Epithelial microvilli establish an electrostatic barrier to microbial adhesion. Infect Immun. 2014;82:2860-2871. [PMID: 24778113 DOI: 10.1128/iai.01681-14]

Revolutionizing type 1 diabetes management: Exploring oral insulin and adjunctive treatments

Type 1 diabetes (T1D) is a chronic autoimmune condition that affects millions of people worldwide. Insulin pumps or injections are the standard treatment options for this condition. This article provides a comprehensive overview of the several type 1 diabetes treatment options, focusing on oral insulin. The article is divided into parts that include immune-focused treatments, antigen vaccination, cell-directed interventions, cytokine-directed interventions, and non-immunomodulatory adjuvant therapy. Under the section on non-immunomodulatory adjunctive treatment, the benefits and drawbacks of medications such as metformin, amylin, sodium-glucose cotransporter inhibitors, glucagon-like peptide-1 receptor agonists (GLP-1 Ras), and verapamil are discussed. The article also discusses the advantages of oral insulin, including increased patient compliance and more dependable and regular blood sugar control. However, several variables, including the enzymatic and physical barriers of the digestive system, impair the administration of insulin via the mouth. Researchers have looked at a few ways to get over these challenges, such as changing the structure of the insulin molecule, improving absorption with the use of absorption enhancers or nanoparticles, and taking oral insulin together with other medications. Even with great advancements in the use of these treatment strategies, T1D still needs improvement in the therapeutic difficulties. Future studies in these areas should focus on creating tailored immunological treatments, looking into combination medications, and refining oral insulin formulations in an attempt to better control Type 1 Diabetes. The ultimate objective is to create accurate, customized strategies that will enhance glycemic management and the quality of life for individuals with the condition.

Peyer's Patch: Possible target for modulating the Gut-Brain-Axis through microbiota

The gastrointestinal (GI) tract and the brain form bidirectional nervous, immune, and endocrine communications known as the gut-brain axis. Several factors can affect this axis; among them, various studies have focused on the microbiota and imply that alterations in microbiota combinations can influence both the brain and GI. Also, many studies have shown that the immune system has a vital role in varying gut microbiota combinations. In the current paper, we will review the multidirectional effects of gut microbiota, immune system, and nervous system on each other. Specifically, this review mainly focuses on the impact of Peyer's patches as a critical component of the gut immune system on the gut-brain axis through affecting the gut's microbial composition. In this way, some factors were discussed as proposed elements of missing gaps in this field.

Deciphering the M-cell niche: insights from mouse models on how microfold cells "know" where they are needed

Known for their distinct antigen-sampling abilities, microfold cells, or M cells, have been well characterized in the gut and other mucosa including the lungs and nasal-associated lymphoid tissue (NALT). More recently, however, they have been identified in tissues where they were not initially suspected to reside, which raises the following question: what external and internal factors dictate differentiation toward this specific role? In this discussion, we will focus on murine studies to determine how these cells are identified (e.g., markers and function) and ask the broader question of factors triggering M-cell localization and patterning. Then, through the consideration of unconventional M cells, which include villous M cells, Type II taste cells, and medullary thymic epithelial M cells (microfold mTECs), we will establish the M cell as not just a player in mucosal immunity but as a versatile niche cell that adapts to its home tissue. To this end, we will consider the lymphoid structure relationship and apical stimuli to better discuss how the differing cellular programming and the physical environment within each tissue yield these cells and their unique organization. Thus, by exploring this constellation of M cells, we hope to better understand the multifaceted nature of this cell in its different anatomical locales.

Self-assembled nanomicelles for oral delivery of luteolin utilizing the intestinal lymphatic pathway to target pancreatic cancer

Pancreatic cancer is one of the major cause of cancer-related deaths worldwide, and is mainly associated with carcinomas of the pancreatic tissue. Current therapies for treating pancreatic cancer have a major drawback related to their low bioavailability and non-specificity, which leads to low therapeutic efficacy and side effects. Luteolin (LUT) has been clinically used for treatment of various types of cancer, although its clinical use has declined owing to its low oral bioavailability. In this work, we prepared an effervescent-based nanocarrier (NG) that rapidly triggers an effervescent reaction and transforms into nanomicelles to modulate the oral bioavailability of the hydrophobic drug Luteolin (LUT). Furthermore, we performed tests to assess its in vitro epithelial cell permeability and cellular internalization on a Caco-2 monolayer. We also performed in vivo toxicity assessment using animal models. Further, we evaluated the nanocarrier system's in vivo efficacy in tumor xenograft pancreatic cancer models. We validated that being pH responsive, our effervescent carrier disassembles at intestinal pH and is absorbed through the intestinal lymphatic system (ILS) to further site-specifically invade the pancreatic cancer cells. Furthermore, the negative surface charge and particle size (450 ± 100 nm) of the nanomicelles helped to internalize LUT through the ILS. We observed that LUT-loaded nanomicelles have significant antipancreatic cancer efficacy by activating caspase-3 activity and downregulating VEGF-A, FAK, TNF-α, and Ki-67. Unlike other drug-delivery systems, we developed noninvasive nanocarrier system has the capability of transporting the hydrophobic drug LUT from the intestine to the tumor site by utilizing the ILS.

