Evaluating β-1,3-glucan synthesis inhibition using emulsion formation as an indicator

Abstract

Introduction: The cell wall β-1,3-glucan of fungal pathogen Candida albicans is an attractive antifungal target. β-1,3-Glucan is the skeletal structure in the cell wall and the major scaffold for cell wall proteins. In previous studies using Saccharomyces cerevisiae, strong emulsification was detected by mixing cell wall proteins with oil. To date, there have been no reports of applying an emulsification phenomenon to assessing β-1,3-glucan synthesis inhibition.

Objective: The aim of this study was to clarify that emulsification is useful as an indicator for evaluating β-1,3-glucan synthesis inhibition in C. albicans.

Methods: At first, whether cell wall proteins released from cells by β-1,3-glucanase treatment worked as an effective emulsifier in C. albicans was examined. Next, whether emulsification occurred even in the culture supernatant brought about by treating with bioactive compounds, including β-1,3-glucan synthesis inhibitors, under osmotic protection was investigated. In addition, the release of cell wall proteins into the culture medium by treating with those compounds was examined. Finally, a simpler evaluation method using emulsion formation was examined for application to screening of inhibitors.

Results: Emulsification occurred by cell wall proteins obtained by treating with β-1,3-glucanase in C. albicans. In addition, cell wall proteins were released into the culture medium by treating with β-1,3-glucan synthesis inhibitors, resulting in emulsification. However, such phenomena were not observed in the case of other bioactive compounds. Furthermore, emulsification could be detected in the culture broth obtained by static culture on a small scale.

Conclusions: The obtained results strongly implied that emulsification results from decreased β-1,3-glucan levels in the cell wall. As emulsification can be simply evaluated by mixing the culture broth with oil, in the future application to the initial assessment and screening of β-1,3-glucan synthesis inhibitors is expected.

Keywords: Antifungal; Candida albicans; Cell wall protein; Emulsification; Inhibition; β-1,3-Glucan.