On the role of skin in the regulation of local and systemic steroidogenic activities

Melatonin inhibits neuronal dysfunction-associated with neuroinflammation by atopic psychological stress in NC/Nga atopic-like mouse models

Atopic dermatitis (AD), also known as atopic eczema, is chronic pruritic skin disease. AD can increase psychological stress as well, increasing glucocorticoid release and exacerbating the associated symptoms. Chronic glucocorticoid elevation disturbs neuroendocrine signaling and can induce neuroinflammation, neurotoxicity, and cognitive impairment; however, it is unclear whether AD-related psychological stress elevates glucocorticoids enough to cause neuronal damage. Therefore, we assessed the effects of AD-induced stress in a mouse AD model. AD-related psychological stress increased astroglial and microglial activation, neuroinflammatory cytokine expression, and markers of neuronal loss. Notably, melatonin administration inhibited the development of skin lesions, scratching behavior, and serum IgE levels in the model mice, and additionally caused a significant reduction in corticotropin-releasing hormone responsiveness, and a significant reduction in neuronal damage. Finally, we produced similar results in a corticosterone-induced AD-like skin model. This is the first study to demonstrate that AD-related psychological stress increases neuroendocrine dysfunction, exacerbates neuroinflammation, and potentially accelerates other neurodegenerative disease states.

Ultraviolet- and infrared-induced 11 beta-hydroxysteroid dehydrogenase type 1 activating skin photoaging is inhibited by red ginseng extract containing high concentration of ginsenoside Rg3(S)

BACKGROUND

Sun irradiation is one of major extrinsic stressors responsible for premature skin aging through activation and expression of 11 beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts inactive cortisone to active cortisol. The aim of this study was to evaluate the inhibitory effects of red ginseng extract containing high concentrations of ginsenoside Rg3 (S) (GERg3) on 11β-HSD1-induced skin photoaging.

METHODS

To evaluate the inhibitory effects of GERg3 on ultraviolet- (UV) or infrared (IR)-induced skin photoaging, human dermal fibroblasts or a normal human 3D skin model was exposed to UV or an IR. RT-PCR, ELISA, Western blot, and H&E staining were used for evaluations. GERg3 was isolated from crude red ginseng.

RESULTS

GERg3 inhibited the increased expressions of 11β-HSD1, interleukin (IL)-6, and matrix metalloproteinase-1 (MMP-1) in UVB- or IR-exposed Hs68 cells. Additionally, the increased cortisol, IL-6, and MMP-1 expressions were effectively reduced by GERg3 in UVA-exposed 3D skin models. The photoinduced decrease in type 1 procollagen also recovered as a result of GERg3 treatment in Hs68 cells and the 3D skin model. In addition, the UVA-exposed dermal thickness was decreased in comparison with the UVA-protected 3D skin model, recovered with GERg3 treatment.

CONCLUSION

GERg3 had antiphotoaging effects in UV- or IR-exposed human dermal fibroblasts and normal human 3D skin model.

Glucocorticoids Inhibit Wound Healing: Novel Mechanism of Action

Jozic et al. describe mechanisms of glucocorticoid (GC) downregulation of wound healing by interaction with the membrane bound GC receptor, followed by stimulation of β-catenin and c-myc pathways. Targeting the membrane bound GC receptor or the recently discovered interaction of GC with mineralocorticoid receptors may counteract negative effects of GC on the skin barrier and potentially could serve as a remedy for age-related skin atrophy.

Cutaneous transcriptome analysis in NIH hairless mice

Mice with spontaneous coat mutations are ideal animal models for studying skin development and tumorigenesis. In this study, skin hair growth cycle abnormalities were examined in NIH hairless mice 42 days after birth (P42) by using hematoxylin-eosin (H&E) staining. To examine the gene expression patterns in the skin of mutant mice, the dorsal skin of P42 female NIH mice and NIH hairless mice was sequenced by RNA-Seq, and 5,068 differentially expressed genes (DEGs) were identified (false discovery rate [FDR] ≥ 2, P < 0.05). A pathway analysis showed that basal cell carcinoma, the cell cycle and the Hippo, Hedgehog and Wnt signaling pathways were up-regulated in NIH hairless mice. Previous studies have shown that these pathways are closely associated with cell proliferation, cell cycle, organ size and cancer development. In contrast, signal transduction, bacterial and parasitic infection, and receptor-mediated pathways, including calcium signaling, were down-regulated in NIH hairless mice. A gene interaction network analysis was performed to identify genes related to hair follicle development. To verify the reliability of the RNA-Seq results, we used q-PCR to analyze 12 key genes identified from the gene interaction network analysis, including eight down-regulated and four up-regulated genes, and the results confirmed the reliability of the RNA-Seq results. Finally, we constructed the differential gene expression profiles of mutant mice by RNA-Seq. NIH hairless mice exhibited abnormalities in hair development and immune-related pathways. Pik3r1 and Pik3r3 were identified as key genes, laying the foundation for additional in-depth studies of hairless mice.

