Okanin in Coreopsis tinctoria Nutt is a major quorum-sensing inhibitor against Chromobacterium violaceum

Anti-quorum sensing effects of batatasin III: in vitro and in silico studies

The spread of multidrug resistant bacteria has fueled the development of new antibiotics to combat bacterial infections. Disrupting the quorum sensing (QS) mechanism with biomolecules is a promising approach against bacterial infections. Plants used in Traditional Chinese Medicine (TCM) represent a valuable resource for the identification of QS inhibitors. In this study, the in vitro anti-QS activity of 50 TCM-derived phytochemicals against the biosensor Chromobacterium violaceum CV026 was tested. Among the 50 phytochemicals, 7-methoxycoumarin, flavone, batatasin III, resveratrol, psoralen, isopsoralen, and rhein inhibited violacein production and showed good QS inhibitory effects. Batatasin III was selected as the best QS inhibitor based on drug-likeness, physicochemical properties, toxicity, and bioactivity score prediction analyses using SwissADME, PreADMET, ProtoxII, and Molinspiration. At 30 μg/ mL, Batatasin III inhibited violacein production and biofilm formation in C. violaceum CV026 by more than 69% and 54% respectively without affecting bacterial growth. The in vitro cytotoxicity evaluation by MTT assay demonstrated that batatasin III reduced the viability of 3T3 mouse fibroblast cells to 60% at 100 μg/mL. Furthermore, molecular docking studies showed that batatasin III has strong binding interactions with the QS-associated proteins CViR, LasR, RhlR, PqsE, and PqsR. Molecular dynamic simulation studies showed that batatasin III has strong binding interactions with 3QP1, a structural variant of CViR protein. The binding free energy value of batatasin III-3QP1 complex was -146.295 ± 10.800 KJ/mol. Overall results suggested that batatasin III could serve as a lead molecule that could be developed into a potent QS inhibitor.Communicated by Ramaswamy H. Sarma.

Protective effects of flavonoids in Coreopsis tinctoria Nutt. in a mouse model of type 2 diabetes

ETHNOPHARMACOLOGICAL RELEVANCE

Coreopsis tinctoria Nutt., a popular tea drink used in the Xinjiang region of China, has been traditionally used to treat diabetes and chronic metabolic diseases in China, Portugal, and North America. The bioactive extraction and potential mechanism have not been fully elucidated until now.

AIM OF THE STUDY

Traditional herbal medicines usually share network targets due to multicomponent therapeutics. Therefore, we tried to explore the protective effects of C. tinctoria on diabetes and the related molecular mechanism.

MATERIALS AND METHODS

A flavonoid-rich fraction of C. tinctoria (CTF) was prepared. After 15 weeks of continuous treatment with CTF, the blood glucose and blood lipid levels of experimental mice were evaluated. Tissue was collected for differentially expressed genes (DEGs), bioinformatics analysis, RT‒PCR and Western blot for target-related DEGs.

RESULTS

After 15 weeks of continuous treatment with CTF, db/db mice showed reversed levels of glucose, insulin, glucagon and glycated hemoglobin A1c. CTF treatment also regulated total cholesterol, triglycerides, low density lipoprotein, nonesterified fatty acid, alanine transaminase, and aspartate transaminase. Major metabolic pathways were found to be dysregulated in the liver using a combined analysis of transcriptomics and network pharmacology. CTF treatment regulated 48.2% of 6357 dysregulated genes in db/db mice. The mitochondrial electron transport chain and tricarboxylic acid cycle were mainly affected. The sequencing data showed that fifty-nine predicted target genes for CTF were reverse regulated. Together with 1528 coexpressed genes, these genes reflected the main characteristics of the whole perturbed transcriptomic profile, i.e., dysregulated mitochondrial metabolism. The important genes of the target and coexpressed genes were further verified at the gene and protein levels.

