Vorinostat, a HDAC inhibitor, showed anti-osteoarthritic activities through inhibition of iNOS and MMP expression, p38 and ERK phosphorylation and blocking NF-κB nuclear translocation

Obacunone acts as a histone deacetylase 1 inhibitor to limit p38MAPK signaling and alleviate osteoarthritis progression

BACKGROUND

Osteoarthritis (OA) is an age-related progressive degenerative disorder characterized by cartilage extracellular matrix degradation and inflammation. In this study, we explored the function and mechanism of action of obacunone (OB) in inhibiting OA progression.

METHODS

The degradation of articular cartilage and its severity were examined using Safranin O-fast green and hematoxylin and eosin (HE) staining. Chondrocyte survival was evaluated using a cell counting kit-8 assay. In addition, qRT-PCR, western blot analysis, immunohistochemical staining, and enzyme-linked immunosorbent assay were performed to evaluate the effects of OB on cartilage injury.

RESULTS

OB mitigated cartilage lesions in rats with anterior cruciate ligament transaction-induced OA. The protein expression of collagen II was increased and the protein expression of ADAM metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS-5), matrix metalloproteinase (MMP)-13, and RUNX family transcription factor 2 (RUNX2) was reduced in the articular cartilage of OB-treated rats. Moreover, OB exhibited anti-inflammatory activities by reducing the serum levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-1β, and IL-18. In IL-1β-stimulated primary chondrocytes, OB dose-dependently elevated the expression of collagen II, and decreased the expression of ADAMTS-5, MMP-13, RUNX2 and inflammatory cytokines. Histone deacetylase 1 (HDAC1) was identified as a predicted OB target. OB inhibited HDAC1 expression to limit the activation of p38MAPK signaling. The transfection of chondrocytes with HDAC1 or p38MAPK overexpression plasmids reversed the chondroprotective effects of OB.

CONCLUSION

OB mitigated OA progression by binding to HDAC1 and inhibiting p38MAPK signaling, indicating that OB may be a promising drug for the treatment of OA.

Epigenetic Biomarkers in Temporomandibular Joint Osteoarthritis: An Emerging Target in Treatment

Osteoarthritis (OA) of the temporomandibular joint (TMJ) is a progressive disease characterized by the progressive destruction of the internal surfaces of the joint. Certain epigenetic biomarkers have been detected in TMJ-OA. We summarized the available evidence on the epigenetic biomarkers in TMJ-OA. There is an increase in the expression of non-coding RNAs related to the degradation of the extracellular matrix, chondrocyte apoptosis, and proinflammatory cytokines, while there is a decrease in the expression of those related to COL2A1, as well as the osteogenic and chondrogenic differentiation of mesenchymal stem cells. Certain methylated genes and histone modifications in TMJ-OA were also identified. In the early stage, DNA methylation was significantly decreased; that is, the expression of inflammation-related genes such as TNF and genes associated with extracellular matrix degradation, such as Adamts, were increased. While in the late stage, there was an increase in the expression of genes associated with the TGF-β and MAPK signaling pathway and angiogenesis-related genes. Although research on the role of epigenetic markers in TMJ-OA is still ongoing, the results here contribute to improving the basis for the identification of accurate diagnostic and prognostic markers and the development of new therapeutic molecules for the prevention and management of TMJ-OA. It also represents a significant advancement in elucidating its pathogenesis.

HDAC inhibitors and IBD: Charting new approaches in disease management

Inflammatory bowel disease (IBD) represents a group of chronic inflammatory disorders of the gastrointestinal tract. Despite substantial advances in our understanding of IBD pathogenesis, the currently available therapeutic options remain limited in their efficacy and often come with significant side effects. Therefore, there is an urgent need to explore novel approaches for the management of IBD. One promising avenue of investigation revolves around the use of histone deacetylase (HDAC) inhibitors, which have garnered considerable attention for their potential in modulating gene expression and curbing inflammatory responses. This review emphasizes the pressing need for innovative drugs in the treatment of IBD, and drawing from a wealth of preclinical studies and clinical trials, we underscore the multifaceted roles and the therapeutic effects of HDAC inhibitors in IBD models and patients. This review aims to contribute significantly to the understanding of HDAC inhibitors' importance and prospects in the management of IBD, ultimately paving the way for improved therapeutic strategies in this challenging clinical landscape.

Epigenetic modifications and emerging therapeutic targets in cardiovascular aging and diseases

The complex mechanisms underlying the development of cardiovascular diseases remain not fully elucidated. Epigenetics, which modulates gene expression without DNA sequence changes, is shedding light on these mechanisms and their heritable effects. This review focus on epigenetic regulation in cardiovascular aging and diseases, detailing specific epigenetic enzymes such as DNA methyltransferases (DNMTs), histone acetyltransferases (HATs), and histone deacetylases (HDACs), which serve as writers or erasers that modify the epigenetic landscape. We also discuss the readers of these modifications, such as the 5-methylcytosine binding domain proteins, and the erasers ten-eleven translocation (TET) proteins. The emerging role of RNA methylation, particularly N6-methyladenosine (m6A), in cardiovascular pathogenesis is also discussed. We summarize potential therapeutic targets, such as key enzymes and their inhibitors, including DNMT inhibitors like 5-azacytidine and decitabine, HDAC inhibitors like belinostat and givinotide, some of which have been approved by the FDA for various malignancies, suggesting their potential in treating cardiovascular diseases. Furthermore, we highlight the role of novel histone modifications and their associated enzymes, which are emerging as potential therapeutic targets in cardiovascular diseases. Thus, by incorporating the recent studies involving patients with cardiovascular aging and diseases, we aim to provide a more detailed and updated review that reflects the advancements in the field of epigenetic modification in cardiovascular diseases.

Roseburia intestinalis: A possible target for vascular calcification

With the advancement of metagenomics and metabolomics techniques, the crucial role of the gut microbiome in intestinal, cardiovascular, and metabolic disorders has been extensively explored. Vascular calcification (VC) is common in atherosclerosis, hypertension, diabetes mellitus, and chronic kidney disease. Moreover, it is a significant cause of cardiovascular diseases and mortality. Roseburia intestinalis, as a promising candidate for the next generation of probiotics, plays a substantial role in inhibiting the systemic inflammatory response and holds great potential in the treatment of intestinal diseases, cardiovascular diseases, and metabolic disorders. Its primary metabolite, butyrate, acts on specific receptors (GPR43, GPR41, GPR109a). It enters cells via transporters (MCT1, SMCT1), affecting gene expression through HDACs, PPARγ and Nrf2, promoting energy metabolism and changing the concentration of other metabolites (including AGEs, LPS, BHB) in the circulation to affect the body's life activities. In this paper, we focus on the possible mechanism of the primary metabolite butyrate of Roseburia intestinalis in inhibiting VC, which may become a potential therapeutic target for the treatment of VC and the ways to enhance its effect.

Targeting Parkin-regulated metabolomic change in cartilage in the treatment of osteoarthritis

Articular cartilage degeneration may lead to osteoarthritis (OA) during the aging process, but its underlying mechanism remains unknown. Here, we found that chondrocytes exhibited an energy metabolism shift from glycolysis to oxidative phosphorylation (OXPHOS) during aging. Parkin regulates various cellular metabolic processes. Reprogrammed cartilage metabolism by Parkin ablation decreased OXPHOS and increased glycolysis, with ameliorated aging-related OA. Metabolomics analysis indicated that lauroyl-L-carnitine (LLC) was decreased in aged cartilage, but increased in Parkin-deficient cartilage. In vitro, LLC improved the cartilage matrix synthesis of aged chondrocytes. In vivo, intra-articular injection of LLC in mice with anterior cruciate ligament transaction (ACLT) ameliorated OA progression. These results suggest that metabolic changes are regulated by Parkin-impaired cartilage during aging, and targeting this metabolomic changes by supplementation with LLC is a promising treatment strategy for ameliorating OA.

