Effects of lovastatin (mevinolin) on sterol levels and on activity of azoles in Saccharomyces cerevisiae

Topical statins as antifungals: a review

Cutaneous fungal infections affect millions around the world. However, severe, multi-resistant fungal infections are increasingly being reported over the past years. As a result of the high rate of resistance which urged for drug repurposing, statins were studied and found to have multiple pleiotropic effects, especially when combined with other already-existing drugs. An example of this is the synergism found between several typical antifungals and statins, such as antifungals Imidazole and Triazole with a wide range of statins shown in this review. The main mechanisms in which they exert an antifungal effect are ergosterol inhibition, protein prenylation, mitochondrial disruption, and morphogenesis/mating inhibition. This article discusses multiple in vitro studies that have proven the antifungal effect of systemic statins against many fungal species, whether used alone or in combination with other typical antifungals. However, as a result of the high rate of drug-drug interactions and the well-known side effects of systemic statins, topical statins have become of increasing interest. Furthermore, patients with dyslipidemia treated with systemic statins who have a new topical fungal infection could benefit from the antifungal effect of their statin. However, it is still not indicated to initiate systemic statins in patients with topical mycotic infections if they do not have another indication for statin use, which raises the interest in using topical statins for fungal infections. This article also tackles the different formulations that have been studied to enhance topical statins' efficacy, as well as the effect of different topical statins on distinct dermatologic fungal diseases.

Inhibitors of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase Decrease the Growth, Ergosterol Synthesis and Generation of petite Mutants in Candida glabrata and Candida albicans

Candida glabrata and Candida albicans, the most frequently isolated candidiasis species in the world, have developed mechanisms of resistance to treatment with azoles. Among the clinically used antifungal drugs are statins and other compounds that inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), resulting in decreased growth and ergosterol levels in yeasts. Ergosterol is a key element for the formation of the yeast cell membrane. However, statins often cause DNA damage to yeast cells, facilitating mutation and drug resistance. The aim of the current contribution was to synthesize seven series of compounds as inhibitors of the HMGR enzyme of Candida ssp., and to evaluate their effect on cellular growth, ergosterol synthesis and generation of petite mutants of C. glabrata and C. albicans. Compared to the reference drugs (fluconazole and simvastatin), some HMGR inhibitors caused lower growth and ergosterol synthesis in the yeast species and generated fewer petite mutants. Moreover, heterologous expression was achieved in Pichia pastoris, and compounds 1a, 1b, 6g and 7a inhibited the activity of recombinant CgHMGR and showed better binding energy values than for α-asarone and simvastatin. Thus, we believe these are good candidates for future antifungal drug development.

In vivo efficacy of pitavastatin combined with itraconazole against Aspergillus fumigatus in silkworm models

Azole resistance in Aspergillus fumigatus is a worldwide concern and new antifungal drugs are required to overcome this problem. Statin, a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, has been reported to suppress the growth of A. fumigatus, but little is known about its in vivo antifungal effect against A. fumigatus. In this study, we evaluated the in vivo efficacy of pitavastatin (PIT) combined with itraconazole (ITC) against azole-susceptible and azole-resistant strains with silkworm models. Prolongation of survival was confirmed in the combination-therapy (PIT and ITC) group compared to the no-treatment group in both azole-susceptible and azole-resistant strain models. Furthermore, when the azole-susceptible strain was used, the combination-therapy resulted in a higher survival rate than with ITC alone. Histopathological analysis of the silkworms revealed a reduction of the hyphal amount in both azole-susceptible and azole-resistant strain models. Quantitative evaluation of fungal DNA by qPCR in azole-susceptible strain models clarified the reduction of fungal burden in the combination-therapy group compared with the no-treatment group and ITC-alone group. These results indicate that the efficacy of PIT was enhanced when combined with ITC in vivo. As opposed to most statins, PIT has little drug-drug interaction with azoles in humans and can be used safely with ITC. This combination therapy may be a promising option as an effective treatment in clinical settings in the future. IMPORTANCE Azole resistance among A. fumigatus isolates has recently been increasingly recognized as a cause of treatment failure, and alternative antifungal therapies are required to overcome this problem. Our study shows the in vivo efficacy of PIT combined with ITC against A. fumigatus using silkworm models by several methods including evaluation of survival rates, histopathological analysis, and assessment of fungal burden. Contrary to most statins, PIT can be safely administered with azoles because of less drug-drug interactions, so this study should help us to verify how to make use of the drug in clinical settings in the future.

Exploitation of Sugarcane Bagasse and Environmentally Sustainable Production, Purification, Characterization, and Application of Lovastatin by Aspergillus terreus AUMC 15760 under Solid-State Conditions

Using the internal transcribed spacer (ITS) region for identification, three strains of Aspergillus terreus were identified and designated AUMC 15760, AUMC 15762, and AUMC 15763 for the Assiut University Mycological Centre culture collection. The ability of the three strains to manufacture lovastatin in solid-state fermentation (SSF) using wheat bran was assessed using gas chromatography-mass spectroscopy (GC-MS). The most potent strain was strain AUMC 15760, which was chosen to ferment nine types of lignocellulosic waste (barley bran, bean hay, date palm leaves, flax seeds, orange peels, rice straw, soy bean, sugarcane bagasse, and wheat bran), with sugarcane bagasse turning out to be the best substrate. After 10 days at pH 6.0 at 25 °C using sodium nitrate as the nitrogen source and a moisture content of 70%, the lovastatin output reached its maximum quantity (18.2 mg/g substrate). The medication was produced in lactone form as a white powder in its purest form using column chromatography. In-depth spectroscopy examination, including ¹H, ¹³C-NMR, HR-ESI-MS, optical density, and LC-MS/MS analysis, as well as a comparison of the physical and spectroscopic data with published data, were used to identify the medication. At an IC₅₀ of 69.536 ± 5.73 µM, the purified lovastatin displayed DPPH activity. Staphylococcus aureus and Staphylococcus epidermidis had MICs of 1.25 mg/mL, whereas Candida albicans and Candida glabrata had MICs of 2.5 mg/mL and 5.0 mg/mL, respectively, against pure lovastatin. As a component of sustainable development, this study offers a green (environmentally friendly) method for using sugarcane bagasse waste to produce valuable chemicals and value-added commodities.

Transcriptome reveals BCAAs biosynthesis pathway is influenced by lovastatin and can act as a potential control target in Phytophthora sojae

AIMS

Lovastatin has been indicated to impair growth and development of Phytophthora sojae. Therefore, this study was performed to understand the inhibitory mechanism of lovastatin and investigate the metabolic pathway potentially serviced as a new control target for this plant pathogen.

METHODS AND RESULTS

Whole transcriptome analysis of lovastatin-treated P. sojae was performed by RNA-sequencing. The results revealed that 84 genes were upregulated and 58 were downregulated with more than four-fold changes under treatment. Kyoto Encyclopedia of Genes and Genomes analysis indicated that the branched-chain amino acids (BCAAs) biosynthesis pathway was abundantly enriched. All enzymes in the BCAAs biosynthesis pathway were identified in the P. sojae genome. Moreover, the study found that the herbicide flumetsulam targeting acetohydroxyacid synthase (AHAS) of the BCAAs biosynthesis pathway could effectively inhibit mycelial growth of P. sojae.

CONCLUSIONS

Lovastatin treatment significantly influences the BCAAs biosynthesis pathway in P. sojae. Moreover, the herbicide flumetsulam targets AHAS and inhibits growth of P. sojae.

