Cyclin D1 activation through ATF-2 in Reg-induced pancreatic beta-cell regeneration

Controversial Roles of Regenerating Family Proteins in Tissue Repair and Tumor Development

Background: Over the past 40 years since the discovery of regenerating family proteins (Reg proteins), numerous studies have highlighted their biological functions in promoting cell proliferation and resisting cell apoptosis, particularly in the regeneration and repair of pancreatic islets and exocrine glands. Successively, short peptides derived from Reg3δ and Reg3α have been employed in clinical trials, showing favorable therapeutic effects in patients with type I and type II diabetes. However, continued reports have been limited, presumably attributed to the potential side effects. Methods: This review summarizes extensive research on Reg proteins over the past decade, combined with our own related studies, proposing that Reg proteins exhibit dimorphic effects. Results: The activity of Reg proteins is not as simplistic as previously perceived but shows auto-immunogenicity depending on different pathophysiological microenvironments. The immunogenicity of Reg proteins could recruit immune cells leading to an anti-tumor effect. Such functional diversity is correlated with their structural characteristics: the N-terminal region contributes to autoantigenicity, while the C-type lectin fragment near the C-terminal determines the trophic action. It should be noted that B-cell masking antigens might also reside within the C-type lectin domain. Conclusions: Reg proteins have dual functional roles under various physiological and pathological conditions. These theoretical foundations facilitate the subsequent development of diagnostic reagents and therapeutic drugs targeting Reg proteins.

N6-methyladenosine modification of REG1α facilitates colorectal cancer progression via β-catenin/MYC/LDHA axis mediated glycolytic reprogramming

Aerobic glycolysis has been considered as a hallmark of colorectal cancer (CRC). However, the potential functional regulators of glycolysis in CRC remains to be elucidated. In the current study, we found that Regenerating islet-derived protein 1-alpha (REG1α) was significantly increased in both CRC tissues and serum, and positively associated with CRC patients' lymph node metastasis, advanced tumor stage, and unfavorable prognosis. Ectopic expression of REG1α contributed to various tumorigenic properties, including cell proliferation, cell cycle, migration, invasion, and glycolysis. In contrast, REG1α deficiency in CRC cells attenuated malignant properties and glucose metabolism. Mechanically, REG1α promoted CRC proliferation and metastasis via β-catenin/MYC axis-mediated glycolysis upregulation. Moreover, the malignant behaviors governed by REG1α could be effectively abolished by silencing of Wnt/β-catenin/MYC axis or glycolysis process using specific inhibitors. Besides, REG1α expression was mediated by METTL3 in an m6A-dependent manner. Overall, our work defines a novel regulatory model of the METTL3/REG1α/β-catenin/MYC axis in CRC, which indicates that REG1α could function as a novel biomarker and a potential therapeutic target for patients with CRC.

Notch signaling-induced cyclin d1 in diabetes ameliorating effects of the isolated polysaccharide from Rosa canina: In vitro and in vivo studies

Notch signaling has a role in the expansion of the pancreas and the pathogenesis of diabetes. Modulation of Notch signaling by natural products seems to pave the way for treating diabetes. This research aimed to scrutinize the involvement of the Notch cascade in the diabetes-ameliorating effects of an isolated polysaccharide from Rosa canina. The isolated polysaccharide was characterized using Fourier transform infrared, nuclear magnetic resonance, high-performance gel-permeation chromatography, and liquid chromatography with tandem mass spectrometry techniques. Rat pancreatic β cells and STZ-induced diabetic rats were treated with the isolated polysaccharide. MTT assay, cell cycle analysis, quantative realtime-polymerase chain reaction, immunohistochemistry, and immunoblotting were used to reveal the growth and the expression levels of Notch1, DLL4, Jagged-1, hes1, Ins-1, Pdx-1, and cyclin d1 in treated and untreated pancreatic cells and tissues. The ameliorating effect of the polysaccharide in STZ-treated cells was accomplished by upregulation of cyclin d1 and hes1 as well as cell cycle progression. Notch inhibition by LY-411575 was associated with the downregulation of cyclin d1 which upregulates with polysaccharide treatment. The significant expression of cyclin d1 (90%) and nuclear expression of hes1 in the pancreas of the polysaccharide group were accompanied by improvement of hyperglycemia and associated biochemical factors as well as regeneration of islet cells as compared to untreated diabetic rats. Based on these findings, upregulation of Notch signaling-induced cyclin d1 could be proposed as the underlying diabetes-reducing effects of the isolated polysaccharide derivative implying that cyclin d1 actuation through activation of the Notch-DLL4 circuit may play the causal role in the treatment of diabetes.

Recombinant Reg3α Prevents Islet β-Cell Apoptosis and Promotes β-Cell Regeneration

Progressive loss and dysfunction of islet β-cells has not yet been solved in the treatment of diabetes. Regenerating protein (Reg) has been identified as a trophic factor which is demonstrated to be associated with pancreatic tissue regeneration. We previously produced recombinant Reg3α protein (rReg3α) and proved that it protects against acute pancreatitis in mice. Whether rReg3α protects islet β-cells in diabetes has been elusive. In the present study, rReg3α stimulated MIN6 cell proliferation and resisted STZ-caused cell death. The protective effect of rReg3α was also found in mouse primary islets. In BALB/c mice, rReg3α administration largely alleviated STZ-induced diabetes by the preservation of β-cell mass. The protective mechanism could be attributed to Akt/Bcl-2/-xL activation and GRP78 upregulation. Scattered insulin-expressing cells and clusters with small size, low insulin density, and exocrine distribution were observed and considered to be neogenic. In isolated acinar cells with wheat germ agglutinin (WGA) labeling, rReg3α treatment generated insulin-producing cells through Stat3/Ngn3 signaling, but these cells were not fully functional in response to glucose stimulation. Our results demonstrated that rReg3α resists STZ-induced β-cell death and promotes β-cell regeneration. rReg3α could serve as a potential drug for β-cell maintenance in anti-diabetic treatment.

Upregulation of REG IV gene in human intestinal epithelial cells by lipopolysaccharide via downregulation of microRNA-24

The pathophysiology of inflammatory bowel diseases (IBD) reflects a balance between mucosal injury and reparative mechanisms. Some regenerating gene (Reg) family members (REG Iα, REG Iβ and REG IV) are expressed in Crohn's disease (CD) and ulcerative colitis (UC) and involved as proliferative mucosal factors in IBD. We revealed that REG Iα and REG Iβ were induced in cell culture system by IL‐6/IL‐22. Although REG IV was upregulated in IBD biopsy samples, the upregulation of REG IV was not at all induced in cell culture by autoimmune‐related cytokines such as IL‐6, IL‐22 and TNFα. Here, we analysed REG IV expression in LS‐174 T and HT‐29 human intestinal epithelial cells by real‐time RT–PCR and elisa. REG IV expression was induced by lipopolysaccharide (LPS). However, LPS did not activate REG IV promoter activity. As the LPS‐induced upregulation of REG IV was considered to be regulated post‐transcriptionally, we searched targeted microRNA (miR), which revealed that REG IV mRNA has a potential target sequence for miR‐24. We measured the miR‐24 level of LPS‐treated cells and found that the level was significantly lower. The LPS‐induced increase of REG IV mRNA was abolished by the introduction of miR‐24 mimic but not by non‐specific control RNA.

Duodenal Anaerobutyricum soehngenii infusion stimulates GLP-1 production, ameliorates glycaemic control and beneficially shapes the duodenal transcriptome in metabolic syndrome subjects: a randomised double-blind placebo-controlled cross-over study

OBJECTIVE

Although gut dysbiosis is increasingly recognised as a pathophysiological component of metabolic syndrome (MetS), the role and mode of action of specific gut microbes in metabolic health remain elusive. Previously, we identified the commensal butyrogenic Anaerobutyricum soehngenii to be associated with improved insulin sensitivity in subjects with MetS. In this proof-of-concept study, we investigated the potential therapeutic effects of A. soehngenii L2-7 on systemic metabolic responses and duodenal transcriptome profiles in individuals with MetS.

