Platelet-activating Factor Receptor Research Articles

Cardioprotective properties of a novel enriched yogurt with inhibitors of Platelet Activating Factor (PAF)

AbstractPlatelet Activating Factor (PAF) is a pro-inflammatory mediator of atherogenesis. Food enriched with PAF inhibitors may have potential cardioprotective properties. In this attempt our group along with a well-known Greek dairy company incorporated bioactive ingredients (BAL) from olive-oil by-products, rich in PAF receptor specific inhibitors, into another typical food of the Mediterranean diet, namely yogurt. The aim of the present study was to evaluate the cardioprotective properties of the enriched yogurt in apparently healthy volunteers.Ninety two apparently healthy volunteers (35–65 years) were randomly allocated into three groups by block-randomization based on age, sex and BMI. The volunteers in Group A did not consume any yogurt. The volunteers of Group B consumed a non-enriched yogurt daily. The Group C volunteers ate daily an enriched yogurt. The intervention lasted 8 weeks. Volunteers’ adherence to the study protocol was assessed by two 24 h recalls every two weeks conducted by trained personnel. Blood and urine samples were collected at baseline, at 4th week and at 8th week of the intervention and biochemical and inflammatory markers were determined. In addition, platelet aggregation in volunteers’ platelet rich plasma against PAF, ADP and TRAP were measured and the results expressed as the concentration of the agonist that cause 50% of the maximum aggregation (EC50, efficient concentration fifty values).Among classical anthropometric and biochemical markers, only a decrease of blood pressure (systolic and diastolic) levels was observed (p0–8weeks < 0.05) in group B but with no clinical significance. Reduced levels of IL-10 was observed in group C compared to B both in the meantime (p4weeks = 0.01) and at the end of the intervention (p8weeks = 0.04). Furthermore, platelet sensitivity against PAF was only decreased (higher EC50 PAF,) in group C (p0–4weeks = 0.005 and p0–8weeks = 0.05). A trial effect was observed in the meantime among the three groups (p = 0.03).The consumption of the enriched yogurt led to attenuation of subclinical inflammation and platelet sensitivity to thrombotic stimuli in apparently healthy volunteers, indicating a potential cardioprotective role of PAF inhibitors.The work is funded by SYNERGASIA 2011 PROGRAMME. This Programme is co-funded by the European Regional Development Fund and National Resources, Project Code 11SYN-2-652.

ROBO4 deletion ameliorates PAF-mediated skin inflammation via regulating the mRNA translation efficiency of LPCAT1/LPCAT2 and the expression of PAF receptor.

The diminished level of platelet-activating factor acetylhydrolase (PAFAH) in milk causes an enhanced level of platelet activating factor (PAF) in the skin, leading to a severe hair loss phenotype during neonatal pup's lactation. The deletion of very-low-density-lipoprotein receptor (VLDLR) prevents the expression and secretion of PAFAH. Here we revealed that deletion of Roundabout 4 (ROBO4) in mice ameliorated hair loss phenotype via reducing PAF concentration in skin. As a consequence, the neonatal pups with ROBO4 deletion lactated by mother with VLDLR deletion showed normal hair phenotype during lactation. In details,ROBO4 deletion reduced the protein but not mRNA expression of two PAF synthetic enzymes LPCAT1/LPCAT2 in macrophage as well as the expression of PAF receptor in both macrophage and ocular tissue, but increased PAFAH protein in serum. On the other hand, RNA expression profile analysis in macrophages revealed that the genes involving in oxidative phosphorylation and ribosome obviously decreased their expression in response to ROBO4 deletion. Moreover, through High Performance Liquid Chromatography (HPLC) analysis, we found that ATP concentration also reduced in ROBO4 deletion macrophages. Because ribosome and energy are very important factors for the mRNA translation, we then tested whether ROBO4 deletion affects LPCAT1/LPCAT2 mRNA translation using polyribosome assay. As expected, the mRNA level of LPCAT1/LPCAT2 significantly decreased in polyribosome in ROBO4 deletion macrophage comparing to that of wild type. Additionally, mice with ROBO4 deletion suppressed LPS-induced IL-6 expression as well as the phosphorylation of p44/42 and p65, but enhanced the AKT phosphorylation. Collectively, ROBO4 deletion alleviates PAF- and LPS-mediated inflammation. And above results also indicate PAF signal might be a crosstalk point of ROBO4- and VLDLR-activated pathways.

