ABSTRACT
BACKGROUND: High-performance sunscreen protects both healthy consumers and photosensitive patients from strong ultraviolet (UV) exposure. The sun-protection factor (SPF), which indicates the efficacy of UV protection, is determined using a prescribed sunscreen application thickness of 2.0 mg/cm(2). Therefore, users should apply at least 2.0 mg/cm(2) of sunscreen to obtain the level of UV protection expected from a product. In most cases, however, users apply insufficient amounts of sunscreen. AIM: To determine the amount of sunscreen applied under specific conditions, and the relationship between application thickness and SPF value in high-performance sunscreen. METHODS: The amount of applied sunscreen was calculated under practical conditions and conditions that directed a double application. The SPF values of high-performance sunscreen applied at three thicknesses (2.0, 1.0 and 0.5 mg/cm(2)) were determined according to the international SPF testing method. RESULTS. The relationship between SPF value and application thickness correlated in a logarithmic curve. The mean application thickness under practical conditions was approximately 1 mg/cm(2), and directing subjects to use a double application increased the application thickness to nearly 2 mg/cm(2). CONCLUSION: Encouraging a double application of sunscreen will help users apply products at a thickness sufficient to achieve expected SPF efficacy. We recommend that guidance on double application of sunscreen should be posted in public locations where sunscreen is likely to be in use.
Subject(s)
Skin/radiation effects , Sun Protection Factor , Sunburn/prevention & control , Sunscreening Agents/administration & dosage , Adult , Asian People , Female , Humans , Japan , Male , Middle AgedABSTRACT
Ultraviolet (UV) irradiation induces damage of the skin, and in particular, photoageing is known to be the result of chronic UV irradiation. Many investigations have attempted to clarify the mechanisms of photoageing induced by chronic UVA irradiation, but consensus has not been achieved yet by in vivo experiments, mostly due to differences among UV sources and animals used for experiments. In vitro experiments have shown that a single exposure to UVA irradiation causes overexpression of matrix metalloproteinases and denaturation of collagen, but the mechanisms of the photoageing effects of chronic UVA irradiation are still unclear. To examine the effects of chronic UVA irradiation, we used an in vitro fibroblast cellular ageing system as a model of photoageing. Chronic UVA irradiation of normal human fibroblasts induced shortening of the cellular life span and an increase of cellular diameter, in parallel with expression of senescence-associated beta-galactosidase. Extracellular degradation enzyme, matrix metalloproteinase 1 (MMP-1) was overexpressed after repeated UVA irradiation, but tissue inhibitor of metalloproteinase 1 (TIMP-1) expression was hardly changed by chronic UVA irradiation. We conclude that chronic UVA irradiation of normal human fibroblasts induces cellular functional changes, leading to accelerated cellular ageing and MMP-1 overexpression.
Subject(s)
Cellular Senescence/radiation effects , Dermis/radiation effects , Skin Aging/radiation effects , Biomarkers/analysis , Cell Proliferation/drug effects , Cell Proliferation/radiation effects , Cells, Cultured , Dermis/cytology , Dermis/enzymology , Fibroblasts/cytology , Fibroblasts/enzymology , Fibroblasts/radiation effects , Humans , Matrix Metalloproteinase 1/genetics , RNA, Messenger/analysis , Reactive Oxygen Species/pharmacology , Staining and Labeling , Tissue Inhibitor of Metalloproteinase-1/genetics , beta-Galactosidase/analysisABSTRACT
Singlet oxygen (1O2), a highly reactive and toxic intermediate, may play a role in photo-induced aging. We examined singlet oxygen generation from hematoporphyrin (HP) with UV-A, by monitoring the emission at 1,268 nm corresponding to 1O2 --> 3O2. Singlet oxygen was formed HP-dose-dependently in this system. We then investigated the reaction of singlet oxygen generated by UV-A irradiation with collagen, which is related to skin elasticity and softness. Collagen from skin was rapidly and dose-dependently cross-linked by singlet oxygen. The reaction was inhibited by NaN3, a selective quencher of singlet oxygen. In contrast, SOD (superoxide dismutase) and mannitol had no effect. These results suggested that cross-linking of collagen was caused by UV-A-generated singlet oxygen, not by any other reactive oxygen species. Compared with another multisubunit protein, alcohol dehydrogenase, collagen was cross-linked much more efficiently. Further, the finding that semicarbazide inhibited cross-linking of collagen showed that cross-links were formed between photooxidized histidyl residues and amino groups. Singlet oxygen generated by UV-A irradiation may contribute to cross-linking of collagen in the process of skin photoaging.
