Natural harmaline acts as novel fluorescent probe for hypochlorous acid and promising therapeutic candidate for rheumatoid arthritis.

Endogenous hypochlorous acid (HOCl) is one of the most important reactive oxygen species (ROS) and acts as a distinct biomarker that is involved in various inflammatory responses including rheumatoid arthritis (RA). Therefore, it's crucial to develop an efficient method for the tracking and analysis of HOCl levels in vivo. Natural products continue to be compounds of interest, because they not only offer diverse and specific molecular scaffolds but also provide invaluable sources for new drug discovery. Herein, we firstly demonstrated harmaline (HML), a natural alkaloid mainly found in Peganum harmala L, could be acted as a novel fluorescent probe for HOCl with exceptional precision and responsiveness. Remarkably, this probe not only specifically tracked HOCl levels in cells and inflammatory RA mouse models, but also exhibited effective anti-inflammatory effects on RAW264.7 cells and anti-proliferative effects on fibroblast-like synoviocytes. Furthermore, HML has the potential to alleviate LPS-induced inflammation by inhibiting the NF-κB signaling pathway. This study represents the first example of a natural product that can simultaneously act as a fluorescent probe for specific ROS and a promising therapeutic candidate for a specific disease, which will undoubtedly extend the application of fluorophore-rich natural products.

IGJ depletion suppresses proliferation, inflammation, and motility of rheumatoid arthritis fibroblast-like synoviocytes via targeting NF-κB pathway.

OBJECTIVE: To investigate the impact of IGJ on the proliferation, inflammation, and motility of rheumatoid arthritis (RA) fibroblast-like synoviocytes and elucidate the underlying mechanism. METHODS: The expression of IGJ RA fibroblast-like synoviocytes was assessed using immunoblot and qPCR. Cell growth was evaluated using CCK-8 and FCM assays. The effects on inflammatory response were determined by ELISA and immunoblot assays. Cell motility was assessed using transwell and immunoblot assays. The mechanism was further confirmed using immunoblot assays. RESULTS: IGJ expression was found to be elevated in fibroid synovial cells of RA. IGJ ablation inhibited the growth of MH7A cells and suppressed the inflammatory response. Knockdown of IGJ also blocked cell motility. Mechanically, the knockdown of IGJ suppressed the NF-κB axis in MH7A cells. CONCLUSION: IGJ suppresses RA in fibroblast-like synoviocytes via NF-κB pathway.

Effects of polysaccharide from Pueraria lobata on osteoarthritis in rats.

The effects of Pueraria lobata polysaccharide (PPL-1) on osteoarthritis (OA) disease were comprehensively evaluated by using chondrocytes and synoviocytes extracted from the joints of SD rats based on in vitro cell experiments and by establishing pathological models of OA rats. The results showed that concentrations of 1.25-10 and 0.2-1.6 µg/mL, PPL-1 did not inhibit or promote chondrocytes and synoviocytes in vitro. However, at concentrations of 1.25-10 and 0.2-1.6 µg/mL, it can promote cartilage and synovial membrane cells after LPS stimulation of cell activity and inhibite LPS-induced apoptosis. The results of animal experiments showed that PPL-1 can reduce the symptoms of joint swelling in OA rats, decrease the production of serum inflammatory cytokines TNF-α, IL-1ß, and IL-6, and slow down the occurrence of inflammation. Therefore, from the perspective of symptoms, inflammatory factors and pathology, PPL-1 has therapeutic effects on OA rats and alleviates the development of inflammation. It indicated that PPL-1 has the potential to be developed into an OA therapeutic drug with anti-inflammatory properties that protects and activates chondrocytes.

17ß-estradiol promotes the progression of temporomandibular joint osteoarthritis by regulating the FTO/IGF2BP1/m6A-NLRC5 axis.

