Changes in the expression and dynamics of SHP-1 and SHP-2 during cerulein-induced acute pancreatitis in rats

Da Cheng Qi Decoction Alleviates Cerulein-Stimulated AR42J Pancreatic Acinar Cell Injury via the JAK2/STAT3 Signaling Pathway

Background

Acute pancreatitis (AP) is a common acute abdomen inflammation, characterized by the dysregulation of digestive enzyme production and secretion. Many studies have shown that Da Cheng Qi Decoction (DCQD) is a secure, effective prescription on AP. In this study, cerulein-stimulated AR42J cells damage model was established to further explore the feasibility and underlying mechanism of DCQD as a potential inhibitor of JAK2/STAT3 pathway for the treatment of AP.

Methods

Cell viability of DCQD was measured using a cell counting Kit-8 assay. Pancreatic biochemical markers such as amylase, lipase, and C-reactive protein production were measured by assay kits, respectively. Cytokines (TNF-α, IL-6, IL-10, and IL-1β) were assayed by ELISA. Protein location and protein expression were detected by immunofluorescence staining and Western blotting, respectively. Gene expression was assessed by real-time PCR. For mechanistic analysis of the effect of DCQD on JAK2/STAT3 signaling pathway, selective JAK2 inhibitor (Fedratinib) and STAT3 inhibitor (Stattic) as well as STAT3 activator (Garcinone D) were used.

Results

DCQD protected cells by regulating cerulein-induced inflammation and reducing the secretion of pancreatic biochemical markers. Moreover, DCQD could not only inhibit the nuclear translocation of p-STAT3, but also decrease the mRNA expression of JAK2 and STAT3 as well as the ratio of p-JAK2/JAK2 and p-STAT3/STAT3 in protein level. Additionally, DCQD could regulate the mRNA and protein expression of JAK2/STAT3 downstream effectors, Bax and Bcl-XL. The activated effect of cerulein on JAK2/STAT3 pathway was also reversed by JAK2 inhibitor Fedratinib or STAT3 inhibitor Stattic. And the overexpression of JAK2/STAT3 pathway, via STAT3 activator Garcinone D, did exert damage on cells, which bore a resemblance to cerulein.

Conclusion

The activation of JAK2/STAT3 pathway may play a key role in the pathogenesis of cerulein-stimulated AR42J pancreatic acinar cell injury. DCQD could improve inflammatory cytokines and cell injury, which might be mediated by suppressing the activation of JAK2/STAT3 signaling pathway.

SHP-1 suppresses endotoxin-induced uveitis by inhibiting the TAK1/JNK pathway

We investigated how Src-homology 2-domain phosphatase-1 (SHP-1) regulates the inflammatory response in endotoxin-induced uveitis (EIU), and the signalling pathways involved. One week after intravitreal injection of short hairpin RNA targeting SHP-1 or SHP-1 overexpression lentivirus in rats, we induced ocular inflammation with an intravitreal injection of lipopolysaccharide (LPS). We then assessed the extent of inflammation and performed full-field electroretinography. The concentrations and retinal expression of various inflammatory mediators were examined with enzyme-linked immunosorbent assays and Western blotting, respectively. SHP-1 overexpression and knockdown were induced in Müller cells to study the role of SHP-1 in the LPS-induced inflammatory response in vitro. Retinal SHP-1 expression was up-regulated by LPS. SHP-1 knockdown exacerbated LPS-induced retinal dysfunction and increased the levels of proinflammatory mediators in the retina, which was abrogated by a c-Jun N-terminal kinase (JNK) inhibitor (SP600125). SHP-1 overexpression had the opposite effects. In Müller cells, the LPS-induced inflammatory response was enhanced by SHP-1 knockdown and suppressed by SHP-1 overexpression. SHP-1 negatively regulated the activation of the transforming growth factor-β-activated kinase-1 (TAK1)/JNK pathway, but not the nuclear factor-κB pathway. These results indicate that SHP-1 represses EIU, at least in part, by inhibiting the TAK1/JNK pathway and suggest that SHP-1 is a potential therapeutic target for uveitis.