Administration of probiotics affects Artemia franciscana metanauplii intestinal ultrastructure and offers resistance against a Photobacterium damselae ssp. piscicida induced oxidative stress response

The effects of Photobacterium damselae ssp. piscicida (Phdp) on immune responses and intestinal ultrastructure of Artemia franciscana following infection and their amelioration by the probiotic bacteria Bacillus subtilis, Lactobacillus plantarum and Lactococcus lactis were evaluated. Pathogen growth inhibition in coculture with each probiotic and its virulence against Artemia were confirmed with an LC50 of 105 CFU mL-1. Phdp administration to Artemia at sublethal levels resulted in depletion of superoxide dismutase, glutathione reductase, glutathione transferase and phenoloxidase activities, extensive lipid peroxidation and reduced survival. Following a combined administration of each probiotic and the pathogen, enzyme activities and survival were significantly higher, while lipid peroxidation was reduced, compared to the infected group with no probiotic treatment (P < 0.05). The transmission electron microscopy study revealed that pathogen infection resulted in disarranged and fragmented microvilli, formation of empty or pathogen containing cytoplasmic vacuoles and damaged mitochondria. In the probiotic-treated and Phdp-infected series, intestinal cells showed normal appearance, except for the presence of pathogen-containing vacuoles and highly ordered but laterally stacked microvilli. The results of the present study indicate that Phdp induces cell death through an oxidative stress response and probiotics enhance Artemia immune responses to protect it against the Phdp induced damage.

Oral delivery of RNAi for cancer therapy

Cancer is a major health concern worldwide and is still in a continuous surge of seeking for effective treatments. Since the discovery of RNAi and their mechanism of action, it has shown promises in targeted therapy for various diseases including cancer. The ability of RNAi to selectively silence the carcinogenic gene makes them ideal as cancer therapeutics. Oral delivery is the ideal route of administration of drug administration because of its patients' compliance and convenience. However, orally administered RNAi, for instance, siRNA, must cross various extracellular and intracellular biological barriers before it reaches the site of action. It is very challenging and important to keep the siRNA stable until they reach to the targeted site. Harsh pH, thick mucus layer, and nuclease enzyme prevent siRNA to diffuse through the intestinal wall and thereby induce a therapeutic effect. After entering the cell, siRNA is subjected to lysosomal degradation. Over the years, various approaches have been taken into consideration to overcome these challenges for oral RNAi delivery. Therefore, understanding the challenges and recent development is crucial to offer a novel and advanced approach for oral RNAi delivery. Herein, we have summarized the delivery strategies for oral delivery RNAi and recent advancement towards the preclinical stages.

Copy Number Variation on ABCC2-DNMBP Loci Affects the Diversity and Composition of the Fecal Microbiota in Pigs

Genetic variation in the pig genome partially modulates the composition of porcine gut microbial communities. Previous studies have been focused on the association between single nucleotide polymorphisms (SNPs) and the gut microbiota, but little is known about the relationship between structural variants and fecal microbial traits. The main goal of this study was to explore the association between porcine genome copy number variants (CNVs) and the diversity and composition of pig fecal microbiota. For this purpose, we used whole-genome sequencing data to undertake a comprehensive identification of CNVs followed by a genome-wide association analysis between the estimated CNV status and the fecal bacterial diversity in a commercial Duroc pig population. A CNV predicted as gain (DUP) partially harboring ABCC2-DNMBP loci was associated with richness (P = 5.41 × 10-5, false discovery rate [FDR] = 0.022) and Shannon α-diversity (P = 1.42 × 10-4, FDR = 0.057). The in silico predicted gain of copies was validated by real-time quantitative PCR (qPCR), and its segregation, and positive association with the richness and Shannon α-diversity of the porcine fecal bacterial ecosystem was confirmed in an unrelated F1 (Duroc × Iberian) cross. Our results advise the relevance of considering the role of host-genome structural variants as potential modulators of microbial ecosystems and suggest the ABCC2-DNMBP CNV as a host-genetic factor for the modulation of the diversity and composition of the fecal microbiota in pigs. IMPORTANCE A better understanding of the environmental and host factors modulating gut microbiomes is a topic of greatest interest. Recent evidence suggests that genetic variation in the pig genome partially controls the composition of porcine gut microbiota. However, since previous studies have been focused on the association between single nucleotide polymorphisms and the fecal microbiota, little is known about the relationship between other sources of genetic variation, like the structural variants and microbial traits. Here, we identified, experimentally validated, and replicated in an independent population a positive link between the gain of copies of ABCC2-DNMBP loci and the diversity and composition of pig fecal microbiota. Our results advise the relevance of considering the role of host-genome structural variants as putative modulators of microbial ecosystems and open the possibility of implementing novel holobiont-based management strategies in breeding programs for the simultaneous improvement of microbial traits and host performance.

Oral Delivery of Nucleic Acid Therapies for Local and Systemic Action

Nucleic acid (NA) therapy has gained importance over the past decade due to its high degree of selectivity and minimal toxic effects over conventional drugs. Currently, intravenous (IV) or intramuscular (IM) formulations constitute majority of the marketed formulations containing nucleic acids. However, oral administration is traditionally preferred due to ease of administration as well as higher patient compliance. To leverage the benefits of oral delivery for NA therapy, the NA of interest must be delivered to the target site avoiding all degrading and inhibiting factors during its transition through the gastrointestinal tract. The oral route presents myriad of challenges to NA delivery, making formulation development challenging. Researchers in the last few decades have formulated various delivery systems to overcome such challenges and several reviews summarize and discuss these strategies in detail. However, there is a need to differentiate between the approaches based on target so that in future, delivery strategies can be developed according to the goal of the study and for efficient delivery to the desired site. The goal of this review is to summarize the mechanisms for target specific delivery, list and discuss the formulation strategies used for oral delivery of NA therapies and delineate the similarities and differences between local and systemic targeting oral delivery systems and current challenges.

Intestinal Barrier and Permeability in Health, Obesity and NAFLD

The largest surface of the human body exposed to the external environment is the gut. At this level, the intestinal barrier includes luminal microbes, the mucin layer, gastrointestinal motility and secretion, enterocytes, immune cells, gut vascular barrier, and liver barrier. A healthy intestinal barrier is characterized by the selective permeability of nutrients, metabolites, water, and bacterial products, and processes are governed by cellular, neural, immune, and hormonal factors. Disrupted gut permeability (leaky gut syndrome) can represent a predisposing or aggravating condition in obesity and the metabolically associated liver steatosis (nonalcoholic fatty liver disease, NAFLD). In what follows, we describe the morphological-functional features of the intestinal barrier, the role of major modifiers of the intestinal barrier, and discuss the recent evidence pointing to the key role of intestinal permeability in obesity/NAFLD.

Nanosecond Pulsed Electric Field Only Transiently Affects the Cellular and Molecular Processes of Leydig Cells

The purpose of this study was to verify whether the nanosecond pulsed electric field, not eliciting thermal effects, permanently changes the molecular processes and gene expression of Leydig TM3 cells. The cells were exposed to a moderate electric field (80 quasi-rectangular shape pulses, 60 ns pulse width, and an electric field of 14 kV/cm). The putative disturbances were recorded over 24 h. After exposure to the nanosecond pulsed electric field, a 19% increase in cell diameter, a loss of microvilli, and a 70% reduction in cell adhesion were observed. Some cells showed the nonapoptotic externalization of phosphatidylserine through the pores in the plasma membrane. The cell proportion in the subG1 phase increased by 8% at the expense of the S and G2/M phases, and the DNA was fragmented in a small proportion of the cells. The membrane mitochondrial potential and superoxide content decreased by 37% and 23%, respectively. Microarray’s transcriptome analysis demonstrated a negative transient effect on the expression of genes involved in oxidative phosphorylation, DNA repair, cell proliferation, and the overexpression of plasma membrane proteins. We conclude that nanosecond pulsed electric field affected the physiology and gene expression of TM3 cells transiently, with a noticeable heterogeneity of cellular responses.

A Focus on "Bio" in Bio-Nanoscience: The Impact of Biological Factors on Nanomaterial Interactions

Bio-nanoscience research encompasses studies on the interactions of nanomaterials with biological structures or what is commonly referred to as the biointerface. Fundamental studies on the influence of nanomaterial properties, including size, shape, composition, and charge, on the interaction with the biointerface have been central in bio-nanoscience to assess nanomaterial efficacy and safety for a range of biomedical applications. However, the state of the cells, tissues, or biological models can also influence the behavior of nanomaterials at the biointerface and their intracellular processing. Focusing on the "bio" in bio-nano, this review discusses the impact of biological properties at the cellular, tissue, and whole organism level that influences nanomaterial behavior, including cell type, cell cycle, tumor physiology, and disease states. Understanding how the biological factors can be addressed or exploited to enhance nanomaterial accumulation and uptake can guide the design of better and suitable models to improve the outcomes of materials in nanomedicine.

Intestinal brush border assembly during the peri-hatch period and its contribution to surface area expansion

Microvilli generate the small intestinal brush border, the main site of nutrient digestion and absorption. Mucosal structuring of the small intestine of chicken during the perihatch period has been widely researched, yet the developmental dynamics of microvilli during this period have not been fully characterized. In this study, we examined the structural and molecular characteristics of microvilli assembly and maturation during the perihatch period. Small intestines of broiler embryos and chicks were sampled at prehatch ages 17 E and 19 E, at day of hatch (DOH) and at 1, 3, 7, and 10 d posthatch. Morphological evaluations and measurements were conducted by scanning electron microscopy (SEM) and light microscopy (LM) (n = 3/timepoint), and expression of microvilli structural genes Plastin 1, Ezrin, and Myo1a was examined by Real-Time qPCR (n = 6/timepoint). Results revealed dissimilar patterns of microvilli and villi development during the perihatch period. From 19 E to 1 d, microvilli lengths increased 4.3-fold while villi lengths increased 2.8-fold (P < 0.0001). From 3 to 7 d, villi lengths increased by 20% (P < 0.005), while microvilli lengths decreased by 41% (P = 0.001). At 10 d, microvilli lengths stabilized, while villi continued to elongate by 26% (P < 0.0001). Estimations of the microvilli amplification factor (MAF) and total enterocyte surface area (TESA) revealed similar trends, with peak values of 78.53 and 1961.67 µm², respectively, at 3 d. Microvilli structural gene expression portrayed diverse patterns. Expression of Plastin 1, which bundles and binds actin cores to the terminal web, increased 8.7-fold between 17 E and DOH (P = 0.005), and gradually increased up to 7 d (P = 0.045). Ezrin and Myo1a, both actin core-cell membrane cross-linkers, portrayed different expression patterns throughout the perihatch period, as Ezrin expression was relatively stable, while Myo1a expression increased 15.8-fold between 17 E and 10 d (P < 0.0001). We conclude that microvilli assembly during the perihatch period is a rapid, coordinated process, which dramatically expands the digestive and absorptive surface area of the small intestine before the completion of villi maturation.

