Metabolic Activation of Carcinogens by Keratinocytes (original) (raw)
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Journal of Dermatological Science, 1998
Cultured human keratinocytes have the property to hydroxylate exogenous 25-hydroxyvitamin D 3 (25OHD 3 ) at the C-1h position thus producing 1h,25-dihydroxyvitamin D 3 (1h,25(OH) 2 D 3 ). In this study we investigated whether keratinocytes can also hydroxylate vitamin D 3 and one of its metabolites at the C-25 position. We could demonstrate that HaCaT keratinocytes can metabolize 1h-hydroxyvitamin D 3 (1h-OHD 3 ) and vitamin D 3 to 1h,25(OH) 2 D 3 . Identification of the generated product as 1h,25(OH) 2 D 3 was based on its elution pattern in two different high performance liquid chromatography systems, on its specific binding in a calf thymus receptor assay and on its gas chromatography-mass spectrometry characteristics. The hydroxylation of vitamin D 3 to 1h,25(OH) 2 D 3 was dose-and time-dependent. Bovine serum albumin added up to 1.5% (w/v) to the culture medium greatly increased the hydroxylation rates. These results show that HaCaT cells have the capacity to hydroxylate vitamin D 3 at the C-1/25 positions. The generation of endogenous 1h,25(OH) 2 D 3 from vitamin D 3 within the skin may indicate a novel pathway which is of importance for the regulation of epidermal cell growth and differentiation.
Was the formation of 1,25-dihydroxyvitamin D3 initially a catabolic pathway?
Medical Hypotheses, 1997
Following solar ultraviolet radiation, epidermal 7-dehydrocholesterol is converted to previtamin D3, which then undergoes a thermal isomerization into vitamin D3. The metabolism of vitamin D3, which is usually considered as an inactive compound, gives rise to the active hormone 1,25-dihydroxyvitamin D3, following two hydroxylation steps occurring in liver and kidney. Here, we propose that this anabolic pathway can also be interpreted as a catabolic one leading to the degradation of the photoproducts of 7-dehydrocholesterol, for which a specific biological role in the skin is proposed.
1,25-Dihydroxyvitamin D3 Regulates Estrogen Metabolism in Cultured Keratinocytes*
Endocrinology, 1997
Local estrogen metabolism may play an important role in modulating cell development in peripheral tissues such as breast, adipose, and bone. C 19 androgens are converted to C 18 estrogens by the enzyme aromatase, overexpression of which is associated with breast cancer. Interconversion of active estradiol (E 2) to inactive estrone is controlled by various isoforms of the enzyme 17-hydroxysteroid dehydrogenase (17HSD). We have studied the expression of these two enzymes in human keratinocytes and report rapid changes in 17HSD activity in response to treatment with 1,25-dihydroxyvitamin D 3 [1,25-(OH) 2 D 3 ]. Keratinocytes cultured in serum-free medium showed aromatase activity of 2.5 fmol/h⅐mg cell protein, which was unaffected by any culture treatment. A much higher level of 17HSD activity was observed in the keratinocytes, predominantly conversion of E 2 to estrone (ϳ120 pmol/h⅐mg cell protein). This inactivation of E 2 increased in a dose-dependent fashion after treatment of the cells with antiproliferative doses of 1,25-(OH) 2 D 3 (0.1-200 nM). The effect of 1,25-(OH) 2 D 3 on 17HSD activity was enhanced by simultaneous treatment with dexamethasone, which also increased the antiproliferative action of 1,25-(OH) 2 D 3. Reverse transcription-PCR and Northern analysis showed that keratinocytes expressed messenger RNA for three 17HSD isoenzymes (types I, II, and IV). Treatment with 1,25-(OH) 2 D 3 (10 nM for 20 h) resulted in the up-regulation of messenger RNA levels for type 2 17HSD. Further RNA studies combined with E 2 binding experiments demonstrated the presence of estrogen receptors in the cultured keratinocytes. These data indicate that keratinocytes are potential targets for systemically or locally produced estrogens, which may, in turn, play a key role in the development of normal skin. In particular, we propose that 17HSD isoenzymes are key target genes for 1,25-(OH) 2 D 3 in keratinocytes and may be an important feature of the antipsoriatic effects of vitamin D and its analogs.
