Activation of Wnt3a signaling stimulates intestinal epithelial repair by promoting c-Myc-regulated gene expression

Maintenance of stem cell self-renewal by sex chromosomal zinc-finger transcription factors

In this Editorial review, we would like to focus on a very recent discovery showing the global autosomal gene regulation by Y- and inactivated X-chromosomal transcription factors, zinc finger gene on the Y chromosome (ZFY) and zinc finger protein X-linked (ZFX). ZFX and ZFY are both zinc-finger proteins that encode general transcription factors abundant in hematopoietic and embryonic stem cells. Although both proteins are homologs, interestingly, the regulation of self-renewal by these transcriptional factors is almost exclusive to ZFX. This fact implies that there are some differential roles between ZFX and ZFY in regulating the maintenance of self-renewal activity in stem cells. Besides the maintenance of stemness, ZFX overexpression or mutations may be linked to certain cancers. Although cancers and stem cells are double-edged swords, there is no study showing the link between ZFX activity and the telomere. Thus, stemness or cancers with ZFX may be linked to other molecules, such as Oct4, Sox2, Klf4, and others. Based on very recent studies and a few lines of evidence in the past decade, it appears that the ZFX is linked to the canonical Wnt signaling, which is one possible mechanism to explain the role of ZFX in the self-renewal of stem cells.

Ulcerative colitis: the healing power of macrophages

Ulcerative colitis (UC) is a chronic and debilitating disorder that falls under the broad category of inflammatory bowel disease (IBD). Therefore, affects the colon and rectum, resulting in inflammation and ulcers in the lining of these organs. Over the years, there has been a significant shift in the management of UC. The focus has moved from achieving symptom-free daily living to attaining mucosal healing. Mucosal healing means completely restoring the colon and rectum's lining, significantly reducing the risk of complications and relapse. Macrophages are a crucial component of the immune system that play a vital role in the regeneration and repair of colonic ulcers. These immune cells are responsible for production of a variety of cytokines and growth factors that facilitate tissue repair. Macrophages are responsible for maintaining a balance between inflammation and healing. When this balance is disrupted, it can lead to chronic inflammation and tissue damage, exacerbating UC symptoms. Thus, this review aims to investigate the contribution of macrophages to mucosal repair and remission maintenance in UC patients.

Total ginsenosides promote the IEC-6 cell proliferation via affecting the regulatory mechanism mediated by polyamines

Epithelial cell proliferation has been demonstrated to be a critical modality for mucosal repair after gastrointestinal mucosal injury. This research aimed to investigate the effect of total ginsenosides upon the proliferation of intestinal epithelial cells (IEC-6), and elucidate its potential mechanisms through polyamine-regulated pathway including the expression of proliferation-related proteins. Total ginsenosides (PGE3) were extracted from Panax ginseng, a Chinese herbal medicine, whose chromatogram was obtained by high performance liquid chromatographic method with evaporative light scattering detection (HPLC-ELSD). The cell proliferation, cell cycle distribution and the level of c-Myc, RhoA, Cdk2 proteins were detected to determine the effects of PGE3 at 25, 50 and100 mg/l doses on IEC-6. Furthermore, rats model of intestinal mucosal injury were induced by the subcutaneous injection of indomethacin, and the effect of Panax ginseng aqueous extracts (PGE1) on intestinal mucosal injury was observed. PGE3 could promote IEC-6 cell proliferation, reduce the proportion of G0/G1 phase cells and elevate the proportion of G2/M + S phase cells, and revert the proliferation and cell cycle arrest induced by DFMO (DL-a-difluoromethylornithine, an inhibitor of polyamines synthesis). PGE3 exposure enhanced the level of c-Myc, RhoA and Cdk2 proteins, and reversed the inhibition of these proteins expression induced by DFMO. The results of gross and pathological scores showed administration of PGE1 significantly alleviated intestinal mucosal injury of rats. Our findings indicate that total ginsenosides promoted the IEC-6 proliferation presumably via its regulation on cell cycle and the expression of proliferation-related proteins regulated by polyamines, and provided a novel perspective for exploring the repair effect of Panax ginseng upon gastrointestinal mucosal injury.

Inhibiting Hyper-O-GlcNAcylation of c-Myc accelerate diabetic wound healing by alleviating keratinocyte dysfunction

Background

Diabetic foot ulcers characterized by delayed healing are one of the main complications of diabetes. Epidermal keratinocyte dysfunction has been found to play a pivotal role in the poor healing ability of diabetic wounds. In this study, we aimed to explore the relationship between c-Myc and its O-linked N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation) modification and keratinocyte dysfunction in diabetic wounds.

Methods

Clinical wound samples were collected and a full-thickness skin defect wound model of diabetic rats was established. Re-epithelialization of wounds was observed by H&E staining and expressions of proliferating cell nuclear antigen, transglutaminase 1, loricrin, c-Myc and O-GlcNAc were measured by immunohistochemistry. The functional changes of proliferation, migration and differentiation of human immortalized epidermal cells (HaCaT) cells after overexpression or knockdown of c-Myc were observed. O-GlcNAcylation of c-Myc was confirmed using immunoprecipitation and proximity ligation assay. Stability of the c-Myc protein was measured using cycloheximide. Wound healing was observed after topical application of compounds that inhibited c-Myc or O-GlcNAc on diabetic wounds.

