Prophylactic and therapeutic mouse models for evaluating immunologic resilience to infection with influenza virus by Immulina® (Part 1).

BACKGROUND: Illness resulting from influenza is a global health problem that has significant adverse socioeconomic impact. Although various strategies such as flu vaccination have beneficial effects, the risk of this illness has not been eliminated. The use of botanicals may provide a complementary approach by enhancement of the host antiviral immune response. PURPOSE: Generate preclinical data using rodent models to determine the most effective utility of a Limnospira (formerly Arthrospira)-derived oral supplement (Immulina®) for enhancing host immunity to improve antiviral resilience. STUDY DESIGN: Two non-lethal mouse models (prophylactic and therapeutic) were used to evaluate the impact of Immulina® on increasing host resilience against experimental influenza infection. METHODS: Mice were fed Immulina® only for the 2 weeks prior to viral infection (prophylactic regime) or starting 3 days post-viral infection (at the onset of symptoms, therapeutic design). Three doses of Immulina® were evaluated in each model using both female and male mice. RESULTS: Significant protective effect of Immulina® against viral illness was observed in the prophylactic model (improved clinical scores, less body weight loss, decreased lung/body weight ratio, lower lung viral load, and increased lung IFN-γ and IL-6). Substantially less (minimal) protective effect was observed in the therapeutic model. CONCLUSION: This study demonstrates that Immulina® exerts a protective effect against influenza illness when administered using a prophylactic regime and may not be effective if given after the onset of symptoms. The results will help to optimally design future clinical trials.

Immulina® mitigates the development of illness when administered during the prodromal period of influenza viral infection in mice (Part 2).

BACKGROUND: Immulina®, a dietary supplement derived from Limnospira (formerly Arthrospira), is being investigated as a potential agent to increase antiviral resilience. In our recently published manuscript, we described the effects of Immulina® on influenza when taken daily, beginning before infection (prophylaxis) or after the onset of clinical symptoms of viral illness (therapeutic). However, the benefit of Immulina® in infected individuals before the manifestation of any symptoms (prodromal) has not been investigated yet. PURPOSE: To evaluate Immulina®'s potential use to increase the host antiviral immune response using a prodromal therapy regime. STUDY DESIGN: The efficacy of Immulina® extract was evaluated in rodents using a prodromal protocol (test material administered prior to the emergence of viral illness symptoms). METHODS: Immulina® (25, 50 and 100 mg/kg body weight) was orally administered to both genders of mice, 2 h following influenza A viral infection, and continued daily for 14 days. RESULTS: Compared to the infected control mice, animals fed Immulina® exhibited statistically significant reduction in the emergence of various physical symptoms of viral-induced illness and decreased viral RNA levels. The effects are likely mediated through the host immune system since the level of various cytokines (IL-6 and IFN-γ) were significantly increased in lung tissue. CONCLUSION: This study, together with our previous paper, indicate that Immulina® was most effective at enhancing immune antiviral resilience if administered before or soon after initial infection. The data generated can be used to guide additional research using human subjects.

Identification of Botanicals that Unmask ß-Glucan from the Cell Surface of an Opportunistic Fungal Pathogen.

Dectin-1 expressed on host immune cells recognizes ß-glucans within the cell walls of fungal pathogens and plays an important role in the clearance of fungal infections. However, because ß-glucan is masked by an outer layer of mannoproteins, fungal pathogens can evade detection by host immune cells. In this study, a microplate-based screen was developed to identify ß-glucan unmasking activity exhibited by botanicals. This screen measures the activity of a reporter gene in response to the transcriptional activation of NF-κB due to the interaction between ß-glucan on the fungal cell surface and Dectin-1 present on host immune cells. In this proof-of-concept study, we screened a collection of botanicals (10 plants and some of their reported pure compound actives) used in traditional medicine for their antifungal properties. Several hits were identified in samples that unmasked ß-glucan at sub-inhibitory concentrations. The hit samples were confirmed by fluorescent staining with a ß-glucan antibody, verifying that the samples identified in the screen did indeed unmask ß-glucan. These results indicate that the purported antifungal activities attributed to some botanicals may be due, at least in part, to the presence of compounds that exhibit ß-glucan unmasking activity. Enhanced exposure of cell wall ß-glucans would allow the host to build resilience against fungal infections by helping the immune system to detect the pathogen and mount a more effective clearance mechanism. This screen, together with direct killing/growth inhibition assays, may therefore serve as a valuable tool for substantiating the use of botanicals in preventing and/or treating fungal infections.