SIGNIFICANCE AND IMPACT OF STUDY

The present study revealed that BCAAs biosynthesis pathway was influenced by lovastatin treatment and its key enzyme AHAS was identified as a potential new control target, which provides clues for exploring more oomycides to control plant diseases caused by P. sojae.

Lovastatin production by an oleaginous fungus, Aspergillus terreus KPR12 using sago processing wastewater (SWW)

Background

Lovastatin is one of the first statins to be extensively used for its cholesterol-lowering ability. It is commercially produced by fermentation. Species belonging to the genus Aspergillus are well-studied fungi that have been widely used for lovastatin production. In the present study, we produced lovastatin from sago processing wastewater (SWW) under submerged fermentation using oleaginous fungal strains, A. terreus KPR12 and A. caespitosus ASEF14.

Results

The intra- and extracellular concentrations of lovastatin produced by A. terreus KPR12 and A. caespitosus ASEF14 were lactonized. Because A. caespitosus ASEF14 produced a negligible amount of lovastatin, further kinetics of lovastatin production in SWW was studied using the KPR12 strain for 9 days. Lovastatin concentrations in the intra- and extracellular fractions of the A. terreus KPR12 cultured in a synthetic medium (SM) were 117.93 and 883.28 mg L–1, respectively. However, these concentrations in SWW were 142.23 and 429.98 mg L–1, respectively. The yeast growth inhibition bioassay confirmed the antifungal property of fungal extracts. A. terreus KPR12 showed a higher inhibition zone of 14 mm than the ASEF14 strain. The two-way analysis of variance (ANOVA; p < 0.01) showed significant differences in the localization pattern, fungal strains, growth medium, and their respective interactions. The lovastatin yield coefficient values were 0.153 g g–1 on biomass (YLOV/X) and 0.043 g g–1 on the substrate, starch (YLOV/S). The pollutant level of treated SWW exhibited a reduction in total solids (TS, 59%), total dissolved solids (TDS, 68%), biological oxygen demand (BOD, 79.5%), chemical oxygen demand (COD, 57.1%), phosphate (88%), cyanide (65.4%), and void of nutrients such as nitrate (100%), and ammonia (100%).

Conclusion

The starch-rich wastewater serves as a suitable medium for A. terreus KPR12 for the production of lovastatin. It simultaneously decontaminates the sago processing wastewater, enabling its reuse for irrigation/recreation.

Graphical Abstract

The Mevalonate Pathway Is Important for Growth, Spore Production, and the Virulence of Phytophthora sojae

The mevalonate (MVA) pathway in eukaryotic organisms produces isoprenoids, sterols, ubiquinone, and dolichols. These molecules are vital for diverse cellular functions, ranging from signaling to membrane integrity, and from post-translational modification to energy homeostasis. However, information on the MVA pathway in Phytophthora species is limited. In this study, we identified the MVA pathway genes and reconstructed the complete pathway in Phytophthora sojae in silico. We characterized the function of the MVA pathway of P. sojae by treatment with enzyme inhibitor lovastatin, deletion of the geranylgeranyl diphosphate synthase gene (PsBTS1), and transcriptome profiling analysis. The MVA pathway is ubiquitously conserved in Phytophthora species. Under lovastatin treatment, mycelial growth, spore production, and virulence of P. sojae were inhibited but the zoospore encystment rate increased. Heterozygous mutants of PsBTS1 showed slow growth, abnormal colony characteristics, and mycelial morphology. Mutants showed decreased numbers of sporangia and oospores as well as reduced virulence. RNA sequencing analysis identified the essential genes in sporangia formation were influenced by the enzyme inhibitor lovastatin. Our findings elucidate the role of the MVA pathway in P. sojae and provide new insights into the molecular mechanisms underlying the development, reproduction, and virulence of P. sojae and possibly other oomycetes. Our results also provide potential chemical targets for management of plant Phytophthora diseases.

In vitro study on the potential fungicidal effects of atorvastatin in combination with some azole drugs against multidrug resistant Candida albicans

The resistance of Candida albicans to azole drugs represents a great global challenge. This study investigates the potential fungicidal effects of atorvastatin (ATO) combinations with fluconazole (FLU), itraconazole (ITR), ketoconazole (KET) and voriconazole (VOR) against thirty-four multidrug-resistant (MDR) C. albicans using checkerboard and time-kill methods. Results showed that 94.12% of these isolates were MDR to ≥ two azole drugs, whereas 5.88% of them were susceptible to azole drugs. The tested isolates exhibited high resistance rates to FLU (58.82%), ITR (52.94%), VOR (47.06%) and KET (35.29%), whereas only three representative (8.82%) isolates were resistant to all tested azoles. Remarkably, the inhibition zones of these isolates were increased at least twofold with the presence of ATO, which interacted in a synergistic (FIC index ≤ 0.5) manner with tested azoles. In silico docking study of ATO and the four azole drugs were performed against the Lanosterol 14-alpha demethylase enzyme (ERG11) of C. albicans. Results showed that the mechanism of action of ATO against C. albicans is similar to that of azole compounds, with a docking score (−4.901) lower than azole drugs (≥5.0) due to the formation a single H-bond with Asp 225 and a pi–pi interaction with Thr 229. Importantly, ATO combinations with ITR, VOR and KET achieved fungicidal effects (≥ 3 Log₁₀ cfu/ml reduction) against the representative isolates, whereas a fungistatic effect (≤ 3 Log₁₀ cfu/ml reduction) was observed with FLU combination. Thus, the combination of ATO with azole drugs could be promising options for treating C. albicans infection.

Complex interactions of lovastatin with 10 chemotherapeutic drugs: a rigorous evaluation of synergism and antagonism

Background

Evidence bearing on the role of statins in the prevention and treatment of cancer is confounded by the diversity of statins, chemotherapeutic agents and cancer types included in the numerous published studies; consequently, the adjunctive value of statins with chemotherapy remains uncertain.

Methods

We assayed lovastatin in combination with each of ten commonly prescribed chemotherapy drugs in highly reproducible in vitro assays, using a neutral cellular substrate, Saccharomyces cerevisiae. Cell density (OD₆₀₀) data were analyzed for synergism and antagonism using the Loewe additivity model implemented with the Combenefit software.

Results

Four of the ten chemotherapy drugs – tamoxifen, doxorubicin, methotrexate and rapamycin – exhibited net synergism with lovastatin. The remaining six agents (5-fluorouracil, gemcitabine, epothilone, cisplatin, cyclophosphamide and etoposide) compiled neutral or antagonistic scores. Distinctive patterns of synergism and antagonism, often coexisting within the same concentration space, were documented with the various combinations, including those with net synergism scores. Two drug pairs, lovastatin combined with tamoxifen or cisplatin, were also assayed in human cell lines as proof of principle.

Conclusions

The synergistic interactions of tamoxifen, doxorubicin, methotrexate and rapamycin with lovastatin – because they suggest the possibility of clinical utility - merit further exploration and validation in cell lines and animal models. No less importantly, strong antagonistic interactions between certain agents and lovastatin argue for a cautious, data-driven approach before adding a statin to any chemotherapeutic regimen. We also urge awareness of adventitious statin usage by patients entering cancer treatment protocols.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07963-w.

