Rationale: Tolerogenic dendritic cells (tol-DCs) play essential roles in immune-related diseases and induce immune tolerance by shaping T-cell responses. Accumulating evidence suggests that long noncoding RNAs (lncRNAs) play important regulatory roles in the immune system. However, the potential roles and underlying mechanisms of lncRNAs in tol-DCs remain unclear. Methods: RNA in-situ hybridization, histochemistry, and qRT-PCR were performed to determine the distribution and expression of NEAT1 in DCs. Flow cytometry was used to analyze the tolerogenic function of DCs. Small sequencing, followed by bioinformatic analysis, was performed to determine the target genes of NEAT1. The mechanism of NEAT1 was explored using a luciferase reporter, chromatin immunoprecipitation assays, and Immunofluorescence. In-vivo experiments were used to investigate the induction of immune tolerance via NEAT1-knockdown DCs. Results: Our results show that lncRNA NEAT1 can induce tolerogenic phenotype in DCs. Mechanistically, small RNA-seq analysis revealed that NEAT1 knockdown preferentially affected the expression of miR-3076-3p. Furthermore, NEAT1 used the NLRP3 inflammasome as a molecular decoy for miR-3076-3p, thus facilitating the expression of tolerogenic phenotype in DCs. Moreover, the transcription factor E2F1 acted as a repressor of NEAT1 transcription via activity of H3K27ac. Our results also indicate that NEAT1 knockdown in DCs can induce immune tolerance in models of experimental autoimmune myocarditis and heart transplantation. Conclusions: Taken together, our study shows the mechanism used by NEAT1 in inducing tol-DCs and highlights the therapeutic potential of targeting NEAT1 for the treatment of immune-related diseases.

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The inflammatory response of macrophages has been reported to play a critical role in atherosclerosis. The inflammatory state of macrophages is modified by epigenetic reprogramming. m6A RNA methylation is an epigenetic modification of RNAs. However, little is known about the potential roles and underlying mechanisms of m6A modification in macrophage inflammation. Herein, we showed that the expression of the m6A modification “writer” Mettl14 was increased in coronary heart disease and LPS-stimulated THP-1 cells. Knockdown of Mettl14 promoted M2 polarization of macrophages, inhibited foam cell formation and decreased migration. Mechanistically, the expression of Myd88 and IL-6 was decreased in Mettl14 knockdown cells. Through m6A modification, Mettl14 regulated the stability of Myd88 mRNA. Furthermore, Myd88 affected the transcription of IL-6 via the distribution of p65 in nuclei rather than directly regulating the expression of IL-6 through m6A modification. In vivo, Mettl14 gene knockout significantly reduced the inflammatory response of macrophages and the development of atherosclerotic plaques. Taken together, our data demonstrate that Mettl14 plays a vital role in macrophage inflammation in atherosclerosis via the NF-κB/IL-6 signaling pathway, suggesting that Mettl14 may be a promising therapeutic target for the clinical treatment of atherosclerosis.