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Platelet-activating Factor (platelet-activating + factor)
Selected AbstractsAcetyl-CoA:1- O -alkyl- sn -glycero-3-phosphocholine acetyltransferase (lyso-PAF AT) activity in cortical and medullary human renal tissueFEBS JOURNAL, Issue 14 2003Tzortzis N Nomikos Platelet-activating factor (PAF) is one of the most potent inflammatory mediators. It is biosynthesized by either the de novo biosynthesis of glyceryl ether lipids or by remodeling of membrane phospholipids. PAF is synthesized and catabolized by various renal cells and tissues and exerts a wide range of biological activities on renal tissue suggesting a potential role during renal injury. The aim of this study was to identify whether cortex and medulla of human kidney contain the acetyl-CoA:1- O -alkyl- sn -glycero-3-phosphocholine acetyltransferase (lyso-PAF AT) activity which catalyses the last step of the remodeling biosynthetic route of PAF and is activated in inflammatory conditions. Cortex and medulla were obtained from nephrectomized patients with adenocarcinoma and the enzymatic activity was determined by a trichloroacetic acid precipitation method. Lyso-PAF AT activity was detected in both cortex and medulla and distributed among the membrane subcellular fractions. No statistical differences between the specific activity of cortical and medullary lyso-PAF AT was found. Both cortical and medullary microsomal lyso-PAF ATs share similar biochemical properties indicating common cellular sources. [source] Molecular mechanisms underlying inflammatory lung diseases in the elderly: Development of a novel therapeutic strategy for acute lung injury and pulmonary fibrosis,GERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 3 2005Takahide Nagase In the elderly, inflammatory lung diseases, including acute lung injury and pulmonary fibrosis, are significant in terms of both mortality and difficulty in management. Acute respiratory distress syndrome (ARDS) is an acute lung injury and the mortality rate for ARDS ranges from 40 to 70% despite intensive care. Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disorder of the lung parenchyma. No useful drugs are currently available to treat IPF. However, molecular mechanisms underlying these lung diseases are little understood and the development of a novel therapeutic strategy is urgently needed. Platelet-activating factor (PAF) and metabolites of arachidonic acid, i.e. eicosanoids, are lipid mediators that have various biological effects. A key enzyme for the production of these inflammatory mediators, including eicosanoids and PAF, is phospholipase A2. In particular, cytosolic PLA2 (cPLA2) is especially important. The purpose of this article is to report novel findings regarding the role of PAF and cPLA2 in lung inflammatory diseases, especially, acute lung injury and pulmonary fibrosis. To address this question, we used mutant mice, i.e. PAFR transgenic mice, PAFR gene-disrupted mice and cPLA2 gene-disrupted mice. We have shown that PAF and eicosanoids, downstream mediators of cPLA2, may be involved in the pathogenesis of ARDS and IPF, which are important diseases in the elderly. Although there exist extreme differences in clinical features between ARDS and IPF, both diseases are fatal disorders for which no useful drugs are currently available. On the basis of recent reports using mutant mice, cPLA2 might be a potential target to intervene in the development of pulmonary fibrosis and acute lung injury in the elderly. [source] Platelet-activating factor-induced NF-,B activation and IL-8 production in intestinal epithelial cells are Bcl10-dependentINFLAMMATORY BOWEL DISEASES, Issue 4 2010Alip Borthakur PhD Abstract Background: Platelet-activating factor (PAF), a potent proinflammatory phospholipid mediator, has been implicated in inducing intestinal inflammation in diseases such as inflammatory bowel disease (IBD) and necrotizing enterocolitis (NEC). However, its mechanisms of inducing inflammatory responses are not fully understood. Therefore, studies were designed to explore the mechanisms of PAF-induced inflammatory cascade in intestinal epithelial cells. Methods: Nuclear factor kappa B (NF-,B) activation was measured by luciferase assay and enzyme-linked immunosorbent assay (ELISA), and interleukin 8 (IL-8) production was determined by ELISA. B-cell lymphoma 10 (Bcl10), caspase recruitment domain-containing membrane-associated guanylate kinase protein 3 (CARMA3), and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) mRNA and protein levels were assessed by real-time reverse-transcription polymerase chain reaction (RT-PCR) and Western blot, respectively. siRNA silencing of Bcl10 was used to examine its role in PAF-induced NF-,B activation and IL-8 production. The promoter region of the Bcl10 gene was cloned with the PCR method and promoter activity measured by luciferase assay. Results: The adaptor protein Bcl10 appeared to play an important role in the PAF-induced inflammatory pathway in human intestinal epithelial cells. Bcl10 was required for PAF-induced I,B, phosphorylation, NF-,B activation, and