Effect of cyclobutane pyrimidine dimers on apoptosis induced by different wavelengths of UV.

Ultraviolet radiation within three different wavelength ranges, UVA (340-400 nm), UVB (290-320 nm) or UVC (200-290 nm), was shown to induce apoptosis in OCP13 cells, derived from the medaka fish. Morphological changes such as cell shrinkage and a decrease in the number of nucleoli appeared 4 h after UVA, UVB or UVC irradiation, although with different relative efficiencies. Doses required to induce apoptosis with similar efficiencies were about 2500-fold higher for UVA and 10-fold higher for UVB than for UVC. The following phenomena occurred after UVA irradiation but not after UVB or UVC irradiation. (1) Ultraviolet-A-induced cell detachment occurred with or without cycloheximide pretreatment. (2) Cells attached to plastic showed morphological changes such as rounding up of nuclei without a change in the cell distribution. (3) Morphological changes after UVA irradiation could not be evaded by photorepair treatment. (4) Morphological changes did not occur in cells attached to glass coverslips but only those in plastic dishes. (5) Apoptosis occurred without detectable increase of caspase-3-like activity. (6) Morphological changes were inhibited by N-acetylcysteine, a scavenger of active oxygen species. These results suggest the existence of two different pathways leading to apoptosis, one for long- (UVA) and the other for short- (UVB or UVC) wavelength radiation.     

SPECTRAL DEPENDENCE OF UV-INDUCED IMMEDIATE AND DELAYED APOPTOSIS: THE ROLE OF MEMBRANE AND DNA DAMAGE

Abstract— The phototoxicity of each waveband region of UV radiation (UVR), i.e., UVA (32CM100 nm), UVB (290–320 nm) and UVC (200–290 nm), was correlated with an apoptotic mechanism using equilethal doses (10% survival) on murine lymphoma L5178Y-R cells. Apoptosis was qualitatively monitored for DNA "ladder" formation (multiples of 200 base pair units) using agarose gel electrophoresis, while the percentages of apoptotic and membrane-permeabilized cells were quantified over a postexposure time course using flow cytometry. The UVA1 radiation (340–400 nm) induced both an immediate (<4 h) and a delayed (>20 h) apoptotic mechanism, while UVB or UVC radiation induced only the delayed mechanism. The role of membrane damage was examined using a lipophilic free-radical scavenger, vitamin E. Immediate apoptosis and membrane permeability increased in a UVA1 dose-dependent manner, both of which were reduced by vitamin E. However, vitamin E had little effect on UVR-induced delayed apoptosis. In contrast, the DNA damaging agents 2,4- and 2,6-diaminotoluene exclusively induced delayed apoptosis. Thus, immediate apoptosis can be initiated by UVA 1-induced membrane damage, while delayed apoptosis can be initiated by DNA damage. Moreover, the results suggest that immediate and delayed apoptosis are two independent mechanisms that exist beyond the realm of photobiology.     

Induction of 8-Oxo-7,8-Dihydro-2'-Deoxyguanosine by Ultraviolet Radiation in Calf Thymus DNA and HeLa Cells

Abstract— The levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in purified calf thymus DNA and HeLa cells were measured following exposure to either UVC, UVB or UVA wavelengths. This DNA damage was quantitated using HPLC coupled with an electrochemical detector. The 8-oxodGuo was induced in purified DNA in a linear dose-dependent fashion by each portion of the UV spectrum at yields of 100, 0.46 and 0.16 8-oxodGuo per 10⁵ 2'-deoxyguanosine (dGuo) per kJ/m² for UVC, UVB and UVA, respectively. However, the amount of 8-oxodGuo in HeLa cells irradiated with these UV sources decreased to approximately 2.0, 0.013 and 0.0034 8-oxodGuo per 10⁵ dGuo per kJ/m², respectively. In contrast, the levels of cyclobutyl pyrimidine dimers were similar in both irradiated DNA and cells. Therefore, 8-oxodGuo is induced in cells exposed to wavelengths throughout the UV spectrum although it appears that protective precesses exist within cells that reduce the UV-induced formation of this oxidative DNA damage. Cell survival was also measured and the number of dimers or 8-oxodGuo per genome per lethal event determined. These calculations are consistent with the conclusion that dimers play a major role in cell lethality for UVC- or UVB-irradiated cells but only a minor role in cells exposed to UVA wavelengths. In addition, it was found that the relative yield of 8-oxodGuo to dimers increased nearly 1000-fold in both UVA-irra-diated cells and DNA compared with cells subjected to either UVC or UVB. These results are supportive of the hypothesis that 8-oxodGuo, and possible other forms of oxidative damage, play an important role in the induction of biological effects caused by wavelengths in the UVA portion of the solar spectrum.     

