Colonic crypt stem cell functions are controlled by tight junction protein claudin-7 through Notch/Hippo signaling.

The tight junction protein claudin-7 is essential for tight junction function and intestinal homeostasis. Cldn7 deletion in mice leads to an inflammatory bowel disease-like phenotype exhibiting severe intestinal epithelial damage, weight loss, inflammation, mucosal ulcerations, and epithelial hyperplasia. Claudin-7 has also been shown to be involved in cancer metastasis and invasion. Here, we test our hypothesis that claudin-7 plays an important role in regulating colonic intestinal stem cell function. Conditional knockout of Cldn7 in the colon led to impaired epithelial cell differentiation, hyperproliferative epithelium, a decrease in active stem cells, and dramatically altered gene expression profiles. In 3D colonoid culture, claudin-7-deficient crypts were unable to survive and form spheroids, emphasizing the importance of claudin-7 in stem cell survival. Inhibition of the Hippo pathway or activation of Notch signaling partially rescued the defective stem cell behavior. Concurrent Notch activation and Hippo inhibition resulted in restored colonoid survival, growth, and differentiation to the level comparable to those of wild-type derived crypts. In this study, we highlight the essential role of claudin-7 in regulating Notch and Hippo signaling-dependent colonic stem cell functions, including survival, self-renewal, and differentiation. These new findings may shed light on potential avenues to explore for drug development in colorectal cancer.

The substantia nigra modulates proximal colon tone and motility in a vagally-dependent manner in the rat.

A monosynaptic pathway connects the substantia nigra pars compacta (SNpc) to neurons of the dorsal motor nucleus of the vagus (DMV). This monosynaptic pathway modulates the vagal control of gastric motility. It is not known, however, whether this nigro-vagal pathway also modulates the tone and motility of the proximal colon. In rats, microinjection of retrograde tracers in the proximal colon and of anterograde tracers in SNpc showed that bilaterally labelled colonic-projecting neurons in the DMV received inputs from SNpc neurons. Microinjections of the ionotropic glutamate receptor agonist, NMDA, in the SNpc increased proximal colonic motility and tone, as measured via a strain gauge aligned with the colonic circular smooth muscle; the motility increase was inhibited by acute subdiaphragmatic vagotomy. Upon transfection of SNpc with pAAV-hSyn-hM3D(Gq)-mCherry, chemogenetic activation of nigro-vagal nerve terminals by brainstem application of clozapine-N-oxide increased the firing rate of DMV neurons and proximal colon motility; both responses were abolished by brainstem pretreatment with the dopaminergic D1-like antagonist SCH23390. Chemogenetic inhibition of nigro-vagal nerve terminals following SNpc transfection with pAAV-hSyn-hM4D(Gi)-mCherry decreased the firing rate of DMV neurons and inhibited proximal colon motility. These data suggest that a nigro-vagal pathway modulates activity of the proximal colon motility tonically via a discrete dopaminergic synapse in a manner dependent on vagal efferent nerve activity. Impairment of this nigro-vagal pathway may contribute to the severely reduced colonic transit and prominent constipation observed in both patients and animal models of parkinsonism. KEY POINTS: Substantia nigra pars compacta (SNpc) neurons are connected to the dorsal motor nucleus of the vagus (DMV) neurons via a presumed direct pathway. Brainstem neurons in the lateral DMV innervate the proximal colon. Colonic-projecting DMV neurons receive inputs from neurons of the SNpc. The nigro-vagal pathway modulates tone and motility of the proximal colon via D1-like receptors in the DMV. The present study provides the mechanistic basis for explaining how SNpc alterations may lead to a high rate of constipation in patients with Parkinson's Disease.

Experimental models of gut-first Parkinson's disease: A systematic review.

BACKGROUND: There is strong support from studies in humans and in animal models that Parkinson's disease (PD) may begin in the gut. This brings about a unique opportunity for researchers in the field of neurogastroenterology to contribute to advancing the field and making contributions that could lead to the ability to diagnose and treat PD in the premotor stages. Lack of familiarity with some of the aspects of the experimental approaches used in these studies may present a barrier for neurogastroenterology researchers to enter the field. Much remains to be understood about intestinal-specific components of gut-first PD pathogenesis and the field would benefit from contributions of enteric and central nervous system neuroscientists. PURPOSE: To address these issues, we have conducted a systematic review of the two most frequently used experimental models of gut-first PD: transneuronal propagation of α-synuclein preformed fibrils and oral exposure to environmental toxins. We have reviewed the details of these studies and present methodological considerations for the use of these models. Our aim is that this review will serve as a framework and useful reference for neuroscientists, gastroenterologists, and neurologists interested in applying their expertise to advancing our understanding of gut-first PD.

