Relationship between genomic damage and clinical features in dialysis patients.

Patients with end-stage renal disease display enhanced genomic damage. We investigated the presence of genomic damage in the peripheral lymphocytes by using the micronucleus (MN) test and the factors associated with the MN frequency in hemodialysis (HD) and peritoneal dialysis (PD) patients. We studied 121 dialysis patients (60 HD and 61 PD) and 129 age- and gender-matched healthy controls. The MN analysis, used as a biomarker of chromosomal/DNA damage, was performed in peripheral lymphocytes by the cytokinesis-block method. Univariate analysis showed a significantly higher MN frequency in all patients in comparison with the controls (7.6% ± 0.3% vs. 4.9% ± 0.2%, respectively, p<0.001). Significantly higher frequency of MN was observed in both HD and PD patients compared to controls (7.7% ± 0.5% vs. 4.9% ± 0.2%, p<0.001 and 7.5% ± 0.5% vs. 4.9% ± 0.2%, p<0.001, respectively). Multivariate analysis was performed, and it showed that the low-density lipoprotein level was the only independent determinant of increasing MN frequency in our patients (ß=0.16, t=2.172, p<0.05). There is no significant difference in terms of genomic damage between two dialysis modalities, which suggests that PD may not be a more reliable choice in terms of genomic damage.

DNA repair XRCC1 Arg399Gln polymorphism is associated with the risk of development of end-stage renal disease.

Patients with end-stage renal disease (ESRD) display enhanced genomic damage. DNA repair gene polymorphisms may affect DNA repair capacity and modulate susceptibility to ESRD. In this study, we aimed to determine the frequency of polymorphisms in two DNA repair enzyme genes, Xeroderma pigmentosum complementation group D (XPD) and X-ray cross-complementing group 1 (XRCC1), in patients with ESRD and to evaluate their association with ESRD development. By using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP), we genotyped four single nucleotide polymorphisms (SNPs) in XPD codons 312 and 751 and XRCC1 codons 194 and 399 in 136 dialysis patients (71 patients undergoing hemodialysis and 65 subjected to peritoneal dialysis) and 147 healthy controls. Patients having XRCC1 399 Arg/Gln (OR:1.98; 95% CI: 1.21-3.25, P = 0.007) or XRCC1-399 Gln/Gln (OR: 3.95; 95% CI: 1.45-10.76, P = 0.005) genotype had a significantly higher risk of ESRD than those with XRCC1 399 Arg/Arg genotype. We also found a significantly higher frequency of the XRCC1 399Gln allele in patients with ESRD than in controls, with OR = 2.03 (95% CI = 1.08-3.81, P = 0.03). We further investigated the potential combined effect of these DNA repair variants on the risk of ESRD development. It was found that combination of the Arg/Gln or Gln/Gln genotypes of XRCC1 Arg399Gln polymorphism with the two possible genotypes of XPD-Asp312Asn or with the Lys/Gln or Gln/Gln genotypes of XPD Lys751Gln was significantly associated with the development of ESRD. This is the first report showing an association between DNA repair gene polymorphisms and ESRD development, and suggests that XRCC1 Arg399Gln polymorphism may confer increased risk for the development of the disease. Further larger studies should be conducted to confirm these results.

Glutathione S-transferase M1, GSTT1 and GSTP1 genetic polymorphisms and the risk of age-related macular degeneration.

PURPOSE: To determine the possible effects of glutathione S-transferase (GST) M1, GSTT1 and GSTP1 genetic polymorphisms on the risk of developing age-related macular degeneration (AMD). PATIENTS AND METHODS: This case-control study included a total of 120 patients with AMD (65 with dry-type AMD and 55 with wet-type AMD) and 198 disease-free controls. GSTM1 and GSTT1 polymorphisms were analyzed by using a multiplex polymerase chain reaction (PCR), and GSTP1 polymorphism was detected by real-time PCR assay. RESULTS: GSTM1-null genotype was significantly associated with the development of AMD (p = 0.01, OR = 1.82, 95% CI = 1.14-2.91). Stratification by AMD subtypes revealed a significant relationship between GSTM1-null genotype and dry-type AMD (p = 0.02, OR = 1.98, 95% CI = 1.10-3.53). In a stepwise regression model, only GSTM1-null genotype was significantly associated with the development of AMD (p = 0.01, OR = 1.77, 95% CI = 1.11-2.81). CONCLUSIONS: Our findings suggest that genetic polymorphisms of GST may have a role in the development of AMD.

Polymorphisms of the DNA repair genes XPD and XRCC1 and the risk of age-related macular degeneration.

