scholarly journals Expression of human platelet-activating factor receptor gene in EoL-1 cells following butyrate-induced differentiation

1995 ◽  
Vol 305 (3) ◽  
pp. 829-835 ◽  
Author(s):  
T Izumi ◽  
S Kishimoto ◽  
T Takano ◽  
M Nakamura ◽  
Y Miyabe ◽  
...  
Keyword(s):  
Receptor Gene ◽  
Platelet Activating Factor ◽  
Allergic Inflammation ◽  
Genomic Analysis ◽  
Receptor Protein ◽  
Cell Surface Expression ◽  
Lipid Mediator ◽  
Mrna Accumulation ◽  
Leukaemia Cell Line ◽  
Paf Receptor

Platelet-activating factor (PAF) is a potent lipid mediator of allergic inflammation through its interaction with eosinophils. Expression of the PAF receptor is modulated by many agents, including those responsible for cell differentiation. We report here that differentiation of a human eosinophilic leukaemia cell line, EoL-1, by sodium n-butyrate is associated with induction of PAF receptor gene expression, as indicated by: PAF receptor mRNA accumulation; increases in the binding of [3H]WEB 2086, a PAF antagonist; analysis of cell-surface expression of PAF receptor protein using a monoclonal anti-(PAF receptor) antibody; and augmentation of PAF-induced increase in the intracellular concentration of calcium. Using cDNA cloning, the receptor expressed in EoL-1 cells was identified as ‘Transcript 1’, one of two transcripts which was previously reported from human genomic analysis (Mutoh, Bito, Minami, Nakamura, Honda, Izumi, Nakata, Kurachi, Terano and Shimizu (1993) FEBS Lett. 322, 129-134). The PAF-induced calcium response and phosphoinositide turnover were decreased by pertussis toxin (PTX) treatment, suggesting that these signals are coupled largely with PTX-sensitive G-protein(s) in EoL-1 cells. These systems may provide a useful experimental model with which to investigate the relationship between eosinophilic differentiation and PAF receptor induction, and the role of eosinophils in allergic responses.

scholarly journals Platelet-activating Factor, a Molecular Sensor for Cellular Damage, Activates Systemic Immune Suppression

2002 ◽  
Vol 195 (2) ◽  
pp. 171-179 ◽  
Author(s):  
Jeffrey P. Walterscheid ◽  
Stephen E. Ullrich ◽  
Dat X. Nghiem
Keyword(s):  
Skin Cancer ◽  
Uv Radiation ◽  
Immune Suppression ◽  
Critical Role ◽  
Platelet Activating Factor ◽  
Cellular Damage ◽  
Uv Exposure ◽  
Delayed Type Hypersensitivity ◽  
Lipid Mediator ◽  
Paf Receptor

Ultraviolet (UV) radiation plays a critical role in the induction of nonmelanoma skin cancer. UV radiation is also immune suppressive, and the immune suppression induced by UV irradiation has been identified as a major risk factor for skin cancer induction. Previously, we showed that UV exposure activates a cytokine cascade involving prostaglandin (PG)E2, interleukin (IL)-4, and IL-10 that induces immune suppression. However, the earliest molecular events that occur immediately after UV exposure, especially those upstream of PGE2, are not well defined. UV-irradiated keratinocytes secrete the inflammatory phospholipid mediator, platelet-activating factor (PAF). Because PAF upregulates the production of immunomodulatory compounds, including PGE2, we tested the hypothesis that UV-induced PAF activates cytokine production and initiates UV-induced immune suppression. Both UV and PAF activated cyclooxygenase (COX)-2 and IL-10 reporter gene construct transcription. PAF mimicked the effects of UV in vivo and suppressed delayed-type hypersensitivity (DTH). Furthermore, immune suppression was blocked when UV-irradiated mice were injected with PAF receptor antagonists. In addition to the well-known role of PAF as a proinflammatory lipid mediator, we propose that the PAF receptor senses cellular damage through the recognition of PAF and/or PAF-like molecules, such as oxidized phosphatidylcholine, which activates cytokine transcription and induces systemic immune suppression.

scholarly journals Agonist-induced down-regulation of platelet-activating factor receptor gene expression in U937 cells

