Nomilin targets the Keap1-Nrf2 signalling and ameliorates the development of osteoarthritis

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.

Cinobufotalin prevents bone loss induced by ovariectomy in mice through the BMPs/SMAD and Wnt/β-catenin signaling pathways

BACKGROUND

Osteoporosis is a chronic bone disease characterized by bone loss and decreased bone strength. However, current anti-resorptive drugs carry a risk of various complications. The deep learning-based efficacy prediction system (DLEPS) is a forecasting tool that can effectively compete in drug screening and prediction based on gene expression changes. This study aimed to explore the protective effect and potential mechanisms of cinobufotalin (CB), a traditional Chinese medicine (TCM), on bone loss.

METHODS

DLEPS was employed for screening anti-osteoporotic agents according to gene profile changes in primary osteoporosis. Micro-CT, histological and morphological analysis were applied for the bone protective detection of CB, and the osteogenic differentiation/function in human bone marrow mesenchymal stem cells (hBMMSCs) were also investigated. The underlying mechanism was verified using qRT-PCR, Western blot (WB), immunofluorescence (IF), etc. RESULTS: A safe concentration (0.25 mg/kg in vivo, 0.05 μM in vitro) of CB could effectively preserve bone mass in estrogen deficiency-induced bone loss and promote osteogenic differentiation/function of hBMMSCs. Both BMPs/SMAD and Wnt/β-catenin signaling pathways participated in CB-induced osteogenic differentiation, further regulating the expression of osteogenesis-associated factors, and ultimately promoting osteogenesis.

CONCLUSION

Our study demonstrated that CB could significantly reverse estrogen deficiency-induced bone loss, further promoting osteogenic differentiation/function of hBMMSCs, with BMPs/SMAD and Wnt/β-catenin signaling pathways involved.

Pharmacokinetic and pharmacodynamic drug-drug interaction of Nomilin with atorvastatin in hyperlipidemic mice

Atorvastatin (Atv) is widely used to lower cholesterol levels and treat hyperlipidemia in clinical application. Nomilin (Nom) is a kind of limonoids, which is found and isolated from the citrus herbs of Rutaceae family, which are widely used as patent medicines, functional foods, and nutritional supplements in many countries. In previous studies, Nom has the effect of anti-obesity and curing other metabolic diseases. Nevertheless, in recent years, the drug-drug interaction (DDI) caused by the administration of drugs with synergistic effects have raised worldwide concerns. To investigate the DDI of Nom and Atv in vivo, the pharmacokinetic studies were performed with using C57BL/6 mice. The plasma concentrations of Nom and Atv were measured after oral administration of different drug combinations by a simple and sensitive UHPLC-MS/MS method. The experimental mice were randomly divided into five groups, including control group, model group, administered Nom individually group, administered Atv individually group and co-administered of Nom and Atv group. The lipid levels including total cholesterol (TC), triglycerides (TG), high density lipoproteins-cholesterol (HDL-C), low density lipoproteins-cholesterol (LDL-C) were measured for pharmacodynamic study. The hepatic microsomal Cytochrome P450 (CYP1A2, CYP2E1 and CYP3A11) activities were probed using cocktail assay. The gene and protein expressions of CYP3A11 were detected via qPCR and Western blot method. The results shown that the area under the plasma concentration-time curve (AUC) of Atv in administered Atv individually group was 69.30 ± 15.45 ng/mL × h, while that of combined Nom with Atv group was 42.37 ± 10.15 ng/mL × h (p＜0.05). The degree of reduction in lipid levels of mice treated with co-administration of Atv and Nom was less than that of mice treated with Atv alone. In addition, Nom could cause an increased hepatic microsomal CYP3A11 activity significantly, and induce the gene levels and protein expressions of CYP3A11 elevated in mice livers. In conclusion, Nom could up-regulate CYP3A11 activity, thereby impacting on the pharmacokinetic profile and pharmacodynamic effect of Atv. The findings provide more insight for the use risk of these two drugs to treat hyperlipidemia diseases.

