metallothionein and Sunburn

Photoaging and photocarcinogenesis are the two Janus faces of skin photodamage. Reactivity-based design of prototype agents that antagonize, modulate and reverse the chemistry of skin photodamage holds promise in delivering unprecedented therapeutic benefit. In contrast to structure-based approaches that use selective ligands to target macromolecules, reactivity-based drug discovery uses chemical reagents as therapeutics to target reactive chemical species as key mediators of skin photo-oxidative stress. The following classes of reactivity-based agents for skin photoprotection can be distinguished based on their mechanism of action: direct antagonists of photo-oxidative stress (sunscreens, quenchers of photo-excited states, antioxidants, redox modulators and glycation inhibitors) and skin photo-adaptation inducers (nuclear factor erythroid 2-related factor 2 [Nrf2] activators, heat-shock response inducers and metallothionein inducers).

Topics: Animals; Antioxidants; Chelating Agents; Drug Design; Glycation End Products, Advanced; Glycosylation; Heat-Shock Response; Humans; Metallothionein; Neoplasms, Radiation-Induced; NF-E2-Related Factor 2; Oxidation-Reduction; Oxidative Stress; Photochemistry; Reactive Oxygen Species; Signal Transduction; Skin; Skin Aging; Skin Neoplasms; Sunburn; Sunscreening Agents; Ultraviolet Rays; Up-Regulation

The goji berry, Lycium barbarum, has long been recognised in traditional Chinese medicine for various therapeutic properties based on its antioxidant and immune-modulating effects. This study describes the potential for orally consumed goji berry juice to alter the photodamage induced in the skin of mice by acute solar simulated UV (SSUV) irradiation. In Skh:hr-1 hairless mice, 5% goji berry juice significantly reduced the inflammatory oedema of the sunburn reaction. Dilutions of goji berry juice between 1% and 10% dose-dependently protected against SSUV-induced immunosuppression, and against suppression induced by the mediator, cis-urocanic acid, measured by the contact hypersensitivity reaction. The immune protection could not be ascribed to either the minor excipients in the goji juice, pear and apple juice, nor the vitamin C content, nor the preservative, and appeared to be a property of the goji berry itself. Antioxidant activity in the skin was demonstrated by the significant protection by 5% goji juice against lipid peroxidation induced by UVA radiation. Furthermore, two known inducible endogenous skin antioxidants, haem oxygenase-1 and metallothionein, were found to be involved in the photoimmune protection. The results suggest that consumption of this juice could provide additional photoprotection for susceptible humans.

Topics: Animals; Antioxidants; Beverages; Drinking; Edema; Female; Heme Oxygenase-1; Hypersensitivity; Immunosuppression Therapy; Inflammation; Lipid Peroxidation; Lycium; Metallothionein; Mice; Mice, Hairless; Oleic Acids; Oxidative Stress; Radiation Injuries, Experimental; Skin Diseases; Sunburn; Ultraviolet Rays

Events that induce expression of the metallothionein (MT) gene, such as injection of cadmium chloride, cold stress or topical application of 1,25-dihydroxyvitamin D3, can deplete the number of ultraviolet (UV) B-induced sunburn cells (SBC) in mouse skin in vivo. MT-null mouse skin explants exhibit reduced tolerance to UVB injury in vitro. However, the in vivo response of MT-null mice to UVB injury has not been investigated. In the present study, we investigated the role of the MT gene on UVB injury in vivo. MT-null mice that are deficient in MT-I and MT-II genes were studied and compared with homozygous wild-type mice. Mouse dorsal skin was irradiated with 0.05, 0.70 and 1.40 J/cm2 UVB. The thickness of the dorsal skin was measured with a spring micrometer before and 24 h after UVB irradiation. In addition, SBC were counted 24 h after UVB irradiation. No significant difference was found in the change of skin thickness between MT-null mice and control mice irradiated with low-dose UVB (0.05 J/cm2) (Student's t-test, t = 1.519, P = 0.167). At higher doses (0.70 and 1.40 J/cm2), the skin of MT-null mice became much thicker than that of control mice (Student's t-test, t = 6.576, P < 0.01 and t = 3.142, P = 0.007, respectively). More SBC were detected in MT-null mice skin irradiated with the highest dose of UVB (1.40 J/cm2) (Student's t-test, t = 4.258, P < 0.01). These results suggest that the MT gene in mice has a photoprotective role in vivo.

Topics: Animals; Dose-Response Relationship, Radiation; Female; Metallothionein; Mice; Mice, Knockout; Skin; Sunburn; Ultraviolet Rays

We have shown previously that injection of cadmium chloride (Cd(2+)) depletes the number of ultraviolet B (UVB)-induced sunburn cells (SBC) in the mouse skin in vivo and that Cd(2+) treatment enhances UVB resistance in cultured keratinocytes in vitro, indicating the photoprotective role of Cd(2+)-induced metallothioneins (MTs) with antioxidant property against UVB injury. However, there has been no direct evidence for the role of MTs in UV protection. To improve our understanding of MTs in photoprotection, MT-null mouse deficient in MT-1 and MT-2 genes was studied. Skin explants were preliminarily exposed to medium alone, Cd(2+) and Cd(2+) plus buthionine S, R-sulfoximine (BSO), an inhibitor of glutathione synthesis. We then compared the number of UVB-induced SBC and apoptotic cells (AC) in the epidermis of MT-null mice with that of control mice using organ culture systems. The skin of MT-null mice developed a greater number of SBC and AC than did that of normal mice in all experimental conditions. These findings indicate that the skin of MT-null mouse is readily injured by UVB irradiation. MT-null mouse provided direct evidence of the photoprotective effect of cellular MTs in the skin.

