PARP-1 overexpression does not protect HaCaT cells from DNA damage induced by SiO2 nanoparticles

Nano-SiO₂ is increasingly used in diagnostic and biomedical research because of its ease of production and relatively low cost and which is generally regarded as safe and has been approved for use as a food or animal feed ingredient. Although recent literature reveals that nano-SiO₂ may present toxicity and DNA damage, however, the underlying mechanism remains poorly understood. Since in previous studies, we found that nano-SiO₂ treatment down-regulated the expression of the poly(ADP-ribose) polymerases-1 (PARP-1), a pivotal DNA repair gene, in human HaCaT cells and PAPR-1 knockdown can aggravate DNA damage induced by nano-SiO₂. Therefore, we speculate whether PARP-1 overexpression can protect DNA from damage induced by nano-SiO₂. However, our data demonstrated that overexpression of PARP-1 in HaCaT cells slightly enhanced the cellular proliferation of undamaged cells, when compared with both empty vector control cells and parental cells, but had drastic consequences for cells treated with nano-SiO₂. The PARP-1 overtransfected cells were sensitized to the cytotoxic effects and DNA damage of nano-SiO₂ compared with control parental cells. Meanwhile, flow cytometric analysis of nano-SiO₂ stimulated poly(ADP-ribose) synthesis revealed consistently larger fractions of cells positive for this polymer in the PARP-1 overexpression cells than in control clones. Combining our previous research on PARP-1 knockdown HaCaT cells, we hypothesize that an optimal level of cellular poly(ADP-ribose) accumulation exists for the cellular recovery from DNA damage.

[Changes of the expression for genes related with senescence and the telomerase activity during cellular replicative and premature senescence in human embryonic lung fibroblasts]

Objective: To detect the alterations of telomerase activity and the expression for oxidative stress responsive genes related with senescence during cellular replicative senescence and hydrogen peroxide-induced premature senescence in human embryonic lung fibroblasts (HELFs) in vitro. Methods: The HELFs were divided into young cells (22 population doubling levels, 22PDL) , mid-aged cells (35PDL) and replicative senes-cent cells (49PDL) and premature senescent cells induced by H(2)O(2)(premature senescence, PS). The telomerase activity was detected by ELISA assay during cellular replicative and premature senescence. The mRNA level of oxidative stress responsive genes related with senescence for Foxo1, Foxo3, Pdx1, apoA-I and MMP1 was per-formed by RT-Q-PCR separately. Results: The mRNA level for Foxo1, Foxo3, apoA-I and Pdx1 was decreased separately during cellular replicative senescence compared to that in the young-stage cells with statistical signifi-cance (P<0.05). The expression of MMP1 was up-regulated 5.1-fold obviously (P<0.05). In premature senes-cence, the mRNA level was only decreased for Foxo1, Foxo3 and apoA-I, but up-regulated 2.3-fold and 6.2-fold for Pdx1 and MMP1 respcetively vs 22PDL significantly (P<0.05). The telomerase activity in young cells was not detected, and it increased in mid-aged cells and replicative senescence stages during cellular replicative se-nescence as compared to 22PDL with statistical significance (P<0.05). The telomerase activity in premature se-nescence was highly active. Conclusion: The expression for genes related with senescence has differences be-tween replicative and premature senescence and hydrogen peroxide modifies their expression levels. The telomer-ase activity has been going up with increased PDLs.

Association of NOS2 and NOS3 gene polymorphisms with susceptibility to type 2 diabetes mellitus and diabetic nephropathy in the Chinese Han population

Inducible nitric oxide synthase (NOS2) and endothelial nitric oxide synthase (NOS3) gene play important roles in the susceptibility to type 2 diabetes mellitus (T2DM). The present study aims to detect the potential association of NOS2 and NOS3 gene polymorphisms with the susceptibility toT2DM and diabetic nephropathy (DN) in the Chinese Han population. Four hundred and ninety T2DM patients and 485 healthy controls were enrolled in this case-control study. The genotypes of NOS2 and NOS3 gene polymorphisms were analyzed by the polymerase chain reaction (PCR)-ligase detection reaction (LDR) method. Our data demonstrated that the NOS2 rs2779248 and NOS2 rs1137933 genetic polymorphisms were significantly associated with the increased susceptibility to T2DM in the heterozygote comparison, dominant model, and allele contrast; and NOS3 rs3918188 genetic polymorphism was significantly associated with the increased susceptibility to T2DM in the homozygote comparison and recessive model. The allele-C and genotype-TC of NOS2 rs2779248, allele-A and genotype-GA of NOS2 rs1137933 and genotype-AA of NOS3 rs3918188 genetic polymorphisms might be the risk factors for increasing the susceptibility to T2DM. And a significant haplotype effect of NOS2 rs10459953/C- rs1137933/G- rs2779248/T was found between T2DM cases and controls. Moreover, NOS3 rs1800783 polymorphism was significantly associated with the increased susceptibility to DN in the heterozygote comparison, recessive model and allele contrast. At last, a positive correlation of family history of diabetes with NOS3 rs11771443 polymorphism was found in DN. These preliminary findings indicate that the NOS2 rs2779248, NOS2 rs1137933, and NOS3 rs3918188 genetic polymorphisms are potentially related to the susceptibility to T2DM, and the rs1800783 polymorphism might be considered as genetic risk factors for diabetic nephropathy, and family history of diabetes was closely associated with rs11771443 polymorphism in DN, and the genetic variants might be used as molecular markers for evaluating the risk of T2DM and diabetic nephropathy. © 2016 IUBMB Life, 68(7):516-525, 2016.

