scholarly journals PAF-acetylhydrolase expressed during megakaryocyte differentiation inactivates PAF-like lipids

Blood ◽  
2009 ◽  
Vol 113 (26) ◽  
pp. 6699-6706 ◽  
Author(s):  
Jason M. Foulks ◽  
Gopal K. Marathe ◽  
Noemi Michetti ◽  
Diana M. Stafforini ◽  
Guy A. Zimmerman ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Platelet Activating Factor ◽  
Lipid Mediators ◽  
Target Cells ◽  
Signaling System ◽  
Human Cd34 ◽  
Paf Acetylhydrolase ◽  
Cd34 Cells ◽  
Paf Receptor ◽  
And Function

Abstract Platelet activating factor (PAF) and PAF-like lipids induce inflammatory responses in target cells. These lipid mediators are inactivated by PAF-acetylhydrolase (PAF-AH). The PAF signaling system affects the growth of hematopoietic CD34+ cells, but roles for PAF-AH in this process are unknown. Here, we investigated PAF-AH function during megakaryopoiesis and found that human CD34+ cells accumulate this enzymatic activity as they differentiate toward megakaryocytes, consistent with the expression of mRNA and protein for the plasma PAF-AH isoform. Inhibition of endogenous PAF-AH activity in differentiated megakaryocytes increased formation of lipid mediators that signaled the PAF receptor (PAFR) in fully differentiated human cells such as neutrophils, as well as megakaryocytes themselves. PAF-AH also controlled megakaryocyte αIIbβ3-dependent adhesion, cell spreading, and mobility that relied on signaling through the PAFR. Together these data suggest that megakaryocytes generate PAF-AH to modulate the accumulation of intracellular phospholipid mediators that may detrimentally affect megakaryocyte development and function.

Abstract 256: Paracrine miRNA-Crosstalk Between Human CD34+ Stem Cells and Selective Myocardial Cells Via Therapeutic Exosomes Promotes Repair of the Ischemic Heart

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Susmita Sahoo ◽  
David Kim ◽  
Sol Misener ◽  
Christine E Kamide ◽  
Douglas E Vaughan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Endothelial Cells ◽  
Ischemic Myocardium ◽  
Ischemic Heart ◽  
Target Cells ◽  
Myocardial Repair ◽  
Human Cd34 ◽  
Therapeutic Benefits ◽  
Cd34 Cells

Introduction: Earlier, in a first study of its kind, we have demonstrated a novel mechanism that therapeutically significant human CD34+ stem cells secrete membrane bound nano-vesicles called exosomes (CD34Exo). CD34Exo are angiogenic and constitute a critical component of the pro-angiogenic paracrine activity of the cells. Further, when transplanted locally, cell-free CD34Exo induce ischemic tissue repair in a murine hindlimb ischemia model. Here, we hypothesize that exosomes released via paracrine secretion from human CD34+ cells mediate myocardial repair by direct transfer of microRNAs to target cells in the heart. Methods and Results: When injected into mouse ischemic myocardium, cell-free CD34Exo replicated the therapeutic activity of human CD34+ cells by significantly improving ischemia (ejection fraction, 42±4 v 22±6%; capillary density, 113±7 v 66±6/HPF; fibrosis, 27±2 v 48±7%; p<0.05, n=7-12) compared with PBS control. Interestingly, confocal imaging and flow cytometry analyses of the exosomes-injected ischemic myocardial tissue revealed that CD34Exo was selectively internalized into endothelial cells and cardiomyocytes. CD34Exo, which is enriched with miR126, induced the expression of miR126 and several pro-angiogenic mRNAs in the exosomes-treated ischemic myocardium, but did not affect the endogenous synthesis of miR126. CD34Exo lacking miR126 had decreased angiogenic activity in vitro and decreased proangiogenic gene expression in vivo indicating that miR126 is important for CD34Exo function. Imaging using fluorescent miR126 confirms that CD34Exo directly transferred miR126 and possibly other yet to be identified moieties from its cargo, selectively to endothelial cells and cardiomyocytes in the ischemic heart. Conclusion: Our results reveal a novel molecular and trafficking mechanism of CD34Exo that may be responsible for intercellular transfer of genetic information such as miRNAs from human CD34+ stem cells, selectively to endothelial cells and cardiomyocytes inducing changes in gene expression, angiogenesis and myocardial recovery. Exosomes-shuttled miRNAs may signify amplification of stem cell function and may explain the therapeutic benefits associated with human CD34+ cell therapy.

