Expression of ubiquitin gene in Microsporum canis and Trichophyton mentagrophytes cultured with fluconazole

Effect of miconazole nitrate on immunological response and its preventive efficacy in Labeo rohita fingerlings against oomycetes Saprolegnia parasitica

This study evaluated the effect of sublethal doses of antifungal drug miconazole nitrate (MCZ) on immunological responses and its role as a prophylactic drug against S. parasitica in Labeo rohita fingerlings. Fish were fed with sublethal doses of MCZ, that is, T1-6.30 mgMCZ kgBW^-1 , T2-12.61 mgMCZ kgBW^-1 and T3-25.22 mgMCZ kgBW^-1 , and sampling was done at different time intervals for 240 hr. Immunological parameters viz. lysozyme activity, oxygen radical production and plasma antiprotease activity showed significant enhancement (p < 0.05) in fish fed with T2 and T3 doses. Expression of immune-relevant genes such as TLR-22 and β2-M showed significantly higher expression at 6 hr and 24 hr of sampling in both liver and head kidney. However, these genes showed a downregulation after 120 hr of sampling in both the tissues. Preventive efficacy study showed that single dose of MCZ provides protection against oomycetes up to the fourth day of infection. Significantly higher mortality was observed in control diet-fed fish as compared to fish fed with MCZ medicated diet. Thus, it can be concluded that the MCZ can act as a potent antifungal agent for preventing oomycetes infection as well as to enhance the immune response.

Dosage rescue by UBC4 restores cell wall integrity in Saccharomyces cerevisiae lacking the myosin type II gene MYO1

Myosin II is important for normal cytokinesis and cell wall maintenance in yeast cells. Myosin II-deficient (myo1) strains of the budding yeast Saccharomyces cerevisiae are hypersensitive to nikkomycin Z (NZ), a competitive inhibitor of chitin synthase III (Chs3p), a phenotype that is consistent with compromised cell wall integrity in this mutant. To explain this observation, we hypothesized that the absence of myosin type II will alter the normal levels of proteins that regulate cell wall integrity and that this deficiency can be overcome by the overexpression of their corresponding genes. We further hypothesized that such genes would restore normal (wild-type) NZ resistance. A haploid myo1 strain was transformed with a yeast pRS316-GAL1-cDNA expression library and the cells were positively selected with an inhibitory dose of NZ. We found that high expression of the ubiquitin-conjugating protein cDNA, UBC4, restores NZ resistance to myo1 cells. Downregulation of the cell wall stress pathway and changes in cell wall properties in these cells suggested that changes in cell wall architecture were induced by overexpression of UBC4. UBC4-dependent resistance to NZ in myo1 cells was not prevented by the proteasome inhibitor clasto-lactacystin-beta-lactone and required the expression of the vacuolar protein sorting gene VPS4, suggesting that rescue of cell wall integrity involves sorting of ubiquitinated proteins to the PVC/LE-vacuole pathway. These results point to Ubc4p as an important enzyme in the process of cell wall remodelling in myo1 cells.

Fluconazole upregulates sconC expression and inhibits sulphur metabolism in Microsporum canis

Azole derivatives such as fluconazole are the mainstay of therapeutic agents for the treatment of fungal infections. Their mode of action involving alteration in the conversion of lanosterol to ergosterol is well established. Here we report the effect of fluconazole on the sulphur metabolism negative regulator gene (sconC) in Microsporum canis. Characterization of the M. canis sconC gene revealed that its ORF is comprised of 495bp interrupted by four introns of 47-70bp. Exposure of M. canis in suspension to fluconazole upregulates sconC mRNA level and protein expression as determined by Northern and Western blot analysis, respectively. Upregulation of sconC was accompanied by inhibition of sulphur metabolism of the fungus resulting in a greatly reduced incorporation of radioactive labelled sulphuric acid into fungal proteins. These data establish that in addition to its action on ergosterol synthesis, fluconazole acts on other biological pathways in fungal cells.

Antifungal Activities of the Combination of Tacrolimus and Itraconazole Against Trichophyton mentagrophytes

Tacrolimus was reported to have no antifungal activity against dermatophytes, but it might show a synergistic fungicidal activity with azoles against dermatophytes as in the case of pathogenic yeasts. Therefore, we examined the antifungal activity of tacrolimus combined with itraconazole (ITZ) against five strains of Trichophyton mentagrophytes by measuring cell growth and performing MIC (minimum inhibitory concentration) testing. The mean colony diameter of T. mentagrophytes on 1/10 diluted Sabouraud dextrose agar (dSDA) with tacrolimus combined with ITZ was significantly shorter than that on dSDA with tacrolimus or ITZ. MICs of tacrolimus, ITZ, and tacrolimus combined with ITZ against T. mentagrophytes were determined, respectively. The results revealed a synergistic activity of tacrolimus in combination with ITZ against T. mentagrophytes.

Fluconazole downregulates metallothionein expression and increases copper cytotoxicity in Microsporum canis

Azole antifungals are widely used to treat infections with dermatophyte fungi. Whereas it is well established that this class of drugs interferes with fungal ergosterol synthesis, little is known about its potential other biological effects. Here we report the isolation and structural organization of Microsporum canis metallothionein gene and demonstrate that fluconazole is able to downregulate the baseline as well as copper-induced expression of this gene. Since this effect occurred within 30 min after exposure of the fungus to fluconazole, it is unlikely that it is due to impaired ergosterol synthesis. Our additional demonstration that fluconazole enhances copper toxicity for M. canis suggests that inhibition of metallothionein expression by fluconazole is biologically relevant and may represent an important additional mode of the antifungal action of this drug. Therefore our data indicate that antifungal effects of azole derivatives might not only be due to interference with cell wall synthesis but may also affect other biological circuits within the fungal cells.