Repression of Biotin-Related Proteins by Benzo[a]Pyrene-Induced Epigenetic Modifications in Human Bronchial Epithelial Cells

Benzo[a]pyrene (B[a]P) exposure has been associated with the alteration in epigenetic marks that are involved in cancer development. Biotinidase (BTD) and holocarboxylase synthetase (HCS) are 2 major enzymes involved in maintaining the homeostasis of biotinylation, and the deregulation of this pathway has been associated with a number of cancers. However, the link between B[a]P exposure and the dysregulation of BTD/HCS in B[a]P-associated tumorigenesis is unknown. Here we showed that the expression of both BTD and HCS was significantly decreased upon B[a]P treatment in human bronchial epithelial (16HBE) cells. Benzo[a]pyrene exposure led to the global loss of DNA methylation by immunofluorescence, which coincided with the reduction in acetylation levels on histones H3 and H4 in 16HBE cells. Consistent with decreased histone acetylation, histone deacetylases (HDACs) HDAC2 and HDAC3 were significantly upregulated in a dosage-dependent manner. When DNA methylation or HDAC activity was inhibited, we found that the reduction in BTD and HCS was separately regulated through distinct epigenetic mechanisms. Together, our results suggested the potential link between B[a]P toxicity and deregulation of biotin homeostasis pathway in B[a]P-associated cancer development.

[The profile of IGF2R gene expression and H3 histone modifications in replicative cell senescence]

OBJECTIVE

To study the profile of IGF2R expression and histone modifications in replicative cell senescence.

METHODS

The changes of biological characteristics of young human pulmonary fibroblast (HPF) cells [at population doubling level (PDL) 23] and aging HPF cells (at PDL50) were observed and real-time quantitative PCR was utilized to investigate human IGF2R gene expressions profile during the process of cellular aging (at different PDL). Then chromatinimmunoprecipitation-real time quantitative PCR (CHIP-QPCR) methods were conducted to analyze histone modifications of the regions around the transcriptional start site of IGF2R (H3-Ac, H3K9-tri-Me, H3K9-Ac and H3K4-tri-Me).

RESULTS

In contrast to young cells, the aging cells were bigger and less proliferative, their cell cycles arrest, and aging specific beta-galactosidase staining was positive. IGF2R gene expression was in positive correlation with PDL. H3-Ac, H3K9-Ac and H3K4-tri-Me were dominant in the upstream region (-0.6 kb) to the downstream region (+1.2 kb) of transcriptional start site (TSS). While in the downstream of TSS from +1.6 kb to +4.0 kb, H3K9-Ac was declined and H3K9-tri-Me was elevated in turn, but H3K4-tri-Me still prevailed in these areas.

CONCLUSION

IGF2R is related to cell replicative senescence and its gene expression is regulated by histone modification of H3. Therefore, epigenetics may play a role in cell senescence.

Effects of passive smoking on breast cancer risk in pre/post-menopausal women as modified by polymorphisms of PARP1 and ESR1

OBJECTIVES

The association between passive smoking and breast cancer risk differs in pre- and post-menopausal women. We aimed to explore the modification effects of PARP1 rs1136410 and ESR1 rs2234693 on the association between passive smoking and breast cancer risk among pre- and post-menopausal women.

DESIGN AND METHODS

A case-control study of 839 breast cancer cases and 863 controls was conducted. The gene-environment interactions were tested after adjusting for potential breast cancer risk factors with unconditional logistic regression models.

RESULTS

We found that the effect of passive smoking was modified by the genotypes in both pre- and post-menopausal women, but in opposite directions. The combination of the TC/CC genotypes of ESR1 rs2234693 and passive smoking significantly increased the risk of breast cancer [OR (95%CI): 2.06 (1.39-3.05)] in pre-menopausal women. A significant association was observed between TT genotype and passive smoking [OR (95%CI): 2.40 (1.27-4.53)] in postmenopausal women. For PARP1 rs1136410, similar differential associations were observed, but the interactions were not significant.

CONCLUSIONS

These results imply that the risk of breast cancer from passive smoking may be influenced by genetic factors, and that the association may differ depending on menopausal status.

