Limonin Inhibits IL-1β-Induced Inflammation and Catabolism in Chondrocytes and Ameliorates Osteoarthritis by Activating Nrf2

The Multifaceted Protective Role of Nuclear Factor Erythroid 2-Related Factor 2 in Osteoarthritis: Regulation of Oxidative Stress and Inflammation

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by the degradation of joint cartilage, subchondral bone sclerosis, synovitis, and structural changes in the joint. Recent research has highlighted the role of various genes in the pathogenesis and progression of OA, with nuclear factor erythroid 2-related factor 2 (NRF2) emerging as a critical player. NRF2, a vital transcription factor, plays a key role in regulating the OA microenvironment and slowing the disease's progression. It modulates the expression of several antioxidant enzymes, such as Heme oxygenase-1 (HO-1) and NAD(P)H oxidoreductase 1 (NQO1), among others, which help reduce oxidative stress. Furthermore, NRF2 inhibits the nuclear factor kappa-B (NF-κB) signaling pathway, thereby decreasing inflammation, joint pain, and the breakdown of cartilage extracellular matrix, while also mitigating cell aging and death. This review discusses NRF2's impact on oxidative stress, inflammation, cell aging, and various cell death modes (such as apoptosis, necroptosis, and ferroptosis) in OA-affected chondrocytes. The role of NRF2 in OA macrophages, and synovial fibroblasts was also discussed. It also covers NRF2's role in preserving the cartilage extracellular matrix and alleviating joint pain. The purpose of this review is to provide a comprehensive understanding of NRF2's protective mechanisms in OA, highlighting its potential as a therapeutic target and underscoring its significance in the development of novel treatment strategies for OA.

Machine learning algorithm-based biomarker exploration and validation of mitochondria-related diagnostic genes in osteoarthritis

The role of mitochondria in the pathogenesis of osteoarthritis (OA) is significant. In this study, we aimed to identify diagnostic signature genes associated with OA from a set of mitochondria-related genes (MRGs). First, the gene expression profiles of OA cartilage GSE114007 and GSE57218 were obtained from the Gene Expression Omnibus. And the limma method was used to detect differentially expressed genes (DEGs). Second, the biological functions of the DEGs in OA were investigated using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Wayne plots were employed to visualize the differentially expressed mitochondrial genes (MDEGs) in OA. Subsequently, the LASSO and SVM-RFE algorithms were employed to elucidate potential OA signature genes within the set of MDEGs. As a result, GRPEL and MTFP1 were identified as signature genes. Notably, GRPEL1 exhibited low expression levels in OA samples from both experimental and test group datasets, demonstrating high diagnostic efficacy. Furthermore, RT-qPCR analysis confirmed the reduced expression of Grpel1 in an in vitro OA model. Lastly, ssGSEA analysis revealed alterations in the infiltration abundance of several immune cells in OA cartilage tissue, which exhibited correlation with GRPEL1 expression. Altogether, this study has revealed that GRPEL1 functions as a novel and significant diagnostic indicator for OA by employing two machine learning methodologies. Furthermore, these findings provide fresh perspectives on potential targeted therapeutic interventions in the future.

SNORC knockdown alleviates inflammation, autophagy defect and matrix degradation of chondrocytes in osteoarthritis development

Excessive inflammation and autophagy defect of chondrocytes play important roles in the pathological process of osteoarthritis (OA). The present study aimed to clarify the roles of small novel rich in cartilage (SNORC) in these pathological changes of chondrocytes in OA. Bioinformatics analysis of GEO dataset GSE207881 displayed that SNORC was a potential biomarker for OA. As confirmed by quantitative real-time PCR, immunohistochemical staining and western blotting, SNORC was significantly up-regulated in cartilage of OA rat model and interleukin (IL)-1β-stimulated primary rat articular chondrocytes in contrast to their corresponding normal control. Knocking down SNORC in IL-1β-induced chondrocytes obviously suppressed the production of nitric oxide (NO), IL-6, tumor necrosis factor (TNF)-α and prostaglandin E2 (PGE2) to alleviate inflammation, and reduced the protein levels of a disintegrin and metalloproteinase with thrombospondin 5 (ADAMTS5) and matrix metallopeptidase (MMP)13 and elevated collagen type 2 alpha 1 (COL2A1) level to improve matrix degradation. Down-regulation of SNORC increased Beclin1 expression and LC3II/LC3I ratio, but suppressed p62 expression to restore impaired autophagy in IL-1β-induced chondrocytes. Moreover, down-regulating SNORC mitigated mitochondrial dysfunction and apoptosis in IL-1β-stimulated chondrocytes. Mechanically, SNORC simultaneously activated the phosphatidylinositol-3-kinase/serine threonine kinase (PI3K/AKT) and c-Jun N-terminal kinase (JNK)/c-Jun signaling pathway in the IL-1β-induced chondrocyte, while re-activating the PI3K and JNK signals abolished the suppressive effect of down-regulating SNORC on IL-1β-induced chondrocyte damage. In a word, SNORC knockdown alleviates inflammation, matrix degradation, autophagy defect and excessive apoptosis of chondrocytes during OA development via suppressing the PI3K and JNK signaling pathway.