Therapeutic Potential of Natural Compounds Acting through Epigenetic Mechanisms in Cardiovascular Diseases: Current Findings and Future Directions

Cardiovascular diseases (CVDs) remain a leading global cause of morbidity and mortality. These diseases have a multifaceted nature being influenced by a multitude of biochemical, genetic, environmental, and behavioral factors. Epigenetic modifications have a crucial role in the onset and progression of CVD. Epigenetics, which regulates gene activity without altering the DNA's primary structure, can modulate cardiovascular homeostasis through DNA methylation, histone modification, and non-coding RNA regulation. The effects of environmental stimuli on CVD are mediated by epigenetic changes, which can be reversible and, hence, are susceptible to pharmacological interventions. This represents an opportunity to prevent diseases by targeting harmful epigenetic modifications. Factors such as high-fat diets or nutrient deficiencies can influence epigenetic enzymes, affecting fetal growth, metabolism, oxidative stress, inflammation, and atherosclerosis. Recent studies have shown that plant-derived bioactive compounds can modulate epigenetic regulators and inflammatory responses, contributing to the cardioprotective effects of diets. Understanding these nutriepigenetic effects and their reversibility is crucial for developing effective interventions to combat CVD. This review delves into the general mechanisms of epigenetics, its regulatory roles in CVD, and the potential of epigenetics as a CVD therapeutic strategy. It also examines the role of epigenetic natural compounds (ENCs) in CVD and their potential as intervention tools for prevention and therapy.

Pan-histone deacetylase inhibitor vorinostat suppresses osteoclastic bone resorption through modulation of RANKL-evoked signaling and ameliorates ovariectomy-induced bone loss

BACKGROUND

Estrogen deficiency-mediated hyperactive osteoclast represents the leading role during the onset of postmenopausal osteoporosis. The activation of a series of signaling cascades triggered by RANKL-RANK interaction is crucial mechanism underlying osteoclastogenesis. Vorinostat (SAHA) is a broad-spectrum pan-histone deacetylase inhibitor (HDACi) and its effect on osteoporosis remains elusive.

METHODS

The effects of SAHA on osteoclast maturation and bone resorptive activity were evaluated using in vitro osteoclastogenesis assay. To investigate the effect of SAHA on the osteoclast gene networks during osteoclast differentiation, we performed high-throughput transcriptome sequencing. Molecular docking and the assessment of RANKL-induced signaling cascades were conducted to confirm the underlying regulatory mechanism of SAHA on the action of RANKL-activated osteoclasts. Finally, we took advantage of a mouse model of estrogen-deficient osteoporosis to explore the clinical potential of SAHA.

RESULTS

We showed here that SAHA suppressed RANKL-induced osteoclast differentiation concentration-dependently and disrupted osteoclastic bone resorption in vitro. Mechanistically, SAHA specifically bound to the predicted binding site of RANKL and blunt the interaction between RANKL and RANK. Then, by interfering with downstream NF-κB and MAPK signaling pathway activation, SAHA negatively regulated the activity of NFATc1, thus resulting in a significant reduction of osteoclast-specific gene transcripts and functional osteoclast-related protein expression. Moreover, we found a significant anti-osteoporotic role of SAHA in ovariectomized mice, which was probably realized through the inhibition of osteoclast formation and hyperactivation.

CONCLUSION

These data reveal a high affinity between SAHA and RANKL, which results in blockade of RANKL-RANK interaction and thereby interferes with RANKL-induced signaling cascades and osteoclastic bone resorption, supporting a novel strategy for SAHA application as a promising therapeutic agent for osteoporosis.

Research Progress on the Pathogenesis of Knee Osteoarthritis

Knee osteoarthritis (KOA) is a chronic joint bone disease characterized by inflammatory destruction and hyperplasia of bone. Its main clinical symptoms are joint mobility difficulties and pain, severe cases can lead to limb paralysis, which poses major pressure to the quality of life and mental health of patients, but also brings serious economic burden to society. The occurrence and development of KOA is influenced by many factors, including systemic factors and local factors. The joint biomechanical changes caused by aging, trauma and obesity, abnormal bone metabolism caused by metabolic syndrome, the effects of cytokines and related enzymes, genetic and biochemical abnormalities caused by plasma adiponectin, etc. all directly or indirectly lead to the occurrence of KOA. However, there is little literature that systematically and comprehensively integrates macro- and microscopic KOA pathogenesis. Therefore, it is necessary to comprehensively and systematically summarize the pathogenesis of KOA in order to provide a better theoretical basis for clinical treatment.

The Role of Genetics and Epigenetic Regulation in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is progressive disease characterised by cartilage degradation, subchondral bone remodelling and inflammation of the synovium. The disease is associated with obesity, mechanical load and age. However, multiple pro-inflammatory immune mediators regulate the expression of metalloproteinases, which take part in cartilage degradation. Furthermore, genetic factors also contribute to OA susceptibility. Recent studies have highlighted that epigenetic mechanisms may regulate the expression of OA-associated genes. This review aims to present the mechanisms of OA pathogenesis and summarise current evidence regarding the role of genetics and epigenetics in this process.

The Protective Effect of Selenium Nanoparticles in Osteoarthritis: In vitro and in vivo Studies

Introduction

Osteoarthritis (OA) is a common chronic joint disease characterized by articular cartilage degeneration. OA usually manifests as joint pain, limited mobility, and joint effusion. Currently, the primary OA treatment is non-steroidal anti-inflammatory drugs (NSAIDs). Although they can alleviate the disease's clinical symptoms and signs, the drugs have some side effects. Selenium nanoparticles (SeNPs) may be an alternative to relieve OA symptoms.

Materials and Results

We confirmed the anti-inflammatory effect of selenium nanoparticles (SeNPs) in vitro and in vivo experiments for OA disease in this study. In vitro experiments, we found that SeNPs could significantly reduce the expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), the major inflammatory factors, and had significant anti-inflammatory and anti-arthritic effects. SeNPs can inhibit reactive oxygen species (ROS) production and increased glutathione peroxidase (GPx) activity in interleukin-1beta (IL-1β)-stimulated cells. Additionally, SeNPs down-regulated matrix metalloproteinase-13 (MMP-13) and thrombospondin motifs 5 (ADAMTS-5) expressions, while up-regulated type II collagen (COL-2) and aggrecan (ACAN) expressions stimulated by IL-1β. The findings also indicated that SeNPs may exert their effects through suppressing the NF-κB p65 and p38/MAPK pathways. In vivo experiments, the prevention of OA development brought on by SeNPs was demonstrated using a DMM model.

Discussion

Our results suggest that SeNPs may be a potential anti-inflammatory agent for treating OA.

FMRP activity and control of Csw/SHP2 translation regulate MAPK-dependent synaptic transmission

Noonan syndrome (NS) and NS with multiple lentigines (NSML) cognitive dysfunction are linked to SH2 domain-containing protein tyrosine phosphatase-2 (SHP2) gain-of-function (GoF) and loss-of-function (LoF), respectively. In Drosophila disease models, we find both SHP2 mutations from human patients and corkscrew (csw) homolog LoF/GoF elevate glutamatergic transmission. Cell-targeted RNAi and neurotransmitter release analyses reveal a presynaptic requirement. Consistently, all mutants exhibit reduced synaptic depression during high-frequency stimulation. Both LoF and GoF mutants also show impaired synaptic plasticity, including reduced facilitation, augmentation, and post-tetanic potentiation. NS/NSML diseases are characterized by elevated MAPK/ERK signaling, and drugs suppressing this signaling restore normal neurotransmission in mutants. Fragile X syndrome (FXS) is likewise characterized by elevated MAPK/ERK signaling. Fragile X Mental Retardation Protein (FMRP) binds csw mRNA and neuronal Csw protein is elevated in Drosophila fragile X mental retardation 1 (dfmr1) nulls. Moreover, phosphorylated ERK (pERK) is increased in dfmr1 and csw null presynaptic boutons. We find presynaptic pERK activation in response to stimulation is reduced in dfmr1 and csw nulls. Trans-heterozygous csw/+; dfmr1/+ recapitulate elevated presynaptic pERK activation and function, showing FMRP and Csw/SHP2 act within the same signaling pathway. Thus, a FMRP and SHP2 MAPK/ERK regulative mechanism controls basal and activity-dependent neurotransmission strength.

