Powerful Skin Cancer Protection by a CPD-Photolyase Transgene (original) (raw)
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Frontiers in Immunology
Ultraviolet (UV) radiation is one of the most genotoxic, universal agents present in the environment. UVB (280-315 nm) radiation directly damages DNA, producing cyclobutane pyrimidine dimers (CPDs) and pyrimidine 6-4 pyrimidone photoproducts (6-4PPs). These photolesions interfere with essential cellular processes by blocking transcription and replication polymerases, and may induce skin inflammation, hyperplasia and cell death eventually contributing to skin aging, effects mediated mainly by keratinocytes. Additionally, these lesions may also induce mutations and thereby cause skin cancer. Photolesions are repaired by the Nucleotide Excision Repair (NER) pathway, responsible for repairing bulky DNA lesions. Both types of photolesions can also be repaired by distinct (CPD- or 6-4PP-) photolyases, enzymes that specifically repair their respective photolesion by directly splitting each dimer through a light-dependent process termed photoreactivation. However, as photolyases are absent ...
UV wavelength-dependent DNA damage and human non-melanoma and melanoma skin cancer
Photochemical & Photobiological Sciences, 2012
Ultraviolet (UV) irradiation from the sun has been epidemiologically and mechanistically linked to skin cancer, a spectrum of diseases of rising incidence in many human populations. Both nonmelanoma and melanoma skin cancers are associated with sunlight exposure. In this review, we discuss the UV wavelength-dependent formation of the major UV-induced DNA damage products, their repair and mutagenicity and their potential involvement in sunlight-associated skin cancers. We emphasize the major role played by the cyclobutane pyrimidine dimers (CPDs) in skin cancer mutations relative to that of (6-4) photoproducts and oxidative DNA damage. Collectively, the data implicate the CPD as the DNA lesion most strongly involved in human cancers induced by sunlight.
Molecular Medicine Reports, 2012
The exposure of human skin to ultraviolet radiation (UVR) results in the formation of DNA photolesions that give rise to photoaging, mutations, cell death and the onset of carcinogenic events. Photolyase (EC 4.1.99.3) is a DNA repair enzyme that reverses damage caused by exposure to UVR. We sought to investigate whether addition of photolyase enhances the protection provided by a traditional sunscreen (SS), by reducing the in vivo formation of cyclobutane-type pyrimidine dimers (CPDs) and UVR-induced apoptosis in human skin. Ten volunteers (Fitzpatrick skin type II) were exposed to solar-simulated (ss) UVR at a three times minimal erythema dose for 4 consecutive days. Thirty minutes prior to each exposure, the test materials [vehicle, SS (sun protection factor 50) alone, and SS plus photolyase from Anacystis nidulans] were applied topically to three different sites. One additional site was left untreated and one received ssUVR only. Biopsy specimens were taken 72 h after the last irradiation. The amount of CPDs and the extent of apoptosis were measured by ELISA. Photolyase plus SS was superior to SS alone in reducing both the formation of CPDs and apoptotic cell death (both P<0.001). In conclusion, the addition of photolyase to a traditional SS contributes significantly to the prevention of UVR-induced DNA damage and apoptosis when applied topically to human skin.
Enzyme plus light therapy to repair DNA damage in ultraviolet-B-irradiated human skin
Proceedings of the National Academy of Sciences, 2000
Ultraviolet-B (UVB) (290-320 nm) radiation-induced cyclobutane pyrimidine dimers within the DNA of epidermal cells are detrimental to human health by causing mutations and immunosuppressive effects that presumably contribute to photocarcinogenesis. Conventional photoprotection by sunscreens is exclusively prophylactic in nature and of no value once DNA damage has occurred. In this paper, we have therefore assessed whether it is possible to repair UVB radiationinduced DNA damage through topical application of the DNA-repair enzyme photolyase, derived from Anacystis nidulans, that specifically converts cyclobutane dimers into their original DNA structure after exposure to photoreactivating light. When a dose of UVB radiation sufficient to induce erythema was administered to the skin of healthy subjects, significant numbers of dimers were formed within epidermal cells. Topical application of photolyase-containing liposomes to UVB-irradiated skin and subsequent exposure to photoreactivating light decreased the number of UVB radiation-induced dimers by 40-45%. No reduction was observed if the liposomes were not filled with photolyase or if photoreactivating exposure preceded the application of filled liposomes. The UVB dose administered resulted in suppression of intercellular adhesion molecule-1 (ICAM-1), a molecule required for immunity and inflammatory events in the epidermis. In addition, in subjects hypersensitive to nickel sulfate, elicitation of the hypersensitivity reaction in irradiated skin areas was prevented. Photolyase-induced dimer repair completely prevented these UVB radiation-induced immunosuppressive effects as well as erythema and sunburn-cell formation. These studies demonstrate that topical application of photolyase is effective in dimer reversal and thereby leads to immunoprotection.
