Structural and Metabolic Effects of Candida albicans Yeast-to-Hyphae Transition Induced by Fetal Bovine Serum (FBS) and RPMI-1640 Media in Response to Dietary Ferulic Acid and Galic Acid

Candida albicans is a harmless commensal human fungus but causing infections when the host is immunocompromised. The advent of antifungal resistant Candida along with limited availability of antifungals pose a critical threat to public health. Phenolic compounds may be alternative to antifungal drugs, but their anti-pathogenicity mechanisms have been primarily evaluated using isolated components. Yet, a critical gap of knowledge exists on the effects of phenolic treatments on cellular conformation and metabolism when exposed to different environments that induce the virulent hyphae phenotype. Therefore, the objective of this work was to determine the potential mechanism of ferulic acid (FA) and gallic acid (GA) suppression against C. albicans A72 yeast-to-hyphae induced with an undefined medium (FBS) and a defined medium (RPMI-1640-medium). Hyphae induced under the cited media showed structural differences in the polysaccharide, phospholipids and nucleic acids region. Predicted pathway analysis revealed that eleven pathways were upregulated in the hyphae phenotype. For both hyphae phenotypes, only arginine and proline, nicotinate and nicotinamide, and nitrogen metabolism were downregulated. FBS-induced yeast-to-hyphae transition was inhibited by 50% (IC50) when treated with FA and GA in isolation or combination. Isobologram analysis confirmed that FA+GA acted synergistically. Possible preventative mechanisms include stimulating reactive oxygen species (ROS) overproduction, hyphae cell wall disruption and TCA cycle and glyoxylate shunt downregulation. Alternatively, both FA and GA failed to achieve an IC50 when supplemented into the RPMI-1640 media, but cells exposed to the GA resulted in mainly pseudohyphae. ROS production and global structural changes were not different between two phenotypes. However, the expression of virulence genes ECE1 and HWP1 were downregulated while ALS3 was upregulated. Analysis of predicted pathways showed that pseudohyphae upregulated 8 pathways while downregulating of 21 pathways. In summary, this study showed that the environmental cues must be considered when developing efficacious phenol-based treatments against the yeast-to-hyphae transition. If not, the outcome could be ineffective and even detrimental