Tumour targetable and microenvironment-responsive nanoparticles simultaneously disrupt the PD-1/PD-L1 pathway and MAPK/ERK/JNK pathway for efficient treatment of colorectal cancer

The present study was aimed to develop a novel combination therapeutic strategy of gene therapy and immunotherapy for efficiently treatment of colorectal cancer (CRC). To achieve that goal, the polyethylene glycol-modified poly (2-(N,N-dimethylamino) ethyl methacrylate) (PEG-PDMAEMA)-based nanoparticles loaded with protein tyrosine phosphatase non-receptor type 6 (PTPN6) (NP-PTPN6) was developed first followed by conjugation with anti-PD-L1 monoclonal antibodies (aPD-L1) atezolizumab (aPD-L1NP-PTPN6). Importantly, the aPD-L1 was conjugated on the surface of NP-PTPN6 by the matrix metalloproteinases (MMPs)-cleavable linkage PLGLAG. Therefore, the aPD-L1 would be completely released once the aPD-L1NP-PTPN6 was entrapped into tumour tissues as demonstrated by the release assay. Tumour targeting assay demonstrated the aPD-L1NP-PTPN6 have high affinity to CRC cells and resulted in excellent tumour targeting drug delivery efficacy. Additionally, anti-tumour effect evaluation revealed that the aPD-L1NP-PTPN6 has greater ability to inhibit the growth, invasion and migration of CRC cells and finally led to longer survival time of tumour-bearing mice than other treatments. Further mechanisms studies demonstrated that treatment of CRC cells with aPD-L1NP-PTPN6 contributed to significant suppression of the MAPK/ERK signalling pathway. Besides, it was further demonstrated that treating CRC with aPD-L1NP-PTPN6 resulted in up-regulation of NK cells and T cells percentage within the tumour tissues.

Data for Tandem Mass Tag (TMT) proteomic analysis of the pancreas during the early phase of experimental pancreatitis

The quantitative proteomics data reported here pertain to the research article entitled “A Tandem Mass Tag (TMT) proteomic analysis during the early phase of experimental pancreatitis reveals new insights in the disease pathogenesis” (García-Hernández et al., 2018) [1].

The development of acute pancreatitis (AP, an important pathological inflammatory state of the exocrine pancreas) would be based on early changes in protein expression and signaling pathways whose unmasking would be crucial for deciphering AP at the molecular level. We reported here a Tandem Mass Tag (TMT)-based proteomics analysis of rat subcellular fractions of the pancreas during the early phase of experimental AP, using a sixplex isobaric chemical labeling technique. We identified 997 unique proteins, of which 353 were significantly different (22, 276 or 55 in both, the soluble or the membrane fractions, respectively).

Accordingly, using TMT proteomics and bioinformatic tools, in García-Hernández et al., 2018- [1] we were able to detect significant changes in protein expression related to many pathobiological pathways of AP as from the early phase of the disease, including some changes never described before in this disease. Proteomics data are publicly available in ProteomeXchange via PRIDE through the identifier PXD007096.

Quantitative proteomic analysis of pancreatic cyst fluid proteins associated with malignancy in intraductal papillary mucinous neoplasms

Background

The application of advanced imaging technologies for identifying pancreatic cysts has become widespread. However, accurately differentiating between low-grade dysplasia (LGD), high-grade dysplasia (HGD), and invasive intraductal papillary mucinous neoplasms (IPMNs) remains a diagnostic challenge with current biomarkers, necessitating the development of novel biomarkers that can distinguish IPMN malignancy.

Methods

Cyst fluid samples were collected from nine IPMN patients (3 LGD, 3 HGD, and 3 invasive IPMN) during their pancreatectomies. An integrated proteomics approach that combines filter-aided sample preparation, stage tip-based high-pH fractionation, and high-resolution MS was applied to acquire in-depth proteomic data of pancreatic cyst fluid and discover marker candidates for IPMN malignancy. Biological processes of differentially expressed proteins that are related to pancreatic cysts and aggressive malignancy were analyzed using bioinformatics tools such as gene ontology analysis and Ingenuity pathway analysis. In order to confirm the validity of the marker candidates, 19 cyst fluid samples were analyzed by western blot.

