Cutaneous androgen metabolism: basic research and clinical perspectives

Inactivation by UDP-glucuronosyltransferase enzymes: the end of androgen signaling

Conjugation by UDP-Glucuronosyltransferase (UGT) is the major pathway of androgen metabolism and elimination in the human. High concentrations of glucuronide conjugates of androsterone (ADT) and androstane-3alpha,17beta-diol (3alpha-diol) are present in circulation and several studies over the last 30 years have concluded that the serum levels of these metabolites might reflect the androgen metabolism in several tissues, including the liver and androgen target tissues. Three UGT2B enzymes are responsible for the conjugation of DHT and its metabolites ADT and 3alpha-diol: UGT2B7, B15 and B17. UGT2B7 is expressed in the liver and skin whereas UGT2B15 and B17 were found in the liver, prostate and skin. Very specific antibodies against each UGT2B enzyme have been obtained and used for immunohistochemical studies in the human prostate. It was shown that UGT2B17 is expressed in basal cells whereas UGT2B15 is only localized in luminal cells, where it inactivates DHT. By using LNCaP cells, we have also demonstrated that the expression and activity of UGT2B15 and B17 are modulated by several endogenous prostate factors including androgen. Finally, to study the physiological role of UGT2B enzymes, transgenic mice bearing the human UGT2B15 gene were recently obtained. A decrease in reproductive tissue weight from transgenic animals compared to those from control animals was observed. In conclusion, the conjugation by UGT2B7, B15 and B17, which represents a non-reversible step in androgen metabolism, is an important means by which androgens are regulated locally. It is also postulated that UGT enzymes protect the tissue from deleteriously high concentrations of active androgen.

An analysis of the androgens of musth in the Asian bull elephant (Elephas maximus)

During musth in bull elephants, the androgens testosterone (T), dihydrotestosterone (DHT), and androstenedione all increase significantly. Given the unusual endocrine physiology that has been discovered in female elephants, it is also possible that bull elephants produce some unusual androgens. A cell-based androgen receptor assay was used to explore this possibility using two different methods. The first method compared the level of T measured by radioimmunoassay (RIA) with the level of androgen receptor (AR) activity measured in the serum of eight bull elephants during musth and non-musth periods. A ratio was calculated for T/AR activity for non-musth and musth, to determine if there was a change in the ratio between these two states. The second method used HPLC to separate two pooled serum samples (one non-musth and one musth) into fractions using a protocol which separates known androgens into specific, previously identified fractions. Each fraction was then tested with the AR assay to determine the androgenicity of any compounds present. This was done to determine if there were any fractions which had androgenic activity but did not contain any previously identified androgens. Results from the first analysis indicated no change in the T/AR ratio between non-musth and musth states. Clearly whatever active androgens are present during musth, they increase proportionately with T. Findings from the second analysis suggested that the only bioactive androgen present in the serum of non-musth Asian bulls is a low level of T. During musth, the only bioactive androgens detected were T and DHT; of these, T was by far the predominant active androgen present. Taken together, these two analyses suggest that T is by far the predominant active androgen present during musth in Asian bull elephants, and that no previously unidentified bioactive androgen is present.

Preparation of 4-aryl-2-trifluoromethylbenzonitrile derivatives as androgen receptor antagonists for topical suppression of sebum production

A series of substituted 4-aryl-2-trifluoromethylbenzonitrile analogs were evaluated in the human androgen receptor binding and cellular functional assays. Analogs with sufficient in vitro binding and cellular potency (IC(50)<200 nM) were tested in the progesterone receptor binding assay for selectivity and in the Golden Syrian hamster ear model for in vivo efficacy. Within the series, compound 4 e was identified to be the most active analog in vivo (wax ester inhibition=86%).

Steroid metabolism and profile of steroidogenic gene expression in Episkin: high similarity with human epidermis

The skin is a well-recognized site of steroid formation and metabolism. Episkin is a cultured human epidermis. In this report, we investigate whether Episkin possesses a steroidogenic machinery able to metabolize adrenal steroid precursors into active steroids. Episkin was incubated with [14C]-dehydroepiandrosterone (DHEA) and 4-androstenedione (4-dione) and their metabolites were analyzed by liquid chromatography/mass spectrometry (LC/MS/MS). The results show that the major product of DHEA metabolism in Episkin is DHEA sulfate (DHEAS) (88% of the metabolites) while the other metabolites are 7alpha-OH-DHEA (8.2%), 4-dione (1.3%), 5-androstenediol (1.3%), dihydrotestosterone (DHT) (1.4%) and androsterone (ADT) (2.3%). When 4-dione is used as substrate, much higher levels of C19-steroids are produced with ADT representing 77% of the metabolites. These data indicate that 5alpha-reductase, 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and 3alpha-hydroxysteroid dehdyrogenase (3alpha-HSD) activities are present at moderate levels in Episkin, while 3beta-HSD activity is low and represents a rate-limiting step in the conversion of DHEA into C19-steroids. Using realtime PCR, we have measured the level of mRNAs encoding the steroidogenic enzymes in Episkin. A good agreement is found between the mRNAs expression in Episkin and the metabolic profile. High expression levels of steroid sulfotransferase SULT2B1B and type 3 3alpha-HSD (AKR1C2) correspond to the high levels of DHEA sulfate (DHEAS) and ADT formed from DHEA and 4-dione, respectively. 3beta-HSD is almost undetectable while the other enzymes such as type 1 5alpha-reductase, types 2, 4, 5, 7, 8, and 10 17beta-HSD and 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) (AKR1C1) are highly expressed. Except for UGT-glucuronosyl transferase, similar mRNA expression profiles between Episkin and human epidermis are observed.

Glucocorticoid and Sex Hormone Receptors: Clinical Implications and Therapeutic Relevance

In general, steroid hormones exert their effects through intracellular receptors, the glucocorticoid (GR), mineralocorticoid (MR), androgen (AR), estrogen (ER), and progesterone (PR) receptors. In this brief review, we will focus on glucocorticoid and sex hormone actions in the skin through their distinct receptors and discuss their clinical relevance.

