Activation of the Nrf-2 pathway by pinocembrin safeguards vertebral endplate chondrocytes against apoptosis and degeneration caused by oxidative stress

Role of oxidative stress in intervertebral disc degeneration: mechanisms, pathogenesis, and therapeutic strategies

Intervertebral disc degeneration (IDD) is a prevalent and debilitating spinal condition, characterised by the progressive degradation of disc structure and function, often accompanied by pain. Despite our increasing understanding of IDD, the precise mechanisms underlying its development and potential therapeutic targets remain incompletely understood. Recent research has highlighted that oxidative stress, along with immune abnormalities, mechanical loading imbalances, and metabolic disruptions, play a pivotal role in IDD initiation and progression. Oxidative stress in IDD results from an overproduction of reactive oxygen species (ROS) and a compromised ability to eliminate them, disrupting the redox homeostasis within the intervertebral disc. This disturbance in redox balance leads to extracellular matrix degradation (ECM), induces cellular apoptosis, and worsens the damage to disc tissues. This review provides a comprehensive overview of the pathophysiological processes of IDD, with a particular focus on the role of oxidative stress. Additionally, we explore current advancements in therapeutic strategies targeting oxidative stress, including antioxidant drugs, biomaterials, and stem cell-based approaches, offering promising avenues for the management and treatment of IDD.

Myristic acid beneficially modulates intervertebral disc degeneration by preventing endplate osteochondral remodeling and vertebral osteoporosis in naturally aged mice

Background

The origin of intervertebral disc degeneration (IDD) is highly complex, where both cartilage endplate remodeling and vertebral osteoporosis are of utmost importance. Myristic acid (MA), a saturated fatty acid derived from nutmeg, a traditional Chinese herb, has been shown to boost memory. Additionally, its isomers have been verified to have anti-osteoporotic characteristics. However, the precise mechanism by which MA functions in relation to IDD remains unclear.

Methods

In vivo, a naturally aged animal model was used. The drug-administration method of MA was intraperitoneal injection to mice aged 22 months at a dose of 2 mg/kg·d for 2 months. Micro-CT observed vertebral bone mass and endplate changes, followed by Hematoxylin‒eosin (H&E), Masson, and Safranin-O staining of tissues. TRAP staining counted osteoclasts; immunohistochemistry detected the expressions of Aggrecan and Collagen II. Bioinformatics explored MA's anti-IDD mechanism. In vitro, MA-treated senescent endplate chondrocytes (induced by TBHP) were analyzed by RT-qPCR and immunofluorescence (IF) for senescence and matrix synthesis markers. TRAP and F-actin detected MA's effect on RAW264.7 osteoclast differentiation (induced by RANKL); qPCR examined the expressions of osteoclast genes.

Results

Using the naturally aged model, we found that MA tended to improve vertebral osteoporosis and endplate osteochondral remodeling, decreased the TRAP activity of the endplate, and alleviated IDD in naturally aged mice. Bioinformatics analysis suggested that the relationships among IDD, osteoporosis, and endplate degeneration were mainly linked to cellular senescence. In vitro, MA postponed the senescence of TBHP-induced endplate chondrocytes by increasing the expression of Aggrecan and decreasing the expressions of MMP-3, MMP-9, and the senescence markers p16 and p21. Additionally, MA notably inhibited osteoclast activity, as evidenced by a decrease in the number of osteoclasts and a significant suppression of F-actin formation. At the molecular level, MA efficiently reduced the expressions of osteoclast marker genes like ACP-5, CTSK, and DC-STAMP.

Conclusion

The findings of this research suggest that MA is capable of inhibiting endplate osteochondral remodeling and vertebral osteoporosis, diminishing osteoclastogenesis to preserve bone mass, and consequently delaying IDD in naturally aged mice. Hence, MA holds the potential to serve as an alternative therapeutic approach for IDD.

