The negligible effects of the antifungal natamycin on cholesterol-dipalmitoyl phosphatidylcholine monolayers may explain its low oral and topical toxicity for mammals.

Natamycin is an effective, broad spectrum antifungal with no reported resistance, in contrast to most antimicrobials. It also exhibits reduced (oral and topical) toxicity to humans, which is probably associated with the lack of effects on mammalian cell membranes. In this paper we employ Langmuir monolayers to mimic a cell membrane, whose properties are interrogated with various techniques. We found that natamycin has negligible effects on Langmuir monolayers of dipalmitoyl phosphatidylcholine (DPPC), but it strongly affects cholesterol monolayers. Natamycin causes the surface pressure isotherm of a cholesterol monolayer to expand even at high surface pressures since it penetrates into the hydrophobic chains. It also reduces the compressibility modulus, probably because natamycin disturbs the organization of the cholesterol molecules, as inferred with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). In mixed cholesterol/DPPC monolayers, strong effects from natamycin were only observed when the cholesterol concentration was 50mol% or higher, well above its concentration in a mammalian cell membrane. For a sterol concentration that mimics a real cell membrane in mammals, i.e. with 25mol% of cholesterol, the effects were negligible, which may explain why natamycin has low toxicity when ingested and/or employed to treat superficial fungal infections.

Predictive genomic biomarkers for drug-induced nephrotoxicity in mice.

The present study aimed to establish candidate biomarker genes for the early detection of nephrotoxicity in mice, with a particular focus on nephrotoxicity caused by polyene macrolides. Comprehensive gene expression changes were evaluated using microarrays in a mouse model in which acute nephrotoxicity was induced by amphotericin B deoxycholate, trade name Fungizone. The upregulated genes identified through microarray analysis of kidney tissue of Fungizone-treated mice included several genes that have been reported as nephrotoxicity biomarkers in rats, and 14 genes were selected as candidate nephrotoxicity biomarkers. The usefulness of these genes as nephrotoxicity biomarkers in mice was evaluated further through expression profiling under several experimental conditions using real time RT-PCR. Expression of genes encoding kidney injury molecule 1, lipocalin 2, tissue inhibitor of metalloproteinase 1, and secreted phosphoprotein 1 was highly upregulated by Fungizone, nystatin, natamycin, amphotericin B methyl ester, and liposomal amphotericin B, and their area under the ROC curve values were more than 0.95. These genes were more sensitive at detecting nephrotoxicity than traditional clinical chemistry and histopathology parameters. This study provides novel evidence that these nephrotoxicity biomarker genes identified are translatable to mice, and that they are useful for early and sensitive detection of nephrotoxicity.

Chromosome aberrations, micronucleus and sperm head abnormalities in mice treated with natamycin, [corrected] a food preservative.

Natamycin [corrected] is used as preservative in foods. The genotoxic effects of the food preservative natamycin [corrected] were evaluated using chromosome aberrations and micronucleus test in bone marrow cells and sperm head abnormality assays in mice. Blood samples were taken from mice and levels of total testosterone in serum were also determined. Natamycin [corrected] was intraperitoneally (ip) injected at 200, 400 and 800 mg/kg. Natamycin [corrected] did not induce chromosome aberrations but significantly increased the number of micronucleated polychromatic erythrocytes in bone marrow and sperm head abnormalities at all concentrations and treatment periods. It also decreased MI at all concentrations for 6, 12 and 24h treatment periods. Natamycin [corrected] decreased PCE/NCE ratio at all concentrations for 48h in female mice, for 24 and 48h treatment periods in male mice. At the 800 mg/kg concentration, natamycin [corrected] decreased PCE/NCE ratio for 24 and 72h in female mice. A dose dependent increase was observed in the percentage of sperm head abnormalities. The levels of serum testosterone decreased dose-dependently. The obtained results indicate that natamycin [corrected] is not clastogenic, but it is aneugenic in mice bone marrow and it is a potential germ cell mutagen in sperm cells.

Effects of natamycin on sister chromatid exchanges, chromosome aberrations and micronucleus in human lymphocytes.

Natamycin (pimaricin) (E235) is an antifungal that can be used as an antibiotic to treat most fungus infections. It has been globally used in a variety of foods and beverages. In the present study, the effects of natamycin on chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and micronucleus (MN) formation in human lymphocytes cells were investigated. The human lymphocytes were treated with 13, 18, 23, and 28 microg/mL of natamycin for 24 and 48 h. Natamycin induced the SCE frequency at the highest concentration for 48 h only; however, it induced the structural CA and MN frequency at all concentrations when compared to control and at all concentrations, except the lowest concentration (13 microg/mL), when compared to solvent control. Natamycin showed a cytotoxic effect by decreasing the replication index, mitotic index, and nuclear division index (NDI), especially at the highest concentrations for two treatment periods.

Selective activity of polyene macrolides produced by genetically modified Streptomyces on Trypanosoma cruzi.

The growth inhibitory effects on Trypanosoma cruzi of several natural tetraene macrolides and their derivatives were studied and compared with that of amphotericin B. All tetraenes strongly inhibited in vitro multiplication. Proliferation of epimastigotes was arrested by all these drugs at < or =3.6 microM, which were also active on amastigotes proliferating in fibroblasts. Compared with amphotericin B, the compounds were less effective but also less toxic, showing no effect on the proliferation of J774 and NCTC 929 mammalian cells at concentrations active against the parasites. CE-108B (a polyene amide) appeared to be an especially potent trypanocidal compound, with strong in vivo trypanocidal activity and very low or no toxic side effects, and thus should be considered for further studies.

