Acetyltransferase from Akkermansia muciniphila blunts colorectal tumourigenesis by reprogramming tumour microenvironment

OBJECTIVE

The protein post-translational modification (PTM) in host cells can be rewritten by bacterial enzymes and represents an unprecedented mechanism in the communication between intestinal flora and the host. Although Akkermansia muciniphila has been widely investigated as a probiotic and blunts colitis-associated tumourigenesis in mice, there is little understanding regarding whether A. muciniphila is involved in the PTM of colorectal cancer (CRC). This study investigates whether and how A. muciniphila engages in the PTM of host CRC.

DESIGN

The secreting extracellular vesicles from A. muciniphila and purified Amuc_2172 were used for different tumourigenesis mice models. Amuc_2172-induced immune activity of CD8⁺ cytotoxic T lymphocytes (CTLs) were evaluated in vitro and in vivo. The acetyltransferase activity and downstream target genes of Amuc_2172 were investigated.

RESULTS

Amuc_2172, a general control non-derepressible 5-related acetyltransferase of A. muciniphila, was accessible to colorectal cells by macropinocytosis and functioned as an acetyltransferase of Lys14 on histone H3 (H3K14ac). Elevated H3K14ac on Hspa1a loci promoted the transcription and secretion of heat-shock protein 70 (HSP70) in cancer cells. High level of HSP70 promoted the immune activity of CTLs in vitro and in vivo. Moreover, bioengineered nanoparticles provided a safe and reliable drug delivery strategy of Amuc_2172 for CRC treatment in an allograft mice model.

CONCLUSION

Amuc_2172 reprogrammed tumour microenvironment by inducing HSP70 secretion and promoting CTL-related immune response in the process of tumourigenesis.

Tissue-infiltrating neutrophils represent the main source of IL-23 in the colon of patients with IBD

OBJECTIVE

In IBD, interleukin-23 (IL-23) and its receptor (IL-23R) are implicated in disease initiation and progression. Novel insight into which cells produce IL-23 at the site of inflammation at an early stage of IBD will promote the development of new tools for diagnosis, treatment and patient monitoring. We examined the cellular source of IL-23 in colon tissue of untreated newly diagnosed paediatric patients with IBD.

DESIGN

Colon tissues from IBD and non-IBD patients were analysed by quantitative real-time PCR (qPCR), immunofluorescence confocal microscopy and flow cytometry after appropriate sample preparation. Blood samples from IBD and non-IBD patients and healthy controls were analysed using flow cytometry and qPCR.

RESULTS

We discovered that tissue-infiltrating neutrophils were the main source of IL-23 in the colon of paediatric patients with IBD, while IL-23(+) human leucocyte antigen-DR(+) or IL-23(+)CD14(+) cells were scarce or non-detectable, respectively. The colonic IL-23(+) neutrophils expressed C-X-C motif (CXC)R1 and CXCR2, receptors for the CXC ligand 8 (CXCL8) chemokine family, and a corresponding CXCR1(+)CXCR2(+)IL-23(+)subpopulation of neutrophils was also identified in the blood of both patients with IBD and healthy individuals. However, CXCL8-family chemokines were only elevated in colon tissue from patients with IBD.

CONCLUSIONS

This study provides the first evidence of CXCR1(+)CXCR2(+)IL-23-producing neutrophils that infiltrate and accumulate in inflamed colon tissue of patients with IBD. Thus, this novel source of IL-23 may play a key role in disease progression and will be important to take into consideration in the development of future strategies to monitor, treat and prevent IBD.

Abnormal thymic stromal lymphopoietin expression in the duodenal mucosa of patients with coeliac disease

OBJECTIVE

The short isoform of thymic stromal lymphopoietin (TSLP), a cytokine constitutively expressed by epithelial cells, is crucial in preserving immune tolerance in the gut. TSLP deficiency has been implicated in sustaining intestinal damage in Crohn's disease. We explored mucosal TSLP expression and function in refractory and uncomplicated coeliac disease (CD), a T-cell-mediated enteropathy induced by gluten in genetically susceptible individuals.

