Inhibitory Effect Of Rhein Research Articles

Rhein Inhibits Proliferation, Extracellular Matrix Deposition, and Inflammation in Mesangial Cells via ROS/Akt Signaling Pathway

It has been reported that rhein, a Chinese herbal compound, has a potent anti-inflammatory effect on various diseases. However, it remains elusive whether rhein has a protective effect on chronic kidney disease (CKD) and what its underlying mechanism may be. In the present study, we evaluated whether rhein could prevent lipopolysaccharide (LPS)-induced proliferation, expression of extracellular matrix (ECM) proteins, and inflammation in rat mesangial cells (MCs), and whether these effects were mediated by reactive oxygen species (ROS) and Akt signaling. We also investigated the protective effect of rhein on renal function in a rat CKD model. Results showed that rhein significantly suppressed LPS-initiated proliferation in MCs in a cell counting kit-8 (CCK8) assay. Meanwhile, rhein significantly inhibited LPS-induced expression of ECM proteins and inflammation, as indicated by the decreased expression of fibronectin, α smooth muscle actin (α-SMA), tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), interleukin 6 (IL-6), and interferon γ (IFN-γ). Of note, rhein significantly enhanced LPS-induced production of reactive oxygen species (ROS) and inhibited LPS-induced Akt phosphorylation. Furthermore, the inhibitory effect of rhein on Akt phosphorylation was inhibited by H2O2 scavenger catalase. Importantly, the protective effect of rhein was almost totally lost in the presence of phosphatidylinositol 3-kinase (PI3K) protagonist insulin-like growth factor 1 (IGF-1). Finally, rhein significantly decreased 24 h urinary protein, serum creatinine (SCr), and blood urea nitrogen (BUN) in CKD rats. Collectively, these results suggested that rhein improved CKD through inhibition of proliferation, ECM synthesis, and inflammation via ROS/Akt signaling in MCs.

Rhein ameliorates transverse aortic constriction-induced cardiac hypertrophy via regulating STAT3 and p38 MAPK signaling pathways.

The progression from compensatory hypertrophy to heart failure is difficult to reverse, in part due to extracellular matrix fibrosis and continuous activation of abnormal signaling pathways. Although the anthraquinone rhein has been examined for its many biological properties, it is not clear whether it has therapeutic value in the treatment of cardiac hypertrophy and heart failure. In this study, we report for the first time that rhein can ameliorate transverse aortic constriction (TAC)-induced cardiac hypertrophy and other cardiac damage in vivo and in vitro. In addition, rhein can reduce cardiac hypertrophy by attenuating atrial natriuretic peptide, brain natriuretic peptide, and β-MHC expression; cardiac fibrosis; and ERK phosphorylation and transport into the nucleus. Furthermore, the inhibitory effect of rhein on myocardial hypertrophy was similar to that of specific inhibitors of STAT3 and ERK signaling. In addition, rhein at therapeutic doses had no significant adverse effects or toxicity on liver and kidney function. We conclude that rhein reduces TAC-induced cardiac hypertrophy via targeted inhibition of the molecular function of ERK and downregulates STAT3 and p38 MAPK signaling. Therefore, rhein might be a novel and effective agent for treating cardiac hypertrophy and other cardiovascular diseases.

Rhein regulates redox-mediated activation of NLRP3 inflammasomes in intestinal inflammation through macrophage-activated crosstalk.

Macrophage infiltration and activation is a critical step during acute colitis. Redox-mediated activation of NLRP3 inflammasomes in macrophages plays a critical role in mediating colonic inflammatory responses. Rhein isolated from the rhizome of rhubarb exhibits anti-inflammatory effects in various diseases. However, its role in regulating acute colonic inflammation is unexplored. Here, we investigated the protective mechanisms of rhein during acute gut inflammation and its regulation of macrophage activation. Inhibitory effects of rhein on NLRP3 inflammasomes were evaluated in activated macrophages and a mouse model of colitis. Expression of inflammatory mediators, inflammasome complex and redox-related signalling were analysed by ELISA, Western blots, immunofluorescence staining, and qRT-PCR. The phenotype of macrophages was assessed by flow cytometry. Colonic inflammation was evaluated by histological analysis. Rhein significantly decreased IL-1β secretion via NLRP3 inflammasomes by disturbing their assembly in macrophages. Rhein also activated the Nrf2-HO1-NQO1 pathway and inhibited expression of Nox2 subunits and translocation to regulate redox balance. Moreover, rhein attenuated inflammatory responses by mediating macrophage polarization from M1 to M2 phenotype. NF-κB, AP-1, and MAPK signalling were also involved in improving inflammatory conditions by rhein. In mice with acute intestinal inflammation, rhein treatment attenuated clinical features and reduced macrophage infiltration into damaged tissue to alleviate colonic inflammation. Rhein regulated redox-mediated NLRP3 inflammasome activation to protect against acute colitis, by interfering with macrophage accumulation and polarization. These findings provide a promising strategy of novel compounds for regulating mucosal inflammation in gastrointestinal disorders.

A new method for detecting Na+ , K+ -ATPase activity by ICP-MS: Quantitative analysis on the inhibitory effect of rhein on Na+ , K+ -ATPase activity by ICP-MS in HCT116 cells.

