Rhein inhibits interleukin-1 beta-induced activation of MEK/ERK pathway and DNA binding of NF-kappa B and AP-1 in chondrocytes cultured in hypoxia: a potential mechanism for its disease-modifying effect in osteoarthritis

NGF facilitates ICAM-1-dependent monocyte adhesion and M1 macrophage polarization in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder in which monocytes adhering to synovial tissue differentiate into the pro-inflammatory M1 macrophage phenotype. Nerve growth factors (NGF) referred to as neurotrophins have been associated with inflammatory events; however, researchers have yet to elucidate the role of NGF in RA. Our examination of clinical tissue samples and analysis of data sourced from the Gene Expression Omnibus dataset unveiled elevated expression levels of M1 macrophage markers in human RA synovial tissue samples compared to normal tissue, with no such distinction observed for M2 markers. Furthermore, immunofluorescence data depicted increased expression levels of NGF and M1 macrophages in RA mice in contrast to normal mice. It appears that NGF stimulation facilitates macrophage polarization from the M0 to the M1 phenotype. It also appears that NGF promotes ICAM-1 production in human RA synovial fibroblasts, which enhances monocyte adhesion through the TrkA, MEK/ERK, and AP-1 signaling cascades. Our findings indicate NGF/TrkA axis as a novel target for the treatment of RA.

Fermented jellyfish (Rhopilema esculentum) collagen enhances antioxidant activity and cartilage protection on surgically induced osteoarthritis in obese rats

Collagen has been considered a key treatment option in preventing damage to the articular cartilage over time and supporting the healing process, following the onset of osteoarthritis (OA). This study aimed to investigate the effect of collagen fermented from jellyfish (FJC) by Bacillus subtilis natto on anterior cruciate ligament transection with medial meniscectomy (ACLT + MMx)-induced knee OA in high-fat diet (HFD)-induced obesity in rats. The male Sprague-Dawley rats were fed an HFD for 6 weeks before ACLT + MMx surgery, after which they were administered a daily oral gavage of saline (control, OA, and OBOA), either with FJC (20 mg/kg, 40 mg/kg, and 100 mg/kg body weight) or glucosamine sulfate as a positive control (GS; 200 mg/kg body weight) for 6 weeks. Treatment with FJC decreased the fat weight, triglyceride, and total cholesterol levels in obese rats. Additionally, FJC downregulated the expression of some proinflammatory cytokines, including tumor necrosis factor-α, cyclooxygenase-2, and nitric oxide; suppressed leptin and adiponectin expression; and attenuated cartilage degradation. It also decreased the activities of matrix metalloproteinase (MMP)-1 and MMP-3. These results demonstrated that FJC showed a protective effect on articular cartilage and also suppressed the degradation of cartilage in an animal OA model, suggesting its potential efficacy as a promising candidate for OA treatment.

Chondroitin sulfate-functionalized lipid nanoreservoirs: a novel cartilage-targeting approach for intra-articular delivery of cassic acid for osteoarthritis treatment

Novel intra-articular nanoreservoirs were implemented employing different cartilage targeting approaches to improve cartilage bioavailability of a chondroprotective drug, cassic acid (CA), for effective amelioration of cartilage deterioration off-targeting CA gastrointestinal disorders. Herein, we compared active cartilage-targeting approach via chondroitin sulfate (CHS) functionalization versus passive targeting using positively charged nanoparticles to target negatively charged cartilage matrix. Firstly, CA integrated nanoreservoirs (CA-NRs) were fabricated based on ionic conjugation between CA and cationic hydrophobic surface modifier octadecylamine (ODA) and were further functionalized with CHS to develop CHS-CA-NRs. Confocal laser microscope was used to visualize the accumulation of nanoparticles into the cartilage tissue. Both targeting approaches promoted CA local cartilage availability and prolonged its residence time. Compared to passive targeted CA-NRs, active targeted CHS-CA-NRs showed higher fluorescence signals in proximity to and inside chondrocytes which lasted for up to 21 days. In MIA-osteoarthritic rats, CHS-CA-NRs showed superior antiosteoarthritic activity, exhibiting highest cartilage repair compared to CA-NRs. Additionally, CHS-CA-NRs significantly inhibited OA inflammatory cytokine, degradation enzyme and oxidative stress and improved cartilage matrix biosynthesis. Conclusively, CHS-CA-NRs improved OA repair showing a superior efficacy for articular cartilage targeting with CHS which could be a potential advance for OA therapy.

Elucidation of Potential Targets of San-Miao-San in the Treatment of Osteoarthritis Based on Network Pharmacology and Molecular Docking Analysis

Background

To examine the potential therapeutic targets of Chinese medicine formula San-Miao-San (SMS) in the treatment of osteoarthritis (OA), we analyzed the active compounds of SMS and key targets of OA and investigated the interacting pathways using network pharmacological approaches and molecular docking analysis.

Methods

The active compounds of SMS and OA-related targets were searched and screened by TCMSP, DrugBank, Genecards, OMIM, DisGeNet, TTD, and PharmGKB databases. Venn analysis and PPI were performed for evaluating the interaction of the targets. The topological analysis and molecular docking were used to confirm the subnetworks and binding affinity between active compounds and key targets, respectively. The GO and KEGG functional enrichment analysis for all targets of each subnetwork were conducted.

Results

A total of 57 active compounds and 203 targets of SMS were identified by the TCMSP and DrugBank database, while 1791 OA-related targets were collected from the Genecards, OMIM, DisGeNet, TTD, and PharmGKB databases. By Venn analysis, 108 intersection targets between SMS targets and OA targets were obtained. Most of these intersecting targets involve quercetin, kaempferol, and wogonin. Moreover, intersecting targets identified by PPI analysis were introduced into Cytoscape plug-in CytoNCA for topological analysis. Hence, nine key targets of SMS for OA treatment were obtained. Furthermore, the potential binding conformations between active compounds and key targets were found through molecular docking analysis. According to the DAVID enrichment analysis, the main biological processes of SMS in the treatment of OA include oxidative stress, response to reactive oxygen species, and apoptotic signaling pathways. Finally, we found wogonin, the key compound in SMS, might play a pivotal role on Toll-like receptor, IL-17, TNF, osteoclast differentiation, and apoptosis signaling pathways through interacting with four key targets.

Conclusions

Therefore, this study elucidated the potential active compounds and key targets of SMS in the treatment of OA based on network pharmacology.

Molecular signaling in temporomandibular joint osteoarthritis

Objective

Temporomandibular joint (TMJ) osteoarthritis (OA) is a type of TMJ disorders with clinical symptoms of pain, movement limitation, cartilage degeneration and joint dysfunction. This review article is aiming to summarize recent findings on signaling pathways involved in TMJ OA development and progression.

Methods

Most recent findings in TMJ OA studies have been reviewed and cited.

