Molecular and histological responses in rat skin exposed to m-xylene

Solvents, surfactants, cutting fluids, hydrocarbons, and oils cause skin irritation by incompletely understood mechanisms. This study examined histological and molecular changes in rodent skin caused by brief topical exposures to m-xylene. At 0, 1, 2, 4, and 6 h after 1-h exposure, skin samples were removed and analyzed for histopathological changes and interleukin-1 alpha (IL-1 alpha) and inducible nitric oxide synthase (iNOS) protein levels. Histopathological changes (epidermal-dermal separation and granulocyte infiltration) and increases in IL-1 alpha and iNOS protein expression occurred during our observation period. IL-1 alpha levels increased by 80% immediately after exposure and iNOS levels increased about 60% 4 hours after exposure. Our study demonstrates that dermal exposure to m-xylene promotes IL-1 alpha and iNOS production in skin and these proteins may serve as early indicators of skin irritation.     

Mechanisms of sulfur mustard analog 2-chloroethyl ethyl sulfide-induced DNA damage in skin epidermal cells and fibroblasts

Employing mouse skin epidermal JB6 cells and dermal fibroblasts, here we examined the mechanisms of DNA damage by 2-chloroethyl ethyl sulfide (CEES), a monofunctional analog of sulfur mustard (SM). CEES exposure caused H2A.X and p53 phosphorylation as well as p53 accumulation in both cell types, starting at 1 h, that was sustained for 24 h, indicating a DNA-damaging effect of CEES, which was also confirmed and quantified by alkaline comet assay. CEES exposure also induced oxidative stress and oxidative DNA damage in both cell types, measured by an increase in mitochondrial and cellular reactive oxygen species and 8-hydroxydeoxyguanosine levels, respectively. In the studies distinguishing between oxidative and direct DNA damage, 1 h pretreatment with glutathione (GSH) or the antioxidant Trolox showed a decrease in CEES-induced oxidative stress and oxidative DNA damage. However, only GSH pretreatment decreased CEES-induced total DNA damage measured by comet assay, H2A.X and p53 phosphorylation, and total p53 levels. This was possibly due to the formation of GSH–CEES conjugates detected by LC-MS analysis. Together, our results show that CEES causes both direct and oxidative DNA damage, suggesting that to rescue SM-caused skin injuries, pleiotropic agents (or cocktails) are needed that could target multiple pathways of mustard skin toxicities.     

Noise-Induced Hearing Loss in Korean Workers: Co-Exposure to Organic Solvents and Heavy Metals in Nationwide Industries

Background

Noise exposure is a well-known contributor to work-related hearing loss. Recent biological evidence suggests that exposure to ototoxic chemicals such as organic solvents and heavy metals may be additional contributors to hearing loss. However, in industrial settings, it is difficult to determine the risks of hearing loss due to these chemicals in workplaces accompanied by excessive noise exposure. A few studies suggest that the effect of noise may be enhanced by ototoxic chemicals. Therefore, this study investigated whether co-exposure to organic solvents and/or heavy metals in the workplace modifies the risk of noise exposure on hearing loss in a background of excessive noise.

Methods

We examined 30,072 workers nationwide in a wide range of industries from the Korea National Occupational Health Surveillance 2009. Data on industry-based exposure (e.g., occupational noise, heavy metals, and organic solvents) and subject-specific health outcomes (e.g., audiometric examination) were collected. Noise was measured as the daily 8-h time-weighted average level. Air conduction hearing thresholds were measured from 0.5 to 6 kHz, and pure-tone averages (PTA) (i.e., means of 2, 3, and 4 kHz) were computed.

Results

In the multivariate linear model, PTA increment with occupational noise were 1.64-fold and 2.15-fold higher in individuals exposed to heavy metals and organic solvents than in unexposed individuals, respectively.

Conclusion

This study provides nationwide evidence that co-exposure to heavy metals and/or organic solvents may exacerbate the effect of noise exposure on hearing loss in workplaces. These findings suggest that workers in industries dealing with heavy metals or organic solvents are susceptible to such risks.     

