AUTHOR=Xie Yufei , Hua Hong , Zhou Peiru 

TITLE=Magnolol as a potent antifungal agent inhibits Candida albicans virulence factors via the PKC and Cek1 MAPK signaling pathways

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2022.935322

DOI=10.3389/fcimb.2022.935322

ISSN=2235-2988

ABSTRACT=<p>Magnolol, a lignin compound extracted from <italic>Magnolia officinalis</italic> Cortex, has been found to have prominent antifungal effects against <italic>Candida albicans</italic>. However, the specific mechanism still remains unclear. Therefore, this study aimed to further explore the inhibition mechanism of magnolol against <italic>Candida albicans</italic> virulence factors and the related signaling pathways. By an XTT reduction assay, a hyphal formation assay, confocal laser scanning microscopy, transmission electron microscopy, a calcofluor white staining assay, and a cell wall β-glucan quantitative detection assay, we evaluated the inhibitory effects of magnolol against the adhesion, hyphal formation, biofilm viability, biofilm spatial structure, and cell wall ultrastructure of <italic>Candida albicans</italic>. Moreover, by RNA sequencing and qRT-PCR, we confirmed the effects of magnolol in inhibiting the gene expression of <italic>Candida albicans</italic> virulence factors and the related signaling pathways. The results revealed that the adhesion and hyphal formation of <italic>Candida albicans</italic> were inhibited significantly by magnolol. The viability and spatial structures of <italic>Candida albicans</italic> biofilms were further weakened. <italic>Candida albicans</italic> ultrastructure showed partial thinning of cell walls and even rupture, with cytoplasmic leakage. The cell wall intergrity and β-glucan content were also radically reduced. Moreover, magnolol caused significant inhibition of the expression of <italic>Candida albicans</italic> adhesion, invasion, hyphal formation, biofilm formation, β-1,3-glucan synthesis, and hydrolase secretion-related genes, including <italic>ALS1</italic>, <italic>ALS3</italic>, <italic>EFG1</italic>, <italic>EAP1</italic>, <italic>FKS1</italic>, <italic>FKS2</italic>, <italic>PLB2</italic>, and <italic>SAP2</italic>. Furthermore, the PKC pathway-related genes (<italic>RHO1</italic>, <italic>PKC1</italic>, <italic>BCK1</italic>, <italic>MKK2</italic>, <italic>MKC1</italic>) and Cek1 pathway-related genes (<italic>CDC42</italic>, <italic>CST20</italic>, <italic>STE11, HST7</italic>, <italic>CEK1</italic>) were also significantly downregulated, indicating that the inhibition of magnolol against <italic>Candida albicans</italic> virulence factors might be related to PKC and Cek1 MAPK signaling pathways. In conclusion, the findings of this study confirmed the inhibition mechanism of magnolol against <italic>Candida albicans</italic> virulence factors, which might be related to PKC and Cek1 MAPK pathways, thus laying the theoretical foundation for its clinical antifungal applications.</p>