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

Efficacy and Safety of Topical Morphine: A Narrative Review

Background. Opioids are the cornerstone of the therapy used in both acute and chronic pain syndromes to treat pain of moderate to severe intensity. The knowledge that opioid receptors also occur in other tissues outside the central nervous system has created a possibility for the topical use of opioids. Thus, local analgesia may be obtained without systemic adverse effects. Methods. A narrative review of scientific papers discussing the topical use of morphine was conducted. For this purpose, the PubMed, Google Scholar, Cochrane Library, and Mendeley databases were searched. Results. The current knowledge on topical morphine does not allow for its recommended use in everyday medical practice, but suggests it may be effective, particularly in the treatment of ulcers and erosions of inflammatory etiology and painful skin lesions including persistent post-mastectomy pain due to breast cancer. Conclusions. Topical morphine has its place beside other analgesics. An important issue is the practical possibility to meet the demand for topical formulations, which is limited by technical difficulties.

Metabolism and plasma protein binding of 16 straight- and branched-chain parabens in in vitro liver and skin models

Parabens are alkyl esters of 4-hydroxybenzoic acid (4-HBA), with short-chain parabens used as antimicrobials in cosmetics. We investigated the impact of chain structure on skin and liver metabolism. Incubations with primary human hepatocytes and human liver S9 indicated that methyl-, ethyl-, propyl- and butylparaben were rapidly metabolized to similar metabolites, including 4-HBA plus the corresponding alcohols. Liver and EpiSkin™ S9 were used to investigate the metabolism of 16 short and long straight- and branched-chain parabens. The rate of hydrolysis generally decreased with increasing chain length in liver S9, whereas the reverse was true for EpiSkin™ S9. Chain length also correlated with the number of metabolites, with more oxidized metabolites detected from longer chain parabens. The identity of the alcohol group impacted metabolism the most, in terms of the rate of metabolism and the contribution of cofactors. The majority of parabens (13/16) exhibited high plasma protein binding (PPB) (>90%); whereas, 4-HBA PPB was 38%. PPB was related to the LogP of the parabens. In conclusion, the major and common paraben metabolite in PHH, liver S9 and EpiSkin™ S9 was 4-HBA. The rate of metabolism, type of metabolite and contribution of hydrolysis was tissue-specific (liver, skin) and was influenced by the chain length (and hence LogP), structural isomeric form (straight vs branched), and/or the identity of the alkyl group. SHORT ABSTRACT: We investigated how the chain structure of parabens affects their metabolism by liver and EpiSkin™ S9. The major and common metabolite in primary human hepatocytes, liver S9 and EpiSkin™ S9 was 4-HBA plus the corresponding alcohols. The rate of metabolism, type of metabolite and contribution of hydrolysis was tissue-specific and influenced by the chain length, structural isomeric form (straight vs branched), and/or the identity of the alkyl group. Most parabens exhibited high PPB (>90%), whereas the PPB of 4-HBA was 38%.

Comparison of the metabolism of 10 cosmetics-relevant chemicals in EpiSkin™ S9 subcellular fractions and in vitro human skin explants