Stimulation of poly(ADP-ribose) synthetase activity in the lungs of mice exposed to a low level of ozone

Toxic effects of O3 are mediated through the formation of free radicals, which can cause DNA strand breaks. Cellular DNA repair is dependent upon the formation of poly(ADP-ribose) (polyADPR) catalyzed by polyADPR synthetase. In order to evaluate whether O3 exposure inflicted DNA damage in lung tissue, we measured the activity of polyADPR synthetase (known to be activated in response to DNA damage) in mouse lungs after exposure to 0.45 ppm (882 micrograms/m3) O3 for up to 7 days. The enzyme activity was stimulated with O3 exposure relative to unexposed controls, showing a 20% (P less than 0.05) increase at Day 5 and 42% (P less than 0.001) at Day 7 of O3 exposure. In addition, the activity of superoxide dismutase (SOD), known to be stimulated in response to production of superoxide anion (.O2-), was measured as an indicator of free radical involvement. Relative to unexposed controls, the SOD activity in exposed animal lungs increased to the peak level at Day 5 (48%, P less than 0.001) and then declined at Day 7 of O3 exposure but was still higher than controls (17%, P less than 0.05). When animals, after 5 days of O3 exposure, were allowed to recover in filtered room air, the activities of both enzymes declined to their respective control values in 6 days. These results suggest a possible temporal relationship between O3 injury and the activities of polyADPR synthetase and a free radical scavenging enzyme, SOD. The stimulation of polyADPR synthetase activity with O3 exposure, reflecting a response to lung cellular DNA repair, may be a sensitive indicator for assessing DNA damage in oxidant injury.     

The relationship between biomarkers of oxidative DNA damage, polycyclic aromatic hydrocarbon DNA adducts, antioxidant status and genetic susceptibility following exposure to environmental air pollution in humans

Polycyclic aromatic hydrocarbons (PAHs) appear to be significant contributors to the genotoxicity and carcinogenicity of air pollution present in the urban environment for humans. Populations exposed to environmental air pollution show increased levels of PAH DNA adducts and it has been postulated that another contributing cause of carcinogenicity by environmental air pollution may be the production of reactive oxygen species following oxidative stress leading to oxidative DNA damage. The antioxidant status as well as the genetic profile of an individual should in theory govern the amount of protection afforded against the deleterious effects associated with exposure to environmental air pollution. In this study we investigated the formation of total PAH (bulky) and B[a]P DNA adducts following exposure of individuals to environmental air pollution in three metropolitan cities and the effect on endogenously derived oxidative DNA damage. Furthermore, the influence of antioxidant status (vitamin levels) and genetic susceptibility of individuals with regard to DNA damage was also investigated. There was no significant correlation for individuals between the levels of vitamin A, vitamin E, vitamin C and folate with M₁dG and 8-oxodG adducts as well as M₁dG adducts with total PAH (bulky) or B[a]P DNA adducts. The interesting finding from this study was the significant negative correlation between the level of 8-oxodG adducts and the level of total PAH (bulky) and B[a]P DNA adducts implying that the repair of oxidative DNA damage may be enhanced. This correlation was most significant for those individuals that were non smokers or those unexposed to environmental air pollution. Furthermore the significant inverse correlation between 8-oxodG and B[a]P DNA adducts was confined to individuals carrying the wild type genotype for both the GSTM1 and the GSTT1 gene (separately and interacting). This effect was not observed for individuals carrying the null variant.     

Monitoring occupational exposure to carcinogens: detection by 32P-postlabelling of aromatic DNA adducts in white blood cells from iron foundry workers

