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Minoxidil Acts as an Antiandrogen: A Study of 5α-reductase Type 2 Gene Expression in a Human Keratinocyte Cell Line

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Although more than three decades have passed since the first use of minoxidil in androgenetic alopecia (AGA), its mechanisms of action have still not been comprehensively understood. 5α-reductase (5α-R) has an active role as the predominant enzyme in both AGA and female pattern hair loss (FPHL), which are also the main therapeutic indications of topical minoxidil. But there is insufficient literature data regarding the interaction of minoxidil and the enzyme 5α-R. Herein, we studied the in vitro expression levels of 5α-R type 2 (5α-R2) in a minoxidiltreated human keratinocyte cell line (HaCaT) in order to elucidate the relation of these two parameters. Cell proliferation assay was performed by a XTT reagent (a yellow tetrazolium salt). After determination of non-cytotoxic concentration, HaCaT cells were treated with minoxidil. Ribonucleic acid (RNA) isolations were carried out from both non-treated and treated cell groups using a TRI reagent (an RNA, DNA, and protein isolation reagent). Gene expressions of 5α-R2 as study material and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as the control were determined by real time-quantitative polymerase chain reaction (RT-qPCR) analysis. Results were represented as 5α-R2/GAPDH fold change. Minoxidil treatment resulted in a 0.22 fold change for 5α-R2 (p < 0.0001). This antiandrogenic effect of minoxidil, shown by significant downregulation of 5α-R2 gene expression in HaCaT cells, may be one of its mechanisms of action in alopecia. © 2017, Croatian Dermatovenerological Society. All rights reserved.
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ACTA DERMATOVENEROLOGICA CROATICA
Minoxidil Acts as an Antiandrogen: A Study of
5α-reductase Type 2 Gene Expression in a Human
Keratinocyte Cell Line
Acta Dermatovenerol Croat 2017;25(4):271-275 ORIGINAL SCIENTIFIC ARTICLE
271
Corresponding author:
Erkin Pekmezci, MD
Gozde Hastanesi
Inonu Cd. No 145
44100 Malatya
Turkey
erkinpekmezci@gmail.com
Received: April 12, 2016
Accepted: November 4, 2017
ABSTRACT Although more than three decades have passed since the rst use
of minoxidil in androgenetic alopecia (AGA), its mechanisms of action have
still not been comprehensively understood. 5α-reductase (5α-R) has an ac-
tive role as the predominant enzyme in both AGA and female pattern hair loss
(FPHL), which are also the main therapeutic indications of topical minoxidil.
But there is insucient literature data regarding the interaction of minoxidil
and the enzyme 5α-R. Herein, we studied the in vitro expression levels of 5α-R
type 2 (5α-R2) in a minoxidil-treated human keratinocyte cell line (HaCaT) in
order to elucidate the relation of these two parameters. Cell proliferation assay
was performed by a XTT reagent (a yellow tetrazolium salt). After determina-
tion of non-cytotoxic concentration, HaCaT cells were treated with minoxidil.
Ribonucleic acid (RNA) isolations were carried out from both non-treated and
treated cell groups using a TRI reagent (an RNA, DNA, and protein isolation
reagent). Gene expressions of 5α-R2 as study material and glyceraldehyde-3-
phosphate dehydrogenase (GAPDH) as the control were determined by real
time-quantitative polymerase chain reaction (RT-qPCR) analysis. Results were
represented as 5α-R2 / GAPDH fold change. Minoxidil treatment resulted in a
0.22 fold change for 5α-R2 (p < 0.0001). This antiandrogenic eect of minoxidil,
shown by signicant downregulation of 5α-R2 gene expression in HaCaT cells,
may be one of its mechanisms of action in alopecia.
