UVA Exposure Research Articles

Photoprotective Effects of Ice Plant (Mesembryanthemum crystallinum) Callus Extract on Gene Expression of Human Dermal Fibroblast Against UV Exposure

UV exposure is the principal cause of extrinsic photoaging. Antioxidant-related genes (SOD2 and CAT) and collagen-related genes (COL1A1 and TIMP1) were selected for analysis of the mRNA expression in human dermal fibroblasts (CCD-966SK) using qPCR. In this study, UVA-exposed (15 J/cm2 cells showed decrease in SOD2 , CAT (p < 0 001) and COL1A1 (p < 0 05) gene expression, indicating the decline of antioxidant ability and collagen formation. However, treatment with ice plant callus extract (2 mg/mL, 24 h) before UVA exposure significantly up-regulated SOD2 , CAT , COL1A1 and TIMP1 genes (p < 0 01) by 9.5, 2.7, 1.7 and 3.8 times, respectively, compared with those of the control group, and by 10.2, 4.3 (p < 0 001), 2.1 and 3.8 times, respectively, compared with those of the UVA (only) group. These results demonstrated that ice plant extracts affect both antioxidant- and collagen-related gene expressions, and show positive effects on endogenous antioxidant activity and skin collagen preservation.

Reflex of oleandrin production and molecular changes on the Nerium oleander L. cell suspension culture under UV-A radiation stress effect.

THE AIM of this study is to determine the oleandrin concentrations in the Nerium oleander cell suspension culture after being exposed to UV-A (365nm), at different time intervals (0 controls, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50min). The results showed that the maximum time limits for carrying N. oleander cells suspension culture to exposure of UV-A is 30min.The present study also aims at investigating changes of the protein bands, peroxidase isozyme and oleandrin concentration at the same condition. Oleandrin was separated and quantified by HPLC. The investigation of protein changes was conducted using SDS PAGE electrophoresis techniques. The results revealed that the changes of the protein bands depend on different time intervals of exposure to A-UV radiation. Thus, the changes of the oleandrin production were consequent to gene expression changes. Peroxidase isozyme analysis, showed that exposure to UV-A for the 5, 15 and 20min had a clear impact on the peroxidase isozyme, but the greatest impact was in the sample exposed to UV-A for a period of 15 minutes (0.093±0.01) μg/ml, the same sample showed the highest concentration of oleandrin compared to the control (0.022±0.001) μg/ml. However, the other samples were less affected by the exposure to UV-A.

Influence of clouds on OMI satellite total daily UVA exposure over a 12-year period at a southern hemisphere site

ABSTRACT This research investigated and evaluated the influence of clouds on the total daily UVA (320–400 nm) exposures calculated from the three Ozone Monitoring Instrument (OMI) UV spectral irradiances at solar noon. These evaluated satellite total daily UVA exposure data were compared to the total daily UVA exposures of a ground-based instrument over the period of October 2004 to December 2014 at a sub-tropical Australian site (27.5°S, 151.9°E) under all cloud cover conditions including sun obscured and not obscured conditions. The aim was to evaluate the influence of clouds on the total daily UVA. When the sun was not obscured by clouds, there was good agreement between satellite and ground-based daily UVA exposure measurements with coefficient of determination (R 2) between 0.80 and 0.84, for the cloud conditions 0 to 2, >2 to 4, >4 to 6 and >6 to 8 oktas. For sun obscured by clouds, the R 2 was 0.71, 0.64 and 0.75, respectively, for >2 to 4, >4 to 6 and >6 to 8 oktas. The method was validated using total daily UVA exposures from ground measurements taken in 2015 and 2016 giving a mean absolute error of 84.2 kJ m−2 (10%) and 138.8 kJ m−2 (30%) respectively, for the cases of sun not obscured cloudy days and sun obscured by cloud cover. Total daily UVA exposures were able to be calculated from the OMI satellite spectral irradiance for all cloud conditions, including cases where the sun was obscured, demonstrating the potential application of the technique to be applied in locations that do not record surface UVA measurements directly.

Pathogen reduction with amotosalen/UVA reduces platelet refractoriness in a dog platelet transfusion model.