IL-8 production in NCM460, a cell line derived from normal human colon, and Caco-2, a transformed human intestinal cell line. PAF also stimulated Bcl10 interactions with CARMA3 and MALT1, and upregulated Bcl10 expression in these cells via transcriptional regulation. Conclusions: These findings highlight a novel PAF-induced inflammatory pathway in intestinal epithelial cells, requiring Bcl10 as a critical mediator and involving CARMA3/Bcl10/MALT1 interactions. The proinflammatory effects of PAF play prominent roles in the pathogenesis of IBD and this pathway may present important targets for intervention in chronic inflammatory diseases of the intestine. (Inflamm Bowel Dis 2009;) [source] Differential platelet-activating factor synthesis by monocytes and polymorphonuclear leukocytes from subjects with localized aggressive periodontitisJOURNAL OF PERIODONTAL RESEARCH, Issue 3 2007C. R. Shin Background and Objective:, Platelet-activating factor is elevated in localized aggressive periodontitis. We previously demonstrated that the elevated level of platelet-activating factor in localized aggressive periodontitis is at least partially attributable to low levels of platelet-activating factor acetylhydrolase, the enzyme that catabolizes platelet-activating factor. The objective of this study was to determine if platelet-activating factor synthesis was also elevated in localized aggressive periodontitis. To test this, platelet-activating factor synthesis was quantified in the monocytes and polymorphonuclear neutrophils of periodontally healthy patients and of subjects with localized aggressive periodontitis. Material and Methods:, Cells were labeled with [3H]acetate and treated with vehicle or stimulated with calcium ionophore A23187. Platelet-activating factor was extracted and quantified by scintillation counting. Results:, For both subject groups, resting monocytes and polymorphonuclear neutrophils produced platelet-activating factor, and calcium ionophore A23187 stimulated platelet-activating factor production in both cell types. However, calcium ionophore A23187-activated monocytes from subjects with localized aggressive periodontitis produced less platelet-activating factor than did activated periodontally healthy monocytes (p < 0.0001), suggesting an aberrant calcium ionophore A23187 response in monocytes from subjects with localized aggressive periodontitis. Indeed, when the data were expressed as fold induction of platelet-activating factor synthesis in response to calcium ionophore A23187, monocytes from subjects with localized aggressive periodontitis exhibited only a fourfold increase in platelet-activating factor synthesis, whereas calcium ionophore A23187-stimulated monocytes from periodontally healthy, chronic periodontitis and generalized aggressive periodontitis subjects produced ,,12 times more platelet-activating factor than did resting monocytes. In contrast, both resting and activated localized aggressive periodontitis polymorphonuclear neutrophils synthesized more platelet-activating factor than did periodontally healthy polymorphonuclear neutrophils. Conclusion:, These data suggest that high levels of platelet-activating factor in subjects with localized aggressive periodontitis result from both increased synthesis and reduced catabolism. While localized aggressive periodontitis polymorphonuclear neutrophils contribute to increased platelet-activating factor mass through synthesis, the contribution of monocytes is probably the result of reduced catabolism by platelet-activating factor acetylhydrolase. [source] Platelet-activating factor and human meningiomasNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 6 2006Y. Denizot Meningiomas are common primary intracranial tumours. Platelet-activating factor (PAF) is an inflammatory and angiogenic lipid mediator involved in several types of cancer. The presence of PAF receptor (PAF-R) transcripts, the levels of PAF, the phospholipase A2 activity (PLA2, the enzymatic activity implicated in PAF formation) and the PAF acetylhydrolase activity (AHA, the PAF degrading enzyme) were investigated in 49 human meningiomas. PAF-R transcripts, PAF, PLA2 and AHA were detected in meningiomas. However, their levels did not correlate with biological parameters such as the tumour grade, the presence of associated oedema, necrosis, mitotic index as well as intensity of the neovascularization and chronic inflammatory response. In conclusion, PAF is present in meningiomas where it might act on tumour growth by altering the local angiogenic and/or cytokine networks as previously suggested for human breast and colorectal cancer. [source] The Role of Platelet-activating Factor in the Mammalian Female Reproductive TractREPRODUCTION IN DOMESTIC ANIMALS, Issue 6 2008U Tiemann Contents Platelet-activating factor (PAF) is a potent lipid mediator produced by various cell types of mammals and is involved in an inflammatory-like process with increased vascular permeability. Platelet-activating factor exerts its actions through the activation of specific PAF receptors (PAF-R) found in cells and tissues of the female reproductive tract. The aim of this article was summarized briefly in the current research on the role of PAF in female reproductive functions. Platelet-activating factor has been implicated in processes of ovulation, implantation and parturition because of its angiogenic and growth factor properties. This factor is influenced by ovarian steroid hormones in bringing about changes in the uterus and is a candidate molecule for initial embryo,maternal dialogue. Tissue concentrations of PAF are regulated by the equilibrium between biosynthesis and degradation by PAF-acetylhydrolase (PAF-AH). Antagonists of PAF interfere with ovulation and implantation. Platelet-activating factor, its receptor, and PAF-AH activity play an important role in the maintenance of pregnancy. [source] Platelet-activating factor stimulates ovine foetal pulmonary vascular smooth muscle cell proliferation: role of nuclear factor-kappa B and cyclin-dependent kinasesCELL PROLIFERATION, Issue 2 2008B. O. Ibe Objective: Platelet-activating factor (PAF) is implicated in pathogenesis of persistent pulmonary hypertension of the neonate (PPHN); PAF is a mitogen for lung fibroblasts. PAF's role in pulmonary vascular smooth muscle cell (PVSMC) proliferation and in hypoxia-induced pulmonary vein (PV) remodelling has not been established and mechanisms for PAF's cell-proliferative effects are not well understood. We investigated involvement of PAF and PAF receptors in PVSMC proliferation. Materials and methods: Cells from pulmonary arteries (SMC-PA) and veins (SMC-PV) were serum starved for 72 h in 5% CO2 in air (normoxia). They were cultured for 24 h more in normoxia or 2% O2 (hypoxia) in 0.1% or 10% foetal bovine serum with 5 µCi/well of [3H]-thymidine, with and without 10 nm PAF. Nuclear factor-kappa B (NF-,B), CDK2 and CDK4 protein expression, and their roles in cell proliferation control were studied. Results: PAF and hypoxia increased SMC-PA and SMC-PV proliferation. WEB2170 inhibited PAF-induced cell proliferation while lyso-PAF had no effect. SMC-PV proliferated more than SMC-PA and PAF plus hypoxia augmented NF-,B protein expression. NF-,B inhibitory peptide attenuated PAF-induced cell proliferation by 50% and PAF increased CDK2 and CDK4 protein expression. The data show that hypoxia and PAF up-regulate PVSMC proliferation via PAF receptor-specific pathway involving NF-,B, CDK2 and CDK4 activations. Conclusion: They suggest that in vivo, in foetal lung low-oxygen environment, where PAF level is high, proliferation of PVSMC will occur readily to modulate PV development and that failure of down-regulation of PAF effects postnatally may result in PPHN. [source] Post-ischaemic activation of kinases in the pre-conditioning-like cardioprotective effect of the platelet-activating factorACTA PHYSIOLOGICA, Issue 3 2009C. Penna Abstract Aim:, Platelet-activating factor (PAF) triggers cardiac pre-conditioning against ischemia/reperfusion injury. The actual protection of ischaemic pre-conditioning occurs in the reperfusion phase. Therefore, we studied in this phase the kinases involved in PAF-induced pre-conditioning. Methods:, Langendorff-perfused rat hearts underwent 30 min of ischaemia and 2 h of reperfusion (group 1, control). Before ischaemia, group 2 hearts were perfused for 19 min with PAF (2 × 10,11 m); groups 3,5 hearts were co-infused during the initial 20 min of reperfusion, with the protein kinase C (PKC) inhibitor chelerythrine (5 × 10,6 m) or the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (5 × 10,5 m) and atractyloside (2 × 10,5 m), a mitochondrial permeability transition pore (mPTP) opener respectively. Phosphorylation of PKC,, PKB/A,t, GSK-3, and ERK1/2 at the beginning of reperfusion was also checked. Left ventricular pressure and infarct size were determined. Results:, PAF pre-treatment reduced infarct size (33 ± 4% vs. 64 ± 5% of the area at risk of control hearts) and improved pressure recovery. PAF pre-treatment enhanced the phosphorylation/activation of PKC,, PKB/A,t and the phosphorylation/inactivation of GSK-3, at reperfusion. Effects on ERK1/2 phosphorylation were not consistent. Infarct-sparing effect and post-ischaemic functional improvement induced by PAF pre-treatment were abolished by post-ischaemic infusion of either chelerythrine, LY294002 or atractyloside. Conclusions:, The cardioprotective effect exerted by PAF pre-treatment involves activation of PKC and PI3K in post-ischaemic phases and might be mediated by the prevention of mPTP opening in reperfusion via GSK-3, inactivation. [source] Human resting CD16,, CD16+ and IL-2-, IL-12-, IL-15- or IFN-,-activated natural killer cells differentially respond to sphingosylphosphorylcholine, lysophosphatidylcholine and platelet-activating factorEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2005Yixin Jin Abstract The phosphorylcholine-containing lipid lysophosphatidylcholine (LPC) is abundant in the bloodstream, whereas sphingosylphosphorylcholine (SPC) and platelet-activating factor (PAF) highly accumulate at inflamed sites. Utilizing RT-PCR, flow cytometry and immunoblot analyses, we show for the first time that ovarian cancer G,protein-coupled receptor,1, the receptor for SPC, is expressed in IL-2-, IL-12- and IL-15-activated but not in resting CD16,, resting CD16+ or IFN-,-activated NK,cells. Similarly, G2 accumulation and PAF receptor are variably expressed in these subsets of NK,cells. SPC, LPC and PAF differentially induce the chemotaxis of resting and activated NK,cells. In the chemotaxis assay, it is observed that resting CD16,CD56bright and CD16+CD56dim cells predominantly respond to LPC, whereas activated NK,cells, regardless of the sort of stimulus, robustly respond to PAF. SPC is also a potent chemoattractant for IL-2-, IL-12- and IL-15- but not for IFN-,-activated NK,cells. Further analysis shows that, depending on the cytokine pattern of NK,cell activation, phosphorylcholine-containing lipids differentially affect IFN-, secretion by these cells. Our results provide one possible explanation for the tissue compartmentation of NK,cells and their ability to secrete IFN-,. Furthermore, these results may provide novel information regarding NK,cell regulation during inflammation. [source] Regulation of Wnt/,-catenin pathway by cPLA2, and PPAR,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2008Chang Han Abstract Cytosolic phospholipase A2, (cPLA2,) is a rate-limiting key enzyme that releases arachidonic acid (AA) from membrane phospholipid for the production of biologically active lipid mediators including prostaglandins, leukotrienes and platelet-activating factor. cPLA2, is translocated to nuclear envelope in response to intracellular calcium increase and the enzyme is also present inside the cell nucleus; however, the biological function of cPLA2, in the nucleus remains unknown. Here we show a novel role of cPLA2, for activation of peroxisome proliferator-activated receptor-, (PPAR,) and ,-catenin in the nuclei. Overexpression of cPLA2, in human cholangiocarcinoma cells induced the binding of PPAR, to ,-catenin and increased their association with the TCF/LEF response element. These effects are inhibited by the cPLA2, siRNA and inhibitors as well as by siRNA knockdown of PPAR,. Overexpression of PPAR, or treatment with the selective PPAR, ligand, GW501516, also increased ,-catenin binding to TCF/LEF response element and increased its reporter activity. Addition of AA and GW501516 to nuclear extracts induced a comparable degree of ,-catenin binding to TCF/LEF response element. Furthermore, cPLA2, protein is present in the PPAR, and ,-catenin binding complex. Thus the close proximity between cPLA2, and PPAR, provides a unique advantage for their efficient functional coupling in the nucleus, where AA produced by cPLA2, becomes immediately available for PPAR, binding and subsequent ,-catenin activation. These results depict a novel interaction linking cPLA2,, PPAR, and Wnt/,-catenin signaling pathways and provide insight for further understanding the roles of these key molecules in human cells and diseases. J. Cell. Biochem. 105: 534,545, 2008. © 2008 Wiley-Liss, Inc. [source] BIOACTIVE POLAR LIPIDS IN OLIVE OIL, POMACE AND WASTE BYPRODUCTSJOURNAL OF FOOD BIOCHEMISTRY, Issue 4 2008HARALABOS C. KARANTONIS ABSTRACT Olive oil protects against atherosclerosis because of biologically active microconstituents. In this study, total polar lipids from olive oil, pomace, pomace oil and waste byproducts were extracted, fractionated by thin layer chromatography and tested for their bioactivity. The most active ones were further purified on high-performance liquid chromatography, and the resulting lipid fractions were tested for their bioactivity. Bioactive compounds were determined in all samples with the exception of olive pomace oil. These lipids inhibited platelet-activating factor (PAF)-induced platelet aggregation and also induced platelet aggregation. The bioactive compound from olive pomace has been chemically characterized as a glycerylether-sn-2-acetyl glycolipid based on mass spectra. Chemical determinations and mass spectrometry data reinforce the assumption that these active microconstituents share both similar bioactivity and common structural features. The existence of PAF antagonists in polar lipid extracts from olive oil waste by-products render them biologically valuable materials for the food industry that could be used for the production of functional foods. PRACTICAL APPLICATIONS Isolated bioactive polar lipids from waste by-products of the olive oil industry that act as inhibitors of platelet-activating factor (PAF) may be used for enrichment and production of foods with higher nutritional value, as PAF plays a major role in inflammatory disorders, including atherosclerosis development. [source] The significance of platelet-activating factor and fertility in the male primate: a reviewJOURNAL OF MEDICAL PRIMATOLOGY, Issue 1 2005William E. Roudebush Abstract:, Since its discovery nearly 30 years ago platelet-activating factor (PAF) has emerged as one of the more important lipid mediators known. PAF (1- O -alkyl-2- O -acetyl- sn -glycero-3-phosphorylcholine) exists endogenously as a mixture of molecular species with structural variants of the alkyl moiety. PAF is a