SP1‑mediated ADAMTS5 transcription promotes IL‑1β‑induced chondrocyte injury via Wnt/β‑catenin pathway in osteoarthritis

Osteoarthritis (OA) is a chronic disease that involves chondrocyte injury. ADAMTS5 has been confirmed to mediate chondrocyte injury and thus regulate OA progression, but its underlying molecular mechanisms remain unclear. In the present study, interleukin‑1β (IL‑1β)‑induced chondrocytes were used to mimic OA in vitro. Cell proliferation and apoptosis were assessed by MTT assay, EdU assay and flow cytometry, and protein levels of ADAMTS5, specificity protein 1 (SP1), matrix‑related markers and Wnt/β‑catenin pathway‑related markers were examined using western blotting. In addition, ELISA was performed to measure the concentrations of inflammation factors, and oxidative stress was evaluated by detecting SOD activity and MDA levels. The mRNA expression levels of ADAMTS5 and SP1 were determined by reverse transcription‑quantitative PCR, and the interaction between SP1 and ADAMTS5 was analyzed using a dual‑luciferase reporter assay and chromatin immunoprecipitation assay. IL‑1β suppressed proliferation, but promoted apoptosis, extracellular matrix degradation, inflammation and oxidative stress in chondrocytes. ADAMTS5 was upregulated in IL‑1β‑induced chondrocytes, and its knockdown alleviated IL‑1β‑induced chondrocyte injury. SP1 could bind to the ADAMTS5 promoter region to promote its transcription, and SP1 knockdown relieved IL‑1β‑induced chondrocyte injury by reducing ADAMTS5 expression. The SP1/ADAMTS5 axis activated the Wnt/β‑catenin pathway, and the Wnt/β‑catenin pathway agonist, SKL2001, reversed the protective effect of ADAMTS5 knockdown on chondrocyte injury induced by IL‑1β. To the best of our knowledge, the present study was the first to reveal the interaction between SP1 and ADAMTS5 in OA progression and indicated that the SP1/ADAMTS5 axis mediates OA progression by regulating the Wnt/β‑catenin pathway.

Cathelicidin-BF regulates the AMPK/SIRT1/NF-κB pathway to ameliorate murine osteoarthritis: In vitro and in vivo studie

Osteoarthritis (OA) is a chronic degenerative disease with a significant prevalence that causes cartilage damage and can lead to disability. The main factors contributing to the onset and progression of OA include inflammation and degeneration of the extracellular matrix. Cathelicidin-BF (BF-30), a natural peptide derived from Bungarus fasciatus venom, has shown multiple important pharmacological effects. However, the action mechanism of BF-30 in OA treatment remains to be elucidated. In this research, X-ray and Safranin O staining were employed to evaluate the imageology and histomorphology differences in the knee joints of mice in vivo. Techniques such as Western blot analysis, RT-qPCR, ELISA, and immunofluorescence staining were applied to examine gene and protein level changes in in vitro experiments. It was found that BF-30 significantly decreased inflammation and enhanced extracellular matrix metabolism. For the first time, it was demonstrated that the positive effects of BF-30 are mediated through the activation of the AMPK/SIRT1/NF-κB pathway. Moreover, when BF-30 was co-administered with Compound C, an AMPK inhibitor, the therapeutic benefits of BF-30 were reversed in both in vivo and in vitro settings. In conclusion, the findings suggest that BF-30 could be a novel therapeutic agent for OA improvement.

Causal association between dried fruit intake and risk of osteoarthritis: A Mendelian randomization study

This study aimed to examine whether dried fruit intake is causally associated with Osteoarthritis (OA). A two-sample Mendelian randomization (MR) analysis using the inverse-variance weighted (IVW), weighted median (WM), and MR-Egger regression methods was performed. We used the publicly available summary statistics data sets of genome-wide association studies (GWAS) meta-analyses for dried fruit intake in individuals included in the UK Biobank (n = 421,764; MRC-IEU consortium) as the exposure and a GWAS publicly available in PubMed for OA (total n = 484,598; case = 39,515, control = 445,083) as the outcome. We selected 41 single nucleotide polymorphisms at genome-wide significance from GWASs on dried fruit intake as the instrumental variables. The IVW method showed evidence to support a causal association between dried fruit intake and OA (beta = -0.020, SE = 0.009, P = .039). MR-Egger regression indicated no directional pleiotropy (intercept = 1E-05; P = .984), but it showed no causal association between dried fruit intake and OA (beta = -0.020, SE = 0.043, P = .610). However, the WM approach yielded evidence of a causal association between dried fruit intake and OA (beta = -0.026, SE = 0.012, P = .026). Cochran's Q test showed the existence of heterogeneity, but the statistics of I2 showed low heterogeneity. The results of MR analysis support that dried fruit intake may be causally associated with a decreased risk of OA.

Koumine inhibits IL-1β-induced chondrocyte inflammation and ameliorates extracellular matrix degradation in osteoarthritic cartilage through activation of PINK1/Parkin-mediated mitochondrial autophagy

Osteoarthritis (OA) is a degenerative joint disease, Increasingly, mitochondrial autophagy has been found to play an important regulatory role in the prevention and treatment of osteoarthritis. Koumine is a bioactive alkaloid extracted from the plant Gelsemium elegans. In previous research, Koumine was found to have potential in improving the progression of OA in rats. However, the specific mechanism of its action has not been fully explained. Therefore, the aim of this study was to investigate whether Koumine can alleviate OA in rats by influencing mitochondrial autophagy. In the in vitro study, rat chondrocytes (RCCS-1) were induced with IL-1β (10 ng/mL) to induce inflammation, and Koumine (50 μg/mL) was co-treated. In the in vivo study, a rat OA model was established by intra-articular injection of 2% papain, and Koumine was administered orally (1 mg/kg, once daily for two weeks). It was found that Koumine effectively reduced cartilage erosion in rats with osteoarthritis. Additionally, it decreased the levels of inflammatory factors such as IL-1β, IL-6, and extracellular matrix (ECM) components MMP13 and ADAMTS5 in chondrocytes and articular cartilage tissue, while increasing the level of Collagen II.Koumine inhibited the production of reactive oxygen species (ROS) in cartilage tissue and increased the number of autophagosomes in chondrocytes and articular cartilage tissue. Additionally, it upregulated the expression of mitochondrial autophagy proteins LC3Ⅱ/Ⅰ, PINK1, Parkin, and Drp1. The administration of Mdivi-1 (50 μM) reversed the enhanced effect of Koumine on mitochondrial autophagy, as well as its anti-inflammatory and anti-ECM degradation effects in rats with OA. These findings suggest that Koumine can alleviate chondrocyte inflammation and improve the progression of OA in rats by activating PINK1/Parkin-mediated mitochondrial autophagy.