A central role for polyprenol reductase in plant dolichol biosynthesis

Dolichol is an essential polyisoprenoid within the endoplasmic reticulum of all eukaryotes. It serves as a membrane bound anchor onto which N-glycans are assembled prior to being transferred to nascent polypeptides, many of which enter the secretory pathway. Historically, it has been posited that the accumulation of dolichol represents the 'rate-limiting' step in the evolutionary conserved process of N-glycosylation, which ultimately affects the efficacy of approximately one fifth of the entire eukaryotic proteome. Therefore, this study aimed to enhance dolichol accumulation by manipulating the enzymes involved in its biosynthesis using an established Nicotiana benthamiana platform. Co-expression of a Solanum lycopersicum (tomato) cis-prenyltransferase (CPT) and its cognate partner protein, CPT binding protein (CPTBP), that catalyze the antepenultimate step in dolichol biosynthesis led to a 400-fold increase in the levels of long-chain polyprenols but resulted in only modest increases in dolichol accumulation. However, when combined with a newly characterized tomato polyprenol reductase, dolichol biosynthesis was enhanced by approximately 20-fold. We provide further evidence that in the aquatic macrophyte, Lemna gibba, dolichol is derived exclusively from the mevalonic acid (MVA) pathway with little participation from the evolutionary co-adopted non-MVA pathway. Taken together these results indicate that to effectively enhance the in planta accumulation of dolichol, coordinated synthesis and reduction of polyprenol to dolichol, is strictly required.

Statins interfere with the attachment of S. cerevisiae mtDNA to the inner mitochondrial membrane

The 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme of the mevalonate pathway for the synthesis of cholesterol in mammals (ergosterol in fungi), is inhibited by statins, a class of cholesterol lowering drugs. Indeed, statins are in a wide medical use, yet statins treatment could induce side effects as hepatotoxicity and myopathy in patients. We used Saccharomyces cerevisiae as a model to investigate the effects of statins on mitochondria. We demonstrate that statins are active in S.cerevisiae by lowering the ergosterol content in cells and interfering with the attachment of mitochondrial DNA to the inner mitochondrial membrane. Experiments on murine myoblasts confirmed these results in mammals. We propose that the instability of mitochondrial DNA is an early indirect target of statins.

Antifungal Drug Repurposing

Control of fungal pathogens is increasingly problematic due to the limited number of effective drugs available for antifungal therapy. Conventional antifungal drugs could also trigger human cytotoxicity associated with the kidneys and liver, including the generation of reactive oxygen species. Moreover, increased incidences of fungal resistance to the classes of azoles, such as fluconazole, itraconazole, voriconazole, or posaconazole, or echinocandins, including caspofungin, anidulafungin, or micafungin, have been documented. Of note, certain azole fungicides such as propiconazole or tebuconazole that are applied to agricultural fields have the same mechanism of antifungal action as clinical azole drugs. Such long-term application of azole fungicides to crop fields provides environmental selection pressure for the emergence of pan-azole-resistant fungal strains such as Aspergillus fumigatus having TR34/L98H mutations, specifically, a 34 bp insertion into the cytochrome P450 51A (CYP51A) gene promoter region and a leucine-to-histidine substitution at codon 98 of CYP51A. Altogether, the emerging resistance of pathogens to currently available antifungal drugs and insufficiency in the discovery of new therapeutics engender the urgent need for the development of new antifungals and/or alternative therapies for effective control of fungal pathogens. We discuss the current needs for the discovery of new clinical antifungal drugs and the recent drug repurposing endeavors as alternative methods for fungal pathogen control.

Antifungal effects of statins

Fungal infections are estimated to be responsible for 1.5 million deaths annually. Global anti-microbial resistance is also observed for fungal pathogens, and scientists are looking for new antifungal agents to address this challenge. One potential strategy is to evaluate currently available drugs for their possible antifungal activity. One of the suggested drug classes are statins, which are commonly used to decrease plasma cholesterol and reduce cardiovascular risk associated with low density lipoprotein cholesterol (LDL-c). Statins are postulated to possess pleiotropic effects beyond cholesterol lowering; improving endothelial function, modulating inflammation, and potentially exerting anti-microbial effects. In this study, we reviewed in-vitro and in-vivo studies, as well as clinical reports pertaining to the antifungal efficacy of statins. In addition, we have addressed various modulators of statin anti-fungal activity and the potential mechanisms responsible for their anti-fungal effects. In general, statins do possess anti-fungal activity, targeting a broad spectrum of fungal organisms including human opportunistic pathogens such as Candida spp. and Zygomycetes, Dermatophytes, alimentary toxigenic species such as Aspergillus spp., and fungi found in device implants such as Saccharomyces cerevisiae. Statins have been shown to augment a number of antifungal drug classes, for example, the azoles and polyenes. Synthetic statins are generally considered more potent than the first generation of fungal metabolites. Fluvastatin is considered the most effective statin with the broadest and most potent fungal inhibitory activity, including fungicidal and/or fungistatic properties. This has been demonstrated with plasma concentrations that can easily be achieved in a clinical setting. Additionally, statins can potentiate the efficacy of available antifungal drugs in a synergistic fashion. Although only a limited number of animal and human studies have been reported to date, observational cohort studies have confirmed that patients using statins have a reduced risk of candidemia-related complications. Further studies are warranted to confirm our findings and expand current knowledge of the anti-fungal effects of statins.

Antifungal combinations in Mucorales: A microbiological perspective

Mucormycosis mostly affects immunocompromised patients and is associated with a high morbidity and mortality despite currently available treatments. In that context, combination therapy might be the key to a better outcome for these patients. Purpose of this review is to summarise and to discuss the current combination data obtained in vitro, in vivo in animal models of mucormycosis, and in patients. In vitro combination studies showed that most of the interactions between antifungal drugs were indifferent, even though that some synergistic interactions were achieved for the combination of echinocandins with either azoles or amphotericin B. Importantly, antagonism was never observed. Animal models of mucormycosis focused on infections caused by Rhizopus arrhizus, neglecting most other species responsible for human disease. In these experimental animal models, no strong interactions have been demonstrated, although a certain degree of synergism has been reported in some instances. Combinations of antifungals with non-antifungal drugs have also been largely explored in vitro and in animal models and yielded interesting results. In patients with ketoacidosis and rhino-orbito-cerebral infection, combination of polyene with caspofungin was effective. In contrast, despite promising experimental data, adjunctive therapy with the iron chelator deferasirox was unfavourable and was associated with a higher mortality than monotherapy with liposomal amphotericin B. More combinations have to be tested in vitro and a much larger panel of Mucorales species has to be tested in vivo to give a valuable statement if antifungal combination therapy could be an effective treatment strategy in patients with mucormycosis.

Simvastatin Efficiently Reduces Levels of Alzheimer's Amyloid Beta in Yeast

A large-scale epidemiology study on statins previously showed that simvastatin was unique among statins in reducing the incidence of dementia. Since amyloid beta (Aβ42) is the protein that is most associated with Alzheimer's disease, this study has focused on how simvastatin influences the turnover of native Aβ42 and Aβ42 fused with green fluorescent protein (GFP), in the simplest eukaryotic model organism, Saccharomyces cerevisiae. Previous studies have established that yeast constitutively producing Aβ42 fused to GFP offer a convenient means of analyzing yeast cellular responses to Aβ42. Young cells clear the GFP fusion protein and do not have green fluorescence while the older population of cells retains the fusion protein and exhibits green fluorescence, offering a fast and convenient means of studying factors that affect Aβ42 turnover. In this study the proportion of cells having GFP fused to Aβ after exposure to simvastatin, atorvastatin and lovastatin was analyzed by flow cytometry. Simvastatin effectively reduced levels of the cellular Aβ42 protein in a dose-dependent manner. Simvastatin promoted the greatest reduction as compared to the other two statins. A comparison with fluconazole, which targets that same pathway of ergosterol synthesis, suggests that effects on ergosterol synthesis do not account for the reduced amounts of Aβ42 fused to GFP. The levels of native Aβ42 following treated with simvastatin were also examined using a more laborious approach, quantitative MALDI TOF mass spectrometry. Simvastatin efficiently reduced levels of native Aβ42 from the population. This work indicates a novel action of simvastatin in reducing levels of Aβ42 providing new insights into how simvastatin exerts its neuroprotective role. We hypothesize that this reduction may be due to protein clearance.

