Bacteroides fragilis enterotoxin induces human beta-defensin-2 expression in intestinal epithelial cells via a mitogen-activated protein kinase/I kappaB kinase/NF-kappaB-dependent pathway

Intraduodenal fecal microbiota transplantation ameliorates gut atrophy and cholestasis in a novel parenteral nutrition piglet model

Total parenteral nutrition (TPN) provides lifesaving nutritional support intravenously; however, it is associated with significant side effects. Given gut microbial alterations noted with TPN, we hypothesized that transferring fecal microbiota from healthy controls would restore gut-systemic signaling in TPN and mitigate injury. Using our novel ambulatory model (US Patent: US 63/136,165), 31 piglets were randomly allocated to enteral nutrition (EN), TPN only, TPN + antibiotics (TPN-A), or TPN + intraduodenal fecal microbiota transplant (TPN + FMT) for 14 days. Gut, liver, and serum were assessed through histology, biochemistry, and qPCR. Stool samples underwent 16 s rRNA sequencing. Permutational multivariate analysis of variance, Jaccard, and Bray-Curtis metrics were performed. Significant bilirubin elevation in TPN and TPN-A versus EN (P < 0.0001) was prevented with FMT. IFN-G, TNF-α, IL-β, IL-8, and lipopolysaccharide (LPS) were significantly higher in TPN (P = 0.009, P = 0.001, P = 0.043, P = 0.011, P < 0.0001), with preservation upon FMT. Significant gut atrophy by villous-to-crypt ratio in TPN (P < 0.0001) and TPN-A (P = 0.0001) versus EN was prevented by FMT (P = 0.426 vs. EN). Microbiota profiles using principal coordinate analysis demonstrated significant FMT and EN overlap, with the largest separation in TPN-A followed by TPN, driven primarily by Firmicutes and Fusobacteria. TPN-altered gut barrier was preserved upon FMT; upregulated cholesterol 7 α-hydroxylase and bile salt export pump in TPN and TPN-A and downregulated fibroblast growth factor receptor 4, EGF, farnesoid X receptor, and Takeda G Protein-coupled Receptor 5 (TGR5) versus EN was prevented by FMT. This study provides novel evidence of prevention of gut atrophy, liver injury, and microbial dysbiosis with intraduodenal FMT, challenging current paradigms into TPN injury mechanisms and underscores the importance of gut microbes as prime targets for therapeutics and drug discovery.NEW & NOTEWORTHY Intraduodenal fecal microbiota transplantation presents a novel strategy to mitigate complications associated with total parenteral nutrition (TPN), highlighting gut microbiota as a prime target for therapeutic and diagnostic approaches. These results from a highly translatable model provide hope for TPN side effect mitigation for thousands of chronically TPN-dependent patients.

Kidney-tonifying blood-activating decoction delays ventricular remodeling in rats with chronic heart failure by regulating gut microbiota and metabolites and p38 mitogen-activated protein kinase/p65 nuclear factor kappa-B/aquaporin-4 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Myocardial infarction has likely contributed to the increased prevalence of heart failure(HF).As a result of ventricular remodeling and reduced cardiac function, colonic blood flow decreases, causing mucosal ischemia and hypoxia of the villous structure of the intestinal wall.This damage in gut barrier function increases bowel wall permeability, leading to fluid metabolism disorder,gut microbial dysbiosis, increased gut bacteria translocation into the circulatory system and increased circulating endotoxins, thus promoting a typical inflammatory state.Traditional Chinese Medicine plays a key role in the prevention and treatment of HF.Kidney-tonifying Blood-activating(KTBA) decoction has been proved for clinical treatment of chronic HF.However,the mechanism of KTBA decoction on chronic HF is still unclear.

AIMS OF THE STUDY

The effect of KTBA decoction on gut microbiota and metabolites and p38MAPK/p65NF-κB/AQP4 signaling in rat colon was studied to investigate the mechanism that KTBA decoction delays ventricular remodeling and regulates water metabolism disorder in rats with HF after myocardial infarction based on the theory of "Kidney Storing Essence and Conducting Water".

MATERIAL AND METHODS

In vivo,a rat model of HF after myocardial infarction was prepared by ligating the left anterior descending coronary artery combined with exhaustive swimming and starvation.The successful modeling rats were randomly divided into five groups:model group, tolvaptan group(gavaged 1.35mg/(kg•D) tolvaptan),KTBA decoction group(gavaged 15.75g/(kg•D) of KTBA decoction),KTBA decoction combined with SB203580(p38MAPK inhibitor) group(gavaged 15.75g/(kg•D) of KTBA decoction and intraperitoneally injected 1.5mg/(kg•D) of SB203580),and KTBA decoction combined with PDTC(p65NF-kB inhibitor) group(gavaged 15.75g/(kg•D) of KTBA decoction and intraperitoneally injected 120mg/(kg•D) of PDTC).The sham-operation group and model group were gavaged equal volume of normal saline.After 4 weeks of intervention with KTBA decoction,the effect of KTBA decoction on the cardiac structure and function of chronic HF model rats was observed by ultrasonic cardiogram.General state and cardiac index in rats were evaluated.Enzyme linked immunosorbent assay(ELISA) was used to measure N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration in rat serum.Hematoxylin and eosin(H&E) staining,and transmission electron microscope(TEM) were used to observe the morphology and ultrastructure of myocardial and colonic tissue,and myocardial fibrosis was measured by Masson's staining.Cardiac E-cadherin level was detected by Western blot.The mRNA expression and protein expression levels of p38MAPK,I-κBα, p65NF-κB,AQP4,Occludin and ZO-1 in colonic tissue were detected by reverse transcription-quantitative real-time polymerase chain reaction(RT-qPCR) and immunohistochemistry. Protein expression of p38MAPK, p-p38MAPK,I-κBα,p-I-κBα,p65NF-κB, p-p65NF-κB,AQP4,Occludin and ZO-1 in rat colon was detected using Western blot.Colonic microbiota and serum metabolites were respectively analyzed by amplicon sequencing and liquid chromatography-mass spectrometry.In vitro, CCD-841CoN cell was placed in the ischemic solution under hypoxic conditions (94%N2,5%CO2,and 1%O2) in a 37 °C incubator to establish an ischemia and hypoxia model.The CCD-841CoN cells were divided into 7 groups, namely blank group and model group with normal rat serum plus control siRNA, tolvaptan group with rat serum containing tolvaptan plus control siRNA, KTBA group with rat serum containing KTBA plus control siRNA, KTBA plus p38MAPK siRNA group, KTBA plus p65NF-κB siRNA group,and KTBA plus AQP4siRNA group.After 24h and 48h of intervention with KTBA decoction,RT-qPCR,immunofluorescence and Western blot was used to detect the mRNA expression and protein expression levels of p38MAPK,I-κBα,p65NF-κB,AQP4, Occludin and ZO-1 in CCD-841CoN cells.

RESULTS

Compared with the model, KTBA decoction improved the general state, decraesed the serum NT-proBNP level,HW/BW ratio, LVIDd and LVIDs, increased E-cadherin level,EF and FS,reduced number of collagen fibers deposited in the myocardial interstitium,and recovered irregular arrangement of myofibril and swollen or vacuolated mitochondria with broken crista in myocardium.Moreover, KTBA decoction inhibited the expression of p38MAPK,I-κBα,and p65NF-κB and upregulated AQP4, Occludin and ZO-1 in colon tissues and CCD-841CoN cells.Additionally,p38siRNA or SB203580, p65siRNA or PDTC, and AQP4siRNA partially weakened the protective effects of KTBA in vitro and vivo.Notably,The LEfSe analysis results showed that there were six gut biomaker bacteria in model group, including Allobaculum, Bacillales,Turicibacter, Turicibacterales,Turicibacteraceae,and Bacilli. Besides, three gut biomaker bacteria containing Deltaproteobacteria, Desulfovibrionaceae,and Desulfovibrionales were enriched by KTBA treatment in chronic HF model.There were five differential metabolites, including L-Leucine,Pelargonic acid, Capsidiol,beta-Carotene,and L- Erythrulose, which can be regulated back in the same changed metabolic routes by the intervention of KTBA.L-Leucine had the positive correlation with Bacillales, Turicibacterales,Turicibacteraceae,and Turicibacter.L-Leucine significantly impacts Protein digestion and absorption, Mineral absorption,and Central carbon metabolism in cancer regulated by KTBA, which is involved in the expression of MAPK and tight junction in intestinal epithelial cells.

CONCLUSIONS

KTBA decoction manipulates the expression of several key proteins in the p38MAPK/p65NF-κB/AQP4 signaling pathway, modulates gut microbiota and metabolites toward a more favorable profile, improves gut barrier function, delays cardiomyocyte hypertrophy and fibrosis,and improves cardiac function.

