Directional Chemotaxis Research Articles

DNA origami assembled spheroid for evaluating cytotoxicity and infiltration of chimeric antigen receptor macrophage (CAR-M)

Chimeric antigen receptor (CAR) T-cell therapies have shown remarkable results in patients with hematological malignancies. However, their success in treating solid tumors has been limited. As an alternative candidate for the CAR therapy, CAR-macrophages (CAR-M) have demonstrated activation and phagocytosis directed by tumor-associated antigen (TAA), showing promise in the treatment of solid tumors. Nevertheless, the mechanisms by which CARs direct tumor chemotaxis and invasion of CAR-M remain poorly understood. In this study, we aim to investigate the role of CARs in CAR-M attachment and infiltration using 3D tumor spheroids, which were created by utilizing a novel self-assembling nucleic acid nanostructure decorated living cells (NAC). Our results demonstrated that CAR-M exhibited higher invasion and killing capacity in 2D model and 3D tumor spheroids. In summary, the 3D NAC assembled tumor spheroid model provides a suitable platform for target screening and pharmacodynamic evaluation of CAR-M.

NLRP3 is essential for neutrophil polarization and chemotaxis in response to leukotriene B4 gradient

Neutrophil recruitment to sites of infection and inflammation is an essential process in the early innate immune response. Upon activation, a subset of neutrophils rapidly assembles the multiprotein complex known as the NLRP3 inflammasome. The NLRP3 inflammasome forms at the microtubule organizing center, which promotes the formation of interleukin (IL)-1β and IL-18, essential cytokines in the immune response. We recently showed that mice deficient in NLRP3 (NLRP3-/-) have reduced neutrophil recruitment to the peritoneum in a model of thioglycolate-induced peritonitis. Here, we tested the hypothesis that this diminished recruitment could be, in part, the result of defects in neutrophil chemotaxis. We find that NLRP3-/- neutrophils show loss of cell polarization, as well as reduced directionality and velocity of migration toward increasing concentrations of leukotriene B4 (LTB4) in a chemotaxis assay in vitro, which was confirmed through intravital microscopy of neutrophil migration toward a laser-induced burn injury of the liver. Furthermore, pharmacologically blocking NLRP3 inflammasome assembly with MCC950 in vitro reduced directionality but preserved nondirectional movement, indicating that inflammasome assembly is specifically required for polarization and directional chemotaxis, but not cell motility per se. In support of this, pharmacological breakdown of the microtubule cytoskeleton via nocodazole treatment induced cell polarization and restored nondirectional cell migration in NLRP3-deficient neutrophils in the LTB4 gradient. Therefore, NLRP3 inflammasome assembly is required for establishment of cell polarity to guide the directional chemotactic migration of neutrophils.

SDF-1 induces directional chemotaxis of BMSCs at the intervertebral fusion site and promotes osteogenic differentiation by regulating Wnt/β-catenin in the bone marrow chimera spinal intervertebral fusion mouse model.

Clinical observations show that the current spinal fusion with internal fixation has a nonfusion rate of 5%-35%; however, methods to promote spinal fusion are limited. This study aimed to investigate the role of SDF-1-induced directional chemotaxis of BMSCs in bone marrow chimera spinal intervertebral fusion mouse model. BMSCs were isolated from bone marrow and identified by detecting CD44/CD34 positive cells. BMSCs (GFP-BMSCs) were labeled with GFP for tracking in vivo. Mice were inoculated with GFP-BMSCs to construct bone marrow chimera spinal intervertebral fusion model, which were divided into BM-SIF model, BM-SIF+SDF-1, BM-SIF+SDF-1-Anta group. The callus area of intervertebral fusion site was detected by radiology. HE staining was used to detect trabeculae formation. Expressions of osteogenic molecules and fibroblast markers were detected by RT-PCR and Western blotting. GFP-BMSCs showed obvious osteogenic and adipogenic differentiation ability, according to oil-red O and alizarin-red staining. Bone marrow chimera spinal intervertebral fusion mouse model was successfully established, with efficient localization of GFP-BMSCs at intervertebral fusion site. SDF-1 significantly promoted bone trabeculae formation in callus at intervertebral fusion site. SDF-1 significantly increased osteogenic molecules transcription/expression in callus at intervertebral bone graft fusion site of mice; however, SDF-1-Anta (AMD3100) significantly decreased osteogenic molecules transcrition/expression, compared to those of mice from the BM-SIF model group (p < 0.05). SDF-1 markedly induced and SDF-1-Anta significantly decreased fibroblast proliferations in the callus at the intervertebral fusion site of mice, compared to those of mice from the BM-SIF model group (p < 0.05). SDF-1 enhanced expression of Wnt10b and β-catenin in callus at intervertebral fusion site of mice compared to mice of the BM-SIF model group (p < 0.05). In conclusion, SDF-1 induced directional chemotaxis of BMSCs to the intervertebral fusion site and promoted osteogenic differentiation in bone marrow chimera spinal intervertebral fusion mice by regulating Wnt/β-catenin pathway and modulating the proliferation of BMSCs.

