Effect of UVA fluence rate on indicators of oxidative stress in human dermal fibroblasts

Mitochondria-Targeted Hydrogen Sulfide Delivery Molecules Protect Against UVA-Induced Photoaging in Human Dermal Fibroblasts, and in Mouse Skin In Vivo

Aims: Oxidative stress and mitochondrial dysfunction play a role in the process of skin photoaging via activation of matrix metalloproteases (MMPs) and the subsequent degradation of collagen. The activation of nuclear factor E2-related factor 2 (Nrf2), a transcription factor controlling antioxidant and cytoprotective defense systems, might offer a pharmacological approach to prevent skin photoaging. We therefore investigated a pharmacological approach to prevent skin photoaging, and also investigated a protective effect of the novel mitochondria-targeted hydrogen sulfide (H₂S) delivery molecules AP39 and AP123, and nontargeted control molecules, on ultraviolet A light (UVA)-induced photoaging in normal human dermal fibroblasts (NHDFs) in vitro and the skin of BALB/c mice in vivo. Results: In NHDFs, AP39 and AP123 (50-200 nM) but not nontargeted controls suppressed UVA (8 J/cm²)-mediated cytotoxicity and induction of MMP-1 activity, preserved cellular bioenergetics, and increased the expression of collagen and nuclear levels of Nrf2. In in vivo experiments, topical application of AP39 or AP123 (0.3-1 μM/cm²; but not nontargeted control molecules) to mouse skin before UVA (60 J/cm²) irradiation prevented skin thickening, MMP induction, collagen loss of oxidative stress markers 8-hydroxy-2'-deoxyguanosine (8-OHdG), increased Nrf2-dependent signaling, as well as increased manganese superoxide dismutase levels and levels of the mitochondrial biogenesis marker peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α). Innovation and Conclusion: Targeting H₂S delivery to mitochondria may represent a novel approach for the prevention and treatment of skin photoaging, as well as being useful tools for determining the role of mitochondrial H₂S in skin disorders and aging. Antioxid. Redox Signal. 36, 1268-1288.

Wavelengths and temporal effects on the response of mammalian cells to UV radiation: Limitations of action spectra illustrated by genotoxicity

All photobiological events depend on the wavelength of the incident radiation. In real-life situations and in the vast majority of laboratory experiments, exposure always involves sources with various emission spectra spreading over a wide wavelength range. Action spectra are often used to describe the efficiency of a process at different wavelengths and to predict the effects of a given light source by summation of the individual effects at each wavelength. However, a full understanding of the biological effects of complex sources requires more than considering these concomitant events at each specific wavelength. Indeed, photons of different energies may not have additive but synergistic or inhibitory effects on photochemical processes and cellular responses. The evolution of a photobiological response with post-irradiation time must also be considered. These two aspects may represent some limitations to the use of action spectra. The present review, focused on mammalian cells, illustrates the concept of action spectrum and discusses its drawbacks using theoretical considerations and examples taken from the literature. Emphasis is placed on genotoxicity for which wavelength effects have been extensively studied. Other effects of UV exposure are also mentioned.

Caffeic acid derivatives isolated from Galinsoga parviflora herb protected human dermal fibroblasts from UVA-radiation

BACKGROUND

Among solar radiation, ultraviolet light is the most harmful for the skin, because of intracellular reactive oxygen species formation, leading to oxidative stress, cell damage and apoptosis. Crucial role in skin protection against oxidative stress play antioxidant enzymes regulated by Nrf2 transcription factor. Some plant-derived polyphenols are known to protect skin fibroblasts against UV through induction of Nrf2-dependent antioxidant genes expression.

PURPOSE

We previously found out that water extracts from Galinsoga sp. herb protected human dermal fibroblasts against UVA-induced oxidative stress and apoptosis. However, which compounds were responsible for such protective action remained unclear. Here, we investigated photoprotective potential and mechanism of action of two main isolated compounds, 2,3,5(2,4,5)-tricaffeoylaltraric acid and 2,4(3,5)-dicaffeoylglucaric acid, on human dermal fibroblasts (NHDF).