The role of the microscopic world: Exploring the role and potential of intratumoral microbiota in cancer immunotherapy

Microorganisms, including bacteria, viruses, and fungi, coexist in the human body, forming a symbiotic microbiota that plays a vital role in human health and disease. Intratumoral microbial components have been discovered in various tumor tissues and are closely linked to the occurrence, progression, and treatment results of cancer. The intratumoral microbiota can enhance antitumor immunity through mechanisms such as activating the stimulator of interferon genes signaling pathway, stimulating T and NK cells, promoting the formation of TLS, and facilitating antigen presentation. Conversely, the intratumoral microbiota might suppress antitumor immune responses by increasing reactive oxygen species levels, creating an anti-inflammatory environment, inducing T cell inactivation, and enhancing immune suppression, thereby promoting cancer progression. The impact of intratumoral microbiota on antitumor immunity varies based on microbial composition, interactions with cancer cells, and the cancer's current state. A deep understanding of the complex interactions between intratumoral microbiota and antitumor immunity holds the potential to bring new therapeutic strategies and targets to cancer immunotherapy.

Intratumoral microorganisms in tumors of the digestive system

Tumors of the digestive system pose a significant threat to human health and longevity. These tumors are associated with high morbidity and mortality rates, leading to a heavy economic burden on healthcare systems. Several intratumoral microorganisms are present in digestive system tumors, and their sources and abundance display significant heterogeneity depending on the specific tumor subtype. These microbes have a complex and precise function in the neoplasm. They can facilitate tumor growth through various mechanisms, such as inducing DNA damage, influencing the antitumor immune response, and promoting the degradation of chemotherapy drugs. Therefore, these microorganisms can be targeted to inhibit tumor progression for improving overall patient prognosis. This review focuses on the current research progress on microorganisms present in the digestive system tumors and how they influence the initiation, progression, and prognosis of tumors. Furthermore, the primary sources and constituents of tumor microbiome are delineated. Finally, we summarize the application potential of intratumoral microbes in the diagnosis, treatment, and prognosis prediction of digestive system tumors. Video Abstract.

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

Intratumoral microbiota: roles in cancer initiation, development and therapeutic efficacy

Microorganisms, including bacteria, viruses, fungi, and other eukaryotes, play critical roles in human health. An altered microbiome can be associated with complex diseases. Intratumoral microbial components are found in multiple tumor tissues and are closely correlated with cancer initiation and development and therapy efficacy. The intratumoral microbiota may contribute to promotion of the initiation and progression of cancers by DNA mutations, activating carcinogenic pathways, promoting chronic inflammation, complement system, and initiating metastasis. Moreover, the intratumoral microbiota may not only enhance antitumor immunity via mechanisms including STING signaling activation, T and NK cell activation, TLS production, and intratumoral microbiota-derived antigen presenting, but also decrease antitumor immune responses and promote cancer progression through pathways including upregulation of ROS, promoting an anti-inflammatory environment, T cell inactivation, and immunosuppression. The effect of intratumoral microbiota on antitumor immunity is dependent on microbiota composition, crosstalk between microbiota and the cancer, and status of cancers. The intratumoral microbiota may regulate cancer cell physiology and the immune response by different signaling pathways, including ROS, β-catenin, TLR, ERK, NF-κB, and STING, among others. These viewpoints may help identify the microbiota as diagnosis or prognosis evaluation of cancers, and as new therapeutic strategy and potential therapeutic targets for cancer therapy.

Lower systemic inflammation is associated with gut firmicutes dominance and reduced liver injury in a novel ambulatory model of parenteral nutrition

BACKGROUND

Total Parenteral Nutrition (TPN) provides lifesaving nutritional support to patients unable to maintain regular enteral nutrition (EN). Unfortunately, cholestasis is a significant side effect affecting 20-40% of paediatric patients. While the aetiology of TPN-associated injury remains ill-defined, an altered enterohepatic circulation in the absence of gut luminal nutrient content during TPN results in major gut microbial clonal shifts, resulting in metabolic endotoxemia and systemic inflammation driving liver injury and cholestasis.

HYPOTHESIS

To interrogate the role of gut microbiota, using our novel ambulatory TPN piglet model, we hypothesized that clonal reduction of bacteria in Firmicutes phylum (predominant in EN) and an increase in pathogenic Gram-negative bacteria during TPN correlates with an increase in serum lipopolysaccharide and systemic inflammatory cytokines, driving liver injury.

METHODS

Upon institutional approval, 16 animals were allocated to receive either TPN (n = 7) or EN only (n = 9). The TPN group was subdivided into a low systemic inflammation (TPN-LSI) and high systemic inflammation (TPN-HSI) based on the level of serum lipopolysaccharide. Culture-independent identification of faecal bacterial populations was determined by 16S rRNA.

RESULTS

Piglets on TPN, in the TPN-HSI group, noted a loss of enterocyte protective Firmicutes bacteria and clonal proliferation of potent inflammatory and lipopolysaccharide containing pathogens: Fusobacterium, Bacteroidetes and Campylobacter compared to EN animals. Within the TPN group, the proportion of Firmicutes phylum correlated with lower portal lipopolysaccharide levels (r = -0.89). The TPN-LSI had a significantly lower level of serum bile acids compared to the TPN-HSI group (7.3 vs. 60.4 mg/dL; p = .018), increased day 14 weight (5.67 vs. 5.07 kg; p = .017) as well as a 13.7-fold decrease in serum conjugated bilirubin.

CONCLUSION

We demonstrate a novel relationship between the gut microbiota and systemic inflammation in a TPN animal model. Pertinently, the degree of gut dysbiosis correlated with the severity of systemic inflammation. This study underscores the role of gut microbiota in driving liver injury mechanisms during TPN and supports a paradigm change in therapeutic targeting of the gut microbiota to mitigate TPN-related injury. KEY MESSAGESThis study identified a differential link between gut microbiota and inflammation-the higher the dysbiosis, the worse the systemic inflammatory markers.Higher levels of Firmicutes species correlated with reduced inflammation.

Novel Therapeutic Approaches for Mitigating Complications in Short Bowel Syndrome

Short bowel syndrome (SBS) is a particularly serious condition in which the small intestine does not absorb sufficient nutrients for biological needs, resulting in severe illness and potentially death if not treated. Given the important role of the gut in many signaling cascades throughout the body, SBS results in disruption of many pathways and imbalances in various hormones. Due to the inability to meet sufficient nutritional needs, an intravenous form of nutrition, total parental nutrition (TPN), is administered. However, TPN presents difficulties such as severe liver injury and altered signaling secondary to the continued lack of luminal contents. This manuscript aims to summarize relevant studies into the systemic effects of TPN on systems such as the gut-brain, gut-lung, and gut-liver axis, as well as present novel therapeutics currently under use or investigation as mitigation strategies for TPN induced injury.

A systemic review of the role of enterotoxic Bacteroides fragilis in colorectal cancer

Enterotoxigenic Bacteroides fragilis (ETBF) has received significant attention for a possible association with, or causal role in, colorectal cancer (CRC). The goal of this review was to assess the status of the published evidence supporting (i) the association between ETBF and CRC and (ii) the causal role of ETBF in CRC. PubMed and Scopus searches were performed in August 2021 to identify human, animal, and cell studies pertaining to the role of ETBF in CRC. Inclusion criteria included the use of cell lines, mice, exposure to BFT or ETBF, and detection of bft. Review studies were excluded, and studies were limited to the English language. Quality of study design and risk of bias analysis was performed on the cell, animal, and human studies using ToxRTools, SYRCLE, and NOS, respectively. Ninety-five eligible studies were identified, this included 22 human studies, 24 animal studies, 43 cell studies, and 6 studies that included both cells and mice studies. We found that a large majority of studies supported an association or causal role of ETBF in CRC, as well as high levels of study bias was detected in the in vitro and in vivo studies. The high-level heterogeneity in study design and reporting made it difficult to synthesize these findings into a unified conclusion, suggesting that the need for future studies that include improved mechanistic models, longitudinal in vitro and in vivo evidence, and appropriate control of confounding factors will be required to confirm whether ETBF has a direct role in CRC etiopathogenesis.

Beyond lipids: Novel mechanisms for parenteral nutrition-associated liver disease

Parenteral nutrition (PN) is a therapy that delivers essential nutrients intravenously to patients who are unable to meet their nutrition requirements via standard enteral feeding. This methodology is often referred to as PN when accompanied by minimal or no enteral nutrition (EN). Although PN is lifesaving, significant complications can arise, such as intestinal failure-associated liver disease and gut-mucosal atrophy. The exact mechanism of injury remains ill defined. This review was designed to explore the available literature related to the drivers of injury mechanisms. The Farnesoid X receptor and fibroblast growth factor 19 signaling pathway seems to play an important role in gut-systemic signaling, and its alteration during PN provides insights into mechanistic links. Central line infections also play a key role in mediating PN-associated injury. Although lipid reduction strategies, as well as the use of multicomponent lipid emulsions and vitamin E, have shown promise, the cornerstone of preventing injury is the early establishment of EN.

