Primary murine small intestinal epithelial cells, maintained in long-term culture, are susceptible to rotavirus infection

Organoids as a novel tool in modelling infectious diseases

Infectious diseases worldwide affect human health and have important societal impacts. A better understanding of infectious diseases is urgently needed. In vitro and in vivo infection models have brought notable contributions to the current knowledge of these diseases. Organoids are multicellular culture systems resembling tissue architecture and function, recapitulating many characteristics of human disease and elucidating mechanisms of host-infectious agent interactions in the respiratory and gastrointestinal systems, the central nervous system and the skin. Here, we discuss the applicability of the organoid technology for modeling pathogenesis, host response and features, which can be explored for the development of preventive and therapeutic treatments.

NAIL: an evolutionarily conserved lncRNA essential for licensing coordinated activation of p38 and NFκB in colitis

OBJECTIVE

NFκB is the key modulator in inflammatory disorders. However, the key regulators that activate, fine-tune or shut off NFκB activity in inflammatory conditions are poorly understood. In this study, we aim to investigate the roles that NFκB-specific long non-coding RNAs (lncRNAs) play in regulating inflammatory networks.

DESIGN

Using the first genetic-screen to identify NFκB-specific lncRNAs, we performed RNA-seq from the p65^-/- and Ikkβ^-/- mouse embryonic fibroblasts and report the identification of an evolutionary conserved lncRNA designated mNAIL (mice) or hNAIL (human). hNAIL is upregulated in human inflammatory disorders, including UC. We generated mNAIL^ΔNFκB mice, wherein deletion of two NFκB sites in the proximal promoter of mNAIL abolishes its induction, to study its function in colitis.

RESULTS

NAIL regulates inflammation via sequestering and inactivating Wip1, a known negative regulator of proinflammatory p38 kinase and NFκB subunit p65. Wip1 inactivation leads to coordinated activation of p38 and covalent modifications of NFκB, essential for its genome-wide occupancy on specific targets. NAIL enables an orchestrated response for p38 and NFκB coactivation that leads to differentiation of precursor cells into immature myeloid cells in bone marrow, recruitment of macrophages to inflamed area and expression of inflammatory genes in colitis.

CONCLUSION

NAIL directly regulates initiation and progression of colitis and its expression is highly correlated with NFκB activity which makes it a perfect candidate to serve as a biomarker and a therapeutic target for IBD and other inflammation-associated diseases.

Type I IFN signaling limits hemorrhage-like disease after infection with Japanese encephalitis virus through modulating a prerequisite infection of CD11b+Ly-6C+ monocytes

Background

The crucial role of type I interferon (IFN-I, IFN-α/β) is well known to control central nervous system (CNS) neuroinflammation caused by neurotrophic flaviviruses such as Japanese encephalitis virus (JEV) and West Nile virus. However, an in-depth analysis of IFN-I signal-dependent cellular factors that govern CNS-restricted tropism in JEV infection in vivo remains to be elucidated.

Methods

Viral dissemination, tissue tropism, and cytokine production were examined in IFN-I signal-competent and -incompetent mice after JEV inoculation in tissues distal from the CNS such as the footpad. Bone marrow (BM) chimeric models were used for defining hematopoietic and tissue-resident cells in viral dissemination and tissue tropism.

Results

The paradoxical and interesting finding was that IFN-I signaling was essentially required for CNS neuroinflammation following JEV inoculation in distal footpad tissue. IFN-I signal-competent mice died after a prolonged neurological illness, but IFN-I signal-incompetent mice all succumbed without neurological signs. Rather, IFN-I signal-incompetent mice developed hemorrhage-like disease as evidenced by thrombocytopenia, functional injury of the liver and kidney, increased vascular leakage, and excessive cytokine production. This hemorrhage-like disease was closely associated with quick viral dissemination and impaired IFN-I innate responses before invasion of JEV into the CNS. Using bone marrow (BM) chimeric models, we found that intrinsic IFN-I signaling in tissue-resident cells in peripheral organs played a major role in inducing the hemorrhage-like disease because IFN-I signal-incompetent recipients of BM cells from IFN-I signal-competent mice showed enhanced viral dissemination, uncontrolled cytokine production, and increased vascular leakage. IFN-I signal-deficient hepatocytes and enterocytes were permissive to JEV replication with impaired induction of antiviral IFN-stimulated genes, and neuron cells derived from both IFN-I signal-competent and -incompetent mice were vulnerable to JEV replication. Finally, circulating CD11b⁺Ly-6C⁺ monocytes infiltrated into the distal tissues inoculated by JEV participated in quick viral dissemination to peripheral organs of IFN-I signal-incompetent mice at an early stage.

Conclusion

An IFN-I signal-dependent model is proposed to demonstrate how CD11b⁺Ly-6C⁺ monocytes are involved in restricting the tissue tropism of JEV to the CNS.

Histo-blood group antigens as divergent factors of groups A and C rotaviruses circulating in humans and different animal species

Histo-blood group antigens (HBGAs) have been found to be important host susceptibility factors or receptors for human rotavirus (RVs) with genotype-specific host ranges, impacting the disease patterns, epidemiology, and strategy development against RV diseases in humans. However, how the glycan factors contribute to RV diversity and host ranges to different animal species remains unclear. In this study using recombinant VP8* proteins as probes to perform glycan array analyses of RVs, we observed a wide range of glycan-binding profiles, including those binding to sialic acid-containing glycans, among group A (RVA) and group C (RVC) RVs that mainly infect different animal species. A tri-saccharide glycan Galα1-3Galβ1-4Glc containing a terminal α-Gal was recognised by multiple RVA/RVC genotypes, providing valuable information on RV evolution under selection of the step-wisely synthesised HBGAs in many animals before they were introduced to humans to be human pathogens. Saliva binding studies of VP8* also revealed strain-specific host ranges or species barriers between humans and these animal RV genotypes, further improved our understanding on RV host ranges, disease burdens, epidemiology, and vaccine strategy against RVs.

Lactoferrin translocates to the nucleus of bovine rectal epithelial cells in the presence of Escherichia coli O157:H7

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a foodborne pathogen which causes illness in humans. Ruminants are the main reservoirs and EHEC predominantly colonizes the epithelium of the recto-anal junction of cattle. Immunosuppression by EHEC promotes re-infection of cattle. However, bovine lactoferrin (bLF) apparently can overrule the immunosuppression by inducing EHEC-specific IgA responses at the mucosal site. The IgA responses are significantly correlated with reduced EHEC shedding and the absence of colonization at the rectal mucosa following re-infection. Therefore, to examine the interaction between bLF and bovine rectal epithelial cells, we first developed a method to establish a primary cell culture of epithelial cells of the rectum of cattle. Furthermore, we used LC–MS/MS to demonstrate the presence of secreted lactoferrin in bovine milk and the absence of a “delta” isoform which is known to translocate to the nucleus of cells. Nevertheless, lactoferrin derived from bovine milk was internalized by rectal epithelial cells and translocated to the nuclei. Moreover, nuclear translocation of bLF was significantly enhanced when the epithelial cells were inoculated with EHEC, as demonstrated by confocal fluorescence microscopy and confirmed by Raman microscopy and 3D imaging.

Aichi Virus Induces Antiviral Host Defense in Primary Murine Intestinal Epithelial Cells

The picornavirus Aichi virus (AiV) is a non-enveloped RNA virus that causes acute gastroenteritis symptoms, such as diarrhea, abdominal pain, nausea, vomiting, and fever. Antiviral host defense involves the fast response of type I interferon (IFN) and the secretion of inflammatory cytokines against pathogens. However, the intestinal inflammatory and antiviral response to AiV infection is poorly understood. This study evaluated the antiviral activity of intestinal epithelial cells (IECs), which form a single-cell layer separating the bowel wall from pathogens. Isolated primary mouse IECs were subjected to AiV infection and virion production, inducing the mRNA expression of type I/type III IFNs and inflammatory cytokines. The mechanism involved induced the expression of phospho-IFN regulatory factor 3 and mitochondrial antiviral-signaling protein of type I IFN signaling. These findings were also observed in AiV-infected human colon carcinoma cells. In summary, a viral productive and pathogenic infection of AiV in primary murine IECs is validated.