novel potent signaling phospholipid that has unique pleiotropic biological properties in addition to platelet activation. PAF also plays a significant role in reproduction and is present in the sperm of a number of primate species. PAF content in squirrel monkey sperm is significantly higher during the breeding season than the non-breeding season. PAF content in rhesus sperm has a significant relationship with sperm motility. PAF content in human sperm has a positive correlation with seminal parameters and pregnancy outcomes. The enzymes (lyso-PAF-acetyltransferase and PAF-acetylhydrolase) necessary for PAF activation and deactivation are present in primate sperm. PAF-acetylhydrolase may act as a ,decapacitation factor'. Removal of this enzyme during capacitation promotes PAF synthesis increasing primate motility and fertilization. PAF also plays a significant role in the fertilization process, enhancing the fertilization rates of oocytes. Enhanced embryo development has also been reported in oocytes fertilized with PAF-treated sperm. Exogenous PAF will also significantly improve primate artificial insemination pregnancy outcomes. PAF antagonists inhibit sperm motility, acrosome reaction, and fertilization thus suggesting the presence of receptors for PAF. The PAF-receptor is present on primate sperm, with altered transcript levels and distribution patterns on abnormal cells. Whereas, the exact mechanism of PAF in sperm function and reproduction is uncertain, its importance in normal primate fertility is substantial. [source] Modulation of inflammation in brain: a matter of fatJOURNAL OF NEUROCHEMISTRY, Issue 3 2007Akhlaq A. Farooqui Abstract Neuroinflammation is a host defense mechanism associated with neutralization of an insult and restoration of normal structure and function of brain. Neuroinflammation is a hallmark of all major CNS diseases. The main mediators of neuroinflammation are microglial cells. These cells are activated during a CNS injury. Microglial cells initiate a rapid response that involves cell migration, proliferation, release of cytokines/chemokines and trophic and/or toxic effects. Cytokines/chemokines stimulate phospholipases A2 and cyclooxygenases. This results in breakdown of membrane glycerophospholipids with the release of arachidonic acid (AA) and docosahexaenoic acid (DHA). Oxidation of AA produces pro-inflammatory prostaglandins, leukotrienes, and thromboxanes. One of the lyso-glycerophospholipids, the other products of reactions catalyzed by phospholipase A2, is used for the synthesis of pro-inflammatory platelet-activating factor. These pro-inflammatory mediators intensify neuroinflammation. Lipoxin, an oxidized product of AA through 5-lipoxygenase, is involved in the resolution of inflammation and is anti-inflammatory. Docosahexaenoic acid is metabolized to resolvins and neuroprotectins. These lipid mediators inhibit the generation of prostaglandins, leukotrienes, and thromboxanes. Levels of prostaglandins, leukotrienes, and thromboxanes are markedly increased in acute neural trauma and neurodegenerative diseases. Docosahexaenoic acid and its lipid mediators prevent neuroinflammation by inhibiting transcription factor NF,B, preventing cytokine secretion, blocking the synthesis of prostaglandins, leukotrienes, and thromboxanes, and modulating leukocyte trafficking. Depending on its timing and magnitude in brain tissue, inflammation serves multiple purposes. It is involved in the protection of uninjured neurons and removal of degenerating neuronal debris and also in assisting repair and recovery processes. The dietary ratio of AA to DHA may affect neurodegeneration associated with acute neural trauma and neurodegenerative diseases. The dietary intake of docosahexaenoic acid offers the possibility of counter-balancing the harmful effects of high levels of AA-derived pro-inflammatory lipid mediators. [source] Differential platelet-activating factor synthesis by monocytes and polymorphonuclear leukocytes from subjects with localized aggressive periodontitisJOURNAL OF PERIODONTAL RESEARCH, Issue 3 2007C. R. Shin Background and Objective:, Platelet-activating factor is elevated in localized aggressive periodontitis. We previously demonstrated that the elevated level of platelet-activating factor in localized aggressive periodontitis is at least partially attributable to low levels of platelet-activating factor acetylhydrolase, the enzyme that catabolizes platelet-activating factor. The objective of this study was to determine if platelet-activating factor synthesis was also elevated in localized aggressive periodontitis. To test this, platelet-activating factor synthesis was quantified in the monocytes and polymorphonuclear neutrophils of periodontally healthy patients and of subjects with localized aggressive periodontitis. Material and Methods:, Cells were labeled with [3H]acetate and treated with vehicle or stimulated with calcium ionophore A23187. Platelet-activating factor was extracted and quantified by scintillation counting. Results:, For both subject groups, resting monocytes and polymorphonuclear neutrophils produced platelet-activating