Neutrophil interactions with epithelial-expressed ICAM-1 enhances intestinal mucosal wound healing

Eimeria falciformis extracellular vesicles differentially express host cell lncRNAs

Long noncoding RNAs (lncRNAs) are regulatory transcripts during protozoan infections in the host intestinal epithelial cells (IECs). Apicomplexan Eimeria falciformis sporozoite extracellular vesicles (EVs) contain virulence factors that modulate host IECs pro-inflammatory genes and immune responses. In this study, E. falciformis sporozoites were made to interact with inactivated host cells, and the parasite EVs were separated from total secretome by ultracentrifugation and purified on density gradient medium. Dose-dependent bio-activity of E. falciformis EVs was investigated by RNA sequencing, functional annotation and quantitative PCR. It was found that E. falciformis EVs induced mRNA, circRNA, and lncRNA expressions in mouse IECs. Of 38, 217 lncRNAs assembled, 157 and 152 were upwardly and downwardly expressed respectively. Differentially expressed lncRNAs were associated with cytokines, pyroptosis, and immune signaling pathways including FoxO, NF-κB, MAPK, and TGF-β. In essence, E. falciformis EVs altered host cell RNA expressions during the interaction with host IECs. Also, differentially expressed lncRNAs are potential diagnostic transcripts during Eimeria infections.

Phenotypic and Functional Diversity of Neutrophils in Gut Inflammation and Cancer

Neutrophils [polymorphonuclear leukocytes (PMNs)] execute important effector functions protecting the host against invading pathogens. However, their activity in tissue can exacerbate inflammation and inflammation-associated tissue injury and tumorigenesis. Until recently, PMNs were considered to be short-lived, terminally differentiated phagocytes. However, this view is rapidly changing with the emerging evidence of increased PMN lifespan in tissues, PMN plasticity, and phenotypic heterogeneity. Specialized PMN subsets have been identified in inflammation and in developing tumors, consistent with both beneficial and detrimental functions of PMNs in these conditions. Because PMN and tumor-associated neutrophil activity and the resulting beneficial/detrimental impacts primarily occur after homing to inflamed tissue/tumors, studying the underlying mechanisms of PMN/tumor-associated neutrophil trafficking is of high interest and clinical relevance. This review summarizes some of the key findings from over a decade of work from my laboratory and others on the regulation of PMN recruitment and identification of phenotypically and functionally diverse PMN subtypes as they pertain to gut inflammation and colon cancer.

Blockade of Syk modulates neutrophil immune-responses via the mTOR/RUBCNL-dependent autophagy pathway to alleviate intestinal inflammation in ulcerative colitis

Background

Ulcerative colitis (UC) is a progressive chronic inflammatory disorder. Neutrophils play a critical role in regulating intestinal mucosal homeostasis in UC. Spleen tyrosine kinase (Syk) is involved in several inflammatory diseases. Here, we evaluated the effects and underlying mechanisms of Syk on neutrophil immune-responses in UC.

Methods

Syk expression in the colonic tissues of patients with UC was determined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blotting, and immunohistochemistry. Colonic biopsies from patients with UC were obtained for single-cell RNA-sequencing. Neutrophils isolated from peripheral blood were pre-treated with R788 (a Syk inhibitor) and gene differences were determined using RNA sequencing. Neutrophil functions were analyzed using qRT-PCR, flow cytometry, and Transwell assay. R788 was administered daily to mice with dextran sulfate sodium (DSS)-induced colitis to verify the effects of Syk on intestinal inflammation.

Results

Syk expression was increased in inflamed mucosa and neutrophils of patients with UC and positively correlated with disease activity. Pharmacological inhibition of Syk in neutrophils decreased the production of pro-inflammatory cytokines, chemokines, neutrophil extracellular traps, reactive oxygen species, and myeloperoxidase. Apoptosis and migration of neutrophils were suppressed by Syk blockade. Syk blockade ameliorated mucosal inflammation in DSS-induced murine colitis by inhibiting neutrophil-associated immune responses. Mechanistically, Syk regulated neutrophil immune-responses via the mammalian target of rapamycin kinase/rubicon-like autophagy enhancer-dependent autophagy pathway.

Conclusions

Our findings indicate that Syk facilitates specific neutrophil functional responses to mucosal inflammation in UC, and its inhibition ameliorates mucosal inflammation in DSS-induced murine colitis, suggesting its potential as a novel therapeutic target for UC treatment.

Silver Nanoparticles and Graphene Oxide Complex as an Anti-Inflammatory Biocompatible Liquid Nano-Dressing for Skin Infected with Staphylococcus aureus

Background

Bacterial skin infections, including Staphylococcus aureus, are a powerful and still not fully resolved problem. The aim of this research was to determine the possibility of using a complex of graphene oxide (GO) encrusted with silver nanoparticles as an effective antibacterial agent against S. aureus and to assess its pro-inflammatory properties.

Methods

The tests were carried out in vitro on EpiDerm™ Skin, an artificial skin model (MatTek in vitro Life Science Laboratories, Slovak Republic), and the fibroblast cell line (HFF-2 from ATCC, USA). Both models were infected with S. aureus bacteria (ATCC 25923) and then treated with antibiotics or our experimental factors: silver nanoparticles (AgNPs, Nano-koloid, Poland), graphene oxide (GO, NanoPoz, Poland), and complex AgNP-GO (hydrocolloid created by self-assembly).

Results

The antibacterial effectiveness of the AgNP-GO complex was equivalent to that of the antibiotic. In addition, an increase in the level of pro-inflammatory cytokines was observed under the influence of antibiotic administration, in contrast to the effect of AgNP-GO, which showed very limited pro-inflammatory activity.

Conclusion

Hydrocolloid of the AgNP-GO complex, administered in the form of a liquid dressing, may act as an antibacterial agent and also reduce inflammation induced by S. aureus infection.

Tocotrienols Provide Radioprotection to Multiple Organ Systems through Complementary Mechanisms of Antioxidant and Signaling Effects

Tocotrienols have powerful radioprotective properties in multiple organ systems and are promising candidates for development as clinically effective radiation countermeasures. To facilitate their development as clinical radiation countermeasures, it is crucial to understand the mechanisms behind their powerful multi-organ radioprotective properties. In this context, their antioxidant effects are recognized for directly preventing oxidative damage to cellular biomolecules from ionizing radiation. However, there is a growing body of evidence indicating that the radioprotective mechanism of action for tocotrienols extends beyond their antioxidant properties. This raises a new pharmacological paradigm that tocotrienols are uniquely efficacious radioprotectors due to a synergistic combination of antioxidant and other signaling effects. In this review, we have covered the wide range of multi-organ radioprotective effects observed for tocotrienols and the mechanisms underlying it. These radioprotective effects for tocotrienols can be characterized as (1) direct cytoprotective effects, characteristic of the classic antioxidant properties, and (2) other effects that modulate a wide array of critical signaling factors involved in radiation injury.

NADPH Oxidase 4-mediated Alveolar Macrophage Recruitment to Lung Attenuates Neutrophilic Inflammation in Staphylococcus aureus Infection

When the lungs are infected with bacteria, alveolar macrophages (AMs) are recruited to the site and play a crucial role in protecting the host by reducing excessive lung inflammation. However, the regulatory mechanisms that trigger the recruitment of AMs to lung alveoli during an infection are still not fully understood. In this study, we identified a critical role for NADPH oxidase 4 (NOX4) in the recruitment of AMs during Staphylococcus aureus lung infection. We found that NOX4 knockout (KO) mice showed decreased recruitment of AMs and increased lung neutrophils and injury in response to S. aureus infection compared to wild-type (WT) mice. Interestingly, the burden of S. aureus in the lungs was not different between NOX4 KO and WT mice. Furthermore, we observed that depletion of AMs in WT mice during S. aureus infection increased the number of neutrophils and lung injury to a similar level as that observed in NOX4 KO mice. Additionally, we found that expression of intercellular adhesion molecule-1 (ICAM1) in NOX4 KO mice-derived lung endothelial cells was lower than that in WT mice-derived endothelial cells. Therefore, we conclude that NOX4 plays a crucial role in inducing the recruitment of AMs by controlling ICAM1 expression in lung endothelial cells, which is responsible for resolving lung inflammation during acute S. aureus infection.