Results

TMJ OA is caused by inflammation, abnormal mechanical loading and genetic abnormalities. The molecular mechanisms related to TMJ OA have been determined using different genetic mouse models. Recent studies demonstrated that several signaling pathways are involved in TMJ OA pathology, including Wnt/β-catenin, TGF-β and BMP, Indian Hedgehog, FGF, NF-κB, and Notch pathways, which are summarized in this review article. Alterations of these signaling pathways lead to the pathological changes in TMJ tissues, affecting cartilage matrix degradation, catabolic metabolism and chondrocyte apoptosis.

Conclusion

Multiple signaling pathways were involved in the pathological process of TMJ OA. New therapeutic strategies, such as stem cell application, gene editing and other techniques may be utilized for TMJ OA treatment.

The translational potential of this article

TMJ OA is a most important subtype of TMJ disorders and may lead to substantial joint pain, dysfunction, dental malocclusion, and reduced health-related quality of life. This review article summarized current findings of signaling pathways involved in TMJ OA, including Wnt/β-catenin, TGF-β and BMP, Indian Hedgehog, FGF, NF-κB, and Notch pathways, to better understand the pathological mechanisms of TMJ OA and define the molecular targets for TMJ OA treatment.

An Update of Anthraquinone Derivatives Emodin, Diacerein, and Catenarin in Diabetes

Diabetes is part of metabolic diseases and is characterized by high blood sugar levels over a prolonged period as result of an insulin-deficient production or an inappropriate response to insulin by our cells. This chronic disease was the direct cause of 1.6 million deaths in 2016 as reported by the World Health Organization. Emodin is a natural product and active ingredient of various Chinese herbs with the chemical formula 1,3,8-trihydroxy-6-methylanthraquinone. Diacerein is another naturally occurring anthraquinone (1,8-diacetoxy-3-carboxyanthraquinone) commonly used as commercial drug to treat osteoarthritis. These two anthraquinone derivatives have been shown to exert antidiabetic activities. Emodin seems to enhance the glucose tolerance and insulin sensibility via activation of PPARγ and modulation of metabolic-related genes. Diacerein seems to decrease inflammatory cytokines and increase insulin secretion enhancing insulin sensibility and therefore improving glucose control. Other naturally occurring anthraquinone derivatives, such as catenarin (1,4,6,8-tetrahydroxy-3-methylanthraquinone), have been shown to have antidiabetic activities although few studies have been performed. The synthesis of new emodin derivatives is increasing, but these new molecules have not been tested for diabetes treatment. In the current work, available literature on anthraquinone derivatives' effects in diabetes disease is reviewed. Moreover, we discuss the chemistry, food sources, bioavailability, and toxicity of the naturally occurring anthraquinone with antidiabetic effects.

Rhein Derivatives, A Promising Pivot?

Rhein, an anthraquinone derivative, has been employed widely, especially for the treatment of intractable diseases like diabetic nephropathy, arthritis, and cancer in a unique action mechanism. In the last decades, considerable efforts have been made in structural modification of rhein. This paper reviewed patents on pharmacological activity and therapeutic application of rhein and its derivatives from 1978 to 2018. Particularly, an analysis of patents was made, with the top 10 most valuable patents presented, and the interpretation of the legal status of patents was given. Given the properties of superior pharmacological activity, rich resources, cheap price, low toxicity, and mature extraction process, it is believed that an in-depth investigation on rhein and its derivatives is worth trying.

Rhein attenuates PTZ‑induced epilepsy and exerts neuroprotective activity via inhibition of the TLR4-NFκB signaling pathway

BACKGROUND

Epilepsy is a common neurological disease that cannot be well controlled by existing antiepileptic drugs. Studies have implicated oxidative stress and inflammation in the pathophysiology of epilepsy. Rhein has a comprehensive pharmacological function in reducing inflammation and can play a neuroprotective role in many neurological diseases, however little is known about its effects on epilepsy.

METHODS

A model of acute epilepsy in mice was established using the Pentylenetetrazol (PTZ) ignition method to evaluate the effects of Rhein on the duration and latency of convulsions, and the number and severity of seizures. Modified Neurological Severity Score (mNSS), Rotarod and open-field behavioral task tests were performed to evaluate the neuroprotective effect of Rhein. TUNEL staining was used to assess neuronal damage, and western blot, qPCR and ELISA kits were utilized to determine the expression of inflammatory signaling protein molecules and levels of inflammatory cytokines.

RESULTS

In this study, we demonstrate that Rhein delayed the onset of seizures, decreased their severity, and reduced the duration and frequency of seizures in PTZ-induced epileptic mice. Furthermore, we found that Rhein blocked neurological deficits induced by PTZ. In addition, our results show that Rhein inhibited the activation of the TLR4-NFκB signaling pathway and decreased the secretion of the inflammatory cytokines TNF-α, IL-6, IL-1β, and IL-18.

CONCLUSION

Our results suggest that the anticonvulsant and neuroprotective effects of Rhein are achieved by disrupting the processes involved in PTZ acquisition of epilepsy.

Pharmacokinetics and Pharmacodynamics of the Combination of Rhein and Curcumin in the Treatment of Chronic Kidney Disease in Rats

Objectives: The interaction between the components of traditional Chinese medicine (TCM) is an important basis for their synergy. Rhein and curcumin exert various pharmacological activities, including anti-tumour, anti-inflammatory, antioxidant, anti-fibrosis and renoprotective effects. However, no investigation has reported the synergistic anti-fibrosis effect yet. This study aims at determine the pharmacokinetics and pharmacodynamics of the combination of rhein and curcumin in the treatment for chronic kidney disease in rats.

Design: Fifty two male Sprague-Dawley (SD) rats were randomly divided into rhein group, curcumin group and their combination group for pharmacodynamics studies. HE and Masson staining was conducted to observe the changes of renal morphology. Kits were used to detect the level of urea nitrogen (BUN) and creatinine (Scr). For pharmacokinetic study, 36 SD rats were randomly divided into rhein group, curcumin group and a combination group, the content of rhein and curcumin in plasma and renal tissue was determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). In additon, molecular docking method and cell experiments was used to disclose the interaction mechanism between curcumin and rhein.

Results: The pharmacodynamic results showed that the degree of renal fibrosis was improved obviously by co-administration rhein and curcumin. Meanwhile, compared to single administration, the Cmax and AUC of rhein and curcumin in plasma and renal tissue were enhanced significantly after co-administration. Moreover, the result of molecular docking and cell experiments showed that both two compounds could interact with P-gp, CYP2C9 and CYP2C19.

Conclusion: Together, these findings demonstrated that rhein and curcumin had a synergistic effect in ameliorateing chonic kidney disease, providing an important explanation on the synergistic mechanism of curcumin and rhein from a pharmacokinetic viewpoint.

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.

