Anethole potentiates dodecanol's fungicidal activity by reducing PDR5 expression in budding yeast

Deciphering the antifungal mechanism and functional components of cinnamomum cassia essential oil against Candida albicans through integration of network-based metabolomics and pharmacology, the greedy algorithm, and molecular docking

ETHNOPHARMACOLOGICAL RELEVANCE

Fungal pathogens can cause deadly invasive infections and have become a major global public health challenge. There is an urgent need to find new treatment options beyond established antifungal agents, as well as new drug targets that can be used to develop novel antifungal agents. Cinnamomum cassia is a tropical aromatic plant that has a wide range of applications in traditional Chinese medicine, especially in the treatment of bacterial and fungal infections.

AIM OF THE STUDY

The present study aimed to explore the mechanism of action and functional components of Cinnamomum cassia essential oil (CEO) against Candida albicans using an integrated strategy combining network-based metabolomics and pharmacology, the greedy algorithm and molecular docking.

MATERIALS AND METHODS

CEO was extracted using hydrodistillation and its chemical composition was identified by GC-MS. Cluster analysis was performed on the compositions of 19 other CEOs from the published literature, as well as the sample obtained in this study. The damages of C. albicans cells upon treatment with CEO was observed using a scanning electron microscope. The mechanisms of its antifungal effect at a subinhibitory concentration of 0.1 × MIC were determined using microbial metabolomics and network analysis. The functional components were studied using the greedy algorithm and molecular docking.

RESULTS

A total of 69 compounds were identified in the chemical analysis of CEO, which accounted for 90% of the sample. The major compounds were terpenoids (34.04%), aromatic compounds (4.52%), aliphatic compounds (0.9%), and others. Hierarchical cluster analysis of the compositions of 20 essential oils extracted from Cinnamomum cassia grown in different geographical locations showed a wide diversity of chemical composition with four major chemotypes. CEO showed strong antifungal activity and caused destruction of cell membranes in a concentration-dependent way. Metabolic fingerprint analysis identified 29 metabolites associated with lipid metabolism, which were mapped to 23 core targets mainly involved in fatty acid biosynthesis and metabolism. Six antifungal functional components of CEO were identified through network construction, greedy algorithm and molecular docking, including trans-cinnamaldehyde, δ-cadinol, ethylcinnamate, safrole, trans-anethole, and trans-cinnamyl acetate, which showed excellent binding with specific targets of AKR1B1, PPARG, BCHE, CYP19A1, CYP2C19, QPCT, and CYP51A1.

CONCLUSIONS

This study provides a systematic understanding of the antifungal activity of CEO and offers an integrated strategy for deciphering the potential metabolism and material foundation of complex component drugs.

Development and characterization of trans-anethole-containing solid lipid microparticles: antiinflammatory and gastroprotective effects in experimental inflammation

The present study prepared, optimized, and characterized solid lipid microparticles that contained trans-anethole (SLMAN), evaluated their antiinflammatory activity in acute and chronic inflammation models, and investigated their effects on the gastric mucosa in arthritic rats. The microparticles were obtained by a hot homogenization process and characterized by physicochemical analyses. The acute inflammatory response was induced by an intradermal injection of 0.1 ml of carrageenan solution (200 μg) in the hind paw. The rats were treated orally with a single dose of SLMAN 1 h before induction of the inflammatory response. The chronic inflammatory response was induced by the subcutaneous application of 0.1 ml of complete Freund's adjuvant suspension (500 µg) in the hind paw. SLMAN was orally administered, starting on the day of arthritis induction, and continued for 21 days. The results showed that SLMAN was obtained with good encapsulation efficiency. Treatment with SLMAN at doses of 25 and 50 mg/kg was as effective as trans-anethole (AN) at a dose of 250 mg/kg on acute and chronic inflammatory responses. Histological analyses showed that treatment with SLMAN did not aggravate lesions in the gastric mucosa in arthritic rats. These results indicated that treatment with SLMAN at a dose that was 5-10 times lower than non-encapsulated AN exerted an inhibitory effect on acute and chronic inflammatory responses, suggesting the better bioavailability and efficacy of microencapsulated AN without aggravating lesions in the gastric mucosa in arthritic rats.