Wavelength dependence of ultraviolet-induced DNA damage distribution: involvement of direct or indirect mechanisms and possible artefacts.

DNA damage profiles have been established in plasmid DNA using purified DNA repair enzymes and a plasmid relaxation assay, following exposure to UVC, UVB, UVA or simulated sunlight (SSL). Cyclobutane pyrimidine dimers (CPDs) are revealed as T4 endonuclease V-sensitive sites, oxidation products at purine and pyrimidine as Fpg- and Nth-sensitive sites, and abasic sites are detected by Nfo protein from Escherichia coli. CPDs are readily detected after UVA exposure, though produced 10(3) and 10(5) times less efficiently than by UVB or UVC, respectively. We demonstrate that CPDs are induced by UVA radiation and not by contaminating UVB wavelengths. Furthermore, they are produced at doses compatible with human exposure and are likely to contribute to the mutagenic specificity of UVA [E. Sage et al., Proc. Natl. Acad. Sci. USA 93 (1996) 176-180]. Oxidative damage is induced with a linear dose dependence, for each region of the solar spectrum, with the exception of oxidized pyrimidine and abasic sites, which are not detectable after UVB irradiation. The distribution of the different classes of photolesions varies markedly, depending on wavelengths. However, the unexpectedly high yield of oxidative lesions, as compared to CPDs, by UVA and SSL led us to investigate their production mechanism. An artificial formation of hydroxyl radicals is observed, which depends on the material of the sample holder used for UVA irradiation and is specific for long UV wavelengths. Our study sheds light on a possible artefact in the production of oxidative damage by UVA radiation. Meanwhile, after eliminating some potential sources of the artefact ratios of CPDs to oxidized purine of three and five upon irradiation with UVA and SSL, respectively, are still observed, whereas these ratios are about 140 and 200 after UVC and UVB irradiation.     

Oxidation of guanine in cellular DNA by solar UV radiation: biological role.

The formation of cyclobutane pyrimidine dimers (CPD) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) was investigated in Chinese hamster ovary cells upon exposure to either UVC, UVB, UVA or simulated sunlight (SSL). Two cell lines were used, namely AT3-2 and UVL9, the latter being deficient in nucleotide excision repair and consequently UV sensitive. For all types of radiation, including UVA, CPD were found to be the predominant lesions quantitatively. At the biologically relevant doses used, UVC, UVB and SSL irradiation yielded 8-oxodGuo at a rather low level, whereas UVA radiation produced relatively higher amounts. The formation of CPD was 10(2) and 10(5) more effective upon UVC than UVB and UVA exposure. These yields of formation followed DNA absorption, even in the UVA range. The calculated relative spectral effectiveness in the production of the two lesions showed that efficient induction of 8-oxodGuo upon UVA irradiation was shifted toward longer wavelengths, in comparison with those for CPD formation, in agreement with a photosensitization mechanism. In addition, after exposure to SSL, about 19% and 20% of 8-oxodGuo were produced between 290-320 nm and 320-340 nm, respectively, whereas CPD were essentially (90%) induced in the UVB region. However, the ratio of CPD to 8-oxodGuo greatly differed from one source of light to the other: it was over 100 for UVB but only a few units for UVA source. The extent of 8-oxodGuo and CPD was also compared to the lethality for the different types of radiation. The involvement of 8-oxodGuo in cell killing by solar UV radiation was clearly ruled out. In addition, our previously reported mutation spectra demonstrated that the contribution of 8-oxodGuo in the overall solar UV mutagenic process is very minor.     