Pathogen reduction of donor platelets with amotosalen/UVA has been shown to effectively inactivate pathogens and also contaminating white blood cells (WBCs). We wanted to determine whether WBC inactivation could also decrease alloimmune refractoriness to donor platelets. Platelets were prepared from a donor dog's whole blood, and the platelets were either transfused without modification [standard (STD) platelets] or treated with amotosalen/UVA under conditions modelling the amotosalen/UVA Blood System for human platelets (APR) using either 4 or 3J/cm2 of UVA exposure. Platelets were transfused weekly from a single donor dog for 8weeks or until the recipient dog became refractory to their donor's platelets. Antibody samples were drawn weekly and tested against the donor dog's platelets and WBCs (CD8 and B cells). Only 1/7 (14%) dogs that received STD platelets accepted 8weeks of donor transfusions. Following APR 4J/cm2 donor transfusions, 3/9 (33%) recipients accepted their donor's transfusions, but only one recipient remained antibody negative. Following APR 3J/cm2 donor transfusions, the same dose as used for human platelet transfusions, 7/10 (70%) recipients accepted their donor's transfusions, but only two remained antibody negative. As a very high percentage of recipient dogs (70%) accepted APR 3J/cm2 donor transfusions, these data suggest that preventing alloimmune platelet refractoriness may be another benefit of pathogen reduction using amotosalen/UVA.

Enhanced bacterial inactivation in apple juice by synergistic interactions between phenolic acids and mild food processing technologies

This study demonstrated an innovative processing approach based on synergistic antimicrobial activity of two phenolic acids with mild thermal and non-thermal processing technologies. The two selected model phenolic acids were gallic acid (GA; 10 mM) and ferulic acid (FA; 1 mM). The processing technologies evaluated for processing of a model clarified apple juice were UV-A light, mild heat (55 °C) and moderate pressure (250 MPa), with processing times ranging from 1 to 30 min. The results demonstrated that combinations of selected phenolic acids and a mild physical processing were able to lower E. coli O157:H7 and Listeria innocua counts from 6-log CFU mL −1 to below the detection limit of 1-log CFU mL −1 . Bacterial inactivation was significantly enhanced by the combination of UV-A light processing and FA, where 10 min of treatment enhanced bacterial inactivation by 5-log as compared to light processing alone, which presented no bacterial inactivation. In contrast, the combination of GA and mild-temperature thermal processing (55 °C) or mild-levels of high-pressure processing (250 MPa), enhanced bacterial inactivation by 4-log as compared to the physical treatments alone, which presented only 1-log of inactivation. The influence of these synergistic combinations on bacterial membrane damage was assessed by selective plating technique under osmotic pressure. Furthermore, the total intracellular thiol content was also measured to assess for thiol oxidation. Overall, the results demonstrated enhanced bacterial inactivation based on synergistic interactions of selected phenolic acids with both mild-thermal and non-thermal technologies in a model food system and illustrate potential to create diversity of novel antimicrobial strategies for food processing. This study showed that the presence of naturally-based compounds can significantly reduce intensity levels of physical processing required to inactivate model gram-positive and gram-negative bacteria in apple juice. In this study two phenolic acids, ferulic acid and gallic acids were selected as these compounds are naturally present in many fruits and other food products including grains. Furthermore, the levels of these natural phenolic acids used in this study are comparable to the levels naturally present in some of the food materials. • Ferulic acid plus UV-A and gallic acid plus 55 °C or pressure showed synergistic inactivation in apple juice. • Ferulic acid at 1 mM resulted in 5-log CFU/mL bacterial inactivation with UV-A exposure. • Gallic acid at 10 mM resulted in 4-log CFU/mL bacterial inactivation with 55 °C or 250 MPa exposure. • Combination of gallic acid with heat or pressure increased intracellular thiol oxidation. • All observed synergistic combinations showed damage to bacterial membranes.

Fueling Melanocytes with ATP from Keratinocytes Accelerates Melanin Synthesis

Melanocyte homoeostasis and their response to ultraviolet radiation (UVR) are mediated to a large extent by keratinocyte-derived factors, many of which have been well-characterized. Lee et al. describe novel effects of adenosine 5'-triphosphate (ATP), which is secreted by keratinocytes and can stimulate melanogenesis by melanocytes following UVA exposure. The investigators attribute the melanogenic effect of ATP to binding purinergic receptors type 2 X7 (P2X7), which are expressed on human melanocytes, leading to activation of the protein kinase C pathway. This report is the first to identify expression of specific purinergic receptors on human melanocytes, and it suggests ATP as a signaling molecule that stimulates pigmentation. Follow up on these results should clarify the physiological role of ATP in mediating the tanning response to solar UVR.

