Human intestinal epithelial and smooth muscle cells are potent producers of IL-6

Potential therapeutic strategies for osteoarthritis via CRISPR/Cas9 mediated gene editing

Osteoarthritis (OA) is an incapacitating and one of the most common physically degenerative conditions with an assorted etiology and a highly complicated molecular mechanism that to date lacks an efficient treatment. The capacity to design biological networks and accurately modify existing genomic sites holds an apt potential for applications across medical and biotechnological sciences. One of these highly specific genomes editing technologies is the CRISPR/Cas9 mechanism, referred to as the clustered regularly interspaced short palindromic repeats, which is a defense mechanism constituted by CRISPR associated protein 9 (Cas9) directed by small non-coding RNAs (sncRNA) that bind to target DNA through Watson-Crick base pairing rules where subsequent repair of the target DNA is initiated. Up-to-date research has established the effectiveness of the CRISPR/Cas9 mechanism in targeting the genetic and epigenetic alterations in OA by suppressing or deleting gene expressions and eventually distributing distinctive anti-arthritic properties in both in vitro and in vivo osteoarthritic models. This review aims to epitomize the role of this high-throughput and multiplexed gene editing method as an analogous therapeutic strategy that could greatly facilitate the clinical development of OA-related treatments since it's reportedly an easy, minimally invasive technique, and a comparatively less painful method for osteoarthritic patients.

Pancreatic Tumor Organoid-Derived Factors from Cachectic Patients Disrupt Contractile Smooth Muscle Cells

Patients with pancreatic cancer often suffer from cachexia and experience gastrointestinal symptoms that may be related to intestinal smooth muscle cell (SMC) dysfunction. We hypothesized that pancreatic tumor organoids from cachectic patients release factors that perturb the SMC's contractile characteristics. Human visceral SMCs were exposed to conditioned medium (CM) from the pancreatic tumor organoid cultures of cachectic (n = 2) and non-cachectic (n = 2) patients. Contractile proteins and markers of inflammation, muscle atrophy, and proliferation were evaluated by qPCR and Western blot. SMC proliferation and migration were monitored by live cell imaging. The Ki-67-positive cell fraction was determined in the intestinal smooth musculature of pancreatic cancer patients. CM from the pancreatic tumor organoids of cachectic patients did not affect IL-1β, IL-6, IL-8, MCP-1, or Atrogin-1 expression. However, CM reduced the α-SMA, γ-SMA, and SM22-α levels, which was accompanied by a reduced SMC doubling time and increased expression of S100A4, a Ca2+-binding protein associated with the synthetic SMC phenotype. In line with this, Ki-67-positive nuclei were increased in the intestinal smooth musculature of patients with a low versus high L3-SMI. In conclusion, patient-derived pancreatic tumor organoids release factors that compromise the contractile SMC phenotype and increase SMC proliferation. This may contribute to the frequently observed gastrointestinal motility problems in these patients.

The effects of alpha-pinene on inflammatory responses and oxidative stress in the formalin test

Alpha-pinene (α- pinene), an essential oil that falls under the category of monoterpenes, has various advantages. This research delves into the potential benefits of α-pinene in alleviating nociception caused by the formalin test and the molecular mechanisms involved. Alpha-pinene (1, 5, or 10 mg/kg/day, i.p.) was administrated for 7 days before the formalin test. Observations of nociceptive behaviors were made during the formalin test. We examined the levels of TNF-α and IL-1β, as well as the expression of COX-1 in the spinal cord. Additionally, we evaluated the levels of TNF-α, IL-1β, SOD, GSH, CAT, and MDA in the skin of the hind paw that received a formalin injection. The peripheral injection of formalin triggered nociceptive behaviors, which was notably diminished by α-pinene 5 or 10 mg/kg. The biochemical evaluation revealed that α-pinene significantly moderated the evaluation in TNF-α and IL-1β in the spinal cord induced by formalin injection. Additionally, it was found that α-pinene had a decreasing effect on the expression of COX-1 protein in the spinal cord. Also, α-pinene 5 or 10 mg/kg caused a decrease of TNF-α, IL-1β, and MDA and an increase of SOD, GSH, and CAT at the formalin injection site. The study discovered that doses of 5 or 10 mg/ml of α-pinene can effectively relieve nociceptive response in the formalin test. Alpha-pinene pretreatment reduced the presence of pro-inflammatory cytokines. It also improved the oxidative stress condition by enhancing antioxidant factors and reducing oxidant factors.

Sodium benzoate exacerbates hepatic oxidative stress and inflammation in lipopolysaccharide-induced liver injury in rats

BACKGROUND

Liver damage is a global health concern associated with a high mortality rate. Sodium benzoate (SB) is a widely used preservative in the food industry with a wide range of applications. However, there's a lack of scientific reports on its effect on lipopolysaccharide-induced hepatic dysfunction.

OBJECTIVE

The present study investigated the influence of SB on lipopolysaccharide (LPS)-induced liver injury.

MATERIALS AND METHODS

Twenty-eight rats were randomly allocated into four groups: control (received distilled water), SB (received 600 mg/kg), LPS (received 0.25 mg/kg), and LPS + SB (received LPS, 0.25 mg/kg, and SB, 600 mg/kg). SB was administered orally for 14 days while LPS was administered intraperitoneally for 7 days.

RESULTS

Administration of SB to rats with hepatocyte injury exacerbated liver damage with a significant increase in the activities of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP). We also observed that SB aggravated LPS-mediated hepatic oxidative stress occasioned by a marked decrease in antioxidant status with a concomitant increase in lipid peroxidation. Furthermore, LPS - mediated increase in inflammatory biomarkers as well as histological deterioration in the liver was exacerbated following the administration of SB to rats.

CONCLUSION

Taken together, the study provides experimental evidence that SB exacerbates hepatic oxidative stress and inflammation in LPS-mediated liver injury.

How to Evaluate Fibrosis in IBD?