BACKGROUND: Temporomandibular joint osteoarthritis (TMJOA) is a degenerative cartilage disease. 17ß-estradiol (E2) aggravates the pathological process of TMJOA; however, the mechanisms of its action have not been elucidated. Thus, we investigate the influence of E2 on the cellular biological behaviors of synoviocytes and the molecular mechanisms. METHODS: Primary fibroblast-like synoviocytes (FLSs) isolated from rats were treated with TNF-α to establish cell model, and phenotypes were evaluated using cell counting kit-8, EdU, Tanswell, enzyme-linked immunosorbent assay, and quantitative real-time PCR (qPCR). The underlying mechanism of E2, FTO-mediated NLRC5 m6A methylation, was assessed using microarray, methylated RNA immunoprecipitation, qPCR, and western blot. Moreover, TMJOA-like rat model was established by intra-articular injection of monosodium iodoacetate (MIA), and bone morphology and pathology were assessed using micro-CT and H&E staining. RESULTS: The results illustrated that E2 facilitated the proliferation, migration, invasion, and inflammation of TNF-α-treated FLSs. FTO expression was downregulated in TMJOA and was reduced by E2 in FLSs. Knockdown of FTO promoted m6A methylation of NLRC5 and enhanced NLRC5 stability by IGF2BP1 recognition. Moreover, E2 promoted TMJ pathology and condyle remodeling, and increased bone mineral density and trabecular bone volume fraction, which was rescued by NLRC5 knockdown. CONCLUSION: E2 promoted the progression of TMJOA.

Intron retention in PI-PLC γ1 mRNA as a key mechanism affecting MMP expression in human primary fibroblast-like synovial cells.

The intron retention (IR) is a phenomenon utilized by cells to allow diverse fates at the same mRNA, leading to a different pattern of synthesis of the same protein. In this study, we analyzed the modulation of phosphoinositide-specific phospholipase C (PI-PLC) enzymes by Harpagophytum procumbens extract (HPE) in synoviocytes from joins of osteoarthritis (OA) patients. In some samples, the PI-PLC γ1 isoform mature mRNA showed the IR and, in these synoviocytes, the HPE treatment increased the phenomenon. Moreover, we highlighted that as a consequence of IR, a lower amount of PI-PLC γ1 was produced. The decrease of PI-PLC γ1 was associated with the decrease of metalloprotease-3 (MMP-3), and MMP-13, and ADAMTS-5 after HPE treatment. The altered expression of MMPs is a hallmark of the onset and progression of OA, thus substances able to decrease their expression are very desirable. The interesting outcomes of this study are that 35% of analyzed synovial tissues showed the IR phenomenon in the PI-PLC γ1 mRNA and that the HPE treatment increased this phenomenon. For the first time, we found that the decrease of PI-PLC γ1 protein in synoviocytes interferes with MMP production, thus affecting the pathways involved in the MMP expression. This finding was validated by the silencing of PI-PLC γ1 in synoviocytes where the IR phenomenon was not present. Our results shed new light on the biochemical mechanisms involved in the degrading enzyme production in the joint of OA patients, suggesting a new therapeutic target and highlighting the importance of personalized medicine.

[MMPs/pH synergically responsive XTS-Prussian blue nanoparticles inhibiting proliferation and migration of RAFLS assisted with laser irradiation].

Rheumatoid arthritis(RA) is a condition in which the joints are in a weakly acidic environment. In RA, RA fibroblastlike synoviocytes( RAFLS) in the joints become abnormally activated and secrete a large amount of matrix metalloproteinases(MMPs), and the receptor protein CD44 on the cell membrane is specifically upregulated. Xuetongsu(XTS), an active ingredient in the Tujia ethnomedicine Xuetong, is known to inhibit the proliferation of RAFLS. However, its development and utilization have been limited due to poor targeting ability. A biomimetic XTS-Prussian blue nanoparticles(PB NPs) drug delivery system called THMPX NPs which can target CD44 was constructed in this study. The surface of THMPX NPs was modified with hyaluronic acid(HA) and a long chain of triglycerol monostearate(TGMS) and 3-aminobenzeneboronic acid(PBA)(PBA-TGMS). The overexpressed MMPs and H+ in inflammatory RAFLS can synergistically cleave the PBA-TGMS on the surface of the nanoparticles, exposing HA to interact with CD44. This allows THMPX NPs to accumulate highly in RAFLS, and upon near-infrared light irradiation, generate heat and release XTS, thereby inhibiting the proliferation and migration of RAFLS. Characterization revealed that THMPX NPs were uniform cubes with a diameter of(190. 3±4. 7) nm and an average potential of(-15. 3± 2. 3) m V. Upon near-infrared light irradiation for 5 min, the temperature of THMPX NPs reached 41. 5 ℃, indicating MMPs and H+-triggered drug release. Safety assessments showed that THMPX NPs had a hemolysis rate of less than 4% and exhibited no cytotoxicity against normal RAW264. 7 and human fibroblast-like synoviocytes(HFLS). In vitro uptake experiments demonstrated the significant targeting ability of THMPX NPs to RAFLS. Free radical scavenging experiments revealed excellent free radical clearance capacity of THMPX NPs, capable of removing reactive oxygen species in RAFLS. Cell counting kit-8 and scratch assays demonstrated that THMPX NPs significantly suppressed the viability and migratory ability of RAFLS. This study provides insights into the development of innovative nanoscale targeted drugs from traditional ethnic medicines for RA treatment.

