Inflammation and apoptosis in Clostridium difficile enteritis is mediated by PGE2 up-regulation of Fas ligand

Advances in the mechanism of metformin with wide-ranging effects on regulation of the intestinal microbiota

Metformin is of great focus because of its high safety, low side effects, and various effects other than lowering blood sugar, such as anti-inflammation, anti-tumor, and anti-aging. Studies have shown that metformin has a modulating effect on the composition and function of the intestinal microbiota other than acting on the liver. However, the composition of microbiota is complex and varies to some extent between species and individuals, and the experimental design of each study is also different. Multiple factors present a major obstacle to better comprehending the effects of metformin on the gut microbiota. This paper reviews the regulatory effects of metformin on the gut microbiota, such as increasing the abundance of genus Akkermansia, enriching short-chain fatty acids (SCFAs)-producing bacterial genus, and regulating gene expression of certain genera. The intestinal microbiota is a large and vital ecosystem in the human body and is considered to be the equivalent of an "organ" of the human body, which is highly relevant to human health and disease status. There are a lot of evidences that the gut microbiota is responsible for metformin's widespread effects. However, there are only a few systematic studies on this mechanism, and the specific mechanism is still unclear. This paper aims to summarize the possible mechanism of metformin in relation to gut microbiota.

Budesonide, an anti-inflammatory drug, exacerbate clostridioides difficile colitis in mice

BACKGROUND AND AIMS

Clostridioides difficile infection (CDI) induces intense acute inflammatory responses through toxin release. A combination of antibiotic and anti-inflammatory agents is sometimes recommended in severe, non-responsive cases, although clinical trials have been inconclusive, raising concerns about potential complications. This study aims to investigate the effect of budesonide and mesalamine in the treatment of CDI in a murine model, by evaluating the combination of fidaxomicin and these anti-inflammatory drugs.

METHOD

C57BL/6 J female mice pretreated with an antimicrobial mixture were challenged with C. difficile VPI 10463 or culture media by gavage. After the challenge, mice received placebo, fidaxomicin alone (20 mg/kg), or fidaxomicin combined with mesalamine (200, 400 mg/kg) or budesonide (0.2, 1, 10 mg/kg) for 5 days. The mice were monitored for 7 days with weight and survival. Colon and cecum tissues were harvested for histological assessment.

RESULTS

CDI of mice caused 80% mortality. Fidaxomicin completely protected against CDI in all parameters (weight, survival and pathscores). Mortality rates were up to 90%, 70% in budesonide(10 mg/kg) and mesalamine (400 mg/kg) treatment group, respectively. Budesonide (0.02,0.1 and 1 mg/kg) adjunction to fidaxomicin worsened the disease outcome according to all tested parameters. While mesalamine in combination with fidaxomicin (200, 400 mg/kg) did not lead to any deaths during CDI treatment, it did not provide additional benefits.

CONCLUSIONS

Anti-inflammatory drugs including corticosteroid therapy may worsen the incidence and severity of CDI in this mouse model. These studies may have important clinical implications for understanding the role of anti-inflammatory/ corticosteroid therapy in CDI and inflammatory bowel disease management.

Direct and indirect effects of pathogenic bacteria on the integrity of intestinal barrier

Bacterial translocation is a pathological process involving migration of pathogenic bacteria across the intestinal barrier to enter the systemic circulation and gain access to distant organs. This phenomenon has been linked to a diverse range of diseases including inflammatory bowel disease, pancreatitis, and cancer. The intestinal barrier is an innate structure that maintains intestinal homeostasis. Pathogenic infections and dysbiosis can disrupt the integrity of the intestinal barrier, increasing its permeability, and thereby facilitating pathogen translocation. As translocation represents an essential step in pathogenesis, a clear understanding of how barrier integrity is disrupted and how this disruption facilitates bacterial translocation could identify new routes to effective prophylaxis and therapy. In this comprehensive review, we provide an in-depth analysis of bacterial translocation and intestinal barrier function. We discuss currently understood mechanisms of bacterial-enterocyte interactions, with a focus on tight junctions and endocytosis. We also discuss the emerging concept of bidirectional communication between the intestinal microbiota and other body systems. The intestinal tract has established 'axes' with various organs. Among our regulatory systems, the nervous, immune, and endocrine systems have been shown to play pivotal roles in barrier regulation. A mechanistic understanding of intestinal barrier regulation is crucial for the development of personalized management strategies for patients with bacterial translocation-related disorders. Advancing our knowledge of barrier regulation will pave the way for future research in this field and novel clinical intervention strategies.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Albiflorin ameliorates inflammation and oxidative stress by regulating the NF-κB/NLRP3 pathway in Methotrexate-induced enteritis

Methotrexate (MTX) treats various diseases but also damages intestinal barrier and leads to enteritis. Albiflorin (ALB) has a variety of pharmacological effects, including antioxidant, anti-inflammation and anti-apoptosis. In the present study, we evaluated the therapeutic effect of ALB on MTX-induced enteritis and investigated the possible mechanisms involved. Male SD rats were intraperitoneally injected with 7 mg/kg MTX for three consecutive days to establish the enteritis model. ALB (20 or 40 mg/kg/day) was intragastrically administrated since two days prior MTX treatment and lasted for six days. We found that ALB treatment increased body weight and intestinal weight of rats with MTX injection. The disease activity index (DAI) score was also decreased after ALB administration. In histological examination, ALB treatment attenuated inflammatory cells infiltration and promoted survival of goblet cells. In detection of inflammatory-associated factors, ALB treatment decreased CD68⁺ cells infiltration, inhibited myeloperoxidase activity, and suppressed intercellular cell adhesion molecule-1 and cyclooxygenase-2 expression. Additionally, ALB reduced malondialdehyde, glutathione levels, inhibited superoxide dismutase activity and suppressed reactive oxygen species production. Moreover, ALB treatment effectively inhibited NLRP3, as well as caspase 1 p20 and interleukin (IL)-1β and 18 expression. Finally, nuclear factor-κB (NF-κB) p65 phosphorylation and nuclear translocation were also demonstrated to be blocked upon ALB treatment. In conclusion, our findings indicated that ALB alleviated MTX-induced enteritis via inhibiting the NF-κB/NLRP3 pathway.

Mechanism of preservation of the intestinal mucosa architecture and NF-κB/PGE2 reduction by hydrogen sulfide on cholera toxin-induced diarrhea in mice

AIMS

Investigate the involvement of Hydrogen sulfide (H₂S) in inflammatory parameters and intestinal morphology caused by cholera toxin (CT) in mice.

MAIN METHODS

Mice were subjected to the procedure of inducing diarrhea by CT in the isolated intestinal loop model. The intestinal loops were inoculated with H₂S donor molecules (NaHS and GYY 4137) or saline and CT. To study the role of EP2 and EP4 prostaglandin E2 (PGE2) receptors in the H₂S antisecretory effect, PAG (DL-propargylglycine - inhibitor of cystathionine-γ-lyase (CSE)), PF-04418948 (EP2 antagonist) and ONO-AE3-208 (EP4 antagonist) were used. The intestinal loops were evaluated for intestinal secretion, relation of the depth of villi and intestinal crypts, and real-time PCR for the mRNA of the CXCL2, IL-6, NOS-2, IL-17, NF-κB1, NF-κBIA, SLC6A4 and IFN-γ genes.

