Tangeretin suppresses osteoarthritis progression via the Nrf2/NF-κB and MAPK/NF-κB signaling pathways

Phytochemistry, pharmacological properties and pharmacokinetics of Citri Reticulatae Pericarpium: A systematic review

ETHNOPHARMACOLOGICAL RELEVANCE

Citri Reticulatae Pericarpium (CRP), known as Chen Pi in China, is the most commonly used medicine for regulating qi. As a traditional medicine, CRP has been extensively used in the clinical treatment of nausea, vomiting, cough and phlegm for thousands of years. It is mainly distributed in Guangdong, Sichuan, Fujian and Zhejiang in China. Due to its high frequency of use, many scholars have conducted a lot of research on it and the related chemical constituents it contains. In this review, the research progress on phytochemistry, pharmacology, pharmacokinetics and toxicology of CRP are summarized.

AIM OF THE REVIEW

The review aims to sort out the methods of extraction and purification, pharmacological activities and mechanisms of action, pharmacokinetics and toxicology of the chemical constituents in CRP, in order to elaborate the future research directions and challenges for the study of CRP and related chemical constituents.

MATERIALS AND METHODS

Valid and comprehensive relevant information was collected from China National Knowledge Infrastructure, Web of Science, PubMed and so on.

RESULTS

CRP contains a variety of compounds, of which terpenes, flavonoids and alkaloids are the main components, and they are also the primary bioactive components that play a pharmacological role. Flavonoids and terpenes are extracted and purified by aqueous and alcoholic extraction methods, assisted by ultrasonic and microwave extraction, in order to achieve higher yields with less resources. Pharmacological studies have shown that CRP possesses a variety of highly active chemical components and a wide range of pharmacological activities, including anti-tumor, anti-inflammatory, immunomodulatory, hepatoprotective, therapeutic for cardiovascular-related disorders, antioxidant, antibacterial, and neuroprotective effects.

CONCLUSIONS

There is a diversity in the chemical compositions of CRP, which have multiple biological activities and promising applications. However, the pharmacological activities of CRP are mainly dependent on the action of its chemical components, but the relationship between the structure of chemical components and the biological effects has not been thoroughly investigated, and therefore, the structure-activity relationship is an issue that needs to be elucidated urgently. In addition, the pharmacokinetic studies of the relevant components can be further deepened and the correlation studies between pharmacological effects and syndromes of TCM can be expanded to ensure the effectiveness and rationality of CRP for human use.

Liensinine inhibits IL-1β-stimulated inflammatory response in chondrocytes and attenuates papain-induced osteoarthritis in rats

Osteoarthritis (OA) is a joint disease caused by inflammation of cartilage and synovial tissue. Suppressing the process of inflammatory reaction and the generation of oxidative stress is an effective strategy to alleviate the progression of OA. Liensinine is one of the main components of lotus seeds, which has anti-hypertensive and anti-arrhythmia activities. In this study, we aimed to determine the anti-inflammatory effect of liensinine in an OA. Here, we found that liensinine significantly inhibited the inflammatory response of SW1353 cells and primary chondrocytes by inhibiting the release of inflammatory cytokines and oxidative stress. Moreover, we showed that liensinine was able to inhibit the activation of the NF-κB signaling pathway in IL-1β-induced SW1353 cells. Lastly, we found that liensinine significantly ameliorated cartilage damage and inflammatory response in papain-induced rats. Our study demonstrated a significant protective effect of liensinine against OA, which might be by inhibiting the activation of the NF-κB signaling pathway, and provide a new insight for the treatment of OA using liensinine.

Picroside II suppresses chondrocyte pyroptosis through MAPK/NF-κB/NLRP3 signaling pathway alleviates osteoarthritis

BACKGROUND

Picroside II (P-II) is the main bioactive constituent of Picrorhiza Kurroa, a traditional Chinese herb of interest for its proven anti-inflammatory properties. Its beneficial effects have been noted across several physiological systems, including the nervous, circulatory, and digestive, capable of treating a wide range of diseases. Nevertheless, the potential of Picroside II to treat osteoarthritis (OA) and the mechanisms behind its efficacy remain largely unexplored.

AIM

This study aims to evaluate the efficacy of Picroside II in the treatment of osteoarthritis and its potential molecular mechanisms.

METHODS

In vitro, we induced cellular inflammation in chondrocytes with lipopolysaccharide (LPS) and subsequently treated with Picroside II to assess protective effect on chondrocyte. We employed the Cell Counting Kit-8 (CCK-8) assay to assess the impact of Picroside II on cell viability and select the optimal Picroside II concentration for subsequent experiments. We explored the effect of Picroside II on chondrocyte pyroptosis and its underlying molecular mechanisms by qRT-PCR, Western blot (WB) and immunofluorescence. In vivo, we established the destabilization of the medial meniscus surgery to create an OA mouse model. The therapeutic effects of Picroside II were then assessed through Micro-CT scanning, Hematoxylin-eosin (H&E) staining, Safranin O-Fast Green (S&F) staining, immunohistochemistry and immunofluorescence.

