title: Polyamines are required for activation of c-Jun NH2-terminal kinase and apoptosis in response to TNF-alpha in IEC-6 cells.
abstract: Intracellular polyamine homeostasis is important for the regulation of cell proliferation and apoptosis and is necessary for the balanced growth of cells and tissues. Polyamines have been shown to play a role in the regulation of apoptosis in many cell types, including IEC-6 cells, but the mechanism is not clear. In this study, we analyzed the mechanism by which polyamines regulate the process of apoptosis in response to tumor necrosis factor-alpha (TNF-alpha). TNF-alpha or cycloheximide (CHX) alone did not induce apoptosis in IEC-6 cells. Significant apoptosis was observed when CHX was given along with TNF-alpha, as indicated by a significant increase in the detachment of cells, caspase-3 activity, and DNA fragmentation. Polyamine depletion by treatment with alpha-difluoromethylornithine significantly reduced the level of apoptosis, as judged by DNA fragmentation and the caspase-3 activity of attached cells. Apoptosis in IEC-6 cells was accompanied by the activation of upstream caspases-6, -8, and -9 and NH2-terminal c-Jun kinase (JNK). Inhibition of JNK activation prevented caspase-9 activation. Polyamine depletion prevented the activation of JNK and of caspases-6, -8, -9, and -3. SP-600125, a specific inhibitor of JNK activation, prevented cytochrome c release from mitochondria, JNK activation, DNA fragmentation, and caspase-9 activation in response to TNF-alpha/CHX. In conclusion, we have shown that polyamine depletion delays and decreases TNF-alpha-induced apoptosis in IEC-6 cells and that apoptosis is accompanied by the release of cytochrome c, the activation of JNK, and of upstream caspases as well as caspase-3. Polyamine depletion prevented JNK activation, which may confer protection against apoptosis by modulation of upstream caspase-9 activation.
authors.affiliation: Dept. of Physiology, The Univ. of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163, USA.
authors.forename: Sujoy
authors.initials: S
authors.lastname: Bhattacharya
authors.forename: Ramesh M
authors.initials: RM
authors.lastname: Ray
authors.forename: Mary Jane
authors.initials: MJ
authors.lastname: Viar
authors.forename: Leonard R
authors.initials: LR
authors.lastname: Johnson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D045304:Cytochromes c / Q000037:antagonists & inhibitors; D000518:Eflornithine / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011073:Polyamines / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D011073:Polyamines; D011500:Protein Synthesis Inhibitors; D014409:Tumor Necrosis Factor-alpha; D045304:Cytochromes c; D003513:Cycloheximide; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505410:Casp3 protein, rat; C506435:Casp9 protein, rat; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D000518:Eflornithine