In this review, we will describe the importance of fibrosis in inflammatory bowel disease (IBD) by discussing its distinct impact on Crohn's disease (CD) and ulcerative colitis (UC) through their translation to histopathology. We will address the existing knowledge on the correlation between inflammation and fibrosis and the still not fully explained inflammation-independent fibrogenesis. Finally, we will compile and discuss the recent advances in the noninvasive assessment of intestinal fibrosis, including imaging and biomarkers. Based on the available data, none of the available cross-sectional imaging (CSI) techniques has proved to be capable of measuring CD fibrosis accurately, with MRE showing the most promising performance along with elastography. Very recent research with radiomics showed encouraging results, but further validation with reliable radiomic biomarkers is warranted. Despite the interesting results with micro-RNAs, further advances on the topic of fibrosis biomarkers depend on the development of robust clinical trials based on solid and validated endpoints. We conclude that it seems very likely that radiomics and AI will participate in the future non-invasive fibrosis assessment by CSI techniques in IBD. However, as of today, surgical pathology remains the gold standard for the diagnosis and quantification of intestinal fibrosis in IBD.

Clostridioides difficile infection: traversing host-pathogen interactions in the gut

C. difficile is the primary cause for nosocomial infective diarrhoea. For a successful infection, C. difficile must navigate between resident gut bacteria and the harsh host environment. The perturbation of the intestinal microbiota by broad-spectrum antibiotics alters the composition and the geography of the gut microbiota, deterring colonization resistance, and enabling C. difficile to colonize. This review will discuss how C. difficile interacts with and exploits the microbiota and the host epithelium to infect and persist. We provide an overview of C. difficile virulence factors and their interactions with the gut to aid adhesion, cause epithelial damage and mediate persistence. Finally, we document the host responses to C. difficile, describing the immune cells and host pathways that are associated and triggered during C. difficile infection.

The intestine: A highly dynamic microenvironment for IgA plasma cells

To achieve longevity, IgA plasma cells require a sophisticated anatomical microenvironment that provides cytokines, cell-cell contacts, and nutrients as well as metabolites. The intestinal epithelium harbors cells with distinct functions and represents an important defense line. Anti-microbial peptide-producing paneth cells, mucus-secreting goblet cells and antigen-transporting microfold (M) cells cooperate to build a protective barrier against pathogens. In addition, intestinal epithelial cells are instrumental in the transcytosis of IgA to the gut lumen, and support plasma cell survival by producing the cytokines APRIL and BAFF. Moreover, nutrients are sensed through specialized receptors such as the aryl hydrocarbon receptor (AhR) by both, intestinal epithelial cells and immune cells. However, the intestinal epithelium is highly dynamic with a high cellular turn-over rate and exposure to changing microbiota and nutritional factors. In this review, we discuss the spatial interplay of the intestinal epithelium with plasma cells and its potential contribution to IgA plasma cell generation, homing, and longevity. Moreover, we describe the impact of nutritional AhR ligands on intestinal epithelial cell-IgA plasma cell interaction. Finally, we introduce spatial transcriptomics as a new technology to address open questions in intestinal IgA plasma cell biology.

Jejunal epithelial barrier disruption triggered by reactive oxygen species in early SIV infected rhesus macaques

Intestinal epithelial barrier destruction occurs earlier than mucosal immune dysfunction in the acute stage of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections. At present, however, the cause of compromised gastrointestinal integrity in early SIV infection remains unknown. In the current study, we investigated the effects of SIV infection on epithelial barrier integrity and explored oxidative stress-mediated DNA damage and apoptosis in epithelial cells from early acute SIVmac239-infected Chinese rhesus macaques (Macaca mulatta). Results showed that the sensitive molecular marker of small intestinal barrier dysfunction, i.e., intestinal fatty acid-binding protein (IFABP), was significantly increased in plasma at 14 days post-SIV infection. SIV infection induced a profound decrease in the expression of tight junction proteins, including claudin-1, claudin-3, and zonula occludens (ZO)-1, as well as a significant increase in the active form of caspase-3 level in epithelial cells. RNA sequencing (RNA-seq) analysis suggested that differentially expressed genes between pre- and post-SIV-infected jejuna were enriched in pathways involved in cell redox homeostasis, oxidoreductase activity, and mitochondria. Indeed, a SIV-mediated increase in reactive oxygen species (ROS) in the epithelium and macrophages, as well as an increase in hydrogen peroxide (H₂O₂) and decrease in glutathione (GSH)/glutathione disulfide (GSSG) antioxidant defense, were observed in SIV-infected jejuna. In addition, the accumulation of mitochondrial dysfunction and DNA oxidative damage led to an increase in senescence-associated β-galactosidase (SA-β-gal) and early apoptosis in intestinal epithelial cells. Furthermore, HIV-1 Tat protein-induced epithelial monolayer disruption in HT-29 cells was rescued by antioxidant N-acetylcysteine (NAC). These results indicate that mitochondrial dysfunction and oxidative stress in jejunal epithelial cells are primary contributors to gut epithelial barrier disruption in early SIV-infected rhesus macaques.

Genome-wide association study of circulating interleukin 6 levels identifies novel loci

Interleukin 6 (IL-6) is a multifunctional cytokine with both pro- and anti-inflammatory properties with a heritability estimate of up to 61%. The circulating levels of IL-6 in blood have been associated with an increased risk of complex disease pathogenesis. We conducted a two-staged, discovery and replication meta genome-wide association study (GWAS) of circulating serum IL-6 levels comprising up to 67 428 (ndiscovery = 52 654 and nreplication = 14 774) individuals of European ancestry. The inverse variance fixed effects based discovery meta-analysis, followed by replication led to the identification of two independent loci, IL1F10/IL1RN rs6734238 on chromosome (Chr) 2q14, (Pcombined = 1.8 × 10-11), HLA-DRB1/DRB5 rs660895 on Chr6p21 (Pcombined = 1.5 × 10-10) in the combined meta-analyses of all samples. We also replicated the IL6R rs4537545 locus on Chr1q21 (Pcombined = 1.2 × 10-122). Our study identifies novel loci for circulating IL-6 levels uncovering new immunological and inflammatory pathways that may influence IL-6 pathobiology.

Out of the Laboratory and Into the Field: Validation of Portable Cell Culture Protocols

OBJECTIVE

Field-based research on inflammation and health is typically limited to baseline measures of circulating cytokines or acute-phase proteins, whereas laboratory-based studies can pursue a more dynamic approach with ex vivo cell culture methods. The laboratory infrastructure required for culturing leukocytes limits application in community-based settings, which in turn limits scientific understandings of how psychosocial, behavioral, and contextual factors influence the regulation of inflammation. We aim to address this gap by validating two "field-friendly" cell culture protocols, one using a small volume of venous whole blood and another using finger-stick capillary whole blood.

