Endotoxin-induced autocrine ATP signaling inhibits neutrophil chemotaxis through enhancing myosin light chain phosphorylation

Characteristics of Neonatal Sepsis and Predictive Values of Polyfunctional Assessment of Umbilical Cord Neutrophils Based on Single Cell Proteomic Secretion

The early diagnosis of neonatal sepsis is crucial as it remains a prevalent cause of neonatal mortality. In this study, we conducted an analysis on the clinical data and detection indicators of 22 cases with sepsis and 62 cases without sepsis among neonates. Our findings indicate that the clinical signs observed in neonates with sepsis lack specificity. In addition, the commonly used clinical inflammatory indicators (such as leukocyte count, neutrophil-to-lymphocyte ratio [NLR], C-reactive protein [CRP], procalcitonin) exhibit limited sensitivity and specificity. Furthermore, the current clinical measures lack the assessment of inflammatory factors. Therefore, in order to enhance the accuracy of early sepsis diagnosis in neonates, we have employed a novel microfluidic-based single-cell technology platform for the analysis of 32 cytokines secreted by neutrophils at the individual cell level under various toxin stimulation conditions. We have further investigated and compared the disparities in single-cell protein secretomics between umbilical cord blood neutrophils and healthy adult peripheral neutrophils within an in vitro sepsis model. Our findings indicate that in a resting state UCB neutrophils exhibited lower polyfunctionality compared with healthy adult blood neutrophils, and notable variations in cytokine secretion profiles were detected between the two groups. However, the polyfunctionality of UCB neutrophils significantly increased and surpassed that of healthy adult neutrophils when exposed to alpha-hemolysin or lipopolysaccharide. UCB neutrophils secreted a wide range of chemokines and inflammatory factors, among which GM-CSF and IL-18 were the most significant. Furthermore, we initially categorized the functional subgroups of neutrophils by considering the secretion of five primary cytokines by neutrophils (GM-CSF, IL-18, IL-8, MIP-1β, and MIF). The current study, for the first time, examined in detail the heterogeneity of protein secretion and the functional diversity of UCB neutrophils stimulated by different antigens. Moreover, new insight into neonatal sepsis, early diagnosis, and wider clinical applications of UCB neutrophils are provided by these data.

The landscape of immune dysregulation in pediatric sepsis at a single-cell resolution

Recognizing immune dysregulation as a hallmark of sepsis pathophysiology, leukocytes have attracted major attention of investigation. While adult and pediatric sepsis are clinically distinct, their immunological delineation remains limited. Single cell technologies facilitated the characterization of immune signatures. We tackled to delineate immunological profiles of pediatric sepsis at a single-cell level by analyzing blood samples from six septic children, at both acute and recovery phases, and four healthy children. 16 single-cell transcriptomic datasets were analyzed and compared to adult sepsis dataset. We showed a unique shift in neutrophil subpopulations and functions between acute and recovery phases, along with the regulatory role of resistin. Neutrophil signatures were comparable between adult and pediatric sepsis. Innate-like CD4 T cells were predominantly and uniquely observed in acute phase of pediatric sepsis. Our study serves as a rich source of information about the phenotypic diversity and trajectory of circulating immune cells during pediatric sepsis.

Stomatin promotes neutrophil degranulation and vascular leakage in the early stage after severe burn via enhancement of the intracellular binding of neutrophil primary granules to F-actin

BACKGROUND

The pathophysiology of severe burn injuries in the early stages involves complex emergency responses, inflammatory reactions, immune system activation, and a significant increase in vascular permeability. Neutrophils, crucial innate immune cells, undergo rapid mobilization and intricate pathophysiological changes during this period. However, the dynamic alterations and detailed mechanisms governing their biological behavior remain unclear. Stomatin protein, an essential component of the cell membrane, stabilizes and regulates the membrane and participates in cell signal transduction. Additionally, it exhibits elevated expression in various inflammatory diseases. While Stomatin expression has been observed in the cell and granule membranes of neutrophils, its potential involvement in post-activation functional regulation requires further investigation.

METHODS

Neutrophils were isolated from human peripheral blood, mouse peripheral blood, and mouse bone marrow using the magnetic bead separation method. Flow cytometry was used to assess neutrophil membrane surface markers, ROS levels, and phagocytic activity. The expression of the Stomatin gene and protein was examined using quantitative real-time polymerase chain reaction and western blotting methods, respectively. Furthermore, the enzyme-linked immunosorbent assay was used to evaluate the expression of neutrophil-derived inflammatory mediators (myeloperoxidase (MPO), neutrophil elastase (NE), and matrix metalloproteinase 9 (MMP9)) in the plasma. Images and videos of vascular leakage in mice were captured using in vivo laser confocal imaging technology, whereas in vitro confocal microscopy was used to study the localization and levels of the cytoskeleton, CD63, and Stomatin protein in neutrophils.

RESULTS

This study made the following key findings: (1) Early after severe burn, neutrophil dysfunction is present in the peripheral blood characterized by significant bone marrow mobilization, excessive degranulation, and impaired release and chemotaxis of inflammatory mediators (MPO, NE, and MMP9). (2) After burn injury, expression of both the stomatin gene and protein in neutrophils was upregulated. (3) Knockout (KO) of the stomatin gene in mice partially inhibited neutrophil excessive degranulation, potentially achieved via reduced production of primary granules and weakened binding of primary granules to the cell skeleton protein F-actin. (4) In severely burned mice, injury led to notable early-stage vascular leakage and lung damage, whereas Stomatin gene KO significantly ameliorated lung injury and vascular leakage.

CONCLUSIONS

Stomatin promotes neutrophil degranulation in the early stage of severe burn injury via increasing the production of primary granules and enhancing their binding to the cell skeleton protein F-actin in neutrophils. Consequently, this excessive degranulation results in aggravated vascular leakage and lung injury.

The landscape of immune dysregulation in pediatric sepsis at a single-cell resolution

Recognizing immune dysregulation as a hallmark of sepsis pathophysiology, leukocytes have attracted major attention of investigation. While adult and pediatric sepsis are clinically distinct, their immunological delineation remains limited. Breakthrough of single cell technologies facilitated the characterization of immune signatures. We tackled to delineate immunological profiles of pediatric sepsis at a single-cell level by analyzing blood samples from six septic children, at both acute and recovery phases, and four healthy children. 16 single-cell transcriptomic datasets (96,156 cells) were analyzed and compared to adult sepsis dataset. We showed a unique shift in neutrophil subpopulations and functions between acute and recovery phases, along with examining the regulatory role of resistin. Neutrophil signatures were comparable between adult and pediatric sepsis. Innate-like CD4 T cells were predominantly and uniquely observed in acute phase of pediatric sepsis. Our study provides a thorough and comprehensive understanding of immune dysregulation in pediatric sepsis.

DNase aggravates intestinal microvascular injury in IBD patients by releasing NET-related proteins

Neutrophils accumulate in the inflammatory mucosa of patients with inflammatory bowel disease (IBD), and excessive release of NETs (neutrophil extracellular traps may be one of the important factors that cause IBD progression. However, the specific mechanism underlying vascular injury caused by NETs remains unclear. Immunofluorescence, ELISA, and flow cytometry were used in this study to detect the expression of NETs and DNase in the tissue and peripheral blood samples of patients with IBD. DSS mouse model was used to detect colon injury and vascular permeability. We found that NETs and DNase levels increased in the colon of patients with IBD. We found an increase in the activity of NET-related MPO released by DNase. DNase released NET-related proteins and damaged vascular endothelial cells in vitro. In DSS mouse model, the synchronous increase of DNase and NETs in the colon leads to an increase in vascular injury markers (CD44, sTM). DNase aggravated colon injury and increased vascular permeability in vivo, which was inhibited by gentamicin sulfate (GS). GS does not reduce the expression of DNase, but rather reduces the release of NET-related proteins to protect vascular endothelium by inhibiting DNase activity. MPO and histones synergistically damaged the vascular endothelium, and vascular injury can be improved by their active inhibitors. We further found that H2 O2 is an important substrate for MPO induced vascular damage. In conclusion, in IBD, DNase, and NET levels increased synchronously in the lesion area and released NET-related proteins to damage the vascular endothelium. Therefore, targeting DNase may be beneficial for the treatment of IBD.

ATP breakdown in plasma of children limits the antimicrobial effectiveness of their neutrophils

Neutrophils (PMNs) require extracellular ATP and adenosine (ADO) to fight bacterial infections, which often have life-threatening consequences in pediatric patients. We wondered whether the ATP and ADO levels in the plasma of children change with age and if these changes influence the antimicrobial efficacy of the PMNs of these children. We measured plasma concentrations of ATP and ADO and the activities of the enzymes responsible for the breakdown of these mediators in plasma samples from healthy children and adolescents (n = 45) ranging in age from 0.2 to 15 years. In addition, using blood samples of these individuals, we compared how effective their PMNs were in the phagocytosis of bacteria. In an experimental sepsis model with young (10 days) and adolescent mice (10 weeks), we studied how age influenced the resilience of these animals to bacterial infections and whether addition of ATP could improve the antimicrobial capacity of their PMNs. We found that plasma ATP levels correlated with age and were significantly lower in infants (< 1 year) than in adolescents (12-15 years). In addition, we observed significantly higher plasma ATPase and adenosine deaminase activities in children (< 12 years) when compared to the adolescent population. The activities of these ATP and ADO breakdown processes correlated inversely with age and with the ability of PMNs to phagocytize bacteria. Similar to their human counterparts, young mice also had significantly lower plasma ATP levels when compared to adolescent animals. In addition, we found that mortality of young mice after bacterial infection was significantly higher than that of adolescent mice. Moreover, bacterial phagocytosis by PMNs of young mice was weaker when compared to that of older mice. Finally, we found that ATP supplementation could recover bacterial phagocytosis of young mice to levels similar to those of adolescent mice. Our findings suggest that rapid ATP hydrolysis in the plasma of young children lowers the antimicrobial functions of their PMNs and that this may contribute to the vulnerability of pediatric patients to bacterial infections.