A Human Skin Equivalent Model That Mimics the Photoproduction of Vitamin D3 in Human Skin
In Vitro Cellular and Developmental Biology--Animal, 2000
A human skin equivalent was prepared by culturing human keratinocytes on the surface of nylon filtration meshes containing human skin fibroblasts and by growing the epidermal cells at the air-liquid interface. This human skin equivalent model was used to mimic the photoproduction of vitamin Dz in human skin. It was found that the concentration of 7-dehydrocholesterol and its photoconversion to previtamin D3 and its subsequent thermal isomerization to vitamin D 3 in the human skin equivalent was essentially identical to that of human skin. The 7-dehydrocholesterol content in the skin equivalent and human skin was 2187 + 296 and 2352-320 ng/cm 2, respectively. The percentage of the major photoproducts of 7-dehydrocholesterol in the skin equivalent following ultraviolet B radiation (0.5 J/cm 2) was 35% previtamin D3, 29% lumisterol, and 6% tachysterol; 30% remained as 7-dehydrocholesterol. Similarly, in human skin they were 36%, 29%, 7%, and 28%, respectively. After incubation at 37 ~ C for 30 min, 11% and 12% of the previtamin D 3 had thermally isomerized to vitamin D3 in the skin equivalent and human skin. In conclusion, compared with cultured keratinocytes or fibroblasts, the human skin equivalent model provides a superior in vitro system that better mimics the physiology and biochemistry of the photosynthesis of vitamin D 3 in human skin.
Novel vitamin D photoproducts and their precursors in the skin
Dermato-Endocrinology, 2013
An overview. While defining neuroendocrine activities of the skin, 1-3 we discovered novel metabolic pathways initiated by the enzymatic action of cytochrome P450scc (CYP11A1) on 7-dehydrocholesterol (7DHC; pro-vitamin D 3 ), 4-6 ergosterol, 7,8 vitamin D 3 9-16 and vitamin D 2 . 17,18 These substrates have structural similarity to the well characterized substrate for CYP11A1, cholesterol, where cleavage of its side chain between C20 and C22 producing pregnenolone represents the initial reaction in the synthesis of steroid hormones. We have now established that P450scc can hydroxylate vitamin D 3 in a sequential manner at positions C17, C20, C22 and C23 to produce 20-hydroxyvitamin D 3 (20(OH)D 3 ), 20,23(OH) 2 D 3 , 20,22(OH) 2 D 3 and 17,20,23(OH) 3 D 3 as the main products, with additional production of 17(OH)D 3 , 22(OH)D 3 , 23(OH)D 3 and 17,20(OH) 2 D 3 . Novel metabolic pathways initiated by the enzymatic action of CYP11A1 on 7DHC (7-dehydrocholesterol), ergosterol, vitamins D 3 and D 2 were characterized with help of chemical synthesis, Uv and mass spectrometry and NMr analyses. The first pathway follows the sequence 7DHC→ 22(OH)7DHC → 20,22(OH) 2 7DHC → 7DHP (7-dehydropregnenolone), which can further be metabolized by steroidogenic enzymes. The resulting 5,7-dienes can be transformed by UvB to corresponding, biologically active, secosteroids. Action of CYP11A1 on vitamin D 3 and D 2 produces novel hydroxyderivatives with OH added at positions C17, C20, C22, C23 and C24, some of which can be hydroxylated by CYP27B1 and/or by CYP27A1 and/ or by CYP24A1. The main products of these pathways are biologically active with a potency related to their chemical structure and the target cell type. Main products of CYP11A1-mediated metabolism on vitamin D are non-calcemic and non-toxic at relatively high doses and serve as partial agonists on the vitamin D receptor. New secosteroids are excellent candidates for therapy of fibrosing, inflammatory or hyperproliferative disorders including cancers and psoriasis.
Cancer Prevention Research, 2011
Exposure to ultraviolet radiation (UVR) can lead to a range of deleterious responses in the skin. An important form of damage is the DNA photolesion cyclobutane pyrimidine dimer (CPD). CPDs can be highly mutagenic if not repaired prior to cell division and can lead to UV-induced immunosuppression, making them potentially carcinogenic. UVR exposure also produces vitamin D, a prehormone. Different shapes of the steroid hormone 1a,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] can produce biological responses through binding either to its cognate nuclear receptor (VDR) to regulate gene transcription or to the VDR associated with plasma membrane caveolae to produce, via signal transduction, nongenomic physiologic responses. Here, we show that both 1,25(OH) 2 D 3 and 1a,25(OH) 2-lumisterol (JN), a conformationally restricted analogue that can generate only nongenomic responses, are effective inhibitors of UV damage in an immunocompetent mouse (Skh:hr1) model susceptible to UV-induced tumors. Both 1,25(OH) 2 D 3 and JN significantly reduced UVR-induced CPD, apoptotic sunburn cells, and immunosuppression. Furthermore, these compounds inhibited skin tumor development, both papillomas and squamous cell carcinomas, in these mice. The observed reduction of these UV-induced effects by 1,25 (OH) 2 D 3 and JN suggests a role for these compounds in prevention against skin carcinogenesis. To the best of our knowledge, this is the first comprehensive report of an in vivo long-term biological response generated by chronic dosing with a nongenomic-selective vitamin D steroid. Cancer Prev Res; 4(9); 1485-94. Ó2011 AACR.
