Increased mitochondrial arginine metabolism supports bioenergetics in asthma
Weiling Xu, Sudakshina Ghosh, Suzy A.A. Comhair, Kewal Asosingh, Allison J. Janocha, Deloris A. Mavrakis, Carole D. Bennett, Lourdes L. Gruca, Brian B. Graham, Kimberly A. Queisser, Christina C. Kao, Samuel H. Wedes, John M. Petrich, Rubin M. Tuder, Satish C. Kalhan, Serpil C. Erzurum
Weiling Xu, Sudakshina Ghosh, Suzy A.A. Comhair, Kewal Asosingh, Allison J. Janocha, Deloris A. Mavrakis, Carole D. Bennett, Lourdes L. Gruca, Brian B. Graham, Kimberly A. Queisser, Christina C. Kao, Samuel H. Wedes, John M. Petrich, Rubin M. Tuder, Satish C. Kalhan, Serpil C. Erzurum
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Research Article Metabolism

Increased mitochondrial arginine metabolism supports bioenergetics in asthma

Abstract

High levels of arginine metabolizing enzymes, including inducible nitric oxide synthase (iNOS) and arginase (ARG), are typical in asthmatic airway epithelium; however, little is known about the metabolic effects of enhanced arginine flux in asthma. Here, we demonstrated that increased metabolism sustains arginine availability in asthmatic airway epithelium with consequences for bioenergetics and inflammation. Expression of iNOS, ARG2, arginine synthetic enzymes, and mitochondrial respiratory complexes III and IV was elevated in asthmatic lung samples compared with healthy controls. ARG2 overexpression in a human bronchial epithelial cell line accelerated oxidative bioenergetic pathways and suppressed hypoxia-inducible factors (HIFs) and phosphorylation of the signal transducer for atopic Th2 inflammation STAT6 (pSTAT6), both of which are implicated in asthma etiology. Arg2-deficient mice had lower mitochondrial membrane potential and greater HIF-2α than WT animals. In an allergen-induced asthma model, mice lacking Arg2 had greater Th2 inflammation than WT mice, as indicated by higher levels of pSTAT6, IL-13, IL-17, eotaxin, and eosinophils and more mucus metaplasia. Bone marrow transplants from Arg2-deficient mice did not affect airway inflammation in recipient mice, supporting resident lung cells as the drivers of elevated Th2 inflammation. These data demonstrate that arginine flux preserves cellular respiration and suppresses pathological signaling events that promote inflammation in asthma.

Authors

Weiling Xu, Sudakshina Ghosh, Suzy A.A. Comhair, Kewal Asosingh, Allison J. Janocha, Deloris A. Mavrakis, Carole D. Bennett, Lourdes L. Gruca, Brian B. Graham, Kimberly A. Queisser, Christina C. Kao, Samuel H. Wedes, John M. Petrich, Rubin M. Tuder, Satish C. Kalhan, Serpil C. Erzurum

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Figure 7

Arg2 genetic deletion in inflammation and goblet cell metaplasia in OVA model.

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Arg2 genetic deletion in inflammation and goblet cell metaplasia in OVA...
(A) Representative protein expressions in lungs of Arg2 KO challenged with aerosolized OVA or PBS. Lamin B as loading control for nuclear protein. Enolase as a loading control for whole cell extract. n ≥ 3 replicate experiments. (B) Flow cytometry of IL-13 in cytokeratin-positive cells from lungs of OVA/OVA–treated Arg2 KO and WT. IL-13 expression in cytokeratin-positive cells (cytokeratin+, epithelial marker) increases in WT and Arg2 KO in the OVA/OVA model, but IL-13 is higher in Arg2 KO compared with WT. n ≥ 3 replicate experiments. (C–F) IHC of IL-13. Positive staining in airway epithelium of Arg2 KO OVA/OVA and WT OVA/OVA. Arg2 KO OVA/OVA has greater IL-13 expression than WT OVA/OVA. n ≥ 3 replicate experiments. Scale bars: 40 μm. (G–K) Elevated total cells (G), eosinophils (H), eotaxin-1 (I), IL-13 (J), and IL-17 (K) in BAL of OVA/OVA–treated Arg2 KO. n ≥ 3 replicate experiments. K, 2-tailed t test; G, H, J, Wilcoxon, and I, median test. (L) Mucin-positive cells by PAS in airways of Arg2 KO compared with WT in OVA/OVA. n ≥ 4 replicate experiments. Two-tailed t test. (M–T) Airway goblet cell metaplasia (PAS staining) in Arg2 KO OVA/OVA mice. N, close-up of M, P of O, R of Q, and T of S. Goblet cells not observed in medium-sized or small airways in OVA/PBS–treated WT (M and N) or Arg2 KO (Q and R). Goblet cell metaplasia (red cells, black arrowheads) is more prominent in Arg2 KO OVA/OVA (S and T) than WT OVA/OVA (O and P). n ≥ 4 replicate experiments. Black arrows show inflammatory infiltrate; arrowheads, positive PAS staining. a, airways. Scale bars: 40 μm.