Vibrio cholerae Cholix Toxin-Induced HepG2 Cell Death is Enhanced by Tumor Necrosis Factor-Alpha Through ROS and Intracellular Signal-Regulated Kinases.

ABSTRACT: Cholix toxin (Cholix) from Vibrio cholerae is a potent virulence factor exhibiting ADP-ribosyltransferase activity on eukaryotic elongation factor 2 (eEF2) of host cells, resulting in the inhibition of protein synthesis. Administration of Cholix or its homologue Pseudomonas exotoxin A (PEA) to mice causes lethal hepatocyte damage. In this study, we demonstrate cytotoxicity of Cholix on human hepatocytes in the presence of tumor necrosis factor ? (TNF-?), which has been reported to play a fatal role in PEA administered to mice. Compared with incubating HepG2 cells with Cholix alone, co-treatment with TNF-? and Cholix (TNF-?/Cholix) significantly enhanced the activation of caspases, cytochrome c release from mitochondria into cytoplasm, and poly-ADP-ribose polymerase (PARP) cleavage, while incubation with TNF-? alone or co-treatment with TNF-?/catalytically inactive Cholix did not. In the early stage of cell death, Cholix increased phosphorylation of mitogen-activated protein kinases (e.g., p38, ERK, JNK) and Akt, which was not affected by TNF-? alone. MAPK inhibitors (SP600125, SB20852, and U0126) suppressed PARP cleavage induced by TNF-?/Cholix. Protein kinase inhibitor Go6976 suppressed JNK phosphorylation and PARP cleavage by TNF-?/Cholix. In contrast, PKC activator PMA in the absence of TNF-? promoted Cholix-induced PARP cleavage. Reactive oxygen species (ROS) inhibitor, N-acetyl cysteine (NAC), suppressed TNF-?/Cholix-induced JNK and ERK phosphorylation, resulting in inhibition of PARP cleavage. These data suggest that ROS and JNK pathways are important mediators of TNF-?/Cholix-induced HepG2 cell death.

SUBMITTER: Ogura K 

PROVIDER: S-EPMC5837519 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature