Expression of human platelet-activating factor receptor gene in EoL-1 cells following butyrate-induced differentiation.
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ABSTRACT:
SUBMITTER: Izumi T
PROVIDER: S-EPMC1136334 | biostudies-other | 1995 Feb
REPOSITORIES: biostudies-other
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Project description: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.
| S-EPMC1137072 | biostudies-other
Project description:A competitive PCR assay was developed to quantify platelet-activating factor (PAF) receptor (PAF-R) transcripts in rat tissues using a synthetic RNA as a competitor. We found PAF-R mRNA constitutively expressed in the eight organs tested, with the ileum containing the highest concentration [(3.49+/-0.15) x 10(7) molecules/microg of RNA]. Significant but lower levels were also detected in the jejunum, spleen, lungs, kidneys, heart, stomach and liver. Furthermore we defined the regulatory role of inflammatory mediators in ileal PAF-R gene expression using a rat model of intestinal injury induced by PAF or lipopolysaccharide (LPS). Injection of LPS or low-dose PAF resulted in a marked increase in ileal PAF-R mRNA within 30 min. The up-regulation on PAF-R elicited by PAF was biphasic, peaking first at 90 min, then again at 6 h. In contrast, LPS elicited a weak monophasic response. The second phase of PAF-R mRNA increase after PAF administration was completely abolished by WEB 2170, a PAF antagonist, and partially inhibited by antitumour necrosis factor (TNF) antibody. These observations indicate the involvement of endogenous PAF and TNF in this event. In conclusion, we found: (a) preferential PAF-R expression in the ileum, suggesting a role for PAF in intestinal inflammation; (b) induction of PAF-R expression in vivo by its own agonist; (c) a complex regulation of PAR-R gene expression in vivo involving a network of various pro-inflammatory mediators.
| S-EPMC1218232 | biostudies-other
Project description:This data series contains spotted oligo microarray data from 10 different experiments using Agilent Rat v2 microarrays. This data is being made public in support of Fillon S et al. Journal of Immunology, (2006). Proinflammatory bacterial components are at least partially responsible for causing the clinical features of sepsis, a syndrome that causes >100,000 deaths each year in the US (1). In the case of Gram positive infection, a key bacterial element recognized by the innate immune system is the cell wall, a complex network of peptidoglycan covalently linked to teichoic acids, proteins and lipoproteins. The current model of innate immune recognition of Gram positive bacteria suggests bacterial cell wall interacts with host recognition proteins, such as toll-like receptors (TLR) and Nod proteins. We describe an additional recognition system mediated by the platelet activating factor receptor (PAFr) and directed to the pathogen associated molecular pattern (PAMP) phosphorylcholine that results in uptake of bacterial components into host cells. Intravascular choline-containing cell walls bound to endothelial cells and caused rapid lethality in wild type, Tlr2-/- and Nod2-/- mice, but not in Pafr-/- mice. Cell wall exited the vasculature into the heart and brain, accumulating within endothelial cells, cardiomyocytes and neurons in a PAFr-dependent way. Physiological consequences of the cell wall/PAFr interaction were cell specific, being noninflammatory in endothelial cells and neurons, but causing rapid loss of cardiomyocyte contractility that contributed to death. Thus, PAFr shepherds phosphorylcholine-containing bacterial components such as cell wall into host cells from where the response ranges from quiescence to severe pathophysiology. Keywords: Competitive hybridizations The ten experiments in this series comprise of four distinct experiments, two of which were performed as biological triplicates and two as biological duplicates. The table below describes the overall design in detail: File Name Experiment 16011868017643v41_GEO_format.txt RBCEC Replicate 1 16011868017644v41_GEO_format.txt RBCEC Replicate 2 251186821865v41_GEO_format.txt Neuron Replicate 1 16011868021377v41_GEO_format.txt Neuron Replicate 2 251186821690v41_GEO_format.txt CW/Lyt44 Replicate 1 251186821691v41_GEO_format.txt CW/Lyt44 Replicate 2 251186821692v41_GEO_format.txt CW/Lyt44 Replicate 1 251186821693v41_GEO_format.txt CW+TNF/Lyt44+TNF Replicate 1 251186821694v41_GEO_format.txt CW+TNF/Lyt44+TNF Replicate 2 251186829677v41_GEO_format.txt CW+TNF/Lyt44+TNF Replicate 3
2010-07-01 | E-GEOD-5545 | biostudies-arrayexpress
Project description:This data series contains spotted oligo microarray data from 10 different experiments using Agilent Rat v2 microarrays. This data is being made public in support of Fillon S et al. Journal of Immunology, (2006). Proinflammatory bacterial components are at least partially responsible for causing the clinical features of sepsis, a syndrome that causes >100,000 deaths each year in the US (1). In the case of Gram positive infection, a key bacterial element recognized by the innate immune system is the cell wall, a complex network of peptidoglycan covalently linked to teichoic acids, proteins and lipoproteins. The current model of innate immune recognition of Gram positive bacteria suggests bacterial cell wall interacts with host recognition proteins, such as toll-like receptors (TLR) and Nod proteins. We describe an additional recognition system mediated by the platelet activating factor receptor (PAFr) and directed to the pathogen associated molecular pattern (PAMP) phosphorylcholine that results in uptake of bacterial components into host cells. Intravascular choline-containing cell walls bound to endothelial cells and caused rapid lethality in wild type, Tlr2-/- and Nod2-/- mice, but not in Pafr-/- mice. Cell wall exited the vasculature into the heart and brain, accumulating within endothelial cells, cardiomyocytes and neurons in a PAFr-dependent way. Physiological consequences of the cell wall/PAFr interaction were cell specific, being noninflammatory in endothelial cells and neurons, but causing rapid loss of cardiomyocyte contractility that contributed to death. Thus, PAFr shepherds phosphorylcholine-containing bacterial components such as cell wall into host cells from where the response ranges from quiescence to severe pathophysiology. Keywords: Competitive hybridizations
2006-08-17 | GSE5545 | GEO
Project description:Irradiation generates oxidized phospholipids that activate platelet-activating factor receptor (PAFR) associated with pro-tumorigenic effects. Here, we investigated the involvement of PAFR in tumor cell survival after irradiation. Cervical cancer samples presented higher levels of PAF-receptor gene (PTAFR) when compared with normal cervical tissue. In cervical cancer patients submitted to radiotherapy (RT), the expression of PTAFR was significantly increased. Cervical cancer-derived cell lines (C33, SiHa, and HeLa) and squamous carcinoma cell lines (SCC90 and SCC78) express higher levels of PAFR mRNA and protein than immortalized keratinocytes. Gamma radiation increased PAFR expression and induced PAFR ligands and prostaglandin E2 (PGE2) in these tumor cells. The blocking of PAFR with the antagonist CV3938 before irradiation inhibited PGE2 and increased tumor cells death. Similarly, human carcinoma cells transfected with PAFR (KBP) were more resistant to radiation compared to those lacking the receptor (KBM). PGE2 production by irradiated KBP cells was also inhibited by CV3988. These results show that irradiation of carcinoma cells generates PAFR ligands that protect tumor cells from death and suggests that the combination of RT with a PAFR antagonist could be a promising strategy for cancer treatment.
| S-EPMC5807395 | biostudies-literature
Project description:Ultraviolet (UV)-irradiated keratinocytes secrete the lipid mediator of inflammation, platelet-activating factor (PAF). PAF plays an essential role in UV-induced immune suppression and skin cancer induction. Dermal mast cell migration from the skin to the draining lymph nodes plays a prominent role in activating systemic immune suppression. UV-induced PAF activates mast cell migration by up-regulating mast cell CXCR4 surface expression. Recent findings indicate that PAF up-regulates CXCR4 expression via histone acetylation. UV-induced PAF also activates cell cycle arrest and disrupts DNA repair, in part by increasing p21 expression. Do epigenetic alterations play a role in p21 up-regulation??Here we show that PAF increases Acetyl-CREB-binding protein (CBP/p300) histone acetyltransferase expression in a time and dose-dependent fashion. Partial deletion of the HAT domain in the CBP gene, blocked these effects. Chromatin immunoprecipitation assays indicated that PAF-treatment activated the acetylation of the p21 promoter. PAF-treatment had no effect on other acetylating enzymes (GCN5L2, PCAF) indicating it is not a global activator of histone acetylation. This study provides further evidence that PAF activates epigenetic mechanisms to affect important cellular processes, and we suggest this bioactive lipid can serve as a link between the environment and the epigenome.
| S-EPMC5291204 | biostudies-other
Project description:Platelet-activating factor (PAF) is a potent, bioactive phospholipid that acts on multiple cells and tissues through its G protein-coupled receptor (GPCR). PAF is not stored but is rapidly generated via enzymatic acetylation of the precursor 1-O-hexadecyl-2-hydroxy-sn-glycero-3-phosphocholine (lysoPAF). The bioactivity of PAF is effectively and tightly regulated by PAF acetylhydrolases, which convert PAF back to lysoPAF. Previous studies report that lysoPAF is an inactive precursor and metabolite of PAF. However, lysoPAF has not been carefully studied in its own context. Here we report that lysoPAF has an opposing effect of PAF in the activation of neutrophils and platelets. Whereas PAF potentiates neutrophil NADPH oxidase activation, lysoPAF dose-dependently inhibits this function. Inhibition by lysoPAF is not affected by the use of a PAF receptor antagonist or genetic deletion of the PAF receptor gene. The mechanism of lysoPAF-mediated inhibition of neutrophils involves an elevation in the intracellular cAMP level, and pharmacological blockade of adenylyl cyclase completely reverses the inhibitory effect of lysoPAF. In addition, lysoPAF increases intracellular cAMP levels in platelets and inhibits thrombin-induced platelet aggregation, which can be reversed by inhibition of protein kinase A. These findings identify lysoPAF as a bioactive lipid with opposing functions of PAF and suggest a novel and intrinsic regulatory mechanism for balance of the potent activity of PAF.
| S-EPMC2646610 | biostudies-literature
Project description:Platelet-activating factor (PAF) is a pleiotropic phospholipid with proinflammatory, procoagulant and angiogenic actions on the vasculature. We and others have reported the presence of PAF receptor (Ptafr) at intracellular sites such as the nucleus. However, mechanisms of localization and physiologic functions of intracellular Ptafr remain poorly understood. We hereby identify the importance of C-terminal motif of the receptor and uncover novel roles of Rab11a GTPase and importin-5 in nuclear translocation of Ptafr in primary human retinal microvascular endothelial cells. Nuclear localization of Ptafr is independent of exogenous PAF stimulation as well as intracellular PAF biosynthesis. Moreover, nuclear Ptafr is responsible for the upregulation of unique set of growth factors, including vascular endothelial growth factor, in vitro and ex vivo. We further corroborate the intracrine PAF signaling, resulting in angiogenesis in vivo, using Ptafr antagonists with distinct plasma membrane permeability. Collectively, our findings show that nuclear Ptafr translocates in an agonist-independent manner, and distinctive functions of Ptafr based on its cellular localization point to another dimension needed for pharmacologic selectivity of drugs.
| S-EPMC4941644 | biostudies-literature
Project description:"Let's Move!" is a comprehensive initiative, launched by the First Lady, Michelle Obama, dedicates to solving problems of obesity, which is growing in child. The life behaviors do affect obesity; however, the mechanistic insight in molecular level is still not clear. In this study, by continually monitoring mouse body weight under chow and high fat western diets as well as metabolic, physical activity and food intake behaviors assessed in a CLAMS Comprehensive Lab Animal Monitoring System, we demonstrated that the platelet-activating factor receptor (PTAFR) contributes to modification of life behaviors. PTAFR does not affect metabolism of ingested dietary fat and carbohydrate in young animals; however, Ptafr ablation dramatically increased weight gain without affecting adipose tissue accumulation. Ptafr-/- mice possess new habits that increased food intake and decreased movement. Our studies suggest that regulation of PTAFR activity may be a novel strategy to control obesity in children or young adults.
| S-EPMC5773056 | biostudies-literature
Project description:Chronic inflammatory milieu in the tumor microenvironment (TME) leads to the recruitment and differentiation of myeloid-derived suppressor cells (MDSCs). Polymorphonuclear (PMN)-MDSCs, which are phenotypically and morphologically defined as a subset of neutrophils, cause major immune suppression in the TME, posing a significant challenge in the development of effective immunotherapies. Despite recent advances in our understanding of PMN-MDSC functions, the mechanism that gives rise to immunosuppressive neutrophils within the TME remains elusive. Both in vivo and in vitro, newly recruited neutrophils into the tumor sites remained activated and highly motile for several days and developed immunosuppressive phenotypes, as indicated by increased arginase 1 (Arg1) and dcTrail-R1 expression and suppressed anti-cancer CD8 T cell cytotoxicity. The strong suppressive function was successfully recapitulated by incubating naïve neutrophils with cancer cell culture supernatant in vitro. Cancer metabolite secretome analyses of the culture supernatant revealed that both murine and human cancers released lipid mediators to induce the differentiation of immunosuppressive neutrophils. Liquid chromatography–mass spectrometry (LC-MS) lipidomic analysis identified platelet activation factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) as a common tumor-derived lipid mediator that induces neutrophil differentiation. Lysophosphatidylcholine acyltransferase 2 (LPCAT2), the PAF biosynthetic enzyme, is upregulated in human pancreatic ductal adenocarcinoma (PDAC) and shows an unfavorable correlation with patient survival across multiple cancer types. Our study identifies PAF as a novel lipid-driven mechanism of MDSC differentiation in the TME, providing a potential target for cancer immunotherapy.
2024-09-13 | GSE273979 | GEO