autophagy is a catabolic cellular process that regulates cell homeostasis by recycling surplus or damaged cell components. Impaired autophagy results in β cell loss of function and apoptosis and, as a result, diabetes initiation and progress. It has been shown that in response to endoplasmic reticulum stress, inflammation, and high metabolic demands, autophagy affects β cell function, insulin synthesis, and secretion. This review highlights recent evidence regarding how autophagy can affect β cells' fate in the pathogenesis of diabetes. Furthermore, we discuss the role of important intrinsic and extrinsic autophagy modulators, which can lead to β cell failure.

Inhibition of Notch activity suppresses hyperglycemia-augmented polarization of macrophages to the M1 phenotype and alleviates acute pancreatitis

Acute pancreatitis (AP) is an acute inflammatory disorder characterized by acinar cell death and inflammation. Multiple factors cause hyperglycemia after AP. Macrophage polarization is involved in tissue injury and repair, and is regulated by Notch signaling during certain inflammatory diseases. The present study explores the relationship among hyperglycemia, macrophage polarization, and Notch signaling during AP and the related mechanisms. A cerulein-induced AP model was established in FVB/N mice, and AP with hyperglycemia was initiated by injection of 50% concentration glucose. Tissue damage, Notch activity, and macrophage polarization were assessed in pancreatic tissues. The role of Notch signaling in macrophage polarization during AP was also assessed in vitro by co-culturing primary macrophages and pancreatic acinar cells, and establishing a lipopolysaccharide (LPS)-induced inflammatory model in RAW264.7 cells. Pancreatic acinar cells were damaged and proinflammatory factor levels were increased in pancreatic tissues during AP. The hyperglycemic conditions aggravated pancreatic injury, increased macrophage infiltration, promoted macrophage polarization towards an M1 phenotype, and led to excessive up-regulation of Notch activity. Inhibition of Notch signaling by DAPT or Notch1 knockdown decreased the proportion of M1 macrophages and reduced the production of proinflammatory factors, thus mitigating pancreatic injury. These findings suggest that hyperglycemia induces excessive Notch signaling after AP and further aggravates AP by promoting pancreatic macrophage polarization towards the M1 phenotype. The Notch signaling pathway is a potential target for the prevention and treatment of AP.

P53 Activated by ER Stress Aggravates Caerulein-Induced Acute Pancreatitis Progression by Inducing Acinar Cell Apoptosis

BACKGROUND AND AIMS

Acute pancreatitis (AP) is a severe pancreatic disorder that remains associated with high mortality due to a lack of effective drugs and management strategies. This study aimed to investigate the molecular pathogenic mechanisms of AP involving p53 and endoplasmic reticulum (ER) stress pathways.

METHODS

Expression of PRSS1 and p53 in human AP tissues was detected by immunohistochemistry and Western blotting. AP was induced with caerulein in humanized PRSS1 transgenic mice, and its severity was verified by histological imaging, evaluation of edema, serum amylase, and trypsin activity assays. A transferase-mediated d-UTP nick end-labeling assay was performed to evaluate acinar cell apoptosis associated with AP. The expression of ER stress genes was assessed by quantitative RT-PCR (qRT-PCR) and Western blotting.

RESULTS

PRSS1 and p53 were highly expressed in human AP tissues. Expression of human PRSS1 in caerulein-treated mice induced significant acinar cell apoptosis and AP progression. P53 knockout significantly suppressed AP progression in humanized PRSS1 transgenic mice. The ER stress pathway was activated by PRSS1 and mediated the progression of AP in mouse pancreatic tissues. Application of a p53 inhibitor effectively ameliorated caerulein-induced AP in PRSS1 transgenic mice, while a p53 activator promoted the progression of AP.

CONCLUSION

P53, which was activated by the ER stress pathway, promoted the progression of AP in mice expressing PRSS1 by inducing acinar cell apoptosis.

