Cytokine association with bacterial DNA in serum of patients with inflammatory bowel disease

The role of gut microbiota and bacterial translocation in the pathogenesis and management of type 2 diabetes mellitus: Mechanisms, impacts, and dietary therapeutic strategies

PURPOSE OF REVIEW

The influence of gut microbiota on Type 2 Diabetes Mellitus (T2DM) is an emerging area of research. This review investigates the relationship between gut microbiota dysbiosis, bacterial translocation, and T2DM. It aims to elucidate how microbial imbalances contribute to the progression of T2DM through bacterial translocation and to evaluate dietary and therapeutic strategies to manage these effects.

RECENT FINDINGS

Recent studies highlight that dysbiosis in T2DM patients often leads to increased systemic inflammation, impaired glucose metabolism, and disrupted gut barrier integrity. These disruptions promote elevated levels of harmful bacterial components, such as lipopolysaccharides, in the bloodstream. This, in turn, is linked to worsening insulin resistance and metabolic dysfunction. Advances in molecular methods and biomarkers have provided deeper insights into bacterial translocation and its impact on diabetes. Dietary interventions, including nutraceutical agents, high-fiber and low-glycemic index diets, as well as the use of probiotics and prebiotics, have shown promise in restoring gut health and mitigating bacterial translocation.

CONCLUSION

Maintaining a balanced gut microbiota and intestinal barrier integrity is crucial for managing T2DM. Therapeutic strategies, including dietary modifications and nutraceuticals, have demonstrated potential in reducing bacterial translocation and systemic inflammation. Continued research is needed to refine these approaches and explore novel treatment modalities for improving metabolic health in T2DM patients.

Recent advances in measuring the effects of diet on gastrointestinal physiology: Probing the "leaky gut" and application of real-time ultrasound

There is a large pool of ideas in both mainstream and non-mainstream medicine on how diet can be manipulated in order to treat or prevent illnesses. Despite this, our understanding of how specific changes in diet influence the structure and function of the gastrointestinal tract is limited. This review aims to describe two areas that might provide key information on the integrity and function of the gastrointestinal tract. First, demystifying the "leaky gut syndrome" requires rational application and interpretation of tests of intestinal barrier function. Multiple ways of measuring barrier function have been described, but the inherent difficulties in translation from animal studies to humans have created misinterpretations and misconceptions. The intrinsic nature of intestinal barrier function is dynamic. This is seldom considered in studies of intestinal barrier assessment. To adequately understand the effects of dietary interventions on intestinal barrier function, background barrier function in different regions of the gut and the dynamic responses to stressors (such as psychological stress) should be assessed as a minimum. Second, intestinal ultrasound, which is now established in the assessment and monitoring of inflammatory bowel disease, has hitherto been poorly evaluated in assessing real-time intestinal function and novel aspects of structure in patients with disorders of gut-brain interaction. In conclusion, a more complete functional and structural profile that these investigations enable should permit a greater understanding of the effects of dietary manipulation on the gastrointestinal tract and provide clinically relevant information that, amongst other advantages, might permit opportunities for personalized health care delivery.

How gut microbiota may impact ocular surface homeostasis and related disorders

Changes in the bacterial flora in the gut, also described as gut microbiota, are readily acknowledged to be associated with several systemic diseases, especially those with an inflammatory, neuronal, psychological or hormonal factor involved in the pathogenesis and/or the perception of the disease. Maintaining ocular surface homeostasis is also based on all these four factors, and there is accumulating evidence in the literature on the relationship between gut microbiota and ocular surface diseases. The mechanisms involved are mostly interconnected due to the interaction of central and peripheral neuronal networks, inflammatory effectors and the hormonal system. A better understanding of the influence of the gut microbiota on the maintenance of ocular surface homeostasis, and on the onset or persistence of ocular surface disorders could bring new insights and help elucidate the epidemiology and pathology of ocular surface dynamics in health and disease. Revealing the exact nature of these associations could be of paramount importance for developing a holistic approach using highly promising new therapeutic strategies targeting ocular surface diseases.

CRP in Outpatients with Inflammatory Bowel Disease Is Linked to the Blood Microbiota

The circulation is a closed system that has been assumed to be free from bacteria, but evidence for the existence of a low-density blood microbiota is accumulating. The present study aimed to map the blood microbiota of outpatients with Crohn's disease (CD) or with ulcerative colitis (UC) by 16S metagenomics. A diverse microbiota was observed in the blood samples. Regardless of the type of disease, the alpha diversity of the microbiota was positively associated with C-reactive protein (CRP). The blood microbiota had a surprisingly high proportion of Proteobacteria in comparison with human oral and colonic microbiotas. There was no clear difference in the overall pattern of the microbiota between CD and UC. A non-template control (NTC) was included in the whole process to control for the potential contamination from the environment and reagents. Certain bacterial taxa were concomitantly detected in both blood samples and NTC. However, Acinetobacter, Lactobacillus, Thermicanus and Paracoccus were found in blood from both CD and UC patients but not in NTC, indicating the existence of a specific blood-borne microbiota in the patients. Achromobacter dominated in all blood samples, but a minor amount was also found in NTC. Micrococcaceae was significantly enriched in CD, but it was also detected in high abundance in NTC. Whether the composition of the blood microbiota could be a marker of a particular phenotype in inflammatory bowel disease (IBD) or whether the blood microbiota could be used for diagnostic or therapeutic purposes deserves further attention.

Bacterial DNA promoting inflammation via the Sgk1/Nedd4L/Syk pathway in mast cells contributes to antihistamine-nonresponsive CSU

Inflammation centered on non-IgE-mediated mast cell activation characterizes chronic spontaneous urticaria resistant to nonsedating H1-antihistamines. We recently uncovered a strong positive association between inflammation and the fecal Escherichia. To further explore the actions of bacterial DNA derived from Escherichia on mast cells, intestinal permeability of patients with chronic spontaneous urticaria with or without nonsedating H1-antihistamine resistance and healthy controls were determined, and LAD2 cells with knockdown of Syk, Nedd4L, or Sgk1 or with incubation of inhibitors GS9973, GSK650394, and MG132 were posttreated with btDNA. We found that (i) serum intestinal permeability indices and bacterial DNA markedly increased in patients with chronic spontaneous urticaria with nonsedating H1-antihistamine resistance compared with those without (all P < 0.001), and bacterial DNA positively correlated with the degree of inflammation; (ii) IL-6 and TNF-α levels were time- and dose-dependently upregulated in bacterial DNA-stimulated LAD2 cells, which relied on unmethylated CpG in bacterial DNA and Toll-like receptor 9 protein in cells; (iii) Syk knockdown or inhibition of Syk Tyr525/526 phosphorylation blocked bacterial DNA-initiated cytokine production; (iv) Nedd4L interacted with Tyr525/526-phosphorylated Syk, and inhibition of Nedd4L Ser448 phosphorylation induced by bacterial DNA-activated Sgk1 was mandatory for bacterial DNA's proinflammatory property; and (v) Sgk1 suppression showed an inhibitory effect on bacterial DNA-induced inflammation by ensuring Nedd4L-mediated ubiquitination of Tyr525/526-phosphorylated Syk. Collectively, we identified previously unknown contributory roles of bacterial translocation and serum bacterial DNA on the inflammation phenotype in patients with chronic spontaneous urticaria with nonsedating H1-antihistamine resistance and further uncovered a vital negative regulatory role for the Sgk1/Nedd4L/Syk pathway in bacterial DNA-induced inflammation in LAD2 cells.

