Platelet-Activating Factor as an Effector for Environmental Stressors

Environmental stressors exert a profound effect on humans. Many environmental stressors have in common the ability to induce reactive oxygen species. The goal of this chapter is to present evidence that the potent lipid mediator platelet-activating factor (PAF) is involved in the effects of many stressors ranging from cigarette smoke to ultraviolet B radiation. These environmental stressors can generate PAF enzymatically as well as PAF-like lipids produced by free radical-mediated attack of glycerophosphocholines. Inasmuch as PAF exerts both acute inflammation and delayed immunosuppressive effects, involvement of the PAF system can provide an explanation for many consequences of environmental stressor exposures.

Metabolomics analyses identify platelet activating factors and heme breakdown products as Lassa fever biomarkers

Lassa fever afflicts tens of thousands of people in West Africa annually. The rapid progression of patients from febrile illness to fulminant syndrome and death provides incentive for development of clinical prognostic markers that can guide case management. The small molecule profile of serum from febrile patients triaged to the Viral Hemorrhagic Fever Ward at Kenema Government Hospital in Sierra Leone was assessed using untargeted Ultra High Performance Liquid Chromatography Mass Spectrometry. Physiological dysregulation resulting from Lassa virus (LASV) infection occurs at the small molecule level. Effects of LASV infection on pathways mediating blood coagulation, and lipid, amino acid, nucleic acid metabolism are manifest in changes in the levels of numerous metabolites in the circulation. Several compounds, including platelet activating factor (PAF), PAF-like molecules and products of heme breakdown emerged as candidates that may prove useful in diagnostic assays to inform better care of Lassa fever patients.

Lassa fever afflicts tens of thousands of people in West Africa each year. The disease progresses rapidly, but there are no tests available to determine which patients are at high risk for dying. We measured the levels of small molecules in the blood of febrile patients with and without infection by LASV that presented to Kenema Government Hospital in Sierra Leone using Ultra High Performance Liquid Chromatography Mass Spectrometry (LCMS), which identifies compounds based on their precise mass. Computational analyses were used to identify compounds that differed in patients with an acute LASV infection, patients with evidence of prior exposure to LASV and patients with fever, but who did not have evidence of exposure to LASV. Several serum metabolites, including factors that are involved in blood clotting and breakdown products of heme, were identified that may prove useful in diagnostic assays that will inform better care of Lassa fever patients or development of therapeutic interventions.

Prognostic factors of clinical endpoints in elderly patients with atrial fibrillation during a 2-year follow-up in China: An observational cohort study

This study aimed to reveal the incidence of clinical endpoints in elderly patients with atrial fibrillation (AF) during a 2-year follow-up and evaluate the related prognostic factors of these endpoints.In total, 200 elderly patients with AF and 400 age- and sex-matched patients without AF were enrolled in this prospective observational cohort study. The incidence of clinical endpoints, including thromboembolism, hemorrhage, and all-cause death, during the 2-year follow-up was analyzed. Other follow-up data, including disease history, laboratory examinations, medication status, and other clinical endpoints, were collected. The prognostic factors of these clinical endpoints were then evaluated by Cox-survival analysis. In addition, the predicative role of C-reactive protein (CRP) and platelet-activating factor (PAF) on these clinical endpoints was analyzed.The incidence of clinical endpoints, including thromboembolism, hemorrhage, and all-cause death, was significantly higher in patients with AF than in those without AF (27.8% vs 9.8%, 29.4% vs 12.7%, and 28.7% vs 11.6%, respectively; all P < .001). Antithrombotic therapy significantly reduced the incidences of all-cause deaths (P < .05). Body mass index (BMI) and digoxin were prognostic risk factors of thromboembolism; age, massive hemorrhage history, and digoxin were prognostic risk factors of hemorrhage and age, renal insufficiency history, massive hemorrhage history, and digoxin were prognostic risk factors of all-cause death (P < .05). Further, both CRP and PAF were prognostic risk factors of thromboembolism and massive hemorrhage (P < .05).Age, BMI, massive hemorrhage history, and digoxin appear to be prognostic risk factors of clinical endpoints in elderly patients with AF. Appropriate drug use during follow-up may be beneficial in preventing the occurrence of clinical endpoints in elderly patients with AF.

TRIAL REGISTRATION NUMBER

ChiCTR-OCH-13003479.

[Association between platelet-activating factor acetylhydrolase gene polymorphisms and gastrointestinal bleeding in children with Henoch-Schönlein purpura]

OBJECTIVE

To study the association between the single nucleotide polymorphisms (SNPs) of the ninth exon Val279Phe of platelet-activating factor acetylhydrolase (PAF-AH) gene and gastrointestinal bleeding in children with Henoch-Schönlein purpura (HSP).

METHODS

A total 516 children with HSP were enrolled, among whom 182 had gastrointestinal bleeding and 334 had no gastrointestinal bleeding. PCR was used to investigate the distribution of genotypes and alleles in the SNPs of Val97Phe. The plasma PAF-AH activity was measured, as well as the levels of platelet-activating factor (PAF), granular membrane protein-140 (GMP-140), β-thromboglobulin (β-TG), and platelet factor 4 (PF4).

RESULTS

The Val279Phe genotype and allele frequencies were in Hardy-Weinberg equilibrium, and the homozygous genotype TT and heterozygotes accounted for 0.97% and 6.05% respectively. The gastrointestinal bleeding group had a significantly higher allele frequency than the control group (5.22% vs 3.33%; P<0.01). The HSP patients with GG genotype in the gastrointestinal bleeding group had significantly higher levels of plasma PAF and GMP-140 than those in the non-gastrointestinal bleeding group (P<0.05), while the non-gastrointestinal bleeding group had a significantly higher PAF-AH activity than the gastrointestinal bleeding group (P<0.05). There were no significant differences in β-TG and PF4 between the two groups (P>0.05).

CONCLUSIONS

Val279Phe gene polymorphisms in PAF-AH are associated with PAF-AH activity and PAF and GMP-140 levels and may be a risk factor for HSP with gastrointestinal bleeding.

Quantitative determination of major platelet activating factors from human plasma

Platelet activating factor (PAF) is a potent lipid mediator that is involved in many important biological functions, including platelet aggregation and neuronal differentiation. Although an ELISA assay has been used to measure PAF levels, it cannot distinguish between its isoforms. To achieve this, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been used instead. However, isobaric lysophosphatidylcholine (lyso PC), which is often present in large amounts in complex biological samples and has similar retention times in many LC conditions, can affect the accurate measurement of PAF. The present study examined the fragmentation behavior of major PAF and lyso PC during various MS/MS conditions. Fragment ions at m/z 184 and at m/z 104 were abundantly observed from MS/MS of lyso PCs. PAF provided a dominant fragment ion at m/z 184, but a fragment ion at m/z 104 was almost never produced, regardless of the collision energy. Thus, the two fragment ions at m/z 184 and m/z 104 were used to accurately measure PAF levels. First, the fragment ion at m/z 184 and the retention time of PAF in LC-MS/MS were used to identify and quantitate PAF. However, if there were small retention time shifts, which are common in multiple sample runs, and lipid composition in a sample is very complicated, the fragment ion at m/z 104 was used to confirm whether the fragment ion at m/z 184 belonged to PAF. This novel method accurately determined the major PAF (C16:0 PAF, C18:0 PAF, and C18:1 PAF) levels in human plasma.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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].

CONCLUSIONS

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.

[Microcirculation in the injured spleen by different operations in children]

43 children were operated on spleen injury: 14 were splenectomized; 29 splenectomy were completed with partial spleen tissue autotransplantation into the omentum. Changes of homeostatic system, hemoreology and immune status were followed up within 1 year after the operation, Connections between the type of the operation performed and the listed above changes were followed.

