Aire-Overexpressing Dendritic Cells Induce Peripheral CD4⁺ T Cell Tolerance

Berberine alleviates diabetic retinopathy by regulating the Th17/Treg ratio

BACKGROUND

Diabetic retinopathy (DR) stands as a prominent complication of diabetes. Berberine (BBR) has reported to be effective to ameliorate the retinal damage of DR. Studying the potential immunological mechanisms of BBR on the streptozotocin (STZ) induced DR mouse model will explain the therapeutic mechanisms of BBR and provide theoretical basis for the clinical application of this drug.

METHODS

C57BL/6 J mice were induced into a diabetic state using a 50 mg/(kg·d) dose of STZ over a 5-day period. Subsequently, they were subjected to a high-fat diet (HFD) for one month. Following a 5-week treatment with 100 mg/(kg·d) BBR, the concentrations of inflammatory factors in the mice's peripheral blood were determined using an enzyme-linked immunosorbent assay (ELISA). Hematoxylin-eosin staining was employed to scrutinize pathological changes in the mice's retinas, while flow cytometry assessed the proportions of T-lymphocyte subsets and the activation status of dendritic cells (DCs) in the spleen and lymph nodes. CD4+T cells and DC2.4 cell lines were utilized to investigate the direct and indirect effects of BBR on T cells under high glucose conditions in vitro.

RESULTS

Following 5 weeks of BBR treatment in the streptozotocin (STZ) mouse model of DR, we observed alleviation of retinal lesions and a down-regulation in the secretion of inflammatory cytokines, namely TNF-α, IL-1β, and IL-6, in the serum of these mice. And in the spleen and lymph nodes of these mice, BBR inhibited the proportion of Th17 cells and promoted the proportion of Treg cells, thereby down-regulating the Th17/Treg ratio. Additionally, in vitro experiments, BBR directly inhibited the expression of the transcription factor RORγt and promoted the expression of the transcription factor Foxp3 in T cells, resulting in a down-regulation of the Th17/Treg ratio. Furthermore, BBR indirectly modulated the Th17/Treg ratio by suppressing the secretion of TNF-α, IL-1β, and IL-6 by DCs and enhancing the secretion of indoleamine 2,3-dioxygenase (IDO) and transforming growth factor-beta (TGF-β) by DCs. This dual action inhibited Th17 cell differentiation while promoting Treg cells.

CONCLUSION

Our findings indicate that BBR regulate T cell subpopulation differentiation, reducing the Th17/Treg ratio by directly or indirectly pathway. This represents a potential therapeutic avenue of BBR for improving diabetic retinopathy.

From bench to bedside: targeting lymphocyte activation gene 3 as a therapeutic strategy for autoimmune diseases

BACKGROUND

Immune checkpoints negatively regulate immune response, thereby playing an important role in maintaining immune homeostasis. Substantial studies have confirmed that blockade or deficiency of immune checkpoint pathways contributes to the deterioration of autoimmune diseases. In this context, focusing on immune checkpoints might provide alternative strategies for the treatment of autoimmunity. Lymphocyte activation gene 3 (LAG3), as a member of immune checkpoint, is critical in regulating immune responses as manifested in multiple preclinical studies and clinical trials. Recent success of dual-blockade of LAG3 and programmed death-1 in melanoma also supports the notion that LAG3 is a crucial regulator in immune tolerance.

METHODS

We wrote this review article by searching the PubMed, Web of Science and Google Scholar databases.

CONCLUSION

In this review, we summarize the molecular structure and the action mechanisms of LAG3. Additionally, we highlight its roles in diverse autoimmune diseases and discuss how the manipulation of the LAG3 pathway can serve as a promising therapeutic strategy as well as its specific mechanism with the aim of filling the gaps from bench to bedside.

Effects of Aire on perforin expression in BMDCs via TLR7/8 and its therapeutic effect on type 1 diabetes

AIMS

Type 1 diabetes, as a kind of autoimmune diseases, usually results from the broken-down of self-tolerance. Autoimmune regulator (Aire), as a transcription factor, induces peripheral tolerance by regulating Toll-like receptor (TLR) expression in dendritic cells (DCs). Several studies have recently identified a small population of perforin-expressing DCs, which is an important population of tolerogenic DCs (tolDCs) that restricts autoreactive T cells in vivo through a perforin-mediated mechanism. Thus, the present study explored the specific relationship among Aire, perforin-expressing DCs and immune tolerance, as well as their roles in type 1 diabetes.

