Rhein inhibits lipopolysaccharide-induced intestinal injury during sepsis by blocking the toll-like receptor 4 nuclear factor-κB pathway

Advances in molecular agents targeting toll-like receptor 4 signaling pathways for potential treatment of sepsis

Sepsis is a systemic inflammatory response syndrome caused by an infection. Toll-like receptor 4 (TLR4) is activated by endogenous molecules released by injured or necrotic tissues. Additionally, TLR4 is remarkably sensitive to infection of various bacteria and can rapidly stimulate host defense responses. The TLR4 signaling pathway plays an important role in sepsis by activating the inflammatory response. Accordingly, as part of efforts to improve the inflammatory response and survival rate of patients with sepsis, several drugs have been developed to regulate the inflammatory signaling pathways mediated by TLR4. Inhibition of TLR4 signal transduction can be directed toward either TLR4 directly or other proteins in the TLR4 signaling pathway. Here, we review the advances in the development of small-molecule agents and peptides targeting regulation of the TLR4 signaling pathway, which are characterized according to their structural characteristics as polyphenols, terpenoids, steroids, antibiotics, anthraquinones, inorganic compounds, and others. Therefore, regulating the expression of the TLR4 signaling pathway and modulating its effects has broad prospects as a target for the treatment of lung, liver, kidneys, and other important organs injury in sepsis.

Recent Advances in Biologically Active Ingredients from Natural Drugs for Sepsis Treatment

Sepsis refers to the dysregulated host response to infection; its incidence and mortality rates are high. It is a worldwide medical problem but there is no specific drug for it. In recent years, clinical and experimental studies have found that many monomer components of traditional Chinese medicine have certain effects on the treatment of sepsis. This paper reviews the advances in research on the active ingredients of traditional Chinese medicine involved in the treatment of sepsis in recent years according to their chemical structure; it could provide ideas and references for further research and development in Chinese materia medica for the treatment of sepsis.

The role of regulatory T cells in the pathogenesis of acute kidney injury

The incidence of acute kidney injury (AKI) is on the rise and is associated with high mortality; however, there are currently few effective treatments. Moreover, the relationship between Tregs and other components of the immune microenvironment (IME) in the pathogenesis of AKI remains unclear. We downloaded four publicly accessible AKI datasets, GSE61739, GSE67401, GSE19130, GSE81741, GSE19288 and GSE106993 from the gene expression omnibus (GEO) database. Additionally, we gathered two kidney single-cell sequencing (scRNA-seq) samples from the Department of Organ Transplantation at Zhujiang Hospital of Southern Medical University to investigate chronic kidney transplant rejection (CKTR). Moreover, we also collected three samples of normal kidney tissue from GSE131685. By analysing the differences in immune cells between the AKI and Non-AKI groups, we discovered that the Non-AKI group contained a significantly greater number of Tregs than the AKI group. Additionally, the activation of signalling pathways, such as inflammatory molecules secretion, immune response, glycolytic metabolism, NOTCH, FGF, NF-κB and TLR4, was significantly greater in the AKI group than in the Non-AKI group. Additionally, analysis of single-cell sequencing data revealed that Tregs in patients with chronic kidney rejection and in normal kidney tissue have distinct biology, including immune activation, cytokine production, and activation fractions of signalling pathways such as NOTCH and TLR4. In this study, we found significant differences in the IME between AKI and Non-AKI, including differences in Tregs cells and activation levels of biologically significant signalling pathways. Tregs were associated with lower activity of signalling pathways such as inflammatory response, inflammatory molecule secretion, immune activation, glycolysis.

Diacerein versus adipoRon as adiponectin modulators in experimentally-induced end-stage type 2 diabetes mellitus in rats

The objective of the present study is to evaluate and compare the possible anti-diabetic effects of adipoRon and diacerein in type 2 diabetes mellitus (T2DM) rats. T2DM is marked by impaired oxidative, inflammatory and metabolic signaling. Indeed, T2DM progression is associated with elevated HbA1C%, low adiponectin and insulin concentration. Moreover, in this study epididymal adipose tissue and soleus muscle MDA contents significantly escalated, while serum TAC and epididymal adipose Nrf2 significantly declined. Nevertheless, serum TNF-α, epididymal NLRP3, NF-κB, PPARγ and CD68 expression rose significantly with a parallel significant reduction in serum IL-10 and soleus muscle expression of IRS1. Both adipoRon and diacerein significantly improved adiponectin and insulin secretion with augmentation of anti-oxidant defenses and diminution of oxidative burden, with obvious anti-inflammatory consequences (p < 0.05). Thus, adipoRon and diacerein positively modulated adiponectin expression with down-regulation of NF-κB/NLRP3/PPARγ expression with subsequent improvement in glycemic control, inflammatory and oxidative signaling.