Results

Keratinocytes at the diabetic wound margin were characterized by active proliferation and division, slow migration and poor differentiation. Similar phenomena were observed in HaCaT cells cultured in 30 mM glucose and keratinocytes at the wound margin of the diabetic rats. The expression of c-Myc was increased in keratinocytes at the wound margin of diabetic rats, patients, and in HaCaT cells cultured with 30 mM glucose. Increased expression of c-Myc promoted the proliferation while inhibiting the migration and differentiation of the HaCaT cells, and inhibition of c-Myc promoted diabetic wound healing. Increased O-GlcNAcylation of c-Myc with 30 mM glucose stabilized the c-Myc proteins. Inhibition of O-GlcNAc ameliorated keratinocyte dysfunction and promoted diabetic wound healing.

Conclusions

Increased expression of c-Myc promoted abnormal proliferation and inhibited migration and differentiation of keratinocytes at the diabetic wound margin. Increased O-GlcNAcylation of c-Myc with 30 mM glucose stabilized the c-Myc proteins. Inhibition of c-Myc or O-GlcNAc alleviated delayed diabetic wound healing. These findings make c-Myc and O-GlcNAc potential therapeutic targets for diabetic wounds.

Nischarin downregulation attenuates cell injury induced by oxidative stress via Wnt signaling

Nischarin (NISCH) is a key protein functioning as a molecular scaffold and thereby hosting interactions with several protein partners. Here, we aimed to investigate whether NISCH downregulation could protect rat pheochromocytoma (PC12) cells against oxidative stress-induced injury using a model of cell injury induced by hydrogen peroxide (H2O2). Cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis rate was evaluated using flow cytometry. The expressions of apoptosis-related proteins Bax, Bcl-2, caspase-3 and NISCH were examined via Western blot analysis and immunofluorescence staining analyses. The expressions of NISCH, glycogen synthase kinase-3β (GSK-3β) and T-cell factor-1 (TCF-1) were examined using Western blot analysis. The results showed that incubation of H2O2 for 48 h significantly decreased the cell viability, increased the cell apoptosis rate and the NISCH expression in PC12 cells, whereas NISCH downregulation blocked the effects of H2O2 on cells. In addition, the expression of Bcl-2 was significantly reduced, and the expression of Bax and caspase-3 were significantly increased by H2O2 treatment. However, these effects were partially inhibited by the downregulation of NISCH. Furthermore, H2O2 significantly weakened the transduction of Wnt signaling, including the increases of GSK-3β and TCF-1 expressions and the decrease of β-catenin expression, while NISCH downregulation attenuated the effect of H2O2 on Wnt signaling. Moreover, inhibition of the Wnt pathway further decreased the cell viability and promoted the cell apoptosis induced by H2O2 in PC12 cells. Our results suggest that NISCH downregulation may protect cells against oxidative stress-induced injury through regulating the transduction of Wnt signaling.

Maternal Vitamin D Deficiency Increases Intestinal Permeability and Programs Wnt/β-Catenin Pathway in BALB/C Mice

BACKGROUND

Recent studies suggest that vitamin D deficiency is associated with intestinal dysfunctions, but the underlying mechanism remains unclear. This study aimed to investigate whether maternal vitamin D deficiency increases intestinal permeability in offspring and its related mechanism.

METHODS

Timed-pregnant mice were fed with either a standard chow diet (SC) or a vitamin D-deprived chow diet (VD-) 6 weeks prior to breeding and kept on the same diet until the end of gestation. All offspring were fed an SC for 3 weeks after weaning and then observed for effects associated with maternal vitamin D deficiency.

RESULTS

Maternal vitamin D deficiency increased intestinal permeability in offspring, which corresponded with the decreased expression of the tight junction protein claudin-1. Maternal vitamin D deficiency also repressed the messenger RNA expression of wingless/integrated family member 3a (Wnt3a) and the protein expression of nuclear β-catenin. The decreased Wnt3a gene expression in male was concurrent with the changes in histone H4 acetylation at either promoter or coding regions. The activation of the Wnt/β-catenin pathway protected against the impairment of intestinal permeability induced by maternal vitamin D deficiency.

CONCLUSIONS

Maternal vitamin D deficiency increased intestinal permeability and decreased tight junction protein expression in offspring. The suppression of the Wnt/β-catenin signaling pathway through histone modification might be involved in the underlying mechanism.

