Acute infection of mice with Clostridium difficile leads to eIF2α phosphorylation and pro-survival signalling as part of the mucosal inflammatory response

BDNF-enriched small extracellular vesicles protect against noise-induced hearing loss in mice

Noise-induced hearing loss (NIHL) is one of the most prevalent acquired sensorineural hearing loss etiologies and is characterized by the loss of cochlear hair cells, synapses, and nerve terminals. Currently, there are no agents available for the treatment of NIHL because drug delivery to the inner ear is greatly limited by the blood-labyrinth barrier. In this study, we used mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) as nanoscale vehicles to deliver brain-derived neurotrophic factor (BDNF) and evaluated their protective effects in a mouse model of NIHL. Following intravenous administration, BDNF-loaded sEVs (BDNF-sEVs) efficiently increased the expression of BDNF protein in the cochlea. Systemic application of sEVs and BDNF-sEVs significantly attenuated noise-induced cochlear hair cell loss and NIHL in CBA/J mice. BDNF-sEVs also alleviated noise-induced loss of inner hair cell ribbon synapses and cochlear nerve terminals. In cochlear explants, sEVs and BDNF-sEVs effectively protected hair cells against H2O2-induced cell loss. Additionally, BDNF-sEVs remarkably ameliorated H2O2-induced oxidative stress, cell apoptosis, and cochlear nerve terminal degeneration. Transcriptomic analysis revealed that many mRNAs and miRNAs were involved in the protective actions of BDNF-sEVs against oxidative stress. Collectively, our findings reveal a novel therapeutic strategy of MSC-sEVs-mediated BDNF delivery for the treatment of NIHL.

Surface layer protein A from hypervirulent Clostridioides difficile ribotypes induce significant changes in the gene expression of tight junctions and inflammatory response in human intestinal epithelial cells

Background

Surface layer protein A (SlpA), the primary outermost structure of Clostridioides difficile, plays an essential role in C. difficile pathogenesis, although its interaction with host intestinal cells are yet to be understood. The aim of this study was to investigate the effects of SlpA extracted from C. difficile on tight junction (TJ) proteins expression and induction of pro-inflammatory cytokines in human colon carcinoma cell line HT-29. SlpA was extracted from three toxigenic C. difficile clinical strains including RT126, RT001, RT084 as well as C. difficile ATCC 700057 as non-toxigenic strain. Cell viability was performed by MTT assay, and the mRNA expression of TJ proteins and inflammation-associated genes was determined using quantitative RT-PCR. Additionally, the secretion of IL-8, IL-1β and TNF-α cytokines was measured by ELISA.

Results

C. difficile SlpA from selected RTs variably downregulated the expression level of TJs-assassinated genes and increased the expression level of TLR-4 and pro-inflammatory cytokines in HT-29 treated cells. SlpA from RT126 significantly (p_adj<0.05) decreased the gene expression level of claudins family and JAM-A and increased the secretion of IL-8, TNF-α and IL1-β as compared to untreated cells. Moreover, only SlpA from RT001 could significantly induce the expression of IL-6 (p_adj<0.05).

Conclusion

The results of the present study highlighted the importance of SlpA in the pathogenesis of CDI and C. difficile-induced inflammatory response in the gut. Further studies are required to unravel the significance of the observed results in promoting the intestinal inflammation and immune response induced by C. difficile SlpA from different RTs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02665-0.

Multi-Omics Analysis Reveals Aberrant Gut-Metabolome-Immune Network in Schizophrenia

Schizophrenia (SCZ) is associated with several immune dysfunctions, including elevated levels of pro-inflammatory cytokines. Microorganisms and their metabolites have been found to regulate the immune system, and that intestinal microbiota is significantly disturbed in schizophrenic patients. To systematically investigate aberrant gut-metabolome-immune network in schizophrenia, we performed an integrative analysis of intestinal microbiota, serum metabolome, and serum inflammatory cytokines in 63 SCZ patients and 57 healthy controls using a multi-omics strategy. Eighteen differentially abundant metabolite clusters were altered in patients displayed higher cytokine levels, with a significant increase in pro-inflammatory metabolites and a significant decrease in anti-inflammatory metabolites (such as oleic acid and linolenic acid). The bacterial co-abundance groups in the gut displayed more numerous and stronger correlations with circulating metabolites than with cytokines. By integrating these data, we identified that certain bacteria might affect inflammatory cytokines by modulating host metabolites, such as amino acids and fatty acids. A random forest model was constructed based on omics data, and seven serum metabolites significantly associated with cytokines and α-diversity of intestinal microbiota were able to accurately distinguish the cases from the controls with an area under the receiver operating characteristic curve of 0.99. Our results indicated aberrant gut-metabolome-immune network in SCZ and gut microbiota may influence immune responses by regulating host metabolic processes. These findings suggest a mechanism by which microbial-derived metabolites regulated inflammatory cytokines and insights into the diagnosis and treatment of mental disorders from the microbial-immune system in the future.

