The Fli1 transcription factor aggravates lipopolysaccharide-induced human pulmonary microvascular endothelial cell dysfunction by regulating CXCL2 promoter.

Abstract

Objective: Pulmonary microvascular endothelial cell (PMEC) injury is a hallmark of septic acute lung injury (ALI). Elevation of chemokine C-X-C motif ligand 2 (CXCL2) is associated with inflammatory response in various diseases. Recent studies have demonstrated the involvement of CXCL2 in septic ALI. Herein, the role and mechanism of CXCL2 in regulating PMEC inflammation and apoptosis in septic ALI were explored.

Materials and methods: Human PMECs (HPMECs) were treated with lipopolysaccharide (LPS) for the establishment of in vitro septic ALI models. HPMEC viability was validated using CCK-8 assay. HPMEC apoptosis was evaluated by flow cytometry analysis. Measurement of proinflammatory cytokine concentration was conducted using enzyme-linked immunosorbent assay kits. RT-qPCR were required for determining gene levels. Western blotting was prepared for testing friend leukemia integration 1 (Fli1) and CXCL2 protein levels. The binding of Fli-1 to CXCL2 promoter was confirmed by chromatin immunoprecipitation and luciferase reporter assays.

Results: LPS upregulated CXCL2 expression in HPMECs. Moreover, LPS administration suppressed HPMEC viability and accelerated HPMEC inflammation and apoptosis, which was antagonized by CXCL2 depletion. Mechanistically, Fli1 served as a transcription factor and bound to CXCL2 promoter. In rescue assays, CXCL2 overexpression counteracted the restrictive impact of Fli1 deficiency on LPS-induced HPMEC apoptotic behaviors and inflammatory response.

Conclusions: The Fli1 transcription factor aggravates LPS-induced HPMEC dysfunction via binding to CXCL2 promoter in septic ALI.