Hypoxia-Inducible Factor-1α Knockdown Plus Glutamine Supplementation Attenuates the Predominance of Necrosis over Apoptosis by Relieving Cellular Energy Stress in Acute Pancreatitis

The present study was conducted to investigate the effect and potential mechanism of hypoxia-inducible factor-1α (HIF-1α) genetic inhibition plus glutamine (Gln) supplementation on necrosis-apoptosis imbalance during acute pancreatitis (AP), with a specific focus on the regulations of intracellular energy metabolism status. Wistar rats and AR42J cells were used to establish AP models. When indicated, a HIF-1α knockdown with or without a Gln supplementation was administered. In vivo, local and systemic inflammatory injuries were assessed by serum cytokine measurement, H&E staining, and transmission electron microscope (TEM) observation of pancreatic tissue. In vitro, intracellular energy metabolism status was evaluated by measuring the intracellular adenosine triphosphate (ATP), lactic acid, and Ca²⁺ concentrations and the mitochondrial potential. In addition, changes in the apoptotic activity were analyzed using TUNEL staining in vivo and an apoptosis assay in vitro. HIF-1α knockdown alleviated AP-related inflammatory injury as indicated by the measurements of serum cytokines and examinations of TEM and H&E staining of pancreatic tissues. HIF-1α knockdown played an antioxidative role against AP-related injuries by preventing the increase in the intracellular Ca²⁺ concentration and the decrease in the mitochondrial membrane potential and subsequently by suppressing the glycolysis pathway and increasing energy anabolism in AR42J cells after AP induction. Apoptosis was significantly upregulated when HIF-1α was knocked down before AP induction due to an attenuation of the translocation of nuclear factor-kappa B to the nuclei. Furthermore, these merits of HIF-1α knockdown in the relief of the metabolic stress and upregulation of apoptosis were more significant when Gln was administered concomitantly. In conclusion, Gln-supplemented HIF-1α knockdown might be promising for the future management of AP by relieving the intracellular energy stress, thereby attenuating the predominance of necrosis over apoptosis.

β Cell Hypoxia-Inducible Factor-1α Is Required for the Prevention of Type 1 Diabetes

The development of autoimmune disease type 1 diabetes (T1D) is determined by both genetic background and environmental factors. Environmental triggers include RNA viruses, particularly coxsackievirus (CV), but how they induce T1D is not understood. Here, we demonstrate that deletion of the transcription factor hypoxia-inducible factor-1α (HIF-1α) from β cells increases the susceptibility of non-obese diabetic (NOD) mice to environmentally triggered T1D from coxsackieviruses and the β cell toxin streptozotocin. Similarly, knockdown of HIF-1α in human islets leads to a poorer response to coxsackievirus infection. Studies in coxsackievirus-infected islets demonstrate that lack of HIF-1α leads to impaired viral clearance, increased viral load, inflammation, pancreatitis, and loss of β cell mass. These findings show an important role for β cells and, specifically, lack of β cell HIF-1α in the development of T1D. These data suggest new strategies for the prevention of T1D.

Stabilization of HIF-2α impacts pancreas growth

Hypoxia inducible factors (HIFs) are critical regulators of the response to oxygen deficiency by activating target genes involved in a variety of biological functions. HIFs have been implicated in the pathophysiology of numerous pathologies including cancer. Patients with mutations in the von Hippel-Lindau (VHL) gene, an essential regulator of HIF activity, develop tumors in several organs including the pancreas. Previous functional studies of HIF activation in the pancreas have used Vhlh (the murine homolog of VHL) deficient mice. However, the role of each specific HIF transcription factors in the pancreas has not been thoroughly examined. We derived mice that constitutively express a normoxia-stable form of HIF2α in the pancreas. Activation of HIF2α in the pancreas severely impairs postnatal exocrine pancreas. Mice with pancreas-specific activation of HIF2α develop histological features reminiscent of pancreatitis including loss of acinar cells, ductal dilation and fibrosis. Moreover, we provide evidence that signaling pathways important for acinar cell homeostasis are altered in HIF2α-overexpressing pancreata.

