The protective effect of myricitrin in osteoarthritis: An in vitro and in vivo study

Natural products in osteoarthritis treatment: bridging basic research to clinical applications

Osteoarthritis (OA) is the most prevalent degenerative musculoskeletal disease, severely impacting the function of patients and potentially leading to disability, especially among the elderly population. Natural products (NPs), obtained from components or metabolites of plants, animals, microorganisms etc., have gained significant attention as important conservative treatments for various diseases. Recently, NPs have been well studied in preclinical and clinical researches, showing promising potential in the treatment of OA. In this review, we summed up the main signaling pathways affected by NPs in OA treatment, including NF-κB, MAPKs, PI3K/AKT, SIRT1, and other pathways, which are related to inflammation, anabolism and catabolism, and cell death. In addition, we described the therapeutic effects of NPs in different OA animal models and the current clinical studies in OA patients. At last, we discussed the potential research directions including in-depth analysis of the mechanisms and new application strategies of NPs for the OA treatment, so as to promote the basic research and clinical transformation in the future. We hope that this review may allow us to get a better understanding about the potential bioeffects and mechanisms of NPs in OA therapy, and ultimately improve the effectiveness of NPs-based clinical conservative treatment for OA patients.

An auxiliary diagnostic technology and clinical efficacy evaluation in knee osteoarthritis based on serum surface-enhanced Raman spectroscopy

Knee osteoarthritis (KOA), a progressive joint disease, is a leading source of chronic pain and disability, and its diagnosis mainly depends on medical imaging findings and clinical symptoms. This study aimed to explore an auxiliary diagnostic technology and clinical efficacy evaluation in KOA based on surface-enhanced Raman scattering (SERS). Three sequential experiments were performed: 1) preliminary observation of the therapeutic effects of icariin (ICA); 2) using serum SERS spectra obtained from rat models belonging to sham group, KOA group and icariin treatment group, respectively, to analyze the KOA-related expression profiles; 3) employing partial least squares (PLS) and support vector machines (SVM) algorithms to establish KOA diagnosis model. Pathological changes verified the efficacy of icariin in KOA. Raman peak assignment combined with spectral difference analysis reflected the biochemical changes associated with KOA, including amino acid, carbohydrates and collagen. ICA intervention significantly reversed these changes, although full recovery could not be achieved. Based on PLS-SVM approach, the sensitivity, specificity and accuracy of 100%, 98.33% and 98.89%, respectively, were obtained for screening KOA. This work proves that SERS has great potential to be used as an auxiliary diagnostic technology for KOA, and is also helpful for the exploration of novel KOA treatment agent.

A Study on the Interactions of Proteinase K with Myricetin and Myricitrin by Multi-Spectroscopy and Molecular Modeling

Myricetin (MYR) and myricitrin (MYT) are well recognized for their nutraceutical value, such as antioxidant, hypoglycemic, and hypotensive effects. In this work, fluorescence spectroscopy and molecular modeling were adopted to investigate the conformational and stability changes of proteinase K (PK) in the presence of MYR and MYT. The experimental results showed that both MYR and MYT could quench fluorescence emission via a static quenching mechanism. Further investigation demonstrated that both hydrogen bonding and van der Waals forces play significant roles in the binding of complexes, which is consistent with the conclusions of molecular modeling. Synchronous fluorescence spectroscopy, Förster resonance energy transfer, and site-tagged competition experiments were performed to prove that the binding of MYR or MYT to PK could alter its micro-environment and conformation. Molecular docking results revealed that either MYR or MYT spontaneously interacted with PK at a single binding site via hydrogen bonding and hydrophobic interactions, which is consistent with the results of spectroscopic measurements. A 30 ns molecular dynamics simulation was conducted for both PK-MYR and PK-MYT complexes. The calculation results showed that no large structural distortions or interaction changes occurred during the entire simulation time span. The average RMSD changes of PK in PK-MYR and PK-MYT were 2.06 and 2.15 Å, respectively, indicating excellent stability of both complexes. The molecular simulation results suggested that both MYR and MYT could interact with PK spontaneously, which is in agreement with spectroscopic results. This agreement between experimental and theoretical results indicates that the method herein could be feasible and worthwhile for protein–ligand complex studies.

Connection between Osteoarthritis and Nitric Oxide: From Pathophysiology to Therapeutic Target

Osteoarthritis (OA), a disabling joint inflammatory disease, is characterized by the progressive destruction of cartilage, subchondral bone remodeling, and chronic synovitis. Due to the prolongation of the human lifespan, OA has become a serious public health problem that deserves wide attention. The development of OA is related to numerous factors. Among the factors, nitric oxide (NO) plays a key role in mediating this process. NO is a small gaseous molecule that is widely distributed in the human body, and its synthesis is dependent on NO synthase (NOS). NO plays an important role in various physiological processes such as the regulation of blood volume and nerve conduction. Notably, NO acts as a double-edged sword in inflammatory diseases. Recent studies have shown that NO and its redox derivatives might be closely related to both normal and pathophysiological joint conditions. They can play vital roles as normal bone cell-conditioning agents for osteoclasts, osteoblasts, and chondrocytes. Moreover, they can also induce cartilage catabolism and cell apoptosis. Based on different conditions, the NO/NOS system can act as an anti-inflammatory or pro-inflammatory agent for OA. This review summarizes the studies related to the effects of NO on all normal and OA joints as well as the possible new treatment strategies targeting the NO/NOS system.