Antifungal drugs: New insights in research & development

The need for better antifungal therapy is commonly accepted in view of the high mortality rates associated with systemic infections, the low number of available antifungal classes, their associated toxicity and the increasing number of infections caused by strains with natural or acquired resistance. The urgency to expand the range of therapeutic options for the treatment of fungal infections has led researchers in recent decades to seek alternative antifungal targets when compared to the conventional ones currently used. Although new potential targets are reported, translating the discoveries from bench to bedside is a long process and most of these drugs fail to reach the patients. In this review, we discuss the development of antifungal drugs focusing on the approach of drug repurposing and the search for novel drugs for classical targets, the most recently described gene targets for drug development, the possibilities of immunotherapy using antibodies, cytokines, therapeutic vaccines and antimicrobial peptides.

Statin resistance in Candida glabrata

OBJECTIVES

Reduced efficacy of statins has been observed in people but the mechanism of this resistance is unclear and no statin-resistance mutations in the catalytic domain of HMGCR have been reported. The present study focused on looking for statin-resistance mutations and examining the mechanism of statin resistance using Candida glabrata as a model organism.

RESULTS

C. glabrata was cultured in media containing lovastatin, simvastatin or atorvastatin to obtain lovastatin-, simvastatin- and atorvastatin-resistant mutants. A single mutant from each was purified for further analysis. In each mutant, gene sequencing showed there were no changes in the catalytic domain of HMGCR. HMGCR was overexpressed in two resistant isolates suggesting that increased production of HMGCR can lead to resistance. In a third mutant, HMGCR activity was unaltered, suggesting a non-HMGCR related mechanism, such as increased drug efflux, could be operating.

CONCLUSIONS

Candida glabrata is a useful model organism for examining resistance to statins. Further studies are warranted to examine the precise molecular mechanisms of statin resistance.

Lovastatin synergizes with itraconazole against planktonic cells and biofilms of Candida albicans through the regulation on ergosterol biosynthesis pathway

The increase of fungal infectious diseases and lack of safe and efficacious antifungal drugs result in the urgent need of new therapeutic strategies. Here, we repurposed the lovastatin (LOV) as a synergistic antifungal potentiator to itraconazole (ITZ) against Candida albicans planktonic cells and biofilms in vitro for the first time. Mutants from ergosterol biosynthesis pathway were employed and key gene expression profiles of ergosterol pathway were also measured. LOV single treatment was unable to inhibit C. albicans strains except the ERG3 and ERG11 double mutant. LOV and ITZ combination was capable of inhibiting the C. albicans planktonic cells and biofilms synergistically including the ITZ resistant mutants. The synergistic antifungal ability was stronger in either ERG11 or ERG3 dysfunctional mutants compared to wild type. The combination lost the synergistic activities in the ERG11 and ERG3 double mutant, while it was sensitive to LOV single treatment. The expression of HMG1, encoding HMG-CoA the target of LOV, was significantly upregulated in ERG11 and ERG3 double mutant strain by the treatment of the combination at 1.5 and 3 h. The combination also significantly increased the HMG1 expression in mutants from ergosterol pathway compared with wild type. The ERG11 and ERG3 gene expressions were upregulated by ITZ and its combination with LOV, but seemingly not by LOV single treatment after 1.5 and 3 h. The combination of LOV and ITZ on C. albicans planktonic cells and biofilms highlights its potential clinical practice especially against the azole drug-resistant mutants.

Atorvastatin as a promising anticryptococcal agent

Cryptococcosis caused by Cryptococcus gattii leads to pneumonia and meningoencephalitis, and has a high mortality rate worldwide due to the inadequacy of available therapy and increasing drug resistance. There is a need to develop effective treatments, and drug repositioning is an interesting alternative to achieve new strategies to treat cryptococcosis. Atorvastatin (ATO), a statin currently used to treat hypercholesterolaemia, was tested in this study as an adjuvant to control infections caused by C. gattii. Several aspects of the effect of ATO on the host and the yeast were evaluated, with particular focus on the association of ATO with fluconazole (FLC), which (i) reduced ergosterol content in the cell membrane and altered properties of the polysaccharide capsule of C. gattii; (ii) increased the production of reactive oxygen species by macrophages; and (iii) reduced yeast phagocytosis and the intracellular proliferation rate. In an animal model, infected mice treated with ATO + FLC showed increased survival, improved clinical condition, and reduced fungal burden in the lungs and brain. This study is the first to perform in vivo tests with ATO + FLC for the treatment of cryptococcosis. The results suggest that ATO may be an important adjuvant for the treatment of cryptococcosis.

Production of statins by fungal fermentation

Fungi are used industrially to obtain a variety of products, from low value bulk chemicals to high value drugs like, immunosuppressants, antibiotics, alkaloids and statins. Lovastatin and compactin are natural statins produced as secondary metabolites by predominantly Aspergillus and Penicillium species, following a polyketide pathway. Lovastatin was one of the first cholesterol-lowering drugs. Many statins are now chemically synthesised but lovastatin is still required to produce simvastatin. Apart from reducing blood cholesterol levels simvastatin causes pleotropic effects and has potential to treat various kinds of disorders including neurodegenerative disease and cancer.

Functional analysis of an AMP forming acetyl CoA synthetase from Leishmania donovani by gene overexpression and targeted gene disruption approaches

Leishmaniasis, a neglected tropical disease is endemic in 98 countries and >350 million people are at risk of getting the infection. The existing chemotherapy of Leishmaniasis is limited due to adverse effects, resistance to existing drugs and increasing cases of HIV-Leishmaniasis co-infection. Hence, there is a need to identify novel metabolic pathways for design of new chemical entities. Acetyl-CoA synthetase (AceCS) is an enzyme of acetate metabolic pathway whose functions are unknown in Leishmania parasite. AceCS from Leishmania donovani (LdAceCS) is significantly different from human host to be explored as a potential drug candidate to develop parasite specific inhibitors. To dissect the functions of LdAceCS in Leishmania promastigotes, two approaches were followed. LdAceCS overexpressing parasites were generated by episomal expression of LdAceCS in promastigotes and single knockout (SKO) cell lines of LdAceCS were generated by targeted gene disruption. An insight into the phenotypic changes undergone by the overexpressors revealed an increase in LdAceCS activity, total lipid content, infectivity and ergosterol levels by ~2.2, 2.2, 1.65 and 3 fold respectively with respect to wild type. Similarly SKO transgenic parasites exhibited ~2.5, 3, 1.5 and 3 fold decrease in activity, total lipid content, infectivity and ergosterol respectively. Repeated attempts to generate null mutants failed thus indicating that LdAceCS is essential for the parasite and can be selectively targeted to combat Leishmania infection. The present study demonstrates that LdAceCS is important for in vitro macrophage infection and is also essential for biosynthesis of total lipids and ergosterol.

