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Identification of the Additional Mitochondrial Liabilities of 2-Hydroxyflutamide When Compared With its Parent Compound, Flutamide in HepG2 Cells

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ABSTRACT

The androgen receptor antagonist, flutamide, is strongly associated with idiosyncratic drug-induced liver injury (DILI). Following administration, flutamide undergoes extensive first-pass metabolism to its primary metabolite, 2-hydroxyflutamide. Flutamide is a known mitochondrial toxicant; however there has been limited investigation into the potential mitochondrial toxicity of 2-hydroxyflutamide and its contribution to flutamide-induced liver injury. In this study we have used the acute glucose or galactose-conditioning of HepG2 cells to compare the mitochondrial toxicity of flutamide, 2-hydroxyflutamide and the structurally-related, non-hepatotoxic androgen receptor antagonist, bicalutamide. Compound-induced changes in mitochondrial oxygen consumption rate were assessed using Seahorse technology. Permeabilization of cells and delivery of specific substrates and inhibitors of the various respiratory complexes provided more detailed information on the origin of mitochondrial perturbations. These analyses were supported by assessment of downstream impacts including changes in cellular NAD+/NADH ratio. Bicalutamide was not found to be a mitochondrial toxicant, yet flutamide and 2-hydroxyflutamide significantly reduced basal and maximal respiration. Both flutamide and 2-hydroxyflutamide significantly reduced respiratory complex I-linked respiration, though 2-hydroxyflutamide also significantly decreased complex II and V-linked respiration; liabilities not demonstrated by the parent compound. This study has identified for the first time, the additional mitochondrial liabilities of the major metabolite, 2-hydroxyflutamide compared with its parent drug, flutamide. Given the rapid production of this metabolite upon administration of flutamide, but not bicalutamide, we propose that the additional mitochondrial toxicity of 2-hydroxyflutamide may fundamentally contribute to the idiosyncratic DILI seen in flutamide-treated, but not bicalutamide-treated patients.

No MeSH data available.


Flutamide, 2-hydroxyflutamide and bicalutamide chemical structures. Flutamide is rapidly hydroxylated (A) to 2-hydroxyflutamide upon administration. This primary metabolite has been shown to have higher androgen receptor binding affinity than its parent compound (Shet et al., 1997). Bicalutamide was derived from flutamide by the addition of a 4-fluorophenylsulfonyl moiety (B) and also notably replaces the nitroaromatic structural alert in flutamide with a cyano group (C).
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kfw126-F1: Flutamide, 2-hydroxyflutamide and bicalutamide chemical structures. Flutamide is rapidly hydroxylated (A) to 2-hydroxyflutamide upon administration. This primary metabolite has been shown to have higher androgen receptor binding affinity than its parent compound (Shet et al., 1997). Bicalutamide was derived from flutamide by the addition of a 4-fluorophenylsulfonyl moiety (B) and also notably replaces the nitroaromatic structural alert in flutamide with a cyano group (C).

Mentions: In vitro studies have shown the inhibition of mitochondrial respiratory complex I (NADH ubiquinone oxidoreductase) activity by flutamide (Coe et al., 2007). However, upon administration, flutamide undergoes extensive first-pass metabolism, primarily by conversion to 2-hydroxyflutamide via cytochrome P450 1A2 (CYP1A2), followed by glucuronidation before excretion (Figure 1) (Coe et al., 2007; Shet et al., 1997). Following a single 250 mg dose of flutamide its maximum plasma concentration (Cmax) is 72.2 nM, yet the Cmax of 2-hydroxyflutamide is 4.4 µM (Schulz et al., 1988). Despite the longer half-life (9.6 vs 7.8 h) and higher Cmax of 2-hydroxyflutamide compared with its parent compound, the potential mitochondrial toxicity of 2-hydroxyflutamide as a contributor to flutamide-induced liver injury has not been fully investigated (Kostrubsky et al., 2007). We hypothesized that because patients are exposed to such a high concentration of the 2-hydroxyflutamide metabolite that it may contribute significantly to the toxicity exhibited upon flutamide administration and possibly through a mitochondrial mechanism.FIG. 1