Adenosine in cancer immunotherapy: Taking off on a new plane

As a new pillar of cancer therapy, tumor immunotherapy has brought irreplaceable durable responses in tumors. Considering its low response rate, additional immune regulatory mechanisms will be critical for the development of next-generation immune therapeutics. As a key regulatory mechanism, adenosine (ADO) protects tissues from excessive immune responses, but as a metabolite highly concentrated in tumor microenvironments, extracellular adenosine acts on adenosine receptors (mainly A2A receptors) expressed on MDSCs, Tregs, NK cells, effector T cells, DCs, and macrophages to promote tumor cell escape from immune surveillance by inhibiting the immune response. Amounting preclinical studies have demonstrated the adenosine pathway as a novel checkpoint for immunotherapy. Large number of adenosine pathway targeting clinical trials are now underway, including antibodies against CD39 and CD73 as well as A2A receptor inhibitors. There has been evidence of antitumor efficacy of these inhibitors in early clinical trials among a variety of tumors such as breast cancer, prostate cancer, non-small cell lung cancer, etc. As more clinical trial results are published, the combination of blockade of this pathway with immune checkpoint inhibitors, targeted drugs, traditional chemotherapy medications, radiotherapy and endocrine therapy will provide cancer patients with better clinical outcomes. We would elaborate on the role of CD39-CD73-A2AR pathway in the contribution of tumor microenvironment and the targeting of the adenosinergic pathway for cancer therapy in the review.

Besnoitia besnoiti-induced neutrophil clustering and neutrophil extracellular trap formation depend on P2X1 purinergic receptor signaling

Bovine besnoitiosis is a re-emerging cattle disease caused by the cyst-forming apicomplexan parasite Besnoitia besnoiti. Neutrophil extracellular trap (NET) formation represents an efficient innate immune mechanism of polymorphonuclear neutrophils (PMN) against apicomplexan parasites, including B. besnoiti. PMN purinergic signaling was proposed as a critical factor for NET formation. One important purinergic ligand is ATP, which is recognized as a danger signal and released into the extracellular space acting as an autocrine/paracrine signaling molecule. ATP-driven effects on PMN via the nucleotide P2 receptor family include chemotaxis, reactive oxygen species (ROS) production, and NET formation. So far, data on both PMN ATP concentrations and the role of ATP as a key modulator of purinergic signaling in B. besnoiti tachyzoite-triggered bovine NETosis is scarce. Current data showed that B. besnoiti tachyzoite exposure to bovine PMN neither changed total PMN ATP nor extracellular ATP quantities even though it significantly triggered NET formation. Moreover, B. besnoiti tachyzoite-exposed PMN revealed enhanced oxygen consumption rates (OCR) as quantified by the Seahorse metabolic analyzer. Exogenous supplementation of ATP or non-hydrolizable ATP (ATPγS) led to increased extracellular acidification rates (ECAR) but failed to alter tachyzoite-induced oxidative responses (OCR) in exposed PMN. In addition, exogenous supplementation of ATPγS, but not of ATP, boosted B. besnoiti tachyzoite-induced anchored NET formation. Referring to purinergic signaling, B. besnoiti tachyzoite-triggered anchored NET formation revealed P2X1 purinergic as receptor-dependent since it was blocked by the P2X1 inhibitor NF449 at an IC50 of 1.27 µM. In contrast, antagonists of P2Y2, P2Y6, P2X4, and P2X7 purinergic receptors all failed to affect parasite-driven NETosis. As an interesting finding, we additionally observed that B. besnoiti tachyzoite exposure induced PMN clustering in a P2X1-dependent manner. Thus, we identified P2X1 purinergic receptor as a pivotal molecule for both B. besnoiti tachyzoite-induced PMN clustering and anchored NET formation.

PFKFB3 promotes sepsis-induced acute lung injury by enhancing NET formation by CXCR4hi neutrophils

CXCR4hi neutrophils, which are a subset of neutrophils with high CXCR4 expression, are important contributors to sepsis-induced acute lung injury (ALI). PFKFB3, a key glycolysis gene, plays an essential role in neutrophil inflammatory activation. However, the specific involvement of PFKFB3 in sepsis-induced ALI remains unclear. Here, we observed that PFKFB3 was upregulated in CXCR4hi neutrophils and facilitated sepsis-induced ALI. Mechanistically, we observed that PFKFB3 promoted sepsis-induced ALI by enhancing neutrophil extracellular trap (NET) formation by CXCR4hi neutrophils. Further study indicated that PFKFB3 promoted NET formation by upregulating glycolytic metabolism in CXCR4hi neutrophils. In summary, our study uncovered a new mechanism by which CXCR4hi neutrophils trigger sepsis-induced ALI by promoting NET formation, which is supported by PFKFB3-mediated glycolytic metabolism.

Neutrophil swarming: Is a good offense the best defense?

The phenomenon of swarming has long been observed in nature as a strategic event that serves as a good offense toward prey and predators. Imaging studies have uncovered that neutrophils employ this swarm-like tactic within infected and inflamed tissues as part of the innate immune response. Much of our understanding of neutrophil swarming builds from observations during sterile inflammation and various bacterial, fungal, and parasitic infections of the skin. However, the architecture and function of the skin differ significantly from vital organs where highly specialized microenvironments carry out critical functions. Therefore, the detrimental extent this perturbation may have on organ function remains unclear. In this review, we examine organ-specific swarming within the skin, liver, and lungs, with a detailed focus on swarming within microvascular environments. In addition, we examine potential "swarmulants" that initiate both transient and persistent swarms that have been implicated in disease.

Disseminated intravascular coagulation phenotype is regulated by the TRPM7 channel during sepsis

BACKGROUND

Sepsis is an uncontrolled inflammatory response against a systemic infection that results in elevated mortality, mainly induced by bacterial products known as endotoxins, producing endotoxemia. Disseminated intravascular coagulation (DIC) is frequently observed in septic patients and is associated with organ failure and death. Sepsis activates endothelial cells (ECs), promoting a prothrombotic phenotype contributing to DIC. Ion channel-mediated calcium permeability participates in coagulation. The transient reception potential melastatin 7 (TRPM7) non-selective divalent cation channel that also contains an α-kinase domain, which is permeable to divalent cations including Ca²⁺, regulates endotoxin-stimulated calcium permeability in ECs and is associated with increased mortality in septic patients. However, whether endothelial TRPM7 mediates endotoxemia-induced coagulation is not known. Therefore, our aim was to examine if TRPM7 mediates coagulation during endotoxemia.

RESULTS

The results showed that TRPM7 regulated endotoxin-induced platelet and neutrophil adhesion to ECs, dependent on the TRPM7 ion channel activity and by the α-kinase function. Endotoxic animals showed that TRPM7 mediated neutrophil rolling on blood vessels and intravascular coagulation. TRPM7 mediated the increased expression of the adhesion proteins, von Willebrand factor (vWF), intercellular adhesion molecule 1 (ICAM-1), and P-selectin, which were also mediated by the TRPM7 α-kinase function. Notably, endotoxin-induced expression of vWF, ICAM-1 and P-selectin were required for endotoxin-induced platelet and neutrophil adhesion to ECs. Endotoxemic rats showed increased endothelial TRPM7 expression associated with a procoagulant phenotype, liver and kidney dysfunction, increased death events and an increased relative risk of death. Interestingly, circulating ECs (CECs) from septic shock patients (SSPs) showed increased TRPM7 expression associated with increased DIC scores and decreased survival times. Additionally, SSPs with a high expression of TRPM7 in CECs showed increased mortality and relative risk of death. Notably, CECs from SSPs showed significant results from the AUROC analyses for predicting mortality in SSPs that were better than the Acute Physiology and Chronic Health Evaluation II (APACHE II) and the Sequential Organ Failure Assessment (SOFA) scores.

CONCLUSIONS

Our study demonstrates that sepsis-induced DIC is mediated by TRPM7 in ECs. TRPM7 ion channel activity and α-kinase function are required by DIC-mediated sepsis-induced organ dysfunction and its expression are associated with increased mortality during sepsis. TRPM7 appears as a new prognostic biomarker to predict mortality associated to DIC in SSPs, and as a novel target for drug development against DIC during infectious inflammatory diseases.

