Artesunate has its enhancement on antibacterial activity of β-lactams via increasing the antibiotic accumulation within methicillin-resistant Staphylococcus aureus (MRSA)

Recent advances in nanoantibiotics against multidrug-resistant bacteria

Multidrug-resistant (MDR) bacteria-caused infections have been a major threat to human health. The abuse of conventional antibiotics accelerates the generation of MDR bacteria and makes the situation worse. The emergence of nanomaterials holds great promise for solving this tricky problem due to their multiple antibacterial mechanisms, tunable antibacterial spectra, and low probabilities of inducing drug resistance. In this review, we summarize the mechanism of the generation of drug resistance, and introduce the recently developed nanomaterials for dealing with MDR bacteria via various antibacterial mechanisms. Considering that biosafety and mass production are the major bottlenecks hurdling the commercialization of nanoantibiotics, we introduce the related development in these two aspects. We discuss urgent challenges in this field and future perspectives to promote the development and translation of nanoantibiotics as alternatives against MDR pathogens to traditional antibiotics-based approaches.

Phytochemistry, Pharmacology and Mode of Action of the Anti-Bacterial Artemisia Plants

Over 70,000 people die of bacterial infections worldwide annually. Antibiotics have been liberally used to treat these diseases and, consequently, antibiotic resistance and drug ineffectiveness has been generated. In this environment, new anti-bacterial compounds are being urgently sought. Around 500 Artemisia species have been identified worldwide. Most species of this genus are aromatic and have multiple functions. Research into the Artemisia plants has expanded rapidly in recent years. Herein, we aim to update and summarize recent information about the phytochemistry, pharmacology and toxicology of the Artemisia plants. A literature search of articles published between 2003 to 2022 in PubMed, Google Scholar, Web of Science databases, and KNApSAcK metabolomics databases revealed that 20 Artemisia species and 75 compounds have been documented to possess anti-bacterial functions and multiple modes of action. We focus and discuss the progress in understanding the chemistry (structure and plant species source), anti-bacterial activities, and possible mechanisms of these phytochemicals. Mechanistic studies show that terpenoids, flavonoids, coumarins and others (miscellaneous group) were able to destroy cell walls and membranes in bacteria and interfere with DNA, proteins, enzymes and so on in bacteria. An overview of new anti-bacterial strategies using plant compounds and extracts is also provided.

18β-Glycyrrhetinic Acid Induces Metabolic Changes and Reduces Staphylococcus aureus Bacterial Cell-to-Cell Interactions

The rise in bacterial resistance to common antibiotics has raised an increased need for alternative treatment strategies. The natural antibacterial product, 18β-glycyrrhetinic acid (GRA) has shown efficacy against community-associated methicillin-resistant Staphylococcus aureus (MRSA), although its interactions against planktonic and biofilm modes of growth remain poorly understood. This investigation utilized biochemical and metabolic approaches to further elucidate the effects of GRA on MRSA. Prolonged exposure of planktonic MRSA cell cultures to GRA resulted in increased production of staphyloxanthin, a pigment known to exhibit antioxidant and membrane-stabilizing functions. Then, 1D ¹H NMR analyses of intracellular metabolite extracts from MRSA treated with GRA revealed significant changes in intracellular polar metabolite profiles, including increased levels of succinate and citrate, and significant reductions in several amino acids, including branch chain amino acids. These changes reflect the MRSA response to GRA exposure, including potentially altering its membrane composition, which consumes branched chain amino acids and leads to significant energy expenditure. Although GRA itself had no significant effect of biofilm viability, it seems to be an effective biofilm disruptor. This may be related to interference with cell–cell aggregation, as treatment of planktonic MRSA cultures with GRA leads to a significant reduction in micro-aggregation. The dispersive nature of GRA on MRSA biofilms may prove valuable for treatment of such infections and could be used to increase susceptibility to complementary antibiotic therapeutics.

Artemisinin elevates ergosterol levels of Candida albicans to synergise with amphotericin B against oral candidiasis

Oral candidiasis, especially caused by Candida albicans, is the most common fungal infection of the oral cavity. The increase in drug resistance and lack of new antifungal agents call for new strategies of antifungal treatment. This study repurposed artemisinin (Art) as a potentiator to the polyene amphotericin B (AmB) and characterised their synergistic mechanism against C. albicans and oral candidiasis. The synergistic antifungal activity between Art and AmB was identified by the checkerboard and recovery plate assays according to the fractional inhibitory concentration index (FICI). Art showed no antifungal activity even at >200 mg/L. However, it significantly reduced AmB dosages against the wild-type strain and 75 clinical isolates of C. albicans (FICI ≤ 0.5). Art significantly upregulated expression of genes from the ergosterol biosynthesis pathway (ERG1, ERG3, ERG9 and ERG11), as shown by RT-qPCR, and elevated the ergosterol content of Candida cells. Increased ergosterol content significantly enhanced binding between fungal cells and the polyene agent, resulting in sensitisation of C. albicans to AmB. Drug combinations of Art and AmB showed synergistic activity against oral mucosal infection in vivo by reducing the epithelial infection area, fungal burden and inflammatory infiltrates in murine oropharyngeal candidiasis. These findings indicate a novel synergistic antifungal drug combination and a new Art mechanism of action, suggesting that drug repurposing is a clinically practical means of antifungal drug development and treatment of oral candidiasis.