Chromium(VI) causes down regulation of biotinidase in human bronchial epithelial cells by modifications of histone acetylation

Hexavalent chromium (Cr(VI)), a commonly used industrial metal, is a well-known mutagen and carcinogen, and occupational exposure can induce a broad spectrum of adverse health effects, including cancers. Although Cr(VI)-induced DNA damage is thought to be the primary mechanism of chromate genotoxicity and mutagenicity, there is an increasing number of reports showing that epigenetic mechanisms of gene regulation might be a central target of Cr(VI) toxicity. Epigenetic changes, such as changes in phosphorylation, altered DNA methylation status, histone acetylation and signaling pathways, have been observed after chromium exposure. Nevertheless, to better demonstrate the roles of epigenetic modifications in Cr(VI)-induced carcinogenesis, more work needs to be carried out. This study is aimed to investigate changes in biotinidase (BTD) and holocarboxylase synthetase (HCS), two major proteins which maintain homeostasis of the newfound epigenetic modification: histone biotinylation, in cells exposed to Cr(VI). The data showed that Cr(VI) decreased BTD expression at the transcriptional level in human bronchial epithelial cells (16HBE). In addition, using the epigenetic modifiers, 5-Aza-2'-deoxycytidine (Aza) and Trichostatin A (TSA), we found that modifications of histone acetylation reversed the inhibition of BTD, suggesting that Cr(VI) may cause down regulation of BTD by modifications of histone acetylation.

A study on the relationship between BOD(5) and COD in a coastal seawater environment with a rapid BOD measurement system

The dual objectives of this study are to: (1) examine the relationship between COD and BOD in seawater environment with a rapid but reliable method for the measurement of BOD in seawater, and (2) establish the relationship model between BOD(5) and COD in the firth of Dongbao River to predict the values of BOD(5). The first objective is met by the successful development of a technique utilizing bacteria-immobilized membrane flow cell for biodegradation process, coupled with fibre optic fluorescence detection for oxygen depletion quantitation. The technique has been applied to coastal seawater samples collected in the coastal area of Shenzhen, China. The BOD(5) and COD values for the samples are acquired and the results show that there is no apparent linear relationship existing between BOD(5) and COD in relatively clean seawater samples away from the shore. However, in estuary water samples containing relatively high concentration of sewage contamination, a linear correlation does exist between BOD(5) and COD. The linear relationship between the two parameters allows for the calculation of BOD(5) values based on COD data which can be measured more readily and precisely.

A study on the relationship between BOD5 and COD in coastal seawater environment with a rapid BOD measurement system

The dual objectives of this study are to: (1) examine the relationship between COD and BOD in seawater environment with a rapid but reliable method for the measurement of BOD in seawater, and (2) establish the relationship model between BOD(5) and COD in the firth of Dongbao River to predict the values of BOD(5). The first objective is met by the successful development of a technique utilizing bacteria-immobilized membrane flow cell for biodegradation process, coupled with fibre optic fluorescence detection for oxygen depletion quantitation. The technique has been applied to coastal seawater samples collected in the coastal area of Shenzhen, China. The BOD(5) and COD values for the samples are acquired and the results show that there is no apparent linear relationship existing between BOD(5) and COD in relatively clean seawater samples away from the shore. However, in estuary water samples containing relatively high concentration of sewage contamination, a linear correlation does exist between BOD(5) and COD. The linear relationship between the two parameters allows for the calculation of BOD(5) values based on COD data which can be measured more readily and precisely.

Breast cancer resistance protein expression and 5-fluorouracil resistance

OBJECTIVE

To filtrate breast cancer resistance protein (BCRP)-mediated resistant agents and to investigate clinical relationship between BCRP expression and drug resistance.

METHODS

MTT assay was performed to filtrate BCRP-mediated resistant agents with BCRP expression cell model and to detect chemosensitivity of breast cancer tissue specimens to these agents. A high performance liquid chromatography (HPLC) assay was established, and was used to measure the relative dose of intracellular retention resistant agents. RT-PCR and immunohistochemistry (IHC) were employed to investigate the BCRP expression in breast cancer tissue specimens.

RESULTS

MTT assay showed that the expression of BCRP increased with the increasing resistance of 5-fluorouracil (5-Fu) (P<0.05, n=3) in the cell model, while HPLC assay indicated that the intracellular retention dose of 5-Fu was significantly correlated with the expression of BCRP (r=-0.897, P<0.05, n=3). A total of 140 breast cancer tissue specimens were collected. BCRP-positive expression was detected in forty-seven specimens by both RT-PCR and IHC. As shown by MTT assay subsequently, the resistance index (RI) of 47 BCRP-positive breast cancer tissue specimens to 5-Fu was 7-12 times as high as that of adjacent normal tissue samples. BCRP expression was related to 5-Fu resistance (R2=0.8124, P<0.01).

CONCLUSION

Resistance to 5-Fu can be mediated by BCRP. Clinical chemotherapy for breast cancer patients can be optimized based on BCRP-positive expression.

[Study on the relationship between breast cancer resistance protein expression and 5-fluorouracil resistance]

OBJECTIVE

To screen breast cancer resistance protein BCRP-mediated resistance agents and to investigate the relations between BCRP expression and drug resistance.

METHODS

MT assay was performed to screen BCRP-mediated resistant agents with established BCRP expression cell model. While, the high performance liquid chromatography (HPLC) assay was administrated to measure the related dosage of intracellular retention resistant agents. The BCRP expression was investigated by both real-time RT-PCR and immunohistochemistry (IHC) assay in 140 clinical breast cancer tissue specimens. Chemosensitivity to resistant agents for clinical breast cancer tissue specimens was analyzed by MT assay. The Nonparametric variance statistics method was used to analyze the correlations between clinical breast cancer tissue of BCRP expression and drug resistance.

