Associations between healthy food groups and platelet-activating factor, lipoprotein-associated phospholipase A2 and C-reactive protein: a cross-sectional study

PURPOSE

To investigate the association between pro-inflammatory markers platelet-activating factor (PAF), lipoprotein-associated phospholipase A2 (Lp-PLA2), hsCRP, and intake of core food groups including fruit, cruciferous and other vegetables, grains, meat and poultry, fish and seafood, nuts and legumes, and dairy.

METHODS

A cross-sectional study was conducted. 100 adults (49 ± 13 years, 31% male) with variable cardiovascular disease risk were recruited. Data were collected in 2021 and 2022. Fasting PAF, Lp-PLA2 activity, hsCRP and usual dietary intake (via a validated food frequency questionnaire) were measured. Intake of foods were converted into serves and classified into food groups. Correlations and multiple regressions were performed with adjustment for confounders.

RESULTS

A one-serve increase in cruciferous vegetables per day was associated with 20-24% lower PAF levels. An increase of one serve per day of nuts and legumes was associated with 40% lower hsCRP levels. There were small correlations with PAF and Lp-PLA2 and cheese, however, these were not significant at the Bonferroni-adjusted P < 0.005 level.

CONCLUSION

The lack of associations between PAF and Lp-PLA2 and other healthy foods may be due to confounding by COVID-19 infection and vaccination programs which prevents any firm conclusion on the relationship between PAF, Lp-PLA2 and food groups. Future research should aim to examine the relationship with these novel markers and healthy food groups in a non-pandemic setting.

Protective effect of arctiin against Toxoplasma gondii HSP70-induced allergic acute liver injury by disrupting the TLR4-mediated activation of cytosolic phospholipase A2 and platelet-activating factor

Toxoplasma gondii (T. gondii)-derived heat shock protein 70 (T.g.HSP70) is a toxic protein that downregulates host defense responses against T. gondii infection. T.g.HSP70 was proven to induce fatal anaphylaxis in T. gondii infected mice through cytosolic phospholipase A2 (cPLA2) activated-platelet-activating factor (PAF) production via Toll-like receptor 4 (TLR4)-mediated signaling. In this study, we investigated the effect of arctiin (ARC; a major lignan compound of Fructus arctii) on allergic liver injury using T.g.HSP70-stimulated murine liver cell line (NCTC 1469) and a mouse model of T. gondii infection. Localized surface plasmon resonance, ELISA, western blotting, co-immunoprecipitation, and immunofluorescence were used to investigate the underlying mechanisms of action of ARC on T. gondii-induced allergic acute liver injury. The results showed that ARC suppressed the T.g.HSP70-induced allergic liver injury in a dose-dependent manner. ARC could directly bind to T.g.HSP70 or TLR4, interfering with the interaction between these two factors, and inhibiting activation of the TLR4/mitogen-activated protein kinase/nuclear factor-kappa B signaling, thereby inhibiting the overproduction of cPLA2, PAF, and interferon-γ. This result suggested that ARC ameliorates T.g.HSP70-induced allergic acute liver injury by disrupting the TLR4-mediated activation of inflammatory mediators, providing a theoretical basis for ARC therapy to improve T.g.HSP70-induced allergic liver injury.

B-cell-activating factor (BAFF) and platelet-activating factor (PAF) in pregnancies complicated by maternal obesity and diabetes: a preliminary study

OBJECTIVE

In pregnancies complicated by maternal obesity and diabetes, a disruption in inflammatory mediators occurs, resulting in endothelial microvascular dysfunction, oxidative stress, tissue damage, and maternal and feto-neonatal complications. To outline this proinflammatory status, an innovative approach is represented by the measurement of proinflammatory cytokines. Among these biomarkers, B-cell-activating factor (BAFF) and platelet-activating factor (PAF) play a key role in metabolic regulation, immune response to infections, tissue homeostasis, and "food-related inflammation." The aim of the present study is to investigate the blood expression of BAFF and PAF in a cohort of pregnant women affected by obesity and diabetes compared with a control group of healthy pregnant women.

METHODS

A prospective longitudinal cohort study has been conducted on pregnant women referred to Fondazione Policlinico Universitario Gemelli IRCCS in Rome. For each pregnant woman, a capillary sample was collected with a swab in three different consecutive evaluations carried out in the three trimesters of pregnancy.

RESULTS

A total of 77 pregnant women have been enrolled. No significant differences in BAFF and PAF levels were longitudinally observed between groups. Focusing on the exposed group, in the third trimester of pregnancy, both PAF and BAFF levels were lower than the basal time. Among the selected group of patients who developed Gestational Diabetes, only PAF values were longitudinally lower when compared to other groups. The multivariate analysis showed that BAFF levels were positively correlated with thyroid-stimulating hormone levels. No macrosomia, no shoulder dystocia, no major perineal lacerations at birth, and no intrauterine growth restriction were observed in the whole population.

CONCLUSIONS

This study supports the involvement of metabolic and proinflammatory biomarkers in the mechanisms related to pregnancy complications. Improving a good metabolic environment for obese and diabetic pregnant women could break the vicious cycle connecting inflammation, oxidative stress, and metabolic disorders.

Anti-heat shock protein 10 IgG in chronic spontaneous urticaria: Relation with miRNA-101-5p and platelet-activating factor

BACKGROUND

Anti-heat shock protein (HSP) autoantibodies are detected in autoimmune diseases. We sought to ascertain whether anti-HSP10 IgG is present in patients with CSU and to elucidate the role of HSP10 in CSU pathogenesis.

METHOD

Using a human proteome microarray, six potential autoantibodies had higher expression in 10 CSU samples compared with 10 normal controls (NCs). Among them, HSP10 IgG autoantibody was quantified by immune dot-blot assay in sera from 86 CSU patients and 44 NCs. The serum levels of HSP10 and microRNA-101-5p were measured in CSU patients and NCs. The effects of HSP10 and miR-101-5p on mast cell degranulation in response to IgE, compound 48/80, and platelet-activating factor (PAF) were investigated.

RESULTS

CSU patients had higher IgG positivity to HSP10 (40.7% vs. 11.4%, p = .001), lower serum HSP10 levels (5.8 ± 3.6 vs. 12.2 ± 6.6 pg/mL, p < .001) than in NCs, and their urticaria severity was associated with anti-HSP10 IgG positivity, while HSP10 levels were related to urticaria control status. MiR-101-5p was increased in CSU patients. PAF enhanced IL4 production in PBMCs from CSU patients. IL-4 upregulated miR-101-5p and reduced HSP10 expression in keratinocytes. Transfection of miR-101-5p reduced HSP10 expression in keratinocytes. MiR-101-5p promoted PAF-induced mast cell degranulation, while HSP10 specifically prevented it.

CONCLUSION

A new autoantibody, anti-HSP10 IgG was detected in CSU patients, which showed a significant correlation with UAS7 scores. A decreased serum HSP10 level was associated with upregulation of miR-101-5p due to increased IL-4 and PAF in CSU patients. Modulation of miR-101-5p and HSP10 may be a novel therapeutic approach for CSU.

Biosynthesis of Phomactin Platelet Activating Factor Antagonist Requires a Two-Enzyme Cascade

Phomactin diterpenoids possess a unique bicyclo[9.3.1]pentadecane skeleton with multiple oxidative modifications, and are good platelet-activating factor (PAF) antagonists that can inhibit PAF-induced platelet aggregation. In this study, we identified the gene cluster (phm) responsible for the biosynthesis of phomactins from a marine fungus, Phoma sp. ATCC 74077. Despite the complexity of their structures, phomactin biosynthesis only requires two enzymes: a type I diterpene cyclase PhmA and a P450 monooxygenase PhmC. PhmA was found to catalyze the formation of the phomactatriene, while PhmC sequentially catalyzes the oxidation of multiple sites, leading to the generation of structurally diverse phomactins. The rearrangement mechanism of the diterpene scaffold was investigated through isotope labeling experiments. Additionally, we obtained the crystal complex of PhmA with its substrate analogue FGGPP and elucidated the novel metal-ion-binding mode and enzymatic mechanism of PhmA through site-directed mutagenesis. This study provides the first insight into the biosynthesis of phomactins, laying the foundation for the efficient production of phomactin natural products using synthetic biology approaches.

