[Association of hOGG1 genotype with life style and oxidative DNA damage in five ethnic populations in China]

OBJECTIVE

To assess the natural variation of hOGG1 gene and the gene-environmental interactions.

METHODS

The hOGG1 codon 326 polymorphism and urinary 8-OHdG levels were investigated in a large sample of healthy individuals (n = 953) from five ethnic populations in China by using PCR-RFLP and HPLC-ECD. Life style parameters were obtained through a questionnaire survey.

RESULTS

The allelic frequencies of hOGG1 gene in whole subjects were 0.16 (Ser/Ser), 0.49 (Ser/Cys) and 0.35 (Cys/Cys). The frequency of Ser326Cys was significantly different among the five ethnic populations (P = 0.002). No association was found between the hOGG1 gene polymorphism and other life style parameters except for the association between Ser326Cys and smoking (P = 0.027). A significant increase of urinary 8-OHdG level was observed in Cys326Cys allelic healthy subjects (P = 0.033).

CONCLUSION

There are natural variations of hOGG1 gene in different ethnic populations in China. Smoking is related to the frequencies of Cys/Cys polymorphism, and the repairing of oxidative DNA damage is lower in individuals with the hOGG1 Cys326Cys genotype.

The role of reactive oxygen species in silicon dioxide nanoparticle-induced cytotoxicity and DNA damage in HaCaT cells

The increasing applications of silicon dioxide (SiO(2)) nanomaterials have been widely concerned over their biological effects and potential hazard to human health. In this study, we explored the effects of SiO(2) nanoparticles (15, 30, and 100 nm) and their micro-sized counterpart on cultured human epidermal Keratinocyte (HaCaT) cells. Cell viability, cell morphology, reactive oxygen species (ROS), DNA damage (8-OHdG, γH2AX and comet assay) and apoptosis were assessed under control and SiO(2) nanoparticles exposed conditions. As observed in the Cell Counting Kit-8 (CCK-8) assay, exposure to 15, 30 or 100 nm SiO(2) nanoparticles at dosage levels between 0 and 100 μg/ml decreased cell viability in a concentration- and size dependent manner and the IC50 of 24 hour exposure was 19.4 ± 1.3, 27.7 ± 1.5 and 35.9 ± 1.6 μg/ml for 15, 30 and 100 nm SiO(2) nanoparticles, respectively. Morphological examination revealed cell shrinkage and cell wall missing after SiO(2) nanoparticle exposure. Increase in intracellular ROS level and DNA damage as well as apoptosis were also observed in SiO(2) nanoparticle-exposed HaCaT cells. Exposure to SiO(2) nanoparticles results in a concentration- and size-dependent cytotoxicity and DNA damage in cultural HaCaT cells which is closely correlated to increased oxidative stress.

CpG site-specific hypermethylation of p16INK4α in peripheral blood lymphocytes of PAH-exposed workers

BACKGROUND

Sufficient epidemiologic evidence shows an etiologic link between polycyclic aromatic hydrocarbons (PAH) exposure and lung cancer risk. While the genetic modifications have been found in PAH-exposed population, it is unclear whether gene-specific methylation involves in the process of PAH-associated biologic consequence.

METHODS

Sixty-nine PAH-exposed workers and 59 control subjects were recruited. Using bisulfite sequencing, we examined the methylation status of p16(INK4α) promoter in peripheral blood lymphocytes (PBL) from PAH-exposed workers and in benzo(a)pyrene (BaP)-transformed human bronchial epithelial (HBE) cells. The relationships between p16(INK4α) methylation and the level of urinary 1-hydroxypyrene (1-OHP) or the frequency of cytokinesis block micronucleus (CBMN) were analyzed.

RESULTS

Compared with the control group, PAH-exposed workers exhibited higher levels of urinary 1-OHP (10.62 vs. 2.52 μg/L), p16(INK4α) methylation (7.95% vs. 1.14% for 22 "hot" CpG sites), and CBMN (7.28% vs. 2.92%) in PBLs. p16(INK4α) hypermethylation in PAH-exposed workers exhibited CpG site specificity. Among the 35 CpG sites we analyzed, 22 were significantly hypermethylated. These 22 hypermethylated CpG sites were positively correlated to levels of urinary 1-OHP and CBMN in PBLs. Moreover, the hypermethylation and suppression of p16 expression was also found in BaP-transformed HBER cells.

