Ketoconazole, an underestimated anti-AGA compound

1a)http://www.ehrs.org/conferenceabstracts/2001tokyo/researchabstracts/023-ohuchi.htm

A Significant Role of Aromatase Cytochrome P450 on Hair Re-growth and Pigmentation.

A. Ohuchi1, K. Ohguchi1, N. Tsuji1, S. Moriwaki1, Y. Takema1, S. Honda2, N. Harada2 Biological Science Laboratories, Kao Corp. Tochigi, Japan1 and Dept. of Bio-chemistry, Fujita Health University School of Medicine, Aichi, Japan2

It is well known that sex hormones such as androgen and estrogen influence the hair growth in several animals. Aromatase is a member of cytochrome P-450 gene superfamily and catalyzes the conversion of androgen to estrogen, a rate-limiting step of estrogen biosynthesis. Previous reports have suggested that aromatase exists in various extra-gonadal tissue as well as in gonadal tissue, and that the expression is regulated by alternative use of multiple exons 1 and promoters. In this study, in order to examine the involvement of aromatase in hair growth, we investigated the localization of aromatase at hair follicles in human and murine, and evaluated the role of this enzyme on hair re-growth using aromatase knockout mice. Immunohistological technique for anagen hair follicles revealed that aromatase positive cells localized in outer root sheath tissue while were not observed in hair matrix, follicular papilla and epidermis. RT-PCR analysis of aromatase mRNA in plucked human hair suggested that aromatase transcripts were mainly composed of placenta-specific exon 1. Next, we examined the effect of aromatase inhibitor on the hair regrowth of C3H mouse. The topical application of 1% aminoglutethimide significantly promotes the hair re-growth. Moreover, hair re-growth was significantly accelerated in aromatase knockout female mice in compared with wild type. Intriguingly, the color of re-grown hair of those mice was blacker than wild type and heterozygotes. Alteration of hair color was caused by the increase of melanin contents (total melanin and eu-melanin). These results suggest that aromatase plays an important role on hair growth and melanin synthesis in hair follicles through the local synthesis of estrogen.

1b) J Clin Invest. 1983 May; 71(5): 1495–1499

Ketoconazole blocks adrenal steroidogenesis by inhibiting cytochrome P450-dependent enzymes. D S Loose, P B Kan, M A Hirst, R A Marcus, and D Feldman This article has been cited by other articles in PMC. AbstractKetoconazole 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, dibutyrl 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 enzym

Re:

Well, it promotes apoptosis as well :

http://www.nature.com/cdd/journal/v6/n10/abs/4400582a.html

Nitric oxide (NO): an effector of apoptosis Bernhard Brüne, Andreas von Knethen and Katrin B Sandau University of Erlangen-Nürnberg, Faculty of Medicine, Department of Medicine IV-Experimental Division, 91054 Erlangen, Germany Correspondence to: Bernhard Brüne, University of Erlangen-Nürnberg, Faculty of Medicine, Loschgestrasse 8, 91054 Erlangen, Germany. tel: +49-9131-85 36311; fax: +49-9131-85 39202; e-mail: mfm423@rzmail.uni-erlangen.de

Edited by J Stamler Abstract It is appreciated that the production of nitric oxide (NO) from L-arginine metabolism is an essential determinate of the innate immune system, important for nonspecific host defense, as well as tumor and pathogen killing. Cytotoxicity as a result of a substantial NO-formation is established to initiate apoptosis, characterized by upregulation of the tumor suppressor p53, changes in the expression of pro- and anti-apoptotic Bcl-2 family members, cytochrome c relocation, activation of caspases, chromatin condensation, and DNA fragmentation. Proof for the involvement of NO was demonstrated by blocking adverse effects by NO-synthase inhibition. However, NO-toxicity is not a constant value and NO may achieve cell protection as well. In part this is understood by transcription and translation of protective proteins, such as cyclooxygenase-2. Alternatively, protection may result as a consequence of a diffusion controlled NO/O2- (superoxide) interaction that redirects the apoptotic initiating activity of NO towards protection. NO is endowed with the unique ability to initiate and to block apoptosis, depending on multiple variables that exist to be elucidated. The crosstalk between cell destructive and protective signaling pathways under the modulatory influence of NO will determine the impact of NO in apoptotic cell death and survival.

Inhibition of cytochromes P450 by nitric oxide and a nitric oxide-releasing agent.Wink DA, Osawa Y, Darbyshire JF, Jones CR, Eshenaur SC, Nims RW. Chemistry Section, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702.

