Effects Of UVA Research Articles

UVA-induced immunosuppression

It has previously been demonstrated that chronic low-dose solar-simulated ultraviolet (UV) radiation can induce both local and systemic immunosuppression as well as tolerance to a topically applied hapten. Epidermal cells from UV-irradiated mice inhibit spontaneous regression of tumours indicating that UV-induced immunosuppression is likely to permit the outgrowth of developing UV-induced skin tumours. We have used a chronic low-dose UV-irradiation protocol to investigate the effects of UVA on the skin immune system of C3H/HeJ mice. Irradiation with UVA+B significantly suppressed the local and systemic primary contact sensitivity (CS) response to the hapten TNCB. Furthermore UVA+B reduced Langerhans cell (LC) and dendritic epidermal T cell (DETC) numbers in chronically UV-irradiated mice. UVA-irradiation induced local, but not systemic, immunosuppression and reduced LC (32%) but not DETC from the epidermis compared to the shaved control animals. Treatment of mice with UVA+B or UVA radiation also induced an impaired secondary CS response, and this tolerance was transferable with spleen cells. Therefore exposure of C3H/HeJ mice 5 days per week for 4 weeks with UVA can induce local immunosuppression and tolerance. One of the mechanisms by which UVA affects biological systems is production of reactive oxygen species. We have also shown that Vitamin E, an inhibitor of lipid peroxidation, prevents UV-induced immunosuppression and loss of LC. It is possible that the UVA in UV radiation induces epidermal lipid peroxidation which stimulates LC migration from the epidermis, thus contributing to UV-induced immunosuppression. Hence, inhibition of epidermal lipid peroxidation by Vitamin E may provide some protection to the skin immune system from these effects of UV.

Photobiological and molecular mechanisms of ultraviolet a radiation-induced gene expression in human keratinocytes

The incidence and mortality rates of melanoma have risen for many decades in the United States. Increased exposure to ultraviolet (UV) radiation is generally considered to be responsible. Sunburns, a measure of excess sun exposure, have been identified as a risk factor for the development of melanoma. Because sunburns are primarily due to UVB (280-320 nm) radiation, UVB has been implicated as a potential contributing factor to the pathogenesis of melanoma. The adverse role of UVA (320-400 nm) in this regard is less well studied, and currently there is a great deal of controversy regarding the relationship between UVA exposure and the development of melanoma. This article reviews evidence in the English-language literature that surrounds the controversy concerning a possible role for UVA in the origin of melanoma. Our search found that UVA causes DNA damage via photosensitized reactions that result in the production of oxygen radical species. UVA can induce mutations in various cultured cell lines. Furthermore, in two animal models, the hybrid Xiphophorus fish and the opossum (Mondelphis domestica), melanomas and melanoma precursors can be induced with UVA. UVA radiation has been reported to produce immunosuppression in laboratory animals and in humans. Some epidemiologic studies have reported an increase in melanomas in users of sunbeds and sunscreens and in patients exposed to psoralen and UVA (PUVA) therapy. There is basic scientific evidence of the harmful effects of UVA on DNA, cells and animals. Collectively, these data suggest a potential role for UVA in the pathogenesis of melanoma. To date evidence from epidemiologic studies and clinical observations are inconclusive but seem to be consistent with this hypothesis. Additional research on the possible role of UVA in the pathogenesis of melanoma is required. (J Am Acad Dermatol 2001;44:837-46.)

Fluorescence study of maize irradiated by UVA

Effects of UVA on the growth of maize ( Zea mays L.) plants were investigated by growing them under two different controlled conditions. The weight of plants, length of stem, and length and width of the second leaf of each plant were measured. It was found that the growth of plants was reduced under UVA treatment at an early stage. We observed a clear-cut reduction in the growth of plants. The fluorescence spectra of green maize leaf induced by 337 nm radiation were obtained in each case, consisting of four peak bands at 435 nm (F435), 525 nm (F525), 684 nm (F684) and 740 nm (F740), respectively. The ratios of blue to green bands (F435/F525), blue to red bands (F435/F684) and the chlorophyll fluorescence (F684/F740) ratio were calculated and discussed.