METHODS

We conducted studies based on the Aire-overexpressing bone marrow-derived dendritic cell (BMDC) model. And through in vitro and in vivo experiments to observe that Aire-overexpressing BMDCs which express perforin induce immune tolerance and treat type 1 diabetes via TLR7/8.

RESULTS

Aire enhances the expression of perforin in BMDCs after treatment with the TLR7/8 ligand as well as promotes the expression of TLR7/8 and myeloid differentiation primary response gene 88 (MyD88)-dependent pathway molecules. Aire-overexpressing BMDCs mediate apoptosis of allogeneic CD8⁺ T cells via perforin in vitro. Moreover, Aire-overexpressing BMDCs enhance the therapeutic effect of type 1 diabetes in non-obese diabetic (NOD) mice via perforin and induce apoptosis of autoreactive CD8⁺ T cells in vivo.

CONCLUSIONS

These results provide an experimental basis for comprehensively elucidating the role and significance of Aire expression in peripheral DCs, thereby providing new ideas for the treatment of autoimmune diseases by using Aire as a target to induce the production of perforin-expressing DCs.

Extrathymic AIRE-expressing cells: Friends or foes in autoimmunity and cancer?

Auto-immune regulator (AIRE) is a transcription factor that is mainly known for its crucial role in the thymus. Here, AIRE ensures central tolerance by promoting the expression of peripheral tissue antigens in thymic epithelial cells, which is essential for the negative selection of autoreactive T cells. Intriguingly, AIRE expressing cells have recently been identified in other tissues outside the thymus as well. However, the exact function of these extrathymic AIRE expressing cells (eTACs) remains largely enigmatic. Human eTACs are mainly found in secondary lymphoid tissues under homeostatic conditions, but are also found in pathologies such as the inflamed tissues of patients with autoimmune diseases and in various cancer tissues. eTACs have been demonstrated to express dendritic cell (DC)-like markers, such as MHCII, CD40 and CD127, but also CCR7, IDO and PD-L1. Interestingly, eTACs lack high expression of co-stimulatory molecules, such as CD80 or CD86. In mice, different types of peripheral AIRE expressing cells have been described, including cells with an innate lymphoid cell-like phenotype and antigen presenting cell (APC) function. These findings suggest that eTACs are APCs with the possibility to modulate or inhibit immune responses, which is confirmed by functional murine studies demonstrating the ability of eTACs to induce tolerance in autoreactive T cells. The potential immunomodulatory function of eTACs makes them promising targets to restore tolerance in autoimmunity or improve immunotherapy in cancer settings. Yet, this requires a better understanding of these cells and the molecular mechanisms involved. In this review we aim to summarize the current knowledge and understanding of eTACs, including their putative roles in health and disease.

Development of Novel Markers for Yield in Hevea brasiliensis Muell. Arg. Based on Candidate Genes from Biosynthetic Pathways Associated with Latex Production

Scarcity of functional genetic markers associated with candidate genes (CGs) is a serious constraint for marker-assisted selection in the natural rubber producing tree, Hevea brasiliensis. In order to develop markers associated with rubber yield, five CGs involved in latex biosynthesis were characterized from 16 popular Hevea varieties. Novel SNPs and indels were identified and developed into markers using simple genotyping techniques like allele-specific PCR, CAPS, etc. A progeny population was genotyped using these markers to validate them, to understand their segregation pattern and to map them to a genetic linkage map. Parent-specific maps were constructed using pseudo-test cross strategy with the help of additional markers. The sequence structure information generated will be useful for future studies on gene mapping, functional relevance of coding SNPs and evolution of rubber biosynthesis genes in Hevea. Concurrently, the markers developed may serve as powerful tools for yield-based selection and for genetic diversity and pedigree studies in Hevea. Above all, the marker assays designed for genotyping could be economically carried out in any laboratory having basic molecular biology infrastructure and expertise.

Mechanisms and therapeutic strategies of immune checkpoint molecules and regulators in type 1 diabetes

BACKGROUND

Considered a significant risk to health and survival, type 1 diabetes (T1D) is a heterogeneous autoimmune disease characterized by hyperglycemia caused by an absolute deficiency of insulin, which is mainly due to the immune-mediated destruction of pancreatic beta cells.