Nutritional programming by glucocorticoids in breast milk: Targets, mechanisms and possible implications

Vertical transmission of glucocorticoids via breast milk might pose a mechanism through which lactating women could prepare their infants for the postnatal environment. The primary source of breast-milk glucocorticoids is probably the systemic circulation. Research from our group showed that milk cortisol and cortisone concentrations follow the diurnal rhythm of maternal hypothalamus-pituitary-adrenal axis activity, with a higher abundance of cortisone compared to cortisol. Measurement of breast-milk glucocorticoid concentrations is challenging due to possible cross-reactivity with progestagens and sex steroids, which are severely elevated during pregnancy and after parturition. This requires precise methods that are not hindered by cross reactivity, such as LC-MS/MS. There are some data suggesting that breast-milk glucocorticoids could promote intestinal maturation, either locally or after absorption into the systemic circulation. Breast-milk glucocorticoids might also have an effect on the intestinal microbiome, although this has not been studied thus far. Findings from studies investigating the systemic effects of breast-milk glucocorticoids are difficult to interpret, since none took the diurnal rhythm of glucocorticoids in breast milk into consideration, and various analytical methods were used. Nevertheless, glucocorticoids in breast milk might offer a novel potential pathway for signal transmission from mothers to their infants.

Cell type-specific regulatory effects of glucocorticoids on cutaneous TLR2 expression and signalling

Glucocorticoids (GCs) induce Toll-like receptor (TLR) 2 expression and synergistically upregulate TLR2 with pro-inflammatory cytokines or bacteria. These paradoxical effects have drawn attention to the inflammatory initiating or promoting effects of GCs, as GC treatment can provoke inflammatory skin diseases. Here, we aimed to investigate the regulatory effects of GCs in human skin cells of different epidermal and dermal layers. We found that Dex induced TLR2 expression mainly in undifferentiated and less in calcium-induced differentiated keratinocytes but not in HaCaT cells or fibroblasts, however, Dex reduced TLR1/6 expression. Stimulation with Dex under inflammatory conditions further increased TLR2 but not TLR1 or TLR6 levels in keratinocytes. Increased ligand-induced interaction of TLR2 with MyD88 and expression of the adaptor protein TRAF6 indicated enhanced TLR2 signalling, whereas TLR2/1 or TLR2/6 signalling was not increased in Dex-pretreated keratinocytes. GC-increased TLR2 expression was negatively regulated by JNK MAPK signalling when stimulated with Propionibacterium acnes. Our results provide novel insights into the molecular mechanisms of glucocorticoid-mediated expression and function of TLR2 in human skin cells and the understanding of the mechanisms of corticosteroid side effects.

Defective glucocorticoid receptor signaling and keratinocyte-autonomous defects contribute to skin phenotype of mouse embryos lacking the Hsp90 co-chaperone p23

p23 is a small acidic protein with intrinsic molecular chaperone activity. It is best known as a co-chaperone of the major cytosolic molecular chaperone Hsp90. p23 binds the N-terminus of Hsp90 and stabilizes the ATP-bound and N-terminally closed Hsp90 dimer. It is in this configuration that many Hsp90 clients are most stably bound. Considering the important role of p23 in the Hsp90 cycle, it came as a surprise that it is not absolutely essential for viability in the budding yeast or for mouse development. Mice without p23 develop quite normally until birth and then all die perinatally because of immature lungs. The only other apparent phenotype of late stage embryos and newborns is a skin defect, which we have further characterized here. We found that skin differentiation is impaired, and that both apoptosis and cell proliferation are augmented in the absence of p23; the consequences are a severe thinning of the stratum corneum and reduced numbers of hair follicles. The altered differentiation, spontaneous apoptosis and proliferation are all mimicked by isolated primary keratinocytes indicating that they do require p23 functions in a cell-autonomous fashion. Since the phenotype of p23-null embryos is strikingly similar to that of embryos lacking the glucocorticoid receptor, a paradigmatic Hsp90-p23 client protein, we investigated glucocorticoid signaling. We discovered that it is impaired in vivo and for some aspects in isolated keratinocytes. Our results suggest that part of the phenotype of p23-null embryos can be explained by an impact on this particular Hsp90 client, but do not exclude that p23 by itself or in association with Hsp90 affects skin development and homeostasis through yet other pathways.

Vitamin D signaling and melanoma: role of vitamin D and its receptors in melanoma progression and management

