Quantitative determination of SH groups in low- and high-molecular-weight compounds by an electron spin resonance method

Khramtsov, Valery V.; Yelinova, V.I.; Weiner, Lev; Berezina, T. A.; Martin, Valérie; Volodarsky, L. B.

doi:10.1016/0003-2697(89)90718-5

Cited by 89 publications

(81 citation statements)

References 16 publications

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“…GSH does not reduce the NR directly [1,30,31]. Figure 8 demonstrates the stability of EPR signal of 1 mM solution of the tetraethylsubstituted imidazolidine NR 4 in the presence of 50 mM GSH for 40 minutes.…”

Section: Facilitating Nr Reduction By Glutathionementioning

confidence: 99%

See 1 more Smart Citation

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Bobko

Kirilyuk

Grigor'ev

et al. 2007

Free Radical Biology and Medicine

134

123

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Biological applications of stable nitroxyl radicals, NR, include their use as contrast agents for magnetic resonance imaging, spin labels, superoxide dismutase mimics, and antioxidants. The rapid reduction of NR in biological samples into hydroxylamines, HA, significantly limits their application. In its turn, reoxidation of HA back to the NR has been used for detection of reactive oxygen species, ROS. In this work comparative studies of the reduction of pyrrolidine, imidazoline and imidazolidine NR by ascorbate were performed taking advantage of recently synthesized tetraethyl substituted NR with much higher stability towards reduction both in vitro and in vivo. Surprisingly, these NR kept 10-50% of initial intensity of electron paramagnetic resonance signal for about 1 h in the presence of hundred fold excess of ascorbate. To explain this data, reoxidation of the corresponding HA by ascorbate radical and dehydroascorbic acid back to the NR was proposed. This hypothesis was supported by direct measurement of the NR appearance from the HA upon ascorbate radical generation by ascorbate oxidase, or in the presence of the dehydroascorbic acid. The reversible reaction between NR and ascorbate was observed for the various types of the NR, and the rate constants for direct and reverse reactions were determined. The equilibrium constants for oneelectron reduction of the tetraethyl substituted NR by ascorbate were found to be in the range from 2.65×10 −6 to 10 −5 which is significantly lower than corresponding values for the tetramethyl substituted NR (less or about 10 −4 ). This explains an establishment of EPR-detectable quasiequilibrium level of tetraethyl substituted NR in the presence of excess of ascorbate. The redox reactions of the NR-HA couple in ascorbate containing medium was found to be significantly affected by glutathione, GSH. This effect was attributed to the reduction of ascorbate radical by GSH, and the rate constant of this reaction was found to be equal to 10 M −1 s −1 . In summary, the data provide new insight into the redox chemistry of NR and HA, and significantly affect interpretation and strategy of their use as redox-and ROS-sensitive probes, or as antioxidants.

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Section: Facilitating Nr Reduction By Glutathionementioning

confidence: 99%

“…Appreciable chemical reduction of NR by glutathione does not occur over a few hours [1,[30][31][32]. However glutathione can significantly contribute in the reduction of NR in biological systems indirectly by acting as a secondary source of reducing equivalents [10].…”

Section: Introductionmentioning

confidence: 99%

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Bobko

Kirilyuk

Grigor'ev

et al. 2007

Free Radical Biology and Medicine

134

123

View full text Add to dashboard Cite

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“…Cellular levels of GSH were determined by EPR spectroscopy, which was based on the application of an imidazoline biradical label (24). The label reacts with reduced thiol and shows a characteristic EPR spectrum, which can be quantified by using known amounts of GSH.…”

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confidence: 99%

Reversal to cisplatin sensitivity in recurrent human ovarian cancer cells by NCX-4016, a nitro derivative of aspirin