Results

A dataset of 2992 proteins was constructed from pancreatic cyst fluid samples. A subsequent analysis found 2963 identified proteins in individual samples, 2837 of which were quantifiable. Differentially expressed proteins between histological grades of IPMN were associated with pancreatic diseases and malignancy according to ingenuity pathway analysis. Eighteen biomarker candidates that were differentially expressed across IPMN histological grades were discovered—7 DEPs that were upregulated and 11 that were downregulated in more malignant grades. HOOK1 and PTPN6 were validated by western blot in an independent cohort, the results of which were consistent with our proteomic data.

Conclusions

This study demonstrates that novel biomarker candidates for IPMN malignancy can be discovered through proteomic analysis of pancreatic cyst fluid.

Electronic supplementary material

The online version of this article (10.1186/s12014-018-9193-1) contains supplementary material, which is available to authorized users.

A tandem mass tag (TMT) proteomic analysis during the early phase of experimental pancreatitis reveals new insights in the disease pathogenesis

Changes in the protein expression occurring within the initiation phase of acute pancreatitis (AP) might be vital in the development of this complex disease. However, the exact mechanisms involved in the onset of AP remains elusive and most of our knowledge about the pathobiology of AP comes from animal models. We performed in a rat pancreatitic model a high-throughput shotgun proteomic profiling of the soluble and whole membrane fractions from the pancreas during the early phase of cerulein (Cer)-induced AP. We identified 997 proteins, of which 353 were significantly different (22, 276 or 55 in both, the soluble or the membrane fractions, respectively). Gene Ontology and KEGG PATHWAY analyses revealed that these proteins were implicated in molecular mechanisms relevant to AP pathogenesis, including vesicle-mediated and protein transport, lysosomal and mitochondrial impairment or proteolysis. Numerous metabolic processes were downregulated apparently to reduce energy consumption, and a remarkable increase in inflammatory and stress responses was also highlighted. The proteomic data were verified by immunoblotting of 11 and 7 different soluble or membrane-associated proteins, either novel (VPS29 and MCTS1) or known factors in AP. Also, our first observation of the imbalance of some COP proteins during AP early phase deserves further characterization.

BIOLOGICAL SIGNIFICANCE

AP is one of the most important pathological inflammatory states of the exocrine pancreas but its pathophysiology remains incompletely understood, especially the early acinar events. Proteomic analysis of pancreatic subcellular fractions simplifies protein maps and helps in the identification of new protein alterations and biomarkers characterizing pancreatic tissue damage. Our shotgun approach has not been previously used to profile the early proteomic alterations of the disease, which are considered crucial for its development and for the founding of clinical procedures. Furthermore, our subcellular fractionation protocol allowed us to detect changes in membrane proteins so far overlooked in the proteomic study of AP. Accordingly, using TMT proteomics and bioinformatic tools, we were able to detect significant changes in protein expression related to many pathobiological pathways of acute pancreatitis as from the early phase of the disease. To our knowledge, some of these changes, such as the imbalance of some COP proteins, have never been described in this disease.

Pancreatic Protein Tyrosine Phosphatase 1B Deficiency Exacerbates Acute Pancreatitis in Mice

Acute pancreatitis (AP) is a common and devastating gastrointestinal disorder that causes significant morbidity. The disease starts as local inflammation in the pancreas that may progress to systemic inflammation and complications. Protein tyrosine phosphatase 1B (PTP1B) is implicated in inflammatory signaling, but its significance in AP remains unclear. To investigate whether PTP1B may have a role in AP, we used pancreas PTP1B knockout (panc-PTP1B KO) mice and determined the effects of pancreatic PTP1B deficiency on cerulein- and arginine-induced acute pancreatitis. We report that PTP1B protein expression was increased in the early phase of AP in mice and rats. In addition, histological analyses of pancreas samples revealed enhanced features of AP in cerulein-treated panc-PTP1B KO mice compared with controls. Moreover, cerulein- and arginine-induced serum amylase and lipase were significantly higher in panc-PTP1B KO mice compared with controls. Similarly, pancreatic mRNA and serum concentrations of the inflammatory cytokines IL-1B, IL-6, and tumor necrosis factor-α were increased in panc-PTP1B KO mice compared with controls. Furthermore, panc-PTP1B KO mice exhibited enhanced cerulein- and arginine-induced NF-κB inflammatory response accompanied with increased mitogen-activated protein kinases activation and elevated endoplasmic reticulum stress. Notably, these effects were recapitulated in acinar cells treated with a pharmacological inhibitor of PTP1B. These findings reveal a novel role for pancreatic PTP1B in cerulein- and arginine-induced acute pancreatitis.

