The effect of platelet activating factor on nasal hypersensitivity

Abstract

Platelet activating factor (PAF) is known to have a wide range of biological activities. In the lower airways PAF has been suggested as the biochemical mediator partly responsible for the bronchial hyperreactivity which is a feature of asthma. In order to study whether PAF has a similar effect in the upper airways, we carried out a double blind, placebo-controlled cross-over study in twelve patients with strictly seasonal allergic rhinitis. The study was performed in pollen-free winter months. 26 micrograms PAF or placebo was sprayed into each nasal cavity 8 h and 1 h before a nasal allergen challenge. The nasal response to PAF and the allergen challenge that followed was monitored by repeated measurements of nasal expiratory peak flow rate and symptom scores. PAF induced only minor changes in nasal patency and nasal symptoms as compared to placebo. However, pretreatment with PAF induced an increase in responsiveness of the nasal vasculature to the allergen challenge that followed. This was registered as a small, but statistically significant increase in the symptom scores for nasal blockage, from 1.7 (0.3; SEM) after placebo pretreatment to 2.4 (0.36; SEM) after PAF (p less than 0.05). A similar trend was also noted for the measurements of nasal peak flow. The other response parameters, sneezes and secretion, remained identical. These results suggest that PAF may play a role in human nasal hyperreactivity, but it appears that PAF is not a major mediator involved in the induction of this phenomenon.

Nasal eosinophilia induced by PAF-acether is accompanied by the release of eosinophil cationic protein

“…LTC 4 . Aliquots of the supernatants for the leukotriene assay were aspirated, decanted and extracted following the method of ANDERSON et al [21].…”

“…Every sample was assayed in duplicate and the results were expressed as ng·ml -1 lavage fluid. The results of the radioimmunological assay for iLTC 4 in nasal lavage fluids were previously validated by high performance liquid chromatography analysis [2,18], performed according to the technique of SAUTEBIN et al [23].…”

“…We have investigated the possible involvement of PAF in allergic rhinitis, and have found that PAF can be released, along with its precursor/metabolite lyso-PAF, in nasal lavage fluids during the early antigen-induced reaction in patients with respiratory allergy [2]. Nasal challenge with PAF provokes nasal obstruction with an increase in nasal airway resistances [3], and nasal hyperreactivity [4,5]. Furthermore, nasal neutrophilia and eosinophilia have been observed after challenge with PAF, with a more rapid and more marked response in atopic than in normal subjects [6].…”

“…We have performed nasal challenge with PAF in 10 allergic subjects and 10 normal subjects. In addition, we have evaluated accompanying cytological changes and mediator release (histamine, LTC 4 , eosinophil cationic protein) in nasal lavage fluids.…”

Glucocorticosteroids and rhinitis

“…Whether any particular mediator or cytokine alone or in combination is responsible for the change in reactivity remains to be clarified. Challenge with single mediators, such as histamine, methacholine, and PAF has failed to induce an increase in responsiveness (5,61), although challenge with PAF can induce local eosinophilia (81).…”