Upregulation of TLR4-Dependent ATP Production Is Critical for Glaesserella parasuis LPS-Mediated Inflammation

Glaesserella parasuis (G. parasuis), an important pathogenic bacterium, cause Glässer's disease, and has resulted in tremendous economic losses to the global swine industry. G. parasuis infection causes typical acute systemic inflammation. However, the molecular details of how the host modulates the acute inflammatory response induced by G. parasuis are largely unknown. In this study, we found that G. parasuis LZ and LPS both enhanced the mortality of PAM cells, and at the same time, the level of ATP was enhanced. LPS treatment significantly increased the expressions of IL-1β, P2X7R, NLRP3, NF-κB, p-NF-κB, and GSDMD, leading to pyroptosis. Furthermore, these proteins' expression was enhanced following extracellular ATP further stimulation. When reduced the production of P2X7R, NF-κB-NLRP3-GSDMS inflammasome signaling pathway was inhibited, and the mortality of cells was reduced. MCC950 treatment repressed the formation of inflammasome and reduced mortality. Further exploration found that the knockdown of TLR4 significantly reduced ATP content and cell mortality, and inhibited the expression of p-NF-κB and NLRP3. These findings suggested upregulation of TLR4-dependent ATP production is critical for G. parasuis LPS-mediated inflammation, provided new insights into the molecular pathways underlying the inflammatory response induced by G. parasuis, and offered a fresh perspective on therapeutic strategies.

Inhibition of CD39 unleashes macrophage antibody-dependent cellular phagocytosis against B-cell lymphoma

Redirection of tumor-associated macrophages to eliminate tumor cells holds great promise for overcoming therapeutic resistance to rituximab and other antibody drugs. Here, we determined the expression of ectonucleotidases CD39 and CD73 in diffuse large B-cell lymphoma (DLBCL), and examined the impact of extracellular ATP (eATP) metabolism on macrophage-mediated anti-lymphoma immunity. Immunostaining of tissue microarray samples showed that CD39 (the ecto-enzyme for eATP hydrolysis) was highly expressed in tumors with the non-germinal center B-cell-like (non-GCB) subtype, and to a lesser extent tumors with the GCB subtype. By contrast, the expression of CD73 (the ecto-enzyme for adenosine generation) was undetectable in tumor cells. Pharmacological blockade of CD39 prevented eATP degradation and enhanced engulfment of antibody-coated lymphoma cells by macrophages in a P2X7 receptor-dependent manner, indicating that eATP fueled antibody-dependent cellular phagocytosis (ADCP) activity. Importantly, inhibition of CD39 augmented in vivo anti-lymphoma effects by therapeutic antibodies including rituximab and daratumumab. Furthermore, the addition of a CD39 inhibitor to anti-CD20 and anti-CD47 combination therapy significantly improved survival in a disseminated model of aggressive B-cell lymphoma, supporting the benefit of dual targeting CD39-mediated eATP hydrolysis and CD47-mediated "don't eat me" signal. Together, preventing eATP degradation may be a potential approach to unleash macrophage-mediated anti-lymphoma immunity.

Identification of a forkhead box protein transcriptional network induced in human neutrophils in response to inflammatory stimuli

Introduction

Neutrophils represent the largest proportion of circulating leukocytes and, in response to inflammatory stimuli, are rapidly recruited to sites of infection where they neutralize pathogens.

Methods and results

We have identified a novel neutrophil transcription network induced in response to inflammatory stimuli. We performed the first RNAseq analysis of human neutrophils exposed to lipopolysaccharide (LPS), followed by a meta-analysis of our dataset and previously published studies of LPS-challenged neutrophils. This revealed a robustly enhanced transcriptional network driven by forkhead box (FOX) transcription factors. The network is enriched in genes encoding proinflammatory cytokines and transcription factors, including MAFF and ATF3, which are implicated in responses to stress, survival and inflammation. Expression of transcription factors FOXP1 and FOXP4 is induced in neutrophils exposed to inflammatory stimuli, and potential FOXP1/FOXP4 binding sites were identified in several genes in the network, all located in chromatin regions consistent with neutrophil enhancer function. Chromatin immunoprecipitation (ChIP) assays in neutrophils confirmed enhanced binding of FOXP4, but not FOXP1, to multiple sites in response to LPS. Binding to numerous motifs and transactivation of network genes were also observed when FOXP proteins were transiently expressed in HEK293 cells. In addition to LPS, the transcriptional network is induced by other inflammatory stimuli, indicating it represents a general neutrophil response to inflammation.

Discussion

Collectively, these findings reveal a role for the FOXP4 transcription network as a regulator of responses to inflammatory stimuli in neutrophils.

Contribution of large-pore channels to inflammation induced by microorganisms

Plasma membrane ionic channels selectively permeate potassium, sodium, calcium, and chloride ions. However, large-pore channels are permeable to ions and small molecules such as ATP and glutamate, among others. Large-pore channels are structures formed by several protein families with little or no evolutionary linkages including connexins (Cxs), pannexins (Panxs), innexin (Inxs), unnexins (Unxs), calcium homeostasis modulator (CALHMs), and Leucine-rich repeat-containing 8 (LRRC8) proteins. Large-pore channels are key players in inflammatory cell response, guiding the activation of inflammasomes, the release of pro-inflammatory cytokines such as interleukin-1 beta (IL-1ß), and the release of adenosine-5'-triphosphate (ATP), which is considered a danger signal. This review summarizes our current understanding of large-pore channels and their contribution to inflammation induced by microorganisms, virulence factors or their toxins.

PD-L1 negatively regulates antifungal immunity by inhibiting neutrophil release from bone marrow

Programmed death ligand 1 (PD-L1) has been shown to be inducibly expressed on neutrophils to suppress host immunity during polymicrobial sepsis, virus and parasite infections. However, the role of PD-L1 on neutrophil-mediated antifungal immunity remains wholly unknown. Here, we show that the expression of PD-L1 on murine and human neutrophils was upregulated upon the engagement of C-type lectin receptor Dectin-1 with its ligand β-glucans, exposed on fungal pathogen Candida albicans yeast. Moreover, β-glucan stimulation induced PD-L1 translocation into nucleus to regulate the production of chemokines CXCL1 and CXCL2, which control neutrophil mobilization. Importantly, C. albicans infection-induced expression of PD-L1 leads to neutrophil accumulation in bone marrow, through mediating their autocrine secretion of CXCL1/2. Furthermore, neutrophil-specific deficiency of PD-L1 impaired CXCL1/2 secretion, which promoted neutrophil migration from bone marrow into the peripheral circulation, thereby conferring host resistance to C. albicans infection. Finally, either PD-L1 blockade or pharmacological inhibition of PD-L1 expression significantly increased neutrophil release from bone marrow to enhance host antifungal immunity. Our data together indicate that activation of Dectin-1/PD-L1 cascade by β-glucans inhibits neutrophil release from bone marrow reserve, contributing to the negative regulation of antifungal innate immunity, which functions as a potent immunotherapeutic target against life-threatening fungi infections.

Helicobacter pylori-infected human neutrophils exhibit impaired chemotaxis and a uropod retraction defect

Helicobacter pylori is a major human pathogen that colonizes the gastric mucosa and plays a causative role in development of peptic ulcers and gastric cancer. Neutrophils are heavily infected with this organism in vivo and play a prominent role in tissue destruction and disease. Recently, we demonstrated that H. pylori exploits neutrophil plasticity as part of its virulence strategy eliciting N1-like subtype differentiation that is notable for profound nuclear hypersegmentation. We undertook this study to test the hypothesis that hypersegmentation may enhance neutrophil migratory capacity. However, EZ-TAXIScan™ video imaging revealed a previously unappreciated and progressive chemotaxis defect that was apparent prior to hypersegmentation onset. Cell speed and directionality were significantly impaired to fMLF as well as C5a and IL-8. Infected cells oriented normally in chemotactic gradients, but speed and direction were impaired because of a uropod retraction defect that led to cell elongation, nuclear lobe trapping in the contracted rear and progressive narrowing of the leading edge. In contrast, chemotactic receptor abundance, adhesion, phagocytosis and other aspects of cell function were unchanged. At the molecular level, H. pylori phenocopied the effects of Blebbistatin as indicated by aberrant accumulation of F-actin and actin spikes at the uropod together with enhanced ROCKII-mediated phosphorylation of myosin IIA regulatory light chains at S19. At the same time, RhoA and ROCKII disappeared from the cell rear and accumulated at the leading edge whereas myosin IIA was enriched at both cell poles. These data suggest that H. pylori inhibits the dynamic changes in myosin IIA contractility and front-to-back polarity that are essential for chemotaxis. Taken together, our data advance understanding of PMN plasticity and H. pylori pathogenesis.

Adenosine, Schizophrenia and Cancer: Does the Purinergic System Offer a Pathway to Treatment?

For over a century, a complex relationship between schizophrenia diagnosis and development of many cancers has been observed. Findings from epidemiological studies are mixed, with reports of increased, reduced, or no difference in cancer incidence in schizophrenia patients. However, as risk factors for cancer, including elevated smoking rates and substance abuse, are commonly associated with this patient population, it is surprising that cancer incidence is not higher. Various factors may account for the proposed reduction in cancer incidence rates including pathophysiological changes associated with disease. Perturbations of the adenosine system are hypothesized to contribute to the neurobiology of schizophrenia. Conversely, hyperfunction of the adenosine system is found in the tumor microenvironment in cancer and targeting the adenosine system therapeutically is a promising area of research in this disease. We outline the current biochemical and pharmacological evidence for hypofunction of the adenosine system in schizophrenia, and the role of increased adenosine metabolism in the tumor microenvironment. In the context of the relatively limited literature on this patient population, we discuss whether hypofunction of this system in schizophrenia, may counteract the immunosuppressive role of adenosine in the tumor microenvironment. We also highlight the importance of studies examining the adenosine system in this subset of patients for the potential insight they may offer into these complex disorders.

