IL-2 and GM-CSF are regulated by DNA demethylation during activation of T cells, B cells and macrophages

Cortisol inhibits CSF2 and CSF3 via DNA methylation and inhibits invasion in first-trimester trophoblast cells

PROBLEM

Heightened maternal stress affects trophoblast function and increases risk for adverse pregnancy outcomes.

METHODS OF STUDY

Studies were performed using the first-trimester trophoblast cell line, Sw.71. Cytokines were quantified using qPCR and ELISA. Epigenetic regulation of cytokines was characterized by inhibiting histone deacetylation (1 μmol/L suberoylanilide hydroxamic acid [SAHA]) or methylation (5 μmol/L 5-azacytidine), or with chromatin immunoprecipitation (ChIP) with a pan-acetyl histone-3 antibody. Invasion assays used Matrigel chambers.

RESULTS

Cortisol inhibited expression of CSF2 (GM-CSF) and CSF3 (G-CSF) in trophoblast cells. Cortisol-associated inhibition was dependent on DNA methylation and was not affected by acetylation. There was also a modest decrease in trophoblast invasion, not dependent on loss of CSFs.

CONCLUSION

In first-trimester trophoblast cells, the physiological glucocorticoid, cortisol, inhibited two cytokines with roles in placental development and decreased trophoblast invasion. Cortisol-associated changes in trophoblast function could increase the risk for immune-mediated abortion or other adverse pregnancy outcomes.

Epigenetic Control of Macrophage Polarisation and Soluble Mediator Gene Expression during Inflammation

Macrophages function as sentinel cells, which constantly monitor the host environment for infection or injury. Macrophages have been shown to exhibit a spectrum of activated phenotypes, which can often be categorised under the M1/M2 paradigm. M1 macrophages secrete proinflammatory cytokines and chemokines, such as TNF-α, IL-6, IL-12, CCL4, and CXCL10, and induce phagocytosis and oxidative dependent killing mechanisms. In contrast, M2 macrophages support wound healing and resolution of inflammation. In the past decade, interest has grown in understanding the mechanisms involved in regulating macrophage activation. In particular, epigenetic control of M1 or M2 activation states has been shown to rely on posttranslational modifications of histone proteins adjacent to inflammatory-related genes. Changes in methylation and acetylation of histones by methyltransferases, demethylases, acetyltransferases, and deacetylases can all impact how macrophage phenotypes are generated. In this review, we summarise the latest advances in the field of epigenetic regulation of macrophage polarisation to M1 or M2 states, with particular focus on the cytokine and chemokine profiles associated with these phenotypes.

Development of 5' LTR DNA methylation of latent HIV-1 provirus in cell line models and in long-term-infected individuals

BACKGROUND

Human immunodeficiency virus type 1 (HIV-1) latency represents the major barrier to virus eradication in infected individuals because cells harboring latent HIV-1 provirus are not affected by current antiretroviral therapy (ART). We previously demonstrated that DNA methylation of HIV-1 long terminal repeat (5' LTR) restricts HIV-1 reactivation and, together with chromatin conformation, represents an important mechanism of HIV-1 latency maintenance. Here, we explored the new issue of temporal development of DNA methylation in latent HIV-1 5' LTR.

RESULTS

In the Jurkat CD4(+) T cell model of latency, we showed that the stimulation of host cells contributed to de novo DNA methylation of the latent HIV-1 5' LTR sequences. Consecutive stimulations of model CD4(+) T cell line with TNF-α and PMA or with SAHA contributed to the progressive accumulation of 5' LTR DNA methylation. Further, we showed that once established, the high DNA methylation level of the latent 5' LTR in the cell line model was a stable epigenetic mark. Finally, we explored the development of 5' LTR DNA methylation in the latent reservoir of HIV-1-infected individuals who were treated with ART. We detected low levels of 5' LTR DNA methylation in the resting CD4(+) T cells of the group of patients who were treated for up to 3 years. However, after long-term ART, we observed an accumulation of 5' LTR DNA methylation in the latent reservoir. Importantly, within the latent reservoir of some long-term-treated individuals, we uncovered populations of proviral molecules with a high density of 5' LTR CpG methylation.