Nomilin and its analogue obacunone alleviate NASH and hepatic fibrosis in mice via enhancing antioxidant and anti-inflammation capacity

Nonalcoholic steatohepatitis (NASH) and hepatic fibrosis are leading causes of cirrhosis with rising morbidity and mortality worldwide. Currently, there is no appropriate treatment for NASH and hepatic fibrosis. Many studies have shown that oxidative stress is a main factor inducing NASH. Nomilin (NML) and obacunone (OBA) are limonoid compounds naturally occurring in citrus fruits with various biological properties. However, whether OBA and NML have beneficial effects on NASH remains unclear. Here, we demonstrated that OBA and NML inhibited hepatic tissue necrosis, inflammatory infiltration and liver fibrosis progression in methionine and choline-deficient (MCD) diet, carbon tetrachloride (CCl4 )-treated and bile duct ligation (BDL) NASH and hepatic fibrosis mouse models. Mechanistic studies showed that NML and OBA enhanced anti-oxidative effects, including reduction of malondialdehyde (MDA) level, increase of catalase (CAT) activity and the gene expression of glutathione S-transferases (GSTs) and Nrf2-keap1 signaling. Additional, NML and OBA inhibited the expression of inflammatory gene interleukin 6 (Il-6), and regulated the bile acid metabolism genes Cyp3a11, Cyp7a1, multidrug resistance-associated protein 3 (Mrp3). Overall, these findings indicate that NML and OBA may alleviate NASH and liver fibrosis in mice via enhancing antioxidant and anti-inflammation capacity. Our study proposed that NML and OBA may be potential strategies for NASH treatment.

Oxidative stress as a key modulator of cell fate decision in osteoarthritis and osteoporosis: a narrative review

During aging and after traumatic injuries, cartilage and bone cells are exposed to various pathophysiologic mediators, including reactive oxygen species (ROS), damage-associated molecular patterns, and proinflammatory cytokines. This detrimental environment triggers cellular stress and subsequent dysfunction, which not only contributes to the development of associated diseases, that is, osteoporosis and osteoarthritis, but also impairs regenerative processes. To counter ROS-mediated stress and reduce the overall tissue damage, cells possess diverse defense mechanisms. However, cellular antioxidative capacities are limited and thus ROS accumulation can lead to aberrant cell fate decisions, which have adverse effects on cartilage and bone homeostasis. In this narrative review, we address oxidative stress as a major driver of pathophysiologic processes in cartilage and bone, including senescence, misdirected differentiation, cell death, mitochondrial dysfunction, and impaired mitophagy by illustrating the consequences on tissue homeostasis and regeneration. Moreover, we elaborate cellular defense mechanisms, with a particular focus on oxidative stress response and mitophagy, and briefly discuss respective therapeutic strategies to improve cell and tissue protection.

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.

Engeletin alleviates erastin-induced oxidative stress and protects against ferroptosis via Nrf2/Keap1 pathway in bone marrow mesenchymal stem cells

Ferroptosis is a novel form of cell death, which is a unique modality of cell death and closely associated with iron concentrations, generation of reactive oxygen species (ROS), and accumulation of the lipid reactive oxygen species. In the present study, the anti-ferroptosis effects of Engeletin was studied in erastin-induced bone marrow mesenchymal stem cells (BMSCs). After treatment with Engeletin, cell viability was determined by CCK-8 assay. The production of ROS, malonaldehyde (MDA), Superoxide dismutase (SOD) activities and glutathione peroxidase (GSH) were detected by using commercially-available kits. Ferroptosis-related proteins (GPX4, SLC7A11, TFR1, FPN1, Nrf2, Keap1) were evaluated by Western blotting. Osteogenic capacity was evaluated by ALP staining and ARS staining. The expression of osteogenic-related proteins (OPN, Runx2, OCN) were evaluated by Western blotting and changes in mRNA (ALP, BMP-2, COL-1, Osterix) were evaluated by RT-PCR. Consistent improvements in angiogenesis are observed with Engeletin in the presence of erastin. Engeletin significantly alleviated erastin-induced oxidative damage and protected against ferroptosis in BMSCs. Ferroptosis was inhibited by Engeletin, leading to decreasing reducing accumulation of ROS and lipid peroxidation products. Moreover, Engeletin promoted osteogenic differentiation in BMSCs and angiogenesis in human umbilical vein endothelial cells (HUVECs). Taken together, these findings indicate that Engeletin can protect BMSCs from erastin-induced ferroptosis through the Nrf2/Keap1 antioxidant pathway and identify Engeletin as a novel ferroptosis inhibitor, suggesting that Engeletin may promote resistance to ferroptosis and enable osteogenic function of BMSCs.