Blocking pro-inflammatory platelet-activating factor receptors and activating cell survival pathways: A novel therapeutic strategy in experimental ischemic stroke.

OBJECTIVE:Acute ischemic stroke triggers complex neurovascular, neuroinflammatory, and synaptic alterations. This study explores whether blocking pro-inflammatory platelet-activating factor receptor (PAF-R) plus selected docosanoids after middle cerebral artery occlusion (MCAo) would lead to neurological recovery. The following small molecules were investigated: (a) LAU-0901, a PAF-R antagonist that blocks pro-inflammatory signaling; and (b) derivatives of docosahexaenoic acid (DHA), neuroprotectin D1 (NPD1), and aspirin-triggered NPD1 (AT-NPD1), which activates cell survival pathways and are exert potent anti-inflammatory activity in the brain.MATERIALS AND METHODS:Sprague-Dawley rats received 2 h MCAo and LAU-0901 (30 or 60 mg/kg, 2 h after stroke), NPD1, and AT-NPD1 (333 μg/kg), DHA (5 mg/kg), and their combination were administered intravenous at 3 h after stroke. Behavior testing and ex vivo magnetic resonance imaging were conducted on day 3 or 14 to assess lesion characteristics and lipidomic analysis on day 1. Series 1 (LAU-0901 + NPD1, 14d), Series 2 (LAU-0901 + AT-NPD1, 3d), and Series 3 (LAU-0901 + DHA, 1d).RESULTS:All combinatory groups improved behavior compared to NPD1, AT-NPD1, or DHA treatments alone. Total lesion volumes were reduced with LAU-0901 + NPD1 by 62% and LAU-0901 + AT-NPD1 by 90% treatments versus vehicle groups. LAU-0901 and LAU-0901 + DHA increased the production of vasoactive lipid mediators (prostaglandins: PGE2, PGF2-α, 6-keto-PGF1-α, and PGD2) as well an inflammatory regulating mediator hydroxyoctadecadienoic acid. In contrast, LAU-0901 and LAU-0901 + DHA decreased the production of 12-hydroxyeicosatetraenoic acid, a pro-inflammatory mediator.CONCLUSION:Combination therapy with LAU-0901 and selected docosanoids is more effective than the single therapy, affording synergistic neuroprotection, with restored pro-homeostatic lipid mediators and improved neurological recovery. Altogether, our findings support the combinatory therapy as the basis for future therapeutics for ischemic stroke.

A1 adenosine receptor signaling reduces Streptococcus pneumoniae adherence to pulmonary epithelial cells by targeting expression of platelet-activating factor receptor.

Extracellular adenosine production is crucial for host resistance against Streptococcus pneumoniae (pneumococcus) and is thought to affect antibacterial immune responses by neutrophils. However, whether extracellular adenosine alters direct host-pathogen interaction remains unexplored. An important determinant for lung infection by S. pneumoniae is its ability to adhere to the pulmonary epithelium. Here we explored whether extracellular adenosine can directly impact bacterial adherence to lung epithelial cells. We found that signaling via A1 adenosine receptor significantly reduced the ability of pneumococci to bind human pulmonary epithelial cells. A1 receptor signaling blocked bacterial binding by reducing the expression of platelet-activating factor receptor, a host protein used by S. pneumoniae to adhere to host cells. In vivo, A1 was required for control of pneumococcal pneumonia as inhibiting it resulted in increased host susceptibility. As S. pneumoniae remain a leading cause of community-acquired pneumonia in the elderly, we explored the role of A1 in the age-driven susceptibility to infection. We found no difference in A1 pulmonary expression in young versus old mice. Strikingly, triggering A1 signaling boosted host resistance of old mice to S. pneumoniae pulmonary infection. This study demonstrates a novel mechanism by which extracellular adenosine modulates resistance to lung infection by targeting bacterial-host interactions.

Hypoxia-inducible factor and bacterial infections in chronic obstructive pulmonary disease.