METHODS

We evaluated the performance of both protocols against a standard laboratory-based protocol using matched venous and capillary blood samples collected from young adults (n = 24). Samples were incubated with lipopolysaccharide and hydrocortisone, and the production of proinflammatory cytokines interleukin 1β, interleukin 6, and tumor necrosis factor α was measured in response.

RESULTS

Comparisons indicate a high level of agreement in responses across the protocols and culture conditions. The overall correlation in results was 0.88 between the standard and small-volume protocols and 0.86 between the standard and capillary blood protocols. Repeatability for the small-volume and capillary blood protocols was high, with mean coefficients of variation across five replicates of 6.2% and 5.4%, respectively.

CONCLUSIONS

These results demonstrate the feasibility of culturing cells and quantifying the inflammatory response to challenge outside the laboratory, with a wide range of potential applications in biobehavioral research in community-based and remote field settings.

B and T Cell Immunity in Tissues and Across the Ages

B and T cells are key components of the adaptive immune system and coordinate multiple facets of immunity including responses to infection, vaccines, allergens, and the environment. In humans, B- and T-cell immunity has been determined using primarily peripheral blood specimens. Conversely, human tissues have scarcely been studied but they host multiple adaptive immune cells capable of mounting immune responses to pathogens and participate in tissue homeostasis. Mucosal tissues, such as the intestines and respiratory track, are constantly bombarded by foreign antigens and contain tissue-resident memory T (T_RM) cells that exhibit superior protective capacity to pathogens. Also, tissue-resident memory B (B_RM) cells have been identified in mice but whether humans have a similar population remains to be confirmed. Moreover, the immune system evolves throughout the lifespan of humans and undergoes multiple changes in its immunobiology. Recent studies have shown that age-related changes in tissues are not necessarily reflected in peripheral blood specimens, highlighting the importance of tissue localization and subset delineation as essential determinants of functional B and T cells at different life stages. This review describes our current knowledge of the main B- and T-cell subsets in peripheral blood and tissues across age groups.

Clostridium Difficile Infection in Inflammatory Bowel Disease Patients

BACKGROUND

The rising incidence of Clostridium difficile infection (CDI) in the general population has been recognized by health care organizations worldwide. The emergence of hypervirulent strains has made CDI more challenging to understand and treat. Inflammatory bowel disease (IBD) patients are at higher risk of infection, including CDI.

OBJECTIVE

A diagnostic approach for recurrent CDI has yet to be validated, particularly for IBD patients. Enzyme immunoassay (EIA) for toxins A and B, as well as glutamate dehydrogenase EIA, are both rapid testing options for the identification of CDI. Without a high index of suspicion, it is challenging to initially differentiate CDI from an IBD flare based on clinical evaluation alone.

METHODS

Here, we provide an up-to-date review on CDI in IBD patients. When caring for an IBD patient with suspected CDI, it is appropriate to empirically treat the presumed infection while awaiting further test results.

RESULTS

Treatment with vancomycin or fidaxomicin, but not oral metronidazole, has been advocated by an expert review from the clinical practice update committee of the American Gastroenterology Association. Recurrent CDI is more common in IBD patients compared to non-IBD patients (32% versus 24%), thus more aggressive treatment is recommended for IBD patients along with early consideration of fecal microbiota transplant.

CONCLUSION

Although the use of infliximab during CDI has been debated, clinical experience exists supporting its use in an IBD flare, even with active CDI when needed.

Interactions among glomerulus infiltrating macrophages and intrinsic cells via cytokines in chronic lupus glomerulonephritis

Inflammation plays a key role in the pathogenesis of lupus nephritis (LN) and inflammatory cytokines within the glomeruli are critical in this process. However, little information is available for the identities of the cell types that are primarily responsible for the production and function of the various cytokines. We have devised a novel method to visualize cytokine signals in the kidney by confocal microscopy and found that cytokine production within the glomerulus is cell type-specific and under translational control. In the lupus-prone NZM2328 mice with chronic glomerulonephritis, IL-6, IL-1β, and TNF-α in the glomerulus were produced predominantly by mesangial cells, podocytes, and glomerulus-infiltrating blood-derived macrophages, respectively. Microarray and RNASeq analyses showed that these cells expressed the receptors for these cytokines. Together the 3 cell types form a cytokine circuit in amplifying cytokine responses in LN. The intrinsic cells and infiltrating macrophages also produced other cytokines including M-CSF, SCF, and IL-34 that constituted within the enclosed glomerular space the soluble effector milieu which may mediate cellular damage and proliferation, and cytokine transcriptional and translation regulation. IL-10 and IL-1β were translationally regulated in the glomeruli in the intact kidney in a cell type-specific manner. The production of these 2 cytokines by infiltrating macrophages was undetectable in a visualization system for in situ protein accumulation despite high mRNA expression levels. However, these macrophages in isolated glomeruli which are released from Bowman's capsules produced large amounts of IL-10 and IL-1β. These data reveal the complexity of cytokine regulation, production, and function in the glomerulus and provide a model in which cytokine blocking may be beneficial in LN treatment.

Pathogenesis of fibrostenosing Crohn's disease

Crohn's disease (CD) is a chronic inflammatory disease, which could affect any part of the gastrointestinal tract. A severe complication of CD is fibrosis-associated strictures, which can cause bowel obstruction. Unfortunately, there is no specific antifibrotic therapy available. More than 80% of the patients with CD will have to undergo at least 1 surgery in their life and recurrence of strictures after surgery is common. Investigations on the mechanism of fibrostenosing CD have revealed that fibrosis is mainly driven by expansion of mesenchymal cells including fibroblasts, myofibroblasts, and smooth muscle cells. Being exposed to a pro-fibrotic milieu, these cells increase the secretion of extracellular matrix, as well as crosslinking enzymes, which drive tissue stiffness and remodeling. Fibrogenesis can become independent of inflammation in later stages of disease, which offers unique therapeutic potential. Exciting new evidence suggests smooth muscle cell hyperplasia as a strong contributor to luminal narrowing in fibrostenotic CD. Approval of new drugs in other fibrotic diseases, such as idiopathic pulmonary fibrosis, as well as new targets associated with fibrosis found in CD, such as cadherins or specific integrins, shed light on the development of novel antifibrotic approaches in CD.

