Angiotensin-(1-7)/MasR axis promotes migration of monocytes/macrophages with a regulatory phenotype to perform phagocytosis and efferocytosis.
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ABSTRACT:
SUBMITTER: Zaidan I
PROVIDER: S-EPMC8765051 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The tissue microenvironment in the mouse pancreas has been shown to promote very different polarizations of resident macrophages with islet-resident macrophages displaying an inflammatory "M1" profile and macrophages in the exocrine tissue mostly displaying an alternatively activated "M2" profile. The impact of this polarization on tissue homeostasis and diabetes development is unclear. In this study, the ability of pancreas-resident macrophages to phagocyte bacterial and endogenous debris was investigated. Mouse endocrine and exocrine tissues were separated, and tissue-resident macrophages were isolated by magnetic immunolabeling. Isolated macrophages were subjected to flow cytometry for polarization markers and qPCR for phagocytosis-related genes. Functional in vitro investigations included phagocytosis and efferocytosis assays using pH-sensitive fluorescent bacterial particles and dead fluorescent neutrophils, respectively. Intravital confocal imaging of in situ phagocytosis and efferocytosis in the pancreas was used to confirm findings in vivo. Gene expression analysis revealed no significant overall difference in expression of most phagocytosis-related genes in islet-resident vs. exocrine-resident macrophages included in the analysis. In this study, pancreas-resident macrophages were shown to differ in their ability to phagocyte bacterial and endogenous debris depending on their microenvironment. This difference in abilities may be one of the factors polarizing islet-resident macrophages to an inflammatory state since phagocytosis has been found to imprint macrophage heterogeneity. It remains unclear if this difference has any implications in the development of islet dysfunction or autoimmunity.
| S-EPMC8185276 | biostudies-literature
Project description:Development of immunity-based strategy to manage bacterial infection is urgently needed in aquaculture due to the widespread of antibiotic-resistant bacteria. Phagocytosis serves as the first line defense in innate immunity that engulfs bacteria and restricts their proliferations and invasions. However, the mechanism underlying the regulation of phagocytosis is not fully elucidated and the way to boost phagocytosis is not yet explored. In this manuscript, we profiled the metabolomes of monocytes/macrophages isolated from Nile tilapia, prior and after phagocytosis on Vibrio alginolyticus. Monocytes/macrophages showed a metabolic shift following phagocytosis. Interestingly, succinate was accumulated after phagocytosis and was identified as a crucial biomarker to distinguish before and after phagocytosis. Exogenous succinate increased the phagocytotic rate of monocytes/macrophages in a dose-dependent manner. This effect was dependent on the TCA cycle as the inhibitor of malonate that targets succinate dehydrogenase abrogated the effect. Meanwhile, exogenous succinate regulated the expression of genes associated with innate immune and phagocytosis. In addition, succinate-potentiated phagocytosis was applicable to both gram-negative and -positive cells, including V. alginolyticus, Edwardsiella tarda, Streptococcus agalactiae, and Streptococcus iniae. Our study shed light on the understanding of how modulation on host's metabolism regulates immune response, and this can be a potent therapeutic approach to control bacterial infections in aquaculture.
| S-EPMC8082191 | biostudies-literature
Project description:Cigarette smoking (CS), the main risk factor for COPD (chronic obstructive pulmonary disease) in developed countries, decreases alveolar macrophages (AM) clearance of both apoptotic cells and bacterial pathogens. This global deficit of AM engulfment may explain why active smokers have worse outcomes of COPD exacerbations, episodes characterized by airway infection and inflammation that carry high morbidity and healthcare cost. When administered as intravenous supplementation, the acute phase-reactant alpha-1 antitrypsin (A1AT) reduces the severity of COPD exacerbations in A1AT deficient (AATD) individuals and of bacterial pneumonia in murine models, but the effect of A1AT on AM scavenging functions has not been reported. Apoptotic cell clearance (efferocytosis) was measured in human AM isolated from patients with COPD, in primary rat AM or differentiated monocytes exposed to CS ex vivo, and in AM recovered from mice exposed to CS. A1AT (100 ?g/mL, 16 h) significantly ameliorated efferocytosis (by ~50%) in AM of active smokers or AM exposed ex vivo to CS. A1AT significantly improved AM global engulfment, including phagocytosis, even when cells were simultaneously challenged with apoptotic and Fc-coated (bacteria-like) targets. The improved efferocytosis in A1AT-treated macrophages was associated with inhibition of tumor necrosis factor-? converting enzyme (TACE) activity, decreased mannose receptor shedding, and markedly increased abundance of efferocytosis receptors (mannose- and phosphatidyl serine receptors and the scavenger receptor B2) on AM plasma membrane. Directed airway A1AT treatment (via inhalation of a nebulized solution) restored in situ airway AM efferocytosis after CS exposure in mice. The amelioration of CS-exposed AM global engulfment may render A1AT as a potential therapy for COPD exacerbations.