A polysaccharide from Fagopyrum esculentum Moench bee pollen alleviates microbiota dysbiosis to improve intestinal barrier function in antibiotic-treated mice

Antibiotics are the most commonly used clinical drugs for anti-infection, but they can also destroy normal microorganisms and cause intestinal barrier dysfunction. To elucidate the effects and mechanism of a water-soluble polysaccharide from Fagopyrum esculentum Moench bee pollen (WFPP) on intestinal barrier integrity in antibiotic-treated mice, BALB/c mice were exposed to a broad-spectrum antibiotic (ceftriaxone) or not (control), and were administered low-, medium- and high-dose WFFP (100 mg kg^-1, 200 mg kg^-1 and 400 mg kg^-1, respectively) daily by oral gavage for 3 weeks. Mice treated with ceftriaxone displayed symptoms of growth retardation, atrophy of immune organs including thymus and spleen, increased gut permeability, and intestinal barrier damage, which were restored after intervention with WFFP at different doses. Moreover, the beneficial effects of WFFP were closely associated with enhanced intestinal sIgA secretion and reduced inflammatory response. Furthermore 16S rDNA gene sequencing revealed that WFPP elevated microbial diversity and richness and changed the community structure, therefore, alleviating microbiota dysbiosis caused by ceftriaxone. Interestingly, WFPP could modulate the abundance of sIgA secretion-related bacteria (e.g. Proteobacteria) and inflammation-related bacteria (e.g. Enterococcus). Therefore, WFPP can relieve antibiotic-induced microbiota dysbiosis to improve intestinal barrier integrity by increasing intestinal sIgA secretion and inhibiting inflammation.

Liver Steatosis, Gut-Liver Axis, Microbiome and Environmental Factors. A Never-Ending Bidirectional Cross-Talk

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide and parallels comorbidities such as obesity, metabolic syndrome, dyslipidemia, and diabetes. Recent studies describe the presence of NAFLD in non-obese individuals, with mechanisms partially independent from excessive caloric intake. Increasing evidences, in particular, point towards a close interaction between dietary and environmental factors (including food contaminants), gut, blood flow, and liver metabolism, with pathways involving intestinal permeability, the composition of gut microbiota, bacterial products, immunity, local, and systemic inflammation. These factors play a critical role in the maintenance of intestinal, liver, and metabolic homeostasis. An anomalous or imbalanced gut microbial composition may favor an increased intestinal permeability, predisposing to portal translocation of microorganisms, microbial products, and cell wall components. These components form microbial-associated molecular patterns (MAMPs) or pathogen-associated molecular patterns (PAMPs), with potentials to interact in the intestine lamina propria enriched in immune cells, and in the liver at the level of the immune cells, i.e., Kupffer cells and stellate cells. The resulting inflammatory environment ultimately leads to liver fibrosis with potentials to progression towards necrotic and fibrotic changes, cirrhosis. and hepatocellular carcinoma. By contrast, measures able to modulate the composition of gut microbiota and to preserve gut vascular barrier might prevent or reverse NAFLD.

Retinoic Acid and Lymphotoxin Signaling Promote Differentiation of Human Intestinal M Cells

BACKGROUND & AIMS

Intestinal microfold (M) cells are a unique subset of intestinal epithelial cells in the Peyer's patches that regulate mucosal immunity, serving as portals for sampling and uptake of luminal antigens. The inability to efficiently develop human M cells in cell culture has impeded studies of the intestinal immune system. We aimed to identify signaling pathways required for differentiation of human M cells and establish a robust culture system using human ileum enteroids.

METHODS

We analyzed transcriptome data from mouse Peyer's patches to identify cell populations in close proximity to M cells. We used the human enteroid system to determine which cytokines were required to induce M-cell differentiation. We performed transcriptome, immunofluorescence, scanning electron microscope, and transcytosis experiments to validate the development of phenotypic and functional human M cells.

RESULTS

A combination of retinoic acid and lymphotoxin induced differentiation of glycoprotein 2-positive human M cells, which lack apical microvilli structure. Upregulated expression of innate immune-related genes within M cells correlated with a lack of viral antigens after rotavirus infection. Human M cells, developed in the enteroid system, internalized and transported enteric viruses, such as rotavirus and reovirus, across the intestinal epithelium barrier in the enteroids.

CONCLUSIONS

We identified signaling pathways required for differentiation of intestinal M cells, and used this information to create a robust culture method to develop human M cells with capacity for internalization and transport of viruses. Studies of this model might increase our understanding of antigen presentation and the systemic entry of enteric pathogens in the human intestine.

