Epidermal localization and protective effects of topically applied superoxide dismutase

Protective effects of Cu/Zn-SOD and Mn-SOD on UVC radiation-induced damage in NIH/3T3 cells and murine skin

Superoxide dismutase (SOD) is an antioxidant enzyme with multiple metal cofactors that can specifically clear reactive oxygen species (ROS), which plays an important role in a variety of ultraviolet-induced lesions. Therefore, SOD has the anti-ultraviolet radiation effect. The objective of this study was to compare the differences in the anti-ultraviolet radiation effect of SOD with distinct metal cofactors: Cu/Zn-SOD and Mn-SOD. SOD was first purified using hydrophobic interaction chromatography and ion-exchange chromatography. Second, the Methylthiazolyldiphenyl-tetrazolium bromide method and cell senescence kits were used to study the protective effect of SOD on ultraviolet-induced cell damage. Finally, the protective effect of SOD on ultraviolet -induced skin damage was histopathologically evaluated, and the expression levels of malondialdehyde (MDA) and matrix metalloproteinases (MMPs) in tissues were detected. The results showed that Cu/Zn-SOD was superior to Mn-SOD in promoting cell proliferation, alleviating cell damage, protecting skin structure, and regulating the expression levels of MDA and MMPs, and it has no side effects. In conclusion, Cu/Zn-SOD had a better anti-ultraviolet radiation effect than Mn-SOD, and it can be used in anti-aging and anti-ultraviolet skin-care products.

Copper/Zinc-Superoxide Dismutase in Human Epidermis: An Immunochemical Study

The localization of copper and zinc-superoxide dismutase in normal and neoplastic human skin was examined with immunochemical techniques. Skin samples were taken from males and females of different ages, UV exposed and non-exposed areas and basal-/spino-cellular carcinomas. The enzyme was localized diffusely in the cytoplasm and was also found in the nuclei of epidermal cells, endothelial cells and other dermis cell types. The dismutase content in the epidermis was higher in males than females, UV-exposed than non-exposed and young than old people. In the tumors, the enzyme content of the superficial epidermal layers was higher than in the deep tumoral epithelial cells. These data suggest that the localization of Cu, Zn-SOD in skin tissues reflects the gender and age of the subject, the cell types and their normal or diseased state. Further studies based on the investigation of systemic changes of this enzyme in physiological and pathological epidermis could provide additional information on tumor cell generation.

Protective Effect of Superoxide Dismutase Against Hair Graying in a Mouse Model¶

Oxygen free radicals play a role in the aging process, and the protective effect of various antioxidants has been intensively studied, in particular for cutaneous aging. Besides hereditary factors, free radical-mediated damage to melanocytes of the hair follicle has been considered as a mechanism for aging of the hair. It was the aim of this study to evaluate the role of photosensitization reactions for hair graying and to demonstrate potential protective effects of superoxide dismutase (SOD). Mice with black hair were depilated with the fingertips on a surface of 6 x 2.5 cm on both sides of the dorsum. The right side received five applications of a SOD-containing gel before exposure to psoralen (concentration 0.5 mg/mL) plus UV-A (365 nm, 4 J/cm2). The left side was pretreated in the same way with a gel free of SOD. When the hair started growing again, the SOD-protected side was covered with black hair, whereas the hair on the vehicle-treated side was gray or white in 27 of the 30 animals studied. The 0.01% SOD concentration was as protective as the 0.1% concentration. Heat-inactivated SOD, applied in another five animals, was not protective. Using fluorescent labeling of the SOD with fluorescein isothiocyanate, epifluorescence microscopy and digital imaging processing, we show that SOD applied to the skin surface penetrates through the follicular appendages, as well as through the unbroken stratum corneum. Our findings suggest that superoxide radicals, generated by interaction of UV-A light with the sensitizer, initiated the formation of secondary products with well-known DNA-damaging effects, such as lipid peroxidation products and tumor necrosis factor alpha. SOD prevented the damage to melanocyte DNA by dismutating superoxide. Photosensitization may be another mechanism for hair graying, which can be influenced by antioxidants. Given the large number of exogenous and endogenous sensitizers, this mechanism deserves further study for human hair graying.