Association between gene polymorphism of GRK5 and breast cancer risk in Chinese population.

PURPOSE: Potential influences of GRK5 polymorphism on cancer risks have been reported. This study aimed to explore the distribution of GRK5 genotypes and alleles in Chinese breast cancer (BCa) patients, and to analyze the association between GRK5 and BCa risk. METHODS: Blood samples were collected from 412 BCa patients and 533 healthy individuals for isolating genomic DNA. GRK5 polymorphisms of Gln41Leu A > T and Arg304His G > A, and their alleles were detected using PCR-RFLP. Their influences on BCa susceptibility and pathological indexes were analyzed using Logistic regression model. RESULTS: No significant differences in age, body mass index (BMI) and smoking status were found between BCa patients and healthy persons, while significant differences were detected in drinking status, family history of cancer, hypertension and diabetes. GRK5Gln41Leu A > T and its allele frequency distribution were correlated to BCa susceptibility, while GRK5 Arg304His G > A was not. Higher risks of GRK5 Gln41Leu A > T and Arg304His G > A indicated a higher susceptibility to BCa. Compared with people carrying 0-1 risk allele, those carrying 2-4 risk alleles of GRK5 Gln41Leu A > T and Arg304His G > A of had a higher susceptibility to BCa, manifesting as worse tumor staging and grading, and higher rates of estrogen receptor (ER) (-), progesterone receptor (PR) (-) and HER2 (-). CONCLUSIONS: Gln41Leu A > T and Arg304His G > A fusion gene polymorphisms of GRK5 are vital genetic susceptibility genes to BCa. Our findings require to be validated in a multicenter study with a high-quality large sample size.

Tight Junction Protein Claudin-7 Is Essential for Intestinal Epithelial Stem Cell Self-Renewal and Differentiation.

BACKGROUND & AIMS: Claudin-7 (Cldn7) is a tight junction (TJ) membrane protein located at the apical TJ and basolateral side of intestinal epithelial cells. Deletion of Cldn7 by gene targeting leads to the inflammatory bowel disease-like phenotype in mice, which includes weight loss, diarrhea, mucosa ulceration, and severe intestinal epithelial damage. In this study, we test our hypothesis that Cldn7 plays a critical role in regulating intestinal crypt stem cell functions. METHODS: Gene expression microarray, quantitative reverse-transcription polymerase chain reaction, in situ hybridization, histologic examinations, immunoblotting, 3-dimensional organoid culture, and various treatments to rescue Cldn7-deficient organoid defects were conducted using global Cldn7 knockout mice and inducible, conditional Cldn7 knockout mice. RESULTS: Gene deletion of Cldn7 in intestines showed significant alteration of expression profiles with striking down-regulation of intestinal crypt stem cell markers such as Olfm4, dislocated proliferative cells, and disrupted epithelial cell differentiation. In addition, the isolated Cldn7-deficient crypts where the stem cells reside were either unable to survive at all or formed defective spheroids, highlighting the functional impairment of crypt stem cells in the absence of Cldn7. Remarkably, the Cldn7-expressing organoids with buddings underwent rapid cell degeneration within days after turning off Cldn7 expression in the culture. We identified that activation of Wnt/ß-catenin signaling rescued the organoid defects caused by Cldn7 deletion. CONCLUSIONS: In this study, we show that Cldn7 is indispensable in controlling Wnt/ß-catenin signaling-dependent intestinal epithelial stem cell survival, self-renewal, and cell differentiation. This study could open a door to study roles of TJ proteins in stem cell regulations in other tissues and organs.

The 3-Phosphoinositide-Dependent Protein Kinase 1 Inhibits Rod Photoreceptor Development.