Prolonged inflammatory resolution in allergic asthma relates to dysfunctional interactions between neutrophils and airway epithelium

BACKGROUND

Allergic asthma is a heterogeneous disorder involving chronic airway inflammation, reversible airflow limitation, and tissue remodeling, causing chronic airflow limitation. Most of the asthma research has been focused on elucidating the proinflammatory pathways underlying disease pathogenesis. Paradoxically, the necessity of appropriate termination and resolution of inflammation has not been recognized until recently. The latter has led to the concept of chronic inflammation developing as a result of lack of specific "stop" signals for the inflammatory process.

OBJECTIVE

To investigate the interaction between neutrophils and airway epithelium during inflammatory resolution in patients with allergic asthma.

METHODS

An in vitro scratch assay with cultured epithelial cells, based on live-imaging microscopy, was used to evaluate regeneration and the influence of neutrophils on resolution. Epithelial cells and autologous neutrophils were derived from healthy donors and patients with allergic asthma. Supernatants and cells were collected for enzyme-linked immunosorbent assay and transcriptional analyses at the end of the experiment.

RESULTS

Healthy epithelial cells regenerated faster than epithelial cells from patients with allergic asthma. Autologous neutrophils improved the regeneration of healthy epithelial cells but not asthmatic epithelial cells. Interleukin (IL)-8 and β-catenin were down-regulated in healthy epithelial cells after resolution, but not in allergic asthmatic epithelial cells.

CONCLUSION

The prolonged duration of inflammation in the respiratory tract in patients with allergic asthma could be due to the impaired healing pattern of epithelial cells and their compromised interactions with the neutrophils.

Fetal Muse-based therapy prevents lethal radio-induced gastrointestinal syndrome by intestinal regeneration

BACKGROUND

Human multilineage-differentiating stress enduring (Muse) cells are nontumorigenic endogenous pluripotent-like stem cells that can be easily obtained from various adult or fetal tissues. Regenerative effects of Muse cells have been shown in some disease models. Muse cells specifically home in damaged tissues where they exert pleiotropic effects. Exposition of the small intestine to high doses of irradiation (IR) delivered after radiotherapy or nuclear accident results in a lethal gastrointestinal syndrome (GIS) characterized by acute loss of intestinal stem cells, impaired epithelial regeneration and subsequent loss of the mucosal barrier resulting in sepsis and death. To date, there is no effective medical treatment for GIS. Here, we investigate whether Muse cells can prevent lethal GIS and study how they act on intestinal stem cell microenvironment to promote intestinal regeneration.

METHODS

Human Muse cells from Wharton's jelly matrix of umbilical cord (WJ-Muse) were sorted by flow cytometry using the SSEA-3 marker, characterized and compared to bone-marrow derived Muse cells (BM-Muse). Under gas anesthesia, GIS mice were treated or not through an intravenous retro-orbital injection of 50,000 WJ-Muse, freshly isolated or cryopreserved, shortly after an 18 Gy-abdominal IR. No immunosuppressant was delivered to the mice. Mice were euthanized either 24 h post-IR to assess early small intestine tissue response, or 7 days post-IR to assess any regenerative response. Mouse survival, histological stainings, apoptosis and cell proliferation were studied and measurement of cytokines, recruitment of immune cells and barrier functional assay were performed.

RESULTS

Injection of WJ-Muse shortly after abdominal IR highly improved mouse survival as a result of a rapid regeneration of intestinal epithelium with the rescue of the impaired epithelial barrier. In small intestine of Muse-treated mice, an early enhanced secretion of IL-6 and MCP-1 cytokines was observed associated with (1) recruitment of monocytes/M2-like macrophages and (2) proliferation of Paneth cells through activation of the IL-6/Stat3 pathway.

CONCLUSION

Our findings indicate that a single injection of a small quantity of WJ-Muse may be a new and easy therapeutic strategy for treating lethal GIS.

MicroRNA-146a negatively regulates inflammation via the IRAK1/TRAF6/NF-κB signaling pathway in dry eye

Inflammation is a key factor in the pathogenesis of dry eye disease (DED). We aimed to investigate the role of microRNA-146a (miR-146a) in regulating corneal inflammation in a mouse model of benzalkonium chloride (BAC)-induced dry eye and the TNF-α-induced NF-κB signaling pathway in human corneal epithelial cells (HCECs). A mouse model of dry eye was established by administering with BAC to BALB/c mice, and the expression of TNF-α, IL-1β, IL-6, IL-8, cyclooxygenase 2 (COX2), interleukin-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6) in the corneas of dry eye model mice was significantly increased; this was accompanied by the upregulation of miR-146a and activation of the NF-κB pathway. In vitro, TNF-α induced miR-146a expression in HCECs, while the NF-κB inhibitor SC-514 reduced the expression of miR-146a. Overexpression of miR-146a decreased the expression of IRAK1 and TRAF6, which have been identified as targets of miR-146a. Furthermore, overexpression of miR-146a suppressed NF-κB p65 translocation from the cytoplasm to the nucleus. Moreover, overexpression of miR-146a attenuated the TNF-α-induced expression of IL-6, IL-8, COX2 and intercellular adhesion molecule 1 (ICAM1), while inhibition of miR-146a exerted the opposite effect. Our results suggest that miR-146a mediates the inflammatory response in DED. MiR-146a negatively regulates inflammation in HCECs through the IRAK1/TRAF6/NF-κB pathway, and this may serve as a potential therapeutic approach for the treatment of DED.

Conjunctival infiltrates and cytokines in an experimental immune-mediated blepharoconjunctivitis rat model

Purpose

To characterize the histopathological and immunological findings of a rat model of allergic blepharoconjunctivitis (BC) and demonstrate its potential utility for the assessment of BC therapies.

Methods

Sprague-Dawley (SD) rats were immunized with ovalbumin (OVA) and topically challenged with OVA (BC group) or PBS (control group), while a corticosteroid group was pre-treated with triamcinolone acetate 24 h before the challenge. Morphological features were evaluated and tissues were harvested for histological, flow cytometry and cytokine analysis.

Results

The BC group rats developed eyelid excoriations, redness, and conjunctival edema 24 h after the OVA challenge, while corticosteroid pre-treated and PBS-challenged rats were unaffected. The BC features were reduced despite repeated challenges for 5 days. Massive immune cell infiltration was observed in conjunctivae of BC rats, while no significant infiltration was seen in the other groups. Populations of T cells, mono-macrophages, neutrophils, and NK cells made up more than 77% of CD45⁺7AAD^- cells in the conjunctival tissues. T cell proportions were increased at 96 h compared to 24 h post-challenge, while macrophages decreased during the same time period. Eosinophils and intraepithelial neutrophils were detected in the BC rats, but not in the PBS and corticosteroid groups. BC eyes had significantly higher levels of IFN-γ and IL-2, while IL-4 and IL-6 levels were similar to controls.

Conclusion

A robust BC response was detected in this rat model which was suppressed by corticosteroid pre-treatment. Immune cell composition and cytokine profiles changed over time.

Intercellular Adhesion Molecule 1: More than a Leukocyte Adhesion Molecule

Intercellular adhesion molecule 1 (ICAM-1) is a transmembrane protein in the immunoglobulin superfamily expressed on the surface of multiple cell populations and upregulated by inflammatory stimuli. It mediates cellular adhesive interactions by binding to the β2 integrins macrophage antigen 1 and leukocyte function-associated antigen 1, as well as other ligands. It has important roles in the immune system, including in leukocyte adhesion to the endothelium and transendothelial migration, and at the immunological synapse formed between lymphocytes and antigen-presenting cells. ICAM-1 has also been implicated in the pathophysiology of diverse diseases from cardiovascular diseases to autoimmune disorders, certain infections, and cancer. In this review, we summarize the current understanding of the structure and regulation of the ICAM1 gene and the ICAM-1 protein. We discuss the roles of ICAM-1 in the normal immune system and a selection of diseases to highlight the breadth and often double-edged nature of its functions. Finally, we discuss current therapeutics and opportunities for advancements.