[Mechanism of Huangqin Qingre Chubi Capsules in improving rheumatoid arthritis based on METTL3-SFRP4/Wnt/ß-catenin pathway].

The effect and mechanism of Huangqin Qingre Chubi Capsules(HQC) on rheumatoid arthritis(RA) were studied.Seventy male SPF rats were randomly divided into normal group, model group, low-(0. 18 g·kg~(-1)), middle-(0. 36 g·kg~(-1)), and high-(0. 72 g·kg~(-1)) dose groups of HQC, methotrexate group(MTX, 0. 75 mg·kg~(-1)), and negative control group(NC group, model +saline). Adjuvant arthritis fibroblast-like synoviocytes(AA-FLS) were divided into normal group, model group, low-, middle-, and high-dose groups of HQC, and negative control group. RT-qPCR and Western blot were used to detect the m RNA and protein expressions of METTL3, SFRP4, ß-catenin, CCND1, c-Myc, MMP3, and fibronectin. The protein expression of MMP3 and ß-catenin was detected by immunofluorescence. The gene expression level of METTL3 on AA-FLS was knocked down to further examine the expression of each gene. ELISA measured the levels of IL-1ß, IL-6, and IL-8. The results showed that compared with the normal group, rats in the model group found redness and swelling in their limbs and significantly increased joint swelling. Compared with the model group, the joint swelling degree of each treatment group significantly decreased(P<0. 05). The paw retraction threshold and body weight mass index both significantly increased(P<0. 05). METTL3 was highly expressed on AA and negatively correlated with the expression of SFRP4. After treatment, the m RNA and protein expression of METTL3, ß-catenin, CCND1, c-Myc, fibronectin, and MMP3 were significantly decreased on AA-FLS(P< 0. 05). Compared with the model group, knocking down METTL3 resulted in reduced m RNA and protein expression of ß-catenin, CCND1, c-Myc, fibronectin, and MMP3(P< 0. 05). At the same time, the m RNA and protein expressions of ß-catenin, CCND1, c-Myc, fibronectin, and MMP3 in the HQC+METTL3 knockdown group were significantly lower than those in the METTL3 knockdown group(P<0. 05). HQC could reduce the levels of IL-1ß, IL-6, and IL-8 to varying degrees(P<0. 05). The results indicate that HQC has a significant improvement effect on arthritis in AA rats. The expression of METTL3 is significantly increased in synovial tissue and AA-FLS of AA rats, which may be a potential target for the diagnosis and treatment of RA. HQC improves RA through the METTL3-SFRP4/Wnt/ß-catenin signaling pathway and has significant antiinflammatory and anti-rheumatic effects.

Gastrodin Ameliorates the Inflammation, Oxidative Stress, and Extracellular Matrix Degradation of IL-1ß-Mediated Fibroblast-Like Synoviocytes via Suppressing the Gremlin-1/NF-κB Pathway.