COPD is a seriously disabling respiratory condition that inexorably progresses to disability and mortality. It affects approximately 10% of the population globally with a greater prevalence at advanced ages. Airway bacterial infections complicate the disease course in most COPD patients, leading to increased symptoms, more rapid decline in lung function, acute exacerbations and reduced quality of life. With increasing bacterial resistance to antibiotics and adverse effects of conventional treatments, new effective non-antibiotic antimicrobial therapies are urgently needed to manage COPD. Hypoxia-inducible factor (HIF)-1α is an important transcriptional regulator of cellular responses to hypoxia, oxidants and inflammation, and is overexpressed in the lungs of COPD patients. Recent evidence shows that increased HIF-1α expression can upregulate the platelet-activating factor receptor (PAFR) on the airway epithelial surface that is increased in smokers and particularly COPD patients. The receptor is utilized by PAFR-dependent bacteria (Streptococcus pneumoniae, Haemophilus influenzae and Pseudomonas aeruginosa) to induce infection in both the respiratory and gastrointestinal (GI) tracts. However, the importance and mechanism of HIF-1α in augmenting PAFR-dependent bacterial infections in COPD are poorly understood. Here, we review the evidence for the roles of local tissue hypoxia-induced inflammation, HIF-1α and PAFR in facilitating bacterial infections in COPD. Blocking PAFR may provide a novel antimicrobial approach to manage bacterial infections in COPD.

Mechanisms underlying fat pad remodeling induced by fasting: role of PAF receptor.

Fasting has long been practiced for political and religious reasons and to lose weight. However, biological responses during fasting have yet to be fully understood. Previous studies have shown that cytokines may control fat pad expansion, at least in part, owing to the induction of lipolysis. Indeed, we have previously shown that mice with a lower inflammatory response, such as platelet-activating factor receptor knockout mice (PAFR-/-), are prone to gain weight and adiposity. The aims of this study were to determine whether adipose tissue becomes inflamed after fasting and to evaluate whether the PAF signaling is a factor in the fat loss induced by fasting. Wild-type (WT) and PAFR-/- mice were fasted for 24 h. Adiposity, leukocyte recruitment, and cytokine levels were evaluated. Multiple comparisons were performed using two-way analysis of variance and post hoc Fisher exact test. After fasting, male WT mice showed lower adiposity (P < 0.001), higher recruitment of immune cells (P < 0.001), and increased cytokine levels (P < 0.05) in adipose tissue. Although WT mice lost ~79% of their adipose tissue mass, PAFR-/- mice lost only 36%. Additionally, PAFR-/- mice did not show enhanced cytokine and chemokine levels after fasting (P > 0.05). Despite low-grade inflammation being associated with metabolic syndrome, at least in part, the inflammatory milieu is also important to induce proper fat mobilization and remodeling of adipose tissue.

Lysophosphatidylcholine triggers cell differentiation in the protozoan parasite Herpetomonas samuelpessoai through the CK2 pathway.

Protozoa are distantly related to vertebrates but present some features of higher eukaryotes, making them good model systems for studying the evolution of basic processes such as the cell cycle. Herpetomonas samuelpessoai is a trypanosomatid parasite isolated from the hemipteran insect Zelus leucogrammus. Lysophosphatidylcholine (LPC) is implicated in the transmission and establishment of Chagas disease, whose etiological agent is Trypanosoma cruzi. LPC is synthesized by T. cruzi and its vectors, the hemipteran Rhodnius prolixus and Triatoma infestans. Platelet-activating factor (PAF), a phospholipid with potent and diverse physiological and pathophysiological actions, is a powerful inducer of cell differentiation in Herpetomonas muscarum muscarum and T. cruzi. The enzyme phospholipase A2 (PLA2) catalyzes the hydrolysis of the 2-ester bond of 3-sn-phosphoglyceride, transforming phosphatidylcholine (PC) into LPC. In this study, we evaluated cellular differentiation, PLA2 activity and protein kinase CK2 activity of H. samuelpessoai in the absence and in the presence of LPC and PAF. We demonstrate that both PC and LPC promoted a twofold increase in the cellular differentiation of H. samuelpessoai, through CK2, with a concomitant inhibition of its cell growth. Intrinsic PLA2 most likely directs this process by converting PC into LPC. Our results suggest that the actions of LPC on H. samuelpessoai occur upon binding to a putative PAF receptor and that the protein kinase CK2 plays a major role in this process. Cartoon depicting a model for the synthesis and functions of LPC in Herpetomonas samuelpessoai, based upon our results regarding the role of LPC on the cell biology of Trypanosoma cruzi [28-32]. N nucleus, k kinetoplast, PC phosphatidylcholine, LPC lysophosphatidylcholine, PLA2 phospholipase A2, PAFR putative PAF receptor in trypanosomatids [65], CK2 protein kinase CK2 [16].

