Photobiomodulation enhances macrophage phagocytic capacity via Rac1 activation

The strongest genetic risk factor influencing susceptibility to late-onset Alzheimer’s disease (AD) is apolipoprotein E (APOE) genotype. APOE has three common isoforms in humans, E2, E3, and E4. The presence of two copies of the E4 allele increases risk by ∼12-fold whereas E2 allele is associated with an ∼twofold decreased risk for AD. These data put APOE central to AD pathophysiology, but it is not yet clear how APOE alleles modify AD risk. Recently we found that astrocytes, a major central nervous system cell type that produces APOE, are highly phagocytic and participate in normal synapse pruning and turnover. Here, we report a novel role for APOE in controlling the phagocytic capacity of astrocytes that is highly dependent on APOE isoform. APOE2 enhances the rate of phagocytosis of synapses by astrocytes, whereas APO4 decreases it. We also found that the amount of C1q protein accumulation in hippocampus, which may represent the accumulation of senescent synapses with enhanced vulnerability to complement-mediated degeneration, is highly dependent on APOE alleles: C1q accumulation was significantly reduced in APOE2 knock-in (KI) animals and was significantly increased in APOE4 KI animals compared with APOE3 KI animals. These studies reveal a novel allele-dependent role for APOE in regulating the rate of synapse pruning by astrocytes. They also suggest the hypothesis that AD susceptibility of APOE4 may originate in part from defective phagocytic capacity of astrocytes which accelerates the rate of accumulation of C1q-coated senescent synapses, enhancing synaptic vulnerability to classical-complement-cascade mediated neurodegeneration.

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Loss of melanoregulin (MREG) enhances cathepsin-D secretion by the retinal pigment epithelium

Visual Neuroscience ◽

10.1017/s0952523813000096 ◽

2013 ◽

Vol 30 (3) ◽

pp. 55-64 ◽

Cited By ~ 6

Author(s):

LAURA S. FROST ◽

VANDA S. LOPES ◽

FRANK P. STEFANO ◽

ALVINA BRAGIN ◽

DAVID S. WILLIAMS ◽

...

Keyword(s):

Retinal Pigment Epithelium ◽

Cathepsin D ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Retinal Disease ◽

Protective Role ◽

Phagocytic Cells ◽

Phagocytic Capacity ◽

Photoreceptor Outer Segments ◽

Age Dependent

AbstractCathepsin-D (Cat-D) is a major proteolytic enzyme in phagocytic cells. In the retinal pigment epithelium (RPE), it is responsible for the daily degradation of photoreceptor outer segments (POSs) to maintain retinal homeostasis. Melanoregulin (MREG)-mediated loss of phagocytic capacity has been linked to diminished intracellular Cat-D activity. Here, we demonstrate that loss of MREG enhances the secretion of intermediate Cat-D (48 kDa), resulting in a net enhancement of extracellular Cat-D activity. These results suggest that MREG is required to maintain Cat-D homeostasis in the RPE and likely plays a protective role in retinal health. In this regard, in the Mregdsu/dsu mouse, we observe increased basal laminin. Loss of the Mregdsu allele is not lethal and therefore leads to slow age-dependent changes in the RPE. Thus, we propose that this model will allow us to study potential dysregulatory functions of Cat-D in retinal disease.

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Comparison of a Classical Phagocytosis Assay and a Flow Cytometry Assay for Assessment of the Phagocytic Capacity of Sera from Adults Vaccinated with a Pneumococcal Conjugate Vaccine

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.8.2.245-250.2001 ◽

2001 ◽

Vol 8 (2) ◽

pp. 245-250 ◽

Cited By ~ 13

Author(s):

Wouter T. M. Jansen ◽

Merja Väkeväinen-Anttila ◽

Helena Käyhty ◽

Moon Nahm ◽

N. Bakker ◽

...