BACKGROUND: Synovial inflammation plays a crucial role in osteoarthritis (OA). Gastrodin (GAS), an active ingredient derived from the Gastrodia elata Blume rhizome, possesses antioxidant and anti-inflammatory pharmacological effects. This research aimed to evaluate the function and molecular mechanism of GAS on human fibroblast-like synoviocytes of osteoarthritis (HFLS-OA) induced by interleukin (IL)-1ß. METHODS: The impact of GAS on the viability of IL-1ß-treated HFLS-OA cells was assessed using the cell counting kit-8 (CCK-8). Quantitative real-time reverse transcription PCR (qRT-PCR) was employed to detect changes in IL-8, IL-6, monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor (TNF)-α, and Gremlin-1 mRNA expression in each group. Corresponding kits were utilized to measure the catalase (CAT) and superoxide dismutase (SOD) activities, as well as the nitric oxide (NO) level. Western blot analysis was conducted to examine the expression of extracellular matrix degradation-associated proteins and nuclear factor kappa-B (NF-κB) pathway-correlated proteins in each group. RESULTS: GAS significantly promoted the proliferation of IL-1ß-induced HFLS-OA cells and concurrently down-regulated Gremlin-1 mRNA expression (p < 0.05). Through the down-regulation of Gremlin-1 expression, GAS exhibited the following effects: decreased IL-8, IL-6, and TNF-α mRNA expression, as well as NO levels (p < 0.05); increased SOD and CAT activities (p < 0.05); down-regulated matrix metallopeptidase 13 (MMP-13) and MMP-1 protein expression levels (p < 0.01); and up-regulated collagen II protein expression level (p < 0.01) in IL-1ß-treated HFLS-OA cells. Additionally, GAS decreased phospho-inhibitory kappa B (p-IκB)/IκB, phospho-inhibitory kappa B kinase (p-IKK)/IKK, and p-p65/p65 ratios in IL-1ß-induced HFLS-OA cells by inhibiting Gremlin-1 expression (p < 0.01). CONCLUSION: GAS demonstrates a positive impact on inflammation, oxidative stress, and extracellular matrix degradation in IL-1ß-mediated HFLS-OA cells. This effect is achieved by suppressing Gremlin-1 expression and reducing NF-κB pathway activity.

Graphene oxide quantum dots-loaded sinomenine hydrochloride nanocomplexes for effective treatment of rheumatoid arthritis via inducing macrophage repolarization and arresting abnormal proliferation of fibroblast-like synoviocytes.

The characteristic features of the rheumatoid arthritis (RA) microenvironment are synovial inflammation and hyperplasia. Therefore, there is a growing interest in developing a suitable therapeutic strategy for RA that targets the synovial macrophages and fibroblast-like synoviocytes (FLSs). In this study, we used graphene oxide quantum dots (GOQDs) for loading anti-arthritic sinomenine hydrochloride (SIN). By combining with hyaluronic acid (HA)-inserted hybrid membrane (RFM), we successfully constructed a new nanodrug system named HA@RFM@GP@SIN NPs for target therapy of inflammatory articular lesions. Mechanistic studies showed that this nanomedicine system was effective against RA by facilitating the transition of M1 to M2 macrophages and inhibiting the abnormal proliferation of FLSs in vitro. In vivo therapeutic potential investigation demonstrated its effects on macrophage polarization and synovial hyperplasia, ultimately preventing cartilage destruction and bone erosion in the preclinical models of adjuvant-induced arthritis and collagen-induced arthritis in rats. Metabolomics indicated that the anti-arthritic effects of HA@RFM@GP@SIN NPs were mainly associated with the regulation of steroid hormone biosynthesis, ovarian steroidogenesis, tryptophan metabolism, and tyrosine metabolism. More notably, transcriptomic analyses revealed that HA@RFM@GP@SIN NPs suppressed the cell cycle pathway while inducing the cell apoptosis pathway. Furthermore, protein validation revealed that HA@RFM@GP@SIN NPs disrupted the excessive growth of RAFLS by interfering with the PI3K/Akt/SGK/FoxO signaling cascade, resulting in a decline in cyclin B1 expression and the arrest of the G2 phase. Additionally, considering the favorable biocompatibility and biosafety, these multifunctional nanoparticles offer a promising therapeutic approach for patients with RA.

