Rhein, the metabolite of diacerhein, reduces the proliferation of osteoarthritic chondrocytes and synoviocytes without inducing apoptosis

MiR-4270 acts as a tumor suppressor by directly targeting Bcl-xL in human osteosarcoma cells

Chondrosarcomas and osteosarcomas are malignant bone tumors with a poor prognosis when unresectable or metastasized. Moreover, radiotherapy and chemotherapy could be ineffective. MiRNAs represent an alternative therapeutic approach. Based on high-throughput functional screening, we identified four miRNAs with a potential antiproliferative effect on SW1353 chondrosarcoma cells. Individual functional validations were then performed in SW1353 cells, as well as in three osteosarcoma cell lines. The antiproliferative and cytotoxic effects of miRNAs were evaluated in comparison with a positive control, miR-342-5p. The cytotoxic effect of four selected miRNAs was not confirmed on SW1353 cells, but we unambiguously revealed that miR-4270 had a potent cytotoxic effect on HOS and MG-63 osteosarcoma cell lines, but not on SaOS-2 cell line. Furthermore, like miR-342-5p, miR-4270 induced apoptosis in these two cell lines. In addition, we provided the first report of Bcl-xL as a direct target of miR-4270. MiR-4270 also decreased the expression of the anti-apoptotic protein Mcl-1, and increased the expression of the pro-apoptotic protein Bak. Our findings demonstrated that miR-4270 has tumor suppressive activity in osteosarcoma cells, particularly through Bcl-xL downregulation.

The Effects of the Combination of Rhein and Platelet-Rich Plasma on Human Articular Chondrocytes

BACKGROUND

The presence of side effects and low bioavailability of rhein has limited its use in the treatment of osteoarthritis. We aimed to evaluate the in vitro response of human articular chondrocytes to the presence of the combination of platelet-rich plasma (PRP) and rhein.

METHODS

Solutions of rhein were prepared to assess solubility and select a working concentration. A stimulus with interleukin-1β (IL-β, 10 ng/mL) was induced for 24 h on human chondrocytes. Five treatment groups were established: control, IL-β control, PRP, rhein, and PRP + rhein. Cell viability, cell migration, nitric oxide (NO) production, tumor necrosis factor-α (TNF-α), and gene expression analyses were carried out.

RESULTS

A concentration of 50 mg/L was selected after a dose-response curve assay. Both NO and tumor TNF-α production significantly decreased after PRP and PRP + rhein treatments at 24 and 48 h. The wound healing assay revealed a significant stimulation of migration after 72 h with the PRP and PRP + rhein treatments. Expression of IL-1β, IL-6, MMP-13, and ADAMTS-5 was significantly downregulated, particularly after treatment with the combination of PRP + rhein.

CONCLUSIONS

Much of the determinations denoted a better performance of the combination of PRP and rhein in decreasing the levels of the different targets evaluated; however, this was not great enough to detect a significant difference in comparison with the PRP treatment alone.

Inhibition of hypoxia-induced HIF-1α-mediated autophagy enhances the in vitro anti-tumor activity of rhein in pancreatic cancer cells

A hypoxic microenvironment results in significantly elevated hypoxia-inducible factor-1 (HIF-1) level in pancreatic cancer. HIF-1 functions to maintain the survival of cancer cells. The present study was performed to investigate whether inhibition of HIF-1α expression was involved in the in vitro anti-tumor effect of rhein in pancreatic cancer cells and to explore the underlying mechanism. sh-RNA knockout technique and western blotting were used to investigate the role of HIF-1α in autophagy activation in MiaPaCa-2 and PANC-1 cells. The survival and glycolysis were assessed using MTT assay and colorimetric kits, respectively. Apoptosis was evaluated by detecting the levels of apoptosis-related proteins using western blotting. Among the five pancreatic cancer cell lines, MiaPaCa-2 and PANC-1 cells were more sensitive to hypoxia-induced autophagy. HIF-1α regulated hypoxia-induced autophagy in MiaPaCa-2 and PANC-1 cells. Treatment with rhein inhibited the survival and suppressed glycolysis in MiaPaCa-2 and PANC-1 cells exposed to hypoxia. Bafilomycin A1 enhanced the suppressive effects of rhein on cell survival and glycolysis under hypoxia. Treatment with rhein, but not bafilomycin A1, significantly reduced HIF-1α expression. In conclusion, inhibition of HIF-1α-mediated autophagy enhances the in vitro anti-tumor activity of rhein in pancreatic cancer cells under hypoxia.