Role of CD34 in inflammatory bowel disease

Inflammatory bowel disease (IBD) is caused by a variety of pathogenic factors, including chronic recurrent inflammation of the ileum, rectum, and colon. Immune cells and adhesion molecules play an important role in the course of the disease, which is actually an autoimmune disease. During IBD, CD34 is involved in mediating the migration of a variety of immune cells (neutrophils, eosinophils, and mast cells) to the inflammatory site, and its interaction with various adhesion molecules is involved in the occurrence and development of IBD. Although the function of CD34 as a partial cell marker is well known, little is known on its role in IBD. Therefore, this article describes the structure and biological function of CD34, as well as on its potential mechanism in the development of IBD.

HetIG-PreDiG: A Heterogeneous Integrated Graph Model for Predicting Human Disease Genes based on gene expression

Graph analytical approaches permit identifying novel genes involved in complex diseases, but are limited by (i) inferring structural network similarity of connected gene nodes, ignoring potentially relevant unconnected nodes; (ii) using homogeneous graphs, missing gene-disease associations' complexity; (iii) relying on disease/gene-phenotype associations' similarities, involving highly incomplete data; (iv) using binary classification, with gene-disease edges as positive training samples, and non-associated gene and disease nodes as negative samples that may include currently unknown disease genes; or (v) reporting predicted novel associations without systematically evaluating their accuracy. Addressing these limitations, we develop the Heterogeneous Integrated Graph for Predicting Disease Genes (HetIG-PreDiG) model that includes gene-gene, gene-disease, and gene-tissue associations. We predict novel disease genes using low-dimensional representation of nodes accounting for network structure, and extending beyond network structure using the developed Gene-Disease Prioritization Score (GDPS) reflecting the degree of gene-disease association via gene co-expression data. For negative training samples, we select non-associated gene and disease nodes with lower GDPS that are less likely to be affiliated. We evaluate the developed model's success in predicting novel disease genes by analyzing the prediction probabilities of gene-disease associations. HetIG-PreDiG successfully predicts (Micro-F1 = 0.95) gene-disease associations, outperforming baseline models, and is validated using published literature, thus advancing our understanding of complex genetic diseases.

Contact-dependent, polarized acidification response during neutrophil-epithelial interactions

Neutrophil (PMN) infiltration during active inflammation imprints changes in the local tissue environment. Such responses are often accompanied by significant extracellular acidosis that result in predictable transcriptional responses. In this study, we explore the mechanisms involved in inflammatory acidification as a result of PMN-intestinal epithelial cell (IEC) interactions. Using recently developed tools, we revealed that PMN transepithelial migration (TEM)-associated inflammatory acidosis is dependent on the total number of PMNs present during TEM and is polarized toward the apical surface. Extending these studies, we demonstrate that physical separation of the PMNs and IECs prevented acidification, whereas inhibition of PMN TEM using neutralizing antibodies enhanced extracellular acidification. Utilizing pharmaceutical inhibitors, we demonstrate that the acidification response is independent of myeloperoxidase and dependent on reactive oxygen species generated during PMN TEM. In conclusion, inflammatory acidosis represents a polarized PMN-IEC-dependent response by an as yet to be fully determined mechanism.

Phellopterin cream exerts an anti-inflammatory effect that facilitates diabetes-associated cutaneous wound healing via SIRT1

BACKGROUND

Diabetic ulcers, which are characterized by chronic nonhealing wounds with a long-lasting inflammatory state, are a typical symptom in individuals with diabetes, and there is still no effective treatment for these lesions. Angelica dahurica plays a critical role in inflammatory diseases. Among numerous monomeric compounds, phellopterin has been shown to have anti-inflammatory properties.

PURPOSE

To research the bioactive constituents in Angelica dahurica and their mechanism of action in treating diabetic ulcers.

STUDY DESIGN

Chemical research of Angelica dahurica led to the identification of a new coumarin, dahuricoumarin A (1), along with seven known compounds (2 - 8). All compounds were tested for anti-inflammatory activity, and phellopterin, compound (3), significantly decreased the expression of intercellular cell adhesion molecule-1 (ICAM-1), a representative indicator of inflammation. Phellopterin can also increase SIRT1 protein, a key target for inflammation. In our research, we confirmed the anti-inflammatory effects of phellopterin on diabetic ulcers and explored the underlying mechanism of action.

METHODS

The expression of IFN-γ, SIRT1, and ICAM-1 in human diabetic ulcer tissues was studied using immunohistochemistry. Streptozotocin was used to induce a diabetic model in C57BL/6J mice, and ulcers were surgically introduced. After phellopterin treatment, the skin lesions of diabetic mice were observed over a period of time. The protein and mRNA expression levels of SIRT1 and ICAM-1 were measured using H&E, qRT-PCR and immunohistochemical staining. A HaCaT cell inflammatory model was induced by IFN-γ. Using a lentiviral packaging technique, MTT assay, and Western blotting, the effect of phellopterin on the proliferation of HaCaT cells and the expression of ICAM-1 was evaluated under normal and SIRT1 knockdown conditions.

RESULTS

High levels of ICAM-1 and IFN-γ were identified, but low levels of SIRT1 were found in human diabetic ulcer tissues, and phellopterin showed therapeutic benefits in the healing process by attenuating chronic inflammation and promoting re-epithelialization, along with SIRT1 upregulation and ICAM-1 downregulation. However, inhibiting SIRT1 reversed its proliferative and anti-inflammatory effects.

CONCLUSION

In vitro and in vivo, phellopterin exerts anti-inflammatory and proliferative effects that promote diabetic wound healing, and the potential mechanism depends on SIRT1.

Neutrophil-Epithelial Crosstalk During Intestinal Inflammation

Neutrophils are the most abundant leukocyte population in the human circulatory system and are rapidly recruited to sites of inflammation. Neutrophils play a multifaceted role in intestinal inflammation, as they contribute to the elimination of invading pathogens. Recently, their role in epithelial restitution has been widely recognized; however, they are also associated with bystander tissue damage. The intestinal epithelium provides a physical barrier to prevent direct contact of luminal contents with subepithelial tissues, which is extremely important for the maintenance of intestinal homeostasis. Numerous studies have demonstrated that transepithelial migration of neutrophils is closely related to disease symptoms and disruption of crypt architecture in inflammatory bowel disease and experimental colitis. There has been growing interest in how neutrophils interact with the epithelium under inflammatory conditions. Most studies focus on the effects of neutrophils on intestinal epithelial cells; however, the effects of intestinal epithelial cells on neutrophils during intestinal inflammation need to be well-established. Based on these data, we have summarized recent articles on the role of neutrophil-epithelial interactions in intestinal inflammation, particularly highlighting the epithelium-derived molecular regulators that mediate neutrophil recruitment, transepithelial migration, and detachment from the epithelium, as well as the functional consequences of their crosstalk. A better understanding of these molecular events may help develop novel therapeutic targets for mitigating the deleterious effects of neutrophils in inflammatory bowel disease.

Starch-based NP act as antigen delivery systems without immunomodulating effect

The nasal route of immunization has become a real alternative to injections. It is indeed described as more efficient at inducing immune protection, since it initiates both mucosal and systemic immunity, thus protecting against both the infection itself and the transmission of pathogens by the host. However, the use of immunomodulators should be limited since they induce inflammation. Here we investigated in vitro the mechanisms underlying the enhancement of antigen immunogenicity by starch nanoparticles (NPL) delivery systems in H292 epithelial cells, as well as the NPL’s immunomodulatory effect. We observed that NPL had no intrinsic immunomodulatory effect but enhanced the immunogenicity of an E. coli lysate (Ag) merely by increasing its intracellular delivery. Moreover, we demonstrated the importance of the NPL density on their efficiency by comparing reticulated (NPL) and non-reticulated particles (NPL·NR). These results show that an efficient delivery system is sufficient to induce a mucosal immune response without the use of immunomodulators.

