Increased expressions of DNA methyltransferases contribute to CD70 promoter hypomethylation and over expression of CD70 in ITP

Pathogenesis of refractory ITP: Overview

A subset of individuals with 'primary' or 'idiopathic' immune thrombocytopenia (ITP) who fail to respond to conventional first- and second-line agents or who lose responsiveness are considered to have 'refractory' disease (rITP), placing them at increased risk of bleeding and complications of intensive treatment. However, the criteria used to define the refractory state vary among studies, which complicates research and clinical investigation. Moreover, it is unclear whether rITP is simply 'more severe' ITP, or if there are specific pathogenic pathways that are more likely to result in refractory disease, and whether the presence or development of rITP can be established or anticipated based on these differences. This paper reviews potential biological features that may be associated with rITP, including genetic and epigenetic risk factors, dysregulation of T cells and cytokine networks, antibody affinity and specificity, activation of complement, impaired platelet production and alterations in platelet viability and clearance. These findings indicate the need for longitudinal studies using novel clinically available methodologies to identify and monitor pathogenic T cells, platelet antibodies and other clues to the development of refractory disease.

Scoping Review on Epigenetic Mechanisms in Primary Immune Thrombocytopenia

Immune Thrombocytopenia (ITP) is an autoimmune blood disorder that involves multiple pathways responsible for the homeostasis of the immune system. Numerous pieces of literature have proposed the potential of immune-related genes as diagnostic and prognostic biomarkers, which mostly implicate the role of B cells and T cells in the pathogenesis of ITP. However, a more in-depth understanding is required of how these immune-related genes are regulated. Thus, this scoping review aims to collate evidence and further elucidate each possible epigenetics mechanism in the regulation of immunological pathways pertinent to the pathogenesis of ITP. This encompasses DNA methylation, histone modification, and non-coding RNA. A total of 41 studies were scrutinized to further clarify how each of the epigenetics mechanisms is related to the pathogenesis of ITP. Identifying epigenetics mechanisms will provide a new paradigm that may assist in the diagnosis and treatment of immune thrombocytopenia.

Low-dose decitabine modulates myeloid-derived suppressor cell fitness via LKB1 in immune thrombocytopenia

Myeloid-derived suppressor cells (MDSCs) are heterogeneous immature cells and natural inhibitors of adaptive immunity. Metabolic fitness of MDSCs is fundamental for its suppressive activity toward effector T cells. Our previous studies showed that the number and inhibitory function of MDSCs were impaired in patients with immune thrombocytopenia (ITP) compared with healthy controls. In this study, we analyzed the effects of decitabine on MDSCs from patients with ITP, both in vitro and in vivo. We found that low-dose decitabine promoted the generation of MDSCs and enhanced their aerobic metabolism and immunosuppressive functions. Lower expression of liver kinase 1 (LKB1) was found in MDSCs from patients with ITP, which was corrected by decitabine therapy. LKB1 short hairpin RNA (shRNA) transfection effectively blocked the function of MDSCs and almost offset the enhanced effect of decitabine on impaired MDSCs. Subsequently, anti-CD61 immune-sensitized splenocytes were transferred into severe combined immunodeficient (SCID) mice to induce ITP in murine models. Passive transfer of decitabine-modulated MDSCs significantly raised platelet counts compared with that of phosphate buffered saline-modulated MDSCs. However, when LKB1 shRNA-transfected MDSCs were transferred into SCID mice, the therapeutic effect of decitabine in alleviating thrombocytopenia was quenched. In conclusion, our study suggests that the impaired aerobic metabolism of MDSCs is involved in the pathogenesis of ITP, and the modulatory effect of decitabine on MDSC metabolism contributes to the improvement of its immunosuppressive function. This provides a possible mechanism for sustained remission elicited by low-dose decitabine in patients with ITP.

High-throughput DNA methylation analysis in ITP confirms NOTCH1 hypermethylation through the Th1 and Th2 cell differentiation pathways

BACKGROUND

Immune thrombocytopenia (ITP) is a prevalent autoimmune disease with a complex aetiology where DNA methylation changes are becoming triggers.