Ultraviolet B (UVB), in addition to having carcinogenic activity, is required for the production of vitamin D3 (D3) in the skin which supplies >90% of the body's requirement. Vitamin D is activated through hydroxylation by 25-hydroxylases (CYP2R1 or CYP27A1) and 1α-hydroxylase (CYP27B1) to produce 1,25(OH)₂D3, or through the action of CYP11A1 to produce mono-di- and trihydroxy-D3 products that can be further modified by CYP27B1, CYP27A1, and CYP24A1. The active forms of D3, in addition to regulating calcium metabolism, exert pleiotropic activities, which include anticarcinogenic and anti-melanoma effects in experimental models, with photoprotection against UVB-induced damage. These diverse effects are mediated through an interaction with the vitamin D receptor (VDR) and/or as most recently demonstrated through action on retinoic acid orphan receptors (ROR)α and RORγ. With respect to melanoma, low levels of 25(OH)D are associated with thicker tumors and reduced patient survival. Furthermore, single-nucleotide polymorphisms of VDR and the vitamin D-binding protein (VDP) genes affect melanomagenesis or disease outcome. Clinicopathological analyses have shown positive correlation between low or undetectable expression of VDR and/or CYP27B1 in melanoma with tumor progression and shorter overall (OS) and disease-free survival (DFS) times. Paradoxically, this correlation was reversed for CYP24A1 (inactivating 24-hydroxylase), indicating that this enzyme, while inactivating 1,25(OH)₂D3, can activate other forms of D3 that are products of the non-canonical pathway initiated by CYP11A1. An inverse correlation has been found between the levels of RORα and RORγ expression and melanoma progression and disease outcome. Therefore, we propose that defects in vitamin D signaling including D3 activation/inactivation, and the expression and activity of the corresponding receptors, affect melanoma progression and the outcome of the disease. The existence of multiple bioactive forms of D3 and alternative receptors affecting the behavior of melanoma should be taken into consideration when applying vitamin D management for melanoma therapy.

Linalool prevents oxidative stress activated protein kinases in single UVB-exposed human skin cells

Ultraviolet-B radiation (285–320 nm) elicits a number of cellular signaling elements. We investigated the preventive effect of linalool, a natural monoterpene, against UVB-induced oxidative imbalance, activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling in HDFa cells. We observed that linalool treatment (30 μM) prevented acute UVB-irradiation (20 mJ/cm²) mediated loss of activities of antioxidant enzymes in HDFa cells. The comet assay results illustrate that linalool significantly prevents UVB-mediated 8-deoxy guanosine formation (oxidative DNA damage) rather than UVB-induced cyclobutane pyrimidine (CPD) formation. This might be due to its ability to prevent UVB-induced ROS formation and to restore the oxidative imbalance of cells. This has been reflected in UVB-induced overexpression of MAPK and NF-κB signaling. We observed that linalool inhibited UVB-induced phosphorylation of ERK1, JNK and p38 proteins of MAPK family. Linalool inhibited UVB-induced activation of NF-κB/p65 by activating IκBa. We further observed that UVB-induced expression of TNF-α, IL6, IL-10, MMP-2 and MMP-9 was modulated by linalool treatment in HDFa cells. Thus, linalool protects the human skin cells from the oxidative damages of UVB radiation and modulates MAPK and NF-κB signaling in HDFa cells. The present findings substantiate that linalool may act as a photoprotective agent against UVB-induced skin damages.

PAMs ameliorates the imiquimod-induced psoriasis-like skin disease in mice by inhibition of translocation of NF-κB and production of inflammatory cytokines

Psoriasis is a chronic and persistent inflammatory skin disease seriously affecting the quality of human life. In this study, we reported an ancient formula of Chinese folk medicine, the natural plant antimicrobial solution (PAMs) for its anti-inflammatory effects and proposed the primary mechanisms on inhibiting the inflammatory response in TNF-α/IFN-γ-induced HaCaT cells and imiquimod-induced psoriasis-like skin disease mouse model. Two main functional components of hydroxysafflor Yellow A and allantoin in PAMs were quantified by HPLC to be 94.2±2.2 and 262.9±12.5 μg/mL respectively. PAMs could significantly reduce the gene expression and inflammatory cytokines production of Macrophage-Derived Chemokine (MDC), IL-8 and IL-6 in TNF-α/IFN-γ-induced HaCaT cells. PAMs also significantly ameliorates the psoriatic-like symptoms in a mouse model with the evaluation scores for both the single (scales, thickness, erythema) and cumulative features were in the order of blank control < Dexamethasone < PAMs < 50% ethanol < model groups. The results were further confirmed by hematoxylin-eosin staining, RT-qPCR and immunohistochemistry. The down-regulated gene expression of IL-8, TNF-α, ICAM-1 and IL-23 in mouse tissues was consistent with the results from those of the HaCaT cells. The inhibition of psoriasis-like skin inflammation by PAMs was correlated with the inactivation of the translocation of P65 protein into cellular nucleus, indicating the inhibition of the inflammatory NF-κB signaling pathway. Taken together, these findings suggest that PAMs may be a promising drug candidate for the treatment of inflammatory skin disorders, such as psoriasis.

Dysfunctional Skin-Derived Glucocorticoid Synthesis Is a Pathogenic Mechanism of Psoriasis

Glucocorticoids (GC) are the primary steroids that regulate inflammation and have been exploited therapeutically in inflammatory skin diseases. Despite the broad-spectrum therapeutic use of GC, the biochemical rationale for locally treating inflammatory skin conditions is poorly understood, as systemic GC production remains largely functional in these patients. GC synthesis has been well characterized in healthy skin, but the pathological consequence has not been examined. Here we show de novo GC synthesis, and GC receptor expression is dysfunctional in both nonlesional and lesional psoriatic skin. Use of GC receptor epidermal knockout mice with adrenalectomy allowed for the distinction between local (keratinocyte) and systemic GC activity. Compensation exhibited by adult GC receptor epidermal knockout mice demonstrated that keratinocyte-derived GC synthesis protected skin from topical phorbol 12-myristate 13-acetate-induced inflammatory assault. Thus, localized de novo GC synthesis in skin is essential for controlling inflammation, and loss of the GC pathway in psoriatic skin represents an additional pathological process in this complex inflammatory skin disease.