The transition of rod precursor cells to post-mitotic rod photoreceptors can be promoted by extrinsic factors such as insulin-like growth factor 1 (IGF-1), which regulates phosphatidylinositide concentration, and consequently the 3-phosphoinositide-dependent protein kinase-1 (PDPK-1). PDPK-1 is a 63 kDa cytoplasmic kinase that controls cell proliferation and differentiation. In the mouse retina, PDPK-1 and its phosphorylated derivative p-PDPK-1 (Ser241), showed peak expression during the first postnatal (PN) day with a substantial decline by PN7 and in the adult retina. Though initially widely distributed among cell types, PDPK-1 expression decreased first in the inner retina and later in the outer retina. When PDPK-1 is inhibited in neonatal retinal explants by BX795, there is a robust increase in rod photoreceptor numbers. The increase in rods depended on the activity of PKC, as BX795 had no effect when PKC is inhibited. Inhibition of PDPK-1-dependent kinases, such as P70-S6K, but not others, such as mTORC-1, stimulated rod development. The P70-S6K-dependent increase in rods appears to be correlated with phosphorylation of Thr252 and not at Thr389, a substrate of mTORC-1. This pathway is also inactive while PKC activity is inhibited. We also found that inhibition of the kinase mTORC-2, also stimulated by insulin activity, similarly increased rod formation, and this effect appears to be independent of PKC activity. This may represent a novel intracellular signaling pathway that also stimulates photoreceptor development. Consistent with previous studies, stimulation of STAT3 activity is sufficient to prevent any PDPK-1, P70-S6K, or mTORC2-dependent increase in rods. Together the data indicate that PDPK-1 and other intrinsic kinases downstream of IGF-1 are key regulators of rod photoreceptor formation.

Severe Intestinal Inflammation in the Small Intestine of Mice Induced by Controllable Deletion of Claudin-7.

BACKGROUND: As a potential tumor suppressor gene, Claudin-7 (Cldn7), which is a component of tight junctions, may play an important role in colorectal cancer occurrence and development. AIMS: To generate a knockout mouse model of inducible conditional Cldn7 in the intestine and analyze the phenotype of the mice after induction with tamoxifen. METHODS: We constructed Cldn7-flox transgenic mice and crossed them with Villin-CreERT2 mice. The Cldn7 inducible conditional knockout mice appeared normal and were well developed at birth. We induced Cldn7 gene deletion by injecting different dosages of tamoxifen into the mice and then conducted a further phenotypic analysis. RESULTS: After induction for 5 days in succession at a dose of 200 µl tamoxifen in sunflower oil at 10 mg/ml per mouse every time, the mice appeared dehydrated, had a lower temperature, and displayed inactivity or death. The results of hematoxylin-eosin staining showed that the intestines of the Cldn7 inducible conditional knockout mice had severe intestinal defects that included epithelial cell sloughing, necrosis, inflammation and hyperplasia. Owing to the death of ICKO mice, we adjusted the dose of tamoxifen to a dose of 100 µl in sunflower oil at 10 mg/ml per mouse (aged more than 8 weeks old) every 4 days. And we could induce atypical hyperplasia and adenoma in the intestine. Immunofluorescent staining indicated that the intestinal epithelial structure was destroyed. Electron microscopy experimental analysis indicated that the intercellular gap along the basolateral membrane of Cldn7 inducible conditional knockout mice in the intestine was increased and that contact between the cells and matrix was loosened. CONCLUSIONS: We generated a model of intestinal Cldn7 inducible conditional knockout mice. Intestinal Cldn7 deletion induced by tamoxifen initiated inflammation and hyperplasia in mice.

Epithelial Mesenchymal Transition in Embryonic Development, Tissue Repair and Cancer: A Comprehensive Overview.

The epithelial mesenchymal transition (EMT) plays a central role in both normal physiological events (e.g., embryonic development) and abnormal pathological events (e.g., tumor formation and metastasis). The processes that occur in embryonic development are often reactivated under pathological conditions such as oncogenesis. Therefore, defining the regulatory networks (both gene and protein levels) involved in the EMT during embryonic development will be fundamental in understanding the regulatory networks involved in tumor development, as well as metastasis. There are many molecules, factors, mediators and signaling pathways that are involved in the EMT process. Although the EMT is a very old topic with numerous publications, recent new technologies and discoveries give this research area some new perspective and direction. It is now clear that these important processes are controlled by a network of transcriptional and translational regulators in addition to post-transcriptional and post-translational modifications that amplify the initial signals. In this review article, we will discuss some key concepts, historical findings, as well as some recent progresses in the EMT research field.

Animal models for studying epithelial barriers in neonatal necrotizing enterocolitis, inflammatory bowel disease and colorectal cancer.