An understanding of the bioavailability of topically applied cosmetics ingredients is key to predicting their local skin and systemic toxicity and making a safety assessment. We investigated whether short-term incubations with S9 from the reconstructed epidermal skin model, EpiSkin™, would give an indication of the rate of chemical metabolism and produce similar metabolites to those formed in incubations with human skin explants. Both have advantages: EpiSkin™ S9 is a higher-throughput assay, while the human skin explant model represents a longer incubation duration (24 hours) model integrating cutaneous distribution with metabolite formation. Here, we compared the metabolism of 10 chemicals (caffeine, vanillin, cinnamyl alcohol, propylparaben, 4-amino-3-nitrophenol, resorcinol, 4-chloroaniline, 2-amino-3-methyl-3H-imidazo[4,5-F]quinoline and 2-acetyl aminofluorene) in both models. Both models were shown to have functional Phase 1 and 2 enzymes, including cytochrome P450 activities. There was a good concordance between the models with respect to the level of metabolism (stable vs. slowly vs. extensively metabolized chemicals) and major early metabolites produced for eight chemicals. Discordant results for two chemicals were attributed to a lack of the appropriate cofactor (NADP⁺ ) in S9 incubations (cinnamyl alcohol) and protein binding influencing chemical uptake in skin explants (4-chloroaniline). These data support the use of EpiSkin™ S9 as a screening assay to provide an initial indication of the metabolic stability of a chemical applied topically. If required, chemicals that are not metabolized by EpiSkin™ S9 can be tested in longer-term incubations with in vitro human explant skin to determine whether it is slowly metabolized or not metabolized at all.

C21-steroids inactivation and glucocorticoid synthesis in the developing lung

Glucocorticoids (GCs) are important regulators of lung development. The genes normally involved in GC synthesis in adrenals are co-expressed with 20α-hydroxysteroid dehydrogenase (20α-HSD) in the developing lung. In this study, C21-steroid metabolism was investigated in fetal and postnatal mouse lungs. Incubation of [(3)H]-progesterone with lung explant cultures of different perinatal developmental time points revealed two different (antenatal vs. postnatal) complex metabolization patterns. Progesterone inactivation was predominant. 20αOH-derivatives were more abundant after birth and some metabolites were 5α-reduced. Using [(3)H]-progesterone as substrate, corticosterone synthesis was only observed in a fraction of lung explants from gestation day (GD) 15.5. Neither aldosterone synthase nor P450c17 activity was observed. With epithelial-enriched primary cell cultures, deoxycorticosterone synthesis from [(3)H]-progesterone was observed. With lung explants incubated with [(3)H]-corticosterone as substrate, [(3)H]-4-pregnen-21-ol-3,11,20-trione (11-dehydrocorticosterone), the product of 11β-HSD2, accumulated in higher proportion on GD 15.5 than at later developmental time points. The temporal correlation observed between levels of progesterone inactivation by 20α-HSD (higher after birth) and the sensitivity of lung development to GCs suggests a role for 20α-HSD in the modulation of GR occupancy through the control of 21-hydroxylase substrate and product levels. In conclusion, the developing lung is characterized by effective inactivation of c21-steroids by 20α-HSD. The formation of active GCs from the "adrenal"-like pathway was observed with some lung explants and primary epithelial cell cultures. Coexistence of this GC synthesis pathway with 20α-HSD activity strongly suggests local regulation of GC action and is compatible with intracrine/paracrine actions of GC.

State-of-the-art of 3D cultures (organs-on-a-chip) in safety testing and pathophysiology

Integrated approaches using different in vitro methods in combination with bioinformatics can (i) increase the success rate and speed of drug development; (ii) improve the accuracy of toxicological risk assessment; and (iii) increase our understanding of disease. Three-dimensional (3D) cell culture models are important building blocks of this strategy which has emerged during the last years. The majority of these models are organotypic, i.e., they aim to reproduce major functions of an organ or organ system. This implies in many cases that more than one cell type forms the 3D structure, and often matrix elements play an important role. This review summarizes the state of the art concerning commonalities of the different models. For instance, the theory of mass transport/metabolite exchange in 3D systems and the special analytical requirements for test endpoints in organotypic cultures are discussed in detail. In the next part, 3D model systems for selected organs--liver, lung, skin, brain--are presented and characterized in dedicated chapters. Also, 3D approaches to the modeling of tumors are presented and discussed. All chapters give a historical background, illustrate the large variety of approaches, and highlight up- and downsides as well as specific requirements. Moreover, they refer to the application in disease modeling, drug discovery and safety assessment. Finally, consensus recommendations indicate a roadmap for the successful implementation of 3D models in routine screening. It is expected that the use of such models will accelerate progress by reducing error rates and wrong predictions from compound testing.

