Platelet-activating Factor Levels Research Articles

Baseline and 6-Week Follow-Up Levels of PAF and Activity of Its Metabolic Enzymes in Patients With Heart Failure and Healthy Volunteers—A Pilot Study

This study aimed at evaluating the changes in platelet-activating factor (PAF) and its metabolic enzymes over a 6-week follow-up period in patients with newly diagnosed heart failure ([HF] n = 12) compared with age-, sex-, and BMI-matched apparently healthy volunteers (n = 10). The PAF, its key biosynthetic enzymes (lyso-PAF acetyltransferase [lyso-PAF-AT] and dithiothreitol [DTT]-insensitive CDP choline: 1-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase [PAF-CPT]), and its catabolic isoenzymes (PAF-acetylhydrolase [PAF-AH] and lipoprotein-associated phospholipase A2 [Lp-PLA2]) were measured in serum and leukocytes of participants. At baseline, patients with HF had lower median activities of lyso-PAF-AT (P < .001) and PAF-CPT (P = .07) in parallel with PAF levels (P = .05) and higher activities of PAF-AH (P = .02) and Lp-PLA2 (P < .001) than controls. At follow-up, PAF-CPT and PAF levels marginally increased (P = .1), lyso-PAF-AT (P < .001) remained downregulated, while PAF-AH (P = .004) and Lp-PLA2 (P < .001) remained elevated compared with the controls. Newly diagnosed patients with HF under drug treatment have an affected profile of PAF biosynthetic enzymes and especially lyso-PAF-AT.

Platelet activating factor levels and metabolism in tangier disease: a case study

BackgroundTangier disease (TD) is a phenotypic expression of rare familial syndrome with mutations in the ABCA1 transporter. The risk of coronary artery disease in patients with TD is variable. On the other hand the pivotal role of Platelet-Activating Factor (PAF) mediator in atheromatosis was found. Plasma lipoproteins are transporters of the PAF acetylhydrolase (PAF-AH) in cells and known as lipoprotein-phospholipase A2 (Lp-PLA2) in plasma and regulators of PAF levels in blood. In addition, PAF can be biosynthesized from the remodeling and the de novo pathways in which Lyso-platelet activating factor-acetyltransferase (Lyso-PAF-AT) and platelet activating factor-cholinephosphotransferase (PAF-CPT) are the regulatory enzymes. The aim of this study is to investigate in a TD patient with a unique mutation (C2033A), the concentration of PAF in blood, the Equivalent Concentration for 50% aggregation (EC50) values of platelet rich plasma (PRP) toward PAF, adenosine diphosphate (ADP) and thrombin, and the activities of PAF metabolic enzymes Lp-PLA2, PAF-AH, Lyso-PAF-AT and PAF-CPT.MethodsThe EC50 value of PRP was measured by an aggregometer. The determination of the specific activity of PAF-CPT and Lyso-PAF-AT was made after in vitro enzymatic assay, chromatographic separation and measurement of the produced PAF in a biological assay with washed rabbit platelets. The determination of PAF-AH and Lp-PLA2 was made after an in vitro enzymatic assay from the decay of radioactive PAF.ResultsThe TD patient had lower bound-PAF values in blood, decreased specific activity of PAF-CPT and Lyso-PAF-AT, increased specific activity of PAF-AH in platelets and leukocytes and Lp-PLA2 activity in plasma compared to healthy women. The EC50 of PAF and Thrombin were higher compared to healthy women.ConclusionThe increased Lp-PLA2 activity, as well as, the decreased activities of PAF-CPT and Lyso-PAF-AT, explain the decreased bound-PAF level in TD patient and the EC50 of PAF. However, total PAF is in a normal range and this probably can explain one of the reasons this TD patient has no CAD.

Changes in coagulation and fibrinolysis in the patients with coronary heart disease in acute period and effect of drug intervention

