Autoimmune pancreatic disease: preparation of pancreatic juice for proteome analysis

Pancreas 2000. My journey with the central organ

The European Pancreatic Club Lifetime Achievement Award is a distinction awarded for research on the pancreas and service to European Pancreatology. It comes with the obligation to submit a review article to our society's journal, Pancreatology. It was awarded to me 2023 and I take this opportunity to highlight my journey with the central organ AKA the pancreas, that is inseparatable from "Pancreas 2000" - an educational program for future pancreatologists, inaugurated by Karolinska Institutet.

The heparin-binding proteome in normal pancreas and murine experimental acute pancreatitis

Acute pancreatitis (AP) is acute inflammation of the pancreas, mainly caused by gallstones and alcohol, driven by changes in communication between cells. Heparin-binding proteins (HBPs) play a central role in health and diseases. Therefore, we used heparin affinity proteomics to identify extracellular HBPs in pancreas and plasma of normal mice and in a caerulein mouse model of AP. Many new extracellular HBPs (360) were discovered in the pancreas, taking the total number of HBPs known to 786. Extracellular pancreas HBPs form highly interconnected protein-protein interaction networks in both normal pancreas (NP) and AP. Thus, HBPs represent an important set of extracellular proteins with significant regulatory potential in the pancreas. HBPs in NP are associated with biological functions such as molecular transport and cellular movement that underlie pancreatic homeostasis. However, in AP HBPs are associated with additional inflammatory processes such as acute phase response signalling, complement activation and mitochondrial dysfunction, which has a central role in the development of AP. Plasma HBPs in AP included known AP biomarkers such as serum amyloid A, as well as emerging targets such as histone H2A. Other HBPs such as alpha 2-HS glycoprotein (AHSG) and histidine-rich glycoprotein (HRG) need further investigation for potential applications in the management of AP. Pancreas HBPs are extracellular and so easily accessible and are potential drug targets in AP, whereas plasma HBPs represent potential biomarkers for AP. Thus, their identification paves the way to determine which HBPs may have potential applications in the management of AP.

Mass spectrometry-based proteomics of endoscopically collected pancreatic fluid in chronic pancreatitis research

MS-based investigation of pancreatic fluid enables the high-throughput identification of proteins present in the pancreatic secretome. Pancreatic fluid is a complex admixture of digestive, inflammatory, and other proteins secreted by the pancreas into the duodenum, and thus is amenable to MS-based proteomic analysis. Recent advances in endoscopic techniques, in particular the endoscopic pancreatic function test (ePFT), have improved the collection methodology of pancreatic fluid for proteomic analysis. Here, we provide an overview of MS-based proteomic techniques as applied to the study of pancreatic fluid. We address sample collection, protein extraction, MS sample preparation and analysis, and bioinformatic approaches, and summarize current MS-based investigations of pancreatic fluid. We then examine the limitations and the future potential of such technologies in the investigation of pancreatic disease. We conclude that pancreatic fluid represents a rich reservoir of potential biomarkers and that the study of the molecular mechanisms of chronic pancreatitis may benefit substantially from MS-based proteomics.

Optimized sample preparation of endoscopic collected pancreatic fluid for SDS-PAGE analysis

The standardization of methods for human body fluid protein isolation is a critical initial step for proteomic analyses aimed to discover clinically relevant biomarkers. Several caveats have hindered pancreatic fluid proteomics, including the heterogeneity of samples and protein degradation. We aim to optimize sample handling of pancreatic fluid that has been collected using a safe and effective endoscopic collection method (endoscopic pancreatic function test). Using SDS-PAGE protein profiling, we investigate (i) precipitation techniques to maximize protein extraction, (ii) auto-digestion of pancreatic fluid following prolonged exposure to a range of temperatures, (iii) effects of multiple freeze-thaw cycles on protein stability, and (iv) the utility of protease inhibitors. Our experiments revealed that TCA precipitation resulted in the most efficient extraction of protein from pancreatic fluid of the eight methods we investigated. In addition, our data reveal that although auto-digestion of proteins is prevalent at 23 and 37 degrees C, incubation on ice significantly slows such degradation. Similarly, when the sample is maintained on ice, proteolysis is minimal during multiple freeze-thaw cycles. We have also determined the addition of protease inhibitors to be assay-dependent. Our optimized sample preparation strategy can be applied to future proteomic analyses of pancreatic fluid.

