J. Am. Chem. SOC. 1995,117, 9578-9579
9578
Peroxynitrite-InducedDNA Strand Scission Mediated by a Manganese Porphyrin John T. Groves* and Sudhakar S . Marla
Department of Chemistry, Princeton University Princeton, New Jersey 08544
2 0.5
Received June 6, 1995 Peroxynitrite (ONOO-) is a potent oxidant' generated by the reaction between nitric oxide (NO') and superoxide ion ( 0 ~ 7 . ~ Thus, the macrophage immune response3 or pathological conditions such as endotoxic shock and ischemidreperfusion, which 0.0 raise the concentrations of both NO' and 0 2 ' - , could generate 3 0 0 400 5 0 0 600 significant levels of ONOO- in vivo? Peroxynitrite and its Wavelength (nm) conjugate acid are capable of nitrating tyrosine residues in proteins5 and oxidizing DNA: lipids,' sulfhydryls,8 and Figure 1. Reversion of oxoMn(1V) (2)(428 nm) to MnTMPyP (462 m e t h i ~ n i n e . Hence, ~ the toxicity of ONOO- has been considnm) (0-600 s). OxoMn(IV) was generated by a stoichiometric reaction ered in light of this reactivity.I0 Oxidative damage in cells has between MnTMPyP (10 p M ) and ONOO- (1 equiv) in 50 mM Tris been linked to the metal ion-catalyzed generation of free radicals (pH 7.4). and peroxides." Thus, we have examined the metal-mediated activation of peroxynitrite toward biological targets. Described similar oxoMncV)intermediate (1) has a very short lifetime under here is evidence that a manganese porphyrin-peroxynitrite these conditions." system generates reactive metal-oxo species which potentiate Peroxynitrite in the presence of MnTMPyP caused extensive oxidative cleavage of plasmid DNA and catalyze the nitration strand scission of plasmid DNA.ISa Formation of the same of phenols. oxoMn(IV) chromophore was observed under these conditions. DNA cleavage by ONOO- alone has been reported at much We find that peroxynitriteI2reacts rapidly and efficiently with MnTMPyPt3 under physiological conditions to generate an higher doses, but, notably, this cleavage was quenched in Tris oxomanganese intermediate (Figure 1). A 1:1 stoichiometry is buffer.6 As can be seen in Figure 2, a dose-dependent increase observed for the reaction, even though the half-life of ONOOof plasmid DNA cleavage was observed in lanes containing is
