Lithostathine, the presumed pancreatic stone inhibitor, does not interact specifically with calcium carbonate crystals

Anti-urolithiatic effect of Cucumis melo L. var inodorous in male rats with kidney stones

Melon seed extracts have high antioxidant activities and are effective against a variety of diseases, including kidney stones. In kidney stone model rats, the anti-urolithiatic effects of the hydro-ethanolic extract of melon seed and potassium citrate were studied and compared. After urolithiasis induction by ethylene glycol, the extract and potassium citrate were treated orally for 38 days concurrent with ethylene glycol. Then, urine and kidney sampling were done, and the urinary parameter levels were measured. The melon and potassium citrate treatments reduced the kidney index, the levels of urinary calcium and oxalate, calcium oxalate deposit numbers, the score of crystal deposits, histo-pathological damages, and the score of inflammation in the kidney sections, while elevating the urinary pH, magnesium, and citrate levels, and also the expression of the UMOD, spp1, and reg1 genes in the kidney of treated animals. The effect of potassium citrate is the same as the effect of melon in treated animals. So, their effects could be by normalizing urinary parameters, reducing crystal deposits, excreting small deposits from the kidney, reducing the chance of them being retained in the urinary tract, and elevating the expression of the UMOD, spp1, and reg1 genes, which are involved in kidney stone formation.

Pancreatic stone protein - sepsis and the riddles of the exocrine pancreas

Pancreatic stone protein (PSP), discovered in the 1970ies, was first associated with stone formation during chronic pancreatitis. Later, the same protein was independently detected in islet preparations and named regenerating protein 1 (REG1). Additional isoforms of PSP, including pancreatitis-associated protein (PAP), belong to the same protein family. Although the names indicate a potential function in stone formation or islet regeneration, involvements in cellular processes were only suggestive and never unequivocally proven. We established an association between PSP levels in patient blood samples and the development of sepsis. In this review, written in connection with receiving the Lifetime Achievement Award of the European Pancreatic Club, the evolution of the sepsis aspect of PSP is described. We conclude that the true functional properties of this fascinating pancreatic protein still remain an enigma.

Bovine pancreatolithiasis: case report and review of the literature

An 8-y-old lactating Holstein cow was presented to the herd veterinarian with a history of acute ataxia, and because of poor prognosis, the animal was euthanized and submitted for postmortem examination. A lumbar vertebra was incompletely fractured and had an adjacent subdural hematoma. The pancreas had a hard texture with exaggerated nodular appearance, and on cut surface, the pancreatic ducts appeared fibrotic and contained scores of round-to-faceted pancreatoliths of 0.5-2.0 mm diameter. These calculi extended from the major ducts to the pancreatic duct, sphincter, and into the duodenal lumen. Microscopically, the pancreas had severe acinar atrophy and dissecting glandular fibrosis. The major pancreatic ducts were ulcerated with fibrosis and inflammation. In humans, chronic pancreatitis has been linked to osteoporosis and increased risk of bone fractures. Manual evaluation of ribs at the time of autopsy did not reveal abnormalities in bone pliability or fragility in our cow.

CaCO₃ vaterite microparticles for biomedical and personal care applications

Among the polymorph modifications of calcium carbonate, the metastable vaterite is the most practically important. Vaterite particles are applied in regenerative medicine, drug delivery and a broad range of personal care products. This manuscript scopes to review the mechanism of the calcium carbonate crystal growth highlighting the factors stabilizing the vaterite polymorph in the most cost efficient synthesis routine. The size of vaterite particles is a crucial parameter for practical applications. The options for tuning the particle size are also discussed.

Monitoring bacterially induced calcite precipitation in porous media using magnetic resonance imaging and flow measurements

A range of nuclear magnetic resonance (NMR) techniques are employed to provide novel, non-invasive measurements of both the structure and transport properties of porous media following a biologically mediated calcite precipitation reaction. Both a model glass bead pack and a sandstone rock core were considered. Structure was probed using magnetic resonance imaging (MRI) via a combination of quantitative one-dimensional profiles and three-dimensional images, applied before and after the formation of calcite in order to characterise the spatial distribution of the precipitate. It was shown through modification and variations of the calcite precipitation treatment that differences in the calcite fill would occur but all methods were successful in partially blocking the different porous media. Precipitation was seen to occur predominantly at the inlet of the bead pack, whereas precipitation occurred almost uniformly along the sandstone core. Transport properties are quantified using pulse field gradient (PFG) NMR measurements which provide probability distributions of molecular displacement over a set observation time (propagators), supplementing conventional permeability measurements. Propagators quantify the local effect of calcite formation on system hydrodynamics and the extent of stagnant region formation. Collectively, the combination of NMR measurements utilised here provides a toolkit for determining the efficacy of a biological-precipitation reaction for partially blocking porous materials.

