Neutrophils Promote Amphiregulin Production in Intestinal Epithelial Cells through TGF-β and Contribute to Intestinal Homeostasis

Unraveling the web of defense: the crucial role of polysaccharides in immunity

The great potential of polysaccharides in immunological regulation has recently been highlighted in pharmacological and clinical studies. Polysaccharides can trigger immunostimulatory responses through molecular identification, intra- and intercellular communication via direct or indirect interactions with the immune system. Various immunostimulatory polysaccharides or their derivative compounds interacts at cellular level to boost the immune system, including arabinogalactans, fucoidans, mannans, xylans, galactans, hyaluronans, fructans, pectin and arabinogalactans, etc. These natural polysaccharides are derived from various plants, animals and microbes. A unique structural diversity has been identified in polysaccharides, while monosaccharides and glucosidic bonds mainly confer diverse biological activities. These natural polysaccharides improve antioxidant capacity, reduce the production of pro-inflammatory mediators, strengthen the intestinal barrier, influence the composition of intestinal microbial populations and promote the synthesis of short-chain fatty acids. These natural polysaccharides are also known to reduce excessive inflammatory responses. It is crucial to develop polysaccharide-based immunomodulators that could be used to prevent or treat certain diseases. This review highlights the structural features, immunomodulatory properties, underlying immunomodulatory mechanisms of naturally occurring polysaccharides, and activities related to immune effects by elucidating a complex relationship between polysaccharides and immunity. In addition, the future of these molecules as potential immunomodulatory components that could transform pharmaceutical applications at clinical level will also be highlighted.

The roles of migrasomes in immunity, barriers, and diseases

Migrasomes are recently identified extracellular vesicles and organelles formed in conjunction with cell migration. They are situated at the rear of migrating cells, exhibit a circular or elliptical membrane-enclosed structure, and function as a new organelle. Migrasomes selectively sort intercellular components, mediating a cell migration-dependent release mechanism known as migracytosis and modulating cell-cell communication. Accumulated evidence clarifies migrasome formation processes and indicates their diverse functional roles. Migrasomes may also be potentially correlated with the occurrence, progression, and prognosis of certain diseases. Migrasomes' involvement in physiological and pathological processes highlights their potential for expanding our understanding of biological procedures and as a target in clinical therapy. However, the precise mechanisms and full extent of their involvement in immunity, barriers, and diseases remain unclear. This review aimed to provide a comprehensive overview of the roles of migrasomes in human immunity and barriers, in addition to providing insights into their impact on human diseases. STATEMENT OF SIGNIFICANCE: Migrasomes, newly identified extracellular vesicles and organelles, form during cell migration and are located at the rear of migrating cells. These circular or elliptical structures mediate migracytosis, selectively sorting intercellular components and modulating cell-cell communication. Evidence suggests diverse functional roles for migrasomes, including potential links to disease occurrence, progression, and prognosis. Their involvement in physiological and pathological processes highlights their significance in understanding biological procedures and potential clinical therapies. However, their exact mechanisms in immunity, barriers, and diseases remain unclear. This review provides an overview of migrasomes' roles in human immunity and barriers, and their impact on diseases.

Jejunal transcriptomic profiling of carnosine synthesis precursor-related genes and pathways in slow-growing Korat chicken

Carnosine is a physiologically important molecule in normal human body functions. Chicken meat is an excellent source of carnosine; especially slow-growing Korat chicken (KR) females have a high carnosine content in their meat. The carnosine content of chicken meat can be increased by dietary supplementation of β-alanine (βA) and L-histidine (L-His). Our objective was to reveal the pathways and genes through jejunal transcriptomic profiling related to βA and L-His absorption and transportation. We collected whole jejunum samples from 5 control and 5 experimental KR chicken, fed with 1% βA and 0.5% L-His supplementation. A total of 407 differentially expressed genes (P < 0.05, log2 fold change ≥2) were identified, 272 of which were down-regulated and 135 up-regulated in the group with dietary supplementation compared to the control group. Based on the integrated analysis of the protein-protein interaction network and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway maps, 87 gene ontology terms were identified and 6 KEGG pathways were significantly (P < 0.05) enriched in the jejunum. The analyses revealed 6 key genes, KCND3, OPRM1, CCK, GCG, TRH, and GABBR2, that are related to neuroactive ligand-receptor interaction and the calcium signaling pathway. These findings give insight regarding the molecular mechanism related to carnosine precursor absorption and transportation in the jejunum and help to identify useful molecular markers for improving the carnosine content in slow-growing KR chicken meat.

Mrgprb2-dependent Mast Cell Activation Plays a Crucial Role in Acute Colitis

BACKGROUND & AIMS

Mast cells (MCs) are typically found at mucosal surfaces, where their immunoglobulin E (IgE)-dependent activation plays a central role in allergic diseases. Over the past years, signaling through Mas-related G protein-coupled receptor b2 (Mrgprb2) in mice and MRGPRX2 in humans has gained a lot of interest as an alternative MC activation pathway with high therapeutic potential. The aim of this study was to explore the relevance of such IgE-independent, Mrgprb2-mediated signaling in colonic MCs in the healthy and acutely inflamed mouse colon.

METHODS

Mrgprb2 expression and functionality was studied using a genetic labeling strategy combined with advanced microscopic imaging. Furthermore, Mrgprb2 knockout (Mrgprb2-/-) mice were used to determine the role of this pathway in a preclinical dextran sodium sulphate (DSS) colitis model.

RESULTS

We found that Mrgprb2 acts as a novel MC degranulation pathway in a large subset of connective tissue MCs in the mouse distal colon. Acute DSS colitis induced a pronounced increase of Mrgprb2-expressing MCs, which were found in close association with Substance P-positive nerve fibers. Loss of Mrgprb2-mediated signaling impaired DSS-induced neutrophil influx and significantly impacted on acute colitis progression.

CONCLUSIONS

Our findings uncover a novel, IgE-independent MC degranulation pathway in the mouse colon that plays a central role in acute colitis pathophysiology, mainly by safeguarding acute colitis progression and severity in mice. This pseudo allergic, Mrgprb2-induced signaling is part of a hitherto unconsidered colonic neuro-immune pathway and might have significant potential for the further development of effective therapeutic treatment strategies for gastrointestinal disorders, such as ulcerative colitis.

