Arthritis models: usefulness and interpretation

Omics-based pharmacological evaluation reveals Yuanhu Zhitong oral liquid ameliorates arthritis by regulating PKC/ERK/NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Successful use of herbal medicine in the treatment of rheumatoid arthritis (RA) creates opportunities for alternative therapies. Yuanhu Zhitong oral liquid (YZOL) is an herbal preparation known for its potent analgesic and anti-inflammatory properties in traditional use. However, the pharmacological mechanism of YZOL for treating RA remains unclear.

AIM OF THE STUDY

The aim of this study was to evaluate the efficacy of YZOL in the treatment of RA and to explore its potential mechanisms through omics analysis.

MATERIALS AND METHODS

Type II collagen was used to induce an arthritis rat model. The effects of YZOL on paw swelling, inflammatory cytokines, oxidative stress, and histopathological changes were systematically investigated. A pathway-driven transcriptomic analysis was performed to identify key signaling pathways associated with YZOL therapy. The key alterations were validated by qRT-PCR, Western blot, and immunohistochemistry assays.

RESULTS

YZOL significantly attenuated arthritis progression, reduced paw swelling rate, and lowered arthritis score in CIA rats. YZOL also inhibited systemic inflammation and associated oxidative stress during RA. Transcriptomic analysis identified 341 genes with significantly altered expression following YZOL treatment. These genes were enriched in inflammation-related pathways, particularly in the NF-κB and MAPK signaling pathways. In addition, we discovered that YZOL can alleviate inflammation in the local synovial tissue. The effect of YZOL was confirmed by the suppression of PKC/ERK/NF-κB p65 signaling at systemic and local levels.

CONCLUSIONS

This study provides novel evidence that YZOL treatment ameliorates RA by suppressing the PKC/ERK/NF-κB pathway, suggesting its potential as an alternative therapy for RA.

White adipose tissue, a novel antirheumatic target: Clues from its secretory capability and adipectomy-based therapy

BACKGROUND AND PURPOSE

White adipose tissue (WAT) is involved in rheumatoid arthritis (RA). This study explored its potential as an antirheumatic target.

EXPERIMENTAL APPROACH

WAT status of healthy and adjuvant-induced arthritis (AIA) rats were compared. The contribution of WAT to RA pathology was evaluated by pre-adipocyte transplant experiments and by dissecting perirenal fat pads of AIA rats. The impact of RA on WAT was investigated by culturing pre-adipocytes. Proteins differentially expressed in WAT of healthy and AIA rats were identified by the UPLC/MS2 method. These together with PPARγ siRNA and agonist were used to treat pre-adipocytes in vitro. The medium was used for THP-1 monocyte culture.

KEY RESULTS

Compared with healthy controls, AIA WAT was smaller but secreted more leptin, eNAMPT, MCP-1, TNF-α, and IL-6. AIA rat pre-adipocytes increased the levels of these adipokines in healthy recipients. RA patients' serum induced a similar secretion change and impaired differentiation of pre-adipocytes. Adipectomy eased AIA-related immune abnormalities and arthritic manifestations. Hepatokines PON1, IGFBP4, and GPIHBP1 were among the differential proteins in high levels in RA blood, and induced inflammatory secretions by pre-adipocytes. GPIHBP1 inhibited PPARγ expression and caused differentiation impairment and inflammatory secretion by pre-adipocytes, a similar outcome to PPARγ-silencing. This endowed the cells with an ability to activate monocytes, which can be abrogated by rosiglitazone.

CONCLUSION AND IMPLICATIONS

Certain hepatokines potentiate inflammatory secretions by pre-adipocytes and expedite RA progression by inhibiting PPARγ. Targeting this signalling or abnormal WAT secretion by various approaches may reduce RA severity.

Intra-articular hydrogel formulation prolongs the in vivo stability of Toll-like receptor antagonistic peptides for rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is an autoimmune disease characterized by systemic inflammation that primarily affects joint tissue and requires frequent medication. Recently, we developed cyclic phage-display-derived inhibitory peptides (CPs), which act as Toll-like Receptor 4 antagonists. These CPs exhibited therapeutic efficacy against joint diseases by alleviating inflammatory factors. Nonetheless, CP exhibits in vivo instability and a short half-life. Therefore, this study sought to improve the in vivo stability of CP, thereby reducing the frequency of CP administration through the development of an injectable hydrogel depot formulation. To improve in vivo stability, CP was chemically conjugated to hyaluronic acid (HA-CP) and subsequently mixed into a temperature-sensitive hydrogel [methoxy polyethylene glycol-b-poly(ε-caprolactone)-ran-poly(lactide) (PC)] as an injectable depot (PC+(HA-CP)). For comparison, CP was physically mixed with HA and PC (PC+(HA+CP)). Both PC+(HA-CP) and PC+(HA+CP) were found to rapidly form depots upon injection into the joint space. Cell viability assays confirmed the non-toxic nature of PC+(HA-CP) and PC+(HA+CP), whereas both formulations exhibited inhibition of inflammatory factors. Furthermore, PC+(HA-CP) retained CP for a longer duration compared to PC+(HA+CP) in the presence of hyaluronidase and within the RA joint space. Following intra-articular injection, both the PC+(HA-CP) and PC+(HA+CP) depots exhibited reductions in RA symptoms, cartilage regeneration, and suppression of pro-inflammatory cytokine levels. Specifically, by extending the in vivo retention of CP, PC+(HA-CP) demonstrated superior RA treatment efficacy compared to PC+(HA+CP). In conclusion, intra-articular injection of PC+(HA-CP) was validated as an effective strategy for treating RA, owing to its ability to prolong the in vivo retention of CP. This approach holds promise for improving RA management and patient outcomes.

Clinical Scoring of Disease Activity in Animal Models

Disease severity in murine arthritis models, such as collagen-induced arthritis (CIA), is commonly assessed by clinical scoring of paw swelling and histological examination of joints. Clinical scoring using a qualitative scoring system of paw inflammation (paw thickness, width, or volume) over time is the standard method used for subjective quantification of arthritis activity. To evaluate paw swelling status, a quantitative method using three-dimensional T2-weighted flash sequence magnetic resonance imaging (MRI) is introduced. The efficacy of a therapeutic approach can be semiologically quantified using a clinical scoring system and an index of paw inflammation in CIA mice.

Collagen-Induced Arthritis Models

Due to the limitations of using patient-derived samples for systemic kinetic studies in rheumatoid arthritis (RA) research, animal models are helpful for further understanding the pathophysiology of RA and seeking potential therapeutic targets or strategies. The collagen-induced arthritis (CIA) model is one of the standard RA models used in preclinical research. The CIA model shares several pathological features with RA, such as breach of tolerance and generation of autoantibodies targeting collagen, synovial inflammatory cell infiltration, synovial hyperplasia, cartilage destruction, and bone erosion. In this chapter, a protocol for the successful induction of CIA in mice is described. In this protocol, CIA is induced by active immunization by inoculation with type II heterologous collagen in Freund's adjuvant in susceptible DBA/1 mice.

Triterpenes Drug Delivery Systems, a Modern Approach for Arthritis Targeted Therapy

Arthritis is a major cause of disability. Currently available anti-arthritic drugs, such as disease-modifying anti-rheumatic drugs (DMARDs), have serious side-effects associated with long-term use. Triterpenoids are natural products with known anti-inflammatory properties, and many have revealed efficiency against arthritis both in vitro and in vivo in several animal models, with negligible cytotoxicity. However, poor bioavailability due to low water solubility and extensive metabolism upon oral administration hinder the therapeutic use of anti-arthritic triterpenoids. Therefore, drug delivery systems (DDSs) able to improve the pharmacokinetic profile of triterpenoids and achieve sustained drug release are useful alternatives for targeted delivery in arthritis treatment. Several DDSs have been described in the literature for triterpenoid delivery, including microparticulate and nanoparticulate DDSs, such as polymeric micro and nanoparticles (NPs), polymeric micelles, liposomes, micro and nanoemulsions, and hydrogels. These systems have shown superior therapeutic effects in arthritis compared to the free drugs and are similar to currently available anti-arthritic drugs without significant side-effects. This review focuses on nanocarriers for triterpenoid delivery in arthritis therapy, including osteoarthritis (OA), rheumatoid arthritis (RA) and gout that appeared in the literature in the last ten years.