Antifungal adjuvants: Preserving and extending the antifungal arsenal

As the rates of systemic fungal infections continue to rise and antifungal drug resistance becomes more prevalent, there is an urgent need for new therapeutic options. This issue is exacerbated by the limited number of systemic antifungal drug classes. However, the discovery, development, and approval of novel antifungals is an extensive process that often takes decades. For this reason, there is growing interest and research into the possibility of combining existing therapies with various adjuvants that either enhance activity or overcome existing mechanisms of resistance. Reports of antifungal adjuvants range from plant extracts to repurposed compounds, to synthetic peptides. This approach would potentially prolong the utility of currently approved antifungals and mitigate the ongoing development of resistance.

Exploitation of Aspergillus terreus for the Production of Natural Statins

The fungus Aspergillus (A.) terreus has dominated the biological production of the “blockbuster” drugs known as statins. The statins are a class of drugs that inhibit HMG-CoA reductase and lead to lower cholesterol production. The statins were initially discovered in fungi and for many years fungi were the sole source for the statins. At present, novel chemically synthesised statins are produced as inspired by the naturally occurring statin molecules. The isolation of the natural statins, compactin, mevastatin and lovastatin from A. terreus represents one of the great achievements of industrial microbiology. Here we review the discovery of statins, along with strategies that have been applied to scale up their production by A. terreus strains. The strategies encompass many of the techniques available in industrial microbiology and include the optimization of media and fermentation conditions, the improvement of strains through classical mutagenesis, induced genetic manipulation and the use of statistical design.

Simvastatin inhibits planktonic cells and biofilms of Candida and Cryptococcus species

The antifungal activity of some statins against different fungal species has been reported. Thus, at the first moment, the in vitro antifungal activity of simvastatin, atorvastatin and pravastatin was tested against Candida spp. and Cryptococcus spp. Then, in a second approach, considering that the best results were obtained for simvastatin, this drug was evaluated in combination with antifungal drugs against planktonic growth and tested against biofilms of Candida spp. and Cryptococcus spp. Drug susceptibility testing was performed using the microdilution broth method, as described by the Clinical and Laboratory Standards Institute. The interaction between simvastatin and antifungals against planktonic cells was analyzed by calculating the fractional inhibitory concentration index. Regarding biofilm susceptibility, simvastatin was tested against growing biofilm and mature biofilm of one strain of each tested yeast species. Simvastatin showed inhibitory effect against Candida spp. and Cryptococcus spp. with minimum inhibitory concentration values ranging from 15.6 to 1000 mg L⁻¹ and from 62.5 to 1000 mg L⁻¹, respectively. The combination of simvastatin with itraconazole and fluconazole showed synergism against Candida spp. and Cryptococcus spp., while the combination of simvastatin with amphotericin B was synergistic only against Cryptococcus spp. Concerning the biofilm assays, simvastatin was able to inhibit both growing biofilm and mature biofilm of Candida spp. and Cryptococcus spp. The present study showed that simvastatin inhibits planktonic cells and biofilms of Candida and Cryptococcus species.

Susceptibility of clinically important dermatophytes against statins and different statin-antifungal combinations

The investigation of the antifungal activities of drugs whose primary activities are not related to their antimicrobial potential is in the current forefront of research. Statin compounds, which are routinely used as cholesterol-lowering drugs, may also exert direct antimicrobial effects. In this study, the in vitro antifungal activities of various statins (lovastatin, simvastatin, fluvastatin, atorvastatin, rosuvastatin and pravastatin) were examined against one isolate each of four dermatophyte species (Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis and Microsporum gypseum). Basically, statins were effective in inhibiting all dermatophyte studied, but were particularly active against M. canis and T. mentagrophytes. Fluvastatin and simvastatin were active against all of the tested fungi causing a complete inhibition of their growth at very low concentrations (6.25-12.5 μg/ml). Lovastatin and rosuvastatin had inhibitory effects at higher concentrations (25-128 μg/ml), while atorvastatin and pravastatin proved the less effective. The in vitro interactions between statins and different antifungals (ketoconazole, itraconazole, fluconazole, amphotericin B, nystatin, griseofulvin, terbinafine and primycin) were also investigated using a standard chequerboard broth microdilution method. Synergetic interactions were observed in several cases, most of them were noticed when statins were combined with terbinafine and the different azoles. Some combinations were particularly active (ketoconazole-simvastatin or terbinafine-simvastatin), as they were found to exert synergistic effect against all of the investigated isolates. The other antifungals showed synergistic interactions with statins in only certain cases. These results suggest that statins exert substantial antifungal effects against dermatophyte fungi and they should be promising components in a combination therapy as they can act synergistically with a number of clinically used antifungal agents.

The 3-hydroxy-3-methylglutaryl coenzyme-A reductases from fungi: a proposal as a therapeutic target and as a study model

The enzyme 3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMGR) catalyzes the conversion of HMG-Co-A into mevalonate. This step is the limiting point for the synthesis of cholesterol in mammals and ergosterol in fungi. We describe in this article the genome organization of HMGR coding genes and those deduced from different fungi, recount the evidence showing statins as HMGR inhibitors for ergosterol synthesis and its effect in yeast viability, and propose fungal HMGR (HMGRf) as a model to study the use of pharmaceutical compounds to inhibit cholesterol and ergosterol synthesis. Bibliographical search and bioinformatic analyses were performed and discussed. HMGRfs belong to the class I with a high homology in the catalytic region. The sterol biosynthetic pathway in humans and fungi share many enzymes in the initial steps (such as the HMGR enzyme), but in the last steps enzymes are different rendering the two final products: cholesterol in mammals and ergosterol in fungi. With regards to inhibitors such as statins and other compounds, these affect also fungal viability. Since HMGR from Schizosaccharomyces pombe and Ustilago maydis are very similar to the human HMGR in the catalytic regions, we propose that fungal enzymes can be used to test inhibitors for a potential use in humans. We consider that HMGRf is a good therapeutic target to design and test new antifungal compounds. This manuscript is part of the series of works presented at the "V International Workshop: Molecular genetic approaches to the study of human pathogenic fungi" (Oaxaca, Mexico, 2012).

Comparison of sterol import under aerobic and anaerobic conditions in three fungal species, Candida albicans, Candida glabrata, and Saccharomyces cerevisiae

Sterol import has been characterized under various conditions in three distinct fungal species, the model organism Saccharomyces cerevisiae and two human fungal pathogens Candida glabrata and Candida albicans, employing cholesterol, the sterol of higher eukaryotes, as well as its fungal equivalent, ergosterol. Import was confirmed by the detection of esterified cholesterol within the cells. Comparing the three fungal species, we observe sterol import under three different conditions. First, as previously well characterized, we observe sterol import under low oxygen levels in S. cerevisiae and C. glabrata, which is dependent on the transcription factor Upc2 and/or its orthologs or paralogs. Second, we observe sterol import under aerobic conditions exclusively in the two pathogenic fungi C. glabrata and C. albicans. Uptake emerges during post-exponential-growth phases, is independent of the characterized Upc2-pathway and is slower compared to the anaerobic uptake in S. cerevisiae and C. glabrata. Third, we observe under normoxic conditions in C. glabrata that Upc2-dependent sterol import can be induced in the presence of fetal bovine serum together with fluconazole. In summary, C. glabrata imports sterols both in aerobic and anaerobic conditions, and the limited aerobic uptake can be further stimulated by the presence of serum together with fluconazole. S. cerevisiae imports sterols only in anaerobic conditions, demonstrating aerobic sterol exclusion. Finally, C. albicans imports sterols exclusively aerobically in post-exponential-growth phases, independent of Upc2. For the first time, we provide direct evidence of sterol import into the human fungal pathogen C. albicans, which until now was believed to be incapable of active sterol import.