Hiding in Plain Sight: Formation and Function of Stress Granules During Microbial Infection of Mammalian Cells

Stress granule (SG) formation is a host cell response to stress-induced translational repression. SGs assemble with RNA-binding proteins and translationally silent mRNA. SGs have been demonstrated to be both inhibitory to viruses, as well as being subverted for viral roles. In contrast, the function of SGs during non-viral microbial infections remains largely unexplored. A handful of microbial infections have been shown to result in host SG assembly. Nevertheless, a large body of evidence suggests SG formation in hosts is a widespread response to microbial infection. Diverse stresses caused by microbes and their products can activate the integrated stress response in order to inhibit translation initiation through phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α). This translational response in other contexts results in SG assembly, suggesting that SG assembly can be a general phenomenon during microbial infection. This review explores evidence for host SG formation in response to bacterial, fungal, and protozoan infection and potential functions of SGs in the host and for adaptations of the pathogen.

Clostridioides difficile toxins enhanced the in vitro production of CXC chemokine ligand 2 and tumor necrosis factor-α via Toll-like receptors in macrophages

Introduction. Clostridioides difficile infection (CDI) causes toxin-mediated enteropathy, such as antibiotic-associated diarrhoea and pseudomembranous colitis. Rho-glucosylating toxin A (TcdA) and toxin B (TcdB) have been clearly implicated in pathogenesis, whereas the virulence of binary toxin (CDT) is still debated.Hypothesis statement. We hypothesized that CDT is involved in the host immune response and plays a pivotal role in establishing virulence by modulating pro-inflammatory cytokine production; this is achieved through the integral Toll-like receptor (TLR) signalling pathways.Aim. The aim of the present study was to determine whether and how CDT impacts macrophages compared to TcdA or TcdB by examining the induction of CXC chemokine ligand 2 (CXCL2) and tumour necrosis factor-α (TNF-α), both of which are crucial in mediating local and systematic inflammatory responses.Methodology. RAW264.7 cells or transfected human embryonic kidney (HEK) 293 T cells were incubated with TcdA, TcdB, or CDT. In some experiments, a neutralizing antibody against TLR2 or TLR4, or myeloid differentiation 88 inhibitory peptide were added. The amount of CXCL2 and TNF-α secreted was then measured.Results. In RAW264.7 macrophages, CXCL2 and TNF-α were produced via the Toll-like receptor 2 (TLR2) or Toll-like receptor 4 (TLR4) pathway in a TcdA, TcdB, or CDT dose-dependent manner. Interleukin-8 secretion was induced in TLR4/MD2/CD14-transfected, but not in TLR2-transfected, HEK 293 T cells following TcdB or CDT exposure.Conclusion. Our results showed that C. difficile toxins, including CDT, enhanced macrophage-mediated CXCL2 and TNF-α production via TLR2 and TLR4, indicating that CDT affects host immune responses.

The host glycomic response to pathogens

Glycans play important roles in the biology of infectious diseases. Although glycans are expressed on both the pathogens and the host, the functions and dynamics of the host glycome during infection are not well understood. Recent years have witnessed new discoveries on the host glycome respsonse to infection, as well as related mechanisms and their implications. Herein, we present a brief review on the latest findings in this field and put them in the context of host immunity.

Interleukin-22 and intestinal homeostasis: Protective or destructive?

Interleukin (IL)-22 is a member of IL-10 family cytokines with various immunologic functions. As its name implies, IL-22 is known to be secreted mainly by Th22 cells, a recently discovered lineage of CD4+ T cells. Also, Th17, Th1, natural killer cells, γδT cells, and innate immune cells along with some nonlymphoid cells have been confirmed as secondary cellular sources of IL-22. Different cell types such as bronchial and intestinal epithelial cells, keratinocytes, hepatocytes, dermal fibroblasts, and tubular epithelial cells are affected by IL-22. Both pathologic and protective roles have been attributed to IL-22 in maintaining gut homeostasis and inflammation. According to the latest fast-growing investigations, IL-22 is significantly involved in various pathologies including allergic diseases, infection, autoimmunity, and cancer development. Regulating gut immune responses, barrier integrity, and inflammation is dependent on a diverse complex of cytokines and mediators which are secreted by mucosal immune cells. Several investigations have been designed to recognize the role of IL-22 in gastrointestinal immunity. This article tries to discuss the latest knowledge on this issue and clarify the potential of IL-22 to be used in the future therapeutic approaches of intestinal disorders including inflammatory bowel diseases and colon cancer.

