Study on the antibacterial activities of emodin derivatives against clinical drug-resistant bacterial strains and their interaction with proteins

Emodin ameliorates acute radiation proctitis in mice by regulating AKT/MAPK/NF-κB/VEGF pathways

BACKGROUND

Emodin, a natural anthraquinone derivative isolated from the roots of Rheum officinale Baill, has many pharmacological effects including anti-inflammatory, antioxidant, antiviral, antibacterial and anti-cancer. However, little is known about the effect of emodin on acute radiation proctitis (ARP). The present study was conducted to determine its effects and elucidate its mechanisms involving AKT/MAPK/NF-κB/VEGF pathways in ARP mice.

METHODS

Total 60 C57BL/6 mice were divided randomly into control group, ARP group, AKT inhibitor MK-2206 group, and different doses of emodin groups. ARP mice were induced by 27 Gy of 6 MV X-ray pelvic local irradiation. MK-2206 was given orally for 2 weeks on alternate days. Emodin was administered daily by oral gavage for 2 weeks. Subsequently, all mice were sacrificed on day 15. The rectal tissues were obtained for further tests. The general signs score and the pathological grade were used to evaluate the severity of ARP. The expression of NF-κB, VEGF and AQP1 were determined by immunohistochemistry and western blot. The expression of p-AKT, p-ERK, p-JNK, p-p38, Bcl-2 and Bax were assessed using western blot.

RESULTS

The worse general signs and damaged tissue structure of ARP mice were profoundly ameliorated by emodin. The expression of p-AKT, p-ERK, NF-κB, VEGF and AQP1 were significantly increased, resulting in the inflammation-induced angiogenesis in ARP mice. However, the expression of p-JNK and p-p38 were decreased, leading to the reduction of apoptosis in ARP mice. Excitedly, emodin reversed these changes, not only inhibited inflammation-induced angiogenesis, but also promoted apoptosis. Notably, the effects of emodin were similar to that of AKT inhibitor MK-2206, suggesting the involvement of AKT signaling in the effect of emodin.

CONCLUSION

These results suggest that emodin attenuates ARP in mice, and the underlying mechanism might involve inhibition of the AKT/ERK/NF-κB/VEGF pathways and the induction of apoptosis mediated by JNK and p38.

Emodin suppresses alkali burn-induced corneal inflammation and neovascularization by the vascular endothelial growth factor receptor 2 signaling pathway

OBJECTIVE

To investigate the effects of emodin on alkali burn-induced corneal inflammation and neovascularization.

METHODS

The ability of emodin to target vascular endothelial growth factor receptor 2 (VEGFR2) was predicted by molecular docking. The effects of emodin on the invasion, migration, and proliferation of human umbilical vein endothelial cells (HUVEC) were determined by cell counting kit-8, Transwell, and tube formation assays. Analysis of apoptosis was performed by flow cytometry. CD31 levels were examined by immunofluorescence. The abundance and phosphorylation state of VEGFR2, protein kinase B (Akt), signal transducer and activator of transcription 3 (STAT3), and P38 were examined by immunoblot analysis. Corneal alkali burn was performed on 40 mice. Animals were divided randomly into two groups, and the alkali-burned eyes were then treated with drops of either 10 μM emodin or phosphate buffered saline (PBS) four times a day. Slit-lamp microscopy was used to evaluate inflammation and corneal neovascularization (CNV) in all eyes on Days 0, 7, 10, and 14. The mice were killed humanely 14 d after the alkali burn, and their corneas were removed and preserved at －80 ℃ until histological study or protein extraction.

RESULTS

Molecular docking confirmed that emodin was able to target VEGFR2. The findings revealed that emodin decreased the invasion, migration, angiogenesis, and proliferation of HUVEC in a dose-dependent manner. In mice, emodin suppressed corneal inflammatory cell infiltration and inhibited the development of corneal neovascularization induced by alkali burn. Compared to those of the PBS-treated group, lower VEGFR2 expression and CD31 levels were found in the emodin-treated group. Emodin dramatically decreased the expression of VEGFR2, p-VEGFR2, p-Akt, p-STAT3, and p-P38 in VEGF-treated HUVEC.

CONCLUSION

This study provides a new avenue for evaluating the molecular mechanisms underlying corneal inflammation and neovascularization. Emodin might be a promising new therapeutic option for corneal alkali burns.

Trichoderma-derived emodin competes with ExpR and ExpI of Pectobacterium carotovorum subsp. carotovorum to biocontrol bacterial soft rot

BACKGROUND

Quorum sensing inhibitors (QSIs) are an emerging control tool that inhibits the quorum sensing (QS) system of pathogenic bacteria. We aimed to screen for potential QSIs in the metabolites of Trichoderma and to explore their inhibitory mechanisms.

