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

Xenobiotica-metabolizing enzymes in the skin of rat, mouse, pig, guinea pig, man, and in human skin models

Studies on the metabolic fate of medical drugs, skin care products, cosmetics and other chemicals intentionally or accidently applied to the human skin have become increasingly important in order to ascertain pharmacological effectiveness and to avoid toxicities. The use of freshly excised human skin for experimental investigations meets with ethical and practical limitations. Hence information on xenobiotic-metabolizing enzymes (XME) in the experimental systems available for pertinent studies compared with native human skin has become crucial. This review collects available information of which—taken with great caution because of the still very limited data—the most salient points are: in the skin of all animal species and skin-derived in vitro systems considered in this review cytochrome P450 (CYP)-dependent monooxygenase activities (largely responsible for initiating xenobiotica metabolism in the organ which provides most of the xenobiotica metabolism of the mammalian organism, the liver) are very low to undetectable. Quite likely other oxidative enzymes [e.g. flavin monooxygenase, COX (cooxidation by prostaglandin synthase)] will turn out to be much more important for the oxidative xenobiotic metabolism in the skin. Moreover, conjugating enzyme activities such as glutathione transferases and glucuronosyltransferases are much higher than the oxidative CYP activities. Since these conjugating enzymes are predominantly detoxifying, the skin appears to be predominantly protected against CYP-generated reactive metabolites. The following recommendations for the use of experimental animal species or human skin in vitro models may tentatively be derived from the information available to date: for dermal absorption and for skin irritation esterase activity is of special importance which in pig skin, some human cell lines and reconstructed skin models appears reasonably close to native human skin. With respect to genotoxicity and sensitization reactive-metabolite-reducing XME in primary human keratinocytes and several reconstructed human skin models appear reasonably close to human skin. For a more detailed delineation and discussion of the severe limitations see the Conclusions section in the end of this review.

Characterization of xenobiotic metabolizing enzymes of a reconstructed human epidermal model from adult hair follicles

In this study, a comprehensive characterization of xenobiotic metabolizing enzymes (XMEs) based on gene expression and enzyme functionality was made in a reconstructed skin epidermal model derived from the outer root sheath (ORS) of hair follicles (ORS-RHE). The ORS-RHE model XME gene profile was consistent with native human skin. Cytochromes P450 (CYPs) consistently reported to be detected in native human skin were also present at the gene level in the ORS-RHE model. The highest Phase I XME gene expression levels were observed for alcohol/aldehyde dehydrogenases and (carboxyl) esterases. The model was responsive to the CYP inducers, 3-methylcholanthrene (3-MC) and β-naphthoflavone (βNF) after topical and systemic applications, evident at the gene and enzyme activity level. Phase II XME levels were generally higher than those of Phase I XMEs, the highest levels were GSTs and transferases, including NAT1. The presence of functional CYPs, UGTs and SULTs was confirmed by incubating the models with 7-ethoxycoumarin, testosterone, benzo(a)pyrene and 3-MC, all of which were rapidly metabolized within 24h after topical application. The extent of metabolism was dependent on saturable and non-saturable metabolism by the XMEs and on the residence time within the model. In conclusion, the ORS-RHE model expresses a number of Phase I and II XMEs, some of which may be induced by AhR ligands. Functional XME activities were also demonstrated using systemic or topical application routes, supporting their use in cutaneous metabolism studies. Such a reproducible model will be of interest when evaluating the cutaneous metabolism and potential toxicity of innovative dermo-cosmetic ingredients.

Age and skin site related differences in steroid metabolism in male skin point to a key role of sebocytes in cutaneous hormone metabolism

Hormone concentrations decline with aging. Up to now it was not clear, whether the decrease of hormone concentrations in blood samples are also present in cutaneous suction blister fluids, and whether skin from different anatomical sites shows different hormone concentrations.

Analysis of suction blister fluids and paired blood samples from young (mean 27.8 y) and old (mean 62.6 y) male subjects by UPLC-MS/MS showed that DHEA concentration in blood samples was age-dependently significantly reduced, but increased in suction blister fluids, while androstenedione behaved in an opposite manner to DHEA. Testosterone decreased age-dependently in blood samples and in suction blister fluids. Regarding skin sites, DHEA was lower in samples from upper back compared with samples from the forearm. In contrast, the concentrations of androstenedione and testosterone were higher in samples from upper back.

In vitro analyses showed that SZ95 sebocytes, but neither primary fibroblasts nor keratinocytes, were able to use DHEA as precursor for testosterone biosynthesis, which was confirmed by expression analysis of 3β-hydroxysteroiddehydrogenase in skin biopsies.