DESIGN

TSLP isoforms-long and short-and receptors-TSLPR and interleukin (IL)-7Rα-were assessed by immunofluorescence, immunoblotting and qRT-PCR in the duodenum of untreated, treated, potential and refractory patients with CD. The ability of the serine protease furin or CD biopsy supernatants to cleave TSLP was evaluated by immunoblotting. The production of interferon (IFN)-γ and IL-8 by untreated CD biopsies cultured ex vivo with TSLP isoforms was also assessed.

RESULTS

Mucosal TSLP, but not TSLPR and IL-7Rα, was reduced in untreated CD and refractory CD in comparison to treated CD, potential CD and controls. Transcripts of both TSLP isoforms were decreased in active CD mucosa. Furin, which was overexpressed in active CD biopsies, was able to cleave TSLP in vitro. Accordingly, refractory and untreated CD supernatants showed higher TSLP-degrading capacity in comparison to treated CD and control supernatants. In our ex vivo model, both TSLP isoforms significantly downregulated IFN-γ and IL-8 production by untreated CD biopsies.

CONCLUSIONS

Reduced mucosal TSLP expression may contribute to intestinal damage in refractory and untreated CD. Further studies are needed to verify whether restoring TSLP might be therapeutically useful especially in refractory patients with CD.

The composition and differentiation potential of the duodenal intraepithelial innate lymphocyte compartment is altered in coeliac disease

OBJECTIVE

Coeliac disease (CD), a gluten-induced enteropathy, alters the composition and function of duodenal intraepithelial T cells. The intestine also harbours four types of CD3-negative intraepithelial lymphocytes (IELs) with largely unknown function: CD56(-)CD127(-), CD56(-)CD127(+), CD56(+)CD127(-) and CD56(+)CD127(+). Here we aimed to gain insight into the potential function of these innate IELs in health and disease.

DESIGN

We determined the phenotypes, relative abundance and differentiation potential of these innate IEL subsets in duodenal biopsies from controls and patients with CD or patients with refractory CD type II (RCDII).

RESULTS

Hierarchical clustering analysis of the expression of 15 natural killer and T cell surface markers showed that innate IELs differed markedly from innate peripheral blood lymphocytes and divided innate IEL subsets into two main branches: a CD127(-) branch expressing high levels of interleukin (IL) 2/15Rβ but no IL-21R, and a CD127(+) branch with the opposite phenotype. While CD was characterised by the contraction of all four innate IEL subsets, a selective expansion of CD56(-)CD127(-) and CD56(-)CD127(+) innate IEL was detected in RCDII. In vitro, in the presence of IL-15, CD56(-)CD127(-) IEL from controls and patients with CD, but not from patients with RCDII, differentiated into functional natural killer and T cells, the latter largely dependent on notch-signalling. Furthermore, compared with non-coeliac controls, CD56(-)CD127(-) IEL from patients with CD expressed more intracellular CD3ε and CD3γ and gave more pronounced T cell differentiation.

CONCLUSIONS

Thus, we demonstrate previously unappreciated diversity and plasticity of the innate IEL compartment and its loss of differentiation potential in patients with RCDII.

Antibiotics promote inflammation through the translocation of native commensal colonic bacteria

OBJECTIVE

Antibiotic use is associated with an increased risk of developing multiple inflammatory disorders, which in turn are linked to alterations in the intestinal microbiota. How these alterations in the intestinal microbiota translate into an increased risk for inflammatory responses is largely unknown. Here we investigated whether and how antibiotics promote inflammation via the translocation of live native gut commensal bacteria.

DESIGN

Oral antibiotics were given to wildtype and induced mutant mouse strains, and the effects on bacterial translocation, inflammatory responses and the susceptibility to colitis were evaluated. The sources of the bacteria and the pathways required for bacterial translocation were evaluated using induced mutant mouse strains, 16s rRNA sequencing to characterise the microbial communities, and in vivo and ex vivo imaging techniques.

