Ultraviolet radiation and reactive oxygen generation as inducers of keratinocyte apoptosis: protective role of tea polyphenols

Comparative analysis of helium and air surface micro-discharge plasma treatment on the microbial reduction and quality attributes of beef slices

This work aimed to compare the effects of helium and air surface micro-discharge (SMD) plasma on the microbial safety and quality of beef tissues. For the beef tissue model, the concentration and diffusion depth of hydroxyl radical and ozone have different change patterns over plasma treatment time and distance in helium and air SMD plasma. The inactivation efficiency of helium plasma depended on the plasma treatment time and distance, while the inactivation efficiency of air plasma only depended on the treatment time. For the fresh beef slices, air SMD plasma treatment exhibited a higher antimicrobial activity against S. aureus and E. coli than helium SMD plasma treatment (1.5 versus 0.9; 0.9 versus 0.28 log CFU/g at 10 min). However, air SMD plasma treatment caused more adverse effects on beef quality, leading to a smooth surface, extensive lipid oxidation, protein structure damage, low pH and discoloration compared to helium SMD plasma treatment. This work provides valuable guidelines for the working gas choice in the practical application of plasma to meat decontamination.

Digital gene expression profiling in larvae of Tribolium castaneum at different periods post UV-B exposure

UV-B radiation is an important environmental factor. Exposure to excess UV-B radiation can cause serious effects on the development, survival, and reproduction of different organisms. Plants and animals have developed many different strategies to cope with UV-B-induced damage, but the physiological response of insects to UV-B remains unclear. In the present study, the red flour beetle Tribolium castaneum (Herbst) was used to assess the stress response of UV-B. The underlying molecular mechanisms were explored using RNA sequencing. We investigated the transcriptomic profile of T. castaneum larvae at 4 and 24 h after treatment with UV-B radiation via digital gene expression analysis. The 310 and 996 differentially expressed genes were detected at 4 and 24 h, respectively. Then the biological functions and associated metabolic processes of these genes were determined by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis. The reliability of the data was verified using qRT-PCR. The results indicated that several differentially expressed genes are involved in antioxidation, DNA repair, protein folding, carbon flux diversion, and the extracellular matrix to protect against UV-B-induced damage. This study will increase our understanding of the molecular mechanism underlying insect response to UV-B radiation.

The Protecting Effect of Deoxyschisandrin and Schisandrin B on HaCaT Cells against UVB-Induced Damage

Schisandra chinensis is a traditional Chinese medicine that has multiple biological activities, including antioxidant, anticancer, tonic, and anti-aging effects. Deoxyschisandrin (SA) and schisandrin B (SB), the two major lignans isolated from S. chinensis, exert high antioxidant activities in vitro and in vivo by scavenging free radicals, such as reactive oxygen species (ROS). Ultraviolet B-ray (UVB) radiation induces the production of ROS and DNA damage, which eventually leads to cell death by apoptosis. However, it is unknown whether SA or SB protects cells against UVB-induced cellular DNA damage. Our study showed that both SA and SB effectively protected HaCaT cells from UVB-induced cell death by antagonizing UVB-mediated production of ROS and induction of DNA damage. Our results showed that both SA and SB significantly prevented UVB-induced loss of cell viability using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assays. Dichloro-dihydro-fluorescein diacetate (DCFH-DA) assays showed that the production of ROS following UVB exposure was inhibited by treatment with SA and SB. Moreover, SA and SB decreased the UVB-induced DNA damage in HaCaT cells by comet assays. In addition, SA and SB also prevented UVB-induced cell apoptosis and the cleavage of caspase-3, caspase-8 and caspase-9. In a word, our results imply that the antioxidants SA and SB could protect cells from UVB-induced cell damage via scavenging ROS.

