Cigarette smoke extract promotes DNA methyltransferase 3a expression in dendritic cells, inducing Th-17/Treg...

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disorder. Although numerous studies on COPD have been conducted, therapeutic strategies for COPD are limited, and its pathological mechanism is still unclear. The present study aimed to explore the role of DNA methyltransferase 3a (DNMT3a) in dendritic cells (DCs) and the possible role of the Th-17/Treg cell balance in COPD. Immature DCs (iDCs) were induced and cocultured with CD4⁺ T cells. An in vitro COPD model was established by treatment with cigarette smoke extract (CSE). DNMT3a or allograft inflammatory factor 1 (AIF1) and c-Jun N-terminal kinase (JNK) were inhibited and overexpressed, respectively, by transfection with sh-DNMT3a or sh-AIF1 and JNK overexpression plasmids. The 3- (4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to measure cell viability. The Th17/Treg cell ratio was determined by flow cytometry. The expression levels of DNMT3a, c-Jun and AIF1 were measured using RT-qPCR or western blotting. Chromatin immunoprecipitation (CHIP) was used to confirm the interaction between c-Jun and the AIF1 promoter region. CSE stimulation promoted the expression of DNMT3a, and AIF1, and the ratio of p-c-Jun/c-Jun in iDCs. Besides, the iDC-mediated differentiation of Th17 cells was in a dose-dependent manner. However, knockdown of DNMT3a or AIF1 reversed the above effects caused by CSE. Inhibition of c-Jun signaling by treatment with the JNK inhibitor SP600125 also suppressed the iDC-mediated differentiation of Th17 cells, which was promoted by CSE. CHIP analysis showed that c-Jun could bind to the promoter region of AIF1. DNMT3a could regulate the iDC-mediated Th17/Treg balance by regulating the c-Jun/AIF1 axis.