Inhibition of Aldo-keto Reductases by Phenobarbital Alters Metabolism, Pharmacokinetics and Toxicity of Doxorubicin in Rats

Abstract

Doxorubicin is an effective anticancer agent that is limited by numerous adverse effects, cardiotoxicity causing the most concern. Its alcohol metabolite, doxorubicinol, and free radicals have been implicated in the aetiology of this toxicity. This study was based on the premise that inhibition of aldo-keto reductases would improve the efficacy of doxorubicin by reducing its toxic metabolites and modifying its pharmacokinetics. We assessed the effect of in-vitro inhibition of aldo-keto reductases on the metabolism of doxorubicin in cytosolic fractions of heart and liver of rats in the presence of Na-phenobarbital. The inhibition was confirmed by a significant reduction in the formation of doxorubicinol. The results of the in-vitro study were further evaluated in-vivo. The concentrations of doxorubicin in plasma, bile and urine and its major metabolites in bile and urine were measured in Na-phenobarbital-pretreated rats. Each rat received 100 mg kg(-1)/day intraperitoneal injection of sodium phenobarbital for three days followed by a single intravenous dose of 10 mg kg(-1) [14C-14]doxorubicin (sp. act. 0.2 microCi mg(-1)) on the fourth day. The levels of drug in all biological samples were measured by HPLC. The pretreatment resulted in an increase in biological half-life (5.8 +/- 1.5 vs 3.7 +/- 0.93 h control group, P < 0.05) and area under plasma concentration-time curve (19.6 +/- 1.7 vs 14.65 +/- 1.68 mg h L(-1) control group, P < 0.05). The cumulative amount of doxorubicinol in the bile and urine of pretreated animals was reduced significantly. In terms of % dose, the amount in the bile declined from 4.2 +/- 0.8% in control to 2.4 +/- 0.3% and in urine from 0.18 +/- 0.08% to 0.12 +/- 0.07%. There were no significant changes in doxorubicin aglycone and doxorubicinol aglycone. Serum creatine kinase levels were measured as a biomarker of damage to cardiac muscle. The area under creatine kinase level-time curve was reduced by approximately 50% in phenobarbital-pretreated animals. The results indicate that the inhibition of aldo-keto reductase could provide a useful approach to improve the safety of doxorubicin by reducing its alcohol metabolite. Furthermore, if the reduction in the area under the serum creatine kinase-time curve represents a reduced damage to heart muscle, it can be concluded that doxorubicinol plays an important role in this injury.

Paclitaxel and Docetaxel Stimulation of Doxorubicinol Formation in the Human Heart: Implications for Cardiotoxicity of Doxorubicin-Taxane Chemotherapies

“…We showed that both paclitaxel and docetaxel stimulated an NADPH-dependent reduction of doxorubicin to doxorubicinol in isolated human cardiac cytosol (Minotti et al, 2001b), a translational model that obviated potential pitfalls caused by the different enzymology of anthracycline secondary alcohol metabolite formation in laboratory animals versus humans (Maessen et al, 1987;Behnia and Boroujerdi, 1999;Minotti et al, 2004;Salvatorelli et al, 2006). The effect of paclitaxel or docetaxel did not require Cremophor EL or polysorbate 80, nor was it observed on replacing the taxanes with the structurally unrelated tubulin-active Vinca alkaloid vinorelbine; this showed that stimulation of doxorubicinol formation was inherently related to the taxoid backbone of paclitaxel or docetaxel (Minotti et al, 2001b).…”

Mechanistic Basis for Use of Aldose Reductase Inhibitors to Treat Breast Cancer

“…Furthermore, increases in aldose reductase protein have also been observed in carcinoma cells 14,15 . Importantly, it has been suggested that increased aldose reductase expression and intracellular sorbitol accumulation may be partly responsible for reduced efficacy of chemotherapeutic drugs used to treat breast cancer 6 . In such cases, aldose reductase activity appears to influence cell growth and the response of tumor cells to anti-cancer drugs.…”

Aldo-Keto Reductase 1C2 Fails to Metabolize Doxorubicin and Daunorubicin in Vitro

“…Although the mechanism by which this side effect develops is not yet identified, evidence implicates metabolism as an important factor (Olson and Mushlin, 1990). Following DOX or DAUN administration, the C-13 alcohol metabolites, DOXol and DAUNol, are the major identified metabolites (Takanashi and Bachur, 1976), and these metabolites are speculated to be responsible for causing cardiac tissue damage (Del Tacca et al, 1985;Boucek et al, 1987;Cusack et al, 1993;Behnia and Boroujerdi, 1999;Olson et al, 2003;Sacco et al, 2003).…”

“…Inhibition of the anthracycline-metabolizing enzymes is suggested as a strategy for avoiding treatment-related cardiotoxicity (Behnia and Boroujerdi, 1999), and chemical inhibitors for reductases and anthracycline derivatives that are metabolically less labile have been explored for their potential roles as safer alternatives to the currently used anthracycline drug treatments. In part, the success of these strategies relies on accurately identifying the enzymes responsible for anthracycline metabolism.…”