β-Glucan training reprograms long chain fatty acid peroxidation for reactive oxygen species production in neutrophils

Neutrophils exposed to certain microbial stimuli undergo metabolic reprogramming, is a critical process for initiating trained immunity; however, the underlying molecular mechanisms remain largely unknown. In this study, by establishing a β-glucan training model in turbot, we found that this training enhanced the reactive oxygen species (ROS) production and intracellular fatty acid metabolism in head kidney-derived neutrophils. Notably, the acyl-CoA oxidase 1 (ACOX1) was revealed to be significantly upregulated in trained neutrophils and contributed to ROS generation, through direct peroxidation of long-chain fatty acids. Pharmacological inhibition of the ACOX1-ROS axis markedly impaired the myeloperoxidase (MPO) activity and suppressed neutrophil extracellular traps (NETs) formation in trained neutrophils, thereby reducing bacterial clearance capacity. Based on these observations, we extended our findings to a murine model and found that β-glucan training induced a conserved phenotype in bone marrow-derived neutrophils, which exhibited increased peroxisomal ACOX1-dependent ROS generation, further supporting the conserved role of this pathway in reprogramming the function of neutrophils. Taken together, our work demonstrates that β-glucan training reprograms the intracellular ACOX1-ROS axis of neutrophils, which may contribute to better understanding the metabolic mechanisms for trained immunity, and identifies the ROS generation pathway as a potential target for modulating the function of neutrophils.