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.

Distribution of lithostathine in the mouse lemur brain with aging and Alzheimer's-like pathology

We analyzed the cellular distribution of the pancreatic inflammatory protein lithostathine and its receptor EXTL3 in the brain of the lemurian primate Microcebus murinus which develops amyloid deposits along with aging. In adult animals (2-4.5 years old), lithostathine and EXTL3 immunoreactivities were largely distributed in the whole brain, and more intensively in almost all cortical layers and hippocampal formation. Lithostathine was observed in the perikarya and neurites of cortical neurons but also in glial cells in the border of the ventricle and the corpus callosum. In healthy aged animals (8-13 years old), highest densities of lithostathine-containing cells were observed, mainly in occipital and parietal cortex. In aged animals with Aβ deposits, the increase in lithostathine immunoreactivity was lower as compared with aged animals. Noteworthy, lithostathine-immunopositive cells did almost never colocalize with Aβ plaques. In conclusion, lithostathine immunoreactivity in adult Microcebus murinus appeared ubiquitous and particularly in visual, sensorial, and cognitive brain areas. Immunoreactivity increased with aging and appeared markedly affected in neuropathological conditions. Its possible neuroprotection or neurodegeneration role in Alzheimer pathology deserves therefore to be investigated.

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.

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.

The C-type lectin-like domain superfamily

The superfamily of proteins containing C-type lectin-like domains (CTLDs) is a large group of extracellular Metazoan proteins with diverse functions. The CTLD structure has a characteristic double-loop ('loop-in-a-loop') stabilized by two highly conserved disulfide bridges located at the bases of the loops, as well as a set of conserved hydrophobic and polar interactions. The second loop, called the long loop region, is structurally and evolutionarily flexible, and is involved in Ca2+-dependent carbohydrate binding and interaction with other ligands. This loop is completely absent in a subset of CTLDs, which we refer to as compact CTLDs; these include the Link/PTR domain and bacterial CTLDs. CTLD-containing proteins (CTLDcps) were originally classified into seven groups based on their overall domain structure. Analyses of the superfamily representation in several completely sequenced genomes have added 10 new groups to the classification, and shown that it is applicable only to vertebrate CTLDcps; despite the abundance of CTLDcps in the invertebrate genomes studied, the domain architectures of these proteins do not match those of the vertebrate groups. Ca2+-dependent carbohydrate binding is the most common CTLD function in vertebrates, and apparently the ancestral one, as suggested by the many humoral defense CTLDcps characterized in insects and other invertebrates. However, many CTLDs have evolved to specifically recognize protein, lipid and inorganic ligands, including the vertebrate clade-specific snake venoms, and fish antifreeze and bird egg-shell proteins. Recent studies highlight the functional versatility of this protein superfamily and the CTLD scaffold, and suggest further interesting discoveries have yet to be made.

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.

Microarray analysis of selection lines from outbred populations to identify genes involved with nematode parasite resistance in sheep

Gastrointestinal nematodes infect sheep grazing contaminated pastures. Traditionally, these have been controlled with anthelmintic drenching. The selection of animals resistant to nematodes is an alternative to complete reliance on drugs, but the genetic basis of host resistance is poorly understood. Using a 10,204 bovine cDNA microarray, we have examined differences in gene expression between genetically resistant and susceptible lambs previously field challenged with larval nematodes. Northern blot analysis for a selection of genes validated the data obtained from the microarrays. The results identified over one hundred genes that were differentially expressed based on conservative criteria. The microarray results were further analyzed to identify promoter motifs common to the differentially expressed genes. Motifs identified in upregulated gene promoters were primarily restricted to those promoters; however, motifs identified in downregulated gene promoters were also found in the promoters of upregulated genes but not in the promoters of genes whose expression was unaltered. Protein Annotators’ Assistant was used for lexical analysis of the differentially expressed genes, and Gene Ontology was used to look for metabolic and cell signaling pathways associated with parasite resistance. Two pathways represented by genes differentially expressed in resistant animals were those involved with the development of an acquired immune response and those related to the structure of the intestine smooth muscle. Genes involved in these processes appear from our analysis to be key genetic determinants of parasite resistance.

