ABSTRACT
Somatic mutations in DNA-binding sites for CCCTC-binding factor (CTCF) are significantly elevated in many cancers. Prior analysis has suggested that elevated mutation rates at CTCF-binding sites in skin cancers are a consequence of the CTCF-cohesin complex inhibiting repair of UV damage. Here, we show that CTCF binding modulates the formation of UV damage to induce mutation hot spots. Analysis of genome-wide CPD-seq data in UV-irradiated human cells indicates that formation of UV-induced cyclobutane pyrimidine dimers (CPDs) is primarily suppressed by CTCF binding but elevated at specific locations within the CTCF motif. Locations of CPD hot spots in the CTCF-binding motif coincide with mutation hot spots in melanoma. A similar pattern of damage formation is observed at CTCF-binding sites in vitro, indicating that UV damage modulation is a direct consequence of CTCF binding. We show that CTCF interacts with binding sites containing UV damage and inhibits repair by a model repair enzyme in vitro. Structural analysis and molecular dynamic simulations reveal the molecular mechanism for how CTCF binding modulates CPD formation.
Subject(s)
CCCTC-Binding Factor/chemistry , DNA Repair , Melanoma/genetics , Protein Serine-Threonine Kinases/chemistry , Pyrimidine Dimers/radiation effects , Skin Neoplasms/genetics , Binding Sites , Binding, Competitive , CCCTC-Binding Factor/genetics , CCCTC-Binding Factor/metabolism , Cell Line, Tumor , DNA Damage , Gene Expression , Humans , Melanoma/metabolism , Melanoma/pathology , Molecular Dynamics Simulation , Mutation , Protein Binding , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Pyrimidine Dimers/biosynthesis , Pyrimidine Dimers/chemistry , Skin Neoplasms/metabolism , Skin Neoplasms/pathology , Ultraviolet RaysABSTRACT
Under natural conditions, plants are exposed to solar ultraviolet (UV) radiation, which damages chromosomal DNA. Although plant responses to UV-induced DNA damage have recently been elucidated in detail, revealing a set of DNA repair mechanisms and translesion synthesis (TLS), limited information is currently available on UV-induced mutations in plants. We previously reported the development of a supF-based system for the detection of a broad spectrum of mutations in the chromosomal DNA of Arabidopsis. In the present study, we used this system to investigate UV-induced mutations in plants. The irradiation of supF-transgenic plants with UV-C (500 and 1000 J/m2) significantly increased mutation frequencies (26- and 45-fold, respectively). G:C to A:T transitions (43-67% of base substitutions) dominated in the mutation spectrum and were distributed throughout single, tandem, and multiple base substitutions. Most of these mutations became undetectable with the subsequent illumination of UV-irradiated plants with white light for photoreactivation (PR). These results indicated that not only G:C to A:T single base substitutions, but also tandem and multiple base substitutions were caused by two major UV-induced photoproducts, cyclobutane-type pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4 PPs). In contrast, a high proportion of A:T to T:A transversions (56% of base substitutions) was a characteristic feature of the mutation spectrum obtained from photoreactivated plants. These results define the presence of the characteristic feature of UV-induced mutations, and provide insights into DNA repair mechanisms in plants.
Subject(s)
Arabidopsis/genetics , Arabidopsis/radiation effects , Chromosomes, Plant/radiation effects , DNA, Plant/radiation effects , Mutation , Arabidopsis/growth & development , Base Sequence , Plants, Genetically Modified , Pyrimidine Dimers/biosynthesis , Pyrimidine Dimers/genetics , Sequence Analysis, DNA/methods , Ultraviolet RaysABSTRACT
Sequencing of whole cancer genomes has revealed an abundance of recurrent mutations in gene-regulatory promoter regions, in particular in melanoma where strong mutation hotspots are observed adjacent to ETS-family transcription factor (TF) binding sites. While sometimes interpreted as functional driver events, these mutations are commonly believed to be due to locally inhibited DNA repair. Here, we first show that low-dose UV light induces mutations preferably at a known ETS promoter hotspot in cultured cells even in the absence of global or transcription-coupled nucleotide excision repair (NER). Further, by genome-wide mapping of cyclobutane pyrimidine dimers (CPDs) shortly after UV exposure and thus before DNA repair, we find that ETS-related mutation hotspots exhibit strong increases in CPD formation efficacy in a manner consistent with tumor mutation data at the single-base level. Analysis of a large whole genome cohort illustrates the widespread contribution of this effect to recurrent mutations in melanoma. While inhibited NER underlies a general increase in somatic mutation burden in regulatory elements including ETS sites, our data supports that elevated DNA damage formation at specific genomic bases is at the core of the prominent promoter mutation hotspots seen in skin cancers, thus explaining a key phenomenon in whole-genome cancer analyses.