A2ML1 and otitis media: novel variants, differential expression, and relevant pathways

A genetic basis for otitis media is established, however, the role of rare variants in disease etiology is largely unknown. Previously a duplication variant within A2ML1 was identified as a significant risk factor for otitis media in an indigenous Filipino population and in US children. In this report exome and Sanger sequencing was performed using DNA samples from the indigenous Filipino population, Filipino cochlear implantees, US probands, Finnish, and Pakistani families with otitis media. Sixteen novel, damaging A2ML1 variants identified in otitis media patients were rare or low-frequency in population-matched controls. In the indigenous population, both gingivitis and A2ML1 variants including the known duplication variant and the novel splice variant c.4061 + 1 G>C were independently associated with otitis media. Sequencing of salivary RNA samples from indigenous Filipinos demonstrated lower A2ML1 expression according to the carriage of A2ML1 variants. Sequencing of additional salivary RNA samples from US patients with otitis media revealed differentially expressed genes that are highly correlated with A2ML1 expression levels. In particular, RND3 is upregulated in both A2ML1 variant carriers and high-A2ML1 expressors. These findings support a role for A2ML1 in keratinocyte differentiation within the middle ear as part of otitis media pathology and the potential application of ROCK inhibition in otitis media.

Tumour Necrosis Factor Alpha in Intestinal Homeostasis and Gut Related Diseases

The intestinal epithelium constitutes an indispensable single-layered barrier to protect the body from invading pathogens, antigens or toxins. At the same time, beneficial nutrients and water have to be absorbed by the epithelium. To prevent development of intestinal inflammation or tumour formation, intestinal homeostasis has to be tightly controlled and therefore a strict balance between cell death and proliferation has to be maintained. The proinflammatory cytokine tumour necrosis factor alpha (TNFα) was shown to play a striking role for the regulation of this balance in the gut. Depending on the cellular conditions, on the one hand TNFα is able to mediate cell survival by activating NFκB signalling. On the other hand, TNFα might trigger cell death, in particular caspase-dependent apoptosis but also caspase-independent programmed necrosis. By regulating these cell death and survival mechanisms, TNFα exerts a variety of beneficial functions in the intestine. However, TNFα signalling is also supposed to play a critical role for the pathogenesis of inflammatory bowel disease (IBD), infectious diseases, intestinal wound healing and tumour formation. Here we review the literature about the physiological and pathophysiological role of TNFα signalling for the maintenance of intestinal homeostasis and the benefits and difficulties of anti-TNFα treatment during IBD.

Salubrinal protects against Clostridium difficile toxin B-induced CT26 cell death

Clostridium difficile (C. difficile) is considered to be the major cause of the antibiotic-associated diarrhea and pseudomembranous colitis in animals and humans. The prevalence of C. difficile infections (CDI) has been increasing since 2000. Two exotoxins of C. difficile, Toxin A (TcdA) and Toxin B (TcdB), are the main virulence factors of CDI, which can induce glucosylation of Rho GTPases in host cytosol, leading to cell morphological changes, cell apoptosis, and cell death. The mechanism of TcdB-induced cell death has been investigated for decades, but it is still not completely understood. It has been reported that TcdB induces endoplasmic reticulum stress via PERK-eIF2α signaling pathway in CT26 cell line (BALB/C mouse colon tumor cells). In this study, we found that salubrinal, a selective inhibitor of eIF2α dephosphorylation, efficiently protects CT26 cell line against TcdB-induced cell death and tried to explore the mechanism underlying in this protective effect. Our results demonstrated that salubrinal protects CT26 cells from TcdB-mediated cytotoxic and cytopathic effect, inhibits apoptosis and death of the toxin-exposed cells via caspase-9-dependent pathway, eIF2α signaling pathway, and autophagy. These findings will be helpful for the development of CDI therapies.

Role of interferon-γ and inflammatory monocytes in driving colonic inflammation during acute Clostridium difficile infection in mice

The inflammatory response to the colonic pathogen Clostridium difficile is characterized by the induction of inflammatory cytokines including Interleukin-23 (IL-23) and interferon-γ (IFN-γ) and the recruitment of myeloid cells including Ly6C^High monocytes. IL-23 knockout mice showed reduced expression of the monocyte chemokines Ccl4 and Ccl7, but not Ccl2, as well as reduced Ly6C^High Ly6G^Mid monocyte recruitment to the colon in response to C. difficile colitis. Clostridium difficile-infected CCR2^-/- (CCR2 KO) mice showed a significant defect in Ly6C^High Ly6G^Mid monocyte recruitment to the colon in response to C. difficile. Although there was no decrease in expression of the inflammatory cytokines Il1b, Il6 or Tnf or reduction in the severity of colonic histopathology associated with ablation of monocyte recruitment, Slpi and Inos expression was significantly reduced in the colons of these animals. Additionally, neutralization of IFN-γ through the administration of anti-IFN-γ monoclonal antibody resulted in a significant reduction in the expression of the IFN-γ-inducible chemokines Cxcl9 and Cxcl10, but not a reduction in the neutrophil chemokines Cxcl1, Cxcl2 and Ccl3 or the monocyte chemokine Ccl2. Consistently, monocyte and neutrophil recruitment were unchanged following anti-IFN-γ treatment. Additionally, Inos and Slpi expression were unchanged following anti-IFN-γ treatment, suggesting that Inos and Slpi regulation is independent of IFN-γ during C. difficile colitis. Taken together, these data strongly suggest that IL-23 and CCR2 signalling are required for monocyte recruitment during C. difficile colitis. Additionally, these studies also suggest that monocytes, but not IFN-γ, are necessary for full expression of Inos and Slpi in the colon.