Rhein is an active component from Chinese herbal medicine. It can cause diarrhea by inhibiting Na+ , K+ -ATPase activity on intestinal epithelial cells, thus decreasing the re-absorption of Na+ from intestinal tract to blood. However, when this Na+ , K+ -ATPase inhibition was quantitated by a colorimetric method that measures ATPase-catalyzed release of inorganic phosphorus, the data obtained were inconsistent and showed great variation. We developed a novel method using inductively coupled plasma mass spectrometry (ICP-MS) to quantitate the amount of intracellular Rb+ . This method largely mimics the 86 RbCl tracer flux assay, but it uses non-radioactive RbCl as a flux substrate. The results demonstrated that this method has better precision and accuracy than the conventional colorimetric method. More importantly, this method is free from radioactive substances, which is expected to make it safer and more convenient than the radioactive 86 RbCl tracer flux method. In conclusion, the ICP-MS method for Na+ , K+ -ATPase activity determination is novel and accurate. It can also provide a reference for studying the transport of other metal ions across membranes under biological conditions.

Study on potential hepatotoxicity of rhein in Rhei Radix et Rhizoma based on liver metabolism

The bilirubin metabolism mediated by the phase Ⅱ metabolizing enzyme UGT1A1 in the liver was evaluated to study the potential hepatotoxicity risk based on investigation on the inhibitory effect of rhein and its metabolites on the UGT1A1 enzyme in Rhei Radix et Rhizoma. Firstly, in vitro liver microsomes incubation was used to initiate the phase Ⅱ metabolic reaction to investigate the inhibitory effect of rheinon UGT1A1 enzyme. Secondly, the phase Ⅰ and phase Ⅱ metabolic reactions were initiated to investigate the hepatotoxicity risk of rhein metabolites. It was found that the rhein and its phase Ⅱ metabolites had no significant inhibitory effect on UGT1A1 enzyme, but its phase Ⅰ metabolites significantly reduced UGT1A1 enzyme activity. Based on the metabolites analysis, it is speculated that the rhein phase Ⅰ metabolite rheinhydroxylate and its tautomers have certain hepatotoxicity risks, while the toxicity risk induced by the prototype and phase Ⅱ metabolites of rheinglucoside, rheinglucuronic acid and rhein sulfate is small.

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.

Rhein suppresses matrix metalloproteinase production by regulating the Rac1/ROS/MAPK/AP-1 pathway in human ovarian carcinoma cells.

Matrix metalloproteinases (MMPs) are a family of calcium-dependent zinc-containing endopeptidases, which play an integral role in migration and invasion of ovarian cancer. Rac1 proteins might mostly influence cell migration and invasion by generating endogenous reactive oxygen species. Therefore, inhibiting MMPs and regulating the Rac1/ROS/MAPK/AP-1 pathway may be a new therapeutic strategy for ovarian cancer. In this study, we found that rhein could suppress the invasion and migration of SKOV3-PM4 cells with characteristics of directional highly lymphatic metastasis. Phorbol 12-myristate 13-acetate (PMA), which is a Rac1 activator, significantly enhanced the expression levels of MMP-2, -3, -9 and -19 proteins, whereas the results of rhein and Rac1 inhibitor NSC23766 were just the opposite. The inhibitory effects of rhein were associated with the upregulation of tissue inhibitors of metalloproteinase (TIMP)-1, TIMP-2 and NM23-H1. Subsequent mechanism studies revealed that rhein reduce the production of reactive oxygen species (ROS) and lower NADPH oxidase activity. Furthermore, rhein significantly inhibited JNK, AP-1 phosphorylation in the cells treated with PMA. The results obtained from the cells treated with NSC23766 alone or NSC23766 combined with rhein, were consistent with rhein treatment alone. Taken together, these results indicate that rhein may be a potential inhibitor of Rac1 and can inhibit the migration and invasion of SKOV3-PM4 cells through modulating matrix metalloproteinases and RAC1/ROS/MAPK/AP-1 signaling pathway-associated proteins.

The inhibitory effect of rhein on proliferation of high glucose-induced mesangial cell through cell cycle regulation and induction of cell apoptosis

The inhibitory effect of rhein on proliferation of high glucose-induced mesangial cell through cell cycle regulation and induction of cell apoptosis

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 ([Ca2+]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 [Ca2+]c increase, pore formation, ROS production, phagocytosis attenuation, IL-1β release and cell apoptosis by antagonizing the P2X7 receptor in rat peritoneal macrophages.

The anthraquinone drug rhein potently interferes with organic anion transporter-mediated renal elimination

Rhein, a major metabolite of the prodrug diacerein and a major component of the medicinal herb Rheum sp., is used for its beneficial effects in a variety of clinical applications including the treatment of osteoarthritis and diabetic nephropathy. The physicochemical properties of rhein are consistent with those of known organic anion transporter (OAT) substrates and inhibitors. Therefore, the inhibitory effect of rhein on human (h) OAT1, hOAT3, hOAT4, and murine (m) Oat1 and mOat3 was examined in heterologous cell lines stably expressing each transporter in isolation. Rhein was shown to potently inhibit hOAT1 and hOAT3, with IC50 estimates in the low nanomolar range (IC50=77.1±5.5nM and 8.4±2.5nM, respectively), while poor affinity was observed for hOAT4 (IC50>100μM). Marked species differences were observed with hOAT1 and hOAT3 exhibiting 3- and 28-fold higher affinity for rhein as compared to their murine orthologs. The estimated drug–drug interaction (DDI) indices (≫0.1) indicated a very strong potential for clinically relevant, rhein perpetrated DDIs mediated by inhibition of hOAT1 (DDI index=5.0; 83% inhibition) and/or hOAT3 (DDI index=46; 98% inhibition) transport activity. These results suggested that rhein, from herbal medicines and/or prodrug conversion, may significantly impact the dosing, efficacy and toxicity (i.e., pharmacokinetics and pharmacodynamics) of co-administered hOAT1 and/or hOAT3 drug substrates.