In conclusion, we show an inverse pattern of DHEA and androstenedione concentrations in blood vs. suction blister fluids, highlighting age-dependent changes of dermal testosterone biosynthesis, and a stronger metabolism in young skin. Furthermore, sebocytes play a central role in cutaneous androgen metabolism.

Aldo-keto reductase 1C3 is expressed in differentiated human epidermis, affects keratinocyte differentiation, and is upregulated in atopic dermatitis

Aldo-keto reductase 1C3 (AKR1C3) has been shown to mediate the metabolism of sex hormones and prostaglandin D(2) (PGD(2)), a lipid mediator that promotes skin inflammation in atopic dermatitis (AD). As both have a role in skin function and pathology, we first sought to investigate the expression pattern of AKR1C3 in normal human epidermis. Immunofluorescence revealed a strong expression of AKR1C3 in the differentiated suprabasal layers compared with the basal layer. Western blot analysis and quantitative PCR confirmed that AKR1C3 expression was also upregulated in differentiation-induced primary human keratinocytes (PHKs). To investigate the functional role of AKR1C3 during PHK differentiation, its expression and activity (measured as PGD(2) reduction to 9α,11β-PGF(2) by ELISA) were impaired by small interfering RNA or 2'-hydroxyflavanone, respectively. Cytokeratin 10 (K10) and loricrin expression were then examined by western blot analysis, thus revealing altered expression of these differentiation markers. Finally, following an observation that the AD-associated mediator, PGD(2), upregulated AKR1C3 expression in PHKs, we used immunofluorescence to examine AKR1C3 expression in AD and psoriasis lesions. AKR1C3 was found to be upregulated in AD but not in psoriasis lesions compared with non-lesional skin. Our work demonstrates a function for AKR1C3 in differentiation-associated gene regulation and also suggests a role in supporting inflammation in AD.

Carotenoids in human skin

The interaction of free radicals with antioxidants is a topic of increasing interest in the development of prevention strategies against skin ageing. Carotenoids can serve as marker substances for the complete antioxidative network of human skin. Recently, it has become possible to measure the carotenoids non-invasively and online using resonance Raman spectroscopy. This method has been used in various studies to investigate the interaction of carotenoid antioxidants and free radicals in human skin. In this review, the results of the selected studies are summarized and compared. It could be demonstrated that the carotenoid concentration of the skin reflects the lifestyle of individuals. A high level of carotenoids can be achieved with a healthy diet rich, for instance, in fruit and vegetables. Stress factors such as illness, UV and IR radiation of the sun, and smoking and alcohol consumption reduce the concentration of the carotenoids in the skin. It could be demonstrated that premature skin ageing was less in people with a high level of antioxidants in their tissue. Consequently, the furrows and wrinkles were not so deep and dense as in the skin of individuals with a low antioxidant level. The measurements are highly suited for the development of anti-ageing strategies and can be efficiently used in the medical diagnostics and therapy control.

Day-to-day co-variations of psychological and physical symptoms of the menstrual cycle: insights to individual differences in steroid reactivity

The associations between physical and psychological symptoms of the menstrual cycle have not been carefully studied in past research, but may lead to a better understanding of the underlying mechanisms of these symptoms. The present study examines the day-to-day co-variations among physical and psychological symptoms of the menstrual cycle. These symptoms were evaluated on a daily basis across one entire menstrual cycle, with a non-clinical sample of 92 university students. Results showed that headaches, gastrointestinal problems, lower abdominal bloating, skin changes, and breast changes, were all significantly associated with higher levels of psychological symptoms; whereas back and joint pain, lower abdominal cramps, cervical mucous, and menstrual flow, were not associated with psychological symptoms. However, significant differences in these associations were observed across individuals for back and joint pain, headaches, lower abdominal cramps, skin changes, and menstrual flow: Whereas some women demonstrated higher levels of psychological symptoms associated with these physical symptoms, other women demonstrated lower levels of psychological symptoms. Finally, correlations among the associations between physical and psychological symptoms (slopes) demonstrated clear differences across the different physical symptoms. These results indicate that, although higher levels of some physical symptoms are associated with higher levels of psychological symptoms, there are significant differences in the magnitude and direction of these relations across individuals. Further consideration of physical symptoms may provide useful information for understanding individual differences in symptom profiles and response to steroid fluctuations, and for improving differential diagnosis and treatment planning and evaluation.