Nomilin and Its Analogues in Citrus Fruits: A Review of Its Health Promotion Effects and Potential Application in Medicine

Nomilin is one of the major limonoids, which are plant secondary metabolites also known as tetranortriterpenoids. Nomilin is found mostly in common edible citrus fruits including lemons, limes, oranges, grapefruits, mandarins, along with traditional Chinese medicines derived from citrus fruits, such as tangerine seed, tangerine peel, fructus aurantii immaturus, etc. A number of studies have demonstrated that nomilin and its analogues exhibit a variety of biological and pharmacological activities. These include anti-cancer, immune-modulatory, anti-inflammatory, anti-obesity, anti-viral, anti-osteoclastogenic, anti-oxidant, and neuro-protective effects. Thus, nomilin and its analogues have emerged as a potential therapy for human diseases. The purpose of this review is to chronicle the evolution of nomilin research from examining its history, structure, occurrence, to its pharmacological and disease-preventing properties as well as its potential utilization in medicine and food science.

Research progress on the mechanism of interleukin-1β on epiphyseal plate chondrocytes

Epiphyseal plate injury, a common problem in pediatric orthopedics, may result in poor bone repair or growth defects. Epiphyseal plate, also known as growth plate is a layer of hyaline cartilage tissue between the epiphysis and metaphyseal and has the ability to grow longitudinally. Under normal physiological conditions, the epiphyseal plate has a certain axial resistance to stress, but it is fragile in growth phase and can be damaged by excessive stress, leading to detachment or avulsion of the epiphysis, resulting in life-long devastating consequences for patients. There is an obvious inflammatory response in the phase of growth plate injury, the limited physiological inflammatory response locally favors tissue repair and the organism, but uncontrolled chronic inflammation always leads to tissue destruction and disease progression. Interleukin-1β (IL-1β), as representative inflammatory factors, not only affect the inflammatory phase response to bone and soft tissue injury, but have a potentially important role in the later repair phase, though the exact mechanism is not fully understood. At present, epiphyseal plate injuries are mainly treated by corrective and reconstructive surgery, which is highly invasive with limited effectiveness, thus new therapeutic approaches are urgently needed, so a deeper understanding and exploration of the pathological mechanisms of epiphyseal plate injuries at the cellular molecular level is an entry point. In this review, we fully introduced the key role of IL-1 in the progression of epiphyseal plate injury and repair, deeply explored the mechanism of IL-1 on the molecular transcript level and endocrine metabolism of chondrocytes from multiple aspects, and summarized other possible mechanisms to provide theoretical basis for the clinical treatment and in-depth study of epiphyseal plate injury in children.

Carnosine Alleviates Knee Osteoarthritis and Promotes Synoviocyte Protection via Activating the Nrf2/HO-1 Signaling Pathway: An In-Vivo and In-Vitro Study

The most common joint disease in the elderly is knee osteoarthritis (OA). It is distinguished by cartilage degradation, subchondral bone loss, and a decrease in joint space. We studied the effects of carnosine (CA) on knee OA in male Wistar rats. OA is induced by anterior cruciate ligament transection combined with medial meniscectomy (ACLT+MMx) method and in vitro studies are conducted in fibroblast-like synoviocyte cells (FLS). The pain was assessed using weight-bearing and paw-withdrawal tests. CA supplementation significantly reduced pain. The enzyme-linked immunosorbent assay (ELISA) method was used to detect inflammatory proteins in the blood and intra-articular synovial fluid (IASF), and CA reduced the levels of inflammatory proteins. Histopathological studies were performed on knee-tissue samples using toluidine blue and hematoxylin and eosin (H and E) assays. CA treatment improved synovial protection and decreased cartilage degradation while decreasing zonal depth lesions. Furthermore, Western blotting studies revealed that the CA-treated group activated nuclear factor erythroid 2-related factor (Nrf2) and heme oxygenase (HO-1) and reduced the expression of cyclooxygenase-2 (COX-2). FLS cells were isolated from the knee joints and treated with IL-1β to stimulate the inflammatory response and increase reactive oxygen species (ROS). The matrix metalloproteinase protein (MMP's) levels (MMP-3, and MMP-13) were determined using the reverse transcription-polymerase chain reaction (RT-PCR), and CA treatment reduced the MMP's expression levels. When tested using the 2',7'-dicholorodihydrofluroscene diacetate (DCFDA) assay and the 5,5',6,6'-tetracholoro-1,1',3,3'-tertraethylbenzimidazolcarboc janine iodide (JC-1) assay in augmented ROS FLS cells, CA reduced the ROS levels and improved the mitochondrial membrane permeability. This study's investigation suggests that CA significantly alleviates knee OA both in vitro and in vivo.