DESIGN

In this randomised double-blind placebo-controlled cross-over study, 12 male subjects with MetS received duodenal infusions of A. soehngenii/ placebo and underwent duodenal biopsies, mixed meal tests (6 hours postinfusion) and 24-hour continuous glucose monitoring.

RESULTS

A. soehngenii treatment provoked a markedly increased postprandial excursion of the insulinotropic hormone glucagon-like peptide 1 (GLP-1) and an elevation of plasma secondary bile acids, which were positively associated with GLP-1 levels. Moreover, A. soehngenii treatment robustly shaped the duodenal expression of 73 genes, with the highest fold induction in the expression of regenerating islet-protein 1B (REG1B)-encoding gene. Strikingly, duodenal REG1B expression positively correlated with GLP-1 levels and negatively correlated with peripheral glucose variability, which was significantly diminished in the 24 hours following A. soehngenii intake. Mechanistically, Reg1B expression is induced upon sensing butyrate or bacterial peptidoglycan. Importantly, A. soehngenii duodenal administration was safe and well tolerated.

CONCLUSIONS

A single dose of A. soehngenii improves peripheral glycaemic control within 24 hours; it specifically stimulates intestinal GLP-1 production and REG1B expression. Further studies are needed to delineate the specific pathways involved in REG1B induction and function in insulin sensitivity.

TRIAL REGISTRATION NUMBER

NTR-NL6630.

The Potential Role of REG Family Proteins in Inflammatory and Inflammation-Associated Diseases of the Gastrointestinal Tract

Regenerating gene (REG) family proteins serve as multifunctional secretory molecules with trophic, antiapoptotic, anti-inflammatory, antimicrobial and probably immuno-regulatory effects. Since their discovery, accumulating evidence has clarified the potential roles of the REG family in the occurrence, progression and development of a wide range of inflammatory and inflammation-associated diseases of the gastrointestinal (GI) tract. However, significant gaps still exist due to the undefined nature of certain receptors, regulatory signaling pathways and possible interactions among distinct Reg members. In this narrative review, we first describe the structural features, distribution pattern and purported regulatory mechanisms of REG family proteins. Furthermore, we summarize the established and proposed roles of REG proteins in the pathogenesis of various inflammation-associated pathologies of the GI tract and the body as a whole, focusing particularly on carcinogenesis in the ulcerative colitis—colitic cancer sequence and gastric cancer. Finally, the clinical relevance of REG products in the context of diagnosis, treatment and prognostication are also discussed in detail. The current evidence suggests a need to better understanding the versatile roles of Reg family proteins in the pathogenesis of inflammatory-associated diseases, and their broadened future usage as therapeutic targets and prognostic biomarkers is anticipated.

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.

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.

Expression of human REG family genes in inflammatory bowel disease and their molecular mechanism

The pathophysiology of inflammatory bowel disease (IBD) reflects a balance between mucosal injury and reparative mechanisms. Some regenerating gene (Reg) family members have been reported to be expressed in Crohn's disease (CD) and ulcerative colitis (UC) and to be involved as proliferative mucosal factors in IBD. However, expression of all the REG family genes in IBD is still unclear. Here, we analyzed expression of all the REG family genes (REGIα, REGIβ, REG III, HIP/PAP, and REG IV) in biopsy specimens of UC and CD by real-time RT-PCR. REG Iα, REG Iβ, and REG IV genes were overexpressed in CD samples. REG IV gene was also overexpressed in UC samples. We further analyzed the expression mechanisms of REG Iα, REG Iβ, and REG IV genes in LS-174T and HT-29 human colonic epithelial cells. The expression of REG Iα was significantly induced by IL-6 or IL-22, and REG Iβ was induced by IL-22. Deletion analyses revealed that three regions (- 220~- 211, - 179~- 156, and - 146~- 130) in REG Iα and the region (- 274~- 260) in REG Iβ promoter were responsible for the activation by IL-22/IL-6. The promoters contain consensus transcription factor binding sequences for MZF1, RTEF1/TEAD4, and STAT3 in REG Iα, and HLTF/FOXN2F in REG Iβ, respectively. The introduction of siRNA for MZF1, RTEF1/TEAD4, STAT3, and HLTF/FOXN2F abolished the transcription of REG Iα and REG Iβ. The gene activation mechanisms of REG Iα/REG Iβ may play a role in colon mucosal regeneration in IBD.

Dimorphic autoantigenic and protective effects of Reg2 peptide in the treatment of diabetic β-cell loss

AIMS

The potential effect of regenerating (Reg) proteins in the treatment of diabetes has been indicated in the past decade, but the clinical use of Reg proteins requires more advances in translational medicine. In the present study, we produced recombinant regenerating protein 2 (rReg2), to prove its protective effect against streptozocin (STZ)-induced diabetes in BALB/c mice.

MATERIALS AND METHODS

rReg2 was administrated in STZ-induced diabetic mice. Blood glucose, body weight, serum insulin and islet β-cell loss were determined. However, Reg2 has also been reported to serve as an autoantigen that induces autoimmune attacks on islets and aggravates diabetic development in non-obese diabetic mice. To address this contradiction, complete Freund's adjuvant was injected to generate a model that was hypersensitive to Reg2. In this model, islet CD8 T-cell infiltration, serum Reg2 antibody and interleukin (IL)-4 and IL-10, and splenic CD4+/interferon (IFN)-γ+ T cells were determined.

RESULTS

Direct rReg2 pretreatment preserved islet β-cell mass against STZ and improved glycaemia, body weight and serum insulin content. The protection against cell death was further confirmed in cultured mouse islets and MIN6 cells. On the other hand, significant elevations of serum Reg2 antibody and splenic CD4+/IFN-γ+ T cells, and decreases in serum IL-4 and IL-10 were detected in rReg2-vaccinated mice, which may contribute to the accelerated diabetes. Interestingly, these mice, upon further rReg2 treatment, exhibited alleviated diabetic conditions with less islet CD8+ T-cell infiltration.

CONCLUSION

rReg2 treatment ameliorated STZ-induced diabetes in normal BALB/c mice. By contrast, rReg2 vaccination exacerbated, but further rReg2 treatment alleviated, the severity of STZ-induced diabetes. Thus, the protective effect of rReg2 is predominant over the autoantigenic β-cell destruction, supporting the potential of rReg2 in the clinical treatment of diabetes.

Knockdown of REG Iα Enhances the Sensitivity to 5-Fluorouracil of Colorectal Cancer Cells via Cyclin D1/CDK4 Pathway and BAX/BCL-2 Pathways

Objective: The reverse of chemoresistance and the improvement of sensitivity to chemotherapeutic agents of colorectal cancer cells have great clinical significance and the mechanism underlying the drug resistance is still unclear. REG Iα was reported to be upregulated in colorectal cancer tissues, but the roles of chemoresistance are still unclear. Materials and Methods: The expression of REG Iα in colorectal cancer cell lines was assessed by quantitative real-time polymerase chain reaction (Q-PCR). The expression of REG Iα in HCT116 and LOVO cells was knockdown by siRNA. The cell viability and IC₅₀ (half maximal inhibitory concentration) values were analyzed by the CCK8 assay. The proportion of apoptosis and cell cycles were analyzed by flow cytometry. The migration potency of HCT116 and LOVO cells was analyzed by cell migration assay. The protein level of Cyclin D1, CDK4 (cyclin-dependent kinase 4), Bax and Bcl-2 were analyzed by western blot. Results: Knockdown of REG Iα enhances the sensitivity to 5-Fu of colorectal cancer cells. REG Iα knockdown promoted the cell apoptosis of HCT116 and LOVO under the 5-Fu treatment. The cell migration and cycle of colorectal cancer cells was also inhibited by REG Iα knockdown. We also found that REG Iα knockdown induced cell cycle arrest and cell apoptosis by Cyclin D1/CDK4 pathway and BAX/BCL-2 pathways. Conclusions: Knockdown of REG Iα enhances the sensitivity to 5-Fu of colorectal cancer cells via cyclin D1/CDK4 pathway and BAX/BCL-2 pathways.