Identification of a gene signature of a pre-transformation process by senescence evasion in normal human epidermal keratinocytes

BACKGROUND

Epidemiological data show that the incidence of carcinomas in humans is highly dependent on age. However, the initial steps of the age-related molecular oncogenic processes by which the switch towards the neoplastic state occurs remain poorly understood, mostly due to the absence of powerful models. In a previous study, we showed that normal human epidermal keratinocytes (NHEKs) spontaneously and systematically escape from senescence to give rise to pre-neoplastic emerging cells.

METHODS

Here, this model was used to analyze the gene expression profile associated with the early steps of age-related cell transformation. We compared the gene expression profiles of growing or senescent NHEKs to post-senescent emerging cells. Data analyses were performed by using the linear modeling features of the limma package, resulting in a two-sided t test or F-test based on moderated statistics. The p-values were adjusted for multiple testing by controlling the false discovery rate according to Benjamini Hochberg method.The common gene set resulting of differential gene expression profiles from these two comparisons revealed a post-senescence neoplastic emergence (PSNE) gene signature of 286 genes.

RESULTS

About half of these genes were already reported as involved in cancer or premalignant skin diseases. However, bioinformatics analyses did not highlight inside this signature canonical cancer pathways but metabolic pathways, including in first line the metabolism of xenobiotics by cytochrome P450. In order to validate the relevance of this signature as a signature of pretransformation by senescence evasion, we invalidated two components of the metabolism of xenobiotics by cytochrome P450, AKR1C2 and AKR1C3. When performed at the beginning of the senescence plateau, this invalidation did not alter the senescent state itself but significantly decreased the frequency of PSNE. Conversely, overexpression of AKR1C2 but not AKR1C3 increased the frequency of PSNE.

CONCLUSIONS

To our knowledge, this study is the first to identify reprogrammation of metabolic pathways in normal keratinocytes as a potential determinant of the switch from senescence to pre-transformation.

State-of-the-art of 3D cultures (organs-on-a-chip) in safety testing and pathophysiology

Integrated approaches using different in vitro methods in combination with bioinformatics can (i) increase the success rate and speed of drug development; (ii) improve the accuracy of toxicological risk assessment; and (iii) increase our understanding of disease. Three-dimensional (3D) cell culture models are important building blocks of this strategy which has emerged during the last years. The majority of these models are organotypic, i.e., they aim to reproduce major functions of an organ or organ system. This implies in many cases that more than one cell type forms the 3D structure, and often matrix elements play an important role. This review summarizes the state of the art concerning commonalities of the different models. For instance, the theory of mass transport/metabolite exchange in 3D systems and the special analytical requirements for test endpoints in organotypic cultures are discussed in detail. In the next part, 3D model systems for selected organs--liver, lung, skin, brain--are presented and characterized in dedicated chapters. Also, 3D approaches to the modeling of tumors are presented and discussed. All chapters give a historical background, illustrate the large variety of approaches, and highlight up- and downsides as well as specific requirements. Moreover, they refer to the application in disease modeling, drug discovery and safety assessment. Finally, consensus recommendations indicate a roadmap for the successful implementation of 3D models in routine screening. It is expected that the use of such models will accelerate progress by reducing error rates and wrong predictions from compound testing.