CONCLUSION

PAH exposure induced CpG site-specific hypermethylation of p16(INK4α) gene. The degree of p16(INK4α) methylation was associated with the levels of DNA damage and internal exposure.

IMPACT

p16(INK4α) hypermethylation might be an essential biomarker for the exposure to PAHs and for early diagnosis of cancer.

Effects of long-term low-dose formaldehyde exposure on global genomic hypomethylation in 16HBE cells

Formaldehyde (FA), a volatile organic compound, is a ubiquitous air pollutant that is classified as 'Carcinogenic to humans (Group 1)' by IARC (2006). As a well-recognized human carcinogen, its carcinogenic mechanisms are still poorly understood. Previous studies have emphasized on genetic changes. However, little is known about the epigenetic mechanisms of FA exposure. In this study, We not only characterized the epigenomic response to long-term low-dose FA exposure in 16HBE cells, but also examined the expression of DNA methyltransferases (DNMTs) and the methyl-CpG-binding protein DNA-binding domain protein 2 (MBD2). Each week the 16HBE cells were treated with 10 μM FA for 24 h (h). After 24 weeks (W) of exposure to FA, the level of genomic DNA methylation gradually decreased in a time-related manner. Moreover, our results showed that FA exposure down-regulated the expression of DNMT3a and DNMT3b at both mRNA and protein level, and up-regulated the levels of DNMT1 and MBD2 at both mRNA and protein level. Our study indicated that long-term FA exposure could disrupt genomic DNA methylation, which may be one of the possible underlying carcinogenic mechanisms of FA.

Nano-hydroxyapatite/poly(L-lactic acid) composite synthesized by a modified in situ precipitation: preparation and properties

Nano-hydroxyapatite/poly(L-lactic acid) (nano-HA/PLLA) composites with uniform HA distribution and good mechanical performance were fabricated by a modified in situ precipitation method, using Ca(OH)(2) and H(3)PO(4) as precursors for the synthesis of HA phase. This method has solved the aggregation problem of the nano-sized particles in the polymer matrix. The X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy were used to characterize the phase composition, chemical interactions and morphology of the composites, while the mechanical properties were determined by compressive measurements. The results show that the rod-like nano-HA particles synthesized by this method were uniformly distributed in the PLLA matrix. The compressive strength and Young's modulus of the composites were greatly enhanced and reached the values of 155 MPa and 3.6 GPa at 20 wt% HA content, respectively, which are much higher than those of the reference samples fabricated by direct mixing of PLLA with nano-HA particles. This supports the potential of these composites for applications in bone tissue engineering and load bearing bone defects repair.

[Expression changes of glutathione transferase omega 1 induced by low dose trichloroethylene]

OBJECTIVE

To determine the expression of glutathione transferase omega 1 (GSTO-1) during hormesis induced by low dose trichloroethylene (TCE).

METHODS

Based on the dose-response of hormesis induced by TCE, the total protein and mRNA from four groups was extracted, and expression of GSTO-1 was detected by western blotting and RT-PCR technology.

RESULTS

The study showed that increases of GSTO-1 protein expression were induced by TCE at low dose (0.1 mmol/L) TCE, but there was no significant different between the high-dose group and the control (P < 0.05). RT-PCR analysis presented the expression of GSTO-1 gene in low-dose group was increased, but the opposite effect was observed in the high-dose group.

CONCLUSION

GSTO-1 may be play a key role in hormesis induced by TCE.

Epigenetic enhancement of p66Shc during cellular replicative or premature senescence

The cytoplasmic protein p66Shc is expressed in a wide range of cell types, initially believed to be involved in signaling pathways that regulate cell growth and oxidative stress. Here the epigenetic alterations in the promoter of p66Shc were investigated in replicative senescence and in premature senescence induced by hydrogen peroxide in human embryonic pulmonary fibroblast cells. In both cases p66Shc expression was elevated compared to that seen in growing cultures. However, methylation-specific PCR and bisulfite sequencing revealed that the CpG sites were hypermethylated in all cultures. In addition, quantitative chromatin immunoprecipitation showed increased histone H4 acetylation and histone H3 Lys-4 methylation during replicative senescence, while the increased acetylation of histone H3 and H4, as well as increased H3 Lys-4 methylation, was seen in premature senescence persistence. These findings suggest that histone modifications of p66Shc might be the molecular event in cellular senescence. Taken together, the epigenetic enhancement of p66Shc is associated with the specifically increased histone acetylation and methylation, which may contribute to cellular replicative senescence or premature senescence.