Xuanbai Chengqi Decoction Ameliorates Pulmonary Inflammation via Reshaping Gut Microbiota and Rectifying Th17/Treg Imbalance in a Murine Model of Chronic Obstructive Pulmonary Disease

Purpose

Chronic obstructive pulmonary disease (COPD), a prevalent obstructive airway disease, has become the third most common cause of death globally. Xuanbai Chengqi decoction (XBCQ) is a traditional Chinese medicine prescription for the acute exacerbation of COPD. Here, we aimed to reveal the therapeutic effects of XBCQ administration and its molecular mechanisms mediated by Th17/Treg balance and gut microbiota.

Methods

We determined the counts of Th17 and Treg cells in the serum of 15 COPD and 10 healthy subjects. Then, cigarette smoke extract-induced COPD mice were gavaged with low, middle, and high doses of XBCQ, respectively. Weight loss, pulmonary function and inflammation, Th17/Treg ratio, and gut microbiota were measured to evaluate the efficacy of XBCQ on COPD.

Results

COPD patients had a higher Th17/Treg ratio in the serum than healthy controls, which was consistent with the results in the lung and colon of COPD mice. The middle dose of XBCQ (M-XBCQ) significantly decreased the weight loss and improved the pulmonary function (FEV0.2/FVC) in COPD mice. Moreover, M-XBCQ alleviated lung inflammation by rectifying the Th17/Treg imbalance, reducing the expressions of TNF-α, IL-1β, and MMP-9, and suppressing inflammatory cells infiltration. Meanwhile, M-XBCQ greatly improved the microbial homeostasis in COPD mice by accumulating probiotic Gordonibacter and Akkermansia but inhibiting the growth of pathogenic Streptococcus, which showed significant correlations with pulmonary injury.

Conclusion

Oral M-XBCQ could alleviate COPD exacerbations by reshaping the gut microbiota and improving the Th17/Treg balance, which aids in elucidating the mechanism through which XBCQ as a therapy for COPD.

Update on Pharmacological Activities, Security, and Pharmacokinetics of Rhein

Rhein, belonging to anthraquinone compounds, is one of the main active components of rhubarb and Polygonum multiflorum. Rhein has a variety of pharmacological effects, such as cardiocerebral protective effect, hepatoprotective effect, nephroprotective effect, anti-inflammation effect, antitumor effect, antidiabetic effect, and others. The mechanism is interrelated and complex, referring to NF-κB, PI3K/Akt/MAPK, p53, mitochondrial-mediated signaling pathway, oxidative stress signaling pathway, and so on. However, to some extent, its clinical application is limited by its poor water solubility and low bioavailability. Even more, rhein has potential liver and kidney toxicity. Therefore, in this paper, the pharmacological effects of rhein and its mechanism, pharmacokinetics, and safety studies were reviewed, in order to provide reference for the development and application of rhein.

Assessment of the anti-inflammatory effects of three rhubarb anthraquinones in LPS-Stimulated RAW264.7 macrophages using a pharmacodynamic model and evaluation of the structure-activity relationships

ETHNOPHARMACOLOGICAL RELEVANCE

Rhubarb (Rhei Radix et Rhizoma) is a traditional Chinese medicine, has been used as a strong astringent in China to treat inflammation-related diseases, such as acute pancreatitis, acute cholecystitis, appendicitis and so on. Rhein, emodin and aloe-emodin are the important active anthraquinone in rhubarb, and are considered to be the main ingredients contributing to anti-inflammatory.

AIM OF THE STUDY

Rhein, emodin and aloe-emodin, anthraquinones with the same parent structure that are found in rhubarb, have beneficial anti-inflammatory effects in vitro and in vivo. Anthraquinone derivatives also have important clinical roles. However, their pharmacodynamic differences and the structure-activity relationships associated with their anti-inflammatory properties have not been systematically explored. The present study was designed to quantify the effects of three rhubarb anthraquinones on inflammation and to explore the structure-activity relationships of these compounds.

MATERIALS AND METHODS

In this study, we detected NF-κB phosphorylation, iNOS protein expression, and IL-6 and NO production in LPS-stimulated RAW264.7 cells and then calculated median effect equations and built a dynamic pharmacodynamic model to quantitatively evaluate the efficacy of these three anthraquinones. Additionally, to determine the structure-activity relationships, we investigated the physicochemical properties and molecular electrostatic potentials of the drug molecules.

RESULTS

We found that rhein, emodin, and aloe-emodin exerted at least dual-target (NF-κB, iNOS) inhibition of LPS-induced inflammatory responses. Compared with rhein and emodin, aloe-emodin had a stronger anti-inflammatory effect, and its inhibition of iNOS protein expression was approximately twice that of NF-κB phosphorylation. In addition, aloe-emodin had the strongest hydrophobic effect among the three anthraquinones.

CONCLUSIONS

Overall, we concluded that the receptor binding the rhubarb anthraquinones had a hydrophobic pocket. Anthraquinone molecules with stronger hydrophobic effects had higher affinity for the receptor, resulting in greater anti-inflammatory activity. These results suggest that the addition of a hydrophobic group is a potential method for structural modification to design anti-inflammatory anthraquinone derivatives with enhanced potency.