Mangiferin induces islet regeneration in aged mice through regulating p16INK4a

Previous studies by our group on mangiferin demonstrated that it exerts an anti‑hyperglycemic effect through the regulation of cell cycle proteins in 3‑month‑old, partially pancreatectomized (PPx) mice. However, β‑cell proliferation is known to become severely restricted with advanced age. Therefore, it is unknown whether mangiferin is able to reverse the diabetic condition and retain β‑cell regeneration capability in aged mice. In the present study, 12‑month‑old C57BL/6J mice that had undergone PPx were subjected to mangiferin treatment (90 mg/kg) for 28 days. Mangiferin‑treated aged mice exhibited decreased blood glucose levels and increased glucose tolerance, which was accompanied with higher serum insulin levels when compared with those in untreated PPx control mice. In addition, islet hyperplasia, elevated β‑cell proliferation and reduced β‑cell apoptosis were also identified in the mice that received mangiferin treatment. Further studies on the mRNA transcript and protein expression levels indicated comparatively increased levels of cyclins D1 and D2 and cyclin‑dependent kinase 4 in mangiferin‑treated mice, while the levels of p27Kip1 and p16INK4a were decreased relative to those in the untreated PPx controls. Of note, mangiferin treatment improved the proliferation rate of islet β‑cells in adult mice overexpressing p16INK4a, suggesting that mangiferin induced β‑cell proliferation via the regulation of p16INK4a. In addition, the mRNA transcription levels of critical genes associated with insulin secretion, including pancreatic and duodenal homeobox 1, glucose transporter 2 and glucokinase, were observed to be upregulated after mangiferin treatment. Taken together, it was indicated that mangiferin treatment significantly induced β‑cell proliferation and inhibited β‑cell apoptosis by regulating cell cycle checkpoint proteins. Furthermore, mangiferin was also demonstrated to regulate genes associated with insulin secretion. Collectively these, results suggest the therapeutic potential of mangiferin in the treatment of diabetes in aged individuals.

Diverse effects of interleukin-22 on pancreatic diseases

Interleukin-22 (IL-22) is involved in the development of lymphocytes and serves as a rapid and early source of the effector cytokines that are released in response to pathogen-induced changes in the microenvironment. Recent research has implicated IL-22 as a potential contributing factor to the spectrum of inflammation-related pancreatic diseases, particularly pancreatitis, fibrosis, carcinoma and diabetes. In this review, we summarize the current knowledge on the roles of IL-22 in the various pancreatic pathogenesis, providing insights into the underlying cellular and signaling mechanisms that will help guide future research into promising interventional targets with therapeutic potential.

Significance of Interleukin-6/STAT Pathway for the Gene Expression of REG Iα, a New Autoantigen in Sjögren's Syndrome Patients, in Salivary Duct Epithelial Cells

The regenerating gene, Reg, was originally isolated from a rat regenerating islet complementary DNA (cDNA) library, and its human homologue was named REG Iα. Recently, we reported that REG Iα messenger RNA (mRNA), as well as its product, was overexpressed in ductal epithelial cells in the salivary glands of Sjögren's syndrome patients. Furthermore, autoantibodies against REG Iα were found in the sera of Sjögren's syndrome patients, and the patients who were positive for the anti-REG Iα antibody showed significantly lower saliva secretion than antibody-negative patients. We found the mechanism of REG Iα induction in salivary ductal epithelial cells. Reporter plasmid containing REG Iα promoter (-1190/+26) upstream of a luciferase gene was introduced into human NS-SV-DC and rat A5 salivary ductal cells. The cells were treated with several cytokines (interleukin (IL)-6, IL-8, etc.), upregulated in Sjögren's syndrome salivary ducts, and the transcriptional activity was measured. IL-6 stimulation significantly enhanced the REG Iα promoter activity in both cells. Deletion analysis revealed that the -141∼-117 region of the REG Iα gene was responsible for the promoter activation by IL-6, which contains a consensus sequence for signal transducer and activator of transcription (STAT) binding. The introduction of small interfering RNA for human STAT3 abolished IL-6-induced REG Iα transcription. These results indicated that IL-6 stimulation induced REG Iα transcription through STAT3 activation and binding to the REG Iα promoter in salivary ductal cells. This dependence of REG Iα induction upon IL-6/STAT in salivary duct epithelial cells may play an important role in the pathogenesis/progression of Sjögren's syndrome.

Reg Gene Expression in Periosteum after Fracture and Its In Vitro Induction Triggered by IL-6

The periosteum is a thin membrane that surrounds the outer surface of bones and participates in fracture healing. However, the molecular signals that trigger/initiate the periosteal reaction are not well established. We fractured the rat femoral bone at the diaphysis and fixed it with an intramedullary inserted wire, and the expression of regenerating gene (Reg) I, which encodes a tissue regeneration/growth factor, was analyzed. Neither bone/marrow nor muscle showed RegI gene expression before or after the fracture. By contrast, the periosteum showed an elevated expression after the fracture, thereby confirming the localization of Reg I expression exclusively in the periosteum around the fractured areas. Expression of the Reg family increased after the fracture, followed by a decrease to basal levels by six weeks, when the fracture had almost healed. In vitro cultures of periosteal cells showed no Reg I expression, but the addition of IL-6 significantly induced Reg I gene expression. The addition of IL-6 also increased the cell number and reduced pro-apoptotic gene expression of Bim. The increased cell proliferation and reduction in Bim gene expression were abolished by transfection with Reg I siRNA, indicating that these IL-6-dependent effects require the Reg I gene expression. These results indicate the involvement of the IL-6/Reg pathway in the osteogenic response of the periosteum, which leads to fracture repair.

Expression of REG family genes in human inflammatory bowel diseases and its regulation

The pathophysiology of inflammatory bowel disease (IBD) reflects a balance between mucosal injury and reparative mechanisms. Some regenerating gene (Reg) family members have been reported to be expressed in Crohn's disease (CD) and ulcerative colitis (UC) and to be involved as proliferative mucosal factors in IBD. However, expression of all REG family genes in IBD is still unclear. Here, we analyzed expression of all REG family genes (REG Iα, REG Iβ, REG III, HIP/PAP, and REG IV) in biopsy specimens of UC and CD by real-time RT-PCR. REG Iα, REG Iβ, and REG IV genes were overexpressed in CD samples. REG IV gene was also overexpressed in UC samples. We further analyzed the expression mechanisms of REG Iα, REG Iβ, and REG IV genes in human colon cells. The expression of REG Iα was significantly induced by IL-6 or IL-22, and REG Iβ was induced by IL-22. Deletion analyses revealed that three regions (- 220 to - 211, - 179 to - 156, and - 146 to - 130) in REG Iα and the region (- 274 to- 260) in REG Iβ promoter were responsible for the activation by IL-22/IL-6. The promoters contain consensus transcription factor binding sequences for MZF1, RTEF1/TEAD4, and STAT3 in REG Iα, and HLTF/FOXN2F in REG Iβ, respectively. The introduction of siRNAs for MZF1, RTEF1/TEAD4, STAT3, and HLTF/FOXN2F abolished the transcription of REG Iα and REG Iβ. The gene activation mechanisms of REG Iα/REG Iβ may play a role in colon mucosal regeneration in IBD.

Statins decrease vascular epithelial growth factor expression via down-regulation of receptor for advanced glycation end-products

Aims

Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, possess pleiotropic effects that have been extended to modulation of various cellular behaviors. This study aimed to examine whether statins modulate vascular endothelial growth factor A (VEGF-A) expression in human retinal pigment epithelium (RPE) cells.

