Maria G. Salgo

Scavenging of peroxynitrite by a phenolic/peroxidase system prevents oxidative damage to DNA1

We examined the ability of horseradish peroxidase (HRP), an analog of human myeloperoxidase, to protect DNA against oxidative damage caused by peroxynitrite in the presence of chlorogenic acid (CGA), a naturally occurring polyphenol. Chlorogenic acid inhibits the formation of single strand breaks in supercoiled pBR322 DNA by acting as a scavenger of peroxynitrite. Horseradish peroxidase markedly enhances the extent of DNA protection by catalyzing the decomposition of peroxynitrite in the presence of CGA. Horseradish peroxidase alone does not inhibit peroxynitrite‐induced DNA strand breaks, indicating that CGA is required as an electron donor to regenerate the active enzyme. The apparent second order rate constant for the HRP‐mediated oxidation of CGA in the presence of peroxynitrite at pH 6.9 is 3.4×107 M−1 s−1. This high rate suggests that CGA and other dietary polyphenols might efficiently scavenge peroxynitrite in peroxidase‐containing systems in vivo.

Effect of lipid ozonation products on liposomal membranes detected by Laurdan fluorescence

We report here the influence of the lipid ozonation products, 1-palmitoyl-2-(9-oxononanoyl)-sn-glycero-3-phosphocholine (PC-aldehyde) and 1-palmitoyl-2[8-(5-octyl-1, 2, 4,-trioxolan-3-yl)- octanoyl]-sn-glycero-3-phosphocholine (PC-Criegee ozonide), on the phase domains of small unilamellar vesicles. (See Scheme 1 for structures.) 6-Lauroyl-2-dimethylaminonaphtalene (Laurdan) fluorescence excitation and emission spectra and generalized polarization measurements allowed us to study how lipid ozonation products affect the phase components of phospholipid membranes. A shift of excitation and emission spectra and a decrease in generalized polarization reveal the presence of a more polar environment surrounding the probe. We find that when either PC-aldehyde or PC-Criegee ozonide are incorporated into a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane, or when the POPC membrane is directly ozonated, a change in polarity of the phospholipid environment occurs that changes the properties of the bilayer. The introduction of more oxygenated and more polar phospholipids creates a more polar environment allowing the deeper penetration of water molecules into the membrane. Water penetration also is facilitated by the membrane disorder-producing effect of the ozonation products. The presence of an increased number of water molecules in the membrane effects the bilayer, altering packing order and cooperatively among fatty acyl chains as well as enhancing membrane fluidity.

[52] Synthesis of inflammatory signal transduction species formed during ozonation and/or peroxidation of tissue lipids

Publisher Summary Lipid peroxidation and ozonation produce oxidized lipids that are bioactive and can act as signal transducers. The synthesis and isolation of these oxidized lipid products in pure form will allow the testing of hypotheses regarding their role as potential relay molecules. Of special interest are oxidized lipids derived from 1,2-diacyl- sn -glycero-3-phosphocholine that feature a shortened acyl chain on the second position ending with an aldehyde function. These platelet-activating factor analogs are not only produced during ozonation but also during the peroxidation of 1,2-diacyl- sn -glycero-3-phosphocholines. Another class of biologically active lipids is the 1-hydroxy-l-hydroperoxyalkanes formed in vivo from the addition of water to the carbonyl oxides that are intermediates in the ozonation of unsaturated lipids in aqueous media. 1-Hydroxy-1-hydroperoxyalkanes are conveniently generated in situ from the hydrolysis of bis(1-hydroxyalkyl) peroxides. Bis(1-hydroxyalkyl)peroxides are not themselves direct lipid ozonation products, but are stable crystalline compounds that slowly hydrolyze to the corresponding 1-hydroxy-1-hydroperoxyalkanes and aldehydes. This chapter reports the syntheses of 1-palmitoyl-2-[3-(8-octanoyl)-5-(1-octyl)-l,2,4-trioxolane]- sn -glycero-3-phosphocholine (the Criegee ozonide of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine), 1-palmitoyl-2-(9-oxononanoyl)-sn-glycero-3-phosphocholine, 1-palmitoyl-2-(1-hydroxy-1-hydroperoxynonanoyl)- sn -glycero-3-phosphocholine, bis(1-hydroxyheptyl) peroxide, and bis(1-hydroxynonyl)peroxide (the percursors of the corresponding 1-hydroxy-1-hydroperoxyalkanes).