Isolation of Two Plasticizers, Bis(2-ethylhexyl) Terephthalate and Bis(2-ethylhexyl) Phthalate, from Capparis spinosa L. Leaves.

Many plants have been known to be contaminated and accumulate plasticizers from the environment, including water sources, soil, and atmosphere. Plasticizers are used to confer elasticity and flexibility to various fiber and plastic products. Consumption of plasticizers can lead to many adverse effects on human health, including reproductive and developmental toxicity, endocrine disruption, and cancer. Herein, we report for the first time that two plasticizers, bis(2-ethylhexyl) terephthalate (DEHT) and bis(2-ethylhexyl) phthalate (DEHP), have been isolated from the leaves of Capparis spinosa L. (the caper bush), a plant that is widely used in food seasonings and traditional medicine. 297 mg/kg of DEHT and 48 mg/kg of DEHP were isolated from dried and grounded C. spinosa L. leaves using column chromatography and semi-preparative high-performance liquid chromatography. Our study adds to the increase in the detection of plasticizers in our food and medicinal plants and to the alarming concern about their potential adverse effects on human health.

The Oligostilbene Gnetin H Is a Novel Glycolysis Inhibitor That Regulates Thioredoxin Interacting Protein Expression and Synergizes with OXPHOS Inhibitor in Cancer Cells.

Since aerobic glycolysis was first observed in tumors almost a century ago by Otto Warburg, the field of cancer cell metabolism has sparked the interest of scientists around the world as it might offer new avenues of treatment for malignant cells. Our current study claims the discovery of gnetin H (GH) as a novel glycolysis inhibitor that can decrease metabolic activity and lactic acid synthesis and displays a strong cytostatic effect in melanoma and glioblastoma cells. Compared to most of the other glycolysis inhibitors used in combination with the complex-1 mitochondrial inhibitor phenformin (Phen), GH more potently inhibited cell growth. RNA-Seq with the T98G glioblastoma cell line treated with GH showed more than an 80-fold reduction in thioredoxin interacting protein (TXNIP) expression, indicating that GH has a direct effect on regulating a key gene involved in the homeostasis of cellular glucose. GH in combination with phenformin also substantially enhances the levels of p-AMPK, a marker of metabolic catastrophe. These findings suggest that the concurrent use of the glycolytic inhibitor GH with a complex-1 mitochondrial inhibitor could be used as a powerful tool for inducing metabolic catastrophe in cancer cells and reducing their growth.

Structure and Antimicrobial Activity of Rare Lactone Lipids from the Sooty Mold (Scorias spongiosa).

Two new lactone lipids, scoriosin (1) and its methyl ester (2), with a rare furylidene ring joined to a tetrahydrofurandione ring, were isolated from Scorias spongiosa, commonly referred to as sooty mold. The planar structure of these compounds was assigned by 1D and 2D NMR. The conformational analysis of these molecules was undertaken to evaluate the relative and absolute configuration through GIAO NMR chemical shift analysis and ECD calculation. In addition to the potent antimicrobial activities, compound 2 strongly potentiated the activity of amphotericin B against Cryptococcus neoformans, suggesting the potential utility of this compound in combination therapies for treating cryptococcal infections.

Synthesis and In vitro Evaluation of Hydrazonomethyl-Quinolin-8-ol and Pyrazol-3-yl-Quinolin-8-ol Derivatives for Antimicrobial and Antimalarial Potential.

