Increased flux through the mevalonate pathway mediates fibrotic repair without injury
Jennifer L. Larson-Casey, … , Veena B. Antony, A. Brent Carter
Jennifer L. Larson-Casey, … , Veena B. Antony, A. Brent Carter
Published October 14, 2019
Citation Information: J Clin Invest. 2019;129(11):4962-4978. https://doi.org/10.1172/JCI127959.
View: Text | PDF
Research Article Immunology Pulmonology

Increased flux through the mevalonate pathway mediates fibrotic repair without injury

Abstract

Macrophages are important in mounting an innate immune response to injury as well as in repair of injury. Gene expression of Rho proteins is known to be increased in fibrotic models; however, the role of these proteins in idiopathic pulmonary fibrosis (IPF) is not known. Here, we show that BAL cells from patients with IPF have a profibrotic phenotype secondary to increased activation of the small GTPase Rac1. Rac1 activation requires a posttranslational modification, geranylgeranylation, of the C-terminal cysteine residue. We found that by supplying more substrate for geranylgeranylation, Rac1 activation was substantially increased, resulting in profibrotic polarization by increasing flux through the mevalonate pathway. The increased flux was secondary to greater levels of acetyl-CoA from metabolic reprogramming to β oxidation. The polarization mediated fibrotic repair in the absence of injury by enhancing macrophage/fibroblast signaling. These observations suggest that targeting the mevalonate pathway may abrogate the role of macrophages in dysregulated fibrotic repair.

Authors

Jennifer L. Larson-Casey, Mudit Vaid, Linlin Gu, Chao He, Guo-Qiang Cai, Qiang Ding, Dana Davis, Taylor F. Berryhill, Landon S. Wilson, Stephen Barnes, Jeffrey D. Neighbors, Raymond J. Hohl, Kurt A. Zimmerman, Bradley K. Yoder, Ana Leda F. Longhini, Vidya Sagar Hanumanthu, Ranu Surolia, Veena B. Antony, A. Brent Carter

×

Figure 7

Fibroblast differentiation and collagen production are macrophage dependent.

Options: View larger image (or click on image) Download as PowerPoint
Fibroblast differentiation and collagen production are macrophage depend...
Ten days after exposure of WT mice to saline or bleomycin, pumps containing vehicle or GGOH were s.c. implanted, and lungs were extracted 11 days later. Cell suspensions from WT mice were incubated with IgG or CD11b and Ly6C antibodies. (A) Representative histograms of sorted cells (n = 4/group). The percentage indicates cells removed for each condition. (B) Representative phase contrast microscopy pulmosphere images after a 16-hour incubation (n = 4/group). Scale bars: 200 µm. (C) Percentage of the ZOI (n = 4/group). ZOI percentage = [(total area after invasion – inner core of pulmosphere)/inner core of pulmosphere] × 100. (D) Immunoblot analysis of fibroblasts cultured in BALF from exposed WT and Rac1–/– Lyz2-Cre mice (n = 2–3 mice/group). (E) RhoA activity in fibroblasts cultured in BALF from exposed WT and Rac1–/– Lyz2-Cre mice (n = 3 mice/group). (F) RhoA activity in primary mouse lung fibroblasts isolated from vehicle- or GGOH-treated mice (n = 8–10). (G) RhoA activity in IMR-90 fibroblasts (n = 3). IMR-90 fibroblasts were cultured in conditioned media from vehicle- or GGOH-treated MH-S cells containing IgG control or TGF-β1–neutralizing antibody. (H) RhoA activity in IMR-90 fibroblasts (n = 6/group). (I) Immunoblot analysis in IMR-90 fibroblasts. mRNA analysis of (J) Fn1 (n = 3/group) and (K) Col1a1 mRNA in IMR-90s (n = 3/group). IMR-90 fibroblasts cultured in BALF from saline- or bleomycin-exposed mice that received vehicle or GGOH. BALF was preincubated with IgG or neutralized with a TGF-β1 antibody. (L) RhoA activity in IMR-90 fibroblasts (n = 3/group). (M) Immunoblot analysis of IMR-90 fibroblasts. Values indicate the mean ± SEM. **P < 0.001 and ***P < 0.0001, by 1-way ANOVA followed by Tukey’s multiple comparisons test (C, E, H, and J–L) and 2-tailed t test (F and G).