Keyword(s):

Flow Cytometry ◽

Defense Mechanism ◽

Worker Safety ◽

Enzyme Linked Immunosorbent Assay ◽

Phagocytosis Assay ◽

Phagocytic Capacity ◽

Killing Assay ◽

Potential Efficacy ◽

Antibody Titers ◽

Low Sensitivity

ABSTRACT Antibody- and complement-mediated phagocytosis is the main defense mechanism against Streptococcus pneumoniae. A standardized, easy to perform phagocytosis assay for pneumococci would be a great asset for the evaluation of the potential efficacy of (experimental) pneumococcal vaccines. Such an assay could replace the laborious phagocytosis assay of viable pneumococci (classical killing assay). Therefore, a newly developed phagocytosis assay based on flow cytometry (flow assay) was compared with the conventional killing assay and enzyme-linked immunosorbent assay (ELISA), using sera obtained from adults pre- and postvaccination with either a bivalent conjugate, a tetravalent conjugate, or the 23-valent polysaccharide vaccine. Highly significant correlations were observed between flow assay phagocytosis titers, killing assay phagocytosis titers, and ELISA antibody titers for serotype 6B and 23F as well. For serotype 19F, strong correlations were only observed between killing assay and ELISA titers. A potential drawback of the flow assay might be the low sensitivity compared with that of the killing assay. The choice of what assay to use, however, will depend on the objectives of the assay. When speed, easy performance, sample throughput, improved worker safety, absence of influence of antibiotics, and absence of false positives are the major criteria, the flow assay is the method of choice. When higher sensitivity is the major requirement, the classical killing assay should be used.

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Abstract WP98: Role of Hydrogen Peroxide in Preconditioning of Microglia to Achieve Improved Hematoma Cleanup After ICH

Stroke ◽

10.1161/str.48.suppl_1.wp98 ◽

2017 ◽

Vol 48 (suppl_1) ◽

Author(s):

Xiurong Zhao ◽

Guanghua Sun ◽

Shun-Ming Ting ◽

Jaroslaw Aronowski

Keyword(s):

Oxidative Injury ◽

Repair Process ◽

Brain Parenchyma ◽

Secondary Brain Injury ◽

Related Factor ◽

Blood Components ◽

Phagocytic Function ◽

Phagocytic Capacity ◽

Biologically Relevant

Background: Red blood cells ( RBC ) and other blood components deposited in brain parenchyma during intracerebral hemorrhage ( ICH ) are the source of secondary brain injury, inflammation, and oxidative stress. Therefore, a fast and efficient removal of the blood from the brain is essential for ameliorating secondary injury and for recovery and repair process. Microglia/macrophages ( MΦ )-mediated phagocytosis is a key component of hematoma clearance after ICH. However, the high levels of pro-oxidative molecules (including H 2 O 2 ) generated by MΦ during phagocytosis could be highly cytotoxic not only to brain cells, but also to MΦ themselves. Thus, an efficient coupling between MΦ-mediated phagocytosis and anti-oxidative processes is essential for the safe and efficient hematoma cleanup. Methods and Results: H 2 O 2 at higher concentrations is known to be neurotoxic. In this study, we established that H 2 O 2 at submicromolar, biologically relevant concentrations, acts as a pro-survival factor for MΦ. By activating transcription factor nuclear factor-erythroid 2 p45-related factor 2 ( Nrf2 ), a master regulator of anti-oxidative regulation, H 2 O 2 stimulates the expression of many antioxidant proteins, which protects MΦ from oxidative injury and damaging components of inflammation. We established that Nrf2-deficient MΦ are more susceptible to H 2 O 2 -mediated or toxic blood components-mediated damage (“ICH-like” injury). Nrf2-KO mice subjected to ICH experienced more severe brain edema and delayed hematoma resolution. In addition, the phagocytosis of RBCs (in vitro model of hematoma clearance) was significantly diminished in MΦ treated with Nrf2 decoy or in MΦ that were harvested from Nrf2-KO mice. On the other hand, pharmacologic activation of Nrf2 or administration of low dosages of H 2 O 2 improved phagocytic capacity of MΦ toward RBC. Furthermore, low levels of H 2 O 2 protected MΦ from ICH-like injury, suggesting that improved phagocytic function could involve preservation of MΦ’ integrity by activating Nrf2. Conclusion: H 2 O 2 at low doses could protect MΦ for oxidative injury and facilitate their phagocytic function, which could benefit hematoma clearance, inflammation resolution, and improve neurological recovery after ICH.

