Effects of Explicit and Implicit Solvent Models on the Hydrolysis Cleavage of N-Glycosidic Bond in 8-Oxo-7,8-dihydro-2'-deoxyguanosine

8-Oxoguanine （8-oxoG）, a critical mutagenic DNA lesion induced by reactive oxy- gen species, gives rise to a G·C→T·A transversion during replication and thereby must be repaired. The effects of explicit and implicit solvent molecules on the hydrolysis cleavage of N-Glycosidic bond in 8-oxo-7,8-dihydro-2＇-deoxyguanosine （8-oxo-dG） have been systematically clarified in the present work based upon two types of computational models. Detailed potential energy surface （PES） scans and full unconstraint optimizations for all the representative points on PESs were carried out at the B3LYP/6-31＋G（d） level of theory. The effect of implicit solvent was tested by single-point calculation at the SCRF/IEF-PCM model. The results illustrate that the direct hydrolysis model involving one explicit water molecule can’t provide a complete depiction of the hydrolysis process of 8-oxo-dG, attributed to the insufficiency of nucleophile activation and leaving group stabilization. The expansion hydrolysis model involving four explicit water molecules, however, facilitates discrete proton transfer and therefore produces smooth reaction surfaces for both the dissociative （SN1） and concerted （SN2） pathways. The presence of the implicit solvent substantially lowers all activation energies and the SN1 process is more favorable than the SN2 process. The data and insights present here agree well with the experimental results and have given out a baseline for the enzymatic deglycosylation reaction of 8-oxo-dG.

Determination of urinary 8-hydroxy-2′-deoxyguanosine by capillary electrophoresis with molecularly imprinted monolith in-tube solid phase microextraction

Urinary 8-hydroxy-2 -deoxyguanosine(8-OHdG) is an excellent marker of oxidative DNA damage.In this study,employing guanosine as dummy template a novel molecularly imprinted(MIP) monolithic capillary column had been synthesized,and that was used as medium of in-tube solid phase microextraction(SPME).Coupled with capillary electrophoresis-electrochemical detection(CE-ECD),the system of extraction and detection of 8-OHdG in urinary sample had been developed.Because of its greater phase ratio combined with conv...

Expression of 8-hydroxy-2'-deoxyguanosine in gastric carcinomas

Reactive oxygen species may be involved in the progression of gastric carcinomas. To clarify whether the pathology of gastric carcinoma are related to oxidative DNA damage, the expression of 8-hydroxy-2＇-deoxyguanosine （8-OHdG） was examined in 30 patients with gastric carcinomas. Methods： The expression of 8-OHdG and apoptosis in the gastric carcinoma were measured using the methods of immunocytochemistry and deoxynucleartididyl transferase-mediated dUTP-biotin nick end labeling （TUNEL）, respectively. Results： Of the 30 cases, 25（83%） showed stronger immunoreactivity than normal control. The patients with poorly differentiated gastric carcinoma had a larger tumor size and higher labeling indices of TUNEL- and 8-OHdG-positive cells than those with well and moderately differentiated gastric carcinoma. Conclusion： Our findings suggest that oxidative DNA damage is increased in association with necroinflammation in chronic gastric injuries and determination of 8-OHdG is useful in assessing high-grade malignancy in gastric carcinomas.

Synthesis,Crystal Structure and Cytotoxic Activities of 1-(Prop-2-yn-1-yl)-7,8-dihydro-1H-benzo[d][1,3]-thiazine-2,5(4H,6H)-dione Derivatives

The important synthetic precursor（Ⅲ）, 1-（prop-2-yn-1-yl）-7,8-dihydro-1Hbenzo[d][1,3]thiazine-2,5（4H,6H）-dione（C（11）H（11）NO2S）, was prepared through a three-component reaction, which was further transferred into cytotoxic triazoles by alkylation and ＂click＂ synthesis in satisfactory yields of 87%^95%. Their structures were characterized by IR, H-RESI-MS and NMR analysis. Meanwhile, the crystal of Ⅲ was obtained and determined by X-ray single-crystal diffraction. Crystal data： orthorhombic system, space group P212121, a = 5.189（4）, b = 8.661（6）, c = 23.498（17） A, V = 1056.2（13） A^3, Z = 4, F（000） = 464, Dc = 1.392 g/cm^3, μ =0.284 mm^-1, R = 0.0637 and wR = 0.1668 for 8182 independent reflections（R（int） = 0.1580） and 2166 observed ones（I 〉 2σ（I））.

Studies on the esterifications of 9-(hydroxyimino)-4-methyl-8,9-dihydrofuro[2,3-h]chromen-2-one with acid chlorides under different conditions

The esterifications of 9-（hydroxyimino）-4-methyl-8,9-dihydrofuro[2,3-h]chromen-2-one （4） with acid chlorides afforded normal oxime-esters 3a-e in 35-78% yields in presence of excessive 4-dimethylaminopyridine as the acid scavenger, whereas the reactions gave unexpected 8-substituted products N-（8-chloro-4-methyl-2-oxo-2H-furo-[2,3-h]chromen-9-yl）amides （5a-c） and 4-methyl-2,9-dioxo-8,9-dihydro-2H-furo[2,3-h]chromen-8-ylcarboxyloates （6d-e） by using excessive acid chlorides. The structures of 10 new compounds were determined by 1H NMR, 13C NMR, MS and HRMS, and the possible mechanism for the formation of unexpected products 5a--c and 6d-e was also proposed.

Elevated 8-oxo-7,8-dihydro-2'-deoxyguanosine in genome of T24 bladder cancer cells induced by halobenzoquinones

Halobenzoquinones（HBQs） are an emerging class of halogenated disinfection byproducts（DBPs） in drinking water, which raised public concerns due to potential carcinogenic effects to human bladder. Our previous work demonstrated that HBQs and hydrogen peroxide（H_2O_2）together generated oxidative DNA damage via a metal-independent and intercalationenhanced oxidation mechanism in vitro. This study further investigated the efficiency of various HBQs to induce oxidative DNA damage in T24 bladder cancer cells. Compared with T24 cells without treatment（3.1 lesions per 10~6 d G）, the level of 8-oxo-7,8-dihydro-2′-deoxyguanosine（8-oxod G） significantly increased by 1.4, 3.2, 8.8, and 9.2 times after treatment with tetrabromo-1,4-benzoquinone（TBBQ）, terachloro-1,4-benzoquinone（TCBQ）,2,6-dichloro-1,4-benzoquinone（2,6-DCBQ） and 2,5-dichloro-1,4-benzoquinone（2,5-DCBQ） for24 hr, respectively. Interestingly, we found that the oxidative potency of HBQs in T24 cells（2,5-DCBQ ≈ 2,6-DCBQ 〉 TCBQ 〉 TBBQ） is inconsistent with that of in vitro ds DNA oxidation（TCBQ 〉 TBBQ 〉 2,5-DCBQ 〉 2,6-DCBQ）, suggesting HBQs induce oxidative lesions in cellular genomic DNA probably involved with a complex mechanism.

Study on the regioselective alkylation of 2-thiopyrimidine

Aim To investigate the alkylation of 2-thiopyrimidine. Methods Treating the starting material 2-thiopyrimidine with chloromethyl ethers via a procedure of K2CO3 in DMF or with alkyl halide in CH3ONa-CH3OH at room temperature, to obtain the corresponding regioselective 2-S-allkyl pyrimidines. The products were determined by JH NMR, 2D NMR, IR and MS spectra. Results 2-S-alkyl-pyrimidines were regioselectively synthesized. Conclusion In different conditions with different alkyl halides, 2- thiouracil could be converted into the corresponding 2-S-alkylpyrimidines regioselectively.

