The emerging role of neutrophilic extracellular traps in intestinal disease

Methane saline suppresses ferroptosis via the Nrf2/HO-1 signaling pathway to ameliorate intestinal ischemia-reperfusion injury

OBJECTIVES

Intestinal ischemia-reperfusion (I/R) injury is a multifactorial and complex clinical pathophysiological process. Current research indicates that the pathogenesis of intestinal I/R injury involves various mechanisms, including ferroptosis. Methane saline (MS) has been demonstrated to primarily exert anti-inflammatory and antioxidant effects in I/R injury. In this study, we mainly investigated the effect of MS on ferroptosis in intestinal I/R injury and determined its potential mechanism.

METHODS

In vivo and in vitro intestinal I/R injury models were established to validate the relationship between ferroptosis and intestinal I/R injury. MS treatment was applied to assess its impact on intestinal epithelial cell damage, intestinal barrier disruption, and ferroptosis.

RESULTS

MS treatment led to a reduction in I/R-induced intestinal epithelial cell damage and intestinal barrier disruption. Moreover, similar to treatment with ferroptosis inhibitors, MS treatment reduced ferroptosis in I/R, as indicated by a decrease in the levels of intracellular pro-ferroptosis factors, an increase in the levels of anti-ferroptosis factors, and alleviation of mitochondrial damage. Additionally, the expression of Nrf2/HO-1 was significantly increased after MS treatment. However, the intestinal protective and ferroptosis inhibitory effects of MS were diminished after the use of M385 to inhibit Nrf2 in mice or si-Nrf2 in Caco-2 cells.

DISCUSSION

We proved that intestinal I/R injury was mitigated by MS and that the underlying mechanism involved modulating the Nrf2/HO-1 signaling pathway to decrease ferroptosis. MS could be a promising treatment for intestinal I/R injury.

Baker's yeast beta glucan supplementation was associated with an improved innate immune mRNA expression response after exercise

Beta glucans are found in many natural sources, however, only Baker's Yeast Beta Glucan (BYBG) has been well documented to have structure-function effects that are associated with improved innate immune response to stressors (e.g., exercise, infection, etc.). The purpose was to identify a BYBG-associated mRNA expression pattern following exercise. Participants gave IRB-approved consent and were randomized to BYBG (Wellmune®; N=9) or Placebo (maltodextrin; N=10) for 6-weeks prior to performing 90 min of whole-body exercise. Paxgene blood samples were collected prior to exercise (PRE), after exercise (POST), two hours after exercise (2H), and four hours after exercise (4H). Total RNA was isolated and analyzed for the expression of 770 innate immune response mRNA (730 mRNA targets; 40 housekeepers/controls; Nanostring nCounter). The raw data were normalized against housekeeping controls and expressed as Log2 fold change from PRE for a given condition. Significance was set at p < 0.05 with adjustments for multiple comparisons and false discovery rate. We identified 47 mRNA whose expression was changed after exercise with BYBG and classified them to four functional pathways: 1) Immune Cell Maturation (8 mRNA), 2) Immune Response and Function (5 mRNA), 3) Pattern Recognition Receptors and DAMP or PAMP Detection (25 mRNA), and 4) Detection and Resolution of Tissue Damage (9 mRNA). The identified mRNA whose expression was altered after exercise with BYBG may represent an innate immune response pattern and supports previous conclusions that BYBG improves immune response to a future sterile inflammation or infection.

Dihydromyricetin ameliorates experimental ulcerative colitis by inhibiting neutrophil extracellular traps formation via the HIF-1α/VEGFA signaling pathway