Glial regulators of ions and solutes required for specific chemosensory functions in Caenorhabditis elegans.

Glia and accessory cells regulate the microenvironment around neurons and primary sensory cells. However, the impact of specific glial regulators of ions and solutes on functionally diverse primary cells is poorly understood. Here, we systemically investigate the requirement of ion channels and transporters enriched in Caenorhabditis elegans Amsh glia for the function of chemosensory neurons. Although Amsh glia ablated worms show reduced function of ASH, AWC, AWA, and ASE neurons, we show that the loss of glial enriched ion channels and transporters impacts these neurons differently, with nociceptor ASH being the most affected. Furthermore, our analysis underscores the importance of K+, Cl-, and nucleoside homeostasis in the Amphid sensory organ and uncovers the contribution of glial genes implicated in neurological disorders. Our findings build a unique fingerprint of each glial enriched ion channel and transporter and may provide insights into the function of supporting cells of mammalian sensory organs.

The role of CXCR3 and its ligands in cancer.

Chemokines are a class of small cytokines or signaling proteins that are secreted by cells. Owing to their ability to induce directional chemotaxis of nearby responding cells, they are called chemotactic cytokines. Chemokines and chemokine receptors have now been shown to influence many cellular functions, including survival, adhesion, invasion, and proliferation, and regulate chemokine levels. Most malignant tumors express one or more chemokine receptors. The CXC subgroup of chemokine receptors, CXCR3, is mainly expressed on the surface of activated T cells, B cells, and natural killer cells, and plays an essential role in infection, autoimmune diseases, and tumor immunity by binding to specific receptors on target cell membranes to induce targeted migration and immune responses. It is vital to treat infections, autoimmune diseases, and tumors. CXCR3 and its ligands, CXCL9, CXCL10, and CXCL11, are closely associated with the development and progression of many tumors. With the elucidation of its mechanism of action, CXCR3 is expected to become a new indicator for evaluating the prognosis of patients with tumors and a new target for clinical tumor immunotherapy. This article reviews the significance and mechanism of action of the chemokine receptor CXCR3 and its specific ligands in tumor development.

Lactate-driving Pt nanoflower with positive chemotaxis for deep intratumoral penetration

The deep penetration in response to specific intratumoral conditions holds considerable potential in achieving a more effective therapy. Lactate is mainly produced by exuberant-metabolism tumor cells growing in the deep center of solid tumor, which would form the characteristic of higher-level lactate deep inside tumor in distance with blood vessels. Herein, inspired by the in vitro directional chemotaxis of enzyme-powered nanomotor driven by substrate gradient, a novel lactate oxidase (LOX)-powered Pt Nanoflowers (Pt NFs) was developed to achieve deep intratumoral penetration triggered by the lactate-driving positive chemotaxis that was confirmed both in vitro and in vivo for the first time. Besides, LOX-powered Pt NFs with self-oxygenation could achieve a more thorough effect on hypoxic relief via the cascading catalysis: (1) the orthotopic extra H2O2 production from lactate catalyzed by LOX, and (2) the effective conversion of both extra-supplement and endogenous H2O2 into O2 catalyzed by Pt NFs, further overcoming the hypoxia-induced radioresistance. Meanwhile, the X-ray radiation deposited inside Pt NFs could improve low-dose radiotherapy effect with increasing ROS level and enhancing nuclear DNA damage. Collectively, this work would provide a blueprint for developing substrate gradient-driving "smart" delivery systems and radiosensitization strategy.

