Neuroimmune Crosstalk in Rheumatoid Arthritis

Fibroblast expression of neurotransmitter receptor HTR2A associates with inflammation in rheumatoid arthritis joint

The study of neuroimmune crosstalk and the involvement of neurotransmitters in inflammation and bone health has illustrated their significance in joint-related conditions. One important mode of cell-to-cell communication in the synovial fluid (SF) is through extracellular vesicles (EVs) carrying microRNAs (miRNAs). The role of neurotransmitter receptors in the pathogenesis of inflammatory joint diseases, and whether there are specific miRNAs regulating differentially expressed HTR2A, contributing to the inflammatory processes and bone metabolism is unclear. Expression of neurotransmitter receptors and their correlated inflammatory molecules were identified in rheumatoid arthritis (RA) and osteoarthritis (OA) synovium from a scRNA-seq dataset. Immunohistochemistry staining of synovial tissue (ST) from RA and OA patients was performed for validation. Expression of miRNAs targeting HTR2A carried by SF EVs was screened in low- and high-grade inflammation RA from a public dataset and validated by qPCR. HTR2A reduction by target miRNAs was verified by miRNAs mimics transfection into RA fibroblasts. HTR2A was found to be highly expressed in fibroblasts derived from RA synovial tissue. Its expression showed a positive correlation with the degree of inflammation observed. 5 miRNAs targeting HTR2A were decreased in RA SF EVs compared to OA, three of which, miR-214-3p, miR-3120-5p and miR-615-3p, mainly derived from monocytes in the SF, were validated as regulators of HTR2A expression. The findings suggest that fibroblast HTR2A may play a contributory role in inflammation and the pathogenesis of RA. Additionally, targeting miRNAs that act upon HTR2A could present novel therapeutic strategies for alleviating inflammation in RA.

Exploring the mechanism of Celastrol in the treatment of rheumatoid arthritis based on systems pharmacology and multi-omics

To explore the molecular network mechanism of Celastrol in the treatment of rheumatoid arthritis (RA) based on a novel strategy (integrated systems pharmacology, proteomics, transcriptomics and single-cell transcriptomics). Firstly, the potential targets of Celastrol and RA genes were predicted through the database, and the Celastrol-RA targets were obtained by taking the intersection. Then, transcriptomic data and proteomic data of Celastrol treatment of RA were collected. Subsequently, Celastrol-RA targets, differentially expressed genes, and differentially expressed proteins were imported into Metascape for enrichment analysis, and related networks were constructed. Finally, the core targets of Celastrol-RA targets, differentially expressed genes, and differentially expressed proteins were mapped to synoviocytes of RA mice to find potential cell populations for Celastrol therapy. A total of 195 Celastrol-RA targets, 2068 differential genes, 294 differential proteins were obtained. The results of enrichment analysis showed that these targets, genes and proteins were mainly related to extracellular matrix organization, TGF-β signaling pathway, etc. The results of single cell sequencing showed that the main clusters of these targets, genes, and proteins could be mapped to RA synovial cells. For example, Mmp9 was mainly distributed in Hematopoietic cells, especially in Ptprn+fibroblast. The results of molecular docking also suggested that Celastrol could stably combine with molecules predicted by network pharmacology. In conclusion, this study used systems pharmacology, transcriptomics, proteomics, single-cell transcriptomics to reveal that Celastrol may regulate the PI3K/AKT signaling pathway by regulating key targets such as TNF and IL6, and then play an immune regulatory role.

Mechanistic role of quercetin as inhibitor for adenosine deaminase enzyme in rheumatoid arthritis: systematic review

Rheumatoid arthritis (RA) is an autoimmune disease involving T and B lymphocytes. Autoantibodies contribute to joint deterioration and worsening symptoms. Adenosine deaminase (ADA), an enzyme in purine metabolism, influences adenosine levels and joint inflammation. Inhibiting ADA could impact RA progression. Intracellular ATP breakdown generates adenosine, which increases in hypoxic and inflammatory conditions. Lymphocytes with ADA play a role in RA. Inhibiting lymphocytic ADA activity has an immune-regulatory effect. Synovial fluid levels of ADA are closely associated with the disease's systemic activity, making it a useful parameter for evaluating joint inflammation. Flavonoids, such as quercetin (QUE), are natural substances that can inhibit ADA activity. QUE demonstrates immune-regulatory effects and restores T-cell homeostasis, making it a promising candidate for RA therapy. In this review, we will explore the impact of QUE in suppressing ADA and reducing produced the inflammation in RA, including preclinical investigations and clinical trials.

Ondansetron or beta-sitosterol antagonizes inflammatory responses in liver, kidney, lung and heart tissues of irradiated arthritic rats model

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disorder mainly affecting joints, yet the systemic inflammation can influence other organs and tissues. The objective of this study was to unravel the ameliorative capability of Ondansetron (O) or β-sitosterol (BS) against inflammatory reactions and oxidative stress that complicates Extra-articular manifestations (EAM) in liver, kidney, lung, and heart of arthritic and arthritic irradiated rats.

METHODS

This was accomplished by exposing adjuvant-induced arthritis (AIA) rats to successive weekly fractions of total body γ-irradiation (2 Gray (Gy)/fraction once per week for four weeks, up to a total dose of 8 Gy). Arthritic and/or arthritic irradiated rats were either treated with BS (40 mg/kg b.wt. /day, orally) or O (2 mg/kg) was given ip) or were kept untreated as model groups.

