Differential expression of eicosanoid pathways after whole blood stimulation in asthma patients

Abstract

Objectives: Asthma is a heterogeneous disease regarding its pathophysiology, clinical symptoms, and response to treatment. Eicosanoids are important inflammatory mediators, able to either promote or attenuate the underlying chronic airway inflammation. We compared eicosanoid expression patterns in the blood circulation and in stimulated blood leukocytes of asthma patients to identify differences in eicosanoid release which may be related to airway inflammation.

Methods: Blood was collected from 198 adult asthmatic patients and 63 healthy controls, participating in the German Center for Lung Research (DZL) ALLIANCE cohort. Eicosanoid release from leukocytes was analyzed using heparinized whole blood after in vitro stimulation with zymosan. Additionally, circulating eicosanoids were measured directly from ethylenediaminetetraacetic acid (EDTA) plasma. Eicosanoids were extracted via solid phase extraction and quantified by high-performance-liquid-chromatography-tandem-mass-spectrometry (HPLC-MS²).

Results: Eicosanoid levels were low in blood circulation with no significant differences between asthmatics and controls, except for leukotriene E₄ (LTE₄) which was slightly elevated in asthmatics. After in vitro stimulation we observed an inhibition of prostaglandin and thromboxane biosynthesis only in patients with severe asthma which was related to the regular use of systemic corticosteroids. In contrast, a significant increase was shown for formation of the 5-Lipoxygenase (5-LOX) product LTE₄ in steroid-naïve asthmatics with moderate as well as severe disease severity but not in subjects with systemic steroid treatment. Furthermore 15-Hydorxyeicosatetraenoic acid (15-HETE) production was elevated in asthmatic patients with mild-to-moderate disease activity but dropped down in severe asthmatics.

Conclusions: Profiling of eicosanoid production in stimulated whole blood samples showed a specific biosynthesis pattern of asthmatic patients, which is influenced by the use of systemic corticosteroids.

Keywords: Asthma; Eicosanoids; Inflammation.

Fig. 1

Expression of COX derived eicosanoids after whole blood stimulation with zymosan. Metabolite levels of healthy controls (Ctrl) were compared to asthmatic subjects which were grouped according to their asthma severity into mild-to-moderate (Mod) and severe (Sev) asthmatics. ∗p-value ≤0.05, ∗∗ p-value ≤0.01, ∗∗∗p-value ≤0.001, ∗∗∗∗p-value ≤0.0001. Abbreviations: COX: cyclooxygenase, PGES: prostaglandin E synthase, PGFS: prostaglandin F synthase, PGIS: prostaglandin I synthase, TXAS: thromboxane A synthase

Fig. 2

Expression of LOX derived eicosanoids after whole blood stimulation with zymosan. Metabolite levels of healthy controls (Ctrl) were compared to asthmatic subjects which were grouped according to their asthma severity into mild-to-moderate (Mod) and severe (Sev) asthmatics. ∗p-value ≤0.05, ∗∗ p-value ≤0.01, ∗∗∗p-value ≤0.001, ∗∗∗∗p-value ≤0.0001. Abbreviations: 5(15)-LOX: 5(15)-lipoxygenase, LTCS: leukotriene C₄ synthase, LTAH: leukotriene A₄ hydrolase

Fig. 3

Effects of oral glucocorticoids (OCS) on expression of COX (A) and LOX (B) derived eicosanoids in zymosan stimulated whole blood. Metabolite levels of healthy controls (Ctrl) were compared to subjects with severe asthma grouped into steroid naïve (no OCS) and steroid treated (OCS) asthmatics. ∗p-value ≤0.05, ∗∗ p-value ≤0.01, ∗∗∗p-value ≤0.001, ∗∗∗∗p-value ≤0.0001