Pharmacokinetics and Changes in Lipid Mediator Profiling after Consumption of Specialized Pro-Resolving Lipid-Mediator-Enriched Marine Oil in Healthy Subjects

Omega-3 polyunsaturated fatty acids (PUFAs) play a vital role in human health, well-being, and the management of inflammatory diseases. Insufficient intake of omega-3 is linked to disease development. Specialized pro-resolving mediators (SPMs) are derived from omega-3 PUFAs and expedite the resolution of inflammation. They fall into categories known as resolvins, maresins, protectins, and lipoxins. The actions of SPMs in the resolution of inflammation involve restricting neutrophil infiltration, facilitating the removal of apoptotic cells and cellular debris, promoting efferocytosis and phagocytosis, counteracting the production of pro-inflammatory molecules like chemokines and cytokines, and encouraging a pro-resolving macrophage phenotype. This is an experimental pilot study in which ten healthy subjects were enrolled and received a single dose of 6 g of an oral SPM-enriched marine oil emulsion. Peripheral blood was collected at baseline, 3, 6, 9, 12, and 24 h post-administration. Temporal increases in plasma and serum SPM levels were found by using LC-MS/MS lipid profiling. Additionally, we characterized the temporal increases in omega-3 levels and established fundamental pharmacokinetics in both aforementioned matrices. These findings provide substantial evidence of the time-dependent elevation of SPMs, reinforcing the notion that oral supplementation with SPM-enriched products represents a valuable source of essential bioactive SPMs.

The Interplay among Glucocorticoid Therapy, Platelet-Activating Factor and Endocannabinoid Release Influences the Inflammatory Response to COVID-19

COVID-19 is associated with a dysregulated immune response. Currently, several medicines are licensed for the treatment of this disease. Due to their significant role in inhibiting pro-inflammatory cytokines and lipid mediators, glucocorticoids (GCs) have attracted a great deal of attention. Similarly, the endocannabinoid (eCB) system regulates various physiological processes including the immunological response. Additionally, during inflammatory and thrombotic processes, phospholipids from cell membranes are cleaved to produce platelet-activating factor (PAF), another lipid mediator. Nonetheless, the effect of GCs on this lipid pathway during COVID-19 therapy is still unknown. This is a cross-sectional study involving COVID-19 patients (n = 200) and healthy controls (n = 35). Target tandem mass spectrometry of plasma lipid mediators demonstrated that COVID-19 severity affected eCBs and PAF synthesis. This increased synthesis of eCB was adversely linked with systemic inflammatory markers IL-6 and sTREM-1 levels and neutrophil counts. The use of GCs altered these lipid pathways by reducing PAF and increasing 2-AG production. Corroborating this, transcriptome analysis of GC-treated patients blood leukocytes showed differential modulation of monoacylglycerol lipase and phospholipase A2 gene expression. Altogether, these findings offer a breakthrough in our understanding of COVID-19 pathophysiology, indicating that GCs may promote additional protective pharmacological effects by influencing the eCB and PAF pathways involved in the disease course.

Malabaricone C derived from nutmeg inhibits arachidonate 5-lipoxygenase activity and ameliorates psoriasis-like skin inflammation in mice

As pro-inflammatory lipid mediators, leukotrienes have pathophysiological activities in several inflammatory diseases, including psoriasis. In the biosynthesis of leukotrienes from arachidonic acid, 5-lipoxygenase catalyzes the first two steps. In the present study, we showed that nutmeg (Myristica fragrans) strongly inhibited the catalytic activity of 5-lipoxygenase. To characterize the bioactive component(s) of nutmeg, we performed 5-lipoxygenase inhibitory activity-guided fractionation of aqueous ethanol extract of nutmeg, resulting in the isolation of malabaricone C having antioxidant activity. Malabaricone C exhibited potent competitive inhibition of 5-lipoxygenase with an IC₅₀ value of 0.2 μM. In mice with imiquimod-induced psoriasis-like skin lesions, topical application of 2 mM malabaricone C significantly ameliorated hyperplasia and inflammatory cell infiltration, and suppressed the expression of the psoriasis-associated genes S100a9, Krt1, Il17a, and Il22. Lipid metabolome analysis of these psoriasis-like skin lesions showed that malabaricone C markedly decreased the level of leukotriene B₄ but did not significantly increase the other pro-inflammatory lipid mediators. These findings suggest that malabaricone C decreases LTB₄ by the 5-lipoxygenase inhibition and ameliorates the symptoms of psoriasis-like skin inflammation.

PAF-induced inflammatory and immuno-allergic ophthalmic diseases and their mitigation with PAF receptor antagonists: Cell and nuclear effects

Ocular allergies are becoming more prevalent as more airborne pollutants, irritants and microbes pervade our environment. Inflammatory and allergic mediators released by dendritic and mast cells within the conjunctiva cause allergic conjunctivitis (AC), a prevalent ocular surface disorder that affects >40% of the world's human population on a seasonal or perennial basis. Even though histamine is a major culprit, platelet-activating factor (PAF) also contributes to AC, acting either directly or synergistically with histamine and other mediators. PAF receptor-meditated inflammatory reactions, via cell-membrane-bound and nuclear-membrane-bound and nuclear PAF receptors, are also implicated in the etiology of other eye diseases such as uveitis, diabetic retinopathy, corneal and choroidal neovascularization, and age-related macular degeneration which cause serious visual impairment and can lead to blindness. This review highlights the various deleterious elements implicated in the pathological aspects of ocular allergic reactions and inflammation and provides concepts and treatment options to mitigate these eye disorders with a special focus on PAF and PAF receptor antagonists.

Critical role of PAFR/YAP1 positive feedback loop in cardiac fibrosis

Aberrant activation of cardiac fibroblasts is the main cause and character of cardiac fibrosis, and inhibition of cardiac fibrosis becomes a promising treatment for cardiac diseases. Platelet-activating factor (PAF) and Hippo pathway is recently recognized as key signaling mechanisms in cardiovascular diseases. In this study we explored the potential roles of PAF and Hippo signaling pathway in cardiac fibrosis. Myocardial infarction (MI) was induced in mice by left anterior descending artery ligation. After 28 days, the mice were sacrificed, and the hearts were collected for analyses. We showed that PAF receptor (PAFR) and yes-associated protein 1 (YAP1, a key effector in the Hippo pathway) were significantly increased in the heart of MI mice. Increased expression of PAFR and YAP1 was also observed in angiotensin II (Ang II)-treated mouse cardiac fibroblasts. In mouse cardiac fibroblasts, forced expression of YAP1 increased cell viability, resulted in collagen deposition and promoted fibroblast-myofibroblast transition. We showed that PAF induced fibrogenesis through activation of YAP1 and promoted its nuclear translocation via interacting with PAFR, while YAP1 promoted the expression of PAFR by binding to and activating transcription factor TEAD1. More importantly, silencing PAFR or YAP1 by shRNA, or using transgenic mice to induce the conditional deletion of YAP1 in cardiac fibroblasts, impeded cardiac fibrosis and improved cardiac function in MI mice. Taken together, this study elucidates the role and mechanisms of PAFR/YAP1 positive feedback loop in cardiac fibrosis, suggesting a potential role of this pathway as novel therapeutic targets in cardiac fibrosis.

Is there an interplay between the SARS-CoV-2 spike protein and Platelet-Activating factor?

Previous publications have reported a potent effect of COVID-19 on platelet function and that the Spike protein enhances washed human platelet aggregation induced by various agonists. This study aims to evaluate whether mRNA vaccination for COVID-19 affects human platelet-rich plasma (hPRP) aggregation response, whether a recombinant Spike protein modulates PAF-induced aggregation in hPRP and in washed rabbit platelets (WRP), and to investigate the effect of recombinant Spike protein on the PAF production in the U-937 cell line. Our results showed that PRP from vaccinated individuals exhibited ex vivo lower EC₅₀ values in response to PAF, ADP, and collagen. Platelet incubation with the Spike protein alone did not induce aggregation either in hPRP or in WRP, but resulted in augmentation of in vitro PAF-induced aggregation in hPRP from non-vaccinated individuals and in WRP. When PRP from vaccinated individuals was incubated with the Spike protein and PAF was subsequently added, elimination of the secondary wave of the biphasic aggregation curve was recorded compared with the aggregation induced by PAF alone. Collagen-induced in vitro aggregation was dose-dependently reduced when platelets were pre-incubated with the Spike protein in all tested aggregation experiments. Stimulation of U-937 by the Spike protein induced an increase in intracellular PAF production accompanied by elevation of the activities of all three PAF biosynthetic enzymes. In conclusion, since the Spike protein appears to modulate PAF production and activity, the use of compounds that act as PAF inhibitors, could be considered at least in mild cases of patients infected with SARS-CoV-2.

