Abstract
Hydroxamic acid (HA)-based histone deacetylase (HDAC) inhibitors, with trichostatin A (TSA) as the reference compound, are potential antitumoral drugs and show promise in the creation of long-term primary cell cultures. However, their metabolic properties have barely been investigated. TSA is rapidly inactivated in rodents both in vitro and in vivo. We previously found that 5-(4-dimethylaminobenzoyl)aminovaleric acid hydroxyamide or 4-Me2N-BAVAH (compound 1) is metabolically more stable upon incubation with rat hepatocyte suspensions. In this study, we show that human hepatocytes also metabolize TSA more rapidly than compound 1 and that similar pathways are involved. Furthermore, structural analogs of compound 1 (compounds 2-9) are reported to have the same favorable metabolic properties. Removal of the dimethylamino substituent of compound 1 creates a very stable but 50% less potent inhibitor. Chain lengthening (4 to 5 carbon spacer) slightly improves both potency and metabolic stability, favoring HA reduction to hydrolysis. On the other hand, Cα-unsaturation and spacer methylation not only reduce HDAC inhibition but also increase the rate of metabolic inactivation approximately 2-fold, mainly through HA reduction. However, in rat hepatocyte monolayer cultures, compound 1 is shown to be extensively metabolized by phase II conjugation. In conclusion, this study suggests that simple structural modifications of amide-linked TSA analogs can improve their phase I metabolic stability in both rat and human hepatocyte suspensions. Phase II glucuronidation, however, can compensate for their lower phase I metabolism in rat hepatocyte monolayers and could play a yet unidentified role in the determination of their in vivo clearance.
Footnotes
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This work was supported by grants from the Fund for Scientific Research-Flanders (FWO) and the Research Council (OZR) of the Vrije Universiteit Brussel (Brussels, Belgium). This work is also part of the European Specific Targeted Research Project-Project Predictomics 504761.
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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.106.116202.
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ABBREVIATIONS: FBS, fetal bovine serum; HA, hydroxamic acid; HDAC, histone deacetylase; HDACi, histone deacetylase inhibitor(s); HPLC, high-performance (pressure) liquid chromatography; LDH, lactate dehydrogenase; 4-Me2N-BAVAH, 5-(4-dimethylaminobenzoyl)aminovaleric acid hydroxyamide; QSAR, quantitative structure-activity relationship; SAHA, suberoylanilide hydroxamic acid; TSA, R-(+)-trichostatin A or 7-[4-(dimethylamino)phenyl]-4,6-dimethyl-7-oxo-hepta-2,4-dienoic acid hydroxamide; DMSO, dimethyl sulfoxide.
- Received October 26, 2006.
- Accepted January 10, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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