Effectiveness and safety of traditional Chinese medical bath therapy combined with ultraviolet irradiation in the treatment of psoriasis: A systematic review and meta-analysis of randomized controlled trials

Background and objective

To systematically evaluate the clinical effects and safety of traditional Chinese medical bath therapy (TCMBT) combined with ultraviolet irradiation in the treatment of psoriasis.

Methods

Electronic database retrieval was utilized. The foreign retrieval databases consulted included those of the Cochrane Library, PubMed and EMBASE; the domestic retrieval databases included the Chinese Biomedical Literature Database (Sino-Med), the China National Knowledge Infrastructure (CNKI), VIP and the WangFang Database. Clinical randomized controlled trials were conducted to evaluate the effects of TCMBT combined with ultraviolet irradiation in the treatment of psoriasis; the language of the retrieved articles was Chinese or English. Each database was searched from its inception to August 1, 2015. Two researchers independently collected the data and analyzed the methodology of the documented literature. The researchers conducted a meta-analysis with RevMan 5.2.3 software.

Results

According to the available literature, 25 RCTs (randomized controlled trials) of low research quality were conducted. According to the meta-analysis, the total effective rate of TCMBT combined with ultraviolet irradiation was relatively higher than that of ultraviolet irradiation alone. The recurrence rate, incidence of adverse reactions and Psoriasis Area and Severity Index (PASI) for the combined therapy was lower than that of ultraviolet irradiation (P<0.05).

Conclusion

For the treatment of psoriasis, the clinical effects and safety of TCMBT combined with ultraviolet irradiation are generally better than those of ultraviolet irradiation alone. However, the original literature was written in Chinese, and the quality of the studies was not high. Thus, it is difficult to confirm the clinical effects and safety of TCMBT combined with ultraviolet irradiation. It is necessary to conduct a scientific, normalized and high-quality RCT with multiple large samples and centers.

Preventive effect of dietary astaxanthin on UVA-induced skin photoaging in hairless mice

Astaxanthin, a carotenoid found mainly in seafood, has potential clinical applications due to its antioxidant activity. In this study, we evaluated the effect of dietary astaxanthin derived from Haematococcus pluvialis on skin photoaging in UVA-irradiated hairless mice by assessing various parameters of photoaging. After chronic ultraviolet A (UVA) exposure, a significant increase in transepidermal water loss (TEWL) and wrinkle formation in the dorsal skin caused by UVA was observed, and dietary astaxanthin significantly suppressed these photoaging features. We found that the mRNA expression of lympho-epithelial Kazal-type-related inhibitor, steroid sulfatase, and aquaporin 3 in the epidermis was significantly increased by UVA irradiation for 70 days, and dietary astaxanthin significantly suppressed these increases in mRNA expression to be comparable to control levels. In the dermis, the mRNA expression of matrix metalloprotease 13 was increased by UVA irradiation and significantly suppressed by dietary astaxanthin. In addition, HPLC-PDA analysis confirmed that dietary astaxanthin reached not only the dermis but also the epidermis. Our results indicate that dietary astaxanthin accumulates in the skin and appears to prevent the effects of UVA irradiation on filaggrin metabolism and desquamation in the epidermis and the extracellular matrix in the dermis.

Ultraviolet A eye irradiation ameliorates colon carcinoma induced by azoxymethane and dextran sodium sulfate through β-endorphin and methionine-enkephalin

BACKGROUND

We previously reported that ultraviolet (UV) A eye irradiation reduces the ulcerative colitis induced by dextran sodium sulfate (DSS). This study examined the effects of UVA on colon carcinoma induced by azoxymethane (AOM) and DSS.

METHODS

We irradiated the eyes of ICR mice with UVA at a dose of 110 kJ/m² using an FL20SBLB-A lamp for the experimental period.

RESULTS

In mice treated with these drugs, the symptom of colon carcinoma was reduced by UVA eye irradiation. The levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α in the blood were increased in AOM + DSS-treated mice; however, those levels were reduced by UVA eye irradiation. The expression of β-endorphin, methionine-enkephalin (OGF), μ-opioid receptor, and opioid growth factor receptor (OGFR) of the colon was increased in the AOM + DSS-treated mice, and these levels were increased further following UVA eye irradiation. When β-endorphin inhibitor was administered, the ameliorative effect of UVA eye irradiation was reduced, and the effect of eye irradiation disappeared entirely following the administration of naltrexone (inhibitor of both opioid receptor and OGFR).

CONCLUSIONS

These results suggested that UVA eye irradiation exerts major effects on AOM + DSS-induced colon carcinoma.