Dehydroepiandrosterone 7alpha-hydroxylation in human tissues: possible interference with type 1 11beta-hydroxysteroid dehydrogenase-mediated processes

Dehydroepiandrosterone (DHEA) is 7alpha-hydroxylated by the cytochome P450 7B1 (CYP7B1) in the human brain and liver. This produces 7alpha-hydroxy-DHEA that is a substrate for 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) which exists in the same tissues and carries out the inter-conversion of 7alpha- and 7beta-hydroxy-DHEA through a 7-oxo-intermediary. Since the role of 11beta-HSD1 is to transform the inactive cortisone into active cortisol, its competitive inhibition by 7alpha-hydroxy-DHEA may support the paradigm of native anti-glucocorticoid arising from DHEA. Therefore, our objective was to use human tissues to assess the presences of both CYP7B1 and 11beta-HSD1. Human skin was selected then and used to test its ability to produce 7alpha-hydroxy-DHEA, and to test the interference of 7alpha- and 7beta-hydroxy-DHEA and 7-oxo-DHEA with the 11beta-HSD1-mediated oxidoreduction of cortisol and cortisone. Immuno-histochemical studies showed the presence of both CYP7B1 and 11beta-HSD1 in the liver, skin and tonsils. DHEA was readily 7alpha-hydroxylated when incubated using skin slices. A S9 fraction of dermal homogenates containing the 11beta-HSD1 carried out the oxidoreduction of cortisol and cortisone. Inhibition of the cortisol oxidation by 7alpha-hydroxy-DHEA and 7beta-hydroxy-DHEA was competitive with a Ki at 1.85+/-0.495 and 0.255+/-0.005 microM, respectively. Inhibition of cortisone reduction by 7-oxo-DHEA was of a mixed type with a Ki at 1.13+/-0.15 microM. These findings may support the previously proposed native anti-glucocorticoid paradigm and suggest that the 7alpha-hydroxy-DHEA production is a key for the fine tuning of glucocorticoid levels in tissues.

Serum levels of 3α-androstanediol glucuronide in young women with polycystic ovary syndrome, idiopathic hirsutism and in normal subjects

OBJECTIVE

The study objective was to assess the role of 3alpha-androstanediol glucuronide (3alpha-diolG) as the marker of peripheral androgen action in the young women with hirsutism diagnosed as polycystic ovary syndrome (PCOS), in patients with idiopathic hirsutism (IH) and in normal non-hirsute women.

STUDY DESIGN

Fifty-nine young women with mean age 21.90+/-3.52 years suffered from hirsutism were included in the study. Among these 59 hirsute women 31 women with mean age 21.60+/-3.56 years were diagnosed as PCOS and 28 women with mean age 22.20+/-3.59 years were classified as idiopathic hirsutism patients. Twenty-seven normal women, age-matched (mean age 22.60+/-2.90 years), without signs of hirsutism and with normal menstrual cycle served as control for this study. Serum was collected from women with hirsutism (due to PCOS or idiopathic hirsutism) and from non-hirsute women. Serum levels of 3alpha-androstanediol glucuronide (3alpha-diolG), main androgens such as: testosterone, free testosterone, dehydroepiandrosterone (DHEAS) and also others hormones such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and sex hormone-binding globuline (SHBG) were measured using radioimmunoassay (RIA) method in the study and control group. Hirutism was assessed using modified Ferriman-Gallwey method. Serum 3alpha-diolG levels in PCOS women were significantly higher than in controls.

RESULTS

There were no significant differences between serum 3alpha-diolG levels in PCOS group and IH group. Similarly, there were significant differences between serum 3alpha-diolG levels in IH group and control subjects.

CONCLUSION

We conclude that 3alpha-diolG is not useful as the marker for peripheral androgen metabolism and for differentiation between idiopathic hirsutism and PCO-related hirsutism.

A longitudinal study of LH, gonadal and adrenal steroids in four intact Asian bull elephants (Elephas maximus) and one castrate African bull (Loxodonta africana) during musth and non-musth periods

During their annual musth cycle, adult African and Asian bull elephants have increased gonadal androgens (testosterone [T], dihydrotestosterone [DHT], androstenedione [A4]). Because musth is a physiologically and psychologically stressful time, this study was conducted to investigate whether the adrenal glands (stimulated by stress) increase production of both glucocorticoids and androgens during musth. Weekly serum samples were taken for 11-15 months from four intact adult Asian bull elephants, and from a castrate African bull elephant who exhibits musth. Testosterone, androstenediol (A5), A4, luteinizing hormone (LH), cortisol, and dehydroepiandrosterone (DHEA) were measured in each sample. In three of the four intact bulls, all hormones measured increased during musth. Adrenal androgens were strongly correlated with LH and testicular androgens, though not to cortisol. None of the hormones measured in the castrate bull increased during his musth cycles. While the significance of adrenal activity in the elephant during musth has yet to be determined, this study provides evidence that the adrenal gland actively produces both glucocorticoids and androgens during musth in the Asian elephant.

Gender Differences of Enzymatic Activity and Distribution of 17β-Hydroxysteroid Dehydrogenase in Human Skin in vitro

The interconversion of estrone (E1) and 17beta-estradiol (E2) is catalyzed by 17beta-hydroxysteroid dehydrogenase (17beta-HSD) in peripheral steroidogenic organs such as the skin. To investigate gender differences of activity and skin distribution of 17beta-HSD in human skin, enzymatic activity was measured in skin homogenates and skin horizontally sliced by 10 microm thickness in vitro. Reductive 17beta-HSD (E2 formation from E1) in female skin has a lower substrate affinity than in male skin; Km (Michaelis-Menten constant) of female and male skin is 11.8 +/- 6.5 and 2.0 +/- 2.0 microM, respectively. Female skin had a tendency to activate estrogen; Vmax (maximum rate) for E2 formation, 5.8 +/- 4.0 pmol/min/mg protein, is 1.7 times larger than E1 formation, 3.5 +/- 1.5 pmol/min/mg protein, and, on the other hand, male skin tends to deactivate estrogen; Vmax for E1 and E2 is 10.5 +/- 6.1 and 4.2 +/- 3.7 pmol/min/mg protein, respectively. The concentration of metabolite had a peak value at 80-120 microm from the skin surface. Therefore, these in vitro results suggest that the enzymatic activities of 17beta-HSDs have a gender difference in estrogen formation/metabolism and are distributed around the basement layer of the epidermis irrespective of sex. 17Beta-HSDs distributed around the basement epidermis may be effectively supplied with circulating estrogen from the papillary plexus to maintain the estrogen level in skin. This distribution pattern having a peak surrounding 100 microm from the skin surface indicates the importance for defense from noxae (e.g. detoxication) and maintenance of the internal environment (e.g. biosynthesis of hormones). Future studies should increase sample size and confirm these results by stricter statistical analysis.

Serum levels of specific glucuronidated androgen metabolites predict BMD and prostate volume in elderly men

Androgens are important regulators of bone and prostate health in elderly men. The role of serum levels of glucuronidated androgen metabolites as predictors of BMD and prostate volume in men is unclear. We show that specific glucuronidated androgen metabolites predict BMD and prostate volume in elderly men.

