Blood Eosinophils Subtypes and Their Survivability in Asthma Patients

Abstract

Eosinophils subtypes as lung-resident (rEOS) and inflammatory (iEOS) eosinophils are different in surface protein expression, functions, response to IL-5 and localization in lungs. rEOS- and iEOS-like eosinophils are found in blood; thus, we aimed to investigate their quantity and survivability in asthma patients. A total of 40 individuals were included: 10 steroid-free non-severe allergic asthma (AA), and 18 severe non-allergic eosinophilic asthma (SNEA) patients, the control group consisted of 12 healthy non-smoking subjects (HS). A bronchial challenge with Dermatophagoides pteronysinnus allergen was performed for AA patients and HS. Blood eosinophils subtyping was completed with magnetic beads’ conjugated antibodies against surface CD62L. Eosinophils adhesion to hTERT airway smooth muscle (ASM) cells was measured by evaluating their peroxidase activity and viability by annexin V and propidium iodide staining. We found that the predominant blood eosinophil subtype in AA patients was iEOS, while rEOS prevailed in SNEA patients (p < 0.05). Moreover, rEOS demonstrated higher adhesion intensity compared with iEOS in all investigated groups. Both eosinophils subtypes of SNEA patients had higher survivability over the AA group. However, iEOS survivability from AA and SNEA groups was higher compared with rEOS under standard conditions, when rEOS survivability increased after their incubation with ASM cells. Bronchial allergen challenge abolished the dominance of blood iEOS in AA patients and prolonged only iEOS survivability. Though the challenge did not affect the adhesion of any eosinophils subtypes, the direct dependence of rEOS and iEOS survivability on their interaction with ASM cells was revealed (p < 0.05). These findings provide the premise for eosinophils subtype-oriented asthma treatment.

α4β1 and αMβ2 Integrin Expression and Pro-Proliferative Properties of Eosinophil Subtypes in Asthma

“…An ultrasonic spirometer was used to test the lung function (Ganshorn Medizin Electronic, Niederlauer, Germany). The results of forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC), and the FEV 1 /FVC ratio were considered the largest of the three independent measurements, as described in [ 4 ].…”

“…Aerosolized methacholine was inhaled at 2 min intervals with a dose starting at 0.0101 mg that was gradually increased to 0.121, 0.511, and 1.31 mg until the total cumulative dose was achieved or a 20% decrease in FEV1 from the baseline was achieved. The bronchoconstriction effect of each methacholine dose was expressed as described in [ 4 ].…”

“…Fractional exhaled nitric oxide (FeNO) analysis was performed on all study participants through an online method using a single exhalation and electrochemical assay (NIOX VERO, Circassia, UK) according to the methodology described in [ 4 ].…”

“…Similar markers expressing eosinophils can be found in circulation and are called rEOS-like cells and iEOS-like cells. Furthermore, the subtypes of blood-circulating eosinophils are specific for asthma phenotypes: iEOS-like cells predominate in allergic asthma (AA), and rEOS-like cells in severe non-allergic eosinophilic asthma (SNEA) [ 4 ].…”

“…We speculated that rEOS-like and iEOS-like cells could differ in their effects on the proliferation and apoptosis of ASM cells in asthma. Moreover, as we know that allergen-provoked acute asthma episodes could not equally affect the pro-proliferative properties of eosinophil subtypes [ 4 ], we hypothesized that a bronchial allergen challenge with D. pteronyssinus might result in accelerated eosinophil subtype-related development of airway remodeling during acute asthma. Lastly, eosinophil adhesion via integrins is essential for their functions.…”