Skin Targeting Approaches in Cosmetics

Abstract: Objective: To emphasize and summarize the main component of skin and approaches to target them. Methods: Skin targeting approaches in cosmetics is a review of all the relevant papers known to the author was conducted. Results: The exhaustive review on the basis of the previously reported paper revealed that the skin is a complicated and intact structure having vast of targeting component such as Keratin, Elastin fibres, ECM, MMPs, collagen, Hyaluronic Acid etc and apart from that the receptor and signalling pathway mediated skin targeting is also a promising approach to deliver bioactive at specific site of skin by the help of Surface engineered nanocarriers. Receptors like Epidermal Growth Factor Receptor (EGFr), interleukin-1 receptor (IL-1r), Tumor Necrosis Factor Receptor (TNFr), Platelet-Derived Growth Factor Receptor (PDGFr) and Platelet- Activating Factor Receptor (PAF-r) are the types of receptor present in skin cells. These receptors are targeted by nanocarriers which are surface engineered by conjugating them ligands which show the specific affinity towards receptor present in the skin cells. Key words: Skin, Targeting, ECM, MMPs, Collagen, EGFr, IL-1r, TNFr, PDGFr, PAF-r, Nanocarriers.

Platelet-activating factor receptor (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is an ether phospholipid mediator associated with platelet coagulation, but also subserves inflammatory roles. The PAF receptor (provisional nomenclature recommended by NC-IUPHAR [37]) is activated by PAF and other suggested endogenous ligands are oxidized phosphatidylcholine [73] and lysophosphatidylcholine [96]. It may also be activated by bacterial lipopolysaccharide [89].

Inhibitory Effects of Mitrella kentii Extracts on Inflammatory Mediators’ Biosynthesis and Binding

ABSTRACTThe inhibitory effects of Mitrella kentii leaf and stem extracts on the production prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) and antagonist effect on platelet-activating factor (PAF) receptor binding were evaluated. The inhibition of PGE2 and TXB2 productions were determined using the radioimmunoassay technique, and the inhibitory effect of PAF receptor binding to rabbit platelet was determined using the 3H-PAF as a ligand. Among the extracts tested, ethyl acetate, methanol and hexane leaf extracts, and methanol stems extract showed inhibitory effects on PGE2 and TXB2 productions and antagonistic effect on PAF receptor binding. M. kentii extracts may have the potential of being developed as supplements for inflammatory conditions.

Repeated Exposure to Streptococcus pneumoniae Exacerbates Chronic Obstructive Pulmonary Disease

Streptococcus pneumoniae is commonly found in patients with chronic obstructive pulmonary disease (COPD) and is linked to acute exacerbation of COPD. However, current clinical therapy neglects asymptomatic insidious S. pneumoniae colonization. We studied the roles of repeated exposure to S. pneumoniae in COPD progression using a mouse model. C57BL/6J mice were intranasally inoculated with S. pneumoniae ST262 every 4 weeks with or without cigarette smoke (CS) exposure up to 20 weeks to maintain persistent S. pneumoniae presence in the lower airways. Streptococcus pneumoniae enhanced CS-induced inflammatory cell infiltration at 12 to 20 weeks of exposure. Streptococcus pneumoniae also increased CS-induced release of inflammatory cytokines, including IL-1β, tumor necrosis factor-α, IL-12 (p70), and IL-5 at 20 weeks of exposure. Moreover, a combination of CS and S. pneumoniae caused alveolar epithelial injury, a decline in lung function, and an increased expression of platelet-activating factor receptor and bacterial load. Our results suggest that repeated exposure to S. pneumoniae in lower airways exacerbates CS-induced COPD.

Design, Synthesis and Anti-Platelet Aggregation Activity Study of Ginkgolide-1,2,3-triazole Derivatives.

Ginkgolides are the major active component of Ginkgo biloba for inhibition of platelet activating factor receptor. An azide-alkyne Huisgen cycloaddition reaction was used to introduce a triazole nucleus into the target ginkgolide molecules. A series of ginkgolide-1,2,3-triazole conjugates with varied functional groups including benzyl, phenyl and heterocycle moieties was thus synthesized. Many of the designed derivatives showed potent antiplatelet aggregation activities with IC50 values of 5~21 nM.