Platelet-activating factor levels of serum and gingival crevicular fluid in nonsmoking patients with periodontitis and/or coronary heart disease

The purpose of the present study was to investigate systemic and local levels of platelet-activating factor (PAF), a potent proinflammatory mediator implicated in cardiovascular pathophysiology in adult nonsmoking patients with periodontitis with or without coronary heart disease (CHD). Eighty-seven volunteers, 25 periodontitis patients, 19 periodontitis with CHD patients, 19 CHD patients, and 24 healthy controls were included, and periodontal conditions were assessed. Gingival crevicular fluid (GCF) and venous blood were collected, and PAF levels were measured by enzyme-linked immunosorbent assay. PAF levels in serum (303.3 ± 204 pg/ml) and in GCF (26.3 ± 6 pg/μl) of the periodontitis group with CHD, the periodontitis group (serum, 302.4 ± 241 pg/ml and GCF, 26.3 ± 8 pg/μl) and the CHD group (serum, 284.7 ± 192 pg/ml and GCF, 20.8 ± 6 pg/μl) were significantly higher than the healthy control group (serum, 65.4 ± 35 pg/ml and GCF, 7.7 ± 3 pg/μl; p < 0.05). In summary, the present study could demonstrate that in patients with periodontitis, the inflammatory mediator PAF is released into serum at least in the same range as for patients with coronary heart disease. However, no additive effects were seen when both conditions were present.

Platelet-Activating Factor in Human Normal Tears

PURPOSE

To measure the concentrations of platelet-activating factor (PAF) and lyso-PAF in tears of human eyes.

METHODS

Unilateral tear samples were collected from the conjunctival cul-de-sac of 12 healthy volunteers without any past histories of ocular surface diseases and 10 patients with allergic conjunctivitis (AC) by graduated disposable microcapillaries. C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF levels were determined by liquid chromatography-tandem mass spectrometry (LC/MS/MS).

RESULTS

The concentrations of C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF in tears from healthy volunteers were 0.44 +/- 0.39, 51.7 +/- 63.4, 61.9 +/- 75.9, and 10.7 +/- 14.7 ng/ml, respectively. Higher, but not significantly different, concentrations of all the four kinds of PAF molecules were detected in tears from AC patients. Significant correlations were demonstrated between the concentrations of C18:0-PAF and C18:0-lyso-PAF (r = 0.906; p < 0.01 in normal healthy volunteers and r = 0.939; p < 0.01 in AC patients), and between those of C16:0-PAF and C16:0-lyso-PAF (r = 0.944; p < 0.01 in normal healthy volunteers and r = 0.806; p = 0.015 in AC patients). Moreover, C18:0-PAF concentrations correlated significantly with those of C16:0-PAF (r = 0.885; p < 0.01 in normal healthy volunteers and r = 0.927; p < 0.01 in AC patients), while C18:0-lyso-PAF concentrations correlated significantly with those of C16:0-lyso-PAF (r = 0.972; p < 0.01 in normal healthy volunteers and r = 0.891; p < 0.01 in AC patients).

CONCLUSIONS

To our knowledge, this is the first report of the concentrations of different species of PAF (C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF) in human tears.

Platelet-activating factor, PAF acetylhydrolase, and severe anaphylaxis

BACKGROUND

Platelet-activating factor (PAF) is an important mediator of anaphylaxis in animals, and interventions that block PAF prevent fatal anaphylaxis. The roles of PAF and PAF acetylhydrolase, the enzyme that inactivates PAF, in anaphylaxis in humans have not been reported.

METHODS

We measured serum PAF levels and PAF acetylhydrolase activity in 41 patients with anaphylaxis and in 23 control patients. Serum PAF acetylhydrolase activity was also measured in 9 patients with peanut allergy who had fatal anaphylaxis and compared with that in 26 nonallergic pediatric control patients, 49 nonallergic adult control patients, 63 children with mild peanut allergy, 24 patients with nonfatal anaphylaxis, 10 children who died of nonanaphylactic causes, 15 children with life-threatening asthma, and 19 children with non-life-threatening asthma.

RESULTS

Mean (+/-SD) serum PAF levels were significantly higher in patients with anaphylaxis (805+/-595 pg per milliliter) than in patients in the control groups (127+/-104 pg per milliliter, P<0.001 after log transformation) and were correlated with the severity of anaphylaxis. The proportion of subjects with elevated PAF levels increased from 4% in the control groups to 20% in the group with grade 1 anaphylaxis, 71% in the group with grade 2 anaphylaxis, and 100% in the group with grade 3 anaphylaxis (P<0.001). There was an inverse correlation between PAF levels and PAF acetylhydrolase activity (P<0.001). The proportion of patients with low PAF acetylhydrolase values increased with the severity of anaphylaxis (P<0.001 for all comparisons). Serum PAF acetylhydrolase activity was significantly lower in patients with fatal peanut anaphylaxis than in control patients (P values <0.001 for all comparisons).

CONCLUSIONS

Serum PAF levels were directly correlated and serum PAF acetylhydrolase activity was inversely correlated with the severity of anaphylaxis. PAF acetylhydrolase activity was significantly lower in patients with fatal anaphylactic reactions to peanuts than in patients in any of the control groups. Failure of PAF acetylhydrolase to inactivate PAF may contribute to the severity of anaphylaxis.

Differential platelet-activating factor synthesis by monocytes and polymorphonuclear leukocytes from subjects with localized aggressive periodontitis

BACKGROUND AND OBJECTIVE

Platelet-activating factor is elevated in localized aggressive periodontitis. We previously demonstrated that the elevated level of platelet-activating factor in localized aggressive periodontitis is at least partially attributable to low levels of platelet-activating factor acetylhydrolase, the enzyme that catabolizes platelet-activating factor. The objective of this study was to determine if platelet-activating factor synthesis was also elevated in localized aggressive periodontitis. To test this, platelet-activating factor synthesis was quantified in the monocytes and polymorphonuclear neutrophils of periodontally healthy patients and of subjects with localized aggressive periodontitis.

MATERIAL AND METHODS

Cells were labeled with [(3)H]acetate and treated with vehicle or stimulated with calcium ionophore A23187. Platelet-activating factor was extracted and quantified by scintillation counting.

RESULTS

For both subject groups, resting monocytes and polymorphonuclear neutrophils produced platelet-activating factor, and calcium ionophore A23187 stimulated platelet-activating factor production in both cell types. However, calcium ionophore A23187-activated monocytes from subjects with localized aggressive periodontitis produced less platelet-activating factor than did activated periodontally healthy monocytes (p < 0.0001), suggesting an aberrant calcium ionophore A23187 response in monocytes from subjects with localized aggressive periodontitis. Indeed, when the data were expressed as fold induction of platelet-activating factor synthesis in response to calcium ionophore A23187, monocytes from subjects with localized aggressive periodontitis exhibited only a fourfold increase in platelet-activating factor synthesis, whereas calcium ionophore A23187-stimulated monocytes from periodontally healthy, chronic periodontitis and generalized aggressive periodontitis subjects produced approximately 12 times more platelet-activating factor than did resting monocytes. In contrast, both resting and activated localized aggressive periodontitis polymorphonuclear neutrophils synthesized more platelet-activating factor than did periodontally healthy polymorphonuclear neutrophils.

CONCLUSION

These data suggest that high levels of platelet-activating factor in subjects with localized aggressive periodontitis result from both increased synthesis and reduced catabolism. While localized aggressive periodontitis polymorphonuclear neutrophils contribute to increased platelet-activating factor mass through synthesis, the contribution of monocytes is probably the result of reduced catabolism by platelet-activating factor acetylhydrolase.

Levels of gingival tissue platelet activating factor after conventional and regenerative periodontal surgery

The hypothesis, a relationship between gingival tissue platelet activating factor (PAF) levels and healing after periodontal surgery, was tested by measuring PAF levels in gingival tissues collected from sites that had undergone flap surgery and guided tissue regeneration (GTR) or flap surgery alone. Using a split-mouth design, 20 intrabony defects were randomly assigned to treatment with flap surgery and GTR (group 1) or with flap surgery alone (group 2). Gingival tissue samples were obtained at surgery (baseline) and at 6-month follow-up evaluation visit. One half of each sample was used for analysis of PAF levels by high-performance liquid chromatography, and the other half of the sample was used for histomorphometric analysis that included measurements of number and diameter of blood vessels. PAF levels and diameter of blood vessels were significantly decreased (p < 0.01), and the number of blood vessels was significantly increased (p < 0.05) in both groups after 6 months compared to the baseline values. Postoperative number of blood vessels were significantly higher in group 1 (p < 0.05), whereas there was no significant difference in postoperative PAF levels between the two groups (p > 0.05). Based on the reported results, it is suggested that a decrease in gingival PAF levels might be found after conventional and regenerative periodontal surgery.

