Sunburn Cell Formation Research Articles

Inhibition of the CXCR3-mediated pathway suppresses ultraviolet B-induced pigmentation and erythema in skin

Skin pigmentation by ultraviolet (UV) B radiation is caused in part by inflammation mediated by chemokines and cytokines secreted by keratinocytes in the irradiated area. However, such inflammatory processes have not been well documented. To elucidate the inflammation processes caused by UVB irradiation using skin-lightening agents that suppress melanin synthesis after UVB irradiation. Utilizing a three-dimensional (3D) skin model, agents that suppressed formation of sunburn cells (SBC) after UVB irradiation were screened. Molecules whose expression was upregulated by UVB irradiation and attenuated by pretreatment with the agent were then screened by gene microarray to explore the mechanism of UVB irradiation. Messenger RNA expression of the molecules identified to be responsible for melanin biosynthesis was knocked down with a Tet-off shRNA lentivirus construct to confirm the involvement of the molecule in the pigmentation pathway following UVB irradiation. Paeonia suffruticosa Andrews (PSA) pretreatment suppressed SBC formation in the 3D skin model, and erythema formation and pigmentation in volunteers exposed to UVB irradiation. Comprehensive gene analysis after UVB irradiation showed upregulation of CXCR3 and its ligands, CXCL9/monokine induced by interferon (IFN)-γ (MIG), CXCL10/10-kDa IFN-γ-induced protein (IP-10) and CXCL11/inducible T-cell α-chemoattractant (I-TAC). Upregulation of these genes was partially suppressed by PSA pretreatment. Melanin biosynthesis increased upon stimulation of CXCR3 ligands (MIG, IP-10 or I-TAC) and decreased following CXCR3 downregulation by shRNA knockdown. UVB irradiation activates CXCR3-mediated signalling that leads to melanin synthesis. PSA pretreatment shows a lightening effect partly by attenuating CXCR3-mediated signalling at the transcriptional level.

UVB Radiation Induces Apoptosis in Keratinocytes by Activating a Pathway Linked to “BLT2-Reactive Oxygen Species”

The role of reactive oxygen species (ROS) in UVB-induced apoptosis has been established, but the molecular mechanisms of their production in response to UVB irradiation in keratinocytes are not well understood. In this study, we demonstrate that levels of BLT2, a low-affinity leukotriene B(4) receptor, and its ligands (LTB(4) and 12(S)-HETE) are greatly increased by UVB irradiation and are responsible for the UVB-induced ROS generation in human keratinocytes. Blockade of BLT2 with a BLT2-specific antagonist, LY255283, or with siBLT2 attenuated ROS production and apoptotic cell death detected by a number of criteria. Moreover, we found that the NADPH oxidase family protein Nox1 lies downstream of BLT2 and mediates UVB-induced ROS production and apoptosis. Topical treatment of mouse epidermal skin with LY255283 gave significant protection against UVB-induced sunburn-associated apoptotic damage. Finally, when BLT2-overexpressing transgenic mice were irradiated with UVB, we observed more extensive skin apoptosis. Taken together, our results demonstrate that a "BLT2-Nox1"-linked pathway has a crucial role in UVB-induced ROS generation and mediates apoptosis in human keratinocytes.

Regulation of DHICA-mediated antioxidation by dopachrome tautomerase: Implication for skin photoprotection against UVA radiation

Dopachrome tautomerase (Dct) is a critical enzyme in the melanogenesis pathway that isomerizes the intermediate dopachrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and influences the proportion of DHICA monomer incorporated into the 5,6-dihydroxyindole (DHI) polymer in eumelanin. To investigate whether Dct inactivation affects skin photoprotection against ultraviolet radiation, we examined levels of reactive oxygen species (ROS), sunburn cell formation, epidermal cell apoptosis, and melanin composition in skins of Dct −/− knockout mice compared with skins of wild-type C57BL/6 mice under UVA-induced oxidative stress. The results demonstrate that Dct inactivation elevates the level of ROS, increases the numbers of sunburn cells and apoptotic cells, and decreases the amount of eumelanin in the epidermis upon exposure to chronic UVA radiation. Moreover, we determined the effects of DHICA-melanin, DHI-melanin, and a mixture of both on hydroxyl radical generation in the Fenton reaction utilizing an electron spin resonance assay. DHICA-melanin exhibits a potent hydroxyl radical-scavenging activity, whereas DHI-melanin does not. Thus, this study suggests that DHICA monomers are required to incorporate into the DHI polymer backbone of eumelanin, which highlights the important role of Dct in the regulation of DHICA-mediated antioxidation.