The Role of WNT Signaling in Mature T Cells: T Cell Factor Is Coming Home

T cell factor, the effector transcription factor of the WNT signaling pathway, was so named because of the primary observation that it is indispensable for T cell development in the thymus. Since this discovery, the role of this signaling pathway has been extensively studied in T cell development, hematopoiesis, and stem cells; however, its functional role in mature T cells has remained relatively underinvestigated. Over the last few years, various studies have demonstrated that T cell factor can directly influence T cell function and the differentiation of Th1, Th2, Th17, regulatory T cell, follicular helper CD4⁺ T cell subsets, and CD8⁺ memory T cells. In this paper, we discuss the molecular mechanisms underlying these observations and place them in the general context of immune responses. Furthermore, we explore the implications and limitations of these findings for WNT manipulation as a therapeutic approach for treating immune-related diseases.

Upregulated claudin-1 expression promotes colitis-associated cancer by promoting β-catenin phosphorylation and activation in Notch/p-AKT-dependent manner

In IBD patients, integration between a hyper-activated immune system and epithelial cell plasticity underlies colon cancer development. However, molecular regulation of such a circuity remains undefined. Claudin-1(Cld-1), a tight-junction integral protein deregulation alters colonic epithelial cell (CEC) differentiation, and promotes colitis severity while impairing colitis-associated injury/repair. Tumorigenesis is a product of an unregulated wound healing process and therefore we postulated that upregulated Cld-1 levels render IBD patients susceptible to the colitis-associated cancer (CAC). Villin Cld-1 mice is used to carryout overexpressed studies in mice. The role of deregulated Cld-1 expression in CAC and underlying mechanism using a well-constructed study scheme and mouse models of DSS colitis/recovery and CAC. Using an inclusive investigative scheme, we here report that upregulated Cld-1 expression promotes susceptibility to the CAC and its malignancy. Increased mucosal inflammation, defective epithelial homeostasis accompanied the increased CAC in Villin-Cld1-Tg mice. We further found significantly increased levels of pro-tumorigenic M2 macrophages and β-CateninSer552 (β-CatSer552) expression in the CAC in Cld-1Tg versus WT mice. Mechanistic studies identified the role of PI3K/Akt signaling in Cld-1 dependent activation of the β-CatSer552, which, in turn, was dependent on pro-inflammatory signals. Our studies identify a critical role of Cld-1 in promoting susceptibility to CAC. Importantly, these effects of deregulated Cld-1 were not associated with altered tight junction integrity, but on its non-canonical role in regulating Notch/PI3K/Wnt/ β-CatSer552 signaling. Overall, outcome from our current studies identifies Cld-1 as potential prognostic biomarker for IBD severity and CAC, and a novel therapeutic target.

The novel protein C3orf43 accelerates hepatocyte proliferation

Background

Our previous study found that single-pass membrane protein with coiled-coil domains 1 (C3orf43; XM_006248472.3) was significantly upregulated in the proliferative phase during liver regeneration. This indicates that C3orf43 plays a vital role in liver cell proliferation. However, its physiological functions remains unclear.

Methods

The expressions of C3orf43 in BRL-3A cells transfected with C3orf43-siRNA (C3-siRNA) or overexpressing the vector plasmid pCDH-C3orf43 (pCDH-C3) were measured via RT-qPCR and western blot. Cell growth and proliferation were determined using MTT and flow cytometry. Cell proliferation-related gene expression was measured using RT-qPCR and western blot.

Results

It was found that upregulation of C3orf43 by pCDH-C3 promoted hepatocyte proliferation, and inhibition of C3orf43 by C3-siRNA led to the reduction of cell proliferation. The results of qRT-PCR and western blot assay showed that the C3-siRNA group downregulated the expression of cell proliferation-related genes like JUN, MYC, CCND1 and CCNA2, and the pCDH-C3 group upregulated the expression of those genes.

Conclusion

These findings reveal that C3orf43 may contribute to hepatocyte proliferation and may have the potential to promote liver repair and regeneration.

The novel protein C9orf116 promotes rat liver cell line BRL-3A proliferation

Our previous study has proved that the chromosome 9 open reading frame 116 (C9orf116) (NM_001106564.1) was significantly up-regulated in the proliferation phase of liver regeneration. To study its possible physiological function, we analyzed the effect of C9orf116 on BRL-3A cells via over-expression and interference technique. MTT results showed that the cell viability of the interference group was significantly lower than the control group at 48h after transfection (P<0.05), whereas it was significantly higher in the over-expression group (P<0.05). The flow cytometry results showed that C9orf116 knockdown or over-expression had little effect on BRL-3A cell apoptosis. However, the number of cells in division phase (G2/M) was significantly reduced in the interference group (P<0.05), but significantly increased in the over-expression group (P<0.01). Furthermore, the expressions of cell proliferation-related genes CCNA2, CCND1 and MYC both at mRNA and protein levels were down-regulated in the interference group and up-regulated in the over-expression group. Therefore, we concluded that C9orf116 may promote cell proliferation by modulating cell cycle transition and the expression of key genes CCNA2, CCND1 and MYC in BRL-3A cells.