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

Ferulic Acid Metabolites Attenuate LPS-Induced Inflammatory Response in Enterocyte-like Cells

Ferulic acid (FA) is a polyphenol pertaining to the class of hydroxycinnamic acids present in numerous foods of a plant origin. Its dietary consumption leads to the formation of several phase I and II metabolites in vivo, which represent the largest amount of ferulates in the circulation and in the intestine in comparison with FA itself. In this work, we evaluated their efficacy against the proinflammatory effects induced by lipopolysaccharide (LPS) in intestinal Caco-2 cell monolayers, as well as the mechanisms underlying their protective action. LPS-induced overexpression of proinflammatory enzymes such as inducible nitric oxide synthase (iNOS) and the consequent hyperproduction of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) were limited by physiological relevant concentrations (1 µM) of FA, its derivatives isoferulic acid (IFA) and dihydroferulic acid (DHFA), and their glucuronidated and sulfated metabolites, which acted upstream by limiting the activation of MAPK p38 and ERK and of Akt kinase, thus decreasing the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB) translocation into the nucleus. Furthermore, the compounds were found to promote the expression of Nrf2, which may have contributed to the downregulation of NF-ĸB activity. The overall data show that phase I/II metabolites retain the efficacy of their dietary free form in contrasting inflammatory response.

Recombinant Bacteroides fragilis enterotoxin-1 (rBFT-1) promotes proliferation of colorectal cancer via CCL3-related molecular pathways

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers worldwide and stands among the leading causes of cancer-related deaths. Although deregulation of the microbiota in the gastrointestinal tract has been frequently described in CRC, very little is known about the precise molecular mechanisms by which bacteria and their toxins modulate the process of tumorigenesis and behavior of cancer cells. In this study, we produced recombinant Bacteroides fragilis enterotoxin-1 (rBFT1) and demonstrate that rBFT1 could promote cell proliferation in colorectal cancer cells and accelerate tumor growth in vivo. To identify the mechanisms, we further investigated CCL3/CCR5 and NF-κB pathway. We found that CCL3, CCR5, NF-κB, and TRAF-6 were dramatically upregulated after rBFT1 treatment, thus suggesting that the role of rBFT1 in CRC progression may be associated with CCL3/CCR5 and NF-κB pathways. Collectively, our results indicate that rBFT1 serves as a tumor promoter and plays a crucial role in inducing the proliferation of CRC via accelerating CCL3-related molecular pathway, thus giving insights into mechanistic underpinnings for the prevention and treatment of CRC.

Bacteroides fragilis Enterotoxin Induces Sulfiredoxin-1 Expression in Intestinal Epithelial Cell Lines Through a Mitogen-Activated Protein Kinases- and Nrf2-Dependent Pathway, Leading to the Suppression of Apoptosis

Enterotoxigenic Bacteroides fragilis is a causative agent of colitis and secrets enterotoxin (BFT), leading to the disease. Sulfiredoxin (Srx)-1 serves to protect from oxidative damages. Although BFT can generate reactive oxygen species in intestinal epithelial cells (IECs), no Srx-1 expression has been reported in ETBF infection. In this study, we explored the effects of ETBF-produced BFT on Srx-1 induction in IECs. Treatment of IECs with BFT resulted in increased expression of Srx-1 in a time-dependent manner. BFT treatment also activated transcriptional signals including Nrf2, AP-1 and NF-κB, and the Srx-1 induction was dependent on the activation of Nrf2 signals. Nrf2 activation was assessed using immunoblot and Nrf2-DNA binding activity and the specificity was confirmed by supershift and competition assays. Suppression of NF-κB or AP-1 signals did not affect the upregulation of Srx-1 expression. Nrf2-dependent Srx-1 expression was associated with the activation of p38 mitogen-activated protein kinases (MAPKs) in IECs. Furthermore, suppression of Srx-1 significantly enhanced apoptosis while overexpression of Srx-1 significantly attenuated apoptosis during exposure to BFT. These results imply that a signaling cascade involving p38 and Nrf2 is essential for Srx-1 upregulation in IECs stimulated with BFT. Following this upregulation, Srx-1 may control the apoptosis in BFT-exposed IECs.

Mechanisms of Parenteral Nutrition-Associated Liver and Gut Injury

Parenteral nutrition (PN) has revolutionized the care of patients with intestinal failure by providing nutrition intravenously. Worldwide, PN remains a standard tool of nutrition delivery in neonatal, pediatric, and adult patients. Though the benefits are evident, patients receiving PN can suffer serious cholestasis due to lack of enteral feeding and sometimes have fatal complications from liver injury and gut atrophy, including PN-associated liver disease or intestinal failure-associated liver disease. Recent studies into gut-systemic cross talk via the bile acid-regulated farnesoid X receptor (FXR)-fibroblast growth factor 19 (FGF19) axis, gut microbial control of the TGR5-glucagon-like peptide (GLP) axis, sepsis, and role of prematurity of hepatobiliary receptors are greatly broadening our understanding of PN-associated injury. It has also been shown that the composition of ω-6/ω-3 polyunsaturated fatty acids given parenterally as lipid emulsions can variably drive damage to hepatocytes and cell integrity. This manuscript reviews the mechanisms for the multifactorial pathogenesis of liver disease and gut injury with PN and discusses novel ameliorative strategies.

Good Gone Bad: One Toxin Away From Disease for Bacteroides fragilis

The human gut is colonized by hundreds of trillions of microorganisms whose acquisition begins during early infancy. Species from the Bacteroides genus are ubiquitous commensals, comprising about thirty percent of the human gut microbiota. Bacteroides fragilis is one of the least abundant Bacteroides species, yet is the most common anaerobe isolated from extraintestinal infections in humans. A subset of B. fragilis strains carry a genetic element that encodes a metalloprotease enterotoxin named Bacteroides fragilis toxin, or BFT. Toxin-bearing strains, or Enterotoxigenic B. fragilis (ETBF) cause acute and chronic intestinal disease in children and adults. Despite this association with disease, around twenty percent of the human population appear to be asymptomatic carriers of ETBF. BFT damages the colonic epithelial barrier by inducing cleavage of the zonula adherens protein E-cadherin and initiating a cell signaling response characterized by inflammation and c-Myc-dependent pro-oncogenic hyperproliferation. As a consequence, mice harboring genetic mutations that predispose to colonic inflammation or tumor formation are uniquely susceptible to toxin-mediated injury. The recent observation of ETBF-bearing biofilms in colon biopsies from humans with colon cancer susceptibility loci strongly suggests that ETBF is a driver of colorectal cancer. This article will address ETBF biology from a host-pathobiont perspective, including clinical data, analysis of molecular mechanisms of disease, and the complex ecological context of the human gut.

Intestinal Epithelial Cells Exposed to Bacteroides fragilis Enterotoxin Regulate NF-κB Activation and Inflammatory Responses through β-Catenin Expression

The Bacteroides fragilis enterotoxin (BFT), a virulence factor of enterotoxigenic B. fragilis (ETBF), interacts with intestinal epithelial cells and can provoke signals that induce mucosal inflammation. Although β-catenin signaling is reported to be associated with inflammatory responses and BFT is known to cleave E-cadherin linked with β-catenin, little is known about the β-catenin-mediated regulation of inflammation in ETBF infection. This study was conducted to investigate the role of β-catenin as a cellular signaling intermediate in the induction of proinflammatory responses to stimulation of intestinal epithelial cells with BFT. Expression of β-catenin in intestinal epithelial cells was reduced relatively early after stimulation with BFT and then recovered to normal levels relatively late after stimulation. In contrast, phosphorylation of β-catenin in BFT-exposed cells occurred at high levels early in stimulation and decreased as time passed. Concurrently, late after stimulation the nuclear levels of β-catenin were relatively higher than those early after stimulation. Suppression of β-catenin resulted in increased NF-κB activity and interleukin-8 (IL-8) expression in BFT-stimulated cells. However, suppression or enhancement of β-catenin expression neither altered the phosphorylated IκB kinase α/β complex nor activated activator protein 1 signals. Furthermore, inhibition of glycogen synthase kinase 3β was associated with increased β-catenin expression and attenuated NF-κB activity and IL-8 expression in BFT-exposed cells. These findings suggest the negative regulation of NF-κB-mediated inflammatory responses by β-catenin in intestinal epithelial cells stimulated with BFT, resulting in attenuation of acute inflammation in ETBF infection.

Vascular smooth muscle-MAPK14 is required for neointimal hyperplasia by suppressing VSMC differentiation and inducing proliferation and inflammation

Injury-induced stenosis is a serious vascular complication. We previously reported that p38α (MAPK14), a redox-regulated p38MAPK family member was a negative regulator of the VSMC contractile phenotype in vitro. Here we evaluated the function of VSMC-MAPK14 in vivo in injury-induced neointima hyperplasia and the underlying mechanism using an inducible SMC-MAPK14 knockout mouse line (iSMC-MAPK14^-/-). We show that MAPK14 expression and activity were induced in VSMCs after carotid artery ligation injury in mice and ex vivo cultured human saphenous veins. While the vasculature from iSMC-MAPK14^-/- mice was indistinguishable from wildtype littermate controls at baseline, these mice exhibited reduced neointima formation following carotid artery ligation injury. Concomitantly, there was an increased VSMC contractile protein expression in the injured vessels and a decrease in proliferating cells. Blockade of MAPK14 through a selective inhibitor suppressed, while activation of MAPK14 by forced expression of an upstream MAPK14 kinase promoted VSMC proliferation in cultured VSMCs. Genome wide RNA array combined with VSMC lineage tracing studies uncovered that vascular injury evoked robust inflammatory responses including the activation of proinflammatory gene expression and accumulation of CD45 positive inflammatory cells, which were attenuated in iSMC-MAPK14^-/- mice. Using multiple pharmacological and molecular approaches to manipulate MAPK14 pathway, we further confirmed the critical role of MAPK14 in activating proinflammatory gene expression in cultured VSMCs, which occurs in a p65/NFkB-dependent pathway. Finally, we found that NOX4 contributes to MAPK14 suppression of the VSMC contractile phenotype. Our results revealed that VSMC-MAPK14 is required for injury-induced neointima formation, likely through suppressing VSMC differentiation and promoting VSMC proliferation and inflammation. Our study will provide mechanistic insights into therapeutic strategies for mitigation of vascular stenosis.

