Metabolic Profiling of Human Eosinophils

Abstract

Immune cells face constant changes in their microenvironment, which requires rapid metabolic adaptation. In contrast to neutrophils, which are known to rely near exclusively on glycolysis, the metabolic profile of human eosinophils has not been characterized. Here, we assess the key metabolic parameters of peripheral blood-derived human eosinophils using real-time extracellular flux analysis to measure extracellular acidification rate and oxygen consumption rate, and compare these parameters to human neutrophils. Using this methodology, we demonstrate that eosinophils and neutrophils have a similar glycolytic capacity, albeit with a minimal glycolytic reserve. However, compared to neutrophils, eosinophils exhibit significantly greater basal mitochondrial respiration, ATP-linked respiration, maximum respiratory capacity, and spare respiratory capacity. Of note, the glucose oxidation pathway is also utilized by eosinophils, something not evident in neutrophils. Furthermore, using a colorimetric enzymatic assay, we show that eosinophils have much reduced glycogen stores compared to neutrophils. We also show that physiologically relevant levels of hypoxia (PO2 3 kPa), by suppressing oxygen consumption rates, have a profound effect on basal and phorbol–myristate–acetate-stimulated eosinophil and neutrophil metabolism. Finally, we compared the metabolic profile of eosinophils purified from atopic and non-atopic subjects and show that, despite a difference in the activation status of eosinophils derived from atopic subjects, these cells exhibit comparable oxygen consumption rates upon priming with IL-5 and stimulation with fMLP. In summary, our findings show that eosinophils display far greater metabolic flexibility compared to neutrophils, with the potential to use glycolysis, glucose oxidation, and oxidative phosphorylation. This flexibility may allow eosinophils to adapt better to diverse roles in host defense, homeostasis, and immunomodulation.

Transcriptomic Analysis of Human Astrocytes In Vitro Reveals Hypoxia-Induced Mitochondrial Dysfunction, Modulation of Metabolism, and Dysregulation of the Immune Response

“…The authors measured maximal glycolytic capacity which they reported to be increased after hypoxia but again they did not measure reserve capacity and, unlike in this study, only looked at total ECAR rather than non-glycolytic and glycolytic ECAR. A loss of mitochondrial spare respiratory capacity after hypoxia has also been reported in CD4+ T cells, eosinophils, and neutrophils [ 39 , 40 ]. In these studies, glycolytic reserve capacity was not lost in CD4+ T cells; however, non-glycolytic ECAR was not taken into account or was not reported in eosinophils and neutrophils.…”

Adipose Tissue Immunomodulation: A Novel Therapeutic Approach in Cardiovascular and Metabolic Diseases

“…Nevertheless, enhancing AT eosinophil abundance is debated since several studies demonstrated no beneficial or even negative outcomes of this approach (220). Required for the production of ROS LPS-treated mouse bone marrow-derived neutrophils treated with Antimycin A or myxothiazol (190) Required for migration Polg CRISPR/Cas9-mediated neutrophil-specific knockout in Zebra fish (191) Pentose phosphate pathway ⇑ Required for NETosis Amyloid fibril-and phorbol myristate acetate-stimulated human neutrophils (192) Required for ROS generation and NETosis G6PD-deficient patients G6PD-deficient mice (193,194) TCA cycle ⇑ Required for chemotaxis Isocitrate dehydrogenase 1 mutant mice (195) Required for differentiation Mouse Atg5-deficient neutrophils and an in vitro model of differentiating neutrophils (196) Lipogenesis ⇑ Required for differentiation Atg7-deficient neutrophil precursors (197) Required for neutrophil maintanence FASlox/lox-Rosa26-CreER mice (198) Glutamine metabolism It was suggested that circulating eosinophils display a greater metabolic flexibility in comparison to neutrophils (200,201). Further investigation into the metabolic rewiring of eosinophils (shown in Table 3) is required as emerging roles of eosinophils suggest a central modulatory function in AT homeostasis.…”

Novel Insights Into Tissue-Specific Biochemical Alterations in Pediatric Eosinophilic Esophagitis Using Raman Spectroscopy

“…This inverse relationship seemed to be majorly driven by the degree of eosinophilic inflammation (and PEC) and BZH. We hypothesize that a combination of increased glycogen uptake by the large numbers of eosinophils, abundance of immature epithelial cells in basal zone with lower amounts of cytoplasm and cytoplasmic glycogen, and ongoing metabolic activity related to the eosinophilic inflammation ( 23 ) in epithelial (and possibly in subepithelial) compartment might explain these findings. The intensity of Raman peaks assigned to lipid content in iEoE was higher than that of aEoE but comparable with that of non-EoE controls.…”