Changes in the expression of LIMP-2 during cerulein-induced pancreatitis in rats: Effect of inhibition of leukocyte infiltration, cAMP and MAPKs early on in its development

Lysosomal integral membrane protein-2 (LIMP-2) is an important protein in lysosomal biogenesis and function and also plays a role in the tissue inflammatory response. It is known that lysosomes play a central role in acute pancreatitis, with inflammatory cell infiltration triggering the disease early on. In this study we report increases in pancreatic LIMP-2 protein and mRNA levels as early events that occur during the development of cerulein (Cer)-induced acute pancreatitis (AP) in rats. GdCl3, a macrophage inhibitor, but not FK506, a T lymphocyte inhibitor, was able to reverse the increase in LIMP-2 expression after Cer treatment, although such reversion was abolished if the animals were depleted of neutrophils due to a vinblastine sulfate pre-treatment. Immunostaining revealed that the cellular source of LIMP-2 was mainly acinar cells. Additionally, pre-treatments with the MAPKs inhibitors SP600125 and PD98059, inhibitors of JNK and ERK½ activation, respectively, but not of rolipram, a type IV phosphodiesterase inhibitor, suppressed the increase in the expression of LIMP-2 after Cer administration. Together, these results indicate that neutrophils are able to drive a macrophage activation that would regulate the increase in LIMP-2 expression during the early phase of Cer-induced AP, with the stress kinases JNK and ERK½ also playing a coordinated role in the increase of LIMP-2 expression due to Cer.

Effects of soluble epoxide hydrolase deficiency on acute pancreatitis in mice

Background

Acute pancreatitis (AP) is a frequent gastrointestinal disorder that causes significant morbidity, and its incidence has been progressively increasing. AP starts as a local inflammation in the pancreas that often leads to systemic inflammatory response and complications. Soluble epoxide hydrolase (sEH) is a cytosolic enzyme whose inhibition in murine models has beneficial effects in inflammatory diseases, but its significance in AP remains unexplored.

Methodology/Principal Findings

To investigate whether sEH may have a causal role in AP we utilized Ephx2 knockout (KO) mice to determine the effects of sEH deficiency on cerulein- and arginine-induced AP. sEH expression increased at the protein and messenger RNA levels, as well as enzymatic activity in the early phase of cerulein- and arginine-induced AP in mice. In addition, amylase and lipase levels were lower in cerulein-treated Ephx2 KO mice compared with controls. Moreover, pancreatic mRNA and serum concentrations of the inflammatory cytokines IL-1B and IL-6 were lower in cerulein-treated Ephx2 KO mice compared with controls. Further, Ephx2 KO mice exhibited decreased cerulein- and arginine-induced NF-κB inflammatory response, MAPKs activation and decreased cell death. Conclusions -These findings demonstrate a novel role for sEH in the progression of cerulein- and arginine-induced AP.

Pancreatic T cell protein-tyrosine phosphatase deficiency ameliorates cerulein-induced acute pancreatitis

Background

Acute pancreatitis (AP) is a common clinical problem whose incidence has been progressively increasing in recent years. Onset of the disease is trigged by intra-acinar cell activation of digestive enzyme zymogens that induce autodigestion, release of pro-inflammatory cytokines and acinar cell injury. T-cell protein tyrosine phosphatase (TCPTP) is implicated in inflammatory signaling but its significance in AP remains unclear.

Results

In this study we assessed the role of pancreatic TCPTP in cerulein-induced AP. TCPTP expression was increased at the protein and messenger RNA levels in the early phase of AP in mice and rats. To directly determine whether TCPTP may have a causal role in AP we generated mice with pancreatic TCPTP deletion (panc-TCPTP KO) by crossing TCPTP floxed mice with Pdx1-Cre transgenic mice. Amylase and lipase levels were lower in cerulein-treated panc-TCPTP KO mice compared with controls. In addition, pancreatic mRNA and serum concentrations of the inflammatory cytokines TNFα and IL-6 were lower in panc-TCPTP KO mice. At the molecular level, panc-TCPTP KO mice exhibited enhanced cerulein-induced STAT3 Tyr705 phosphorylation accompanied by a decreased cerulein-induced NF-κB inflammatory response, and decreased ER stress and cell death.

