1. Beneficial effect of indapamide in experimental myocardial ischemia
D M Guez, F R Boucher, J G de Leiris, C J Schatz Am J Hypertens . 1992 Jan;5(1):22-5. doi: 10.1093/ajh/5.1.22.
Indapamide, a nonthiazide chlorosulfamoyl diuretic, which possesses well-known antihypertensive properties, is able to scavenge free radical intermediates involved in lipid peroxidation. In this respect, it has almost the same level of action as alpha-tocopherol. Using an isolated working rat heart preparation, we investigated the effect of indapamide on the myocardial resistance to global total normothermic ischemia followed by reperfusion. The heart, isolated at the end of chronic oral pretreatment (7 day at 3 mg/kg body weight/day), was submitted to ischemia for 15 min and then reperfused. The main results were as follows: in the indapamide-treated group, 1) postischemic recovery of cardiac function was significantly better as compared to the untreated control group; 2) lactate dehydrogenase (LDH) release measured after 15 min of reperfusion was significantly reduced; 3) the myocardial content of organic hydroperoxides (HPO), taken as an index of lipid peroxidation, was significantly lowered, whereas the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) remained unchanged; and 4) electron spin resonance (ESR) analysis of coronary effluents, collected during the first minutes of reperfusion in the presence of the spin-trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), revealed a significant modification in the treated group. These findings suggest that indapamide treatment is able to afford some protective effect to cardiac tissue during the early stage of postischemic reperfusion, and that this effect might be related to the antioxidant properties of inadapamide.
2. Direct detection of ototoxicant-induced reactive oxygen species generation in cochlear explants
D L DiMartino, K Hensley, D A Butterfield, W J Clerici Hear Res . 1996 Sep 1;98(1-2):116-24. doi: 10.1016/0378-5955(96)00075-5.
The proposal that free-radical generation contributes to the ototoxicities of several chemical agents was studied utilizing electron paramagnetic resonance (EPR) spectrometry to detect directly ototoxicant-induced reactive oxygen species formation in cochlear tissue. Guinea pig cochlear explants in chelexed artificial perilymph (AP: 200 microliters) were exposed to an ototoxicant or AP for 10 min. Ototoxic agents included gentamicin sulfate (4.0 mM), kanamycin monosulfate (4.0 mM), ethacrynic acid (0.5 mM), furosemide (0.3 mM), cisplatin (0.1 mM), trimethyltin chloride (0.1 mM), and quinine HCl (3.0 mM). Following incubation, 20 microliters of AP/ototoxicant mixture was replaced by the filtered spin trap, 5,5-dimethylpyrroline-N-oxide (DMPO). After 10 min, the EPR spectrum of the mixture was obtained. Four line EPR spectra of relative intensities 1:2:2:1, associated with hydroxyl radical (OH)/DMPO adduct formation, were evidenced by reaction mixtures containing cochlear explants exposed to each ototoxicant. Cisplatin, quinine and the loop diuretics produced weak OH-associated EPR signals in the absence of a cochlear explant, which were amplified in its presence. Deferoxamine quenched all OH spectral peaks. Peroxide levels, assayed in parallel experiments, were diminished by each ototoxicant relative to those seen following AP exposure, suggesting possible H2O2 conversion to OH. These data support the proposal that various ototoxic agents are capable of reactive oxygen species generation or promotion in cochlear tissues.
3. Detection and characterization of the product of hydroethidine and intracellular superoxide by HPLC and limitations of fluorescence
Joy Joseph, B Kalyanaraman, Rodney L Levine, Edward A Sokoloski, Jeannette Vasquez-Vivar, Hongtao Zhao, Henry M Fales Proc Natl Acad Sci U S A . 2005 Apr 19;102(16):5727-32. doi: 10.1073/pnas.0501719102.
Here we report the structural characterization of the product formed from the reaction between hydroethidine (HE) and superoxide (O(2)(.-)). By using mass spectral and NMR techniques, the chemical structure of this product was determined as 2-hydroxyethidium (2-OH-E(+)). By using an authentic standard, we developed an HPLC approach to detect and quantitate the reaction product of HE and O(2)(.-) formed in bovine aortic endothelial cells after treatment with menadione or antimycin A to induce intracellular reactive oxygen species. Concomitantly, we used a spin trap, 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO), to detect and identify the structure of reactive oxygen species formed. BMPO trapped the O(2)(.-) that formed extracellularly and was detected as the BMPO-OH adduct during use of the EPR technique. BMPO, being cell-permeable, inhibited the intracellular formation of 2-OH-E(+). However, the intracellular BMPO spin adduct was not detected. The definitive characterization of the reaction product of O(2)(.-) with HE described here forms the basis of an unambiguous assay for intracellular detection and quantitation of O(2)(.-). Analysis of the fluorescence characteristics of ethidium (E(+)) and 2-OH-E(+) strongly suggests that the currently available fluorescence methodology is not suitable for quantitating intracellular O(2)(.-). We conclude that the HPLC/fluorescence assay using HE as a probe is more suitable [corrected] for detecting intracellular O(2)(.-).