Lovastatin-enriched rice straw enhances biomass quality and suppresses ruminal methanogenesis

The primary objective of this study was to test the hypothesis that solid state fermentation (SSF) of agro-biomass (using rice straw as model); besides, breaking down its lignocellulose content to improve its nutritive values also produces lovastatin which could be used to suppress methanogenesis in the rumen ecosystem. Fermented rice straw (FRS) containing lovastatin after fermentation with Aspergillus terreus was used as substrate for growth study of rumen microorganisms using in vitro gas production method. In the first experiment, the extract from the FRS (FRSE) which contained lovastatin was evaluated for its efficacy for reduction in methane (CH4) production, microbial population, and activity in the rumen fluid. FRSE reduced total gas and CH4 productions (P < 0.01). It also reduced (P < 0.01) total methanogens population and increased the cellulolytic bacteria including Ruminococcus albus, Fibrobacter succinogenes (P < 0.01), and Ruminococcus flavefaciens (P < 0.05). Similarly, FRS reduced total gas and CH4 productions, methanogens population, but increased in vitro dry mater digestibility compared to the non-fermented rice straw. Lovastatin in the FRSE and the FRS significantly increased the expression of HMG-CoA reductase gene that produces HMG-CoA reductase, a key enzyme for cell membrane production in methanogenic Archaea.

Reconstruction and evaluation of the synthetic bacterial MEP pathway in Saccharomyces cerevisiae

Isoprenoids, which are a large group of natural and chemical compounds with a variety of applications as e.g. fragrances, pharmaceuticals and potential biofuels, are produced via two different metabolic pathways, the mevalonate (MVA) pathway and the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. Here, we attempted to replace the endogenous MVA pathway in Saccharomyces cerevisiae by a synthetic bacterial MEP pathway integrated into the genome to benefit from its superior properties in terms of energy consumption and productivity at defined growth conditions. It was shown that the growth of a MVA pathway deficient S. cerevisiae strain could not be restored by the heterologous MEP pathway even when accompanied by the co-expression of genes erpA, hISCA1 and CpIscA involved in the Fe-S trafficking routes leading to maturation of IspG and IspH and E. coli genes fldA and fpr encoding flavodoxin and flavodoxin reductase believed to be responsible for electron transfer to IspG and IspH.

Statins as antifungal agents

Fungal infections are increasing and their treatment is difficult, because the most widely used antifungal drugs are relatively toxic and have serious side effects. Therefore, interest has focused on safely applicable and clinically introduced non-antifungal drugs, which have potent antifungal activity. Statins were originally used as cholesterol lowering agents in human therapy, but recent studies demonstrated their in vitro antifungal activity against yeasts and filamentous fungi. This indicated their potential application, alone or in combination with other drugs, in the treatment of such diseases. Their effective concentrations are higher than their maximum achievable serum levels; therefore, the application of statins for the treatment of invasive fungal infections is only possible in combination with antifungal agents. These synergistic combinations establish a basis for a new safely applicable therapy. This review focuses on the antifungal activity of statins alone and in combination with antifungal and non-antifungal drugs, and their possible application in clinical therapy.

Mevalonate governs interdependency of ergosterol and siderophore biosyntheses in the fungal pathogen Aspergillus fumigatus

Aspergillus fumigatus is the most common airborne fungal pathogen for humans. In this mold, iron starvation induces production of the siderophore triacetylfusarinine C (TAFC). Here we demonstrate a link between TAFC and ergosterol biosynthetic pathways, which are both critical for virulence and treatment of fungal infections. Consistent with mevalonate being a limiting prerequisite for TAFC biosynthesis, we observed increased expression of 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase (Hmg1) under iron starvation, reduced TAFC biosynthesis following lovastatin-mediated Hmg1 inhibition, and increased TAFC biosynthesis following Hmg1 overexpression. We identified enzymes, the acyl-CoA ligase SidI and the enoyl-CoA hydratase SidH, linking biosynthesis of mevalonate and TAFC, deficiency of which under iron starvation impaired TAFC biosynthesis, growth, oxidative stress resistance, and murine virulence. Moreover, inactivation of these enzymes alleviated TAFC-derived biosynthetic demand for mevalonate, as evidenced by increased resistance to lovastatin. Concordant with bilateral demand for mevalonate, iron starvation decreased the ergosterol content and composition, a phenotype that is mitigated in TAFC-lacking mutants.

Transcription factors CgUPC2A and CgUPC2B regulate ergosterol biosynthetic genes in Candida glabrata

Zn[2]-Cys[6] binuclear transcription factors Upc2p and Ecm22p regulate the expression of genes involved in ergosterol biosynthesis and exogenous sterol uptake in Saccharomyces cerevisiae. We identified two UPC2/ECM22 homologues in the pathogenic fungus Candida glabrata which we designated CgUPC2A and CgUPC2B. The contribution of these two genes to sterol homeostasis was investigated. Cells that lack CgUPC2A (upc2AΔ) exhibited enhanced susceptibility to the sterol biosynthesis inhibitors, fluconazole and lovastatin, whereas upc2BΔ-mutant cells were as susceptible to the drugs as wild-type cells. The growth of upc2AΔ cells was also severely attenuated under anaerobic conditions. Lovastatin treatment enhanced the expression of ergosterol biosynthetic genes, ERG2 and ERG3 in wild-type and upc2BΔ but not in upc2AΔ cells. Similarly, serum-induced expression of ERG2 and ERG3 was completely impaired in upc2AΔ cells but was unaffected in upc2BΔ cells, whereas serum-induced expression of the sterol transporter gene CgAUS1 was impaired in both upc2AΔ and upc2BΔ cells. These results suggest that in C. glabrata CgUPC2A but not in CgUPC2B is the main transcriptional regulator of the genes responsible for maintaining sterol homeostasis as well as susceptibility to sterol inhibitors.

Growth defects resulting from inhibiting ERG20 and RAM2 in Candida glabrata

Farnesyl pyrophosphate (FPP) is utilized for many cellular processes, including the production of dolichols, ubiquinone (CoQ), sterols, farnesylated heme A and prenylated proteins. This lipid synthesized by FPP synthetase (ERG20) becomes attached to target proteins by the prenyltransferases, CDC43/RAM2 and RAM1/RAM2 complexes after the formation of the C15 and C20 units, respectively. Defects in protein prenylation as a result of inhibiting these enzyme complexes lead to pleiotropic effects in all eukaryotes. In this study, using Candida glabrata conditional mutants, the importance of the ERG20 and RAM2 genes for growth using both in vivo and in vitro assays was assessed by placing the RAM2 and ERG20 genes under the control of a regulatable promoter. Repression of RAM2 gene expression revealed growth defects under both conditions. However, repression of ERG20 gene expression did not impair fungal growth in a mouse host, but did result in growth defects on laboratory media. Thus, FPP synthase is not required for survival in an infected mouse, but the RAM2-encoded prenyltransferase was critical for growth under both conditions. This study strongly suggests that inhibitors of prenyltransferase may be promising antifungals.