Differential effects of UVB and UVA vs. UVA1 on cytokine regulation of tropoelastin gene expression

Differential effects of UVB and UVA vs. UVA1 on cytokine regulation of tropoelastin gene expression

Kinetics of DNA strand breaks and protection by antioxidants in UVA- or UVB-irradiated HaCaT keratinocytes using the single cell gel electrophoresis assay

The aim of this study was to characterize the genotoxic action of UVA and UVB in human keratinocytes by application of the single cell gel electrophoresis assay (SCGE assay). Dose dependence of DNA damage, the time course of its repair, and the influence of cellular antioxidant status were assessed. Irradiation with UVA or UVB both resulted in a dose-dependent increase in the level of DNA damage. A time course study to evaluate the repair kinetics in keratinocytes irradiated with 5 J/cm2 UVA revealed an immediate occurrence of DNA effects which subsequently disappeared within about 1 h, indicating removal of DNA lesions. This rapid repair of DNA damage is consistent with the observation that 5 J/cm2 UVA did not impair cellular viability. In contrast, exposure to 15 mJ/cm2 UVB resulted in a prolonged repair of DNA damage which lasted about 25 h. Thus, the repair kinetics of UVA- and UVB-induced DNA damage clearly differed from each other, implicating the induction of different types of DNA lesions by UVA and UVB. Neither a pretreatment with Mg–ascorbyl phosphate or d,l-α-tocopherol, nor depletion of endogenous glutathione altered cellular sensitivity to UVB. In contrast, the DNA damaging effects of UVA could be counteracted by a pretreatment with these antioxidants. These observations confirm that the UVA-induced effects on DNA are related to radical mediated strand breaks and DNA lesions forming alkali-labile sites. The UVB-induced effects mainly occur as a consequence of excision repair-related strand breaks. The observed repair kinetics of DNA lesions and the influence of cellular antioxidant status may help to elucidate protective mechanisms against the carcinogenic effects of UV radiation present in sunlight.

The Effects of UVA and UVB Irradiation on the Viscoelastic Properties of Hairless Mouse Skin in vivo

Background: Age-related changes in the elasticity of the human skin have been demonstrated as well as those due to proto ageing. Aims and Methods: To investigate if UV irradiation causes similar changes in the elastic properties of skin, hairless mice (HR/ICR) were irradiated chronically with suberythemal doses of UVA or UVB. Using a recently designed, commercially available noninvasive in vivo instrument, we compared skin thickness and elasticity after 8 weeks of UV exposure with age-matched control mice. Results: Skin thickness increased significantly after UVB irradiation. Skin elasticity (Ur/Uf) decreased significantly after UVA and UVB irradiation, and the ratio of viscosity to elasticity (Uv/Ue) increased significantly after UVA irradiation. Intrinsic immediate strain (Ue*) and intrinsic delayed strain (Uv*) decreased significantly after UVB and UVA exposure. These changes were similar to those reported previously in an in vivo study on human face skin using the same instrument. Conclusion: This finding suggests that the Ue* and Uv* changes observed in human facial skin are associated with actinic ageing caused by chronic UV exposure.

The effect of solar UVA and UVB on subarctic Daphnia pulicaria in its natural habitat

The effect of solar radiation, especially the ultraviolet regime (UVA and UVB), has been examined on Daphnia pulicaria (Forbes) in a subarctic lake. Daphnia were exposed to four radiation regimes: total radiation, exclusion of UVB, exclusion of UVA and UVB and dark controls. Exposure lasted 2–4 days in 2 depths (8 cm and 24 cm). In the subsurface (8 cm) exposure survival was significantly increased when UVB or UVB and UVA were excluded. In addition, the percentage of egg carrying Daphnia and the number of live offspring increased significantly when UVB was excluded. In 24 cm depth, an increase of survival was noticeable only in some of the experiments. Differences in reproduction due to different radiation regimes, too, were not significant. The results demonstrate that not only UVB, but UVA also may have a significant effect on Daphnia in their natural habitat.