RESULTS

We screened a strain of Trichoderma asperellum LN004, which demonstrated the ability to inhibit the color development of Chromobacterium subtsugae CV026, primarily attributed to the presence of emodin as its key QSI component. The quantitative polymerase chain reaction with reverse transcription results showed that after emodin treatment of Pectobacterium carotovorum subsp. carotovorum (Pcc), plant cell wall degrading enzyme-related synthetic genes were significantly downregulated, and the exogenous enzyme synthesis gene negative regulator (rsmA) was upregulated 3.5-fold. Docking simulations indicated that emodin could be a potential ligand for ExpI and ExpR proteins because it exhibited stronger competition than the natural ligands in Pcc. In addition, western blotting showed that emodin attenuated the degradation of n-acylhomoserine lactone on the ExpR protein and protected it. Different concentrations of emodin reduced the activity of pectinase, cellulase, and protease in Pcc by 20.81%-72.21%, 8.38%-52.73%, and 3.57%-47.50%. Lesion size in Chinese cabbages, carrots and cherry tomatoes following Pcc infestation was reduced by 10.02%-68.57%, 40.17%-88.56% and 11.36%-86.17%.

CONCLUSION

Emodin from T. asperellum LN004 as a QSI can compete to bind both ExpI and ExpR proteins, interfering with the QS of Pcc and reducing the production of virulence factors. The first molecular mechanism reveals the ability of emodin as a QSI to competitively inhibit two QS proteins simultaneously. © 2023 Society of Chemical Industry.

Emodin is a Potential Drug Targeting CD44-positive Hepatocellular Cancer

BACKGROUND

Liver cancer is one of the most prevalent forms of cancer of the digestive system in our country. The most common subtype of this disease is hepatocellular carcinoma (HCC). Currently, treatment options for HCC patients include surgical resection, liver transplantation, radiofrequency ablation, chemoembolization, and biologic-targeted therapy. However, the efficacy of these treatments is suboptimal, as they are prone to drug resistance, metastasis, spread, and recurrence. These attributes are closely related to cancer stem cells (CSCs). Therefore, the utilization of drugs targeting CSCs may effectively inhibit the development and recurrence of HCC.

METHODS

HepG2 and Huh7 cells were used to analyze the antitumor activity of emodin by quantifying cell growth and metastasis, as well as to study its effect on stemness.

RESULTS

Emodin effectively suppressed the growth and movement of HCC cells. Emodin also significantly inhibited the proliferation of CD44-positive hepatoma cells.

CONCLUSION

Emodin shows promise as a potential therapeutic agent for HCC by targeting CD44-- positive hepatoma cells.

Antibacterial activities of anthraquinones: structure-activity relationships and action mechanisms

With the increasing prevalence of untreatable infections caused by antibiotic-resistant bacteria, the discovery of new drugs from natural products has become a hot research topic. The antibacterial activity of anthraquinones widely distributed in traditional Chinese medicine has attracted much attention. Herein, the structure and activity relationships (SARs) of anthraquinones as bacteriostatic agents are reviewed and elucidated. The substituents of anthraquinone and its derivatives are closely related to their antibacterial activities. The stronger the polarity of anthraquinone substituents is, the more potent the antibacterial effects appear. The presence of hydroxyl groups is not necessary for the antibacterial activity of hydroxyanthraquinone derivatives. Substitution of di-isopentenyl groups can improve the antibacterial activity of anthraquinone derivatives. The rigid plane structure of anthraquinone lowers its water solubility and results in the reduced activity. Meanwhile, the antibacterial mechanisms of anthraquinone and its analogs are explored, mainly including biofilm formation inhibition, destruction of the cell wall, endotoxin inhibition, inhibition of nucleic acid and protein synthesis, and blockage of energy metabolism and other substances.

The In Vitro Anti-Parasitic Activities of Emodin toward Toxoplasma gondii

Currently, toxoplasmosis affects nearly one-third of the world’s population, but the available treatments have several limitations. This factor underscores the search for better therapy for toxoplasmosis. Therefore, in the current investigation, we investigated the potential of emodin as a new anti-Toxoplasma gondii while exploring its anti-parasitic mechanism of action. We explored the mechanisms of action of emodin in the presence and absence of an in vitro model of experimental toxoplasmosis. Emodin showed strong anti-T. gondii action with an EC50 value of 0.03 µg/mL; at this same effective anti-parasite concentration, emodin showed no appreciable host cytotoxicity. Likewise, emodin showed a promising anti-T. gondii specificity with a selectivity index (SI) of 276. Pyrimethamine, a standard drug for toxoplasmosis, had an SI of 2.3. The results collectively imply that parasite damage was selective rather than as a result of a broad cytotoxic effect. Furthermore, our data confirm that emodin-induced parasite growth suppression stems from parasite targets and not host targets, and indicate that the anti-parasite action of emodin precludes oxidative stress and ROS production. Emodin likely mediates parasite growth suppression through means other than oxidative stress, ROS production, or mitochondrial toxicity. Collectively, our findings support the potential of emodin as a promising and novel anti-parasitic agent that warrants further investigation.