Glycolysis, monocarboxylate transport, and purinergic signaling are key events in Eimeria bovis-induced NETosis

The protozoan parasite Eimeria bovis is the causative agent of bovine coccidiosis, an enteric disease of global importance that significantly affects cattle productivity. Previous studies showed that bovine NETosis—an important early host innate effector mechanism of polymorphonuclear neutrophil (PMN)—is elicited by E. bovis stages. So far, the metabolic requirements of E. bovis-triggered NET formation are unknown. We here studied early glycolytic and mitochondrial responses of PMN as well as the role of pH, distinct metabolic pathways, P2 receptor-mediated purinergic signaling, and monocarboxylate transporters 1 and 2 (MCT1, MCT2) in E. bovis sporozoite-induced NET formation. Seahorse-based experiments revealed a rapid induction of both neutrophil oxygen consumption rate (OCR) and early glycolytic responses, thereby reflecting immediate PMN activation and metabolic changes upon confrontation with sporozoites. The impact of these metabolic changes on NET formation was studied via chemical inhibition experiments targeting glycolysis and energy generation by the use of 2-fluor-2-deoxy-D-glucose (FDG), 6-diazo-5-oxo-L-norleucin (DON), sodium dichloroacetate (DCA), oxythiamine (OT), sodium oxamate (OXA), and oligomycin A (OmA) to block glycolysis, glutaminolysis, pyruvate dehydrogenase kinase, pyruvate dehydrogenase, lactate dehydrogenase, and mitochondrial ATP-synthase, respectively. Overall, sporozoite-induced NET formation was significantly diminished via PMN pretreatments with OmA and OXA, thereby indicating a key role of ATP- and lactate-mediated metabolic pathways. Consequently, we additionally studied the effects of extracellular pH, MCT1, MCT2, and purinergic receptor inhibitors (AR-C141900, AR-C155858, theobromine, and NF449, respectively). Pretreatment with the latter inhibitors led to blockage of sporozoite-triggered DNA release from exposed bovine PMN. This report provides first evidence on the pivotal role of carbohydrate-related metabolic pathways and purinergic receptors being involved in E. bovis sporozoite-induced NETosis.

Contribution of prognostic ferroptosis-related subtypes classification and hub genes of sepsis

BACKGROUND

Sepsis in patients is a great threat to human health due to its high incidence rate, its rapid and unpredictable progression, as well as it is difficult to treat, and it has poor prognosis. Ferroptosis is a newly discovered type of cell death characterized by the iron-dependent peroxide aggregation. Furthermore, ferroptosis is different from other forms of cell death, namely apoptosis, necrosis, pyroptosis and autophagy. Our study investigated the role of ferroptosis-related genes in sepsis.

METHODS

The GSE65682 dataset from the Gene Expression Omnibus (GEO) database was used to screen ferroptosis-related genes associated with sepsis, and the GSE134347 dataset for the external validation of selected hub genes. The univariate Cox regression analysis, Kaplan-Meier (K-M) survival analysis and weighted gene co-expression network analysis (WGCNA) were used to identify hub genes. Evaluation of the immune cell infiltration in sepsis was used to explain the immune heterogeneity among the cell subtypes. Gene set variation analysis (GSVA) and transcriptional regulatory analysis of selected hub genes further elucidated the probable mechanism of ferroptosis-related genes associated with prognosis in sepsis. Finally, we constructed a competing endogenous RNA (ceRNA) network model.

RESULTS

A total of 479 RNA-seq data points were used for analysis, including 365 samples from patients who survived sepsis and 114 samples from patients who succumbed to sepsis from the available GSE65682 dataset. Consequently, the univariate Cox regression analysis and consensus clustering analysis divide all 479 sepsis samples into two clusters of "survivals" vs. "non-survivals". Following complex analysis were identified as the most important ferroptosis-related genes. Indeed, the WGCNA and K-M analyses associated the expression patterns of NEDD4L and SIAH2 hub genes as the best prognosis for the survival of sepsis (p < 0.05). The expression trend was also consistent with the survival trend of the NEDD4L and SIAH2 hub genes by the external validation of GSE134347 (p < 0.05). Immune cell infiltration analysis indicated that the types and numbers of different immune cells vary among different subtypes and NEDD4L and SIAH2 hub genes. For example, NEDD4L and SIAH2 gene expression had a positive correlation with M0 macrophages and a negative correlation with neutrophils (p > 0.05). Finally, analysis of two hub genes and transcription factors (TFs) showed that 71 TFs were predicted to be related to NEDD4L while 64 TFs to SIAH2 by the Cistrome DB online database.

CONCLUSION

We suggest that NEDD4L and SIAH2 hub genes are involved in the ferroptosis-associated sepsis. The pattern of NEDD4L and SIAH2 expression in patients undergoing sepsis may have prognostic potential for the severity of sepsis and eventually for patients' survival.

NcRNAs-mediated P2RX1 expression correlates with clinical outcomes and immune infiltration in patients with breast invasive carcinoma

The development of novel treatments for breast invasive carcinoma (BC) has been stagnant. P2RX1, a member of the purinergic receptor family, has been found to have a prognostic impact in several tumors. Therefore, we analyzed the expression pattern of P2RX1 in pan-cancers including BC and its impact on survival and found that the expression level of P2RX1 was lower in BC compared with para-cancerous tissues, and higher P2RX1 expression indicated better prognoses. But real-time quantitative reverse transcription PCR (RT-qPCR) and Western blot detected that the P2RX1 expression in normal mammary epithelial cells was lower than that in tumor cells. Then we comprehensively analyzed the regulatory mechanism and protein-protein interaction network, and found that P2RX1 was significantly positively linked with immune cell infiltration and immune checkpoints.

Effects of Hormone, NEFA and SCFA on the Migration of Neutrophils and the Formation of Neutrophil Extracellular Traps in Dairy Cows

Simple Summary

Perinatal dairy cows face the challenge of maintaining the resilience of defense against invading pathogens. During the perinatal period, hormonal or metabolic changes cause the decline of immune function of dairy cows and further lead to varying degrees of immunosuppression. The results of this study indicate that, hormones, nonesterified fatty acids (NEFAs) and short-chain fatty acids (SCFAs) can regulate neutrophil migration and the NETs formation of dairy cows in vitro. These results help to further explain the effects of changes in hormone secretion and metabolites on immunosuppression and the increased risk of disease in perinatal dairy cows.

Abstract

Polymorphonuclear neutrophils (PMN) are the first line of defense against the invasion of foreign pathogenic microorganisms and play an essential role in the immune system of dairy cows. The changes in hormone secretion and metabolites of dairy cows during the perinatal period are the key factors that cause immunosuppression and increased risk of diseases. However, the effects of the hormone, nonesterified fatty acid (NEFA), and short-chain fatty acid (SCFA) on the transmammary epithelial migration of dairy cows and the formation of neutrophil extracellular traps (NETs) have rarely been studied. This study explored the effects of hormones, NEFAs and SCFAs on the neutrophil migration and NETs formation of dairy cows in vitro. It was found that P₄ and Ac can regulate the transepithelial migration of PMN; SA and Pr can regulate the formation of NETs; E₂, OA and Bt can regulate PMN transepithelial migration and NET formation. These results help to further explain the effects of changes in hormone secretion and metabolites on immunosuppression and the increased risk of disease in perinatal dairy cows.

Pannexin Channel Regulation of Cell Migration: Focus on Immune Cells

The role of Pannexin (PANX) channels during collective and single cell migration is increasingly recognized. Amongst many functions that are relevant to cell migration, here we focus on the role of PANX-mediated adenine nucleotide release and associated autocrine and paracrine signaling. We also summarize the contribution of PANXs with the cytoskeleton, which is also key regulator of cell migration. PANXs, as mechanosensitive ATP releasing channels, provide a unique link between cell migration and purinergic communication. The functional association with several purinergic receptors, together with a plethora of signals that modulate their opening, allows PANX channels to integrate physical and chemical cues during inflammation. Ubiquitously expressed in almost all immune cells, PANX1 opening has been reported in different immunological contexts. Immune activation is the epitome coordination between cell communication and migration, as leukocytes (i.e., T cells, dendritic cells) exchange information while migrating towards the injury site. In the current review, we summarized the contribution of PANX channels during immune cell migration and recruitment; although we also compile the available evidence for non-immune cells (including fibroblasts, keratinocytes, astrocytes, and cancer cells). Finally, we discuss the current evidence of PANX1 and PANX3 channels as a both positive and/or negative regulator in different inflammatory conditions, proposing a general mechanism of these channels contribution during cell migration.