Eicosanoid production from porcine neutrophils and platelets: differential production with various agonists

1997 ◽  
Vol 272 (6) ◽  
pp. C1821-C1828 ◽  
Author(s):  
G. L. Stahl ◽  
D. S. Morse ◽  
S. L. Martin
Keyword(s):  
Human Disease ◽  
Cytochalasin B ◽  
Flow Cytometric Analysis ◽  
Platelet Activating Factor ◽  
Lipid Mediators ◽  
Polymorphonuclear Neutrophils ◽  
Lipoxin A4 ◽  
Flow Cytometric ◽  
A 23187 ◽  
Paf Receptor

Polymorphonuclear neutrophils (PMN) and platelets interact to produce both inflammatory and anti-inflammatory lipid mediators during human disease. Because swine models of human disease are used, it is important to understand the mechanisms involved in the formation of lipid mediators from porcine PMN-platelet interactions. In the present study, we investigated the mechanism of thromboxane (Tx) A2 and lipoxin A4 (LXA4) formation from porcine PMN and platelets, respectively. PMN (10(7)/ml) and platelet (30 x 10(7)/ml) suspensions stimulated with porcine C5a (pC5a), but not recombinant human C5a (rhC5a), significantly enhanced TxB2 formation. After cytochalasin B treatment, pC5a or rhC5a significantly and equally enhanced TxB2 formation from PMN-platelet suspensions. A-23187-induced TxB2 formation from platelets was not significantly augmented by the presence of PMN in these suspensions. A-23187 induced significant LXA4 production from porcine PMN that was not augmented by addition of platelets. Flow cytometric analysis of PMN-platelet suspensions revealed activated platelets adherent to PMN following pC5a stimulation. CV-6209, a platelet-activating factor (PAF) receptor antagonist, dose dependently prevented pC5a-induced platelet adherence to PMN and TxB2 formation. These data demonstrate that 1) porcine PMN alone can biosynthesize LXA4 without the assistance of platelets, which is in sharp contrast to human PMN-platelet interactions, and 2) in the absence of cytochalasin B, pC5a stimulates PAF biosynthesis from porcine PMN, resulting in TxB2 formation from platelets.

scholarly journals Continuous binding of the PAF molecule to its receptor is necessary for the long-term aggregation of platelets

1998 ◽  
Vol 274 (1) ◽  
pp. C47-C57 ◽  
Author(s):  
Masahiro Suzuki ◽  
Junko Sugatani ◽  
Mitsuhiro Ino ◽  
Masahiko Shimura ◽  
Masaki Akiyama ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Cell Surface ◽  
Platelet Activating Factor ◽  
Signaling System ◽  
Platelet Disaggregation ◽  
Rabbit Platelets ◽  
Paf Receptor ◽  
Aggregation Of Platelets ◽  
Web 2086

Human and rabbit platelets fully aggregated by platelet-activating factor (PAF) underwent slow disaggregation but were rapidly disaggregated by the PAF receptor antagonists WEB-2086, Y-24180, SM-12502, and CV-3988. Whereas the 1-alkyl-2-[3H]acetyl- sn-glycero-3-phosphocholine ([3H]acetyl-PAF) specifically bound to platelet receptors underwent slow and spontaneous dissociation, it dissociated promptly from its receptor when WEB-2086 was added, in parallel with platelet disaggregation and disappearance of P-selectin on the cell surface. Extracellular [3H]acetyl-PAF was rapidly deacetylated by normal rabbit platelets; some of the [3H]acetyl-PAF was bound to the cells and a very small amount of [3H]acetate was detected in the cells. In contrast, when 1-[3H]alkyl-2-acetyl- sn-glycero-3-phosphocholine was added to the platelets, the radioactivity was rapidly incorporated into the 1-alkyl-2-acyl- sn-glycero-3-phosphocholine fraction. These results indicate that 1) continuous binding of PAF to its receptor is necessary for prolonged platelet aggregation, which may be mediated through an unknown signaling system for a long-term cell response rather than a transient signaling system, and 2) most of the [3H]acetyl-PAF bound to platelets is metabolized extracellularly by ecto-type PAF acetylhydrolase, with the lyso-PAF generated being incorporated rapidly into the cells and converted to 1-alkyl-2-acyl- sn-glycero-3-phosphocholine.