STUDY DESIGN/METHODS

NHDF cells were pretreated with tested compounds (6.25-50 µM) and irradiated with UVA (25 J/cm²). Intracellular ROS and GSH level, cell viability, cell membrane integrity and apoptosis were measured. HO-1 protein expression and Nrf2 transcription factor activation were also assessed.

RESULTS

Cells pretreated with tested compounds prior to UVA showed inhibition of intracellular ROS formation and increase of GSH level. Significant increase of cell viability was also observed, as well as decrease of LDH release and a the rate of apoptotic cells in comparison to untreated cells. Furthermore, tested compounds increased HO-1 expression and activated the Nrf2 transcription factor in NHDF cells.

CONCLUSION

Present study demonstrated that caffeic acid derivatives present in Galinsoga parviflora herb, in particular tricaffeoylaltraric acid may protect dermal fibroblasts against UVA-induced oxidative stress through activation of intracellular antioxidative system. Such caffeic acid derivatives are bioactive compounds which might prevent UV-induced photoageing and photocarcinogenesis.

UVA1 impairs the repair of UVB-induced DNA damage in normal human melanocytes

The exact correlation between melanoma and sun-light is still a controversially debated issue. Although natural sunlight contains various ratios of UVA and UVB, most investigators so far focused on the effects of single solar wavebands and neglected possible interactions. Therefore, in this study primary human melanocytes of three donors were simultaneously exposed to physiologic doses of UVA1 and UVB. Effects on apoptosis were analysed using annexin V assays and cell death ELISAs, and effects on DNA damage were investigated using southwestern slot blots. While UVA1 did not influence UVB-induced apoptosis, UVA1 impaired the repair of UVB-induced cyclobutane pyrimidine dimers (CPD) as the amount of CPD was 1.8 times higher in UVA1 + UVB than in UVB only exposed melanocytes six hours after irradiation. We conclude that UVA1 might contribute to melanomagenesis as it partially inhibits the repair of UVB-induced CPD in human melanocytes while it does not affect UVB-mediated apoptosis.

3-Amino-1,2,4-triazole Limits the Oxidative Damage in UVA-Irradiated Dysplastic Keratinocytes

Reactive oxygen species (ROS) generated by UVA irradiation affect the keratinocyte cell membrane, DNA, and proteins and may cause serious injury to the skin. Treating human dysplastic keratinocytes (DOK) with 3-amino-1,2,4-triazole (AMT), a common catalase inhibitor, induced a compensatory mechanism for the hydrogen peroxide detoxification, which included a rise in glutathione peroxidase and glutathione reductase activities. Here, we examined a possible role of AMT in protecting a human DOK cell line against UVA-induced damage. In DOK cells exposed to UVA irradiation, we observed a substantial decrease in antioxidant enzymatic activities, such as catalase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase and an increase in lipid peroxidation and protein oxidation levels. Treating DOK cells with AMT prior to UVA exposure enhanced the activities of glutathione peroxidase, glutathione reductase, and glutathione-S-transferase, relative to nontreated cells. The enhanced antioxidant activities were correlated with decreased protein oxidation levels. Based on these results, we suggest that AMT may protect dysplastic keratinocytes against the harmful effects of UVA radiation.