The potential roles of JAK/STAT signaling in the progression of osteoarthritis

Osteoarthritis (OA) is an age-related chronic progressive degenerative disease that induces persistent pain and disabilities. The development of OA is a complex process, and the risk factors are various, including aging, genetics, trauma and altered biomechanics. Inflammation and immunity play an important role in the pathogenesis of OA. JAK/STAT pathway is one of the most prominent intracellular signaling pathways, regulating cell proliferation, differentiation, and apoptosis. Inflammatory factors can act as the initiators of JAK/STAT pathway, which is implicated in the pathophysiological activity of chondrocyte. In this article, we provide a review on the importance of JAK/STAT pathway in the pathological development of OA. Potentially, JAK/STAT pathway becomes a therapeutic target for managing OA.

Therapeutic Potential of Diacerein in Management of Pain

Diacerein (DCN), an analogue of rhein (a glycosidal compound of natural origin), is currently used in the treatment of osteoarthritis and is given a fast-track designation for development to treat epidermolysis bullosa (EB). It is a nonsteroidal anti-inflammatory drug having disease-modifying properties in osteoarthritis and anti-inflammatory effects for the treatment of EB. Diacerein has a beneficial effect on pain relief and demonstrated antioxidant and anti-apoptotic effects, which are useful in renal disease, diabetes, and other disorders. This review discusses the possible mechanism of diacerein in the management of pain. The potential role of rhein and diacerein in the treatment of neuropathic, inflammatory and nociceptive pain is also reviewed. The effect of diacerein and rhein on mediators of pain, such as transient receptor potential cation channel subfamily V (TRPV1), Substance P, glutamate, inflammatory cytokines, nitric oxide, matrix metalloproteinases, histamine, palmitoylethanolamide, nuclear factor-kappa B (NFkB), and prostaglandin, has also been discussed. The data highlights the role of diacerein in neuropathic, nociceptive and inflammatory pain. Clinical trials and mechanism of action studies are needed to ascertain the role of diacerein, rhein or their analogues in the management of pain, alone or in combination with other approved therapies.

Experts document about an adequate utilization of SYSADOAs in controversial clinical situations

BACKGROUND AND OBJECTIVE

SYSADOAs (Symptomatic Slow-Acting Drugs for Osteoarthritis) are natural compounds that have been shown to be useful and safe in the treatment of osteoarthritis (OA). However, their use in certain clinical situations still lacks scientific evidence and clear recommendations. The objective of this work was to learn the opinion of a group of experts regarding the appropriate use of SYSADOA in the treatment of OA in controversial clinical situations.

MATERIALS AND METHODS

Following the Delphi technique, 206 specific consultations, structured in 24 clinical questions, were evaluated. A panel of experts composed of a total of 15 specialists, answered the two rounds of consultation through an online platform. The results were analysed and discussed in a face-to-face meeting with the coordinators and the scientific committee. According to the percentage of panellists who agreed on their findings, the results were classified in terms of unanimity, consensus, majority and discrepancy.

RESULTS

The following points were agreed upon: (1) the patient's phenotype determines the use of SYSADOAs; (2) SYSADOAs are considered appropriate in primary OA (knee, hand and hip) and in some types of secondary OA; they are not considered appropriate in OA of the shoulder, spine, ankle and erosive OA of the hands; (3) SYSADOAs may be prescribed for patients at risk of or with cardiovascular disease, digestive disease, hypertension, dyslipaemia, peripheral vascular disease, type 2 diabetes and, excluding Diacerein, for patients with oesophageal reflux. No agreement was obtained on the prescription of SYSADOAs for patients with hepatic and renal disease.

CONCLUSIONS

There is limited literature on the use of SYSADOAs for the treatment of OA in controversial situations. Through this work it has been possible to establish the position of a group of experts regarding clinical situations for which there is no scientific evidence concerning their use. This work may contribute towards improving the management protocols of SYSADOAs in the treatment of OA and offer a useful approach in uncertain situations.

Tumor Suppressive Role of miR-342-5p in Human Chondrosarcoma Cells and 3D Organoids

Chondrosarcomas are malignant bone tumors. Their abundant cartilage-like extracellular matrix and their hypoxic microenvironment contribute to their resistance to chemotherapy and radiotherapy, and no effective therapy is currently available. MicroRNAs (miRNAs) may be an interesting alternative in the development of therapeutic options. Here, for the first time in chondrosarcoma cells, we carried out high-throughput functional screening using impedancemetry, and identified five miRNAs with potential antiproliferative or chemosensitive effects on SW1353 chondrosarcoma cells. The cytotoxic effects of miR-342-5p and miR-491-5p were confirmed on three chondrosarcoma cell lines, using functional validation under normoxia and hypoxia. Both miRNAs induced apoptosis and miR-342-5p also induced autophagy. Western blots and luciferase reporter assays identified for the first time Bcl-2 as a direct target of miR-342-5p, and also Bcl-xL as a direct target of both miR-342-5p and miR-491-5p in chondrosarcoma cells. MiR-491-5p also inhibited EGFR expression. Finally, only miR-342-5p induced cell death on a relevant 3D chondrosarcoma organoid model under hypoxia that mimics the in vivo microenvironment. Altogether, our results revealed the tumor suppressive activity of miR-342-5p, and to a lesser extent of miR-491-5p, on chondrosarcoma lines. Through this study, we also confirmed the potential of Bcl-2 family members as therapeutic targets in chondrosarcomas.

