Dual regulatory roles of HMGB1 in inflammatory reaction of chondrocyte cells and mice

Cbx4 SUMOylates BRD4 to regulate the expression of inflammatory cytokines in post-traumatic osteoarthritis

Brominated domain protein 4 (BRD4) is a chromatin reader known to exacerbate the inflammatory response in post-traumatic osteoarthritis (PTOA) by controlling the expression of inflammatory cytokines. However, the extent to which this regulatory effect is altered after BRD4 translation remains largely unknown. In this study, we showed that the E3 SUMO protein ligase CBX4 (Cbx4) is involved in the SUMO modification of BRD4 to affect its ability to control the expression of the proinflammatory genes IL-1β, TNF-α, and IL-6 in synovial fibroblasts. Specifically, Cbx4-mediated SUMOylation of K1111 lysine residues prevents the degradation of BRD4, thereby activating the transcriptional activities of the IL-1β, TNF-α and IL-6 genes, which depend on BRD4. SUMOylated BRD4 also recruits the multifunctional methyltransferase subunit TRM112-like protein (TRMT112) to further promote the processing of proinflammatory gene transcripts to eventually increase their expression. In vivo, treatment of PTOA with a Cbx4 inhibitor in rats was comparable to treatment with BRD4 inhibitors, indicating the importance of SUMOylation in controlling BRD4 to alleviate PTOA. Overall, this study is the first to identify Cbx4 as the enzyme responsible for the SUMO modification of BRD4 and highlights the central role of the Cbx4-BRD4 axis in exacerbating PTOA from the perspective of inflammation.

Pyroptosis-related crosstalk in osteoarthritis: Macrophages, fibroblast-like synoviocytes and chondrocytes

The pathogenesis of osteoarthritis (OA) involves a multifaceted interplay of inflammatory processes. The initiation of pyroptosis involves the secretion of pro-inflammatory cytokines and has been identified as a critical factor in regulating the development of OA. Upon initiation of pyroptosis, a multitude of inflammatory mediators are released and can be disseminated throughout the synovial fluid within the joint cavity, thereby facilitating intercellular communication across the entire joint. The main cellular components of joints include chondrocytes (CC), fibroblast-like synoviocytes (FLS) and macrophages (MC). Investigating their interplay can enhance our understanding of OA pathogenesis. Therefore, we comprehensively examine the mechanisms underlying pyroptosis and specifically investigate the intercellular interactions associated with pyroptosis among these three cell types, thereby elucidating their collective contribution to the progression of OA. We propose the concept of ' CC-FLS-MC pyroptosis-related crosstalk', describe the various pathways of pyroptotic interactions among these three cell types, and focus on recent advances in intervening pyroptosis in these three cell types for treating OA. We hope this will provide a possible direction for diversification of treatment for OA. The Translational potential of this article. The present study introduces the concept of 'MC-FLS-CC pyroptosis-related crosstalk' and provides an overview of the mechanisms underlying pyroptosis, as well as the pathways through which it affects MC, FLS, and CC. In addition, the role of regulation of these three types of cellular pyroptosis in OA has also been concerned. This review offers novel insights into the interplay between these cell types, with the aim of providing a promising avenue for diversified management of OA.

A Review of Proposed Mechanisms in Rheumatoid Arthritis and Therapeutic Strategies for the Disease

Rheumatoid arthritis (RA) is characterized by synovial edema, inflammation, bone and cartilage loss, and joint degradation. Patients experience swelling, stiffness, pain, limited joint movement, and decreased mobility as the condition worsens. RA treatment regimens often come with various side effects, including an increased risk of developing cancer and organ failure, potentially leading to mortality. However, researchers have proposed mechanistic hypotheses to explain the underlying causes of synovitis and joint damage in RA patients. This review article focuses on the role of synoviocytes and synoviocytes resembling fibroblasts in the RA synovium. Additionally, it explores the involvement of epigenetic regulatory systems, such as microRNA pathways, silent information regulator 1 (SIRT1), Peroxisome proliferatoractivated receptor-gamma coactivator (PGC1-α), and protein phosphatase 1A (PPM1A)/high mobility group box 1 (HMGB1) regulators. These mechanisms are believed to modulate the function of receptors, cytokines, and growth factors associated with RA. The review article includes data from preclinical and clinical trials that provide insights into potential treatment options for RA.

