Neutrophil recruitment is an important early step in controlling tissue infections or injury. Here, we report that this influx depends on both tissue-resident mast cells and macrophages. Mice with ...mast cell deficiency recruit reduced numbers of neutrophils in the first few hours of intraperitoneal lipopolysaccharide (LPS) stimulation. Conversely, in mice with clodronate-ablated macrophages, neutrophils extravasate, but have limited ability to reach the peritoneal fluid. Tissue macrophages synthesize neutrophil chemoattractants CXCL1/CXCL2 (CXC chemokine ligands 1/2) in response to LPS. Mast cells also produce these chemokines of which a proportion are preformed in granules. Release of the granules and new CXCL1/CXCL2 synthesis is Toll-like receptor 4–dependent. Both in vivo studies with blocking monoclonal antibodies and in vitro chemotaxis experiments show the neutrophil response to mast cells and macrophages to be CXCL1/CXCL2-dependent. The data are in keeping with the model that mast cells, optimally positioned in close proximity to the vasculature, initiate an early phase of neutrophil recruitment by releasing the chemoattractants CXCL1/CXCL2. Having arrived within the stimulated tissue, neutrophils penetrate further in a macrophage-dependent manner. Therefore, we demonstrate a positive role for mast cells in tissue inflammation and define how this comes about with contribution from a second tissue cell, the macrophage.
• Mast cells contribute to early neutrophil recruitment.• Mast cells and macrophages both make CXCL1 and CXCL2.
Metastasis and chemoresistance in cancer are linked phenomena, but the molecular basis for this link is unknown. We uncovered a network of paracrine signals between carcinoma, myeloid, and ...endothelial cells that drives both processes in breast cancer. Cancer cells that overexpress CXCL1 and 2 by transcriptional hyperactivation or 4q21 amplification are primed for survival in metastatic sites. CXCL1/2 attract CD11b+Gr1+ myeloid cells into the tumor, which produce chemokines including S100A8/9 that enhance cancer cell survival. Although chemotherapeutic agents kill cancer cells, these treatments trigger a parallel stromal reaction leading to TNF-α production by endothelial and other stromal cells. TNF-α via NF-kB heightens the CXCL1/2 expression in cancer cells, thus amplifying the CXCL1/2-S100A8/9 loop and causing chemoresistance. CXCR2 blockers break this cycle, augmenting the efficacy of chemotherapy against breast tumors and particularly against metastasis. This network of endothelial-carcinoma-myeloid signaling interactions provides a mechanism linking chemoresistance and metastasis, with opportunities for intervention.
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► CXCL1/2 mediate breast cancer metastasis through myeloid cell recruitment ► CXCL1/2 promote breast cancer cell survival through myeloid-cell-derived S100A8/9 ► Chemotherapeutic agents induce TNF-α to hyperactivate the CXCL1/2–S100A8/9 axis ► Blocking CXCL1 signaling improves chemotherapy efficacy and diminishes metastasis
A paracrine cascade that triggers the production of survival factors by surrounding stromal cells, enabling the survival of metastatic cancer cells, is also elicited by chemotherapeutic agents and is central to chemoresistance. Blocking this chemokine axis may improve the efficacy of chemotherapy and reduce metastatic burden in breast cancer.
The S100A8/A9 heterodimer is expressed by myeloid cells where its function has been extensively investigated. Immune cell S100A8/A9 promotes proinflammatory effects, and its absence is often ...associated with lack of leukocyte recruitment resulting in protection in terms of disease progression. S100A8/A9 is also expressed by certain epithelia, either constitutively as in mucosal epithelia or following stimulation as in skin keratinocytes. The role of the heterodimer in this context has not been as frequently explored. In this study, the incidence of skin papillomas induced by 7,12‐dimethylbenz(a)anthracene (DMBA)/12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in S100a9−/− mice has been investigated. Unlike the immune disorders and certain models of cancer, absence of S100A8/A9 caused an increased incidence in skin of papillomas and, subsequently, squamous cell carcinomas. Although associated in S100a9−/− mice with increased recruitment of neutrophils and T cells, a bone marrow chimera experiment revealed the major defect to be primarily due to the absence of S100A8/A9 in the skin keratinocytes. S100a9−/− skin displayed enhanced Ki‐67 expression over the time period of appearance of the papillomas suggesting an effect of S100A8/A9 in regulating proliferation in the epidermal layer. Thus, despite immune cell recruitment in S100a9−/− mouse skin that might have been predicted to promote tumor growth, it was the absence of S100A8/A9 in skin keratinocytes that dominated in terms of papilloma formation. The study highlights the importance of the S100A8/A9‐expressing skin epidermal layer in controlling skin tumor formation and suggests that the influence of the heterodimer is dependent on the tissue context in which it is expressed.
What's new?
