Arthritis models: usefulness and interpretation

In vivo exposure to hydroquinone during the early phase of collagen-induced arthritis aggravates the disease

Robust correlation between the severity of rheumatoid arthritis (RA) and cigarette smoking has been clinically demonstrated. Nevertheless, cigarette compounds responsible for this toxic effect and their mechanisms have not been described. Considering that hydroquinone (HQ) is an abundant, pro-oxidative compound of the matter particle phase of cigarette smoke, we investigated whether HQ exposure during the initial phase of collagen-induced arthritis (CIA) could aggravate the disease. For this purpose, male Wistar rats were exposed to aerosolized HQ (25 ppm), saline or 5% ethanol solution (HQ vehicle) for 1 h per day during 14 days. CIA was induced through s.c. injection of bovine collagen Type II (0.4 mg/100 μL) at days seven and 14 of exposure. Clinical signs of disease and the cell profile and chemical mediators in the synovial fluid and membrane were analysed at day 35 after the beginning of exposure. HQ exposure aggravated CIA-related paw edema and increased the cell infiltrate and interleukin-6 (IL-6) levels in the synovial fluid, promoted intense tissue collagen deposition and enhanced synoviocyte proliferation and higher frequency of aryl hydrocarbon receptor (AhR⁺) and interleukin (IL-17⁺) neutrophils in the synovial membrane. in vitro data also highlighted that neutrophils expressed increased levels of AhR, IL-17 and reactive oxygen species (ROS) generation. However, only AhR expression and ROS generation were blocked by in vitro treatment with AhR antagonist. Therefore, we conclude that in vivo HQ exposure at the early phase of AR onset worsens RA, leading to high frequency of AhR/IL-17⁺ neutrophils into the joint.

Hydroquinone exposure worsens the symptomatology of rheumatoid arthritis

The genesis of rheumatoid arthritis (RA) is complex and dependent on genetic background and exposure to environmental xenobiotic. Indeed, smoking is associated to developing and worsening pre-existing RA. Nevertheless, the mechanisms and cigarette compounds involved in the harmful processes have not been elucidated. Here, we investigated if the exposure to hydroquinone (HQ), an abundant pro-oxidative compound of cigarette and benzene metabolite, could worsen the ongoing RA. Hence, collagen-induced arthritis (CIA) was induced in male Wistar rats by s.c. injection of 400 μg (200 μL) of bovine collagen type II emulsified in complete Freund's adjuvant on day 1, and a booster injection was performed on day 7. Exposures to nebulized HQ (25 ppm), saline solution or HQ vehicle solution (5% ethanol in saline) were carried out for 1 h, once a day, on days 21-27 after CIA induction. On day 27, animals were euthanized and samples were collected for further analyses. Exposure to HQ caused loss of weight, intensified paw edema, enhanced levels of tumor necrosis factor-α (TNF-α) and anti-citrullinated protein antibody (ACPA) in the serum; augmented synoviocyte proliferation and influx of aril hydrocarbon receptor (AhR) positive cells into the synovial membrane, altered collagen fibre rearrangement in the synovia, and synoviocytes isolated from HQ exposed rats secreted higher levels of pro-inflammatory cytokines, TNF-α and interleukin-1β. Associated, we point out HQ as an environmental pollutant that aggravates RA, suggesting its participation on worsening RA in smoking patients.

Thinking BIG rheumatology: how to make functional genomics data work for you

High-throughput sequencing assays have become an increasingly common part of biological research across multiple fields. Even as the resulting sequences pile up in public databases, it is not always obvious how to make use of these data sets. Functional genomics offers approaches to integrate these "big" data into our understanding of rheumatic diseases. This review aims to provide a primer on thinking about big data from functional genomics in the context of rheumatology, using examples from the field's literature as well as the author's own work to illustrate the execution of functional genomics research. Study design is crucial to ensure the right samples are used to address the question of interest. In addition, sequencing assays produce a variety of data types, from gene expression to 3D chromatin structure and single-cell technologies, that can be integrated into a model of the underlying gene regulatory networks. The best approach for this analysis uses the scientific process: bioinformatic methods should be used in an iterative, hypothesis-driven manner to uncover the disease mechanism. Finally, the future of functional genomics will see big data fully integrated into rheumatology, leading to computationally trained researchers and interactive databases. The goal of this review is not to provide a manual, but to enhance the familiarity of readers with functional genomic approaches and provide a better sense of the challenges and possibilities.

Collagen-Induced Arthritis Models

Due to 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 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.

Model answers: Rational application of murine models in arthritis research

Advances in targeted immune therapeutics have profoundly improved clinical outcomes for patients with inflammatory arthropathies particularly rheumatoid arthritis. The landscape of disease that is observed and the treatment outcomes desired for the future have also progressed. As such there is an increasing move away from traditional models of end‐stage, chronic disease with recognition of the need to consider the earliest phases of pathogenesis as a target for treatment leading to resolution and/or cure. In order to continue the discovery process and enhance our understanding of disease and treatment, we therefore need to continuously revisit the animal models we employ and assess their relevance and utility in the light of contemporary therapeutic goals. In this review, we highlight the areas where we consider new developments in animal models and their application are most required. Thus, we have contextualised the relevant mouse models and their use within the current concepts of human inflammatory arthritis pathogenesis and highlight areas of need.

The Role of High-Mobility Group Box-1 and Its Crosstalk with Microbiome in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, definitely disabling, and potentially severe autoimmune disease. Although an increasing number of patients are affected, a key treatment for all patients has not been discovered. High-mobility group box-1 (HMGB1) is a nuclear protein passively and actively released by almost all cell types after several stimuli. HMGB1 is involved in RA pathogenesis, but a convincing explanation about its role and possible modulation in RA is still lacking. Microbiome and its homeostasis are altered in patients with RA, and the microbiota restoration has been proposed to patients with RA. The purpose of the present review is to analyze the available evidences regarding HMGB1 and microbiome roles in RA and the possible implications of the crosstalk between the nuclear protein and microbiome in understanding and possibly treating patients affected by this harmful condition.

The role of gut microbiota in the pathogenesis of rheumatic diseases

Rheumatic diseases refer to many diseases with a loss of immune self-tolerance, leading to a chronic inflammation, degeneration, or metabolic derangement in multiple organs or tissues. The cause of rheumatic diseases remains to be elucidated, though both environmental and genetic factors are required for the development of rheumatic diseases. Over the past decades, emerging studies suggested that alteration of intestinal microbiota, known as gut dysbiosis, contributed to the occurrence or development of a range of rheumatic diseases, including rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, systemic sclerosis, and Sjogren's syndrome, through profoundly affecting the balance between pro- and anti-inflammatory immune responses. In this article, we discussed the role of gut microbiota in the pathogenesis of rheumatic diseases based on a large number of experimental and clinical materials, thereby providing a new insight for microbiota-targeted therapies to prevent or cure rheumatic diseases.