Clostridium difficile colitis: pathogenesis and host defence

Clostridium difficile is a major cause of intestinal infection and diarrhoea in individuals following antibiotic treatment. Recent studies have begun to elucidate the mechanisms that induce spore formation and germination and have determined the roles of C. difficile toxins in disease pathogenesis. Exciting progress has also been made in defining the role of the microbiome, specific commensal bacterial species and host immunity in defence against infection with C. difficile. This Review will summarize the recent discoveries and developments in our understanding of C. difficile infection and pathogenesis.

Interleukin-23 (IL-23), independent of IL-17 and IL-22, drives neutrophil recruitment and innate inflammation during Clostridium difficile colitis in mice

Our objective was to determine the role of the inflammatory cytokine interleukin-23 (IL-23) in promoting neutrophil recruitment, inflammatory cytokine expression and intestinal histopathology in response to Clostridium difficile infection. Wild-type (WT) and p19(-/-) (IL-23KO) mice were pre-treated with cefoperazone in their drinking water for 5 days, and after a 2-day recovery period were challenged with spores from C. difficile strain VPI 10463. Interleukin-23 deficiency was associated with significant defects in both the recruitment of CD11b(High) Ly6G(H) (igh) neutrophils to the colon and the expression of neutrophil chemoattractants and stabilization factors including Cxcl1, Cxcl2, Ccl3 and Csf3 within the colonic mucosa as compared with WT animals. Furthermore, the expression of inflammatory cytokines including Il33, Tnf and Il6 was significantly reduced in IL-23-deficient animals. There was also a trend towards less severe colonic histopathology in the absence of IL-23. The induction of Il17a and Il22 was also significantly abrogated in IL-23KO mice. Inflammatory cytokine expression and neutrophilic inflammation were not reduced in IL-17a-deficient mice or in mice treated with anti-IL-22 depleting monoclonal antibody. However, induction of RegIIIg was significantly reduced in animals treated with anti-IL-22 antibody. Taken together, these data indicate that IL-23, but not IL-17a or IL-22, promotes neutrophil recruitment and inflammatory cytokine and chemokine expression in the colon in response to C. difficile infection.

Co-Transcriptomes of Initial Interactions In Vitro between Streptococcus Pneumoniae and Human Pleural Mesothelial Cells

Streptococcus pneumoniae (Spn) is a major causative organism of empyema, an inflammatory condition occurring in the pleural sac. In this study, we used human and Spn cDNA microarrays to characterize the transcriptional responses occurring during initial contact between Spn and a human pleural mesothelial cell line (PMC) in vitro. Using stringent filtering criteria, 42 and 23 Spn genes were up-and down-regulated respectively. In particular, genes encoding factors potentially involved in metabolic processes and Spn adherence to eukaryotic cells were up-regulated e.g. glnQ, glnA, aliA, psaB, lytB and nox. After Spn initial contact, 870 human genes were differentially regulated and the largest numbers of significant gene expression changes were found in canonical pathways for eukaryotic initiation factor 2 signaling (60 genes out of 171), oxidative phosphorylation (32/103), mitochondrial dysfunction (37/164), eIF4 and p70S6K signaling (28/142), mTOR signaling (27/182), NRF2-mediated oxidative stress response (20/177), epithelial adherens junction remodeling (11/66) and ubiquitination (22/254). The cellular response appeared to be directed towards host cell survival and defense. Spn did not activate NF-kB or phosphorylate p38 MAPK or induce cytokine production from PMC. Moreover, Spn infection of TNF-α pre-stimulated PMC inhibited production of IL-6 and IL-8 secretion by >50% (p<0.01). In summary, this descriptive study provides datasets and a platform for examining further the molecular mechanisms underlying the pathogenesis of empyema.