IgA Responses to Microbiota

Various immune mechanisms are deployed in the mucosa to confront the immense diversity of resident bacteria. A substantial fraction of the commensal microbiota is coated with immunoglobulin A (IgA) antibodies, and recent findings have established the identities of these bacteria under homeostatic and disease conditions. Here we review the current understanding of IgA biology, and present a framework wherein two distinct types of humoral immunity coexist in the gastrointestinal mucosa. Homeostatic IgA responses employ a polyreactive repertoire to bind a broad but taxonomically distinct subset of microbiota. In contrast, mucosal pathogens and vaccines elicit high-affinity, T cell-dependent antibody responses. This model raises fundamental questions including how polyreactive IgA specificities are generated, how these antibodies exert effector functions, and how they exist together with other immune responses during homeostasis and disease.

Cellular and Molecular Mediators of Intestinal Fibrosis

Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.

Cellular and Molecular Mediators of Intestinal Fibrosis

Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.

The role of toxins in Clostridium difficile infection

Clostridium difficile is a bacterial pathogen that is the leading cause of nosocomial antibiotic-associated diarrhea and pseudomembranous colitis worldwide. The incidence, severity, mortality and healthcare costs associated with C. difficile infection (CDI) are rising, making C. difficile a major threat to public health. Traditional treatments for CDI involve use of antibiotics such as metronidazole and vancomycin, but disease recurrence occurs in about 30% of patients, highlighting the need for new therapies. The pathogenesis of C. difficile is primarily mediated by the actions of two large clostridial glucosylating toxins, toxin A (TcdA) and toxin B (TcdB). Some strains produce a third toxin, the binary toxin C. difficile transferase, which can also contribute to C. difficile virulence and disease. These toxins act on the colonic epithelium and immune cells and induce a complex cascade of cellular events that result in fluid secretion, inflammation and tissue damage, which are the hallmark features of the disease. In this review, we summarize our current understanding of the structure and mechanism of action of the C. difficile toxins and their role in disease.

The human intestinal B-cell response

The intestinal immune system is chronically challenged by a huge plethora of antigens derived from the lumen. B-cell responses in organized gut-associated lymphoid tissues and regional lymph nodes that are driven chronically by gut antigens generate the largest population of antibody-producing cells in the body: the gut lamina propria plasma cells. Although animal studies have provided insights into mechanisms that underpin this dynamic process, some very fundamental differences in this system appear to exist between species. Importantly, this prevents extrapolation from mice to humans to inform translational research questions. Therefore, in this review we will describe the structures and mechanisms involved in the propagation, dissemination, and regulation of this immense plasma cell population in man. Uniquely, we will seek our evidence exclusively from studies of human cells and tissues.

Intestinal fibrosis in Crohn's disease: role of microRNAs as fibrogenic modulators, serum biomarkers, and therapeutic targets

Inflammation often precedes fibrosis and stricture formation in patients with Crohn's disease. Established medical therapies reduce inflammation, but there are currently no specific therapies to prevent fibrosis or treat established fibrosis. Our understanding of the pathogenic processes underpinning fibrogenesis is limited compared with our knowledge of the events initiating and propagating inflammation. There are several biomarkers for intestinal inflammation, but there are none that reflect the development of fibrosis. MicroRNAs (miRNAs) are regulators of cellular activities including inflammation and fibrosis and may serve as biomarkers of disease processes. Differential serum and mucosal miRNA expression profiles have been identified between patients with inflammatory bowel disease with active and inactive inflammatory disease. In contrast, studies in patients with fibrotic phenotypes are comparatively few, although specific miRNAs have defined roles in the development of fibrosis in other organ systems. Here, we discuss the most recent research on miRNA and fibrogenesis with a particular emphasis on Crohn's disease. We also anticipate the potential of miRNAs in fulfilling current unmet translational needs in this patient group by focusing on the role of miRNAs as modulators of fibrogenesis and on their potential value as serum biomarkers and therapeutic targets in the management of fibrosis.

Clostridium difficile toxin B intoxicated mouse colonic epithelial CT26 cells stimulate the activation of dendritic cells

Clostridium difficile causes antibiotic-associated diarrhea and pseudomembranous colitis mainly through two exotoxins TcdA and TcdB that target intestinal epithelial cells. Dendritic cells (DCs) play an important role in regulating intestinal inflammatory responses. In the current study, we explored the interaction of TcdB-intoxicated epithelial cells with mouse bone marrow-derived DCs. TcdB induced cell death and heat shock protein translocation in mouse intestinal epithelial CT26 cells. The intoxicated epithelial cells promoted the phagocytosis and the TNF-α secretion by DCs. Incubation with TcdB-intoxicated CT26 cells stimulated DC maturation. Moreover, TcdB-treated CT26 cells induced DC immigration when they were injected into mice subcutaneously. Taken together, these data demonstrate that TcdB-intoxicated intestinal epithelial cells are able to stimulate DC activation in vitro and attract DCs in vivo, indicating that epithelial cells may be able to regulate DC activation under the exposure of TcdB during C. difficile infection.

Utility of Clostridium difficile toxin B for inducing anti-tumor immunity

Clostridium difficile toxin B (TcdB) is a key virulence factor of bacterium and induces intestinal inflammatory disease. Because of its potent cytotoxic and proinflammatory activities, we investigated the utility of TcdB in developing anti-tumor immunity. TcdB induced cell death in mouse colorectal cancer CT26 cells, and the intoxicated cells stimulated the activation of mouse bone marrow-derived dendritic cells and subsequent T cell activation in vitro. Immunization of BALB/c mice with toxin-treated CT26 cells elicited potent anti-tumor immunity that protected mice from a lethal challenge of the same tumor cells and rejected pre-injected tumors. The anti-tumor immunity generated was cell-mediated, long-term, and tumor-specific. Further experiments demonstrated that the intact cell bodies were important for the immunogenicity since lysing the toxin-treated tumor cells reduced their ability to induce antitumor immunity. Finally, we showed that TcdB is able to induce potent anti-tumor immunity in B16-F10 melanoma model. Taken together, these data demonstrate the utility of C. difficile toxin B for developing anti-tumor immunity.

