Goblet cell-specific expression mediated by the MUC2 mucin gene promoter in the intestine of transgenic mice

Fighting eimeriosis by using the anti-eimerial and anti-apoptotic properties of rhatany root extract

Background

Over the last decade, extensive use of coccidiostats to treat and control Eimeria infection has developed drug resistance, prompting the search for new alternative therapies. Rhatany is proven to have various pharmacological properties.

Objective

The present study aimed to in vitro and in vivo evaluate the effect of Rhatany roots extract (RRE) as an anti-eimerial and anti-apoptotic agent against murine eimeriosis induced by Eimeria papillata.

Methods

Phytochemical screening by gas chromatography-mass spectrometry analysis (GC-MS) was used to detect active compounds in RRE. In vitro anti-eimerial activity of RRE (200, 100, 50 mg/ml), amprolium, phenol, Dettol™, and formalin were studied after incubation with non-sporulated Eimeria oocysts. For the in vivo study, twenty-five male C57BL/6 mice were randomly allocated into five groups. Animals in the first group were just given distilled H2O, while those in the second group were given 200 mg/kg RRE for 5 days. The Eimeria parasite's oocysts were infected into the third, fourth, and fifth groups. For treatment, RRE (200 mg/kg) and amprolium (120 mg/kg) were orally given to the 4th and 5th groups for five days, respectively. All mice were euthanized, on day 5 post-infection, to collect the jejunal tissues under study. Investigations were undertaken into the oocyst output in feces and goblet cells in mice jejuna. Assays for glutathione peroxidase (GPx), hydrogen peroxide (H2O2), and myeloperoxidase (MPO) were also performed. In jejunal tissue, cysteine aspartic acid protease-3 (Caspase-3) was counted using immunohistochemistry, while BCL2-associated X protein (Bax) and B-cell lymphoma-2 (BCL-2) were assayed using ELISA. In addition, mRNA expression of the goblet cell response gene (MUC2) was detected using real-time PCR.

Results

Phytochemical screening by GC-MS demonstrated the presence of 22 compounds in the RRE. The in vitro study revealed that RRE significantly inhabited the oocyst sporulation in a dose-dependent manner. By day 5 after infection with the Eimeria parasite, the number of oocysts in mice feces was significantly reduced after RRE treatment (1.308 × 106 ± 1.36 × 105 oocysts/g feces) compared to the infected group (5.387 × 106 ± 4.29 × 105 oocysts/g feces). Moreover, the Eimeria infection reduced the number of goblet cells of mice jejuna and its specific gene, MUC2. The treatment with RRE increased the number of goblet cells/villus from 3.45 ± 0.17 to 6.04 ± 0.23, associated with upregulation for MUC2 from 0.26 to 2.39-fold. Also, the Eimeria experimental infection lowered the activity of the antioxidant enzyme represented by GPx (23.99 ± 3.68 mg/g tissue), while increasing the stress parameters of hydrogen peroxide (0.07 ± 0.01 mM/g) as well as the activity of MPO (66.30 ± 3.74 U/mg). The production of apoptotic markers including Caspase-3 (68.89 ± 2.67 U/g) and Bax (159.05 ± 6.50 pg/ml) was significantly elevated while decreasing the anti-apoptotic marker of BCL2 (0.42 ± 0.07 pg/ml). Our study proved that RRE significantly reduced oxidative stress, and apoptotic markers as well as the inflammatory activity of MPO. Also, antioxidant enzyme and anti-apoptotic activity in the jejunum of E. papillata-infected mice were enhanced after RRE treatment.

Conclusion

Our study highlights the potential of RRE as a natural solution for coccidiosis management by modulating apoptosis in E. papillata host cells. However, further research is needed to fully understand the underlying mechanisms and enhance our understanding of its therapeutic efficacy.