A proteomic perspective of the interplay of Staphylococcus aureus and human alveolar epithelial cells during infection

Infectious diseases caused by pathogens such as Staphylococcus aureus are still a major threat for human health. Proteome analyses allow detailed monitoring of the molecular interplay between pathogen and host upon internalization. However, the investigation of the responses of both partners is complicated by the large excess of host cell proteins compared to bacterial proteins as well as by the fact that only a fraction of host cells are infected. In the present study we infected human alveolar epithelial A549 cells with S. aureus HG001 pMV158GFP and separated intact bacteria from host cell debris or infected from non-infected A549 cells by cell sorting to enable detailed proteome analysis. During the first 6.5h in the intracellular milieu S. aureus displayed reduced growth rate, induction of the stringent response, adaptation to microaerobic conditions as well as cell wall stress. Interestingly, both truly infected host cells and those not infected but exposed to secreted S. aureus proteins and host cell factors showed differences in the proteome pattern compared to A549 cells which had never been in contact with S. aureus. However, adaptation reactions were more pronounced in infected compared to non-infected A549 bystander cells.

Innate Immune Defenses Mediated by Two ILC Subsets Are Critical for Protection against Acute Clostridium difficile Infection

Infection with the opportunistic enteric pathogen Clostridium difficile is an increasingly common clinical complication that follows antibiotic treatment-induced gut microbiota perturbation. Innate lymphoid cells (ILCs) are early responders to enteric pathogens; however, their role during C. difficile infection is undefined. To identify immune pathways that mediate recovery from C. difficile infection, we challenged C57BL/6, Rag1(-/-) (which lack T and B cells), and Rag2(-/-)Il2rg(-/-) (Ragγc(-/-)) mice (which additionally lack ILCs) with C. difficile. In contrast to Rag1(-/-) mice, ILC-deficient Ragγc(-/-) mice rapidly succumbed to infection. Rag1(-/-) but not Ragγc(-/-) mice upregulate expression of ILC1- or ILC3-associated proteins following C. difficile infection. Protection against infection was restored by transferring ILCs into Ragγc(-/-) mice. While ILC3s made a minor contribution to resistance, loss of IFN-γ or T-bet-expressing ILC1s in Rag1(-/-) mice increased susceptibility to C. difficile. These data demonstrate a critical role for ILC1s in defense against C. difficile.

Staphylococcus aureus induces IL-8 expression through its lipoproteins in the human intestinal epithelial cell, Caco-2

Staphylococcus aureus can cause the intestinal inflammatory diseases. However, little is known about the molecular mechanism of S. aureus infection in the intestine. In the present study, we investigated whether S. aureus could stimulate human intestinal epithelial cells triggering inflammation. When the human intestinal epithelial cell-line, Caco-2, and the primary colon cells were stimulated with ethanol-inactivated S. aureus, IL-8 expression was induced in a dose-dependent manner. The inactivated S. aureus preferentially stimulated Toll-like receptor (TLR) 2 rather than TLR4. Lipoproteins, lipoteichoic acid (LTA), and peptidoglycan (PGN) are considered as potential TLR2 ligands of S. aureus. Interestingly, S aureus lipoproteins and Pam2CSK4 mimicking Gram-positive bacterial lipoproteins, but not LTA and PGN of S. aureus, significantly induced IL-8 expression in Caco-2 cells. Furthermore, lipoprotein-deficient S. aureus mutant strain failed to induce IL-8 production. Collectively, these results suggest that S. aureus stimulates the human intestinal epithelial cells to induce the chemokine IL-8 production through its lipoproteins, potentially contributing the development of intestinal inflammation.

The role of Gr-1(+) cells and tumour necrosis factor-α signalling during Clostridium difficile colitis in mice

The host response to Clostridium difficile infection in antibiotic-treated mice is characterized by robust recruitment of Gr-1(+) cells, increased expression of inflammatory cytokines including tumour necrosis factor-α (TNF-α), and the development of severe epithelial damage. To investigate the role of Gr-1(+) cells and TNF-α during C. difficile colitis, we treated infected mice with monoclonal antibodies against Gr-1 or TNF-α. Mice were challenged with vegetative cells of C. difficile strain VPI 10463 following treatment with the third-generation cephalosporin ceftriaxone. Ceftriaxone treatment alone was associated with significant changes in cytokine expression within the colonic mucosa but not overt inflammatory histopathological changes. In comparison, C. difficile infection following ceftriaxone treatment was associated with increased expression of inflammatory cytokines and chemokines including Cxcl1, Cxcl2, Il1b, Il17f and Tnfa, as well as robust recruitment of Ly6C(Mid)  Gr-1(High) neutrophils and Ly6C(High) Gr-1(Mid) monocytes and the development of severe colonic histopathology. Anti-Gr-1 antibody treatment resulted in effective depletion of both Ly6C(Mid) Gr-1(High) neutrophils and Ly6C(High) Gr-1(Mid) monocytes: however, we observed no protection from the development of severe pathology or reduction in expression of the pro-inflammatory cytokines Il1b, Il6, Il33 and Tnfa following anti-Gr-1 treatment. By contrast, anti-TNF-α treatment did not affect Gr-1(+) cell recruitment, but was associated with increased expression of Il6 and Il1b. Additionally, Ffar2, Ffar3, Tslp, Tff and Ang4 expression was significantly reduced in anti-TNF-α-treated animals, in association with marked intestinal histopathology. These studies raise the possibility that TNF-α may play a role in restraining inflammation and protecting the epithelium during C. difficile infection.