Suppression of UVC-induced cell damage and enhancement of DNA repair by the fermented milk, Kefir

An aqueous extract of Kefir, fermented milk originally produced in the Caucasus mountains, suppressed morphological changes of human melanoma HMV-1 and SK-MEL cells and human normal fibroblastTIG-1 cells caused by UVC-irradiation, suggesting that UV damage can be suppressed by the Kefir extract. The addition of the Kefir extract after UVC-irradiation of HVM-1 cells resulted in a remarkable decrease in intracellular reactive oxygen species (ROS) which had been increased by UVC irradiation. The Kefir extract also stimulated unscheduled DNA synthesis and suppressed UVC-induced apoptosis of HMV-1 cells. A colony formation assay revealed that the Kefir extract rescued HMV-1 cells from cell death caused by UVC irradiation. The Kefir extract, as well as methyl methanethiosulfonate which is known to enhance the nucleotide excision repair (NER) activity, exhibited strong thymine dimer repair-enhancing activity. Epigalocatechin exhibited a weak NER activity but vitamins A, C, and E and catechin showed no NER activity. The thymine dimer repair-enhancing factors in the Kefir extract were heat-stable and assumed to be molecules with a molecular weight of less than 5000. The treatment of HMV-1 cells with the Kefir extract during or before UVC- irradiation also prevented the generation of ROS and thymine dimmer, and suppressed the apoptosis of HMV-1 cells, suggesting that application of Kefir can prevent UV damage.

Effects of ultraviolet A on the activity of two metabolic enzymes, DNA damage and lipid peroxidation during early developmental stages of the African catfish, Clarias gariepinus (Burchell, 1822)

Many ultraviolet-A (UVA)-induced biochemical and physiological changes are valid as biomarkers using aquatic species for detection of the degree of stress. Changes in the concentration and activities of enzymes, such as glucose-6-phosphate dehyderogenase (G6PDH), lactate dehyderogenase (LDH), DNA damage and lipid peroxidation (LPO), can be used as biomarkers to identify possible environmental contamination in fish. This study aimed to investigate the impact of UVA on the activity of the selected enzymes, DNA damage and LPO during early developmental stages of the African catfish Clarias gariepinus. Embryo hemogenates were used for measurements of G6PDH, LDH, DNA damage and LPO concentrations and activities spectrophotometrically at 37 degrees C. The normal ontogenetic variations in enzyme activities, DNA damage and LPO of the early developmental stages (24-168 h-PFS; hours-post fertilization stage) were studied. There was a significant decrease in the activity of G6PDH till 120 h-PFS. Then after 120 h-PFS, the activity of such enzymes insignificantly increased toward higher stages. The LDH activity was recorded with a pattern of decrease till 96 h-PFS, followed by a significant increase toward 168 h-PFS. The polynomial pattern of variations in DNA damage and LPO was also evident. The patterns of the enzyme activities, corresponding DNA damage and LPO of the early ontogenetic stages under the influence of three different UVA doses (15, 30 and 60 min), were recorded. The pattern of variations in G6PDH activity in UVA-induced groups was similar to that of the control group with variation in the magnitude of such activity. In all treated groups, LDH activity decreased till 96 h-PFS, then increased till 168 h-PFS. Within each of the embryonic stages, the increase in UVA led to a significant increase in DNA damage. A significant increase in lipid peroxidation under UVA doses was recorded. The variability in number and molecular weight of proteins under exposure to UVA was evident, reflecting some of the genetic and transcriptional changes during exposure and development.

Inhibitory effect of proanthocyanidin on ultraviolet B irradiation-induced melanogenesis

Repetitive exposure of the skin to ultraviolet (UV) radiation induces various adverse effects, including skin thickening, wrinkle formation, inflammation, and pigmentation. Various natural and synthetic compounds were studied to determine whether they might prevent UV induction of these adverse effects. In particular, naturally occurring antioxidants were used for regulating skin damage induced by UV radiation since several antioxidants were found to inhibit photoaging through prevention of collagen synthesis via inhibition of matrix metalloproteinases (MMP) and/or decrease of melanin synthesis. The L values in pigmented skin were lower at 4 wk (52.97 +/- 2.09) than at the start of this study (0 wk, 62.89 +/- 0.56) in the control. In the proanthocyanidin mixture group, the L value was increased (56.83 +/- 1.71) similar to the control (52.97 +/- 2.09). Proanthocyanidin also suppressed the expression levels of tyrosinase by 20-40%, and blocked the expression of MITF, TRP-1, and TRP-2, which are factors implicated in the control of melanogenesis. Taken together, these data indicate that proanthocyanidin may be useful to attenuate UVB-induced melanogenesis.

