Toll-like receptor 4-mediated signaling by epithelial surfaces: necessity or threat?

Biophysiology of in ovo administered bioactive substances to improve gastrointestinal tract development, mucosal immunity, and microbiota in broiler chicks

Early embryonic exogenous feeding of bioactive substances is a topic of interest in poultry production, potentially improving gastrointestinal tract (GIT) development, stimulating immunization, and maximizing the protection capability of newly hatched chicks. However, the biophysiological actions and effects of in ovo administered bioactive substances are inconsistent or not fully understood. Thus, this paper summarizes the functional effects of bioactive substances and their interaction merits to augment GIT development, the immune system, and microbial homeostasis in newly hatched chicks. Prebiotics, probiotics, and synbiotics are potential bioactive substances that have been administered in embryonic eggs. Their biological effects are enhanced by a variety of mechanisms, including the production of antimicrobial peptides and antibiotic responses, regulation of T lymphocyte numbers and immune-related genes in either up- or downregulation fashion, and enhancement of macrophage phagocytic capacity. These actions occur directly through the interaction with immune cell receptors, stimulation of endocytosis, and phagocytosis. The underlying mechanisms of bioactive substance activity are multifaceted, enhancing GIT development, and improving both the innate and adaptive immune systems. Thus summarizing these modes of action of prebiotics, probiotics and synbiotics can result in more informed decisions and also provides baseline for further research.

Location-specific cell identity rather than exposure to GI microbiota defines many innate immune signalling cascades in the gut epithelium

OBJECTIVE

The epithelial layer of the GI tract is equipped with innate immune receptors to sense invading pathogens. Dysregulation in innate immune signalling pathways is associated with severe inflammatory diseases, but the responsiveness of GI epithelial cells to bacterial stimulation remains unclear.

DESIGN

We generated 42 lines of human and murine organoids from gastric and intestinal segments of both adult and fetal tissues. Genome-wide RNA-seq of the organoids provides an expression atlas of the GI epithelium. The innate immune response in epithelial cells was assessed using several functional assays in organoids and two-dimensional monolayers of cells from organoids.

RESULTS

Results demonstrate extensive spatial organisation of innate immune signalling components along the cephalocaudal axis. A large part of this organisation is determined before birth and independent of exposure to commensal gut microbiota. Spatially restricted expression of Toll-like receptor 4 (Tlr4) in stomach and colon, but not in small intestine, is matched by nuclear factor kappa B (NF-κB) responses to lipopolysaccharide (LPS) exposure. Gastric epithelial organoids can sense LPS from the basal as well as from the apical side.

CONCLUSION

We conclude that the epithelial innate immune barrier follows a specific pattern per GI segment. The majority of the expression patterns and the function of TLR4 is encoded in the tissue-resident stem cells and determined primarily during development.

Gastrointestinal epithelial innate immunity-regionalization and organoids as new model

The human gastrointestinal tract is in constant contact with microbial stimuli. Its barriers have to ensure co-existence with the commensal bacteria, while enabling surveillance of intruding pathogens. At the centre of the interaction lies the epithelial layer, which marks the boundaries of the body. It is equipped with a multitude of different innate immune sensors, such as Toll-like receptors, to mount inflammatory responses to microbes. Dysfunction of this intricate system results in inflammation-associated pathologies, such as inflammatory bowel disease. However, the complexity of the cellular interactions, their molecular basis and their development remains poorly understood. In recent years, stem cell-derived organoids have gained increasing attention as promising models for both development and a broad range of pathologies, including infectious diseases. In addition, organoids enable the study of epithelial innate immunity in vitro. In this review, we focus on the gastrointestinal epithelial barrier and its regional organization to discuss innate immune sensing and development.

Lipopolysaccharide Administration Alters Extracellular Vesicles in Cell Lines and Mice

Extracellular vesicles (EVs) play a fundamental role in cell and infection biology and have the potential to act as biomarkers for novel diagnostic tools. In this study, we explored the in vitro impact of bacterial lipopolysaccharide administration on cell lines that represents a target for bacterial infection in the host. Administration of lipopolysaccharide at varying concentrations to A549 and BV-2 cell lines caused only modest changes in cell death, but EV numbers were significantly changed. After treatment with the highest concentration of lipopolysaccharide, EVs derived from A549 cells packaged significantly less interleukin-6 and lysosomal-associated membrane protein 1. EVs derived from BV-2 cells packaged significantly less tumor necrosis factor after administration of lipopolysaccharide concentrations of 0.1 µg/mL and 1 µg/mL. We also examined the impact of lipopolysaccharide administration on exosome biogenesis and cargo composition in BALB/c mice. Serum-isolated EVs from lipopolysaccharide-treated mice showed significantly increased lysosomal-associated membrane protein 1 and toll-like receptor 4 levels compared with EVs from control mice. In summary, this study demonstrated that EV numbers and cargo were altered using these in vitro and in vivo models of bacterial infection.

Microbial interactions and immunity response in oral Candida species

Oral candidiasis are among the most common noncommunicable diseases, related with serious local and systemic illnesses. Although these infections can occur in all kinds of patients, they are more recurrent in immunosuppressed ones such as patients with HIV, hepatitis, cancer or under long antimicrobial treatments. Candida albicans continues to be the most frequently identified Candida spp. in these disorders, but other non-C. albicans Candida are rising. Understanding the immune responses involved in oral Candida spp. infections is a key feature to a successful treatment and to the design of novel therapies. In this review, we performed a literature search in PubMed and WoS, in order to examine and analyze common oral Candida spp.-bacteria/Candida-Candida interactions and the host immunity response in oral candidiasis.

Variable Responsiveness to Agonists for TLR2 and TLR7 in Myometrial Cells from Different Sources: Correlation with Receptor Expression

The myometrium plays a vital role in maintenance of pregnancy. Disruption of myometrial sensitivity to pro-contractile stimuli might lead to preterm labor. Inflammation and/or infection are common precursors to preterm birth, in part by initiating pro-contractile stimuli through toll-like receptor (TLRs) activation. In this study, we investigated the responses specific to inflammatory stimuli for both human primary myometrial cells (HPMCs) and PHM1-41 cells, a human immortalized myometrial cell line. Both these types of cells are commonly used to study labor and pregnancy. Both cell lines were treated with lipopolysaccharide (LPS), peptidoglycan (PGN), or imiquimod (IQ) (ligands for TLRs 2, 4, and 7, respectively). We demonstrate that inflammatory cytokines increase significantly with LPS treatment; however, no change occurs with PGN and IQ, suggesting lack of TLR2- and TLR7-specific signaling in both HPMCs and in the PHM1-41 cell line. Absence of TLR2- and TLR7-specific protein bands on western blots confirmed the lack of these receptors in both HPMCs maintained in long-term culture and PHM1-41 cells. However, TLR2 expression was present in freshly collected matched human myometrial tissue (i.e., the tissues used to create the HPMC cultures), showing loss of TLR2 receptors by HPMCs during the cell culturing process. TLR7 protein expression was lacking both in myometrial tissue and in cultured cells. These results demonstrate the limited applicability and reliability of cellular models to investigate the role of the myometrium during pregnancy and labor.

