Influence Of UV-B Irradiation Research Articles

Comprehensive Analysis of Exosomal MicroRNAs Derived from UVB-Irradiated Keratinocytes as Potential Melanogenesis Regulators.

The exosomes derived from keratinocytes can have a substantial impact on melanogenesis by influencing melanocytes. MicroRNAs (miRNAs) encapsulated within exosomes are implicated in the control of melanogenesis, particularly when under the influence of UVB irradiation. This investigation explores UVB-induced exosomal miRNAs from keratinocytes as potential regulators of melanogenesis. UVB-irradiated, keratinocyte-derived exosomes were observed to augment melanogenesis in melanocytes, resulting in an upregulation of MITF, TRP1, TRP2, and TYR expression compared to non-UVB-irradiated exosomes. Additionally, a subset of exosomal miRNAs was differentially selected and confirmed to exert both enhancing and inhibitory effects on melanogenesis through functional assays. Notably, hsa-miR-644a, hsa-miR-365b-5p, and hsa-miR-29c-3p were found to upregulate melanogenesis, while hsa-miR-18a-5p, hsa-miR-197-5p, and hsa-miR-4281 downregulated melanogenesis. These findings suggest the involvement of keratinocyte-derived exosomal miRNAs in melanogenesis regulation within melanocytes. The expression levels of exosomal miRNAs from keratinocytes exhibited a UVB-dependent increase, indicating a potential role for these miRNAs as regulators of melanogenesis in response to UVB irradiation. Furthermore, melanogenesis was found to be dependent on exosomes derived from keratinocytes. This underscores the potential of UVB-induced exosomal miRNAs derived from keratinocytes as regulators of melanogenesis. Moreover, this study unveils a significant role for exosomes in melanocyte pigmentation, presenting a novel pathway in the intricate process of melanogenesis.

Influence of UVB-Irradiation on the Structures and Solid Particle Erosion Resistance for CF/PC Composites

The service life and properties of Carbon fiber reinforced polycarbonate (CF/PC) composites are seriously affected by ultraviolet radiation from outdoor exposure during aging. In this work, the changes of structure and solid particle erosion resistance for CF/PC composites after ultraviolet irradiation were studied. It was shown that ultraviolet irradiation causes photo-oxygen aging and photo-fries re-arrangement of the composite, and the result was confirmed by FTIR. We correlated the solid particle erosion resistance with aging time, and found that the solid particle erosion resistance of CF/PC composites greatly decreased by UVB irradiation during 15 hours. Furthermore, the eroded material surface was analyzed using scanning electron microscope (SEM). It suggests that ultraviolet aging leads to plasticization and degradation, resulting in reduction of erosion resistance of the composite.

Human mesenchymal stem cells are resistant to UV-B irradiation

Albeit being an effective therapy for various cutaneous conditions, UV-B irradiation can cause severe skin damage. While multipotent mesenchymal stem cells (MSCs) may aid the regeneration of UV-B-induced skin injuries, the influence of UV-B irradiation on MSCs remains widely unknown. Here, we show that human MSCs are relatively resistant to UV-B irradiation compared to dermal fibroblasts. MSCs exhibited higher clonogenic survival, proliferative activity and viability than dermal fibroblasts after exposure to UV-B irradiation. Cellular adhesion, morphology and expression of characteristic surface marker patterns remained largely unaffected in UV-irradiated MSCs. The differentiation ability along the adipogenic, osteogenic and chondrogenic lineages was preserved after UV-B treatment. However, UV-B radiation resulted in a reduced ability of MSCs and dermal fibroblasts to migrate. MSCs exhibited low apoptosis rates after UV-B irradiation and repaired UV-B-induced cyclobutane pyrimidine dimers more efficiently than dermal fibroblasts. UV-B irradiation led to prolonged p53 protein stability and increased p21 protein expression resulting in a prolonged G2 arrest and senescence induction in MSCs. The observed resistance may contribute to the ability of these multipotent cells to aid the regeneration of UV-B-induced skin injuries.

Influence of UV-B radiation on lead speciation in the presence of natural particles of estuarine waters.

The influence of UV-B irradiation on filtered and non-filtered water samples collected in a non-polluted area of Tagus estuary was evaluated in this study. In the laboratory, both samples were titrated with lead (Pb(+2)) followed by differential pulse anodic stripping voltammetry (DPASV), before and after 1 and 10days under UV-B irradiation. Metal-ligand complexing parameters were obtained based on a macromolecular heterogeneous ligand described by two distinct sites with a labile behavior, and a third small homogeneous weaker group, which concentration was determined from a potentiometric titration. Under UV-B radiation, the complexing strength decreased with time in both (filtered and non-filtered) irradiated samples, but this effect was more pronounced in the non-filtered water, which might be due to some adsorption of dissolved macromolecular ligands on the particles and/or to further degradation of dissolved organic matter (DOM). Furthermore, the presence of particles favored the break-down of the macromolecular ligand under long UV-B exposure time. These results present ecological implications for the estuarine ecosystems such as bioavailability and toxicity.