Main methods

Human RPE cells (h1RPE7), damaged by hydroquinone (HQ) + advanced glycation endproducts (AGE) in an in vitro AMD model, were treated with atorvastatin or lovastatin for 24 h. The expression of VEGF-A and receptor for AGE (RAGE) was evaluated by real-time RT-PCR. VEGF-A secretion was measured by ELISA. To investigate the impact of RAGE on VEGF-A expression, small interfering RNA (siRNA) for RAGE (siRAGE) was introduced into h1RPE7 cells and VEGF-A expression was measured by real-time RT-PCR. Deletions of VEGF-A and RAGE promoters were performed and transcriptional activities were measured after the addition of statins to HQ + AGE-damaged RPE cells.

Key findings

The mRNA levels of VEGF-A and RAGE and the levels of VEGF-A in the culture medium were increased by HQ + AGE. Both atorvastatin and lovastatin attenuated HQ + AGE-induced VEGF-A and RAGE expression. These statins also decreased VEGF-A levels in the culture medium. RNA interference of RAGE attenuated the up-regulation of VEGF-A in the HQ + AGE treated cells. The deletion analysis demonstrated that these statins attenuated RAGE promoter activation in HQ + AGE-damaged RPE cells.

Significance

Statins attenuated HQ + AGE-induced VEGF expression by decreasing RAGE expression. As VEGF is an important factor in developing wet AMD, statins could decrease the risk of wet-type AMD and be used as preventive medicines.

Up-regulation of selenoprotein P and HIP/PAP mRNAs in hepatocytes by intermittent hypoxia via down-regulation of miR-203

Sleep apnea syndrome is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]) and is a risk factor for insulin resistance/type 2 diabetes. However, the mechanisms linking IH stress and insulin resistance remain elusive. We exposed human hepatocytes (JHH5, JHH7, and HepG2) to experimental IH or normoxia for 24 h, measured mRNA levels by real-time reverse transcription polymerase chain reaction (RT-PCR), and found that IH significantly increased the mRNA levels of selenoprotein P (SELENOP) — a hepatokine — and hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein (HIP/PAP) — one of REG (Regenerating gene) family. We next investigated promoter activities of both genes and discovered that they were not increased by IH. On the other hand, a target mRNA search of micro RNA (miRNA) revealed that both mRNAs have a potential target sequence for miR-203. The miR-203 level of IH-treated cells was significantly lower than that of normoxia-treated cells. Thus, we introduced miR-203 inhibitor and a non-specific control RNA (miR-203 inhibitor NC) into HepG2 cells and measured the mRNA levels of SELENOP and HIP/PAP. The IH-induced expression of SELENOP and HIP/PAP was abolished by the introduction of miR-203 inhibitor but not by miR-203 inhibitor NC. These results demonstrate that IH stress up-regulates the levels of SELENOP in human hepatocytes to accelerate insulin resistance and up-regulates the levels of HIP/PAP mRNAs to proliferate such hepatocytes, via the miR-203 mediated mechanism.

Decreased REG1α expression suppresses growth, invasion and angiogenesis of bladder cancer

BACKGROUND

Previous study has indicated association between REG1α and bladder cancer. The aim of this study was to investigate the role of Regenerating gene I alpha (REG1α) in bladder cancer.

METHODS

The role of REG1α in bladder cancer cell proliferation, migration and VEGF-induced angiogenesis was explored in vitro and in vivo. Immunohistochemistry (IHC) analysis was assessed to determine the expression of REG1α in ten paired bladder cancer and adjacent non-cancerous tissues, and in 296 bladder cancer samples.

RESULTS

Down-regulation of REG1α expression significantly reduced the proliferation, migration, invasion and VEGF-induced angiogenesis in vitro and the growth of xenograft tumors in vivo. VEGF expression in bladder cancer is associated with REG1α expression and recurrence. REG1α was overexpressed in bladder cancer tissues compared with adjacent normal samples. Patients with elevated REG1α exhibited shorter recurrence times and poor survival.

CONCLUSION

Downregulation of REG1α expression can reduce tumor growth, migration, invasion and angiogenesis. Our study demonstrates that REG1α can be used as a marker of recurrence and prognosis in bladder cancer. Therefore, REG1α targeting in bladder cancer patients represents a promising therapeutic strategy.

Deteriorated high-fat diet-induced diabetes caused by pancreatic β-cell-specific overexpression of Reg3β gene in mice

Reg family proteins have long been implicated in islet β-cell proliferation, survival, and regeneration. In our previous study, we reported that Reg3β overexpression did not increase islet growth but prevented streptozotocin-induced islet damage by inducing specific genes. In order to explore its role in type 2 diabetes (T2D), we established high-fat diet (HFD)-induced obesity and diabetes in RIP-I/Reg3β mice. Glucose and insulin tolerance tests, immunofluorescence for insulin, eIF2α, and GLUT2 in islets, Western blots on phosphorylated AMPKα and hepatic histology were performed. Both RIP-I/Reg3β and wild-type mice gained weight rapidly and became hyperglycemic after 10 weeks on the HFD. However, the transgenic mice exhibited more significant acceleration in blood glucose levels, further deterioration of glucose intolerance and insulin resistance, and a lower intensity of insulin staining. Immunofluorescence revealed similar magnitude of islet compensation to a wild-type HFD. The normal GLUT2 distribution in the transgenic β-cells was disrupted and the staining was obviously diminished on the cell membrane. HFD feeding also caused a further decrease in the level of AMPKα phosphorylation in the transgenic islets. Our results suggest that unlike its protective effect against T1D, overexpressed Reg3β was unable to protect the β-cells against HFD-induced damage.

Recombinant Reg3β protein protects against streptozotocin-induced β-cell damage and diabetes

Regenerating genes (Reg) have been found during the search for factors involved in pancreatic islet regeneration. Our recent study discovered that pancreatic β-cell-specific overexpression of Reg3β protects against streptozotocin (Stz) -induced diabetes in mice. To investigate its potential roles in the treatment of diabetes, we produced a recombinant Reg3β protein and provided evidence that it is active in promoting islet β-cell survival against Stz- triggered cell death. Though ineffective in alleviating preexisting diabetes, pretreatment of recombinant Reg3β was capable of minimizing the Stz-induced hyperglycemia and weight loss, by preserving serum and pancreatic insulin levels, and islet β-cell mass. No obvious changes were observed in the rate of cell proliferation and hypertrophy in α- or acinar-cells after treatment with recombinant Reg3β. The underlying mechanism of Reg3β-mediated protection seems to involve Akt activation which upregulates Bcl-2 and Bcl-xL levels and consequently promotes cell survival.

ATF7 is stabilized during mitosis in a CDK1-dependent manner and contributes to cyclin D1 expression

The transcription factor ATF7 undergoes multiple post-translational modifications, each of which has distinct effects upon ATF7 function. Here, we show that ATF7 phosphorylation on residue Thr112 exclusively occurs during mitosis, and that ATF7 is excluded from the condensed chromatin. Both processes are CDK1/cyclin B dependent. Using a transduced neutralizing monoclonal antibody directed against the Thr112 epitope in living cells, we could demonstrate that Thr112 phosphorylation protects endogenous ATF7 protein from degradation, while it has no effect on the displacement of ATF7 from the condensed chromatin. The crucial role of Thr112 phosphorylation in stabilizing ATF7 protein during mitosis was confirmed using phospho-mimetic and phospho-deficient mutants. Finally, silencing ATF7 by CRISPR/Cas9 technology leads to a decrease of cyclin D1 protein expression levels. We propose that mitotic stabilized ATF7 protein re-localizes onto chromatin at the end of telophase and contributes to induce the cyclin D1 gene expression.