KEY FINDINGS

H₂S restored the villus/crypt depth ratio caused by CT. NaHS and GYY 4137 increased the expression of NF-κB1 and for the NF-κBIA gene, only GYY 4137 increased the expression of this gene. The increased expression of NF-κB inhibitors, NF-κB1 and NF-κBIA by H₂S indicates a possible decrease in NF-κB activity. The pretreatment with PAG reversed the protective effect of PF-04418948 and ONO-AE3-208, indicating that H₂S probably decreases PGE2 because in the presence of antagonists of this pathway, PAG promotes intestinal secretion.

SIGNIFICANCE

Our results point to a protective activity of H₂S against CT for promoting a protection of villus and crypt intestine morphology and also that its mechanism occurs at least in part due to decreasing the activity of NF-κB and PGE2.

The mechanisms and safety of probiotics against toxigenic clostridium difficile

INTRODUCTION

Toxigenic Clostridium difficile (C. difficile) is the main cause of antibiotic-associated diarrhea and can induce pseudomembranous colitis and infrequent toxic megacolon, which are potentially fatal. The standard antibiotic therapy for C. difficile infection (CDI) is limited by antibiotics' broad spectrum and further disruptive effects on indigenous microbiota. Probiotics may offer a prospective and alternative strategy for the prevention and treatment of CDI.

AREAS COVERED

In this article, the mechanisms implying the probiotic effect against C. difficile and the safety profile highlighting the patient groups with inappropriate application of probiotics were reviewed from 2015 to 2020.

EXPERT OPINION

Although many strains with ability against C. difficile have been reported, the usage of probiotics for CDI prevention and/or treatment is scarce since the number of clinical trials is not sufficient to prove probiotics' efficacy and safety in CDI treatment, especially for premature infant and immunocompromised patient. Especially, there are few well-defined clinical studies supporting safety of probiotics for CDI. A few strains from Lactobacillus and Saccharomyces genus have been studied more extensively than other probiotic strains through clinical trials for CDI. Thus, more clinical intervention studies regarding the benefit and the comprehensive safety assessments of probiotics for CDI are needed.

Alteration of Gut Microbiota in Inflammatory Bowel Disease (IBD): Cause or Consequence? IBD Treatment Targeting the Gut Microbiome

Inflammatory bowel disease (IBD) is a chronic complex inflammatory gut pathological condition, examples of which include Crohn’s disease (CD) and ulcerative colitis (UC), which is associated with significant morbidity. Although the etiology of IBD is unknown, gut microbiota alteration (dysbiosis) is considered a novel factor involved in the pathogenesis of IBD. The gut microbiota acts as a metabolic organ and contributes to human health by performing various physiological functions; deviation in the gut flora composition is involved in various disease pathologies, including IBD. This review aims to summarize the current knowledge of gut microbiota alteration in IBD and how this contributes to intestinal inflammation, as well as explore the potential role of gut microbiota-based treatment approaches for the prevention and treatment of IBD. The current literature has clearly demonstrated a perturbation of the gut microbiota in IBD patients and mice colitis models, but a clear causal link of cause and effect has not yet been presented. In addition, gut microbiota-based therapeutic approaches have also shown good evidence of their effects in the amelioration of colitis in animal models (mice) and IBD patients, which indicates that gut flora might be a new promising therapeutic target for the treatment of IBD. However, insufficient data and confusing results from previous studies have led to a failure to define a core microbiome associated with IBD and the hidden mechanism of pathogenesis, which suggests that well-designed randomized control trials and mouse models are required for further research. In addition, a better understanding of this ecosystem will also determine the role of prebiotics and probiotics as therapeutic agents in the management of IBD.

Nonsteroidal Anti-inflammatory Drugs Alter the Microbiota and Exacerbate Clostridium difficile Colitis while Dysregulating the Inflammatory Response

Clostridium difficile infection (CDI) is a major public health threat worldwide. The use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with enhanced susceptibility to and severity of CDI; however, the mechanisms driving this phenomenon have not been elucidated. NSAIDs alter prostaglandin (PG) metabolism by inhibiting cyclooxygenase (COX) enzymes. Here, we found that treatment with the NSAID indomethacin prior to infection altered the microbiota and dramatically increased mortality and the intestinal pathology associated with CDI in mice. We demonstrated that in C. difficile-infected animals, indomethacin treatment led to PG deregulation, an altered proinflammatory transcriptional and protein profile, and perturbed epithelial cell junctions. These effects were paralleled by increased recruitment of intestinal neutrophils and CD4⁺ cells and also by a perturbation of the gut microbiota. Together, these data implicate NSAIDs in the disruption of protective COX-mediated PG production during CDI, resulting in altered epithelial integrity and associated immune responses.IMPORTANCEClostridium difficile infection (CDI) is a spore-forming anaerobic bacterium and leading cause of antibiotic-associated colitis. Epidemiological data suggest that use of nonsteroidal anti-inflammatory drugs (NSAIDs) increases the risk for CDI in humans, a potentially important observation given the widespread use of NSAIDs. Prior studies in rodent models of CDI found that NSAID exposure following infection increases the severity of CDI, but mechanisms to explain this are lacking. Here we present new data from a mouse model of antibiotic-associated CDI suggesting that brief NSAID exposure prior to CDI increases the severity of the infectious colitis. These data shed new light on potential mechanisms linking NSAID use to worsened CDI, including drug-induced disturbances to the gut microbiome and colonic epithelial integrity. Studies were limited to a single NSAID (indomethacin), so future studies are needed to assess the generalizability of our findings and to establish a direct link to the human condition.

Protective Effects of Bifidobacterial Strains Against Toxigenic Clostridium difficile

Probiotics might offer an attractive alternative to prevent and control Clostridium difficile (C. difficile) infection (CDI). Limited information is available on the ability of commercially used bifidobacterial strains to inhibit C. difficile. This study examined the anti-clostridial effects of Bifidobacterium longum JDM301, a widely used commercial probiotic strain in China, in vitro and in vivo. In vitro evaluation revealed a significant reduction in C. difficile counts when JDM301 was co-cultured with C. difficile, which was correlated with the significant decrease in clostridial toxin titres (TcdA and TcdB). Furthermore, the cell-free culture supernatants (CFS) of JDM301 inhibited C. difficile growth and degraded TcdA and TcdB. Notably, the results showed that acid pH promoted the degradation of TcdA by CFS from JDM301. Furthermore, comparative studies among 10 B. longum strains were performed, which showed that the inhibitory effect of CFS from JDM301 was similar with the other 8 B. longum strains and higher than strain BLY1. However, when it was neutralized, the significant different was lost. When present together, it was suggested that the acid pH induced by probiotics not only played important roles in the growth inhibition against C. difficile resulting in the reduction of toxins titres, but also directly promoted the degradation of clostridial toxin. In vivo studies proved that JDM301 partially relieved damage to tissues caused by C. difficile and also decreased the number of C. difficile and toxin levels. In summary, our results demonstrated that the commercial strain, JDM301 could be considered a probiotic able to exert anti-toxin capability and most of the CFS from Bifidobacterium were able to inhibit the growth of C. difficile, depending on acid pH. These results highlighted a potential that JDM301 could be helpful in preventing CDI and that most of the bifidobacterial strains could (at least partially) exert protective effects by reducing toxin titres through growth inhibition against toxigenic C. difficile.