Anti-inflammatory Effects and Mechanisms of Rhein, an Anthraquinone Compound, and Its Applications in Treating Arthritis: A Review

Inflammation is a defensive response of living tissues to damaging agents, which exists in two forms, acute inflammation and chronic inflammation, and chronic inflammation is closely related to arthritis. Currently, the commonly prescribed anti-inflammatory medications are greatly limited by high incidence of gastrointestinal erosions in the clinical applications. Rhein, a bioactive constituent of anthraquinone, exhibits excellent anti-inflammatory activities and therapeutic effects on arthritis with less gastrointestinal damages. Although there are numbers of studies on anti-inflammatory effects and mechanisms of rhein in the last few decades, to the best of our knowledge, only a few review articles pay attention to the interactive relationships of rhein on multiple inflammatory signaling pathways and cellular processes from a comprehensive perspective. Herein, we summarized anti-inflammatory effects and mechanisms of rhein and its practical applications in the treatment of arthritis, thereby providing a reference for its basic researches and clinical applications.

Experts Document About an Adequate Utilization of SYSADOAs in Controversial Clinical Situations

BACKGROUND AND OBJECTIVE

SYSADOAs (symptomatic slow-acting drugs for osteoarthritis) are natural compounds that have been shown to be useful and safe in the treatment of osteoarthritis (OA). However, their use in certain clinical situations still lacks scientific evidence and clear recommendations. The objective of this work was to learn the opinion of a group of experts regarding the appropriate use of SYSADOA in the treatment of OA in controversial clinical situations.

MATERIALS AND METHODS

Following the Delphi technique, 206 specific consultations, structured in 24 clinical questions, were evaluated. A panel of experts composed of a total of 15 specialists, answered the two rounds of consultation through an online platform. The results were analysed and discussed in a face-to-face meeting with the coordinators and the scientific committee. According to the percentage of panellists who agreed on their findings, the results were classified in terms of unanimity, consensus, majority and discrepancy.

RESULTS

The following points were agreed upon: (1) the patient's phenotype determines the use of SYSADOAs; (2) SYSADOAs are considered appropriate in primary OA (knee, hand and hip) and in some types of secondary OA; they are not considered appropriate in OA of the shoulder, spine, ankle and erosive OA of the hands; (3) SYSADOAs may be prescribed for patients at risk of or with cardiovascular disease, digestive disease, hypertension, dyslipaemia, peripheral vascular disease, type 2 diabetes and, excluding diacerein, for patients with oesophageal reflux. No agreement was obtained on the prescription of SYSADOAs for patients with hepatic and renal disease.

CONCLUSIONS

There is limited literature on the use of SYSADOAs for the treatment of OA in controversial situations. Through this work it has been possible to establish the position of a group of experts regarding clinical situations for which there is no scientific evidence concerning their use. This work may contribute towards improving the management protocols of SYSADOAs in the treatment of OA and offer a useful approach in uncertain situations.

Rhein, a novel Histone Deacetylase (HDAC) inhibitor with antifibrotic potency in human myocardial fibrosis

Although fibrosis depicts a reparative mechanism, maladaptation of the heart due to excessive production of extracellular matrix accelerates cardiac dysfunction. The anthraquinone Rhein was examined for its anti-fibrotic potency to mitigate cardiac fibroblast-to-myofibroblast transition (FMT). Primary human ventricular cardiac fibroblasts were subjected to hypoxia and characterized with proteomics, transcriptomics and cell functional techniques. Knowledge based analyses of the omics data revealed a modulation of fibrosis-associated pathways and cell cycle due to Rhein administration during hypoxia, whereas p53 and p21 were identified as upstream regulators involved in the manifestation of cardiac fibroblast phenotypes. Mechanistically, Rhein acts inhibitory on HDAC classes I/II as enzymatic inhibitor. Rhein-mediated cellular effects were linked to the histone deacetylase (HDAC)-dependent protein stabilization of p53 under normoxic but not hypoxic conditions. Functionally, Rhein inhibited collagen contraction, indicating anti-fibrotic property in cardiac remodeling. This was accompanied by increased abundance of SMAD7, but not SMAD2/3, and consistently SMAD-specific E3 ubiquitin ligase SMURF2. In conclusion, this study identifies Rhein as a novel potent direct HDAC inhibitor that may contribute to the treatment of cardiac fibrosis as anti-fibrotic agent. As readily available drug with approved safety, Rhein constitutes a promising potential therapeutic approach in the supplemental and protective intervention of cardiac fibrosis.