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.

Calcium pectinate and hyaluronic acid modified lactoferrin nanoparticles loaded rhein with dual-targeting for ulcerative colitis treatment

Herein, dual-bioresponsive of Rhein (RH) in promoting colonic mucous damage repair and controlling inflammatory reactions were combined by the dual-targeting (intestinal epithelial cells and macrophages) oral nano delivery strategy for effective therapy of ulcerative colitis (UC). Briefly, two carbohydrates, calcium pectinate (CP) and hyaluronic acid (HA) were used to modify lactoferrin (LF) nanoparticles (NPs) to encapsulate RH (CP/HA/RH-NPs). CP layer make CP/HA/RH-NPs more stable and protect against the destructive effects of the gastrointestinal environment and then release HA/RH-NPs to colon lesion site. Cellular uptake evaluation confirmed that NPs could specifically target and enhance the uptake rate via LF and HA ligands. in vivo experiments revealed that CP/HA/RH-NPs significantly alleviated inflammation by inhibiting the TLR4/MyD88/NF-κB signaling pathway and accelerated colonic healing. Importantly, with the help of CP, this study was the first to attempt for LF as a targeting nanomaterial in UC treatment and offers a promising food-based nanodrug in anti-UC.

Diacerein: A potential multi-target therapeutic drug for COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 19 (COVID-19), was declared pandemic by the World Health Organization in March 2020. SARS-CoV-2 binds its host cell receptor, angiotensin-converting enzyme 2 (ACE2), through the viral spike (S) protein. The mortality related to severe acute respiratory distress syndrome (ARDS) and multi-organ failure in COVID-19 patients has been suggested to be connected with cytokine storm syndrome (CSS), an excessive immune response that severely damages healthy lung tissue. In addition, cardiac symptoms, including fulminant myocarditis, are frequent in patients in a severe state of illness. Diacerein (DAR) is an anthraquinone derivative drug whose active metabolite is rhein. Different studies have shown that this compound inhibits the IL-1, IL-2, IL-6, IL-8, IL-12, IL-18, TNF-α, NF-κB and NALP3 inflammasome pathways. The antiviral activity of rhein has also been documented. This metabolite prevents hepatitis B virus (HBV) replication and influenza A virus (IAV) adsorption and replication through mechanisms involving regulation of oxidative stress and alterations of the TLR4, Akt, MAPK, and NF-κB signalling pathways. Importantly, rhein inhibits the interaction between the SARS-CoV S protein and ACE2 in a dose-dependent manner, suggesting rhein as a potential therapeutic agent for the treatment of SARS-CoV infection. Based on these findings, we hypothesize that DAR is a multi-target drug useful for COVID-19 treatment. This anthraquinone may control hyperinflammatory conditions by multi-faceted cytokine inhibition and by reducing viral infection.

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.

SOCS3 protects against neonatal necrotizing enterocolitis via suppressing NLRP3 and AIM2 inflammasome activation and p65 nuclear translocation

BACKGROUND

Necrotizing enterocolitis (NEC) is an acquired disorder of mucosal damage characterized by the diffuse or local necrosis of the intestine. The suppressor of cytokine signaling 3 (SOCS3) has been demonstrated to possess anti-inflammatory action in gastritis, ulcerative colitis and other inflammatory diseases. The present study aims to explore the effects of SOCS3 on LPS-induced colonic cell model of NEC, and investigate the underlying mechanisms.

METHODS

Expression of SOCS3 in tissue samples of NEC and LPS-induced enterocytes were evaluated by real-time quantitative PCR (RT-qPCR). Western blotting and enzyme-linked immunosorbent assay (ELISA) were applied to examine the effect of SOCS3 on inflammatory molecules. Co-immunoprecipitation assay were devoted to explore the relation between SOCS3 and TLR4.

RESULTS

We proved that SOCS3 was expressed at a low level in tissue samples of NEC and LPS-induced enterocytes, and LPS inhibited SOCS3 expression via JAK2/STAT3 pathway. Overexpression of SOCS3 weaken the LPS-induced inflammatory response in FHC and CACO2 cells. Moreover, SOCS3 downregulates proinflammatory cytokines by targeting TLR4, thus mediating the p65 nuclear translocation, and the activation of NLR family pyrin domain containing 3/absent in melanoma-2 (NLRP3/AIM2) inflammasome, ultimately reveals its anti-inflammatory effects.

CONCLUSIONS

Taken together, our data revealed that LPS inhibited SOCS3 expression via JAK2/STAT3 pathway, and SOCS3 protects enterocytes against NEC through mediating p65 nuclear translocation and NLRP3/AIM2 inflammasome activation in a TLR4 dependent manner.