To investigate the changes in coagulation and fibrinolysis parameters during acute phase of coronary heart disease, and to explore the effects of drug intervention in same period. A prospective study was conducted. The changes in plasma von Willebrand factor (vWF), platelet activating factor (PAF), tissue type plasminogen activator (t-PA) of 110 patients with coronary heart disease [50 patients with acute myocardial infarction (AMI), 35 patients with unstable angina pectoris (UAP), 25 patients with ischemic cardiomyopathy (ICM)] were determined immediately at admission and 14 days after treatment. The indexes of 19 healthy individuals were collected as control. At the same time, randomized and double-blind observation of the changes in plasma coagulation and fibrinolysis system indexes including vWF, PAF and t-PA was made in AMI and UAP patients who received conventional treatment (aspirin + low molecular weight heparin) or combination of conventional treatment and clopidogrel for 14 days. The vWF and PAF levels (nmol/L) of AMI and UAP patients at admission were significantly higher than those in healthy control group [vWF: (202.31 ± 27.38)%, (188.65 ± 31.08)% vs. (120.37 ± 18.79)%; PAF: 50.64 ± 13.25, 48.87 ± 13.24 vs. 15.43 ± 9.27, all P < 0.05], however, t-PA (μg/L) was remarkably lower than that in healthy control group (3.52 ± 1.57, 4.03 ± 2.04 vs. 9.54 ± 1.32, both P < 0.01). After 14 days of treatment, the levels of vWF, PAF, t-PA, fibrinogen (Fib, g/L), D-dimer (mg/L) in plasma of AMI and UAP patients were close to those of healthy control group [vWF: (116.56 ± 26.10)%, (111.28 ± 22.31)% vs. (120.37 ± 18.79)%; PAF: 17.48 ± 9.16, 16.23 ± 9.17 vs. 15.43 ± 9.27; t-PA: 7.91 ± 2.42, 9.01 ± 2.01 vs. 9.54 ± 1.32; Fib: 3.64 ± 0.53, 2.74 ± 0.72 vs. 2.92 ± 0.91; D-dimer: 0.370 ± 0.150, 0.288 ± 0.169 vs. 0.255 ± 0.109, all P>0.05]. However, there was no statistical difference in vWF, PAF, t-PA, Fib and D-dimer levels before and after treatment in ICM group compared with healthy control group [vWF: (124.14 ± 21.17)%, (119.44 ± 26.28)% vs. (120.37 ± 18.79)%; PAF: 15.69 ± 7.14, 14.84 ± 9.16 vs. 15.43 ± 9.27; t-PA: 8.62 ± 2.24, 8.07 ± 2.51 vs. 9.54 ± 1.32; Fib: 3.24 ± 0.74, 3.04 ± 0.77 vs. 2.92 ± 0.91; D-dimer: 0.257 ± 0.132, 0.268 ± 0.117 vs. 0.255 ± 0.109, all P>0.05]. Multiple linear regression analysis showed that, in patients with coronary heart disease, PAF be positively correlated with vWF (r = 0.42, P < 0.01), but negatively correlated with t-PA (r = -0.31, P < 0.01). In patients with AMI and UAP, using the treatment of clopidogrel for 14 days, the levels of vWF, PAF, t-PA, Fib and D-dimer in plasma showed no significant differences compared with those of conventional treatment group [vWF: (120.16 ± 16.57)% vs. (118.12 ± 14.32)%; PAF: 12.01 ± 3.70 vs. 13.33 ± 1.10; t-PA: 9.75 ± 1.60 vs. 7.59 ± 2.46; Fib: 2.73 ± 0.49 vs. 3.09 ± 0.50; D-dimer: 0.233 ± 0.101 vs. 0.252 ± 0.088, all P>0.05]. There were changes in coagulation and fibrinolysis status in patients with AMI and UAP at the initial stage, the level of t-PA was decreased significantly. For patients with AMI and UAP, there were no obvious differences in coagulation and fibrinolysis parameters between combination therapy of clopidogrel and aspirin and aspirin alone.

Effects of Chinese herbal medicine Xinfeng Capsule on expressions of platelet-activating factor and interleukins 6 and 17 in peripheral blood of rats with adjuvant arthritis

To observe the levels of platelet-activating factor (PAF), interleukin-6 (IL-6) and IL-17 in peripheral blood of rats with adjuvant arthritis (AA), and the effects of Xinfeng Capsule (XFC), a compound traditional Chinese herbal medicine. A total of 40 male Sprague-Dawley rats were randomized into normal control group, model group, methotrexate (MTX) group, Tripterygium Wilfordii polycoride Tablet (TPT) group, and XFC group, respectively. AA was induced in rats by intracutaneous injection of 0.1 mL Freund's complete adjuvant in the right hindlimb. Contents of PAF, IL-6 and IL-17 in peripheral blood were measured by enzyme-linked immunosorbent assay. Body weight of rats, paw swelling and arthritis index (AI) were also observed. Compared with the normal control group, the levels of PAF, IL-6 and IL-17 in peripheral blood, paw swelling and AI were significantly increased in the model group (P<0.01). Compared with the model group, levels of PAF, IL-6 and IL-17, paw swelling and AI of the three drug-treated groups were significantly decreased (P<0.01). The body weight of the XFC group was significantly higher than those of the MTX- and TPT-treated groups. Compared with the MTX- and TPT-treated groups, level of PAF in the XFC group was significantly increased (P<0.05). The level of PAF in peripheral blood of the AA rats was positively correlated with IL-6 and IL-17 levels in peripheral blood, paw swelling and AI (P<0.01). The expression of PAF increases in peripheral blood of rats with AA, and it correlates with IL-6, IL-17, paw swelling and AI. XFC can decrease the expression of PAF, restrain infection induced by the activation of platelets, decrease the levels of IL-6 and IL-17, and hence decrease the paw swelling of rats with AA.