Prostaglandin E2 promotes nitric oxide synthase 2, platelet-activating factor receptor, and matrix metalloproteinase-2 expression in Escherichia coli-challenged ex vivo endometrial explants via the prostaglandin E2 receptor 4/protein kinase a signaling pathway

Prostaglandin E2 (PGE2) is an inflammatory mediator involved in the pathogenesis of several chronic inflammatory conditions, including endometritis. Previous studies have shown that PGE2 accumulates in Escherichia coli-challenged ex vivo endometrial explants, increasing the expression of pro-inflammatory factors and aggravating tissue damage; these alterations are linked to key enzymes involved in the synthesis of PGE2, including cyclooxygenases-2 (COX-2) and microsomal PGES-1 (mPGES-1). In this study, we aimed to investigate whether administration of PGE2 modulated the activities of nitric oxide synthase 2 (NOS2), platelet-activating factor receptor (PAFR), and matrix metalloproteinase (MMP)-2 in E. coli-challenged ex vivo bovine endometrial explants. Our findings showed that COX-2 and mPGES-1 inhibitors significantly reduced NOS2, PAFR, and MMP-2 expression in the E. coli-challenged ex vivo endometrial explants. In addition, NOS2, PAFR, and MMP-2 expression levels were strongly increased in response to treatment with 15-prostaglandin dehydrogenase inhibitors in the E. coli-challenged ex vivo endometrial explants. However, these stimulatory effects could be blocked by PGE2 receptor 4 (EP4) and protein kinase A (PKA) inhibitors. Overall, these findings show that pathogenic PGE2 upregulated NOS2, PAFR, and MMP-2 expression, which may enhance inflammatory damage via the EP4/PKA signaling pathway in E. coli-challenged ex vivo endometrial explants.

Role of PAFR-MHC-II-CD38 interactions in infections

Abstract Infectious diseases are the most prevalent cause of deaths around the world. Chronic contagious ailments will account for seven out of ten deaths in the world by 2020. The most significant problem in the treatment of the infectious disease is the ever-increasing rate of resistance to drugs mounted by pathogens. Our preliminary results suggest that during antigen presentation the major histocompatibility complex II (MHC-II) engages two associate protein molecules CD38 and Platelet Activating Factor Receptor (PAFR). CD38 and PAFR elicit two counteractive signaling pathways in APCs resulting in the release of either proinflammatory cytokine such as IL-12 or anti-inflammatory cytokines such as IL-10 respectively. Pathogens show remarkable adaptability to the drugs by either metabolizing the drug molecules or by changing the surface profile to neutralize binding of drugs to the pathogens. Therefore, there is a requirement to find new treatment modalities that do not target the pathogens but aid the immune system to eliminate the pathogens. Our preliminary data further suggest that the use of associate molecule during antigen presentation decides the fate of pathogens such as Salmonella Typhimurium or Staphylococcus aureus in macrophages. For example, if MHC-II engages CD38 to signal inside the macrophages leading to reduced pathogen survival in macrophages and mice, while MHC-II-signaling via PAFR aid the pathogen survival in macrophages and mice. Our studies also suggest that combinatorial use of PAFR inhibitor (WEB2086) and antibiotics ampicillin reduced the growth of S. Typhimurium or S. aureus in macrophages and mice.

Platelet activating factor receptor regulates colitis-induced pulmonary inflammation through the NLRP3 inflammasome.

Extra-intestinal manifestations (EIM) are common in inflammatory bowel disease (IBD). One such EIM is sub-clinical pulmonary inflammation, which occurs in up to 50% of IBD patients. In animal models of colitis, pulmonary inflammation is driven by neutrophilic infiltrations, primarily in response to the systemic bacteraemia and increased bacterial load in the lungs. Platelet activating factor receptor (PAFR) plays a critical role in regulating pulmonary responses to infection in conditions, such as chronic obstructive pulmonary disease and asthma. We investigated the role of PAFR in pulmonary EIMs of IBD, using dextran sulfate sodium (DSS) and anti-CD40 murine models of colitis. Both models induced neutrophilic inflammation, with increased TNF and IL-1β levels, bacterial load and PAFR protein expression in mouse lungs. Antagonism of PAFR decreased lung neutrophilia, TNF, and IL-1β in an NLRP3 inflammasome-dependent manner. Lipopolysaccharide from phosphorylcholine (ChoP)-positive bacteria induced NLRP3 and caspase-1 proteins in human alveolar epithelial cells, however antagonism of PAFR prevented NLRP3 activation by ChoP. Amoxicillin reduced bacterial populations in the lungs and reduced NLRP3 inflammasome protein levels, but did not reduce PAFR. These data suggest a role for PAFR in microbial pattern recognition and NLRP3 inflammasome signaling in the lung.