Subject(s)
Melanoma/etiology , Melanoma/genetics , Mutation , Neoplasms, Radiation-Induced/etiology , Neoplasms, Radiation-Induced/genetics , Pyrimidine Dimers/biosynthesis , Skin Neoplasms/etiology , Skin Neoplasms/genetics , Ultraviolet Rays/adverse effects , Base Sequence , Binding Sites/genetics , Cell Line, Tumor , DNA Damage , DNA, Neoplasm/genetics , Humans , Melanoma/metabolism , Neoplasms, Radiation-Induced/metabolism , Promoter Regions, Genetic , Proto-Oncogene Proteins c-ets/metabolism , Pyrimidine Dimers/genetics , Pyrimidine Dimers/radiation effects , Skin Neoplasms/metabolism , Whole Genome SequencingABSTRACT
Photodynamic therapy (PDT) is an office-based treatment for precancerous and early cancerous skin changes. PDT induces cell death through the production of reactive oxygen species (ROS). Cyclobutane pyrimidine dimers (CPDs) are the most important DNA changes responsible for ultraviolet (UV) carcinogenesis. Recently ROS induced by UVA were shown to generate CPDs via activating melanin. This raised the possibility that PDT induced ROS may also induce CPDs and mutagenesis in melanin containing cells. Previously the effect of PDT on CPDs in melanin containing cells has not been assessed. Our current work aimed to compare the generation of CPDs in melanin containing cells subjected to UVA treatment and porfimer sodium red light PDT. We used ELISA to detect CPDs. After UVA we found a dose dependent increase in CPDs in melanoma cells (B16-F10, MNT-1) with CPD levels peaking hours after discontinuation of UVA treatment. This indicated the generation of UVA induced dark-CPDs in the model. Nevertheless, PDT in biologically relevant doses was unable to induce CPDs. Our work provides evidence for the lack of CPD generation by PDT in melanin containing cells.
Subject(s)
Dihematoporphyrin Ether/pharmacology , Melanins/metabolism , Photochemotherapy/methods , Photosensitizing Agents/pharmacology , Pyrimidine Dimers/biosynthesis , Ultraviolet Rays/adverse effects , DNA Damage/physiology , Enzyme-Linked Immunosorbent Assay , Humans , Melanocytes/drug effects , Melanoma/drug therapyABSTRACT
The amount of photolesions produced in DNA after exposure to physiological doses of ultraviolet radiation (UVR) can be estimated with high sensitivity and at low cost through an immunological assay, ELISA, which, however, provides only a relative estimate that cannot be used for comparisons between different photolesions such as cyclobutane pyrimidine dimer (CPD) and pyrimidine(6-4)pyrimidone photoproduct (64PP) or for analysis of the genotoxicity of photolesions on a molecular basis. To solve this drawback of ELISA, we introduced a set of UVR-exposed, calibration DNA whose photolesion amounts were predetermined and estimated the absolute molecular amounts of CPDs and 64PPs produced in mouse skin exposed to UVC and UVB. We confirmed previously reported observations that UVC induced more photolesions in the skin than UVB at the same dose, and that both types of UVR produced more CPDs than 64PPs. The UVR protection abilities of the cornified and epidermal layers for the lower tissues were also evaluated quantitatively. We noticed that the values of absorbance obtained in ELISA were not always proportional to the molecular amounts of the lesion, especially for CPD, cautioning against the direct use of ELISA absorbance data for estimation of the photolesion amounts. We further estimated the mutagenicity of a CPD produced by UVC and UVB in the epidermis and dermis using the mutation data from our previous studies with mouse skin and found that CPDs produced in the epidermis by UVB were more than two-fold mutagenic than those by UVC, which suggests that the properties of CPDs produced by UVC and UVB might be different. The difference may originate from the wavelength-dependent methyl CpG preference of CPD formation. In addition, the mutagenicity of CPDs in the dermis was lower than that in the epidermis irrespective of the UVR source, suggesting a higher efficiency in the dermis to reduce the genotoxicity of CPDs produced within it. We also estimated the minimum amount of photolesions required to induce the mutation induction suppression (MIS) response in the epidermis to be around 15 64PPs or 100 CPDs per million bases in DNA as the mean estimate from UVC and UVB-induced MIS.
