Lysine enhances the effect of amphotericin B against Candida albicans in vitro.

Amphotericin B (AmB) is a polyene antibiotic produced by Streptomyces nodosus and has been used for >50 years in the treatment of acute systemic fungal infections. In the present study, we demonstrated that lysine, an essential amino acid, could enhance the effect of AmB against Candida albicans in vitro, although lysine itself did not exert a fungicidal effect. In addition, the combination of AmB with lysine could provide an enhanced action against Candida parapsilosis and Cryptococcus neoformans compared with AmB alone. Lysine could also enhance the antifungal effect of caspofungin or nystatin. An enhanced effect of the combination of lysine with AmB was observed for the prevention of biofilm and hypha formation. Furthermore, our results demonstrated that lysine-mediated oxidative damage, such as the generation of endogenous reactive oxygen species, may be the mechanism underlying the enhancing effect of lysine on AmB. Our results also showed that CaMCA1 gene plays an important role in increasing the sensitivity of C. albicans cells upon AmB treatment. Using AmB together with lysine may be a promising strategy for the therapy of disseminated candidiasis.

Structural features and mechanism of translocation of non-LTR retrotransposons in Candida albicans.

A number of abundant mobile genetic elements called retrotransposons reverse transcribe RNA to generate DNA for insertion into eukaryotic genomes. Non-long-terminal repeat (non-LTR) retrotransposons represent a major class of retrotransposons, and transposons that move by target-primed reverse transcription lack LTRs characteristic of retroviruses and retroviral-like transposons. Yeast model systems in Candida albicans and Saccharomyces cerevisiae have been developed for the study of non-LTR retrotransposons. Non-LTR retrotransposons are divided into LINEs (long interspersed nuclear elements), SINEs (short interspersed nuclear elements), and SVA (SINE, VNTR, and Alu). LINE-1 elements have been described in fungi, and several families called Zorro elements have been detected from C. albicans. They are all members of L1 clades. Through a mechanism named target-primed reverse transcription (TPRT), LINEs translocate the new copy into the target site to initiate DNA synthesis primed by the 3' OH of the broken strand. In this article, we describe some advances in the research on structural features and origin of non-LTR retrotransposons in C. albicans, and discuss mechanisms underlying their reverse transcription and integration of the donor copy into the target site.

Effect of amphotericin B on the metabolic profiles of Candida albicans.

Amphotericin B (AmB) is a polyene antifungal drug widely used for systemic fungal infections. In this study, a metabonomic method using gas chromatography-mass spectrometry (GC/MS) was developed to characterize the metabolic profiles of Candida albicans cells exposed to AmB. Thirty-one differentially produced metabolites between AmB-treated and the control groups were identified, among which 10 metabolites were upregulated and 21 metabolites were downregulated. These differentially produced metabolites were mainly involved in polyamines synthesis, tricarboxylic acid (TCA) cycle, oxidative stress, glutathione metabolism, lipid synthesis and glycolysis. Further experiments showed that the polyamines including putrescine, spermidine, and spermine played an important role in the sensitivity of C. albicans cells upon AmB treatment, and combined use of AmB and inhibitors of polyamine biosynthesis pathway might be a potential antifungal strategy. This study provided a systemic view of the metabolic pattern in C. albicans upon exposure to AmB, which shed new light on the mechanisms of action of antifungal agents.

Inhibitory effect of Shikonin on Candida albicans growth.

Our study showed that Shikonin (SK) could provide an action against almost all Candida albicans isolates tested. More importantly, to some Fluconazole (FCZ)-resistant Candida albicans, the action of SK (MIC(80) value 4 µg/mL) was shown to be >16 times higher than that of FCZ (MIC(80) >64 µg/mL). To clarify the mechanism underlying this action, we performed a comparative study in untreated control C. albicans and C. albicans treated with SK. In this study, we found that SK treatment increased generation of endogenous reactive oxygen species (ROS) and decreased mitochondrial membrane potential. Furthermore, anti-oxidants N-acetylcysteine (NAC) and glutathione (GSH) could reduce the antifungal activity of SK significantly in C. albicans. Our analyses also identified 9 differentially expressed genes, which were related to glycolysis-related genes (CDC19 and HXK2), fermentation-related genes (ALD5 and ADH1), antioxidant defense-related genes (SOD2 and SOD5), thioredoxin reductase-related gene (TRR1), mitochondrial respiratory electron transport chain-related gene (MRF1) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidoreductase-related gene (EBP1). These results suggest that mitochondrial aerobic respiration shift and endogenous ROS augmentation contribute to the action of SK against C. albicans.