Mechanisms and modeling of wound repair in the intestinal epithelium

The intestinal epithelial barrier is susceptible to injury from insults, such as ischemia or infectious disease. The epithelium's ability to repair wounded regions is critical to maintaining barrier integrity. Mechanisms of intestinal epithelial repair can be studied with models that recapitulate the in vivo environment. This review focuses on in vitro injury models and intestinal cell lines utilized in such systems. The formation of artificial wounds in a controlled environment allows for the exploration of reparative physiology in cell lines modeling diverse aspects of intestinal physiology. Specifically, the use of intestinal cell lines, IPEC-J2, Caco-2, T-84, HT-29, and IEC-6, to model intestinal epithelium is discussed. Understanding the unique systems available for creating intestinal injury and the differences in monolayers used for in vitro work is essential for designing studies that properly capture relevant physiology for the study of intestinal wound repair.

γδ T cell costimulatory ligands in antitumor immunity

Antitumor immunity relies on the ability of T cells to recognize and kill tumor targets. γδ T cells are a specialized subset of T cells that predominantly localizes to non-lymphoid tissue such as the skin, gut, and lung where they are actively involved in tumor immunosurveillance. γδ T cells respond to self-stress ligands that are increased on many tumor cells, and these interactions provide costimulatory signals that promote their activation and cytotoxicity. This review will cover costimulatory molecules that are known to be critical for the function of γδ T cells with a specific focus on mouse dendritic epidermal T cells (DETC). DETC are a prototypic tissue-resident γδ T cell population with known roles in antitumor immunity and are therefore useful for identifying mechanisms that may control activation of other γδ T cell subsets within non-lymphoid tissues. This review concludes with a brief discussion on how γδ T cell costimulatory molecules can be targeted for improved cancer immunotherapy.

MiR-15p-5p Mediates the Coordination of ICAM-1 and FAK to Promote Endothelial Cell Proliferation and Migration

Intercellular adhesion molecule-1 (ICAM-1) in endothelial cells is critical for neutrophil adhesion and transmigration across the endothelium. Focal adhesion kinase (FAK), which controls the turnover of focal adhesion to regulate cell adhesion and migration, plays a role in the resolution of inflammation. However, the coordinated involvement of ICAM-1 and FAK during endothelial inflammation has yet to be elucidated. This study reports that, as part of an inflammatory response, ICAM-1 controls FAK expression in endothelial cells via the microRNA miR-15b-5p. Induction of lung injury by lipopolysaccharide (LPS) resulted in higher levels of FAK expression in inflammatory tissues, while in ICAM-1 knockout mice, FAK expression was reduced in the lungs. FAK expression was also reduced in endothelial cells following ICAM-1 siRNA downregulation. Furthermore, ICAM-1 inhibited miR-15b-5p expression while increasing FAK mRNA and protein expression via binding of miR-15b-5p to the 3' untranslated region (UTR) of FAK. ICAM-1 inhibited miR-15b-5p promoter activity and hence reduced miR-15b-5p expression. FAK increased endothelial cell proliferation and migration, whereas miR-15b-5p inhibited cell proliferation and migration. These findings indicate that the inflammatory molecule ICAM-1 regulates FAK expression via miR-15b-5p levels, which in turn controls endothelial cell proliferation and migration.

Cells and mediators of inflammation as effectors of epithelial repair in the inflamed intestine

Mucosal and histological healing have become the gold standards for assessing the efficacy of therapy in patients living with inflammatory bowel diseases (IBD). Despite these being the accepted goals in therapy, the mechanisms that underlie the healing of the mucosa after an inflammatory insult are not well understood, and many patients fail to meet this therapeutic endpoint. Here we review the emerging evidence that mediators (e.g., prostaglandins, cytokines, proteases, reactive oxygen, and nitrogen species) and innate immune cells (e.g., neutrophils and monocytes/macrophages), that are involved in the initiation of the inflammatory response, are also key players in the mechanisms underlying mucosal healing to resolve chronic inflammation in the colon. The dual function mediators comprise an inflammation/repair program that returns damaged tissue to homeostasis. Understanding details of the dual mechanisms of these mediators and cells may provide the basis for the development of drugs that can help to stimulate epithelial repair in patients affected by IBD.

Unveiling the gut-brain axis: structural and functional analogies between the gut and the choroid plexus vascular and immune barriers

The vasculature plays an essential role in the development and maintenance of blood-tissue interface homeostasis. Knowledge on the morphological and functional nature of the blood vessels in every single tissue is, however, very poor, but it is becoming clear that each organ is characterized by the presence of endothelial barriers with different properties fundamental for the maintenance of tissue resident immune homeostasis and for the recruitment of blood-trafficking immune cells. The tissue specificity of the vascular unit is dependent on the presence of differentiated endothelial cells that form continues, fenestrated, or sinusoidal vessels with different grades of permeability and different immune receptors, according to how that particular tissue needs to be protected. The gut-brain axis highlights the prominent role that the vasculature plays in allowing a direct and prompt exchange of molecules between the gut, across the gut vascular barrier (GVB), and the brain. Recently, we identified a new choroid plexus vascular barrier (PVB) which receives and integrates information coming from the gut and is fundamental in the modulation of the gut-brain axis. Several pathologies are linked to functional dysregulation of either the gut or the choroid plexus vascular barriers. In this review, we unveil the structural and functional analogies between the GVB and PVB, comparing their peculiar features and highlighting the functional role of pitcher and catcher of the gut-brain axis, including their role in the establishment of immune homeostasis and response upon systemic stimuli. We propose that when the gut vascular barrier-the main protecting system of the body from the external world-is compromised, the choroid plexus gatekeeper becomes a second barrier that protects the central nervous system from systemic inflammation.

Coix Seed Diet Ameliorates Immune Function Disorders in Experimental Colitis Mice

Coix seed is a functional food in the Chinese diet that possesses the ability to alleviate ulcerative colitis clinically. However, the underlying mechanisms remain ambiguous. In this study, we investigated the protective effect of the Coix seed diet on experimental colitis mice. The mice were randomly divided into four groups: control group, model group, Coix seed feed group, and positive control group. The maintenance feed of the mice was replaced with Coix seed feed 10 days before orally administering the mice 5% (w/v) dextran sulfate sodium drink. As a result, the Coix seed feed alleviated colitis symptoms, maintained the complete blood count at a normal level, reduced the pathological score, relieved inflammatory cytokine secretion, and alleviated oxidative stress. Network pharmacology analysis was used for further exploration of the targets of Coix seed feed. The results showed that T-cell regulation is one of the targets of Coix seed feed, and the analysis of the T-lymphocyte subset and innate immune cell distribution of the colon tissue supported the network pharmacology results. In conclusion, Coix seed, as a staple food, can alleviate experimental colitis, and the mechanism may be related to the immune regulation effect of Coix seeds.

Loss of PTPN22 Promotes Intestinal Inflammation by Compromising Granulocyte-mediated Antibacterial Defence

BACKGROUND AND AIMS

A single nucleotide polymorphism in protein tyrosine phosphatase non-receptor type 22 [PTPN22] has been associated with the onset of autoimmune disorders, but protects from Crohn's disease. PTPN22 deficiency in mice promotes intestinal inflammation by modulating lymphocyte function. However, the impact of myeloid PTPN22 in colitis development remains unclear. The aim of this study was to investigate the role of PTPN2 in the IL-10 and the T cell transfer colitis models.

METHODS

PTPN22-deficient mice were crossed with IL-10-/- and RAG2-/- mice. Naïve T cells were injected in RAG-/- mice to induce T-cell transfer colitis. Spontaneous colitis in IL-10-/- mice was monitored for up to 200 days.