Recent Updates on Oncogenic Signaling of Aurora Kinases in Chemosensitive, Chemoresistant Cancers: Novel Medicinal Chemistry Approaches for Targeting Aurora Kinases

The Aurora Kinase family (AKI) is composed of serine-threonine protein kinases involved in the modulation of the cell cycle and mitosis. These kinases are required for regulating the adherence of hereditary-related data. Members of this family can be categorized into aurora kinase A (Ark-A), aurora kinase B (Ark-B), and aurora kinase C (Ark-C), consisting of highly conserved threonine protein kinases. These kinases can modulate cell processes such as spindle assembly, checkpoint pathway, and cytokinesis during cell division. The main aim of this review is to explore recent updates on the oncogenic signaling of aurora kinases in chemosensitive/chemoresistant cancers and to explore the various medicinal chemistry approaches to target these kinases. We searched Pubmed, Scopus, NLM, Pubchem, and Relemed to obtain information pertinent to the updated signaling role of aurora kinases and medicinal chemistry approaches and discussed the recently updated roles of each aurora kinases and their downstream signaling cascades in the progression of several chemosensitive/chemoresistant cancers; subsequently, we discussed the natural products (scoulerine, Corynoline, Hesperidin Jadomycin-B, fisetin), and synthetic, medicinal chemistry molecules as aurora kinase inhibitors (AKIs). Several natural products' efficacy was explained as AKIs in chemosensitization and chemoresistant cancers. For instance, novel triazole molecules have been used against gastric cancer, whereas cyanopyridines are used against colorectal cancer and trifluoroacetate derivatives could be used for esophageal cancer. Furthermore, quinolone hydrazine derivatives can be used to target breast cancer and cervical cancer. In contrast, the indole derivatives can be preferred to target oral cancer whereas thiosemicarbazone-indole could be used against prostate cancer, as reported in an earlier investigation against cancerous cells. Moreover, these chemical derivatives can be examined as AKIs through preclinical studies. In addition, the synthesis of novel AKIs through these medicinal chemistry substrates in the laboratory using in silico and synthetic routes could be beneficial to develop prospective novel AKIs to target chemoresistant cancers. This study is beneficial to oncologists, chemists, and medicinal chemists to explore novel chemical moiety synthesis to target specifically the peptide sequences of aurora kinases in several chemoresistant cancer cell types.

Advances in understanding effects of miRNAs on apoptosis, autophagy, and pyroptosis in knee osteoarthritis

MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs. MicroRNAs-mediated signaling pathways play a critical regulatory role in inducing apoptosis, autophagy, and pyroptosis in developing knee osteoarthritis (KOA). Given this, we searched databases, such as PubMed, using keywords including "miRNA," "knee osteoarthritis," "apoptosis," "autophagy," "pyroptosis", and their combinations. Through an extensive literature review, we conclude that miRNAs can be modulated through various signaling pathways, such as Wnt/β-catenin, TGF-β, PI3K/AKT/mTOR, and NLRP3/Caspase-1, to regulate apoptosis, autophagy, and pyroptosis in KOA. Furthermore, we note that P2X7R and HMGB1 may be crucial regulatory molecules involved in the interconnected regulation of apoptosis, autophagy, and pyroptosis in KOA. Additionally, we describe that miR-140-5p and miR-107 can modulate the advancement of KOA chondrocytes by targeting distinct molecules involved in apoptosis, autophagy, and pyroptosis, respectively. Therefore, we conclude that miRNAs may be potential biomarkers and therapeutic targets for the early prediction, diagnosis, and effective therapeutic approaches of KOA.

