Griseofulvin

Antitumor properties of griseofulvin and its toxicity

Griseofulvin (GF), which is mainly extracted from Penicillium griseofulvum, is a heat-resistant, chlorine-containing non-polyene antifungal antibiotic. Previous research shows that GF has a variety of pharmacological effects, such as anti-inflammatory, antifungal, antiviral, and antitumor effects. In recent years, GF has received extensive attention for its antitumor effects as a natural compound, offering a low price, a wide range of uses, and other beneficial characteristics. However, no comprehensive review of GF pharmacological activity in tumors has been published so far. In order to fully elucidate the antitumor activities of GF, this review focuses on the antitumor potential and toxicity of GF and its derivatives, based on a literature search using PubMed, Web of Science, and other databases, to lay a good foundation for further research of GF and the development of new drugs for antitumor activities.

Recent drug development and treatments for fungal infections

Fungal infections are now becoming a hazard to individuals which has paved the way for research to expand the therapeutic options available. Recent advances in drug design and compound screening have also increased the pace of the development of antifungal drugs. Although several novel potential molecules are reported, those discoveries have yet to be translated from bench to bedside. Polyenes, azoles, echinocandins, and flucytosine are among the few antifungal agents that are available for the treatment of fungal infections, but such conventional therapies show certain limitations like toxicity, drug interactions, and the development of resistance which limits the utility of existing antifungals, contributing to significant mortality and morbidity. This review article focuses on the existing therapies, the challenges associated with them, and the development of new therapies, including the ongoing and recent clinical trials, for the treatment of fungal infections. Advancements in antifungal treatment: a graphical overview of drug development, adverse effects, and future prospects.

Fungal Drug Discovery for Chronic Disease: History, New Discoveries and New Approaches

Fungal-derived drugs include some of the most important medicines ever discovered, and have proved pivotal in treating chronic diseases. Not only have they saved millions of lives, but they have in some cases changed perceptions of what is medically possible. However, now the low-hanging fruit have been discovered it has become much harder to make the kind of discoveries that have characterised past eras of fungal drug discovery. This may be about to change with new commercial players entering the market aiming to apply novel genomic tools to streamline the discovery process. This review examines the discovery history of approved fungal-derived drugs, and those currently in clinical trials for chronic diseases. For key molecules, we discuss their possible ecological functions in nature and how this relates to their use in human medicine. We show how the conservation of drug receptors between fungi and humans means that metabolites intended to inhibit competitor fungi often interact with human drug receptors, sometimes with unintended benefits. We also plot the distribution of drugs, antimicrobial compounds and psychoactive mushrooms onto a fungal tree and compare their distribution to those of all fungal metabolites. Finally, we examine the phenomenon of self-resistance and how this can be used to help predict metabolite mechanism of action and aid the drug discovery process.

Computational benchmarking of putative KIFC1 inhibitors

The centrosome in animal cells is instrumental in spindle pole formation, nucleation, proper alignment of microtubules during cell division, and distribution of chromosomes in each daughter cell. Centrosome amplification involving structural and numerical abnormalities in the centrosome can cause chromosomal instability and dysregulation of the cell cycle, leading to cancer development and metastasis. However, disturbances caused by centrosome amplification can also limit cancer cell survival by activating mitotic checkpoints and promoting mitotic catastrophe. As a smart escape, cancer cells cluster their surplus of centrosomes into pseudo-bipolar spindles and progress through the cell cycle. This phenomenon, known as centrosome clustering (CC), involves many proteins and has garnered considerable attention as a specific cancer cell-targeting weapon. The kinesin-14 motor protein KIFC1 is a minus end-directed motor protein that is involved in CC. Because KIFC1 is upregulated in various cancers and modulates oncogenic signaling cascades, it has emerged as a potential chemotherapeutic target. Many molecules have been identified as KIFC1 inhibitors because of their centrosome declustering activity in cancer cells. Despite the ever-increasing literature in this field, there have been few efforts to review the progress. The current review aims to collate and present an in-depth analysis of known KIFC1 inhibitors and their biological activities. Additionally, we present computational docking data of putative KIFC1 inhibitors with their binding sites and binding affinities. This first-of-kind comparative analysis involving experimental biology, chemistry, and computational docking of different KIFC1 inhibitors may help guide decision-making in the selection and design of potent inhibitors.

Unprecedented Combination of Polyketide Natural Product Fragments Identifies the New Hedgehog Signaling Pathway Inhibitor Grismonone

Pseudo-natural products (pseudo-NPs) are de novo combinations of natural product (NP) fragments that define novel bioactive chemotypes. For their discovery, new design principles are being sought. Previously, pseudo-NPs were synthesized by the combination of fragments originating from biosynthetically unrelated NPs to guarantee structural novelty and novel bioactivity. We report the combination of fragments from biosynthetically related NPs in novel arrangements to yield a novel chemotype with activity not shared by the guiding fragments. We describe the synthesis of the polyketide pseudo-NP grismonone and identify it as a structurally novel and potent inhibitor of Hedgehog signaling. The insight that the de novo combination of fragments derived from biosynthetically related NPs may also yield new biologically relevant compound classes with unexpected bioactivity may be considered a chemical extension or diversion of existing biosynthetic pathways and greatly expands the opportunities for exploration of biologically relevant chemical space by means of the pseudo-NP principle.

Spray-Dried Griseofulvin-Lactose Matrix for Enhanced Solubility Using a Spray-Drying Biochemical Process

Griseofulvin (GF) is a hydrophobic drug with a low solubility. In order to improve the solubility of GF, which has low water solubility, this report uses the spray-drying technique to prepare complexes with lactose to promote the solubility and oral bioavailability of GF. The solution samples were spray dried using different ratios of ethanol or acetone solutions as dissolution media. By characterization of the obtained spray-dried powders, we found that the solubility of the different groups of samples obtained by spray drying was increased, and similarly, their dissolution rates were also increased to different degrees. By comparison, the greatest increase in solubility was obtained in an aqueous acetone solution, showing the greatest ability and efficiency of acetone in promoting the solubility of GF during the spray-drying process.

Novel bioreactor internals for the cultivation of spore-forming fungi in pellet form

This study introduced an automated long-term fermentation process for fungals grown in pellet form. The goal was to reduce the overgrowth of bioreactor internals and sensors while better rheological properties in the fermentation broth, such as oxygen transfer and mixing time, can be achieved. Because this could not be accomplished with continuous culture and fed-batch fermentation, repeated-batch fermentation was implemented with the help of additional bioreactor internals ("sporulation supports"). This should capture some biomass during fermentation. After harvesting the suspended biomass, intermediate cleaning was performed using a cleaning device. The biomass retained on the sporulation support went through the sporulation phase. The spores were subsequently used as inocula for the next batch. The reason for this approach was that the retained pellets could otherwise cause problems (e.g., overgrowth on sensors) in subsequent batches because the fungus would then show undesirable hyphal growth. Various sporulation supports were tested for sufficient biomass fixation to start the next batch. A reproducible spore concentration within the range of the requirements could be achieved by adjusting the sporulation support (design and construction material), and an intermediate cleaning adapted to this.