The Expression of the Alpha7 Nicotinic Acetylcholine Receptor and the Effect of Smoking in Curdlan-Administered SKG Mice

Nicotine, an abundant molecule in tobacco, has immunomodulatory effects on inflammatory diseases, primarily due to the activation of alpha7 nicotinic acetylcholine receptor (α7 nAChR). We aim to evaluate the expression of the α7 nAChR+ cells in joint tissue and the effect of smoking on immune cells and peripheral arthritis in curdlan-administered SKG mice, a murine model of spondyloarthropathy (SpA). The SKG mice were injected with curdlan two times at 2-week intervals and were divided into two groups; one exposed to cigarette smoke and the other not exposed. We found that the α7 nAChR+ cells increased in the joint tissue of curdlan-administered SKG mice compared to in the wild type. Furthermore, the peripheral arthritis scores and histological scores for synovial inflammation were lower in smoke-exposed curdlan-administered SKG mice than in mice not exposed to smoke. Immunofluorescence staining of the α7 nAChR+ and IL-17A+ cells was lower in the synovia of smoke-exposed mice than the control mice. The proportions of α7 nAChR+IL-17A+ and α7 nAChR+IL-17A+FOXP3+ cells also decreased in the synovia of smoke-exposed mice compared with the controls. We observed an increase in the α7 nAChR+ cells within the joint tissue of curdlan-administered SKG mice and that cigarette smoke had an influence on both peripheral arthritis and immune cell population, especially α7 nAChR+ cells. Thus, exposure to cigarette smoke after arthritogenic stimuli may have an anti-arthritogenic effect in curdlan-administered SKG mice.

The newly engineered monoclonal antibody ON104, targeting the oxidized Macrophage Migration Inhibitory Factor (oxMIF), ameliorates clinical and histopathological signs of collagen-induced arthritis

Macrophage Migration Inhibitory Factor (MIF) is a pleiotropic inflammatory cytokine that emerged as a pivotal regulator in the pathogenesis of several autoimmune diseases including rheumatoid arthritis (RA). MIF occurs in two immunologically distinct conformational isoforms, indicated as reduced (redMIF) and oxidized MIF (oxMIF) where the latter exerts disease-related activities. In this study we demonstrate the presence of circulating oxMIF in RA patients and investigate the in vivo effects of an oxMIF-neutralizing antibody in a murine model of RA. By advanced antibody engineering we generated the fully human anti-oxMIF antibody ON104 with abolished effector functions. The therapeutic potential of ON104 was tested in a model of Collagen-Induced Arthritis (CIA) in DBA/1j mice. At disease onset, the mice received ON104 twice a week for three weeks. Clinical symptoms were assessed daily, and histological examinations of the joints were performed at the end of the study. Antibody ON104, specifically targeting human and murine oxMIF, is highly affine and does not elicit effector functions in vitro. The treatment of CIA mice with ON104 profoundly modulated disease progression with marked amelioration of clinical signs of arthritis that was associated with reduced synovial and cartilage damage and reduced F4/80-positive macrophages in the joints. These data prove that oxMIF is a relevant target in a well-known model of human RA and its specific neutralization by the antibody ON104 ameliorates clinical and histological signs of the disease in the so-treated mice. Thus, ON104 represents a new and promising treatment option for RA and possibly other autoimmune diseases.

Bacterial DNA and osteoarthritis in dogs with patellar luxation and cranial cruciate ligament rupture

Background and Aim

The association between bacterial DNA in stifle joints, including those with cranial cruciate ligament rupture (CCLR) and medial patellar luxation (MPL), and osteoarthritis in dogs remains elusive. This study investigated the potential association between the detection of bacterial DNA and osteoarthritis in dogs using a broad-range polymerase chain reaction technique targeting the 16S ribosomal RNA gene.

Materials and Methods

Synovial fluid (35 samples) and knee tissue samples (32 samples) were obtained from 35 dogs diagnosed with CCLR (n = 20; 11 males and nine females) or MPL (n = 15; five males and 10 females) who underwent a surgical operation between October 2014 and April 2015.

Results

Dogs with CCLR had a higher average osteoarthritis score than those with MPL (2.0 ± 0.9 vs. 0.5 ± 0.9; p = 0.005). Bacterial DNA was detected in the stifle joints of 60.71% of dogs with MPL. Pelomonas spp. (25.00%), Halomonas spp. (17.86%), and 5 other species (17.86%) were the most frequently identified bacteria. Bacterial DNA was detected in 41.03% of dogs with CCLR. Pelomonas spp. (15.38%), Sphingomonas spp. (10.26%), Halomonas spp. (5.13%), and 4 other species (10.26%) were the most frequently identified bacteria. No significant difference was observed in the prevalence of bacterial DNA obtained from tissue samples (46.88%) or joint fluid samples (51.43%). The presence of bacterial DNA was not associated with the type of knee injury (MPL or CCLR; p = 1.000). There was a higher prevalence of bacterial DNA in samples from dogs with moderate-to-severe osteoarthritis (94.44%) than in those with minimal osteoarthritis (41.18%), and a significant association between the presence of bacterial DNA and moderate-to-severe osteoarthritis was identified (p < 0.01).

Conclusion

Dogs with moderate-to-severe osteoarthritis were more likely to have bacterial DNA in their stifle joints than those with no or minimal osteoarthritis. These findings provide valuable insight into the potential role of bacterial DNA in joint tissue or joint fluid and the development of osteoarthritis in dogs.

The Underlying Mechanism of Duanteng Yimu Decoction in Inhibiting Synovial Hyperplasia in Rheumatoid Arthritis

Dysregulation of microRNAs (miRNAs) is associated with the pathogenesis of rheumatoid arthritis (RA). Our previous studies confirmed that Duanteng Yimu decoction (DTYMT) effectively inhibits RA fibroblast-like synoviocyte (FLS) proliferation. In this study, we investigated the influence of DTYMT on miR-221 in RA individuals. Hematoxylin-eosin (HE) staining was performed to assess histopathological alterations in collagen-induced arthritis (CIA) mice. The expression of miR-221-3p and TLR4 in PBMC, FLS, and cartilage was measured by RT-qPCR. In the in vitro experiments, DTYMT-containing serum was incubated with FLS-transfected miR-221 mimic or inhibitor. CCK-8 was performed to determine FLS proliferation, and the secretion of IL-1β, IL-6, IL-18, and TNF-α was quantified by ELISA assay. In addition, the regulation of miR-221 expression on FLS apoptosis was assessed using flow cytometry. Finally, western blot was employed to reflect TLR4/MyD88 protein levels. HE results showed that DTYMT effectively reduced synovial hyperplasia in the joints of CIA mice. RT-qPCR assay of FLS and cartilage of the model group showed that miR-221-3p and TLR4 significantly increased compared with those in the normal group. All outcomes were improved by DTYMT. The miR-221 mimic reversed the inhibitory effect of DTYMT-containing serum on FLS proliferation, the release of IL-1β, IL-18, IL-6, and TNF-α, and FLS apoptosis, as well as TLR4/MyD88 protein levels. The results showed that miR-221 promotes the activity of RA-FLS by activating TLR4/MyD88 signaling, and DTYMT treats RA by reducing miR-221 in CIA mice.

Targeting strategies for bone diseases: signaling pathways and clinical studies

Since the proposal of Paul Ehrlich's magic bullet concept over 100 years ago, tremendous advances have occurred in targeted therapy. From the initial selective antibody, antitoxin to targeted drug delivery that emerged in the past decades, more precise therapeutic efficacy is realized in specific pathological sites of clinical diseases. As a highly pyknotic mineralized tissue with lessened blood flow, bone is characterized by a complex remodeling and homeostatic regulation mechanism, which makes drug therapy for skeletal diseases more challenging than other tissues. Bone-targeted therapy has been considered a promising therapeutic approach for handling such drawbacks. With the deepening understanding of bone biology, improvements in some established bone-targeted drugs and novel therapeutic targets for drugs and deliveries have emerged on the horizon. In this review, we provide a panoramic summary of recent advances in therapeutic strategies based on bone targeting. We highlight targeting strategies based on bone structure and remodeling biology. For bone-targeted therapeutic agents, in addition to improvements of the classic denosumab, romosozumab, and PTH1R ligands, potential regulation of the remodeling process targeting other key membrane expressions, cellular crosstalk, and gene expression, of all bone cells has been exploited. For bone-targeted drug delivery, different delivery strategies targeting bone matrix, bone marrow, and specific bone cells are summarized with a comparison between different targeting ligands. Ultimately, this review will summarize recent advances in the clinical translation of bone-targeted therapies and provide a perspective on the challenges for the application of bone-targeted therapy in the clinic and future trends in this area.

Potential Anti-Rheumatoid Arthritis Activities and Mechanisms of Ganoderma lucidum Polysaccharides

Rheumatoid arthritis (RA) is a chronic and autoimmune disease characterized by inflammation, autoimmune dysfunction, and cartilage and bone destruction. In this review, we summarized the available reports on the protective effects of Ganoderma lucidum polysaccharides (GLP) on RA in terms of anti-inflammatory, immunomodulatory, anti-angiogenic and osteoprotective effects. Firstly, GLP inhibits RA synovial fibroblast (RASF) proliferation and migration, modulates pro- and anti-inflammatory cytokines and reduces synovial inflammation. Secondly, GLP regulates the proliferation and differentiation of antigen-presenting cells such as dendritic cells, inhibits phagocytosis by mononuclear macrophages and nature killer (NK) cells and regulates the ratio of M1, M2 and related inflammatory cytokines. In addition, GLP produced activities in balancing humoral and cellular immunity, such as regulating immunoglobulin production, modulating T and B lymphocyte proliferative responses and cytokine release, exhibiting immunomodulatory effects. Thirdly, GLP inhibits angiogenesis through the direct inhibition of vascular endothelial cell proliferation and induction of cell death and the indirect inhibition of vascular endothelial growth factor (VEGF) production in the cells. Finally, GLP can inhibit the production of matrix metalloproteinases and promote osteoblast formation, exerting protective effects on bone and articular cartilage. It is suggested that GLP may be a promising agent for the treatment of RA.