Contribution of Blood Vessel Activation, Remodeling and Barrier Function to Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBDs) consist of a group of chronic inflammatory disorders with a complex etiology, which represent a clinical challenge due to their often therapy-refractory nature. In IBD, inflammation of the intestinal mucosa is characterized by strong and sustained leukocyte infiltration, resulting in the loss of epithelial barrier function and subsequent tissue destruction. This is accompanied by the activation and the massive remodeling of mucosal micro-vessels. The role of the gut vasculature in the induction and perpetuation of mucosal inflammation is receiving increasing recognition. While the vascular barrier is considered to offer protection against bacterial translocation and sepsis after the breakdown of the epithelial barrier, endothelium activation and angiogenesis are thought to promote inflammation. The present review examines the respective pathological contributions of the different phenotypical changes observed in the microvascular endothelium during IBD, and provides an overview of potential vessel-specific targeted therapy options for the treatment of IBD.

PADs and NETs in digestive system: From physiology to pathology

Peptidylarginine deiminases (PADs) are the only enzyme class known to deiminate arginine residues into citrulline in proteins, a process known as citrullination. This is an important post-translational modification that functions in several physiological and pathological processes. Neutrophil extracellular traps (NETs) are generated by NETosis, a novel cell death in neutrophils and a double-edged sword in inflammation. Excessive activation of PADs and NETs is critically implicated in their transformation from a physiological to a pathological state. Herein, we review the physiological and pathological functions of PADs and NETs, in particular, the involvement of PAD2 and PAD4 in the digestive system, from inflammatory to oncological diseases, along with related therapeutic prospects.

Microbiome in Hidradenitis Suppurativa—What We Know and Where We Are Heading

Recently, interest in the microbiome of cutaneous diseases has increased tremendously. Of particular interest is the gut-brain-skin axis proposed by Stokes and Pillsbury in 1930. The microbiome has been suggested in the pathogenesis of hidradenitis suppurativa, however the link between the commensals and the host is yet to be established. Across all studies, the increased abundance of Porphyromonas, Peptoniphilus, and Prevotella spp., and a loss of skin commensal species, such as Cutibacterium in HS lesions, is a consistent finding. The role of gut and blood microbiome in hidradenitis suppurativa has not been fully elucidated. According to studies, the main link with the intestine is based on the increased risk of developing Crohn’s disease and ulcerative colitis, however, further research is highly needed in this area. Lifestyle, dietary approaches, and probiotics all seem to influence the microbiome, hence being a promising modality as adjuvant therapy. The aim of this review was to present the latest reports in the field of research on skin, blood, and gut microbiome in terms of hidradenitis suppurativa.

Lactobacillus rhamnosus sepsis, endocarditis and septic emboli in a patient with ulcerative colitis taking probiotics

A man in his 60s presented to the emergency room with fever and fatigue after a 2.5-month course of corticosteroids. His medical history was significant for bioprosthetic aortic valve replacement and moderately severe ulcerative colitis treated with balsalazide and daily lactobacillus-containing probiotics. Initial investigations revealed Lactobacillus rhamnosus bacteraemia without complication. Four days after hospital discharge, the patient experienced acute-onset right-sided paraesthesia and lower-limb paresis. On return to the emergency room, MRI of the brain demonstrated innumerable ring-enhancing lesions with haemorrhagic transformation. Transoesophageal echocardiogram revealed a small mobile density on the bioprosthetic aortic valve, raising the suspicion for L. rhamnosus infective endocarditis with secondary septic emboli to the brain. The patient was subsequently treated with intravenous gentamycin and ampicillin, with transition to indefinite oral amoxicillin suppressive therapy. The current case highlights the potential risk of lactobacilli translocation in an immunosuppressed patient with ulcerative colitis taking probiotics.

Gut Microbiota as a Hidden Player in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD), the most common neurodegenerative disorder, is accompanied by cognitive impairment and shows representative pathological features, including senile plaques and neurofibrillary tangles in the brain. Recent evidence suggests that several systemic changes outside the brain are associated with AD and may contribute to its pathogenesis. Among the factors that induce systemic changes in AD, the gut microbiota is increasingly drawing attention. Modulation of gut microbiome, along with continuous attempts to remove pathogenic proteins directly from the brain, is a viable strategy to cure AD. Seeking a holistic understanding of the pathways throughout the body that can affect the pathogenesis, rather than regarding AD solely as a brain disease, may be key to successful therapy. In this review, we focus on the role of the gut microbiota in causing systemic manifestations of AD. The review integrates recently emerging concepts and provides potential mechanisms about the involvement of the gut-brain axis in AD, ranging from gut permeability and inflammation to bacterial translocation and cross-seeding.

Preventing Bacterial Translocation in Patients with Leaky Gut Syndrome: Nutrition and Pharmacological Treatment Options

Leaky gut syndrome is a medical condition characterized by intestinal hyperpermeability. Since the intestinal barrier is one of the essential components maintaining homeostasis along the gastrointestinal tract, loss of its integrity due to changes in bacterial composition, decreased expression levels of tight junction proteins, and increased concentration of pro-inflammatory cytokines may lead to intestinal hyperpermeability followed by the development of gastrointestinal and non-gastrointestinal diseases. Translocation of microorganisms and their toxic metabolites beyond the gastrointestinal tract is one of the fallouts of the leaky gut syndrome. The presence of intestinal bacteria in sterile tissues and distant organs may cause damage due to chronic inflammation and progression of disorders, including inflammatory bowel diseases, liver cirrhosis, and acute pancreatitis. Currently, there are no medical guidelines for the treatment or prevention of bacterial translocation in patients with the leaky gut syndrome; however, several studies suggest that dietary intervention can improve barrier function and restrict bacteria invasion. This review contains current literature data concerning the influence of diet, dietary supplements, probiotics, and drugs on intestinal permeability and bacterial translocation.