Subject(s)
Cyclobutanes/radiation effects , Cyclobutanes/toxicity , Mutagens/radiation effects , Mutagens/toxicity , Pyrimidine Dimers/radiation effects , Pyrimidine Dimers/toxicity , Skin/metabolism , Skin/radiation effects , Ultraviolet Rays , Animals , Cattle , Cyclobutanes/analysis , DNA/drug effects , DNA/genetics , DNA Damage , Enzyme-Linked Immunosorbent Assay , Mice , Mice, Transgenic , Mutagens/analysis , Mutation/drug effects , Pyrimidine Dimers/analysis , Pyrimidine Dimers/biosynthesisABSTRACT
Pyrimidine dimers are the most common DNA lesions generated under UV radiation. To reveal the molecular mechanisms behind their formation, it is of significance to reveal the roles of each pyrimidine residue. We thus replaced the 5'-pyrimidine residue with a photochemically inert xylene moiety (X). The electron-rich X can be readily oxidized but not reduced, defining the direction of interbase electron transfer (ET). Irradiation of the XpT dinucleotide under 254â nm UV light generates two major photoproducts: a pyrimidine (6-4) pyrimidone analog (6-4PP) and an analog of the so-called spore photoproduct (SP). Both products are formed by reaction at C4=O of the photo-excited 3'-thymidine (T), which indicates that excitation of a single "driver" residue is sufficient to trigger pyrimidine dimerization. Our quantum-chemical calculations demonstrated that photo-excited 3'-T accepts an electron from 5'-X. The resulting charge-separated radical pair lowers its energy upon formation of interbase covalent bonds, eventually yielding 6-4PP and SP.
Subject(s)
Dinucleoside Phosphates/metabolism , Electrons , Pyrimidine Dimers/biosynthesis , Dinucleoside Phosphates/chemistryABSTRACT
Sunlight's ultraviolet wavelengths induce cyclobutane pyrimidine dimers (CPDs), which then cause mutations that lead to melanoma or to cancers of skin keratinocytes. In pigmented melanocytes, we found that CPDs arise both instantaneously and for hours after UV exposure ends. Remarkably, the CPDs arising in the dark originate by a novel pathway that resembles bioluminescence but does not end in light: First, UV activates the enzymes nitric oxide synthase (NOS) and NADPH oxidase (NOX), which generate the radicals nitric oxide (NO) and superoxide (O2(-)); these combine to form the powerful oxidant peroxynitrite (ONOO(-)). A fragment of the skin pigment melanin is then oxidized, exciting an electron to an energy level so high that it is rarely seen in biology. This process of chemically exciting electrons, termed "chemiexcitation", is used by fireflies to generate light but it had never been seen in mammalian cells. In melanocytes, the energy transfers radiationlessly to DNA, inducing CPDs. Chemiexcitation is a new source of genome instability, and it calls attention to endogenous mechanisms of genome maintenance that prevent electronic excitation or dissipate the energy of excited states. Chemiexcitation may also trigger pathogenesis in internal tissues because the same chemistry should arise wherever superoxide and nitric oxide arise near cells that contain melanin.
Subject(s)
Electrons , Melanins/chemistry , Melanoma/chemistry , Neoplasms, Radiation-Induced/chemistry , Peroxynitrous Acid/chemistry , Skin Neoplasms/chemistry , DNA Damage , Humans , Keratinocytes/metabolism , Keratinocytes/pathology , Keratinocytes/radiation effects , Melanins/agonists , Melanins/metabolism , Melanoma/etiology , Melanoma/metabolism , Melanoma/pathology , NADPH Oxidases/metabolism , Neoplasms, Radiation-Induced/etiology , Neoplasms, Radiation-Induced/metabolism , Neoplasms, Radiation-Induced/pathology , Nitric Oxide/biosynthesis , Nitric Oxide/chemistry , Nitric Oxide Synthase/metabolism , Peroxynitrous Acid/biosynthesis , Pyrimidine Dimers/biosynthesis , Pyrimidine Dimers/chemistry , Skin/metabolism , Skin/pathology , Skin/radiation effects , Skin Neoplasms/etiology , Skin Neoplasms/metabolism , Skin Neoplasms/pathology , Sunlight/adverse effects , Superoxides/chemistry , Superoxides/metabolism , Ultraviolet Rays/adverse effectsABSTRACT
