Platelet-activating factor (PAF) [1] is a potent etherlinked phospholipid mediator of inflammation which is considered to have a potential role in the pathogenesis of bronchial asthma. Recently, we have shown that PAF (dosage range 24-12 µg) disturbed pulmonary gas exchange in normal individuals [2][3][4] and in patients with mild asthma [5,6] in an identical manner to the entire spectrum of ventilation-perfusion (V 'A/Q ') mismatching shown in patients with bronchial asthma [7,8]. We suggested that the V 'A/Q ' defects could be preferentially related to an augmented bronchial vascular permeability due to post-capillary venoconstriction induced by PAF, thereby supporting the notion that PAF may play a key role, as a putative potent mediator of inflammation in human airways [5,8]. However, negative results have been obtained over the last few years, in stable patients with mild to moderate asthma with different PAF antagonists, and these question the role of PAF in the pathobiology of asthma.The compound SR 27417A (N-(2-dimethylaminoethyl)-N-(pyridinylmethyl)(4-(2,4,6 triisopropylphenyl) thiazol-2-yl)) amine difumarate is a novel class of anti-PAF medication that has been shown to be a potent, long-lasting and selective second generation PAF antagonist [9,10]. The present study was undertaken to assess the efficacy of this new PAF receptor antagonist, SR 27471A, in attenuating or preventing the PAF-induced systemic, neutropenic, lung mechanical and pulmonary gas exchange effects observed in patients with mild asthma [5,6]. To our knowledge, the efficacy of this class of anti-asthma compounds on pulmonary gas exchange abnormalities provoked by PAF has not been investigated previously. Methods Study populationTwelve patients with mild asthma (table 1) were recruited from our Outpatient Department for the study, which was approved by the Ethical Research Committee of the Hospital Clinic. All subjects gave informed written consent after the purpose, risks and potential benefits of the study were explained to them. The inclusion criteria were: no respiratory infection or exacerbation of asthma within the preceding 6 weeks; forced expiratory volume in one second (FEV1) Š80% predicted and positive methacholine bronchial challenge; maintenance therapy with aerosol short-acting beta-adrenergics and/or inhaled corticosteroids, but no previous treatment with oral corticosteroids; and absence of any systemic or cardiopulmonary disease We conclude that SR 27417A is effective in inhibiting systemic, cellular and pulmonary effects after platelet-activating factor challenge in patients with mild bronchial asthma.
Bronchoprovocation with cysteinyl-leukotrienes (LTs) induces airflow obstruction and gas exchange abnormalities, namely ventilation-perfusion ratio (V9A/Q9) imbalance. However, it is unknown which of the two different receptors for cysteinyl-LTs mediate these V9A/Q9 disturbances.In a double-blinded, crossover design, 10 patients with mild asthma were randomised to receive an oral single dose of the selective cysteinyl-LT 1 receptor antagonist montelukast (40 mg) or placebo before leukotriene (LT)D 4 inhalation challenge. Gas exchange, including V9A/Q9 descriptors were measured at baseline, 3 h after montelukast/placebo pretreatment and 5, 15 and 45 min after the LTD 4 challenge.Compared with montelukast, inhalation of LTD 4 induced a marked fall in forced expiratory volume in one second (mean¡SE 33¡2%) and profound V9A/Q9 mismatching, reflected by a decreased arterial oxygen tension (from 100¡4 to 75¡3 mmHg) and an increased overall index of V9A/Q9 heterogeneity dispersion of retention minus excretion inert gases corrected for dead space (from 4.9¡1.2 to 8.4¡1.1; normalf3.0; dimensionless), 5 min after placebo. Following montelukast, LTD 4 produced no significant changes in any of the variables.In conclusion, these findings point to the view that leukotriene D 4 -induced gas exchange disturbances and bronchoconstriction are both mediated by the cysteinyl-leukotriene 1 receptor.
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