Bacterial Translocation as Inflammatory Driver in Crohn's Disease

Crohn’s disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract responsible for intestinal lesions. The multifactorial etiology attributed to CD includes a combination of environmental and host susceptibility factors, which result in an impaired host–microbe gut interaction. Bacterial overgrowth and dysbiosis, increased intestinal barrier permeability, and altered inflammatory responses in patients with CD have been described in the past. Those events explain the pathogenesis of luminal translocation of bacteria or its products into the blood, a frequent event in CD, which, in turn, favors a sustained inflammatory response in these patients. In this review, we navigate through the interaction between bacterial antigen translocation, permeability of the intestinal barrier, immunologic response of the host, and genetic predisposition as a combined effect on the inflammatory response observed in CD. Several lines of evidence support that translocation of bacterial products leads to uncontrolled inflammation in CD patients, and as a matter of fact, the presence of gut bacterial genomic fragments at a systemic level constitutes a marker for increased risk of relapse among CD patients. Also, the significant percentage of CD patients who lose response to biologic therapies may be influenced by the translocation of bacterial products, which are well-known drivers of proinflammatory cytokine production by host immune cells. Further mechanistic studies evaluating cellular and humoral immune responses, gut microbiota alterations, and genetic predisposition will help clinicians to better control and personalize the management of CD patients in the future.

Metabolic Host-Microbiota Interactions in Autophagy and the Pathogenesis of Inflammatory Bowel Disease (IBD)

Inflammatory bowel disease (IBD) is a family of conditions characterized by chronic, relapsing inflammation of the gastrointestinal tract. IBD afflicts over 3 million adults in the United States and shows increasing prevalence in the Westernized world. Current IBD treatments center on modulation of the damaging inflammatory response and carry risks such as immunosuppression, while the development of more effective treatments is hampered by our poor understanding of the molecular mechanisms of IBD pathogenesis. Previous genome-wide association studies (GWAS) have demonstrated that gene variants linked to the cellular response to microorganisms are most strongly associated with an increased risk of IBD. These studies are supported by mechanistic work demonstrating that IBD-associated polymorphisms compromise the intestine's anti-microbial defense. In this review, we summarize the current knowledge regarding IBD as a disease of defects in host-microbe interactions and discuss potential avenues for targeting this mechanism for future therapeutic development.

Endocrine disruption in Crohn's disease: Bisphenol A enhances systemic inflammatory response in patients with gut barrier translocation of dysbiotic microbiota products

The relevance of environmental triggers in Crohn's disease remains poorly explored, despite the well-known association between industrialization and disease onset/progression. We have aimed at evaluating the influence of endocrine disrupting chemicals in CD patients. We performed a prospective observational study on consecutive patients diagnosed of CD. Serum levels of endocrine disruptors, short-chain fatty acids, tryptophan and cytokines were measured. Bacterial-DNA and serum endotoxin levels were also evaluated. Gene expression of ER-α, ER-β and GPER was measured in PBMCs. All patients were genotyped for NOD2 and ATG16L1 polymorphisms. A series of 200 CD patients (140 in remission, 60 with active disease) was included in the study. Bisphenol A was significantly higher in patients with active disease versus remission and in colonic versus ileal disease. GPER was significantly increased in active patients and correlated with BPA levels. BPA was significantly increased in patients with bacterial-DNA and correlated with serum endotoxin levels, (r = 0.417; P = .003). Serum butyrate and tryptophan levels were significantly lower in patients with bacterial-DNA and an inverse relationship was present between them and BPA levels (r = -0.491; P = .001) (r = -0.611; P = .001). Serum BPA levels correlated with IL-23 (r = 0.807; P = .001) and IL-17A (r = 0.743; P = .001). The multivariate analysis revealed an independent significant contribution of BPA and bacterial-DNA to serum levels of IL-23 and IL-17A. In conclusion, bisphenol A significantly affects systemic inflammatory response in CD patients with gut barrier disruption and dysbiotic microbiota secretory products in blood. These results provide evidence of an endocrine disruptor playing an actual pathogenic role on CD.

Neutrophil Extracellular Traps in Colorectal Cancer Progression and Metastasis

Neutrophils form sticky web-like structures known as neutrophil extracellular traps (NETs) as part of innate immune response. NETs are decondensed extracellular chromatin filaments comprising nuclear and cytoplasmic proteins. NETs have been implicated in many gastrointestinal diseases including colorectal cancer (CRC). However, the regulatory mechanisms of NET formation and potential pharmacological inhibitors in the context of CRC have not been thoroughly discussed. In this review, we intend to highlight roles of NETs in CRC progression and metastasis as well as the potential of targeting NETs during colon cancer therapy.

Non-alcoholic fatty liver disease is associated with bacterial translocation and a higher inflammation response in psoriatic patients

Psoriasis and non-alcoholic fatty liver disease (NAFLD) are both inflammatory diseases. The study objective was to estimate the risk of NAFLD, non-alcoholic steatohepatitis, and liver fibrosis (by liver stiffness and liver biopsy) in patients with psoriasis and to determine the epidemiological, clinical, immunological (TNF-α, IL-2, IL-6, IL-12, IL-17, IL-23, and TGF-β) characteristics, and bacterial translocation. Of the 215 psoriatic patients included, 91 presented NAFLD (prevalence: 42.3%). Compared to patients with psoriasis alone, those with NAFLD were significantly more likely to have metabolic syndrome, diabetes, dyslipidemia, body mass index ≥ 30 kg/m², homeostatic model assessment of insulin resistance ≥ 2.15, and greater psoriasis area severity index. NAFLD patients also had significantly higher levels of TNF-α (p = 0.002) and TGF-β (p = 0.007) and a higher prevalence of bacterial translocation (29.7% vs. 13.7%; p = 0.004). Liver stiffness measurement was over 7.8 kPa in 17.2% (15/87) of NAFLD patients; 13 of these underwent liver biopsy, and 5.7% (5/87) had liver fibrosis, while 1.1% (1/87) had advanced fibrosis or non-alcoholic steatohepatitis. In conclusion the prevalence of NAFLD in patients with psoriasis is high and associated with a higher prevalence of metabolic syndrome features, bacterial translocation and a higher pro-inflammatory state. It is worth mentioning that liver fibrosis and non-alcoholic steatohepatitis are not frequent in this population of patients.

Neutrophil Extracellular Traps in Inflammatory Bowel Disease: Pathogenic Mechanisms and Clinical Translation

The Inflammatory Bowel Diseases (IBD), Ulcerative Colitis (UC) and Crohn's Disease (CD) are characterised by chronic non-resolving gut mucosal inflammation involving innate and adaptive immune responses. Neutrophils, usually regarded as first responders in inflammation, are a key presence in the gut mucosal inflammatory milieu in IBD. Here, we review the role of neutrophil extracellular trap (NET) formation as a potential effector disease mechanism. NETs are extracellular webs of chromatin, microbicidal proteins and oxidative enzymes that are released by neutrophils to contain pathogens. NETs contribute to the pathogenesis of several immune-mediated diseases such as systemic lupus erythematosus and rheumatoid arthritis; and recently, as a major tissue damaging process involved in the host response to severe acute respiratory syndrome coronavirus 2 infection. NETs are pertinent as a defence mechanism at the gut mucosal interphase exposed to high levels of bacteria, viruses and fungi. On the other hand, NETs can also potentiate and perpetuate gut inflammation. In this review, we discuss the broad protective vs. pathogenic roles of NETs, explanatory factors that could lead to an increase in NET formation in IBD and how NETs may contribute to gut inflammation and IBD-related complications. Finally, we summarise therapeutic opportunities to target NETs in IBD.