CD44/ERM/F-actin complex mediates targeted nuclear degranulation and excessive neutrophil extracellular trap formation during sepsis

Neutrophils release neutrophil extracellular traps (NETs) to capture and kill pathogens, but excessive NET release can damage the surrounding tissues. Myeloperoxidase (MPO) and neutrophil elastase (NE) are thought to be important in promoting histone depolymerization and DNA breakage in the nucleus. However, the detailed path by which MPO and NE enter the nucleus is unknown. In the present study, we observed that delayed fusion of azurophilic granules with the nuclear membrane 15–20 min after extracellular degranulation in activated neutrophils. In a subsequent experiment, we further demonstrated that this fusion leads to MPO entry into the nucleus and promotes nuclear histone depolymerization and DNA breakage, a process called ‘targeted nuclear degranulation’. This process can be effectively inhibited by dexamethasone and accompanied by the continuous low levels of MPO in the nucleus after PMA stimulation. Meanwhile, we found that ‘targeted nuclear degranulation’ is dependent on the CD44 translocation and subsequent redistribution of CD44 / ERM (Ezrin/Radixin/Moesin) / F‐actin complexes, which guides the movement of azurophilic granules towards the nucleus. Application of ERM phosphorylation inhibitors and importin activity inhibitors significantly reduced the complexes formation and redistribution. Taken together, these findings indicate for the first time that delayed ‘targeted nuclear degranulation’ after neutrophil activation is a key mechanism of NET formation. CD44/ERM/F‐actin complex mediates this process, which providing targets with promising prospects for the precise regulation of NET formation.

The Role of Connexin Hemichannels in Inflammatory Diseases

The connexin protein family consists of approximately 20 members, and is well recognized as the structural unit of the gap junction channels that perforate the plasma membranes of coupled cells and, thereby, mediate intercellular communication. Gap junctions are assembled by two preexisting hemichannels on the membranes of apposing cells. Non-junctional connexin hemichannels (CxHC) provide a conduit between the cell interior and the extracellular milieu, and are believed to be in a protectively closed state under physiological conditions. The development and characterization of the peptide mimetics of the amino acid sequences of connexins have resulted in the development of a panel of blockers with a higher selectivity for CxHC, which have become important tools for defining the role of CxHC in various biological processes. It is increasingly clear that CxHC can be induced to open by pathogen-associated molecular patterns. The opening of CxHC facilitates the release of damage-associated molecular patterns, a class of endogenous molecules that are critical for the pathogenesis of inflammatory diseases. The blockade of CxHC leads to attenuated inflammation, reduced tissue injury and improved organ function in human and animal models of about thirty inflammatory diseases and disorders. These findings demonstrate that CxHC may contribute to the intensification of inflammation, and serve as a common target in the treatments of various inflammatory diseases. In this review, we provide an update on the progress in the understanding of CxHC, with a focus on the role of these channels in inflammatory diseases.

Dysfunction of low-density neutrophils in peripheral circulation in patients with sepsis

Low-density neutrophils (LDNs) have been described in tumors and various autoimmune diseases, where they exhibit immune dysfunction and alter disease progression. Nevertheless, LDNs have been rarely reported in sepsis. We studied sepsis patients admitted to the intensive care unit. Wright-Giemsa stain assay and Transmission electron microscopy were performed to detect the morphology of neutrophils. Flow cytometry was used to analyze the number and function of LDNs. Concentration of cytokines was measured using ELISA. Neutrophil chemotaxis was examined using an under-agarose chemotaxis model. We found that LDNs were significantly elevated in patients with sepsis. Phenotypes and morphological characteristics suggest that LDNs may be formed by mixtures of neutrophils at various maturation stages. In vitro experiments showed that LDN formation was closely associated with neutrophil degranulation. We preliminarily discussed changes in immune function in LDNs. Compared with high-density neutrophils, expression levels of CXC chemokine receptor 4 on LDN surfaces were increased, phagocytotic capacity was decreased, and life span was prolonged. The chemotactic ability of LDNs was significantly reduced, possibly related to the increased expression of P2X1. These data suggest that LDNs are essential components of neutrophils in sepsis. To clarify the source and dysfunction mechanism of LDN in sepsis may be helpful for the diagnosis and treatment of sepsis in the future.

Long noncoding RNA GSEC promotes neutrophil inflammatory activation by supporting PFKFB3-involved glycolytic metabolism in sepsis

Metabolic reprogramming is a hallmark of neutrophil activation in sepsis. LncRNAs play important roles in manipulating cell metabolism; however, their specific involvement in neutrophil activation in sepsis remains unclear. Here we found that 11 lncRNAs and 105 mRNAs were differentially expressed in three transcriptome datasets (GSE13904, GSE28750, and GSE64457) of gene expression in blood leukocytes and neutrophils of septic patients and healthy volunteers. After Gene Ontology biological process analysis and lncRNA-mRNA pathway network construction, we noticed that GSEC lncRNA and PFKFB3 were co-expressed and associated with enhanced glycolytic metabolism. Our clinical observations confirmed the expression patterns of GSEC lncRNA and PFKFB3 genes in neutrophils in septic patients. Performing in vitro experiments, we found that the expression of GSEC lncRNA and PFKFB3 was increased when neutrophils were treated with inflammatory stimuli. Knockdown and overexpression experiments showed that GSEC lncRNA was essential for mediating PFKFB3 mRNA expression and stability in neutrophil-like dHL-60 cells. In addition, we found that GSEC lncRNA-induced PFKFB3 expression was essential for mediating dHL-60 cell inflammatory cytokine expression. Performing mechanistic experiments, we found that glycolytic metabolism with PFKFB3 involvement supported inflammatory cytokine expression. In summary, our study uncovers a mechanism by which GSEC lncRNA promotes neutrophil inflammatory activation in sepsis by supporting glycolytic metabolism with PFKFB3.

Mitochondrial calcium uniporter affects neutrophil bactericidal activity during Staphylococcus aureus infection

Neutrophils simultaneously restrict Staphylococcus aureus dissemination and facilitate bactericidal activity during infection through the formation of neutrophil extracellular traps (NETs). Neutrophils that produce higher levels of mitochondrial superoxide undergo enhanced terminal NET formation (suicidal NETosis) in response to S. aureus; however, mechanisms regulating mitochondrial homeostasis upstream of neutrophil antibacterial processes are not fully resolved. Here, we demonstrate that mitochondrial calcium uptake 1 (MICU1)-deficient (MICU1^-/-) neutrophils accumulate higher levels of calcium and iron within the mitochondria in a mitochondrial calcium uniporter (MCU)-dependent manner. Corresponding with increased ion flux through the MCU, mitochondrial superoxide production is elevated, thereby increasing the propensity for MICU1^-/- neutrophils to undergo suicidal NETosis rather than primary degranulation in response to S. aureus. Increased NET formation augments macrophage killing of bacterial pathogens. Similarly, MICU1^-/- neutrophils alone are not more antibacterial towards S. aureus, but rather enhanced suicidal NETosis by MICU1^-/- neutrophils facilitates increased bactericidal activity in the presence of macrophages. Similarly, mice with a deficiency in MICU1 restricted to cells expressing LysM exhibit lower bacterial burdens in the heart with increased survival during systemic S. aureus infection. Coinciding with the decrease in S. aureus burdens, MICU1^-/- neutrophils in the heart produced higher levels of mitochondrial superoxide and undergo enhanced suicidal NETosis. These results demonstrate that ion flux by the MCU affects the antibacterial function of neutrophils during S. aureus infection.

Splenic T lymphocytes induce the formation of immunosuppressive neutrophils through IFN-γ in sepsis

BACKGROUND

Despite many advances in treatment, the prognosis of patients with sepsis still remains poor. Polymorphonuclear leukocytes (PMNs) are the first line of defense against infection. This study aimed to reveal the reason and mechanism of the production of PD-L1⁺ PMNs in sepsis.

METHODS

Cecal ligation and perforation mouse model was established to simulate sepsis. And PMNs were treated for 4 h, 12 h with or without 100 ng/mL (IFN-γ) for further gene sequencing. PD-L1, PD-1, Ly6G, and CD3 were detected by multiplexed immunofluorescence. In addition, expression of PD-L1 and function of PMNs were assessed by flow cytometry. Serum and cell culture supernatant were measured with ELISA assays. Western blot was used to verify the JAK2/STAT1 pathway.

RESULTS

Our study demonstrates that PMNs are the main immune cells with high expression of PD-L1 during sepsis, and these cells, therefore, play a critical role in immunosuppression. In vivo studies demonstrated a specific interaction between PD-L1⁺ PMNs and PD-1⁺ T cells. In vitro studies further demonstrated that IFN-γ induced the production of PD-L1⁺ PMNs through the JAK2/STAT1 pathway. In addition, Fedratinib, an inhibitor of Jak2, was shown to significantly reduce the expression of PD-L1 in neutrophils.

CONCLUSIONS

These data demonstrate that secretion of IFN-γ by splenic T lymphocytes induces the production of PD-L1 + PMNs through the JAK2/STAT1 pathway in sepsis.

Neutrophil-derived heparin binding protein triggers vascular leakage and synergizes with myeloperoxidase at the early stage of severe burns (With video)

Background

Burn shock caused by vascular leakage is one of the main causes of high mortality in severe burn injury. However, the pathophysiological mechanism of vascular leakage is still unclear. The purpose of this study was to explore the molecular mechanism of vascular leakage in the early stage of severe burn and provide a new target for the treatment of severe burns.