Mechanisms of cell death in oxidative stress

Reactive oxygen or nitrogen species (ROS/RNS) generated endogenously or in response to environmental stress have long been implicated in tissue injury in the context of a variety of disease states. ROS/RNS can cause cell death by nonphysiological (necrotic) or regulated pathways (apoptotic). The mechanisms by which ROS/RNS cause or regulate apoptosis typically include receptor activation, caspase activation, Bcl-2 family proteins, and mitochondrial dysfunction. Various protein kinase activities, including mitogen-activated protein kinases, protein kinases-B/C, inhibitor-of-I-kappaB kinases, and their corresponding phosphatases modulate the apoptotic program depending on cellular context. Recently, lipid-derived mediators have emerged as potential intermediates in the apoptosis pathway triggered by oxidants. Cell death mechanisms have been studied across a broad spectrum of models of oxidative stress, including H2O2, nitric oxide and derivatives, endotoxin-induced inflammation, photodynamic therapy, ultraviolet-A and ionizing radiations, and cigarette smoke. Additionally ROS generated in the lung and other organs as the result of high oxygen therapy or ischemia/reperfusion can stimulate cell death pathways associated with tissue damage. Cells have evolved numerous survival pathways to counter proapoptotic stimuli, which include activation of stress-related protein responses. Among these, the heme oxygenase-1/carbon monoxide system has emerged as a major intracellular antiapoptotic mechanism.

Oxidative stress-related markers and langerhans cells in a hairless rat model exposed to UV radiation

Biomarkers related to the oxidative stress in blood and epidermis and the number of Langerhans cells were determined in hairless rats after acute irradiation with 1.54, 1.93, or 2.41 J/cm2 of ultraviolet (UV) light and chronic exposure to 13 suberythemal UV doses of 1.1 J/cm2 for 2 mo. After acute UV irradiation, in epidermis, the thiobarbituric acid-reactive substances (TBARS) content increased at the highest UV dose, whereas the activities of glutathione S-transferase and catalase rose and the oxidized glutathione (GSSG) content diminished at all UV doses. In erythrocytes, glutathione S-transferase activity increased at the two lowest UV doses, glutathione peroxidase activity rose at all UV doses, and catalase activity increased after the highest UV dose. In plasma, the TBARS content and the reduced glutathione (GSH)/GSSG ratio increased at the highest UV dose; the number of Langerhans cells decreased at all UV doses. Linear Pearson correlation analysis revealed many relationships between different biomarkers, and multiple linear regression analysis indicated that the number of Langerhans cells was predicted by epidermal GSSG and catalase (R2 = .64) and by erythrocytic glutathione peroxidase and GSSG (R2 = .72). After suberythemal UV radiation, in epidermis, the GST activity and the content of GSH and GSSG increased; in erythrocytes, the GST activity decreased and the GSH/GSSG ratio increased. Thus, the hairless rat appears to be a useful model for studying the oxidative stress-related mechanisms after UV radiation, which are involved in the loss of the immune capacity mediated by Langerhans cells, even at suberythemal doses.

Porcine skin as a model system for studies of ultraviolet a effects in human skin

The range of diagnostic and therapeutic applications of ultraviolet A (UVA) radiation has been continuously expanding. UVA radiation is a well-known mutagenic factor capable of damaging both cells and tissues. At the same time there is a very limited information on long-term consequences of irradiating the skin with different doses of UVA and long-wavelength ultraviolet B (UVB) radiation used in therapies of skin disorders. It was demonstrated that for UVA doses of 0.1 to 1000 mJ/cm2 the sensitivity of the porcine skin to the UVA-induced breaking of nuclear DNA is similar to that of the human skin. Results indicate that porcine skin may serve as a model system for population studies of the deleterious effects of UVA irradiation of the skin cells.

