Exosomes mediate LTB4 release during neutrophil chemotaxis

Leukotriene B4 (LTB4) is secreted by chemotactic neutrophils, forming a secondary gradient that amplifies the reach of primary chemoattractants. This strategy increases the recruitment range for neutrophils and is important during inflammation. Here, we show that LTB4 and its synthesizing enzymes localize to intracellular multivesicular bodies, which, upon stimulation, release their content as exosomes. Purified exosomes can activate resting neutrophils and elicit chemotactic activity in an LTB4 receptor-dependent manner. Inhibition of exosome release leads to loss of directional motility with concomitant loss of LTB4 release. Our findings establish that the exosomal pool of LTB4 acts in an autocrine fashion to sensitize neutrophils towards the primary chemoattractant, and in a paracrine fashion to mediate the recruitment of neighboring neutrophils in trans. We envision that this mechanism is used by other signals to foster communication between cells in harsh extracellular environments.

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A specific phase of transcranial alternating current stimulation at the β frequency boosts repetitive paired-pulse TMS-induced plasticity

Scientific Reports ◽

10.1038/s41598-021-92768-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hisato Nakazono ◽

Katsuya Ogata ◽

Akinori Takeda ◽

Emi Yamada ◽

Shinichiro Oka ◽

...

Keyword(s):

Cortical Excitability ◽

Motor Evoked Potentials ◽

Single Pulse ◽

Alternating Current ◽

Dependent Manner ◽

Synaptic Efficacy ◽

Paired Pulse ◽

Transcranial Alternating Current Stimulation ◽

In Trans ◽

Specific Phase

AbstractTranscranial alternating current stimulation (tACS) at 20 Hz (β) has been shown to modulate motor evoked potentials (MEPs) when paired with transcranial magnetic stimulation (TMS) in a phase-dependent manner. Repetitive paired-pulse TMS (rPPS) with I-wave periodicity (1.5 ms) induced short-lived facilitation of MEPs. We hypothesized that tACS would modulate the facilitatory effects of rPPS in a frequency- and phase-dependent manner. To test our hypothesis, we investigated the effects of combined tACS and rPPS. We applied rPPS in combination with peak or trough phase tACS at 10 Hz (α) or β, or sham tACS (rPPS alone). The facilitatory effects of rPPS in the sham condition were temporary and variable among participants. In the β tACS peak condition, significant increases in single-pulse MEPs persisted for over 30 min after the stimulation, and this effect was stable across participants. In contrast, β tACS in the trough condition did not modulate MEPs. Further, α tACS parameters did not affect single-pulse MEPs after the intervention. These results suggest that a rPPS-induced increase in trans-synaptic efficacy could be strengthened depending on the β tACS phase, and that this technique could produce long-lasting plasticity with respect to cortical excitability.

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Neutrophil chemotaxis, random migration, and adherence in patients with hyperthyroidism

Acta Endocrinologica ◽

10.1530/acta.0.1210817 ◽

1989 ◽

Vol 121 (6) ◽

pp. 817-820 ◽

Cited By ~ 5

Author(s):

B. Wolach ◽

B. Lebanon ◽

A. Jedeikin ◽

M. S. Shapiro ◽

L. Shenkman

Keyword(s):

Thyroid Function ◽

Chemotactic Activity ◽

Neutrophil Chemotaxis ◽

Phagocytic Cells ◽

Random Migration ◽

Significant Difference ◽

Neutrophil Adherence ◽

Hyperthyroid Patients ◽

Normal Controls ◽

Neutrophil Chemotactic Activity

Abstract. We have examined neutrophil adherence, chemotactic activity, and random migration in 35 hyperthyroid patients with Graves' disease and 106 normal volunteers. No statistically significant differences were found between granulocyte adherence of 17 hyperthyroid subjects (67 ± 15.6%) and 81 healthy volunteers (63.1 ± 17%). In 3 thyrotoxic patients, impaired neutrophil adherence was found, which resolved when thyroid function returned to normal. The neutrophil chemotactic activity of 32 normal controls was 107.5 ± 21.4 cells, and the random migration 36 ± 15.5 cells. No statistically significant difference was demonstrated in 13 hyperthyroid patients who had a neutrophil chemotactic activity of 102 ± 14.6 cells and a random migration of 31.2 ± 13.2 cells. Defective chemotactic activity and random migration was found in 2 patients. Neutrophil functions returned to normal in one of the two subjects who were re-evaluated when thyroid function recovered. In summary, 14% of hyperthyroid patients had impaired leukocyte functions. However, severe pyogenic infections are quite rare in hyperthyroid patients, indicating that the observed alterations in function of phagocytic cells are not clinically important.