Protein Kinase Cε Inhibits UVR-Induced Expression of FADD, an Adaptor Protein, Linked to both Fas- and TNFR1-Mediated Apoptosis

Protein kinase C (PKC)epsilon overexpression in FVB/N transgenic mice sensitized skin to UVR-induced development of squamous cell carcinomas and suppressed formation of sunburn cells, which are DNA-damaged keratinocytes undergoing apoptosis. Here, we elucidated the mechanisms associated with the inhibition of UVR-induced appearance of sunburn cells in PKCepsilon transgenic mice. We found that the inhibition of UVR-induced sunburn cell formation in PKCepsilon transgenic mice may be the result of the inhibition of the expression of Fas, Fas ligand, and the mammalian death adaptor protein termed Fas-associated with death domain (FADD). The adaptor protein FADD is the key component of the death-inducing signaling complex of both Fas and tumor necrosis factor receptor 1. A decreased expression of epidermal FADD was observed after a single UVR exposure. However, a complete loss of FADD expression was found after four (Monday, Wednesday, Friday, and Monday) repeated UVR exposures. FADD transmits apoptotic signals from death receptors to the downstream initiator caspase-8 and connects to the mitochondrial intrinsic apoptotic signal transduction pathway by the cleavage of Bid, a Bcl-2 family member. PKCepsilon-mediated loss of FADD expression inhibited UVR signals to the activation of both extrinsic and intrinsic apoptotic pathways.

Prevention of the ultraviolet effects on clinical and histopathological changes, as well as the heat shock protein-70 expression in mouse skin by topical application of algal UV-absorbing compounds

Sunscreens have long been used to protect against the acute effects of UV radiation. They can also have protective effects on chronic UV-induced changes, such as photoaging and skin cancer. Recent studies have focused on marine organisms as a source of natural bioactive molecules and some UV-absorbing algal compounds are under investigation as candidates for new natural sunscreens. The cutaneous photoprotective ability of the mycosporine-like aminoacids (MAAs) Porphyra-334 and shinorine (P-334+SH), high UV-absorbing compounds isolated from the red alga Porphyra rosengurttii, was evaluated by in vivo procedures in mouse skin. The expression of the heat shock protein HSP70 as a potential biomarker for acute UV damage was also investigated. A galenic formulation containing the MAA combination of P-334+SH was applied topically to the dorsal skin of SkhR-1 H hairless mice, which were irradiated with a single UV radiation dose of 3.87Jcm(-2) and compared with a combination of UVB- and UVA-absorbing reference filters. Clinical signs of sunburn, such as erythema and edema, as well as other quantifiable histological and biochemical parameters, such as the expression of the heat shock protein 70 and antioxidant enzyme activities, were measured from skin biopsies at 6, 24, 48 and 72h post-radiation. The formulation containing MAA prevented sunburn cell formation, as well as corneum stratum, malphigian, dermal and hypodermal thickening and other structural and morphological alterations observed in biopsies of non-photoprotected skin. A significant increase in Hsp70 was observed in the epidermis of non-photoprotected mouse skin, besides a de novo expression in deeper layers. P-334+SH protected against the significant decrease in superoxide dismutase and catalase activities observed in non-photoprotected mice. The topical application of P-334+SH protected against UV-induced skin damage in mice and contributed to maintaining the antioxidant defence system of the skin as well as Hsp70 expression.