INTRODUCTION

Androgens are important regulators of bone and prostate health in elderly men. Local synthesis and degradation of androgens are likely to be important parameters of biological action of androgens in androgen-responsive tissues. The aim of this study was to determine the role of serum levels of glucuronidated androgen metabolites as predictors of BMD and prostate volume in elderly men.

MATERIALS AND METHODS

A subsample of the population-based Swedish part of the MrOS study (n = 631, average age = 75.9 years) was investigated. Bone parameters were measured using DXA. Serum levels of total testosterone (T) and dihydrotestosterone (DHT) were measured by gas chromatography/mass spectroscopy (GC-MS); androstane-3alpha,17beta-diol-3glucuronide (3G) and androstane-3alpha,17beta-diol-17glucuronide (17G) were measured by liquid chromatography/mass spectroscopy. Prostate volume (n = 159) was measured by transrectal ultrasound.

RESULTS

The general pattern is that two of the glucuronidated androgen metabolites, namely 17G and 3G, are stronger positive predictors of BMD than the bioactive androgens (T and DHT). In addition, 17G is a clear positive predictor of prostate volume, explaining 4.5% of the variance in prostate volume, whereas the bioactive androgens do not display any association with prostate volume.

CONCLUSIONS

Serum levels of specific glucuronidated androgen metabolites predict BMD and prostate volume in elderly men. Future studies should determine if the glucuronidated androgen metabolites also reflect other biological correlates of androgenic activity, including prostate cancer, and if low levels might be a marker of general androgen deficiency in men.

Expression of sex-determining genes in human sebaceous glands and their possible role in the pathogenesis of acne

BACKGROUND

The human skin, especially the sebaceous gland, is a steroidogenic organ similar to the gonads and adrenal cortex, possessing all the enzymes required for steroid sex-hormone synthesis and metabolism. Factors regulating cutaneous steroidogenesis associated with disease status remain largely unknown.

OBJECTIVE

We hypothesized that transcription factors involved in sex formation and regulation of steroidogenesis in the classical steroidogenic organs are also expressed in the sebaceous glands. Their possible role in the pathogenesis of acne were investigated.

METHODS

We used reverse transcription polymerase chain reaction (RT-PCR), in situ hybridization and Western blotting to analyse the expression of SF-1, WT-1, SRY, SOX-9 and DAX-1 mRNAs and their proteins in cultured human sebocytes and the facial skin of acne patients.

RESULTS

The in situ hybridization study showed SOX-9 mRNA mainly localized in basal keratinocytes, the basal layer of the sebaceous glands and eccrine glands. Immortalized human sebaceous gland cells (SZ95) expressed mRNA for SOX-9, WT-1 and DAX-1 but not for SF-1 or SRY. The expression of DAX-1 protein was slightly inhibited by 10(-6) m oestradiol (E2) at 6 h but enhanced by 10(-6) m dihydrotestosterone (DHT) at 48 h. The facial expression of SOX-9 seemed to be higher in the acne-prone male patients, while DAX-1 was stronger in subjects without acne, although both were statistically insignificant.

CONCLUSION

Our findings confirm the expression of some sex-determining genes in human sebaceous glands. Further studies on a larger patient population including the normal controls are needed to elucidate the functional significance of these transcription factors in the pathogenesis of acne.

Dermatology of androgen-related disorders

Hyperandrogenism in women can be caused by various conditions, the most prevalent of which is polycystic ovary syndrome. Common dermatologic manifestations of hyperandrogenism include hirsutism, acne, acanthosis nigricans, and androgenic alopecia. Hirsute women often have increased activity of 5 alpha-reductase, the enzyme that converts the androgen testosterone to its active metabolite, in hair follicles. Likewise, androgens affect the formation of acne by increasing sebum production from sebaceous glands in the skin. The diagnosis of polycystic ovary syndrome includes a complete history, physical examination with emphasis on evidence of androgen excess, and appropriate laboratory investigation to exclude other causes of hyperandrogenism. Treatments for the dermatologic conditions of hyperandrogenism include lifestyle modification, oral contraceptives, antiandrogens, and insulin-sensitizing medications.

Metabolism and excretion of anabolic steroids in doping control--new steroids and new insights

The use of anabolic steroids in sports is prohibited by the World Anti-Doping Agency. Until the 1990s, anabolic steroids were solely manufactured by pharmaceutical companies, albeit sometimes on demand from national sports agencies as part of their doping program. Recently the list of prohibited anabolic steroids in sports has grown due to the addition of numerous steroids that have been introduced on the market by non-pharmaceutical companies. Moreover, several designer steroids, specifically developed to circumvent doping control, have also been detected. Because anabolic steroids are most often intensively subjected to phase I metabolism and seldom excreted unchanged, excretion studies need to be performed in order to detect their misuse. This review attempts to summarise the results of excretion studies of recent additions to the list of prohibited steroids in sports. Additionally an update and insight on new aspects for "older" steroids with respect to doping control is given.

The hair follicle as an estrogen target and source

For many decades, androgens have dominated endocrine research in hair growth control. Androgen metabolism and the androgen receptor currently are the key targets for systemic, pharmacological hair growth control in clinical medicine. However, it has long been known that estrogens also profoundly alter hair follicle growth and cycling by binding to locally expressed high-affinity estrogen receptors (ERs). Besides altering the transcription of genes with estrogen-responsive elements, 17beta-estradiol (E2) also modifies androgen metabolism within distinct subunits of the pilosebaceous unit (i.e., hair follicle and sebaceous gland). The latter displays prominent aromatase activity, the key enzyme for androgen conversion to E2, and is both an estrogen source and target. Here, we chart the recent renaissance of estrogen research in hair research; explain why the hair follicle offers an ideal, clinically relevant test system for studying the role of sex steroids, their receptors, and interactions in neuroectodermal-mesodermal interaction systems in general; and illustrate how it can be exploited to identify novel functions and signaling cross talks of ER-mediated signaling. Emphasizing the long-underestimated complexity and species-, gender-, and site-dependence of E2-induced biological effects on the hair follicle, we explore targets for pharmacological intervention in clinically relevant hair cycle manipulation, ranging from androgenetic alopecia and hirsutism via telogen effluvium to chemotherapy-induced alopecia. While defining major open questions, unsolved clinical challenges, and particularly promising research avenues in this area, we argue that the time has come to pay estrogen-mediated signaling the full attention it deserves in future endocrinological therapy of common hair growth disorders.