Dihydromyricetin (DHM), which has various biological functions, possesses therapeutic potential for ulcerative colitis (UC). Neutrophil extracellular traps (NETs) and their components play a crucial role in several pathological processes in UC. However, whether DHM alleviates UC by regulating NETs remains unclear. Mice with dextran sulfate sodium (DSS)-induced acute colitis were treated with DHM at different concentrations, and the severity of colitis was evaluated by assessing body weight, colon length, histological scores, cytokine production, and epithelial barrier integrity. To quantify and visualize NETs, the expression of cell free-DNA (cf-DNA) in serum and Cit-H3 in colonic tissue was analyzed via western blotting and immunofluorescence analysis. HL-60 cells and mouse bone marrow-derived neutrophils (BMDNs) were used to evaluate the effects of DHM on NETs in vitro. NETs were treated with DHM at varying concentrations or DNase I and used to repair the intestinal epithelial barrier in a Caco-2/HIEC-6 cell monolayer model. Furthermore, the genes targeted by DHM through neutrophils for alleviating UC were identified by screening online databases, and the results of network pharmacological analysis were verified via western blotting and quantitative real-time polymerase chain reaction. DHM alleviated DSS-induced colitis in mice by reversing weight loss, increased DAI score, colon length shortening, enhanced spleen index, colonic pathological damage, cytokine production, and epithelial barrier loss in a dose-dependent manner. In addition, it inhibited the formation of NETs both in vivo and in vitro. Based on the results of network pharmacological analysis, DHM may target HIF-1α and VEGFA through neutrophils to alleviate UC. Treatment with PMA increased the expression of HIF-1α and VEGFA in D-HL-60 cells and BMDNs, whereas treatment with DHM or DNase I reversed this effect. Treatment with DMOG, an inhibitor of HIF prolyl hydroxylase (HIF-PH), counteracted the suppressive effects of DHM on NETs formation in D-HL-60 cells and BMDNs. Accordingly, it partially counteracted the protective effects of DHM on the intestinal epithelial barrier in Caco-2 and HIEC-6 cells. These results indicated that DHM alleviated DSS-induced UC by regulating NETs formation via the HIF-1α/VEGFA signaling pathway, suggesting that DHM is a promising therapeutic candidate for UC.

A comprehensive immunobiology review of IBD: With a specific glance to Th22 lymphocytes development, biology, function, and role in IBD

The two primary forms of inflammatory disorders of the small intestine andcolon that make up inflammatory bowel disease (IBD) are ulcerative colitis (UC) and Crohn's disease (CD). While ulcerative colitis primarily affects the colon and the rectum, CD affects the small and large intestines, as well as the esophagus,mouth, anus, andstomach. Although the etiology of IBD is not completely clear, and there are many unknowns about it, the development, progression, and recurrence of IBD are significantly influenced by the activity of immune system cells, particularly lymphocytes, given that the disease is primarily caused by the immune system stimulation and activation against gastrointestinal (GI) tract components due to the inflammation caused by environmental factors such as viral or bacterial infections, etc. in genetically predisposed individuals. Maintaining homeostasis and the integrity of the mucosal barrier are critical in stopping the development of IBD. Specific immune system cells and the quantity of secretory mucus and microbiome are vital in maintaining this stability. Th22 cells are helper T lymphocyte subtypes that are particularly important for maintaining the integrity and equilibrium of the mucosal barrier. This review discusses the most recent research on these cells' biology, function, and evolution and their involvement in IBD.

Chromatin as alarmins in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease primarily affecting premature neonates, marked by poorly understood pro-inflammatory signaling cascades. Recent advancements have shed light on a subset of endogenous molecular patterns, termed chromatin-associated molecular patterns (CAMPs), which belong to the broader category of damage-associated molecular patterns (DAMPs). CAMPs play a crucial role in recognizing pattern recognition receptors and orchestrating inflammatory responses. This review focuses into the realm of CAMPs, highlighting key players such as extracellular cold-inducible RNA-binding protein (eCIRP), high mobility group box 1 (HMGB1), cell-free DNA, neutrophil extracellular traps (NETs), histones, and extracellular RNA. These intrinsic molecules, often perceived as foreign, have the potential to trigger immune signaling pathways, thus contributing to NEC pathogenesis. In this review, we unravel the current understanding of the involvement of CAMPs in both preclinical and clinical NEC scenarios. We also focus on elucidating the downstream signaling pathways activated by these molecular patterns, providing insights into the mechanisms that drive inflammation in NEC. Moreover, we scrutinize the landscape of targeted therapeutic approaches, aiming to mitigate the impact of tissue damage in NEC. This in-depth exploration offers a comprehensive overview of the role of CAMPs in NEC, bridging the gap between preclinical and clinical insights.

