Effect of reg protein on rat pancreatic ductal cells

Frederick Banting's observations leading to the potential for islet neogenesis without transplantation

On 31 October 1920, Sir Frederick Banting, while preparing for a medical student lecture on diabetes, a topic that he knew little about, learned how pancreatic stones resulted in the formation of new islets of Langerhans. He then scribbled down a potential research study of tying off the ducts of the pancreas and collecting the secretions to improve diabetes. These secretions became known as insulin. A century later, 60 different oral medications and 20 different insulins are available for the treatment of diabetes, yet none stimulate new islet formation. One hundred years later, after the discovery of insulin, more than a dozen research teams from around the world have demonstrated that similar studies to Banting's pancreatic ligation studies have resulted in upregulation of the REG gene. There are now more than 200 publications on the role of Reg gene proteins and shorter Reg peptides in initiating new islet formation islet from exocrine pancreatic ducts and protecting against inflammation to islets resulting in islet death. Human data through Phase 2b in both type 1 and 2 diabetes patients with diabetes for an average of 20 years have demonstrated that the use of a shorter bioactive Reg peptide can generate new endogenous insulin production, resulting in significant reductions in hemoglobin A1C and increases in stimulated C-peptide. The observations of Frederick Banting, one century ago, may now lead to the generation of therapeutics that form new islets without the need for transplantation.

Okamoto model for necrosis and its expansions, CD38-cyclic ADP-ribose signal system for intracellular Ca2+ mobilization and Reg (Regenerating gene protein)-Reg receptor system for cell regeneration

In pancreatic islet cell culture models and animal models, we studied the molecular mechanisms involved in the development of insulin-dependent diabetes. The diabetogenic agents, alloxan and streptozotocin, caused DNA strand breaks, which in turn activated poly(ADP-ribose) polymerase/synthetase (PARP) to deplete NAD+, thereby inhibiting islet β-cell functions such as proinsulin synthesis and ultimately leading to β-cell necrosis. Radical scavengers protected against the formation of DNA strand breaks and inhibition of proinsulin synthesis. Inhibitors of PARP prevented the NAD+ depletion, inhibition of proinsulin synthesis and β-cell death. These findings led to the proposed unifying concept for β-cell damage and its prevention (the Okamoto model). The model met one proof with PARP knockout animals and was further extended by the discovery of cyclic ADP-ribose as the second messenger for Ca2+ mobilization in glucose-induced insulin secretion and by the identification of Reg (Regenerating gene) for β-cell regeneration. Physiological and pathological events found in pancreatic β-cells have been observed in other cells and tissues.

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.

Effect of Nitric Oxide Synthesis Blockade on the Morphology of Langerhans Islets in August and Wistar Rats with Acute Alloxan Diabetes

Alloxan diabetes was modeled in August rats with high activity of the NO system and in Wistar rats, and the effects of NO system blockade (by a course treatment with L-NNA) on Langerhans islet β cells were studied in 15 days. The toxic effects of diabetes on the rat β cells and islets were similar: the content of active β cells in the islets decreased to 15-20%, the number of islets to 24-29% of control. A course of L-NNA reduced the β cell and islet death, in August cells greater than in Wistar: the number of islets in August rats was restored to 81%, in Wistar rats to 60% of initial level; the activity of β cells remained at the control level in the former and 2-fold lower than in the control in the latter. It seems that a less pronounced protective effect of L-NNA in Wistar rats was explained by excessive reduction of NO level essential for β cell regeneration.

Distinctions between the islets of mice and men: implications for new therapies for type 1 and 2 diabetes

OBJECTIVE

To elucidate why diabetes is so difficult to treat despite the present tools and pharmacologic armamentarium and to provide insights into emerging therapies by describing human and rodent data that demonstrates the ability to transform progenitor cells within the adult pancreas into new islets.

METHODS

A literature review focused on the distinctions between human and rodent islets.

RESULTS

We are beginning to elucidate important differences between the architecture and composition of the islets of Langerhans in humans and rodents. In contrast to rodent islets, human islets are more heterogeneous in cellular composition and have more prominent intra-islet vascularity, with smooth muscle-containing blood vessels that are not present in rodent islets. Some studies report that more than 70% of human beta cells have direct physical contact with other cell types, whereas others describe that smaller human islets possess features more typical of rodents, while larger islets exhibit greater vascularity and a cellular distribution distinct from centrally clustered beta cells surrounded by a mantle of alpha and delta cells found in rodents.