The Role of TLR4 Asp299Gly and TLR4 Thr399Ile Polymorphisms in the Pathogenesis of Urinary Tract Infections: First Evaluation in Infants and Children of Greek Origin

Urinary tract infections are one of the most common and serious bacterial infections in a pediatric population. So far, they have mainly been related to age, gender, ethnicity, socioeconomic level, and the presence of underlying anatomical or functional, congenital, or acquired abnormalities. Recently, both innate and adaptive immunities and their interaction in the pathogenesis and the development of UTIs have been studied. The aim of this study was to assess the role and the effect of the two most frequent polymorphisms of TLR4 Asp299Gly and Thr399Ile on the development of UTIs in infants and children of Greek origin. We studied 51 infants and children with at least one episode of acute urinary tract infection and 109 healthy infants and children. We found that 27.5% of patients and 8.26% of healthy children carried the heterozygote genotype for TLR4 Asp299Gly. TLR4 Thr399Ile polymorphism was found to be higher in healthy children and lower in the patient group. No homozygosity for both studied polymorphisms was detected in our patients. In the group of healthy children, a homozygote genotype for TLR4 Asp299Gly (G/G) as well as for TLR4 Thr399Ile (T/T) was showed (1.84% and 0.92 respectively). These results indicate the role of TLR4 polymorphism as a genetic risk for the development of UTIs in infants and children of Greek origin.

The Protective Roles of Urinary Trypsin Inhibitor in Brain Injury Following Fat Embolism Syndrome in a Rat Model

Fat embolism syndrome (FES) is a common complication following long bone fracture; fat droplets are released into the blood circulation and form embolisms, mainly in lung and brain. However, the potential mechanisms involved remain to be clarified. In this study, the mechanism of brain injury following FES and the protective effects of urinary trypsin inhibitor (UTI)—a serine protease inhibitor—were investigated. Sixty male Sprague-Dawley rats were divided randomly into sham, FES and FES+UTI treatment groups. The FES model was established using tail vein injection of glycerol trioleate, and UTI was administered by intraperitoneal injection immediately following FES. Brain/lung water content evaluation, Evans blue content and magnetic resonance imaging examination were used to assess the effects of UTI. Furthermore, immunohistochemistry and western blot were also applied to explore the protective mechanism of UTI following FES. The results of oil red O staining indicated that the FES model was successfully established. UTI could significantly attenuate blood-brain-barrier (BBB) disruption, as seen through brain edema evaluation and Evans blue content examination. Immunofluorescence staining results indicated that the TLR4-JNK pathway was involved in brain injury after FES; this effect could be quenched by UTI treatment. Furthermore, UTI could decrease the levels of downstream target proteins of the TLR4-JNK pathway, phosphorylated-NF- κB (p65) and p53 in brain. Our results showed that UTI could alleviate BBB injury after FES through blocking activity of the TLR4-JNK pathway.

Polymyxin-Induced Lipid A Deacylation in Pseudomonas aeruginosa Perturbs Polymyxin Penetration and Confers High-Level Resistance

Polymyxins are last-line antibiotics against life-threatening multidrug-resistant Gram-negative bacteria. Unfortunately, polymyxin resistance is increasingly reported, leaving a total lack of therapies. Using lipidomics and transcriptomics, we discovered that polymyxin B induced lipid A deacylation via pagL in both polymyxin-resistant and -susceptible Pseudomonas aeruginosa. Our results demonstrated that the deacylation of lipid A is an "innate immunity" response to polymyxins and a key compensatory mechanism to the aminoarabinose modification to confer high-level polymyxin resistance in P. aeruginosa. Furthermore, cutting-edge neutron reflectometry studies revealed that an assembled outer membrane (OM) with the less hydrophobic penta-acylated lipid A decreased polymyxin B penetration, compared to the hexa-acylated form. Polymyxin analogues with enhanced hydrophobicity displayed superior penetration into the tail regions of the penta-acylated lipid A OM. Our findings reveal a previously undiscovered mechanism of polymyxin resistance, wherein polymyxin-induced lipid A remodeling affects the OM packing and hydrophobicity, perturbs polymyxin penetration, and thereby confers high-level resistance.

Altered Toll-like receptor expression and function in HPV-associated oropharyngeal carcinoma

Toll-like receptors (TLRs) have been widely investigated due to their importance in the inflammatory response and possible links to tumor promotion/regression and prognosis. In cancers with an infective etiology, such as human papillomavirus (HPV)-associated Oropharyngeal Squamous Cell Carcinoma (OPSCC), TLR responses may be activated and play a role in tumorigenesis. Our aim was to assess the expression of all TLRs in OPSCC cell lines (both HPV+ and HPV-) by qPCR, Western Blot and flow cytometry and assess their response to TLR ligands lipopolysaccharide (LPS), LPS ultra-pure (LPS-UP) and peptidoglycan (PGN) by analyzing IL-8 and IL-6 production. We also immunostained 61 OPSCC tissue samples with anti-TLR4. Results showed lower TLR1 and TLR6 mRNA expression and higher TLR9 protein expression in HPV+ when compared to HPV-OPSCC cells. TLR4 expression did not vary by HPV status in OPSCC cells, but TLR4 expression was significantly lower in HPV+OPSCC tissues. After stimulation with PGN, only one cell line (HPV+) did not secrete IL-6 or IL-8. Furthermore, HPV+OPSCC lines showed no IL-6 or IL-8 production on treatment with LPS/LPS-UP. The data suggest changes in TLR4 signaling in HPV+OPSCC, since we have shown lower tissue expression of TLR4 and no pro-inflammatory response after stimulation with LPS and LPS-UP. Also, it suggests that OPSCC may respond to HPV infection by increased expression of TLR9. This study demonstrates differences in expression and function of TLRs in OPSCC, which are dependent on HPV status, and may indicate subversion of the innate immune response by HPV infection.

Mucosal immune system of the gastrointestinal tract: maintaining balance between the good and the bad

The gastrointestinal tract (GI tract) is a unique organ inhabited by a range of commensal microbes, while also being exposed to an overwhelming load of antigens in the form of dietary antigens on a daily basis. The GI tract has dual roles in the body, in that it performs digestion and uptake of nutrients while also carrying out the complex and important task of maintaining immune homeostasis, i.e., keeping the balance between the good and the bad. It is equally important that we protect ourselves from reacting against the good, meaning that we stay tolerant to harmless food, commensal bacteria and self-antigens, as well as react with force against the bad, meaning induction of immune responses against harmful microorganisms. This complex task is achieved through the presence of a highly efficient mucosal barrier and a specialized multifaceted immune system, made up of a large population of scattered immune cells and organized lymphoid tissues termed the gut-associated lymphoid tissue (GALT). This review provides an overview of the primary components of the human mucosal immune system and how the immune responses in the GI tract are coordinated and induced.