Microencapsulated essential oils alleviate diarrhea in weaned piglets by modulating the intestinal microbial barrier as well as not inducing antibiotic resistance: a field research

Microencapsulated essential oils (MEO)have been used as antibiotic alternatives that can be applied to alleviate diarrhea in weaning piglet. We examined a large group of weaned piglets and incorporated essential oil containing thymol (2%), carvacrol (5%) and cinnamaldehyde (3%) in the feed of weaned piglets on an intensive production farm. The piglets were divided into four groups; Control (no additions) and chlortetracycline (Chl), essential oil (EO) and microencapsulated essential oil (MEO) were fed ad libitum over a 28-day trial period. We found MEO significantly reduced the incidence of diarrhea in the piglets that was also accompanied by increased average daily weight gains from days 14-28 (p < 0.05). MEO enhanced the antioxidant capacity in the piglets and serum total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-px) levels were significantly increased (p < 0.05). MEO also significantly reduced expression of genes related to ileal inflammation (IL-6, TNF-α and TGF-β1) (p < 0.05) and significantly (p < 0.05) increased in sIgA antibody levels. MEO influenced the composition of the intestinal microbiome and reduced Bacteroidota (p < 0.05) and thus altered the Firmicutes/Bacteroidota ratio. However, none of the treatments produced significant changes in the most common tetracycline resistance genes (p > 0.05). Metagenomic analysis indicated that MEO impacted DNA expression, virulence factors, antioxidant activity and antimicrobial activity. Metabolomic analysis of the intestinal content also indicated that MEO impacted tyrosine metabolism and primary bile acid biosynthesis suggesting improved intestinal health and nutrient absorption. This study paves the way for further research into the development and optimization of MEO-based interventions aimed at improving piglet health and performance while also providing a reference for reducing reliance on antibiotics in animal agriculture.

Investigating the impact of antibiotic-induced dysbiosis on protection from Clostridium difficile colitis by mouse colonic innate lymphoid cells

Innate lymphoid cells (ILCs) play a critical role in maintaining intestinal health in homeostatic and diseased conditions. During Clostridium difficile infection (CDI), IL-33 activates ILC2 to protect from colonic damage and mortality. The function of IL-33 and ILC is tightly regulated by the intestinal microbiota. We set out to determine the impact of antibiotic-induced disruption of the microbiome on ILC function. Our goal was to understand antibiotic-induced changes in ILC function on susceptibility to C. difficile colitis in a mouse model. We utilized high-throughput single-cell RNAseq to investigate the phenotypic features of colonic ILC at baseline, after antibiotic administration with or without IL-33 treatment. We identified a heterogeneous landscape of colonic ILCs with gene signatures of inflammatory, anti-inflammatory, migratory, progenitor, plastic, and antigen-presenting ILCs. Antibiotic treatment decreased ILC2 while coordinately increasing ILC1 and ILC3 phenotypes. Notably, Ifng+, Ccl5+, and Il23r+ ILC increased after antibiotics. IL-33 treatment counteracted the antibiotic effect by downregulating ILC1 and ILC3 and activating ILC2. In addition, IL-33 treatment markedly induced the expression of type 2 genes, including Areg and Il5. Finally, we identified amphiregulin, produced by ILC2, as protective during C. difficile infection. Together, our data expand our understanding of how antibiotics induce susceptibility to C. difficile colitis through their impact on ILC subsets and function.IMPORTANCEClostridium difficile infection (CDI) accounts for around 500,000 symptomatic cases and over 20,000 deaths annually in the United States alone. A major risk factor of CDI is antibiotic-induced dysbiosis of the gut. Microbiota-regulated IL-33 and innate lymphoid cells (ILCs) are important in determining the outcomes of C. difficile infection. Understanding how antibiotic and IL-33 treatment alter the phenotype of colon ILCs is important to identify potential therapeutics. Here, we performed single-cell RNAseq of mouse colon ILCs collected at baseline, after antibiotic treatment, and after IL-33 treatment. We identified heterogeneous subpopulations of all three ILC subtypes in the mouse colon. Our analysis revealed several potential pathways of antibiotic-mediated increased susceptibility to intestinal infection. Our discovery that Areg is abundantly expressed by ILCs, and the protection of mice from CDI by amphiregulin treatment, suggests that the amphiregulin-epidermal growth factor receptor pathway is a potential therapeutic target for treating intestinal colitis.

Bidirectional regulation effect of rhubarb as laxative and astringent by metabolomics studies

ETHNOPHARMACOLOGICAL RELEVANCE

Rhubarb, a prominent traditional Chinese medicine, has been employed as a potent laxative for centuries and garnered particular popularity among the youth owing to its notable efficacy in weight management. Historical records indicated that rhubarb initially exhibited robust laxative properties, but extended and consistent usage may lead to an astringent response in the later stage of long-term use. In contrast, steamed pieces of rhubarb (SR), preparing through the process of steaming with wine, have demonstrated a gentle laxative effect with no reported adverse effects.

AIM OF THE STUDY

Our study was designed to explore the intricate mechanisms underlying laxative and astringent properties of rhubarb through metabolomics research.

MATERIALS AND METHODS

In this investigation, we employed a serum metabolomics approach utilizing the UPLC-Q-Extractive-Orbitrap-MS method to delve into the contrasting laxative and astringent effects of rhubarb, as well as to unravel the mechanisms of underpinning its bidirectional regulatory influence. To commence, we assessed alterations in Evacuation Index (EI) values, intestinal hormone levels, and colon histopathology in mice to gauge rhubarb's laxative and astringent effects. Subsequently, metabolomics methodology was employed for cluster analysis through Principal Component Analysis (PCA) and biomarker identification via Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA). Then, we delved into the distinctions in characteristic biomarkers, metabolic pathways, their association with pathological changes, and correlation heatmap for biomarkers between raw pieces of rhubarb (RR) and SR to gain insights into the potential mechanisms behind rhubarb's bidirectional regulatory effects.

RESULTS

Our findings revealed that RR exhibited a laxative effect in the early stage and transitioned to an astringent effect in the later stage, as indicated by the EI values. In contrast, SR consistently demonstrated a mild laxative effect. Biochemical indexes and histopathological assessments unveiled that RR triggered its astringent effect by inhibiting secretion of motilin (MTL), promoting secretion of vasoactive intestinal peptide (VIP) and epinephrine (EPI), and inducing onset of inflammation. Furthermore, serum metabolomics analysis identified 59 discriminative biomarkers modulated by RR and SR. Through comprehensive analysis, we elucidated the in vivo transformation relationships among multiple endogenous metabolites. Notably, our results underscored the down-regulation of certain phosphatidylcholines (PCs), amino acids, acylcarnitines, and up-regulation of lysophosphatidylcholines (LysoPCs) played pivotal roles in the onset of gut dysfunction, intestinal inflammation, gut barrier damage, and gastrointestinal motility disorder upon prolonging RR administration, ultimately contributing to its astringent effect. Additionally, our correlation analysis elucidated that anthraquinones, stilbenes, and phenylbutanones were the pharmacodynamic material basis responsible for inducing the astringent effect of RR.

