Functional activity of peripheral blood eosinophils in allergen-induced late-phase airway inflammation in asthma patients

Abstract

ObjectiveWe aimed to investigate peripheral blood eosinophil chemotaxis, generation of spontaneous reactive oxygen species (ROS), and apoptosis in patients with allergic asthma after bronchial allergen challenge.Material and methodsA total of 18 patients with allergic asthma (AA), 14 with allergic rhinitis (AR), and 10 healthy subjects (HS) underwent bronchial challenge with a specific allergen extract. Eosinophils from peripheral blood were isolated 24 h before as well as 7 and 24 h after bronchial allergen challenge. Chemotaxis, spontaneous ROS production in eosinophils, and apoptosis were analyzed by flow cytometry. Serum and induced sputum IL-5 levels were measured by ELISA; the cell count in sputum was analyzed by the May-Grünwald-Giemsa method.ResultsBefore bronchial allergen challenge, peripheral blood eosinophil chemotaxis, spontaneous ROS production was enhanced and eosinophil apoptosis was reduced in the patients with AA as compared with AR patients and HS (P < 0.05). Meanwhile, eosinophil chemotaxis and ROS generation markedly increased in the patients with AA 7 h and 24 h after challenge compared with other groups and baseline values (P < 0.05). The percentage of apoptotic eosinophils in the patients with AA decreased at 7 h as well as 24 h after challenge when compared with other groups and the baseline values (P < 0.05). There was a significant correlation between the migrated peripheral blood eosinophil count and the sputum eosinophil count (Rs = 0.89, P < 0.0001) and the sputum IL-5 level (Rs = 0.68, P = 0.002) at 24 h after bronchial challenge only in the patients with AA. Furthermore, the percentage of peripheral blood apoptotic eosinophils significantly correlated with eosinophil count in sputum (Rs = −0.53, P = 0.02), and ROS production correlated with the serum IL-5 levels (Rs = 0.71, P = 0.01).ConclusionDuring allergen-induced late-phase airway inflammation, peripheral blood eosinophils demonstrated further alterations of their functional activity manifested by enhanced spontaneous ROS production, increased chemotaxis, and diminished apoptosis in patients with AA.

In Vivo Allergen-Activated Eosinophils Promote Collagen I and Fibronectin Gene Expression in Airway Smooth Muscle Cells via TGF-β1 Signaling Pathway in Asthma

“…It means that in the airways, there is not only more migrated eosinophils, but their apoptosis is reduced. In the previous study, we showed that blood eosinophils apoptosis from AA patients and allergic rhinitis patients were significantly lower compared to HS [59]. Similar results were shown in another study where asthma was phenotyping using sputum cell analysis or looking at the associations between sputum eosinophils apoptosis level and asthma severity [80].…”

“…The proteases such as MMP-2 and MMP-9, ROS, pH, and integrins contribute to the liberation of active TGF-β from ECM. Eosinophils produce increased levels of MMP-9, ROS as well as TGF-β in asthma [59][60][61]. Prolonged viability of eosinophils after migration to airways and adhesion to ECM and/or ASM cells creates conditions for the secretion of mediators by eosinophils [33].…”

Clinical implications of blood eosinophil count in patients with non-asthma&ndash;COPD overlap syndrome COPD

“…This finding implies that the eosinophilic activity of patients with non-ACOS COPD may be different from that of patients with asthma or ACOS. In patients with allergic asthma, the eosinophilic activity may be altered by the enhanced production of spontaneous reactive oxygen species, increased chemotaxis, and diminished apoptosis, 29 while the eosinophilic activity in COPD is not reported. Recently, a patient-level meta-analysis reported that patients with an eosinophil count of <2% had a higher risk of pneumonia, 30 which may reflect the importance of other inflammatory cells such as neutrophils, which has a key role in immune reaction of COPD, 31 in this subpopulation.…”

The impact of allergen exposure and specific immunotherapy on circulating blood cells in allergic rhinitis

“…Interestingly, in symptomatic AR patients granules of circulating eosinophils were found mostly intact, implying that circulating eosinophils retain their granule contents until they home in target tissues [ 100 ]. Also, blood eosinophil chemotaxis and spontaneous ROS production did not significantly differ between AR patients and healthy controls [ 101 ].…”