Myricitrin inhibits fibroblast-like synoviocyte-mediated rheumatoid synovial inflammation and joint destruction by targeting AIM2

Treatment of rheumatoid arthritis using dual-targeted and dual-response intelligent micelles: a "three birds with one stone" strategy

Rheumatoid arthritis (RA) is an autoimmune disease whose pathophysiology is closely related to inflammation-associated cells and the microenvironment of inflamed joints. This study aimed to develop dual-targeted, reactive oxygen species (ROS)/pH dual-responsive, size-shrinkable intelligent micelles targeting M1 macrophages and fibroblast-like synoviocytes (FLSs) to enhance drug efficacy and safety. These micelles were surface-modified with PEG5000 to prolong their circulation time in the bloodstream and hide the targeting molecules. The optimized particle size allowed the micelles to reside in inflamed joints through the extravasation through leaky vasculature and subsequent inflammatory cell-mediated sequestration (ELVIS) effect. The high concentration of ROS in the inflamed joint caused the detachment of the hydration layer of PEG5000, which was then specifically recognized and internalized by M1 macrophages and FLSs via CD44 receptor-mediated endocytosis, ultimately allowing the release of the drug into the acidic environment of the inflamed cells. The in vivo and in vitro evaluation showed that micelles precisely targeted the inflammatory site, thus inhibiting the expression of pro-inflammatory cytokines, reversing the polarization of M1 macrophages, inhibiting the invasion and migration of proliferative FLSs, and, at the same time, regulating the seeds and soils of RA. This "three birds with one stone" approach targeted multiple aspects of RA, opening new horizons for comprehensive treatment of RA.

The role of AIM2 in inflammation and tumors

Absent in melanoma 2 (AIM2) serves as an intracellular nucleic acid sensor that predominantly detects double-stranded DNA (dsDNA) within the cells. This detection initiates the assembly of inflammasome and activates the inflammasome signaling cascade, resulting in the production of inflammatory mediators and the cleavage of Gasdermins. Consequently, these processes culminate in inflammatory responses and pyroptotic cell death. AIM2 plays a pivotal role in modulating inflammation and tumorigenesis, functioning through both inflammasome-dependent and independent mechanisms. Its influence on the host immune response is dual-faceted, exhibiting both promotive and inhibitory effects in the contexts of inflammation and tumors. These effects are predominantly contingent upon the specific cell type expressing AIM2 and the nature of the host's disease. This article seeks to review the latest advancements in understanding the cell-specific functions of AIM2 in inflammation and tumorigenesis, with the objective of offering insights for further research on AIM2 and informing the development of targeted therapeutic strategies for clinical application.

Cytoplasmic DNA and AIM2 inflammasome in RA: where they come from and where they go?

Rheumatoid arthritis is a chronic autoimmune disease of undetermined etiology characterized by symmetric synovitis with predominantly destructive and multiple joint inflammation. Cytoplasmic DNA sensors that recognize protein molecules that are not themselves or abnormal dsDNA fragments play an integral role in the generation and perpetuation of autoimmune diseases by activating different signaling pathways and triggering innate immune signaling pathways and host defenses. Among them, melanoma deficiency factor 2 (AIM2) recognizes damaged DNA and double-stranded DNA and binds to them to further assemble inflammasome, initiating the innate immune response and participating in the pathophysiological process of rheumatoid arthritis. In this article, we review the research progress on the source of cytoplasmic DNA, the mechanism of assembly and activation of AIM2 inflammasome, and the related roles of other cytoplasmic DNA sensors in rheumatoid arthritis.

Sinomenine ameliorates fibroblast-like synoviocytes dysfunction by promoting phosphorylation and nuclear translocation of CRMP2

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and arthritic pain. Sinomenine (SIN), derived from the rhizome of Chinese medical herb Qing Teng (scientific name: Sinomenium acutum (Thunb.) Rehd. Et Wils), has a longstanding use in Chinese traditional medicine for treating rheumatoid arthritis. It has been shown to possess anti-inflammatory, analgesic, and immunosuppressive effects with minimal side-effects clinically. However, the mechanisms governing its effects in treatment of joint pathology, especially on fibroblast-like synoviocytes (FLSs) dysfunction, and arthritic pain remains unclear.

AIM

This study aimed to investigate the effect and underlying mechanism of SIN on arthritic joint inflammation and joint FLSs dysfunctions.