Conclusion

These findings revealed a novel role for pancreatic TCPTP in the progression of cerulein-induced AP.

Modulation in the expression of SHP-1, SHP-2 and PTP1B due to the inhibition of MAPKs, cAMP and neutrophils early on in the development of cerulein-induced acute pancreatitis in rats

The protein tyrosine phosphatases (PTPs) SHP-1, SHP-2 and PTP1B are overexpressed early on during the development of cerulein -induced acute pancreatitis (AP) in rats, and their levels can be modulated by some species of mitogen-activated protein kinases (MAPKs), the intracellular levels of cAMP and by general leukocyte infiltration, the latter at least for SHP-2 and PTP1B. In this study we show that cerulein treatment activates extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) but not p38 MAPK during the early phase of cerulein-induced AP (2h after the first injection of cerulein). Therefore, by using the MAPK inhibitors SP600125 (a specific JNK inhibitor) and PD98059 (a specific ERK inhibitor), we have unmasked the particular MAPK that underlies the modulation of the expression levels of these PTPs. JNK would act by preventing SHP-1 protein expression from increasing beyond a certain level. ERK 1/2 was the main MAPK involved in the increase in SHP-2 protein expression due to cerulein. JNK negatively modulated the SH2-domain containing PTPs. Both MAPKs played a role in the increase in PTP1B protein expression due to cerulein. Finally, by using the white blood cell inhibitors vinblastine sulfate, gadolinium chloride and FK506 (tacrolimus), we show that the macrophage activity or T-lymphocytes does not modulate the expression of any of the PTPs, although neutrophil infiltration was found to be a regulator of SHP-2 and PTP1B protein expression due to cerulein.

Proteomic analysis of the soluble and the lysosomal+mitochondrial fractions from rat pancreas: Implications for cerulein-induced acute pancreatitis

Alterations in protein expression within the initiation phase of acute pancreatitis (AP) might play an important role in the development of this disease, lysosomes being involved in its pathophysiology. The use of pancreatic subcellular fractions in proteomic analysis, simplifies protein maps and helps in the identification of new protein changes and biomarkers characterizing tissue damage. The present study aims to determine the differentially expressed acidic proteins in the pancreatic soluble and lysosomal+mitochondrial (L+M) fractions from rats during the early phase of the experimental model of cerulein (Cer)-induced AP. Subcellular pancreatic extracts from diseased and control rats were analyzed by 2-DE (3-5.6 pH range) and MALDI-TOF/TOF MS. Comparative analysis afforded the conclusive identification of 13 (soluble fraction) and 7 (L+M fraction) proteins or protein fragments occuring in different amounts between diseased and control pancreas, some of them being newly described in AP. In the soluble fraction, we detected changes related to inflammation and apoptosis (α1-inhibitor-3, α-1 antitrypsin, α-1 macroglobulin, haptoglobin, STRAP), oxidative stress and stress response (peroxiredoxin-2, thioredoxin-like 1, GRP94/TRA1, heat shock cognate 71kDa protein), digestive proteases (elastase 3B), serine protease inhibition (serpins B6 and A3L) and translation processes (EF 1-δ). In the L+M fraction, we detected changes mainly related to energy generation or cellular metabolism (ATP synthase β subunit, chymotrypsinogen B, triacylglycerol lipase), cell redox homeostasis (iodothyronine 5´monodeiodinase) and digestive proteases (carboxypeptidase B1). The data should provide valuable information for unraveling the early pathophysiologic mechanisms of Cer-induced AP.

Redox signaling and histone acetylation in acute pancreatitis

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

Potential role of NADPH oxidase-mediated activation of Jak2/Stat3 and mitogen-activated protein kinases and expression of TGF-β1 in the pathophysiology of acute pancreatitis

OBJECTIVE

NADPH oxidase is potentially associated with acute pancreatitis by producing reactive oxygen species (ROS). We investigated whether NADPH oxidase mediates the activation of Janus kinase (Jak)2/signal transducers and activators of transcription (Stat)3 and mitogen-activated protein kinases (MAPKs) to induce the expression of transforming growth factor-β1 (TGF-β1) in cerulein-stimulated pancreatic acinar cells.

