Platelet-activating Factor In Patients Research Articles

Role of Platelet Activation Factor in Patients with Hypersensitive Vasculitis, Autoimmune and Allergic Urticaria

Cutaneous syndrome is a relevant issue not only among allergic diseases but also among autoimmune disorders. Urticaria is a widespread problem, as its prevalence among the population can reach up to 9%. The main goal of the article is to analyze the role of platelet-activating factor in patients with hypersensitive vasculitis, autoimmune, and allergic urticaria. Urticarial rash is at the intersection of allergic and autoimmune diseases, where is observed active immunopathogenetic influence of platelet-activating factor in the initiation and maintenance of systemic vasculitis, including hypersensitive/urticarial and cryoglobulinemic vasculitis Considering the significant role of this factor in the pathogenesis of hypersensitive vasculitis and allergic reactions, selective targeting of platelet-activating factor represents a promising therapeutic approach. These include platelet-activating factor receptor antagonists such as rupatadine and apafant, as well as platelet-activating factor acetylhydrolase inhibitors, enzymes responsible for platelet-activating factor degradation. Targeted intervention on platelet-activating factor holds promise for the improving the quality of life of patients with hypersensitive vasculitis, autoimmune disorders, and allergic urticaria.

Role of micronutrients in the modulation of immune system and platelet activating factor in patients with COVID-19; a narrative review.

Dietary micronutrients may play important roles in the improvement of the immune responses against SARS-CoV-2. This study aimed to assess the effect of micronutrients on platelet activating factor (PAF) and immunity with a special focus on the coronavirus disease 2019 (COVID-19). All paper published in English on the effects of micronutrients including fat soluble vitamins, water soluble vitamins, and minerals on PAF, immunity, and COVID-19 were collected from online valid databases. Vitamin A may modulate the expression of PAF-receptor gene in patients with COVID-19. Vitamin D may modulate inflammatory response through influencing PAF pathway. Vitamin E may improve COVID-19 related heart injuries by exert anti-PAF activities. Vitamin C status may have PAF related anti-inflammatory and micro-thrombotic effects in SARS-CoV-2 patients. Furthermore, some trace elements such as copper, selenium, and iron may have key roles in strengthens immunity by inactivate PAF acetyl hydrolase. This narrative review study highlighted the importance of micronutrients in the improvement of immune function through modulation of PAF in patients with COVID-19. Further longitudinal studies are warranted.

Serum platelet activating factor levels predicts refractoriness to antihistamine treatment in chronic spontaneous urticaria

This work was supported by a grant from the National Research Foundation of Korea (NRF) funded by the Korea government (MSIP) (NRF-2018R1A2B6006199) and a research grant from Ahn-Gook Pharmaceutical Co, Ltd, Seoul, Republic of Korea. Platelet activating factor (PAF) is one of the most potent phospholipid released from platelets as well as various inflammatory cells. PAF has been known to play a role in the regulation of immune responses and allergic inflammation. This study was aimed to compare circulating levels of PAF and PAF-acetylhydrolase (AH) which can catabolize PAF in patients with chronic spontaneous urticarial (CSU) and healthy controls (NC) and to investigate relationships of their levels and urticaria severity and therapeutic response. Serum PAF and PAF-AH levels were measured by ELISA in 283 CSU patients and 111 age- and sex-matched NCs. Urticaria severity was evaluated by urticaria activity score over 7 days (UAS7). Within 3 months after measuring PAF levels, patients whose urticaria was not controlled by antihistamine treatment were classified as histamine receptor 1 antagonist (H1RA) non-responders. Serum PAF levels were higher in CSU patients than in NCs (median 4368.9 [17.0–14768.3] vs. 3256.4 [27.1–13886.7] pg/ml, p = 0.015), while serum PAF-AH levels were lower in CSU patients (105.6 [2.6–296.4] vs. 125.7 [2.0–291.1] ng/ml, p = 0.001). H1RA non-responders had higher levels of PAF (3804.5 [17.0–11716.3] vs. 5426.3 [53.1–14768.3], p < 0.001) in their sera. A generalized linear model revealed that a higher UAS7 score (odds ratio 1.023) and a PAF level ≥ 5000 pg/ml (1.409) were significant predictors of a poor response to H1RA treatment. CSU patients, particularly those with H1RA refractoriness, showed significant increases in serum PAF levels and decreases in PAF-AH as compared with NCs. Therapies modulating PAF and PAF-AH levels could be effective in patients with CSU refractory to antihistamines.

