N6-methyladenosine modification of THBS1 induced by affluent WTAP promotes Graves' ophthalmopathy progression through glycolysis to affect Th17/Treg balance.

Abstract

Graves' ophthalmopathy (GO) obvious manifestation is the imbalance of Th17/Treg. N6-methyladenosine (m6A) methylation is an important regulator of Th17/Treg balance. However, few reports narrate how m6A regulators mediate the role of genes in GO progression. We explored the m6A modification of THBS1 mediated by WTAP, and the mechanism by which THBS1 regulated glycolysis and Th17/Treg balance. A total of 12 peripheral blood (4 GO samples, 4 GH samples, and 4 health samples) were collected to measure the percentage of Th17/Treg in monocytes by flow cytometry. RNA sequencing (RNA-seq) combined with MeRIP sequencing (MeRIP-seq) was used to screen differentially expressed and methylated genes. MeRIP-qPCR was performed to evaluate the m6A abundance of THBS1 after WTAP silencing. Glycolysis of CD4⁺ T cells was reflected by the lactate content and glucose uptake. The number of Th17 cells was increased in GO peripheral blood, whereas the Treg cells decreased. RNA-seq acquired 679 differentially expressed genes (308 up-regulated, and 371 down-regulated) in the CD4⁺ T cells of GO compared to healthy control. MeRIP-seq identified 3277 m6A peaks between the GO group and the healthy control group, corresponding with 2744 genes (1143 hypermethylated and 1601 hypomethylated). Combined analysis of RNA-seq and MeRIP-seq showed 81 hypermethylated and up-regulated genes. Among the six candidate genes in the PI3K-signaling pathway, THBS1 was the most significantly differentially expressed and hypermethylated. THBS1 silencing resulted in decreased lactate content and glucose uptake in CD4⁺ T cells. WTAP was significantly upregulated in CD4⁺ T cells of GO, and WTAP silencing significantly reduced m6A abundance and expression of THBS1. Upregulated and hypermethylated THBS1 mediated by WTAP promoted glycolysis of CD4⁺ T cells, affected Th17/Treg balance, and facilitated GO progression. We provided a novel potential target for GO treatment and revealed the molecular mechanism of WTAP and THBS1 in GO under the m6A perspective.