Apigenin, a potent suppressor of dendritic cell maturation and migration, protects against collagen-induced arthritis

Novel artesunate and isatin hybrid CT3-1 suppresses collagen-induced arthritis through abrogating dendritic cell chemotaxis-induced by CCR5

BACKGROUND

Chemotaxis and trafficking of dendritic cells (DCs) induced by cytokine receptors are crucial steps in rheumatoid arthritis (RA) pathogenesis. C-C chemokine receptor type 5 (CCR5) plays a key role in DC movement and has been implicated in multitudinous inflammatory and immunology diseases. Thus, targeting CCR5 to suppress DC chemotaxis is considered as a potential strategy for the management of RA.

METHODS

Herein, we first synthesized a new hybrid named CT3-1 which based on artesunate and isatin. Besides, we studied the regulating effectiveness of CT3-1 on bone marrow-derived DCs (BMDCs) and on collagen-induced arthritis (CIA) through RNA-seq analysis, cell function experiments in vitro and mice model in vivo.

RESULTS

The results shown that CT3-1 mainly reduced CCR5 expression of immature BMDCs and importantly inhibited immature BMDC migration induced by CCR5 in vitro, with no or minor influence on other functions of DCs, such as phagocytosis and maturation. In the mouse model, CT3-1 relieved arthritis severity and inhibited CIA development. Furthermore, CT3-1 intervention decreased the expression of CCR5 in DCs and reduced the proportion of DCs in the peripheral blood of CIA mice.

CONCLUSIONS

Our findings suggest that CCR5-induced chemotaxis and trafficking of immature DCs are important in RA. Targeting CCR5 and inhibiting immature DC chemotaxis may provide a novel choice for the treatment of RA and other similar autoimmune diseases. Moreover, we synthesized a new hybrid compound CT3-1 that could inhibit immature DC trafficking and effectively relieve RA by directly reducing the CCR5 expression of immature DCs.

Apigenin: A Bioflavonoid with a Promising Role in Disease Prevention and Treatment

Apigenin is a powerful flavone compound found in numerous fruits and vegetables, and it offers numerous health-promoting benefits. Many studies have evidenced that this compound has a potential role as an anti-inflammatory and antioxidant compound, making it a promising candidate for reducing the risk of pathogenesis. It has also been found to positively affect various systems in the body, such as the respiratory, digestive, immune, and reproductive systems. Apigenin is effective in treating liver, lung, heart, kidney, neurological diseases, diabetes, and maintaining good oral and skin health. Multiple studies have reported that this compound is capable of suppressing various types of cancer through the induction of apoptosis and cell-cycle arrest, suppressing cell migration and invasion, reduction of inflammation, and inhibiting angiogenesis. When used in combination with other drugs, apigenin increases their efficacy, reduces the risk of side effects, and improves the response to chemotherapy. This review broadly analyzes apigenin's potential in disease management by modulating various biological activities. In addition, this review also described apigenin's interaction with other compounds or drugs and the potential role of nanoformulation in different pathogeneses. Further extensive research is needed to explore the mechanism of action, safety, and efficacy of this compound in disease prevention and treatment.

RNA methylation: A potential therapeutic target in autoimmune disease

Autoimmune diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD) are caused by the body's immune response to autoantigens. The pathogenesis of autoimmune diseases is unclear. Numerous studies have demonstrated that RNA methylation plays a key role in disease progression, which is essential for post-transcriptional regulation and has gradually become a broad regulatory mechanism that controls gene expression in various physiological processes, including RNA nuclear output, translation, splicing, and noncoding RNA processing. Here, we outline the writers, erasers, and readers of RNA methylation, including N6-methyladenosine (m6A), 2'-O-methylation (Nm), 2'-O-dimethyladenosine (m6Am), N1-methyladenosine (m1A), 5-methylcytidine (m5C) and N7-methylguanosine (m7G). As the role of RNA methylation modifications in the immune system and diseases is explained, the potential treatment value of these modifications has also been demonstrated. This review reports the relationship between RNA methylation and autoimmune diseases, highlighting the need for future research into the therapeutic potential of RNA modifications.

Rheumatoid arthritis molecular targets and their importance to flavonoid-based therapy

Rheumatoid arthritis (RA) is a progressive, chronic, autoimmune, inflammatory, and systemic condition that primarily affects the synovial joints and adjacent tissues, including bone, muscle, and tendons. The World Health Organization recognizes RA as one of the most prevalent chronic inflammatory diseases. In the last decade, there was an expansion on the available RA therapeutic options which aimed to improve patient's quality of life. Despite the extensive research and the emergence of new therapeutic approaches and drugs, there are still significant unwanted side effects associated to these drugs and still a vast number of patients that do not respond positively to the existing therapeutic strategies. Over the years, several references to the use of flavonoids in the quest for new treatments for RA have emerged. This review aimed to summarize the existing literature about the flavonoids' effects on the major pathogenic/molecular targets of RA and their potential use as lead compounds for the development of new effective molecules for RA treatment. It is demonstrated that flavonoids can modulate various players in synovial inflammation, regulate immune cell function, decrease synoviocytes proliferation and balance the apoptotic process, decrease angiogenesis, and stop/prevent bone and cartilage degradation, which are all dominant features of RA. Although further investigation is necessary to determine the effectiveness of flavonoids in humans, the available data from in vitro and in vivo models suggest their potential as new disease-modifying anti-rheumatic drugs. This review highlights the use of flavonoids as a promising avenue for future research in the treatment of RA.

EPCR deficiency ameliorates inflammatory arthritis in mice by suppressing the activation and migration of T cells and dendritic cells

OBJECTIVES

Endothelial protein C receptor (EPCR) is highly expressed in synovial tissues of patients with RA, but the function of this receptor remains unknown in RA. This study investigated the effect of EPCR on the onset and development of inflammatory arthritis and its underlying mechanisms.

METHODS

CIA was induced in EPCR gene knockout (KO) and matched wild-type (WT) mice. The onset and development of arthritis was monitored clinically and histologically. T cells, dendritic cells (DCs), EPCR and cytokines from EPCR KO and WT mice, RA patients and healthy controls (HCs) were detected by flow cytometry and ELISA.

RESULTS

EPCR KO mice displayed >40% lower arthritis incidence and 50% less disease severity than WT mice. EPCR KO mice also had significantly fewer Th1/Th17 cells in synovial tissues with more DCs in circulation. Lymph nodes and synovial CD4 T cells from EPCR KO mice expressed fewer chemokine receptors CXCR3, CXCR5 and CCR6 than WT mice. In vitro, EPCR KO spleen cells contained fewer Th1 and more Th2 and Th17 cells than WT and, in concordance, blocking EPCR in WT cells stimulated Th2 and Th17 cells. DCs generated from EPCR KO bone marrow were less mature and produced less MMP-9. Circulating T cells from RA patients expressed higher levels of EPCR than HC cells; blocking EPCR stimulated Th2 and Treg cells in vitro.

CONCLUSION

Deficiency of EPCR ameliorates arthritis in CIA via inhibition of the activation and migration of pathogenic Th cells and DCs. Targeting EPCR may constitute a novel strategy for future RA treatment.

Therapeutic effects of Siegesbeckia orientalis L. and its active compound luteolin in rheumatoid arthritis: network pharmacology, molecular docking and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a common difficult disease with a high disability rate. Siegesbeckia orientalis L. (SO), a Chinese medicinal herb that is commonly used for treating RA in clinical practice. While, the anti-RA effect and the mechanisms of action of SO, as well as its active compound(s) have not been elucidated clearly.

AIM OF THE STUDY

We aim to explore the molecular mechanism of SO against RA by using network pharmacology analysis, as well as the in vitro and in vivo experimental validations, and to explore the potential bioactive compound(s) in SO.

METHODS

Network pharmacology is an advanced technology that provides us an efficient way to study the therapeutic actions of herbs with the underlying mechanisms of action delineated. Here, we used this approach to explore the anti-RA effects of SO, and then the molecular biological approaches were used to verify the prediction. We first established a drug-ingredient-target-disease network and a protein-protein interaction (PPI) network of SO-related RA targets, followed by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Further, we used lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages and vascular endothelial growth factor-A (VEGFA)-induced human umbilical vein endothelial cell (HUVEC) models, as well as adjuvant-induced arthritis (AIA) rat model to validate the anti-RA effects of SO. The chemical profile of SO was also determined by using the UHPLC-TOF-MS/MS analysis.