Role of the Gut⁻Liver Axis in Driving Parenteral Nutrition-Associated Injury

For decades, parenteral nutrition (PN) has been a successful method for intravenous delivery of nutrition and remains an essential therapy for individuals with intolerance of enteral feedings or impaired gut function. Although the benefits of PN are evident, its use does not come without a significant risk of complications. For instance, parenteral nutrition-associated liver disease (PNALD)—a well-described cholestatic liver injury—and atrophic changes in the gut have both been described in patients receiving PN. Although several mechanisms for these changes have been postulated, data have revealed that the introduction of enteral nutrition may mitigate this injury. This observation has led to the hypothesis that gut-derived signals, originating in response to the presence of luminal contents, may contribute to a decrease in damage to the liver and gut. This review seeks to present the current knowledge regarding the modulation of what is known as the “gut–liver axis” and the gut-derived signals which play a role in PN-associated injury.

Soy isoflavones enhance β-defensin synthesis and secretion in endometrial epithelial cells with exposure to TLR3 agonist polyinosinic-polycytidylic acid

PROBLEM

β-defensins are important innate chemical barriers that protect the endometrium from pathogen invasion. The effects of soy isoflavones, genistein and daidzein, on the expression and secretion of porcine β-defensins (PBD) in endometrial epithelial cells were investigated under normal or poly I:C-stimulated conditions.

METHOD OF STUDY

Primary cultured porcine endometrial epithelial (PE) cells were pretreated with genistein or daidzein followed by poly I:C inoculation. During treatment, the culture media were analyzed for PBD 1-4 secretion by ELISA and the total RNA for PBD gene expression by quantitative RT-PCR.

RESULTS

Porcine endometrial epithelial cells constitutively expressed PBD 1-4 and secreted PBD-1, PBD-2, and PBD-4. Genistein and daidzein enhanced PBD-2 expression and PBD-2 and PBD-3 secretion. These compounds also potentiated PBD-2 and PBD-3 expression and secretion which were upregulated by poly I:C.

CONCLUSION

Soy isoflavones, genistein and daidzein, could be potentially used for promoting the innate host defense of endometrium against infection.

Preserved Gut Microbial Diversity Accompanies Upregulation of TGR5 and Hepatobiliary Transporters in Bile Acid-Treated Animals Receiving Parenteral Nutrition

BACKGROUND

Parenteral nutrition (PN) is a lifesaving therapy but is associated with gut atrophy and cholestasis. While bile acids (BAs) can modulate intestinal growth via gut receptors, the gut microbiome likely influences gut proliferation and inflammation. BAs also regulate the bile salt export pump (BSEP) involved in cholestasis. We hypothesized that the BA receptor agonist oleanolic acid (OA) regulates gut TGR5 receptor and modulates gut microbiota to prevent PN-associated injury.

MATERIALS AND METHODS

Neonatal piglets were randomized to approximately 2 weeks of isocaloric enteral nutrition (EN), PN, or PN + enteral OA. Serum alanine aminotransferase, bilirubin, BAs, hepatic BSEP, gut TGR5, gut, liver morphology, and fecal microbiome utilizing 16S rRNA sequencing were evaluated. Kruskal-Wallis test, pairwise Mann-Whitney U test, and multilevel logistic regression analysis were performed.

RESULTS

PN support resulted in gut atrophy substantially prevented by OA. The median (interquartile range) for villous/crypt ratio was as follows: EN, 3.37 (2.82-3.80); PN, 1.73 (1.54-2.27); and OA, 2.89 (2.17-3.34; P = .006). Pairwise comparisons yielded P = .002 (EN vs PN), P = .180 (EN vs OA), P = .026 (PN vs OA). OA upregulated TGR5 and BSEP without significant improvement in serum bilirubin ( P = .095). A decreased microbial diversity and shift toward proinflammatory phylum Bacteroidetes were seen with PN, which was prevented by OA.

CONCLUSIONS

OA prevented PN-associated gut mucosal injury, Bacterioides expansion, and the decreased microbial diversity noted with PN. This study demonstrates a novel relationship among PN-associated gut dysfunction, BA treatment, and gut microbial changes.

Bacteroides fragilis Enterotoxin Upregulates Heme Oxygenase-1 in Intestinal Epithelial Cells via a Mitogen-Activated Protein Kinase- and NF-κB-Dependent Pathway, Leading to Modulation of Apoptosis

The Bacteroides fragilis enterotoxin (BFT), a virulence factor of enterotoxigenic B. fragilis (ETBF), interacts with intestinal epithelial cells and can provoke signals that induce mucosal inflammation. Although expression of heme oxygenase-1 (HO-1) is associated with regulation of inflammatory responses, little is known about HO-1 induction in ETBF infection. This study was conducted to investigate the effect of BFT on HO-1 expression in intestinal epithelial cells. Stimulation of intestinal epithelial cells with BFT resulted in upregulated expression of HO-1. BFT activated transcription factors such as NF-κB, AP-1, and Nrf2 in intestinal epithelial cells. Upregulation of HO-1 in intestinal epithelial cells was dependent on activated IκB kinase (IKK)-NF-κB signals. However, suppression of Nrf2 or AP-1 signals in intestinal epithelial cells did not result in significant attenuation of BFT-induced HO-1 expression. HO-1 induction via IKK-NF-κB in intestinal epithelial cells was regulated by p38 mitogen-activated protein kinases (MAPKs). Furthermore, suppression of HO-1 activity led to increased apoptosis in BFT-stimulated epithelial cells. These results suggest that a signaling pathway involving p38 MAPK-IKK-NF-κB in intestinal epithelial cells is required for HO-1 induction during exposure to BFT. Following this induction, increased HO-1 expression may regulate the apoptotic process in responses to BFT stimulation.

Flagellin Induces β-Defensin 2 in Human Colonic Ex vivo Infection with Enterohemorrhagic Escherichia coli

Enterohemorrhagic E.coli (EHEC) is an important foodborne pathogen in the developed world and can cause life-threatening disease particularly in children. EHEC persists in the human gut by adhering intimately to colonic epithelium and forming characteristic attaching/effacing lesions. In this study, we investigated the innate immune response to EHEC infection with particular focus on antimicrobial peptide and protein expression by colonic epithelium. Using a novel human colonic biopsy model and polarized T84 colon carcinoma cells, we found that EHEC infection induced expression of human β-defensin 2 (hBD2), whereas hBD1, hBD3, LL-37, and lysozyme remained unchanged. Infection with specific EHEC deletion mutants demonstrated that this was dependent on flagellin, and apical exposure to purified flagellin was sufficient to stimulate hBD2 and also interleukin (IL)-8 expression ex vivo and in vitro. Flagellin-mediated hBD2 induction was significantly reduced by inhibitors of NF-κB, MAP kinase p38 and JNK but not ERK1/2. Interestingly, IL-8 secretion by polarized T84 cells was vectorial depending on the side of stimulation, and apical exposure to EHEC or flagellin resulted in apical IL-8 release. Our results demonstrate that EHEC only induces a modest immune response in human colonic epithelium characterized by flagellin-dependent induction of hBD2 and low levels of IL-8.

Platelet-released growth factors induce the antimicrobial peptide human beta-defensin-2 in primary keratinocytes

Platelet-released growth factors (PRGF) and its related clinically used formulations [e.g. Vivostat platelet-rich fibrin (PRF(®) )] are thrombocyte concentrate lysates that support healing of chronic, hard-to-heal and infected wounds. Human beta-defensin-2 (hBD-2) is an antimicrobial peptide expressed in human keratinocytes exhibiting potent antimicrobial activity against wound-related bacteria. In this study, we analysed the influence of PRGF on hBD-2 expression in human primary keratinocytes and the influence of Vivostat PRF(®) on hBD-2 expression in experimentally generated skin wounds in vivo. Treatment of primary keratinocytes with PRGF caused a significant increase in hBD-2 gene and protein expressions in a concentration- and time-dependent manner. The use of blocking antibodies revealed that the PRGF-mediated hBD-2 induction was partially mediated by the epidermal growth factor receptor and the interleukin-6 receptor (IL-6R). Luciferase gene reporter assays indicated that the hBD-2 induction through PRGF required activation of the transcription factor activator protein 1 (AP-1), but not of NF-kappaB. In concordance with these cell culture data, Vivostat PRF(®) induced hBD-2 expression when applied to experimentally generated skin wounds. Together, our results indicate that the induction of hBD-2 by thrombocyte concentrate lysates can contribute to the observed beneficial effects in the treatment of chronic and infected wounds.