Activating transcription factor 3 promotes loss of the acinar cell phenotype in response to cerulein-induced pancreatitis in mice

Pancreatitis is a debilitating disease of the exocrine pancreas that, under chronic conditions, is a major susceptibility factor for pancreatic ductal adenocarcinoma (PDAC). Although down-regulation of genes that promote the mature acinar cell fate is required to reduce injury associated with pancreatitis, the factors that promote this repression are unknown. Activating transcription factor 3 (ATF3) is a key mediator of the unfolded protein response, a pathway rapidly activated during pancreatic insult. Using chromatin immunoprecipitation followed by next-generation sequencing, we show that ATF3 is bound to the transcriptional regulatory regions of >30% of differentially expressed genes during the initiation of pancreatitis. Of importance, ATF3-dependent regulation of these genes was observed only upon induction of pancreatitis, with pathways involved in inflammation, acinar cell differentiation, and cell junctions being specifically targeted. Characterizing expression of transcription factors that affect acinar cell differentiation suggested that acinar cells lacking ATF3 maintain a mature cell phenotype during pancreatitis, a finding supported by maintenance of junctional proteins and polarity markers. As a result, Atf3-/- pancreatic tissue displayed increased tissue damage and inflammatory cell infiltration at early time points during injury but, at later time points, showed reduced acinar-to-duct cell metaplasia. Thus our results reveal a critical role for ATF3 as a key regulator of the acinar cell transcriptional response during injury and may provide a link between chronic pancreatitis and PDAC.

Network Pharmacological Screening of Herbal Monomers that Regulate Apoptosis-Associated Genes in Acute Pancreatitis

OBJECTIVES

In this study, we screened for differentially expressed genes in acute pancreatitis and the herbal monomers that regulate these genes.

METHODS

Gene expression profile data were downloaded from the Gene Expression Omnibus database (GSE3644). We used the Human Protein Reference Database to determine the protein-protein interaction network and CFinder software (Department of Biological Physics of Eötvös University, Budapest, Hungary) to identify several functional modules. Then, we used Database for Annotation, Visualization and Integrated Discovery software (Frederick, Md) to perform a gene ontology-biological process functional enrichment analysis. Based on a database of herbal monomers and a literature search, we constructed a gene-herbal monomer regulatory network using Cytoscape software (San Diego, Calif), and we analyzed the relationships between apoptosis, genes, and herbal monomers.

RESULTS

A total of 1745 differentially expressed genes were identified. Nine modules were identified, and the main function of module 3 was closely related to apoptosis. Within module 3, we selected 13 genes that were closely related to apoptosis for further analysis. In the gene-herbal monomer regulatory network, 18 herbal monomers that regulate multiple target genes were selected as the focus of this study.

CONCLUSIONS

These herbal monomers regulate multiple target genes to induce apoptosis and may potentially be used as new drugs for acute pancreatitis treatment in the future.

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.

Effects of hypoxia-inducible factor-1α and matrix metalloproteinase-9 on alveolar-capillary barrier disruption and lung edema in rat models of severe acute pancreatitis-associated lung injury