The protective activity of natural flavonoids against osteoarthritis by targeting NF-κB signaling pathway

Osteoarthritis (OA) is a typical joint disease associated with chronic inflammation. The nuclear factor-kappaB (NF-κB) pathway plays an important role in inflammatory activity and inhibiting NF-κB-mediated inflammation can be a potential strategy for treating OA. Flavonoids are a class of naturally occurring polyphenols with anti-inflammatory properties. Structurally, natural flavonoids can be divided into several sub-groups, including flavonols, flavones, flavanols/catechins, flavanones, anthocyanins, and isoflavones. Increasing evidence demonstrates that natural flavonoids exhibit protective activity against the pathological changes of OA by inhibiting the NF-κB signaling pathway. Potentially, natural flavonoids may suppress NF-κB signaling-mediated inflammatory responses, ECM degradation, and chondrocyte apoptosis. The different biological actions of natural flavonoids against the NF-κB signaling pathway in OA chondrocytes might be associated with the differentially substituted groups on the structures. In this review, the efficacy and action mechanism of natural flavonoids against the development of OA are discussed by targeting the NF-κB signaling pathway. Potentially, flavonoids could become useful inhibitors of the NF-κB signaling pathway for the therapeutic management of OA.

Current understanding of osteoarthritis pathogenesis and relevant new approaches

Osteoarthritis (OA) is the most common degenerative joint disease that causes painful swelling and permanent damage to the joints in the body. The molecular mechanisms of OA are currently unknown. OA is a heterogeneous disease that affects the entire joint, and multiple tissues are altered during OA development. To better understand the pathological mechanisms of OA, new approaches, methods, and techniques need to be used to understand OA pathogenesis. In this review, we first focus on the epigenetic regulation of OA, with a particular focus on DNA methylation, histone modification, and microRNA regulation, followed by a summary of several key mediators in OA-associated pain. We then introduce several innovative techniques that have been and will continue to be used in the fields of OA and OA-associated pain, such as CRISPR, scRNA sequencing, and lineage tracing. Next, we discuss the timely updates concerning cell death regulation in OA pathology, including pyroptosis, ferroptosis, and autophagy, as well as their individual roles in OA and potential molecular targets in treating OA. Finally, our review highlights new directions on the role of the synovial lymphatic system in OA. An improved understanding of OA pathogenesis will aid in the development of more specific and effective therapeutic interventions for OA.

Epigenetic regulation in cardiovascular disease: mechanisms and advances in clinical trials

Epigenetics is closely related to cardiovascular diseases. Genome-wide linkage and association analyses and candidate gene approaches illustrate the multigenic complexity of cardiovascular disease. Several epigenetic mechanisms, such as DNA methylation, histone modification, and noncoding RNA, which are of importance for cardiovascular disease development and regression. Targeting epigenetic key enzymes, especially the DNA methyltransferases, histone methyltransferases, histone acetylases, histone deacetylases and their regulated target genes, could represent an attractive new route for the diagnosis and treatment of cardiovascular diseases. Herein, we summarize the knowledge on epigenetic history and essential regulatory mechanisms in cardiovascular diseases. Furthermore, we discuss the preclinical studies and drugs that are targeted these epigenetic key enzymes for cardiovascular diseases therapy. Finally, we conclude the clinical trials that are going to target some of these processes.

Epigenetic therapy targeting bone marrow mesenchymal stem cells for age-related bone diseases

As global aging accelerates, the prevention and treatment of age-related bone diseases are becoming a critical issue. In the process of senescence, bone marrow mesenchymal stem cells (BMSCs) gradually lose the capability of self-renewal and functional differentiation, resulting in impairment of bone tissue regeneration and disorder of bone tissue homeostasis. Alteration in epigenetic modification is an essential factor of BMSC dysfunction during aging. Its transferability and reversibility provide the possibility to combat BMSC aging by reversing age-related modifications. Emerging evidence demonstrates that epigenetic therapy based on aberrant epigenetic modifications could alleviate the senescence and dysfunction of stem cells. This review summarizes potential therapeutic targets for BMSC aging, introduces some potential approaches to alleviating BMSC aging, and analyzes its prospect in the clinical application of age-related bone diseases.

HDAC6 regulates NF-κB signalling to control chondrocyte IL-1-induced MMP and inflammatory gene expression

Elevated pro-inflammatory signalling coupled with catabolic metalloproteinase expression is a common feature of arthritis, leading to cartilage damage, deterioration of the joint architecture and the associated pain and immobility. Countering these processes, histone deacetylase inhibitors (HDACi) have been shown to suppress matrix metalloproteinase (MMP) expression, block cytokine-induced signalling and reduce the cartilage degradation in animal models of the arthritis. In order to establish which specific HDACs account for these chondro-protective effects an HDAC1-11 RNAi screen was performed. HDAC6 was required for both the interleukin (IL)-1 induction of MMP expression and pro-inflammatory interleukin expression in chondrocytes, implicating an effect on NF-κB signalling. Depletion of HDAC6 post-transcriptionally up-regulated inhibitor of κB (IκB), prevented the nuclear translocation of NF-κB subunits and down-regulated NF-κB reporter activation. The pharmacological inhibition of HDAC6 reduced MMP expression in chondrocytes and cartilage collagen release. This work highlights the important role of HDAC6 in pro-inflammatory signalling and metalloproteinase gene expression, and identifies a part for HDAC6 in the NF-κB signalling pathway. By confirming the protection of cartilage this work supports the inhibition of HDAC6 as a possible therapeutic strategy in arthritis.

Dexamethasone Attenuates the Expression of MMP-13 in Chondrocytes through MKP-1

Mitogen-activated protein kinase phosphatase-1 (MKP-1) is upregulated in inflammation and reduces the activity of proinflammatory mitogen-activated protein kinases (MAP kinases) by dephosphorylation. MAP kinases are intracellular signaling pathways that mediate the cellular effects of proinflammatory cytokines. In the present study, we investigated the effects of the glucocorticoid dexamethasone on the expression of catabolic enzymes in chondrocytes and tested the hypothesis that these effects are mediated through MKP-1. Dexamethasone was found to significantly attenuate the expression of matrix metalloproteinase (MMP)-13 in human OA chondrocytes as well as in chondrocytes from MKP-1 WT mice, but not in chondrocytes from MKP-1 KO mice. Dexamethasone also increased the expression of MKP-1 in murine and human OA chondrocytes. Furthermore, p38 MAP kinase inhibitors significantly attenuated MMP-13 expression in human OA chondrocytes, while JNK MAP kinase inhibitors had no effect. The results indicate that the effect of dexamethasone on MMP-13 expression in chondrocytes was mediated by an MKP-1 and p38 MAP kinase-dependent manner. These findings, together with previous results, support the concept of MKP-1 as a protective factor in articular chondrocytes in inflammatory conditions and as a potential drug target to treat OA.