Anti-inflammatory effect of the combined treatment of LMT-28 and kaempferol in a collagen-induced arthritis mouse model.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation and swelling. Several studies have demonstrated that RA fibroblast-like synovial cells (RA-FLS) play an important role in RA pathogenesis. Activated RA-FLS contribute to synovial inflammation by secreting inflammatory cytokines including interleukin (IL)-1ß, IL-6 and tumor necrosis factor-α. LMT-28 is derivative of oxazolidone and exerts anti-inflammatory effects on RA via IL-6 signaling pathway regulation. LMT-28 also regulates T cell differentiation in RA condition. However, the effect of LMT-28 on the migration and invasion of RA-FLS remains unknown. Kaempferol has been reported to have pharmacological effects on various diseases, such as inflammatory diseases, autoimmune diseases, and cancer. Additionally, kaempferol has been reported to inhibit RA-FLS migration and invasion, but it is not known about the therapeutic mechanism including molecular mechanism such as receptor. The present study aimed to investigate the synergistic effects of the combined treatment of LMT-28 and kaempferol on RA-FLS activation and RA pathogenesis in mouse model. LMT-28 and kaempferol co-administration inhibited RA disease severity and histological collapse in the joint tissues of CIA mice, as well as downregulated the levels of pro-inflammatory cytokines in mouse serum. Additionally, the combined treatment inhibited excessive differentiation of T helper 17 cells and osteoclasts. Furthermore, compared with single treatments, combined treatment showed enhanced inhibitory effects on the hyperactivation of IL-6-induced signaling pathway in RA-FLS. Combined treatment also inhibited RA-FLS cell proliferation, migration, and invasion and suppressed the expression of matrix metalloproteinase in RA-FLS. Furthermore, we confirmed that the combined treatment inhibited chondrocyte proliferation, migration, and invasion. In conclusion, our results suggest that the combined treatment of LMT-28 and kaempferol exerts a synergistic effect on the RA development via the regulation of IL-6-induced hyperactivation of RA-FLS. Furthermore, this study suggests that combination therapies can be an effective therapeutic option for arthritis.

Exploring the supplementary potential of all-trans retinoic acid with methotrexate in rheumatoid arthritis: modulation of synovial cell apoptosis and autophagy.

OBJECTIVES: The imbalance between apoptosis and proliferation in fibroblast-like synoviocytes (FLSs) plays a key role in the pathogenesis of rheumatoid arthritis (RA). This study aims to investigate the potential of all-trans retinoic acid (ATRA) as a supplementary therapeutic agent alongside methotrexate (MTX) for RA, by examining its ability to inhibit synovial cell proliferation and enhance apoptosis through the ROS-JNK signalling pathway. METHODS: The viability, apoptosis, and autophagy levels of human rheumatoid arthritis fibroblast-like synovial cells (HFLS-RA) were evaluated, while ROS generation was measured through the DCFH-DA fluorescence microplate assay. Western blotting was used to analyse the expression levels of JNK signalling pathway-related proteins. To assess therapeutic potential in vivo, a collagen-induced arthritis (CIA) model was established in Wistar rats. RESULTS: Small doses of MTX did not significantly affect the viability of HFLS-RAs or induce apoptosis. However, when ATRA was added to the treatment, the therapy markedly inhibited cell proliferation and induced apoptosis and excessive autophagy. Mechanistically, ATRA activated the ROS/JNK signalling pathway in HFLS-RAs. ROS scavengers and JNK inhibitors significantly attenuated ATRA-induced apoptosis and autophagy. In vivo, the combination therapy demonstrated a remarkable enhancement of the anti-arthritic efficacy in CIA rats. CONCLUSIONS: The ability of ATRA to inhibit proliferation in RA FLSs through autophagy and apoptosis underscores its potential as a supplementary therapeutic agent alongside MTX for RA, particularly when compared to the limited impact of MTX on these processes. This combined strategy holds promise for enhancing therapeutic outcomes and warrants further investigation in the management of RA.

TAK-242 (Resatorvid) inhibits proinflammatory cytokine production through the inhibition of NF-κB signaling pathway in fibroblast-like synoviocytes in osteoarthritis patients.

BACKGROUND: Fibroblast-like synoviocytes (FLSs) are involved in osteoarthritis (OA) pathogenesis through pro-inflammatory cytokine production. TAK-242, a TLR4 blocker, has been found to have a significant impact on the gene expression profile of pro-inflammatory cytokines such as IL1-ß, IL-6, TNF-α, and TLR4, as well as the phosphorylation of Ikßα, a regulator of the NF-κB signaling pathway, in OA-FLSs. This study aims to investigate this effect because TLR4 plays a crucial role in inflammatory responses. MATERIALS AND METHODS: Ten OA patients' synovial tissues were acquired, and isolated FLSs were cultured in DMEM in order to assess the effectiveness of TAK-242. The treated FLSs with TAK-242 and Lipopolysaccharides (LPS) were analyzed for the mRNA expression level of IL1-ß, IL-6, TNF-α, and TLR4 levels by Real-Time PCR. Besides, we used western blot to assess the protein levels of Ikßα and pIkßα. RESULTS: The results represented that TAK-242 effectively suppressed the gene expression of inflammatory cytokines IL1-ß, IL-6, TNF-α, and TLR4 which were overexpressed upon LPS treatment. Additionally, TAK-242 inhibited the phosphorylation of Ikßα which was increased by LPS treatment. CONCLUSION: According to our results, TAK-242 shows promising inhibitory effects on TLR4-mediated inflammatory responses in OA-FLSs by targeting the NF-κB pathway. TLR4 inhibitors, such as TAK-242, may be useful therapeutic agents to reduce inflammation and its associated complications in OA patients, since traditional and biological treatments may not be adequate for all of them.

