A New Antifungal Agent (4-phenyl-1, 3-thiazol-2-yl) Hydrazine Induces Oxidative Damage in Candida albicans.

A gradual rise in immunocompromised patients over past years has led to the increasing incidence of invasive fungal infections. Development of effective fungicides can not only provide new means for clinical treatment, but also reduce the occurrence of fungal resistance. We identified a new antifungal agent (4-phenyl-1, 3-thiazol-2-yl), hydrazine (numbered as 31C) which showed high-efficiency, broad-spectrum and specific activities. The minimum inhibitory concentration of 31C against pathogenic fungi was between 0.0625-4 µg/ml in vitro, while 31C had no obvious cytotoxicity to human umbilical vein endothelial cells with the concentration of 4 µg/ml. In addition, 31C of 0.5 µg/ml could exhibit significant fungicidal activity and inhibit the biofilm formation of C. albicans. In vivo fungal infection model showed that 31C of 10 mg/kg significantly increased the survival rate of Galleria mellonella. Further study revealed that 31C-treatment increased the reactive oxygen species (ROS) in C. albicans and elevated the expression of some genes related to anti-oxidative stress response, including CAP1, CTA1, TRR1, and SODs. Consistently, 31C-induced high levels of intracellular ROS resulted in considerable DNA damage, which played a critical role in antifungal-induced cellular death. The addition of ROS scavengers, such as glutathione (GSH), N-Acetyl-L-cysteine (NAC) or oligomeric proanthocyanidins (OPC), dramatically reduced the antifungal activities of 31C and rescued the 31C-induced filamentation defect. Collectively, these results showed that 31C exhibited strong antifungal activity and induced obvious oxidative damage, which indicated that compounds with a structure similar to 31C may provide new sight for antifungal drug development.

New Triazole NT-a9 Has Potent Antifungal Efficacy against Cryptococcus neoformans In Vitro and In Vivo.

In the past decades, the incidence of cryptococcosis has increased dramatically, which poses a new threat to human health. However, only a few drugs are available for the treatment of cryptococcosis. Here, we described a leading compound, NT-a9, an analogue of isavuconazole, that showed strong antifungal activities in vitro and in vivo NT-a9 showed a wide range of activities against several pathogenic fungi in vitro, including Cryptococcus neoformans, Cryptococcus gattii, Candida albicans, Candida krusei, Candida tropicalis, Candida glabrata, and Candida parapsilosis, with MICs ranging from 0.002 to 1 µg/ml. In particular, NT-a9 exhibited excellent efficacy against C. neoformans, with a MIC as low as 0.002 µg/ml. NT-a9 treatment resulted in changes in the sterol contents in C. neoformans, similarly to fluconazole. In addition, NT-a9 possessed relatively low cytotoxicity and a high selectivity index. The in vivo efficacy of NT-a9 was assessed using a murine disseminated-cryptococcosis model. Mice were infected intravenously with 1.8 × 106 CFU of C. neoformans strain H99. In the survival study, NT-a9 significantly prolonged the survival times of mice compared with the survival times of the control group or the isavuconazole-, fluconazole-, or amphotericin B-treated groups. Of note, 4 and 8 mg/kg of body weight of NT-a9 rescued all the mice, with a survival rate of 100%. In the fungal-burden study, NT-a9 also significantly reduced the fungal burdens in brains and lungs, while fluconazole and amphotericin B only reduced the fungal burden in lungs. Taken together, these data suggested that NT-a9 is a promising antifungal candidate for the treatment of cryptococcosis infection.

Chemogenomic Profiling of the Fungal Pathogen Candida albicans.

There is currently a small number of classes of antifungal drugs, and these drugs are known to target a very limited set of cellular functions. We derived a set of approximately 900 nonessential, transactivator-defective disruption strains from the tetracycline-regulated GRACE collection of strains of the fungal pathogen Candida albicans This strain set was screened against classic antifungal drugs to identify gene inactivations that conferred either enhanced sensitivity or increased resistance to the compounds. We examined two azoles, fluconazole and posaconazole; two echinocandins, caspofungin and anidulafungin; and a polyene, amphotericin B. Overall, the chemogenomic profiles within drug classes were highly similar, but there was little overlap between classes, suggesting that the different drug classes interacted with discrete networks of genes in C. albicans We also tested two pyridine amides, designated GPI-LY7 and GPI-C107; these drugs gave very similar profiles that were distinct from those of the echinocandins, azoles, or polyenes, supporting the idea that they target a distinct cellular function. Intriguingly, in cases where these gene sets can be compared to genetic disruptions conferring drug sensitivity in other fungi, we find very little correspondence in genes. Thus, even though the drug targets are the same in the different species, the specific genetic profiles that can lead to drug sensitivity are distinct. This implies that chemogenomic screens of one organism may be poorly predictive of the profiles found in other organisms and that drug sensitivity and resistance profiles can differ significantly among organisms even when the apparent target of the drug is the same.

Berberine inhibits fluphenazine-induced up-regulation of CDR1 in Candida albicans.

Over-expression of the Candida drug resistance gene CDR1 is a common mechanism generating azole-resistant Candida albicans in clinical isolates. CDR1 is transcriptionally activated through the binding of the transcription factor Tac1p to the cis-acting drug-responsive element (DRE) in its promoter. We previously demonstrated that the combination of fluconazole (FLC) and berberine (BBR) produced significant synergy when used against FLC-resistant C. albicans in vitro. In this study, we found that BBR inhibited both the up-regulation of CDR1 mRNA and the transport function of Cdr1p induced by fluphenazine (FNZ). Further, electrophoretic mobility shift assays suggested that the transcription activation complex of protein-DRE was disrupted by BBR, and electrospray ionization mass spectrometry analysis showed that BBR bound to the DRE of CDR1. Thus we propose that BBR inhibits the FNZ-induced transcriptional activation of CDR1 in C. albicans by blocking transcription factor binding to the DRE of CDR1. These results contribute to our understanding of the mechanism of synergistic effect of BBR and FLC.

[Derivatization of berberine based on its synergistic antifungal activity with fluconazole against fluconazole-resistant Candida albicans].

Abstract: Our previous work revealed berberine can significantly enhance the susceptibility of fluconazole against fluconazole-resistant Candida albicans, which suggested that berberine has synergistic antifungal activity with fluconazole. Preliminary SAR of berberine needs to be studied for the possibility of investigating its target and SAR, improving its drug-likeness, and exploring new scaffold. In this work, 13-substitutited benzyl berberine derivatives and N-benzyl isoquinoline analogues were synthesized and characterized by 1H NMR and MS. Their synergetic activity with fluconazole against fluconazole-resistant Candida albicans was evaluated in vitro. The 13-substitutited benzyl berberine derivatives 1a-1e exhibited comparable activity to berberine, which suggested that the introduction of functional groups to C-13 can maintain its activity. The N-benzyl isoquinolines, which were designed as analogues of berberine with its D ring opened, exhibited lower activity than berberine. However, compound 2b, 2c, and 4b showed moderate activity, which indicated that berberine may be deconstructed to new scaffold with synergistic antifungal activity with fluconazole. The results of our research may be helpful to the SAR studies on its other biological activities.