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Original Article

Oxygen-Dependent Fragmentation of Cellular DNA by Nitric Oxide

, , , , , & show all
Pages 245-255 | Received 19 Apr 1996, Accepted 09 Sep 1996, Published online: 07 Jul 2009
 

Abstract

Although active oxygen species and related metabolites, such as nitric oxide (NO), have been postulated to play important roles in the apoptosis of various cells, a precise mechanism leading to cell death remains to be elucidated. Recently we found that the lifetime of NO depends greatly on the concentration of environmental oxygen and that NO reversibly inhibits mitochondrial respiration and ATP synthesis; the inhibitory effect is stronger at physiologically low oxygen tension than under atmospheric conditions (Arch. Biochem. Biophys. 323, 27–32, 1995). The present work describes the effects of the NO-generating agent, l-hydroxy-2–oxo-3,3–bis(2–aminoethyl)-l-triazene (NOC 18) and oxygen tension on the respiration, ATP synthesis and apoptosis of HL-60 cells. When respiration was inhibited by NOC 18, cellular ATP levels decreased significantly and DNA fragmentation was elici/ted. Both events were enhanced by decreasing oxygen tension and suppressed by adding NO-trapping agents, such as 2–(4–carboxyphenyl)-4,4,5,5–tetramethylimidazo-line-1–oxyl-3–oxide (carboxy-PTIO) and oxyhemoglo-bin. The fragmentation of cellular DNA was inhibited in a dose dependent manner by herbimycin A, a tyrosine kinase inhibitor. Fragmentation of the DNA of HL-60 cells was also induced either by peroxynitrite, superoxide or hydroxyl radical by some mechanism which was diminished by lowering the oxygen tension. These results indicated that the decrease in cellular ATP and activation of tyrosine kinase might play important roles in NO-induced apoptosis particularly under physiologically low oxygen tensions.

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