Sunlight damage to cellular DNA: Focus on oxidatively generated lesions

The routine and often unavoidable exposure to solar ultraviolet (UV) radiation makes it one of the most significant environmental DNA-damaging agents to which humans are exposed. Sunlight, specifically UVB and UVA, triggers various types of DNA damage. Although sunlight, mainly UVB, is necessary for the production of vitamin D, which is necessary for human health, DNA damage may have several deleterious consequences, such as cell death, mutagenesis, photoaging and cancer. UVA and UVB photons can be directly absorbed not only by DNA, which results in lesions, but also by the chromophores that are present in skin cells. This process leads to the formation of reactive oxygen species, which may indirectly cause DNA damage. Despite many decades of investigation, the discrimination among the consequences of these different types of lesions is not clear. However, human cells have complex systems to avoid the deleterious effects of the reactive species produced by sunlight. These systems include antioxidants, that protect DNA, and mechanisms of DNA damage repair and tolerance. Genetic defects in these mechanisms that have clear harmful effects in the exposed skin are found in several human syndromes. The best known of these is xeroderma pigmentosum (XP), whose patients are defective in the nucleotide excision repair (NER) and translesion synthesis (TLS) pathways. These patients are mainly affected due to UV-induced pyrimidine dimers, but there is growing evidence that XP cells are also defective in the protection against other types of lesions, including oxidized DNA bases. This raises a question regarding the relative roles of the various forms of sunlight-induced DNA damage on skin carcinogenesis and photoaging. Therefore, knowledge of what occurs in XP patients may still bring important contributions to the understanding of the biological impact of sunlight-induced deleterious effects on the skin cells.

Skin Treatment with Pulsed Monochromatic UVA1 355 Device and Computerized Morphometric Analysis of Histochemically Identified Langerhans Cells

Fluorescent or metal halide lamps are widely used in therapeutic applications in dermatological diseases, with broadband or narrow band emission UVA/UVA1 (320–400 nm) obtained with suitable passive filters. Recently, it has been possible for us to use a new machine provided with solid state source emitting pulsed monochromatic UVA1 355 nm. In order to evaluate the effects of this emission on immunocells of the skin, human skin samples were irradiated with monochromatic 355 nm UVA1 with different energetic fluences and after irradiation Langerhans cells were labeled with CD1a antibodies. The immunohistochemical identification of these cells permitted evaluating their modifications in terms of density into the skin. Obtained results are promising for therapeutical applications, also considering that a monochromatic radiation minimizes thermic load and DNA damage in the skin tissues.

Identification of influential events concerning the Antarctic ozone hole over southern Brazil and the biological effects induced by UVB and UVA radiation in an endemic treefrog species

The increased incidence of solar ultraviolet radiation (UV) due to ozone depletion has been affecting both terrestrial and aquatic ecosystems and it may help to explain the enigmatic decline of amphibian populations in specific localities. In this work, influential events concerning the Antarctic ozone hole were identified in a dataset containing 35 years of ozone measurements over southern Brazil. The effects of environmental doses of UVB and UVA radiation were addressed on the morphology and development of Hypsiboas pulchellus tadpole (Anura: Hylidae), as well as on the induction of malformation after the conclusion of metamorphosis. These analyzes were complemented by the detection of micronucleus formation in blood cells. 72 ozone depletion events were identified from 1979 to 2013. Surprisingly, their yearly frequency increased three-fold during the last 17 years. The results clearly show that H. pulchellus tadpole are much more sensitive to UVB than UVA light, which reduces their survival and developmental rates. Additionally, the rates of micronucleus formation by UVB were considerably higher compared to UVA even after the activation of photolyases enzymes by a further photoreactivation treatment. Consequently, a higher occurrence of malformation was observed in UVB-irradiated individuals. These results demonstrate the severe genotoxic impact of UVB radiation on this treefrog species and its importance for further studies aimed to assess the impact of the increased levels of solar UVB radiation on declining species of the Hylidae family.

Topical retinoids in skin ageing: a focused update with reference to sun-induced epidermal vitamin A deficiency

Vitamin A is an important constituent of the epidermis, where it plays a crucial role in epidermal turnover. A deficiency of epidermal vitamin A may be the consequence of nutritional vitamin A deficiency, exposure to sunlight or any UV source, oxidative stress or chronological ageing. As a consequence, any treatment aiming at increasing epidermal vitamin A would exert a protective effect against these deleterious conditions. Retinoids may counteract some deleterious actions of UV radiation by physical and biological mechanisms. Topical natural retinoic acid precursors such as retinaldehyde or retinol are less irritant than acidic retinoids and may prevent epidermal vitamin A deficiency due to nutritional deficiency, exposure to sunlight or any condition leading to free radical production. Retinoids may be combined with other compounds with complementary actions against ageing, nutritional deficiency and cancer, such as antioxidants, to potentiate their beneficial effects in the skin.