Rhein Inhibits the Migration of Ovarian Cancer Cells through Down-Regulation of Matrix Metalloproteinases

The root of Rheum officinale BAILL as a traditional Chinese medicine, which main function is removing heat from the blood, promoting blood circulation and clearing toxins away. Rhein (4,5-dihydroxyanthraquinone-2-carboxylic acid) is one of the most important active components in the root of Rheum officinale BAILL, which could inhibit the proliferation of tumor cells. However, the study on the mechanism of anti-cell migration capacity of Rhein on ovarian cancer is not yet clear. Here, we demonstrated that Rhein had dose-dependent effects of ovarian tumors on drugs and could inhibit the proliferations and migration of two typical ovarian cancer cell lines, A2780 and OV2008. Furthermore, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays showed that the survival rate of ovarian cancer cells was significantly decreased when treated with Rhein. Rhein inhibited the proliferation of ovarian cancer cells in dose-dependent manner. Moreover, the wound healing assay and transwell assay indicated that the cell migratory potential and expression of matrix metalloproteinases were markedly inhibited by Rhein. Our findings suggested that Rhein could be a potential candidate to be developed as a drug for the prevention of ovarian cancer cell migration.

Rhein inhibits ATP-triggered inflammatory responses in rheumatoid rat fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic and systemic inflammatory disorder, which may lead to joint disabilities. So far the pathogenesis of RA remains largely undetermined, and there are still no potent drugs for clinical treatment. Rhein, a natural bioactive anthraquinone derivative, exhibited significant anti-inflammatory activities demonstrated by previous studies. Here we aimed to investigate the effects of rhein on ATP-induced inflammation responses in fibroblast-like synoviocytes isolated from a rat model of collagen induced arthritis (CIA). Our results showed that ATP triggered rapid cytosolic calcium concentration ([Ca²⁺]_c) increase depending on extracellular Ca²⁺ entry. Given the major P2 subtypes expressed in rat synoviocytes were P2X₄ and P2Y₂ receptors, ATP-elicited calcium entry should be mainly resulted from activating P2X₄. Interestingly, rhein could effectively block the ATP-induced [Ca²⁺]_c increases in a dose-dependent manner. Besides, rhein also suppressed the production of intracellular reactive oxygen species (ROS) induced by ATP in synoviocytes that was resulted from P2X₄-mediated Ca²⁺ entry. Brilliant blue G (BBG), which can block P2X₄ receptor at high concentration, showed similar suppressive effects on above responses. Furthermore, in lipopolysaccharide-primed cells, application of ATP synergistically promoted the gene expression of cyclooxygenase-2, interleukin-6 and matrix metalloproteinase-9. Both rhein and BBG attenuated these inflammatory gene expressions enhanced by ATP. Above data together suggested a potential anti-arthritic role of rhein by inhibiting ATP-induced [Ca²⁺]_c increase, ROS production and inflammatory gene expression targeting P2X₄ in CIA rat synoviocytes, which will provide a novel insight in the therapy of RA.

Long non-coding RNA ANRIL-mediated inflammation response is involved in protective effect of rhein in uric acid nephropathy rats

Background

The aim of this study was to investigate the role of long non-coding RNAs (LncRNAs) antisense non-coding RNA in the INK4 locus (ANRIL) in anti-inflammation of rhein in uric acid nephropathy (UAN) rats.

Methods

Rat models of UAN were induced by adenine and potassium oxonate. Enzyme-linked immunosorbent assay (ELISA) was performed to assess inflammation factor in serum and supernatant. ANRIL mRNA level was detected using real-time reverse transcription PCR (qRT-PCR). Immunostaining was used to observe pathological changes of renal tissues in rats.

Results

ANRIL and inflammatory factor levels were highly expressed in patient with UAN. Furthermore, rhein showed an observable effect on anti-inflammatory and renal protection in UAN rats, rhein inhibited expressions of ANRIL in vivo or in vitro. Besides, ANRIL-mediated inflammatory response attenuated protective effect of rhein.