Interleukin-22 and CD160 play additive roles in the host mucosal response to Clostridium difficile infection in mice

Our previous work has shown the significant up-regulation of Il22 and increased phosphorylation of signal transducer and activator of transcription 3 (STAT3) as part of the mucosal inflammatory response to Clostridium difficile infection in mice. Others have shown that phosphorylation of STAT3 at mucosal surfaces includes interleukin-22 (IL-22) and CD160-mediated components. The current study sought to determine the potential role(s) of IL-22 and/or CD160 in the mucosal response to C. difficile infection. Clostridium difficile-infected mice treated with anti-IL-22, anti-CD160 or a combination of the two showed significantly reduced STAT3 phosphorylation in comparison to C. difficile-infected mice that had not received either antibody. In addition, C. difficile-infected mice treated with anti-IL-22/CD160 induced a smaller set of genes, and at significantly lower levels than the untreated C. difficile-infected mice. The affected genes included pro-inflammatory chemokines and cytokines, and anti-microbial peptides. Furthermore, histopathological and flow cytometric assessments both showed a significantly reduced influx of neutrophils in C. difficile-infected mice treated with anti-IL-22/CD160. These data demonstrate that IL-22 and CD160 are together responsible for a significant fraction of the colonic STAT3 phosphorylation in C. difficile infection. They also underscore the additive effects of IL-22 and CD160 in mediating both the pro-inflammatory and pro-survival aspects of the host mucosal response in this infection.

Evaluation of body growth and immunity-related differentially expressed genes through deep RNA sequencing in the piglets of Jeju native pig and Berkshire

This study was carried out with the objective to investigate the differentially expressed genes (DEGs) between Jeju native pig (JNP) and Berkshire piglets. The RNA-Seq technique was used to investigate the transcriptomes in the fat, liver and longissimus dorsi muscle from these two breeds. Paired-end reads of the sequences that passed the quality filters were aligned to the Sus scrofa genome using tophat2 (v2.0.2). In this study, 65% of muscle, 20% of fat and 54% of liver genes showed higher expression in the piglets of JNP than in Berkshire. Gene Ontology and signaling pathways showed that immune response and lipid metabolisms were commonly enriched pathways in all three tissues. It was found that the genes pertaining to body growth and immune system are significantly (P < 0.01) more highly expressed in Berkshire piglets. DEGs explored between the piglets of the two breeds might influence the identification of the genetic markers for further breed improvement programs. Our findings provide a new perspective for understanding and identifying candidate genes that are involved in various biological functions. Moreover, transcriptome analysis makes it easier to understand the differences between genetic mechanisms of breeds.

Analysis of the upper respiratory tract microbiotas as the source of the lung and gastric microbiotas in healthy individuals

No studies have examined the relationships between bacterial communities along sites of the upper aerodigestive tract of an individual subject. Our objective was to perform an intrasubject and intersite analysis to determine the contributions of two upper mucosal sites (mouth and nose) as source communities for the bacterial microbiome of lower sites (lungs and stomach). Oral wash, bronchoalveolar lavage (BAL) fluid, nasal swab, and gastric aspirate samples were collected from 28 healthy subjects. Extensive analysis of controls and serial intrasubject BAL fluid samples demonstrated that sampling of the lungs by bronchoscopy was not confounded by oral microbiome contamination. By quantitative PCR, the oral cavity and stomach contained the highest bacterial signal levels and the nasal cavity and lungs contained much lower levels. Pyrosequencing of 16S rRNA gene amplicon libraries generated from these samples showed that the oral and gastric compartments had the greatest species richness, which was significantly greater in both than the richness measured in the lungs and nasal cavity. The bacterial communities of the lungs were significantly different from those of the mouth, nose, and stomach, while the greatest similarity was between the oral and gastric communities. However, the bacterial communities of healthy lungs shared significant membership with the mouth, but not the nose, and marked subject-subject variation was noted. In summary, microbial immigration from the oral cavity appears to be the significant source of the lung microbiome during health, but unlike the stomach, the lungs exhibit evidence of selective elimination of Prevotella bacteria derived from the upper airways.

We have demonstrated that the bacterial communities of the healthy lung overlapped those found in the mouth but were found at lower concentrations, with lower membership and a different community composition. The nasal microbiome, which was distinct from the oral microbiome, appeared to contribute little to the composition of the lung microbiome in healthy subjects. Our studies of the nasal, oral, lung, and stomach microbiomes within an individual illustrate the microbiological continuity of the aerodigestive tract in healthy adults and provide culture-independent microbiological support for the concept that microaspiration is common in healthy individuals.