BACKGROUND: Quinoline is a well-established nucleus displaying various biological activities. Quinolin-8-ol-containing compounds are reported for antimicrobial as well as antimalarial activity. Hydrazone- and pyrazole-containing compounds are also reported for antimicrobial activity. In this work, we have synthesized hydrazonomethyl-quinolin-8-ol and pyrazol-3-yl-quinolin-8-ol derivatives retaining quinolin-8-ol along with hydrazone/pyrazole pharmacophores. OBJECTIVE: The objective of this work was to synthesise and evaluate in vitro hydrazonomethylquinolin- 8-ol and pyrazol-3-yl-quinolin-8-ol derivatives for antifungal, antibacterial and antimalarial activity. METHODS: Designed and synthesized hydrazonomethyl-quinolin-8-ol and pyrazol-3-yl-quinolin-8- ol derivatives were evaluated for antifungal (against Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans), antibacterial (against methicillin resistant Staphylococcus aureus (MRSA), Escherichia Coli, Pseudomonas aeruginosa and Klebsillae pneumoniae) as well as antimalarial (against Plasmodium falciparum D6 and W2 strains) activity. RESULTS: Hydrazonomethyl-quinolin-8-ol (15.1-15.28) and pyrazol-3-yl-quinolin-8-ol derivatives (16.1-16.21 and 20.1-20.18) were synthesized in good to moderate yield. One-pot synthesis of pyrazol- 3-yl-quinolin-8-ol derivatives (16.1-16.21 and 20.1-20.18) was achieved. Compounds 15.3, 15.6, 15.7, 15.9-15.14, 15.16-15.19, 15.22 and 15.24 were found more potent compared to reference standard fluconazole (IC50 = 3.20 µM) against C. albicans with IC50 value less than 3 µM. Compounds 15.1, 15.2, 15.21 and 15.23 showed almost similar activity to reference standard fluconazole against C. albicans. Compounds 15.1-15.3, 15.9-15.12, 15.14-15.17, and 15.21-15.23 also showed good activity against fluconazole-resistant strain A. fumigatus with IC50 value less than 3 µM. Compounds 15.2-15.4, 15.7, 15.9, 15.17, 15.20 showed good antimalarial activity against P. falciparum D6 as well as P. falciparum W2 with IC50 values of 1.84, 1.83, 1.56, 1.49, 1.45, 1.97, 1.68 µM and 1.86, 1.40, 1.19, 1.71, 1.16, 1.34, 1.61 µM, respectively. 5-Pyrazol-3-yl-quinolin-8-ol derivatives, such as 16.3, 16.5, 16.11, 16.13, 16.19, 16.20, also showed antimalarial activity against P. falciparum D6 and W2 strains with IC50 values of 2.23, 2.16, 2.99, 2.99, 2.73, 2.12 µM and 2.91, 3.60, 4.61, 2.71, 2.31, 2.66 µM, respectively. CONCLUSION: Most of the 5-hydrazonomethyl-quinolin-8-ol derivatives showed good antifungal activity against C. albicans, A. fumigatus and C. neoformans. Most of the 5-hydrazonomethylquinolin- 8-ol derivatives were found more potent than reference standard fluconazole. These derivatives may be considered as leads for further development of antifungal agents.

Benzoylcyclopropane Derivatives from Hypoxis hemerocallidea Corms.