Association between higher triglyceride glucose index and increased risk of osteoarthritis: data from NHANES 2015-2020

BACKGROUND

The relationship between the triglyceride glucose (TyG) index and osteoarthritis (OA) remains unclear. The objective of this study was to examine potential associations between an elevated TyG index and an increased risk of OA prevalence.

METHODS

3,921 participants with OA from the National Health and Nutrition Examination Survey (2015-2020) were included in this study. Participants were categorized into quartiles based on TyG index, which was determined using the formula: Ln [triglyceride (mg/dL) fasting blood glucose (mg/dL)/2]. Weighted multivariable regression, subgroup analyses, and threshold effect analyses were performed to calculate the independent association between TyG index and OA.

RESULTS

A total of 25,514 people were enrolled, with a mean TyG index of 8.48 ± 0.65. The results of multivariable logistic regression analysis after full adjustment showed a significant association between higher TyG index values and an increased risk of OA. Specifically, each incremental unit increase in the TyG index was associated with a 634% higher risk of OA [OR = 7.34; 95% CI: 2.25, 23.93; p = 0.0010]. Based on interaction tests, age, gender, BMI, and smoking status did not significantly affect the relationship between the TyG index and OA, while diabetes showed a stronger positive correlation between the TyG index and OA.

CONCLUSION

An increased risk of OA was associated with a higher TyG index. TyG could be a valuable predictor of OA and offer novel perspectives on the assessment and treatment of OA.

Oral Ingestion of Yuzu Seed Oil Suppresses the Development of Atopic Dermatitis-like Skin Lesions in NC/Nga Mice

Long-term oral ingestion of unheated yuzu seed oil in humans reduces lipid peroxides in the blood. Moreover, yuzu seed oil contains limonin, which can induce antioxidant and anti-inflammatory effects by activating the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2). Previously, Nrf2 has been shown to reduce atopic dermatitis (AD). Therefore, we hypothesized that ingesting unheated yuzu seed oil can regulate AD through Nrf2. An AD model was established using NC/Nga mice through repeated local exposure to mite antigens. Unheated and purified yuzu seed oil (100 µL/mice) or water (control, 100 µL/mice) was administered orally once a day using a gastric cannula for rodents for 28 days. On day 28, mice in the unheated yuzu seed oil group exhibited significantly lower clinical skin severity scores and ear thickness than those in the purified yuzu seed oil and water groups. Serum histamine levels remained unaltered among the three AD-induced groups. Serum Dermatophagoides farina body (Dfb)-specific immunoglobulin E (IgE) levels were significantly lower in the unheated yuzu seed oil group. Oral ingestion of yuzu seed oil in NC/Nga AD model mice significantly suppressed dermatitis deterioration and decreased serum IgE levels. Clinical trials (n = 41) have already confirmed that unheated yuzu oil is safe for long-term intake, further suggesting its potential use in improving AD symptoms.

Chemical profiling of Simiao pill and quantification of main effective constituents in it by ultra-high-performance liquid chromatography coupled with Q Exactive Orbitrap and triple quadrupole mass spectrometry

Simiao pill is one of the most commonly used prescriptions in traditional Chinese medicine for the treatment of hyperuricemia and gout. However, methods based on more accurate and comprehensive qualitative and quantitative analyses of the active ingredients are not yet perfect due to limited methodology. This not only hinders the elucidation of the pharmacological mechanism of Simiao pill, but also its comprehensive clinical development and utilization. In this study, we employed ultra-high-performance liquid chromatography-Q Exactive Orbitrap-mass spectrometry technology to perform rapid analysis and identification of the chemical constituents in Simiao pill. A total of 101 chemical components were identified, including 26 alkaloids, 15 terpenoids, 11 flavonoids, eight steroids, six fatty acids, five limonoids, four saponins, five phenylpropanoids, and 21 other compounds. In addition, we established a new method by high-throughput ultra-high-performance liquid chromatography-Q Exactive Orbitrap-mass spectrometry combined with ultra-high-performance liquid chromatography-triple quadrupole-tandem mass spectrometry technology for quantification of 14 main active ingredients, such as adenosine (1), phellodendrine (2), mangnoflorine (3), β-ecdysterone (4), 25R-inokosterone (5), 25S-inokosterone (6), jatrorrhizine (7), palmatine (8), chikusetsu saponin IVa (9), limonin (10), atractylenolide III (11), atractylenolide I (12), obacunone (13), and atractylenolide II (14) in Simiao pill. This work laid a foundation for further analysis and quality control of effective components in Simiao pill.