Association between changes in the mRNA expression of platelet-activating factor receptor in peripheral blood mononuclear cells and progression of diabetic nephropathy.

Several studies have recently pointed out the role of many inflammatory mediators in the progression of diabetes complications. We had previously demonstrated that mRNA expression of platelet-activating factor receptor (PAFR) in peripheral blood mononuclear cells (PBMCs) was associated with urinary albumin to creatinine ratio (ACR) and forearm flow-mediated dilatation in patients with type 2 diabetes. In an attempt to elucidate this association, patients were followed up for 1year. We recruited 95 patients from the hospital outpatient clinic, among whom 86 were followed up for 1year (normoalbuminuria: 40 patients, microalbuminuria: 25 patients, macroalbuminuria: 21 patients). We then measured their baseline and 12month characteristics and collected blood samples to extract PBMCs and measure gene expressions. Despite higher mRNA expression of PAFR in PBMCs among patients with macroalbuminuria, the rise in its value was not associated with biomarkers of nephropathy, while baseline values were not associated with progression of nephropathy. Moreover, changes in mRNA expression of PAFR were correlated with changes in ACR in all patients (r = 0.225, p = 0.037) and estimated glomerular filtration rate in patients with macroalbuminuria (r = - 0.438, p = 0.047) during the follow-up period. Our findings indicate that even though no causal relationship exists between diabetic nephropathy and elevated expression of PAFR in PBMCs, their close association signifies the presence of another common mechanism that could induce both events. Given these findings, the PAF/PAFR interaction could clarify corresponding mechanisms involved in diabetic complications.

TNFα promotes mucosal wound repair through enhanced platelet activating factor receptor signaling in the epithelium.

Pathobiology of several chronic inflammatory disorders including ulcerative colitis and Crohn’s disease is related to intermittent, spontaneous injury/ulceration of mucosal surfaces. Disease morbidity has been associated with pathologic release of the pro-inflammatory cytokine Tumor Necrosis Factor alpha (TNFα). In this report, we show that TNFα promotes intestinal mucosal repair through upregulation of the GPCR Platelet Activating Factor Receptor (PAFR) in the intestinal epithelium. Platelet Activating Factor (PAF) was increased in healing mucosal wounds and its engagement with epithelial PAFR leads to activation of epidermal growth factor receptor, Src and Rac1 signaling to promote wound closure. Consistent with these findings, delayed colonic mucosal repair was observed after administration of a neutralizing TNFα antibody and in mice lacking PAFR. These findings suggest that in the injured mucosa, the pro-inflammatory milieu containing TNFα and PAF sets the stage for reparative events mediated by PAFR signaling.

Consumption of plant extract supplement reduces platelet activating factor-induced platelet aggregation and increases platelet activating factor catabolism: a randomised, double-blind and placebo-controlled trial.

Platelet-activating factor (PAF) is a potent mediator of inflammation that plays a crucial role in atherosclerosis. The purpose of this study was to evaluate the effect of a dietary supplement containing mainly plant extracts on PAF actions and metabolism in healthy volunteers. A double-blind, placebo-controlled, 8 weeks' duration study was performed. Healthy volunteers were randomly allocated into the supplement or the placebo group and fifty-eight of them completed the study. The supplement contained plant extracts (Aloe gel, grape juice, Polygonum cuspidatum) and vitamins. The activities of PAF metabolic enzymes: the two isoforms of acetyl-CoA:lyso-PAF acetyltransferase, cytidine 5'-diphospho-choline:1-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase (PAF-cholinephosphotransferase) and platelet-activating factor-acetylhydrolase (PAF-AH) in leucocytes and lipoprotein associated phospholipase-A2 in plasma were measured along with several markers of endothelial function. Platelet aggregation against PAF, ADP and thrombin receptor activating peptide was measured in human platelet-rich plasma by light transmission aggregometry. No difference was observed on soluble vascular cell adhesion molecule-1, sP-selectin and IL-6 levels at the beginning or during the study period between the two groups. Concerning PAF metabolism enzymes' activity, no difference was observed at baseline between the groups. PAF-AH activity was only increased in the supplement group at 4 and 8 weeks compared with baseline levels. In addition, supplement consumption led to lower platelet sensitivity against PAF and ADP compared with baseline levels. However, a trial effect was only observed when platelets were stimulated by PAF. In conclusion, supplementation with plant extracts and vitamins ameliorates platelet aggregation primarily against PAF and secondarily against ADP and affects PAF catabolism by enhancing PAF-acetylhydrolase activity in healthy subjects.