Fidaxomicin and OP-1118 Inhibit Clostridium difficile Toxin A- and B-Mediated Inflammatory Responses via Inhibition of NF-κB Activity

Clostridium difficile causes diarrhea and colitis by releasing toxin A and toxin B. In the human colon, both toxins cause intestinal inflammation and stimulate tumor necrosis factor alpha (TNF-α) expression via the activation of NF-κB. It is well established that the macrolide antibiotic fidaxomicin is associated with reduced relapses of C. difficile infection. We showed that fidaxomicin and its primary metabolite OP-1118 significantly inhibited toxin A-mediated intestinal inflammation in mice in vivo and toxin A-induced cell rounding in vitro We aim to determine whether fidaxomicin and OP-1118 possess anti-inflammatory effects against toxin A and toxin B in the human colon and examine the mechanism of this response. We used fresh human colonic explants, NCM460 human colonic epithelial cells, and RAW264.7 mouse macrophages to study the mechanism of the activity of fidaxomicin and OP-1118 against toxin A- and B-mediated cytokine expression and apoptosis. Fidaxomicin and OP-1118 dose-dependently inhibited toxin A- and B-induced TNF-α and interleukin-1β (IL-1β) mRNA expression and histological damage in human colonic explants. Fidaxomicin and OP-1118 inhibited toxin A-mediated NF-κB phosphorylation in human and mouse intestinal mucosae. Fidaxomicin and OP-1118 also inhibited toxin A-mediated NF-κB phosphorylation and TNF-α expression in macrophages, which was reversed by the NF-κB activator phorbol myristate acetate (PMA). Fidaxomicin and OP-1118 prevented toxin A- and B-mediated apoptosis in NCM460 cells, which was reversed by the addition of PMA. PMA reversed the cytoprotective effect of fidaxomicin and OP-1118 in toxin-exposed human colonic explants. Fidaxomicin and OP-1118 inhibit C. difficile toxin A- and B-mediated inflammatory responses, NF-κB phosphorylation, and tissue damage in the human colon.

The American cockroach peptide periplanetasin-4 inhibits Clostridium difficile toxin A-induced cell toxicities and inflammatory responses in the mouse gut

Many reports have shown that crude extracts of the American cockroach have therapeutic effects on inflammation. In a previous study, our research group showed that an antimicrobial peptide (Periplanetasin-2) derived from the American cockroach via de novo transcriptome analysis inhibited apoptosis of human colonocytes and inflammatory responses of the mouse gut caused by Clostridium difficile toxin A. Here, we examined whether Periplanetasin-4 (Peri-4), another antimicrobial peptide identified via de novo transcriptome analysis of the American cockroach, could also inhibit the various toxicities induced by C. difficile toxin A. We found that Peri-4 significantly reduced the cell viability loss and cell apoptosis caused by toxin A in vitro. Peri-4 also ameliorated the severe inflammatory responses seen in the toxin A-induced mouse enteritis model, rescuing the villus disruption and interleukin-6 production induced by luminal injection of toxin A into the mouse gut. Mechanistically, we found that Peri-4 could reduce toxin A-induced reactive oxygen species production to inhibit the activations of p38MAPK and p21^Cip1/Waf1 , which are critical for the cell damages induced by toxin A. These results collectively suggest that the Peri-4 may be a potential therapeutic agent for treating toxin A-induced pseudomembranous colitis. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Risk factors and clinical outcome of Clostridium difficile infection in patients with IBD: A single-center retrospective study of 260 cases in China

OBJECTIVE

Clostridium difficile infection (CDI) may lead to poor outcomes in patients with inflammatory bowel disease (IBD). In this study we aimed to investigate the cumulative incidence, risk factors and outcome of CDI in patients with IBD in a single center in China.

METHODS

The clinical features and endoscopic profiles of consecutive IBD patients admitted to Ruijin Hospital, Shanghai Jiaotong University School of Medicine between January 2013 and December 2015 were retrospectively analyzed. CDI was diagnosed based on a positive polymerase chain reaction (PCR) stool test.

RESULTS

A total of 260 patients with IBD were enrolled, including 176 with Crohn's disease (CD) and 84 with ulcerative colitis (UC). Altogether 13 (5.0%) patients were diagnosed with CDI. The incidence of CDI was 4.0% (7/176) in CD and 7.1% (6/84) in UC, respectively. The endoscopic feature of pseudomembrane was found in four (33.3%) IBD-CDI patients, and pseudomembrane and deep ulcers were significantly correlated with CDI (P < 0.001 and P = 0.006, respectively). Hemoglobin (Hb) <100 g/L was found to be associated with CDI (OR 3.48, 95% CI 1.04-11.61, P = 0.043). Patients in the CDI group showed a higher risk of developing abdominal abscesses than those in the non-CDI group (OR 6.09, 95% CI 1.8-15.2, P = 0.003).

CONCLUSIONS

PCR-based fecal test for CDI should be performed in these IBD patients. Hb <100 g/L may be an important risk factor for CDI in IBD. For patients with CDI, antibiotics should be administered promptly to prevent abdominal abscess.

Dissecting the Interplay Between Intestinal Microbiota and Host Immunity in Health and Disease: Lessons Learned from Germfree and Gnotobiotic Animal Models

This review elaborates the development of germfree and gnotobiotic animal models and their application in the scientific field to unravel mechanisms underlying host-microbe interactions and distinct diseases. Strictly germfree animals are raised in isolators and not colonized by any organism at all. The germfree state is continuously maintained by birth, raising, housing and breeding under strict sterile conditions. However, isolator raised germfree mice are exposed to a stressful environment and exert an underdeveloped immune system. To circumvent these physiological disadvantages depletion of the bacterial microbiota in conventionally raised and housed mice by antibiotic treatment has become an alternative approach. While fungi and parasites are not affected by antibiosis, the bacterial microbiota in these "secondary abiotic mice" have been shown to be virtually eradicated. Recolonization of isolator raised germfree animals or secondary abiotic mice results in a gnotobiotic state. Both, germfree and gnotobiotic mice have been successfully used to investigate biological functions of the conventional microbiota in health and disease. Particularly for the development of novel clinical applications germfree mice are widely used tools, as summarized in this review further focusing on the modulation of bacterial microbiota in laboratory mice to better mimic conditions in the human host.

The Intestinal Microbiota in Inflammatory Bowel Disease

The intestinal microbiota has important metabolic and host-protective functions. Conversely to these beneficial functions, the intestinal microbiota is thought to play a central role in the etiopathogenesis of inflammatory bowel disease (IBD; Crohn's disease and ulcerative colitis), a chronic inflammation of the gut mucosa. Genetic screens and studies in experimental mouse models have clearly demonstrated that IBD can develop due to excessive translocation of bacteria into the bowel wall or dysregulated handling of bacteria in genetically susceptible hosts. In healthy individuals, the microbiota is efficiently separated from the mucosal immune system of the gut by the gut barrier, a single layer of highly specialized epithelial cells, some of which are equipped with innate immune functions to prevent or control access of bacterial antigens to the mucosal immune cells. It is currently unclear whether the composition of the microbial flora or individual bacterial strains or pathogens induces or supports the pathogenesis of IBD. Further research will be necessary to carefully dissect the contribution of individual bacterial species to this disease and to ascertain whether specific modulation of the intestinal microbiome may represent a valuable further option for future therapeutic strategies.

