engleski

Cytotoxicity screening of low-molecular-weight metabolites of Candida spp.

Opportunistic yeast-like fungi of Candida spp. are still the main fungal isolates, especially in the case of debilitated, immunocommpromised patients, patients under solid-organ transplantation, etc. With the exception of the host factors, which promote invasiveness of commensal flora, several virulence factors can contribute to the pathogenicity of mycoses caused by Candida spp. These factors are: polymorphism and phenotypic switching, secretion of hydrolytic enzymes, such as proteinases, phospholipases, haemolysins. The expression of these factors differes among species, and even between strains. Our recent studies showed that during exponential growth in vitro of several species of clinical Candida spp., almost all species secreted low-molecular-weight metabolite (LMW) 3-indol-ethanol (syn. tryptophol as the end product in tryptophan catabolism). We did not identified secretion of a highly toxic LMW metabolite gliotoxin, the production of which by C. albicans is probably controversial, since gene cluster involved in the gliotoxin biosynthesis pathway was identified in A. fumigatus genome, although C. albicans does not contain such a cluster [1]. The aim of our study was to screen cytotoxicity of tryptophol and its precursor 3-indolelactic acid, together with gliotoxin using MTT colorimetric assay. The screening was evaluated on five cell lines from the ECACC cell archive: human monocytic leukemia (THP-1, monocyte), human lung carcinoma (A549, epithelial), human Caucasian hepatocyte carcinoma (Hep G2, epithelial), Chinese hamster ovary (CHO, epithelial) and African green monkey kidney (COS-7, fibroblast), and the results were expresses as IC50. Gliotoxin showed 1000x lower IC50 than tryptophol and 3-indolelactic acid, whereas IC50s were between 2 and 11 μ M, with the THP-1 and A549 being the most sensitive. Tryptophol showed IC50 concentration between 2 and 7 mM, with the lowest IC50 value on the THP-1 cell line. 3-indolelactic acid had 2 or 3 times higher IC50 values (between 4 and 9 mM), indicating a lower cytotoxic potential than tryptophol. The next step in our research is to evaluate the in vivo secretion of these LMW metabolites during mycoses caused by Candida spp. as possible virulence factor. [1]. Gardiner DM et al., Microbiology 151, 1021-1032 (2005).

cytotoxicity; Candida spp.; metabolites; tryptophol; MTT

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