Platelet Activating Factor (PAF): A Mediator of Inflammation

Platelet-activating factor (PAF) is a phospholipid-derived mediator with an established role in multiple inflammatory states. PAF is synthesized and secreted by multiple cell types and is then rapidly hydrolyzed and degraded to an inactive metabolite, lyso-PAF, by the enzyme PAF acetylhydrolase. In addition to its role in platelet aggregation and activation, PAF contributes to allergic and nonallergic inflammatory diseases such as anaphylaxis, sepsis, cardiovascular disease, neurological disease, and malignancy as demonstrated in multiple animal models and, increasingly, in human disease states. Recent research has demonstrated the importance of the PAF pathway in multiple conditions including the prediction of severe pediatric anaphylaxis, effects on blood-brain barrier permeability, effects on reproduction, ocular diseases, and further understanding of its role in cardiovascular risk. Investigation of PAF as both a biomarker and a therapeutic target continues because of the need for directed management of inflammation. Collectively, studies have shown that therapies focused on the PAF pathway have the potential to provide targeted and effective treatments for multiple inflammatory conditions.

Serum Levels of Vascular Endothelial Growth Factor, Platelet Activating Factor and Eosinophil-Derived Neurotoxin in Chronic Spontaneous Urticaria—A Pilot Study in Adult Patients

Chronic spontaneous urticaria (CSU) is a skin disease characterized by the presence of wheals, angioedema, or both for at least 6 weeks. Although, CSU is often regarded as autoimmune in nature, its etiology is not fully explained and interactions between various small molecules are still taken under account. The aim of this research was to investigate the mean serum concentration of vascular endothelial growth factor (VEGF), platelet activating factor (PAF), and eosinophil-derived neurotoxin (EDN) in relation to the disease activity and pruritus intensity in adult patients with CSU. Fifteen patients with CSU and 15 healthy subjects participated in this pilot study. Blood samples were taken to examine the mean serum levels of VEGF, PAF, and EDN by the enzyme-linked immunosorbent assay test (ELISA). The Urticaria Activity Score (UAS7) and The Visual Analogue Scale (VAS) were used to assess the disease activity and the pruritus intensity, respectively. Obtained results revealed that VEGF, PAF, and EDN concentrations were higher in patients with CSU compared with those of the control group, but only for VEGF it was statistically significant (p = 0.008). However, levels of all investigated cytokines were not significantly correlated neither with the disease activity nor with the pruritus intensity. Our results showed higher serum levels of VEGF, PAF, and EDN among CSU patients which may highlight a functional role of these cytokines in the disease’s pathogenesis. In contrast, VEGF, PAF, or EDN might not be useful to reflect the severity of symptoms.

The association between dietary patterns and the novel inflammatory markers platelet-activating factor and lipoprotein-associated phospholipase A2: a systematic review

CONTEXT

Atherosclerosis is a disease of chronic inflammation. Recent research has identified 2 novel inflammatory biomarkers: platelet-activating factor (PAF) and lipoprotein-associated phospholipase A2 (Lp-PLA2). Diet has been proposed as a mediator of inflammation, but to date, the focus for these novel biomarkers has been on individual foods and nutrients rather than overall dietary patterns.

OBJECTIVE

To systematically review the literature on the association between dietary patterns and PAF and Lp-PLA2.

DATA SOURCES

The PubMed, Embase, CINAHL, and Cochrane CENTRAL literature databases were searched.

DATA ANALYSIS

Study quality was evaluated using the Quality Criteria Checklist. Sixteen studies (n = 4 observational and n = 12 interventional) were included and assessed for associations between dietary patterns and PAF and Lp-PLA2.

CONCLUSION

Study quality varied from neutral (n = 10) to positive (n = 6). Mediterranean, heart healthy, and vegetarian dietary patterns were associated with improved levels of PAF and Lp-PLA2. Conversely, Western dietary patterns were less favorable. A range of well-established, healthier dietary patterns may lower inflammation and the risk of atherosclerosis. More well-designed studies are needed to confirm these findings and identify other dietary patterns that improve inflammation.

Utility of the Specialized Pro-Resolving Mediators as Diagnostic and Prognostic Biomarkers in Disease

A precision medicine approach is widely acknowledged to yield more effective therapeutic strategies in the treatment of patients with chronic inflammatory conditions than the prescriptive paradigm currently utilized in the management and treatment of these patients. This is because such an approach will take into consideration relevant factors including the likelihood that a patient will respond to given therapeutics based on their disease phenotype. Unfortunately, the application of this precision medicine paradigm in the daily treatment of patients has been greatly hampered by the lack of robust biomarkers, in particular biomarkers for determining early treatment responsiveness. Lipid mediators are central in the regulation of host immune responses during both the initiation and resolution of inflammation. Amongst lipid mediators, the specialized pro-resolving mediators (SPM) govern immune cells to promote the resolution of inflammation. These autacoids are produced via the stereoselective conversion of essential fatty acids to yield molecules that are dynamically regulated during inflammation and exert potent immunoregulatory activities. Furthermore, there is an increasing appreciation for the role that these mediators play in conveying the biological actions of several anti-inflammatory therapeutics, including statins and aspirin. Identification and quantitation of these mediators has traditionally been achieved using hyphenated mass spectrometric techniques, primarily liquid-chromatography tandem mass spectrometry. Recent advances in the field of chromatography and mass spectrometry have increased both the robustness and the sensitivity of this approach and its potential deployment for routine clinical diagnostics. In the present review, we explore the evidence supporting a role for specific SPM as potential biomarkers for patient stratification in distinct disease settings together with methodologies employed in the identification and quantitation of these autacoids.

Coronavirus 2019, Microthromboses, and Platelet Activating Factor

Recent articles have reported elevated markers of coagulation, endothelial injury, and microthromboses in lungs from deceased patients with coronavirus 2019 (COVID-19). Platelets are critical in the formation of thrombi, and their most potent trigger is platelet activating factor (PAF). PAF is produced by cells involved in host defense, and its biological actions bear similarities with COVID-19 disease manifestations, including pulmonary microthromboses and inflammation, possibly via activation of mast cells. The histamine1 receptor antagonist rupatadine was developed to have anti-PAF activity and inhibits activation of human mast cells in response to PAF. Rupatadine could be repurposed for COVID-19 prophylaxis.

Leukotrienes and sex: strange bedfellows?

Leukotrienes are proinflammatory lipid mediators that have been shown to be upregulated in several diseases, including asthma, aspirin-exacerbated respiratory disease (AERD), inflammatory bowel disease, and acute respiratory distress syndrome. Leukotrienes have been explored as therapeutic targets for these diseases and others; however, leukotriene inhibitors have had limited success in the clinic. There are noted differences in the incidence of leukotriene-mediated diseases in males and females, but sex as a factor in the response to leukotriene inhibitors has not been fully explored. In this issue of the JCI, Pace and colleagues present evidence that there are sex-specific differences in the effectiveness of certain leukotriene inhibitors and link the differences in response to the presence of androgens. The results of this study indicate that sex needs to be taken into consideration in the future evaluation of leukotriene inhibitors to treat disease.