CONCLUSIONS

The differences between the islets of mice and men may influence why treatments hailed as reversing diabetes among rodents have not been successfully translated into humans. Increased understanding of the complexities within the human islet may yield unique insights into reversing diabetes in humans.

INS-1 cells undergoing caspase-dependent apoptosis enhance the regenerative capacity of neighboring cells

OBJECTIVE

In diabetes, β-cell mass is not static but in a constant process of cell death and renewal. Inactivating mutations in transcription factor 1 (tcf-1)/hepatocyte nuclear factor1a (hnf1a) result in decreased β-cell mass and HNF1A-maturity onset diabetes of the young (HNF1A-MODY). Here, we investigated the effect of a dominant-negative HNF1A mutant (DN-HNF1A) induced apoptosis on the regenerative capacity of INS-1 cells.

RESEARCH DESIGN AND METHODS

DN-HNF1A was expressed in INS-1 cells using a reverse tetracycline-dependent transactivator system. Gene(s)/protein(s) involved in β-cell regeneration were investigated by real-time quantitative RT-PCR, Western blotting, and immunohistochemistry. Pancreatic stone protein/regenerating protein (PSP/reg) serum levels in human subjects were detected by enzyme-linked immunosorbent assay.

RESULTS

We detected a prominent induction of PSP/reg at the gene and protein level during DN-HNF1A-induced apoptosis. Elevated PSP/reg levels were also detected in islets of transgenic HNF1A-MODY mice and in the serum of HNF1A-MODY patients. The induction of PSP/reg was glucose dependent and mediated by caspase activation during apoptosis. Interestingly, the supernatant from DN-HNF1A-expressing cells, but not DN-HNF1A-expressing cells treated with zVAD.fmk, was sufficient to induce PSP/reg gene expression and increase cell proliferation in naïve, untreated INS-1 cells. Further experiments demonstrated that annexin-V-positive microparticles originating from apoptosing INS-1 cells mediated the induction of PSP/reg. Treatment with recombinant PSP/reg reversed the phenotype of DN-HNF1A-induced cells by stimulating cell proliferation and increasing insulin gene expression.

CONCLUSIONS

Our results suggest that apoptosing INS-1 cells shed microparticles that may stimulate PSP/reg induction in neighboring cells, a mechanism that may facilitate the recovery of β-cell mass in HNF1A-MODY.

Distinctions between islet neogenesis and β-cell replication: implications for reversal of Type 1 and 2 diabetes

The terms "islet" and "β-cell" are often used interchangeably, yet islets are highly complex multicellular organelles that contain the insulin-producing β-cells and four other cells types, all of which play a role in maintaining glucose homeostasis within a very narrow range. Although the formation of new islets in adults is rare, occurring primarily in response to pancreatic injury and major stress to the pancreas, β-cell replication from existing cells occurs throughout adulthood. An understanding of the regulatory factors controlling pancreatic development has more clearly defined the differences between new islet formation from progenitor cells located throughout the adult pancreas and β-cell replication occurring within existing islets. The present review sets forth to more clearly distinguish the differences between the postnatal pathways of islet neogenesis and β-cell replication with a discussion of the potential implications for reversal of Type 1 and 2 diabetic patients using islet neogenesis agents that are now in development. For Type 1 diabetic patients, an immune tolerance agent in conjunction with an islet neogenesis agent may allow achievement of adequate islet mass, perhaps with subsequent potential to withdraw medications. For Type 2 diabetic patients, lifestyle changes and/or medications may sustain the production of new islets and limit the accelerated β-cell apoptosis characteristic of the condition.

Pancreatic regenerating gene I and acinar cell differentiation: influence on cellular lineage

OBJECTIVES

Pancreatic regenerating gene I (reg I) has been implicated in cellular differentiation. Acinar cells can transdifferentiate into other pancreatic-derived cells, and we postulated that changes in intracellular levels of reg I would affect the state of differentiation.

