UVA Photons Research Articles

UV LED ageing of polymers for PV cell encapsulation

Encapsulation polymers in terrestrial solar modules degrade due to ultraviolet radiation from the sun. To assess a polymer’s durability under UV light, accelerated aging tests can be conducted. A new LEDs device allows us to investigate the effects of temperature, irradiation, and UV source spectrum on the photooxidation mechanism and kinetics of two polyethylene-based commercial encapsulants, differentiated by the presence or absence of UV absorbers. The photooxidation rate of the polymer matrix increases as the temperature and irradiance increase between 62 and 82 °C, and 12 and 28 W.m−2, respectively. In the last case, the photooxidation rate is not proportional to the number of photons. Finally, we observed different distributions of degradation products under UVB radiation at 305 nm compared to those under UVA radiation at 365 nm. UVB photons enable Norrish reactions that are not possible with UVA alone. Special care is needed to maintain a balance between UVA and UVB photons to ensure representative durability tests. With a few adjustments to their emission spectrum, UV LED devices appear to be good candidates for accelerated aging of encapsulation polymers.

Fast Sulfate Formation Initiated by the Spin-Forbidden Excitation of SO2 at the Air-Water Interface.

The multiphase oxidation of SO2 to sulfate in aerosol particles is a key process in atmospheric chemistry. However, there is a large gap between the observed and simulated sulfate concentrations during severe haze events. To fill in the gaps in understanding SO2 oxidation chemistry, a combination of experiments and theoretical calculations provided evidence for the direct, spin-forbidden excitation of SO2 to its triplet states using UVA photons at an air-water interface, followed by reactions with water and O2 that facilitate the rapid formation of sulfate. The estimated reaction energy for the whole process, 3SO2 + H2O + 1/2O2 → HSO4- + H+ (298 K, 1 M), was ΔGr = -107.8 kcal·mol-1. Moreover, calculations revealed that this was a multistep reaction involving submerged, small energy barriers (∼10 kcal·mol-1). These results indicate that photochemical oxidation of SO2 at the air-water interface with solar actinic light may be an important unaccounted source of sulfate aerosols under polluted haze conditions.

Effect of the flavonoids quercetin and taxifolin on UVA-induced damage to human primary skin keratinocytes and fibroblasts.

The ultraviolet (UV) part of solar radiation can permanently affect skin tissue. UVA photons represent the most abundant UV component and stimulate the formation of intracellular reactive oxygen species (ROS), leading to oxidative damage to various biomolecules. Several plant-derived polyphenols are known as effective photoprotective agents. This study evaluated the potential of quercetin (QE) and its structurally related flavonoid taxifolin (TA) to reduce UVA-caused damage to human primary dermal fibroblasts (NHDF) and epidermal keratinocytes (NHEK) obtained from identical donors. Cells pre-treated with QE or TA (1h) were then exposed to UVA light using a solar simulator. Both flavonoids effectively prevented oxidative damage, such as ROS generation, glutathione depletion, single-strand breaks formation and caspase-3 activation in NHDF. These protective effects were accompanied by stimulation of Nrf2 nuclear translocation, found in non-irradiated and irradiated NHDF and NHEK, and expression of antioxidant proteins, such as heme oxygenase-1, NAD(P)H:quinone oxidoreductase 1 and catalase. For most parameters, QE was more potent than TA. On the other hand, TA demonstrated protection within the whole concentration range, while QE lost its protective ability at the highest concentration tested (75μM), suggesting its pro-oxidative potential. In summary, QE and TA demonstrated UVA-protective properties in NHEK and NHDF obtained from identical donors. However, due to the in vitro phototoxic potential of QE, published elsewhere and discussed herein, further studies are needed to evaluate QE safety in dermatological application for humans as well as to confirm our results on human skin ex vivo and in clinical trials.