Recombinant Reg3α protein protects against experimental acute pancreatitis in mice

Regenerating gene 3α (Reg3α) protein is a trophic factor that stimulates cell and tissue proliferation, neogenesis and also acts against apoptosis and necrosis. In order to explore the potential roles of recombinant Reg3α (rReg3α), we produced a mature rReg3α polypeptide for direct administration in l-arginine (L-Arg) induced acute pancreatitis (AP) in mice. Our results showed that rReg3α stimulated cell proliferation through Erk1/2 and p38 phosphorylation and also cyclin D1 upregulation mediated by Akt/ATF-2 signaling. Moreover, rReg3α administration significantly reduced the pancreatic damage caused by L-Arg injection, as shown in histological examination and serum amylase, lipase and C-reactive protein (CRP) assays. Not only acinar cell necrosis but also apoptosis found in the pancreas of AP mice were alleviated by rReg3α. Finally, upregulated Bcl-2 and Bcl-xL and suppressed poly (ADP-ribose) synthetase/polymerase (PARP) levels were detected as being relevant to the mechanism of rReg3α protection. We therefore conclude that rReg3α acts as a protective polypeptide against AP in mice by enhancing Bcl-2 and Bcl-xL expressions and suppressing PARP level.

Regenerating gene (REG) product and its potential clinical usage

INTRODUCTION

The regenerating gene (Reg) was identified in regenerating islets and its related genes were revealed to constitute the Reg gene family. Reg family proteins act as growth factors for several cells. Recently, autoimmunity against the Reg family proteins has been reported in several diseases. In addition, the Reg family genes were found to be expressed in a large number of cancers and to influence prognosis.

AREAS COVERED

The historical background and current view of the structure, function, and expression of Reg family genes/proteins and their physiological/pathological significance in several diseases are described. Based on the findings, the diagnostic/therapeutic potential of Reg family genes/proteins is also discussed.

EXPERT OPINION

Autoimmunity against Reg family proteins may be a new diagnostic marker and/or therapeutic target for immune-mediated diseases. Treatment aimed at the expansion of the β-cell mass by the Reg genes/proteins, combined with the abrogation of autoimmunity, constitutes a potential approach for the treatment of diabetes. Conversely, some cancer cells have gained the ability to overexpress the Reg genes/proteins, thereby enhancing their proliferative capacities, resulting in these cells having a considerable growth advantage. Thus, the Reg genes/proteins are expected to be a new prognostic marker in cancer and/or a future therapeutic target.

Using stem cells to produce insulin

INTRODUCTION

Tremendous progress has been made in generating insulin-producing cells from pluripotent stem cells. The best outcome of the refined protocols became apparent in the first clinical trial announced by ViaCyte, based on the implantation of pancreatic progenitors that would further mature into functional insulin-producing cells inside the patient's body.

AREAS COVERED

Several groups, including ours, have contributed to improve strategies to generate insulin-producing cells. Of note, the latest results have gained a substantial amount of interest as a method to create a potentially functional and limitless supply of β-cell to revert diabetes mellitus. This review analyzes the accomplishments that have taken place over the last few decades, summarizes the state-of-art methods for β-cell replacement therapies based on the differentiation of embryonic stem cells into glucose-responsive and insulin-producing cells in a dish and discusses alternative approaches to obtain new sources of insulin-producing cells.

EXPERT OPINION

Undoubtedly, recent events preface the beginning of a new era in diabetes therapy. However, in our opinion, a number of significant hurdles still stand in the way of clinical application. We believe that the combination of the private and public sectors will accelerate the process of obtaining the desired safe and functional β-cell surrogates.

Human retinal pigment epithelial cell proliferation by the combined stimulation of hydroquinone and advanced glycation end-products via up-regulation of VEGF gene

Although recent research showed that advanced glycation endproduct (AGE) and hydroquinone (HQ) are related to the pathogenesis of age-related macular degeneration (AMD), the mechanism how AGE and HQ induce or accelerate AMD remains elusive. In the present study, we examined the effects of AGE and HQ on changes of human retinal pigment epithelial (RPE) cell numbers and found that the viable cell numbers were markedly reduced by HQ by apoptosis and that AGE prevented the decreases of HQ-treated cell numbers by increased replicative DNA synthesis of RPE cells without changing apoptosis. Real-time RT-PCR revealed that vascular endothelial growth factor (VEGF)-A mRNA was increased by HQ treatment and the addition of HQ+AGE resulted in a further increment. The increase of VEGF secretion was confirmed by ELISA, and inhibition of VEGF signaling by chemical inhibitors and small interfering RNA decreased the HQ+AGE-induced increases in RPE cell numbers. The deletion analysis demonstrated that -102 to -43 region was essential for the VEGF-A promoter activation. Site-directed mutaions of specificity protein 1 (SP1) binding sequences in the VEGF-A promoter and RNA interference of SP1 revealed that SP1 is an essential transcription factor for VEGF-A expression. These results indicate that HQ induces RPE cell apoptosis, leading to dry AMD, and suggest that AGE stimulation in addition to HQ enhances VEGF-A transcription via the AGE-receptor for AGE pathway in HQ-damaged cells. As a result, the secreted VEGF acts as an autocrine/paracrine growth factor for RPE and/or adjacent vascular cells, causing wet AMD.

Interleukin-6/STAT pathway is responsible for the induction of gene expression of REG Iα, a new auto-antigen in Sjögren׳s syndrome patients, in salivary duct epithelial cells

The regenerating gene, Reg, was originally isolated from a rat regenerating islet cDNA library, and its human homolog was named REG Iα. Recently, we reported that REG Iα mRNA as well as its product were overexpressed in ductal epithelial cells in the minor salivary glands of Sjögren׳s syndrome (SS) patients. This study was undertaken to elucidate the role of cytokines and the subsequent intracellular mechanism for induction of REG Iα in the salivary glands of SS patients. We prepared a reporter plasmid containing REG Iα promoter (−1190/+26) upstream of a luciferase reporter gene. The promoter plasmid was introduced by lipofection into human NS-SV-DC and rat A5 salivary ductal cells. The cells were treated with interleukin (IL)-6, IL-8, and a combination of the two. Thereafter transcriptional activity of REG Iα was measured by luciferase assay. We found that IL-6 stimulation, but not IL-8, significantly enhanced the REG Iα promoter activity in salivary ductal cells. Deletion analysis revealed that the region of −141 to −117 of the REG Iα gene was responsible for the promoter activation by IL-6, which contains a consensus sequence for signal transduction and activation of transcription (STAT). The introduction of siRNA for human STAT3 abolished IL-6-induced REG Iα transcription. These results showed that IL-6 stimulation induced REG Iα transcription through STAT3 activation and binding to the consensus sequence of REG Iα promoter in salivary ductal cells. This IL-6/STAT dependent REG Iα induction might play a role in the pathogenesis of SS.

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REG Iα was overexpressed in salivary ductal cells of patients with Sjögren׳s syndrome.

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IL-6 stimulation enhanced the REG Iα gene transcription in salivary ductal cells.

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STAT3 mediated IL-6-induced REG Iα transcription in salivary ductal cells.

Synergistic activations of REG I α and REG I β promoters by IL-6 and Glucocorticoids through JAK/STAT pathway in human pancreatic β cells

Reg (Regenerating gene) gene was originally isolated from rat regenerating islets and its encoding protein was revealed as an autocrine/paracrine growth factor for β cells. Rat Reg gene is activated in inflammatory conditions for β cell regeneration. In human, although five functional REG family genes (REG Iα, REG Iβ, REG III, HIP/PAP, and REG IV) were isolated, their expressions in β cells under inflammatory conditions remained unclear. In this study, we found that combined addition of IL-6 and dexamethasone (Dx) induced REG Iα and REG Iβ expression in human 1.1B4 β cells. Promoter assay revealed that a signal transducer and activator of transcription- (STAT-) binding site in each promoter of REG Iα (TGCCGGGAA) and REG Iβ (TGCCAGGAA) was essential for the IL-6+Dx-induced promoter activation. A Janus kinase 2 (JAK2) inhibitor significantly inhibited the IL-6+Dx-induced REG Iα and REG Iβ transcription. Electrophoretic mobility shift assay and chromatin immunoprecipitation revealed that IL-6+Dx stimulation increased STAT3 binding to the REG Iα promoter. Furthermore, small interfering RNA-mediated targeting of STAT3 blocked the IL-6+Dx-induced expression of REG Iα and REG Iβ. These results indicate that the expression of REG Iα and REG Iβ should be upregulated in human β cells under inflammatory conditions through the JAK/STAT pathway.