Molecular docking study of GSK-3β interaction with nomilin, kihadanin B, and related limonoids and triterpenes with a furyl-δ-lactone core

Glycogen synthase kinase-3β (GSK-3β) is a target enzyme considered for the treatment of multiple human diseases, from neurodegenerative pathologies to viral infections and cancers. Numerous inhibitors of GSK-3β have been discovered but thus far only a few have reached clinical trials and only one drug, tideglusib (1), has been registered. Natural products targeting GSK-3β have been identified, including the two anticancer limonoids obacunone (5) and gedunin (4), both presenting a furyl-δ-lactone core. To help identifying novel GSK-3β ligands, we have performed a molecular docking study with 15 complementary natural products bearing a furyl-δ-lactone unit (such as limonin (6) and kihadanins A (8) and B (9)) or a closely related structure (such as cedrelone (10) and nimbolide (11)). The formation of GSK-3β-binding complexes for those natural products was compared to reference GSK-3β ATP-competitive inhibitors LY2090314 (3) and AR-A014418 (2). Our in silico analysis led to the identification of two new GSK-3β-binding natural products: kihadanin B (9) and nomilin (7). The latter surpassed the reference compounds in terms of calculated empirical energy of interaction (ΔE). Nomilin (7) can possibly bind to the active site of GSK-3β, notably via the furyl-δ-lactone core and its 1-acetyl group, implicated in the protein interaction. Compound structure-binding relationships are discussed. The study should help the discovery of novel natural products targeting GSK-3β.

Puerarin inhibits the development of osteoarthritis through antiinflammatory and antimatrix-degrading pathways in osteoarthritis-induced rat model

Puerarin is an isoflavone isolated from the medicinal plant Pueraria lobata. The purpose of this study was to study the antiinflammatory and antimatrix-degrading effects of puerarin in a rat osteoarthritis (OA) model and its protective effects on joints. The rat OA model was established by anterior cruciate ligament transection (ACLT) surgery. Rats (n = 40) were divided into nontreated OA, OA + celecoxib (2.86 mg/kg), OA + puerarin (50 and 100 mg/kg), and control groups. Two weeks after surgical induction, puerarin was administered by gavage daily for 8 weeks. After 8 weeks, macroscopic observation and histopathological images showed that cartilage damage was reduced after puerarin and celecoxib treatment, the intensity of Safranin O staining was high, and the OARSI scores were significantly reduced compared to the OA group. Puerarin reduced the expression of MMP-3, MMP-13, ADAMTS-5, and COX-2 in the cartilage tissue of ACLT rats, inhibited the production of IL-1β, IL-6, and TNF-α inflammatory factors, increased Type II collagen content, and altered the expression of serum OA cartilage degradation/bone turnover biomarkers (CTX-I, CTX-II, COMP, and PIINP). Based on these findings, we speculate that puerarin supplement to attain recovery from OA damage.

Engeletin Protects Against TNF-α-Induced Apoptosis and Reactive Oxygen Species Generation in Chondrocytes and Alleviates Osteoarthritis in vivo

Purpose

Osteoarthritis (OA) is a progressive disease characterized by pain and impaired joint functions. Engeletin is a natural compound with anti-inflammatory and antioxidant effects on other diseases, but the effect of engeletin on OA has not been evaluated. This study aimed to elucidate the protective effect of engeletin on cartilage and the underlying mechanisms.