Two monobenzoylcyclopropane (hypoxhemerol A (1: ) and hypoxhemeroloside G (2: )) and three dibenzoylcyclopropane (hypoxhemerol B (3: ), hypoxhemeroloside H (4: ), and hypoxhemeroloside I (5: )) derivatives were isolated from the hydro-alcoholic extract of Hypoxis hemerocallidea corms. This is the first instance where benzoylcyclopropane analogs were isolated from any natural source. Structure elucidation was mainly based on 1D- and 2D-NMR and HRESIMS data. The absolute configuration (2R, 4R) of 1: was determined via NOESY NMR and experimental and calculated ECD data analyses. Compounds 1: -5: and 11 recently reported metabolites (hypoxoside, obtuside A, interjectin, acuminoside, curcapicycloside, and hypoxhemerolosides A - F) were screened for in vitro antimicrobial activity against various bacterial and fungal strains. Curcapicycloside and acuminoside exhibited antibacterial activity against Escherichia coli with 78 and 79% inhibition at 20 µg/mL, respectively. Hypoxhemeroloside A showed mild antifungal activity against Cryptococcus neoformans with 63% inhibition at 20 µg/mL.

Schottiin, a new prenylated isoflavones from Psorothamnus schottii and antibacterial synergism studies between methicillin and fremontone against methicillin-resistant Staphylococcus aureus ATCC 1708.

Bioactivity guided isolation of an ethanol extract of the root of Psoromanthus schottii (Family Fabaceae) afforded a new prenylated isoflavone, named schottiin (5,7,5'-trihydroxy-4'-O-methyl-6'-(3,3-dimethylallyl)-isoflavone) (1), together with four other isoflavones, including fremontone (2), 5,7,4',5'-tetrahydroxy-2'-(3,3-dimethylallyl)-isoflavone (3), glycyrrhisoflavone (4) and fremontin (5), of which 3 and 4 identified as isomeric mixture. Structures of 1-5 were determined by full spectroscopic analyses. A comprehensive 2 D NMR spectral data has allowed revising the structure of fremontone as 2 from previously reported 2 A. Compound 2 showed weak in-vitro antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). A combination study using a checkerboard assay between fremontone (2) and methicillin exhibited a synergistic activity with 8-fold decrease in MIC of methicillin, as well as an additive effect with vancomycin against MRSA ATCC 1708. Compounds 1 and 2 also showed moderate antiplasmodial activity against chloroquine-sensitive (D6) and -resistant (W2) strains of Plasmodium falciparum with no cytotoxicity to mammalian Vero cells.

Efforts towards the inhibitor design for New Delhi metallo-beta-lactamase (NDM-1).

Antimicrobial stewardship is imperative when treating bacterial infections because the misuse and overuse of antibiotics have caused pathogens to develop life-threatening resistance mechanisms. The New Delhi metallo-beta-lactamase (NDM-1) is one of many enzymes that enable bacterial resistance. NDM-1 is a more recently discovered beta-lactamase with the ability to inactivate a wide range of beta-lactam antibiotics. Multiple NDM-1 inhibitors have been designed and tested; however, due to the complexity of the NDM-1 active site, there is currently no inhibitor on the market. Consequently, an infection caused by bacteria possessing the gene for the NDM-1 enzyme is a serious and potentially fatal complication. An abundance of research has been invested over the past decade in search of an NDM-1 inhibitor. This review aims to summarize various NDM-1 inhibitor designs that have been developed in recent years.

Phytochemical, Antiplasmodial, Cytotoxic and Antimicrobial Evaluation of a Southeast Brazilian Brown Propolis Produced by Apis mellifera Bees.

