Autocrine lysophosphatidic acid signaling activates β-catenin and promotes lung allograft fibrosis
Pengxiu Cao, … , Eric R. Fearon, Vibha N. Lama
Pengxiu Cao, … , Eric R. Fearon, Vibha N. Lama
Published February 27, 2017
Citation Information: J Clin Invest. 2017;127(4):1517-1530. https://doi.org/10.1172/JCI88896.
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Research Article Cell biology Transplantation

Autocrine lysophosphatidic acid signaling activates β-catenin and promotes lung allograft fibrosis

Abstract

Tissue fibrosis is the primary cause of long-term graft failure after organ transplantation. In lung allografts, progressive terminal airway fibrosis leads to an irreversible decline in lung function termed bronchiolitis obliterans syndrome (BOS). Here, we have identified an autocrine pathway linking nuclear factor of activated T cells 2 (NFAT1), autotaxin (ATX), lysophosphatidic acid (LPA), and β-catenin that contributes to progression of fibrosis in lung allografts. Mesenchymal cells (MCs) derived from fibrotic lung allografts (BOS MCs) demonstrated constitutive nuclear β-catenin expression that was dependent on autocrine ATX secretion and LPA signaling. We found that NFAT1 upstream of ATX regulated expression of ATX as well as β-catenin. Silencing NFAT1 in BOS MCs suppressed ATX expression, and sustained overexpression of NFAT1 increased ATX expression and activity in non-fibrotic MCs. LPA signaling induced NFAT1 nuclear translocation, suggesting that autocrine LPA synthesis promotes NFAT1 transcriptional activation and ATX secretion in a positive feedback loop. In an in vivo mouse orthotopic lung transplant model of BOS, antagonism of the LPA receptor (LPA1) or ATX inhibition decreased allograft fibrosis and was associated with lower active β-catenin and dephosphorylated NFAT1 expression. Lung allografts from β-catenin reporter mice demonstrated reduced β-catenin transcriptional activation in the presence of LPA1 antagonist, confirming an in vivo role for LPA signaling in β-catenin activation.

Authors

Pengxiu Cao, Yoshiro Aoki, Linda Badri, Natalie M. Walker, Casey M. Manning, Amir Lagstein, Eric R. Fearon, Vibha N. Lama

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Figure 8

PF-8380 attenuates lung allograft fibrosis and BO development in murine orthotopic lung transplant model.

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PF-8380 attenuates lung allograft fibrosis and BO development in murine ...
(A) Time line of murine orthotopic lung transplantation and administration of the ATX inhibitor PF-8380. (B) Trichrome and H&E staining of lung grafts harvested on day 40 after transplantation demonstrated decreased airway remodeling and fibrosis in allografts treated with PF-8380 (n = 3 for isograft, 5 for placebo- and PF-8380–treated allograft). Images were taken by an Olympus BX41 microscope with an Olympus DP20 camera. Scale bars: 200 μm for ×40 images and 40 μm for ×200 images. (C) Morphometric analysis of airway wall thickness in transplanted lung isografts, placebo allografts, and PF-8380–treated allografts (n = 4/group with ANOVA). Data for each graft are represented as a floating bar ranging from minimum to maximum, with a line showing the mean value. Data for isografts and allograft placebos were obtained by measuring from different slides of the same animal groups as in Figure 7C. (D) Collagen content quantitation by hydroxyproline assay in lung grafts. PF-8380 treatment significantly reduced hydroxyproline content in allografts (n = 7 for isograft and 6 for the rest of the groups, with ANOVA). Samples for isograft and allograft placebo were from the same corresponding groups as in Figure 7D and were measured again together with PF-8380–treated allografts. **P < 0.01, ***P < 0.001, ****P < 0.0001. (E) Western blot analysis demonstrated decreased expression of dephosphorylated NFAT1 and total and active β-catenin proteins in allografts treated with PF-8380 (n = 4/group). All representative blots shown were from the same biological samples. Total and active β-catenin were blotted simultaneously on 2 parallel gels.