RESULTS

MT assay showed that increasing resistance of 5-fluorouracil (5-Fu) climbed with the increases of the BCRP expressions by 10.58 times (P < 0.05, n = 3) in cell model. HPLC assay also proved that a significant negative correlation between the intracellular retention dose of 5-Fu with different expression of BCRP (r = -0.897, P < 0.05, n = 3). Forty-seven tissue specimens of BCRP-positive expression were rapidly determined by using both real-time RT-PCR and IHC in 140 clinical breast cancer tissue specimens. Subsequently, the resistance index (RI) for 47 BCRP-positive clinical breast cancer tissues to 5-Fu was shown from 7 to 12 times compared with normal cancer-side tissues through MT assay. The statistical correlation between BCRP expression and 5-Fu resistance was observed in clinical breast cancer tissue specimens (R2 = 0.8124, P < 0.01).

CONCLUSION

This study results showed that there is a significant relationship between BCRP expression and 5-Fu resistance. Moreover, the results suggest that the chemotherapy scheme could be optimized on BCRP-positive expression breast cancer patients.

Arsenite-induced alterations in Ku70-deficient cells: a model to study genotoxic effects

As one of three subunits of DNA-dependent protein kinase (DNA-PK), Ku70 protein plays an important role in repair of DNA double-strand breaks (DNA DSB). To further understand the functions of Ku70 protein and the mechanisms underlying arsenite-induced genotoxic effects, the effects of Ku70 deficiency were examined. The Ku70-deficient cell line HLFK and null vector cell line HLFC were established after recombinant plasmid of Ku70 gene antisense RNA and null pEGFP-C1 vector were transferred into human embryo lung fibroblasts (HLF) cells. Experiments were undertaken to detect DNA DSB damage by neutral single-cell gel electrophoresis assay (SCGE), chromosomal alterations by micronucleus test, and cell cycle progression by flow cytometry in HLFC and HLFK cells treated with control, 1, 2.5, 5, or 10 microM sodium arsenite for 2, 4, or 24 h, respectively. Western blot analysis results showed that Ku70 protein content in HLFK cells decreased to 38% of those in HLFC cells. The median lethal concentrations (LC50) of sodium arsenite to HLFC and HLFK cells for 24 h were 27.38 microM and 21.80 microM, respectively. Results of neutral SCGE assay showed that there were concentration-dependent increases in tail length of DNA DSB, in percent of cells with DNA DSB tails, and in severity of DNA DSB damage in HLFK and HLFC cells. The increases in these indices in HLFK cells were significantly higher than those found in HLFC cells exposed to similar amounts of metal. The ability of DNA DSB to repair in HLFK cells was less than that seen in HLFC cells. Sodium arsenite produced concentration-dependent elevation in micronuclei and abnormal nuclei formation. The Ku70-deficiency enhanced the susceptibility to chromosomal alterations induced by sodium arsenite. Low concentrations of sodium arsenite induced cell arrest at G1; however, at high concentrations of metal this G1 arrest effect disappeared. These results suggested that Ku70 protein plays an important role in repair of DNA DSB damage and for maintainance of genome stability.

Possible role of DNA polymerase beta in protecting human bronchial epithelial cells against cytotoxicity of hydroquinone

OBJECTIVE

To explore the toxicological mechanism of hydroquinone in human bronchial epithelial cells and to investigate whether DNA polymerase beta is involved in protecting cells from damage caused by hydroquinone.

METHODS

DNA polymerase beta knock-down cell line was established via RNA interference as an experimental group. Normal human bronchial epithelial cells and cells transfected with the empty vector of pEGFP-C1 were used as controls. Cells were treated with different concentrations of hydroquinone (ranged from 10 micromol/L to 120 micromol/L) for 4 hours. MTT assay and Comet assay [single-cell gel electrophoresis (SCGE)] were performed respectively to detect the toxicity of hydroquinone.

RESULTS

MTT assay showed that DNA polymerase beta knock-down cells treated with different concentrations of hydroquinone had a lower absorbance value at 490 nm than the control cells in a dose-dependant manner. Comet assay revealed that different concentrations of hydroquinone caused more severe DNA damage in DNA polymerase beta knock-down cell line than in control cells and there was no significant difference in the two control groups.

CONCLUSIONS

Hydroquinone has significant toxicity to human bronchial epithelial cells and causes DNA damage. DNA polymerase beta knock-down cell line appears more sensitive to hydroquinone than the control cells. The results suggest that DNA polymerase beta is involved in protecting cells from damage caused by hydroquinone.

Immune responses to trichloroethylene and skin gene expression profiles in Sprague Dawley rats

OBJECTIVE

To characterize the immune reaction in SD rats exposed to trichloroethylene (TCE) and to identify the gene expression profiles involved in skin after TCE exposure.

METHODS

Fifteen percent of TCE was injected intradermally into the rat back (100 microL/120 g) at intervals of 7 days. Whole blood was collected 24 h after the fifth or seventh intradermic administration of TCE. The percentages of CD4+ and CD8+ of T lymphocytes were measured by a flow cytometer. The concentrations of IFN-gamma and IL-4 in the serum were semi-quantified by ELISA. Total RNAs of skin samples at 3 h or 24 h after the seventh dose of TCE in SD rats were extracted, and gene expression profiles of these tissues were analyszed by rat toxicology U34 array of Affymetrix.