Comparative analysis of solar radiation‐induced cellular damage between ex vivo porcine skin organ culture and in vitro reconstructed human epidermis

Reconstructed human epidermis models (RHE) constitute an innovative alternative to study phototoxicity and photoprotection in the cosmetic industry. However, little information is currently available concerning the harmful effects of solar-simulated radiation (SSR) in these in vitro skin models. In this study, the phototoxic effects of a single acute SSR dose of 275 kJ m(-2) were evaluated in a validated RHE model (from SkinEthic), and were compared with those obtained from an ex vivo skin organ culture recently developed from domestic pig ears. The RHE model was well differentiated in vitro and released a significant level of the cytosolic enzymes lactate dehydrogenase (LDH) and extracellular signal-related kinase 2 (ERK2) protein in the culture medium 24 h after SSR exposure. The SSR-induced cytotoxicity was related to the formation of sunburn cells and the appearance of DNA damage (thymine dimer and DNA fragmentation) in keratinocytes. Interestingly, these DNA alterations were associated with the activation of the caspase-3 protease, mainly in the basal layers of the epidermis. In addition, the RHE model responses were comparable with porcine skin following solar irradiation, and none of the above cellular responses was observed in non-irradiated skin models. Finally, topical application of a broad-spectrum UVB + A sunscreen formulation efficiently protected both the RHE and pig skin against the deleterious effects of SSR. Thus, both RHE and ex vivo pig skin organ culture models are complementary tools in the assessment of SSR-induced DNA damage and apoptosis, and they may be used to evaluate the photoprotective capacity of cosmetic formulations.

The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin

alpha-Hydroxy acids (alphaHAs) are reported to reduce signs of aging in the skin and are widely used cosmetic ingredients. Several studies suggest that alphaHA can increase the sensitivity of skin to ultraviolet radiation. More recently, beta-hydroxy acids (betaHAs), or combinations of alphaHA and betaHA have also been incorporated into antiaging skin care products. Concerns have also arisen about increased sensitivity to ultraviolet radiation following use of skin care products containing beta-HA. To determine whether topical treatment with glycolic acid, a representative alphaHA, or with salicylic acid, a betaHA, modifies the short-term effects of solar simulated radiation (SSR) in human skin. Fourteen subjects participated in this study. Three of the four test sites on the mid-back of each subject were treated daily Monday-Friday, for a total of 3.5 weeks, with glycolic acid (10%), salicylic acid (2%), or vehicle (control). The fourth site received no treatment. After the last treatment, each site was exposed to SSR, and shave biopsies from all four sites were obtained. The endpoints evaluated in this study were erythema (assessed visually and instrumentally), DNA damage and sunburn cell formation. Treatment with glycolic acid resulted in increased sensitivity of human skin to SSR, measured as an increase in erythema, DNA damage and sunburn cell formation. Salicylic acid did not produce significant changes in any of these biomarkers. Short-term topical application of glycolic acid in a cosmetic formulation increased the sensitivity of human skin to SSR, while a comparable treatment with salicylic acid did not.

Influence of grape seed proanthocyanidin extract on sunburn cell formation and p53 protein expression induced by acute ultraviolet injury

Objective To evaluate the influence of grape seed proanthocyanidin extract (GSPE) on sunburn cell formation and p53 protein expression induced by acute ultraviolet injury. Methods Ten volunteers were enrolled in this study. The buttock region served as the exposed region. Four areas were randomized and delineated on the buttock: one area (control area) received no exposure or product, the other 3 areas were exposed to two minimal erythema doses (MED) of simulated solar radiation (SSR) for 3 days. Of the 3 exposed areas, one area (SSR) received no product before exposure, one area (SSR + Veh) was pretreated with vehicle, the third area (SSR + GSPE) with the samples of GSPE. GSPE or vehicle was applied 30 minutes before each exposure at 2 μL/cm2. Skin biopsy was performed 24 hours after the last exposure, and skin specimens were subjected to hematoxylin eosin (HE) staining and histochemical analysis for p53 protein. Results There was a statistical difference in the number of sunburn cells per high power field (×200) between SSR sites and SSR + GSPE sites (29.8±11.1 cells vs 2.2±0.2 cells, P<0.01). A significant decrease was noticed in the account of p53 protein-positive cells per high power field (×200) in SSR + GSPE sites com-pared with the SSR sites (4.6±0.7 cells vs 19.3±3.4 cells, P<0.05). Conclusion GSPE exerts a poten-tial protective effect against acute ultraviolet injury and can serve as a natural sunscreen. Key words: Vitis; Proanthocyanidins; Light; Sunburn; Genes, p53

Ginsenoside Rb1 Suppresses Ultraviolet Radiation-Induced Apoptosis by Inducing DNA Repair