Cyclobutane Pyrimidine Dimer Density as a Predictive Biomarker of the Biological Effects of Ultraviolet Radiation in Normal Human Fibroblast

This study compared biological responses of normal human fibroblasts (NHF1) to three sources of ultraviolet radiation (UVR), emitting UVC wavelengths, UVB wavelengths, or a combination of UVA and UVB (solar simulator; emission spectrum, 94.3% UVA and 5.7% UVB). The endpoints measured were cytotoxicity, intra‐S checkpoint activation, inhibition of DNA replication and mutagenicity. Results show that the magnitude of each response to the indicated radiation sources was best predicted by the density of DNA cyclobutane pyrimidine dimers (CPD). The density of 6‐4 pyrimidine–pyrimidone photoproducts was highest in DNA from UVC‐irradiated cells (14% of CPD) as compared to those exposed to UVB (11%) or UVA–UVB (7%). The solar simulator source, under the experimental conditions described here, did not induce the formation of 8‐oxo‐7,8‐dihydroguanine in NHF1 above background levels. Taken together, these results suggest that CPD play a dominant role in DNA damage responses and highlight the importance of using endogenous biomarkers to compare and report biological effects induced by different sources of UVR.     

UVA, UVB and UVC induce differential response signaling pathways converged on the eIF2α phosphorylation

It is clear that solar UV irradiation is a crucial environmental factor resulting in skin diseases partially through activation of cell signaling toward altered gene expression and reprogrammed protein translation. Such a key translational control mechanism is executed by the eukaryotic initiation factor 2α subunit (eIF2α) and the downstream events provoked by phosphorylation of eIF2α at Ser(51) are clearly understood, but the upstream signaling mechanisms on the eIF2α-Ser(51) phosphorylation responses to different types of UV irradiations, namely UVA, UVB and UVC, are still not well elucidated. Herein, our evidence reveals that UVA, UVB and UVC all induce a dose- and time-dependent phosphorylation of eIF2α-Ser(51) through distinct signaling mechanisms. UVA-induced eIF2α phosphorylation occurs through MAPKs, including ERKs, JNKs and p38 kinase, and phosphatidylinositol (PI)-3 kinase. By contrast, UVB-induced eIF2α phosphorylation is through JNKs and p38 kinase, but not ERKs or PI-3 kinase, whereas UVC-stimulated response to eIF2α phosphorylation is via JNKs alone. Furthermore, we have revealed that ATM is involved in induction of the intracellular responses to UVA and UVB, rather than UVC. These findings demonstrate that wavelength-specific UV irradiations activate differential response signaling pathways converged on the eIF2α phosphorylation. Importantly, we also show evidence that a direct eIF2α kinase PKR is activated though phosphorylation by either RSK1 or MSK1, two downstream kinases of MAPKs/PI-3 kinase-mediated signaling pathways.     

Simultaneous Irradiation with Different Wavelengths of Ultraviolet Light has Synergistic Bactericidal Effect on Vibrio parahaemolyticus

Ultraviolet (UV) irradiation is an increasingly used method of water disinfection. UV rays can be classified by wavelength into UVA (320–400 nm), UVB (280‐320 nm), and UVC (<280 nm). We previously developed UVA sterilization equipment with a UVA light‐emitting diode (LED). The aim of this study was to establish a new water disinfection procedure using the combined irradiation of the UVA‐LED and another UV wavelength. An oxidative DNA product, 8‐hydroxy‐2’‐deoxyguanosine (8‐OHdG), increased after irradiation by UVA‐LED alone, and the level of cyclobutane pyrimidine dimers (CPDs) was increased by UVC alone in Vibrio parahaemolyticus. Although sequential irradiation of UVA‐LED and UVC‐induced additional bactericidal effects, simultaneous irradiation with UVA‐LED and UVC‐induced bactericidal synergistic effects. The 8‐OHdG and CPDs production showed no differences between sequential and simultaneous irradiation. Interestingly, the recovery of CPDs was delayed by simultaneous irradiation. The synergistic effect was absent in SOS response‐deficient mutants, such as the recA and lexA strains. Because recA‐ and lexA‐mediated SOS responses have crucial roles in a DNA repair pathway, the synergistic bactericidal effect produced by the simultaneous irradiation could depend on the suppression of the CPDs repair. The simultaneous irradiation of UVA‐LED and UVC is a candidate new procedure for effective water disinfection.     