REG Iα activates c-Jun through MAPK pathways to enhance the radiosensitivity of squamous esophageal cancer cells

Identification of the key molecules that mediate susceptibility to anticancer treatments would be highly desirable. Based on clinical and cell biological studies, we recently proposed that regenerating gene (REG) Iα may be such a molecule. In the present study, we hypothesized that REG Iα increases radiosensitivity through activation of mitogen-activated protein kinase (MAPK) pathways. To test that idea, we transfected TE-5 and TE-9 squamous esophageal cancer cells with REG Iα and examined its involvement in MAPK signaling and its effect on susceptibility to radiotherapy. We found that REG Iα-expressing cells showed increased expression of c-Jun messenger RNA (mRNA) and phospho-c-Jun protein mediated via the c-Jun N-terminal kinase (JNK) pathway and extracellular signal-regulated kinase (ERK) pathway, as well as increased radiosensitivity. Immunohistochemical analysis confirmed the activation of c-Jun in tumors expressing REG Iα. Collectively, these findings suggest that REG Iα activates c-Jun via the JNK and ERK pathway, thereby enhancing radiosensitivity.

Veratric acid inhibits iNOS expression through the regulation of PI3K activation and histone acetylation in LPS-stimulated RAW264.7 cells

In the present study, we investigated regulatory effects of veratric acid on the production of nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. NO production was significantly decreased by veratric acid in the LPS-stimulated RAW264.7 cells in a dose-dependent manner. The reduction in nitric oxide production was induced by the downregulation of inducible NO synthase (iNOS) expression. Veratric acid suppressed the LPS-induced effects on the regulatory and catalytic subunits of phosphoinositide 3-kinase (PI3K), comprised of p85, p110α, p110β and Akt. The acetylation of p300 and the phosphorylation of activating transcription factor 2 (ATF-2) induced by LPS were downregulated following treatment with veratric acid; similar effects were observed following treatment with LY294002, a specific inhibitor of PI3K/Akt. The LPS-induced expression of histone deacetylase (HDAC)3 decreased to basal levels following treatment with veratric acid, and its expression was also downregulated by LY294002. In the measurement of histone acetylation levels, the LPS-stimulated acetylation of histone H4 was significantly attenuated by veratric acid, and was also reduced following the inhibition of PI3K/Akt with LY294002. From our data, it can be concluded that veratric acid exerts a regulatory effect on LPS-induced iNOS expression. Our results suggest that veratric acid impedes the PI3K/Akt-mediated histone acetyl-transferase (HAT) activation and HDAC expression induced by LPS, thereby abrogating iNOS expression.

Relationship between Reg proteins and intestinal mucosa barrier damage in rats with severe acute pancreatitis

AIM: To detect the expression of regenerating islet-derived proteins (Reg)Ⅰand Ⅲ in the intestinal mucosa of rats with severe acute pancreatitis (SAP), and to evaluate the relationship between the levels of RegⅠand Ⅲ and intestinal mucosal barrier damage.

METHODS: Seventy-two adult SD rats were randomly divided into three groups: a normal control (N) group, an SAP (S) group, and a pyrrolidine dithiocarbamate (PDTC, 10 mg/kg) pretreatment (P) group. Each group was further divided into two subgroups for testing at different time points (12 and 24 h), with 12 rats in each subgroup. The rats in the S group were given 20% L-arginine (L-Arg, 2.5 g/kg) by intraperitoneal injection twice at one-hour interval to induce SAP. The N group was given equal volume of normal saline. The P group was given PDTC 10 mg/kg by intraperitoneal injection 1 h before the first injection of L-Arg. All rats were killed 12 h or 24 h after L-Arg injection to collect blood, pancreatic and intestinal tissue samples. The pathological changes in pancreatic and intestinal tissues were observed and graded under an optical microscope. ELISA was used to detect the levels of serum interleukin 22 (IL-22), tumor necrosis factor-α (TNF-α) and intestinal fatty acid binding protein (I-FABP). The expression of RegⅠand Ⅲ mRNAs in intestinal tissue was evaluated by RT-PCR. The levels of RegⅠ, Ⅲ and nuclear-factor κB (NF-κB) proteins in intestinal tissue were detected by Western blot.

RESULTS: In the SAP group, the scores of pancreatic changes (12 h: 8.92 ± 1.130; 24 h: 11.31 ± 1.609) and intestinal mucosal changes (12 h: 3.79 ± 0.689, 24 h: 4.33 ± 0.354), and the levels of IL-22 (12 h: 712.46 ng/mL ± 81.549 ng/mL, 24 h: 751.02 ng/mL ± 104.054 ng/mL), TNF-α (12 h: 138.08 ng/mL ± 20.369 ng/mL, 24 h: 159.43 ng/mL ± 24.46 ng/mL), I-FABP (12 h: 338.04 IU/mL ± 61.876 IU/mL, 24 h: 395.26 IU/mL ± 58.547 IU/mL), intestinal NF-κB p65 (12 h: 0.51 ± 0.065, 24 h: 0.60 ± 0.066), RegⅠprotein (12 h: 0.45 ± 0.047, 24 h: 0.56 ± 0.033), and Reg Ⅲ protein (12 h: 0.70 ± 0.084, 24 h: 0.92 ± 0.163) were significantly higher (P < 0.05) than those in the control group. Compared with the S group, pretreatment with different doses of PDTC significantly decreased the above parameters (P < 0.05), although the levels of these parameters were still significantly higher than those in the N group (P < 0.05). There were positive correlations among RegⅠand Ⅲ protein expression, intestinal mucosal pathological score, IL-22, I-FABP, TNF-α, and NF-κB p65 expression.

CONCLUSION: RegⅠand Ⅲ protein expression is upregulated in SAP, which is possibly associated with intestinal mucosa damage and NF-κB signaling pathway activation.

Attenuation of unfolded protein response and apoptosis by mReg2 induced GRP78 in mouse insulinoma cells

Murine regenerating (mReg) genes have been implicated in preserving islet cell biology. Expanding on our previous work showing that overexpression of mReg2 protects MIN6 insulinoma cells against streptozotocin-induced apoptosis, we now demonstrate that mReg2 induces glucose-regulated peptide 78 (GRP78) expression via the Akt-mTORC1 axis and protects MIN6 cells against ER stress induced by thapsigargin and glucolipotoxicity. Activation of mTORC1 activity results from both mReg2-induced increased mTOR phosphorylation as well as increased expression of Raptor and GβL. Inhibition of Akt and mTORC1 blunted the ability of mReg2 to induce GRP78 and attenuate unfolded protein response (UPR). Knockdown of GRP78 sensitized the cells overexpressing mReg2 to UPR without affecting its ability to activate Akt-mTORC1 signaling. Induced expression of mReg2 may protect insulin producing cells from ER stress in diabetes.

Expression of Ins1 and Ins2 genes in mouse fetal liver

A possible cure for diabetes is explored by using non-pancreatic cells such as fetal hepatocytes. The expression of insulin and transcription factors for insulin is investigated in mouse fetal liver. We detected mRNAs for insulin I (Ins1) and insulin II (Ins2) and proinsulin- and mature insulin-positive cells in mouse fetal liver by reverse transcription plus the polymerase chain reaction and immunohistochemistry. Glucagon, somatostatin and pancreatic polypeptide were not expressed throughout development. Mouse Ins2 and Ins1 promoters were transiently activated in mouse fetal hepatocytes of embryonic days 13.5 and 16.5, respectively. Pancreatic and duodenal homeobox 1 (Pdx1) mRNA was not expressed during development of the liver. In contrast, mRNAs and proteins of neurogenic differentiation (NeuroD)/β cell E-box transactivator 2 (Beta2) and v-maf musculoaponeurotic fibrosarcoma oncogene homolog (MafA) were almost simultaneously expressed with insulin genes in the liver. Ins2 and Ins1 promoters were activated in hepatoma cells by the transfection of the expression vector for NeuroD/Beta2 alone and by the combination of NeuroD/Beta2 and MafA, respectively. These results indicate that the expression of NeuroD/Beta2 and MafA is linked temporally with the transcription of Ins2 and Ins1 genes in mouse fetal liver and suggest the potential usage of fetal hepatocytes to make insulin-producing β cells by introducing transcription factors.