SiO(2) nanoparticles induce global genomic hypomethylation in HaCaT cells

The increasing amount of nanotechnological products, found in our environment and those applicable in engineering, material sciences and medicine has stimulated a growing interest in examining their long-term impact on genetic and epigenetic processes. We examined here the epigenomic response to nm-SiO(2) particles in human HaCaT cells and methyltransferases (DNMTs) and DNA-binding domain proteins (MBDs) induced by nano-SiO(2) particles. Nm-SiO(2) treatment induced global hypoacetylation implying a global epigenomic response. The levels of DNMT1, DNMT3a and methyl-CpG binding protein 2 (MBD2) were also decreased in a dose dependent manner at mRNA and protein level. Epigenetic changes may have long-term effects on gene expression programming long after the initial signal has been removed, and if these changes remain undetected, it could lead to long-term untoward effects in biological systems. These studies suggest that nanoparticles could cause more subtle epigenetic changes which merit thorough examination of environmental nanoparticles and novel candidate nanomaterials for medical applications.

Generation and analysis of 10 000 ESTs from the half-smooth tongue sole Cynoglossus semilaevis and identification of microsatellite and SNP markers

Three normalized cDNA libraries were constructed, two of which were constructed from reproductive tissues ovary and testis, and the other one from pooled immune tissues including head kidney, intestine, liver and spleen. A total of 10 542 clones were sequenced generating 10 128 expressed sequence tags (ESTs). Cluster analysis indicated a total of 5808 unique sequences including 1712 contigs and 4096 singletons. A total of 4249 (73%) of the unique ESTs had significant hits to the non-redundant protein database, 2253 of which were annotated using Gene Ontology (GO) terms. A total of 311 microsatellites (with 246 having sufficient flanking sequences for primer design) and 6294 putative SNPs were identified. These genome resources provide the material basis for future microarray development, marker validation and genetic linkage and QTL analysis.

SiO2 nanoparticles induce cytotoxicity and protein expression alteration in HaCaT cells

Background

Nanometer silicon dioxide (nano-SiO₂) has a wide variety of applications in material sciences, engineering and medicine; however, the potential cell biological and proteomic effects of nano-SiO₂ exposure and the toxic mechanisms remain far from clear.

Results

Here, we evaluated the effects of amorphous nano-SiO₂ (15-nm, 30-nm SiO₂). on cellular viability, cell cycle, apoptosis and protein expression in HaCaT cells by using biochemical and morphological analysis, two-dimensional differential gel electrophoresis (2D-DIGE) as well as mass spectrometry (MS). We found that the cellular viability of HaCaT cells was significantly decreased in a dose-dependent manner after the treatment of nano-SiO₂ and micro-sized SiO₂ particles. The IC₅₀ value (50% concentration of inhibition) was associated with the size of SiO₂ particles. Exposure to nano-SiO₂ and micro-sized SiO₂ particles also induced apoptosis in HaCaT cells in a dose-dependent manner. Furthermore, the smaller SiO₂ particle size was, the higher apoptotic rate the cells underwent. The proteomic analysis revealed that 16 differentially expressed proteins were induced by SiO₂ exposure, and that the expression levels of the differentially expressed proteins were associated with the particle size. The 16 proteins were identified by MALDI-TOF-TOF-MS analysis and could be classified into 5 categories according to their functions. They include oxidative stress-associated proteins; cytoskeleton-associated proteins; molecular chaperones; energy metabolism-associated proteins; apoptosis and tumor-associated proteins.

Conclusions

These results showed that nano-SiO₂ exposure exerted toxic effects and altered protein expression in HaCaT cells. The data indicated the alterations of the proteins, such as the proteins associated with oxidative stress and apoptosis, could be involved in the toxic mechanisms of nano-SiO₂ exposure.