Reaction-Free Concentration Gradient Generation in Spatially Nonuniform AC Electric Fields.

The ability to generate stable, spatiotemporally controllable concentration gradients is critical for both electrokinetic and biological applications such as directional wetting and chemotaxis. Electrochemical techniques for generating solution and surface gradients display benefits such as simplicity, controllability, and compatibility with automation. Here, we present an exploratory study for generating microscale spatiotemporally controllable gradients using a reaction-free electrokinetic technique in a microfluidic environment. Methanol solutions with ionic fluorescein isothiocyanate (FITC) molecules were used as an illustrative electrolyte. Spatially nonuniform alternating current (AC) electric fields were applied using hafnium dioxide (HfO2)-coated Ti/Au electrode pairs. Results from spatial and temporal analyses along with control experiments suggest that the FITC ion concentration gradient in bulk fluid (over 50 μm from the electrode) was established due to spatial variation of electric field density, and was independent of electrochemical reactions at the electrode surface. The established ion concentration gradients depended on both amplitudes and frequencies of the oscillating AC electric field. Overall, this work reports a novel approach for generating stable and spatiotemporally tunable gradients in a microfluidic chamber using a reaction-free electrochemical methodology.

Boundedness criteria for a class of indirect (and direct) chemotaxis-consumption models in high dimensions

In a bounded and smooth domain Ω of Rn, n≥5, we, mainly, consider for some ξ,χ,δ positive and Tmax∈(0,∞] the zero-flux chemotaxis model with indirect signal absorption ut=ξΔu−χ∇⋅(u∇v),vt=Δv−wv,wt=−δw+u,inΩ×(0,Tmax),equipped with sufficiently regular initial data u(x,0)=u0(x)≥0, v(x,0)=v0(x)≥0 and w(x,0)=w0(x)≥0. We establish the existence of ξ∗=ξ∗(n)>1 such that whenever χ‖v0‖L∞(Ω) obeys certain constraints, functions of n and ξ (0<ξ<ξ∗), the initial–boundary value problem has a unique classical solution in Ω×(0,∞), which is bounded. In the frame of both direct and indirect chemotaxis models, our work (partially) improves and generalizes known results.

TREM2 regulates purinergic receptor-mediated calcium signaling and motility in human iPSC-derived microglia.

The membrane protein TREM2 (Triggering Receptor Expressed on Myeloid cells 2) regulates key microglial functions including phagocytosis and chemotaxis. Loss-of-function variants of TREM2 are associated with increased risk of Alzheimer's disease (AD). Because abnormalities in Ca2+ signaling have been observed in several AD models, we investigated TREM2 regulation of Ca2+ signaling in human induced pluripotent stem cell-derived microglia (iPSC-microglia) with genetic deletion of TREM2. We found that iPSC-microglia lacking TREM2 (TREM2 KO) show exaggerated Ca2+ signals in response to purinergic agonists, such as ADP, that shape microglial injury responses. This ADP hypersensitivity, driven by increased expression of P2Y12 and P2Y13 receptors, results in greater release of Ca2+ from the endoplasmic reticulum stores, which triggers sustained Ca2+ influx through Orai channels and alters cell motility in TREM2 KO microglia. Using iPSC-microglia expressing the genetically encoded Ca2+ probe, Salsa6f, we found that cytosolic Ca2+ tunes motility to a greater extent in TREM2 KO microglia. Despite showing greater overall displacement, TREM2 KO microglia exhibit reduced directional chemotaxis along ADP gradients. Accordingly, the chemotactic defect in TREM2 KO microglia was rescued by reducing cytosolic Ca2+ using a P2Y12 receptor antagonist. Our results show that loss of TREM2 confers a defect in microglial Ca2+ response to purinergic signals, suggesting a window of Ca2+ signaling for optimal microglial motility.