RESULTS

Here, we demonstrate that PTPN22 in non-lymphoid immune cells is required to protect against T cell transfer-mediated and IL-10 knock-out colitis. Analysis of the intestinal immune landscape demonstrated a marked reduction of granulocyte influx into the inflamed colon in PTPN22-deficient mice. On a molecular level, granulocytes were not only reduced by numbers, but also revealed a defective function. In particular, granulocyte activation and granulocyte-mediated bacteria killing was impaired upon loss of PTPN22, resulting in elevated bacterial burden and translocation beyond the intestinal epithelial barrier in PTPN22-deficient mice. Consistently, antibiotic-induced depletion of bacteria reverted the increased colitis susceptibility in PTPN22-deficient mice, whereas granulocyte depletion induced acolitis phenotype in wild-type mice similar to that observed in PTPN22-deficient mice.

CONCLUSIONS

In conclusion, our data demonstrate that PTPN22 is essential for adequate granulocyte activation and antimicrobial defence to protect the inflamed intestine from bacterial invasion and exacerbated colitis.

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.

Dichotomous roles of neutrophils in modulating pathogenic and repair processes of inflammatory bowel diseases

Neutrophils are considered as complex innate immune cells and play a critical role in maintaining intestinal mucosal homeostasis. They exert robust pro-inflammatory effects and recruit other immune cells in the acute phase of pathogen infection and intestinal inflammation, but paradoxically, they also limit exogenous microbial invasion and facilitate mucosal restoration. Hyperactivation or dysfunction of neutrophils results in abnormal immune responses, leading to multiple autoimmune and inflammatory diseases including systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel diseases (IBD). As a refractory intestinal inflammatory disease, the pathogenesis and progression of IBD are associated with complicated immune response processes in which neutrophils are profoundly involved. However, the consensus on potential roles of neutrophils in modulating pathogenic and repair processes of IBD remains not fully understood. Accumulated infiltrating neutrophils cross the epithelial barrier and contribute to microbial dysbiosis, aggravated intestinal architectural damage, compromised resolution of intestinal inflammation and increased risk of thrombosis during IBD. Paradoxically, activated neutrophils are also associated with effective elimination of invaded microbiota, promoted angiogenesis and tissue restoration of gut mucosa in IBD. Here, we discuss the beneficial and detrimental roles of neutrophils in the onset and resolution of intestinal mucosal inflammation, hoping to provide a precise overview of neutrophil functions in the pathogenesis of IBD.

Connecting the dots: Neutrophils at the interface of tissue regeneration and cancer

Knowledge about neutrophil biology has exponentially grown over the past decades. A high volume of investigations focusing on the characterization of their initially unappreciated multifaceted functions have grown in parallel with the immunity and the cancer fields. This has led to a significant gain in knowledge about their functions not only in tissue defence against pathogens and the collateral damage their overactivation can cause, but also their role in tissue repair and regeneration especially in the context of sterile injuries. On the other hand, the cancer field has also intensively focused its attention on neutrophil engagement in the many steps of the tumorigenic process. This review aims to draw the readers' attention to the similar functions described for neutrophils in tissue repair and in cancer. By bridging the two fields, we provide support for the hypothesis that the underlying program driving cancer-dependent exploitation of neutrophils is rooted in their physiologic tissue protection functions. In this view, cross-fertilization between the two fields will expedite the discovery of therapeutic interventions based on neutrophil targeting or their manipulation.

Protease-activated receptor-2 activation enhances epithelial wound healing via epidermal growth factor receptor

The intestinal barrier function relies on the presence of a single layer of epithelial cells. Barrier dysfunction is associated with the inflammatory bowel diseases (IBD). Understanding the mechanisms involved in intestinal wound healing in order to sustain the barrier function has a great therapeutic potential. Activation of protease-activated receptor-2 (PAR2) induces COX-2 expression in intestinal epithelial cells via EGFR transactivation. COX-2 is well known for its protective effects in the gastrointestinal tract. Therefore, we hypothesized that PAR-2 activation induces a wound healing response in intestinal epithelial cells through COX-2-derived lipid mediators and EGFR transactivation. Immunofluorescence and calcium assay were used to characterize CMT-93 mouse colonic epithelial cell line for PAR2 expression and its activity, respectively. Treatment with PAR2 activating peptide 2-furoyl-LIGRLO-NH₂ (2fLI), but not by its inactive reverse-sequence peptide (2fO) enhanced wound closure in scratch wounded monolayers. The EGFR tyrosine kinase inhibitor (PD153035), broad-spectrum matrix metalloproteinase inhibitor (GM6001) and Src tyrosine kinase inhibitor (PP2) inhibited PAR2-induced wound healing. However, PAR2 activation did not induce COX-2 expression in CMT-93 cells and inhibition of COX-2 by COX-2 selective inhibitor (NS-398) did not alter PAR2-induced wound healing. In conclusion, PAR2 activation drives wound healing in CMT-93 cells via EGFR transactivation. Matrix metalloproteinases and Src tyrosine kinase activity may involve in EGFR transactivation and PAR2-induced wound healing is independent of COX-2 activity. These findings provide a mechanism whereby PAR2 can participate in the resolution of intestinal wounds in gastrointestinal inflammatory diseases.

Molecular Characterization and Expression Analysis of Intercellular Adhesion Molecule-1 (ICAM-1) Genes in Rainbow Trout (Oncorhynchus mykiss) in Response to Viral, Bacterial and Parasitic Challenge

The intercellular adhesion molecule-1 (ICAM-1), known as CD54, is a transmembrane cell surface glycoprotein that interacts with two integrins (i.e., LFA-1 and Mac-l) important for trans-endothelial migration of leukocytes. The level of ICAM-1 expression is upregulated in response to some inflammatory stimulations, including pathogen infection and proinflammatory cytokines. Yet, to date, our knowledge regarding the functional role of ICAM-1 in teleost fish remains largely unknown. In this study, we cloned and characterized the sequence of ICAM-1 in rainbow trout (Oncorhynchus mykiss) for the first time, which exhibited that the molecular features of ICAM-1 in fishes were relatively conserved compared with human ICAM-1. The transcriptional level of ICAM-1 was detected in 12 different tissues, and we found high expression of this gene in the head kidney, spleen, gills, skin, nose, and pharynx. Moreover, upon stimulation with infectious hematopoietic necrosis virus (IHNV), Flavobacterium columnare G₄ (F. columnare), and Ichthyophthirius multifiliis (Ich) in rainbow trout, the morphological changes were observed in the skin and gills, and enhanced expression of ICAM-1 mRNA was detected both in the systemic and mucosal tissues. These results indicate that ICAM-1 may be implicated in the mucosal immune responses to viral, bacterial, and parasitic infections in teleost fish, meaning that ICAM-1 emerges as a master regulator of mucosal immune responses against pathogen infections in teleost fish.

ICAM-1 and ICAM-2 Are Differentially Expressed and Up-Regulated on Inflamed Pulmonary Epithelium, but Neither ICAM-2 nor LFA-1: ICAM-1 Are Required for Neutrophil Migration Into the Airways In Vivo

Neutrophil migration into the airways is an important process to fight infection and is mediated by cell adhesion molecules. The intercellular adhesion molecules, ICAM-1 (CD54) and ICAM-2 (CD102) are known ligands for the neutrophil integrins, lymphocyte function associated antigen (LFA)-1 (αLβ2; CD11a/CD18), and macrophage-1 antigen (Mac-1;αMβ2;CD11b/CD18) and are implicated in leukocyte migration into the lung. However, it is ill-defined how neutrophils exit the lung and the role for ICAMs in trans-epithelial migration (TEpM) across the bronchial or alveolar epithelium. We found that human and murine alveolar epithelium expressed ICAM-1, whilst the bronchial epithelium expressed ICAM-2, and both were up-regulated during inflammatory stimulation in vitro and in inflammatory lung diseases such as cystic fibrosis. Although β2 integrins interacting with ICAM-1 and -2 mediated neutrophil migration across human bronchial epithelium in vitro, neither ICAM-2 nor LFA-1 binding of ICAM-1 mediated murine neutrophil migration into the lung or broncho-alveolar space during LPS-induced inflammation in vivo. Furthermore, TEpM of neutrophils themselves resulted in increased epithelial junctional permeability and reduced barrier function in vitro. This suggests that although β2 integrins interacting with ICAMs may regulate low levels of neutrophil traffic in healthy lung or early in inflammation when the epithelial barrier is intact; these interactions may be redundant later in inflammation when epithelial junctions are disrupted and no longer limit TEpM.