COMPARISON OF EFFECTS OF UVA, UVB AND UVC ON GROWTH AND VIABILITY OF MITOGEN-STIMULATED HUMAN PERIPHERAL BLOOD CELLS

Abstract— Peripheral blood mononuclear cells were irradiated with UVA, UVB or UVC. The highest exposure dose used in each waveband reduced the number of viable cells to one-third the control cell population after 3 days in culture. Exposure of these cells to half as much UV from each waveband resulted in an equivalent or greater degree of inhibition of their proliferative response to mitogen as measured by lymphoblast transformation, [³H]-thymidine uptake and viable cell number on day 3 in culture. The pattern of inhibition was distinct for each waveband. UVA interfered with blastogenesis on the first 2 days of culture at doses which had considerably less effect on viable cell number. UVA also depressed the first round of DNA synthesis, which was detectable on the second day of culture. By day 3 in culture, however, the UVA-induced reduction in both the number of lymphoblasts and the uptake of [³H]-thymidine was a direct reflection of reduced numbers of viable cells. UVB did not interfere with blastogenesis in mitogen-stimulated cultures to the same degree as did UVA. Only the highest dose of UVB depressed blast transformation more than viable cell number on day 1; by day 2 lower doses were also inhibitory. In contrast UVC had little effect on blastogenesis at any time; a reduced number of lymphoblasts observed on days 2 and 3 in culture was a direct reflection of a reduced number of viable cells rather than a reduced percent of these cells undergoing blast transformation. As with UVA-irradiated, mitogen-stimulated cells, [³H]-thymidine uptake was also depressed in both UVB and UVC irradiated, mitogen-stimulated cells on day 2. However, only UVB continued to depress DNA synthesis more than viable cell number after 3 days of culture. These results suggest that UVA, UVB and UVC may interfere with any one or more of the signals involved in the response to mitogen, be they the recognition of mitogen by T cells or accessory cells, the transformation of lymphocytes into lymphoblasts or the activation of lymphoblasts to synthesize DNA.     

REASSESSMENT OF THE DIFFERENTIAL EFFECTS OF ULTRAVIOLET AND IONIZING RADIATION ON HIV PROMOTER: THE USE OF CELL SURVIVAL AS THE BASIS FOR COMPARISONS

Abstract: Effects of different radiation treatments on the human immunodeficiency virus-1 (HIV) promoter were reassessed for exposures comparable to those encountered in clinical or cosmetic practice, using survival of the host cell as a basis for comparisons. The exposures were performed with two ultraviolet radiation sources commonly used as medical or cosmetic devices (UVASUN 2000 and FS20 lamps), a germicidal (G15T8) lamp and an X-ray machine. The UVC component of the FS20 lamp was filtered out. The emission spectra of the lamps were determined. The characteristics of these sources allowed us to discriminate among effects of UVA1 (340–400 nm), UVB + UVA2 (280–340 nm) and UVC (254 nm) radiations. Effects of irradiation were ascertained using cultures of HeLa cells stably transfected with the HIV promoter linked to a reporter—chloramphenicol acetyl transferase—gene. The exposures used caused at least two logs of cell killing. In this cytotoxicity range, UVA1 or X radiations had no effect on the HIV promoter, whereas UVB + UVA2 or UVC radiations activated the HIV promoter in a fluence-dependent manner. Survivals following exposure to UVB + UVA2 or UVC radiation were (1) at the lowest measurable HIV promoter activation, 30 and 20%, respectively, (2) at one-half maximal activation, 6 and 3%, respectively and (3) at the maximal activation, 0.5 and 0.2%, respectively. The results suggest that, among the radiations studied, UVB is the most important modality from the viewpoint of its potential effects on HIV-infected individuals, since (1) UVA1 or X radiations have no effects on the HIV promoter, (2) human exposure to UVC radiation is infrequent and (3) human UVB exposure is very common.     