RESULTS

In in vitro studies, toluidine blue and CCK-8 results showed that a certain concentration of Picroside II had a restorative effect on the viability of chondrocytes inhibited by LPS. Picroside II notably suppressed the expression levels of caspase-1, IL-18, and IL-1β, which consequently led to the reduction of pyroptosis. Moreover, Picroside II was shown to decrease NLRP3 inflammasome activation, via the MAPK/NF-κB signaling pathway. In vivo studies have shown that Picroside II can effectively reduce subchondral bone destruction and osteophyte formation in the knee joint of mice after DMM surgery.

CONCLUSIONS

Our research suggests that Picroside II can inhibit chondrocyte pyroptosis and ameliorate osteoarthritis progression by modulating the MAPK/NF-κB signaling pathway.

Natural products: A potential immunomodulators against inflammatory-related diseases

The incidence and prevalence of inflammatory-related diseases (IRDs) are increasing worldwide. Current approved treatments for IRDs in the clinic are combat against inhibiting the pro-inflammatory cytokines. Though significant development in the treatment in the IRDs has been achieved, the severe side effects and inefficiency of currently practicing treatments are endless challenge. Drug discovery from natural sources is efficacious over a resurgence and also natural products are leading than the synthetic molecules in both clinical trials and market. The use of natural products against IRDs is a conventional therapeutic approach since it is a reservoir of unique structural chemistry, accessibility and bioactivities with reduced side effects and low toxicity. In this review, we discuss the cause of IRDs, treatment of options for IRDs and the impact and adverse effects of currently practicing clinical drugs. As well, the significant role of natural products against various IRDs, the limitations in the clinical development of natural products and thus pave the way for development of natural products as immunomodulators against IRDs are also discussed.

Tangeretin alleviates inflammation and oxidative response induced by spinal cord injury by activating the Sesn2/Keap1/Nrf2 pathway

Spinal cord injury (SCI) is a severe disabling disease that is characterized by inflammation and oxidative reactions. Tangeretin has been shown to possess significant antioxidant and anti-inflammatory activities. The Keap1/Nrf2 pathway, downstream of the Sesn2 gene, is involved in regulating the inflammation and oxidative response. The main objective of this study was to investigate the effect of tangeretin on SCI and its possible mechanism through cell and animal models. A T9 clamp injury was used for the mouse model and the LPS-induced stimulation of BV-2 cells was used for the cell model. The improvement of motor function after SCI was assessed by open field, swimming, and footprint experiments. The morphological characteristics of mouse spinal cord tissue and the levels of INOS, Sesn2, TNF-α, Keap1, Nrf2, IL-10, and reactive oxygen species (ROS) in vivo and in vitro were measured by several methods including western blotting, qPCR, immunofluorescence, HE, and Nissl staining. In vivo data showed that tangeretin can improve motor function recovery and reduce neuron loss and injury size in mice with SCI. Simultaneously, the in vitro findings suggested that treatment of BV-2 cells with tangeretin after LPS stimulation reduced the production of inflammatory factors and ROS, and could convert BV-2 cells from the M1 to the M2 type. Furthermore, Sesn2 knockout suppressed Keap1/Nrf2, inflammatory factors, ROS levels, and the M1 to M2 transition. Tangeretin can alleviate the inflammation and oxidative response induced by SCI by activating the Sesn2/Keap1/Nrf2 pathway.

Elucidating Cyathula Officinals' mechanism in osteoarthritis treatment: Network pharmacology and empirical evidence on anti-inflammatory actions

In this study, we explored the therapeutic potential of Cyathula Officinals (CNX) in Knee Osteoarthritis (KOA) treatment. Utilizing network pharmacology and in vitro experiments, we identified active ingredients, action targets and pathways in CNX. Our analysis, integrating databases like TCMSP, SwissTarget Prediction, Genecards, CTD, STRING, and DAVID, highlighted 396 action targets and 283 disease targets, pinpointing 64 intersection genes linked to KOA. The significant involvement of the MAPK and NF-κB pathways in CNX's anti-inflammatory action was validated through qPCR, which might underlie CNX's efficacy in inhibiting chondrocyte apoptosis and IL-6 expression. These findings suggest CNX's potential in KOA management, offering insights for its clinical application.