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Fc-dependent depletion of tumor-infiltrating regulatory T cells co-defines the efficacy of anti–CTLA-4 therapy against melanoma

Journal of Experimental Medicine ◽

10.1084/jem.20130579 ◽

2013 ◽

Vol 210 (9) ◽

pp. 1695-1710 ◽

Cited By ~ 779

Author(s):

Tyler R. Simpson ◽

Fubin Li ◽

Welby Montalvo-Ortiz ◽

Manuel A. Sepulveda ◽

Katharina Bergerhoff ◽

...

Keyword(s):

T Cells ◽

Cytotoxic T Lymphocyte ◽

Tumor Regression ◽

Cell Activity ◽

Dependent Manner ◽

Antitumor Effector ◽

Tumor Environment ◽

In Trans ◽

Immunomodulatory Therapies ◽

Insight Into

Treatment with monoclonal antibody specific for cytotoxic T lymphocyte–associated antigen 4 (CTLA-4), an inhibitory receptor expressed by T lymphocytes, has emerged as an effective therapy for the treatment of metastatic melanoma. Although subject to debate, current models favor a mechanism of activity involving blockade of the inhibitory activity of CTLA-4 on both effector (T eff) and regulatory (T reg) T cells, resulting in enhanced antitumor effector T cell activity capable of inducing tumor regression. We demonstrate, however, that the activity of anti–CTLA-4 antibody on the T reg cell compartment is mediated via selective depletion of T reg cells within tumor lesions. Importantly, T reg cell depletion is dependent on the presence of Fcγ receptor–expressing macrophages within the tumor microenvironment, indicating that T reg cells are depleted in trans in a context-dependent manner. Our results reveal further mechanistic insight into the activity of anti-CTLA-4–based cancer immunotherapy, and illustrate the importance of specific features of the local tumor environment on the final outcome of antibody-based immunomodulatory therapies.

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Expression and secretion of transforming growth factor-beta by bleomycin-stimulated rat alveolar macrophages

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1993.264.1.l36 ◽

1993 ◽

Vol 264 (1) ◽

pp. L36-L42 ◽

Cited By ~ 2

Author(s):

E. M. Denholm ◽

S. M. Rollins

Keyword(s):

Growth Factor ◽

Alveolar Macrophages ◽

Transforming Growth Factor Beta ◽

Transforming Growth Factor ◽

Chemotactic Activity ◽

Beta Activity ◽

Dependent Manner ◽

Tgf Beta ◽

Growth Factor Beta

Bleomycin-induced fibrosis in rodents has been used extensively as a model of human pulmonary fibrosis. The influx of monocytes observed during the early stages of fibrosis is at least partially regulated by the elaboration of chemotactic factors in the lung. Exposure of alveolar macrophages (AM phi) to bleomycin either in vivo or in vitro stimulated secretion of monocyte chemotactic activity (MCA). This MCA has been previously characterized as being primarily due to fibronectin fragments. The present experiments revealed that bleomycin also induced AM phi to secrete a second chemotactic factor, transforming growth factor-beta (TGF-beta). However, the TGF-beta secreted by macrophages was in latent form, since no TGF-beta activity was detected unless AM phi conditioned medium (CM) was acid-activated. After acidification, chemotactic activity in CM from AM phi stimulated with bleomycin in vitro was increased by 3.6, whereas activity in AM phi CM from fibrotic rats increased by 2 and that of a bleomycin-stimulated AM phi cell line increased by 1.6. This acid-activatable chemotactic activity was inhibited by antibody to TGF-beta. Bleomycin-stimulated AM phi s secreted significantly more TGF-beta than did unstimulated controls. Further, in vitro exposure of AM phi to bleomycin induced TGF-beta mRNA expression in a time- and concentration-dependent manner, with maximal mRNA being detected following a 16-h incubation with 1 microgram/ml bleomycin.