Autoantibodies against the exocrine pancreas in autoimmune pancreatitis: gene and protein expression profiling and immunoassays identify pancreatic enzymes as a major target of the inflammatory process

OBJECTIVES

Autoimmune pancreatitis (AIP) is thought to be an immune-mediated inflammatory process, directed against the epithelial components of the pancreas. The objective was to identify novel markers of disease and to unravel the pathogenesis of AIP.

METHODS

To explore key targets of the inflammatory process, we analyzed the expression of proteins at the RNA and protein level using genomics and proteomics, immunohistochemistry, western blot, and immunoassay. An animal model of AIP with LP-BM5 murine leukemia virus-infected mice was studied in parallel. RNA microarrays of pancreatic tissue from 12 patients with AIP were compared with those of 8 patients with non-AIP chronic pancreatitis.

RESULTS

Expression profiling showed 272 upregulated genes, including those encoding for immunoglobulins, chemokines and their receptors, and 86 downregulated genes, including those for pancreatic proteases such as three trypsinogen isoforms. Protein profiling showed that the expression of trypsinogens and other pancreatic enzymes was greatly reduced. Immunohistochemistry showed a near-loss of trypsin-positive acinar cells, which was also confirmed by western blotting. The serum of AIP patients contained high titers of autoantibodies against the trypsinogens PRSS1 and PRSS2 but not against PRSS3. In addition, there were autoantibodies against the trypsin inhibitor PSTI (the product of the SPINK1 gene). In the pancreas of AIP animals, we found similar protein patterns and a reduction in trypsinogen.

CONCLUSIONS

These data indicate that the immune-mediated process characterizing AIP involves pancreatic acinar cells and their secretory enzymes such as trypsin isoforms. Demonstration of trypsinogen autoantibodies may be helpful for the diagnosis of AIP.

[Proteome analysis--basis for individualized pancreatic carcinoma therapy?]

Ductal pancreatic adenocarcinoma is a dismal disease, having the worst prognosis of all solid tumors. While genomics and transcriptomics have provided a wealth of data, no contribution has been made to clinical medicine in terms of diagnostic or prognostic markers. Hope lies in yet another novel technology, proteomics. Conceptually, proteomics bears the advantage of incorporating both posttranslational modifications as well as host factors. This is thought to be important in factors influencing survival such as chemoresistance. This tutorial review discusses the state of the art in pancreatic cancer proteomics in light of technical developments. At this moment, proteomics is still at the beginning in clinical application. First results, however, suggest some hope for the development of a new understanding of the molecular biology in pancreatic cancer yielding into very specific markers of disease or allowing a rational and individualized therapy.

Comparative proteomic analysis of human pancreatic juice: methodological study

Pancreatic cancer is the most lethal of all the common malignancies. Markers for early detection of this disease are urgently needed. Here, we optimized and applied a proteome analysis of human pancreatic juice to identify biomarkers for pancreatic cancer. Pancreatic juice samples, devoid of blood or bile contamination, were collected from patients with pancreatic cancer (n = 5), benign pancreatic diseases (n = 6), or cholelithiasis (n = 3) during endoscopic retrograde cholangiopancreatography (ERCP). After ultramembrane centrifugation sample preparation, pancreatic juice proteins were separated by 2-DE and identified by MALDI-TOF-MS. A 2-DE dataset of pancreatic juice from patients with cholelithiasis was established, consisting of 76 protein spots representing 22 different proteins. Disease-associated obstruction of the pancreatic duct strongly effected the protein composition of pancreatic juice. Concurrently, pancreatic juice from patients with pancreatic cancer was compared to nonmalignant controls with comparable obstruction of pancreatic ducts. Seven protein spots were identified that consistently appeared at changed levels in pancreatic juice from patients with pancreatic cancer. In conclusion, comparative proteomic analysis of human pancreatic juice can be used to identify biomarkers of pancreatic cancer.