Ultraviolet (UV) radiation induces DNA damage, oxidative stress, and inflammatory processes in human keratinocytes, resulting in skin inflammation, photoaging, and photocarcinogenesis. Adequate protection of skin against the harmful effects of UV irradiation is essential. Therefore, in this study, we investigated the protective effects of afzelin, one of the flavonoids, against UV irradiation in human keratinocytes and epidermal equivalent models. Spectrophotometric measurements revealed that the afzelin extinction maxima were in the UVB and UVA range, and UV transmission below 376 nm was <10%, indicating UV-absorbing activity of afzelin. In the phototoxicity assay using the 3T3 NRU phototoxicity test (3T3-NRU-PT), afzelin presented a tendency to no phototoxic potential. In addition, in order to investigate cellular functions of afzelin itself, cells were treated with afzelin after UVB irradiation. In human keratinocyte, afzelin effectively inhibited the UVB-mediated increase in lipid peroxidation and the formation of cyclobutane pyrimidine dimers. Afzelin also inhibited UVB-induced cell death in human keratinocytes by inhibiting intrinsic apoptotic signaling. Furthermore, afzelin showed inhibitory effects on UVB-induced release of pro-inflammatory mediators such as interleukin-6, tumor necrosis factor-α, and prostaglandin-E2 in human keratinocytes by interfering with the p38 kinase pathway. Using an epidermal equivalent model exposed to UVB radiation, anti-apoptotic activity of afzelin was also confirmed together with a photoprotective effect at the morphological level. Taken together, our results suggest that afzelin has several cellular activities such as DNA-protective, antioxidant, and anti-inflammatory as well as UV-absorbing activity and may protect human skin from UVB-induced damage by a combination of UV-absorbing and cellular activities.
Subject(s)
Antioxidants/pharmacology , Keratinocytes/drug effects , Mannosides/pharmacology , Proanthocyanidins/pharmacology , Radiation-Protective Agents/pharmacology , Animals , Apoptosis , Cell Line , Comet Assay , Cytoprotection , DNA Fragmentation/drug effects , DNA Fragmentation/radiation effects , Dinoprostone/antagonists & inhibitors , Dinoprostone/biosynthesis , Humans , Interleukin-6/antagonists & inhibitors , Interleukin-6/biosynthesis , Keratinocytes/cytology , Keratinocytes/metabolism , Keratinocytes/radiation effects , Lipid Peroxidation/drug effects , Lipid Peroxidation/radiation effects , Mice , NIH 3T3 Cells , Oxidative Stress , Pyrimidine Dimers/antagonists & inhibitors , Pyrimidine Dimers/biosynthesis , Tumor Necrosis Factor-alpha/antagonists & inhibitors , Tumor Necrosis Factor-alpha/biosynthesis , Ultraviolet RaysABSTRACT
The UVA is currently thought to be carcinogenic because, similar to UVB, it induces the formation of cyclobutane pyrimidine dimers (CPDs). Various drugs have been reported to cause photosensitive drug eruptions as an adverse effect. Although the precise mechanism of photosensitive drug eruption remains to be elucidated, it is generally accepted that free radicals and other reactive molecules generated via UV-irradiated drugs play important roles in the pathogenesis of photosensitive drug eruptions. The waveband of concern for photo-reactive drugs is UVA-visible light, but some extend into the UVB region. We tested whether photosensitive drugs could enhance CPD formation after UVA exposure by using isolated DNA in the presence of several reported photosensitive drugs using high-performance liquid chromatography. We found that the diuretic agent hydrochlorothiazide (HCT) significantly enhanced the production of TT dimers over a wide range of UVA. Furthermore, we investigated whether UVA plus HCT could enhance CPD production in xeroderma pigmentosum model mice defective in nucleotide excision repair. Immunofluorescence studies showed that CPD formation in the skin significantly increased after 365 nm narrow-band UVA irradiation in the presence of HCT, compared with that in wild-type mice. HCT could be used with caution because of its enhancement of UVA-induced DNA damage.