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The macrophage capacity for phagocytosis

Journal of Cell Science ◽

10.1242/jcs.101.4.907 ◽

1992 ◽

Vol 101 (4) ◽

pp. 907-913 ◽

Cited By ~ 11

Author(s):

G.J. Cannon ◽

J.A. Swanson

Keyword(s):

Surface Area ◽

Membrane Surface ◽

Fc Receptors ◽

Phagocytic Capacity ◽

Membrane Surface Area ◽

Murine Bone Marrow ◽

Latex Beads ◽

Endocytic Compartments ◽

Frustrated Phagocytosis

Murine bone marrow-derived macrophages, which measure 13.8 +/− 2.3 microns diameter in suspension, can ingest IgG-opsonized latex beads greater than 20 microns diameter. A precise assay has allowed the determination of the phagocytic capacity, and of physiological parameters that limit that capacity. Ingestion of beads larger than 15 microns diameter required IgG-opsonization, and took 30 minutes to reach completion. Despite the dependence on Fc-receptors for phagocytosis of larger beads, cells reached their limit before all cell surface Fc-receptors were occupied. The maximal membrane surface area after frustrated phagocytosis of opsonized coverslips was similar to the membrane surface area required to engulf particles at the limiting diameter, indicating that the capacity was independent of particle shape. Vacuolation of the lysosomal compartment with sucrose, which expanded endocytic compartments, lowered the phagocytic capacity. This decrease was reversed when sucrose vacuoles were collapsed by incubation of cells with invertase. These experiments indicate that the phagocytic capacity is limited by the amount of available membrane, rather than by the availability of Fc-receptors. The capacity was also reduced by depolymerization of cytoplasmic microtubules with nocodazole. Nocodazole did not affect the area of maximal cell spreading during frustrated phagocytosis, but did alter the shape of the spread cells. Thus, microtubules may coordinate cytoplasm for engulfment of the largest particles.

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Demonstration of a phagocytic cell system belonging to the hemopoietic lineage and originating from the yolk sac in the early avian embryo

Development ◽

10.1242/dev.115.1.157 ◽

1992 ◽

Vol 115 (1) ◽

pp. 157-168 ◽

Cited By ~ 4

Author(s):

M.A. Cuadros ◽

P. Coltey ◽

M. Carmen Nieto ◽

C. Martin

Keyword(s):

Acid Phosphatase ◽

Developmental Stages ◽

Cell Lineage ◽

Cell System ◽

Yolk Sac ◽

Double Labelling ◽

Avian Embryo ◽

Phagocytic Cell ◽

Phagocytic Capacity ◽

Hemopoietic Cells

It is well established that hemopoietic cells arising from the yolk sac invade the avian embryo. To study the fate and role of these cells during the first 2.5-4.5 days of incubation, we constructed yolk sac chimeras (a chick embryo grafted on a quail yolk sac and vice versa) and immunostained them with antibodies specific to cells of quail hemangioblastic lineage (MB1 and QH1). This approach revealed that endothelial cells of the embryonic vessels are of intraembryonic origin. In contrast, numerous hemopoietic cells of yolk sac origin were seen in embryos ranging from 2.5 to 4.5 days of incubation. These cells were already present within the vessels and in the mesenchyme at the earliest developmental stages analyzed. Two hemopoietic cell types of yolk sac origin were distinguishable, undifferentiated cells and macrophage-like cells. The number of the latter cells increased progressively as development proceeded, and they showed marked acid phosphatase activity and phagocytic capacity, as revealed by the presence of numerous phagocytic inclusions in their cytoplasm. The macrophage-like cells were mostly distributed in the mesenchyme and also appeared within some organ primordia such as the neural tube, the liver anlage and the nephric rudiment. Comparison of the results in the two types of chimeras and the findings obtained with acid phosphatase/MB1 double labelling showed that some hemopoietic macrophage-like cells of intraembryonic origin were also present at the stages considered. These results support the existence in the early avian embryo of a phagocytic cell system of blood cell lineage, derived chiefly from the yolk sac. Cells belonging to this system perform phagocytosis in cell death and may also be involved in other morphogenetic processes.