METHODS

We transfected AR42J cells with a plasmid containing the entire coding sequence of reg I and isolated clones with complementary DNA in sense (SS) or antisense (AS) orientation. Levels of messenger RNA (mRNA) and protein expression were examined by Western blotting and real-time polymerase chain reaction.

RESULTS

Expression of reg I was confirmed in SS or AS clones. AR42J transfected with SS demonstrated more acinarlike phenotype, whereas those transfected with AS showed a less differentiated state. Specifically, amylase mRNA and protein levels increased in SS cells, whereas AS cells showed increased pancreatic and duodenal homeobox 1 (Pdx1) and insulin mRNAs and cytokeratin protein. Conversely, cytokeratin and Pdx1 were depressed in SS cells.

CONCLUSIONS

These data demonstrate that in acinar cells, reg I overexpression is linked to acinar cell differentiation, whereas inhibition of reg I leads to beta cell and possibly ductal phenotype. Reg I expression in acinar cells is important in maintaining pancreatic cell lineage, and when decreased, cells can dedifferentiate and move toward becoming other pancreatic cells.

Pancreatic regenerating protein I in chronic pancreatitis and aging: implications for new therapeutic approaches to diabetes

OBJECTIVES

We investigated the relationship of pancreatic regenerating protein (reg) in models of acinar cell atrophy and aging, and the effect of reg I protein replacement on glucose tolerance.

METHODS

Rats underwent pancreatic duct ligation (PDL) and were followed through 12 months. Aging rats were studied at 12 and 20 months. Intraperitoneal glucose tolerance tests (IPGTTs) were performed, pancreatic reg I, reg I receptor, insulin gene expression, and reg I protein levels were measured. Pancreatic duct ligation and aged animals were treated with exogenous reg I protein and assessed for glucose metabolism.

RESULTS

After PDL, chronic atrophic pancreatitis developed, with a progressive loss of acinar cells and pancreatic reg I. During aging, a similar depression of reg I gene expression was also noted. The reg I levels correlated with pancreatic insulin levels. Twelve months after PDL, IPGTT results were abnormal, which were significantly improved by administration of reg I protein. Aged animals demonstrated depressed IPGTT, which marginally improved after reg I administration. Anti-reg antibody administration to young rats depressed IPGTT to elderly levels.

CONCLUSIONS

Depletion of the acinar product reg I is associated with the pathogenesis of impaired glucose tolerance of pancreatitis-associated diabetes and aging, and replacement therapy could be useful in these patients. Reg I is an acinar cell product, which affects islet function.

Beneficial effects of L-arginine nitric oxide-producing pathway in rats treated with alloxan

In an attempt to elucidate molecular mechanisms and factors involved in beta cell regeneration, we evaluated a possible role of the L-arginine-nitric oxide (NO)-producing pathway in alloxan-induced diabetes mellitus. Diabetes was induced in male Mill Hill rats with a single alloxan dose (120 mg kg(-1)). Both non-diabetic and diabetic groups were additionally separated into three subgroups: (i) receiving L-arginine . HCl (2.25%), (ii) receiving L-NAME . HCl (0.01%) for 12 days as drinking liquids, and (iii) control. Treatment of diabetic animals started after diabetes induction (glucose level > or = 12 mmol l(-1)). We found that disturbed glucose homeostasis, i.e. blood insulin and glucose levels in diabetic rats was restored after L-arginine treatment. Immunohistochemical findings revealed that L-arginine had a favourable effect on beta cell neogenesis, i.e. it increased the area of insulin-immunopositive cells. Moreover, confocal microscopy showed colocalization of insulin and pancreas duodenum homeobox-1 (PDX-1) in both endocrine and exocrine pancreas. This increase in insulin-expressing cells was accompanied by increased cell proliferation (observed by proliferating cell nuclear antigen-PCNA immunopositivity) which occurred in a regulated manner since it was associated with increased apoptosis (detected by the TUNEL method). Furthermore, L-arginine enhanced both nuclear factor-kB (NF-kB) and neuronal nitric oxide synthase (nNOS) immunopositivities. The effect of L-arginine on antioxidative defence was observed especially in restoring to control level the diabetes-induced increase in glutathione peroxidase activity. In contrast to L-arginine, diabetic pancreas was not affected by L-NAME supplementation. In conclusion, the results suggest beneficial L-arginine effects on alloxan-induced diabetes resulting from the stimulation of beta cell neogenesis, including complex mechanisms of transcriptional and redox regulation.