KEY WORDS: minoxidil, 5α-R, mechanism of action
Erkin Pekmezci1, Murat Türkoğlu2
1Gozde Group Hospitals, Dermatology Department, Malatya, Turkey; 2Biota
Laboratories, Istanbul, Turkey
INTRODUCTION
Oral minoxidil has been used to treat hypertension
since 1960s. Hypertrichosis as a consequence of min-
oxidil treatment was observed shortly thereafter, and
these observations led to the development of topical
minoxidil as a treatment for hair loss. Although it is
being used for the treatment of male androgenetic
alopecia (AGA) and female pattern hair loss (FPHL) for
approximately three decades, but our understanding
of its mechanisms of action on the hair follicle is still
very limited (1,2). Due to the blood pressure lower-
ing eect of oral minoxidil through relaxing the vas-
cular smooth muscle by the action of its sulphated
metabolite, as an opener of sarcolemmal adenosine
triphosphate sensitive potassium channels (KATP ), it is
postulated that its stimulatory eect on hair growth
is also related with the opening of potassium chan-
nels (1,3,4). Cutaneous blood ow was observed to
increase 10-15 minutes after the application of topi-
cal minoxidil (5). A number of in vitro eects of min-
oxidil have been described in monocultures of vari-
ous skin and hair follicle cell types including stimu-
lation of cell proliferation, slowing the senescence of
272 ACTA DERMATOVENEROLOGICA CROATICA
keratinocytes, inhibition of collagen synthesis, stimu-
lation of vascular endothelial growth factor (VEGF),
and prostaglandin synthesis (1,6-8). Some or all of
these eects may be relevant to hair growth, but the
application of results obtained in cell culture studies
to the complex biology of the hair follicle is uncertain
(1).
Although polygenic heredity is assumed to be
the primary cause, androgens play an important
role in both AGA and FPHL, seemingly independent
of genetic predisposition (9). Androgen-dependent
processes are predominantly due to the binding of
dihydrotestoerone (DHT) to the androgen receptor
(AR). The predisposed scalp exhibits high levels of
DHT and increased expression of AR. DHT-related cell
functions depend on the availability of weak andro-
gens, i.e. their conversion to more potent androgens
via the action of 5α-reductase (5α-R), low enzymatic
activity of androgen inactivating enzymes, and func-
tionally active ARs present in high numbers (10).
Although 5α-R has an active role as the predomi-
nant enzyme in both AGA and FPHL, which are also
the main therapeutic indications of topical minoxidil,
there is insucient literature data about the interac-
tion of the two. Herein, we studied in vitro expression
levels of 5α-R type 2 (5α-R2) in a minoxidil-treated hu-
man keratinocyte cell line (HaCaT) in order to eluci-
date the relation of these two parameters.
PATIENTS AND METHODS
Cell Culture
HaCaT was cultured in Dulbecco’s Modied Eagle’s
medium with high glucose, supplemented with 10%
heat-inactivated fetal bovine serum and 100 U/mL
gentamicin. The cells were maintained at 37°C in a
humidied atmosphere at 5% CO2 in a Newbruns-
wick incubator. All supplements and media were pur-
chased from Sigma Aldrich.
Preparation of Minoxidil Solution
We dissolved 522.5 mg minoxidil in 25 mL distilled
water – 25 mL ethanol mixture to get a 5 mM minoxi-
dil solution. This solution was used as a 100% sample,
and other concentrations (10.0%, 5.0%, 3.0%, 1.0%,
and 0.2%) of the solution were prepared by dilution
with distilled water.
Cell Proliferation Assay
HaCaT cells were seeded into 96-well plates (1×104
cells/well) and were subjected to dierent concentra-
tions of minoxidil solution to assess the cell prolifera-
tion. An XTT reagent (a yellow tetrazolium salt), was
added to the plates after a 72-hour incubation period
according to the manufacturer’s (Roche) instructions.
Cells were then incubated at 37oC for 4 hours in or-
der to reduce the XTT reagent to an orange formazan
compound. The optical density of the soluble forma-
zan compound was measured at 495 nm by a micro-
plate reader (Bio-Rad).
Ribonucleic Acid (RNA) Isolation and Re-
verse Transcription
Total RNA was extracted from cells treated with
minoxidil solution and from untreated cells using a TRI
reagent (an RNA, DNA, and protein isolation reagent),
according to the manufacturer’s (Sigma Aldrich) in-
structions. The concentration and purity of isolated
RNA samples were determined by measuring opti-
cal densities at 260 nm and 280 nm using BioSpec-
nano. The Transcriptor First Strand cDNA Synthesis Kit
(Roche) was used for reverse transcription. Comple-
mentary deoxyribonucleic acid (cDNA) synthesis was
performed with 500 ng total RNA; 2 µM of each nal
concentration of gene-specic primers of 5α-R2 as
study material and glyceraldehyde-3-phosphate de-
hydrogenase (GAPDH) as the control (Integrated DNA
Technologies); 10 U of Transcriptor Reverse Transcrip-
tase; 20 U of Protector RNase Inhibitor; 1 mM each
of dNTP mix and Transcriptor Reverse Transcription
Buer (5X) according to the manufacturers (Roche)
instructions. Primer sequences (5 ‘ – 3’) are presented
in Table 1.
