Fungal Reactive Oxygen Species Secreted by Candida albicans Induce Barrier Disruption and Cell Death in HaCaT Keratinocytes

<i>Candida albicans</i> is a pathogenic fungus that expresses a fungal NADPH oxidase known as <i>C. albicans</i> Cfl11, which produces reactive oxygen species (ROS). Secretion of these ROS triggers caspase 3-mediated cell death in hepatocytes, which was attenuated in a mutant with a disrupted <i>CaCFL11</i> gene (designated <i>Cacfl11Δ</i> mutant). Here, we compared the effects of the <i>C. albicans</i> wild-type strain and the <i>Cacfl11Δ</i> mutant. Our findings revealed that <i>C. albicans</i> reduces the viability of HaCaT keratinocytes in a contact-independent manner. Furthermore, exposure to <i>C. albicans</i> increased intracellular ROS production and caspase 3 activity in HaCaT keratinocytes. These changes were attenuated when HaCaT keratinocytes were exposed to the <i>Cacfl11Δ</i> mutant or when HaCaT keratinocytes were treated with the known antioxidant N-acetylcysteine. Furthermore, wild-type <i>C. albicans,</i> but not the <i>Cacfl11Δ</i> mutant, disrupted transepithelial electrical resistance and modulated the downregulation of the tight-junction genes occludin and junction adhesion molecule 1 in HaCaT keratinocytes. Collectively, these results show that fungal ROS secretion via <i>CaCFL11</i> is a potent virulence factor in mediating keratinocyte viability and barrier function.