The aim of this study was to investigate the effects of hypoxia-inducible factor-1α (HIF-1α) and matrix metalloproteinase-9 (MMP-9) on alveolar-capillary barrier disruption and lung edema in rat models of severe acute pancreatitis-associated lung injury (PALI). A total of 40 male Sprague-Dawley rats were randomly divided into a sham surgery group (n=10) and three PALI groups, in which acute pancreatitis was induced by the retrograde infusion of 5% sodium taurocholate (1 ml/kg). The PALI groups were as follows: i) Untreated PALI group (n=10); ii) 2-methoxyestradiol (2ME2) group (5 mg/kg body mass; n=10); and iii) 2ME2 group (15 mg/kg body mass; n=10). In the two 2ME2 groups, the HIF-1α inhibitor 2ME2 was administered intraperitoneally 1 h after the induction of AP. The severity of the pancreatitis was evaluated by the serum amylase levels and pathology. The severity of the lung injury was evaluated by the wet/dry ratio, blood gas analysis and pathology. The alveolar-capillary barrier disruption was assessed by Evans blue dye extravasation. The protein and mRNA expression levels of HIF-1α and MMP-9 were studied using enzyme-linked immunosorbent assays (ELISAs), western blot analysis and reverse transcription-polymerase chain reaction. The active tumor necrosis factor-α levels were measured using an ELISA. The HIF-1α inhibitor 2ME2 attenuated the severity of the pancreatitis and PALI, while the lung edema and alveolar-capillary barrier disruption were significantly ameliorated compared with those in the untreated PALI group. Administration of the higher dose of 2ME2 significantly suppressed the protein expression of MMP-9 in the lung tissues. The results indicate that HIF-1α has a major function in alveolar-capillary barrier disruption and lung edema in PALI via a molecular pathway cascade involving MMP-9. Inhibition of HIF-1α by 2ME2 attenuates alveolar-capillary barrier disruption and lung edema. Pharmacological blockade of this pathway in patients with PALI may provide a novel therapeutic strategy.

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.

Pancreatitis activates pancreatic apelin-APJ axis in mice

Pancreatitis is classified into acute pancreatitis (AP) and chronic pancreatitis (CP). Apelin, a small regulatory peptide, is the endogenous ligand for the APJ receptor. Apelin and APJ are expressed in the pancreas. The aims of this study were to examine whether apelin influences the inflammatory and fibrosis responses to pancreatitis in mice and to identify mechanisms behind apelin's activities. Supramaximal cerulein induction of AP or CP caused significant (P < 0.05) elevations in pancreatic apelin and APJ expression. Levels declined during the recovery phases. In apelin gene-knockout mice with pancreatitis, pancreatic neutrophil invasion and myeloperoxidase activity were enhanced significantly, and apelin treatment suppressed both. Apelin exposure reduced CP-induced elevations of extracellular matrix-associated proteins. Apelin inhibited PDGF-simulated connective tissue growth factor production and proliferation of pancreatic stellate cells (PSCs). Serum granulocyte colony-stimulating factor and keratinocyte cytokine levels were higher in apelin gene-knockout than wild-type mice with pancreatitis. Apelin reduced AP- and CP-induced elevations in pancreatic NF-κB activation. Together, these findings imply that the pancreatic apelin-APJ system functions to curb the inflammatory and fibrosis responses during pancreatitis. Furthermore, findings suggest that apelin reduces inflammation and fibrosis by reducing neutrophil recruitment and PSC activity. Inhibition of neutrophil invasion may be mediated by reduced keratinocyte cytokine and granulocyte colony-stimulating factor secretion. Apelin-induced reductions in PSC proliferation and connective tissue growth factor production are putative mechanisms underlying apelin's inhibition of extracellular matrix production. The apelin-associated changes in NF-κB binding may be linked to apelin's regulation of pancreatic inflammatory and fibrosis responses during pancreatitis.

The many faces of wnt and pancreatic ductal adenocarcinoma oncogenesis

Pancreatic ductal adenocarcinoma (PDAC) remains amongst the most lethal human cancers. PDAC is characterized by the tumor mass containing a paucity of malignant cells in association with a large desmoplastic reaction comprised of a variety of stromal components. Sporadic PDAC oncogenesis occurs as a result of the sequential acquisition of genetic aberrations occurring in core genetic pathways. Unfortunately, the average PDAC contains a large number of genetic aberrations that are not uniform between individual cancers. The interplay between the complex genetics and stromal component may represent a significant barrier to the development of effective therapy for this disease and ultimately be an important factor in PDAC lethality. The Wnt pathway has been identified as a one of the common pathways undergoing genetic alterations in PDAC. Wnt is a complex signal transduction pathway utilizing both a β-catenin dependent (canonical) and β-catenin independent (noncanonical) signals to affect a wide array of intracellular events. Wnt signal transduction is an integral component of pancreas organogenesis promoting the expansion and development of the exocrine pancreas. Pancreatic cancer may utilize the Wnt signaling pathway in concert with other signaling pathways such as notch during tumorigenesis. This review will focus on the role of Wnt signal transduction in pancreatic cancer biology.