Expression of the proinflammatory protein S100A8/A9 in epithelial tissue can be induced following stress such as that caused by skin carcinogen exposure. Here, the ability of the carcinogens 7,12‐dimethylbenz(a)anthracene (DMBA) and 2‐O‐ tetradecanoylphorbol‐13‐acetate (TPA) to induce skin papillomas was investigated in S100a9‐/‐ mice. The experiments show that the absence of S100A8/A9 results in increased incidence of skin papillomas, apparently due to a loss of S100A8/A9 regulation resulting in over proliferation in the epidermal layer. The findings suggest that S100A8/A9 plays a protective role against skin papillomas specifically in skin keratinocytes, indicating that the heterodimer acts in a tissue‐dependent context.
Neutrophils are the first immune cells to migrate into infected tissue sites. Therefore an important step in the initiation of an immune response is the synthesis of the neutrophil-recruiting ...chemokines. In this in vivo study in mice, we show that resident tissue macrophages are the source of the major neutrophil chemoattractants, KC and MIP-2. Synthesis of these chemokines is rapidly regulated at the transcriptional level by signaling through TLR2, TLR3, and TLR4 that have diverse specificities for pathogens. The major and alternative TLR signaling pathways are characterized by the adaptor proteins MyD88 or TRIF, respectively. KC and MIP-2 are both produced by signaling through MyD88. However MIP-2, but not KC, is also synthesized through the TRIF adaptor protein, identifying it as a new product of this alternative pathway. Use of both pathways by TLR4 ensures maximal levels of KC and MIP-2 that lead to robust neutrophil recruitment. However the MIP-2 generated exclusively by the TRIF pathway is still sufficient to cause an influx of neutrophils. In summary we show that TLR signaling by tissue macrophages directly controls the synthesis of neutrophil-attracting chemokines that are essential for the earliest recruitment step in the innate immune response to microbial challenge.
Inherited bleeding, thrombotic, and platelet disorders (BPDs) are diseases that affect ∼300 individuals per million births. With the exception of hemophilia and von Willebrand disease patients, a ...molecular analysis for patients with a BPD is often unavailable. Many specialized tests are usually required to reach a putative diagnosis and they are typically performed in a step-wise manner to control costs. This approach causes delays and a conclusive molecular diagnosis is often never reached, which can compromise treatment and impede rapid identification of affected relatives. To address this unmet diagnostic need, we designed a high-throughput sequencing platform targeting 63 genes relevant for BPDs. The platform can call single nucleotide variants, short insertions/deletions, and large copy number variants (though not inversions) which are subjected to automated filtering for diagnostic prioritization, resulting in an average of 5.34 candidate variants per individual. We sequenced 159 and 137 samples, respectively, from cases with and without previously known causal variants. Among the latter group, 61 cases had clinical and laboratory phenotypes indicative of a particular molecular etiology, whereas the remainder had an a priori highly uncertain etiology. All previously detected variants were recapitulated and, when the etiology was suspected but unknown or uncertain, a molecular diagnosis was reached in 56 of 61 and only 8 of 76 cases, respectively. The latter category highlights the need for further research into novel causes of BPDs. The ThromboGenomics platform thus provides an affordable DNA-based test to diagnose patients suspected of having a known inherited BPD.
•Developed a targeted sequencing platform covering 63 genes linked to heritable bleeding, thrombotic, and platelet disorders.•The ThromboGenomics platform provides a sensitive genetic test to obtain molecular diagnoses in patients with a suspected etiology.
Intracellular adhesion molecule-1 (ICAM-1) is a transmembrane glycoprotein expressed on the cell surface of numerous cell types such as endothelial and epithelial cells, vascular smooth muscle cells, ...and certain leukocyte subsets. With respect to the latter, ICAM-1 has been detected on neutrophils in several clinical and experimental settings, but little is known about the regulation of expression or function of neutrophil ICAM-1. In this study, we report on the de novo induction of ICAM-1 on the cell surface of murine neutrophils by lipopolysaccharide (LPS), tumor necrosis factor, and zymosan particles in vitro. The induction of neutrophil ICAM-1 was associated with enhanced phagocytosis of zymosan particles and reactive oxygen species (ROS) generation. Conversely, neutrophils from ICAM-1–deficient mice were defective in these effector functions. Mechanistically, ICAM-1–mediated intracellular signaling appeared to support neutrophil ROS generation and phagocytosis. In vivo, LPS-induced inflammation in the mouse cremaster muscle and peritoneal cavity led to ICAM-1 expression on intravascular and locally transmigrated neutrophils. The use of chimeric mice deficient in ICAM-1 on myeloid cells demonstrated that neutrophil ICAM-1 was not required for local neutrophil transmigration, but supported optimal intravascular and extravascular phagocytosis of zymosan particles. Collectively, the present results shed light on regulation of expression and function of ICAM-1 on neutrophils and identify it as an additional regulator of neutrophil effector responses in host defense.
•Murine neutrophils can be stimulated by LPS to express de novo ICAM-1 in vitro and in murine models of endotoxemia in vivo.•Neutrophil ICAM-1 expression correlated with enhanced phagocytosis and ROS generation, and ICAM-1 deficiency caused defective phagocytosis.