RESULTS

Obvious decline of CD4+ in T lymphocytes was observed in the TCE-administer group. No significant concentration differences in IFN-gamma and IL-4 were found between TCE-treated and control rats. Gadd45a and Mel were significantly up regulated in skin tissue 24 h after TCE exposure. The expression regulation of immune response factors was as active as proteins associated with lipid metabolism and synthesis process in these skin samples of SD rats exposed to TCE.

CONCLUSION

T-helper type 1 cells mediate immune response can not be elicited in TCE-treated SD rats, but certain immune disorder can be induced.

[Construction of short hairpin RNA vector of inhibiting poly ADP-ribose polymerase activity]

OBJECTIVE

To construct expressing vector of short hairpin RNA (shRNA) in order to inhibit human PARP1 activity.

METHODS

2 pairs of 64 base oligos for hairpin RNA expression which targeted PARP1 gene were chemically synthesized and annealed then ligased with pSIREN-RetroQ vector with BamH II and EcoR I . Cut by EcoR t and Bgl II, shRNA and its upstream U6, which have 330 bp, were inserted into the same treated pEGFP-C1 vecter to construct GFP expression plasmids that inhibited hPARP1 protein shRNA plasmid (pEGFP-C1P). Oligos with a scrambled sequence were used as a negative control.

RESULTS

Recombinant pEGFP-C1P1, pEGFP-C1P2 and pEGFP-C1N vectors was identified by digestion with EcoR I and Bgl II and confirmed by sequencing analysis with U6 primer. The results demonstrated that the 330 bp had been inserted into the expected site. Furthermore, the insertion sequence was exactly correct.

CONCLUSION

pEGFP-C1-shRNA system has been constructed successfully. This will facilitate the study of PARP1's DNA repairing function.

[Construction of "pEGFP-C1-pU6-dsRNA" recombinant for human DNA polymerase beta RNA interference]

OBJECTIVE

To clone the "pEGFP-C1-pU6-dsRNA" recombinant for human DNA polymerase beta RNA interference, to provide research tool for the study on the function of DNA polymerase beta in repairing of human DNA damaged by environmental chemical pollutants (ECPs).

METHODS

According to the gene sequence of polymerase beta cDNA published in Genbank, double strand RNA(dsRNA) sequence which was used in RNA interference was designed by dsRNA oligonucleotide designer and synthesized by chemical methods. DNA recombination technology was used to insert the up related dsRNA sequence into the vector of pSIREN-RetroQ, and then the "pSIREN-RetroQ-dsRNA" recombinant was obtained. After E. coli DH5alpha was transformed with the "pSIREN-RetroQ-dsRNA" recombinant and screened with ampicillin for positive clones, plasmid was extracted and digested by EcoR I and Bgl II , the fragment of"pU6-dsRNA"was purified. And then the "pU6-dsRNA"fragment was cloned into the vector of pEGFP-C1 by recombination technology, the recombinant of "pEGFP-C1-pU6-dsRNA" was obtained and identified by restriction endonuclease analysis and sequencing.

RESULTS

The "pEGFP-C1-pU6-dsRNA" recombinant lied in the predicted band, and the sequence of insert was identical to the designed target fragment.

CONCLUSION

The "pEGFP-C1-pU6-dsRNA" recombinant was successfully cloned for human DNA polymerase beta RNA interference, it was an important research tool for the further study.

[Study on the adaptive reaction of low dose hydroquinone inducement in human embryo lung fibroblasts cells]

OBJECTIVE

To study the adaptive reaction and its possible mechanisms in eukaryotic cells, the oxidize of adaptive mode was established by studying the dose-effect relation of inducing the adaptive reaction.

METHODS

Human embryo lung fibroblasts (HLF) were attacked 1 hour by 80.0 micromol/L concentration respectively after using a different concentration HQ to pretreat the 12 hours. The adaptive reaction of a low concentration HQ inducement was observed by combining the micronucleus test, the comet test and the cell cycle change.

RESULTS

The results showed that, in cellular viability, HLF induced by pretreated with HQ at 0.001 micromol/L and 0.0 micromol/L appeared to be tolerated when retreated by the following 80.0 micromol/L concentration of HQ. Compared with control respectively, the micronucleus rate and abnormal nuclei rate increased obviously by pretreatment with HQ concentration from 0.5 micromol/L to 80 micromol/L in HLF. Phenomena of cells with tails appeared, tail length and percentage of cells with tails increased significantly in HLF (P < 0.01). From 0.1 micromol/L pretreatment dose on, proportion of DNA lesion cells belonged to three and four grade increase gradually by the dose increasing. G2 phase arrest and cell numbers decreasing in G1. When compared with only high dose attack respectively, micronucleus rate, abnormal nuclei rate, tail length, percentage of cells with tails decreased significantly. proportion of severely damaged cells descended markedly by pretreatment with HQ from 0 micromol/L from 0.1 micromol/L in HLF (P < 0.05). It showed that there was a dose-related increase in the rate of micronucleus or abnormal nuclei, tail length and in percentage of cells with tails after pretreatment with HQ from 0 micromol/L to 80 micromol/L in HLF (P < 0.05).