Cortisol Homeostasis in the Epidermis is Influenced by Topical Corticosteroids in Patients with Atopic Dermatitis

Background:

The skin produces cortisol by itself and regulates its own proliferation and differentiation. There is a possibility that topical corticosteroids (TCSs) influence the cortisol homeostasis in the skin.

Aims and Objectives:

The author described the density and distribution of cortisol and its parties in the epidermis after application of topical steroids immunohistologically.

Materials and Methods:

The forearm skin was biopsied before and after 2 weeks’ application of clobetasol propionate 0.05% two times a day in one healthy volunteer. The biopsied skin was stained immunohistologically by ant-MLN64, StAR, CPY11A1, cortisol, HSD11B1, HSD11B2, glucocorticoid receptor alpha, glucocorticoid receptor beta (GRB), and mineralocorticoid receptor (MCR) antibodies. The skin biopsy was performed similarly in 19 adult patients with atopic dermatitis who had used TCS for a considerable period. They were 4 TCS present users (TCS+), 12 TCS nonusers with skin manifestation on the biopsied site (TCS-E+) and 3 TCS nonusers without skin manifestation on the biopsied site (TCS-E−).

Results:

The staining density increased during TCS application in MLN64, cortisol and HSD11B2 in a healthy volunteer. The staining density was stronger in HSD11B2 of the basal layer and MCR of the spinous layer in the TCS-E+ patients than in the TCS+ and TCS-E− patients. The staining density was weaker in MLN64 of the basal and granular layers, HSD11B1 of the basal layer and GRB of the whole layer in the TCS-E+ patients than in the TCS+ and TCS-E− patients.

Conclusion:

The hypertrophy of the epidermis and insufficient keratinization recognized in the TCS-E+ patients might be caused by the decreased cortisol synthesis regulated by MLN64 and the increased cortisol inactivation by HSD11B2. Decreased GRB and increased MCR might enhance the reactivity of cortisol in the keratinocytes.

Stress Signals, Mediated by Membranous Glucocorticoid Receptor, Activate PLC/PKC/GSK-3β/β-catenin Pathway to Inhibit Wound Closure

Glucocorticoids (GCs), key mediators of stress signals, are also potent wound healing inhibitors. To understand how stress signals inhibit wound healing, we investigated the role of membranous glucocorticoid receptor (mbGR) by using cell-impermeable BSA-conjugated dexamethasone. We found that mbGR inhibits keratinocyte migration and wound closure by activating a Wnt-like phospholipase (PLC)/ protein kinase C (PKC) signaling cascade. Rapid activation of mbGR/PLC/PKC further leads to activation of known biomarkers of nonhealing found in patients, β-catenin and c-myc. Conversely, a selective inhibitor of PKC, calphostin C, blocks mbGR/PKC pathway, and rescues GC-mediated inhibition of keratinocyte migration in vitro and accelerates wound epithelialization of human wounds ex vivo. This novel signaling mechanism may have a major impact on understanding how stress response via GC signaling regulates homeostasis and its role in development and treatments of skin diseases, including wound healing. To test tissue specificity of this nongenomic signaling mechanism, we tested retinal and bronchial human epithelial cells and fibroblasts. We found that mbGR/PLC/PKC signaling cascade exists in all cell types tested, suggesting a more general role. The discovery of this nongenomic signaling pathway, in which glucocorticoids activate Wnt pathway via mbGR, provides new insights into how stress-mediated signals may activate growth signals in various epithelial and mesenchymal tissues.

Ginsenoside Rg1 attenuates ultraviolet B-induced glucocortisides resistance in keratinocytes via Nrf2/HDAC2 signalling

Oxidative stress, which occurs after ultraviolet (UV) radiation, usually results in Glucocorticoid (GC) resistance and the subsequent development of skin inflammation. One approach to protecting the skin against UV radiation is the use of antioxidants. The ginsenoside Rg1 is a novel natural antioxidant isolated from the medicinal plant Panax ginseng C.A. Mey. We demonstrated that UVB exposure exacerbated inflammation and reduced both the level of the glucocorticoid receptor (GR) and the efficacy of dexamethasone (Dex) in human keratinocytes (HaCaT cells). Pretreatment with Rg1 increased the expression of GR and restored Dex responsiveness to inflammation in UVB-irradiated HaCaT cells. Mechanistically, Rg1 rescued UVB-induced HDAC2 degradation. HDAC2 knockdown partially abolished the Rg1-induced up-regulation of GR and the enhancement of GC sensitivity. In addition, Rg1 reduced the production of reactive oxygen species (ROS), which preceded the up-regulation of HDAC2, and consequent sensitization of cells to Dex. Moreover, Rg1 treatment promoted the translocation and activation of Nrf2. Nrf2 knockdown partially abolished the Rg1-induced decrease of ROS production and increase of HDAC2. Rg1 also potentiated the anti-inflammatory effects of Dex in UVB-irradiated mouse skin. In conclusion, we demonstrated that Rg1 attenuated UVB-induced GC insensitivity. Notably, these effects were partially mediated by the Nrf2/HDAC2 pathway.

