Abstract
BackgroundLysophosphatidic acid (LPA), generated extracellularly by the action of autotaxin and phospholipase A2, functions through LPA receptors (LPARs) or sphingosine-1-phosphate receptors (S1PRs) to induce pro-fibrotic signaling in the lower respiratory tract of patients with idiopathic pulmonary fibrosis (IPF). We hypothesized that LPA induces changes in small airway epithelial (SAE) basal cells (BC) that create cross-talk between the BC and normal human lung fibroblasts (NHLF), enhancing myofibroblast formation.MethodsTo assess LPA-induced signaling, BC were treated with LPA for 2.5 min and cell lysates were analyzed by phosphokinase array and Western blot. To assess transcriptional changes, BC were treated with LPA for 3 h and harvested for collection and analysis of RNA by quantitative polymerase chain reaction (qPCR). To assess signaling protein production and function, BC were washed thoroughly after LPA treatment and incubated for 24 h before collection for protein analysis by ELISA or functional analysis by transfer of conditioned medium to NHLF cultures. Transcription, protein production, and proliferation of NHLF were assessed.ResultsLPA treatment induced signaling by cAMP response element-binding protein (CREB), extracellular signal-related kinases 1 and 2 (Erk1/2), and epithelial growth factor receptor (EGFR) resulting in elevated expression of connective tissue growth factor (CTGF), endothelin-1 (EDN1/ET-1 protein), and platelet derived growth factor B (PDGFB) at the mRNA and protein levels. The conditioned medium from LPA-treated BC induced NHLF proliferation and increased NHLF expression of collagen I (COL1A1), smooth muscle actin (ACTA2), and autotaxin (ENPP2) at the mRNA and protein levels. Increased autotaxin secretion from NHLF correlated with increased LPA in the NHLF culture medium. Inhibition of CREB signaling blocked LPA-induced changes in BC transcription and translation as well as the pro-fibrotic effects of the conditioned medium on NHLF.ConclusionInhibition of CREB signaling may represent a novel target for alleviating the LPA-induced pro-fibrotic feedback loop between SAE BC and NHLF.
Highlights
Idiopathic pulmonary fibrosis (IPF) is a chronic, lung disorder of unknown etiology characterized by the development of fibrosis of the alveoli and small airways, leading to progressive decline of respiratory function with a high morbidity and mortality [1,2,3,4,5,6]
To help understand the mechanism by which Lysophosphatidic acid (LPA) contributes to the pathogenesis of the fibrosis associated with idiopathic pulmonary fibrosis (IPF), we developed an in vitro model focused on basal cells (BC)-fibroblast interactions relevant to the formation and maintenance of fibrotic foci
To evaluate the potential roles of the cAMP response element-binding protein (CREB), ERK1/2, and epithelial growth factor receptor (EGFR) signaling in LPA-induced expression of profibrotic growth factors, small airway epithelial (SAE) BC were treated with 1 μg/ ml LPA for 3 h in the absence or presence of signaling pathway inhibitors and either collected immediately for RNA analysis or washed and placed in basal medium for 24 h when proteins in the cell culture medium were assessed
Summary
Idiopathic pulmonary fibrosis (IPF) is a chronic, lung disorder of unknown etiology characterized by the development of fibrosis of the alveoli and small airways, leading to progressive decline of respiratory function with a high morbidity and mortality [1,2,3,4,5,6]. The aberrant activation of BC in the IPF fibrotic foci produce mediators that contribute to the proliferation and differentiation of the fibroblast/myofibroblast population. These factors include CTGF, ET-1, TGFβ, PDGF, matrix metalloproteinases, tumor necrosis factor and a number of chemokines [6, 22, 23]. We hypothesized that LPA induces changes in small airway epithelial (SAE) basal cells (BC) that create cross-talk between the BC and normal human lung fibroblasts (NHLF), enhancing myofibroblast formation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