Phytochemical Screening, Nutritional Value, Anti-Diabetic, Anti-Cancer, and Anti-Bacterial Assessment of Aqueous Extract from Abelmoschus esculentus Pods

Known for its high nutritional and medicinal value, okra (Abelmoschus esculentus) is commonly used for replacing plasma and expanding blood volume in humans. It is a major economic crop cultivated in tropical and subtropical regions worldwide. The present study aimed to investigate and evaluate the nutritional properties and prospective applications of the consumable parts of okra. The total ash content (mineral content), carbohydrate, crude fiber, fat, protein, and moisture fractions of okra pod aqueous extract were determined. The results show that okra aqueous extract contained 84.670–87.650% moisture, 1.514–1.197% ash, 7.857–8.261% carbohydrate, 2.367–3.410% crude protein, and 6.781–8.314% crude fiber. Okra was determined to have high nutritional value, with γ-tocopherol and α-tocopherol contents about 2.67 mg/100 g and 1.62 mg/100 g, respectively. High-performance liquid chromatography (HPLC) was performed to determine the sugars present in okra aqueous extract. The water-soluble polysaccharide content was 10.22–16.45 g/100 g. The tested aqueous extract was a rich source of total phenolic compounds in gallic acid equivalents (288.2–3426.2 mg/100 g), chlorophyll a (3.53 mg/100), chlorophyll b (2.43 mg/100), and carotenoids (1.3 mg/100 g). The detected minerals were Ca, Mg, Cu, Zn, Fe, K, Na, and Mn. Atomic absorption spectrometry analysis of these ashed minerals was performed. In addition to the nutritional benefits, okra pods exhibited antimicrobial, anticancer, and antioxidant properties. The aqueous extract was found to be potentially active against bacterial strains of Staphylococcus aureus (MIC value = 21.8 mg/mL), Escherichia coli (MIC value = 18.7 mg/mL), Bacillus cereus (MIC value = 20.7 mg/mL), and Klebsiella pneumoniae (MIC value = 20.2 mg/mL). Okra aqueous extract exhibited inhibitory activity against α-amylase (IC50 = 120 µg/mL) and α-glucosidase (IC50 = 115 µg/mL). The okra extract exhibited high anticancer activity, concentration-dependent and with an IC50 value of about 158.3 mg/mL. The results indicated that okra pods have nutritional and medicinal properties and, hence, can be used as a functional food and broad-spectrum nutraceutical supplement.

Structure-activity relationships of antifungal phenylpropanoid derivatives and their synergy with n-dodecanol and fluconazole

trans-Anethole (anethole) is a phenylpropanoid; with other drugs, it exhibits synergistic activity against several fungi and is expected to be used in new therapies that cause fewer patient side effects. However, the detailed substructure(s) of the molecule responsible for this synergy has not been fully elucidated. We investigated the structure-activity relationships of phenylpropanoids and related derivatives, with particular attention on the methoxy group and the double bond of the propenyl group in anethole, as well as the length of the p-alkyl chain in p-alkylanisoles. Antifungal potency was largely related to p-alkyl chain length and the methoxy group of anethole, but not to the double bond of its propenyl group. Production of reactive oxygen species also played a role in these fungicidal activities. Inhibition of drug efflux was associated with the length of the p-alkyl chain and the double bond of the propenyl group in anethole, but not with the methoxy group. Although a desirable synergy was observed between n-dodecanol and anethole or p-alkylanisoles with a length of C2-C6 in alkyl chains, it cannot be explained away as being solely due to the inhibition of drug efflux. Similar results were obtained when phenylpropanoid derivatives were combined with fluconazole against Candida albicans.

Exploring the biological function of efflux pumps for the development of superior industrial yeasts

Among the mechanisms used by yeasts to overcome the deleterious effects of chemical and other environmental stresses is the activity of plasma membrane efflux pumps involved in multidrug resistance (MDR), a role on the focus of intensive research for years in pathogenic yeasts. More recently, these active transporters belonging to the MFS (Drug: H⁺ antiporters) or the ABC superfamily have been involved in resistance to xenobiotic compounds and in the transport of substrates with a clear physiological role. This review paper focuses on these putative efflux pumps concerning their tolerance phenotypes towards bioprocess-specific multiple stress factors, expression levels, physiological roles, and mechanisms by which they may lead to multistress resistance. Their association with the increased secretion of metabolites and other bioproducts and in the development of more robust superior strains for Yeast Chemical Biotechnology is highlighted.