Phenols in Pharmaceuticals: Analysis of a Recurring Motif

Phenols and phenolic ethers are significant scaffolds recurring both in nature and among approved small-molecule pharmaceuticals. This compendium presents the first comprehensive compilation and analysis of the structures of U.S. FDA-approved molecules containing phenol or phenolic ether fragments. This dataset comprises 371 structures, which are strongly represented by natural products. A total of 55 of the compounds described here are on the World Health Organization's list of essential medicines. Structural analysis reveals significant differences in the physicochemical properties imparted by phenols versus phenol ethers, each having benefits and drawbacks for drug developability. Despite trends over the past decade to increase the fraction of sp³ centers in drug leads, thereby "escaping flatland", phenols and phenolic ethers are represented in 62% of small-molecule drugs approved in 2020, suggesting that this aromatic moiety holds a special place in drugs and natural products.

Augmenting Azoles with Drug Synergy to Expand the Antifungal Toolbox

Fungal infections impact the lives of at least 12 million people every year, killing over 1.5 million. Wide-spread use of fungicides and prophylactic antifungal therapy have driven resistance in many serious fungal pathogens, and there is an urgent need to expand the current antifungal arsenal. Recent research has focused on improving azoles, our most successful class of antifungals, by looking for synergistic interactions with secondary compounds. Synergists can co-operate with azoles by targeting steps in related pathways, or they may act on mechanisms related to resistance such as active efflux or on totally disparate pathways or processes. A variety of sources of potential synergists have been explored, including pre-existing antimicrobials, pharmaceuticals approved for other uses, bioactive natural compounds and phytochemicals, and novel synthetic compounds. Synergy can successfully widen the antifungal spectrum, decrease inhibitory dosages, reduce toxicity, and prevent the development of resistance. This review highlights the diversity of mechanisms that have been exploited for the purposes of azole synergy and demonstrates that synergy remains a promising approach for meeting the urgent need for novel antifungal strategies.

Natural product fragment combination to performance-diverse pseudo-natural products

Natural product structure and fragment-based compound development inspire pseudo-natural product design through different combinations of a given natural product fragment set to compound classes expected to be chemically and biologically diverse. We describe the synthetic combination of the fragment-sized natural products quinine, quinidine, sinomenine, and griseofulvin with chromanone or indole-containing fragments to provide a 244-member pseudo-natural product collection. Cheminformatic analyses reveal that the resulting eight pseudo-natural product classes are chemically diverse and share both drug- and natural product-like properties. Unbiased biological evaluation by cell painting demonstrates that bioactivity of pseudo-natural products, guiding natural products, and fragments differ and that combination of different fragments dominates establishment of unique bioactivity. Identification of phenotypic fragment dominance enables design of compound classes with correctly predicted bioactivity. The results demonstrate that fusion of natural product fragments in different combinations and arrangements can provide chemically and biologically diverse pseudo-natural product classes for wider exploration of biologically relevant chemical space.

Anticancer fungal natural products: Mechanisms of action and biosynthesis

Many fungal metabolites show promising anticancer properties both in vitro and in animal models, and some synthetic analogs of those metabolites have progressed into clinical trials. However, currently, there are still no fungi-derived agents approved as anticancer drugs. Two potential reasons could be envisioned: 1) lacking a clear understanding of their anticancer mechanism of action, 2) unable to supply enough materials to support the preclinical and clinic developments. In this review, we will summarize recent efforts on elucidating the anticancer mechanisms and biosynthetic pathways of several promising anticancer fungal natural products.

Exploring the binding sites and binding mechanism for hydrotrope encapsulated griseofulvin drug on γ-tubulin protein

The protein γ-tubulin plays an important role in centrosomal clustering and this makes it an attractive therapeutic target for treating cancers. Griseofulvin, an antifungal drug, has recently been used to inhibit proliferation of various types of cancer cells. It can also affect the microtubule dynamics by targeting the γ-tubulin protein. So far, the binding pockets of γ-tubulin protein are not properly identified and the exact mechanism by which the drug binds to it is an area of intense speculation and research. The aim of the present study is to investigate the binding mechanism and binding affinity of griseofulvin on γ-tubulin protein using classical molecular dynamics simulations. Since the drug griseofulvin is sparingly soluble in water, here we also present a promising approach for formulating and achieving delivery of hydrophobic griseofulvin drug via hydrotrope sodium cumene sulfonate (SCS) cluster. We observe that the binding pockets of γ-tubulin protein are mainly formed by the H8, H9 helices and S7, S8, S14 strands and the hydrophobic interactions between the drug and γ-tubulin protein drive the binding process. The release of the drug griseofulvin from the SCS cluster is confirmed by the coordination number analysis. We also find hydrotrope-induced alteration of the binding sites of γ-tubulin protein and the weakening of the drug-protein interactions.

Colonization of grapes berries and cider by potential producers of patulin

The aim of this study was to detect potential producers of mycotoxin patulin from grapes (berries, surface sterilized berries - endogenous mycobiota and grape juice) of Slovak origin. We analyzed 47 samples of grapes, harvested in 2011, 2012 and 2013 from various wine-growing regions. For the isolation of species we used the method of direct plating berries and surface-sterilized berries (using 1% freshly pre-pared chlorine) berries on DRBC (Dichloran Rose Bengal Chloramphenicol agar). For the determination of fungal contamination of grape juice we used plate-dilution method and DRBC and DG18 (Dichloran 18% Glycerol agar) as media. The cultivation in all modes of inoculation was carried at 25 ±1 °C, for 5 to 7 days. After incubation Aspergillus and Pencillium isolates were inoculated on the identification media. The potential producers of patulin were isolated from 23 samples berries, 19 samples of surface-sterilized berries and 6 samples of grape juice. Overall, the representatives of producers of patulin were detected in 32 (68.1%) samples (75 isolates). In this work we focused on the detection of potential producers of patulin, Penicillium expansum (the most important producer of patulin in fruits), Penicillium griseofulvum and Aspergillus clavatus were isolated. Chosen isolates of potential patulin producers were tested for the ability to produce relevant mycotoxins in in vitro conditions using thin layer chromatography method. The ability to produce patulin in in vitro condition was detected in 82% of isolates of Penicillium expansum, 65% of Penicillium griseofuvum and 100% of Aspergillus clavatus. Some isolates of Penicillium expansum were able to produce citrinin and roquefortine C, Penicillium griseofulvum cyclopiazonic acid, griseofulvin and roquefortin C, also.

Effects of griseofulvin on apoptosis through caspase-3- and caspase-9-dependent pathways in K562 leukemia cells: An in vitro study

BACKGROUND

Griseofulvin, an oral nontoxic antifungal drug, has been reported to possess anticancer effect in human cancer cells, while the mechanisms are not completely understood.

OBJECTIVE

The aim of this study was to investigate the cytotoxic effect of griseofulvin on K562 cells and to understand its underlying molecular pathways.

METHODS

K562 cells were treated with griseofulvin at different concentrations for 24 hours, and the inhibition effect of griseofulvin on K562 cell proliferation was assessed by tetrazolium salt colorimetric assay. Apoptosis was assessed by examining nuclear morphology and quantifying phosphatidylserine externalization, and alterations in cellular morphology were analyzed by laser scanning confocal microscopy for fluorescent analysis. Flow cytometry was used in the analysis of cell cycle, mitochondrial membrane potential, and caspase pathways.

