A hydrogen peroxide-generating agent, 6-formylpterin, enhances heat-induced apoptosis.

Abstract

The enhancement of heat-induced apoptosis by 6-formylpterin, an intra-cellular generator of hydrogen peroxide (H2O2), was examined in human myelomonocytic lymphoma U937 cells. The cells were treated with either 6-formylpterin alone at a nontoxic concentration of 300 microM (37 degrees C), heat shock (44 degrees C per 20 min) alone or a combination of the two, then incubated at 37 degrees C for 6 h. Assessments of apoptosis, mitochondrial membrane potential and caspase-3 activation were performed by flow cytometry. Moreover, caspase-8 activation and changes in the intra-cellular Ca2+ concentration ([Ca2+]i) were examined. Bax, Bcl-2, Bcl-XL, Bid, cytochrome c and PKCd were detected by Western blotting. The induction of heat-induced apoptosis evaluated by morphological observation and DNA fragmentation were promoted by the addition of 6-formylpterin. Mitochondrial membrane potential was decreased and the activation of caspase-3 and -8 was enhanced in the cells treated with the combination. A decreased-expression of Bid was noted, although no significant changes in Bax, Bcl-2 and Bcl-XL expression were observed after the combined treatment. Furthermore, both the release of cytochrome c from mitochondria to cytosol and the translocation of PKCd from cytosol to mitochondria, which were induced by heat shock, were enhanced by the addition of 6-formylpterin. The number of cells with a higher [Ca2+]i was also increased by the addition of 6-formylpterin. These findings suggest that the increase in [Ca2+]i, the activation of the mitochondria-caspase dependent pathway and the translocation of PKCd to mitochondria play principal roles in the enhancement of heat-induced apoptosis by 6-FP.

• Authors: S Wada, Z-G Cui, T Kondo, Q-L Zhao, R Ogawa, M Shoji, T Arai, K Makino, I Furuta
• Journal: International journal of hyperthermia : the official journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group (Int J Hyperthermia) Vol. 21 Issue 3 Pg. 231-46 (May 2005) ISSN: 0265-6736 [Print] England
• PMID: 16019850 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Proto-Oncogene Proteins c-bcl-2
• Pterins
• 2-amino-4-hydroxy-6-formylpteridine
• Cytochromes c
• Hydrogen Peroxide
• PRKCD protein, human
• Protein Kinase C
• Protein Kinase C-delta
• CASP3 protein, human
• CASP8 protein, human
• Caspase 3
• Caspase 8
• Caspases
• Calcium

Topics

• Apoptosis
• Calcium (metabolism)
• Caspase 3
• Caspase 8
• Caspases (metabolism)
• Cell Line, Tumor
• Cytochromes c (metabolism)
• DNA Fragmentation
• Flow Cytometry
• Hot Temperature
• Humans
• Hydrogen Peroxide
• Hyperthermia, Induced
• Membrane Potentials (drug effects)
• Mitochondria (physiology)
• Protein Kinase C (biosynthesis)
• Protein Kinase C-delta
• Proto-Oncogene Proteins c-bcl-2 (metabolism)
• Pterins (pharmacology)