The membrane attack complex of complement contributes to plasmin-induced synthesis of platelet-activating factor by endothelial cells and neutrophils.

Thrombolytic agents, used to restore blood flow to ischaemic tissues, activate several enzymatic systems with pro-inflammatory effects, thus potentially contributing to the pathogenesis of ischaemia-reperfusion injury. Platelet-activating factor (PAF), a phospholipid mediator of inflammation, has been implicated in the pathogenesis of this process. We previously showed that the infusion of streptokinase (SK) induces the intravascular release of PAF in patients with acute myocardial infarction (AMI), and that cultured human endothelial cells (EC) synthesized PAF in response to SK and plasmin (PLN). In the present study, we investigated the role of the membrane attack complex (MAC) of complement in the PLN-induced synthesis of PAF. In vivo, we showed a correlation between the levels of soluble terminal complement components (sC5b-9) and the concentrations of PAF detected in blood of patients with AMI infused with SK. In vitro both EC and polymorphonuclear neutrophils (PMN), incubated in the presence of PLN and normal human serum, showed an intense staining for the MAC neoepitope, while no staining was detected when they were incubated with PLN in the presence of heat-inactivated normal human serum. Moreover, the insertion of MAC on EC and PMN plasmamembrane elicited the synthesis of PAF. In conclusion, our results elucidate the mechanisms involved in PAF production during the activation of the fibrinolytic system, showing a role for complement products in this setting. The release of PAF may increase the inflammatory response, thus limiting the beneficial effects of thrombolytic therapy. Moreover, it may have a pathogenic role in other pathological conditions, such as transplant rejection, tumoral angiogenesis, and septic shock, where fibrinolysis is activated.

Production of platelet-activating factor in patients with sepsis-associated acute renal failure.

Studies in experimental animals have suggested that platelet-activating factor (PAF) is a mediator of sepsis-associated acute renal failure (ARF). In the present study we have evaluated whether an increased concentration of PAF within circulation or urine of septic patients correlated with the worsening of renal function. The concentration of PAF and selected cytokines (TNF, IL-1, IL-6, IL-8) was evaluated in blood and urine of 12 patients with septic shock and ARF for 4 consecutive days. The data obtained indicate that blood and urinary concentrations of PAF and of IL-1, IL-6 and IL-8 were significantly higher in septic patients than in controls subjects and in patients with chronic renal failure. The concentration of TNF was significantly increased only in urine. A significantly positive correlation was found among blood concentration of PAF and heart rate (r = 0.4193, P < 0.017), serum creatinine (r = 0.3671, P < 0.038), serum IL-6 (r = 0.5475, P < 0.005) and urine excretion of IL-8 (r = 0.3984, P < 0.044), whereas a negative correlation was present with the number of circulating platelets (r = -0.4285, P < 0.018). Moreover, a positive correlation among the concentration of PAF in urine and the serum concentration of IL-6 (r = 0.5654, P < 0.006) and urine excretion of IL-6 (r = 0.6589, P < 0.0008) and IL-8 (r = 0.6371, P < 0.0004) were found. These results demonstrate in humans during ARF associated with septic shock the production of PAF, a mediator that has been previously implicated in the pathogenesis of experimental endotoxin-induced shock and renal injury. The observation that blood and urinary concentrations of PAF correlated with some of the clinical and laboratory parameters related to the severity of ARF and sepsis suggests that PAF may contribute to the development of renal injury in septic patients.

Platelet Activating Factor and Thromboxane B2 Production After Cardiopulmonary Bypass