Assessment of steroidogenesis and steroidogenic enzyme functions

There is some confusion in the literature about steroidogenesis in endocrine glands and steroidogenesis in peripheral intracrine tissues. The objective of the present review is to bring some clarifications and better understanding about steroidogenesis in these two types of tissues. Concerns about substrate specificity, kinetic constants and place of enzymes in the pathway have been discussed. The role of 17α-hydroxylase/17-20 lyase (CYP17A1) in the production of dehydroepiandrosterone and back-door pathways of dihydrotestosterone biosynthesis is also analyzed. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Sex steroid synthesis in human skin in situ: the roles of aromatase and steroidogenic acute regulatory protein in the homeostasis of human skin

Sex steroids have been known to play important roles in the homeostasis of human skin, but little is known about their biosyntheses in that tissue. In this study, we characterized the correlation between the concentrations of sex steroids and the expression levels of the factors involved in their synthesis or metabolism in human skin. The expression levels of aromatase (ARO) and steroidogenic acute regulatory protein (StAR) were positively correlated with estrogens and testosterone concentrations, respectively. We demonstrated that estrogen synthesis was markedly decreased by ARO inhibitor and that skins with higher ARO expression had thicker elastic fibers than those with lower ARO expression. While pregnenolone and testosterone concentrations were increased by cholesterol administration to epidermal keratinocytes. Scalp skin with higher StAR expression was cleared to have significantly fewer hair follicles than that with lower expression. Our results suggest that the status of ARO and StAR contribute to estrogen synthesis in situ, especially for the regulation of elastic fiber formation, and to testosterone synthesis, which may be associated with hair growth, respectively.

Oxidative metabolism of dehydroepiandrosterone (DHEA) and biologically active oxygenated metabolites of DHEA and epiandrosterone (EpiA)--recent reports

Dehydroepiandrosterone (DHEA) is a multifunctional steroid with a broad range of biological effects in humans and animals. DHEA can be converted to multiple oxygenated metabolites in the brain and peripheral tissues. The mechanisms by which DHEA exerts its effects are not well understood. However, evidence that the effects of DHEA are mediated by its oxygenated metabolites has accumulated. This paper will review the panel of oxygenated DHEA metabolites (7, 16 and 17-hydroxylated derivatives) including a number of 5α-androstane derivatives, such as epiandrosterone (EpiA) metabolites. The most important aspects of the oxidative metabolism of DHEA in the liver, intestine and brain are described. Then, this article reviews the reported biological effects of oxygenated DHEA metabolites from recent findings with a specific focus on cancer, inflammatory and immune processes, osteoporosis, thermogenesis, adipogenesis, the cardiovascular system, the brain and the estrogen and androgen receptors.

The role of estrogen-metabolizing enzymes and estrogen receptors in human epidermis

Local estrogen metabolism and its sensitivities in the skin have been also suggested to contribute to skin homeostasis in addition to age- and/or gender-dependent circulating estrogen, even though their local mechanisms have been largely unknown. To characterize their potential correlations, age- and gender-dependencies were evaluated focusing on 5 pivotal estrogen-metabolizing enzymes including aromatase, estrogen sulfotransferase, steroid sulfatase, and 17β-hydroxysteroid dehydrogenases and estrogen receptors (ERα and ERβ) using immunohistochemistry of 100 human skin specimens. When their epidermal expression levels were compared among 7 age groups, ranging from the teens to the seventies, the highest expression in the teens group and the lowest expression in the seventies group were found in the expression of aromatase and ERβ, respectively, while no significant differences between the male and the female groups were found in the immunoreactivities of our interested proteins. Our results suggest that age-related differences in aromatase and ERβ expressions impact epidermal homeostasis.

Endocrine correlates of pregnancy in the ring-tailed lemur (Lemur catta): implications for the masculinization of daughters

