Epigenetic Regulation of Notch1/2 Signaling Modulates CD4+ T cell Phenotype and Impairs Diabetic Wound Healing

Abstract

Abstract T cell plasticity, allowing for transition of CD4+ T cells from an inflammatory to a reparative phenotype, is critical for normal wound healing. In pathologic conditions, such as type 2 diabetes (T2D), wounds fail to heal due to persistent inflammation. Notch activation has been associated with CD4+ TH17/T regulatory (Treg) polarization, in several inflammatory diseases; however, it has not been examined in diabetic wounds. Recently, there is increasing evidence that epigenetic mechanisms control T cell plasticity in tissue. Using FoxP3GFP+ reporter mice we find that FoxP3+CD4+ Tregs were markedly upregulated in normal wounds at late time points. In contrast, wounds from a murine T2D model (DIO) displayed decreased FoxP3+CD4+ Tregs and an overabundance of RORγt+CD4+ TH17 cells with elevated IL17A production. We find that Notch 1 and 2 expression were markedly upregulated in DIO CD4+ T cells. Our prior work has demonstrated that MLL1, a histone methyltransferase, increases gene expression via H3K4 trimethylation (H3K4me3). DIO CD4+ T cells displayed increased Mll1 resulting in elevated H3K4me3 on the Notch 1 and 2 gene promoters increasing receptor expression and activation. Mice with a CD4+ T cell specific depletion of MLL1 (Mll1f/fCD4Cre+) had decreased H3K4me3 on the Notch 1 and 2 promoters with decreased Notch expression. Further, genetic depletion of Notch signaling in CD4+ T cells (DNMAMLf/fCD4Cre+) reduced IL17A production and TH17 cells in diabetic wound tissue. In conclusion, MLL1-mediated activation of Notch 1 and 2 in diabetic wound CD4+ T cells contributes to a persistent TH17 inflammatory response and results in impaired diabetic tissue repair.