Gene therapy for type 1 diabetes

The most intensively studied autoimmune disorder, type 1 diabetes mellitus (DM1), has attracted perhaps the greatest interest for gene-based therapeutic and prophylactic interventions. The final clinical manifestation of this immunologically and genetically complex disease, the absence of insulin, is the major starting point for almost all the gene therapy modalities attempted to date. Insulin replacement by transplantation of islets of Langerhans or surrogate beta cells is the obvious choice, but the allogeneic nature of the transplants activates potent antidonor immunoreactivity necessitating gene and cell-based immunosuppressive strategies as an alternative to the toxic pharmacologic immunosuppressives indicated for classic solid organ transplants. Accumulating knowledge of the cellular mechanisms involved in onset, however, have yielded promising tolerance induction prophylactic approaches using genes and cells. Despite the early successes in a number of animal models, the true test of efficacy in humans remains to be demonstrated.

PAP IB, a new member of the Reg gene family: cloning, expression, structural properties, and evolution by gene duplication

Reg proteins are expressed in various organs and are involved in cancers and neurodegenerative diseases. They display a typical C-type lectin-like domain but possess additional highly conserved amino acids. By studying human databases and Expressed Sequence Tags library, we identified a new member called PAP IB. Using probabilistic approaches, we established a phylogenetic tree of eighteen Reg proteins. The dendogram showed that they constitute a superfamily composed of three distinct families (FI to FIII) of paralogues that resulted from duplication. We therefore focused on two proteins, REG Ialpha and PAP IB, belonging to the more closely related FI and FII families, respectively. REG Ialpha and PAP IB share 50% sequence identity. After cloning PAP IB, however, we found that it was expressed almost only in pancreas, unlike REG Ialpha, whose expression is ubiquitous. In addition, by building a model of the structure of PAP IB based on the X-ray structure of REG Ialpha, we observed that the two proteins displayed distinctive surface charge distribution, which may lead to different ligands binding. In spite of their common fold that should result in closely related functions, REG Ialpha and PAP IB are a good example of duplication and divergence, probably with the acquisition of new functions, thus participating in the evolution of the protein repertoire.

Regeneration of β-cells and neogenesis from small ducts or acinar cells promote recovery of endocrine pancreatic function in alloxan-treated rats

BACKGROUND

We previously showed by using biochemical parameters that male Sprague-Dawley rats receiving a single intraperitoneal (i.p.) administration of alloxan (120 mg/kg body weight) with no further treatment recovered endocrine pancreatic function after 12 days.

METHODS

Male Sprague-Dawley rats received an i.p. injection of alloxan (120 mg/kg body wt), were killed at 3, 6, 9, or 12 days (n=7), and their capacity to recover endocrine function was evaluated by means of a) biochemical parameters, which included glucose, triglyceride, and total cholesterol measurements and b) nuclear incorporation of 5'-bromodeoxyuridine (BrdU) by beta and acinar cells as well as presence of neogenesis from either ductal or acinar cells using double-staining BrdU-insulin immunohistochemical technique.

RESULTS

Three days after receiving a single i.p. administration of alloxan, rats showed increase in serum glucose, triglyceride, and total cholesterol concentrations, reaching levels of 542.4+/-63.1, 907.6+/-154.9, and 106.0+/-2.7 mg/dL (mean+/-standard deviation [SD]), respectively. At this time, increase in beta-cell replication was also observed, although this reached maximum by day 6 (p <0.001). Replication was also present in acinar cells, but these cells showed their maximum at day 3 (p <0.001) and subsequently decreased, as did beta-cells, almost steadily to normal values by day 12. Neogenesis of beta-cells was observed mainly as transdifferentiation from acinar cells at day 3 and from ductal cells at day 6, after which it tended to be normal.

CONCLUSIONS

Male Sprague-Dawley rats receiving a single i.p. alloxan dose tended to normalize their endocrine function by day 12 after alloxan administration. This process included both regeneration and neogenesis of pancreatic beta-cells from either ductal or acinar cells.

