Inhibition of Respiration of Candida albicans by Small Molecules Increases Phagocytosis Efficacy by Macrophages

Abstract

Candida albicans adapts to various conditions in different body niches by regulating gene expression, protein synthesis, and metabolic pathways. These adaptive reactions not only allow survival but also influence the interaction with host cells, which is governed by the composition and structure of the fungal cell wall. Numerous studies had shown linkages between mitochondrial functionality, cell wall integrity and structure, and pathogenicity. Thus, we decided to inhibit single complexes of the respiratory chain of C. albicans and to analyze the resultant interaction with macrophages via their phagocytic activity. Remarkably, inhibition of the fungal bc1 complex by antimycin A increased phagocytosis, which correlated with an increased accessibility of β-glucans. To contribute to mechanistic insights, we performed metabolic studies, which highlighted significant changes in the abundance of constituents of the plasma membrane. Collectively, our results reinforce the strong linkage between fungal energy metabolism and other components of fungal physiology, which also determine the vulnerability to immune defense reactions. IMPORTANCE The yeast Candida albicans is one of the major fungal human pathogens, for which new therapeutic approaches are required. We aimed at enhancements of the phagocytosis efficacy of macrophages by targeting the cell wall structure of C. albicans, as the coverage of the β-glucan layer by mannans is one of the immune escape mechanisms of the fungus. We unambiguously show that inhibition of the fungal bc1 complex correlates with increased accessibilities of β-glucans and improved phagocytosis efficiency. Metabolic studies proved not only the known direct effects on reactive oxygen species (ROS) production and fermentative pathways but also the clear downregulation of the ergosterol pathway and upregulation of unsaturated fatty acids. The changed composition of the plasma membrane could also influence the interaction with the overlying cell wall. Thus, our work highlights the far-reaching relevance of energy metabolism, indirectly also for host-pathogen interactions, without affecting viability.

Respiring to infect: Emerging links between mitochondria, the electron transport chain, and fungal pathogenesis

“…Fungal cells pretreated with the inhibitors were taken up at a higher rate by the murine J774.1 macrophagelike cell line and by macrophages in a zAU : PleasenotethatasperPLOSstyle; thetermzebradanioispreferr ebrafish model. Similarly, increased phagocytosis was observed by Cui and colleagues upon treatment with the complex III inhibitor antimycin A but not with inhibitors of other complexes in the ETC [13].…”

Microbial Sensing and Removal of Heavy Metals: Bioelectrochemical Detection and Removal of Chromium(VI) and Cadmium(II)

“…Therefore, measuring the efficiency of microbial respiration and the activity of the electron transport chain are considered main indicators of cellular activity, as they are essential for the replication and proliferation of aerobic organisms [ 38 ]. Consequently, the electron transfer process from living-microorganisms towards electrodes in microbial electrochemical systems (MESs) is exploited in microbial fuel cells or diagnostic tools for rapid assessment of microbial activity [ 39 , 40 , 41 ]. In these regards, many MES approaches were designed and tested for biological purposes [ 42 , 43 , 44 , 45 ].…”

“…Afterwards, the absorbance at 450 nm has been measured and reflected as a zero time. Lastly, the stained microbial cultures have been incubated for further 30 min prior detecting the yellow color intensity that represents the cell viability and metabolic activity [ 39 ]. The inhibition in cell viability has been calculated according to the following formula: …”

Microbial Electrochemical Systems: Principles, Construction and Biosensing Applications

“…Hence, earlier efforts were made to employ the measurement of dissolved oxygen consumption by living cells as a direct measure of the microbial survival [ 7 ]. Consequently, the electron transfer process from living-microorganisms towards electrodes in MES is exploited in microbial fuel cells [ 8 , 9 ] or diagnostic tools for rapid assessment of microbial activity [ 10 , 11 , 12 ]. In these regards, many MES approaches were designed and tested for biological purposes [ 13 , 14 , 15 , 16 ].…”