Fabrication of the DNA/poly(3-methylthiophene) composite film modified electrode and its application for the study on the voltammetric behavior and determination of 8-hydroxy-2'-deoxyguanosine

A composite film of DNA/poly(3-methylthiophene)(P3MT) modified glassy carbon electrode(GCE) has been fabricated by electro-deposition method.P3MT film was first electropolymerized at the GCE and the DNA layer was then immobilized on the P3MT layer by electrochemical method.The voltammetric behavior of 8-hydroxy-2'-deoxyguanosine(8-OH-dG) at the composite film modified electrode was studied.The effects of scan rates,pH and the interference of uric acid(UA) on the voltammetric behavior and detection of 8-OH-dG were also discussed.The experimental results suggest that the electrochemical behavior of 8-OH-dG at the composite film modified electrode was greatly improved due to the combination of the advantages of P3MT and DNA.In 0.1 M pH 7.0 phosphate buffer solution(PBS),the anodic peak currents of 8-OH-dG were linear with the 8-OH-dG concentration in two intervals,viz.0.28―4.2 μM and 4.2―19.6 μM.The detection limit of 56 nM 8-OH-dG could be estimated(S/N=3).This proposed composite film modified electrode shows excellent reproducibility and stability.It may have the potential application for the detection of 8-OH-dG in human urine.

Nitrative and oxidative DNA damage in intrahepatic cholangiocarcinoma patients in relation to tumor invasion

AIM： Nitrative and oxidative DNA damage such as 8-nitroguanine and 8-oxo-7,8-dihydro-2＇-deoxyguanosine （8-oxodG） formation has been implicated in initiation and/ or promotion of inflammation-mediated carcinogenesis. The aim of this study is to clarify whether these DNA lesions participate in the progression of intrahepatic cholangiocarcinoma. METHODS： We investigated the relation of the formation of 8-nitroguanine and 8-oxodG and the expression of hypoxia-inducible factor-1α （HIF-1α） with tumor invasion in 37 patients with intra-hepatic cholangiocarcinoma. RESULTS： Immunohistochemical analyses revealed that 8-nitroguanine and 8-oxodG formation occurred to a much greater extent in cancerous tissues than in non-cancerous tissues. HIF-1α could be detected in cancerous tissues in all patients, suggesting low oxygen tension in the tumors. HIF-1α expression was correlated with inducible niltric oxide synthase （iNOS） expression （r = 0.369 and P = 0.025） and 8-oxodG formation （r = 0.398 and P = 0.015）. Double immunofluorescence study revealed that iNOS and HIF-1α co-localized in cancerous tissues. Notably, the formation of 8-oxodG was correlated significantly with lymphatic invasion （r = 0.386 and P = 0.018）. Moreover, 8- nitroguanine and 8-oxodG in non-cancerous tissues were associated significantly with neural invasion （P = 0.042 and P = 0.026, respectively）. These results suggest that reciprocal activation between HIF-1α and iNOS mediates persistent DNA damage, which induces tumor invasiveness via mutations, resulting in poor prognosis. CONCLUSION： The formation of 8-nitroguanine and 8-oxodG plays an important role in multiple steps of genetic changes leading to tumor progression, including invasiveness.

Puerarin prevents high glucose-induced apoptosis of Schwann cells by inhibiting oxidative stress

Oxidative stress may be the unifying factor for the injury caused by hyperglycemia in diabetic peripheral neuropathy. Puerarin is the major isoflavonoid derived from Radix puerariae and has been shown to be effective in increasing superoxide dismutase activity. This study sought to investigate the neuroprotective effect of puerarin on high glucose-induced oxidative stress and Schwann cell apoptosis in vitro. Intracellular reactive oxygen radicals and mitochondrial transmembrane potential were detected by flow cytometry analysis. Apoptosis was confirmed by TUNEL and oxidative stress was monitored using an enzyme-linked immunosorbent assay for the DNA marker 8-hydroxy-2-deoxyguanosine. The expression levels of bax and bcl-2 were analyzed by quantitative real-time reverse transcriptase-PCR, while protein expression of cleaved caspase-3 and -9 were analyzed by means of western blotting. Results suggested that puerarin treatment inhibited high glucose-induced oxidative stress, mitochondrial depolarization and apoptosis in a dose-dependent manner. Furthermore, puerarin treatment downregulated Bax expression, upregulated bcl-2 expression and attenuated the activation of caspase-3 and -9. Overall, our results indicated that puerarin antagonized high glucose-induced oxidative stress and apoptosis in Schwann cells.