CONCLUSION

HLF induced by pretreated with HQ at low concentration appeared to adaptive reaction when retreated by high concentration of HQ.

[Research on differential display genes of tolerant-damage induced by trichloroethylene]

OBJECTIVE

To observe the differentially expressed genes of the human normal liver cell (L-02) induced by low concentration of trichloroethylene (TCE).

METHODS

The dose-effect relation of TCE toxicity was analyzed by means of MTT. 5 micromol/L was chosen as low concentration while 40 micromol/L as high concentration. Then L-02 were treated with low concentration, high concentration, pretreated with low concentration then attacked with high concentration of TCE respectively. Fluorescence differential display polymerase chain reaction (Fluoro DD-PCR) was used to search differentially expressed genes of the different treatment groups of TCE. Results 51 differential expressed strap were found, 11 differential straps have been cloned and sequenced. 9 of them were known gene, while 2 of them were new genes.

CONCLUSION

The differential straps would be identified to provide scientific base for research deeply the mechanism of low concentration TCE inducing adaptive response of L-02.

[Modified molecular beacon-based dual real-time PCR for detection of SARS virus and its application]

OBJECTIVE

To develop the modified molecular beacon-based dual fluorescent PCR assays for detection of SARS virus. The assay was applied to the early clinic diagnosis & animal tracking.

METHODS

On the basis of the obtained core sequence of open reading frame 1b of the coronavirus polymerase gene sequences, which was published in GenBank, using modified molecular beacon probe, artifical virus techinique and two different fragments amplification with different fluoresce, one set of primers and probe were designed. Then fluorescent PCR assays for specific and sensitive detection of the SARS virus was established, while the ELISA & the traditional method were used as control. 368 clinical specimens such as the throat swab, serum, feces, and urine from different cases, 52 cell cultures and 50 animal specimens were detected by the molecular beacon-based PCR.

RESULTS

The sensitivity of real -time PCR was 10 - 100 copies/ml, there was no cross reaction to other respiratory viruses such as influenza virus etc. Of 368 specimens, 20 were positive by using molecular beacon-based fluorescence PCR. The positive rate of SARS case (10/47) were 21.27%, the positive rate of the throat swab of SARS cases (10/23) were 43.87% . Among 52 SARS cell cultures, 29 were positive. The positive rate of SARS cell cultures was 55.77% . Of 50 animal specimens, 23 were positive. The positive rate was 46%. Furthermore, SARS virus RNA was detected in feces and in serum during the acute phase.

CONCLUSION

The molecular beacon-based PCR is sensitive and specific, it could be applied to the early diagnosis and animal tracking. This molecular beacon-based PCR kit is useful for the different units.

[Adaptive response induced by low concentration of hydroquinone in human embryonic fibroblasts cells]

OBJECTIVE

To study the adaptive response induced by hydroquinone(HQ) on eukaryocyte and its possible mechanism.

METHODS

After hydroquinone treatment, AlamarBlue reduce rate, LDH release rate were observed to determine the cell proliferation and death. Annexin V/propidium iodide (PI) staining was performed for each treatment to distinguish viable, early, and late apoptosis or dead cells. The total cellular proteins were separated using two- dimensional gel electrophoresis and visualized by sliver staining. Digital images were analyzed using ImageMaster 2D platinum 5.0 software. The differentially expressed protein spots were picked and digested in gel then identified by tandem mass spectrum.

RESULTS

The results of AlamarBlue reduce rate, LDH leakage and Annexin V-FITC/PI staining showed that no effect on cell viability was observed at a concentration of 10 micromol/L HQ while 250 micromol/L HQ significantly decreased cell viability. Cells pretreated with 10 micromol/L HQ for 12h show increasing survival to the following expose to 250 micromol/L HQ. In control MRC-5 cells 1429 +/- 369 protein spots were detected and, 1453 +/- 307 in low HQ group, 1191 +/- 393 in high HQ group, and 1107 +/- 247 in adaptive group by two dimensional gel electrophoresis. Twenty-four protein spots showed significant change after HQ stimulation and 22 protein spots were identified by tandems mass spectra. These identified proteins involved in energy metabolism, translation and RNA processing, protein folding, redox regulation, cell structure and cell signaling.

CONCLUSION

Adaptive response can be induced by low concentration of HQ on MRC-5 cells and cellular adaptation is a complex process involving in a modulation of diverse cellular functions.

[Study on differential display genes of tolerant-damage of MRC-5 induced by formaldehyde of low dose]

OBJECTIVE

To observe the differentially expressed genes of the human embryo lung fibroblast (MRC-5) induced by formaldehyde (FA) of low dose using fluoro DD-PCR.

METHODS

The dose-effect relation of FA toxicity to MRC-5 was acquired, No observed damage effect or proliferation concentration was used as low dose, and obvious damage concentration was used as high dose. MRC-5 was treated with low and high dose, and treated with high dose after pretreated with low dose for some time. Then Fluoro differential display polymerase chain reaction (Fluoro DD-PCR) was used to search differentially expressed genes of the differently treated groups of FA. 61 differential display straps were acquired and 11 of them were reamplified, cloned, sequenced and blasted.