Glucosamine suppresses platelet-activating factor-induced activation of microglia through inhibition of store-operated calcium influx

Microglia activation and subsequent release of inflammatory mediators are implicated in the pathophysiology of neurodegenerative diseases. Platelet-activating factor (PAF), a potent lipid mediator synthesized by microglia, is known to stimulate microglia functional responses. In this study, we determined that endogenous PAF exert autocrine effects on microglia activation, as well as the underlying mechanism involved. We also investigated the effect of D-glucosamine (GlcN) on PAF-induced cellular activation in human HMO6 microglial cells. PAF induced sustained intracellular Ca(2+) ([Ca(2+)]i) increase through store-operated Ca(2+) channels (SOC) and reactive oxygen species (ROS) generation. PAF also induced pro-inflammatory markers through NFκB/COX-2 signaling. GlcN significantly inhibited PAF-induced Ca(2+) influx and ROS generation without significant cytotoxicity. GlcN downregulated excessive expression of pro-inflammatory markers and promoted filopodia formation through NFκB/COX-2 inhibition in PAF-stimulated HMO6 cells. Taken together, these data suggest that GlcN may offer substantial therapeutic potential for treating inflammatory and neurodegenerative diseases accompanied by microglial activation.

Hematopoietic α7 nicotinic acetylcholine receptor deficiency increases inflammation and platelet activation status, but does not aggravate atherosclerosis

BACKGROUND

The autonomic nervous system attenuates inflammation through activation of the α7 nicotinic acetylcholine receptor (α7nAChR), a pathway termed the cholinergic anti-inflammatory reflex. Interestingly, α7nAChR is expressed on immune cells and platelets, both of which play a crucial role in the development of atherosclerosis.

OBJECTIVE

To investigate the role of hematopoietic α7nAChR in inflammation and platelet function in atherosclerotic ldlr(-/-) mice and to identify its consequences for atherosclerotic lesion development.

METHODS

Bone marrow from α7nAChR(-/-) mice or wild-type littermates was transplanted into irradiated ldlr(-/-) mice. After a recovery period of 8 weeks, the mice were fed an atherogenic Western-type diet for 7 weeks.

RESULTS

Hematopoietic α7nAChR deficiency clearly increased the number of leukocytes in the peritoneum (2.6-fold, P < 0.001), blood (2.9-fold; P < 0.01), mesenteric lymph nodes (2.0-fold; P < 0.001) and spleen (2.2-fold; P < 0.01), indicative of an increased inflammatory status. Additionally, expression of inflammatory mediators was increased in peritoneal leukocytes (TNFα, 1.6-fold, P < 0.01; CRP, 1.8-fold, P < 0.01) as well as in the spleen (TNFα, 1.6-fold, P < 0.01). The lack of α7nAChR on platelets from these mice increased the expression of active integrin αIIb β3 upon stimulation by ADP (1.9-fold, P < 0.01), indicating increased activation status, while incubation of human platelets with an α7nAChR agonist decreased aggregation (-35%, P < 0.05). Despite the large effects of hematopoietic α7nAChR deficiency on inflammatory status and platelet function, it did not affect atherosclerosis development or composition of lesions.

CONCLUSIONS

Hematopoietic α7nAChR is important for attenuation of inflammatory responses and maintaining normal platelet reactivity, but loss of hematopoietic α7nAChR does not aggravate development of atherosclerosis.

Report: Platelet aggregation inhibition activity of selected legumes of Pakistan

The current study was designed to explore the platelet aggregation activity of methanolic extracts of green gram, lentil, mash bean and soya bean. The extracts dose-dependently inhibited platelet aggregation initiated by arachidonic acid (AA) and platelet activating factor (PAF). Extract of green gram was effective only against AA mediated activity while mash bean and soya bean extracts were effective against both AA and PAF mediated activity. But lentil extract has no activity. The order of activity based on IC(50) value is, Mash bean > Soya bean > Green gram. This preliminary result suggests that legume seed extract may be taken as a candidate lead natural compound to be considered in the search for natural products with beneficial effects on aberrant platelet activation mediated cardiovascular disorders.

Platelet aggregation and anti-inflammatory effects of garden pea, Desi chickpea and Kabuli chickpea

Inflammation is the natural body defense mechanism for the removal of injurious agents, necrosed cells and tissues from the body. This study was aimed to evaluate the anti-inflammatory and platelet aggregation effects of three medicinal plants of Pakistan. Methanolic extract of garden pea inhibited arachidonic acid (AA)-induced platelet aggregation (IC50 = 35 microg/mL) and platelet activating factor (PAF)-induced platelet aggregation (IC50 = 38 microg/mL) in a dose dependent fashion. Methanolic extract of Desi chickpea inhibited arachidonic acid (AA) induced platelet aggregation (IC50 value = AA = 46 microg/mL) in dose dependent fashion while was found not active against PAF-induced platelet aggregation. Methanolic extract of Kabuli chickpea was found not active against both arachidonic acid (AA)-induced platelet aggregation and PAF-induced platelet aggregation. The best potential to inhibit in vitro COX-2 activity showed garden pea (Pisum sativum: the synthesis of PGE2 reduced by 92% in comparison with untreated control wells) followed by Desi chickpea (Cicer arietinum var; 87% inhibition) and Kabuli chickpea extracts (Cicer arietinum var: 65% inhibition). All extracts were tested at concentration 20 microg/mL. in COX-2 assay. The results indicate that if the same were happening in vito, Garden pea, Desi chickpea and Kabuli chickpea could be useful as natural antithrombotic anti-inflammatory materials.

[Detection of platelet-activating factor in unstimulated mixed saliva and gingival crevicular fluid of periodontitis patients with coronary heart disease]

PURPOSE

To explore the correlation between periodontitis and coronary heart diseases(CHD) by comparing the levels of platelet-activating factor (PAF) in saliva and gingival crevicular fluid (GCF) among 4 groups.

METHODS

One hundred and twenty subjects were divided into 4 groups according to the diagnostic angiography and periodontal examination as group (C+P), group C, group P and group H.Group (C+P) was made up of 24 CHD patients with moderate to advanced periodontitis.36 CHD patients without periodontitis were as group C.Group P was made up of 32 patients suffering moderate to advanced periodontitis.Group H was 28 healthy volunteers. The general information and periodontal status of all the subjects were recorded and unstimulated mixed saliva and GCF samples were collected.The PAF level was detected by ELISA. Then the difference in PAF level of each group was analyzed with SPSS13.0 software package.

RESULTS

One way analysis of variance showed that the levels of PAF in saliva and GCF from the patients of group (C+P) and P were significantly higher than the group C and group H. The results of Pearson correlation analysis showed that the levels of PAF in saliva and GCF positively correlated with pocket depth (PD) and attachment loss (AL) (P<0.05).

CONCLUSIONS

Inflammation of periodontal tissues can increase the level of PAF which may be a risk factor of coronary heart diseases. It indicates that the raising level of PAF may be another significant factor in the process of periodontitis affecting the progress of coronary heart disease.

Structure-activity relationship studies on chalcone derivatives: potent inhibition of platelet aggregation

In an effort to develop potent antiplatelet agents with anti-inflammatory action, a novel series of anti-inflammatory chalcones was screened to evaluate their antiplatelet effects. Structure-activity relationships and mode of action were investigated and characterized. The antiplatelet effects of the chalcones on washed rabbit platelets and human platelet-rich plasma were evaluated. Arachidonic acid-induced platelet aggregation was potently inhibited by almost all the chalcone derivatives. Collagen-induced platelet aggregation was potently inhibited by all the chalcone derivatives at 300 μm, except for compound 4 at 100 μm. Compounds 6, 7 and 9 significantly inhibited the aggregation of washed rabbit platelets induced by platelet-activating factor at 300 μm. Of the compounds tested in human platelet-rich plasma, compounds 2, 8 and 9 showed significant inhibition of secondary aggregation induced by adrenaline. It is concluded that the antiplatelet effect of 2, 8 and 9 is mainly owing to an inhibitory effect on thromboxane formation. The inhibitory effect of 6, 7 and 9 on platelet aggregation induced by platelet-activating factor could be owing to a calcium antagonizing effect or inhibition of intracellular calcium mobilization.

General changes in hemostasis in gastric cancer

Disorders of haemostasis and haemocoagulation are often seen in patients with cancer as a part of paraneoplastic syndrome. Thrombotic and/or haemorrhagic complications are the second most common cause of mortality in patients with cancer. The evaluation of the haemostatic parameters of 67 patients with gastric cancer have indicated tendency to thrombophilia and activation of intravascular coagulation, of which 31.3% showed tendency to hypercoagulation and 47.8% disseminated intravascular coagulation (DIC). Only 7.5% of subjects have yielded normal laboratory findings while 5.9% of patients had DIC with remarkable hypocoagulation. Thrombocytosis, platelet hyperaggregability and elevation of beta-thromboglobulin are the indicators of changes in primary haemostasis and elevation of thrombomodulin indicates vascular wall damage. Lower antithrombin III levels, C-protein and S-protein in plasma have indicated lower antithrombotic potential in patients with gastric cancer. It can be concluded that patients suffering from gastric cancer are at higher risk of thromboembolism as for haemorrhagic diathesis (20.1% thromboembolism, 11.94% fatal thromboembolic events vs 5.9 % haemorrhagic diathesis) (Tab. 5, Ref. 22). Full Text (Free, PDF) www.bmj.sk.

Hemostatic markers and platelet aggregation factors as predictive markers for type of stroke and neurological disability following cerebral infarction

We investigated the plasma levels of D-dimer, fibrinogen, beta-thromboglobulin (BTG) and platelet factor-4 (PF-4), indices of the occurrence of platelet activation in vivo, to find out their role in pathophysiology of ischemic stroke and whether or not such a role has any effect on the disability and the prognosis of stroke patients. A total of 76 patients with AIS aged from 26 to 85 (32 men, 44 women) and 30 cases as controls with similar age (18 men, 12 women) were included in the study. The plasma levels of D-dimer, BTG and PF-4 were measured by ELISA method using a special commercial kit. The cases were allocated into two groups as non-embolic (NEI) and cardioembolic stroke (CEI). The D-dimer levels in 76% of 42 patients in NEI group (p<0.05) and 85.2% of 34 patients in CEI group (p<0.05) were outside the confidence interval (CI) defined for the control group. The levels of BTG were elevated in 81% of 42 cases with NEI (p<0.05) and in 76% of 34 cases with CEI, with reference to CI of control group. The levels of PF-4 were significantly increased in 86% of cases with NEI (p<0.05) and in 88% of cases with CEI than controls (p<0.05). It was observed that the cases with high Rankin scores had higher levels of D-dimer (p<0.005), BTG (p<0.01) and PF-4 (p<0.01) than those with lower scores. There was a correlation between hemostatic markers, platelet activation and functional disability. D-dimer levels were an important marker that determined to degree of the activation of hemostatic system, especially in CEI subtype. The platelet aggregation had an important role in pathophysiology of ischemic stroke and this condition is significant in NEI subgroup and subjects with large infarcts and high disability scores.

Platelet transfusions in infants with necrotizing enterocolitis

Severe thrombocytopenia (< 50 x 10(9)/L) frequently accompanies advanced necrotizing enterocolitis (NEC). In premature infants with severe thrombocytopenia, despite a paucity of evidence to support the practice, platelet transfusions are commonly used to maintain arbitrary levels of platelet counts in an effort to prevent hemorrhage. However, platelet transfusions contain a variety of bioactive factors, including platelet activating factor (PAF), which can augment systemic inflammatory processes. A growing body of evidence that incriminates PAF in the pathogenesis of NEC has emerged over the past few decades from both animal and human data. Both severe thrombocytopenia and multiple platelet transfusions have been associated with increased mortality, but it is admittedly difficult to differentiate between the effects of the underlying disease and the effects, if any, of the platelet transfusions. In this report, we review the roles of PAF and platelet transfusions in infants with severe NEC.

Lipid mediator networks and leukocyte transmigration

In intact tissues, vascular endothelial cells lie anatomically positioned as the central coordinator of inflammation. Endothelia communicate with underlying cells (e.g. smooth muscle, fibroblasts, epithelia) in ways that both coordinate leukocyte trafficking, and control the composition of the inflammatory microenvironment. Such coordination occurs through both direct communication (e.g. cell adhesion) as well as via soluble mediators liberated at sites of inflammation (e.g. chemokines, cytokines, lipids). Locally generated mediators bind to surface receptors, and mediate both physiologic and pathophysiologic functional responses. Important in this regard, both endothelial and subendothelial cell populations express enzymes capable of utilizing arachidonic acid substrates to generate bioactive lipid mediators (e.g. lipoxygenases, cyclooxygenases). Such lipid mediators can signal via autocrine or paracrine pathways and, depending on the tissue microenvironment, can convey a pro- or anti-inflammatory message. This review will highlight recent studies characterizing inflammatory responses to lipid mediators liberated at sites of inflammation, with a particular emphasis on neutrophil (polymorphonuclear leukocyte or PMN) trafficking.

Clinically relevant osmolar stress inhibits priming-induced PMN NADPH oxidase subunit translocation

BACKGROUND

The plasma membrane NADPH oxidase is responsible for the external generation of superoxide by neutrophils (polymorphonucleocytes [PMNs]). The oxidase is a multicomponent enzyme, active only when all subunits are translocated to and assembled at the membrane. We have recently demonstrated that platelet-activating factor (PAF) priming of PMNs translocates the cytosolic p67 subunit to the membrane position. Osmolar stress attenuates PAF priming of the oxidase. Consequently, we hypothesized that clinically relevant osmolar stress inhibits PAF priming-induced p67 translocation.

METHODS

Isolated human PMNs were incubated at 37 degrees C for 5 minutes in buffer or 180 mmol/L hypertonic saline (HTS) followed by 3 minutes of incubation with or without 2 mumol/L PAF (resting, PAF, HTS, and HTS-PAF). Digital microscopy was used to determine p67 location in whole PMNs. Subcellular fractions were prepared and membrane translocation of p67 determined by protein electrophoresis. Resting cytosol fractions were immunodepleted of p67 and NADPH oxidase activity measured using p67-deficient sodium dodecyl sulfate cell-free oxidase assays: resting, PAF, or HTS-PAF membrane (1 mug) was combined with immunodepleted resting cytosol (25 mug).

RESULTS

By all methodologies, PAF stimulated translocation of p67 to the PMN membrane and this translocation was prevented by osmolar stress (HTS-PAF). In cell-free oxidase assays, the membrane content of p67 after PAF stimulation was increased sufficiently to induce oxidase activity, whereas resting and HTS-PAF membrane did not (0.1 +/- 0.02, 0.23 +/- 0.04, and 0.14 +/- 0.04, respectively, p < 0.01) (resting versus HTS-PAF, no difference).

CONCLUSION

PAF priming of the PMN oxidase involves translocation of p67 to the plasma membrane. Clinically relevant osmolar stress with hypertonic saline prevents this PAF-induced translocation of the p67 oxidase subunit. This finding provides new insight into the mechanisms responsible for osmolar control of PMN functional responses.

The inositol trisphosphate pathway mediates platelet-activating-factor-induced pulmonary oedema

Platelet-activating factor (PAF) is a pro-inflammatory lipid mediator that increases vascular permeability by simultaneous activation of two pathways, one dependent on the cyclooxygenase metabolite prostaglandin E2 and the other on the sphingomyelinase metabolite ceramide. The hypothesis that part of the PAF-induced oedema is mediated via the inositol 1,4,5-trisphosphate (IP3) pathway or Rho kinase pathway was investigated. Oedema formation was induced in isolated perfused rat lungs by injection of 5 nmol PAF into the pulmonary artery. Lungs were pre-treated with specific inhibitors: edelfosine (L108) to block phosphatidyl-inositol-specific phospholipase C, xestospongin to block the IP3 receptor, 5-iodonaphthalene-1-sulphonyl-homopiperazine (ML-7) to block myosin light chain kinase, and (+)-R-trans-4-(aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide (Y27632) to block Rho-associated protein kinase. Pre-treatment with L108 or xestospongin reduced PAF-induced oedema formation by 58 and 56%, respectively. The effect of L108 was additive to that of the cyclooxygenase inhibitor acetyl salicylic acid (88% oedema reduction). PAF-induced oedema formation was also reduced if extracellular calcium concentrations were lowered. Furthermore, treatment with ML-7 reduced oedema formation by 54%, whereas Y27632 was without effect. It is concluded that platelet-activating-factor-triggered oedema is mediated by activation of the inositol 1,4,5-trisphosphate pathway, influx of extracellular calcium and subsequent activation of a myosin light chain kinase-dependent and Rho-associated-protein-kinase-independent mechanism.

