Isolation, characterization, and distribution of an unusual pancreatic human secretory protein

Role of regenerating islet-derived proteins in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an inflammatory disorder of the gastrointestinal tract that affects millions of patients worldwide. It has a complex and multifactorial etiology leading to excessive exposure of intestinal epithelium to microbial antigens, inappropriate activation of the immune system and ultimately to the damage of intestinal tissues. Although numerous efforts have been made to improve the disease management, IBD remains persistently recurring and beyond cure. This is due largely to the gaps in our understanding of the pathogenesis of IBD that hamper the development of timely diagnoses and effective treatment. However, some recent discoveries, including the beneficial effects of interleukin-22 (IL-22) on the inflamed intestine, have shed light on a self-protective mechanism in IBD. Regenerating islet-derived (REG/Reg) proteins are small secretory proteins which function as IL-22's downstream effectors. Mounting studies have demonstrated that IBD patients have significantly increased REG expressions in the injured intestine, but with undefined mechanisms and roles. The reported functions of REG/Reg proteins in intestinal homeostasis, such as those of antibacterial, anti-inflammatory and tissue repair, lead us to discuss their potential mechanisms and clinical relevance in IBD in order to advance IBD research and management.

Four Decades After the Discovery of Regenerating Islet-Derived (Reg) Proteins: Current Understanding and Challenges

Regenerating islet-derived (Reg) proteins have emerged as multifunctional agents with pro-proliferative, anti-apoptotic, differentiation-inducing and bactericidal properties. Over the last 40 years since first discovered, Reg proteins have been implicated in a gamut of maladies including diabetes, various types of cancer of the digestive tract, and Alzheimer disease. Surprisingly though, a consensus is still absent on the regulation of their expression, and molecular underpinning of their function. Here, we provide a critical appraisal of recent findings in the field of Reg protein biology. Specifically, the structural characteristics are reviewed particularly in connection with established or purported functions of different members of the Reg family. Moreover, Reg expression patterns in different tissues both under normal and pathophysiological conditions are summarized. Putative receptors and cascades reported to relay Reg signaling inciting cellular responses are presented aiming at a better appreciation of the biological activities of the distinct Reg moieties. Challenges are also discussed that have hampered thus far the rapid progress in this field such as the use of non-standard nomenclature for Reg molecules among various research groups, the existence of multiple Reg members with significant degree of homology and possibly compensatory modes of action, and the need for common assays with robust readouts of Reg activity. Coordinated research is warranted going forward, given that several research groups have independently linked Reg proteins to diseased states and raised the possibility that these biomolecules can serve as therapeutic targets and biomarkers.

Regenerating islet-derived protein 1 inhibits the activation of islet stellate cells isolated from diabetic mice

Emerging evidence indicates that the islet fibrosis is attributable to activation of islet stellate cells (ISCs). In the present study, we compared the differences in biological activity of ISCs isolated from diabetic db/db and non-diabetic db/m mice, and the effects of the regenerating islet-derived protein 1 (Reg1) on ISC function. We showed that ISCs isolated from db/db mice were activated more rapidly than those from db/m mice during culture. Both Reg1 and its putative receptor exostosin-like glycosyltransferase 3 (EXTL3) were highly expressed by diabetic ISCs. Treatment with Reg1 inhibited migration, viability, and synthesis and secretion of Type I Collagen(Col-I), Type III Collagen(Col-III) and Fibronectin(FN) by diabetic ISCs, and this was associated with deactivation of the PI3K/Akt, MAPK/Erk1/2 signaling pathway in an EXTL3-dependent manner. In conclusion, our observations (i) confirmed the presence of fibrogenic stellate cells within pancreatic islets, which are prone to be activated in Type 2 diabetes, and (ii) revealed a potential role for Reg1 in preventing ISC activation.

Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Low birth weight and poor foetal growth following low protein (LP) exposure are associated with altered islet development and glucose intolerance in adulthood. Additionally, LP-fed offspring fail to regenerate their β-cells following depletion with streptozotocin (STZ) in contrast to control-fed offspring that restore β-cell mass. Our objective was to identify signalling pathways and cellular functions that may be critically altered in LP offspring rendering them susceptible to developing long-term glucose intolerance and decreased β-cell plasticity. Pregnant Balb/c mice were fed a control (C; 20% protein) or an isocaloric LP (8% protein) diet throughout gestation and C diet thereafter. Female offspring were injected intraperitoneally with 35 mg/kg STZ or vehicle on days 1 to 5 for each dietary treatment. At 30 days of age, total RNA was extracted from pancreatic tissue for microarray analysis using the Affymetrix GeneChip Mouse Genome 430 2.0. Gene and protein expression were quantified from isolated islets. Finally, β-cell proliferation was determined in vitro following REG1α treatment. The microarray data and GO enrichment analysis indicated that foetal protein restriction alters the early expression of genes necessary for many cell functions, such as oxidative phosphorylation and free radical scavenging. Expression of Reg1 was upregulated following STZ, whereas protein content was decreased in LP + STZ islets. Furthermore, REG1α failed to stimulate β-cell proliferation in vitro in LP + STZ islets. Therefore, early nutritional insults may programme the Reg1 pathway resulting in a limited ability to increase β-cell mass during metabolic stress. In conclusion, this study implicates the Reg1 pathway in β-cell regeneration and describes altered programming of gene expression in LP offspring, which underlies later development of cell dysfunction and glucose intolerance in adulthood.

Regenerating proteins and their expression, regulation and signaling

The regenerating (Reg) protein family comprises C-type lectin-like proteins discovered independently during pancreatitis and pancreatic islet regeneration. However, an increasing number of studies provide evidence of participation of Reg proteins in the proliferation and differentiation of diverse cell types. Moreover, Reg family members are associated with various pathologies, including diabetes and forms of gastrointestinal cancer. These findings have led to the emergence of key roles for Reg proteins as anti-inflammatory, antiapoptotic and mitogenic agents in multiple physiologic and disease contexts. Yet, there are significant gaps in our knowledge regarding the regulation of expression of different Reg genes. In addition, the pathways relaying Reg-triggered signals, their targets and potential cross-talk with other cascades are still largely unknown. In this review, the expression patterns of different Reg members in the pancreas and extrapancreatic tissues are described. Moreover, factors known to modulate Reg levels in different cell types are discussed. Several signaling pathways, which have been implicated in conferring the effects of Reg ligands to date, are also delineated. Further efforts are necessary for elucidating the biological processes underlying the action of Reg proteins and their involvement in various maladies. Better understanding of the function of Reg genes and proteins will be beneficial in the design and development of therapies utilizing or targeting this protein group.

Pancreatic stone protein/regenerating protein family in pancreatic and gastrointestinal diseases

Pancreatic stone protein (PSP; reported in 1979), pancreatitis-associated protein (PAP; 1984) and regenerating protein (Reg I; 1988) were discovered independently in the fields of the exocrine (pancreatitis) and endocrine (diabetes) pancreas. Subsequent analysis revealed that PSP and Reg I are identical and PAP belongs to the same protein family. PSP/Reg I and PAP share a selective and specific trypsin cleavage site and result in insoluble fibrils (PTP, PATP). Search for a functional role of PSP had led to the idea that it might serve as an inhibitor in pancreatic stone formation and PSP was renamed lithostathine. Inhibitory effects of lithostathine in stone formation have been questioned. Evidence so far obtained can support a lithogenic role rather than a lithostatic role of PSP. PAP and its isoforms have been investigated mainly regarding responses to inflammation and stress. Reg I and its isoforms have been examined on regeneration, growth and mitogenesis in gastrointestinal neoplastic diseases as well as diabetes. Evidence obtained can be applied in the prediction of prognosis and therapy for inflammatory and neoplastic diseases.