Opposite effects of WEB2086 on angiogenesis in atheromas and ischemic hindlimb of apoE gene deficient mice

BACKGROUND

Our previous research has suggested that platelet activating factor receptor was related to atherosclerosis. The present study investigated the effect of a platelet activating factor receptor antagonist-WEB2086 on angiogenesis in aortal plaque and ischemic hindlimb of apolipoprotein E-deficient mice.

METHODS

Eight-week-old apolipoprotein E-deficient mice were fed with a 0.15% cholesterol diet to develop advanced lesions. At age 32 weeks unilateral hindlimb ischemia was surgically induced and the mice were divided into two groups: with or without WEB2086 mixed with their drinking water (4.3 mg in 100 ml). At age 40 weeks blood was collected from the orbit for measurement of serum lipids and an enzyme linked immunosorbent assay was used to determine platelet activating factor and oxidized low density lipoprotein in the gastrocnemius and aorta. Whole-Mount CD31 stain and plaque-associated sprouting have been used to estimate angiogenesis in plaque from the aorta and laser Doppler perfusion imaging and immunohistochemical expression of von Willebrand factor have been used to estimate angiogenesis in ischemic hindlimb.

RESULTS

The lipid composition of serum was not different between the groups. However, the amount of platelet activating factor and oxidized low density lipoprotein detected in the aorta was significantly higher than that in the gastrocnemius of ischemic hindlimb. The ratio of lesion to aorta levels was significantly reduced by administration of WEB2086, (31.52 +/- 6.18)% vs (55.58 +/- 8.34)%, P < 0.01. The mean density of intimal capillaries in atherosclerotic plaque, (31.13 +/- 9.20)% vs (57.74 +/- 11.28)%, P < 0.01, and the mean number of sprouts per aorta were significantly reduced, 183.92 +/- 34.17 vs 392.54 +/- 76.79, P < 0.01, in the WEB2086 group. Blood flow (0.85 +/- 0.12 vs 0.45 +/- 0.06, P < 0.01) and capillary density of ischemic hindlimb (1.18 +/- 0.17 vs 0.53 +/- 0.09, P < 0.01) were markedly increased in apolipoprotein E-deficient mice treated with WEB2086 versus controls.

CONCLUSION

The study provides evidence that WEB2086 can inhibit angiogenesis in atherosclerotic plaque but promote it in ischemic hindlimb.

Acute pancreatitis: models, markers, and mediators

Acute pancreatitis has an incidence of approximately 40 cases per year per 100,000 adults. Although usually self-limiting, 10% to 20% of afflicted patients will progress to severe pancreatitis. The mortality rate among patients with severe pancreatitis may approach 30% when they progress to multisystem organ failure. The development of acute pancreatitis illustrates the requirement for understanding the basic mechanisms of disease progression to drive the exploration of therapeutic options. The pathogenesis of acute pancreatitis involves the interplay of local and systemic immune responses that are often difficult to characterize, particularly when results from animal models are used as a foundation for human trials. Experimental studies suggest that the prognosis for acute pancreatitis depends upon the degree of pancreatic necrosis and the intensity of multisystem organ failure generated by the systemic inflammatory response. This suggests an intricate balance between localized tissue damage with proinflammatory cytokine production and a systemic, anti-inflammatory response that restricts the inappropriate movement of proinflammatory agents into the circulation. The critical players of this interaction include the proinflammatory cytokines IL-1beta, TNF-alpha, IL-6, IL-8, and platelet activating factor (PAF). The anti-inflammatory cytokines IL-10, as well as TNF-soluble receptors and IL-1 receptor antagonist, have also been shown to be intimately involved in the inflammatory response to acute pancreatitis. Other compounds implicated in disease pathogenesis in experimental models include complement, bradykinin, nitric oxide, reactive oxygen intermediates, substance P, and higher polyamines. Several of these mediators have been documented to be present at increased concentrations in the plasma of patients with severe, acute pancreatitis. Preclinical work has shown that some of these mediators are markers for disease activity, whereas other inflammatory components may actually drive the disease process as important mediators. Implication of such mediators suggests that interruption or blunting of an inappropriate immune response has the potential to improve outcome. Although the manipulations of specific mediators in animal models may be promising, they may not transition well to the human clinical setting. However, continued reliance on experimental animal models of acute pancreatitis may be necessary to determine the underlying causes of disease. Full understanding of these basic mechanisms involves determining not only which mediators are present, but also closely documenting the kinetics of their appearance. Measurement of the inflammatory response may also serve to identify diagnostic markers for the presence of acute pancreatitis and provide insight into prognosis. Understanding the models, documenting the markers, and deciphering the mediators have the potential to improve treatment of acute pancreatitis.

Levels of platelet activating factor in gingival crevice fluid following periodontal surgical therapy

BACKGROUND AND OBJECTIVE

Elevated levels of platelet activating factor (PAF), a potent inflammatory phospholipid mediator, have been previously detected in gingival tissues and gingival crevice fluid (GCF) in periodontal disease. However, the role of this mediator during wound healing after periodontal surgery remains unclear. The hypothesis, a relationship between PAF levels and periodontal healing, was tested by measuring PAF levels in GCF samples collected from sites that had undergone guided tissue regeneration (GTR) or flap surgery.

MATERIAL AND METHODS

Using a split-mouth design, 30 intrabony defects were randomly assigned to treatment with GTR (group 1) or to flap surgery (group 2). GCF was sampled pre-operatively and at 6-, 12- and 24-wk follow-up evaluation visits. PAF levels in GCF were analyzed by high-performance liquid chromatography (HPLC).

RESULTS

Both treatment modalities significantly reduced the probing pocket depth and improved the clinical attachment level (p < 0.01). Compared with pre-operative values, the GCF volume and PAF levels were significantly decreased at postoperative weeks 6, 12 and 24 in both groups (p < 0.01). There were also significant differences in GCF volume and PAF levels at all time points up to 24 wks in both groups (p < 0.01). No statistically significant differences were observed in any of the parameters investigated between the two groups (p > 0.05).

CONCLUSION

PAF is detectable in GCF by HPLC and showed a continuous decrease at all the time points monitored following periodontal surgical therapy. This suggests that changes in the levels of this mediator in GCF might be useful for monitoring the progress of periodontal repair and regeneration.

Pharmacokinetic Analysis of Platelet-Activating Factor in the Tears of Guinea Pigs with Allergic Conjunctivitis

PURPOSE

The aim of this study was to examine the levels of platelet-activating factor (PAF) and lyso-PAF in tears from experimental animals developing allergic conjunctivitis (AC).

METHODS

AC was induced in guinea pigs by application of ovalbumin in eye drops. Tear samples were collected from 5 actively sensitized animals and from 5 unsensitized control animals before the challenge, and 1, 2, 4, and 6 h postchallenge. C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF levels in the tear samples were determined using liquid chromatography-tandem mass spectrometry.

RESULTS

The concentrations of C16:0-PAF, C16:0-lyso-PAF, and C18:0-lyso-PAF were measurable in both unsensitized and sensitized groups, whereas C18:0-PAF was undetectable in tear samples from either group. The levels of C16:0-PAF, C16:0-lyso-PAF, and C18:0-lyso-PAF in sensitized animals increased throughout the time course of the experiment, whereas there was no corresponding increase in the levels of these molecules in the unsensitized group. There were strong correlations between the concentrations of C16:0-PAF and C16:0-lyso-PAF, both in the sensitized and in the unsensitized group, and the concentrations of C16:0-lyso-PAF and C18:0-lyso-PAF within each group.

CONCLUSIONS

The data from this study demonstrated that the levels of PAF and lyso-PAF increase in tears in a guinea pig model of AC development and implicate a role for PAF for the development of AC.