RESULTS

Griseofulvin could inhibit the growth of K562 cells in a dose-dependent manner with a mean (SD) inhibitory concentration of 50% value of 15.38 (1.35) μg/mL compared with untreated controls. Apoptosis was induced in K562 cells (38.35% [2.73%]; P < 0.01) by griseofulvin with the observation of both an increase in phosphatidylserine level and accumulation of chromatin nucleation in griseofulvintreated cells. In addition, cell-cycle analysis using propidium iodide staining suggested a significant G2/M accumulation (increase from mean 17.64% [4.49%] to 48.29 [1.89%]; P < 0.01) as a result of griseofulvin treatment. Flow cytometry analysis found that griseofulvin treatment was associated with the depolarization of the mitochondrial membrane in K562 cells. Furthermore, increased activities of caspase-3 by 22.15-fold (P < 0.01) and caspase-9 by 16.73-fold (P < 0.01) were observed in K562 cells after griseofulvin treatment compared with the untreated control; a decrease of caspase-8 activity was also observed, but the change was not statistically significant.

CONCLUSIONS

These findings suggest that griseofulvin inhibited growth of K562 cells and induced cell apoptosis through cell-cycle arrest and mitochondrial membrane potential decrease as well as caspase-3 and -9 activation. Further testing is needed to evaluate the potential of griseofulvin as a candidate in the chemotherapy of hematologic malignancies.

Comparison of the aneugenic properties of nocodazole, paclitaxel and griseofulvin in vitro. Centrosome defects and alterations in protein expression profiles

We have comparatively investigated the aneugenic activity of two anticancer drugs, nocodazole (NOC) and paclitaxel (PTX), and the antifungal griseofulvin with promising role in cancer treatment (GF), which affect microtubule dynamics in different ways. The comparison was achieved in HFFF2 human fibroblasts, MCF-7 human breast cancer cells and C2C12 mouse myoblasts, and focused on three issues: (i) induction of chromosome delay by estimation of MN frequency using CREST analysis; (ii) disturbance of spindle organization with Aurora-A/β-tubulin immunofluorescence; and (iii) alterations in the expression of Aurora-A, β- and γ-tubulin by western blotting. They induced chromosome delay, provoked metaphase arrest and promoted microtubule disorganization, reflecting their common characteristic of generating aneuploidy. In particular, NOC induced mainly monopolar metaphases, although PTX induced only multipolar metaphases. GF generated different types of abnormal metaphases, exhibiting cell specificity. Additionally, NOC decreased the expression of Aurora-A and β-tubulin, while the opposite held true for PTX and GF. γ-Tubulin expression was not modulated owing to NOC treatment, whereas PTX and GF increased γ-tubulin expression. Our findings throw a light on the manifestation of the aneugenicity of the studied compounds through centrosome proliferation/separation and protein expression, reflecting their different effects on microtubule dynamics.

Microtubules as antifungal and antiparasitic drug targets

INTRODUCTION

Diseases caused by fungi and parasites are major illnesses in humans as well as in animals. Microtubule-targeted drugs are highly effective for the treatment of fungal and parasitic infections; however, several human parasitic infections such as malaria, trypanosomiasis and leishmaniasis do not have effective remedial drugs. In addition, the emergence of drug-resistant fungi and parasites makes the discovery of new drugs imperative.

AREAS COVERED

This article describes similarities and dissimilarities between parasitic, fungal and mammalian tubulins and focuses on microtubule-targeting agents and therapeutic approaches for the treatment of fungal and parasitic diseases. New microtubule-targeted antileishmanial, antimalarial and antifungal drugs, with structures, biological activities and related patents, are described. The potential of dsRNA against tubulin to inhibit proliferation of protozoan and helminthic parasites is also discussed. Patent documents up to 2010 have been searched on USPTO, Patentscope, and Espacenet resources.

EXPERT OPINION

The article suggests that vaccination with tubulin may offer novel opportunities for the antiparasitic treatment. Native or recombinant tubulin used as antigen has been shown to elicit immune response and cure infection partially or fully in animals upon challenge by protozoan parasites and helminths, thus indicating the suitability of tubulin as a vaccine against parasitic diseases.

Griseofulvin stabilizes microtubule dynamics, activates p53 and inhibits the proliferation of MCF-7 cells synergistically with vinblastine

Background

Griseofulvin, an antifungal drug, has recently been shown to inhibit proliferation of various types of cancer cells and to inhibit tumor growth in athymic mice. Due to its low toxicity, griseofulvin has drawn considerable attention for its potential use in cancer chemotherapy. This work aims to understand how griseofulvin suppresses microtubule dynamics in living cells and sought to elucidate the antimitotic and antiproliferative action of the drug.

Methods

The effects of griseofulvin on the dynamics of individual microtubules in live MCF-7 cells were measured by confocal microscopy. Immunofluorescence microscopy, western blotting and flow cytometry were used to analyze the effects of griseofulvin on spindle microtubule organization, cell cycle progression and apoptosis. Further, interactions of purified tubulin with griseofulvin were studied in vitro by spectrophotometry and spectrofluorimetry. Docking analysis was performed using autodock4 and LigandFit module of Discovery Studio 2.1.

Results

Griseofulvin strongly suppressed the dynamic instability of individual microtubules in live MCF-7 cells by reducing the rate and extent of the growing and shortening phases. At or near half-maximal proliferation inhibitory concentration, griseofulvin dampened the dynamicity of microtubules in MCF-7 cells without significantly disrupting the microtubule network. Griseofulvin-induced mitotic arrest was associated with several mitotic abnormalities like misaligned chromosomes, multipolar spindles, misegregated chromosomes resulting in cells containing fragmented nuclei. These fragmented nuclei were found to contain increased concentration of p53. Using both computational and experimental approaches, we provided evidence suggesting that griseofulvin binds to tubulin in two different sites; one site overlaps with the paclitaxel binding site while the second site is located at the αβ intra-dimer interface. In combination studies, griseofulvin and vinblastine were found to exert synergistic effects against MCF-7 cell proliferation.

Conclusions

The study provided evidence suggesting that griseofulvin shares its binding site in tubulin with paclitaxel and kinetically suppresses microtubule dynamics in a similar manner. The results revealed the antimitotic mechanism of action of griseofulvin and provided evidence suggesting that griseofulvin alone and/or in combination with vinblastine may have promising role in breast cancer chemotherapy.

Efficacy of eleven antimicrobials against a gregarine parasite (Apicomplexa: Protozoa)

Background

The Apicomplexa are a diverse group of obligate protozoan parasites infesting a wide range of invertebrate and vertebrate hosts including humans. These parasites are notoriously difficult to control and many species continue to evolve resistance to commercial antibiotics. In this study, we sought to find an effective chemotherapeutic treatment against arthropod gregarines (Apicomplexa), and to identify candidate compounds for testing against other groups of protozoan parasites.

Methods

We tested eleven commercial antibiotics against a gregarine parasite of Romalea microptera grasshoppers. Infected insects were fed daily, lettuce containing known amounts of specific antibiotics. On Days 15 or 20, we measured the number of gregarines remaining in the digestive tract of each grasshopper.

Results

Treatment with metronidazole and griseofulvin in host insects significantly reduced gregarine counts, whereas, gregarine counts of insects fed, albendazole, ampicillin, chloramphenicol, fumagillin, quinine, streptomycin, sulfadimethoxine, thiabendazole or tetracycline, were not significantly different from the controls. However, albendazole produced a strong, but non-significant reduction in gregarine count, and streptomycin exhibited a non-significant antagonistic trend.