NON-NUCLEAR DAMAGE AND CELL LYSIS ARE INDUCED BY UVA, BUT NOT UVB OR UVC, RADIATION IN THREE STRAINS OF L5178Y CELLS

The potential to induce non-nuclear changes in mammalian cells has been examined for (1) UVA1 radiation (340–400 nm, UVASUN 2000 lamp), (2) UVA + UVB (peak at 313 nm) radiation (FS20 lamp), and (3) UVC (254 nm) radiation (GI5T8 lamp). The effects of irradiation were monitored in vitro using three strains of L5178Y (LY) mouse lymphoma cells that markedly differ in sensitivity to UV radiation. Comparisons were made for the effects of approximately equitoxic fluences that reduced cell survival to 1–15%. Depending on the cell strain, the fluences ranged from 830 to 1600 kJ/m² for the UVASUN lamp, 75 to 390 J/m² for the FS20 lamp and 3.8 to 17.2 J/m² for the G15T8 lamp. At the exposure level used in this study, irradiation with the UVASUN, but not the FS20 or G15T8, lamp induced a variety of non-nuclear changes including damage to cytoplasmic organelles and increased plasma membrane permeability and cell lysis. Cell lysis and membrane permeabilization were induced by the UVA1 emission of the UVASUN lamp, but not by its visible + IR components (>400 nm). The results show that the plasma membrane and other organelles of LY cells are highly sensitive to UVA1 but not to UVB or UVC radiation. Also UVA1, but not UVB or UVC radiation, causes rapid and extensive lysis of LY cells. In conclusion, non-nuclear damage contributes substantially to UVA cytotoxicity in all three strains of LY cells.     

Cell Cycle Kinetics Following UVA Irradiation in Comparison to UVB and UVC Irradiation

Abstract— There is limited information about the carcinogenic effect of longwave ultraviolet radiation (UVA: 315-400 nm). In particular very little is known about the relevant genotoxic damage caused by physiological doses of UVA radiation. A general response of cells to DNA damage is a delay or arrest of the cell cycle. Conversely, such cellular responses after UVA irradiation would indicate significant genotoxic damage. The aim of this study is to compare cell cycle kinetics of human fibroblasts after UVC (190-280 nm radiation), UVB (280-315 nm radiation) and UVA irradiation. Changes in the cell cycle kinetics were assessed by bivariate flow cytometric analysis of DNA synthesis and of DNA content. After UVC, UVB or UVA irradiation of human fibroblasts a suppression was seen of bromodeoxyuridine (BrdU) incorporation at all stages of S phase. The magnitude of this suppression appeared dose dependent. Maximum suppression was reached at 5-7 h after UVB exposure and directly after UVA exposure, and normal levels were reached 25 h after UVB and 7 h after UVA exposure. The lowered BrdU uptake corresponded with a lengthening of the S phase. No dramatic changes in percentages of cells in G₁, S and G₂/M were seen after the various UV irradiations. Apparently, UVA irradiation, like UVB and UVC irradiation, can temporarily inhibit DNA synthesis, which is indicative of genotoxic damage.     

Photoprotective and Antigenotoxic Effects of the Flavonoids Apigenin,Naringenin and Pinocembrin

This work evaluated the photoprotective and antigenotoxic effects against ultraviolet B (UVB) radiation of flavonoid compounds apigenin, naringenin and pinocembrin. The photoprotective efficacy of these compounds was estimated using in vitro photoprotection indices, and the antigenotoxicity against UVB radiation was evaluated using the SOS chromotest and an enzymatic (proteinase K/T4 endonuclease V enzyme) comet assay in UV‐treated Escherichia coli and human (HEK‐293) cells, respectively. Naringenin and pinocembrin showed maximum UV‐absorption peak in UVC and UVB zones, while apigenin showed UV‐absorption capability from UVC to UVA range. These compounds acted as UV filters reducing UV‐induced genotoxicity, both in bacteria and in human cells. The enzymatic comet assay resulted highly sensitive for detection of UVB‐induced DNA damage in HEK‐293 cells. In this work, the photoprotective potential of these flavonoids was widely discussed.     

Akt1-mediated intracellular oxidation after UVB irradiation suppresses apoptotic cell death induced by cell detachment and serum starvation

Apoptosis is an important cell death system that deletes damaged and mutated cells to prevent cancer. We have previously reported that a certain dose of UVB irradiation inhibited the apoptosis induced by serum starvation and cell detachment, leading to cell transformation. This antiapoptotic effect was partially inhibited by phosphatidylinositol 3-kinase (PI3-kinase) inhibitors. UVB irradiation is known to cause the phosphorylation of Akt via the activation of PI3-kinase; however, the Akt isoform-specific relationship has not yet been clarified. Notably, the role in antiapoptotic effect of UVB has yet to be elucidated. In this study, the role of Akt1 in the UVB-induced inhibition of apoptosis was examined by Akt1 knockdown using small interfering RNA (siRNA). NIH3T3 cells showed typical apoptotic cell death by serum starvation and cell detachment, which was significantly inhibited by UVB irradiation. Akt1 knockdown decreased the antiapoptotic effect of UVB. Hydrogen peroxide-induced suppression of cell death was also decreased in Akt1 knockdown cells. An antioxidant, N-acetylcysteine, inhibited the antiapoptotic effect by UVB irradiation, whereas no inhibition was observed in Akt1 knockdown cells. Furthermore, UVB-induced intracellular peroxidation was not observed in the knockdown cells, indicating that Akt1 played an important role in mediating the intracellular redox status. Treatment with insulin had a similar antiapoptotic effect as UVB irradiation involving intracellular peroxidation, which was also attenuated in Akt1 knockdown cells. These findings suggest that appropriate intracellular oxidation after UVB irradiation prevented apoptosis, a process which might be partially regulated by the production of reactive oxygen species mediated by Akt1.     