Fisetin suppresses chondrocyte senescence and attenuates osteoarthritis progression by targeting sirtuin 6

Osteoarthritis (OA) is the most common type of arthritis and is an age-related joint disease that is particularly prevalent in subjects over 65 years old. The chronic rise of senescent cells has a close correlation with age-related diseases such as OA, and the senescence-associated secretory phenotype (SASP) is implicated in OA cartilage degeneration pathogenesis. Sirtuin 6 (SIRT6) is likely to be a key senescence-related regulator. Fisetin (FST) is a natural flavonol of the flavonoid family that is recommended as a senolytic drug to extend health and lifespan. However, the potential chondroprotective effects of FST on OA rats are largely unclarified. The aim of this study is to investigate the ameliorative effects of FST on OA joint cartilage and the relationship with SIRT6 and the detailed mechanisms from anti-inflammatory and anti-senescent perspectives. Rats were subjected to destabilization of the medial meniscus (DMM) surgery as a means of inducing the experimental OA model in vivo. Chondrocytes treated with IL-1β were utilized for mimicking the OA cell model in vitro. Intra-articular injection of FST, OSS_128,167 (OSS, SIRT6 inhibitor), and MDL800 (MDL, SIRT6 agonist) in vivo or administering them in IL-1β-induced rat chondrocytes in vitro were performed in order to determine the effects FST has on OA and the link with SIRT6. This study found SIRT6 level to be negatively correlated with OA severity. SIRT6 downregulation was validated in the joint cartilages of DMM rats and IL-1β-treated chondrocytes. It was also notably demonstrated that FST can activate SIRT6. Both the administration of FST and activation of SIRT6 using MDL were found to rescue cartilage erosion, decrease extracellular matrix (ECM) degradation, prevent cartilage from apoptosis, and improve detrimental senescence-related phenotype. The alleviative effects of FST against inflammation, ECM degradation, apoptosis, and senescence in IL-1β-stimulated chondrocytes were also confirmed. SIRT6 loss occurs in articular cartilage in OA pathogenesis, which is linked to aging. FST attenuates injury-induced aging-related phenotype changes in chondrocytes through the targeting of SIRT6.

Tangeretin Attenuates Cerebral Ischemia-Reperfusion-Induced Neuronal Pyroptosis by Inhibiting AIM2 Inflammasome Activation via Regulating NRF2

Pyroptosis is closely involved in the pathopoiesis of cerebral ischemia and reperfusion (I/R) injury which seriously dangers human's life. Studies report that tangeretin (TANG), which is enriched in the peel of Citrus reticulata, has neuroprotective effects. Here, we explored whether absent in melanoma 2 (AIM2) inflammasome-mediated pyroptosis is involved in the cerebral I/R injury and the protective mechanism of TANG against cerebral I/R injury. In this study, we found that TANG treatment effectively alleviated I/R-induced brain injury and inhibited neuronal pyroptosis in an in vivo mice model with middle cerebral artery occlusion/reperfusion (MCAO/R) injury and in an in vitro hippocampal HT22 cell model with oxygen-glucose deprivation and reoxygenation (OGD/R) injury. Furthermore, we found TANG inhibited cerebral I/R-induced neuronal AIM2 inflammasome activation in vivo and in vitro via regulating nuclear factor E2-related factor 2 (NRF2). Moreover, administration of ML385, a chemical inhibitor of NRF2, notably blocked the neuroprotective effects of TANG against cerebral I/R injury. In conclusion, TANG attenuates cerebral I/R-induced neuronal pyroptosis by inhibiting AIM2 inflammasome activation via regulating NRF2. These findings indicate TANG is a potential therapeutic agent for cerebral I/R injury.

Tangeretin attenuates acute lung injury in septic mice by inhibiting ROS-mediated NLRP3 inflammasome activation via regulating PLK1/AMPK/DRP1 signaling axis

OBJECTIVE

NLRP3 inflammasome-mediated pyroptosis of macrophage acts essential roles in the progression of sepsis-induced acute lung injury (ALI). Tangeretin (TAN), enriched in citrus fruit peel, presents anti-oxidative and anti-inflammatory effects. Here, we aimed to explore the potentially protective effect of TAN on sepsis-induced ALI, and the underlying mechanism of TAN in regulating NLRP3 inflammasome.

MATERIAL AND METHODS

The effect of TAN on sepsis-induced ALI and NLRP3 inflammasome-mediated pyroptosis of macrophage were examined in vivo and in vitro using a LPS-treated mice model and LPS-induced murine macrophages, respectively. The mechanism of TAN regulating the activation of NLRP3 inflammasome in sepsis-induced ALI was investigated with HE staining, Masson staining, immunofluorescent staining, ELISA, molecular docking, transmission electron microscope detection, qRT-PCR, and western blot.

