The Anti-Biofilm Activity and Mechanism of Apigenin-7-O-Glucoside Against Staphylococcus aureus and Escherichia coli.

Introduction: This study aimed to examine the anti-biofilm activity and mechanism of gallic acid (GA), kaempferol-7-O-glucoside (K7G) and apigenin-7-O-glucoside (A7G) against Staphylococcus aureus and Escherichia coli. Methods: The antibacterial activity of the natural compounds was determined by serial dilution method. The inhibitory activity of natural compounds on biofilms was determined by crystal violet staining method. The effects and mechanisms of natural compounds on bacterial biofilms were analyzed by atomic force microscopy. Results: In our study, compared with GA and K7G, A7G was found to exhibit the strongest anti-biofilm and antibacterial activities. The minimum biofilm inhibitory concentration (MBIC) of A7G against S. aureus and E. coli was 0.20 mg/mL and 0.10 mg/mL, respectively. The inhibition rates of 1/2 MIC of A7G on biofilms of S. aureus and E. coli were 88.9%, and 83.2% respectively. Moreover, atomic force microscope (AFM) images showed the three-dimensional biofilm morphology of S. aureus and E. coli, and the results indicated that A7G was highly effective in biofilm inhibition. Discussion: It was found that the inhibition of A7G on biofilm was achieved through inhibiting on exopolysaccharides (EPS), quorum sensing (QS), and cell surface hydrophobicity (CSH). A7G exerted strong anti-biofilm activities by inhibiting EPS production, QS, and CSH. Hence, A7G, as a natural substance, could be a promising novel antibacterial and anti-biofilm agent for control of biofilm in food industry.

Theoretical study of myriocin-binding mechanism targeting serine palmitoyltransferase.

Sphingolipids (SLs) are vital for cells as forming membrane and transducing signals. The first step for de novo biosynthesis of SLs is catalyzed by the pyridoxal-5'-phosphate (PLP)-dependent enzyme serine palmitoyltransferase (SPT), which has been proven to be a promising drug target for treating various diseases. However, there are few SPT-specific inhibitors have been identified so far. Myriocin, a natural fungal product, is confirmed as the most potent inhibitor of SPT and has been widely used, but studies of its molecular mechanism are still underway. Besides, there is no intact co-crystal structure of SPT-binding myriocin until now. Aiming to uncover the interaction mechanism between SPT- and PLP-binding myriocin at the molecular level, a systematic computational strategy was performed in this present study. Firstly, covalent docking was implemented to preliminarily predict the binding pose SPT/PLP-myriocin aldimine and its structurally similar intermediate SPT/PLP-ß-ketoacid aldimine. Secondly, two binding complexes were treated as initial structures to perform molecular dynamics simulations and binding free energy calculations. The calculated docking scores and predicted binding energies were consistent with the reported bioactivities. Finally, the binding mechanism of myriocin binding with SPT was meticulously described, and the key residues making favorable contributions were highlighted. Taken together, the current study could provide some important information and valuable guidance for further rational screening, design, and modification of potent specific SPT inhibitors.

Mechanism of Cordyceps Cicadae in Treating Diabetic Nephropathy Based on Network Pharmacology and Molecular Docking Analysis.

OBJECTIVE: To systematically study the mechanism of cordyceps cicadae in the treatment of diabetic nephropathy (DN) with the method of network pharmacology and molecular docking analysis, so as to provide theoretical basis for the development of new drugs for the treatment of DN. METHODS: TCMSP, Symmap, PubChem, PubMed, and CTD database were used to predict and screen the active components and therapeutic targets for DN. The network of active components and targets was drawn by Cytoscape 3.6.0, the protein-protein interaction (PPI) was analyzed by the STRING database, and the DAVID database was used for the enrichment analysis of intersection targets. Molecular docking studies were finished by Discovery Studio 3.5. RESULTS: A total of 36 active compounds, including myriocin, guanosine, and inosine, and 378 potential targets of cordyceps cicadae were obtained. PPI network analysis showed that AKT1, MAPK8, and TP53 and other targets were related to both cordyceps cicadae and DN. GO and KEGG pathway analysis showed that these targets were mostly involved in R-HSA-450341, 157.14-3-3 cell cycle, and PDGF pathways. Docking studies suggested that myriocin can fit in the binding pocket of two target proteins (AKT1 and MAPK8). CONCLUSION: Active ingredients of cordyceps cicadae such as myriocin may act on DN through different targets such as AKT1, MAPK8, and TP53 and other targets, which can help to develop innovative drugs for effective treatment of DN.