CONCLUSION

This study provides valuable insights into the bidirectional regulatory effects of rhubarb and sheds light on its underlying mechanisms through a comprehensive metabolomics approach.

Inhibition of the CoREST Repressor Complex Promotes Wound Re-Epithelialization through the Regulation of Keratinocyte Migration

Wound healing is a complex process involving phases of hemostasis, inflammation, proliferation, and remodeling. The regenerative process in the skin requires coordination between many regulators, including signaling molecules, transcription factors, and the epigenetic machinery. In this study, we show that chromatin regulators HDAC1 and LSD1, key components of the CoREST repressor complex, are upregulated in the regenerating epidermis during wound repair. We also show that corin, a synthetic dual inhibitor of the CoREST complex and HDAC1/LSD1 activities, significantly accelerates wound closure through enhanced re-epithelialization in a mouse tail wound model. Acetylated H3K9 (methylation of histone H3 at lysine 9) expression, a histone modification targeted by HDAC1, is increased in keratinocytes after topical treatment with 100 nM and 1 μM of corin. In vitro experiments demonstrate that corin promotes migration and inhibits the proliferation of human keratinocytes. Furthermore, expression levels of genes promoting keratinocyte migration, such as AREG, CD24, EPHB2, ITGAX, PTGS, SCT1, SERPINB2, SERPINE1, SLPI, SNAI2, and TWIST, increased in keratinocytes treated with corin. These data demonstrate that dual inhibition of class I histone deacetylases and LSD1 by corin may serve as a new approach for promoting wound re-epithelialization and provide a platform for further applications of corin for the treatment of chronic wounds.

The NF-κB signaling system in the immunopathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD) is an idiopathic, chronic condition characterized by episodes of inflammation in the gastrointestinal tract. The nuclear factor κB (NF-κB) system describes a family of dimeric transcription factors. Canonical NF-κB signaling is stimulated by and enhances inflammation, whereas noncanonical NF-κB signaling contributes to immune organogenesis. Dysregulation of NF-κB factors drives various inflammatory pathologies, including IBD. Signals from many immune sensors activate NF-κB subunits in the intestine, which maintain an equilibrium between local microbiota and host responses. Genetic association studies of patients with IBD and preclinical mouse models confirm the importance of the NF-κB system in host defense in the gut. Other studies have investigated the roles of these factors in intestinal barrier function and in inflammatory gut pathologies associated with IBD. NF-κB signaling modulates innate and adaptive immune responses and the production of immunoregulatory proteins, anti-inflammatory cytokines, antimicrobial peptides, and other tolerogenic factors in the intestine. Furthermore, genetic studies have revealed critical cell type-specific roles for NF-κB proteins in intestinal immune homeostasis, inflammation, and restitution that contribute to the etiopathology of IBD-associated manifestations. Here, we summarize our knowledge of the roles of these NF-κB pathways, which are activated in different intestinal cell types by specific ligands, and their cross-talk, in fueling aberrant intestinal inflammation. We argue that an in-depth understanding of aberrant immune signaling mechanisms may hold the key to identifying predictive or prognostic biomarkers and developing better therapeutics against inflammatory gut pathologies.

β-adrenergic signaling triggers enteric glial reactivity and acute enteric gliosis during surgery

BACKGROUND

Enteric glia contribute to the pathophysiology of various intestinal immune-driven diseases, such as postoperative ileus (POI), a motility disorder and common complication after abdominal surgery. Enteric gliosis of the intestinal muscularis externa (ME) has been identified as part of POI development. However, the glia-restricted responses and activation mechanisms are poorly understood. The sympathetic nervous system becomes rapidly activated by abdominal surgery. It modulates intestinal immunity, innervates all intestinal layers, and directly interfaces with enteric glia. We hypothesized that sympathetic innervation controls enteric glia reactivity in response to surgical trauma.

METHODS

Sox10iCreERT2/Rpl22HA/+ mice were subjected to a mouse model of laparotomy or intestinal manipulation to induce POI. Histological, protein, and transcriptomic analyses were performed to analyze glia-specific responses. Interactions between the sympathetic nervous system and enteric glia were studied in mice chemically depleted of TH+ sympathetic neurons and glial-restricted Sox10iCreERT2/JellyOPfl/+/Rpl22HA/+ mice, allowing optogenetic stimulation of β-adrenergic downstream signaling and glial-specific transcriptome analyses. A laparotomy model was used to study the effect of sympathetic signaling on enteric glia in the absence of intestinal manipulation. Mechanistic studies included adrenergic receptor expression profiling in vivo and in vitro and adrenergic agonism treatments of primary enteric glial cell cultures to elucidate the role of sympathetic signaling in acute enteric gliosis and POI.

RESULTS

With ~ 4000 differentially expressed genes, the most substantial enteric glia response occurs early after intestinal manipulation. During POI, enteric glia switch into a reactive state and continuously shape their microenvironment by releasing inflammatory and migratory factors. Sympathetic denervation reduced the inflammatory response of enteric glia in the early postoperative phase. Optogenetic and pharmacological stimulation of β-adrenergic downstream signaling triggered enteric glial reactivity. Finally, distinct adrenergic agonists revealed β-1/2 adrenoceptors as the molecular targets of sympathetic-driven enteric glial reactivity.

CONCLUSIONS

Enteric glia act as early responders during post-traumatic intestinal injury and inflammation. Intact sympathetic innervation and active β-adrenergic receptor signaling in enteric glia is a trigger of the immediate glial postoperative inflammatory response. With immune-activating cues originating from the sympathetic nervous system as early as the initial surgical incision, adrenergic signaling in enteric glia presents a promising target for preventing POI development.

TGFB1 induces fetal reprogramming and enhances intestinal regeneration

The gut epithelium has a remarkable ability to recover from damage. We employed a combination of high-throughput sequencing approaches, mouse genetics, and murine and human organoids and identified a role for TGFB signaling during intestinal regeneration following injury. At 2 days following irradiation (IR)-induced damage of intestinal crypts, a surge in TGFB1 expression is mediated by monocyte/macrophage cells at the location of damage. The depletion of macrophages or genetic disruption of TGFB signaling significantly impaired the regenerative response. Intestinal regeneration is characterized by the induction of a fetal-like transcriptional signature during repair. In organoid culture, TGFB1 treatment was necessary and sufficient to induce the fetal-like/regenerative state. Mesenchymal cells were also responsive to TGFB1 and enhanced the regenerative response. Mechanistically, pro-regenerative factors, YAP/TEAD and SOX9, are activated in the epithelium exposed to TGFB1. Finally, pre-treatment with TGFB1 enhanced the ability of primary epithelial cultures to engraft into damaged murine colon, suggesting promise for cellular therapy.