Energy Drink Administration Ameliorates Intestinal Epithelial Barrier Defects and Reduces Acute DSS Colitis

BACKGROUND

The rise in the prevalence of inflammatory bowel diseases in the past decades coincides with changes in nutritional habits, such as adaptation of a Western diet. However, it is largely unknown how certain nutritional habits, such as energy drink consumption, affect intestinal inflammation. Here, we assessed the effect of energy drink supplementation on the development of intestinal inflammation in vitro and in vivo.

METHODS

HT-29 and T84 intestinal epithelial cells and THP-1 monocytic cells were treated with IFNγ in presence or absence of different concentrations of an energy drink. Colitis was induced in C57BL/6 mice by addition of dextran sodium sulfate (DSS) to drinking water with or without supplementation of the energy drink.

RESULTS

Energy drink supplementation caused a dose-dependent decrease in IFNγ-induced epithelial barrier permeability, which was accompanied by upregulation of the pore-forming protein claudin-2. Administration of the energy drink reduced secretion of the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-α from HT-29, T84, and THP-1 cells. In vivo, energy drink administration reduced clinical symptoms of DSS-induced colitis and epithelial barrier permeability. Endoscopic and histologic colitis scores and expression of pro-inflammatory cytokines were significantly reduced by energy drink co-administration.

CONCLUSION

Energy drink consumption seems to exert an unexpected anti-inflammatory effect in vitro and in vivo in our experimental setting. However, our experimental approach focuses on intestinal inflammation and neglects additional effects of energy drink consumption on the body (eg, on metabolism or sleep). Therefore, the translation of our findings into the human situation must be taken with caution.

Fabrication of In Situ Layered Hydrogel Scaffold for the Co-delivery of PGDF-BB/Chlorhexidine to Regulate Proinflammatory Cytokines, Growth Factors, and MMP-9 in a Diabetic Skin Defect Albino Rat Model

Diabetes mellitus (DM)-associated impairments in wound healing include prolonged inflammation, the overexpression of matrix metalloproteases (MMPs), and low levels of growth factors at the wound site. To this end, a layer-by-layer scaffold (S_L-B-L) made of cross-linked silk fibroin and hyaluronic acid is developed to deliver chlorhexidine, an antimicrobial agent and an MMP-9 inhibitor, along with the PDGF-BB protein. S_L-B-L exhibited highly porous morphology. Diabetic rats treated with S_L-B-L demonstrated an early wound closure, a fully reconstructed epithelial layer by 14 days, and reduced levels of IL-6, TNF-α, TGF-β1, and MMP-9. Interestingly, S_L-B-L treatment increased angiogenesis, the bioavailability of collagen, DNA content, and VEGF-A levels. Furthermore, enhanced keratinocyte-fibroblast interaction along with ordered collagen deposition was observed in S_L-B-L-treated rats. Most interestingly, when compared with a clinically used scaffold SEESKIN+, S_L-B-L outperformed in promoting wound healing in a diabetic rat model by regulating the inflammation while delivering growth factor and the MMP-9 inhibitor.

Released Myeloperoxidase Attenuates Neutrophil Migration and Accumulation in Inflamed Tissue

Neutrophil (PMN) recruitment to sites of insult is critical for host defense, however excessive PMN activity and tissue accumulation can lead to exacerbated inflammation and injury. Myeloperoxidase (MPO) is a PMN azurophilic granule enzyme, which together with H₂O₂, forms a powerful antimicrobial system designed to kill ingested bacteria. Intriguingly, in addition to intracellular killing of invading microorganisms and extracellular tissue damage due generation of ROS, soluble MPO has been directly implicated in modulating cellular responses and tissue homeostasis. In the current work, we used several models of inflammation, murine and human PMNs and state-of-the-art intravital microscopy to examine the effect of MPO on PMN migration and tissue accumulation. We found that in the absence of functional MPO (MPO knockout, KO mice) inflammatory PMN tissue accumulation was significantly enhanced. We determined that the elevated numbers of PMNs in MPO knockout mice was not due to enhanced viability, but due to increased migratory ability. Acute PMN migration in models of zymosan-induced peritonitis or ligated intestinal loops induced by intraluminal administration of PMN-chemokine CXCL1 was increased over 2-fold in MPO KO compared to wild type (WT) mice. Using real-time intravital imaging of inflamed mouse cremaster muscle and ex vivo PMN co-culture with inflamed endothelial cells (ECs) we demonstrate that elevated migration of MPO KO mice was due to enhanced adhesive interactions. In contrast, addition of soluble recombinant MPO both in vivo and ex vivo diminished PMN adhesion and migration. Although MPO has been previously suggested to bind CD11b, we found no significant difference in CD11b expression in either resting or activated PMNs and further showed that the MPO binding to the PMN surface is not specific to CD11b. As such, our data identify MPO as a novel regulator of PMN trafficking in inflammation.

Cross-Talk among Polymorphonuclear Neutrophils, Immune, and Non-Immune Cells via Released Cytokines, Granule Proteins, Microvesicles, and Neutrophil Extracellular Trap Formation: A Novel Concept of Biology and Pathobiology for Neutrophils

Polymorphonuclear neutrophils (PMNs) are traditionally regarded as professional phagocytic and acute inflammatory cells that engulf the microbial pathogens. However, accumulating data have suggested that PMNs are multi-potential cells exhibiting many important biological functions in addition to phagocytosis. These newly found novel activities of PMN include production of different kinds of cytokines/chemokines/growth factors, release of neutrophil extracellular traps (NET)/ectosomes/exosomes and trogocytosis (membrane exchange) with neighboring cells for modulating innate, and adaptive immune responses. Besides, PMNs exhibit potential heterogeneity and plasticity in involving antibody-dependent cellular cytotoxicity (ADCC), cancer immunity, autoimmunity, inflammatory rheumatic diseases, and cardiovascular diseases. Interestingly, PMNs may also play a role in ameliorating inflammatory reaction and wound healing by a subset of PMN myeloid-derived suppressor cells (PMN-MDSC). Furthermore, PMNs can interact with other non-immune cells including platelets, epithelial and endothelial cells to link hemostasis, mucosal inflammation, and atherogenesis. The release of low-density granulocytes (LDG) from bone marrow initiates systemic autoimmune reaction in systemic lupus erythematosus (SLE). In clinical application, identification of certain PMN phenotypes may become prognostic factors for severe traumatic patients. In the present review, we will discuss these newly discovered biological and pathobiological functions of the PMNs.

LasR-deficient Pseudomonas aeruginosa variants increase airway epithelial mICAM-1 expression and enhance neutrophilic lung inflammation

Pseudomonas aeruginosa causes chronic airway infections, a major determinant of lung inflammation and damage in cystic fibrosis (CF). Loss-of-function lasR mutants commonly arise during chronic CF infections, are associated with accelerated lung function decline in CF patients and induce exaggerated neutrophilic inflammation in model systems. In this study, we investigated how lasR mutants modulate airway epithelial membrane bound ICAM-1 (mICAM-1), a surface adhesion molecule, and determined its impact on neutrophilic inflammation in vitro and in vivo. We demonstrated that LasR-deficient strains induce increased mICAM-1 levels in airway epithelial cells compared to wild-type strains, an effect attributable to the loss of mICAM-1 degradation by LasR-regulated proteases and associated with enhanced neutrophil adhesion. In a subacute airway infection model, we also observed that lasR mutant-infected mice displayed greater airway epithelial ICAM-1 expression and increased neutrophilic pulmonary inflammation. Our findings provide new insights into the intricate interplay between lasR mutants, LasR-regulated proteases and airway epithelial ICAM-1 expression, and reveal a new mechanism involved in the exaggerated inflammatory response induced by lasR mutants.