Restraint Stress-Induced Neutrophil Inflammation Contributes to Concurrent Gastrointestinal Injury in Mice

Psychological stress increases risk of gastrointestinal tract diseases. However, the mechanism behind stress-induced gastrointestinal injury is not well understood. The objective of our study is to elucidate the putative mechanism of stress-induced gastrointestinal injury and develop an intervention strategy. To achieve this, we employed the restraint stress mouse model, a well-established method to study the pathophysiological changes associated with psychological stress in mice. By orally administering gut-nonabsorbable Evans blue dye and monitoring its plasma levels, we were able to track the progression of gastrointestinal injury in live mice. Additionally, flow cytometry was utilized to assess the viability, death, and inflammatory status of splenic leukocytes, providing insights into the stress-induced impact on the innate immune system associated with stress-induced gastrointestinal injury. Our findings reveal that neutrophils represent the primary innate immune leukocyte lineage responsible for stress-induced inflammation. Splenic neutrophils exhibited elevated expression levels of the pro-inflammatory cytokine IL-1, cellular reactive oxygen species, mitochondrial burden, and cell death following stress challenge compared to other innate immune cells such as macrophages, monocytes, and dendritic cells. Regulated cell death analysis indicated that NETosis is the predominant stress-induced cell death response among other analyzed regulated cell death pathways. NETosis culminates in the formation and release of neutrophil extracellular traps, which play a crucial role in modulating inflammation by binding to pathogens. Treatment with the NETosis inhibitor GSK484 rescued stress-induced neutrophil extracellular trap release and gastrointestinal injury, highlighting the involvement of neutrophil extracellular traps in stress-induced gastrointestinal inflammation. Our results suggest that neutrophil NETosis could serve as a promising drug target for managing psychological stress-induced gastrointestinal injuries.

Diagnostic value of anti-integrin αvβ6 antibodies in ulcerative colitis

Ulcerative colitis (UC)-related mucosal inflammation is characterized by the production of various autoantibodies with limited clinical relevance. Recent studies have shown that circulating levels of IgG against integrin αvβ6 are increased in UC patients as compared to Crohn's disease (CD) patients and healthy controls (HC). The present study assessed the diagnostic value of circulating IgG anti-αvβ6 in UC. Sera were prospectively collected from 108 outpatients with UC, 103 patients with CD, and 62 HC, and the levels of IgG anti-αvβ6 were measured using a commercially available ELISA kit. The cut-off for positive results was defined as the 95th percentile of the values of the autoantibodies in HC serum samples. Levels of IgG anti-αvβ6 were significantly higher in UC than in CD patients, including those with colonic localization, and HC. Fifty-six of the 108 (51.8%) UC patients had a positive test whereas only 17/103 (16.5%) patients with CD, and among these, 4/16 (25%) patients with colonic CD, were positive. In UC, there was no statistical difference between patients with IgG anti-αvβ6 positivity and those negative in terms of clinical disease activity, fecal calprotectin values, and disease extent. The sensitivity, specificity, predictive positive value, and predictive negative value of the test to differentiate between UC and CD were 51.9% (C.I.42.4-61.3), 83.5% (C.I. 76.3-90.7), 76.7% (C.I. 67.0-86.4), and 62.3% (C.I. 54.2-70.4) respectively. Our study confirms that anti-αvβ6 antibodies are demonstrable in the serum of the majority of UC patients and suggests the necessity of further research to understand if the anti-αvβ6 antibody determination could have a place in the clinical decision-making of IBD.

Hippo pathway in intestinal diseases: focusing on ferroptosis

The incidence of intestinal diseases, such as inflammatory bowel disease, gastric cancer, and colorectal cancer, has steadily increased over the past decades. The Hippo pathway is involved in cell proliferation, tissue and organ damage, energy metabolism, tumor formation, and other physiologic processes. Ferroptosis is a form of programmed cell death characterized by the accumulation of iron and lipid peroxides. The Hippo pathway and ferroptosis are associated with various intestinal diseases; however, the crosstalk between them is unclear. This review elaborates on the current research on the Hippo pathway and ferroptosis in the context of intestinal diseases. We summarized the connection between the Hippo pathway and ferroptosis to elucidate the underlying mechanism by which these pathways influence intestinal diseases. We speculate that a mutual regulatory mechanism exists between the Hippo pathway and ferroptosis and these two pathways interact in several ways to regulate intestinal diseases.