MATERIALS AND METHODS

Collagen-induced arthritis (CIA) was induced in rats and the therapeutic effects of SIN on joint pathology were evaluated histopathologically. Next, we conducted a series of experiments using LPS-induced FLSs, which were divided into five groups (Naïve, LPS, SIN 10, 20, 50 μg/ml). The expression of inflammatory factors was measured by qPCR and ELISA. The invasive ability of cells was detected by modified Transwell assay and qPCR. Transwell migration and cell scratch assays were used to assess the migration ability of cells. The distribution and content of relevant proteins were observed by immunofluorescence and laser confocal microscopy, as well as Western Blot and qPCR. FLSs were transfected with plasmids (CRMP2 T514A/D) to directly modulate the post-translational modification of CRMP2 protein and downstream effects on FLSs function was monitored.

RESULTS

SIN alleviated joint inflammation in rats with CIA, as evidenced by improvement of synovial hyperplasia, inflammatory cell infiltration and cartilage damage, as well as inhibition of pro-inflammatory cytokines release from FLSs induced by LPS. In vitro studies revealed a concentration-dependent suppression of SIN on the invasion and migration of FLSs induced by LPS. In addition, SIN downregulated the expression of cellular CRMP2 that was induced by LPS in FLSs, but increased its phosphorylation at residue T514. Moreover, regulation of pCRMP2 T514 by plasmids transfection (CRMP2 T514A/D) significantly influenced the migration and invasion of FLSs. Finally, SIN promoted nuclear translocation of pCRMP2 T514 in FLSs.

CONCLUSIONS

SIN may exert its anti-inflammatory and analgesic effects by modulating CRMP2 T514 phosphorylation and its nuclear translocation of FLSs, inhibiting pro-inflammatory cytokine release, and suppressing abnormal invasion and migration. Phosphorylation of CRMP2 at the T514 site in FLSs may present a new therapeutic target for treating inflammatory joint's destruction and arthritic pain in RA.

Myricetin reduces neutrophil extracellular trap release in a rat model of rheumatoid arthritis, which is associated with a decrease in disease severity

Rheumatoid arthritis (RA) is a chronic disease characterized by joint inflammation and severe disability. However, there is a lack of safe and effective drugs for treating RA. In our previous study, we discovered that myricetin (MC) and celecoxib have a synergistic effect in the treatment of RA. We conducted in vitro and in vivo experiments to further investigate the effects and mechanisms of action of MC. Our findings demonstrated that MC treatment effectively reduced the release of neutrophil extracellular traps (NETs) and alleviated the inflammatory response in RA. Mechanistic studies showed that MC prevents the entry of PADI4 and MPO into the cell nucleus, thereby protecting DNA from decondensation. In a rat arthritis model, MC improved histological changes in ankle joints and suppressed NET-related signaling factors. In conclusion, MC protects the ankle joints against arthritis by inhibiting MPO and PADI4, thereby reducing NET release. The pharmacological mechanism of MC in RA involves the inhibition of NET release.

A novel single domain bispecific antibody targeting VEGF and TNF-α ameliorates rheumatoid arthritis

Anti-TNF-α therapy fails in 30% of patients, where TNF-α may not be the key causative factor in these patients. We developed a bispecific single-domain antibody block TNF-α and VEGF (V5-3).The experiments showed that V5-3 effectively activated proliferation and migration of RA-FLS and HUVEC, tube-forming role of HUVEC, and expression of inflammatory factors in vitro. Besides, the experiments indicated that the anti-RA activity of V5-3 was superior to Anbainuo in vivo. Application of V5-3 reduced the expression of inflammatory factors, extent of synovial inflammation and angiogenesis and attenuated the severity of autoimmune arthritis in collagen-induced arthritis (CIA) mice. Mechanistically, V5-3 suppressed p65, AKT and VEGFR2 phosphorylation, as well as production of TNF-α and VEGF in joint tissues. These results demonstrated that V5-3 displayed a superior effect of anti-RA, may be a new therapy to overcome the limitations of anti-TNF-α monoclonal antibody.

Schisandrin treatment suppresses the proliferation, migration, invasion, and inflammatory responses of fibroblast-like synoviocytes from rheumatoid arthritis patients and attenuates synovial inflammation and joint destruction in CIA mice

BACKGROUND

Rheumatoid arthritis (RA) is a systemic autoimmune disease causing joint dysfunction. As disease-modifying anti-rheumatic drugs (DMARDs) have poor efficacy in 20% to 25% of RA patients, additional novel RA medications are urgently needed. Schisandrin (SCH) has multiple therapeutic effects. However, whether SCH is effective against RA remains unknown.

PURPOSE

To investigate how SCH affects the abnormal behaviours of RA fibroblast-like synoviocytes (FLSs) and further elucidate the underlying mechanism of SCH in RA FLSs and collagen-induced arthritis (CIA) mice.