Controversies in the Mechanism of Total Parenteral Nutrition Induced Pathology

Over 30,000 patients are permanently dependent on Total Parenteral Nutrition (TPN) for survival with several folds higher requiring TPN for a prolonged duration. Unfortunately, it can cause potentially fatal complications. TPN infusion results in impairment of gut mucosal integrity, enhanced inflammation, increased cytokine expression and trans-mucosal bacterial permeation. It also causes endotoxin associated down regulation of bile acid transporters and Parenteral Nutrition Associated Liver Disease (PNALD), which includes steatosis, disrupted glucose metabolism, disrupted lipid metabolism, cholestasis and liver failure. Despite multiple theories, its etiology and pathophysiology remains elusive and is likely multifactorial. An important cause for TPN related pathologies appears to be a disruption in the normal enterohepatic circulation due to a lack of feeding during such therapy. This is further validated by the fact that in clinical settings, once cholestasis sets in, its reversal occurs when a patient is receiving a major portion of calories enterally. There are several other postulated mechanisms including gut bacterial permeation predisposing to endotoxin associated down regulation of bile acid transporters. An additional potential mechanism includes toxicity of the TPN solution itself, such as lipid mediated hepatic toxicity. Prematurity, leading to a poor development of bile acid regulating nuclear receptors and transporters has also been implicated as a causative factor. This review presents the current controversies and research into mechanisms of TPN associated injury.

Dehydroandrographolide enhances innate immunity of intestinal tract through up-regulation the expression of hBD-2

Background

Dehydroandrographolide (DA) is one of major active components in the well-known oriental herbal medicine Andrographis paniculata (Burm.f) Nees which belongs to the Acanthaceae family. DA is used for the treatment of infections in China. However, DA has not been found to significantly inhibit bacterial and viral growth directly. The current study investigates the effect of DA on the expression of human β –defensin-2 (hBD-2) in human intestinal epithelial cells and the possible signaling pathways.

Methods

Human intestinal epithelial HCT-116 cells were incubated with 1–100 μM DA for 2–24 h. RT–PCR and Western blot were used to assess the expression of hBD-2. The specific inhibitors were used and the levels of phosphorylation of signaling molecules were detected for dissecting the signaling pathways leading to the induction of hBD-2.

Results

MTT assay showed there was no obvious cytotoxicity for HCT-116 cells by 1–100 μM DA treatment. RT-PCR and Western blot assays showed that DA (1–100 μM) could up-regulate the expression of hBD-2, and the effect lasted longer than 24 h. By using SB203580 and SB202190 (inhibitors of p38), the enhancement of hBD-2 expression were significantly attenuated. However, inhibitor of ERK and inhibitor of JNK could not block the effect of DA. Furthermore, Western blot found activation of p38 but not ERK and JNK in DA-treated HCT-116 cells.

Conclusion

The results suggested that DA enhanced innate immunity of intestinal tract by up-regulating the expression of hBD-2 through the p38 MAPK pathways.

Differential modulation of avian β-defensin and Toll-like receptor expression in chickens infected with infectious bronchitis virus

The host innate immune response either clears invading viruses or allows the adaptive immune system to establish an effective antiviral response. In this study, both pathogenic (passage 3, P3) and attenuated (P110) infectious bronchitis virus (IBV) strains were used to study the immune responses of chicken to IBV infection. Expression of avian β-defensins (AvBDs) and Toll-like receptors (TLRs) in 16 tissues of chicken were compared at 7 days PI. The results showed that P3 infection upregulated the expression of AvBDs, including AvBD2, 4, 5, 6, 9, and 12, while P110 infection downregulated the expression of AvBDs, including AvBD3, 4, 5, 6, and 9 in most tissues. Meanwhile, the expression level of several TLRs showed a general trend of upregulation in the tissues of P3-infected chickens, while they were downregulated in the tissues of P110-infected chickens. The result suggested that compared with the P110 strain, the P3 strain induced a more pronounced host innate immune response. Furthermore, we observed that recombinant AvBDs (including 2, 6, and 12) demonstrated obvious anti-viral activity against IBV in vitro. Our findings contribute to the proposal that IBV infection induces an increase in the messenger RNA (mRNA) expression of some AvBDs and TLRs, which suggests that AvBDs may play significant roles in the resistance of chickens to IBV replication.

The flavone eupatilin inhibits eotaxin expression in an NF-κB-dependent and STAT6-independent manner

The CC chemokine eotaxin contributes to epithelium-induced inflammation in airway diseases such as asthma. Eupatilin (5,7-dihydroxy-3',4',6'-trimethoxyflavone), a bioactive component of Artemisia asiatica Nakai (Asteraceae), is reported to inhibit the adhesion of eosinophils to bronchial epithelial cells. However, little is known about the molecular mechanism of eupatilin-induced attenuation of bronchial epithelium-induced inflammation. In this study, we investigated the effect of eupatilin on expression of eotaxin-1 (CCL11), a potent chemoattractant for eosinophils. Eupatilin significantly inhibited eotaxin expression in bronchial epithelial cells stimulated with TNF-α, while NF-κB and IκBα kinase (IKK) activities declined concurrently. Eupatilin also inhibited mitogen-activated protein kinase (MAPK) activity; however, all of these anti-inflammatory activities were reversed by MAPK overexpression. In contrast, eupatilin did not affect the signal transducer and activator of transcription 6 (STAT6) signalling in bronchial epithelial cells stimulated with IL-4. Furthermore, eupatilin significantly attenuated TNF-α-induced eosinophil migration. These results suggest that the eupatilin inhibits the signalling of MAPK, IKK, NF-κB and eotaxin-1 in bronchial epithelial cells, leading to inhibition of eosinophil migration.

IL-22 Up-Regulates β-Defensin-2 Expression in Human Alveolar Epithelium via STAT3 but Not NF-κB Signaling Pathway

Human β-defensin-2(HBD-2) is one of the two major vertebrate antimicrobial peptide families (α and β), which is highly expressed by proinflammatory induction in the lung and exhibit broad-spectrum antimicrobial activity. We observed that IL-22 receptors high expressed on the membrane of A549 cells; HBD-2 mRNA was expressed in a time- and concentration-dependent manners in A549 cells when treated with IL-22; further studies demonstrated that HBD-2 expression was attenuated by AG490, but to JSH-23, inhibitors of p-STAT3 DNA binding and NF-κB/p65 subunit nuclear translocation, respectively. These results support that IL-22-mediated signalling pathway of HBD-2 gene expression involved STAT3 but not NF-κB in human alveolar epithelium. These findings provide a new insight into how IL-22 may play an important link between innate and adaptive immunity, thereby anti-infection locally in the alveolar epithelium.

Host Antimicrobial Peptides in Bacterial Homeostasis and Pathogenesis of Disease

Innate immune responses function as a first line of host defense against the development of bacterial infection, and in some cases to preserve the sterility of privileged sites in the human host. Bacteria that enter these sites must counter host responses for colonization. From the host's perspective, the innate immune system works expeditiously to minimize the bacterial threat before colonization and subsequent dysbiosis. The multifactorial nature of disease further challenges predictions of how each independent variable influences bacterial pathogenesis. From bacterial colonization to infection and through disease, the microenvironments of the host are in constant flux as bacterial and host factors contribute to changes at the host-pathogen interface, with the host attempting to eradicate bacteria and the bacteria fighting to maintain residency. A key component of this innate host response towards bacterial infection is the production of antimicrobial peptides (AMPs). As an early component of the host response, AMPs modulate bacterial load and prevent establishment of infection. Under quiescent conditions, some AMPs are constitutively expressed by the epithelium. Bacterial infection can subsequently induce production of other AMPs in an effort to maintain sterility, or to restrict colonization. As demonstrated in various studies, the absence of a single AMP can influence pathogenesis, highlighting the importance of AMP concentration in maintaining homeostasis. Yet, AMPs can increase bacterial virulence through the co-opting of the peptides or alteration of bacterial virulence gene expression. Further, bacterial factors used to subvert AMPs can modify host microenvironments and alter colonization of the residential flora that principally maintain homeostasis. Thus, the dynamic interplay between host defense peptides and bacterial factors produced to quell peptide activity play a critical role in the progression and outcome of disease.

Antimicrobial proteins in intestine and inflammatory bowel diseases

Mucosal surface of the intestinal tract is continuously exposed to a large number of microorganisms. To manage the substantial microbial exposure, epithelial surfaces produce a diverse arsenal of antimicrobial proteins (AMPs) that directly kill or inhibit the growth of microorganisms. Thus, AMPs are important components of innate immunity in the gut mucosa. They are frequently expressed in response to colonic inflammation and infection. Expression of many AMPs, including human β-defensin 2-4 and cathelicidin, is induced in response to invasion of pathogens or enteric microbiota into the mucosal barrier. In contrast, some AMPs, including human α-defensin 5-6 and human β-defensin 1, are constitutively expressed without microbial contact or invasion. In addition, specific AMPs are reported to be associated with inflammatory bowel disease (IBD) due to altered expression of AMPs or development of autoantibodies against AMPs. The advanced knowledge for AMPs expression in IBD can lead to its potential use as biomarkers for disease activity. Although the administration of exogenous AMPs as therapeutic strategies against IBD is still at an early stage of development, augmented induction of endogenous AMPs may be another interesting future research direction for the protective and therapeutic purposes. This review discusses new advances in our understanding of how intestinal AMPs protect against pathogens and contribute to pathophysiology of IBD.