RESULTS

Network pharmacology analysis highlighted inflammatory- and angiogenesis-related signaling pathways as promising pathways that mediate the anti-RA effects of SO. Further, in both in vivo and in vitro models, we found that the anti-RA effect of SO is at least partially due to the inhibition of toll like receptor 4 (TLR4) signaling. Molecular docking analysis revealed that luteolin, an active compound in SO, shows the highest degree of connections in compound-target network; moreover, it has a direct binding to the TLR4/MD-2 complex, which is confirmed in cell models. Besides, more than forty compounds including luteolin, darutoside and kaempferol corresponding to their individual peaks were identified tentatively via matching with the empirical molecular formulae and their mass fragments.

CONCLUSION

We found that SO and its active compound luteolin exhibit anti-RA activities and potently inhibit TLR4 signaling both in vitro and in vivo. These findings not only indicate the advantage of network pharmacology in the discovery of herb-based therapeutics for treating diseases, but also suggest that SO and its active compound(s) could be developed as potential anti-RA therapeutic drugs.

The mechanism of dendritic cell-T cell crosstalk in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterised by joint pain and swelling, synovial hyperplasia, cartilage damage, and bone destruction. The mechanisms of dendritic cell (DC) and T cell-mediated crosstalk have gradually become a focus of attention. DCs regulate the proliferation and differentiation of CD4+ T cell subtypes through different cytokines, surface molecules, and antigen presentation. DC-T cell crosstalk also blocks antigen presentation by DCs, ultimately maintaining immune tolerance. DC-T cell crosstalk mainly involves chemokines, surface molecules (TonEBP, NFATc1), the PD-L1/PD-1 signalling axis, and the TGF-β signalling axis. In addition, DC-T cell crosstalk in RA is affected by glycolysis, reactive oxygen species, vitamin D, and other factors. These factors lead to the formation of an extremely complex regulatory network involving various mechanisms. This article reviews the key immune targets of DC-T cell crosstalk and elucidates the mechanism of DC-T cell crosstalk in RA to provide a basis for the treatment of patients with RA.

CXC chemokine receptor 4 (CXCR4) blockade in cancer treatment

CXC chemokine receptor type 4 (CXCR4) is a member of the G protein-coupled receptors (GPCRs) superfamily and is specific for CXC chemokine ligand 12 (CXCL12, also known as SDF-1), which makes CXCL12/CXCR4 axis. CXCR4 interacts with its ligand, triggering downstream signaling pathways that influence cell proliferation chemotaxis, migration, and gene expression. The interaction also regulates physiological processes, including hematopoiesis, organogenesis, and tissue repair. Multiple evidence revealed that CXCL12/CXCR4 axis is implicated in several pathways involved in carcinogenesis and plays a key role in tumor growth, survival, angiogenesis, metastasis, and therapeutic resistance. Several CXCR4-targeting compounds have been discovered and used for preclinical and clinical cancer therapy, most of which have shown promising anti-tumor activity. In this review, we summarized the physiological signaling of the CXCL12/CXCR4 axis and described the role of this axis in tumor progression, and focused on the potential therapeutic options and strategies to block CXCR4.

Regulation of Myeloid Dendritic Cells by Synthetic and Natural Compounds for the Treatment of Rheumatoid Arthritis

Different subsets of dendritic cells (DCs) participate in the development of rheumatoid arthritis (RA). In particular, myeloid DCs play a key role in the generation of autoreactive T and B cells. Herein, we undertook a literature review on those synthetic and natural compounds that have therapeutic efficacy/potential for RA and act through the regulation of myeloid DCs. Most of these compounds inhibit both the maturation of DCs and their secretion of inflammatory cytokines and, subsequently, alter the downstream T-cell response (suppression of Th1 and Th17 responses while expanding the Treg response). The majority of the synthetic compounds are approved for the treatment of patients with RA, which is consistent with the importance of DCs in the pathogenesis of RA. All of the natural compounds are derived from plants. Their DC-modulating effect has been demonstrated both in vitro and in vivo. In addition, these natural products ameliorate arthritis in rodents and are potential therapeutics for human RA.

Epimedii Herba: An ancient Chinese herbal medicine in the prevention and treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, progressive inflammatory and systemic autoimmune disease resulting in severe joint destruction, lifelong suffering and considerable disability. Diverse prescriptions of traditional Chinese medicine (TCM) containing Epimedii Herba (EH) achieve greatly curative effects against RA. The present review aims to systemically summarize the therapeutic effect, pharmacological mechanism, bioavailability and safety assessment of EH to provide a novel insight for subsequent studies. The search terms included were "Epimedii Herba", "yinyanghuo", "arthritis, rheumatoid" and "Rheumatoid Arthritis", and relevant literatures were collected on the database such as Google Scholar, Pubmed, Web of Science and CNKI. In this review, 15 compounds from EH for the treatment of RA were summarized from the aspects of anti-inflammatory, immunoregulatory, cartilage and bone protective, antiangiogenic and antioxidant activities. Although EH has been frequently used to treat RA in clinical practice, studies on mechanisms of these activities are still scarce. Various compounds of EH have the multifunctional traits in the treatment of RA, so EH may be a great complementary medicine option and it is necessary to pay more attention to further research and development.

Natural medicines of targeted rheumatoid arthritis and its action mechanism

Rheumatoid arthritis (RA) is an autoimmune disease involving joints, with clinical manifestations of joint inflammation, bone damage and cartilage destruction, joint dysfunction and deformity, and extra-articular organ damage. As an important source of new drug molecules, natural medicines have many advantages, such as a wide range of biological effects and small toxic and side effects. They have become a hot spot for the vast number of researchers to study various diseases and develop therapeutic drugs. In recent years, the research of natural medicines in the treatment of RA has made remarkable achievements. These natural medicines mainly include flavonoids, polyphenols, alkaloids, glycosides and terpenes. Among them, resveratrol, icariin, epigallocatechin-3-gallate, ginsenoside, sinomenine, paeoniflorin, triptolide and paeoniflorin are star natural medicines for the treatment of RA. Its mechanism of treating RA mainly involves these aspects: anti-inflammation, anti-oxidation, immune regulation, pro-apoptosis, inhibition of angiogenesis, inhibition of osteoclastogenesis, inhibition of fibroblast-like synovial cell proliferation, migration and invasion. This review summarizes natural medicines with potential therapeutic effects on RA and briefly discusses their mechanisms of action against RA.

Transcriptomic profiling revealed the role of apigenin-4'-O-α-L-rhamnoside in inhibiting the activation of rheumatoid arthritis fibroblast-like synoviocytes via MAPK signaling pathway

BACKGROUND

Activated fibroblast-like synoviocyte (FLS) played a significant role in the pathogenesis and progression of rheumatoid arthritis (RA). Apigenin-4'-O-α-L-rhamnoside showed remarkable effects against RA, however, no relevant studies on pharmacology of apigenin-4'-O-α-L-rhamnoside yet, the effects and underlying molecular mechanism of apigenin-4'-O-α-L-rhamnoside on RA are still unclear.

PURPOSE

This study aimed to investigate the therapeutic effects and mechanisms of apigenin-4'-O-α-L-rhamnoside on RA-FLS cells by transcriptomic analysis.

METHODS

In vitro, RA-FLS cell viability and migration were measured by CCK-8 and scratch assays, respectively. The effects of apigenin-4'-O-α-L-rhamnoside on inflammatory levels of MMP-1, MMP-3, RANKL and TNF-α in RA-FLS cells were detected using ELISA kits. High-throughput transcriptome analysis was performed to screen the key genes and related pathways of apigenin-4'-O-α-L-rhamnoside inhibit RA-FLSs, and the result of which were validated by RT-qPCR and western blot. Furthermore, in vivo, we also evaluated the effects of apigenin-4'-O-α-L-rhamnoside in rat with CIA.