Solar UV-B/A radiation is highly effective in inactivating SARS-CoV-2

Solar UV-C photons do not reach Earth’s surface, but are known to be endowed with germicidal properties that are also effective on viruses. The effect of softer UV-B and UV-A photons, which copiously reach the Earth’s surface, on viruses are instead little studied, particularly on single-stranded RNA viruses. Here we combine our measurements of the action spectrum of Covid-19 in response to UV light, Solar irradiation measurements on Earth during the SARS-CoV-2 pandemics, worldwide recorded Covid-19 mortality data and our “Solar-Pump” diffusive model of epidemics to show that (a) UV-B/A photons have a powerful virucidal effect on the single-stranded RNA virus Covid-19 and that (b) the Solar radiation that reaches temperate regions of the Earth at noon during summers, is sufficient to inactivate 63% of virions in open-space concentrations (1.5 × 103 TCID50/mL, higher than typical aerosol) in less than 2 min. We conclude that the characteristic seasonality imprint displayed world-wide by the SARS-Cov-2 mortality time-series throughout the diffusion of the outbreak (with temperate regions showing clear seasonal trends and equatorial regions suffering, on average, a systematically lower mortality), might have been efficiently set by the different intensity of UV-B/A Solar radiation hitting different Earth’s locations at different times of the year. Our results suggest that Solar UV-B/A play an important role in planning strategies of confinement of the epidemics, which should be worked out and set up during spring/summer months and fully implemented during low-solar-irradiation periods.

Perception of solar UV radiation by plants: photoreceptors and mechanisms.

About 95% of the ultraviolet (UV) photons reaching the Earth’s surface are UV-A (315–400 nm) photons. Plant responses to UV-A radiation have been less frequently studied than those to UV-B (280–315 nm) radiation. Most previous studies on UV-A radiation have used an unrealistic balance between UV-A, UV-B, and photosynthetically active radiation (PAR). Consequently, results from these studies are difficult to interpret from an ecological perspective, leaving an important gap in our understanding of the perception of solar UV radiation by plants. Previously, it was assumed UV-A/blue photoreceptors, cryptochromes and phototropins mediated photomorphogenic responses to UV-A radiation and “UV-B photoreceptor” UV RESISTANCE LOCUS 8 (UVR8) to UV-B radiation. However, our understanding of how UV-A radiation is perceived by plants has recently improved. Experiments using a realistic balance between UV-B, UV-A, and PAR have demonstrated that UVR8 can play a major role in the perception of both UV-B and short-wavelength UV-A (UV-Asw, 315 to ∼350 nm) radiation. These experiments also showed that UVR8 and cryptochromes jointly regulate gene expression through interactions that alter the relative sensitivity to UV-B, UV-A, and blue wavelengths. Negative feedback loops on the action of these photoreceptors can arise from gene expression, signaling crosstalk, and absorption of UV photons by phenolic metabolites. These interactions explain why exposure to blue light modulates photomorphogenic responses to UV-B and UV-Asw radiation. Future studies will need to distinguish between short and long wavelengths of UV-A radiation and to consider UVR8’s role as a UV-B/UV-Asw photoreceptor in sunlight.

Whole human blood DNA degradation associated with artificial ultraviolet and solar radiations as a function of exposure time

Laboratory investigations were conducted to evaluate the effect of ultraviolet radiation components and solar radiation exposure as a function of time on the degradation of whole human blood DNA from the standpoint of forensic analysis. Ten μL of whole human male blood samples were exposed to UV-A, UV-B, UV-C, and solar radiation at 20 min intervals up to 120 min. Allele frequencies of 16 short tandem repeat (STR) markers were monitored by employing current forensic typing DNA techniques. The STR markers were grouped into high, medium, and low molecular weight categories. Results revealed that even 20 min exposure to 4.89 eV UV-C photons (ʎ = 254 nm) with radiation intensity of 1200 μW/cm2 would degrade whole human male blood DNA samples significantly, making them unfit for human identification due to the breakdown of high molecular weight STRs. Exposure of blood samples to 4.11 eV UV-B photons (ʎ = 302 nm) with radiation intensity of 900 μW/cm2 resulted in complete degradation of high molecular weight STRs after 60 min. Partial breakdown of medium and low molecular weight STRs started after 80 min exposure. The degradation index (DI) values appear to show that the degradation of the DNA template molecule was relatively less in the low molecular weight DNA fragments as compared with high molecular weight DNA fragments. This finding indicates that genetic profiles obtained from whole human male blood exposed to this radiation for 60 min will give inconclusive results. Samples exposed up to 120 min to 3.40 eV UV-A photons (ʎ = 365 nm) and 3.10–3.94 eV photons of solar radiation did not appear to produce appreciable degradation in any of three molecular weight STRs in the whole human blood DNA samples.