What are the useful biological and functional markers of early-stage chronic pancreatitis?

Early-stage chronic pancreatitis may be undetected as a clinical entity. However, it may carry a definite risk for subsequent secondary damage, depending on the etiology of the disease. Therefore, the most important question is whether indeed the patient in question does have early-stage chronic pancreatitis rather than oligosymptomatic advanced-stage chronic pancreatitis. This can be easily determined by appropriate imaging such as abdominal computed tomography. For early changes, endoscopic ultrasound is superior to any other technique. Endosonography may also tell about anatomical obstacles (e.g., papillary stenosis, pancreas divisum) that may be treated to prevent progression of the disease. Treatment options at this stage are endoscopic for the most part. Depending on the etiology and familiar/hereditary background of the given patient, one must look further into molecular markers. Such markers may give an estimate on the progression or dynamics of the disease in the future and include mutations in the cationic (PRSS1) and anionic (PRSS2) trypsinogen genes as well as mutations in the serine protease (SPINK1) or cystic fibrosis (CFTR) genes. Admitted ly, these are not markers of early-stage chronic pancreatitis but must be investigated if and when such pathogenesis is suspected. Further, rare forms of chronic pancreatitis, such as autoimmune pancreatitis, which can be cured by appropriate medical treatment with steroids, must be excluded. Markers for autoimmune pancreatitis are elevated serum IgG, especially IgG4, and autoantibodies to carbonic anhydrase (type II) and lactoferrin. It is noteworthy that these markers, present in almost every Asian patient with autoimmune pancreatitis, are mostly lacking in Caucasian populations of patients with autoimmune pancreatitis.

[Autoimmune pancreatitis--a surgical disease?]

The term autoimmune pancreatitis (AIP) describes a nonalcoholic, chronic lymphoplasmocytic pancreatitis. The lymphoplasmocytic infiltration is characterized by periductal localization of predominantly CD4-positive T cells, fibrosis, and acinar atrophy, frequently resulting in stenosis of the main pancreatic and distal common bile ducts. Imaging studies often reveal a diffuse narrowing of the pancreatic main duct and swelling of the pancreatic head wrongly suggesting the presence of a malignant tumor. Clinical signs include mild abdominal pain, jaundice, recurrent episodes of acute pancreatitis, and even new-onset diabetes mellitus. Additionally, AIP can be associated with other autoimmune diseases such as Sjögren's syndrome, primary sclerosing cholangitis, chronic inflammatory bowel diseases, and retroperitoneal fibrosis. Serological markers include autoantibodies and increased levels of gamma globulin and especially IgG4. Steroids seem to be effective in improving clinical symptoms as well as in the resolution of pancreatic and bile duct narrowing. This distinguishes AIP from other forms of pancreatitis and from pancreatic neoplasms. Further studies of the underlying pathophysiologic mechanisms, prognosis, and new diagnostic tools are needed to provide adequate and effective treatment in the future. In this article, we summarize the current knowledge about AIP and present 17 cases that underwent surgical resection at our institution from 2003 to 2004.

Proteomic technologies and their application to pancreatic cancer

Pancreatic ductal adenocarcinoma is a devastating disease that represents an important health problem. It spreads rapidly at a time when patients have relatively few symptoms and consequently is often only detected at an advanced stage when treatment options are limited. Rapid developments in technology and bioinformatics have recently led to a surge in proteomics-based cancer research. Comparative analysis of protein profiles from nonmalignant and malignant pancreas cells or tissue, or from different stages of pancreatic cancer, potentially offer unique insight into the biology of this tumor type. Furthermore, proteomic approaches may provide novel diagnostic or therapeutic markers for this disease. Although such analyses are still in their infancy, they show great potential in the ongoing battle against this dismal disease.