Histone Deacetylase Inhibitors Downregulate Calcium Pyrophosphate Crystal Formation in Human Articular Chondrocytes

Calcium pyrophosphate (CPP) deposition disease (CPPD) is a form of CPP crystal-induced arthritis. A high concentration of extracellular pyrophosphate (ePPi) in synovial fluid is positively correlated with the formation of CPP crystals, and ePPi can be upregulated by ankylosis human (ANKH) and ectonucleotide pyrophosphatase 1 (ENPP1) and downregulated by tissue non-specific alkaline phosphatase (TNAP). However, there is currently no drug that eliminates CPP crystals. We explored the effects of the histone deacetylase (HDAC) inhibitors (HDACis) trichostatin A (TSA) and vorinostat (SAHA) on CPP formation. Transforming growth factor (TGF)-β1-treated human primary cultured articular chondrocytes (HC-a cells) were used to increase ePPi and CPP formation, which were determined by pyrophosphate assay and CPP crystal staining assay, respectively. Artificial substrates thymidine 5′-monophosphate p-nitrophenyl ester (p-NpTMP) and p-nitrophenyl phosphate (p-NPP) were used to estimate ENPP1 and TNAP activities, respectively. The HDACis TSA and SAHA significantly reduced mRNA and protein expressions of ANKH and ENPP1 but increased TNAP expression in a dose-dependent manner in HC-a cells. Further results demonstrated that TSA and SAHA decreased ENPP1 activity, increased TNAP activity, and limited levels of ePPi and CPP. As expected, both TSA and SAHA significantly increased the acetylation of histones 3 and 4 but failed to block Smad-2 phosphorylation induced by TGF-β1. These results suggest that HDACis prevented the formation of CPP by regulating ANKH, ENPP1, and TNAP expressions and can possibly be developed as a potential drug to treat or prevent CPPD.

Histone deacetylase inhibitors attenuated interleukin-1β-induced chondrogenesis inhibition in synovium-derived mesenchymal stem cells of the temporomandibular joint

Aims

In the repair of condylar cartilage injury, synovium-derived mesenchymal stem cells (SMSCs) migrate to an injured site and differentiate into cartilage. This study aimed to confirm that histone deacetylase (HDAC) inhibitors, which alleviate arthritis, can improve chondrogenesis inhibited by IL-1β, and to explore its mechanism.

Methods

SMSCs were isolated from synovium specimens of patients undergoing temporomandibular joint (TMJ) surgery. Chondrogenic differentiation potential of SMSCs was evaluated in vitro in the control, IL-1β stimulation, and IL-1β stimulation with HDAC inhibitors groups. The effect of HDAC inhibitors on the synovium and condylar cartilage in a rat TMJ arthritis model was evaluated.

Results

Interleukin (IL)-1β inhibited the chondrogenic differentiation potential of SMSCs, while the HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and panobinostat (LBH589), attenuated inhibition of IL-1β-induced SMSC chondrogenesis. Additionally, SAHA attenuated the destruction of condylar cartilage in rat TMJ arthritis model. IL-6 (p < 0.001) and matrix metalloproteinase 13 (MMP13) (p = 0.006) were significantly upregulated after IL-1β stimulation, while SAHA and LBH589 attenuated IL-6 and MMP13 expression, which was upregulated by IL-1β in vitro. Silencing of IL-6 significantly downregulated MMP13 expression and attenuated IL-1β-induced chondrogenesis inhibition of SMSCs.

Conclusion

HDAC inhibitors SAHA and LBH589 attenuated chondrogenesis inhibition of SMSC induced by IL-1β in TMJ, and inhibition of IL-6/MMP13 pathway activation contributes to this biological progress. This study provides a theoretical basis for the application of HDAC inhibitors in the treatment of TMJ arthritis.

Cite this article: Bone Joint Res 2022;11(1):40–48.

HPA Axis in the Pathomechanism of Depression and Schizophrenia: New Therapeutic Strategies Based on Its Participation

The hypothalamic-pituitary-adrenal (HPA) axis is involved in the pathophysiology of many neuropsychiatric disorders. Increased HPA axis activity can be observed during chronic stress, which plays a key role in the pathophysiology of depression. Overactivity of the HPA axis occurs in major depressive disorder (MDD), leading to cognitive dysfunction and reduced mood. There is also a correlation between the HPA axis activation and gut microbiota, which has a significant impact on the development of MDD. It is believed that the gut microbiota can influence the HPA axis function through the activity of cytokines, prostaglandins, or bacterial antigens of various microbial species. The activity of the HPA axis in schizophrenia varies and depends mainly on the severity of the disease. This review summarizes the involvement of the HPA axis in the pathogenesis of neuropsychiatric disorders, focusing on major depression and schizophrenia, and highlights a possible correlation between these conditions. Although many effective antidepressants are available, a large proportion of patients do not respond to initial treatment. This review also discusses new therapeutic strategies that affect the HPA axis, such as glucocorticoid receptor (GR) antagonists, vasopressin V1B receptor antagonists and non-psychoactive CB1 receptor agonists in depression and/or schizophrenia.

NF-κB signalling pathways in nucleus pulposus cell function and intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common clinical degenerative disease of the spine. A series of factors, such as inflammation, oxidative stress and mechanical stress, promote degradation of the extracellular matrix (ECM) of the intervertebral discs (IVD), leading to dysfunction and structural destruction of the IVD. Nuclear factor-κB (NF-κB) transcription factor has long been regarded as a pathogenic factor of IDD. Therefore, NF-κB may be an ideal therapeutic target for IDD. As NF-κB is a multifunctional functional transcription factor with roles in a variety of biological processes, a comprehensive understanding of the function and regulatory mechanism of NF-κB in IDD pathology will be useful for the development of targeted therapeutic strategies for IDD, which can prevent the progression of IDD and reduce potential risks. This review discusses the role of the NF-κB signalling pathway in the nucleus pulposus (NP) in the process of IDD to understand pathological NP degeneration further and provide potential therapeutic targets that may interfere with NF-κB signalling for IDD therapy.

Suberoylanilide Hydroxamic Acid Attenuates Interleukin-1β-Induced Interleukin-6 Upregulation by Inhibiting the Microtubule Affinity-Regulating Kinase 4/Nuclear Factor-κB Pathway in Synovium-Derived Mesenchymal Stem Cells from the Temporomandibular Joint

Synovium-derived mesenchymal stem cells (SMSCs) can migrate to the site of destroyed condylar cartilage and differentiate into chondrocytes to repair temporomandibular joint (TMJ) damage. Interleukin (IL)-1β-induced IL-6 secretion has been shown to inhibit the chondrogenic potential of SMSCs. The histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) has recently been shown to be closely related to the inflammation induced by IL-1β. However, the relationship between SAHA and IL-6 secretion induced by IL-1β in SMSCs remains unclear. In this study, we evaluated the relationships between IL-1β and IL-6 in synovial specimens from patients with TMD and in model rats with osteoarthritis (OA). We found that IL-1β and IL-6 were positively correlated and that IL-6 expression in SMSCs increased with IL-1β stimulation in vitro. Moreover, microtubule affinity-regulating kinase 4 (MARK4) was significantly upregulated in IL-1β-stimulated SMSCs and in the synovium of rats with OA. MARK4 knockdown inhibited IL-6 secretion and nuclear factor (NF)-κB pathway activation in IL-1β-stimulated SMSCs. SAHA attenuated IL-6 secretion in IL-1β-induced SMSCs through NF-κB pathway inhibition, and MARK4 was also downregulated in SAHA-treated SMSCs. However, inhibition of the NF-κB pathway did not suppress MARK4 expression. Thus, these results showed that SAHA attenuated IL-6 secretion in IL-1β-induced SMSCs through inhibition of the MARK4/NF-κB pathway.