Subject(s)
DNA Repair/genetics , DNA/chemistry , Diuretics/adverse effects , Hydrochlorothiazide/adverse effects , Photosensitizing Agents/adverse effects , Pyrimidine Dimers/biosynthesis , Skin/drug effects , Xeroderma Pigmentosum/chemistry , Animals , DNA/metabolism , DNA Damage , Disease Models, Animal , Diuretics/chemistry , Hydrochlorothiazide/chemistry , Mice , Mice, Knockout , Photosensitizing Agents/chemistry , Pyrimidine Dimers/chemistry , Skin/chemistry , Skin/pathology , Skin/radiation effects , Ultraviolet Rays/adverse effects , Xeroderma Pigmentosum/genetics , Xeroderma Pigmentosum/pathologyABSTRACT
People can get oral cancers from UV (290-400 nm) exposures. Besides high outdoor UV exposures, high indoor UV exposures to oral tissues can occur when consumers use UV-emitting tanning devices to either tan or whiten their teeth. We compared the carcinogenic risks of skin to oral tissue cells after UVB (290-320 nm) exposures using commercially available 3D-engineered models for human skin (EpiDerm™), gingival (EpiGing™) and oral (EpiOral™) tissues. To compare the relative carcinogenic risks, we investigated the release of cytokines, initial DNA damage in the form of cyclobutane pyrimidine dimers (CPDs), repair of CPDs and apoptotic cell numbers. We measured cytokine release using cytometric beads with flow cytometry and previously developed a fluorescent immunohistochemical assay to quantify simultaneously CPD repair rates and apoptotic cell numbers. We found that interleukin-8 (IL-8) release and the initial CPDs are significantly higher, whereas the CPD repair rates and apoptotic cell numbers are significantly lower for oral compared with skin tissue cells. Thus, the increased release of the inflammatory cytokine IL-8 along with inefficient CPD repair and decreased death rates for oral compared with skin tissue cells suggests that mutations are accumulating in the surviving population of oral cells increasing people's risks for getting oral cancers.
Subject(s)
Apoptosis/radiation effects , DNA Damage , Interleukin-8/biosynthesis , Mouth Mucosa/radiation effects , Mouth Neoplasms/pathology , Skin Neoplasms/pathology , Skin/radiation effects , Cell Line, Tumor , DNA Repair/genetics , Dose-Response Relationship, Radiation , Humans , Interleukin-8/immunology , Mouth Mucosa/immunology , Mouth Mucosa/pathology , Mouth Neoplasms/immunology , Organ Specificity , Pyrimidine Dimers/biosynthesis , Skin/immunology , Skin/pathology , Skin Neoplasms/immunology , Ultraviolet RaysABSTRACT
Daily skin exposure to solar radiation causes cells to produce reactive oxygen species (ROS), which are a primary factor in skin damage. Although the contribution of the UV component to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology. Solar radiation comprises <10% of UV, and thus the purpose of this study was to examine the physiological response of skin to visible light (400-700 nm). Irradiation of human skin equivalents with visible light induced production of ROS, proinflammatory cytokines, and matrix metalloproteinase (MMP)-1 expression. Commercially available sunscreens were found to have minimal effects on reducing visible light-induced ROS, suggesting that UVA/UVB sunscreens do not protect the skin from visible light-induced responses. Using clinical models to assess the generation of free radicals from oxidative stress, higher levels of free radical activity were found after visible light exposure. Pretreatment with a photostable UVA/UVB sunscreen containing an antioxidant combination significantly reduced the production of ROS, cytokines, and MMP expression in vitro, and decreased oxidative stress in human subjects after visible light irradiation. Taken together, these findings suggest that other portions of the solar spectrum aside from UV, particularly visible light, may also contribute to signs of premature photoaging in skin.
Subject(s)
Light , Matrix Metalloproteinases/biosynthesis , Reactive Oxygen Species/metabolism , Skin/radiation effects , Antioxidants/pharmacology , Cells, Cultured , Cytokines/biosynthesis , ErbB Receptors/physiology , Extracellular Signal-Regulated MAP Kinases/physiology , Humans , Luminescent Measurements , Pyrimidine Dimers/biosynthesis , Signal Transduction/radiation effects , Skin/metabolism , Ultraviolet RaysABSTRACT
In this issue, Tewari et al. show that although UVB most effectively causes cyclobutane pyrimidine dimers (CPDs) at the human epidermal surface, UVA-induced CPDs predominate in the basal layer. Previous studies found higher accumulation of UVA-induced 8-oxo-7,8-dihydro-2'-deoxyguanosine and mutations in the basal layer. Therefore, the epidermal basal layer is particularly sensitive to UVA-induced genetic damage and the formation of mutations.