Activated leukocytes and endothelial cells enhance retention of ultrasound contrast microspheres containing perfluoropropane in inflamed venules

PURPOSE

To characterize the flow dynamics of albumin ultrasound contrast microspheres containing perfluoropropane (PFP) in normal and inflamed microvasculature.

MATERIALS AND METHODS

Mesenteric microvessels of rats were examined after an intravenous injection of fluorocein-labeled erythrocytes or PFP microspheres by fluorescence intravital microscopy with and without local application of 10(-8) M platelet activating factor (PAF) as an experimental form of inflammation.

RESULTS

All the microspheres passed freely through arterioles and capillaries. Mean velocities of the microspheres in each vessel were closely correlated with those of erythrocytes. Only a minor fraction of the microspheres was retained in the venules (> or =0.1 s stoppage) by attachment to endothelial cells. The frequency of microsphere retention in venules was significantly enhanced by PAF (2.6+/-2.1%, P<0.01 vs. control), especially in regions with leukocyte adhesion. Treatment with a monoclonal antibody to intercellular adhesion molecule-1, P-selectin or the common leukocyte antigen inhibited PAF-induced microsphere retention in venules (P<0.05). In the inflamed microcirculation, a small subgroup of microspheres becomes attached to venular endothelial cells in regions with leukocyte adhesion via interaction among microspheres, activated leukocytes and endothelial cells via adhesion molecules.

CONCLUSION

In inflamed microcirculation, a small subgroup of microspheres becomes attached to venular endothelial cells in regions with leukocyte adhesion via interaction among microspheres, activated leukocytes and endothelial cells via adhesion molecules. These results suggest that ultrasonography with microspheres has the potential to evaluate inflammatory site distribution as well as tissue perfusion.

Inhibition of platelet activating factor (PAF)-induced aggregation of human thrombocytes by ginkgolides: considerations on possible bleeding complications after oral intake of Ginkgo biloba extracts

The special Ginkgo biloba leaf extract EGb 761 is marketed for more then two decades. During this time its therapeutic efficacy and favorable safety profile have been proven in numerous clinical trails as well as by postmarketing surveillance in accordance with German drug regulations. During recent years, however, several cases of hemorrhage have been reported to occur in coincidence with the use of Ginkgo products. Although a clear causality between Ginkgo intake and bleeding could not be established, these observations have generally been explained by the platelet-activating factor (PAF)-antagonistic action of ginkgolides, which represent characteristic constituents of Ginkgo extracts. PAF was originally characterized by inducing aggregation and secretion of serotonin and histamine from rabbit platelets. We now confirmed that induction of aggregation of human platelets by PAF requires at least 200 times higher concentration when compared to rabbit cells. Under the chosen experimental conditions, PAF-mediated aggregation of human platelets was half-maximally inhibited by ginkgolide B, A, C and J at concentrations of 2.5, 15.8, 29.8 and 43.5 microg/ml, respectively. These concentrations are generally more than 100 times higher as the peak plasma values measured after oral intake of EGb 761 at recommended doses between 120 and 240 mg. As PAF is a 'weak' platelet activator, which does not appear to be of importance for primary hemostasis, our results rise serious doubts that the PAF antagonistic effect of ginkgolides could be responsible for hemorrhage in patients taking EGb 761.

Inhibitory effects of xanthones from guttiferae plants on PAF-induced hypotension in mice

The inhibitory effects of 22 xanthones from three Guttiferae plants (Hypericum patulum, Calophyllum inophyllum and C. austroindium) on exogenous platelet activating factor (PAF)-induced hypotension were examined using a blood pressure monitoring in vivo assay method. Guanandin (2), caloxanthone E (3), 1,3,5,6-tetrahydroxy-2-isoprenylxanthone (8), 6-deoxyjacareubin (11) and patulone (18) showed strong inhibition of PAF-induced hypotension, with inhibitory effects of more than 60 %. Their ID50 values were greater than that of ginkgolide B (BN-52 021), a natural PAF-antagonist from the Ginkgo biloba.

Effects of recombinant platelet activating factor acetylhydrolase in obstructive jaundice

BACKGROUND/AIMS

The aim of this study was to investigate effects of recombinant PAH (platelet activating factor acetylhydrolase), on tissue damage and on antioxidant response.

METHODOLOGY

A total of 30 Wistar-Albino type rats were used in this PAH treatment, and the subjects were divided into 3 groups namely sham, ligation and PAH treatment groups, each containing 10 rats. In PAH treatment and ligation groups, laparotomy was made; common bile duct was ligated and incised. Following ligation, blood and liver tissue were taken. In the sham group, the common bile duct was turned but no other procedure was applied. The subjects in the ligation group were given intraperitoneal placebo on the 2nd to 6th days; and those in the PAH treatment group were applied PAH at a 5-mg/kg dose. Blood and liver tissue were taken on postoperative day 7. The parameters examined in the blood sample included, liver function tests, superoxide dismutase, glutathione peroxidase, tumor necrosis factor-alpha and interleukin-6. In liver tissue, histopathologic examination was made.

RESULTS

Levels of AST, ALT, GGT, ALP, tumor necrosis factor-alpha and interleukin-6 were significantly higher than the levels in the sham group. These parameters, measured on the 7th day in the PAH treatment group were found to be significantly lower than the ligation group. Portal inflammation in the PAH given group was significantly lower than the ligation group.

CONCLUSIONS

Administration of PAH in experimental jaundice has produced improvement in liver functions, significant reductions in serum GGT and ALP, tumor necrosis factor-alpha and interleukin-6, and in liver damage whereas it has brought about an increase in the levels of antioxidant enzymes.

Relation between serum 3-deoxyglucosone and development of diabetic microangiopathy

OBJECTIVE

3-Deoxyglucosone (3-DG), a highly reactive intermediate of the glycation reaction, has been suggested to contribute to the development of diabetes complications. To verify this hypothesis, we assessed the relation between serum 3-DG concentrations and the severity of diabetic microangiopathy in diabetic patients.

RESEARCH DESIGN AND METHODS

We conducted a high-performance liquid chromatography assay to determine the serum 3-DG concentrations of 110 diabetic patients with different degrees of severity of diabetic microangiopathy and 57 age-matched control subjects.

RESULTS

The fasting serum 3-DG level in diabetic patients was significantly (P < 0.001) higher than that in control subjects (353 +/- 110 vs. 199 +/- 53 nmol/l). The 3-DG levels were significantly (P < 0.001) elevated even in the diabetic patients showing normoalbuminuria (n = 62, 322 +/- 79 nmol/l) compared with control subjects. The 3-DG levels were further elevated in the patients with microalbuminuria (n = 30, 383 +/- 146 nmol/l) and overt proteinuria (n = 18, 410 +/- 100 nmol/l) (P = 0.027 and P < 0.001 vs. normoalbuminuria group, respectively). This phenomenon was basically reproduced in a category of retinopathy. Furthermore, the diabetic patients with low nerve conduction velocity showed a tendency to display higher 3-DG levels.

CONCLUSIONS

The present results show that the fasting serum 3-DG level is elevated in diabetic patients and that the patients with relatively higher 3-DG levels were prone to suffer from more severe complications, indicating a possible association of 3-DG with diabetic microangiopathy.

Nitric oxide attenuates platelet-activating factor induced nasal airway plasma extravasation in healthy subjects

BACKGROUND

Paranasal sinuses and the nose are important sources of nitric oxide (NO) in humans but the relevance of NO production to the control of nasal airway plasma exudation and its response to inflammatory mediators such as platelet-activating factor (PAF) in healthy subjects is not well known.

DESIGN

In this study we aimed to evaluate the effect of the nitric oxide synthase (NOS) inhibitor NG L-arginine methyl ester (L-NAME) on nasal airway plasma extravasation at baseline and after an acute challenge with PAF that induces most symptoms of rhinitis. Eleven healthy subjects were enrolled in the study. Plasma extravasation in the nasal airway was assessed by measuring the albumin content of nasal lavage.

RESULTS

PAF challenge caused a significant increase in concentrations of albumin in the nasal lavage fluid (from 0.59 +/- 0.13 mg dL(-1) to 2.46 +/- 0.45 mg dL(-1)) after placebo. Pretreatment with L-NAME significantly prevented the increase of albumin in the nasal lavage fluid induced by PAF as compared to placebo (from 0.53 +/- 0.11 mg dL(-1) to 1.70 +/- 0.28 mg dL(-1); P < 0.005).