Limonin, a novel AMPK activator, protects against LPS-induced acute lung injury

AMP-activated protein kinase (AMPK) activation plays crucial roles in the treatment of many oxidative stress- and inflammation-induced diseases, including acute lung injury (ALI). Limonin is a naturally occurring tetracyclic triterpenoid extracted from the plants of Rutaceae and Meliaceae. Limonin also serves as an AMPK activator with anti-inflammatory and anti-oxidation effects. However, the potential beneficial effects of limonin on ALI and the possible mechanisms have never been disclosed till now. Here, the effects of limonin on lipopolysaccharide (LPS)-induced ALI in C57 BL/6 mice, plus bone marrow-derived macrophages (BMDM) stimulated with LPS to induce in vitro ALI model were investigated. Limonin significantly improved pulmonary function and alleviated lung pathological injury in LPS-induced mice. Meanwhile, limonin also markedly decreased inflammation and oxidative stress in lung tissues from LPS-treated mice. In vitro experiments also unveiled that limonin could decrease inflammation and oxidative stress in LPS-induced BMDM in a concentration-dependent manner. Mechanically, limonin could promote the activation of AMPKα and upregulate the expression of nuclear factor erythroid 2-related factor 2 (NRF2) in lung tissues and BMDM. Pharmacological inhibition of AMPKα by Compound C or AMPKα knockout could abolish the pulmonary protection from limonin during ALI. In conclusion, limonin mediates the activation of AMPKα/NRF2 pathway, providing an attractive therapeutic target for ALI in the future.

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.

miR-181a-5p targets DDX3X to inhibit the progression of osteoarthritis via NF-ΚB signaling pathway

Osteoarthritis (OA) is the most common age-related joint disease, characterized by chronic inflammation, progressive articular cartilage destruction and subchondral osteosclerosis. More and more evidence showed that microRNAs (miRNAs) play a key role in various diseases, but the specific mechanism of miRNAs in OA is not clear. The purpose of this study was to investigate the expression level and role of miR-181a-5p in OA and its related mechanism. Here we identified the key gene DEAD-box RNA helicase 3X (DDX3X) in the OA dataset by bioinformatics analysis. At the same time, miRNAs targeting DDX3X were screened, and miR-181a-5p was selected as the next research object. Then we used different concentrations of interleukin-1 beta (IL-1β)-induced in vitro model of arthritis, and found that IL-1β can stimulate cells to release nitric oxide. The expression levels of miR-181a-5p and DDX3X in mouse chondrocyte cell line ATDC5 induced by IL-1β at a concentration of 10ug/mL were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). IL-1β induced a decrease in the expression of miR-181a-5p and an increase in the expression of DDX3X in ATDC5 cells. mimic miR-181a-5p or inhibitor miR-181a-5p were transfected into ATDC5 cells, and the levels of inflammatory mediators in the cells were detected by enzyme-linked immunosorbent assay, and the results showed that miR-181a-5p could reduce the release of tumor necrosis factor-α, IL-1β, IL-6 and inducible nitric oxide nitric oxide synthase in a cellular model of arthritis. Luciferase reporter assays confirmed that the miR-181a-5p binding site was in the DDX3X gene 3'-untranslated region (3'-UTR), and DDX3X was negatively regulated by miR-181a-5p. Rescue assays confirmed that miR-181a-5p reduced the expression of DDX3X by targeting the 3'-UTR region of DDX3X, thereby reducing the release of inflammatory factors. Finally, in this paper, western blot was used to detect the mechanism of miR-181a-5p regulating OA. The results showed that interfering with the expression of miR-181a-5p could up-regulate the expression of DDX3X protein, increase the expression of nuclear factor- kappaB (NF-κB) related proteins, and reduce the inflammatory response of OA, thereby increasing the secretion of the matrix proteinases MMP-3 and MMP-13. Taken together, the results of the study suggested that miR-181a-5p may be a promising therapeutic target for the treatment of human OA.

Effects of Terpenes on the Osteoarthritis Cytokine Profile by Modulation of IL-6: Double Face versus Dark Knight?

BACKGROUND

Hemp seed oil and terpenes are emerging as a dietary supplement and complementary therapy for patients suffering from knee osteoarthritis (KOA). However, the mechanisms and effects induced by these molecules on inflammatory cytokines are not yet fully understood. The aim of this study was to evaluate the changes in the cytokine IL-1β, IL-1α, IL-2, IL-6, and TNF-α levels from two oral hemp seed oil-based dietary supplements, of which only one included the addition of terpenes, in a population of KOA patients.

METHODS

Sera from venous blood samples were collected from thirty-eight patients who were divided into two subgroups. The control group underwent a 45-day treatment with a dietary supplement containing only hemp seed oil, while the treatment group assumed a hemp seed oil and terpene-based dietary supplement for the same number of days. A Bio-Plex Human Cytokine assay was performed by a customized human cytokine five-plex panel for IL-1β, IL-1α, IL-2, IL-6, and TNF-α. Patients were evaluated before the beginning of the treatment (T0) and soon after it (T1).

RESULTS

No measurable levels of IL-2 and TNF-α were found in any of the subjects. Low levels of IL-1β were found, which were significantly decreased in the treatment group. No change in IL-1α levels was observed, while treated patients had a significant increase in IL-6 levels.

CONCLUSIONS

Hemp seed oil and terpene treatment modified the IL-1β and IL-6 levels, counteracting KOA inflammation in this way. In this study, IL-6 revealed its new and alternative action, since it is traditionally known as a pro-inflammatory factor, but it recently has been found to have anti-inflammatory activity in the muscle-derived form, which is the one it assumes as a myokine when activated by terpenes.