The protective activity of natural flavonoids against osteoarthritis by targeting NF-κB signaling pathway

Osteoarthritis (OA) is a typical joint disease associated with chronic inflammation. The nuclear factor-kappaB (NF-κB) pathway plays an important role in inflammatory activity and inhibiting NF-κB-mediated inflammation can be a potential strategy for treating OA. Flavonoids are a class of naturally occurring polyphenols with anti-inflammatory properties. Structurally, natural flavonoids can be divided into several sub-groups, including flavonols, flavones, flavanols/catechins, flavanones, anthocyanins, and isoflavones. Increasing evidence demonstrates that natural flavonoids exhibit protective activity against the pathological changes of OA by inhibiting the NF-κB signaling pathway. Potentially, natural flavonoids may suppress NF-κB signaling-mediated inflammatory responses, ECM degradation, and chondrocyte apoptosis. The different biological actions of natural flavonoids against the NF-κB signaling pathway in OA chondrocytes might be associated with the differentially substituted groups on the structures. In this review, the efficacy and action mechanism of natural flavonoids against the development of OA are discussed by targeting the NF-κB signaling pathway. Potentially, flavonoids could become useful inhibitors of the NF-κB signaling pathway for the therapeutic management of OA.

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

Objective: To explore the effect and underlying mechanism of Myricitrin (Myr) in regulating fibroblast-like synoviocyte (FLS)-mediated synovitis and joint destruction in RA.

Methods: FLSs were isolated from synovial tissues from patients with RA. Gene expression was measured using quantitative RT-qPCR. Protein expression was detected by immunohistochemistry or Western blot. Cell apoptosis was performed by an Annexin-PI staining assay. EdU incorporation was used to assess the proliferation of RA FLS. Transwell assay was used to characterize the cell migration and invasion ability of RA FLS. The potential target of Myr was identified by RNA sequencing analysis. The in vivo effect of Myr was assessed in a collagen-induced arthritis (CIA) model.

Results: Myr treatment inhibited the lamellipodia formation, migration, and invasion, but not the apoptosis and proliferation, of RA FLSs. Myr also reduced the expression of CCL2, IL-6, IL-8, MMP-1, MMP-3, and MMP-13 induced by TNF-α. The RNA-seq results indicated that AIM2 may be a target gene of Myr in RA FLSs. Furthermore, compared to healthy controls, AIM2 expression showed higher levels in synovial tissues and FLSs from RA patients. AIM2 knockdown also inhibited RA FLS migration, invasion, cytokine, and MMP expression. In addition, either Myr treatment or AIM2 knockdown reduced the phosphorylation of AKT induced by TNF-α stimulation. Importantly, Myr administration relieved arthritis symptoms and inhibited AIM2 expression in the synovium of CIA mice.

Conclusion: Our results indicate that Myr exerts an anti-inflammatory and anti-invasion effect in RA FLSs and provide evidence of the therapeutic potential of Myr for RA.

The Protective Effect of Evodiamine in Osteoarthritis: An In Vitro and In Vivo Study in Mice Model

Osteoarthritis (OA) is a chronic disease with high economic burden characterized by cartilage degradation and joint inflammation. Evodiamine (EV), which can be extracted from Evodia rutaecarpa (Rutaceae), is a traditional Chinese medicine to treat inflammation, cardiovascular disorders, infection, and obesity. Studies have shown that EV can suppress the activation of immune cells and restrain the secretion of pro-inflammatory cytokines. However, it is still not well known about its role in the treatment of OA. In this study, we utilized interleukin-1β (IL-1β)–stimulated mouse chondrocytes in vitro and the destabilization of the medial meniscus (DMM) model in vivo to demonstrate the anti-inflammatory properties of EV in OA. The results suggested that EV decreased the generation of NO, IL-6, TNF-α, and PGE2. Meanwhile, the increased expression of iNOS, COX-2, and MMP-13 and the degradation of aggrecan and Col-II were significantly alleviated by EV in IL-1β–activated mouse chondrocytes. Moreover, EV can inhibit the considerable IL-1β–stimulated phosphorylation of the NF-κB signaling pathway and nuclear translocation of p65, compared with the control group. Furthermore, EV alleviated cartilage degeneration and reversed the increased Osteoarthritis Research Society International (OARSI) scores in the OA model in vivo. Our study demonstrates that EV can suppress inflammation in vitro and cartilage degeneration in vivo in OA, which implies that EV may be a potential candidate for the treatment of OA.