UVB irradiation-induced impairment of keratinocytes and adaptive responses to oxidative stress

UVB irradiation of human skin is known to induce pathophysiological processes as oxidative stress and inflammation. HaCaT keratinocytes represent a well-established in vitro model system to investigate the influence of UVB irradiation on cell cultures. It was the aim of these investigations to study the effects of moderate UVB doses on cellular and mitochondrial integrity of HaCaT keratinocytes, biomarkers of oxidative stress and antioxidant protection by superoxide dismutases. F2-isoprostane concentrations were UVB dose-dependently enhanced reaching a plateau at 50 mJ/cm2. Cell viability was reduced and apoptosis was enhanced with increasing UVB doses. The activities of the respiratory chain complexes were practically not altered at lower UVB doses, up to 50 mJ/cm2, whereas remarkable decreases, also for the levels of cardiolipin species, were seen at 100 mJ/cm2. As an adaptive response to the enhanced oxidative stress, protein levels of MnSOD increased about 3-fold at 50 mJ/cm2 and decreased at higher doses. From the data it can be concluded that keratinocytes are sufficiently protected at low UVB doses, whereas higher doses lead to irreversible cell damage.

Effect of UVB Irradiation on Cu2+-Binding Organic Ligands and Cu2+ Speciation in Alpine Lake Waters of New Zealand

Environmental Context. The bioavailability of dissolved metals in natural waters is directly affected by metal-sequestering agents. These agents include soil-derived matter and compounds released by microorganisms, since copper can support or inhibit aquatic microorganisms depending on concentration. During summer the levels of copper increase in surface waters, an effect intuitively attributable to increased ultraviolet light degrading the sequestering agents more effectively, leading to a concurrent release of the metal. This paper shows that the amount of degradation attributable to light is too low to explain the metal release and that a biological influence may instead be responsible. Abstract. The influence of UVB irradiation on the Cu2+ binding by natural organic ligands in six alpine lakes on the South Island, New Zealand, has been investigated using competitive ligand equilibration with salicylaldoxime and detection by cathodic stripping voltammetry (CLE-CSV). During austral summer 2002–2003 the total dissolved Cu ([Cu]T), the concentration of strong Cu2+-binding ligands ([L]T), and their conditional stability constant K´´ were determined in surface samples of all six lakes. All lakes exhibited appreciable concentrations of a strong Cu2+ binding ligand with similar K´´ values and concentrations always exceeding [CuT], thus dominating Cu2+ speciation. Four lakes (Hayes, Manapouri, Wanaka, Te Anau) showed no appreciable trend in [LT] throughout the summer, whereas in Lakes Wakatipu and Hawea [LT] increased steadily throughout this period. Laboratory UVB irradiation of lake water samples using a 400 W mercury lamp with a Pyrex glass filter (λ > 280 nm) showed that Cu2+-binding ligands are destroyed by UVB radiation, causing [L]T to decrease with a rate of –0.588 nmol L–1 h–1 (r2 0.88). From this we calculate that the in situ ligand destruction rate by UVB in summer for surface waters of these lakes is too small to significantly affect [LT], and conclude that variations in ligand concentrations must result from seasonally variable biological factors.

Cytokinin oxidase/dehydrogenase in Pisum sativum plants during vegetative development. Influence of UV-B irradiation and high temperature on enzymatic activity

Cytokinin oxidase/dehydrogenase (EC 1.5.99.12) specific activity was determined in leaves and roots of two P. sativum cultivars (cv. Scinado and cv. Manuela) during vegetative development and the effect of UV-B irradiation or elevated temperature was assessed. The measurement of CKX activity during development showed localisation of this enzyme to roots. The reduction in CKX activity in leaves after UV-B irradiation and the increased levels of the enzyme in high temperature-treated plants suggests that the enzymes from the CKX gene family have a different expression during stress responses provoked by different factors and probably are tissue specific. Differences regarding cytokinin oxidase/dehydrogenase activity stress response were observed between the two pea cultivars.

Influence of UV-B irradiation on the carotenoid content of Vitis vinifera tissues

The carotenoid content was examined in leaf and berry tissues of grapevines (cv. Cabernet Sauvignon) grown either under ambient conditions or under a polyester film to reduce UV light by 98%. Total carotenoids in leaves were less in vines grown under the UV screen. Levels of β-carotene decreased with berry development around veraison. This effect was more pronounced in vines grown under reduced UV light. The lutein content of berries appeared to remain relatively constant with berry development, but levels were decreased under the UV screen. These observations are important for the wine industry because of the biosynthetic link between carotenoids and wine flavour and aroma compounds.