Cronobacter sakazakii induces necrotizing enterocolitis by regulating NLRP3 inflammasome expression via TLR4

Introduction. Neonatal infection with Cronobacter sakazakii can cause severe intestinal damage and necrotizing enterocolitis (NEC). The inflammasome and Toll-like receptors mediate intestinal damage caused by other intestinal pathogens causing NEC, but the exact mechanism is unclear.Aim. We evaluated the molecular mechanisms underlying C. sakazakii-induced NEC.Methodology. The effects of C. sakazakii treatment on two cell lines and a Sprague-Dawley rat model of NEC were evaluated by a cell death assay, western blot and real-time PCR analyses of the NLRP3 inflammasome and downstream factors, and observation of cell and intestinal damage.Results. C. sakazakii caused cellular damage in vitro, as well as intestinal damage in an animal model. NLRP3, caspase-1, TLR4 and MyD88, as well as the downstream factor IL-1β, were upregulated in C. sakazakii-infected J774A.1 and HT-29 cells. Western blotting showed that C. sakazakii-infected J774A.1 and HT-29 cells and the NEC rat model had higher expression levels of N-terminal gasdermin D (GSDMD) compared with those in the control groups. C. sakazakii and its components promote NF-κB expression via the TLR4/MyD88 signalling pathway, thereby regulating the NLRP3 inflammasome and mediating GSDMD cleavage, resulting in pyroptosis-induced intestinal damage.Conclusion. We found that C. sakazakii upregulates NF-κB via TLR4/MyD88 to promote activation of the NLRP3 inflammasome, leading to the up-regulation of downstream caspase-1, release of IL-1β, GSDMD-mediated pyroptosis and development of NEC. These findings clarify the mechanisms by which C. sakazakii contributes to NEC.

Protopine Protects Mice against LPS-Induced Acute Kidney Injury by Inhibiting Apoptosis and Inflammation via the TLR4 Signaling Pathway

Corydalis humosa Migo is a traditional Chinese medicine that clears away damp heat, relieves sore. Protopine (PRO) is an alkaloid component isolated from C. humosa Migo. However, the role of protopine in acute kidney injury (AKI) has not yet been reported. This study aims to investigate the effect and mechanism of protopine isolated from C. humosa Migo on lipopolysaccharide (LPS)-induced AKI in mice. Inflammation accumulation was assessed by small animal living imaging. The blood urea nitrogen (BUN), and serum creatinine (Scr) were measured to assess the effects of protopine on renal function in LPS-induced AKI. The levels of tumor necrosis factor (TNF), interleukin-2 (IL-2), interferon-γ (IFN-γ), and (interleukin-10) IL-10 in serum were detected by cytometric bead array. Flow cytometry was used to detect the levels of reactive oxygen species (ROS) in primary kidney cells. The proportions of granulocytes, neutrophils, and macrophages in peripheral blood were examined to evaluate the effect of protopine on immune cells in mice with AKI. Toll-like receptor (TLR4) and apoptotic signaling pathway were detected by Western blot analysis. The results showed that protopine markedly improved the renal function, relieve inflammation, reversed inflammatory cytokines, transformed apoptosis markers, and regulated the TLR4 signaling pathway in mice with AKI induced by LPS. The protopine isolated from C.humosa Migo protected mice against LPS-induced AKI by inhibiting apoptosis and inflammation via the TLR4 signaling pathway, thus providing a molecular basis for a novel medical treatment of AKI.

Rhein attenuates lipopolysaccharide-primed inflammation through NF-κB inhibition in RAW264.7 cells: targeting the PPAR-γ signal pathway

Inflammation is a common inducer of numerous severe diseases such as sepsis. The NF-κB signaling pathway plays a key role in the inflammatory process. Its activation promotes the release of pro-inflammatory mediators like inducible nitric oxide synthase and tumor necrosis factor alpha. Peroxisome proliferator-activated receptor gamma (PPAR-γ) inactivates nuclear factor kappa B (NF-κB) and subsequently attenuates inflammation. Rhein, an agent isolated from rhubarb, has been known to have anti-inflammatory effects. However, its influence on PPAR-γ remains largely unknown. In this study, an inflammation model was constructed by stimulating RAW264.7 cells with lipopolysaccharide. Rhein was used as a therapeutic agent, while rosiglitazone (PPAR-γ activator) and GW9662 (PPAR-γ inhibitor) were used as disrupters for in depth studies. The results demonstrated that rhein inhibits NF-κB activation and inflammatory factor release. However, GW9662 significantly reduced this effect, indicating that PPAR-γ is a critical mediator in the rhein-mediated anti-inflammatory process. Additionally, positive modulation of PPAR-γ expression and activity by rosiglitazone correspondingly influenced the effects of rhein on inflammatory factors and NF-κB expression. We also found that rhein could enhance PPAR-γ, NF-κB, and histone deacetylase 3 (HDAC3) binding. These results indicate that rhein exerts its anti-inflammation function by regulating the PPAR-γ-NF-κB-HDAC3 axis.