Low band-gap energy photocatalytic membrane based on SrTiO3–Cr and PVDF substrate: BSA protein degradation and separation application

A series of ultrafiltration (UF) membranes based on mixed matrix of chromium-doped strontium titanate (SrTiO3–Cr) photocatalyst and polyvinylidene difluoride (PVDF) were systematically prepared by non-solvent induced phase inversion technique. Porous PVDF membrane and mixed matrix membranes (MMMs) incorporated with 3–10 wt% SrTiO3–Cr were produced in the UF range using polyethylene glycol as a porogen additive. The crystal morphology and electronic property of as-synthesized Cr-doped SrTiO3 nanoparticles were characterized by XRD and UV–Vis DRS. We found that the SrTiO3–Cr nanoparticles are cubic perovskite structure of approximately 30–40 nm in size with a low band gap energy of 2.05 eV. The morphology, surface roughness, hydrophilicity and textural properties of SrTiO3–Cr/PVDF MMMs were comprehensively characterized using field emission-scanning electron microscope with energy-dispersive X-ray spectroscopy, atomic force microscope, sessile drop technique, and capillary flow porometer. The SrTiO3–Cr was observed to be homogeneously dispersed in all the MMMs and provided additional anti-fouling properties from Bovine Serum Albumin (BSA) protein. The membrane UF property and tri-cycling performance were evaluated under three distinct protocols in (1) Dark, (2) constant UVA exposure, and (3) UVA during post-treatment clean only. By increasing the SrTiO3–Cr concentration, the MMMs displayed an improved homogeneity and macropore distribution with enhanced water permeability given by 51–110 LMH bar−1 pure water flux and 37 to 45 LMH bar−1 BSA water flux in the Dark. A consistently high BSA rejection of 95% and an improved anti-fouling property under constant UVA irradiation were achieved due to a combination of photo-induced hydrophilic and photocatalytic effect. Also, a significant improvement in UF performance in terms of membrane flux recovery was observed in the 3rd protocol signifying that the effect of protein fouling on membrane filtration was further reduced due to a lower degree of BSA fragment deposition in the membrane pores. The findings in this study dramatically lower the operational constraints (transmembrane pressure, membrane cleaning, use of UVA) in the protein filtration process and offer an innovative membrane material for the research of photo-induced, anti-fouling membranes for protein separation applications.

Differential sensitivity of marine algae Dunaliella salina and Chlorella sp. to P25 TiO2 NPs.

The use of P25 TiO2 NPs in consumer products, their release, and environmental accumulation will have harmful effects on the coastal ecosystems. The sensitivity to TiO2 NPs may vary depending on the structural property and physiological mechanism of algal species. Therefore, the present study investigates the differences in sensitivity of two marine algae, Dunaliella salina and Chlorella sp., towards P25 TiO2 NPs. Among the two species, Chlorella sp. was more sensitive to TiO2 NPs than Dunaliella salina. The different working concentrations of TiO2 NPs, 0.1, 1, and 10 mg L-1, were selected based on the EC50 value. The EC50 value of TiO2 NPs for Dunaliella salina was found to be 1.8 and 13.3 mg L-1 under UV-A and dark conditions, respectively. The EC50 value of TiO2 NPs for Chlorella sp. was found to be 1.6 and 5.0 mg L-1 under UV-A and dark conditions, respectively. The decrease in cell viability was significantly higher for Chlorella sp. compared to Dunaliella salina at all concentrations except 0.1 mg L-1. The cellular viability data was in correlation with the oxidative stress markers such as total ROS and LPO. A concentration-dependent increase in ROS and lipid peroxidation was noted under UV-A exposure, which was higher in Chlorella sp. compared to Dunaliella salina. The decrease in the SOD activity with NP concentration was more in Dunaliella salina than Chlorella sp. under both conditions, whereas Chlorella sp. showed increased CAT activity with increasing concentration. The uptake of TiO2 NPs was more in Chlorella sp. than Dunaliella salina.

Ultraviolet radiation exposure during daylight Photodynamic Therapy.