Monitoring the interactions between bovine serum albumin and ZnO/Ag nanoparticles by spectroscopic techniques

Inducing the bio-functionalization in noble metal nanoparticles like gold, silver, zinc is very important to accomplish their biocompatibility in biological activities. These metal nanoparticles are being rigorously used in bio-sensing tools keeping their remarkable properties in mind. Amongst the serum albumins, the most ample proteins in plasma are bovine serum albumin and human serum albumin. A broad variety of physiological functions of bovine serum albumin has made it a model protein for bio-functionalization. In the present study, ZnO/Ag nanoparticles were synthesized and characterized by SEM and XRD techniques and the interaction between bovine serum albumin and ZnO/Ag nanoparticles was evaluated by employing ultra-violet, steady state fluorescence, circular dichroism and FTIR spectroscopic techniques. Upon the excitation of bovine serum albumin, ZnO/Ag nanoparticles appreciably reduced the intrinsic fluorescence intensity of bovine serum albumin. The number of binding locations and apparent binding constants at different temperatures were calculated by the fluorescence quenching method. Static mechanism of quenching and conformational modifications in bovine serum albumin were also found.Communicated by Ramaswamy H. Sarma.

In-silico predicting as a tool to develop plant-based biomedicines and nanoparticles: Lycium shawii metabolites

INTRODUCTION AND PURPOSE

In silico approach helps develop biomedicines and is useful for exploring the pharmacology of potential therapeutics using computer-simulated models. In vitro assays were used to determine the anti-microbial and cytotoxic efficacies of silver nanoparticles (AgNPs) synthesized with the shrub Lycium shawii.

METHODS

In silico predicting was performed to assess the L. shawii metabolites identified using QTOF-LCMS for their pharmacological properties. L. shawii mediated AgNPs were synthesized and characterized (FTIR, TEM, SEM, DLS and EDX). The anti-bacterial efficacies of L. shawii extract, AgNPs, and penicillin-conjugated AgNPs (pen-AgNPs) were determined. The cytotoxicity of the AgNPs was measured against colorectal cancer cell line (HCT116), normal breast epithelium (MCF 10 A), and breast cancer cell line (MDA MB 231).

RESULTS AND DISCUSSION

Five molecules (costunolide, catechin, emodin, lyciumaside, and aloe emodin 11-O-rhamnoside) were detected in the L. shawii extract. AgNPs (69 nm) were spherical with crystallographic structure. All three agents prepared showed inhibitory activity against the tested bacteria, the most efficacious being pen-AgNPs. High cytotoxicity of AgNPs (IC₅₀ 62 μg/ml) was observed against HCT116, IC₅₀ was 78 μg/ml for MCF 10 A, and 250 μg/ml for MDA MB 231, of which cells showed apoptotic features under TEM examination. The in silico approach indicated that the carbonic anhydrase IX enzyme was the target molecule mediating anti-cancer and anti-bacterial activities and that emodin was the metabolite in action.

CONCLUSIONS

Combining in vitro studies and in silico molecular target prediction helps find novel therapeutic agents. Among L. shawii metabolites, emodin is suggested for further studies as an agent for drug development against pathogenic bacteria and cancer.

Ethyl 2-Succinate-Anthraquinone Attenuates Inflammatory Response and Oxidative Stress via Regulating NLRP3 Signaling Pathway

Aloe-emodin widely possesses antibacterial, anti-inflammatory, antioxidant, antiviral, and anti-infectious properties. This study investigated the effect of ethyl 2-succinate-anthraquinone (Luhui derivative, LHD) on inflammation. In vitro, a THP-1 macrophage inflammation model, made by 100 ng/ml phorbol-12-myristate-13-acetate (PMA) and 1 μg/ml LPS for 24 h, was constructed. The LHD group (6.25 μmol/L, 12.5 μmol/L, 25 μmol/L, 50 μmol/L) had no effect on THP-1 cell activity, and the expression of IL-6 mRNA was down-regulated in a concentration-dependent manner, of which the 25 μmol/L group had the best inhibitory effect. The migration of THP-1 macrophages induced by LPS was decreased by the LHD. Moreover, the LHD suppressed ROS fluorescence expression by inhibiting MDA expression and increasing SOD activity. In vivo, we revealed that the LHD, in different doses (6.25 mg/kg, 12.5 mg/kg, 25 mg/kg, 50 mg/kg), has a protective effect on stress physiological responses by assessing the body temperature of mice. Interestingly, acute lung injury (e.g., the structure of the alveoli disappeared and capillaries in the alveolar wall were dilated and congested) and liver damage (e.g., hepatocyte swelling, neutrophil infiltration, and hepatocyte apoptosis) were obviously improved at the same condition. Furthermore, we initially confirmed that the LHD can down-regulate the expression of NLRP3, IL-1β, and caspase-1 proteins, thereby mediating the NLRP3 inflammasome signaling pathway to produce anti-inflammatory effects. In conclusion, our results indicate that the LHD exerts anti-inflammatory activity via regulating the NLRP3 signaling pathway, inhibition of oxidative stress, and THP-1 macrophage migration.