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.

Targeting Notch signaling in pancreatic cancer patients--rationale for new therapy

Pancreatic cancer is one of the most aggressive and devastating human malignancies. Despite new knowledge in the molecular profile of pancreatic cancer and its precursor lesions, survival rates have changed very little over the last 40 years. Therefore, a better understanding of the detailed mechanisms underlying the pathogenesis of this disease is critical if we expect to develop new and effective strategies for prevention, early diagnosis and treatment of pancreatic cancer. The review herein focuses on a distinctive signaling pathway, the Notch pathway, which has recently been associated with carcinogenesis, including pancreatic cancer. It is aimed at summarizing key results which support a role for this pathway in the initiation, progression and maintenance of pancreatic cancer as a rationale for targeting and inhibiting this pathway in pancreatic cancer patients.

Notch signaling in solid tumors

In recent years a substantial body of evidence derived from not only preclinical but also clinical studies has accumulated in support of Notch signaling playing important oncogenic roles in several types of cancer. The finding that activating Notch mutations are frequently found in patients suffering from acute lymphoblastic leukemia is one of the best examples for a critical role of Notch signaling in cancer, a fact that motivated many researchers and clinicians to study the role of Notch also in solid tumors. Hence Notch signaling has gained increasing attention as a potential therapeutic target. In this book chapter we would like to discuss our current knowledge of Notch signaling within different types of solid cancers as well as advantages and disadvantages of potential new therapies that try to target the oncogenic properties of Notch signaling.

Context-dependent transformation of adult pancreatic cells by oncogenic K-Ras

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies. To investigate the cellular origin(s) of this cancer, we determined the effect of PDAC-relevant gene mutations in distinct cell types of the adult pancreas. We show that a subpopulation of Pdx1-expressing cells is susceptible to oncogenic K-Ras-induced transformation without tissue injury, whereas insulin-expressing endocrine cells are completely refractory to transformation under these conditions. However, chronic pancreatic injury can alter their endocrine fate and allow them to serve as the cell of origin for exocrine neoplasia. These results suggest that one mechanism by which inflammation and/or tissue damage can promote neoplasia is by altering the fate of differentiated cells that are normally refractory to oncogenic stimulation.

Down-regulation of hypoxia-inducible factor-1alpha by hyperbaric oxygen attenuates the severity of acute pancreatitis in rats

OBJECTIVES

This study investigated the role of hypoxia-inducible factor 1alpha (HIF-1alpha) in acute pancreatitis (AP) and whether HIF-1alpha is involved in the therapeutic effects of hyperbaric oxygen (HBO) on AP.

METHODS

Thirty Wistar rats with taurocholate-induced AP were randomly assigned to 3 groups (each group had 10 rats) receiving oxygen, HBO, or no therapeutic treatment 4 hours after induction. Ten healthy sham-operated rats also served as controls. The arterial oxygen saturation, PaO2, pH, lactate dehydrogenase in the arterial sera, and amylase and tumor necrosis factor alpha in the venous sera were measured 6 hours after induction. Pancreatic tissues were subjected to histopathologic analysis, immunohistochemical and Western-blotted analyses of HIF-1alpha and vascular endothelial growth factor, and measuring of myeloperoxidase activity.

RESULTS

The HBO therapy attenuated the severity of acute pancreatitis; reduced histopathologic scores, dry weight-wet weight ratio of pancreatic tissues, and levels of amylase and lactate dehydrogenase; and elevated blood arterial oxygen saturation, PaO2, and pH values. The HBO therapy inhibited AP-induced up-regulation of HIF-1alpha and its downstream effector vascular endothelial growth factor and the production of tumor necrosis factor alpha and myeloperoxidase activity.