Age-dependent generation of reactive oxygen species in the skin of live hairless rats exposed to UVA light

Aging proceeds by highly complicated biochemical processes, in which the involvement of the reactive oxygen species (ROS) and free radicals has been implicated. Although the relationship between UV-induced photoaging and ROS generation has been proposed, it has been difficult to establish direct proof of the generation of ROS in the skin under UV exposure. Recently, we reported finding endogenously generated ROS in the skin of live mice after UVA light exposure by a method of in vivo chemiluminescent detection, in which superoxide anion radical (*O2-) and singlet oxygen species (1O2) are contributed. In light of the results, we tried to understand the age-dependent changes in ROS generation in the skin of hairless rats under UVA exposure. Chemiluminescent levels due to ROS in the untreated and UVA-exposed skin decreased age dependently, and the signal intensities in old rats were significantly lower than those in young rats. However, the ratios of chemiluminescent intensities in the UVA-exposed skin to those in the untreated skin were significantly enhanced in an age-dependent manner. These results suggest that the antioxidative ability against ROS generation in the skin, possessed by antioxidant enzymes and low molecular weight antioxidants, is lowered age dependently.

Antioxidant enzyme activity in human stratum corneum shows seasonal variation with an age-dependent recovery

The stratum corneum, as the body's principal barrier to the environment, is continuously exposed to environmental sources of reactive oxygen species like ultraviolet light, ozone, and pollution. Reactive oxygen species are believed to be involved in cancer, aging, and inflammatory skin disorders. We have developed a method to measure catalase and superoxide dismutase activity on tape strippings from the human stratum corneum and demonstrated a gradient of antioxidant enzyme activity across the stratum corneum with decreasing levels towards the skin surface. Sun exposure resulted in a seasonal variation of the catalase activity in stratum corneum, with low activities in summer and higher activities in winter for the same person, whereas superoxide dismutase activity in stratum corneum did not seem to vary in those conditions. Exposure of human skin to broadband ultraviolet-A resulted in a dose-dependent deactivation of the catalase activity in stratum corneum within 24 h, whereas exposure to ultraviolet-B had no effect. Superoxide dismutase activity in stratum corneum was not affected by ultraviolet-A or ultraviolet-B irradiation within 24 h. After exposure to a dose of 15 J per cm2 broadband ultraviolet-A, full recovery of the catalase activity occurred in 3-4 wk at an age-dependent rate. We conclude that sun exposure results in a disturbed catalase to superoxide dismutase ratio in the stratum corneum. This may lead to an increased vulnerability to oxidative damage in stratum corneum barrier components. These results therefore stress the importance of providing efficient protection for this internal defense mechanism in sun-exposed areas of the skin.

Parameters related to oxygen free radicals in human skin: a study comparing healthy epidermis and skin cancer tissue

In vitro studies with tumor cells have demonstrated that oxygen free radicals are involved in the development of skin cancers and that variations in the body's defense mechanisms can modify the course of the disease. To assess the validity of this hypothesis in spontaneous tumors, we determined glutathione S-transferase, superoxide dismutase, reduced and oxidized glutathione, and thiobarbituric acid reactive substances in healthy whole skin (n = 95), dermis (n = 73), and epidermis (n = 69). The values were compared with those obtained in three types of skin cancer: basal cell carcinoma (n = 16), squamous cell carcinoma (n = 6), and melanoma (n = 33). In healthy skin, glutathione S-transferase, superoxide dismutase, reduced glutathione, and oxidized glutathione were higher in epidermis than in dermis, whereas thiobarbituric acid reactive substances were higher in dermis than in epidermis; whole skin had intermediate values. These results suggest that there is an induction of some anti-oxygen free radicals mechanisms in epidermis as a result of increased oxygen free radicals production. Glutathione S-transferase and thiobarbituric acid reactive substances were higher in all types of tumor than in healthy epidermis but oxidized glutathione was lower. Reduced glutathione and superoxide dismutase activity were lower in basal cell carcinoma and squamous cell carcinoma samples. Glutathione S-transferase increased, whereas superoxide dismutase and thiobarbituric acid reactive substances decreased in melanoma samples in direct relation to the Clark levels. Higher glutathione S-transferase activity, particularly in the most invasive forms of melanoma, indicates that this type of cancer is more malignant. Similarly, a decrease in superoxide dismutase activity can also encourage progression of the tumor. These results are in accord with those from tumor cell cultures and could suggest new strategies (gene therapy) for managing skin cancer.