Daylight photodynamic therapy (dPDT) is an effective treatment for field-change actinic keratoses (AK), with similar efficacy to conventional PDT but lower patient pain scores. Whilst AK occur consequent to chronic solar ultraviolet (UV) exposure, paradoxically solar visible radiation is used during PDT. To investigate the nature and levels of UV exposure, both erythemal UV and UVA, occurring during dPDT. Four years of solar erythemally effective UV (UVE) irradiance, UVA irradiance and illuminance data were obtained from Pubic Health England for 12 locations. For a standard 2 h treatment period, the data were converted into standard erythemal doses (SEDs), UVA dose and protoporphyrin-IX (PpIX)-weighted dose from UVE irradiance, UVA irradiance and illuminance respectively. These three parameters were compared ascertaining the UV exposure received during dPDT. Analysis of UV exposure during dPDT showed a UK maximum average UVE exposure of 8.2 SED at Camborne (PpIX dose 23.4 J cm-2). Treatment earlier in the day reduces average UV exposure (Camborne 5.2 SED, PpIX dose 18.2 J cm-2), whilst PpIX dose achieves threshold during winter months (Camborne, November, 0.8 SED, PpIX dose 7.1 J cm-2). Cyprus and Gibraltar (with high UV exposure during dPDT) experience a maximum of 14.3 SED and 12.9 SED, with respective PpIX doses of 36.1 J cm-2 and 35.1 J cm-2, in June. UVA exposure is also presented for comparison. Therapeutically effective dPDT doses can be achieved at times of the day and year when UV exposure is minimal.

Silymarin: Friend or Foe of UV Exposed Keratinocytes?

The application of natural plant extracts in UV-protection is popular and intensively studied. Silymarin (from Silibum marianum), a naturally occurring polyphenol, has recently received attention due to its antioxidant, anti-inflammatory and anti-apoptotic effects. However, its role in the UV-mediated keratinocyte cell response is still controversial. In this study, we investigated the effects of Silibum marianum extracts with different origins and formulations on UVA-exposed HaCaT keratinocytes in vitro. Our results show, that silymarin treatment caused an inverse dose-dependent photosensitivity relationship (at higher doses, a decrease in cell viability and ROS production) after UVA exposure. The attenuation of the UVA-induced ROS generation after silymarin treatment was also observed. Moreover, silymarin pre-treatment increased the cyclobutane pyrimidine dimer photolesions in keratinocytes after UVA exposure. These results indicated the dual role of silymarin in UVA-exposed keratinocytes. It scavenges ROS but still induces phototoxicity. Based on our results dermatological applications of silymarin and related compounds should be considered very carefully.

Photoprotective benefits of pigmentation in the transparent plankton community: a comparative species experimental test.

Plankton live under the countervailing selective pressures of predation and ultraviolet radiation (UVR). In lakes, zooplankton are transparent reducing visibility to predatory fishes but are pigmented in the absence of fishes, hypothetically reducing UVR damage. In the sea, planktivorous fishes are widespread, so plankton typically are transparent and ascend to productive surface waters at night to forage and descend during the day to reduce visibility to predators. However, larvae of some species face the unique constraint of traveling in surface currents in the daytime during migrations between adult and larval habitats. We would expect these larvae to be transparent since companion studies demonstrated increased predation risk of pigmented larvae under strong sunlight. Paradoxically, larvae range from being darkly to lightly pigmented. We hypothesize that some larvae are more heavily pigmented to reduce UVR damage, while other species travelling in subsurface currents with low UVR might be more transparent. Linking larval morphology to depth-dependent selective pressures would add a key element to help improve predictions of larval vertical distributions, which are important for simulating larval transport trajectories. We quantitatively tested the hypothesis that selection may have favored photoprotective pigmentation for larvae in the predominantly transparent plankton community while testing the differential effects of UVA and UVB radiation. We measured larval pigmentation of 12 species of crabs and exposed them to visible light only, visible+UVA, or visible+UVA+UVB in the tropics. Controlling for phylogeny, more pigmented species survived UVR better than less pigmented species, especially on sunnier days, though intraspecific comparisons for four species were equivocal. Most species died even from UVA exposure, which has long been regarded as relatively harmless despite penetrating deeper underwater than UVB. Thus, we demonstrate with a phylogenetically controlled analysis that crab larvae are pigmented in the predominantly transparent planktonic community to protect from UVR, improving our understanding of the selective forces acting on animal coloration and the factors determining planktonic distributions, survival, and dispersal. This linkage of morphology with susceptibility will be important for developing mechanistic models of environmental stress responses to better predict larval dispersal in current and future climates.