Gut microbiota homeostasis restoration may become a novel therapy for breast cancer

Breast cancer is the most diagnosed cancer in women. It significantly impairs a patient's physical and mental health. Gut microbiota comprise the bacteria residing in a host's gastrointestinal tract. Through studies over the last decade, we now know that alterations in the composition of the gut microbiome are associated with protection against colonization by pathogens and other diseases, such as diabetes and cancer. This review focuses on how gut microbiota can affect breast cancer development through estrogen activity and discusses the types of bacteria that may be involved in the onset and the progression of breast cancer. We also describe potential therapies to curtail the risk of breast cancer by restoring gut microbiota homeostasis and reducing systemic estrogen levels. This review will further explore the relationship between intestinal microbes and breast cancer and propose a method to treat breast cancer by improving intestinal microbes. We aimed at discovering new methods to prevent or treat BC by changing intestinal microorganisms.

Antimicrobial peptide LL-37 forms complex with bacterial DNA to facilitate blood translocation of bacterial DNA and aggravate ulcerative colitis

Bacterial DNA (bacDNA) is frequently found in serum of patient with ulcerative colitis (UC) and Crohn's disease, even blood bacterial culture is negative. How bacDNA evades immune elimination and is translocated into blood remain unclear. Here, we showed that bacDNA avoids elimination and disables bacteria-killing function of antimicrobial peptide LL-37 (Cramp in mice) by forming complex with LL-37, which is inducible after culture with bacteria or bacterial products. Elevated LL-37-bacDNA complex was found in plasma and lesions of patients with UC. LL-37-bacDNA promoted inflammation by inducing Th1, Th2 and Th17 differentiation and activating toll-like receptor-9 (TLR9). The complex also increased paracellular permeability, which possibly combines its inflammatory effects to promote local damage and bacDNA translocation into blood. Cramp-bacDNA aggravated mouse colitis severity while interference with the complex ameliorated the disease. The study identifies that inflammatogenic bacDNA utilizes LL-37 as a vehicle for blood translocation and to evade immune elimination. Additionally, bacteria may make a milieu by releasing bacDNA to utilize and resist host antimicrobial peptides as a 'trojan horse'.

Modified Floating Electrode-Based Sensors for the Quantitative Monitoring of Drug Effects on Cytokine Levels Related with Inflammatory Bowel Diseases

Modified floating electrode-based sensors were developed to quantitatively monitor the levels of tumor necrosis factor α (TNF-α), a pro-inflammatory cytokine related with inflammatory bowel disease (IBD), and to evaluate the effect of drugs on the cytokine levels. Here, antibodies (anti-TNF-α) were immobilized on the floating electrodes of carbon nanotube devices, enabling selective and real-time detection of TNF-α among various cytokines linked to IBD. This sensor was able to measure the concentrations of TNF-α with a detection limit of 1 pg/L, allowing the quantitative estimation of TNF-α secretion from mouse macrophage Raw 264.7 cells stimulated by lipopolysaccharides (LPS). Notably, this method also allowed us to monitor the anti-inflammatory effect of a drug, lupeol, on the activation of the LPS-induced nuclear factor κB signaling in Raw 264.7 cells. These results indicate that our novel TNF sensor can be a versatile tool for biomedical research and clinical applications such as screening drug effects and monitoring inflammation levels.

Intestinal Bacteria Composition and Translocation of Bacteria in Inflammatory Bowel Disease

BACKGROUND

Live commensal intestinal bacteria are present in the peripheral blood where they can induce inflammation.

OBJECTIVE

To evaluate the intestinal bacteria composition and translocation of bacteria in IBD.

METHODS

Both blood and tissue biopsy samples were collected from adult patients with active/inactive Crohn's disease (CD), active/inactive ulcerative colitis (UC) and healthy individuals. Most of the patients were newly diagnosed and none of them received antibiotics. Using a reverse transcription-quantitative real-time PCR (RT-qPCR) method, we determined the composition of microbiota. NOD2/CARD15 genotyping was also studied.

RESULTS

Total bacterial DNA concentration was increased in tissue and blood samples of IBD patients compared to healthy controls. Furthermore, the active IBD cases had higher total bacterial DNA concentration levels compared to the inactive cases. Three species characterized dysbiosis in IBD, namely an increase of Bacteroides spp in active and inactive IBD samples, and a decrease in Clostridium leptum group (IV), and Faecalibacterium prausnitzi in both active and inactive IBD patients. No significant association between bacterial translocation and NOD2/CARD15 mutations was found.

CONCLUSIONS

The composition of the microbiota in IBD patients differs from that of healthy controls. The high rate of bacterial DNA in the blood samples indicates translocation in inflammatory bowel disease.

Gut Bacterial DNA Translocation is an Independent Risk Factor of Flare at Short Term in Patients With Crohn's Disease

OBJECTIVES

We aimed at evaluating bacterial DNA (bactDNA) presence in blood of Crohn's disease (CD) patients in remission as an independent risk factor of flare at 6 months.

METHODS

This is a prospective, multicenter study on CD patients with Crohn's disease activity index (CDAI)<150. The primary end point was time-to-relapse as evaluated by CDAI>150 in the following 6 months. BactDNA in blood, the nucleotide-binding oligomerization domain containing 2 (NOD2) genotype, and serum cytokine levels were determined at baseline.

RESULTS

A total of 288 patients were included. BactDNA was detected in 98 patients (34.0%). A variant-NOD2 genotype was identified in 114 patients (39.6%). Forty patients (14%) relapsed during follow-up. Multivariate survival analysis identified bactDNA as an independent risk factor of flare (hazard ratio (HR) 8.75 (4.02-19.06) 95% confidence interval (CI)). Hospitalization, surgery, switch of treatment, initiation and escalation of anti-tumor necrosis factor (TNF) therapy, steroids initiation, and increased fecal calprotectin levels at 6 months were associated with bactDNA at baseline. A logistic regression analysis showed bactDNA as an independent and significant predictive factor of hospitalization (odds ratio (OR) 11.9 (3.4-42.3); P<0.001), steroids startup (OR 8.5 (2.7-27.1); P<0.001), and switch of treatment (OR 3.5 (1.6-7.7); P=0.002) at 6 months. No relationship was observed between bactDNA and mucosal lesions in patients with colonoscopy at admission. Serum pro-inflammatory cytokines were significantly increased in patients with bactDNA or a variant-NOD2 genotype. The combination of both factors induced decreased anti-TNF-α levels and a higher percentage of patients on intensified anti-TNF therapy.