Methods

Chondrocytes were isolated from rat knee cartilage, and TNF-α was used to simulate OA in vitro. After treatment with engeletin, the expression of extracellular matrix (ECM) components (collagen II and aggrecan) and matrix catabolic enzymes (MMP9 and MMP3) was determined by Western blotting and qPCR. Chondrocyte apoptosis was evaluated using Annexin V-FITC/PI and flow cytometry. Apoptosis-related proteins (Bax, Bcl-2, and cleaved caspase-3) were evaluated by Western blotting. The mitochondrial membrane potential of chondrocytes was measured with JC-1, and intracellular reactive oxygen species (ROS) levels were determined with DCFH-DA. Changes in signaling pathways (Nrf2, NF-κB and MAPK) were evaluated by Western blotting. In vivo, anterior cruciate ligament transection (ACLT) was used to induce the rat OA model, and engeletin was administered intraarticularly. The therapeutic effect of engeletin was analyzed by histopathological analysis.

Results

Pretreatment with engeletin alleviated TNF-α-induced inhibition of ECM components (collagen II and aggrecan) and upregulation of matrix catabolic enzymes (MMP9 and MMP3). Engeletin ameliorated chondrocyte apoptosis by inhibiting Bax expression and upregulating Bcl-2 expression. Engeletin maintained the mitochondrial membrane potential of chondrocytes and scavenged intracellular ROS by activating the Nrf2 pathway. The NF-κB and MAPK pathways were inhibited by treatment with engeletin. In vivo, ACLT-induced knee OA in rats was alleviated by intraarticular injection of engeletin.

Conclusion

Engeletin ameliorated OA in vitro and in vivo. It may be a potential therapeutic drug for OA.

Pharmacological Targeting of Heme Oxygenase-1 in Osteoarthritis

Osteoarthritis (OA) is a common aging-associated disease that clinically manifests as joint pain, mobility limitations, and compromised quality of life. Today, OA treatment is limited to pain management and joint arthroplasty at the later stages of disease progression. OA pathogenesis is predominantly mediated by oxidative damage to joint cartilage extracellular matrix and local cells such as chondrocytes, osteoclasts, osteoblasts, and synovial fibroblasts. Under normal conditions, cells prevent the accumulation of reactive oxygen species (ROS) under oxidatively stressful conditions through their adaptive cytoprotective mechanisms. Heme oxygenase-1 (HO-1) is an iron-dependent cytoprotective enzyme that functions as the inducible form of HO. HO-1 and its metabolites carbon monoxide and biliverdin contribute towards the maintenance of redox homeostasis. HO-1 expression is primarily regulated at the transcriptional level through transcriptional factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), specificity protein 1 (Sp1), transcriptional repressor BTB-and-CNC homology 1 (Bach1), and epigenetic regulation. Several studies report that HO-1 expression can be regulated using various antioxidative factors and chemical compounds, suggesting therapeutic implications in OA pathogenesis as well as in the wider context of joint disease. Here, we review the protective role of HO-1 in OA with a focus on the regulatory mechanisms that mediate HO-1 activity.

Nomilin targets the Keap1-Nrf2 signalling and ameliorates the development of osteoarthritis

Osteoarthritis (OA) is a long-term and inflammatory disorder featured by cartilage erosion. Here, we describe nomilin (NOM), a triterpenoid with inflammation modulatory properties in variety of disorders. In this study, we demonstrated the latent mechanism of NOM in alleviating the progress of OA both in vitro and in vivo studies. The results showed that NOM pre-treatment suppressed the IL-1β-induced over-regulation of pro-inflammation factors, such as NO, IL-6, PGE2 , iNOS, TNF-α and COX-2. Moreover, NOM also down-regulates the degradation of ECM induced by IL-1β. Mechanistically, the NOM suppressed NF-κB signalling via disassociation of Keap1-Nrf2 in chondrocytes. Furthermore, NOM delays the disease progression in the mouse OA model. To sum up, this research indicated NOM possessed a new potential therapeutic option in osteoarthritis.