Saikosaponin A protects chickens against pullorum disease via modulation of cholesterol

Saikosaponin a promotes neutrophil extracellular trap formation and bactericidal activity

This study aimed to investigate the effects of SSa, one of the major triterpenoid saponins extracted from Radix bupleuri, on neutrophil extracellular trap (NET) formation and the mechanism associated with this process. Using Sytox green and immunofluorescence assays, we found SSa rapidly induced NET formation, which depended on NADPH oxidase (NOX)-independent ROS production and autophagy. Pharmacologic inhibitor studies indicated that ERK and PI3K/AKT signalling were also required for SSa-induced NET formation, whereas protein arginine deiminase 4 (PAD4) was not required. Furthermore, we found that SSa promoted neutrophil bactericidal activity mainly through NET formation. Based on flow cytometry and the Cell Counting Kit-8 (CCK-8) assays, the results demonstrated that SSa-induced NET formation occurred without neutrophil death. Taken together, these findings indicated that SSa could be a potential natural product to boost innate immune defense against pathogen attack via NET formation.

Antitumor mechanism of Saikosaponin A in the Xiaoying Sanjie Decoction for treatment of anaplastic thyroid cancer by network pharmacology analysis and experiments in vitro and in vivo

Effective therapies for anaplastic thyroid cancer (ATC) are still limited due to its dedifferentiated phenotype and high invasiveness. Xiaoying Sanjie Decoction (XYSJD), a clinically empirical Chinese medicine compound, has shown positive effects for ATC treatment and recovery. However, the pharmacological mechanisms of effective active compound in XYSJD remain unclear. In this study, we aimed at elucidating the antitumor mechanism of the active compound and identifying the kernel molecular mechanisms of XYSJD against ATC. Firstly, the main chemical constituents of XYSJD were identified by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). Then we used network pharmacology and ClusterONE algorithm to analyze the possible targets and pathways of the prescription and active compound Saikosaponin A (SSA). Seven core targets, including P2RY12, PDK1, PPP1CC, PPP2CA, TBK1, ITGB1 and ITGB6, which may be involved in the anti-tumor activity of XYSJD were screened. Finally, using cell biology, molecular biology and experimental zoology techniques, we investigated the mechanism of active compound SSA in the treatment of ATC. The results of qRT-PCR indicated that these seven nuclear targets might play an important role in SSA, the active compound of XYSJD. The combined data provide preliminary study of the pharmacological mechanisms of SSA in XYSJD. SSA may be a promising potential therapeutic and chemopreventive candidate for ATC.

Protective effect of 13-methylberberine against mouse enteritis caused by MRSA

ETHNOPHARMACOLOGICAL RELEVANCE

The emergence and spread of antibiotic resistance bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), urgently need to develop alternative strategies or novel antibacterial drugs. Coptis chinensis Franch., one ancient Chinese herb, has been widely used for the treatment of intestine disease, such as diarrhea. Alkaloids are the major active compounds of Coptis chinensis Franch., and has anti-inflammatory, antioxidant, and antimicrobial effects.

AIM OF THE STUDY

The aim of the study was tried to investigate the potential antibacterial effects of the alkaloids from Coptis chinensis Franch. and explore the mechanism.

MATERIALS AND METHODS

A checkerboard assay, time-killing analysis, membrane functions assay, transcriptome analysis, and inducible resistance test showed the antibacterial effects and mechanisms of alkaloids from Coptis chinensis Franch. Hemolytic assay and MRSA-infected RAW264.7 cells were used to evaluate anti-virulence and anti-inflammatory activities of 13-methylberberine (13-MB). MRSA-infected Vero cells and mouse enteritis models were used to evaluate the anti-infectious effect of 13-MB against MRSA both in vitro and in vivo.

RESULTS

13-methylberberine (13-MB) displayed high bactericidal efficiency against methicillin-resistant S. aureus (MRSA). Mechanistic studies showed that 13-MB rapidly killed MRSA by interfering with the proton motive force, ROS generation and membrane fluidity via direct interaction with membrane phospholipids. 13-MB suppressed the virulence of MRSA, modulated the host immune response, and effectively eliminated MRSA in Vero cells. Importantly, 13-MB suppressed weight loss, inflammatory response, bacterial colonization and intestinal lesion in mouse enteritis caused by 13-MB susceptible and resistant S. aureus.

CONCLUSION

These results supported the 13-MB has promising potential to be developed as natural drug with antibacterial activity, anti-virulence activity, and host modulation activity for the treatment of enteritis caused by MRSA.

Mechanistic study of the antibacterial potential of the prenylated flavonoid auriculasin against Escherichia coli

Bacterial resistance is spreading in an alarming manner, outpacing the rate of development of new antibacterial agents and surging the need for effective alternatives. Prenylated flavonoids are a promising class of natural antibiotics with reported activity against a wide range of resistant pathogens. Here, a large library of natural flavonoids (1718 structures) was virtually screened for potential candidates inhibiting the B-subunit of gyrase (Gyr-B). Twenty-eight candidates, predominated by prenylated flavonoids, appeared as promising hits. Six of them were selected for further in vitro antibacterial and Gyr-B enzyme inhibitory activities. Auriculasin is presented as the most potent antibacterial candidate, with a MIC ranging from 2 to 4 µg/ml against two clinically isolated multidrug-resistant Escherichia coli strains. Mechanistic antibacterial analysis revealed auriculasin inhibitory activity towards the Gyr-B enzyme on the micromolar scale (IC₅₀  = 0.38 ± 0.15 µM). Gyr-B interaction was further detailed by conducting an isothermal titration calorimetric experiment, which revealed a competitive inhibition with a high affinity for the Gyr-B active site, achieved mostly through enthalpic interactions (ΔG_binding  = -10.69 kcal/mol). Molecular modeling and physics-based simulations demonstrated the molecule's manner of fitting inside the Gyr-B active site, indicating a very potential nucleus for the future generation of more potent derivatives. To conclude, prenylated flavonoids are interesting antibacterial candidates with anti-Gyr-B mechanism of action that can be obtained from a plant-derived flavonoid.