The effect of nitric oxide (NO) on cytochrome P450-mediated benzyloxyresorufin and ethoxyresorufin O-dealkylase activity of rat hepatic postmitochondrial (S-9) or microsomal subfractions, or purified rat liver CYP2B1, was examined. Two distinct inhibitory phases were observed regardless of whether the NO was added prior to initiation of the reactions with NADPH or during the course of substrate turnover. The first was a reversible inhibition characterized by complete cessation of catalytic activity, the duration of which was NO concentration-dependent with an IC50 in the range of 8-60 microM. This phase was followed by a second, irreversible, inhibitory phase characterized by a varying extent of recovery of activity, with inhibition ranging from < 1 to approximately 100%. The extent of this diminution in substrate conversion rate was also NO concentration-dependent, with an IC50 in the range of 13-72 microM, and could be partially abrogated by the inclusion of bovine serum albumin in the reaction mixture. Lower IC50 values for both inhibitory phases were obtained in the case of benzyloxyresorufin O-dealkylase activity than in the case of ethoxyresorufin O-dealkylase activity, suggesting a differential susceptibility to inhibition by NO for the two O-dealkylase activities. A nitric oxide-releasing compound ([Et2NN(O)NO]Na,DEA/NO) caused qualitatively similar inhibitory effects on benzyloxyresorufin O-dealkylase activity when added prior to the initiation of the reactions with NADPH, or during the course of substrate turnover. Based upon these results, it is possible that NO may play a role in the regulation of P450 activity in vivo.

So that would explain partially how growth stimulators like minoxidil work - they inhibit P450 as well.

I've rephrased the NO thing in my initial post.

""applying topically to said area of skin a dermatologically acceptable composition comprising an inhibitor of cytochrome P450 reductase in an amount effective to reduce hair growth. ""

Therefore in the adrenal gland and gonads, Ketoconazole inhibits synthesis of adrenal corticosteroids. However, much higher concentrations are necessary to affect Cytochrome P450-dependent enzymes in mammals compared with those in fungi. Extensive clinical trials to prove the efficacy of Ketoconazole have not been carried out. In fact, there are only anecdotal reports of Ketoconazole use in hirsutism, but none in women with pattern hair loss. In one particular study, 27 subjects used 2% Ketoconazole shampoo exclusively 2–4 times a week for 21 weeks. The remaining 12 in the control group used an un-medicated shampoo. The group using the Ketoconazole shampoo showed results of an increase in hair density, size and proportion of anagen hair follicles post treatment.

Although the effects of Ketoconazole on 5 alpha - reductase had been documented earlier, the authors of the study asserted that androgenetic alopecia has a multi-factorial pathogenesis with an inflammatory reaction caused by a Malassezia fungal infection, and claimed that the Ketoconazole shampoo was probably effective due to its beneficial effect on fungal scalp infections in genetically predisposed individuals. It was concluded that Ketoconazole was therapeutic by reducing inflammation through its anti-inflammatory properties and by clearing the adjacent fungal infection.

Exploration of the inflammatory aspect of androgenetic alopecia was largely based on the results of a biopsy study by Jaworsky et al., showing that androgenetic alopecia patients had signs of T-cell infiltration of follicular stem cell epithelium. However, the veracity of the conclusions drawn from the Jaworsky study is uncertain as the study included 4 subjects and only 3 of them were men.

However, another school of thought believes that the clinical efficacy of Ketoconazole shampoo in the treatment of androgenetic alopecia is primarily a function of dihydrotestosterone (DHT) pathway disruption rather than an anti-inflammatory effect. The development of androgenetic alopecia in genetically susceptible individuals has been linked to an overproduction of 5 -reductase and an over expression of androgen receptor, and in rat studies, Ketoconazole has been seen to cause 5 -reductase inhibition. Additionally, in humans Ketoconazole has also been shown to inhibit the binding of 5 -reductase to sex hormone globulins. All these clinical studies therefore suggest that Ketoconazole may inhibit the production of DHT just like Finasteride. In fact, the effect of Ketoconazole may be two fold, as it has been shown additionally to bind to human androgen receptor, having a distinct advantage over Finasteride. Therefore these authors believe that Ketoconazole inhibits the pathway that leads to the characteristic miniaturization of hair follicles in androgenetic alopecia by inhibiting DHT and/or inhibiting the binding of DHT to AR.

L'oreal has a patent on 5-lipoxygenases for hair growth. A note about patents: when the "big" guys file them...believe it.They have spent the money on R&D.

http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=3006695&ordinalpos=60&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=2128178&ordinalpos=48&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

It has now been found that mammalian (including human) hair growth can be inhibited by applying to the skin a composition including an inhibitor of 5-lipoxygenase in an amount effective to reduce hair growth in the applied area.

Examples of 5-lipoxygenase inhibitors that have been found effective in reducing hair growth include quercetin (3,3', 4',5,7-pentahydroxy flavone), dl-a-tocopherol, apigenin (4',5,7-trihydroxy flavone), propyl gallate, NDGA (nondihydrouaiaretic acid), and caffeic acid (3,4-dihydroxycinnamic acid). All of these compounds are known in the art and are commercially available. Other inhibitors of 5-lipoxygenase are known in the art; see, for example, Laughton et al., 42 Biochemical Pharmacology 1673 (1991).