CONCLUSIONS

Hypoxia-inducible factor 1alpha plays a key role in the pathogenesis of AP, and the ability to down-regulate the expression of HIF-1alpha may partially explain the therapeutic effect of HBO on AP.

Inhibition of transforming growth factor beta signaling by halofuginone as a modality for pancreas fibrosis prevention

OBJECTIVES

Chronic pancreatitis is characterized by inflammation and fibrosis. We evaluated the efficacy of halofuginone, an inhibitor of collagen synthesis and myofibroblast activation, in preventing cerulein-induced pancreas fibrosis.

METHODS

Collagen synthesis was evaluated by in situ hybridization and staining. Levels of prolyl 4-hydroxylase beta (P4Hbeta), cytoglobin/stellate cell activation-associated protein (Cygb/STAP), transgelin, tissue inhibitors of metalloproteinases, serum response factor, transforming growth factor beta (TGFbeta), Smad3, and pancreatitis-associated protein 1 (PAP-1) were determined by immunohistochemistry. Metalloproteinase activity was evaluated by zymography.

RESULTS

Halofuginone prevented cerulein-dependent increase in collagen synthesis, collagen cross-linking enzyme P4Hbeta, Cygb/STAP, and tissue inhibitors of metalloproteinase 2. Halofuginone did not affect TGFbeta levels in cerulein-treated mice but inhibited serum response factor synthesis and Smad3 phosphorylation. In culture, halofuginone inhibited pancreatic stellate cell (PSC) proliferation and TGFbeta-dependent increase in Cygb/STAP and transgelin synthesis and metalloproteinase 2 activity. Halofuginone increased c-Jun N-terminal kinase phosphorylation in PSCs derived from cerulein-treated mice. Halofuginone prevented the increase in acinar cell proliferation and further increased the cerulein-dependent PAP-1 synthesis.

CONCLUSIONS

Halofuginone inhibits Smad3 phosphorylation and increases c-Jun N-terminal kinase phosphorylation, leading to the inhibition of PSC activation and consequent prevention of fibrosis. Halofuginone increased the synthesis of PAP-1, which further reduces pancreas fibrosis. Thus, halofuginone might serve as a novel therapy for pancreas fibrosis.

Inhibition of gamma-secretase activity inhibits tumor progression in a mouse model of pancreatic ductal adenocarcinoma

BACKGROUND & AIMS

The Notch signaling pathway is required for the expansion of undifferentiated pancreatic progenitor cells during embryonic development and has been implicated in the progression of pancreatic ductal adenocarcinoma (PDAC). The interaction of Notch ligands with their receptors promotes a gamma-secretase-dependent cleavage of the Notch receptor and release of the Notch intracellular domain, which translocates to the nucleus and activates transcription. We investigated the role of this pathway in PDAC progression.

METHODS

We tested the effects of a gamma-secretase inhibitor (GSI) that blocks Notch signaling in PDAC cell lines and a genetically engineered mouse model of PDAC (Kras p53 L/+ mice).

RESULTS

Notch signaling was activated in PDAC precursors and advanced tumors. The GSI inhibited the growth of premalignant pancreatic duct-derived cells in a Notch-dependent manner. Additionally, in a panel of over 400 human solid tumor-derived cell lines, PDAC cells, as a group, were more sensitive to the GSI than any other tumor type. Finally, the GSI completely inhibited tumor development in the genetically engineered model of invasive PDAC (P < .005, chi2 test; compared with mice exposed to vehicle).

CONCLUSIONS

These results suggest that Notch signaling is required for PDAC progression. Pharmacologic targeting of this pathway offers therapeutic potential in this treatment-refractory malignancy.

