Influence of the microenvironment on modulation of the host response by typhoid toxin

Exploring Gut Microbiome Composition and Circulating Microbial DNA Fragments in Patients with Stage II/III Colorectal Cancer: A Comprehensive Analysis

BACKGROUND

Colorectal cancer (CRC) significantly contributes to cancer-related mortality, necessitating the exploration of prognostic factors beyond TNM staging. This study investigates the composition of the gut microbiome and microbial DNA fragments in stage II/III CRC.

METHODS

A cohort of 142 patients with stage II/III CRC and 91 healthy controls underwent comprehensive microbiome analysis. Fecal samples were collected for 16S rRNA sequencing, and blood samples were tested for the presence of microbial DNA fragments. De novo clustering analysis categorized individuals based on their microbial profiles. Alpha and beta diversity metrics were calculated, and taxonomic profiling was conducted.

RESULTS

Patients with CRC exhibited distinct microbial composition compared to controls. Beta diversity analysis confirmed CRC-specific microbial profiles. Taxonomic profiling revealed unique taxonomies in the patient cohort. De novo clustering separated individuals into distinct groups, with specific microbial DNA fragment detection associated with certain patient clusters.

CONCLUSIONS

The gut microbiota can differentiate patients with CRC from healthy individuals. Detecting microbial DNA fragments in the bloodstream may be linked to CRC prognosis. These findings suggest that the gut microbiome could serve as a prognostic factor in stage II/III CRC. Identifying specific microbial markers associated with CRC prognosis has potential clinical implications, including personalized treatment strategies and reduced healthcare costs. Further research is needed to validate these findings and uncover underlying mechanisms.

Current understandings of colibactin regulation

The biosynthetic machinery for the production of colibactin is encoded by 19 genes (clbA - S) within the pks pathogenicity island harboured by many E. coli of the B2-phylogroup. Colibactin is a potent genotoxic metabolite which causes DNA-damage and which has potential roles in microbial competition and fitness of pks+ bacteria. Colibactin has also been strongly implicated in the development of colorectal cancer. Given the genotoxicity of colibactin and the metabolic cost of its synthesis, the regulatory system governing the clb cluster is accordingly highly complex, and many of the mechanisms remain to be elucidated. In this review we summarise the current understanding of regulation of colibactin biosynthesis by internal molecular components and how these factors are modulated by signals from the external environment.

Diagnostic Challenges during Inflammation and Cancer: Current Biomarkers and Future Perspectives in Navigating through the Minefield of Reactive versus Dysplastic and Cancerous Lesions in the Digestive System

In the setting of pronounced inflammation, changes in the epithelium may overlap with neoplasia, often rendering it impossible to establish a diagnosis with certainty in daily clinical practice. Here, we discuss the underlying molecular mechanisms driving tissue response during persistent inflammatory signaling along with the potential association with cancer in the gastrointestinal tract, pancreas, extrahepatic bile ducts, and liver. We highlight the histopathological challenges encountered in the diagnosis of chronic inflammation in routine practice and pinpoint tissue-based biomarkers that could complement morphology to differentiate reactive from dysplastic or cancerous lesions. We refer to the advantages and limitations of existing biomarkers employing immunohistochemistry and point to promising new markers, including the generation of novel antibodies targeting mutant proteins, miRNAs, and array assays. Advancements in experimental models, including mouse and 3D models, have improved our understanding of tissue response. The integration of digital pathology along with artificial intelligence may also complement routine visual inspections. Navigating through tissue responses in various chronic inflammatory contexts will help us develop novel and reliable biomarkers that will improve diagnostic decisions and ultimately patient treatment.

Genotoxin-producing Salmonella enterica induces tissue-specific types of DNA damage and DNA damage response outcomes

Introduction

Typhoid toxin-expressing Salmonella enterica causes DNA damage in the intestinal mucosa in vivo, activating the DNA damage response (DDR) in the absence of inflammation. To understand whether the tissue microenvironment constrains the infection outcome, we compared the immune response and DDR patterns in the colon and liver of mice infected with a genotoxigenic strain or its isogenic control strain.

Methods

In situ spatial transcriptomic and immunofluorescence have been used to assess DNA damage makers, activation of the DDR, innate immunity markers in a multiparametric analysis.