Blood samples were volunteered by workers in a Finnish iron foundry who were occupationally exposed to polycyclic aromatic hydrocarbons and from control subjects not known to be occupationally exposed to this class of chemical carcinogens. DNA was isolated from peripheral white blood cells and digested with micrococcal nuclease, spleen phosphodiesterase and nuclease P1. The DNA digest was then incubated with [gamma-32P]ATP and polynucleotide kinase. Aromatic adducts present in the digest that were resistant to nuclease P1 were thus 32P-labelled while unmodified nucleotides were not. The 32P-labelled adducts were resolved by t.l.c. and detected by autoradiography. Foundry workers were classified as belonging to high, medium or low exposure groups according to their exposure to airborne benzo[a]pyrene (high greater than 0.2, medium 0.05-0.2, low less than 0.05 microgram BP/m3 air). Aromatic adducts were found to be present in DNA from 3/4 samples from the high exposure group, 8/10 samples from the medium exposure group. 4/18 samples from the low exposure group and 1/9 samples from the unexposed controls. The levels of adducts found in the high and medium group samples ranged up to 1 adduct in 10(7) nucleotides but the levels formed in the low exposure group samples were not significantly different from those in unexposed controls. No differences related to the smoking habits of the subjects were observed. Most of the DNA adducts detected had chromatographic mobilities distinct from those formed when the 7,8-diol 9,10-oxide of BP reacted with DNA. The results indicate that highly-exposed individuals are more likely to contain aromatic DNA adducts in their white blood cells, but large interindividual variations were evident. In addition, multiple samples from the same subjects indicate that qualitative and quantitative changes in adduct patterns occur with time. This pilot study suggests that 32P-postlabelling may be useful in monitoring human exposure to known and to previously unidentified environmental genotoxic agents.     

Oxidative Stress and Apoptosis in Relation to Exposure to Magnetic Field

We investigated the effect of extremely low-frequency electromagnetic field (ELF-EMF) with pulse trains exposure on lipid peroxidation, and, hence, oxidative stress in the rat liver tissue. The parameters that we measured were the levels of plasma alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase as well as plasma albumin, bilirubin, and total protein levels in 30 adult male Wistar rats exposed to ELF. We also determined the percentage of apoptotic and necrotic cells of the kidney extracts from the animals by flow cytometry method. Apoptotic cell death was further characterized by monitoring DNA degradation using gel electrophoresis. The results showed an increase in the levels of oxidative stress indicators, and the flow cytometric data suggested a possible relationship between the exposure to magnetic field and the cell death. We showed significantly lower necrotic cell percentages in experimental animals compared to either unexposed or sham control groups. However, DNA ladder analyses did not differentiate between the groups. Our results were discussed in relation to the response of biological systems to EMF.     

A neurokinin-1 receptor antagonist that reduces intra-abdominal adhesion formation decreases oxidative stress in the peritoneum

Oxidative stress has been implicated in intra-abdominal adhesion formation. Substance P, a neurokinin-1 receptor (NK-1R) ligand, facilitates leukocyte recruitment and reactive oxygen species (ROS) generation. We have shown in a rat model of adhesion formation that intraperitoneal administration of a NK-1R antagonist at the time of abdominal operation reduces postoperative adhesion formation. Thus we determined the effects of NK-1R antagonist administration on peritoneal leukocyte recruitment and oxidative stress within 24 h of surgery. Adhesions were induced in Wistar rats randomly assigned to receive the antagonist or vehicle intraperitoneally. Peritoneal tissue was isolated at 2, 4, 6, and 24 h after surgery for analysis of the oxidative stress biomarkers 8-isoprostane (8-IP), protein carbonyl, NADPH oxidase, myeloperoxidase (MPO), and ICAM-1 and VCAM-1 mRNAs. Total antioxidant capacity of peritoneal fluid was also determined. MPO, NADPH oxidase, 8-IP, and protein carbonyl were elevated (P < 0.05) by 6 h. ICAM-1 mRNA was elevated (P < 0.05) by 2 h, whereas VCAM-1 levels decreased (P < 0.05) at 24 h. The NK-1R antagonist delayed the MPO rise and reduced (P < 0.05) 8-IP levels by 6 h and ICAM-1 mRNA, VCAM-1 mRNA, and protein carbonyl at 2 h. The antagonist also increased (P < 0.05) the antioxidant capacity of peritoneal fluid at all time points. These data further support a role for oxidative stress in adhesion formation and suggest that the NK-1R antagonist may limit adhesions, in part, by reducing postoperative oxidative stress through an inhibition of neutrophil recruitment and an increase in peritoneal fluid antioxidant capacity.     