The roles of host and pathogen factors and the innate immune response in the pathogenesis of Clostridium difficile infection

Clostridium difficile (C. difficile) is the most common cause of nosocomial antibiotic-associated diarrhea and the etiologic agent of pseudomembranous colitis. The clinical manifestation of C. difficile infection (CDI) is highly variable, from asymptomatic carriage, to mild self-limiting diarrhea, to the more severe pseudomembranous colitis. Furthermore, in extreme cases, colonic inflammation and tissue damage can lead to toxic megacolon, a condition requiring surgical intervention. C. difficile expresses two key virulence factors; the exotoxins, toxin A (TcdA) and toxin B (TcdB), which are glucosyltransferases that target host-cell monomeric GTPases. In addition, some hypervirulent strains produce a third toxin, binary toxin or C. difficile transferase (CDT), which may contribute to the pathogenesis of CDI. More recently, other factors such as surface layer proteins (SLPs) and flagellin have also been linked to the inflammatory responses observed in CDI. Although the adaptive immune response can influence the severity of CDI, the innate immune responses to C. difficile and its toxins play crucial roles in CDI onset, progression, and overall prognosis. Despite this, the innate immune responses in CDI have drawn relatively little attention from clinical researchers. Targeting these responses may prove useful clinically as adjuvant therapies, especially in refractory and/or recurrent CDI. This review will focus on recent advances in our understanding of how C. difficile and its toxins modulate innate immune responses that contribute to CDI pathogenesis.

New concepts in the generation and functions of IgA

The intestinal mucosa contains the largest population of antibody-secreting plasma cells in the body, and in humans several grams of secretory immunoglobulin A (SIgA) are released into the intestine each day. In the gut lumen, SIgA serves as a first-line barrier that protects the epithelium from pathogens and toxins. Recently, next-generation sequencing has revolutionized our understanding of the nature of the intestinal microbiota and has also shed new light on the important roles of SIgA in the regulation of host-commensal homeostasis. Here, I discuss pathways of IgA induction in the context of SIgA specificity and function.

Intrarectal instillation of Clostridium difficile toxin A triggers colonic inflammation and tissue damage: development of a novel and efficient mouse model of Clostridium difficile toxin exposure

Clostridium difficile, a major cause of hospital-acquired diarrhea, triggers disease through the release of two toxins, toxin A (TcdA) and toxin B (TcdB). These toxins disrupt the cytoskeleton of the intestinal epithelial cell, increasing intestinal permeability and triggering the release of inflammatory mediators resulting in intestinal injury and inflammation. The most prevalent animal model to study TcdA/TcdB-induced intestinal injury involves injecting toxin into the lumen of a surgically generated "ileal loop." This model is time-consuming and exhibits variability depending on the expertise of the surgeon. Furthermore, the target organ of C. difficile infection (CDI) in humans is the colon, not the ileum. In the current study, we describe a new model of CDI that involves intrarectal instillation of TcdA/TcdB into the mouse colon. The administration of TcdA/TcdB triggered colonic inflammation and neutrophil and macrophage infiltration as well as increased epithelial barrier permeability and intestinal epithelial cell death. The damage and inflammation triggered by TcdA/TcdB isolates from the VPI and 630 strains correlated with the concentration of TcdA and TcdB produced. TcdA/TcdB exposure increased the expression of a number of inflammatory mediators associated with human CDI, including interleukin-6 (IL-6), gamma interferon (IFN-γ), and IL-1β. Finally, we were able to demonstrate that TcdA was much more potent at inducing colonic injury than was TcdB but TcdB could act synergistically with TcdA to exacerbate injury. Taken together, our data indicate that the intrarectal murine model provides a robust and efficient system to examine the effects of TcdA/TcdB on the induction of inflammation and colonic tissue damage in the context of human CDI.

Cellular and molecular mechanisms of intestinal fibrosis

Fibrosis is a chronic and progressive process characterized by an excessive accumulation of extracellular matrix (ECM) leading to stiffening and/or scarring of the involved tissue. Intestinal fibrosis may develop in several different enteropathies, including inflammatory bowel disease. It develops through complex cell, extracellular matrix, cytokine and growth factor interactions. Distinct cell types are involved in intestinal fibrosis, such as resident mesenchymal cells (fibroblasts, myofibroblasts and smooth muscle cells) but also ECM-producing cells derived from epithelial and endothelial cells (through a process termed epithelial- and endothelial-mesenchymal transition), stellate cells, pericytes, local or bone marrow-derived stem cells. The most important soluble factors that regulate the activation of these cells include cytokines, chemokines, growth factors, components of the renin-angiotensin system, angiogenic factors, peroxisome proliferator-activated receptors, mammalian target of rapamycin, and products of oxidative stress. It soon becomes clear that although inflammation is responsible for triggering the onset of the fibrotic process, it only plays a minor role in the progression of this condition, as fibrosis may advance in a self-perpetuating fashion. Definition of the cellular and molecular mechanisms involved in intestinal fibrosis may provide the key to developing new therapeutic approaches.

Anti-oxidant, anti-inflammatory and immunomodulating properties of an enzymatic protein hydrolysate from yellow field pea seeds

PURPOSE

Enzymatic protein hydrolysates of yellow pea seed have been shown to possess high anti-oxidant and anti-bacterial activities. The aim of this work was to confirm the anti-oxidant, anti-inflammatory and immunomodulating activities of an enzymatic protein hydrolysate of yellow field pea seeds.

METHODS

The anti-oxidant and anti-inflammatory properties of peptides from yellow field pea proteins (Pisum sativum L.) were investigated in LPS/IFN-γ-activated RAW 264.7 NO⁻ macrophages. The immunomodulating potential of pea protein hydrolysate (PPH) was then studied in a murine model.

RESULTS

Pea protein hydrolysate, after a 12 h pre-treatment, showed significant inhibition of NO production by activated macrophages up to 20%. Moreover, PPH significantly inhibited their secretion of pro-inflammatory cytokines, TNF-α- and IL-6, up to 35 and 80%, respectively. Oral administration of PPH in mice enhanced the phagocytic activity of their peritoneal macrophages and stimulated the gut mucosa immune response. The number of IgA+ cells was elevated in the small intestine lamina propria, accompanied by an increase in the number of IL-4+, IL-10+ and IFN-γ+ cells. This was correlated to up-regulation of IL-6 secretion by small intestine epithelial cells (IEC), probably responsible for B-cell terminal differentiation to IgA-secreting cells. Moreover, PPH might have increased IL-6 production in IECs via the stimulation of toll-like receptors (TLRs) family, especially TLR2 and TLR4 since either anti-TLR2 or anti-TLR4 was able to completely abolish PPH-induced IL-6 secretion.

CONCLUSIONS

Enzymatic protein degradation confers anti-oxidant, anti-inflammatory and immunomodulating potentials to pea proteins, and the resulted peptides could be used as an alternative therapy for the prevention of inflammatory-related diseases.