What is the role of the neutrophil extracellular traps in the cardiovascular disease burden associated with hemodialysis bioincompatibility?

Despite significant progress in dialysis modalities, intermittent renal replacement therapy remains an "unphysiological" treatment that imperfectly corrects uremic disorders and may lead to low-grade chronic inflammation, neutrophil activation, and oxidative stress due to repetitive blood/membrane interactions contributing to the "remaining uremic syndrome" and cardiovascular disease burden of hemodialysis patients. Understanding dialysis bioincompatibility pathways still remains a clinical and biochemical challenge. Indeed, surrogate biomarkers of inflammation including C-reactive protein could not discriminate between all components involved in these complex pathways. A few examples may serve to illustrate the case. Cytokine release during dialysis sessions may be underestimated due to their removal using high-flux dialysis or hemodiafiltration modalities. Complement activation is recognized as a key event of bioincompatibility. However, it appears as an early and transient event with anaphylatoxin level normalization at the end of the dialysis session. Complement activation is generally assumed to trigger leukocyte stimulation leading to proinflammatory mediators' secretion and oxidative burst. In addition to being part of the innate immune response involved in eliminating physically and enzymatically microbes, the formation of Neutrophil Extracellular Traps (NETs), known as NETosis, has been recently identified as a major harmful component in a wide range of pathologies associated with inflammatory processes. NETs result from the neutrophil degranulation induced by reactive oxygen species overproduction via NADPH oxidase and consist of modified chromatin decorated with serine proteases, elastase, bactericidal proteins, and myeloperoxidase (MPO) that produces hypochlorite anion. Currently, NETosis remains poorly investigated as a sensitive and integrated marker of bioincompatibility in dialysis. Only scarce data could be found in the literature. Oxidative burst and NADPH oxidase activation are well-known events in the bioincompatibility phenomenon. NET byproducts such as elastase, MPO, and circulating DNA have been reported to be increased in dialysis patients more specifically during dialysis sessions, and were identified as predictors of poor outcomes. As NETs and MPO could be taken up by endothelium, NETs could be considered as a vascular memory of intermittent bioincompatibility phenomenon. In this working hypothesis article, we summarized the puzzle pieces showing the involvement of NET formation during hemodialysis and postulated that NETosis may act as a disease modifier and may contribute to the comorbid burden associated with dialysis bioincompatibility.

Exosomal miR-127-5p from BMSCs alleviated sepsis-related acute lung injury by inhibiting neutrophil extracellular trap formation

Neutrophil extracellular traps (NETs) play an important role in sepsis-related acute lung injury (ALI). Bone marrow mesenchymal stem cells (BMSCs)-derived exosomes and miRNA are becoming promising agents for the treatment of ALI. The current study aimed to elucidate the mechanism by BMSCs-derived exosomes carrying miR-127-5p inhibiting to the formation of NETs in sepsis-related ALI. We successfully isolated exosomes from BMSCs and confirmed that miR-127-5p was enriched in the exosomes. ALI mice treated with BMSCs-derived exosomes histologically improved, and the release of NETs and inflammatory factors in lung tissue and peripheral blood of mice also decreased compared with LPS group, while the protective effect of exosomes was attenuated after the knockdown of miR-127-5p. Using dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay, we identified CD64 as a direct target of miR-127-5p. Meanwhile, BMSCs-derived exosomes can synergize with anti-CD64 mab in ALI mice to reduce tissue damage, inhibit the release of inflammatory factors and NETs formation. The synergistic effect of exosomes was attenuated when miR-127-5p was down-regulated. These findings suggest that exosomal miR-127-5p derived from BMSCs is a potential therapeutic agent for treatment of sepsis-induced ALI through reducing NETs formation by targeting CD64.

[Levels of neutrophil extracellular traps in neonates with acute respiratory distress syndrome]

OBJECTIVES

To study the changes in cell free-DNA (cf-DNA), a marker of neutrophil extracellular traps (NETs), in neonates with acute respiratory distress syndrome (ARDS), and to evaluate its relationship with the severity and early diagnosis of ARDS.