Conclusion

Our results confirm that gregarine infections are difficult to control and suggest the possibility that streptomycin might aggravate gregarine infection. In addition, the insect system described here, provides a simple, inexpensive, and effective method for screening antibiotics.

Identification of griseofulvin as an inhibitor of centrosomal clustering in a phenotype-based screen

A major drawback of cancer chemotherapy is the lack of tumor-specific targets which would allow for the selective eradication of malignant cells without affecting healthy tissues. In contrast with normal cells, most tumor cells contain multiple centrosomes, associated with the formation of multipolar mitotic spindles and chromosome segregation defects. Many tumor cells regain mitotic stability after clonal selection by the coalescence of multiple centrosomes into two functional spindle poles. To overcome the limitations of current cancer treatments, we have developed a cell-based screening strategy to identify small molecules that inhibit centrosomal clustering and thus force tumor cells with supernumerary centrosomes to undergo multipolar mitoses, and subsequently, apoptosis. Using a chemotaxonomic selection of fungi from a large culture collection, a relatively small but diverse natural product extract library was generated. Screening of this compound library led to the identification of griseofulvin, which induced multipolar spindles by inhibition of centrosome coalescence, mitotic arrest, and subsequent cell death in tumor cell lines but not in diploid fibroblasts and keratinocytes with a normal centrosome content. The inhibition of centrosome clustering by griseofulvin was not restricted to mitotic cells but did occur during interphase as well. Whereas the formation of multipolar spindles was dynein-independent, depolymerization of interphase microtubules seemed to be mechanistically involved in centrosomal declustering. In summary, by taking advantage of the tumor-specific phenotype of centrosomal clustering, we have developed a screening strategy that might lead to the identification of drugs which selectively target tumor cells and spare healthy tissues.

NF-κB pathway is involved in griseofulvin-induced G2/M arrest and apoptosis in HL-60 cells

Griseofulvin (GF), an oral antifungal agent, has been shown to exert antitumorigenesis effect through G2/M cell cycle arrest in colon cancer cells. But the underlying mechanisms remained obscure. The purpose of this study is to test the cytotoxic effect of GF on HL-60 and HT-29 cells and elucidate its underlying molecular pathways. Dose-dependent and time-course studies by flow cytometry demonstrated that 30 to 60 microM GF significantly induced G2/M arrest and to a less extend, apoptosis, in HL-60 cells. In contrast, only G2/M arrest was observed in HT-29 cells under similar condition. Pretreatment of 30 microM TPCK, a serine protease inhibitor, completely reversed GF-induced G2/M cell cycle arrest and apoptosis in HL-60 cells but not in HT-29 cells. The GF-induced G2/M arrest in HL-60 cells is reversible. Using EMSA and super-shift analysis, we demonstrated that GF stimulated NF-kappaB binding activity in HL-60 cells, which was completely inhibited by pretreatment of TPCK. Treatment of HL-60 with 30 microM GF activated JNK but not ERK or p38 MAPK and subsequently resulted in phosphorylation of Bcl-2. Pretreatment of TPCK to HL-60 cells blocked the GF-induced Bcl-2 phosphorylation but not JNK activation. Time course study demonstrated that activation of cdc-2 kinase activity by GF correlated with Bcl-2 phosphorylation. Taken together, our results suggest that activation of NF-kappaB pathway with cdc-2 activation and phosphorylation of Bcl-2 might be involved in G2/M cell cycle arrest in HL-60 cells.

SFTG international collaborative study on in vitro micronucleus test

In this report, are presented the results of an international collaborative study on the in vitro micronucleus assay, using CHL cells. Fourteen laboratories participated in this study which was coordinated by an organizing committee supported by the SFTG (the French branch of the European Environmental Mutagen Society). Nine coded substances, having different modes of action and at different levels were assessed in the in vitro micronucleus test, using a common protocol. Mitomycin C was used as a positive control. In order to help to define a standard protocol on CHL cells, short and long treatment periods followed by various recovery times, with or without cytochalasin B, were compared. After an evaluation of the acceptability of the assays, the tested chemicals were classified as negative, positive or equivocal. Mannitol and clofibrate were judged as negative in all treatment schedules. Bleomycin was positive in all the treatment schedules, with an increase in the number of micronucleated cells in both mononucleate and binucleate cells when using cytochalasin B. This was also shown for the aneugens colchicine, diethylstilboestrol and griseofulvin, as expected. Urethane was judged as equivocal only after long treatment with cytochalasin B, and negative in all other treatment schedules. In any case, no genotoxic compound would have been missed with schedules including a short and a long treatment time, whether the treatment was followed by a recovery period or not and whether cytochalasin B was used or not. Thus, these results show that CHL cells were suitable for accurately detecting clastogenic and aneugenic compounds of various types in the in vitro micronucleus test.

Current state of three-dimensional characterisation of antifungal targets and its use for molecular modelling in drug design

The alarming rise in life-threatening systemic fungal infections due to the emergence of drug-resistant fungal strains had produced an increased demand for new antimycotics, especially those targeting novel antifungal structures. Drug discovery has developed from screening natural products and chemical synthesis to a modern approach, namely structure-based drug design. Whilst many antifungal agents currently in use were discovered more than 30 years ago, characterisation of various drug targets has only been achieved recently, contributing immensely to understanding the structure-activity relationships of antifungals and their targets. Three-dimensional characterisation has become a well established tool for modern antifungal drug research and should play an important role in investigations for new antifungal agents.

Kinetic suppression of microtubule dynamic instability by griseofulvin: implications for its possible use in the treatment of cancer

The antifungal drug griseofulvin inhibits mitosis strongly in fungal cells and weakly in mammalian cells by affecting mitotic spindle microtubule (MT) function. Griseofulvin also blocks cell-cycle progression at G(2)/M and induces apoptosis in human tumor cell lines. Despite extensive study, the mechanism by which the drug inhibits mitosis in human cells remains unclear. Here, we analyzed the ability of griseofulvin to inhibit cell proliferation and mitosis and to affect MT polymerization and organization in HeLa cells together with its ability to affect MT polymerization and dynamic instability in vitro. Griseofulvin inhibited cell-cycle progression at prometaphase/anaphase of mitosis in parallel with its ability to inhibit cell proliferation. At its mitotic IC(50) of 20 muM, spindles in blocked cells displayed nearly normal quantities of MTs and MT organization similar to spindles blocked by more powerful MT-targeted drugs. Similar to previously published data, we found that very high concentrations of griseofulvin (>100 microM) were required to inhibit MT polymerization in vitro. However, much lower drug concentrations (1-20 microM) strongly suppressed the dynamic instability behavior of the MTs. We suggest that the primary mechanism by which griseofulvin inhibits mitosis in human cells is by suppressing spindle MT dynamics in a manner qualitatively similar to that of much more powerful antimitotic drugs, including the vinca alkaloids and the taxanes. In view of griseofulvin's lack of significant toxicity in humans, we further suggest that it could be useful as an adjuvant in combination with more powerful drugs for the treatment of cancer.

