Project description:Extracellular cold-inducible RNA-binding protein (eCIRP) is a key mediator of severity and mortality in sepsis. We found that stimulation of mouse bone marrow–derived neutrophils (BMDNs) with eCIRP generated a distinct neutrophil subpopulation, characterized by cell surface markers of both antigen-presenting cells and aged neutrophils as well as expression of IL-12, which we named antigen-presenting aged neutrophils (APANs). The frequency of APANs was significantly increased in the blood, spleen, and lungs of WT mice subjected to cecal ligation and puncture–induced sepsis but not in CIRP–/– mice. Patients with sepsis had a significant increase in circulating APAN counts compared with healthy individuals. Compared with non–APAN-transferred mice, APAN-transferred septic mice had increased serum levels of injury and inflammatory markers, exacerbated acute lung injury (ALI), and worsened survival. APANs and CD4+ T cells colocalized in the spleen, suggesting an immune interaction between these cells. APANs cocultured with CD4+ T cells significantly induced the release of IFN-γ via IL-12. BMDNs stimulated with eCIRP and IFN-γ underwent hyper-NETosis. Stimulating human peripheral blood neutrophils with eCIRP also induced APANs, and stimulating human neutrophils with eCIRP and IFN-γ caused hyper-NETosis. Thus, eCIRP released during sepsis induced APANs to aggravate ALI and worsen the survival of septic animals via CD4+ T cell activation, Th1 polarization, and IFN-γ–mediated hyper-NETosis.
Project description:Extracellular cold-inducible RNA-binding protein (eCIRP) is a key mediator of severity and mortality in sepsis. We found that stimulation of mouse bone marrow-derived neutrophils (BMDNs) with eCIRP generated a distinct neutrophil subpopulation, characterized by cell surface markers of both antigen-presenting cells and aged neutrophils as well as expression of IL-12, which we named antigen-presenting aged neutrophils (APANs). The frequency of APANs was significantly increased in the blood, spleen, and lungs of WT mice subjected to cecal ligation and puncture-induced sepsis but not in CIRP-/- mice. Patients with sepsis had a significant increase in circulating APAN counts compared with healthy individuals. Compared with non-APAN-transfered mice, APAN-transferred septic mice had increased serum levels of injury and inflammatory markers, exacerbated acute lung injury (ALI), and worsened survival. APANs and CD4+ T cells colocalized in the spleen, suggesting an immune interaction between these cells. APANs cocultured with CD4+ T cells significantly induced the release of IFN-γ via IL-12. BMDNs stimulated with eCIRP and IFN-γ underwent hyper-NETosis. Stimulating human peripheral blood neutrophils with eCIRP also induced APANs, and stimulating human neutrophils with eCIRP and IFN-γ caused hyper-NETosis. Thus, eCIRP released during sepsis induced APANs to aggravate ALI and worsen the survival of septic animals via CD4+ T cell activation, Th1 polarization, and IFN-γ-mediated hyper-NETosis.
Project description:Disseminated intravascular coagulation (DIC) is a deadly complication of sepsis lacking effective managements. Although excessive inflammatory responses are emerging as key triggers of coagulopathy in sepsis, the interplays between immune system and coagulation are not fully understood. In a murine model of sepsis induced by intraperitoneal lipopolysaccharide (LPS), we found neutrophils in circulation mitigate the occurrence of DIC, thereby preventing the subsequent septic death. We found circulating neutrophils constantly release extracellular vesicles (EVs) containing mitochondria, which carry substantial amount of Superoxide Dismutase 2 (Sod2) upon LPS exposure. The extracellular Sod2 is necessary to bring about neutrophils’ antithrombotic function by eliminating endothelial reactive oxygen species (ROS) accumulation and alleviating endothelial dysfunction. Intervening endothelial ROS accumulation by antioxidants significantly ameliorates DIC with correspondingly improved survival in sepsis. These findings revealed a novel interaction between neutrophils and vascular endothelium which critically regulates coagulation in sepsis and had potential implications for the management of septic DIC.
Project description:The mechanisms underlying the increased mortality of secondary infections during the immunosuppressive phase of sepsis remain elusive. We established a mouse model of sepsis-induced immunosuppression followed by secondary infection. Compared to other organs, we observed a significant reduction in pro-inflammatory cytokines in the spleen, accompanied by a marked increase in IL-10 production, primarily by infiltrating neutrophils. Furthermore, we confirmed that these infiltrating neutrophils in the spleen during the immunosuppressive phase of sepsis undergo phenotypic change in the local microenvironment, exhibiting high expression of neutrophil biomarkers such as Siglec-F, Ly6G, and Siglec-E. These neutrophils subsequently produced IL-10 to suppress T lymphocytes. Depletion of neutrophils or specifically targeting Siglec-F leads to a notable improvement in the survival of mice with secondary infections. The identification of Siglec-F+ neutrophils as key regulators of immunosuppression following sepsis represents a novel finding with potential therapeutic implications.