HuR Enhances Early Restitution of the Intestinal Epithelium by Increasing Cdc42 Translation

The mammalian intestinal mucosa exhibits a spectrum of responses after acute injury and repairs itself rapidly to restore the epithelial integrity. The RNA-binding protein HuR regulates the stability and translation of target mRNAs and is involved in many aspects of gut epithelium homeostasis, but its exact role in the regulation of mucosal repair after injury remains unknown. We show here that HuR is essential for early intestinal epithelial restitution by increasing the expression of cell division control protein 42 (Cdc42) at the posttranscriptional level. HuR bound to the Cdc42 mRNA via its 3' untranslated region, and this association specifically enhanced Cdc42 translation without an effect on the Cdc42 mRNA level. Intestinal epithelium-specific HuR knockout not only decreased Cdc42 levels in mucosal tissues, but it also inhibited repair of damaged mucosa induced by mesenteric ischemia/reperfusion in the small intestine and by dextran sulfate sodium in the colon. Furthermore, Cdc42 silencing prevented HuR-mediated stimulation of cell migration over the wounded area by altering the subcellular distribution of F-actin. These results indicate that HuR promotes early intestinal mucosal repair after injury by increasing Cdc42 translation and demonstrate the importance of HuR deficiency in the pathogenesis of delayed mucosal healing in certain pathological conditions.

Nurr1 promotes intestinal regeneration after ischemia/reperfusion injury by inhibiting the expression of p21 (Waf1/Cip1)

Intestinal ischemia/reperfusion (I/R) injury is a potentially life-threatening condition that can cause injuries to remote organs at the end stage. The damage caused by intestinal I/R insult induces changes in the barrier functions of the intestine, and the intrinsic mechanism of regeneration is often insufficient to restore barrier functions, as indicated by the high mortality rate of patients experiencing intestinal I/R injury. However, little is known about the mechanisms of intestinal regeneration after I/R injury. Here, we reported that nuclear receptor-related protein 1 (Nurr1), a nuclear orphan receptor, was induced during intestinal regeneration after I/R. Our findings showed that Nurr1 expression was consistent with the expression of Ki-67 and phosphorylated histone H3 (pH 3) in the intestine after I/R injury. Nurr1 knockdown led to G1-phase arrest mediated by p21 (Waf1/Cip1) activation, but Nurr1 overexpression reduced the proportion of IEC-6 cells in G1 phase as a result of p21 inhibition in a p53-independent manner. Using chromatin immunoprecipitation assays, luciferase assays, and mutational analysis, we demonstrated that Nurr1 directly inhibited the transcription of p21. These results define a novel Nurr1/p21 pathway that is involved in intestinal regeneration after I/R injury. These findings provide novel molecular insights into the pathogenesis of intestinal regeneration after I/R and possibly support the development of new potential therapies for intestinal I/R injury.

KEY MESSAGE

Nurr1 was induced during intestinal regeneration after I/R injury. Nurr1 promoted proliferation of intestinal epithelial cells after H/R injury. Nurr1 inhibited p21 expression in a p53-independent manner. Nurr1 inhibited p21 gene transcription by binding to p21 promoter directly.

M1 Macrophages Activate Notch Signalling in Epithelial Cells: Relevance in Crohn's Disease

BACKGROUND

The Notch signalling pathway plays an essential role in mucosal regeneration, which constitutes a key goal of Crohn's disease (CD) treatment. Macrophages coordinate tissue repair and several phenotypes have been reported which differ in the expression of surface proteins, cytokines and hypoxia-inducible factors (HIFs). We analysed the role of HIFs in the expression of Notch ligands in macrophages and the relevance of this pathway in mucosal regeneration.

METHODS

Human monocytes and U937-derived macrophages were polarized towards the M1 and M2 phenotypes and the expression levels of HIF-1α, HIF-2α, Jagged 1 (Jag1) and delta-like 4 (Dll4) were evaluated. The effects of macrophages on the expression of hairy and enhancer of split-1 (HES1, the main target of Notch signalling) and intestinal alkaline phosphatase (IAP, enterocyte marker) in epithelial cells in co-culture were also analysed. Phenotype macrophage markers and Notch signalling were evaluated in the mucosa of CD patients.

RESULTS

M1 macrophages were associated with HIF-1-dependent induction of Jag1 and Dll4, which increased HES1 protein levels and IAP activity in co-cultured epithelial cells. In the mucosa of CD patients a high percentage of M1 macrophages expressed both HIF-1α and Jag1 while M2 macrophages mainly expressed HIF-2α and we detected a good correlation between the ratio of M1/M2 macrophages and both HES1 and IAP protein levels.

CONCLUSION

M1, but not M2, macrophages are associated with HIF-1-dependent induction of Notch ligands and activation of epithelial Notch signalling pathway. In the mucosa of chronic CD patients, the prevalence of M2 macrophages is associated with diminution of Notch signalling and impaired enterocyte differentiation.