Natural flavonoids from herbs and nutraceuticals as ferroptosis inhibitors in central nervous system diseases: current preclinical evidence and future perspectives

Flavonoids are a class of important polyphenolic compounds, renowned for their antioxidant properties. However, recent studies have uncovered an additional function of these natural flavonoids: their ability to inhibit ferroptosis. Ferroptosis is a key mechanism driving cell death in central nervous system (CNS) diseases, including both acute injuries and chronic neurodegenerative disorders, characterized by iron overload-induced lipid peroxidation and dysfunction of the antioxidant defense system. This review discusses the therapeutic potential of natural flavonoids from herbs and nutraceuticals as ferroptosis inhibitors in CNS diseases, focusing on their molecular mechanisms, summarizing findings from preclinical animal models, and providing insights for clinical translation. We specifically highlight natural flavonoids such as Baicalin, Baicalein, Chrysin, Vitexin, Galangin, Quercetin, Isoquercetin, Eriodictyol, Proanthocyanidin, (-)-epigallocatechin-3-gallate, Dihydromyricetin, Soybean Isoflavones, Calycosin, Icariside II, and Safflower Yellow, which have shown promising results in animal models of acute CNS injuries, including ischemic stroke, cerebral ischemia-reperfusion injury, intracerebral hemorrhage, subarachnoid hemorrhage, traumatic brain injury, and spinal cord injury. Among these, Baicalin and its precursor Baicalein stand out due to extensive research and favorable outcomes in acute injury models. Mechanistically, these flavonoids not only regulate the Nrf2/ARE pathway and activate GPX4/GSH-related antioxidant pathways but also modulate iron metabolism proteins, thereby alleviating iron overload and inhibiting ferroptosis. While flavonoids show promise as ferroptosis inhibitors for CNS diseases, especially in acute injury settings, further studies are needed to evaluate their efficacy, safety, pharmacokinetics, and blood-brain barrier penetration for clinical application.

Bee Pollen Potential to Modulate Ferroptosis: Phytochemical Insights for Age-Related Diseases

Bee pollen (BP) is one of the richest known natural resources of micronutrients and bioactive phytochemicals. Some captivating bioactivities of BP compounds, although being largely investigated for the latter as individual molecules, remain very scarcely investigated or completely uninvestigated in bee pollen as a whole product. Among the most intriguing of these bioactivities, we identified ferroptosis as a major one. Ferroptosis, a recently discovered form of cell death (connecting oxidative stress and inflammation), is a complex pathophysiological process and one of the most crucial and perplexing events in current challenging human diseases such as cancer, neurodegeneration, and general aging diseases. Many BP compounds were found to intricately modulate ferroptosis depending on the cellular context by inducing this cell death mechanism in malignant cells and preventing it in non-malignant cells. Since research in both fields, i.e., BP and ferroptosis, is still recent, we deemed it necessary to undertake this review to figure out the extent of BP potential in modulating ferroptosis mechanisms. Our research proved that a wide range of BP compounds (polyphenols, phenolamides, carotenoids, vitamins, minerals, and others) substantially modulate diverse ferroptosis mechanisms. Accordingly, these phytochemicals and nutrients showed interesting potential in preclinical studies to lead to ferroptosis-mediated outcomes in important pathophysiological processes, including many aging-related disorders. One of the most paramount challenges that remain to be resolved is to determine how different BP compounds act on ferroptosis in different biological and pathophysiological contexts, either through synergistic or antagonistic behaviors. We hope that our current work constitutes a valuable incentive for future investigations in this promising and very relevant research avenue.

Chronic Kidney Disease and Osteoarthritis: Current Understanding and Future Research Directions

Chronic kidney disease (CKD) is a significant public health concern. Osteoarthritis (OA), a common form of arthritis, has been shown to have a dramatically increased prevalence, particularly among individuals aged 40-50 and older, in the presence of CKD. Furthermore, CKD may exacerbate the progression and impact of OA. A survey study revealed that 53.9% of CKD patients undergoing long-term hemodialysis were diagnosed with OA. These findings underscore the potential association between CKD and OA. Uremic toxins, such as indoxyl sulfate, p-cresyl sulfate, transforming growth factor-β, and advanced glycation end-products, are regarded as potential risk factors in various CKD-related conditions, affecting bone and joint metabolism. However, whether these factors serve as a bridging mechanism between CKD and OA comorbidities, as well as their detailed roles in this context, remains unclear. Addressing the progression of OA in CKD patients and identifying effective treatment and prevention strategies is an urgent challenge that warrants immediate attention. This review focuses on describing and discussing the molecular pathological mechanisms underlying CKD-associated OA and the possible therapeutic strategies.