| S-EPMC5407578 | biostudies-literature
Project description:BackgroundMonocyte-derived macrophages (MDMs) and microglia elicit neural inflammation and clear debris for subsequent tissue repair and remodeling. The role of infiltrating MDMs in the injured brain, however, has been controversial due to overlapping antigen expression with microglia. In this study, we define the origin and function of MDMs in cerebral ischemia.MethodsUsing adoptive transfer of GFP+ splenocytes into adult asplenic mice subjected to transient middle cerebral artery occlusion, we compared the role of CD11b+/CD45+/NK1.1-/Ly6G- MDMs and microglia in the ischemic brain. The phagocytic activities of MDMs and microglia were measured by the uptake of fluorescent beads both in vivo with mice infused with GFP+ splenocytes and ex vivo with cultures of isolated brain immune cells.ResultsStroke induced an infiltration of MDMs [GFP+] into the ipsilateral hemisphere at acute (3 days) and sub-acute phases (7 days) of post-stroke. At 7 days, the infiltrating MDMs contained both CD45High and CD45Low subsets. The CD45High MDMs in the injured hemisphere exhibited a significantly higher proliferation capacity (Ki-67 expression levels) as well as higher expression levels of CD11c when compared to CD45Low MDMs. The CD45High and CD45Low MDM subsets in the injured hemisphere were approximately equal populations, indicating that CD45High MDMs infiltrating the ischemic brain changes their phenotype to CD45Low microglia-like phenotype. Studies with fluorescent beads reveal high levels of MDM phagocytic activity in the post-stroke brain, but this phagocytic activity was exclusive to post-ischemic brain tissue and was not detected in circulating monocytes. By contrast, CD45Low microglia-like cells had low levels of phagocytic activity when compared to CD45High cells. Both in vivo and ex vivo studies also show that the phagocytic activity in CD45High MDMs is associated with an increase in the CD45Low/CD45High ratio, indicating that phagocytosis promotes MDM phenotype conversion.ConclusionsThis study demonstrates that MDMs are the predominant phagocytes in the post-ischemic brain, with the CD45High subset having the highest phagocytic activity levels. Upon phagocytosis, CD45High MDMs in the post-ischemic brain adopt a CD45Low phenotype that is microglia-like. Together, these studies reveal key roles for MDMs and their phagocytic function in tissue repair and remodeling following cerebral ischemia.
| S-EPMC9295522 | biostudies-literature
Project description:Monocyte-derived macrophages orchestrate tissue regeneration by homing to sites of injury, phagocytosing pathological debris, and stimulating other cell types to repair the tissue. Accordingly, monocytes have been investigated as a translational and potent source for cell therapy, but their utility has been hampered by their rapid acquisition of a pro-inflammatory phenotype in response to the inflammatory injury microenvironment. To overcome this problem, we designed a cell therapy strategy where monocytes are exogenously reprogrammed by intracellularly loading the cells with biodegradable microparticles containing an anti-inflammatory drug in order to modulate and maintain an anti-inflammatory phenotype over time. To test this concept, poly(lactic-co-glycolic) acid microparticles were loaded with the anti-inflammatory drug dexamethasone (Dex) and administered to primary human monocytes for four hours to facilitate phagocytic uptake. After removal of non-phagocytosed microparticles, microparticle-loaded monocytes differentiated into macrophages and stored the microparticles intracellularly for several weeks in vitro, releasing drug into the extracellular environment over time. Cells loaded with intracellular Dex microparticles showed decreased expression and secretion of inflammatory factors even in the presence of pro-inflammatory stimuli up to 7 days after microparticle uptake compared to untreated cells or cells loaded with blank microparticles, without interfering with phagocytosis of tissue debris. This study represents a new strategy for long-term maintenance of anti-inflammatory macrophage phenotype using a translational monocyte-based cell therapy strategy without the use of genetic modification. Because of the ubiquitous nature of monocyte-derived macrophage involvement in pathology and regeneration, this strategy holds potential as a treatment for a vast number of diseases and disorders. STATEMENT OF SIGNIFICANCE: We report a unique and translational strategy to overcome the challenges associated with monocyte- and macrophage-based cell therapies, in which the cells rapidly take on inflammatory phenotypes when administered to sites of injury. By intracellularly loading monocytes with drug-loaded microparticles prior to administration via phagocytosis, we were able to inhibit inflammation while preserving functional behaviors of human primary macrophages derived from those monocytes up to seven days later. To our knowledge, this study represents the first report of reprogramming macrophages to an anti-inflammatory phenotype without the use of genetic modification.