Interleukin-22: immunobiology and pathology

Interleukin-22 (IL-22) is a recently described IL-10 family cytokine that is produced by T helper (Th) 17 cells, γδ T cells, NKT cells, and newly described innate lymphoid cells (ILCs). Knowledge of IL-22 biology has evolved rapidly since its discovery in 2000, and a role for IL-22 has been identified in numerous tissues, including the intestines, lung, liver, kidney, thymus, pancreas, and skin. IL-22 primarily targets nonhematopoietic epithelial and stromal cells, where it can promote proliferation and play a role in tissue regeneration. In addition, IL-22 regulates host defense at barrier surfaces. However, IL-22 has also been linked to several conditions involving inflammatory tissue pathology. In this review, we assess the current understanding of this cytokine, including its physiologic and pathologic effects on epithelial cell function.

Role of obesity and adipose tissue-derived cytokine leptin during Clostridium difficile infection

Obesity is among the most pressing health concerns in the world since it is increasingly common even in the developing world, and is clearly associated with increased risk for chronic debilitating diseases and death. Furthermore, obesity can influence the pathogenesis of infectious diseases by affecting the balance of pathogen clearance and pathological inflammation. The mechanisms that result in enhanced inflammation in obese individuals are poorly understood. Clostridium difficile is a major cause of nosocomial infections worldwide. Recent studies have shown that obesity is associated with increased risk of C. difficile infections. In this review, we will discuss our current knowledge of the role of obesity in determining risk of C. difficile infections, and focus on the role of the adipose tissue-derived cytokine leptin in C. difficile infections.

Recombinant Clostridium difficile toxin B induces endoplasmic reticulum stress in mouse colonal carcinoma cells

Clostridium difficile is the main cause of antibiotic-associated diarrhea and pseudomembranous colitis in humans and animals. Its pathogenicity is primarily linked to the secretion of two exotoxins (TcdA and TcdB). Although great progress in the toxic mechanism of TcdA and TcdB has been achieved, there are many conflicting reports about the apoptotic mechanism. More importantly, apoptotic endoplasmic reticulum (ER) stress has been reported in cells treated with Shiga toxins-another kind of cytotoxins that can cause diarrhea and colitis. Herein we checked whether TcdB can induce ER stress. The results showed that recombinant TcdB (rTcdB) activated molecular markers of unfolded protein response, suggesting that rTcdB induced ER stress in CT26 cells. However, rTcdB did not induce the up-regulation of C/EBP homologous protein (CHOP), a classic mediator of apoptotic ER stress, but it activated the precursor of cysteine aspartic acid-specific protease 12 (caspase-12), a controversial mediator of apoptotic ER stress. Besides, glucosyltransferase activity-deficient mutant recombinant TcdB induced ER stress, though it has no cytotoxic or cytopathic effect on CT26 cells. Altogether, these data demonstrated that ER stress induced by rTcdB is glucosyltransferase-independent, indicating that ER stress induced by rTcdB is non-apoptotic. This work also offers us a new insight into the molecular mechanism of CHOP protein expression regulation and the role of CHOP expression in ER stress.

GBA2-encoded β-glucosidase activity is involved in the inflammatory response to Pseudomonas aeruginosa

Current anti-inflammatory strategies for the treatment of pulmonary disease in cystic fibrosis (CF) are limited; thus, there is continued interest in identifying additional molecular targets for therapeutic intervention. Given the emerging role of sphingolipids (SLs) in various respiratory disorders, including CF, drugs that selectively target the enzymes associated with SL metabolism are under development. Miglustat, a well-characterized iminosugar-based inhibitor of β-glucosidase 2 (GBA2), has shown promise in CF treatment because it reduces the inflammatory response to infection by P. aeruginosa and restores F508del-CFTR chloride channel activity. This study aimed to probe the molecular basis for the anti-inflammatory activity of miglustat by examining specifically the role of GBA2 following the infection of CF bronchial epithelial cells by P. aeruginosa. We also report the anti-inflammatory activity of another potent inhibitor of GBA2 activity, namely N-(5-adamantane-1-yl-methoxy)pentyl)-deoxynojirimycin (Genz-529648). In CF bronchial cells, inhibition of GBA2 by miglustat or Genz-529648 significantly reduced the induction of IL-8 mRNA levels and protein release following infection by P. aeruginosa. Hence, the present data demonstrate that the anti-inflammatory effects of miglustat and Genz-529648 are likely exerted through inhibition of GBA2.

