CREB-dependent LPA-induced signaling initiates a pro-fibrotic feedback loop between small airway basal cells and fibroblasts

• Published in: Respiratory research 2021-04, Vol.22 (1), p.97-97, Article 97
• Main Authors: Nathan, Shyam, Zhang, Haijun, Andreoli, Mirko, Leopold, Philip L, Crystal, Ronald G
• Format: Article
• Language: English
• Subjects: Actin; Airway basal cell; Basal cells; Cell culture; Cell interaction; Cellular signal transduction; Collagen; Collagen (type I); Connective tissue growth factor; Connective tissues; CREB; Crosstalk; Cyclic AMP response element-binding protein; Development and progression; DNA-directed RNA polymerase; Endothelin 1; Epidermal growth factor receptors; Epithelial cells; Extracellular signal-regulated kinase; Feedback; Feedback loops; Fibroblast; Fibroblast growth factor 2; Fibroblasts; Fibrosis; Functional analysis; Gene expression; Growth factors; Health aspects; Idiopathic pulmonary fibrosis; Intracellular signaling; Kinases; Lung diseases; Lysates; Lysophosphatidic acid; Medical research; Medicine, Experimental; Muscles; Pathogenesis; Phospholipase A2; Phospholipids; Physiological aspects; Polymerase chain reaction; Proteins; Pulmonary fibrosis; Receptors; Respiratory tract; Signaling; Smooth muscle; Sphingosine 1-phosphate; Transcription; Transcription factors
• ISSN: 1465-993X; 1465-9921; 1465-993X; 1465-9921
• DOI: 10.1186/s12931-021-01677-0

Lysophosphatidic 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. To 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. LPA 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. Inhibition of CREB signaling may represent a novel target for alleviating the LPA-induced pro-fibrotic feedback loop between SAE BC and NHLF.