Microbiome, Metabolome and Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD) is a multifactorial disorder that conceptually occurs as a result of altered immune responses to commensal and/or pathogenic gut microbes in individuals most susceptible to the disease. During Crohn’s Disease (CD) or Ulcerative Colitis (UC), two components of the human IBD, distinct stages define the disease onset, severity, progression and remission. Epigenetic, environmental (microbiome, metabolome) and nutritional factors are important in IBD pathogenesis. While the dysbiotic microbiota has been proposed to play a role in disease pathogenesis, the data on IBD and diet are still less convincing. Nonetheless, studies are ongoing to examine the effect of pre/probiotics and/or FODMAP reduced diets on both the gut microbiome and its metabolome in an effort to define the healthy diet in patients with IBD. Knowledge of a unique metabolomic fingerprint in IBD could be useful for diagnosis, treatment and detection of disease pathogenesis.

The Insect Peptide CopA3 Increases Colonic Epithelial Cell Proliferation and Mucosal Barrier Function to Prevent Inflammatory Responses in the Gut

The epithelial cells of the gut form a physical barrier against the luminal contents. The collapse of this barrier causes inflammation, and its therapeutic restoration can protect the gut against inflammation. EGF enhances mucosal barrier function and increases colonocyte proliferation, thereby ameliorating inflammatory responses in the gut. Based on our previous finding that the insect peptide CopA3 promotes neuronal growth, we herein tested whether CopA3 could increase the cell proliferation of colonocytes, enhance mucosal barrier function, and ameliorate gut inflammation. Our results revealed that CopA3 significantly increased epithelial cell proliferation in mouse colonic crypts and also enhanced colonic epithelial barrier function. Moreover, CopA3 treatment ameliorated Clostridium difficile toxin As-induced inflammation responses in the mouse small intestine (acute enteritis) and completely blocked inflammatory responses and subsequent lethality in the dextran sulfate sodium-induced mouse model of chronic colitis. The marked CopA3-induced increase of colonocyte proliferation was found to require rapid protein degradation of p21(Cip1/Waf1), and an in vitro ubiquitination assay revealed that CopA3 directly facilitated ubiquitin ligase activity against p21(Cip1/Waf1). Taken together, our findings indicate that the insect peptide CopA3 prevents gut inflammation by increasing epithelial cell proliferation and mucosal barrier function.

The antimicrobial peptide cathelicidin modulates Clostridium difficile-associated colitis and toxin A-mediated enteritis in mice

BACKGROUND

Clostridium difficile mediates intestinal inflammation by releasing toxin A (TxA), a potent enterotoxin. Cathelicidins (Camp as gene name, LL-37 peptide in humans and mCRAMP peptide in mice) are antibacterial peptides that also posses anti-inflammatory properties.

OBJECTIVES

To determine the role of cathelicidins in models of Clostridium difficile infection and TxA-mediated ileal inflammation and cultured human primary monocytes.

DESIGN

Wild-type (WT) and mCRAMP-deficient (Camp(-/-)) mice were treated with an antibiotic mixture and infected orally with C difficile. Some mice were intracolonically given mCRAMP daily for 3 days. Ileal loops were also prepared in WT mice and treated with either saline or TxA and incubated for 4 h, while some TxA-treated loops were injected with mCRAMP.

RESULTS

Intracolonic mCRAMP administration to C difficile-infected WT mice showed significantly reduced colonic histology damage, apoptosis, tissue myeloperoxidase (MPO) and tumour necrosis factor (TNF)α levels. Ileal mCRAMP treatment also significantly reduced histology damage, tissue apoptosis, MPO and TNFα levels in TxA-exposed ileal loops. WT and Camp(-/-) mice exhibited similar intestinal responses in both models, implying that C difficile/TxA-induced endogenous cathelicidin may be insufficient to modulate C difficile/TxA-mediated intestinal inflammation. Both LL-37 and mCRAMP also significantly reduced TxA-induced TNFα secretion via inhibition of NF-κB phosphorylation. Endogenous cathelicidin failed to control C difficile and/or toxin A-mediated inflammation and even intestinal cathelicidin expression was increased in humans and mice.

CONCLUSION

Exogenous cathelicidin modulates C difficile colitis by inhibiting TxA-associated intestinal inflammation. Cathelicidin administration may be a new anti-inflammatory treatment for C difficile toxin-associated disease.

Probiotics for the treatment of Clostridium difficile associated disease

The purpose of this review paper is to update the current and potential future role of probiotics for Clostridium difficile-associated disease (CDAD). Included in this review, is an update on the testing of newer probiotics (e.g., Bacillus coagulans GBI-30, 6086) in animal models of CDAD. There is a focus on the modulation of signal transduction pathways (i.e., transcription factors like cAMP response element-binding, activator protein 1, and nuclear factor kappa B), as well as the inhibition of certain kinases (e.g., p38 mitogen activated protein kinases) by probiotics. Inhibition of signal transduction by probiotics, such as Saccharomyces boulardii, result in multiple effects on intestinal fluid secretion, neutrophil influx into the colon, inflammation, and colonocyte apoptosis that may positively impact CDAD. Recent clinical approaches with probiotics, for the prevention of primary and recurrent CDAD, are also summarized in this review paper. Future directions for the treatment of CDAD by probiotics are also mentioned in this review. In particular, the use of multi-strain probiotic formulations such as Ecologic^® AAD and VSL #3^® may represent a rationale pharmacological approach, particularly as adjunctive therapies for CDAD. Understanding the mechanistic basis of CDAD, and how probiotics interfere at ceratin steps in the pathogenic process, may also present the opportunity to design other multi-strain probiotics that could have a future impact on CDAD.

Elevated lactoferrin is associated with moderate to severe Clostridium difficile disease, stool toxin, and 027 infection

We evaluated blood and fecal biomarkers as indicators of severity in symptomatic patients with confirmed Clostridium difficile infection (CDI). Recruitment included patients with CDI based on clinical symptoms and supporting laboratory findings. Disease severity was defined by physician’s assessment and blood and fecal biomarkers were measured. Toxigenic culture done using spore enrichment and toxin B detected by tissue culture were done as confirmatory tests. Polymerase chain reaction (PCR) ribotyping was performed on each isolate. There were 98 patients recruited, with 85 (87 %) confirmed cases of toxigenic CDI (21 severe, 57 moderate, and seven mild), of which 68 (80 %) were also stool toxin-positive. Elevated lactoferrin (p = 0.01), increased white blood cell (WBC) count (p = 0.08), and low serum albumin (p = 0.03) were all associated with the more severe cases of CDI. Ribotype 027 infection accounted for 71 % of severe cases (p < 0.01) and patients with stool toxin had significantly higher lactoferrin levels and WBC counts (p < 0.05). Our findings show that elevated fecal lactoferrin, along with increased WBC count and low serum albumin, were associated with more severe CDI. In addition, patients infected with ribotype 027 and those with stool toxin had significantly higher fecal lactoferrin and WBC counts.

Informatics-Driven Infectious Disease Research

Informatics-driven approaches change how research and development are conducted, who participates, and enables systems-oriented views of science and research. Most life sciences researchers have a very strong desire for the full integration of data and analysis tools delivered through a single interface. Infectious disease (ID) research and development provides a uniquely challenging and high impact opportunity. The biological complexity of infectious disease systems, which are composed of multiple scales of interactions between potential pathogens, hosts, vectors, and the environment, challenges information resources because of the breadth of organism-organism and organism-environment interactions. Applications of integrated data for ID serves a variety of constituencies, such as clinicians, diagnostician, drug and vaccine developers, and epidemiologists. Thus there is a complexity that makes ID an opportune area in which to develop, deploy and use CyberInfrastructure.