RESULTS

Apigenin-4'-O-α-L-rhamnoside significantly suppressed RA-FLS migration, exerted remarkable inhibiting effects on the expression levels on MMP-1, MMP3, RANKL and TNF-α in RA-FLS cells. It seemed that MAPK signaling pathway might be closely related to the pathogenesis of RA by down-regulated relevant core targets (MAPK1, HRAS, ATF-2, p38 and JNK). Moreover, apigenin-4'-O-α-L-rhamnoside attenuated the severity of arthritis in CIA rat.

CONCLUSION

Apigenin-4'-O-α-L-rhamnoside inhibited pro-inflammatory cytokine, chemokine and MMPs factors production of RA-FLS by targeting the MAPK signaling pathway, which provided a scientific basis for potential application in the treatment of RA.

Indigenous Nigeria medicinal herbal remedies: A potential source for therapeutic against rheumatoid arthritis

Rheumatoid arthritis (RA) is a debilitating disease associated with locomotion impairment, and conventional therapeutic drugs are not optimal for managing RA. There is an avalanche of medications used for the management of RA. Still, studies have shown that they are associated with severe side effects, including hepatotoxicity, retinopathy, and cardiotoxicity disorders of the central nervous system (CNS), skin, blood, and infections. Complementary and alternative medicine (CAM) is currently gaining attention as a novel panacea for managing debilitating diseases, such as RA. Nigerian folk herbal remedies are replete with a plethora of curative medicine, albeit unvalidated scientifically but with seemingly miraculous provenance. Studies of the identification of bioactive compounds present in these botanicals using advanced spectral analytical techniques have enhanced our understanding of the role of Nigerian herbal remedies in the treatment and management of RA. Interestingly, experimental studies abound that the bioactive compounds present in the extracts of plant botanicals protected animals from the development of RA in different experimental models and reduced the toxicity associated with conventional therapeutics. Validated mechanisms of RA amelioration in human and animal models include suppression of the expression of NF-κB, IL-1β, TNF-α, IL-6, IL-8, IL-17, IL-23, chemokines, TGF-β, RANKL, RANK, iNOS, arginase, COX-2, VEGFA, VEGFR, NFATC1, and TRAP in the synoviocytes. Decreased ROS, NO, MDA, carbonyl groups, and PGE₂ in the synovial fluid increased the expression of PPARα/γ; antioxidant and anti-inflammatory molecules also improve RA etiology. In this mini-review, we discuss the global burden of RA, the novel role of plant-based botanicals as potential therapeutics against signaling pathways in RA. Also addressed is the possible repurposing/reprofiling of plant botanicals to increase their therapeutic index among RA patients that patronize traditional healers in Nigeria with a global projection.

Quercetin Impedes Th17 Cell Differentiation to Mitigate Arthritis Involving PPARγ-Driven Transactivation of SOCS3 and Redistribution Corepressor SMRT from PPARγ to STAT3

SCOPE

Quercetin (QU) is one of the most abundant flavonoids in plants and has attracted the attention of researchers because of its remarkable antirheumatoid arthritis (RA) effects and extremely low adverse reactions. However, the underlying mechanism needs further study.

METHODS AND RESULTS

Flow cytometry, immunofluorescence, enzyme linked immunosorbent assay （ELISA）, and quantitative real-time polymerase chain reaction （qRT-PCR） reveal the obvious inhibitory effects of QU on Th17 cell differentiation in arthritic mice. More importantly, QU markedly limits the development of Th17 cell polarization, which is virtually compromised by the treatment with peroxisome proliferator activated receptor γ (PPARγ) inhibitor GW9662 and knockdown of PPARγ. Additionally, molecular dynamics simulation and immunofluorescence exhibit QU directly binds to PPARγ and increases PPARγ nuclear translocation. Besides, QU confers its moderation effect on suppressor of cytokine signaling protein (SOCS3)/signal transducer and activator of transcription 3 (STAT3) axis partially depending on PPARγ. Furthermore, coimmunoprecipitation shows QU redistributes the corepressor silencing mediator for retinoid and thyroid-hormone receptors (SMRT) from PPARγ to STAT3. Finally, the inhibition of Th17 response and the antiarthritic effect of QU are nullified by GW9662 treatment in arthritic mice.

CONCLUSION

QU targets PPARγ and consequently inhibits Th17 cell differentiation by dual inhibitory activity of STAT3 to exert antiarthritic effect. The findings facilitate its development and put forth a stage for uncovering the mechanism of other naturally occurring compounds with chemical structures similar to QU.

CD209/CD14+ Dendritic Cells Characterization in Rheumatoid and Psoriatic Arthritis Patients: Activation, Synovial Infiltration, and Therapeutic Targeting

Dendritic cells (DC) have a key role in the initiation and progression of inflammatory arthritis (IA). In this study, we identified a DC population that derive from monocytes, characterized as CD209/CD14⁺ DC, expressing classical DC markers (HLADR, CD11c) and the Mo-DC marker (CD209), while also retaining the monocytic marker CD14. This CD209/CD14⁺ DC population is present in the circulation of Healthy Control (HC), with increased frequency in Rheumatoid Arthritis (RA) and Psoriatic arthritic (PsA) patients. We demonstrate, for the first time, that circulatory IA CD209/CD14⁺ DC express more cytokines (IL1β/IL6/IL12/TNFα) and display a unique chemokine receptor expression and co-expression profiles compared to HC. We demonstrated that CD209/CD14⁺ DC are enriched in the inflamed joint where they display a unique inflammatory and maturation phenotype, with increased CD40 and CD80 and co-expression of specific chemokine receptors, displaying unique patterns between PsA and RA. We developed a new protocol of magnetic isolation and expansion for CD209⁺ DC from blood and identified transcriptional differences involved in endocytosis/antigen presentation between RA and PsA CD209⁺ DC. In addition, we observed that culture of healthy CD209⁺ DC with IA synovial fluid (SF), but not Osteoarthritis (OA) SF, was sufficient to induce the development of CD209/CD14⁺ DC, leading to a poly-mature DC phenotype. In addition, differential effects were observed in terms of chemokine receptor and chemokine expression, with healthy CD209⁺ DC displaying increased expression/co-expression of CCR6, CCR7, CXCR3, CXCR4 and CXCR5 when cultured with RA SF, while an increase in the chemokines CCR3, CXCL10 and CXCL11 was observed when cultured with PsA SF. This effect may be mediated in part by the observed differential increase in chemokines expressed in RA vs PsA SF. Finally, we observed that the JAK/STAT pathway, but not the NF-κB pathway (driven by TNFα), regulated CD209/CD14⁺ DC function in terms of activation, inflammatory state, and migratory capacity. In conclusion, we identified a novel CD209/CD14⁺ DC population, which is active in the circulation of RA and PsA, an effect potentiated once they enter the joint. Furthermore, we demonstrated that JAK/STAT inhibition can be used as a therapeutic strategy to decrease the inflammatory state of the pathogenic CD209/CD14⁺ DC.

Re-appraising the role of flavonols, flavones and flavonones on osteoblasts and osteoclasts- A review on its molecular mode of action

Bone disorders have become a global concern illustrated with decreased bone mineral density and disruption in microarchitecture of natural bone tissue organization. Natural compounds that promote bone health by augmenting osteoblast functions and suppressing osteoclast functions has gained much attention and offer greater therapeutic value compared to conventional therapies. Amongst several plant-based molecules, flavonoids act as a major combatant in promoting bone health through their multi-faceted biological activities such as antioxidant, anti-inflammatory, and osteogenic properties. They protect bone loss by regulating the signalling cascades involved in osteoblast and osteoclast functions. Flavonoids augment osteoblastogenesis and inhibits osteoclastogenesis through their modulation of various signalling pathways. This review discusses the role of various flavonoids and their molecular mechanisms involved in maintaining bone health by regulating osteoblast and osteoclast functions.

