Background/Purpose:  B cells contribute to disease pathophysiology through several mechanisms, including cytokine secretion. A wide variety of stimuli can activate B cells to produce cytokines including B cell receptor and Toll-like receptor engagement. Recently, numerous observations have established the role of metabolic pathways in the diverse array of immune cell functions. It is unknown though how these metabolic pathways influence B cell cytokine production. We sought to elucidate the metabolic programs required for B cell cytokine production.

Methods:  B cells were isolated from the spleens of C57Bl/6J mice and activated overnight individually by the following agents: anti-μ antibody, anti-CD40 agonist antibody, poly(I:C), LPS, loxoribine, and CpG. Supernatants were collected and analyzed for the quantification of cytokines using the Milliplex cytokine kit (EMD Millipore). Real-time analysis of extracellular acidification rates and oxygen consumption rates of activated B cells were performed using the XF-96 Extracellular Flux Analyzer (Seahorse Bioscience). Three or more consecutive measurements were obtained under basal conditions and after the sequential addition of 1 μM oligomycin, to inhibit mitochondrial ATP synthase; 1.5 μM FCCP (fluoro-carbonyl cyanide phenylhydrazone), a protonophore that uncouples ATP synthesis from oxygen consumption by the electron-transport chain; and 100 nM rotenone plus 1 μM antimycin A, which inhibit the electron transport chain. To assess 3-carbon sources for oxidative phosphorylation, inhibitors to fatty acid oxidation (etomoxir, which irreversibly inhibits carnitine palmitoyltransferase-1), pyruvate transfer to mitochondria (UK-5099), and glutamine usage (BPTES, which inhibits mitochondrial glutaminases) were used.

Results:  CpG stimulation of mouse splenic B cells increased both glycolysis and mitochondrial respiration to a larger extent that by other stimuli such as LPS or B cell receptor alone. These processes are highly dependent on glutamine, as inhibition of glutaminolysis with BPTES significantly reduced both processes. Importantly, production of TNF-α, IL-6, and IL-10 by CpG-stimulated B cells also heavily relied on glutaminolysis.

Conclusion: B cells undergo metabolic reprogramming when stimulated with CpG, requiring glutaminolysis. Cytokine production is intrinsically linked with this reprogramming. These data are the among first to demonstrate a relationship between B cell effector function and metabolic reprogramming, and suggest that B cell cytokine secretion can be manipulated by altering the local metabolic environment. Manipulating metabolic pathways may represent an interesting therapeutic approach for modulating B cells in autoimmune diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cpg-stimulated-b-cells-require-glutaminolysis-for-glycolysis-mitochondrial-respiration-and-cytokine-production/