Platelet-activating factor (PAF) is believed to have a central role in the pathogenesis of ischemia-reperfision injury. The purpose of this study was to investigate the relationships among production of PAF, thromboxane B2 (TαB2), and cardiopulmonary sequelae in patients undergoing coronary artery bypass graft surgery (CABGS). Venous blood from nine patients (eight men, one woman) undergoing scheduled CABGS, was sampled from central venous catheters before anesthetic induction, pre-cardiopulmonary bypass (CPB), 10 and 30 minutes post-CPB, 10 and 30 minutes post-aortic declamping, and 120 minutes and 24 hours after the conclusion of CPB. Plasma levels of PAF and TαB2 were determined by radioimmunoassay kits (Amersham Canada Ltd.). PAF and TαB2 were significantly different between high-risk patients (group I; Canadian Cardiovascular Society class 3-4; n = 4) and low-risk patients (group II; Canadian Cardiovascular Society class 2; n = 5): group I PAF = 960 pg/mL, group II PAF = 159 pg/mL (P = 0.0029); group I TαB2 = 320 pg/mL, group II TαB2 = 229 pg/mL (P = 0.0262). Group I PAF was significantly greater than group II PAF: before CPB = 825 pg/mL (group I), 138 pg/mL (group II); during initiation of CPB = 1600-2015 pg/mL (group I), 158-200 pg/mL (group II) (P = 0.0143). Correlations between duration of CPB and peak PAF (r = 0.7049, P = 0.0339), peak PAF level, and time to extubation (r = 0.8863, P = 0.0079) were significant. PAF levels were different in patients requiring postoperative epinephrine (2124 ± 700 pg/mL) or dopamine (667 ± 266 pg/mL) (P = 0.0042). The production of PAF is determined by preoperative patient characteristics and duration of CPB. Increased levels of PAF in patients with unstable angina, left main coronary artery disease, or recent myocardial infarction are associated with the need for increased inotropy and prolonged ventilatory support following CABGS. The degree of PAF production during CPB may be a factor in postoperative instability in high-risk patients.

Antibodies against platelet-activating factor in patients with antiphospholipid antibodies.

We have studied the specificity of antiphospholipid antibodies in 148 patients with autoimmune diseases, 120 patients with systemic lupus erythematosus and 28 with the primary antiphospholipid syndrome. In addition, 20 patients suffering from syphilis were studied. As a control group, 64 healthy volunteers were investigated. Patient and control serum samples were tested for binding to seven different phospholipid antigens by ELISA. Interestingly, 90% of the sera from syphilis patients and 6% of the autoimmune patients exhibited a significant binding to platelet-activating factor (PAF), a molecule similar to the structure of phosphatidylcholine. In addition, the IgG fraction from one of the lupus patients, which showed a high binding activity to PAF, was further affinity-purified using both liposomes and an affinity chromatography column. Preincubation of these antibodies with PAF inhibited subsequent binding to immobilized PAF. These observations might suggest a putative interaction of antiphospholipid autoantibodies with PAF 'in vivo', which may have, in some patients, important pathophysiological consequences.

Urinary excretion of platelet activating factor in patients with immune-mediated glomerulonephritis

We have investigated whether human immune-mediated glomerulonephritis is associated with changes in platelet activating factor (PAF) biosynthesis. Urinary PAF, taken as a marker of its renal synthesis, was significantly higher in patients with membranous nephropathy (N = 9) than in healthy controls (N = 8). This was not due to a lower degradation of PAF since urinary acetylhydrolase activity was comparable in patients and controls. A significant positive correlation between urinary excretion of PAF and proteinuria was observed. PAF generation was comparable in polymorphonuclear cells isolated from patients with membranous nephropathy and controls. PAF levels in blood from patients with membranous nephropathy were significantly lower than in controls, suggesting that the excessive generation of PAF is confined to the kidney. The results document that signs of renal disease activity in human membranous nephropathy are associated with an excessive renal synthesis of PAF.

Elevated blood levels of platelet activating factor in patients with unstable angina

Elevated blood levels of platelet activating factor in patients with unstable angina

Occupancy of platelet receptors for platelet-activating factor in patients with septicemia.

The possible involvement of platelet-activating factor (PAF) in the pathogenesis of endotoxemia, was investigated by using a binding assay to patients' platelets, complemented with the extraction and chemical characterization of PAF obtained from patients' platelets. Platelets from 12 human volunteers had 281 +/- 63 freely accessible high affinity binding sites (PAF-receptors) per platelet; whereas this number was of 49 +/- 37 PAF-receptors per platelet, n = 14 samples, P less than 0.01, in a group of 13 patients with positive blood culture. A group of patients with respiratory or cardiovascular disturbances and negative blood culture had 253 +/- 74, accessible receptors per platelet (n = 19 samples from 16 patients, P less than 0.01 as compared to septic patients, which was not significantly different when compared to control individuals). Patients with sepsis possessed significant amounts of PAF associated to their platelets, whereas this mediator could not be isolated from platelets of patients with respiratory or cardiovascular disturbances and negative blood culture, nor from platelets of control individuals. PAF was also assayed in whole blood samples and found at high concentrations in sepsis patients. These data indicate that occupancy of PAF receptors in combination with high amounts of platelet-associated PAF, is a common finding in patients with sepsis.