E2F1-Activated lncRNA FTX Promotes Asthma Progression via Regulating the SRSF1/RBPJ Axis.
Abstract
Purpose
Long non-coding RNA five prime to Xist (FTX) is considered a regulator for asthma. Therefore, we aimed to explore its more roles and molecular mechanisms in asthma process.
Methods
Serum samples from controls and asthmatics were collected. Asthma mouse models were induced with ovalbumin (OVA), and cell models were established using airway smooth muscle cells (ASMCs) treated with platelet-derived growth factor BB (PDGF-BB). The inspiratory and expiratory airway resistances of mice were examined by measuring airway hyperresponsiveness. The pathological changes of mice lung tissues were observed by hematoxylin & eosin, periodic acid-Schiff, and Masson staining. Serum immunoglobulin E and inflammatory factor levels were detected using an enzyme-linked immunosorbent assay. The CCK-8, Transwell, and flow cytometry were used to assess cell function. FTX, E2F family transcription factor 1 (E2F1), serine rich/arginine splicing factor 1 (SRSF1), and recombination signal binding protein J (RBPJ) levels measured by quantitative real-time-polymerase chain reaction or Western blotting. The relationships among FTX, E2F1, SRSF1, and RBPJ were evaluated by dual-luciferase report, ChIP, RNA pull-down and RIP assay. The effect of FTX/SRSF1 on RBPJ mRNA stability was analyzed by the actinomycin D treatment assay.
Results
Upregulated FTX was detected in asthmatic patients, asthma mice, and PDGF-BB-induced ASMCs. FTX downregulation repressed PDGF-BB-induced ASMCs viability, migration, and inflammation. E2F1 bound to the FTX promoter region to activate its expression, and E2F1 downregulation could repress PDGF-BB-induced ASMCs function via reducing FTX expression. Also, FTX stabilized RBPJ mRNA by interacting with SRSF1. RBPJ overexpression reversed the downregulation effect of FTX knockdown on PDGF-BB-induced ASMCs viability, migration, and inflammation. Meanwhile, E2F1 downregulation alleviated mouse asthma symptoms by inhibiting the FTX/SRSF1/RBPJ pathway.
Conclusions
FTX, transcriptionally activated by E2F1, promoted asthma progression via the the regulation of the SRSF1/RBPJ pathway, thereby providing a possible therapeutic target for asthma treatment that warrants further validation.