Bioactive Compounds from Propolis on Bone Homeostasis: A Narrative Review

This narrative review explores the potential effects of Propolis and its bioactive compounds on bone health. Propolis, a resinous product collected by bees, is renowned for its antimicrobial, anti-inflammatory, and antioxidant properties. Recent research emphasizes its positive role in osteogenesis, primarily through the modulation of osteoclast and osteoblast activity via molecular pathways. Key mechanisms include reducing inflammatory cytokines, protecting against oxidative stress, and upregulating growth factor essential for bone formation. While compounds such as Caffeic Acid Phenethyl Ester, Apigenin, Quercetin, and Ferulic Acid have been well-documented, emerging evidence points to the significant roles of less-studied compounds like Pinocembrin, Kaempferol, p-Coumaric acid, and Galangin. This review synthesizes the current literature, focusing on the mechanisms by which these bioactive compounds influence osteogenesis. Firstly, it explores the techniques for characterizing bioactive compounds presented in propolis, the chemogeographic variations in its composition, and the effects of both crude extracts and isolated compounds on bone tissue, offering a comprehensive analysis of recent findings across different experimental models. Further, it discusses the effects of Propolis compounds on bone health. In summary, these compounds modulate signaling pathways, including nuclear factor kappa beta, wingless-related integration site, mitogen-activated protein kinase, vascular endothelial growth factor, and reactive oxygen species. These pathways influence the receptor activator of nuclear factor kappa-β/receptor activator of nuclear factor kappa-β ligand/osteoprotegerin system, fostering bone cell differentiation. This regulation mitigates excessive osteoclast formation, stimulates osteoblast activity, and ultimately contributes to the restoration of bone homeostasis by maintaining a balanced bone remodeling process.

Chemical Composition of Mexicali Propolis and Its Effect on Gastric Repair in an Indomethacin-Induced Gastric Injury Murine Model

Propolis is a resinous substance produced by bees that has several biomedical properties that could contribute to the repair process of the gastric mucosa, such as antioxidant, anti-inflammatory, healing, and gastroprotective properties. Thus, this study aimed to determine the chemical composition of Mexicali propolis, its antioxidant capacity, and its effect on gastric repair. Three polarity-directed extracts were obtained: the ethanolic extract, the ethyl acetate extract, and the hexane extract. The antioxidant activity, total phenolic content (TPC), and flavone/flavonol content were determined for each extract. The chemical composition was analysed using HPLC-TOF-MS (High-Performance Liquid Chromatography-Time-Of-Flight Mass Spectrometry) and GC-MS (Gas Chromatography-Mass Spectrometry), and a total of 52 compounds were identified. The results revealed that the ethanolic extract had the greatest effect on free radical scavenging and the content of bioactive compounds. On the basis of these results, the effect of the Mexicali ethanolic extract of propolis (MeEEP) on gastric repair was subsequently evaluated. Prior to the evaluation, MeEEP was found to exhibit low oral toxicity, as determined under the Organisation for Economic Co-operation and Development (OECD) 425 guidelines. Gastric injury was induced in male C57BL/6 mice by intragastric administration of indomethacin (10 mg/kg). MeEEP (300 mg/kg) was administered 6 h after the induction of injury using indomethacin and daily thereafter. The mice were sacrificed at 12, 24, and 48 h to assess the effect. As a result, MeEEP enhanced the repair of the gastric lesion by decreasing the percentage of the bleeding area and attenuating the severity of histological damage, as demonstrated by H&E staining. This effect was associated with a reduction in MPO enzyme activity and in the levels of the proinflammatory cytokines TNF-α, IL-1β, and IL-6, maintaining controlled inflammation in gastric tissue. Furthermore, the administration of the extract increased SOD enzymatic activity and GSH levels, reducing the degree of oxidative damage in the gastric tissue, as demonstrated by low MDA levels. Finally, after evaluating the effect on apoptosis via immunohistochemistry, MeEEP was shown to reduce the expression of the proapoptotic marker Bax and increase the expression of the antiapoptotic marker Bcl-2. In conclusion, these findings suggest that MeEEP may enhance gastric repair through a cytoprotective mechanism by controlling inflammation exacerbation, reducing oxidative stress, and regulating apoptosis. These mechanisms are primarily attributed to the presence of pinocembrin, tectochrysin, chrysin, apigenin, naringenin, acacetin, genistein, and kaempferol. It is important to highlight that this study provides a preliminary exploration of the reparative effect of Mexican propolis, describing the potential mechanisms of action of the compounds present in Mexicali propolis.

Role of mitophagy in intervertebral disc degeneration: A narrative review

OBJECTIVE

The pivotal role of mitophagy in the initiation and progression of intervertebral disc (IVD) degeneration (IDD) has become increasingly apparent due to a growing body of research on its pathogenesis. This review summarizes the role of mitophagy in IDD and the therapeutic potential of targeting this process.