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Effects of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans on phagocytic response of Eisenia andrei coelomocytes

Journal of Xenobiotics ◽

10.4081/xeno.2011.e6 ◽

2011 ◽

Vol 1 (1) ◽

pp. 6 ◽

Cited By ~ 2

Author(s):

Hayet Belmeskine ◽

Pauline Brousseau ◽

Sami Haddad ◽

Louise Vandelac ◽

Michel Fournier

Keyword(s):

Flow Cytometry ◽

Phagocytic Activity ◽

Cytotoxic Effect ◽

Polychlorinated Dibenzofurans ◽

Eisenia Andrei ◽

Phagocytic Capacity ◽

Excessive Secretion ◽

Phagocytic Response

The immunotoxicological effects of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) mixtures on Eisenia andrei earthworms have never been studied. In this work we investigated these effects both for in vitro and in vivo exposure, using the viability and the phagocytic activity of coelomocytes as immunological biomarkers and the flow cytometry was used for analysis. The in vitro exposure revealed a cytotoxic effect of PCDD/Fs mixture (C2) containing 50¥10-3 ng/mL of 2, 3, 7, 8-TCDD and an induction of the phagocytic capacity at the mixture (C1) containing 25¥10-3 ng/mL of 2, 3, 7, 8-TCDD. In the in vivo filter paper exposure, the immunocompetence of earthworms was assessed after 3 h-exposure to mixtures of PCDD/Fs at the levels of C1, C2, C3 and C4 containing about; 0.05, 0.3, 0.5 and 0.83 ng of 2, 3, 7, 8-TCDD/cm², respectively. Morphological observations showed an excessive secretion of mucus and body surface lesions in worms exposed to higher concentrations (C3 and C4), which revealed that these organisms were affected by PCDD/Fs either through skin and/or by feeding. The levels of the extruded cell yield decreased significantly at all the concentrations tested. However, the cell viability was shown to be unaffected by PCDD/Fs concentrations. It was also shown, that exposure to the highest PCDD/Fs concentrations; C2, C3 and C4 inhibited both phagocytic activity and efficiency.

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Glycerol-3-phosphate acyltransferases 3 and 4 direct glycerolipid synthesis and affect functionality in activated macrophages

Biochemical Journal ◽

10.1042/bcj20180381 ◽

2019 ◽

Vol 476 (1) ◽

pp. 85-99 ◽

Cited By ~ 4

Author(s):

Ivana Y. Quiroga ◽

Magali Pellon-Maison ◽

Amanda L. Suchanek ◽

Rosalind A. Coleman ◽

Maria R. Gonzalez-Baro

Keyword(s):

Lipid Accumulation ◽

Macrophage Activation ◽

Lipid A ◽

Inflammatory Responses ◽

Activated Macrophages ◽

Phagocytic Capacity ◽

Activity Increase ◽

Cytokines And Chemokines ◽

Lipid Mass ◽

Glycerolipid Synthesis

AbstractMacrophage classical M1 activation via TLR4 triggers a variety of responses to achieve the elimination of foreign pathogens. During this process, there is also an increase in lipid droplets which contain large quantities of triacylglycerol (TAG) and phospholipid (PL). The functional consequences of this increment in lipid mass are poorly understood. Here, we studied the contribution of glycerolipid synthesis to lipid accumulation, focusing specifically on the first and rate-limiting enzyme of the pathway: glycerol-3-phosphate acyltransferase (GPAT). Using bone marrow-derived macrophages (BMDMs) treated with Kdo2-lipid A, we showed that glycerolipid synthesis is induced during macrophage activation. GPAT4 protein level and GPAT3/GPAT4 enzymatic activity increase during this process, and these two isoforms were required for the accumulation of cell TAG and PL. The phagocytic capacity of Gpat3−/− and Gpat4−/− BMDM was impaired. Additionally, inhibiting fatty acid β-oxidation reduced phagocytosis only partially, suggesting that lipid accumulation is not necessary for the energy requirements for phagocytosis. Finally, Gpat4−/− BMDM expressed and released more pro-inflammatory cytokines and chemokines after macrophage activation, suggesting a role for GPAT4 in suppressing inflammatory responses. Together, these results provide evidence that glycerolipid synthesis directed by GPAT4 is important for the attenuation of the inflammatory response in activated macrophages.

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