Veterinary pharmacovigilance. Part 6. Predictability of adverse reactions in animals from laboratory toxicology studies

Toxicological studies are conducted on constituents of veterinary medicinal products for a number of reasons. Aside from being a requirement of legislation, they are carried out for predictive purposes in the assessment of user safety or for the determination of consumer safety, for example, in the elaboration of maximum residue limits or tolerances. Alternatively, the results of toxicology studies may be available as they have been generated for registration of the drug for human medicinal purposes. This paper examines if the results of such studies have any predictive value for adverse reactions, which might occur during clinical use in animals. A number of adverse reactions, notably the Type A (toxicology or pharmacology dependent) should be predictable from these laboratory studies. However, as with human pharmaceutical products, they have less utility in predicting Type-B reactions (idiosyncratic in nature).

Influence of Griseofulvin treatment on semen quality in the dog

Griseofulvin is used to treat dermatomycosis in many species and causes oligospermia in supra-pharmacological doses. The aim of the present study was to evaluate the effect of Griseofulvin administered at therapeutic doses upon semen quality in dogs. Four dogs were treated with Griseofulvin (25 mg/kg per day) for 30 days. Semen collections and analyses were performed before, during and for 100 days after treatment for the Griseofulvin group and 10 untreated control dogs. Semen analyses included mean percentage of forward progressively motile sperm, total sperm output, normal live sperm and normal dead sperm. There was no significant difference between control and treated dogs for each of the semen quality parameters. Therapeutic dosage of Griseofulvin had no deleterious effect upon semen quality in dogs, although this does not preclude potential embryotoxic and teratogenic effects.

Antifungal agents of use in animal health--chemical, biochemical and pharmacological aspects

A limited number of antifungal agents is licensed for use in animals, however, many of those available for the treatment of mycoses in humans are used by veterinary practitioners. This review includes chemical aspects, spectra of activity, mechanisms of action and resistance, adverse reactions and drug interactions of the antifungals in current use.

Effects of griseofulvin in medium-term liver carcinogenesis assay and peripheral blood micronucleus test in rat

Published data have suggested a possible link between the tumor promoting activity and the aneugenic properties of griseofulvin. The present study was conducted to explore this relationship. Griseofulvin was evaluated both for its potential promoting activity in liver carcinogenesis in partially hepatectomized F344 male rats initiated by diethylnitrosamine and for its genotoxic potential in the peripheral blood micronucleus assay. Rats were treated daily with 2,000 mg/kg body weight by oral gavage for 12 weeks in the medium-term carcinogenesis bioassay. GST-P-positive foci (mean number and surface area) and altered cell foci were compared in the liver of rats treated with griseofulvin alone, diethylnitrosamine alone,and griseofulvin in addition to diethylnitrosamine by using immunohistochemical and histopathological evaluation, respectively. This evaluation allowed the conclusion that griseofulvin did not initiate the carcinogenic process but rather had a potential in the liver for tumor promoting activity. Griseofulvin was found to be negative in the rat peripheral blood micronucleus test when given at a daily oral dose of 2,000 mg/kg body weight for at least 3 weeks.

3-Phenyl-5-methyl-2H,5H-furan-2-ones: tuning antifungal activity by varying substituents on the phenyl ring

A series of racemic 3-phenyl-5-methyl-2H,5H-furan-2-ones related to a natural product, (-)incrustoporine, was synthesized, and their antifungal activity evaluated. The key structural feature, furanone ring, was closed via H2SO4-mediated cyclization of 2-phenylpent-4-enoic acids. The compounds displayed antifungal activity, especially against filamentous fungi. Expressed as the minimum inhibition concentration (MIC) in micromol/L, the activity of the most promising derivative against Absidia corymbifera matched that of ketoconazole (31.25 micromol/L). In terms of microg/mL, the substance was more active (7.6 microg/mL) than this standard antifungal drug (16.6 microg/mL).

Griseofulvin-induced aneuploidy and meiotic delay in male mouse germ cells: detected by using conventional cytogenetics and three-color FISH

Griseofulvin (GF) was tested in male mouse germ cells for the induction of meiotic delay and aneuploidy. Starved mice were orally treated with 500, 1000 and 2000 mg/kg of GF in corn oil and testes were sampled 22 h later for meiotic delay analysis and chromosome counting in spermatocytes at the second meiotic metaphase (MMII). A dose-related increase in meiotic delay by dose-dependently arresting spermatocytes in first meiotic metaphase (MMI) or/and prolonging interkinesis was observed. Hyperhaploid MMII cells were not significantly increased. Sperm were sampled from the Caudae epididymes 22 days after GF-treatment of the males for three-color fluorescence in situ hybridization (FISH). The frequencies of diploidies were 0.01-0.02% in sperm of the solvent control animals and increased dose-dependently to 0.03%, 0.068% and 0.091%, respectively, for 500, 1000 and 2000 mg/kg of GF. The frequencies of disomic sperm were increased significantly above the controls in all GF-treated groups but showed no dose response. The data for individual classes of disomic sperm indicated that MII was more sensitive than MI to GF-induced non-disjunction in male mice. A comparison of the present data from male mice and literature data from female mice suggests that mouse oocytes are more sensitive than mouse spermatocytes to GF-induced meiotic delay and aneuploidy.

Toxic effects of griseofulvin: disease models, mechanisms, and risk assessment

Griseofulvin (GF) has been in use for more than 30 years as a pharmaceutical drug in humans for the treatment of dermatomycoses. Animal studies give clear evidence that it causes a variety of acute and chronic toxic effects, including liver and thyroid cancer in rodents, abnormal germ cell maturation, teratogenicity, and embroyotoxicity in various species. No sufficient data from human studies are available at present to exclude a risk in humans: therefore, attempts were made to elucidate the mechanisms responsible for the toxic effects of GF and to address the question whether such effects might occur in humans undergoing GF therapy. It is well documented that GF acts as a spindle poison and its reproductive toxicity as well as the induction of numerical chromosome aberrations and of micronuclei in somatic cells possibly may result from disturbance of microtubuli formation. Likewise, a causal relationship between aneuploidy and cancer has been repeatedly postulated. However, a critical survey of the data available on aneuploidogenic chemicals revealed insufficient evidence for such an association. Conceivably, other mechanisms may be responsible for the carcinogenic effects of the drug. The induction of thyroid tumors in rats by GF is apparently a consequence of the decrease of thyroxin levels and it is unlikely that such effects occur in GF-exposed humans. The appearance of hepatocellular carcinomas (HCC) in mice on GF-supplemented diet is preceded by various biochemical and morphological changes in the liver. Among these, hepatic porphyria is prominent, it may result from inhibition of ferrochelatase and (compensatory) induction of ALA synthetase. GF-induced accumulation of porphyrins in mouse liver is followed by cell damage and necrotic and inflammatory processes. Similar changes are known from certain human porphyrias which are also associated with an increased risk for HCC. However, the porphyrogenic effect of GF therapy in humans is moderate compared with that in the mouse model, although more detailed studies should be performed in order to clarify this relationship on a quantitative basis. A further important effect of GF-feeding in mice is the formation of Mallory bodies (MBs) in hepatocytes. These cytoskeletal abnormalities occur also in humans, although under different conditions; their appearance is associated with the induction of liver disease and HCC. Chronic liver damage associated with porphyria and MB formation, enhanced cell proliferation, liver enlargement, and enzyme induction all may contribute to the hepatocarcinogenic effect of GF in mice. In conclusion, further investigation is required for adequate assessment of health risks to humans under GF therapy.