Conclusions

ANRIL-mediated inflammatory response attenuated the protective effect of rhein in UAN rats. This study showed an understanding of the role and mechanism of ANRIL in UAN, which provides a new target and therapy for the prevention and treatment of UAN.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Regulation of Extracellular Matrix Synthesis by Shell Extracts from the Marine Bivalve Pecten maximus in Human Articular Chondrocytes- Application for Cartilage Engineering

The shells of the bivalve mollusks are organo-mineral structures predominantly composed of calcium carbonate, but also of a minor organic matrix, a mixture of proteins, glycoproteins, and polysaccharides. These proteins are involved in mineral deposition and, more generally, in the spatial organization of the shell crystallites in well-defined microstructures. In this work, we extracted different organic shell extracts (acid-soluble matrix, acid-insoluble matrix, water-soluble matrix, guanidine HCl/EDTA-extracted matrix, referred as ASM, AIM, WSM, and EDTAM, respectively) from the shell of the scallop Pecten maximus and studied their biological activities on human articular chondrocytes (HACs). We found that these extracts differentially modulate the biological activities of HACs, depending on the type of extraction and the concentration used. Furthermore, we showed that, unlike ASM and AIM, WSM promotes maintenance of the chondrocyte phenotype in monolayer culture. WSM increased the expression of chondrocyte-specific markers (aggrecan and type II collagen), without enhancing that of the main chondrocyte dedifferentiation marker (type I collagen). We also demonstrated that WSM could favor redifferentiation of chondrocyte in collagen sponge scaffold in hypoxia. Thus, this study suggests that the organic matrix of Pecten maximus, particularly WSM, may contain interesting molecules with chondrogenic effects. Our research emphasizes the potential use of WSM of Pecten maximus for cell therapy of cartilage.

Diacerein inhibits the pro-atherogenic & pro-inflammatory effects of IL-1 on human keratinocytes & endothelial cells

We investigated IL-1-induced regulation of genes related to inflammation and atherogenesis in human keratinocytes and endothelial cells, and if ‘diacerein’, an oral IL-1 inhibiting drug currently approved for use in osteoarthritis, would reverse IL-1’s effects on these cells. Primary human keratinocytes and coronary artery endothelial cells were treated with either IL-1α or IL-1β, with and without diacerein. Using PCR-array, we assessed differential gene-expression regulated by IL-1 and diacerein. We identified 34 pro-atherogenic genes in endothelial cells and 68 pro-inflammatory genes in keratinocytes significantly (p<0.05) regulated at least 2-fold by IL-1, in comparison to control. Diacerein completely or partially reversed this regulation on almost all genes. Using ELISA, we confirmed diacerein’s ability to reverse IL-1-driven gene-regulation of 11 selected factors, at the protein level. The results support a novel idea that diacerein acts as an inhibitor of the pro-atherogenic and pro-inflammatory effects of IL-1. Diacerein may have therapeutic applications to diminish IL-1-induced skin inflammation in psoriasis and attenuate IL-1-induced development of atherosclerosis. Further investigation into diacerein’s effect on skin inflammation, atherogenesis and cardiovascular risk in animal models or humans is warranted.

A Comprehensive and System Review for the Pharmacological Mechanism of Action of Rhein, an Active Anthraquinone Ingredient

Rhein is a major medicinal ingredient isolated from several traditional Chinese medicines, including Rheum palmatum L., Aloe barbadensis Miller, Cassia angustifolia Vahl., and Polygonum multiflorum Thunb. Rhein has various pharmacological activities, such as anti-inflammatory, antitumor, antioxidant, antifibrosis, hepatoprotective, and nephroprotective activities. Although more than 100 articles in PubMed are involved in the pharmacological mechanism of action of rhein, only a few focus on the relationship of crosstalk among multiple pharmacological mechanisms. The mechanism of rhein involves multiple pathways which contain close interactions. From the overall perspective, the pathways which are related to the targets of rhein, are initiated by the membrane receptor. Then, MAPK and PI3K-AKT parallel signaling pathways are activated, and several downstream pathways are affected, thereby eventually regulating cell cycle and apoptosis. The therapeutic effect of rhein, as a multitarget molecule, is the synergistic and comprehensive result of the involvement of multiple pathways rather than the blocking or activation of a single signaling pathway. We review the pharmacological mechanisms of action of rhein by consulting literature published in the last 100 years in PubMed. We then summarize these pharmacological mechanisms from a comprehensive, interactive, and crosstalk perspective. In general, the molecular mechanism of action of drug must be understood from a systematic and holistic perspective, which can provide a theoretical basis for precise treatment and rational drug use.