Systemic dissemination of Clostridium difficile toxins A and B is associated with severe, fatal disease in animal models

BACKGROUND

Clostridium difficile infection (CDI) can cause a wide range of disease, from mild diarrhea to fulminant systemic disease. The incidence of systemic CDI with fatal consequence has increased rapidly in recent years.

METHODS

Using an ultrasensitive cytotoxicity assay, we measured C. difficile toxin A (TcdA) and C. difficile toxin B (TcdB) in sera and body fluids of piglets and mice exposed to C. difficile to investigate the relationship between the presence of toxins in body fluids and systemic manifestations of CDI.

RESULTS

We found that both TcdA and TcdB disseminate systemically, with toxins present in the sera and body fluids of infected animals, and toxemia is significantly correlated with the development of systemic CDI. The systemic administration of neutralizing antibodies against both toxins blocked the development of systemic disease in mice. We measured cytokine concentrations in the sera of mice and piglets with systemic and nonsystemic CDI and found that proinflammatory mediators were considerably elevated in animals with systemic CDI.

CONCLUSION

Our study demonstrates the existence of a strong correlation between toxemia and the occurrence of systemic disease, supporting the hypothesis that systemic CDI is most likely due to the toxicity of TcdA and TcdB and the induction of proinflammatory cytokines by the toxins.

Statins potently reduce the cytokine-mediated IL-6 release in SMC/MNC cocultures

Inflammatory pathways are involved in the development of atherosclerosis. Interaction of vessel wall cells and invading monocytes by cytokines may trigger local inflammatory processes. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are standard medications used in cardiovascular diseases. They are thought to have anti-inflammatory capacities, in addition to their lipid-lowering effects. We investigated the anti-inflammatory effect of statins in the cytokine-mediated-interaction-model of human vascular smooth muscle cells (SMC) and human mononuclear cells (MNC). In this atherosclerosis-related inflammatory model LPS (lipopolysaccharide, endotoxin), as well as high mobility group box 1 stimulation resulted in synergistic (i.e. over-additive) IL-6 (interleukin-6) production as measured in ELISA. Recombinant IL-1, tumour necrosis factor-α and IL-6 mediated the synergistic IL-6 production. The standard anti-inflammatory drugs aspirin and indomethacin (Indo) reduced the synergistic IL-6 production by 60%. Simvastatin, atorvastatin, fluvastatin or pravastatin reduced the IL-6 production by 53%, 50%, 64% and 60%, respectively. The inhibition by the statins was dose dependent. Combination of statins with aspirin and/or Indo resulted in complete inhibition of the synergistic IL-6 production. The same inhibitors blocked STAT3 phosphorylation, providing evidence for an autocrine role of IL-6 in the synergism. MNC from volunteers after 5 day aspirin or simvastatin administration showed no decreased IL-6 production, probably due to drug removal during MNC isolation. Taken together, the data show that anti-inflammatory functions (here shown for statins) can be sensitively and reproducibly determined in this novel SMC/MNC coculture model. These data implicate that statins have the capacity to affect atherosclerosis by regulating cytokine-mediated innate inflammatory pathways in the vessel wall.

Long-lived plasma cells from human small intestine biopsies secrete immunoglobulins for many weeks in vitro

To understand the biology of Ab-secreting cells in the human small intestine, we examined Ab production of intestinal biopsies kept in culture. We found sustained IgA and IgM secretion as well as viable IgA- or IgM-secreting cells after >4 wk of culture. The Ab-secreting cells were nonproliferating and expressing CD27 and CD138, thus having a typical plasma cell phenotype. Culturing of biopsies without tissue disruption gave the highest Ab production and plasma cell survival suggesting that the environment regulates plasma cell longevity. Cytokine profiling of the biopsy cultures demonstrated a sustained presence of IL-6 and APRIL. Blocking of the activity of endogenous APRIL and IL-6 with BCMA-Fc and anti-human IL-6 Ab demonstrated that both these factors were essential for plasma cell survival and Ab secretion in the biopsy cultures. This study demonstrates that the human small intestine harbors a population of nonproliferating plasma cells that are instructed by the microenvironment for prolonged survival and Ab secretion.

The Antiinfective Effects of Velvet Antler of Formosan Sambar Deer (Cervus unicolor swinhoei) on Staphylococcus aureus-Infected Mice

We assayed the effects of velvet antler (VA) of Formosan sambar deer (Cervus unicolor swinhoei) and its extracts on the anti-infective activity against pathogenic Staphylococcus aureus in vitro and in vivo in this study. In vitro data indicated that the VA extracts stimulated the proliferation of resting splenocytes and macrophages in a dose-dependent manner up to the highest concentration used (150 μg mL(-1)). The production of proinflammatory cytokines (TNF-α, IL-6, IL-12) by lipoteichoic acid was significantly suppressed after being cocultured with the VA extracts in a dose-dependent manner. Animal test in S. aureus-infected mice demonstrated that the numbers of bacteria determined in the kidneys and peritoneal lavage fluid of S. aureus-infected mice were significantly higher than those found in the same organs of mice pretreated with the VA samples. Moreover, the highly enhanced phagocytic activity of macrophages was further verified after in vitro treatment with the VA samples. The protective mechanisms of the VA samples might include an immune enhancer and an inflammatory cytokine suppressor.

The enterotoxicity of Clostridium difficile toxins

The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic and proinflammatory in the human intestine. Both purified TcdA and TcdB are capable of inducing the pathophysiology of CDI, although most studies have focused on TcdA. C. difficile toxins exert a wide array of biological activities by acting directly on intestinal epithelial cells. Alternatively, the toxins may target immune cells and neurons once the intestinal epithelial barrier is disrupted. The toxins may also act indirectly by stimulating cells to produce chemokines, proinflammatory cytokines, neuropeptides and other neuroimmune signals. This review considers the mechanisms of TcdA- and TcdB-induced enterotoxicity, and recent developments in this field.