Recovery of the endogenous beta cell function in the NOD model of autoimmune diabetes

In light of accumulating evidence that the endocrine pancreas has regenerative properties and that hematopoietic chimerism can abrogate destruction of beta cells in autoimmune diabetes, we addressed the question of whether recovery of physiologically adequate endogenous insulin regulation could be achieved in the nonobese diabetic (NOD) mice rendered allogeneic chimerae. Allogeneic bone marrow (BM) was transplanted into NOD mice at the preclinical and overtly clinical stages of the disease using lethal and nonlethal doses of radiation for recipient conditioning. Islets of Langerhans, syngeneic to the BM donors, were transplanted under kidney capsules of the overtly diabetic animals to sustain euglycemia for the time span required for recovery of the endogenous pancreas. Nephrectomies of the graft-bearing organs were performed 14 weeks later to confirm the restoration of endogenous insulin regulation. Reparative processes in the pancreata were assessed histologically and immunohistochemically. The level of chimerism in NOD recipients was evaluated by flow cytometric analysis. We have shown that as low as 1% of initial allogeneic chimerism can reverse the diabetogenic processes in islets of Langerhans in prediabetic NOD mice, and that restoration of endogenous beta cell function to physiologically sufficient levels is achievable even if the allogeneic BM transplantation is performed after the clinical onset of diabetes. If the same pattern of islet regeneration were shown in humans, induction of an autoimmunity-free status by establishment of a low level of chimerism, or other alternative means, might become a new therapy for type 1 diabetes.

RELP, a novel human REG-like protein with up-regulated expression in inflammatory and metaplastic gastrointestinal mucosa

We screened expressed sequence tag databases for genes with up-regulated expression in inflammatory bowel diseases. A gene encoding a regenerating protein (REG)-like protein called RELP was identified and characterized. The relp gene encodes a major transcript of 1518 nucleotides, and two truncated splice variants. Unlike the reg genes, which form a cluster in chromosome 2, relp maps to chromosome 1p12-13.1. The predicted translation product is a 158-amino acid preprotein, showing 43% to 47% similarity to the REG proteins. It contains a 22-amino acid signal peptide, and a conserved calcium-dependent carbohydrate-recognition domain. Complementary DNA for the orthologous mouse gene was also cloned. The RELP protein is constitutively expressed in epithelial neuroendocrine cells of the small intestine and in parietal cells of the gastric mucosa. An up-regulated expression of RELP was seen in epithelial cells of inflammatory mucosa in ulcerative colitis and Crohn's disease, in regenerating epithelial borders of gastric ulcers, and in metaplastic epithelium in the antrum and the esophagus. Our findings suggest that RELP might be involved in inflammatory and metaplastic responses of the gastrointestinal epithelium.

Gene- and cell-based therapeutics for type I diabetes mellitus

Type 1 diabetes mellitus, an autoimmune disorder is an attractive candidate for gene and cell-based therapy. From the use of gene-engineered immune cells to induce hyporesponsiveness to autoantigens to islet and beta cell surrogate transplants expressing immunoregulatory genes to provide a local pocket of immune privilege, these strategies have demonstrated proof of concept to the point where translational studies can be initiated. Nonetheless, along with the proof of concept, a number of important issues have been raised by the choice of vector and expression system as well as the point of intervention; prophylactic or therapeutic. An assessment of the current state of the science and potential leads to the conclusion that some strategies are ready for safety trials while others require varying degrees of technical and conceptual refinement.