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 protects against barrier disruption and inhibits inflammation in intestinal epithelial cells

BACKGROUND AND AIMS

Intestinal epithelial barrier and intestinal inflammation play indispensable roles in the development of intestinal diseases. The major aims of the current study were to investigate the potential of rhein, a major flavonoid compound isolated from Rheum rhabarbarum, in the treatment of intestinal diseases and its underlying mechanisms in vitro.

METHODS

The protective role of rhein on intestinal epithelial barrier was evaluated in a monolayer of IEC-6 cells stimulated by TNF-α, while the anti-inflammatory effects were investigated in an IEC-6 cell model with LPS stimulation.

RESULTS

Rhein inhibited the increase of phenol red flux and the decrease of TEER, as well as recovered the expression and distribution of ZO-1 and weakened MLC phosphorylation, MLCK expression and NF-κB activation. Meanwhile, LPS-stimulated IL-1β and IL-6 were down-regulated, expression levels of TLR4, NLRP3 and cleaved caspase1 were weakened and NF-κB was inactivated.

CONCLUSIONS

These results suggested that rhein has potential therapeutic effects against intestinal diseases by maintaining intestinal epithelial barrier and suppressing intestinal inflammation.

Rhein from Rheum rhabarbarum Inhibits Hydrogen-Peroxide-Induced Oxidative Stress in Intestinal Epithelial Cells Partly through PI3K/Akt-Mediated Nrf2/HO-1 Pathways

Rheum rhabarbarum has been widely used as a herbal medicine and food in China. The objective of this study was to investigate the cytoprotective action and underlying mechanisms of rhein, one active ingredient isolated from R. rhabarbarum, on H₂O₂-challenged rat small intestine epithelial cells (IEC-6 cells). H₂O₂-challenged IEC-6 cells were incubated in the pretreatment with or without rhein or LY294002, a PI3K/Akt inhibitor. The cell viability, apoptosis, intracellular reactive oxygen species (ROS), and antioxidants were measured. The expressions of heme oxygenase 1 (HO-1), nuclear factor erythroid 2-related factor (Nrf2), Akt, and p-Akt were evaluated by western blotting. Meanwhile, LY294002 was also used to investigate the role of PI3K/Akt in the rhein-induced cytoprotective role. The results showed that pretreatment of rhein could reverse the inhibition of cell viability and suppress the apoptosis, caspase-3 activity, and intracellular ROS induced by H₂O₂. Rhein also supported SOD activity catalase activity, glutathione S-transferase activity, and glutathione content. Furthermore, rhein induced the protein expression of HO-1 together with its upstream mediator Nrf2 and activated the phosphorylation of Akt in IEC-6 cells. LY294002 inhibited increased cell viability, upregulated the lowered apoptotic rate, and enhanced the weakened ROS levels. Although the inhibition of PI3K/Akt did not inhibit the Nrf2 nuclear level under 4 μM rhein, LY294002 inhibited the Nrf2 nuclear level under 2 μM rhein and blocked HO-1 expression. These data demonstrated that rhein protected IEC-6 cells against oxidative damage partly via PI3K/Akt and Nrf2/HO-1 pathways.

Rhein ameliorates lipopolysaccharide-induced intestinal barrier injury via modulation of Nrf2 and MAPKs

AIMS

In this study, we explored the underlying mechanisms of protective effects of rhein against intestinal barrier injury in a rat model, induced by intraperitoneal injection of lipopolysaccharide (LPS).

MAIN METHODS

Twenty-four male rats were assigned equally to three groups. Rats were given an oral administration of rhein (66.7 mg/kg/day) or not for three continuous days. LPS or saline were injected intraperitoneally in an hour after the last oral administration. The rats were sacrificed at 7 h after LPS or saline administration. Both blood samples and intestinal samples were collected.

KEY FINDINGS

Rhein pretreatment markedly inhibited the levels of serum diamine oxidase (DAO), D-lactate (D-lac) and intestinal histological damage, significantly recovered the levels of intestinal DAO, ZO-1 and occludin. Additionally, rhein suppressed LPS-induced intestinal inflammation and oxidative stress, by decreased serum and intestinal, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and nitric oxide levels, up-regulated intestinal catalase, glutathione peroxidase (GSH-Px) activities and HO-1 expression, and down-regulated malondialdehyde (MDA) level in the small intestine. Finally, rhein inhibited JNK, p38 MAPK phosphorylation and activated Nrf2 pathway.

SIGNIFICANCE

Rhein could exert the anti-inflammatory and anti-oxidative effects against LPS-induced intestinal barrier injury by suppressing p38 MAPK and JNK and activating Nrf2 pathway.

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.