Differential Responses of Growth and Photosynthesis in Cyamopsis Tetragonoloba L. Grown under Ultraviolet-B and supplemental long-wavelength radiations

Cyamopsis tetragonoloba L. seedlings were subjected to continuous ultraviolet (UV)-B radiation for 18 h and post-irradiated with white light (WL) and UV-A enhanced fluorescent radiations. UV-B treatment alone reduced plant growth, pigment content, and photosynthetic activities. Supplementation of UV-A promoted the overall seedling growth and enhanced the synthesis of chlorophyll and carotenoids with a relatively high photosystem 1 activity. Post UV-B irradiation under WL failed to photoreactive the UV-B damage whereas a positive photoregulatory effect of UV-A was noticed in electron transport rates and low temperature fluorescence emission spectra.

Measurements of the protective effect of topically applied sunscreens using in vitro three-dimensional dermal and skin equivalents.

For preventing or minimizing acute and chronic skin damage caused by UV radiation, the use of sunscreens is probably the most important measure. To screen the protective efficacy of new sunscreen molecules or formulations against UV rays, we evaluated as in vitro testing methods the use of two three-dimensional models, a dermal equivalent (DE) and a skin equivalent (SE). The DE is composed of a porous collagen-glycosaminoglycans-chitosan matrix populated by normal human fibroblasts. The SE is comprised of a fully differentiated epidermis realized by seeding keratinocytes onto the DE. In this study, we demonstrated that the DE and SE models react to the deleterious effects of UVA and UVB. Then, we extended our research to the evaluation of their usefulness for photoprotection trials. Sunscreen agents (Eusolex 8020 and 6300) and commercially available sunscreens (chemical and physical filter formulations) that protect the skin against either UVA or UBV were evaluated. The tested products were applied (n = 6) topically (10 microL) and incubated for 30 min prior to irradiation over a range of UVA (0-50 J/cm2) or UVB (0-5 J/cm2). The photoprotection provided by the tested sunscreen molecules and formulations was evaluated by measurement of residual cellular viability 24 h postirradiation using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and assessment of the inflammation response by interleukin-1 alpha release assay. When sunscreens were applied prior to UV exposure, a higher residual cellular viability versus control was obtained, demonstrating the photoprotective effects of the tested products. These in vitro models could be used for screening tests to evaluate the protective effects of sunscreen molecules and formulations, especially for UVA trials because there is a lack of consensus for an in vivo method.

Strategies of adaptation by Antarctic cyanobacteria to ultraviolet radiation

Effects of UVA and UVB radiation were evaluated on two cyanobacterial strains (Phormidium murrayi and Oscillatoria priestleyi) isolated from the McMurdo Ice Shelf, Antarctica. The two isolates showed some similarities, but also major differences in their qualitative and quantitative responses to ultraviolet radiation (UVR). Growth decreased with increasing UVR, but with a 5-fold (UVA) or 10-fold (UVB) greater effect on O. priestleyi than P. murrayi. In both isolates, cellular concentrations of phycobiliproteins (measured by in vivo absorbance), and to a lesser extent chlorophyll a, diminished with increasing UVR exposure. Spectral scans of methanol extracts indicated the presence of UVR-screening compounds in O. priestleyi but not P. murrayi; however, the absorbance per unit dry weight was low, and similar in cultures with and without UVR. Carotenoid pigments increased up to a threshold UVB flux and thereafter decreased. In both isolates, moderate UVA lessened the effect of growth inhibition by UVB, consistent with a UVA-activated repair mechanism. Comparative motility tests showed that O. priestleyi is a fast gliding species that can rapidly relocate in response to changes in ambient light, while P. murrayi is non-motile. The ability of O. priestleyi to escape UVR by gliding, and the greater ability of P. murrayi to tolerate UVA and UVB exposure, illustrate the differences in UVR survival strategies even between closely related species of cyanobacteria.