Comparative transcriptomic analysis to identify differentially expressed genes in fat tissue of adult Berkshire and Jeju Native Pig using RNA-seq

Pork is a major source of animal protein for humans. The subcutaneous, intermuscular and the intramuscular fat are the factors responsible for meat quality. RNA-seq is rapidly adopted for the profiling of the transcriptomes in the studies related to gene regulation. The discovery of differentially expressed genes (DEGs) between adult animals of Jeju Native Pig (JNP) and Berkshire breeds are of particular interest for the current study. RNA-seq was used to investigate the transcriptome profiling in the fat tissue. Sequence reads were obtained from Ilumina HiSeq2000 and mapped to the pig genome using Tophat2. Total 153 DEGs were identified and 71 among the annotated genes, have BLAST matches in the non- redundant database. Metabolic, immune response and protein binding are enriched pathways in the fat tissue. In our study, biological adhesion, cellular, developmental and multicellular organismal processes in fat were up-regulated in JNP as compare to Berkshire. Multicellular organismal process, developmental process, embryonic morphogenesis and skeletal system development were the most significantly enriched terms in fat of JNP and Berkshire breeds (p = 1.17E-04, 0.044, 3.47E-04 and 4.48E-04 respectively). COL10A1, COL11A2, PDK4 and PNPLA3 genes responsible for skeletal system morphogenesis and body growth were down regulated in JNP. This study is the first statistical analysis for the detection of DEGs from RNA-seq data generated from fat tissue sample. This analysis can be used as stepping stone to understand the difference in the genetic mechanisms that might influence the identification of novel transcripts, sequence polymorphisms, isoforms and noncoding RNAs.

Role of GM-CSF in the inflammatory cytokine network that regulates neutrophil influx into the colonic mucosa during Clostridium difficile infection in mice

Clostridium difficile infection in antibiotic-treated mice results in acute colitis characterized by severe intestinal histopathology, robust neutrophil influx, and increased expression of numerous inflammatory cytokines, including GM-CSF. We utilized a neutralizing monoclonal antibody (mAb) against GM-CSF in a murine model to study the role of GM-CSF during acute C. difficile colitis. Cefoperazone-treated mice were challenged with C. difficile (strain 630) spores. Expression of GM-CSF was significantly increased in animals challenged with C. difficile. Treatment with an anti-GM-CSF mAb did not alter C. difficile colonization levels, weight loss, or expression of IL-22 and RegIIIγ. However, expression of the inflammatory cytokines TNFα and IL-1β, as well as iNOS, was significantly reduced following anti-GM-CSF treatment. Expression of the neutrophil chemokines CXCL1 and CXCL2, but not the chemokines CCL2, CCL4, CXCL9, and CXCL10, was significantly reduced by anti-GM-CSF treatment. Consistent with a decrease in neutrophil-attractant chemokine expression, there were fewer neutrophils in histology sections and a reduction in the expression of secretory leukocyte protease inhibitor (SLPI), a tissue anti-protease that protects against damage by secreted neutrophil elastase. These data indicate that GM-CSF plays a role in the inflammatory signaling network that drives neutrophil recruitment in response to C. difficile infection but does not appear to play a role in clearance of the infection.

Phosphorylation of eIF2α is dispensable for differentiation but required at a posttranscriptional level for paneth cell function and intestinal homeostasis in mice

BACKGROUND

Recent studies link endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) to inflammatory bowel disease. Altered eIF2α phosphorylation (eIF2α-P), a regulatory hub of the UPR, was observed in mucosal tissue of patients with inflammatory bowel disease. In this study, we examined the mechanistic role of eIF2α-P in intestinal epithelial cell (IEC) function and intestinal homeostasis in mice.

METHODS

We generated mice with villin-Cre-mediated conditional expression of nonphosphorylatable Ser51Ala mutant eIF2α in IECs (AA mice). We analyzed AA mice under normal conditions and on challenge with oral infection of Salmonella Typhimurium or dextran sulfate sodium-induced colitis.

RESULTS

Loss of eIF2α-P did not affect the normal proliferation or differentiation of IECs. However, AA mice expressed decreased secretory proteins including lysozyme, suggesting eIF2α-P is required for Paneth cell function. The ultrastructure of AA Paneth cells exhibited a reduced number of secretory granules, a fragmented ER, and distended mitochondria under normal conditions. UPR gene expression was defective in AA IECs. Translation of Paneth cell specific messenger RNAs encoding lysozyme and cryptidins was significantly defective leading to the observed granule-deficient phenotype, which was associated with reduced ribosomal recruitment of these messenger RNAs to the ER membrane. Consequently, AA mice were more susceptible to oral Salmonella infection and dextran sulfate sodium-induced colitis.

CONCLUSIONS

We conclude eIF2α phosphorylation is required for the normal function of intestinal Paneth cells and mucosal homeostasis by activating UPR signaling and promoting messenger RNA recruitment to the ER membrane for translation.