Involvement of a Multidrug Efflux Pump and Alterations in Cell Surface Structure in the Synergistic Antifungal Activity of Nagilactone E and Anethole against Budding Yeast Saccharomyces cerevisiae

Nagilactone E, an antifungal agent derived from the root bark of Podocarpus nagi, inhibits 1,3-β glucan synthesis; however, its inhibitory activity is weak. Anethole, the principal component of anise oil, enhances the antifungal activity of nagilactone E. We aimed to determine the combinatorial effect and underlying mechanisms of action of nagilactone E and anethole against the budding yeast Saccharomyces cerevisiae. Analyses using gene-deficient strains showed that the multidrug efflux pump PDR5 is associated with nagilactone E resistance; its transcription was gradually restricted in cells treated with the drug combination for a prolonged duration but not in nagilactone-E-treated cells. Green-fluorescent-protein-tagged Pdr5p was intensively expressed and localized on the plasma membrane of nagilactone-E-treated cells but not in drug-combination-treated cells. Quick-freeze deep-etch electron microscopy revealed the smoothening of intertwined fiber structures on the cell surface of drug-combination-treated cells and spheroplasts, indicating a decline in cell wall components and loss of cell wall strength. Anethole enhanced the antifungal activity of nagilactone E by enabling its retention within cells, thereby accelerating cell wall damage. The combination of nagilactone E and anethole can be employed in clinical settings as an antifungal, as well as a food preservative to restrict food spoilage.

Functional and transcriptional profiling of non-coding RNAs in yeast reveal context-dependent phenotypes and in trans effects on the protein regulatory network

Non-coding RNAs (ncRNAs), including the more recently identified Stable Unannotated Transcripts (SUTs) and Cryptic Unstable Transcripts (CUTs), are increasingly being shown to play pivotal roles in the transcriptional and post-transcriptional regulation of genes in eukaryotes. Here, we carried out a large-scale screening of ncRNAs in Saccharomyces cerevisiae, and provide evidence for SUT and CUT function. Phenotypic data on 372 ncRNA deletion strains in 23 different growth conditions were collected, identifying ncRNAs responsible for significant cellular fitness changes. Transcriptome profiles were assembled for 18 haploid ncRNA deletion mutants and 2 essential ncRNA heterozygous deletants. Guided by the resulting RNA-seq data we analysed the genome-wide dysregulation of protein coding genes and non-coding transcripts. Novel functional ncRNAs, SUT125, SUT126, SUT035 and SUT532 that act in trans by modulating transcription factors were identified. Furthermore, we described the impact of SUTs and CUTs in modulating coding gene expression in response to different environmental conditions, regulating important biological process such as respiration (SUT125, SUT126, SUT035, SUT432), steroid biosynthesis (CUT494, SUT053, SUT468) or rRNA processing (SUT075 and snR30). Overall, these data capture and integrate the regulatory and phenotypic network of ncRNAs and protein-coding genes, providing genome-wide evidence of the impact of ncRNAs on cellular homeostasis.

A quarter of the yeast genome comprises non-coding RNA molecules (ncRNAs), which do not translate into proteins but are involved in the regulation of gene expression. ncRNAs can affect nearby genes by physically interfering with their transcription (cis mode of action), or they interact with DNA, proteins or other RNAs to regulate the expression of distant genes (trans mode of action). Examples of cis-acting ncRNAs have been broadly described, however, genome-wide studies to identify functional trans-acting ncRNAs involved in global gene regulation are still lacking. Here, we used a ncRNA yeast deletion collection to score ncRNA impact on cellular function in different environmental conditions. A group of 20 ncRNA deletion mutants with broad fitness diversity were selected to investigate the ncRNA effect on the protein and ncRNA expression network. We showed a high correlation between altered phenotypes and global transcriptional changes, in an environmental dependent manner. We confirmed the trans acting regulation of ncRNAs in the genome and their role in altering the expression of transcription factors. These findings support the notion of the involvement of ncRNAs in fine tuning cellular expression via regulation of transcription factors, as an advantageous RNA-mediated mechanism that can be fast and cost-effective for the cells.