Notch and Kras reprogram pancreatic acinar cells to ductal intraepithelial neoplasia

Efforts to model pancreatic cancer in mice have focused on mimicking genetic changes found in the human disease, particularly the activating KRAS mutations that occur in pancreatic tumors and their putative precursors, pancreatic intraepithelial neoplasia (PanIN). Although activated mouse Kras mutations induce PanIN lesions similar to those of human, only a small minority of cells that express mutant Kras go on to form PanINs. The basis for this selective response is unknown, and it is similarly unknown what cell types in the mature pancreas actually contribute to PanINs. One clue comes from the fact that PanINs, unlike most cells in the adult pancreas, exhibit active Notch signaling. We hypothesize that Notch, which inhibits differentiation in the embryonic pancreas, contributes to PanIN formation by abrogating the normal differentiation program of tumor-initiating cells. Through conditional expression in the mouse pancreas, we find dramatic synergy between activated Notch and Kras in inducing PanIN formation. Furthermore, we find that Kras activation in mature acinar cells induces PanIN lesions identical to those seen upon ubiquitous Kras activation, and that Notch promotes both initiation and dysplastic progression of these acinar-derived PanINs, albeit short of invasive adenocarcinoma. At the cellular level, Notch/Kras coactivation promotes rapid reprogramming of acinar cells to a duct-like phenotype, providing an explanation for how a characteristically ductal tumor can arise from nonductal acinar cells.

Progressive metaplastic and dysplastic changes in mouse pancreas induced by cyclooxygenase-2 overexpression

Cyclooxygenase-2 (COX-2) overexpression is an established factor linking chronic inflammation with metaplastic and neoplastic change in various tissues. We generated transgenic mice (BK5.COX-2) in which elevation of COX-2 and its effectors trigger a metaplasia-dysplasia sequence in exocrine pancreas. Histologic evaluation revealed a chronic pancreatitis-like state characterized by acinar-to-ductal metaplasia and a well-vascularized fibroinflammatory stroma that develops by 3 months. By 6 to 8 months, strongly dysplastic features suggestive of pancreatic ductal adenocarcinoma emerge in the metaplastic ducts. Increased proliferation, cellular atypia, and loss of normal cell/tissue organization are typical features in transgenic pancreata. Alterations in biomarkers associated with human inflammatory and neoplastic pancreatic disease were detected using immunohistochemistry. The abnormal pancreatic phenotype can be completely prevented by maintaining mice on a diet containing celecoxib, a well-characterized COX-2 inhibitor. Despite the high degree of atypia, only limited evidence of invasion to adjacent tissues was observed, with no evidence of distant metastases. However, cell lines derived from spontaneous lesions are aggressively tumorigenic when injected into syngeneic or nude mice. The progressive nature of the metaplastic/dysplastic changes observed in this model make it a valuable tool for examining the transition from chronic inflammation to neoplasia.

Notch signaling is required for exocrine regeneration after acute pancreatitis

BACKGROUND & AIMS

The mechanisms for tissue regeneration and renewal after acute pancreatitis are not well understood but may involve activation of Notch signaling. To study the effect of Notch signaling ablation during acute experimental pancreatitis, we used a chemical and genetic approach to ablate Notch signaling in cerulein-induced pancreatitis in mice.

METHODS

Acute pancreatitis was induced by cerulein treatment in mice treated with the gamma-secretase inhibitor dibenzazepine or in conditional Notch1 knockout mice. Mice were characterized using immunohistologic, biochemical, and molecular methods. To investigate Notch and beta-catenin interaction, acinar 266-6 cells were analyzed using transfection and biochemical assays.

RESULTS

Loss of Notch signaling results in impaired regeneration after acute pancreatitis with fewer mature acinar cells in dibenzazepine-treated and Notch1-deficient mice in the regenerative phase 3 days after induction. beta-catenin expression was increased and prolonged during exocrine regeneration. Crosstalk between Notch and beta-catenin-mediated signaling was identified, with Notch1-IC inhibiting beta-catenin-mediated transcriptional activity. This inhibition was dependent on a functional RAM domain.