Suppression of pyrimidine biosynthesis by targeting DHODH enzyme robustly inhibits rotavirus replication

Rotavirus infection remains a great health burden worldwide especially in some developing countries. It causes severe dehydrating diarrhea in infants, young children, as well as immunocompromised and organ transplanted patients. Viral replication heavily relies on the host to supply nucleosides. Thus, host enzymes involved in nucleotide biosynthesis represent potential targets for antiviral development. Dihydroorotate dehydrogenase (DHODH) is the rate-limiting enzyme in the de novo biosynthesis pathway of pyrimidines. In this study, we demonstrated that two specific DHODH enzyme inhibitors, brequinar (BQR) and leflunomide (LFM) robustly inhibited rotavirus replication in conventional human intestinal Caco2 cell line as well as in human primary intestinal organoids. The antiviral effect is conserved in both laboratory strain SA11 and rotavirus strain 2011K isolated from clinical sample. Mechanistic study indicated that BQR and LFM exerted their anti-rotavirus effect through targeting DHODH to deplete pyrimidine nucleotide pool. Therefore, targeting pyrimidine biosynthesis represents a potential approach for developing antiviral strategies against rotavirus.

Modeling Host-Virus Interactions in Viral Infectious Diseases Using Stem-Cell-Derived Systems and CRISPR/Cas9 Technology

Pathologies induced by viral infections have undergone extensive study, with traditional model systems such as two-dimensional (2D) cell cultures and in vivo mouse models contributing greatly to our understanding of host-virus interactions. However, the technical limitations inherent in these systems have constrained efforts to more fully understand such interactions, leading to a search for alternative in vitro systems that accurately recreate in vivo physiology in order to advance the study of viral pathogenesis. Over the last decade, there have been significant technological advances that have allowed researchers to more accurately model the host environment when modeling viral pathogenesis in vitro, including induced pluripotent stem cells (iPSCs), adult stem-cell-derived organoid culture systems and CRISPR/Cas9-mediated genome editing. Such technological breakthroughs have ushered in a new era in the field of viral pathogenesis, where previously challenging questions have begun to be tackled. These include genome-wide analysis of host-virus crosstalk, identification of host factors critical for viral pathogenesis, and the study of viral pathogens that previously lacked a suitable platform, e.g., noroviruses, rotaviruses, enteroviruses, adenoviruses, and Zika virus. In this review, we will discuss recent advances in the study of viral pathogenesis and host-virus crosstalk arising from the use of iPSC, organoid, and CRISPR/Cas9 technologies.

Surfactant Proteins-A and -D Attenuate LPS-Induced Apoptosis in Primary Intestinal Epithelial Cells (IECs)

INTRODUCTION

SP-A/D KO mice with sepsis demonstrate more severe lung, kidney, and gut injury/apoptosis than WT controls. We hypothesize SP-A and SP-D directly regulate lipopolysaccharide (LPS)-induced P38 mitogen-activated protein kinase (MAPK) activation and gut apoptosis during sepsis.

METHODS

Primary IECs were established from SP-A/D KO or C57BL/6 WT mice, stimulated with LPS and harvested at 24 h. IECs from WT mice were treated with SP-A, SP-D, or vehicle for 20 h, then LPS for 24 h. Apoptosis, cleaved caspase-3 levels and the ratio of BAX/Bcl-2 were assayed. The role of P38 MAPK was examined using the P38 MAPK-agonist U46619 and inhibitor SB203580 in LPS-treated cells. p-P38 MAPK/t-P38 MAPK, TLR4, and CD14 were measured by Western Blot.

RESULTS

LPS-induced apoptosis, caspase-3 levels, BAX/Bcl-2, and p-P38/t-P38 MAPK were increased in SP-A/D KO IECs. SP-A and SP-D attenuate LPS-induced increase in apoptosis, cleaved caspase-3, BAX/Bcl-2, and p-P38/t-P38 MAPK in WT IECs. U46619 increased apoptosis, caspase-3, and BAX/Bcl-2 in IECs which was attenuated by SP-A/D. SB203580 attenuates the LPS-induced increase in apoptosis, caspase-3, and BAX/Bcl-2 in WT IECs. Addition of SP-A or SP-D to SB203580 completely ameliorates LPS-induced apoptosis. The LPS-induced increase in TLR4 and CD14 expression is greater in IECs from SP-A/D KO mice and treatment of WT IECs with SP-A or SP-D prevents the LPS-induced increase in TLR4 and CD14.

CONCLUSIONS

SP-A and SP-D attenuate LPS-induced increases in apoptosis, caspase-3, and BAX/Bcl-2 in IECs. Attenuation of LPS-induced activation of TLR4 and P38 MAPK signaling pathways represents potential mechanisms for the protective effects of SP-A/D on apoptosis.

Establishment and long-term maintenance of primary intestinal epithelial cells cultured from the rainbow trout, Oncorhynchus mykiss

A novel method for the establishment and long-term maintenance of ex vivo cultures from intestinal regions of the rainbow trout, Oncorhynchus mykiss (Walbaum), is reported. Adherence of cells was observed within hours, epithelial island formation recorded at 48 h and rapid proliferation with confluence achieved between 9-14 days. In addition to metabolic characterisation, basic morphology of growing cells was characterised using histology, immunofluorescence, transmission electron microscopy (TEM) and transepithelial electrical resistance (TEER). Regional differences in intestinal ethoxyresorufin-O-deethylase (EROD) and 7-ethoxycoumarin-O-deethylation (ECOD) activities in these primary grown enterocytes were compared following exposure to model inducers [i.e. α-NF, β-NF, B(a)P] which demonstrated significant differences. Regional differences in dietary uptake and metabolism of contaminants can therefore be studied in this in vitro system to increase our understanding of fundamental processes, while concurrently providing a means to reduce the number of fish required for biological studies in line with the principles of the 3Rs (Reduce, Refine and Replace).

This article has an associated First Person interview with the first author of the paper.

Summary: Understanding chemical uptake from the diet is difficult in live fish: we developed long-term intestinal cell cultures that enables the science and provides an alternative method.

The role of Pygo2 for Wnt/ß-catenin signaling activity during intestinal tumor initiation and progression

Pygo2 acts as a co-activator of Wnt signaling in a nuclear complex with ß-catenin/BCL9/BCL9-2 to increase target gene transcription. Previous studies showed that Pygo2 is upregulated in murine intestinal tumors and human colon cancer, but is apparently dispensable for normal intestinal homeostasis. Here, we have evaluated the in vivo role of Pygo2 during intestinal tumorigenesis using Pygo2 deficient mice. We analyzed chemically induced colon tumor development and conditional intestine specific mouse models harboring either Apc loss-of-function (LOF) or Ctnnb1 gain-of-function (ß-catenin GOF). Remarkably, the number and size of chemically induced tumors was significantly reduced in Pygo2 deficient mice, suggesting that Pygo2 has a tumor promoting function. Furthermore, loss of Pygo2 rescued early tumorigenesis of Ctnnb1 GOF mutants. In contrast, Pygo2 ablation was not sufficient to prevent tumor development of Apc LOF mice. The effect on tumor formation by Pygo2 knockout was linked to the repression of specific deregulated Wnt target genes, in particular of c-Myc. Moreover, the role of Pygo2 appears to be associated with the signaling output of deregulated Wnt signaling in the different tumor models. Thus, targeting Pygo2 might provide a novel strategy to suppress tumor formation in a context dependent manner.