Bratasz¹,

Weir

Parinandi

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Ovarian cancer is a gynecological malignancy that is commonly treated by cytoreductive surgery followed by cisplatin treatment. However, the cisplatin treatment, although successful initially, is not effective in the treatment of the recurrent disease that invariably surfaces within a few months of the initial treatment. The refractory behavior is attributed to the increased levels of cellular thiols apparently caused by the cisplatin treatment. This observation prompted us to choose a cytotoxic drug whose activity is potentiated by cellular thiols with enhanced specificity toward the thiol-rich cisplatin-resistant cells. We used NCX-4016 [2-(acetyloxy) benzoic acid 3-(nitrooxymethyl)phenyl ester], a derivative of aspirin containing a nitro group that releases nitric oxide in a sustained fashion for several hours in cells and in vivo, and we studied its cytotoxic efficacy against human ovarian cancer cells (HOCCs). Cisplatin-sensitive and cisplatin-resistant (CR) HOCCs were treated with 100 M NCX-4016 for 6 h, and͞or 0.5 g͞ml cisplatin for 1 h and assayed for clonogenecity. NCX-4016 significantly reduced the surviving fractions of cisplatin-sensitive (63 ؎ 6%) and CR (70 ؎ 10%) HOCCs. NCX-4016 also caused a 50% reduction in the levels of cellular glutathione in CR HOCCs. Treatment of cells with NCX-4016 followed by cisplatin showed a significantly greater extent of toxicity when compared with treatment of cells with NCX-4016 or cisplatin alone. In conclusion, this study showed that NCX-4016 is a potential inhibitor of the proliferation of CR HOCCs and thus might specifically kill cisplatin-refractory cancer cells in patients with recurrent ovarian cancer.cisplatin resistance ͉ glutathione ͉ nitric oxide ͉ cytotoxicity ͉ nonsteroidal antiinflammatory drug O varian cancer is the second most commonly diagnosed gynecological malignancy and the fourth leading cause of mortality among women in the United States (1). The high mortality rate is attributed to the lack of early diagnosis of the malignancy and difficulties associated with treatment. The standard treatment includes cytoreductive surgery followed by the administration of chemotherapeutic agents. Platinum-based compounds (e.g., cisplatin and carboplatin) in combination with taxanes (e.g., taxol or paclitaxel), anthracyclines (e.g., doxorubicin), or alkylating agents (e.g., melphalan) are administered to treat the advanced-stage disease (2). However, the overall clinical response with such treatments is only 40-60%. The primary factor that limits the success of chemotherapy in ovarian cancer is the acquired drug resistance in the tumor cell population. Administration of cisplatin results in the development of drug resistance in the cancer cells. Postulated mechanisms of drug resistance include decreased intracellular accumulation of the drug, increased levels of thiols, which inactivate the platinum compound, and the enhancement of DNA repair (3). Even a slight increase in the cisplatin resistance of the tumor may pose a clinically important problem requiring ...

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“…Half a century of continuous progress in nitroxide chemistry has resulted in the design of specific NRs for spin labeling (Berliner, 1998), sitedirected spin labeling (Hubbell et al, 2000), EPR oximetry (Halpern et al, 1994;Swartz, 2004), pH (Khramtsov et al, 1982, thiols (Khramtsov et al, 1989(Khramtsov et al, , 1997, redox (Swartz et al, 2007) and NO measurements (Akaike et al, 1993;Joseph et al, 1993;Woldman et al, 1994). Over the past decade low-field L-band (1.2 GHz) EPR spectrometers and imagers have become commercially available allowing for functional EPR measurements in isolated organs (Komarov et al, 2012) and small animals such as mice Bobko et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

In vivo Spectroscopy and Imaging of Nitroxide Probes

Khramtsov¹

2012

Nitroxides - Theory, Experiment and Applications

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Quantitative determination of SH groups in low- and high-molecular-weight compounds by an electron spin resonance method

Cited by 89 publications

References 16 publications

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Reversal to cisplatin sensitivity in recurrent human ovarian cancer cells by NCX-4016, a nitro derivative of aspirin

In vivo Spectroscopy and Imaging of Nitroxide Probes

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