Inflammatory cell recruitment after myocardial infarction needs to be tightly controlled to permit infarct healing while avoiding fatal complications such as cardiac rupture. Growth differentiation ...factor-15 (GDF-15), a transforming growth factor-β (TGF-β)-related cytokine, is induced in the infarcted heart of mice and humans. We show that coronary artery ligation in Gdf15-deficient mice led to enhanced recruitment of polymorphonuclear leukocytes (PMNs) into the infarcted myocardium and an increased incidence of cardiac rupture. Conversely, infusion of recombinant GDF-15 repressed PMN recruitment after myocardial infarction. In vitro, GDF-15 inhibited PMN adhesion, arrest under flow and transendothelial migration. Mechanistically, GDF-15 counteracted chemokine-triggered conformational activation and clustering of β(2) integrins on PMNs by activating the small GTPase Cdc42 and inhibiting activation of the small GTPase Rap1. Intravital microscopy in vivo in Gdf15-deficient mice showed that Gdf-15 is required to prevent excessive chemokine-activated leukocyte arrest on the endothelium. Genetic ablation of β(2) integrins in myeloid cells rescued the mortality of Gdf15-deficient mice after myocardial infarction. To our knowledge, GDF-15 is the first cytokine identified as an inhibitor of PMN recruitment by direct interference with chemokine signaling and integrin activation. Loss of this anti-inflammatory mechanism leads to fatal cardiac rupture after myocardial infarction.
Integrins in immunity Evans, Rachel; Patzak, Irene; Svensson, Lena ...
Journal of cell science,
01/2009, Letnik:
122, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A successful immune response depends on the capacity of immune cells to travel from one location in the body to another-these cells are rapid migrators, travelling at speeds of μm/minute. Their ...ability to penetrate into tissues and to make contacts with other cells depends chiefly on the β2 integrin known as LFA-1. For this reason, we describe the control of its activity in some detail. For the non-immunologist, the fine details of an immune response often seem difficult to fathom. However, the behaviour of immune cells, known as leukocytes (Box 1), is subject to the same biological rules as many other cell types, and this holds true particularly for the functioning of the integrins on these cells. In this Commentary, we highlight, from a cell-biology point of view, the integrin-mediated immune-cell migration and cell-cell interactions that occur during the course of an immune response.
Exosomes are secreted vesicles formed in late endocytic compartments. Mature dendritic cells (DCs) secrete exosomes bearing functional MHC-peptide complexes and high levels of ICAM-1. Such exosomes ...can activate Ag-specific naive T cells but only after recapture by recipient APCs. In this study, we addressed the molecular mechanisms of interaction between exosomes and recipient DCs. We show that exosomes can be presented by mouse DCs without the need for internalization and processing. Exosomes interact with DCs through a specific saturable receptor. Although the two major ligands of ICAM-1, LFA-1 and Mac-1, are expressed by lymphoid organ DCs, only LFA-1 is required for exosome capture by these cells. Accordingly, we show that CD8(+) DCs express higher levels of LFA-1 than CD8(-) DCs, and that they are the main recipients of exosomes in vivo. We propose a new role for LFA-1 on DCs, as a receptor for exosomes to favor Ag transfer between DCs in vivo.
The protein kindlin 3 is mutated in the leukocyte adhesion deficiency III (LAD-III) disorder, leading to widespread infection due to the failure of leukocytes to migrate into infected tissue sites. ...To gain understanding of how kindlin 3 controls leukocyte function, we have focused on its pleckstrin homology (PH) domain and find that deletion of this domain eliminates the ability of kindlin 3 to participate in adhesion and migration of B cells mediated by the leukocyte integrin lymphocyte function-associated antigen 1 (LFA-1). PH domains are often involved in membrane localization of proteins through binding to phosphoinositides. We show that the kindlin 3 PH domain has binding affinity for phosphoinositide PI(3,4,5)P3 over PI(4,5)P2. It has a major role in membrane association of kindlin 3 that is enhanced by the binding of LFA-1 to intercellular adhesion molecule 1 (ICAM-1). A splice variant, kindlin 3-IPRR, has a four-residue insert in the PH domain at a critical site that influences phosphoinositide binding by enhancing binding to PI(4,5)P2 as well as by binding to PI(3,4,5)P3. However kindlin 3-IPRR is unable to restore the ability of LAD-III B cells to adhere to and migrate on LFA-1 ligand ICAM-1, potentially by altering the dynamics or PI specificity of binding to the membrane. Thus, the correct functioning of the kindlin 3 PH domain is central to the role that kindlin 3 performs in guiding lymphocyte adhesion and motility behavior, which in turn is required for a successful immune response.
Background: Kindlin 3 is mutated in LAD-III causing widespread infection, but its role in leukocyte function is incompletely understood.
Results: Deletion of the PH domain removes kindlin 3 from lymphocyte cell membrane and eliminates adhesion and migration.
Conclusion: The PH domain is intrinsic to kindlin 3 regulation of integrin LFA-1-mediated lymphocyte function.
Significance: A successful immune response depends on kindlin 3, and its PH subdomain is crucial.
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