Triclosan Enhances the Clearing of Pathogenic Intracellular Salmonella or Candida albicans but Disturbs the Intestinal Microbiota through mTOR-Independent Autophagy

Triclosan (TCS) is a broad-spectrum antimicrobial agent, whose well-known antibacterial mechanism is inhibiting lipid synthesis. Autophagy, an innate immune response, is an intracellular process that delivers the cargo including pathogens to lysosomes for degradation. In this study, we first demonstrated that TCS induced autophagy in a dose-dependent manner in non-phagocytic cells (HeLa) and in macrophages (Raw264.7) and in vivo. The western blot results also revealed that TCS induced autophagy via the AMPK/ULK1 and JNK/ERK/p38 pathways independent of mTOR. The immunofluorescence results indicated that TCS up-regulated the expression of the ubiquitin receptors NDP52 and p62 and strengthened the co-localization of these receptors with Salmonella enterica Typhimurium (S. typhimurium) or Candida albicans (C. albicans) in infected MΦ cells. In addition, sub-lethal concentrations of TCS enhanced the clearing of the pathogens S. typhimurium or C. albicans in infected MΦ and in corresponding mouse infection models in vivo. Specifically, we found that a sub-inhibitory concentration of TCS induced autophagy, leading to an imbalance of the intestinal microflora in mice through the analysis of 16s rRNA Sequencing. Together, these results demonstrated that TCS induced autophagy, which enhanced the killing against pathogenic S. typhimurium or C. albicans within mammal cells but broke the balance of the intestinal microflora.

Surfactant Proteins SP-A and SP-D Ameliorate Pneumonia Severity and Intestinal Injury in a Murine Model of Staphylococcus Aureus Pneumonia

Staphylococcus aureus pneumonia is an important cause of sepsis which causes gut injury, inflammation, and apoptosis. The surfactant proteins surfactant protein A (SP-A) and surfactant protein D (SP-D) bind bacterial pathogens and facilitate clearance of pathogens, apoptotic bodies, and modulate immune responses. SP-A and SP-D are expressed in both lung and gut epithelia. We hypothesize SP-A and SP-D regulate pneumonia severity and gut injury during pneumonia.

METHODS

Wild-type (WT) and SP-A and SP-D double knockout (SP-A/D KO) mice were subjected to S. aureus or sham pneumonia. Bronchoalveolar lavage and tissue harvest were performed 24 h later. Pneumonia severity, gut mucosal injury, inflammation, and apoptosis were measured using a combination of histology, immunohistochemistry, cytokine assay, TUNEL assay, quantitative real-time polymerase chain reaction, and Western blot analyses.

RESULTS

Pneumonia increased gut inflammation, apoptosis, and mucosal injury in both groups. Pneumonia histology and bacterial growth in bronchoalveolar lavage fluid demonstrate more severe infection in SP-A/D KO mice compared with WT controls. SP-A/D KO mice with pneumonia also demonstrate more severe histologic gut mucosal injury, increased gut apoptosis, elevated caspase-3 levels, and Bax/Bcl-2 mRNA expression compared with WT pneumonia mice. Nuclear factor κB (NF-κB) p65 expression and its nuclear translocation, gut levels of tumor necrosis factor α and interleukin-1β were all increased in SP-A/D KO mice with pneumonia compared with WT controls.

CONCLUSIONS

These data provide evidence SP-A and SP-D attenuate S. aureus pneumonia severity resulting in decreased intestinal mucosal injury, apoptosis, and inflammation. Improved pulmonary clearance of S. aureus decreased caspase-3 and Bax/Bcl-2 expressions and decreased activation of the NF-κB signaling pathway in intestine represent potential mechanisms for the effects of SP-A and SP-D on gut injury during pneumonia.

Intestinal Inflammation-Mediated Clearance of Amebic Parasites Is Dependent on IFN-γ

Intestinal amebiasis is a major cause of diarrhea. However, research on host-amebae interactions has been hampered owing to a lack of appropriate animal models. Recently, a mouse model of intestinal amebiasis was established, and using it, we reported that Entamoeba moshkovskii colonized the intestine in a manner similar to that of the pathogenic Entamoeba histolytica In this study, we evaluated the protective mechanisms present against amebae using this model. CBA/J mice infected with E. histolytica had a persistent infection without apparent symptoms. In contrast, E. moshkovskii-infected mice rapidly expelled the ameba, which was associated with weight loss, diarrhea, and intestinal damage characterized by apoptosis of intestinal epithelial cells (IECs). Expression of NKG2D on intestinal intraepithelial lymphocytes (IELs) and IFN-γ-producing cells in Peyer's patches were significantly induced after infection with E. moshkovskii but not with E. histolytica IFN-γ-deficient mice infected with E. moshkovskii showed no obvious symptoms. Notably, none of these mice expelled E. moshkovskii, indicating that IFN-γ is responsible not only for intestinal symptoms but also for the expulsion of amebae. Furthermore, apoptosis of IECs and expression of NKG2D on IELs observed in E. moshkovskii-infected mice did not occur in the absence of IFN-γ. In vivo blocking of NKG2D in mice infected with E. moshkovskii enabled ameba to survive longer and remarkably reduced apoptotic IECs. Our results clearly demonstrate a novel protective mechanism exerted by IFN-γ against intestinal amebae, including induction of cytotoxicity of IELs toward IECs.

Development and characterization of 2-dimensional culture for buffalo intestinal cells

Small intestinal epithelial cells (IEC) play a major role in the absorption of nutrients and toxins. Due to the similarity of genome-wide single copy protein orthologues between cattle and human, establishment of ruminant's primary small IEC culture could be a valuable tool for toxicity studies. Therefore, the current study focused on the development and characterization of buffalo IEC culture, as cattle slaughter is banned in India. The buffalo jejunum fragments were washed consecutively several times in saline, warm phosphate buffered saline (PBS), PBS with 5 mM dithiothreitol, digesting solution and 2% sorbitol in PBS. The cells were cultured on 17 µg/cm² collagen coated plates and transwell plates with serum (2% Fetal bovine serum (FBS) and 10% FBS) and serum-free culture conditions. The cells were differentiated into typical epithelial cobblestone morphology from day 5 onwards in 50% successful cultures. The cultured IEC were characterized by gene expression of epithelial cell markers, cytokeratin and vimentin, and enterocyte markers like villin, zonula occluden (ZO1), fatty acid binding protein 2 (FABP2) and small intestinal peptidase (IP). Based on the morphology and gene expression profile, 10% FBS has been recommended for culturing primary buffalo IEC on collagen coated plates for 10 days. However, 50% of the successful cultures could not show epithelial phenotype on 10% FBS culture conditions even on collagen coated plates. Interestingly, undifferentiated IEC showed an increasing expression of FABP2, IP and ZO1 transcripts compared to differentiated intestinal cells with 10% FBS on collagen plates. Therefore, future studies are needed to understand the role of FABP2, IP and ZO1 in differentiation of buffalo IEC.

TLR9 Regulates the NF-κB-NLRP3-IL-1β Pathway Negatively in Salmonella-Induced NKG2D-Mediated Intestinal Inflammation

TLRs are key sensors for conserved bacterial molecules and play a critical role in host defense against invading pathogens. Although the roles of TLRs in defense against pathogen infection and in maintaining gut immune homeostasis have been studied, the precise functions of different TLRs in response to pathogen infection in the gut remain elusive. The present study investigated the role of TLR signaling in defense against the Gram-negative bacterial pathogen Salmonella typhimurium The results indicated that TLR9-deficient mice were more susceptible to S. typhimurium infection compared with wild-type and TLR2- or TLR4-deficient mice, as indicated by more severe intestinal damage and the highest bacterial load. TLR9 deficiency in intestinal epithelial cells (IECs) augmented the activation of NF-κB and NLRP3 inflammasomes significantly, resulting in increased secretion of IL-1β. IL-1β increased the expression of NKG2D on intestinal intraepithelial lymphocytes and NKG2D ligands on IECs, resulting in higher susceptibility of IECs to cytotoxicity of intestinal intraepithelial lymphocytes and damage to the epithelial barrier. We proposed that TLR9 regulates the NF-κB-NLRP3-IL-1β pathway negatively in Salmonella-induced NKG2D-mediated intestinal inflammation and plays a critical role in defense against S. typhimurium infection and in the protection of intestinal integrity.