1Alpha,25-dihydroxyvitamin D3-mediated stimulation of steroid sulphatase activity in myeloid leukaemic cell lines requires VDRnuc-mediated activation of the RAS/RAF/ERK-MAP kinase signalling pathway

1Alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) stimulates the activity of steroid sulphatase (STS) in myeloid cells [Hughes et al., 2001, 2005]. This was attenuated by inhibitors of phospholipase D (PLD) (n-butanol, 2,3-diphosphoglyceric acid, C(2)-ceramide) and phosphatidate phosphohydrolase (PAP) (propranolol and chlorpromazine), but was unaffected by inhibitors of phospholipase C. The 1alpha,25(OH)(2)D(3)-induced STS activity was also attenuated by inhibitors of protein kinase Calpha and protein kinase Cdelta (Go 6976, HBDDE and rottlerin), but not by an inhibitor of protein kinase Cbeta (LY379196). Additionally, 1alpha,25(OH)(2)D(3)-induced STS activity was attenuated by inhibitors of RAS (manumycin A), RAF (GW5074), MEK (PD098059 and U1026) and JNK (SP600125), but not p38 (PD169316). 1alpha,25(OH)(2)D(3) produced a rapid and long lasting stimulation of the ERK-MAP kinase signalling cascade in HL60 myeloid leukaemic cells. This 'non-genomic' effect of 1alpha,25(OH)(2)D(3) blocked by pharmacological antagonists of nuclear vitamin D receptors (VDR(nuc)) and does not appear to require hetero-dimerisation with the retinoid-X receptor (RXR). Inhibitors of the Src tyrosine kinase (PP1), RAS (manumycin A), RAS-RAF interactions (sulindac sulphide and RAS inhibitory peptide), RAF (GW5074 or chloroquine), and protein kinase Calpha (HBDDE) abrogated the 1alpha,25(OH)(2)D(3)-stimulated increase in ERK-MAP kinase activity. Taken together, these results show that 1alpha,25(OH)(2)D(3)/VDR(nuc) activation of the RAS/RAF/ERK-MAP kinase signalling pathway plays an important role in augmenting STS activity in human myeloid leukaemic cell lines.

Retinoid-mediated stimulation of steroid sulfatase activity in myeloid leukemic cell lines requires RARalpha and RXR and involves the phosphoinositide 3-kinase and ERK-MAP kinase pathways

All-trans retinoic acid and 9-cis-retinoic acid stimulate the activity of steroid sulfatase in HL60 acute myeloid leukemia cells in a concentration- and time-dependent manner. Neither of these 'natural retinoids' augmented steroid sulfatase activity in a HL60 sub-line that expresses a dominant-negative retinoic acid receptor alpha (RARalpha). Experiments with synthetic RAR and RXR agonists and antagonists suggest that RARalpha/RXR heterodimers play a role in the retinoid-stimulated increase in steroid sulfatase activity. The retinoid-driven increase in steroid sulfatase activity was attenuated by inhibition of phospholipase D (PLD), but not by inhibitors of phospholipase C. Experiments with inhibitors of protein kinase C (PKC) show that PKCalpha and PKCdelta play an important role in modulating the retinoid-stimulation of steroid sulfatase activity in HL60 cells. Furthermore, we show that pharmacological inhibition of the RAF-1 and ERK MAP kinases blocked the retinoid-stimulated increase in steroid sulfatase activity in HL60 cells and, by contrast, inhibition of the p38-MAP kinase or JNK-MAP kinase had no effect. Pharmacological inhibitors of the phosphatidylinositol 3-kinase, Akt, and PDK-1 also abrogated the retinoid-stimulated increase in steroid sulfatase activity in HL60 cells. These results show that crosstalk between the retinoid-stimulated genomic and non-genomic pathways is necessary to increase steroid sulfatase activity in HL60 cells.

Acne vulgaris: a review of antibiotic therapy

Antibiotic therapy has been integral to the management of inflammatory acne vulgaris for many years. Systemic antibiotics work via antibacterial, anti-inflammatory and immunomodulatory modes of action, and have been found to be useful in managing moderate-to-severe acne. Commonly prescribed antibiotics include tetracyclines, erythromycin and trimethoprim, with or without sulfamethoxazole. In selecting the appropriate antibiotic for patients needing to receive topical or systemic antibiotic therapy, the clinician should take into account the severity of the acne, cost-effectiveness, the safety profile of the drug and the potential for development of resistance. The widespread and long-term use of antibiotics over the years has unfortunately led to the emergence of resistant bacteria. The global increase in the antibiotic resistance of Propionibacterium acnes may be a significant contributing factor in treatment failures. It is therefore essential that clinicians prescribing antibiotics for the treatment of acne adopt strategies to minimise further development of bacterial resistance. This includes addressing compliance issues, using combination therapies, avoiding prolonged antibiotic treatment, and avoiding concomitant topical and oral antibiotics with chemically dissimilar antibiotics.

Neuroendocrine system of the skin

Evidence is accumulating that the skin can serve as a peripheral neuroendocrine organ. The skin neuroendocrine activities are predominantly independent of regulation from the central level (which controls classical hormone secretion) but are rather regulated by local cutaneous factors. These endocrine factors would represent an exquisite regulatory layer addressed at restricting maximally the effect of noxious agents in the skin to preserve local and consequently global homeostasis.

Hirsutism and the variable response of the pilosebaceous unit to androgen

The pilosebaceous unit (PSU) response to androgen is variable. Certain population of PSU respond to androgen in a distinctive pattern that results in sexual hair development in some, sebaceous gland development in others. Furthermore, androgen excess is variably manifest in women as hirsutism, acne vulgaris, seborrhea, or pattern alopecia. Although sebaceous cells act as intracrine cells, activating pro-hormones to potent androgens that act within the sebocyte, hair follicle metabolism predominantly inactivates testosterone. Androgen action in the sexual hair follicle appears to be mediated by the dermal papilla and possibly, by inducing expression of a specific keratin, hHa7, in the hair medulla. The data do not clearly support a relationship between idiopathic hirsutism, the hirsutism that occurs in the absence of androgen excess, and variations in androgen mechanism of action. Androgens are prominent among the hormones that modulate the biological mechanism regulating the hair cycle. However, the basis for the variable pattern of PSU response to androgen is unclear, as is the basis for the variable development of hirsutism in response to androgen excess and the incomplete reversal of hirsutism by anti-androgen treatment. Improved treatment of hirsutism awaits improved understanding of the nature of the interaction between androgens and other determinants of hair follicle biology.