Cellular Photoprotective and Antioxidant Properties of Lipids in an Oral Skincare Supplement

BackgroundOverexposure to ultraviolet (UV) light is associated with multiple health risks from sunburn to skin cancers. The ingestion of natural product photoprotectors can increase skin's UV‐resistance. Our research focuses on the cellular effects of Bend Beauty, Inc.'s oral supplement called “Bend Skincare Anti‐Aging Formula” (AAF), which contains daily doses of the ω‐3 fatty acids eicosapentaenoic acid (EPA; 1050 mg) and docosahexaenoic acid (DHA; 350 mg), ω‐6 fatty acid gamma‐linolenic acid (GLA; 120 mg), carotenoids zeaxanthin (2.5 mg) and lutein (5 mg), and vitamin D3 (1,000 IU). A clinical trial found that ingestion of AAF increased the minimal erythema doses (UV exposure required to induce skin redness) of volunteers' skin by 84% after 8 weeks, warranting further research into AAF's photoprotective properties.ObjectiveTo quantify AAF's photoprotective and antioxidant properties in human dermal fibroblasts.Methods & ResultsExperiments were completed in primary human dermal fibroblasts (passage #3) treated with 0.005% AAF or vehicle control (10% H2O, 10% THF, 75% DMSO, 5% FBS). For the initial photoprotection assays, cells were treated with AAF or vehicle for 1, 7, or 14 days and exposed to UVA (365 nm; 216 J/cm2) or UVB (312 nm; 15.6 – 8,000 J/cm2). The viability of 1, 7, and 14‐day AAF‐treated cells after UVA exposure was 2.9, 4.2, and 3.5‐fold higher, respectively, vs. control (P < 0.05), and the UVB IC50s were 2.6 and 3.2‐fold higher in 7 and 14‐day AAF‐treated cells, respectively, vs. control (P < 0.05) as measured with MTT assays. For morphological analysis, 14‐day AAF‐ or vehicle‐treated fibroblasts were exposed to UVA (100 J/cm2) or UVB (1 J/cm2), stained with propidium iodide (PI; cell death marker), phalloidin (cytoskeleton stain), and Hoechst 32258 (nucleic stain) and imaged using confocal microscopy. After UVA or UVB exposure, the vehicle‐treated cells were visibly more damaged than AAF‐treated cells as assessed by actin staining, and PI staining was present in > 97% of the vehicle‐treated vs. < 8% of AAF‐treated fibroblasts (Figure 1). To quantify AAF's antioxidant effects, MTT assays were completed in 1, 7, and 14‐day AAF‐treated fibroblasts after 48 hours of treatment with the reactive oxygen species (ROS), H2O2 (11.1 – 2,700 mM); H2O2's IC50 values were calculated to be 2.0, 2.4, and 2.5‐fold higher, respectively, vs. control (P < 0.05). In identically AAF‐treated fibroblasts, assays to measure the intracellular ROS activity induced by H2O2 (0.9 mM, 1 h) using a ROS‐fluorescent probe (CM‐DCFH2‐DA) were completed. H2O‐2‐induced ROS activity was 67%, 63%, and 62% as high in 1, 7, and 14‐day AAF‐treated cells vs. control, respectively (P < 0.05).ConclusionsAAF helps to protect human dermal fibroblasts from the damaging effects of UVA, UVB, and H2O2, demonstrating its cellular photoprotective and antioxidant properties.Support or Funding InformationProject funding provided by Bend Beauty, Inc., Mitacs Elevate, and the Dalhousie Pharmacy Endowment FundThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Evaluation of Low-Dose, Low-Frequency Oral Psoralen–UV-A Treatment With or Without Maintenance on Early-Stage Mycosis Fungoides