Glutamine and alanyl-glutamine increase RhoA expression and reduce Clostridium difficile toxin-a-induced intestinal epithelial cell damage

Clostridium difficile is a major cause of antibiotic-associated colitis and is associated with significant morbidity and mortality. Glutamine (Gln) is a major fuel for the intestinal cell population. Alanyl-glutamine (Ala-Gln) is a dipeptide that is highly soluble and well tolerated. IEC-6 cells were used in the in vitro experiments. Cell morphology was evaluated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cell proliferation was assessed by WST-1 and Ki-67 and apoptosis was assessed by TUNEL. Cytoskeleton was evaluated by immunofluorescence for RhoA and F-actin. RhoA was quantified by immunoblotting. TcdA induced cell shrinkage as observed by AFM, SEM, and fluorescent microscopy. Additionally, collapse of the F-actin cytoskeleton was demonstrated by immunofluorescence. TcdA decreased cell volume and area and increased cell height by 79%, 66.2%, and 58.9%, respectively. Following TcdA treatment, Ala-Gln and Gln supplementation, significantly increased RhoA by 65.5% and 89.7%, respectively at 24 h. Ala-Gln supplementation increased cell proliferation by 137.5% at 24 h and decreased cell apoptosis by 61.4% at 24 h following TcdA treatment. In conclusion, TcdA altered intestinal cell morphology and cytoskeleton organization, decreased cell proliferation, and increased cell apoptosis. Ala-Gln and Gln supplementation reduced intestinal epithelial cell damage and increased RhoA expression.

Bacillus coagulans GBI-30, 6086 limits the recurrence of Clostridium difficile-Induced colitis following vancomycin withdrawal in mice

Background

Recently, we found that the probiotic strain Bacillus coagulans GBI-30, 6086 (GanedenBC³⁰) improved indices of Clostridium difficile (C. difficile)-induced colitis in mice (Fitzpatrick et al., Gut Pathogens, 2011). Our goal was to determine if BC30 could also prevent the recurrence of C. difficile-induced colitis in mice, following initial treatment with vancomycin. During study days 0 through 5, mice were treated with antibiotics. On day 6, the C. difficile strain VPI 10463 was given by oro-gastric gavage at ≈ 5x10⁴ CFU to induce colitis. Mice were treated on study days 6 to 10 with vancomycin (50 mg/kg) (vanco) or vehicle (saline) by gavage. On days 10 to16, mice were dosed by gavage with saline vehicle or BC30 (2 x 10⁹ CFU per day). Mice were monitored for mortality, weight loss and diarrhea. On study days 14, 16 and 17, stools and colons were collected for analyzing other parameters of colitis.

Results

The mean stool consistency score in Vehicle/C.difficile/Vanco mice increased from 0.4 (day 10) to a range of 1.1 to 1.4 (days 14 to 17), indicating the recurrence of colitis. On days 13 through 17, the stool consistency scores for the vancomycin/BC30 mice were significantly lower (p< 0.05) than for the vancomycin/vehicle cohort of animals. On day 17, 88.9% of mice treated with BC30 had normal stools, while this value was 0% with vehicle treatment (p value = 0.0004). Colonic myeloperoxidase (Units/2 cm colon) was significantly (p < 0.05) reduced from 4.3 ± 0.7 (Vehicle/C.difficile/Vanco) to 2.6 ± 0.2 (BC30/C. Difficle/Vanco). The colonic histology score and Keratinocyte derived-chemokine level in the colon were also lower in BC30 treated mice.

Summary

In BC30-treated mice, there was evidence of better stool consistency, as well as improved biochemical and histological indices of colitis, following initial treatment of animals with vancomycin.

Conclusion

BC30 limited the recurrence of CD-induced colitis following vancomycin withdrawal in mice.

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

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

Induction of P-glycoprotein and Bcrp at the rat blood-brain barrier following a subchronic morphine treatment is mediated through NMDA/COX-2 activation

Subchronic morphine treatment induces P-glycoprotein (P-gp) up-regulation at the blood-brain barrier. This study investigates the rate and extent to which P-gp and breast cancer-resistance protein (Bcrp) increase at the rat blood-brain barrier following subchronic morphine treatment. Rats were given increasing doses of morphine (10-40 mg/kg) or saline i.p. twice daily for 5 days. The brain cortex large vessels and microvessels were then mechanical isolated 6, 9, 12, 24, and 36 h after the last injection. The gene and protein expression of P-gp and Bcrp in morphine-treated and control rats were compared by qRT-PCR and western blotting. The levels of Mdr1a and Bcrp mRNAs were not significantly modified 6 h post morphine, but the Mdr1a mRNA increased 1.4-fold and Bcrp mRNA 2.4-fold at 24 h. P-gp and Bcrp protein expression in brain microvessels was unchanged 6 h post morphine and increased 1.5-fold at 24 h. This effect was more pronounced in large vessels than in microvessels. However, extracellular morphine concentrations of 0.01-10 μM did not modify the expressions of the MDR1 and BCRP genes in hCMEC/D3 human endothelial brain cells in vitro. MK-801 (NMDA antagonist) and meloxicam (cyclo-oxygenase-2 inhibitor) given after morphine treatment completely blocked P-gp and Bcrp up-regulation. Interestingly, misoprostol and iloprost, two well-known agonists of prostaglandin E2 receptors induced both MDR1 and BCRP mRNA levels in hCMEC/D3. Thus, morphine does not directly stimulate P-gp and Bcrp expression by the brain endothelium, but glutamate released during morphine withdrawal may do so by activating the NMDA/cyclo-oxygenase-2 cascade.

CopA3 peptide from Copris tripartitus induces apoptosis in human leukemia cells via a caspase-independent pathway

Our previous study demonstrated that CopA3, a disulfide dimer of the coprisin peptide analogue (LLCIALRKK), has antibacterial activity. In this study, we assessed whether CopA3 caused cellular toxicity in various mammalian cell lines. CopA3 selectively caused a marked decrease in cell viability in Jurkat T, U937, and AML-2 cells (human leukemia cells), but was not cytotoxic to Caki or Hela cells. Fragmentation of DNA, a marker of apoptosis, was also confirmed in the leukemia cell lines, but not in the other cells. CopA3-induced apoptosis in leukemia cells was mediated by apoptosis inducing factor (AIF), indicating induction of a caspase-independent signaling pathway.

Clostridium difficile of the ileum following total abdominal colectomy, with or without proctectomy: who is at risk?

BACKGROUND

Clostridium difficile enteritis is considered a rare entity, although recent data suggest a significant increase in prevalence and incidence. There is paucity of data evaluating risk factors of C difficile enteritis following total colectomy.

OBJECTIVE

The aim of this study was to determine the incidence and risk factors of C difficile enteritis for patients who had undergone total abdominal colectomy with or without proctectomy.

DESIGN

This study involves a retrospective chart review of 310 patients. Univariate analysis was performed on potential risk factors (p ≤ 0.05) with the use of a logistic regression model, and a Fisher exact test was used for variables that had no occurrences of C difficile. These groups of variables were then examined in a multiple variate setting with stepwise logistic regression analysis.

SETTINGS

This study was conducted at a tertiary referral center.

PATIENTS

A data analysis was performed on patients who had undergone total abdominal colectomy with or without proctectomy who were tested for C difficile of the ileum.

RESULTS

Twenty-two of 137 patients that were tested (16%) were positive for C difficile of the ileum. Univariate analysis of known risk factors for C difficile demonstrated that black race was a protective factor against C difficile (p = 0.016). The multivariate analysis demonstrated that emergency surgery (p = 0.035), race (p = 0.003), and increasing age by decade (p = 0.033) were risk factors for C difficile.