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Septin 2/6/7 complexes tune microtubule plus-end growth and EB1 binding in a concentration- and filament-dependent manner

Molecular Biology of the Cell ◽

10.1091/mbc.e19-07-0362 ◽

2019 ◽

Vol 30 (23) ◽

pp. 2913-2928 ◽

Cited By ~ 6

Author(s):

Konstantinos Nakos ◽

Megan R. Radler ◽

Elias T. Spiliotis

Keyword(s):

Membrane Trafficking ◽

Binding Proteins ◽

Live Cells ◽

Dependent Manner ◽

Guanosine Diphosphate ◽

In Vitro Reconstitution ◽

In Trans ◽

In Cis ◽

Precise Role

Septins (SEPTs) are filamentous guanosine-5′-triphosphate (GTP)-binding proteins, which affect microtubule (MT)-dependent functions including membrane trafficking and cell division, but their precise role in MT dynamics is poorly understood. Here, in vitro reconstitution of MT dynamics with SEPT2/6/7, the minimal subunits of septin heteromers, shows that SEPT2/6/7 has a biphasic concentration-dependent effect on MT growth. Lower concentrations of SEPT2/6/7 enhance MT plus-end growth and elongation, while higher and intermediate concentrations inhibit and pause plus-end growth, respectively. We show that SEPT2/6/7 has a modest preference for GTP- over guanosine diphosphate (GDP)-bound MT lattice and competes with end-binding protein 1 (EB1) for binding to guanosine 5′- O-[γ-thio]triphosphate (GTPγS)-stabilized MTs, which mimic the EB1-preferred GDP-Pi state of polymerized tubulin. Strikingly, SEPT2/6/7 triggers EB1 dissociation from plus-end tips in cis by binding to the MT lattice and in trans when MT plus ends collide with SEPT2/6/7 filaments. At these intersections, SEPT2/6/7 filaments were more potent barriers than actin filaments in pausing MT growth and dissociating EB1 in vitro and in live cells. These data demonstrate that SEPT2/6/7 complexes and filaments can directly impact MT plus-end growth and the tracking of plus end–binding proteins and thereby may facilitate the capture of MT plus ends at intracellular sites of septin enrichment. [Media: see text]

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Effects of reactive oxygen and nitrogen metabolites on MCP-1-induced monocyte chemotactic activity in vitro

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1999.277.3.l543 ◽

1999 ◽

Vol 277 (3) ◽

pp. L543-L549 ◽

Cited By ~ 4

Author(s):

Etsuro Sato ◽

Keith L. Simpson ◽

Matthew B. Grisham ◽

Sekiya Koyama ◽

Richard A. Robbins

Keyword(s):

Protein Function ◽

Inhibitory Effect ◽

Chemotactic Activity ◽

Dependent Manner ◽

No Donor ◽

Monocyte Chemoattractant Protein 1 ◽

Dependent Inhibition ◽

Monocyte Chemotaxis ◽

Dose Dependent

Peroxynitrite, an oxidant generated by the interaction between superoxide and nitric oxide (NO), can nitrate tyrosine residues, resulting in compromised protein function. Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that attracts monocytes and has a tyrosine residue critical for function. We hypothesized that peroxynitrite would alter MCP-1 activity. Peroxynitrite attenuated MCP-1-induced monocyte chemotactic activity (MCA) in a dose-dependent manner ( P < 0.05) but did not attenuate leukotriene B4 or complement-activated serum MCA. The reducing agents dithionite, deferoxamine, and dithiothreitol reversed the MCA inhibition by peroxynitrite, and exogenous l-tyrosine abrogated the inhibition by peroxynitrite. PAPA-NONOate, an NO donor, or superoxide generated by xanthine and xanthine oxidase did not show an inhibitory effect on MCA induced by MCP-1. The peroxynitrite generator 3-morpholinosydnonimine caused a concentration-dependent inhibition of MCA by MCP-1. Peroxynitrite reduced MCP-1 binding to monocytes and resulted in nitrotyrosine formation. These findings are consistent with nitration of tyrosine by peroxynitrite, with subsequent inhibition of MCP-1 binding to monocytes, and suggest that peroxynitrite may play a role in regulation of MCP-1-induced monocyte chemotaxis.

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Point centromere activity requires an optimal level of centromeric noncoding RNA

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1821384116 ◽

2019 ◽

Vol 116 (13) ◽

pp. 6270-6279 ◽

Cited By ~ 23

Author(s):

Yick Hin Ling ◽

Karen Wing Yee Yuen

Keyword(s):

