Tolerogenic dendritic cells and rheumatoid arthritis: current status and perspectives

Emerging Potential Therapeutic Targets of Ferroptosis in Skeletal Diseases

Ferroptosis is a new programmed cell death characterized by the accumulation of lipid peroxidation mediated by iron and inflammation. Since the transcentury realization of ferroptosis as an iron-dependent modality of nonapoptotic cell death in 2012, there has been growing interest in the function of ferroptosis and its relationship to clinical diseases. Recent studies have shown that ferroptosis is associated with multiple diseases, including degenerative diseases, ischemia reperfusion injury, cardiovascular disease, and cancer. Cell death induced by ferroptosis has also been related to several skeletal diseases, such as inflammatory arthritis, osteoporosis, and osteoarthritis. Research on ferroptosis can clarify the pathogenesis of skeletal diseases and provide a novel therapeutic target for its treatment. In this review, we summarize current information about the molecular mechanism of ferroptosis and describe its emerging role and therapeutic potential in skeletal diseases.

Biomaterial-based immunotherapeutic strategies for rheumatoid arthritis

Rheumatoid arthritis (RA) is an extremely painful autoimmune disease characterized by chronic joint inflammation leading to the erosion of adjacent cartilage and bone. Rheumatoid arthritis pathology is primarily driven by inappropriate infiltration and activation of immune cells within the synovium of the joint. There is no cure for RA. As such, manifestation of symptoms entails lifelong management via various therapies that aim to generally dampen the immune system or impede the function of immune mediators. However, these treatment strategies lead to adverse effects such as toxicity, general immunosuppression, and increased risk of infection. In pursuit of safer and more efficacious therapies, many emerging biomaterial-based strategies are being developed to improve payload delivery, specific targeting, and dose efficacy, and to mitigate adverse reactions and toxicity. In this review, we highlight biomaterial-based approaches that are currently under investigation to circumvent the limitations of conventional RA treatments.

Tolerogenic dendritic cells suppress titanium particle-induced inflammation

Aseptic loosening is a major complication of prosthetic joint surgery. The leading cause of arthroplasty failure is particulate wear debris such as titanium particles. Dendritic cells (DCs) are one type of immune cells that play an important role in the initiation and progression of inflammatory processes. DCs can develop into tolerogenic DCs (tolDCs), which present an alternative therapeutic strategy for inflammatory disorders. Previously, antigen-specific tolDCs were generated, which showed a promising effect in treating inflammatory arthritis and immune thrombocytopenia. The present study reports that tolDCs effectively inhibited titanium particle-induced inflammation in an air-pouch mouse model by decreasing pro-inflammatory cytokines. In addition, a mechanistic study demonstrated that tolDCs significantly protected against titanium particle-induced inflammatory processes in vitro by releasing anti-inflammatory cytokines, such as interleukin-10. Collectively, these findings not only demonstrate that tolDCs play an important role in inhibiting titanium particle-induced inflammation but also provide a potential alternative for the prevention or treatment of titanium particle-induced inflammation.

ROS-Dependent Lipid Peroxidation and Reliant Antioxidant Ferroptosis-Suppressor-Protein 1 in Rheumatoid Arthritis: a Covert Clue for Potential Therapy

Rheumatoid arthritis (RA) is a common systemic autoimmune disease with a prevalence of about 1% in which genetic and environmental risk factors both participate in performance of disease. Though several studies contributed in identifying its etiology and pathogenesis, the underlying mechanisms are still unknown. To date, so as palliative for RA, cure strategies are still popular. Hypoxia and oxidative stress are implicated to RA development and subsequent ROS-mediated cell death which is a critical feature for RA progression. As for cell death and lipid peroxidation, ferroptosis is a newly discovered, iron-dependent, and non-apoptotic cell death which draws various attention due to its potential strategies for cancer therapy. Meanwhile, ferroptosis-suppressor-protein 1 (FSP1) is recently identified as a seminal breakthrough owing to its property of versus ferroptosis. By virtue of the complicated research progress on FSP1 with ferroptosis, in this review, we summarize the whole region of relevance between ROS and RA. Taken together, we hypothesize that ROS accompanied with ferroptosis may function as a reciprocal with cell death that interplays with RA; besides, FSP1 might become a potential therapeutic target for RA because of its potential interaction with TNF-α/ROS-positive feedback loop. This review systematically concludes the previous understandings about identification of ROS and FSP1 and, in turn, aims to provide references for further achievements of them and hints on elucidation of its thorough underlying mechanisms.

Vasoactive intestinal peptide-induced tolerogenic dendritic cells attenuated arthritis in experimental collagen-induced arthritic mice

AIM

Cumulative evidence has revealed that tolerogenic dendritic cells (tolDC) could relieve inflammation reactions in various autoimmune diseases. This study investigated the potential therapeutic application of vasoactive intestinal peptide (VIP)-induced tolDC (VIP-DC) on arthritis using collagen-induced arthritis (CIA) mice.