PURPOSE: Oxidative stress seems to be an important factor in the development of age-related macular degeneration (AMD). The role of DNA repair mechanisms has also received attention recently in AMD pathogenesis. This case-control study was conducted to determine the frequency of polymorphisms in two DNA repair enzyme genes, xeroderma pigmentosum complementation group D (XPD), codons 312 and 751, and x-ray cross-complementing group 1 (XRCC1), codons 194 and 399, in patients with AMD and in disease-free control subjects. METHODS: Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to analyze XPD Asp312Asn and Lys751Gln and XRCC1 Arg194Trp and Arg399Gln in 120 patients with AMD (65 with dry type and 55 with wet type) and in age-matched 205 disease-free control subjects. RESULTS: Genotypic and allelic distributions of the polymorphisms were detected. For the XPD polymorphism, although the allele frequencies were not different between the patients and healthy control subjects, there was a significant difference between frequencies for the XPD751 Gln/Gln genotype in AMD patients (9%) and healthy control subjects (19%; P=0.02). The XPD751 Gln/Gln genotype seemed to have a protective effect against development of AMD (odds ratio, 0.41; 95% confidence interval, 0.19-0.88). Stratification by subtype of AMD revealed that the XPD751 Gln/Gln genotype was significantly lower only in the patients with dry type (P=0.02). These interactions remained nearly significant after Bonferroni correction (P<0.0125). Haplotype analysis for the two XPD polymorphisms revealed that the haplotype GC (312Asp-(751)Gln) was a protective haplotype against AMD. No statistically significant difference was found for the genotypic and allelic distributions of the polymorphisms in the XRCC1 gene between the patients and the control subjects. CONCLUSIONS: Polymorphism in XPD codon 751 may be associated with the development of AMD.

DNA repair gene XRCC1 and XPD polymorphisms and their association with coronary artery disease risks and micronucleus frequency.

Coronary artery disease (CAD) is a multifactorial process that appears to be caused by the interaction of environmental risk factors with multiple predisposing genes. In this study, we investigated the effects of the XPD Lys751Gln and XRCC1 Arg399Gln polymorphisms on the presence and the severity of CAD. We also investigated the presence of DNA damage in the peripheral lymphocytes of patients with CAD by using the micronucleus (MN) test and the effect of XPD Lys751Gln and XRCC1 Arg399Gln polymorphisms on this damage. The study population consisted of 147 patients with angiographically documented CAD and 48 healthy controls. No association between XPD Lys751Gln or XRCC1 Arg399Gln polymorphisms and the presence or the severity of CAD was observed. On the other hand, a significantly higher frequency of MN was observed in CAD patients compared with controls (5.7 +/- 1.9 vs 5.0 +/- 2.1, respectively, P = 0.018). We found an elevated frequency of MN in CAD patients with the XPD 751Gln allele (Gln/Gln genotype) or the XRCC1 399Gln (Arg/Gln or Gln/Gln genotypes) allele compared with the XPD 751Lys (Lys/Lys genotype) allele or XRCC1 399 Arg (Arg /Arg genotype) allele, respectively. These preliminary results suggest that XPD Lys751Gln and XRCC1 Arg399Gln polymorphisms may not be a significant risk factor for developing CAD. In addition, our results indicate that the MN frequency is associated with presence, but not severity, of CAD and is related to the XRCC1 Arg399Gln and XPD Lys751Gln polymorphisms, suggesting an elevated frequency of MN in CAD patients with the XPD 751Gln or XRCC1 399Gln alleles.

Metformin does not prevent DNA damage in lymphocytes despite its antioxidant properties against cumene hydroperoxide-induced oxidative stress.

Metformin (1-(diaminomethylidene)-3,3-dimethyl-guanidine), which is the most commonly prescribed oral antihyperglycaemic drug in the world, was reported to have several antioxidant properties such as the inhibition of advanced glycation end-products. In addition to its use in the treatment of diabetes, it has been suggested that metformin may be a promising anti-aging agent. The present work was aimed at assessing the possible protective effects of metformin against DNA-damage induction by oxidative stress in vitro. The effects of metformin were compared with those of N-acetylcysteine (NAC). For this purpose, peripheral blood lymphocytes from aged (n=10) and young (n=10) individuals were pre-incubated with various concentrations of metformin (10-50microM), followed by incubation with 15microM cumene hydroperoxide (CumOOH) for 48h, under conditions of low oxidant level, which do not induce cell death. Protection against oxidative DNA damage was evaluated by use of the Comet assay and the cytokinesis-block micronucleus technique. Changes in the levels of malondialdehyde+4-hydroxy-alkenals, an index of oxidative stress, were also measured in lymphocytes. At concentrations ranging from 10microM to 50microM, metformin did not protect the lymphocytes from DNA damage, while 50microM NAC possessed an effective protective effect against CumOOH-induced DNA damage. Furthermore, NAC, but not metformin, inhibited DNA fragmentation induced by CumOOH. In contrast to the lack of protection against oxidative damage in lymphocyte cultures, metformin significantly protected the cells from lipid peroxidation in both age groups, although not as effective as NAC in preventing the peroxidative damage at the highest doses. Within the limitations of this study, the results indicate that pharmacological concentrations of metformin are unable to protect against DNA damage induced by a pro-oxidant stimulus in cultured human lymphocytes, despite its antioxidant properties.