Ultraviolet (UV)-induced DNA damage is a crucial molecular trigger for sunburn cell formation and skin cancer. Nucleotide excision repair (NER) is the main mechanism in repairing UVB-induced DNA damage to mammalian cells. The purpose of this study was to investigate the functional role of ginsenoside Rb1 in UV-induced DNA damage and apoptosis in HaCaT (keratinocyte cell line) cells, and Xpc(-) knockout mouse keratinocytes. Flow cytometry and Hoechst 33258 staining were performed in analyzing UV-induced apoptosis in keratinocytes treated with ginsenoside Rb1. The ImmunoDotBlot assay was used to detect cyclobutane pyrimidine dimers, the main sign of DNA damage. Western blot analysis was applied for analyzing Xeroderma pigmentosum-C (XPC) and excision repair cross-complementing 1 (ERCC1), two of the NER proteins. Ginsenoside Rb1 inhibited UV-induced apoptosis of keratinocytes and caused a notable reduction in UV-specific DNA lesions which was due to induction of DNA repair. This reduction was not observed in Xpc(-) knockout keratinocytes. Ginsenoside Rb1 induced the expression of specific components of the NER complex, such as XPC and ERCC1. Our results demonstrate that ginsenoside Rb1 can protect cells from apoptosis induced by UV radiation by inducing DNA repair.

Protective effects of a topical antioxidant mixture containing vitamin C, ferulic acid, and phloretin against ultraviolet‐induced photodamage in human skin

Ultraviolet (UV) irradiation of the skin leads to acute inflammatory reactions, such as erythema, sunburn, and chronic reactions, including premature skin aging and skin cancer. In this study, the effects of a topical antioxidant mixture consisting of vitamin C, ferulic acid, and phloretin on attenuating the harmful effects of UV irradiation on normal healthy volunteers were studied using biomarkers of skin damage. Ten subjects (age, 18-60 years; Fitzpatrick skin types II and III) were randomized and treated with antioxidant product or vehicle control on the lower back for four consecutive days. On day 3, the minimal erythema dose (MED) was determined for each subject at a different site on the back. On day 4, the two test sites received solar-simulated UV irradiation 1-5x MED at 1x MED intervals. On day 5, digital images were taken, and 4-mm punch biopsies were collected from the two 5x MED test sites and a control site from each subject for morphology and immunohistochemical studies. UV irradiation significantly increased the erythema of human skin in a linear manner from 1x to 5x MED. As early as 24 h after exposure to 5x MEDs of UV irradiation, there were significant increases in sunburn cell formation, thymine dimer formation, matrix metalloproteinase-9 expression, and p53 protein expression. All these changes were attenuated by the antioxidant composition. UV irradiation also suppressed the amount of CD1a-expressing Langerhans cells, indicating immunosuppressive effects of a single 5x MED dose of UV irradiation. Pretreatment of skin with the antioxidant composition blocked this effect. This study confirms the protective role of a unique mixture of antioxidants containing vitamin C, ferulic acid, and phloretin on human skin from the harmful effects of UV irradiation. Phloretin, in addition to being a potent antioxidant, may stabilize and increase the skin availability of topically applied vitamin C and ferulic acid. We propose that antioxidant mixture will complement and synergize with sunscreens in providing photoprotection for human skin.

Compound K suppresses ultraviolet radiation-induced apoptosis by inducing DNA repair in human keratinocytes

Ultraviolet (UV)-induced DNA damage is a crucial molecular trigger for sunburn cell formation and skin cancer. Nucleotide excision repair (NER) is the main mechanism in repairing UVB-induced DNA damage of mammalian cells. The purpose of this study is to investigate the functional role of ginsenoside compound K on HaCaT cells (a keratinocyte-derived permanent cell line) irradiated by UV. Hoechst 33258 staining were performed in analyzing UV-induced apoptosis on keratinocytes which were treated with compound K. ImmunoDotBlot assay was used in detecting cyclobutane pyrimidine dimers, the main DNA damage. Western blot analysis was applied for analyzing XPC and ERCC1, two of the NER proteins. Compound K inhibited UV-induced apoptosis of keratinocytes and caused a notable reduction in UV-specific DNA lesions which was due to induction of DNA repair. In agreement with this, compound K induced the expression of particular components of the NER complex, such as XPC and ERCC1. Our results demonstrate that compound K can protect cells from apoptosis induced by UV radiation by inducing DNA repair.