Rhein Protects Against Neurological Deficits After Traumatic Brain Injury in Mice via Inhibiting Neuronal Pyroptosis

Neurological dysfunction provoked by traumatic brain injury (TBI) makes a huge impact on individual learning ability, memory level, social participation, and quality of life. Pyroptosis, the caspase-1-dependent cell death, which is associated with the release of numerous pro-inflammatory factors, plays a major role in the pathological process after TBI. Inhibition of pyroptosis has been shown to be an attractive strategy for the treatment of various neurological disorders. Here, we found that Rhein, an anthraquinone derived from the medicinal plant rhubarb, attenuated TBI-induced upregulation of pro-inflammatory cytokines, blood lactate dehydrogenase (LDH), and pyroptosis-related proteins, as well as reduced neurological dysfunction in a mouse TBI model. Consistently, Rhein inhibitd equiaxial stretch-induced neuron pyroptosis, LDH release, and upregulation of pro-inflammatory factors in vitro. Thus, our study suggested that Rhein protected against neurological deficits after TBI via inhibiting neuronal pyroptosis.

Rhein Suppresses Neuroinflammation via Multiple Signaling Pathways in LPS-Stimulated BV2 Microglia Cells

As a bioactive absorbed compound of rhubarb, Rhein is applied for the treatment of brain injury. However, the underlying pharmacological mechanisms remain unclear. In this study, we aimed to explore antineuroinflammatory functions and underlying mechanisms of Rhein in vitro. BV2 microglia cells were chosen and irritated by LPS. The influence of Rhein on cell viability was determined using MTT assay. We finely gauged the proinflammatory cytokines of TNF-α and IL-1β through tests of immunofluorescence staining, ELISA, RT-qPCR, and western blot. Additionally, mediators including IL-6, IL-12, iNOS, and IL-10 were surveyed by ELISA. Furthermore, protein levels of the underlying signaling pathways (PI3K/Akt, p38, ERK1/2, and TLR4/NF-κB) were tested adopting western blot. We found that Rhein reduced the secretion of pivotal indicators including TNF-α and IL-1β, effectively restraining their mRNA and protein expression in LPS-activated BV2 microglial cells. Besides, Rhein treatment demoted the production of IL-6, IL-12, and iNOS and promoted the excretion of IL-10. Subsequent mechanistic experiments revealed that Rhein obviously downregulated the phosphorylation levels of PI3K, Akt, p38, and ERK1/2 and simultaneously upregulated the PTEN expression. In addition, Rhein antagonized the increase of TLR4, p-IκBα, and NF-κB. In summary, Rhein suppresses neuroinflammation via multiple signaling pathways (PI3K/Akt, p38, ERK1/2, and TLR4/NF-κB) in LPS-stimulated BV2 microglia cells. This study highlights a natural agent for prevention and treatment of neuroinflammation.

Therapeutic Potential Low-Intensity Pulsed Ultrasound for Osteoarthritis: Pre-clinical and Clinical Perspectives

Osteoarthritis (OA), degeneration of cartilage associated with aging, lifestyle, and trauma, is one of the most common diseases that leads to lower quality of life and socioeconomic burden in the United States. Clinically, OA is initially managed by non-steroidal anti-inflammatory drugs, but eventually requires surgical intervention to reduce pain and increase function. Cartilage is a mechanotransductive tissue and requires a mechanical stimulus to sustain its mechanical and physiologic properties. Low-intensity pulsed ultrasound (LIPUS) is a cyclic acoustic wave that can provide essential mechanical stimuli to activate molecular and cellular pathways leading to chondrocyte proliferation, differentiation and activity, as well as to inhibit inflammatory pathways associated with OA. The activation of chondrocyte proliferation and inhibition of anti-inflammatory cytokines make LIPUS a potential therapy for mild to moderate OA. Although a few review articles have described the effects of ultrasound on chondrocytes and cartilage, there remains a need for a comprehensive analysis of our current understanding of the basic science and clinical status of the effects of low-intensity ultrasound on chondrocytes and cartilage and the implications of these studies on LIPUS as a therapeutic option for OA. This review analyzes recent literature describing the results of LIPUS using in vitro and in vivo pre-clinical models and clinical studies, as well as future directions for research.

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.

β-Conglycinin-Induced Intestinal Porcine Epithelial Cell Damage via the Nuclear Factor κB/Mitogen-Activated Protein Kinase Signaling Pathway

Soybean allergy is a serious health risk to humans and animals; β-conglycinin is the primary antigenic protein in soybean. Intestinal porcine epithelial (IPEC-J2) cells were used as an in vitro physiological model of the intestinal epithelium to study the effects of different concentrations of soybean antigen protein β-conglycinin to identify the involved signaling pathways. The cells were divided into eight groups and either untreated or treated with different concentrations of β-conglycinin, pyrrolidine dithiocarbamate (PDTC), Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME), SP600125, and SB202190 either alone or in combination. The cells were incubated with 1, 5, and 10 mg·mL-1 β-conglycinin or 5 mg·mL-1 β-conglycinin and 1 μmol·L-1 nuclear factor κB (NF-κB) inhibitor (PDTC), inducible nitric oxide synthase inhibitor (l-NAME), c-Jun N-terminal kinase (JNK) inhibitor (SP600125), and p38 inhibitor (SB202190) for 24 h, separately; controls were left untreated. The mRNA, protein, and phosphorylation levels of NF-κB, p38, and JNK were higher in the treated groups than in the control group. β-Conglycinin decreased tight junction distribution, destroyed the cytoskeleton of IPEC-J2 cells, and caused cell death. After the addition of the inhibitors, β-conglycinin-induced IPEC-J2 cell damage was significantly reduced. β-Conglycinin caused damage to IPEC-J2 cells via the mitogen-activated protein kinase/NF-κB signaling pathway. The results of this study are crucial for exploring the mechanisms underlying allergic reactions caused by soybean antigen proteins.

Effects of IL-1β on MMP-9 Expression in Cementoblast-Derived Cell Line and MMP-Mediated Degradation of Type I Collagen

It has been reported that matrix metalloproteinases (MMPs) are induced by many cytokines, and they are involved in various inflammatory processes, including periodontitis. However, the effects of interleukin-1β (IL-1β) on MMP-9 expression in cementoblasts, the cells responsible for cementum production, remain largely unknown. In this study, we used qPCR and gelatin zymogram analysis to show that IL-1β upregulated MMP-9 expression in cementoblast-derived cell line. Several signaling pathways, such as ERK1/2, JNK, p38, and AP-1 (c-Fos and ATF-2), were activated in response to IL-1β stimulation. Furthermore, enhancement of AP-1 activity by IL-1β was further confirmed by the AP-1 reporter assay and the electrophoretic mobility shift assay (EMSA). Pretreatment with specific inhibitors of ERK1/2 (U0126), JNK (SP600125), and AP-1 (tanshinone IIA) attenuated IL-1β-induced MMP-9 expression. In addition, inhibitors of ERK1/2 (U0126) and JNK (SP600125) attenuated IL-1β-enhanced AP-1 activity. This suggested that IL-1β stimulated AP-1 activation, at least partially, through ERK1/2 and JNK signaling pathways. Moreover, we found that IL-1β also upregulated the expression of MMP-13 and enhanced MMP-mediated degradation of type I collagen. Collectively, these results suggested that IL-1β induced MMP-9 expression by activation of AP-1 through the ERK1/2 and JNK signaling pathways in cementoblast-derived cell line and enhanced MMP-mediated collagen degradation possibly by MMP-13 and MMP-9.

