title: Differential Requirements for L-Citrulline and L-Arginine during Antimycobacterial Macrophage Activity.
abstract: Microbicidal NO production is reliant on inducible NO synthase-mediated L-arginine metabolism in macrophages (MΦs). However, L-arginine supply can be restricted by arginase activity, resulting in inefficient NO output and inhibition of antimicrobial MΦ function. MΦs circumvent this by converting L-citrulline to L-arginine, thereby resupplying substrate for NO production. In this article, we define the metabolic signature of mycobacteria-infected murine MΦs supplied L-arginine, L-citrulline, or both amino acids. Using liquid chromatography-tandem mass spectrometry, we determined that L-arginine synthesized from L-citrulline was less effective as a substrate for arginase-mediated L-ornithine production compared with L-arginine directly imported from the extracellular milieu. Following Mycobacterium bovis bacillus Calmette-Guérin infection and costimulation with IFN-γ, we observed that MΦ arginase activity did not inhibit production of NO derived from L-citrulline, contrary to NO inhibition witnessed when MΦs were cultured in L-arginine. Furthermore, we found that arginase-expressing MΦs preferred L-citrulline over L-arginine for the promotion of antimycobacterial activity. We expect that defining the consequences of L-citrulline metabolism in MΦs will provide novel approaches for enhancing immunity, especially in the context of mycobacterial disease.
authors: Division of Infectious Diseases, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229; and.
authors: Shannon M
authors: SM
authors: Rapovy
authors: Division of Pathology and Laboratory Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229.
authors: Junfang
authors: J
authors: Zhao
authors: Division of Infectious Diseases, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229; and.
authors: Rebecca L
authors: RL
authors: Bricker
authors: Division of Infectious Diseases, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229; and.
authors: Stephanie M
authors: SM
authors: Schmidt
authors: Division of Pathology and Laboratory Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229.
authors: Kenneth D R
authors: KD
authors: Setchell
authors: Division of Infectious Diseases, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229; and joseph.qualls@cchmc.org.
authors: Joseph E
authors: JE
authors: Qualls
mesh_terms: D000818:Animals; D001119:Arginase / Q000378:metabolism; D001120:Arginine / Q000096:biosynthesis / Q000378:metabolism*; D002478:Cells, Cultured; D002956:Citrulline / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009163:Mycobacterium bovis / Q000276:immunology; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D014376:Tuberculosis / Q000276:immunology* / Q000382:microbiology
chemical_list: D002956:Citrulline; D009569:Nitric Oxide; D007371:Interferon-gamma; D001120:Arginine; D052247:Nitric Oxide Synthase Type II; D001119:Arginase