Bioactive forms of vitamin D selectively stimulate the skin analog of the hypothalamus-pituitary-adrenal axis in human epidermal keratinocytes

Ultraviolet radiation B stimulates both the production of vitamin D3 in the skin and the activation of the skin analog of the hypothalamic-pituitary-adrenal axis (HPA) as well as the central HPA. Since the role of vitamin D3 in the regulation of the HPA is largely unknown, we investigated the impact of 1,25(OH)2D3 and its noncalcemic analogs, 20(OH)D3 and 21(OH)pD, on the expression of the local HPA in human epidermal keratinocytes. The noncalcemic analogs showed similar efficacy to 1,25(OH)2D3 in stimulating the expression of neuropeptides, CRF, urocortins and POMC, and their receptors, CRFR1, CRFR2, MC1R, MC2R, MC3R and MC4R. Interestingly, unlike other secosteroids, the activity of 21(OH)pD did not correlate with induction of differentiation, suggesting a separate but overlapping mechanism of action. Thus, biologically active forms of vitamin D can regulate different elements of the local equivalent of the HPA with implications for the systemic HPA.

Skin Exposure to Ultraviolet B Rapidly Activates Systemic Neuroendocrine and Immunosuppressive Responses

The back skin of C57BL/6 mice was exposed to a single 400 mJ cm^-2 dose of ultraviolet B (UVB), and parameters of hypothalamic-pituitary-adrenal (HPA) axis in relation to immune activity were tested after 30-90 min following irradiation. Levels of brain and/or plasma corticotropin-releasing hormone (CRH), β-endorphin, ACTH and corticosterone (CORT) were enhanced by UVB. Hypophysectomy had no effect on UVB-induced increases of CORT. Mitogen-induced IFNγ production by splenocytes from UVB-treated mice was inhibited at 30, 90 min and after 24 h. UVB also led to inhibition of IL-10 production indicating an immunosuppressive effect on both Th1 and Th2 cytokines. Conditioned media from splenocytes isolated from UVB-treated animals had no effect on IFNγ production in cultured normal splenocytes; however, IFNγ increased with conditioned media from sham-irradiated animals. Sera from UVB-treated mice suppressed T-cell mitogen-induced IFNγ production as compared to sera from sham-treated mice. IFNγ production was inhibited in splenocytes isolated from UVB-treated animals with intact pituitary, while stimulated in splenocytes from UVB-treated hypophysectomized mice. Thus, cutaneous exposure to UVB rapidly stimulates systemic CRH, ACTH, β-endorphin and CORT production accompanied by rapid immunosuppressive effects in splenocytes that appear to be independent of the HPA axis.

Differentiation of Keratinocytes Modulates Skin HPA Analog

It is well established, that epidermal keratinocytes express functional equivalent of hypothalamus-pituitary-adrenal axis (HPA) in order to respond to changing environment and maintain internal homeostasis. We are presenting data indicating that differentiation of primary neonatal human keratinocytes (HPEKp), induced by prolonged incubation or calcium is accompanied by significant changes in the expression of the elements of skin analog of HPA (sHPA). Expression of CRF, UCN1-3, POMC, ACTH, CRFR1, CRFR2, MC1R, MC2R, and GR (coded by NR3C1 gene) were observed on gene/protein levels along differentiation of keratinocytes in culture with similar pattern seen by immunohistochemistry on full thickness skin biopsies. Expression of CRF was more pronounced in less differentiated keratinocytes, which corresponded to the detection of CRF immunoreactivity preferentially in the stratum basale. POMC expression was enhanced in more differentiated keratinocytes, which corresponded to detection of ACTH immunoreactivity, predominantly in the stratum spinosum and stratum granulosum. Expression of urocortins was also affected by induction of HPEKp differentiation. Immunohistochemical studies showed high prevalence of CRFR1 in well differentiated keratinocytes, while smaller keratinocytes showed predominantly CRFR2 immunoreactivity. MC2R mRNA levels were elevated from days 4 to 8 of in vitro incubation, while MC2R immunoreactivity was the highest in the upper layers of epidermis. Similar changes in mRNA/protein levels of sHPA elements were observed in HPEKp keratinocytes treated with calcium. Summarizing, preferential expression of CRF and POMC (ACTH) by populations of keratinocytes on different stage of differentiation resembles organization of central HPA axis suggesting their distinct role in physiology and pathology of the epidermis. J. Cell. Physiol. 232: 154-166, 2017. © 2016 Wiley Periodicals, Inc.

