Citations

Abstract In the accompanying study, we demonstrated that following Ag challenge, membrane (m)IL-5Rα expression is attenuated on bronchoalveolar lavage eosinophils, soluble (s)IL-5Rα is detectable in BAL fluid in the absence of increased steady state levels of sIL-5Rα mRNA, and BAL eosinophils become refractory to IL-5 for ex vivo degranulation. We hypothesized that IL-5 regulates its receptor through proteolytic release of mIL-5Rα, which in turn contributes to the presence of sIL-5Rα. Purified human peripheral blood eosinophils were incubated with IL-5 under various conditions and in the presence of different pharmacological agents. A dose-dependent decrease in mIL-5Rα was accompanied by an increase in sIL-5Rα in the supernatant. IL-5 had no ligand-specific effect on mIL-5Rα or sIL-5Rα mRNA levels. The matrix metalloproteinase-specific inhibitors BB-94 and GM6001 and tissue inhibitor of metalloproteinase-3 partially inhibited IL-5-mediated loss of mIL-5Rα, suggesting that sIL-5Rα may be produced by proteolytic cleavage of mIL-5Rα. IL-5 transiently reduced surface expression of β-chain, but had no effect on the expression of GM-CSFRα. Pretreatment of eosinophils with a dose of IL-5 that down-modulated mIL-5Rα rendered these cells unable to degranulate in response to further IL-5 stimulation, but they were fully responsive to GM-CSF. These findings suggest that IL-5-activated eosinophils may lose mIL-5Rα and release sIL-5Rα in vivo, which may limit IL-5-dependent inflammatory events in diseases such as asthma.

Abstract IL-5 is a key cytokine for eosinophil maturation, recruitment, activation, and possibly the development of inflammation in asthma. High concentrations of IL-5 are present in the airway after Ag challenge, but the responsiveness of airway eosinophils to IL-5 is not well characterized. The objectives of this study were to establish, following airway Ag challenge: 1) the expression of membrane (m)IL-5Rα on bronchoalveolar lavage (BAL) eosinophils; 2) the responsiveness of these cells to exogenous IL-5; and 3) the presence of soluble (s)IL-5Rα in BAL fluid. To accomplish these goals, blood and BAL eosinophils were obtained from atopic subjects 48 h after segmental bronchoprovocation with Ag. There was a striking reduction in mIL-5Rα on airway eosinophils compared with circulating cells. Furthermore, sIL-5Rα concentrations were elevated in BAL fluid, but steady state levels of sIL-5Rα mRNA were not increased in BAL compared with blood eosinophils. Finally, BAL eosinophils were refractory to IL-5 for ex vivo degranulation, suggesting that the reduction in mIL-5Rα on BAL eosinophils may regulate IL-5-mediated eosinophil functions. Together, the loss of mIL-5Rα, the presence of sIL-5Rα, and the blunted functional response (degranulation) of eosinophils to IL-5 suggest that when eosinophils are recruited to the airway, regulation of their functions becomes IL-5 independent. These observations provide a potential explanation for the inability of anti-IL-5 therapy to suppress airway hyperresponsiveness to inhaled Ag, despite a reduction in eosinophil recruitment.

Abstract Airway inflammation is increasingly recognized as a pivotal component of asthma. Because allergens provoke bronchial constriction and inflammation in allergic subjects, bronchial antigen challenge has emerged as a powerful technique for evaluating mechanisms involved in this process. In this study, we compare whole lung antigen challenge (WLAC) with segmentai bronchoprovocation (SBP) in eight allergic, non-asthmatic, non-smoking subjects, and evaluated the response by bronchoalveolar lavage (BAL) prior to, and 48 h after antigen challenge. Both challenge techniques evoked airway inflammation, manifest as an increase in total cells and eosinophils recovered by BAL, an increase in total protein concentration, and enhanced production of superoxide anion by airspace cells. The degree to which these changes occurred was significantly greater with SBP than WLAC, and only SBP evoked persistent measurable change in alveolar macrophage density and eosinophil granule protein concentrations. Moreover, although both techniques were associated with a comparable immediate fall in FEV1, only WLAC resulted in statistically significant persistent physiologic changes 48 h afterwards. We conclude that, as anticipated, SBP produces more intense airway inflammation in allergic subjects, does not result in late airway obstruction, and offers specific advantages in studying allergen-driven airway inflammation.