RESULTS

TAN could evidently attenuate sepsis-induced ALI in mice, evidenced by reducing pulmonary edema, pulmonary congestion and lung interstitial fibrosis, and inhibiting macrophage infiltration in the lung tissue. Besides, TAN significantly suppressed inflammatory cytokine IL-1β and IL-18 expression in the serum or bronchoalveolar lavage fluid (BALF) samples of mice with LPS-induced ALI, and inhibited NLRP3 inflammasome-mediated pyroptosis of macrophages. Furthermore, we found TAN inhibited ROS production, preserved mitochondrial morphology, and alleviated excessive mitochondrial fission in LPS-induced ALI in mice. Through bioinformatic analysis and molecular docking, Polo-like kinase 1 (PLK1) was identified as a potential target of TAN for treating sepsis-induced ALI. Moreover, TAN significantly inhibited the reduction of PLK1 expression, AMP-activated protein kinase (AMPK) phosphorylation, and Dynamin related protein 1 (Drp1) phosphorylation (S637) in LPS-induced ALI in mice. In addition, Volasertib, a specific inhibitor of PLK1, abolished the protective effects of TAN against NLRP3 inflammasome-mediated pyroptosis of macrophage and lung injury in the cell and mice septic models.

CONCLUSION

TAN attenuates sepsis-induced ALI by inhibiting ROS-mediated NLRP3 inflammasome activation via regulating PLK1/AMPK/DRP1 signaling axis, and TAN is a potentially therapeutic candidate against ALI through inhibiting pyroptosis.

Capsicum annuum var. abbreviatum Induces a Macrophage M2-Like Phenotype Mediated by Nrf2/HO-1 in LPS-Stimulated Macrophages

Capsicum annuum var. abbreviatum (CAAE), which is in the genus Capsicum L. (Solanaceae), was found to be richer in polyphenols and flavonoids than other prevalent peppers of Capsicum annuum var. angulosum and Capsicum annuum. L. Yet, it is still unclear how CAAE reduces inflammation. In this study, we used the lipopolysaccharide-stimulated RAW264.7 macrophage cell line and bone marrow-derived macrophages to assess its anti-inflammatory activities. Initially, we discovered that CAAE decreased the levels of nitric oxide and inducible nitric oxide synthase. In addition, CAAE decreased the intracellular reactive oxygen species levels and increased the nuclear factor-erythroid 2-related factor 2 and heme oxygenase-1 compared with the phenotype of M2 macrophages. CAAE inhibited the activation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases, c-Jun N-terminal kinases, and p38 MAPKs. CAAE also inhibited the translocation of nuclear factor kappa B into nuclear, hence preventing the production of proinflammatory cytokines. Therefore, we suggest that CAAE might have potential as a candidate therapeutic agent for inflammatory diseases.

WGA-M001, a Mixture of Total Extracts of Tagetes erecta and Ocimum basilicum, Synergistically Alleviates Cartilage Destruction by Inhibiting ERK and NF-κB Signaling

Tagetes erecta and Ocimum basilicum are medicinal plants that exhibit anti-inflammatory effects against various diseases. However, their individual and combined effects on osteoarthritis (OA) are unknown. Herein, we aimed to demonstrate the effects of T. erecta, O. basilicum, and their mixture, WGA-M001, on OA pathogenesis. The administration of total extracts of T. erecta and O. basilicum reduced cartilage degradation and inflammation without causing cytotoxicity. Although WGA-M001 contained lower concentrations of the individual extracts, it strongly inhibited the expression of pathogenic factors. In vivo OA studies also supported that WGA-M001 had protective effects against cartilage destruction at lower doses than those of T. erecta and O. basilicum. Moreover, its effects were stronger than those observed using Boswellia and Perna canaliculus. WGA-M001 effectively inhibited the interleukin (IL)-1β-induced nuclear factor kappa-light-chain-enhancer of the activated B cell (NF-κB) pathway and ERK phosphorylation. Furthermore, RNA-sequence analysis also showed that WGA-M001 decreased the expression of genes related to the IL-1β-induced NF-κB and ERK signaling pathways. Therefore, WGA-M001 is more effective than the single total extracts of T. erecta and O. basilicum in attenuating OA progression by regulating ERK and NF-κB signaling. Our results open new possibilities for WGA-M001 as a potential therapeutic agent for OA treatment.

Silencing of STUB1 relieves osteoarthritis via inducing NRF2-mediated M2 macrophage polarization

OBJECTIVES

Shifting macrophages towards an anti-inflammatory state is key in treating osteoarthritis (OA) by reducing inflammation and tissue damage. However, the underlying mechanisms guiding this shift remain largely undefined. STUB1, an E3 ubiquitin ligase, known for its regulatory role in macrophage polarization. This study aims to explore the function and underlying action mechanisms of STUB1 in OA.

METHODS

An in vivo OA model was established in rats. Hematoxylin-Eosin and safranin O-fast green staining were performed to reveal the hispathological injuries in knee-joint tissues. Immunohistochemistry and flow cytometry were performed to detect the distribution of M1 and M2 macrophages. The inflammatory response (TNF-α and IL-6 levels) was evaluated by ELISA. In vitro, the interaction between STUB1 and NFR2 was determined by CO-IP and pull-down assays. After treated with LPS (an in vitro model of OA), the viability and apoptosis of chondrocytes were measured by CCK-8 and flow cytometry, respectively.