Effects of Chronic Low-Dose Ultraviolet B Radiation on DNA Damage and Repair in Mouse Skin1
Cancer Research, 1999
Chronic exposure to sunlight causes skin cancer in humans, yet little is known about how habitual exposure to low doses of ultraviolet B radiation (UVB) affects DNA damage in the skin. We treated Skh-1 hairless mice with daily doses of suberythemal UVB for 40 days and analyzed the amount and distribution of DNA photodamage using RIAs and immunofluorescence micrography. We found that DNA damage accumulated in mouse skin as a result of chronic irradiation and that this damage persisted in the dermis and epidermis for several weeks after the chronic treatment was terminated. Although the persistent damage was evenly distributed throughout the dermis, it remained in the epidermis as a small number of heavily damaged cells at the dermal-epidermal boundary. Rates of DNA damage induction and repair were determined at different times over the course of chronic treatment in response to a higher challenge dose of UVB light. The amount of damage induced by the challenge dose increased in response to chronic exposure, and excision repair of cyclobutane pyrimidine dimers and pyrimidine(6-4)pyrimidone dimers was significantly reduced. The sensitization of mouse epidermal DNA to photoproduct induction, the reduction in excision repair, and the accumulation of nonrepairable DNA damage in the dermis and epidermis suggest that chronic low-dose exposure to sunlight may significantly enhance the predisposition of mammalian skin to sunlight-induced carcinogenesis.
Journal of Investigative Dermatology, 2002
We have investigated the photoprotective properties of induced pigmentation using erythema and epidermal DNA photodamage as endpoints. Previously unexposed buttock skin of 12 young, healthy adults (six skin type II and six skin type IV) was exposed daily (Monday to Friday) for 2 wk (days 1±12) with 0.65 minimal erythema dose of solar simulated radiation. Mean skin type IV minimal erythema dose was 1.8-fold greater than for skin type II. Compared to skin type II, solar simulated radiation treatments produced less erythema and more tanning in skin type IV. To assess DNA photodamage, biopsies were taken and prepared for paraf®n sections that were stained with a monoclonal antibody for thymine dimers. Thymine dimers were quanti®ed by image analysis. The single exposure data (0.65 and 2 minimal erythema dose) showed that DNA damage was related to physical dose (J per cm 2 ) independent of skin type. Our data also showed that DNA photodamage accumulates in both skin types with repeated, suberythemal doses of solar simulated radiation. On day 12, there were more thymine dimers in skin type IV than skin type II, again indicating that physical rather than biologic dose determines the level of DNA damage. Comparisons on days 12 and 19, however, showed a much greater loss of thymine dimers in skin type IV, suggesting better thymine dimer repair. Protection factors for erythema and thymine dimers were calculated and shown to be about 2 in both skin types. This provides further indirect evidence that DNA is a chromophore for erythema, but also suggests that a tan may not be the major factor in natural photoprotection.
Different types of DNA damage play different roles in the etiology of sunlight-induced melanoma
Pigment Cell & Melanoma Research, 2010
The relationship between DNA damage, mutations and the initiation and progression of sunlight-induced melanoma has not yet been resolved. Recently, it has become apparent that the etiology of sunlight-induced melanoma is fundamentally different from sunlight-induced carcinoma, although both appear to be dependent on specific photoproducts produced in DNA by ultraviolet radiation (UVR). How DNA photoproducts are involved in the unique etiology of cutaneous malignant melanoma (CMM) compared to other types of skin cancer is central to understanding the nature of this disease and its prevention. Based on our results and published data, we propose a model for melanoma distinct from carcinoma, in which different types of DNA damage contribute to different stages of tumorigenesis. Epidemiological observations of human skin cancer as well as data from experimental animal models offers considerable insight into skin cancer etiology and the DNA damage involved. Because human CMM develops on parts of the body exposed to chronic (head and neck) as well as sporadic sunlight (trunk), divergent etiologies have been proposed (Walker, 2008). Murine and piscine melanoma models expose neonatal animals to a small number of erythemal UVB doses after which they receive no additional UVR. This is analogous to the "intermittent" or "sporadic" early childhood exposures often associated with truncal melanomas and differs from the "chronic" exposure history more closely associated with carcinoma and head and neck CMM. Additionally, in response to transgenic manipulation or interspecific hybridization, animal models acquire genetic factors that predispose them to CMM that mimic more the human UV-dependent