Real-Time Quantitative Polymerase Chain
Reaction (RT-qPCR)
RT-qPCR was carried out in Light Cycler 96 (Roche).
Amplication of products was detected via interca-
lation of the SYBR green uorescent dye (Fast Start
DNA Green Master Kit, Roche). Briey, total volume of
reaction mix was 20 µL; containing 10 µL SYBR Green
Master Mix (×2), 0.5 µM of reverse and forward prim-
ers, 2.5 ng cDNA, and the appropriate amount of nu-
clease free water. All samples were run as triplicates in
Table 1. Primers (5’ – 3’) of the genes studied
Primers Forward primer Reverse primer
5α-R2 CGCTCTACCAGTACGCCAG AATTAAGCACCGATGCCCGT
GAPDH ATGGGTGTGAACCATGAGAA GTGCTAAGCAGTTGGTGGTG
5α-R2: 5α-reductase; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase used as control
Pekmezci and Turkoglu Acta Dermatovenerol Croat
Minoxidil acts as an antiandrogen 2017;25(4):271-275
ACTA DERMATOVENEROLOGICA CROATICA 273
each run, including a non-template control and four
standards (1:1, 1:10, 1:100, 1:1000). The RT-qPCR pa-
rameters were determined separately for each target
according to melting and annealing temperatures of
primers. Each parameter included a pre-incubation
step for 10 min at 95°C and followed by 45 cycles of
three amplication and melting steps. Melting curve
analysis was performed to verify specicity. For quan-
titation of RT-qPCR results, the Ct method was
used (2-Ct).
Statistical Analysis
All data are representative of three repetitions
(n=3) and expressed as mean ± standard error of the
means (SEM). Statistical evaluation was performed by
an unpaired t-test, using Graph Pad Prism 5 Software
(USA); results with a P value less than 0.05 were ac-
cepted as signicant.
RESULTS
Cytotoxicity Analysis (Cell Proliferation
Assay)
Based on cell proliferation ratios of treated cells
with respect to the control cells, cytotoxicity levels
of the minoxidil solution were determined. Higher
concentrations were found to be cytotoxic for HaCaT
cells. For the subsequent analysis, the possible high-
est concentration was determined as 1%, and HaCaT
cells were incubated with 1% concentration of min-
oxidil solution before total RNA isolation (Figure 1).
Gene Expression Analysis (RT-qPCR)
Results were represented as Target / GAPDH Fold
Change. Results of gene expression analysis via RT-
qPCR showed that minoxidil solution caused sta-
tistically signicant downregulation of 5α-R2 gene
expressions, compared with untreated control cells.
Minoxidil treatment resulted in 0.22 fold changes
(P<0.0001) for 5α-R2 (Figure 2).
DISCUSSION
The pilosebaceous unit is the site of numerous cell
interactions, and although the histology and struc-
ture of the follicle is well-known today, the molecular
events controlling the hair cycle remain obscure. The
development of in vitro and in vivo models, however,
have provided some insights on the role of growth
factors such as insulin like growth factor-1 (IGF-1),
transforming growth factor-α (TGF-α), and VEGF, as
well as androgens such as DHT and cytokines such as
interleukin-1 (IL-1) (7,11).
Although the basic etiopathogenesis is not thor-
oughly understood, besides the aspect of genetic
predisposition, the role of androgens in AGA is well
established (2,10,12,13). The concentrations of DHT,
5α-R, and ARs are increased in a balding scalp. The
higher the concentration of androgens and ARs, the
greater the eect on the expression of genes which
control follicular cycling (14). The nding indicate
Xq12, the X chromosome region which encodes the
AR, may represent a common genetic factor under-
lying both AGA and FPHL (15-18). Although the X
chromosomal location of the AR gene indicates that
the maternal line is the major inheritance of AGA in
men, family studies showing resemblance of hair loss
between fathers and sons suggest that some autoso-
mal genes might also contribute to the phenotype
(2,16,19). In a study on the identication of new sus-
ceptibility genes, strong evidence was found for an
alopecia susceptibility locus on chromosome 3q26
(19). In another study, signicant association was
found with AGA on chromosome 20p11, suggesting
that the 20p11 locus has a role in a yet-to-be-identi-
ed androgen independent pathway (20). It was later
reported that although this locus is responsible from
AGA, it has no association with FPHL (17,18).