Injectable hypoxia-preconditioned cartilage progenitor cells-laden GelMA microspheres system for enhanced osteoarthritis treatment

Osteoarthritis (OA) is the most common age-related degenerative joint disease mainly characterized by the destruction of articular cartilage. Owing to its native avascular property, intrinsic repair of articular cartilage is very limited. Thus, a chondrogenic microenvironment in the joint is essential to the preservation of healthy chondrocytes and OA treatment. Recently, cartilage progenitor cells (CPCs)-based therapy is emerging as a promising strategy to repair degenerated and damaged articular cartilage. In this study, injectable hypoxia-preconditioned three-dimensional (3D) cultured CPCs-laden gelatin methacryloyl (GelMA) microspheres (CGMs) were constructed and characterized. Compared to normoxia-pretreated 3D CPCs and two-dimensional (2D) cultured CPCs, hypoxia-preconditioned 3D cultured CPCs exhibited enhanced cartilage extracellular matrix (ECM) secretion and greater chondrogenic ability. In addition, hypoxia-preconditioned 3D cultured CPCs more effectively maintained cartilage matrix metabolism balance and attenuated articular cartilage degeneration in subacute and chronic rat OA models. Mechanistically, our results demonstrated hypoxia-preconditioned 3D cultured CPCs exerted chondro-protective effects by inhibiting inflammation and oxidative stress via NRF2/HO-1 pathway in vitro and in vivo. Together, through the 3D culture of CPCs using GelMA microspheres (GMs) under hypoxia environment, our results proposed an efficient articular cartilage regeneration strategy for OA treatment and could provide inspiration for other stem cells-based therapies.

Natural compounds protect against the pathogenesis of osteoarthritis by mediating the NRF2/ARE signaling

Osteoarthritis (OA), a chronic joint cartilage disease, is characterized by the imbalanced homeostasis between anabolism and catabolism. Oxidative stress contributes to inflammatory responses, extracellular matrix (ECM) degradation, and chondrocyte apoptosis and promotes the pathogenesis of OA. Nuclear factor erythroid 2-related factor 2 (NRF2) is a central regulator of intracellular redox homeostasis. Activation of the NRF2/ARE signaling may effectively suppress oxidative stress, attenuate ECM degradation, and inhibit chondrocyte apoptosis. Increasing evidence suggests that the NRF2/ARE signaling has become a potential target for the therapeutic management of OA. Natural compounds, such as polyphenols and terpenoids, have been explored to protect against OA cartilage degeneration by activating the NRF2/ARE pathway. Specifically, flavonoids may function as NRF2 activators and exhibit chondroprotective activity. In conclusion, natural compounds provide rich resources to explore the therapeutic management of OA by activating NRF2/ARE signaling.

Stevioside protects primary articular chondrocytes against IL-1β-induced inflammation and catabolism by targeting integrin

Osteoarthritis (OA) is a common, progressive, and chronic disorder of the joints that is characterized by the inflammation and degradation of articular cartilage and is known to significantly impair quality of daily life. Stevioside (SVS) is a natural diterpenoid glycoside that has anti-inflammatory benefits. Hence, in the current research, it was hypothesized that SVS might exert anti-inflammatory effects on articular chondrocytes and alleviate cartilage degradation in mice with OA. The expression of inflammatory cytokines, like inducible nitric oxide synthase (iNOS), NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3), and cyclooxygenase-2 (COX-2) in chondrocytes after interleukin-1β (IL-1β) exposure, was inhibited by the pretreatment of SVS. As well, SVS inhibited the reduction of collagen II and sry-box transcription factor 9 (SOX9) in chondrocytes stimulated by IL-1β and suppressed the expression of MMP3 and MMP13. Further, after treatment with SVS, cell cytometry, autophagy flux, and related protein expression showed diminished cell apoptosis and reduced autophagy impairment. Moreover, SVS blocked the activation of phosphoinositide-3-kinase/Akt/nuclear factor-kappa beta (PI3K/Akt/NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways stimulated by IL-1β. This resulted in decreased cellular inflammation. In vivo experiments with intra-articular injections of SVS in mice with the DMM mouse model demonstrated a decrease in cartilage degradation and an improvement in subchondral bone remodeling. After the integrin αVβ3-related knockdown using siRNA, a reversed effect was observed on the anti-inflammatory, anabolic promoting, catabolic blocking, and NF-κB and MAPK signaling pathway inhibition of SVS on chondrocytes treated with IL-1β. The above findings highlighted that SVS blocked IL-1β, triggered an inflammatory response in mice chondrocytes, and prevented cartilage degradation in vivo through integrin αVβ3. This suggested that SVS might serve as a novel therapeutic option for OA.

Limonin ameliorates indomethacin-induced intestinal damage and ulcers through Nrf2/ARE pathway

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) can cause intestinal damage and ulcers and the incidence is increasing. Limonin plays an important role in the regulation of inflammatory diseases, but it has not been reported in the treatment of intestinal injury and ulcers.

METHODS

Indomethacin (INDO) induced intestinal injury and ulcer model in rats. The indexes related to intestinal injury were detected. Western blot and molecular docking techniques were used to detect the docking between Limonin and Nrf2. Next, ML385, an inhibitor of Nrf2/ARE signaling pathway, was applied to treat intestinal epithelial IEC-6 cells induced by INDO. And CCK8, Western blot, TUNEL, ELISA, DCFH-DA assay, kits, and immunofluorescence were conducted to detect cell activity, apoptosis, inflammatory response, oxidative stress, and tight junction again.

RESULTS

INDO can significantly induce intestinal ulcerative lesions in rats. Limonin could improve intestinal ulcerative lesions induced by INDO in rats. Limonin could reduce INDO-induced inflammatory response and oxidative stress in the small intestine of rats, and improve the intestinal barrier dysfunction induced by INDO. Limonin could dock with Nrf2 structure and activate Nrf2/ARE signaling pathway. ML385 could reverse the protective effect of Limonin against INDO-induced cell damage.

CONCLUSION

Limonin ameliorates INDO-induced intestinal damage and ulcers through Nrf2/ARE pathway.