Subject(s)
Pyrimidine Dimers/biosynthesis , Skin/radiation effects , Ultraviolet Rays/adverse effects , HumansABSTRACT
UVB readily induces cyclobutane pyrimidine dimers, mainly thymine dimers (TTs), and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) in DNA. These lesions result in "UVB signature mutations" found in skin cancers. We have investigated the induction of TTs and 6-4PPs in human skin in vivo by broadband UVA1, and have compared this with comparable erythemal doses of monochromatic UVB (300 nm). In vitro and ex vivo studies have shown the production of TTs, without 6-4PPs, by UVA1. We show that UVA1 induces TTs, without 6-4PPs, in the epidermis of healthy volunteers in vivo, whereas UVB induced both photoproducts. UVB induced more TTs than UVA1 for the same level of erythema. The level of UVA1-induced TTs increased with epidermal depth in contrast to a decrease that was seen with UVB. UVA1- and UVB-induced TTs were repaired in epidermal cells at a similar rate. The mechanism by which UVA1 induces TTs is unknown, but a lack of intra-individual correlation between our subjects' UVB and UVA1 minimal erythema doses implies that UVA1 and UVB erythema occur by different mechanisms. Our data suggest that UVA1 may be more carcinogenic than has previously been thought.
Subject(s)
Pyrimidine Dimers/biosynthesis , Skin/radiation effects , Ultraviolet Rays/adverse effects , DNA Repair , Dose-Response Relationship, Radiation , Erythema/etiology , Humans , Neoplasms, Radiation-Induced/etiology , Pyrimidine Dimers/analysis , Skin/metabolism , Skin Neoplasms/etiologyABSTRACT
The ongoing anthropogenically caused ozone depletion and climate change has increased the amount of biologically harmful UV-B radiation, which is detrimental to fish in embryonal stages. The effects of UV-B radiation on the levels and locations of DNA damage manifested as cyclobutane pyrimidine dimers (CPDs), heat shock protein 70 (HSP70) and p53 protein in newly hatched embryos of pike were examined. Pike larvae were exposed in the laboratory to current and enhanced doses of UV-B radiation. UV-B exposure caused the formation of CPDs in a fluence rate-dependent manner, and the CPDs were found deeper in the tissues with increasing fluence rates. UV-B radiation induced HSP70 in epidermis, and caused plausible p53 activation in the brain and epidermis of some individuals. Also at a fluence rate occurring in nature, the DNA damage in the brain and eyes of pike and changes in protein expression were followed by severe behavioral disorders, suggesting that neural molecular changes were associated with functional consequences.
Subject(s)
Brain/radiation effects , Epidermis/radiation effects , Eye/radiation effects , Gene Expression/radiation effects , Ultraviolet Rays/adverse effects , Animals , Blotting, Western , Brain/embryology , Brain/metabolism , DNA Damage , Embryo, Nonmammalian , Epidermis/embryology , Epidermis/metabolism , Esocidae , Eye/embryology , Eye/metabolism , HSP70 Heat-Shock Proteins/genetics , HSP70 Heat-Shock Proteins/metabolism , Immunohistochemistry , Pyrimidine Dimers/biosynthesis , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolismSubject(s)
Antioxidants/pharmacology , Carotenoids/pharmacology , Fibroblasts/drug effects , Free Radicals/antagonists & inhibitors , Oxygen/antagonists & inhibitors , Radiation-Protective Agents/pharmacology , Skin/drug effects , Antioxidants/chemical synthesis , Antioxidants/chemistry , Carotenoids/chemical synthesis , Carotenoids/chemistry , Cells, Cultured , Fibroblasts/metabolism , Fibroblasts/radiation effects , Heme Oxygenase-1/antagonists & inhibitors , Heme Oxygenase-1/biosynthesis , Heme Oxygenase-1/radiation effects , Humans , Liposomes/chemistry , Liposomes/radiation effects , Lutein/pharmacology , Molecular Structure , Oxidation-Reduction/drug effects , Oxidation-Reduction/radiation effects , Oxygen Consumption/drug effects , Phospholipids/chemistry , Phospholipids/radiation effects , Pyrimidine Dimers/antagonists & inhibitors , Pyrimidine Dimers/biosynthesis , Pyrimidine Dimers/radiation effects , Radiation-Protective Agents/chemical synthesis , Radiation-Protective Agents/chemistry , Skin/metabolism , Skin/radiation effects , Stereoisomerism , Ultraviolet RaysABSTRACT
Organic osmolytes, such as taurine, are involved in cell volume homeostasis and cell protection. Epidermal keratinocytes possess an osmolyte strategy, i.e., they take up taurine upon hyperosmotic stress and express the corresponding transporter TAUT. UVB irradiation also triggers taurine uptake and TAUT expression in this cell type. We therefore asked whether taurine plays a role in photoprotection. By using a TAUT-deficient mouse model, lack of taurine in the skin was found to cause a significantly higher sensitivity to UVB-induced immunosuppression. This was not due to an increased generation or decreased repair of UVB-induced DNA photoproducts in the skin of these animals. Instead, decreased skin taurine levels were associated with an increased formation of the soluble immunosuppressive molecule platelet-activating factor (PAF) from the membranes of UVB-irradiated epidermal cells. Blocking PAF activity in taut-deficient mice with a PAF receptor antagonist abrogated their increased sensitivity to UVB-induced immunosuppression. Moreover, taut -/- mice were more sensitive to PAF-mediated immunosuppression than taut +/+ mice. These data suggest that taurine uptake by epidermal cells prevents undue PAF formation, and thereby photoimmunosuppression. Thus, similar to nucleotide excision repair, taurine uptake is critically involved in photoprotection of the skin.