In vitro chondroprotective potential of Senna alata and Senna tora in porcine cartilage explants and their species differentiation by DNA barcoding-high resolution melting (Bar-HRM) analysis

Senna species and anthraquinone derivatives generated by these organisms, rhein and aloe-emodin, exert anti-inflammatory effects. These species present a similar morphology but produce different ingredients when they are used as medicinal products. In this study, a DNA barcoding- (Bar-) high-resolution melting (HRM) technique was developed using internal transcribed sequence 2 (ITS2) to differentiate between Senna alata and Senna tora as a result of significant differences in their melting profiles. We used this approach for confirmation of S. alata and S. tora raw materials, and we examined the chondroprotective properties of the ethanolic extracts of S. alata and S. tora using a porcine model of cartilage degradation induced by a combination of interleukin-17A (IL-17A) and IL-1β. We found that both Senna ethanolic extracts, at a concentration of 25 μg/mL, effectively prevented cartilage degradation. Rhein and aloe-emodin were present in the extract of S. alata but not in that of S. tora. We observed a reduction in the release of sulfated glycosaminoglycans (S-GAGs) and hyaluronic acid (HA) into media in both treatments of Senna extracts, which indicated proteoglycan preservation in explant tissues. These results suggest that neither rhein nor aloe-emodin are the main factors responsible for cartilage-protecting properties. Taken together, results show that both S. alata and S. tora are promising for further development as anti-osteoarthritic agents and that Bar-HRM using ITS2 could be applied for species confirmation with Senna products.

Rhein, An Anthraquinone Drug, Suppresses the NLRP3 Inflammasome and Macrophage Activation in Urate Crystal-Induced Gouty Inflammation

Rhein, an anthraquinone drug, is a widely used traditional Chinese medicine. Rhein is a major bioactive metabolite of diacerein which has been approved for treating osteoarthritis with a good safety profile in humans. Gouty arthritis is an inflammatory disease characterized by urate crystal-induced NLRP3 inflammasome activation with up-regulated caspase-1 protease and IL-1 β in macrophages. Inhibition of the NLRP3 inflammasome formation has been considered as a potential therapeutic avenue for treating or preventing many inflammatory diseases. This study aimed to evaluate the anti-inflammatory effects of rhein on gouty arthritis. Rhein within the physiological levels of humans showed no toxicity on the cell viability and differentiation, but significantly decreased the production of IL-1 β , TNF- α and caspase-1 protease in urate crystal-activated macrophages. Compared to medium controls, rhein at the therapeutic concentration (2.5 μ g/mL) effectively inhibited IL-1 β production by 47% ( P=0.002 ). Rhein did not affect the mRNA levels of CASP1, NLRP3 and ASC, but suppressed the protein expression and enzyme activity of caspase-1. Immunofluorescence confocal microscopy further revealed that rhein suppressed the aggregation of ASC speck and inhibited the formation of NLRP3 inflammasome. Rhein of 5 μ g/mL significantly decreased the ASC speck to 36% ( P=0.0011 ), and reduced the NLRP3 aggregates to 37.5% ( P=0.014 ). Our data demonstrate that rhein possesses pharmacological activity to suppress caspase-1 protease activity and IL-1 β production by interfering with the formation of NLRP3 multiprotein complex. These results suggest that rhein has therapeutic potential for treating NLRP3 inflammasome-mediated diseases such as gouty arthritis.

Mechanical exposure and diacerein treatment modulates integrin-FAK-MAPKs mechanotransduction in human osteoarthritis chondrocytes

BACKGROUND

Progression of osteoarthritis (OA) is characterized by an excessive production of matrix degrading enzymes and insufficient matrix repair. Despite of active research in this area, it is still unclear how the combination of mechanical exposure and drug therapy works. This study was done to explore the impact of the disease modifying OA drug (DMOAD) diacerein and moderate tensile strain on the anabolic metabolism and the integrin-FAK-MAPKs signal transduction cascade of OA and non-OA chondrocytes.

METHODS

Cyclic tensile strain was applied in terms of three different intensities by the Flexcell tension system. Influence on catabolic parameters such as MMPs, ADAMTS, and IL-6 were assessed by qPCR. Changes in phosphorylation of FAK, STAT3 as well as MAP kinases were verified by western blot analysis. Intracellular calcium was measured fluorimetrically using fura-2.

RESULTS

Tensile strain at moderate intensity (SM/SA profile) proved to be most efficient in terms of reducing production of matrix degrading enzyme and IL-6 expression. Treatment with diacerein by itself and diacerein in combination with SM/SA stimulation reduced phosphorylation of FAK and STAT3, which is more pronounced in OA cells. Pretreatment with diacerein for 7 days resulted in an increase in the sensitivity to Yoda1, the agonist for the mechanically activated ion channel Piezo1. However, in OA chondrocytes a significant reduction in Piezo1 expression was observed following treatment with diacerein.

CONCLUSION

Our results demonstrated for the first time that diacerein intensively intervenes in the regulation of FAK and STAT3 and influences components considered relevant for the progression of OA, even in the presence of mechanical stimulation.

An integrated strategy for identifying new targets and inferring the mechanism of action: taking rhein as an example

Background

Target identification is necessary for the comprehensive inference of the mechanism of action of a compound. The application of computational methods to predict the targets of bioactive compounds saves cost and time in drug research and development. Therefore, we designed an integrated strategy consisting of ligand-protein docking, network analysis, enrichment analysis, and an experimental surface plasmon resonance (SPR) method to identify and validate new targets, and then used enriched pathways to elucidate the underlying pharmacological mechanisms. Here, we used rhein, a compound with various pharmacological activities, as an example to find some of its previously unknown targets and to determine its pharmacological activity.

Results

A total of nine candidate targets were discovered, including LCK, HSP90AA1, RAB5A, EGFR, CDK2, CDK6, GSK3B, p38, and JNK. LCK was confirmed through SPR experiments, and HSP90AA1, EGFR, CDK6, p38, and JNK were validated through previous reports. Rhein network regulations are complex and interconnected. The therapeutic effect of rhein is the synergistic and comprehensive result of this vast and complex network, and the perturbation of multiple targets gives rhein its various pharmacological activities.