Wound healing activity of aqueous dispersion of fullerene C60 produced by "green technology"

In addition to exhibited antioxidant and anti-inflammatory activity, fullerene C60 is a promising wound healing agent. An important stage in the production of fullerene-based ointments is the stability of the aqueous fullerene dispersion (AFD) with minimum size of colloidal fullerene aggregates and sufficiently high concentration. To achieve these parameters tangential flow filtration of fullerene C60 was used ("green technology"). As estimated by small-angle neutron scattering and dynamic light scattering purified AFDs with narrow-size distribution nanoclusters have a size of 6 nm and are assembled into agglomerates which reach a size of 150 nm. The ability of the AFD to exhibit regenerative activity was studied using the animal wound model. This study shows for the first time that the fullerene-based composition stimulates the healing of wounds of various origins. We assume that the mechanism of the AFD wound-healing activity is associated with the aryl hydrocarbon receptor and macrophages activity.

Glycyrrhizin regulates rat TMJOA progression by inhibiting the HMGB1-RAGE/TLR4-NF-κB/AKT pathway

To investigate the role of glycyrrhizin on the progression of temporomandibular joint osteoarthritis (TMJOA) and the underlying mechanism by regulation of the high‐mobility group box 1 (HMGB1) receptor for advanced glycation end products (RAGE)/toll‐like receptor 4 (TLR4)‐nuclear factor kappa B (NF‐κB)/protein kinase B (AKT) pathway. After a rat model of TMJOA was built by intra‐articular injection of monosodium iodoacetate, glycyrrhizin was intragastrically administered at low concentration (20 mg/kg) or high concentration (50 mg/kg). Micro‐computed tomography, histological and immunohistochemical analysis were used to reveal the progression of TMJOA. Rat TMJ chondrocytes and disc cells were cultured in inflammatory condition with different doses of glycyrrhizin. Western blot was used to evaluate the effect of glycyrrhizin on the HMGB1‐RAGE/TLR4‐NF‐κB/AKT pathway. Administration of glycyrrhizin alleviated cartilage degeneration, lowered the levels of inflammatory and catabolic mediators and reduced the production of HMGB1, RAGE and TLR4 in TMJOA animal model. Increased production of RAGE and TLR4, and activated intracellular NF‐κB and/or AKT signalling pathways in chondrocytes and disc cells were found in inflammatory condition. Upon activation, matrix metalloprotease‐3 and interleukin‐6 were upregulated. Glycyrrhizin inhibited not only HMGB1 release but also RAGE and TLR4 in inflammatory condition. Glycyrrhizin alleviated the pathological changes of TMJOA by regulating the HMGB1‐RAGE/TLR4‐NF‐kB/AKT signalling pathway. This study revealed the potential of glycyrrhizin as a novel therapeutic drug to suppress TMJ cartilage degradation.

An Evidence-Based Systematic Review of Human Knee Post-Traumatic Osteoarthritis (PTOA): Timeline of Clinical Presentation and Disease Markers, Comparison of Knee Joint PTOA Models and Early Disease Implications

Understanding the causality of the post-traumatic osteoarthritis (PTOA) disease process of the knee joint is important for diagnosing early disease and developing new and effective preventions or treatments. The aim of this review was to provide detailed clinical data on inflammatory and other biomarkers obtained from patients after acute knee trauma in order to (i) present a timeline of events that occur in the acute, subacute, and chronic post-traumatic phases and in PTOA, and (ii) to identify key factors present in the synovial fluid, serum/plasma and urine, leading to PTOA of the knee in 23-50% of individuals who had acute knee trauma. In this context, we additionally discuss methods of simulating knee trauma and inflammation in in vivo, ex vivo articular cartilage explant and in vitro chondrocyte models, and answer whether these models are representative of the clinical inflammatory stages following knee trauma. Moreover, we compare the pro-inflammatory cytokine concentrations used in such models and demonstrate that, compared to concentrations in the synovial fluid after knee trauma, they are exceedingly high. We then used the Bradford Hill Framework to present evidence that TNF-α and IL-6 cytokines are causal factors, while IL-1β and IL-17 are credible factors in inducing knee PTOA disease progresssion. Lastly, we discuss beneficial infrastructure for future studies to dissect the role of local vs. systemic inflammation in PTOA progression with an emphasis on early disease.

MiR-129-5p shuttled by human synovial mesenchymal stem cell-derived exosomes relieves IL-1β induced osteoarthritis via targeting HMGB1

AIMS

To explore the therapeutic effect of miR-129-5p carried by exosomes from Human Synovial Mesenchymal Stem Cell (HS-MSC) on osteoarthritis(OA).

MATERIALS AND METHODS

The levels of miR-129-5p and high mobility group protein -1 (HMGB1) and interleukin-1β (IL-1β) in the joint fluid of OA patients were respectively detected via real-time quantitative reverse transcription-PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). IL-1β was taken to act on chondrocytes for the establishment of OA model in vitro. Ultracentrifugation was conducted to isolate HS-MSC exosomes (HS-MSC-Exo) from the supernatant. Western blot and ELISA were carried out to measure the expression of iNOS, COX2, MMP13, Collagen 2, TLR4, NF-κB, Caspase3, Bcl-2, HMGB1 in chondrocytes. Flow cytometry was conducted to detect the apoptosis of chondrocytes. Besides, bioinformatics was employed to predict the targeted relationship between miR-129-5p and HMGB1, which was further verified via dual luciferase activity experiments.

KEY FINDINGS

The results illustrated that miR-129-5p was decreased in OA patients and IL-1β-induced chondrocytes, while HMGB1 was notably upregulated. HS-MSC-Exo rich in miR-129-5p remarkably declined the inflammatory response and apoptosis of chondrocytes, while HS-MSC-Exo deficient in miR-129-5p increased the IL-1β-mediated inflammatory response and apoptosis of chondrocytes. In terms of mechanism, miR-129-5p targets the 3'UTR end of HMGB1 and inhibits IL-1β-mediated upregulation of HMGB1.

SIGNIFICANCE

In a word, this paper proved that miR-129-5p, existing in HS-MSC-Exo, can suppress the IL-1β-mediated OA by inhibiting HMGB1 release.

Active vitamin D activates chondrocyte autophagy to reduce osteoarthritis via mediating the AMPK–mTOR signaling pathway

Osteoarthritis (OA) is a common joint degenerative disease. Vitamin D (VD) is essential for bone health. We hypothesized that active VD could be used as a therapeutic treatment for OA. Low serum levels of 25-hydroxyvitamin D [25(OH)D] have been found in patients with OA, and thus the serum level of VD could be diagnostic of OA. To test this, we established a mouse model of OA. The results from staining with hematoxylin–eosin and Safranin O – Fast Green indicated that active VD reduced the symptoms of OA in mice. The results from Western blotting indicated that treatment with VD increased the activity of the p-AMPK–AMPK signaling pathway and decreased the p-mTOR–mTOR pathway; it also increased the ratio of LC3II:LC3I antibodies and the protein expression levels of Beclin-1, but decreased the level of p62. Further, treatment with VD reduced the levels of tumor necrosis factor-α and interleukin-6 both in cartilage tissues and in chondrocytes. Administration of the AMPK inhibitor compound C and autophagy inhibitor 3-methyladenine (3-MA) reversed these changes following VD treatment. In addition, the results from transfection with mRFP-GFP-LC3 indicated that active VD led to autophagosome aggregation in OA chondrocytes. 3-MA inhibited cell autophagy and promoted inflammation in OA. This study provides evidence that active VD activate chondrocyte autophagy to reduce OA inflammation via activating the AMPK–mTOR signaling pathway. Treatment with active VD could be a novel therapeutic option for OA.

Early stage blockade of the alarmin HMGB1 reduces cartilage destruction in experimental OA

OBJECTIVE

The alarmin HMGB1 is an endogenous molecule that is released into the extracellular space upon trauma or cell activation. Extracellular HMGB1 initiates innate immune responses and besides mediating inflammation, has osteoclast-activating features and mediates pain, all important features in OA. The aim of this study was to examine the involvement of HMGB1 in experimental OA and to explore the effect of local anti-HMGB1-therapy on disease progression.