Seven phenolic compounds (ferulic acid, caffeic acid, 4-methoxycinnamic acid, 3,4-dimethoxycinnamic acid, 3-hydroxy-4-methoxybenzaldehyde, 3-methoxy-4-hydroxypropiophenone and 1-O,2-O-digalloyl-6-O-trans-p-coumaroyl-ß-D-glucopyranoside), a flavanonol (7-O-methylaromadendrin), two lignans (pinoresinol and matairesinol) and six diterpenic acids/alcohol (19-acetoxy-13-hydroxyabda-8(17),14-diene, totarol, 7-oxodehydroabietic acid, dehydroabietic acid, communic acid and isopimaric acid) were isolated from the hydroalcoholic extract of a Brazilian Brown Propolis and characterized by NMR spectral data analysis. The volatile fraction of brown propolis was characterized by CG-MS, composed mainly of monoterpenes and sesquiterpenes, being the major α-pinene (18.4 %) and ß-pinene (10.3 %). This propolis chemical profile indicates that Pinus spp., Eucalyptus spp. and Araucaria angustifolia might be its primary plants source. The brown propolis displayed significant activity against Plasmodium falciparum D6 and W2 strains with IC50 of 5.3 and 9.7 µg/mL, respectively. The volatile fraction was also active with IC50 of 22.5 and 41.8 µg/mL, respectively. Among the compounds, 1-O,2-O-digalloyl-6-O-trans-p-coumaroyl-ß-D-glucopyranoside showed IC50 of 3.1 and 1.0 µg/mL against D6 and W2 strains, respectively, while communic acid showed an IC50 of 4.0 µg/mL against W2 strain. Cytotoxicity was determined on four tumor cell lines (SK-MEL, KB, BT-549, and SK-OV-3) and two normal renal cell lines (LLC-PK1 and VERO). Matairesinol, 7-O-methylaromadendrin, and isopimaric acid showed an IC50 range of 1.8-0.78 µg/mL, 7.3-100 µg/mL, and 17-18 µg/mL, respectively, against the tumor cell lines but they were not cytotoxic against normal cell lines. The crude extract of brown propolis displayed antimicrobial activity against C. neoformans, methicillin-resistant Staphylococcus aureus, and P. aeruginosa at 29.9 µg/mL, 178.9 µg/mL, and 160.7 µg/mL, respectively. The volatile fraction inhibited the growth of C. neoformans at 53.0 µg/mL. The compounds 3-hydroxy-4-methoxybenzaldehyde, 3-methoxy-4-hydroxypropiophenone and 7-oxodehydroabietic acid were active against C. neoformans, and caffeic and communic acids were active against methicillin-resistant Staphylococcus aureus.

Identification of Antifungal Bisphosphocholines from Medicinal Gentiana Species.

Gentiana species including G. crassicaulis, G. macrophylla, G. dahurica, and G. straminea are used in traditional Chinese medicine as "Qinjiao" for the treatment of rheumatism, hepatitis, and pain. Four antifungal bisphosphocholines [irlbacholine (2) and three new analogues, gentianalines A-C (1, 3, and 4)] were identified from G. crassicaulis by a bioassay-guided fractionation and structure elucidation approach. Subsequent chemical analysis of 56 "Qinjiao" samples (45 from G. crassicaulis, five from G. macrophylla, three from G. dahurica, and three from G. straminea) showed that bisphosphocholines were present in all four Gentiana species, with irlbacholine as the major compound ranging from 2.0 to 6.2 mg per gram of dried material. Irlbacholine exhibited potent in vitro antifungal activity against Cryptococcus neoformans, Aspergillus fumigatus, Candida albicans, and Candida glabrata with minimum inhibitory concentration (MIC) values of 0.63, 1.25, 10.0, and 5.0 µg/mL, respectively. Identification of the bisphosphocholines, a rare class of antifungal natural products, in these medicinal plants provides scientific evidence to complement their medicinal use. The bisphosphocholines carrying a long aliphatic chain possess amphiphilic molecule-like properties with a tendency of retention in both normal and reversed-phase silica gel column chromatography and thereby may be neglected in natural products discovery. This report may stimulate interest in this class of compounds, which warrant the further study of other biological activities as well.

Puupehenone, a Marine-Sponge-Derived Sesquiterpene Quinone, Potentiates the Antifungal Drug Caspofungin by Disrupting Hsp90 Activity and the Cell Wall Integrity Pathway.

