Abstract
Cytotoxic effects of the combined use of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), a radical scavenger and an approved medicine for acute brain infarction in Japan, with a pterin derivative, were examined in vitro. When pancreatic cancer cell line Panc-1 cells were incubated with 50 to 400 μM of a pterin derivative, 2-(N,N-dimethylaminomethyleneamino)-6-formyl-3-pivaloylpteridine-4-one (DFP), and the equivalent dose of edaravone, reactive oxygen species (ROS), were generated, and cell death was induced. ROS generation and the loss of mitochondrial membrane potential (MMP) preceding cell death were simultaneously monitored using time-lapse microscopy with an ROS-sensitive dye and a probe to monitor MMP, respectively. Cell death was also estimated quantitatively by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. ROS generation and cell death were prominent when more than 100 μM of each agent was used in combination, whereas the sole use of each agent did not show any effects even at the highest dose, 400 μM. Chemical analysis revealed that DFP and edaravone react immediately in aqueous solution and produce a new compound named DFP-E. DFP-E chemically reacted with NADH much faster than DFP and generated ROS, and biologically, it was much more cell-permeable than DFP. These findings collectively indicated that the combined use of DFP with edaravone produced DFP-E, which caused intracellular ROS generation and cell death. Cell death was observed in normal cells, and edaravone reacted with another pterin derivative to yield an ROS-generating compound. As a result, care should be taken with the clinical use of edaravone when pterin derivatives stay in the body.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.107.131391.
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ABBREVIATIONS: edaravone, 3-methyl-1-phenyl-2-pyrazolin-5-one; ROS, reactive oxygen species; H2O2, hydrogen peroxide; ·OH, hydroxyl radical(s); DFP, 2-(N,N-dimethylaminomethyleneamino)-6-formyl-3-pivaloylpteridine-4-one; HUVEC, human umbilical vein endothelial cell; 6FP, 6-formylpterin; FCS, fetal calf serum; DCFH-DA, 2′,7′-dichlorofluorescein diacetate; TMRM, tetramethylrhodamine methyl ester; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; DETAPAC, diethylenetriaminepentaacetic acid; DMPO, 5,5-dimethyl-1-pyrroline-N-oxide; NAC, N-acetyl-l-cysteine; PBS, phosphate-buffered saline; HPLC, high-performance liquid chromatography; DFP-E, reaction product of DFP with edaravone; br, broad; s, singlet; br s, broad singlet; br d, broad doublet; RP, reversed-phase; EPR, electron paramagnetic resonance; MMP, mitochondrial membrane potential.
- Received September 12, 2007.
- Accepted November 19, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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