Comparative Action Spectrum for Ultraviolet Light Killing of Mouse Melanocytes from Different Genetic Coat Color Backgrounds

The photobiology of mouse melanocyte lines with different pigment genotypes was studied by measuring colony-forming ability after irradiation. The cell lines were wild-type black (melan-a) and the mutants brown (melan-b) and albino (melan-c). Four lamps emitting various UV wavelengths were used. These were germicidal (UVC, 200–280 Dm), 82.3% output at 254 nm, TL01 (UVB, 280–320 nm), 64.2% at 310–311 nm, FS20, broadband with peak output at 312 nm and Alisun-S (UVA, 320–400 nm), broadband with peak output at 350–354 nm. Appropriate filtration reduced the contaminating UVC to nonlethal levels for the longer waverange lamps. Wild-type melan-a was resistant to UVC and UVA compared to the other two cell lines, but the differences were small. The melan-c cell line was more resistant to UVB and markedly more resistant to FS20 than the pigmented lines. With the exception of FS20 responses, melan-b was more sensitive than melan-a to killing by the various UV lamps. There were more pyrimidine dimers (cyclobutane dimers and 6–4 photoproducts) produced in melan-a than in melan-c cells by UVC, UVB and FS20 lamps. Unlike melan-c, melan-a and melan-b showed a strong free radical signal of melanin character with a detectable contribution of pheomelanin-like centers. The contribution of pheome-lanin was higher in melan-b than in melan-a, while the total melanin content in these two cell lines was comparable. The abundant melanin granules of wild-type melan-a melanocytes were well melanized and ellipsoidal, whereas those of melan-b melanocytes tended to be spherical. In the albino line (melan-c) the melanocytes contained only early-stage melanosomes, all of which were devoid of melanin. The results indicate that pigment does not protect against direct effect DNA damage in the form of pyrimidine dimers nor does it necessarily protect against cell death. High pigment content is not very protective against killing by UVC and UVA, and it may photosensitize in UVB the very wavelength range that is of greatest concern with respect to the rising incidence in skin cancer, especially melanoma. It is clear from these studies that, in pigment cells, monochromatic results cannot predict polychromatic responses and that cell death from solar irradiations is a complex phenomenon that depends on more than DNA damage.     

LONG-WAVELENGTH UVA RADIATION INDUCES OXIDATIVE STRESS,CYTOSKELETAL DAMAGE and HEMOLYSIS*

Abstract— We investigated the ability of the different wavelength regions of UV radiation, UVA(320–400 nm), UVB(290–320 nm) and UVC(200–290 nm), to induce hemolysis. Sheep erythrocytes were exposed to radiation from either a UVA1 (>340 nm) sunlamp, a UVB sunlamp, or a UVC germicidal lamp. The doses used for the three wavelength regions were approximately equilethal to the survival of L5178Y murine lymphoma cells. Following exposure, negligible hemolysis was observed in the UVB- and UVC-irradiated erythrocytes, whereas a decrease in the relative cell number (RCN), indicative of hemolysis, was observed in the UVA 1-exposed samples. The decrease in RCN was dependent on dose(0–1625 kj/m²), time(0–78 h postirradiation) and cell density (10⁶-10⁷ cells/mL). Hemolysis decreased with increasing concentration of glutathione, hemoglobin or cell number, while the presence of pyruvate drastically enhanced it. Because scanning spectroscopy(200–700 nm) showed that hemoproteins and nicotinamide adenine dinucleotides were oxidized, cytoplasmic oxidative stress was implicated in the lytic mechanism. Further evidence of oxidation was obtained from electron micrographs, which revealed the formation of Heinz bodies near the plasma membrane. The data demonstrate that exposure of erythrocytes to UVA1, but not UVB or UVC, radiation causes oxidation of cytoplasmic components, which results in cytoskeletal damage and hemolysis.     