Proteome analysis of isolated myenteric plexus reveals significant changes in protein expression during postnatal development

The enteric nervous system in vertebrates is the most complex part of the peripheral nervous system. Concerning chemical coding, ultrastructure and neuronal circuits, it is more similar to the central than to the peripheral nervous system. Its networks, the myenteric and submucous plexus are integrated in the gut wall. The enteric nervous system is a system of high plasticity, which not only changes during pre- and postnatal development, but also with disease or changing dietary habits. The Aim of this study was to elucidate changes in protein expression during the first two postnatal weeks in the rat myenteric plexus. Colonic and duodenal myenteric plexus from newborn (P1) and fourteen-day old (P14) Sprague-Dawley rats was isolated following a procedure that combines enzymatic digestion and mechanical agitation. The neuronal tissue was collected and processed for two-dimensional gel electrophoresis (2-DE). The obtained 2-D gels were stained with silver for image analysis or with colloidal Coomassie for subsequent protein identification. Gels from the various samples showed a high degree of consistence concerning protein-spots found in all preparations. Nevertheless, there was a number of proteins that were clearly detected in one sample but not, or only in significantly smaller amounts in the other. Several differentially expressed proteins in the postnatal myenteric plexus were identified with MALDI-TOF mass spectrometry. Especially stathmin, polyubiquitin and heterogeneous nuclear ribonucleoprotein seem to play an important role in pre- and postnatal development. 2-DE combined with mass spectrometry can help to identify pathological relevant proteins in the enteric nervous system, and so deliver a valuable tool for the early diagnosis of also central nervous system diseases by using biopsies from the gut.

Proteomic profiling of pancreatic cancer for biomarker discovery

Pancreatic cancer is a uniformly lethal disease that is difficult to diagnose at early stage and even more difficult to cure. In recent years, there has been a substantial interest in applying proteomics technologies to identify protein biomarkers for early detection of cancer. Quantitative proteomic profiling of body fluids, tissues, or other biological samples to identify differentially expressed proteins represents a very promising approach for improving the outcome of this disease. Proteins associated with pancreatic cancer identified through proteomic profiling technologies could be useful as biomarkers for the early diagnosis, therapeutic targets, and disease response markers. In this article, we discuss recent progress and challenges for applying quantitative proteomics technologies for biomarker discovery in pancreatic cancer.

Proteomics in pancreatic disease

Proteomics represents a novel methodological approach to investigate the expression of all proteins by a cell or organism in its entireness, similar to global strategies for DNA (genomics) and RNA (transcriptomics). This review focuses on the history of protein analysis, which made up the golden age of pancreatic physiology, the current methodology for proteomics (2D gel electrophoresis, mass spectrometry) and the few published experiences with proteomics in the field of pancreatology until now. Finally, potential applications of proteomics for the pancreas, in concert with other techniques, are cited.

Protein and antibody microarray technology

Following the age of genomics having sequenced the human genome, interest is shifted towards the function of genes. This new age of proteomics brings about a change of methods to study the properties of gene products on a large scale. Protein separation technologies are now applied to allow high-throughput purification and characterisation of proteins. Two-dimensional-gel electrophoresis (2DE) and mass spectrometry (MS) have become widely used tools in the field of proteomics. At the same time, protein and antibody microarrays have been developed as successor of DNA microarrays to soon allow the proteome-wide screening of protein function in parallel. This review is aimed to introduce this new technology and to highlight its current prospects and limitations.

Autoimmune pancreatitis: pathological, clinical, and immunological features

INTRODUCTION

In recent years a type of chronic pancreatitis has been described that is clearly distinct from alcoholic chronic pancreatitis. It is characterized by its special pathology, immunologic features, clinical presentation, and steroid responsiveness. Because of its histologic hallmarks, i.e., ductal and periductal infiltration by lymphocytes, plasma cells, and granulocytes, it has been called duct-destructive chronic pancreatitis. The frequent association of this type of pancreatitis with other autoimmune diseases such as Sjögren's disease and a number of other immune phenomena has led to the concept that it is an autoimmune disease. Hence, the term autoimmune pancreatitis has been introduced and will be used in this review.

AIMS

This review focuses on the pathology and related clinical and immunologic features of this new type of pancreatitis.

CONCLUSIONS

As the ability to diagnose autoimmune pancreatitis on the basis of clinical, imaging, and laboratory findings improves, it seems likely that fewer patients with this diagnosis will undergo resection. Thus, there is a need to accumulate and study additional retrospective series of patients undergoing resection because of mass-forming chronic pancreatitis.