Bardoxolone methyl ameliorates osteoarthritis by inhibiting osteoclastogenesis and protecting the extracellular matrix against degradation

Inflammation and oxidative damage are closely related to the development of osteoarthritis. Bardoxolone methyl (CDDO-Me), a semisynthetic oleanane triterpenoid, plays a strong anti-inflammatory and antioxidant role. The purpose of our research was to explore fundamental mechanisms of CDDO-Me in orthopaedics development. The results showed that CDDO-Me inhibited nuclear factor-κB ligand (RANKL)-induced osteoclast formation and extracellular matrix (ECM) degradation by activating the Nrf2/HO-1 signaling pathways and inhibiting NF-κB pathway activation and excess ROS production. In vivo, CDDO-Me significantly attenuated articular cartilage proteoglycan loss and the number of TRAP-positive osteoclasts in a destabilized medial meniscus (DMM) mouse model of OA. Taken together, these data demonstrate that CDDO-Me inhibits osteoclastogenesis and ECM degradation, underscoring its potential therapeutic value in treating OA.

Effects of limonin treatment on the survival of random skin flaps in mice

Random skin flap is commonly used in plastic and reconstructive surgery, however, distal part of skin flap often occurs ischemia and necrosis. Limonin, with bioactivities of anti-inflammation, anti-apoptosis and anti-oxidative stress, may be effective for skin flap survival. In our study, random flap model was performed in mice to explore the role of limonin in the survival of skin flap. On postoperative day 7, the necrosis of skin flaps was observed, while visualization of blood flow below the tissue surface was detected through Laser Doppler blood flow imaging (LDBFI). Then flap tissues were acquired to assess and levels of angiogenesis, apoptosis and oxidative stress. The results showed that limonin decreased necrosis and edema of skin flaps compared with the control group, with more blood flow in the flap under LDBFI detection. Limonin treatment also increased the mean vessels density, elevated the expression levels of angiogenic proteins (matrix metallopeptidase 9, vascular endothelial growth factor, Cadherin5) and antioxidant proteins [superoxide dismutase 1 (SOD1), endothelial nitric oxide synthase, heme oxygenase], and reduced the expression of apoptotic factors (BAX, CYC, Caspase3). In summary, limonin could effectively enhance the survival of random skin flap, the potential mechanism may attribute to the induction of angiogenesis, and inhibition of apoptosis and oxidative stress.

Network Pharmacology to Reveal the Molecular Mechanisms of Rutaceous Plant-derived Limonin Ameliorating Non-alcoholic Steatohepatitis

BACKGROUND

Limonin shows promise in alleviating non-alcoholic fatty liver disease. We investigated the mechanisms of limonin against non-alcoholic steatohepatitis (NASH) using network pharmacology and molecular docking.

METHODS

Public databases provided NASH- and limonin-associated targets. VennDiagram identified potential limonin targets for NASH. Enrichment analysis explored the limonin-NASH relationship. PPI network analysis, CytoHubba models, and bioinformatics identified hub genes for NASH treatment. Molecular docking assessed limonin's binding ability to hub targets.

RESULTS

We found 37 potential limonin targets in NASH, involved in oxidative stress, inflammation, and signaling pathways. PPI network analysis revealed seven hub genes (STAT3, NFKBIA, MTOR, TLR4, CASP8, PTGS2, NFKB1) as NASH treatment targets. Molecular docking confirmed limonin's binding to STAT3, CASP8, and PTGS2. Animal experiments on high-fat diet mice showed limonin reduced hepatic steatosis, lipid accumulation, and expression of p-STAT3/STAT3, CASP8, and PTGS2.

CONCLUSION

Limonin's therapeutic effects in NASH may stem from its antioxidant and anti-inflammatory properties. STAT3, CASP8, and PTGS2 are potential key targets for NASH treatment, warranting further investigation.

The Biomimetics of Mg2+-Concentration-Resolved Microenvironment for Bone and Cartilage Repairing Materials Design

With the increase in population aging, the tendency of osteochondral injury will be accelerated, and repairing materials are increasingly needed for the optimization of the regenerative processes in bone and cartilage recovery. The local environment of the injury sites and the deficiency of Mg2+ retards the repairing period via inhibiting the progenitor osteogenesis and chondrogenesis cells’ recruitment, proliferation, and differentiation, which results in the sluggish progress in the osteochondral repairing materials design. In this article, we elucidate the Mg2+-concentration specified effect on the cell proliferation, osteochondral gene expression, and differentiation of modeling chondrocytes (extracted from New Zealand white rabbit) and osteoblasts (MC3T3-E1). The concentration of Mg2+ in the culture medium affects the proliferation, chondrogenesis, and osteogenesis: (i) Appropriate concentrations of Mg2+ promote the proliferation of chondrocytes (1.25−10.0 mM) and MC3T3-E1 cells (2.5−30.0 mM); (ii) the optimal concentration of Mg2+ that promotes the gene expression of noncalcified cartilage is 15 mM, calcified cartilage 10 mM, and subchondral bone 5 mM, respectively; (iii) overdosed Mg2+ leads to the inhibition of cell activity for either chondrocytes (>20 mM) or osteoblasts (>30 mM). The biomimetic elucidation for orchestrating the allocation of gradient concentration of Mg2+ in accordance of the physiological condition is crucial for designing the accurate microenvironment in osteochondral injury defects for optimization of bone and cartilage repairing materials in the future.