Indole Alkaloids from the Roots of Ervatamia hainanensis

Two new indole alkaloids, named ibogamine-18-carboxylic acid, 3, 4-didehydro-7, 8-dioxo-methyl ester 1, ibogamine-18-carboxylic acid, 16, 17-didehydro-9, 17-dihydro-9-hydroxy （2-oxopropyl）-methyl ester 2, were isolated from Ervatamia hainanensis. Their structures were elucidated on the basis of spectroscopic methods.

Influence of Therapy on Some Important Final Products of Oxidation of Lipids, Proteins and Nucleic Acids in Patients with Parkinson’s Diseases

The major clinical disturbances in Parkinson’s disease (PD) are consequence of dopamine depletion in the neostriatum, due to degeneration of dopaminergic neurons. The aim of the present study was to determine whether oxidative stress (OS) occurs during the clinical course of Parkinson’s disease and to evaluate the influence of therapy on the levels of some important final products of oxidation of lipids, proteins and nucleic acids in PD patients with drug therapy. For this purpose, we investigated the levels of malondialdehid (MDA), protein carbonyl content (PCC) and 8-hydroxy-2’-deoxyguanosine quantity (8-OHdG) in PD patients with and without drug therapy. The observed changes in MDA levels, PCC and 8-OHdG quantity in blood of untreated PD patients, suggested impaired antioxidant status and presence of oxidative stress in Parkinson disease. After treatment with Madopar, the elevation in by-products significantly progresses. Our results demonstrate that administration of Madopar causes in greater degree oxidative stress than that induced by Parkinson disease, by itself.

Fast Evaluation of Oxidative DNA Damage by Liquid Chromatography-Electrospray Tandem Mass Spectrometry Coupled With Precision-cut Rat Liver Slices

Objective To establish a fast and sensitive method for the detection of 8-hydroxy-2’-deoxyguanosine （8-OHdG） in precision-cut rat liver slices by HPLC-MS/MS and to investigate isoniazid （INH） -induced oxidative DNA damage. Methods Precision-cut liver slices （300 μm） were prepared from male rats, and incubated with INH （0.018 mol/L） for 2 h after 1 h preincubation. DNA in the slices was extracted and digested into free nucleosides at 37℃ . The samples were injected into HPLC-MS/MS after the proteins were removed. The level of oxidative DNA damage was estimated using the ratio of 8-OHdG to deoxyguanosine （dG）. Results The limit of detection of 8-OHdG was 1 ng/mL （S/N=3） and the intra-assay relative standard variation was 3.38% when one transition 284.3/168.4 was used as a quantifier and another two transitions 284.3/140.2, 306.1/190.2 as qualifiers. 8-OHdG and dG were well separated, as indicated by elution at 10.02 and 7.37 min, respectively. INH significantly increased the ratio of 8-OHdG to dG in rat liver slices （P〈0.05）. Conclusion 8-OHdG in precision-cut liver slices could be sensitively determined by HPLC-MS/MS. HPLC-MS/MS coupled with precision-cut tissue slices is a fast and reliable analytical technique to evaluate oxidative DNA damage of target tissues caused by procarcinogens and cytotoxins.