Periodontal parameters and platelet-activating factor levels in serum and gingival crevicular fluid in a Chinese population

AIM

Platelet-activating factor (PAF) is a potent proinflammatory mediator and has been implicated in cardiovascular pathophysiology. The present clinical study assessed the relation between the severity of periodontal disease and PAF levels in gingival crevicular fluid (GCF) and serum.

METHODS

A total of 60 non-smoking subjects (21 periodontitis, 19 gingivitis patients and 20 healthy individuals) were included. Probing depth, attachment level, bleeding on probing, plaque index and sulphide levels were recorded at six sites of each tooth. GCF and blood samples were collected from all individuals, and PAF levels were investigated by enzyme-linked immunoabsorbent assay.

RESULTS

The periodontitis group showed significantly higher PAF levels in the serum (329.3+/-287.3 pg/ml) and GCF (21.8+/-7.0 pg/sample) compared with the gingivitis group (138.0+/-77.9 pg/ml, 13.8+/-3.6 pg/sample) and with healthy controls (68.9+/-42.8 pg/ml, 2.4+/-2.7 pg/sample). The differences between patients and controls were statistically significant (p<or=0.05). Positive correlations were observed between PAF levels in GCF and serum and for PAF levels and clinical parameters.

CONCLUSION

The present findings suggest a role of PAF in the pathogenesis of periodontitis. Based on the observed close correlation of GCF and serum PAF levels, future studies are warranted to test the hypothesis of a possible link between periodontitis and adverse systemic events mediated by PAF.

Mechanism for acute oral desensitization to antibiotics

BACKGROUND

Despite the widespread use of an acute oral desensitization procedure in patients with allergic reactions to a variety of antibiotics, the precise mechanism of this procedure is poorly understood.

OBJECTIVE

To investigate the mechanisms underlying acute oral desensitization to antibiotics.

METHODS

Using a murine model of active systemic anaphylaxis to penicillin V (Pen V), mice previously sensitized to Pen V were desensitized by oral feeding of Pen V. The dose was doubled every 15 min and five feedings were given. The achievement of acute oral desensitization was evaluated by induction of active systemic and active cutaneous anaphylaxis, and by measuring the plasma levels of platelet-activating factor and histamine. Antigen-specific serum IgE antibody (Ab) levels were determined by passive cutaneous anaphylaxis.

RESULTS

Mice fed more than 3 mg of cumulative dose of Pen V were completely protected from fatal systemic anaphylactic reaction and the desensitized state lasted approximately 1 h. Antigen-specific mast cell desensitization, but not hapten inhibition, consumption of IgE Abs, or depletion of mast cell mediators, occurred during acute oral desensitization.

CONCLUSIONS

Acute oral desensitization to Pen V occurred in the mice, and antigen-specific mast cell desensitization was associated with the underlying mechanism for oral desensitization.

Determination of platelet-activating factor by reverse phase high-performance liquid chromatography and its application in viral hepatitis

AIM

To detect the platelet-activating factor (PAF) and the plasma or serum levels of tumor necrosis factor-alpha (TNF-alpha) malondialdehyde (MDA), endotoxin (ET) and to discuss their significance in various types of viral hepatitis.

METHODS

PAF, TNF-alpha, MDA, and ET levels in 60 controls, 16 cases of acute viral hepatitis, 71 cases of chronic viral hepatitis, 19 cases of severe viral hepatitis were detected by reverse phase high-performance liquid chromatography (rHPLC), bio-assay, ELISA, thiobarbituric acid (TBA), and limulus lysate test (LLT), respectively.

RESULTS

The rHPLC was more sensitive and specific than bio-assay (r = 0.912, P<0.01). The plasma levels of PAF, TNF-alpha, MDA, and ET in patients with viral hepatitis were higher than those in controls (P<0.01).

CONCLUSION

rHPLC is more reliable and accurate for the detection of PAF.

Platelet-activating factor-like activity isolated from Trypanosoma cruzi

Platelet-activating factor is a phospholipid mediator that exhibits a wide variety of physiological and pathophysiological effects, including induction of inflammatory response, chemotaxis and cellular differentiation. Trypanosoma cruzi, the etiological agent of Chagas' disease, is transmitted by triatomine insects and while in the triatomine midgut the parasite differentiates from a non-infective epimastigote stage into the pathogenic trypomastigote metacyclic form. We have previously demonstrated that platelet activating factor triggers in vitro cell differentiation of T. cruzi. Here we show a platelet activating factor-like activity isolated from lipid extract of T. cruzi epimastigotes incubated in the presence of [14C]acetate. Trypanosoma cruzi-platelet activating factor-like lipid induced the aggregation of rabbit platelets, which was prevented by platelet activating factor-acetylhydrolase. Mouse macrophage infection by T. cruzi was stimulated when epimastigotes were kept for 5 days in the presence of T. cruzi-platelet activating factor, before interacting with the macrophages. The differentiation of epimastigotes into metacyclic trypomastigotes was also triggered by T. cruzi-platelet activating factor. These effects were abrogated by a platelet activating factor antagonist, WEB 2086. Polyclonal antibody raised against mouse platelet activating factor receptor showed labelling for T. cruzi epimastigotes using immunoblotting and immunofluorescence assays. These data suggest that T. cruzi contain the components of an autocrine platelet activating factor-like ligand-receptor system that modulates cell differentiation towards the infectious stage.

A multiplex quantitation method for eicosanoids and platelet-activating factor using column-switching reversed-phase liquid chromatography-tandem mass spectrometry

Eicosanoids and platelet-activating factor (PAF) are phospholipid-derived lipid mediators produced by various tissues and cells through a cascade pathway. For a comprehensive analysis of these lipid mediators, a simultaneous quantitation method with sensitivity and reliability is necessary. This article details a development of column-switching reversed-phase liquid chromatography-tandem mass spectrometry for multiplex quantitation of eicosanoids and PAF. The adsorptive nature of lipids caused significant loss of signal in a conventional column-switching configuration. The use of an online-dilution method allowed use of 100% methanol as a sample solvent, which prevented sample adsorption to contacting surfaces. Addition of 0.2% formic acid to the sample solvent was required for the successful introduction of LTC4 to the trapping column and minimizing its carryover. The optimized method provided rapid analysis of 14 lipid mediators with a throughput of 96 samples/24 h, lower limits of quantitation of 5 pg on column, and linear calibration ranges up to 2000-5000 pg. The system was highly compatible with solid-phase-extracted samples, as methanol-eluted fractions were directly injected without reconstitution. The analysis of lipid mediator production of macrophage-like RAW264.7 cells demonstrated that the cell-based assay can be performed in a 96-well format, suitable for metabolomics analyses and/or screening strategies.

Feasibility of assessment of regulatory lipids in breath condensate as potential presymptomatic harbingers of pulmonary pathobiology