Identification of the Additional Mitochondrial Liabilities of 2-Hydroxyflutamide When Compared With its Parent Compound, Flutamide in HepG2 Cells
Flutamide, 2-hydroxyflutamide and bicalutamide chemical structures. Flutamide is rapidly hydroxylated (A) to 2-hydroxyflutamide upon administration. This primary metabolite has been shown to have higher androgen receptor binding affinity than its parent compound (Shet et al., 1997). Bicalutamide was derived from flutamide by the addition of a 4-fluorophenylsulfonyl moiety (B) and also notably replaces the nitroaromatic structural alert in flutamide with a cyano group (C).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036617&req=5

kfw126-F1: Flutamide, 2-hydroxyflutamide and bicalutamide chemical structures. Flutamide is rapidly hydroxylated (A) to 2-hydroxyflutamide upon administration. This primary metabolite has been shown to have higher androgen receptor binding affinity than its parent compound (Shet et al., 1997). Bicalutamide was derived from flutamide by the addition of a 4-fluorophenylsulfonyl moiety (B) and also notably replaces the nitroaromatic structural alert in flutamide with a cyano group (C).
Mentions: In vitro studies have shown the inhibition of mitochondrial respiratory complex I (NADH ubiquinone oxidoreductase) activity by flutamide (Coe et al., 2007). However, upon administration, flutamide undergoes extensive first-pass metabolism, primarily by conversion to 2-hydroxyflutamide via cytochrome P450 1A2 (CYP1A2), followed by glucuronidation before excretion (Figure 1) (Coe et al., 2007; Shet et al., 1997). Following a single 250 mg dose of flutamide its maximum plasma concentration (Cmax) is 72.2 nM, yet the Cmax of 2-hydroxyflutamide is 4.4 µM (Schulz et al., 1988). Despite the longer half-life (9.6 vs 7.8 h) and higher Cmax of 2-hydroxyflutamide compared with its parent compound, the potential mitochondrial toxicity of 2-hydroxyflutamide as a contributor to flutamide-induced liver injury has not been fully investigated (Kostrubsky et al., 2007). We hypothesized that because patients are exposed to such a high concentration of the 2-hydroxyflutamide metabolite that it may contribute significantly to the toxicity exhibited upon flutamide administration and possibly through a mitochondrial mechanism.FIG. 1

View Article: PubMed Central - PubMed

ABSTRACT

The androgen receptor antagonist, flutamide, is strongly associated with idiosyncratic drug-induced liver injury (DILI). Following administration, flutamide undergoes extensive first-pass metabolism to its primary metabolite, 2-hydroxyflutamide. Flutamide is a known mitochondrial toxicant; however there has been limited investigation into the potential mitochondrial toxicity of 2-hydroxyflutamide and its contribution to flutamide-induced liver injury. In this study we have used the acute glucose or galactose-conditioning of HepG2 cells to compare the mitochondrial toxicity of flutamide, 2-hydroxyflutamide and the structurally-related, non-hepatotoxic androgen receptor antagonist, bicalutamide. Compound-induced changes in mitochondrial oxygen consumption rate were assessed using Seahorse technology. Permeabilization of cells and delivery of specific substrates and inhibitors of the various respiratory complexes provided more detailed information on the origin of mitochondrial perturbations. These analyses were supported by assessment of downstream impacts including changes in cellular NAD+/NADH ratio. Bicalutamide was not found to be a mitochondrial toxicant, yet flutamide and 2-hydroxyflutamide significantly reduced basal and maximal respiration. Both flutamide and 2-hydroxyflutamide significantly reduced respiratory complex I-linked respiration, though 2-hydroxyflutamide also significantly decreased complex II and V-linked respiration; liabilities not demonstrated by the parent compound. This study has identified for the first time, the additional mitochondrial liabilities of the major metabolite, 2-hydroxyflutamide compared with its parent drug, flutamide. Given the rapid production of this metabolite upon administration of flutamide, but not bicalutamide, we propose that the additional mitochondrial toxicity of 2-hydroxyflutamide may fundamentally contribute to the idiosyncratic DILI seen in flutamide-treated, but not bicalutamide-treated patients.

No MeSH data available.