On the other hand, contradicting results have
been reported on the interaction of minoxidil and
Figure 1. Cytotoxicity analysis result of minoxidil solution.
The dashed bar represents the concentration chosen for
incubation. Figure 2. Gene expression level of 5α-reductase type 2 af-
ter minoxidil treatment, compared with untreated control
cells
Pekmezci and Turkoglu Acta Dermatovenerol Croat
Minoxidil acts as an antiandrogen 2017;25(4):271-275
274 ACTA DERMATOVENEROLOGICA CROATICA
its androgen-dependent mechanisms of action: In
a study on the eect of minoxidil on testosterone
metabolism through cultured dermal papilla cells of
balding or non-balding scalp and dermal broblasts,
5α-R activity was slightly increased in dermal papilla
cells of a balding scalp, while there was no increase in
other groups of cells. In the same study, the increase
of 17β-hydroxysteroid dehydrogenase activity was
much higher with minoxidil in dermal papilla cells of
a balding scalp (21). In another study, minoxidil was
found to be a weak inhibitor of human hair follicle 5α-
R (22). Although one study found no antiandrogenic
potential of minoxidil on androgen-dependent cuta-
neous structures in an animal model (23), it was con-
tradicted by another group because female animals
were used in the trial, and testosterone which can
be converted to estradiol in hair follicles, rather than
DHT, was chosen. The later study analyzing the anti-
androgenic potential of minoxidil claimed that min-
oxidil suppresses AR-related functions by decreasing
AR transcriptional activity and reducing the expres-
sion of AR targets at the protein level (24).
The signicant suppression of 5α-R2 in HaCaT cells
by minoxidil in our study, although not at the recep-
tor level, supports the thesis of minoxidil’s antiandro-
genic mechanism of action. This thesis, together with
the literature data on the X chromosome-linked AR
pathway and the autosomal chromosome-linked an-
drogen independent pathway in the etiopathogen-
esis of alopecia, it may provide a better explanation
of why some patients do not respond well to minoxi-
dil therapy. Although further studies are needed, this
thesis may also allow the exclusion of poor respond-
ers to minoxidil therapy and avoid waste of time in
clinical practice by identifying probable androgen-in-
dependent alopecia patients to some extent.
CONCLUSION
The antiandrogenic eect of minoxidil, demon-
strated by signicant downregulation of 5α-R2 gene
expression in HaCaT cells in our study, may be one
of its mechanisms of action in AGA and FPHL, which
is not being emphasized well in the dermatology
literature.
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Pekmezci and Turkoglu Acta Dermatovenerol Croat
Minoxidil acts as an antiandrogen 2017;25(4):271-275
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... It has shown an effect of reducing the expression of the 5-alpha-reductase type 2 gene in keratocyte cells. However, these results require further study [50]. A meta-analysis by Adil et al. indicates the efficacy of minoxidil relative to the study group versus placebo. ...
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... Indeed, several studies demonstrated that dutasteride and finasteride diminished the mRNA levels of SRD5A genes [47][48][49]. In this study, minoxidil, a potassium channel opener, significantly suppressed the SRD5A expression in DU-145, which was consistent with the previous study [50]. In addition, minoxidil was found to be a weak 5α-reductase inhibitor [51]. ...