Lrig1 drives cryptogenesis and restrains proliferation during colon development

Growth and specification of the mouse intestine occurs in utero and concludes after birth. Although numerous studies have examined this developmental process in the small intestine, far less is known about the cellular and molecular cues required for colon development. In this study, we examine the morphological events leading to crypt formation, epithelial cell differentiation, proliferation, and the emergence and expression of a stem and progenitor cell marker Lrig1. Through multicolor lineage tracing, we show Lrig1-expressing cells are present at birth and behave as stem cells to establish clonal crypts within 3 wk of life. In addition, we use an inducible knockout mouse to eliminate Lrig1 and show Lrig1 restrains proliferation within a critical developmental time window, without impacting colonic epithelial cell differentiation. Our study illustrates morphological changes during crypt development and the importance of Lrig1 in the developing colon.NEW & NOTEWORTHY Our studies define the importance of studying Lrig1 in colon development. We address a critical gap in the intestinal development literature and provide new information about the molecular cues that guide colon development. Using a novel, inducible knockout of Lrig1, we show Lrig1 is required for appropriate colon epithelial growth and illustrate the importance of Lrig1-expressing cells in the establishment of colonic crypts.

The Role of Lrig1 in the Development of the Colonic Epithelium

Growth and specification of the mouse intestine occurs in utero and concludes after birth. While numerous studies have examined this developmental process in the small intestine, far less is known about the cellular and molecular cues required for colon development. In this study, we examine the morphological events leading to crypt formation, epithelial cell differentiation, areas of proliferation, and the emergence and expression of a stem and progenitor cell marker Lrig1. Through multicolor lineage tracing, we show Lrig1 expressing cells are present at birth and behave as stem cells to establish clonal crypts within three weeks after birth. In addition, we use an inducible knockout mouse to eliminate Lrig1 during colon development and show loss of Lrig1 restrains proliferation within a critical developmental time window, without impacting colonic epithelial cell differentiation. Our study illustrates the morphological changes that occur during crypt development and the importance of Lrig1 in the developing colon.

Biosynthesized selenium nanoparticles to rescue coccidiosis-mediated oxidative stress, apoptosis and inflammation in the jejunum of mice

One of the most crucial approaches for treating human diseases, particularly parasite infections, is nanomedicine. One of the most significant protozoan diseases that impact farm and domestic animals is coccidiosis. While, amprolium is one of the traditional anticoccidial medication, the advent of drug-resistant strains of Eimeria necessitates the development of novel treatments. The goal of the current investigation was to determine whether biosynthesized selenium nanoparticles (Bio-SeNPs) using Azadirachta indica leaves extract might treat mice with Eimeria papillata infection in the jejunal tissue. Five groups of seven mice each were used, as follows: Group 1: Non-infected-non-treated (negative control). Group 2: Non-infected treated group with Bio-SeNPs (0.5 mg/kg of body weight). Groups 3-5 were orally inoculated with 1×10³ sporulated oocysts of E. papillata. Group 3: Infected-non-treated (positive control). Group 4: Infected and treated group with Bio-SeNPs (0.5 mg/kg). Group 5: Infected and treated group with the Amprolium. Groups 4 and 5 daily received oral administration (for 5 days) of Bio-SeNPs and anticoccidial medication, respectively, after infection. Bio-SeNPs caused a considerable reduction in oocyst output in mice feces (97.21%). This was also accompanied by a significant reduction in the number of developmental parasitic stages in the jejunal tissues. Glutathione reduced (GSH), glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels were dramatically reduced by the Eimeria parasite, whereas, nitric oxide (NO) and malonaldehyde (MDA) levels were markedly elevated. The amount of goblet cells and MUC2 gene expression were used as apoptotic indicators, and both were considerably downregulated by infection. However, infection markedly increased the expression of inflammatory cytokines (IL-6 and TNF-α) and the apoptotic genes (Caspase-3 and BCL2). Bio-SeNPs were administrated to mice to drastically lower body weight, oxidative stress, and inflammatory and apoptotic indicators in the jejunal tissue. Our research thus showed the involvement of Bio-SeNPs in protecting mice with E. papillata infections against jejunal damage.

Mucin-Type O-Glycans: Barrier, Microbiota, and Immune Anchors in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), which affects about 7 million people globally, is a chronic inflammatory condition of the gastrointestinal tract caused by gut microbiota alterations, immune dysregulation, and genetic and environmental factors. The association of microbial and immune molecules with mucin-type O-glycans has been increasingly noticed by researchers. Mucin is the main component of mucus, which forms a protective barrier between the microbiota and immune cells in the colon. Mucin-type O-glycans alter the diversity of gastrointestinal microorganisms, which in turn increases the level of O-glycosylation of host intestinal proteins via the utilization of glycans. Additionally, alterations in mucin-type O-glycans not only increase the activity and stability of immune cells but are also involved in the maintenance of intestinal mucosal immune tolerance. Although there is accumulating evidence indicating that mucin-type O-glycans play an important role in IBD, there is limited literature that integrates available data to present a complete picture of exactly how O-glycans affect IBD. This review emphasizes the roles of the mucin-type O-glycans in IBD. This seeks to provide a better understanding and encourages future studies on IBD glycosylation and the design of novel glycan-inspired therapies for IBD.