Anti-rheumatic property and physiological safety of KMU-11342 in in vitro and in vivo models.

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder characterized by joint destruction due to synovial hypertrophy and the infiltration of inflammatory cells. Despite substantial progress in RA treatment, challenges persist, including suboptimal treatment responses and adverse effects associated with current therapies. This study investigates the anti-rheumatic capabilities of the newly identified multi-protein kinase inhibitor, KMU-11342, aiming to develop innovative agents targeting RA. In this study, we synthesized the novel multi-protein kinase inhibitor KMU-11342, based on indolin-2-one. We assessed its cardiac electrophysiological safety using the Langendorff system in rat hearts and evaluated its toxicity in zebrafish in vivo. Additionally, we examined the anti-rheumatic effects of KMU-11342 on human rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS), THP-1 cells, and osteoclastogenesis in RAW264.7 cells. KMU-11342 demonstrated the ability to inhibit LPS-induced chemokine inhibition and the upregulation of pro-inflammatory cytokines, cyclooxygenase-2, inducible nitric oxide synthase, p-IKKα/ß, p-NF-κB p65, and the nuclear translocation of NF-κB p65 in RA-FLS. It effectively suppressed the upregulation of NLR family pyrin domain containing 3 (NLRP3) and caspase-1 cleavage. Furthermore, KMU-11342 hindered the activation of osteoclast differentiation factors such as RANKL-induced TRAP, cathepsin K, NFATc-1, and c-Fos in RAW264.7 cells. KMU-11342 mitigates LPS-mediated inflammatory responses in THP-1 cells by inhibiting the activation of NLRP3 inflammasome. Notably, KMU-11342 exhibited minimal cytotoxicity in vivo and electrophysiological cardiotoxicity ex vivo. Consequently, KMU-11342 holds promise for development as a therapeutic agent in RA treatment.

Asiatic acid induces ferroptosis of RA-FLS via the Nrf2/HMOX1 pathway to relieve inflammation in rheumatoid arthritis.

BACKGROUND: Ferroptosis is a distinct iron-dependent non-apoptotic type of programmed cell death that is implicated in the pathophysiology of rheumatoid arthritis (RA). Although asiatic acid (AA) is documented to have significant anti-inflammatory effects in various diseases, it is not known whether it can regulate RA via ferroptosis. METHODS: The effects of AA on rheumatoid arthritis fibroid-like synoviocytes (RA-FLS) were assessed in vitro, and a rat model of type II collagen-induced arthritis (CIA) was established to evaluate the effectiveness of AA treatment in vivo. RESULTS: AA significantly reduced both viability and colony formation in cultured RA-FLS, while increasing the levels of reactive oxygen species (ROS), ferrous iron (Fe2+), malondialdehyde (MDA), and lactate dehydrogenase (LDH), as well as the expression of COX2. Furthermore, AA induced ferroptosis in RA-FLS by promoting Fe2+ accumulation through downregulation of the expression of Keap1 and FTH1 and upregulation of Nrf2 and HMOX1. In vivo, AA treatment was found to reduce toe swelling and the arthritis score in CIA rats, as well as relieve inflammation and ankle damage and significantly upregulate the expression of Nrf2 and HMOX1 in the synovial fluid. CONCLUSION: Treatment with AA significantly reduced the viability of RA-FLS and triggered ferroptosis by promoting accumulation of Fe2+via the Nrf2-HMOX1 pathway, and was effective in relieving inflammation in CIA model rats. These findings suggest that the use of AA may be a promising strategy for the clinical treatment of RA.

Discovery of calcite as a new pro-inflammatory calcium-containing crystal in human osteoarthritic synovial fluid.