CONCLUSIONS

The results confirm that the metabolic changes induced by hyperglycemia are closely related to mitochondrial metabolism in the liver. CTF alters a core gene set that exerts regulatory effects at the biological pathway level in db/db mice. In conclusion, our data reveal that an important molecular event for CTF treatment is the regulation of mitochondrial metabolism and support the idea that herbs or natural compounds are potential therapeutic substances for mitochondrial dysfunction-related diabetes.

Three New Xanthones from Hypericum scabrum and Their Quorum Sensing Inhibitory Activities against Chromobacterium violaceum

Quorum sensing (QS) plays an important role in the production of virulence factors and pathogenicity in pathogenic bacteria and is, therefore, a hopeful target to fight against bacterial infections. During our search for natural QS inhibitors, two new xanthonolignoids (1 and 2), each existing as a racemic mixture, one new simple oxygenated xanthone (7), and eight known analogs (3–6, 8–11) were isolated from Hypericum scabrum Linn. Chiral separation of 1 yielded a pair of enantiomers 1a and 1b. The structures of these compounds were elucidated by spectroscopic analysis and ECD (electrostatic circular dichroism) calculations. All isolates were evaluated for their QS inhibitory activity against Chromobacterium violaceum. Both 9 and 10 exhibited the most potent QS inhibitory effects with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 31.25 and 62.5 μM, respectively. Crystal violet staining was used to further evaluate the biofilm inhibition potential of compounds 7, 9 and 10, and the formation of biofilms increased with decreasing drug concentration in a classic dose-dependent manner. The results of a cytotoxicity assay revealed that compounds 7, 9 and 10 exhibited no cytotoxic activity on PC-12 cells at the tested concentration.

The Derived Components of Gnaphalium hypoleucum DC. Reduce Quorum Sensing of Chromobacterium violaceum

Gnaphalium hypoleucum DC. was first recorded in the Chinese National Pharmacopoeia “Yi Plant Medicine”. There is no detailed report on its main components’ activity in suppressing the quorum sensing activity (QS) of bacteria. Our study aimed to screen the main components in extracts of G. hypoleucum DC. in order to measure their effects on bacterial QS activity and to explore specific quorum sensing mechanisms that are affected by G. hypoleucum DC. extracts. Crude extracts of G. hypoleucum DC. contained significant amounts of two compounds shown to inhibit bacterial QS activity, namely apigenin and luteolin. Apigenin and luteolin in crude extracts of G. hypoleucum DC. showed substantial inhibition of pigment formation, biofilm production, and motility in Chromobacterium violaceum ATCC 12472 compared to the effects of other phytochemicals from G. hypoleucum DC. Apigenin and luteolin exhibited a strong QS inhibitory effect on C. violaceum, interfering with the violacein pigment biosynthesis by downregulating the vioB, vioC, and vioD genes. In the presence of signal molecules, the QS effect is prevented, and the selected compounds can still inhibit the production of the characteristic purple pigment in C. violaceum. Based on qualitative and quantitative research using genomics and bioinformatics, we concluded that apigenin and luteolin in crude extracts of G. hypoleucum DC can interfere with the generation of QS in C. violaceum by downregulating the vioB, vioC, and vioD genes. Indeed, G. hypoleucum DC. is used for the treatment of bacterial infections, and this research provides new ideas and potential alternative uses for medicinal plants.

Improvement in Violacein Production by Utilizing Formic Acid to Induce Quorum Sensing in Chromobacterium violaceum