Development of a compound oral liquid containing herbal extracts and its effect on immunity and gastric mucosa.

Nowadays, consumers have an increasing demand for health products. In this study, an oral liquid was developed using a compound extract consisting of three herbal extracts (Dendrobium nobile Lindl., Lycium barbarum, and Puerariae lobatae Radix) because the compound extract (a combination of all three extracts) was superior to every single extract in promoting the phagocytic capacity of RAW264.7 macrophages and the proliferation ability of GES-1 cells. In this oral liquid, the dosage of the stabilizer and the sweetener was selected using a stability test and sensory quality evaluation. When 0.30% (m/v) xanthan gum and 0.20% (m/v) mogroside were added, the oral liquid had not only a good stability but also the highest sensory score for overall acceptability. The chemical composition analysis showed that the oral liquid had various functional ingredients including polysaccharides, phenols, alkaloids, and so forth. The immune-enhancing efficacy of the oral liquid was evaluated in BALB/c mice by measuring the levels of different immune indicators. The results indicated that the oral liquid obviously enhanced nonspecific and specific immunity. A rat model with ethanol-induced gastric ulcer was used to examine the protective effect of the oral liquid on the gastric mucosa and to explore the related mechanisms. The oral administration of the oral liquid for days significantly prevented the formation of gastric ulcer. This study provided an effective oral liquid that could enhance immunity and protect gastric mucosa.

Identification of a novel SPT inhibitor WXP-003 by docking-based virtual screening and investigation of its anti-fungi effect.

Serine palmitoyltransferase (SPT) plays the key role on catalysing the formation of 3-ketodihydrosphingosine, which is the first step of the de novo biosynthesis of sphingolipids. SPT is linked to many diseases including fungal infection, making it a potential therapeutic target. Thus, a logical docking-based virtual screening method was used to screen selective SPT inhibitor against fungi, not human. We used myriocin-similarity database to identify compounds with good binding with fungal SPT and poor binding with homology human SPT model. Preliminary bio-assay led to the discovery of a promising inhibitor WXP-003, which displayed good inhibitory activity against diversity fungi strains with MIC ranging from 0.78 to 12.5 µg/mL. WXP-003 could significantly reduce sphingolipids content in fungi and no effect on mouse fibroblast cell line L929. Molecular dynamics simulation depicted that SPT/WXP-003 complex formed the favoured interactions. Taken together, discovery of WXP-003 provided valuable guide for the development of novel anti-fungal agents.

Evaluation of Anti-Biofilm Capability of Cordycepin Against Candida albicans.

INTRODUCTION: The opportunistic pathogen Candida albicans can form biofilms, resulting in drug resistance with great risk to medical treatment. METHODOLOGY: We investigated the ability of C. albicans to form biofilms on different materials, as well as the inhibitory and eradicating effects of cordycepin on biofilm. The action mechanism of cordycepin against biofilm was studied by crystal violet staining, XTT [2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction method, phenol-sulfuric acid method, cellular superficial hydrophobicity (CSH) assay, and confocal laser scanning microscope observation. We also evaluated the acute toxicity of cordycepin in vivo. RESULTS: The results showed facile formation of biofilms by C. albicans on polypropylene. The 50% minimum inhibitory concentration (MIC50) of cordycepin was 0.062 mg/mL. A concentration of 0.125 mg/mL significantly decreased biofilm formation, metabolic activity, secretion of extracellular polysaccharides, and relative CSH. Cordycepin could inhibit biofilm formation at low concentration without affecting fungal growth. In addition, cordycepin effectively eradicated 59.14% of mature biofilms of C. albicans at a concentration of 0.5 mg/mL. For acute toxicity, the LD50 (50% of lethal dose) of cordycepin was determined as higher than 500 mg/kg for mice. CONCLUSION: The results of this study show that cordycepin significantly inhibited and eradicated biofilms by decreasing metabolic activity, the ratio of living cells, the hydrophobicity, and damaging the extracellular polysaccharides of biofilm. These findings should facilitate more effective application of cordycepin and suggest a new direction for the treatment of fungal infections.

Study on the Inhibitory Activity and Possible Mechanism of Myriocin on Clinically Relevant Drug-Resistant Candida albicans and Its Biofilms.