Cytarabine Induced Pericardial Tamponade

Abstract 4298A 69 year old woman with a history of well controlled hypertension and a single episode of viral pericarditis initially presented to her physician with persistent leukocytosis and anemia. Bone marrow biopsy and aspiration revealed acute monocytic leukemia (FAB M5b) with normal cytogenetics. Induction chemotherapy was given with idarubicin 12 mg/m2 for 3 days and continous infusion cytarabine 200 mg/m2 for 7 days. Repeat bone marrow biopsy and aspiration on day 14 showed complete remission. Consolidation chemotherapy was administered with idarubicin 12 mg/m2 for 2 days and continuous infusion cytarabine 100 mg/m2 for 5 days. Prior to discharge from the hospital, she developed sudden onset of substernal chest pain associated with tachycardia and shortness of breath. Physical exam did not reveal jugular-venous distension; however, a slight friction rub was auscultated. Development of a pericardial effusion was suspected. Chest roenterogram demonstrated a mildly enlarged cardiac silhouette with a small left pleural effusion. Serum troponin-I and beta natriutretic peptide levels were within normal limits. Transthoracic echocardiogram was performed immediately which showed a moderate pericardial effusion with right ventricular collapse consistent with pericardial tamponade. A pericardial drain was placed which drained 900 cc of serous fluid. Laboratory studies on the fluid showed WBC of 6,500, LDH 1069, glucose 93, RBC 150, total protein of 4.1, albumin of 2.1 and pH of 7.0. Cultures did not yield bacterial or viral growth. Cytological analysis did not reveal evidence of leukemia. Based on these findings, a diagnosis of cytarabine induced pericardial effusion was strongly suspected.The patient improved rapidly and within 24 hours, pericardial drain was removed and a repeat TTE showed complete resolution of the pericardial effusion. Repeat bone marrow biopsy and aspiration after consolidation chemotherapy continued to show complete remission. Given that her effusion was likely cytarabine induced, the decision to discontinue further consolidation chemotherapy with cytarabine was made. Instead, maintenance therapy with azacytidine at 50 mg/m2 intravenously daily for 5 days to be repeated every four to six weeks was initiated. After five cycles, surveillance bone marrow biopsy and aspiration has continued to show complete remission. Of the known cardiac toxicities associated with chemotherapy drugs, pericarditis and pericardial effusion are uncommon. They have been reported in association with high dose cyclophosphamide, bleomycin, cytarabine, busulphan, imatinib and all trans retinoic acid. Specifically, capillary leak syndrome, non cardiogenic pulmonary edema and pericardial effusion have been reported with high dose cytarabine. This is the first case of a concurrent pericardial effusion with tamponade with cytarabine evolving so rapidly. The pathophysiology regarding the development of pericardial effusion in this setting is unknown. It has been speculated that direct cellular damage occurs leading to a cascade of events developing eventually into an effusion as well as an immune mediated delayed hypersensitivity. Elevated levels of tumor necrosis factor and platelet activating factor in two patients who developed a capillary leak syndrome after high dose cytarabine therapy have been reported. The strongest theory of a delayed immune mediated mechanism is most accepted given the development of pericardial effusions have been documented after multiple doses of chemotherapy.Clinicians should maintain a high level of suspicion for this complication as it has a rapid onset and potentially lethal complications. A literature search yielded four cases of acute pericardial effusions in which the only commonality was the use of cytarabine. In regards to our patient, a baseline nuclear heart scan was normal. To note, she did have a previous episode of suspected viral pericarditis without effusion, two months prior to her diagnosis of AML, which may have some role in the subsequent development of a pericardial effusion. It is reported that 10–30% of patients with acute pericarditis have recurrent disease that is often associated with an effusion. It may be postulated that perhaps those patients predisposed to recurrent pericarditis are sensitized to develop this complication upon the treatment with cytarabine or other chemotherapeutic agents. Disclosures:No relevant conflicts of interest to declare. [Display omitted]

Inhibition of Lipoprotein-Associated Phospholipase A2 Ameliorates Inflammation and Decreases Atherosclerotic Plaque Formation in ApoE-Deficient Mice

