TLR4 Overexpression Inhibits Endothelial PAS Domain-Containing Protein 1 Expression in the Lower Respiratory Tract of Patients with Chronic COPD

Abstract

Background/Aims: The study was designed to explore the potential relationship of TLR4 and endothelial PAS domain-containing protein 1 (EPAS1) in vivo and vitro experiments. Methods: Bronchoalveolar lavage fluid (BALF) samples were collected from 55 chronic obstructive pulmonary disease (COPD) patients and 25 healthy subjects. The differential cell count was performed using Wright-Giemsa staining. The expression levels of TLR4 and TLR5 were detected by RT-qPCR. The levels of methylation and mRNA expression of EPAS1 were assayed by bisulfite sequencing PCR and real-time PCR. The correlation of TLR4 and EPAS1 was also analyzed in TLR 4-overexpressing endothelial cells. Results: The results showed that the number of neutrophils, lymphocytes and macrophages and expression of TLR 4 were significantly increased in lower respiratory tract of COPD patients. Moreover, decreased EPAS1 mRNA and increased EPAS1 promoter methylation were detected in COPD, which were closely associated with increased TLR4 expression. According to in vitro experiments, TLR 4 inhibited EPAS1 mRNA expression and promoted promoter methylation in endothelial cells. Conclusion: These findings suggest that TLR4 over-expression decreased EPAS1expression which contributes to the progress of COPD.