Result

The presence of the typhoid toxin protected from colonic bacteria-induced inflammation, despite nuclear localization of p53, enhanced co-expression of type-I interferons (IfnbI) and the inflammasome sensor Aim2, both classic features of DNA-break-induced DDR activation. These effects were not observed in the livers of either infected group. Instead, in this tissue, the inflammatory response and DDR were associated with high oxidative stress-induced DNA damage.

Conclusions

Our work highlights the relevance of the tissue microenvironment in enabling the typhoid toxin to suppress the host inflammatory response in vivo.

Inactivation of the tumor suppressor gene Apc synergizes with H. pylori to induce DNA damage in murine gastric stem and progenitor cells

Helicobacter pylori infection is a major risk factor for the development of gastric cancer. The bacteria reside in close proximity to gastric surface mucous as well as stem and progenitor cells. Here, we take advantage of wild-type and genetically engineered murine gastric organoids and organoid-derived monolayers to study the cellular targets of H. pylori-induced DNA damage and replication stress and to explore possible interactions with preexisting gastric cancer driver mutations. We find using alkaline comet assay, single-molecule DNA fiber assays, and immunofluorescence microscopy of DNA repair foci that H. pylori induces transcription-dependent DNA damage in actively replicating, Leucine-rich-repeat containing G-Protein-Coupled Receptor 5 (Lgr5)-positive antral stem and progenitor cells and their Troy-positive corpus counterparts, but not in other gastric epithelial lineages. Infection-dependent DNA damage is aggravated by Apc inactivation, but not by Trp53 or Smad4 loss, or Erbb2 overexpression. Our data suggest that H. pylori induces DNA damage in stem and progenitor cells, especially in settings of hyperproliferation due to constitutively active Wnt signaling.

Typhoid toxin hijacks Wnt5a to establish host senescence and Salmonella infection

Damage to our genome causes acute senescence in mammalian cells, which undergo growth arrest and release a senescence-associated secretory phenotype (SASP) that propagates the stress response to bystander cells. Thus, acute senescence is a powerful tumor suppressor. Salmonella enterica hijacks senescence through its typhoid toxin, which usurps unidentified factors in the stress secretome of senescent cells to mediate intracellular infections. Here, transcriptomics of toxin-induced senescent cells (TxSCs) and proteomics of their secretome identify the factors as Wnt5a, INHBA, and GDF15. Wnt5a establishes a positive feedback loop, driving INHBA and GDF15 expression. In fibroblasts, Wnt5a and INHBA mediate autocrine senescence in TxSCs and paracrine senescence in naive cells. Wnt5a synergizes with GDF15 to increase Salmonella invasion. Intestinal TxSCs undergo apoptosis without Wnt5a, which is required for establishing intestinal TxSCs. The study reveals how an innate defense against cancer is co-opted by a bacterial pathogen to cause widespread damage and mediate infections.

Escape from senescence: molecular basis and therapeutic ramifications

Cellular senescence constitutes a stress response mechanism in reaction to a plethora of stimuli. Senescent cells exhibit cell-cycle arrest and altered function. While cell-cycle withdrawal has been perceived as permanent, recent evidence in cancer research introduced the so-called escape-from-senescence concept. In particular, under certain conditions, senescent cells may resume proliferation, acquiring highly aggressive features. As such, they have been associated with tumour relapse, rendering senescence less effective in inhibiting cancer progression. Thus, conventional cancer treatments, incapable of eliminating senescence, may benefit if revisited to include senolytic agents. To this end, it is anticipated that the assessment of the senescence burden in everyday clinical material by pathologists will play a crucial role in the near future, laying the foundation for more personalised approaches. Here, we provide an overview of the investigations that introduced the escape-from-senescence phenomenon, the identified mechanisms, as well as the major implications for pathology and therapy. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Curative anti-typhoid effect of Detarium microcarpum Guill. & Perr. (Leguminosae) hydroethanolic extract root bark based-on in vivo and molecular docking analyses

ETHNOPHARMACOLOGICAL RELEVANCE

Detarium microcarpum is used to treat typhoid fever, a major public health problem, by indigenous population in Africa. Though its preventive activities have been documented, the curative effect is still to be confirmed.