Conclusions

This study provided a new integrated strategy to identify new targets of bioactive compounds and reveal their molecular mechanisms of action.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2346-4) contains supplementary material, which is available to authorized users.

Effect of Fucoidan on Anterior Cruciate Ligament Transection and Medial Meniscectomy Induced Osteoarthritis in High-Fat Diet-Induced Obese Rats

Osteoarthritis (OA) has become one of the most common disabilities among elders, especially in females. Obesity and mechanical injuries caused by OA are attributed to joint loading, cartilage disintegration, and bone loss, as well as inflammation. Pharmacological and non-pharmacological treatments can be used for OA. Fucoidan possesses several bioactivities such as antitumor, antiviral, anticoagulation, anti-obesity, and immunomodulation. This study aims to investigate the effect of fucoidan in surgery-induced OA on rats with diet-induced obesity. OA was induced by an anterior cruciate ligament transection and a partial medial meniscectomy (ACLT + MMx). The male SD rats were fed with a high-fat diet (HFD) for 4 weeks to induce obesity before causing ACLT + MMx to induce OA. The OA rats were administered with intragastric water or fucoidan in three different concentrations (32 mg/kg, 64 mg/kg, and 320 mg/kg) after the surgeries for 40 days with an HFD. We observed that the swelling in the knee joint was alleviated and the hind paw weight distribution was rectified after feeding them with fucoidan and that there was no significant effect on the weight gain and feed intake. Fucoidan administration indicated no significant variation on the high-density lipoprotein (HDL)-Cholesterol level, but it did indicate reduced plasma triglycerides and low-density lipoprotein (LDL)-Cholesterol levels. In addition, the weight-bearing tests showed an improvement in the fucoidan-treated group. Our results suggested that fucoidan may improve meniscal/ligamentous injury and obesity-induced OA.

Loss of Fgfr1 in chondrocytes inhibits osteoarthritis by promoting autophagic activity in temporomandibular joint

Temporomandibular joint osteoarthritis (TMJ OA) is a common degenerative disease with few effective disease-modifying treatments in the clinic. Fibroblast growth factor (FGF) signaling is implicated in articular cartilage homeostasis, but the functional roles of FGFR1 in TMJ OA remain largely unknown. In this study, we report that deletion of Fgfr1 in TMJ chondrocytes delayed TMJ OA progression in the age-associated spontaneous OA model and the abnormal dental occlusion OA model. Immunohistochemical staining revealed that Fgfr1 deficiency decreased the expressions of MMP13 (matrix metalloproteinase-13), ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5), and COL10A1 but increased aggrecan expression level in two TMJ OA models. Furthermore, our data show that inactivation of FGFR1 signaling may promote autophagic activity in TMJ. FGFR1 inhibitor decreased the expressions of Mmp13, Adamts5, and Runx2 in IL-1β-stimulated condylar chondrocytes, whereas autophagy inhibitors abrogated the protective effects of the FGFR1 inhibitor. Thus, our study indicates inactivated FGFR1 signaling ameliorates TMJ OA progression partially by promoting autophagic activity. Manipulation of this signaling may be a potential therapeutic approach to modify TMJ OA.

Optimization of rhein-loaded polymeric nanoparticles using a factorial design and evaluation of the cytotoxic and anti-inflammatory effects

The aim of the work was to develop rhein loaded polymeric nanoparticles (R-PNPs). Nanoparticles were prepared by three methods, solvent emulsion-evaporation, double emulsion, and nanoprecipitation, by means of experimental design. Additionally, the effects of the best formulation on in vitro cytotoxicity and inflammation were evaluated. The solvent emulsion-evaporation method presented the highest encapsulation efficiency of the three techniques (38.41%), as well as had a mean diameter of 189.33 nm and a polydispersity index of less than 0.1. Despite efforts to optimize the encapsulation of rhein, the drug release from nanoparticles was close to 50% during the first 5 min, followed by a continuous release within 60 min. It was observed that macrophages exposed to the highest concentration of R-PNPs showed cell viability about 80% and at the lowest nanoparticle concentrations was closed to 100%. IL-1β in cell culture supernatants was decreased in the presence of R-PNPs and TNFα concentrations were lower than the sensitivity of the assay. ROS production was only inhibited with R-PNPs at concentrations of 2.5 and 5 μM. In conclusion, the solvent emulsion-evaporation was the best method evaluated to obtain nanoparticles with the desired specifications. It was possible to assess R-PNPs with low cytotoxicity and anti-inflammatory properties showed by the inhibition of IL-1β production and a low decrease in ROS production.

The natural agent rhein induces β-catenin degradation and tumour growth arrest

The natural agent rhein is an ananthraquinone derivative of rhubarb, which has anticancer effects. To determine the mechanisms underlying the anticancer effects of rhein, we detected the effect of rhein on several oncoproteins. Here, we show that rhein induces β‐catenin degradation in both hepatoma cell HepG2 and cervical cancer cell Hela. Treatment of HepG2 and Hela cells with rhein shortens the half‐life of β‐catenin. The proteasome inhibitor MG132 blunts the downregulation of β‐catenin by rhein. The induction of β‐catenin degradation by rhein is dependent on GSK3 but independent of Akt. Treatment of HepG2 and Hela cells with GSK3 inhibitor or GSK3β knockdown abrogates the effect of rhein on β‐catenin. GSK3β knockdown compromises the inhibition of HepG2 and Hela cell growth by rhein. Furthermore, rhein dose not downregulate β‐catenin mutant that is deficient of phosphorylation at multiple residues including Ser33, Ser37, Thr41 and Ser45. Moreover, rhein induces cell cycle arrest at S phase in both HepG2 and Hela cells. Intraperitoneal administration of rhein suppresses tumour cells proliferation and tumour growth in HepG2 xenografts model. Finally, the levels of β‐catenin are reduced in rhein‐treated tumours. These data demonstrate that rhein can induce β‐catenin degradation and inhibit tumour growth.

Rhein and polydimethylsiloxane functionalized carbon/carbon composites as prosthetic implants for bone repair applications

A major issue in bone tissue engineering is the selection of biocompatible materials for implants, to reduce unwanted inflammatory reactions and promote cell adhesion. Bone tissue growth on suitable biomedical implants can shorten recovery and hospitalization after surgery. Therefore, a method to improve tissue-implant integration and healing would be of scientific and clinical interest. In this work, we permeated polydimethylsiloxane (PDMS) into carbon/carbon (C/C) composites (PDMS-C/C) and then coated it with 4,5-dihydroxyanthraquinone-2-carboxylic acid (rhein) to create rhein-PDMS-C/C to increase its biocompatibility and reduce the occurrence of inflammatory reactions. We measured in vitro adhesion and proliferation of MC3T3-E1 cells and bacteria to evaluate the biocompatibility and antimicrobial properties of C/C, PDMS-C/C, and rhein-PDMS-C/C. In vivo, x-ray and micro-CT evaluation three, six and nine weeks after surgery revealed that rhein-PDMS-C/C was more effective than PDMS-C/C and C/C composite in terms of antibacterial activity, cell adhesion and tissue growth. Compared with C/C and PDMS-C/C, rhein-PDMS-C/C could be suitable for clinical applications for bone tissue engineering.