The cutaneous serotoninergic/melatoninergic system: securing a place under the sun

It was recently discovered that mammalian skin can produce serotonin and transform it into melatonin. Pathways for the biosynthesis and biodegradation of serotonin and melatonin have been characterized in human and rodent skin and in their major cellular populations. Moreover, receptors for serotonin and melatonin receptors are expressed in keratinocytes, melanocytes, and fibroblasts and these mediate phenotypic actions on cellular proliferation and differentiation. Melatonin exerts receptor-independent effects, including activation of pathways protective of oxidative stress and the modification of cellular metabolism. While serotonin is known to have several roles in skin-e.g., pro-edema, vasodilatory, proinflammatory, and pruritogenic-melatonin has been experimentally implicated in hair growth cycling, pigmentation physiology, and melanoma control. Thus, the widespread expression of a cutaneous seorotoninergic/melatoninergic syste,m(s) indicates considerable selectivity of action to facilitate intra-, auto-, or paracrine mechanisms that define and influence skin function in a highly compartmentalized manner. Notably, the cutaneous melatoninergic system is organized to respond to continuous stimulation in contrast to the pineal gland, which (being insulated from the external environment) responds to discontinuous activation by the circadian clock. Overall, the cutaneous serotoninergic/melatoninergic system could counteract or buffer external (environmental) or internal stresses to preserve the biological integrity of the organ and to maintain its homeostasis.-Slominski, A. J., Wortsman, J., Tobin, D. J. The cutaneous serotoninergic/melatoninergic system: securing a place under the sun.

Influence of physiological androgen levels on wound healing and immune status in men

Aging in men is associated with a progressive decline in the production of several hormones, including androgens. The extent to which an age-dependent decline in androgen levels lead to health problems or can affect quality of life remains under debate. Clinical results on replacement therapy do not yet provide a definitive clue on the benefit/risk balance. A sexual dimorphism of the immune system is well established, and the differences between female and male immune responses under normal, as well as pathological, conditions are generally attributed to the influence of estrogens, progestins, and androgens. The suppressive effects of male sex hormones on immune functions have been observed in a wide variety of disease processes and appear to be testosterone-mediated. Endogenous testosterone inhibits skin wound healing response in males and is associated with an enhanced inflammatory response. Although there are no known gender-related differences in permeability barrier function in adults, estrogens accelerates--whereas testosterone retards--barrier development in fetal skin, and male fetuses demonstrate slower barrier development than female littermates.

CRH stimulates POMC activity and corticosterone production in dermal fibroblasts

It has been previously documented that human skin cells including epidermal keratinocytes and dermal fibroblasts produce and process proopiomelanocortin (POMC), corticotropin releasing hormone (CRH), and express functional CRH receptors type-1 (CRH-R1). The skin also has corticosteroidogenic activity, suggesting a functional connection between these elements. In the current study, we found that human dermal fibroblasts (but not normal epidermal keratinocytes) respond to CRH with stimulation of cAMP, with POMC gene and protein expression, and ACTH production and release. Furthermore, CRH and ACTH stimulate production of corticosterone in fibroblasts, with ACTH being more potent. Although cortisol-immunoreactivity accumulation/production in fibroblasts has been detected by ELISA, it appears to be constitutive (not affected by CRH or ACTH). These effects are absent in keratinocytes. Therefore, we propose that fibroblasts but not keratinocytes display a functional CRH-POMC-corticosteroid axis organized similarly to the hypothalamus-pituitary-adrenal (HPA) axis. However, it diverges from the HPA organization in its distal step, where CRH and ACTH stimulate production of corticosterone, instead of cortisol.

Patients with a large prostate show a higher prevalence of androgenetic alopecia

Androgenetic alopecia (AGA) and benign prostatic hyperplasia (BPH) are both androgen-dependent disorders, displaying in situ high levels of dihydrotestosterone with a good therapeutic response to finasteride. Embryological development of both the hair follicle and the prostate depends on mesenchymal-epithelial interaction, which is influenced by the expression of type 2 5alpha-reductase. The aim of this study was to elucidate the association between the size of the prostate gland and the prevalence and severity of AGA. A total of 46 patients age between 56 and 87 years were retrospectively recruited. They fulfilling the clinical diagnosis of BPH defined as (1) prostate volume > 30 cm3, measured by transrectal ultrasound, (2) maximal urine flow rate < 15 ml/s and mean urine flow rate < 10 ml/s, and (3) prostate serum albumin < 10 ng/ml. The control group comprised 34 patients aged between 49 and 81 years with urogenital infection, cystitis or urolithiasis. The expression and severity of AGA were evaluated by dermatologists using modified Norwood/Hamilton classification. Patients with a prostate volume > 30 cm3 had a higher prevalence of AGA than patients with a smaller prostate (< 30 cm3) (83.3% vs 61.3%; P < 0.05). The prostate size, however, did not correlate with the severity of AGA in either group or in the whole patient group. The prevalence of AGA was not significantly different in patients with or without BPH (85.7% vs 70.6%). The prostate was slightly larger among patients with AGA than among those without AGA (mean+/-SD 42.7+/-17.4 vs 35.4+/-14.9 cm3), but this was not statistically significant. There was no significant correlation between the age of onset of AGA and the development of BPH. Our results suggest that a larger prostate is associated with a higher prevalence of AGA. It remains to be seen if long-term use of finasteride in AGA patients will prophylactically lower the incidence of BPH.

Steroid sulfatase: molecular biology, regulation, and inhibition

Steroid sulfatase (STS) is responsible for the hydrolysis of aryl and alkyl steroid sulfates and therefore has a pivotal role in regulating the formation of biologically active steroids. The enzyme is widely distributed throughout the body, and its action is implicated in physiological processes and pathological conditions. The crystal structure of the enzyme has been resolved, but relatively little is known about what regulates its expression or activity. Research into the control and inhibition of this enzyme has been stimulated by its important role in supporting the growth of hormone-dependent tumors of the breast and prostate. STS is responsible for the hydrolysis of estrone sulfate and dehydroepiandrosterone sulfate to estrone and dehydroepiandrosterone, respectively, both of which can be converted to steroids with estrogenic properties (i.e., estradiol and androstenediol) that can stimulate tumor growth. STS expression is increased in breast tumors and has prognostic significance. The role of STS in supporting tumor growth prompted the development of potent STS inhibitors. Several steroidal and nonsteroidal STS inhibitors are now available, with the irreversible type of inhibitor having a phenol sulfamate ester as its active pharmacophore. One such inhibitor, 667 COUMATE, has now entered a phase I trial in postmenopausal women with breast cancer. The skin is also an important site of STS activity, and deficiency of this enzyme is associated with X-linked ichthyosis. STS may also be involved in regulating part of the immune response and some aspects of cognitive function. The development of potent STS inhibitors will allow investigation of the role of this enzyme in physiological and pathological processes.