CONCLUSIONS

BactDNA is an independent risk factor of relapse at 6 months in CD patients. BactDNA is also independently associated with an increased risk of hospitalization, switch of treatment, and steroids initiation.

Anti-TNF-alpha loss of response is associated with a decreased percentage of FoxP3+ T cells and a variant NOD2 genotype in patients with Crohn's disease

BACKGROUND

Anti-TNF-α therapies interact with the tolerogenic response in patients with Crohn's disease, modulating inflammation. However, drug levels and the genetic background may affect this interaction.

METHODS

Patients with Crohn's disease in remission on biologic monotherapy were enrolled in this study. FoxP3+ lymphocytes, NOD2 genotype, serum cytokine, anti-TNF-α levels, and anti-drug antibodies were evaluated. Regulatory T cell response to infliximab was evaluated in vitro.

RESULTS

Fifty-seven patients were included. Thirty-nine patients (68.4%) were receiving non-intensified biologic therapy whereas 18 patients (31.6%) were under an intensified biologic schedule due to loss of response. Eleven intensified patients (61.1%) showed a variant NOD2 genotype vs 9 on non-intensified biologics (23%, p < 0.01). Percentage of FoxP3+ T cells and serum free anti-TNF-α levels were significantly higher in patients with a wild-type vs variant NOD2 genotype, either under non-intensified or intensified schedule. Increasing amounts of infliximab significantly increased the expression of FoxP3+ T cells and anti-TNF-α levels in the supernatant from wild-type NOD2 patients cultured cells whereas the induction of FoxP3+ T cells and anti-TNF-α levels in the supernatant from variant NOD2 patients cultured cells were significantly lower. TNF-α and IL-10 showed a correlation with the FoxP3+ T cell population percentage and serum levels of anti-TNF-α, irrespective of NOD2 genotype. Eight variant NOD2 patients (66.6%) vs 4 wild-type NOD2 patients (8.8%) showed a perianal phenotype (p = 0.01). A significant reduction of the percentage of FoxP3+ T cells and serum levels of anti-TNF-α was observed in patients with the associated perianal disease.

CONCLUSION

Anti-TNF-α loss of response is associated with a decreased percentage of FoxP3+ T cells and a variant NOD2 genotype in patients with CD.

Characterization of Serum Cytokine Profile in Predominantly Colonic Inflammatory Bowel Disease to Delineate Ulcerative and Crohn's Colitides

BACKGROUND

As accessible diagnostic approaches fail to differentiate between ulcerative colitis (UC) and Crohn's colitis (CC) in one-third of patients with predominantly colonic inflammatory bowel disease (IBD), leading to inappropriate therapy, we aim to investigate the serum cytokine levels in these patients in search of molecular biometric markers delineating UC from CC.

METHODS

We measured 38 cytokines, chemokines, and growth factors using magnetic-bead-based multiplex immunoassay in 25 UC patients, 28 CC patients, and 30 controls. Our results are compared with those from a review of current literature regarding advances in serum cytokine profiles and associated challenges preventing their use for diagnostic/prognostic purposes.

RESULTS

Univariate analysis showed statistically significant increases of eotaxin, GRO, and TNF-α in UC patients compared to controls (Ctrl); interferon γ, interleukin (IL)-6, and IL-7 in CC group compared to Ctrl; and IL-8 in both UC and CC versus Ctrl. No cytokines were found to be different between UC and CC. A generalized linear model identified combinations of cytokines, allowing the identification of UC and CC patients, with area under the curve (AUC) = 0.936, as determined with receiver operating characteristic (ROC) analysis.

CONCLUSIONS

The current knowledge available about circulating cytokines in IBD is often contradictory. The development of an evidence-based tool using cytokines for diagnostic accuracy is still preliminary.

The impact of bacterial DNA translocation on early postoperative outcomes in Crohn's patients undergoing abdominal surgery

BACKGROUND AND AIMS

Bacterial DNA (bactDNA) translocation occurs frequently in patients with Crohn's disease and can be present in patients with a negative blood microbiological culture. We aimed to determine the effects of bactDNA translocation on postoperative outcomes in Crohn's disease patients undergoing abdominal surgery.

METHODS

Patients with Crohn's disease who underwent abdominal surgery between January 2012 and March 2014 were identified. General and postoperative outcome-related information was retrieved from a database, and the data were compared between patients with and without bactDNA translocation. Multivariate analysis was used to determine the independent effect of bactDNA translocation on postoperative morbidity.

RESULTS

One hundred and seven patients who underwent abdominal surgery were included in our study. The presence of bactDNA in blood samples was identified in 29 patients (27.1%). There was a total of 55 complications in 28 patients (26.2%). Patients with bactDNA in their blood had a mean postoperative hospital stay of 12.7±4.2 days and patients without DNA translocation had a mean postoperative hospital stay of 10.1±4.8 days (p = 0.009). The readmission rate was increased in patients with bactDNA translocation (p = 0.032). A low preoperative level of serum albumin (p = 0.024), preoperative immunosuppressive agent use (p = 0.046), and the presence of bactDNA in blood (p = 0.005) were independently associated with increased postoperative adverse outcomes.

CONCLUSIONS

Preoperative bactDNA translocation into the blood increases the incidence of postoperative adverse outcomes in patients with Crohn's disease who undergo abdominal surgery.

Anatomical localization of commensal bacteria in immune cell homeostasis and disease

The mammalian gastrointestinal (GI) tract is colonized by trillions of beneficial commensal bacteria that are essential for promoting normal intestinal physiology. While the majority of commensal bacteria are found in the intestinal lumen, many species have also adapted to colonize different anatomical locations in the intestine, including the surface of intestinal epithelial cells (IECs) and the interior of gut-associated lymphoid tissues. These distinct tissue localization patterns permit unique interactions with the mammalian immune system and collectively influence intestinal immune cell homeostasis. Conversely, dysregulated localization of commensal bacteria can lead to inappropriate activation of the immune system and is associated with numerous chronic infectious, inflammatory, and metabolic diseases. Therefore, regulatory mechanisms that control proper anatomical containment of commensal bacteria are essential to maintain tissue homeostasis and limit pathology. In this review, we propose that commensal bacteria associated with the mammalian GI tract can be anatomically defined as (i) luminal, (ii) epithelial-associated, or (iii) lymphoid tissue-resident, and we discuss the role and regulation of these microbial populations in health and disease.

Genetic susceptibility to increased bacterial translocation influences the response to biological therapy in patients with Crohn's disease

OBJECTIVE

The aetiology of Crohn's disease (CD) has been related to nucleotide-binding oligomerisation domain containing 2 (NOD2) and ATG16L1 gene variants. The observation of bacterial DNA translocation in patients with CD led us to hypothesise that this process may be facilitated in patients with NOD2/ATG16L1-variant genotypes, affecting the efficacy of anti-tumour necrosis factor (TNF) therapies.