Keratinocyte apoptosis in epidermal development and disease

Keratinocyte (KC) apoptosis plays a critical role in regulating epidermal development and restraining carcinogenesis. Apoptosis balances proliferation to maintain epidermal thickness, contributes to stratum corneum formation and may eliminate pre-malignant cells. Apart from the normal developmental program, KC apoptosis can be triggered by UV light and other stimuli. Dysfunctional apoptosis occurs in some skin diseases, such as psoriasis and skin cancer. Here we review the current state of knowledge of KC apoptosis, with particular focus on apoptotic signaling pathways and molecular mechanisms of apoptosis control, and discuss new insights into the complex role of apoptosis in skin carcinogenesis that are emerging from mouse models.

Effect of genetic polymorphisms of MnSOD and MPO on the relationship between PAH exposure and oxidative DNA damage

To investigate the effect of genetic polymorphisms on the oxidative damage caused by PAH exposure, we measured urinary 1-hydroxypyrene (1-OHP) and 8-hydroxydeoxyguanosine (8-OHdG) levels to determine exposure and oxidative injury in university students. After examining myeloperoxidase (MPO) and manganese superoxide dismutase (MnSOD) genotypes by PCR and RFLP, we evaluated the effects of these polymorphisms on the relationship between the urinary levels of 1-OHP and 8-OHdG. No significant relation was observed between log 1-OHP and 8-OHdG concentrations in the whole study group (p=0.182), or between urinary 8-OHdG levels and polymorphisms of MnSOD or MPO (p=0.539 and 0.993, respectively). However, significant differences of regression coefficient were found for the relation between urinary log 1-OHP and urinary 8-OHdG concentrations in the presence of different MnSOD or MPO genotypes by multiple regression after controlling for age, sex, body mass index, cotinine, and smoking. In those with the MnSOD Val/Ala or Ala/Ala genotypes this regression coefficient was 1.480 (p=0.040), whereas for the MnSOD Val/Val genotype it was 0.088 (p=0.859). The higher regression coefficient was obtained for the subject group with the MnSOD Val/Ala or Ala/Ala genotype in combination with the MPO G/G genotype (p=0.012). We suggest that the oxidative injury caused by PAH exposure is modulated by genetic polymorphisms such as MnSOD and MPO.

Green tea and the skin

Plant extracts have been widely used as topical applications for wound-healing, anti-aging, and disease treatments. Examples of these include ginkgo biloba, echinacea, ginseng, grape seed, green tea, lemon, lavender, rosemary, thuja, sarsaparilla, soy, prickly pear, sagebrush, jojoba, aloe vera, allantoin, feverwort, bloodroot, apache plume, and papaya. These plants share a common character: they all produce flavonoid compounds with phenolic structures. These phytochemicals are highly reactive with other compounds, such as reactive oxygen species and biologic macromolecules, to neutralize free radicals or initiate biological effects. A short list of phenolic phytochemicals with promising properties to benefit human health includes a group of polyphenol compounds, called catechins, found in green tea. This article summarizes the findings of studies using green tea polyphenols as chemopreventive, natural healing, and anti-aging agents for human skin, and discusses possible mechanisms of action.

Lack of in vitro protection by a common sunscreen ingredient on UVA-induced cytotoxicity in keratinocytes

As an extension of our previous investigations on sunscreen ingredients, the present work was aimed at assessing the possible protective effects of a common UVA-absorbing agent, Parsol 1789 (4-tert-butyl-4'-methoxydibenzoylmethane) in contact with human keratinocytes under UVA illumination. Cell viability was evaluated by determining lactate dehydrogenase (LDH) release, uptake of propidium iodide and fluorescein diacetate, total protein content and percentage of cell detachment. Apoptosis was detected by recognition of translocated phosphatidylserine using annexin V-FITC uptake. Oxidative stress was evaluated through the carboxy-H2DCFDA assay while the total oxyradical scavenging capacity (TOSC) assay was used for determining the total antioxidant capacity level in these cells. Lipid peroxidation was also assessed by checking hydroperoxide (HP) levels. The results obtained show that UVA exposure induces significant cell mortality, decrease in protein concentration, release of LDH, increase in apoptosis, oxidative stress and lipid peroxidation with a concomitant reduction in the response of the antioxidant cellular defense system. The presence of 10 microM Parsol 1789 did not minimize these UVA-induced effects, on the contrary, for some parameters measured such as lipid hydroperoxides, there was a significant enhancement. Furthermore, the presence of glutathione (GSH) alone decreased the level of ROS and lipid hydroperoxides, but in combination with Parsol 1789, this protective effect was reduced. The overall results indicate that the compound does not protect these cells from UVA exposure under our experimental conditions confirming previous findings on the lack of photoprotective efficiency of this sunscreen in contact with biologically relevant molecules. However, the biological role and significance of these results to the consequences of sunscreen use in humans are not known, hence extrapolation from laboratory experiments must be done with caution.