Nuclear Factor-Kappa B Regulation of Osteoclastogenesis and Osteoblastogenesis

Maintenance of skeletal integrity requires the coordinated activity of multinucleated bone-resorbing osteoclasts and bone-forming osteoblasts. Osteoclasts form resorption lacunae on bone surfaces in response to cytokines by fusion of precursor cells. Osteoblasts are derived from mesenchymal precursors and lay down new bone in resorption lacunae during bone remodeling. Nuclear factorkappa B (NF-κB) signaling regulates osteoclast and osteoblast formation and is activated in osteoclast precursors in response to the essential osteoclastogenic cytokine, receptor activator of NF-κB ligand (RANKL), which can also control osteoblast formation through RANK-RANKL reverse signaling in osteoblast precursors. RANKL and some pro-inflammatory cytokines, including tumor necrosis factor (TNF), activate NF-κB signaling to positively regulate osteoclast formation and functions. However, these cytokines also limit osteoclast and osteoblast formation through NF-κB signaling molecules, including TNF receptor-associated factors (TRAFs). TRAF6 mediates RANKL-induced osteoclast formation through canonical NF-κB signaling. In contrast, TRAF3 limits RANKL- and TNF-induced osteoclast formation, and it restricts transforming growth factor β (TGFβ)-induced inhibition of osteoblast formation in young and adult mice. During aging, neutrophils expressing TGFβ and C-C chemokine receptor type 5 (CCR5) increase in bone marrow of mice in response to increased NF-κB-induced CC motif chemokine ligand 5 (CCL5) expression by mesenchymal progenitor cells and injection of these neutrophils into young mice decreased bone mass. TGFβ causes degradation of TRAF3, resulting in decreased glycogen synthase kinase-3β/β-catenin-mediated osteoblast formation and age-related osteoporosis in mice. The CCR5 inhibitor, maraviroc, prevented accumulation of TGFβ+/CCR5+ neutrophils in bone marrow and increased bone mass by inhibiting bone resorption and increasing bone formation in aged mice. This paper updates current understanding of how NF-κB signaling is involved in the positive and negative regulation of cytokine-mediated osteoclast and osteoblast formation and activation with a focus on the role of TRAF3 signaling, which can be targeted therapeutically to enhance bone mass.

Neutrophil diversity in inflammation and cancer

Neutrophils are the most abundant circulating leukocytes in humans and the first immune cells recruited at the site of inflammation. Classically perceived as short-lived effector cells with limited plasticity and diversity, neutrophils are now recognized as highly heterogenous immune cells, which can adapt to various environmental cues. In addition to playing a central role in the host defence, neutrophils are involved in pathological contexts such as inflammatory diseases and cancer. The prevalence of neutrophils in these conditions is usually associated with detrimental inflammatory responses and poor clinical outcomes. However, a beneficial role for neutrophils is emerging in several pathological contexts, including in cancer. Here we will review the current knowledge of neutrophil biology and heterogeneity in steady state and during inflammation, with a focus on the opposing roles of neutrophils in different pathological contexts.

Identification of a prototype human gut Bifidobacterium longum subsp. longum strain based on comparative and functional genomic approaches

Bifidobacteria are extensively exploited for the formulation of probiotic food supplements due to their claimed ability to exert health-beneficial effects upon their host. However, most commercialized probiotics are tested and selected for their safety features rather than for their effective abilities to interact with the host and/or other intestinal microbial players. In this study, we applied an ecological and phylogenomic-driven selection to identify novel B. longum subsp. longum strains with a presumed high fitness in the human gut. Such analyses allowed the identification of a prototype microorganism to investigate the genetic traits encompassed by the autochthonous bifidobacterial human gut communities. B. longum subsp. longum PRL2022 was selected due to its close genomic relationship with the calculated model representative of the adult human-gut associated B. longum subsp. longum taxon. The interactomic features of PRL2022 with the human host as well as with key representative intestinal microbial members were assayed using in vitro models, revealing how this bifidobacterial gut strain is able to establish extensive cross-talk with both the host and other microbial residents of the human intestine.

TGFβ1+CCR5+ neutrophil subset increases in bone marrow and causes age-related osteoporosis in male mice

TGFβ1 induces age-related bone loss by promoting degradation of TNF receptor-associated factor 3 (TRAF3), levels of which decrease in murine and human bone during aging. We report that a subset of neutrophils (TGFβ1+CCR5+) is the major source of TGFβ1 in murine bone. Their numbers are increased in bone marrow (BM) of aged wild-type mice and adult mice with TRAF3 conditionally deleted in mesenchymal progenitor cells (MPCs), associated with increased expression in BM of the chemokine, CCL5, suggesting that TRAF3 in MPCs limits TGFβ1+CCR5+ neutrophil numbers in BM of young mice. During aging, TGFβ1-induced TRAF3 degradation in MPCs promotes NF-κB-mediated expression of CCL5 by MPCs, associated with higher TGFβ1+CCR5+ neutrophil numbers in BM where they induce bone loss. TGFβ1+CCR5+ neutrophils decreased bone mass in male mice. The FDA-approved CCR5 antagonist, maraviroc, reduced TGFβ1+CCR5+ neutrophil numbers in BM and increased bone mass in aged mice. 15-mon-old mice with TGFβRII specifically deleted in MPCs had lower numbers of TGFβ1+CCR5+ neutrophils in BM and higher bone volume than wild-type littermates. We propose that pharmacologic reduction of TGFβ1+CCR5+ neutrophil numbers in BM could treat or prevent age-related osteoporosis.