The cell wall-targeting echinocandin antifungals, although potent and well tolerated, are inadequate in treating fungal infections due to their narrow spectrum of activity and their propensity to induce pathogen resistance. A promising strategy to overcome these drawbacks is to combine echinocandins with a molecule that improves their activity and also disrupts drug adaptation pathways. In this study, we show that puupehenone (PUUP), a marine-sponge-derived sesquiterpene quinone, potentiates the echinocandin drug caspofungin (CAS) in CAS-resistant fungal pathogens. We have conducted RNA sequencing (RNA-seq) analysis, followed by genetic and molecular studies, to elucidate PUUP's CAS-potentiating mechanism. We found that the combination of CAS and PUUP blocked the induction of CAS-responding genes required for the adaptation to cell wall stress through the cell wall integrity (CWI) pathway. Further analysis showed that PUUP inhibited the activation of Slt2 (Mpk1), the terminal mitogen-activated protein (MAP) kinase in this pathway. We also found that PUUP induced heat shock response genes and inhibited the activity of heat shock protein 90 (Hsp90). Molecular docking studies predicted that PUUP occupies a binding site on Hsp90 required for the interaction between Hsp90 and its cochaperone Cdc37. Thus, we show that PUUP potentiates CAS activity by a previously undescribed mechanism which involves a disruption of Hsp90 activity and the CWI pathway. Given the requirement of the Hsp90-Cdc37 complex in Slt2 activation, we suggest that inhibitors of this complex would disrupt the CWI pathway and synergize with echinocandins. Therefore, the identification of PUUP's CAS-potentiating mechanism has important implications in the development of new antifungal combination therapies.IMPORTANCE Fungal infections cause more fatalities worldwide each year than malaria or tuberculosis. Currently available antifungal drugs have various limitations, including host toxicity, narrow spectrum of activity, and pathogen resistance. Combining these drugs with small molecules that can overcome these limitations is a useful strategy for extending their clinical use. We have investigated the molecular mechanism by which a marine-derived compound potentiates the activity of the antifungal echinocandin caspofungin. Our findings revealed a mechanism, different from previously reported caspofungin potentiators, in which potentiation is achieved by the disruption of Hsp90 activity and signaling through the cell wall integrity pathway, processes that play important roles in the adaptation to caspofungin in fungal pathogens. Given the importance of stress adaptation in the development of echinocandin resistance, this work will serve as a starting point in the development of new combination therapies that will likely be more effective and less prone to pathogen resistance.

Two plant-derived aporphinoid alkaloids exert their antifungal activity by disrupting mitochondrial iron-sulfur cluster biosynthesis.

Eupolauridine and liriodenine are plant-derived aporphinoid alkaloids that exhibit potent inhibitory activity against the opportunistic fungal pathogens Candida albicans and Cryptococcus neoformans However, the molecular mechanism of this antifungal activity is unknown. In this study, we show that eupolauridine 9591 (E9591), a synthetic analog of eupolauridine, and liriodenine methiodide (LMT), a methiodide salt of liriodenine, mediate their antifungal activities by disrupting mitochondrial iron-sulfur (Fe-S) cluster synthesis. Several lines of evidence supported this conclusion. First, both E9591 and LMT elicited a transcriptional response indicative of iron imbalance, causing the induction of genes that are required for iron uptake and for the maintenance of cellular iron homeostasis. Second, a genome-wide fitness profile analysis showed that yeast mutants with deletions in iron homeostasis-related genes were hypersensitive to E9591 and LMT. Third, treatment of wild-type yeast cells with E9591 or LMT generated cellular defects that mimicked deficiencies in mitochondrial Fe-S cluster synthesis including an increase in mitochondrial iron levels, a decrease in the activities of Fe-S cluster enzymes, a decrease in respiratory function, and an increase in oxidative stress. Collectively, our results demonstrate that E9591 and LMT perturb mitochondrial Fe-S cluster biosynthesis; thus, these two compounds target a cellular pathway that is distinct from the pathways commonly targeted by clinically used antifungal drugs. Therefore, the identification of this pathway as a target for antifungal compounds has potential applications in the development of new antifungal therapies.

Exploring the molecular basis of antifungal synergies using genome-wide approaches.