CRH stimulation of corticosteroids production in melanocytes is mediated by ACTH

The response to systemic stress is organized along the hypothalamic-pituitary-adrenal axis (HPA), whereas the response to a peripheral stress (solar radiation) is mediated by epidermal melanocytes (cells of neural crest origin) responsible for the pigmentary reaction. Melanocytes express proopiomelanocortin (POMC), corticotropin-releasing hormone (CRH), and CRH receptor-1 (CRH-R1) and can produce corticosterone. In the present study, incubation of normal epidermal melanocytes with CRH was found to trigger a functional cascade structured hierarchically and arranged along the same algorithm as in the HPA axis: CRH activation of CRH-R1 stimulated cAMP accumulation and increased POMC gene expression and production of ACTH. CRH and ACTH also enhanced production of cortisol and corticosterone, and cortisol production was also stimulated by progesterone. The chemical identity of the cortisol was confirmed by liquid chromatography-mass spectrometry (LC/MS2) with [corrected] mass spectrometry-mass spectrometry analyses. POMC gene silencing abolished the stimulatory effect of CRH on corticosteroid synthesis, indicating that this is indirect and mediated via production of ACTH. Thus the melanocyte response to CRH is highly organized along the same functional hierarchy as the HPA axis. This pattern demonstrates the fractal nature of the response to stress with similar activation sequence at the single-cell and whole body levels.

Practical Approach to the Hormonal Treatment of Acne

Acne is a disease of the pilosebaceous units and these are mainly under hormonal control. In female patients, hormonal therapy is a unique opportunity for the treatment of acne. Several combined oral contraceptives (COCs), cyproterone acetate, spironolactone, flutamide, and others, have been tried for the control of acne. An overview on the use of the most useful drugs in clinical practice was conducted. COCs are thoroughly discussed, also taking into consideration their potential side effects. A practical approach with guidelines on the use of COC in acne is proposed.

Mild cutaneous manifestation in two young women with extraordinary hyperandrogenemia

Hyperandrogenism with hyperandrogenemia should be considered in those with severe acne of sudden onset or conspicuous male-pattern baldness with hairline recession, although the majority of female patients with acne or androgenetic alopecia possess no endocrine disorder. Herein we describe on the contrary 2 young women with primary amenorrhea displaying prominent hyperandrogenemia but subtle cutaneous manifestation. The first one presenting vertical alopecia had an elevated level of serum dehydroepiandrosterone sulfate (>800 microg/dl) and was suspected to be a case of late-onset, non-classical adrenal hyperplasia. The second case with mild acne had a soaring serum level of total testosterone >9,000 ng/dl derived from an androgen-secreting adrenal adenoma overexpressing steroidogenic acute regulatory protein, P450 side-chain cleavage enzyme and aromatase. A careful patient history and a complete physical examination are mandatory in each individual female case with acne or alopecia. The possibility of adrenal tumor should be explored in patients with escalated circulating testosterone.

Acne: hormonal concepts and therapy

Acne vulgaris is the most common skin condition observed in the medical community. Although we know that hormones are important in the development of acne, many questions remain unanswered regarding the mechanisms by which hormones exert their effects. Androgens such as dihydrotestosterone (DHT) and testosterone, the adrenal precursor dehydroepiandrosterone sulfate (DHEAS), estrogens such as estradiol, and other hormones, including growth hormone and insulin-like growth factors (IGFs), may be important in acne. It is not known whether these hormones are taken up from the serum by the sebaceous gland, whether they are produced locally within the gland, or whether a combination of these processes is involved. Finally, the cellular and molecular mechanisms by which these hormones exert their influence on the sebaceous gland have not been fully elucidated. Hormonal therapy is an option in women with acne not responding to conventional treatment or with signs of endocrine abnormalities.

Androgen action on human skin - from basic research to clinical significance

Androgens affect several functions of the human skin, such as sebaceous gland growth and differentiation, hair growth, epidermal barrier homeostasis and wound healing. Their effects are mediated by binding to nuclear androgen receptors. Androgen activation and deactivation are mainly intracellular events. They differ from cell type to cell type and between cells at different locations. The major circulating androgens, dehydroepiandrosterone sulfate and androstenedione, are predominantly produced in the adrenal glands, and testosterone and 5alpha-dihydrotestosterone are mainly synthesized in the gonads. Testosterone in women and 5alpha-dihydrotestosterone in both genders are also synthesized in the skin. Skin cells express all androgen metabolizing enzymes required for the independent cutaneous synthesis of androgens and the development of hyperandrogenism-associated conditions and diseases, such as seborrhea, acne, hirsutism and androgenetic alopecia. The major thrust of drug design for the treatment of androgen-associated disorders has been directed against several levels of androgen function and metabolism. Partial effectiveness has only been achieved either by androgen depletion, inhibition of androgen metabolism or blockade of the androgen receptor.

6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate, a steroid sulfatase inhibitor for the treatment of androgen- and estrogen-dependent diseases

Steroid sulfatase (STS) offers a new target for the treatment of steroid hormone-dependent diseases, such as breast and prostate cancer and androgen-dependent skin diseases. We here characterize a novel non-estrogenic inhibitor of the enzyme, namely 6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate (AHBS), with special attention to its potential use in the treatment of acne. The compound blocks STS activity in homogenates of human skin with IC(50)=16 nM. Following a single oral dose (5 mg/kg) in rats, the compound blocks STS in the skin by 95% at 8 h, followed by recovery of activity over 5 days. Following topical application to the skin, both in vitro and in vivo, AHBS passes through the stratum corneum leading to inhibition of STS activity in the dermal compartment with rapid onset and long duration. Topical application of AHBS to Göttingen minipigs for a period of 2 weeks does not induce symptoms of ichthyosis as seen in STS-deficient human subjects, but leads to a reduction of sebum secretion to the skin surface. Based on these data, clinical studies with AHBS in acne patients are warranted, in order to verify the hypothesis on the importance of the sulfatase pathway in androgen-dependent skin diseases.

Hirsutism: diagnosis and management

Hirsutism can be a source of great distress and social embarrassment and in some cases can indicate underlying endocrine or malignant disease. More is known about the metabolic consequences of hyperandrogenism including risk of developing cardiovascular disease, insulin resistance or diabetes. Full assessment is vital in light of the potential health consequences of hirsutism.