Efficient recognition of protein fold at low sequence identity by conservative application of Psi-BLAST: validation

A substantial fraction of protein sequences derived from genomic analyses is currently classified as representing 'hypothetical proteins of unknown function'. In part, this reflects the limitations of methods for comparison of sequences with very low identity. We evaluated the effectiveness of a Psi-BLAST search strategy to identify proteins of similar fold at low sequence identity. Psi-BLAST searches for structurally characterized low-sequence-identity matches were carried out on a set of over 300 proteins of known structure. Searches were conducted in NCBI's non-redundant database and were limited to three rounds. Some 614 potential homologs with 25% or lower sequence identity to 166 members of the search set were obtained. Disregarding the expect value, level of sequence identity and span of alignment, correspondence of fold between the target and potential homolog was found in more than 95% of the Psi-BLAST matches. Restrictions on expect value or span of alignment improved the false positive rate at the expense of eliminating many true homologs. Approximately three-quarters of the putative homologs obtained by three rounds of Psi-BLAST revealed no significant sequence similarity to the target protein upon direct sequence comparison by BLAST, and therefore could not be found by a conventional search. Although three rounds of Psi-BLAST identified many more homologs than a standard BLAST search, most homologs were undetected. It appears that more than 80% of all homologs to a target protein may be characterized by a lack of significant sequence similarity. We suggest that conservative use of Psi-BLAST has the potential to propose experimentally testable functions for the majority of proteins currently annotated as 'hypothetical proteins of unknown function'.

Theories, mechanisms, and models of alcoholic chronic pancreatitis

Alcoholic chronic pancreatitis is a severe, disabling, chronic inflammatory condition of the pancreas that is seen in fewer than 5% of alcoholics. The severity and unpredictability of this condition has lead to several theories on the mechanism causing chronic pancreatitis based on careful clinical observation. Hypothetical mechanisms were applied to various animal models. Finally, following multiple lines of evidence, there is a convergence of thought and development of some new models that are quite instructive. Taken together, chronic alcohol consumption by rats results in multiple effects on the pancreas that increase the risk of acute pancreatitis, including ongoing acinar cell injury that lowers the threshold for hyperstimulation-induced acute pancreatitis, neurohormonal injury, and adaptation that results in acinar cell hyperstimulation, increased susceptibility to viral mediated acute pancreatitis, and possibly other factors. After acute pancreatitis initiates the inflammatory process, the chronic inflammation and fibrosis of alcoholic chronic pancreatitis are driven by diet, the acinar cell stress response to continued alcohol that may be potentiated by toxic alcohol metabolites, hypoxia, hyperstimulation, and partial duct obstruction; plus the effects of proinflammatory immunocytes and cytokines; and by stellate cell-mediated fibrosis driven by anti-inflammatory cytokines, alcohol, and alcohol metabolites. The factors determining which alcoholic will develop alcoholic chronic pancreatitis likely involve genetic factors, dietary factors, and susceptibility to pancreatic injury through several mechanisms ranging from trauma to gallstones to viruses.

Pathogenesis of chronic pancreatitis: an evidence-based review of past theories and recent developments

In the past several decades, four prominent theories of chronic pancreatitis pathogenesis have emerged: the toxic-metabolic theory, the oxidative stress hypothesis, the stone and duct obstruction theory, and the necrosis-fibrosis hypothesis. Although these traditional theories are formulated based on compelling scientific observations, substantial contradictory data also exist for each. Furthermore, the basic premises of some of these theories are directly contradictory. Because of the recent scientific progress in the underlying genetic, cellular, and molecular pathophysiology, there have been substantial advances in the understanding of chronic pancreatitis pathogenesis. This paper will provide an evidence-based review and critique of the traditional pathogenic theories, followed by a discussion of the new advances in pancreatic fibrogenesis. Moreover, we will discuss plausible pathogenic sequences applied to each of the known etiologies.

Coordinate regulation of PSP/reg and PAP isoforms as a family of secretory stress proteins in an animal model of chronic pancreatitis

BACKGROUND

PSP/reg and PAP are secretory stress proteins (SSP) and may be part of a protective mechanism. They share structural homologies and form insoluble fibrils after tryptic activation. To further explore the regulation of these proteins, we investigated the male WBN/Kob rat, a model of pancreatic inflammatory and fibrotic disease similar to chronic pancreatitis.

MATERIALS AND METHODS

Expression of PSP/reg and PAP I, II and III in the WBN/Kob rat pancreas was evaluated on the mRNA and protein level, by immunohistochemistry and by highly sensitive isoform specific ELISAs.