Use of a Collagen Membrane to Enhance the Survival of Primary Intestinal Epithelial Cells

Intestinal epithelial cell culture is important for biological, functional, and immunological studies. Since enterocytes have a short in vivo life span due to anoikis, we aimed to establish a novel and reproducible method to prolong the survival of mouse and human cells. Cells were isolated following a standard procedure, and cultured on ordered-cow's collagen membranes. A prolonged cell life span was achieved; cells covered the complete surface of bio-membranes and showed a classical enterocyte morphology with high expression of enzymes supporting the possibility of cryopreservation. Apoptosis was dramatically reduced and cultured enterocytes expressed cytokeratin and LGR5 (low frequency). Cells exposed to LPS or flagellin showed the induction of TLR4 and TLR5 expression and a functional phenotype upon exposure to the probiotic Bifidobacterium bifidum or the pathogenic Clostridium difficile. The secretion of the homeostatic (IL-25 and TSLP), inhibitory (IL-10 and TGF-β), or pro-inflammatory mediators (IL-1β and TNF) were induced. In conclusion, this novel protocol using cow's collagen-ordered membrane provides a simple and reproducible method to maintain intestinal epithelial cells functional for cell-microorganism interaction studies and stem cell expansion. J. Cell. Physiol. 232: 2489-2496, 2017. © 2016 Wiley Periodicals, Inc.

Establishment of immortalized mouse intestinal epithelial cells line and study of effects of Arg-Arg on inflammatory response

Primary mouse intestinal epithelial cells (MIEs) are not ideal models for long-term culture in vitro and a limited amount of approximate three generations. In addition, the mechanism that arginine-arginine dipeptide (Arg-Arg) regulates mouse intestinal inflammatory response remains unknown. Therefore, the aim of this study was to establish immortal MIEs and study the effects of Arg-Arg on inflammatory response after challenging the MIEs with lipopolysaccharide (LPS) or staphylococcal enterotoxin C (rSEC). Our data showed that immortalized MIEs could be cultured over 100 generations. The immortalized MIEs showed positive reaction against cytokeratine 18 antigen, E-cadherin, and peptide transporters (Pept1) using indirect immunofluorescence. Cytokeratine 18 and Pept1 can be expressed in immortalized MIEs by immunoblotting. Fatty acid-binding proteins (FABPs) and villin known as intestinal epithelial cell functional protein were constitutively expressed in immortalized MIEs. For inflammatory response, these results showed that Arg-Arg can decrease the LPS-induced expression of IL-1β and the rSEC-induced expression of TNF-α; however, it can upregulate the LPS-induced expression of IL-6 and TNF-α and the rSEC-induced expression level of IL-1β. In addition, in the MAPK signaling pathway, pSAPK/JNK and p-Erk1/2 in LPS with Arg-Arg treatment were upregulated than that in LPS treatment. p-p38 in LPS with Arg-Arg treatment was attenuated than that in LPS treatment. pSAPK/JNK and p-p38 in rSEC with Arg-Arg treatment were enhanced than that in rSEC treatment. Conversely, p-Erk1/2 in rSEC with Arg-Arg treatment was attenuated than that in rSEC treatment. These novel findings suggest that Arg-Arg dipeptide plays an important role for regulation of the immunologic balance in mouse intestinal inflammatory response.

A Combination of Podophyllotoxin and Rutin Attenuates Radiation Induced Gastrointestinal Injury by Negatively Regulating NF-κB/p53 Signaling in Lethally Irradiated Mice

Development of an effective radio protector to minimise radiation-inflicted damages have largely failed owing to inherent toxicity of most of the agents examined so far. This study is centred towards delivering protection to lethally irradiated mice by pre-administration of a safe formulation G-003M (combination of podophyllotoxin and rutin) majorly through regulation of inflammatory and cell death pathways in mice. Single intramuscular dose of G-003M injected 60 min prior to 9 Gy exposure rescued 89% of whole body lethally irradiated C57BL/6J mice. Studies have revealed reduction in radiation induced reactive oxygen species (ROS), nitric oxide (NO) generation, prostaglandin E2 (PGE2) levels and intestinal apoptosis in G-003M pre-treated mice intestine. Restricted nuclear translocation of redox-sensitive Nuclear factor-κB (NF-κB) and subsequent downregulation of cyclo-oxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS; EC 1.14.13.39) and tumor necrosis factor (TNF-α) levels demonstrated the anti-inflammatory effect that G-003M exerts. Support to early hematopoietic recovery was exhibited through G-003M mediated induction of granulocyte colony stimulating factor (G-CSF) and interleukin (IL-6) levels in lethally irradiated mice. Considerable attenuation in radiation induced morphological damage to the intestinal villi, crypts and mucosal layers was observed in G-003M pre-treated mice. Additionally, our formulation did not reduce the sensitivity of tumor tissue to radiation. Altogether, these results suggest that G-003M ameliorates the deleterious effects of radiation exposure by minimising ROS and NO generation and effectively regulating inflammatory and cell death pathways. Mechanism of protection elucidated in the current study demonstrates that G-003M can be used as a safe and effective radio protective agent in radiotherapy for human application.

Interacciones de las proteínas disulfuro isomerasa y de choque térmico Hsc70 con proteínas estructurales recombinantes purificadas de rotavirus

<p>Introducción. La entrada de rotavirus a las células parece estar mediado por interacciones secuenciales entre las proteínas estructurales virales y algunas moléculas de la superficie celular. Sin embargo, los mecanismos por los cuales el rotavirus infecta la célula diana aún no se comprenden bien. Existe alguna evidencia que muestra que las proteínas estructurales de rotavirus VP5* y VP8* interactúan con algunas moléculas de la superficie celular. La disponibilidad de las proteínas estructurales de rotavirus recombinantes en cantidad suficiente se ha convertido en un aspecto importante para la identificación de las interacciones específicas de los receptores virus-célula durante los eventos tempranos del proceso infeccioso. Objetivo. El propósito del presente trabajo es realizar un análisis de las interacciones entre las proteínas estructurales de rotavirus recombinante VP5*, VP8* y VP6, y las proteínas celulares Hsc70 y PDI utilizando sus versiones recombinantes purificadas. Materiales y métodos. Las proteínas recombinantes de rotavirus VP5* y VP8* y las proteínas recombinantes celulares Hsc70 y PDI se expresaron en E. BL21 (DE3), mientras que VP6 se expresó en células MA104 con virus vaccinia recombinante transfectada. La interacción entre el rotavirus y las proteínas celulares se estudió mediante ELISA, co-inmunoprecipitación y SDS-PAGE/ Western. Resultados. Las condiciones óptimas para la expresión de proteínas recombinantes se determinaron y se generaron anticuerpos contra ellas. Los resultados sugirieron que las proteínas virales rVP5* y rVP6 interactúan con Hsc70 y PDI in vitro. También se encontró que éstas proteínas virales recombinantes interactúan con Hsc70 en las balsas lipídicas (“Rafts”) en un cultivo celular. El tratamiento de las células, ya sea con DLP o rVP6 produjo significativamente la inhibición de la infección por rotavirus. Conclusión. Los resultados permiten concluir que rVP5 * y rVP6 interactúan con Hsc70 y PDI durante el proceso de la infección por rotavirus.</p>

Modeling rotavirus infection and antiviral therapy using primary intestinal organoids

Despite the introduction of oral vaccines, rotavirus still kills over 450,000 children under five years of age annually. The absence of specific treatment prompts research aiming at further understanding of pathogenesis and the development of effective antiviral therapy, which in turn requires advanced experimental models. Given the intrinsic limitations of the classical rotavirus models using immortalized cell lines infected with laboratory-adapted strains in two dimensional cultures, our study aimed to model infection and antiviral therapy of both experimental and patient-derived rotavirus strains using three dimensional cultures of primary intestinal organoids. Intestinal epithelial organoids were successfully cultured from mouse or human gut tissues. These organoids recapitulate essential features of the in vivo tissue architecture, and are susceptible to rotavirus. Human organoids are more permissive to rotavirus infection, displaying an over 10,000-fold increase in genomic RNA following 24h of viral replication. Furthermore, infected organoids are capable of producing infectious rotavirus particles. Treatment of interferon-alpha or ribavirin inhibited viral replication in organoids of both species. Importantly, human organoids efficiently support the infection of patient-derived rotavirus strains and can be potentially harnessed for personalized evaluation of the efficacy of antiviral medications. Therefore, organoids provide a robust model system for studying rotavirus-host interactions and assessing antiviral medications.