Acute Oral Administration of Single-Walled Carbon Nanotubes Increases Intestinal Permeability and Inflammatory Responses: Association with the Changes in Gut Microbiota in Mice

With the increasing production and widespread potential applications of single-walled carbon nanotubes (SWCNTs), the possible impacts of oral administration of SWCNTs on gastrointestinal tract at currently occupational exposure limits and potential biomedical applications should be concerned. To address the concerns, mice are orally administrated of SWCNTs at doses of 0.05, 0.5, and 2.5 mg kg^-1 body weight per day for 7 d. The investigation shows that SWCNT treatment had promoted intestinal injuries at the acute dose of 2.5 mg kg^-1 per day, including increase of histological lesion scores, intestinal permeability, and proinflammatory cytokine (IL-1β, IL-6, and TNF-α) secretion. Analysis of gut microbiota composition using 16S rRNA gene sequencing approach reveals that acute oral administration of SWCNTs induces significant shifts of the predominant microbe phyla from Firmicutes to Bacteroidetes and increases abundance of proinflammatory bacteria Alitipes_uncultured_bacterium and Lachnospiraceae bacterium A4. These notable findings suggest that SWCNT-induced intestinal injury is linked to SWCNT interaction with intestinal tract and gut bacteria and the consequent triggering of "metabolic inflammation" responses. Furthermore, the study has shown that oral administration of carbon nanomaterials, including SWCNTs, multiwalled CNTs, and graphene oxide, can lead to different inflammatory responses and specific alteration in gut microbiota in mice.

Klotho preservation by Rhein promotes toll-like receptor 4 proteolysis and attenuates lipopolysaccharide-induced acute kidney injury

Renal anti-aging protein Klotho exhibits impressive properties of anti-inflammation and renal protection, however is suppressed early after renal injury, making Klotho restoration an attractive strategy of treating renal inflammatory disorders. Here, we reported that Klotho is enriched in macrophages and Klotho preservation by Rhein, an anthraquinone derived from medicinal plant rhubarb, attenuates lipopolysaccharide (LPS)-induced acute inflammation essentially via promoting toll-like receptor 4 (TLR4) degradation. LPS-induced pro-inflammatory NF-κB signaling and cytokine expressions coincided with Klotho repression and toll-like receptor 4 (TLR4) elevation in macrophages, renal epithelial cells, and acutely- inflamed kidney. Intriguingly, Rhein treatment effectively corrected the inverted alterations of Klotho and TLR4 and mitigated the TLR4 downstream inflammatory response in a Klotho restoration and TLR4 repression-dependent manner. Klotho inducibly associated with TLR4 after LPS stimulation and suppressed TLR4 protein abundance mainly via a proteolytic process sensitive to the inhibition of Klotho's putative β-glucuronidase activity. Consistently, Klotho knockdown by RNA interferences largely diminished the anti-inflammatory and renal protective effects of Rhein in a mouse model of acute kidney injury incurred by LPS. Thus, Klotho suppression of TLR4 via deglycosylation negatively controls TLR-associated inflammatory signaling and the endogenous Klotho preservation by Rhein or possibly other natural or synthetic compounds possesses promising potentials in the clinical treatment of renal inflammatory disorders.

KEY MESSAGES

• Klotho is highly expressed in macrophages and repressed by LPS in vitro and in vivo. • Klotho inhibits LPS-induced TLR4 accumulation and the downstream signaling. • Klotho decreases TLR4 via a deglycosylation-associated proteolytic process. • Rhein effectively prevents acute inflammation-incurred Klotho suppression. • Rhein reversal of Klotho attenuates LPS-induced acute inflammation and kidney injury.

Resveratrol protects against early polymicrobial sepsis-induced acute kidney injury through inhibiting endoplasmic reticulum stress-activated NF-κB pathway

Resveratrol, a polyphenol compound derived from various edible plants, protects against sepsis-induced acute kidney injury (AKI) via its anti-inflammatory activity, but the underlying mechanisms remain largely unknown. In this study, a rat model of sepsis was established by cecal ligation and puncture (CLP), 30 mg/kg resveratrol was intraperitoneally administrated immediately after the CLP operation. HK-2 cells treated by 1 μg/ml lipopolysaccharide, 0.2 μM tunicamycin, 2.5 mM irestatin 9389 and 20 μM resveratrol were used for in vitro study. The results demonstrated that resveratrol significantly improved the renal function and tubular epithelial cell injury and enhanced the survival rate of CLP-induced rat model of sepsis, which was accompanied by a substantial decrease of the serum content and renal mRNA expressions of TNF-α, IL-1β and IL-6. In addition, resveratrol obviously relieved the endoplasmic reticulum stress, inhibited the phosphorylation of inositol-requiring enzyme 1(IRE1) and nuclear factor-κB (NF-κB) in the kidney. In vitro studies showed that resveratrol enhanced the cell viability, reduced the phosphorylation of NF-κB and production of inflammatory factors in lipopolysaccharide and tunicamycin-induced HK-2 cells through inhibiting IRE1 activation. Taken together, administration of resveratrol as soon as possible after the onset of sepsis could protect against septic AKI mainly through inhibiting IRE1-NF-κB pathway-triggered inflammatory response in the kidney. Resveratrol might be a readily translatable option to improve the prognosis of sepsis.