Gut microbiota and hepatitis-B-virus-induced chronic liver disease: implications for faecal microbiota transplantation therapy

Hepatitis B is one of the most common infectious diseases globally. It has been estimated that there are 350 million chronic hepatitis B virus (HBV) carriers worldwide. The liver is connected to the small intestine by the bile duct, which carries bile formed in the liver to the intestine. Nearly all of the blood that leaves the stomach and intestines must pass through the liver. Human intestines contain a wide diversity of microbes, collectively termed the 'gut microbiota'. Gut microbiota play a significant role in host metabolic processes and host immune modulation, and influence host development and physiology (organ development). Altered gut microbiota is a common complication in liver disease. Changes in intestinal microbiota seem to play an important role in induction and promotion of HBV-induced chronic liver disease progression, and specific species among the intestinal commensal bacteria may play either a pathogenic or a protective role in the development of HBV-induced chronic liver disease. Thus, the gut microbiome may represent fertile targets for prevention or management of HBV-induced chronic liver disease. Faecal microbiota transplantation (FMT) may be a useful therapy for HBV-related disease in the future. However, the data available in this field remain limited, and relevant scientific work has only just commenced. New technologies have enabled systematic studies of gut microbiota, and provided more realistic information about its composition and pathological variance. This review summarizes the cutting edge of research into the relationship between gut microbiota and HBV-induced chronic liver disease, and the future prospects of FMT therapy.

Toll-Like Receptor 4 Activation Contributes to Diabetic Bladder Dysfunction in a Murine Model of Type 1 Diabetes

Diabetic bladder dysfunction (DBD) is a common urological complication of diabetes. Innate immune system activation via Toll-like receptor 4 (TLR4) leads to inflammation and oxidative stress and was implicated in diabetes pathophysiology. We hypothesized that bladder hypertrophy and hypercontractility in DBD is mediated by TLR4 activation. Wild-type (WT) and TLR4 knockout (TLR4KO) mice were made diabetic by streptozotocin (STZ) treatment, and bladder contractile function and TLR4 pathway expression were evaluated. Immunohistochemistry confirmed the expression of TLR4 in human and mouse bladder. Recombinant high-mobility group box protein 1 (HMGB1) increased bladder TLR4 and MyD88 expression and enhanced contractile response to electrical field stimulation. Bladder expression of TLR4 and MyD88 and serum expression of HMGB1 were increased in STZ compared with control mice. Carbachol (CCh)-mediated contraction was increased in bladders from STZ mice, and TLR4 inhibitor CLI-095 attenuated this increase. Induction of diabetes by STZ in WT mice increased bladder weight and contractile responses to CCh and to electrical field stimulation. TLR4KO mice were not protected from STZ-induced diabetes; however, despite levels of hyperglycemia similar to those of WT STZ mice, TLR4KO STZ mice were protected from diabetes-induced bladder hypertrophy and hypercontractility. These data suggest that TLR4 activation during diabetes mediates DBD-associated bladder hypertrophy and hypercontractility.

The role of epithelial Toll-like receptor expression in host defense and microbial tolerance

The recognition of microbial structures by Toll-like receptors (TLRs) on professional immune cells situated at sterile internal body sites occurs during invasive microbial infection. It indicates infectious non-self and thereby represents the adequate co-stimulatory signal to initiate activation of the adaptive immune system against the invading pathogen. In contrast, most epithelial body surfaces are permanently colonized by microbial organisms of the normal flora and thus TLR ligands are present under physiological conditions. In the following, we discuss the characteristics of TLR-mediated recognition by epithelial cells, the subsequent activation of the host immune system, and protective mechanisms that might help to avoid inadequate stimulation and allow differentiation between commensal or pathogenic micro-organisms. Recent findings suggest that the role of epithelial cells in the maintenance of stable microbial colonization of host surfaces and the immediate host response to infectious challenges might have to be revised.

Role of testosterone in regulating induction of TNF-α in rat spleen via ERK signaling pathway

Spleen is a pivotal organ for regulating immune homeostasis. It has been shown that testosterone diminishes secretion of various inflammatory molecules under multiple conditions. However, the mechanisms of action of endogenous testosterone affecting immune responses in the spleen remain unknown. The aim of the present study was to evaluate the immune functions of the spleen in response to testosterone withdrawal after orchidectomy, and the impact of splenocytes on the bacterial endotoxin lipopolysaccharide (LPS)-induced secretion of inflammatory molecules. Male rats were divided into 3 groups, i.e. intact, orchidectomized (Orch) and orchidectomized plus replacement of testosterone propionate (TP) (Orch+TP). The Orch and Orch+TP rats underwent bilateral orchidectomy one week before TP replacement (2mg/kg body weight) or sesame oil in intact rats as controls for seven days. Orch resulted in a significant increase of spleen weight and basal secretion of nitric oxide (NO) from splenocytes. Additionally, LPS up-regulated cell proliferation and the secretion of tumor necrosis factor-alpha (TNF-α) in splenocytes of Orch rats. Orch further up-regulated phosphorylation of extracellular signal-regulated kinases. Interestingly, the plasma corticosterone concentration in the Orch group was higher than that in the intact and Orch+TP groups. Deficiency of testosterone-elevated TNF-α and NO secretion in response to LPS were confirmed in the rat splenocytes. Testosterone also significantly attenuated LPS-elicited release of TNF-α and NO in a dose-dependent manner. However, testosterone did not suppress splenic blastogenesis at doses in the 10(-10)-10(-7)M concentration range. In this context, testosterone might have a protective role against inflammatory responses in the spleen. The present study provides evidence to indicate that testosterone might modulate the immune system.

LPS/TLR4 Signaling Enhances TGF-β Response Through Downregulating BAMBI During Prostatic Hyperplasia

Compelling evidence suggests that benign prostatic hyperplasia (BPH) development involves accumulation of mesenchymal-like cells derived from the prostatic epithelium by epithelial-mesenchymal transition (EMT). Transforming growth factor (TGF)-β induces EMT phenotypes with low E-cadherin and high vimentin expression in prostatic epithelial cells. Here we report that LPS/TLR4 signalling induces down-regulation of the bone morphogenic protein and activin membrane-bound inhibitor (BAMBI), which enhances TGF-β signalling in the EMT process during prostatic hyperplasia. Additionally, we found that the mean TLR4 staining score was significantly higher in BPH tissues with inflammation compared with BPH tissues without inflammation (5.13 ± 1.21 and 2.96 ± 0.73, respectively; P < 0.001). Moreover, patients with inflammatory infiltrate were more likely to have a higher age (P = 0.020), BMI (P = 0.026), prostate volume (P = 0.024), total IPSS score (P = 0.009) and IPSS-S (P < 0.001). Pearson’s correlation coefficient and multiple regression analyses demonstrated that TLR4 mRNA expression level was significantly positively associated with age, BMI, serum PSA levels, urgency and nocturia subscores of IPSS in the inflammatory group. These findings provide new insights into the TLR4-amplified EMT process and the association between TLR4 levels and storage LUTS, suggesting chronic inflammation as vital to the pathogenesis of BPH.