Post-transcriptional regulation of Wnt co-receptor LRP6 and RNA-binding protein HuR by miR-29b in intestinal epithelial cells

MicroRNAs (miRNAs) control gene expression by binding to their target mRNAs for degradation and/or translation repression and are implicated in many aspects of cellular physiology. Our previous study shows that miR-29b acts as a biological repressor of intestinal mucosal growth, but its exact downstream targets remain largely unknown. In the present study, we found that mRNAs, encoding Wnt co-receptor LRP6 (low-density lipoprotein-receptor-related protein 6) and RNA-binding protein (RBP) HuR, are novel targets of miR-29b in intestinal epithelial cells (IECs) and that expression of LRP6 and HuR is tightly regulated by miR-29b at the post-transcriptional level. miR-29b interacted with both Lrp6 and HuR mRNAs via their 3′-UTRs and inhibited LRP6 and HuR expression by destabilizing Lrp6 and HuR mRNAs and repressing their translation. Studies using heterologous reporter constructs revealed a greater repressive effect of miR-29b through a single binding site in the Lrp6 or HuR 3′-UTR, whereas deletion mutation of this site prevented miR-29b-induced repression of LRP6 and HuR expression. Repression of HuR by miR-29b in turn also contributed to miR-29b-induced LRP6 inhibition, since ectopic overexpression of HuR in cells overexpressing miR-29b restored LRP6 expression to near normal levels. Taken together, our results suggest that miR-29b inhibits expression of LRP6 and HuR post-transcriptionally, thus playing a role in the regulation of IEC proliferation and intestinal epithelial homoeostasis.

A Role for MYC in Lithium-Stimulated Repair of the Colonic Epithelium After DSS-Induced Damage in Mice

BACKGROUND

Chronic inflammation disrupts the colonic epithelial layer in patients afflicted by ulcerative colitis (UC). The use of inhibitors of glycogen synthase kinase three beta (GSK3β) has proven efficacious to mitigate disease symptoms in rodent models of UC by reducing the pro-inflammatory response. Less is known about whether these inhibitors promote colonic regeneration by stimulating proliferation of colonic epithelial cells.

AIMS

We investigated whether delivery of the GSK3β inhibitor, lithium chloride (LiCl), during the recovery period from acute DSS-induced colitis in mice promoted colonic regeneration and ameliorated disease symptoms. We also tested whether the c-MYC transcription factor (MYC) was involved in this response.

METHODS

Acute colitis was induced by administration of 2.5 % dextran sodium sulfate (DSS) to wild-type C57BL/6 mice for 5 days. During the recovery period, mice received a daily intraperitoneal (IP) injection of LiCl or 1X PBS as a control. Mice were weighed, colon lengths measured, disease activity index (DAI) scores were assessed, and histological analyses were performed on colonic sections. We analyzed transcripts and proteins in purified preparations of the colonic epithelium. We delivered the MYC inhibitor 10058-F4 via IP injection to assess the role of MYC in colonic regeneration.

RESULTS

Lithium treatments promoted recovery from acute DSS-induced damage by increasing expression of Myc transcripts, MYC proteins, and expression of a subset of Wnt/MYC target genes in the colonic epithelium. Inhibiting MYC function with 10058-F4 blunted the lithium response.

CONCLUSIONS

By inducing Myc expression in the colonic epithelium, lithium promotes colonic regeneration after DSS-induced colitis. Therefore, the use of lithium may be of therapeutic value to manage individuals afflicted by UC.

Bioinformatics Knowledge Map for Analysis of Beta-Catenin Function in Cancer

Given the wealth of bioinformatics resources and the growing complexity of biological information, it is valuable to integrate data from disparate sources to gain insight into the role of genes/proteins in health and disease. We have developed a bioinformatics framework that combines literature mining with information from biomedical ontologies and curated databases to create knowledge "maps" of genes/proteins of interest. We applied this approach to the study of beta-catenin, a cell adhesion molecule and transcriptional regulator implicated in cancer. The knowledge map includes post-translational modifications (PTMs), protein-protein interactions, disease-associated mutations, and transcription factors co-activated by beta-catenin and their targets and captures the major processes in which beta-catenin is known to participate. Using the map, we generated testable hypotheses about beta-catenin biology in normal and cancer cells. By focusing on proteins participating in multiple relation types, we identified proteins that may participate in feedback loops regulating beta-catenin transcriptional activity. By combining multiple network relations with PTM proteoform-specific functional information, we proposed a mechanism to explain the observation that the cyclin dependent kinase CDK5 positively regulates beta-catenin co-activator activity. Finally, by overlaying cancer-associated mutation data with sequence features, we observed mutation patterns in several beta-catenin PTM sites and PTM enzyme binding sites that varied by tissue type, suggesting multiple mechanisms by which beta-catenin mutations can contribute to cancer. The approach described, which captures rich information for molecular species from genes and proteins to PTM proteoforms, is extensible to other proteins and their involvement in disease.

Transgenic Expression of miR-222 Disrupts Intestinal Epithelial Regeneration by Targeting Multiple Genes Including Frizzled-7

Defects in intestinal epithelial integrity occur commonly in various pathologies. miR-222 is implicated in many aspects of cellular function and plays an important role in several diseases, but its exact biological function in the intestinal epithelium is underexplored. We generated mice with intestinal epithelial tissue-specific overexpression of miR-222 to investigate the function of miR-222 in intestinal physiology and diseases in vivo. Transgenic expression of miR-222 inhibited mucosal growth and increased susceptibility to apoptosis in the small intestine, thus leading to mucosal atrophy. The miR-222-elevated intestinal epithelium was vulnerable to pathological stress, since local overexpression of miR-222 not only delayed mucosal repair after ischemia/reperfusion-induced injury, but also exacerbated gut barrier dysfunction induced by exposure to cecal ligation and puncture. miR-222 overexpression also decreased expression of the Wnt receptor Frizzled-7 (FZD7), cyclin-dependent kinase 4 and tight junctions in the mucosal tissue. Mechanistically, we identified the Fzd7 messenger ribonucleic acid (mRNA) as a novel target of miR-222 and found that [miR-222/Fzd7 mRNA] association repressed Fzd7 mRNA translation. These results implicate miR-222 as a negative regulator of normal intestinal epithelial regeneration and protection by downregulating expression of multiple genes including the Fzd7. Our findings also suggest a novel role of increased miR-222 in the pathogenesis of mucosal growth inhibition, delayed healing and barrier dysfunction.

Anti-inflammatory activity of Wnt signaling in enteric nervous system: in vitro preliminary evidences in rat primary cultures

Background

In the last years, Wnt signaling was demonstrated to regulate inflammatory processes. In particular, an increased expression of Wnts and Frizzled receptors was reported in inflammatory bowel disease (IBD) and ulcerative colitis to exert both anti- and pro-inflammatory functions regulating the intestinal activated nuclear factor κB (NF-кB), TNFa release, and IL10 expression.

Methods

To investigate the role of Wnt pathway in the response of the enteric nervous system (ENS) to inflammation, neurons and glial cells from rat myenteric plexus were treated with exogenous Wnt3a and/or LPS with or without supporting neurotrophic factors such as basic fibroblast growth factor (bFGF), epithelial growth factor (EGF), and glial cell-derived neurotrophic factor (GDNF). The immunophenotypical characterization by flow cytometry and the protein and gene expression analysis by qPCR and Western blotting were carried out.

Results

Flow cytometry and immunofluorescence staining evidenced that enteric neurons coexpressed Frizzled 9 and toll-like receptor 4 (TLR4) while glial cells were immunoreactive to TLR4 and Wnt3a suggesting that canonical Wnt signaling is active in ENS.

Under in vitro LPS treatment, Western blot analysis demonstrated an active cross talk between canonical Wnt signaling and NF-кB pathway that is essential to negatively control enteric neuronal response to inflammatory stimuli. Upon costimulation with LPS and Wnt3a, a significant anti-inflammatory activity was detected by RT-PCR based on an increased IL10 expression and a downregulation of pro-inflammatory cytokines TNFa, IL1B, and interleukin 6 (IL6). When the availability of neurotrophic factors in ENS cultures was abolished, a changed cell reactivity by Wnt signaling was observed at basal conditions and after LPS treatment.

Conclusions

The results of this study suggested the existence of neuronal surveillance through FZD9 and Wnt3a in enteric myenteric plexus. Moreover, experimental evidences were provided to clarify the correlation among soluble trophic factors, Wnt signaling, and anti-inflammatory protection of ENS.

Beta-catenin is elevated in human benign prostatic hyperplasia specimens compared to histologically normal prostate tissue

Benign prostatic hyperplasia (BPH) is linked to lower urinary tract symptoms (LUTS) such as incomplete bladder emptying, urinary frequency and urgency. Mechanisms responsible for BPH are not fully known. Here, we tested whether beta-catenin (CTNNB1) immunostaining intensity and distribution differ in human glandular BPH tissue specimens compared to normal prostate tissue. Multiplex immunostaining of CTNNB1, its putative transcriptional target gene lymphoid enhancer binding factor 1 (LEF1), and the epithelial marker E-cadherin were examined in clinical human prostate specimens with or without histological BPH (pure epithelial or mixed stromal-epithelial nodules). BPH specimens were obtained from 24 men who experienced LUTS and underwent transurethral resection of the prostate surgery. Control specimens were tumor-adjacent histologically normal prostate tissue from 48 patients who underwent radical prostatectomy. The resulting multispectral images were unmixed and optical densities recorded to quantify staining abundance, cellular (membranous, cytoplasmic, and nuclear) and tissue localization (stromal versus epithelial), and determination of percentage of CTNNB1-positive cells. The following CTNNB1 indices were significantly higher in BPH compared to normal prostate tissue: overall staining intensity, staining intensity in prostate stromal cell membranes, cytoplasm and nuclei, and prostate epithelial cell nuclei. The following LEF1 indices were significantly lower in BPH compared to tumor-adjacent normal prostate tissue: stromal LEF1 staining intensity, percentage of LEF1-positive stromal cells, and intensity of LEF1 staining in stromal cell membranes, cytoplasm, and nuclei. The percentage of stromal cells with CTNNB1(+)/LEF1(-) nuclei was higher and percentage of stromal cells with CTNNB1(-)/LEF1(+) nuclei was lower in BPH compared to tumor-adjacent normal prostate tissues. These results support the hypothesis that CTNNB1 expression increases in specific BPH tissue compartments. Further, since nuclear LEF1 staining does not coincide with cytoplasmic or nuclear CTNNB1 staining, it does not appear to be a reliable index of CTNNB1 activity in adult human prostate.