Intestinal permeability in the pathogenesis of liver damage: From non-alcoholic fatty liver disease to liver transplantation

The intimate connection and the strict mutual cooperation between the gut and the liver realizes a functional entity called gut-liver axis. The integrity of intestinal barrier is crucial for the maintenance of liver homeostasis. In this mutual relationship, the liver acts as a second firewall towards potentially harmful substances translocated from the gut, and is, in turn, is implicated in the regulation of the barrier. Increasing evidence has highlighted the relevance of increased intestinal permeability and consequent bacterial translocation in the development of liver damage. In particular, in patients with non-alcoholic fatty liver disease recent hypotheses are considering intestinal permeability impairment, diet and gut dysbiosis as the primary pathogenic trigger. In advanced liver disease, intestinal permeability is enhanced by portal hypertension. The clinical consequence is an increased bacterial translocation that further worsens liver damage. Furthermore, this pathogenic mechanism is implicated in most of liver cirrhosis complications, such as spontaneous bacterial peritonitis, hepatorenal syndrome, portal vein thrombosis, hepatic encephalopathy, and hepatocellular carcinoma. After liver transplantation, the decrease in portal pressure should determine beneficial effects on the gut-liver axis, although are incompletely understood data on the modifications of the intestinal permeability and gut microbiota composition are still lacking. How the modulation of the intestinal permeability could prevent the initiation and progression of liver disease is still an uncovered area, which deserves further attention.

Current understanding of the gut microbiota shaping mechanisms

Increasing evidences have shown strong associations between gut microbiota and many human diseases, and understanding the dynamic crosstalks of host-microbe interaction in the gut has become necessary for the detection, prevention, or therapy of diseases. Many reports have showed that diet, nutrient, pharmacologic factors and many other stimuli play dominant roles in the modulation of gut microbial compositions. However, it is inappropriate to neglect the impact of host factors on shaping the gut microbiota. In this review, we highlighted the current findings of the host factors that could modulate the gut microbiota. Particularly the epithelium-associated factors, including the innate immune sensors, anti-microbial peptides, mucus barrier, secretory IgAs, epithelial microvilli, epithelial tight junctions, epithelium metabolism, oxygen barrier, and even the microRNAs are discussed in the context of the microbiota shaping. With these shaping factors, the gut epithelial cells could select the residing microbes and affect the microbial composition. This knowledge not only could provide the opportunities to better control many diseases, but may also be used for predicting the success of fecal microbiota transplantation clinically.

Dynamic Gene Network Analysis of Caco-2 Cell Response to Shiga Toxin-Producing Escherichia coli-Associated Hemolytic-Uremic Syndrome

Shiga toxin-producing Escherichia coli (STEC) O113:H21 strains are associated with human diarrhea and some strains may cause hemolytic-uremic syndrome (HUS). In Brazil, these strains are commonly found in cattle but, so far, were not isolated from HUS patients. Here, a system biology approach was used to investigate the differential transcriptomic and phenotypic responses of enterocyte-like Caco-2 cells to two STEC O113:H21 strains with similar virulence factor profiles (i.e. expressing stx2, ehxA, epeA, espA, iha, saa, sab, and subA): EH41 (Caco-2/EH41), isolated from a HUS patient in Australia, and Ec472/01 (Caco-2/Ec472), isolated from bovine feces in Brazil, during a 3 h period of bacteria-enterocyte interaction. Gene co-expression network analysis for Caco-2/EH41 revealed a quite abrupt pattern of topological variation along 3 h of enterocyte-bacteria interaction when compared with networks obtained for Caco-2/Ec472. Transcriptional module characterization revealed that EH41 induces inflammatory and apoptotic responses in Caco-2 cells just after the first hour of enterocyte-bacteria interaction, whereas the response to Ec472/01 is associated with cytoskeleton organization at the first hour, followed by the expression of immune response modulators. Scanning electron microscopy showed more intense microvilli destruction in Caco-2 cells exposed to EH41 when compared to those exposed to Ec472/01. Altogether, these results show that EH41 expresses virulence genes, inducing a distinctive host cell response, and is likely associated with severe pathogenicity.

M Cells: Intelligent Engineering of Mucosal Immune Surveillance

M cells are specialized intestinal epithelial cells that provide the main machinery for sampling luminal microbes for mucosal immune surveillance. M cells are usually found in the epithelium overlying organized mucosal lymphoid tissues, but studies have identified multiple distinct lineages of M cells that are produced under different conditions, including intestinal inflammation. Among these lineages there is a common morphology that helps explain the efficiency of M cells in capturing luminal bacteria and viruses; in addition, M cells recruit novel cellular mechanisms to transport the particles across the mucosal barrier into the lamina propria, a process known as transcytosis. These specializations used by M cells point to a novel engineering of cellular machinery to selectively capture and transport microbial particles of interest. Because of the ability of M cells to effectively violate the mucosal barrier, the circumstances of M cell induction have important consequences. Normal immune surveillance insures that transcytosed bacteria are captured by underlying myeloid/dendritic cells; in contrast, inflammation can induce development of new M cells not accompanied by organized lymphoid tissues, resulting in bacterial transcytosis with the potential to amplify inflammatory disease. In this review, we will discuss our own perspectives on the life history of M cells and also raise a few questions regarding unique aspects of their biology among epithelia.

Oral delivery of non-viral nucleic acid-based therapeutics - do we have the guts for this?

Gene therapy with RNA and pDNA-based drugs is limited by poor enzymatic stability and poor cellular permeation. The delivery of nucleic acids, in particular by the oral route, remains a major hurdle. This review will focus on the barriers to the oral delivery of nucleic acids and the strategies, in particular formulation strategies, which have been developed to overcome these barriers. Due to their very low oral bioavailability, the most obvious and most investigated biomedical applications for their oral delivery are related to the local treatment of inflammatory bowel diseases and colorectal cancers. Preclinical data but not yet clinical studies support the potential use of the oral route for the local delivery of formulated nucleic acid-based drugs.