DNA damage as a biological sensor for environmental sunlight

Solar ultraviolet (UV) radiation is widely known as an environmental genotoxic agent that affects ecosystems and the human population, generating concerns and motivating worldwide scientific efforts to better understand the role of sunlight in the induction of DNA damage, cell death, mutagenesis, and ultimately, carcinogenesis. In this review, general aspects of UV radiation at the Earth's surface are reported, considering measurements by physical and biological sensors that monitor solar UV radiation under different environmental conditions. The formation of DNA photoproducts and other types of DNA damage by different UV wavelengths are compared with the present information on their roles in inducing biological effects. Moreover, the use of DNA-based biological dosimeters is presented as a feasible molecular and cellular tool that is focused on the evaluation of DNA lesions induced by natural sunlight. Clearly, direct environmental measurements demonstrate the biological impact of sunlight in different locations worldwide and reveal how this affects the DNA damage profile at different latitudes. These tools are also valuable for the quantification of photoprotection provided by commercial sunscreens against the induction of DNA damage and cell death, employing DNA repair-deficient cells that are hypersensitive to sunlight. Collectively, the data demonstrate the applicability of DNA-based biosensors as alternative, complementary, and reliable methods for registering variations in the genotoxic impact of solar UV radiation and for determining the level of photoprotection sunscreens provided at the level of DNA damage and cell death.

Hydrogen water intake via tube-feeding for patients with pressure ulcer and its reconstructive effects on normal human skin cells in vitro

Background

Pressure ulcer (PU) is common in immobile elderly patients, and there are some research works to investigate a preventive and curative method, but not to find sufficient effectiveness. The aim of this study is to clarify the clinical effectiveness on wound healing in patients with PU by hydrogen-dissolved water (HW) intake via tube-feeding (TF). Furthermore, normal human dermal fibroblasts OUMS-36 and normal human epidermis-derived cell line HaCaT keratinocytes were examined in vitro to explore the mechanisms relating to whether hydrogen plays a role in wound-healing at the cellular level.

Methods

Twenty-two severely hospitalized elderly Japanese patients with PU were recruited in the present study, and their ages ranged from 71.0 to 101.0 (86.7 ± 8.2) years old, 12 male and 10 female patients, all suffering from eating disorder and bedridden syndrome as the secondary results of various underlying diseases. All patients received routine care treatments for PU in combination with HW intake via TF for 600 mL per day, in place of partial moisture replenishment. On the other hand, HW was prepared with a hydrogen-bubbling apparatus which produces HW with 0.8-1.3 ppm of dissolved hydrogen concentration (DH) and −602 mV to −583 mV of oxidation-reduction potential (ORP), in contrast to reversed osmotic ultra-pure water (RW), as the reference, with DH of < 0.018 ppm and ORP of +184 mV for use in the in vitro experimental research. In in vitro experiments, OUMS-36 fibroblasts and HaCaT keratinocytes were respectively cultured in medium prepared with HW and/or RW. Immunostain was used for detecting type-I collagen reconstruction in OUMS-36 cells. And intracellular reactive oxygen species (ROS) were quantified by NBT assay, and cell viability of HaCaT cells was examined by WST-1 assay, respectively.

Results

Twenty-two patients were retrospectively divided into an effective group (EG, n = 12) and a less effective group (LG, n = 10) according to the outcomes of endpoint evaluation and the healing criteria. PU hospitalized days in EG were significantly shorter than in LG (113.3 days vs. 155.4 days, p < 0.05), and the shortening rate was approximately 28.1%. Either in EG or in LG, the reducing changes (EG: 91.4%; LG: 48.6%) of wound size represented statistically significant difference versus before HW intake (p < 0.05, p < 0.001). The in vitro data demonstrate that intracellular ROS as quantified by NBT assay was diminished by HW, but not by RW, in ultraviolet-A (UVA)-irradiated HaCaT cells. Nuclear condensation and fragmentation had occurred for UVA-irradiated HaCaT cells in RW, but scarcely occurred in HW as demonstrated by Hoechst 33342 staining. Besides, under UVA-irradiation, either the mitochondrial reducing ability of HaCaT cells or the type-I collagen construction in OUMS-36 cells deteriorated in RW-prepared culture medium, but was retained in HW-prepared culture medium as shown by WST-1 assay or immunostain, respectively.