Local cortisol/corticosterone activation in skin physiology and pathology

Cortisol and corticosterone are the endogenous glucocorticoids (GCs) in humans and rodents, respectively. Systemic GC is released through the hypothalamic-pituitary-adrenal (HPA) axis in response to various stressors. Over the last decade, extra-adrenal production/activation of cortisol/corticosterone has been reported in many tissues. The enzyme that catalyzes the conversion of hormonally inactive cortisone/11-dehydrocorticosterone (11-DHC) into active cortisol/corticosterone in cells is 11β-hydroxysteroid dehydrogenase (11β-HSD). The 11β-HSD1 isoform is predominantly a reductase, which catalyzes nicotinamide adenine dinucleotide phosphate hydrogen-dependent conversion of cortisone/11-DHC to cortisol/corticosterone, and is widely expressed and present at the highest levels in the liver, lungs, adipose tissues, ovaries, and central nervous system. The 11β-HSD2 isoform, which catalyzes nicotinamide adenine dinucleotide⁺-dependent inactivation of cortisol/corticosterone to cortisone/11-DHC, is highly expressed in distal nephrons, the colon, sweat glands, and the placenta. In healthy skin, 11β-HSD1 is expressed in the epidermis and in dermal fibroblasts. On the other hand, 11β-HSD2 is expressed in sweat glands but not in the epidermis. The role of 11β-HSD in skin physiology and pathology has been reported recently. In this review, we summarize the recently reported role of 11β-HSD in the skin, focusing on its function in cell proliferation, wound healing, inflammation, and aging.

Vitamin D derivatives enhance cytotoxic effects of H2O2 or cisplatin on human keratinocytes

Although the skin production of vitamin D is initiated by ultraviolet radiation type B (UVB), the role vitamin D plays in antioxidative or pro-oxidative responses remains to be elucidated. We have used immortalized human HaCaT keratinocytes as a model of proliferating epidermal cells to test the influence of vitamin D on cellular response to H2O2 or the anti-cancer drug, cisplatin. Incubation of keratinocytes with 1,25(OH)2D3 or its low calcemic analogues, 20(OH)D3, 21(OH)pD or calcipotriol, sensitized cells to ROS resulting in more potent inhibition of keratinocyte proliferation by H2O2 in the presence of vitamin D compounds. These results were supported by cell cycle and apoptosis analyses, and measurement of the mitochondrial transmembrane potentials (MMP), however some unique properties of individual secosteroids were observed. Furthermore, in HaCaT keratinocytes treated with H2O2, 1,25(OH)2D3, 21(OH)pD and calcipotriol stimulated the expression of SOD1 and CAT genes, but not SOD2, indicating a possible role of mitochondria in ROS-modulated cell death. 1,25(OH)2D3 also showed a short-term, protective effect on HaCaT keratinocytes, as exemplified by the inhibition of apoptosis and the maintenance of MMP. However, with prolonged incubation with H2O2 or cisplatin, 1,25(OH)2D3 caused an acceleration in the death of the keratinocytes. Therefore, we propose that lead vitamin D derivatives can protect the epidermis against neoplastic transformation secondary to oxidative or UV-induced stress through activation of vitamin D-signaling. Furthermore, our data suggest that treatment with low calcemic vitamin D analogues or the maintenance of optimal level of vitamin D by proper supplementation, can enhance the anticancer efficacy of cisplatin.

Hydroxylation of 20-hydroxyvitamin D3 by human CYP3A4

20S-Hydroxyvitamin D3 [20(OH)D3] is the biologically active major product of the action of CYP11A1 on vitamin D3 and is present in human plasma. 20(OH)D3 displays similar therapeutic properties to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], but without causing hypercalcaemia and therefore has potential for development as a therapeutic drug. CYP24A1, the kidney mitochondrial P450 involved in inactivation of 1,25(OH)2D3, can hydroxylate 20(OH)D3 at C24 and C25, with the products displaying more potent inhibition of melanoma cell proliferation than 20(OH)D3. CYP3A4 is the major drug-metabolising P450 in liver endoplasmic reticulum and can metabolise other active forms of vitamin D, so we examined its ability to metabolise 20(OH)D3. We found that CYP3A4 metabolises 20(OH)D3 to three major products, 20,24R-dihydroxyvitamin D3 [20,24R(OH)2D3], 20,24S-dihydroxyvitamin D3 [20,24S(OH)2D3] and 20,25-dihydroxyvitamin D3 [20,25(OH)2D3]. 20,24R(OH)2D3 and 20,24S(OH)2D3, but not 20,25(OH)2D3, were further metabolised to trihydroxyvitamin D3 products by CYP3A4 but with low catalytic efficiency. The same three primary products, 20,24R(OH)2D3, 20,24S(OH)2D3 and 20,25(OH)2D3, were observed for the metabolism of 20(OH)D3 by human liver microsomes, in which CYP3A4 is a major CYP isoform present. Addition of CYP3A family-specific inhibitors, troleandomycin and azamulin, almost completely inhibited production of 20,24R(OH)2D3, 20,24S(OH)2D3 and 20,25(OH)2D3 by human liver microsomes, further supporting that CYP3A4 plays the major role in 20(OH)D3 metabolism by microsomes. Since both 20,24R(OH)2D3 and 20,25(OH)2D3 have previously been shown to display enhanced biological activity in inhibiting melanoma cell proliferation, our results show that CYP3A4 further activates, rather than inactivates, 20(OH)D3.