Mitogen-activated protein kinase/IκB kinase/NF-κB-dependent and AP-1-independent CX3CL1 expression in intestinal epithelial cells stimulated with Clostridium difficile toxin A

Clostridium difficile toxin A causes acute colitis associated with inflammatory cell infiltration and increased production of proinflammatory mediators. Although CX3CL1 (fractalkine) plays a role in chemoattracting monocytes/macrophages, NK cells, and T cells, little information is available on the regulated expression of CX3CL1 in response to toxin A stimulation. In this study, we investigated the role of C. difficile toxin A on CX3CL1 induction in intestinal epithelial cells. Stimulation of murine intestinal epithelial cells with toxin A resulted in the upregulation of CX3CL1. Expression of CX3CL1 was dependent on nuclear factor-kappaB (NF-κB) and IκB kinase (IKK) activation, while the suppression of activator protein-1 (AP-1) did not affect toxin A-induced CX3CL1 expression. Suppression of p38 mitogen-activated protein kinase (MAPK) significantly inhibited IKK-NF-κB signaling leading to CX3CL1 induction in C. difficile toxin A-stimulated cells. CX3CL1 was mainly secreted from the basolateral surfaces in toxin A-treated cells. Furthermore, inhibition of p38 activity attenuated the toxin A-induced upregulation of CX3CL1 in the mouse ileum in vivo. These results suggest that a pathway, including p38 MAPK, IKK, and NF-κB activation, is required for CX3CL1 induction in intestinal epithelial cells exposed to C. difficile toxin A and may regulate the development of intestinal inflammation induced by infection with toxigenic C. difficile.

KEY MESSAGE

C. difficile toxin A causes colitis with inflammatory cell infiltration. CX3CL1 plays a role in chemoattracting immune cells. MAPK-NF-κB signaling is required for CX3CL1 induction in toxin A-exposed cells. CX3CL1 is mainly secreted from the basolateral surfaces. CX3CL1 may contribute to the regulation of toxigenic C. difficile infection.

Substrate cleavage profiling suggests a distinct function of Bacteroides fragilis metalloproteinases (fragilysin and metalloproteinase II) at the microbiome-inflammation-cancer interface

Enterotoxigenic anaerobic Bacteroides fragilis is a significant source of inflammatory diarrheal disease and a risk factor for colorectal cancer. Two distinct metalloproteinase types (the homologous 1, 2, and 3 isoforms of fragilysin (FRA1, FRA2, and FRA3, respectively) and metalloproteinase II (MPII)) are encoded by the B. fragilis pathogenicity island. FRA was demonstrated to be important to pathogenesis, whereas MPII, also a potential virulence protein, remained completely uncharacterized. Here, we, for the first time, extensively characterized MPII in comparison with FRA3, a representative of the FRA isoforms. We employed a series of multiplexed peptide cleavage assays to determine substrate specificity and proteolytic characteristics of MPII and FRA. These results enabled implementation of an efficient assay of MPII activity using a fluorescence-quenched peptide and contributed to structural evidence for the distinct substrate cleavage preferences of MPII and FRA. Our data imply that MPII specificity mimics the dibasic Arg↓Arg cleavage motif of furin-like proprotein convertases, whereas the cleavage motif of FRA (Pro-X-X-Leu-(Arg/Ala/Leu)↓) resembles that of human matrix metalloproteinases. To the best of our knowledge, MPII is the first zinc metalloproteinase with the dibasic cleavage preferences, suggesting a high level of versatility of metalloproteinase proteolysis. Based on these data, we now suggest that the combined (rather than individual) activity of MPII and FRA is required for the overall B. fragilis virulence in vivo.

Bacteroides fragilis enterotoxin upregulates lipocalin-2 expression in intestinal epithelial cells

Enterotoxigenic Bacteroides fragilis (ETBF) produces an ≈ 20 kDa B. fragilis enterotoxin (BFT), which plays an essential role in mucosal inflammation. Lipocalin (Lcn)-2, a siderophore-binding antimicrobial protein, is critical for control of bacterial infection; however, expression of Lcn-2 in BFT-exposed intestinal epithelial cells has not been elucidated. In the present study, stimulation of human intestinal epithelial cells with BFT resulted in the upregulation of Lcn-2 expression that was a relatively late response of intestinal epithelial cells compared with human β-defensin (hBD)-2 expression. The upregulation of Lcn-2 was dependent on AP-1 but not on NF-κB signaling. Lcn-2 induction via AP-1 was regulated by mitogen-activated protein kinases (MAPKs) including ERK and p38. Lcn-2 was secreted from the apical and basolateral surfaces in BFT-treated cells. These results suggest that a signaling pathway involving MAPKs and AP-1 is required for Lcn-2 induction in intestinal epithelial cells exposed to BFT, after which the secreted Lcn-2 may facilitate antimicrobial activity within ETBF-infected mucosa.

Toll-like receptor signaling activation by Entamoeba histolytica induces beta defensin 2 in human colonic epithelial cells: its possible role as an element of the innate immune response

Background

Entamoeba histolytica, a protozoan parasite of humans, produces dysenteric diarrhea, intestinal mucosa damage and extraintestinal infection. It has been proposed that the intestinal microbiota composition could be an important regulatory factor of amebic virulence and tissue invasion, particularly if pathogenic bacteria are present. Recent in vitro studies have shown that Entamoeba histolytica trophozoites induced human colonic CaCo2 cells to synthesize TLR-2 and TLR-4 and proinflammatory cytokines after binding to the amebic Gal/GalNac lectin carbohydrate recognition domain. The magnitude of the inflammatory response induced by trophozoites and the subsequent cell damage were synergized when cells had previously been exposed to pathogenic bacteria.

Methodology/Principal Findings

We show here that E. histolytica activation of the classic TLR pathway in CaCo2 cells is required to induce β defensin-2 (HBD2) mRNA expression and production of a 5-kDa cationic peptide with similar properties to the antimicrobial HBD2 expressed by CaCo2 cells exposed to enterotoxigenic Escherichia coli. The induced peptide showed capacity to permeabilize membranes of bacteria and live trophozoites. This activity was abrogated by inhibition of TLR2/4-NFκB pathway or by neutralization with an anti-HBD2 antibody.

Conclusions/Significance

Entamoeba histolytica trophozoites bind to human intestinal cells and induce expression of HBD2; an antimicrobial molecule with capacity to destroy pathogenic bacteria and trophozoites. HDB2's possible role as a modulator of the course of intestinal infections, particularly in mixed ameba/bacteria infections, is discussed.

Entamoeba histolytica ameba/bacteria mixed intestinal infections are common in endemic regions of Amebiasis. Recent investigations support the idea that pathogen interplay in these infections may have a role in invasive disease, activating signals that increase intestinal inflammation. We have studied interactions of amebic trophozoites with human colonic CaCo2 cells, using as positive control pathogenic intestinal bacteria E. coli (ETEC). Both pathogens activated a chain of chemical reactions in the cells that led to production of the antimicrobial peptide β defensin-2 (HBD2), an element of the innate immune response. Pathogen activation of CaCo2 cell response and production of HBD2 were analyzed employing biochemical, cell, molecular biology, and immunology methods. Amebas induced HBD2 via the same classic Toll-receptor signaling pathway activated by ETEC. Amebic-induced HBD2 showed capacity to permeabilize and cause severe damage to bacteria and ameba membranes. Although this study was done in vitro, due to lack of an adequate animal model in which to monitor ameba/bacteria interactions, it provides a new insight into intestinal infections, showing that presence of amebas induces synthesis of elements of an innate immune response that could affect the equilibrium of the intestinal microbiota and modify the course of intestinal infections by other pathogens.

The guggulsterone derivative GG-52 inhibits NF-κB signaling in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice

Gastric mucosal inflammation can develop after challenge with noxious stimuli such as alcohol. Specially, alcohol stimulates the release of inflammatory cytokines but does not increase gastric acid secretion, leading to gastric mucosal damage. The plant sterol guggulsterone and its novel derivative GG-52 have been reported to inhibit nuclear factor-κB (NF-κB) signaling in intestinal epithelial cells and experimental colitis. In the present study, we investigated the anti-inflammatory effects of GG-52 on gastric epithelial cells and on ethanol-induced gastric mucosal inflammation in mice. GG-52 inhibited the expression of interleukin-8 (IL-8) in gastric epithelial AGS and MKN-45 cell lines stimulated with tumor necrosis factor (TNF)-α in a dose-dependent manner. Pretreatment with GG-52 suppressed TNF-α-induced activation of IκB kinase (IKK) and NF-κB signaling in MKN-45 cells. In contrast, the inactive analog GG-46 did not produce significant changes in IL-8 expression or NF-κB activation. In a model of ethanol-induced murine gastritis, administration of GG-52 significantly reduced the severity of gastritis, as assessed by macroscopic and histological evaluation of gastric mucosal damage. In addition, the ethanol-induced upregulation of chemokine KC, a mouse homolog of IL-8, and phosphorylated p65 NF-κB signals were significantly inhibited in murine gastric mucosa pretreated with GG-52. These results indicate that GG-52 suppresses NF-κB activation in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice, suggesting that GG-52 may be a potential gastroprotective agent.