RESULTS

According to the dose-effect relation of FA toxicity to MRC-5, 100 micromol/L was choosed as low dose and 10 mmol/L was choosed as high dose. Samples of differently treated groups were amplified by means of fluro-DD-PCR, 61 differentially expressed straps were acquired. 11 differential display straps have been cloned, sequenced and blasted. Two of them were known genes: one was highly homologous to nuclear factor of activated T-cells 5 (NFAT5) and the other was highly homologous to tetratricopeptide repeat domain 3(TPRD-3). Nine of them were new genes.

CONCLUSION

It seemed that FA of low dose could promote MRC-5 proliferation and find 61 differentially expressed genes of differently treated groups, and the result of clone could provide scientific base for mechanism of FA toxicity research.

[Genetic polymorphisms of nucleotide repair gene hMTH1 in southern Chinese Han population]

In order to study the genetic polymorphisms of nucleotide repair gene hMTH1 in southern Chinese Han population, the polymorphisms of the gene's promoter and its five exons among peripheral blood lymphocytes of 172 Chinese Han people were analyzed with polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing. The sequences of the promoter and exon 1 of hMTH1 gene were conserved. A T to C polymorphism was detected at the 73th base in exon 2. The genotype frequencies of TT and TC were 93.02% and 6.98%, respectively. The allelic frequencies of T and C were 96.51% and 3.49%, respectively. A T to C polymorphism was detected at codon 45 in exon 3, which was first reported. The genotype frequencies of TT and TC were 95.35% and 4.65%, respectively. The allelic frequencies of T and C were 97.67% and 2.33%, respectively. A G to A polymorphism was detected at codon 83 in exon 4. The genotype frequencies of GG and GA were 89.53% and 10.47%, respectively. The allelic frequencies of G and A were 94.77% and 5.23%, respectively. A C to T polymorphism was detected at codon 119 in exon 5. The genotype frequencies of CC and CT were 95.93% and 4.07%, respectively. The allelic frequencies of C and T were 97.97% and 2.03%, respectively.

Biological monitoring of kidney function among workers occupationally exposed to trichloroethylene

AIMS

To investigate the nephrotoxic potential of trichloroethylene in a currently exposed population using sensitive urinary markers of kidney toxicity.

METHODS

Renal dysfunction was monitored in a cross-sectional study of 70 workers currently exposed to trichloroethylene. An age and sex matched control population of 54 individuals was drawn from hospital and administrative staff.

RESULTS

The mean exposure to trichloroethylene, estimated from urinary trichloroacetic acid concentrations, was 32 ppm (range 0.5-252 ppm) with an average duration of exposure of 4.1 years (range 1-20 years). Significant differences between the exposed and control populations were found for nephrotoxicity markers N-acetylglucosaminidase (NAG) and albumin, and for the mode of action marker, formic acid. However, neither NAG nor albumin showed a significant correlation with either the magnitude or duration of exposure to trichloroethylene. There was a significant correlation between urinary formic acid and trichloroacetic acid concentrations. Within the exposed population there were dose dependent increases in urinary methylmalonic acid concentrations and urinary glutathione S-transferase alpha activity. Although still within the control range, these changes were clearly dose dependent and consistent with one of the proposed mechanisms of trichloroethylene induced kidney toxicity.

CONCLUSION

Although there was no evidence of kidney toxicity within the population studied, the results suggest that kidney damage could occur at exposure concentrations higher (>250 ppm) than those encountered in this study.

Isolation and characterization of viruses related to the SARS coronavirus from animals in southern China

A novel coronavirus (SCoV) is the etiological agent of severe acute respiratory syndrome (SARS). SCoV-like viruses were isolated from Himalayan palm civets found in a live-animal market in Guangdong, China. Evidence of virus infection was also detected in other animals (including a raccoon dog, Nyctereutes procyonoides) and in humans working at the same market. All the animal isolates retain a 29-nucleotide sequence that is not found in most human isolates. The detection of SCoV-like viruses in small, live wild mammals in a retail market indicates a route of interspecies transmission, although the natural reservoir is not known.

Chromium (VI)-induced production of reactive oxygen species, change of plasma membrane potential and dissipation of mitochondria membrane potential in Chinese hamster lung cell cultures

OBJECTIVE

To examine whether Reactive Oxygen Species (ROS) is generated, and whether plasma membrane potential and mitochondrial membrane potential are depolarized in Chinese Hamster Lung (CHL) cell lines exposed to Cr (VI).

METHODS

CHL cells were incubated with Cr(VI) at 10 mumol/L, 2.5 mumol/L, 0.65 mumol/L for 3 and 6 hours, respectively. The production of ROS was performed by using 2,7-dichlorofluorescin diacetate; The changes in plasma membrane potential were estimated using fluorescent cationic dye DiBAC4; And the changes in mitochondria membrane potential were estimated using fluorescent dye Rhodamine 123.

RESULTS

The ROS levels in CHL cells increased in all treated groups compared with the control group (P < 0.01); The plasma membrane potential and mitochondrial membrane potential in CHL cells dissipated after incubated with Cr(VI) at 10 mumol/L for 3 hours and 6 hours (P < 0.01), at 2.5 mumol/L for 6 hours (P < 0.01 or 0.05).