factor, and calcium ionophore A23187 stimulated platelet-activating factor production in both cell types. However, calcium ionophore A23187-activated monocytes from subjects with localized aggressive periodontitis produced less platelet-activating factor than did activated periodontally healthy monocytes (p < 0.0001), suggesting an aberrant calcium ionophore A23187 response in monocytes from subjects with localized aggressive periodontitis. Indeed, when the data were expressed as fold induction of platelet-activating factor synthesis in response to calcium ionophore A23187, monocytes from subjects with localized aggressive periodontitis exhibited only a fourfold increase in platelet-activating factor synthesis, whereas calcium ionophore A23187-stimulated monocytes from periodontally healthy, chronic periodontitis and generalized aggressive periodontitis subjects produced ,,12 times more platelet-activating factor than did resting monocytes. In contrast, both resting and activated localized aggressive periodontitis polymorphonuclear neutrophils synthesized more platelet-activating factor than did periodontally healthy polymorphonuclear neutrophils. Conclusion:, These data suggest that high levels of platelet-activating factor in subjects with localized aggressive periodontitis result from both increased synthesis and reduced catabolism. While localized aggressive periodontitis polymorphonuclear neutrophils contribute to increased platelet-activating factor mass through synthesis, the contribution of monocytes is probably the result of reduced catabolism by platelet-activating factor acetylhydrolase. [source] Antiatherogenic properties of lipid minor constituents from seed oilsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2003Haralabos C Karantonis Abstract A number of lines of evidence suggest that seed oils exhibit a protective effect against atherogenesis. Most of the protective compounds are still unidentified. In this study, polar lipids of seed oil samples from sesame, corn and sunflower were successively fractionated by high-performance liquid chromatography. Each isolated lipid compound was tested in vitro for its ability to inhibit platelet-activating factor (PAF) and thrombin-induced washed rabbit platelet aggregation or to cause platelet aggregation. A significant number of lipids that exerted the above biological activities were detected. The most biologically active compounds were subjected to biological, chemical and spectroscopic analyses, and their structural data are presented. These results give a different explanation for the antiatherogenic action that seed oils exert. Given that PAF plays a pivotal role in atherogenesis, the fact that these oils contain PAF antagonists suggests their high nutritional value. Copyright © 2003 Society of Chemical Industry [source] Independent Regulation of Periarteriolar and Perivenular Nitric Oxide Mechanisms in the In Vivo Hamster Cheek Pouch MicrovasculatureMICROCIRCULATION, Issue 4 2009DAVID D. KIM ABSTRACT Objective: We tested the hypothesis that differential stimulation of nitric oxide (NO) production can be induced in pre- and postcapillary segments of the microcirculation in the hamster cheek pouch. Materials and Methods: We applied acetylcholine (ACh) or platelet-activating factor (PAF) topically and measured perivascular NO concentration ([NO]) with NO-sensitive microelectrodes in arterioles and venules of the hamster cheek pouch. We also measured NO in cultured coronary endothelial cells (CVEC) after ACh or PAF. Results: ACh increased periarteriolar [NO] significantly in a dose-dependent manner. ACh at 1 ,M increased [NO] from 438.1±43.4 nM at baseline to 647.9±66.3 nM, while 10 ,M of ACh increased [NO] from baseline to 1,035.0±59.2 nM (P<0.05). Neither 1 nor 10 ,M of ACh changed perivenular [NO] in the hamster cheek pouch. PAF, at 100 nM, increased perivenular [NO] from 326.6±50.8 to 622.8±41.5 nM. Importantly, 100 nM of PAF did not increase periarteriolar [NO]. PAF increased [NO] from 3.6±2.1 to 455.5±19.9 in CVEC, while ACh had no effect. Conclusions: We conclude that NO production can be stimulated in a differential manner in pre- and postcapillary segments in the hamster cheek pouch. ACh selectively stimulates the production of NO only in arterioles, while PAF stimulates the production of NO only in venules. [source] Ultraviolet B Radiation of Human Skin Generates Platelet-activating Factor Receptor AgonistsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2010Jared B. Travers Ultraviolet B radiation (UVB) is a potent stimulator of epidermal cytokine production. In addition to cytokines, such as tumor necrosis factor-alpha (TNF-,), UVB generates bioactive lipids including platelet-activating factor (PAF). Our previous in vitro studies in keratinocytes or epithelial cell lines have demonstrated that UVB-mediated production of PAF agonists is due primarily to the pro-oxidative effects of this stimulant, resulting in the nonenzymatic production of modified phosphocholines (oxidized glycerophosphocholines). The current studies use human skin to assess whether UVB irradiation generates