Inhibition of MAPK/ERK, PKC and CaMKII signaling blocks cytolysin-induced human glioma cell death.
ABSTRACT Cytolysins are pore-forming toxins that show anticancer activity by a mechanism hitherto poorly investigated.
To investigate how cytolysins are cytotoxic to resistant cancer cells, proliferation and cell death were evaluated on U87 glioblastoma cells treated with toxin Bc2 or equinatoxin-II (EqTx-II).
Toxins Bc2 and EqTx-II decreased cell viability and increased lactate dehydrogenase (LDH) release in a concentration-dependent manner. Swollen, dead or dying cells were negative for TUNEL staining. The pre-treatment with inhibitors of mitogen-activated/extracellular regulated kinase (MEK1), protein kinase C (PKC) or Ca(2+)/calmodulin-dependent kinase II (CaMKII) blocked the toxic effects of toxin Bc2 and EqTx-II, suggesting that calcium entry, activation of MEK1, PKC and CaMKII pathways are involved in the cytotoxicity induced by these cytolysins.
Cytolysins were shown to be toxic to glioblastoma cells by activating several intracellular signaling pathways and resulting in necrosis-like cell death.
Article: Gene-trap mutagenesis identifies mammalian genes contributing to intoxication by Clostridium perfringens ε-toxin.[show abstract] [hide abstract]
ABSTRACT: The Clostridium perfringens ε-toxin is an extremely potent toxin associated with lethal toxemias in domesticated ruminants and may be toxic to humans. Intoxication results in fluid accumulation in various tissues, most notably in the brain and kidneys. Previous studies suggest that the toxin is a pore-forming toxin, leading to dysregulated ion homeostasis and ultimately cell death. However, mammalian host factors that likely contribute to ε-toxin-induced cytotoxicity are poorly understood. A library of insertional mutant Madin Darby canine kidney (MDCK) cells, which are highly susceptible to the lethal affects of ε-toxin, was used to select clones of cells resistant to ε-toxin-induced cytotoxicity. The genes mutated in 9 surviving resistant cell clones were identified. We focused additional experiments on one of the identified genes as a means of validating the experimental approach. Gene expression microarray analysis revealed that one of the identified genes, hepatitis A virus cellular receptor 1 (HAVCR1, KIM-1, TIM1), is more abundantly expressed in human kidney cell lines than it is expressed in human cells known to be resistant to ε-toxin. One human kidney cell line, ACHN, was found to be sensitive to the toxin and expresses a larger isoform of the HAVCR1 protein than the HAVCR1 protein expressed by other, toxin-resistant human kidney cell lines. RNA interference studies in MDCK and in ACHN cells confirmed that HAVCR1 contributes to ε-toxin-induced cytotoxicity. Additionally, ε-toxin was shown to bind to HAVCR1 in vitro. The results of this study indicate that HAVCR1 and the other genes identified through the use of gene-trap mutagenesis and RNA interference strategies represent important targets for investigation of the process by which ε-toxin induces cell death and new targets for potential therapeutic intervention.PLoS ONE 01/2011; 6(3):e17787. · 4.09 Impact Factor