METHOD

OA was induced in mice by surgical destabilization of knee joints and HMGB1 expression and localization was assessed by immunohistochemistry. For therapy evaluation, HMGB1-neutralizing antibodies were injected intraarticularly, alone or encapsulated in an injectable hyaluronan-based delivery vehicle. Human primary chondrocytes were stimulated with rHMGB1 and analyzed by qPCR and cytometric bead-array.

RESULTS

HMGB1 immunostaining of mouse OA joints demonstrated intra- and pericellular expression in chondrocytes, overlapping with proteoglycan depleted areas. Intra-articular injection of anti-HMGB1 antibodies had cartilage-protective effects, comparable to treatment with a TNF inhibitor. Direct and vehicle-based delivery had similar ameliorating effects and the effect of a single, early injection could not be enhanced by repeated injections. In vitro stimulation of chondrocytes with rHMGB1 affected chondrocyte function by inducing protein expression of IL6 and IL8 and downregulating mRNA of COL2A1.

CONCLUSIONS

Our results suggest that the alarmin HMGB1 might be a new target for OA therapy development as we could observe an aberrant HMGB1 expression in mouse OA joints, stimulation of chondrocytes with rHMGB1 induced cytokine production and decreased matrix production and finally that HMGB1 blockade suppressed disease progression.

Comparison of early-stage changes of osteoarthritis in cartilage and subchondral bone between two different rat models

Osteoarthritis (OA) is a chronic degenerative joint disease and the major cause of joint pain and disability in the elderly. It is mainly characterized by articular cartilage degradation and subchondral bone remodeling. There are two main types of OA: natural occurring OA and secondary OA, mainly associated with aging and trauma, respectively. In this study, we established two OA models in rat knee joints to simulate the two types of OA, using the type II collagenase injection (CI) and anterior cruciate ligament transection (ACLT), respectively. After intervention for 2-6 weeks, cartilage and subchondral bone changes were detected in histological staining, immunochemistry, and micro-CT. Results showed that both models with typical pathology changes of OA were successfully induced, while the development and severity of OA process in the models were different. In ACLT rats, the cartilage damage was milder, lasted for a shorter time, and subchondral bone reconstruction occurred earlier, compared with the changes in CI rats. The cartilage damage was secondary to subchondral bone change in ACLT rats, while subchondral bone change was secondary to cartilage degeneration in CI rats. In conclusion, the interaction between cartilage and subchondral bone is different between the natural-occurring and secondary OA models. These two models not only suggest potential different mechanisms of the two types of OA, but also provide new directions for OA treatment and prevention.

Identification of microRNA‑363‑3p as an essential regulator of chondrocyte apoptosis in osteoarthritis by targeting NRF1 through the p53‑signaling pathway

Osteoarthritis (OA) is a degenerative joint disease that affects the physical, and mental health of middle-aged and elderly people. The aims of the present study were to determine the biological function and molecular mechanisms of miR-363-3p in chondrocyte apoptosis. Exploration of the molecular mechanisms of OA may be helpful in the understand of the causes, and facilitating the prevention and treatment of OA. In the present study, the expression of nuclear respiratory factor1 (NRF1) was downregulated in the articular cartilage of OA rats in vivo and lipopolysaccharide (LPS)-treated chondrocytes in vitro. MicroRNAs (miRNA) are regulators of gene expression in the progression of OA. TargetScan software was used to predict that NRF1 was a potential target for miRNA (miR)-363, and this was confirmed in subsequent experiments. The expression of miR-363-3p was negatively correlated with the expression of NRF1, and its expression was significantly upregulated in OA model rats and in LPS-induced chondrocytes compared with the expression in the respective controls. In addition, the overexpression of miR-363-3p increased the levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α in vivo, and was demonstrated to promote chondrocyte injury and apoptosis by Safranin O staining and TUNEL. Moreover, the inhibition of miR-363-3p expression increased the expression of NRF1 and protected chondrocytes from apoptosis in vitro and in vivo, whereas the overexpression of miR-363-3p downregulated NRF1 expression and promoted LPS-induced chondrocyte apoptosis through the p53 pathway in vitro. The results of this study suggested that miR-363-3p-mediated inhibition of NRF1may be associated with chondrocyte apoptosis in OA.