Mettl3 promotes oxLDL-mediated inflammation through activating STAT1 signaling

Atherosclerosis (AS) is the main cause of cerebrovascular diseases, and macrophages act important roles during the AS pathological process through regulating inflammation. Modification of the novel N(6)-methyladenine (m6A) RNA is reported to be associated with atherosclerosis, but its role in AS is largely unknown. The aim of this study was to investigate the role and mechanism of m6A modification in oxidised low-density lipoprotein (oxLDL) triggered inflammation in macrophages during AS. Dot blot, Immunoprecipitation, western blot, Rip and Chip experiments were used in our study. We find oxLDL stimulation significantly promotes m6A modification level of mRNA in macrophages and knockdown of Methyltransferase-Like Protein 3 (Mettl3) inhibits oxLDL-induced m6A modification and inflammatory response. Mettl3 promotes oxLDL-induced inflammatory response in macrophages through regulating m6A modification of Signal transducer and activator of transcription 1 (STAT1) mRNA, thereby affecting STAT1 expression and activation. Moreover, oxLDL stimulation obviously enhances Mettl3 interacting with STAT1 protein to promote STAT1 transcriptional regulation of inflammatory factor expression in macrophages, which was also demonstrated in the monocytes from patients with angiographically proven coronary artery disease. These results indicate that Mettl3 promotes inflammatory responses through interacting with STAT1 protein and mRNA in macrophages, suggesting that Mettl3 may be as a potential target for the clinical treatment of atherosclerosis.

STAT1: A novel candidate biomarker and potential therapeutic target of the recurrent aphthous stomatitis

At present, the recurrent aphthous stomatitis (RAS) are not completely clear. Therefore, identifying the underlying diagnostic biomarkers of RAS can provide new ideas for the diagnosis and treatment of RAS. The gene chip data of RAS (GSE37265) were downloaded from the NCBI Gene Expression Omnibus (GEO) database. Weighted Gene Co-Expression Network Analysis (WGCNA) was used to construct a co-expression module. A total of 16 co-expression modules were identified, and 30 hub genes in the turquoise module were identified. In addition, functional analysis of hub genes in modules of interest was performed, which indicated that such hub genes were mainly involved in pathways related to immune response, virus infection, epithelial cell, signal transduction. module two clusters (highly interconnected regions) were determined in the network, with score=17.647 and 10, respectively, cluster 1 and cluster 2 are linked by STAT1 and ICAM1, it is speculated that STAT1 may be a primary gene of RAS. Finally, genistein, daidzein, kaempferol, resveratrol, rosmarinic acid, triptolide, quercetin and (-)-epigallocatechin-3-gallate were selected from the TCMSP database, and both of them is the STAT-1 inhibitor. The results of reverse molecular docking suggest that in addition to triptolide, (-)-Epigallocatechin-3-gallate and resveratrol, the other 5 compounds (flavonoids) with similar structures may bind to the same position of STAT1 protein with different docking score. In conclusion, our results screened potential biomarkers that might contribute to the diagnosis and treatment of RAS, STAT1 protein is one of the potential therapeutic targets of RAS, and this target can be used to screen potential compounds.

Human gain-of-function STAT1 mutation disturbs IL-17 immunity in mice

Gain-of-function (GOF) mutations in the gene for signal transducer and activator of transcription 1 (STAT1) account for approximately one-half of patients with chronic mucocutaneous candidiasis (CMC) disease. Patients with GOF-STAT1 mutations display a broad variety of infectious and autoimmune manifestations in addition to CMC, and those with severe infections and/or autoimmunity have a poor prognosis. The establishment of safe and effective treatments based on a precise understanding of the molecular mechanisms of this disorder is required to improve patient care. To tackle this problem, we introduced the human R274Q GOF mutation into mice [GOF-Stat1 knock-in (GOF-Stat1R274Q)]. To investigate the immune responses, we focused on the small intestine (SI), which contains abundant Th17 cells. Stat1R274Q/R274Q mice showed excess phosphorylation of STAT1 in CD4+ T cells upon IFN-γ stimulation, consistent with the human phenotype in patients with the R274Q mutation. We identified two subpopulations of CD4+ T cells, those with ‘normal’ or ‘high’ level of basal STAT1 protein in Stat1R274Q/R274Q mice. Upon IFN-γ stimulation, the ‘normal’ level CD4+ T cells were more efficiently phosphorylated than those from WT mice, whereas the ‘high’ level CD4+ T cells were not, suggesting that the level of STAT1 protein does not directly correlate with the level of pSTAT1 in the SI. Inoculation of Stat1R274Q/R274Q mice with Candida albicans elicited decreased IL-17-producing CD4+RORγt+ cells. Stat1R274Q/R274Q mice also excreted larger amounts of C. albicans DNA in their feces than control mice. Under these conditions, there was up-regulation of T-bet in CD4+ T cells. GOF-Stat1R274Q mice thus should be a valuable model for functional analysis of this disorder.