Okadaic acid–induced apoptosis in malignant glioma cells

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Okadaic acid (OA), a potent protein phosphatase inhibitor, has been known to induce apoptosis in a variety of cell types. The authors attempted to characterize further this model by identifying proteins involved in this form of programmed cell death.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Cellular proliferation was assessed using a colorimetric nonradioactive proliferation assay and cell counts. Apoptosis was determined by fluorescent microscopy. Activation of the mitogen-activated protein kinase (MAPK) pathways was determined by immunoprecipitation of extracellular signal–regulated kinase (ERK), c-Jun-<jats:sc>n</jats:sc>-terminal kinase (JNK), and p38 followed by in vitro kinase assays. Western blot analyses were conducted to show inhibitory-κB (IκB) phosphorylation and degradation as well as Bax upregulation. The binding of nuclear factor–κB (NFκB) was shown by electrophoretic mobility shift assay.</jats:p> <jats:p>Okadaic acid induced cell death in T98G human malignant cell lines (50% inhibiting concentration = 20–25 nM). In T98G cells YO-PRO fluorescent staining was identified, thus indicating an apoptotic mechanism with a smaller percentage of cells undergoing necrotic cell death. Additionally OA induced JNK and MAPK activities in a time-dependent manner, increased the expression of Bax, and increased IκB phosphorylation and NFκB activation. There was a temporal correlation between these subcellular events and the detection of apoptosis morphology in glioma cells.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The authors believe that OA acts by blocking dephosphorylation events, thus activating apoptotic pathways through ERK and JNK activity. Additionally Bax, IκB and NFκB may also play a role in regulating these pathways.</jats:p></jats:sec>

Quantitative proteomic analysis of okadaic acid treated mouse small intestines reveals differentially expressed proteins involved in diarrhetic shellfish poisoning

“…A recent study indicates that the physiological function of villin is not only as a cytoskeletal protein, but also as an epithelial cellspecific anti-apoptotic protein and it can protect cells from apoptosis by maintaining mitochondrial integrity and thus inhibiting the activation of caspase-9 and caspase-3 [45]. Many studies demonstrate that apoptosis is induced by OA through the inhibition of PP1 and PP2A activities [46][47][48][49][50]. Our study found that the down-regulation of villin was accompanied by damage of mitochondrial structure, suggesting that villin might play a key role in inducing the apoptosis of epithelial cells by OA.…”

Potent cytotoxicity of the phosphatase inhibitor microcystin LR and microcystin analogues in OATP1B1- and OATP1B3-expressing HeLa cells

“…For example, the phosphatase inhibitor okadaic acid has been shown to induce apoptosis in a variety of cell lines, with increased sensitivity reported in cells carrying mutated Ras (28). Okadaic acid also induced apoptosis in malignant glioma cells, in studies that suggested an integral role for ERK and c-Jun NH 2 -terminal kinase (JNK kinase) in promoting cell death (29). Rapid apoptosis has also been seen in primary hepatocytes following microinjection with both microcystin LR and nodularin, characterized by cytoplasmic shrinkage, chromatin condensation, membrane blebbing, and procaspase-3 cleavage (30).…”

Lead Affects Apoptosis and Related Gene XIAP and Smac Expression in the Hippocampus of Developing Rats

“…Among the growing number of cellular proteins that regulate caspase activation are the IAPs (Inhibitor of apoptosis proteins), including c-IAP1, c-IAP2, XIAP, and survivin [22,23]. These proteins have been reported to block mitochondria-mediated apoptotic pathways by directly inhibiting the initiator and effector caspases [24].…”