Abstract 3: Human CD34+ Cells Deficient in miR-377 Attenuates Cardiac Dysfunction and Repair After Ischemia-reperfusion Injury

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Darukeshwara Joladarashi ◽  
Rajarajan A Thandavarayan ◽  
Sahana Suresh Babu ◽  
Prince Jeyabal ◽  
Shashirekha Krishnamurthy ◽  
...  
Keyword(s):  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Tube Formation ◽  
Lv Function ◽  
Serine Threonine Kinase ◽  
Mirna Array ◽  
Human Cd34 ◽  
Cell Based Therapy ◽  
Cd34 Cells ◽  
And Function

microRNAs (miRNA/miR) dysregulation has been implicated in cardiac remodeling after injury or stress, however its effects on Human CD34 + cells (hCD34 + ) biology and function, particularly in the context of cell-based therapy for cardiomyopathy is not fully understood. miRNA array data analysis indicates that miR-377 is a potential interest. pre-miR-377 transfection in EPCs inhibits their migration and vascular tube formation ability in HUVECs. Furthermore, hCD34 + cells treated with miR-377 mimic showed decrease in expression of STK35 (a novel serine/threonine kinase). Moreover, STK35 is predicted as a potential target gene of miR-377 by computational analysis. Interestingly, in a relevant mouse model of ischemia reperfusion, intramyocardial transplantation of miR-377-silenced hCD34 + cells promotes neovascularization leading to improvement in myocardial function and repair. Echocardiography showed LV function was significantly improved in mice receiving miR-377-silenced hCD34 + cells compared to control-miR-transfected hCD34 + cells. Taken together, these data suggest that inhibiting miR-377 in hCD34 + cells promotes their angiogenic ability after transplantation into ischemic myocardial tissue, potentially through activation of STK35 signaling.

scholarly journals Regulation of platelet-activating-factor receptors and the desensitization response in polymorphonuclear neutrophils

1992 ◽  
Vol 288 (1) ◽  
pp. 241-248 ◽  
Author(s):  
J T O'Flaherty ◽  
D P Jacobson ◽  
J F Redman
Keyword(s):  
Actinomycin D ◽  
Platelet Activating Factor ◽  
Receptor Expression ◽  
Polymorphonuclear Neutrophils ◽  
Target Cells ◽  
Surface Compound ◽  
Down Regulation ◽  
High Affinity ◽  
Kinase C ◽  
Paf Receptor

Platelet-activating factor (PAF) desensitizes as well as stimulates its various target cells, We find that human polymorphonuclear neutrophils (PMN) exposed to PAF became maximally unresponsive to a second PAF challenge within 15-90 s in assays of Ca2+ mobilization and degranulation. The cells regained full PAF-sensitivity over the ensuing 20-40 min. These effects correlated with changes in PAF receptor availability. PMN treated with PAF, washed in regular buffer and assayed for PAF binding exhibited falls (maximal in 15 s), followed by rises (reaching control levels by 60 min), in the number of high-affinity PAF receptors. However, tracking studies showed that [3H]PAF accumulated on the cell surface for approximately 2 min before being internalized. Regular-buffer washes did not remove this superficial PAF, whereas a washing regimen using excess albumin to adsorb PAF removed 99% of the surface compound. PMN washed by the latter regimen after PAF exposure lost PAF receptors relatively slowly (maximal at approximately 5 min), but the ultimate extent of this loss and the rate at which receptor expression normalized were similar to those of cells washed in regular buffer. Neither cycloheximide nor actinomycin D influenced the course of the receptor changes, but two protein kinase C (PKC) blockers, staurosporine and 1-(5-isoquinolinesulphonyl)piperazine, inhibited the receptor-receptor-depleting actions of PAF. Indeed, a phorbol diester activator of PKC also caused PMN to decrease high-affinity PAF receptor numbers, and the two PKC blockers antagonized this action at concentrations that inhibited PAF-induced PAF receptor losses. We conclude that: (a) PAF induces PMN to down-regulate and then to re-express PAF receptors independently of protein synthesis; (b) these changes are likely to underlie the later stages and reversal of desensitization; (c) the onset (t < or = 2 min) of desensitization, however, precedes receptor down-regulation and must be due to receptor uncoupling from transductional elements; and (d) down-regulation of receptors for PAF appears to be mediated by PKC and/or elements inhibited by PKC blockers.