AIM OF THE STUDY

This study aimed at evaluating the curative effects of the hydroethanolic extract of Detarium microcarpum root bark on Salmonella typhimurium-induced typhoid in rat and exploring the in-silico inhibition of some bacterial key enzymes.

STUDY DESIGN

In vitro antioxydant, in vivo antisalmonella of the extract and in silico molecular docking assay on the isolated compounds were carried out to explore the anti-salmonella effects of Detarium microcarpum.

MATERIAL AND METHODS

The in vitro antioxidant properties of the extract were evaluated using DPPH, ABTS and FRAP tests. The anti-salmonella activity of the extract was assessed through feacal sample from Salmonella typhimurium-infected rat cultured in Salmonella-Shigella agar (SS agar) medium. The affinity of isolated compounds (Rhinocerotinoic acid and Microcarposide) from the extract were performed on four key enzymes (Adenylosuccinate lyase, Acetyl coenzyme A synthetase, Thymidine phosphorylase and LuxS-Quorum sensor) using molecular docking simulation to elucidate the molecular level inhibition mechanism.

RESULTS

Crude extract of D. microcarpum root bark showed variable activities on DPPH (RSa50: 6.09 ± 1.04 μg/mL), ABTS (RSa50: 24.46 ± 0.27), and FRAP (RSa50: 23.30 ± 0.23). The extract at all the doses exhibited significant healing effect of infected rats, with the complete clearance. The extract restored hematological, biochemical and histological parameters closed to the normal control. The molecular docking results indicates that rhinocerotinoic acid and microcarposide present more affinity to the LuxS-Quorum sensor and Acetyl coenzyme A synthetase protein as compared to the others.

CONCLUSION

These results demonstrate potent anti-typhoid activities of the hydroethanolic of Detarium microcarpum root bark extract through antioxidant properties and high inhibitory affinity of its compounds on some bacterial key enzymes that justify its use as traditional medicine to typhoid fever.

Exosomal-miR-129-2-3p derived from Fusobacterium nucleatum-infected intestinal epithelial cells promotes experimental colitis through regulating TIMELESS-mediated cellular senescence pathway

Fusobacterium nucleatum (Fn) infection is known to exacerbate ulcerative colitis (UC). However, the link between Fn-infected intestinal epithelial cell (IEC)-derived exosomes (Fn-Exo) and UC progression has not been investigated. Differentially expressed miRNAs in Fn-Exo and non-infected IECs-derived exosomes (Con-Exo) were identified by miRNA sequencing. Then, the biological role and mechanism of Fn-Exo in UC development were determined in vitro and in vivo. We found that exosomes delivered miR-129-2-3p from Fn-infected IECs into non-infected IECs, exacerbating epithelial barrier dysfunction and experimental colitis. Mechanically, Fn-Exo induces DNA damage via the miR-129-2-3p/TIMELESS axis and subsequently activates the ATM/ATR/p53 pathway, ultimately promoting cellular senescence and colonic inflammation. In conclusion, Exo-miR-129-2-3p/TIMELESS/ATM/ATR/p53 pathway aggravates cellular senescence, barrier damage, and experimental colitis. The current study revealed a previously unknown regulatory pathway in the progression of Fn-infectious UC. Furthermore, Exosomal-miR-129-2-3p in serum and TIMELESS may function as novel potential diagnostic biomarkers for UC and Fn-high-UC.

Anti-inflammatory and anti-apoptotic effects of Shaoyao decoction on X-ray radiation-induced enteritis of C57BL/6 mice

ETHNOPHARMACOLOGICAL RELEVANCE

As a typical heat-clearing prescription, Shaoyao decoction (SYD) has a robust function of clearing viscera heat for the treatment of several intestinal discomfort symptoms. Clinical evidence indicated that it had the potential to cure radiation enteritis. However, its underlying mechanisms remain unclear.

AIM OF THE STUDY

The present study was designed to probe the protective effects and the involved mechanisms of SYD on X-ray radiation-induced enteritis of C57BL/6 mice.

