Changes in Neutrophil Metabolism upon Activation and Aging

Abstract

Neutrophil activation is an important mechanism of host defense against pathogens. Chronic inflammation and autoimmunity are often associated with abnormalities in phenotype and functions of neutrophils. Since effector functions of immune cells during inflammation are tightly linked to their metabolic state, changes in neutrophil metabolome upon activation have been investigated in this study. Human neutrophils from healthy blood donors (n = 6) were treated either with tumor necrosis factor α (TNF-α) or lipopolysaccharide (LPS), whereas untreated neutrophils were used as control. Since apoptotic cells are abundant at sites of inflammation, the metabolome of aged, mainly apoptotic neutrophils was analyzed too. NMR spectroscopy of water-soluble metabolites revealed a clear distinction between aged neutrophils and neutrophils in control and activated samples. Higher levels of NAD (4- to 9-fold) and lower levels of ATP (0.3-fold), glutathione (0.8-fold), hypotaurine (0.8-fold), and phosphocholine (0.6-fold) were detected in aged neutrophils than in the other samples. Differences in metabolic profiles between LPS and TNF-α-stimulated cells as well as between stimulated and control neutrophils were statistically not significant. Replication with additional six blood donors confirmed increased NAD levels in aged cells compared to activated and control neutrophils.

Rejuvenation of Neutrophil Functions in Association With Reduced Diabetes Risk Following Ten Weeks of Low-Volume High Intensity Interval Walking in Older Adults With Prediabetes – A Pilot Study

“…Compared to T-cells, neutrophil metabolic pathways and metabolite availability are not as clearly understood. The common dogma holds that neutrophils from young healthy individuals rely almost exclusively on glycolysis for energy production, with little to no need for mitochondrial energy production (3,44,45). Glycolysis is essential for optimal function at sites of inflammation, which are typically hypoxic (46).…”

“…Glycolysis is essential for optimal function at sites of inflammation, which are typically hypoxic (46). However, suggesting impaired glycolysis and more reliance on mitochondrial produced ATP, both aging and diabetes are associated with reduced ATP and lactate production (45,47). Chemical uncoupling of mitochondrial oxidative phosphorylation with FCCP results in impaired neutrophil chemotaxis, but not activation of respiratory burst or phagocytosis (48).…”

“…Chemical uncoupling of mitochondrial oxidative phosphorylation with FCCP results in impaired neutrophil chemotaxis, but not activation of respiratory burst or phagocytosis (48). Therefore, neutrophil metabolism may be regulated according to specific function (e.g., phagocytosis and chemotaxis), while perturbations to health (e.g., exercise, diabetes and aging) may alter neutrophil metabolic regulation (44,45,48).…”

Multi-omic profiling of primary mouse neutrophils reveals a pattern of sex and age-related functional regulation

“…Among nucleotides, the impact of adenine derivatives in neutrophils has been studied more extensively. ATP/ADP levels are regulated in neutrophils as a function of activation state and 'cellular age' (Richer et al, 2018). Adenine nucleotides derived from neutrophils have been suggested to have antiinflammatory effects (Cadieux et al, 2005;Eltzschig et al, 2004;Hasko and Cronstein, 2013), increase endothelial barrier function, attenuate neutrophil adhesion to endothelial cells, and thus modulate transendothelial migration (Eltzschig et al, 2006).…”

A robust intracellular metabolite extraction protocol for human neutrophil metabolic profiling

“…Importantly, we wanted to optimise our protocols for low amounts of starting material (<5 million neutrophils) to enable translation of the technology into clinical research, where ethical and practical restrictions often mean only small volumes of blood are available for analysis, particularly from paediatric samples. A recent application of NMR metabolomics to the study of neutrophils required at least 20 million cells per condition for metabolite extraction[26], which is in excess of the cell numbers routinely available from clinical studies. Our optimised protocol presented here has enabled, for the first time, metabolic profiling of less than 5 million neutrophils using NMR metabolomics.…”