Ketoconazole blocks adrenal steroidogenesis by inhibiting cytochrome P450-dependent enzymes.

Abstract

A B S T R A C T Ketoconazole has recently been shown to interfere with steroidogenesis in patients and rat in vitro systems. In this study we attempted to elucidate the site of inhibition in the adrenal gland. Although ketoconazole impaired adrenocorticotropic hormone stimulated cyclic (c)AMP production, dibutyryl cAMP addition did not bypass the steroidogenic blockade indicating that the critical ketoconazole-inhibited step was distal to cAMP. Addition of radiolabeled substrates to isolated adrenal cells and analysis of products by high performance liquid chromatography demonstrated a ketoconazole block between deoxycorticosterone (DOC) and corticosterone. This 11-hydroxylase step is carried out by a P450-dependent mitochondrial enzyme. No restriction of progesterone or pregnenolone conversion to DOC was detected, steps carried out by non-P450-dependent microsomal enzymes. Inhibition of cholesterol conversion to pregnenolone by mitochondrial fractions indicated a second block at the side chain cleavage step, another mitochondrial P450-dependent enzyme. Adrenal malate dehydrogenase, a non-P450-dependent mitochondrial enzyme was not inhibited while renal 24-hydroxylase, a P450-dependent mitochondrial enzyme in another organ, was blocked by ketoconazole. We conclude that ketoconazole may be a general inhibitor of mitochondrial P450 enzymes. This finding suggests that patients receiving ketoconazole be monitored for side effects relevant to P450 enzyme inhibition. Further, we raise the possibility that this drug action may be beneficially exploited in situations where inhibition of steroidogenesis is a therapeutic goal.

Tumor apoptosis induced by ruthenium(II)‐ketoconazole is enhanced in nonsusceptible carcinoma by monoclonal antibody to EGF receptor

“…Alamar blue studies also revealed a negligible effect of active RuCl 2 (KTZ) 2 RuCl 2 (KTZ) 2 led to inhibition of Ͼ80% as measured by alamar blue and cell detachment in C8161 melanoma (not shown). Treatment of the latter cells at 25 M of either RuCl 2 (CTZ) 2 or RuCl 2 (KTZ) 2 led to apoptosis-associated PARP cleavage, 25 although the extent of PARP fragmentation was clearly greater with the latter complex (Fig. 2, lower right).…”

“…2, lower right). In contrast, neither RuCl 2 (MeCN) 4 , KTZ nor CTZ were as effective against C8161 melanoma as RuCl 2 (KTZ) 2 or RuCl 2 (CTZ) 2 (Fig. 2).…”

“…This was followed by 4 hr with alamar blue (resazurin) dye prior to multiwell fluorometric quantitation. 23 This revealed, in 3 different experiments, that a 25 M concentration was required to show reproducible inhibition in parental C8161 melanoma cells treated with either RuCl 2 (KTZ) 2 or RuCl 2 (CTZ) 2 . No comparable effect was evident in C8161 cells treated with the same concentrations of RuCl 2 (MeCN) 4 , KTZ, CTZ or DMSO control culture (Fig.…”

“…1 KTZ is a cytochrome P-450 inhibitor that inhibits adrenal steroidogenesis 2 and shows antiglucocorticoid activity. 3 KTZ synergizes with docetaxel in the treatment of hormone-dependent cancer.…”

Hormonal impact of the 17α-hydroxylase/C17,20-lyase inhibitor abiraterone acetate (CB7630) in patients with prostate cancer

“…Ketoconazole is relatively unselective, inhibiting both cholesterol side chain cleavage and 11b-hydroxylation (Loose et al, 1983). A direct antitumour effect of ketoconazole in vitro has also been demonstrated (Eichenberger and Trachtenberg, 1988).…”