Project description:Background: Severe septic syndromes deeply impair innate and adaptive immunity. While neutrophils represent the first line of defense against infection, little is known about their phenotype and functions during sepsis-induced immunosuppression. The objective of this study was thus to perform for the first time a global evaluation of neutrophil alterations in immunosuppressed septic patients based on phenotypic, functional and transcriptomic studies. In addition, the potential association of these parameters and deleterious outcomes was assessed. Methods: Peripheral blood was collected from 9 septic shock patients at D3-4 and D6-8 presenting with features of sepsis-induced immunosuppression and compared to 8 healthy controls. Results: In order to get on overview of potential neutrophil alterations after sepsis, we performed transcriptomic analyses on purified neutrophils from 9 septic shock patients and 8 healthy volunteers. For each time point, comparisons were made between patients and controls. Venn diagrams indicated that 364 up-regulated genes and 328 down-regulated genes were common between the two analyses (Supplementary Tables 1 and 2). Interestingly, most of the differentially expressed genes are involved in cell maturation (CD177), apoptosis (STK4, Caspase 8), cell recruitment and chemotaxis (CD44, TPST, MMP9, CREB1), and antimicrobial properties (ARG1, STOM, ADAM9, CD63, YKL40) of neutrophils. Conclusions: The aim of the current study was to perform an extensive investigation of neutrophil alterations during sepsis-induced immunosuppression through phenotypic, functional and transcriptomic studies. Notably, transcriptomic study on purified neutrophils revealed differentially expressed genes between septic patients and healthy volunteers.
Project description:Gram-negative bacillary bacteremia poses a significant threat, ranking among the most severe infectious diseases capable of triggering life-threatening sepsis. Despite the unambiguous involvement of neutrophils in this potentially fatal disease, there are limited data about the molecular signaling mechanisms, phenotype, and function of human neutrophils during the early phase of gram-negative bacillary bacteremia. By using an unbiased proteomics and flow cytometry approach, we identified an antigen-presenting cell (APC)-like phenotype in human peripheral blood neutrophils (PMN) with MHC class II molecule expression in the early phase of bacteremia. Using an in-vitro model of GM-CSF-mediated induction of APC-like phenotype in PMN, we investigated downstream signaling pathways leading to MHC class II expression. GM-CSF stimulation of neutrophils leads to the activation of three major signaling pathways, the JAK-STAT, the mitogen-activated protein kinase (MAPK), and the phosphoinositide 3-kinase (PI3K)-Akt-mTOR pathways, while MHC class II induction is mediated by a MAPK-p38-MSK1-CREB1 signaling cascade and the MHC class II transactivator CIITA in a strictly JAK12 kinase-dependent manner. Our data describing details of signaling pathways inducing MHC class II expression in neutrophils open new possibilities of therapeutic targeting of JAK12 signaling during different stages of gram-negative bacteremia and sepsis.
Project description:aD is one of the b2 integrin family members. The role of aD in sepsis has not been examined yet. aD is previously reported to be expressed on neutrophils. We performed cecal ligation and puncture sepsis model in wild type and aD knockout and examined the role of aD in neutrophils.
Project description:Classical dendritic cells (cDC) are professional antigen presenting cells (APC) that regulate immunity and tolerance. Neutrophil-derived cells with properties of DCs (nAPC) are observed after culture of neutrophils with cytokines and in human diseases. Here, we show that FcgR-mediated endocytosis of antigen-antibody complexes or an anti-FcgRIIIB-antigen conjugate converts neutrophils into nAPCs that, in contrast to those generated with cytokines alone, activate T cells to levels observed with cDCs and elicit CD8 T cell-dependent anti-tumor immunity. Single cell transcript analyses and validation studies implicate the transcription factor PU.1 in neutrophil to nAPC conversion. In humans, nAPC frequency in lupus patient blood containing IgG-immune complexes correlates with disease. Moreover, conjugate treatment of neutrophils from individuals with myeloid neoplasms that harbor neoantigens or those who are vaccinated against bacterial toxins generates nAPCs that activate autologous T cells. Thus, anti-FcgRIIIB-antigen conjugate-induced conversion of neutrophils to immunogenic nAPCs may represent a new immunotherapy for cancer and infectious diseases.