RESULTS

The SSPs are constitutively secreted, PAP in nanomolar, PSP/reg in micromolar concentrations. Before conventional morphological changes are detectable in the WBN/Kob rat, focally increased expression of secretory stress protein is visible. SSP levels in pancreatic juice of WBN/Kob rats reach peak values 10- to 50-fold higher than in Wistar control rats. The highest expression was localized to acini with inflammatory infiltration.

CONCLUSIONS

There is a tight spatial and temporal association between pre-inflammatory changes or inflammation and SSP-expression. These results support our concept that PSP/reg and PAP are coordinately regulated SSP.

Osteopontin expression in chronic pancreatitis

INTRODUCTION

Chronic pancreatitis (CP) is frequently associated with stone formation within the pancreatic duct system. The mechanism of pancreatic stone formation, however, is still unclear.

AIMS

Osteopontin expression is related to urinary stone formation and several diseases associated with calcification such as atherosclerosis, breast cancer, and meningioma. We therefore hypothesized and studied whether that osteopontin may contribute to the formation of calculi in CP.

METHODOLOGY

Twenty patients with CP who underwent elective surgery were included in the study. As controls, normal pancreas specimens were collected from five additional patients. We used reverse transcription polymerase chain reaction and reverse transcription in situ polymerase chain reaction to evaluate osteopontin mRNA expression and immunohistochemical staining to evaluate osteopontin-producing cells.

RESULTS

No expression of osteopontin was seen in normal pancreas cells. Osteopontin expression was detected in acinar or ductal cells in all 11 cases of chronic calcifying pancreatitis, whereas in 5 of 9 CP cases without pancreatic stones there was no expression of osteopontin in acinar or ductal cells. The data revealed a high incidence of osteopontin expression in chronic calcifying pancreatitis in comparison with its expression in CP without stones (p = 0.0081). Osteopontin mRNA expression was observed in chronic calcifying pancreatitis samples but not in normal pancreas tissues. Signals corresponding to osteopontin mRNA were observed in the cytoplasm of ductal cells and macrophages.

CONCLUSION

These results provide the first evidence that osteopontin may play an important role in stone formation in CP. Better understanding of the pancreatic stone formation process may lead to an effective therapeutic approach to the inhibition of pancreatic calcification associated with CP.

Xanthine oxidase-derived oxygen radicals play significant roles in the development of chronic pancreatitis in WBN/Kob rats

BACKGROUND

Although oxygen-derived free radicals are known to play a role in cell injury and DNA alterations, the role of active oxidants in chronic pancreatitis has not been fully elucidated. Using WBN/Kob rats, which spontaneously develop chronic pancreatitis-like lesions, we investigated whether xanthine oxidase (XOD)-derived oxygen radicals are involved in pancreatic tissue injury.

METHODS

WBN/Kob rats were fed a control or a tungsten diet. The latter depletes XOD activity. Histologic al changes, glutathione (GSH) content and XOD and superoxide dismutase (SOD) activities were determined in pancreatic tissue. Pancreatic 8-hydroxy-deoxyguanosine (8-OH-dG) levels and lithostathine mRNA were also examined.

RESULTS

In WBN/Kob rats, parenchymal destruction and fibrosis developed at approximately 12 weeks of age and progressed with each month. The activity of XOD was significantly higher in the early period (8-12 weeks), whereas the levels of GSH and SOD decreased after 16 weeks. Levels of 8-OH-dG in WBN/Kob rats were significantly elevated at 16 weeks. Lithostathine mRNA levels started to increase at 8 weeks, but were suppressed at 16 weeks. The tungsten diet significantly attenuated the histological changes in WBN/Kob rats. The increase in pancreatic XOD activity and 8-OH-dG content in WBN/Kob rats was significantly inhibited by the tungsten diet and lithostathine mRNA levels remained high at 16 weeks.

CONCLUSION

These results suggest that oxygen radicals generated by XOD play an important role in oxidative DNA damage and the development of chronic pancreatic injury.

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.

Protein determination by high-performance gel-permeation chromatography: applications to human pancreatic juice, human bile and tissue homogenate

A high-performance gel-permeation chromatography (HPGPC) method to determine the proteins of human pancreatic juice, bile, and tissue homogenate has been developed. A diol-type silica gel column (35 x 8 mm I.D., 5 nm average pore diameter) was used under a column temperature of 8 degrees C. The eluent was acidic phosphate buffer with a high concentration of sodium chloride, nonionic detergent of polyoxyethylene (20) cetyl ether (Brij 58), glycerol and 2-propanol. The UV wavelength used for the protein detection was 210 nm. Analytical time was within 3.5 min. Good correlation coefficients were obtained with this HPLC method at a column temperature of 8 degrees C and a spectrophotometric bicinchoninic acid (BCA) method. A photometric pyrogallol-red molybdate complex method was found to correlate well with this HPLC method and with the BCA method only for tissue homogenate. Since this HPGPC protein assay method is simple, convenient, rapid, reproducible, and reliable, it is expected to be generally applicable to clinical and also to biochemical research.