Subject(s)
Immunosuppression Therapy , Membrane Glycoproteins/physiology , Membrane Transport Proteins/physiology , Skin/immunology , Skin/radiation effects , Taurine/physiology , Ultraviolet Rays/adverse effects , Animals , Cells, Cultured , DNA Repair/radiation effects , Female , Genetic Predisposition to Disease , Interleukin-10/antagonists & inhibitors , Interleukin-10/biosynthesis , Interleukin-10/radiation effects , Langerhans Cells/radiation effects , Male , Membrane Glycoproteins/biosynthesis , Membrane Glycoproteins/deficiency , Membrane Glycoproteins/genetics , Membrane Transport Proteins/biosynthesis , Membrane Transport Proteins/deficiency , Membrane Transport Proteins/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Osmotic Pressure/radiation effects , Platelet Activating Factor/metabolism , Platelet Activating Factor/radiation effects , Platelet Membrane Glycoproteins/antagonists & inhibitors , Pyrimidine Dimers/biosynthesis , Pyrimidine Dimers/radiation effects , Receptors, G-Protein-Coupled/antagonists & inhibitors , Skin/cytology , Skin/metabolism , Taurine/deficiency , Taurine/metabolismABSTRACT
Malignant transformation of melanocytes leads to melanoma, the most fatal form of skin cancer. Ultraviolet radiation (UVR)-induced DNA photoproducts play an important role in melanomagenesis. Cutaneous melanin content represents a major photoprotective mechanism against UVR-induced DNA damage, and generally correlates inversely with the risk of skin cancer, including melanoma. Melanoma risk is also determined by susceptibility genes, one of which is the melanocortin 1 receptor (MC1R) gene. Certain MC1R alleles are strongly associated with melanoma. We hereby present experimental evidence for the role of two melanoma risk factors, constitutive pigmentation, as assessed by total melanin, eumelanin and pheomelanin contents, and MC1R genotype and function, in determining the induction and repair of DNA photoproducts in cultured human melanocytes after irradiation with increasing doses of UVR. We found that total melanin and eumelanin contents (MC and EC) correlated inversely with the extent of UVR-induced growth arrest, apoptosis and induction of cyclobutane pyrimidine dimers (CPD), but not with hydrogen peroxide release in melanocytes expressing functional MC1R. In comparison, melanocytes with loss-of-function MC1R, regardless of their MC or EC, sustained more UVR-induced apoptosis and CPD, and exhibited reduced CPD repair. Therefore, MC, mainly EC, and MC1R function are independent determinants of UVR-induced DNA damage in melanocytes.
Subject(s)
DNA Damage/radiation effects , Melanins/physiology , Melanocytes/physiology , Melanocytes/radiation effects , Receptor, Melanocortin, Type 1/physiology , Ultraviolet Rays/adverse effects , Adult , Apoptosis/radiation effects , Biopsy , Cell Division/radiation effects , Cells, Cultured , DNA Repair , Humans , Hydrogen Peroxide/metabolism , Infant, Newborn , Male , Melanins/analysis , Melanins/metabolism , Melanocytes/metabolism , Melanocytes/pathology , Melanoma/genetics , Neoplasms, Radiation-Induced/genetics , Pyrimidine Dimers/biosynthesis , Pyrimidine Dimers/radiation effects , Receptor, Melanocortin, Type 1/metabolism , Risk Factors , Skin/cytologyABSTRACT
We have previously observed that preirradiation with naturally occurring doses of near-infrared (IR) protects normal human dermal fibroblasts from ultraviolet (UV) cytotoxicity in vitro. This effect was observed in temperature-controlled conditions, without heat shock protein (Hsp72-70) induction. Moreover, IR inhibited UVB-induced apoptosis by modulating the Bcl2/Bax balance, pointing to a role of p53. Here, we show for the first time that p53-deficient SaOs cells are not protected from UVB cytotoxicity by IR preirradiation, suggesting that the response to IR is p53-dependent. Thus, we investigated the effect of IR on the p53 signaling pathway. Normal human dermal fibroblasts exposed in vitro to IR accumulated p53 protein, involving p53 stabilization and phosphorylation of serine 15 (Ser15) and Ser20. IR-induced p53 accumulation correlated with increased expression of p21 and GADD45, showing that IR also stimulates p53 transcriptional activity. By modulating UVB-induced targets of the p53 signaling pathway, IR irradiation appears to anticipate the UVB response and to prepare cells to better resist subsequent UV-induced stress. This is reinforced by the fact that IR preirradiation reduces the formation of UVB-induced thymine dimers.