Conclusions

HW intake via TF was demonstrated, for severely hospitalized elderly patients with PU, to execute wound size reduction and early recovery, which potently ensue from either type-I collagen construction in dermal fibroblasts or the promoted mitochondrial reducing ability and ROS repression in epidermal keratinocytes as shown by immunostain or NBT and WST-1 assays, respectively.

UVA irradiation of dysplastic keratinocytes: oxidative damage versus antioxidant defense

UVA affects epidermal cell physiology in a complex manner, but the harmful effects have been studied mainly in terms of DNA damage, mutagenesis and carcinogenesis. We investigated UVA effects on membrane integrity and antioxidant defense of dysplastic keratinocytes after one and two hours of irradiation, both immediately after exposure, and 24 h post-irradiation. To determine the UVA oxidative stress on cell membrane, lipid peroxidation was correlated with changes in fatty acid levels. Membrane permeability and integrity were assessed by propidium iodide staining and lactate dehydrogenase release. The effects on keratinocyte antioxidant protection were investigated in terms of catalase activity and expression. Lipid peroxidation increased in an exposure time-dependent manner. UVA exposure decreased the level of polyunsaturated fatty acids, which gradually returned to its initial value. Lactate dehydrogenase release showed a dramatic loss in membrane integrity after 2 h minimum of exposure. The cell ability to restore membrane permeability was noted at 24 h post-irradiation (for one hour exposure). Catalase activity decreased in an exposure time-dependent manner. UVA-irradiated dysplastic keratinocytes developed mechanisms leading to cell protection and survival, following a non-lethal exposure. The surviving cells gained an increased resistance to apoptosis, suggesting that their pre-malignant status harbors an abnormal ability to control their fate.

Extrafollicular dermal melanocyte stem cells and melanoma

Recent studies suggest that extrafollicular dermal melanocyte stem cells (MSCs) persist after birth in the superficial nerve sheath of peripheral nerves and give rise to migratory melanocyte precursors when replacements for epidermal melanocytes are needed on the basal epidermal layer of the skin. If a damaged MSC or melanocyte precursor can be shown to be the primary origin of melanoma, targeted identification and eradication of it by antibody-based therapies will be the best method to treat melanoma and a very effective way to prevent its recurrence. Transcription factors and signaling pathways involved in MSC self-renewal, expansion and differentiation are reviewed. A model is presented to show how the detrimental effects of long-term UVA/UVB radiation on DNA and repair mechanisms in MSCs convert them to melanoma stem cells. Zebrafish have many advantages for investigating the role of MSCs in the development of melanoma. The signaling pathways regulating the development of MSCs in zebrafish are very similar to those found in humans and mice. The ability to easily manipulate the MSC population makes zebrafish an excellent model for studying how damage to MSCs may lead to melanoma.

Ellagic acid protects human keratinocyte (HaCaT) cells against UVA-induced oxidative stress and apoptosis through the upregulation of the HO-1 and Nrf-2 antioxidant genes

UV radiation from the sun is a potent environmental risk factor in the pathogenesis of skin damage. Much of the skin damage caused by ultraviolet A (UVA) irradiation from the sun is associated with oxidative stress. The aim of this study was to investigate the protective role of ellagic acid (25-75 μM), a natural antioxidant, against UVA (5-20 J/cm(2))-induced oxidative stress and apoptosis in human keratinocyte (HaCaT) cells and to reveal the possible mechanisms underlying this protective efficacy. Ellagic acid pre-treatment markedly increased HaCaT cell viability and suppressed UVA-induced ROS generation and MDA formation. Moreover, ellagic acid pre-treatment prevented UVA-induced DNA damage as evaluated by the comet assay. Ellagic acid treatment also significantly inhibited the UVA-induced apoptosis of HaCaT cells, as measured by a reduction of DNA fragmentation, mitochondria dysfunction, ER stress, caspase-3 activation, and Bcl-2/Bax deregulation. Notably, the antioxidant potential of ellagic acid was directly correlated with the increased expression of HO-1 and SOD, which was followed by the downregulation of Keap1 and the augmented nuclear translocation and transcriptional activation of Nrf2 with or without UVA irradiation. Nrf2 knockdown diminished the protective effects of ellagic acid. Therefore, ellagic acid may be useful for the treatment of UVA-induced skin damage.