BackgroundLipoprotein-associated phospholipase A2 (Lp-PLA2) is thought to play modulatory roles in the development of atherosclerosis. Here we evaluated the effects of a specific lp-PLA2 inhibitor on atherosclerosis in ApoE-deficient mice and its associated mechanisms.Methodology/Principal FindingsApoE-deficient mice fed an atherogenic high-fat diet for 17 weeks were divided into two groups. One group was administered the specific lp-PLA2 inhibitor, darapladib (50 mg/kg/day; p.o.) daily for 6 weeks, while the control group was administered saline. We observed no differences in body weight and serum lipids levels between the two groups at the end of the dietary period. Notably, serum lp-PLA2 activity as well as hs-CRP (C-reactive protein) and IL-6 (Interleukin-6) levels were significantly reduced in the darapladib group, compared with the vehicle group, while the serum PAF (platelet-activating factor) levels were similar between the two groups. Furthermore, the plaque area through the arch to the abdominal aorta was reduced in the darapladib group. Another finding of interest was that the macrophage content was decreased while collagen content was increased in atherosclerotic lesions at the aortic sinus in the darapladib group, compared with the vehicle group. Finally, quantitative RT-PCR performed to determine the expression patterns of specific inflammatory genes at atherosclerotic aortas revealed lower expression of MCP-1, VCAM-1 and TNF-α in the darapladib group.Conclusions/SignificanceInhibition of lp-PLA2 by darapladib leads to attenuation of in vivo inflammation and decreased plaque formation in ApoE-deficient mice, supporting an anti-atherogenic role during the progression of atherosclerosis.

The inhibition of lipoprotein-associated phospholipase A2 exerts beneficial effects against atherosclerosis in LDLR-deficient mice

To investigate the effects of darapladib, a specific inhibitor of lipoprotein-associated phospholipase A2 (lp-PLA2), on inflammation and atherosclerotic formation in the low density lipoprotein receptor (LDLR)-deficient mice. Six-week-old LDLR-deficient mice were fed an atherogenic high-fat diet for 17 weeks and then randomly divided into two groups. One group was administered darapladib (50 mg·kg(-1)·d(-1); po) for 6 weeks. The other group was administered saline as a control. Serum lipid levels were measured using the corresponding kits, and three inflammatory markers--interleukin-6 (IL-6), C reactive protein (hs-CRP), and platelet activating factor (PAF)--were determined using ELISA. Atherosclerotic plaque areas were stained with Sudan IV, and inflammatory gene expression at the lesions was evaluated using quantitative real-time PCR. The body weight and serum lipid level between the two groups were similar at the end of the dietary period. The serum lp-PLA2 activity, hs-CRP and IL-6 levels, however, were significantly reduced in the darpladib group. The inhibition of lp-PLA2 did not alter the serum PAF level. Furthermore, the plaque area, from the aortic arch to the abdominal aorta, was significantly reduced in the darpladib group. Additionally, the expression of inflammatory genes monocyte chemotactic protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) was significantly reduced at the lesions in the darapladib group. Inhibition of lp-PLA2 by darapladib decreases the inflammatory burden and atherosclerotic plaque formation in LDLR-deficient mice, which may be a new strategy for the treatment of atherosclerosis.

Serum heart-type fatty acid-binding protein and platelet activating factor levels in Kawasaki disease and their clinical significance

Forty six children with Kawasaki disease (observer group) were classified as coronary artery lesions (CAL) subgroup (19 cases) and non-coronary artery lesions (NCAL) subgroup (27 cases)according to echocardiography; 50 healthy children served as control group.Serum heart-type fatty acidbinding protein (h-FABP), platelet activating factor (PAF), cardiac tropnin Ⅰ (cTnI) and creatine kinase isoenzyme MB (CK-MB) levels of all subjects were detected.The results showed that the h-FABP and cTnI levels and positive rate in observer group were higher those in control group (P ＜ 0.05 ), while there were no differences in CK-MB level and positive rate between two groups ( P ＞ 0.05 ).The h-FABP positive rate in observation group was higher than the positive rates of cTnI and CK-MB (P ＜0.05).The PAF level, PLT and polymorphonuclear neutrophil count in observer group were higher than those in control group ( P ＜0.05).The h-FABP and PAF levels in CAL subgroup were higher than those in NCAL subgroup (P ＜0.05).The results suggest that serum h-FABP and PAF can be used as diagnostic indicators for Kawasaki disease complicated with coronary artery lesions. Key words: Mucocutaneous lymph node syndrome; Fatty acid-binding proteins

Platelet-Activating Factor Blockade Inhibits the T-Helper Type 17 Cell Pathway and Suppresses Psoriasis-Like Skin Disease in K5.hTGF-β1 Transgenic Mice