Artesunate inhibits Staphylococcus aureus biofilm formation by reducing alpha-toxin synthesis

Staphylococcus aureus is one of the most common pathogens in bacterial biofilm infections. Antibiotic treatment for infection caused by S. aureus biofilms is challenging, and few effective strategies have been developed to combat these infections. The aim of this study was to investigate the effect and possible mechanisms of artesunate on the biofilm formation of S. aureus. Bacterial growth curves were determined by a microtiter plate. Biofilm formation was determined by the crystal violet staining method and confocal laser scanning microscopy. Bacterial adhesion was assayed by the colony-counting method. The expression of virulence and adhesion genes was determined by real-time PCR. The hemolytic activity and expression of ɑ-hemolysin were analyzed using rabbit erythrocytes and Western blotting. The results showed that artesunate could significantly inhibit the biofilm formation of S. aureus in a dose-dependent manner. Artesunate could also inhibit bacterial adhesion and the expression of hla, RNAIII and agrA as well as ɑ-hemolysin production. The effect of artesunate on adhesion genes (clfA, clfB, fnbA, fnbB) had strain specificity, but it did not affect the expression of ica genes. The results indicated that artesunate might inhibit ɑ-hemolysin synthesis by the agr system, which inhibits biofilm formation.

Efficacy of Artesunate against Pseudomonas aeruginosa Biofilm Mediated by Iron

Pseudomonas aeruginosa is capable of causing a variety of chronic infections due to the formation of biofilms. Iron is essential for growth of Pseudomonas aeruginosa, and therapies that interfere with iron may help treat P. aeruginosa infections. Herein, we investigated whether artesunate, which is a type of iron-dependent drug, could influence Pseudomonas aeruginosa biofilm formation and structure, including the underlying mechanisms. Artesunate could enhance twitching motility significantly and decrease the proportion of surviving cells in Pseudomonas aeruginosa biofilms in a dose-dependent manner. Artesunate treatment also reduced biofilm thickness, diffusion in the biomass, and the content of Fe(II). However, changes in biofilm structure and ion concentration were very similar following treatment with 512 μg/ml and 1024 μg/ml artesunate. Interestingly, both biofilm structure and surviving cell fraction were recovered after iron supplementation. These results suggest that artesunate interferes with Pseudomonas aeruginosa biofilms by decreasing bacterial viability and enhancing twitching motility in an iron-independent manner.

Use of artesunate in non-malarial indications

INTRODUCTION

Artesunate and other artemisinin derivatives are used in various infectious and non-infectious diseases. We aimed to analyze available data on artesunate and artemisinin derivatives activity in humans and their potential clinical benefits in non-malarial indications.

MATERIAL AND METHODS

Literature review performed on PubMed and the Cochrane Library databases using the PRISMA method. We analyzed studies published in English from January 2008 to August 2017 using the same indicators of drug efficacy.

RESULTS

We included 19 studies performed in humans (1 meta-analysis, 1 literature review, 4 randomized controlled trials, 3 prospective controlled trials, 3 prospective uncontrolled trials, 2 exploratory phase 1 or 2 trials, 1 case series, and 4 case reports). Artesunate and artemisinin derivatives demonstrated efficacy in the treatment of schistosomiasis in combination with praziquantel (P=0.003). Artesunate monotherapy was less effective than praziquantel alone (P<0.001) probably because its activity only affects the early stages of Schistosoma parasites. Artesunate monotherapy could be interesting as a chemoprophylactic drug against schistosomiasis (P<0.001). Findings seem promising but are still controversial in the treatment of multidrug-resistant CMV infections. Studies do not conclude on artesunate and artemisinin derivatives efficacy in the treatment of cervix, breast, colorectal, and lung cancers.

CONCLUSION

Artesunate and artemisinin derivatives in combination with praziquantel were effective against schistosomiasis, and could be used as a chemoprophylactic drug alone. They could be interesting as anti-CMV and anti-tumor treatment. Additional trials in humans are required to assess the efficacy of artesunate and artemisinin derivatives in diseases other than malaria.