Oxidative stress in digestive gland and gill of the brown mussel (Perna perna) exposed to air and re-submersed

Mussels Perna perna were exposed to air for 24 h showing a clear increase in the levels of lipid peroxidation and oxidative DNA damage, measured as 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo). The levels of lipid peroxidation increased both in the digestive gland and gills, while oxidative DNA damage increased only in the gills. After the 24 h of air exposure, mussels were re-submersed for a period of 3 h, leading values to return to a pre-aerial exposure levels. Control animals were kept immersed during the whole period. Several antioxidant and complementary enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), glutathione S-transferase (GST) and the levels of total glutathione (Total GSH) were assayed in a second set of experiments where one group of mussels were exposed to air for 18 h and other to 1 h re-submersion after 18 h aerial exposure. Only a 52% increase in the glutathione S-transferase activity was observed in the digestive gland, which remained elevated to about 40% after 1 h re-submersion, showing that defense systems can be modulated even during oxygen deprivation in P. perna. The DNA and lipid oxidative damage observed after aerial exposure indicates that mussels face an oxidative challenge, and are able to counteract such an “insult” as values of lipid peroxidation and DNA damage returned to control values after 3 h re-submersion.     

Effects of environmental air pollution on endogenous oxidative DNA damage in humans

Epidemiological studies conducted in metropolitan areas have demonstrated that exposure to environmental air pollution is associated with increases in mortality. Carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) are the major source of genotoxic activities of organic mixtures associated with respirable particulate matter, which is a constituent of environmental air pollution. In this study,we wanted to evaluate the relationship between exposure to these genotoxic compounds present in the air and endogenous oxidative DNA damage in three different human populations exposed to varying levels of environmental air pollution. As measures of oxidative DNA damage we have determined 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and cyclic pyrimidopurinone N-1,N² malondialdehyde-2′-deoxyguanosine (M₁dG) by the immunoslot blot assay from lymphocyte DNA of participating individuals. The level of endogenous oxidative DNA damage was significantly increased in individuals exposed to environmental air pollution compared to unexposed individuals from Kosice (8-oxodG adducts) and Sofia (M₁dG adducts). However, there was no significant difference in the level of endogenous oxidative DNA and exposure to environmental air pollution in individuals from Prague (8-oxodG and M₁dG adducts) and Kosice (M₁dG adducts). The average level of M₁dG adducts was significantly lower in unexposed and exposed individuals from Kosice compared to those from Prague and Sofia. The average level of 8-oxodG adducts was significantly higher in unexposed and exposed individuals from Kosice compared to those from Prague. A significant increasing trend according to the interaction of c-PAHs exposure and smoking status was observed in levels of 8-oxodG adducts in individuals from Kosice. However, no other relationship was observed for M₁dG and 8-oxodG adduct levels with regard to the smoking status and c-PAH exposure status of the individuals. The conclusion that can be made from this study is that environmental air pollution may alter the endogenous oxidative DNA damage levels in humans but the effect appears to be related to the country where the individuals reside. Genetic polymorphisms of the genes involved in metabolism and detoxification and also differences in the DNA repair capacity and antioxidant status of the individuals could be possible explanations for the variation observed in the level of endogenous oxidative DNA damage for the different populations.     

Catalytic antioxidant AEOL 10150 treatment ameliorates sulfur mustard analog 2-chloroethyl ethyl sulfide-associated cutaneous toxic effects

Our previous studies and other published reports on the chemical warfare agent sulfur mustard (SM) and its analog 2-chloroethyl ethyl sulfide (CEES) have indicated a role of oxidative stress in skin injuries caused by these vesicating agents. We examined the effects of the catalytic antioxidant AEOL 10150 in the attenuation of CEES-induced toxicity using our established skin injury models (skin epidermal cells and SKH-1 hairless mice) to validate the role of oxidative stress in the pathophysiology of mustard vesicating agents. Treatment of mouse epidermal JB6 and human HaCaT cells with AEOL 10150 (50 μM) 1 h post-CEES exposure resulted in significant (p < 0.05) reversal of CEES-induced decreases in both cell viability and DNA synthesis. Similarly, AEOL 10150 treatment 1 h after CEES exposure attenuated CEES-induced DNA damage in these cells. Similar AEOL 10150 treatments also caused significant (p < 0.05) reversal of CEES-induced decreases in cell viability in normal human epidermal keratinocytes. Cytoplasmic and mitochondrial reactive oxygen species measurements showed that AEOL 10150 treatment drastically ameliorated the CEES-induced oxidative stress in both JB6 and HaCaT cells. Based on AEOL 10150 pharmacokinetic studies in SKH-1 mouse skin, mice were treated with a topical formulation plus subcutaneous injection (5 mg/kg) of AEOL 10150 1 h after CEES (4 mg/mouse) exposure and every 4 h thereafter for 12 h. This AEOL 10150 treatment regimen resulted in over 50% (p < 0.05) reversal of CEES-induced skin bi-fold and epidermal thickness, myeloperoxidase activity, and DNA oxidation in mouse skin. Results from this study demonstrate the potential therapeutic efficacy of AEOL 10150 against CEES-mediated cutaneous lesions, supporting AEOL 10150 as a medical countermeasure against SM-induced skin injuries.     