Heterogeneous photocatalytic degradation of pharmaceuticals in synthetic and real matrices using a tube-in-tube membrane reactor with radial addition of H2O2

A tube-in-tube membrane reactor, with radial addition of hydrogen peroxide, was used for the oxidation of four pharmaceuticals, paracetamol (PCT), furosemide (FRS), nimesulide (NMD), and diazepam (DZP), in a continuous-mode operation, using photochemical and photocatalytic processes, driven by UVA or UVC photons. This reactor allows a controlled titration of small H2O2 doses (inside-out mode) to the catalyst particles immobilized in the membrane shell side and to the annular space between the membrane inner tubing and the concentric outer quartz tubing, where water to be treated flows. Tests were performed using synthetic (SWW) and real (urban wastewater after secondary treatment) (UWW) matrices, both spiked with the pharmaceutical mix solution (200 μg L−1 of each). The photochemical and photocatalytic oxidation efficiency was evaluated as a function of H2O2 dose (5–20 mg L−1), oxidant injection mode (radial permeation vs injection upstream from the reactor inlet), light source (UVA vs UVC lamps) and aqueous matrix (synthetic vs real matrix). At steady-state regime, the UVC/H2O2/TiO2 system, with radial H2O2 addition (20 mg L−1), showed the highest pharmaceuticals removal percentage, PCT (27.4%), FRS (35.0%), NMD (24.2%) and DZP (30.0%) in SWW. A substantial decrease in pharmaceuticals elimination was observed for UWW (PCT - 11.5%, FRS - 20.3%, NMD - 8.2% and DZP - 12.6%), in comparison with the SWW matrix. Finally, twelve transformation products (TPs) were identified; most of them showed in their structures hydroxylation in aromatic moiety; all TPs chemical structures were evaluated by BIOWIN software indicating that the TPs are non-biodegradables.

Effect of UVA radiation on the Nrf2 signalling pathway in human skin cells

The harmful effects of low energy UVA photons (315–400 nm) are associated with the massive production of reactive oxygen species resulting in oxidative stress. In response to oxidative damage, NF-E2-related factor 2 (Nrf2) is translocated to the nucleus and drives the expression of detoxication and antioxidant enzymes. UVA's effect on Nrf2 has been quite well characterised in dermal fibroblasts. However, there is a dearth of such information for keratinocytes. This study aimed to evaluate and compare the effect of UVA radiation on the Nrf2 pathway and oxidative stress related proteins in primary human dermal fibroblasts (NHDF), epidermal keratinocytes (NHEK) and human keratinocyte cell line HaCaT. NHDF were exposed to doses of 2.5–7.5 J/cm2, NHEK and HaCaT to 10–20 J/cm2 using a solar simulator. Effects on Nrf2 translocation were evaluated after 1, 3 and 6 h and Nrf2-controlled proteins (heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1), glutathione reductase (GSR), glutathione-S-transferase (GST), interleukine-6 (IL-6), and matrix metalloproteinases (MMP-1, MMP-2)) after 3, 6 and 24 h. The results showed the fastest Nrf2 translocation was in UVA-irradiated HaCaT (1 h), persisting until the subsequent time interval (3 h), while in primary keratinocytes the effect of radiation was minimal. In NHDF, UVA-stimulated Nrf2 translocation was conspicuous 3 h after UVA treatment. In NHDF, most of the studied proteins (NQO1, HO-1, GSR, GSTM1 and MMP-1) showed the highest level 24 h after UVA exposure, except for MMP-2 and IL-6 which had their highest level at a shorter time incubation interval (3 h). In NHEK, NQO1, HO-1 and GST were increased 6 h after UVA exposure, GSR and MMP-2 level was slightly below or above the control level, and MMP-1 and IL-6 increased at shorter time intervals. When comparing NHEK and HaCaT, these cells displayed contrary responses in most of the Nrf2-controlled proteins. Thus, primary keratinocytes cannot be replaced with HaCaT when studying cell signalling such as the Nrf2 driven pathway and Nrf2-controlled proteins.

Ultraviolet A protective potential of plant extracts and phytochemicals.