The inactivation of doxorubicin by long ultraviolet light.

Irradiation of doxorubicin (DOX) dissolved in RPMI medium 1640 by long ultraviolet (UVA) light results in a rapid decline in the cytotoxic activity of the drug. The present study was designed to sort out which component(s) of this medium are associated with the UVA inactivation of DOX. The effects of UVA irradiation of DOX in solutions of various compositions were evaluated by measuring the changes in the drug growth inhibitory activity in P388 cells and in the DOX absorbance spectrum. Riboflavin seemed to be the major photosensitizing component in the medium and the effect was enhanced by the presence of histidine, methionine, tryptophan and tyrosine but not by other amino acids. The changes in DOX resulting from UVA irradiation in the presence of riboflavin, were not blocked by 1,4-diazabicyclo [2.2.2]octane (5 mM), superoxide dismutase (300 units/ml), catalase (150 units/ml) or sodium benzoate (50 mM). The effects of UVA light on doxorubicin could be prevented by excess ascorbic acid. The effects of UVA on DOX are mediated by riboflavin. The photoexcited riboflavin apparently interacts directly with DOX rather than by first forming reactive oxygen species. The results suggest that the photoinactivation of DOX may involve an oxidation step. The mechanism by which certain amino acids facilitate the photoinactivation of DOX is not known. It is suggested that patient intake of riboflavin and exposure to the sun and fluorescent light could affect the outcome of anthracycline treatment.

Effect of UV-A and UV-B radiation on pigments, free amino acids and adenylate content of Dunaliella tertiolecta Butcher (chlorophyta)

The marine chlorophycean Dunaliella tertiolecta Butcher grown under controlled laboratory conditions was exposed to UV-A (10.2 W m −2), UV-B (1.6 W m 2) or UV-A plus UV-B (10 W m −2/1.5 W m −2) in connection with white light (100 W m −2) radiation for up to 5 h at 20°C. Uptake of 15N-ammonium (5 or 100 μM) was more affected by UV-B and UV-A plus UV-B radiation than by UV-A. Pattern of pigments varied in dependence on the exposure time (2 or 5 h) and the waveband of the applied UV as well as of the used ammonium concentration. The xanthophyll cycle was more affected by UV-A plus UV-B radiation than by V-B or UV-A. UV-A and UV-B irradiance resulted in an increase of main amino acid biosynthesis and an enhancement of the main free amino acid pools. Changes in the pattern of the free amino acid pools were found in dependence on the applied ammonium concentration (5 or 100 μM). Contents of AMP, ADP and ATP were also differently affected by UV radiation in dependence on the ammonium concentration 1. Results are discussed in relation to the UV effects on photosynthetic pigments, energy supply and the key enzymes of the carbon and nitrogen metabolism.

Feeding Deterrence of Spodoptera exigua (Lepidoptera: Noctuidae) Larvae by Low Concentrations of Linear Furanocoumarins

We conducted choice tests and behavioral observations of Spodoptera exigua (Hubner) larvae to study the effect of linear furanocoumarins (bergapten, xanthotoxin, and psoralen) individually or in combination at concentrations commonly found in Apium graveolens L. and UV-A light on larval preference and feeding behavior. Linear furanocoumarins had a negative and concentration-dependent effect on diet preference by S. exigua larvae. Behavioral observations showed that preference of control diet is the result of feeding deterrence by these compounds. The larvae leave the furanocoumarin-containing diet more frequently by becoming more mobile after ingestion of the treated diet, as measured by time spent questing (in which larvae walk or lift their thoraxes, and move from side to side in a searching motion) and number of questing occurrences. The UV-A effect was not significant. We conclude that linear furanocoumarins (at the concentrations found in A. graveolens ) can play an important role as behavioral modifiers rather than as toxic defenses against larvae of the generalist herbivore S. exigua .