PAF-receptor agonists, and the role of oxidative stress in their production. These studies demonstrate that UVB irradiation of human skin results in PAF agonists, which are blocked by the antioxidant vitamin C and the epidermal growth factor receptor inhibitor PD168393. Inasmuch as UVB-generated PAF agonists have been implicated in animal model systems as being involved in photobiologic processes including systemic immunosuppression and cytokine (TNF-,) production, these studies indicate that this novel activity could be involved in human disease. [source] Neutrophil dysfunction in a family with a SAPHO syndrome,like phenotypeARTHRITIS & RHEUMATISM, Issue 10 2008Polly J. Ferguson SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, osteitis) is an inflammatory disorder of the bone, skin, and joints. We describe a family with multiple affected members who segregate a SAPHO syndrome,like phenotype, and we report the results of neutrophil studies and candidate gene analysis. We obtained written informed consent and a family history and reviewed medical records. We collected DNA and sequenced candidate genes, and we performed functional studies on neutrophils isolated from the proband and her mother. The pedigree segregated chronic osteomyelitis and cutaneous inflammation in a pattern that suggested an autosomal-dominant disorder. No coding sequence mutations were detected in PSTPIP1,PSTPIP2, LPIN2, SH3BP2, or NCF4. Analysis of neutrophil function in the proband, including nitroblue tetrazolium tests, myeloperoxidase assays, neutrophil chemotaxis, and neutrophil chemotaxis assays, revealed no identifiable abnormalities. However, an abnormality in the luminol, but not the isoluminol, respiratory burst assays following stimulation with phorbol myristate acetate (PMA) was detected in neutrophils isolated from the affected proband. Internal oxidant production was also reduced in the proband and her mother when neutrophils were treated with fMLP with or without platelet-activating factor, PMA alone, or tumor necrosis factor , alone. This family segregates a disorder characterized by chronic inflammation of the skin and bone. Functional differences in neutrophils exist between affected individuals and controls. The biologic significance of this defect remains unknown. Identification of the gene defect will help identify an immunologic pathway that, when dysregulated, causes inflammation of the skin and bone. [source] Effects of heparin and related molecules upon neutrophil aggregation and elastase release in vitroBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2003Rachel A Brown Neutrophil-derived elastase is an enzyme implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Heparin inhibits the enzymatic activity of elastase and here we provide evidence for the first time that heparin can inhibit the release of elastase from human neutrophils. Unfractionated and low molecular weight heparins (UH and LMWH, 0.01,1000 U ml,1) and corresponding concentrations (0.06,6000 ,g ml,1) of nonanticoagulant O-desulphated heparin (ODH), dextran sulphate (DS) and nonsulphated poly- L -glutamic acid (PGA) were compared for their effects on both elastase release from and aggregation of neutrophils. UH, ODH and LMWH inhibited (P<0.05) the homotypic aggregation of neutrophils, in response to both N -formyl-methionyl-leucyl-phenylalanine (fMLP, 10,6M) and platelet-activating factor (PAF, 10,6M), as well as elastase release in response to these stimuli, in the absence and presence of the priming agent tumour necrosis factor-alpha (TNF- ,, 100 U ml,1). DS inhibited elastase release under all the conditions of cellular activation tested (P<0.05) but had no effect on aggregation. PGA lacked efficacy in either assay, suggesting general sulphation to be important in both effects of heparin on neutrophil function and specific patterns of sulphation to be required for inhibition of aggregation. Further investigation of the structural requirements for inhibition of elastase release confirmed the nonsulphated GAG hyaluronic acid and neutral dextran, respectively, to be without effect, whereas the IP3 receptor antagonist 2-aminoethoxydiphenylborate (2-APB) mimicked the effects of heparin, itself an established IP3 receptor antagonist, suggesting this to be a possible mechanism of action. British Journal of Pharmacology (2003) 139, 845,853. doi:10.1038/sj.bjp.0705291 [source] The Ether Lipid Inositol-C2-PAF is a Potent Inhibitor of Cell Proliferation in HaCaT CellsCHEMBIOCHEM, Issue 3 2006Annette Fischer Abstract The search for specific anticancer drugs that do not interfere with DNA synthesis or influence the cytoskeleton has led to the development of modified phospholipids with antiproliferative properties. These compounds cause remodeling of the structure and function of plasma membranes. Recently, we described novel compounds, the glycosidated phospholipids, that surprisingly inhibit cell proliferation. These compounds contain ,- D -glucose in the sn -2 position of the glycerol backbone of phosphatidylcholine (PC) and platelet-activating factor (PAF), which gives rise to 2-glucophosphatidylcholine (Glc-PC) and 1- O -octadecyl-2- O -,- d- glucopyranosyl- sn -2-glycero-3-phosphatidylcholine (Glc-PAF), respectively. Glc-PC and Glc-PAF inhibit the growth of HaCaT cells at nontoxic concentrations. Here we report the introduction of myo -inositol, in place of ,- D -glucose, in the sn -2 position of the glycerol backbone; this leads to two diastereomeric 1- O -octadecyl-2- O -(2-(myo -inositolyl)-ethyl)- sn -glycero-3-(R/S)-phosphatidylcholines (Ino-C2-PAF). The inositol-containing PAF enhances the antiproliferative capacity (IC50=1.8 ,M) and reduces the cytotoxicity relative to Glc-PAF (LC50=15 ,M). Through biological assays, we showed that, in HaCaT cells, Ino-C2-PAF causes upregulation of the keratinocyte-specific differentiation marker involucrin, increases the activity of the differentiation marker transglutaminase, and induces apoptosis at nontoxic concentrations. Ino-C2-PAF therefore seems to be a promising candidate for development as an antiproliferative drug for the treatment of hyperproliferative diseases of the skin. [source] Itraconazole-mediated inhibition of calcium entry into platelet-activating factor-stimulated human neutrophils is due to interference with production of leukotriene B4CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 1 2007H. C. Steel Summary The primary objective of this study was to probe the involvement of leukotriene B4 (LTB4) in itraconazole (0·1,5 µM)-mediated inhibition of Ca2+ uptake by chemoattractant-activated human neutrophils. Following exposure of the cells to platelet-activating factor (PAF, 200 nM), LTB4 was measured by immunoassay, while neutrophil cytosolic Ca2+ concentrations were determined by a fura-2/AM-based spectrofluorimetric procedure. Activation of neutrophils was accompanied by an abrupt and sustained (for about 1 min) elevation in cytosolic Ca2+ which was associated with increased generation of LTB4, both of which were attenuated significantly by itraconazole at 0·5 µM and higher. The inhibitory effect of the anti-mycotic on Ca2+ uptake by PAF-activated cells was mimicked by an LTB4 antibody, as well as by LY255283 (1 µM) and MK886 (0·5 µM), an antagonist of LTB4 receptors and an inhibitor of 5,-lipoxygenase-activating protein, respectively, while addition of itraconazole to purified 5,-lipoxygenase resulted in inhibition of enzyme activity. A mechanistic relationship between itraconazole-mediated inhibition of LTB4 production and Ca2+ influx was also supported by the observation that pulsed addition of purified LTB4 to PAF-activated neutrophils caused substantial restoration of Ca2+ uptake by cells treated with the anti-mycotic. Taken together, these observations suggest that the potentially beneficial anti-inflammatory interactions of itraconazole with activated neutrophils result from interference with production of LTB4, with consequent attenuation of a secondary LTB4 -mediated wave of Ca2+ uptake by the cells. [source] Fibronectin-binding proteins of Staphylococcus aureus mediate activation of human platelets via fibrinogen and fibronectin bridges to integrin GPIIb/IIIa and IgG binding to the Fc,RIIa receptorMOLECULAR MICROBIOLOGY, Issue 1 2006J. Ross Fitzgerald Summary Staphylococcus aureus is a leading cause of infective endocarditis (IE). Platelet activation promoted by S. aureus resulting in aggregation and thrombus formation is an important step in the pathogenesis of IE. Here, we report that the fibrinogen/fibronectin-binding proteins FnBPA and FnBPB are major platelet-activating factors on the surface of S. aureus from the exponential phase of growth. Truncated derivatives of FnBPA, presenting either the fibrinogen-binding A domain or the fibronectin-binding BCD region, each promoted platelet activation when expressed on the surface of S. aureus or Lactococcus lactis, indicating two distinct mechanisms of activation. FnBPA-promoted platelet activation is mediated by fibrinogen and fibronectin bridges between the A domain and the BCD domains, respectively, to the low affinity form of the integrin GPIIb/IIIa on resting platelets. Antibodies recognizing the FnBPA A domain or the complex between the FnBPA BCD domains and fibronectin were essential for activation promoted by bacteria expressing the A domain or the BCD domain respectively. Activation was inhibited by a monoclonal antibody (IV-3) specific for the Fc,RIIa IgG receptor on platelets. We propose that the activation of quiescent platelets by bacteria expressing FnBPs involves the formation of a bridge between the bacterial cell and the platelet surface by (i) fibronectin and fibrinogen interacting with the low affinity form of GPIIb/IIIa and (ii) by antibodies specific to FnBPs that engage the platelet Fc receptor Fc,RIIa. Platelet activation by S. aureus clinical IE isolates from both the exponential and stationary phases of growth was completely inhibited by monoclonal antibody IV-3 suggesting that the IgG,Fc,RIIa interaction is of fundamental importance for platelet activation mediated by this organism. This suggests new avenues for development of therapeutics against vascular infections. [source] | ||||||||||||||||