Caspase‐3 Activation and DNA Damage in Pig Skin Organ Culture After Solar Irradiation

In the present study, a convenient and easy-to-handle skin organ culture was developed from domestic pig ears using polycarbonate Transwell culture inserts in 12-well plate. This alternative model was then tested for its suitability in analyzing the short-term effects of a single solar radiation dose (from 55 to 275 kJ.m(-2)). Differentiation of the pig skin was maintained for up to 48 h in culture, and its morphology was similar to that of fresh human skin. Solar irradiation induced a significant release of the cytosolic enzymes lactate dehydrogenase and extracellular signal-related kinase 2 protein in the culture medium 24 h after exposure. These photocytotoxic effects were associated with the formation of sunburn cells, thymine dimers and DNA strand breaks in both the epidermis and dermis. Interestingly, cell death was dose dependent and associated with p53 protein upregulation and strong caspase-3 activation in the basal epidermis. None of these cellular responses was observed in non-irradiated skin. Finally, topical application of a broad-spectrum UVB + A sunfilter formulation afforded efficient photoprotection in irradiated explants. Thus, the ex vivo pig ear skin culture may be a useful tool in the assessment of solar radiation-induced DNA damage and apoptosis, and for evaluating the efficacy of sunscreen formulations.

Attenuation of UVB-Induced Sunburn Reaction and Oxidative DNA Damage with no Alterations in UVB-Induced Skin Carcinogenesis in Nrf2 Gene-Deficient Mice

UV radiation is an important environmental factor in the pathogenesis of skin aging and cancer. Many harmful effects of UV radiation are associated with generation of reactive oxygen species. Cellular antioxidants prevent the occurrence and reduce the severity of UV-induced photoaging and diseases of the skin. The transcription factor Nrf2 (NF-E2-related factor 2) and its negative regulator protein, Keap1 (Kelch-like-ECH-associated protein 1), are central regulators of cellular antioxidant responses. We used nrf2-null mice to investigate the roles of the Nrf2-Keap1 system in protection of skin from harmful effects of UVB irradiation. A single irradiation with UVB induced stronger and longer lasting sunburn reaction in nrf2-null mice. Histological changes, including epidermal necrosis, dermal edema, inflammatory cell infiltration, sunburn cell formation, TUNEL-positive apoptotic cell formation, and accumulation of oxidative DNA products such as 8-hydroxy-2'-deoxyguanosine after UVB irradiation, were more prominent in nrf2-null mice. These findings indicate that the Nrf2-Keap1 pathway plays an important role in protection of the skin against acute UVB reactions, including cutaneous cell apoptosis and oxidative damage. However, there were no significant differences in skin carcinogenesis between nrf2-null and wild-type mice exposed to chronic UVB irradiation, suggesting that there is a complex and subtle balance between factors promoting and preventing photocarcinogenesis. Journal of Investigative Dermatology (2008) 128, 1773-1779; doi:10.1038/sj.jid.5701245; published online 17 January 2008.

Inhibition of Photocarcinogenesis by Platelet-Activating Factor or Serotonin Receptor Antagonists

The UV radiation in sunlight is the primary cause of nonmelanoma skin cancer. Moreover, UV exposure induces immune suppression. Early steps in the cascade of events leading to immune suppression are the binding of UV-induced platelet-activating factor (PAF) to its receptor and the binding of cis-urocanic acid, a photoreceptor for UVB radiation, to the serotonin (5-HT(2A)) receptor. Here, we tested the hypothesis that blocking the binding of PAF and 5-HT(2A) to their receptors would also block skin cancer induction. Hairless mice were injected with PAF or serotonin receptor antagonists and then exposed to solar-simulated UV radiation. We noted a significant and substantial decrease in skin cancer incidence in mice treated with the PAF or 5-HT(2A) receptor antagonists. Also, the PAF and/or serotonin receptor antagonists blocked skin cancer progression. The PAF and serotonin receptor antagonists worked in a synergistic fashion to block skin cancer induction. We also measured the effect that injecting PAF and 5-HT(2A) receptor antagonists had on UV-induced skin damage after a single UV exposure. We noted a significant decrease in UV-induced hypertrophy, sunburn cell formation, and apoptosis when the mice were injected with PAF and/or 5-HT(2A) receptor antagonists. These data indicate that treating UV-irradiated mice with PAF and 5-HT(2A) receptor antagonists blocks skin cancer induction in vivo, in part by reversing UV-induced damage to the skin and by preventing the induction of immune suppression.