GM-CSF production by epithelial cell line: upregulation by ultraviolet A.

It was demonstrated that UVB increases synthesis and expression of IL-1 alpha and GM-CSF by keratinocytes. Upregulation of GM-CSF by UVB is reported to be mediated by IL-1 alpha. However, regulation of IL-1 alpha and GM-CSF by UVA is not well-known. The purpose of the present study was to evaluate the effects of UVA on IL-1 alpha and GM-CSF production. Here we used a competitive RT-PCR for measuring cytokine gene expression in an epidermal cell line after UVA irradiation. IL-1 alpha and GM-CSF mRNA did not show any change at 1 h and 6 h following exposure to UVA. After UVA irradiation, however, IL-1 alpha mRNA decreased and GM-CSF mRNA increased at 24 h and the level of GM-CSF in culture supernatant increased at 24 h and 48 h. Addition of antihuman IL-1 alpha neutralizing antibody to UVA irradiated cells did not prevent the increase of GM-CSF mRNA expression. These results suggest that UVA radiation may induce GM-CSF production through an IL-1 alpha independent pathway.

Epidermal stratification reduces the effects of UVB (but not UVA) on keratinocyte cytokine production and cytotoxicity

Ultraviolet (UV) radiation induces cytokine release from cultured keratinocytes as well as from epidermis in vivo. The purpose of this study was to determine whether differentiation of cultured keratinocytes into stratified epithelium decreases the effects of UVA and UVB radiation on cytokine release. Interleukin-1 (IL-1) alpha, IL-1 beta and tumor necrosis factor (TNF)-alpha release from human keratinocytes and reconstituted human epidermis was measured after exposure to UVA or UVB radiation. Release of IL-1 alpha, IL-1 beta, and TNF-alpha was induced by both UVA and UVB radiation from both keratinocytes and reconstituted epidermis. Release of these cytokines was correlated with cytotoxicity. Keratinocyte cultures were far more sensitive to UVB radiation than reconstituted epidermis, in terms of both cytotoxicity and cytokine release. In contrast, epidermal stratification/differentiation had much less effect on the sensitivity to UVA radiation. We conclude that epidermal stratification and the formation of a stratum corneum provide protection against UVB radiation but have limited barrier effect against UVA radiation.

UV-absorbing substances in zooxanthellate and azooxanthellate clams

The effects of UV-A and UV-B radiation on photosynthesis of zooxanthellae within the siphonal mantle of the giant clam, Tridacna crocea, and in isolation were studied. While UV-B irradiation (2.4 W m−2, 20 min) completely suppressed photosynthesis of the isolated zooxanthellae, it had little effect on their photosynthetic ability if they were irradiated while within the siphonal mantle of the host tissue. Chemical analysis of the siphonal mantle of T. crocea showed the presence of significant amounts of mycosporine-like amino acids (MAAs), which absorb UV-A and -B light. However, no MAA was detected in the isolated zooxanthellae. MAAs were concentrated in the siphonal mantle and kidney tissues in comparison with other tissues. In the siphonal mantle, MAA concentrations were the highest in the outermost surface layer where most of the zooxanthella cells resided. This indicates that the zooxanthellae are protected from UV radiation by a screen of concentrated MAAs in the host clam. Aside from T. crocea, significant amounts of MAAs were found not only in other zooxanthellate clams, such as T. derasa, Hippopus hippopus, Colculum cardissa and Fragum unedo, but also in a closely related azooxanthellate clam, Vasticardium subrugosum. On the other hand, no MAA was detected in any of the zooxanthellae from these zooxanthellate clams. No MAA was detected in the tissues of a deep-sea bivalve, Calyptogena soyoae. Although MAAs seem to block strong UV radiation in the shallow-water clam, they are probably not essential for the clam's life in the dark. MAAs in shallow-water clams may be derived from food and accumulated in their tissues, especially in the siphonal mantle and kidney.

