Combination of Baicalein and Amphotericin B Accelerates Candida albicans Apoptosis

Abstract

Candida albicans is the most important human fungal pathogen, causing various diseases from superficial mucosal infections to life-threatening systemic disorders.1,2) Compared to bacterial infections, few drugs are available to treat fungal infections. The polyene macrolide antibiotic amphotericin B (AmB) is effective in the treatment of many systemic mycoses. But due to its poor permeability across the membrane, an increased amount of AmB must be administered to patients in clinical situations, thus often resulting in severe side effects. [3][4][5] To lessen the severity of the side effects, AmB is often combined with other antifungal drugs such as the azoles, but coincident with the increased use of antifungal azole derivatives, the incidences of drug resistance have been recently increasing.6-8) Thus investigation of reducing the AmB dose by combining it with other compounds is necessary.Programmed cell death responses have been described in a variety of fungi after exposure of the organisms to a range of conditions such as weak acid stress, oxidative stress, or ultraviolet irradiation. [9][10][11] It was demonstrated that C. albicans could be triggered to undergo an apoptotic cell death response when exposed to H 2 O 2 , intracellular acidification, or AmB. A single-cell death assay was used to show that a majority of AmB-treated cells were nonviable and impermeable to propidium iodide. Apoptotic changes were further confirmed by electron microscopy and by the production of intracellular reactive oxygen species (ROS).12,13) However, the mechanism by which C. albicans undergoes apoptosis remains unclear. In mammalian cells, acquisition of an apoptotic morphology depends on the activation of cysteine dependent aspartate specific proteases (caspases). Functional analyses of genes in Saccharomyces cerevisiae have revealed similarities between fungal apoptosis and apoptosis in mammalian cells. A homologue of mammalian caspases, YCA1 (Yeast Caspase 1), has been identified. Overexpression of YCA1 increases hydrogen peroxide-induced caspase-like activity and apoptosis in S. cerevisiae.14-17) Caspase superfamily consists of three families; YCA1 belongs to the metacaspase family of enzymes which are found in plants, fungi and protozoa. We recently found that CaMCA1, a homologue of S. cerevisiae metacaspase YCA1, was involved in oxidative stress-induced apoptosis in C. albicans. 18)Baicalein (BE) is a compound that was originally extracted from the Scutellaria baicalensis root, and it is a promising herbal medicine in Chinese Pharmacopoeia (Fig. 1). BE exhibits antioxidant, antibacterial, antiviral, and antifungal activities. [19][20][21][22][23] In this study, we described a synergic effect of BE with AmB against C. albicans and the potential mechanism. Our results showed that combination of BE and AmB enhanced C. albicans apootosis accompanied with an increase of reactive oxygen species (ROS). We also found that AmB could induce the caspase activity and mRNA expression of the gene encoding C. albicans caspase, CaMCA1...

Caspofungin Kills Candida albicans by Causing both Cellular Apoptosis and Necrosis

“…Caspase activity was detected by staining C. albicans cells exposed to caspofungin with D2R (CaspScreen flow cytometric apoptosis detection kit; BioVision) (9,20). The cells were observed by laser scanning confocal microscopy and quantitated using flow cytometry.…”

Reactive Oxygen Species-Inducing Antifungal Agents and Their Activity Against Fungal Biofilms

“…Alternatively, compounds that can increase the oxidative damage or ROS accumulation by ROS-inducing antimycotics (however, without targeting oxidative defenserelated proteins) are also useful in combination therapy. Different reports describe a synergistic enhancement of the activity of azoles and amphotericin B against C. albicans, based on elevation of oxidative stress by compounds such as baicalein [119], allicin [120], paraquat [121] and curcumin [122]. Furthermore, dihydroxybenzaldehydes, which target the cellular antioxidant system, can enhance the activity of amphotericin B against several Candida spp.…”

Synergistic Antifungal Effect of Glabridin and Fluconazole

“…Similar studies on the mode of synergism as follows: increasing reactive oxygen species (ROS) to accelerate apoptosis [31], inhibiting drug efflux pumps to increase intracellular drug concentration [11], [32], targeting the ergosterol biosynthesis pathway to increase the fluidity for the resulted ergosterol depletion [32]. We tested the membrane sterols of C. albicans after treated with Gla alone or in combination with FLC by GC/MS, but none obvious sterols change was observed in Gla treatment cells (data not shown).…”