Copper, zinc-superoxide dismutase protects from ultraviolet B-induced apoptosis of SV40-transformed human keratinocytes: the protection is associated with the increased levels of antioxidant enzymes

It has been reported that cellular oxidative stress induces apoptosis. Ultraviolet radiation that generates reactive oxygen intermediates (ROIs) also induces apoptosis. Superoxide dismutase (SOD) is among the most active scavengers of ROIs, providing defense against the cellular oxidative stress. Mammalian cells express two isozymes of SOD, copper, zinc-SOD (Cu, Zn-SOD) and manganese-SOD (Mn-SOD). Using SV40-transformed human keratinocytes (SVHK cells), we investigated the role of SODs in the ultraviolet B (UVB) irradiation-induced apoptosis. UVB irradiation decreased transiently Cu, Zn- and Mn-SOD activities and their protein levels, with subsequent recovery to the basal levels by 24 h. The UVB-induced decrease in SOD activity was dose-dependent and the maximal effect was obtained at 75 mJ/cm(2). The decrease in Cu, Zn-SOD was more marked than that in Mn-SOD. The cell death assay, annexin-V/propidium iodide flow cytometry, and DNA fragmentation analysis revealed that UVB irradiation induces apoptosis in SVHK cells. The UVB-induced apoptosis was suppressed by the treatment of antioxidants, catalase, glutathione, and alpha-tochopherol. The stable transfection of Cu, Zn-SOD expression vectors into SVHK cells was accompanied by the increased activities of antioxidant enzymes, catalase, and glutathione reductase, as well as glutathione and the cells were shown to be more resistant to UVB-induced apoptosis. In contrast, the transfection of Mn-SOD affected neither activities of antioxidant enzymes nor the UVB-induced apoptosis. The transfection of Cu, Zn-SOD antisense oligomers but not sense oligomers into SVHK or Cu, Zn-SOD cDNA-transfected SVHK (C2) cells significantly decreased the antioxidant enzyme activities and increased the UVB-induced apoptosis. On the other hand, the transfection of Mn-SOD antisense oligomers did not affect the UVB-induced apoptosis. These results suggest that the transfection of Cu, Zn-SOD expression vector, which is accompanied by the increased level of antioxidant enzymes, suppresses the UVB-induced apoptosis of SVHK cells.

Oxyradical-mediated clastogenic plasma factors in psoriasis: increase in clastogenic activity after PUVA

Psoriasis is a common skin disorder characterized by hyperproliferation and incomplete differentiation of epidermal keratinocytes. Psoralen plus UVA (PUVA) is one of the treatments proposed for this disease. We had reported previously that exposure of regular blood cultures from healthy donors to PUVA leads to chromosomal breakage via the formation of transferable clastogenic materials, a phenomenon inhibitable by superoxide dismutase. In the present paper we show that these clastogenic factors (CF) are also formed in vivo. The CF were found in about 50% of the psoriasis patients studied (14 out of 31). In PUVA-treated psoriasis patients, the clastogenic activity of the plasma increased significantly between the first and the last (16th) exposure to PUVA. We hypothesize that CF formation in psoriasis is similar to that in other diseases accompanied by oxidative stress, in particular chronic inflammatory diseases with autoimmune reactions such as lupus erythematosus, progressive systemic sclerosis, rheumatoid arthritis and others. Increased superoxide production by phagocytes, formation of lipid peroxidation products and release of cytokines are considered to be responsible for the superoxide-stimulating and chromosome-damaging properties of patients' plasma. During PUVA therapy, superoxide generated via the interaction of psoralen with UVA may contribute to CF formation in addition to superoxide from inflammatory cells. An increased risk of cancer and leukemia is observed in diseases accompanied by CF formation. Therefore CF may contribute to the well-known risk of photocarcinogenesis by PUVA therapy. This additional risk may be preventable by antioxidants and superoxide scavengers.