Know your neighbor: Microbiota and host epithelial cells interact locally to control intestinal function and physiology

Interactions between the host and its associated microbiota differ spatially and the local cross talk determines organ function and physiology. Animals and their organs are not uniform but contain several functional and cellular compartments and gradients. In the intestinal tract, different parts of the gut carry out different functions, tissue structure varies accordingly, epithelial cells are differentially distributed and gradients exist for several physicochemical parameters such as nutrients, pH, or oxygen. Consequently, the microbiota composition also differs along the length of the gut, but also between lumen and mucosa of the same intestinal segment, and even along the crypt-villus axis in the epithelium. Thus, host-microbiota interactions are highly site-specific and the local cross talk determines intestinal function and physiology. Here we review recent advances in our understanding of site-specific host-microbiota interactions and discuss their functional relevance for host physiology.

Lipopolysaccharide-promoted proliferation of Caco-2 cells is mediated by c-Src induction and ERK activation

As a major component of the cell wall of Gram-negative bacteria, lipopolysaccharide (LPS) can be released into the bloodstream to cause a spectrum of pathophysiological reactions. Despite the fact that colon epithelium cells in situ are continuously exposed to LPS, their biological responses as provoked by LPS as well as the underlying mechanisms are poorly defined. In the present study, we observed that LPS directly stimulated growth of Caco-2 cells as well as enhanced the amounts of c-Src, which could be partly attributable to increased c-src transcript. Parallel to LPS-induced c-Src expression was FAK activation and ERK activation. Remarkably, activation of ERK and cellular proliferation by LPS could be inhibited by PP2, the specific Src inhibitor, implicating the essential role of c-Src in this process. To our knowledge, this is the first report indicating that LPS can increase cellular growth via upregulation of c-Src in colon epithelial cells.

Toll-like receptor 2 and 4 expression in the pregnant and non-pregnant human uterine cervix

Pelvic infections and sexually transmitted diseases place a burden on health resources and may be associated with premature birth. The mechanisms by which the female reproductive tract (FRT) combats these infections remain ill understood, but are likely to involve the pattern recognition Toll-like receptors (TLR). We sought to compare the expression of TLR-2 and -4 by human pregnant and non-pregnant ectocervical epithelium as a prelude to the investigation of the function of these receptors in this tissue during pregnancy. Using the techniques of reverse-transcriptase polymer chain reaction (RT-PCR) and immunohistochemistry, the gene and protein expression of TLR-2 and -4 were studied in the biopsies of ectocervix obtained from non-pregnant premenopausal women (n=21) undergoing hysterectomy, women in the first trimester of pregnancy undergoing non-medically indicated suction pregnancy termination (n=6), and women at term undergoing elective caesarean section (n=11). The expression of TLR2 and TLR4 genes and proteins were upregulated in early and late pregnant ectocervical epithelium, compared with non-pregnant tissue. These findings suggest that the upregulation of TLR2 and TLR4 in the lower FRT may play a key role in the modulation of the innate immune and inflammatory mechanisms of the ectocervix during pregnancy, interacting with other neuroendocrine factors.

Interaction of cyclic mechanical stretch and toll-like receptor 4-mediated innate immunity in rat alveolar type II cells

BACKGROUND AND OBJECTIVE

In cases of infection-induced acute lung injury, mechanical ventilation might be necessary to maintain oxygenation. Although low tidal volume ventilation is applied, alveolar over-distension may occur and result in ventilator-induced lung injury. In this study, we investigate (i) the influence of lipopolysaccharide (LPS) stimulation on high-amplitude stretching; and (ii) the effect of stretching on LPS-mediated immune response in isolated rat alveolar type II cells.

METHODS

Type II cells were incubated with LPS and stretched for 24 h on elastic membranes. Initially we examined apoptosis and lactic acid dehydrogenase release in LPS-treated stretched cells. Furthermore we determined toll-like receptor (TLR) 4 expression, TLR4 signalling by analysis of nuclear factor κB (NF-κB) activation and the secretion of inflammatory cytokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-2, interleukin-1 beta, tumour necrosis factor alpha).

RESULTS

Our results show that LPS increases apoptosis and cytotoxicity in high amplitude stretched cells. Stretching and LPS activate NF-κB. The LPS influence is the prevailing one while no synergistic effects were observed by additional stretching. LPS stimulates an increased secretion of the inflammatory mediators only. Stretching had no influence on cytokines secretion.

CONCLUSIONS

We conclude that activation of TLR4 mediated immunity intensifies cell damage caused by stretching whereas in return stretching had no influence on TLR4 mediated innate immunity.

Negatively regulating TLR4/NF-κB signaling via PPARα in endotoxin-induced uveitis

Toll-like receptor (TLR) signaling plays a fundamental role in the induction and progression of autoimmune disease. In the present study, we showed that lipopolysaccharide (LPS), a TLR4 ligand, functions as an antagonist of peroxisome proliferator-activated receptor alpha (PPARα), a nuclear transcription factor. Using endotoxin induced uveitis (EIU) as a model, we found that TLR was negatively regulated by PPARα. Our data revealed that treatment with the PPARα agonist fenofibrate dramatically prevented LPS-induced uveitis and inhibited TLR/ Nuclear factor-kappaB (NF-κB) signaling during inflammation. Evaluation of the severity of anterior uveitis further showed that PPARα agonist treatment significantly decreased inflammatory cell infiltration, total protein concentration, vessel density, inflammatory cytokine production, and clinical scores in the anterior section of the eye during EIU. Moreover, fenofibrate administration recovered retinal function and decreased the production of inflammatory cytokines, retinal vascular leukostasis, and inflammatory cell infiltration into the posterior section of the eyes during EIU. In vitro studies further showed that down-regulation or deletion of PPARα led to increased TLR4 levels and the activation of NF-κB signaling in RPE cells and also blocked the anti-inflammatory effects of fenofibrate. Furthermore, activation or up-regulation of PPARα decreased TLR4 levels and inhibited the NF-κB signaling pathway induced by LPS in RPE cells. In TLR4-expressing reporter cells, activation or up-regulation of PPARα partially inhibited the activation of NF-κB and also decreased TLR4 transcriptional activity. In conclusion, the activation of PPARα represents a novel therapeutic strategy for human uveitis, as PPARα negatively regulates TLR4 activity and therefore exerts anti-inflammatory actions.

Ingestion of bacterial lipopolysaccharide inhibits peripheral taste responses to sucrose in mice

A fundamental role of the taste system is to discriminate between nutritive and toxic foods. However, it is unknown whether bacterial pathogens that might contaminate food and water modulate the transmission of taste input to the brain. We hypothesized that exogenous, bacterially-derived lipopolysaccharide (LPS), modulates neural responses to taste stimuli. Neurophysiological responses from the chorda tympani nerve, which innervates taste cells on the anterior tongue, were unchanged by acute exposure to LPS. Instead, neural responses to sucrose were selectively inhibited in mice that drank LPS during a single overnight period. Decreased sucrose sensitivity appeared 7days after LPS ingestion, in parallel with decreased lingual expression of Tas1r2 and Tas1r3 transcripts, which are translated to T1R2+T1R3 subunits forming the sweet taste receptor. Tas1r2 and Tas1r3 mRNA expression levels and neural responses to sucrose were restored by 14 days after LPS consumption. Ingestion of LPS, rather than contact with taste receptor cells, appears to be necessary to suppress sucrose responses. Furthermore, mice lacking the Toll-like receptor (TLR) 4 for LPS were resistant to neurophysiological changes following LPS consumption. These findings demonstrate that ingestion of LPS during a single period specifically and transiently inhibits neural responses to sucrose. We suggest that LPS drinking initiates TLR4-dependent hormonal signals that downregulate sweet taste receptor genes in taste buds. Delayed inhibition of sweet taste signaling may influence food selection and the complex interplay between gastrointestinal bacteria and obesity.