Lgr5 positive stem cells sorted from small intestines of diabetic mice differentiate into higher proportion of absorptive cells and Paneth cells in vitro

Intestinal epithelial stem cells (IESCs) can differentiate into all types of intestinal epithelial cells (IECs) and Leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) is a marker for IESC. Previous studies reported enhanced proliferation of IECs in diabetic mice. In this study, the in vitro differentiation of Lgr5 positive IESCs sorted from diabetic mice was further investigated. The diabetic mouse model was induced by streptozotocin (STZ), and crypt IECs were isolated from small intestines. Subsequently, Lgr5 positive IESCs were detected by flow cytometry (FCM) and sorted by magnetic activated cell sorting (MACS). Differentiation of the sorted IESCs was investigated by detecting the IEC markers in the diabetic mice using immunostaining, quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR), and Western blot analysis, which was compared with normal mice. We found that the proportion of Lgr5 positive cells in the crypt IECs of diabetic mice was higher than that of control mice (P < 0.05). Lgr5 positive IESCs could be significantly enriched in Lgr5 positive cell fraction sorted by MACS. Furthermore, the absorptive cell marker sucrase-isomaltase (SI) and the Paneth cell marker lysozyme 1 (Lyz1) were more highly expressed in the differentiated cells derived from Lgr5 positive IESCs of diabetic mice in vitro (P < 0.05). We demonstrate that the number of Lgr5 positive IESCs is significantly increased in the small intestines of STZ-induced diabetic mice. Lgr5 positive IESCs sorted from the diabetic mice can differentiate into a higher proportion of absorptive cells and Paneth cells in vitro. We characterized the expression of Lgr5 in the small intestine of diabetic mice, and sorted Lgr5 positive intestinal epithelial stem cells (IESCs) for investigating their differentiation in vitro. We proved that the quantity of Lgr5 positive IESCs was significantly increased in the small intestines of diabetic mice. IESCs sorted from the diabetic mice can differentiate into a higher proportion of absorptive cells and Paneth cells in vitro.

Radiation persistently promoted oxidative stress, activated mTOR via PI3K/Akt, and downregulated autophagy pathway in mouse intestine

While acute effects of toxic radiation doses on intestine are well established, we are yet to acquire a complete spectrum of sub-lethal radiation-induced chronic intestinal perturbations at the molecular level. We investigated persistent effects of a radiation dose (2 Gy) commonly used as a daily fraction in radiotherapy on oxidants and anti-oxidants, and autophagy pathways, which are interlinked processes affecting intestinal homeostasis. Six to eight weeks old C57BL/6J mice (n=10) were exposed to 2 Gy γ-ray. Mice were euthanized two or twelve months after radiation, intestine surgically removed, and flushed using sterile PBS. Parts of the intestine from jejunal-ilial region were fixed, frozen, or used for intestinal epithelial cell (IEC) isolation. While oxidant levels and mitochondrial status were assessed in isolated IEC, autophagy and oxidative stress related signaling pathways were probed in frozen and fixed samples using PCR-based expression arrays and immunoprobing. Radiation exposure caused significant alterations in the expression level of 26 autophagy and 17 oxidative stress related genes. Immunoblot results showed decreased Beclin1 and LC3-II and increased p62, PI3K/Akt, and mTOR. Flow cytometry data showed increased oxidant production and compromised mitochondrial integrity in irradiated samples. Immunoprobing of intestinal sections showed increased 8-oxo-dG and nuclear PCNA, and decreased autophagosome marker LC3-II in IEC after irradiation. We show that sub-lethal radiation could persistently downregulate anti-oxidants and autophagy signaling, and upregulate oxidant production and proliferative signaling. Radiation-induced promotion of oxidative stress and downregulation of autophagy could work in tandem to alter intestinal functions and have implications for post-radiation chronic gastrointestinal diseases.

Characteristic and functional analysis of a newly established porcine small intestinal epithelial cell line

The mucosal surface of intestine is continuously exposed to both potential pathogens and beneficial commensal microorganisms. Recent findings suggest that intestinal epithelial cells, which once considered as a simple physical barrier, are a crucial cell lineage necessary for maintaining intestinal immune homeostasis. Therefore, establishing a stable and reliable intestinal epithelial cell line for future research on the mucosal immune system is necessary. In the present study, we established a porcine intestinal epithelial cell line (ZYM-SIEC02) by introducing the human telomerase reverse transcriptase (hTERT) gene into small intestinal epithelial cells derived from a neonatal, unsuckled piglet. Morphological analysis revealed a homogeneous cobblestone-like morphology of the epithelial cell sheets. Ultrastructural indicated the presence of microvilli, tight junctions, and a glandular configuration typical of the small intestine. Furthermore, ZYM-SIEC02 cells expressed epithelial cell-specific markers including cytokeratin 18, pan-cytokeratin, sucrase-isomaltase, E-cadherin and ZO-1. Immortalized ZYM-SIEC02 cells remained diploid and were not transformed. In addition, we also examined the host cell response to Salmonella and LPS and verified the enhanced expression of mRNAs encoding IL-8 and TNF-α by infection with Salmonella enterica serovars Typhimurium (S. Typhimurium). Results showed that IL-8 protein expression were upregulated following Salmonella invasion. TLR4, TLR6 and IL-6 mRNA expression were upregulated following stimulation with LPS, ZYM-SIEC02 cells were hyporeponsive to LPS with respect to IL-8 mRNA expression and secretion. TNFα mRNA levels were significantly decreased after LPS stimulation and TNF-α secretion were not detected challenged with S. Typhimurium neither nor LPS. Taken together, these findings demonstrate that ZYM-SIEC02 cells retained the morphological and functional characteristics typical of primary swine intestinal epithelial cells and thus provide a relevant in vitro model system for future studies on porcine small intestinal pathogen-host cell interactions.

Exposure to heavy ion radiation induces persistent oxidative stress in mouse intestine

Ionizing radiation-induced oxidative stress is attributed to generation of reactive oxygen species (ROS) due to radiolysis of water molecules and is short lived. Persistent oxidative stress has also been observed after radiation exposure and is implicated in the late effects of radiation. The goal of this study was to determine if long-term oxidative stress in freshly isolated mouse intestinal epithelial cells (IEC) is dependent on radiation quality at a dose relevant to fractionated radiotherapy. Mice (C57BL/6J; 6 to 8 weeks; female) were irradiated with 2 Gy of γ-rays, a low-linear energy transfer (LET) radiation, and intestinal tissues and IEC were collected 1 year after radiation exposure. Intracellular ROS, mitochondrial function, and antioxidant activity in IEC were studied by flow cytometry and biochemical assays. Oxidative DNA damage, cell death, and mitogenic activity in IEC were assessed by immunohistochemistry. Effects of γ radiation were compared to ⁵⁶Fe radiation (iso-toxic dose: 1.6 Gy; energy: 1000 MeV/nucleon; LET: 148 keV/µm), we used as representative of high-LET radiation, since it's one of the important sources of high Z and high energy (HZE) radiation in cosmic rays. Radiation quality affected the level of persistent oxidative stress with higher elevation of intracellular ROS and mitochondrial superoxide in high-LET ⁵⁶Fe radiation compared to unirradiated controls and γ radiation. NADPH oxidase activity, mitochondrial membrane damage, and loss of mitochondrial membrane potential were greater in ⁵⁶Fe-irradiated mice. Compared to γ radiation oxidative DNA damage was higher, cell death ratio was unchanged, and mitotic activity was increased after ⁵⁶Fe radiation. Taken together our results indicate that long-term functional dysregulation of mitochondria and increased NADPH oxidase activity are major contributing factors towards heavy ion radiation-induced persistent oxidative stress in IEC with potential for neoplastic transformation.

