Does hydrocortisone modify thein vitrosusceptibility ofAspergillus fumigatusto itraconazole and amphotericin B?

Drug repurposing strategies in the development of potential antifungal agents

Abstract

The morbidity and mortality caused by invasive fungal infections are increasing across the globe due to developments in transplant surgery, the use of immunosuppressive agents, and the emergence of drug-resistant fungal strains, which has led to a challenge in terms of treatment due to the limitations of three classes of drugs. Hence, it is imperative to establish effective strategies to identify and design new antifungal drugs. Drug repurposing is a potential way of expanding the application of existing drugs. Recently, various existing drugs have been shown to be useful in the prevention and treatment of invasive fungi. In this review, we summarize the currently used antifungal agents. In addition, the most up-to-date information on the effectiveness of existing drugs with antifungal activity is discussed. Moreover, the antifungal mechanisms of existing drugs are highlighted. These data will provide valuable knowledge to stimulate further investigation and clinical application in this field.

Key points

• Conventional antifungal agents have limitations due to the occurrence of drug-resistant strains.

• Non-antifungal drugs act as antifungal agents in various ways toward different targets.

• Non-antifungal drugs with antifungal activity are demonstrated as effective antifungal strategies.

Mycologic Endocrinology

The interactions of fungi and chemical messenger molecules, hormones or pheromones, are addressed in this chapter. These interactions include mammalian fungal pathogens, also plant pathogens, or non-pathogenic fungi, which can result in functional responses in receptor- or non-receptor-mediated fashions. Endogenous ligands in the fungi have been demonstrated to be important for mating in a number of systems. Mammalian hormones have been demonstrated to have stimulatory or inhibitory effects on growth for organisms such as Candida albicans, Paracoccidioides brasiliensis, Saccharomyces cerevisiae, Rhizopus nigricans, Aspergillus fumigatus, Coccidioides, and dermatophytic fungi. A number of fungi have been shown to have specific binding proteins for corticosteroid, estrogen and progesterone that are stereo-specific and high affinity. In some instances, the interactions of a mammalian hormone with the organism, in vivo, affects pathogenesis. Genome expression profiles of C. albicans in the presence of estradiol or progesterone, and S. cerevisiae with progesterone, indicate major up-regulation of various drug resistance pumps, like CDR1, and CDR2, can affect antifungal susceptibility. Azole antifungal interactions occur with fungal hormone binding proteins. Azoles also can block mammalian steroidogenesis. The finding of interactions of mammalian hormones with fungi and subsequent functional responses by the fungi, suggest that hormonal interactions with fungal systems has been conserved throughout evolution and have an important role in fungal pathogenesis, as well as in the overall biology of the organisms.

Direct effects of non-antifungal agents used in cancer chemotherapy and organ transplantation on the development and virulence of Candida and Aspergillus species

Conventional antineoplastic, novel immunosuppressive agents and antibiotics used in cancer treatment can directly affect the growth, development and virulence of Candida and Aspergillus species. Cytotoxic and cisplatin compounds have anti-Candida activity and may be synergistic with antifungal drugs; they also inhibit Candida and Aspergillus filamentation/conidation and effect increased virulence in vitro. Glucocorticoids enhance Candida adherence to epithelial cells, germination in serum and in vitro secretion of phospholipases and proteases, as well as growth of A. fumigatus. Calcineurin and target of rapamycin inhibitors perturb Candida and Aspergillus morphogenesis, stress responses and survival in serum, reduce azole tolerance in Candida, but yield conflicting in vivo data. Inhibition of candidal heat shock protein 90 and candidal-specific histone deacetylase represent feasible therapeutic approaches for candidiasis. Tyrosine kinase inhibitors inhibit fungal cell entry into epithelial cells and phagocytosis. Quinolone and other antibiotics may augment activity of azole and polyene agents. The correlation of in vitro effects with clinically meaningful in vivo systems is warranted.