RNA-binding protein HuR promotes growth of small intestinal mucosa by activating the Wnt signaling pathway

Inhibition of growth of the intestinal epithelium, a rapidly self-renewing tissue, is commonly found in various critical disorders. The RNA-binding protein HuR is highly expressed in the gut mucosa and modulates the stability and translation of target mRNAs, but its exact biological function in the intestinal epithelium remains unclear. Here, we investigated the role of HuR in intestinal homeostasis using a genetic model and further defined its target mRNAs. Targeted deletion of HuR in intestinal epithelial cells caused significant mucosal atrophy in the small intestine, as indicated by decreased cell proliferation within the crypts and subsequent shrinkages of crypts and villi. In addition, the HuR-deficient intestinal epithelium also displayed decreased regenerative potential of crypt progenitors after exposure to irradiation. HuR deficiency decreased expression of the Wnt coreceptor LDL receptor-related protein 6 (LRP6) in the mucosal tissues. At the molecular level, HuR was found to bind the Lrp6 mRNA via its 3'-untranslated region and enhanced LRP6 expression by stabilizing Lrp6 mRNA and stimulating its translation. These results indicate that HuR is essential for normal mucosal growth in the small intestine by altering Wnt signals through up-regulation of LRP6 expression and highlight a novel role of HuR deficiency in the pathogenesis of intestinal mucosal atrophy under pathological conditions.

Stem cells and biopharmaceuticals: vital roles in the growth of tissue-engineered small intestine

Tissue engineering currently constitutes a complex, multidisciplinary field exploring ideal sources of cells in combination with scaffolds or delivery systems in order to form a new, functional organ to replace native organ lack or loss. Short bowel syndrome (SBS) is a life-threatening condition with high morbidity and mortality rates in children. Current therapeutic strategies consist of costly and risky allotransplants that demand lifelong immunosuppression. A promising alternative is the implantation of autologous organoid units (OU) to create a tissue-engineered small intestine (TESI). This strategy is proven to be stem cell and mesenchyme dependent. Intestinal stem cells (ISCs) are located at the base of the crypt and are responsible for repopulating the cycling mucosa up to the villus tip. The stem cell niche governs the biology of ISCs and, together with the rest of the epithelium, communicates with the underlying mesenchyme to sustain intestinal homeostasis. Biopharmaceuticals are broadly used in the clinic to activate or enhance known signaling pathways and may greatly contribute to the development of a full-thickness intestine by increasing mucosal surface area, improving blood supply, and determining stem cell fate. This review will focus on tissue engineering as a means of building the new small intestine, highlighting the importance of stem cells and recombinant peptide growth factors as biopharmaceuticals.

The metastasis suppressor NDRG1 modulates the phosphorylation and nuclear translocation of β-catenin through mechanisms involving FRAT1 and PAK4

N-myc downstream-regulated gene 1 (NDRG1) is a potent metastasis suppressor that has been demonstrated to inhibit the transforming growth factor β (TGF-β)-induced epithelial-to-mesenchymal transition (EMT) by maintaining the cell-membrane localization of E-cadherin and β-catenin in prostate and colon cancer cells. However, the precise molecular mechanism remains unclear. In this investigation, we demonstrate that NDRG1 inhibits the phosphorylation of β-catenin at Ser33/37 and Thr41 and increases the levels of non-phosphorylated β-catenin at the plasma membrane in DU145 prostate cancer cells and HT29 colon cancer cells. The mechanism of inhibiting β-catenin phosphorylation involves the NDRG1-mediated upregulation of the GSK3β-binding protein FRAT1, which prevents the association of GSK3β with the Axin1-APC-CK1 destruction complex and the subsequent phosphorylation of β-catenin. Additionally, NDRG1 is shown to modulate the WNT-β-catenin pathway by inhibiting the nuclear translocation of β-catenin. This is mediated through an NDRG1-dependent reduction in the nuclear localization of p21-activated kinase 4 (PAK4), which is known to act as a transporter for β-catenin nuclear translocation. The current study is the first to elucidate a unique molecular mechanism involved in the NDRG1-dependent regulation of β-catenin phosphorylation and distribution.

Sodium glucose cotransporter 1 ligand BLF501 as a novel tool for management of gastrointestinal mucositis

Background

Recent studies demonstrated that engagement of sodium glucose transporter 1 (SGLT-1) by orally administered D-glucose protects the intestinal mucosa from lipopolysaccharide (LPS)-induced injury. We tested whether SGLT-1 engagement might protect the intestinal mucosa from doxorubicin (DXR)- and 5-fluorouracil (5-FU)-induced injury in animal models mimicking acute or chronic mucositis.

