Intestinal epithelial cell apoptosis due to a hemolytic toxin from Vibrio vulnificus and protection by a 36 kDa glycoprotein from Rhus verniciflua Stokes

Abstract

Rhus verniciflua stokes (RVS) has been used as a functional food to cure inflammatory diseases in Korea. In the present study, we carry out an investigation of the cellular mechanism of a 36 kDa glycoprotein isolated from RVS fruit (RVS glycoprotein) during the apoptosis of human gastrointestinal epithelial HCT116 cells induced by the hemolytic toxin (VvhA) produced by V. vulnificus. Recombinant protein (r) VvhA produced by V. vulnificus stimulated apoptosis by activating the phosphorylation of protein kinase C (PKC) through the production of intracellular reactive oxygen species (ROS). However, RVS glycoprotein significantly inhibited the level of ROS production and PKC activation in rVvhA-stimulated HCT116 cells. Interestingly, we found that RVS glycoprotein has inhibitory effects on the phosphorylation of c-Jun N-terminal kinase (JNK) and nuclear factor-kappa B (NF-κB), which are responsible for the expression of Bax and cleaved caspase-3 in HCT116 cells treated with rVvhA, respectively. On the basis of these results, we suggest that RVS glycoprotein blocks mitochondrial apoptotic cell death induced by rVvhA via the inhibition of ROS-mediated signaling events in HCT116 cells.

Keywords: Apoptosis; Caspase-3; Gastrointestinal epithelial cells; Rhus verniciflua Stokes; Vibrio vulnificus; VvhA.