An Immunohistochemical Study of Osteopontin in Pigment Gallstone Formation

Mucin glycoproteins from the gallbladder epithelium are thought to contribute to the matrix or nucleus of gallstones and other biomineralization systems. The involved acidic glycoproteins have been reported in bile and gallstones. In addition, osteopontin (Opn) is a noncollagenous acidic bone matrix glycoprotein that possesses calcium-binding properties. To investigate the role of Opn in pigment gallstone formation, the involvement of Opn in pigment gallstone formation was studied immunohistochemically in the gallbladder wall and in the stones. Staining for Opn was strongly positive in the epithelium of stone-laden gallbladders and in their stones. The stone-laden gallbladders were infiltrated by macrophages, which intensely stained for Opn. Sections of the pigment stones, under low magnification, showed a lamellar pattern of Opn immunolabeling and showed a reticular pattern under high magnification. Our results indicate that Opn, an acidic glycoprotein from the gallbladder epithelium, seems to be involved in lithiasis. Opn from macrophages and/or the epithelium seems to help form the matrix protein.

Administration of anti-Reg I and anti-PAPII antibodies worsens pancreatitis

CONTEXT

The regeneration protein family (Reg), which includes Reg I and PAPII, is expressed in pancreas acinar cells, and increases in acute pancreatitis. We have demonstrated that Reg gene knockdown worsens severity of acute pancreatitis in the rat and hypothesize that the proteins offer a protective effect in this disease.

OBJECTIVE

We investigated the ability of anti-Reg and anti-PAP antibody to neutralize pancreatic Reg protein and affect pancreatitis severity.

INTERVENTION

Pancreatitis was induced in rats by retrograde ductal injection of 4% sodium taurocholate.

ANIMALS

Eighty-four rats: 48 with induced pancreatitis, 30 sham operated, and 6 normal animals.

SETTING

Intraductal anti-Reg I and/or anti-PAPII antibody was administered at induced pancreatitis and sham operated subgroups of 6 rats each.

MAIN OUTCOME MEASURE

Serum and pancreata were harvested 24 and/or 48 hours later and assessed for pancreatitis severity by pancreatic wet weight, serum C-reactive protein (CRP), amylase, PAPII levels, and histopathology.

RESULTS

Animals induced with pancreatitis with administration of anti-Reg/PAP antibodies had significantly higher wet weights compared with taurocholate and histopathological analysis revealed that anti-Reg/PAP treated animals had worse tissue inflammation and necrosis compared with controls. Serum CRP, amylase, and Reg levels did not significantly differ between experimental and sham control groups.

CONCLUSIONS

Administration of anti-Reg/PAP antibody worsened taurocholate-induced organ specific pancreatitis. These data suggest that the Reg family of proteins is protective in acute pancreatitis.

Practical utility of urinary assay in the diagnosis of Alzheimer's disease: AlzheimAlert

Urinary assay (Alzheimer's disease reaction titer [ADRT]) adds significant information in the diagnosis of Alzheimer's disease (AD), particularly for the nonspecialist. Clinical studies of ADRT in series of AD and non-AD patients have found sensitivity of 89-92.3%, specificity of 90-96.8%, positive predictive value (PPV) of 94.8-97.4% and negative predictive value (NPV) of 78.9-91.8%. The added information from the improvements of PPV and NPV are particularly helpful for the nonspecialist in the community. As a laboratory assay that requires a first-morning noncontaminated sample, ADRT is noninvasive, convenient and safe. ADRT is based on reagents derived from human AD brain cDNA. The pathophysiological roles of these genetic fragments and reagents are still under investigation. ADRT should have a positive impact on primary-care AD clinical practice.

Helicobacter and gastrin stimulate Reg1 expression in gastric epithelial cells through distinct promoter elements

The gastric pathogen Helicobacter pylori accelerates the progression to gastric cancer but the precise mechanisms that mediate carcinogenesis remain unidentified. We now describe how Helicobacter and gastrin stimulate the expression of a putative growth factor, Reg1, in primary gastric epithelial cells. RT-PCR and Western immunoblotting of human gastric corpus and antrum showed significantly increased Reg1alpha in H. pylori-infected patients. Similarly, Reg1 was increased in the stomachs of H. felis-infected INS-GAS mice. To study transcriptional regulation of the Reg1 gene, we transfected primary mouse gastric glands with -2111 bp and -104 bp Reg1 promoter-luciferase reporter constructs. Expression of both constructs was detected in pepsinogen- and VMAT-2-expressing cells, which corresponds to the normal pattern of expression of human and mouse endogenous Reg1. The expression of both constructs was increased in response to gastrin and H. pylori, and there were potentiating interactions between them; in contrast, only the -2111 bp construct responded to H. felis. Mutation of a C-rich putative regulatory element within the -104 bp sequence abolished the response to gastrin but not to H. pylori whereas mutation of the proximal -98 to -93 region of the promoter reduced the response to H. pylori but not to gastrin. Stimulation of Reg1 by H. pylori required the virulence factor CagA. These data indicate that expression of the putative growth factor Reg1 is controlled through separate promoter elements by gastrin and Helicobacter.

The role of Islet Neogenesis-Associated Protein (INGAP) in islet neogenesis

Islet Neogenesis-Associated Protein (INGAP) is a member of the Reg family of proteins implicated in various settings of endogenous pancreatic regeneration. The expression of INGAP and other RegIII proteins has also been linked temporally and spatially with the induction of islet neogenesis in animal models of disease and regeneration. Furthermore, administration of a peptide fragment of INGAP (INGAP peptide) has been demonstrated to reverse chemically induced diabetes as well as improve glycemic control and survival in an animal model of type 1 diabetes. Cultured human pancreatic tissue has also been shown to be responsive to INGAP peptide, producing islet-like structures with function, architecture and gene expression matching that of freshly isolated islets. Likewise, studies in normoglycemic animals show evidence of islet neogenesis. Finally, recent clinical studies suggest an effect of INGAP peptide to improve insulin production in type 1 diabetes and glycemic control in type 2 diabetes.

Prospects and challenges for islet regeneration as a treatment for diabetes: a review of islet neogenesis associated protein

Diabetes mellitus results from inadequate insulin action, which can be viewed as a consequence of the limited ability to restore beta cells after they are lost as the result of metabolic exhaustion, autoimmune destruction, or surgical insult. Arguably, a uniformly effective therapeutic pathway to address all forms of diabetes would be to reverse the restrictions on beta-cell and islet regeneration. The development from progenitor cells of islets with normal endocrine function does occur in adult humans; it is referred to as islet neogenesis. The induction of islet neogenesis is an important, if not essential, therapeutic approach for curing type 1 diabetes mellitus (T1DM) and could be valuable in the treatment of type 2 diabetes mellitus (T2DM) as well. Islet neogenesis associated protein (INGAP) is the first therapeutic candidate to be identified as the result of a purposeful search for an endogenous molecule with islet neogenic activity. It was found that partial obstruction of the pancreatic duct in hamsters induced islet neogenesis; under this condition, a neogenesis-promoting activity was identified and partially purified from a soluble tissue fraction. A 168-kDa protein product of the cloned gene was found to be responsible for the neogenesis activity. This molecule named INGAP contains an active core sequence of amino acids called INGAP peptide. Results from in vitro, animal, and human studies suggest that INGAP and INGAP peptide are neogenic in at least several vertebrate species, including humans. INGAP has since been found to be a member of the family of Reg proteins, which are found across and in multiple versions within species and are closely associated with embryonic and regenerative processes. Clinical results suggest that INGAP peptide can be a suitable neogenesis therapy, but optimization of the therapy and more data are required to fully access this potential. Understanding of the signaling pathways of INGAP and other related Reg proteins is a promising means of advancing therapeutic development for people with T1DM and T2DM. The quest for the fundamental restorative approach to lost insulin secretion is an enticing target for drug development.

Is genetic analysis helpful for diagnosing chronic pancreatitis in its early stage?