Drosophila RASopathy models identify disease subtype differences and biomarkers of drug efficacy

RASopathies represent a family of mostly autosomal dominant diseases that are caused by missense variants in the rat sarcoma viral oncogene/mitogen activated protein kinase (RAS/MAPK) pathway including KRAS, NRAS, BRAF, RAF1, and SHP2. These variants are associated with overlapping but distinct phenotypes that affect the heart, craniofacial, skeletal, lymphatic, and nervous systems. Here, we report an analysis of 13 Drosophila transgenic lines, each expressing a different human RASopathy isoform. Similar to their human counterparts, each Drosophila line displayed common aspects but also important differences including distinct signaling pathways such as the Hippo and SAPK/JNK signaling networks. We identified multiple classes of clinically relevant drugs-including statins and histone deacetylase inhibitors-that improved viability across most RASopathy lines; in contrast, several canonical RAS pathway inhibitors proved less broadly effective. Overall, our study compares and contrasts a large number of RASopathy-associated variants including their therapeutic responses.

Histone Modifications and Chondrocyte Fate: Regulation and Therapeutic Implications

The involvement of histone modifications in cartilage development, pathology and regeneration is becoming increasingly evident. Understanding the molecular mechanisms and consequences of histone modification enzymes in cartilage development, homeostasis and pathology provides fundamental and precise perspectives to interpret the biological behavior of chondrocytes during skeletal development and the pathogenesis of various cartilage related diseases. Candidate molecules or drugs that target histone modifying proteins have shown promising therapeutic potential in the treatment of cartilage lesions associated with joint degeneration and other chondropathies. In this review, we summarized the advances in the understanding of histone modifications in the regulation of chondrocyte fate, cartilage development and pathology, particularly the molecular writers, erasers and readers involved. In addition, we have highlighted recent studies on the use of small molecules and drugs to manipulate histone signals to regulate chondrocyte functions or treat cartilage lesions, in particular osteoarthritis (OA), and discussed their potential therapeutic benefits and limitations in preventing articular cartilage degeneration or promoting its repair or regeneration.

The Role of HDACs and HDACi in Cartilage and Osteoarthritis

Epigenetics plays an important role in the pathogenesis and treatment of osteoarthritis (OA). In recent decades, HDAC family members have been associated with OA. This paper aims to describe the different role of HDACs in the pathogenesis of OA through interaction with microRNAs and the regulation of relevant signaling pathways. We found that HDACs are involved in cartilage and chondrocyte development but also play a crucial role in OA. However, the distinct HDAC mechanism in the pathogenesis and treatment of OA require further investigation. Furthermore, HDAC inhibitors (HDACi) can protect cartilage from disease, which may represent a potential therapeutic approach against OA.

Dexmedetomidine inhibits the NF-κB pathway and NLRP3 inflammasome to attenuate papain-induced osteoarthritis in rats

Context: Dexmedetomidine (Dex) has been reported to have an anti-inflammatory effect. However, its role on osteoarthritis (OA) has not been explored. Objective: This study investigates the effect of Dex on OA rat model induced by papain. Materials and methods: The OA Wistar rat model was induced by intraluminal injection of 20 mL of papain mixed solution (4% papain 0.2 mL mixed with 0.03 mol L^-1 l-cysteine 0.1 mL) into the right knee joint. Two weeks after papain injection, OA rats were treated by intra-articular injection of Dex (5, 10, or 20 μg kg^-1) into the right knee (once a day, continuously for 4 weeks). Articular cartilage tissue was obtained after Dex treatment was completed. Results: The gait behavior scores (2.83 ± 0.49), PWMT (15.2 ± 1.78) and PTWL (14.81 ± 0.92) in H-DEX group were higher than that of OA group, while Mankin score (5.5 ± 0.81) was decreased (p < 0.05). Compared with the OA group, the IL-1β (153.11 ± 16.05 pg mg^-1), IL-18 (3.71 ± 0.7 pg mg^-1), IL-6 (14.15 ± 1.94 pg/mg) and TNF-α (40.45 ± 10.28 pg mg^-1) levels in H-DEX group were decreased (p < 0.05). MMP-13, NLRP3, and caspase-1 p10 expression in Dex groups were significantly lower than that of OA group (p < 0.05), while collagen II was increased (p < 0.05). p65 in the nucleus of Dex groups was significantly down-regulated than that of OA group (p < 0.05). Discussion and Conclusions: Dex can improve pain symptoms and cartilage tissue damage of OA rats, which may be related to its inhibition of the activation of NF-κB and NLRP3 inflammasome.

Extracellular Signal-Regulated Kinase: A Regulator of Cell Growth, Inflammation, Chondrocyte and Bone Cell Receptor-Mediated Gene Expression

Extracellular signal-regulated kinase (ERK) is a member of the mitogen-activated protein kinase family of signaling molecules. ERK is predominantly found in two forms, ERK1 (p44) and ERK2 (p42), respectively. There are also several atypical forms of ERK, including ERK3, ERK4, ERK5 and ERK7. The ERK1/2 signaling pathway has been implicated in many and diverse cellular events, including proliferation, growth, differentiation, cell migration, cell survival, metabolism and transcription. ERK1/2 is activated (i.e., phosphorylated) in the cytosol and subsequently translocated to the nucleus, where it activates transcription factors including, but not limited to, ETS, c-Jun, and Fos. It is not surprising that the ERK1/2 signaling cascade has been implicated in many pathological conditions, namely, cancer, arthritis, chronic inflammation, and osteoporosis. This narrative review examines many of the cellular events in which the ERK1/2 signaling cascade plays a critical role. It is anticipated that agents designed to inhibit ERK1/2 activation or p-ERK1/2 activity will be developed for the treatment of those diseases characterized by dysregulated gene expression through ERK1/2 activation.

NF-κB Signaling Pathways in Osteoarthritic Cartilage Destruction

Osteoarthritis (OA) is a type of joint disease associated with wear and tear, inflammation, and aging. Mechanical stress along with synovial inflammation promotes the degradation of the extracellular matrix in the cartilage, leading to the breakdown of joint cartilage. The nuclear factor-kappaB (NF-κB) transcription factor has long been recognized as a disease-contributing factor and, thus, has become a therapeutic target for OA. Because NF-κB is a versatile and multi-functional transcription factor involved in various biological processes, a comprehensive understanding of the functions or regulation of NF-κB in the OA pathology will aid in the development of targeted therapeutic strategies to protect the cartilage from OA damage and reduce the risk of potential side-effects. In this review, we discuss the roles of NF-κB in OA chondrocytes and related signaling pathways, including recent findings, to better understand pathological cartilage remodeling and provide potential therapeutic targets that can interfere with NF-κB signaling for OA treatment.

Redox and NF-κB signaling in osteoarthritis

Human cells have to deal with the constant production of reactive oxygen species (ROS). Although ROS overproduction might be harmful to cell biology, there are plenty of data showing that moderate levels of ROS control gene expression by maintaining redox signaling. Osteoarthritis (OA) is the most common joint disorder with a multi-factorial etiology including overproduction of ROS. ROS overproduction in OA modifies intracellular signaling, chondrocyte life cycle, metabolism of cartilage matrix and contributes to synovial inflammation and dysfunction of the subchondral bone. In arthritic tissues, the NF-κB signaling pathway can be activated by pro-inflammatory cytokines, mechanical stress, and extracellular matrix degradation products. This activation results in regulation of expression of many cytokines, inflammatory mediators, transcription factors, and several matrix-degrading enzymes. Overall, NF-κB signaling affects cartilage matrix remodeling, chondrocyte apoptosis, synovial inflammation, and has indirect stimulatory effects on downstream regulators of terminal chondrocyte differentiation. Interaction between redox signaling and NF-κB transcription factors seems to play a distinctive role in OA pathogenesis.