OBJECTIVE: We aimed to characterize calcium-containing crystals present in synovial fluid from patients with knee osteoarthritis (OA) using Raman spectroscopy, and specifically investigate the biological effects of calcite crystals. DESIGN: Thirty-two synovial fluid samples were collected pre-operatively from knee OA patients undergoing total joint arthroplasty. An integrated Raman polarized light microscope was used for identification of crystals in synovial fluid. Human peripheral blood mononuclear cells (PBMC's), human OA articular chondrocytes (HACs) and fibroblast-like synoviocytes (FLSs) were exposed to calcite crystals. Expression of relevant cytokines and inflammatory genes were measured using enzyme-linked immuno sorbent assay (ELISA) and real-time polymerase chain reaction (PCR). RESULTS: Various calcium-containing crystals were identified, including calcium pyrophosphate (37.5 %) and basic calcium phosphate (21.8 %), but they were never found simultaneously in the same OA synovial fluid sample. For the first time, we discovered the presence of calcite crystals in 93.8 % of the samples, while dolomite was detected in 25 % of the cases. Characterization of the cellular response to calcite crystal exposure revealed increased production of innate immune-derived cytokines by PBMC's, when co-stimulated with lipopolysaccharide (LPS). Additionally, calcite crystal stimulation of HACs and FLSs resulted in enhanced secretion of pro-inflammatory molecules and alterations in the expression of extracellular matrix remodeling enzymes. CONCLUSIONS: This study highlights the unique role of Raman spectroscopy in OA crystal research and identified calcite as a novel pro-inflammatory crystal type in OA synovial fluid. Understanding the role of specific crystal species in the OA joint may open new avenues for pharmacological interventions and personalized approaches to treating OA.

Chinese medicine Di-long (Pheretima vulgaris) and its active fraction exhibit anti-rheumatoid arthritis effects by inhibiting CXCL10/CXCR3 chemotaxis in synovium.

ETHNOPHARMACOLOGICAL RELEVANCE: Di-Long (Pheretima vulgaris) is a classic animal sourced traditional Chinese medicine. It has been used for the treatment of joint inflammation and arthralgia for over two thousand years due to its effects of Tong-Luo-Zhi-Tong (dredging collaterals and alleviating pain). Our previous study showed that Chinese medicine Di-Long has significant anti-rheumatoid arthritis (RA) effects. AIM OF THE STUDY: Considering Di-Long as a potential source of active compounds with specific anti-RA therapeutic effects, this research was to obtain the anti-RA target-specific active fraction from Di-Long extracts (DL), and to further explore the chemical basis and verify the anti-RA mechanism of this active fraction. MATERIALS AND METHODS: Transcriptomic was applied to obtain the main anti-RA targets of DL on human RA fibroblast-like synoviocytes (FLS) and validated by qPCR. The target-corresponding active fraction was isolated from DL by ethanol precipitation and gel chromatography, and analyzed by nanoliter chromatography-mass spectrometry. Anti-RA effects of this active fraction was investigated by collagen-induced arthritis (CIA) in mice, and anti-RA mechanisms were verified in cocultured model of rat FLS and peripheral blood lymphocytes. RESULTS: We confirmed that CXCL10/CXCR3 was the main anti-RA target of DL. The active fraction - A (2182 - 890 Da) was isolated from DL based on its CXCL10 inhibiting effects in RA-FLS. Fraction A contains 195 peptides (192 were newly discovered), 26 of which might be bioactive and were considered to be the chemical basis of its anti-RA effects. Fraction A significantly ameliorated the joint destruction and overall inflammation in CIA mice, and downregulated CXCR3 expression in mice joint. Fraction A inhibited the chemotaxis of Th-cells in rat peripheral blood lymphocytes towards the TNF-α-induced rat FLS through CXCL10/CXCR3 pathway. CONCLUSIONS: Our work indicated that active fraction from DL containing small peptides exhibits promising therapeutic effects for RA through inhibiting CXCL10/CXCR3 chemotaxis.

Gut microbial metabolite targets HDAC3-FOXK1-interferon axis in fibroblast-like synoviocytes to ameliorate rheumatoid arthritis.