Experimental Dermatology, 2005
UV-exposition is considered as the main reason for the development of cancers of the skin. However, 90 to 100% of the Vitamin-D reqirement is formed within the skin through the action of sunlight. Considering the results of epidemiological studies, that have detected an association of Vitamin-D deficiency with various types of cancer (e.g. colon-, prostate-and breast cancer), this is a real dilema. The cancer protective effect of vitamin-D is contributed to the extra renal, local production of 1a,25(OH) 2 D 3 by the 25-hydroxyvitamin D-1a-hydroxylase, which has been detected in various tissues. In respect of the novel functions of vitamin-D and the risk of adverse consequences in case of deficiency we have screened sun deprived risk groups (A: patients with genodermatoses connected with defects in sun-induced DNA repair: n ¼ 4: 3 patients with xeroderma pigmentosum and 1 patient with basal cell nevus syndrome; and B: non vitamin-D substituted renal transplant recipients under immunosuppressants: n ¼ 33) for their vitamin-D status. As measure of the vitamin-D store and as substrate for the 25-hydroxyvitamin D-1a-hydroxylase basal 25(OH)D 3 serum levels (Nichols Institute Diagnostika GmbH, Bad Nauheim, Germany) have been analysed. In both groups decreased basal 25(OH)D 3 serum levels were detected. Therefore we demand a monitoring of vitamin-D status in patients practising sun protection, in case of vitamin-D deficiency an oral substitution should be recommended.
Vitamin D in the skin physiology and pathology
Vitamin D plays important, pleiotropic role in the maintenance of global homeostasis. Its influence goes far beyond the regulation of calcium and phosphorus balance , as diverse activities of vitamin D and its natural metabolites assure proper functioning of major human organs, including skin. Recently, we reviewed the current understanding of vitamin D impact on human health from historical perspective (Wierzbicka et al. (2014) The renaissance of vitamin D. Acta Biochim Pol 61: 679–686). This article focuses on its functions in the skin. The skin and its appendages, creates a platform connecting and protecting internal organs against, usually harmful, external environment. It uppermost layer — epidermis in order to maintain a protective barrier undergoes a constant exchange of cornified keratinocytes layer. Its disturbance leads to development of serious skin disorders including psoriasis, vitiligo, atopic dermatitis and skin cancer. All of those dermatopathologies have a huge impact on modern societies, affecting not only the physical , but also mental state of patients as well as their social status. Furthermore, multiple human systemic diseases (autoimmune, blood and digestive diseases) have skin manifestation, thus " condition of the skin " often reflects the condition and pathological changes within the internal organs. In humans, the skin is the natural source of vitamin D, which is produced locally from 7-dehydro-cholesterol in photoreaction induced by ultraviolet B (UVB) radiation from the sun. It is also well established, that the process of proliferation and differentiation of keratinocytes is tightly regulated by calcium and the active form of vitamin D (1,25(OH) 2 D 3). Thus, the skin physiology is inseparably connected with vitamin D production and activity. Unfortunately, UVB, which is required for vitamin D production, is also known as the main cause of a skin cancer, including melanoma. Here, we are going to review benefits of vitamin D and its analogues in the maintenance of epidermal barrier and its potential use in the treatment of common skin diseases.
Protection from Ultraviolet Damage and Photocarcinogenesis by Vitamin D Compounds
2020
Exposure of skin cells to UV radiation results in DNA damage, which if inadequately repaired, may cause mutations. UV-induced DNA damage and reactive oxygen and nitrogen species also cause local and systemic suppression of the adaptive immune system. Together, these changes underpin the development of skin tumours. The hormone derived from vitamin D, calcitriol (1,25-dihydroxyvitamin D3) and other related compounds, working via the vitamin D receptor and at least in part through endoplasmic reticulum protein 57 (ERp57), reduce cyclobutane pyrimidine dimers and oxidative DNA damage in keratinocytes and other skin cell types after UV. Calcitriol and related compounds enhance DNA repair in keratinocytes, in part through decreased reactive oxygen species, increased p53 expression and/or activation, increased repair proteins and increased energy availability in the cell when calcitriol is present after UV exposure. There is mitochondrial damage in keratinocytes after UV. In the presence ...