Relationship between the capacity to repair 8-oxoguanine, biomarkers of genotoxicity and individual susceptibility in styrene-exposed workers

Genotoxic effects related to exposure to styrene have been a matter of investigation for many years by employing markers of exposure, effect and susceptibility. The role of individual DNA-repair capacity in response to exposure to styrene may explain the controversial results so far obtained, but it is still scarcely explored. In the present study, we measured capacity to repair oxidative DNA damage in cell extracts obtained from 24 lamination workers occupationally exposed to styrene and 15 unexposed controls. The capacity to repair oxidative DNA damage was determined by use of a modified comet assay, as follows: HeLa cells, pre-treated with photosensitizer and irradiated with a halogen lamp in order to induce 7,8-dihydroxy-8-oxoguanine, were incubated with cell extracts from mononuclear leukocytes of each subject. The level of strand breaks reflects the removal of 7,8-dihydroxy-8-oxoguanine from substrate DNA by the enzymatic extract. In styrene-exposed subjects a moderate, non-significant increase in oxidative DNA repair was observed. Stratification for sex and smoking habit showed that unexposed males (P=0.010) and unexposed smokers (P=0.037) exhibited higher DNA-repair rates. The repair capacity did not correlate with parameters of styrene exposure and biomarkers of genotoxic effects (DNA strand breaks, N1-styrene-adenine DNA adducts, chromosomal aberrations and mutant frequencies at the HPRT locus). Significantly higher levels of DNA-repair capacity were observed in carriers of GSTM1-plus, compared to those with a deletion in GSTM1. The DNA-repair capacity was significantly lower in individuals with variant Gln/Gln genotype in XRCC1 Arg399Gln than in those with heterozygous Arg/Gln and wild-type Arg/Arg genotypes. Significantly lower repair capacity was also found in individuals with the wild-type Lys/Lys genotype in XPC Lys939Gln as compared with those homozygous for the Gln/Gln variant genotype.     

Etheno DNA-base adducts from endogenous reactive species

Promutagenic etheno (epsilon) adducts in DNA are generated through reactions of DNA bases with LPO products derived from endogenous sources or from exposure to several xenobiotics. The availability of sensitive methods has made it possible to detect three epsilon-adducts in vivo, namely epsilon dA, epsilon dC and N2,3-epsilon dG. One probable endogenous source for the formation of these adducts arises from LPO products such as trans-4-hydroxy-2-nonenal (HNE), resulting in highly variable background epsilon-adduct levels in tissues from unexposed humans and rodents. The range of background levels of epsilon dAx10-8dA detected inhuman tissues was <0.05 to 25 and in rodent tissues 0.02 to 10; the corresponding values for epsilon dCx10-8dC were 0.01 to 11 and 0.03 to 24, respectively. Part of this variability may be associated with different dietary intake of antioxidants and/or omega-6 PUFAs which oxidize readily to form 4-hydroxyalkenals, as epsilon dA and epsilon dC levels in WBC-DNA of female volunteers on a high omega-6 PUFA diet were drastically elevated. Increased levels of etheno adducts were also found in the liver of cancer-prone patients suffering from hereditary metal storage diseases, i.e., Wilson's disease (WD) and primary hemochromatosis (PH) as well as in Long-Evans Cinnamon rats, an animal model for WD. Increased metal-induced oxidative stress and LPO-derive epsilon-adducts, along with other oxidative damage, may trigger this hereditary liver cancer. Epsilon-Adducts could hence be explored as biomarkers (i) to ascertain the role of LPO mediated DNA damage in human cancers associated with oxidative stress imposed by certain lifestyle patterns, chronic infections and inflammations, and (ii) to verify the reduction of these epsilon-adducts by cancer chemopreventive agents. This article summarizes recent results on the formation, occurrence and possible role of epsilon-DNA adducts in carcinogenesis and mutagenesis.     