Mucin in cancer: a stealth cloak for cancer cells

Mucins are high molecular-weight epithelial glycoproteins and are implicated in many physiological processes, including epithelial cell protection, signaling transduction, and tissue homeostasis. Abnormality of mucus expression and structure contributes to biological properties related to human cancer progression. Tumor growth sites induce inhospitable conditions. Many kinds of research suggest that mucins provide a microenvironment to avoid hypoxia, acidic, and other biological conditions that promote cancer progression. Given that the mucus layer captures growth factors or cytokines, we propose that mucin helps to ameliorate inhospitable conditions in tumor-growing sites. Additionally, the composition and structure of mucins enable them to mimic the surface of normal epithelial cells, allowing tumor cells to escape from immune surveillance. Indeed, human cancers such as mucinous carcinoma, show a higher incidence of invasion to adjacent organs and lymph node metastasis than do non-mucinous carcinoma. In this mini-review, we discuss how mucin provides a tumor-friendly environment and contributes to increased cancer malignancy in mucinous carcinoma.

Mucins in Intestinal Mucosal Defense and Inflammation: Learning From Clinical and Experimental Studies

Throughout the gastrointestinal (GI) tract, a distinct mucus layer composed of highly glycosylated proteins called mucins plays an essential role in providing lubrication for the passage of food, participating in cell signaling pathways and protecting the host epithelium from commensal microorganisms and invading pathogens, as well as toxins and other environmental irritants. These mucins can be broadly classified into either secreted gel-forming mucins, those that provide the structural backbone for the mucus barrier, or transmembrane mucins, those that form the glycocalyx layer covering the underlying epithelial cells. Goblet cells dispersed among the intestinal epithelial cells are chiefly responsible for the synthesis and secretion of mucins within the gut and are heavily influenced by interactions with the immune system. Evidence from both clinical and animal studies have indicated that several GI conditions, including inflammatory bowel disease (IBD), colorectal cancer, and numerous enteric infections are accompanied by considerable changes in mucin quality and quantity. These changes include, but are not limited to, impaired goblet cell function, synthesis dysregulation, and altered post-translational modifications. The current review aims to highlight the structural and functional features as well as the production and immunological regulation of mucins and the impact these key elements have within the context of barrier function and host defense in intestinal inflammation.

Epithelial changes of congenital intestinal obstruction in a rat model

Introduction

Intestinal atresia is a rare congenital affliction that is often associated with severe bacterial infections despite adequate neonatal surgery. Previous studies have focused on enteric nervous system variations. We hypothesized that epithelial systems (ES) may also be involved in the pathophysiology of postnatal disorders.

Materials and methods

Global gene expression was measured by transcriptomic analysis in a rat model of induced intestinal atresia. The analyses then focused on genes involved in ES (enterocytes and goblet cells). Rat fetus small intestines at various stages of development (ED15, ED17, ED19, and ED21, n = 22), were used as non-operated controls and compared to the upper and lower segments of rat fetus small intestines with an induced atresia (n = 14; ligature at ED18). The pattern of gene expression was then confirmed by histochemistry, electron microscopy, and RT-qPCR.

Results

From ED15 to ED21, the expression of several genes exhibited a physiological increase of ES markers, with a significant increase at the end of gestation. The operated embryos exhibited significantly higher variations of gene expression in the proximal segment than in the distal segment in terms of absorption and the epithelial barrier. An increase in goblet cells and markers was observed in the proximal segment compared to the controls.

Conclusion

Fetal intestinal obstruction accelerates maturation in the proximal segment and disrupts the intestinal wall in the distal segment, with a decrease in the number of mucosal cells. Moreover, the epithelial cells underwent significant changes, supporting the notion that intestinal disorders involve more than the ENS.