Diagnosis of chronic pancreatitis in its early stage is an extremely difficult task. If the genetic predispositions are identified, it may help make possible the earlier diagnosis of chronic pancreatitis or the detection of patients at risk. There are two major hypotheses about the pathogenesis of chronic pancreatitis known as the "necrosis-fibrosis" and "pancreatic stone protein" hypotheses. Recent molecular and genetic evidence suggests that both pathways contribute to the pathogenesis of chronic pancreatitis. Chronic pancreatitis may be caused by either increased proteolytic activity [the cationic trypsinogen (PRSS1) gene] or decreased protease inhibition (the pancreatic secretory trypsin inhibitor (PSTI) gene]. The impaired pancreatic duct function [cystic fibrosis transmembrane conductance regulator (CFTR) gene] may also be involved in the pathogenesis of the disease. Except for PRSS1 mutations, the known genetic risk for chronic pancreatitis is not high. The high individual variability and low incidence of chronic pancreatitis suggest that yet unidentified genetic and environmental factors are important. Further genetic analysis is necessary for understanding the pathogenesis of chronic pancreatitis, which may be helpful for the earlier diagnosis of the juvenile- or young-onset disease.

Exocrine Meets Endocrine: Pancreatic Stone Protein and Regenerating Protein—Two Sides of the Same Coin

BACKGROUND

Regenerating protein (reg) and pancreatic stone protein (PSP) have been discovered independently in the fields of diabetes and pancreatitis.

MATERIALS AND METHODS

These proteins are identical; however, because of the gap between the endocrine and exocrine field, there was never a consensus and the nomenclature has not been rectified. Since the time of the initial discovery, more isoforms have been unified. Historically, PSP was discovered long before reg, yet, in many areas outside of the pancreatitis research field, reg is being used.

RESULTS

For PSP/reg, a role in proliferation and regeneration of islet cells has been postulated. A hitherto insufficiently understood phenomenon is the massive up-regulation of PSP/reg in pancreatic tissue and juice under conditions of stress. Similarly, PAP (pancreatitis-associated protein)/reg III has been attributed various functional roles. Structurally, the ability to form fibrils after tryptic cleavage is a striking common features of both proteins. However, this biochemical transformation is in itself not enough to gain functional insight. Thus, physiological and genetic approaches are required to further characterize the role of these proteins in the pancreas. Recently, more evidence has been presented in support of the theory that PSP/reg plays a key role in islet neogenesis/regeneration.

CONCLUSIONS

In this review we discuss the debate on the localization and functional roles of PSP/reg and PAP/regIII. Therefore, we have summarized hypotheses and experimental results supporting such hypotheses.

Cerebrospinal fluid protein biomarkers for Alzheimer's disease

The introduction of acetylcholine esterase (AChE) inhibitors as a symptomatic treatment of Alzheimer's disease (AD) has made patients seek medical advice at an earlier stage of the disease. This has highlighted the importance of diagnostic markers for early AD. However, there is no clinical method to determine which of the patients with mild cognitive impairment (MCI) will progress to AD with dementia, and which have a benign form of MCI without progression. In this paper, the performance of cerebrospinal fluid (CSF) protein biomarkers for AD is reviewed. The diagnostic performance of the three biomarkers, total tau, phospho-tau, and the 42 amino acid form of beta-amyloid have been evaluated in numerous studies and their ability to identify incipient AD in MCI cases has also been studied. Some candidate AD biomarkers including ubiquitin, neurofilament proteins, growth-associated protein 43 (neuromodulin), and neuronal thread protein (AD7c) show interesting results but have been less extensively studied. It is concluded that CSF biomarkers may have clinical utility in the differentiation between AD and several important differential diagnoses, including normal aging, depression, alcohol dementia, and Parkinson's disease, and also in the identification of Creutzfeldt-Jakob disease in cases with rapidly progressive dementia. Early diagnosis of AD is not only of importance to be able to initiate symptomatic treatment with AChE inhibitors, but will be the basis for initiation of treatment with drugs aimed at slowing down or arresting the degenerative process, such as gamma-secretase inhibitors, if these prove to affect AD pathology and to have a clinical effect.

Differentially expressed proteins in the pancreas of diet-induced diabetic mice

The pancreas is a heterogeneous organ mixed with both exocrine and endocrine cells. The pancreas is involved in metabolic activities with the endocrine cells participating in the regulation of blood glucose, while the exocrine portion provides a compatible environment for the pancreatic islets and is responsible for secretion of digestive enzymes. The purpose of this study was to identify pancreatic proteins that are differentially expressed in normal mice and those with diet-induced type 2 diabetes (T2DM). In this study, C57BL/6J male mice fed a high fat diet became obese and developed T2DM. The pancreatic protein profiles were compared between control and diabetic mice using two-dimensional gel electrophoresis. Differentially expressed protein "spots" were identified by mass spectrometry. REG1 and REG2 proteins, which may be involved in the proliferation of pancreatic beta cells, were up-regulated very early in the progression of obese mice to T2DM. Glutathione peroxidase, which functions in the clearance of reactive oxidative species, was found to be down-regulated in the diabetic mice at later stages. The RNA levels encoding REG2 and glutathione peroxidase were compared by Northern blot analysis and were consistent to the changes in protein levels between diabetic and control mice. The up-regulation of REG1 and REG2 suggests the effort of the pancreas in trying to ameliorate the hyperglycemic condition by stimulating the proliferation of pancreatic beta cells and enhancing the subsequent insulin secretion. The down-regulation of glutathione peroxidase in pancreas could contribute to the progressive deterioration of beta cell function due to the hyperglycemia-induced oxidative stress.

Control of expression of the lectin-like protein Reg-1 by gastrin: role of the Rho family GTPase RhoA and a C-rich promoter element

The expression of members of the Reg family of secreted lectin-like proteins is increased in response to stress, inflammation and damage in many tissues. In the stomach, Reg is located in enterochromaffin-like cells, where its expression is stimulated by the gastric hormone gastrin. We have examined the mechanisms by which gastrin stimulates expression of Reg-1. Deletional mutations of 2.1 to 0.1 kb of the rat Reg-1 promoter in a luciferase reporter vector were transiently transfected into gastric cancer AGS-G(R) cells. All promoter fragments tested showed similar relative increases in luciferase expression in response to gastrin (1 nM). The response to gastrin of the smallest (104 bp) construct was 4.2+/-0.4-fold over basal. These responses were reduced by Ro-32-0432, a protein kinase C inhibitor, by C3-transferase, a Clostridium botulinum toxin and a selective inhibitor of the Rho family GTPase RhoA, and by co-transfection with a dominant negative form of RhoA. Co-transfection with a constitutively active form of RhoA stimulated expression 11.6+/-1.7-fold over basal. Mutations through the 104 bp construct identified a C-rich element (C-79CCCTCCC-72) required for responses to gastrin, PKC (protein kinase C) and L63RhoA (the constitutively active form of human RhoA protein containing a glutamine-to-leucine substitution at position 63). EMSAs (electrophoretic-mobility-shift assays) using nuclear extracts of control and gastrin-stimulated AGS-G(R) cells and a probe spanning -86 to -64 bp revealed multiple binding proteins. There was no effect of gastrin on the pattern of binding. Supershift assays indicated that transcription factors Sp1 and Sp3 bound the C-rich sequence. We conclude that gastrin stimulates Reg expression via activation of PKC and RhoA, that a C-rich region (-79 to -72) is critical for the response and that Sp-family transcription factors bind to this region of the promoter.