Regulatory lipids from the airway surface readily form aerosols that can be recovered non-invasively by cooling expired breath to form breath condensate (BC). Regulatory lipids have been detected previously utilizing enzyme-linked-immunosorbent serologic assay (ELISA). Here we test the feasibility of assessment of regulatory lipids in BC by mass spectrometry so presently unknown lipid regulatory components can be detected without addition of specific antibodies as in the ELISA procedure. Baseline regulatory lipids were detected in >pg/mL BC in control animals or human lung tissue culture cells. In nearly every case animals exposed to toxins or infectious bacteria showed increases in the BC regulatory components. Lipids were recovered from BC by solid phase extraction. Phosphatidylcholine (PC) based lipids were detected as the progenitor (parent) ions of isomers that fragmented in producing product positive ions at m/z 184 (of phosphocholine) in tandem MS using capillary HPLC and electrospray ionization. BC eicosanoids such as prostaglandins, thromboxane, and isoprostanes require capillary gas chromatography for separation and detection that necessitates methoximation, pentafluorobenzyl (PFB) ester formation, and trimethyl silylation of hydroxyls prior to gas chromatography/ion trap tandem mass spectrometry of negative ions after chemical ionization (NICI). Tetradeuterated internal standards were utilized for quantitation with the GC/NICI/MS. Changes in concentrations of lipids and eicosanoids were observed in piglets, and rats exposed to aerosolized 100 mug/kg lipopolysaccharide (LPS), or 50 mug/kg and 150 mug/kg aerosolized Staphylococcal enterotoxin B (SEB) in BC as well as in human THP-1 cell culture cell supernatants and bronchoalveolar lavage (BAL) samples in rats. Responses of the molecular species of phosphatidylcholines (PCs), platelet activating factors (PAFs) and specific eicosanoids correlated to the toxin and bacterial infections suggesting that patterns of differential responses could be detected with further experimentation. Initial targets included prostaglandins (PGE(2), PGF(2alpha)), thromboxane (TXB2), and prostacyclin (as 6-Keto PGF(1alpha)) that show differential responses to inflammation, the leukotriene (LTB4) and PGD2 for allergic responses, isoprostanes (8-iso-PGF(2alpha)) for free radical oxidative stress responses, and HETEs for differential lipoxygenase activities. PAFs and lysoPAFs have been shown to increase with inflammation and in the feasibility experiments reported here. Preliminary studies show pulmonary responses of piglets to intrathecal exposure of toxicants (LPS and SEB) or infections with Actinobacillus pleuropneumoniae induce increased levels of lipids and two eicosanoids with the suggestion that differential patterns might be detected with expanded testing. Preliminary experience indicates numerous other eicosanoids were available for assay in BC. This suggests an important potential application of BC to observe a wide array of factors to establish comprehensive profiles for physiological and pathophysiological states. Ultimately this technique could be used as a non-invasive possibly presymptomatic assessment of pulmonary pathobiology.

Molecular and mechanistic characterization of platelet-activating factor-like bioactivity produced upon LDL oxidation

Oxidation of LDL is thought to be involved in both initiating and sustaining atherogenesis through the formation of proinflammatory lipids and the covalent modification of LDL particles. Platelet-activating factor (PAF; 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a potent phospholipid mediator involved in inflammation. Upon oxidation of LDL, oxidized phospholipids with PAF-like structure are generated, and some of them may act via the PAF receptor. We evaluated the contribution of 1-0-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16:0 PAF) and of other PAF analogs on the PAF-like bioactivity formed upon Cu2+-initiated oxidation of LDL. Reverse-phase HPLC purification and electrospray ionization-MS analyses showed that upon oxidation of LDL with inactivated PAF-acetylhydrolase (PAF-AH), C16:0 PAF accounted for >30% of PAF-like biological activity and its sn-2 butenoyl analog accounted for >50%. However, upon LDL oxidation in the presence of exogenous 1-0-alkyl-sn-glycero-3-phosphocholine (lyso-PAF) without PAF-AH inactivation, C16:0 PAF formation accounted for >90% of the biological activity recovered. We suggest that the C16:0 PAF, despite being a minor constituent of the LDL peroxidation products, may contribute substantially to the bioactivity formed in oxidized LDL. The higher bioactivity of C16:0 PAF, and the higher selectivity of the LDL-attached lyso-PAF transacetylase toward very short acyl chains [acetate (C2) vs. butanate (C4)], may explain the contribution described above.

[Effects of the platelet activating factor on the proliferation and IgE secretion by U-266BL human myeloma cells]

Platelet activating factor (PAF) influences the proliferation and IgE secretion by U-266BL human myeloma (HM) cells. At a relatively high PAF concentration (up to 10(-8) M), the rate of proliferation is significantly decreased, while the IgE secretion rate is increased. At low PAF concentrations (10(-11) M), the HM cell proliferation rate increases, whereas their ability to IgE secretion decreases. The specific secretion activity (per cell) is a linear function in the range of PAF concentrations from 10(-11) to 10(-8) M. This behavior can be used for the quantitative determination of PAF in biological media.

Therapeutic versus prophylactic plus therapeutic administration of omega-3 fatty acid on endotoxin-induced periodontitis in rats

BACKGROUND

The aim of the present study was 1) to evaluate the possible effects of therapeutic usage of omega-3 fatty acid on the gingival tissue levels of prostaglandin E2 (PGE2), prostaglandin F2alpha (PGF2alpha), platelet activating factor (PAF), and leukotriene B4 (LTB4) in endotoxin-induced periodontitis in rats and 2) to investigate whether prophylactic usage provides any additional benefits to therapeutic doses of omega-3 fatty acid.

METHODS

Experimental periodontitis was induced by repeated injection of Escherichia coli lipopolysaccharide (LPS). Thirty-six adult male Sprague-Dawley rats were divided into four study groups: 1) saline controls; 2) LPS; 3) therapeutic omega-3 fatty acid (TO3); and 4) prophylactic plus therapeutic omega-3 fatty acid (P + TO3) groups. In TO3 group, omega-3 fatty acid was given for 15 days following induction of experimental periodontitis. In P + TO3 group, omega-3 fatty acid was started 15 days before baseline, and then periodontitis was induced at baseline and omega-3 fatty acid was continued for 15 days after baseline. On day 15 after baseline, all rats were anesthetized and sacrificed. PGE2, PGF2alpha, and LTB4 levels in gingival tissue samples were analyzed by enzyme immunoassay and PAF levels were analyzed by radioimmonoassay. Data were evaluated statistically by using parametric tests.

RESULTS

LPS injection resulted in significant amount of bone loss (P<0.05). Neither therapeutic nor prophylactic plus therapeutic administration of omega-3 fatty acid with the doses and duration of therapy used in the present study was effective in preventing endotoxin-induced alveolar bone loss. TO3 group exhibited significant decreases in the gingival tissue levels of PGE2, PGF2alpha, LTB4, and PAF compared to the LPS group (P<0.05). PGE2 and PGF2alpha levels in TO3 group were similar to those of the saline group (P>0.05), while LTB4 and PAF levels were statistically higher than the saline group (P<0.05). Prophylactic plus therapeutic usage of omega-3 fatty acid provided similar levels of all these mediators to those of the saline controls (P>0.05).

CONCLUSIONS

Therapeutic omega-3 fatty acid significantly reduced the gingival tissue levels of PGE2, PGF2alpha, LTB4, and PAF in experimental periodontitis. Furthermore, prophylactic usage of omega-3 fatty acid provided additional beneficial effects to the therapeutic administration by decreasing the gingival tissue levels of these mediators to levels of healthy tissue. These findings should be verified by longitudinal clinical trials investigating clinical and biochemical periodontal parameters to better define the possible role of omega-3 fatty acids in periodontal treatment.

Platelet-activating factor (PAF) in internal jugular venous blood of migraine without aura patients assessed during migraine attacks

The aim of the study was to verify the production of PAF and the activity of PAF acetyl-hydrolase (PAF-AH), the enzyme involved in the catabolism of this phospholipid mediator, in migraine attacks. Their levels were determined during migraine crises in serial samples of internal jugular venous blood taken from five migraine patients without aura, who were admitted to the hospital during the crises. Internal jugular venous blood samples were taken immediately after catheter insertion at 1, 2, and 4 h after attack onset, and within 2 h from its cessation. PAF was purified by high-performance liquid chromatography (HPLC) and determined by radioimmunoassay method. The enzymatic activity of PAF-AH was measured by reverse-phase HPLC, based on the derivatization with 7-diethylaminocoumarin-3-carbonylazide. In the internal jugular venous blood of migraine patients without aura (MO), an increase was observed in PAF levels, which was already evident at the time of catheter insertion (885.6 +/- 82.8) and at the first hour (868.4 +/- 65.24) (ANOVA: P < 0.0001). PAF levels remained elevated through the second (746.8 +/- 82.95), fourth (700.6 +/- 34.93) and sixth hours (644.4 +/- 42.85), and then decreased at the end of the attack, reaching levels significantly lower than those measured at the time of catheter insertion (565.5 +/- 38.34). The activity of PAF-AH showed an opposite trend with higher values at the first hour and significantly lower values at the second and fourth hours from the beginning of the migraine attack (ANOVA: P < 0.02). The increased production of PAF may account for persistent platelet activation during migraine crises, even in the presence of an increased production of nitric oxide (NO) end-products which, on the other hand, should instead intervene in counteracting and limiting platelet activation. Potential sources of PAF production are the endothelial cells from cerebral vessels, stimulated by trigeminal neuropeptides, platelets themselves, and mast cells, as suggested by the neurogenic inflammation model.