RESULTS

Silencing STUB1 alleviated OA in rats, as indicated by reduced subchondral bone thickness, knee synovitis score, histopathological damages, and inflammatory response. STUB1 silencing also decreased M1 macrophages and increased M2 macrophages in both in vivo and in vitro settings. NRF2 was identified as a target of STUB1, with STUB1 mediating its ubiquitination. Silencing NRF2 reversed the effects of STUB1 silencing on inducing M2 macrophage polarization. Furthermore, silencing STUB1 upregulated NRF2 expression in LPS-treated chondrocytes, promoting cell viability and inhibiting apoptosis.

CONCLUSION

Silencing STUB1 induces M2 macrophage polarization by inhibiting NRF2 ubiquitination, thereby contributing to the mitigation of OA.

Nrf2: A promising therapeutic target in bone-related diseases

Nuclear factor erythroid-2-related factor 2 (Nrf2) plays an important role in maintaining cellular homeostasis, as it suppresses cell damage caused by external stimuli by regulating the transcription of intracellular defense-related genes. Accumulating evidence has highlighted the crucial role of reduction-oxidation (REDOX) imbalance in the development of bone-related diseases. Nrf2, a transcription factor linked to nuclear factor-erythrocyte 2, plays a pivotal role in the regulation of oxidative stress and induction of antioxidant defenses. Therefore, further investigation of the mechanism and function of Nrf2 in bone-related diseases is essential. Considerable evidence suggests that increased nuclear transcription of Nrf2 in response to external stimuli promotes the expression of intracellular antioxidant-related genes, which in turn leads to the inhibition of bone remodeling imbalance, improved fracture recovery, reduced occurrence of osteoarthritis, and greater tumor resistance. Certain natural extracts can selectively target Nrf2, potentially offering therapeutic benefits for osteogenic arthropathy. In this article, the biological characteristics of Nrf2 are reviewed, the intricate interplay between Nrf2-regulated REDOX imbalance and bone-related diseases is explored, and the potential preventive and protective effects of natural products targeting Nrf2 in these diseases are elucidated. A comprehensive understanding of the role of Nrf2 in the development of bone-related diseases provides valuable insights into clinical interventions and can facilitate the discovery of novel Nrf2-targeting drugs.

Nrf2-mediated therapeutic effects of dietary flavones in different diseases

Oxidative stress (OS) is a pathological status that occurs when the body's balance between oxidants and antioxidant defense systems is broken, which can promote the development of many diseases. Nrf2, a redox-sensitive transcription encoded by NFE2L2, is the master regulator of phase II antioxidant enzymes and cytoprotective genes. In this context, Nrf2/ARE signaling can be a compelling target against OS-induced diseases. Recently, natural Nrf2/ARE regulators like dietary flavones have shown therapeutic potential in various acute and chronic diseases such as diabetes, neurodegenerative diseases, ischemia-reperfusion injury, and cancer. In this review, we aim to summarize nrf2-mediated protective effects of flavones in different conditions. Firstly, we retrospected the mechanisms of how flavones regulate the Nrf2/ARE pathway and introduced the mediator role Nrf2 plays in inflammation and apoptosis. Then we review the evidence that flavones modulated Nrf2/ARE pathway to prevent diseases in experimental models. Based on these literature, we found that flavones could regulate Nrf2 expression by mechanisms below: 1) dissociating the binding between Nrf2 and Keap1 via PKC-mediated Nrf2 phosphorylation and P62-mediated Keap1 autophagic degradation; 2) regulating Nrf2 nuclear translocation by various kinases like AMPK, MAPKs, Fyn; 3) decreasing Nrf2 ubiquitination and degradation via activating sirt1 and PI3K/AKT-mediated GSK3 inhibition; and 4) epigenetic alternation of Nrf2 such as demethylation at the promoter region and histone acetylation. In conclusion, flavones targeting Nrf2 can be promising therapeutic agents for various OS-related disorders. However, there is a lack of investigations on human subjects, and new drug delivery systems to improve flavones' treatment efficiency still need to be developed.

Ajugol's upregulation of TFEB-mediated autophagy alleviates endoplasmic reticulum stress in chondrocytes and retards osteoarthritis progression in a mouse model

BACKGROUND

Osteoarthritis (OA), a degenerative disease with a high global prevalence, is characterized by the degradation of the extracellular matrix (ECM) and the apoptosis of chondrocytes. Ajugol, a extract derived from the herb Rehmannia glutinosa, has not yet been investigated for its potential in modulating the development of OA.

METHODS

We employed techniques such as western blotting, immunofluorescence, immunohistochemistry, X-ray imaging, HE staining, and SO staining to provide biological evidence supporting the role of Ajugol as a potential therapeutic agent for modulating OA. Furthermore, in an in vivo experiment, intra-peritoneal injection of 50 mg/kg Ajugol effectively mitigated the progression of OA following destabilization of the medial meniscus (DMM) surgery.