A fully human connective tissue growth factor blocking monoclonal antibody ameliorates experimental rheumatoid arthritis through inhibiting angiogenesis

BACKGROUND

Connective tissue growth factor (CTGF) plays a pivotal role in the pathogenesis of rheumatoid arthritis (RA) by facilitating angiogenesis and is a promising therapeutic target for RA treatment. Herein, we generated a fully human CTGF blocking monoclonal antibody (mAb) through phage display technology.

RESULTS

A single-chain fragment variable (scFv) with a high affinity to human CTGF was isolated through screening a fully human phage display library. We carried out affinity maturation to elevate its affinity for CTGF and reconstructed it into a full-length IgG1 format for further optimization. Surface plasmon resonance (SPR) data showed that full-length antibody IgG mut-B2 bound to CTGF with a dissociation constant (KD) as low as 0.782 nM. In the collagen-induced arthritis (CIA) mice, IgG mut-B2 alleviated arthritis and decreased the level of pro-inflammatory cytokines in a dose-dependent manner. Furthermore, we confirmed that the TSP-1 domain of CTGF is essential for the interaction. Additionally, the results of Transwell assays, tube formation experiments, and chorioallantoic membrane (CAM) assays showed that IgG mut-B2 could effectively inhibit angiogenesis.

CONCLUSION

The fully human mAb that antagonizes CTGF could effectively alleviate arthritis in CIA mice, and its mechanism is tightly associated with the TSP-1 domain of CTGF.

Saussurea involucrata oral liquid regulates gut microbiota and serum metabolism during alleviation of collagen‐induced arthritis in rats

Saussurea involucrata oral liquid (SIOL) can clinically relieve symptoms, such as joint pain and swelling, and morning stiffness, in patients with rheumatoid arthritis (RA). However, the mechanism of action remains unclear. This study used a combination of gut microbiota and serum metabolomics analysis to investigate the effects and potential mechanisms of SIOL intervention on rats with RA induced by type II bovine collagen and Freund's complete adjuvant. Results showed that SIOL treatment consequently improved the degree of ankle joint swelling, joint histopathological changes, joint pathological score, and expression of serum-related inflammatory cytokines (interleukin (IL)-1β, IL-4, IL-6, IL-10, and tumor necrosis factor-α) in RA model rats. 16 S rRNA sequencing results showed that SIOL increased the relative richness of the Lactobacillus and Bacteroides genus and decreased the relative richness of Romboutsia, Alloprevotella, Blautia, and Helicobacter genus. Serum nontargeted metabolomic results indicated that SIOL could regulate metabolites related to metabolic pathways, such as glycine, serine, threonine, galactose, cysteine, and methionine metabolism. Spearman correlation analysis showed that the regulatory effects of SIOL on the tricarboxylic acid (TCA) cycle, phenylalanine metabolism, phenylalanine, tyrosine, and tryptophan biosynthesis, and glyoxylate and dicarboxylate metabolism pathways were correlated with changes in the richness of the Lactobacillus, Romboutsia, Bacteroides, and Alloprevotella genus in the gut microbiome. In conclusion, this study revealed the ameliorative effects of SIOL on RA and suggested that the therapeutic effects of SIOL on RA may be related to the regulation of the community richness of the Lactobacillus, Romboutsia, Bacteroides, and Alloprevotella genus, thereby improving the TCA cycle; phenylalanine metabolism; phenylalanine, tyrosine, and tryptophan biosynthesis, and glyoxylate and dicarboxylate metabolism-related pathways.

A Self-Assembling Peptide as a Model for Detection of Colorectal Cancer

Patient-derived organoid (PDO) models have been widely used in precision medicine. The inability to standardize organoid creation in pre-clinical models has become apparent. The common mouse-derived extracellular matrix can no longer meet the requirements for the establishment of PDO models. Therefore, in order to develop effective methods for 3D cultures of organoids, we designed a self-assembling peptide, namely DRF3, which can be self-assembled into ordered fibrous scaffold structures. Here, we used the co-assembly of self-assembling peptide (SAP) and collagen type I, fibronectin, and laminin (SAP-Matrix) to co-simulate the extracellular matrix, which significantly reduced the culture time of PDO, improved the culture efficiency, and increased the self-assembly ability of cells. Compared with the results from the 2D cell line, the PDO showed a more significant expression of cancer-related genes. During organoid self-assembly, the expression of cancer-related genes is increased. These findings provide a theoretical basis for the establishment of precision molecular modeling platforms in the future.

Pro-resolving and anti-arthritic properties of the MC1 selective agonist PL8177

Background

Melanocortins are peptides endowed with anti-inflammatory and pro-resolving activities. Many of these effects are mediated by the Melanocortin receptor 1 (MC₁) as reported in several experimental settings. As such, MC₁ can be a viable target for the development of new therapies that mimic endogenous pro-resolving mediators. The aim of this study was to assess the immunopharmacology of a selective MC₁ agonist (PL8177) in vitro and in a mouse model of inflammatory arthritis.

Methods

PL8177 and the natural agonist αMSH were tested for activation of mouse and human Melanocortin receptors (MC_1,3,4,5), monitoring cAMP accumulation and ERK1/2 phosphorylation, using transiently transfected HEK293A cells. The anti-inflammatory and pro-resolving effects of PL8177 and αMSH were evaluated using mouse peritoneal Macrophages. Finally, a model of K/BxN serum transfer induced arthritis was used to determine the in vivo potential of PL8177.

Results

PL8177 activates mouse and human MC₁ with apparent EC₅₀ values of 0.01 and 1.49 nM, respectively, using the cAMP accumulation assay. Similar profiles were observed for the induction of ERK phosphorylation (EC₅₀: 0.05 and 1.39 nM). PL8177 displays pro-resolving activity (enhanced Macrophage efferocytosis) and counteracts the inflammatory profile of zymosan-stimulated macrophages, reducing the release of IL-1β, IL-6, TNF-α and CCL-2. In the context of joint inflammation, PL8177 (3mg/kg i.p.) reduces clinical score, paw swelling and incidence of severe disease as well as the recruitment of immune cells into the arthritic joint.

Conclusion

These results demonstrate that the MC₁ agonism with PL8177 affords therapeutic effects in inflammatory conditions including arthritis.

Significance

Drugs targeting the Melanocortin system have emerged as promising therapeutics for several conditions including inflammation or obesity. Multiple candidates are under clinical development, and some have already reached approval. Here we present the characterization of a novel drug candidate, PL8177, selective for the Melanocortin 1 receptor (MC₁), demonstrating its selectivity profile on cAMP and ERK1/2 phosphorylation signaling pathways, of relevance as selective drugs will translate into lesser off-target effect. PL8177 also demonstrated, not only anti-inflammatory activity, but pro-resolving actions due to its ability to enhance efferocytosis (i.e. the phagocytosis of apoptotic cells), endowing this molecule with therapeutic advantages compared to classical anti-inflammatory drugs. Using a mouse model of inflammatory arthritis, the compound demonstrated in vivo efficacy by reducing clinical score, paw swelling and overall disease severity. Taken together, these results present Melanocortin-based therapies, and specifically targeting MC₁ receptor, as a promising strategy to manage chronic inflammatory diseases.

Latest models for the discovery and development of rheumatoid arthritis drugs

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune disease that reduces the quality of life. The current speed of development of therapeutic agents against RA is not satisfactory. Models on which initial experiments are conducted do not fully reflect human pathogenesis. Overcoming this oversimplification might be a crucial step to accelerate studies on RA treatment.

AREAS COVERED

The current approaches to produce novel models or to improve currently available models for the development of RA drugs have been discussed. Advantages and drawbacks of two- and three-dimensional cell cultures and animal models have been described based on recently published results of the studies. Moreover, approaches such as tissue engineering or organ-on-a-chip have been reviewed.

EXPERT OPINION

The cell cultures and animal models used to date appear to be of limited value due to the complexity of the processes involved in RA. Current models in RA research should take into account the heterogeneity of patients in terms of disease subtypes, course, and activity. Several advanced models and tools using human cells and tissues have been developed, including three-dimensional tissues, liquid bioreactors, and more complex joint-on-a-chip devices. This may increase knowledge of the molecular mechanisms leading to disease development, to help identify new biomarkers for early detection, and to develop preventive strategies and more effective treatments.

Effect of Saffron Extract, Astaxanthin, and Carnosic Acid on the Levels of Matrix Metalloproteinase-9 and on Body Weight Changes in Arthritis Experiments

AIM

The aim of this study was to explore the potential effect of natural compounds and their combination with methotrexate (M) on levels of matrix metalloproteinase-9 (MMP-9) as a key biochemical parameter in rat adjuvant arthritis. Further change of body weight was selected as one of clinical parameters monitored in this animal model.