RESULTS

Oral antibiotics induced the translocation of live native commensal bacteria across the colonic epithelium, promoting inflammatory responses, and predisposing to increased disease in response to coincident injury. Bacterial translocation resulted from decreased microbial signals delivered to colonic goblet cells (GCs), was associated with the formation of colonic GC-associated antigen passages, was abolished when GCs were depleted and required CX3CR1(+) dendritic cells. Bacterial translocation occurred following a single dose of most antibiotics tested, and the predisposition for increased inflammation was only associated with antibiotics inducing bacterial translocation.

CONCLUSIONS

These findings reveal an unexpected outcome of antibiotic therapy and suggest that bacterial translocation as a result of alterations in the intestinal microflora may provide a link between increasing antibiotic use and the increased incidence of inflammatory disorders.

Presence of commensal house dust mite allergen in human gastrointestinal tract: a potential contributor to intestinal barrier dysfunction

BACKGROUND

Abnormal gut barrier function is the basis of gut inflammatory disease. It is known that house dust mite (HDM) aero-allergens induce inflammation in respiratory mucosa. We have recently reported allergen from Dermatophagoides pteronyssinus (Der p1) to be present in rodent gut.

OBJECTIVE

To examine whether Der p1 is present in human gut and to assess its effect on gut barrier function and inflammation.

DESIGN

Colonic biopsies, gut fluid, serum and stool were collected from healthy adults during endoscopy. Der p1 was measured by ELISA. Effect of HDM was assessed on gut permeability, tight-junction and mucin expression, and cytokine production, in presence or absence of cysteine protease inhibitors or serine protease inhibitors. In vivo effect of HDM was examined in mice given oral HDM or protease-neutralised HDM. Role of HDM in low-grade inflammation was studied in patients with IBS.

RESULTS

HDM Der p1 was detected in the human gut. In colonic biopsies from healthy patients, HDM increased epithelial permeability (p<0.001), reduced expression of tight-junction proteins and mucus barrier. These effects were associated with increased tumour necrosis factor (TNF)-α and interleukin (IL)-10 production and were abolished by cysteine-protease inhibitor (p<0.01). HDM effects did not require Th2 immunity. Results were confirmed in vivo in mice. In patients with IBS, HDM further deteriorated gut barrier function, induced TNF-α but failed to induce IL-10 secretion (p<0.001).

CONCLUSIONS

HDM, a ubiquitous environmental factor, is present in the human gut where it directly affects gut function through its proteolytic activity. HDM may be an important trigger of gut dysfunction and warrants further investigation.

Compartment-specific immunity in the human gut: properties and functions of dendritic cells in the colon versus the ileum

OBJECTIVE

Dendritic cells (DC) mediate intestinal immune tolerance. Despite striking differences between the colon and the ileum both in function and bacterial load, few studies distinguish between properties of immune cells in these compartments. Furthermore, information of gut DC in humans is scarce. We aimed to characterise human colonic versus ileal DC.

DESIGN

Human DC from paired colonic and ileal samples were characterised by flow cytometry, electron microscopy or used to stimulate T cell responses in a mixed leucocyte reaction.

RESULTS

A lower proportion of colonic DC produced pro-inflammatory cytokines (tumour necrosis factor-α and interleukin (IL)-1β) compared with their ileal counterparts and exhibited an enhanced ability to generate CD4(+)FoxP3(+)IL-10(+) (regulatory) T cells. There were enhanced proportions of CD103(+)Sirpα(-) DC in the colon, with increased proportions of CD103(+)Sirpα(+) DC in the ileum. A greater proportion of colonic DC subsets analysed expressed the lymph-node-homing marker CCR7, alongside enhanced endocytic capacity, which was most striking in CD103(+)Sirpα(+) DC. Expression of the inhibitory receptor ILT3 was enhanced on colonic DC. Interestingly, endocytic capacity was associated with CD103(+) DC, in particular CD103(+)Sirpα(+) DC. However, expression of ILT3 was associated with CD103(-) DC. Colonic and ileal DC differentially expressed skin-homing marker CCR4 and small-bowel-homing marker CCR9, respectively, and this corresponded to their ability to imprint these homing markers on T cells.

CONCLUSIONS

The regulatory properties of colonic DC may represent an evolutionary adaptation to the greater bacterial load in the colon. The colon and the ileum should be regarded as separate entities, each comprising DC with distinct roles in mucosal immunity and imprinting.