RESULTS

Our findings revealed that treatment with 50 μM Ajugol activated TFEB-mediated autophagy, alleviating ER stress-induced chondrocyte apoptosis and ECM degradation caused by TBHP. Furthermore, in an in vivo experiment, intra-peritoneal injection of 50 mg/kg Ajugol effectively mitigated the progression of OA following destabilization of the medial meniscus (DMM) surgery.

CONCLUSION

These results provide compelling biological evidence supporting the role of Ajugol as a potential therapeutic agent for modulating OA by activating autophagy and attenuating ER stress-induced cell death and ECM degradation. The promising in vivo results further suggest the potential of Ajugol as a treatment strategy for OA progression.

Pharmacological activation of the Nrf2 pathway by Taxifolin remodels articular cartilage microenvironment for the therapy of Osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a widely prevalent degenerative disease marked by extracellular matrix (ECM) degradation, inflammation, and apoptosis. Taxifolin (TAX) is a natural antioxidant possessing various pharmacological benefits, such as combating inflammation, oxidative stress, apoptosis, and serves as a potential chemopreventive agent by regulating genes through an antioxidant response element (ARE)-dependent mechanism. Currently, no studies have investigated the therapeutic impact and precise mechanism of TAX on OA.

PURPOSE

The aim of this study is to examine the potential role and mechanism of TAX in reshaping the cartilage microenvironment, thereby offering a stronger theoretical foundation for pharmacologically activating the Nrf2 pathway to manage OA.

STUDY DESIGN AND METHODS

The pharmacological effects of TAX were examined in chondrocytes through in vitro studies and in a destabilization of the medial meniscus (DMM) rat model for in vivo analysis.

RESULTS

TAX suppresses IL-1β triggered secretion of inflammatory agents, chondrocyte apoptosis, and ECM degradation, contributing to the remodeling of the cartilage microenvironment. In vivo experiment results demonstrated that TAX counteracted cartilage degeneration induced by DMM in rats. Mechanistic investigations revealed that TAX hinders OA development by reducing NF-κB activation and ROS production through the activation of the Nrf2/HO-1 axis.

CONCLUSION

TAX reshapes the articular cartilage microenvironment by suppressing inflammation, mitigating apoptosis, and decreasing ECM degradation through the activation of the Nrf2 pathway. As a result, pharmacological activation of the Nrf2 pathway by TAX holds potential clinical significance in remodeling the joint microenvironment for OA treatment.

A Combination of Polymethoxyflavones from Citrus sinensis and Prenylflavonoids from Humulus lupulus Counteracts IL-1β-Induced Differentiated Caco-2 Cells Dysfunction via a Modulation of NF-κB/Nrf2 Activation

We here investigated the anti-inflammatory activity of a polymethoxylated flavone-containing fraction (PMFF) from Citrus sinensis and of a prenylflavonoid-containing one (PFF) from Humulus lupulus, either alone or in combination (MIX). To this end, an in vitro model of inflammatory bowel disease (IBD), consisting of differentiated, interleukin (IL)-1β-stimulated Caco-2 cells, was employed. We demonstrated that non-cytotoxic concentrations of either PMFF or PFF or MIX reduced nitric oxide (NO) production while PFF and MIX, but not PMFF, also inhibited prostaglandin E2 release. Coherently, MIX suppressed both inducible NO synthase and cyclooxygenase-2 over-expression besides NF-κB activation. Moreover, MIX increased nuclear factor erythroid 2-related factor 2 (Nrf2) activation, heme oxygenase-1 expression, restoring GSH and reactive oxygen and nitrogen species (RONs) levels. Remarkably, these effects with MIX were stronger than those produced by PMFF or PFF alone. Noteworthy, nobiletin (NOB) and xanthohumol (XTM), two of the most represented phytochemicals in PMFF and PFF, respectively, synergistically inhibited RONs production. Overall, our results demonstrate that MIX enhances the anti-inflammatory and anti-oxidative effects of the individual fractions in a model of IBD, via a mechanism involving modulation of NF-κB and Nrf2 signalling. Synergistic interactions between NOB and XTM emerge as a relevant aspect underlying this evidence.

