Abstract
We investigated the in vitro metabolism of two (nitrooxy)butyl ester nitric oxide (NO) donor derivatives of flurbiprofen and ferulic acid, [1,1′-biphenyl]-4-acetic acid-2-fluoro-α-methyl-4-(nitrooxy)butyl ester (HCT 1026) and 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid 4-(nitrooxy)butyl ester (NCX 2057), respectively, in rat blood plasma and liver subcellular fractions compared with (nitrooxy)butyl alcohol (NOBA) and glyceryl trinitrate (GTN). HCT 1026 and NCX 2057 undergo rapid ubiquitous carboxyl ester hydrolysis to their respective parent compounds and NOBA. The nitrate moiety of this latter is subsequently metabolized to inorganic nitrogen oxides (NOx), predominantly in liver cytosol by glutathione S-transferase (GST) and to a lesser extent in liver mitochondria. If, however, in liver cytosol, the carboxyl ester hydrolysis is prevented by an esterase inhibitor, the metabolism at the nitrate moiety level does not occur. In blood plasma, HCT 1026 and NCX 2057 are not metabolized to NOx, whereas a slow but sustained NO generation in deoxygenated whole blood as detected by electron paramagnetic resonance indicates the involvement of erythrocytes in the bioactivation of these compounds. Differently from NOBA, GTN is also metabolized in blood plasma and more quickly metabolized by different GST isoforms in liver cytosol. The cytosolic GST-mediated denitration of these organic nitrates in liver limits their interaction with other intracellular compartments to possible generation of NO and/or their subsequent availability and bioactivation in the systemic circulation and extrahepatic tissues. We show the possibility of modulating the activity of hepatic cytosolic enzymes involved in the metabolism of (nitrooxy)butyl ester compounds, thus increasing the therapeutic potential of this class of compounds.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.097469.
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ABBREVIATIONS: GTN, glyceryl trinitrate; NO, nitric oxide; NO2-, nitrite; NO3-, nitrate; GST, glutathione S-transferase; XO, xanthine oxidoreductase; P450, cytochrome P-450; CINOD, cyclooxygenase-inhibiting nitric oxide donator; HCT 1026, [1,1′-biphenyl]-4-acetic acid 2-fluoro-α-methyl,4-(nitrooxy)butyl ester; NCX 2057, 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid 4-(nitrooxy)butyl ester; NOBA, (nitrooxy)butyl alcohol; HCT 1027, [1,1′-biphenyl]-4-acetic acid 2-fluoro-α-methyl,4-hydroxybutyl ester; NCX 2059, 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid 4-hydroxybutyl ester; HPLC, high-performance liquid chromatography; EA, ethacrynic acid; BSP, bromosulfophthalein; NEM, N-ethylmaleimide; isoOMPA, tetraisopropylpyrophosphoramide; EPR, electron paramagnetic resonance; NOx, inorganic nitrogen oxide(s); HbFe(II)NO, nitrosyl hemoglobin.
- Received October 21, 2005.
- Accepted January 18, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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