The intestinal epithelial cells line the luminal surface of the entire gastrointestinal tract which is crucial for the absorption of nutrients and prevention of pathogens entering from the external environment. The epithelial barrier plays an important role in organ development, disease pathogenesis, and aging. The major component of an epithelial barrier is the single columnar epithelium and tight junctions. Tight junctions are located at the most apical region of the junctional complex and contain many integral membrane proteins, such as occludin, the claudin family, and junctional adhesion molecules (JAMs). The disruption of intestinal epithelial barriers may lead to several pathophysiological conditions causing malabsorption of nutrition and chronic inflammation. In this review, we provide an update on the alterations of epithelial barriers associated with gut diseases using experimental animal models; we appraise the role of tight junctions in neonatal necrotizing enterocolitis (NEC), inflammatory bowel disease (IBD), and colorectal cancer; we also compare some common features as well as differences and similarities in the pathophysiology of intestinal inflammation in neonatal (NEC) and adult (IBD) gut.

Decreased CD8+CD28+/CD8+CD28- T cell ratio can sensitively predict poor outcome for patients with complicated Crohn disease.

Crohn disease (CD) with complications such as penetrating, stricturing, and perianal disease is called complicated CD. The aim of this study is to test the efficiency with which the CD8CD28/CD8CD28 cell balance can predict a subsequent active stage in patients with newly diagnosed complicated CD.Seventeen patients with complicated CD and 48 CD patients with no complications were enrolled. Blood CD8 T cells were tested from all of the 65 newly diagnosed CD patients upon enrollment. The potential risk factors were compared between the 2 groups. A 30-week follow-up was performed, and the efficiency of the CD8 cell balance at predicting active CD was analyzed using receiver-operating characteristic curves. The cumulative remission lasting rates (CRLRs) were analyzed using the Kaplan-Meier method.Compared with the control CD group, patients with complicated CD were predominantly male and younger in age; they also had lower body mass indices (BMIs), higher Crohn disease activity indices (CDAIs), higher immunosuppressant and steroid prescription rates, and significantly higher surgical rates. The CD8CD28/CD8CD28 balance was associated with BMI, CDAI, steroids, and surgery. The CD8CD28/CD8CD28 ratios were significantly lower at week 0 and on the 6th, 22nd, and 30th week during follow-up with a shorter lasting time of remission for the complicated CD patients. The CD8CD28/CD8CD28 ratio could accurately predict the active stage for the patients with complicated CD, and the highest sensitivity (89.2%) and specificity (85.3%) were found when the ratio was 1.03. Treatment with steroids and surgery, along with a significantly lower CD8CD28/CD8CD28 ratio and lower CRLRs, was closely related to a worse outcome for the patients with complicated CD.Patients requiring steroids and surgery experience more severe disease activity and thus a disequilibrated immunological balance, which could be the main reason for a decreased CD8CD28/CD8CD28 ratio. This ratio can sensitively predict the active stage for patients with complicated CD, and more care should be taken when this ratio is <1.03.

CD8+CD28+/CD8+CD28- T cell equilibrium can predict the active stage for patients with inflammatory bowel disease.

BACKGROUND/AIM: The balance of blood CD8+CD28+/CD8+CD28- T cells has been verified to be vital for patients with ulcerative colitis (UC), but their role in inflammatory bowel disease (IBD) remains unknown. This investigation aimed to evaluate the efficiency of the balance in predicting the active stage in IBD patients. METHODS: Fifty-three IBD subjects, including 31 UC and 22 Crohn's disease (CD) patients, were enrolled, and their peripheral blood CD8+CD28+ and CD8+CD28- T cell levels were tested using flow cytometry. The risk factors related to prognosis were compared between UC and CD patients. A 1-year follow-up was performed for all the IBD patients, and the CD8+ T cells and their ratio were compared at the 3rd, 6th, 9th, and 12th months during follow-up. The sensitivity and specificity of the CD8+ T cell level and balance were analyzed through receiver operator characteristic (ROC) curves. The cumulative remission lasting rates (CRLRs) under the different factors were analyzed using the Kaplan-Meier method. RESULTS: Higher prescription rates of immunosuppressants, steroids, probiotics, and biological agents (BAs) were found in CD subjects in comparison to UC subjects (P=0.005, 0.024, 0.034, and 0.001), as was a higher active rate during follow-up (95.5% of CD patients vs 67.7% of UC patients, P=0.035). The CD8+CD28+ T cell level and the CD8+CD28+/CD8+CD28- T cell ratio were significantly higher in UC patients than in CD patients, but the reverse was true for CD8+CD28- T cells during follow-up at the 9th and 12th month (all P<0.05). The diagnostic models of the initial CD8+CD28+ and CD8+CD28- T cell numbers and the CD8+CD28+/CD8+CD28- T cell ratio in predicting the active stage were found to be significant, with areas under the curves (AUCs) of 0.883, 0.098, and 0.913 for UC subjects (with 95% CI: 0.709-0.940, 0.009-0.188, and 0.842-1.003; P=0.001, 0.00, and 0.000) and 0.812, 0.078, and 0.898 for CD subjects (with 95% CI: 0.683-0.957, 0.003-0.158, and 0.837-0.998; P=0.003, 0.00, and 0.000). The cut-off values showed that when the ratios were 1.30 for UC and 1.22 for CD patients, the best sensitivity and specificity were observed, with 91.6% and 89.0% for UC and 88.5% and 85.1% for CD, respectively. The CRLRs were significantly higher in female, non-BA-treated, non-surgical IBD subjects when compared to male, BA-treated, surgical subjects (P=0.031, 0.000, and 0.000). The number of CD8+CD28+ and CD8+CD28- T cells and the CD8+CD28+/CD8+CD28- T cell ratio were correlated with BA treatment and surgery (all P<0.05). CONCLUSION: The CD8+CD28+/CD8+CD28- T cell balance, expected to be a novel immunologic marker, presented a satisfactory efficiency with high sensitivity and specificity in predicting the active stage in UC and CD patients, and the balance was closely related to the use of BAs and surgery.

