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A3860 - Serine Glycine One-Carbon Metabolism Drives Effector Responses to Influenza Infection in Macrophages
Author Block: P. Woods1, R. Nigdelioglu1, A. Y. Meliton1, K. A. Sun1, L. Witt2, D. Wu1, R. B. Hamanaka1, G. M. Mutlu1; 1The University of Chicago, Chicago, IL, United States, 2UCSF, San Francisco, CA, United States.
Rationale: Influenza infection is the 8th leading cause of death in the U.S and ranks 1st in mortality amongst infectious agents. Influenza infection can rapidly progress into the lower respiratory tract resulting in acute lung injury (ALI), which is characterized by diffuse tissue damage and impaired gas exchange. Influenza-induced ALI is thought to be a consequence of an exaggerated immune response to virus with proinflammatory macrophages being implicated in the disease process. Macrophages are known to preferentially metabolize glucose as an immediate energy source when generating a pro-inflammatory response to virus; however, the mechanisms underlying metabolic alterations in response to influenza are poorly defined. We have found that several enzymes involved in serine, glycine, one-carbon (SGOC) metabolism, which relies on glycolytic intermediates to support amino acid homeostasis and nucleotide synthesis, are upregulated in influenza-infected macrophages. Thus, we hypothesized that manipulation of SGOC, an off-shoot of glycolysis, could alter macrophage phenotype following influenza infection. Methods: Bone marrow cells were isolated from C57BL/6 mice and stimulated with CSF-1 to generate bone marrow-derived macrophages (BMDMs). BMDMs were cultured in the presence or absence of compounds that inhibit PHGDH, which is the first enzyme in the SGOC metabolic pathway. Cells were then infected with influenza (A/PR8/34) at an MOI of 2.5 for 24 hours and inflammatory phenotype and viral replication was assessed via western blot and qRT-PCR. Glycolytic rate was measured using the Seahorse XF24 assay. Results: Influenza virus induces glycolysis and upregulates SGOC pathway enzymes in macrophages. Influenza-infected BMDMs treated with PHGDH inhibitors exhibited reductions in glycolytic metabolism, iNOS protein expression, and NFκB activation. Moreover, the same treatments led to reduced TNFα gene expression and cytokine production, which is representative of an attenuated inflammatory phenotype. Interestingly, PHGDH inhibition lead to reductions in viral protein and gene expression. Supplementation of formate, which can replenish the one-carbon pool needed for nucleotide generation when SGOC metabolism is blocked, failed to rescue alterations in viral gene expression. Conclusions: Inhibition of SGOC metabolism blunted proinflammatory effector responses and viral replication in influenza-infected macrophages. These data suggest short-term treatment with SGOC pathway inhibitors may be a viable approach to reducing disease severity within the context of ALI.