Anti-influenza A virus activity of rhein through regulating oxidative stress, TLR4, Akt, MAPK, and NF-κB signal pathways

Rhein, an anthraquinone compound existing in many traditional herbal medicines, has anti-inflammatory, antioxidant, antitumor, antiviral, hepatoprotective, and nephroprotective activities, but its anti-influenza A virus (IAV) activity is ambiguous. In the present study, through plaque inhibition assay, time-of-addition assay, antioxidant assay, qRT-PCR, ELISA, and western blotting assays, we investigated the anti-IAV effect and mechanism of action of rhein in vitro and in vivo. The results showed that rhein could significantly inhibit IAV adsorption and replication, decrease IAV-induced oxidative stress, activations of TLR4, Akt, p38, JNK MAPK, and NF-κB pathways, and production of inflammatory cytokines and matrix metalloproteinases in vitro. Oxidant H2O2 and agonists of TLR4, Akt, p38/JNK and IKK/NF-κB could significantly antagonize the inhibitory effects of rhein on IAV-induced cytopathic effect (CPE) and IAV replication. Through an in vivo test in mice, we also found that rhein could significantly improve the survival rate, lung index, pulmonary cytokines, and pulmonary histopathological changes. Rhein also significantly decreased pulmonary viral load at a high dose. In conclusion, rhein can inhibit IAV adsorption and replication, and the mechanism of action to inhibit IAV replication may be due to its ability to suppress IAV-induced oxidative stress and activations of TLR4, Akt, p38, JNK MAPK, and NF-κB signal pathways.

Deciphering the mechanism of Huang-Lian-Jie-Du-Decoction on the treatment of sepsis by formula decomposition and metabolomics: Enhancement of cholinergic pathways and inhibition of HMGB-1/TLR4/NF-κB signaling

Sepsis is the major cause of morbidity and mortality in surgical patients. Huang-Lian-Jie-Du-Decoction (HLJDD), a well-known Chinese herb formula, has long been used for the treatment of sepsis. In this investigation, by leaving one herb out each time, the four component herbs of HLJDD were reformulated to four HLJDD variants Form1-4, corresponding to the removal of Phellodendri Chinensis Cortex, Scutellariae Radix, Gardeniae Fructu and Coptidis Rhizoma, respectively. Metabolomics approach combined with histological inspection, biochemical measurement and molecular biology was used to investigate the treatment effects of HLJDD and its four variants on cecal ligation and puncture (CLP) model of sepsis, which were compared to decipher the formulating principles of HLJDD. Our results showed that HLJDD exhibit the strongest therapeutic effects in the CLP models as compared with the four variants, which could be ascribed to its most significant enhancement of cholinergic anti-inflammatory pathway and inhibition of HMGB-1/TLR4/NF-κB signaling pathway. Most of all, metabolites changed specifically between groups of HLJDD and its four variants were related with the exceptional treatment effects of HLJDD.

San-Huang-Xie-Xin-Tang Constituents Exert Drug-Drug Interaction of Mutual Reinforcement at Both Pharmacodynamics and Pharmacokinetic Level: A Review

Inflammatory disorders underlie varieties of human diseases. San-Huang-Xie-xin-Tang (SHXXT), composed with Rhizoma Rhei (Rheum palmatum L.), Rhizoma Coptidis (Coptis chinensis Franch), and Radix Scutellaria (Scutellaria baicalensis Georgi), is a famous formula which has been widely used in the fight against inflammatory abnormalities. Mutual reinforcement is one of the basic theories of traditional Chinese medicine. Here this article reviewed and analyzed the recent research on (1) How the main constituents of SHXXT impact on inflammation-associated signaling pathway molecules. (2) The interaction between the main constituents and efflux pumps or intestinal transporters. The goal of this work was to, (1) Provide evidence to support the theory of mutual reinforcement. (2) Clarify the key targets of SHXXT and suggest which targets need further investigation. (3) Give advice for the clinical use of SHXXT to elevated the absorption of main constituents and eventually promote oral bioavailability. We search literatures in scientific databases with key words of “each main SHXXT constituent,” in combination with “each main inflammatory pathway target molecule” or each main intestinal transporter, respectively. We report the effect of five main constituents on target molecules which lies in three main inflammatory signaling pathways, we as well investigate the interaction between constituents and intestinal transporter. We conclude, (1) The synergistic effect of constituents at both levels confirm the mutual reinforcement theory of TCM as it is proven in this work. (2) The effect of main constituents on downstream targets in nuclear need more further investigation. (3) Drug elevating the absorption of rhein, berberine and baicalein can be employed to promote oral bioavailability of SHXXT.

Zhikang Capsule ameliorates dextran sodium sulfate-induced colitis by inhibition of inflammation, apoptosis, oxidative stress and MyD88-dependent TLR4 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Zhikang Capsule (ZKC) is a traditional Chinese medicine (TCM) modified from classic formulas Qi-Li-San (an ancient formula dating to Qing Dynasty) and Fu-Jin-Sheng-Ji-San (written into The Golden Mirror of Medicine). ZKC contains 14 kinds of materials and has been widely used for the clinical therapy of inflammatory bowel diseases (IBD) for a long time. However, the therapeutic mechanisms of ZKC are still unclear.

