Opinion on Immune Tolerance Therapeutic Development

HDAC6 inhibition: a significant potential regulator and therapeutic option to translate into clinical practice in renal transplantation

Histone deacetylase 6 (HDAC6), an almost exclusively cytoplasmic enzyme, plays an essential role in many biological processes and exerts its deacetylation-dependent/independent effects on a variety of target molecules, which has contributed to the flourishing growth of relatively isoform-specific enzyme inhibitors. Renal transplantation (RT) is one of the alternatively preferred treatments and the most cost-effective treatment approaches for the great majority of patients with end-stage renal disease (ESRD). HDAC6 expression and activity have recently been shown to be increased in kidney disease in a number of studies. To date, a substantial amount of validated studies has identified HDAC6 as a pivotal modulator of innate and adaptive immunity, and HDAC6 inhibitors (HDAC6i) are being developed and investigated for use in arrays of immune-related diseases, making HDAC6i a promising therapeutic candidate for the management of a variety of renal diseases. Based on accumulating evidence, HDAC6i markedly open up new avenues for therapeutic intervention to protect against oxidative stress-induced damage, tip the balance in favor of the generation of tolerance-related immune cells, and attenuate fibrosis by inhibiting multiple activations of cell profibrotic signaling pathways. Taken together, we have a point of view that targeting HDAC6 may be a novel approach for the therapeutic strategy of RT-related complications, including consequences of ischemia-reperfusion injury, induction of immune tolerance in transplantation, equilibrium of rejection, and improvement of chronic renal graft interstitial fibrosis after transplantation in patients. Herein, we will elaborate on the unique function of HDAC6, which focuses on therapeutical mechanism of action related to immunological events with a general account of the tantalizing potential to the clinic.

EZH2 inhibition dampens autoantibody production in lupus by restoring B cell immune tolerance

OBJECTIVE

The aim of this study was to elucidate the role of enhancer of zeste homolog 2 (EZH2) in the breakdown of B cell immune tolerance and production of autoantibodies in systemic lupus erythematosus (SLE), and to explore the therapeutic effects of EZH2 inhibition on lupus.

METHODS

Peripheral blood mononuclear cells (PBMCs) were collected from new-onset SLE patients for flow cytometric analysis. Pristane-induced lupus mice were constructed, and the EZH2 inhibitor was administrated by intraperitoneal injection to treat lupus mice. Blood and urine were collected from lupus mice to detect autoantibodies and proteinuria, and renal pathology scores were assessed. Mouse spleen B cells were sorted with magnetic beads and subjected to flow cytometric apoptosis detection, real time quantitative PCR (RT-qPCR), and western blotting (WB).

RESULTS

EZH2 expression was elevated in diverse B-cell subsets in both SLE patients and pristane-induced lupus mice. The EZH2 inhibitor attenuated lupus-like symptoms and dampened autoantibody production in pristane-induced lupus mice. Inhibition of EZH2 also reduced autoantibody secretion by plasma cells from lupus patients. Mechanistically, EZH2 mediated the impaired apoptosis of autoreactive B cells and the differentiation of autoantibody producing plasma cells by inhibiting multiple cyclin-dependent kinase inhibitor (CKI) genes.

CONCLUSION

EZH2 mediated the breakdown of B-cell peripheral immune tolerance by inhibiting CKI genes and participated in the generation of autoantibodies in SLE. EZH2 inhibition could serve as a promising drug intervention for the treatment of SLE.

Antigen-specific immunotherapies in type 1 diabetes

Type 1 diabetes mellitus (T1DM) is an autoimmune disease caused by the destruction of pancreatic beta cells, in which immune system disorder plays an important role. Finding a cure for T1DM and restoring beta cell function has been a long-standing goal. Research has shown that immune regulation with pancreatic islet auto-antigens may be the most specific and safe treatment for T1DM. Immunological intervention using diabetogenic auto-antigens as a target can help identify T1DM in high-risk individuals by early screening of autoantibodies (AAbs) before the loss of pancreatic islet function and thus achieve primary prevention of T1DM. However, induction of self-tolerance in patients with pre-diabetes can also slow down the attack of autoimmunity, and achieve secondary prevention. Antigen-based immune therapy opens up new avenues for the prevention and treatment of T1DM. The zinc transporter 8 (ZnT8) protein, presents in the serum of pre-diabetic and diabetic patients, is immunogenic and can cause T1D autoimmune responses. ZnT8 has become a potential target of humoral autoimmunity; it is of great significance for the early diagnosis of T1D. ZnT8-specific CD8⁺ T cells can be detected in most T1DM patients, and play a key role in the progression of T1D. As an immunotherapy target, it can improve the dysfunction of beta cells in T1DM and provide new ideas for the treatment of T1D. In this review, we summarize research surrounding antigen-specific immunotherapies (ASI) over the past 10 years and the ZnT8 antigen as an autoimmune target to induce self-tolerance for T1DM.

Characterization of the immune regulatory property of CD22+ CD9+ B cells

Immunodisruptive homeostasis is recognized in allergic disorders. The mechanism of restoration of immunologic homeostasis in the body is not fully understood. Galectin-9 (Gal9) and CD22 have immune regulatory functions. The goal of this study is to test the role of CD22⁺ CD9⁺ B regulatory cells in immune homeostasis the body. A much smaller amount of IL-10 in B10 cells was detected in patients with AR in contrast to healthy subjects. The IL-10 expression levels in B10 cells were positively correlated with the CD22 expression. CD22 mediated the effects of Gal9 on the enhanced expression of IL-10 in AR B10 cells. Gal9 overcame the refractory induction of IL-10 in B-cells of AR subjects. The immune regulatory ability of AR B10 cells could be restored by Gal9. Combination of Gal9 and SIT induced and activated antigen-specific B10 cells. The B10 cells of Gal9/specific immunotherapy-treated AR mice showed immunosuppressive functions on T-cell activities and induction of type 1 regulatory T cells in an antigen-specific manner. Administration of Gal9 potentiated the effects of specific immunotherapy in mice with AR. In summary, a fraction of regulatory B cells, the CD19⁺ CD22⁺ CD9⁺ B cells, was characterized in the present study. CD22 mediates the effects of Gal9 to promote immunotherapy for allergic diseases by inducing B10 cells. In an antigen specific manner, the B10 cells suppressed CD4⁺ T cell activities, and alleviated experimental AR.