Recombinant Salmonella enterica serovar Typhimurium as a vaccine vector for HIV-1 Gag

The HIV/AIDS epidemic remains a global health problem, especially in Sub-Saharan Africa. An effective HIV-1 vaccine is therefore badly required to mitigate this ever-expanding problem. Since HIV-1 infects its host through the mucosal surface, a vaccine for the virus needs to trigger mucosal as well as systemic immune responses. Oral, attenuated recombinant Salmonella vaccines offer this potential of delivering HIV-1 antigens to both the mucosal and systemic compartments of the immune system. So far, a number of pre-clinical studies have been performed, in which HIV-1 Gag, a highly conserved viral antigen possessing both T- and B-cell epitopes, was successfully delivered by recombinant Salmonella vaccines and, in most cases, induced HIV-specific immune responses. In this review, the potential use of Salmonella enterica serovar Typhimurium as a live vaccine vector for HIV-1 Gag is explored.

Shrimp anti-lipopolysaccharide factor (SALF), an antimicrobial peptide, inhibits proinflammatory cytokine expressions through the MAPK and NF-κB pathways in LPS-induced HeLa cells

Recently, an antimicrobial peptide (AMP), the shrimp anti-lipopolysaccharide factor (SALF), was shown to act against vaginal pathogens as demonstrated by a minimum inhibitory concentration (MIC) assay and suggested that the SALF might play a protective role in orchestrating various defensive responses. The demonstration of a protective role of the SALF in cervical cancer epithelial cells (HeLa cells) led us to investigate the anti-inflammatory effects of the SALF by determining its inhibitory effects on proinflammatory markers in LPS-stimulated cervical cancer HeLa cells. The SALF was shown to inhibit the production of inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-1α, and monocyte chemoattractant protein (MCP)-1 according to an ELISA analysis. The SALF also suppressed mRNA levels of il-6, il-8, il-1α, and mcp-1 according to an RT-PCR. We also found that the SALF might regulate vaginal epithelial cell immune responses through the MAPK and NF-κB pathways. These findings suggest that the SALF is a potential drug candidate for treating chronic inflammatory diseases, such as urethritis, vaginitis, cervicitis, and pelvic inflammatory diseases.

Dynamic changes of lipopolysaccharide levels in different phases of acute on chronic hepatitis B liver failure

Background

High serum levels of lipopolysaccharide (LPS) with LPS-MD-2/TLR4 complex activated NF-kb and cytokine cause hepatic necrosis in animal models. We investigated the dynamic changes of LPS levels in patients with acute on chronic hepatitis B liver failure (ACHBLF).

Methods

We enrolled ACHBLF patients for a 12-week study. Patients’ LPS levels were measured along with 10 healthy controls. Patients on supportive care and recovered without intervention(s) were analyzed. Patients’ LPS levels during the disease progression phase, peak phase, and remission phase were compared with healthy controls.

Results

Among 30 patients enrolled, 25 who received interventions or expired during the study period were excluded from the analysis, five patients on supportive care who completed the study were analyzed. Significant abnormal distributions of LPS levels were observed in patients in different phases (0.0168±0.0101 in progression phase; 0.0960±0.0680 in peak phase; 0.0249±0.0365 in remission phase; and 0.0201±0.0146 in controls; respectively, p<0.05). The highest level of LPS was in the peak phase and significantly elevated when compared to controls (0.0201±0.0146 vs. 0.0960±0.0680, p = 0.007). There were no statistically significant differences in LPS levels between healthy controls and subjects in the progression phase or remission phase. Dynamic changes of LPS were correlated with MELD-Na in the progression phase (p = 0.01, R = 0.876) and in the peak phase (p = 0.000, R = −1.00).

Conclusions

Significant abnormal distributions of LPS levels were observed in ACHBLF with the highest level in the peak phase. The dynamic changes of LPS were correlated with disease severity and suggested LPS causing secondary hepatic injury.

Microbiome and immunological interactions

The healthy human gut supports a complex and diverse microbiota, dominated by bacterial phylotypes belonging to Bacteroidetes and Firmicutes. In the inflamed gut, overall diversity decreases, coincident with a greater representation of Proteobacteria. There is growing evidence supporting an important role for human gut bacteria in mucosal immunity; interactions at the level of both intestinal and colonic epithelial cells, dendritic cells, and T and B immune cells have been documented. These interactions influence gut barrier and defense mechanisms that include antimicrobial peptide and secretory IgA synthesis. The functional effects of commensal bacteria on T helper cell differentiation have led to the emerging concept that microbiota composition determines T effector- and T regulatory-cell balance, immune responsiveness, and homeostasis. The importance of this biology in relation to immune homeostasis, inflammatory bowel disease, and the rising incidence of autoimmune diseases will be discussed. The detailed description of the human gut microbiota, integrated with evidence-based mechanisms of immune modulation, provides an exciting platform for the identification of next-generation probiotics and related pharmaceutical products.

New approaches in the development of a vaccine for mucosal candidiasis: progress and challenges

The commensal fungus Candida albicans causes mucosal candidiasis in the rapidly expanding number of immunocompromised patients. Mucosal candidiasis includes oropharyngeal, esophageal, gastrointestinal, and vaginal infections. Vulvovaginal candidiasis (VVC) and antimycotic-refractory recurrent VVC is a frequent problem in healthy childbearing women. Both these mucosal infections can affect the quality of life and finding new therapeutical and preventive approaches is a challenge. A vaccine against candidal infections would be a new important tool to prevent and/or cure mucosal candidiasis and would be of benefit to many patients. Several Candida antigens have been proposed as vaccine candidates including cell wall components and virulence factors. Here we discuss the recent progress and problems associated with vaccination against mucosal candidiasis.

MARCKS as a negative regulator of lipopolysaccharide signaling

Myristoylated alanine-rich C kinase substrate (MARCKS) is an intrinsically unfolded protein with a conserved cationic effector domain, which mediates the cross-talk between several signal transduction pathways. Transcription of MARCKS is increased by stimulation with bacterial LPS. We determined that MARCKS and MARCKS-related protein specifically bind to LPS and that the addition of the MARCKS effector peptide inhibited LPS-induced production of TNF-α in mononuclear cells. The LPS binding site within the effector domain of MARCKS was narrowed down to a heptapeptide that binds to LPS in an extended conformation as determined by nuclear magnetic resonance spectroscopy. After LPS stimulation, MARCKS moved from the plasma membrane to FYVE-positive endosomes, where it colocalized with LPS. MARCKS-deficient mouse embryonic fibroblasts (MEFs) responded to LPS with increased IL-6 production compared with the matched wild-type MEFs. Similarly, small interfering RNA knockdown of MARCKS also increased LPS signaling, whereas overexpression of MARCKS inhibited LPS signaling. TLR4 signaling was enhanced by the ablation of MARCKS, which had no effect on stimulation by TLR2, TLR3, and TLR5 agonists. These findings demonstrate that MARCKS contributes to the negative regulation of the cellular response to LPS.