Profiling and Structural Characterization of High Neu5Gc or Sulfate-containing O-glycans from Hyla Rabbit Intestinal Mucin

Intestinal mucins constitute the major component of the mucus covering the epithelium of the gastrointestinal tract, thereby forming a barrier against microbial colonization. Rabbits are bred in large numbers worldwide, with little known about intestinal O-glycosylation despite this insight being crucial to the understanding of host-pathogen interactions. In the present study, a major mucin-type glycopeptide (RIF6) of hyla rabbit intestine was isolated and the O-glycans were extensively characterized based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with bioinformatics approaches. Thirty-three O-glycans were identified, and most of them were sulfated or sialylated glycans. It was worth noting that Neu5Gc-containing structures within sialylated O-glycans accounted for 91%, which were extremely different from that of other species including humans, mice, chickens, etc. Sulfated glycans accounted for 58%, unique disufated and sulfated-sialylated glycans were also detected in rabbit intestinal mucin. These structural characterization reflected species diversity and may provide deeper insights into explaining the adaptability of hyla rabbit to the environment.

β-Glucanase specific expression in the intestine of transgenic pigs

Producing heterologous enzymes in the animal digestive tract to improve feed utilization rate is a new research strategy by transgenic technology. In this study, transgenic pigs specifically expressing β-glucanase gene in the intestine were successfully produced by somatic cell nuclear transfer technology in order to improve digestibility of dietary β-glucan and absorption of nutrients. The β-glucanase activity in the intestinal juice of 4 transgenic pigs was found to be 8.59 ± 2.49 U/mL. The feeding trial results showed that the crude protein digestion of 4 transgenic pigs was significantly increased compared with that of the non-transgenic pigs. In order to investigate the inheritance of the transgene, 7 G₁ transgenic pigs were successfully obtained. The β-glucanase activity in the intestinal juice of 7 G₁ transgenic pigs was found to be 2.35 ± 0.72 U/mL. The feeding trial results showed the crude protein digestion and crude fat digestion were significantly higher in 7 G1 transgenic pigs than in non-transgenic pigs. Taken together, our study demonstrated that the foreign β-glucanase expressing in the intestine of the transgenic pigs could reduce the anti-nutritional effect of β-glucans in feed. In addition, β-glucanase gene could be inherited to the offsprings and maintain its physiological function. It is a promising approach to improve feed utilization by producing transgenic animals.

Intestinal Organoids-Current and Future Applications

Recent technical advances in the stem cell field have enabled the in vitro generation of complex structures resembling whole organs termed organoids. Most of these approaches employ culture systems that allow stem cell-derived or tissue progenitor cells to self-organize into three-dimensional (3D)-structures. Since organoids can be grown from different species (human, mouse, cat, dog), organs (intestine, kidney, brain, liver), and from patient-derived induced pluripotent stem cells, they create significant prospects for modelling development and diseases, for toxicology and drug discovery studies, and in the field of regenerative medicine. Here, we report on intestinal stem cells, organoid culture, organoid disease modeling, transplantation, specifically covering the current and future uses of this exciting new insight model to the field of veterinary medicine.

β-Casein(94-123)-derived peptides differently modulate production of mucins in intestinal goblet cells

We recently reported the identification of a peptide from yoghurts with promising potential for intestinal health: the sequence (94-123) of bovine β-casein. This peptide, composed of 30 amino acid residues, maintains intestinal homoeostasis through production of the secreted mucin MUC2 and of the transmembrane-associated mucin MUC4. Our study aimed to search for the minimal sequence responsible for the biological activity of β-CN(94-123) by using several strategies based on (i) known bioactive peptides encrypted in β-CN(94-123), (ii) in silico prediction of peptides reactivity and (iii) digestion of β-CN(94-123) by enzymes of intestinal brush border membranes. The revealed sequences were tested in vitro on human intestinal mucus-producing HT29-MTX cells. We demonstrated that β-CN(108-113) (an ACE-inhibitory peptide) and β-CN(114-119) (an opioid peptide named neocasomorphin-6) up-regulated MUC4 expression whereas levels of the secreted mucins MUC2 and MUC5AC remained unchanged. The digestion of β-CN(94-123) by intestinal enzymes showed that the peptides β-CN(94-108) and β-CN(117-123) were present throughout 1·5 to 3 h of digestion, respectively. These two peptides raised MUC5AC expression while β-CN(117-123) also induced a decrease in the level of MUC2 mRNA and protein. In addition, this inhibitory effect was reproduced in airway epithelial cells. In conclusion, β-CN(94-123) is a multifunctional molecule but only the sequence of 30 amino acids has a stimulating effect on the production of MUC2, a crucial factor of intestinal protection.