Physiological properties of a Pseudomonas strain which grows with p-xylene in a two-phase (organic-aqueous) medium.

Pseudomonas putida Idaho utilizes toluene, m-xylene, p-xylene, 1,2,4-trimethylbenzene, and 3-ethyltoluene as growth substrates when these hydrocarbons are provided in a two-phase system at 5 to 50% (vol/vol). Growth also occurs on Luria-Bertani medium in the presence of a wide range of organic solvents. The ability of the organism to grow in the presence of organic solvents is correlated with the logarithm of the octanol-water partition coefficient, with dimethyl-phthalate (log P(OCT) = 2.3) being the most polar solvent tolerated. During growth with p-xylene (20% [vol/vol]), there was an initial lag period accompanied by cell death, which was followed by a period of exponential growth. The stationary phase of growth was characterized by a dramatic decrease in cell viability, although cell dry weight and turbidity measurements slowly increased. Electron micrographs revealed that during growth in the presence of p-xylene, the outer cell membrane becomes convoluted and membrane fragments are shed into the culture medium. At the same time, the cytoplasmic membrane invaginates, forming vesicles, and becomes disorganized. Electron-dense intracellular inclusions were observed in cells grown with p-xylene (20% [vol/vol]) and p-xylene vapors, which are not present in cells grown with succinate. Attempts to demonstrate the presence of plasmid DNA in P. putida Idaho were negative. However, polarographic studies indicated that the organism utilizes the same pathway for the degradation of toluene, m-xylene, and p-xylene as that used by P. putida mt-2 which contains the TOL plasmid pWWO.(ABSTRACT TRUNCATED AT 250 WORDS)     

Physiological properties of a Pseudomonas strain which grows with p-xylene in a two-phase (organic-aqueous) medium.

Pseudomonas putida Idaho utilizes toluene, m-xylene, p-xylene, 1,2,4-trimethylbenzene, and 3-ethyltoluene as growth substrates when these hydrocarbons are provided in a two-phase system at 5 to 50% (vol/vol). Growth also occurs on Luria-Bertani medium in the presence of a wide range of organic solvents. The ability of the organism to grow in the presence of organic solvents is correlated with the logarithm of the octanol-water partition coefficient, with dimethyl-phthalate (log P(OCT) = 2.3) being the most polar solvent tolerated. During growth with p-xylene (20% [vol/vol]), there was an initial lag period accompanied by cell death, which was followed by a period of exponential growth. The stationary phase of growth was characterized by a dramatic decrease in cell viability, although cell dry weight and turbidity measurements slowly increased. Electron micrographs revealed that during growth in the presence of p-xylene, the outer cell membrane becomes convoluted and membrane fragments are shed into the culture medium. At the same time, the cytoplasmic membrane invaginates, forming vesicles, and becomes disorganized. Electron-dense intracellular inclusions were observed in cells grown with p-xylene (20% [vol/vol]) and p-xylene vapors, which are not present in cells grown with succinate. Attempts to demonstrate the presence of plasmid DNA in P. putida Idaho were negative. However, polarographic studies indicated that the organism utilizes the same pathway for the degradation of toluene, m-xylene, and p-xylene as that used by P. putida mt-2 which contains the TOL plasmid pWWO.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of DNA fragmentation in mouse embryos exposed to an extremely low-frequency electromagnetic field