GPR120 promotes neutrophil control of intestinal bacterial infection

G-protein coupled receptor 120 (GPR 120) has been implicated in anti-inflammatory functions. However, how GPR120 regulates the neutrophil function remains unknown. This study investigated the role of GPR120 in the regulation of neutrophil function against enteric bacteria. 16S rRNA sequencing was used for measuring the gut microbiota of wild-type (WT) mice and Gpr120-/- mice. Citrobacter rodentium infection and dextran sulfate sodium (DSS)-induced colitis models were performed in WT and Gpr120-/- mice. Mouse peritoneal-derived primary neutrophils were used to determine the neutrophil functions. Gpr120-/- mice showed altered microbiota composition. Gpr120-/- mice exhibited less capacity to clear intestinal Citrobacter rodentium and more severe intestinal inflammation upon infection or DSS insults. Depletion of neutrophils decreased the intestinal clearance of Citrobacter rodentium. GPR120 agonist, CpdA, enhanced WT neutrophil production of reactive oxygen species (ROS) and extracellular traps (NETs), and GPR120-deficient neutrophils demonstrated a lower level of ROS and NETs. CpdA-treated neutrophils showed an enhanced capacity to inhibit the growth of Citrobacter rodentium, which was abrogated by the inhibition of either NETs or ROS. CpdA promoted neutrophil inhibition of the growth of commensal bacteria Escherichia coli O9:H4 and pathobiont Escherichia coli O83:H1 isolated from a Crohn's disease patient. Mechanically, mTOR activation and glycolysis mediated GPR120 induction of ROS and NETs in neutrophils. Additionally, CpdA promoted the neutrophil production of IL-17 and IL-22, and treatment with a conditioned medium of GPR120-activated neutrophils increased intestinal epithelial cell barrier functions. Our study demonstrated the critical role of GPR120 in neutrophils in protection against enteric bacterial invasion.

Th17 Cell-Derived Amphiregulin Promotes Colitis-Associated Intestinal Fibrosis Through Activation of mTOR and MEK in Intestinal Myofibroblasts

BACKGROUND & AIMS

Intestinal fibrosis is a significant complication of Crohn's disease (CD). Gut microbiota reactive Th17 cells are crucial in the pathogenesis of CD; however, how Th17 cells induce intestinal fibrosis is still not completely understood.

METHODS

In this study, T-cell transfer model with wild-type (WT) and Areg-/- Th17 cells and dextran sulfate sodium (DSS)-induced chronic colitis model in WT and Areg-/- mice were used. CD4+ T-cell expression of AREG was determined by quantitative reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. The effect of AREG on proliferation/migration/collagen expression in human intestinal myofibroblasts was determined. AREG expression was assessed in healthy controls and patients with CD with or without intestinal fibrosis.

RESULTS

Although Th1 and Th17 cells induced intestinal inflammation at similar levels when transferred into Tcrβxδ-/- mice, Th17 cells induced more severe intestinal fibrosis. Th17 cells expressed higher levels of AREG than Th1 cells. Areg-/- mice developed less severe intestinal fibrosis compared with WT mice on DSS insults. Transfer of Areg-/- Th17 cells induced less severe fibrosis in Tcrβxδ-/- mice compared with WT Th17 cells. Interleukin (IL)6 and IL21 promoted AREG expression in Th17 cells by activating Stat3. Stat3 inhibitor suppressed Th17-induced intestinal fibrosis. AREG promoted human intestinal myofibroblast proliferation, motility, and collagen I expression, which was mediated by activating mammalian target of rapamycin and MEK. AREG expression was increased in intestinal CD4+ T cells in fibrotic sites compared with nonfibrotic sites from patients with CD.

CONCLUSIONS

These findings reveal that Th17-derived AREG promotes intestinal fibrotic responses in experimental colitis and human patients with CD. Thereby, AREG might serve as a potential therapeutic target for fibrosis in CD.

Dietary Polysaccharides as Modulators of the Gut Microbiota Ecosystem: An Update on Their Impact on Health

A polysaccharide is a macromolecule composed of more than ten monosaccharides with a wide distribution and high structural diversity and complexity in nature. Certain polysaccharides are immunomodulators and play key roles in the regulation of immune responses during the progression of some diseases. In addition to stimulating the growth of certain intestinal bacteria, polysaccharides may also promote health benefits by modulating the gut microbiota. In the last years, studies about the triad gut microbiota-polysaccharides-health have increased exponentially. In consequence, in the present review, we aim to summarize recent knowledge about the function of dietary polysaccharides on gut microbiota composition and how these effects affect host health.

Cellular and biological factors involved in healing wounds and burns and treatment options in tissue engineering

Severe traumatic wounds and burns have a high chance of mortality and can leave survivors with many functional disabilities and cosmetic problems, including scars. The healing process requires a harmonious interplay of various cells and growth factors. Different structures of the skin house numerous cells, matrix components and growth factors. Any disturbance in the balance between these components can impair the healing process. The function of cells and growth factors can be manipulated and facilitated to aid tissue repair. In the current review, the authors focus on the importance of the skin microenvironment, the pathophysiology of various types of burns, mechanisms and factors involved in skin repair and wound healing and regeneration of the skin using tissue engineering approaches.

Neutrophils in chronic inflammatory diseases

Chronic inflammation is a component of many disease conditions that affect a large group of individuals worldwide. Chronic inflammation is characterized by persistent, low-grade inflammation and is increased in the aging population. Neutrophils are normally the first responders to acute inflammation and contribute to the resolution of inflammation. However, in chronic inflammation, the role of neutrophils is less well understood and has been described as either beneficial or detrimental, causing tissue damage and enhancing the immune response. Emerging evidence suggests that neutrophils are important players in several chronic diseases, such as atherosclerosis, diabetes mellitus, nonalcoholic fatty liver disease and autoimmune disorders. This review will highlight the interaction of neutrophils with other cells in the context of chronic inflammation, the contribution of neutrophils to selected chronic inflammatory diseases, and possible future therapeutic strategies.

Microbiota metabolite butyrate constrains neutrophil functions and ameliorates mucosal inflammation in inflammatory bowel disease

Host-microbial cross-talk plays a crucial role in maintenance of gut homeostasis. However, how microbiota-derived metabolites, e.g., butyrate, regulate functions of neutrophils in the pathogenesis of inflammatory bowel disease (IBD) remains elusive. We sought to investigate the effects of butyrate on IBD neutrophils and elucidate the therapeutic potential in regulating mucosal inflammation. Peripheral neutrophils were isolated from IBD patients and healthy donors, and profiles of proinflammatory cytokines and chemokines were determined by qRT-PCR and ELISA, respectively. The migration and release of neutrophil extracellular traps (NETs) were studied by a Transwell model and immunofluorescence, respectively. The in vivo role of butyrate in regulating IBD neutrophils was evaluated in a DSS-induced colitis model in mice. We found that butyrate significantly inhibited IBD neutrophils to produce proinflammatory cytokines, chemokines, and calprotectins. Blockade of GPCR signaling with pertussis toxin (PTX) did not interfere the effects whereas pan-histone deacetylase (HDAC) inhibitor, trichostatin A (TSA) effectively mimicked the role of butyrate. Furthermore, in vitro studies confirmed that butyrate suppressed neutrophil migration and formation of NETs from both CD and UC patients. RNA sequencing analysis revealed that the immunomodulatory effects of butyrate on IBD neutrophils were involved in leukocyte activation, regulation of innate immune response and response to oxidative stress. Consistently, oral administration of butyrate markedly ameliorated mucosal inflammation in DSS-induced murine colitis through inhibition of neutrophil-associated immune responses such as proinflammatory mediators and NET formation. Our data thus reveal that butyrate constrains neutrophil functions and may serve as a novel therapeutic potential in the treatment of IBD.