Female ring-tailed lemurs (Lemur catta) are Malagasy primates that are size monomorphic with males, socially dominate males, and exhibit a long, pendulous clitoris, channeled by the urethra. These masculine traits evoke certain attributes of female spotted hyenas (Crocuta crocuta) and draw attention to the potential role of androgens in lemur sexual differentiation. Here, hormonal correlates of prenatal development were assessed to explore the possibility that maternal androgens may shape the masculine morphological and behavioral features of developing female lemurs. Maternal serum 17α-hydroxyprogesterone, dehydroepiandrosterone sulphate (DHEA-S), ∆⁴ androstenedione (androst-4-ene-3,17,dione), testosterone, and 17β-estradiol were charted throughout the 19 pregnancies of 11 ring-tailed lemurs. As in spotted hyenas, lemur pregnancies were associated with an immediate increase in androgen concentrations (implicating early maternal derivation), followed by continued increases across stages of gestation. Pregnancies that produced singleton males, twin males, or mixed-sex twins were marked by greater androgen and estrogen concentrations than were pregnancies that produced singleton or twin females, especially in the third trimester, implicating the fetal testes in late-term steroid profiles. Concentrations of DHEA-S were mostly below detectable limits, suggesting a minor role for the adrenals in androgen biosynthesis. Androgen concentrations of pregnant lemurs bearing female fetuses, although less than those of pregnant hyenas, exceeded preconception and postpartum values and peaked in the third trimester. Although a maternal (and, on occasion, fraternal) source of androgen may exist for fetal lemurs, further research is required to confirm that these steroids would reach the developing female and contribute to her masculinization.

3D-wound healing model: influence of morphine and solid lipid nanoparticles

For efficient pain reduction in severe skin wounds, topically applied opioids may be a new option. Moreover, by stimulating keratinocyte migration opioids may also accelerate wound healing. Yet, conventional formulations failed to consistently provide sufficient pain control in patients which may be due to local drug degradation or insufficient concentrations at the target site. After having excluded major morphine glucuronidation by keratinocytes and fibroblasts, we next aimed for an optimised formulation. Since long intervals for painful wound dressing changes are intended, the formulations should allow for prolonged opioid release and should not impair the healing process. We developed morphine-loaded solid lipid nanoparticles (SLN, mean size about 180 nm), and tested improvement of wound closure in a new human-based 3D-wound healing model. Standardised wounds were induced by CO(2)-laser irradiation of reconstructed human full-thickness skin equivalents (EpiDermFT). Morphine, morphine-loaded and unloaded SLN accelerated reepithelialization. Keratinocytes almost completely covered the dermis equivalent after 4 days, which was not the case when applying the vehicle. In conclusion, acceleration of wound closure, low cytotoxicity and irritation as well as possible prolonged morphine release make SLN an interesting approach for innovative wound management.

Expression profiles of phases 1 and 2 metabolizing enzymes in human skin and the reconstructed skin models Episkin and full thickness model from Episkin

BACKGROUND

Episkin and full thickness model from Episkin (FTM) are human skin models obtained from in vitro growth of keratinocytes into the five typical layers of the epidermis. FTM is a full thickness reconstructed skin model that also contains fibroblasts seeded in a collagen matrix.

OBJECTIVES

To assess whether enzymes involved in chemical detoxification are expressed in Episkin and FTM and how their levels compare with the human epidermis, dermis and total skin.

METHODS

Quantification of the mRNA expression levels of phases 1 and 2 metabolizing enzymes in cultured Episkin and FTM and human epidermis, dermis and total skin using Realtime PCR.

RESULTS

The data show that the expression profiles of 61 phases 1 and 2 metabolizing enzymes in Episkin, FTM and epidermis are generally similar, with some exceptions. Cytochrome P450-dependent enzymes and flavin monooxygenases are expressed at low levels, while phase 2 metabolizing enzymes are expressed at much higher levels, especially, glutathione-S-transferase P1 (GSTP1) catechol-O-methyl transferase (COMT), steroid sulfotransferase (SULT2B1b), and N-acetyl transferase (NAT5). The present study also identifies the presence of many enzymes involved in cholesterol, arachidonic acid, leukotriene, prostaglandin, eicosatrienoic acids, and vitamin D3 metabolisms.

CONCLUSION

The present data strongly suggest that Episkin and FTM represent reliable and valuable in vitro human skin models for studying the function of phases 1 and 2 metabolizing enzymes in xenobiotic metabolisms. They could be used to replace invasive methods or laboratory animals for skin experiments.