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Leaves of guava (Psidium guajava L.) have been used in Thai folk medicine without any supporting evidence as a traditional herbal remedy for hair loss. Androgenetic alopecia (AGA) is chronic hair loss caused by effects of androgens in those with a genetic predisposition, resulting in hair follicle miniaturization. Our objectives were to provide the mechanistic assessment of guava leaf extract on gene expressions related to the androgen pathway in well-known in vitro models, hair follicle dermal papilla cells (HFDPC), and human prostate cancer cells (DU-145), and to determine its bioactive constituents and antioxidant activities. LC-MS analysis demonstrated that the main components of the ethanolic extract of guava leaves are phenolic substances, specifically catechin, gallic acid, and quercetin, which contribute to its scavenging and metal chelating abilities. The guava leaf extract substantially downregulated SRD5A1, SRD5A2, and SRD5A3 genes in the DU-145 model, suggesting that the extract could minimize hair loss by inhibiting the synthesis of a potent androgen (dihydrotestosterone). SRD5A suppression by gallic acid and quercetin was verified. Our study reveals new perspectives on guava leaf extract’s anti-androgen properties. This extract could be developed as alternative products or therapeutic adjuvants for the treatment of AGA and other androgen-related disorders.
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We carried out a genome-wide association study in 296 individuals with male-pattern baldness (androgenetic alopecia) and 347 controls. We then investigated the 30 best SNPs in an independent replication sample and found highly significant association for five SNPs on chromosome 20p11 (rs2180439 combined P = 2.7 x 10(-15)). No interaction was detected with the X-chromosomal androgen receptor locus, suggesting that the 20p11 locus has a role in a yet-to-be-identified androgen-independent pathway.
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The aetiology of female pattern hair loss (FPHL) is largely unknown. However, it is hypothesized that FPHL and male pattern baldness (AGA) share common susceptibility alleles. The two major susceptibility loci for AGA are the androgen receptor (AR)/ectodysplasin A2 receptor (EDA2R) locus on the X-chromosome, and a locus on chromosome 20p11, for which no candidate gene has yet been identified. To examine the role of the AR/EDA2R and 20p11 loci in the development of FPHL using 145 U.K. and 85 German patients with FPHL, 179 U.K. supercontrols and 150 German blood donors. Patients and controls were genotyped for 25 single nucleotide polymorphisms (SNPs) at the AR/EDA2R locus and five SNPs at the 20p11 locus. Analysis of the AR/EDA2R locus revealed no significant association in the German sample. However, a nominally significant association for a single SNP (rs1397631) was found in the U.K. sample. Subgroup analysis of the U.K. patients revealed significant association for seven markers in patients with an early onset (P = 0·047 after adjustment for the testing of multiple SNPs by Monte Carlo simulation). No significant association was obtained for the five 20p11 variants, either in the overall samples or in the analysis of subgroups. The observed association suggests that the AR/EDA2R locus confers susceptibility to early-onset FHPL. Our results do not implicate the 20p11 locus in the aetiology of FPHL.
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The opening of intracellular potassium channels has been suggested as a mechanism regulating hair growth. Enhancing the flux of potassium ions is a mechanism shared by several structurally diverse antihypertensive agents including minoxidil sulfate (the active metabolite of minoxidil), pinacidil, P-1075 (a potent pinacidil analog), RP-49,356, diazoxide, cromakalim, and nicorandil. Of these drugs, minoxidil, pinacidil, and diazoxide have been reported to elicit hypertrichosis in humans. This potassium channel hypothesis was examined by testing these drugs for effects on hair growth both in vitro and in vivo. For the in vitro studies, mouse vibrissae follicles were cultured for 3 d with drug and the effects on hair growth were measured by metabolic labeling. All drugs, except diazoxide, enhanced cysteine incorporation into the hair shafts of the cultured vibrissae. Diazoxide was poorly soluble and thus was tested only at low doses. Minoxidil, P-1075, cromakalim, and RP-49,356 were also evaluated in vivo by measuring hair growth effects in balding stumptail macaque monkeys. The drugs were administered topically to defined sites on balding scalps once per day for 4-5 months and the amount of hair grown was determined by monthly measurements of shaved hair weight. Three of the drugs produced significant increases in hair weight whereas, the RP-49,356 had no effect. These studies provide correlative evidence that the opening of potassium channels is an important regulatory mechanism for hair growth. This provides the impetus for further studies on this potentially important mechanism affecting hair biology.
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The gene for the androgen receptor, mutations at which cause the X-linked androgen insensitivity syndrome, has been localized to the q11----q12 region of the human X chromosome by analysis, using a cloned cDNA for the androgen receptor, of somatic cell hybrid panels segregating portions of the X chromosome. A moderate-frequency HindIII RFLP has been found which should be useful in genetic linkage analysis of the various inherited forms of androgen insensitivity.