Gene and cell therapies for diabetes mellitus: strategies and clinical potential

The last 5 years have witnessed an explosion in the use of genes and cells as biomedicines. While primarily aimed at cancer, gene engineering and cell therapy strategies have additionally been used for Mendelian, neurodegenerative and metabolic disorders. The main focus of gene and cell therapy strategies in metabolism has been diabetes mellitus. This disease is a disorder of glucose homeostasis, either due to the immune-mediated eradication of pancreatic beta cells in the islets of Langerhans (type 1 diabetes) or resulting from insulin resistance and obesity syndromes where the insulin-producing capability of the beta cell is ultimately exhausted in the face of insensitivity to the effects of insulin in the peripheral glucose-utilising tissues (type 2 diabetes). A significant number of animal studies have demonstrated the potential in restoring normoglycaemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of type 1 diabetes or rodent recipients of allogeneic/xenogeneic islet transplants. The achievements of gene and cell therapy in type 2 diabetes are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease. Here we present an overview of the current status of gene and cell therapy for type 1 and 2 diabetes and we propose potential therapeutic options that could be clinically useful. For type 1 diabetes, transplantation of islets engineered to evade or suppress the recipient immune response is the most readily-available technology today. A number of gene delivery vectors encoding proteins that impair a variety of immune cells have already been examined and proven versatile. More challenging but, nonetheless, just over the horizon are attempts to promote tolerance to islet allografts. Type 2 diabetes will likely require a better understanding of the processes that determine insulin sensitivity in the periphery. Targeting tissues such as muscle and fat with vectors encoding genes whose products promote insulin sensitivity and glucose uptake is an approach that does not carry with it the side-effects often associated with pharmacologic agents currently in use. In the end, progress in vector design, elucidation of antigen-specific immunity and insulin sensitivity will provide the framework for gene drug use in the treatment of type 1 and type 2 diabetes.

Models of pancreatic regeneration in diabetes

The number of functionally intact beta cells in the islet organ is of decisive importance for the development, course and outcome of diabetes mellitus. Generally speaking, the total beta-cell mass reflects the balance between the renewal and loss of these cells. Assuming that virtually all forms of diabetes mellitus are characterized by an insufficient extent of beta cell replication needed to compensate for the loss or dysfunction of beta cells occurring in diabetes, elucidation of the regenerating potential in experimentally induced diabetic animal would be of interest as alternative therapy for diabetes. Here we have attempted to take a stock of different models developed in the last few years, which permit investigation of regenerative process from various angles. The review focuses on factors responsible for induction of islet neogenesis in the diabetic pancreas, ultimately leading to pancreatic regeneration and possible reversal of diabetes. On the whole the study of these models will enhance our understanding of regenerative potential of diabetic pancreas and factors necessary to trigger stem cells' population within the pancreas so as to suggest an alternative therapeutic approach for the control and/or cure of diabetes.

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.

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 Reg family protein is overexpressed in islets from a patient with new-onset type 1 diabetes and acts as T-cell autoantigen in NOD mice

Genes overexpressed in pancreatic islets of patients with new-onset type 1 diabetes are potential candidates for novel disease-related autoantigens. RT-PCR-based subtractive hybridization was used on islets from a patient who died at the onset of type 1 diabetes, and it identified a type 1 diabetes-related cDNA encoding hepatocarcinoma-intestine-pancreas/pancreatic-associated protein (HIP/PAP). This protein belongs to the family of Reg proteins implicated in islet regeneration; its gene contains a putative interleukin-6 (IL-6) response element. Islets from healthy cadaveric human donors released HIP/PAP protein into the culture medium, and this release was enhanced by the addition of IL-6. The expression pattern of mouse homologues of HIP/PAP was determined in pancreata of prediabetic and diabetic NOD mice. Both groups showed positive immunostaining for HIP/PAP in islets and ductal epithelium. To test whether HIP/PAP is a target of islet-directed autoimmunity, we measured splenic T-cell responses against HIP/PAP in NOD mice. Spontaneous proliferation was detected after 4 weeks. Lymphocytes from islet infiltrates and pancreatic lymph nodes from 7- to 10-week-old NOD mice were used to establish an HIP/PAP-specific I-A(g7)-restricted T-cell line, termed WY1, that also responded to mouse islets. WY1 cells homed to islets of NOD-SCID mice and adoptively transferred disease when coinjected with purified CD8(+) cells from diabetic NOD mice. Our conclusion was that differential cloning of Reg from islets of a type 1 diabetic patient and the response of Reg to the cytokine IL-6 suggests that HIP/PAP becomes overexpressed in human diabetic islets because of the local inflammatory response. HIP/PAP acts as a T-cell autoantigen in NOD mice. Therefore, autoimmunity to HIP/PAP might create a vicious cycle, accelerating the immune process leading to diabetes.