Health Benefits of Silybum marianum: Phytochemistry, Pharmacology, and Applications

Silybum marianum (SM), a well-known plant used as both a medicine and a food, has been widely used to treat various diseases, especially hepatic diseases. The seeds and fruits of SM contain a flavonolignan complex called silymarin, the active compounds of which include silybin, isosilybin, silychristin, dihydrosilybin, silydianin, and so on. In this review, we thoroughly summarize high-quality publications related to the pharmacological effects and underlying mechanisms of SM. SM has antimicrobial, anticancer, hepatoprotective, cardiovascular-protective, neuroprotective, skin-protective, antidiabetic, and other effects. Importantly, SM also counteracts the toxicities of antibiotics, metals, and pesticides. The diverse pharmacological activities of SM provide scientific evidence supporting its use in both humans and animals. Multiple signaling pathways associated with oxidative stress and inflammation are the common molecular targets of SM. Moreover, the flavonolignans of SM are potential agonists of PPARγ and ABCA1, PTP1B inhibitors, and metal chelators. At the end of the review, the potential and perspectives of SM are discussed, and these insights are expected to facilitate the application of SM and the discovery and development of new drugs. We conclude that SM is an interesting dietary medicine for health enhancement and drug discovery and warrants further investigation.

Comparative Effect of Aqueous and Methanolic Bupleuri Radix Extracts on Hepatic Uptake of High-Density Lipoprotein and Identification of the Potential Target in HFD-Fed Mice

Our previous study found saikosaponin b₂ (SSb₂) increased high-density lipoprotein (HDL) uptake in HepG2 cells. SSb₂ is only found in aqueous Bupleuri Radix extract, and it is one of the secondary saponins derived from saikosaponin d (SSd), which exists in the methanolic extract. This study aimed to compare the effect of aqueous extract of Bupleuri Radix on hepatic uptake of HDL with methanolic extract and to reveal the underlying mechanism of enhancing HDL uptake in mice fed with high-fat diet (HFD). Cellular HDL uptake in each group was quantified by flow cytometry. Bioactive components bound to the HepG2 cytomembrane were detected with HPLC-DAD. RNA sequencing was performed to screen the underlying target on hepatic HDL-uptake, and western blotting was conducted to verify differential protein expression. Significant increases of HDL uptake by HepG2 cells were observed in all groups of aqueous extract of Bupleuri Radix, while no effect or negative effect was observed in the methanolic extract. Saikosaponin b₁ (SSb₁) and SSb₂ were detected in the desorption elute of the aqueous extract from the HepG2 cytomembrane, while saikosaponin a (SSa) and SSd were not found. Remarkable upregulation of FGF21 in HFD-fed mice liver was affirmed after treatment with aqueous extract. This study suggested that aqueous Bupleuri Radix extract could promote hepatic HDL uptake in vitro but methanolic extract could not, and FGF21 might be the potential target.

Natural Products That Target Virulence Factors in Antibiotic-Resistant Staphylococcus aureus

The increase in the incidence of antibiotic-resistant Staphylococcus aureus (S. aureus) associated infections necessitates the urgent development of novel therapeutic strategies and antibacterial drugs. Antivirulence strategy is an especially compelling alternative strategy due to its low selective pressure for the development of drug resistance in bacteria. Plants and microorganisms are not only important food and medicinal resources but also serve as sources for the discovery of natural products that target bacterial virulence factors. This review discusses the mechanisms of the major virulence factors of S. aureus, including the accessory gene regulator quorum-sensing system, bacterial biofilm formation, α-hemolysin, sortase A, and staphyloxanthin. We also provide an overview of natural products isolated from plants and microorganisms with activity against the major virulence factors of S. aureus and their adjuvant effects on existing antibiotics to overcome antibiotic-resistant S. aureus. Finally, the limitations and solutions of these antivirulence compounds are discussed, which will help in the development of novel antibacterial drugs against antibiotic-resistant S. aureus.

Antibacterial Effect and Mode of Action of Flavonoids From Licorice Against Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is a bacterial pathogen that causes food poisoning, various infections, and sepsis. Effective strategies and new drugs are needed to control S. aureus associated infections due to the emergence and rapid dissemination of antibiotic resistance. In the present study, the antibacterial activity, potential mode of action, and applications of flavonoids from licorice were investigated. Here, we showed that glabrol, licochalcone A, licochalcone C, and licochalcone E displayed high efficiency against methicillin-resistant Staphylococcus aureus (MRSA). Glabrol, licochalcone A, licochalcone C, and licochalcone E exhibited low cytotoxicity without hemolytic activity based on safety evaluation. Glabrol displayed rapid bactericidal activity with low levels of resistance development in vitro. Meanwhile, glabrol rapidly increased bacterial membrane permeability and dissipated the proton move force. Furthermore, we found that peptidoglycan, phosphatidylglycerol, and cardiolipin inhibited the antibacterial activity of glabrol. Molecular docking showed that glabrol binds to phosphatidylglycerol and cardiolipin through the formation of hydrogen bonds. Lastly, glabrol showed antibacterial activity against MRSA in both in vivo and in vitro models. Altogether, these results suggest that glabrol is a promising lead compound for the design of membrane-active antibacterial agents against MRSA and can be used as a disinfectant candidate as well.