Inflammatory cues acting on the adult intestinal stem cells and the early onset of cancer (review)

The observation that cancer often arises at sites of chronic inflammation has prompted the idea that carcinogenesis and inflammation are deeply interwoven. In fact, the current literature highlights a role for chronic inflammation in virtually all the steps of carcinogenesis, including tumor initiation, promotion and progression. The aim of the present article is to review the current literature on the involvement of chronic inflammation in the initiation step and in the very early phases of tumorigenesis, in a type of cancer where adult stem cells are assumed to be the cells of origin of neoplasia. Since the gastrointestinal tract is regarded as the best-established model system to address the liaison between chronic inflammation and neoplasia, the focus of this article will be on intestinal cancer. In fact, the anatomy of the intestinal epithelial lining is uniquely suited to study adult stem cells in their niche, and the bowel crypt is an ideal developmental biology system, as proliferation, differentiation and cell migration are all distributed linearly along the long axis of the crypt. Moreover, crypt stem cells are regarded today as the most likely targets of neoplastic transformation in bowel cancer. More specifically, the present review addresses the molecular mechanisms whereby a state of chronic inflammation could trigger the neoplastic process in the intestine, focusing on the generation of inflammatory cues evoking enhanced proliferation in cells not initiated but at risk of neoplastic transformation because of their stemness. Novel experimental approaches, based on triggering an inflammatory stimulus in the neighbourhood of adult intestinal stem cells, are warranted to address some as yet unanswered questions. A possible approach, the targeted transgenesis of Paneth cells, may be aimed at 'hijacking' the crypt stem cell niche from a status characterized by the maintenance of homeostasis to local chronic inflammation, with the prospect of initiating neoplastic transformation in that site.

Intestine-specific expression of the β-glucanase in mice

Guan, L.-Z., Xi, Q.-Y., Sun, Y.-P., Wang, J.-L., Zhou, J.-Y., Shu, G., Jiang, Q.-Y. and Zhang, Y.-L. 2014. Intestine-specific expression of the β-glucanase in mice. Can. J. Anim. Sci. 94: 287–293. The β-glucanase gene (GLU, from Paenibacillus polymyxa CP7) was cloned into a specific expression plasmid (MUC2-GLU-LV). Transgenic mice were prepared by microinjection. Polymerase chain reaction and Southern blot analysis of genomic DNA extracted from the tail tissue of transgenic mice showed that the mice carried the β-glucanase gene. Northern blot analysis indicated that β-glucanase was specifically expressed in the intestine of the transgenic mice. The β-glucanase activity in the intestinal contents was found to be 1.23±0.32 U mL−1. The crude protein, crude fat digestibility of transgenic mice were increased by 9.32 and 5.09% (P<0.05), respectively, compared with that of the non-transgenic mice, while moisture in feces was reduced by 12.16% (P<0.05). These results suggest that the expression of β-glucanase in the intestine of animals offers a promising biological approach to reduce the anti-nutritional effect of β-glucans in feed.

Evidence that two distinct crypt cell types secrete chloride and potassium in human colon

BACKGROUND

Human colon may secrete substantial amounts of water secondary to chloride (Cl(-)) and/or potassium (K(+)) secretion in a variety of diarrhoeal diseases. Ion secretion occurs via Cl(-) and K(+) channels, which are generally assumed to be co-located in the colonocyte apical membrane, although their exact cellular sites remain unclear.

OBJECTIVE

 To investigate the location of apical Cl(-) (CFTR) and apical K(+) (large conductance; BK) channels within human colonic epithelium.

DESIGN

Whole-cell patch clamp recordings were obtained from intact human colonic crypts. Specific blockers of K(+) channels and CFTR identified different types of K(+) channel and CFTR under resting conditions and after stimulating intracellular cAMP with forskolin. The BK channel β3-subunit was localised by immunostaining.

RESULTS

Two types of crypt cells were identified. One (73% of cells) had whole-cell currents dominated by intermediate conductance (IK) K(+) channels under resting conditions, which developed large CFTR-mediated currents in response to increasing intracellular cAMP. The other (27% of cells) had resting currents dominated by BK channels inhibited by the BK channel blocker penitrem A, but insensitive to both forskolin and the IK channel blocker clotrimazole. Immunostaining showed co-localisation of the BK channel β3-subunit and the goblet cell marker, MUC2.

