Phosphoinositide 3-kinase (PI3K) is thought to contribute to the pathogenesis of asthma by effecting the recruitment, activation, and apoptosis of inflammatory cells. We examined the role of class IA PI3K in antigen-induced airway inflammation and hyperresponsiveness by i.p. administration into mice of Δp85 protein, a dominant negative form of the class IA PI3K regulatory subunit, p85α, which was fused to HIV-TAT (TAT-Δp85). Intraperitoneal administration of TAT-Δp85 caused time-dependent transduction into blood leukocytes, and inhibited activated phosphorylation of protein kinase B (PKB), a downstream target of PI3K, in lung tissues in mice receiving intranasal FMLP. Antigen challenge elicited pulmonary infiltration of lymphocytes, eosinophils and neutrophils, increase in mucus-containing epithelial cells, and airway hyperresponsiveness to methacholine. Except for modest airway neutrophilia, these effects all were blocked by treatment with 3–10 mg/kg of TAT-Δp85. There was also significant reduction in IL-5 and IL-4 secretion into the BAL. Intranasal administration of IL-5 caused eosinophil migration into the airway lumen, which was attenuated by systemic pretreatment with TAT-Δp85. We conclude that PI3K has a regulatory role in Th2-cell cytokine secretion, airway inflammation, and airway hyperresponsiveness in mice.

In this study, we determined the functional significance and mechanism of the exogenous hVPLA 2 -induced arachidonic acid (AA) release and leukotriene C 4 (LTC 4 ) synthesis in isolated human peripheral blood eosinophils. As low a concentration as 10 nM exogenous hVPLA 2 was able to elicit the significant release of AA and LTC 4 from unstimulated eosinophils, which depended on its ability to act on phosphatidylcholine membranes. hVPLA 2 also augmented the release of AA and LTC 4 from eosinophils activated with formyl-Met-Leu-Phe ؉ cytochalasin B. A cellular fluorescent PLA 2 assay showed that hVPLA 2 had a lipolytic action first on the outer plasma membrane and then on the perinuclear region. hVPLA 2 also caused the translocation of 5-lipoxygenase from the cytosol to the nuclear membrane and a 2-fold increase in 5-lipoxygenase activity. However, hVPLA 2 induced neither the increase in intracellular calcium concentration nor cPLA 2 phosphorylation; consequently, cPLA 2 activity was not affected by hVPLA 2 . Pharmacological inhibition of cPLA 2 and the hVPLA 2 -induced activation of eosinophils derived from the cPLA 2 -deficient mouse corroborated that hVPLA 2 mediates the release of AA and leukotriene in a cPLA 2 -independent manner. As such, this study represents a unique example in which a secretory phospholipase induces the eicosanoid formation in inflammatory cells, completely independent of cPLA 2 activation.

We examined the role of a cytosolic phospholipase A2 (cPLA2) in antigen-induced eosinophil infiltration of airways and in airway hyperresponsiveness to methacholine. Inhibition of cPLA2, or blockade of the platelet-activating factor (PAF) receptor, blocked antigen-induced airway hyperresponsiveness and suppressed eosinophil infiltration. Neither cyclooxygenase nor 5-lipoxygenase inhibition had either effect. We show here that, in antigen-sensitized guinea pigs, cPLA2 inhibition prevents both eosinophilic infiltration and subsequent airway hyperresponsiveness after antigen challenge. We also show that this effect is mediated by first-step hydrolysis of membrane phospholipid into lysophospholipid rather than by prostanoid or leukotriene metabolites of arachidonate.

It has been reported that acetaldehyde may be a main factor of alcohol-induced bronchoconstriction in Japanese patients with asthma. The purpose of this study was to investigate the direct action of acetaldehyde on the airway in asthmatic and healthy nonasthmatic subjects. We investigated the bronchial response to inhalation of ascending doses (5, 10, 20, and 40 mg/ml) of acetaldehyde in nine asthmatic subjects, who were treated with placebo or terfenadine for 4 days in a double-blind, randomized, placebo-controlled, crossover fashion, and in nine age- and sex-matched healthy subjects. The bronchial responsiveness to inhaled methacholine was also measured in the same asthmatics on a separate day. Inhaled acetaldehyde caused marked (more than 20%) significant decrease in FEV1 in asthmatics after placebo, which was larger than that in asthmatics after terfenadine and in healthy subjects. There was no significant difference in the decrease in FEV1 between asthmatics treated with terfenadine and healthy subjects. There was a significant correlation between the methacholine and acetaldehyde concentrations producing a 20% fall in FEV1 in asthmatics. We conclude that acetaldehyde causes bronchoconstriction indirectly via histamine release in asthmatics, and that nonspecific bronchial hyperresponsiveness is a necessary precondition for the expression of acetaldehyde-produced bronchoconstriction.