Age-related increase of plasma platelet-activating factor concentrations in Chinese

BACKGROUND

Platelet-activating factor (PAF) is a potent bioactive phospholipid, which may be one of the determinants of atherogenesis. The purpose of this study was to investigate the relationship between the concentrations of plasma platelet-activating factor and age in a common Chinese population.

METHODS

Two-hundred seventy-nine Han nation subjects (male: n=162; female: n=117) who had visited two hospitals for overall health survey, as an annual medical check-up or for other reasons by clinical examinations were recruited and divided into six age groups (21-30, 31-40, 41-50, 51-60, 61-70, 71-80 years). PAF was extracted from their plasma and purified by thin-layer chromatography (TLC). The PAF concentrations were detected by radioimmunoassay.

RESULTS

The PAF concentrations (pg/ml) in plasma showed significantly age-related increase (r=0.3348, P<0.01, n=279). In the 21-30-year group, the PAF concentration was 338+/-96 pg/ml. Except for the 31-40-year group, the PAF concentrations in other four groups were all higher than that of the 21-30-year group (P<0.05, P<0.01, P<0.001 and P<0.001, respectively).

CONCLUSIONS

Considering PAF is one of the key factors relevant to progression of atherogenesis, and the high concentrations of plasma PAF may therefore serve as a marker for the risk of atherosclerosis. Adjustment of the concentrations of plasma PAF correlated with aging may be helpful to reducing the prevalence rate of multi-senile arteriosclerosis occlusive diseases.

Protective Effect of Pentoxifylline on Volume-Induced Lung Injury in Newborn Piglets

To evaluate the efficacy of pentoxifylline (PTXF) in the attenuation of lung inflammation during volume-induced lung injury (VILI) in newborn piglets, 17 newborn piglets were mechanically ventilated with a large tidal volume (50 ml/kg) for a period of 8 h. They were randomly assigned to a placebo (PL, n = 9) or a treatment group (PTXF, n = 8) that received PTXF (20 mg/kg as a bolus, followed by a continuous infusion of 5 mg/kg/h). Hemodynamics, lung mechanics and arterial blood gases were measured during the 8 h of study. Serum and tracheoalveolar fluid (TAF) platelet-activating factor (PAF) and thromboxane (TXB(2)) levels were obtained at baseline and at 8 h, while lung tissue myeloperoxidase (MPO) and wet to dry weight were assessed after the completion of the study. In the PL group, a marked increase in TAF PAF and TXB(2) levels was observed only in TAF, suggesting that the inflammatory process was localized within the lungs. A significant decrease in lung tissue MPO activity (p < 0.005) and lung wet to dry weight ratio (p < 0.04) was observed in the PTXF group. There were no differences in hemodynamics, arterial blood gases or lung mechanics measurements between groups. A significant reduction in pulmonary inflammatory response was observed during VILI in the PTXF pretreated animals. These results suggest that PTXF may be effective in modulating lung inflammation associated with mechanical ventilation in neonates.

Creation of reversed phase high-performance liquid chromatographic technique to assay platelet-activating factor

OBJECTIVE

To establish a new assay for platelet-activating factor (PAF), to compare it with bio-assay; and to discuss its significance in some elderly people diseases such as cerebral infarction and coronary heart disease.

METHODS

To measure PAF levels in 100 controls, 23 elderly patients with cerebral infarction and 65 cases with coronary heart disease by reversed phase high-performance liquid chromatographic technique (rHPLC).

RESULTS

rHPLC is more convenient, sensitive, specific, and less confusing, compared with bio-assay. The level of plasma PAF in patients with cerebral infarction was higher than that in the controls (P<0.01), and in patients with coronary heart disease.

CONCLUSION

Detection of PAF with rHPLC is more reliable and more accurate. The new assay has important significance in PAF research.

Platelet-activating factor and P-selectin activities in thrombotic and nonthrombotic Behçet’s patients

OBJECTIVE

The aim of this study was to compare plasma Platelet-activating factor (PAF) and P-selectin (CD62P) activities in Behçet's disease patients with and without thrombosis.

METHODS

In this cross-sectional and descriptive study, 30 consecutive Behçet's patients were included, 15 of them with venous thrombosis. All patients were also divided into two subgroups according to the presence or absence of clinical activity. Plasma PAF levels, basal and Ca++ ionophore (A23187)-induced leukocyte (cellular) PAF activities, and platelet-rich plasma DeltaCD62P activity (the mean fluorescent density difference between CD62P phycoerythrin-positive and -negative stains) were evaluated.

RESULTS

In the thrombotic group, plasma PAF (P=0.001), basal leukocyte PAF (P=0.017), induced leukocyte PAF (P=0.024), and DeltaCD62P (P=0.023) levels were significantly higher than in the nonthrombotic group. In the whole group of Behçet's patients, there was a positive correlation between plasma PAF and DeltaCD62P levels (r=0.533, P=0.002). When we compared clinically active and inactive patients with respect to the above parameters, there was no significant difference, irrespective of thrombosis. Plasma PAF (P=0.001), basal leukocyte PAF (P=0.004), and DeltaCD62P (P=0.038) levels were significantly higher in the presence of both clinical activity and thrombosis than of clinical activity alone.

CONCLUSION

Platelet-activating factor and CD62P may contribute to endothelial injury and thrombosis development in Behçet's disease. These two parameters seem related to the presence of thrombosis rather than clinical activity.

The Impact of Intravenous Fat Emulsion Administration in Acute Lung Injury

The aim of this study was to evaluate the effect of parenteral nutrition containing medium- and long-chain triglycerides on the function of the respiratory system and to investigate mechanisms involved in this process. We studied 13 patients with acute respiratory distress syndrome (ARDS), 8 receiving lipid and 5 placebo, and 6 without ARDS, receiving lipid. Bronchoalveolar lavage (BAL) was performed before and 1 hour after administration of lipid or placebo. In patients with ARDS, lipid administration resulted in deterioration of oxygenation (Pa(O(2))/FI(O(2)): from 129 +/- 37 to 95 +/- 42), compliance of respiratory system (from 39.2 +/- 12 to 33.1 +/- 9.2 ml/cm H(2)O), and pulmonary vascular resistance (from 258 +/- 47 to 321 +/- 58 dyne x s x cm(-5)). In the BAL fluid of the same group, an increase in total protein and phospholipid concentrations, phospholipase activities, platelet-activating factor and neutrophils, as well as alterations in BAL lipid profile were observed. No significant changes were observed in the control or in the ARDS-Placebo groups. In conclusion, this study indicates that administration of medium- and long-chain triglycerides in patients with ARDS causes alterations in lung function and hemodynamics. Inflammatory cells, possibly activated by lipids, release phospholipase A(2) and platelet-activating factor, enhancing edema formation, inflammation, and surfactant alterations.

Familial cancer and developmental dyslexia: an observational pilot study

The aim of the study was to test the hypothesis that raised platelet-activating factor (PAF) may contribute to the aetiology of developmental dyslexia. PAF is a potent proinflammatory mediator which signals cell damage and facilitates natural killer cell activity. Raised PAF may help protect against tumourigenesis. As dyslexia has a partial genetic basis, the PAF hypothesis predicts that dyslexia may be negatively associated with a family history of cancer. To test this prediction, children with dyslexia (n=163) and children without dyslexia (n=154), with (n=152) and without (n=165) a family history of cancer (total n=317; mean age 11 years 5 months, SD 2 years 11 months), were compared on standard psychometrics (British Ability Scales subtests). Results showed that proportionately fewer children with dyslexia (38%) than controls (58.4%) had a family history of cancer, and there was some evidence of a 'dose' effect: children who had more relatives with cancer showed better reading and spelling. It was concluded that children at genetic risk of dyslexia who have a family history of cancer have better reading and spelling than those without a family history of cancer, confirming the prediction of the PAF hypothesis.