Chronic exposure to solar radiation is related to an increased incidence of various skin disorders, including premature skin aging and melanoma and non-melanoma skin cancers. Ultraviolet (UV) photons in particular are responsible for skin damage. Solar UV photons mainly belong to UVA wavebands, however UVA radiation has been mostly ignored for a long time. At the cellular level, UVA photons mainly provoke indirect oxidative damage to biomolecules via the massive generation of unstable and highly reactive compounds. Human skin has several effective mechanisms that forestall, repair and eliminate damage caused by solar radiation. Regardless, some damage persists and can accumulate with chronic exposure. Therefore, conscious protection against solar radiation (UVB+UVA) is necessary. Besides traditional types of photoprotection such as sunscreen use, new strategies are being searched for and developed. One very popular protective strategy is the application of phytochemicals as active ingredients of photoprotection preparations instead of synthetic chemicals. Phytochemicals usually possess additional biological activities besides absorbing the energy of photons, and those properties (e.g. antioxidant, anti-inflammatory) magnify the protective potential of phytochemicals and extracts. Therefore, compounds of natural origin are in the interest of researchers as well as developers. In this review, only studies on UVA protection with well-documented experimental conditions are summarized. This article includes 17 well standardized plant extracts (Camellia sinensis (L.) Kuntze, Silybum marianum L. Gaertn., Punica granatum L., Polypodium aureum L., Vaccinium myrtillus L., Lonicera caerulea L., Thymus vulgaris L., Opuntia ficus-indica (L.) Mill., Morinda citrifolia L., Aloe vera (L.) Burm.f., Oenothera paradoxa Hudziok, Galinsoga parviflora Cav., Galinsoga quadriradiata Ruiz et Pavón, Hippophae rhamnoides L., Cola acuminata Schott & Endl., Theobroma cacao L. and Amaranthus cruentus L.) and 26 phytochemicals.

Treatment of olive oil mill wastewater by single electrocoagulation with different electrodes and sequential electrocoagulation/electrochemical Fenton-based processes

The treatment of olive oil mill wastewater (OOMW) by novel sequential processes involving electrocoagulation (EC) followed by electro-Fenton (EF) or photoelectro-Fenton (PEF) under UVA irradiation has been studied using a boron-doped diamond anode and an air-diffusion cathode for H2O2 electrogeneration. Their performance was monitored from the removal of total organic carbon (TOC), chemical oxygen demand, turbidity, total solids and total nitrogen, as well as from the energy consumption. Preliminary EC assays were performed with one pair of electrodes made of Al, Fe, AISI 304 or AISI 316L. The Fe/Fe cell showed the best performance, yielding 40% TOC decay in 20 min. Subsequent EF or PEF at natural pH 7.2 performed similarly, whereas PEF became superior at pH 3.0 due to the action of UVA photons. Comparison between EC/PEF and single EF or PEF at pH 3.0 and 25 mA cm−2 with 0.50 mM Fe2+ revealed the positive outcome of the sequential process, attaining 97.1% TOC abatement after 600 min. GC–MS analysis of the raw wastewater allowed identifying 18 cyclic and 27 aliphatic compounds, most of which could not be removed by EC. The final solutions in EC/EF and EC/PEF contained a large plethora of persistent long-chain aliphatic acids and alkanes.

Laser-induced fluorescence in fish scales to evaluate the environmental integrity of ecosystems

The aim of this study was to evaluate the fluorescence of Astyanax lacustris fish scales when excited in the UV-A and blue regions for use as a bioindicator of aquatic ecosystems. This species was firstly defined as Astyanax altiparanae, popularly known as “lambari-do-rabo-amarelo”. Currently, abiotic/biotic environmental integrity is generally assessed using limnological and physicochemical parameters related to biological indicators in streams or rivers, which are not sufficient to evaluate the real environmental conditions: in some cases, these parameters can be strongly dependent on local weather conditions. In this study, after the fish scales were excited with UV-A (360nm) and blue (405nm) photons, a strong and broad visible fluorescence band (from blue to red) could be observed that was mainly related to collagen and hydroxyapatite, independent of whether the excitation was applied to the inside or outside of the scale. Selected emission wavelengths were used as variables and the fluorescence intensities were interpreted using multivariate discriminant statistical analysis to compare streams with known different levels of integrity. The fluorescence data showed strong correlation with the electrical conductivity of the water, indicating that the scales of A. lacustris could be employed as bioindicators of environmental integrity on water chemistry monitoring programs.

Singlet Oxygen-Mediated Oxidation during UVA Radiation Alters the Dynamic of Genomic DNA Replication.