MATERIALS AND METHODS

Adjuvant arthritis (AA) was induced in Lewis rats. Methotrexate (M) was administrated twice a week in a dose of 0.3 mg/kg b.w. The saffron extract was administrated daily in two doses: 25 mg/kg b.w. (SF1) and 50 mg/kg b.w. (SF2). Both doses were administrated alone and in combination with M. Astaxanthin was administrated also daily in two doses: 1 mg/kg b.w. (AS1) and 5 mg/kg b.w. (AS2) only as monotherapy. Carnosic acid was administrated daily in one dose: 100 mg/kg (C) in monotherapy and in combination with M. All compounds and M were administrated orally. Plasma samples were collected on the 21st experimental day and used for ELISA determination. The 21st experimental day was used also for the analysis of body weight changes.

RESULTS

We observed a significant decrease of MMP-9 plasmatic levels in SF1 and SF2 monotherapy in AA animal groups. The decrease in levels of MMP-9 in combined therapy of SF1 and M had higher significance than the effect of M only in AA. The same decreasing effect on the levels of MMP-9 was observed in the combined therapy of C and M. Astaxanthin and saffron extract had a very similar effect on clinical parameters and the change in body weight: both have significantly increased body weight in monotherapy in both doses used. The combined therapy of M and saffron extract doses showed no significant difference from M itself. Carnosic acid did not affect the change of body weight, and the combination of C with M reached the same level as M alone.

CONCLUSION

Astaxanthin in monotherapy and saffron extract in monotherapy and in combined therapy with M have significantly decreased plasmatic levels of MMP-9 and increased body weight in animals suffering from AA. Lower doses were more efficient for both experiments: astaxanthin and saffron extract. Carnosic acid has no effect in monotherapy in both parameters, but a combination with M has a significant effect with respect to the improvement of cachexia as well as the inhibition of inflammation.

Efficacy and Safety of Curcumin and Curcuma longa Extract in the Treatment of Arthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trial

Background

Modern pharmacological research found that the chemical components of Curcuma longa L. are mainly curcumin and turmeric volatile oil. Several recent randomized controlled trials (RCT) have shown that curcumin improves symptoms and inflammation in patients with arthritis.

Methods

Pubmed, Cochran Library, CNKI, and other databases were searched to collect the randomized controlled trials (RCTs). Then, the risk of bias of RCTs were assessed and data of RCTs were extracted. Finally, RevMan 5.3 was utilized for meta-analysis.

Results

Twenty-nine (29) RCTs involving 2396 participants and 5 types of arthritis were included. The arthritis included Ankylosing Spondylitis (AS), Rheumatoid Arthritis (RA), Osteoarthritis (OA), Juvenile idiopathic arthritis (JIA) and gout/hyperuricemia. Curcumin and Curcuma longa Extract were administered in doses ranging from 120 mg to 1500 mg for a duration of 4-36 weeks. In general, Curcumin and Curcuma longa Extract showed safety in all studies and improved the severity of inflammation and pain levels in these arthritis patients. However, more RCTs are needed in the future to elucidate the effect of Curcumin and Curcuma longa Extract supplementation in patients with arthritis, including RA, OA, AS and JIA.

Conclusion

Curcumin and Curcuma longa Extract may improve symptoms and inflammation levels in people with arthritis. However, due to the low quality and small quantity of RCTs, the conclusions need to be interpreted carefully.

Age-associated B cells contribute to the pathogenesis of rheumatoid arthritis by inducing activation of fibroblast-like synoviocytes via TNF-α-mediated ERK1/2 and JAK-STAT1 pathways

OBJECTIVES

Age-associated B cells (ABCs) are a recently identified B cell subset, whose expansion has been increasingly linked to the pathogenesis of autoimmune disorders. This study aimed to investigate whether ABCs are involved in the pathogenesis and underlying mechanisms of rheumatoid arthritis (RA).

METHODS

ABCs were assessed in collagen-induced arthritis (CIA) mice and patients with RA using flow cytometry. Transcriptomic features of RA ABCs were explored using RNA-seq. Primary fibroblast-like synoviocytes (FLS) derived from the synovial tissue of patients with RA were cocultured with ABCs or ABCs-conditioned medium (ABCsCM). IL-6, MMP-1, MMP-3 and MMP-13 levels in the coculture supernatant were detected by ELISA. Signalling pathways related to ABCs-induced FLS activation were examined using western blotting.

RESULTS

Increased ABCs levels in the blood, spleen and inflammatory joints of CIA mice were observed. Notably, ABCs were elevated in the blood, synovial fluid and synovial tissue of patients with RA and positively correlated with disease activity. RNA-seq revealed upregulated chemotaxis-related genes in RA ABCs compared with those in naive and memory B cells. Coculture of FLS with RA ABCs or ABCsCM led to an active phenotype of FLS, with increased production of IL-6, MMP-1, MMP-3 and MMP-13. Mechanistically, ABCsCM-derived TNF-α promoted the upregulation of interferon-stimulated genes in FLS, with elevated phosphorylation of ERK1/2 and STAT1. Furthermore, blockage of ERK1/2 and Janus Kinase (JAK)-STAT1 pathways inhibited the activation of FLS induced by ABCsCM.

CONCLUSIONS

Our results suggest that ABCs contribute to the pathogenesis of RA by inducing the activation of FLS via TNF-α-mediated ERK1/2 and JAK-STAT1 pathways.

Traditional Tibetan Medicine Twenty-Five Wei’er Tea Pills Ameliorate Rheumatoid Arthritis Based on Chemical Crosstalk Between Gut Microbiota and the Host

Twenty-Five Wei’er Tea Pills (TFP), a traditional Tibetan medicine, has shown to have a promising therapeutic effect in patients with Rheumatoid arthritis (RA), as well as being safe. Nonetheless, there have been limited pharmacological studies that have explored this therapeutic option. As gut microbiota has been proven to have a critical role in the pathogenesis of RA, this study aims to explore and reveal relevant ways by which TFP interacts with the chemical crosstalk between the gut microbiome and its host. 16S rRNA sequencing, combined with un-targeted metabolomics, were conducted on collagen-induced arthritis (CIA) rats. CIA model rats treated with TFP showed significant improvement in weight gain, pathological phenomena in joints, as well as decreased serum levels of TNF-α, IL-6 and increased level of IL-4 and IL-10. Significant dysfunction in the gut microbiome and alteration in serum metabolites were observed in CIA model rats, which were restored by TFP treatment. Coherence analysis indicated that TFP modulated the pathways of histidine metabolism, phenylalanine metabolism, alanine, aspartate, glutamate metabolism, amino sugar and nucleotide sugar metabolism owing to the abundances of Lactobacillus, Bacteroides, Prevotellaceae_UCG-001 and Christensenellaceae_R-7_group in the gut microflora. The corresponding metabolites involved L-histidine, histamine, phenylethylamine, asparagine, L-aspartic acid, D-fructose 1-phosphate, D-Mannose 6-phosphate, D-Glucose 6-phosphate, and Glucose 1-phosphate. In conclusion, this study reveals the ameliorative effects of TFP on RA through the chemical crosstalk that exists between the gut microbiota and its host, and also further enriches our understandings of the pathogenesis of RA.

Low-Salt Diet Attenuates B-Cell- and Myeloid-Cell-Driven Experimental Arthritides by Affecting Innate as Well as Adaptive Immune Mechanisms

A link between high sodium chloride (salt) intake and the development of autoimmune diseases was previously reported. These earlier studies demonstrated exacerbation of experimental autoimmune encephalomyelitis and colitis by excess salt intake associated with Th17- and macrophage-mediated mechanisms. Little is known about the impact of dietary salt intake on experimental arthritides. Here, we investigated if salt restriction can exert beneficial effects on collagen-induced arthritis (CIA) and K/BxN serum transfer-induced arthritis (STIA). CIA depends on both adaptive and innate immunity, while STIA predominantly mimics the innate immune cell-driven effector phase of arthritis. In both models, low salt (LS) diet significantly decreased arthritis severity compared to regular salt (RS) and high salt (HS) diet. We did not observe an aggravation of arthritis with HS diet compared to RS diet. Remarkably, in STIA, LS diet was as effective as IL-1 receptor blocking treatment. Complement-fixing anti-CII IgG2a antibodies are associated with inflammatory cell infiltration and cartilage destruction. LS diet reduced anti-CII IgG2a levels in CIA and decreased the anti-CII IgG2a/IgG1 ratios pointing toward a more Th2-like response. Significantly less inflammatory joint infiltrates and cartilage breakdown associated with reduced protein concentrations of IL-1 beta (CIA and STIA), IL-17 (CIA), and the monocyte chemoattractant protein-1 (MCP-1) (CIA) were detected in mice receiving LS diet compared to HS diet. However, we did not find a reduced IL-17A expression in CD4+ T cells upon salt restriction in CIA. Analysis of mRNA transcripts and immunoblots revealed a link between LS diet and inhibition of the p38 MAPK (mitogen-activated protein kinase)/NFAT5 (nuclear factor of activated T-cells 5) signaling axis in STIA. Further experiments indicated a decreased leukodiapedesis under LS conditions. In conclusion, dietary salt restriction ameliorates CIA and STIA, indicating a beneficial role of LS diet during both the immunization and effector phase of immune-mediated arthritides by predominantly modulating the humoral immunity and the activation status of myeloid lineage cells. Hence, salt restriction might represent a supportive dietary intervention not only to reduce cardiovascular risk, but also to improve human inflammatory joint diseases like rheumatoid arthritis.