Subject(s)
Infrared Rays , Skin/radiation effects , Tumor Suppressor Protein p53/radiation effects , Ultraviolet Rays/adverse effects , Adolescent , Adult , Apoptosis/radiation effects , Cell Cycle Proteins/biosynthesis , Cell Line , Cyclin-Dependent Kinase Inhibitor p21/biosynthesis , Fibroblasts/metabolism , Fibroblasts/radiation effects , Humans , In Vitro Techniques , Middle Aged , Nuclear Proteins/biosynthesis , Phosphorylation , Pyrimidine Dimers/biosynthesis , Pyrimidine Dimers/radiation effects , Signal Transduction/radiation effects , Skin/metabolism , Tumor Suppressor Protein p53/chemistry , Tumor Suppressor Protein p53/deficiency , Tumor Suppressor Protein p53/metabolismABSTRACT
In the gradual process of evolution, plants have developed natural sun protecting substances that enable continuous survival under direct and intense ultraviolet (UV) radiation. As part of our studies of plant-derived pigments that might constitute an alternative to conventional sunscreens, we have tested the ethanolic extracts of roots, stalks, and inflorescences of populations of wild Cichorum endivia subsp. Divaricatum (Asteraceae) in terms of protection against sunburn, and in prevention of UVB-induced pyrimidine dimer formation and IL-6 mRNA expression in the human keratinocyte cell line, HaCaT. Using ELISA technique for detection of pyrimidine dimers and RT-PCR for detection of IL-6, we found that the ethanolic extract of C. endivia roots absorbs radiation in the UVB spectrum and partially prevents induction of pyrimidine dimers and IL-6 expression. Application of the root extract on the skin prior to UVB irradiation totally prevented erythema. Our findings suggest that C. endivia extracts might possess sun-protective qualities that make them useful as sunscreens.
Subject(s)
Asteraceae/chemistry , Erythema/prevention & control , Interleukin-6/biosynthesis , Phytotherapy , Pyrimidine Dimers/biosynthesis , Sunscreening Agents/therapeutic use , Ultraviolet Rays/adverse effects , Administration, Cutaneous , Cell Line , Cell Survival , Erythema/etiology , Erythema/pathology , Gas Chromatography-Mass Spectrometry , Humans , Interleukin-6/genetics , Keratinocytes/drug effects , Keratinocytes/metabolism , Keratinocytes/radiation effects , Plant Extracts/radiation effects , Plant Extracts/therapeutic use , Plant Roots/chemistry , Plant Stems/chemistry , Pyrimidine Dimers/genetics , RNA, Messenger/biosynthesis , Reverse Transcriptase Polymerase Chain Reaction , Sunscreening Agents/radiation effectsABSTRACT
BACKGROUND: Ultraviolet (UV) irradiation has a broad spectrum of biological effects and a capacity to initiate skin carcinogenesis through DNA damage. The effect of different wave bands of UV light on the production of DNA damage in human skin in situ was studied with a broadband UV-B lamp TL-12 and a narrowband UV-B lamp TL-01. METHODS: Eight psoriasis patients participated in the study. Their minimal erythema dose was assessed separately for the two UV-B wave band ranges. Test areas of buttock skin were irradiated with the two spectrally differing lamps using erythemally equivalent UV doses of 40 and 80 mJ/cm2 CIE (Commission International de I'Eclairage). Punch biopsies were taken from the irradiated areas, and UV-induced DNA lesions (cyclobutane pyrimidine dimers, CPDs) in the skin were analyzed with a 32P high-performance liquid chromatography postlabelling method. RESULTS: No UV source-dependent differences in the induced levels of CPDs were detected in this study. CONCLUSION: CPD production with broadband TL-12 and narrowband TL-01 UV-B lamps in situ did not differ when erythemally equivalent UV doses were used. The preliminary result needs to be confirmed in a larger study.