DESIGN

179 patients with Crohn's disease were included. CD-related NOD2 and ATG16L1 variants were genotyped. Phagocytic and bactericidal activities were evaluated in blood neutrophils. Bacterial DNA, TNFα, IFNγ, IL-12p40, free serum infliximab/adalimumab levels and antidrug antibodies were measured.

RESULTS

Bacterial DNA was found in 44% of patients with active disease versus 23% of patients with remitting disease (p=0.01). A NOD2-variant or ATG16L1-variant genotype was associated with bacterial DNA presence (OR 4.8; 95% CI 1.1 to 13.2; p=0.001; and OR 2.4; 95% CI 1.4 to 4.7; p=0.01, respectively). This OR was 12.6 (95% CI 4.2 to 37.8; p=0.001) for patients with a double-variant genotype. Bacterial DNA was associated with disease activity (OR 2.6; 95% CI 1.3 to 5.4; p=0.005). Single and double-gene variants were not associated with disease activity (p=0.19). Patients with a NOD2-variant genotype showed decreased phagocytic and bactericidal activities in blood neutrophils, increased TNFα levels in response to bacterial DNA and decreased trough levels of free anti-TNFα. The proportion of patients on an intensified biological therapy was significantly higher in the NOD2-variant groups.

CONCLUSIONS

Our results characterise a subgroup of patients with CD who may require a more aggressive therapy to reduce the extent of inflammation and the risk of relapse.

Human β-defensin 3 peptide is increased and redistributed in Crohn's ileitis

BACKGROUND

Antimicrobial peptides (AMPs) maintain a sterile environment in intestinal crypts, limiting microbial colonization and invasion. Decreased AMP expression is proposed to increase the risk for inflammatory bowel disease. Expression and function of inducible AMPs, human β-defensin 2 and 3 (hBD-2 and hBD-3), remain poorly characterized in healthy and chronically inflamed intestine.

METHODS

Peptide concentrations of hBD-2 and hBD-3 in serum and intestinal biopsies of subjects with ulcerative colitis and Crohn's disease (CD), and those of healthy subjects were measured by ELISA. Messenger RNA of hBD-2 and hBD-3 was quantified by quantitative PCR in biopsies from the terminal ileum (TI) of patients with CD and healthy controls. Peptide localization of hBD-3 in the TI was visualized by confocal microscopy.

RESULTS

Immunoreactive hBD-3 peptide is present in the TI and colon in healthy subjects. In the TI of patients with CD, hBD-3, but not hBD-2 peptide, is increased 4-fold, whereas hBD-2 peptide is elevated in the serum. Messenger RNA of hBD-3 in the CD TI remains unchanged and does not correlate with hBD-3 peptide expression. However, hBD-3 is localized to Paneth cell granules and the apical surface of the healthy columnar epithelium. In CD, hBD-3 peptide location switches to the basolateral surface of the columnar epithelium and is diffusely distributed within the lamina propria.

CONCLUSION

The peptide hBD-3 throughout the healthy gastrointestinal tract suggests a role in maintaining balance between host defenses and commensal microbiota. Increased and relocalized secretion of hBD-3 toward the lamina propria in the CD TI indicates possible local immunomodulation during chronic inflammation, whereas increased serum hBD-2 in CD implicates its systemic antimicrobial and immunomodulatory role.

Circulating levels of HMGB1 are correlated strongly with MD2 in HIV-infection: possible implication for TLR4-signalling and chronic immune activation

Progressive HIV infection is characterized by profound enterocyte damage, microbial translocation and chronic immune activation. We aimed to test whether High Mobility Group Box protein 1(HMGB1), a marker of cell death, alone, or in combination with LPS, might contribute to HIV-associated immune activation and progression. Altogether, 29 untreated HIV-infected individuals, 25 inflammatory bowel disease (IBD) patients and 30 controls were included. HIV-infected patients had lower plasma LPS levels than IBD patients, but higher levels of soluble CD14 and Myeloid Differentiation (MD) 2, which interacts with TLR4 to initiate LPS-signalling. Furthermore, plasma levels of HMGB1 and MD2 were correlated directly within the HIV-infected cohort (r = 0.89, P < 0.001) and the IBD-cohort (r = 0.85, P < 0.001), implying HMGB1 signalling through the MD2/TLR4-pathway. HMGB1 and LPS, although not inter-correlated, were both moderately (r = 0.4) correlated with CD38 density on CD8+ T cells in HIV progressors. The highest levels of CD38 density and MD2 were found in progressors with plasma levels of both LPS and HMGB1 above the fiftieth percentile. Our results could imply that, in some patients, immune activation is triggered by microbial translocation, in some by cell death and in some by HMGB1 in complex with bacterial products through activation of the MD2/TLR4-pathway.

Microbial dysbiosis in pediatric patients with Crohn's disease

Microbial dysbiosis has been suggested to be involved in the pathogenesis of Crohn's disease (CD); however, many studies of gut microbial communities have been confounded by environmental and patient-related factors. In this study, the microbial flora of fecal samples from 19 children newly diagnosed with CD and 21 age-matched controls were analyzed using high-throughput sequencing to determine differences in the microbial composition between CD patients and controls. Analysis of the microbial composition of specific bacterial groups revealed that Firmicutes percentages were significantly lower in CD patients than in controls and that this was due largely to changes in the class Clostridia. Bacteroidetes and Proteobacteria percentages were higher and significantly higher in CD patients than in controls, respectively. Both the detection frequencies of Bacteroidetes and Firmicutes correlated (positively and negatively, respectively) with the calculated pediatric Crohn's disease activity index scores of patients. Upon further analysis, differences in the microbial compositions of patients with mild disease and moderate to severe disease were identified. Our findings indicate that a combination of different bacterial species or a dynamic interplay between individual species is important for disease and is consistent with the dysbiosis hypothesis of CD.

Exogenous alkaline phosphatase treatment complements endogenous enzyme protection in colonic inflammation and reduces bacterial translocation in rats

Alkaline phosphatase (AP) inactivates bacterial lipopolysaccharide and may therefore be protective. The small intestine and colon express intestinal (IAP) and tissue nonspecific enzyme (TNAP), respectively. The aim of this study was to assess the therapeutic potential of exogenous AP and its complementarity with endogenous enzyme protection in the intestine, as evidenced recently. IAP was given to rats by the oral or intrarectal route (700U/kgday). Oral budesonide (1mg/kgday) was used as a reference treatment. Treatment with intrarectal AP resulted in a 54.5% and 38.0% lower colonic weight and damage score, respectively, and an almost complete normalization of the expression of S100A8, LCN2 and IL-1β (p<0.05). Oral AP was less efficacious, while budesonide had a more pronounced effect on most parameters. Both oral and intrarectal AP counteracted bacterial translocation effectively (78 and 100%, respectively, p<0.05 for the latter), while budesonide failed to exert a positive effect. AP activity was increased in the feces of TNBS colitic animals, associated with augmented sensitivity to the inhibitor levamisole, suggesting enhanced luminal release of this enzyme. This was also observed in the mouse lymphocyte transfer model of chronic colitis. In a separate time course study, TNAP was shown to increase 2-3 days after colitis induction, while dextran sulfate sodium was a much weaker inducer of this isoform. We conclude that exogenous AP exerts beneficial effects on experimental colitis, which includes protection against bacterial translocation. AP of the tissue-nonspecific isoform is shed in higher amounts to the intestinal lumen in experimental colitis, possibly aiding in intestinal protection.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.