5,7-Dihydroxy-3,4,6-trimethoxyflavone inhibits intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 via the Akt and nuclear factor-κB-dependent pathway, leading to suppression of adhesion of monocytes and eosinophils to bronchial epithelial cells

5,7-Dihydroxy-3',4',6'-trimethoxyflavone (eupatilin), the active pharmacological ingredient from Artemisia asiatica Nakai (Asteraceae), is reported to have a variety of anti-inflammatory properties in intestinal epithelial cells. However, little information is known about the molecular mechanism of eupatilin-induced attenuation of bronchial epithelial inflammation. This study investigates the role of eupatilin in the adhesion of inflammatory cells such as monocytes and eosinophils to bronchial epithelial cells. Stimulation of a human bronchial epithelial cell line (BEAS-2B) with tumour necrosis factor-α (TNF-α) increased the expression of surface adhesion molecules, including intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), in which eupatilin significantly inhibited the expression of those adhesion molecules in a dose-dependent manner. Eupatilin suppressed the TNF-α-induced activation of IκBα and nuclear factor-κB (NF-κB) signals in BEAS-2B cells. The IκB kinase (IKK) activation was also significantly reduced in eupatilin-pre-treated BEAS-2B and primary normal human bronchial epithelial (NHBE) cells. However, eupatilin did not influence AP-1 activity in TNF-α-stimulated cells. Suppression of NF-κB signalling induced by eupatilin resulted in the inhibition of the expression of adhesion molecules and the adhesion of monocytes and eosinophils to BEAS-2B cells. Furthermore, eupatilin suppressed the phosphorylation of Akt in TNF-α-stimulated BEAS-2B and NHBE cells, leading to down-regulation of NF-κB activation and adhesion molecule expression and finally to suppression of the inflammatory cell adhesion to epithelial cells. These results suggest that eupatilin can inhibit the adhesion of inflammatory cells to bronchial epithelial cells via a signalling pathway, including activation of Akt and NF-κB, as well as expression of adhesion molecules.

Digested and fermented green kiwifruit increases human β-defensin 1 and 2 production in vitro

The intestinal mucosa is constantly exposed to a variety of microbial species including commensals and pathogens, the latter leaving the host susceptible to infection. Antimicrobial peptides (AMP) are an important part of the first line of defense at mucosal surfaces. Human β-defensins (HBD) are AMP expressed by colonic epithelial cells, which act as broad spectrum antimicrobials. This study explored the direct and indirect effects of green kiwifruit (KF) on human β-defensin 1 and 2 (HBD-1 and 2) production by epithelial cells. In vitro digestion of KF pulp consisted of a simulated gastric and duodenal digestion, followed by colonic microbial fermentation using nine human faecal donors. Fermenta from individual donors was sterile filtered and independently added to epithelial cells prior to analysis of HBD protein production. KF products obtained from the gastric and duodenal digestion had no effect on the production of HBD-1 or 2 by epithelial cells, demonstrating that KF does not contain substances that directly modulate defensin production. However, when the digested KF products were further subjected to in vitro colonic fermentation, the fermentation products significantly up-regulated HBD-1 and 2 production by the same epithelial cells. We propose that this effect was predominantly mediated by the presence of short-chain fatty acids (SCFA) in the fermenta. Exposure of cells to purified SCFA confirmed this and HBD-1 and 2 production was up-regulated with acetate, propionate and butyrate. In conclusion, in vitro colonic fermentation of green kiwifruit digest appears to prime defense mechanisms in gut cells by enhancing the production of antimicrobial defensins.

Expression of hBD-2 induced by 23-valent pneumococcal polysaccharide vaccine, Haemophilus influenzae type b vaccine and split influenza virus vaccine

Human β-defensin-2 (hBD-2) is an antimicrobial peptide with high activity and broad spectrum activity. hBD-2 expression may be highly elevated by microorganisms and inflammation. We reported that the majority of common vaccines used, including 23-valent pneumococcal polysaccharide vaccine, Haemophilus influenzae type b vaccine and split influenza virus vaccine, could induce the expression of hBD-2 in epithelial cells. Among them, the 23-valent pneumococcal polysaccharide vaccine was effective at a lower concentration (0.5 µg/ml), while Haemophilus influenzae type b vaccine and split influenza virus vaccine were effective at the concentration of 1 µg/ml. However, bacteriostatic experiments revealed that the split influenza virus vaccine was capable of inducing the highest antimicrobial activity. The medium of the 23-valent pneumococcal polysaccharide vaccine treatment group had a higher antimicrobial activity than the medium of the Haemophilus influenzae type b vaccine treatment group. The transcriptional regulator of hBD-2, that is, the NF-κB subunit, had a high level of activity, while the normal epithelial cells showed barely detectable activity, indicating that these vaccines have potential for clinical application.

Andrographolide exerted its antimicrobial effects by upregulation of human β-defensin-2 induced through p38 MAPK and NF-κB pathway in human lung epithelial cells

Andrographis paniculata (Burm. f) Nees is a traditional herbal medicine for the treatment of infection and inflammation in China. Andrographolide (andro) is one of the major components. Human β-defensin-2 (hBD-2) is an inducible antimicrobial peptide that plays an important role in innate immunity. The present study aimed to investigate the effect of andro on upregulation of hBD-2 and the key signaling pathways involved in andro-induced hBD-2 expression. Real-time reverse transcription – PCR and Western blot assays showed that andro (1.0–10 µmol/L) can upregulate the expression of hBD-2 in a dose-dependent manner. Further studies suggested that hBD-2 mRNA and protein expression in responsive to andro were attenuated by pretreatment with SB203580 (an inhibitor of p38 mitogen-activated protein kinase (p38 MAPK)), MG-132 (an inhibitor of nuclear factor κB (NF-κB)), and an NF-κB activator inhibitor, but not by an inhibitor of ERK (PD98059) or by an inhibitor of JNK(SP600125). Moreover, we found that a second p38 MAPK inhibitor (SB202190) significantly blocked andro-mediated hBD-2 induction in SPC-A-1 lung epithelial cells. Finally, the p-c-Jun transcription factor activity assay also showed that AP-1 activity was induced by andro compared with the untreated group. We conclude that andro may exert its antimicrobial effects by upregulating the expression of hBD-2 through the p38 MAPK and NF-κB pathway.

[Inflammatory bowel diseases and inflammasome]

Inflammatory bowel disease (IBD), the most important entities being ulcerative colitis and Crohn's disease, are chronic, relapsing and remitting inflammatory conditions that result from chronic dysregulation of the mucosal immune system in the intestinal tract. Although the precise pathogenesis of IBD is still incompletely understood, increased levels of proinflammatory cytokines, including interleukin (IL)-1b, IL-18 and tumor necrosis factor-a, are detected in active IBD and correlate with the severity of inflammation, indicating that these cytokines may play a key role in the development of IBD. Recently, the intracellular nucleotide-binding oligomerization domain-like receptor (NLR) family members, including NLRP1, NLRP3, NLRC4 and NLRP6, are emerging as important regulators of intestinal homeostasis. Together, one of those aforementioned molecules or the DNA sensor absent in melanoma 2 (AIM2), apoptosis-associated speck-like protein containing 'a caspase recruitment domain (CARD)' (ASC) and caspase-1 form a large (> 700 kDa) multi-protein complex called the inflammasome. Stimulation with specific microbial and endogenous molecules triggers inflammasome assembly and caspase-1 activation. Activated caspase-1 leads to the secretion of proinflammatory cytokines, including IL-1b and IL-18, and the promotion of pyroptosis, a form of phagocyte cell death induced by bacterial pathogens, in an inflamed tissue. Therefore, inflammasomes are assumed to mediate host defense against microbial pathogens and gut homeostasis, so that their dysregulation might contribute to IBD pathogenesis. This review focuses on recent advances of the role of NLRP3 inflammasome signaling in IBD pathogenesis. Improving knowledge of the inflammasome could provide insights into potential therapeutic targets for patients with IBD.

Extracellular HIV-1 Tat induces human beta-defensin-2 production via NF-kappaB/AP-1 dependent pathways in human B cells

Defensins, a family of antimicrobial peptides, are one of the first lines of host defense. Human beta-defensins (hBD) such as hBD-2 and -3 have anti-HIV activity. Previous studies have shown that HIV-1 virion can induce the expression of hBD, although the exact components of HIV-1 virion that are responsible for hBD expression have not yet been elucidated. In this study, we examined the effect of HIV-1 Tat on the expression of hBD in B cells. Stimulation of B cells with HIV-1 Tat protein significantly increased the mRNA and protein levels of hBD-2. HIV-1 Tat also induced the activation of a reporter gene for hBD-2 in a dose-dependent manner in B cells. Pretreatment of B cells with a JNK inhibitor suppressed HIV-1 Tat-induced hBD-2 expression. Pretreatment of B cells with AP-1 inhibitors or NF-κB inhibitors led to a decrease in HIV-1 Tat-induced protein and mRNA expression of hBD-2. Taken together, our results indicate that HIV-1 Tat can up-regulate the expression of hBD-2 via JNK-NF-κB/AP-1-dependent pathways in human B cells.