Live-Cell Microscopy Reveals That Human T Cells Primarily Respond Chemokinetically Within a CCL19 Gradient That Induces Chemotaxis in Dendritic Cells.

The ability to study migratory behavior of immune cells is crucial to understanding the dynamic control of the immune system. Migration induced by chemokines is often assumed to be directional (chemotaxis), yet commonly used end-point migration assays are confounded by detecting increased cell migration that lacks directionality (chemokinesis). To distinguish between chemotaxis and chemokinesis we used the classic “under-agarose assay” in combination with video-microscopy to monitor migration of CCR7+ human monocyte-derived dendritic cells and T cells in response to a concentration gradient of CCL19. Formation of the gradients was visualized with a fluorescent marker and lasted several hours. Monocyte-derived dendritic cells migrated chemotactically towards the CCL19 gradient. In contrast, T cells exhibited a biased random walk that was largely driven by increased exploratory chemokinesis towards CCL19. This dominance of chemokinesis over chemotaxis in T cells is consistent with CCR7 ligation optimizing T cell scanning of antigen-presenting cells in lymphoid tissues.

Microglial remodeling of actin network by Tau oligomers, via G protein-coupled purinergic receptor, P2Y12R-driven chemotaxis.

Alzheimer's disease (AD) is associated with age-related neurodegeneration, synaptic deformation and chronic inflammation mediated by microglia and infiltrated macrophages in the brain. Tau oligomers can be released from damaged neurons via various mechanisms such as exosomes, neurotransmitter, membrane leakage etc. Microglia sense the extracellular Tau through several cell-surface receptors and mediate chemotaxis and phagocytosis. The purinergic receptor P2Y12R recently gained interest in neurodegeneration for neuro-glial communication and microglial chemotaxis towards the site of plaque deposition. To understand the effect of extracellular Tau oligomers in microglial migration, the P2Y12R-mediated actin remodeling, reorientation of tubulin network and rate of migration were studied in the presence of ATP. The extracellular Tau species directly interacted with P2Y12R and also induced this purinoceptor expression in microglia. Microglial P2Y12R colocalized with remodeled membrane-associated actin network as a component of migration in response to Tau oligomers. As an inducer of P2Y12R, ATP facilitated the localization of P2Y12R in lamellipodia and filopodia during accelerated microglial migration. The direct interaction of extracellular Tau oligomers with microglial P2Y12R would facilitate the signal transduction in both way, directional chemotaxis and receptor-mediated phagocytosis. These unprecedented findings emphasize that microglia can modulate the membrane-associated actin structure and incorporate P2Y12R to perceive the axis and rate of chemotaxis in Tauopathy.

Chemotaxis: Active Degradation of Attractant Enables Optimal Maze Navigation

How signals coordinate and direct chemotaxis is an issue that is actively investigated. A new study shows how the dynamic alteration of chemoattractant flux by chemotaxing cells provides an efficient way to solve complex navigational tasks, including finding the optimal path through a complex maze.