CONCLUSION

Topical administration of a NO inhibitor is able to attenuate the nasal airway plasma extravasation induced by PAF, suggesting that NO release in vivo is involved in the nasal response to PAF.

Platelet-activating factor-induced pulmonary edema is partly mediated by prostaglandin E(2), E-prostanoid 3-receptors, and potassium channels

Platelet-activating factor (PAF) is an important endogenous mediator of pulmonary edema in many models of acute lung injury. PAF triggers edema formation by simultaneous activation of two independent pathways; one is mediated by a cyclooxygenase metabolite, and the other is blocked by quinine. We examined the hypothesis that the cyclooxygenase-dependent part of PAF-induced edema is mediated by prostaglandin E(2) (PGE(2)). In isolated rat lungs, PAF administration stimulated release of PGE(2) into the venous effluate and increased lung weight as a measure of edema formation. Perfusion with a neutralizing PGE(2) antibody attenuated the PAF-induced edema formation. In vivo, E-prostanoid 3-receptor-deficient mice showed less pulmonary Evans blue extravasation in response to PAF injection than did mice deficient in EP1, EP2, or EP4 receptors. Perfusion of rat lungs with PGE(2) caused pulmonary edema, which was largely prevented by inhibition of voltage-gated potassium channels (25 nM beta-dendrotoxin), but not by blocking calcium-dependent potassium currents (100 micro M paxilline). In line with its effects on PGE(2)-induced edema formation, beta-dendrotoxin attenuated PAF-induced edema partly if given alone, and completely in combination with quinine. Our findings suggest that PAF-triggered edema is partly mediated by the release of PGE(2), activation of EP3 receptors, and activation of voltage-gated potassium channels.

A neutrophil multitarget functional bioassay to detect anti-inflammatory natural products

A multitarget functional bioassay was optimized as a method for detecting substances interacting with the inflammatory process of activated neutrophil granulocytes, mainly to release elastase detected by p-nitroanilide (pNA) formation. Using this bioassay, 100 fractionated extracts of 96 plants were screened, with results presented in a manner that links recorded biological activity to phylogenetic information. The plants were selected to represent a major part of the angiosperms, with emphasis on medicinal plants, Swedish anti-inflammatory plants, and plants known to contain peptides. Of the tested extracts, 41% inhibited pNA formation more than 60%, and 3% stimulated formation. The extract of Digitalis purpurea enhanced pNA formation, and digitoxin, the active compound, was isolated and identified. Plant extracts that exhibited potent nonselective inhibition (>80% inhibition) were evaluated further for direct inhibition of isolated elastase and trypsin enzyme. The inhibitory effect of most tested extracts on the isolated enzyme elastase was similar to that of PAF- and fMLP-induced pNA formation. Compared to trypsin, inhibition of elastase by extracts of Rubus idaeus and Tabernaemontana dichotoma was significantly higher (80% and 99%, respectively). Inhibition of trypsin by the extract of Reseda luteola was high (97%). Orders such as Lamiales and Brassicales were shown to include a comparably high proportion of plants with inhibitory extracts.

[Inflammatory mediators (leukotrienes, thromboxane A2, tachykinins and others)]

Bronchial asthma is characterized by airway nallowing and hypersensitivity, for the occurrence of which (chemical) mediators are almost entirely responsible. Recent clinical as well as experimental reports have strongly suggested that arachidonate metabolites, especially cysteinyl leukotrienes (CysLTs), are involved in the attack of not only allergic asthma but also exercise- or aspirin-induced asthma. Because the receptor of CysLT1 but not CysLT2 largely contributes to the various pulmonary pharmacological actions of CysLTs, CysLT1 antagonists with high potency have rapidly developed recently. Other chemical mediators, tachykinins, endothelins and so on can be also candidates for the cause of the disease.

The effects of follicular fluid and platelet-activating factor on motion characteristics of poor-quality cryopreserved human sperm

PURPOSE

To evaluate the effects of follicular fluid and platelet-activating factor on sperm motion characteristics of cryopreserved oligospermic and normospermic samples.

METHODS

Sperm motion characteristics were evaluated prior to cryopreservation, immediately after thawing and following incubation in human tubal fluid, follicular fluid, or 1-microM platelet-activating factor cultures. Sixteen oligospermic samples and 20 normospermic samples were examined. Sperm motion characteristics were analyzed manually according to WHO criteria (1999) and also with an automated videomicrography system.

RESULT(S)

Incubation in follicular fluid increased overall motility and the percentage of sperm with fast progressive motility in normospermic but not oligospermic samples. Incubation with platelet-activating factor increased overall motility and the percentage of sperm showing nonprogressive motility in both oligospermic and normospermic samples.

CONCLUSION(S)

The stimulatory effects of culture in follicular fluid as seen in normospermic samples do not show a significant benefit in oligospermic cryopreserved samples. Platelet-activating factor and follicular fluid increase motility via different mechanisms. Incubation of oligospermic cryopreserved sperm with PAF increases the number of motile sperm, thereby enabling easier identification of viable sperm for intracytoplasmic sperm injection in samples with severe asthenozoospermia.

A novel treatment for lupus nephritis: lignan precursor derived from flax

BACKGROUND

Flaxseed has renoprotective effects in animal and human lupus nephritis. We have recently extracted the lignan precursor (secoisolariresinol diglucoside) (SDG) to determine if this more palatable derivative of flaxseed would exert renoprotection similar to the whole flaxseed in the aggressive MRL/lpr lupus mouse model.

METHODS

131 MRL/lpr mice were randomly assigned to saline gavage, 600, 1,200 and 4,800 microg lignan gavage groups. At 7 weeks, 6 animals underwent platelet aggregating factor (PAF) lethal challenge and 40 were studied with urine collection to determine the levels of secoisolariresinol, enterodiol and enterolactone in the gavaged animals. A baseline study of 10 saline gavaged animals took place at 6 weeks. 25 animals in the saline gavage, 600 and 1200 microg lignan groups were studied at 14 and 22 weeks for GFR, spleen lymphocyte S-phase and organ weight studies.

RESULTS

Metabolic studies indicated that secoisolariresinol is the major metabolite absorbed and the lowest lignan dose provides a lengthening in survival for the PAF lethal challenge. Body weight, fluid and water intake studies demonstrated that the lignan was well tolerated. Changes in proteinuria, GFR and renal size showed a time- and dose-dependent protection for the lignan precursor. Cervical lymph node size and spleen lymphocyte cells in the S-phase demonstrated modest dose-dependent reductions in the lignan gavaged groups.

CONCLUSION

SDG was converted in the gut to secoisolariresinol, which was absorbed and well tolerated by the MRL/lpr mice. Renoprotection was evidenced, in a dose-dependent fashion, by a significant delay in the onset of proteinuria with preservation in GFR and renal size. This study suggests that SDG may have a therapeutic role in lupus nephritis.

Oxidative response and membrane modification of diabetic platelets challenged with PAF

Alterations in the functional activities of platelets (PLT) in type I diabetes have been widely observed. These changes play a key role in the development of cardiovascular complications in diabetes. Various functional activities of PLT are the result of the interaction of numerous stimuli with PLT plasma membrane. This study was designed to evaluate the oxidative response and membrane modifications of diabetic PLT stimulated by platelet activating factor (PAF). The oxidative response was assessed by employing luminol- and lucigenin-amplified chemiluminescence. Luminol-amplified chemiluminescence is sensitive to the release of hydrogen peroxide whereas lucigenin-amplified chemiluminescence is sensitive to the production of superoxide anion. Membrane fluidity and polarity were studied using fluorescence spectroscopy. Membrane fluidity was investigated by measuring steady-state fluorescence anisotropy of 1-[4-trimethylammonium-phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) and membrane polarity was studied by measuring the steady-state fluorescence emission and excitation spectra of 2-dimethylamino[6-lauroyl]-naphthalene (Laurdan). The diabetic group consisted of 20 type I diabetic children with good metabolic control. Our results show a significant decrease in the luminol- and lucigenin-amplified chemiluminescence of PAF stimulated PLT in the diabetic group with respect to controls. These data indicate a decrement in the release of reactive oxygen species by diabetic PLT. We observed a significant increase in steady-state fluorescence anisotropy of diabetic PLT membrane that reflects a decrease in membrane fluidity. Laurdan showed a blue shift of the fluorescence emission and excitation spectra in diabetic PLT with respect to the control group, indicating a decrease in membrane polarity. The addition of PAF to PLT induced a red shift of Laurdan spectra in both groups, indicating an increase in membrane polarity. Our study [table: see text] demonstrates an altered oxidative response to PAF stimulation of diabetic PLT, probably due to altered generation or handling of reactive oxygen species, and alterations in the physico-chemical properties of the plasma membrane which could influence various functional activities of PLT.