Pathogenesis of alcohol-induced chronic pancreatitis: facts, perceptions, and misperceptions

The pathogenesis of chronic pancreatitis secondary to chronic alcoholism is not fully understood. A major hurdle in the understanding of the pathogenesis is the inability to study early lesions of the pancreas and the sequential changes. Facts are few; observations are many. Each new hypothesis argues against all previous hypotheses; however, clinical chronic pancreatitis is initiated by one or more of the mechanisms. Good experimental models for alcoholic pancreatitis are not available, limiting the ability to study the pathogenesis. Additional studies on genetic markers and immunologic mechanisms might explain acinar cell injury, which seems to be the earliest lesion in most, if not all, types of chronic pancreatitis. Opie's common channel and obstruction regurgitation theories seem unrelated to chronic pancreatitis. Although biochemical changes of the pancreatic secretion in alcoholic patients promote protein-plug formation, evidence is too weak to consider protein plug as the earliest change. The theory of necrosis of the acinar cell by some unknown mechanism, subsequently leading to fibrosis, is gaining support; however, it is clear that the pathogenesis of alcoholic pancreatitis is not yet fully understood.

Diabetes and tumor formation in transgenic mice expressing Reg I

To examine the effect of overexpressed regenerating gene (Reg) I on pancreatic beta-cells, we generated transgenic mice expressing Reg I in islets (Reg-Tg mice). Three lines of Reg-Tg mice were established. In line-1 Reg-Tg mice, the expression level of Reg I mRNA in islets was 7 times higher than those in lines 2 and 3 of Reg-Tg mice, and line 1 mice developed diabetes by apoptosis of beta-cells, as well as various malignant tumors. In addition to the decrease in beta-cells, compensatory islet regeneration and proliferation of ductal epithelial cells were observed in line-1 Reg-Tg mice. Because Reg I protein was secreted primarily into pancreatic ducts from acinar cells, it may primarily stimulate the proliferation of ductal epithelial cells, and not beta-cells, and their differentiation into islets. Moreover, the tumor-promoting activity of Reg I protein should be considered for its possible clinical applications.

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.

Mechanism of calcite crystal growth inhibition by the N-terminal undecapeptide of lithostathine

Pancreatic juice is supersaturated with calcium carbonate. Calcite crystals therefore may occur, obstruct pancreatic ducts, and finally cause a lithiasis. Human lithostathine, a protein synthesized by the pancreas, inhibits the growth of calcite crystals by inducing a habit modification: the rhombohedral (10 14) usual habit is transformed into a needle-like habit through the (11 0) crystal form. A similar observation was made with the N-terminal undecapeptide (pE(1)R(11)) of lithostathine. We therefore aimed at discovering how peptides inhibit calcium salt crystal growth. We solved the complete x-ray structure of lithostathine, including the flexible N-terminal domain, at 1.3 A. Docking studies of pE(1)R(11) with the (10 14) and (11 0) faces through molecular dynamics simulation resulted in three successive steps. First, the undecapeptide progressively unfolded as it approached the calcite surface. Second, mobile lateral chains of amino acids made hydrogen bonds with the calcite surface. Last, electrostatic bonds between calcium ions and peptide bonds stabilized and anchored pE(1)R(11) on the crystal surface. pE(1)R(11)-calcite interaction was stronger with the (11 0) face than with the (10 14) face, confirming earlier experimental observations. Energy contributions showed that the peptide backbone governed the binding more than did the lateral chains. The ability of peptides to inhibit crystal growth is therefore essentially based on backbone flexibility.

C-type lectin-like domains

Carbohydrate-recognition domains of C-type (Ca2+-dependent) animal lectins serve as prototypes for an important family of protein modules. Only some domains in this family bind Ca2+ or sugars. A comparison of recent structures of C-type lectin-like domains reveals diversity in the modular fold, particularly in the region associated with Ca2+ and sugar binding. Some of this diversity reflects the changes that occur during normal physiological functioning of the domains. C-type lectin-like domains associate with each other through several different surfaces to form dimers and trimers, from which ligand-binding sites project in a variety of different orientations.