DESIGN

This narrative review is divided into three parts: the regulatory mechanisms of mitophagy, the role of mitophagy in IDD, and the applications and prospects of mitophagy for the treatment of IDD.

RESULTS

Mitophagy protects cells against harmful external stimuli and plays a crucial protective role by promoting extracellular matrix (ECM) production, inhibiting ECM degradation, and reducing apoptosis, senescence, and cartilage endplate calcification. However, excessive mitophagy is often detrimental to cells. Currently, the regulatory mechanisms governing appropriate and excessive mitophagy remain unclear.

CONCLUSIONS

Proper mitophagy effectively maintains IVD cell homeostasis and slows the progression of IDD. Conversely, excessive mitophagy may accelerate IDD development. Further research is needed to elucidate the regulatory mechanisms underlying appropriate and excessive mitophagy, which could provide new theoretical support for the application of mitophagy targeting to the treatment of IDD.

Molecular mechanism of mechanical pressure induced changes in the microenvironment of intervertebral disc degeneration

BACKGROUND

Lower back pain, as a typical clinical symptom of spinal degenerative diseases, is emerging as a major social problem. According to recent researches, the primary cause of this problem is intervertebral disc degeneration (IVDD). IVDD is closely associated with factors such as age, genetics, mechanical stimulation (MS), and inadequate nutrition. In recent years, an increasing number of studies have further elucidated the relationship between MS and IVDD. However, the exact molecular mechanisms by which MS induces IVDD remain unclear, highlighting the need for in-depth exploration and study of the relationship between MS and IVDD.

METHODS

Search for relevant literature on IVDD and MS published from January 1, 2010, to the present in the PubMed database.

RESULTS

One of the main causes of IVDD is MS, and loading modalities have an impact on the creation of matrix metalloproteinase, the metabolism of the cellular matrix, and other biochemical processes in the intervertebral disc. Nucleus pulposus cell death induced by MS, cartilage end-plate destruction accompanied by pyroptosis, apoptosis, iron death, senescence, autophagy, oxidative stress, inflammatory response, and ECM degradation interact with one another to form a cooperative signaling network.

CONCLUSION

This review discusses the molecular mechanisms of the changes in the microenvironment of intervertebral discs caused by mechanical pressure, explores the interaction between mechanical pressure and IVDD, and provides new insights and approaches for the clinical prevention and treatment of IVDD.

Bioinformatics proved the existence of potential hub genes activating autophagy to participate in cartilage degeneration in osteonecrosis of the femoral head

The obvious degeneration of articular cartilage occurs in the late stage of osteonecrosis of the femoral head (ONFH), which aggravates the condition of ONFH. This study aimed to demonstrate aberrant activation of autophagy processes in ONFH chondrocytes through bioinformatics and to predict and identify relevant hub genes and pathways. Differentially expressed genes (DEGs) were identified using R software in the GSE74089 dataset from the GEO database. DEGs were crossed with the Human Autophagy Database (HADb) autophagy genes to screen out autophagy-related differential genes (AT-DEGs). GSEA, GSVA, GO, and KEGG pathway enrichment analyses of AT-DEGs were performed. The STRING database was used to analyze the protein-protein interaction (PPI) of the AT-DEGs network, and the MCODE and CytoHubba plugin in the Cytoscape software was used to analyze the key gene cluster module and screen the hub genes. The PPI network of hub genes was constructed using the GeneMANIA database, and functional enrichment and gene connectivity categories were analyzed. The expression levels of hub genes of related genes in the ONFH patients were verified in the dataset GSE123568, and the protein expression was verified by immunohistochemistry in tissues. The analysis of DEGs revealed abnormal autophagy in ONFH cartilage. AT-DEGs in ONFH have special enrichment in macroautophagy, autophagosome membrane, and phosphatidylinositol-3-phosphate binding. In the GSE123568 dataset, it was also found that ATG2B, ATG4B, and UVRAG were all significantly upregulated in ONFH patients. By immunohistochemistry, it was verified that ATG2B, ATG4B, and UVRAG were significantly overexpressed. These three genes regulate the occurrence and extension of autophagosomes through the PI3KC3C pathway. Finally, we determined that chondrocytes in ONFH undergo positive regulation of autophagy through the corresponding pathways involved in three genes: ATG2B, ATG4B, and UVRAG.