Epigallocatechin 3-gallate attenuates neuronal damage induced by 3-hydroxykynurenine

3-Hydroxykynurenine (3-HK), which is an endogenous metabolite of tryptophan in the kynurenine pathway, is a potential neurotoxin in several neurodegenerative disorders. Epigallocatechin 3-gallate (EGCG), a major compound of green tea, is recognized as a promising natural substance for protection against neuronal diseases. This study investigated the possible protective roles and mechanism of EGCG, against 3-HK-induced cell death. It was found that 3-HK induces neuronal cell death in the human neuroblastoma SH-SY5Y cell line. The reduced cell viability produced characteristic features such as cell shrinkages, plasma membrane blebbing, chromatin condensation, and nuclear fragmentation. The cells treated with 3-HK showed an increase in the concentration of reactive oxygen species (ROS) as well as in caspase activity. In addition, both are involved in the 3-HK-induced apoptosis. EGCG attenuated the cell viability reduction by 3-HK in both a dose- and time-dependent manner. Optical microscopy showed that EGCG inhibited the cell morphological features in the 3-HK-treated cells. Furthermore, the increase in the ROS concentration and the caspase activities by 3-HK were also attenuated by EGCG. These results showed that EGCG has a protective effect on the 3-HK induced cell death by inhibiting ROS production and caspase activity. The results suggest that EGCG might be a promising protective substance against the neuronal degenerative diseases.

Effects of genetic polymorphisms in metabolic enzymes on the relationships between 8-hydroxydeoxyguanosine levels in human leukocytes and urinary 1-hydroxypyrene and 2-naphthol concentrations

This study was designed to investigate the relationship between environmental exposure to polycyclic aromatic hydrocarbons (PAHs) and oxidative stress, and to evaluate the effects of cigarette smoking and the genetic polymorphisms of CYP1A1, CYP2E1, GSTM1, NAT2 and UGT1A6 on the relationship. The subjects of this study were 105 healthy Korean males without occupational exposure to PAHs. The 8-hydroxydeoxyguanosine (8-OHdG) level in leukocytes, and urinary 1-hydroxypyrene (1-OHP) and 2-naphthol concentrations, were measured by high-performance liquid chromatography. Genetic polymorphisms of CYP1A1, CYP2E1, GSTM1, NAT2 and UGT1A6 were identified by PCR and PCR-RFLP methods. The 8-OHdG level showed a significant correlation with the 1-OHP concentration in all subjects (p<.001) and in smokers (p<.01), and with the 2-naphthol level in non-smokers (p<.01). The 8-OHdG level was significantly higher in smoking rapid acetylators than in smoking slow or intermediate acetylators, and in individuals with the UGT1A6 wild-type than in those with the UGT1A6 mutant genotype. Significant positive correlations between 8-OHdG and 1-OHP concentrations were found in subjects with every genotype of the CYP1A1 and CYP2E1 genes, with the GSTM1 null-type, with the NAT2 genotype of a rapid acetylator, and with the UGT1A6 wild-type, respectively. The urinary 2-naphthol level significantly correlated with the 8-OHdG level only in subjects with the GSTM1 null-type. In conclusion, there is a significant correlation between the 8-OHdG level in leukocytes and the urinary 1-OHP concentration in the population not occupationally exposed to PAHs. This relationship is affected by genetic polymorphisms in PAH metabolic enzymes.