Disequilibrium in the CD8+CD28+/CD8+CD28- T Lymphocyte Balance Is Related to Prognosis in Rats with Trinitrobenzenesulfonic Acid-Induced Colitis.

PURPOSE: The CD8+CD28+/CD8+CD28- T lymphocyte balance is vital for human ulcerative colitis (UC) but has not been defined in experimental colitis. This investigation will try to identify the changes that occur in the CD8+CD28+/CD8+CD28- T lymphocyte balance during the progression of trinitrobenzenesulfonic acid (TNBS)-induced colitis in rats. METHODS: The frequencies of blood CD8+CD28+ and CD8+CD28- T lymphocytes were detected in the rats belonging to the normal, model, and treated groups on five days using flow cytometry. The treated rats were administered with mesalazine and were euthanized after a 14-day treatment, as were the normal and model rats. The sensitivity and specificity of the CD8+CD28+/CD8+CD28- T lymphocyte balance in diagnosing early colitis were analyzed by receiver operating characteristics (ROC) curves. The frequencies of CD8+CD28+ and CD8+CD28- T lymphocytes in the colon tissue were tested via immunofluorescence. ELISA was used to measure the levels of the cytokines. Immunohistochemistry and Western blotting were used to detect the colonic expression of JAK3, STAT6, NFATc2, and GATA3. RESULTS: We found that the ratio of CD8+CD28+/CD8+CD28- T lymphocytes decreased, as did the level of interleukin-7, but not IL-12p40, IL-13, or IL-15, in the blood; however, the ratio increased along with JAK3, STAT6, NFATc2, and GATA3 in the colon of the rats with colitis. The changes were effectively reversed through the administration of mesalazine for 13 days. Surprisingly, the balance in the blood could sensitively distinguish rats with early colitis from normal rats. CONCLUSION: These data show that increase in CD8+CD28+ T cells in blood and decrease in CD8+CD28- T cells in colon are associated with experimental colitis.

Regulation of rod photoreceptor differentiation by STAT3 is controlled by a tyrosine phosphatase.

Signal pathways that reduce the levels of tyrosine-phosphorylated STAT3 (pSTAT3) allow late retinal progenitors to exit the cell cycle and enter a terminal differentiation pathway into rod photoreceptors. In the mouse retina, we previously identified PKC-ß1 and PKC-γ isoforms as essential components of a key signal pathway and IGF-1 as a major extrinsic factor regulating rod formation. In this manuscript, we demonstrate that PKC decreases phosphotyrosine but not phosphoserine on STAT3 in neonatal mouse retinas. Neither IGF-1 nor PMA induced a significant change in the levels of STAT3 or in the levels of the key proteins regulating STAT3 degradation, SOCS3, and PIAS3. Treatment of neonatal mouse retinal explants with sodium orthovanadate inhibited the PKC-mediated reduction in pSTAT3, indicating a role for a phosphatase. Addition of the PTEN inhibitor bpV(phen) to explant cultures treated with IGF-1 or PMA had no effect on the reduction in pSTAT3 levels, but the effect of both IGF-1 and PMA was blocked by a concentration of the inhibitor NSC87877 that is selective for the phosphatases Shp1 and Shp2. Inhibition of Shp1/2 phosphatases was also sufficient to abolish the IGF1-mediated induction of rod photoreceptor differentiation in the retina explant cultures. We conclude that one or both of these phosphatases are key components regulating the formation of rod photoreceptors in mouse retina.