Panaxynol induces fibroblast-like synovial cell apoptosis, inhibits proliferation and invasion through TLR4/NF-κB pathway to alleviate rheumatoid arthritis

BACKGROUND AND PURPOSE

Panaxynol (PAL, PubChem CID: 5281149) is a common natural minor component in Umbelliferae plants, such as Radix Saposhnikoviae Divaricatae. Modern pharmacology studies show that PAL has nutritional value and anti-inflammatory and other pharmaceutical activities. Therefore, the scientific hypothesis of PAL in the treatment of rheumatoid arthritis was put forward, and the hypothesis was further verified by Fibroblast-like synovial cells (RA-FLS) and Collagen Induced Arthritis (CIA) rats models.

EXPERIMENTAL METHOD

CIA method was used to establish a rat arthritis model. After extracting RA-FLS, flow cytometry and immunofluorescence were used to explore the effect of PAL on the apoptosis and proliferation of RA-FLS. Wound healing and transwell experiment explored the effect of PAL on the migration and invasion of RA-FLS. Western blot analysis explored the inner mechanism of the effect of PAL on RA-FLS. At the same time, it also explored the role of PAL in CIA rats, including pathological section detection and western blot analysis.

MAIN RESULTS

PAL can promote the apoptosis and inhibit the proliferation, migration and invasion of RA-FLS. PAL can also reduce joint swelling in CIA rats, reduce pannus formation and inflammatory infiltration in the joints. Western blot analysis showed that PAL mainly played a role through the TLR4/NF-κB signaling pathway.

CONCLUSION

The results of in vivo and in vitro experiments show that PAL can effectively alleviate the condition of RA, and may be a potential drug for the treatment of RA.

Differential inflammation-mediated function of prokineticin 2 in the synovial fibroblasts of patients with rheumatoid arthritis compared with osteoarthritis

Prokineticin 2 (PK2) is a secreted protein involved in several pathological and physiological processes, including the regulation of inflammation, sickness behaviors, and circadian rhythms. Recently, it was reported that PK2 is associated with the pathogenesis of collagen-induced arthritis in mice. However, the role of PK2 in the pathogenesis of rheumatoid arthritis (RA) or osteoarthritis (OA) remains unknown. In this study, we collected synovial tissue, plasma, synovial fluid, and synovial fibroblasts (SF) from RA and OA patients to analyze the function of PK2 using immunohistochemistry, enzyme-linked immunosorbent assays, and tissue superfusion studies. PK2 and its receptors prokineticin receptor (PKR) 1 and 2 were expressed in RA and OA synovial tissues. PKR1 expression was downregulated in RA synovial tissue compared with OA synovial tissue. The PK2 concentration was higher in RA synovial fluid than in OA synovial fluid but similar between RA and OA plasma. PK2 suppressed the production of IL-6 from TNFα-prestimulated OA-SF, and this effect was attenuated in TNFα-prestimulated RA-SF. This phenomenon was accompanied by the upregulation of PKR1 in OA-SF. This study provides a new model to explain some aspects underlying the chronicity of inflammation in RA.

Preclinical models of arthritis for studying immunotherapy and immune tolerance

Increasingly earlier identification of individuals at high risk of rheumatoid arthritis (RA) (eg, with autoantibodies and mild symptoms) improves the feasibility of preventing or curing disease. The use of antigen-specific immunotherapies to reinstate immunological self-tolerance represent a highly attractive strategy due to their potential to induce disease resolution, in contrast to existing approaches that require long-term treatment of underlying symptoms.

Preclinical animal models have been used to understand disease mechanisms and to evaluate novel immunotherapeutic approaches. However, models are required to understand critical processes supporting disease development such as the breach of self-tolerance that triggers autoimmunity and the progression from asymptomatic autoimmunity to joint pain and bone loss. These models would also be useful in evaluating the response to treatment in the pre-RA period.

This review proposes that focusing on immune processes contributing to initial disease induction rather than end-stage pathological consequences is essential to allow development and evaluation of novel immunotherapies for early intervention. We will describe and critique existing models in arthritis and the broader field of autoimmunity that may fulfil these criteria. We will also identify key gaps in our ability to study these processes in animal models, to highlight where further research should be targeted.

Probiotic Supplementation for Rheumatoid Arthritis: A Promising Adjuvant Therapy in the Gut Microbiome Era

Rheumatoid arthritis (RA) is a chronic immune-mediated inflammatory disease that ultimately leads to joint destruction and functional disability. Although the exact etiology of RA is not fully understood, it is well established that gut microbiota (GM) plays a vital role in the pathogenesis of RA, with accumulating evidence suggesting that gut dysbiosis induces a chronic inflammatory response that may be linked to disease development. Of interest, patients with RA have significant changes in the intestinal microbiota compared to healthy controls, and several studies have suggested the use of probiotics as a possible adjuvant therapy for RA. Benefits of probiotic supplementation were reported in animal models of arthritis and human studies, but the current evidence regarding the effect of probiotic supplementation in the management of RA remains insufficient to make definite recommendations. Several different strains of Lactobacillus and Bifidobacteria, as single species or in mixed culture, have been investigated, and some have demonstrated beneficial effects on disease activity in RA human subjects. As of now, L.casei probiotic bacteria seems to be the strongest candidate for application as adjuvant therapy for RA patients. In this review, we highlight the role of GM in the development and progression of RA and summarize the current knowledge on the use of probiotics as a potential adjuvant therapy for RA. We also review the proposed mechanisms whereby probiotics regulate inflammation. Finally, the role of fermented foods is discussed as a possible alternative to probiotic supplements since they have also been reported to have health benefits.

Inhibition of lipid phosphatase SHIP1 expands myeloid-derived suppressor cells and attenuates rheumatoid arthritis in mice

Rheumatoid arthritis (RA) is a debilitating autoimmune disease of unknown cause, characterized by infiltration and accumulation of activated immune cells in the synovial joints where cartilage and bone destructions occur. Myeloid-derived suppressor cells (MDSCs) are of myeloid origin and are able to suppress T cell responses. Src homology 2 domain containing inositol polyphosphate 5-phosphatase 1 (SHIP1) was shown to be involved in the regulation of MDSC differentiation. The purpose of the present study was to investigate the effect of inhibition of SHIP1 on expansion of MDSCs in RA using a collagen-induced inflammatory arthritis (CIA) mouse model. In DBA/1 mice treatment with a small molecule specific SHIP1 inhibitor 3α-aminocholestane (3AC) induced a marked expansion of MDSCs in vivo. Both pre-treatment with 3AC of DBA/1 mice prior to CIA induction and intervention with 3AC during CIA progression significantly reduced disease incidence and severity. Adoptive transfer of MDSCs isolated from 3AC-treated mice, but not naïve MDSCs from normal mice, into CIA mice significantly reduced disease incidence and severity, indicating that the 3AC-induced MDSCs were the cellular mediators of the observed amelioration of the disease. In conclusion, inhibition of SHIP1 expands MDSCs in vivo and attenuates development of CIA in mice. Small molecule specific inhibition of SHIP1 may therefore offer therapeutic benefit to patients with RA and other autoimmune diseases.

Applicability and implementation of the collagen-induced arthritis mouse model, including protocols (Review)

Animal models of rheumatoid arthritis (RA) are essential for studying the pathogenesis of RA in vivo and determining the efficacy of anti-RA drugs. During the past decades, numerous rodent models of arthritis have been evaluated as potential models and the modeling methods are relatively well-developed. Among these models, the collagen-induced arthritis (CIA) mouse model is the first choice and the most widely used because it may be generated rapidly and inexpensively and is relatively similar in pathogenesis to human RA. To date, there have been numerous classic studies and reviews discussing related pathogeneses and modeling methods. Based on this knowledge, combined with the latest convenient and effective methods for CIA model construction, the present review aims to introduce the model to beginners and clarify important details regarding its use. Information on the origin and pathogenesis of the CIA model, the protocol for establishing it, the rate of successful arthritis induction and the methods used to evaluate the severity of arthritis are briefly summarized. With this information, it is expected that researchers who have recently entered the field or are not familiar with this information will be able to start quickly, avoid unnecessary errors and obtain reliable results.