Implication of Reg I in human pancreatic duct-like cells in vivo in the pathological pancreas and in vitro during exocrine dedifferentiation

A feature associated frequently with the pathologic pancreas is the presence of tubular complexes produced by a phenotypic modulation of acinar cells that take on the characteristics of ductular cells. Since the type I Reg gene, an acinar cell product, is increased in the pancreas following an acinar injury, we aimed to evaluate whether the Reg I protein might be involved in this dedifferentiation process in the human pancreas. We studied duct-like structures in fixed human pathologic pancreatic tissues and human cells with a ductal phenotype obtained by culturing human exocrine preparations. Immunocytochemistry, Western blotting, and RT-PCR were applied for detection of type I Reg. Reg I was observed not only in acinar cells but also in the duct-like cells and dilated duct cells, both positive for cytokeratin 19. However, none of the other acinar markers was observed in these cells. In vitro, human acinar cells dedifferentiated, losing their acinar phenotype, but expression of Reg I remained constant throughout the culture duration. Furthermore, Reg I was not associated with proliferation. We demonstrated that Reg I expression was linked to acinar cell dedifferentiation. We postulate that Reg I might be used as a marker to understand the events leading to phenotypic changes of acinar cells to address the physiological role of Reg I in the pancreas.

Expression of the regenerating gene family in inflammatory bowel disease mucosa: Reg Ialpha upregulation, processing, and antiapoptotic activity

BACKGROUND

The pathophysiology of inflammatory bowel disease (IBD) reflects a balance between mucosal injury related to an ongoing inflammatory process and mucosal reparative mechanisms. Proreparative mucosal factors may offer new therapeutic paradigms. Transcriptional profiling can be applied to identify candidate gene products involved in colonic mucosal regeneration.

METHODS

Resection specimens from patients who underwent colonic resection for IBD or non-IBD indications were analyzed by performing Affymetrix GeneChip hybridization (Affymetrix, Inc., Santa Clara, Calif) and histopathologic scoring. Expression and physiologic processing of Reg Ialpha, the most highly expressed member of the regenerating (Reg) gene family, was further studied by performing specific immunohistochemistry, protein sequencing, and mass spectroscopy.

RESULTS

Foregut-derived tissues normally express human Reg proteins with minimal expression in the colon. In the setting of tissue injury associated with IBD, Reg Ialpha Reg Ibeta, and Reg III mRNA were highly expressed in colonic mucosa. Paired histopathologic scoring demonstrated that Reg expression was not related to the presence or the degree of mucosal inflammation. Studies of the Reg Ialpha protein revealed evidence of proteolytic cleavage at the N-terminus. In IBD, intact Reg Ialpha protein was expressed by the metaplastic Paneth granular cell population. Whereas Reg Ialpha cleaved at the N-terminus, it was also deposited throughout the lamina propria. Reg Ialpha treatment was shown to reduce epithelial apoptosis that occurred in response to treatment with hydrogen peroxide.

CONCLUSION

Ectopic expression, physiologic processing, and directed tissue deposition of Reg Ialpha are components of the colonic mucosal regenerative response in IBD. Reg Ialpha may serve to reduce epithelial apoptosis in inflammation.

Human aspartyl (asparaginyl) beta-hydroxylase monoclonal antibodies: potential biomarkers for pancreatic carcinoma

INTRODUCTION

Pancreatic adenocarcinoma is among the top 10 leading causes of death due to cancer in the United States. The lack of reliable and sensitive biomarkers for this disease makes it difficult to render an early diagnosis.

AIMS

To evaluate carcinoma-associated monoclonal antibodies (MoAbs), including AF-20, SF-25, and FB-50, for their binding specificity to pancreatic adenocarcinoma relative to normal pancreatic tissue. In addition, binding of the Th9 MoAb to human Reg 1 protein was studied because of its potential role in cell growth.

METHODOLOGY

Adjacent histologic sections were immunostained with each of the MoAbs and graded on a scale of 0 to 4+, corresponding to the relative distribution and intensity of immunoreactivity within the tumor and normal adjacent tissue.

RESULTS

Intense levels (grade 3 or 4) of FB50 immunoreactivity were detected in 19 of 19 tumors but not in normal adjacent pancreatic tissue. In addition, increased levels of FB50 immunoreactivity were detected in at least 75% of the tumor cells in 18 of the 19 cases. SF-25 immunoreactivity similarly distinguished pancreatic adenocarcinoma from normal pancreas in 14 of 19 cases. In contrast, AF20 immunoreactivity was detected in 6 of 19 pancreatic adenocarcinomas, and for the most part, the labeling was focal and of a low level. TH9 immunoreactivity was detected in 5 of 19 tumors but also in normal as well as inflamed adjacent pancreatic tissue.

CONCLUSION

These results suggest that the FB50 and SF25 MoAbs represent excellent potential biomarkers of pancreatic adenocarcinoma and could be configured in an immunoassay for detecting pancreatic adenocarcinoma cells in biologic fluids.

A family of 16-kDa pancreatic secretory stress proteins form highly organized fibrillar structures upon tryptic activation

A group of 16-kDa proteins, synthesized and secreted by rat pancreatic acinar cells and composed of pancreatic stone protein (PSP/reg) and isoforms of pancreatitis-associated protein (PAP), show structural homologies, including conserved amino acid sequences, cysteine residues, and highly sensitive N-terminal trypsin cleavage sites, as well as conserved functional responses in conditions of pancreatic stress. Trypsin activation of recombinant stress proteins or counterparts contained in rat pancreatic juice (PSP/reg, PAP I and PAP III) resulted in conversion of 16-kDa soluble proteins into 14-kDa soluble isoforms (pancreatic thread protein and pancreatitis-associated thread protein, respectively) that rapidly polymerize into insoluble sedimenting structures. Activated thread proteins show long lived resistance to a wide spectrum of proteases contained in pancreatic juice, including serine proteases and metalloproteinases. In contrast, PAP II, following activation with trypsin or pancreatic juice, does not form insoluble structures and is rapidly digested by pancreatic proteases. Scanning and transmission electron microscopy indicate that activated thread proteins polymerize into highly organized fibrillar structures with helical configurations. Through bundling, branching, and extension processes, these fibrillar structures form dense matrices that span large topological surfaces. These findings suggest that PSP/reg and PAP I and III isoforms consist of a family of highly regulated soluble secretory stress proteins, which, upon trypsin activation, convert into a family of insoluble helical thread proteins. Dense extracellular matrices, composed of helical thread proteins organized into higher ordered matrix structures, may serve physiological functions within luminal compartments in the exocrine pancreas.

Preferential expression of reg I beta gene in human adult pancreas

In human pancreas two genes, reg I alpha and reg I beta, have been characterized but only the reg I alpha protein has been isolated from human pancreatic secretion. To examine their respective physiological roles in fetal and adult pancreas we have compared the patterns of gene expression using a specific RT-PCR method. No progressive evolution in the two mRNAs levels was observed during fetal development (16--41 weeks). A discoordinate expression of the two genes was found with a higher level of reg I alpha mRNA in fetus and a higher level of regI beta in adult. In addition, if reg I alpha mRNA level was correlated with the expression of genes encoding exocrine proteins in adults, reg I beta mRNA level presented no correlation with any ductular, endocrine, or exocrine gene expression. In human pancreatic cell lines we showed the only expression of reg I beta gene and protein. All these data suggest that the two reg genes and proteins could play different roles in the pancreas.

Overexpression of the reg gene in non-obese diabetic mouse pancreas during active diabetogenesis is restricted to exocrine tissue

We demonstrated pancreatic reg gene overexpression in non-obese diabetic (NOD) mice during active diabetogenesis. The aim of this study was to determine in which part of the pancreas (endocrine and/or exocrine) the gene(s) and the protein(s) were expressed and if their localization changed with progression of the disease. In situ hybridization analysis and immunocytochemical studies were carried out on pancreas of female and male NOD mice. Both develop insulitis but diabetes develops only in females and in males only when treated by cyclophosphamide. Our results show that whatever the age, sex, and presence of insulitis and/or diabetes, the expression of reg mRNAs and of the corresponding protein(s) was restricted to exocrine tissue. Moreover, reg remains localized in acinar cells in the two opposite situations of (a) cyclophosphamide-treated males in a prediabetic stage presenting a high level of both insulin and reg mRNAs, and (b) the overtly diabetic females with no insulin but a high level of reg mRNA. These findings suggest that overexpression of the reg gene(s) might represent a defense of the acinar cell against pancreatic aggression.