Simvastatin prevents articular chondrocyte dedifferentiation induced by nitric oxide by inhibiting the expression of matrix metalloproteinases 1 and 13

IMPACT STATEMENT

Dedifferentiation of chondrocytes is the main character of cartilage degradation. Therefore the understanding of chondrocytes dedifferentiation is essential for arthritis therapy. However, the molecular mechanism of cartilage destroy is mostly unknown. In this work we show that simvastatin (SVT) inhibits dedifferentiation by nitric oxide by blocking the expression of matrix metalloproteinases 1 and 13. These effects of SVT on dedifferentiation suggest that SVT may be used as a drug for the cure of arthritis.

Interleukin-1β signaling in osteoarthritis - chondrocytes in focus

Osteoarthritis (OA) can be regarded as a chronic, painful and degenerative disease that affects all tissues of a joint and one of the major endpoints being loss of articular cartilage. In most cases, OA is associated with a variable degree of synovial inflammation. A variety of different cell types including chondrocytes, synovial fibroblasts, adipocytes, osteoblasts and osteoclasts as well as stem and immune cells are involved in catabolic and inflammatory processes but also in attempts to counteract the cartilage loss. At the molecular level, these changes are regulated by a complex network of proteolytic enzymes, chemokines and cytokines (for review: [1]). Here, interleukin-1 signaling (IL-1) plays a central role and its effects on the different cell types involved in OA are discussed in this review with a special focus on the chondrocyte.

Alterations in histone acetylation following exposure to 60Co γ-rays and their relationship with chromosome damage in human lymphoblastoid cells

Chromosome damage is related to DNA damage and erroneous repair. It can cause cell dysfunction and ultimately induce carcinogenesis. Histone acetylation is crucial for regulating chromatin structure and DNA damage repair. Ionizing radiation (IR) can alter histone acetylation. However, variations in histone acetylation in response to IR exposure and the relationship between histone acetylation and IR-induced chromosome damage remains unclear. Hence, this study investigated the variation in the total acetylation levels of H3 and H4 in human lymphocytes exposed to 0-2 Gy ⁶⁰Co γ-rays. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor, was added to modify the histone acetylation state of irradiated cells. Then, the total acetylation level, enzyme activity, dicentric plus centric rings (dic + r) frequencies, and micronucleus (MN) frequencies of the treated cells were analyzed. Results indicated that the acetylation levels of H3 and H4 significantly decreased at 1 and 24 h, respectively, after radiation exposure. The acetylation levels of H3 and H4 in irradiated groups treated with SAHA were significantly higher than those in irradiated groups that were not treated with SAHA. SAHA treatment inhibited HDAC activity in cells exposed to 0-1 Gy ⁶⁰Co γ-rays. SAHA treatment significantly decreased dic + r/cell and MN/cell in cells exposed to 0.5 or 1.0 Gy ⁶⁰Co γ-rays relative to that in cells that did not receive SAHA treatment. In conclusion, histone acetylation is significantly affected by IR and is involved in chromosome damage induced by ⁶⁰Co γ-radiation.

17β-Estradiol inhibits testosterone-induced cell proliferation in HepG2 by modulating the relative ratios of 3 estrogen receptor isoforms to the androgen receptor

Sex hormones, especially 17β-estradiol (E2) and testosterone (TEST), play crucial roles in the oncogenesis and progression of liver cancer via hormone-related receptors. As women have a lower rate of hepatocellular carcinoma (HCC) than men, estrogens might attenuate the occurrence and development of HCC. This study aimed to investigate the inhibitory effects and mechanisms of E2 on TEST-induced HCC development; the HepG2 cell line was used as an in vitro model. Five endpoints, including cell viability, cell apoptosis, cell cycle, receptor protein expression, and messenger RNA transcription, were investigated. Different roles and the ratios of androgen receptor (AR) and 3 estrogen receptor (ER) subtypes were also estimated. Cell viability assay showed that co-treatment of E2 and TEST resulted in a significant inhibition of E2-induced or TEST-induced cell proliferation. Flow cytometry analysis revealed that combined treatment of E2 and TEST blocked the cell cycle in the G0/G1 phase as well as induced cell early apoptosis, characterized by decreased cyclin-dependent kinase transcription and the ratio of Bcl-2/Bax. Real-time quantitative polymerase chain reaction and Western blot analysis results further demonstrated that estrogen receptor estrogen receptor α66 (ERα66) and estrogen receptor β (ERβ) were upregulated, whereas AR and estrogen receptor α36 (ERα36) were downregulated, irrespective of whether E2 and TEST were considered separately or together, whereas the combined treatment of E2 and TEST resulted in a decrease in the ERα66/ERβ ratio, the ERα66/ERα36 ratio, and the ERβ/ERα36 ratio, but with an increase in the ERα66/AR ratio, the ERα36/AR ratio, and the ERβ/AR ratio. To sum up, E2 could inhibit TEST-induced cell proliferation by modulating the ratio of different hormone-related receptors.

Emodin ameliorates cartilage degradation in osteoarthritis by inhibiting NF-κB and Wnt/β-catenin signaling in-vitro and in-vivo

The overproduction of MMPs (matrix metalloproteinases) and members of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) protein family plays an important role in the pathogenesis of osteoarthritis (OA). The potential of selective MMPs or ADAMTS inhibitors as chemopreventive agents for OA has been demonstrated in several studies. In this study, we investigated the protective effects of emodin (1,3,8-trihydroxy-6-methylanthaquinone), isolated from the root of Rheum palmatum L., in the inhibition of MMP and ADAMTS expression in both rat chondrocytes and an animal model of OA. The expression of MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, aggrecan, and collagen II mRNA and protein in interleukin-1beta (IL-1β)-induced rat chondrocytes was followed by quantitative real-time PCR and western blot. The activation of the NF-κB and Wnt/β-catenin pathways by IL-1β was assessed by western blot. The in vivo effects of emodin were evaluated by intra-articular injection in rats in an experimental model of OA induced by anterior cruciate ligament transection. Emodin dose-dependently down-regulated the expression of MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5 at both the mRNA and protein level in IL-1β-stimulated rat chondrocytes. In addition, the IL-1β-induced activation of NF-κB and Wnt signals was attenuated by emodin, as determined by western blotting. The intra-articular injection of emodin in a rat OA model ameliorated OA progression, as determined in morphological and histological analyses in vivo. Taken together, our findings demonstrate that emodin is a promising therapeutic agent for the prevention and treatment of OA.

The Epigenomic Landscape in Osteoarthritis

PURPOSE OF REVIEW

Epigenomics has emerged as a key player in our rapidly evolving understanding of osteoarthritis. Historical studies implicated epigenetic alterations, particularly DNA methylation, in OA pathogenesis; however, recent technological advances have resulted in numerous epigenome-wide studies examining in detail epigenetic modifications in OA. The purpose of this article is to introduce basic concepts in epigenetics and their recent applications to the study of osteoarthritis development and progression.

RECENT FINDINGS

Epigenetics describes three major phenomena: DNA modification via methylation, histone sidechain modifications, and short noncoding RNA sequences which work in concert to regulate gene transcription in a heritable fashion. Cartilage has been the most widely studied tissue in OA, and differential methylation of genes involved in inflammation, cell cycle, TGFβ, and HOX genes have been confirmed several times. Bone studies suggest similar findings, and the intriguing possibility of epigenetic changes in subchondral bone during many OA processes. Multiple studies have demonstrated the involvement of certain noncoding RNAs, particularly miR-140, in OA development via modulation of key catabolic factors. Although much work has been done, much is still unknown. Future epigenomic studies will no doubt continue to widen our understanding of extraarticular tissues and OA pathogenesis, and studies in animal models may offer glimpses into epigenome alterations in the earliest stages of OA.