Immunosuppressive effects of dimethyl fumarate on dendritic cell maturation and migration: a potent protector for coronary heart disease

Dendritic cells (DCs), as a bridge between innate and adaptive immunity, play key roles in atherogenesis, particularly in plaque rupture, the underlying pathophysiologic cause of myocardial infarction. Targeting DC functions, including maturation and migration to atherosclerotic plaques, may be a novel therapeutic approach to atherosclerotic disease. Dimethyl fumarate (DMF), an agent consisting of a combination of fumaric acid esters, in current study were found to be able to suppress DC maturation by reducing the expression of costimulatory molecules and MHC class II and by blocking cytokine secretion. In addition, DMF efficiently inhibited the migration of activated DCs in vitro and in vivo by reducing the expression of chemokine receptor 7 (CCR7). Additionally, DMF efficiently inhibited the expression of the costimulatory molecule CD86, as well as the chemokine receptor CCR7 and the C-X-C motif chemokine receptor 4 (CXCR4), in healthy donor-derived purified DCs that had been stimulated by ST-segment elevation myocardial infarction (STEMI) patient serum. This study points to the potent therapeutic value of DMF for protecting against cardiovascular disease by suppressing DC functions.

miR-205-5p in exosomes divided from chondrogenic mesenchymal stem cells alleviated rheumatoid arthritis via regulating MDM2 in fibroblast-like synoviocytes

OBJECTIVE

To explore the role and mechanism of chondrogenic bone marrow mesenchymal stem cells (BMSCs)-derived exosomes on Rheumatoid arthritis (RA).

METHODS

The chondrogenesis of BMSCs was induced by chondrogenic medium. Exosomes from BMSCs and chondrogenic BMSCs were isolated and characterized by transmission electron microscope (TEM), laser particle size analyzer and western blot. ELISA was used to analyze the expression levels of pro-inflammatory cytokines and matrix metalloproteinases (MMPs). Western bolt was performed to assess MAPK and NF-κB pathways expression. The inflammation score and the pathological damage of RA mice were evaluated. Luciferase reporter assay and RIP were carried out to examine the relationship between microRNA-205-5p (miR-205-5p) and mouse double minute 2 (MDM2).

RESULTS

Chondrogenic BMSCs-derived exosomes suppressed pro-inflammatory cytokines, MMPs and MAPK and NF-κB pathways in RA-FLSs. miR-205-5p had a high expression in chondrogenic BMSCs-derived exosomes. Functionally, exosomal miR-205-5p also played the anti-inflammation effects. Besides, MDM2 was a direct target of miR-205-5p. Additionally, chondrogenic BMSCs-secreted exosomal miR-205-5p suppressed the inflammation score, joint destruction, and inflammatory response in collagen-induced arthritis (CIA) mice through MDM2.

CONCLUSION

Chondrogenic BMSCs-derived exosomal miR-205-5p suppressed inflammatory response, MAPK and NF-κB pathways through MDM2 in RA, indicating exosomal miR-205-5p might be a potential target for RA treatment.

Herbal Formula Longteng Decoction Promotes the Regression of Synovial Inflammation in Collagen-Induced Arthritis Mice by Regulating Type 2 Innate Lymphocytes

The etiology and pathogenesis of rheumatoid arthritis (RA) have not yet been fully elucidated, with greater adverse drug effects in traditional treatment of RA. It is particularly necessary to develop and study Chinese herbal formula as a supplement and alternative drug for the treatment of RA. The traditional Chinese medicine compound Longteng Decoction (LTD), as an empirical prescription in the treatment of RA in Dongzhimen Hospital of Beijing University of Chinese Medicine, has been widely used in clinic. Type 2 innate lymphocytes (ILC2s) have specific transcription factors and signature cytokines that are very similar to Th cells, which have been proved to be necessary in addressing RA inflammation, and are potential targets for RA prevention and treatment. Our previous studies have confirmed that LTD can intervene in the differentiation of peripheral blood Th17 and Treg cells, reduce joint pain index and swelling degree, shorten the time of morning stiffness, reduce ESR, and inhibit joint inflammation. However, it is unclear whether LTD can promote the regression of RA synovial inflammation by regulating the immune response mechanism of ILC2s.Therefore, our team established a collagen-induced arthritis mouse model and conducted an experimental study with LTD as the intervention object. The results showed that joint swelling, synovial inflammatory infiltration, and articular cartilage destruction were alleviated in CIA mice after intervention with LTD. The proliferation and differentiation of Th17 inflammatory cells and the secretion of proinflammatory cytokines (IL-17 and IFN-γ) were inhibited. In addition, LTD can also activate ILC2s to secrete the anti-inflammatory cytokine IL-4, activate the STAT6 signaling pathway, and act synergistic with Treg cells to inhibit the infiltration of type M1 macrophages in synovial tissue and promote its transformation to M2 phenotype. Taken together, these results confirm that LTD can be used as an adjunct or alternative to RA therapy by modulating the ILC2s immune response network and slowing down the inflammatory process of synovial tissue.

A molecular insight of inflammatory cascades in rheumatoid arthritis and anti-arthritic potential of phytoconstituents

Rheumatoid arthritis (RA) is an auto-immune inflammatory disorder of the synovial lining of joints marked by immune cells infiltration and hyperplasia of synovial fibroblasts which results in articular cartilage destruction and bone erosion. The current review will provide comprehensive information and results obtained from the recent research on the phytochemicals which were found to have potential anti-arthritic activity along with the molecular pathway that were targeted to control RA progression. In this review, we have summarized the scientific data from various animal studies about molecular mechanisms, possible side effects, associations with conventional therapies, and the role of complementary and alternative medicines (CAM) for RA such as ayurvedic medicines in arthritis. In the case of RA, phytochemicals have been shown to act through different pathways such as regulation of inflammatory signaling pathways, T cell differentiation, inhibition of angiogenic factors, induction of the apoptosis of fibroblast-like synoviocytes (FLS), inhibition of autophagic pathway by inhibiting High-mobility group box 1 protein (HMGB-1), Akt/ mTOR pathway and HIF-1α mediated Vascular endothelial growth (VEGF) expression. Also, osteoclasts differentiation is inhibited by down-regulating the VEGF expression by decreasing the accumulation of the ARNT (Aryl Hydrocarbon Receptor Nuclear Translocator)-HIF-1α complex Although phytochemicals have shown to exert potential anti-arthritic activity in many animal models and further clinical data is needed to confirm their safety, efficacy, and interactions in humans.

Traditional herbal medicine: Therapeutic potential in rheumatoid arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease influenced by diverse endogenous and exogenous factors. It is characterized by cartilage and bone destruction. The current conventional allopathic therapy is expensive and carries adverse side effects. Recently, there were some ethnopharmacological studies on RA including anti-RA effects and therapeutic targets of distinct dosage forms of traditional herbal medicines (THMs).

AIM OF THE REVIEW

This review provides a brief overview of the current understanding of the potential pharmacological mechanisms of THMs (active constituents, extracts and prescriptions) in RA. This study is intended to provide comprehensive information and reference for exploring new therapeutic strategies of THMs in the RA treatment.

MATERIALS AND METHODS

This review captured scientific literatures invivo and vitro experiments on effects of anti-RA THMs published between 2016 and 2021 from journals and electronic databases (e.g. PubMed, Elsevier, Science Direct, Web of Science and Google Scholar). Relevant literatures were searched and analyzed by using keywords such as 'rheumatoid arthritis AND traditional herbal medicines', 'rheumatoid arthritis AND immune cells', 'rheumatoid arthritis AND inflammation', 'rheumatoid arthritis AND miRNA', 'rheumatoid arthritis AND Angiogenesis', 'rheumatoid arthritis AND oxidative stress', 'rheumatoid arthritis AND osteoclasts', 'rheumatoid arthritis AND CIA model', 'rheumatoid arthritis AND AA model' AND 'rheumatoid arthritis herbal prescription'.

RESULTS

Experiments in vitro and in vivo jointly demonstrated the potential of THMs in the RA treatment. There are plentiful therapeutic targets in RA. THMs and active ingredients could alleviate RA symptoms through different therapeutic targets, such as immunoregulation, inflammation, fibroblast-like synoviocytes (FLSs), microRNAs (miRNAs), angiogenesis, oxidative stress, osteoclasts and multiple targets interaction. Anti-RA THMs, active ingredients and prescriptions through corresponding therapeutic targets were summarized and classified.

CONCLUSIONS

Flavonoids, phenolic acids, alkaloids and triterpenes of THMs are identified as the main components to ameliorate RA. Regulation of different and multiple related therapeutic targets by THMs and their active ingredients were associated with greater therapeutic benefits, among which inflammation is the main therapeutic target. Nonetheless, further studies are required to unravel the complexities and in-depth mechanisms of THMs in alleviating RA.