Methods

Neutrophils were isolated from human peripheral blood by magnetic beads sorting. ELISA was used to detect neutrophil-derived granule proteins and glycocalyx injury products in plasma. The vascular leakage and neutrophil movement were assessed by in vivo laser confocal imaging in mice, and high-quality video were provided.. Adhesion-related molecules were investigated by qRT-PCR. The damage to glycocalyx of mice vascular endothelial cells was observed by transmission electron microscope and scanning electron microscope. Proteomic analysis, flow cytometry and immunofluorescence were used to further study the relationship between human peripheral blood neutrophil-derived hypochlorite (HOCl) and CD44 of human vascular endothelial cells.

Results

In this study, we found that rapidly increasing activated neutrophils secrete heparin binding protein (HBP) and myeloperoxidase (MPO) after severe burn injury. Increased HBP triggers vascular leakage with synergy of MPO, results in systemic edema and burn shock. Furthermore, we found that the MPO catalytic product HOCl but not MPO triggers CD44 extracellular domain shedding from vascular endothelial cells to damage the glycocalyx. Damage to the glycocalyx results in firm adhesion of neutrophils and increases vascular leakage. However, MPO inhibitors partially protect the glycocalyx of vascular endothelial cells. The combination of HBP and MPO inhibitors markedly reduces vascular leakage and systemic edema in the early stage of severe burns.

Conclusions

Taken together, these data reveal that neutrophil-derived HBP and MPO play an important synergies role in triggering vascular leakage at the early stage of severe burns. Targeted intervention in these two biomolecules may introduce new strategies for helping to reduce large amount of fluid loss and subsequent burn shock.

β-Hydroxybutyrate impairs neutrophil migration distance through activation of a protein kinase C and myosin light chain 2 signaling pathway in ketotic cows

Ketosis in dairy cows often occurs in the peripartal period and is accompanied by immune dysfunction. High concentrations of β-hydroxybutyrate (BHB) in peripheral blood during ketosis are closely related to the impairment of polymorphonuclear neutrophil (PMN) chemotaxis and contribute to immune dysfunction. The specific effect of BHB on PMN chemotaxis in dairy cows and the underlying molecular mechanisms are unclear. Here, 30 multiparous cows (within 3 wk postpartum) classified based on serum BHB as control (n = 15, BHB <0.6 mM) or clinically ketotic (n = 15, BHB >3.0 mM) were used. Blood samples were collected before feeding, and the isolated PMN were treated with platelet-activating factor for 0.5 h to activate their migration. Scanning electron microscopy revealed a longer tail in PMN of ketotic cows. In addition, the phosphorylation and transcription levels of myosin light chain 2 (MLC2) increased in PMN of ketotic cows. Polymorphonuclear neutrophils from control dairy cows were incubated with 3.0 mM BHB for different times in vitro, and 6 h was selected as the proper duration of BHB stimulation according to its inhibition effect on PMN migration using an under-agarose PMN chemotaxis model. Similarly, BHB stimulation in vitro resulted in inhibition of migration distance and deviation of migration direction of PMN, as well as a longer tail in morphology in the scanning electron microscope data, suggesting that BHB-induced PMN migration inhibition may be mediated by impairing the trailing edge contraction. To confirm this hypothesis, sotrastaurin (Sotra)-a specific inhibitor of protein kinase C (PKC), which is the core regulator of cell contraction-was used with or without BHB treatment in vitro. Sotra was pretreated 0.5 h before BHB treatment. Accordingly, BHB treatment increased the phosphorylation level of PKC and MLC2, the protein abundance of RhoA and rho-kinase 1 (ROCK1), and the mRNA abundance of PRKCA, MYL2, RHOA, and ROCK1 in PMN. In contrast, these effects of BHB on PMN were dampened by Sotra. As demonstrated by immunofluorescence experiments in vitro, the BHB-induced inhibition of trailing edge contraction of PMN was relieved by Sotra. In addition, Sotra also dampened the effects of BHB on PMN migration in vitro. Furthermore, as verified by in vivo experiments, compared with the control cows, both abundance and activation of PKC signaling were enhanced in PMN of ketotic cows. Overall, the present study revealed that high concentrations of blood BHB impaired PMN migration distance through inhibition of the trailing edge contraction, mediated by enhancing the activation of PKC-MLC2 signaling. These findings help explain the dysfunctional immune state in ketotic cows and provide information on the pathogenesis of infectious diseases secondary to ketosis.

Multiomics analysis identifies key genes and pathways related to N6-methyladenosine RNA modification in ovarian cancer

Aims: To explore the pathways and target genes related to N6-methyladenosine (m⁶A) methylation in ovarian cancer and their effect on patient prognosis. Methods & materials: The Cancer Genome Atlas was used to screen genes related to m⁶A regulators in terms of gene expression, mutation and copy number variation. These genes were subjected to pathway enrichment analysis. Prognosis-related genes were screened and involved in risk signature construction. Immunohistochemistry was used for verification. Results: We obtained 1408 genes dysregulated in parallel to m⁶A regulators, which were mainly involved in the platelet activation pathway. The m⁶A-related signature was constructed based on the expression of four prognosis-related genes (RPS6KA2, JUNB, HNF4A and P2RX1). Conclusion: This work provides new insights into the mechanism of m⁶A methylation in ovarian cancer.

Neutrophils: fast and furious-the nucleotide pathway

Nucleotide signaling is a key element of the neutrophil activation pathway. Neutrophil recruitment and migration to injured tissues is guided by purinergic receptor sensitization, mostly induced by extracellular adenosine triphosphate (ATP) and its hydrolysis product, adenosine (ADO), which is primarily produced by the CD39-CD73 axis located at the neutrophil cell surface. In inflammation unrelated to cancer, neutrophil activation via purinergic signaling aims to eliminate antigens and promote an immune response with minimal damage to healthy tissues; however, an antagonistic response may be expected in tumors. Indeed, alterations in purinergic signaling favor the accumulation of extracellular ATP and ADO in the microenvironment of solid tumors, which promote tumor progression by inducing cell proliferation, angiogenesis, and escape from immune surveillance. Since neutrophils and their N1/N2 polarization spectrum are being considered new components of cancer-related inflammation, the participation of purinergic signaling in pro-tumor activities of neutrophils should also be considered. However, there is a lack of studies investigating purinergic signaling in human neutrophil polarization and in tumor-associated neutrophils. In this review, we discussed the human neutrophil response elicited by nucleotides in inflammation and extrapolated its behavior in the context of cancer. Understanding these mechanisms in cancerous conditions may help to identify new biological targets and therapeutic strategies, particularly regarding tumors that are refractory to traditional chemo- and immunotherapy.

A novel computer vision-based assessment of neutrophil chemotaxis in patients with severe infection

Objectives

To evaluate the value of chemotactic function of neutrophils in patients with severe infections.

Methods

A computer vision‐based cellular chemotaxis analysis platform was established for the dynamic assessment of neutrophil chemotaxis. Fifty‐three patients in the intensive care unit were eligible for the study. In parallel, 142 healthy volunteers were recruited to detect and establish the normal values for chemotactic function. Four chemotactic function indicators were determined–chemotaxis distance (CD), chemotaxis cell ratio (CCR), chemotaxis index (CI) and maximum speed of chemotaxis (V_max). The chemotaxis function scores (CFS) were calculated for further correlation analysis with clinical data.

Results

The normal ranges of indicators were established as CD ≥ 1755.85 µm, CCR ≥ 3.34%, CI ≥ 39.63, V_max ≥ 14.63 µm min⁻¹ and CFS ≥ 15. We found that the chemotactic function of neutrophils in patients suffering from infections was significantly impaired. The mean values of CD, CCR, CI, V_max and CFS were 1452.8 µm (P < 0.0001), 3.1% (P < 0.0001), 34.5 (P < 0.0001), 12.2 µm min⁻¹ (P < 0.0001) and 9 (P < 0.0001), respectively. CD and CFS were significantly negatively correlated with the APACHE II score (rCD = −0.55, rCFS = −0.39), SOFA score (rCD = −0.68, rCFS = −0.56), procalcitonin concentration (rCD = −0.60, rCFS = −0.5) and the expression of P2RX1 (rCD = −0.76, rCFS = −0.56), respectively.

Conclusions

CD, CCR, CI and V_max can well reflect the neutrophil chemotactic function in patients with severe infections. CFS systematically indicated neutrophil function and has promising clinical application prospects.

On the mechanism of anti-CD39 immune checkpoint therapy

With the coming of age of cancer immunotherapy, the search for new therapeutic targets has led to the identification of immunosuppressive adenosine as an important regulator of antitumor immunity. This resulted in the development of selective inhibitors targeting various components of the adenosinergic pathway, including small molecules antagonists targeting the high affinity A2A adenosine receptor and low affinity A2B receptor, therapeutic monoclonal antibodies (mAbs) and small molecules targeting CD73 and therapeutic mAbs targeting CD39. As each regulator of the adenosinergic pathway present non-overlapping biologic functions, a better understanding of the mechanisms of action of each targeted approach should accelerate clinical translation and improve rational design of combination treatments. In this review, we discuss the potential mechanisms-of-action of anti-CD39 cancer therapy and potential toxicities that may emerge from sustained CD39 inhibition. Caution should be taken, however, in extrapolating data from gene-targeted mice to patients treated with blocking anti-CD39 agents. As phase I clinical trials are now underway, further insights into the mechanism of action and potential adverse events associated with anti-CD39 therapy are anticipated in coming years.