Distinct profiles of systemic biomarkers of oxidative stress in chronic human pathologies:Cardiovascular,psychiatric,neurodegenerative,rheumatic,infectious,neoplasmic and endocrinological diseases

Oxidative stress is involved in chronic and acute pathologies: cardiovascular, neurodegenerative, neoplastic, inflammatory and infectious diseases. Clinical trials focused on prevention of cardiovascular and neoplastic diseases involving antioxidant supplementation have however provided predominantly negative obserations in large-scale studies. Screening of patient cohorts to assess baseline oxidative stress on the basis of a biomarker profile is decisive but lacking. For the first time, we evaluated the level of oxidative stress, testing more than 10 established biomarkers, in a comprehensive initial survey of 617 patients displaying chronic human pathologies. Multiple diseasespecific abnormalities were identified in plasma, whole blood and/or urine. This is the case for vitamins and oligo elements, vitamin C, vitamin E, β-carotene, selenium, zinc and copper;endogenous antioxidants such as reduced and oxidised glutathione, thiols, urate, and glutathione peroxidase activity, and a biomarker of oxidative DNA damage (8-hydroxy-2’-deoxy guanosine). The distinct biomarker profiles suggest the involvment of multiple forms of oxidative insults which arein some way partially specific to each pathological condition. This finding is in favor of the determination of an integrated score to combine contributions of distinct biomarkers, in order to screen patients presenting elevated levels of oxidative stress.

IVlelatonin ameliorates the adverse effects of leptin on sperm

This study examined the effects of melatonin on leptin-induced changes in sperm parameters in adult rats. Five groups of Sprague-Dawley rats were treated with either leptin or leptin and melatonin or melatonin for 6 weeks. Leptin was given daily via the intraperitoneal route （60 μg kg-1 body weight） and melatonin was given in drinking water （10 mg kg-1 or 20 mg kg-1 body weight per day）. Upon completion, sperm count, sperm morphology, 8-hydroxy-2-deoxyguanosine, Comet assay, TUNEL assay, gene expression profiles of antioxidant enzymes, respiratory chain reaction enzymes, DNA damage, and apoptosis genes were estimated. Data were analyzed using ANOVA. Sperm count was significantly lower whereas the fraction of sperm with abnormal morphology, the level of 8-hydroxy-2-deoxyguanosine, and sperm DNA fragmentation were significantly higher in rats treated with leptin only. Micmarray analysis revealed significant upregulation of apoptosis-inducing factor, histone acetyl transferase, respiratory chain reaction enzyme, cell necrosis and DNA repair genes, and downregulation of antioxidant enzyme genes in leptin-treated rats. Real-time polymerase chain reaction showed significant decreases in glutathione peroxidase 1 expression with increases in the expression of apoptosis-inducing factor and histone acetyl transferase in leptin-treated rats. There was no change in the gene expression of caspase-3 （CASP-3）. In conclusion, the adverse effects of leptin on sperm can be prevented by concurrent melatonin administration.

Comparative study of the cytotoxicity of the nanosized and microsized tellurium powders on HeLa cells

To compare the cytotoxicity on HeLa cells induced by nanosized and microsized tellurium powders, HeLa cells were exposed to different concentrations of tellurium powders （0, 50, 100, 150 and 200 μg/mL） for 12 h. In this study, detection of a series of biomarkers, including reactive oxygen species （ROS）, glutathione （GSH）, 8-hydroxy-2＇- deoxyguanosine （8-OHdG）, in addition to DNA and protein crosslink （DPC） and MTT assay, were conducted to evaluate the cytotoxicity. It is indicated that compared with the control group, there was no significant difference in the induced cytotoxicity at concentrations lower than 50 μg/mL for both nanosized and microsized tellurium powders. While there appears a significant difference in the induced cytotoxicity for nanosized tellurium powders when the concentration is higher than 100 μg/mL as well as for microsized tellurium powders when the concentration is higher than 200 μg/mL. Moreover, it is found that the cytotoxicity induced on HeLa cells exhibits a certain dose-effect relationship with the concentration of tellurium powders. A conclusion has been reached that the toxicity on HeLa cells can be induced by both nanosized and microsized tellurium powders, and the toxicity of the nanosized tellurium powders is significantly greater than the microsized one.