Triggering Receptor Expressed on Myeloid Cells-1 Agonist Regulates Intestinal Inflammation via Cd177+ Neutrophils

Triggering receptor expressed on myeloid cell-1 (TREM-1) signaling is expressed on neutrophils and monocytes that is necessary for the successful antimicrobial response and resolution of inflammation in the gut. In this study, we determined the effect of an anti-TREM-1 agonistic antibody (α-TREM-1) on colitis and identify its underlying mechanism of action. Administration of α-TREM-1 alleviated colitis in mice and resolved dysbiosis, which required TLR4/Myd88 signaling. α-TREM-1 increased the production of neutrophil extracellular traps and interleukin-22 by CD177+ neutrophils, which led to pathogen clearance and protection of the intestinal barrier. TREM-1 activation using an α-TREM-1 antibody protects against colitis by rebalancing the microbiota and protecting the epithelium against the immune response as well as modulates the function of neutrophils and macrophages. These results highlight the importance of the TREM-1 pathway in intestinal homeostasis and suggest that α-TREM-1 treatment may be an effective therapeutic strategy for inflammatory bowel disease.

Leptin Receptor q223r Polymorphism Influences Clostridioides difficile Infection-Induced Neutrophil CXCR2 Expression in an Interleukin-1β Dependent Manner

Neutrophils are key first-responders in the innate immune response to C. difficile infection (CDI) and play a central role in disease pathogenesis. Studies have clearly shown that tissue neutrophil numbers need to be tightly regulated for optimal CDI outcomes: while excessive colonic neutrophilia is associated with severe CDI, neutrophil depletion also results in worse outcomes. However, the biological mechanisms that control CDI-induced neutrophilia remain poorly defined. C-X-C chemokine receptor 2 (CXCR2) is a chemotactic receptor that is critical in neutrophil mobilization from bone marrow to blood and tissue sites. We have previously reported that a single nucleotide polymorphism (SNP) in leptin receptor (LEPR), present in up to 50% of people, influenced CDI-induced neutrophil CXCR2 expression and tissue neutrophilia. Homozygosity for mutant LEPR (i.e. RR genotype) was associated with higher CXCR2 expression and more tissue neutrophils. Here, we investigated the biological mechanisms that regulate neutrophil CXCR2 expression after CDI, and the influence of host genetics on this process. Our data reveal that: a) CXCR2 plays a key role in CDI-induced neutrophil extravasation from blood to colonic tissue; b) plasma from C. difficile-infected mice upregulated CXCR2 on bone marrow neutrophils; c) plasma from C. difficile-infected RR mice induced a higher magnitude of CXCR2 upregulation and had more IL-1β; and d) IL-1β neutralization reduced CXCR2 expression on bone marrow and blood neutrophils and their subsequent accrual to colonic tissue. In sum, our data indicate that IL-1β is a key molecular mediator that communicates between gastro-intestinal tract (i.e. site of CDI) and bone marrow (i.e. primary neutrophil reservoir) and regulates the intensity of CDI-induced tissue neutrophilia by modulating CXCR2 expression. Further, our studies highlight the importance of host genetics in affecting these innate immune responses and provide novel insights into the mechanisms by which a common SNP influences CDI-induced neutrophilia.

Distinct Antiviral Properties of Two Different Bacterial Lysates

Oral bacterial lysates (OBLs) can reduce the frequency and severity of recurrent respiratory tract infections in children from viral and bacterial origins. OBL-induced early innate immune reaction was already shown, but the specific features of different OBLs have never been studied and compared. A study was conducted to assess in vitro the protective effects on rhinovirus- (RV-) infected human bronchial epithelial cells (BECs) of two slightly different OBLs: OM-85 and Pulmonarom. Furthermore, since immune cells represent the key arm for antiviral defence, the capacity of these OBLs to induce selected cytokine production in mouse bone marrow-derived DCs (BMDCs) was also evaluated. Although different OBLs may share some mechanisms to protect host cells from virus infection, some product-specific antimicrobial activities were observed on RV-infected human BECs and mouse BMDCs. These results are consistent with a product-specific response possibly triggered by different pathogen-associated molecular patterns (PAMPs) contained in OBLs.

Protective Role of Natural and Semi-Synthetic Tocopherols on TNFα-Induced ROS Production and ICAM-1 and Cl-2 Expression in HT29 Intestinal Epithelial Cells

Vitamin E, a fat-soluble compound, possesses both antioxidant and non-antioxidant properties. In this study we evaluated, in intestinal HT29 cells, the role of natural tocopherols, α-Toc and δ-Toc, and two semi-synthetic derivatives, namely bis-δ-Toc sulfide (δ-Toc)₂S and bis-δ-Toc disulfide (δ-Toc)₂S₂, on TNFα-induced oxidative stress, and intercellular adhesion molecule-1 (ICAM-1) and claudin-2 (Cl-2) expression. The role of tocopherols was compared to that of N-acetylcysteine (NAC), an antioxidant precursor of glutathione synthesis. The results show that all tocopherol containing derivatives used, prevented TNFα-induced oxidative stress and the increase of ICAM-1 and Cl-2 expression, and that (δ-Toc)₂S and (δ-Toc)₂S₂ are more effective than δ-Toc and α-Toc. The beneficial effects demonstrated were due to tocopherol antioxidant properties, but suppression of TNFα-induced Cl-2 expression seems not only to be related with antioxidant ability. Indeed, while ICAM-1 expression is strongly related to the intracellular redox state, Cl-2 expression is TNFα-up-regulated by both redox and non-redox dependent mechanisms. Since ICAM-1 and Cl-2 increase intestinal bowel diseases, and cause excessive recruitment of immune cells and alteration of the intestinal barrier, natural and, above all, semi-synthetic tocopherols may have a potential role as a therapeutic support against intestinal chronic inflammation, in which TNFα represents an important proinflammatory mediator.

ICAM-1 deletion delays the repair process in aging diabetic mice

BACKGROUND

The delayed repair process in the aging diabetic population is becoming an alarming public health concern. ICAM-1 plays an important role in orchestrating the repair process by mediating neutrophil recruitment and phagocytosis. However, little is known about the role of ICAM-1 in aging diabetic repair.

METHODS

By causing injury in aging diabetic mice with ICAM-1 deletion (AD-ICAM-1^-/-), we found that AD-ICAM-1^-/- mice exhibited a delayed repair process with incomplete re-epithelialization and reduced angiogenesis. Additionally, high-throughput Illumina sequencing was performed to evaluate the microbiota of such mice.

RESULTS

The results indicate that the microbiota of the AD-ICAM-1^-/- injury site differed taxonomically at both the phylum and genus levels. Neutrophil recruitment and phagocytic function were also reduced in the AD-ICAM-1^-/- group. Notably, major inflammatory biomarker expression was also detected in AD-ICAM-1^-/- injured tissue.

CONCLUSIONS

Overall, this study demonstrated that AD-ICAM-1^-/- mice exhibit delayed repair. In addition, neutrophil recruitment and phagocytic activity were impaired in the AD-ICAM-1^-/- group, which may have allowed microbes to colonize the injury site.

Hyperglycemia Decreases Epithelial Cell Proliferation and Attenuates Neutrophil Activity by Reducing ICAM-1 and LFA-1 Expression Levels

Delayed repair is a serious public health concern for diabetic populations. Intercellular adhesion molecule 1 (ICAM-1) and Lymphocyte function-associated antigen 1 (LFA-1) play important roles in orchestrating the repair process. However, little is known about their effects on endothelial cell (EC) proliferation and neutrophil activity in subjects with hyperglycemia (HG). We cultured ECs and performed a scratch-closure assay to determine the relationship between ICAM-1 and EC proliferation. Specific internally labeled bacteria were used to clarify the effects of ICAM-1 and LFA-1 on neutrophil phagocytosis. Transwell assay and fluorescence-activated cell sorting analysis evaluated the roles of ICAM-1 and LFA-1 in neutrophil recruitment. ICAM-1+/+ and ICAM-1-/- mice were used to confirm the findings in vivo. The results demonstrated that HG decreased the expression of ICAM-1, which lead to the low proliferation of ECs. HG also attenuated neutrophil recruitment and phagocytosis by reducing the expression of ICAM-1 and LFA-1, which were strongly associated with the delayed repair.