METHODS

Bone marrow cells were differentiated into dendritic cells (DC) using granulocyte macrophage colony-stimulating factor and interleukin (IL)-4. tolDC were induced by either VIP or Bay 11-7082 in vitro. Immunophenotypes and cytokine production of VIP-DC and Bay-DC were detected by fluorescence-activated cell sorting and enzyme-linked immunosorbent assay, respectively. Bay-DC, VIP-DC and untreated DC were ip administrated to CIA mice on day 40 when arthritis was onset. The treatment effects on arthritic and pathological changes, including synovial hyperplasia, pannus formation, inflammation and bone erosion, were assessed.

RESULTS

VIP-DC (40 ng/mL) and Bay-DC (0.5 µg/mL) had a lower level of major histocompatibility complex II, CD40 and CD86 expression, reduced γ-interferon and increased IL-4 production (P < 0.05 or 0.01), compared with untreated DC. The administration of VIP-DC and Bay-DC decreased the arthritis score clinically at the end of the therapy. Pathological assessments showed that bone erosion and inflammation were alleviated in the VIP-DC group compared with those in the untreated DC group (P < 0.05 and P < 0.01, respectively).

CONCLUSION

VIP-DC showed reduced immunogenicity and enhanced anti-inflammatory cytokine production. Both VIP-DC and Bay-DC could ameliorate arthritis in CIA mice clinically. VIP-DC were not inferior to Bay 11-7082-induced tolDC but may exert a better preventive effect on bone destruction.

Immunopathogenic Mechanisms and Novel Immune-Modulated Therapies in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disease of unknown etiology. It is characterized by the presence of rheumatoid factor and anticitrullinated peptide antibodies. The orchestra of the inflammatory process among various immune cells, cytokines, chemokines, proteases, matrix metalloproteinases (MMPs), and reactive oxidative stress play critical immunopathologic roles in the inflammatory cascade of the joint environment, leading to clinical impairment and RA. With the growing understanding of the immunopathogenic mechanisms, increasingly novel marked and potential biologic agents have merged for the treatment of RA in recent years. In this review, we focus on the current understanding of pathogenic mechanisms, highlight novel biologic disease-modifying antirheumatic drugs (DMRADs), targeted synthetic DMRADs, and immune-modulating agents, and identify the applicable immune-mediated therapeutic strategies of the near future. In conclusion, new therapeutic approaches are emerging through a better understanding of the immunopathophysiology of RA, which is improving disease outcomes better than ever.

DNA methylation: roles in rheumatoid arthritis

Rheumatoid arthritis (RA) is an immune-mediated disease of unknown cause that primarily affects the joints and ultimately leads to joint destruction. In recent years, the potential role of DNA methylation in the development of RA is raising great expectations among clinicians and researchers. DNA methylation influences diverse aspects of the disease and regulates epigenetic silencing of genes and behavior of several cell types, especially fibroblast-like synoviocytes (FLS), the most resident cells in joints. The activation of FLS is generally regarded as a key process in the development of RA that actively results in the promotion of ongoing inflammation and joint damage. It has also been shown that aberrant DNA methylation occurs in the pathogenesis of RA and contributes to the development of the disease. Recently, there has been an impressive increase in studies involving DNA methylation in RA. In this paper, we consider the role of DNA methylation in the development of RA.

Human tolerogenic dendritic cells produce IL-35 in the absence of other IL-12 family members

IL-35 is a cytokine of the IL-12 family, existing as a heterodimer of IL-12p35 and Ebi3. IL-35 has anti-inflammatory properties and is produced by regulatory T cells in humans and mice, where it is required for optimal suppression of immune responses. Distinct from other IL-12 cytokines, the expression of IL-35 has not been described in antigen-presenting cells. In view of the immune-regulatory properties of IL-35, we investigated the expression, regulation, and function of IL-12p35 and Ebi3 in human monocyte-derived dendritic cells and tolerogenic DCs (tolDCs). These tolDCs do not produce IL-12p70 or the homodimer IL-12p40. We demonstrate that tolDCs completely lack transcriptional expression of IL-12p40. However, tolDCs maintain mRNA expression of IL-12p35 and Ebi3. Using intracellular flow cytometry and Western blot analysis, we show that tolDCs produce Ebi3 and IL-12p35, and both can be enhanced upon stimulation with IFN-γ, LPS, or CD40L. tolDCs supernatants have the capacity to suppress T-cell activation. Using IL12A silencing, we demonstrate that IL-12p35 is required for tolDCs to reach their full suppressive potential. Taken together, our results indicate that tolDCs produce IL-35, providing an additional novel mechanism by which tolDCs elicit their tolerogenic potential.