Psoralen-UV-A (PUVA) photochemotherapy is standard first-line treatment for skin-limited, early-stage mycosis fungoides capable of producing high initial complete response (CR) rates. However, much remains unknown about PUVA's therapeutic mechanisms, optimal duration and frequency of treatment, dose escalation, or use as maintenance therapy. To evaluate low-dose, low-frequency PUVA, and whether maintenance treatment extends disease-free remission in patients with mycosis fungoides. This prospective randomized clinical trial with defined PUVA dosing regimen was carried out in 5 centers (Graz, Vienna, Hietzing, Innsbruck, and Salzburg) across Austria. Patients with stage IA to IIA mycosis fungoides (n = 27) were enrolled in the study beginning March 13, 2013, with the last patient enrolled March 21, 2016. These patients were treated with oral 8-methoxypsoralen followed by UV-A exposure 2 times per week for 12 to 24 weeks until CR. Patients with CR were randomized to PUVA maintenance for 9 months (14 total exposures) or no maintenance. The study was conducted from April 27, 2012, to July 27, 2018. Data analysis of the primary end point was of the intention-to-treat population, and the secondary end point analysis was of the evaluable population. Efficacy of the PUVA regimen was determined by the rate of CR as defined by a modified severity-weighted assessment tool (mSWAT) score reduction to 0. Levels of proinflammatory molecules in serum and histologic features and percentage of clonal T cells in skin were assessed to search for biomarkers of clinical response. In 27 patients with mycosis fungoides, 19 (70%) were male with mean (range) age 61 (30-80) years. At baseline, patients with CR had a mean (range) mSWAT score of 18.6 (1-66) compared with 16.8 (3-46) in patients with partial response. The 12- to 24-week PUVA induction regimen reduced the mSWAT score in all patients and led to CR in 19 (70%) of 27 patients and a low mean cumulative UV-A dose of 78.5 J/cm2. The subsequent standardized 9-month PUVA maintenance phase prolonged median (range) disease-free remission from 4 (1-20) months to 15 (1-54) months (P = .02). High density of histologic infiltrate and high percentage of clonal TCR sequences in skin biopsy specimens at baseline were inversely associated with therapeutic response. No severe adverse effects were seen during the PUVA induction or maintenance phase. This proof-of-concept study identifies potential biomarkers for therapeutic response to PUVA in mycosis fungoides; it also demonstrates that low-dose, low-frequency PUVA appears to be highly effective, and maintenance treatment may extend disease-free remission. ClinicalTrials.gov identifier: NCT01686594.

Understanding the role of DAF-16 mediated pathway in Caenorhabditis elegans during UV-A mediated photoaging process

Even though Sun is the major source of energy to all living beings in the universe, continuous and prolonged exposure to sunlight will lead to detrimental effects. Human skin will undergo extrinsic aging, known as photoaging upon prolonged exposure to sunlight which is characterized by wrinkles, dryness, loss of elasticity, and so on. The model nematode Caenorhabditis elegans which is widely used in aging studies, could be used to study photoaging also. Transcription factor DAF-16, which regulates longevity, stress resistance and many other physiological events, mediates the photoaging mechanism in C. elegans. Elevation in extracellular ROS and altered expression of SGK-1 indicates the role of DAF-16 during UV-A exposure. Further, the role of daf-2, the receptor gene and lys-7, an effector gene of DAF-16 were characterized through mutant based studies. The long lived daf-2 mutants upon UV-A exposure showed reduction in lifespan, but the upregulation of daf-16 allowed the other molecular mechanisms like healthspan, antimicrobial and stress resistance to be active. In the case of lys-7 mutants, the lifespan was reduced and all other molecular mechanisms were also downregulated. However, the daf-16 mutants showed no change in lifespan irrespective of UV-A exposure. This signifies the role of DAF-16 during UV-A mediated photoaging in C. elegans. The present study helps in understanding the role of daf-16 in UV-A mediated stress response which will be of considerable importance in the field of pharmacy in designing targets for specific agents against photoaging.

Toxicity and photosensitizing assessment of gelatin methacryloyl-based hydrogels photoinitiated with lithium phenyl-2,4,6-trimethylbenzoylphosphinate in human primary renal proximal tubule epithelial cells

Gelatin methacryloyl (GelMA) and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator are commonly used in combination to produce a photosensitive polymer but there are concerns that must be addressed: the presence of unreacted monomer is well known to be cytotoxic, and lithium salts are known to cause acute kidney injury. In this study, acellular 10% GelMA hydrogels cross-linked with different LAP concentrations and cross-linking illumination times were evaluated for their cytotoxicity, photosensitizing potential, and elastic moduli. Alamar Blue and CyQuant Direct Cell viability assays were performed on human primary renal proximal tubule epithelial cells (hRPTECs) exposed to extracts of each formulation. UV exposure during cross-linking was not found to affect extract cytotoxicity in either assay. LAP concentration did not affect extract cytotoxicity as determined by the Alamar Blue assay but reduced hRPTEC viability in the CyQuant Direct cell assay. Photocatalytic activity of formulation extracts toward NADH oxidation was used as a screening method for photosensitizing potential; longer UV exposure durations yielded extracts with less photocatalytic activity. Finally, elastic moduli determined using nanoindentation was found to plateau to approximately 20-25 kPa after exposure to 342 mJ/cm2 at 2.87 mW of UV-A exposure regardless of LAP concentration. LAP at concentrations commonly used in bioprinting (<0.5% w/w) was not found to be cytotoxic although the differences in cytotoxicity evaluation determined from the two viability assays imply cell membrane damage and should be investigated further. Complete cross-linking of all formulations decreased photocatalytic activity while maintaining predictable final elastic moduli.