Select animal models of colitis and their value in predicting clinical efficacy of biological therapies in ulcerative colitis

Introduction: Advancing new therapies from discovery to development usually requires proof-of-concept in animal models to justify the costs of continuing the program. While animal models are useful for understanding the mechanism of action (MOA) of a target, limitations of many published colitis models restrict their value to predict clinical efficacy.Areas covered: The authors focused their literature search on published studies of chronic animal models used to evaluate the pre-clinical efficacy of therapeutic molecules subsequently evaluated in clinical trials for UC. The UC therapies evaluated were anti-α4β7, anti-IL13, anti-IL12p40, and anti-IL23p19. The models of chronic colitis evaluating these molecules were: mdra1a-/-, chronic dextran sulfate sodium (DSS), chronic 2,4,6-trinitrobenzene sulfonic acid (TNBS), and the T cell transfer model.Expert opinion: While some models provide insight into target MOA in UC, none is consistently superior in predicting efficacy. Evaluation of multiple models, with varying mechanisms of colitis induction, is needed to understand potential drug efficacy. Additional models of greater complexity, reflecting the disease chronicity/heterogeneity seen in humans, are needed. Although helpful in prioritizing targets, animal models alone will likely not improve outcomes of UC clinical trials. Transformational changes to clinical efficacy will likely only occur when precision medicine approaches are employed.

Proteomics-Informed Identification of Luminal Targets For In Situ Diagnosis of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic condition resulting in impaired intestinal homeostasis. Current practices for diagnosis of IBD are challenged by invasive, demanding procedures. We hypothesized that proteomics analysis could provide a powerful tool for identifying clinical biomarkers for non-invasive IBD diagnosis. Here, the global intestinal proteomes from commonly used in vitro and in vivo models of IBD were analyzed to identify apical and luminal proteins that can be targeted by orally delivered diagnostic agents. Global proteomics analysis revealed upregulated plasma membrane proteins in intestinal segments of proximal- and distal colon from dextran sulfate sodium-treated mice and also in inflamed human intestinal Caco-2 cells pretreated with pro-inflammatory agents. The upregulated colon proteins in mice were compared to the proteome of the healthy ileum, to ensure targeting of diagnostic agents to the inflamed colon. Promising target proteins for future investigations of non-invasive diagnosis of IBD were found in both systems and included Tgm2/TGM2, Icam1/ICAM1, Ceacam1/CEACAM1, and Anxa1/ANXA1. Ultimately, these findings will guide the selection of appropriate antibodies for surface functionalization of imaging agents aimed to target inflammatory biomarkers in situ.

Emerging neutrophil plasticity: Terminally differentiated cells no more

Discussion on the emerging evidence of phenotypic and functional PMN heterogeneity in tissue and implications for health and disease outcomes.

The Neutrophil: Constant Defender and First Responder

The role of polymorphonuclear neutrophils (PMNs) in biology is often recognized during pathogenesis associated with PMN hyper- or hypo-functionality in various disease states. However, in the vast majority of cases, PMNs contribute to resilience and tissue homeostasis, with continuous PMN-mediated actions required for the maintenance of health, particularly in mucosal tissues. PMNs are extraordinarily well-adapted to respond to and diminish the damaging effects of a vast repertoire of infectious agents and injurious processes that are encountered throughout life. The commensal biofilm, a symbiotic polymicrobial ecosystem that lines the mucosal surfaces, is the first line of defense against pathogenic strains that might otherwise dominate, and is therefore of critical importance for health. PMNs regularly interact with the commensal flora at the mucosal tissues in health and limit their growth without developing an overt inflammatory reaction to them. These PMNs exhibit what is called a para-inflammatory phenotype, and have reduced inflammatory output. When biofilm growth and makeup are disrupted (i.e., dysbiosis), clinical symptoms associated with acute and chronic inflammatory responses to these changes may include pain, erythema and swelling. However, in most cases, these responses indicate that the immune system is functioning properly to re-establish homeostasis and protect the status quo. Defects in this healthy everyday function occur as a result of PMN subversion by pathological microbial strains, genetic defects or crosstalk with other chronic inflammatory conditions, including cancer and rheumatic disease, and this can provide some avenues for therapeutic targeting of PMN function. In other cases, targeting PMN functions could worsen the disease state. Certain PMN-mediated responses to pathogens, for example Neutrophil Extracellular Traps (NETs), might lead to undesirable symptoms such as pain or swelling and tissue damage/fibrosis. Despite collateral damage, these PMN responses limit pathogen dissemination and more severe damage that would otherwise occur. New data suggests the existence of unique PMN subsets, commonly associated with functional diversification in response to particular inflammatory challenges. PMN-directed therapeutic approaches depend on a greater understanding of this diversity. Here we outline the current understanding of PMNs in health and disease, with an emphasis on the positive manifestations of tissue and organ-protective PMN-mediated inflammation.

Intercellular Adhesion Molecule 1 Functions as an Efferocytosis Receptor in Inflammatory Macrophages

Intercellular adhesion molecule-1 (ICAM-1) is up-regulated during inflammation by several cell types. ICAM-1 is best known for its role in mediating leukocyte adhesion to endothelial cells and guiding leukocytes across the vascular wall. Recently, macrophages have been shown to express ICAM-1, however, their role in macrophage function is unclear. We found that ICAM-1 expression was induced during inflammatory macrophage polarization and high numbers of ICAM-1-expressing macrophages were noted in inflamed colon tissue in a murine colitis model and in human inflammatory bowel disease. Because tissue macrophages play a critical role in removing apoptotic/necrotic cells in inflammation and injury, a process termed efferocytosis, it was examined whether ICAM-1 contributes to this process. Genetic deletion (ICAM-1 knockout mice) or siRNA-mediated knockdown of ICAM-1 in isolated murine and human macrophages significantly impaired apoptotic cell (AC) engulfment. Impairment in the engulfment of Jurkat T cells, neutrophils, and epithelial cells was confirmed ex vivo by inflammatory macrophages and in vivo by thioglycolate-recruited peritoneal macrophages. Decreased efferocytosis was also seen in vitro and in vivo with inhibition of ICAM-1 adhesive interactions, using a function blocking anti-ICAM-1 antibody. Mechanistically, it was found that ICAM-1 actively redistributes to cluster around engulfed ACs to facilitate macrophage-AC binding. Our findings define a new role for ICAM-1 in promoting macrophage efferocytosis, a critical process in the resolution of inflammation and restoration of tissue homeostasis.

ICAM-1: A master regulator of cellular responses in inflammation, injury resolution, and tumorigenesis

ICAM-1 is a cell surface glycoprotein and an adhesion receptor that is best known for regulating leukocyte recruitment from circulation to sites of inflammation. However, in addition to vascular endothelial cells, ICAM-1 expression is also robustly induced on epithelial and immune cells in response to inflammatory stimulation. Importantly, ICAM-1 serves as a biosensor to transduce outside-in-signaling via association of its cytoplasmic domain with the actin cytoskeleton following ligand engagement of the extracellular domain. Thus, ICAM-1 has emerged as a master regulator of many essential cellular functions both at the onset and at the resolution of pathologic conditions. Because the role of ICAM-1 in driving inflammatory responses is well recognized, this review will mainly focus on newly emerging roles of ICAM-1 in epithelial injury-resolution responses, as well as immune cell effector function in inflammation and tumorigenesis. ICAM-1 has been of clinical and therapeutic interest for some time now; however, several attempts at inhibiting its function to improve injury resolution have failed. Perhaps, better understanding of its beneficial roles in resolution of inflammation or its emerging function in tumorigenesis will spark new interest in revisiting the clinical value of ICAM-1 as a potential therapeutic target.