A Metabolic Screening Study of Trichostatin A (TSA) and TSA-Like Histone Deacetylase Inhibitors in Rat and Human Primary Hepatocyte Cultures

• Published in: The Journal of pharmacology and experimental therapeutics Vol. 321; no. 1; pp. 400 - 408
• Main Authors: Elaut, G, Laus, G, Alexandre, E, Richert, L, Bachellier, P, Tourwé, D, Rogiers, V, Vanhaecke, T
• Format: Journal Article
• Language: English
• Published: United States American Society for Pharmacology and Experimental Therapeutics 01.04.2007
• Subjects: Animals; Biotransformation; Cell Membrane - drug effects; Cell Membrane - enzymology; Cell Separation; Cells, Cultured; Chromatography, High Pressure Liquid; Enzyme Inhibitors - metabolism; Hepatocytes - drug effects; Hepatocytes - enzymology; Hepatocytes - metabolism; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids - metabolism; In Vitro Techniques; Indicators and Reagents; Male; Rats; Rats, Sprague-Dawley; Spectrophotometry, Ultraviolet
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.106.116202

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-Me 2 N -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.