Construction of a Phenylboronic Acid-Functionalized Nano-Prodrug for pH-Responsive Emodin Delivery and Antibacterial Activity

In this study, a pH-responsive nano-prodrug was fabricated by conjugating emodin to the PEGylated polyethyleneimine (mPEG-PEI) with acid-sensitive boronate ester bonds. ¹H NMR spectra results showed that emodin was effectively bonded to mPEG-PEI, and acid-sensitive assay further confirmed the formation of boronate ester bonds. The size and morphology of the nano-prodrug were ascertained through transmission electron microscopy (TEM) and dynamic light scattering (DLS), which showed that the prodrug has a sphere-like shape with hydrodynamic size around 102 nm at pH 7.4. Subsequently, a drug-release behavior assay was carried out to carefully investigate the acid-sensitive drug-delivery property of the prodrug. Moreover, in vitro cell viability assay confirmed the superior cytotoxic effect of the nano-prodrug against HeLa cells compared to free emodin. Furthermore, the antibacterial study showed that the nano-prodrug could inhibit the bacterial (both Gram-positive and Gram-negative) growth more effectively than free emodin. Overall, this study provides a promising paradigm of the multifunctional nano-prodrug for pH-responsive tumor therapy and antibacterial activity.

Emodin Derivatives as Multi-Target-Directed Ligands Inhibiting Monoamine Oxidase and Antagonizing Vasopressin V1A Receptors

The brain neurotransmitter level is associated with the pathology of various neurodegenerative diseases, and age-dependent increase in the blood level of vasopressin, human brain monoamine oxidase (hMAO) level, oxidative stress, and imbalance in aminergic signaling are common disease-modifying factors leading to various neurodegenerative disorders. Based on the reports of emodin in hMAO inhibition and antagonist effect on the vasopressin V_1A receptor, in this study we synthesized six emodin derivatives and evaluated their effects on MAO activity and G protein-coupled receptors. Among them, 4-hydroxyemodin and 5-hydroxyemodin were potent inhibitors of hMAO, and 2-hydroxyemodin and 5-hydroxyemodin were good V_1AR antagonists. In silico molecular docking simulation revealed that the hydroxyl group at C2, C4, and C5 of the respective compounds interacted with prime residues, which corroborates the in vitro effect. Likewise, these three derivatives were predicted to have good drug-like properties. Overall, our study demonstrates that the hydroxyl derivatives of emodin are multi-target-directed ligands that may act as leads for the design and development of a therapy for central nervous system disorders.

Molecular Mechanisms of Action of Emodin: As an Anti-Cardiovascular Disease Drug

Emodin is a natural occurring anthraquinone derivative isolated from roots and barks of numerous plants, molds, and lichens. It is found to be an active ingredient in different Chinese herbs including Rheum palmatum and Polygonam multiflorum, and it is a pleiotropic molecule with diuretic, vasorelaxant, anti-bacterial, anti-viral, anti-ulcerogenic, anti-inflammatory, and anti-cancer effects. Moreover, emodin has also been shown to have a wide activity of anti-cardiovascular diseases. It is mainly involved in multiple molecular targets such as inflammatory, anti-apoptosis, anti-hypertrophy, anti-fibrosis, anti-oxidative damage, abnormal, and excessive proliferation of smooth muscle cells in cardiovascular diseases. As a new type of cardiovascular disease treatment drug, emodin has broad application prospects. However, a large amount of evidences detailing the effect of emodin on many signaling pathways and cellular functions in cardiovascular disease, the overall understanding of its mechanisms of action remains elusive. In addition, by describing the evidence of the effects of emodin in detail, the toxicity and poor oral bioavailability of mice have been continuously discovered. This review aims to describe a timely overview of emodin related to the treatment of cardiovascular disease. The emphasis is to summarize the pharmacological effects of emodin as an anti-cardiovascular drug, as well as the targets and its potential mechanisms. Furthermore, the treatment of emodin compared with conventional cardiovascular drugs or target inhibitors, the toxicity, pharmacokinetics and derivatives of emodin were discussed.