IGF2BP1 Bolsters the Chondrocytes Ferroptosis of Osteoarthritis by Targeting m6A/MMP3 Axis

Introduction

Chondrocyte degeneration and senescence are characteristics of osteoarthritis (OA) and other joint degenerative diseases, and ferroptosis has been observed to regulate the development of OA. However, the role of the N6-methyladenosine (m6A) modification in OA ferroptosis remains unclear.

Methods

This study performed series of assays to investigate the function of the m6A reader IGF2BP1 in OA ferroptosis, including m6A quantitative analysis, Iron (Fe2+) release analysis, Malondialdehyde (MDA) measurement, lipid peroxidation (ROS) detection and Glutathione (GSH) measurement. The molecular interaction and mechanism analysis was performed by Luciferase reporter assay, mRNA stability analysis and RNA immunoprecipitation (RIP) assay.

Results

These results indicate that IGF2BP1 is upregulated in IL-1β-induced chondrocytes. Functionally, IGF2BP1 silencing represses ferroptosis, including iron (Fe2+) accumulation, malondialdehyde, and reactive oxygen species (ROS). Mechanistically, among the potential downstream targets, matrix metalloproteinase-3 (MMP3) was observed to harbor a significant m6A modified site in the 3'-UTR. IGF2BP1 combines with MMP3 through the binding of m6A sites, thereby enhancing MMP3 mRNA stability.

Discussion

In conclusion, our findings revealed the functions and mechanisms of m6A regulator IGF2BP1 in OA chondrocyte's ferroptosis, providing a novel target for OA treatment.

A High-Throughput Screening of a Natural Products Library for Mitochondria Modulators

Mitochondria, the energy hubs of the cell, are progressively becoming attractive targets in the search for potent therapeutics against neurodegenerative diseases. The pivotal role of mitochondrial dysfunction in the pathogenesis of various diseases, including Parkinson's disease (PD), underscores the urgency of discovering novel therapeutic strategies. Given the limitations associated with available treatments for mitochondrial dysfunction-associated diseases, the search for new potent alternatives has become imperative. In this report, we embarked on an extensive screening of 4224 fractions from 384 Australian marine organisms and plant samples to identify natural products with protective effects on mitochondria. Our initial screening using PD patient-sourced olfactory neurosphere-derived (hONS) cells with rotenone as a mitochondria stressor resulted in 108 promising fractions from 11 different biota. To further assess the potency and efficacy of these hits, the 11 biotas were subjected to a subsequent round of screening on human neuroblastoma (SH-SY5Y) cells, using 6-hydroxydopamine to induce mitochondrial stress, complemented by a mitochondrial membrane potential assay. This rigorous process yielded 35 active fractions from eight biotas. Advanced analysis using an orbit trap mass spectrophotometer facilitated the identification of the molecular constituents of the most active fraction from each of the eight biotas. This meticulous approach led to the discovery of 57 unique compounds, among which 12 were previously recognized for their mitoprotective effects. Our findings highlight the vast potential of natural products derived from Australian marine organisms and plants in the quest for innovative treatments targeting mitochondrial dysfunction in neurodegenerative diseases.

Exploring the Prospective Role of Propolis in Modifying Aging Hallmarks

Aging populations worldwide are placing age-related diseases at the forefront of the research agenda. The therapeutic potential of natural substances, especially propolis and its components, has led to these products being promising agents for alleviating several cellular and molecular-level changes associated with age-related diseases. With this in mind, scientists have introduced a contextual framework to guide future aging research, called the hallmarks of aging. This framework encompasses various mechanisms including genomic instability, epigenetic changes, mitochondrial dysfunction, inflammation, impaired nutrient sensing, and altered intercellular communication. Propolis, with its rich array of bioactive compounds, functions as a potent functional food, modulating metabolism, gut microbiota, inflammation, and immune response, offering significant health benefits. Studies emphasize propolis' properties, such as antitumor, cardioprotective, and neuroprotective effects, as well as its ability to mitigate inflammation, oxidative stress, DNA damage, and pathogenic gut bacteria growth. This article underscores current scientific evidence supporting propolis' role in controlling molecular and cellular characteristics linked to aging and its hallmarks, hypothesizing its potential in geroscience research. The aim is to discover novel therapeutic strategies to improve health and quality of life in older individuals, addressing existing deficits and perspectives in this research area.