Anticancer Activities and Mechanism of Action of Nagilactones, a Group of Terpenoid Lactones Isolated from Podocarpus Species

Nagilactones are tetracyclic natural products isolated from various Podocarpus species. These lactone-based compounds display a range of pharmacological effects, including antifungal, anti-atherosclerosis, anti-inflammatory and anticancer activities reviewed here. The most active derivatives, such as nagilactones C, E and F, exhibit potent anticancer activities against different cancer cell lines and tumor models. A comprehensive analysis of their mechanism of action indicates that their anticancer activity mainly derives from three complementary action: (i) a drug-induced inhibition of cell proliferation coupled with a cell cycle perturbation and induction of apoptosis, (ii) a blockade of the epithelial to mesenchymal cell transition contributing to an inhibition of cancer cell migration and invasion and (iii) a capacity to modulate the PD-L1 immune checkpoint. Different molecular effectors have been implicated in the antitumor activity, chiefly the AP-1 pathway blocked upon activation of the JNK/c-Jun axis. Nag-C is a potent inhibitor of protein synthesis binding to eukaryotic ribosomes and inhibition of different protein kinases, such as RIOK2 and JAK2, has been postulated with Nag-E. The literature survey on nagilactones highlights the therapeutic potential of these little-known terpenoids. The mechanistic analysis also provides useful information for structurally related compounds (podolactones, oidiolactones, inumakilactones) isolated from Podocarpus plants.

Chemical Composition, Nutritional Value, and Biological Evaluation of Tunisian Okra Pods (Abelmoschus esculentus L. Moench)

The aim of this work was to perform an unprecedented in-depth study on the bioactive phytochemicals of Abelmoschus esculentus L. Moench Tunisian landrace (Marsaouia). For this purpose, its nutritional, aroma volatile, and phenolic profiles were characterized, and sundry biological activities were assessed in vitro. The approximate composition revealed that total dietary fiber as the most abundant macronutrient, mainly insoluble dietary fiber, followed by total carbohydrates and proteins. In addition, okra pods were rich in K, Ca, Mg, organic acids, tocopherols, and chlorophylls. Gas Chromatography-Electron Impact Mass Spectrometry (GC-EIMS) analysis showed that oxygenated monoterpenes, sesquiterpene hydrocarbons, and phenylpropanoids were the predominant essential volatile components in A. esculentus pods. A total of eight flavonols were detected by High-Performance Liquid Chromatography coupled to a DAD detector and mass spectrometry by electrospray ionization (HPLC-DAD-MS/ESI); with quercetin-3-O-glucoside being the majority phenolic component, followed by quercetin-O-pentosyl-hexoside and quercetin-dihexoside. This pioneering study, evidences that Tunisian okra display promising antioxidant and cytotoxic actions, in addition to relevant inhibitory effects against α-amylase and α-glucosidase enzymes, and interesting analgesic activity.

Deletion of the Golgi Ca2+-ATPase PMR1 gene potentiates antifungal effects of dodecanol that depend on intracellular Ca2+ accumulation in budding yeast

One strategy for overcoming infectious diseases caused by drug-resistant fungi involves combining drugs rendered inactive by resistance with agents targeting the drug resistance mechanism. The antifungal activity of n-dodecanol disappears as incubation time passes. In Saccharomyces cerevisiae, anethole, a principal component of anise oil, prolongs the transient antifungal effect of dodecanol by downregulating genes of multidrug efflux pumps, mainly PDR5. However, the detailed mechanisms of dodecanol's antifungal action and the anethole-induced prolonged antifungal action of dodecanol are unknown. Screening of S. cerevisiae strains lacking genes related to Ca2+ homeostasis and signaling identified a pmr1Δ strain lacking Golgi Ca2+-ATPase as more sensitive to dodecanol than the parental strain. Dodecanol and the dodecanol + anethole combination significantly increased intracellular Ca2+ levels in both strains, but the mutant failed to clear intracellular Ca2+ accumulation. Further, dodecanol and the drug combination reduced PMR1 expression and did not lead to specific localization of Pmr1p in the parental strain after 4-h treatment. By contrast with the parental strain, dodecanol did not stimulate PDR5 expression in pmr1Δ. Based on these observations, we propose that the antifungal activity of dodecanol is related to intracellular Ca2+ accumulation, possibly dependent on PMR1 function, with anethole enabling Ca2+ accumulation by restricting dodecanol efflux.