Essential role of the glucosyltransferase activity in Clostridium difficile toxin-induced secretion of TNF-alpha by macrophages

Clostridium difficile causes serious and potentially fatal inflammatory diseases of the colon. Two large protein toxins, TcdA and TcdB, have been clearly implicated in pathogenesis. The goal of this study was to determine whether the glucosyltransferase activity of the toxins is critical for the induction of tumor necrosis factor-alpha (TNF-alpha), an important cytokine mediating both local and systematic inflammatory response. A dose-dependent TNF-alpha secretion was demonstrated in murine macrophage cell line RAW 264.7 after exposure to TcdA or TcdB. TNF-alpha production was blocked by anti-toxin antibodies, indicating that the cytokine-driven response is mediated by the toxins. Both toxins disrupted the cytoskeleton of host cells, while cytoskeleton disruptions using Cytochalasin-D and latrunculin B did not affect TNF-alpha production. The TNF-alpha synthesis was inhibited by reagents that target clathrin-dependent endocytosis or prevent endosomal acidification, suggesting that the endocytosis pathway is necessary for the induction of TNF-alpha. Furthermore, knockout of the enzymatic activity by mutating two key amino acids in the catalytic domain of TcdA abolished its cytokine-inducing activity. Our studies demonstrated a crucial role of the glucosyltransferase activity of C. difficile toxins in the induction of TNF-alpha in macrophages.

How reliable an indicator of inflammation is myeloperoxidase activity?

BACKGROUND

Myeloperoxidase (MPO) and interleukin-6 (IL-6) are often used as markers of inflammation. The aim of this study was to ascertain whether MPO activity is as reliable as IL-6 as an indicator of inflammation.

METHODS

Inflammation was induced in mice, using either turpentine or indomethacin. Duodenal tissue was removed from these animals at various time periods ranging from 6 h to 7 days later. Concentrations of IL-6 and MPO activity were estimated in the tissue. Histopathological examination was also carried out at some of the time periods to determine the presence of neutrophil infiltration in turpentine-treated mice.

RESULTS

Concentrations of IL-6 and MPO activity were significantly higher in tissue that had been treated with the agents used, at all the time periods studied, when compared with corresponding control tissue. Fold-increases in MPO activity were higher than fold-increases in IL-6. Concentrations of the 2 parameters showed significant positive correlation. Histopathological examination did not show significantly higher numbers of neutrophils infiltrating the tissue in response to turpentine, at the time periods studied.

CONCLUSIONS

Estimation of MPO activity is a reliable indicator of inflammation, being more sensitive than histopathological examination of tissue and as good as measurement of IL-6 concentrations.

Human alpha-defensins inhibit Clostridium difficile toxin B

BACKGROUND & AIMS

Clostridium difficile toxins A and B are major virulence factors implicated in pseudomembranous colitis and antibiotic-associated diarrhea. The toxins are glucosyltransferases, which inactivate Rho proteins involved in cellular signaling. Human alpha-defensins as part of the innate immune system inactivate various microbial pathogens as well as specific bacterial exotoxins. Here, we studied the effects of alpha-defensins human neutrophil protein (HNP)-1, HNP-3, and enteric human defensin (HD)-5 on the activity of C difficile toxins A and B.

METHODS

Inactivation of C difficile toxins by alpha-defensins in vivo was monitored by microscopy, determination of the transepithelial resistance of CaCo-2 cell monolayers, and analysis of the glucosylation of Rac1 in toxin-treated cells. In vitro glucosylation was used to determine K(m) and median inhibitory concentration (IC(50)) values. Formation of defensin-toxin complexes was analyzed by precipitation and turbidity studies.

RESULTS

Treatment of cells with human alpha-defensins caused loss of cytotoxicity of toxin B, but not of toxin A. Only alpha-defensins, but not beta-defensin-1 or cathelicidin LL-37, inhibited toxin B-catalyzed in vitro glucosylation of Rho guanosine triphosphatases in a competitive manner, increasing K(m) values for uridine 5'-diphosphate-glucose up to 10-fold. The IC(50) values for inhibition of toxin B-catalyzed glucosylation by the alpha-defensins were 0.6-1.5 micromol/L. At high concentrations, defensins (HNP-1 > or = 2 micromol/L) caused high-molecular-mass aggregates, comparable to Bacillus anthracis protective antigen and lethal factor.

CONCLUSION

Our data indicate that toxin B interacts with high affinity with alpha-defensins and suggest that defensins may provide a defense mechanism against some types of clostridial glucosylating cytotoxins.

Tumor Necrosis Factor-alpha- and interleukin-1-induced cellular responses: coupling proteomic and genomic information

The pro-inflammatory cytokines, Tumor Necrosis Factor-alpha (TNFalpha) and Interleukin-1 (IL-1) mediate the innate immune response. Dysregulation of the innate immune response contributes to the pathogenesis of cancer, arthritis, and congestive heart failure. TNFalpha- and IL-1-induced changes in gene expression are mediated by similar transcription factors; however, TNFalpha and IL-1 receptor knock-out mice differ in their sensitivities to a known initiator (lipopolysaccharide, LPS) of the innate immune response. The contrasting responses to LPS indicate that TNFalpha and IL-1 regulate different processes. A large-scale proteomic analysis of TNFalpha- and IL-1-induced responses was undertaken to identify processes uniquely regulated by TNFalpha and IL-1. When combined with genomic studies, our results indicate that TNFalpha, but not IL-1, mediates cell cycle arrest.

Interactions of macrophages with probiotic bacteria lead to increased antiviral response against vesicular stomatitis virus

Macrophages are an important cellular component of the innate immune system and are normally rapidly recruited and/or activated at the site of virus infection. They can participate in the antiviral response by killing infected cells, by producing antiviral cytokines such as nitric oxide and by producing chemokines and immunoregulatory cytokines that enable the adaptive immune response to recognize infected cells and perform antiviral effector functions. Probiotics, as a part of the normal gut intestinal flora, are important in supporting a functional yet balanced immune system. Improving our understanding of their role in the activation of macrophages and their stimulation of proinflammatory cytokine production in early viral infection was the main goal of this study. Our in vitro model study showed that probiotic bacteria, either from the species Lactobacillus or Bifidobacteria have the ability to decrease viral infection by establishing the antiviral state in macrophages, by production of NO and inflammatory cytokines such as interleukin 6 and interferon-gamma. These effects correlated with the mitochondrial activity of infected macrophages, therefore, the measurements of mitochondrial dehydrogenases activity could be implied as the first indicator of potential inhibitory effects of the probiotics on virus replication. The interactions between probiotic bacteria, macrophages and vesicular stomatitis virus (VSV), markedly depended on the bacterial strain studied.

Interleukin-4 and 13 Induce the Expression and Release of Monocyte Chemoattractant Protein 1, Interleukin-6 and Stem Cell Factor From Human Detrusor Smooth Muscle Cells: Synergy With Interleukin-1β and Tumor Necrosis Factor-α

PURPOSE

Interstitial cystitis is characterized by an increased number of activated MCs in the detrusor muscle. However, to our knowledge the factors that influence the anatomical relationship between MCs and HDSMCs are unknown. MCP-1, IL-6 and SCF have a critical role in the regulation of MC development, signaling and function. We investigated whether HDSMCs are capable of expressing and releasing MCP-1, IL-6 and SCF in response to IL-4, IL-13, IL-1beta and tumor necrosis factor-alpha.