Microorganisms inactivation by wavelength combinations of ultraviolet light-emitting diodes (UV-LEDs)

Ultraviolet light-emitting diode (UV-LED) is an emerging UV source with many special features due to the nature of semiconductor devices. One such feature is wavelength diversity that does not exist in conventional mercury based UV lamps, which provides opportunities to selectively combine multiple wavelengths for potentially additional effects by UV-LEDs. In this work, the inactivation of different microorganisms in water was investigated by UV-LEDs wavelength combinations. Various wavelength combinations, including simultaneous and sequential exposures, in different UV ranges such as UVC, UVB and UVA, were examined. These combinations were applied to the inactivation of indicator bacterium E. coli and coliphage MS2 in water. The results showed the effect of UV-LEDs multiple wavelengths depends on which wavelengths (UVC, UVB and UVA) are combined and the manner that different wavelengths (simultaneous, sequential) are used. Also, different microorganisms (bacteria, virus) respond differently to wavelength combinations. Combinations of UVC/UVB always achieved additive effect on microorganisms inactivation due to the same photochemical reaction induced by UVC/UVB on DNA. Combining UVA with UVC/UVB simultaneously or applying UVA after UVC/UVB reduced the inactivation of bacterium E. coli due to DNA repair and photoreactivation effect of UVA. However, applying extended UVA exposure before UVC significantly improved E. coli inactivation. For virus MS2 inactivation, only additive effect was observed under various wavelength combinations. This study presented a comprehensive work on UV-LEDs wavelength combinations, which is of significance on the application of UV-LEDs for water disinfection.

EPR investigations of polymeric and H2O2-modified C3N4-based photocatalysts

The C3N4-based nanopowders prepared by thermal condensation of melamine (MCN) with subsequent thermal etching (MCN-TE) and H2O2-treatment were investigated by Q- and X-band EPR spectroscopy in dark and upon in situ UVA or visible-light exposure. Lorentzian signal at g = 2.003, more pronounced in the case of the thermally etched material, dominates EPR spectra of MCN and MCN-TE. More complex spectra were found for H2O2-treated photocatalysts revealing the presence of signals attributed to the radicals produced via H2O2 interaction with C/N sites in the C3N4 polymeric network. The X-band spectra monitored upon in situ irradiation of the C3N4-based photocatalysts evidenced the intensity growth of the single line at g = 2.0033 indicating the photoinduced generation of electrons in localized paramagnetic states with the Curie dependence on temperature in the temperature range 100–180 K. The response towards UV or visible-light exposure was significantly limited in the case of H2O2-treated photocatalysts. EPR spin trapping experiments performed in aqueous suspensions demonstrated the formation of HO2• and HO• spin-adducts, and the increased stability of the primary photogenerated O2•– in aprotic media was well documented by the irradiation of the photocatalysts in the dimethylsulfoxide/water mixed solvent. The highest activities in the production of the non-persistent radical species spin-adducts were found for the thermally etched and pristine photocatalysts, confirming the negative effect of H2O2-treatment.

Two-Photon Imaging of NADH in SKH1 Mice Reveals Changes in Keratinocyte Metabolism with Chronic UVA Exposure