Stem cell-derived human intestinal organoids as an infection model for rotaviruses

Directed differentiation of stem cell lines into intestine-like tissue called induced human intestinal organoids (iHIOs) is now possible (J. R. Spence, C. N. Mayhew, S. A. Rankin, M. F. Kuhar, J. E. Vallance, K. Tolle, E. E. Hoskins, V. V. Kalinichenko, S. I. Wells, A. M. Zorn, N. F. Shroyer, and J. M. Wells, Nature 470:105-109, 2011). We tested iHIOs as a new model to cultivate and study fecal viruses. Protocols for infection of iHIOs with a laboratory strain of rotavirus, simian SA11, were developed. Proof-of-principle analyses showed that iHIOs support replication of a gastrointestinal virus, rotavirus, on the basis of detection of nonstructural viral proteins (nonstructural protein 4 [NSP4] and NSP2) by immunofluorescence, increased levels of viral RNA by quantitative reverse transcription-PCR (qRT-PCR), and production of infectious progeny virus. iHIOs were also shown to support replication of 12/13 clinical rotavirus isolates directly from stool samples. An unexpected finding was the detection of rotavirus infection not only in the epithelial cells but also in the mesenchymal cell population of the iHIOs. This work demonstrates that iHIOs offer a promising new model to study rotaviruses and other gastrointestinal viruses.

IMPORTANCE

Gastrointestinal viral infections are a major cause of illness and death in children and adults. The ability to fully understand how viruses interact with human intestinal cells in order to cause disease has been hampered by insufficient methods for growing many gastrointestinal viruses in the laboratory. Induced human intestinal organoids (iHIOs) are a promising new model for generating intestine-like tissue. This is the first report of a study using iHIOs to cultivate any microorganism, in this case, an enteric virus. The evidence that both laboratory and clinical rotavirus isolates can replicate in iHIOs suggests that this model would be useful not only for studies of rotaviruses but also potentially of other infectious agents. Furthermore, detection of rotavirus proteins in unexpected cell types highlights the promise of this system to reveal new questions about pathogenesis that have not been previously recognized or investigated in other intestinal cell culture models.

Small intestinal intraepithelial lymphocytes expressing CD8 and T cell receptor γδ are involved in bacterial clearance during Salmonella enterica serovar Typhimurium infection

The intestinal immune system is crucial for the maintenance of mucosal homeostasis and has evolved under the dual pressure of protecting the host from pathogenic infection and coexisting with the dense and diverse commensal organisms in the lumen. Intestinal intraepithelial lymphocytes (iIELs) are the first element of the host T cell compartment available to respond to oral infection by pathogens. This study demonstrated that oral infection by Salmonella enterica serovar Typhimurium promoted the expansion of iIELs, particularly CD8(+) TCRγδ(+) IELs, enhanced expression of NKG2D on iIELs, increased expression of MULT1, and decreased expression of Qa-1 by intestinal epithelial cells (IECs), leading to activation of, particularly, CD8(+) TCRγδ(+) iIELs and cytolytic activity against S. Typhimurium-infected IECs. Blockade of NKG2D recognition or depletion of TCRγδ(+) cells using a depleting monoclonal antibody significantly attenuated the clearance of S. Typhimurium in the intestine and other tissues. This study suggests that iIELs, particularly CD8(+) TCRγδ(+) iIELs, play important roles in the detection of pathogenic bacteria and eradication of infected epithelial cells and, thus, provide protection against invading pathogens. These data further our understanding of the mechanisms by which the immune system of the intestinal mucosa discriminates between pathogenic and commensal organisms.

Analyses of clinical, pathological and virological features of human rotavirus strain, YO induced gastroenteritis in infant BALB/c mice

Experimental studies of human rotavirus infections in mice are limited and there is lack of information on the quantitative assessment of rotaviral replication and its relationship with histological changes. In the present study, consequences of human rotavirus strain, YO induced gastroenteritis in infant BALB/c mice were analyzed for the occurrence of clinical symptoms, histopathology and virological events. The infected animals developed diarrhea and dehydration and showed accumulation of vacuolated enterocytes with lodging of the rotavirus antigens and shortening of villi in the intestine over a period of 5 days. The ileum was identified as the most susceptible and supportive part of small intestine for perpetuation of rotavirus infection in mice. Rotaviral antigen/RNA in stool and RNA in intestine were detected throughout the clinical disease period. At 48-72 h post inoculation, diarrhea was at the peak (90-95%) in the infected animals with increased load of viral RNA and intense pathological lesions suggesting it as the critical time point in the course of infection. The rising titers of antirotavirus neutralizing antibodies ascertained the replication of human rotavirus strain, YO in mice. These data may contribute to the understanding of pathophysiological, immunological and virological characteristics of rotavirus infections in mice.

TRIF mediates Toll-like receptor 5-induced signaling in intestinal epithelial cells

Toll-like receptors (TLRs) associate with adaptor molecules (MyD88, Mal/TIRAP, TRAM, and TRIF) to mediate signaling of host-microbial interaction. For instance, TLR4 utilizes the combination of both Mal/TIRAP-MyD88 (MyD88-dependent pathway) and TRAM-TRIF (MyD88-independent pathway). However, TLR5, the specific receptor for flagellin, is known to utilize only MyD88 to elicit inflammatory responses, and an involvement of other adaptor molecules has not been suggested in TLR5-dependent signaling. Here, we found that TRIF is involved in mediating TLR5-induced nuclear factor κB (NFκB) and mitogen-activated protein kinases (MAPKs), specifically JNK1/2 and ERK1/2, activation in intestinal epithelial cells. TLR5 activation by flagellin permits the physical interaction between TLR5 and TRIF in human colonic epithelial cells (NCM460), whereas TLR5 does not interact with TRAM upon flagellin stimulation. Both primary intestinal epithelial cells from TRIF-KO mice and TRIF-silenced NCM460 cells significantly reduced flagellin-induced NFκB (p105 and p65), JNK1/2, and ERK1/2 activation compared with control cells. However, p38 activation by flagellin was preserved in these TRIF-deficient cells. TRIF-KO intestinal epithelial cells exhibited substantially reduced inflammatory cytokine (keratinocyte-derived cytokine, macrophage inflammatory protein 3α, and IL-6) expression upon flagellin, whereas control cells from TRIF-WT mice showed robust cytokine expression by flagellin. Compare with TRIF-WT mice, TRIF-KO mice were resistant to in vivo intestinal inflammatory responses: flagellin-mediated exacerbation of colonic inflammation and dextran sulfate sodium-induced experimental colitis. We conclude that in addition to MyD88, TRIF mediates TLR5-dependent responses and, thereby regulates inflammatory responses elicited by flagellin/TLR5 engagement. Our findings suggest an important role of TRIF in regulating host-microbial communication via TLR5 in the gut epithelium.

TRIF mediates Toll-like receptor 5-induced signaling in intestinal epithelial cells

Toll-like receptors (TLRs) associate with adaptor molecules (MyD88, Mal/TIRAP, TRAM, and TRIF) to mediate signaling of host-microbial interaction. For instance, TLR4 utilizes the combination of both Mal/TIRAP-MyD88 (MyD88-dependent pathway) and TRAM-TRIF (MyD88-independent pathway). However, TLR5, the specific receptor for flagellin, is known to utilize only MyD88 to elicit inflammatory responses, and an involvement of other adaptor molecules has not been suggested in TLR5-dependent signaling. Here, we found that TRIF is involved in mediating TLR5-induced nuclear factor κB (NFκB) and mitogen-activated protein kinases (MAPKs), specifically JNK1/2 and ERK1/2, activation in intestinal epithelial cells. TLR5 activation by flagellin permits the physical interaction between TLR5 and TRIF in human colonic epithelial cells (NCM460), whereas TLR5 does not interact with TRAM upon flagellin stimulation. Both primary intestinal epithelial cells from TRIF-KO mice and TRIF-silenced NCM460 cells significantly reduced flagellin-induced NFκB (p105 and p65), JNK1/2, and ERK1/2 activation compared with control cells. However, p38 activation by flagellin was preserved in these TRIF-deficient cells. TRIF-KO intestinal epithelial cells exhibited substantially reduced inflammatory cytokine (keratinocyte-derived cytokine, macrophage inflammatory protein 3α, and IL-6) expression upon flagellin, whereas control cells from TRIF-WT mice showed robust cytokine expression by flagellin. Compare with TRIF-WT mice, TRIF-KO mice were resistant to in vivo intestinal inflammatory responses: flagellin-mediated exacerbation of colonic inflammation and dextran sulfate sodium-induced experimental colitis. We conclude that in addition to MyD88, TRIF mediates TLR5-dependent responses and, thereby regulates inflammatory responses elicited by flagellin/TLR5 engagement. Our findings suggest an important role of TRIF in regulating host-microbial communication via TLR5 in the gut epithelium.