Actuation of chitosan-aptamer nanobrush borders for pathogen sensing

We demonstrate a sensing mechanism for rapid detection of Listeria monocytogenes in food samples using the actuation of chitosan-aptamer nanobrush borders. The bio-inspired soft material and sensing strategy mimic natural symbiotic systems, where low levels of bacteria are selectively captured from complex matrices. To engineer this biomimetic system, we first develop reduced graphene oxide/nanoplatinum (rGO-nPt) electrodes, and characterize the fundamental electrochemical behavior in the presence and absence of chitosan nanobrushes during actuation (pH-stimulated osmotic swelling). We then characterize the electrochemical behavior of the nanobrush when receptors (antibodies or DNA aptamers) are conjugated to the surface. Finally, we test various techniques to determine the most efficient capture strategy based on nanobrush actuation, and then apply the biosensors in a food product. Maximum cell capture occurs when aptamers conjugated to the nanobrush bind cells in the extended conformation (pH < 6), followed by impedance measurement in the collapsed nanobrush conformation (pH > 6). The aptamer-nanobrush hybrid material was more efficient than the antibody-nanobrush material, which was likely due to the relatively high adsorption capacity for aptamers. The biomimetic material was used to develop a rapid test (17 min) for selectively detecting L. monocytogenes at concentrations ranging from 9 to 107 CFU mL-1 with no pre-concentration, and in the presence of other Gram-positive cells (Listeria innocua and Staphylococcus aureus). Use of this bio-inspired material is among the most efficient for L. monocytogenes sensing to date, and does not require sample pretreatment, making nanobrush borders a promising new material for rapid pathogen detection in food.

Lipids and polymers in pharmaceutical technology: Lifelong companions

In pharmaceutical technology, lipids and polymers are considered pillar excipients for the fabrication of most dosage forms, irrespective of the administration route. They play various roles ranging from support vehicles to release rate modifiers, stabilizers, solubilizers, permeation enhancers and transfection agents. Focusing on selected applications, which were discussed at the Annual Scientific Meeting of the Gattefossé Foundation 2018, this manuscript recapitulates the fundamental roles of these two important classes of excipients, either employed alone or in combination, and provides insight on their functional properties in various types of drug formulations. Emphasis is placed on oral formulations for the administration of active pharmaceutical ingredients with low aqueous solubilities or poor permeation properties. Additionally, this review article covers the use of lipids and polymers in the design of colloidal injectable delivery systems, and as substrates in additive manufacturing technologies for the production of tailor-made dosage forms.

An Intestinal "Transformers"-like Nanocarrier System for Enhancing the Oral Bioavailability of Poorly Water-Soluble Drugs

Increasing the intestinal dissolution of orally administered poorly water-soluble drugs that have poor oral bioavailability to a therapeutically effective level has long been an elusive goal. In this work, an approach that can greatly enhance the oral bioavailability of a poorly water-soluble drug such as curcumin (CUR) is developed, using a "Transformers"-like nanocarrier system (TLNS) that can self-emulsify the drug molecules in the intestinal lumen to form nanoemulsions. Owing to its known anti-inflammation activity, the use of CUR in treating pancreatitis is evaluated herein. Structural changes of the TLNS in the intestinal environment to form the CUR-laden nanoemulsions are confirmed in vitro. The therapeutic efficacy of this TLNS is evaluated in rats with experimentally induced acute pancreatitis (AP). Notably, the CUR-laden nanoemulsions that are obtained using the proposed TLNS can passively target intestinal M cells, in which they are transcytosed and then transported into the pancreatic tissues via the intestinal lymphatic system. The pancreases in rats that are treated with the TLNS yield approximately 12 times stronger CUR signals than their counterparts receiving free CUR, potentially improving the recovery of AP. These findings demonstrate that the proposed TLNS can markedly increase the intestinal drug dissolution, making oral delivery a favorable noninvasive means of administering poorly water-soluble drugs.

The Rho signalling pathway mediates the pathogenicity of AHPND-causing V. parahaemolyticus in shrimp

An emerging bacterial disease, acute hepatopancreatic necrosis disease (AHPND), is caused by strains of Vibrio parahaemolyticus with an additional AHPND-associated plasmid pVA1 encoding a virulent toxin (Pir^vp ) that damages the shrimp's hepatopancreas. Like other species of Vibrio, these virulent strains initially colonise the shrimp's stomach, but it is not yet understood how the bacteria or toxins are subsequently able to cross the epithelial barrier and reach the hepatopancreas. Here, by using transcriptomics and system biology methods, we investigate AHPND-induced changes in the stomach of AHPND-causing V. parahaemolyticus (5HP)-infected shrimp and identify host molecular mechanisms that might explain how the integrity of the stomach barrier is compromised. We found that the expression of 376 unique genes was differentially regulated by AHPND infection. Gene ontology, protein interaction, and gene-to-gene correlation expression interaction analyses indicated that in addition to the immune system, a number of these genes were involved in cytoskeleton regulation by Rho GTPase. The involvement of Rho pathway regulation during AHPND pathogenesis was further supported by experiments showing that while Rho inhibitor pretreatment delayed the infection, pretreatment with Rho activator enhanced the pathogenicity of 5HP, and both the bacteria and toxin were detected sooner in the hepatopancreas. Further, disruption of the stomach epithelial structure was found in both Rho preactivated shrimp and in 5HP-infected shrimp. Taken together, we interpret our results to mean that Rho signalling helps to mediate AHPND pathogenesis in shrimp.