UVA radiation (320–400 nm) is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers. This leads to the production of reactive oxygen species (ROS), such as singlet oxygen (1O2) and hydrogen peroxide (H2O2), which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids. We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing. The time of recovery post irradiation for each of these events can last from few minutes (reduction of oxidized RRM1) to several hours (replication fork velocity and origin firing). The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing. Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen.

Routes for the electrochemical degradation of the artificial food azo-colour Ponceau 4R by advanced oxidation processes

The performance of three electrochemical advanced oxidation processes, namely electro-oxidation with electrogenerated H2O2 (EO–H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) for the treatment of aqueous solutions of the food azo dye Ponceau 4R in an undivided cell with a BDD anode and an air-diffusion cathode was compared in terms of colour, dye concentration and total organic carbon (TOC) removals. PEF treatments in ultrapure water with Na2SO4 were performed to assess the effect of current density, as well as supporting electrolyte and dye concentrations. At 100mAcm−2, solutions of 130mL of 254mgL−1 of the dye in 0.05M Na2SO4 became colourless and totally mineralized after 50 and 240min, respectively, which can be explained by the synergistic action of BDD(OH) at the anode surface and homogeneous OH formed in the bulk from Fenton’s reaction promoted in the presence of Fe2+ catalyst. Furthermore, UVA photons induced the continuous Fe2+ regeneration and photolytic decomposition of refractory intermediate complexes. In that aqueous matrix, the cleavage of the dye molecules proceeded through several reaction routes to yield N-containing and non-N-containing derivatives with one or two aromatic rings, short-chain aliphatic carboxylic acids and inorganic ions. Oxalic and oxamic acids and sulfate ions were accumulated at different rates in EO–H2O2, EF and PEF. The three methods allowed the progressive decontamination of Ponceau 4R solutions in a real water matrix even without the addition of electrolyte, although complete TOC abatement after 360min at 33.3mAcm−2 was only ensured by the iron-catalyzed PEF process.

Total removal of alachlor from water by electrochemical processes

Concentrated aqueous solutions of the chloroacetanilide herbicide alachlor, a suspected human carcinogen that has been classified as a priority water pollutant by the European Commission, have been quickly degraded and even totally mineralized by different electrochemical advanced oxidation processes (EAOPs) in cells equipped with a carbonaceous air-diffusion cathode able to electrogenerate H2O2 on site and a Pt or boron-doped diamond (BDD) anode. The highest performance was obtained by means of the photoelectro-Fenton (PEF) process with BDD in the presence of 0.5mM Fe2+, thanks to the synergistic action of (i) electron transfer, (ii) coupled oxidation by OH generated by Fenton’s reaction in the solution bulk and BDD(OH) generated at the anode surface, and (iii) photolytic and photodecarboxylation reactions allowed by UVA photons. Good results were also obtained by electro-oxidation (EO) and electro-Fenton (EF) with BDD, resulting in a much higher mineralization current efficiency than EO, EF and PEF with Pt. Based on GC–MS analyses, the initial transformation step of alachlor promoted by the EAOPs involved four different reaction pathways, namely dealkylation, cyclization, scission of the R–N bond and hydroxylation by OH and BDD(OH). Further cleavage of the resulting nine cyclic and/or aromatic by-products led to the appearance of short-chain aliphatic carboxylic acids such as acetic, chloroacetic, oxamic and oxalic. Only PEF with BDD was able to ensure the quick and total degradation of the latter two acids, therefore becoming the best available electrochemical technology at present for the degradation of alachlor. Different amounts of nitrogenated (NH4+ and NO3−) and chlorinated (Cl−, ClO3− and ClO4−) ions were accumulated in the final solutions depending on the anode and the applied current.