Reg proteins and their roles in inflammation and cancer of the human digestive system

The regenerating gene (Reg) family is a group of small molecules that includes four members found in various species, although only three are found in human tissues. Their expression is stimulated by certain growth factors or cytokines. The Reg family plays different roles in proliferation, migration, and anti-apoptosis through activating different signaling pathways. Their dysexpression is closely associated with a number of human conditions and diseases such as inflammation and cancer, especially in the human digestive system. Clinically, upregulation of Reg proteins is usually demonstrated in histological sections and sera from cancer patients. Therefore, Reg proteins can predict the progression and prognosis of cancers, especially those of the digestive tract, and can also act as diagnostic markers and therapeutic targets.

REG Iα gene expression is linked with the poor prognosis of lung adenocarcinoma and squamous cell carcinoma patients via discrete mechanisms

The aim of the present study was to evaluate the effects of the REG Iα and REG Iβ genes on lung cancer cell lines, and thereafter, the expression of REG family genes (REG Iα, REG Iβ, REG III, HIP/PAP and REG IV) in lung cancer in relation to patient prognosis was evaluated. Lung adenocarcinoma (AD) and squamous cell carcinoma (SCC) cell lines expressing REG Iα or REG Iβ (HLC-1 REG Iα/Iβ and EBC-1 REG Iα/Iβ) were established, and cell number, cell invasive activity, and anchorage-independent cell growth were compared with these variables in the control cells. The expression levels of REG family genes were evaluated by real-time RT-PCR in surgically resected lung cancers, and disease-specific survival (DSS) curves were generated. The HLC-1 REG Iα/Iβ cell line showed significant increases in cell number and anchorage-independent cell growth compared with the control cells. EBC-1 REG Iα/Iβ cells showed significant increases in cell invasive activity and anchorage-independent cell growth as compared with the control cells. Except for the REG Iβ gene, expression of other REG family genes was observed in the surgically resected samples; however, DSS was significantly worse only in stage I patients who were positive for REG Iα expression than in patients who were negative for REG Iα expression. The effects of REG Iα on AD and SCC cells were different in the in vitro study, and a correlation between REG Iα expression and patient prognosis was noted in the in vivo study. Therefore, overexpression of REG Iα is a risk factor for poor prognosis caused by discrete mechanisms in AD and SCC patients.

Parp1 deficient mice are protected from streptozotocin-induced diabetes but not caerulein-induced pancreatitis, independent of the induction of Reg family genes

Poly(ADP-ribose) polymerase (Parp) 1 is a key regulator of cell death, its inhibition prevented streptozotocin-induced diabetes and attenuated caerulein-induced acute pancreatitis. Reg family proteins are significantly induced by Parp1 inhibitor, experimental diabetes and/or acute pancreatitis. We propose that Reg proteins are involved in the protection of pancreatic cells by Parp1 inhibition. To test this possibility, Parp1-/- and wild-type mice were injected with streptozotocin to induce diabetes. Separately, acute pancreatitis was induced with repeated injections of caerulein. Upon streptozotocin administration, Parp1-/- mice displayed much decreased hyperglycemia and preserved serum insulin level. The treatment induced similar levels of Reg1, -2, -3α and -3β genes in the pancreas of both wild-type and Parp1-/- mice, suggesting that the upregulation of Reg family genes during streptozotocin-induced diabetes was independent of Parp1 ablation. In caerulein-induced pancreatitis, unlike being reported, Parp1 knockout caused no relief on the severity of pancreatitis; the upregulation of pancreatic Reg1, -2, -3α and -3β genes upon caerulein was unaffected by Parp1 deletion. Our results reconfirmed the protective effect of Parp1 gene deletion on islet β-cells but questioned its effect on the acinar cells. In either case, the significant induction of Reg family genes seemed independent of Parp1-mediated cell death.

Epigenetic regulation of REG1A and chemosensitivity of cutaneous melanoma

Regenerating gene 1A (REG1A) plays an important role in tissue regeneration and in cell proliferation in epithelium origin tumors; however, its role in melanoma has not been explored in details. The objective of this study was to identify whether REG1A is expressed in cutaneous melanoma and if REG1A expression status can predict prognosis in cutaneous melanoma patients with metastasis. We also determined whether epigenetic regulation of the promoter region regulates REG1A expression. AJCC stage III cutaneous melanoma specimens with clinically well annotated stage III lymph node melanoma metastasis tissue microarray were assessed by IHC. MALDI-TOF-mass spectrometry and HM450K array were used to identify REG1A promoter region CpG site methylation. Chemotherapeutic agent response by melanoma cells as related to REG1A protein expression was assessed. Post-surgery melanoma patients followed by adjuvant chemotherapy with high REG1A expression had a significantly better prognosis (disease-specific survival) compared with patients with low REG1A expression (log rank test; p = 0.0013). The demethylating reagent 5-Aza-2'-deoxycytidine activated REG1A promoter region resulting in enhanced REG1A mRNA and protein expression in melanoma cell lines. Promoter region CpG methylation was shown to regulate REG1A expression in melanoma cells. Moreover, melanoma lines with high REG1A mRNA expression were more susceptible to Dacarbazine and Cisplatin, as compared with those with low REG1A mRNA expression. In conclusion, REG1A expression status may be useful as a biomarker in melanoma patients for sensitivity to these chemotherapeutic agents. The epigenetic regulation of the REG1A promoter region may offer a potential therapeutic approach to improve chemotherapy for metastatic melanoma patients.

REG1A expression status suggests chemosensitivity among advanced thoracic esophageal squamous cell carcinoma patients treated with esophagectomy followed by adjuvant chemotherapy

BACKGROUND

Regenerating gene 1A (REG1A) plays an important role in tissue regeneration and in cell proliferation in the mucous membrane of the gastrointestinal tract. We previously reported that the positive expression status of REG1A was predictive of chemoradiosensitivity in patients treated with preoperative chemoradiotherapy before esophagectomy or with definitive chemoradiotherapy. To further confirm the utility of REG1A as a chemosensitivity marker, we carried out an additional retrospective clinical study aimed at determining whether REG1A is a reliable chemosensitivity marker in patients treated with esophagectomy followed by adjuvant chemotherapy.

METHOD

A total of 177 patients with T2-4 thoracic esophageal squamous cell carcinoma received curative surgery without preoperative treatment at Akita University Hospital between 2001 and 2011. A tissue microarray was constructed, and REG1A expression status was analyzed immunohistochemically. We then statistically analyzed the relationships between REG1A expression status and 5-year overall survival (OS), disease-specific survival (DSS), and disease-free survival (DFS).

RESULTS

In the adjuvant group (n=105), REG1A-positive patients showed significantly better prognoses than REG1A-negative patients. (5-year OS, p=.0022; DSS, p=.0004; and DFS, p=.0040). However, there were no significant differences between REG1A-positive and REG1A-negative patients in the surgery group (n=72). Univariate and multivariate analyses showed REG1A expression status to be a significant prognostic factor affecting 5-year DSS, comparable to lymph node metastatic status.

CONCLUSION

The present study suggests REG1A expression status has the potential to be a highly reliable and clinically useful chemosensitivity marker in patients treated with advanced thoracic esophageal squamous cell carcinoma. REG1A expression status will provide a good indication of treatment strategy and enable more individualized treatment for patients.