Primary culture of intestinal epithelial cells as a potential model for Toxoplasma gondii enteric cycle studies

The primary culture of intestinal epithelial cells from domestic cats is an efficient cellular model to study the enteric cycle of Toxoplasma gondii in a definitive host. The parasite-host cell ratio can be pointed out as a decisive factor that determines the intracellular fate of bradyzoites forms. The development of the syncytial-like forms of T. gondii was observed using the 1:20 bradyzoite-host cell ratio, resulting in similar forms described in in vivo systems. This alternative study potentially opens up the field for investigation into the molecular aspects of this interaction. This can contribute to the development of new strategies for intervention of a main route by which toxoplasmosis spreads.

Protective role of mouse MBL-C on intestinal mucosa during Shigella flexneri invasion

Mannan-binding lectin (MBL) is a C-type serum lectin, which is believed to play an important role in the innate immunity against a variety of pathogens. MBL can bind to sugar determinants of a wide variety of microorganisms, neutralize them and inhibit infection by complement activation through the lectin pathway and opsonization by collectin receptors. Given that small intestine is a predominant site of extrahepatic expression of MBL, here we addressed the question whether MBL is involved in mucosal innate immunity. The carbohydrate recognition domain (CRD) genes of mouse MBL-C (mMBL-C) were cloned and expressed in Escherichia coli. Recombinant mMBL-C-CRD binds to Shigella flexneri 2a in a calcium-dependent manner and that interaction could be blocked by the anti-mMBL-C-CRD antibody. mMBL-C-CRD protein could inhibit the adhesion of S. flexneri 2a to intestinal mucosa, while administration of anti-mMBL-C-CRD antibody caused an increased level of bacteria adhesion in vitro. Administration of recombinant mMBL-C-CRD protein reduced the secretion of IL-6 and monocyte chemoattractant protein 1 from primary intestinal epithelial cells stimulated with S. flexneri 2a. Furthermore, neutralization of MBL activity by anti-MBL-C-CRD resulted in a significant increase in the number of S. flexneri 2a that colonized the intestines of BALB/c mice and attenuated the severity of inflammation seen in the areas of bacterial invasion. These findings suggest that mMBL-C may protect host intestinal mucosa by directly binding to the bacteria.

Retroviral self-inactivation in the mouse vagina induced by short DNA

Human immunodeficiency virus (HIV) has been shown to undergo self-destruction upon treatment of cell-free virions with partially double-stranded oligodeoxynucleotides targeting the polypurine tract (PPT) of the viral RNA in the virus particle. The ODN forms a local hybrid with the PPT activating the viral RNase H to prematurely cleave the genomic RNA. Here we are describing the self-destruction of a recombinant lentivirus harboring the PPT of HIV in a mouse vagina model. We showed a decrease in viral RNA levels in cell-free virus particles and a reduction reverse transcribed complementary DNA (cDNA) in virus-infected human and primary murine cells by incubation with ODNs. In the vagina simultaneous, prophylactic or therapeutic ODN treatments led to a significant reduction in viral RNA levels. Our finding may have some relevance for the design of other viral self-destruction approaches. It may lead to a microbicide for reduction of sexual and mother-to-child transmission.

Establishment of fetal bovine intestinal epithelial cell cultures susceptible to bovine rotavirus infection

Mucosal epithelial cells are infected by a wide variety of pathogens and determining their response to infection is critical for understanding disease pathogenesis. A protocol was developed for culturing primary epithelial cells from fetal bovine intestine and the cultured cells were evaluated for susceptibility to an enteric viral infection. Immunohistochemical staining for cytokeratin confirmed that 60–75% of cultured cells were epithelial cells. Furthermore, following infection with bovine rotavirus (BRV) over 80% of cells in the ileal and jejunal cultures contained viral protein at 16 h post-infection. The intestinal epithelial cell cultures also contained fibroblasts so a jejunal fibroblast culture was established and infected with BRV. Viral protein was detected in jejunal fibroblasts but viral-induced cytopathology was delayed in fibroblast cultures when compared to epithelial cell cultures. This study describes an effective protocol for culturing bovine epithelial cells from fetal intestine and confirmed that the epithelial cells were susceptible to BRV infection. Ileal and jejunal cultures displayed limited growth following continuous passage but early passage epithelial cells provide competent target cells for studying host cell responses to an enteric viral pathogen.

Mouse model of colonic adenoma-carcinoma progression based on somatic Apc inactivation

Mutations in the adenomatous polyposis coli (APC) gene are pivotal in colorectal tumorigenesis. Existing mouse intestinal tumor models display mainly small intestinal lesions and carcinomas are rare. We defined human CDX2 sequences conferring colon epithelium-preferential transgene expression in the adult mouse. Mice carrying a CDX2P-NLS Cre recombinase transgene and a loxP-targeted Apc allele developed mainly colorectal tumors, with carcinomas seen in 6 of 36 (17%) of mice followed for 300 days. Like human colorectal lesions, the mouse tumors showed biallelic Apc inactivation, beta-catenin dysregulation, global DNA hypomethylation, and aneuploidy. The predominantly distal colon and rectal distribution of tumors seen in mice where one Apc allele was inactivated in epithelial cells from distal ileum to rectum suggests that regional differences in the intestinal tract in the frequency and nature of secondary genetic and epigenetic events associated with adenoma outgrowth have a contributing role in determining where adenomas develop. The presence of large numbers of small intestine tumors seemed to inhibit colorectal tumor development in the mouse, and gender-specific effects on tumor multiplicity in the distal mouse colon and rectum mimic the situation in humans where males have a larger number of advanced adenomas and carcinomas in the distal colon and rectum than females. The mouse model of colon-preferential gene targeting described here should facilitate efforts to define novel factors and mechanisms contributing to human colon tumor pathogenesis, as well as work on tumor-promoting environmental factors and agents and strategies for cancer prevention and treatment.

Recognition of double-stranded RNA by TLR3 induces severe small intestinal injury in mice

The role of TLRs on intestinal epithelial cells (IECs) is controversial, and the mechanisms by which TLRs influence mucosal homeostasis are obscure. In this study, we report that genomic dsRNA from rotavirus, and its synthetic analog polyinosinic-polycytidylic acid (poly(I:C)), induce severe mucosal injury in the small intestine. Upon engaging TLR3 on IECs, dsRNA triggers IECs to secrete IL-15, which functions to increase the percentage of CD3+NK1.1+ intestinal intraepithelial lymphocytes (IELs) and enhances the cytotoxicity of IELs. Moreover, The CD3+NK1.1+ IELs are proved as CD8alphaalpha+ IELs. These results provide direct evidence that abnormal TLR3 signaling contributes to breaking down mucosal homeostasis and the first evidence of pathogenic effects mediated by CD8alphaalpha+ IELs. The data also suggest that genomic dsRNA may be involved in the pathogenesis of acute rotavirus gastroenteritis.

Intestinal epithelial stem cells and progenitors

The adult intestinal epithelium contains a relatively simple, highly organized, and readily accessible stem cell system. Excellent methods exist for the isolation of intestinal epithelium from adults, and as a result collecting large quantities of intestinal stem and progenitor cells for study or culture and subsequent clinical applications should be routine. It is not, however, for two reasons: (1) adult intestinal epithelial cells rapidly initiate apoptosis on detachment from the basement membrane, and (2) in vitro conditions necessary for survival, proliferation, and differentiation are poorly understood. Thus to date the study of intestinal stem and progenitor cells has been largely dependent on in vivo approaches. We discuss existing in vivo assays for stem and progenitor cell behavior as well as current methods for isolating and culturing the intestinal epithelium.