Increased sensitivity of cough reflex is a fundamental feature of bronchodilator resistant non-productive cough associated with eosinophilic tracheobronchitis. Our hypothesis is that cough sensitivity is increased by airway allergic reaction characterized by airway eosinophilic inflammation. The aim of this study was to elucidate the hypothesis and clarify the characteristics of the increased cough sensitivity. Number of coughs elicited by inhalation of increasing concentrations of capsaicin (10-8, 10-6 and 10-4 M) was counted 24 h after an aerosolized antigen or saline in actively sensitized or non-sensitized (naive) conscious guinea pigs and then bronchoalveolar lavage was performed. The cough response was also measured 1 day before and 1, 2, 3, 5 and 7 days after an aerosolized antigen challenge in sensitized or naive animals. In addition, effect of procaterol (0.1 mg/kg), atropine (1 or 10 mg/kg), phosphoramidon (2.5 mg/kg) given intraperitoneally 30 min before the capsaicin challenge or capsaicin desensitization on the cough response was examined. Furthermore, the thromboxane A2 (TXA2) receptor antagonist S-1452 in a dose of 0.01 or 0.1 mg/kg or vehicle (saline) was given intraperitoneally at 24 and 1 h before the measurement of cough response. Number of coughs caused by capsaicin was extremely increased 24 h after an antigen challenge in sensitized guinea pigs compared with a saline or an antigen challenge in naive animals or a saline challenge in sensitized animals. The increased cough response disappeared at 3-7 days after the antigen challenge. Eosinophils in bronchoalveolar lavage fluid obtained after the measurement of capsaicin-induced coughs, which was performed 24 h after the antigen challenge, were significantly increased in sensitized guinea pigs. The eosinophil count was significantly correlated to the number of capsaicin-induced coughs. Procaterol or atropine did not alter the antigen-induced increase of cough sensitivity, whereas atropine did reduce the cough response in naive animals. Phosphoramidon increased the number of capsaicin-induced coughs in naive guinea pigs but not in sensitized and antigen-challenged animals. Capsaicin desensitization decreased the cough response in both antigen-challenged sensitized guinea pigs and naive animals. S-1452 reduced the antigen-induced increase of cough response in sensitized guinea pigs, but not in naive animals. Airway allergy accompanied with airway eosinophilia induces transient increase in cough sensitivity, which is not mediated by bronchoconstriction. The increased cough sensitivity may result in part from inactivation of neutral endopeptidase and TXA2, one of the inflammatory mediators.

A 21-year-old womanpresented with acute progressive dyspnea. Chest computed tomography (CT) revealed diffuse bilateral infiltrates.Based on the results of transbronchial lung biopsy (TBLB) and bronchoalveolar lavage fluid (BALF) and her clinical course, she was diagnosed as having acute eosinophilic pneumonia. Wesuspected that the disease was related to smoking because she had started smoking ten days before the onset of symptoms. Therefore, a cigarette-smoking challenge test was done with the patient's informed consent. After the challenge, eosinophilic pneumonia was documented by BALF and TBLB findings, which were similar to those detected on admission, without significant radiographic findings.

No abstract

We transduced dominant negative (dn) HIV TAT-Ras protein into mature human eosinophils to determine the signaling pathways and mechanism involved in integrin-mediated adhesion caused by cytokine, chemokine, and chemoattractant stimulation. Transduction of TAT-dnRas into nondividing eosinophils inhibited endogenous Ras activation and extracellular signal-regulated kinase (ERK) phosphorylation caused by IL-5, eotaxin-1, and fMLP. IL-5, eotaxin-1, or fMLP caused 1) change of Mac-1 to its active conformation and 2) focal clustering of Mac-1 on the eosinophil surface. TAT-dnRas or PD98059, a pharmacological mitogen-activated protein/ERK kinase inhibitor, blocked both focal surface clustering of Mac-1 and the change to active conformational structure of this integrin assessed by the mAb CBRM1/5, which binds the activation epitope. Eosinophil adhesion to the endothelial ligand ICAM-1 was correspondingly blocked by TAT-dnRas and PD98059. As a further control, we used PMA, which activates ERK phosphorylation by postmembrane receptor induction of protein kinase C, a mechanism which bypasses Ras. Neither TAT-dnRas nor PD98059 blocked eosinophil adhesion to ICAM-1, up-regulation of CBRM1/5, or focal surface clustering of Mac-1 caused by PMA. In contrast to β2-integrin adhesion, neither TAT-dnRas nor PD98059 blocked the eosinophil adhesion to VCAM-1. Thus, a substantially different signaling mechanism was identified for β1-integrin adhesion. We conclude that H-Ras-mediated activation of ERK is critical for β2-integrin adhesion and that Ras-protein functions as the common regulator for cytokine-, chemokine-, and G-protein-coupled receptors in human eosinophils.