A recombinant rat regenerating protein is mitogenic to pancreatic derived cells

Pancreatic regenerating protein (reg I) is expressed in acinar cells and is mitogenic to beta- and ductal cells. Isolation of large amounts of endogenous reg I for in vivo and in vitro experiments has been difficult. The aim of this study was to develop a recombinant protein and determine its bioactivity on rat pancreatic derived cells. cDNA of the rat reg I coding region was created with unique BamHI flanking sequences using reverse transcriptase PCR. The coding region was then cloned into a bacterial expression vector in which expression is controlled by a T7 promoter. After transformation into the Escherichia coli strain B21(DE3) and induction by isopropyl-beta-d-thiogalactopyranoside, a fusion protein of 24 kDa in size, named reg-PET, was noted in the bacterial lysate. This protein contained a polyhistidine and S-peptide sequence to facilitate isolation and identification, respectively. This protein was purified using affinity chromatography, and identity was confirmed with gel electrophoresis and Western analysis. The reg-PET protein was mitogenic to both ARIP and RIN cells, rat pancreatic ductal and beta-cell lines, respectively. Antibodies raised to the protein reacted against rat reg I in pancreas. The purified recombinant reg I fusion protein, like endogenous reg I, is mitogenic to pancreatic derived cells. It is more potent than reg I isolated from pancreatic tissue. This protein can be isolated rapidly, easily, and with a high amount of purity.

A Brief History of Pancreatic Reg: Implications as to its Clinical Importance

Although the pancreatic regenerating (reg) gene, was first isolated from a rat regenerating islets in 1988, its protein product was originally described in the 1970s. Reg proteins arise from a multigene family with three subtypes, and have a protein structure similar to calcium dependent lectins. Reg I and II have been implicated in control of pancreatic development and may play a role in maintenance of the beta-cell mass in the mature pancreas. Administration of reg I protein has been used in experimental animals as a therapy for surgically-induced diabetes mellitus. Reg I protein is also an inhibitor of calcium carbonate crystalization, important in maintaining the fluidity of pancreatic juice. The reg III gene, whose protein product is pancreatitis associated protein, is induced during pancreatic inflammation. Serum levels of reg III protein are a sensitive marker of severity of pancreatitis. It is an endogenous pancreatic factor that prevents the bacteria infection and scavenges oxygen-derived free radicals. Reg mRNA has been detected in non-pancreatic tissue such as the enterochromaffin-like cells of the stomach, neoplastic tissues of the colon, the small intestine, nervous system, liver tumors, and pituitary. Reg proteins are mitogens to intestinal epithelial cells, pancreatic ductal, beta cells, and Schwann cells, and are likely important to the overall integrity of the pancreas and gastrointestinal tract.

Biophysical characterization of lithostathine. Evidences for a polymeric structure at physiological pH and a proteolysis mechanism leading to the formation of fibrils

Lithostathine is a calcium carbonate crystal habit modifier. It is found precipitated under the form of fibrils in chronic calcifying pancreatitis or Alzheimer's disease. In order to gain better insight into the nature and the formation of fibrils, we have expressed and purified recombinant lithostathine. Analytical ultracentrifugation and quasi-elastic light scattering techniques were used to demonstrate that lithostathine remains essentially monomeric at acidic pH while it aggregates at physiological pH. Analysis of these aggregates by electron microscopy showed an apparently unorganized structure of numerous monomers which tend to precipitate forming regular unbranched fibrils. Aggregated forms seem to occur prior to the apparition of fibrils. In addition, we have demonstrated that these fibrils resulted from a proteolysis mechanism due to a specific cleavage of the Arg(11)-Ile(12) peptide bond. It is deduced that the NH(2)-terminal undecapeptide of lithostathine normally impedes fiber formation but not aggregation. A theoretical model explaining the formation of amyloid plaques in neurodegenerative diseases or stones in lithiasis starting from lithostathine is described. Therefore we propose that lithostathine, whose major function is unknown, defines a new class of molecules which is activated by proteolysis and is not involved in cytoskeleton nor intermediate filament functions.

Expression of REG protein during cell growth and differentiation of two human colon carcinoma cell lines

We localized REG protein in Paneth cells and nonmature columnar cells of the human small intestinal crypts and speculated that this protein was associated with growth and/or differentiation. The aim of this study was to determine whether REG protein is present in two human colon cancer cell lines that exhibit enterocytic differentiation after confluence and to investigate changes in the level of its expression during growth and differentiation. Results were compared to those obtained on cells that remain undifferentiated. Western immunoblotting and immunofluorescence demonstrated the presence of REG protein in the three cell lines. With the antisera against human REG protein, the staining was diffusely spread throughout the cytoplasm at Day 2, and after Days 3-4 it appeared to have migrated to cell boundaries. After confluence, we observed only a punctate staining array along cell boundaries, which disappeared at Day 15. REG mRNA expression was demonstrated by RTPCR and REG mRNA hybridization until Day 13, but not after, in the three cell types. REG protein may be involved in cellular junctions. Its presence appears to be associated with the cell growth period and the protein must be downregulated when growth is achieved and differentiation is induced.

Human pancreatic thread protein, an exocrine thread protein with possible implications to Alzheimer's disease: secondary structure in solution at acid pH

The secondary structure of human pancreatic thread protein (HPTP) in solution at acid pH was derived using Fourier transform infrared (FT-IR) and laser Raman spectroscopic studies. The experimentally derived secondary structure of HPTP was compared with the secondary structure obtained by the Chou-Fasman algorithm. Pancreatic thread protein is a major exocrine secretory protein that in vitro forms filamentous bundles reminiscent of the paired helical filaments of Alzheimer's disease (AD). PTP immunoreactivity in brains afflicted with AD has been demonstrated previously and high levels of its mRNA in the developing human brain have also been reported in the literature. The above studies suggest that AD is associated with enhanced expression of PTP-related transcripts with interneuronal accumulation of PTP-like proteins. The experimentally derived secondary structure of HPTP consists of a significant proportion of beta-sheets and beta-turns and lesser amounts of alpha-helical structures. The beta-sheet component presumably plays an important role in the pH-dependent globule-fibril transformation of HPTP leading to antiparallel beta-sheet structure in the aggregated state. The secondary structure of HPTP and its globule-fibril transformation lend credence to the belief that AD may be viewed as a conformational disease.

Immunoreactive pancreatic Reg protein in sera from cystic fibrosis patients with and without pancreatic insufficiency

BACKGROUND

The biological function of the Reg protein, a non-enzymic protein produced in fairly large amounts by pancreatic acinar cells, remains elusive. Its susceptibility to proteolysis leading to precipitation of the proteolysis product at neutral pH suggests that it could contribute to the protein plugging observed in cystic fibrosis (CF).

AIMS

To study its behaviour in the serum of CF patients with or without pancreatic insufficiency and to compare it with that of other pancreatic secretory proteins.

PATIENTS

170 patients (93 with CF, 55 controls, and 22 with chronic pancreatitis) were studied.

METHODS

Reg protein was measured using a specific enzyme immunoassay and its molecular form in CF sera was characterised by gel filtration. Molecular gene expression was investigated by dot-blot hybridisation.

RESULTS

Reg protein was present in all CF sera studied from patients with or without pancreatic insufficiency, and in all cases the level was significantly higher than in controls. Its chromatographic behaviour in CF sera was identical with that of the protein present in normal serum. No correlation was found between the levels of Reg protein and trypsin(ogen) (or lipase) in CF, nor in control sera or normal pancreatic juice. Molecular gene expression of the corresponding proteins investigated in pancreatic tissues showed an absence of correlation between the mRNA levels.