Platelet-activating factor (PAF), a potent biolipid mediator, is involved in a variety of cellular transduction pathways and plays a prominent role in inducing inflammation in different organs. We used K5.hTGF-β1 transgenic mice, which exhibit an inflammatory skin disorder and molecular and cytokine abnormalities with strong similarities to human psoriasis, to study the pathogenic role of PAF. We found that injecting PAF into the skin of transgenic mice led to inflammation and accelerated manifestation of the psoriatic phenotype by a local effect. In contrast, injecting mice with PAF receptor antagonist PCA-4248 lowered the PAF level (most likely by depressing an autocrine loop) and neutrophil, CD68(+) cell (monocyte/macrophage), and CD3(+) T-cell accumulation in the skin and blocked progression of the psoriasis-like phenotype. This effect of PAF blockade was specific and similar to that of psoralen-UV-A and was paralleled by a decrease in abnormally elevated mRNA and/or protein levels of T-helper type 17 cell-related cytokines IL-17A, IL-17F, IL-23, IL-12A, and IL-6 and its transcription factor signal transducer and activator of transcription 3. In contrast, PCA-4248 treatment up-regulated mRNA levels of cyclooxygenase-2 and IL-10 in dorsal skin and release of IL-10 in serum and skin. Interfering with PAF may offer the opportunity to develop novel therapeutic strategies for inflammatory psoriasis and associated comorbidities, including metabolic syndrome and atherosclerosis, in which the IL-17 axis may be involved.

Investigation of platelet activating factor (PAF) in acute myocardial infarction

Objective To investigate the level of platelet activating factor (PAF) in acute myocardial infarction (AMI) in minipig model and patients, and to study the relationship between PAF and lethal arrhythmia referring to ventricular fibrillation and ventricular tachycardia. Method ( 1 ) The levels of PAF in minipig models ( n = 20) were measured by using ELISA before and 1h after occlusion of left anterior descending coronary artery with balloon at the junction of 1/3 middle and distal portion. The lethal arrythmia was recorded by using electrocardiography. (2) In patients with AMI (n = 72), the levels of PAF were measured on arrival, and 24 h,48 h and 72 h later. The lethal arrythmia, acute heart failure and cardiogenic shock were documented. Results ( 1 ) In minipigs with occlusion of coronary artery for one hour, the mean level of PAF increased from (4.66± 2.89)ng/mL to (6.00±2.82) ng/mL,and thus the increment in PAF was (1 .34± 1.40) ng/mL (P ＜ 0.05). In 13 minipigs with lethal anythmia after occlusion of coronary artery for one hour, the increment in mean level of PAF was ( 1.92 ± 1 .34) ng/mL, whereas the increment in mean level of PAF in other 7 minipigs without lethal arrythmia after occlusion of coronary artery for one hour was as low as (0.28 ± 0. 74 ) ng/mL ( P ＜ 0. 05 ). ( 2 ) In patients, the mean levels of PAF on arrival, 24 h,48 h,and 72 hous after admission were (0.47 ± 0.05) ng/mL,(2.38±0.12) ng/mL,(3.65±0.15) ng/mL and (3.02±0.10) ng/mL, respectively. Of 72 ACI patients, 40 (55%) had complication of lethal arrythnia, heart failure or cardiogenic shock and their mean level of PAF 48 h after admission was (4.72 ± 0.16) ng/mL, whereas mean level of PAF in other 32 (44.44%) without complications was (2.31 ±0.03) ng/mL ( P ＜0.05). Conclusions The level of PAF increased after acute myocardial infarction, and the minipigs and AMI patients complicated with lethal arrythmia had higher levels of PAF. Key words: Platelet activating factor (PAF); Acute myocardial infarction; Ischemic/repeffusion; Arrhythmia

Dual Roles of Endogenous Platelet-Activating Factor Acetylhydrolase in a Murine Model of Necrotizing Enterocolitis

Human preterm infants with necrotizing enterocolitis (NEC) have increased circulating and luminal levels of platelet-activating factor (PAF) and decreased serum PAF-acetylhydrolase (PAF-AH), the enzyme that inactivates PAF. Formula supplemented with recombinant PAF-AH decreases NEC in a neonatal rat model. We hypothesized that endogenous PAF-AH contributes to neonatal intestinal homeostasis and therefore developed PAF-AH mice using standard approaches to study the role of this enzyme in the neonatal NEC model. After exposure to a well-established NEC model, intestinal tissues were evaluated for histology, proinflammatory cytokine mRNA synthesis, and death using standard techniques. We found that mortality rates were significantly lower in PAF-AH pups compared with wild-type controls before 24 h of life but surviving PAF-AH animals were more susceptible to NEC development compared with wild-type controls. Increased NEC incidence was associated with prominent inflammation characterized by elevated intestinal mRNA expression of sPLA2, inducible NOS, and CXCL1. In conclusion, the data support a protective role for endogenous PAF-AH in the development of NEC, and because preterm neonates have endogenous PAF-AH deficiency, this may place them at increased risk for disease.