A case-control teratological study of vaginal natamycin treatment during pregnancy.

The aim of this study was to investigate the teratogenicity of vaginal natamycin treatment during pregnancy, because the data of human epidemiological studies have not been published. Pair analysis of cases with congenital abnormalities and matched healthy controls was carried out. The population-based data set of the Hungarian Case-Control Surveillance of Congenital Abnormalities between 1980 and 1996 included as total, 38,151 pregnant women who delivered newborn infants without any defects (control group) and 22,843 pregnant women who had fetuses or newborns with congenital abnormalities. 62 (0.27%) and 98 (0.26%) pregnant women were treated with the natamycin in the case and control groups, respectively (crude OR 1.1 with 95% CI: 0.8-1.5). A teratogenic potential of vaginal natamycin treatment during the second and third months of pregnancy, the critical period of most major congenital abnormalities, was not indicated in the case-control pair analysis (adjusted OR 0.9 with 95% CI: 0.4-1.8). A somewhat higher mean birth weight (72 g) was found in control newborn infants born to mothers with natamycin treatment compared with the data of control newborn infants without this treatment (adjusted P=0.01), though mean gestational age was shorter. The conclusion of this study is that the treatment with vaginal natamycin during pregnancy presents no detectable teratogenic risk to the fetus.

Cytotoxicity in pig hepatocytes induced by 8-quinolinol, chloramine-T and natamycin.

The potential cytotoxic effects of the compounds 8-quinolinol, chloramine-T and natamycin have been studied in isolated pig hepatocytes. The relative cytotoxicity of these compounds was evaluated on the basis of the leakage of cytosolic lactate dehydrogenase (LDH), 3-(4,5 dimethyl)thiazol-2-yl,-2,5-diphenyl tetrazolium bromide (MTT) reduction by mitochondrial dehydrogenases, uptake of neutral red (NR) by cytosolic lysosomes, glutathion (GSH) depletion and oxidized glutathion (GSSG) efflux after 24 h exposure. Evaluation of the 20%, 50% and 80% reduced absorbance data obtained from the parameters NR20, NR50, and NR80, and MTT20, MTT50 and MTT80 enabled us to rank these compounds in decreasing order of cytotoxicity: 8-quinolinol > natamycin > chloramine-T. Also for the parameters LDH and GSH, chloramine-T appears to be less cytotoxic than natamycin and 8-quinolinol. Our study demonstrated that pig hepatocytes may be a useful model for examining cytotoxic events of drugs to be used in pigs, therefore avoiding possible extrapolation problems due to species differences.

Intravenous effects of pimaricin on mycotic endophthalmitis.

Rabbits weighing 2 to 3 kg with induced Candida endophthalmitis in the left eye were given 5 mg/kg and 10 mg/kg pimaricin intravenously. In the course of investigation, no significant level of pimaricin was found in the vitreous of those animals receiving 5 to 10 mg/kg pimaricin intravenously, and only 3 microgram/ml aqueous was found after chronic therapy for 1 to 3 weeks. No ocular or retinotoxicity was noted, although toxicity was inherent in the liver, kidney, and endocrine glands. From these studies, it is concluded that intravenous therapy alone is not sufficient for treatment of fungal endophthalmitis due to high toxicity and inadequate ocular drug levels.

Polyene macrolide antibiotic cytotoxicity and membrane permeability alterations. I. Comparative effects of four classes of polyene macrolides on mammalian cells.

The relationship between polyene macrolide-induced early membrane damage and cytotoxicity in B1 (hamster), B82 (mouse), and RAG (mouse) cells has been investigated. Filipin (FIL) induced the greatest immediate damage, as monitored by 51Cr release, followed by mediocidin (MED), amphotericin B-deoxycholate (Fungizone) (FZ) and pimaricin (PIM). For long term effect, PIM was the least toxic followed by MED, FZ, and FIL as indicated by 24-hour survival, 72-hour viability, and growth rate of cells. In evaluating polyene macrolide-induced permeability alterations and cytotoxicity two types of interactions with mammalian cells were found: (1) cell toxicity at polyene macrolide levels not eliciting immediate membrane permeability changes; and (2) immediate membrane damage without long range toxicity.

Intraocular effects of pimaricin.

Pigmented rabbits weighing 3 to 6 lbs were given bilateral intraocular injections of 250 to 1,000 mug pimaricin. Following their injection, blood, aqueous and vitreous levels were determined at various time intervals during the first 24 hours and at 24 hour intervals thereafter for one week. In subsequent studies, pigmented rabbits were given bilateral intraocular injections of 5,000 spores of A. fumigatus and 30 hours later received intraocular injections of 250 to 1,000 mug pimaricin. These studies show that 250 mug of intraocular pimaricin is well tolerated in the infected and normal animal eye with therapeutic ocular levels maintained for over 24 hours. Drug levels above 250 mug, although relatively notoxic in the normal eye resulted in irreversible damage to ocular structures in the infected eye that could not be resolved. Thus in the case of fungal endophthalmitis involving the anterior segment which will lead to the ultimate loss of the eye, an injection of 250 mug of pimaricin might preserve useful vision.