Functionality of apigenin as a potent antioxidant with emphasis on bioavailability, metabolism, action mechanism and in vitro and in vivo studies: A review

Numerous diseases such as cancer, diabetes, cardiovascular, neurodegenerative diseases, etc. are linked with overproduction of reactive oxygen species (ROS) and oxidative stress. Apigenin (5,7,4'-trihydroxyflavone) is a widely distributed flavonoid, responsible for antioxidant potential and chelating redox active metals. Being present as glycosides or polymers, the apigenin degrades to variable amount in the digestive tract; during processing, its activity is also reduced due to high temperature or Fe/Cu addition. Although its metabolism remains elusive, enteric absorption occurs sufficiently to reduce plasma indices of oxidant status. Delayed clearance in plasma and slow liver decomposition enhance its systematic bioavailability. Antioxidant mechanism of apigenin includes: oxidant enzymes inhibition, modulation of redox signaling pathways (NF-kB, Nrf2, MAPK, and P13/Akt), reinforcing enzymatic and nonenzymatic antioxidant, metal chelation, and free radical scavenging. DPPH, ORAC, ABTS, and FRAP are the major in vitro methods for determining the antioxidant potential of apigenin, whereas its protective effects in whole and living cells of animals are examined using in vivo studies. Due to limited information on antioxidant potential of apigenin, its in vitro and in vivo antioxidant effects are, therefore, discussed with action mechanism and interaction with the signaling pathways. This paper concludes that apigenin is a potent antioxidant compound to overcome the difficulties related to oxidative stress and other chronic diseases.

Molecular insights into phytochemicals exhibiting anti-arthritic activity: systematic review : John Di Battista

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease with an unclear etiology causing severe inflammation, joint pain, and destruction that increases the chance of disability over time. Dysregulation of various immune signaling cascades regulates the formation of synovial hyperplasia and pannus formation. Imbalance in cytokine levels, predominantly proinflammatory cytokines like TNF-α, IL-1, IL-6, IL-17, and IL-12p70 profoundly influences the disease's pathogenesis. Even though various strategies are adopted to treat arthritis, their side effects and cost limit their usage. This review discusses the multiple pathways involved in the pathogenesis of rheumatoid arthritis, provides a systematic analysis of various phytochemicals, and discusses their potential molecular targets in RA treatment.

METHODS

The literature mining was done from scientific databases such as PubMed, Europe PMC, Web of Science, Scopus, etc. The terminologies used for literature mining were Rheumatoid arthritis, phytochemicals, cell signaling pathways, molecular mechanism, etc. RESULTS: NF-κB, MAPKs, and JAK-STAT are the key pathways potentially targeted for RA treatment. However, specific susceptible pathways and potential targets remain unexplored. Besides, the phytochemicals remain an immense source to be exploited for the effective treatment of RA, overcoming the demerits of the conventional strategies. Various in vitro and in vivo findings suggest that polyphenols and flavonoids effectively treat RA conditions overcoming the demerits, such as limitations in usage and toxicity. The phytochemicals should be explored in par with the pathological mechanisms with all the available targets to determine their therapeutic efficacy. Through the established therapeutic efficacy, phytochemicals can help developing therapeutics that are safe and efficacious for RA treatment.

The Anticancer Potential of Apigenin Via Immunoregulation

Apigenin is an edible flavonoid widely distributed in natural plants, including most vegetables and fruits. Previous studies have revealed that apigenin possesses multiple biological functions by demonstrating antiinflammatory, anti-oxidative, anti-bacterial, anti-viral, anti-tumor and cardiovascular protective effects. Furthermore, recent progressions have disclosed a novel perspective of the anti-cancer roles of apigenin through its immunoregulatory functions. With the rapid progression of the groundbreaking strategies being developed for cancer immunotherapy, its immunoregulatory roles are being recognized as intriguing features of the multifaceted apigenin. However, the current understanding of this emerging role of apigenin still remains limited. Therefore, in the present review, recent advances on the immunoregulatory properties of apigenin in various diseases with a special focus on neoplasm, are summarized. Clinical strategies of cancer immunotherapy are briefly introduced and findings on apigenin linked to immunoregulatory roles in immunotherapy-associated aspects are brought together. The bioactivity, bioavailability, toxicity and potential of apigenin, to be considered as a therapeutic agent in anti-tumor immunotherapy, is discussed. Disclosed molecular mechanisms underlying the immunoregulatory roles of apigenin in cancer immunotherapy are also summarized. Based on findings from the literature, apigenin has the potential to serve as a prospective adjuvant for anti-cancer immunotherapy and warrants further investigations.

A mechanistic insight of phytoestrogens used for Rheumatoid arthritis: An evidence-based review

Assessment of the potential therapeutic benefits offered by naturally occurring phytoestrogens necessitate inspection of their potency and sites of action in impeding the chronic, systemic, autoimmune, joint destructing disorder Rheumatoid arthritis (RA). Possessing structural and functional similarity with human estrogen, phytoestrogen promisingly replaces the use of hormone therapy in eradicating RA symptoms with their anti-inflammatory, anti-oxidative, anti-proliferative, anti-angiogenesis, immunomodulatory, joint protection properties abolishing the harmful side effects of synthetic drugs. Scientific evidences revealed that use of phytoestrogens from different chemical categories including flavonoids, alkaloids, stilbenoids derived from different plant species manifest beneficial effects on RA through various cellular mechanisms including suppression of pro-inflammatory cytokines in particular tumor necrosis factor (TNF-α), interleukin(IL-6) and nuclear factor kappa B (NF-κB) and destructive metalloproteinases, inhibition of oxidative stress, suppressing inflammatory signalling pathways, attenuating osteoclastogenesis ameliorating cartilage degradation and bone erosion. This review summarizes the evidences of different phytoestrogen treatment and their pharmacological mechanisms in both in vitro and in vivo studies along with discussing clinical evaluations in RA patients showing phytoestrogen as a promising agent for RA therapy. Further investigations and more clinical trials are mandatory to clarify the utility of these plant derived compounds in RA prevention and in managing oestrogen deficient diseases in patients.

The mechanisms of hydroxychloroquine in rheumatoid arthritis treatment: Inhibition of dendritic cell functions via Toll like receptor 9 signaling

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HCQ efficiently inhibited DC phenotypic and functional maturation stimulated by serum from RA patients.

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HCQ prevented progression of arthritis by inhibiting DC maturation and migration from peripheral blood to LNs.

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HCQ inhibited CpG ODN 1826-activated BMDC maturation and migration.

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The effect of HCQ on DCs was related to the block in TLR9 signaling.

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The development of arthritis was impaired in TLR9^−/− mice.

Hydroxychloroquine (HCQ) is one of the most commonly prescribed immune-suppressants in treating rheumatoid arthritis (RA). Our previous research showed that HCQ suppressed RA development by inhibiting T follicular helper (Tfh) cells directly. Dendritic cells (DCs) serve as the link between innate and acquired immunity. Whether HCQ suppressed Tfh cell through DCs was not clear. In current study, we found that HCQ efficiently inhibited CD86, chemokine (C-X-C motif) receptor 4 (CXCR4) expression and interferon-α (IFN-α) secretion of healthy donor derived purified DCs stimulated by RA patient serum. To mimic RA, collagen-induced arthritis (CIA) mouse model was used and treated with HCQ daily for fifty-four days prior to sacrifice. We found HCQ inhibited DC maturation and migration to lymph nodes (LNs), manifested as down-regulated expression of CD40, CD80, CD86, MHCII (I-A^q) on LN DCs. In addition, HCQ reduced the level of chemokine receptor 7 (CCR7) and L-selectin on peripheral blood DCs and diminished percentage of LN DCs. Of note, HCQ only inhibited CpG ODN 1826-induced IL-12 secretion by bone marrow DCs (BMDCs) stimulated by various toll like receptor (TLR) agonists. Mechanistically, HCQ down-regulated the expression of TLR9 not only in healthy donor PBMC-derived DCs stimulated by RA patient serum, but also in LN DCs of CIA mice and CpG-activated BMDCs. Furthermore, arthritis scores in TLR9^−/− mice were much lower than that in wild type mice with impaired maturity and migration capability of DCs. Collectively, activation of DCs contributes to the pathogenesis of RA and HCQ shows protective effects on RA by inhibition of DC activation via blocking TLR9.