Propofol Ameliorates Exaggerated Human Neutrophil Activation in a LPS Sepsis Model

Background

Sepsis is a leading cause of morbidity and mortality worldwide. Many patients suffering from sepsis are treated on intensive care units and many of them require mechanical ventilation under sedation or general anesthesia. Propofol, a drug used for these purposes, is known to interact with polymorphonuclear granulocytes (PMNs). Therefore, the aim of this study was to investigate the influence of propofol on PMN functions after experimental Gram-negative induced sepsis using lipopolysaccharide (LPS) stimulation.

Methods

A total of 34 granulocyte-enriched samples were collected from healthy subjects. PMNs were isolated by density gradient centrifugation and incubated simultaneously with either 6 µg/mL or 60 µg/mL propofol, or none (control). Additionally, the experimental sepsis samples were incubated with either 40 pg/mL or 400 pg/mL LPS. Live cell imaging was conducted in order to observe granulocyte chemotactic migration, ROS production, and NETosis. Flow cytometry was used to analyze viability and antigen expression.

Results

Propofol led to significantly reduced PMN track length (p < 0.001) and track speed (p < 0.014) after LPS-induced sepsis in a dose-dependent manner. NETosis (p = 0.018) and ROS production (p = 0.039) were accelerated by propofol without LPS incubation, indicating improved immune function. Propofol also ameliorated LPS-induced increased NETosis and ROS-production. Antigen expression for CD11b, CD62l and CD66b was unaffected by propofol.

Conclusion

Propofol improves LPS-induced exaggerated PMN activation in an ex vivo model. Beneficial effects due to restored immune function in septic patients might be possible, but needs further investigation.

Targeting P2RX1 alleviates renal ischemia/reperfusion injury by preserving mitochondrial dynamics

Renal ischemia/reperfusion injury (IRI) is the major cause of acute kidney injury. However, mechanisms underlying the sudden loss in kidney function and tissue injury remain to be fully elucidated. Here, we performed RNA sequencing to systematically compare the transcriptome differences between IR injured kidneys and sham kidneys. We observed that mitochondrial dynamics was destructed in renal IRI. Expression of mitochondrial fusion-associated genes was reduced, whereas expression of mitochondrial fission-related genes was increased in renal IRI, and these findings were further confirmed by mitochondrial morphological observations. By screening 19 purinergic receptors, we noticed that P2RX1 expression was markedly upregulated in renal IRI. RNA sequencing and mitochondrial morphological observations revealed that mitochondrial dynamics was preserved in P2RX1 genetic knockout (P2rx1-/-) mice. Neutrophil extracellular traps (NETs) were reported to be essential for tissue injury in renal IRI, but the detailed mechanism remained unclear. In the present study, we found that P2RX1 favored the formation of neutrophil extracellular traps (NETs) in IRI, and NETs was essential for the impairment of mitochondrial dynamics. Mechanistically, P2RX1-involved metabolic interaction between platelets and neutrophils supported NETs formation. Activation of P2RX1 promoted platelets ATP release, which subsequently contributed to neutrophil glycolytic metabolism and NETs generation.

Targeting Purinergic Receptor P2RX1 Modulates Intestinal Microbiota and Alleviates Inflammation in Colitis

Inflammatory bowel disease (IBD) remains one of the most prevalent gastrointestinal diseases worldwide. Purinergic signaling has emerged as a promising therapeutic target of inflammation-associated diseases. However, little is known about the specific roles of purinergic receptors in IBD. In the present study, expression profile of purinergic receptors was screened in the public Gene Expression Omnibus (GEO) datasets, and we found that expression of P2RX1 was significantly upregulated in inflamed colon tissues. Then, purinergic receptor P2RX1 was genetically ablated in the background of C57BL/6 mice, and dextran sulfate sodium (DSS) was used to induce mice colitis. RNA sequencing results of colon tissues showed that genetic knockout of P2RX1 suppressed the inflammation responses in DSS-induced mice colitis. Flow cytometry indicated that neutrophil infiltration was inhibited in P2RX1 ablated mice. 16S ribosomal DNA sequencing revealed major differences of intestinal microbiota between WT and P2RX1 ablated mice. Functional metagenomics prediction indicated that the indole alkaloid biogenesis pathway was upregulated in P2RX1 gene ablated mice. Further studies revealed that microbiota metabolites (indole alkaloid)-involved aryl hydrocarbon receptor (AhR)/IL-22 axis was associated with the beneficial effects of P2RX1 ablation. Finally, we found that a specific P2RX1 inhibitor succeeded to improve the therapeutic efficiency of anti-TNF-α therapy in DSS-induced mice colitis. Therefore, our study suggests that targeting purinergic receptor P2RX1 may provide novel therapeutic strategy for IBD.

Bongkrekic acid induced neutrophil extracellular traps via p38, ERK, PAD4, and P2X1-mediated signaling

Bongkrekic acid (BKA) produced by pseudomonas cocovenenans is a deadly toxin, and is mainly found in spoiled or fermented foods. However, less is known on its immunotoxicity. Neutrophil extracellular traps (NETs) are a novel effector mechanism of neutrophils against invading pathogens, but excessive NETs also contribute to tissue damage. This study aimed to investigate NET formation triggered by BKA in murine neutrophils, and describe its characteristics and potential mechanisms. Our results showed that BKA triggered NET formation via co-localization of DNA and histone or MPO by immunostaining. Moreover, BKA-triggered NET formation was dose- and time-dependent via NET quantification based on Picogreen-derived fluorescence intensities. Furthermore, BKA increased ROS production in neutrophils. Pharmacological inhibition indicated that BKA-triggered NET formation was associated with ROS-p38 and -ERK signaling pathways, but independent on NADPH oxidase. Besides, PAD4 and P2X1 receptor also mediated BKA-triggered NET formation. To our knowledge, all these findings provide for the first time an initial understanding of BKA on innate immunity, which might be helpful for further investigation on BKA immunotoxicity.

Investigation and assessment of neutrophil dysfunction early after severe burn injury

BACKGROUND

Extensive burn injury results in a complex immune response that is associated with mortality and prognosis. Studies on acquired immune and the development of sepsis in burn patients have been reported. However, one of the main cells in innate immune, neutrophil dysfunction in the burn shock stage has not been thoroughly characterized.

METHODS

Neutrophil chemotaxis, expression of neutrophil surface markers (P2X1 receptor, [P2RX1]), degranulation (myeloperoxidase [MPO], heparin-binding protein [HBP], matrix metalloproteinase-9 [MMP-9] and neutrophil elastase [NE]), oxidative burst capacity, neutrophil extracellular trap (NET) generation, phagocytosis and apoptosis were measured in 18 patients with major burns (≥30% total body surface area [TBSA]) within 48 h after burn injury. In addition, circulating neutrophils and vascular permeability in mice model with 30% TBSA third-degree burns were also observed and investigated.

RESULTS

Neutrophil functions were reduced considerably in burn shock stage, which was characterized by decreased chemotaxis, phagocytosis and abnormal bactericidal function. Increased release of heparin-binding protein (HBP) and the expression of P2RX1 on the neutrophil surface are related to fluid leakage and decreased chemotaxis during burn shock stage, respectively. The combination of HBP concentration in plasma and P2RX1 expression on neutrophils gives a better prediction of neutrophil dysfunction in burn-injured patients.

CONCLUSION

Neutrophil dysfunction plays a key role in the development of burn injury. Targeting the restoration of neutrophil function may be a feasible therapeutic intervention to help reduce fluid loss during shock and the severity of subsequent infection.

Identification and characterization of neutrophil heterogeneity in sepsis

BACKGROUND

Although the immune function of neutrophils in sepsis has been well described, the heterogeneity of neutrophils remains unclear during the process of sepsis.

METHODS

In this study, we used a mouse CLP model to simulate the clinical scenario of patients with sepsis, neutrophil infiltration, abnormal distribution and dysfunction was analyzed. LPS was used to stimulate neutrophils in vitro to simulate sepsis; single-cell gene sequencing technology was used to explore the immunological typing. To explore the immunological function of immunosuppressive neutrophils, PD-L1 knockout neutrophils were cocultured with lymphocytes from wild-type mice.

RESULTS

We found that neutrophils presented variant dysfunction at the late stage of sepsis, including inhibition of apoptosis, seriously damaged chemotaxis and extensive infiltration into the tissues. Single-cell RNA sequencing revealed that multiple subclusters of neutrophils were differentiated after LPS stimulation. The two-dimensional spatial distribution analysis showed that Foxp3⁺ T cells were much closer to Ly-6G than the CD4⁺ and CD8⁺ cells, indicating that infiltrated neutrophils may play immunomodulatory effect on surrounding T-regs. Further observations showed that LPS mediates PD-L1 over expression through p38α-MSK1/-MK2 pathway in neutrophils. The subsets of highly expressed PD-L1 exert immunosuppressive effect under direct contact mode, including inhibition of T cell activation and induction of T cell apoptosis and trans-differentiation.

CONCLUSIONS

Taken together, our data identify a previously unknown immunosuppressive subset of neutrophils as inhibitory neutrophil in order to more accurately describe the phenotype and characteristics of these cells in sepsis.

Increased Extracellular ATP in Plasma of Rheumatoid Arthritis Patients Activates CD8+T Cells

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disorder with genetic and environmental causes often linked with the disease etiology. A disrupted metabolism has often been a characteristic of RA and an altered metabolic state of immune cells has been associated with their phenotypic and functional changes. The energy in the form of ATP produced by the metabolically active cells may thus initiate a cascade of immune responses there by influencing the disease pathogenesis or progression.