Violacein has attracted increasing attention due to its various biological activities, such as antibacterial, antifungal, antioxidative, and antitumor effects. To improve violacein production, formic acid (FA) was added to a culture medium, which resulted in a 20% increase (1.02 g/L) compared to the no-FA-addition group (0.85 g/L). The use of a stirred-tank bioreactor system also improved violacein production (by 0.56 g/L). A quorum-sensing (QS)-related gene (cviI) was induced by FA treatment, which revealed that the mechanism induced by FA utilized regulation of the cviI gene to induce the vio gene cluster for violacein production. To analyze the antioxidative properties of the violacein produced, 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) scavenging tests were conducted, and results reveal that the values of the 50% inhibitory concentration (IC₅₀) of DPPH and ABTS were 0.286 and 0.182 g/L, respectively. Violacein also showed strong inhibitory activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis). In summary, this study found that the addition of formic acid can promote QS of Chromobacterium violaceum, thereby promoting the synthesis of violacein. Subsequently, the promoting effect was also evaluated in a bioreactor system. These findings will be helpful in establishing an economically beneficial production model for violacein in future work.

The Neuroprotective Effects of Coreopsis tinctoria and Its Mechanism: Interpretation of Network Pharmacological and Experimental Data

Background:Coreopsis tinctoria Nutt. (CT), an annual herb in the genus Coreopsis, is an important traditional medicine to be used for antidiabetes and antioxidation.

Objective: The antioxidant compounds from CT may affect mitochondrial function and apoptosis, which in turn may affect related diseases. The aim of this study was to explore the potential molecular mechanism and new therapeutic opportunities of CT based on network pharmacology.

Methods: A network pharmacology-based method, which combined data collection, drug-likeness filtering, target prediction, disease prediction, and network analysis, was used to decipher the potential targets and new therapeutic opportunities of CT. The potential molecular mechanism and pathway were explored through Gene Ontology (GO) and KEGG analyses. Then MPTP-induced SH-SY5Y cell model was applied to evaluate the neuroprotective effects and key targets.

Results: There were 1,011 targets predicted for 110 compounds. Most targets were regulated by flavones, phenylpropanoids, and phenols and had synergistic effects on memory impairment, pancreatic neoplasm, fatty liver disease, and so on. The compounds–targets–diseases network identified TNF, PTGS2, VEGFA, BCL2, HIF1A, MMP9, PIK3CG, ALDH2, AKT1, and EGFR as key targets. The GO and KEGG analyses revealed that the cell death pathway, mitochondrial energy metabolism, and PI3K-AKT signal pathway were the main pathways. CT showed neuroprotective effects via regulating gene and protein expression levels of key targets in an in vitro model.

Conclusion: CT had potential neuroprotective effects by targeting multiple targets related with apoptosis, which were affected by the BCL-2 and AKT signaling pathways. This study provided a theoretical basis for the research of neuroprotective effects of CT.

Inhibition of Virulence Factors and Biofilm Formation by Wogonin Attenuates Pathogenicity of Pseudomonas aeruginosa PAO1 via Targeting pqs Quorum-Sensing System

Pseudomonas aeruginosa, an important opportunistic pathogen, is capable of producing various virulence factors and forming biofilm that are regulated by quorum sensing (QS). It is known that targeting virulence factor production and biofilm formation instead of exerting selective pressure on growth such as conventional antibiotics can reduce multidrug resistance in bacteria. Therefore, many quorum-sensing inhibitors (QSIs) have been developed to prevent or treat this bacterial infection. In this study, wogonin, as an active ingredient from Agrimonia pilosa, was found to be able to inhibit QS system of P. aeruginosa PAO1. Wogonin downregulated the expression of QS-related genes and reduced the production of many virulence factors, such as elastase, pyocyanin, and proteolytic enzyme. In addition, wogonin decreased the extracellular polysaccharide synthesis and inhibited twitching, swimming, and swarming motilities and biofilm formation. The attenuation of pathogenicity in P. aeruginosa PAO1 by wogonin application was further validated in vivo by cabbage infection and fruit fly and nematode survival experiments. Further molecular docking analysis, pathogenicity examination of various QS-related mutants, and PQS signal molecule detection revealed that wogonin could interfere with PQS signal molecular synthesis by affecting pqsA and pqsR. Taken together, the results indicated that wogonin might be used as an anti-QS candidate drug to attenuate the infection caused by P. aeruginosa.