DC-Based Immunotherapy Combined with Low-Dose Methotrexate Effective in the Treatment of Advanced CIA in Mice

We have previously demonstrated that semimature dendritic cell- (smDC-) based immunotherapy is effective for the treatment of collagen-induced arthritis (CIA) prior to disease onset. In the present study, we examined the efficacy of combination therapy with smDCs and methotrexate (MTX) in advanced CIA with a score of 2-3. Combination therapy with low-dose MTX and type II collagen- (CII-) pulsed smDCs (CII-smDCs) was more effective in inhibiting disease progression than high or low-dose MTX alone or a combination of high dose MTX and CII-smDCs. The effect of CII-smDCs alone was also comparable to the combination therapy. CD4⁺Foxp3⁺ Treg populations and IL-10 secretion markedly increased, and CII-specific autoreactive T cells decreased in mice treated with CII-smDCs alone or in combination with MTX. Combination therapy reduced the secretion of interferon-γ (IFN-γ) and IL-17 with little influence on the IL-4 secretion in the mixed leukocyte reaction. These results imply that the combination therapy with low-dose MTX and smDCs is effective in controlling advanced CIA by enhancing Treg population and suppresses antigen-specific Th1/Th17 immunity, rather than initiating Th1 to Th2 immune deviation. Our findings provide a better understanding of the DC therapy in combination with MTX for the treatment of patients with rheumatoid arthritis (RA).

Antigen-specific tolerogenic dendritic cells ameliorate the severity of murine collagen-induced arthritis

Dendritic cells (DCs) play important roles in initiation of the pathogenic processes of autoimmune disorders, such as rheumatoid arthritis (RA). Tolerogenic dendritic cells (tolDCs) are generated from naïve DCs and induce T cell tolerance; thus, they represent a promising strategy for specific cellular therapy for autoimmune diseases. In this study, we generated green fluorescent protein (GFP)-labeled tolDCs and confirmed their phenotypes and biological functions. We found that tolDCs suppressed the memory lymphocyte response and exhibited strong tolerogenic potential; thus, these cells show promise for the treatment of autoimmune diseases. Additionally, a collagen-induced arthritis (CIA) mouse model was used to test the role of tolDCs in vivo. The results of a further mechanistic experiment revealed that tolDCs suppressed inflammatory arthritis at least partially by up-regulating regulatory T (Treg) cells. Collectively, our data suggest that tolDCs may be used as a promising alternative therapy for inflammatory arthritis.

Immunomodulation in human and experimental arthritis: including vitamin D, helminths and heat-shock proteins

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that is mainly directed to the joints, affecting the synovial membrane, the cartilage and also the bone. This disease affects 1% to 2% of the world population and is associated with significant morbidity and increased mortality. RA experimental models have allowed a great deal of information to be translated to the corresponding human disease. This review summarizes some of the most relevant findings targeting immunomodulation in arthritis. Some general guidelines to choose an adequate experimental model and also our experience with arthritis are supplied.

A mouse model of adoptive immunotherapeutic targeting of autoimmune arthritis using allo-tolerogenic dendritic cells

OBJECTIVE

Tolerogenic dendritic cells (tDCs) are immunosuppressive cells with potent tolerogenic ability and are promising immunotherapeutic tools for treating rheumatoid arthritis (RA). However, it is currently unknown whether allogeneic tDCs (allo-tDCs) induce tolerance in RA, and whether the numbers of adoptively transferred allo-tDCs, or the requirement for pulsing with relevant auto-antigens are important.

METHODS

tDCs were derived from bone marrow precursors of C57BL/B6 mice, which were induced in vitro by GM-CSF, IL-10 and TGF-β1. Collagen-induced arthritis (CIA) was modeled in D1 mice by immunization with type II collagen (CII) to test the therapeutic ability of allo-tDCs against CIA. Clinical and histopathologic scores, arthritic incidence, cytokine and anti-CII antibody secretion, and CD4(+)Th subsets were analyzed.

RESULTS

tDCs were characterized in vitro by a stable immature phonotype and a potent immunosuppressive ability. Following adoptive transfer of low doses (5×10(5)) of CII-loaded allo-tDCs, a remarkable anti-arthritic activity, improved clinical scores and histological end-points were found. Serological levels of inflammatory cytokines and anti-CII antibodies were also significantly lower in CIA mice treated with CII-pulsed allo-tDCs as compared with allo-tDCs. Moreover, treatment with allo-tDCs altered the proportion of Treg/Th17 cells.

CONCLUSION

These findings suggested that allo-tDCs, especially following antigen loading, reduced the severity of CIA in a dose-dependent manner. The dampening of CIA was associated with modulated cytokine secretion, Treg/Th17 polarization and inhibition of anti-CII secretion. This study highlights the potential therapeutic utility of allo-tDCs in autoimmune arthritis and should facilitate the future design of allo-tDC immunotherapeutic strategies against RA.