A human origin strain Lactobacillus acidophilus DDS-1 exhibits superior in vitro probiotic efficacy in comparison to plant or dairy origin probiotics

Background: The health benefits of probiotics are well established and known to be strain-specific. However, the role of probiotics obtained from different origins and their efficacy largely remains unexplored. The aim of this study is to investigate the in vitro efficacy of probiotics from different origins. Methods: Probiotic strains utilized in this study include Lactobacillus acidophilus DDS-1 (human origin), Bifidobacterium animalis ssp. lactis UABla-12 (human origin), L. plantarum UALp-05 (plant origin) and Streptococcus thermophilus UASt-09 (dairy origin). Screening assays such as in vitro digestion simulation, adhesion, cell viability and cytokine release were used to evaluate the probiotic potential. Results: All strains showed good resistance in the digestion simulation process, especially DDS-1 and UALp-05, which survived up to a range of 10⁷ to 10⁸ CFU/mL from an initial concentration of 10⁹ CFU/mL. Two human colonic mucus-secreting cells, HT-29 and LS174T, were used to assess the adhesion capacity, cytotoxicity/viability, and cytokine quantification. All strains exhibited good adhesion capacity. No significant cellular cytotoxicity or loss in cell viability was observed. DDS-1 and UALp-05 significantly upregulated anti-inflammatory IL-10 and downregulated pro-inflammatory TNF-α cytokine production. All the strains were able to downregulate IL-8 cytokine levels. Conclusion: Of the 4 strains tested, DDS-1 demonstrated superior survival rates, good adhesion capacity and strong immunomodulatory effect under different experimental conditions.

A hemolytic-uremic syndrome-associated strain O113:H21 Shiga toxin-producing Escherichia coli specifically expresses a transcriptional module containing dicA and is related to gene network dysregulation in Caco-2 cells

Shiga toxin-producing (Stx) Escherichia coli (STEC) O113:H21 strains are associated with human diarrhea and some of these strains may cause hemolytic uremic syndrome (HUS). The molecular mechanism underlying this capacity and the differential host cell response to HUS-causing strains are not yet completely understood. In Brazil O113:H21 strains are commonly found in cattle but, so far, were not isolated from HUS patients. Here we conducted comparative gene co-expression network (GCN) analyses of two O113:H21 STEC strains: EH41, reference strain, isolated from HUS patient in Australia, and Ec472/01, isolated from cattle feces in Brazil. These strains were cultured in fresh or in Caco-2 cell conditioned media. GCN analyses were also accomplished for cultured Caco-2 cells exposed to EH41 or Ec472/01. Differential transcriptome profiles for EH41 and Ec472/01 were not significantly changed by exposure to fresh or Caco-2 conditioned media. Conversely, global gene expression comparison of both strains cultured in conditioned medium revealed a gene set exclusively expressed in EH41, which includes the dicA putative virulence factor regulator. Network analysis showed that this set of genes constitutes an EH41 specific transcriptional module. PCR analysis in Ec472/01 and in other 10 Brazilian cattle-isolated STEC strains revealed absence of dicA in all these strains. The GCNs of Caco-2 cells exposed to EH41 or to Ec472/01 presented a major transcriptional module containing many hubs related to inflammatory response that was not found in the GCN of control cells. Moreover, EH41 seems to cause gene network dysregulation in Caco-2 as evidenced by the large number of genes with high positive and negative covariance interactions. EH41 grows slowly than Ec472/01 when cultured in Caco-2 conditioned medium and fitness-related genes are hypoexpressed in that strain. Therefore, EH41 virulence may be derived from its capacity for dysregulating enterocyte genome functioning and its enhanced enteric survival due to slow growth.

Vigilance or Subversion? Constitutive and Inducible M Cells in Mucosal Tissues

Microfold (M) cells are epithelial cells present in mucosal tissues and specialized for the capture of luminal microparticles and their delivery to underlying immune cells; thus, they are crucial participants in mucosal immune surveillance. Multiple phenotypic subsets of M cells have now been described, all sharing a unique apical morphology that provides clues to their ability to capture microbial particles. The existence of diverse M cell phenotypes, especially inflammation-inducible M cells, provides an intriguing puzzle: some variants may augment luminal surveillance to boost mucosal immunity, while others may promote microbial access to tissues. Here, I consider the unique induction requirements of each M cell subset and functional differences, highlighting the potentially distinct consequences in mucosal immunity.

Uptake of label-free graphene oxide by Caco-2 cells is dependent on the cell differentiation status

BACKGROUND

Understanding the interaction of graphene-related materials (GRM) with human cells is a key to the assessment of their potential risks for human health. There is a knowledge gap regarding the potential uptake of GRM by human intestinal cells after unintended ingestion. Therefore the aim of our study was to investigate the interaction of label-free graphene oxide (GO) with the intestinal cell line Caco-2 in vitro and to shed light on the influence of the cell phenotype given by the differentiation status on cellular uptake behaviour.