MATERIALS AND METHODS

HDSMCs were isolated and cultured using an explant technique. Protein expression, and the secretion of MCP-1, IL-6 and SCF were assayed by semiquantitative reverse transcriptase-polymerase chain reaction and specific enzyme-linked immunosorbent assay.

RESULTS

Unstimulated cells released low amounts of MCP-1, IL-6 and SCF. In cells stimulated by IL-4 MCP-1 mRNA was up-regulated by a mean factor +/- SD of 3.5 +/- 1.3, IL-6 mRNA was up-regulated by 3.8 +/- 1.3, the soluble form of SCF was up-regulated by 3.2 +/- 0.6 and the membrane bound form of SCF was up-regulated by 7.9 +/- 5.6. For IL-13 stimulated cells the values were 2.6 +/- 1.5, 3.6 +/- 2.1, 2.9 +/- 1.6 and 5.7 +/- 3.7, respectively. Soluble SCF mRNA expression was 5 times higher than the expression of mSCF mRNA. IL-4 and IL-13 given separately stimulated MCP-1, IL-6 and SCF secretion in a concentration (0.01 to 100 ng/ml) and time (0 to 24 hours) dependent manner. Furthermore, IL-1beta and tumor necrosis factor-alpha alone induced significant release of MCP-1, IL-6 and SCF but in combination with IL-4 or IL-13 it induced greater secretion of MCP-1, IL-6 and SCF.

CONCLUSIONS

To our knowledge these findings demonstrate for the first time that HDSMCs express and release MCP-1 and IL-6, and show relatively high expression of soluble SCF. This supports our hypothesis that HDSMCs may have an active role by orchestrating the local inflammatory response in the bladder wall with possible implications for the pathophysiology of detrusor mastocytosis.

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.

Proinflammatory cytokines alter/reduce esophageal circular muscle contraction in experimental cat esophagitis

Cholinergic mechanisms are largely responsible for esophageal contraction in response to swallowing or to in vitro electrical field stimulation (EFS). After induction of experimental esophagitis by repeated acid perfusion, the responses to swallowing and to EFS were significantly reduced but contraction in response to ACh was not affected, suggesting that cholinergic mechanisms are damaged by acid perfusion but that myogenic mechanisms are not. Measurements of ACh release in response to EFS confirmed that release of ACh was reduced in esophagitis compared with normal controls. To examine factors contributing to this neuropathy, normal esophageal strips were incubated for 1-2 h with the proinflammatory cytokines IL-1beta (100 U/ml), IL-6 (1 ng/ml), or TNF-alpha (1 ng/ml). IL-1beta and IL-6 levels, measured by Western blot analysis, increased in esophagitis compared with normal circular muscle. IL-1beta and IL-6 reduced contraction in response to EFS (2-10 Hz, 0.2 ms) but did not affect ACh-induced contraction, suggesting that these cytokines inhibit ACh release without affecting myogenic contractile mechanisms. EFS-induced ACh release was significantly reduced in normal esophageal strips by incubation in IL-1beta or IL-6, suggesting that they may contribute to the contractility changes. TNF-alpha at 1 ng/ml, however, did not affect the response to ACh or to electrical stimulation but inhibited both at higher concentrations. TNF-alpha levels were low in normal muscle and did not increase with esophagitis. The data suggest that the proinflammatory cytokines IL-1beta and IL-6 contribute to reduced esophageal contraction by inhibiting release of ACh from myenteric neurons.

Clostridium difficile toxin A carboxyl-terminus peptide lacking ADP-ribosyltransferase activity acts as a mucosal adjuvant

The receptor binding domains of the most potent mucosal adjuvants, bacterial toxins and plant lectins, are organized in repeat units to recognize specific sugar residues. The lectin-like structure of the C-terminal region of Clostridium difficile toxin A prompted us to investigate the mucosal adjuvant properties of a nontoxigenic peptide corresponding to amino acids 2394 to 2706 (TxA(C314)). We compared TxA(C314) adjuvant activity to those of cholera toxin (CT) and Escherichia coli heat-labile enterotoxin subunit B (EtxB) coadministered orally or nasotracheally with poor peptide antigens (keyhole limpet hemocyanin [KLH] and hen egg lysozyme [HEL]). Levels of anti-KLH-specific serum immunoglobulin G (IgG) and IgA as well as that of mucosal IgA were significantly higher in animals immunized orally with TxA(C314) plus KLH than with KLH alone, CT plus KLH, or EtxB plus KLH. Following intranasal immunization with TxA(C314) plus HEL, levels of serum- and mucosa-specific antibodies were comparable to those induced by coadministering HEL with CT or EtxB. The TxA(C314) adjuvant effect following oral, but not intranasal, immunization was dose dependent. The analysis of the subclasses of anti-KLH-specific IgG isotypes and the cytokines released from splenocytes of immunized mice challenged in vitro with KLH indicates the induction of a mixed Th1/Th2-type immune response, with prevalence of the Th1 branch. We conclude that TxA(C314) enhances immune responses against mucosa-coadministered foreign antigens and represents a promising mucosal adjuvant, especially because its ability to stimulate mixed Th1/Th2 responses with a strong a Th1 component is extremely worthwhile against intracellular pathogens.

Exploiting immune surveillance mechanisms in mucosal vaccine development

Historically, immune responsiveness was regarded by many as an ability to discriminate self from non-self, but this definition has recently been revised to be a distinction between threatening infectious organisms versus innocuous molecules from autologous tissues. Such distinctions can be made in the context of adjuvant effects from triggering of 'pattern recognition receptors' by pathogen-associated molecules. Mucosal sites such as airway and intestinal passages present a particularly interesting challenge to this system, as distinctions must be effectively made between innocuous non-self molecules associated with food and commensal bacteria versus pathogenic viruses and bacteria. Given the simultaneous presence of all these molecular types at mucosal lymphoid sites, immunological discrimination mechanisms must be especially precise, as immune responses must be directed only at pathogen-associated targets. Ongoing research is identifying genes that may be critical to triggering mucosal immunity; an understanding of their role in discrimination may lead to the development of new vaccines.