Topics: Animals; Apoptosis; Cadmium Chloride; Culture Techniques; Keratinocytes; Male; Metallothionein; Mice; Mice, Knockout; Radiation Tolerance; Reactive Oxygen Species; Skin; Sunburn; Ultraviolet Rays

Sunburn cells are thought to represent ultraviolet B-induced apoptotic keratinocytes. It has been demonstrated that enzymatic and nonenzymatic antioxidants effectively suppress sunburn cell formation, indicating that reactive oxygen species may play a role in the progression of ultraviolet B-induced apoptosis. Metallothionein, a cytosol protein, has antioxidant activity, and overexpression of metallothionein has been reported to reduce the number of sunburn cells in mouse skin. We have also demonstrated that overexpression of metallothionein inhibits ultraviolet B-induced DNA ladder formation in mouse keratinocytes. These findings support the hypothesis that cellular metallothionein may play an important role in the inhibition of ultraviolet B-induced apoptosis in keratinocytes through its antioxidant activity. In the present study, we investigated the effects of beta-thujaplicin, an extract from the woods of Thuja plicata D. Don. and Chamaecyparis obtuse, Sieb. et Zucc., on ultraviolet B-induced apoptosis in keratinocytes and on metallothionein induction. Topical application of beta-thujaplicin decreased the number of ultraviolet B-mediated sunburn cells and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling-positive cells in mouse ear skin. Incubation with beta-thujaplicin suppressed ultraviolet B-induced DNA ladder formation in cultured mouse keratinocytes. Histochemical analysis showed that topical application of beta-thujaplicin induced metallothionein protein in mouse skin. Northern analysis and western blotting revealed significant induction of metallothionein mRNA and metallothionein protein, respectively, in beta-thujaplicin-treated cultured mouse keratinocytes. These findings indicate that beta-thujaplicin inhibits ultraviolet B-induced apoptosis in keratinocytes and strongly suggest that the inhibitory mechanism is due to the antioxidant activity of metallothionein induced by the agent.

Topics: Animals; Anti-Infective Agents; Apoptosis; Biotin; Cadmium; Cell Survival; Cells, Cultured; DNA Fragmentation; DNA Nucleotidylexotransferase; Female; Keratinocytes; Metallothionein; Mice; Mice, Inbred BALB C; Monoterpenes; RNA, Messenger; Sunburn; Tropolone; Ultraviolet Rays

We have shown previously that injection of cadmium chloride (Cd2+) depletes the number of ultraviolet B (UVB)-induced sunburn cells in the mouse skin in vivo, and that Cd2+ treatment enhances UVB resistance in cultured keratinocytes in vitro, indicating the photoprotective role of Cd2+-induced metallothioneins (MT) with antioxidant property against UVB injury; however, there has been no direct evidence for the role of MT in UV protection. To improve our understanding of MT in photoprotection, MT-null mouse deficient in its MT-1 and MT-2 genes was studied. Skin explants were preliminarily exposed to medium alone, Cd2+ and Cd2+ plus buthionine S,R-sulfoximine, an inhibitor of glutathione synthesis. We then compared the number of UVB-induced sunburn cells and apoptotic cells in the epidermis of MT-null mice with that of control mice using organ culture systems. The skin of MT-null mice developed a greater number of sunburn cells and apoptotic cells than did that of normal mice in all experimental conditions. These findings indicate that the skin of MT-null mouse is readily injured by UVB irradiation. MT-null mouse provided direct evidence of the photoprotective effect of cellular MT in the skin.

Topics: Animals; Apoptosis; Cadmium; In Situ Nick-End Labeling; Male; Metallothionein; Mice; Skin; Sunburn; Sunscreening Agents; Ultraviolet Rays

Previously cadmium chloride was successfully used to prevent sunburn cell (SBC) induction in mouse skin in vivo and to promote human cell survival in vitro after UVB exposure, indicating a protective effect of cadmium-induced metallothionein (MT) with the property of anti-oxidant action. Although cadmium is a potent inducer of MT, the cytotoxic metal is not available for clinical use. The aim of this study is to affirm MT gene expression by the active for of vitamin D3, 1,25-dihydroxyvitamin D3, [1,25(OH)2D3] in cultured keratinocytes and examine in vivo and in vitro the photo-protective effects of 1,25(OH)2D3. Northern hybridization with human MT-IIa cDNA showed a significant increase in the gene expression of MT in the cells treated with 1,25(OH)2D3. Intraperitoneal injection and topical application of 1,25(OH)2D3 caused a significant reduction in SBC formation in mouse skin after UVB administration. The experiment showed the existence of an optimum level of 1,25(OH)2D3 for reducing photodamage. The cells exposed to 1,25(OH)2D3 showed increased tolerance (cell survival) to UVB injury. 1,25(OH)2D3-induced MT may act as a radical scavenger in oxygen-mediated UV injury including SBC formation in the skin. These results indicate that 1,25(OH)2D3 may be practically applied to humans for the purpose of photoprotection.

Topics: Animals; Calcitriol; Cell Death; Cell Survival; Cells, Cultured; Gene Expression; Keratinocytes; Metallothionein; Mice; Mice, Inbred BALB C; Rats; Skin; Sunburn; Ultraviolet Rays