Rhein exhibits antitumorigenic effects by interfering with the interaction between prolyl isomerase Pin1 and c-Jun

The Pin1 protein (or peptidyl-prolyl cis/trans isomerase) specifically catalyzes the cis/trans isomerization of phosphorylated serine/threonine-proline (Ser/Thr-Pro) bonds and plays an important role in many cellular events through the effects of conformational change in the function of c-Jun, its biological substrate. Pin1 expression is involved in essential cellular pathways that mediate cell proliferation, cell cycle progression, tumorigenesis and apoptosis by altering their stability and function, and it is overexpressed in various types of tumors. Pin1 phosphorylation has been regarded as a marker of Pin1 isomerase activity, and the phosphorylation of Ser/Thr-Pro on protein substrates is prerequisite for its binding activity with Pin1 and subsequent isomerization. Since phosphorylation of proteins on Ser/Thr-Pro is a key regulatory mechanism in the control of cell proliferation and transformation, Pin1 has become an attractive molecule in cancer research. Many inhibitors of Pin1 have been discovered, including several classes of both designed inhibitors and natural products. Anthraquinone compounds possess antitumor properties and have therefore been applied in human and veterinary therapeutics as active substances in medicinal products. Among the anthraquinones, rhein (4,5-dihydroxy-9,10-dioxoanthracene-2-carboxylic acid) is a monomeric anthraquinone derivative found mainly in plants in the Polygonaceae family, such as rhubarb and Polygonum cuspidatum. Recent studies have shown that rhein has numerous pharmacological activities, including antitumor effects. Here, we demonstrated the antitumorigenic effect of rhein using cell proliferation assay, anchorage-independent cell transformation, pull-down assay, luciferase promoter activity, fluorescence-activated cell sorting and western blot analysis. The rhein/Pin1 association was found to play a regulatory role in cell proliferation and neoplastic cell transformation and the binding of phosphorylated c-Jun (Ser73) with Pin1 was markedly decreased and inhibited activator protein 1 or NF-κB reporter activity by rhein. Overall, our findings and the accompanying biochemical data demonstrated the antitumorigenic effect of rhein through its interference in Pin1/c-Jun interaction and suggest the possible use of rhein in suppressing the tumor-promoting effects of Pin1. Therefore, rhein may have practical implications for cancer prevention or therapy.

The Overexpression of NALP3 Inflammasome in Knee Osteoarthritis Is Associated with Synovial Membrane Prolidase and NADPH Oxidase 2

Osteoarthritis is characterized by the presence of proinflammatory cytokines and reactive oxygen species. We aimed to clarify the role of prooxidant enzyme content at the synovial membrane level and how it correlates with the inflammatory process in patients with knee osteoarthritis (KOA). In synovial membranes from KOA patients and control group, we analyzed the protein content of prooxidant enzymes such as Nox2, xanthine oxidase (XO), and prolidase as well as the proinflammatory NALP3. Results show that protein content of prolidase and Nox2 increased 4.8- and 8.4-fold, respectively, and XO showed an increasing trend, while the NALP3 inflammasome increased 5.4-fold with respect to control group. Levels of prolidase and XO had a positive correlation between the levels of NALP3 and Nox2. By principal component analysis the protein expression pattern by study groups was evaluated. Three clusters were identified; protein expression patterns were higher for clusters two (prolidase) and three (XO and Nox2) between KOA patients and controls. Data suggest that prooxidant enzymes increase in synovial membrane of KOA patients and may contribute to the inflammatory state and degradation of the articular cartilage.

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.

Diacerein: Benefits, Risks and Place in the Management of Osteoarthritis. An Opinion-Based Report from the ESCEO

Diacerein is a symptomatic slow-acting drug in osteoarthritis (SYSADOA) with anti-inflammatory, anti-catabolic and pro-anabolic properties on cartilage and synovial membrane. It has also recently been shown to have protective effects against subchondral bone remodelling. Following the end of the revision procedure by the Pharmacovigilance Risk Assessment Committee of the European Medicines Agency, the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) constituted a panel of 11 experts to better define the real place of diacerein in the armamentarium for treating OA. Based on a literature review of clinical trials and meta-analyses, the ESCEO confirms that the efficacy of diacerein is similar to that of non-steroidal anti-inflammatory drugs (NSAIDs) after the first month of treatment, and superior to that of paracetamol. Additionally, diacerein has shown a prolonged effect on symptoms of several months once treatment was stopped. The use of diacerein is associated with common gastrointestinal disorders such as soft stools and diarrhoea, common mild skin reactions, and, uncommonly, hepatobiliary disorders. However, NSAIDs and paracetamol are known to cause potentially severe hepatic, gastrointestinal, renal, cutaneous and cardiovascular reactions. Therefore, the ESCEO concludes that the benefit-risk balance of diacerein remains positive in the symptomatic treatment of hip and knee osteoarthritis. Furthermore, similarly to other SYSADOAs, the ESCEO positions diacerein as a first-line pharmacological background treatment of osteoarthritis, particularly for patients in whom NSAIDs or paracetamol are contraindicated.

DRUG THERAPY IN KNEE OSTEOARTHROSIS

Clinical treatment for osteoarthritis (OA) is very important and is based on patient’s self care and guided by the physician. Drug therapy is additional to losing weight, improving muscular strength, proprioception, flexibility and range of motion. Between the available drugs for osteoarthritis’ treatment, some are basically analgesics and do not interfere on disease’s progression; some are anti-inflammatory with good analgesic power but with side effects that compromise their prolonged usage; and the structure modifying drugs that slow down the progression of OA. The medications are presented in topic, oral, intra-muscular, intra-venous and intra-articular forms. The hyaluronic acid has various presentations with good analgesic effect and some evidence of structure modifying property. There is IA evidence level for the use of diacerhein and of glucosamine to slow down the disease. Still, more technology for diagnosis and therapy control of OA is necessary to define the efficacy of other drugs.

