The Role of Natural Products in Rheumatoid Arthritis: Current Knowledge of Basic In Vitro and In Vivo Research

cGAS-STING pathway in pathogenesis and treatment of osteoarthritis and rheumatoid arthritis

Osteoarthritis (OA) and Rheumatoid Arthritis (RA) are significant health concerns with notable prevalence and economic impact. RA, affecting 0.5% to 1.0% of the global population, leads to chronic joint damage and comorbidities. OA, primarily afflicting the elderly, results in joint degradation and severe pain. Both conditions incur substantial healthcare expenses and productivity losses. The cGAS-STING pathway, consisting of cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING), is a crucial component of mammalian immunity. This pathway is responsible for detecting foreign DNA, particularly double-stranded DNA (dsDNA), triggering innate immune defense responses. When cGAS recognizes dsDNA, it catalyzes the synthesis of cyclic GMP-AMP (cGAMP), which then binds to and activates STING. Activated STING, in turn, initiates downstream signaling events leading to the production of interferons and other immune mediators. The cGAS-STING pathway is essential for defending against viral infections and maintaining cellular balance. Dysregulation of this pathway has been implicated in various inflammatory diseases, including arthritis, making it a target for potential therapeutic interventions. Understanding the intricate molecular signaling network of cGAS-STING in these arthritis forms offers potential avenues for targeted therapies. Addressing these challenges through improved early detection, comprehensive management, and interventions targeting the cGAS-STING pathway is crucial for alleviating the impact of OA and RA on individuals and healthcare systems. This review offers an up-to-date comprehension of the cGAS-STING pathway's role in the development and therapeutic approaches for these arthritis types.

Arecoline hydrobromide suppresses PI3K/AKT pathway in rheumatoid arthritis synovial fibroblasts and relieves collagen-induced arthritis in mice

OBJECTIVE

This study investigated the effectiveness of arecoline hydrobromide (AH) on the functions of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) and collagen-induced arthritis (CIA) mice.

METHODS

Immunofluorescence was used to identify RA-FLSs. Cell Counting Kit-8 (CCK-8) was used to determine the viability of RA-FLSs and the half maximal inhibitory concentration (IC50) of AH. The 5-ethynyl-2'-deoxyuridine (EdU) assay was used to detect DNA replication in RA-FLSs. Cell cycle and apoptosis were examined by flow cytometry. Migration and invasion, as well as wound healing assays, were employed to determine cell migration and invasion ability. Proteins and mRNA expression levels were investigated using Western blot, quantitative real-time PCR (RT-qPCR), and immunofluorescence. The CIA mice model was used to assess the effect of AH in vivo. RNA-sequencing (RNA-seq) was used to find the potential signaling pathways of AH against RA, and Western blot was used to verify the key signaling pathway of AH on RA-FLSs. Network pharmacology and molecular docking were used to predict drug targets.

RESULTS

AH inhibited the proliferation and DNA replication of RA-FLSs, promoted cell cycle arrest by reducing the levels of cyclin-dependent kinase 1 (CDK1), cyclin A2, and cyclin B1, promoted apoptosis by suppressing B-cell lymphoma-2 (Bcl-2) expression, and suppressed migration and invasion by inhibiting vimentin expression in RA-FLSs. AH was also effective in relieving arthritis in vivo. RNA sequencing analyses suggested that AH inhibited the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway in RA-FLSs, which was also confirmed in Western blot analysis. Furthermore, network pharmacology and molecular docking suggested that F2, MAPK14, SRC, AKT1, and CTSK might be the direct targets of AH.

CONCLUSION

AH can modulate the pathological process of RA-FLSs by blocking the PI3K/AKT pathway and relieve CIA in mice, making it a potential new small molecule candidate.

Methotrexate and Sulforaphane loaded PBA-G5-PAMAM dendrimers as a combination therapy for anti-inflammatory response in an intra-articular joint arthritic animal model

L-sulforaphane (LSF), a natural product developed from cruciferous vegetables, have shown potent anti-inflammatory effect in cancer as well as arthritis. However, the stable delivery of LSF remains a major challenge. Methotrexate (MTX) is currently the first line treatment for managing RA and is most effective in patients when used in combination with other anti-inflammatory or anti-rheumatic drugs. Here we developed phenylboronic acid-PAMAM dendrimer (PBA-G5D) nanoparticles conjugated MTX (MTX-PBA-G5D), and L-sulforaphane (LSF/PBA-G5D) loaded dendrimers. The MTX and LSF drug loading and release kinetics was analyzed using HPLC. The lipopolysaccharide (LPS) stimulated macrophages were treated with the formulations to study the inflammatory response in vitro. For in vivo studies, arthritis was induced in five-week-old female Wistar rats, and the MTX- and LSF/PBA-G5-D were injected via intra-articular injection for treatment and the arthritis reduction was scored by weight, knee diameter, and serum cytokine level measurement. The average size of the drug-nanoparticle conjugates ranged from 135-250 nm, with mostly cationic surface charges. The encapsulation efficiency of the drugs to the modified dendrimer was more than 60% with a slow release of drugs from the nanoparticles within 24 h at pH 7.4. Drugs in the nanoparticle formulation were biocompatible, with promising anti-inflammatory effects in vitro against LPS-activated murine macrophages. Further in vivo studies on arthritis induced female Wistar rats, revealed significant anti-arthritic effects based on the arthritic scoring from the knee diameter reading, and anti-inflammatory effects based on the serum cytokine levels. This study provides a promising strategy for utilizing PAMAM dendrimers as a nanocarrier for LSF delivery for RA therapy.