Randomized controlled studies on the efficacy of antiarthritic agents in inhibiting cartilage degeneration and pain associated with progression of osteoarthritis in the rat

Background

As an initial step in the development of a local therapeutic to treat osteoarthritis (OA), a number of agents were tested for their ability to block activation of inflammation through nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), subchondral bone changes through receptor activator of nuclear factor κB ligand (RANKL)-mediated osteoclastogenesis, and proteolytic degradation through matrix metalloproteinase (MMP)-13 activity. Candidates with low toxicity and predicted efficacy were further examined using either of two widely accepted models of OA joint degeneration in the rat: the monoiodoacetic acid (MIA) model or the medial meniscal tear/medial collateral ligament tear (MMT/MCLT) model.

Methods

Potential therapeutics were assessed for their effects on the activation of nuclear factor (NF)-κB, RANKL-mediated osteoclastogenesis, and MMP-13 activity in vitro using previously established assays. Toxicity was measured using HeLa cells, a synovial cell line, or primary human chondrocytes. Drugs predicted to perform well in vivo were tested either systemically or via intraarticular injection in the MIA or the MMT/MCLT model of OA. Pain behavior was measured by mechanical hyperalgesia using the digital Randall-Selitto test (dRS) or by incapacitance with weight bearing (WB). Joint degeneration was evaluated using micro computed tomography and a comprehensive semiquantitative scoring of cartilage, subchondral bone, and synovial histopathology.

Results

Several agents were effective both in vitro and in vivo. With regard to pain behavior, systemically delivered clonidine was superior in treating MIA-induced changes in WB or dRS, while systemic clonidine, curcumin, tacrolimus, and fluocinolone were all somewhat effective in modifying MMT/MCLT-induced changes in WB. Systemic tacrolimus was the most effective in slowing disease progression as measured by histopathology in the MMT/MCLT model.

Conclusions

All of the agents that demonstrated highest benefit in vivo, excepting clonidine, were found to inhibit MMP-13, NF-κB, and bone matrix remodeling in vitro. The MIA and MMT/MCLT models of OA, previously shown to possess inflammatory characteristics and to display associated pain behavior, were affected to different degrees by the same drugs. Although no therapeutic was remarkable across all measures, the several which showed the most promise in either model merit continued study with alternative dosing and therapeutic strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0921-5) contains supplementary material, which is available to authorized users.

Diacerein retards cell growth of chondrosarcoma cells at the G2/M cell cycle checkpoint via cyclin B1/CDK1 and CDK2 downregulation

Background

Chondrosarcoma is characterized for its lack of response to conventional cytotoxic chemotherapy, propensity for developing lung metastases, and low rates of survival. Research within the field of development and expansion of new treatment options for unresectable or metastatic diseases is of particular priority. Diacerein, a symptomatic slow acting drug in osteoarthritis (SYSADOA), implicates a therapeutic benefit for the treatment of chondrosarcoma by an antitumor activity.

Methods

After treatment with diacerein the growth behaviour of the cells was analyzed with the xCELLigence system and MTS assay. Cell cycle was examined using flow cytometric analysis, RT-PCR, and western blot analysis of specific checkpoint regulators. The status for phosophorylation of mitogen-activated protein kinases (MAPKs) was analyzed with a proteome profiler assay. In addition, the possible impact of diacerein on apoptosis was investigated using cleaved caspase 3 and Annexin V/PI flow cytometric analysis.

Results

Diacerein decreased the cell viability and the cell proliferation in two different chondrosarcoma cell lines in a dose dependent manner. Flow cytometric analysis showed a classical G2/M arrest. mRNA and protein analysis revealed that diacerein induced a down-regulation of the cyclin B1-CDK1 complex and a reduction in CDK2 expression. Furthermore, diacerein treatment increased the phosphorylation of p38α and p38β MAPKs, and Akt1, Akt2, and Akt 3 in SW-1353, whereas in Cal-78 the opposite effect has been demonstrated. These observations accordingly to our cell cycle flow cytometric analysis and protein expression data may explain the G2/M phase arrest. In addition, no apoptotic induction after diacerein treatment, neither in the Cal-78 nor in the SW-1353 cell line was observed.

Conclusions

Our results demonstrate for the first time that the SYSADOA diacerein decreased the viability of human chondrosarcoma cells and induces G2/M cell cycle arrest by CDK1/cyclin B1 down-regulation.