Etiology and pathogenesis of basal cell carcinoma

Abstract Basal cell carcinoma (BCC) is the most common cancer among Caucasians. It generally occurs on sun-exposed areas of the body, mostly on the head and neck (80%), trunk (15%), rarely on arms and legs. Basal cell carcinoma is a good example of a disease caused by a combination of genetic and environmental factors. Ultraviolet (UV) radiation plays a dual role in the development of BCC: it causes DNA damage and immunosuppression. UVA and UVB rays damage the DNA via various mechanisms. UVB radiation directly damages DNA within skin cells, causing cytosine → thymine mutations at dipyrimidine sites, whereas UVA radiation is 10.000 times less mutagenic, but it is significantly more present in the natural UV radiation. Also, UVA photons have lower energy than UVB photons and do not induce mutations. UV radiation exerts immune suppression by decreasing the antigen presenting cells ability and by producing immunosuppressive cytokines, such as interleukin-10 (IL-10) and tumor necrosis factor alpha (TNF-α). Mediators of UV-induced immunosuppression are DNA and cis-urocanic acid. Several studies showed a significant association between the development of BCC and sun-exposure during childhood and adolescence, and a strong relation with family history of skin cancer. Exposure to ionizing radiation increases the risk of nonmelanoma skin cancers by three times, while the risk is proportional to the radiation dose. Chemical carcinogens, such as arsenic, tar, psoralen, and pesticides, increase risks for nonmelanoma skin cancers, predominantly for squamous cell carcinoma (SCC). Regarding genetic predisposition, there is glutathione S-transferase (GST) as an important part of cellular defense against endogenous and exogenous chemicals. Several polymorphisms in GST family members have been associated with impaired detoxification, thus influencing the risk for some cancers, including nonmelanoma skin cancers. Cytochrome P450 enzymes are involved in detoxification of photosensitizing agents, and thus involved in BCC carcinogenesis. PTCH is a tumor suppressor gene first identified in patients with Gorlin syndrome. Abnormal activation of this gene and its pathways result in various types of tumorigenesis. BCC is associated with homozygous PTCH gene deletion. With regard to acquired genetic mutations, it was found that aggressive BCCs are significantly associated with increased p53 protein expression, probably representing the mutated form, although that assertion could not be established with certainty. Considering the apparently limited contribution of DNA damage and chromosome instability to the expression of BCC phenotype, the relevance of p53 mutations for BCC growth remains to be demonstrated. Data on the role of Bcl-2 gene family in the development of BCC are scarce. It is unclear whether Bcl-2 has a functional role in the development of BCC, or it only indicates the level of gene expression in tumor stem cells. Activation of Ras gene may play an important role during early stages in the development of nonmelanoma skin cancers, and it is often found on UV-exposed skin in BCC, actinic keratosis and SCC. Concerning immunologic factors, studies have shown that tumor necrosis factor-α (TNF-α) is the critical mast cell product involved in ultraviolet-induced immunosuppression: mast cells contain high quantities of TNF-α which is released after activation; the level of TNF-α is increased in the skin exposed to UV radiation disrupting the morphology and function of Langerhans cells, the principal antigen-presenting cells of the skin. An animal study suggests that the degree of susceptibility to ultraviolet-B-induced local immunosuppression depends on TNF-α level within the epidermis after UVB. It has been established that mast cell-derived histamine stimulates prostaglandin E2 (PGE2) production from keratinocytes. PGE2 alters the cytokine balance in favor of the immunosuppressive interleukin-10 (IL-10) against the immunostimulatory IL-12; histamine also increases suppressor T-cell function by binding to the H2 receptors, which in turn release higher levels of immune suppressive cytokines including IL-10 and induce apoptosis of antigen-presenting cells. All this results in a shift of the immune response from T helper 1 (Th1) cytokine profile to T helper 2 (Th2) cytokine profile, inhibiting antigen-presenting cells to induce antitumor activity.

Lonicera caerulea fruits reduce UVA-induced damage in hairless mice

UVA photons are less energetic than UVB photons but they are more abundant in solar radiation. Modern tools have shown that UVA light has serious adverse effects on the skin. We investigated the effect of consuming Lonicera caerulea berries on UVA-induced damage in SKH-1 mice. The mice were fed a diet containing L. caerulea berries (10%, w/w) for 14days before a single UVA (30J/cm2) treatment. Effects on haematological and antioxidant parameters were evaluated 4 and 24h after irradiation. The bioavailability of L. caerulea phenolics was also assessed. Consuming the L. caerulea berry-enriched diet caused reduced malondialdehyde production and increased catalase activity and glutathione levels were found in skin and erythrocytes. UVA-induced NADPH:quinone oxidoreductase-1 and gamma-L-glutamate-L-cysteine ligase protein in skin were reduced in mice fed L. caerulea berries. Enhanced heme oxygenase-1 level in skin, interleukin-17 in plasma and reduced interleukin-12 levels in plasma were found in the mice on the experimental diet. Histological (pyknotic) changes in the nuclei of basal cells induced by UVA exposure were reduced in L. caerulea berry consuming animals. HLPC-MS analysis showed high concentrations of hippuric acid, one of the main metabolites of aromatic amino acids and phenolic compounds, in skin, liver, urine and faeces of mice consuming the berries.Taken together, consumption of L. caerulea berries affords protection from the adverse effects of a single UVA exposure mainly via modulation of antioxidant parameters.