The levels of platelet-activating factor and nitric oxide synthase in bronchial asthma at high altitude

To investigate levels of platelet- activating factor (PAF) and nitric oxide synthase(NOS) in plateau asthma. Peripheral blood platelet was counted and the serum level of PAF, TNOS, iNOS and cNOS were measured by ELISA in patients with asthma who lived at plateau and at plain respectively and healthy volunteers as the plan control group and in plateau control group. The data were expressed as x(-) ± s, and one way ANOVA was used for comparison of means; The correlation of 2 variables was estimated by Spearson rank correlation coefficience. The PLT count was (166 ± 46) × 10(9)/L in the plateau asthma group and (140 ± 47) × 10(9)/L in the plateau control group, and both were significantly lower than those of the plain control group [(237 ± 98) × 10(9)/L] and the plan asthma group [(232 ± 71) × 10(9)/L, P < 0.01]. The levels of serum PAF in the asthma groups were higher than those of the control groups. The level of serum PAF in the plan asthma group [(877 ± 297) pg/L], was not only higher than that in the plan control group [(290 ± 132) pg/L], but also higher than that in the plateau asthma group [(429 ± 254) pg/L]; the difference being significant among groups (F = 66.08, P < 0.01). The PLT count showed a positive correlation with the level of PAF (r = 0.283, P < 0.01). The levels of TNOS, iNOS, and cNOS were not statistically different (P > 0.05) between the plain control group and the plateau control group. The levels of TNOS, iNOS and cNOS in plain asthmatic group [(36.2 ± 23.0), (20.3 ± 14.7) and (15.9 ± 8.4) U/ml respectively] were significantly higher than those of the plateau control [(11.9 ± 1.3), (9.4 ± 1.5) and (4.9 ± 0.5) U/ml] and the plateau asthmatic [(21.0 ± 2.3), (15.4 ± 2.5) and (5.3 ± 0.8) U/ml] groups(F = 17.197, 8.258, 34.250, respectively, P < 0.01). The increase of iNOS level was more significant. Asthma in plateau area is associated with decrease of the levels of PLT, PAF and NOS.

Role of AKT‐glycogen synthase kinase axis in monocyte activation in human beings with and without type 2 diabetes

Monocyte activation by chemokines is a vital trigger for initiation of atherosclerotic process. Circulating levels of platelet activating factor (PAF), a recognized chemokine, is known to be increased in type 2 diabetes that is linked to accelerated atherosclerosis. To explore the molecular basis we examined the signalling pathways involved in PAF induced monocyte activation. PAF increased migration in monocytes obtained from THP-1 cells, nondiabetic and diabetic subjects. This effect was blocked by AKT inhibition. It did so by phosphorylation of glycogen synthase kinase (GSK)-3βS9, which was completely blocked by AKT inhibition. Additionally, PAF induced GSK-3β phosphorylation was linked to Rac-1 activation and Rho-A inactivation leading to migration. Paradoxically, inhibition of GSK-3β phosphorylation also augmented monocyte migration in THP-1, ND and diabetic monocytes through phosphorylation of AKT and activation of Rho-A that was independent of GSK. This was validated when (i) overexpression of dominant negative mutants of Rho-A reversed GSK inhibitor induced monocyte migration and (ii) AKT inhibition blocked GSK inhibitor induced Rho-A activity. Constitutively active ARAP3 (Rho-GAP) appears to have a regulatory role in monocyte activity during GSK inhibition. Finally, inhibition of monocyte GSK-3β activity (by inhibitors and genetic manipulation) led to enhanced migration in diabetes compared to persons without diabetes. We conclude that diabetic monocytes show increased migratory capacity in response to GSK-3β inhibition. GSK inhibitors developed to treat the metabolic complications of diabetes should therefore be used with caution.