Ultraviolet A radiation induces rapid apoptosis of human leukemia cells by Fas ligand-independent activation of the Fas death pathways

Endogenous cellular chromophores absorb ultraviolet A radiation (UVA, 290-320 nm), the major UV component of terrestrial solar radiation, leading to the formation of reactive oxidizing species that initiate apoptosis, gene expression and mutagenesis. UVA-induced apoptosis of T helper cells is believed to underlie the UVA phototherapy for atopic dermatitis and other T cell-mediated inflammatory skin diseases. We have evaluated the involvement of the Fas-Fas ligand (FasL) pathway in rapid UVA-induced apoptosis in human leukemia HL-60 cells. UVA-induced apoptosis was not inhibited by pretreatment with a neutralizing anti-Fas antibody, although the same UVA treatment initiated cleavage of caspase-8 and subsequent processing of Bid and caspase-3-like proteases. Inhibition of caspase-8 by Lle-Glu (OMe)-Thr-Asp(OMe)-fluoromethyl ketone completely blocked caspase-3 cleavage and apoptosis in UVA-treated cells, suggesting that apoptosis was initiated by the Fas pathway. This inference was supported by demonstrating that immunoprecipitates obtained from UVA-treated cells using anti-Fas antibody contained caspase-8 and Fas-associating protein with death domain (FADD). In addition, Fas clustering in response to UVA treatment was observed by immunofluorescence microscopy. These data support a mechanism for rapid, UVA-induced apoptosis in HL-60 cells involving initial formation of the Fas-FADD-caspase-8 death complex in an FasL-independent manner.     

Glucose is required to maintain high ATP-levels for the energy-utilizing steps during PDT-induced apoptosis

Photodynamic therapy (PDT) may trigger apoptosis or necrosis in cancer cells. Several steps in the induction and execution of apoptosis require high amounts of adenosine-5'-triphosphate (ATP). Because the mitochondrial membrane potential (delta psi) decreases early in apoptosis, we raised the question about the mechanisms of maintaining a sufficiently high ATP level. We therefore monitored delta psi and the intracellular ATP level of apoptotic human epidermoid carcinoma cells (A431) after photodynamic treatment with aluminum (III) phthalocyanine tetrasulfonate. A maximum of caspase-3-like activity and nuclear fragmentation was found at fluences of about 4 J cm(-2). Under these conditions apoptotic cells reduced delta psi rapidly, while the ATP level remained high for 4-6 h after treatment for cells supplied with glucose. To analyze the contribution of glycolysis to the energy supply during apoptosis, experiments were carried out with cells deprived of glucose. These cells showed a rapid drop of ATP content and neither caspase activation nor nuclear fragmentation could be detected. We conclude that the use of glucose as a source of ATP is obligatory for the execution of PDT-induced apoptosis.     

SENSITIVITY OF MONONUCLEAR CELLS TO UV RADIATION

Abstract—The viability of peripheral blood mononuclear cells, as measured by trypan blue dye exclusion, is decreased by exposure to UV radiation in vitro . The toxicity of the UV radiation is doseand wavelength-dependent; UVC is approximately 10 times more effective than UVB and 10⁵ times more effective than UVA.     

发光细菌传感器在纳米氧化物紫外屏蔽性能评估分析中的应用研究

本文发现发光细菌在紫外光照射下能够被杀死，其荧光强度相应地发生降低，而在纳米氧化物的保护下，细菌荧光强度的降低得到了抑制，因此发光细菌可以被用来分析和评价纳米氧化物的紫外屏蔽性能。青海弧菌Q67是发光细菌的一种，本文研究了不同浓度及不同种类的纳米氧化物对本发光细菌在分别受到UVA、UVB、UVC紫外光照射下的发光强度的影响，根据细菌发光强度降低的相对值建立了一种分析和评价纳米氧化物的紫外屏蔽性能的方法。该方法可以对纳米氧化物在UVA、UVB、UVC区的紫外屏蔽性能进行评价，同时也为化妆品等行业提供了一种对防晒剂紫外屏蔽性能评估的有效方法。