Platelet activating factor acetylhydrolase decreases lung reperfusion injury

BACKGROUND

Ischemia-reperfusion injury involves free radical production, polymorphonuclear neutrophil chemotaxis/degranulation, and production of proteolytic enzymes, complement components, coagulation factors, and cytokines. Activated polymorphonuclear neutrophils, endothelial cells, and macrophages produce platelet activating factor, which further promotes these inflammatory reactions. The recently cloned plasma form of platelet activating factor-acetylhydrolase (PAF-AH) demonstrates antiinflammatory effects by degrading platelet activating factor. We evaluated the effects of PAF-AH in an isolated perfused rat lung model by adding it to the flush solutions or to the reperfusion blood.

METHODS

Rat lungs were isolated, flushed with EuroCollins (EC) or University of Wisconsin (UW) solution, stored at 4 degrees C for 6 or 12 hours, and reperfused using a cross-circulating syngeneic support rat. During reperfusion, oxygenation, compliance, and capillary filtration coefficient were calculated. There were four groups in the study; group I (control) had no PAF-AH added, group II had PAF-AH added to the flush solution, group III had PAF-AH added to reperfusion blood, and group IV had PAF-AH added to both flush solution and reperfusion blood.

RESULTS

After 6 hours of storage, oxygenation, compliance, and capillary filtration coefficient significantly improved for EC in group IV. For UW, oxygenation improved in group IV whereas compliance improved in groups II, III, and IV. After 12 hours of storage, compliance improved for EC in group IV and capillary filtration coefficient improved in groups III and IV. For UW, oxygenation and compliance improved in groups II and IV, whereas capillary filtration coefficient improved in group IV.

CONCLUSIONS

Addition of PAF-AH to intracellular organ preservation solutions and to the blood reperfusate significantly improves postreperfusion oxygenation and compliance, and reduces lung capillary permeability.

The inhaled administration of KF19514, a phosphodiesterase 4 and 1 inhibitor, prevents antigen-induced lung inflammation in guinea pigs

We examined in this study the effect of KF19514, a phosphodiesterase 4 and 1 inhibitor, on antigen-induced lung inflammation by inhaled administration in guinea-pigs. It was previously reported that inhaled KF19514 prevented antigen-induced bronchoconstriction and platelet-activating factor (PAF)-induced lung inflammation. In fact, a variety of factors other than PAF are related to lung inflammation in real subjects with asthma. Guinea-pigs were actively sensitized by exposure to ovalbumin (OA). Fifteen to 20 days later, the guinea pigs were challenged by exposure to aerosols of five successively increasing concentrations of OA (0.01, 0.1, 0.5, 1 and 5 mg/ml). Bronchoalveolar lavages (BALs) were performed 24 h after the antigen challenge, and airway hyperresponsiveness to acetylcholine (ACh) was studied 24 h after the challenge by measuring lung resistance and dynamic compliance. Ovalbumin antigen challenge produced a marked and significant eosinophil accumulation in the BAL fluids and airway hyperresponsiveness to ACh 24 h after the challenge. Inhaled KF19514 (0.01-0.1%) inhibited the eosinophil accumulation significantly and dose-dependently but inhaled rolipram (0.01-0.1%) and aminophylline (0.1-1%) did not. In addition, the development of airway hyperresponsiveness was prevented by inhaled KF19514 (0.01%) but not by inhaled rolipram (0.01%) and aminophylline (0.1%). Based on these data, KF19514 was suggested to be a promising drug in the treatment of asthma by local administration to the lung.

Effect of hydrocortisone on platelet activating factor induced lung edema in isolated rabbit lungs

The effect of hydrocortisone on platelet activating factor (PAF)-induced pulmonary edema is studied. Thirty four isolated and perfused rabbit lung preparations were used: eight control preparations, eight PAF preparations with two doses of PAF called low dose (LD = 0.5 microg/kg of rabbit weight) and high dose (HD = 1 microg/kg of rabbit weight). Eighteen preparations divided in three groups of six were pretreated with doses of 20, 200 and 2000 mg of hydrocortisone and later given the same doses of PAF as described above. Hydrocortisone significantly decreased (P < 0.05) the effect of PAF LD over the pulmonary arterial pressure (Ppa) in the 200 and 2000 mg groups (58 and 89% decrease, respectively) and it significantly decreased (P < 0.05) the effect of PAF HD over Ppa in all hydrocortisone pretreated groups (48, 70 and 96% decrease, respectively). Fluid filtration rate (FFR) increases mediated by PAF HD were significantly inhibited (P < 0.05) in the 200 and 2000 mg groups (64 and 96% decrease, respectively). We conclude that hydrocortisone inhibits the effect of PAF over the pulmonary circulation.

Differential determination of phospholipase A(2) and PAF-acetylhydrolase in biological fluids using fluorescent substrates

The purpose of the present study was the development and evaluation of a fluorimetric method for the screening and differential determination of phospholipase A(2) and PAF-acetylhydrolase in bronchoalveolar lavage (BAL) fluid and serum. Phospholipase A(2) was determined using C(12)-NBD-PC in the presence of Ca(2+), from the slope of the fluorescence enhancement due to the formation of C(12)-NBD-fatty acid. PAF-acetylhydrolase was determined using C(6)-NBD-PC, from the slope of the curve due to C(6)-NBD-fatty acid formation in the absence of Ca(2+). The results were confirmed after TLC analysis. The method's selectivity was evaluated by comparing to radiometric measurements. Light scattering did not interfere and inner filter effects was not observed under our experimental conditions. The effects of pH, temperature, and Ca(2+) were investigated. Protein caused an increase in the background fluorescence of both NBD-PCs. The standard curves of both NBD-fatty acids exhibited the same slope. Linearity extended at least up to 4. 5 nmoles per ml of reaction mixture at the normal pH 7.4. The fluorescence of the NBD-fatty acids remained stable for increasing concentrations of BAL fluid and serum and for BSA up to 100 microg/ml of reaction mixture. Porcine pancreatic PLase A(2) showed preference for C(12)-NBD-PC in the presence of Ca(2+), while without Ca(2+), serum PAF-AcH hydrolyzed only C(6)-NBD-PC. The method is highly sensitive, accurate, and reproducible and can be applied for the differential determination of phospholipase A(2) and PAF-acetylhydrolase activities in BAL fluid and serum.

Localization of the platelet-activating factor receptor to rat pancreatic microvascular endothelial cells

Platelet-activating factor (PAF) is a potent lipid autocoid involved in numerous inflammatory processes. Although PAF plays a key role as a mediator of inflammation in acute pancreatitis, the site(s) of action of PAF in the pancreas remains unknown. One of the aims of this study was to identify cell types within the pancreas expressing the PAF receptor using immunohistochemical protocols. Additionally, pancreatic microvascular endothelial cells were isolated and examined for the PAF receptor using immunohistochemistry, reverse transcription-polymerase chain reaction, and intracellular calcium responses to PAF exposure. Immunohistochemical analysis of pancreatic slices using an antibody directed toward the N-terminus of the PAF receptor revealed specific localization to the vascular endothelium with no localization to other pancreatic cell types. Reverse transcription-polymerase chain reaction of RNA isolated from cultured pancreatic islet endothelial cells yielded the predicted amplicon for the PAF receptor. Cultured pancreatic islet endothelial cells responded to PAF as measured by a transient increase in intracellular calcium, which was ameliorated in the presence of a PAF receptor antagonist. The results demonstrate the localization of PAF receptors on the pancreatic vascular endothelium. The presence of PAF receptors on the pancreatic vascular endothelium provides a defined, highly localized target for therapeutic intervention.