B cells exposed to enterobacterial components suppress development of experimental colitis

BACKGROUND

B cells positively contribute to immunity by antigen presentation to CD4(+) T cells, cytokine production, and differentiation into antibody secreting plasma cells. Accumulating evidence implies that B cells also possess immunoregulatory functions closely linked to their capability of IL-10 secretion.

METHODS

Colitis development was followed in CD4(+) CD25(-) T cell transplanted SCID mice co-transferred with B cells exposed to an enterobacterial extract (ebx-B cells). B and T cell cytokine expression was measured by flow cytometry and enzyme-linked immunosorbent assay (ELISA).

RESULTS

We demonstrate that splenic B cells exposed to ebx produce large amounts of IL-10 in vitro and express CD1d and CD5 previously known to be associated with regulatory B cells. In SCID mice transplanted with colitogenic CD4(+) CD25(-) T cells, co-transfer of ebx-B cells significantly suppressed development of colitis. Suppression was dependent on B cell-derived IL-10, as co-transfer of IL-10 knockout ebx-B cells failed to suppress colitis. Ebx-B cell-mediated suppression of colitis was associated with a decrease in interferon gamma (IFN-γ)-producing T(H) 1 cells and increased frequencies of Foxp3-expressing T cells.

CONCLUSIONS

These data demonstrate that splenic B cells exposed to enterobacterial components acquire immunosuppressive functions by which they can suppress development of experimental T cell-mediated colitis in an IL-10-dependent way.

Microbial translocation across the GI tract

The lumen of the gastrointestinal (GI) tract is home to an enormous quantity of different bacterial species, our microbiota, that thrive in an often symbiotic relationship with the host. Given that the healthy host must regulate contact between the microbiota and its immune system to avoid overwhelming systemic immune activation, humans have evolved several mechanisms to attenuate systemic microbial translocation (MT) and its consequences. However, several diseases are associated with the failure of one or more of these mechanisms, with consequent immune activation and deleterious effects on health. Here, we discuss the mechanisms underlying MT, diseases associated with MT, and therapeutic interventions that aim to decrease it.

Antimicrobial peptide response to blood translocation of bacterial DNA in Crohn's disease is affected by NOD2/CARD15 genotype

BACKGROUND

Blood translocation of bacterial-DNA has been described in patients with Crohn's disease (CD). The host's immune cell types cooperate to respond against bacterial insults. Some antimicrobial peptides are inducible after culture with bacterial products and a linkage has been established between them and NOD2/CARD15. The aim was to test whether defensins and cathelicidin (LL-37) expression and NOD2/CARD15 mutations in blood neutrophils are related to molecular bacterial translocation events in CD patients.

METHODS

Fifty consecutively admitted CD patients and 15 healthy controls were included. Clinical and analytical characteristics of patients were considered. NOD2/CARD15 genotyping, presence of bacterial-DNA, defensin and cathelicidin gene, and protein levels in neutrophils and serum cytokine levels were studied.

RESULTS

Twenty patients (40%) presented bacterial-DNA in blood. Eleven were active and 9 were in remission. Bacterial-DNA was not present in controls. NOD2/CARD15 mutations were identified in 25 patients (50%), 15 of which were in remission. Sixty percent of bacterial-DNA(+) and 43% of bacterial-DNA(-) patients showed a NOD2/CARD15 mutation. β-Defensin 2 and LL-37 mRNA and protein levels were upregulated in bacterial-DNA(+) patients. β-Defensin 2 and LL-37 expression correlated with bacterial-DNA concentration only in patients with a wildtype NOD2/CARD15 genotype. Cultured neutrophils of bacterial-DNA(-) patients confirmed the muramyl dipeptide-independent association between DEFB2 and LL-37 with bacterial-DNA concentration in wildtype NOD2/CARD15 patients. Cytokine levels were increased in bacterial-DNA(+) patients and correlated with bacterial-DNA concentration. NOD2/CARD15 genotype did not influence this correlation.

CONCLUSIONS

β-Defensin 2, LL-37, and proinflammatory cytokines are increased in CD patients with bacterial-DNA in a concentration-dependent manner. NOD2/CARD15 plays a key role in the regulation of this response.

The role of bacteria and pattern-recognition receptors in Crohn's disease

Crohn's disease is widely regarded as a multifactorial disease, and evidence from human and animal studies suggests that bacteria have an instrumental role in its pathogenesis. Comparison of the intestinal microbiota of patients with Crohn's disease to that of healthy controls has revealed compositional changes. In most studies these changes are characterized by an increase in the abundance of Bacteroidetes and Proteobacteria and a decrease in that of Firmicutes. In addition, a number of specific mucosa-associated bacteria have been postulated to have a role in Crohn's disease, including Mycobacterium avium subspecies paratuberculosis, adherent and invasive Escherichia coli, Campylobacter and Helicobacter species. The association between mutations in pattern-recognition receptors (Toll-like receptors and Nod-like receptors) and autophagy proteins and Crohn's disease provides further evidence to suggest that defective sensing and killing of bacteria may drive the onset of disease. In this Review, we present recent advances in understanding the role of bacteria and the contribution of pattern-recognition receptors and autophagy in the pathogenesis of Crohn's disease.

Systemic Toll-like receptor ligands modify B-cell responses in human inflammatory bowel disease

BACKGROUND

Bacteria have a central, although poorly understood, role in inflammatory bowel disease (IBD). Host-bacteria interactions primarily take place in the gastrointestinal tract, but cells may also encounter translocated bacteria in the bloodstream. IBD is associated with activated, circulating Toll-like receptor (TLR)2 and TLR4-expressing B cells suggesting that blood-borne microbial TLR ligands modulate B cell responses.

METHODS

Serum levels of lipopolysaccharide (LPS)/endotoxin and high mobility group box 1 (HMGB1), an endogenous TLR ligand, were quantified in Crohn's disease (CD) and ulcerative colitis (UC). Responses of purified B cells to LPS and HMGB1 were correlated with levels of systemic TLR ligands and clinical parameters of disease.

