Beyond Il-5: Metabolic Reprogramming and Stromal Support Are Prerequisite for Generation and Survival of Long-Lived Eosinophil

Abstract

Eosinophils play surprisingly diverse roles in health and disease. Accordingly, we have now begun to appreciate the scope of the functional and phenotypic heterogeneity and plasticity of these cells. Along with tissue-recruited subsets during inflammation, there are tissue resident eosinophil phenotypes with potentially longer life spans and less dependency on IL-5 for survival. Current models to study murine eosinophils ex vivo rely on IL-5-sustained expansion of eosinophils from bone marrow hematopoietic progenitors. Although it does generate eosinophils (bmEos) in high purity, such systems are short-lived (14 days on average) and depend on IL-5. In this report, we present a novel method of differentiating large numbers of pure bone marrow-derived eosinophils with a long-lived phenotype (llEos) (40 days on average) that require IL-5 for initial differentiation, but not for subsequent survival. We identified two key factors in the development of llEos: metabolic adaptation and reprogramming induced by suppressed nutrient intake during active differentiation (from Day 7 of culture), and interaction with IL-5-primed stromal cells for the remainder of the protocol. This regimen results in a higher yield and viability of mature eosinophils. Phenotypically, llEos develop as Siglec-F(+)Ly6G(+) cells transitioning to Siglec-F(+) only, and exhibit typical eosinophil features with red eosin granular staining, as well as the ability to chemotax to eotaxin Ccl11 and process fibrinogen. This culture system requires less reagent input and allows us to study eosinophils long-term, which is a significant improvement over IL-5-driven differentiation protocols. Moreover, it provides important insights into factors governing eosinophil plasticity and the ability to assume long-lived IL-5-independent phenotypes.

Neutrophil membrane-camouflaged nanoparticles alleviate inflammation and promote angiogenesis in ischemic myocardial injury

“…In the absence of increased risk associated with a higher drug dosage, targeting IL-5 to the myocardial tissue can maximize post-injury angiogenesis while minimizing costs. Furthermore, a higher level of IL-5 in the myocardium extends the survival time of eosinophils [ 50 ], allowing them to play a more significant role in promoting healing. The greatest advantage of the targeting delivery nanoparticle is the dual function while reducing the side effects induced by off-target.…”

Eosinophil biology from the standpoint of metabolism: implications for metabolic disorders and asthma

“…Metabolic disorders, which feature chronic hypoxia, insulin resistance, and poor glucose uptake, prompt distinct response in various cells. 45–48 For instance, Peters et al 47 examined homeostatic model assessment for insulin resistance (HOMA-IR) values and lung function in patients with severe asthma. They discovered that insulin resistance is common in asthma and is associated with lower lung function, as well as suboptimal responses to bronchodilator and corticosteroid treatments.…”

“…Similarly, our work shows that subjecting bone marrow–derived murine eosinophils to glucose deprivation in the process of hematopoietic differentiation results in a long-lived phenotype in vitro. 45 These murine eosinophils, derived from bone marrow, exhibit increased metabolic flexibility when faced with sustained glucose starvation. They transition from relying on glucose as their primary energy source to utilizing amino acids and fatty acids.…”

“…A survey of the literature reveals that the microenvironment fostered by metabolic disorders predominantly promotes the inflammatory subset of human and animal eosinophils. 40–42 , 45–48 For instance, a human data analysis shows that a subset of obese asthma patients has high levels of IL-6, which is an important cytokine mediating the interaction between adipose cell and eosinophils. 79 The fate of tissue-resident eosinophils that perform homeostatic functions, such as tissue repair, remodeling, epithelial structure maintenance, and regulation of adipose tissue metabolism, remains a critical question.…”

Pulmonary Eosinophils at the Center of the Allergic Space-Time Continuum

“…Interestingly, eosinophils appear to display greater metabolic flexibility compared to neutrophils, and can switch metabolic programming during in vitro differentiation. Hence, eosinophil swarming in the allergic lung will undoubtedly affect local immunometabolism ( 261 , 262 ).…”