Epigallocatechin-3-O-gallate ameliorates oxidative stress-induced chondrocyte dysfunction and exerts chondroprotective effects via the Keap1/Nrf2/ARE signaling pathway

J-shaped association of dietary catechins intake with the prevalence of osteoarthritis and moderating effect of physical activity: an American population-based cohort study

Background

Catechins are a class of natural compounds with a variety of health benefits, The relationship between catechins and the prevalence of osteoarthritis (OA) is unknown. This study investigated the associations between daily intake of catechins and the prevalence of OA among American adults and assessed the moderating effect of physical activity (PA).

Methods

This study included 10,039 participants from the National Health and Nutrition Examination Survey (2007-2010,2017-2018). The logistic regression, weighted quantile sum (WQS) regression, and restricted cubic spline (RCS) regression models were conducted to explore the associations between daily intake of catechins and the prevalence of OA. Moreover, interaction tests were performed to assess the moderating effect of PA.

Results

After multivariable adjustment, the weighted multivariable logistic regression and RCS regression analyses revealed significant J-shaped non-linear correlations between intakes of epigallocatechin and epigallocatechin 3-gallate had significant associations with the prevalence of OA among in U.S. adults. WQS regression analysis showed that excessive epigallocatechin intake was the most significant risk factor for OA among all subtypes of catechins. In the interaction assay, PA showed a significant moderating effect in the relationship between epigallocatechin intake and OA prevalence.

Conclusions

The intake of gallocatechin and gallocatechin 3-gallate had a significant negative correlation with the prevalence of OA and the dose-response relationship was J-shaped.PA below 150 MET-min/week and the threshold intakes of 32.70mg/d for epigallocatechin and 76.24mg/d for epigallocatechin 3-gallate might be the targets for interventions to reduce the risk of developing OA.

Nrf2: A promising therapeutic target in bone-related diseases

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

Natural anti-inflammatory products for osteoarthritis: From molecular mechanism to drug delivery systems and clinical trials

Osteoarthritis (OA) is a degenerative joint disease that affects millions globally. The present nonsteroidal anti-inflammatory drug treatments have different side effects, leading researchers to focus on natural anti-inflammatory products (NAIPs). To review the effectiveness and mechanisms of NAIPs in the cellular microenvironment, examining their impact on OA cell phenotype and organelles levels. Additionally, we summarize relevant research on drug delivery systems and clinical randomized controlled trials (RCTs), to promote clinical studies and explore natural product delivery options. English-language articles were searched on PubMed using the search terms "natural products," "OA," and so forth. We categorized search results based on PubChem and excluded "natural products" which are mix of ingredients or compounds without the structure message. Then further review was separately conducted for molecular mechanisms, drug delivery systems, and RCTs later. At present, it cannot be considered that NAIPs can thoroughly prevent or cure OA. Further high-quality studies on the anti-inflammatory mechanism and drug delivery systems of NAIPs are needed, to determine the appropriate drug types and regimens for clinical application, and to explore the combined effects of different NAIPs to prevent and treat OA.

Mitochondria-Related Gene MAOB is a Key Biomarker of Osteoarthritis and Inhibition of Its Expression Reduces LPS-induced Chondrocyte Damage

The mitochondria are an important organelle in cells responsible for producing energy, and its abnormal function is closely related to the occurrence and development of osteoarthritis. Finding key genes associated with mitochondrial dysfunction in osteoarthritis can provide new ideas for the study of its pathogenesis. Firstly, 371 differential expressed genes (DEGs) were obtained through bioinformatics analysis of the GSE12021 and GSE55235 datasets in the GEO database, and 24 mitochondria-related DEGs (Mito-DEGs) were obtained by crossing differential genes with mitochondrial related genes. Next, KEGG and GO analysis of Mito-DEGs showed that upregulated Mito-DEGs were mainly enriched in small molecule catabolic process and tryptophan metabolism, while downregulated Mito-DEGs were mainly enriched in acetyl-CoA metabolic process and fatty acid biosynthesis. Furthermore, the key genes ME2 and MAOB were obtained through protein-protein interaction network analysis and lasso cox analysis of the 24 Mito-DEGs. In addition, the comparison results of immune cell scores showed differences between T cells CD4 memory resting, T cells regulatory (Tregs), Mast cells resting, and Mast cells activated in the OA group and the control group. More importantly, the potential regulatory mechanisms of key genes were studied through GSEA analysis and their correlation with immune infiltrating cells, immune checkpoints, m6A, and ferroptosis. Finally, in LPS-induced C28/I2 cells, silencing MAOB reduced inflammation injury and inhibited mitochondrial damage. Our research findings suggest that MAOB may hold potential as a target for the diagnosis and treatment of osteoarthritis.

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.

Potential of green tea EGCG in neutralizing SARS-CoV-2 Omicron variant with greater tropism toward the upper respiratory tract

Background

COVID-19 due to SARS-CoV-2 infection has had an enormous adverse impact on global public health. As the COVID-19 pandemic evolves, the WHO declared several variants of concern (VOCs), including Alpha, Beta, Gamma, Delta, and Omicron. Compared with earlier variants, Omicron, now a dominant lineage, exhibits characteristics of enhanced transmissibility, tropism shift toward the upper respiratory tract, and attenuated disease severity. The robust transmission of Omicron despite attenuated disease severity still poses a great challenge for pandemic control. Under this circumstance, its tropism shift may be utilized for discovering effective preventive approaches.

Scope and approach

This review aims to estimate the potential of green tea epigallocatechin gallate (EGCG), the most potent antiviral catechin, in neutralizing SARS-CoV-2 Omicron variant, based on current knowledge concerning EGCG distribution in tissues and Omicron tropism.