AIM OF THE STUDY

Through this study we have focused on determining the role of ATP in etiology of RA and aberrant cellular functions.

METHODS

Blood samples of 80 healthy controls (HC) and 95 RA patients were screened for extracellular ATP concentration, transcriptome analyses, an inflammatory mediator and the results were statistically analysed.

RESULTS

In this study, ATP is shown to be excessive in the plasma of RA patients (453.5 ± 16.09% in RA vs. 233.9 ± 10.07% in HC, p <0.0001) and significantly increases with the disease severity. The abundant extracellular ATP could activate circulating cytotoxic CD8⁺T cells in RA patients to produce Granzyme B.

CONCLUSION

Plasma ATP is thus identified to have a significant potential in progression and prognosis of RA and may thus be studied further to design better therapeutic approaches for the disease.

Ectonucleotidases in Acute and Chronic Inflammation

Ectonucleotidases are extracellular enzymes with a pivotal role in inflammation that hydrolyse extracellular purine and pyrimidine nucleotides, e.g., ATP, UTP, ADP, UDP, AMP and NAD⁺. Ectonucleotidases, expressed by virtually all cell types, immune cells included, either as plasma membrane-associated or secreted enzymes, are classified into four main families: 1) nucleoside triphosphate diphosphohydrolases (NTPDases), 2) nicotinamide adenine dinucleotide glycohydrolase (NAD glycohydrolase/ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase 1), 3) ecto-5′-nucleotidase (NT5E), and 4) ecto-nucleotide pyrophosphatase/phosphodiesterases (NPPs). Concentration of ATP, UTP and NAD⁺ can be increased in the extracellular space thanks to un-regulated, e.g., cell damage or cell death, or regulated processes. Regulated processes include secretory exocytosis, connexin or pannexin hemichannels, ATP binding cassette (ABC) transporters, calcium homeostasis modulator (CALMH) channels, the ATP-gated P2X7 receptor, maxi-anion channels (MACs) and volume regulated ion channels (VRACs). Hydrolysis of extracellular purine nucleotides generates adenosine, an important immunosuppressant. Extracellular nucleotides and nucleosides initiate or dampen inflammation via P2 and P1 receptors, respectively. All these agents, depending on their level of expression or activation and on the agonist concentration, are potent modulators of inflammation and key promoters of host defences, immune cells activation, pathogen clearance, tissue repair and regeneration. Thus, their knowledge is of great importance for a full understanding of the pathophysiology of acute and chronic inflammatory diseases. A selection of these pathologies will be briefly discussed here.

P2RX1-Involved Glycolytic Metabolism Supports Neutrophil Activation in Acute Pancreatitis

Acute pancreatitis (AP) is characterized by disordered inflammation of the pancreas, and the underlying mechanisms remain unclear. Purinergic signaling plays crucial roles in initiating and amplifying inflammatory signals. Recent evidence reveals that targeting dysregulated purinergic signaling is promising for treating inflammation-associated diseases. To explore the potential involvement of purinergic signaling in AP, we investigated the expression profiles of purinergic signaling molecules in human and mouse pancreas tissues. Results showed that purinergic receptor P2RX1 was among the most highly expressed genes in both human and mouse pancreas tissues. Genetic ablation or specific antagonism of P2RX1 markedly alleviated inflammatory responses in caerulein-induced AP mice. Bone marrow chimeras and adoptive transfer studies revealed that neutrophil-derived P2RX1 contributed to the inflammatory responses in AP. Further studies demonstrated that P2RX1 promoted neutrophil activation by facilitating glycolytic metabolism. Therefore, our study indicates that purinergic receptor P2RX1 may be a potential therapeutic target to treat disordered inflammation in AP.

Identification of a subset of immunosuppressive P2RX1-negative neutrophils in pancreatic cancer liver metastasis

The immunosuppressive microenvironment that is shaped by hepatic metastatic pancreatic ductal adenocarcinoma (PDAC) is essential for tumor cell evasion of immune destruction. Neutrophils are important components of the metastatic tumor microenvironment and exhibit heterogeneity. However, the specific phenotypes, functions and regulatory mechanisms of neutrophils in PDAC liver metastases remain unknown. Here, we show that a subset of P2RX1-negative neutrophils accumulate in clinical and murine PDAC liver metastases. RNA sequencing of murine PDAC liver metastasis-infiltrated neutrophils show that P2RX1-deficient neutrophils express increased levels of immunosuppressive molecules, including PD-L1, and have enhanced mitochondrial metabolism. Mechanistically, the transcription factor Nrf2 is upregulated in P2RX1-deficient neutrophils and associated with PD-L1 expression and metabolic reprogramming. An anti-PD-1 neutralizing antibody is sufficient to compromise the immunosuppressive effects of P2RX1-deficient neutrophils on OVA-activated OT1 CD8+ T cells. Therefore, our study uncovers a mechanism by which metastatic PDAC tumors evade antitumor immunity by accumulating a subset of immunosuppressive P2RX1-negative neutrophils.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive metastatic disease characterized by an immunosuppressive microenvironment. Here the authors show that a subset of P2RX1-negative neutrophils with immunosuppressive properties accumulate in PDAC metastatic liver tissues and promote tumor growth.

Mitochondria-derived ATP participates in the formation of neutrophil extracellular traps induced by platelet-activating factor through purinergic signaling in cows

Neutrophil extracellular trap (NET) formation eliminates/prevents the spread of infectious agents. Platelet activating factor (PAF) is involved in infectious diseases of cattle because it recruits and activates neutrophils. However, its ability to induce NET release and the role of metabolism in this process is not known. We investigated if inhibition of glycolysis, mitochondrial-derived adenosine triphosphate (ATP) synthesis and purinergic signaling though P2X₁ purinoceptors interfered with NET formation induced by PAF. We inhibited bovine neutrophils with 2-deoxy-d-glucose, rotenone, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and NF449 to evaluate PAF-mediated NET extrusion. PAF induced mitochondrial hyperpolarization and triggered extracellular ATP release via pannexin-1. Inhibition of mitochondrial metabolism prevented extracellular ATP release. Inhibition of glycolysis, complex-I activity and oxidative phosphorylation prevented NET formation induced by PAF. Inhibition of P2X₁ purinergic receptors inhibited mitochondrial hyperpolarization and NET formation. We concluded that PAF-induced NET release is dependent upon glycolysis, mitochondrial ATP synthesis and purinergic signaling.

Extracellular ATP: A Feasible Target for Cancer Therapy

Adenosine triphosphate (ATP) is one of the main biochemical components of the tumor microenvironment (TME), where it can promote tumor progression or tumor suppression depending on its concentration and on the specific ecto-nucleotidases and receptors expressed by immune and cancer cells. ATP can be released from cells via both specific and nonspecific pathways. A non-regulated release occurs from dying and damaged cells, whereas active release involves exocytotic granules, plasma membrane-derived microvesicles, specific ATP-binding cassette (ABC) transporters and membrane channels (connexin hemichannels, pannexin 1 (PANX1), calcium homeostasis modulator 1 (CALHM1), volume-regulated anion channels (VRACs) and maxi-anion channels (MACs)). Extracellular ATP acts at P2 purinergic receptors, among which P2X7R is a key mediator of the final ATP-dependent biological effects. Over the years, P2 receptor- or ecto-nucleotidase-targeting for cancer therapy has been proposed and actively investigated, while comparatively fewer studies have explored the suitability of TME ATP as a target. In this review, we briefly summarize the available evidence suggesting that TME ATP has a central role in determining tumor fate and is, therefore, a suitable target for cancer therapy.

Contribution of Connexin Hemichannels to the Pathogenesis of Acute Lung Injury

Connexin (Cx) family members form hemichannels (HCs) and gap junctions (GJs). Biological functions of Cx HCs have not been adequately characterized due to the inability to selectively target HCs or GJs. Recently, we developed a 6-mer peptide mimetic (P5) of the first extracellular loop of Cx43 and showed that it can block the permeability of HCs but not GJs formed by Cx43. In this study, we further characterized the HC blocking property of P5 and investigated the role of Cx HCs in acute lung injury (ALI). We found that P5 administration decreased HC permeability, in pulmonary microvascular endothelial cells, HepG2 cells, and even Cx43-deficient astrocytes, which express different sets of Cxs, suggesting that P5 is a broad spectrum Cx HC blocker. In addition, P5 reduced HC permeability of alveolar cells in vivo. Moreover, P5 decreased endotoxin-induced release, by vascular endothelial cells in vitro, of high mobility group box protein 1 (HMGB1), a critical mediator of acute lung injury (ALI), and reduced HMGB1 accumulation in bronchoalveolar lavage fluid (BALF) of mice subjected to intratracheal endotoxin instillation. Furthermore, P5 administration resulted in a significant decrease in the concentrations of ALT, AST, and LDH in the BALF, the accumulation of leukocytes in alveoli, and the mortality rate of mice subjected to ALI. Wright-Giemsa staining showed that P5 caused similar reductions of both neutrophils and monocytes in BALF of ALI mice. Together, these results suggest that Cx HCs mediate HMGB1 release, augment leukocyte recruitment, and contribute to ALI pathology.