A new possible parameter for the detection of aneuploidy inducing substances: the analysis of qualitative and quantitative abnormalities of the spindle apparatus

In the present study, compared to other cytogenetic methods, we measured the number of aneuploid cells directly by analyzing anomalies of the mitotic spindle. Qualitative and quantitative abnormalities of the mitotic spindle apparatus in transformed and non-transformed cell lines in vitro were classified. We treated the different cell lines with well known aneugenic agents as Benomyl and Griseofulvin and investigated the mitotic spindle under different experimental conditions. The spindle apparatus was stained by indirect immunofluorescence and the chromatin was counterstained by fluorescent dyes. The mitotic spindle showed a great sensitivity to the aneuploidy-inducing substances used in our experiments. The spindle-disturbing effect of the tested substances was demonstrated to be dose- dependent. The morphological alterations appeared to be independent of the aneuploidy-inducing test substance used, but showed a relation to the dose and length of treatment. Thus, the analysis of the mitotic spindle may be a useful screening parameter for the detection of aneuploidy-inducing substances and further investigations will provide additional results to specific parameters.

The detection and evaluation of aneugenic chemicals

Although aneuploidy makes a significant contribution to both somatic and inherited disease the mechanisms by which environmental chemicals may induce numerical chromosome aberrations are only poorly defined. The European Union Project was aimed to further our understanding of those chemical interactions with the components of the mitotic and meiotic cell division cycle which may lead to aneuploidy and to characterise the parameters such as cellular metabolism which may influence the activity of aneugenic chemicals. C-mitosis can be induced by the highly lipophilic polychlorinated biphenyl and the completion of mitosis and cleavage can be modified by agents which deplete cellular levels of reduced glutathione. Modifications of the fidelity of chromosome segregation were produced by inhibiting the functioning of topoisomerase II during chromatid separation. In contrast, the modification of centromere integrity resulted in chromosome breakage as opposed to disturbance of segregation. Modifiers of tubulin assembly and centriolar functioning in somatic cells such as acrylamide, vinblastine and diazepam reproduced their activity in rodent bone marrow and male germ cells. The analysis of chromosome malsegregation in Aspergillus nidulans by a structurally related series of halogenated hydrocarbons was used to develop a QSAR model which had high predictive value for the results of fungal tests for previously untested related chemicals. Metabolic studies of potential aneugens in genetically engineered human lymphoblastoid cells demonstrated the detoxification of the aneugenic activity of chloral hydrate and the activation of 2,3-dichlorobutane, 1,1,2-trichloroethane and trichloroethylene by Phase I biotransforming enzymes. Cell transformation studies in Syrian hamster dermal cultures using a panel of 22 reference and or potential aneugens indicated that 15 of the 22 produced positive results following single exposures. Five of the aneugens which were negative following single exposures produced positive results where cultures were continuously exposed for up to 6 weeks to low concentrations following a single non-transforming exposure to the mutagen dimethyl sulphate. The transformation studies indicate that a significant proportion of chemical aneugens are potential complete carcinogens and/or co-carcinogens. To optimise the enumeration of chromosomes following exposure to potential chemical aneugens whole chromosome paints and centromere specific probes suitable for use in fluorescence in situ hybridisation (FISH) were developed for the rat, mouse and Chinese hamster and selected human probes evaluated for their suitability for routine use. Molecular chromosome probes were used to develop protocols for enumerating chromosomes in metaphase cells and centromeres and micronuclei in interphase cells. The analysis of segregation of specific centromeres in binucleate cells following cytochalasin B treatment was shown to be a potentially valuable system for characterising non-disjunction following chemical exposure. Whole chromosome paints and centromere specific probes were used to demonstrate the presence of dose-response thresholds following treatment with a reference panel of spindle inhibiting chemicals. These data indicate that the FISH technology is suitable for evaluating the relative hazards of low-dose exposures to aneugenic chemicals.

Genotoxic effect of griseofulvin in somatic cells of Drosophila melanogaster

Griseofulvin (GF), a carcinogenic spindle poison, was tested in two types of somatic-cell assays of Drosophila melanogaster, one of which detects the induction of DNA damage and the other mutation/mitotic recombination. In both assays, GF was fed to tester larvae and genetic endpoints examined after emergence. In the wing spot test, trans-heterozygous flies carrying mwh and flr3 wing-hair mutations produced both significant and dose-dependent increases in the frequency of mwh single spots over the control level but no increase of twin spots. In the DNA repair test, double-mutant larvae carrying both mei-9(a) (excision repair-defective) and mei-41(D5) (postreplication repair-defective) mutations showed hypersensitivity to killing by GF compared with their DNA repair-proficient counterparts, suggesting that GF caused potentially lethal DNA damages which were efficiently repaired by the DNA repair-proficient but not -defective larvae. These lines of evidence clearly demonstrate that GF is genotoxic in somatic cells of Drosophila. It is noted that (1) GF-fed larvae showed a developmental delay and (2) surviving adult flies had morphological abnormalities in their eyes and wings.

Detection of aneuploidy-inducing carcinogens in the Syrian hamster embryo (SHE) cell transformation assay

As evidenced by the recent report of the Commission of the European Communities (CEEC) project (Detection of Aneugenic Chemicals-CEEC project, 1993), there currently is a great deal of effort towards developing and validating assays to detect aneuploidy-inducing chemicals. In this report, we describe the utility of the Syrian hamster embryo (SHE) cell transformation assay for detecting carcinogens with known or suspected aneuploidy-inducing activity. The following carcinogens were tested: asbestos, benomyl, cadmium chloride, chloral hydrate, diethylstilbestrol dipropionate, and griseofulvin. Thiabendazole, a noncarcinogen, was also tested. Chemicals of unknown or inconclusive carcinogenicity data, colcemid, diazepam, econazole nitrate, and pyrimethamine were also evaluated. All of the above chemicals except thiabendazole induced a significant increase in morphological transformation (MT) in SHE cells. Based on these results as well as those published in the literature previously, the SHE cell transformation assay appears to have utility for detecting carcinogens with known or suspected aneuploidy-inducing ability.

OTC pharmaceuticals and genotoxicity testing: the paracetamol, anthraquinone, and griseofulvin cases

Genotoxic effects are hardly assessable in an exposed population but are generally considered to be serious due to their unpredictable effects on subsequent generations and to the link between genotoxicity and cancer. Lack of knowledge about a genotoxic/carcinogenic potential has to be stated for numerous compounds which are often in pharmaceutical use known for a long time. A thorough testing programme like it is done for new compounds is essential for such compounds that are not completely unsuspicious with respect to being reactive with macromolecules or that have the potential to generate reactive metabolites in the body. Paracetamol, anthraquinone-containing preparations, and griseofulvin are examples for pharmaceuticals that have been in use for a long time but for which genotoxicity testing revealed a possible deleterious potential only recently. The Federal Health Office/Federal Institute for Drugs and Medical Devices therefore imposed new studies upon companies marketing these compounds in the last years. These studies in part led to a more thorough description of possible adverse effects or even restrictions for use. Paracetamol exhibits a genotoxic potential in vitro and in vivo probably via indirect, cytotoxicity or enzyme inhibition-mediated effects. Further studies will have to clarify whether a threshold could be established and whether effects do not occur at therapeutic dose levels. Genotoxicity data on the mixed group of anthraquinones reveal positive and negative findings. Compounds such as lucidin, danthron, emodin supposedly have a genotoxic and carcinogenic potential. Further studies with anthraquinone-containing plant preparations will have to clarify the content and genotoxic activity of the preparations and the active ingredients. Lucidin- and danthron-containing preparations are currently no longer in use now whereas restrictions apply for other anthraquinone-containing laxatives. Griseofulvin is acknowledged in the meantime as an aneugen for somatic and germ cells. It is in vitro effective in concentrations that correspond to therapeutic plasma levels.