MATERIALS AND METHODS

X-ray irradiation were used to establish the radiation enteritis model. Forty-eight male C57BL/6 mice (20 ± 2 g) were randomly divided into six groups: the control group, model group, dexamethasone group (DEX, 0.12 mg/kg) and SYD groups (0.12, 0.24 and 0.36 g/mL), respectively. All mice (except the control group) were intragastrically administrated for a continuous 7 days. H&E and Masson staining were employed to evaluate the morphological and collagen fibers changes of the colon. ELISA was performed to assess the levels of MDA, SOD, COX, LPS, IL-6, IL-1β and TNF-α in serum. Moreover, TUNEL fluorescence, western blot and qRT-PCR were used to detect the levels of apoptosis-related proteins and genes of Dclk-1, ATM, MRE-11, Bcl-2, Bax, Caspase-3, and Cyto-c. Furthermore, immunofluorescent staining was applied to detect the protein levels of p53 and Claudin-1 in colon.

RESULTS

Treatment with SYD decreased the exfoliated and necrotic epithelial cells and prevent the proliferate from damaged fibrous tissue in the crypt layer of mucos. The levels of serum peroxidation and pro-inflammatory cytokines (MDA, COX, LPS, IL-6, IL-1β and TNF-α) were obviously inhibited, while SOD sharply increased in serum after administration. Moreover, SYD can significantly ameliorate the apoptosis of colon cells, evidenced by the reduced positive expression of TUNEL staining. Meanwhile, the results of qRT-PCR and western blot demonstrated that SYD can dramatically stimulate the expression of genes and proteins Dclk-1, ATM and MRE-11, thus promoting the expression of mitochondrial pro-apoptotic proteins Bax, Caspase-3 and Cyto-c, while increasing the level of anti-apoptotic protein Bcl-2. Furthermore, immunofluorescence revealed that SYD can notably decreased the protein level of p53 while reverse the reduction of Claudin-1.

CONCLUSIONS

These results indicated that radiation enteritis in C57BL/6 mice can be ameliorated by treatment with SYD. The potential protection mechanisms may be involved in ameliorating tissue fibrosis by decreasing inflammatory and apoptotic events.

The Host CYP1A1-Microbiota Metabolic Axis Promotes Gut Barrier Disruption in Methicillin-Resistant Staphylococcus aureus-Induced Abdominal Sepsis

Background

Host-microbiota crosstalk has been implicated in multiple host metabolic pathway axes that regulate intestinal barrier function. Although constitutive cytochrome P4501A1 (CYP1A1) expression perturbs the microbiome-derived autoregulatory loop following enteric infection, little is known about the role of host CYP1A1 in modulating gut microbiome-mediated signaling during methicillin-resistant Staphylococcus aureus (MRSA)-induced abdominal sepsis and its effects on intestinal barrier integrity.

Methods

Abdominal sepsis was induced by the intraperitoneal injection of MRSA in mice. The effect of CYP1A1 deficiency on gut barrier integrity was investigated using RNA sequencing, microbiome analyses, and targeted metabolomics. The microbiota-produced metabolites were validated in patients with sepsis and persistent MRSA infection.

Results

Mice lacking CYP1A1 exhibited an altered gut microbiome, a reduced metabolic shift from lysine to cadaverine in the caecal contents and antimicrobial molecule production (Retnlb, Gbp7, and Gbp3), and they were protected against gut barrier disruption when subjected to MRSA challenge. These beneficial effects were validated in aryl hydrocarbon receptor (AHR) knockout (KO) mice by cohousing with CYP1A1 KO mice and abrogated after supplementation with cadaverine or Enterococcus faecalis, the primary microbiota genus for cadaverine synthesis. Antibiotic-driven gut dysbacteriosis impaired the survival benefit and disrupted the intestinal barrier integrity in CYP1A1 KO mice after MRSA infection. Furthermore, increased cadaverine levels in feces and serum were detected in critically ill patients with gut leakiness during persistent MRSA infection, whereas cadaverine was not detected in healthy controls. Additionally, microbiota-derived cadaverine induced enterocyte junction disruption by activating the histamine H4 receptor/nuclear factor-κB/myosin light-chain kinase signaling pathway.

Conclusion

This study revealed the unexpected function of host CYP1A1 in microbiota-mediated cadaverine metabolism, with crucial consequences for dysbacteriosis following MRSA-induced abdominal sepsis, indicating that inhibiting CYP1A1 or blocking cadaverine-histamine H4 receptor signaling could be a potential therapeutic target against abdominal sepsis.