scholarly journals Eosinophil Lipid Bodies: Specific, Inducible Intracellular Sites for Enhanced Eicosanoid Formation

1997 ◽  
Vol 186 (6) ◽  
pp. 909-920 ◽  
Author(s):  
Patricia T. Bozza ◽  
Wengui Yu ◽  
John F. Penrose ◽  
Ellen S. Morgan ◽  
Ann M. Dvorak ◽  
...  
Keyword(s):  
Platelet Activating Factor ◽  
Lipid Body ◽  
Lipid Bodies ◽  
Enhanced Production ◽  
Kinase C ◽  
Mediators Of Inflammation ◽  
Paf Receptor ◽  
And Function ◽  
Eicosanoid Mediators ◽  
Leukotriene C4 Synthase

The specific intracellular sites at which enzymes act to generate arachidonate-derived eicosanoid mediators of inflammation are uncertain. We evaluated the formation and function of cytoplasmic lipid bodies. Lipid body formation in eosinophils was a rapidly (&lt;1 h) inducible response which was platelet-activating factor (PAF) receptor–mediated, involved signaling through protein kinase C, and required new protein synthesis. In intact and enucleated eosinophils, the PAF-induced increases in lipid body numbers correlated with enhanced production of both lipoxygenase- and cyclooxygenase-derived eicosanoids. All principal eosinophil eicosanoid-forming enzymes, 5-lipoxygenase, leukotriene C4 synthase, and cyclooxygenase, were immunolocalized to native as well as newly induced lipid bodies in intact and enucleated eosinophils. Thus, lipid bodies are structurally distinct, inducible, nonnuclear sites for enhanced synthesis of paracrine eicosanoid mediators of inflammation.

scholarly journals Platelets trigger perivascular mast cell degranulation to cause inflammatory responses and tissue injury

2020 ◽  
Vol 6 (12) ◽  
pp. eaay6314 ◽  
Author(s):  
Jörn Karhausen ◽  
Hae Woong Choi ◽  
Krishna Rao Maddipati ◽  
Joseph P. Mathew ◽  
Qing Ma ◽  
...  
Keyword(s):  
Cardiac Surgery ◽  
Platelet Activation ◽  
Inflammatory Responses ◽  
Tissue Injury ◽  
Platelet Activating Factor ◽  
Organ Injury ◽  
Paf Receptor ◽  
Platelet Aggregates ◽  
Systemic Responses

Platelet responses have been associated with end-organ injury and mortality following complex insults such as cardiac surgery, but how platelets contribute to these pathologies remains unclear. Our studies originated from the observation of microvascular platelet retention in a rat cardiac surgery model. Ensuing work supported the proximity of platelet aggregates with perivascular mast cells (MCs) and demonstrated that platelet activation triggered systemic MC activation. We then identified platelet activating factor (PAF) as the platelet-derived mediator stimulating MCs and, using chimeric animals with platelets defective in PAF generation or MCs lacking PAF receptor, defined the role of this platelet-MC interaction for vascular leakage, shock, and tissue inflammation. In application of these findings, we demonstrated that inhibition of platelet activation in modeled cardiac surgery blunted MC-dependent inflammation and tissue injury. Together, our work identifies a previously undefined mechanism of inflammatory augmentation, in which platelets trigger local and systemic responses through activation of perivascular MCs.