Rhein: A Review of Pharmacological Activities

Rhein (4, 5-dihydroxyanthraquinone-2-carboxylic acid) is a lipophilic anthraquinone extensively found in medicinal herbs, such as Rheum palmatum L., Cassia tora L., Polygonum multiflorum Thunb., and Aloe barbadensis Miller, which have been used medicinally in China for more than 1,000 years. Its biological activities related to human health are being explored actively. Emerging evidence suggests that rhein has many pharmacological effects, including hepatoprotective, nephroprotective, anti-inflammatory, antioxidant, anticancer, and antimicrobial activities. The present review provides a comprehensive summary and analysis of the pharmacological properties of rhein, supporting the potential uses of rhein as a medicinal agent.

The disease modifying osteoarthritis drug diacerein is able to antagonize pro inflammatory state of chondrocytes under mild mechanical stimuli

OBJECTIVE

To investigate the combination of mild mechanical stimuli and a disease modifying osteoarthritis drug (DMOAD) in inflammatory activated chondrocytes and to study the combination of drug and mechanical tension on the cellular level as a model for an integrated biophysical approach for osteoarthritis (OA) treatments.

METHODS

Interleukin-1beta (IL-1β) stimulated C28/I2 cells underwent mild mechanically treatment while cultured in the presence of the DMOAD diacerein. The pharmacological input of diacerein was evaluated by cell viability and cell proliferation measurements. Inflammation and treatment induced changes in key regulatory proteins and components of the extracellular matrix (ECM) were characterized by quantitative real-time PCR (qPCR). The effects on metalloproteinase-1 (MMP-1) activity and glycosaminoglycan (GAG) concentration in cell supernatants of treated cells were investigated.

RESULTS

C28/I2 cells demonstrated significant changes in expression of inflammatory and cartilage destructive proteins in response to IL-1β stimulation. The chondroprotective action of diacerein in mechanically stimulated cells was mediated by a decrease in interleukin-8 (IL-8), fibronectin-1 (FN-1), collagen type I (Col 1) and MMP-1 expression levels, respectively. Augmented expression of interleukin-6 receptor (IL-6R) and the fibroblast growth factor receptors (FGFRs) by diacerein was not abolished by mechanical treatment. The observed effects were accompanied by a reduced cell proliferation rate, attenuated cell viability and extenuated MMP-1 activity.

CONCLUSION

Diacerein diversely regulates the expression of main regulatory proteins as well as components important to regenerate and set up ECM. Mechanical stimulation does not negatively influence the chondroprotective effect induced by diacerein treatment in immortalized human C28/I2 chondrocytes.

Effects of diacerein at the molecular level in the osteoarthritis disease process

In osteoarthritis (OA), the alterations in joint tissues are numerous and involve morphological, biochemical and metabolic changes and an upregulation of the inflammatory pathways. The focus of this article is a brief narrative review of the effects of diacerein, an antirheumatic drug from the anthraquinone chemical class, and its active metabolite, rhein, on the factors that participate in the complex interaction between OA tissues and cells leading to the progression of joint structural changes.

Rhein: a potential biological therapeutic drug for intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is regarded as an important cause of low back pain, which continues to be a common disability. IDD is thought to involve sequential changes of intervertebral disc that lead to the reduction of disc cells and the extracellular matrix. In addition, inflammation is crucially involved in IDD. Currently, there is urgent need to develop biological therapies for IDD that can both relieve symptoms and directly reverse the process of degeneration. Rhein (RH) is an anthraquinone molecule with the abilities of enhancing the synthesis of matrix components and inhibiting inflammatory response. Recently, the metabolic precursor of RH called diacerein has been demonstrated to have significant effects on pain relief and function improvement in the treatment of osteoarthritis. Given the occurrence of matrix degeneration and involvement of inflammation in IDD, we propose that RH might be a promising biological therapeutic drug for IDD due to its bioactivities. In addition, we hypothesize that the underlying mechanisms might be that RH has the ability to diminish interleukin-1 (IL-1) induced apoptosis and inhibit IL-1 induced secretion of MMPs and aggrecanases.

Multiple phospholipase A2 enzymes participate in the inflammatory process in osteoarthritic cartilage

OBJECTIVE

The aim of this study was to determine the involvement of pro-inflammatory phospholipase A2 (PLA2) enzymes in human chondrocytes from patients with osteoarthritis (OA).

METHODS

PLA2 involvement in OA chondrocytes was analysed by (a) arachidonic acid (AA) and oleic acid release, (b) PLA2 mRNA analysis, and (c) prostaglandin E2 (PGE2) production in cultured OA chondrocytes in response to various cytokines and platelet activating factor (PAF).