LIMITATIONS

This study was limited by the small patient sample, and it was not a randomized trial.

CONCLUSIONS

Black race is protective, and whites are 4 times more likely to acquire C difficile of the ileum after undergoing a total abdominal colectomy with or without proctectomy. The data also demonstrated that an increased age by a decade and emergency surgery are risk factors for C difficile enteritis, whereas the described risk factors of C difficile of the colon and type of colon surgery do not appear to influence the risk of C difficile of the ileum.

AMP-activated protein kinase mediates T cell activation-induced expression of FasL and COX-2 via protein kinase C theta-dependent pathway in human Jurkat T leukemia cells

AMP-activated protein kinase (AMPK), an important regulator of energy homeostasis, is known to be activated during T cell activation. T cell activation by T cell receptor (TCR) engagement or its pharmacological mimics, PMA plus ionomycin (PMA/Io), induces immunomodulatory FasL and cyclooxygenase-2 (COX-2) expression. In this study, we examined the role and mechanisms of AMPK in PMA/Io-induced expression of FasL and COX-2 in Jurkat T human leukemic cells. Inhibition of AMPK by a pharmacological agent, compound C, or AMPKα1 siRNA suppressed expression of FasL and COX-2 mRNAs and proteins in PMA/Io-activated Jurkat cells. It also reduced secretion of FasL protein and prostaglandin E2, a main product of COX-2, in Jurkat cells and peripheral blood lymphocytes activated with PMA/Io or monoclonal anti-CD3 plus anti-CD28. Consistently, inhibition of AMPK blocked promoter activities of FasL and COX-2 in activated Jurkat cells. As protein kinase C theta (PKCθ) is a central molecule for TCR signaling, we examined any possible cross-talk between AMPK and PKCθ in activated T cells. Of particular importance, we found that inhibition of AMPK blocked phosphorylation and activation of PKCθ, suggesting that AMPK is an upstream kinase of PKCθ. Moreover, we showed that AMPK was directly associated with PKCθ and phosphorylated Thr538 of PKCθ in PMA/Io-stimulated Jurkat cells. We also showed that inhibition of PKCθ by rottlerin or dominant negative PKCθ reduced AMPK-mediated transcriptional activation of NF-AT and AP-1 in activated Jurkat cells. Taken together, these results suggest that AMPK regulates expression of FasL and COX-2 via the PKCθ and NF-AT and AP-1 pathways in activated Jurkat cells.

Bacillus Coagulans GBI-30 (BC30) improves indices of Clostridium difficile-Induced colitis in mice

Background

Probiotics have beneficial effects in rodent models of Clostridium difficile (C. diffiicle)-induced colitis. The spore forming probiotic strain Bacillus Coagulans GBI-30, 6086 (BC30) has demonstrated anti-inflammatory and immune-modulating effects in vitro. Our goal was to determine if BC30 improved C. difficile-induced colitis in mice. Starting on study day 0, female C57BL/6 mice were dosed by oro-gastric gavage for 15 days with vehicle (saline) or BC30 (2 × 10⁹ CFU per day). Mice in the C. difficile groups received an antibiotic mixture (study days 5 to 8 in the drinking water), and clindamycin (10 mg/kg, i.p., on study day 10). The C. difficile strain VPI 10463 was given by gavage at 10⁴ CFU to induce colitis on day 11. On day 16, stools and colons were collected for further analyses.

Results

All mice treated with BC30 survived on study day 13, while two mice treated with vehicle did not survive. On day 12, a significant difference (p = 0.0002) in the percentage of mice with normal stools (66.7%) was found in the BC30/C. difficile group, as compared to the vehicle/C. diffcile group (13.0%). On study day 16, 23.8% of mice treated with BC30 had normal stools, while this value was 0% with vehicle treatment (p value = 0.0187). On this day, the stool consistency score for the BC30/C. difficile group (1.1 ± 0.2) was significantly lower (p < 0.05) than for the vehicle/C. difficile cohort (1.9 ± 0.2). BC30 modestly attenuated the colonic pathology (crypt damage, edema, leukocyte influx) that was present following C. difficile infection. Colonic MIP-2 chemokine contents (pg/2 cm colon) were: 10.2 ± 0.5 (vehicle/no C. difficile), 24.6 ± 9.5 (vehicle/C. difficile) and 16.3 ± 4.3 (BC30/C. difficle).

Conclusion

The probiotic BC30 improved some parameters of C. difficile-induced colitis in mice. BC30 prolonged the survival of C. diffiicle infected mice. Particularly, this probiotic improved the stool consistency of mice, in this infectious colitis model.

The insect peptide coprisin prevents Clostridium difficile-mediated acute inflammation and mucosal damage through selective antimicrobial activity

Clostridium difficile-associated diarrhea and pseudomembranous colitis are typically treated with vancomycin or metronidazole, but recent increases in relapse incidence and the emergence of drug-resistant strains of C. difficile indicate the need for new antibiotics. We previously isolated coprisin, an antibacterial peptide from Copris tripartitus, a Korean dung beetle, and identified a nine-amino-acid peptide in the α-helical region of it (LLCIALRKK) that had antimicrobial activity (J.-S. Hwang et al., Int. J. Pept., 2009, doi:10.1155/2009/136284). Here, we examined whether treatment with a coprisin analogue (a disulfide dimer of the nine peptides) prevented inflammation and mucosal damage in a mouse model of acute gut inflammation established by administration of antibiotics followed by C. difficile infection. In this model, coprisin treatment significantly ameliorated body weight decreases, improved the survival rate, and decreased mucosal damage and proinflammatory cytokine production. In contrast, the coprisin analogue had no apparent antibiotic activity against commensal bacteria, including Lactobacillus and Bifidobacterium, which are known to inhibit the colonization of C. difficile. The exposure of C. difficile to the coprisin analogue caused a marked increase in nuclear propidium iodide (PI) staining, indicating membrane damage; the staining levels were similar to those seen with bacteria treated with a positive control for membrane disruption (EDTA). In contrast, coprisin analogue treatment did not trigger increases in the nuclear PI staining of Bifidobacterium thermophilum. This observation suggests that the antibiotic activity of the coprisin analogue may occur through specific membrane disruption of C. difficile. Thus, these results indicate that the coprisin analogue may prove useful as a therapeutic agent for C. difficile infection-associated inflammatory diarrhea and pseudomembranous colitis.

The host immune response to Clostridium difficile

Clostridium difficile is the most common cause of nosocomial bacterial diarrhoea in the Western world. Diarrhoea and colitis are caused by the actions of toxins A and B released by pathogenic strains of C. difficile. Adaptive immune responses to these toxins influence the outcomes of C. difficile infection (CDI). Symptomless carriers of toxinogenic C. difficile and those with a single episode of CDI without recurrence show more robust antitoxin immune responses than those with symptomatic and recurrent disease. Immune-based approaches to CDI therapy and prevention have been developed using active vaccination or passive immunotherapy targeting C. difficile toxins. Innate immune responses to C. difficile and its toxins are also central to the pathophysiology of CDI. An acute intestinal inflammatory response with prominent neutrophil infiltration and associated tissue injury is characteristic of CDI. Furthermore, inhibiting this acute inflammatory response can protect against the intestinal injury that results from exposure to C. difficile toxins in animal models. Studies examining host risk factors for CDI have led to validated clinical prediction tools for risk of primary and of recurrent disease. Risk factors associated with severe CDI with poor clinical outcomes have also been identified and include marked elevation of the peripheral white blood cell count and elevated creatinine. However, further work is needed in this area to guide the clinical application of new approaches to disease prevention and treatment including new antimicrobials as well as passive and active immunization.