Immunochemical, biomolecular and biochemical characterization of bovine epithelial intestinal primocultures

BACKGROUND

Cultures of enterocytes and colonocytes represent valuable tools to study growth and differentiation of epithelial cells. In vitro models may be used to evaluate passage or toxicity of drugs, interactions of enteropathogenes bacteria strains with intestinal epithelium and other physiologic or pathologic phenomenon involving the digestive tract.

RESULTS

Cultures of bovine colonocytes and jejunocytes were obtained from organoid-enriched preparations, using a combination of enzymatic and mechanical disruption of the intestine epithelium, followed by an isopicnic centrifugation discarding most single cells. Confluent cell monolayers arising from plated organoids exhibited epithelium typical features, such as the pavement-like structure, the presence of apical microvilli and tight junctions. Accordingly, cells expressed several markers of enterocyte brush border (i.e. maltase, alkaline phosphatase and fatty acid binding protein) as well as an epithelial cytoskeleton component (cytokeratin 18). However, enterocyte primocultures were also positive for the vimentin immunostaining (mesenchyme marker). Vimentin expression studies showed that this gene is constitutively expressed in bovine enterocytes. Comparison of the vimentin expression profile with the pattern of brush border enzymes activities, suggested that the decrease of cell differentiation level observed during the enterocyte isolation procedure and early passages of the primoculture could result from a post-transcriptional de-repression of vimentin synthesis. The low differentiation level of bovine enterocytes in vitro could partly be counteracted adding butyrate (1-2 mM) or using a glucose-deprived culture medium.

CONCLUSION

The present study describes several complementary approaches to characterize bovine primary cultures of intestinal cells. Cultured cells kept their morphologic and functional characteristics during several generations.

Role of intestinal epithelial cells in immune effects mediated by gram-positive probiotic bacteria: involvement of toll-like receptors

The mechanisms by which probiotic bacteria exert their effects on the immune system are not completely understood, but the epithelium may be a crucial player in the orchestration of the effects induced. In a previous work, we observed that some orally administered strains of lactic acid bacteria (LAB) increased the number of immunoglobulin A (IgA)-producing cells in the small intestine without a concomitant increase in the CD4(+) T-cell population, indicating that some LAB strains induce clonal expansion only of B cells triggered to produce IgA. The present work aimed to study the cytokines induced by the interaction of probiotic LAB with murine intestinal epithelial cells (IEC) in healthy animals. We focused our investigation mainly on the secretion of interleukin 6 (IL-6) necessary for the clonal expansion of B cells previously observed with probiotic bacteria. The role of Toll-like receptors (TLRs) in such interaction was also addressed. The cytokines released by primary cultures of IEC in animals fed with Lactobacillus casei CRL 431 or Lactobacillus helveticus R389 were determined. Cytokines were also determined in the supernatants of primary cultures of IEC of unfed animals challenged with different concentrations of viable or nonviable lactobacilli and Escherichia coli, previously blocked or not with anti-TLR2 and anti-TLR4. We concluded that the small intestine is the place where a major distinction would occur between probiotic LAB and pathogens. This distinction comprises the type of cytokines released and the magnitude of the response, cutting across the line that separates IL-6 necessary for B-cell differentiation, which was the case with probiotic lactobacilli, from inflammatory levels of IL-6 for pathogens.

Mammalian intestinal epithelial cells in primary culture: a mini-review

Epithelial cells lining the digestive tract represent a highly organized system built up by multipotent stem cells. A process of asymmetric mitosis produces a population of proliferative cells that are rapidly renewed and migrate along the crypt-villus axis, differentiating into functional mature cells before dying and exfoliating into the intestinal lumen. Isolated crypts or epithelial cells retaining high viability can be prepared within a few h after tissue sampling. After cells are cultured in serum-free media, short-term studies (16-48 h) can be conducted for endocrinology, energy metabolism, or programmed cell death. However, long-term primary culture of intestinal cells (up to 10 d) is still difficult despite progress in isolation methodologies and manipulation of the cell microenvironment. The main problem in developing primary culture is the lack of structural markers specific to the stem cell compartment. The design of a microscopic multidimensional analytic system to record the expression profiles of biomarkers all along the living intestinal crypt should improve basic knowledge of the survival and growth of adult crypt stem cells, and the selection of totipotent embryonic stem cells capable of differentiating into intestinal tissues should facilitate studies of the genomic basis of endodermal tissue differentiation.

Growth of rotaviruses in primary pancreatic cells

Rotavirus infection in children at risk of developing type 1 diabetes has been temporally associated with development of pancreatic islet autoantibodies. In this study, nonobese diabetic mice were shown to be susceptible to rhesus rotavirus infection and pancreatic islets from nonobese diabetic mice, nonobese diabetes-resistant mice, fetal pigs, and macaque monkeys supported various degrees of rotavirus growth. Human rotaviruses replicated in monkey islets only. This islet susceptibility shows that rotavirus infection of the pancreas in vivo might be possible.

Lamina propria CD4+ T lymphocytes synergize with murine intestinal epithelial cells to enhance proinflammatory response against an intracellular pathogen

Acute and lethal ileitis can be elicited in certain strains of inbred mice after oral infection with the intracellular protozoan parasite Toxoplasma gondii. The development of this inflammatory process is dependent upon the induction of a robust Th1 response, including overproduction of IFN-gamma, TNF-alpha, and NO, as has been reported in other experimental models of human inflammatory bowel disease. In this study we have investigated the role of CD4(+) T cells from the lamina propria (LP) in the early inflammatory events after T. gondii infection using isolated and primary cultured intestinal cells from infected mice and immortalized mouse mIC(cl2) intestinal epithelial cells. Primed LP CD4(+) T cells isolated from parasite-infected mice produce substantial quantities of both IFN-gamma and TNF-alpha. IFN-gamma- and TNF-alpha-producing LP CD4(+) T cells synergize with infected mIC(cl2) and enhance the production of several inflammatory chemokines including macrophage-inflammatory protein-2, monocyte chemoattractant protein-1, monocyte chemoattractant protein-3, macrophage-inflammatory protein-1alphabeta, and IFN-gamma-inducible protein-10. Furthermore, primed LP CD4(+) T cells cocultured with infected mIC(cl2) inhibited replication of the parasite in the intestinal epithelial cells. Thus, LP CD4(+) T cells can interact with parasite-infected intestinal epithelial cells and alter the expression of several proinflammatory products that have been associated with the development of intestinal inflammation. The interaction between these two components of the gut mucosal compartment (CD4(+) T cells and enterocytes) may play a role in the immunopathogenesis of this pathogen-driven experimental inflammatory bowel disease model.

Mammalian intestinal epithelial cells in primary culture: a mini-review

Epithelial cells lining the digestive tract represent a highly organized system built up by multipotent stem cells. A process of asymmetric mitosis produces a population of proliferative cells that are rapidly renewed and migrate along the crypt-villus axis, differentiating into functional mature cells before dying and exfoliating into the intestinal lumen. Isolated crypts or epithelial cells retaining high viability can be prepared within a few h after tissue sampling. After cells are cultured in serum-free media, short-term studies (16-48 h) can be conducted for endocrinology, energy metabolism, or programmed cell death. However, long-term primary culture of intestinal cells (up to 10 d) is still difficult despite progress in isolation methodologies and manipulation of the cell microenvironment. The main problem in developing primary culture is the lack of structural markers specific to the stem cell compartment. The design of a microscopic multidimensional analytic system to record the expression profiles of biomarkers all along the living intestinal crypt should improve basic knowledge of the survival and growth of adult crypt stem cells, and the selection of totipotent embryonic stem cells capable of differentiating into intestinal tissues should facilitate studies of the genomic basis of endodermal tissue differentiation.