Localization of Reg receptor in rat fundic mucosa

Reg protein has a trophic effect on gastric mucosal cells and pancreatic islets. Recently, the Reg receptor (Reg-R) has been cloned, and Reg-Reg-R interaction has been reported in the pancreas. The aim of this study was to investigate the localization of Reg-R in rat fundic mucosa. Gene expression of Reg-R was investigated with Northern blot analysis, laser capture microdissection coupled with reverse transcription-polymerase chain reaction, and in situ hybridization in the fundic mucosa, and the types of cells expressing this gene were determined. Reg-R mRNA expression was detected mainly in chief cells and parietal cells of the deep layers and faintly in surface epithelial cells and mucous neck cells of the proliferating zone. Our results suggest that regenerating protein may act not only as a regulator of gastric epithelial cell proliferation but also as a modifier of other multiple physiologic functions.

Upregulation of Reg 1alpha and GW112 in the epithelium of inflamed colonic mucosa

BACKGROUND AND AIMS

Colonic epithelium is involved in the regulation of intestinal function and mucosal immune responses, and its function is altered in inflammatory bowel disease (IBD). However, a comprehensive analysis of the genetic alterations in inflamed colonic epithelium is not available at present. The aim of our study was to detect genes that are preferentially expressed in inflamed colonic epithelia and clarify the biochemical responses of epithelial cells in inflamed colonic mucosa.

METHODS

cDNA representation difference analysis was used to identify candidate genes selectively expressed in inflamed colonic epithelia. Selective expression of these genes in the epithelium of inflamed colonic mucosa, including IBD and non-IBD tissues, was examined by real time polymerase chain reaction and in situ hybridisation. The effect of cell confluence and inflammatory mediators on Reg 1alpha gene expression was examined using a colon cancer cell line (HT29).

RESULTS

We identified seven candidate genes that were presumed to be upregulated in the inflamed colonic epithelium. Of these, Reg 1alpha and GW112 were the dominant species and expression of these genes was confined to the crypt epithelium. In vitro studies using a colonic epithelial cell line suggested that cell confluence regulates Reg 1alpha gene expression.

CONCLUSIONS

Selective expression of Reg 1alpha and GW112 genes in the crypt epithelium of inflamed colonic mucosa suggests the important regulatory functions of these genes.

Isolation and characterization of a cDNA encoding a novel member of the human regenerating protein family: Reg IV

Human Reg and Reg-related genes constitute a multi-gene family belonging to the calcium (C-type) dependent lectin superfamily. Regenerating gene family members are expressed in the proximal gastrointestinal (GI) tract and ectopically at other sites in the setting of tissue injury. By high-throughput sequence analysis of a large inflammatory bowel disease library, two cDNAs have been isolated which encode a novel member of this multigene family. Based on primary sequence homology, tissue expression profiles, and shared exon-intron junction genomic organization, we assign this gene to the regenerating gene family. Specific protein structural differences suggest that the current three regenerating gene subtypes should be expanded to four. We demonstrate that Reg IV has a highly restricted tissue expression pattern, with prominent expression in the gastrointestinal tract. Reg IV mRNA expression is significantly up-regulated by mucosal injury from active Crohn's disease or ulcerative colitis.

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.

Identification of a receptor for reg (regenerating gene) protein, a pancreatic beta-cell regeneration factor

Reg (regenerating gene) was isolated as a gene specifically expressed in regenerating islets (Terazono, K., Yamamoto, H., Takasawa, S., Shiga, K., Yonemura, Y., Tochino, Y., and Okamoto, H. (1988) J. Biol. Chem. 263, 2111-2114). Rat and human Reg gene products, Reg/REG proteins, have been demonstrated to stimulate islet beta-cell growth in vitro and in vivo and to ameliorate experimental diabetes. In the present study, we isolated a cDNA for the Reg protein receptor from a rat islet cDNA library. The cDNA encoded a cell surface 919-amino acid protein, and the cells into which the cDNA had been introduced bound Reg protein with high affinity. When the cDNA was introduced into RINm5F cells, a pancreatic beta-cell line that shows Reg-dependent growth, the transformants exhibited significant increases in the incorporation of 5'-bromo-2'-deoxyuridine as well as in the cell numbers in response to Reg protein. A homology search revealed that the cDNA is a homologue to a human multiple exostoses-like gene, the function of which has hitherto been unknown. These results strongly suggest that the receptor is encoded by the exostoses-like gene and mediates a growth signal of Reg protein for beta-cell regeneration.

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.