Effects of extremely low-frequency electromagnetic fields (ELF-EMFs) on DNA damage in biological systems are still a matter of dispute. The aim of the present study was to investigate the possible effect of electromagnetic field exposure on DNA fragmentation in cells (blastomers) of mouse blastocysts. Eighty female NMRI mice were randomly divided into 2 groups of 40 animals each. The control group was left unexposed whereas the animals in the EMF-group were exposed to a 50-Hz EMF at 0.5?mT 4?h per day, 6 days a week for a duration of 2 weeks. After the 8(th) day of exposure, the female mice in both groups were superovulated (with injections of pregnant mare serum gonadotropin and human chorionic gonadotropin) and then mated overnight. At approximately 4 days after mating (102?h after the human chorionic gonadotropin treatment), blastocysts were obtained by flushing the uterus horns. The mean numbers of pregnant mice, blastocysts after flushing, blastomers within the blastocysts, and the DNA fragmentation index following staining in both groups were compared using statistical methods (SPSS, the Chi-square test, the Student's t-test and the Mann-Whitney U-test, P?相似文献   

Susceptibility to oxidative stress and modulated expression of antioxidant genes in the copper-exposed polychaete Perinereis nuntia

To identify and evaluate potentially useful biomarkers for oxidative stress as early warning indices in the polychaete, Perinereis nuntia, we exposed P. nuntia to copper (Cu) and measured several biomarker enzymes (glutathione S-transferase; GST, glutathione peroxidase; GPx, Metallothionein-like protein; MTLPs, and catalase; CAT) and genes (Pn-GSTs, Pn-CAT, and Pn-MT) with a cellular oxidative index, reactive oxygen species (ROS) level. Accumulated Cu concentrations in P. nuntia increased in a time-dependent manner. Intracellular ROS reached high levels 6h after exposure in P. nuntia with an increase of GST activity and glutathione (GSH) content. Particularly, GSH in polychaetes showed a positive correlation with Cu contents accumulated in P. nuntia. Messenger RNA expressions of GST sigma and GST omega showed relatively high expressions at 50 μg/L of Cu exposure, even though the moderate increase of rest of GST isoforms was also observed. Also regarding long-term exposure, we reared P. nuntia in sediments for 15 days, and found that there was an obvious increase of Pn-GSTs, Pn-CAT, and Pn-MT genes with elevated concentrations of Cu and Cd in polychaete body, compared to initial levels, suggesting that P. nuntia in sediment was affected by metals as well as by other organic pollutants to induce oxidative stress genes and enzymes. These findings suggest that oxidative stress is a potential modulator of defense system of P. nuntia. Several potential biomarker genes are available as early warning signals for environmental biomonitoring.     

Short-time UVA exposure to human keratinocytes instigated polyunsaturated fatty acid without inducing lipid peroxidation

Short-term exposure to ultraviolet A (UVA) radiation can directly injure our skin through inflammatory response and indirectly through oxidative stress, triggering polyunsaturated fatty acid (PUFA) peroxidation in skin cell membrane and formation of DNA adduct, 8-hydroxy-2′-deoxyguanosine (8-OHdG). It is known that UVA exposure leads to photoaging, immunosuppression and skin cancer. However, the changes in PUFA and its oxidized metabolites, and cell cycle after short UVA exposure, are debatable. In this study, human keratinocytes (HaCaT) were exposed to low dose (5?J/cm²) and high dose (20 J/cm²) of UVA and assessed immediately, 8?h, 12?h, and 24?h post-treatment. Both doses showed a transient suppression in S-phase after 8?h of UVA exposure, and G₂/M phase arrest after 12-h UVA exposure in the cell cycle but subsequently returned to normal cycle. Also, no observable DNA damage took place, where 8-OHdG levels were below par after 24-h UVA exposure. A dose of 20 J/cm² UVA stimulated significant amount of arachidonic acid, n-3 docosapentaenoic acid, and docosahexaenoic acid (DHA) but lowered adrenic acid and eicospentaenoic acid after 24-h exposure. Among the 43 oxidized PUFA products determined, enzyme-dependent oxidized PUFAs, namely, 14-hydroxy-DHA (HDoHE) level reduced, and 8- and 13-HDoHE levels elevated significantly in a linear trend with post-treatment time. Out of the nonenzymatic oxidized PUFAs, a significant linear trend with post-treatment time was shown on the reduction of 5-F_2t-Isoprostane (IsoP), 15-F_2t-IsoP, Isofurans, 5-F_3t-IsoP, Neurofurans, and 20-HDoHE. Our observations indicate oxidative stress through short UVA exposure on human keratinocytes did not have detrimental consequences.