The Role of Chemokines in the Pathophysiology of Major Depressive Disorder

Major depressive disorder (MDD) is a debilitating condition, whose high prevalence and multisymptomatic nature set its standing as a leading contributor to global disability. To better understand this psychiatric disease, various pathophysiological mechanisms have been proposed, including changes in monoaminergic neurotransmission, imbalance of excitatory and inhibitory signaling in the brain, hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, and abnormalities in normal neurogenesis. While previous findings led to a deeper understanding of the disease, the pathogenesis of MDD has not yet been elucidated. Accumulating evidence has confirmed the association between chronic inflammation and MDD, which is manifested by increased levels of the C-reactive protein, as well as pro-inflammatory cytokines, such as Interleukin 1 beta, Interleukin 6, and the Tumor necrosis factor alpha. Furthermore, recent findings have implicated a related family of cytokines with chemotactic properties, known collectively as chemokines, in many neuroimmune processes relevant to psychiatric disorders. Chemokines are small (8–12 kDa) chemotactic cytokines, which are known to play roles in direct chemotaxis induction, leukocyte and macrophage migration, and inflammatory response propagation. The inflammatory chemokines possess the ability to induce migration of immune cells to the infection site, whereas their homeostatic chemokine counterparts are responsible for recruiting cells for their repair and maintenance. To further support the role of chemokines as central elements to healthy bodily function, recent studies suggest that these proteins demonstrate novel, brain-specific mechanisms including the modulation of neuroendocrine functions, chemotaxis, cell adhesion, and neuroinflammation. Elevated levels of chemokines in patient-derived serum have been detected in individuals diagnosed with major depressive disorder, bipolar disorder, and schizophrenia. Furthermore, despite the considerable heterogeneity of experimental samples and methodologies, existing biomarker studies have clearly demonstrated the important role of chemokines in the pathophysiology of psychiatric disorders. The purpose of this review is to summarize the data from contemporary experimental and clinical studies, and to evaluate available evidence for the role of chemokines in the central nervous system (CNS) under physiological and pathophysiological conditions. In light of recent results, chemokines could be considered as possible peripheral markers of psychiatric disorders, and/or targets for treating depressive disorders.

Oral Neutrophils Characterized: Chemotactic, Phagocytic, and Neutrophil Extracellular Trap (NET) Formation Properties.

Maintenance of oral health is in part managed by the immune-surveillance and antimicrobial functions of polymorphonuclear leukocytes (PMNs), which migrate from the circulatory system through the oral mucosal tissues as oral PMNs (oPMNs). In any microorganism-rich ecosystem, such as the oral cavity, PMNs migrate toward various exogenous chemoattractants, phagocytose bacteria, and produce neutrophil extracellular traps (NETs) to immobilize and eliminate pathogens. PMNs obtained from the circulation through venipuncture (hereafter called cPMNs) have been widely studied using various functional assays. We aimed to study the potential of oPMNs in maintaining oral health and therefore compared their chemotactic and antimicrobial functions with cPMNs. To establish chemotactic, phagocytic, and NET forming capacities, oPMNs and cPMNs were isolated from healthy subjects without obvious oral inflammation. Directional chemotaxis toward the chemoattractant fMLP was analyzed using an Insall chamber and video microscopy. fMLP expression was assessed by flow cytometry. Phagocytosis was analyzed by flow cytometry, following PMN incubation with heat-inactivated FITC-labeled micro-organisms. Furthermore, agar plate-based killing assays were performed with Escherichia coli (Ec). NET formation by oPMNs and cPMNs was quantified fluorimetrically using SYTOX™ Green, following stimulation with either PMA or RPMI medium (unstimulated control). In contrast to cPMNs, the chemotactic responses of oPMNs to fMLP did not differ from controls (mean velocity ± SEM of cPMNs: 0.79 ± 0.24; of oPMNs; 0.10 ± 0.07 micrometer/min). The impaired directional movement toward fMLP by oPMNs was explained by significantly lower fMLP receptor expression. Increased adhesion and internalization of various micro-organisms by oPMNs was observed. oPMNs formed 13 times more NETs than stimulated cPMNs, in both unstimulated and stimulated conditions. Compared to cPMNs, oPMNs showed a limited ability for intracellular killing of Ec. In conclusion, oPMNs showed exhausted capacity for efficient chemotaxis toward fMLP which may be the result of migration through the oral tissues into the oral cavity, being a highly “hostile” ecosystem. Overall, oPMNs' behavior is consistent with hyperactivity and frustrated killing. Nevertheless, oPMNs most likely contribute to maintaining a balanced oral ecosystem, as their ability to internalize microbes in conjunction with their abundant NET production remains after entering the oral cavity.

Hepatocyte-Derived Lipotoxic Extracellular Vesicle Sphingosine 1-Phosphate Induces Macrophage Chemotaxis.