Network Pharmacology to Identify the Pharmacological Mechanisms of a Traditional Chinese Medicine Derived from Trachelospermum jasminoides in Patients with Rheumatoid Arthritis

BACKGROUND This study used a network pharmacology approach to identify the pharmacological mechanisms of a traditional Chinese medicine derived from Trachelospermum jasminoides (Lindl.) Lem. in patients with rheumatoid arthritis (RA). MATERIAL AND METHODS Known compounds of T. jasminoides were obtained from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database, the Shanghai Institute of Organic Chemistry of Chinese Academy of Science, Chemistry (CASC) database, and a literature search. Putative targets of identified compounds were predicted by SwissTargetPrediction. RA-related targets were achieved from the Therapeutic Target database, Drugbank database, Pharmacogenomics Knowledgebase, and Online Mendelian Inheritance in Man database. The protein-protein interaction (PPI) network was built by STRING. CluGO was utilized for Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis. RESULTS A total of 354 potential targets were predicted for the 17 bioactive compounds in T. jasminoides; 69 of these targets overlapped with RA-related targets. A PPI network was composed and 2 clusters of 59 and 42 nodes each were excavated. GO and KEGG enrichment analysis of the overlapping targets and the 2 clusters was mainly grouped into immunity, inflammation, estrogen, anxiety, and depression processes. CONCLUSIONS Our study illustrated that T. jasminoides alleviates RA through the interleukin-17 signaling pathway, the tumor necrosis factor signaling pathway, and other immune and inflammatory-related processes. It also may exert effects in regulating cell differentiation and potentially has anti-anxiety, anti-depression, and estrogen-like effects.

Natural products action on pathogenic cues in autoimmunity: Efficacy in systemic lupus erythematosus and rheumatoid arthritis as compared to classical treatments

Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), which are characterized by self-perpetuating inflammation and tissue/organ damage, resulting from the failure of lymphocyte auto-tolerance, cause morbidity and mortality worldwide. The current drugs or therapies including conventional non-steroidal anti-inflammatory drugs (NSAIDs) and disease-modifying anti-rheumatic drugs (DMARDs), as well as several biologic therapies such as B cell-targeted, T cell-targeted, cytokines-targeted and cytokines receptors-targeted therapy, cannot completely cure SLE and RA, and are always accompanied by unexpected side effects. Therefore, more studies have explored new methods for therapy and found that the herbal medicine as well as its natural products (NPs) exhibited promising therapeutic value through exerting effects of immunomodulation, anti-inflammation, anti-oxidation, and anti-apoptosis, etc. via regulating abnormal responses in kidney, innate and adaptive immune systems, intestine, synoviocytes, as well as bone system including chondrocytes, osteoclasts, joints and paw tissues. In the present review, we will elucidate the current mainstream drugs and therapies for SLE and RA, and summarize the efficacy and mechanisms of NPs in the treatment of SLE and RA based on available findings including in vitro and in vivo animal models, as well as clinical studies, and further analyze the existing challenges, in order to provide comprehensive evidence for improvement of SLE and RA therapy by NPs and to promote management of these two autoimmune diseases.

Apigenin Modulates Dendritic Cell Activities and Curbs Inflammation Via RelB Inhibition in the Context of Neuroinflammatory Diseases

Neuroinflammation leads to tissue injury causing many of the clinical symptoms of Multiple Sclerosis, an autoimmune disorder of the central nervous system (CNS). While T cells, specifically T_h1 and T_h17 cells, are the ultimate effectors of this disease, dendritic cells (DCs) mediate T cell polarization, activation, etc. In our previous study, Apigenin, a natural flavonoid, has been shown to reduce EAE disease severity through amelioration of demyelination in the CNS as well as the sequestering of DCs and other myeloid cells in the periphery. Here, we show that Apigenin exerts its effects possibly through shifting DC modulated T cell responses from T_h1 and T_h17 type towards T_reg directed responses evident through the decrease in T-bet, IFN-γ (T_h1), IL-17 (T_h17) and increase in IL-10, TGF-β and FoxP3 (T_reg) expression in cells from both normal human donors and EAE mice. RelB, an NF-κβ pathway protein is central to DC maturation, its antigen presentation capabilities and DC-mediated T cell activation. Apigenin reduced mRNA and protein levels of RelB and also reduced its nuclear translocation. Additionally, siRNA-mediated silencing of RelB further potentiated the RelB-mediated effects of Apigenin thus confirming its role in Apigenin directed regulation of DC biology. These results provide key information about the molecular events controlled by Apigenin in its regulation of DC activity marking its potential as a therapy for neuroinflammatory disease. Graphical Abstract.

CCDC88B is required for mobility and inflammatory functions of dendritic cells

The Coiled Coil Domain Containing Protein 88B (CCDC88B) gene is associated with susceptibility to several inflammatory diseases in humans and its inactivation in mice protects against acute neuroinflammation and models of intestinal colitis. We report that mice lacking functional CCDC88B (Ccdc88b^Mut ) are defective in several dendritic cells (DCs)-dependent inflammatory and immune reactions in vivo. In these mice, an inflammatory stimulus (LPS) fails to induce the recruitment of DCs into the draining lymph nodes (LNs). In addition, OVA-pulsed Ccdc88b^Mut DCs injected in the footpad do not induce recruitment and activation of antigen-specific CD4⁺ and CD8⁺ T cells in their draining LN. Experiments in vitro indicate that this defect is independent of the ability of mutant DCs to capture and present peptide antigen to T cells. Rather, kinetic analyses in vivo of wild-type and Ccdc88b^Mut DCs indicate a reduced migration capacity in the absence of the CCDC88B protein expression. Moreover, using time-lapse light microscopy imaging, we show that Ccdc88b^Mut DCs have an intrinsic motility defect. Furthermore, in vivo studies reveal that these reduced migratory properties lead to dampened contact hypersensitivity reactions in Ccdc88b mutant mice. These findings establish a critical role of CCDC88B in regulating movement and migration of DCs. Thus, regulatory variants impacting Ccdc88b expression in myeloid cells may cause variable degrees of DC-dependent inflammatory response in situ, providing a rationale for the genetic association of CCDC88B with several inflammatory and autoimmune diseases in humans.

Exosomal MicroRNA-320a Derived From Mesenchymal Stem Cells Regulates Rheumatoid Arthritis Fibroblast-Like Synoviocyte Activation by Suppressing CXCL9 Expression

Rheumatoid arthritis (RA), a chronic systemic inflammatory disease, is a primary cause of disability worldwide. The involvement of fibroblast-like synoviocytes (FLSs) in the regulation of the pathogenesis of RA has been highlighted. Mesenchymal stem cells (MSCs) are important candidates for cell-based treatment in many inflammatory autoimmune diseases. Herein, we identify whether MSC-derived exosomes loaded with microRNA-320a (miR-320a) regulate RA-FLSs. Synovial tissues from 22 patients with RA and 9 patients with osteoarthritis were collected. RA-FLSs were obtained from patients with RA, and their functions were evaluated by determining levels of interleukin-1β (IL-1β), IL-6, and IL-8 and by transwell migration and invasion assays. Dual luciferase reporter gene assays were employed to identify interaction between miR-320a and CXC chemokine ligand 9 (CXCL9). A co-culture system of MSC-derived exosomes and RA-FLSs were performed. The collagen-induced arthritis (CIA) mouse models with arthritis and bone damage were developed. Our results revealed the existence of reciprocal expression of miR-320a and CXCL9 in the synovial tissues obtained from patients with RA. CXCL9 knockdown or miR-320a upregulation suppressed the activation, migration, and invasion of RA-FLSs. CXCL9 was confirmed to be a target of miR-320a, and CXCL9 overexpression restored RA-FLS function in the presence of miR-320a. MSC-derived exosomes containing miR-320a mimic significantly suppressed RA-FLS activation, migration, and invasion in vitro and attenuated arthritis and bone damage in mice with CIA in vivo. Our study uncovers that MSC-derived exosomes participate in the intercellular transfer of miR-320a and subsequently inhibit the progression of RA. These results provide a novel potential therapeutic approach for RA treatment by increasing miR-320a in exosomes.