Drug resistance poses a significant challenge in antifungal therapy since resistance has been found for all known classes of antifungal drugs. The discovery of compounds that can act synergistically with antifungal drugs is an important strategy to overcome resistance. For such combination therapies to be effective, it is critical to understand the molecular basis for the synergism by examining the cellular effects exerted by the combined drugs. Genomic profiling technologies developed in the model yeast Saccharomyces cerevisiae have been successfully used to investigate antifungal combinations. This review discusses how these technologies have been used not only to identify synergistic mechanisms but also to predict drug synergies. It also discusses how genome-wide genetic interaction studies have been combined with drug-target information to differentiate between antifungal drug synergies that are target-specific versus those that are non-specific. The investigation of the mechanism of action of antifungal synergies will undoubtedly advance the development of optimal and safe combination therapies for the treatment of drug-resistant fungal infections.

A potent plant-derived antifungal acetylenic acid mediates its activity by interfering with fatty acid homeostasis.

6-Nonadecynoic acid (6-NDA), a plant-derived acetylenic acid, exhibits strong inhibitory activity against the human fungal pathogens Candida albicans, Aspergillus fumigatus, and Trichophyton mentagrophytes. In the present study, transcriptional profiling coupled with mutant and biochemical analyses were conducted using the model yeast Saccharomyces cerevisiae to investigate its mechanism of action. 6-NDA elicited a transcriptome response indicative of fatty acid stress, altering the expression of genes that are required for yeast growth in the presence of oleate. Mutants of S. cerevisiae lacking transcription factors that regulate fatty acid ß-oxidation showed increased sensitivity to 6-NDA. Fatty acid profile analysis indicated that 6-NDA inhibited the formation of fatty acids longer than 14 carbons in length. In addition, the growth inhibitory effect of 6-NDA was rescued in the presence of exogenously supplied oleate. To investigate the response of a pathogenic fungal species to 6-NDA, transcriptional profiling and biochemical analyses were also conducted in C. albicans. The transcriptional response and fatty acid profile of C. albicans were comparable to those obtained in S. cerevisiae, and the rescue of growth inhibition with exogenous oleate was also observed in C. albicans. In a fluconazole-resistant clinical isolate of C. albicans, a fungicidal effect was produced when fluconazole was combined with 6-NDA. In hyphal growth assays, 6-NDA inhibited the formation of long hyphal filaments in C. albicans. Collectively, our results indicate that the antifungal activity of 6-NDA is mediated by a disruption in fatty acid homeostasis and that 6-NDA has potential utility in the treatment of superficial Candida infections.

The marine sponge-derived polyketide endoperoxide plakortide F acid mediates its antifungal activity by interfering with calcium homeostasis.

Plakortide F acid (PFA), a marine-derived polyketide endoperoxide, exhibits strong inhibitory activity against the opportunistic fungal pathogens Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus. In the present study, transcriptional profiling coupled with mutant and biochemical analyses were conducted using the model organism Saccharomyces cerevisiae to investigate the mechanism of action of this compound. PFA elicited a transcriptome response indicative of a Ca(2+) imbalance, affecting the expression of genes known to be responsive to altered cellular calcium levels. Several additional lines of evidence obtained supported a role for Ca(2+) in PFA's activity. First, mutants lacking calcineurin and various Ca(2+) transporters, including pumps (Pmr1 and Pmc1) and channels (Cch1 and Mid1), showed increased sensitivity to PFA. In addition, the calcineurin inhibitors FK506 and cyclosporine strongly enhanced PFA activity in wild-type cells. Furthermore, PFA activated the transcription of a lacZ reporter gene driven by the calcineurin-dependent response element. Finally, elemental analysis indicated a significant increase in intracellular calcium levels in PFA-treated cells. Collectively, our results demonstrate that PFA mediates its antifungal activity by perturbing Ca(2+) homeostasis, thus representing a potentially novel mechanism distinct from that of currently used antifungal agents.