Background: The pathophysiology of non-alcoholic steatohepatitis involves hepatocyte lipotoxicity due to excess saturated free fatty acids and concomitant proinflammatory macrophage effector responses. These include the infiltration of macrophages into hepatic cords in response to incompletely understood stimuli. Stressed hepatocytes release an increased number of extracellular vesicles (EVs), which are known to participate in intercellular signaling and coordination of the behavior of immune cell populations via their cargo. We hypothesized that hepatocyte-derived lipotoxic EVs that are enriched in sphingosine 1-phosphate (S1P) are effectors of macrophage infiltration in the hepatic microenvironment.Methods: Lipotoxic EVs were isolated from palmitate treated immortalized mouse hepatocytes and characterized by nanoparticle tracking analysis. Lipotoxic EV sphingolipids were quantified using tandem mass spectrometry. Wildtype and S1P1 receptor knockout bone marrow-derived macrophages were exposed to lipotoxic EV gradients in a microfluidic gradient generator. Macrophage migration toward EV gradients was captured by time-lapse microscopy and analyzed to determine directional migration. Fluorescence-activated cell sorting along with quantitative PCR and immunohistochemistry were utilized to characterize the cell surface expression of S1P1 receptor on intrahepatic leukocytes and hepatic expression of S1P1 receptor, respectively.Results: Palmitate treatment induced the release of EVs. These EVs were enriched in S1P. Palmitate-induced S1P enriched EVs were chemoattractive to macrophages. EV S1P enrichment depended on the activity of sphingosine kinases 1 and 2, such that, pharmacological inhibition of sphingosine kinases 1 and 2 resulted in a significant reduction in EV S1P cargo without affecting the number of EVs released. When exposed to EVs derived from cells treated with palmitate in the presence of a pharmacologic inhibitor of sphingosine kinases 1 and 2, macrophages displayed diminished chemotactic behavior. To determine receptor-ligand specificity, we tested the migration responses of macrophages genetically deleted in the S1P1 receptor toward lipotoxic EVs. S1P1 receptor knockout macrophages displayed a marked reduction in their chemotactic responses toward lipotoxic palmitate-induced EVs.Conclusions:Palmitate-induced lipotoxic EVs are enriched in S1P through sphingosine kinases 1 and 2. S1P-enriched EVs activate persistent and directional macrophage chemotaxis mediated by the S1P1 receptor, a potential signaling axis for macrophage infiltration during hepatic lipotoxicity, and a potential therapeutic target for non-alcoholic steatohepatitis.

IMMUNOSUPPRESSIVE POTENTIAL OF PERIPHERAL REGULATORY T-LYMPHOCYTES IN THE PROCESS OF TUMOR PROGRESSION IN PATIENTS WITH METASTATIC SOFT TISSUE SARCOMAS

In tumor microenvironment the self-maintenance condition of T-regulatory lymphocytes (Treg) are created by tumor cells due to the production of vascular endothelial growth factor VEGF and chemokine CCL2. In the present work there was evaluated the quantitative content of these proteins in cultured cell supernatants of metastatic soft tissue sarcomas (STS) as well as characterized the immunophenotype of peripheral blood Treg by flow cytometry. The study included 35 patients who received treatment at the N.N. Petrov National Medical Research Center of Oncology. For the study- samples of metastatic tumor were taken to obtain sarcoma cell culture and samples of peripheral blood of patients in the absence of tumor growth (stable disease-SD) or disease progression (PD). The statistically significant differences were found in the quantitative content of CCR10+Treg (9.1 % and 4.5 %, respectively, p=0.001), CCR4+Treg (10 % and 3.3 %, respectively, p=0.001), neuropilin-1 (Nrp1+) Treg (6 % and 4.5 %, respectively, p=0.021) in patients with PD and SD. A direct correlation of high strength was found between production of VEGF, CCL2 by metastatic STS cells and expression of Nrp1 (r=0.93, p=0.001), VEGFR-2(r=0.88, p=0.007), CCR4(r=0.81, p=0.024) by Treg cells. Statistically significant differences in the CCR10+Treg (9.5 % and 2.93 %, respectively, p=0.012) and CCR4+Treg (68, 3 % and 3.95 %, respectively, p=0.007) were detected in the group of patients with liposarcoma and synovial sarcoma. Thus in patients with metastatic STS - there was directional chemotaxis of Treg into tumor microenvironment providing the creation of tumor-induced tolerance, which could be associated with DP. The revealed regularities could be used to plan adjuvant and palliative treatment of STS patients.