Phospholipase A2 inhibitors protect against prion and Aβ mediated synapse degeneration

BackgroundAn early event in the neuropathology of prion and Alzheimer's diseases is the loss of synapses and a corresponding reduction in the level of synaptophysin, a pre-synaptic membrane protein essential for neurotransmission. The molecular mechanisms involved in synapse degeneration in these diseases are poorly understood. In this study the process of synapse degeneration was investigated by measuring the synaptophysin content of cultured neurones incubated with the prion derived peptide (PrP82-146) or with Aβ1-42, a peptide thought to trigger pathogenesis in Alzheimer's disease. A pharmacological approach was used to screen cell signalling pathways involved in synapse degeneration.ResultsPre-treatment with phospholipase A2 inhibitors (AACOCF3, MAFP and aristolochic acids) protected against synapse degeneration in cultured cortical and hippocampal neurones incubated with PrP82-146 or Aβ1-42. Synapse degeneration was also observed following the addition of a specific phospholipase A2 activating peptide (PLAP) and the addition of PrP82-146 or Aβ1-42 activated cytoplasmic phospholipase A2 within synapses. Activation of phospholipase A2 is the first step in the generation of platelet-activating factor (PAF) and PAF receptor antagonists (ginkgolide B, Hexa-PAF and CV6029) protected against synapse degeneration induced by PrP82-146, Aβ1-42 and PLAP. PAF facilitated the production of prostaglandin E2, which also caused synapse degeneration and pre-treatment with the prostanoid E receptor antagonist AH13205 protected against PrP82-146, Aβ1-42 and PAF induced synapse degeneration.ConclusionsOur results are consistent with the hypothesis that PrP82-146 and Aβ1-42trigger abnormal activation of cytoplasmic phospholipase A2 resident within synapses, resulting in elevated levels of PAF and prostaglandin E2that cause synapse degeneration. Inhibitors of this pathway that can cross the blood brain barrier may protect against the synapse degeneration seen during Alzheimer's or prion diseases.

The effect of platelet activating factor on the motility and acrosome reaction of ram spermatozoa.

Summary Platelet activating factor (PAF) is a novel signaling phospholipids that in addition to platelet activation has many biological properties. The acrosome reaction, as an essential step in mammalian fertilization, can occur in response to several agents such as PAF. Therefore, the present study aimed to assess the effect of PAF on the motility and acrosome reaction of ram spermatozoa. Semen was collected from 18 fertile rams and incubated with four levels of PAF (10 -7 , 10 -8 , 10 -9 and 10 -10 mol) at 37°C for 15, 30, 60 or 120 min. Sperm motility and acrosome reaction were analyzed at varying levels of PAF with different incubation periods. With increasing PAF concentration, acrosome reaction was enhanced, while sperm motility was reduced (P<0.001). As the period of incubation increased, there was a gradual decrease in sperm motility and increase in acrosome reaction percentages. There were high correlation between PAF concentrations and incubation times on induction of acrosome reaction (R

A regulatory role of LPCAT1 in the synthesis of inflammatory lipids, PAF and LPC, in the retina of diabetic mice

Platelet-activating factor (PAF) and lysophosphatidylcholine (LPC) are potent inflammatory lipids. Elevated levels of PAF and LPC are associated with the onset of diabetic retinopathy and neurodegeneration. However, the molecular mechanisms underlying such defects remain elusive. LPCAT1 is a newly reported lysophospholipid acyltransferase implicated in the anti-inflammatory response by its role in conversion of LPC to PC. Intriguingly, the LPCAT1 enzyme also catalyzes the synthesis of PAF from lyso-PAF with use of acetyl-CoA as a substrate. The present studies investigated regulatory roles of LPCAT1 in the synthesis of inflammatory lipids during the onset of diabetes. Our work shows that LPCAT1 plays an important role in the inactivation of PAF by catalyzing the synthesis of alkyl-PC, an inactivated form of PAF with use of acyl-CoA and lyso-PAF as substrates. In support of a role of LPCAT1 in anti-inflammatory responses in diabetic retinopathy, LPCAT1 is most abundantly expressed in the retina. Moreover, LPCAT1 mRNA levels and acyltransferase activity toward lyso-PAF and LPC were significantly downregulated in retina and brain tissues in response to the onset of diabetes in Ins2(Akita) and db/db mice, mouse models of type 1 and type 2 diabetes, respectively. Conversely, treatment of db/db mice with rosiglitazone, an antidiabetes compound, significantly upregulated LPCAT1 mRNA levels concurrently with increased acyltransferase activity in the retina and brain. Collectively, these findings identified a novel regulatory role of LPCAT1 in catalyzing the inactivation of inflammatory lipids in the retina of diabetic mice.