CONCLUSIONS

Our data showed the presence of 5' LTR DNA methylation in the long-term reservoir of HIV-1-infected individuals and implied that the transient stimulation of cells harboring latent proviruses may contribute, at least in part, to the methylation of the HIV-1 promoter.

Defining CD4 T cell memory by the epigenetic landscape of CpG DNA methylation

Memory T cells are primed for rapid responses to Ag; however, the molecular mechanisms responsible for priming remain incompletely defined. CpG methylation in promoters is an epigenetic modification, which regulates gene transcription. Using targeted bisulfite sequencing, we examined methylation of 2100 genes (56,000 CpGs) mapped by deep sequencing of T cell activation in human naive and memory CD4 T cells. Four hundred sixty-six CpGs (132 genes) displayed differential methylation between naive and memory cells. Twenty-one genes exhibited both differential methylation and gene expression before activation, linking promoter DNA methylation states to gene regulation; 6 of 21 genes encode proteins closely studied in T cells, whereas 15 genes represent novel targets for further study. Eighty-four genes demonstrated differential methylation between memory and naive cells that correlated to differential gene expression following activation, of which 39 exhibited reduced methylation in memory cells coupled with increased gene expression upon activation compared with naive cells. These reveal a class of primed genes more rapidly expressed in memory compared with naive cells and putatively regulated by DNA methylation. These findings define a DNA methylation signature unique to memory CD4 T cells that correlates with activation-induced gene expression.

DNA methylation and primary immune thrombocytopenia

DNA methylation is a heritable, stable, and also reversible way of DNA modification; it can regulate gene expression without changing the nucleotide sequences. Because it takes part in regulation of immune responses, the loss of methylation homeostasis in immune cells will result in autoimmune disease by inducing aberrant gene expression. Primary immune thrombocytopenia (ITP) is an acquired autoimmune disease with many immune deficiencies. Recently, it was well documented that abnormal DNA methylation is also involved in the etiology of ITP. In this review, we elucidate the role of DNA methylation in autoimmune diseases by summarizing the DNA methylation-sensitive genes and the relationship between DNA methylation and ITP.

Overexpression of methyl-CpG-binding protein 2 and autoimmunity: evidence from MECP2 duplication syndrome, lupus, MECP2 transgenic and Mecp2 deficient mice

Methyl-CpG-binding protein 2 (MeCP2) is a key transcriptional regulator that can induce either silencing or activation of target genes. Genetic polymorphisms in the MECP2 /IRAK1 locus have been associated with increased susceptibility to multiple autoimmune diseases such as lupus, primary Sjogren's syndrome, and more recently rheumatoid arthritis. Data from our group suggest that the disease risk variant in this locus is associated with gain of MeCP2 function. Recent findings indicate that MECP2 duplication in human results in defective T helper cell type 1 (TH1) response and IFN-γ production. Herein, we discuss the data from children with MECP2 duplication, human lupus, and from the human MECP2 transgenic and Mecp2 deficient mice to support a link between MECP2 overexpression and autoimmunity. We also provide findings from an Mecp2 deficient mouse that independently support a role for MeCP2 in the immune response and specifically in IFN-γ expression.

Recent thymic emigrants and mature naive T cells exhibit differential DNA methylation at key cytokine loci

Recent thymic emigrants (RTEs) are the youngest T cells in the lymphoid periphery and exhibit phenotypic and functional characteristics distinct from those of their more mature counterparts in the naive peripheral T cell pool. We show in this study that the Il2 and Il4 promoter regions of naive CD4(+) RTEs are characterized by site-specific hypermethylation compared with those of both mature naive (MN) T cells and the thymocyte precursors of RTEs. Thus, RTEs do not merely occupy a midpoint between the thymus and the mature T cell pool, but represent a distinct transitional T cell population. Furthermore, RTEs and MN T cells exhibit distinct CpG DNA methylation patterns both before and after activation. Compared with MN T cells, RTEs express higher levels of several enzymes that modify DNA methylation, and inhibiting methylation during culture allows RTEs to reach MN T cell levels of cytokine production. Collectively, these data suggest that the functional differences that distinguish RTEs from MN T cells are influenced by epigenetic mechanisms and provide clues to a mechanistic basis for postthymic maturation.