SCOPE OF REVIEW

In recent years, the role of immune checkpoints in the treatment of cancer has been increasingly recognized, but unfortunately, little attention has been paid to the significant role they play both in the development of secondary diabetes with immune checkpoint inhibitors and the treatment of T1D, such as cytotoxic T-lymphocyte antigen 4(CTLA-4), programmed cell death protein-1(PD-1), lymphocyte activation gene-3(LAG-3), programmed death ligand-1(PD-L1), and T-cell immunoglobulin mucin protein-3(TIM-3). Here, this review summarizes recent research on the role and mechanisms of diverse immune checkpoint molecules in mediating the development of T1D and their potential and theoretical basis for the prevention and treatment of diabetes.

MAJOR CONCLUSIONS

Immune checkpoint inhibitors related diabetes, similar to T1D, are severe endocrine toxicity induced with immune checkpoint inhibitors. Interestingly, numerous treatment measures show excellent efficacy for T1D via regulating diverse immune checkpoint molecules, including co-inhibitory and co-stimulatory molecules. Thus, targeting immune checkpoint molecules may exhibit potential for T1D treatment and improve clinical outcomes.

Aire deficient dendritic cells promote the T follicular helper cells differentiation

Autoimmune regulator (Aire), primarily expressed in medullary thymic epithelial cells (mTECs), maintains central immune tolerance through the clearance of self-reactive T cells. Aire can also be expressed in dendritic cells (DCs), and DCs can mediate T follicular helper (TFH) cell differentiation and self-reactive B cell activation through inducible costimulator molecule ligand (ICOSL) and interleukin 6 (IL-6), which can cause autoimmune diseases. To confirm whether Aire in DCs affects TFH cell differentiation and to determine the role of Aire in the maintenance of peripheral immune tolerance, this study observed the effects of Aire deficiency on TFH cells using Aire knockout mice. The results showed that Aire deficiency caused increased number of TFH cells, both in vivo and in vitro. Further studies showed that Aire deficiency promoted TFH differentiation through the upregulation of ICOSL and IL-6 in DCs. Thus Aire could suppress the expression of ICOSL and IL-6 to inhibit TFH cell differentiation.

Decreased expression of circulating Aire and increased Tfh/Tfr cells in myasthenia gravis patients

Myasthenia gravis (MG) is a rare prototypical autoimmune disorder caused by antibodies (Ab) against postsynaptic membrane proteins. Most reports have investigated the role of autoimmune regulator gene (Aire) in thymic tissue in machianism of MG initiation. So far, the expression of Aire in human peripheral blood cells (we call it circulating Aire expression in the following passage) has not been reported. Herein, we explore the expression of Aire in peripharal blood, circulating T-follicular helper (cTfh) and T-follicular regulatory (cTfr) cells in MG patients. In our research, we found that the acetylcholine receptor (AChR) Ab level is higher in generalized MG (GMG) than that in ocular MG (OMG). Compared with the control group (CG), lower expression of Aire was found in MG patients, especially in GMG. The ratio of Tfh/Tfr was higher in GMG patients, and then in the OMG patients, and lowest in CG. All these differences above were statistically significant. Negative relation was discovered between expression of Aire in circulating blood and ratio of Tfh/Tfr, so did it exist between Aire expression and the severity of MG. Meanwhile, positive relation was discovered between ratio of Tfh/Tfr and the severity of MG. However, no significant relation was manifested in our study between the subset age of MG and Aire level. Overall, these findings imply circulating Aire might play a role in the imbalance of cTfh and cTfr cells and participate in the pathogenesis of MG.

Transplantation of Aire-overexpressing bone marrow-derived dendritic cells delays the onset of type 1 diabetes

Autoimmune regulator (Aire) plays an indispensable role in maintaining central immune tolerance by promoting the ectopic expression of tissue-restricted antigens (TRAs) in medullary thymic epithelial cells (mTECs) and dendritic cells (DCs), which lead to the deletion of autoreactive T cells or the induction of Tregs and consequently prevent autoimmune disease development. Curing autoimmune diseases has always been a challenge. DC-based immunotherapy represents a new and effective method to establish tolerance. We attempted to transplant Aire-overexpressing bone marrow-derived DCs (Aire-BMDCs) to treat type 1 diabetes (T1D) and to explore a new strategy for autoimmune disease treatment. We observed that the onset of T1D in recipient mice was delayed; insulin autoantibody (IAA) production was significantly decreased; the structure of islets was protected; and the degree of inflammatory infiltration was lower. Furthermore, we found that Aire-BMDCs can promote apoptosis and induce autoreactive CD4+ T cell clonal anergy, inhibit Th1 and Th17 production, and induce Treg production. These results suggest that transplantation of Aire-BMDCs will be a manipulation and effective method for preventing or treating T1D.