CONCLUSIONS

Reg protein may not be a secretory exocrine protein like the digestive enzymes but rather a hormone-like secretory substance with an endocrine or paracrine function.

Alcohol and the pancreas

Alcoholic pancreatitis is a major, often lethal complication of alcohol abuse. Until recently it was generally accepted that alcoholic pancreatitis was a chronic disease from the outset. However, there is now emerging evidence in favour of the necrosis-fibrosis hypothesis that alcoholic pancreatitis begins as an acute process and that repeated acute attacks lead to chronic pancreatitis, resulting in exocrine and endocrine failure. Over the past 10-15 years, the focus of research into the pathogenesis of alcoholic pancreatitis has shifted from possible sphincteric and ductular abnormalities to the acinar cell itself which has increasingly been implicated as the initial site of injury. Recent studies have shown that the acinar cell can metabolize alcohol at rates comparable to those observed in hepatocytes. In addition, it has been demonstrated that alcohol and its metabolites exert direct effects on the pancreatic acinar cell which may promote premature digestive enzyme activation and oxidant stress. The challenge remains to identify predisposing and triggering factors in this disease.

Neuronal thread protein gene modulation with cerebral infarction

Neuronal thread proteins (NTP) are a family of phosphoproteins expressed during neuritic sprouting. The 15 to 18 kD NTP cluster is associated with development and neuronal differentiation, whereas the 21 kD and 39 to 42 kD species are overexpressed in Alzheimer's disease, correlating with neurodegenerative sprouting and synaptic disconnection. Empirical observations suggested that NTP might also be modulated with central nervous system injury and stroke. In this study of both human and experimental (rat) focal cerebral infarcts, in situ hybridization and immunocytochemical staining revealed NTP gene expression up-regulated in perifocal neurons. These findings were confirmed by quantitative Northern and Western blot analyses. Moreover, Western blot analysis demonstrated selectively increased expression of the 15 to 18 kD NTP species during the acute, subacute, and healing phases of cerebral infarction in both humans and experimental animals, corresponding with the expected period of neuronal repair. These results suggest an additional role for the 15 to 18 kD NTP species in neuritic sprouting required for neuronal regeneration after injury in the mature central nervous system.

Cloning and sequencing of the pancreatic islet neogenesis associated protein (INGAP) gene and its expression in islet neogenesis in hamsters

Induction of islet neogenesis by cellophane wrapping (CW) reverses streptozotocin-induced (STZ) diabetes. Administration of Ilotropin, a protein extract isolated from CW pancreata, causes recapitulation of normal islet ontogeny and reverses STZ diabetes, reducing mortality by 50%. We investigated the hypothesis that a novel gene encoding a constituent of Ilotropin was expressed in the hamster pancreas undergoing islet neogenesis. Islet neogenesis associated protein (INGAP) is a product of a novel gene expressed in regenerating hamster pancreas. Northern blot analysis showed a strong single transcript of 850 bp at 1 and 2 d after CW that disappeared by the 6th day and was absent from untreated control pancreata. INGAP gene is expressed in acinar cells, but not in islets. Western blot analysis demonstrated the presence of INGAP in Ilotropin but not in extracts from control pancreata. A synthetic pentadecapeptide, corresponding to a region unique to INGAP, stimulated a 2.4-fold increase in [3H]thymidine incorporation into hamster duct epithelium in primary culture and a rat pancreatic duct cell line but had no effect on a hamster insulinoma tumor cell line. A portion of human INGAP gene was cloned and appears to be highly homologous to the hamster gene. This data suggests that the INGAP gene is a novel pancreatic gene expressed during islet neogenesis whose protein product is a constituent of Ilotropin and is capable of initiating duct cell proliferation, a prerequisite for islet neogenesis.

Pancreatic reg gene expression is inhibited during cellular differentiation

BACKGROUND AND OBJECTIVE

Factors that control pancreatic regenerating (reg I) gene expression are unknown, but it is believed that its expression may correspond with cellular differentiation. The authors recently demonstrated that reg I is expressed in AR42J, a rat acinar cell line whose state of differentiation can be modulated by dexamethasone. They used this line to study reg I expression during cellular proliferation and differentiation.

METHODS

After treatment of cells with 10 nmol/L dexamethasone, proliferation was assayed by thymidine incorporation; differentiation by expression of elastase I mRNA. Reg I mRNA levels were measured using a rat reg I cDNA probe, and reg I protein levels assayed by enzyme-linked immunosorbent assay of cellular lysates with a polyclonal antibody. The effect of gastrin, cholecystokinin and glucagon on reg I expression was also studied.

RESULTS

When compared with controls, treatment with dexamethasone caused thymidine incorporation to decrease and elastase mRNA levels to increase. Reg I mRNA decreased from controls of 100 +/- 16% to 40 +/- 18% (p < 0.05), and reg I protein levels decreased as well. Gastrointestinal hormones had no significant effect on either elastase or reg I gene expression.

CONCLUSIONS

Expression of reg I inversely correlates with the level of cellular differentiation, can be modulated via the glucocorticoid receptor, and is a potential marker of gastrointestinal epithelial differentiation. Despite its presence within a pancreatic acinar cell line, reg I gene expression is not modulated by gastrointestinal hormones.

Ectopic expression of reg protein: A marker of colorectal mucosa at risk for neoplasia

Pancreatic regenerating gene (reg I) messenger RNA is overexpressed within the pancreas following injury and resection. Its level of expression corresponds to the level of cellular dedifferentiation. Human reg I has been localized to chromosome 2p12, and ectopic expression of its mRNA has been found within colorectal tumors. We postulated that colorectal production of reg I might either be a marker for the presence of cancer or define mucosa at risk for development of neoplasia. Using a monoclonal antibody to reg I, regenerating gene protein was histochemically mapped in 56 cases of documented colorectal adenocarcinoma. In sections of colon from normal control subjects no reg I protein was noted, whereas 58.9% of the specimens from cancer patients stained positive for reg I. Although a correlation was noted between reg I staining and Dukes' stage, there was no correlation with histologic grade or 5-year patient survival. In 39 of 55 cancer specimens the transition zone (interface) between the neoplasm and normal mucosa was visualized; 100% of the transition zones contained cells that stained strongly positive for reg I. We conclude that reg I protein is ectopically expressed in colorectal mucosa at the transition zone of colorectal cancer, and occasionally within the tumor itself. Although ectopic reg I expression in colorectal epithelia is not a marker for the presence of carcinoma, it may be a sensitive marker for mucosa at risk for development of neoplasia.

Pancreatic stone protein (lithostathine), a physiologically relevant pancreatic calcium carbonate crystal inhibitor?

Apart from digestive enzymes, pancreatic juice contains several proteins that are not directly involved in digestion. One of these, lithostathine, has been reported to exhibit calcite crystal inhibitor activity in vitro. As pancreatic juice is supersaturated with respect to calcium carbonate, it was hypothesized that lithostathine stabilizes pancreatic juice. Lithostathine is cleaved by trace amounts of trypsin, resulting in a C-terminal polypeptide and an N-terminal undecapeptide, which has been identified as the active site of lithostathine regarding crystal inhibition. We produced rat lithostathine in a baculovirus expression system. In order to test its functional activity, the protein was purified using a nondenaturing multi-step procedure. In the low micromolar range, recombinant rat lithostathine in vitro exhibited calcite crystal inhibitor activity, confirming earlier reports. Limited tryptic proteolysis of recombinant lithostathine was performed, and the two cleavage products were separated; the C-terminal polypeptide was precipitated by centrifugation, and the N-terminal undecapeptide was purified by high performance liquid chromatography. Only the C-terminal peptide displayed measurable calcite crystal inhibitory activity. Furthermore, synthetic undecapeptides with identical sequence to the N-terminal undecapeptides of rat or human lithostathine were inactive. However, when tested in the same in vitro assays, other pancreatic or extra-pancreatic proteins show inhibitory activity in the same concentration range as lithostathine, and inorganic phosphate is active as well. Based on these findings it seems unlikely that lithostathine is a physiologically relevant calcite crystal inhibitor. The name "lithostathine" is therefore inappropriate, and the protein's key function remains to be elucidated.

