Aloe-emodin Attenuates Staphylococcus aureus Pathogenicity by Interfering With the Oligomerization of α-Toxin

Abstract

α-toxin, an essential virulence factor secreted by <i>Staphylococcus aureus</i> (<i>S. aureus</i>), is a critical exotoxin in multiple infections. In this study, we found that aloe-emodin (AE), a natural compound lacking anti-<i>S. aureus</i> activity, could inhibit the hemolytic activity of α-toxin. Oligomerization assays, molecular dynamics simulations, and fluorescence-quenching analyses were used to determine the mechanism of this inhibition. The oligomerization of α-toxin was restricted by the engagement of AE with K110, T112, and M113 of the toxin, which eventually resulted in inhibition of the hemolytic activity. Lactate dehydrogenase and live/dead assays demonstrated that AE decreased the injury of human lung epithelial cells (A549) and mouse lung macrophages (MH-S) mediated by <i>S. aureus</i>. Furthermore, treatment with AE showed robust protective effects in mice infected by <i>S. aureus</i>. These findings suggest that AE effectively inhibited the pore-forming activity of α-toxin and showed a protective effect against <i>S. aureus</i> virulence <i>in vitro</i> and <i>in vivo</i>, which may provide a new strategy and new antibacterial agent for clinical treatment of <i>S. aureus</i> infections.