Antioxidant Capacity and Protective Effects on H2O2-Induced Oxidative Damage in PC12 Cells of the Active Fraction of Brassica rapa L

Brassica rapa L. (BR), a traditional biennial herb belonging to the Brassica species of Brassicaceae, has been widely used for functions of anti-inflammatory, antitumor, antioxidation, antiaging, and regulation of immunity. In this study, antioxidant activity and protective effects on H2O2-induced oxidative damage in PC12 cells of the active fractions of BR were investigated in vitro. Among all active fractions, the ethyl acetate fraction of ethanol extract from BR (BREE-Ea) showed the strongest antioxidant activity. Additionally, it was noted that BREE-Ea and n-butyl alcohol fraction of ethanol extract from BR (BREE-Ba) both have protective effects in oxidatively damaged PC12 cells, while BREE-Ea displayed the best protective effect in all determined experimental doses. Furthermore, flow cytometry (DCFH-DA staining) analysis indicated that BREE-Ea could reduce the H2O2-induced apoptosis in PC12 cells by reducing the production of intracellular reactive oxygen species (ROS) and increasing enzymatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Moreover, BREE-Ea could decrease the malondialdehyde (MDA) content and reduce the release of extracellular lactic dehydrogenase (LDH) from H2O2-induced PC12 cells. All these results demonstrate that BREE-Ea has a good antioxidant capacity and protective effect on PC12 cells against apoptosis induced by H2O2 and that it can be used as a good edible antioxidant to improve the body's endogenous antioxidant defense.

Achyranthoside D attenuates chondrocyte loss and inflammation in osteoarthritis via targeted regulation of Wnt3a

BACKGROUND

Achyranthes bidentata Blume (A. bidentata) is a common Chinese herb used to treat osteoarthritis (OA). Achyranthoside D (Ach-D) is a glucuronide saponin isolated from A. bidentata.

PURPOSE

To assess the mechanisms of action of Ach-D and its effects on OA.

METHODS

The effects of Ach-D were evaluated in rats underwent anterior cruciate ligament transection (ACLT) with medial meniscectomy (MMx) and in interleukin (IL)-1β-induced chondrocytes. Histological changes in rat cartilage tissues were detected using Safranin O-Fast green and haematoxylin-eosin staining. Immunohistochemical staining, qRT-PCR, ELISA, immunoblotting, and immunofluorescence were conducted to examine cartilage degeneration-related and inflammation-related factor expression. CCK-8, LDH assay, and EdU staining were performed to detect chondrocyte death.

RESULTS

Ach-D dose-dependently reduced the Osteoarthritis Research Society International (OARSI) scores, alleviated cartilage injury, and decreased the serum concentrations of CTX-II and COMP in ACLT-MMx models. Ach-D increased the expression levels of collagen II and aggrecan and decreased the levels of cartilage degeneration-related proteins, ADAMTS-5, MMP13, and MMP3, in rat cartilage tissues. Additionally, nod-like receptor protein 3 (NLRP3)-related inflammation was reduced by Ach-D, as shown by the significantly inhibited expression levels of NLRP3, ASC, GSDMD, IL-6, TNF-α, IL-1β, and IL-18 in rat cartilage tissues. In primary rat chondrocytes, Ach-D protected against IL-1β-induced viability loss and LDH release. Wnt3a is the target protein of Ach-D. Mechanistically, Ach-D alleviated OA by inhibiting Wnt signalling.

CONCLUSION

ACH-D may reduce inflammation and cartilage degeneration by inhibiting the Wnt signalling pathway, thereby reducing OA.

Cyasterone inhibits IL-1β-mediated apoptosis and inflammation via the NF-κB and MAPK signaling pathways in rat chondrocytes and ameliorates osteoarthritisin vivo

Osteoarthritis is a prevalent global joint disease, which is characterized by inflammatory reaction and cartilage degradation. Cyasterone, a sterone derived from the roots of Cyathula officinalis Kuan, exerts protective effect against several inflammation-related diseases. However, its effect on osteoarthritis remains unclear. The current study was designed to investigate the potential anti-osteoarthritis activity of cyasterone. Primary chondrocytes isolated from rats induced by interleukin (IL)-1β and a rat model stimulated by monosodium iodoacetate (MIA) were used for in vitro and in vivo experiments, respectively. The results of in vitro experiments showed that cyasterone apparently counteracted chondrocyte apoptosis, increased the expression of collagen II and aggrecan, and restrained the production of the inflammatory factors inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5), metalloproteinase-3 (MMP-3), and metalloproteinase-13 (MMP-13) induced by IL-1β in chondrocytes. Furthermore, cyasterone ameliorated the inflammation and degenerative progression of osteoarthritis potentially by regulating the nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. For in vivo experiments, cyasterone significantly alleviated the inflammatory response and cartilage destruction of rats induced by monosodium iodoacetate, where dexamethasone was used as the positive control. Overall, this study laid a theoretical foundation for developing cyasterone as an effective agent for the alleviation of osteoarthritis.