Fermented Lettuce Extract Containing Nitric Oxide Metabolites Attenuates Inflammatory Parameters in Model Mice and in Human Fibroblast-Like Synoviocytes

Lettuce (Lactuca sativa L.) contains various bioactive compounds that can reduce the severity of inflammatory diseases. This study aimed to identify therapeutic effects and underlying mechanisms of fermented lettuce extract (FLE) containing stable nitric oxide (NO) on collagen-induced arthritis (CIA) in mice and fibroblast-like synoviocytes (MH7A line) from patients with rheumatoid arthritis (RA). DBA/1 mice were immunized with bovine type II collagen and orally administered FLE for 14 days. On day 36, mouse sera and ankle joints were collected for serological and histological analysis, respectively. Consuming FLE inhibited RA development, suppressing pro-inflammatory cytokine productions, synovial inflammation, and cartilage degradation. The therapeutic effects of FLE in CIA mice were similar to those of methotrexate (MTX), which is typically used to treat RA. In vitro, FLE suppressed the transforming growth factor-β (TGF-β)/Smad signaling pathway in MH7A cells. We also demonstrated that FLE inhibited TGF-β-induced cell migration, suppressed MMP-2/9 expression, inhibited MH7A cell proliferation, and increased the expression of autophagy markers LC3B and p62 in a dose-dependent manner. Our data suggest that FLE could induce autophagosome formations in the early of stages of autophagy while inhibiting their degradation in the later stages. In conclusion, FLE is a potential therapeutic agent for RA.

Anti-Arthritic and Anti-Cancer Activities of Polyphenols: A Review of the Most Recent In Vitro Assays

Polyphenols have gained widespread attention as they are effective in the prevention and management of various diseases, including cancer diseases (CD) and rheumatoid arthritis (RA). They are natural organic substances present in fruits, vegetables, and spices. Polyphenols interact with various kinds of receptors and membranes. They modulate different signal cascades and interact with the enzymes responsible for CD and RA. These interactions involve cellular machinery, from cell membranes to major nuclear components, and provide information on their beneficial effects on health. These actions provide evidence for their pharmaceutical exploitation in the treatment of CD and RA. In this review, we discuss different pathways, modulated by polyphenols, which are involved in CD and RA. A search of the most recent relevant publications was carried out with the following criteria: publication date, 2012-2022; language, English; study design, in vitro; and the investigation of polyphenols present in extra virgin olive, grapes, and spices in the context of RA and CD, including, when available, the underlying molecular mechanisms. This review is valuable for clarifying the mechanisms of polyphenols targeting the pathways of senescence and leading to the development of CD and RA treatments. Herein, we focus on research reports that emphasize antioxidant properties.

Mitochondrial Dysfunction and Oxidative Stress in Rheumatoid Arthritis

Control of excessive mitochondrial oxidative stress could provide new targets for both preventive and therapeutic interventions in the treatment of chronic inflammation or any pathology that develops under an inflammatory scenario, such as rheumatoid arthritis (RA). Increasing evidence has demonstrated the role of mitochondrial alterations in autoimmune diseases mainly due to the interplay between metabolism and innate immunity, but also in the modulation of inflammatory response of resident cells, such as synoviocytes. Thus, mitochondrial dysfunction derived from several danger signals could activate tricarboxylic acid (TCA) disruption, thereby favoring a vicious cycle of oxidative/mitochondrial stress. Mitochondrial dysfunction can act through modulating innate immunity via redox-sensitive inflammatory pathways or direct activation of the inflammasome. Besides, mitochondria also have a central role in regulating cell death, which is deeply altered in RA. Additionally, multiple evidence suggests that pathological processes in RA can be shaped by epigenetic mechanisms and that in turn, mitochondria are involved in epigenetic regulation. Finally, we will discuss about the involvement of some dietary components in the onset and progression of RA.

NSAID Treatment Before and on the Early Onset of Acute Kidney Injury Had an Opposite Effect on the Outcome of Patients With AKI

Background: NSAIDs are one of the most frequently used medications and a risk factor for AKI. However, the optimal time of NSAIDs in patients with AKI is unknown. Methods: A secondary analysis of a multicenter, randomized clinical trial including adult inpatients with acute kidney injury was performed. Univariate, multivariate, and subgroup analyses were used to explore the impact of NSAIDs during the early onset of AKI on the outcome of patients with AKI. Results: A total of 6,030 patients with AKI were enrolled in the study. Following are the findings of the multi-factor analysis: NSAID treatments within 72 and 24 h before the onset of AKI were not associated with AKI progression, dialysis, or discharge from dialysis; only NSAID treatment within the 24-h onset of AKI was associated with these outcomes, and their OR values were independently 1.50 (95% CI: 1.02-2.19, p = 0.037), 4.20 (95% CI: 1.47-11.97, p = 0.007), and 0.71 (95% CI: 0.54-0.92, p = 0.011); only NSAID treatment within the 24-h onset of AKI would decrease the 14-day mortality, and the OR value was 0.52 (95% CI: 0.33-0.82, p = 0.005). The subgroup analysis revealed that in patients with age ≥65 years, CKD (chronic kidney disease), congestive heart failure, hypertension, and liver disease, NSAID treatments within the 24-h onset of AKI would deteriorate the outcome of patients with AKI. Conclusion: Before an early onset of AKI, NSAID treatment might be safe, but during the onset of AKI, even early NSAID treatment would deteriorate the outcome of patients with AKI.