Distinct Roles of Vav Family Members in Adaptive and Innate Immune Models of Arthritis

Genetic evidence suggests that three members of the VAV family (VAV1, VAV2 and VAV3) of signal transduction proteins could play important roles in rheumatoid arthritis. However, it is not known currently whether the inhibition of these proteins protects against this disease and, if so, the number of family members that must be eliminated to get a therapeutic impact. To address this issue, we have used a collection of single and compound Vav family knockout mice in experimental models for antigen-dependent (methylated bovine serum albumin injections) and neutrophil-dependent (Zymosan A injections) rheumatoid arthritis in mice. We show here that the specific elimination of Vav1 is sufficient to block the development of antigen-induced arthritis. This protection is likely associated with the roles of this Vav family member in the development and selection of immature T cells within the thymus as well as in the subsequent proliferation and differentiation of effector T cells. By contrast, we have found that depletion of Vav2 reduces the number of neutrophils present in the joints of Zymosan A-treated mice. Despite this, the elimination of Vav2 does not protect against the joint degeneration triggered by this experimental model. These findings indicate that Vav1 is the most important pharmacological target within this family, although its main role is limited to the protection against antigen-induced rheumatoid arthritis. They also indicate that the three Vav family proteins do not play redundant roles in these pathobiological processes.

Hydroquinone Exposure Worsens Rheumatoid Arthritis through the Activation of the Aryl Hydrocarbon Receptor and Interleukin-17 Pathways

Rheumatoid arthritis (RA) development is strongly associated with cigarette smoke exposure, which activates the aryl hydrocarbon receptor (AhR) as a trigger for Th17 inflammatory pathways. We previously demonstrated that the exposure to hydroquinone (HQ), one of the major compounds of cigarette tar, aggravates the arthritis symptomatology in rats. However, the mechanisms related to the HQ-related RA still remain elusive. Cell viability, cytokine secretion, and gene expression were measured in RA human fibroblast-like synoviocytes (RAHFLS) treated with HQ and stimulated or not with TNF-α. Antigen-induced arthritis (AIA) was also elicited in wild type (WT), AhR ^−/− or IL-17R ^−/− C57BL/6 mice upon daily exposure to nebulized HQ (25ppm) between days 15 to 21. At day 21, mice were challenged with mBSA and inflammatory parameters were assessed. The in vitro HQ treatment up-regulated TNFR1, TNFR2 expression, and increased ROS production. The co-treatment of HQ and TNF-α enhanced the IL-6 and IL-8 secretion. However, the pre-incubation of RAHFLS with an AhR antagonist inhibited the HQ-mediated cell proliferation and gene expression profile. About the in vivo approach, the HQ exposure worsened the AIA symptoms (edema, pain, cytokines secretion and NETs formation) in WT mice. These AIA effects were abolished in HQ-exposed AhR ^−/− and IL-17R ^−/− animals though. Our data demonstrated the harmful HQ influence over the onset of arthritis through the activation and proliferation of synoviocytes. The HQ-related RA severity was also associated with the activation of AhR and IL-17 pathways, highlighting how cigarette smoke compounds can contribute to the RA progression.

Therapeutic potential of targeted-gold nanospheres on collagen-induced arthritis in rats

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that causes functional disability due to bone destruction and severe joint pain. Current anti-rheumatic treatments develop severe complications and do not provide complete remission. Gold nanoparticles (AuNPs) have garnered attention because of their unique physical and chemical properties. In this study, we have evaluated the therapeutic effects of gold nanospheres (AuNSs) with two different ligands (targeted-nanoparticles) against collagen-induced arthritis (CIA) and compared the outcomes with conventional methotrexate (MTX) and biological (infliximab) treatments. Clinical evaluation was performed by radiographic and histological examinations. The bioaccumulation of AuNSs in vital organs was assessed. The mechanistic studies targeting pro-inflammatory/anti-inflammatory and angiogenic mediators' expressions were performed. Radiographic examination showed that the targeted AuNSs reduced joint space narrowing and bone erosion. Moreover, histopathological examination of rat ankle joints demonstrated that targeted AuNSs reduce bone and cartilage degeneration/inflammation. Gold nanospheres-conjugated with nucleus localized peptide (nuclear membrane-targeted) (AuNSs@NLS) has resolved bone destruction and inflammation compared to gold nanospheres-conjugated at polyethylene glycol (AuNSs@PEG). Although the AuNSs accumulated in different organs in both cases, they did not induce any toxicity or tissue damage. The two different targeted AuNSs significantly suppress inflammatory and angiogenic mediators' expression and induced anti-inflammatory cytokine production, but the AuNSs@NLS had superior therapeutic efficacy. In conclusion, these results suggested that nuclear membrane-targeted AuNSs effectively attenuated arthritis progression without systemic side effects.

Distinct roles of interleukin-17 and T helper 17 cells among autoimmune diseases

Background

Interleukin (IL)-17 and T helper 17 (T_H17) cells, a distinct subset of CD4⁺ T cells which promotes the expression of IL-17, mediate host defensive mechanisms to various infections and are involved in the pathogenesis of autoimmune diseases including inflammatory bowel disease (IBD), psoriasis, and rheumatic diseases. IL-17 inhibitors have shown to be effective in psoriasis, but failed to demonstrate response in IBD. Further, clinical trials of IL-17 inhibitors reported some cases of new onset IBD. We aim to discuss the roles of IL-17 and T_H17 cells among autoimmune diseases and the possible immunological mechanisms of new onset IBD in patients undergoing IL-17 inhibitors.

Methods

A non-systematic literature review using PubMed/Medline.

Results

IL-17 inhibitors, which either target IL-17 A (secukinumab and ixekizumab) or the IL-17 receptor (brodalumab), have demonstrated clinical benefits in plaque psoriasis, psoriatic arthritis, or axial spondyloarthritis. However, secukinumab and brodalumab have shown no clinical benefit in Crohn's disease and led to frequent serious adverse events including worsening of Crohn's disease. Further, some cases of new onset IBD were reported in clinical trials of IL-17 inhibitors. Consistently, an animal model of colitis has demonstrated that IL-17 can directly inhibit the development of T helper 1 (T_H1) cells and T_H1 cells can induce aggressive colitis in the absence of IL-17 signaling.

Conclusions

IL-17 and T_H17 cells might have protective rather than pro-inflammatory roles in the intestine. IL-17 inhibition may induce inflammation in the intestine by favoring T_H1 pathways, which explain the lack of response to IL-17 inhibitors in IBD.

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IL-17 and T_H17 cells play important roles in the pathologies of autoimmune diseases.

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Monoclonal antibodies targeting IL-17 have demonstrated clinical benefits.

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Clinical trials of IL-17 inhibitors reported new onset inflammatory bowel disease.

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IL-17 can directly inhibit the development of T_H1 cells.

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T_H1 cells may induce aggressive colitis in the absence of IL-17 signaling.

Targeting citrullination in autoimmunity: insights learned from preclinical mouse models

INTRODUCTION

Aberrant citrullination and excessive peptidylarginine deiminase (PAD) activity are detected in numerous challenging autoimmune diseases such as rheumatoid arthritis, inflammatory bowel diseases, systemic lupus erythematosus, multiple sclerosis, and type 1 diabetes. Because excessive PAD activity is a common denominator in these diseases, PADs are interesting potential therapeutic targets for future therapies.

AREAS COVERED

This review summarizes the advances made in the design of PAD inhibitors, their utilization and therapeutic potential in preclinical mouse models of autoimmunity. Relevant literature encompasses studies from 1994 to 2021 that are available on PubMed.gov.

EXPERT OPINION

Pan-PAD inhibition is a promising therapeutic strategy for autoimmune diseases. Drugs achieving pan-PAD inhibition were capable of ameliorating, reversing, and preventing clinical symptoms in preclinical mouse models. However, the implications for PADs in key biological processes potentially present a high risk for clinical complications and could hamper the translation of PAD inhibitors to the clinic. We envisage that PAD isozyme-specific inhibitors will improve the understanding the role of PAD isozymes in disease pathology, reduce the risk of side-effects and enhance prospects for future clinical translation.

Stability of housekeeping genes in inflamed joints of spontaneous and collagen-induced arthritis in DBA/1 mice

BACKGROUND

DBA/1 mice arthritis models have contributed to our understanding of human rheumatoid arthritis (RA) and spondyloarthritis (SpA) pathogenesis, as well as the exploration of therapeutic targets for treatment. Quantitative polymerase chain reaction (qPCR) is an indispensable tool in molecular research, which requires reference gene validation to obtain consistent and reliable results.

OBJECTIVE

To determine the stability of candidate reference genes for qPCR in the joint of collagen-induced arthritis (CIA) and spontaneous arthritis (SpAD) DBA/1 mice.

METHODS

The expression of eleven commonly used reference genes (ACTB, B2M, EF1a, GAPDH, HMBS, HPRT, PPIB, RPL13A, SDHA, TBP, and YWHAZ) was assessed by qPCR and the data were compared using delta-Ct methods and the geNorm, NormFinder, and RefFinder software packages. Genes identified as stable in each model were used for the quantification of inflammatory cytokines RESULTS: The gene stabilities differed between the two arthritis models in the DBA/1 mice. EF1a and RPL13A were the best reference genes for SpAD, while RPL13A and TBP were the best for the CIA. These genes allowed the data normalization for the quantification of the inflammatory cytokines in both models; these results showed an increase in the expression of IL-1B, IL-12B, IL-17A, and IL-6 in the inflamed joints. The use of different primer sequences for the same reference gene resulted in different relative quantification values.

