Aberrant histone methylation in the patients with immune thrombocytopenia

E3 ubiquitin ligase casitas B-lineage lymphoma-b modulates T-cell anergic resistance via phosphoinositide 3-kinase signaling in patients with immune thrombocytopenia

BACKGROUND

The E3 ubiquitin ligase casitas B-lineage lymphoma-b (CBLB) is a newly identified component of the ubiquitin-dependent protein degradation system and is considered an important negative regulator of immune cells. CBLB is essential for establishing a threshold of T-cell activation and regulating peripheral T-cell tolerance through various mechanisms. However, the involvement of CBLB in the pathogenesis of immune thrombocytopenia (ITP) is unknown.

OBJECTIVES

We aimed to investigate the expression and role of CBLB in CD4+ T cells obtained from patients with ITP through quantitative proteomics analyses.

METHODS

CD4+ T cells were transfected with adenoviral vectors overexpressing CBLB to clarify the effect of CBLB on anergic induction of T cells in patients with ITP. DNA methylation levels of the CBLB promoter and 5' untranslated region (UTR) in patient-derived CD4+ T cells were detected via MassARRAY EpiTYPER assay (Agena Bioscience).

RESULTS

CD4+ T cells from patients with ITP showed resistance to anergic induction, highly activated phosphoinositide 3-kinase-protein kinase B (AKT) signaling, decreased CBLB expression, and 5' UTR hypermethylation of CBLB. CBLB overexpression in T cells effectively attenuated the elevated phosphorylated protein kinase B level and resistance to anergy. Low-dose decitabine treatment led to significantly elevated levels of CBLB expression in CD4+ T cells from 7 patients showing a partial or complete response.

CONCLUSION

These results indicate that the 5' UTR hypermethylation of CBLB in CD4+ T cells induces resistance to T-cell anergy in ITP. Thus, the upregulation of CBLB expression by low-dose decitabine treatment may represent a potential therapeutic approach to ITP.

Translating mechanisms into therapeutic strategies for immune thrombocytopenia (ITP): Lessons from clinical trials

Immune thrombocytopenia (ITP) is an autoimmune disorder that causes a significant reduction in peripheral blood platelet count. Fortunately, due to an increased understanding of ITP, there have been significant improvements in the diagnosis and treatment of these patients. Over the past decade, there have been a variety of proven therapeutic options available for ITP patients, including intravenous immunoglobulins (IVIG), Rituximab, corticosteroids, and thrombopoietin receptor agonists (TPO-RAs). Although the effectiveness of current therapies in treating more than two-thirds of patients, still some patients do not respond well to conventional therapies or fail to achieve long-term remission. Recently, a significant advancement has been made in identifying various mechanisms involved in the pathogenesis of ITP, leading to the development of novel treatments targeting these pathways. It seems that new agents that target plasma cells, Bruton tyrosine kinase, FcRn, platelet desialylation, splenic tyrosine kinase, and classical complement pathways are opening new ways to treat ITP. In this study, we reviewed the pathophysiology of ITP and summarized updates in this population's management and treatment options. We also took a closer look at the 315 ongoing trials to investigate their progress status and compare the effectiveness of interventions. May our comprehensive view of ongoing clinical trials serve as a guiding beacon, illuminating the path towards future trials of different drugs in the treatment of ITP patients.

Children with Chronic Immune Thrombocytopenia Exhibit High Expression of Human Endogenous Retroviruses TRIM28 and SETDB1

Chronic immune thrombocytopenia (CITP) is an autoimmune disease whose underlying biologic mechanisms remain elusive. Human endogenous retroviruses (HERVs) derive from ancestral infections and constitute about 8% of our genome. A wealth of clinical and experimental studies highlights their pivotal pathogenetic role in autoimmune diseases. Epigenetic mechanisms, such as those modulated by TRIM28 and SETDB1, are involved in HERV activation and regulation of immune response. We assessed, through a polymerase chain reaction real-time Taqman amplification assay, the transcription levels of pol genes of HERV-H, HERV-K, and HERV-W; env genes of Syncytin (SYN)1, SYN2, and HERV-W; as well as TRIM28 and SETDB1 in whole blood from 34 children with CITP and age-matched healthy controls (HC). The transcriptional levels of all HERV sequences, with the exception of HERV-W-env, were significantly enhanced in children with CITP as compared to HC. Patients on eltrombopag treatment exhibited lower expression of SYN1, SYN2, and HERV-W-env as compared to untreated patients. The mRNA concentrations of TRIM28 and SETDB1 were significantly higher and were positively correlated with those of HERVs in CITP patients. The over-expressions of HERVs and TRIM28/SETDB1 and their positive correlations in patients with CITP are suggestive clues of their contribution to the pathogenesis of the disease and support innovative interventions to inhibit HERV and TRIM28/SETDB1 expressions in patients unresponsive to standard therapies.

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.