Probiotics in Intestinal Mucosal Healing: A New Therapy or an Old Friend?

Inflammatory bowel disease (IBD), Crohn’s disease, and ulcerative colitis are characterized by chronic and relapsing inflammation, while their pathogenesis remains mostly unelucidated. Gut commensal microbiota seem to be one of the various implicated factors, as several studies have shown a significant decrease in the microbiome diversity of patients with IBD. Although the question of whether microbiota dysbiosis is a causal factor or the result of chronic inflammation remains unanswered, one fact is clear; active inflammation in IBD results in the disruption of the mucus layer structure, barrier function, and also, colonization sites. Recently, many studies on IBD have been focusing on the interplay between mucosal and luminal microbiota, underlining their possible beneficial effect on mucosal healing. Regarding this notion, it has now been shown that specific probiotic strains, when administrated, lead to significantly decreased inflammation, amelioration of colitis, and improved mucosal healing. Probiotics are live microorganisms exerting beneficial effects on the host’s health when administered in adequate quantity. The aim of this review was to present and discuss the current findings on the role of gut microbiota and their metabolites in intestinal wound healing and the effects of probiotics on intestinal mucosal wound closure.

Targeting DCs for Tolerance Induction: Don't Lose Sight of the Neutrophils

Chronic inflammatory disorders (CID), such as autoimmune diseases, are characterized by overactivation of the immune system and loss of immune tolerance. T helper 17 (Th17) cells are strongly associated with the pathogenesis of multiple CID, including psoriasis, rheumatoid arthritis, and inflammatory bowel disease. In line with the increasingly recognized contribution of innate immune cells to the modulation of dendritic cell (DC) function and DC-driven adaptive immune responses, we recently showed that neutrophils are required for DC-driven Th17 cell differentiation from human naive T cells. Consequently, recruitment of neutrophils to inflamed tissues and lymph nodes likely creates a highly inflammatory loop through the induction of Th17 cells that should be intercepted to attenuate disease progression. Tolerogenic therapy via DCs, the central orchestrators of the adaptive immune response, is a promising strategy for the treatment of CID. Tolerogenic DCs could restore immune tolerance by driving the development of regulatory T cells (Tregs) in the periphery. In this review, we discuss the effects of the tolerogenic adjuvants vitamin D3 (VD3), corticosteroids (CS), and retinoic acid (RA) on both DCs and neutrophils and their potential interplay. We briefly summarize how neutrophils shape DC-driven T-cell development in general. We propose that, for optimization of tolerogenic DC therapy for the treatment of CID, both DCs for tolerance induction and the neutrophil inflammatory loop should be targeted while preserving the potential Treg-enhancing effects of neutrophils.

The TGF-β Pathway: A Pharmacological Target in Hepatocellular Carcinoma?

Transforming Growth Factor-beta (TGF-β) superfamily members are essential for tissue homeostasis and consequently, dysregulation of their signaling pathways contributes to the development of human diseases. In the liver, TGF-β signaling participates in all the stages of disease progression from initial liver injury to hepatocellular carcinoma (HCC). During liver carcinogenesis, TGF-β plays a dual role on the malignant cell, behaving as a suppressor factor at early stages, but contributing to later tumor progression once cells escape from its cytostatic effects. Moreover, TGF-β can modulate the response of the cells forming the tumor microenvironment that may also contribute to HCC progression, and drive immune evasion of cancer cells. Thus, targeting the TGF-β pathway may constitute an effective therapeutic option for HCC treatment. However, it is crucial to identify biomarkers that allow to predict the response of the tumors and appropriately select the patients that could benefit from TGF-β inhibitory therapies. Here we review the functions of TGF-β on HCC malignant and tumor microenvironment cells, and the current strategies targeting TGF-β signaling for cancer therapy. We also summarize the clinical impact of TGF-β inhibitors in HCC patients and provide a perspective on its future use alone or in combinatorial strategies for HCC treatment.

An intercrypt subpopulation of goblet cells is essential for colonic mucus barrier function

The intestinal mucus layer, an important element of epithelial protection, is produced by goblet cells. Intestinal goblet cells are assumed to be a homogeneous cell type. In this study, however, we delineated their specific gene and protein expression profiles and identified several distinct goblet cell populations that form two differentiation trajectories. One distinct subtype, the intercrypt goblet cells (icGCs), located at the colonic luminal surface, produced mucus with properties that differed from the mucus secreted by crypt-residing goblet cells. Mice with defective icGCs had increased sensitivity to chemically induced colitis and manifested spontaneous colitis with age. Furthermore, alterations in mucus and reduced numbers of icGCs were observed in patients with both active and remissive ulcerative colitis, which highlights the importance of icGCs in maintaining functional protection of the epithelium.

Blood Platelets as an Important but Underrated Circulating Source of TGFβ

When treating diseases related primarily to tissue remodeling and fibrosis, it is desirable to regulate TGFβ concentration and modulate its biological effects. The highest cellular concentrations of TGFβ are found in platelets, with about 40% of all TGFβ found in peripheral blood plasma being secreted by them. Therefore, an understanding of the mechanisms of TGFβ secretion from platelets may be of key importance for medicine. Unfortunately, despite the finding that platelets are an important regulator of TGFβ levels, little research has been carried out into the development of platelet-directed therapies that might modulate the TGFβ-dependent processes. Nevertheless, there are some very encouraging reports suggesting that platelet TGFβ may be specifically involved in cardiovascular diseases, liver fibrosis, tumour metastasis, cerebral malaria and in the regulation of inflammatory cell functions. The purpose of this review is to briefly summarize these few, extremely encouraging reports to indicate the state of current knowledge in this topic. It also attempts to better characterize the influence of TGFβ on platelet activation and reactivity, and its shaping of the roles of blood platelets in haemostasis and thrombosis.