Influence of intensive insulin therapy on the intestinal microcirculatory dysfunction in rats with sepsis

To explore the influence of intensive insulin therapy on the intestinal microcirculatory dysfunction of rats suffering from sepsis. The sepsis model of rat was reproduced by cecal ligation and puncture. Forty-eight male Sprague-Dawley (SD) rats were randomly divided into control group, sepsis group, and insulin treatment group (n =16 in each group). The intestinal tissue was harvested in the experimental groups before and 3, 6, 12 and 24 hours after insulin administration. Platelet activating factor (PAF), prostacyclin (PGI(2)) and thromboxane (TXA(2)) in the intestine were measured by radioimmunoassay. The levels of PAF, PGI and TXA(2) were significantly elevated in sepsis group at 3 hours, and peaked at 6 hours, then decreased gradually. At each time point they were higher in sepsis group compared with that of control group (all P<0.05), especially TXA(2), which was more evident, while PGI(2)/TXA(2) ratio showed a lowering. In contrast, PAF, PGI(2) and TXA(2) were significantly decreased in insulin treatment group compared with the sepsis group, especially TXA(2), which was more evident ( all P<0.05), but PGI(2)/TXA(2) ratio showed an elevation. Insulin plays an important role in amelioration of microcirculatory dysfunction in sepsis. Through improving the disorder of PGI(2)/TXA(2)system and antagonising the expression of PAF, insulin alleviates vasospasm, inhibits platelet aggregation and thrombosis, thus protecting the function of intestine.

Oxidative damage in dengue fever

Oxidative stress may be important in the pathogenesis of dengue infection. Using accurate markers of oxidative damage, we assessed the extent of oxidative damage in dengue patients. The levels of hydroxyeicosatetraenoic acid products (HETEs), F 2-isoprostanes (F 2-IsoPs), and cholesterol oxidation products (COPs) were measured in 28 adult dengue patients and 28 age-matched study controls during the febrile, defervescent, and convalescent stages of infection. We compared the absolute and the percentage change in these markers in relation to key clinical parameters and inflammatory markers. The levels of total HETEs and total HETEs/arachidonate, total F 2-IsoPs/arachidonate, and COPs/cholesterol were higher during the febrile compared to the convalescent level. Total HETEs correlated positively with admission systolic blood pressure ( r = 0.52, p < 0.05), whereas an inverse relationship was found between 7β-hydroxycholesterol and systolic and diastolic blood pressure ( r = −0.61 and −0.59, respectively, p < 0.01). The urinary F 2-IsoP level was higher in urine during the febrile stage compared to the convalescent level. Despite lower total cholesterol levels during the febrile stage compared to convalescent levels, a higher percentage of cholesterol was found as COPs (7β-, 24-, and 27-hydroxycholesterol). The levels of platelet-activating factor–acetylhydrolase activity, vascular cellular adhesion molecule-1, tumor necrosis factor-α, and high-sensitivity C-reactive protein were higher during the febrile stage compared to their convalescent levels ( p < 0.01). Markers of oxidative damage are altered during the various stages of dengue infection.

The emerging roles of PAF acetylhydrolase

Platelet-activating factor (PAF), a phospholipid autacoid with potent effects throughout the innate immune system, is selectively degraded by two small families of PAF acetylhydrolases (PAF-AHs). These Ca2+-independent phospholipases A2 display remarkable specificity for the length of the sn-2 residue, but this selectivity is lost as the residue gains oxygen functions. Two of the PAF-AHs therefore are specific oxidized phospholipid phospholipases that reduce inflammation, but also remove oxidatively truncated phospholipids that induce apoptosis. The roles of these enzymes are manifold, and their separate and combined functions are now being addressed in model systems and clinical studies.

Platelet-Activating Factor Involvement in Thioacetamide-Induced Experimental Liver Fibrosis and Cirrhosis

Platelet-activating factor (PAF) is a potent lipid inflammatory mediator acting on cells through its specific receptor. Plasma PAF-acetylhydrolase (PAF-AH) is the main enzyme that inactivates PAF in blood, participating in its homeostasis. The objective of this study was to investigate the involvement of PAF in the liver fibrotic process using an experimental animal model. Liver fibrosis was induced in adult male Wistar rats by administration of thioacetamide (TAA) in drinking water (300 mg/l) for three months. The animals were sacrificed at time 0 (control group) and after 1, 2, and 3 months. PAF levels in liver and blood and PAF-AH activity in plasma were determined. Liver histopathological examination was also performed. TAA administration resulted in progressively increased liver fibrosis, leading finally to the formation of cirrhotic nodules in the liver. Throughout the experiment PAF levels in liver tissue remained stable. "Total" ("free" plus "bound") PAF levels in blood decreased, reaching statistically significant differences in the first and third months compared with the control group (P < 0.05). "Free" PAF levels in blood were higher at one month (P < 0.05) and decreased gradually thereafter. In all treated groups, "bound" PAF levels in blood decreased whereas plasma PAF-AH activity increased (P < 0.05) compared with the control group. Our data indicated alterations of PAF levels in blood and PAF-AH activity during fibrosis induction, implicating participation of PAF in the liver fibrotic process.