methylnitronitrosoguanidine and Alzheimer-Disease

We have shown that fibroblasts, lymphocytes and lymphoblasts from patients with Alzheimer's disease (AD) are deficient in the repair of DNA damage induced by the alkylating agents methylmethane sulfonate (MMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Unscheduled DNA synthesis and alkaline elution studies of DNA repair using human skin fibroblasts obtained from patients coming to autopsy have shown that the cells from autopsy confirmed cases of AD have lower levels of DNA repair synthesis after exposure to varying concentrations of either MMS or MNNG. Lymphoblasts derived from individuals with dominantly inherited AD have also been used to study DNA repair. Alkaline elution analysis of DNA repair after exposure to 200 uM MMS or 6 uM MNNG indicates that there is significantly less repair in the lymphoblasts from AD patients. When healthy control cell lines repaired and cell lines from AD patients were exposed to MMS or MNNG respectively significantly less repair occurred in the AD cells. After studying five at risk individuals results indicate that cell lines from two of these people have low levels of DNA repair and three lines have normal repair. These findings support the hypothesis of a DNA repair deficiency in familial AD. Monocytes from healthy control subjects and putative AD patients were analyzed for mutant frequency and DNA repair capacity. Results of unscheduled DNA synthesis experiments using monocytes from 7 healthy controls and 9 presumed AD patients indicates that there is a decreased ability of AD cells to repair MMS and MNNG induced DNA damage.

Topics: Alkylating Agents; Alzheimer Disease; DNA Damage; DNA Repair; Fibroblasts; Humans; Methyl Methanesulfonate; Methylnitronitrosoguanidine; Skin

Alterations in the capacity of a cell to repair DNA lesions play an important role in a number of human diseases. We and others have demonstrated defective DNA repair of alkylation damage in cells from patients with Alzheimer's disease. It has been hypothesized that this defect is related to the cause of Alzheimer's disease and results in the accumulation of lesions in the central nervous system neurons. One prediction of this hypothesis is that in dominantly inherited Alzheimer's disease, the repair defect will be present in half of the offspring of affected patients long before they develop symptoms of the disease. In order to test the hypothesis that decreased DNA repair is responsible for familial Alzheimer's disease and their at-risk offspring we have studied DNA repair in these individuals after exposure of lymphoblasts to alkylating agents. Our results indicate that cell lines from affected patients repair significantly less damage in 3 h than cell lines from healthy controls. A small number of at-risk individuals were also studied and some of these had lower levels of repair, although more cell lines from individuals in this group must be studied. These findings provide further support for defective DNA repair playing a role in the pathogenesis of Alzheimer's disease.

Topics: Adult; Aged; Alzheimer Disease; Cell Line, Transformed; Cell Transformation, Viral; DNA; DNA Repair; Female; Humans; Male; Methyl Methanesulfonate; Methylnitronitrosoguanidine; Middle Aged

Cultured fibroblast strains from two normal persons and from two patients with the neurodegeneration of Alzheimer's disease were exposed to the alkylating chemical N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Immediately after exposure and also after a 24-h repair incubation period the single-strand breaks in the cells' DNA were quantified by the alkaline elution technique. In contrast to a report by others using alkaline elution, MNNG, and these same strains, we found no evidence of deficient repair of MNNG-induced DNA damage in the Alzheimer's disease cells. The putative DNA repair defect in Alzheimer's disease should be investigated by methods other than the alkaline elution technique which measures only a small fraction of the damage induced by an alkylating chemical such as MNNG.

Topics: Alzheimer Disease; DNA; DNA Damage; DNA Repair; Fibroblasts; Humans; Methylnitronitrosoguanidine

DNA strand breaks, resulting from treatment with N-methyl-N'-nitro-N-nitrosoguanidine, were repaired more slowly in four strains of familial Alzheimer's disease fibroblasts than in five strains of fibroblasts from age-matched normals. These results were not due to differences between the two cell types in in vitro ages, in the initial DNA damage or in drug-induced cell lysis. Bleomycin-induced DNA double-strand breaks were repaired equally efficiently by both types of cells. Alzheimer's disease cells may have a DNA repair defect, which may be involved in the pathogenesis of this disease.

Topics: Aged; Alzheimer Disease; Bleomycin; Cell Survival; DNA Repair; Fibroblasts; Humans; Methylnitronitrosoguanidine; Middle Aged; Time Factors

Lymphocytes from passive smokers, and patients with FA, Alz, or FPC were studied for SCEs in cultures treated with MMC, 4NQO, or MNNG. Fanconi anemia lymphocytes were also studied for cell cycle Tab. 3. Mean SCE frequencies in FPC or normal cells. (Table; see text) kinetics, and CAs after completion of 1, 2, or 3 or more divisions in MMC-treated cultures. The results can be summarized as follows: (1) lymphocytes from passive smokers showed a slightly higher induction of SCEs than nonsmokers when exposed to MMC. (2) FA cells had about 1.4 times higher frequencies of SCEs than normal cells in both MMC-treated and untreated cultures while they showed several times higher frequencies of CAs in both cultures. Analyses of cell cycle kinetics by the sister chromatid differential staining method revealed that MMC treatments of FA and normal cells led to a clearly dose-related delay in cell turnover times, the duration of delay being much longer in FA than in normal cells. (3) Alz cells showed about 1.5 times higher induction of SCEs in MMC-treated cultures whereas they had only 10% as much SCEs as controls when exposed to 4NQO. Familial polyposis coli cells showed no significant difference in the induction of SCEs in untreated cultures and cultures treated with MMC, 4NQO, and MNNG.

Topics: 4-Nitroquinoline-1-oxide; Adolescent; Adult; Alzheimer Disease; Anemia, Aplastic; Cell Cycle; Cells, Cultured; Child; Colonic Polyps; Fanconi Anemia; Female; Gardner Syndrome; Humans; Lymphocytes; Male; Methylnitronitrosoguanidine; Middle Aged; Mitomycin; Mitomycins; Sister Chromatid Exchange; Tobacco Smoke Pollution