Methods

Mice were treated intraperitoneally with DXR, alone or in combination with 5-FU, and orally with BLF501, a glucose-derived synthetic compound with high affinity for SGLT-1. Intestinal mucosal epithelium integrity was assessed by histological analysis, cellular proliferation assays, real-time PCR gene expression assays and Western blot assays. Student’s t-test (paired two-tailed) and χ² analyses were used for comparisons between groups. Differences were considered significant at p < 0.05.

Results

BLF501 administration in mice treated with DXR and/or 5-FU decreased the injuries to the mucosa in terms of epithelial integrity and cellular proliferative ability. Co-treatment with BLF501 led to a normal expression and distribution of both zonula occludens-1 (ZO-1) and beta-catenin, which were underexpressed after treatment with either chemotherapeutic agent alone. BLF501 administration also restored normal expression of caspase-3 and ezrin/radixin/moesin (ERM), which were overexpressed after treatment with DXR and 5-FU. In SGLT1-/- mice, BLF501 had no detectable effects. BLF501 administration in wild-type mice with growing A431 tumors did not modify antitumor activity of DXR.

Conclusions

BLF501-induced protection of the intestinal mucosa is a promising novel therapeutic approach to reducing the severity of chemotherapy-induced mucositis.

Black raspberries protectively regulate methylation of Wnt pathway genes in precancerous colon tissue

Ulcerative colitis is frequently an intermediate step to colon cancer. The interleukin-10 knockout mouse is a genetic model of this progression. We report that knockout mice fed 5% black raspberries (BRB) had significantly less colonic ulceration as compared with knockout mice that consumed the control diet. Dysfunction of the Wnt signaling pathway is a key event in ulcerative colitis-associated colon carcinogenesis. Therefore, we investigated the effects of BRBs on the Wnt pathway and found that the BRB-fed knockout mice exhibited a significantly lower level of β-catenin nuclear translocation. We followed-up this observation by evaluating the effect of BRBs on selected Wnt pathway antagonists. The mRNA expression levels of wif1, sox17, and qki were diminished in the knockout mice, whereas they were expressed at normal levels in knockout mice that were fed BRBs. The lower mRNA expression of these genes in the colon from the knockout mice correlated with hypermethylation of their promoter regions; BRBs decreased their promoter methylation and increased mRNA expression of these genes. This hypomethylation was associated with elevated protein expression of key proteins/enzymes that augment methylation, for example, dnmt3b, hdac1, hdac2, and mbd2 in the knockout mice; in addition, BRBs decreased the protein expression of these proteins/enzymes. The knockout mouse model recapitulates what occurs in human ulcerative colitis. Promoter methylation of CDH1 and SFRP1 was significantly higher in human ulcerative colitis tissues compared with their adjacent normal tissues. In conclusion, our results suggest that BRBs inhibit colonic ulceration and, ultimately, colon cancer partly through inhibiting aberrant epigenetic events that dysregulate Wnt signaling.

Cell cycle-regulatory cyclins and their deregulation in oral cancer

Oral cancer is a growth-related disorder, and cyclins are the prime regulators of cell division. Cyclins are associated with the pathogenesis of oral cancer and are considered valuable biomarkers for diagnosis and prognosis. These important molecules are regulated in many ways to achieve a gain in function and are involved in promoting neoplastic growth. While the causes of most cyclin overexpression are varied, these cyclins may be induced by buccal mucosal insult mainly with carcinogens that alter various pathways propelling oral cancer. Substantial experimental evidences support a link between oncogenic signaling pathways and the deregulation of cyclins in oral cancer. This review focuses on the mechanisms by which cyclins are regulated and promote oral oncogenesis.

Polyamines and Gut Mucosal Homeostasis

The epithelium of gastrointestinal (GI) mucosa has the most rapid turnover rate of any tissue in the body and its integrity is preserved through the dynamic balance between cell migration, proliferation, growth arrest and apoptosis. To maintain tissue homeostasis of the GI mucosa, the rates of epithelial cell division and apoptosis must be highly regulated by various extracellular and intracellular factors including cellular polyamines. Natural polyamines spermidine, spermine and their precursor putrescine, are organic cations in eukaryotic cells and are implicated in the control of multiple signaling pathways and distinct cellular functions. Normal intestinal epithelial growth depends on the available supply of polyamines to the dividing cells in the crypts, and polyamines also regulate intestinal epithelial cell (IEC) apoptosis. Although the specific molecular processes controlled by polyamines remains to be fully defined, increasing evidence indicates that polyamines regulate intestinal epithelial integrity by modulating the expression of various growth-related genes. In this review, we will extrapolate the current state of scientific knowledge regarding the roles of polyamines in gut mucosal homeostasis and highlight progress in cellular and molecular mechanisms of polyamines and their potential clinical applications.