Key findings and conclusions

EGCG has a low bioavailability. Plasma EGCG levels are in the range of submicromolar concentrations following green tea drinking, or reach at most low μM concentrations after pharmacological intervention. Nonetheless, its levels in the upper respiratory tract could reach concentrations as high as tens or even hundreds of μM following green tea consumption or pharmacological intervention. An approach for delivering sufficiently high concentrations of EGCG in the pharynx has been developed. Convincing data have demonstrated that EGCG at tens to hundreds of μM can dramatically neutralize SARS-CoV-2 and effectively eliminate SARS-CoV-2-induced cytopathic effects and plaque formation. Thus, EGCG, which exhibits hyperaccumulation in the upper respiratory tract, deserves closer investigation as an antiviral in the current global battle against COVID-19, given Omicron's greater tropism toward the upper respiratory tract.

Naturally derived injectable hydrogels with ROS-scavenging property to protect transplanted stem cell bioactivity for osteoarthritic cartilage repair

Intra-articular injection of adipose mesenchymal stem cells (ADSCs) is a potential alternative to the treatment of osteoarthritis (OA) and has aroused great interest of clinical researchers. However, the hostile microenvironment in the joint cavity, characterized by reactive oxygen species (ROS) accumulation and excessive inflammation, disturbs the bioactivity of the transplanted stem cells. The (-)-epigallocatechin-3-O-gallate (EGCG), a green tea catechin, has attracted the researchers' attention owing to its powerful ROS-scavenging and antioxidant properties. In this study, to avoid rapid degradation and/or depletion of EGCG, we prepare a long-lasting injectable hydrogel by EGCG and hyaluronic acid (HA). The naturally derived hydrogels with excellent biocompatibility and durable retention time can capture the redundant ROS continuously and efficiently, thus protecting ADSCs from ROS-mediated death and bioactivity inhibition, including cell survival, proliferation and chondrogenic differentiation. Intra-articular injection of this ADSCs loaded hydrogel significantly induced synovial macrophages polarization to M2 phenotype, decreased pro-inflammatory cytokines (e.g., IL-1β, MMP-13, and TNF-α) expression, promoted cartilage matrix formation, and repaired cartilage destruction in OA. This stem cell-protected hydrogel delivery strategy showed superior efficacy than ADSCs delivering or EGCG-HA injection singly, which providing a potential alternative strategy for OA management.

Comparative in silico and in vitro study of the stability and biological activity of an octapeptide from microalgae Isochrysis zhanjiangensis and its truncated short peptide

In this study, the structural characteristics and active sites of the octapeptide (IIAVEAGC), the pentapeptide (IIAVE) and tripeptide (AGC) were studied in silica and in vitro.

Epigallocatechin Gallate Attenuates Gentamicin-Induced Nephrotoxicity by Suppressing Apoptosis and Ferroptosis

Gentamicin (GEN) is a kind of aminoglycoside antibiotic with the adverse effect of nephrotoxicity. Currently, no effective measures against the nephrotoxicity have been approved. In the present study, epigallocatechin gallate (EG), a useful ingredient in green tea, was used to attenuate its nephrotoxicity. EG was shown to largely attenuate the renal damage and the increase of malondialdehyde (MDA) and the decrease of glutathione (GSH) in GEN-injected rats. In NRK-52E cells, GEN increased the cellular ROS in the early treatment phase and ROS remained continuously high from 1.5 H to 24 H. Moreover, EG alleviated the increase of ROS and MDA and the decrease of GSH caused by GEN. Furthermore, EG activated the protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). After the treatment of GEN, the protein level of cleaved-caspase-3, the flow cytometry analysis and the JC-1 staining, the protein levels of glutathione peroxidase 4 (GPX4) and SLC7A11, were greatly changed, indicating the occurrence of both apoptosis and ferroptosis, whereas EG can reduce these changes. However, when Nrf2 was knocked down by siRNA, the above protective effects of EG were weakened. In summary, EG attenuated GEN-induced nephrotoxicity by suppressing apoptosis and ferroptosis.

Echinacoside alleviates osteoarthritis in rats by activating the Nrf2-HO-1 signaling pathway

OBJECTIVE

Osteoarthritis (OA) is a progressive disease characterized by degeneration of cartilage and echinacoside (Ech) has anti-inflammatory and antioxidant effects in various human diseases. This study aimed to reveal the effect and potential mechanism of Ech on OA.

MATERIALS AND METHODS

The in vitro OA model was established by rat chondrocytes treated with IL-1β, and the in vivo OA model was established by anterior cruciate ligament transaction. The effect of Ech on the viability, inflammatory response, extracellular matrix (ECM) degradation, and oxidative stress of IL-1β-treated rat chondrocytes were evaluated by Cell Counting Kit-8 assay, enzyme-linked immunosorbent assay, quantitative real-time PCR, Western blot, and immunofluorescence assay. Meanwhile, the mechanism of Ech was assessed using Western blot, Cell Counting Kit-8 assay, enzyme-linked immunosorbent assay, and immunofluorescence analysis. Moreover, the function of Ech in vivo was analyzed in rat models of OA.

RESULTS

Functionally, Ech enhanced the viability of rat chondrocytes, repressed the inflammatory response and ECM degradation of rat chondrocytes induced by IL-1β with restrained oxidative stress. Mechanically, Ech repressed IL-1β-induced chondrocyte injury by activating the Nrf2/HO-1 signaling pathway. Meanwhile, Ech alleviated the degree of articular cartilage injury in rats and exerted protective effects on the rat model of OA in vivo.

DISCUSSION AND CONCLUSIONS

Ech alleviated OA in rats by activating the Nrf2-HO-1 signaling pathway.