The involvement of interleukin-22 in the expression of pancreatic beta cell regenerative Reg genes

BACKGROUND

In Type 1 diabetes, the insulin-producing β-cells within the pancreatic islets of Langerhans are destroyed. We showed previously that immunotherapy with Bacillus Calmette-Guerin (BCG) or complete Freund's adjuvant (CFA) of non-obese diabetic (NOD) mice can prevent disease process and pancreatic β-cell loss. This was associated with increased islet Regenerating (Reg) genes expression, and elevated IL-22-producing Th17 T-cells in the pancreas.

RESULTS

We hypothesized that IL-22 was responsible for the increased Reg gene expression in the pancreas. We therefore quantified the Reg1, Reg2, and Reg3δ (INGAP) mRNA expression in isolated pre-diabetic NOD islets treated with IL-22. We measured IL-22, and IL-22 receptor(R)-α mRNA expression in the pancreas and spleen of pre-diabetic and diabetic NOD mice. Our results showed: 1) Reg1 and Reg2 mRNA abundance to be significantly increased in IL-22-treated islets in vitro; 2) IL-22 mRNA expression in the pre-diabetic mouse pancreas increased with time following CFA treatment; 3) a reduced expression of IL-22Rα following CFA treatment; 4) a down-regulation in Reg1 and Reg2 mRNA expression in the pancreas of pre-diabetic mice injected with an IL-22 neutralizing antibody; and 5) an increased islet β-cell DNA synthesis in vitro in the presence of IL-22.

CONCLUSIONS

We conclude that IL-22 may contribute to the regeneration of β-cells by up-regulating Regenerating Reg1 and Reg2 genes in the islets.

Intestinal adaptation and Reg gene expression induced by antidiabetic duodenal-jejunal bypass surgery in Zucker fatty rats

The antidiabetic mechanism of bariatric surgery includes specific changes in the secretion of incretins. To identify additional players originating from the gut, we evaluated the effects of duodenal-jejunal bypass (DJB) in morbidly obese Zucker fatty rats. A fast relief of hyperglycemia and hyperinsulinemia was achieved even before a significant weight loss occurred. Fourteen days after DJB, we characterized the changes in intestinal histochemistry in the bypassed duodenum and shortcut jejunum that was reanastomosed directly to the starting point of the duodenum and compared with the corresponding regions of sham-operated rats. The bypassed duodenum exhibited mucosal atrophy and apoptosis and decreased proliferative renewal. In shortcut jejunum, DJB resulted in 40% significantly enlarged intestinal circumference and increased epithelial proliferation, especially in putative transit-amplifying (TA) cells and the crypt. Because Reg family proteins promote cell growth and survival, we explored their expression in the intestine. With the use of immunohistochemistry, Reg1, -3α, and -3β were normally expressed in intestinal mucosa. After DJB, the level of Reg1 protein was reduced, whereas Reg3α and -3β were not changed in bypassed duodenum. Downstream in shortcut jejunum, the levels of Reg1 and -3β were greatly induced and especially concentrated in the putative TA cells. Our results revealed significant changes in the integrity and proliferation of the intestinal mucosa as a consequence of DJB, and in cell- and isoform-specific expression of Reg proteins within the replicating mucosal epithelium, and provide evidence indicating that the activation of Reg proteins may contribute to intestinal compensation against increased load and/or to improving insulin sensitivity.

Mechanisms of action of islet neogenesis-associated protein: comparison of the full-length recombinant protein and a bioactive peptide

Islet neogenesis-associated protein (INGAP) was discovered in the partially duct-obstructed hamster pancreas as a factor inducing formation of new duct-associated islets. A bioactive portion of INGAP, INGAP(104-118) peptide (INGAP-P), has been shown to have neogenic and insulin-potentiating activity in numerous studies, including recent phase 2 clinical trials that demonstrated improved glucose homeostasis in both type 1 and type 2 diabetic patients. Aiming to improve INGAP-P efficacy and to understand its mechanism of action, we cloned the full-length protein (rINGAP) and compared the signaling events induced by the protein and the peptide in RIN-m5F cells that respond to INGAP with an increase in proliferation. Here, we show that, although both rINGAP and INGAP-P signal via the Ras/Raf/ERK pathway, rINGAP is at least 100 times more efficient on a molar basis than INGAP-P. For either ligand, ERK1/2 activation appears to be pertussis toxin sensitive, suggesting involvement of a G protein-coupled receptor(s). However, there are clear differences between the peptide and the protein in interactions with the cell surface and in the downstream signaling. We demonstrate that fluorescent-labeled rINGAP is characterized by clustering on the membrane and by slow internalization (≤5 h), whereas INGAP-P does not cluster and is internalized within minutes. Signaling by rINGAP appears to involve Src, in contrast to INGAP-P, which appears to activate Akt in addition to the Ras/Raf/ERK1/2 pathway. Thus our data suggest that interactions of INGAP with the cell surface are important to consider for further development of INGAP as a pharmacotherapy for diabetes.

Coffee polyphenols change the expression of STAT5B and ATF-2 modifying cyclin D1 levels in cancer cells

Background. Epidemiological studies suggest that coffee consumption reduces the risk of cancer, but the molecular mechanisms of its chemopreventive effects remain unknown. Objective. To identify differentially expressed genes upon incubation of HT29 colon cancer cells with instant caffeinated coffee (ICC) or caffeic acid (CA) using whole-genome microarrays. Results. ICC incubation of HT29 cells caused the overexpression of 57 genes and the underexpression of 161, while CA incubation induced the overexpression of 12 genes and the underexpression of 32. Using Venn-Diagrams, we built a list of five overexpressed genes and twelve underexpressed genes in common between the two experimental conditions. This list was used to generate a biological association network in which STAT5B and ATF-2 appeared as highly interconnected nodes. STAT5B overexpression was confirmed at the mRNA and protein levels. For ATF-2, the changes in mRNA levels were confirmed for both ICC and CA, whereas the decrease in protein levels was only observed in CA-treated cells. The levels of cyclin D1, a target gene for both STAT5B and ATF-2, were downregulated by CA in colon cancer cells and by ICC and CA in breast cancer cells. Conclusions. Coffee polyphenols are able to affect cyclin D1 expression in cancer cells through the modulation of STAT5B and ATF-2.

Attenuation of glucose-induced insulin secretion by intermittent hypoxia via down-regulation of CD38

AIMS

Sleep apnea syndrome (SAS) is characterized by recurrent episodes of oxygen desaturation during sleep, the development of daytime sleepiness, and deterioration in the quality of life. Accumulating evidence suggests the association of intermittent hypoxia (IH), a hallmark of SAS, and type 2 diabetes independently on body mass index and waist circumference. In addition to insulin resistance, the progression to type 2 diabetes is dependent on the impairment of glucose-induced insulin secretion (GIS) from pancreatic β-cells. However, the direct effects of IH on GIS are elusive.

MAIN METHODS

HIT-T15 hamster β-cells and isolated rat islets were exposed to 64 cycles/24 h of IH (5 min hypoxia/10 min normoxia) or normoxia for 24 h. Changes of GIS and gene expression in IH-treated β-cells were analyzed by ELISA and real-time RT-PCR, respectively.

KEY FINDINGS

After IH treatment, GIS both from IH-treated HIT-T15 cells and isolated rat islets were significantly attenuated. The level of insulin mRNA was unchanged by IH. The mRNA levels of glucose transporter 2 (Glut2), glucokinase (GK), sulfonylurea receptor1 (SUR1), and L-type Ca2+channel1.2 (Cav1.2) in IH-treated-islets were similar to those in normoxia-treated islets. In contrast, the mRNA level of CD38 in IH-treated islets was significantly lower than that in normoxia-treated islets. The reporter gene assay revealed that the transcription of CD38 was attenuated by IH, and the transfection of CD38 expression vector recovered the attenuation of GIS by IH.

SIGNIFICANCE

These results indicate that IH stress directly attenuates GIS from β-cells via the down-regulation of CD38.

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.