Stimulated by a recent controversy regarding pressure drops predicted in a giant aneurysm with a proximal stenosis, the present study sought to assess variability in the prediction of pressures and flow by a wide variety of research groups. In phase I, lumen geometry, flow rates, and fluid properties were specified, leaving each research group to choose their solver, discretization, and solution strategies. Variability was assessed by having each group interpolate their results onto a standardized mesh and centerline. For phase II, a physical model of the geometry was constructed, from which pressure and flow rates were measured. Groups repeated their simulations using a geometry reconstructed from a micro-computed tomography (CT) scan of the physical model with the measured flow rates and fluid properties. Phase I results from 25 groups demonstrated remarkable consistency in the pressure patterns, with the majority predicting peak systolic pressure drops within 8% of each other. Aneurysm sac flow patterns were more variable with only a few groups reporting peak systolic flow instabilities owing to their use of high temporal resolutions. Variability for phase II was comparable, and the median predicted pressure drops were within a few millimeters of mercury of the measured values but only after accounting for submillimeter errors in the reconstruction of the life-sized flow model from micro-CT. In summary, pressure can be predicted with consistency by CFD across a wide range of solvers and solution strategies, but this may not hold true for specific flow patterns or derived quantities. Future challenges are needed and should focus on hemodynamic quantities thought to be of clinical interest.

Background— The clinical significance of incomplete coronary revascularization (ICR) after percutaneous coronary intervention in patients with acute coronary syndromes is unknown. Methods and Results— We performed quantitative angiography of the entire coronary tree in 2954 patients with acute coronary syndromes in the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial. ICR was variably defined if any lesion with diameter stenosis (DS) cutoffs ranging from ≥30% to ≥70% with reference vessel diameter ≥2.0 mm remained after percutaneous coronary intervention. The primary outcome was 1-year composite rate of major adverse cardiac events (death, myocardial infarction, or ischemia-driven unplanned revascularization). With the use of DS cutoffs ≥30%, ≥40%, ≥50%, ≥60%, and ≥70%, the prevalence of ICR after percutaneous coronary intervention was 75%, 55%, 37%, 25%, and 17%, respectively. The 1-year major adverse cardiac event rate was increased among patients with ICR using all of the DS cutoffs. ICR (≥50% DS) was associated with higher 1-year rates of myocardial infarction (12.0% versus 8.2%; hazard ratio, 1.50; 95% confidence interval, 1.18–1.89; P =0.0007) and ischemia-driven unplanned revascularization (15.7% versus 10.2%; hazard ratio, 1.58; 95% confidence interval, 1.28–1.96; P <0.0001), with a trend toward increased mortality (3.1% versus 2.2%; hazard ratio, 1.43; 95% confidence interval, 0.90–2.27; P =0.13). By multivariable analysis, ICR (≥50% DS) was an independent predictor of 1-year major adverse cardiac events (hazard ratio, 1.36; 95% confidence interval, 1.12–1.64; P =0.002). The impact of ICR on major adverse cardiac events was similar regardless of chronic total occlusion presence, but it was more pronounced with a greater number of nonrevascularized lesions. Conclusions— Depending on the threshold of percent DS, ICR was present in 17% to 75% of patients with acute coronary syndromes after percutaneous coronary intervention. Regardless of the threshold, ICR was strongly associated with 1-year myocardial infarction, ischemia-driven unplanned revascularization, and major adverse cardiac events. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00093158.

Abstract Human blood eosinophils exposed ex vivo to hematopoietic cytokines (e.g., IL-5 or GM-CSF) subsequently display enhanced responsiveness to numerous chemoattractants, such as chemokines, platelet-activating factor, or FMLP, through a process known as priming. Airway eosinophils, obtained by bronchoalveolar lavage after segmental Ag challenge, also exhibit enhanced responsiveness to selected chemoattractants, suggesting that they are primed during cell trafficking from the blood to the airway. Earlier work has shown that chemoattractants stimulate greater activation of ERK1 and ERK2 following IL-5 priming in vitro, thus revealing that ERK1/ERK2 activity can be a molecular readout of priming under these circumstances. Because few studies have examined the intracellular mechanisms regulating priming as it relates to human airway eosinophils, we evaluated the responsiveness of blood and airway eosinophils to chemoattractants (FMLP, platelet-activating factor, CCL11, CCL5, CXCL8) with respect to degranulation, adherence to fibronectin, or Ras–ERK signaling cascade activation. When compared with blood eosinophils, airway eosinophils exhibited greater FMLP-stimulated eosinophil-derived neurotoxin release as well as augmented FMLP- and CCL11-stimulated adherence to fibronectin. In airway eosinophils, FMLP, CCL11, and CCL5 stimulated greater activation of Ras or ERK1/ERK2 when compared with baseline. Ras activation by FMLP in blood eosinophils was also enhanced following IL-5 priming. These studies are consistent with a model of in vivo priming of eosinophils by IL-5 or related cytokines following allergen challenge, and further demonstrate the key role of priming in the chemoattractant-stimulated responses of eosinophils. These data also demonstrate the importance of the Ras–ERK signaling pathway in the regulation of eosinophil responses to chemoattractants in the airway. Human airway eosinophils respond to several chemoattractants with increased activation of the Ras–ERK cascade, eosinophil-derived neurotoxin release, and adherence to fibronectin relative to blood eosinophils.