Influence of UV-B irradiation in lead speciation from an estuarine sample

The influence of UV-B irradiation in estuarine water from the salt marsh of Corroios, Tagus river, was studied in the laboratory in terms of lead speciation. The filtered water was exposed to UV-B irradiation with a intensity of 540 μW/cm 2. The effect of UV-B (280–320 nm) was studied from the titration with Pb 2+, followed by anodic stripping voltammetry in differential-pulse mode, after different periods of irradiation time, from 1 h up to 10 days. It was found that, before UV-B irradiation, Pb 2+ speciation can be interpreted assuming two different types of ligands: one macromolecular, with an heterogeneous behaviour represented by two main groups, while the other is a small ligand, homogeneous in terms of Pb 2+ complexation. Stability constant values indicate that the heterogeneous ligand presents a humic-like behaviour, with minor sites related to phenolic, amino or sulphur type groups, and major sites related to carboxylic type groups. Small homogeneous ligands, probably released by bioorganisms, also present stability constants of carboxylic type groups. From the results it can be observed that UV-B irradiation decreases complexing strength of the medium as well as its heterogeneity, both effects becoming evident after 1 h of irradiation. Even so, for the concentration range studied ( C Pb≤2×10 −6 M) more than 80% of Pb II still remains complexed to the weaker group of the macromolecular ligand. Since UV-B doses are similar to maximum spring solar intensity, the results suggest both chemical and ecological implications.

UV protection in cyanobacteria

If the depletion of the stratospheric ozone shield continues, the influx of solar UV-B radiation (280–320 nm) will increase in the near future. In photosynthetic organisms there are several targets for the deleterious UV-B radiation, such as proteins, DNA and membranes. Cyanobacteria use three different types of strategies to counteract UV damage: (i) stress avoidance by gliding mechanisms, (ii) stress defence by synthesis of UV-absorbing compounds, antioxidants and extracellular polysaccharides, and (iii) repair mechanisms including DNA repair and resynthesis of UV-sensitive proteins. In the past, most studies concentrated on the physiological aspects of UV tolerance whereas the molecular basis of UV tolerance in cyanobacteria is poorly understood. We will summarize the effects of and responses to UV-B at the physiological and molecular levels and present data on the influence of UV-B irradiation on the proteome of the terrestrial cyanobacterium Nostoc commune. SDS-PAGE and high-resolution two-dimensional gel electrophoresis were used to analyse the influence of UV-B on the proteome of N. commune. The resolution of SDS-PAGE turned out to be far too low to monitor the UV acclimation process. In contrast to the latter technique, two-dimensional electrophoresis showed that the UV-B response is extremely complex, involving the induction and the repression of a large number of proteins.

Influence of UVB irradiation on nitrate and ammonium assimilating enzymes in Spirodela polyrhiza

The influence of UVB radiation on nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT) and ferredoxin-dependent glutamate synthase (Fd-GOGAT) was investigated in fronds and turions of Spirodela polyrhiza. When white light (4.3 W m −2) was supplemented with UVB (0.55 W m −2; λ max = 311 nm), a 40% transient decrease in the growth rate was observed after 12 h UVB irradiation. In addition, the activities of all enzymes investigated, except for the cytoplasmic isoform of GS, were substantially inhibited (NR, 80%; NiR, 32%; GS, 30%; NADH-GOGAT, 36%; Fd-GOGAT, 54% in green fronds). The extent of the inhibition in fronds as well as in turions is in accordance with the assumption that the light-induced increases of enzyme activities are prevented by simultaneous application of UVB. The uptake of nitrate was not influenced by white light or UVB. As shown by western analysis, a correlation between the enzyme activities and their protein amounts was found. Northern analysis revealed that UVB influenced the transcript accumulation of NR but not of Fd-GOGAT. No obvious correlation was observed between the mRNA and the protein amount. This suggests that UVB damage occurs at the transcriptional and post-transcriptional levels as well as at the protein level.

Pteridines in the Control of Pigmentation

The influence of UVB irradiation on the metabolic pathway for the production of L-tyrosine from L-phenylalanine in the human epidermis has been examined in 12 healthy volunteers with photo skin types I-VI (Fitzpatrick classification). This metabolic pathway involves the induction of GTP-cyclohydrolase 1 (GTP-CH-1), the rate-limiting enzyme for de novo synthesis of (6R)L-erythro-5,6,7,8-tetrahydrobiopterin (6-BH4). This essential cofactor controls the production of L-tyrosine from L-phenylalanine via phenylalanine hydroxylase (PAH). The de novo synthesis of 6-BH4 depends on the induction of GTP-CH-1, e.g., by tumor necrosis factor-alpha (TNF alpha). Epidermal suction blister tissues were taken before (0 h) and after (24 and 72 h) UVB exposure with a standardized dosage [1 minimal erythema dose (MED)]. In all cases, there was a significant increase in TNF alpha release, GTP-CH-1 activity, total 6-biopterin level, and PAH activity, indicative of enhanced L-tyrosine production. The response of this metabolic cascade over baseline activities was pronounced in fair photo skin types (I-III) compared to dark skin (IV-VI). Taken together, our results suggest that UVB can control the direct supply of L-tyrosine in the epidermis, and this process may represent an important factor in de novo melanogenesis.