AIM OF THE STUDY

To determine the protective effect of ZKC on dextran sodium sulfate (DSS)-induced colitis and explore the underlying mechanisms.

MATERIALS AND METHODS

C57BL/6 mice were fed with 3% DSS in drinking water for one week to induce experimental colitis. They were randomly assigned to six groups according to the treatment conditions. The histological changes of colon tissues were observed by hematoxylin and eosin (H&E) staining. The serum concentration of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β, and IL-12) and anti-inflammatory mediators (IL-4 and IL-10) was detected by enzyme-linked immune sorbent assays (ELISAs). The production of MPO, SOD, MDA, NO, and caspase-3 was assessed by biochemical assay kits. The expression of iNOS, ICAM-1, and NF-ΚB was evaluated by immunohistochemistry staining. The levels of TLR4, MyD88, and TRAF6 were determined by western blot.

RESULTS

Histologic analysis exhibited that ZKC alleviated the inflammation, loss of goblet cells, and submucosal edema induced by DSS. ZKC significantly suppressed the pro-inflammatory cytokines and promoted the anti-inflammatory mediators. The antioxidation of ZKC was indicated by increased activity of SOD and reduced production of MDA, NO, and iNOS in ZKC-treated mice. Furthermore, ZKC repressed the colonic expression of caspase-3 and the activity of the MyD88-dependent TLR4 signaling pathway.

CONCLUSIONS

This research demonstrated the protective effect of ZKC on DSS-induced colitis. For the first time, we identified four therapeutic mechanisms of ZKC, including effective inhibition of the inflammatory responses, significant alleviation of intestinal epithelium apoptosis, considerable prevention of oxidative stress, and selective down-regulation of the MyD88-dependent TLR4 signaling pathway. With high therapeutic effects and low toxic effects, ZKC exhibits great superiority over western medicines in IBD treatment.

Chronic rhein treatment improves recognition memory in high-fat diet-induced obese male mice

High-fat (HF) diet modulates gut microbiota and increases plasma concentration of lipopolysaccharide (LPS) which is associated with obesity and its related low-grade inflammation and cognitive decline. Rhein is the main ingredient of the rhubarb plant which has been used as an anti-inflammatory agent for several millennia. However, the potential effects of rhein against HF diet-induced obesity and its associated alteration of gut microbiota, inflammation and cognitive decline have not been studied. In this study, C57BL/6J male mice were fed an HF diet for 8 weeks to induce obesity, and then treated with oral rhein (120 mg/kg body weight/day in HF diet) for a further 6 weeks. Chronic rhein treatment prevented the HF diet-induced recognition memory impairment assessed by the novel object recognition test, neuroinflammation and brain-derived neurotrophic factor (BDNF) deficits in the perirhinal cortex. Furthermore, rhein inhibited the HF diet-induced increased plasma LPS level and the proinflammatory macrophage accumulation in the colon and alteration of microbiota, including decreasing Bacteroides-Prevotella spp. and Desulfovibrios spp. DNA and increasing Bifidobacterium spp. and Lactobacillus spp. DNA. Moreover, rhein also reduced body weight and improved glucose tolerance in HF diet-induced obese mice. In conclusion, rhein improved recognition memory and prevented obesity in mice on a chronic HF diet. These beneficial effects occur via the modulation of microbiota, hypoendotoxinemia, inhibition of macrophage accumulation, anti-neuroinflammation and the improvement of BDNF expression. Therefore, supplementation with rhein-enriched food or herbal medicine could be beneficial as a preventive strategy for chronic HF diet-induced cognitive decline, microbiota alteration and neuroinflammation.

Anti-Hypertensive Herbs and Their Mechanisms of Action: Part II

Traditional medicine has a history extending back to thousands of years, and during the intervening time, man has identified the healing properties of a very broad range of plants. Globally, the use of herbal therapies to treat and manage cardiovascular disease (CVD) is on the rise. This is the second part of our comprehensive review where we discuss the mechanisms of plants and herbs used for the treatment and management of high blood pressure. Similar to the first part, PubMed and ScienceDirect databases were utilized, and the following keywords and phrases were used as inclusion criteria: hypertension, high blood pressure, herbal medicine, complementary and alternative medicine, endothelial cells, nitric oxide (NO), vascular smooth muscle cell (VSMC) proliferation, hydrogen sulfide, nuclear factor kappa-B (NF-κB), oxidative stress, and epigenetics/epigenomics. Each of the aforementioned keywords was co-joined with plant or herb in question, and where possible with its constituent molecule(s). This part deals in particular with plants that are used, albeit less frequently, for the treatment and management of hypertension. We then discuss the interplay between herbs/prescription drugs and herbs/epigenetics in the context of this disease. The review then concludes with a recommendation for more rigorous, well-developed clinical trials to concretely determine the beneficial impact of herbs and plants on hypertension and a disease-free living.