1994 ◽  
Vol 301 (3) ◽  
pp. 911-916 ◽  
Author(s):  
L Y Chau ◽  
K Peck ◽  
H H Yen ◽  
J Y Wang
Keyword(s):  
Prolonged Exposure ◽  
Radioligand Binding ◽  
Receptor Gene ◽  
Platelet Activating Factor ◽  
State Level ◽  
Transcriptional Level ◽  
U937 Cells ◽  
Down Regulation ◽  
Receptor Mrna ◽  
Paf Receptor

Prolonged exposure (8-24 h) of human promonocytic U937 cells to 100 nM 1-O-hexadecyl-2-N-methylcarbamyl-sn-glycero-3-phosphocholine (carbarmyl-PAF), a non-metabolizable analogue of platelet-activating factor (PAF), reduced the numbers of PAF receptors by 50-75%, as determined by the radioligand-binding assay. To clarify whether the down-regulation of receptor numbers is due to decreased expression level of the PAF-receptor gene, the effect of carbamyl-PAF on the steady-state level of PAF-receptor mRNA was examined by a highly sensitive reverse-transcriptase PCR method. A 50% decline in the level of PAF-receptor mRNA was observed in U937 cells pretreated with 100 nM carbamyl-PAF for 24 h. The effect of carbamyl-PAF was dose-dependent, with an EC50 value around 10 nM. PAF-receptor antagonist, SRI-63675, was able to attenuate the effect of carbamyl-PAF. Furthermore lysoPAF, at 1 uM, was unable to induce a significant decrease in PAF-receptor mRNA after incubation for 24 h, indicating that the effect of carbamyl-PAF was specific. The half-life of the PAF-receptor mRNA measured in the presence of actinomycin D was unaffected by carbamyl-PAF treatment. In contrast, nuclear run-off experiments demonstrated that the transcription rate of the PAF-receptor gene in carbamyl-PAF-treated cells was about 65% of that in control cells. These results suggest that the PAF receptor in U937 cells is subject to down-regulation by agonist, at least partly, at the transcriptional level.

Platelet-activating factor receptors in lamb lungs are downregulated immediately after birth

2000 ◽  
Vol 278 (4) ◽  
pp. H1168-H1176 ◽  
Author(s):  
Basil O. Ibe ◽  
Fred C. Sander ◽  
J. Usha Raj
Keyword(s):  
Receptor Binding ◽  
Dissociation Constants ◽  
Receptor Gene ◽  
Choline Chloride ◽  
Platelet Activating Factor ◽  
Scatchard Analysis ◽  
Newborn Period ◽  
Paf Receptor ◽  
G Protein Coupled ◽  
Receptor Gene Expression

Platelet-activating factor (PAF) is a phospholipid with diverse biological functions mediated by a G protein-coupled receptor. We determined PAF receptor binding in lung membranes of four groups of perinatal lambs. Membrane protein (100 μg/ml) was incubated for 60 min at 30°C with 0.5–24 nM of acetyl-[3H]PAF in 30 mM Tris buffer, pH 7.2, containing 0.25% BSA, 10 mM MgCl2, and 125 mM choline chloride. PAF bound to membrane was isolated and quantified by scintillation spectrometry, followed with Scatchard analysis for receptor density (Bmax). The Bmax (means ± SE, fmol/mg protein) were 445.8 ± 12.3, 244.2 ± 3.3, 250.6 ± 3.6, and 419.9 ± 8.6 for the fetal, 90-min-old, <1-day-old, and 6- to 12-day-old lambs, respectively. The Bmax for the 90-min-old and <1-day-old lambs were not different but were significantly lower than those of either the term fetal or 6- to 12-day-old lambs. These data show a significant decrease in PAF binding to its receptor and in PAF Bmax in lung membranes of immediate newborn lambs. The dissociation constants ( K D, nM) were 7.7 ± 0.52, 11.5 ± 0.34, 6.9 ± 0.48, and 5.0 ± 0.53 for fetal, 90-min-old, <1-day-old, and 6- to 12-day-old newborn lamb lungs, respectively. The K D of the 90-min-old lamb was the highest of all. PAF receptor gene measured by RT-PCR showed a significant downregulation of PAF receptor gene mRNA in lungs of lambs <1 day old, suggesting a transcriptional regulation of PAF receptor gene expression in the immediate newborn period. We speculate that decreased PAF receptor binding immediately after birth will facilitate the fall in pulmonary vascular resistance in the immediate newborn period.