RESULTS

Internalisation of two label-free GOs with different lateral size and thickness by undifferentiated and differentiated Caco-2 cells was analysed by scanning electron microscopy and transmission electron microscopy. Semi-quantification of cells associated with GRM was performed by flow cytometry. Undifferentiated Caco-2 cells showed significant amounts of cell-associated GRM, whereas differentiated Caco-2 cells exhibited low adhesion of GO sheets. Transmission electron microscopy analysis revealed internalisation of both applied GO (small and large) by undifferentiated Caco-2 cells. Even large GO sheets with lateral dimensions up to 10 µm, were found internalised by undifferentiated cells, presumably by macropinocytosis. In contrast, no GO uptake could be found for differentiated Caco-2 cells exhibiting an enterocyte-like morphology with apical brush border.

CONCLUSIONS

Our results show that the internalisation of GO is highly dependent on the cell differentiation status of human intestinal cells. During differentiation Caco-2 cells undergo intense phenotypic changes which lead to a dramatic decrease in GRM internalisation. The results support the hypothesis that the cell surface topography of differentiated Caco-2 cells given by the brush border leads to low adhesion of GO sheets and sterical hindrance for material uptake. In addition, the mechanical properties of GRM, especially flexibility of the sheets, seem to be an important factor for internalisation of large GO sheets by epithelial cells. Our results highlight the importance of the choice of the in vitro model to enable better in vitro-in vivo translation.

Induction of Colonic M Cells during Intestinal Inflammation

Intestinal M (microfold) cells are specialized epithelial cells overlying lymphoid tissues in the small intestine. Unlike common enterocytes, M cells lack an organized apical brush border, and are able to transcytose microparticles across the mucosal barrier to underlying antigen-presenting cells. We found that in both the dextran sodium sulfate and Citrobacter rodentium models of colitis, significantly increased numbers of Peyer's patch (PP) phenotype M cells were induced at the peak of inflammation in colonic epithelium, often accompanied by loosely organized lamina propria infiltrates. PP type M cells are thought to be dependent on cytokines, including tumor necrosis factor (TNF)-α and receptor activator of nuclear factor kappa-B ligand; these cytokines were also found to be induced in the inflamed tissues. The induction of M cells was abrogated by anti-TNF-α blockade, suggesting that anti-TNF-α therapies may have similar effects in clinical settings, although the functional consequences are not clear. Our results suggest that inflammatory cytokine-induced PP type M cells may be a useful correlate of chronic intestinal inflammation.

Fecal microbiota transplantation and bacterial consortium transplantation have comparable effects on the re-establishment of mucosal barrier function in mice with intestinal dysbiosis

Fecal microbiota transplantation (FMT) is a promising therapy, despite some reports of adverse side effects. Bacterial consortia transplantation (BCT) for targeted restoration of the intestinal ecosystem is considered a relatively safe and simple procedure. However, no systematic research has assessed the effects of FMT and BCT on immune responses of intestinal mucosal barrier in patients. We conducted complementary studies in animal models on the effects of FMT and BCT, and provide recommendations for improving the clinical outcomes of these treatments. To establish the dysbiosis model, male BALB/c mice were treated with ceftriaxone intra-gastrically for 7 days. After that, FMT and BCT were performed on ceftriaxone-treated mice for 3 consecutive days to rebuild the intestinal ecosystem. Post-FMT and post-BCT changes of the intestinal microbial community and mucosal barrier functions were investigated and compared. Disruption of intestinal microbial homeostasis impacted the integrity of mucosal epithelial layer, resulting in increased intestinal permeability. These outcomes were accompanied by overexpression of Muc2, significant decrease of SIgA secretion, and overproduction of defensins and inflammatory cytokines. After FMT and BCT, the intestinal microbiota recovered quickly, this was associated with better reconstruction of mucosal barriers and re-establishment of immune networks compared with spontaneous recovery (SR). Although based on a short-term study, our results suggest that FMT and BCT promote the re-establishment of intestinal microbial communities in mice with antibiotic-induced dysbiosis, and contribute to the temporal and spatial interactions between microbiota and mucosal barriers. The effects of BCT are comparable to that of FMT, especially in normalizing the intestinal levels of Muc2, SIgA, and defensins.

M cell-derived vesicles suggest a unique pathway for trans-epithelial antigen delivery

M cells are a subset of mucosal epithelial cells with specialized capability to transport antigens across the mucosal barrier, but there is limited information on antigen transfer in the subepithelial zone due to the challenges in tracking microparticles and antigens that are transcytosed by this unique cell. Using transgenic reporter mice expressing dsRed in the cytoplasm of M cells and EGFP in myeloid cells, we observed that the M cell basolateral pocket hosts a close interaction between B lymphocytes and dendritic cells. Interestingly, we identified a population of previously undescribed M cell-derived vesicles (MCM) that are constitutively shed into the subepithelial space and readily taken up by CX3CR1(+)CD11b(+) CD11c(+) dendritic cells. These MCM are characterized by their cytoplasmic dsRed confirming their origin from the M cell cytoplasm. MCM showed preferential colocalization in dendritic cells with transcytosed bacteria but not transcytosed polystyrene beads, indicating a selective sorting of cargo fate in the subepithelial zone. The size and number of MCM were found to be upregulated by bacterial transcytosis and soluble toll-like receptor 2 (TLR2) agonist, further pointing to dynamic regulation of this mechanism. These results suggest that MCM provide a unique function by delivering to dendritic cells, various materials such as M cell-derived proteins, effector proteins, toxins, and particles found in the M cell cytoplasm during infection or surveillance.