Skin Metabolite, Farnesyl Pyrophosphate, Regulates Epidermal Response to Inflammation, Oxidative Stress, and Migration

Skin produces cholesterol and a wide array of sterols and non-sterol mevalonate metabolites, including isoprenoid derivative farnesyl pyrophosphate (FPP). To characterize FPP action in epidermis, we generated transcriptional profiles of primary human keratinocytes treated with zaragozic acid (ZGA), a squalene synthase inhibitor that blocks conversion of FPP to squalene resulting in endogenous accumulation of FPP. The elevated levels of intracellular FPP resulted in regulation of epidermal differentiation and adherens junction signaling, insulin growth factor (IGF) signaling, oxidative stress response and interferon (IFN) signaling. Immunosuppressive properties of FPP were evidenced by STAT-1 downregulation and prominent suppression of its nuclear translocation by IFNγ. Furthermore, FPP profoundly downregulated genes involved in epidermal differentiation of keratinocytes in vitro and in human skin ex vivo. Elevated levels of FPP resulted in induction of cytoprotective transcriptional factor Nrf2 and its target genes. We have previously shown that FPP functions as ligand for the glucocorticoid receptor (GR), one of the major regulator of epidermal homeostasis. Comparative microarray analyses show significant but not complete overlap between FPP and glucocorticoid regulated genes, suggesting that FPP may have wider transcriptional impact. This was further supported by co-transfection and chromatin immunoprecipitation experiments where we show that upon binding to GR, FPP recruits β-catenin and, unlike glucocorticoids, recruits co-repressor GRIP1 to suppress keratin 6 gene. These findings have many clinical implications related to epidermal lipid metabolism, response to glucocorticoid therapy as well as pleiotropic effects of cholesterol lowering therapeutics, statins. J. Cell. Physiol. 231: 2452-2463, 2016. © 2016 Wiley Periodicals, Inc.

The role of hormones in the pathogenesis of psoriasis vulgaris

Psoriasis vulgaris is a chronic, common skin disease, which affects the patient’s quality of life to the highest degree. Several exogenous factors and endogenous hormonal changes may act as triggers for psoriasis.

The skin possesses a true endocrine system, which is very important in multiple systemic diseases. A number of conditions are associated with psoriasis, and its severity can also be influenced by hormones. Even though the sex hormones and prolactin have a major role in psoriasis pathogenicity, there are a lot of other hormones which can influence the psoriasis clinical manifestations: glucocorticoids, epinephrine, thyroid hormones, and insulin.

Role of the steroidogenic acute regulatory protein in health and disease

Steroid hormones are an important class of regulatory molecules that are synthesized in steroidogenic cells of the adrenal, ovary, testis, placenta, brain, and skin, and influence a spectrum of developmental and physiological processes. The steroidogenic acute regulatory protein (STAR) predominantly mediates the rate-limiting step in steroid biosynthesis, i.e., the transport of the substrate of all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane. At the inner membrane, cytochrome P450 cholesterol side chain cleavage enzyme cleaves the cholesterol side chain to form the first steroid, pregnenolone, which is converted by a series of enzymes to various steroid hormones in specific tissues. Both basic and clinical evidence have demonstrated the crucial involvement of the STAR protein in the regulation of steroid biosynthesis. Multiple levels of regulation impinge on STAR action. Recent findings demonstrate that hormone-sensitive lipase, through its action on the hydrolysis of cholesteryl esters, plays an important role in regulating STAR expression and steroidogenesis which involve the liver X receptor pathway. Activation of the latter influences macrophage cholesterol efflux that is a key process in the prevention of atherosclerotic cardiovascular disease. Appropriate regulation of steroid hormones is vital for proper functioning of many important biological activities, which are also paramount for geriatric populations to live longer and healthier. This review summarizes the current level of understanding on tissue-specific and hormone-induced regulation of STAR expression and steroidogenesis, and provides insights into a number of cholesterol and/or steroid coupled physiological and pathophysiological consequences.

Up-regulation of steroid biosynthesis by retinoid signaling: Implications for aging

Retinoids (vitamin A and its derivatives) are critical for a spectrum of developmental and physiological processes, in which steroid hormones also play indispensable roles. The StAR protein predominantly regulates steroid biosynthesis in steroidogenic tissues. We have reported that regulation of retinoid, especially atRA and 9-cis RA, responsive StAR transcription is largely mediated by an LXR-RXR/RAR heterodimeric motif in the mouse StAR promoter. Herein we demonstrate that retinoids are capable of enhancing StAR protein, P-StAR, and steroid production in granulosa, adrenocortical, glial, and epidermal cells. Whereas transient expression of RARα and RXRα enhanced 9-cis RA induced StAR gene transcription, silencing of RXRα with siRNA, decreased StAR and steroid levels. An oligonucleotide probe encompassing an LXR-RXR/RAR motif bound to adrenocortical and epidermal keratinocyte nuclear proteins in EMSAs. ChIP studies revealed association of RARα and RXRα with the StAR proximal promoter. Further studies demonstrated that StAR mRNA levels decreased in diseased and elderly men and women skin tissues and that atRA could restore steroidogenesis in epidermal keratinocytes of aged individuals. These findings provide novel insights into the relevance of retinoid signaling in the up-regulation of steroid biosynthesis in various target tissues, and indicate that retinoid therapy may have important implications in age-related complications and diseases.