t(1;3)(p36;p21): presentation of a patient with MDS/AML (M2) and review of the literature.

t(1;3)(p36;p21) is a recurrent reciprocal translocation found in a subset of myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML) characterized by trilineage dysplasia, especially dysmegakaryopoiesis and poor prognosis. In the literature, some authors have suggested that this recurrent translocation is closely associated with prior chemotherapy including alkylating agents in various hematologic malignancies. We identified a recurring translocation, t(1;3)(p36;p21), in our patient with MDS/AML(M2), although she had not been given any kind of treatment previously.

Individual sensitivity to cytogenetic effects of benzo[ alpha ]pyrene in cultured human lymphocytes: influence of glutathione S-transferase M1 genotype

Sister chromatid exchange (SCE) and chromosome aberrations (CA) in peripheral lymphocytes has been widely used in assessing exposure to mutagens and carcinogens. One of the extensively studied genotoxins is benzo[alpha]pyrene (BaP). We studied the ability of BaP to induce SCE and CA in 16 glutathione S-transferase M1 (GSTM1)-positive and 15 GSTM1-null individuals by analyzing 72-h whole-blood lymphocyte cultures, either BaP-untreated (controls) or treated with 5 æM of BaP for 24 or 48 h. There was no differences in the level of BaP-induced chromosomal aberrations between GSTM1-positive or null individuals when the cells were BaP-exposed for 24 h (0.083 ± 0.059 vs. 0.090 ± 0.058) or 48 h (0.092 ± 0.057 vs. 0.096 ± 0.050. The frequency of SCE in controls was GSTM1-positive = 2.96 ± 0.35 and GSTM1-null = 3.23 ± 0.56 while that for BaP-treated lymphocytes was GSTM1-positive = 5.56 ± 0.83 and GSTM1-null = 6.09 ± 1.11 and were not statistically significant. The rates of BaP-induced in vitro chromatid and chromosome-type gaps and breaks were similar in all groups, although GSTM1-null genotype chromatid-type breaks were more frequent (0.064 ± 0.039 per metaphase) than chromosome-type breaks (0.032 ± 0.027 per metaphase) after 48 h treatment with BaP (p < 0.001). These findings suggest that BaP-induced in vitro SCE and CA are not influenced by the GSTM1 genotype.

Enhanced sensitivity to oxidant-induced micronucleus frequency in elderly individuals is not associated with glutathione S-transferase M1 (GSTM1) null genotype in lymphocytes.

BACKGROUND: A large number of studies have demonstrated that various kinds of DNA damage accumulate during aging and that oxidative stress possibly contributes to this process. Glutathione S-transferase M1 (GSTM1) can prevent their possible effects on DNA via detoxification of reactive substances that induced oxidative stress. OBJECTIVE: To investigate the relationship between GSTM1 polymorphism and DNA sensitivity to oxidative stress with age, we used micronucleus (MN) frequency as a marker of DNA damage in lymphocytes from young and elderly subjects. METHODS: This study was performed in 30 young (age range 20-36 years) and 30 elderly (age range 66-87 years) healthy individuals who were chosen on the basis of their GSTM1 genotype (15 GSTM1 null and 15 GSTM1 positive for each group). Lymphocytes were cultured after Ficoll isolation and treated for 48 h with a 30-muM dose of cumene hydroperoxide (CumOOH), a dose that does not decrease cell viability. RESULTS: There was no significant difference in the MN frequency observed in control cultures from young and elderly individuals. However, the MN frequency in CumOOH-treated cultures was significantly higher in the elderly group than the young group (p < 0.001). No association was found between the GSTM1 phenotype and CumOOH-induced MN frequency. CONCLUSIONS: The results suggest that lymphocytes of elderly individuals are more susceptible to in vitro MN induction by CumOOH. However, this difference in susceptibility is not explained by the lack of GSTM1.