Crystal structure of human lithostathine, the pancreatic inhibitor of stone formation

Human lithostathine (HLIT) is a pancreatic glycoprotein which inhibits the growth and nucleation of calcium carbonate crystals. The crystal structure of the monomeric 17 kDa HLIT, determined to a resolution of 1.55 angstroms, was refined to a crystallographic R-factor of 18.6%. Structural comparison with the carbohydrate-recognition domains of rat mannose-binding protein and E-selectin indicates that the C-terminal domain of HLIT shares a common architecture with the C-type lectins. Nevertheless, HLIT does not bind carbohydrate nor does it contain the characteristic calcium-binding sites of the C-type lectins. In consequence, HLIT represents the first structurally characterized member of this superfamily which is not a lectin. Analysis of the charge distribution and calculation of its dipole moment reveal that HLIT is a strongly polarized molecule. Eight acidic residues which are separated by regular 6 angstrom spacings form a unique and continuous patch on the molecular surface. This arrangement coincides with the distribution of calcium ions on certain planes of the calcium carbonate crystal; the dipole moment of HLIT may play a role in orienting the protein on the crystal surface prior to the more specific interactions of the acidic residues.

Modulation of neuronal thread protein expression with neuritic sprouting: relevance to Alzheimer's disease

Widespread proliferation of dystrophic neurites in the cerebral cortex represents an important neuroanatomical correlate of dementia in Alzheimer's disease (AD). Increased CNS expression of the 21-kDa neuronal thread protein (NTP) species is also correlated with dementia in AD. Pilot in vitro experiments provided evidence that high-level NTP expression might be linked to neuritic growth. The present study examines retinoic acid (RA) modulation of NTP expression during neurite outgrowth and neuronal differentiation in SH-Sy5y neuroblastoma and PNET2 CNS-derived cells. In both cell lines, RA-induced neuronal differentiation resulted in increased synthesis, expression, and phosphorylation of several NTP species, with high steady-state levels and stepwise hyper-phosphorylation of 21-kDa NTP molecules. With neurite outgrowth, NTP molecules were translocated from the perikarya to long, slender, unbranched cell processes (axons) and growth cones. RA-mediated changes in NTP expression were independent of DNA synthesis. The findings suggest that high-level expression of 21-kDa, and closely related phosphorylated NTP molecules correlates with neuritic growth. Therefore, over-expression of 21-kDa NTP molecules in AD probably reflects the widespread cortical neuritic sprouting associated with dementia. In view of the rapid phosphorylation and cell process translocation of NTP that occurs during neurite outgrowth in vitro, the accumulation of NTP in AD cortical neuronal perikarya suggests a further problem related to post-translational processing and transport of NTP molecules in AD neurodegeneration.

Absence of correlation between reg and insulin gene expression in pancreas during fetal development

The reg gene characterized in the exocrine pancreas has been found to be expressed in regenerating islets of 90% depancreatized rats and not in normal islets. In humans, it was identified only in the exocrine pancreas. Because the reg protein has been found to be related to islet cell replication and/or beta cell regeneration, we compared the expression of the reg gene with that of chymotrypsinogen of exocrine origin and insulin of endocrine origin. We investigated the expression of the three pancreatic genes in the fetal pancreas during human development using dot-blot analysis. The levels of expression of the corresponding mRNAs did not appear to undergo great changes between the 17th and the 29th wk of gestation. Nevertheless, the fetal mRNA levels for reg and chymotrypsinogen were below that of the adult, with very low levels of reg gene expression in more than half of the studied pancreases. In contrast, the insulin mRNA levels were significantly higher in fetal than in adult pancreases, suggesting that insulin may function as a growth factor during fetal development. Our results indicate that no correlation between reg and insulin gene expression exists in the fetal pancreas during the developmental period studied but, on the contrary, such a correlation was present in the adult pancreas.

Developmental patterns of neuronal thread protein gene expression in Down syndrome

Neuronal thread proteins (NTP) are a group of immunologically related molecules expressed in brain and neuroectodermal tumor cell lines. NTP gene expression is up-regulated and NTP molecules accumulate in Alzheimer's disease (AD) brains, pathological states associated with regenerative neuritic sprouting, and during brain development. To investigate the role of NTP over-expression in AD, we examined NTP immunoreactivity in brains from differently aged individuals with Down syndrome, since patients with Down syndrome nearly always develop AD neuropathology and dementia. Using SMI monoclonal antibodies to neurofilament protein, we detected age-associated increases in neurofilament immunoreactive (SMI-positive) neurites in Layers I and II of the cerebral cortex beginning at 1 year of age, followed by SMI-positive neurofibrillary tangles beginning at age 5 years, and then SMI-positive plaques beginning in the third decade. Increased NTP immunoreactivity in Down syndrome brains began in the second decade, prior to establishment of widespread AD neurodegeneration (Down syndrome + AD), and at an age when low-level or absent NTP expression was observed in control brains. Analysis of SDS and Triton X-100-treated histological sections and tissue extracts demonstrated that a largely insoluble, denaturation-resistant form of NTP accumulates in both Down syndrome + AD and AD brains. The findings provide further evidence that abnormal NTP expression and accumulation in brain may be an early marker of AD neurodegeneration in Down syndrome.

Identification of differentially expressed genes induced in pancreatic islet neogenesis

Cellophane wrapping of the hamster pancreas induces islet neogenesis. We have used the mRNA differential display technique to select for genes expressed during islet neogenesis but not in control pancreata. Ten candidate clones have been identified. Upon sequencing, 6 clones showed a high degree of homology to known genes, 1 showed some, and 3 showed no homology to genes of known sequence. Thus, mRNA differential display is a useful technique to identify genes induced during islet neogenesis, and in combination with screening hamster pancreatic cDNA libraries for full length clones, will enhance the likelihood of capturing the participants in this process.

Measurement of serum PSP/reg-protein concentration in various diseases with a newly developed enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay, based on two monoclonal antibodies (Hreg1-1 and Hreg101-1) specific for pancreatic stone protein (PSP)/reg-protein, was developed to determine the concentration of this protein in serum from individuals with various diseases. The serum concentration of PSP/reg-protein was significantly higher in patients with various pancreatic diseases than in normal controls, and was also significantly higher in patients with acute pancreatitis or chronic relapsing pancreatitis than in patients with chronic pancreatitis. Furthermore, the serum PSP/reg-protein concentration was also significantly increased in liver cirrhosis, choledocholithiasis, and various cancers of the digestive system, and was extremely high in all patients tested with chronic renal failure. A significant correlation was apparent between the serum concentration of PSP/reg-protein and elastase-I in 68 patients with chronic pancreatitis or pancreatic cancer. Whereas only 7 of these patients showed a normal serum PSP/reg-protein concentration and a significantly increased elastase-I concentration, 15 of these patients showed a significantly increased serum PSP/reg-protein concentration and a normal serum elastase-I concentration. These results indicate that the serum PSP/reg-protein concentration may reflect pancreatic damage, especially in acute pancreatitis, and may be a sensitive a marker for such damage as elastase-1, although false positivity was apparent in renal failure and in some patients with hepatic dysfunction or digestive system malignancies.

