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Previously, we reported an anti-inflammatory effect of mTORC1 in a mouse model of type 2 skin inflammation. TSLP, one of the epithelial cell-derived cytokines, was upregulated by Raptor deficiency or rapamycin treatment, which was inhibited by dimethyloxalylglycine (DMOG). However, it remains unclear how DMOG regulates TSLP expression and type 2 skin inflammation. In this study, we investigated the protective effect of DMOG on MC903 (calcipotriol)-induced type 2 skin inflammation. Morphological and immunological changes were assessed by H-E staining, flow cytometry and RT-qPCR. DMOG treatment attenuated MC903-induced skin inflammation in a T cell-independent manner. The anti-inflammatory effect of DMOG was accompanied by downregulation of TSLP and IL-33, and supplementation with recombinant TSLP and IL-33 abolished the effect of DMOG. MC903 increased ROS levels in skin tissue, which was prevented by DMOG. Furthermore, the ROS scavenger N-acetylcysteine (NAC) downregulated TSLP and ameliorated MC903-induced skin inflammation, as did DMOG. Finally, the effect of DMOG on ROS and TSLP was reduced by HIF knockdown. These results suggest that DMOG downregulates TSLP and ROS through the HIF pathway, which reduces MC903-induced skin inflammation. [ABSTRACT FROM AUTHOR]

Programmed cell death 1 (PD-1) is critical for T regulatory cells (Tregs) to maintain peripheral tolerance to self-antigens. In the tumor microenvironment, interaction between PD-1 and its ligands supports tumor immune evasion. Pembrolizumab blocks interactions of PD-1 with its ligands, enhancing antitumor and clinical responses. We and others have reported that pembrolizumab does not affect function or phenotype of thymic-derived Tregs; however, little is known about its effect on extrathymic differentiation of peripheral Tregs. In this study, we investigated the effect of pembrolizumab on in vitro-induced Tregs (iTregs). Our work showed that PD-1 blockade interferes with iTreg differentiation and has no potential effect on the stability of FOXP3 after differentiation. Additionally, we found that both nontreated and pembrolizumab-treated iTregs were suppressive. However, pembrolizumab-treated iTregs were relatively less suppressive in higher Treg ratios and failed to produce IL-10 compared with their nontreated counterparts. Different methods including transcriptomic analyses confirmed that the downregulation of FOXP3 was mediated by activating mTOR and STAT1 and inhibiting MAPK pathways, shifting the iTreg polarization in favor of Th1 and Th17 subsets. To confirm the role of mTOR activation, we found that rapamycin diminished the effect of pembrolizumab-mediated downregulation of FOXP3. Ingenuity pathway analysis revealed that pembrolizumab-treated iTregs showed upregulation of genes promoting DNA repair and immune cell trafficking, in addition to downregulation of genes supporting cellular assembly and organization. To our knowledge, this is the first study to show that pembrolizumab interferes with differentiation of human FOXP3+ iTregs and to disclose some of the molecular pathways involved. [ABSTRACT FROM AUTHOR]

Demethylation of CpG motifs in the Foxp3 intronic element, conserved noncoding sequence 2 (CNS2), is indispensable for the stable expression of Foxp3 in regulatory T cells (Tregs). In this study, we found that vitamin C induces CNS2 demethylation in Tregs in a ten-eleven-translocation 2 (Tet2)-dependent manner. The CpG motifs of CNS2 in Tregs generated in vitro by TGF-B (iTregs), which were methylated originally, became demethylated after vitamin C treatment. The conversion of 5-methylcytosin into 5-hydroxymethylcytosin was more efficient, and the methyl group from the CpG motifs of Foxp3 CNS2 was erased rapidly in iTregs treated with vitamin C. The effect of vitamin C disappeared in Tet2-/- iTregs. Furthermore, CNS2 in peripheral Tregs in vivo, which were demethylated originally, became methylated after treatment with a sodium-dependent vitamin C transporter inhibitor, sulfinpyrazone. Finally, CNS2 demethylation in thymic Tregs was also impaired in Tea-/- mice, but not in wild type mice, when they were treated with sulfinpyrazone. Collectively, vitamin C was required for the CNS2 demethylation mediated by Tet proteins, which was essential for Foxp3 expression. Our findings indicate that environmental factors, such as nutrients, could bring about changes in immune homeostasis through epigenetic mechanisms. [ABSTRACT FROM AUTHOR]

A correction to this paper has been published: https://doi.org/10.1007/s00262-021-02903-w [ABSTRACT FROM AUTHOR]