Selective non-steroidal inhibitors of 5 alpha-reductase type 1

The enzyme 5 alpha-reductase (5 alpha R) catalyses the reduction of testosterone (T) into the more potent androgen dihydrotestosterone (DHT). The abnormal production of DHT is associated to pathologies of the main target organs of this hormone: the prostate and the skin. Benign prostatic hyperplasia (BPH), prostate cancer, acne, androgenetic alopecia in men, and hirsutism in women appear related to the DHT production. Two isozymes of 5 alpha-reductase have been cloned, expressed and characterized (5 alpha R-1 and 5 alpha R-2). They share a poor homology, have different chromosomal localization, enzyme kinetic parameters, and tissue expression patterns. Since 5 alpha R-1 and 5 alpha R-2 are differently distributed in the androgen target organs, a different involvement of the two isozymes in the pathogenesis of prostate and skin disorders can be hypothesized. High interest has been paid to the synthesis of inhibitors of 5 alpha-reductase for the treatment of DHT related pathologies, and the selective inhibition of any single isozyme represents a great challenge for medical and pharmaceutical research in order to have more specific drugs. At present, no 5 alpha R-1 inhibitor is marketed for the treatment of 5 alpha R-1 related pathologies but pharmaceutical research is very active in this field. This paper will review the major classes of 5 alpha R inhibitors focusing in particular on non-steroidal inhibitors and on structural features that enhance the selectivity versus the type 1 isozyme. Biological tests to assess the inhibitory activity towards the two 5 alpha R isozymes will be also discussed.

Inactivation of androgens by UDP-glucuronosyltransferase enzymes in humans

In humans, 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17beta-HSD and 5alpha-reductase activities in androgen target tissues, such as the prostate and skin, convert dehydroepiandrosterone, androstenedione and testosterone into the most potent natural androgen dihydrotestosterone (DHT). This androgen is converted mainly in situ into two phase I metabolites, androsterone (ADT) and androstane-3alpha,17beta-diol (3alpha-DIOL), which might be back converted to DHT. Here, we discuss the recent findings regarding the characterization of specific UDP-glucuronosyltransferases (UGTs), UGT2B7, B15 and B17, responsible for the glucuronidation of these metabolites. The tissue distribution and cellular localization of the UGT2B transcripts and proteins in humans clearly indicate that these enzymes are synthesized in androgen-sensitive tissues. It is postulated that the conjugating activity of UGT enzymes is the main mechanism for modulating the action of steroids and protecting the androgen-sensitive tissues from deleteriously high concentrations of DHT, ADT and 3alpha-DIOL.

Estimating the contribution of the prostate to blood dihydrotestosterone

The prostate strongly expresses type 2 5 alpha-reductase, which avidly converts on entry most testosterone (T) to 5 alpha-dihydrotestosterone (DHT). However, the quantitative contribution of the prostate to blood DHT is uncertain. We evaluated prostatic contribution to blood DHT by comparing the blood DHT concentrations in androgen-deficient patients with or without a prostate while they were receiving standard dose of T replacement. Androgen-deficient males (ADM) and female to male (F2M) transsexuals were studied in 2 centers, with both groups receiving either testosterone ester injections (250 mg mixed T esters) every 1 wk (Amsterdam) or 800 mg subdermal T implantation (Sydney). Among 39 Dutch patients, F2M (n = 21) were younger and smaller in physique than ADM (n = 18). One week (+/-1 d) after an injection, plasma DHT concentrations were 1.6 +/- 0.2 (F2M) vs. 1.4 +/- 0.2 (ADM) nmol/liter (P = 0.47), but the postinjection time interval to blood sampling was shorter in F2M (5.9 +/- 0.4 vs. 7.2 +/- 0.3 d; P = 0.01). Covariance adjustment for time since last injection, age, and physique did not change the lack of significant difference in postinjection plasma DHT concentration. The rapid and wide excursions in plasma T concentrations after an im T ester injection make the timing of blood sampling critical. To remove confounding by this variable, the experiment was repeated at a second site in similar patients, but using a depot T that achieves steady-state delivery for prolonged periods. Among 29 Australian patients, before and 1 month after subdermal implantation of 800 mg T, plasma DHT concentrations were not significantly different between groups [F2M, 1.1 +/- 0.1 (n = 14); ADM, 1.3 +/- 0.1 (n = 15); P = 0.28]. Correction for covariates, including age, height, weight, body surface area, and body mass index, did not influence the lack of significant difference between treated groups. As both modes of T administration yielded similar plasma DHT concentrations regardless of the presence of a prostate, this study indicates that the normal human prostate is not a major contributor to circulating blood DHT concentrations.

Update on pathogenesis and treatment of acne

Acne vulgaris is a common cutaneous disorder of the pilosebaceous follicle. More than 45 million people are affected with acne vulgaris. In addition, 80% of people in the United States report that they suffered from acne at one point in life. It is estimated that US consumers spend $1.2 billion each year for the treatment of acne. Typically, lesions are pleomorphic and range from open and closed comedones to inflammatory papules, pustules, cysts, and nodules, and scarring may result. The disease is important, with a significant effect on patients' self-esteem. The pathogenesis is only partially understood and is multifactorial. Successful management of acne requires an understanding of the pathophysiology of disease. The first half of this review discusses new discoveries in the pathogenesis of acne, and the second half introduces new and time-honored therapies.

Microtiter plate cellular assay for human steroid sulfatase with fluorescence readout

Steroid sulfatase (STS; E.C. 3.1.6.2) is an enzyme involved in the local production of estrogens and androgens in target organs. Inhibitors of steroid sulfatase activity are considered novel therapeutic agents for the treatment of different pathologic conditions, including cancers of breast, endometrium, and prostate and disorders of the pilosebaceous unit. Evaluation of steroid sulfatase inhibition in cells up to now has been a cumbersome process, involving the extraction of a radioactive cleavage product into organic solvents. Here, we describe a rapid, nonradioactive cellular assay in microtiter plate format, using 4-methylumbelliferyl sulfate as a substrate. The reaction product, 4-methylumbelliferone, is read in a fluorescence microtiter plate reader. Several cell lines were assayed for sulfatase activity. To increase the sensitivity of the assay, we developed a Chinese hamster ovary (CHO) cell line stably transfected with a cDNA encoding the human steroid sulfatase. The steroid sulfatase activity in transfected cells correlated with the presence of the enzyme in these cells, as determined by immunofluorescence. For most STS inhibitors tested, including estrone-3-O-sulfamate, the results from the CHO cellular assay were in good agreement with those from a standard cell-free assay.