Effect of inhibitors of leukotriene and/or platelet activating factor on killed H. influenzae induced experimental otitis media with effusion

Our previous studies have shown that leukotriene (LT) and platelet activating factor (PAF) are important inflammatory mediators (IMs) in the pathogenesis of otitis media with effusion (OME). The purpose of this study was to determine the effect of a LT-inhibitor and/or PAF-antagonist on experimentally induced OME by killed H. influenzae in chinchillas. LT-inhibitor SCH-37224 and/or PAF-antagonist WEB-2170 were systematically administered, each separately or in combination, 2h prior and then at regular intervals after the injection of killed H. influenzae into the superior bullae. After 48h, OME was completely prevented in the combination group while it was only partially prevented in the other two separately treated groups. Animals in the control group all developed OME. Findings of this study suggest the importance of LT and PAF in the pathogenesis of OME and the usefulness of their blockers in the prevention of OME suggesting possible future therapeutic implication.

[Determination of platelet activating factor in middle ear effusion of patients with secretory oitits media]

OBJECTIVE

To study the role of platelet activating factor (PAF) in the pathogenesis of secretory otitis media (SOM).

METHOD

The content of PAF in blood plasma and middle ear effusion(MEE) were measured in 56(68years) patients with secretory otitis media and in 40 normal subjects respectively by RP-HPLC.

RESULT

The concentration of PAF in MEE was remarkably higher than those in blood plasma (P < 0.01). The concentration of PAF in blood plasma in the SOM group was higher than those in the normal control group(P < 0.05). The concentration of PAF of MEE in the mucous fluid group was higher than those in the serous fluid group(P < 0.01).

CONCLUSION

PAF might be an important mediator in MEE of SOM, it might be closely related to the persistence of SOM, and might play an important role in the pathogenesis of SOM.

Platelet-activating factor-mediated NF-kappaB dependency of a late anaphylactic reaction

Anaphylaxis is a life-threatening systemic allergic reaction with the potential for a recurrent or biphasic pattern. Despite an incidence of biphasic reaction between 5 and 20%, the molecular mechanism for the reaction is unknown. Using a murine model of penicillin V-induced systemic anaphylaxis, we show an autoregulatory cascade of biphasic anaphylactic reactions. Induction of anaphylaxis caused a rapid increase in circulating platelet-activating factor (PAF) levels. In turn, the elevated PAF contributes to the early phase of anaphylaxis as well as the subsequent activation of the nuclear factor (NF)-kappaB, a crucial transcription factor regulating the expression of many proinflammatory cytokines and immunoregulatory molecules. The induction of NF-kappaB activity is accompanied by TNF-alpha production, which, in turn, promotes late phase PAF synthesis. This secondary wave of PAF production leads eventually to the late phase of anaphylactic reactions. Mast cells do not appear to be required for development of the late phase anaphylaxis. Together, this work reveals the first mechanistic basis for biphasic anaphylactic reactions and provides possible therapeutic strategies for human anaphylaxis.

Sulfur-related air pollutants induce the generation of platelet-activating factor, 5-lipoxygenase- and cyclooxygenase-products in canine alveolar macrophages via activation of phospholipases A2

Recent studies have shown that long-term in vivo exposure of dogs to neutral sulfur(IV)/sulfite aerosols induces mild inflammatory reactions, whereas the combination of neutral sulfite with acidic sulfur(VI)/sulfate aerosols evokes less pronounced effects. To understand underlying mechanisms, we studied in vitro the role of lipid mediators in the responses of alveolar macrophages (AMs) to sulfur-related compounds under neutral (pH 7) or moderate acidic (pH 6) conditions. Canine AMs incubated with sulfite at pH 7 released threefold higher amounts of platelet-activating factor than control (P < 0.005). Generation of arachidonic acid, leukotriene B4, 5-hydroxy-eicosatetraenoic acid, prostaglandin E2, thromboxane B2 and 12-hydroxyheptadecatrienoic acid increased twofold (P < 0.0005). However, these metabolites remained unchanged following incubation of AMs with sulfite at pH 6 or with sulfate at pH 7 or pH 6. Mediator release by sulfite-treated AMs at pH 7 stimulated respiratory burst activity of neutrophils. Inhibition of MAPK pathway by PD 98059, of cytosolic (cPLA2) and secretory phospholipases A2 by AACOCF3 and thioetheramide-PC, respectively, reduced sulfite-induced eicosanoid formation in AMs. Sulfite activated cPLA2 activity twofold at pH 7. This mechanism of sulfite-stimulated responses in phospholipid metabolism predicts that chronic exposure to sulfur(IV)/sulfite is associated with a considerable health risk.

An experimental model of hemolysis-induced acute pancreatitis

The literature indicates that acute pancreatitis is a complication of massive hemolysis with a prevalence of about 20%. We describe an experimental model of hemolysis-induced acute pancreatitis. Hemolytic anemia was induced in rats by a single ip injection of 60 mg/kg of 20 mg/ml acetylphenylhydrazine (APH) in 20% (v/v) ethanol on the first experimental day (day 0). One hundred and fifty Wistar albino rats weighing 180-200 g were divided into three groups of 50 animals each: groups 1, 2 and 3 were injected ip with APH, 20% ethanol, and physiological saline, respectively. Ten rats from each group were sacrificed on study days 1, 2, 3, 4 and 5. Serum amylase, lipase levels and pancreatic tissue tumor necrosis factor-alpha (TNF-alpha) and platelet-activating factor (PAF) contents were determined and a histological examination of the pancreas was performed. No hemolysis or pancreatitis was observed in any of the rats in groups 2 and 3. In group 1, massive hemolysis was observed in 35 (70%) of 50 rats, moderate hemolysis in seven (14%), and no hemolysis in eight (16%). Thirty-three of 35 (94.2%) rats with massive hemolysis had hyperamylasemia, and 29 of these rats (82.8%) had histologically proven pancreatitis. The most severe pancreatitis occurred on day 3, as demonstrated by histology. Tissue TNF-alpha and PAF levels were statistically higher in group 1 than in groups 2 and 3. Acute massive hemolysis induced acute pancreatitis, as indicated by histology, in almost 80% of cases. Hemolysis may induce acute pancreatitis by triggering the release of proinflammatory and immunoregulatory cytokines.

Platelet function after coronary artery bypass grafting: is there a procoagulant activity after off-pump compared with on-pump surgery?

OBJECTIVE

After off-pump coronary artery bypass (OPCAB) haemostasis might be better preserved compared with on-pump coronary artery bypass grafting (CABG). The aim of this study was to investigate whether this possibly better preserved haemostasis results in a procoagulant activity of the platelets.

DESIGN

Thirty patients were studied prospectively, 15 undergoing on-pump CABG and 15 undergoing OPCAB. Platelet function was evaluated four times within the first 24 h: preoperatively, postoperatively, 4 h and 1 day after surgery with a bedside whole blood clotting test.

RESULTS

A significant increase of platelet-activating-factor-induced platelet aggregation was observed postoperatively after OPCAB (p < 0.01). Only two patients did not reach preoperative values within 1 day postoperatively and four patients had a more than twofold increase. Platelet aggregation immediately after on-pump CABG was reduced to near half of preoperative values, but within 1 day postoperatively normal platelet aggregation was regained in half of the patients.

CONCLUSION

This study has mainly indicated that platelets after OPCAB were more easily activated in the early postoperative period. After CABG with cardiopulmonary bypass we found a temporary platelet dysfunction which seemed to be overcome within the first postoperative day.

Fertilization potential of human sperm is correlated with endogenous platelet-activating factor content

PURPOSE

Platelet-activating factor (PAF) is a potent signaling phospholipid that is found in mammalian sperm and has a positive correlation with fertility. Whereas PAF is present in human sperm, there are no relational reports on its content and the cells fertilization potential. Therefore, the study objective was to determine if PAF content in capacitated-induced sperm is related to fertilization potential as determined by the sperm penetration assay (SPA).

