Platelet-Activating Factor, PAF Acetylhydrolase, and Severe Anaphylaxis
ABSTRACT 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.
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.
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).
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.
- SourceAvailable from: Ana Olivera
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- "However, some studies have reported that the levels of PAF in serum correlates with the severity of the anaphylactic reaction while histamine or tryptase levels do not, and PAF acetylhydrolase activity, the enzyme responsible of PAF inactivation, inversely correlates with severity scores (Vadas et al., 2008), and thus PAF antagonists, alone or in combination with other drugs, may be a consideration as rescue therapy for acute anaphylaxis reactions. "
ABSTRACT: Sphingosine-1phosphate (S1P), platelet activating factor (PAF) and eicosanoids are bioactive lipid mediators abundantly produced by antigen-stimulated mast cells that exert their function mostly through specific cell surface receptors. Although it has long been recognized that some of these bioactive lipids are potent regulators of allergic diseases, their exact contributions to disease pathology have been obscured by the complexity of their mode of action and the regulation of their metabolism. Indeed, the effects of such lipids are usually mediated by multiple receptor subtypes that may differ in their signaling mechanisms and functions. In addition, their actions may be elicited by cell surface receptor-independent mechanisms. Furthermore, these lipids may be converted into metabolites that exhibit different functionalities, adding another layer of complexity to their overall biological responses. In some instances, a second wave of lipid mediator synthesis by both mast cell and non-mast cell sources may occur late during inflammation, bringing about additional roles in the altered environment. New evidence also suggests that bioactive lipids in the local environment can fine-tune mast cell maturation and phenotype, and thus their responsiveness. A better understanding of the subtleties of the spatiotemporal regulation of these lipid mediators, their receptors and functions may aid in the pursuit of pharmacological applications for allergy treatments. Copyright © 2015. Published by Elsevier B.V.European journal of pharmacology 05/2015; DOI:10.1016/j.ejphar.2015.02.058 · 2.68 Impact Factor
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- "In early 70s a platelet-activating factor was first linked with allergy and IgE response . This factor, so-called PAF, has been recently defined as an important mediator playing a pivotal role that correlates with the severity of anaphylaxis  . In fact, the key treatment of anaphylaxis, epinephrine, has also been associated with human smooth muscle cells after stimulation with PAF . "
ABSTRACT: Background. Angiogenesis has a key role in several conditions and is regulated by several factors such as the platelet-derived growth factor (PDGF) or the vascular endothelial growth factor (VEGF). The goal of this study was to investigate the possible role of PDGF and VEGF in a group of patients with severe food allergy. Methods. We design a prospective longitudinal study (íµí± = 30) with patients with persistent cow's milk proteins (CMP) allergy. After achieving a CMP rush desensitization protocol, a clinical followup including SPT and blood samples to determine sIgE, protein levels, PDGF, and VEGF-A and a panel of the most representative Th 1 , Th 2 , T reg , and Th 17 cytokines were also monitored. Results. Baseline levels of PDGF and VEGF in the CMP allergic patients (1170 pg/mL and 253 pg/mL) were different compared to those nonallergic CMP control subjects (501 pg/mL and 108 pg/mL). Both PDGF and VEGF were significantly downregulated (íµí± < 0.05) 6 months after completion of the CMP desensitization process and remained significantly decreased 12 months later. Conclusion. The present study shows a significant increase of PDGF and VEGF in anaphylaxis suffering children compared to a control group. Interestingly, both VEGF and PDGF were significantly downregulated after completing a full CMP rush IgE desensitization.BioMed Research International 06/2014; 2014. DOI:10.1155/2014/372567 · 2.71 Impact Factor
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- "Recently, basophils and probably macrophages , not mast cells, were shown to be the major players in IgG-but not IgE-mediated systemic anaphylaxis involving platelet-activating factor (PAF) (Tsujimura et al., 2008; Mukai et al., 2009). These mechanisms of anaphylaxis may also be relevant in humans, as serum PAF levels are correlated with the severity of anaphylaxis in patients (Vadas et al., 2008). Furthermore, a study of meta-analysis for patients with food allergy reported that although allergen-specifi c IgE in serum was highly relevant to allergic symptoms and useful diagnostic marker, a considerable part of patients did not always increase the specifi c IgE in serum (García et al., 2009). "
ABSTRACT: It is important to evaluate the ability of novel proteins in food crops and products to elicit potentially harmful immunologic responses, including allergic hypersensitivity. We developed a novel mouse model of food allergy involving an oral challenge of a protein antigen after feeding of the antigen in combination with modulating factors often ingested in daily life, namely, dietary oil emulsion and salicylate. In the model, BALB/c mice were sensitized orally for three weeks with ovalbumin (OVA) in linoleic acid/lecithin emulsion, followed immediately by intraperitoneal injection of sodium salicylate. At the end of the sensitization, the incidence of mice positive for serum OVA-specific IgG1 but not IgE had significantly increased in the combined-sensitization group. After the 3-week sensitization, a single or double oral challenge with OVA effectively and significantly caused severe anaphylaxis, as compared with the groups sensitized with OVA in the emulsion or the vehicle alone. Moderate increase of plasma histamine and intestinal abnormality in histology was found only in the combined-sensitization group. Anaphylaxis symptoms in the sensitized mice were induced more by oral challenge than by intravenous challenge, suggesting a critical role for the mucosal system. This is the first model for successful induction of oral anaphylaxis in mice sensitized by feeding of food protein without adjuvant. It will be useful to elucidate the mechanism of food allergy and to detect modulating factors of oral allergy at sensitization using this model, which simulates real life conditions.The Journal of Toxicological Sciences 01/2012; 37(2):307-15. DOI:10.2131/jts.37.307 · 1.38 Impact Factor