CONCLUSIONS

In human colon, Cl(-) secretion originates from the dominant population of colonocytes expressing apical CFTR, whereas K(+) secretion is derived from a smaller population of goblet cells expressing apical BK channels. These findings provide new insights into the pathophysiology of secretory diarrhoea and should be taken into account during the development of anti-diarrhoeal drugs.

Alternative functional in vitro models of human intestinal epithelia

Physiologically relevant sources of absorptive intestinal epithelial cells are crucial for human drug transport studies. Human adenocarcinoma-derived intestinal cell lines, such as Caco-2, offer conveniences of easy culture maintenance and scalability, but do not fully recapitulate in vivo intestinal phenotypes. Additional sources of renewable physiologically relevant human intestinal cells would provide a much needed tool for drug discovery and intestinal physiology. We compared two alternative sources of human intestinal cells, commercially available primary human intestinal epithelial cells (hInEpCs) and induced pluripotent stem cell (iPSC)-derived intestinal cells to Caco-2, for use in in vitro transwell monolayer intestinal transport assays. To achieve this for iPSC-derived cells, intestinal organogenesis was adapted to transwell differentiation. Intestinal cells were assessed by marker expression through immunocytochemical and mRNA expression analyses, monolayer integrity through Transepithelial Electrical Resistance (TEER) measurements and molecule permeability, and functionality by taking advantage the well-characterized intestinal transport mechanisms. In most cases, marker expression for primary hInEpCs and iPSC-derived cells appeared to be as good as or better than Caco-2. Furthermore, transwell monolayers exhibited high TEER with low permeability. Primary hInEpCs showed molecule efflux indicative of P-glycoprotein (Pgp) transport. Primary hInEpCs and iPSC-derived cells also showed neonatal Fc receptor-dependent binding of immunoglobulin G variants. Primary hInEpCs and iPSC-derived intestinal cells exhibit expected marker expression and demonstrate basic functional monolayer formation, similar to or better than Caco-2. These cells could offer an alternative source of human intestinal cells for understanding normal intestinal epithelial physiology and drug transport.

Pretreatment with paricalcitol attenuates inflammation in ischemia-reperfusion injury via the up-regulation of cyclooxygenase-2 and prostaglandin E2

BACKGROUND

The effect of paricalcitol on renal ischemia-reperfusion injury (IRI) has not been investigated. We examined whether paricalcitol is effective in preventing inflammation in a mouse model of IRI, and evaluated the cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) pathways as a protective mechanism of paricalcitol.

METHODS

Paricalcitol (0.3 μg/kg) was administered to male C57BL/6 mice 24 h before IRI. Bilateral kidneys were subjected to 23 min of ischemia, and mice were killed 72 h after IRI. The effects of paricalcitol on renal IRI were evaluated in terms of renal function, tubular necrosis, apoptotic cell death, inflammatory cell infiltration and inflammatory cytokines. The effects of paricalcitol on COX-2, PGE2 and its receptors were investigated.

RESULTS

Paricalcitol pretreatment improved renal function (decreased blood urea nitrogen and serum creatinine levels), tubular necrosis and apoptotic cell death in IRI-mice kidneys. The infiltration of inflammatory cells (T cells and macrophages), and the production of proinflammatory cytokines (RANTES, tumor necrosis factor-α, interleukin-1β and interferon-γ) were reduced in paricalcitol-treated mice with IRI. Paricalcitol up-regulated COX-2 expression, PGE2 synthesis and mRNA expression of receptor subtype EP4 in post-ischemic renal tissue. The cotreatment of a selective COX-2 inhibitor with paricalcitol restored functional injury and tubular necrosis in paricalcitol-treated mice with IRI.

CONCLUSIONS

Our study demonstrates that paricalcitol pretreatment prevents renal IRI via the inhibition of renal inflammation, and the up-regulation of COX-2 and PGE2 is one of the protective mechanisms of paricalcitol in renal IRI.