scholarly journals New Insights Into the Pathologic Roles of the Platelet-Activating Factor System

2021 ◽  
Vol 12 ◽  
Author(s):  
Jeffrey B. Travers ◽  
Joyce G. Rohan ◽  
Ravi P. Sahu
Keyword(s):  
Cell Damage ◽  
Platelet Activating Factor ◽  
Receptor Activation ◽  
Lipid Mediator ◽  
Organ Systems ◽  
Paf Receptor ◽  
Bioactive Agents ◽  
Novel Therapeutic Strategies ◽  
Pathologic Processes ◽  
The Relationship

Described almost 50 years ago, the glycerophosphocholine lipid mediator Platelet-activating factor (PAF) has been implicated in many pathologic processes. Indeed, elevated levels of PAF can be measured in response to almost every type of pathology involving inflammation and cell damage/death. In this review, we provide evidence for PAF involvement in pathologic processes, with focus on cancer, the nervous system, and in photobiology. Importantly, recent insights into how PAF can generate and travel via bioactive extracellular vesicles such as microvesicle particles (MVP) are presented. What appears to be emerging from diverse pathologies in different organ systems is a common theme where pro-oxidative stressors generate oxidized glycerophosphocholines with PAF agonistic effects, which then trigger more enzymatic PAF synthesis via the PAF receptor. A downstream consequence of PAF receptor activation is the generation and release of MVP which provide a mechanism to transmit PAF as well as other bioactive agents. The knowledge gaps which when addressed could result in novel therapeutic strategies are also discussed. Taken together, an enhanced understanding of the PAF family of lipid mediators is essential in our improved comprehension of the relationship amongst the diverse cutaneous, cancerous, neurologic and systemic pathologic processes.

scholarly journals Impaired Anaphylactic Responses with Intact Sensitivity to Endotoxin in Mice Lacking a Platelet-activating Factor Receptor

1998 ◽  
Vol 187 (11) ◽  
pp. 1779-1788 ◽  
Author(s):  
Satoshi Ishii ◽  
Tomoyuki Kuwaki ◽  
Takahide Nagase ◽  
Kazushige Maki ◽  
Fumi Tashiro ◽  
...  
Keyword(s):  
Marked Reduction ◽  
Biological Activities ◽  
Dominant Role ◽  
Receptor Gene ◽  
Endotoxic Shock ◽  
Platelet Activating Factor ◽  
Neuronal Cell ◽  
Paf Receptor ◽  
Deficient Mice ◽  
In Pregnancy

Platelet-activating factor (PAF) is a potent phospholipid mediator with diverse biological activities in addition to its well-known ability to stimulate platelet aggregation. Pharmacologic studies had suggested a role for PAF in pregnancy, neuronal cell migration, anaphylaxis, and endotoxic shock. Here we show that disruption of the PAF receptor gene in mice caused a marked reduction in systemic anaphylactic symptoms. Unexpectedly, however, the PAF receptor–deficient mice developed normally, were fertile, and remained sensitive to bacterial endotoxin. These mutant mice clearly show that PAF plays a dominant role in eliciting anaphylaxis, but that it is not essential for reproduction, brain development, or endotoxic shock.

scholarly journals Components of a platelet-activating factor-signaling loop are assembled in the ovine endometrium late in the estrous cycle

2004 ◽  
Vol 287 (2) ◽  
pp. E233-E240 ◽  
Author(s):  
O. Chami ◽  
G. Evans ◽  
C. O'Neill
Keyword(s):  
Estrous Cycle ◽  
Platelet Activating Factor ◽  
Endometrial Tissue ◽  
Receptor Expression ◽  
Receptor Protein ◽  
Short Term ◽  
Prostaglandin F ◽  
Paf Receptor ◽  
Ovine Uterus ◽  
Circulating Levels

Pulsatile release of uterine prostaglandin F2α (PGF2α) induces luteolysis in ruminants. Exogenous PAF is well known to cause PGF2α release from the ovine uterus. This study examines whether the components of a PAF-signaling loop exist in sheep at the time luteolysis is normally initiated. Day 14 of the cycle was the first day the uterus responded to an infusion of PAF, inducing a significant short-term increase in circulating levels of the PGF2α metabolite. There was a significant increase of PAF concentration ( P < 0.001) in the endometrium and PAF release by tissue explants ( P < 0.001) from day 10 to day 16 of the cycle. Endometrial tissue PAF receptor mRNA expression was induced ( P < 0.01) by estradiol and progesterone treatment of animals, and transcripts were present between days 10 and 16 of the estrous cycle. Western analysis of endometrial tissue showed marked upregulation of PAF receptor protein expression from day 14 of the cycle, and immunolocalization studies showed that the receptor expression was predominantly around the endometrial glands. PAF:acetylhydrolase was primarily located within the lumen of the endometrial glands. The study shows that a PAF-signaling loop was assembled within the ovine endometrium at the time that PGF2α pulsatility was first observed.