Rhein antagonizes P2X7 receptor in rat peritoneal macrophages

P2X7 receptor plays important roles in inflammation and immunity, and thereby it serves as a potential therapeutic target for inflammatory diseases. Rhein, an anthraquinone derivative, exhibits significant anti-inflammatory and immunosuppressive activities in therapy. However, the underlying mechanisms are largely unclear. Here, we aimed to investigate the effects of rhein on P2X7 receptor-mediated responses in vitro. In HEK293 cells expressing rat P2X7 receptor, we first found that rhein concentration-dependently blocked ATP-induced cytosolic calcium concentration ([Ca(2+)]c) elevation and pore formation of the plasma membrane, two hallmarks of the P2X7 receptor activation. These two inhibitory effects of rhein were also observed in rat peritoneal macrophages. Furthermore, rhein counteracted macrophage phagocytosis attenuation and suppressed reactive oxygen species (ROS) production triggered by ATP/BzATP. Meanwhile, rhein reduced ATP/BzATP-induced IL-1β release in lipopolysaccharide-activated macrophages. Prolonged application of ATP caused macrophage apoptosis, while the presence of rhein suppressed this cell cytotoxicity. Such ATP/BzATP-induced cellular reactions were also inhibited by a well-known rat P2X7 receptor antagonist, brilliant blue G, in a similar way to rhein. Together, our results demonstrate that rhein inhibit ATP/BzATP-induced [Ca(2+)]c increase, pore formation, ROS production, phagocytosis attenuation, IL-1β release and cell apoptosis by antagonizing the P2X7 receptor in rat peritoneal macrophages.

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 anthraquinone rhein exhibits synergistic antibacterial activity in association with metronidazole or natural compounds and attenuates virulence gene expression in Porphyromonas gingivalis

OBJECTIVE

Rhein is a major anthraquinone found in rhubarb root. As a continuation of our ongoing studies aimed to identify beneficial properties of this anthraquinone for periodontal disease, in this study, we investigated the ability of rhein to (i) exhibit antibacterial synergy towards the periodontopathogen Porphyromonas gingivalis when used in combination with metronidazole or polyphenols belonging to different families, and (ii) attenuate virulence factor gene expression in P. gingivalis.

METHODS

The minimal inhibitory concentrations (MIC) of compounds under investigation were determined by a broth microdilution assay. The synergistic effects of rhein in association with either metronidazole or polyphenols of various families were evaluated using the chequerboard technique to determine the fractional inhibitory concentration index (FICI). The effect of rhein on virulence factor gene expression in P. gingivalis was determined by quantitative RT-PCR.

RESULTS

Rhein showed a MIC of 2.5 μg/mL, which was similar to that of metronidazole. Except for the association with epigallocatechin-3-gallate that gave an additive effect, all the other combinations (licochalcone A, glabridin, myricetin, and metronidazole) resulted in synergistic effects. The strongest synergy was observed when rhein was used in association with myricetin (FICI=0.12) and licochalcone A (FICI=0.19). At a sub-MIC of rhein (0.5 μg/mL), a significant decrease in the expression of fimA, hagA, and hagB genes, which are involved in host colonization, was observed. Moreover, the expression of rgpA and kgp, two protease genes related to inactivation of host defense mechanisms, tissue destruction, and nutrient acquisition, was also down-regulated.

CONCLUSION

The data presented in our study indicate that rhein possessed antibacterial activity, which can be potentiated in combination with metronidazole or other polyphenols. In addition, rhein can impair the pathogenicity of P. gingivalis by reducing transcription of genes coding for important virulence factors.

The molecular mechanism of rhein in diabetic nephropathy

Diabetic nephropathy (DN) is characterized by unclear pathogenesis. Recent medical data shows that the incidence of DN rises year by year. Rhein is the main compositions of rhubarb, a traditional Chinese medicinal plant, which plays an active role in kidney protection. The prophylaxis and phytotherapeutic effects of rhein are due to its anti-inflammatory and antifibrosis properties. Here, we shed light on the renal protective role of rhein in diabetes mellitus (DM) with a particular focus on the molecular basis of this effect.

Rhein inhibits the expression of vascular cell adhesion molecule 1 in human umbilical vein endothelial cells with or without lipopolysaccharide stimulation

Reducing the expression of endothelial cell adhesion molecules (ECAMs) is known to decrease inflammation-induced vascular complications. In this study, we explored whether rhein can reduce the inflammation-induced expression of ECAMs in human umbilical vein endothelial cells (HUVECs) with or without lipopolysaccharide (LPS) stimulation. HUVECs were treated with different concentrations of rhein with or without 2.5 μg/ml LPS stimulation. Cell viability was assayed using the MTT method. Real-time PCR and Western blot analysis were used to measure the transcription and expression levels of ECAMs, including intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-SELECTIN and related signaling proteins. The results indicated that rhein (0-20 μmol/L) and LPS (0-10 μg/ml) had no effect on the viability of HUVECs. LPS could promote the expression of VCAM-1, ICAM-1 and E-SELECTIN. Rhein appeared to target VCAM-1, ICAM-1 and E-SELECTIN, with the transcription and expression of all three factors being reduced by the rhein treatment (10 and 20 μmol/L). The transcription and expression of VCAM-1 were also reduced by treatment with rhein (10 and 20 μmol/L) in the presence of LPS stimulation. In conclusion, rhein treatment reduced the expression of VCAM-1 in HUVECs via a p38-dependent pathway.

Heme oxygenase-1 regulates matrix metalloproteinase MMP-1 secretion and chondrocyte cell death via Nox4 NADPH oxidase activity in chondrocytes

Interleukin-1β (IL-1β) activates the production of reactive oxygen species (ROS) and secretion of MMPs as well as chondrocyte apoptosis. Those events lead to matrix breakdown and are key features of osteoarthritis (OA). We confirmed that in human C-20/A4 chondrocytes the NADPH oxidase Nox4 is the main source of ROS upon IL-1β stimulation. Since heme molecules are essential for the NADPH oxidase maturation and activity, we therefore investigated the consequences of the modulation of Heme oxygenase-1 (HO-1), the limiting enzyme in heme catabolism, on the IL-1β signaling pathway and more specifically on Nox4 activity. Induction of HO-1 expression decreased dramatically Nox4 activity in C-20/A4 and HEK293 T-REx™ Nox4 cell lines. Unexpectedly, this decrease was not accompanied by any change in the expression, the subcellular localization or the maturation of Nox4. In fact, the inhibition of the heme synthesis by succinylacetone rather than heme catabolism by HO-1, led to a confinement of the Nox4/p22^phox heterodimer in the endoplasmic reticulum with an absence of redox differential spectrum highlighting an incomplete maturation. Therefore, the downregulation of Nox4 activity by HO-1 induction appeared to be mediated by carbon monoxide (CO) generated from the heme degradation process. Interestingly, either HO-1 or CO caused a significant decrease in the expression of MMP-1 and DNA fragmentation of chondrocytes stimulated by IL-1β. These results all together suggest that a modulation of Nox4 activity via heme oxygenase-1 may represent a promising therapeutic tool in osteoarthritis.

Anti-inflammatory activity of a novel family of aryl ureas compounds in an endotoxin-induced airway epithelial cell injury model

Background

Despite our increased understanding of the mechanisms involved in acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS), there is no specific pharmacological treatment of proven benefit. We used a novel screening methodology to examine potential anti-inflammatory effects of a small structure-focused library of synthetic carbamate and urea derivatives in a well established cell model of lipopolysaccharide (LPS)-induced ALI/ARDS.