Ultraviolet radiation and echinoderms: past, present and future perspectives

There is general consensus that solar ultraviolet radiation (UVR) negatively impacts many marine species. Echinoderms are ubiquitous within the marine environment, with members of the phyla often long-lived and numerically dominant within the benthic macrofauna, consequently the impact of UVR on the population dynamics of these organisms will influence marine communities and ecosystems. Research to date has shown that exposure of echinoderms to solar UVR can, affect reproduction and development, change behaviour, cause numerous biochemical and physiological changes and potentially cause increased mutation rates, by causing DNA damage. There is also considerable evidence that echinoderms utilise several different mechanisms to protect themselves against excessive UVR and subsequent UVR-induced damage. However, these protective mechanisms may pose conflicting selection pressures on echinoderms, as UVR is an additional stressor in oceans subjected to anthropogenic-induced climate change. This review summarises our knowledge of the effects of UVR on the Echinodermata. We outline the research conducted to date, highlight key studies on UVR that have utilised echinoderms and look to the future of UVR research in a rapidly changing ocean.

Cellular and sub-cellular responses to UVA in relation to carcinogenesis

PURPOSE

UVA radiation (315-400 nm) contributes to skin aging and carcinogenesis. The aim of this review is to consider the mechanisms that underlie UVA-induced cellular damage, how this damage may be prevented or repaired and the signal transduction processes that are elicited in response to it.

RESULTS

Exposure to ultraviolet (UV) light is well-established as the causative factor in skin cancer. Until recently, most work on the mechanisms that underlie skin carcinogenesis focused on shorter wavelength UVB radiation (280-315 nm), however in recent years there has been increased interest in the contribution made by UVA. UVA is able to cause a range of damage to cellular biomolecules including lipid peroxidation, oxidized protein and DNA damage, such as 8-oxoguanine and cyclobutane pyrimidine dimers. Such damage is strongly implicated in both cell death and malignant transformation and cells have a number of mechanisms in place to mitigate the effects of UVA exposure, including antioxidants, DNA repair, and stress signalling pathways.

CONCLUSIONS

The past decade has seen a surge of interest in the biological effects of UVA exposure as its significance to the process of photo-carcinogenesis has become increasingly evident. However, unpicking the unique complexity of the cellular response to UVA, which is only now becoming apparent, will be a major challenge for the field of photobiology in the 21st century.

Solar disinfection (SODIS) and subsequent dark storage of Salmonella typhimurium and Shigella flexneri monitored by flow cytometry

Pathogenic enteric bacteria are a major cause of drinking water related morbidity and mortality in developing countries. Solar disinfection (SODIS) is an effective means to fight this problem. In the present study, SODIS of two important enteric pathogens, Shigella flexneri and Salmonella typhimurium, was investigated with a variety of viability indicators including cellular ATP levels, efflux pump activity, glucose uptake ability, and polarization and integrity of the cytoplasmic membrane. The respiratory chain of enteric bacteria was identified to be a likely target of sunlight and UVA irradiation. Furthermore, during dark storage after irradiation, the physiological state of the bacterial cells continued to deteriorate even in the absence of irradiation: apparently the cells were unable to repair damage. This strongly suggests that for S. typhimurium and Sh. flexneri, a relatively small light dose is enough to irreversibly damage the cells and that storage of bottles after irradiation does not allow regrowth of inactivated bacterial cells. In addition, we show that light dose reciprocity is an important issue when using simulated sunlight. At high irradiation intensities (>700 W m(-2)) light dose reciprocity failed and resulted in an overestimation of the effect, whereas reciprocity applied well around natural sunlight intensity (<400 W m(-2)).