scholarly journals 291PRESENCE OF PLATELET-ACTIVATING FACTOR (PAF) RECEPTOR IN BULL SPERM AND POSITIVE CORRELATION OF SPERM PAF CONTENT WITH FERTILITY

2004 ◽  
Vol 16 (2) ◽  
pp. 265 ◽  
Author(s):  
B.G. Brackett ◽  
P. Bosch ◽  
R.A. McGraw ◽  
J.M. DeJarnette ◽  
C.E. Marshall ◽  
...  
Keyword(s):  
Reverse Transcription ◽  
Male Fertility ◽  
Platelet Activating Factor ◽  
Receptor Expression ◽  
Epifluorescence Microscopy ◽  
Receptor Protein ◽  
Sperm Cells ◽  
Positive Correlation ◽  
Paf Receptor ◽  
Bull Sperm

Male fertility involves the capacity to obtain viable pregnancy and offspring after insemination. Currently, the most common way to measure bull fertility is through non-return rates (NRR) calculated after insemination of many females. However, this method is time-consuming and expensive. A number of biochemical molecules in sperm have been proposed as potential predictors of male fertility, e.g. platelet-activating factor (PAF). Platelet-activating factor (1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphorylcholine) is a ubiquitous phospholipid that is implicated in the mediation of a wide variety of reproductive processes. The mechanism of PAF’s action is a receptor-mediated event reported to affect intracellular calcium levels. Bull sperm contain PAF and its content has a positive relationship with motility. While the PAF-receptor has been reported in other species, it has not been demonstrated in bull sperm. Therefore, our objectives were to determine: 1. the relationship between PAF content in bull sperm and Estimated Relative Conception Rates (ERCR, a 3-year rolling average of NRR); and 2. the presence of the PAF-receptor in bull sperm. Sperm PAF content for bulls (n=8) with different ERCR was determined by radioimmunoassay. PAF-receptor expression was determined as follows: total RNA was purified by acid phenol extraction and ethanol precipitation. Complementary DNAs were synthesized by reverse transcriptase with dNTPs and random primers at 37°C, 60min; followed by 65°C, 5min. Reverse transcription (cDNA) products were amplified with Taq polymerase, dNTP, and PAF receptor primer pair (upper, 5′-AATCCAGTCACCCTGGTTGTAG-3′; lower, 5′-TGGACTCAGAGTTCCGATACAC-3′) at 94°C, 1min; 55°C, 1min; 72°C, 1min for 35 cycles followed by 72°C, 7min. RT-PCR products were analyzed by 2% agarose gel electrophoresis. PAF-receptor protein was determined as follows: PBS-washed bull sperm was exposed to human PAF-receptor antibody at 4°C for 3h, washed in PBS, then exposed to fluorescein isothiocyanate-conjugated anti-IgG for 90min at 37°C, and again washed in PBS. Specimens were examined by epifluorescence microscopy at 400×. PAF content in bull sperm ranged from 1.39ng/106 sperm cells to 13.68ng/106 sperm cells. There was a positive correlation (P&lt;0.05) between PAF content and ERCR. Presence of PAF-receptors in bull sperm was confirmed by immunofluorescence. However, distribution of PAF-receptors in bull sperm was not uniform within or between specimens. A cDNA clone containing the coding region for PAF-receptor was isolated from bull sperm using a reverse transcription-polymerase chain reaction protocol. There is a positive correlation (R=0.40; P&lt;0.05) between PAF content in sperm and in vivo fertility of individual bulls as determined by NRR. Molecular and immunofluorescence data confirm the presence of PAF-receptor (mRNA and protein) in bull sperm. Additional studies are warranted to elucidate the mechanism of PAF’s action in sperm. Early selection for fertility in bulls represents a potentially valuable application to enhance efficiency in cattle breeding.

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