truncal melanomas rather than the head and neck melanomas that are presumably associated with chronic sunlight exposure. The model we present here addresses truncal CMM that develop in response to early life (intermittent) exposure to UVR. Using Xiphophorus first generation backcross hybrids we recently demonstrated that intermittent early life exposures to UVB but not UVA induce CMM in these fishes (Mitchell et al. 2010) (Fig. 1A). This result corroborates the wavelength-dependence of melanoma found in mammalian models; that is, UVA does not induce melanomas after neonatal exposure in either the South American opossum (Monodephis domestica) (Robinson et al., 1998) or hepatocyte growth factor/scatter factor (HGF/SF) transgenic mice (De Fabo et al., 2004), both of which are susceptible to UVB-induced melanomagenesis. The most abundant damage induced by UVB irradiation results from the direct absorption of photons by DNA and includes the formation of cyclobutane pyrimidine dimers (CPD) and pyrimidine(6-4) pyrimidone dimers [(6-4)PD]. Within Xiphophorus, the amounts of thymine-cytosine CPDs and (6-4)PDs present in pigmented skin cells immediately after UVB irradiation are about the same (Fig. 1). Furthermore, the rate of removal of these lesions by photoreactivation is comparable and proportional to the reduction in melanoma frequency after the same light
The relative roles of DNA damage induced by UVA irradiation in human cells
Photochemical & Photobiological Sciences, 2013
UVA light (320-400 nm) represents approximately 95% of the total solar UV radiation that reaches the Earth's surface. UVA light induces oxidative stress and the formation of DNA photoproducts in skin cells. These photoproducts such as pyrimidine dimers (cyclobutane pyrimidine dimers, CPDs, and pyrimidine (6-4) pyrimidone photoproducts, 6-4PPs) are removed by nucleotide excision repair (NER). In this repair pathway, the XPA protein is recruited to the damage removal site; therefore, cells deficient in this protein are unable to repair the photoproducts. The aim of this study was to investigate the involvement of oxidative stress and the formation of DNA photoproducts in UVA-induced cell death. In fact, similar levels of oxidative stress and oxidised bases were detected in XP-A and NER-proficient cells exposed to UVA light. Interestingly, CPDs were detected in both cell lines; however, 6-4PPs were detected only in DNA repairdeficient cells. XP-A cells were also observed to be significantly more sensitive to UVA light compared to NER-proficient cells, with an increased induction of apoptosis, while necrosis was similarly observed in both cell lines. The induction of apoptosis and necrosis in XP-A cells using adenovirus-mediated transduction of specific photolyases was investigated and we confirm that both types of photoproducts are the primary lesions responsible for inducing cell death in XP-A cells and may trigger the skin-damaging effects of UVA light, particularly skin ageing and carcinogenesis. † Electronic supplementary information (ESI) available. See
Journal of Investigative Dermatology, 1998
It is generally presumed that xeroderma pigmentosum (XP) patients are extremely sensitive to developing UV erythema, and that they have a more than 1000-fold increased skin cancer risk. Recently established mouse models for XP can be employed to investigate the mechanism of these increased susceptibilities. In line with human data, both XPA and XPC knockout mice have been shown to have an increased susceptibility to UVB induced squamous cell carcinomas. In XPA knockouts, nucleotide excision repair of UV induced DNA photolesions is completely defective (i.e., both global genome repair and transcription coupled repair are defective). We determined the strand specific removal of cyclobutane pyrimidine dimers and pyrimidine [6-4] pyrimidone photoproducts from the p53 gene in cells from XPC knockout mice and wild-type littermates. S unburn is a UV induced inflammatory reaction that is characterized by cutaneous vasodilatation (erythema), and that can be followed by an increase in vascular permeability with exudation of fluid (edema) in the affected skin. The pathway leading to sunburn is most commonly thought to be activated by UV induced DNA damage. The evidence that supports a linkage between DNA damage and sunburn is that genetic diseases with defects in the removal of UV photoproducts, such as xeroderma pigmentosum (XP) and Cockayne syndrome (CS), are accompanied by increased sensitivity to sunburn (Cleaver and Kraemer, 1989; Bootsma, 1993). In addition, it has been shown in the opossum Monodelphis domestica that immediate removal of UV photoproducts by photoreactivation leads to a suppression of the erythemal response (Ley, 1985). Furthermore, the wavelengths that are the most effective in producing UV photolesions (namely, the UVB region) are also the most effective in producing erythema (Hacham et al, 1991) or edema (Johnson, 1978). The mechanism that connects DNA damage to the inflammatory reaction is unclear. UVB induced DNA damage may Manuscript