Comparing mast cell immunometabolism shifts induced by IgE mediated and non-IgE mediated degranulation

Abstract Mast cells are immune effector cells with the ability to immediately release an array of pre-formed mediators in response to various stimuli, a process termed degranulation. Degranulation is generally divided into two categories: IgE mediated and non-IgE mediated. Non-IgE mast cell degranulation occurs in response to various environmental agents without prior IgE sensitization often making it difficult to identify the causative agent in patients. To better understand non-IgE mast cell degranulation, we characterized and compared metabolic shifts in response to both mechanisms of degranulation (IgE vs non-IgE) in bone marrow-derived mast cells (BMMCs) grown from C57BL/6 mice. Compound 48/80 and silver nanoparticles were used to trigger non-IgE degranulation. To explore metabolic changes in BMMCs, we used Seahorse XF technology to measure: 1) respiratory mitochondrial metabolism, 2) anaerobic glycolytic metabolism, and 3) performed a phenotype stress test to define metabolic pathways. The mito stress test revealed a decrease in respiration for both mechanisms of degranulation but was consistently lower for non-IgE triggers. Secondly, we observed an increase in glycolysis from both mechanisms which was more prominent in non-IgE degranulation. However, there was a complete depletion of glycolytic reserve with non-IgE degranulation that did not occur with IgE mediated degranulation. The cell phenotype test revealed that BMMCs shift towards glycolysis when activated via a non-IgE pathway more prominently than via an IgE-pathway. In conclusion, mast cell metabolism varies significantly between IgE and non-IgE degranulation with an apparent shift towards glycolytic dependence for non-IgE activated mast cells.