Efficacy of ampicillin against methicillin-resistant Staphylococcus aureus restored through synergy with branched poly(ethylenimine)

Beta-lactam antibiotics kill Staphylococcus aureus bacteria by inhibiting the function of cell-wall penicillin binding proteins (PBPs) 1 and 3. However, β-lactams are ineffective against PBP2a, used by methicillin-resistant Staphylococcus aureus (MRSA) to perform essential cell wall crosslinking functions. PBP2a requires teichoic acid to properly locate and orient the enzyme, and thus MRSA is susceptible to antibiotics that prevent teichoic acid synthesis in the bacterial cytoplasm. As an alternative, we have used branched poly(ethylenimine), BPEI, to target teichoic acid in the bacterial cell wall. The result is restoration of MRSA susceptibility to the β-lactam antibiotic ampicillin with a MIC of 1 μg/mL, superior to that of vancomycin (MIC = 3.7 μg/mL). A checkerboard assay shows synergy of BPEI and ampicillin. Nuclear magnetic resonance (NMR) data show that BPEI alters the teichoic acid chemical environment. Laser scanning confocal microscopy (LSCM) images show BPEI residing on the bacterial cell wall where teichoic acids and PBPs are located.

Effect of artesunate supplementation on bacterial translocation and dysbiosis of gut microbiota in rats with liver cirrhosis

AIM: To evaluate the effect of artesunate (AS) supplementation on bacterial translocation (BT) and gut microbiota in a rat model of liver cirrhosis.

METHODS: Fifty-four male Sprague-Dawley rats were randomly divided into a normal control group (N), a liver cirrhosis group (M) and a liver cirrhosis group intervened with AS (MA). Each group was sampled at 4, 6 and 8 wk. Liver cirrhosis was induced by injection of carbon tetrachloride (CCl₄), intragastric administration of 10% ethanol, and feeding a high fat diet. Rats in the MA group were intragastrically administered with AS (25 mg/kg body weight, once daily). Injuries of the liver and intestinal mucosa were assessed by hematoxylin-eosin or Masson’s trichrome staining. Liver index was calculated as a ratio of the organ weight (g) to body weight (g). The gut microbiota was examined by automated ribosomal intergenic-spacer analysis of fecal DNA. BT was assessed by standard microbiological techniques in the blood, mesenteric lymph nodes (MLNs), liver, spleen, and kidney.

RESULTS: Compared to group N, the body weight was reduced significantly in groups M and MA due to the development of liver cirrhosis over the period of 8 wk. The body weight was higher in group MA than in group M. The liver indices were significantly elevated at 4, 6 and 8 wk in groups M and MA compared to group N. AS supplementation partially decreased the liver indices in group MA. Marked histopathologic changes in the liver and small intestinal mucosa in group M were observed, which were alleviated in group MA. Levels of pro-inflammatory interleukin-6 and tumor necrosis factor-α were significantly elevated at 8 wk in ileal homogenates in group M compared to group N, which were decreased after AS supplementation in group MA. The dysbiosis of gut microbiota indicated by the mean diversity (Shannon index) and mean similarity (Sorenson index) was severe as the liver cirrhosis developed, and AS supplementation had an apparent intervention effect on the dysbiosis of gut microbiota at 4 wk. The occurrence of BT was increased in the liver of group M compared to that of group N. AS supplementation reduced BT in group MA at 8 wk. BT also occurred in the MLNs, spleen, and kidney, which was reduced by AS supplementation. BT was not detected in the blood in any group.

CONCLUSION: Dysbiosis of gut microbiota, injury of intestinal mucosal barrier and BT occurred as liver cirrhosis progressed, which might enhance inflammation and aggravate liver injury. AS may have other non-antimalarial effects that modulate gut microbiota, inhibit BT and alleviate inflammation, resulting in a reduction in CCl₄, alcohol and high fat-caused damages to the liver and intestine.

Artesunate, an anti-malarial drug, has a potential to inhibit HCV replication

Hepatitis C virus (HCV) infection is a major global health issue. Although the search for HCV treatments has resulted in great achievements, the current treatment methods have limitations, and new methods and drugs for hepatitis C treatment are still required. The aim of the present study was to investigate the effects of artesunate (ART) on HCV replication and compared these effects with those of ribavirin (RBV) and interferon-2b (IFN). The study was performed in HCV-infection cell models (JFH1-infected Huh7.5.1 and OR6 cell lines). Our results showed that the antimalarial drug ART inhibited HCV replicon replication in a dose- and time-dependent manner at a concentration that had no effect on the proliferation of exponentially growing host cells, and the inhibitory effect on HCV replication was stronger than RBV but weaker than IFN, as determined by qPCR, luciferase assays, and Western blot analysis. Furthermore, the combination of ART and IFN resulted in a greater inhibition of HCV replication. These findings demonstrated that ART had an inhibitive effect on HCV replication and may be a novel supplemental co-therapy with IFN and RBV for HCV and as an alternative strategy to combat resistance mechanisms that have emerged in the presence of DAA agents.