| S-EPMC6960335 | biostudies-literature
Project description:Pulmonary inflammation and bacterial colonization are central to the pathogenesis of chronic obstructive pulmonary disease (COPD). Defects in macrophage phagocytosis of both bacteria and apoptotic cells contribute to the COPD phenotype. Small molecule inhibitors with anti-inflammatory activity against p38 mitogen activated protein kinases (MAPKs), phosphatidyl-inositol-3 kinase (PI3K) and Rho kinase (ROCK) are being investigated as novel therapeutics in COPD. Concerns exist, however, about off-target effects. We investigated the effect of p38 MAPK inhibitors (VX745 and SCIO469), specific inhibitors of PI3K ? (NVS-P13K-2), ? (NVS-P13K-3) or ? (NVS-P13K-5) and a ROCK inhibitor PF4950834 on macrophage phagocytosis, early intracellular killing of bacteria and efferocytosis of apoptotic neutrophils. Alveolar macrophages (AM) obtained from broncho-alveolar lavage (BAL) or monocyte-derived macrophages (MDM) from COPD patients (GOLD stage II/III) enrolled from a well characterized clinical cohort (MRC COPD-MAP consortium) or from healthy ex-smoker controls were studied. Both COPD AM and MDM exhibited lower levels of bacterial phagocytosis (using Streptococcus pneumoniae and non-typeable Haemophilus influenzae) and efferocytosis than healthy controls. None of the inhibitors altered bacterial internalization or early intracellular bacterial killing in AM or MDM. Conversely PF4950834, but not other inhibitors, enhanced efferocytosis in COPD AM and MDM. These results suggest none of these inhibitors are likely to exacerbate phagocytosis-related defects in COPD, while confirming ROCK inhibitors can enhance efferocytosis in COPD.
| S-EPMC5040258 | biostudies-literature
Project description:Macrophages engulf and destroy pathogens (phagocytosis) and apoptotic cells (efferocytosis), and can subsequently initiate adaptive immune responses by presenting antigens derived from engulfed materials. Both phagocytosis and efferocytosis share a common degradative pathway in which the target is engulfed into a membrane-bound vesicle, respectively, termed the phagosome and efferosome, where they are degraded by sequential fusion with endosomes and lysosomes. Despite this shared maturation pathway, macrophages are immunogenic following phagocytosis but not efferocytosis, indicating that differential processing or trafficking of antigens must occur. Mass spectrometry and immunofluorescence microscopy of efferosomes and phagosomes in macrophages demonstrated that efferosomes lacked the proteins required for antigen presentation and instead recruited the recycling regulator Rab17. As a result, degraded materials from efferosomes bypassed the MHC class II loading compartment via the recycling endosome - a process not observed in phagosomes. Combined, these results indicate that macrophages prevent presentation of apoptotic cell-derived antigens by preferentially trafficking efferocytosed, but not phagocytosed, materials away from the MHC class II loading compartment via the recycling endosome pathway.