Cancer development is characterized by altered cell metabolism. Alterations of growth-factor signaling pathways adjust the metabolic phenotype to better support tumorigenesis and disease progression, which affects the concentration and binding characteristics of endogenous coenzymes such as nicotinamide adenine dinucleotide (NADH) and flavoproteins. To characterize metabolic changes induced by chronic UVA exposure in vivo, we designed and constructed a multiphoton laser scanning imaging platform specifically for in situ metabolic imaging of NADH within the skin of anesthetized mice. Age matched SKH1 hairless mice were divided equally into sham and UV treatment groups, with the treatment group receiving daily illumination of 15 kJ/m2 UVA. NADH phasor FLIM was used to characterize metabolism of keratinocytes as a function of cell layer within the epidermis in both groups over a period of months. Early changes in the enzyme-bound-to-free ratio of NADH were clearly evident prior to the onset of disease, with UVA- treated mice showing significantly greater proportion of enzyme-bound NADH. Basal keratinocytes generally had a lower bound-to-free ratio than keratinocytes from stratum spinosum or granulosa layers. Keratinocytes in vivo had a relatively greater fraction of bound NADH compared to squamous cell carcinoma cells in vitro. Changes in skin metabolism with normal aging was also clearly evident. This study demonstrates the feasibility and challenges of phasor FLIM metabolic imaging for long term longitudinal studies. This study was made possible by grants from the National Institute for General Medical Science (NIGMS) (5P20GM103427), a component of the National Institutes of Health (NIH), and its contents are the sole responsibility of the authors and do not necessarily represent the official views of NIGMS or NIH.

Pollution and Sun Exposure: A Deleterious Synergy. Mechanisms and Opportunities for Skin Protection.

Pollutants are diverse chemical entities, including gases such as ozone and particulate matter PM. PM contains toxic chemicals such as polycyclic aromatic hydrocarbons (PAHs). Some PAHs can induce strong oxidative stress under UVA exposure. Pollution aggravates some skin diseases such as atopy or eczema, but epidemiological data also pointed to a correlation with early occurrence of (photo)-aging markers. This paper aims at reviewing current literature dealing with dermatological effects of pollution, either on in vitro models or using in vivo approaches (including humans). It particularly focuses on the probable deleterious synergy between pollutants and sunlight. An exhaustive analysis of literature suggests that skin may be impacted by external stress through oxidation of some of its surface components. However, pollutants detected in plasma may also be provided to deep skin by the circulation of the blood. Oxidative stress, inflammation and metabolic impairments are among the most probable mechanisms of pollution- derived dermatological hazards. Moreover these stresses should be amplified by the deleterious synergy between pollution and sunlight. Some experiments from our lab identified few PAHs inducing a huge toxic stress, at nanomolar concentrations, when exposed to long UVA wavelengths. Prevention strategies should thus combine surface protection (long UVA sunscreens, antioxidants) and enhanced skin tissue resistance through stimulation of the natural antioxidation/detoxification pathway Nrf2. In people exposed to highly polluted environments, pollutants and sunlight may synergistically damage skin, requiring a specific protection.

Seaberry (&lt;i&gt;Hippophae rhamnoides L.&lt;/i&gt;) and Water Lily (&lt;i&gt;Nymphaeaceae&lt;/i&gt;) Extracts Protect Human Skin against Blue Light, Environmental Pollutants and UV-A Irradiations in an &lt;i&gt;Ex Vivo&lt;/i&gt; Model System

Background: The skin is the outer shell of the mammalian body and it is continuously exposed to a large spectrum of external stimuli including sun irradiation and atmospheric pollutants. These factors present deleterious effects on the cutaneous compartment by altering the skin barrier functions and accelerating the aging of the skin. Objectives: The goal of this study was to investigate the activity of Seaberry and Water Lily extracts, here called Dermina complex, against different external stresses. Methods: Human skin explants were exposed to different stimuli including delipidation by organic solvents, blue light, atmospheric pollutants and UV-A. The activity of the Seaberry and Water Lily extracts was assessed by immunohistochemistry and by biochemical assays. Results: We showed that Dermina complex prevents the delipidation-induced filaggrin decrease, suggesting that these plant extracts exhibited barrier function protecting properties. Also, we observed that Dermina complex showed an antioxidant and DNA protection activity by decreasing the activated form of Nrf2, the oxidized proteins and the formation of γ-H2AX induced upon stress conditions. The Dermina complex also decreased the pro-inflammatory cytokine IL-1 alpha released in the culture medium following atmospheric pollutants and UV-A exposure confirming its anti-inflammatory activity. Moreover, Dermina complex reduced the blue light-induced overexpression of opsin 3, indicating that its skin protection activities may be due, in part, to filter property against environmental stresses. Conclusions: Dermina complex shows a protective activity of the skin against different environmental stresses and these extracts may be able to slow down the aging process of the cutaneous compartment.