Impact of UV-B radiation on 15N-Ammonium and 15N-Nitrate uptake by Haematococcus lacustris (volvocales) II. The influence of a recovery period

Summary The influence of UV-B irradiation (280–320 nm; 0.5 to 5 hours; 1.25 Wm −2 ) applied at the beginning of a 12 hours polychromatic irradiated («white light recovery») period (8 Wm −2 PAR) on the accumulation of 15 N-ammonium and 15 N-nitrate, the content of protein and amino acids/amides was investigated in different developmental stages (flagellates/aplanospores) and pre-cultivation variants (N-supplied/N-starved) of the freshwater green alga Haematococcus lacustris . In a further series of experiments the consequences of a white light recovery period, extended to 24 hours, on the UV-B influenced 15 N-accumulation was examined. Main results indicate: (1) The 12 hours recovery period does not abolish the uptake inhibition by UV-B, but lowers significandy the scope of it (i.e. the decrease of the N-accumulation; exception: N-starved (predark, -N) precultivated flagellates). (2) The cell type specific UV-B dose dependent course of the inhibition was similar to that without a recovery period (stronger in flagellates than in aplanospores). (3) An extension of the recovery period to 24 hours altered drastically the response of the flagellates (stimulated 15N uptake after UV-B irradiation, dose-dependent) but not in the aplanospores. (4) Proteins and pools of free amino acids/amides were specific influenced by the UV-B treatment and the recovery period, respectively. Also the relative content in single amino acids changed differendy on the UV impact, dependent on cell type, pre-treatment and if a recovery was included or not. Also without mentioning the UV-B impact, significant differences in the content of single amino acids were observed between flagellates and aplanospores: Arginine and glutamate were higher in aplanospores, whereas the opposite was found for serine.

Effect of UVB irradiation on enzymes of nitrogen metabolism in turions of Spirodela polyrhiza (L.) Schleiden

The influence of UVB irradiation on the enzymes of nitrogen metabolism (nitrate reductase, EC 1.6.6.1, nitrite reductase, EC 1.7.7.1, alanine aminotransferase, EC 2.6.1.2, aspartate aminotransferase, EC 2.6.1.1, glutamine synthetase, EC 6.3.1.2) and the uptake of ammonium and nitrate in turions of Spirodela polyrhiza was investigated. UVB irradiation was started either immediately after transferring the turions from 5 °C (after-ripening conditions) to 25 °C (germination conditions) or after a storage period at 25 °C in darkness for 72 h. The activities of all enzymes investigated were decreased by UVB irradiation (12 or 24 h). The activity of nitrate reductase was more strongly inhibited than that of nitrite reductase, and the activity of alanine aminotransferase was more strongly decreased than that of aspartate aminotransferase. The inhibitory effect of UVB on glutamine synthetase was only small. Within a period of 5 h neither the uptake of ammonium nor that of nitrate was influenced by UVB irradiation. Because UVB irradiation did not influence the light-dependent germination of turions, the results presented support the conclusion that the regulation of germination and the regulation of nitrate assimilation are unrelated phenomena in turions

Inactivation of photosynthetic oxygen evolution by UV-B irradiation: A thermoluminescence study

The influence of UV-B irradiation on photosynthetic oxygen evolution by isolated spinach thylakoids has been investigated using thermoluminescence measurements. The thermoluminescence bands arising from the S2QB (-) (B band) and S2QA (-) (Q band) charge recombination disappeared with increasing UV-B irradiation time. In contrast, the C band at 50°C, arising from the recombination of QA (-) with an accessory donor of Photosystem II, was transiently enhanced by the UV-B irradiation. The efficiency of DCMU to block QA to QB electron transfer decreased after irradiation as detected by the incomplete suppression of the B band by DCMU. The flash-induced oscillatory pattern of the B band was modified in the UV-B irradiated samples, indicating a decrease in the number of centers with reduced QB. Based on the results of this study, UV-B irradiation is suggested to damage both the donor and acceptor sides of Photosystem II. The damage of the water-oxidizing complex does not affect a specific S-state transition. Instead, charge stabilization is enhanced on an accessory donor. The acceptor-side modifications decrease the affinity of DCMU binding. This effect is assumed to reflect a structural change in the QB/DCMU binding site. The preferential loss of dark stable QB (-) may be related to the same structural change or could be caused by the specific destruction of reduced quinones by the UV-B light.