The Mallory body: morphological, clinical and experimental studies (Part 1 of a literature survey)

To aid understanding of markers of disease and predictors of outcome in alcohol-exposed systems, we undertook a literature survey of more than 700 articles to view the morphological characteristics and the clinical and experimental epidemiology of the Mallory body. Mallory bodies are filaments of intermediate diameter that contain intermediate filament components (e.g., cytokeratins) observable by conventional light microscopy or immunohistochemical methods, identical in structure regardless of initiating factors or putative pathogenesis. Although three morphological types can be identified under electron microscopy (with fibrillar structure parallel, random or absent), they remain stereotypical manifestations of hepatocyte injury. A summary of the conditions associated with Mallory bodies in the literature and their validity and potential etiological relationships is presented and discussed, including estimates on the combined light microscopic and immunohistochemical prevalences and kinetics. Emphasis is placed on proper confounder control (in particular, alcohol history), which is highly essential but often inadequate. These conditions include (mean prevalence of Mallory bodies in parentheses): Indian childhood cirrhosis (73%), alcoholic hepatitis (65%), alcoholic cirrhosis (51%), Wilson's disease (25%), primary biliary cirrhosis (24%), nonalcoholic cirrhosis (24%), hepatocellular carcinoma (23%), morbid obesity (8%) and intestinal bypass surgery (6%). Studies in alcoholic hepatitis strongly suggest a hit-and-run effect of alcohol, whereas other chronic liver diseases show evidence of gradual increase in prevalence of Mallory bodies with severity of hepatic pathology. Mallory bodies in cirrhosis do not imply alcoholic pathogenesis. Obesity, however, is associated with alcoholism and diabetes, and Mallory bodies are only present in diabetic patients if alcoholism or obesity complicates the condition. In addition, case studies on diseases in which Mallory bodies have been identified, along with pharmacological side effects and experimental induction of Mallory bodies by various antimitotic and oncogenic chemicals, are presented. Mallory bodies occur only sporadically in abetalipoproteinemia, von Gierke's disease and focal nodular hyperplasia and during hepatitis due to calcium antagonists or perhexiline maleate. Other conditions and clinical drug side effects are still putative. Finally, a variety of experimental drugs have been developed that cause Mallory body formation, but markedly different cell dynamics and metabolic pathways may raise questions about the relevance of such animal models for human Mallory body formation. In conclusion, the Mallory body is indicative but not pathognomonic of alcohol involvement. A discussion on theories of development and pathological significance transcending the clinical frameworks will be presented in a future paper.

Induction of kinetochore-positive micronuclei in human lymphocytes by the anti-fungal drug griseofulvin

Griseofulvin (GF) is a widely used antifungal drug for the treatment of superficial dermatomycoses. However, because GF is carcinogenic and teratogenic in animal models there is considerable concern regarding its clinical application. Further, it produces numerical chromosome aberrations in human lymphocytes and cell lines. There are conflicting reports on the ability of GF to induce structural chromosomal aberrations. Here, we show GF induces micronucleus formation both in isolated peripheral lymphocytes and lymphocytes from whole blood cultures. An antikinetochore antibody was used to distinguish micronuclei with acentric chromosome fragments (kinetochore-negative) and from those containing whole chromosomes (kinetochore-positive). The micronuclei formed were 99% kinetochore-positive in isolated lymphocytes. In addition, GF was able to alter the cell cycle kinetics of lymphocytes, thereby increasing the percentage of triploid cells. We conclude that GF is a strong aneuploidy-inducing agent in peripheral human lymphocytes and produces effects at concentrations which should be detectable in the blood of persons undergoing therapy.

Metabolic activation of four drugs in the eye mosaic assay measuring principally mitotic recombination in Drosophila melanogaster: differences in strain susceptibility and route of exposure

One mycotoxin and three therapeutic drugs widely used in developing countries were examined for genotoxic activity by means of the w/w + somatic recombination assay. Streptozotocin (SZ), an antibiotic antineoplastic agent, gave a frequency of light spots almost one order of magnitude higher than those obtained with the carcinogen mycotoxin sterigmatocystin (STC), the antiprotozoal and antimicrobial metronidazole (MNZ), and the antifungal griseofulvin (GF). Thus the order of response was SZ > STC > MNZ > GF. Chronic treatment turned out to be the better route of exposure for these genotoxins when compared with surface treatment. The performance of the insecticide-resistant strain Hikone-R was better than that of the wild genotype LS (Leiden Standard). The positive test results obtained with all four chemicals showed that the P450 system of Drosophila is capable of metabolizing these genotoxins into electrophilic intermediates.

Variation of mouse oocyte sensitivity to griseofulvin-induced aneuploidy and meiotic delay during the first meiotic division

The effects of varying the time of chemical treatment on the induction of aneuploidy and meiotic delay in metaphase II (MII) oocytes were studied by administering 1,500 mg/kg griseofulvin (GF) at 0, 2, 4, 6, or 8 hr after an injection of human chorionic gonadotrophin (HCG). The results show that the oocytes have a different sensitivity to GF-induced aneuploidy and meiotic delay during the course of meiotic maturation. Although not restricted to a particular period of meiotic maturation, the frequency of aneuploidy was highest (P < 0.05) when GF was given at 2, 4, or 6 hr after HCG. The maximum frequency of hyperploidy (42.4%) occurred at the 4-hr treatment time. Also, GF treatment resulted in the induction of meiotic delay as demonstrated by ovulated metaphase I (MI) and polyploid MII oocytes. The meiotic delay data depict a period of relative resistance between two periods of sensitivity in that the percentages of ovulated MI oocytes were 53.3, 21.3, 3.5, 6.7, and 25.7 when GF was given at 0, 2, 4, 6, and 8 hr after HCG, respectively. Also, at these treatment times the percentages of polyploid oocytes were 0.6, 1.7, 7.7, 20.1, and 15.4, respectively. Therefore, the oocytes seem to be more sensitive to GF-induced meiotic delay during the periods preceding and following meiotic spindle assembly. In conclusion, the results demonstrate that the time of chemical treatment influences the frequency of aneuploidy and the degree of meiotic delay. Also, the results emphasize that to thoroughly characterize the aneugenic potential of a specific chemical several treatment times may be needed.