METHODS

The neonates diagnosed with ARDS in the Affiliated Hospital of Jiangsu University from January 2021 to June 2022 were enrolled in the prospective study. The neonates were divided into mild, moderate, and severe ARDS groups based on the oxygen index (OI) (4≤OI<8, 8≤OI<16, and OI≥16, respectively). The control group was selected from jaundice neonates who were observed in the neonatal department of the hospital during the same period, and they had no pathological factors causing neonatal jaundice. Peripheral blood samples were collected on day 1, day 3, and day 7 after admission for the ARDS group, and on the day of admission for the control group. Serum cf-DNA levels were measured using a fluorescence enzyme-linked immunosorbent assay. Serum interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels were measured using enzyme-linked immunosorbent assay. A Pearson correlation analysis was used to evaluate the correlation of serum cf-DNA levels with serum IL-6 and TNF-α levels.

RESULTS

A total of 50 neonates were enrolled in the ARDS group, including 15 neonates with mild ARDS, 25 with moderate ARDS, and 10 with severe ARDS. Twenty-five neonates were enrolled in the control group. Compared with the control group, the serum levels of cf-DNA, IL-6, and TNF-α in all ARDS groups were significantly increased (P<0.05). Compared with the mild ARDS group, the serum levels of cf-DNA, IL-6, and TNF-α in the moderate and severe ARDS groups were significantly increased (P<0.05), and the increase was more significant in the severe ARDS group (P<0.05). The serum levels of cf-DNA, IL-6, and TNF-α in all ARDS groups were significantly increased on day 3 after admission and significantly decreased on day 7 after admission compared with those on day 1 after admission (P<0.05). The Pearson correlation analysis showed that there was a positive correlation between serum cf-DNA levels and IL-6 levels as well as TNF-α levels in 50 neonates with ARDS (P<0.05).

CONCLUSIONS

There is an excessive expression of NETs in neonates with ARDS, and dynamic monitoring of serum cf-DNA levels has certain clinical value in evaluating the severity and early diagnosis of ARDS in neonates.

Role of Extracellular DNA in Bacterial Response to SOS-Inducing Drugs

The SOS response is a conserved stress response pathway that is triggered by DNA damage in the bacterial cell. Activation of this pathway can, in turn, cause the rapid appearance of new mutations, sometimes called hypermutation. We compared the ability of various SOS-inducing drugs to trigger the expression of RecA, cause hypermutation, and produce elongation of bacteria. During this study, we discovered that these SOS phenotypes were accompanied by the release of large amounts of DNA into the extracellular medium. The release of DNA was accompanied by a form of bacterial aggregation in which the bacteria became tightly enmeshed in DNA. We hypothesize that DNA release triggered by SOS-inducing drugs could promote the horizontal transfer of antibiotic resistance genes by transformation or by conjugation.

The role of neutrophil extracellular traps in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) continues to be one of the most common causes of mortality and morbidity in preterm infants. Although not fully elucidated, studies suggest that prematurity, formula feeding, imbalanced vascular supply, and altered bacterial colonization play major roles in the pathogenesis of NEC. NEC is characterized by increased cytokine release and leukocyte infiltration. Recent data from preterm infants and animal models of NEC suggest that neutrophil extracellular traps (NETs) are released in intestinal tissue. The contribution of NETs in the pathogenesis and/or prevention/treatment of this disease continues to be controversial. Here, we review the available data on NETs release in NEC in human patients and in different NEC models, highlighting their potential contribution to pathology and resolution of inflammation. Here, we review the available data on NETs release in NEC in human patients and the different NEC models, highlighting their potential contribution to pathology or resolution of inflammation.