Colonic mucosal DNA methylation, immune response, and microbiome patterns in Toll-like receptor 2-knockout mice

The connection between intestinal microbiota and host physiology is increasingly becoming recognized. The details of this dynamic interaction, however, remain to be explored. Toll-like receptor 2 (Tlr2) is important for its role in bacterial recognition, intestinal inflammation, and obesity-related metabolic changes. Therefore, we sought to determine the epigenomic and metagenomic consequences of Tlr2 deficiency in the colonic mucosa of mice to gain insights into biological pathways that shape the interface between the gut microbiota and the mammalian host. Colonic mucosa from wild type (WT) and Tlr2(-/-) C57BL/6 mice was interrogated by microarrays specific for DNA methylation and gene expression. The mucosal microbiome was studied by next-generation pyrosequencing of bacterial 16S rRNA. The expression of genes involved in immune processes was significantly modified by the absence of Tlr2, a number of which correlated with DNA methylation changes. The epigenomic and transcriptomic modifications associated with alteration in mucosal microbial composition. Several bacterial species, including members of the Firmicutes were significantly different in abundance between WT and Tlr2(-/-) animals. This manuscript highlights the intimate interrelationships between expression of immune-related genes and immunity pathways in the host with compositional and functional differences of the mammalian microbiome.

Difference in the biological effects of Clostridium difficile toxin B in proliferating and non-proliferating cells

Toxin A (TcdA) and toxin B (TcdB) from Clostridium difficile are the causative agents of the C. difficile-associated diarrhea (CDAD) and its severe form, the pseudomembranous colitis. TcdA and TcdB both glucosylate and thereby inactivate low molecular weight GTP-binding proteins of the Rho, Rac, and Cdc42 subfamilies. In cultured cell lines, TcdB induces actin re-organization and bi-nucleation ("cytopathic effects") and cell death ("cytotoxic effects"). In this study, the role of cell cycle progression in the cytopathic and the cytotoxic effects of TcdB is evaluated by a differential analysis of these effects in proliferating and non-proliferating cells. Density-synchronized murine fibroblasts and confluent HT29 colonocytes are exploited as cell culture models for non-proliferating cells. Cell death is analyzed in terms of a loss of cell viability, phosphatidylserine exposure, and DNA fragmentation. In proliferating cells, TcdB blocks cell proliferation and induces apoptotic cell death. In contrast, TcdB induces non-apoptotic cell death in non-proliferating cells. TcdB-induced cell rounding turns out to be independent of cell cycle progression. Cell cycle progression is an important determinant in the biological effects of TcdB. With respect to the pathology of CDAD, this study leads to the new hypothesis that necrotic cell death of terminally differentiated colonocytes and inhibition of epithelial renewal of the colon contribute to the pathogenesis of CDAD.

Clostridium difficile toxin A decreases acetylation of tubulin, leading to microtubule depolymerization through activation of histone deacetylase 6, and this mediates acute inflammation

Clostridium difficile toxin A is known to cause actin disaggregation through the enzymatic inactivation of intracellular Rho proteins. Based on the rapid and severe cell rounding of toxin A-exposed cells, we speculated that toxin A may be involved in post-translational modification of tubulin, leading to microtubule instability. In the current study, we observed that toxin A strongly reduced α-tubulin acetylation in human colonocytes and mouse intestine. Fractionation analysis demonstrated that toxin A-induced α-tubulin deacetylation yielded monomeric tubulin, indicating the presence of microtubule depolymerization. Inhibition of the glucosyltransferase activity against Rho proteins of toxin A by UDP-2',3'-dialdehyde significantly abrogated toxin A-induced α-tubulin deacetylation. In colonocytes treated with trichostatin A (TSA), an inhibitor of the HDAC6 tubulin deacetylase, toxin A-induced α-tubulin deacetylation and loss of tight junction were completely blocked. Administration of TSA also attenuated proinflammatory cytokine production, mucosal damage, and epithelial cell apoptosis in mouse intestine exposed to toxin A. These results suggest that toxin A causes microtubule depolymerization by activation of HDAC6-mediated tubulin deacetylation. Indeed, blockage of HDAC6 by TSA markedly attenuates α-tubulin deacetylation, proinflammatory cytokine production, and mucosal damage in a toxin A-induced mouse enteritis model. Tubulin deacetylation is an important component of the intestinal inflammatory cascade following toxin A-mediated Rho inactivation in vitro and in vivo.

Diminished prostaglandin E2 contributes to the apoptosis paradox in idiopathic pulmonary fibrosis

RATIONALE

Patients with idiopathic pulmonary fibrosis (IPF), a progressive disease with a dismal prognosis, exhibit an unexplained disparity of increased alveolar epithelial cell (AEC) apoptosis but reduced fibroblast apoptosis.

OBJECTIVES

To examine whether the failure of patients with IPF to up-regulate cyclooxygenase (COX)-2, and thus the antifibrotic mediator prostaglandin (PG)E(2), accounts for this imbalance.

METHODS

Fibroblasts and primary type II AECs were isolated from control and fibrotic human lung tissue. The effects of COX-2 inhibition and exogenous PGE(2) on fibroblast and AEC sensitivity to Fas ligand (FasL)-induced apoptosis were assessed.

MEASUREMENTS AND MAIN RESULTS

IPF lung fibroblasts are resistant to FasL-induced apoptosis compared with control lung fibroblasts. Inhibition of COX-2 in control lung fibroblasts resulted in an apoptosis-resistant phenotype. Administration of PGE(2) almost doubled the rate of FasL-induced apoptosis in fibrotic lung fibroblasts compared with FasL alone. Conversely, in primary fibrotic lung type II AECs, PGE(2) protected against FasL-induced apoptosis. In human control and, to a greater extent, fibrotic lung fibroblasts, PGE(2) inhibits the phosphorylation of Akt, suggesting that regulation of this prosurvival protein kinase is an important mechanism by which PGE(2) modulates cellular apoptotic responses.

CONCLUSIONS

The observation that PGE(2) deficiency results in increased AEC but reduced fibroblast sensitivity to apoptosis provides a novel pathogenic insight into the mechanisms driving persistent fibroproliferation in IPF.

Clostridial toxins

Clostridia produce the highest number of toxins of any type of bacteria and are involved in severe diseases in humans and other animals. Most of the clostridial toxins are pore-forming toxins responsible for gangrenes and gastrointestinal diseases. Among them, perfringolysin has been extensively studied and it is the paradigm of the cholesterol-dependent cytolysins, whereas Clostridium perfringens epsilon-toxin and Clostridium septicum alpha-toxin, which are related to aerolysin, are the prototypes of clostridial toxins that form small pores. Other toxins active on the cell surface possess an enzymatic activity, such as phospholipase C and collagenase, and are involved in the degradation of specific cell-membrane or extracellular-matrix components. Three groups of clostridial toxins have the ability to enter cells: large clostridial glucosylating toxins, binary toxins and neurotoxins. The binary and large clostridial glucosylating toxins alter the actin cytoskeleton by enzymatically modifying the actin monomers and the regulatory proteins from the Rho family, respectively. Clostridial neurotoxins proteolyse key components of neuroexocytosis. Botulinum neurotoxins inhibit neurotransmission at neuromuscular junctions, whereas tetanus toxin targets the inhibitory interneurons of the CNS. The high potency of clostridial toxins results from their specific targets, which have an essential cellular function, and from the type of modification that they induce. In addition, clostridial toxins are useful pharmacological and biological tools.