UVA II exposure of human skin results in decreased immunization capacity, increased induction of tolerance and a unique pattern of epidermal antigen-presenting cell alteration.

The risks incurred from increased exposure to UVA II (320-340 nm) (i.e. during sunscreen use and extended outdoor exposure, tanning parlors) are not well understood. Therefore, we explored the effects of UVA II on skin immune responses in humans. After a single local exposure (4 minimum erythemal dose [MED]) using a xenon are lamp filtered with a narrow bandpass filter (335 +/- 5 nm full width at half maximum), individuals were contact-sensitized with dinitrochlorobenzene (DNCB) through a UVA II exposure site or through normal skin. UVA II induced a marked decrease in the magnitude of skin immune responses (P < 0.0001). The UVA II group had only 29% successful sensitizations, as compared to 83% in the control group. The percentage of individuals who remained tolerant to DNCB after two sensitizations was 23.6% for the UVA II-exposed group, as compared to 3.8% in the controls (P = 0.006). UVA II also uniquely altered the type of antigen-presenting cells present in the epidermis. Human leukocyte antigen (HLA)-DR+ cells in control epidermal cell suspensions (C-EC) comprised a single, homogeneous population of Langerhans cells (LC) with the phenotype: CD1ahi DRmid CD11b CD36 (1.5 +/- 0.3% of EC). UVA II irradiation reduced the number of such LC to 0.6 +/- 0.2% of EC. Although cells expressing the macrophage phenotype: CD1a- DRhi CD11b+ CD36+ were increased in UVA II skin, relative to C-EC, these comprised only 10.1 +/- 6.1% of the DR+ cells, which is less than that after UVB exposure. Also distinct from UVB, a third population was found in UVA II-EC, which exhibited a novel phenotype: CD1a+ DR+ CD36+ CD11b+; these comprised 11.1 +/- 6.9% of the DR+ UVA II-EC. In conclusion, despite the above differences in infiltrating DR+ cells, both UVB and UVA II reduce the skin's ability to support contact sensitization, induce active suppression (tolerance) and induce a reduction in LC.

Effect of UVA on immunization with epicutaneous antigens — a pilot study

Effect of UVA on immunization with epicutaneous antigens — a pilot study

Near ultraviolet radiation (UVA and UVB) causes a formamidopyrimidine glycosylase-dependent increase in G to T transversions.

In contrast to far-UV (< 290 nm) DNA damage, a large fraction of the DNA damage caused by near-UV is oxygen-dependent, suggesting the involvement of reactive oxygen species (ROS). The oxidized base 8-oxo-7,8-dihydroguanine (GO) is characteristic of ROS-induced DNA damage and is removed by Fapy (formamidopyrimidine) glycosylase. We have recently shown that Escherichia coli strains deficient in Fapy glycosylase (fpg) are hypersensitive to the lethal effects of UVA but not far-UV (UVC), suggesting lesions recognized by this enzyme may be important premutagenic or lethal lesions generated by near-UV radiation. In this study, we have found that while the far-UV-induced mutation rates of Fapy-deficient and wild-type strains were similar, near-UV (UVA and UVB) was hypermutagenic to a Fapy-deficient strain, causing a dose-dependent increase in induced mutation relative to wild type (up to five-fold at 200 kJ/m2). Using a plasmid back mutation assay, the predominant near-UV-induced mutations in both wild-type and Fapy-deficient strains were found to be C-->T transitions and G -->T transversions. The former is probably due to replicative bypass of pyrimidine dimers or (6-4) photoproducts that are known to be generated by near-UV, whereas the latter may be due to mispairing of GO lesions with adenine during replication. Consistent with this, the frequency of near-UV-induced G-->T transversions was 16-fold higher in a Fapy-deficient strain than a wild-type strain.

Short‐ and Long‐Term Effects of UVA and UVB on Marine Phytoplankton Productivity

Short‐ and Long‐Term Effects of UVA and UVB on Marine Phytoplankton Productivity