Arbutin-modified microspheres prevent osteoarthritis progression by mobilizing local anti-inflammatory and antioxidant responses

Osteoarthritis (OA) is a common degenerative joint disease worldwide and currently there is no effective strategy to stop its progression. It is known that oxidative stress and inflammation can promote the development of OA, and therapeutic strategies against these conditions may alleviate OA. Arbutin (ARB), a major ingredient of the Chinese medicinal herb cowberry leaf, exerts good antioxidant and anti-inflammatory activities yet has not been studied in OA. Here we developed ARB-loaded gelatine methacryloyl-Liposome (GM-Lipo@ARB) microspheres which showed long-term release of ARB and excellent cartilage-targeting effects. The ARB-loaded microspheres effectively reduced the inflammatory response in interleukin (IL)-1β-treated arthritic chondrocytes. Moreover, the synthesized GM-Lipo@ARB microspheres regulated cartilage extracellular matrix (ECM) homeostasis through anti-inflammation effect via inhibiting NF-κB signaling and anti-oxidative stress effect via activating Nrf2 pathway. Intra-articular use of GM-Lipo@ARB can effectively reduce inflammation and oxidative stress in the articular cartilage and thus, attenuating OA progression in a mouse model. The study proposed a novel ARB-laden functional microsphere, GM-Lipo@ARB, and demonstrated that this compound may be used as an alternative therapeutics for treating OA.

Agri-Food By-Products in Cancer: New Targets and Strategies

The globalization and the changes in consumer lifestyles are forcing us to face a deep transformation in food demand and in the organization of the entire food production system. In this new era, the food-loss and food-waste security nexus is relevant in the global debate and avoiding unsustainable waste in agri-food systems as well as the supply chain is a big challenge. "Food waste" is useful for the recovery of its valuable components, thus it can assume the connotation of a "food by-product". Sustainable utilization of agri-food waste by-products provides a great opportunity. Increasing evidence shows that agri-food by-products are a source of different bioactive molecules that lower the inflammatory state and, hence, the aggressiveness of several proliferative diseases. This review aims to summarize the effects of agri-food by-products derivatives, already recognized as promising therapeutics in human diseases, including different cancer types, such as breast, prostate, and colorectal cancer. Here, we examine products modulating or interfering in the signaling mediated by the epidermal growth factor receptor.

Calycosin mitigates chondrocyte inflammation and apoptosis by inhibiting the PI3K/AKT and NF-κB pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Shaoyao Gancao Decoction (SG-Tang), originated from the Treatise on Febrile Diseases, is often used to treat OA pain symptoms. Whereas its efficacy has been verified by several clinical studies, the underlying mechanism remained unclear. Network pharmacology and UPLC-QTOF-MS analysis found that calycosin could be regarded as the active components of SG-Tang in treating OA. However, the effect of calycosin on cartilage destruction and the pathogenesis of OA are not known. Therefore, we evaluated the benefits of calycosin for OA and revealed the underlying mechanisms.

AIM OF STUDY

Using network pharmacology, UPLC-QTOF-MS analysis and experiments, the active components of SG-Tang were analyzed to explore their potential therapeutic mechanism in OA.

MATERIALS AND METHODS

The components of SG-Tang were detected by UPLC-QTOF-MS, and the possible active components and mechanism of SG-Tang in the treatment of OA were screened by network pharmacology. The OA mouse model was constructed by DMM. In total, 30 mice were randomly divided into three groups: Sham, DMM, and DMM + Calycosin. H&E, safranin O/fast green staining and the OARSI scores were used to evaluate joint injury in mice. In addition, OA models were established using chondrocytes treated with 10 ng/mL IL-1β. Treatment groups were treated with 100, 200 or 400 μM calycosin. CCK-8 assay was used for assessing the cytotoxic effects of calycosin. TUNEL staining and Western blotting were used to detect chondrocyte apoptosis. In addition, PI3K/Akt and NF-κB signaling pathway-related markers and cartilage matrix-related indicators were also detected.

RESULTS

In vivo studies showed that calycosin inhibited IL-1β-induced IL-6 and TNF-α production, as well as iNOS and COX-2 expression. Meanwhile, calycosin could inhibit IL-1β-induced degradation of cartilage matrix, including downregulation of MMP3, MMP-13, collagen II and aggrecan. NF-κB and PI3K/AKT were also inhibited by calycosin in OA chondrocytes. Furthermore, calycosin inhibited IL-1β-induced apoptosis in mouse chondrocytes. In a mouse model of OA, our results suggest that calycosin has a chondroprotective effect.

CONCLUSIONS

According to this study, calycosin may act as a protective agent against OA by inhibiting the PI3K/AKT and NF-κB pathways. Furthermore, this study suggested that calycosin is a potential candidate for the treatment of OA.

Omaveloxolone inhibits IL-1β-induced chondrocyte apoptosis through the Nrf2/ARE and NF-κB signalling pathways in vitro and attenuates osteoarthritis in vivo

Osteoarthritis (OA) is a common degenerative joint disease. Effective drugs that can halt or decelerate osteoarthritis progression are still lacking. Omaveloxolone is a semisynthetic oleanane triterpenoid exerting antioxidative and anti-inflammatory effects. The present study aims to determine whether omaveloxolone has a therapeutic effect on OA. Chondrocytes were treated with interleukin (IL)-1β to establish an OA cell model in vitro. Indicators of cell viability, oxidative stress, inflammation, cell apoptosis and extracellular matrix (ECM) degradation were investigated. Proteins related to the Nuclear factor erythroid derived-2-related factor 2 (Nrf2)/antioxidant response element (ARE) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signalling pathways were assessed using Western blotting. A destabilized medial meniscus surgery-induced OA rat model was used in vivo. Gait analysis, microcomputed tomography analysis, and histopathological and immunohistochemical analyses were performed to determine the therapeutic effect of omaveloxolone on attenuating osteoarthritis in vivo. The results showed that omaveloxolone exerts antioxidative, anti-inflammatory, antiapoptotic and anti-ECM degradation effects via activation of the Nrf2/ARE signalling pathway and inhibition of the NF-κB signalling pathway in chondrocytes in vitro and attenuates OA progression in vivo, suggesting that omaveloxolone may be a potential therapeutic agent for OA.