Prematurity does not markedly affect intestinal sensitivity to endotoxins and feeding in pigs

Preterm neonates show enhanced sensitivity to nutrient maldigestion and bacteria-mediated gut inflammatory disorders, such as necrotising enterocolitis (NEC). We hypothesised that preterm birth increases the sensitivity of intestinal nutrient absorption to endotoxins and that feeding after birth reduces this response. Hence, we investigated the postnatal development of nutrient digestive and absorptive capacity in the preterm and term pig intestine, and its responsiveness to endotoxins. Pigs were delivered by caesarean section at preterm (n 20) or term (n 17) gestation, and the small intestine was collected at birth or after 2 d of colostrum feeding, followed by ex vivo stimulation with lipopolysaccharide endotoxins and mixed gut contents collected from pigs with NEC. Brush border enzyme activities were reduced in newborn preterm v. term pigs (39–45 % reduction, P < 0·05), but normalised after 2 d of feeding. Ex vivo leucine and glucose uptake increased with prenatal age. Bacterial stimulation reduced the nutrient uptake similarly at birth and after 2 d in preterm and term pigs (23–41 % reduction, P < 0·05), whereas IL-6 and TNF-α expression was stimulated only at birth. Toll-like receptor-4 expression increased markedly at day 2 for preterm and term pigs (22–33-fold, P < 0·05) but with much lower expression levels in newborn preterm pigs (approximately 95 %, P < 0·01). In conclusion, digestive and absorptive functions mature in the prenatal period, but are similarly affected by postnatal feeding and bacterial exposure in both preterm and term pigs. Nutrient maldigestion may contribute to NEC development, while a prematurity-related hyper-responsiveness to endotoxins could be less important, at least in pigs.

Toll-like receptor activation by helminths or helminth products to alleviate inflammatory bowel disease

Helminth infection may modulate the expression of Toll like receptors (TLR) in dendritic cells (DCs) and modify the responsiveness of DCs to TLR ligands. This may regulate aberrant intestinal inflammation in humans with helminthes and may thus help alleviate inflammation associated with human inflammatory bowel disease (IBD). Epidemiological and experimental data provide further evidence that reducing helminth infections increases the incidence rate of such autoimmune diseases. Fine control of inflammation in the TLR pathway is highly desirable for effective host defense. Thus, the use of antagonists of TLR-signaling and agonists of their negative regulators from helminths or helminth products should be considered for the treatment of IBD.

Epithelial cell innate response to Candida albicans

With the advent of treatments and diseases such as AIDS resulting in increasing numbers of patients with suppressed immune systems, fungal diseases are an escalating problem. Candida albicans is the most common of these fungal pathogens, causing infections in many of these patients. It is therefore important to understand how immunity to this fungus is regulated and how it might be manipulated. Although work has been done to identify the receptors, fungal moieties, and responses involved in anti-Candida immunity, most studies have investigated interactions with myeloid or lymphoid cells. Given that the first site of contact of C. albicans with its host is the mucosal epithelial surface, recent studies have begun to focus on interactions of C. albicans with this site. The results are startling yet in retrospect obvious, indicating that epithelial cells play an important role in these interactions, initiating responses and even providing a level of protection. These findings have obvious implications, not just for fungal pathogens, but also for identifying how host organisms can distinguish between commensal and pathogenic microbes. This review highlights some of these recent findings and discusses their importance in the wider context of infection and immunity.

Mucosal immunity and Candida albicans infection

Interactions between mucosal surfaces and microbial microbiota are key to host defense, health, and disease. These surfaces are exposed to high numbers of microbes and must be capable of distinguishing between those that are beneficial or avirulent and those that will invade and cause disease. Our understanding of the mechanisms involved in these discriminatory processes has recently begun to expand as new studies bring to light the importance of epithelial cells and novel immune cell subsets such as T(h)17 T cells in these processes. Elucidating how these mechanisms function will improve our understanding of many diverse diseases and improve our ability to treat patients suffering from these conditions. In our voyage to discover these mechanisms, mucosal interactions with opportunistic commensal organisms such as the fungus Candida albicans provide insights that are invaluable. Here, we review current knowledge of the interactions between C. albicans and epithelial surfaces and how this may shape our understanding of microbial-mucosal interactions.

Antibacterial activity of a synthetic peptide that mimics the LPS binding domain of Indian mud crab, Scylla serrata anti-lipopolysaccharide factor (SsALF) also involved in the modulation of vaginal immune functions through NF-kB signaling

Recently the cDNA coding for anti-lipopolysaccharide factor (ALF) has been identified from the Indian mud crab, Scylla serrata and has been named S. serrata anti-lipopolysaccharide factor (SsALF). SsALF protein sequence demonstrated the presence of two highly conserved cystine residues between which the putative lipopolysaccharide (LPS) binding domain is known to be located. In this study, we have designed and synthesized a 24 amino acid linear (lSsALF24) and a cyclic (cSsALF24) peptides based on this putative LPS binding domain and demonstrated the ability of these peptides to bind to LPS. The peptides were active against vaginal pathogens demonstrated by MIC, CFU and phagocytosis assays. cSsALF24 did not show toxicity to human vaginal epithelial cells (HeLa-S3), macrophages and rabbit erythrocytes even at high concentration (64.64 μM). Flow cytometry results demonstrated that cSsALF24 peptide suppressed LPS induced phagocytosis of FITC labeled E. coli. HeLa cells were stimulated with LPS (10 μg/ml) alone for 6 h or after two washings with PBS, treated for 1 h with cSsALF24 (64.64 μM). After washing, the cells were cultured for 24 h in fresh media. The spent media as well as cells were collected for the determination of cytokine/chemokine levels such as interleukin-6 (IL-6) interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1) and interleukin-1α (IL-1α) using ELISA and RT-PCR respectively. Similar results were obtained with LPS stimulated cells treated with c/nSsALF24 or unstimulated cells treated with c/nSsALF24. The expression of cytokine/chemokines and mRNA's coding these proteins were unaffected in c/nSsALF24 treated cells. In contrast, in LPS stimulated cells, the expression levels of these molecules were up-regulated via the induction of nuclear factor kappa-B (NF-kB) levels. However, the expression of these pro-inflammatory markers was decreased in LPS stimulated cells following the treatment with cSsALF24, attributing anti-inflammatory potential of the peptide. Collectively, these findings suggest that cSsALF24 might regulate the vaginal epithelial cell immune responses indirectly through modulation of LPS-TLR4 binding in NF-kB pathway.