RESULTS

Body weight changes, paw circumference, oxidative stress indices, inflammatory response biomarkers, expression of Janus kinase-2 (JAK-2), Signal transducer and activator of transcription 3 (STAT3), high mobility group box1 (HMGB1), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), as well as pro- and anti-inflammatory mediators in the target organs, besides histopathological examination of ankle joints and extra-articular tissues. Treatment of arthritic and/or arthritic irradiated rats with BS or O powerfully alleviated changes in body weight gain, paw swelling, oxidative stress, inflammatory reactions, and histopathological degenerative alterations in articular and non-articular tissues.

CONCLUSION

The obtained data imply that BS or O improved the articular and EAM by regulating oxidative and inflammatory indices in arthritic and arthritic irradiated rats.

Chronic stress predisposes to the aggravation of inflammation in autoimmune diseases with focus on rheumatoid arthritis and psoriasis

The global incidence of autoimmune diseases is on the rise, and many healthcare professionals believe that chronic stress plays a prominent role in both the aggravation and remission of these conditions. It is believed that prolonged exposure to stress is associated with neuroimmune axis malfunction, which eventually dysregulates multiple immunological factors as well as deregulates autoimmune responses that play a central role in various autoimmune diseases, including rheumatoid arthritis and psoriasis. Herein, we performed validation of an 8-week long rat model of chronic unpredictable stress (CUS) which consisted of exposing groups of rats to random stressors daily for 8 weeks. Additionally, we developed a novel rat model combining 8-week long random stressor-induced CUS with CIA-triggered arthritis and IMQ-triggered psoriasis and have successfully used both these models to assess the role of chronic stress in the aggravation of arthritis and psoriasis, respectively. Notably, the 8-week CUS protocol extensively aggravated and prolonged both arthritis and psoriasis condition in the rat model by upregulating the release of different pro-inflammatory cytokines, dysregulation of immune cell responses and oxidative stress system, which were all related to severe inflammation. Further, CUS aggravated macroscopic features and the increase in destruction of joint tissue and epidermal thickness induced by CIA and IMQ, respectively, in rats. In conclusion, this study suggests that exposure to an 8-week long CUS paradigm aggravates the distinctive characteristics of rheumatoid arthritis and psoriasis in rats via amplifying the inflammatory circuits and immune cell responses linked to these autoimmune diseases.

Inflammation in the CNS and PNS: From Molecular Basis to Therapy

Our understanding of the pathophysiology of the nervous system has advanced significantly in the last few years, but there are still many unanswered questions [...].

Complete Freund's Adjuvant Induces a Fibroblast-like Synoviocytes (FLS) Metabolic and Migratory Phenotype in Resident Fibroblasts of the Inoculated Footpad at the Earliest Stage of Adjuvant-Induced Arthritis

The fibroblast-like synoviocytes (FLS) have a crucial role in the pathogenesis of Rheumatoid Arthritis (RA); however, its precise mechanisms remain partially unknown. The involvement of the fibroblast in activating adjuvant-induced arthritis (AA) has not been previously reported. The objective was to describe the participation of footpads' fibroblasts in the critical initial process that drives the AA onset. Wistar rats were injected with Complete Freund's Adjuvant (CFA) or saline solution in the hind paws' footpads and euthanized at 24 or 48 h for genetic and histological analyses. Microarrays revealed the differentially expressed genes between the groups. The CFA dysregulated RA-linked biological processes at both times. Genes of MAPK, Jak-STAT, HIF, PI3K-Akt, TLR, TNF, and NF-κB signaling pathways were altered 24 h before the arrival of immune cells (CD4, CD8, and CD68). Key markers TNF-α, IL-1β, IL-6, NFκB, MEK-1, JAK3, Enolase, and VEGF were immunodetected in fibroblast in CFA-injected footpads at 24 h but not in the control group. Moreover, fibroblasts in the CFA inoculation site overexpressed cadherin-11, which is linked to the migration and invasion ability of RA-FLS. Our study shows that CFA induced a pathological phenotype in the fibroblast of the inoculation site at very early AA stages from 24 h, suggesting a prominent role in arthritis activation processes.

Macrophages and glial cells: Innate immune drivers of inflammatory arthritic pain perception from peripheral joints to the central nervous system

Millions of people suffer from arthritis worldwide, consistently struggling with daily activities due to debilitating pain evoked by this disease. Perhaps the most intensively investigated type of inflammatory arthritis is rheumatoid arthritis (RA), where, despite considerable advances in research and clinical management, gaps regarding the neuroimmune interactions that guide inflammation and chronic pain in this disease remain to be clarified. The pain and inflammation associated with arthritis are not isolated to the joints, and inflammatory mechanisms induced by different immune and glial cells in other tissues may affect the development of chronic pain that results from the disease. This review aims to provide an overview of the state-of-the-art research on the roles that innate immune, and glial cells play in the onset and maintenance of arthritis-associated pain, reviewing nociceptive pathways from the joint through the dorsal root ganglion, spinal circuits, and different structures in the brain. We will focus on the cellular mechanisms related to neuroinflammation and pain, and treatments targeting these mechanisms from the periphery and the CNS. A comprehensive understanding of the role these cells play in peripheral inflammation and initiation of pain and the central pathways in the spinal cord and brain will facilitate identifying new targets and pathways to aide in developing therapeutic strategies to treat joint pain associated with RA.