The critical role of Hepes in SIN-1 cytotoxicity, peroxynitrite versus hydrogen peroxide.
The cytotoxicity of the superoxide anion radical- and nitric oxide-releasing compound SIN-1 to L929 cells was studied in Krebs-Henseleit buffer. pH 7.4, in the presence and absence of Hepes. SIN-1 cytotoxicity was significantly higher in the presence of Hepes than in the absence of Hepes. The available amount of peroxynitrite formed from SIN-1, however, was significantly decreased by Hepes as indicated by decreased oxidation of dihydrorhodamine 123. On the other hand, Hepes largely increased the formation of H2O2 from SIN-1. Catalase protected the L929 cells from SIN-1 cytotoxicity in the buffer with Hepes. In the buffer without Hepes catalase did not have any protective effect. In contrast, tyrosine and tryptophan provided significant protection against SIN-1 cytotoxicity independent of the presence of Hepes. These results demonstrate that the immediate toxic agent formed from SIN-1 decisively depends on the presence of Hepes. In its absence cytotoxicity is most likely mediated by peroxynitrite while in the presence of Hepes, cytotoxicity is conveyed by co-operative action of hydrogen peroxide and reactive nitrogen species.
Lomonosova
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EE
Institut für Physiologische Chemie, Universitätsklinikum, Essen, Germany.
Kirsch
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M
Rauen
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de Groot
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H
D000818:Animals; D002021:Buffers; D002374:Catalase / Q000494:pharmacology; D016923:Cell Death; D002460:Cell Line; D005347:Fibroblasts; D006531:HEPES / Q000008:administration & dosage / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D051379:Mice; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D009566:Nitrates / Q000378:metabolism / Q000494:pharmacology*
D002021:Buffers; D009566:Nitrates; C039642:peroxynitric acid; C002385:linsidomine; D006861:Hydrogen Peroxide; D008981:Molsidomine; D007770:L-Lactate Dehydrogenase; D002374:Catalase; D006531:HEPES