Impaired mucin synthesis and bicarbonate secretion in the colon of NHE8 knockout mice

Sodium/hydrogen exchanger 8 (NHE8), the newest member of the SLC9 family, is expressed at the apical membrane of the epithelial cells in the intestine and the kidney. Although NHE8 has been shown to be an important player for intestinal sodium absorption early in development, its physiological role in the intestine remains unclear. Here, we successfully created a NHE8 knockout (NHE8(-/-)) mouse model to study the function of this transporter in the intestinal tract. Embryonic stem cells containing interrupted NHE8 gene were injected into mouse blastocyst to produce NHE8(+/-) chimeras. NHE8(-/-) mice showed no lethality during embryonic and fetal development. These mice had normal serum sodium levels and no signs of diarrhea. Apically expressed NHE2 and NHE3 were increased in the small intestine of the NHE8(-/-) mice in compensation. The number of goblet cells and mucin (MUC)-positive cells in the colon was reduced in NHE8(-/-) mice along with mucosal pH, MUC2 expression as well as downregulated in adenoma (DRA) expression. Therefore, the role of NHE8 in the intestine involves both sodium absorption and bicarbonate secretion.

Role of intestinal mucins in innate host defense mechanisms against pathogens

Gastrointestinal mucins produced by goblet cells comprise the main structural components of the mucus layer. Mucins play a critical role in the maintenance of mucosal homeostasis and are responsible for the differential effector and regulatory responses against a plethora of microorganisms, including commensals and pathogens. In this review, we present a comprehensive overview on mucin biology, its properties, classification and gene assembly. We also consider the structure of the mucin gene, its proteins and its role in innate host defenses. We compare the various mucin secretagogues and the differential regulatory pathways involved in mucin biosynthesis and secretion during normal and diverse pathogenic conditions. Finally, we summarize the putative uncharted aspects of mucin-derived innate host defenses, whose exploration will help drug developers to identify factors that can strengthen mucosal integrity and will facilitate basic science research into curative treatments for gastrointestinal diseases.

Mucins in the mucosal barrier to infection

The mucosal tissues of the gastrointestinal, respiratory, reproductive, and urinary tracts, and the surface of the eye present an enormous surface area to the exterior environment. All of these tissues are covered with resident microbial flora, which vary considerably in composition and complexity. Mucosal tissues represent the site of infection or route of access for the majority of viruses, bacteria, yeast, protozoa, and multicellular parasites that cause human disease. Mucin glycoproteins are secreted in large quantities by mucosal epithelia, and cell surface mucins are a prominent feature of the apical glycocalyx of all mucosal epithelia. In this review, we highlight the central role played by mucins in accommodating the resident commensal flora and limiting infectious disease, interplay between underlying innate and adaptive immunity and mucins, and the strategies used by successful mucosal pathogens to subvert or avoid the mucin barrier, with a particular focus on bacteria.

Biliary wound healing, ductular reactions, and IL-6/gp130 signaling in the development of liver disease

Basic and translational wound healing research in the biliary tree lag significantly behind similar studies on the skin and gastrointestinal tract. This is at least partly attributable to lack of easy access to the biliary tract for study. But clinical relevance, more interest in biliary epithelial cell (BEC) pathophysiology, and widespread availability of BEC cultures are factors reversing this trend. In the extra-hepatic biliary tree, ineffectual wound healing, scarring and stricture development are pressing issues. In the smallest intra-hepatic bile ducts either impaired BEC proliferation or an exuberant response can contribute to liver disease. Chronic inflammation and persistent wound healing reactions in large and small bile ducts often lead to liver cancer. General concepts of wound healing as they apply to the biliary tract, importance of cellular processes dependent on IL-6/gp130/STAT3 signaling pathways, unanswered questions, and future directions are discussed.

Regulation and function of trefoil factor family 3 expression in the biliary tree

Microarray analysis identified trefoil factor family 3 (TFF3) as a gene expressed in biliary epithelial cells (BECs), regulated by interleukin (IL)-6, and potentially involved in biliary pathophysiology. We therefore studied the regulation and function of BEC TFF3, in vitro and in vivo in IL-6(+/+) and IL-6(-/-) mice subjected to chronic bile duct ligation for 12 weeks. In vitro studies showed that IL-6 wild-type (IL-6(+/+)) BECs expressed higher TFF3 mRNA and protein levels than IL-6-deficient (IL-6(-/-)) BECs. BEC TFF3 expression is dependent primarily on signal transducer and activator of transcription (STAT3) signaling, but the reciprocal negative regulation known to exist between the intracellular IL-6/gp130 signaling pathways, STAT3 and mitogen-activated protein kinase (MAPK), importantly contributes to BEC TFF3 expression. Specifically blocking STAT3 activity with a dominant-negative molecule or treatment with a growth factor such as hepatocyte growth factor, which increases MAPK signaling, decreases BEC TFF3 expression. In contrast, specifically blocking MAPK activity with PD98059 significantly increased BEC TFF3 expression. Higher BEC TFF3 levels in IL-6(+/+) BECs were associated with significantly better migration than IL-6(-/-) BECs in a wound-healing assay and defective IL-6(-/-) BEC migration was reversed with exogenous TFF3. In vivo, hepatic TFF3 mRNA and protein expression was limited to BECs and dependent significantly on STAT3 signaling, but was influenced by other factors present after bile duct ligation. Comparable results were obtained in normal and diseased human tissue samples. In conclusion the regulation and function of BEC TFF3 expression is similar to the colon. BEC TFF3 expression depends primarily on gp130/STAT3 and contributes to BEC migration and wound healing. Therefore, use of recombinant IL-6 or TFF3 peptides should exert a therapeutic role in preventing biliary strictures in liver allografts.

A silencer inhibitor confers specific expression of intestinal trefoil factor in gobletlike cell lines

Intestinal trefoil factor (ITF) is selectively expressed in intestinal goblet cells. Previous studies identified cis-regulatory elements in the proximal promoter of ITF, but these were insufficient to recapitulate the exquisite tissue- and cell-specific expression of native ITF in vivo. Preliminary studies suggested that goblet cell-specific expression of murine ITF requires elements far upstream that include a silencer element that effectively prevents ITF expression in non-goblet cells. Transient transfection studies using native or mutant ITF 5'-flanking sequences identified a region that restores expression in goblet cells. This element, designated goblet cell silencer inhibitor (GCSI) element, enables human and murine goblet cell-like cell lines to override the silencing effect of more proximal elements. The GCSI has no intrinsic enhancer activity and regulates expression only when the silencer element is present. Ligation of GCSI and silencer elements to sucrase-isomaltase conferred goblet cell-specific expression. Goblet cells but not non-goblet cells possess a nuclear protein that binds to the GCSI regulatory element (GCSI binding protein; GCSI-BP). Both transient transfection and gel mobility shift assay studies localize the GCSI and GCSI-BP to -2216 to -2204. We conclude that goblet cell-specific transcription of ITF in vivo depends on a regulatory element designated GCSI.

Sequence of the 5'-flanking region and promoter activity of the human mucin gene MUC5B in different phenotypes of colon cancer cells

Control of gene expression in intestinal cells is poorly understood. Molecular mechanisms that regulate transcription of cellular genes are the foundation for understanding developmental and differentiation events. Mucin gene expression has been shown to be altered in many intestinal diseases and especially cancers of the gastrointestinal tract. Towards understanding the transcriptional regulation of a member of the 11p15.5 human mucin gene cluster, we have characterized 3.55 kb of the 5'-flanking region of the human mucin gene MUC5B, including the promoter, the first two exons and the first intron. We report here the promoter activity of successively 5'-truncated sections of 956 bases of this region by fusing it to the coding region of a luciferase reporter gene. The transcription start site was determined by primer-extension analysis. The region upstream of the transcription start site is characterized by the presence of a TATA box at bases -32/-26, DNA-binding elements for transcription factors c-Myc, N-Myc, Sp1 and nuclear factor kappaB as well as putative activator protein (AP)-1-, cAMP-response-element-binding protein (CREB)-, hepatocyte nuclear factor (HNF)-1-, HNF-3-, TGT3-, gut-enriched Krüppel factor (GKLF)-, thyroid transcription factor (TTF)-1- and glucocorticoid receptor element (GRE)-binding sites. Intron 1 of MUC5B was also characterized, it is 2511 nucleotides long and contains a DNA segment of 259 bp in which are clustered eight tandemly repeated GA boxes and a CACCC box that bind Sp1. AP-2alpha and GATA-1 nuclear factors were also shown to bind to their respective cognate elements in intron 1. In transfection studies the MUC5B promoter showed a cell-specific activity as it is very active in mucus-secreting LS174T cells, whereas it is inactive in Caco-2 enterocytes and HT-29 STD (standard) undifferentiated cells. Within the promoter, maximal transcription activity was found in a segment covering the first 223 bp upstream of the transcription start site. Finally, in co-transfection experiments a transactivating effect of Sp1 on to MUC5B promoter was seen in LS174T and Caco-2 cells.