Platelet‐activating factor‐receptor dependent pathway mediates gemcitabine chemotherapy‐induced microvesicle particles release in pancreatic cancer cells

Studies including ours have shown that pro‐oxidative stressors such as chemotherapeutic agents generate oxidized lipids with platelet‐activating factor (PAF) agonistic activity. These PAF‐agonists bind with and activate the widely‐expressed G‐protein coupled, PAF‐receptor (PAF‐R), implicated in various pathophysiological diseases including cancer. Notably, recent reports from our group have demonstrated that these PAF‐agonists are transported extracellularly via microvesicle particles (MVP). While the role of PAF‐R in mediating chemotherapy effects has been documented, its significance in chemotherapy‐induced MVP release in pancreatic cancer model has not been studied. To that end, the current studies determined the functional significance of PAF‐R in clinically relevant gemcitabine chemotherapy‐induced MVP release in human pancreatic cancer cells. Our studies using PAF‐R‐expressing (PANC‐1), and deficient (Hs766T) cells demonstrate that gemcitabine induces MVP release in a PAF‐R‐dependent manner. Blocking of PAF‐R via PAF‐R antagonist or inhibition of MVP biogenesis via acid sphingomyelinase (aSMase) enzyme inhibitor, significantly attenuated gemcitabine‐induced MVP release from PANC‐1 cells, however, exerted no effects in Hs766T cells. Importantly, lipid extracts from MVP, isolated from gemcitabine‐treated PANC‐1 cells, contained appreciable amounts of PAF‐agonists. This was measured by a well‐defined and specific approach of accessing PAF‐agonists generation via interleukin‐8 (IL‐8) secretion from PAF‐R‐expressing human epidermoid KBP cells, and not from PAF‐R‐deficient KBM cells. These results indicate that gemcitabine‐generated PAF‐agonists are transported extracellularly via MVP. Mechanistically, pretreatment with extracellular signal‐regulated kinase (ERK1/2) or p38 inhibitors, significantly abrogated gemcitabine‐induced MVP release. These findings indicate the involvement of mitogen‐activated protein kinase (MAPK) pathway in PAF‐R‐dependent gemcitabine‐induced MVP release. In sum, these studies provide the significance of PAF‐R in gemcitabine‐induced MVP release as well as the rationale of evaluating PAF‐R targeting agents with gemcitabine or gemcitabine‐based chemotherapy approaches against pancreatic cancer.Support or Funding InformationThe financial support from the NIH K22 [ES023850] and Elsa U. Pardee Foundation [670645] grants are greatly acknowledged.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Tricarboxylic Acid Cycle Activity and Remodeling of Glycerophosphocholine Lipids Support Cytokine Induction in Response to Fungal Patterns

Increased glycolysis parallels immune cell activation, but the role of pyruvate remains largely unexplored. We found that stimulation of dendritic cells with the fungal surrogate zymosan causes decreases of pyruvate, citrate, itaconate, and α-ketoglutarate, while increasing oxaloacetate, succinate, lactate, oxygen consumption, and pyruvate dehydrogenase activity. Expression of IL10 and IL23A (the gene encoding the p19 chain of IL-23) depended on pyruvate dehydrogenase activity. Mechanistically, pyruvate reinforced histone H3 acetylation, and acetate rescued the effect of mitochondrial pyruvate carrier inhibition, most likely because it is a substrate of the acetyl-CoA producing enzyme ACSS2. Mice lacking the receptor of the lipid mediator platelet-activating factor (PAF; 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine) showed reduced production of IL-10 and IL-23 that is explained by the requirement of acetyl-CoA for PAF biosynthesis and its ensuing autocrine function. Acetyl-CoA therefore intertwines fatty acid remodeling of glycerophospholipids and energetic metabolism during cytokine induction.