| S-EPMC5261003 | biostudies-literature
Project description:Dendritic cells (DCs) are antigen-presenting cells that play an important role in connecting the innate and adaptive immunity of the immune system. To mediate innate and adaptive immunity, DCs pass through two stages: immature and mature. The change of phenotype is closely associated with the morphological and functional characteristics of DCs. Understanding these properties of DCs is important in the context of recent efforts on the developments of biomaterials-based cancer vaccine. In this paper, the morphological and phenotypical status of DCs in both stages were compared, and their relationship to the phagocytic and migratory ability of the cells was studied using bone-marrow derived dendritic cells (BMDCs). Immature DCs were of a circular shape and expressed low levels of costimulatory molecules, while mature DCs had longer dendrites and expressed high levels of costimulatory molecules. The phagocytic and migratory ability studied using the polymer bead uptake test and live imaging indicated that immature DCs have a pronounced phagocytic ability compared to mature DCs, while the mature DCs moves faster than immature DCs. These findings could be helpful for understanding the relationship between immature and mature DCs and analyzing initiation of the adaptive immune response by DCs in DC-mediated immunotherapy.
| S-EPMC9063012 | biostudies-literature
Project description:BackgroundMacrophages stand at the forefront of both innate and adapted immunity through their capacities to recognize, engulf, and eliminate foreign particles, and to stimulate adapted immune cells. They are also involved in controlling pro- and anti-inflammatory pathways. Macrophage activity against Mycobacterium tuberculosis (M. tuberculosis) has been shown to involve Toll-like receptor (TLR) activation and ROS production. Previous studies have shown that lipopolysaccharide (LPS), through TLR4, could activate macrophages, improve their bactericidal ROS production, and facilitate anti-infective immune responses. We sought to better understand the role of the TLR4-NOX2 axis in macrophage activation during M. tuberculosis infection.MethodsTHP-1 macrophages and PMA primed THP-1 macrophages [THP-1(A)] were treated with LPS and infected by M. tuberculosis. Cells were analyzed by flow cytometry for TLR4 expression, ROS production, phagocytosis, and killing of M. tuberculosis. Western blotting was used to analyze NOX2 expression. Inhibitors of the TLR4-NOX2 pathway were used to assess this pathway's role in these processes, and their role in LPS activation of macrophages.ResultsWe found that THP1-derived macrophages or PMA primed THP-1 macrophages exhibit higher surface TLR4 levels and increased NOX2 expression levels following LPS treatment. M. tuberculosis infection reduced these levels, but LPS was able to limit the negative effects of M.tb. Additionally, LPS increases THP-1(A) cells' bactericidal activities including phagocytosis, ROS production, and destruction of M. tuberculosis. Significantly, all of these activities are impaired when TLR4 or NOX2 are inhibited.ConclusionThese studies demonstrate the importance of the TLR4-NOX2 axis in M. tuberculosis elimination by macrophages and may lead to novel therapies for tuberculosis and other bacterial infections.
| S-EPMC5727946 | biostudies-literature
Project description:Tumor-associated macrophages (TAM) play a crucial role in immunosuppression. However, how TAMs are transformed into immunosuppressive phenotypes and influence the tumor microenvironment (TME) is not fully understood. Here, we utilized single-cell RNA sequencing and whole-exome sequencing data of glioblastoma (GBM) tissues and identified a subset of TAMs dually expressing macrophage and tumor signatures, which were termed double-positive TAMs. Double-positive TAMs tended to be bone marrow-derived macrophages (BMDM) and were characterized by immunosuppressive phenotypes. Phagocytosis of glioma cells by BMDMs in vitro generated double-positive TAMs with similar immunosuppressive phenotypes to double-positive TAMs in the GBM TME of patients. The double-positive TAMs were transformed into M2-like macrophages and drove immunosuppression by expressing immune-checkpoint proteins CD276, PD-L1, and PD-L2 and suppressing the proliferation of activated T cells. Together, glioma cell phagocytosis by BMDMs in the TME leads to the formation of double-positive TAMs with enhanced immunosuppressive phenotypes, shedding light on the processes driving TAM-mediated immunosuppression in GBM.SignificanceBone marrow-derived macrophages phagocytose glioblastoma cells to form double-positive cells, dually expressing macrophage and tumor signatures that are transformed into M2-like macrophages and drive immunosuppression.
| S-EPMC9978884 | biostudies-literature