Shikonin, a promising therapeutic drug for osteoarthritis that acts via autophagy activation

Osteoarthritis (OA) is a chronic joint degenerative disease characterised by narrowed articular space, formation of surrounding osteophytes, and subchondral bone sclerosis. OA is caused by cartilage degeneration, which is closely correlated with the disequilibrium of anabolism and catabolism in chondrocytes. Previous studies have revealed that autophagy plays a significant role in maintaining the balance of anabolic and catabolic activities. Thus, targeting autophagy may be a promising therapeutic strategy for OA. Shikonin, a traditional Chinese herbal medicine isolated from flavonoid glucuronide, has drawn focus for its role in activating autophagy. In this study, the mRNA and protein level of a disintegrin and metalloproteinase with thrombospondin motifs-5 and matrix metalloproteinases-1 decreased with shikonin treatment, in the IL-1β-induced OA cell model. On the contrary, IL-1β-induced downregulation of Aggrecan and Collagen II was ameliorated following shikonin treatment. In addition, the upregulation of autophagy-related marker genes Beclin-1 and LC3II/LC3I in chondrocytes indicated that autophagy could be activated upon shikonin treatment. Moreover, shikonin's promotion of anabolism in chondrocytes through autophagy activation corresponded with the results from the examination using chloroquine, an autophagy inhibitor. OA mouse cartilage tissues were stained with safranin O and fast green dyes. Results were analysed using the Osteoarthritis Research Society International (OARSI) score, and suggested that mice cartilage degeneration was alleviated after shikonin treatment. Altogether, we identified that shikonin might be a novel promising drug for OA treatment.

Feature-Based Molecular Network-Guided Dereplication of Natural Bioactive Products from Leaves of Stryphnodendron pulcherrimum (Willd.) Hochr

Stryphnodendron pulcherrimum is a species known to have a high content of tannins. Accordingly, its preparations are used in southern Pará, Brazil, for their anti-inflammatory and antimicrobial activities, but so far, its chemical profile composition remains essentially unknown. We herein describe the compounds present in a hydro-acetonic extract from S. pulcherrimum leaves as revealed by dereplication via ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry. The data were combined with spectral organization, spectral matching through the Global Natural Products Social platform, in silico annotation and taxonomical ponderation. Several types of phenolic compounds were identified such as gallic acids, flavan-3-ols and flavone-like compounds. From these, 5 have been recently reported by our group, whereas 44 are reported here for the first time in this tree species, and 41 (out of 49) for this genus. The results highlight the possible role of Stryphnodendron pulcherrimum as a renewable source for natural bioactive products with potential pharmaceutical applications.

Myricitrin pretreatment ameliorates mouse liver ischemia reperfusion injury

BACKGROUND

Myricitrin has been reported to exert protective effects on liver diseases, but the protective effects of myricitrin against liver ischemia reperfusion (I/R) injury and the underlying mechanisms remain unexplored. This study aimed to investigate the effects of myricitrin on liver I/R injury and elucidate the underlying mechanisms.

METHODS

Mice were pretreated with myricitrin before liver I/R injury modeling. The mice were pretreated with either myricitrin or vehicle prior to liver ischemia. Some mice were further pretreated with the PI3K inhibitor LY294002. Liver tissues and blood samples were collected after 6 h of reperfusion. The degree of liver damage was determined by the serum levels of alanine aminotransferase (ALT), aspartate transaminase (AST), and lactic dehydrogenase (LDH) and histological examinations. The tumour necrosis factor-α (TNF-α), interleukin--1β (IL-1β), IL-4 and IL-10 expression levels were assessed by qRT-PCR and enzyme-linked immunosorbent assays (ELISAs). Serum superoxide dismutase (SOD) activity, catalase (CAT) activity, and contents of malondialdehyde (MDA), glutathione (GSH) and nitric oxide (NO) contents were measured. Western blotting and caspase-3 activity were conducted to determine the effect of myricitrin on apoptosis. The expression levels of proliferation related genes (Cyclin D1 and Cyclin E1) were determined by qRT-PCR and western-blotting. The expression of p-Akt, p-mTOR and p-eNOS in liver tissue were investigated by western-blotting.

RESULTS

Myricitrin not only significantly decreased the ALT, AST and LDH levels but also reduced the necrotic areas in the liver tissue compared with liver I/R injury group. In addition, myricitrin pretreatment alleviated liver injury by inhibiting the inflammatory response and suppressing oxidative stress. Western blotting and caspase-3 activity revealed that myricitrin inhibited liver I/R induced-apoptosis. Myricitrin promoted hepatocyte proliferation following liver I/R injury by upregulating the expression levels of Cyclin D1 and Cyclin E1. Further experiments indicated that the myricitrin pretreatment increased nitric oxide (NO) production by activating the PI3K/Akt signaling pathway. However, myricitrin triggered the hepatocyte proliferation and NO synthase activation was blocked by LY294002.

CONCLUSION

These results demonstrate that myricitrin alleviates liver I/R injury by suppressing oxidative stress, the inflammatory response, and apoptosis, improving liver proliferation and upregulating p-eNOS expression.