UVB light stimulates production of reactive oxygen species: unexpected role for catalase

In keratinocytes, UVB light stimulates the production of reactive oxygen species (ROS). Lysates of these cells were found to possess a non-dialyzable, trypsin- and heat-sensitive material capable of generating ROS in response to UVB light. Using ion exchange, metal affinity, and size exclusion chromatography, a 240-kDa protein was isolated with ROS generating activity. The protein exhibited strong absorption in the 320-360 nm range with additional soret peaks around 400-410 nm, suggesting the presence of heme. Sequencing using liquid chromatography-ion trap mass spectrometry identified the protein as catalase. Using purified catalases from a variety of species, the ROS generating activity was found to be temperature- and O2-dependent, stimulated by inhibitors of the catalatic activity of catalase, including 3-aminotriazole and azide, and inhibited by cyanide. A marked increase in the production of ROS was observed in UVB-treated cells overexpressing catalase and decreased generation of oxidants was found in UVB-treated keratinocytes with reduced levels of catalase. Our data indicate that catalase plays a direct role in generating oxidants in response to UVB light. The finding that catalase mediates the production of ROS following UVB treatment is both novel and highly divergent from the well known antioxidant functions of the enzyme. We hypothesize that, through the actions of catalase, high energy DNA damaging UVB light is absorbed by the enzyme and converted to reactive chemical intermediates that can be detoxified by cellular antioxidant enzymes. Accumulation of excessive ROS, generated through the action of catalase, may lead to oxidative stress, DNA damage, and the development of skin cancer.

Role of reduced glutathione efflux in apoptosis of immortalized human keratinocytes induced by UVA

We have investigated the role played by GSH efflux in apoptosis of human HaCaT keratinocytes induced by UVA irradiation. UVA irradiation of HaCaT cells caused a rapid rise in GSH efflux across the intact cell membrane, followed by an increase in apoptosis. GSH efflux was stimulated by glucose and was reduced by the addition of exogenous GSH and intracellular GSH depletion by buthionine sulfoximine, suggesting that GSH transport is active and is influenced by the GSH concentration gradient across the cell membrane. Verapamil and cyclosporin A, blockers of the multidrug resistance-associated protein, decreased UVA-induced GSH efflux. GSH efflux occurred within 2 h of UVA irradiation, suggesting that the stimulation of GSH efflux is due to an increase in the activity of pre-existing multidrug resistance-associated protein transporter carrier. Although inhibition of GSH efflux did not affect caspase activation and DNA fragmentation, it delayed the gradual increase in plasma membrane permeability and reduced phosphatidylserine translocation in HaCaT cells. It is therefore likely that upon UVA irradiation, GSH efflux increased the intracellular oxidative stress without intervention of reactive oxygen species, thus resulting in more phosphatidylserine externalization and membrane rearrangement. These provide targets for macrophage recognition and phagocytosis and thus minimize the potential to invoke inflammation or neoplastic transformation.

Effects of bisphenol A and artificial UVB radiation on the early development of Rana temporaria

Ultraviolet-B (UVB) radiation is one environmental factor that may act in concert with other stressors, such as xenobiotics, to produce adverse effect on amphibian populations. Embryos (< 24 h old) of the common frog (Rana temporaria) were exposed to four concentrations (0, 10, 100, or 1000 microg/L) of bisphenol A (BPA), with and without ultraviolet-B (UVB) radiation, for 20 d in the laboratory. Throughout the experiment the biologically effective daily UVB dose, calculated with Setlow's DNA action spectrum, was 2.80 kJ m(-2). UVB radiation as such did not have any significant effect on frog embryos. However, a BPA treatment of 1000 microg/L had a significant effect on embryos in both the UVB and no-UVB treatments, with the effect being greater with UVB. UVB produced a significant decrease in survival in the newly hatched frog larvae at all BPA concentrations. These results demonstrate that simultaneous exposure to these two stress factors is more harmful to R. temporaria larvae than exposure to one stressor alone.