Clinical Trial Registration

[http://www.chictr.org.cn/index.aspx], identifier [ChiCTR1800018646].

Moniezia benedeni Infection Restrain IgA+, IgG+, and IgM+ Cells Residence in Sheep (Ovis aries) Small Intestine

Secreted immunoglobulin A (SIgA), IgG, and IgM play a crucial role in forming the intestinal mucosal immune barrier, and parasites could disturb the host's immune response by releasing various immunomodulatory molecules. Moniezia benedeni is an important pathogen parasitizing in the sheep small intestine. It is aimed to explore the residence characteristics of IgA⁺, IgG⁺, and IgM⁺ cells in the sheep small intestine, and the influence of Moniezia benedeni infection on them. Control group (n = 6) and infected group (n = 6) were selected, respectively, and the three subtype cells residing in the small intestine were systematically observed and analyzed. The results showed that in the Control group, the three types of positive cells were all distributed diffusely, and the total densities in jejunum, duodenum and ileum was gradually declined in turn. Notably, the change trend of IgA⁺ and IgG⁺ cells densities were both congruent with the total densities, and the differences among them were significant, respectively (P < 0.05); the IgM⁺ cells density was the highest in duodenum, followed by jejunum and ileum, there was no significant difference between duodenum and jejunum (P > 0.05), but both significantly higher than in ileum (P < 0.05). In the Infected group, their total densities in duodenum, jejunum and ileum were gradually declined in turn. Notably, the IgA⁺ and IgM⁺ cells densities change trend was the same as the total densities, and the differences among them were significant, respectively (P < 0.05). The IgG⁺ cells density in duodenum was the highest, followed by ileum and jejunum and there was significantly difference among them (P < 0.05). The comparison results between Control and Infected groups showed that from the duodenum, jejunum to ileum, IgA⁺, IgG⁺, and IgM⁺ cells were all reduced significantly, respectively. The results suggest that the three types of positive cells were resided heterogeneously in the small intestinal mucosa, that is, significant region-specificity; Moniezia benedeni infection could not change their diffuse distribution characteristics, but strikingly, reduce their resident densities, and the forming mucosal immune barrier were significantly inhibited. It provided powerful evidence for studying on the molecular mechanism of Moniezia benedeni evasion from immune surveillance by strongly inhibiting the host's mucosal immune barrier.

Moniezia benedeni infection enhances neuromedin U (NMU) expression in sheep (Ovis aries) small intestine

BACKGROUND

Neuromedin U (NMU) plays an important role in activating the group 2 innate lymphoid cells (ILC2s) and initiating the host's anti-parasitic immune responses. It is aimed to explore the distribution characteristics of NMU in the sheep small intestine and the influence of Moniezia benedeni infection on them. In the present study, the pET-28a-NMU recombinant plasmids were constructed, and Escherichia coli. BL21 (DE3) were induced to express the recombinant protein. And then, the rabbit anti-sheep NMU polyclonal antibody was prepared and immunofluorescence staining was performed with it. The expression levels of NMU in the intestine of normal and Moniezia benedeni-infected sheep were detected by ELISA.

RESULTS

The results showed that the molecular weight of the obtained NMU recombinant protein was consistent with the expected molecular (13 kDa) and it was expressed in the form of inclusion body. The titer and specificity of obtained rabbit anti-sheep NMU polyclonal antibody were good. The results of immunofluorescence analysis showed that the nerve fibers which specifically expressed NMU mainly extended from the ganglion in the submucosal to lamina propria (LP) in the sheep small intestine, and the expression level was relatively high; especially on the nerve fibers of LP around the intestinal glands. The expression levels were gradually increased from the duodenum to the ileum, and the levels in the jejunum and ileum were significantly higher than that in the duodenum (P < 0.05). In addition, scattered NMU positive cells were distributed in the epithelium of the jejunal crypts. Moniezia benedeni infection increased the expression of NMU in each intestinal segment, especially in the jejunum and ileum there were significant increase (P < 0.05).