[Epigenetic activation of IGF2 during cellular senescence]

OBJECTIVE

Epigenetic regulations of insulin-like growth factor 2 (IGF2) were observed during cellular replicative senescence and premature senescence induced by hydrogen peroxide of human embryonic lung fibroblasts (HEFs).

METHODS

The mRNA level of IGF2 was detected by Q-PCR. The methylation status in the promoter region was observed by methylation-specific PCR. The histone modifications was detected by chromatin immunoprecipitation-Q-PCR assay, including acetylation for H3, H4 and methylation for H3 ( Lys4) and H4 (Lys20).

RESULTS

In the process of cellular senescence, the mRNA level of IGF2 increased in both mid-aged and replicative senescent cells, but increased obviously in premature senescent cells compared with that of young cells. In the promotor region from -658 bp to -456 bp, the methylation level for IGF2 was detected only in replicative senescent cells. About the main histone modifications, IGF2 in the region (-856 bp - -634 bp) was H4 acetylation and H3K4 methylation in replicative senescence, while in the region (+9 bp - +145 bp) was H3K4 and H4K20 methylation in replicative senescence and H3K4 methylation in premature senescence.

CONCLUSION

The histone modifications take part in regulating the mRNA expression for IGF2 during cellular senescence and different mechanisms exist between two types of senescence.

Identification of antigenic proteins associated with trichloroethylene-induced autoimmune disease by serological proteome analysis

Although many studies indicated that trichloroethylene (TCE) could induce autoimmune diseases and some protein adducts were detected, the proteins were not identified and mechanisms remain unknown. To screen and identify autoantigens which might be involved in TCE-induced autoimmune diseases, three groups of sera were collected from healthy donors (I), patients suffering from TCE-induced exfoliative dermatitis (ED) (II), and the healed ones (III). Serological proteome analysis (SERPA) was performed with total proteins of TCE-treated L-02 liver cells as antigen sources and immunoglobins of the above sera as probes. Highly immunogenic spots (2-fold or above increase compared with group I) in group II and III were submitted to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and tandem mass spectrometry sequencing. Western blot analysis was followed using commercial antibodies and individual serum. Six proteins were identified. Among them, Enoyl Coenzyme A hydratase peroxisoma 1 and lactate dehydrogenase B only showed stronger immunogenicity for group II sera, while Purine nucleoside phosphorylase, ribosomal protein P0 and proteasome activator subunit1 isoform1 also showed stronger immunogenicity for group III sera. Noteworthy, NM23 reacted only with group II sera. Western blot analysis of NM23 expression indicated that all of the individual serum of group II showed immune activity, which confirmed the validity of SERPA result. These findings revealed that there exist autoantibodies in group II and III sera. Besides, autoantibodies of the two stages of disease course were different. These autoantigens might serve as biomarkers to elucidate mechanisms underlying TCE toxicity and are helpful for diagnosis, therapy and prognosis of TCE-induced autoimmune diseases.

[Effect of hydroquinone on the expression of ubiquitin-conjugating enzyme Rad6B in human L-02 hepatic cells]

OBJECTIVE

To study the effects of hydroquinone (HQ) on expression of ubiquitin-conjugating enzyme Rad6B in human L-02 hepatic cells.

METHODS

After L-02 hepatic cells were at the concentrations of 0, 5, 10, 20, 40, 80, and 160 micromol/L HQ for 24h, and the levels of Rad6B mRNA and protein expressions in L-02 hepatic cells were detected by real-time fluorescent quantitative polymerase chain reaction (QPCR) technique and Western blot method respectively.

RESULTS

It was found that HQ in the range of 0-160 micromol/L could induce increases in the expressions of Rad6B mRNA and protein, which was in a dose-dependent manner. The levels of Rad6B mRNA and protein expressions in the treated group of 5, 10, 20, 40, 80, and 160 micromol/L were higher than those in the control (P < 0.01), levels of Rad6B mRNA and protein expressions reached the maximun when L-02 hepatic cells were treated by HQ at the concentrations of 160 micromol/L, and the relative quantity values were 4.35 and 0.85, respectively.

CONCLUSION

HQ could regulate up the expression of Rad6B in L-02 hepatic cells.