TREATMENT

AR42J cells were treated with an NADPH oxidase inhibitor diphenyleneiodonium (DPI) or a Jak2 inhibitor AG490. Other cells were transfected with antisense or sense oligonucleotides (AS or S ODNs) for NADPH oxidase subunit p22(phox) or p47(phox).

METHODS

TGF-β1 was determined by enzyme-linked immonosorbent assay. STAT3-DNA binding activity was measured by electrophoretic mobility shift assay. Levels of MAPKs as well as total and phospho-specific forms of Jak1/Stat3 were assessed by Western blot analysis.

RESULTS

Cerulein induced increases in TGF-β1, Stat3-DNA binding activity and the activation of MAPKs in AR42J cells. AG490 suppressed these cerulein-induced changes, similar to inhibition by DPI. Cerulein-induced activation of Jak2/Stat3 and increases in MAPKs and TGF-β1 levels were inhibited in the cells transfected with AS ODN for p22(phox) and p47(phox) compared to S ODN controls.

CONCLUSION

Inhibition of NADPH oxidase may be beneficial for prevention and treatment of pancreatitis by suppressing Jak2/Stat3 and MAPKs and expression of TGF-β1 in pancreatic acinar cells.

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.

Rolipram and SP600125 suppress the early increase in PTP1B expression during cerulein-induced pancreatitis in rats

OBJECTIVES

To analyze the expression modulation of pancreatic protein tyrosine phosphatase (PTP)1B during the development of cerulein (Cer)-induced acute pancreatitis (AP) and the effect of inhibition of type 4 phosphodiesterase and c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2 on its expression levels.

METHODS

Acute pancreatitis was induced in rats by subcutaneous injections of 20 microg Cer per kilogram body weight at hourly intervals, and the animals were killed at 2, 4, or 9 hours after the first injection. Neutropenia was induced with vinblastine sulfate. Phosphodiesterase and the mitogen-activated protein kinases were inhibited with rolipram and SP600125, respectively, before the induction of AP.

RESULTS

Protein tyrosine phosphatase 1B increases its expression at the levels of both protein and messenger RNA during the early phase of Cer-induced AP. The increase in protein expression persisted along the development of the disease, and neutrophil infiltration seemed to play a central role. Rolipram and SP600125 pretreatments mostly suppressed the increase in the expression of PTP1B during the early phase of AP.

CONCLUSIONS

Cerulein-induced AP is associated with an increase in the expression of PTP1B in its early phase. An increase in cyclic adenosine monophosphate levels in inflammatory cells and the inhibition of c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2 are able to suppress the increase in PTP1B protein level.

Inflammatory role of the acinar cells during acute pancreatitis

Pancreatic acinar cells are secretory cells whose main function is to synthesize, store and finally release digestive enzymes into the duodenum. However, in response to noxious stimuli, acinar cells behave like real inflammatory cells because of their ability to activate signalling transduction pathways involved in the expression of inflammatory mediators. Mediated by the kinase cascade, activation of Nuclear factor-κB, Activating factor-1 and Signal transducers and activators of transcription transcription factors has been demonstrated in acinar cells, resulting in overexpression of inflammatory genes. In turn, kinase activity is down-regulated by protein phosphatases and the final balance between kinase and phosphatase activity will determine the capability of the acinar cells to produce inflammatory factors. The kinase/phosphatase pair is a redox-sensitive system in which kinase activation overwhelms phosphatase activity under oxidant conditions. Thus, the oxidative stress developed within acinar cells at early stages of acute pancreatitis triggers the activation of signalling pathways involved in the up-regulation of cytokines, chemokines and adhesion molecules. In this way, acinar cells trigger the release of the first inflammatory signals which can mediate the activation and recruitment of circulating inflammatory cells into the injured pancreas. Accordingly, the role of acinar cells as promoters of the inflammatory response in acute pancreatitis may be considered. This concept leads to amplifying the focus from leukocyte to acinar cells themselves, to explain the local inflammation in early pancreatitis.