Subject(s)
Collagen/chemistry , Hematoporphyrins/chemistry , Oxygen/chemistry , Cross-Linking Reagents , Electrophoresis, Polyacrylamide Gel , Free Radicals/chemistry , Hematoporphyrins/radiation effects , Oxygen/radiation effects , Semicarbazides , Ultraviolet RaysABSTRACT
To elucidate the mechanism of phototoxicity induced as a side effect by some of the new quinolone antibiotics, we studied sparfloxacin (SPFX), lomefloxacin, enoxacin, ofloxacin, and ciprofloxacin. We first examined the photosensitized formation of reactive oxygen species such as singlet oxygen (1O2) and superoxide anion (O2-) mediated by the new quinolones. Although a large number of studies have been reported, there is no direct evidence that these drugs generate reactive oxygen species. We employed a near-infrared emission spectrometer to detect 1O2-specific emission (1268 nm), and the nitroblue tetrazolium reduction method to detect O2-. All the quinolones investigated in this study were found to produce 1O2. Four drugs, but not SPFX, produced O2-. We also examined photodynamic DNA strand-breaking activity as a possible mechanism to explain the participation of reactive oxygen species in the phototoxicity of the drugs. All the drugs exhibited photodynamic DNA strand-breaking activity. The inhibitory effect of scavengers of reactive oxygen species indicated that the main active species was 1O2. The DNA strand-breaking activity was correlated not with the 1O2-forming ability, but with the affinity of the drugs for DNA. This result may be due to the short lifetime of 1O2. These data suggested that the phototoxicity of the new quinolones was related to DNA damage caused by reactive oxygen species, especially 1O2.
Subject(s)
Anti-Infective Agents/toxicity , DNA Damage , Dermatitis, Phototoxic/etiology , Fluoroquinolones , Photosensitizing Agents/toxicity , Reactive Oxygen Species/metabolism , Animals , Anti-Infective Agents/metabolism , Ciprofloxacin/metabolism , Ciprofloxacin/toxicity , DNA/drug effects , DNA/metabolism , Enoxacin/metabolism , Enoxacin/toxicity , Free Radical Scavengers/metabolism , Hematoporphyrins/metabolism , Molecular Structure , Ofloxacin/metabolism , Ofloxacin/toxicity , Oxygen/metabolism , Photosensitizing Agents/metabolism , Quinolones/metabolism , Quinolones/toxicity , Spectroscopy, Near-Infrared , Superoxides/metabolismABSTRACT
Although singlet oxygen has been postulated to be a highly reactive and toxic intermediate, there has been no evidence of considerable generation of singlet oxygen in vivo level except for special cases. In this work, we firstly measured the near-infrared emission spectra corresponding to the O2(1 delta g) --> O2(3 epsilon g-) transition of singlet oxygen of cutaneous Propionibacterium acnes (P. acnes) porphyrin under laser excitation. A comparison of the singlet oxygen production of coproporphyrin, which is produced predominantly from P. acnes, with that of other photosensitizers revealed coproporphyrin to be a highly efficient singlet oxygen generator under ultraviolet light A irradiation on the skin. These results suggest that singlet oxygen can be generated on the skin surface from P. acnes porphyrin under ultraviolet irradiation and induce serious damage to the skin.
Subject(s)
Coproporphyrins/radiation effects , Oxygen , Propionibacterium acnes/metabolism , Skin/microbiology , Ultraviolet Rays , Coproporphyrins/isolation & purification , Humans , Kinetics , Lasers , Photosensitizing Agents/radiation effects , Propionibacterium acnes/isolation & purification , Singlet Oxygen , Spectrophotometry, InfraredABSTRACT
Singlet oxygen generation from laser-excited photosensitive dyes was measured directly using a sensitive near-infrared emission spectrometer to monitor the O2(1 delta g)-->O2(3 sigma -g) transition at 1268 nm. The emission intensity was proportional to both the laser power and the concentration of the dyes. The singlet oxygen producing ability of the dyes was compared with that of eosin YS as a standard in methanol. The relative efficiencies of singlet oxygen generation were determined for rose bengal, erythrosine B, phloxine B and eosin YS as 2.39, 1.73, 1.38, 1.00, respectively, while uranine showed no emission in this spectral region. Using rose bengal, erythrosine B, phloxine B and eosin YS, the efficiency of singlet oxygen generation correlated with the photobleaching reaction rate of azo-dyes by these dyes, suggesting singlet oxygen to be a species responsible for causing the photobleaching of azo-dyes. The halogen substituent effect on the efficiency of singlet oxygen generation from laser-excited photosensitive dyes was also examined systematically.