In vitro synergistic interactions of the effects of various statins and azoles against some clinically important fungi

The treatment of opportunistic fungal infections is often difficult as the number of available antifungal agents is limited. Nowadays, there is increasing interest in the investigation of the antifungal activity of nonantifungal drugs, and in the development of efficient antifungal combination therapy. In this study, the in vitro interactions of the effects of various statins (lovastatin, simvastatin, fluvastatin, atorvastatin (ATO), rosuvastatin (ROS) and pravastatin) and various azole antifungals [miconazole, ketoconazole, itraconazole and fluconazole (FLU)] against different opportunistic pathogenic fungi were investigated using a standard chequerboard broth microdilution method. When the investigated strains were sensitive to both compounds of the combination, additive interactions were frequently noticed. Synergistic interactions were observed in many cases when a strain was sensitive only to the azole compound (as in certain combinations with ATO or ROS) or the statin compound (as in certain combinations with FLU). In many combinations with an additive effect, the concentrations of drugs needed for total growth inhibition could be decreased by several dilution steps. Similar interactions were observed when the variability of the within-species sensitivities to some selected drug combinations was investigated.

A new fluorescence-based method identifies protein phosphatases regulating lipid droplet metabolism

In virtually every cell, neutral lipids are stored in cytoplasmic structures called lipid droplets (LDs) and also referred to as lipid bodies or lipid particles. We developed a rapid high-throughput assay based on the recovery of quenched BODIPY-fluorescence that allows to quantify lipid droplets. The method was validated by monitoring lipid droplet turnover during growth of a yeast culture and by screening a group of strains deleted in genes known to be involved in lipid metabolism. In both tests, the fluorimetric assay showed high sensitivity and good agreement with previously reported data using microscopy. We used this method for high-throughput identification of protein phosphatases involved in lipid droplet metabolism. From 65 yeast knockout strains encoding protein phosphatases and its regulatory subunits, 13 strains revealed to have abnormal levels of lipid droplets, 10 of them having high lipid droplet content. Strains deleted for type I protein phosphatases and related regulators (ppz2, gac1, bni4), type 2A phosphatase and its related regulator (pph21 and sap185), type 2C protein phosphatases (ptc1, ptc4, ptc7) and dual phosphatases (pps1, msg5) were catalogued as high-lipid droplet content strains. Only reg1, a targeting subunit of the type 1 phosphatase Glc7p, and members of the nutrient-sensitive TOR pathway (sit4 and the regulatory subunit sap190) were catalogued as low-lipid droplet content strains, which were studied further. We show that Snf1, the homologue of the mammalian AMP-activated kinase, is constitutively phosphorylated (hyperactive) in sit4 and sap190 strains leading to a reduction of acetyl-CoA carboxylase activity. In conclusion, our fast and highly sensitive method permitted us to catalogue protein phosphatases involved in the regulation of LD metabolism and present evidence indicating that the TOR pathway and the SNF1/AMPK pathway are connected through the Sit4p-Sap190p pair in the control of lipid droplet biogenesis.

Antifungal activity of statins and their interaction with amphotericin B against clinically important Zygomycetes

The in vitro antifungal activity of different statins and the combinations of the two most effective ones (fluvastatin and rosuvastatin) with amphotericin B were investigated in this study on 6 fungal isolates representing 4 clinically important genera, namely Absidia, Rhizomucor, Rhizopus and Syncephalastrum . The antifungal effects of statins revealed substantial differences. The synthetic statins proved to be more effective than the fungal metabolites. All investigated strains proved to be sensitive to fluvastatin. Fluvastatin and rosuvastatin acted synergistically and additively with amphotericin B in inhibiting the fungal growth in clinically available concentration ranges. Results suggest that statins combined with amphotericin B have a therapeutic potential against fungal infections caused by Zygomycetes species.

Inhibition of sterol biosynthesis reduces tombusvirus replication in yeast and plants

The replication of plus-strand RNA viruses depends on subcellular membranes. Recent genome-wide screens have revealed that the sterol biosynthesis genes ERG25 and ERG4 affected the replication of Tomato bushy stunt virus (TBSV) in a yeast model host. To further our understanding of the role of sterols in TBSV replication, we demonstrate that the downregulation of ERG25 or the inhibition of the activity of Erg25p with an inhibitor (6-amino-2-n-pentylthiobenzothiazole; APB) leads to a 3- to 5-fold reduction in TBSV replication in yeast. In addition, the sterol biosynthesis inhibitor lovastatin reduced TBSV replication by 4-fold, confirming the importance of sterols in viral replication. We also show reduced stability for the p92(pol) viral replication protein as well as a decrease in the in vitro activity of the tombusvirus replicase when isolated from APB-treated yeast. Moreover, APB treatment inhibits TBSV RNA accumulation in plant protoplasts and in Nicotiana benthamiana leaves. The inhibitory effect of APB on TBSV replication can be complemented by exogenous stigmasterol, the main plant sterol, suggesting that sterols are required for TBSV replication. The silencing of SMO1 and SMO2 genes, which are orthologs of ERG25, in N. benthamiana reduced TBSV RNA accumulation but had a lesser inhibitory effect on the unrelated Tobacco mosaic virus, suggesting that various viruses show different levels of dependence on sterol biosynthesis for their replication.

Simvastatin inhibits Candida albicans biofilm in vitro

By inhibiting the conversion of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) to mevalonate, statins impair cholesterol metabolism in humans. We reasoned that statins might similarly interfere with the biosynthesis of ergosterol, the major sterol of the yeast cell membrane. As assessed by spectrophotometric and microscopic analysis, significant inhibition of biofilm production was noted after 16-h incubation with 1, 2.5, and 5 muM simvastatin, concentrations that did not affect growth, adhesion, or hyphal formation by C. albicans in vitro. Higher concentrations (10, 20, and 25 muM simvastatin) inhibited biofilm by >90% but also impaired growth. Addition of exogenous ergosterol (90 muM) overcame the effects of 1 and 2.5 muM simvastatin, suggesting that at least one mechanism of inhibition is interference with ergosterol biosynthesis. Clinical isolates from blood, skin, and mucosal surfaces produced biofilms; biofilms from bloodstream isolates were similarly inhibited by simvastatin. In the absence of fungicidal activity, simvastatin's interruption of a critical step in an essential metabolic pathway, highly conserved from yeast to man, has unexpected effects on biofilm production by a eukaryotic pathogen.

Atorvastatin-induced cell toxicity in yeast is linked to disruption of protein isoprenylation

Statins, used to treat hypercholesterolemia, are one of the most frequently prescribed drug classes in the developed world. However, a significant proportion of users suffer symptoms of myotoxicity, and currently, the molecular mechanisms underlying myotoxicity remain ambiguous. In this study, Saccharomyces cerevisiae was exploited as a model system to gain further insight into the molecular mechanisms of atorvastatin toxicity. Atorvastatin-treated yeast cells display marked morphological deformities, have reduced cell viability and are highly vulnerable to perturbed mitochondrial function. Supplementation assays of atorvastatin-treated cells reveal that both loss of viability and mitochondrial dysfunction occur as a consequence of perturbation of the sterol synthesis pathway. This was further investigated by supplementing statin-treated cells with various metabolites of the sterol synthesis pathway that are believed to be essential for cell function. Ergosterol, coenzyme Q and a heme precursor were all ineffective in the prevention of statin-induced mitochondrial disruption and cell death. However, the addition of geranylgeranyl pyrophosphate and farnesyl pyrophosphate significantly restored cell viability, although these did not overcome petite induction. This highlights the pleiotropic nature of statin toxicity, but has established protein prenylation disruption as one of the principal mechanisms underlying statin-induced cell death in yeast.