Rheumatoid arthritis (RA) is an autoimmune disease. Early studies hold an opinion that gut microbiota is environmentally acquired and associated with RA susceptibility. However, accumulating evidence demonstrates that genetics also shape the gut microbiota. It is known that some strains of inbred laboratory mice are highly susceptible to collagen-induced arthritis (CIA), while the others are resistant to CIA. Here, we show that transplantation of fecal microbiota of CIA-resistant C57BL/6J mice to CIA-susceptible DBA/1J mice confer CIA resistance in DBA/1J mice. C57BL/6J mice and healthy human individuals have enriched B. fragilis than DBA/1J mice and RA patients. Transplantation of B. fragilis prevents CIA in DBA/1J mice. We identify that B. fragilis mainly produces propionate and C57BL/6J mice and healthy human individuals have higher level of propionate. Fibroblast-like synoviocytes (FLSs) in RA are activated to undergo tumor-like transformation. Propionate disrupts HDAC3-FOXK1 interaction to increase acetylation of FOXK1, resulting in reduced FOXK1 stability, blocked interferon signaling and deactivation of RA-FLSs. We treat CIA mice with propionate and show that propionate attenuates CIA. Moreover, a combination of propionate with anti-TNF etanercept synergistically relieves CIA. These results suggest that B. fragilis or propionate could be an alternative or complementary approach to the current therapies.

Itaconate reduces proliferation and migration of fibroblast-like synoviocytes and ameliorates arthritis models.

Fibroblast-like synoviocytes (FLS) play critical roles in rheumatoid arthritis (RA). Itaconate (ITA), an endogenous metabolite derived from the tricarboxylic acid (TCA) cycle, has attracted attention because of its anti-inflammatory, antiviral, and antimicrobial effects. This study evaluated the effect of ITA on FLS and its potential to treat RA. ITA significantly decreased FLS proliferation and migration in vitro, as well as mitochondrial oxidative phosphorylation and glycolysis measured by an extracellular flux analyzer. ITA accumulates metabolites including succinate and citrate in the TCA cycle. In rats with type II collagen-induced arthritis (CIA), intra-articular injection of ITA reduced arthritis and bone erosion. Irg1-deficient mice lacking the ability to produce ITA had more severe arthritis than control mice in the collagen antibody-induced arthritis. ITA ameliorated CIA by inhibiting FLS proliferation and migration. Thus, ITA may be a novel therapeutic agent for RA.

[Sinomenine inhibits PDGF/PDGFR signaling pathway to reduce RA-FLS migration induced by NETs].

This study aims to decipher the mechanism of sinomenine in inhibiting platelet-derived growth factor/platelet-derived growth factor receptor(PDGF/PDGFR) signaling pathway in rheumatoid arthritis-fibroblast-like synoviocyte(RA-FLS) migration induced by neutrophil extracellular traps(NETs). RA-FLS was isolated from the synovial tissue of 3 RA patients and cultured. NETs were extracted from the peripheral venous blood of 4 RA patients and 4 healthy control(HC). RA-FLS was classified into control group, HC-NETs group, RA-NETs group, RA-NETs+sinomenine group and RA-NETs+sinomenine+CP-673451 group. RNA-sequencing(RNA-seq) was conducted to identify the differentially expressed genes between HC-NETs and RA-NETs groups. Sangerbox was used to perform the Gene Ontology(GO) function and the Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment. Cytoscape was employed to build the protein-protein interaction(PPI) network. AutoDock Vina and PyMOL were used for molecular docking of sinomenine with PDGFß and PDGFRß. The cell proliferation and migration were determined by the cell counting kit-8(CCK-8) and cell scratch assay, respectively. Western blot was employed to determine the protein level of PDGFRß. Real-time quantitative polymerase chain reaction(RT-qPCR) was carried out to determine the mRNA levels of matrix metalloproteinases(MMPs). The results revealed that neutrophils in RA patients were more likely to produce NETs. Compared with HC-NETs group, RA-NETs group showed up-regulated expression of PDGFß and PDGFRß. Compared with control group, RA-NETs group showed increased cell proliferation and migration and up-regulated protein level of PDGFRß and mRNA levels of PDGFß, PDGFRß, MMP1, MMP3, and MMP9(P<0.05). Compared with RA-NETs group, RA-NETs+sinomenine group presented decreased cell proliferation and migration and down-regulated protein and mRNA level of PDGFRß and mRNA levels of MMP1, MMP3, and MMP9(P<0.05). Compared with RA-NETs+sinomenine group, the proliferation ability of RA-NETs+sinomenine+CP-673451 group decreased(P<0.05). The findings prove that sinomenine reduces the RA-NETs-induced RA-FLS migration by inhibiting PDGF/PDGFR signaling pathway, thus mitigating RA.