Methodology/Principal Findings

After a pilot study to develop an in vitro LPS-induced airway epithelial cell injury model, a library of synthetic carbamate and urea derivates was screened against representative panels of human solid tumor cell lines and bacterial and fungal strains. Molecules that were non-cytotoxic and were inactive in terms of antiproliferative and antimicrobial activities were selected to study the effects on LPS-induced inflammatory response in an in vitro cell culture model using A549 human alveolar and BEAS-2B human bronchial cells. These cells were exposed for 18 h to LPS obtained from Escherichia coli, either alone or in combination with the test compounds. The LPS antagonists rhein and emodin were used as reference compounds. The most active compound (CKT0103) was selected as the lead compound and the impact of CKT0103 on pro-inflammatory IL-6 and IL-8 cytokine levels, expression of toll-like receptor-4 (TLR4) and nuclear factor kappa B inhibitor alpha (IκBα) was measured. CKT0103 significantly inhibited the synthesis and release of IL-6 and IL-8 induced by LPS. This suppression was associated with inhibition of TLR4 up-regulation and IκBα down-regulation. Immunocytochemical staining for TLR4 and IκBα supported these findings.

Conclusions/Significance

Using a novel screening methodology, we identified a compound – CKT0103 – with potent anti-inflammatory effects. These findings suggest that CKT0103 is a potential target for the treatment of the acute phase of sepsis and sepsis-induced ALI/ARDS.

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.

Targeting CpG DNA to screen and isolate anti-sepsis fraction and monomers from traditional Chinese herbs using affinity biosensor technology

Bacterial DNA/CpG DNA is recognized as a key molecule during the pathogenesis of sepsis. Therefore, preventing CpG DNA from binding to its receptor is considered as the most promising strategy. In the present experiments, Radix et Rhizoma Rhei had the highest CpG DNA-binding ability among the seventy-eight traditional Chinese herbs. After the isolation of silica gel chromatography and high performance liquid chromatography (HPLC) and evaluation with affinity biosensor, the active fraction was confirmed and named Fraction D. It was found that in vitro, Fraction D bound to both CpG DNA and lipid A with high affinity, and strongly inhibited LPS- and CpG DNA-induced TNF-alpha release from RAW264.7 cells in a dose-dependent manner. Furthermore, Fraction D reduced the expression of TLR9 mRNA up-regulated by CpG DNA. In vivo, Fraction D protected mice challenged with lethal heat-killed E. coli. Using HPLC method, two monomers with high affinity for CpG DNA were isolated and identified as rhein and emodin. Rhein could significantly reduce CpG DNA- and LPS-induced TNF-alpha release, but emodin only reduced CpG DNA-induced TNF-alpha release. Rhein in combination with emodin could play synergistic inhibitory effect on both CpG DNA and LPS-induced TNF-alpha release, which contributed to the bioactivity of Fraction D. In conclusion, we successfully established the platform to screen anti-CpG DNA components of traditional Chinese herbs using affinity biosensor technology, got active Fraction D from Radix et Rhizoma Rhei and determined rhein and emodin as the main bioactive ingredients in Fraction D.

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

OBJECTIVE

The aim of this study was to determine the effects of pharmacologically relevant concentrations of rhein (1,8-dihydroxy-3-carboxyanthraquinone) on the cell proliferation rate of human chondrocytes and synoviocytes.

METHODS

Cultures of human osteoarthritic synoviocytes and chondrocytes were incubated with 10(-6), 10(-5), and 10(-4) M rhein. [3H]thymidine incorporation was used to determine rhein proliferative effects after incubation periods of 24 h, 48 h, and 1 week. The cytotoxicity of the drug was assayed with a nonradioactive assay kit. Nuclear extracts were used to detect variations in cell-cycle proteins (p21, p27, and cyclin D1) by Western blotting. The effect of rhein on apoptosis was investigated by measurement of caspase-3/7 activity and DNA fragmentation.

RESULTS

Rhein was found to downregulate the proliferation rate of both chondrocytes and synoviocytes, two-fold for 10(-5) M rhein and five- to six-fold for 10(-4) M rhein. No cytotoxicity of the drug was observed. Rhein (10(-4) M) decreased caspase-3/7 activity and did not induce DNA fragmentation. Western blots showed that 10(-4) M rhein increased the expression of p21 and/or p27, but not that of cyclin D1.

CONCLUSIONS

Rhein has previously been shown to reduce the interleukin (IL)-1beta deleterious effects on osteoarthritis (OA) cartilage through inhibition of the expression of degrading enzymes. Here, rhein was also found to inhibit proliferation of both synoviocytes and chondrocytes, suggesting that the drug may decrease the development of the inflammatory synovial tissue that accompanies joint pathologies. Both its anti-catabolic and anti-proliferative effects may explain its beneficial effect in the treatment of joint diseases.

Resveratrol protects bone marrow mesenchymal stem cell derived chondrocytes cultured on chitosan-gelatin scaffolds from the inhibitory effect of interleukin-1beta

AIM

To investigate the effects of resveratrol on interleukin-1beta (IL-1beta) induced catabolism in bone marrow mesenchymal stem cell (MSC) derived chondrocytes cultured on chitosan-gelatin scaffolds (CGS).

METHODS

The chondrogenesis of alginate-encapsulated MSCs was evaluated by toluidine blue staining, RT-PCR, and immunostaing. MSC-derived chondrocyte morphology cultured on CGS was evaluated by a scanning electron microscope (SEM) and a laser confocal microscope (LCM). When these cells on CGS were pre-stimulated with IL-1beta or co-treated with IL-1beta and resveratrol in the absence and presence of the specific beta1-integrin blocking antibody, collagen type II, aggrecan, matrix metalloproteinase-13 (MMP-13) expression, and the translocation of nuclear factor kappaB (NF-kappaB) were analyzed by Western blot analysis.

RESULTS

Transforming growth factor beta 3 (TGF-beta3) combined with insulin-like growth factor I (IGF-I) induced the cartilage-specific collagen type II, aggrecan expression and extracellular matrix (ECM) accumulation at the end of a 3-week culture. CGS supported those differentiated chondrocytes'attachment, proliferation, migration, and ECM formation. When those cells cultured on CGS were stimulated with IL-beta1 alone, collagen type II and aggrecan expression was inhibited. However, MMP-13 expression increased. Resveratrol reversed the catabolic effects by reducing the translocation of NF-kappaB. A specific beta1-integrin blocking antibody abrogated the effects of resveratrol on IL-1beta stimulated MSC-derived chondrocytes.

CONCLUSION

These results indicated that resveratrol acts as a NF-kappaB inhibitor to protect MSC-derived chondrocytes on the CGS from the IL-1beta catabolism and these effects are mediated by beta1-integrin.