Increased mitochondrial arginine metabolism supports bioenergetics in asthma
Weiling Xu, … , Satish C. Kalhan, Serpil C. Erzurum
Weiling Xu, … , Satish C. Kalhan, Serpil C. Erzurum
Published May 23, 2016
Citation Information: J Clin Invest. 2016;126(7):2465-2481. https://doi.org/10.1172/JCI82925.
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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 6

ARG2 expression and metabolic rates in Arg2–/– (KO) mice.

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ARG2 expression and metabolic rates in Arg2–/– (KO) mice. (A) Western bl...
(A) Western blot analyses of lungs, livers, and kidneys of mice with Arg2 KO or WT (n ≥ 4 replicate experiments). GAPDH as a loading control. (B and C) Increased expression of carbonic anhydrase IX (CAIX) in lungs of mice with Arg2 KO (C) compared with WT (B). Images representative of 2 Arg2 KO and 2 WT lungs. a, airways. Scale bars: 40 μm. (D) Western blot analyses of HIF-2α and downstream gene CAIX expression in lungs of mice with Arg2 KO (n = 6) compared with WT (n = 7). Lamin B as a loading control for nuclear protein. Enolase as a loading control for whole cell extract. (E–H) Mitochondrial membrane potential and mitochondrial superoxide in mouse airway epithelial cells. Cells stained with JC-1 (E) and MitoSOX (G), respectively. Contour plots show gating of JC-1 red+ or MitoSOX+ cells. Overlaying black contour graphs show fluorescence levels of unstained controls. Histogram overlays of JC-1 red+ (F) or MitoSOX+ cells (H) show a decrease in Arg2 KO mice (n = 10) compared with WT mice (n = 10). Bar graph quantification of mean fluorescence intensities in JC-1+ or MitoSOX + subsets. Two-tailed t test. (I and J) Mitochondrial (Mito) and cytosolic (Cyto) fractions analyzed via Western blot for peroxiredoxin-SO3 (PRX-SO3) and total PRX3 expression in lungs of mice with Arg2 KO (n = 7) compared with WT (n = 7). Two-tailed t test.