The role of epigenetics in childhood autoimmune diseases with hematological manifestations

Autoimmune diseases with hematological manifestations are often characterized by chronicity and relapses despite treatment, and the underlying pathogenetic mechanisms remain unknown. Epigenetic alterations play a vital role in the deregulation of immune tolerance and the development of autoimmune diseases. In recent years, study of epigenetic mechanisms in both adult and childhood autoimmune disorders has been seeking to explain the pathophysiology of these heterogeneous diseases and to elucidate the interaction between genetic and environmental factors. Various mechanisms, including DNA methylation, histone modifications (chromatin remodeling), and noncoding RNAs (ncRNAs), have been studied extensively in the context of autoimmune diseases. This paper summarizes the epigenetic patterns in some of the most common childhood autoimmune disorders with hematological manifestations, based on epigenetic studies in children with primary immune thrombocytopenia (ITP), systemic lupus erythematosus (SLE), and juvenile idiopathic arthritis (JIA). Research findings indicate that methylation changes in genes expressed on T cells, modifications at a variety of histone sites, and alterations in the expression of several ncRNAs are involved in the pathogenesis of these diseases. These mechanisms not only determine the development of these diseases but also affect the severity of the clinical presentation and biochemical markers. Further studies will provide new tools for the prevention and diagnosis of childhood autoimmune disorders, and possible novel treatment options.

Low-Dose Decitabine Inhibits Cytotoxic T Lymphocytes-Mediated Platelet Destruction via Modulating PD-1 Methylation in Immune Thrombocytopenia

Cytotoxic T lymphocytes (CTLs)-mediated platelet destruction plays an important role in the pathogenesis of primary immune thrombocytopenia (ITP). The programmed cell death protein 1 (PD-1) signaling can turn off autoreactive T cells and induce peripheral tolerance. Herein, we found that the expression of PD-1 and its ligand PD-L1 on CD8⁺ T cells from ITP patients was decreased. Activating PD-1 pathway by PD-L1-Fc fusion protein inhibited CTLs-mediated platelet destruction in ITP in vitro. PD-1 promoter hypermethylation in CD8⁺ T cells was found in ITP patients, resulting in decreased PD-1 expression. The demethylating agent decitabine at a low dose was proved to restore the methylation level and expression of PD-1 on CD8⁺ T cells and reduce the cytotoxicity of CTLs of ITP patients. The phosphorylation levels of phosphatidylinositol 3-kinase (PI3K) and AKT in CD8⁺ T cells were significantly downregulated by low-dose decitabine. Furthermore, blocking PD-1 could counteract the effect of low-dose decitabine on CTLs from ITP patients. Therefore, our data suggest that the aberrant PD-1/PD-L1 pathway is involved in the pathophysiology of ITP and enhancing PD-1/PD-L1 signaling is a promising therapeutic approach for ITP management. Our results reveal the immunomodulatory mechanism of low-dose decitabine in ITP by inhibiting CTLs cytotoxicity to autologous platelets through PD-1 pathway.

Aberrant Histone Methylation in Patients with Graves' Disease

BACKGROUND

Graves' disease (GD) is an organ-specific autoimmune disease. Accumulated data have indicated that aberrant epigenetic modifications are associated with many autoimmune disorders. However, it remains unknown whether histone methylation plays a role in the pathogenesis of GD. In the present study, we aimed to assess histone modification patterns in peripheral blood mononuclear cells (PBMCs) from GD patients. The rate (degree) of H3K4 and H3K9 methylation and the expressions of histone-modifying genes were investigated.

METHODS

A total of 68 GD patients and 32 healthy controls were enrolled in this study. Global histone H3K4/H3K9 methylation of PBMCs was evaluated by the EpiQuik™ global histone H3K4/H3K9 methylation assay kit. The expressions of histone methyltransferases (HMTs) and histone demethylases (HDMs) at the mRNA level were determined by real-time quantitative polymerase chain reaction.

RESULTS

Global histone H3K9 methylation in PBMCs of GD patients was significantly decreased compared with that in the healthy controls (P=0.007). The expressions of HMTs (SUV39H1 and SUV39H2) at the mRNA level were significantly decreased in PBMCs from GD patients compared with healthy controls (P<0.001), whereas the SETD1A expression at the mRNA level was significantly increased in GD patients compared with healthy controls (P=0.004). In addition, the expressions of HDMs, including JHDM2A and JMJD2A, at the mRNA level were significantly increased in GD patients compared with healthy controls (P<0.001; P=0.007). Moreover, the mRNA expression levels of JARID1A and LSD1 did not significantly differ in GD patients and healthy controls (P>0.05).

CONCLUSIONS

These findings firstly suggested that the histone methylation was aberrant in PBMCs of GD patients, which could be possibly attributed to the deregulation of epigenetic modifier genes. Abnormal histone methylation modification may be involved in the pathogenesis of GD.

Low-dose chidamide restores immune tolerance in ITP in mice and humans

Increased macrophage phagocytosis of antibody-coated platelets, as well as decreased numbers and/or impaired function of CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells, has been shown to participate in the pathogenesis of immune thrombocytopenia (ITP). Low-dose histone deacetylase inhibitors (HDACi's) are anti-inflammatory and immunomodulatory agents that can enhance immunosuppression in graft-versus-host disease by increasing the number and function of Foxp3⁺ Treg cells, but it is unclear whether they have the potential to promote immune tolerance and platelet release in ITP. In this study, we performed in vitro and in vivo experiments and found that a low-dose HDACi (chidamide) alleviated thrombocytopenia in passive and active murine models of ITP. Further, low-dose HDACi's attenuated macrophage phagocytosis of antibody-coated platelets, stimulated the production of natural Foxp3⁺ Treg cells, promoted the peripheral conversion of T cells into Treg cells, and restored Treg cell suppression in vivo and in vitro. Finally, we confirmed that low-dose HDACi's could regulate CTLA4 expression in peripheral blood mononuclear cells through modulation of histone H3K27 acetylation. Low-dose HDACi treatment in ITP could be offset by blocking the effect of CTLA4. Therefore, we propose that low-dose chidamide administration has potential as a novel treatment for ITP in the clinic.