CONCLUSION

This study demonstrates that commonly used reference genes may not be suitable for arthritic tissues from DBA/1 mice, and strengthening the principle that meticulous validation of reference genes is essential before each experiment to obtain valid and reproducible qPCR data for analysis or interpretation.

The Joint-Brain Axis: Insights From Rheumatoid Arthritis on the Crosstalk Between Chronic Peripheral Inflammation and the Brain

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by erosive polyarthritis. Beyond joint pathology, RA is associated with neuropsychiatric comorbidity including depression, anxiety, and an increased risk to develop neurodegenerative diseases in later life. Studies investigating the central nervous system (CNS) in preclinical models of RA have leveraged the understanding of the intimate crosstalk between peripheral and central immune responses. This mini review summarizes the current knowledge of CNS comorbidity in RA patients and known underlying cellular mechanisms. We focus on the differential regulation of CNS myeloid and glial cells in different mouse models of RA reflecting different patterns of peripheral immune activation. Moreover, we address CNS responses to anti-inflammatory treatment in human RA patients and mice. Finally, to illustrate the bidirectional communication between the CNS and chronic peripheral inflammation, we present the current knowledge about the impact of the CNS on arthritis. A comprehensive understanding of the crosstalk between the CNS and chronic peripheral inflammation will help to identify RA patients at risk of developing CNS comorbidity, setting the path for future therapeutic approaches in both RA and neuropsychiatric diseases.

Differential Requirement for CCR6 in IL-23-Mediated Skin and Joint Inflammation

CCR6 is important for the trafficking of IL-17A-producing γδ T cells and required for the development of psoriasiform dermatitis in an IL-23 intradermal injection model. The role of CCR6, however, in IL-23-mediated joint inflammation is unclear. We herein hydrodynamically delivered IL-23 minicircle DNA into wild-type and CCR6-deficient (CCR6-knockout) mice to induce overexpression of IL-23 systemically. After IL-23 gene transfer, wild-type mice exhibited concurrent skin and joint changes that recapitulate some features found in human psoriatic skin and joints. CCR6-knockout mice were resistant to IL-23-induced skin inflammation but exhibited no changes in joint inflammation compared with wild-type mice. Depletion of neutrophils protected wild-type mice from skin and joint disease without suppressing T helper type 17 cytokine expression. In contrast, mice lacking γδ T cells showed a partial reduction in neutrophilic recruitment and a significant decrease in IL-17A expression in skin and paw tissue. Thus, in an IL-23-mediated model that allows concurrent assessment of both skin and joint disease, we showed that CCR6 is critical for inflammation in the skin but not in the joint. Furthermore, our data suggest that neutrophils and γδ T cells are key effector cells in IL-23-mediated skin and joint inflammation in mice.

Animal models of pain: Diversity and benefits

Chronic pain is a maladaptive neurological disease that remains a major health problem. A deepening of our knowledge on mechanisms that cause pain is a prerequisite to developing novel treatments. A large variety of animal models of pain has been developed that recapitulate the diverse symptoms of different pain pathologies. These models reproduce different pain phenotypes and remain necessary to examine the multidimensional aspects of pain and understand the cellular and molecular basis underlying pain conditions. In this review, we propose an overview of animal models, from simple organisms to rodents and non-human primates and the specific traits of pain pathologies they model. We present the main behavioral tests for assessing pain and investing the underpinning mechanisms of chronic pathological pain. The validity of animal models is analysed based on their ability to mimic human clinical diseases and to predict treatment outcomes. Refine characterization of pathological phenotypes also requires to consider pain globally using specific procedures dedicated to study emotional comorbidities of pain. We discuss the limitations of pain models when research findings fail to be translated from animal models to human clinics. But we also point to some recent successes in analgesic drug development that highlight strategies for improving the predictive validity of animal models of pain. Finally, we emphasize the importance of using assortments of preclinical pain models to identify pain subtype mechanisms, and to foster the development of better analgesics.

Interactions between Gut Microbiota and Immunomodulatory Cells in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases caused by abnormal immune activation and immune tolerance. Immunomodulatory cells (ICs) play a critical role in the maintenance and homeostasis of normal immune function and in the pathogenesis of RA. The human gastrointestinal tract is inhabited by trillions of commensal microbiota on the mucosal surface that play a fundamental role in the induction, maintenance, and function of the host immune system. Gut microbiota dysbiosis can impact both the local and systemic immune systems and further contribute to various diseases, such as RA. The neighbouring intestinal ICs located in distinct intestinal mucosa may be the most likely intermediary by which the gut microbiota can affect the occurrence and development of RA. However, the reciprocal interaction between the components of the gut microbiota and their microbial metabolites with distinct ICs and how this interaction may impact the development of RA are not well studied. Therefore, a better understanding of the gut microbiota, ICs, and their interactions might improve our knowledge of the mechanisms by which the gut microbiota contribute to RA and facilitate the further development of novel therapeutic approaches. In this review, we have summarized the roles of the gut microbiota in the immunopathogenesis of RA, especially the interactions between the gut microbiota and ICs, and further discussed the strategies for treating RA by targeting/regulating the gut microbiota.

Chebulanin exerts its anti-inflammatory and anti-arthritic effects via inhibiting NF-κB and MAPK activation in collagen-induced arthritis mice

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovial inflammation and progressive joint destruction. Chebulanin is a natural polyphenol acid isolated from the traditional Tibetan medicine Terminalia chebula Retz that has previously been reported to possess anti-inflammatory properties. The present study aimed to investigate the anti-inflammatory and anti-arthritic effects of chebulanin and explore its underlying mechanisms in vivo and in vitro using a collagen-induced arthritis (CIA) mouse model and lipopolysaccharide (LPS) stimulated RAW264.7 cell inflammation model. Arthritis severity scores were assessed twice weekly; the levels of cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in serum were detected using enzyme-linked immunosorbent assay kits; histopathological assessment was performed using micro computed tomography and hematoxylin and eosin staining. Activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways were assessed using western blotting. The inhibition of translocation of cytosolic p38 and p65 into the nucleus was observed using immunofluorescence staining and western blotting in vitro. Chebulanin significantly suppressed the progression and development of RA in CIA mice by decreasing the arthritis severity scores, attenuating paw swelling and joint destruction, and reducing the levels of IL-6 and TNF-α significantly (p < 0.05). Furthermore, chebulanin reduced the levels of excised phosphorylated (p)-p38, phosphorylated-c-JUN N-terminal kinase (p-JNK), p-p65 and phosphorylated NF-κB inhibitor alpha (p-IκBα) in CIA mice, but did not affect the level of phosphorylated extracellular-signal-regulated kinase (ERK). In addition, chebulanin could inhibit the nuclear translocation of p38 and p65 in LPS-stimulated macrophages in dose-dependent manner. In conclusion, this study demonstrated that chebulanin exerts anti-inflammatory and anti-arthritic effects by inhibiting the activation of NF-κB and MAPK signaling pathways.

Effects of adjuvant-induced arthritis on the ventral prostate of rats treated with angiotensin AT1 receptor blocker

AIMS

To analyze the prostatic compartments, extracellular matrix, microvascularization, transforming growth factor-beta (TGF-β) and angiotensin II receptors type 1 (AT₁) levels, and histopathology of the ventral prostate in a rat model for rheumatoid arthritis, and to evaluate the effect of angiotensin II AT₁ receptor blocker (ARB) in the disease.

MAIN METHODS

Fifteen male rats (90 days old) were divided into three groups (n = 5/group): control, adjuvant-induced arthritis without (AIA) or with AT₁ receptor blocker (AIA + ARB). Animals were euthanized 60 days after immunization. The ventral prostate was collected, weighed, and processed for histological and immunohistochemical analysis.

KEY FINDINGS

Our results show that AIA increases production of the prostatic epithelium and extracellular matrix, accompanied by a reduction in the number of tissue capillaries. ARB treatment promotes decreased production of extracellular matrix and increased TGF-β and AT₁ receptor immunostaining.

SIGNIFICANCE

AIA may activate specific mechanisms that modify the prostatic environment; the use of ARB attenuates some altered prostate parameters in a rat model for arthritis.

Involvement of Tumor Necrosis Factor Receptor Type II in FoxP3 Stability and as a Marker of Treg Cells Specifically Expanded by Anti-Tumor Necrosis Factor Treatments in Rheumatoid Arthritis

OBJECTIVE

To study the involvement of Treg cells expressing tumor necrosis factor receptor type II (TNFRII) in exerting control of inflammation in experimental models and in the response to anti-TNF treatments in patients with rheumatoid arthritis (RA) or spondyloarthritis (SpA).

METHODS

The role of TNFRII in Treg cells was explored using a multilevel translational approach. Treg cell stability was evaluated by analyzing the methylation status of the Foxp3 locus using bisulfite sequencing. Two models of inflammation (imiquimod-induced skin inflammation and delayed-type hypersensitivity arthritis [DTHA]) were induced in TNFRII^-/- mice, with or without transfer of purified CD4+CD25+ cells from wild-type (WT) mice. In patients with RA and those with SpA, the evolution of the TNFRII+ Treg cell population before and after targeted treatment was monitored.

