Association between Single-Nucleotide Polymorphisms of the hOGG1,NEIL1,APEX1, FEN1,LIG1, and LIG3 Genes and Alzheimer's Disease Risk.

BACKGROUND: One of the factors that contribute to Alzheimer's disease (AD) is the DNA damage caused by oxidative stress and inflammation that occurs in nerve cells. It has been suggested that the risk of AD may be associated with an age-dependent reduction of the DNA repair efficiency. Base excision repair (BER) is, among other things, a main repair system of oxidative DNA damage. One of the reasons for the reduced efficiency of this system may be single-nucleotide polymorphisms (SNP) of the genes encoding its proteins. METHODS: DNA for genotyping was obtained from the peripheral blood of 281 patients and 150 controls. In the present study, we evaluated the impact of 8 polymorphisms of 6 BER genes on the AD risk. We analyzed the following SNP: c.-468T>G and c.444T>G of APEX1, c.*50C>T and c.*83A>C of LIG3, c.977C>G of OGG1, c.*283C>G of NEIL1, c.-441G>A of FEN1, and c.-7C>T of LIG1. RESULTS: We showed that the LIG1 c.-7C>T A/A and LIG3 c.*83A>C A/C variants increased, while the APEX1 c.444T>G G/T, LIG1 c.-7C>T G/, LIG3 c.*83A>C C/C variants reduced, the AD risk. We also evaluated the relation between gene-gene interactions and the AD risk. We showed that combinations of certain BER gene variants such as c.977C>G×c.*50C>T CC/CT, c.444T>G×c.*50C>T GG/CT, c.-468T>G×c.*50C>T GG/CT, c.-441G>Ac.*50C>T×c.*50C>T GG/CT, c.*83A>C× c.*50C>T CT/AC, and c.-7C>T×c.*50C>T CT/GG can substantially positively modulate the risk of AD. CONCLUSIONS: In conclusion, we revealed that polymorphisms of BER genes may have a significant effect on the AD risk, and the presence of polymorphic variants may be an important marker for AD.

Genotoxicity and cytotoxicity of ZnO and Al2O3 nanoparticles.

OBJECTIVES: Metal oxide nanoparticles (ZnO-NPs and Al2O3-NPs) are used in many fields, including consumer products and biomedical applications. As a result, exposure to these NPs is highly frequent, however, no conclusive information on their potential cytotoxicity and genotoxicity mechanisms are available. For this reason, we studied cytotoxic and genotoxic effects of ZnO-NPs and Al2O3-NPs on human peripheral blood lymphocytes. MATERIALS AND METHODS: We obtained our goals by using MTT assay, Annexin V-FITC flow cytometry, and alkaline, neural and pH 12.1 versions of comet assay. RESULTS: Exposure of lymphocytes to both NPs for 24 h slightly decreased viability of lymphocytes at ≥ 0.5 mM. For the first time, we revealed using the comet assays that both ZnO-NPs and Al2O3-NPs caused a concentration-dependent increase of DNA single-strand breaks, but not alkali-labile sites. Treatment with DNA glycosylases showed that the NPs induced oxidative DNA damage. DNA damage caused by both nanoparticles at 0.05 mM was removed within 120 min, however lymphocytes did not repair DNA damage induced by 0.5 mM NPs. Studied nanoparticles did not induce apoptosis in lymphocytes. CONCLUSION: Our results suggest that ZnO-NPs and Al2O3-NPs at concentration up to 0.5 mM did not exhibit cytotoxic effect but may exert genotoxic effect on lymphocytes, at least partially by the generation of oxidative DNA damage and strand breaks.

Decreased expression level of BER genes in Alzheimer's disease patients is not derivative of their DNA methylation status.

BACKGROUND: Neurodegeneration in Alzheimer's disease can be caused by accumulation of oxidative DNA damage resulting from altered expression of genes involved in the base excision repair system (BER). Promoter methylation can affect the profile of BER genes expression. Decreased expression of BER genes was observed in the brains of AD patients. AIM OF THE STUDY: The aim of our study was to compare the expression and methylation profiles of six genes coding for proteins involved in BER, namely: hOGG1, APE1, MUTYH, NEIL1, PARP1 and XRCC1, in the peripheral blood cells of AD patients and healthy volunteers. METHODS: The study consisted of 100 persons diagnosed with Alzheimer's disease according to DSM-IV criteria, and 110 healthy volunteers. DNA and total RNA were isolated from venous blood cells. Promoter methylation profiles were obtained by High Resolution Melting (HRM) analysis of bisulfide converted DNA samples. Real-time PCR with TaqMan probes was employed for gene expression analysis. RESULTS: APE1, hOGG1, MUTYH, PARP1 and NEIL1 were significantly (p<0.001) down-regulated in the lymphocytes of AD patients, as compared to healthy volunteers. Expression of XRCC1 didn't differ significantly between both groups. We did not find any differences in the methylation pattern of any of the investigated BER genes. CONCLUSIONS: The methylation status of promoters is not associated with downregulation of BER genes. Our results show that downregulation of BER genes detected in peripheral blood samples could reflect the changes occurring in the brain of patients with AD, and may be a useful biomarker of this disease.

Apoptosis of lymphocytes and sialic acid plasma level in patients undergoing cardiac surgery.

Increasing evidence shows that extensive tissue trauma and surgical stress are related to physical alterations of cells and cell death. It was previously reported that total sialic acid (SA) plasma concentration is elevated in patients undergoing coronary artery surgery. Shedding or secreting of SA from the cell membrane surface or releasing intracellular SA may induce apoptosis. It is possible that the terminal SA residues of carbohydrate moieties facilitate recognition and removal of apoptotic cells by phagocytes. The aim of the present study was to estimate the dynamic changes in rate ofapoptosis oflymphocytes and total sialic acid plasma level during coronary artery surgery. In 17 patients undergoing coronary artery bypass grafting surgery plasma total SA concentration was measured and the percentage of apoptotic lymphocytes was determined before operation, after aorta clumping, after the end of operation and at 6, 18, 30 and 48 h after operation. Plasma total SA concentration decreases after aortic clumping and then increases gradually during a 48 hr observation period. The percentage of apoptotic cells increases during and after surgery with the exception of a sample taken at 18 hours after operation. The findings indicate the bimodal character of apoptosis and dynamic increase in total SA plasma level, which may be considered a result of mechanical damage taken place during operation or inflammatory response to surgical trauma.