Therapeutic Potential of Flavonoids in Pain and Inflammation: Mechanisms of Action, Pre-Clinical and Clinical Data, and Pharmaceutical Development

Pathological pain can be initiated after inflammation and/or peripheral nerve injury. It is a consequence of the pathological functioning of the nervous system rather than only a symptom. In fact, pain is a significant social, health, and economic burden worldwide. Flavonoids are plant derivative compounds easily found in several fruits and vegetables and consumed in the daily food intake. Flavonoids vary in terms of classes, and while structurally unique, they share a basic structure formed by three rings, known as the flavan nucleus. Structural differences can be found in the pattern of substitution in one of these rings. The hydroxyl group (-OH) position in one of the rings determines the mechanisms of action of the flavonoids and reveals a complex multifunctional activity. Flavonoids have been widely used for their antioxidant, analgesic, and anti-inflammatory effects along with safe preclinical and clinical profiles. In this review, we discuss the preclinical and clinical evidence on the analgesic and anti-inflammatory proprieties of flavonoids. We also focus on how the development of formulations containing flavonoids, along with the understanding of their structure-activity relationship, can be harnessed to identify novel flavonoid-based therapies to treat pathological pain and inflammation.

Tolerogenic Dendritic Cells Generated by BAFF Silencing Ameliorate Collagen-Induced Arthritis by Modulating the Th17/Regulatory T Cell Balance

Tolerogenic dendritic cells (tolDCs) have received much attention because of their capacity to restore immune homeostasis. RNA interference techniques have been used in several studies to generate tolDCs by inactivating certain molecules that regulate DC maturation and immunologic function. BAFF is a key B cell survival factor that is not only essential for B cell function but also T cell costimulation, and DCs are the major source of BAFF. In this study, we determined whether BAFF gene silencing in mature DCs could lead to a tolerogenic phenotype as well as the potential therapeutic effect of BAFF-silenced DCs on collagen-induced arthritis (CIA) in mice. Meanwhile, CRISPR/Cas9-mediated BAFF^-/- DC2.4 cells were generated to verify the role of BAFF in DC maturation and functionality. BAFF-silenced DCs and BAFF^-/- DC2.4 cells exhibited an immature phenotype and functional state. Further, the transplantation of BAFF-silenced DCs significantly alleviated CIA severity in mice, which correlated with a reduction in Th17 populations and increased regulatory T cells. In vitro, BAFF-silenced DCs promoted Foxp3 mRNA and IL-10 expression but inhibited ROR-γt mRNA and IL-17A expression in CD4⁺ T cells. Together, BAFF-silenced DCs can alleviate CIA, partly by inducing Foxp3⁺ regulatory T cells and suppressing Th17 subsets. Collectively, BAFF plays an important role in interactions between DCs and T cells, which might be a promising genetic target to generate tolDCs for autoimmune arthritis treatment.

Flavonoids: Broad Spectrum Agents on Chronic Inflammation

Flavonoids are major plant constituents with numerous biological/pharmacological actions both in vitro and in vivo. Of these actions, their anti-inflammatory action is prominent. They can regulate transcription of many proinflammatory genes such as cyclooxygenase-2/inducible nitric oxide synthase and many cytokines/chemokines. Recent studies have demonstrated that certain flavonoid derivatives can affect pathways of inflammasome activation and autophagy. Certain flavonoids can also accelerate the resolution phase of inflammation, leading to avoiding chronic inflammatory stimuli. All these pharmacological actions with newly emerging activities render flavonoids to be potential therapeutics for chronic inflammatory disorders including arthritic inflammation, meta-inflammation, and inflammaging. Recent findings of flavonoids are summarized and future perspectives are presented in this review.

Immunomodulatory effect of oleoylethanolamide in dendritic cells via TRPV1/AMPK activation

Oleoylethanolamide (OEA) is an endogenous lipid mediator involved in the control of feeding, body weight, and energy metabolism. However, whether OEA modulates maturation of dendritic cells (DCs) has never been addressed. Hence, we evaluated the effect of OEA on DCs maturation in bone marrow-derived DCs (BMDCs) in four aspects: (a) Cell surface markers were determined using flow cytometric analysis; (b) cell mobile ability was testified with the transwell assay; (c) stimulation of T cells proliferation was performed in a coculture system; and (d) cytokine production was measured using polymerase chain reaction (PCR). The result showed that, in mature BMDCs induced by lipopolysaccharides (LPS), the OEA treatment decreased expressions of cell surface markers, reduced cell migration, diminished the proliferation of cocultured T cells, and regulated cytokine production of BMDCs, indicating the modulatory effect of OEA on DCs maturation. Furthermore, to explore the underlying mechanism of the immunomodulatory effect of OEA, we used antagonists of transient receptor potential vanilloid-1 (TRPV1) and AMP-activated protein kinase (AMPK), determined the protein expressions of TRPV1/AMPK and Toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) using western blot, and measured the intracellular calcium concentration using calcium imaging. The result illustrated that OEA downregulated TLR4/NF-κB, the classical pathway leading to DCs maturation induced by LPS, through the activation of TRPV1 and AMPK. Collectively, the present study suggests that OEA suppresses DCs maturation through the activation of TRPV1/AMPK. These findings increase our understanding of this endogenous lipid OEA.

Potential Role of Flavonoids in Treating Chronic Inflammatory Diseases with a Special Focus on the Anti-Inflammatory Activity of Apigenin

Inflammation has been reported to be intimately linked to the development or worsening of several non-infectious diseases. A number of chronic conditions such as cancer, diabetes, cardiovascular disorders, autoimmune diseases, and neurodegenerative disorders emerge as a result of tissue injury and genomic changes induced by constant low-grade inflammation in and around the affected tissue or organ. The existing therapies for most of these chronic conditions sometimes leave more debilitating effects than the disease itself, warranting the advent of safer, less toxic, and more cost-effective therapeutic alternatives for the patients. For centuries, flavonoids and their preparations have been used to treat various human illnesses, and their continual use has persevered throughout the ages. This review focuses on the anti-inflammatory actions of flavonoids against chronic illnesses such as cancer, diabetes, cardiovascular diseases, and neuroinflammation with a special focus on apigenin, a relatively less toxic and non-mutagenic flavonoid with remarkable pharmacodynamics. Additionally, inflammation in the central nervous system (CNS) due to diseases such as multiple sclerosis (MS) gives ready access to circulating lymphocytes, monocytes/macrophages, and dendritic cells (DCs), causing edema, further inflammation, and demyelination. As the dearth of safe anti-inflammatory therapies is dire in the case of CNS-related disorders, we reviewed the neuroprotective actions of apigenin and other flavonoids. Existing epidemiological and pre-clinical studies present considerable evidence in favor of developing apigenin as a natural alternative therapy against chronic inflammatory conditions.

The effect of the cholinergic anti-inflammatory pathway on collagen-induced arthritis involves the modulation of dendritic cell differentiation

BACKGROUND

The cholinergic anti-inflammatory pathway (CAP) has a strong anti-inflammatory effect on collagen-induced arthritis (CIA), a classic animal model of rheumatoid arthritis (RA). However, the underlying immune regulatory mechanism remains unclear. Here, we investigated the effect of the CAP on arthritis development and the involvement of dendritic cells (DCs).

METHODS

Forty DBA/1 mice were randomly divided into five groups: a control group (sham vagotomy+ phosphate-buffered saline; shamVGX+PBS), a CIA group (shamVGX+CIA + PBS), a vagotomy group (VGX + CIA + PBS), a GTS-21 (4 mg/kg) group (shamVGX+CIA + GTS-4), and a GTS-21 (8 mg/kg) group (shamVGX+CIA + GTS-8). The vagotomy group underwent left cervical vagotomy 4 days before arthritis induction, whereas the sham-vagotomy group underwent vagus nerve exposure. Mice were pretreated with GTS-21 by intraperitoneal injection on the day of surgery. The degree of arthritis was measured by using the arthritis score, hematoxylin and eosin staining, and TRAP (tartrate-resistant acid phosphatase) staining. Flow cytometry was used to detect the expression of CD80 and major histocompatibility complex II (MHC II) on CD11c⁺ DCs in the spleen. Luminex was used to detect the serum concentration of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFα), and IL-10. Immunohistochemistry was used to detect CD11c expression in the synovium. The effects of GTS-21 on DC differentiation and maturation were examined in vitro by treating bone marrow-derived DCs with GTS-21 and assessing differentiation and maturation. Flow cytometry was used to analyze CD80 and MHC II expression on the surface of DCs.