RESULTS

Pro-inflammatory cytokines and PAF stimulation led to increased AA release, interleukin (IL)-1β and tumour necrosis factor (TNF) being the strongest inducers. The pattern of oleic acid release was similar to but less prominent than AA release, suggesting that predominantly arachidonyl selective enzymes were activated. IL-1β, TNF, IL-6, and IL-8 upregulated secretory group IIA, IID, and V phospholipase A2 (sPLA2-IIA, -IID, -V) and cytosolic group IVA phospholipase A2 (cPLA2-IVA) expression, where induction of chondrocyte sPLA2-IID is a novel finding. Furthermore, IL-1β, TNF, and IL-6 also induced COX2 expression. PAF induced expression of group IIA, IID and IVA PLA2, and COX2. In line with its anti-inflammatory properties, IL-4 was unable to induce either AA release or expression of PLA2s or COX2. IL-1β and TNF strongly increased PGE2 production, with IL-1β as the most prominent inducer.

CONCLUSION

Multiple PLA2 isoforms are expressed and influenced by pro-inflammatory stimuli in OA chondrocytes. Hence, several PLA2 enzymes may contribute to chondrocyte function by their upregulation and activation, and increased AA release and PGE2 production may therefore be important effectors in OA pathophysiology. PLA2 enzymes and cPLA2-IVA in particular are thus possible therapeutic targets in OA.

Isoproterenol-induced FKBP12.6/12 downregulation is modulated by ETA and ETB receptors and reversed by argirhein, a derivative of rhein

AIM

To investigate which endothelin receptors mediated isoproterenol (ISO)-induced downregulation of FKBP12.6/12 in cardiomyocytes and study whether argirhein, a novel compound containing rhein and L-arginine that has anti-inflammatory activity, could reverse the downregulation of FKBP12.6/12 induced by ISO.

METHODS

Neonatal rat cardiomyocytes were incubated with ISO to downregulate FKBP12.6/12. Then the cells were treated with a selective ET(A) blocker (PD156707) and a ET(B) blocker (IRL1038), a dual ET(A)/ET(B) antagonist (CPU0213), and argirhein, respectively. FKBP12.6/12 expression was assayed by RT-PCR, Western blot, and immunocytochemistry.

RESULTS

The expression of FKBP12.6 mRNA was reduced by 37.7% (P<0.01) and 28.9% (P<0.05) relative to the control by ISO 1 and 0.1 μmol/L, respectively, but no response to ISO 0.01 μmol/L was observed in vitro. FKBP12.6/12 protein expression was reduced by 47.2% (P<0.01) and 37.8% (P<0.05) by ISO 1 and 0.1 μmol/L, respectively. This decrease was reversed significantly by PD156707, or IRL1038, and CPU0213. CPU0213 was more potent than either PD156707 or IRL-1038. Argirhein 10 μmol/L blunted the downregulation of FKBP12.6/12 by ISO, as demonstrated by the rising mRNA and protein levels and by the fluorescent density of the ISO-incubated cardiomyocytes.

CONCLUSION

In cardiomyocytes, the ISO induced downregulation of FKBP12.6/12 is modulated by both ET(A) and ET(B). A new compound, argirein, reversed the down-regulation of FKBP12.6/12 expression in myocardial cells stimulated with ISO.

Heritability estimates and linkage analysis of 23 short tandem repeat loci on chromosomes 2, 11, and 12 in an endemic osteochondropathy in China

OBJECTIVE

To estimate the heritability of Kashin-Beck disease (KBD) in first-degree relatives and to identify chromosome regions likely to contain susceptibility loci for KBD.

METHODS

A total of 331 probands with confirmed KBD in their pedigrees were selected from 9331 residents in 17 KBD villages of Linyou county, northwestern China. The heritability (h(2)) in first-degree relatives was estimated by using Falconer's formula. The segregation ratio was calculated by the Li-Mantel-Gart method. A total of 23 short tandem repeat (STR) loci on chromosomes 2, 11, and 12 were used to identify the susceptibility genes for KBD by linkage analysis using the GENEHUNTER program in 19 KBD pedigrees.

RESULTS

The general prevalence rate of KBD was 13.75% in the 17 KBD villages, lower than that of 20.88% in the first-degree relatives of the KBD probands. In the first-degree relatives, the heritability was 0.064 and the segregation ratio 35.10% (p < 0.05). Slight evidence for heritability was detected only in locus D12S1725 with a logarithm of odds (LOD) score of 1.95. However, the nonparametric linkage (NPL) scores showed no linkage between KBD and the 23 loci; the maximum NPL score was 1.59 for locus D12S1725.

CONCLUSIONS

Our results show that 35.10% of the heritability is attributable to genetic variation for the KBD phenotype among individuals of Linyou county, and the segregation ratio supports a multifactorial inheritance of KBD. There is no significant linkage between KBD and the 23 markers in the Linyou population examined; however, markers near the locus D12S1725 may indicate loci for further study.