Topical isoflavones provide effective photoprotection to skin

Isoflavones, one main group of phytoestrogens, have antioxidative and photoprotective effects in cellular and mouse studies. The aim of this study is to obtain a more comprehensive understanding of the isoflavone-mediated photoprotection with the pig skin model, a more human-resembling model. The pig skin was treated with five well-known isoflavone compounds (genistein, equol, daidzein, biochanin A, and formononetin) and one antioxidant combination solution of 15% vitamin C and 1% vitamin E and 0.5% ferulic acid (CEF) daily for 4 days. Skin was irradiated with solar-simulated UV irradiation, 1 to 5 minimal erythema dose (MED) at 1-MED intervals. Evaluation was carried out 24 h later by colorimeter-measured erythema and sunburn cell numbers. Topical application of 0.5% solutions of three individual phytoestrogens - genistein, daidzein, biochanin A - are better than similar solutions of equol or formononetin in protecting pig skin from solar-simulated ultraviolet (SSUV)-induced photodamage, as measured by sunburn cell formation and/or erythema. However, the protection was less than that provided by a topical combination antioxidant standard containing 15% L-ascorbic acid, 1%alpha-tocopherol, and 0.5% ferulic acid. Isoflavones provide effective photoprotection and are good candidate ingredients for protection against ultraviolet (UV) photodamage.

Catalase overexpression reduces UVB-induced apoptosis in a human xeroderma pigmentosum reconstructed epidermis

Xeroderma pigmentosum type C (XPC) is a rare autosomal recessive disorder that occurs due to inactivation of the XPC protein, an important DNA damage recognition protein involved in DNA nucleotide excision repair (NER). This defect, which prevents removal of a wide array of direct and indirect DNA lesions, is associated with a decrease in catalase activity. To test the hypothesis of a novel photoprotective approach, we irradiated epidermis reconstructed with XPC human keratinocytes sustainably overexpressing lentivirus-mediated catalase enzyme. Following UVB irradiation, there was a marked decrease in sunburn cell formation, caspase-3 activation and p53 accumulation in human XPC-reconstructed epidermis overexpressing catalase. Moreover, XPC-reconstructed epidermis was more resistant to UVB-induced apoptosis than normal reconstructed epidermis. While not correcting the gene defect, indirect gene therapy using antioxidant enzymes may be of help in limiting photosensitivity in XPC and probably in other monogenic/polygenic photosensitive disorders characterized by ROS accumulation.

Influence of hydroxypropyl-β-cyclodextrin on transdermal penetration and photostability of avobenzone

The objective of the present study was to determine the effects of hydroxypropyl-β-cyclodextrin (HPCD) complexation on the transdermal penetration and photostability of a model ultraviolet A (UVA) absorber, butyl methoxydibenzoylmethane (avobenzone), and to determine the influence of complexation on in vivo photoprotection. Avobenzone–HPCD complexation was demonstrated by differential scanning calorimetry. Formulations containing 0.12 mg/ml avobenzone and up to 30% (w/w) HPCD were prepared. Transdermal penetration was conducted using a modified Franz diffusion cell apparatus. As the concentration of HPCD was increased from 0% to 20%, transdermal permeation increased. Maximum flux occurred at 20% HPCD, where sufficient cyclodextrin was present to completely solubilize all avobenzone. When the concentration of HPCD was increased to 30%, transdermal penetration decreased, suggesting the formation of an avobenzone reservoir on the skin surface. Photostability of avobenzone was investigated under 100, 250, and 500 kJ/m 2 UVA irradiation. The 30% HPCD formulation was the most photostable, followed by 20%, 10%, and 0% formulations. In vivo, the 30% HPCD formulation afforded the best photoprotection, as evidenced by the lowest extent of sunburn cell formation and edema induction. This work indicates that inclusion of HPCD in sunscreen formulations may enhance photoprotection by reducing both skin penetration and photodecomposition of UV absorbers.