RESULTS

GTS-21 treatment ameliorated clinical arthritis in a mouse model of CIA in vivo, decreasing the secretion of pro-inflammatory cytokines in the serum and downregulating CD80 and MHC II expression on DCs in the spleen of CIA mice. GTS-21 treatment strongly suppressed the infiltration of DCs into the synovium. Vagotomy itself did not exacerbate the severity of arthritis in CIA mice. In vitro, GTS-21 (10 μmol/L) significantly downregulated CD80 and MHC II in bone marrow-derived immature DCs and this effect was blocked by the α7-nicotinic acetylcholine receptor antagonist methyllycaconitine (MLA). However, GTS-21 had no effects on mature DCs.

CONCLUSIONS

The present study provides new insight into the mechanism underlying the effects of the CAP on RA and indicates that the immunosuppressive effect of GTS-21 may be mediated by the inhibition of DC differentiation.

Apigenin reverses lung injury and immunotoxicity in paraquat-treated mice

Paraquat (PQ) induces acute lung injury (ALI) and immunotoxicity. Apigenin exerts anti-oxidant and anti-inflammatory properties. The purpose of this study was to investigate the possible protective effects of apigenin on PQ-induced ALI and immunotoxicity in mice. Female C57BL/6 mice received a single injection of PQ (50 mg/kg). Apigenin was given for 7 consecutive days starting 5 days before PQ exposure. The toxicity markers were evaluated in terms of weight loss, lung histopathology, oxidative stress, inflammation, and T cell functions after PQ exposure. Poisoned mice exhibited severe lung tissue lesions, inflammatory cell infiltration and the release of pro-inflammatory cytokines IL-6 and TNF-α. PQ administration increased the lung wet/dry ratios and lipid peroxidation by the increase of MDA levels and decreased anti-oxidase activity including SOD, GSH-PX, and CAT. While such effect on lung was reversed by apigenin. Importantly, PQ-induced immunotoxicity was also observed in a decrease of spleen weight, inhibition of T cell proliferation and T-cell secreting IL-2 from splenocytes. Further mechanism analysis found that PQ administration could decrease total splenocytes, CD4⁺ and CD8⁺ T cells, SOD, GSH-PX, and CAT activity, and increased the levels of MDA and the concentrations of pro-inflammatory cytokines IL-6 and TNF-α compared to control mice. However, apigenin treatment reversed PQ-induced immunotoxicity. In summary, all results suggest that apigenin has beneficial effects on PQ-induced ALI and immunotoxicity possibly, and it could be related, at least in part, to its ability in modulating inflammation and oxidative stress, although in-depth studies might be needed to fully understand the mechanism of action.

The significant impact of apigenin on different aspects of autoimmune disease

Autoimmune diseases are among the highest diseases to diagnose and treat. The current "gold standard" of care for these diseases is immunosuppressive drugs which interfere with overall immune responses; their long-term high-dose treatments would expose the patient to opportunistic, life-threatening and long-term malignant infections. Considering the side effects and toxicity of these drug and also the beneficial effects of herbal compounds among their consumers, the professional investigation on the exact mechanism of the plant's major element has grown much attention in the last years. Apigenin as an extracting compound of plants, such as parsley and celery, which has a variety of biological effects, such as anti-inflammatory, anti-cancer and antioxidant effects. This review is intended to summarize the various effects of Apigenin on several autoimmune diseases which have been worked on so far. The pluralization of the obtained results has revealed Apigenin's effects on pro-inflammatory cytokines such as IL-1β, chemokines such as ICAM-1, immune cells proliferation such as T cells, apoptosis, and various signaling pathways. According to these preclinical findings, we recommend that further robust unbiased studies should be done to use Apigenin as a supplementary or therapeutic element in autoimmune disease.

Targeting of tolerogenic dendritic cells towards heat-shock proteins: a novel therapeutic strategy for autoimmune diseases?

Tolerogenic dendritic cells (tolDCs) are a promising therapeutic tool to restore immune tolerance in autoimmune diseases. The rationale of using tolDCs is that they can specifically target the pathogenic T-cell response while leaving other, protective, T-cell responses intact. Several ways of generating therapeutic tolDCs have been described, but whether these tolDCs should be loaded with autoantigen(s), and if so, with which autoantigen(s), remains unclear. Autoimmune diseases, such as rheumatoid arthritis, are not commonly defined by a single, universal, autoantigen. A possible solution is to use surrogate autoantigens for loading of tolDCs. We propose that heat-shock proteins may be a relevant surrogate antigen, as they are evolutionarily conserved between species, ubiquitously expressed in inflamed tissues and have been shown to induce regulatory T cells, ameliorating disease in various arthritis mouse models. In this review, we provide an overview on how immune tolerance may be restored by tolDCs, the problem of selecting relevant autoantigens for loading of tolDCs, and why heat-shock proteins could be used as surrogate autoantigens.

Isoegomaketone Alleviates the Development of Collagen Antibody-Induced Arthritis in Male Balb/c Mice

In this study, we attempted to identify and assess effects of isoegomaketone (IK) isolated from Perilla frutescens var. crispa on the development of rheumatoid arthritis (RA). RA was induced in male Balb/c mice by collagen antibody injection. Experimental animals were randomly divided into five groups: normal, collagen antibody-induced arthritis (CAIA), CAIA + IK (5 mg/kg/day), CAIA + IK (10 mg/kg/day), and CAIA + apigenin (16 mg/kg/day) and respective treatments were administered via oral gavage once per day for four days. Mice treated with IK (10 mg/kg/day) developed less severe arthritis than the control CAIA mice. Arthritic score, paw volume, and paw thickness were less significant compared to the control CAIA mice at day seven (73%, 15%, and 14% lower, respectively). Furthermore, histopathological examination of ankle for inflammation showed that infiltration of inflammatory cells and edema formation were reduced by IK treatment. Similarly, neutrophil to lymphocyte ratio (NLR) in whole blood was lower in mice treated with IK (10 mg/kg/day) by 85% when compared to CAIA mice. Taken together, treatment with IK delays the onset of the arthritis and alleviates the manifestations of arthritis in CAIA mice.

Dendritic cell migration in health and disease

Dendritic cells (DCs) are potent and versatile antigen-presenting cells, and their ability to migrate is key for the initiation of protective pro-inflammatory as well as tolerogenic immune responses. Recent comprehensive studies have highlighted the importance of DC migration in the maintenance of immune surveillance and tissue homeostasis, and also in the pathogenesis of a range of diseases. In this Review, we summarize the anatomical, cellular and molecular factors that regulate the migration of different DC subsets in health and disease. In particular, we focus on new insights concerning the role of migratory DCs in the pathogenesis of diseases of the skin, intestine, lung, and brain, as well as in autoimmunity and atherosclerosis.

Dendritic Cell-based Immunotherapy for Rheumatoid Arthritis: from Bench to Bedside

Dendritic cells (DCs) are professional antigen presenting cells, and play an important role in the induction of antigen-specific adaptive immunity. However, some DC populations are involved in immune regulation and immune tolerance. These DC populations are believed to take part in the control of immune exaggeration and immune disorder, and maintain immune homeostasis in the body. Tolerogenic DCs (tolDCs) can be generated in vitro by genetic or pharmacological modification or by controlling the maturation stages of cytokine-derived DCs. These tolDCs have been investigated for the treatment of rheumatoid arthritis (RA) in experimental animal models. In the last decade, several in vitro and in vivo approaches have been translated into clinical trials. As of 2015, three tolDC trials for RA are on the list of ClinicalTrial.gov (www.clinicaltrials.gov). Other trials for RA are in progress and will be listed soon. In this review, we discuss the evolution of tolDC-based immunotherapy for RA and its limitations and future prospects.