Advances in research on the effectiveness and mechanism of Traditional Chinese Medicine formulas for colitis-associated colorectal cancer

Inflammatory bowel disease (IBD) can progress into colitis-associated colorectal cancer (CAC) through the inflammation-cancer sequence. Although the mechanism of carcinogenesis in IBD has not been fully elucidated, the existing research indicates that CAC may represent a fundamentally different pathogenesis pattern of colorectal cancer. At present, there is no proven safe and effective medication to prevent IBD cancer. In recent years, Chinese medicine extracts and Chinese medicine monomers have been the subject of numerous articles about the prevention and treatment of CAC, but their clinical application is still relatively limited. Traditional Chinese Medicine (TCM) formulas are widely applied in clinical practice. TCM formulas have demonstrated great potential in the prevention and treatment of CAC in recent years, although there is still a lack of review. Our work aimed to summarize the effects and potential mechanisms of TCM formulas for the prevention and treatment of CAC, point out the issues and limitations of the current research, and provide recommendations for the advancement of CAC research in the future. We discovered that TCM formulas regulated many malignant biological processes, such as inflammation-mediated oxidative stress, apoptosis, tumor microenvironment, and intestinal microecology imbalance in CAC, through a review of the articles published in databases such as PubMed, SCOPUS, Web of Science, Embase, and CNKI. Several major signal transduction pathways, including NF-κB, STAT3, Wnt/β-catenin, HIF-1α, and Nrf2, were engaged. TCM formula may be a promising treatment candidate to control the colitis-cancer transformation, however further high-quality research is required.

Intravital imaging of immune responses in intestinal inflammation

To date, many kinds of immune cells have been identified, but their precise roles in intestinal immunity remain unclear. Understanding the in vivo behavior of these immune cells and their function in gastrointestinal inflammation, including colitis, inflammatory bowel disease, ischemia-reperfusion injury, and neutrophil extracellular traps, is critical for gastrointestinal research to proceed to the next step. Additionally, understanding the immune responses involved in gastrointestinal tumors and tissue repair is becoming increasingly important for the elucidation of disease mechanisms that have been unknown. In recent years, the application of intravital microscopy in gastrointestinal research has provided novel insights into the mechanisms of intestine-specific events including innate and adaptive immunities. In this review, we focus on the emerging role of intravital imaging in gastrointestinal research and describe how to observe the intestines and immune cells using intravital microscopy. Additionally, we outline novel findings obtained by this new technique.

Pathophysiology of Inflammatory Bowel Disease: Innate Immune System

Inflammatory bowel disease (IBD), comprising Crohn's disease (CD) and ulcerative colitis (UC), is a heterogeneous state of chronic intestinal inflammation with no exact known cause. Intestinal innate immunity is enacted by neutrophils, monocytes, macrophages, and dendritic cells (DCs), and innate lymphoid cells and NK cells, characterized by their capacity to produce a rapid and nonspecific reaction as a first-line response. Innate immune cells (IIC) defend against pathogens and excessive entry of intestinal microorganisms, while preserving immune tolerance to resident intestinal microbiota. Changes to this equilibrium are linked to intestinal inflammation in the gut and IBD. IICs mediate host defense responses, inflammation, and tissue healing by producing cytokines and chemokines, activating the complement cascade and phagocytosis, or presenting antigens to activate the adaptive immune response. IICs exert important functions that promote or ameliorate the cellular and molecular mechanisms that underlie and sustain IBD. A comprehensive understanding of the mechanisms underlying these clinical manifestations will be important for developing therapies targeting the innate immune system in IBD patients. This review examines the complex roles of and interactions among IICs, and their interactions with other immune and non-immune cells in homeostasis and pathological conditions.

Emerging Role of Neutrophil Extracellular Traps in Gastrointestinal Tumors: A Narrative Review

Neutrophil extracellular traps (NETs) are extracellular fibrous networks consisting of depolymerized chromatin DNA skeletons with a variety of antimicrobial proteins. They are secreted by activated neutrophils and play key roles in host defense and immune responses. Gastrointestinal (GI) malignancies are globally known for their high mortality and morbidity. Increasing research suggests that NETs contribute to the progression and metastasis of digestive tract tumors, among them gastric, colon, liver, and pancreatic cancers. This article explores the formation of NETs and reviews the role that NETs play in the gastrointestinal oncologic microenvironment, tumor proliferation and metastasis, tumor-related thrombosis, and surgical stress. At the same time, we analyze the qualitative and quantitative detection methods of NETs in recent years and found that NETs are specific markers of coronavirus disease 2019 (COVID-19). Then, we explore the possibility of NET inhibitors for the treatment of digestive tract tumor diseases to provide a new, efficient, and safe solution for the future therapy of gastrointestinal tumors.