scholarly journals Bitis arietans Snake Venom Induces an Inflammatory Response Which Is Partially Dependent on Lipid Mediators

Toxins ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 594
Author(s):  
Angela Alice Amadeu Megale ◽  
Fernanda Calheta Portaro ◽  
Wilmar Dias Da Silva
Keyword(s):  
Inflammatory Response ◽  
Platelet Activating Factor ◽  
Lipid Mediators ◽  
Mice Model ◽  
Permanent Disability ◽  
Paf Receptor ◽  
Inflammatory Drugs ◽  
Pre Treatment ◽  
Clinical Conditions

Bitis arietans is a snake of medical importance, as it is responsible for more accidents in humans and domestic animals than all other African snakes put together. The accidents are characterized by local and systemic alterations, such as inflammation, cardiovascular and hemostatic disturbances, which can lead victims to death or permanent disability. However, little is known about the envenomation mechanism, especially regarding the inflammatory response, which is related to severe clinical conditions triggered by the venom. Therefore, the aim of the present study was to evaluate the inflammatory response related to the B. arietans envenomation using a peritonitis mice model. By pharmacological interventions and use of mice genetically deficient of the 5-lipoxygenase enzyme (5-LO−/−) or platelet-activating factor (PAF) receptor (PAFR−/− the participation of eicosanoids and PAF in this response was also investigated. The obtained results demonstrated that the venom induces an in vivo inflammatory response, characterized by an early increased vascular permeability, followed by an accumulation of polymorphonuclear (PMN) cells in the peritoneal cavity, accompanied by the production of the eicosanoids LTB4, LTC4, TXB2 and PGE2, as well as the local and systemic production of IL-6 and MCP-1. These inflammatory events were attenuated by the pre-treatment with anti-inflammatory drugs that interfere in lipid mediators’ functions. However, 5-LO−/− mice did not show a reduction of inflammatory response induced by the venom, while PAFR−/− mice showed a reduction in both the PMN leukocytes number and the local and systemic production of IL-6 and MCP-1. This study demonstrated that the Bitis arietans venom contains toxins that trigger an inflammatory process, which is partially dependent on lipid mediators, and may contribute to the envenomation pathology.

scholarly journals SARS-CoV-2 Infection Modulates ACE2 Function and Subsequent Inflammatory Responses in Swabs and Plasma of COVID-19 Patients

Viruses ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1715
Author(s):  
Lucía Gutiérrez-Chamorro ◽  
Eva Riveira-Muñoz ◽  
Clara Barrios ◽  
Vanesa Palau ◽  
Maria Nevot ◽  
...  
Keyword(s):  
Inflammatory Response ◽  
Inflammatory Cytokines ◽  
Viral Entry ◽  
Inflammatory Responses ◽  
Target Cells ◽  
Upper Respiratory Tract ◽  
Angiotensin Converting Enzyme 2 ◽  
Early Biomarker ◽  
And Function ◽  
Ace2 Gene

Angiotensin converting enzyme 2 (ACE2) is a host ectopeptidase and the receptor for the SARS-CoV-2 virus, albeit virus-ACE2 interaction goes far beyond viral entry into target cells. Controversial data exists linking viral infection to changes in ACE2 expression and function, which might influence the subsequent induction of an inflammatory response. Here, we tested the significance of soluble ACE2 enzymatic activity longitudinally in nasopharyngeal swabs and plasma samples of SARS-COV-2 infected patients, along with the induction of inflammatory cytokines. Release of soluble functional ACE2 increases upon SARS-CoV-2 infection in swabs and plasma of infected patients, albeit rapidly decreasing during infection course in parallel with ACE2 gene expression. Similarly, SARS-CoV-2 infection also induced the expression of inflammatory cytokines. These changes positively correlated with the viral load. Overall, our results demonstrate the existence of mechanisms by which SARS-CoV-2 modulates ACE2 expression and function, intracellular viral sensing and subsequent inflammatory response, offering new insights into ACE2 dynamics in the human upper respiratory tract and pointing towards soluble ACE2 levels as a putative early biomarker of infection severity.

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