Ethanol inhibits insulin receptor substrate-1 tyrosine phosphorylation and insulin-stimulated neuronal thread protein gene expression

Neuronal thread proteins (NTPs) are molecules that accumulate in the brains of patients with Alzheimer's disease, and may play a key role in both normal and neurodegenerative neuritic sprouting. In this investigation we determined whether NTP expression is up-regulated by insulin, an important neurotrophic factor that stimulates differentiation-associated neurite outgrowth, and studied the effects of ethanol, a known inhibitor of growth factor receptor tyrosine phosphorylation, on NTP expression and insulin-mediated signal transduction cascade in neuronal [primitive neuroectodermal tumour cell line 2; (PNET2)] cells. PNET2 cells were treated with 50 m-units/ml insulin in the presence or absence of 100 mM ethanol for 0.2-96 h, and cell proliferation and expression of NTP molecules were investigated by metabolic labelling, immunoprecipitation and immunohistochemical staining. Insulin stimulation resulted in an immediate increase in the levels of three (38, 18 and 15 kDa) of five NTP species (the others were of 26 and 21 kDa), followed by a decline in expression within 120 min; however, studies performed up to 96 h of culture demonstrated up-regulation by insulin of all five NTP species. Ethanol either abolished or severely muted the short- and long-term insulin-mediated upregulation of NTP expression, and substantially reduced insulin-mediated neuronal differentiation. The effects of ethanol on NTP gene expression were associated with impaired insulin-mediated tyrosine phosphorylation of both the insulin receptor beta subunit and the insulin receptor substrate-1 (IRS-1), resulting in decreased association of phosphatidylinositol 3-kinase with IRS-1. The findings suggest that ethanol may inhibit NTP expression associated with central nervous system neuronal differentiation by uncoupling the IRS-1-mediated insulin signal transduction pathway.

Expression of Reg gene in the Syrian golden hamster pancreatic islet regeneration model

We have reported previously that cellophane wrapping of the hamster pancreas is a stimulus that leads to the induction of duct epithelial cell proliferation, followed by endocrine cell differentiation and new islet formation. Reg is a candidate gene that has been reported to be expressed in regenerating pancreatic islets, suggesting a role in islet growth. We examined Reg gene expression in the cellophane-wrap model by isolating total RNA from hamster pancreata at various times after wrapping. Northern blot analysis using a rat cDNA Reg probe showed no expression of Reg in control non-wrapped hamster pancreas, whereas a strong signal was detected in control wrapped rat pancreas. Using reverse transcription of RNA followed by polymerase chain reaction (PCR) we amplified, isolated and sequenced a 194 base pair product which showed homology to rat Reg in both control and wrapped hamster pancreas. When the PCR product was used as a probe for Northern blot analysis, no signal was detected in control non-wrapped pancreata. In contrast, a strong signal was detected 1 and 2 days after wrapping, which then returned to basal between 4 and 6 days after wrapping. A similar temporal pattern was observed using in situ hybridization to localize the Reg gene. One- and 2-day wrapped but not control pancreas expressed Reg in acinar cells, but not in islets.(ABSTRACT TRUNCATED AT 250 WORDS)

The glycan moiety of human pancreatic lithostathine. Structure characterization and possible pathophysiological implications

Lithostathine, also known as pancreatic stone protein, pancreatic thread protein or regenerating protein, is a glycoprotein which is normally found in the exocrine pancreas, whereas in other tissues it appears either only under pathological conditions, such as Alzheimer's disease (brain), cancer (colon) or during regeneration (endocrine pancreas). In the latter case, it has been shown recently that it acts as a growth factor which stimulates islet regeneration. Little is known about its glycan moiety, which conceivably might be involved in this tissue specificity and pathophysiological characteristics. Therefore we isolated the major oligosaccharide chains of human pancreatic lithostathine and determined their sequences by means of NMR analysis. We obtained eleven different glycoforms and we were able to determine the sequence of seven of them. They all were from the same site of glycosylation (Thr5) and displayed the same core 2 structure: GlcNAc(beta 1-6)[Gal(beta 1-3)]GalNAc alpha-. They ranged in size from 4 to 9 sugar residues. Elongation was found to proceed from a common tetrasaccharidic core: Gal(beta 1-4)GlcNAc(beta 1-6)[Gal(beta 1-3)]GalNAc-ol through N-acetyllactosamine units. The non-reducing ends of some oligosaccharides carry the antigenic determinant H, with presence of external Fuc linked only in (alpha 1-2) to Gal. All the glycans, except one, carry a sialic acid in (alpha 2-3) linkage to Gal, with one disialylated form which displays a supplementary (alpha 2-6) linkage. These findings are consistent with the polymorphism of the protein, shown by means of SDS gel electrophoresis and isoelectric focusing, either in its native form or after enzymic processing. Moreover, sialylation seems to protect to some extent the Arg11-Ile12 bond from in situ hydrolysis, thus preventing the harmful precipitation of the C-terminal polypeptide in the pancreatic ducts.

Insulin-induced differentiation and modulation of neuronal thread protein expression in primitive neuroectodermal tumor cells is linked to phosphorylation of insulin receptor substrate-1

Neuronal thread proteins (NTPs) are a family of developmentally regulated molecules expressed in central nervous system (CNS) neurons and primitive neuroectodermal tumor (PNET) cell lines. NTP gene expression is modulated with DNA synthesis, neuritic sprouting, and neuronal differentiation. The present study explores the mechanism of insulin modulation of NTP gene expression during neuronal differentiation using PNET cell lines of CNS origin. PNET2 cells underwent neuronal differentiation with neurite outgrowth coupled with transient up-regulation of several species of NTP. In contrast, PNET1 cells failed to differentiate in response to insulin stimulation, although insulin receptors were more abundant than in PNET2 cells. Analysis of the insulin-mediated signal transduction pathway demonstrated that the lack of insulin responsiveness in PNET1 cells was primarily caused by impaired insulin-mediated tyrosyl phosphorylation of the insulin receptor substrate-1 (IRS-1). Correspondingly, the association between phosphatidyl-inositol 3 (PI3) kinase and phosphorylated IRS-1 was reduced in PNET1 compared with PNET2 cells. In contrast, the levels of IRS-1 protein were similar in PNET1 and PNET2 cells, and expression of the insulin receptor beta subunit (Ir beta) and insulin-mediated tyrosyl phosphorylation of the Ir beta were greater in PNET1 than PNET2 cells. The findings suggest that insulin effected neuronal differentiation and modulation of NTP gene expression in PNET cells utilizes a signal transduction cascade that requires tyrosyl phosphorylation of IRS-1.

Purification and assay of secretory lithostathine in human pancreatic juice by fast protein liquid chromatography

Impaired secretion of lithostathine, a pancreatic glycoprotein capable of inhibiting the growth of CaCO3 crystals, has been reported in chronic calcifying pancreatitis. Controversial results were obtained, however, using immunoassays with different antibodies. The aim of this study was to purify and to measure juice lithostathine by a non-immunological method. Fast protein liquid chromatography (FPLC) on a cation exchange column eluted by a sodium chloride gradient, was used. The conditions appropriate to separate secretory (S) from hydrolysed (H) isoforms of immunopurified lithostathine were also used for juice analysis. Pancreatic juice was collected by endoscopic cannulation of the major pancreatic duct, after secretin stimulation, from eight patients with chronic pancreatitis (CP) and from eight controls. In all samples, S-isoforms of lithostathine (ranging from 16 to 19 Mr at SDS-PAGE) were the only constituent of two of the 15 peaks in which FPLC resolved the pancreatic proteins. The nature of these two peaks was confirmed by their coelution with immunopurified S-lithostathine and by immunoblot analysis with polyclonal anti-lithostathine antibodies. The ratio between the area of S-lithostathine peaks and the total area of proteic eluates, was always lower in CP patients (5.3 micrograms/mg of protein, median value; 0.2-15.4, range) than in controls (35.2 micrograms/mg; 16.6-55.9). It is concluded that lithostathine can be purified and measured in pancreatic juice by FPLC. Our results with a nonimmunological assay confirm a reduced secretion of lithostathine in patients with CP.