RESULTS

While IBD patients have increased levels of blood LPS, the net effect of endotoxemia has unexpected characteristics illustrating that LPS has both pro- and antiinflammatory roles through TLR4+ B cells. Experimental treatment of B cells demonstrates that the antiinflammatory effect of LPS is due to its hypo-acylation of lipid A suggesting an increased prevalence of systemic, hypo-acylated LPS in CD. In contrast, high levels of LPS are associated with disease activity in UC. HMGB1 activates B cells through TLR2 and CD36. Serum levels of HMGB1 correlate with spontaneous IL-8 production by B cells suggesting that blood-borne TLR2 ligands increase B-cell activation in vivo.

CONCLUSIONS

Systemic TLR ligands modulate B cells towards either proinflammatory or antiinflammatory activity depending on the predominant ligand(s). Further, the circulating B cell may represent an important proxy for quantifying the LPS lipid A acylation burden in patients with IBD.

Bacterial induction of proinflammatory cytokines in inflammatory bowel disease

It has become increasingly clear that inflammatory bowel disease (IBD) develops on the background of genetic defects in the host, conveying an increased susceptibility to an environmental antigen or antigens. The environmental factor implicated in the pathophysiology of gut inflammation, which is undergoing increased scrutiny, is the intestinal flora. The intestinal flora as a whole and specific bacteria and their products have been found to trigger cytokine expression in various cell types. Consistently, multiple bacterial strains were found to induce tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8) in macrophage and epithelial cell systems, respectively, in particular in Crohn's disease. Interestingly, various cell types from patients with IBD display an increased susceptibility to specific bacterial products, including flagellin, pili, and lipopolysaccharides. It remains to be determined whether additional effector proteins regulate cytokine expression and the aberrant mucosal immune response in IBD.

Campylobacter jejuni induces transcytosis of commensal bacteria across the intestinal epithelium through M-like cells

BACKGROUND

Recent epidemiological analyses have implicated acute Campylobacter enteritis as a factor that may incite or exacerbate inflammatory bowel disease (IBD) in susceptible individuals. We have demonstrated previously that C. jejuni disrupts the intestinal barrier function by rapidly inducing epithelial translocation of non-invasive commensal bacteria via a transcellular lipid raft-mediated mechanism ('transcytosis'). To further characterize this mechanism, the aim of this current study was to elucidate whether C. jejuni utilizes M cells to facilitate transcytosis of commensal intestinal bacteria.

RESULTS

C. jejuni induced translocation of non-invasive E. coli across confluent Caco-2 epithelial monolayers in the absence of disrupted transepithelial electrical resistance or increased permeability to a 3 kDa dextran probe. C. jejuni-infected monolayers displayed increased numbers of cells expressing the M cell-specific marker, galectin-9, reduced numbers of enterocytes that stained with the absorptive enterocyte marker, Ulex europaeus agglutinin-1, and reduced activities of enzymes typically associated with absorptive enterocytes (namely alkaline phosphatase, lactase, and sucrase). Furthermore, in Campylobacter-infected monolayers, E. coli were observed to be internalized specifically within epithelial cells displaying M-like cell characteristics.

CONCLUSION

These data indicate that C. jejuni may utilize M cells to promote transcytosis of non-invasive bacteria across the intact intestinal epithelial barrier. This mechanism may contribute to the inflammatory immune responses against commensal intestinal bacteria commonly observed in IBD patients.

Campylobacter jejuni induces transcytosis of commensal bacteria across the intestinal epithelium through M-like cells

BACKGROUND

Recent epidemiological analyses have implicated acute Campylobacter enteritis as a factor that may incite or exacerbate inflammatory bowel disease (IBD) in susceptible individuals. We have demonstrated previously that C. jejuni disrupts the intestinal barrier function by rapidly inducing epithelial translocation of non-invasive commensal bacteria via a transcellular lipid raft-mediated mechanism ('transcytosis'). To further characterize this mechanism, the aim of this current study was to elucidate whether C. jejuni utilizes M cells to facilitate transcytosis of commensal intestinal bacteria.

RESULTS

C. jejuni induced translocation of non-invasive E. coli across confluent Caco-2 epithelial monolayers in the absence of disrupted transepithelial electrical resistance or increased permeability to a 3 kDa dextran probe. C. jejuni-infected monolayers displayed increased numbers of cells expressing the M cell-specific marker, galectin-9, reduced numbers of enterocytes that stained with the absorptive enterocyte marker, Ulex europaeus agglutinin-1, and reduced activities of enzymes typically associated with absorptive enterocytes (namely alkaline phosphatase, lactase, and sucrase). Furthermore, in Campylobacter-infected monolayers, E. coli were observed to be internalized specifically within epithelial cells displaying M-like cell characteristics.

CONCLUSION

These data indicate that C. jejuni may utilize M cells to promote transcytosis of non-invasive bacteria across the intact intestinal epithelial barrier. This mechanism may contribute to the inflammatory immune responses against commensal intestinal bacteria commonly observed in IBD patients.

HIV Infection and Gut Mucosal Immune Function: Updates on Pathogenesis with Implications for Management and Intervention

HIV is primarily a sexually transmitted infection. However, given that the gastrointestinal tract (GIT) houses most of the body’s lymphocytes, including activated memory CD4⁺ T cells that are preferential targets for HIV, recent research has focused on the role of the GIT in transmission and pathogenesis. In health, the GIT maintains a balance between immune tolerance and rapid responsiveness. A complex network of innate and adaptive responses maintains this balance, which is severely perturbed in HIV infection. Recent studies have focused on mechanisms of GIT CD4⁺ T-cell depletion and epithelial disruption in HIV infection, the role of inflammation in accelerating viral dissemination, the kinetics of the adaptive response following transmission, and the extent of T-cell reconstitution following antiretroviral therapy. This review summarizes the results of recent investigations that may have important implications for the development of vaccines, microbicides, and therapeutic interventions for HIV and other mucosal pathogens.

Hyperactivated B cells in human inflammatory bowel disease

IBD is characterized by a chronic, dysregulated immune response to intestinal bacteria. Past work has focused on the role of T cells and myeloid cells in mediating chronic gastrointestinal and systemic inflammation. Here, we show that circulating and tissue B cells from CD patients demonstrate elevated basal levels of activation. CD patient B cells express surface TLR2, spontaneously secrete high levels of IL-8, and contain increased ex vivo levels of phosphorylated signaling proteins. CD clinical activity correlates directly with B cell expression of IL-8 and TLR2, suggesting a positive relationship between these B cell inflammatory mediators and disease pathogenesis. In contrast, B cells from UC patients express TLR2 but generally do not demonstrate spontaneous IL-8 secretion; however, significant IL-8 production is inducible via TLR2 stimulation. Furthermore, UC clinical activity correlates inversely with levels of circulating TLR2+ B cells, which is opposite to the association observed in CD. In conclusion, TLR2+ B cells are associated with clinical measures of disease activity and differentially associated with CD- and UC-specific patterns of inflammatory mediators, suggesting a formerly unappreciated role of B cells in the pathogenesis of IBD.