2. Academic Validation
  3. Effect of arginase inhibition on pulmonary L-arginine metabolism in murine Pseudomonas pneumonia

Effect of arginase inhibition on pulmonary L-arginine metabolism in murine Pseudomonas pneumonia

  • PLoS One. 2014 Mar 3;9(3):e90232. doi: 10.1371/journal.pone.0090232.
Anne Mehl 1,  Peyman Ghorbani 2,  David Douda 3,  Hailu Huang 2,  Nades Palaniyar 2,  Felix Ratjen 4,  Hartmut Grasemann 4
Affiliations

Affiliations

  • 1 Program in Physiology and Experimental Medicine, SickKids Research Institute, The Hospital for Sick Children, and University of Toronto, Toronto, Ontario, Canada; Division of Respiratory Medicine, Department of Pediatrics, The Hospital for Sick Children, and University of Toronto, Toronto, Ontario, Canada; Department of Pediatric Pulmonology and Immunology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
  • 2 Program in Physiology and Experimental Medicine, SickKids Research Institute, The Hospital for Sick Children, and University of Toronto, Toronto, Ontario, Canada.
  • 3 Program in Physiology and Experimental Medicine, SickKids Research Institute, The Hospital for Sick Children, and University of Toronto, Toronto, Ontario, Canada; Pulmonary and Critical Care Medicine Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
  • 4 Program in Physiology and Experimental Medicine, SickKids Research Institute, The Hospital for Sick Children, and University of Toronto, Toronto, Ontario, Canada; Division of Respiratory Medicine, Department of Pediatrics, The Hospital for Sick Children, and University of Toronto, Toronto, Ontario, Canada.
PMID: 24595185 DOI: 10.1371/journal.pone.0090232
Abstract

Rationale: Infection of the lung with Pseudomonas aeruginosa results in upregulation of nitric oxide synthases (NOS) and Arginase expression, and both Enzymes compete for L-arginine as substrate. Nitric oxide (NO) production may be regulated by Arginase as it controls L-arginine availability for NOS. We here studied the effect of systemic Arginase inhibition on pulmonary L-arginine metabolism in Pseudomonas pneumonia in the mouse.

Methods: Mice (C57BL/6, 8-10 weeks old, female) underwent direct tracheal instillation of Pseudomonas (PAO-1)-coated agar beads and were treated by repeated intra-peritoneal injections of the Arginase Inhibitor 2(S)-amino-6-boronohexanoic acid (ABH) or PBS until lungs were harvested on day 3 of the Infection. L-arginine metabolites were quantified using liquid chromatography-tandem mass spectrometry, NO metabolites nitrate and nitrite by Griess reagent and cytokines by ELISA.

Results: NO metabolite concentrations (48.5±2.9 vs. 10.9±2.3 µM, p<0.0001), as well as L-ornithine (29.6±1.7 vs 2.3±0.4 µM, p<0.0001), the product of Arginase activity, were increased in Pseudomonas infected lungs compared to naïve controls. Concentrations of the NOS inhibitor asymmetric dimethylarginine (ADMA) were also increased (0.44±0.02 vs. 0.16±0.01 µM, p<0.0001). Arginase inhibition in the infected Animals resulted in a significant decrease in L-ornithine (14.6±1.6 µM, p<0.0001) but increase in L-arginine concentration (p<0.001), L-arginine/ADMA ratio (p<0.001), L-arginine availability for NOS (p<0.001), and NO metabolite concentrations (67.3±5.7 µM, p<0.05). Arginase Inhibitor treatment also resulted in an increase in NO metabolite levels in Animals following intratracheal injection of LPS (p = 0.015). Arginase inhibition was not associated with an increase in inflammatory markers (IFN-γ, IL-1β, IL-6, MIP-2, KC or TNF-α) in lung. Concentrations of the L-ornithine-dependent polyamines putrescine, spermidine and spermine were increased in Pseudomonas infected lungs (p<0.001, respectively) but were unaffected by ABH treatment.

Conclusions: Systemic Arginase inhibition with ABH during Pseudomonas pneumonia in mice results in an increase in pulmonary NO formation but no pro-inflammatory effect.

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