Overview of Anti-Inflammatory and Anti-Nociceptive Effects of Polyphenols to Halt Osteoarthritis: From Preclinical Studies to New Clinical Insights

Knee osteoarthritis (OA) is one of the most multifactorial joint disorders in adults. It is characterized by degenerative and inflammatory processes that are responsible for joint destruction, pain and stiffness. Despite therapeutic advances, the search for alternative strategies to target inflammation and pain is still very challenging. In this regard, there is a growing body of evidence for the role of several bioactive dietary molecules (BDMs) in targeting inflammation and pain, with promising clinical results. BDMs may be valuable non-pharmaceutical solutions to treat and prevent the evolution of early OA to more severe phenotypes, overcoming the side effects of anti-inflammatory drugs. Among BDMs, polyphenols (PPs) are widely studied due to their abundance in several plants, together with their benefits in halting inflammation and pain. Despite their biological relevance, there are still many questionable aspects (biosafety, bioavailability, etc.) that hinder their clinical application. This review highlights the mechanisms of action and biological targets modulated by PPs, summarizes the data on their anti-inflammatory and anti-nociceptive effects in different preclinical in vitro and in vivo models of OA and underlines the gaps in the knowledge. Furthermore, this work reports the preliminary promising results of clinical studies on OA patients treated with PPs and discusses new perspectives to accelerate the translation of PPs treatment into the clinics.

Zhuifeng tougu capsules inhibit the TLR4/MyD88/NF-κB signaling pathway and alleviate knee osteoarthritis: In vitro and in vivo experiments

Background: Knee osteoarthritis (KOA), a chronic degenerative disease, is mainly characterized by destruction of articular cartilage and inflammatory reactions. At present, there is a lack of economical and effective clinical treatment. Zhuifeng Tougu (ZFTG) capsules have been clinically approved for treatment of OA as they relieve joint pain and inflammatory manifestations. However, the mechanism of ZFTG in KOA remains unknown.

Purpose: This study aimed to investigate the effect of ZFTG on the TLR4/MyD88/NF-κB signaling pathway and its therapeutic effect on rabbits with KOA.

Study design:In vivo, we established a rabbit KOA model using the modified Videman method. In vitro, we treated chondrocytes with IL-1β to induce a pro-inflammatory phenotype and then intervened with different concentrations of ZFTG. Levels of IL-1β, IL-6, TNF-α, and IFN-γ were assessed with histological observations and ELISA data. The effect of ZFTG on the viability of chondrocytes was detected using a Cell Counting Kit-8 and flow cytometry. The protein and mRNA expressions of TLR2, TLR4, MyD88, and NF-κB were detected using Western blot and RT-qPCR and immunofluorescence observation of NF-κB p65 protein expression, respectively, to investigate the mechanism of ZFTG in inhibiting inflammatory injury of rabbit articular chondrocytes and alleviating cartilage degeneration.

Results: The TLR4/MyD88/NF-κB signaling pathway in rabbits with KOA was inhibited, and the levels of IL-1β, IL-6, TNF-α, and IFN-γ in blood and cell were significantly downregulated, consistent with histological results. Both the protein and mRNA expressions of TLR2, TLR4, MyD88, NF-κB, and NF-κB p65 proteins in that nucleus decreased in the ZFTG groups. Moreover, ZFTG promotes the survival of chondrocytes and inhibits the apoptosis of inflammatory chondrocytes.

Conclusion: ZFTG alleviates the degeneration of rabbit knee joint cartilage, inhibits the apoptosis of inflammatory chondrocytes, and promotes the survival of chondrocytes. The underlying mechanism may be inhibition of the TLR4/MyD88/NF-kB signaling pathway and secretion of inflammatory factors.

Saikosaponin D Inhibited IL-1β Induced ATDC 5 Chondrocytes Apoptosis In Vitro and Delayed Articular Cartilage Degeneration in OA Model Mice In Vivo

Osteoarthritis (OA) is the most common joint disease in the elderly, characterized by cartilage degradation and proliferation of subchondral bone. The pathogenesis of OA involves a variety of inflammatory mediators, including nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β. From the molecular mechanism, the nuclear factor-erythroid 2-related factor (Nrf2)/heme oxygenase-1 (HO-1) pathway and the expression of ROS regulated the production of the above inflammatory mediators. Saikosaponin D (SSD), which is an active ingredient isolated from Bupleurum, has various biological functions. In this study, IL-1β was used as a pro-inflammatory factor to create an in vitro OA model. According to the results of high-density culture, qPCR, ROS measurement, Western blot, and immunofluorescence, SSD activated the Nrf2/HO-1/ROS axis, inhibited the production of inflammatory mediators, and protected against ECM destruction. The DMM mouse model was used as a model of OA in mice. From the results of safranin O/fast green staining, hematoxylin–eosin staining, tartrate-resistant acid phosphatase (TRAP) staining, and OARSI scores, SSD protected against the mice knee articular cartilage degeneration and reduced the number of osteoclasts in the subchondral bone. Experimental results found that SSD suppressed IL-1β–induced differentiated ATDC 5 chondrocytes apoptosis via the Nrf2/HO-1/ROS axis in vitro. SSD delayed the progression of OA in DMMs model mice in vivo. Therefore, SSD has the potential to become a drug for clinical treatment of OA.