Biomedical subjects

Herbert Iijima

Publications and source records attributed to Herbert Iijima.

5 recordsLinked to original sources

PubMed2006

Singlet oxygen-induced DNA damage.

Singlet oxygen, hydrogen peroxide, hydroxyl radical and hydrogen peroxide are the reactive oxygen species (ROS) considered most responsible for producing oxidative stress in cells and organisms. Singlet oxygen interacts preferentially with guanine to produce 8-oxo-7,8-dihydroguanine and spiroiminodihydantoin. DNA damage due to the latter lesion has not been detected directly in the DNA of cells exposed to singlet oxygen. In this study, the singlet oxygen-induced lesion was isolated from a short synthetic oligomer after exposure to UVA radiation in the presence of methylene blue. The lesion could be enzymatically excised from the oligomer in the form of a modified dinucleoside monophosphate. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), the singlet oxygen lesion was detected in the form of modified dinucleoside monophosphates in double-stranded DNA and in the DNA of HeLa cells exposed to singlet oxygen. Pentamer containing the singlet oxygen-induced lesion and an isotopic label was synthesized as an internal standard for quantifying the lesion and served as well as for correcting for losses of product during sample preparation.

Animals↗

PubMed2006

A novel approach to DNA damage assessments: measurement of the thymine glycol lesion.

A different approach to the measurement of DNA damage has been developed based on the fact that many lesions can be excised from DNA in the form of modified dinucleoside monophosphates. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used in conjunction with isotopically labeled internal standards to quantify the lesion. The method has several advantages, including high sensitivity for the detection of dinucleoside monophosphates. The method was applied to the measurement of the 5,6-dihydroxy-5,6-dihydrothymine (thymine glycol) lesion in the DNA of mouse fibroblast cells exposed in culture to various treatments including ionizing radiation, UVC light and buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis. The application of the method to the measurement of other DNA lesions is discussed.

Animals↗

PubMed2004

Measurement of DNA adducts in cells exposed to cisplatin.

The two main cisplatin-induced DNA lesions, G--G and A--G, have been measured in cells exposed to the drug. (G--G and A--G denote the intrastrand bifunctional adducts formed between adjacent purine bases.) It has proven feasible, using liquid chromatography-tandem mass spectrometry (LC-MS/MS), observe the G--G and A--G lesions in mouse fibroblast cells exposed for 1 h to a 120 microM concentration of cisplatin. After extraction of the DNA from the cells, the lesions were enzymatically isolated from the DNA in the form of modified dinucleoside monophosphates with the phosphodiester bond intact. MS/MS detection of the modified dinucleoside monophosphates in the negative ion mode manifests two transitions; from the negative ion to the loss of one NH(3) group and from the ion less one NH(3) group to the loss of both NH(3) groups. The multiple reaction monitoring capability of LC-MS/MS was used to measure the three most abundant isotopes of the two main lesions for both transitions of each lesion (i.e., 12 MS/MS values in toto). Ion currents could be detected for all 12 pairs of MS/MS values in the DNA from exposed cells. Although this protocol results in some overlap of MS/MS values between the two lesions, a slight difference in elution times clearly distinguishes between them.

Animals↗

PubMed2003

DNA damage measured by liquid chromatography-mass spectrometry in mouse fibroblast cells exposed to oxidative stress.

Oxidative DNA damage can result from environmental factors, such as radiation, as well as from the untoward consequences of normal metabolic processes. It is of interest to assay oxidative DNA damage in cells and tissues because this damage has been implicated in human disease, particularly cancer. Eleven indicators of oxidative DNA damage have been measured by Liquid Chromatography-Mass Spectrometry (LC-MS) in DNA extracted from cells exposed to oxidative stress. Mouse fibroblast cells were exposed to hydrogen peroxide and to UVC light and to the combined action of both agents. Significant increases of the 8-oxo-7,8-dihydropurine lesions over background were detected. Significant increases of the formamido lesions resulting from breakdown of pyrimidine bases were also observed. Of special interest was the observation of double lesions, tandem combinations of both aforementioned lesions, in cells exposed to oxidative stress.

Animals↗

PubMed2002

Detection and characterization of formamido lesions in DNA by liquid chromatography-mass spectrometry.

DNA X-irradiated in oxygenated aqueous solution produces the formamido lesion from the breakdown of pyrimidine nucleosides. This pyrimidine breakdown product inhibits the hydrolysis by nuclease P1 of the phosphoester bond 3' to the damaged nucleoside. Consequently, the lesion can be obtained from an enzymatic digest of the DNA as a modified dinucleoside monophosphate in which the 5' nucleoside contains the lesion. In this form, the formamido lesion can be detected with good sensitivity by liquid chromatography-mass spectrometry (LC-MS). Nucleosides that have lost the base moiety also inhibit nuclease P1. Together, the formamido and abasic lesions account for all of the substantial peaks in the LC-MS ion current profile.

Chromatography, High Pressure Liquid↗