Protection from photodamage by topical application of caffeine after ultraviolet irradiation

Characterization of mechanisms that can reverse residual damage from prior skin exposure to ultraviolet (UV) would be of considerable biological and therapeutic interest. Topical caffeine application to mouse skin that had previously been treated with UV has been shown to inhibit the subsequent development of squamous cell carcinomas. We used an established mouse photodamage model to investigate other possible effects of topical caffeine application after UV. SKH-1 hairless mice were treated with ultraviolet B (UVB) followed immediately by topical application of caffeine or vehicle three times weekly for 11 weeks. Caffeine applied topically after UV treatment resulted in a significant decrease in UV-induced skin roughness/transverse rhytides as assessed by treatment-blinded examiners. Histologically, topical caffeine application after a single dose of UVB more than doubled the number of apoptotic keratinocytes as evaluated by sunburn cell formation, caspase 3 cleavage and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) staining. A trend towards decreased solar elastosis was noted in the caffeine-treated group although this was not statistically significant. Other histological parameters including epidermal hyperplasia, solar elastosis and angiogenesis were increased in mice treated with UV but topical application of caffeine did not alter these particular UV effects. These findings support the concept that topical application of caffeine to mouse skin after UV irradiation promotes the deletion of DNA-damaged keratinocytes and may partially diminish photodamage as well as photocarcinogenesis.

자외선 B 조사 마우스에서 피부손상에 대한 홍삼의 효과

The effects of red ginseng (RG) on the changes of ultraviolet (UV) light B radiation-induced apoptotic sun-burn cell (SBC) and epidermal ATPase-positive dendritic cell (DC) in SKH 1-hr or ICR mouse were investigated. The mice were treated with UVB (<TEX>$200mJ/cm^2$</TEX>) and were sacrificed 24 hours later. RG (50 mg/kg of body weight) or vehicle (saline) was given i.p. at 36 and 12 hours before irradiation, and 30 minutes after irradiation. RG cream (0.2%) or cream base (vehicle) was also topically treated at 24 hours and 15 minutes before irradiation, and immediately after irradiation. The skin of SKH 1-hr mouse prepared from the back of untreated mice exhibited about 0.3 SBC/cm length of epidermis, and 24 hours after UV irradiation, the applied areas show an increased number of SBCs. But the frequency of UVB-induced SBC formation was significantly reduced by intraperitoneal injection of RG extract. The numbers of DC in normal ICR mouse were <TEX>$628.00{\pm}51.56\;or\;663.20{\pm}62.58\;per\;mm^2$</TEX> of ear epidermis. By 1 day after UVB treatment, the number of ATPase-positive <TEX>$cells/mm^2$</TEX> were decreased by 39.0% or 27.1% in i.p. or topical application group with vehicle. The frequency of UVB (<TEX>$200mJ/cm^2$</TEX>)-induced DC decrease was reduced by treatment of RG as 31.3% in i.p. group and 22.4% in topical application group compared with the irradiation control group. The results presented herein that RG administration could reduce the extent of skill damages produced by UVB.

Protection of normal human reconstructed epidermis from UV by catalase overexpression

Reactive oxygen species (ROS) generated by ultraviolet (UV) irradiation are counterbalanced by endogenous antioxidant systems. To test the hypothesis of a novel photoprotective approach, we irradiated epidermis reconstructed with normal human keratinocytes overexpressing sustainably lentivirus-mediated catalase (CAT), copper/zinc superoxide dismutase (CuZnSOD) or manganese superoxide dismutase (MnSOD) enzymes. We found that following UVB irradiation there was a marked decrease in sunburn cell formation, caspase-3 activation and p53 accumulation in human reconstructed epidermis overexpressing CAT. Moreover, UVA-induced hypertrophy and DNA oxidation (8-oxodeoxyguanosine) were decreased by CAT overexpression. These effects were not achieved by overexpression of CuZnSOD or MnSOD. In conclusion, vector-mediated CAT overexpression could be a promising photoprotective tool against deleterious effects of UV irradiation such skin cancer especially in monogenic/polygenic photosensitive disorders characterized by ROS accumulation.