Recent Insights into the Contribution of the Changing Hypertrophic Chondrocyte Phenotype in the Development and Progression of Osteoarthritis

Osteoarthritis (OA) is an extremely prevalent age-related condition. The economic and societal burden due to the cost of symptomatic treatment, inability to work, joint replacement, and rehabilitation is huge and increasing. Currently, there are no effective medical therapies that delay or reverse the pathological manifestations of OA. Current treatment options are, without exception, focused on slowing down progression of the disease to postpone total joint replacement surgery for as long as possible and keeping the associated pain and joint immobility manageable. Alterations in the articular cartilage chondrocyte phenotype might be fundamental in the pathological mechanisms of OA development. In many ways, the changing chondrocyte phenotype in osteoarthritic cartilage resembles the process of endochondral ossification as seen, for instance, in developing growth plates. However, the relative contribution of endochondral ossification to the changing chondrocyte phenotype in the development and progression of OA remains poorly described. In this review, we will discuss the current knowledge regarding the cartilage endochondral phenotypic changes occurring during OA development and progression, as well as the molecular and environmental effectors driving these changes. Understanding how these molecular mechanisms determine the chondrocyte cell fate in OA will be essential in enabling cartilage regenerative approaches in future treatments of OA.

Histone deacetylase-4 and histone deacetylase-8 regulate interleukin-1β-induced cartilage catabolic degradation through MAPK/JNK and ERK pathways

Interleukin-1β (IL-1β)-induced inflammatory response is associated with osteoarthritis (OA) and its development. Histone deacetylase (HDAC) may be involved in regulating this pathogenesis, but the mechanism has yet to be elucidated. The aim of the present study was to investigate the mechanism underlying the regulation of IL-1β-stimulated catabolic degradation of cartilage by HDAC. An in vitro model of OA was generated using rat articular chondrocytes (rACs) treated with IL-1β. The role of HDAC in IL-1β-induced gene expression was investigated using HDAC inhibitors and specific small interfering RNAs (siRNAs). The association of diverse mitogen-activated protein kinase (MAPK) pathways was examined. The IL-1β-induced expression of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5, and the production of collagen X and cyclo-oxygenase-2 in rACs was accompanied by the expression of HDAC4 and HDAC8, and were significantly downregulated by HDAC inhibitors and specific siRNAs. IL-1β-induced activation of extracellular signal-regulated kinase was downregulated by the HDAC inhibitor Trichostatin A, but not significantly by PCI-34051. The activation of c-Jun N-terminal kinase was observably downregulated by the latter, but only slightly by the former. These results suggest that HDAC4 and HDAC8 may serve as key upstream mediators of MAPK in regulating the IL-1β-induced cartilage catabolic and degradation. Therefore, inhibiting HDAC4 or HDAC8 or both may be a promising therapeutic strategy in preventing and treating OA.

Morphoproteomics and biomedical analytics confirm the mTORC2/Akt pathway as a resistance signature and activated ERK and STAT3 as concomitant prosurvival/antiapoptotic pathways in metastatic renal cell carcinoma (RCC) progressing on rapalogs: pathogenesis and therapeutic options

Background

It has been proposed that resistance to rapalog therapies in renal cell carcinoma (RCC) is due to adaptive switching from mammalian target of rapamycin complex 1 (mTORC1) to mTORC2.

Objective

To combine phosphoprotein staining and applied biomedical analytics to investigate resistance signatures in patients with metastatic RCC progressing on rapalog therapies.

Design

We applied morphoproteomic analysis to biopsy specimens from nine patients with metastatic RCC who continued to show clinical progression of their tumors while being treated with a rapalog.

Results

In patients who were on temsirolimus or everolimus at the time of biopsy, a moderate to strong expression of phosphorylated (p)-mTOR (Ser 2448) in the nuclear compartment with concomitant expression of p-Akt (Ser 473) confirmed the mTORC2 pathway. Concomitant moderate to strong nuclear expression of p-ERK 1/2 (Thr202/Tyr204) and p-STAT3 (Tyr705) was confirmed. Histopathologic changes of hypoxic-type coagulative necrosis in 5 cases as well as identification of insulin-like growth factor-1 receptor (IGF-1R) expression and histone methyltransferase EZH2 in all tumors studied suggested that hypoxia also contributed to the resistance signature. Biomedical analytics provided insight into therapeutic options that could target such adaptive and pathogenetic mechanisms.

Conclusions

Morphoproteomics and biomedical analytics confirm mTORC2/Akt as a resistance signature to rapalog therapy in metastatic RCC and demonstrate activation of the prosurvival ERK and STAT3 pathways and involvement of hypoxic pathways that contribute to pathogenesis of such adaptive resistance. These results highlight the need for a novel combinatorial therapeutic approach in metastatic RCC progressing on rapalogs.

Matrix Metalloproteinases: A challenging paradigm of cancer management

Matrix metalloproteinases (MMPs) are members of zinc-dependent endopeptidases implicated in a variety of physiological and pathological processes. Over the decades, MMPs have been studied for their role in cancer progression, migration, and metastasis. As a result, accumulated evidence of MMPs incriminating role has made them an attractive therapeutic target. Early generations of broad-spectrum MMP inhibitors exhibited potent inhibitory activities, which subsequently led to clinical trials. Unexpectedly, these trials failed to meet the desired goals, mainly due to the lack of efficacy, poor oral bioavailability, and toxicity. In this review, we discuss the regulatory role of MMPs in cancer progression, current strategies in targeting MMPs for cancer treatment including prodrug design and tumor imaging, and therapeutic value of MMPs as biomarkers in breast, lung, and prostate cancers.

Electroacupuncture serum inhibits TNF‑α‑mediated chondrocyte inflammation via the Ras‑Raf‑MEK1/2‑ERK1/2 signaling pathway

The Ras-Raf-mitogen-activated protein kinase kinase (MEK)1/2-extracellular signal-regulated kinase (ERK)1/2 signaling pathway contributes to the release of chondral matrix-degrading enzymes and accelerates the degradation of articular cartilage. Electroacupuncture (EA) treatment has been widely used for the treatment of osteoarthritis (OA); however, the mechanism underlying the effects of EA on OA remains unclear. Therefore, the present study evaluated the anti-inflammatory effects and potential underlying mechanisms of EA serum (EAS) on tumor necrosis factor (TNF)-α-mediated chondrocyte inflammation. A total of 30 Sprague Dawley rats were randomly divided into three groups: The blank group; experimental group I, which received 15 min of EA treatment; and experimental group II, which received 30 min of EA treatment. Subsequently, serum samples were obtained. Chondrocytes were isolated from the knee cartilage of Sprague Dawley rats, and were identified using collagen type II immunohistochemistry. TNF-α-treated chondrocytes were used as a cell model, and subsequently the cells were treated with EAS from each group for various durations. The results demonstrated that EAS treatment significantly promoted the viability and inhibited the apoptosis of TNF-α-treated chondrocytes. In addition, interleukin (IL)-1β concentration was significantly increased in the model group compared with in the control group, whereas EAS significantly reduced IL-1β concentration in TNF-α-treated chondrocytes. Furthermore, the protein expression levels of Ras, Raf and MEK1/2 were reduced in the EAS groups compared with in the model group. EAS also significantly inhibited the phosphorylation of ERK1/2, and the expression of downstream regulators matrix metalloproteinase (MMP)-3 and MMP-13. In conclusion, these results indicated that EAS may inhibit TNF-α-mediated chondrocyte inflammation via the Ras-Raf-MEK1/2-ERK1/2 signaling pathway in vitro, thus suggesting that EAS may be considered a potential therapeutic strategy for the treatment of OA.