RESULTS

Foxp3 gene methylation in Treg cells was greater in TNFRII^-/- mice than in WT mice (50% versus 36.7%). In cultured Treg cells, TNF enhanced the expression, maintenance, and proliferation of Foxp3 through TNFRII signaling. Imiquimod-induced skin inflammation and DTHA were aggravated in TNFRII^-/- mice (P < 0.05 for mice with skin inflammation and P < 0.0001 for mice with ankle swelling during DTHA compared to WT mice). Adoptive transfer of WT mouse Treg cells into TNFRII^-/- mice prevented aggravation of arthritis. In patients with RA receiving anti-TNF treatments, but not those receiving tocilizumab, the frequency of TNFRII+ Treg cells was increased at 3 months of treatment compared to baseline (mean ± SEM 65.2 ± 3.1% versus 49.1 ± 5.5%; P < 0.01). In contrast, in anti-TNF-treated patients with SpA, the frequency of TNFRII+ Treg cells was not modified.

CONCLUSION

TNFRII expression identifies a subset of Treg cells that are characterized by stable expression of Foxp3 via gene hypomethylation, and adoptive transfer of TNFRII-expressing Treg cells ameliorates inflammation in experimental models. Expansion and activation of TNFRII+ Treg cells may be one of the mechanisms by which anti-TNF agents control inflammation in RA, but not in SpA.

Temporomandibular joint damage in K/BxN arthritic mice

Rheumatoid arthritis (RA) is an autoimmune disease affecting 1% of the world population and is characterized by chronic inflammation of the joints sometimes accompanied by extra-articular manifestations. K/BxN mice, originally described in 1996 as a model of polyarthritis, exhibit knee joint alterations. The aim of this study was to describe temporomandibular joint (TMJ) inflammation and damage in these mice. We used relevant imaging modalities, such as micro-magnetic resonance imaging (μMRI) and micro-computed tomography (μCT), as well as histology and immunofluorescence techniques to detect TMJ alterations in this mouse model. Histology and immunofluorescence for Col-I, Col-II, and aggrecan showed cartilage damage in the TMJ of K/BxN animals, which was also evidenced by μCT but was less pronounced than that seen in the knee joints. μMRI observations suggested an increased volume of the upper articular cavity, an indicator of an inflammatory process. Fibroblast-like synoviocytes (FLSs) isolated from the TMJ of K/BxN mice secreted inflammatory cytokines (IL-6 and IL-1β) and expressed degradative mediators such as matrix metalloproteinases (MMPs). K/BxN mice represent an attractive model for describing and investigating spontaneous damage to the TMJ, a painful disorder in humans with an etiology that is still poorly understood.

Periodontal Injection of Lipopolysaccharide Promotes Arthritis Development in Mice

This study evaluated the arthritogenic effect of lipopolysaccharide (LPS) in a mouse model of periodontal disease. Periodontitis was induced in wild-type CD1 mice by nine LPS injections (10 or 50 ng) into the maxillary mucosa. Untreated mice or injected with LPS at the tail were used as controls. Two weeks after final inoculation, mice were sacrificed to collect blood, maxilla, and paw samples. Development and progression of periodontitis and arthritis were monitored using clinical assessment, micro-computed tomography (micro-CT), ultrasound (US), and histological analysis. CXCL1, IL-1β, IL-6, TNF-α, and anti-citrullinated peptide antibodies (ACPA) serum levels were determined by enzyme immunoassay. Ankle swelling and inflammation manifested after the 5th periodontal injection of 50 ng of LPS and progressed until the end of experiments. Periodontal injection of 10 ng of LPS and LPS tail injection did not induce paw changes. Therefore, the subsequent assessments were conducted only in mice periodontally injected with 50 ng of LPS. Maxillary micro-CT and histological analysis showed that LPS-induced alveolar bone resorption and vascular proliferation in periodontal tissue, but not inflammation. US and histology revealed increased joint space, leukocyte infiltration, synovial proliferation, and mild cartilage and bone destruction in the paws of mice orally injected. Cytokines and ACPA showed a trend towards an increase in LPS mice. This study shows that arthritis and periodontal disease can co-occur in wild-type mice after periodontal injection of LPS at optimal dose. Our model may be useful to improve the understanding of the mechanisms linking periodontitis and arthritis.

[Role of erythroblast-like Ter cells in the pathogenesis of collagen-induced arthritis]

OBJECTIVE

To explore the role of Ter cells in the development of the collagen-induced arthritis (CIA), we detected their quantity changes in the spleen of different stages of CIA mice and analyzed the correlation between Ter cells and the joint scores, and we also analyzed the correlation between Ter cells and the frequencies of T and B cell subsets, so as to further understand the pathogenesis of rheumatoid arthritis.

METHODS

The six to eight weeks DBA/1 mice were used to prepare CIA model. After the second immunization, we began to evaluate the joint score. According to the time of CIA onset and the joint score, the CIA mice were divided into three stages: early, peak and late stages. According to the final joint score, the CIA mice at the peak stage were subdivided into the high score group (score>8) and the low score group (score≤8). The frequencies of Ter cells in the spleen of the naïve mice and the CIA mice at various stages and the frequencies of T and B cell subsets in the spleen of the CIA mice at the peak stage were detected by flow cytometry, then we carried on the correlation analysis.

RESULTS

The frequencies of Ter cells in the spleen of the CIA mice was significantly higher than those of the naïve mice (8.522%±2.645% vs. 1.937%±0.725%, P<0.01), the frequencies of Ter cells in the spleen of the high score group mice was significantly lower than those of the low score group (6.217%±0.841% vs. 10.827%±0.917%, P<0.01). The frequencies of Th1 cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.337%±0.110% vs. 0.727%±0.223%, P<0.05). The frequencies of Th17 cells in the spleen of the high score group mice was higher than those of the low score group mice (0.750%±0.171% vs. 0.477%±0.051%, P=0.099). The frequencies of germinal center B cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.243%±0.057% vs. 1.097%±0.015%, P<0.05). Correlation analysis results showed that the frequencies of Ter cells in the spleen of the CIA mice at the peak stage was strongly negatively correlated with the frequencies of CD4+ T, Th1, Th17, and germinal center B cells, and was strongly positively correlated with the frequencies of B10 cells, indicating that these cells might have a protective effect in CIA. Studies on dynamic changes showed that the frequencies of Ter cells in the spleen of the CIA mice at the late stage was significantly lower than those at the peak stage (0.917%±0.588% vs. 8.522%±2.645%, P<0.001), suggesting the protective effect of these cells in arthritis.

CONCLUSION

Ter cells were significantly increased in the spleen of the CIA mice at peak stage, and were negatively correlated with joint scores and pathogenic immune cells, and positively correlated with protective immune cells. Ter cells were significantly decreased in the spleen of the CIA mice at the late stage. What we mentioned above suggests that Ter cells might be involved in the progression of rheumatoid arthritis as an immunomodulatory cell,but further in vivo and in vitro experiments are needed to verify its specific effects and mechanism.

ZAP-70 Regulates Autoimmune Arthritis via Alterations in T Cell Activation and Apoptosis

T cells play an essential role in the pathogenesis of both human rheumatoid arthritis (RA) and its murine models. A key molecule in T cell activation is ZAP-70, therefore we aimed to investigate the effects of partial ZAP-70 deficiency on the pathogenesis of recombinant human G1(rhG1)-induced arthritis (GIA), a well-established mouse model of RA. Arthritis was induced in BALB/c and ZAP-70^+/- heterozygous mice. Disease progression was monitored using a scoring system and in vivo imaging, antigen-specific proliferation, cytokine and autoantibody production was measured and T cell apoptotic pathways were analyzed. ZAP-70^+/- mice developed a less severe arthritis, as shown by both clinical picture and in vitro parameters (decreased T cell proliferation, cytokine and autoantibody production). The amount of cleaved Caspase-3 increased in arthritic ZAP-70^+/- T cells, with no significant changes in cleaved Caspase-8 and -9 levels; although expression of Bim, Bcl-2 and Cytochrome C showed alterations. Tyrosine phosphorylation was less pronounced in arthritic ZAP-70^+/- T cells and the amount of Cbl-b-a negative regulator of T cell activation-decreased as well. We hypothesize that the less severe disease seen in the partial absence of ZAP-70 might be caused by the decreased T cell activation accompanied by increased apoptosis.

Clinical Scoring of Disease Activity in Animal Models

Disease severity in murine arthritis models, such as collagen-induced arthritis (CIA), is commonly assessed by clinical scoring of paw swelling and histological examination of joints. Clinical scoring using a qualitative scoring system of paw inflammation (paw thickness, width, or volume) over time is the standard method used for subjective quantification of arthritis activity. To evaluate paw swelling status, a quantitative method using three-dimensional T2-weighted flash sequence magnetic resonance imaging (MRI) is introduced. The efficacy of a therapeutic approach can be semiologically quantified using a clinical scoring system and an index of paw inflammation in CIA mice.