Paneth Cell-Derived Lysozyme Defines the Composition of Mucolytic Microbiota and the Inflammatory Tone of the Intestine

Paneth cells are the primary source of C-type lysozyme, a β-1,4-N-acetylmuramoylhydrolase that enzymatically processes bacterial cell walls. Paneth cells are normally present in human cecum and ascending colon, but are rarely found in descending colon and rectum; Paneth cell metaplasia in this region and aberrant lysozyme production are hallmarks of inflammatory bowel disease (IBD) pathology. Here, we examined the impact of aberrant lysozyme production in colonic inflammation. Targeted disruption of Paneth cell lysozyme (Lyz1) protected mice from experimental colitis. Lyz1-deficiency diminished intestinal immune responses to bacterial molecular patterns and resulted in the expansion of lysozyme-sensitive mucolytic bacteria, including Ruminococcus gnavus, a Crohn's disease-associated pathobiont. Ectopic lysozyme production in colonic epithelium suppressed lysozyme-sensitive bacteria and exacerbated colitis. Transfer of R. gnavus into Lyz1^-/- hosts elicited a type 2 immune response, causing epithelial reprograming and enhanced anti-colitogenic capacity. In contrast, in lysozyme-intact hosts, processed R. gnavus drove pro-inflammatory responses. Thus, Paneth cell lysozyme balances intestinal anti- and pro-inflammatory responses, with implications for IBD.

Intestinal Mucosal Wound Healing and Barrier Integrity in IBD-Crosstalk and Trafficking of Cellular Players

The intestinal epithelial barrier is carrying out two major functions: restricting the entry of potentially harmful substances while on the other hand allowing the selective passage of nutrients. Thus, an intact epithelial barrier is vital to preserve the integrity of the host and to prevent development of disease. Vice versa, an impaired intestinal epithelial barrier function is a hallmark in the development and perpetuation of inflammatory bowel disease (IBD). Besides a multitude of genetic, molecular and cellular alterations predisposing for or driving barrier dysintegrity in IBD, the appearance of intestinal mucosal wounds is a characteristic event of intestinal inflammation apparently inducing breakdown of the intestinal epithelial barrier. Upon injury, the intestinal mucosa undergoes a wound healing process counteracting this breakdown, which is controlled by complex mechanisms such as epithelial restitution, proliferation and differentiation, but also immune cells like macrophages, granulocytes and lymphocytes. Consequently, the repair of mucosal wounds is dependent on a series of events including coordinated trafficking of immune cells to dedicated sites and complex interactions among the cellular players and other mediators involved. Therefore, a better understanding of the crosstalk between epithelial and immune cells as well as cell trafficking during intestinal wound repair is necessary for the development of improved future therapies. In this review, we summarize current concepts on intestinal mucosal wound healing introducing the main cellular mediators and their interplay as well as their trafficking characteristics, before finally discussing the clinical relevance and translational approaches to therapeutically target this process in a clinical setting.

Neutrophils-derived Spink7 as one safeguard against experimental murine colitis

The uncontrolled abnormal intestinal immune responses play important role in eliciting inflammatory bowel disease (IBD), yet the molecular events regulating intestinal inflammation during IBD remain poorly understood. Here, we describe an endogenous, homeostatic pattern that controls inflammatory responses in experimental murine colitis. We show that Spink7 (serine peptidase inhibitor, kazal type 7), the ortholog of human SPINK7, is significantly upregulated in dextran sodium sulfate (DSS)-induced murine colitis model. Spink7-deficient mice showed highly susceptible to experimental colitis characterized by enhanced weight loss, shorter colon length, higher disease activity index and increased colonic tissue destruction. Bone marrow reconstitution experiments demonstrated that expression of Spink7 in the immune compartment makes main contribution to its protective role in colitis. What's more, neutrophils are the primary sources of Spink7 in experimental murine colitis. Loss of Spink7 leads to augmented productions of multiple chemokines and cytokines in colitis. In summary, this study identifies neutrophils-derived endogenous Spink7-mediated control of chemokines/cytokines production as a molecular mechanism contributing to inflammation resolution during colitis.

A critical role of AREG for bleomycin-induced skin fibrosis

We report our discovery of an important player in the development of skin fibrosis, a hallmark of scleroderma. Scleroderma is a fibrotic disease, affecting 70,000 to 150,000 Americans. Fibrosis is a pathological wound healing process that produces an excessive extracellular matrix to interfere with normal organ function. Fibrosis contributes to nearly half of human mortality. Scleroderma has heterogeneous phenotypes, unpredictable outcomes, no validated biomarkers, and no effective treatment. Thus, strategies to slow down scleroderma progression represent an urgent medical need. While a pathological wound healing process like fibrosis leaves scars and weakens organ function, oral mucosa wound healing is a scarless process. After re-analyses of gene expression datasets from oral mucosa wound healing and skin fibrosis, we discovered that several pathways constitutively activated in skin fibrosis are transiently induced during oral mucosa wound healing process, particularly the amphiregulin (Areg) gene. Areg expression is upregulated ~ 10 folds 24hrs after oral mucosa wound but reduced to the basal level 3 days later. During bleomycin-induced skin fibrosis, a commonly used mouse model for skin fibrosis, Areg is up-regulated throughout the fibrogenesis and is associated with elevated cell proliferation in the dermis. To demonstrate the role of Areg for skin fibrosis, we used mice with Areg knockout, and found that Areg deficiency essentially prevents bleomycin-induced skin fibrosis. We further determined that bleomycin-induced cell proliferation in the dermis was not observed in the Areg null mice. Furthermore, we found that inhibiting MEK, a downstream signaling effector of Areg, by selumetinib also effectively blocked bleomycin-based skin fibrosis model. Based on these results, we concluded that the Areg-EGFR-MEK signaling axis is critical for skin fibrosis development. Blocking this signaling axis may be effective in treating scleroderma.

Blood and Salivary Amphiregulin Levels as Biomarkers for Asthma

Background: Amphiregulin (AREG) expression in asthmatic airways and sputum was shown to increase and correlate with asthma. However, no studies were carried out to evaluate the AREG level in blood and saliva of asthmatic patients. Objective: To measure circulating AREG mRNA and protein concentrations in blood, saliva, and bronchial biopsies samples from asthmatic patients. Methods: Plasma and Saliva AREG protein concentrations were measured using ELISA while PBMCs, and Saliva mRNA expression was measured by RT qPCR in non-severe, and severe asthmatic patients compared to healthy controls. Primary asthmatic bronchial epithelial cells and fibroblasts were assessed for AREG mRNA expression and released soluble AREG in their conditioned media. Tissue expression of AREG was evaluated using immunohistochemistry of bronchial biopsies from asthmatic patients and healthy controls. Publicly available transcriptomic databases were explored for the global transcriptomic profile of bronchial epithelium, and PBMCs were explored for AREG expression in asthmatic vs. healthy controls. Results: Asthmatic patients had higher AREG protein levels in blood and saliva compared to control subjects. Higher mRNA expression in saliva and primary bronchial epithelial cells plus higher AREG immunoreactivity in bronchial biopsies were also observed. Both blood and saliva AREG levels showed positive correlations with allergic rhinitis status, atopy status, eczema status, plasma periostin, neutrophilia, Montelukast sodium use, ACT score, FEV1, and FEV1/FVC. In silico analysis showed that severe asthmatic bronchial epithelium with high AREG gene expression is associated with higher neutrophils infiltration. Conclusion: AREG levels measured in a minimally invasive blood sample and a non-invasive saliva sample are higher in non-allergic severe asthma.