Arvelexin from Brassica rapa suppresses NF-κB-regulated pro-inflammatory gene expression by inhibiting activation of IκB kinase

BACKGROUND AND PURPOSE

Brassica rapa species constitute one of the major sources of food. In the present study, we investigated the anti-inflammatory effects and the underlying molecular mechanism of arvelexin, isolated from B. rapa, on lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages and on a model of septic shock induced by LPS.

EXPERIMENTAL APPROACH

The expression of Inducible nitric oxide synthase (iNOS) and COX-2, TNF-α, IL-6 and IL-1β were determined by Western blot and/or RT-PCR respectively. To elucidate the underlying mechanism(s), activation of NF-κB activation and its pathways were investigated by electrophoretic mobility shift assay, reporter gene and Western blot assays. In addition, the in vivo anti-inflammatory effects of arvelexin were evaluated in endotoxaemia induced with LPS.

KEY RESULTS

Promoter assays for iNOS and COX-2 revealed that arvelexin inhibited LPS-induced NO and prostaglandin E(2) production through the suppression of iNOS and COX-2 at the level of gene transcription. In addition, arvelexin inhibited NF-κB-dependent inflammatory responses by modulating a series of intracellular events of IκB kinase (IKK)-inhibitor κBα (IκBα)-NF-κB signalling. Moreover, arvelexin inhibited IKKβ-elicited NF-κB activation as well as iNOS and COX-2 expression. Serum levels of NO and inflammatory cytokines and mortality in mice challenged injected with LPS were significantly reduced by arvelexin.

CONCLUSION AND IMPLICATIONS

Arvelexin down-regulated inflammatory iNOS, COX-2, TNF-α, IL-6 and IL-1β gene expression in macrophages interfering with the activation of IKKβ and p38 mitogen-activated protein kinase, and thus, preventing NF-κB activation.

Involvement of the mannose receptor and p38 mitogen-activated protein kinase signaling pathway of the microdomain of the integral membrane protein after enteropathogenic Escherichia coli infection

The microdomain of the integral membrane protein (MIMP) has been shown to adhere to mucin and to antagonize the adhesion of enteropathogenic Escherichia coli (EPEC) to epithelial cells; however, the mechanism has not been fully elucidated. In this study, we further identified the receptor of MIMP on NCM460 cells and investigated the mechanism (the p38 mitogen-activated protein kinase [MAPK] pathway) following the interaction of MIMP and its corresponding receptor, mannose receptor. We first identified the target receptor of MIMP on the surfaces of NCM460 cells using immunoprecipitation-mass spectrometry technology. We also verified the mannose receptor and examined the degradation and activation of the p38 MAPK signaling pathway. The results indicated that MIMP adhered to NCM460 cells by binding to the mannose receptor and inhibited the phosphorylation of p38 MAPK stimulated after EPEC infection via inhibition of the Toll-like receptor 5 pathway. These findings indicated that MIMPs relieve the injury of NCM460 cells after enteropathogenic E. coli infection through the mannose receptor and inhibition of the p38 MAPK signaling pathway, both of which may therefore be potential therapeutic targets for intestinal diseases, such as inflammatory bowel disease.

Effect of the oral intake of yogurt containing Bifidobacterium longum BB536 on the cell numbers of enterotoxigenic Bacteroides fragilis in microbiota

Enterotoxigenic Bacteroides fragilis (ETBF) strains have been suggested to be associated with acute and persistent diarrheal disease, inflammatory bowel disease and colorectal cancer, although further epidemiological studies are needed for clarification. Here, a pilot study was performed to examine the effect of the oral administration of yogurt supplemented with a probiotic strain on the cell numbers of fecal ETBF in a healthy population. Among 420 healthy adults, 38 subjects were found to be ETBF carriers, giving a prevalence of approximately 9%. Among them, 32 subjects were enrolled in an open, randomized, parallel-group study to ingest yogurt supplemented with a probiotic strain, Bifidobacterium longum BB536 (BB536Y group), for 8 weeks, with milk provided to the control group (milk group). The cell numbers of ETBF and the dominant species of the B. fragilis group were measured by a quantitative PCR method. Compared with the baseline values, there was a significant decrease in the cell number of ETBF at week 8 in the BB536Y group but not in the milk group. Linear mixed models analysis for longitudinal data revealed a significant difference in the changes of ETBF cell number between the two groups during the intervention phase. These results imply the potential of probiotic yogurt for eliminating ETBF in the microbiota, but its clinical significance needs to be evaluated in the future. This is the first report of a possible effect of probiotic intake on ETBF in the microbiota.

Stimulation of dendritic cells with Helicobacter pylori vacuolating cytotoxin negatively regulates their maturation via the restoration of E2F1

Helicobacter pylori induces an infiltration of dendritic cells (DCs) into the infected gastric mucosa. Although DCs play an important role in the regulation of inflammation, the effects of H. pylori vacuolating cytotoxin (VacA) on DC maturation process have not yet been elucidated. The role of VacA in DC maturation following co-exposure to Escherichia coli lipopolysaccharide (LPS) was investigated. The treatment of immature DCs with LPS up-regulated the expression of surface molecules [e.g. CD40, CD80, CD86 and major histocompatibility complex (MHC) class II], as well as the production of cytokines [e.g. interleukin (IL)-1β, IL-12p70 and tumour necrosis gactor (TNF)-α] compared with those of unstimulated controls. Co-stimulation with H. pylori VacA significantly reduced the up-regulated DC maturation markers induced by LPS. In addition, VacA sustained the immature state of DCs with high endocytosis and low migratory capacity. The LPS-induced down-regulation of E2F1 expression in DCs was recovered by co-stimulation with VacA. Moreover, suppression of E2F1 by small interfering RNA resulted in a significant recovery of the inhibited DC maturation by VacA. In contrast, VacA did not affect nuclear factor (NF)-κB responses to LPS and the NF-κB signal was not associated with VacA-induced inhibition of DC maturation. These results suggest that the exposure of DCs to H. pylori VacA negatively regulates DC maturation via the restoration of E2F1. The immunomodulatory action of VacA on DCs may contribute to the ability of VacA-producing H. pylori to establish a persistent infection in the gastric mucosa.

A mechanism for the action of the compound DA-6034 on NF-κB pathway activation in Helicobacter pylori-infected gastric epithelial cells

DA-6034 is a synthetic derivative of eupatilin, a flavonoid with anti-inflammatory effects. The aim of this study was to investigate the effects of DA-6034 on the interactions between IκB kinase (IKK) and heat shock protein 90 (Hsp90), and activation of the nuclear factor-kappaB (NF-κB) signalling pathway in human gastric epithelial cells infected with Helicobacter pylori. MKN-45 gastric epithelial cell line was treated with DA-6034 and H. pylori. DA-6034 significantly inhibited NF-κB activation and upregulated the expressions of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 in MKN-45 cells infected with H. pylori. However, DA-6034 did not influence activator protein-1 DNA binding activity in H. pylori-infected gastric epithelial cells. Pretreatment with DA-6034 attenuated the H. pylori-induced increase in IKK activity, and Hsp90 was associated with IKK-α and IKK-γ in MKN-45 cells. Treatment with DA-6034 dissociated the Hsp90 and IKK-γ complex in H. pylori-infected cells, leading to the inhibition of IL-8 expression. These results suggest that the eupatilin derivative 7-carboxymethyloxy-3',4',5-trimethoxy flavone has anti-inflammatory activity in gastric epithelial cells infected with H. pylori through the promotion of the dissociation of the IKK-γ-Hsp90 complex and suppression of NF-κB signalling.

Bacteroides fragilis enterotoxin upregulates intercellular adhesion molecule-1 in endothelial cells via an aldose reductase-, MAPK-, and NF-κB-dependent pathway, leading to monocyte adhesion to endothelial cells

Enterotoxigenic Bacteroides fragilis (ETBF) produces a ∼ 20-kDa heat-labile enterotoxin (BFT) that plays an essential role in mucosal inflammation. Although a variety of inflammatory cells is found at ETBF-infected sites, little is known about leukocyte adhesion in response to BFT stimulation. We investigated whether BFT affected the expression of ICAM-1 and monocytic adhesion to endothelial cells (ECs). Stimulation of HUVECs and rat aortic ECs with BFT resulted in the induction of ICAM-1 expression. Upregulation of ICAM-1 was dependent on the activation of IκB kinase (IKK) and NF-κB signaling. In contrast, suppression of AP-1 did not affect ICAM-1 expression in BFT-stimulated cells. Suppression of NF-κB activity in HUVECs significantly reduced monocytic adhesion, indicating that ICAM-1 expression is indispensable for BFT-induced adhesion of monocytes to the endothelium. Inhibition of JNK resulted in a significant attenuation of BFT-induced ICAM-1 expression in ECs. Moreover, inhibition of aldose reductase significantly reduced JNK-dependent IKK/NF-κB activation, ICAM-1 expression, and adhesion of monocytes to HUVECs. These results suggest that a signaling pathway involving aldose reductase, JNK, IKK, and NF-κB is required for ICAM-1 induction in ECs exposed to BFT, and may be involved in the leukocyte-adhesion cascade following infection with ETBF.