Noncoding Rna ◽

Control Point ◽

Optimal Level ◽

Dependent Manner ◽

Histone H2a ◽

Protein Levels ◽

Interference System ◽

Binding Factor ◽

In Trans ◽

Dose Dependent

In budding yeast, which possesses simple point centromeres, we discovered that all of its centromeres express long noncoding RNAs (cenRNAs), especially in S phase. Induction of cenRNAs coincides with CENP-ACse4loading time and is dependent on DNA replication. Centromeric transcription is repressed by centromere-binding factor Cbf1 and histone H2A variant H2A.ZHtz1. Deletion ofCBF1andH2A.ZHTZ1results in an up-regulation of cenRNAs; an increased loss of a minichromosome; elevated aneuploidy; a down-regulation of the protein levels of centromeric proteins CENP-ACse4, CENP-A chaperone HJURPScm3, CENP-CMif2, SurvivinBir1, and INCENPSli15; and a reduced chromatin localization of CENP-ACse4, CENP-CMif2, and Aurora BIpl1. When the RNA interference system was introduced to knock down all cenRNAs from the endogenous chromosomes, but not the cenRNA from the circular minichromosome, an increase in minichromosome loss was still observed, suggesting that cenRNA functionsin transto regulate centromere activity. CenRNA knockdown partially alleviates minichromosome loss incbf1Δ,htz1Δ, andcbf1Δ htz1Δin a dose-dependent manner, demonstrating that cenRNA level is tightly regulated to epigenetically control point centromere function.

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Endothelin-1 Stimulates Monocytesin vitroto Release Chemotactic Activity Identified as Interleukin-8 and Monocyte Chemotactic Protein-1

Mediators of Inflammation ◽

10.1155/s0962935194000207 ◽

1994 ◽

Vol 3 (2) ◽

pp. 155-160 ◽

Cited By ~ 23

Author(s):

E. Helset ◽

T. Sildnes ◽

Z. S. Konopski

Keyword(s):

Human Monocyte ◽

Chemotactic Activity ◽

Dependent Manner ◽

Lipoxygenase Pathway ◽

Lipoxygenase Inhibitors ◽

Endothelin 1 ◽

Monocyte Chemotactic Protein ◽

Chemotactic Protein ◽

Stimulation Of

In the present study we examined whether endothelin-1 stimulation of human monocytes causes release of chemotactic factors. It was found that monocytes released neutrophil- and monocyte-chemotactic activity in a dose- and time-dependent manner in response to ET-1. ET-1 did not show any chemotactic activity by itself. NCA was detected in monocyte supernatants in response to ET-1 (0.01–100 nM) after 1, 4, 8 and 24 h stimulation. MCA was detected only after 24 h stimulation with ET-1 (0.1–100 nM). Preincubation of the monocyte cultures with the lipoxygenase inhibitors nordihydroguaiaretic acid (10−4M) or diethylcarbamazine (10−9M) completely abolished the appearance of NCA and MCA. NCA was neutralized by > 75% using a polyclonal antibody against human interleuktn-8. The ET-1 induced release of IL-8 was confirmed by IL-8 ELISA. A monoclonal antibody against human monocyte chemotactic protein-1 neutralized MCA by > 80%. It is concluded that ET-1 stimulation of monocytesin vitrocauses release of neutrophil- and monocyte-chemotactic activity identified as IL-8 and MCP-I respectively. An intact lipoxygenase pathway is crucial for this effect of ET-1 to occur.

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Coassembly of Mgm1 isoforms requires cardiolipin and mediates mitochondrial inner membrane fusion

The Journal of Cell Biology ◽

10.1083/jcb.200906098 ◽

2009 ◽

Vol 186 (6) ◽

pp. 793-803 ◽

Cited By ~ 194

Author(s):

Rachel M. DeVay ◽

Lenin Dominguez-Ramirez ◽

Laura L. Lackner ◽

Suzanne Hoppins ◽

Henning Stahlberg ◽

...

Keyword(s):

Membrane Fusion ◽

Coiled Coil ◽

Intermembrane Space ◽

Dependent Manner ◽

Related Protein ◽

Mitochondrial Membranes ◽

Inner Membrane ◽

Mitochondrial Inner Membrane ◽

N Terminus ◽

In Trans

Two dynamin-related protein (DRP) families are essential for fusion of the outer and inner mitochondrial membranes, Fzo1 (yeast)/Mfn1/Mfn2 (mammals) and Mgm1 (yeast)/Opa1 (mammals), respectively. Fzo1/Mfns possess two medial transmembrane domains, which place their critical GTPase and coiled-coil domains in the cytosol. In contrast, Mgm1/Opa1 are present in cells as long (l) isoforms that are anchored via the N terminus to the inner membrane, and short (s) isoforms were predicted to be soluble in the intermembrane space. We addressed the roles of Mgm1 isoforms and how DRPs function in membrane fusion. Our analysis indicates that in the absence of a membrane, l- and s-Mgm1 both exist as inactive GTPase monomers, but that together in trans they form a functional dimer in a cardiolipin-dependent manner that is the building block for higher-order assemblies.

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