Therapie der Akne mit Antiandrogenen - Eine evidenzbasierte Ubersicht. Treatment of acne with antiandrogens - an evidence-based review

BACKGROUND

Increased sebaceous gland activity with seborrhea is one of the major pathogenetic factors in acne. Antiandrogen treatment targets the androgen-metabolizing follicular keratinocytes and the sebaceous gland leading to sebostasis, with a reduction of the sebum secretion rate of 12.5-65%. Antiandrogens can be classified based on their mechanism of action as androgen receptor blockers, inhibitors of circulating androgens by affecting ovarian function (oral contraceptives), inhibitors of circulating androgens by affecting the pituitary (gonadotropin-releasing hormone agonists and dopamine agonists in hyperprolactinemia), inhibitors of adrenal function, and inhibitors of peripheral androgen metabolism (5alpha-reductase inhibitors, inhibitors of other enzymes).

METHODS

All original and review publications on antiandrogen treatment of acne as monotherapy or in combination included in the MedLine system were extracted by using the terms "acne", "seborrhea", "polycystic ovary syndrome", "hyperandrog", and "treatment" and classified according to their level of evidence.

RESULTS

The combinations of cyproterone acetate (2 mg)/ethinyl estradiol (35 microg), drospirenone (3 mg)/ethinyl estradiol (30 microg), and desogestrel (25 microg)/ ethinyl estradiol (40 microg) for 1 week followed by desogestrel (125 microg)/ethinyl estradiol (30 microg) for 2 weeks showed the strongest anti-acne activity. Gestagens or estrogens as monotherapy, spironolactone, flutamide, gonadotropin-releasing hormone agonists, and inhibitors of peripheral androgen metabolism cannot be endorsed based on current knowledge. Low dose prednisolone is only effective in late-onset congenital adrenal hyperplasia and dopamine agonists only in hyperprolactinemia. Treatment with antiandrogens should only be considered if none of the contraindications exist.

CONCLUSION

Antiandrogen treatment should be limited to female patients with additional signs of peripheral hyperandrogenism or hyperandrogenemia. In addition, women with late-onset or recalcitrant acne who also desire contraception can be treated with antiandrogens as can those being treated with systemic isotretinoin. Antiandrogen treatment is not appropriate primary monotherapy for noninflammatory and mild inflammatory acne.

The cynomolgus monkey (Macaca fascicularis) is the best animal model for the study of steroid glucuronidation

Intense research efforts performed during the past decade clearly established the major role of glucuronidation and uridine-diphospho-glucuronosyltransferase (UGT) enzymes for steroid metabolism in humans. However, a clear understanding of the physiological importance of this metabolic process requires in vivo studies. Numerous evidences ascertain that simians are the most appropriate animal models for such studies. Indeed human and monkey have a similar pattern of steroidogenesis, unlike common laboratory mammals such as rat or mouse. Furthermore, human and monkey are unique in having high levels of circulating androsterone glucuronide and androstane-3alpha-diol glucuronide (3alpha-Diol-G). In addition, characterization of eight monkey UGT proteins demonstrated the similarity of their conjugation activity toward steroid hormones. Like human ones, monkey enzymes are expressed in steroid target tissues, where they preferentially glucuronidate androgen and estrogen metabolites. In monkey tissues, immunohistochemical studies demonstrated that UGT2B proteins are expressed in a cell-type specific manner in ovary and kidney, where they control androgens and aldosterone inactivation. These results identify the cynomolgus monkey as an appropriate animal model for the determination of cellular localization of UGT enzymes in steroid target tissues and for the identification of endogenous or exogenous stimuli affecting steroid glucuronidation.

13-cis-retinoic acid competitively inhibits 3 alpha-hydroxysteroid oxidation by retinol dehydrogenase RoDH-4: a mechanism for its anti-androgenic effects in sebaceous glands?

Retinol dehydrogenase-4 (RoDH-4) converts retinol and 13-cis-retinol to corresponding aldehydes in human liver and skin in the presence of NAD(+). RoDH-4 also converts 3 alpha-androstanediol and androsterone into dihydrotestosterone and androstanedione, which may stimulate sebum secretion. This oxidative 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) activity of RoDH-4 is competitively inhibited by retinol and 13-cis-retinol. Here, we further examine the substrate specificity of RoDH-4 and the inhibition of its 3 alpha-HSD activity by retinoids. Recombinant RoDH-4 oxidized 3,4-didehydroretinol-a major form of vitamin A in the skin-to its corresponding aldehyde. 13-cis-retinoic acid (isotretinoin), 3,4-didehydroretinoic acid, and 3,4-didehydroretinol, but not all-trans-retinoic acid or the synthetic retinoids acitretin and adapalene, were potent competitive inhibitors of the oxidative 3 alpha-HSD activity of RoDH-4, i.e., reduced the formation of dihydrotestosterone and androstandione in vitro. Extrapolated to the in vivo situation, this effect might explain the unique sebosuppressive effect of isotretinoin when treating acne.

The roles of keratinocyte-derived cytokines in the epidermis and their possible responses to UVA-irradiation

Skin is the largest organ, covering the entire body surface. Keratinocytes (KC) are its major component. The KC, by making keratin protein, function as a protective barrier against exogenous stimuli. As KC have been demonstrated to produce various kinds of cytokines, skin plays an important role in immunologic and inflammatory responses of the body. Cytokines affect other cells and organs, mediating cellular growth and differentiation as well as inflammation and immune reactions. Thus, cytokines maintain the cellular and intercellular homeostasis. Dysregulation and abnormal production of cytokines are detected in various skin diseases. Evidence is accumulating to show the significant contribution of cytokines to the pathogenesis or severity of certain diseases. In this report, the effects of KC-derived cytokines on various components in the skin are briefly summarized. We further demonstrate that ultraviolet (UV) light has a distinct effect on the production and secretion of cytokines from KC, depending upon its wavelength. Although some KC-derived cytokines were induced both by UVA and by UVB, suggesting augmentative effects of UVA on UVB-induced cutaneous responses such as sunburn and suntan, other cytokines, including IL-10 and IL-12, were found to be differentially regulated by UVA and UVB. UVA (less than 20 kJ per m2) was found to induce IL-12 but not IL-10 in normal human KC. Our results suggest an antagonistic effect of UVA against UVB, indicating the contribution of UV irradiation to the balance between Th1 and Th2 cytokines in the in situ skin.