The still obscure attributes of cryptococcal glucuronoxylomannan

Glucuronoxylomannan (GXM) is the major capsular polysaccharide of Cryptococcus neoformans. It is essential for fungal virulence and causes a number of deleterious effects to host cells. During the last decades, most of the experimental models designed to study the roles of GXM during cryptococcal infection were based on the stimulation of animal cells. This most commonly involved macrophages or other effector cells, with polysaccharide fractions obtained by precipitation with cationic detergents. More recently, it has been demonstrated that GXM interferes with the physiological state of other target cells, such as the epithelium. In addition, recent studies indicate that the structure of the polysaccharide and, consequently, its functions vary according with the method used for its purification. This raises questions as to what is native GXM and the significance of prior studies. In this paper, we discuss some of the aspects of GXM that are still poorly explored in the current literature, including the relevance of the polysaccharide in the interaction of cryptococci with non-phagocytic cells and the relationship between its structure and biological activity.

Significance of MD-2 and MD-2B expression in rat liver during acute cholangitis

AIM

To investigate the expression of myeloid differentiation protein-2 (MD-2), MD-2B (a splicing isoform of MD-2 that can block Toll-like receptor 4 (TLR4)/MD-2 LPS-mediated signal transduction) and TLR4 in the liver of acute cholangitis rats.

METHODS

Male Sprague-Dawley rats (SPF level) were randomly divided into four groups: (A) sham-operated group; (B) simple common bile duct ligation group; (C) acute cholangitis group; and (D) acute cholangitis anti-TLR4 intervention group (n = 25 per group). Rat liver tissue samples were used to detect TLR4, MD-2 and MD-2B mRNA expression by fluorescence quantitative PCR in parallel with pathological changes.

RESULTS

In acute cholangitis, liver TLR4 and MD-2 mRNA expression levels at 6, 12, 24, 48 and 72 h were gradually up-regulated but MD-2B mRNA expression gradually down-regulated (P < 0.05). After TLR4 antibody treatment, TLR4 and MD-2 mRNA expression were lower compared with the acute cholangitis group (P < 0.05). However, MD-2B mRNA expression was higher than in the acute cholangitis group (P < 0.05). MD-2 and TLR4 mRNA expressions were positively correlated (r = 0.94981, P < 0.05) and MD-2B mRNA expression was negatively correlated with MD-2 and TLR4 mRNA (r = -0.89031, -0.88997, P < 0.05).

CONCLUSION

In acute cholangitis, MD-2 plays an important role in the process of TLR4- mediated inflammatory response to liver injury while MD-2B plays a negative regulatory role.

Chromogranin A detection in saliva of type 2 diabetes patients

Chromogranin A is present in secretion granules of nerve, endocrine and immune cells and is a precursor of several peptides with antibacterial and antifungal properties at micromolar concentrations.Our aim in this prospective, double blind study, was to determine the expression of chromogranin A and its peptides at protein level in saliva of type 2 diabetic patients and thereby to obtain a new non-invasive diagnostic means for the future.Saliva was taken from 30 type 2 diabetic patients and 30 healthy individuals at the same time interval in the morning without any oral stimuli. Circadianic periodics in protein productions have been avoided. The presence of chromogranin A and its derived peptides was determined in whole saliva, after centrifugation at 40C for 12 min at 14 000 rpm, by SDS-PAGE electrophoresis and Immunoblotting (Western Blot). To ensure same protein concentrations Bradford protein quantification assay has been performed before.For the first time, we have determined an overexpression of chromogranin A in saliva of diabetic patients in 100% of the individuals. Chromogranin A, a circulating biomarker for epithelial tumours, is also overexpressed in saliva of type 2 diabetic patients. To confirm our results, more studies with a large amount of patients is necessary.

An overview of methods used to clarify pathogenesis mechanisms of Campylobacter jejuni

Thermotolerant campylobacters are the most frequent cause of bacterial infection of the lower intestine worldwide. The mechanism of pathogenesis of Campylobacter jejuni comprises four main stages: adhesion to intestinal cells, colonization of the digestive tract, invasion of targeted cells, and toxin production. In response to the high number of cases of human campylobacteriosis, various virulence study models are available according to the virulence stage being analyzed. The aim of this review is to compare the different study models used to look at human disease. Molecular biology tools used to identify genes or proteins involved in virulence mechanisms are also summarized. Despite high cost and limited availability, animal models are frequently used to study digestive disease, in particular to analyze the colonization stage. Eukaryotic cell cultures have been developed because of fewer restrictions on their use and the lower cost of these cultures compared with animal models, and this ex vivo approach makes it possible to mimic the bacterial cell-host interactions observed in natural disease cases. Models are complemented by molecular biology tools, especially mutagenesis and DNA microarray methods to identify putative virulence genes or proteins and permit their characterization. No current model seems to be ideal for studying the complete range of C. jejuni virulence. However, the models available deal with different aspects of the complex pathogenic mechanisms particular to this bacterium.

TLR4 signaling induced by lipopolysaccharide or paclitaxel regulates tumor survival and chemoresistance in ovarian cancer

Toll-like receptors (TLRs) expressed on immune cells trigger inflammatory responses. TLRs are also expressed on ovarian cancer (OvCa) cells, but the consequences of signaling by the TLR4/MyD88 pathway in these cells are unclear. Here, TLR4 and MyD88 expression in OvCa tissues (n=20) and cell lines (OVCAR3, SKOV3, AD10, A2780 and CP70) was evaluated by reverse transcriptase-PCR, western blots and immunohistochemistry. Cell growth, apoptosis, nuclear factor-kappaB (NF-kappaB) translocation, IRAK4 and TRIF expression and cJun phosphorylation were measured following tumor cell exposure to the TLR4 ligands, lipopolysaccharide (LPS) or paclitaxel (PTX). Culture supernatants were tested for cytokine levels. TLR4 was expressed in all tumors, tumor cell lines and normal epithelium. MyD88 was detectable in tumor tissues and in 3/5 OvCa lines but not in normal cells. In MyD88(+) SCOV3 cells, LPS or PTX binding to TLR4 induced IRAK4 activation and cJun phosphorylation, activated the NF-kappaB pathway and promoted interleukin (IL)-8, IL-6, vascular endothelial growth factor and monocyte chemotactic protein-1 production and resistance to drug-induced apoptosis. Silencing of TLR4 in SCOV3 cells with small interference RNA resulted in phosphorylated-cJun (p-cJun) downregulation and a loss of PTX resistance. In PTX-sensitive, MyD88(neg) A2780 cells, TLR4 stimulation upregulated TRIF, and TLR4 silencing eliminated this effect. Thus, TLR4/MyD88 signaling supports OvCa progression and chemoresistance, promoting immune escape.