Griseofulvin-induced aneuploidy and meiotic delay in mouse oocytes: effect of dose and harvest time

The in vivo mouse oocyte assay provides a useful system for studying both structural and numerical cytogenetic abnormalities induced by chemicals in mammalian germ cells. As part of the development of this assay for investigating chemically-induced numerical chromosome changes, the experimental and biological variables that can influence the outcome of the assay are being determined. In this study, we investigated the effect of griseofulvin (GF) administered by oral gavage on the induction of meiotic delay as measured by ovulated metaphase I (MI) oocytes and the induction of aneuploidy in metaphase II (MII) oocytes. The results indicate that GE significantly increased the frequencies of oocytes blocked in MI and of hyperploid MII oocytes compared to controls. The biological fate of delayed MI oocytes was investigated by harvesting oocytes at different times post treatment. With increasing harvest times, the frequency of MI oocytes decreased and, unexpectedly, the frequency of hyperploid MII oocytes also decreased. This suggests that some MI oocytes can overcome the GF-induced meiotic block, form a normal meiotic spindle, and progress to metaphase II as normal MII oocytes. The significance of these findings for the design and interpretation of in vivo mouse oocyte studies is discussed.

Mechanisms of action of systemic antifungal agents

An understanding of the mechanisms of action and in vitro profiles of antifungal agents is pivotal to selecting effective treatments for dermatophytoses. The principal mechanisms of action of antifungal drugs include disruption of spindle and cytoplasmic microtubule function (e.g., griseofulvin), depletion of or binding to ergosterol (e.g., terbinafine, ketoconazole, and amphotericin B), and accumulation of squalene (terbinafine). It is likely that antifungal agents that deplete or bind to ergosterol have fungistatic activity only; agents that produce a concomitant accumulation of intracellular squalene have fungicidal activity. Although the mechanism of action markedly influences the clinical efficacy of an antifungal agents, in vitro and in vivo antimycotic profiles and bioavailability factors such as drug access to the stratum corneum also contribute to the effectiveness of antifungal agents.

Analysis of the six additional chemicals for in vitro assays of the European Economic Communities' EEC aneuploidy programme using Saccharomyces cerevisiae D61.M and the in vitro porcine brain tubulin assembly assay

We tested six additional chemicals (acetaldehyde, benomyl, diethylstilboestrol, diethylstilboestrol dipropionate, griseofulvin, and mercaptoethanol) for in vitro systems of the coordinated programme to study aneuploidy induction sponsored by the Commission of the European Communities in two in vitro test systems. Using Saccharomyces cerevisiae D61.M (mitotic chromosomal malsegregation assay), benomyl showed a dose-dependent increase in the frequency of chromosomal malsegregation with a lowest effective dose tested (LEDT) of 30 micrograms/ml (0.1 mM). Diethylstilboestrol (DES) showed solvent-dependent effects. DES dissolved in ethanol induced an increase in chromosomal malsegregation as well as in the frequency of total resistant colonies (mutations and recombinations) with a LEDT around 13 micrograms/ml (0.048 mM). Using dimethylsulfoxide as the solvent, no increases were observed with DES up to 333 micrograms/ml (1.24 mM). Acetaldehyde induced an increase in chromosomal malsegregation with the cold treatment protocol (LEDT: 1.25 microliters/ml (21 mM) and 0.75 microliters/ml (13 mM), respectively) but no increase with the overnight protocol (highest dose tested (HDT): 1.75 microliters/ml; 30 mM). Concerning the frequency of total cycloheximide-resistant colonies (mutations and recombinations) increases were obtained with both protocols. The other three compounds were negative when tested up to toxic doses (survival below 10%), up to the maximum solubility in the solvent used or up to heavy precipitation in the incubation mix. The HDT were 333 micrograms/ml (0.88 mM) for diethylstilboestrol dipropionate, 1,600 micrograms/ml (4.5 mM) for griseofulvin and 0.5 microliters/ml (7 mM) for mercaptoethanol. Concerning effects on porcine brain tubulin assembly in vitro, diethylstilboestrol and griseofulvin inhibited the assembly process. The IC30% (30% inhibition concentration) values were 12.5 microM and 100 microM for DES and griseofulvin, respectively. Mercaptoethanol showed no effects up to 50 mM.

Griseofulvin-induced aneuploidy and meiotic delay in female mouse germ cells. I. Cytogenetic analysis of metaphase II oocytes

Griseofulvin (GF) was tested in female mouse germ cells for the induction of aneuploidy and meiotic arrest. Superovulated mice were orally treated with 200, 666, 1332 or 2000 mg/kg in olive oil at the time of human chorionic gonadotrophin (HCG) injection and were sacrificed 18 h later. A dose-dependent increase in the frequency of metaphase I (M I) arrested oocytes was observed (maximum of 70%). Aneuploidy was not significantly induced. Also, the kinetics of meiotic progression up to the metaphase II (M II) stage was studied in untreated mice in order to correlate the time of treatment with the time of the first meiotic division. The results demonstrate that the majority of cells was treated with GF approximately 8 h before the M I stage. A second series of experiments were performed to test GF effects at a different treatment time. Doses of 200, 666 or 2000 mg/kg were administered 2 h post HCG. As in the first series of experiments, the animals were sacrificed 18 h post HCG. The results, compared with those obtained in the first experimental series, showed an inverse trend for meiotic arrest and aneuploidy induction. The frequency of M I arrested oocytes dropped from a maximum of 70% to a maximum of 20%, while, at the latest treatment time, a dose-dependent increase in the frequency of hyperploid oocytes was observed up to 56% aberrant cells at 2000 mg/kg. Altogether the results suggest that the arrest of meiotic division and the induction of aneuploidy by GF are caused by interaction with different targets or different developmental stages of the same target. In conclusion, GF has been shown to induce aneuploidy during the first meiotic division in a dose-related manner, together with other effects such as polyploidy, developmental delay and meiotic arrest. Also, these findings demonstrate that the sensitivity of the oocyte target(s) may be restricted to a specific time period and that a correct experimental protocol is critical for assessing the aneugenic activity of a chemical.

Griseofulvin-induced aneuploidy and meiotic delay in female mouse germ cells. II. Cytogenetic analysis of one-cell zygotes

The effects of griseofulvin (GF) upon the first meiotic division of female mouse germ cells were evaluated by cytogenetic analysis of first-cleavage (1-Cl) zygotes. The present study is an extension of an investigation that began with the cytogenetic analysis of metaphase II (M II) oocytes. Different doses (200, 666, 1332, 2000 mg/kg) were tested by oral administration of GF to superovulated animals either at the time of human chorionic gonadotrophin (HCG) injection or 2 h post HCG. When GF was given at the time of HCG, significant dose-dependent increases of different types of cytogenetically abnormal cells were found. These included zygotes containing ostensibly female-derived M I or M II arrested chromosomes and polyploid zygotes. The total yields of these aberrations were 2.9, 4.3, 26.2, 60.6, and 64.1% for control, 200, 666, 1332, and 2000 mg/kg, respectively. The origin of these zygotes was attributed to the fertilization of oocytes that had been previously arrested at M I. No significant induction of hyperploidy was detected. Developmentally abnormal zygotes were still observed when GF was administered 2 h post HCG, although their frequencies were significantly lower than in the first series of experiments. The yields of developmentally abnormal zygotes were 49, 10.2, and 23.6% at 200, 666, and 2000 mg/kg. Additionally, a dose-dependent increase in the frequency of hyperploid zygotes was detected up to a maximum of 36.5% at 2000 mg/kg. These results confirm the cytogenetic observations from M II oocytes after GF treatment under the same experimental conditions; namely, a dramatic change in the oocyte target susceptibility to GF occurred within a short time period. Also, the present study demonstrated that most of GF-induced aneuploid oocytes were fertilized and reached first-cleavage metaphase.