CLINICAL IMPLICATIONS

This is the first report to show the higher level of AREG levels in blood and saliva of non-allergic severe asthma.

Red light-emitting diode treatment improves tissue recovery in DSS-induced colitis in mice

Inflammatory bowel diseases are debilitating illnesses characterized by severe inflammation of the gastrointestinal tract. Treatments currently available are expensive and ineffective. We here investigated the role of red-light emitting diode (LED) on dextran sodium sulfate (DSS)-induced colitis. DSS was added to the drinking water of male mice at days 0, 2, 4 and withdrawn at day 6. LED irradiation was performed daily for 90s from day 6 to 9 on the right and left sides of the ventral surface and beside the external anal region. LED treatment decreased the amount of crypt dysplasia/edema, inflammatory infiltrates and ulcers, attenuated apoptosis and increased proliferation of crypt cells. Also, LED treatment induced expression of annexin A1 in the damaged epithelium, preserved the organization of claudin-1 and skewed cytokine profiling towards a more anti-inflammatory status. Thus, LED treatment promotes structural protection and modulates the inflammatory response, constituting a potential non-invasive and low-cost combined therapy to help patients achieve disease remission.

The immunologic changes during different phases of intestinal anastomotic healing

Intestinal anatomosis is a complex and multicellular process that involving three overlapped phases: exudative phase, proliferative phase, and reparative phase. Undisturbed anastomotic healings are crucial for the recovery of patients after operations but unsuccessful healings are linked with a considerable mortality. This time, we concentrate on the immunologic changes during different phases of intestinal anastomotic healing and select several major immune cells and cytokines of each phase to get a better understanding of these immunologic changes in different phases, which will be significant for more precise therapy strategies in anastomoses.

The Role of Immune Cells and Cytokines in Intestinal Wound Healing

Intestinal wound healing is a complicated process that not only involves epithelial cells but also immune cells. In this brief review, we will focus on discussing the contribution and regulation of four major immune cell types (neutrophils, macrophages, regulatory T cells, and innate lymphoid cells) and four cytokines (interleukin-10, tumor necrosis factor alpha, interleukin-6, and interleukin-22) to the wound repair process in the gut. Better understanding of these immune factors will be important for developing novel targeted therapy.

Stress responses, M2 macrophages, and a distinct microbial signature in fatal intestinal acute graft-versus-host disease

Steroid-refractory intestinal acute graft-versus-host disease (aGVHD) is a frequently fatal condition with little known about mechanisms driving failed steroid responses in gut mucosa. To uncover novel molecular insights in steroid-refractory aGVHD, we compared gene expression profiles of rectosigmoid biopsies from patients at diagnosis of clinical stage 3-4 lower intestinal aGVHD (N=22), to repeat biopsies when the patients became steroid refractory (N=22), and normal controls (N=10). We also performed single gene analyses of factors associated with tolerance (programmed death ligand-1 [PDL1], indoleamine 2,3 dioxygenase [IDO1], and T cell immunoreceptor with Ig and ITIM domains [TIGIT]) and found that significantly higher expression levels of these aGVHD inhibitory genes (PDL1, IDO1, TIGIT) at aGVHD onset became decreased in the steroid-refractory state. We examined genes triggered by microbial ligands to stimulate gut repair, amphiregulin (AREG) and the aryl hydrocarbon receptor (AhR), and found that both AREG and AhR gene expression levels were increased at aGVHD onset and remained elevated in steroid-refractory aGVHD. We also identified higher expression levels of metallothioneines, metal-binding enzymes induced in stress responses, and M2 macrophage genes in steroid-refractory aGVHD. We observed no differences in T-cell subsets between onset and steroid-refractory aGVHD. Patients with a rapidly fatal course showed greater DNA damage and a distinct microbial signature at aGVHD onset, whereas patients with more prolonged survival exhibited a gene expression profile consistent with activation of Smoothened. Our results extend the paradigm beyond T cell-centric therapies for steroid-refractory GI aGVHD and highlight new mechanisms for therapeutic exploration.

Innate immune cell-epithelial crosstalk during wound repair

Skin and intestinal epithelial barriers play a pivotal role in protecting underlying tissues from harsh external environments. The protective role of these epithelia is, in part, dependent on a remarkable capacity to restore barrier function and tissue homeostasis after injury. In response to damage, epithelial wounds repair by a series of events that integrate epithelial responses with those of resident and infiltrating immune cells including neutrophils and monocytes/macrophages. Compromise of this complex interplay predisposes to development of chronic nonhealing wounds, contributing to morbidity and mortality of many diseases. Improved understanding of crosstalk between epithelial and immune cells during wound repair is necessary for development of better pro-resolving strategies to treat debilitating complications of disorders ranging from inflammatory bowel disease to diabetes. In this Review we focus on epithelial and innate immune cell interactions that mediate wound healing and restoration of tissue homeostasis in the skin and intestine.

Gamma-Tocotrienol Protects the Intestine from Radiation Potentially by Accelerating Mesenchymal Immune Cell Recovery

Natural antioxidant gamma-tocotrienol (GT3), a vitamin E family member, provides intestinal radiation protection. We seek to understand whether this protection is mediated via mucosal epithelial stem cells or sub-mucosal mesenchymal immune cells. Vehicle- or GT3-treated male CD2F1 mice were exposed to total body irradiation (TBI). Cell death was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Villus height and crypt depth were measured with computer-assisted software in tissue sections. Functional activity was determined with an intestinal permeability assay. Immune cell recovery was measured with immunohistochemistry and Western blot, and the regeneration of intestinal crypts was assessed with ex vivo organoid culture. A single dose of GT3 (200 mg/kg body weight (bwt)) administered 24 h before TBI suppressed cell death, prevented a decrease in villus height, increased crypt depth, attenuated intestinal permeability, and upregulated occludin level in the intestine compared to the vehicle treated group. GT3 accelerated mesenchymal immune cell recovery after irradiation, but it did not promote ex vivo organoid formation and failed to enhance the expression of stem cell markers. Finally, GT3 significantly upregulated protein kinase B or AKT phosphorylation after TBI. Pretreatment with GT3 attenuates TBI-induced structural and functional damage to the intestine, potentially by facilitating intestinal immune cell recovery. Thus, GT3 could be used as an intestinal radioprotector.