METHOD

To investigate novel abnormally methylated genes in the pathogenesis of ITP, we performed a high-throughput methylation analysis on 21 ITP patients and 9 normal control samples. We analysed the extent of key methylated genes and their downstream cytokines through Luminex assay or qRT-PCR. Then, bone marrow mononuclear cells were extracted from ITP patients, and decitabine (demethylation drug) was added to the culture medium of cultured cells. qRT-PCR and ELISA were used to detect whether decitabine could effectively affect target genes and related cytokines.

RESULTS

Through the STRING and Metascape databases, hypermethylated NOTCH1 can be identified and can influence ITP by regulating many downstream cytokines through Th1 and Th2 cell differentiation pathways. Compared with those in the normal control group, the expression levels of NOTCH1 and its downstream Th2 cytokines (IL-4, IL-10, and GATA3) were significantly decreased and those of Th1 cytokines (IFN-γ, IL-12, and TNF-α) were significantly increased in the ITP group. Decitabine exerts its demethylation effect, so the expression of NOTCH1 and its related cytokines in the ITP group treated with 100 nM decitabine were significantly reversed.

CONCLUSIONS

Our results suggest that the pathogenesis of ITP may exert its influence on epigenetics through alteration of DNA methylation at regulatory regions of the target NOTCH1 gene in the Th1 and Th2 cell differentiation pathways. At the same time, decitabine may achieve a therapeutic effect on ITP by demethylation.

Association of DNA Methyltransferase 3B Promotor Polymorphism With Childhood Chronic Immune Thrombocytopenia

BACKGROUND

DNA methylation is an epigenetic process that refers to chromatin-based mechanisms in the regulation of gene expression without DNA alternation. It is mediated by DNA methyltransferases (DNMTs). The DNA methyltransferase 3B (DNMT3B) gene contains a C-to-T single nucleotide polymorphism (SNP; rs2424913) in the Promotor region, 149 base pairs from the transcription start site, which is reported to significantly increase the Promotor activity.

OBJECTIVE

To investigate the prevalance of rs2424913 single nucleotide polymorphism located in the DNMT3B gene Promotor.

METHODS

In the present study, we investigated the prevalence of rs2424913 single nucleotide polymorphism located in DNMT3B gene Promotor by restriction fragment length polymorphism (PCR-RFLP) in Egyptian pediatric chronic immune thrombocytopenia (ITP) patients and controls.

RESULTS

The homozygous genotype (TT) was significantly higher in our patient and conferred almost 3-fold increased risk of chronic ITP when compared to controls.

CONCLUSION

The present study shows that DNMT3B rs2424913 promotor polymorphism represents a genetic risk factor that may play an important role in understanding the pathogenesis of chronic ITP.

Low-dose decitabine promotes megakaryocyte maturation and platelet production in healthy controls and immune thrombocytopenia

Impaired megakaryocyte maturation and insufficient platelet production have been shown to participate in the pathogenesis of immune thrombocytopenia (ITP). Our previous study demonstrated that low expression of tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) in megakaryocytes contributed to impaired platelet production in ITP. Decitabine (DAC), a demethylating agent, is known to promote cell differentiation and maturation at low doses. However, whether decitabine is potential in promoting megakaryocyte maturation and platelet release in ITP is unclear. In this study, we evaluated the effect of DAC on megakaryocyte maturation and platelet release in the presence of ITP plasma that has been shown to cause impaired megakaryocyte maturation and platelet production. We observed that low-dose DAC (10 nM) could significantly increase the number of mature polyploid (≥ 4N) megakaryocytes in cultures with plasma from healthy controls and more than one-half of ITP patients in vitro. Furthermore, the number of platelets released from these megakaryocytes significantly increased compared with those untreated with DAC. In these megakaryocytes, DAC significantly enhanced TRAIL expression via decreasing its promoter methylation status. These findings demonstrate that low-dose DAC can promote megakaryocyte maturation and platelet production and enhance TRAIL expression in megakaryocytes in healthy controls and ITP. The potential therapeutic role of low-dose DAC may be beneficial for thrombocytopenic disorders.

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.