CONCLUSIONS

It was suggested that Moniezia benedeni infection could be detected by the high expression of NMU in sheep enteric nervous, and which laid the foundation for further studies on whether NMU exerts anti-parasitic immunity by activating ILC2s. In addition, NMU was expressed in some intestinal gland epitheliums, which also provided a basis for studying its roles in regulation of the immune homeostasis. The present study laid the foundation for further revealing the molecular mechanism of sheep's neural-immune interaction network perceiving the colacobiosis of parasites.

Detection of DNA damage by alkaline comet assay in mouse colonic mucosa

We recently characterized the association between DNA damage and immunoresponse in vivo in colonic mucosa of mice infected with a Salmonella Typhimurium strain expressing a genotoxin, known as typhoid toxin. In this protocol, we describe the specific steps for assessing DNA damage by the alkaline comet assay of colonic mucosal samples. The description of the comet assay protocol follows the international guidelines (Minimum Information for Reporting on the Comet Assay [Moller et al., 2020]).

For complete details on the use and execution of this protocol, please refer to Martin et al. (2021).

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Collection of mice colon mucosa for comet assay

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Detailed description and optimization of alkaline comet assay

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Detection of single and double DNA strand breaks

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Assessment of DNA damage extent using the percentage of DNA in the comet tail

Characterization of macrophage infiltration and polarization by double fluorescence immunostaining in mouse colonic mucosa

We recently characterized the association between DNA damage and immunoresponse in vivo in colonic mucosa of mice infected with a Salmonella Typhimurium strain expressing a genotoxin, known as typhoid toxin. In this protocol, we describe how to assess the extent and features of infiltrating macrophages by double immunofluorescence. Total macrophage population was determined using an F4/80 antibody, whereas the specific M2-like population was assessed using a CD206 antibody. For complete details on the use and execution of this protocol, please refer to Martin et al. (2021).

Chronic exposure to Cytolethal Distending Toxin (CDT) promotes a cGAS-dependent type I interferon response

The Cytolethal Distending Toxin (CDT) is a bacterial genotoxin produced by pathogenic bacteria causing major foodborne diseases worldwide. CDT activates the DNA Damage Response and modulates the host immune response, but the precise relationship between these outcomes has not been addressed so far. Here, we show that chronic exposure to CDT in HeLa cells or mouse embryonic fibroblasts promotes a strong type I interferon (IFN) response that depends on the cytoplasmic DNA sensor cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS) through the recognition of micronuclei. Indeed, despite active cell cycle checkpoints and in contrast to other DNA damaging agents, cells exposed to CDT reach mitosis where they accumulate massive DNA damage, resulting in chromosome fragmentation and micronucleus formation in daughter cells. These mitotic phenotypes are observed with CDT from various origins and in cancer or normal cell lines. Finally, we show that CDT exposure in immortalized normal colonic epithelial cells is associated to cGAS protein loss and low type I IFN response, implying that CDT immunomodulatory function may vary depending on tissue and cell type. Thus, our results establish a direct link between CDT-induced DNA damage, genetic instability and the cellular immune response that may be relevant in the context of natural infection associated to chronic inflammation or carcinogenesis.

Bacterial Toxins Are a Never-Ending Source of Surprises: From Natural Born Killers to Negotiators

The idea that bacterial toxins are not only killers but also execute more sophisticated roles during bacteria-host interactions by acting as negotiators has been highlighted in the past decades. Depending on the toxin, its cellular target and mode of action, the final regulatory outcome can be different. In this review, we have focused on two families of bacterial toxins: genotoxins and pore-forming toxins, which have different modes of action but share the ability to modulate the host's immune responses, independently of their capacity to directly kill immune cells. We have addressed their immuno-suppressive effects with the perspective that these may help bacteria to avoid clearance by the host's immune response and, concomitantly, limit detrimental immunopathology. These are optimal conditions for the establishment of a persistent infection, eventually promoting asymptomatic carriers. This immunomodulatory effect can be achieved with different strategies such as suppression of pro-inflammatory cytokines, re-polarization of the immune response from a pro-inflammatory to a tolerogenic state, and bacterial fitness modulation to favour tissue colonization while preventing bacteraemia. An imbalance in each of those effects can lead to disease due to either uncontrolled bacterial proliferation/invasion, immunopathology, or both.