Growth-mediated autochemotactic pattern formation in self-propelling bacteria.

Bacteria, while developing a multicellular colony or biofilm, can undergo pattern formation by diverse intricate mechanisms. One such route is directional movement or chemotaxis toward or away from self-secreted or externally employed chemicals. In some bacteria, the self-produced signaling chemicals or autoinducers themselves act as chemoattractants or chemorepellents and thereby regulate the directional movements of the cells in the colony. In addition, bacteria follow a certain growth kinetics which is integrated in the process of colony development. Here, we study the interplay of bacterial growth dynamics, cell motility, and autochemotactic motion with respect to the self-secreted diffusive signaling chemicals in spatial pattern formation. Using a continuum model of motile bacteria, we show growth can act as a crucial tuning parameter in determining the spatiotemporal dynamics of a colony. In action of growth dynamics, while chemoattraction toward autoinducers creates arrested phase separation, pattern transitions and suppression can occur for a fixed chemorepulsive strength.

S100A4 regulates macrophage invasion by distinct myosin-dependent and myosin-independent mechanisms.

S100A4, a member of the S100 family of Ca2+-binding proteins, is a key regulator of cell migration and invasion. Our previous studies showed that bone marrow–derived macrophages from S100A4−/− mice exhibit defects in directional motility and chemotaxis in vitro and reduced recruitment to sites of inflammation in vivo. We now show that the loss of S100A4 produces two mechanistically distinct phenotypes with regard to macrophage invasion: a defect in matrix degradation, due to a disruption of podosome rosettes caused by myosin-IIA overassembly, and a myosin-independent increase in microtubule acetylation, which increases podosome rosette stability and is sufficient to inhibit macrophage invasion. Our studies point to S100A4 as a critical regulator of matrix degradation, whose actions converge on the dynamics and degradative functions of podosome rosettes.

Chemotactic effect of β-defensin 1 on macrophages in Megalobrama amblycephala

Besides their function as a physical barrier against pathogens, β-defensins possess the ability to induce direct or indirect chemotaxis in leukocytes of mammals. However little is known about the ability of defensins to guide the migration of macrophages in fish. The objective of our study was to investigate whether β-defensin 1 (maBD1) can recruit leukocytes (specifically macrophages) in vivo and in vitro in a farmed cyprinid fish Megalobrama amblycephala. The M. amblycephala β-defensin 1 (maBD1) gene was amplified from the head-kidney transcriptome. Synthetic maBD1 polypeptide (as well as its N-terminus half, but not the C-terminus half) was capable of inducing the migration of leukocytes (specifically macrophages) at concentrations from 26.0 μg/mL to 52.0 μg/mL in head kidney tissue in vitro. When injected intraperitoneally in vivo, the number of leukocytes in the peritoneal cavity was in positive correlation with the maBD1 concentration. maBD1 also induced the expression of two proinflammatory cytokines (IL-1beta and TNF-alpha) in spleen, head and body kidney, and hepatopancreas. These results strongly indicate that BD1 has a chemoattractant capacity for macrophages, as well as the ability to modulate the expression of proinflammatory cytokines in fish.

Lysosomal calcium in dendritic cell migration

Dendritic Cells Activation of dendritic cells (DCs) by stimuli such as bacterial sensing promotes DC maturation. In contrast to random migratory patterns of immature DCs, mature DCs migrate in a continuous and directional manner. Bretou et al. examined the role of lysosomes in regulating mature DC migration. Release of lysosomal calcium connects DC activation with directional migration. Deletion of a lysosomal calcium channel impaired directional DC migration and DC chemotaxis to lymph nodes. Thus, release of lysosomal calcium links stimulus sensing with DC migration. Sci. Immunol. 2 , eaak9573 (2017).