In order to prevent and control the infection of Candida albicans, the antifungal activity, possible mechanism of myriocin against C. albicans and its biofilm were studied. The antifungal activity of myriocin was investigated by microdilution method. The effect of myriocin on fungal cell wall or membrane was evaluated by adding sorbitol, ergosterol or phytosphingosine (PHS). The damage to the cell membrane was investigated with propidium iodide (PI) staining and visualized by scanning electron microscope (SEM). The effects on biofilms and extracellular polysaccharides (EPS) were observed by crystal violet staining method and phenol-sulfuric acid method respectively. The adhesion of C. albicans cells to hydrocarbons was tested to evaluate cell surface hydrophobic (CSH). The combined effects of myriocin and antifungal drugs commonly used in clinical practice were investigated by using the checkerboard microdilution method. Minimal inhibitory concentrations (MICs) were found to be 0.125-4 µg/mL. Myriocin was found to affect both cell wall and cell membrane. After exposure to myriocin, biofilm and EPS were found to be inhibited and removed, and the CSH was decreased. The combined fungistasis of myriocin and voriconazole (VCZ) or amphotericin B (AMB) were additive. Myriocin had significant antifungal activity against C. albicans, and the antifungal mechanisms might be cell wall and membrane damage. Myriocin effectively inhibited and eliminated biofilms, and its mechanism may be related to the inhibition of EPS and CSH.

Heart Rate Variability Based Prediction of Personalized Drug Therapeutic Response: The Present Status and the Perspectives.

Heart rate variability (HRV) signals are reported to be associated with the personalized drug response in many diseases such as major depressive disorder, epilepsy, chronic pain, hypertension, etc. But the relationships between HRV signals and the personalized drug response in different diseases and patients are complex and remain unclear. With the fast development of modern smart sensor technologies and the popularization of big data paradigm, more and more data on the HRV and drug response will be available, it then provides great opportunities to build models for predicting the association of the HRV with personalized drug response precisely. We here review the present status of the HRV data resources and models for predicting and evaluating of personalized drug responses in different diseases. The future perspectives on the integration of knowledge and personalized data at different levels such as, genomics, physiological signals, etc. for the application of HRV signals to the precision prediction of drug therapy and their response will be provided.

Inhibitive Effect of Eugenol and Its Nanoemulsion on Quorum Sensing-Mediated Virulence Factors and Biofilm Formation by Pseudomonas aeruginosa.

The aim of the present study was to evaluate the quorum sensing (QS) inhibition potential of eugenol and eugenol nanoemulsion against QS-dependent virulence factor production and gene expression, as well as biofilm formation in Pseudomonas aeruginosa. In the current study, eugenol nanoemulsion at a sub-MIC of 0.2 mg/mL specifically inhibited about 50% of the QS-mediated violacein production in Chromobacterium violaceum, as well as the production of N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL) and C4-HSL N-acyl homoserine lactone signal molecules, pyocyanin, and swarming motility in P. aeruginosa. The inhibitive effect of eugenol and its nanoemulsion on the expression of the QS synthase genes was concentration dependent, displaying 65 and 52% expression level for lasI, respectively, and 61 and 45% expression level for rhlI, respectively, at a concentration of 0.2 mg/mL. In addition, the inhibitive effect of eugenol and its nanoemulsion on the expression of the rhlA gene responsible for the production of rhamnolipid was also concentration dependent, displaying 65 and 51% expression level for the rhlA gene, respectively, at a concentration of 0.2 mg/mL. Eugenol and its nanoemulsion also displayed 36 and 63% respective inhibition of biofilm formation by P. aeruginosa at the 0.2 mg/mL concentration. Therefore, the nanoemulsion could be used as a novel QS-based antibacterial and antibiofilm agent for the control of harmful bacteria.

Preparation and characterization of silver nanoparticles on silk fibroin/carboxymethylchitosan composite sponge as anti-bacterial wound dressing.

The infection in burn wounds covered by biologic dressings leads to wound deepening and chronic wounds. The introduction of silver nanoparticles (AgNPs) into biologic dressings is a beneficial method to prevent wound infection and simultaneously promote wound healing. In this study, an AgNP-loaded silk fibroin (SF)/carboxymethylchitosan (CMC) composite sponge was fabricated. AgNPs with a mean diameter of 4.9 nm was synthesized in SF solution in situ. While CMC was incorporated and chemically crosslinked, SF was insolubilized by ethanol annealing. SEM imaging determined that the AgNP-loaded SF/CMC sponge was more porous than the pure SF sponge. Anti-bacterial results, measured by disk-diffusion and bacterial suspension assay, showed that the AgNP-loaded SF/CMC sponge demonstrated effective anti-bacterial activity against S. aureus and P. aeruginosa, and that its anti-P. aeruginosa activity was higher than that of AQUACEL®; Ag. The introduction of CMC improved the water absorption capacity, retention ability, and water vapor transmission rate of the sponge, which are all important properties of wound dressings.