Photoaging

Photoaging

Differential modulation of inflammatory markers in plasma and skin after single exposures to UVA or UVB radiation in vivo

Solar light generates inflammatory responses in exposed skin. These effects are generally attributed to UVB light. However, skin is expose d to a huge quantum of UVA photons as UVA is a predominant part of sunlight and the radiation used in tanning beds. We examined the effects of a single exposure to UVA and UVB wavebands on cytokine levels in skin and plasma, myeloperoxidase (MPO) activity, expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) in skin. Hairless mice were irradiated with either UVA (10 or 20 J/cm²) or UVB (200 or 800 mJ/cm²). The effects were assessed after 4/24 h. Plasma cytokine levels were evaluated using a Bio-Plex cytokine assay. Cytokine, iNOS and COX-2 levels in skin were determined by Western blot. Skin MPO activity was monitored spectrophotometrically. UVB induced up-regulation of interleukin-1β (IL-1β) and interleukin-6 (IL-6) and decrease in interleukin-10 (IL-10) mainly after 4 h. In contrast, UVA caused increase in levels of tumor necrosis factor-alpha (TNF-α) and IL-6 after 4 h and up-regulated IL-10 and interleukin-12 (IL-12) after 24 h. The increase in MPO activity from infiltrated leucocytes was observed only in UVB irradiated animals. iNOS was up-regulated 4 h after UVA and UVB treatment. No significant effect on COX-2 expression was detected. UVA and UVB light affected several inflammatory markers. For individual waveband, changes in plasma parameters did not correlate with those in skin. Thus evaluation of plasma samples cannot simply be replaced by determination in skin specimens and vice versa.

DNA Base Damage by Reactive Oxygen Species, Oxidizing Agents, and UV Radiation

Emphasis has been placed in this article dedicated to DNA damage on recent aspects of the formation and measurement of oxidatively generated damage in cellular DNA in order to provide a comprehensive and updated survey. This includes single pyrimidine and purine base lesions, intrastrand cross-links, purine 5',8-cyclonucleosides, DNA-protein adducts and interstrand cross-links formed by the reactions of either the nucleobases or the 2-deoxyribose moiety with the hydroxyl radical, one-electron oxidants, singlet oxygen, and hypochlorous acid. In addition, recent information concerning the mechanisms of formation, individual measurement, and repair-rate assessment of bipyrimidine photoproducts in isolated cells and human skin upon exposure to UVB radiation, UVA photons, or solar simulated light is critically reviewed.

DNA damage after acute exposure of mice skin to physiological doses of UVB and UVA light

Solar ultraviolet (UV) radiation is an important risk factor in skin carcinogenesis. This has been attributed mainly to the UVB waveband because the high-energetic photons are capable of interacting with DNA and inducing DNA damage. Recently, UVA light has also gained increasing interest in relation to DNA alteration. Although UVA photons are less energetic than UVB, they comprise a major fraction of sunlight UV radiation and penetrate deep into the skin. The study was carried out to compare the acute effects of UVA and UVB light on SKH-1 mice in relation to DNA damage and associated parameters. Mice were exposed to UVA (10 and 20 J/cm(2)) or UVB (200 and 800 mJ/cm(2)) radiation. The number of DNA single-strand breaks (SSB) in lymphocytes, amount of phosphorylated histone H2AX (gamma-H2AX) and apoptosis or DNA fragmentation (TUNEL-positive cells) in skin sections and level of gamma-H2AX, activated caspase-3 and phosphorylated p53 in skin were evaluated after 4 and 24 h. SSB analyzed by alkaline comet assay were found to be 4 and 24 h following UVB and UVA treatment, respectively. TUNEL and gamma-H2AX-positive cell were observed only in UVB exposed animals at both time intervals. The level of activated caspase-3 and phospho-p53 was increased 24 h after UVA and UVB radiation and was more apparent in UVB treated mice. The results indicate that the mechanism of DNA damage caused by acute UVA exposure includes formation of SSB (oxidative damage), but not double-strand breaks.