CONCLUSIONS

Inhibition of Notch signaling in vivo leads to impaired regeneration of the exocrine pancreas after acute pancreatitis. Our results suggest an interaction of Notch and Wnt signaling in pancreatic acinar cells, providing evidence for a role of these pathways in the regulation of the maturation process of acinar cells.

Pancreas transcription factor 1alpha expression is regulated in pancreatitis

BACKGROUND

Expression of acinar cell-specific genes requires the pancreas transcription factor 1alpha (Ptf1alpha). p48 is the only component of Ptf1alpha that is involved in both acinar gene regulation and pancreatic ontogenesis.

MATERIALS AND METHODS

To determine whether Ptf1alpha/p48 expression is regulated during pancreatitis, acute pancreatitis was induced in rats by repeated caerulein injections; early chronic pancreatitis by the combined administration of caerulein and cyclosporin A; and focal pancreas fibrosis by trinitrobenzene sulfonic acid infusion into the pancreatic duct. AR42J cells were used to examine caerulein effects on acinar cells. Ptf1alpha/p48 expression was examined using immunohistochemistry, Western blotting, and qRT-PCR methods.

RESULTS

In acute pancreatitis, Ptf1alpha/p48 decreased markedly within 6 h as determined by Western blotting and immunohistochemistry. After 24 h, Ptf1alpha/p48 increased continuously and normalized at day six. In contrast, pancreas amylase reached a nadir at 48 h, when Ptf1alpha/p48 had largely recovered. In the early chronic pancreatitis model Ptf1alpha/p48 levels did not completely recover even at day 14, and this was associated with a failure to restore normal histology and amylase content. qRT-PCR showed that p48 mRNA were reduced after pancreatitis induction and were followed by a decrease in elastase mRNA. In the focal pancreas fibrosis model, Ptf1alpha/p48 expression was undetectable in areas with substantial acinar cell loss and tubular complexes. Caerulein did not affect Ptf1alpha/p48 expression in AR42J cells.

CONCLUSIONS

Ptf1alpha/p48 protein and mRNA levels are regulated in acute and chronic experimental pancreatitis. Inability to re-express Ptf1alpha/p48 after injury may preclude acinar cell differentiation and appropriate pancreatic regeneration.

Vascular endothelial growth factor increases in serum and protects against the organ injuries in severe acute pancreatitis

BACKGROUND

We have demonstrated that apoptosis was detected in liver and kidney cells in severe acute pancreatitis and that cellular injury because of apoptosis may be involved in the mechanism of multiple organ dysfunction syndrome. Vascular endothelial growth factor (VEGF) is a glycoprotein with potent angiogenic, mitogenic, and vascular permeability-enhancing activities specific for endothelial cells. It has been reported that VEGF is implicated in many diseases such as cancer and inflammation.

METHODS

Serum VEGF concentrations were determined in patients with acute pancreatitis at the time of admission, and the relationships with severity, blood biochemical parameters on admission, organ dysfunction during the clinical course, and prognosis were analyzed. Moreover, to clarify the role of VEGF in acute pancreatitis, effects of VEGF were investigated in experimental severe acute pancreatitis.

RESULTS

Serum VEGF levels were significantly elevated in patients with acute pancreatitis. Serum VEGF levels were not related to severity or prognosis. In male patients, among the various blood biochemical parameters, serum lactate dehydrogenase, and blood urea nitrogen levels were positively correlated with serum VEGF levels. Serum VEGF levels with organ dysfunction (liver and kidney) were higher than those without organ dysfunction. In rat experimental severe acute pancreatitis, serum VEGF levels were significantly elevated. Recombinant VEGF did not affect the lung water content, volume of ascitic fluid, hematocrit, or serum amylase, but improved the hepatic and renal dysfunctions. Apoptosis of liver and kidney was significantly inhibited by the administration of VEGF.

CONCLUSIONS

These results suggest that VEGF is closely related to organ dysfunction in severe acute pancreatitis, and that VEGF may function as not a vascular permeability factor, but a protective factor via the anti-apoptotic effect against the organ injuries in this disease.