Models of oral and vaginal candidiasis based on in vitro reconstituted human epithelia for the study of host-pathogen interactions

This protocol describes the setup, maintenance, and characteristics of models of oral and vaginal candidiasis based on well-established three-dimensional organotypic tissues of human oral and vaginal mucosa. Infection experiments are highly reproducible and can be used for the direct analysis of pathogen/epithelial cell interactions. Using the models, the several stages of infection by wild-type Candida albicans strains, the consequence of gene disruption of putative virulence factors in mutant cells, and the evaluation of the host immune response can be evaluated by histologic, biochemical, and molecular methods. As such, the models provide clear answers regarding protein and gene expression that are not complicated by nonepithelial factors. To study the impact of several host components, the mucosal infection models can be supplemented with immune cells, saliva, and probiotic bacteria, which might be relevant for host defense. It requires at least 3 days to be established and can be maintained thereafter for 2 to 4 days.

Toll-like receptors and cytokines as surrogate biomarkers for evaluating vaginal immune response following microbicide administration

Topical microbicides are intended for frequent use by women in reproductive age. Hence, it is essential to evaluate their impact on mucosal immune function in the vagina. In the present study, we evaluated nisin, a naturally occurring antimicrobial peptide (AMP), for its efficacy as an intravaginal microbicide. Its effect on the vaginal immune function was determined by localizing Toll-like receptors (TLRs-3, 9) and cytokines (IL-4, 6 , 10 and TNF-α) in the rabbit cervicovaginal epithelium following intravaginal administration of high dose of nisin gel for 14 consecutive days. The results revealed no alteration in the expression of TLRs and cytokines at both protein and mRNA levels. However, in SDS gel-treated group, the levels were significantly upregulated with the induction of NF-κB signalling cascade. Thus, TLRs and cytokines appear as sensitive indicators for screening immunotoxic potential of candidate microbicides.

Host-pathogen interactions in Campylobacter infections: the host perspective

Campylobacter is a major cause of acute bacterial diarrhea in humans worldwide. This study was aimed at summarizing the current understanding of host mechanisms involved in the defense against Campylobacter by evaluating data available from three sources: (i) epidemiological observations, (ii) observations of patients, and (iii) experimental observations including observations of animal models and human volunteer studies. Analysis of available data clearly indicates that an effective immune system is crucial for the host defense against Campylobacter infection. Innate, cell-mediated, and humoral immune responses are induced during Campylobacter infection, but the relative importance of these mechanisms in conferring protective immunity against reinfection is unclear. Frequent exposure to Campylobacter does lead to the induction of short-term protection against disease but most probably not against colonization. Recent progress in the development of more suitable animal models for studying Campylobacter infection has opened up possibilities to study the importance of innate and adaptive immunity during infection and in protection against reinfection. In addition, advances in genomics and proteomics technologies will enable more detailed molecular studies. Such studies combined with better integration of host and pathogen research driven by epidemiological findings may truly advance our understanding of Campylobacter infection in humans.

TLR4 signaling promotes the expression of VEGF and TGFbeta1 in human prostate epithelial PC3 cells induced by lipopolysaccharide

Chronic inflammation promotes tumor development and progression, and Toll-like receptors (TLRs) may play an important role in this process. In this study, we found that human prostate epithelial PC3 cells constitutively express TLR4 in mRNA and protein level. lipopolysaccharide (LPS) promotes the expression and secretion of immunosuppressive cytokine TGFbeta(1) and proangiogenic factor VEGF in human prostate epithelial PC3 cells. We further elucidated that functionally activation of TLR4 is essential for the increased VEGF and TGFbeta(1) mRNA expression in the cells. In addition, after LPS stimulation, the increased expression of NF-(K)B p65 protein was also detected in human PC3 cells. Our results demonstrate that TLR4 expressed on human PC3 cells is functionally active, and may play important roles in promoting prostate cancer immune escape, survival, progression, and metastasis by inducing immunosuppressive and proangiogenic cytokines.

Human epithelial cells establish direct antifungal defense through TLR4-mediated signaling

Mammalian TLRs are central mediators of the innate immune system that instruct cells of the innate and adaptive response to clear microbial infections. Here, we demonstrate that human epithelial TLR4 directly protected the oral mucosa from fungal infection via a process mediated by polymorphonuclear leukocytes (PMNs). In an in vitro epithelial model of oral candidiasis, the fungal pathogen Candida albicans induced a chemoattractive and proinflammatory cytokine response but failed to directly modulate the expression of genes encoding TLRs. However, the addition of PMNs to the C. albicans-infected model strongly upregulated cytoplasmic and cell-surface epithelial TLR4 expression, which correlated directly with protection against fungal invasion and cell injury. C. albicans invasion and cell injury was restored by the addition of TLR4-specific neutralizing antibodies and knockdown of TLR4 using RNA interference, even in the presence of PMNs, demonstrating the direct role of epithelial TLR4 in the protective process. Furthermore, treatment with neutralizing antibodies specific for TNF-alpha resulted in strongly reduced TLR4 expression accompanied by augmented epithelial cell damage and fungal invasion. To our knowledge, this is the first description of such a PMN-dependent, TLR4-mediated protective mechanism at epithelial surfaces, which may provide significant insights into how microbial infections are managed and controlled in the oral mucosa.

Models of oral and vaginal candidiasis based on in vitro reconstituted human epithelia

This protocol describes the setup, maintenance and characteristics of models of epithelial Candida infections based on well-established three-dimensional organotypic tissues of human oral and vaginal mucosa. Infection experiments are highly reproducible and can be used for the direct analysis of pathogen-epithelial cell interactions. This allows detailed investigations of Candida albicans wild type or mutant strain interaction with epithelial tissue or the evaluation of the host immune response using histological, biochemical and molecular methods. As such, the models can be utilized as a tool to investigate cellular interactions or protein and gene expression that are not complicated by non-epithelial factors. To study the impact of innate immunity or the antifungal activity of natural and non-natural compounds, the mucosal infection models can be supplemented with immune cells, antimicrobial agents or probiotic bacteria. The model requires at least 3 days to be established and can be maintained thereafter for 2-4 days.

Intestinal innate immunity and the pathogenesis of Salmonella enteritis

Acute gastroenteritis caused by Salmonella typhimurium infection is a clinical problem with significant public health impact. The availability of several experimental models of this condition has allowed detailed investigation of the cellular and molecular interactions involved in its pathogenesis. Such studies have shed light on the roles played by bacterial virulence factors and host innate immune mechanisms in the development of intestinal inflammation.

TLR2 activation by proteosomes promotes uptake of particulate vaccines at mucosal surfaces

Proteosome-based vaccines have TLR2-based adjuvant activity and show promise for mucosal immunization. We examined the effects of proteosomes on mucosal uptake in Peyer's patches in vivo. Proteosomes accelerated transepithelial transport of microparticles by M cells and induced migration of dendritic cells (DCs) into the follicle-associated epithelium (FAE); both effects were dependent on TLR2. Proteosomes induced the release of the DC-attracting chemokine MIP3alpha from Caco-2 epithelial cells in vitro. In HEK cells, proteosome-mediated MIP3alpha release was dependent on TLR2 expression and matrix metalloproteinase activation. Thus, TLR2 activation by proteosomes may promote mucosal uptake of particulate vaccines, and this may contribute to their adjuvanticity.