CONCLUSION

Cr(VI) causes the dissipation of plasma membrane potential and mitochondrial membrane potential in CHL cell cultures, and Cr(VI)-induced ROS may play a role in the injuries.

Cadmium-induced oxidative cellular damage in human fetal lung fibroblasts (MRC-5 cells)

Epidemiological evidence suggests that cadmium (Cd) exposure causes pulmonary damage such as emphysema and lung cancer. However, relatively little is known about the mechanisms involved in Cd pulmonary toxicity. In the present study, the effects of Cd exposure on human fetal lung fibroblasts (MRC-5 cells) were evaluated by determination of lipid peroxidation, intra-cellular production of reactive oxygen species (ROS), and changes of mitochondrial membrane potential. A time- and dose-dependent increase of both lactate dehydrogenase leakage and malondialdehyde formation was observed in Cd-treated cells. A close correlation between these two events suggests that lipid peroxidation may be one of the main pathways causing its cytotoxicity. It was also noted that Cd-induced cell injury and lipid peroxidation were inhibited by catalase and superoxide dismutase, two antioxidant enzymes. By using the fluorescent probe 2',7'-dichlorofluorescin diacetate, a significant increase of ROS production in Cd-treated MRC-5 cells was detected. The inhibition of dichlorofluorescein fluorescence by catalase, not superoxide dismutase, suggests that hydrogen peroxide is the main ROS involved. Moreover, the significant dose-dependent changes of mitochondrial membrane potential in Cd-treated MRC-5 cells, demonstrated by increased fluorescence of rhodamine 123 examined using a laser-scanning confocal microscope, also indicate the involvement of mitochondrial damage in Cd cytotoxicity. These findings provide in vitro evidence that Cd causes oxidative cellular damage in human fetal lung fibroblasts, which may be closely associated with the pulmonary toxicity of Cd.

DNA strand breaks and poly (ADP-ribose) polymerase activation induced by crystalline nickel subsulfide in MRC-5 lung fibroblast cells

Nickel compounds are potent carcinogens. Their carcinogenicity is believed to be associated with their solubility and cellular uptake. In the present study, we assessed the in vitro genotoxic effect of a water-insoluble nickel compound, crystalline nickel subsulfide (alpha-Ni3S2) on human embryo lung fibroblast cell line (MRC-5 cells). DNA strand breaks was evaluated using single cell gel electrophoresis, or comet assay. The alpha-Ni3S2 induction of poly (ADP-ribose) polymerase (PADPRP), a nuclear enzyme associated with DNA damage and repair was also studied. Hydrogen peroxide (H2O2) was used as a reference compound. A dose-response relationship was found between alpha-Ni2S2 concentrations (2.5 micrograms/cm2 to 20 micrograms/cm2) and the comet tail length. The increase of PADPRP activity of alpha-Ni2S2 treated MRC-5 cells was also significant and dose-dependent within the concentration range of 2.5 micrograms/ cm2 to 10 micrograms/cm2. Close associations have been found between the comet length and PADPRP level for H2O2 (r = 0.98) and alpha-Ni3S2 (r = 0.97). These results clearly suggest that alpha-Ni3S2 is a potent agent in inducing DNA strand breaks, which may be closely related to its carcinogenic effects. Data from the present study also suggest that both comet assay and PADPRP determination are sensitive techniques for quantitative evaluation of DNA damage induced by nickel compounds.

Study on DNA-protein crosslinks induced by chromate and nickel compounds in vivo with 125I-postlabelling assay

In an attempt to develop biomarkers of chromate and nickel exposure, we have used a rapid, simple and sensitive 125I-postlabelling assay to detect the formation of DNA-protein crosslinks (DPCs) in different tissues from male Sprague-Dawley rats exposed i.p. to potassium chromate (K2CrO4) and nickel chloride (NiCl2). The results demonstrated that 20 h after rats were injected i.p. with these agents, DPCs were observed in WBC, liver and kidney of rats treated with K2CrO4 in doses ranging from 10 to 40 mg/kg body wt. There was a dose-dependent relationship between chromate exposure and DPCs in WBC and liver, but no DPC increase was shown in lung. In the same way, DPCs were found in WBC and lung of rats treated with NiCl2 in doses ranging from 10 to 30 mg/kg in a dose-dependent manner. The formation of DPCs in different tissues was also observed following repeated exposure of rats to K2CrO4 and NiCl2 (10 mg/kg, i.p.) for 3 weeks. These results were similar with the single dose. It is indicated that chromate and nickel compounds possibly cause DNA or protein damage to form DPCs, suggesting DPCs might be useful as a biomarker for quantitative K2CrO4 and NiCl2 exposure and genotoxic lesions. In addition, WBC were shown to be more sensitive to chromate(VI) and nickel(II) induced DPCs than other targets. There were significant correlations between DPCs induced by K2CrO4 in WBC and liver, and by NiCl2 generated DPCs in WBC and lung, indicating that DPCs in WBC may be a good surrogate for some internal organs of humans exposed to chromate(VI) and nickel(II) compounds.