Dioscin Inhibits Virulence Factors of Candida albicans

Candida albicans infections present a heavy burden upon public health, with only a few drugs available, while biofilms formed by C. albicans worsen this situation. Dioscin has antitumor, anti-inflammatory, and hepatoprotective effects, and this study was conducted to evaluate the effects of dioscin on the biofilm formation and development, as well as other virulence factors of C. albicans such as morphological transition, adhesion, and extracellular secreted phospholipase. Our results showed dioscin inhibits these virulence factors and has low cytotoxicity against mammalian cells. Considering protective effects of dioscin against damage on liver and kidney, dioscin may be used as a potential candidate for antifungal development.

Curcumin potentiates the fungicidal effect of dodecanol by inhibiting drug efflux in wild-type budding yeast

Drug resistance commonly occurs when treating immunocompromised patients who have fungal infections. Curcumin, is a compound isolated from Curcuma longa, has been reported to inhibit drug efflux in several human cell lines and nonpathogenic budding yeast Saccharomyces cerevisiae cells that overexpresses the ATP-binding cassette (ABC) transporters S. cerevisiae Pdr5p and pathogenic Candida albicans Cdr1p and Cdr2p. The aim of this study was to examine the effects of curcumin on multidrug resistance in a wild-type strain of the budding yeast with an intrinsic expression system of multidrug efflux-related genes. The antifungal activity of dodecanol alone was temporary against S. cerevisiae; however, restoration of cell viability was completely inhibited when the cells were co-treated with dodecanol and curcumin. Furthermore, restriction of rhodamine 6G (R6G) efflux from the cells and intracellular accumulation of R6G were observed with curcumin treatment. Reverse transcription-polymerase chain reaction analysis revealed that curcumin reduced the dodecanol-induced overexpression of the ABC transporter-related genes PDR1, PDR3 and PDR5 to their control levels in untreated cells. Curcumin can directly restrict the glucose-induced drug efflux and inhibits the expression of the ABC transporter gene PDR5, and can thereby inhibit the efflux of dodecanol from S. cerevisiae cells. Curcumin is effective in potentiating the efficacy of antifungal drugs via its effects on ABC transporters. SIGNIFICANCE AND IMPACT OF THE STUDY: Drug resistance is common in immunocompromised patients with fungal infections. Curcumin, isolated from Curcuma longa, inhibits drug efflux in nonpathogenic budding yeast Saccharomyces cerevisiae cells overexpressing ABC transporters S. cerevisiae Pdr5p and pathogenic Candida albicans Cdr1p and Cdr2p. We examined the effects of curcumin on multidrug resistance in a wild-type strain of the budding yeast with an intrinsic expression system of multidrug efflux-related genes. Curcumin directly inhibited drug efflux and also suppressed the PDR5 expression, thereby enhancing the antifungal effects. Thus, curcumin potentially promotes the efficacy of antifungals via its effects on ABC transporters in wild-type fungal strains.

Effect of nagilactone E on cell morphology and glucan biosynthesis in budding yeast Saccharomyces cerevisiae

Nagilactones are norditerpene dilactones isolated from the root bark of Podocarpus nagi. Although nagilactone E has been reported to show antifungal activities, its activity is weaker than that of antifungals on the market. Nagilactone E enhances the antifungal activity of phenylpropanoids such as anethole and isosafrole against nonpathogenic Saccharomyces cerevisiae and pathogenic Candida albicans. However, the detailed mechanisms underlying the antifungal activity of nagilactone E itself have not yet been elucidated. Therefore, we investigated the antifungal mechanisms of nagilactone E using S. cerevisiae. Although nagilactone E induced lethality in vegetatively growing cells, it did not affect cell viability in non-growing cells. Nagilactone E-induced morphological changes in the cells, such as inhomogeneous thickness of the glucan layer and leakage of cytoplasm. Furthermore, a dose-dependent decrease in the amount of newly synthesized (1, 3)-β-glucan was detected in the membrane fractions of the yeast incubated with nagilactone E. These results suggest that nagilactone E exhibits an antifungal activity against S. cerevisiae by depending on cell wall fragility via the inhibition of (1, 3)-β-glucan biosynthesis. Additionally, we confirmed nagilactone E-induced morphological changes of a human pathogenic fungus Aspergillus fumigatus. Therefore, nagilactone E is a potential antifungal drug candidate with fewer adverse effects.