In vitro interactions between primycin and different statins in their effects against some clinically important fungi

The in vitro antifungal activities of primycin (PN) and various statins against some opportunistic pathogenic fungi were investigated. PN completely inhibited the growth of Candida albicans (MIC 64 microg ml(-1)) and Candida glabrata (MIC 32 microg ml(-1)), and was very effective against Paecilomyces variotii (MIC 2 microg ml(-1)), but had little effect on Aspergillus fumigatus, Aspergillus flavus or Rhizopus oryzae (MICs >64 microg ml(-1)). The fungi exhibited different degrees of sensitivity to the statins; fluvastatin (FLV) and simvastatin (SIM) exerted potent antifungal activities against a wide variety of clinically important fungal pathogens. Atorvastatin, rosuvastatin and lovastatin (LOV) had a slight effect against all fungal isolates tested, whereas pravastatin was completely ineffective. The in vitro interactions between PN and the different statins were investigated using a standard chequerboard titration method. When PN was combined with FLV, LOV or SIM, both synergistic and additive effects were observed. The extent of inhibition was higher when these compounds were applied together, and the concentrations of PN and the given statin needed to block fungal growth completely could be decreased by several dilution steps. Similar interactions were observed when the variability of the within-species sensitivities was investigated.

Modulation of plasma membrane lipid profile and microdomains by H2O2 in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, the rate of hydrogen peroxide (H(2)O(2)) diffusion through the plasma membrane decreases during adaptation to H(2)O(2) by a still unknown mechanism. Here, adaptation to H(2)O(2) was observed to modulate rapidly the expression of genes coding for enzymes involved in ergosterol and lipid metabolism. Adaptation to H(2)O(2) also alters plasma membrane lipid composition. The main changes were the following: (a) there was a decrease in oleic acid (30%) and in the ratio between unsaturated and saturated long-chain fatty acids; (b) the phosphatidylcholine:phosphatidylethanolamine ratio increased threefold; (c) sterol levels were unaltered but there was an increased heterogeneity of sterol-rich microdomains and increased ordered domains; (d) the levels of the sterol precursor squalene increased twofold, in agreement with ERG1 gene down-regulation; and (e) C26:0 became the major very long chain fatty acid owing to an 80% decrease in 2-hydroxy-C26:0 levels and a 50% decrease in C20:0 levels, probably related to the down-regulation of fatty acid elongation (FAS1, FEN1, SUR4) and ceramide synthase (LIP1, LAC1) genes. Therefore, H(2)O(2) leads to a reorganization of the plasma membrane microdomains, which may explain the lower permeability to H(2)O(2), and emerges as an important regulator of lipid metabolism and plasma membrane lipid composition.

Reconstruction of a bacterial isoprenoid biosynthetic pathway in Saccharomyces cerevisiae

A eukaryotic mevalonate pathway transferred and expressed in Escherichia coli, and a mammalian hydrocortisone biosynthetic pathway rebuilt in Saccharomyces cerevisiae are examples showing that transferring metabolic pathways from one organism to another can have a powerful impact on cell properties. In this study, we reconstructed the E. coli isoprenoid biosynthetic pathway in S. cerevisiae. Genes encoding the seven enzymatic steps of the pathway were cloned and expressed in S. cerevisiae. mRNA from the seven genes was detected, and the pathway was shown able to sustain growth of yeast in conditions of inhibition of its constitutive isoprenoid biosynthetic pathway.

Genomewide location analysis of Candida albicans Upc2p, a regulator of sterol metabolism and azole drug resistance

Upc2p, a transcription factor of the zinc cluster family, is an important regulator of sterol biosynthesis and azole drug resistance in Candida albicans. To better understand Upc2p function in C. albicans, we used genomewide location profiling to identify the transcriptional targets of Upc2p in vivo. A triple hemagglutinin epitope, introduced at the C terminus of Upc2p, conferred a gain-of-function effect on the fusion protein. Location profiling identified 202 bound promoters (P < 0.05). Overrepresented functional groups of genes whose promoters were bound by Upc2p included 12 genes involved in ergosterol biosynthesis (NCP1, ERG11, ERG2, and others), 18 genes encoding ribosomal subunits (RPS30, RPL32, RPL12, and others), 3 genes encoding drug transporters (CDR1, MDR1, and YOR1), 4 genes encoding transcription factors (INO2, ACE2, SUT1, and UPC2), and 6 genes involved in sulfur amino acid metabolism (MET6, SAM2, SAH1, and others). Bioinformatic analyses suggested that Upc2p binds to the DNA motif 5'-VNCGBDTR that includes the previously characterized Upc2p binding site 5'-TCGTATA. Northern blot analysis showed that increased binding correlates with increased expression for the analyzed Upc2p targets (ERG11, MDR1, CDR1, YOR1, SUT1, SMF12, and CBP1). The analysis of ERG11, MDR1, and CDR1 transcripts in wild-type and upc2Delta/upc2Delta strains grown under Upc2p-activating conditions (lovastatin treatment and hypoxia) showed that Upc2p regulates its targets in a complex manner, acting as an activator or as a repressor depending upon the target and the activating condition. Taken together, our results indicate that Upc2p is a key regulator of ergosterol metabolism. They also suggest that Upc2p may contribute to azole resistance by regulating the expression of drug efflux pump-encoding genes in addition to ergosterol biosynthesis genes.

Biological consequences of statins in Candida species and possible implications for human health

The statins, simvastatin and atorvastatin are the most widely prescribed drugs. Statins lower cholesterol levels through their action on HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase, an essential enzyme for the biosynthesis of cholesterol. Fungal HMG-CoA reductases are also inhibited by statins, resulting in reduced levels of ergosterol (the fungal equivalent of cholesterol) and concomitant growth inhibition. This effect occurs in a range of fungal species and possibly affects fungal colonization of people on statin therapy. Furthermore, it may suggest that statins could have a role in new antifungal therapies. Possibly associated with the reduction in ergosterol levels, statins also inhibit respiratory growth. In the yeast, Candida glabrata, passage with statins dramatically increased the frequencies of petite mutants that were devoid of mitochondrial DNA, suggesting that statins caused a defect in the maintenance of mitochondrial DNA. These observations in C. glabrata may provide further insights into side effects of statins in humans undergoing treatment for hypercholesterolaemia. In addition, C. glabrata may be highly useful for the preliminary screening of agents to reduce statin side effects.

Antifungal activity of statins against Aspergillus species

The cholesterol-lowering agents known as statins have in vitro activities against human pathogenic fungi, such as Candida species, Cryptococcus neoformans, and Zygomycetes. Synergy between statins and azoles against these fungi has also been reported. We evaluated the in vitro activities of two statins, lovastatin and simvastatin, alone and in combination with azoles and amphotericin B, against clinical isolates of Aspergillus spp. A disk diffusion assay showed that both statins were active against Aspergillus spp. The minimal inhibitory concentration (MIC) ranges for lovastatin and simvastatin against Aspergillus spp. were 16 to >256 microg/ml and 4 to >256 microg/ml, respectively. Although both statins were fungicidal for A. fumigatus, the MICs were vastly higher than clinically achievable concentrations. The results of a combined agar dilution-Epsilometer test as well as a disk diffusion assay showed that neither statin had any effect on the in vitro activities of itraconazole, voriconazole, or amphotericin B against Aspergillus spp.