Epigenetics in osteoarthritis: Potential of HDAC inhibitors as therapeutics

Osteoarthritis (OA) is the most common joint disease and the leading cause of chronic disability in middle-aged and older populations worldwide. The development of disease modifying therapy for OA is in its infancy largely because the regulatory mechanisms for the molecular effectors of OA pathogenesis are poorly understood. Recent studies identified epigenetic events as a critical regulator of molecular players involved in the induction and development of OA. Epigenetic mechanisms include DNA methylation, non-coding RNA and histone modifications. The aim of this review is to briefly highlight the recent advances in the epigenetics of cartilage and potential of HDACs (Histone deacetylases) inhibitors in the therapeutic management of OA. We summarize the recent studies utilizing HDAC inhibitors as potential therapeutics for inhibiting disease progression and preventing the cartilage destruction in OA. HDACs control normal cartilage development and homeostasis and understanding the impact of HDACs inhibitors on the disease pathogenesis is of interest because of its importance in affecting overall cartilage health and homeostasis. These findings also shed new light on cartilage disease pathophysiology and provide substantial evidence that HDACs may be potential novel therapeutic targets in OA.

Oxidative stress and chronic inflammation in osteoarthritis: can NRF2 counteract these partners in crime?

Osteoarthritis (OA) is an age-related joint degenerative disease associated with pain, joint deformity, and disability. The disease starts with cartilage damage but then progressively involves subchondral bone, causing an imbalance between osteoclast-driven bone resorption and osteoblast-driven remodeling. Here, we summarize the data for the role of oxidative stress and inflammation in OA pathology and discuss how these two processes are integrated during OA progression, as well as their contribution to abnormalities in cartilage/bone metabolism and integrity. At the cellular level, oxidative stress and inflammation are counteracted by transcription factor nuclear factor erythroid p45-related factor 2 (NRF2), and we describe the regulation of NRF2, highlighting its role in OA pathology. We also discuss the beneficial effect of some phytonutrients, including the therapeutic potential of NRF2 activation, in OA.

Pentosan polysulfate inhibits IL-1β-induced iNOS, c-Jun and HIF-1α upregulation in canine articular chondrocytes

Osteoarthritic (OA) chondrocytes are shown to express inducible nitric oxide synthase (iNOS) which produces high concentrations of nitric oxide (NO), particularly when stimulated with proinflammatory cytokines. NO is involved in OA cartilage degradation. On the other hand, c-Jun N-terminal Kinase (JNK) pathway mediates the activation and transcription of c-Jun, which is required for interleukin-1 (IL-1)-induction of matrix metalloproteinases-13 (MMP-13) in OA pathogenesis. Therefore, the selective inhibition of iNOS and c-Jun is a promising target for treatment and prevention of OA. The purpose of the study was to investigate the inhibitory effects of pentosan polysulfate (PPS) on IL-1β-induced iNOS, c-Jun and HIF-α isoforms upregulation in canine articular chondrocytes (CACs). Primary (P0) chondrocytes were isolated and cultured from femoral head cartilages of three (3) dogs. First passage (P1) chondrocytes were preincubated with 0, 1, 5, 15 and 40 μg/mL of PPS for 4 hr before treatment with 10 ng/mL rhIL-1β for a further 8 hr. In addition, we evaluated the effects of single and multiple cytokine with or without LPS on iNOS protein induction. PPS significantly inhibited (P < 0.05) IL-1β-induced iNOS, c-Jun and HIF-1α mRNA upregulation in a dose-dependent pattern. iNOS mRNA was significantly inhibited at 15 and 40 μg/mL whereas c-Jun and HIF-1α were significantly downregulated at 5, 15 and 40 μg/mL of PPS compared to chondrocytes treated with only rhIL-1β. Intriguingly, CACs were recalcitrant to single IL-1β, TNF-α or LPS-induction of iNOS protein including to a combination of IL-1β+TNF-α, IL-1β+LPS except to TNF-α+LPS and IL-1β+TNF-α+LPS suggestive of a protective mechanism from iNOS detrimental effects on perpetuating OA. IL-1β+TNF-α+LPS-induced iNOS protein expression was significantly abrogated by PPS. We demonstrate for the first time that PPS is a novel inhibitor of IL-1β-induced iNOS, c-Jun, and HIF-1α mRNA upregulation and iNOS protein induction which may be beneficial for prevention and treatment OA.

Histone deacetylase inhibitor vorinostat (SAHA, MK0683) perturb miR-9-MCPIP1 axis to block IL-1β-induced IL-6 expression in human OA chondrocytes

AIM OF THE STUDY

High levels of IL-6 are believed to contribute to osteoarthritis (OA) pathogenesis. The expression of IL-6 is regulated post-transcriptionally by the miR-9-MCPIP-1 axis in chondrocytes. Vorinostat (SAHA) inhibits the IL-6 expression in OA chondrocytes. We investigated whether SAHA suppresses the expression of IL-6 by perturbing the miR-9-MCPIP1 axis in OA chondrocytes under pathological conditions.

MATERIALS AND METHODS

OA chondrocytes were isolated by enzymatic digestion and treated with IL-1β in the absence or presence of SAHA. Genes and protein expression levels were determined by TaqMan assays and Western blotting, respectively. Secreted IL-6 was quantified by enzyme linked immunosorbent assay (ELISA). MCPIP1 promoter deletion mutants were generated by polymerase chain reaction (PCR). Promoter recruitment of transcription factors was determined by ChIP. Nuclear run-on was employed to measure the ongoing transcription. siRNA-mediated knockdown of the CEBPα expression was employed for loss of function studies.

RESULTS

Expression of MCPIP1 was high in SAHA treated OA chondrocytes but expression of IL-6 mRNAs and secreted IL-6 were reduced by ~70%. SAHA suppressed the expression of miR-9 but enhanced the activity of the MCPIP1 promoter localized to a 156bp region which also harbors the binding site for CEBPα. Treatment with SAHA enhanced the recruitment of CEBPα to the MCPIP1 promoter. Ectopically expressed CEBPα enhanced the promoter activity and the expression of MCPIP1 while siRNA-mediated knockdown of CEBPα inhibited the expression of MCPIP1.

CONCLUSIONS

Taken together our data indicate that SAHA-mediated suppression of the IL-6 expression is achieved through increased recruitment of CEBPα to the MCPIP1 promoter and by relieving the miR-9-mediated inhibition of MCPIP1 expression in OA chondrocytes.

Inflammation and epigenetic regulation in osteoarthritis

Osteoarthritis (OA) was once defined as a non-inflammatory arthropathy, but it is now well-recognized that there is a major inflammatory component to this disease. In addition to synovial cells, articular chondrocytes and other cells of diarthrodial joints are also known to express inflammatory mediators. It has been proposed that targeting inflammation pathways could be a promising strategy to treat OA. There have been many reports of cross-talk between inflammation and epigenetic factors in cartilage. Specifically, inflammatory mediators have been shown to regulate levels of enzymes that catalyze changes in DNA methylation and histone structure, as well as alter levels of non-coding RNAs. In addition, expression levels of a number of these epigenetic factors have been shown to be altered in OA, thereby suggesting potential interplay between inflammation and epigenetics in this disease. This review provides information on inflammatory pathways in arthritis and summarizes published research on how epigenetic regulators are affected by inflammation in chondrocytes. Furthermore, we discuss data showing how altered expression of some of these epigenetic factors can induce either catabolic or anti-catabolic effects in response to inflammatory signals. A better understanding of how inflammation affects epigenetic factors in OA may provide us with novel therapeutic strategies to treat this condition.