Corosolic Acid Protects Rat Chondrocytes Against IL-1β-Induced ECM Degradation by Activating Autophagy via PI3K/AKT/mTOR Pathway and Ameliorates Rat Osteoarthritis

Purpose

Osteoarthritis (OA) is an age-related degenerative disease associated with enhanced degradation of extracellular matrix (ECM) and decreased autophagy. Our study is aimed to explore how corosolic acid (CRA) affect cartilage ECM metabolism and the potential mechanism.

Methods

Rat chondrocytes were pretreated with different concentrations of CRA (0, 2.5, 5, and 10 μM), and were stimulated with IL-1β (10ng/mL) for 24 h, subsequently. RT-qPCR, Western blot, and immunofluorescence were used to detect the expression of genes related to ECM metabolism and explore the potential molecular mechanism. The effect of CRA on articular cartilage was observed in the surgically induced OA rat model with the method of Safranin O/Fast green and immunohistochemical staining.

Results

Results showed that CRA reversed the IL-1β-induced degradation of aggrecan and type II collagen and the high expression of MMP13 and ADAMTS5. Mechanistically, CRA enhanced autophagy through inhibiting the classical PI3K/AKT/mTOR signaling pathway. Furthermore, inhibition of autophagy partly abolished the protective effects of CRA on ECM synthesis in IL-1β-treated chondrocytes. Correspondingly, the protective effect of CRA was also confirmed in a rat OA model.

Conclusion

Herein, we demonstrate that CRA can enhance autophagy by inhibiting PI3K/AKT/mTOR signaling pathway, prevent IL-1β-induced cartilage ECM degradation, and may be a potentially applicable candidate for the treatment of OA.

Limonin stabilises SIRT6 by activating USP10 in cardiac hypertrophy

BACKGROUND AND PURPOSE

Limonin, a natural tetracyclic triterpenoid extract, exerts extensive pharmacological effects; however, its role in cardiac hypertrophy remains to be elucidated. We investigated the beneficial effects of limonin on cardiac hypertrophy and explored the potential mechanisms.

EXPERIMENTAL APPROACH

C57/BL6 male mice were subjected to aortic banding (AB) surgery and neonatal rat cardiac myocytes (NRCMs) were stimulated with phenylephrine (PE) to evaluate the effects of limonin on cardiac hypertrophy.

KEY RESULTS

Limonin markedly improved the cardiac function and heart weight in AB operation mice. In addition, limonin-treated mice and NRCMs produced fewer cardiac hypertrophy markers than those treated with the vehicle in hypertrophic groups. Sustained AB- or PE-stimulation impaired cardiac sirtuin 6 (SIRT6) protein levels, which were partially rescued by limonin and subsequently enhanced the activity of PPARα, and Sirt6 siRNA inhibited the anti-hypertrophic effects of limonin in vitro. Interestingly, limonin did not influence Sirt6 mRNA levels, but controlled its ubiquitin levels. Thus, the protein biosynthesis inhibitor, cycloheximide (CHX), and proteasome inhibitor, MG-132, were used to determine SIRT6 protein expression levels. Under PE stimulation, limonin increased SIRT6 protein levels in the presence of CHX, but it didn't influence SIRT6 expression in the presence of MG-132, suggesting that limonin promotes SIRT6 abundance by inhibiting its ubiquitination degradation. Furthermore, limonin inhibited the degradation of SIRT6 by activating ubiquitin-specific peptidase (Cuspidi et al.)-10, while USP10 siRNA abrogated the beneficial effects of limonin.

CONCLUSION AND IMPLICATIONS

Limonin mediates the ubiquitination and degradation of SIRT6 by activating USP10, providing an attractive therapeutic target for cardiac hypertrophy.

Limonin relieves TGF-β-induced hepatocyte EMT and hepatic stellate cell activation in vitro and CCl4-induced liver fibrosis in mice via upregulating Smad7 and subsequent suppression of TGF-β/Smad cascade

Liver fibrosis is a pathological process as a result of intrahepatic deposition of excessive extracellular matrix. Epithelial-mesenchymal transition (EMT) of hepatocytes and activation of hepatic stellate cells (HSCs) both play important roles in the etiology of liver fibrosis. Here, we found that limonin repressed transforming growth factor-β1 (TGF-β)-induced EMT in AML-12 hepatocytes and activation of LX-2 HSCs. In both kinds of cells, limonin suppressed TGF-β-provoked Smad2/3 C-terminal phosphorylation and subsequent nuclear translocation. Transcription of Smad2/3-downstream genes was in turn reduced. However, limonin exerted few effects on Smad2/3 phosphorylation at linker region. Mechanistically, limonin increased Smad7 at mRNA level in both AML-12 and LX-2 cells. Knockdown of Smad7 abrogated inhibitory effects of limonin on TGF-β-induced EMT in AML-12 cells and activation of LX-2 cells. Further studies revealed that limonin alleviated mouse liver fibrosis induced by CCl₄. In livers of model mice, limonin upregulated Smad7 and declined C-terminal phosphorylation and nuclear translocation of Smad2/3. Transcription of Smad2/3-responsive genes was also attenuated. Our findings indicated that limonin inhibits TGF-β-induced EMT of hepatocytes and activation of HSCs in vitro and CCl₄-induced liver fibrosis in mice. Upregulated Smad7 which suppresses Smad2/3-dependent gene transcription is implicated in the hepatoprotective activity of limonin.