METHODS

Endogenous sperm lipids were measured for PAF content by a specific radioimmunoassay following insemination of zona pellucida-free hamster ova. Data were analyzed by regression analysis and Student's t test.

RESULTS

Regression analysis revealed a positive and significant relation (R2 = 0.806; P < 0.05) between PAF content in human sperm and SPA outcome (pass: > or = 5.0; fail: < 5.0, penetrations/ova). Patients that passed (22.61 +/- 5.21 picomoles/10(6)) the SPA had significantly (P < 0.01) higher PAF levels in their sperm than patients that failed (12.91 +/- 1.76 picomoles/10(6) cells) the test.

CONCLUSIONS

PAF content in capacitated-induced sperm has a significant and positive relationship with fertilization potential. Fertilization potential may be predicted by measuring PAF levels in capacitation-induced human sperm. Determining PAF content in capacitated human sperm may be a beneficial diagnostic tool for the infertility specialist.

Role of platelet-activating factor in the pathophysiology of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal illness that affects predominantly preterm infants. Treatment options are limited and NEC remains a significant cause of morbidity and mortality. The precise aetiology of NEC remains unclear but evidence strongly suggests that the cause is multifactorial and there are four main aetiological factors: prematurity, hypoxia, enteral feeding and bacterial colonization. The presence of similar intestinal lesions, regardless of aetiological trigger, strongly implicates a final common pathway in the pathogenesis. There is now a substantial body of evidence to indicate that endogenous inflammatory mediators, particularly platelet-activating factor (PAF), play a vital role in this final pathway.

CONCLUSION

The use of agents that antagonize PAF may provide therapeutic options in the management of NEC.

Neonatal necrotizing enterocolitis: clinical considerations and pathogenetic concepts

Necrotizing enterocolitis (NEC), a disease affecting predominantly premature infants, is a leading cause of morbidity and mortality in neonatal intensive care units. Although several predisposing factors have been identified, such as prematurity, enteral feeding, and infection, its pathogenesis remains elusive. In the past 20 years, we have established several animal models of NEC in rats and found several endogenous mediators, especially platelet-activating factor (PAF), which may play a pivotal role in NEC. Injection of PAF induces intestinal necrosis, and PAF antagonists prevent the bowel injury induced by bacterial endotoxin, hypoxia, or challenge with tumor necrosis factor-a (TNF) plus endotoxin in adult rats. The same is true for lesions induced by hypoxia and enteral feeding in neonatal animals. Human patients with NEC show high levels of PAF and decreased plasma PAF-acetylhydrolase, the enzyme degrading PAF. The initial event in our experimental models of NEC is probably polymorphonuclear leukocyte (PMN) activation and adhesion to venules in the intestine, which initiates a local inflammatory reaction involving proinflammatory mediators including TNF, complement, prostaglandins, and leukotriene C4. Subsequent norepinephrine release and mesenteric vasoconstriction result in splanchnic ischemia and reperfusion. Bacterial products (e.g., endotoxin) enter the intestinal tissue during local mucosal barrier breakdown, and endotoxin synergizes with PAF to amplify the inflammation. Reactive oxygen species produced by the activated leukocytes and by intestinal epithelial xanthine oxidase may be the final pathway for tissue injury. Protective mechanisms include nitric oxide produced by the constitutive (mainly neuronal) nitric oxide synthase, and indigenous probiotics such as Bifidobacteria infantis. The former maintains intestinal perfusion and the integrity of the mucosal barrier, and the latter keep virulent bacteria in check. The development of tissue injury depends on the balance between injurious and protective mechanisms.

Presence of platelet-activating factor in nasal polyps and eosinophils

Platelet-activating factor (PAF) has been reported to play a role in allergy and inflammatory reactions but its role in the pathogenesis of nasal polyps remains unclear. In this study, we examined both PAF and peptide leukotrienes (peptLTs) in individual preparations from nasal polyps. The amounts of PAF were much greater than those of peptLTs in all preparations. Nasal polyps were divided into two groups according to the severity of eosinophil infiltration: a severe group (eosinophil count > or = 50/mm2) and a mild group (eosinophil count < 50/mm2). The amounts of PAF in the nasal polyps were significantly higher in the severe group than in the mild group (p < 0.01). PAF activity correlated with tissue eosinophilia and polyps obtained from patients with aspirin-sensitive asthma contained relatively large amounts of PAF, with enriched infiltration of eosinophils.

PAF, a putative mediator of oral inflammation

PAF, or platelet-activating factor, is a family of structurally related phospholipids (1-O-alkyl/acyl/alkenyl-2-acetyl-sn-glycero-3-phosphocholine) which possesses a wide spectrum of potent pro-inflammatory actions. These phospholipids are synthesized by a diverse array of cells, including neutrophilic polymorphonuclear leukocytes (PMN), platelets, mast cells, monocytes/macrophages, vascular endothelial cells, and lymphocytes. PAF targets these and other cells via specific, G-protein-coupled receptors to initiate intracrine, autocrine, paracrine, and juxtacrine cell activation. Of importance, these unique acetylated phospholipids are frequently synthesized in concert with pro-inflammatory lipid mediators derived from arachidonic acid. Since PAF synergizes with these and other mediators to amplify the inflammatory response, it seems likely that PAF plays an integral, perhaps pivotal, role in acute and chronic inflammatory processes. PAF is present in the mixed saliva of dentate, but not edentulous, human subjects. The levels of PAF in mixed saliva or in gingival crevicular fluid and tissues are significantly increased during oral inflammatory conditions such as periodontitis and mucositis. Interestingly, the levels of salivary PAF correlate with the extent/severity of these oral diseases. These observations suggest that PAF may participate in pathophysiologic events during the course of oral inflammation. The availability of specific PAF receptor antagonists and human recombinant PAF-acetylhydrolase (PAF-AH), a plasma enzyme which rapidly destroys PAF, should provide clinical tools for the investigation of the role of PAF in these and other inflammatory disorders; and perhaps, ultimately, some of these reagents may prove to be therapeutically useful in the treatment and management of these conditions.

Relationship between platelet-activating factor concentration in rhesus monkey (Macaca mulatta) spermatozoa and sperm motility

Platelet-activating factor (PAF) is a potent signaling phospholipid that has been implicated in a number of biological activities. PAF concentration in primate spermatozoa has a positive correlation with fertility. While PAF is present in rhesus spermatozoa, there are no relational reports on its concentration and the cell's motility. The study objective was to determine if PAF concentration in rhesus spermatozoa was correlated with motility indices (percent motility and forward progression). Semen was collected from sexually mature males and cell counts, and percent motilities and forward progressions were recorded prior to PAF measurement by radioimmunoassay. Spermatozoa-derived PAF concentration ranged from a low of 0.9 picomoles/10(6) cells to a high of 13.0 picomoles/10(6) cells. The overall mean (+/-SEM) PAF concentration was 4.6 (+/-1.6) picomoles/10(6) spermatozoa. Regression analysis revealed a positive and significant relationship between PAF concentration in the spermatozoa and percent motility (R2 = 0.914; P < 0.01) as well as forward progression (R2 = 0.849; P < 0.05). A receiver-operator characteristic curve and the calculation of the probability that a positive forward progression will be predicted indicated a cutoff limit of 1.5 picomoles/10(6) cells for PAF concentration in rhesus sperm. Rhesus monkey spermatozoa motility was significantly greater (P < 0.01) in the high-PAF (> or =2 picomoles/10(6) cells) group (31.0 +/- 7.6) than in the low-PAF (<2 picomoles/10(6) cells) group (6.8 +/- 2.1). Rhesus monkey spermatozoa forward progression was significantly greater (P < 0.05) in the high-PAF (> or =2 picomoles/10(6) cells) group (3.0 +/- 1.0) than in the low-PAF (<2 picomoles/10(6) cells) group (0.7 +/- 0.3). The data demonstrate that PAF concentration in rhesus spermatozoa has a significant relationship with percent motility and the cell's forward progression. Determining PAF concentration in spermatozoa may be a significant predictor of fertility in the primate. Additional studies will elucidate the role of PAF in spermatozoa function and the significance PAF plays in primate fertility.