Clostridium difficile Enteritis after Colectomy

Clostridium difficile infection of the colon is, unfortunately, a relatively common occurrence that typically follows treatment with antibiotics; however, C. difficile infection of the small bowel is a much more rare phenomenon with only 19 cases reported to date. We present three cases of isolated C. difficile enteritis after colectomy. Although all three patients were identified early and successfully treated with medical management without the need for surgical intervention, previous authors have suggested a much higher morbidity and mortality rate with this infection. This article reviews the current available literature on C. difficile enteritis to highlight this potentially serious condition in postoperative colectomy patients who present with low-grade fevers, abdominal or pelvic pain, and increased ileostomy output.

Bacillus polyfermenticus ameliorates colonic inflammation by promoting cytoprotective effects in colitic mice

Although human consumption of Bacillus polyfermenticus provides several health benefits, the probiotic effect of this bacterium against colonic inflammation has not yet, to our knowledge, been studied. Therefore, we induced colitis in mice by oral or intrarectal administration of dextran sodium sulfate (DSS) or trinitrobenzenosulfonic acid (TNBS), respectively, and investigated the effect of B. polyfermenticus on colitis. We found that mice treated with DSS or TNBS along with B. polyfermenticus had reduced mortality and severity of colitis (weight loss, diarrhea, and mucosal damages) than mice treated with DSS or TNBS alone. B. polyfermenticus also reduced the expression of inflammatory molecules, including chemokine (C-X-C motif) ligand 1, intercellular adhesion molecule, and tumor necrosis factor-alpha, but enhanced the expression of the antiinflammatory cytokine interleukin-10 in the inflamed mouse colon. Moreover, B. polyfermenticus suppressed apoptosis both in vivo in inflamed colonic mucosa and in vitro in colonic epithelial cells stimulated with apoptosis-inducing agents (FasL or Clostridium difficile Toxin A) when the apoptotic response was determined by a terminal deoxynucleotidyl transferase dUTP nick end labeling assay and cleavage of poly(ADP-ribose) polymerase or caspase-3, respectively. Treating colonic epithelial cells with B. polyfermenticus-conditioned medium (BPCM) enhanced cell proliferation and induced the phosphoinositide 3-kinases/Akt signaling pathway, suggesting that this bacterium can promote epithelial cell proliferation. BPCM also promoted the migration of colonic epithelial cells. These data suggest that B. polyfermenticus ameliorates colonic inflammation by suppressing apoptosis and promoting epithelial cell proliferation and migration.

Commensal bacteria, traditional and opportunistic pathogens, dysbiosis and bacterial killing in inflammatory bowel diseases

PURPOSE OF REVIEW

The authors present evidence published during the past 2 years of the roles of commensal and pathogenic bacteria in the pathogenesis of the inflammatory bowel diseases.

RECENT FINDINGS

Rodent models conclusively implicate commensal enteric bacteria in chronic, immune-mediated, experimental colitis, and genetically determined defects in bacterial killing by innate immune cells are found in a subset of patients with Crohn's disease. There is no evidence that a single pathogen, including Mycobacterium avium subspecies paratuberculosis, causes Crohn's disease or ulcerative colitis. However, adherent/invasive Escherichia coli are associated with ileal Crohn's disease, with the mechanisms and genetics of adherent/invasive E. coli virulence being elucidated. Molecular characterization of the microbiota in patients with inflammatory bowel diseases reveals decreased biodiversity of commensal bacteria, most notably the phyla Bacteroidetes and Firmicutes, including the clinically relevant Faecalibacterium prausnitzii, and increased E. coli concentrations. VSL#3 is one probiotic preparation shown to be efficacious in certain clinical situations in small clinical trials.

SUMMARY

Further characterization of altered microbiota in patients with inflammatory bowel diseases and linking dysbiosis with host genetic alterations in immunoregulation, innate microbial killing and barrier function are critical, so that individualized treatments to increase beneficial commensals and their metabolic products (probiotic and prebiotic administration) and diminish deleterious species such as adherent/invasive E. coli can be tailored for defined patient subsets.

Prostaglandin E2 stimulates Fas ligand expression via the EP1 receptor in colon cancer cells

Fas ligand (FasL/CD95L) is a member of the tumour necrosis factor superfamily that triggers apoptosis following crosslinking of the Fas receptor. Despite studies strongly implicating tumour-expressed FasL as a major inhibitor of the anti-tumour immune response, little is known about the mechanisms that regulate FasL expression in tumours. In this study, we show that the cyclooxygenase (COX) signalling pathway, and in particular prostaglandin E₂ (PGE₂), plays a role in the upregulation of FasL expression in colon cancer. Suppression of either COX-2 or COX-1 by RNA interference in HCA-7 and HT29 colon tumour cells reduced FasL expression at both the mRNA and protein level. Conversely, stimulation with PGE₂ increased FasL expression and these cells showed increased cytotoxicity against Fas-sensitive Jurkat T cells. Prostaglandin E₂-induced FasL expression was mediated by signalling via the EP1 receptor. Moreover, immunohistochemical analysis using serial sections of human colon adenocarcinomas revealed a strong positive correlation between COX-2 and FasL (r=0.722; P<0.0001) expression, and between EP1 receptor and FasL (r=0.740; P<0.0001) expression, in the tumour cells. Thus, these findings indicate that PGE₂ positively regulates FasL expression in colon tumour cells, adding another pro-neoplastic activity to PGE₂.

Microbial influences in inflammatory bowel diseases

The predominantly anaerobic microbiota of the distal ileum and colon contain an extraordinarily complex variety of metabolically active bacteria and fungi that intimately interact with the host's epithelial cells and mucosal immune system. Crohn's disease, ulcerative colitis, and pouchitis are the result of continuous microbial antigenic stimulation of pathogenic immune responses as a consequence of host genetic defects in mucosal barrier function, innate bacterial killing, or immunoregulation. Altered microbial composition and function in inflammatory bowel diseases result in increased immune stimulation, epithelial dysfunction, or enhanced mucosal permeability. Although traditional pathogens probably are not responsible for these disorders, increased virulence of commensal bacterial species, particularly Escherichia coli, enhance their mucosal attachment, invasion, and intracellular persistence, thereby stimulating pathogenic immune responses. Host genetic polymorphisms most likely interact with functional bacterial changes to stimulate aggressive immune responses that lead to chronic tissue injury. Identification of these host and microbial alterations in individual patients should lead to selective targeted interventions that correct underlying abnormalities and induce sustained and predictable therapeutic responses.

Clostridium difficile toxins: more than mere inhibitors of Rho proteins

Toxin A (TcdA) and Toxin B (TcdB) are the major pathogenicity factors of the Clostridium difficile-associated diarrhoea (CDAD). The single-chained protein toxins enter their target cells by receptor-mediated endocytosis. New data show the critical role of auto-catalytic processing for target cell entry. Inside the cell, the toxins mono-glucosylate and thereby inactivate low molecular mass GTP-binding proteins of the Rho subfamily. Toxin-treated cells respond to RhoA glucosylation with up-regulation and activation of the pro-apoptotic Rho family protein RhoB. These data reinforce the critical role of the glucosyltransferase activity for programmed cell death and show that TcdA and TcdB, generally classified as broad-spectrum inhibitors of Rho proteins, are also capable of activating Rho proteins.