METHODS

Cell Counting Kit-8 (CCK8) assays were used to characterize cell viability. EdU assays were performed to assess cell proliferation. Annexin V-APC/PI assays were used to determine apoptosis. Transwell chamber assays were used to measure cell migration and invasion in vitro. RT-qPCR was used to assess proinflammatory cytokine and MMP mRNA expression. Western blotting was used to detect protein expression. RNA sequencing was performed to explore the potential downstream targets of SCH. CIA model mice were used to assess the treatment efficacy of SCH in vivo.

RESULTS

Treatments with SCH (50, 100, and 200 μΜ) inhibited RA FLSs proliferation, migration, invasion, and TNF-α-induced IL-6, IL-8, and CCL2 expression in a dose-dependent manner but did not affect RA FLSs viability or apoptosis. RNA sequencing and Reactome enrichment analysis indicated that SREBF1 might be the downstream target in SCH treatment. Furthermore, knockdown of SREBF1 exerted effects similar to those of SCH in inhibiting RA FLSs proliferation, migration, invasion, and TNF-α-induced expression of IL-6, IL-8, and CCL2. Both SCH treatment and SREBF1 knockdown decreased activation of the PI3K/AKT and NF-κB signalling pathways. Moreover, SCH ameliorated joint inflammation and cartilage and bone destruction in CIA model mice.

CONCLUSION

SCH controls the pathogenic behaviours of RA FLSs by targeting SREBF1-mediated activation of the PI3K/AKT and NF-κB signalling pathways. Our data suggest that SCH inhibits FLS-mediated synovial inflammation and joint damage and that SCH might have therapeutic potential for RA.

Myricitrin promotes osteogenesis and prevents ovariectomy bone mass loss via the PI3K/AKT signalling pathway

This study aimed to explore the effect of myricitrin on osteoblast differentiation in mice immortalised bone marrow mesenchymal stem cells (imBMSCs). Additionally, ovariectomy (OVX) mice were employed to examine the effect of myricitrin on bone trabecular loss in vivo. The effect of myricitrin on the proliferation of imBMSCs was evaluated using a cell counting kit-8 assay. Alizarin red staining, alkaline phosphatase staining were performed to elucidate osteogenesis. Furthermore, qRT-PCR and western blot determined the expression of osteo-specific genes and proteins. To screen for candidate targets, mRNA transcriptome genes were sequenced using bioinformatics analyses. Western blot and molecular docking analysis were used to examine target signalling markers. Moreover, rescue experiments were used to confirm the effect of myricitrin on the osteogenic differentiation of imBMSCs. OVX mice were also used to estimate the delay capability of myricitrin on bone trabecular loss in vivo using western blot, micro-CT, tartaric acid phosphatase (Trap) staining, haematoxylin and eosin staining, Masson staining and immunochemistry. In vitro, myricitrin significantly enhanced osteo-specific genes and protein expression and calcium deposition. Moreover, mRNA transcriptome gene sequencing and molecular docking analysis revealed that this enhancement was accompanied by an upregulation of the PI3K/AKT signalling pathway. Furthermore, copanlisib, a PI3K inhibitor, partially reversed the osteogenesis promotion induced by myricitrin. In vivo, western blot, micro-CT, hematoxylin and eosin staining, Masson staining, Trap staining and immunochemistry revealed that bone trabecular loss rate was significantly alleviated in the myricitrin low- and high-dose groups, with an increased expression of osteopontin, osteoprotegerin, p-PI3K and p-AKT compared to the OVX group. Myricitrin enhances imBMSC osteoblast differentiation and attenuate bone mass loss partly through the upregulation of the PI3K/AKT signalling pathway. Thus, myricitrin has therapeutic potential as an antiosteoporosis drug.

The regulation of self-tolerance and the role of inflammasome molecules

Inflammasome molecules make up a family of receptors that typically function to initiate a proinflammatory response upon infection by microbial pathogens. Dysregulation of inflammasome activity has been linked to unwanted chronic inflammation, which has also been implicated in certain autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, type 1 diabetes, systemic lupus erythematosus, and related animal models. Classical inflammasome activation-dependent events have intrinsic and extrinsic effects on both innate and adaptive immune effectors, as well as resident cells in the target tissue, which all can contribute to an autoimmune response. Recently, inflammasome molecules have also been found to regulate the differentiation and function of immune effector cells independent of classical inflammasome-activated inflammation. These alternative functions for inflammasome molecules shape the nature of the adaptive immune response, that in turn can either promote or suppress the progression of autoimmunity. In this review we will summarize the roles of inflammasome molecules in regulating self-tolerance and the development of autoimmunity.