N. Xamena

Oxidative DNA damage in chronic renal failure patients

BACKGROUNDnChronic renal failure (CRF) patients present a high incidence of cardiovascular pathologies and cancer. This has been attributed to the existence of genomic instability in these patients, and consequently they should present elevated levels of genetic damage.nnnMETHODSnTo determine the background levels of genetic damage and its specific levels of oxidative damage, a large population of 253 CRF patients (77 in dialysis) was analysed using the comet assay. The percentage of DNA in the tail was used as a measure of basal genetic damage. In addition, the use of endo III and FPG enzymes allowed us to determine the levels of specific oxidative damage in DNA bases.nnnRESULTSnThis is the first study that uses endo III and FPG enzymes to measure oxidative damage in CRF patients. Overall genetic damage, as well as specific oxidative damage, was higher in dialysis patients than in the CRF patients with different stages of uraemic state; genetic damage increased when serum creatinine levels increased. Genomic damage in dialysis patients decreased in those patients submitted to dialysis for a long time.nnnCONCLUSIONSnGenetic damage increases when renal function decreases, being maximum in haemodialysis patients. Although part of the observed damage can be attributed to the uraemic state itself, other individual genetic factors can influence a state of genomic instability responsible for the observed genomic damage.

Role of GST and NAT2 polymorphisms in thyroid cancer

Genetic polymorphisms have shown to be susceptibility factors playing an important role in the development of most cancers. Nevertheless, as far as we know, only few studies have been conducted linking thyroid cancer incidence and GST polymorphisms, and no data are available on the possible association between NAT2 polymorphisms and thyroid cancer risk. The possible relationship between polymorphism at the GSTM1, GSTT1, GSTP1, and NAT2 genes and increased susceptibility to thyroid cancer has been evaluated in 176 thyroid cancer patients and 167 healthy controls, all from the urban district of Barcelona (Spain). The results indicate a clear role of the C481T change, present in several NAT2*5 alleles [odds ratio (OR)=0.58; 95% confidence interval (95% CI)=0.35–0.98]. Thus, those individuals carrying this change are less prone to develop thyroid cancer, mainly of the papillary type. In addition, there is a tendency towards the over-representation of the GSTM1 null genotype among thyroid cancer patients, particularly in those patients with papillary type tumor. The same is observed for the GSTM1 and GSTT1 null genotypes combination, and for other combinations with different NAT2 polymorphisms. The combinations involving the NAT2*6 and NAT2*7 genotypes showed the most important effect, and individuals carrying both alleles present a higher risk of thyroid cancer (OR=7.36; 95% CI=0.85− 63.47), mainly for the follicular type (OR=17.94; 95% CI=1.34–238.70). The combination of NAT2*5 with NAT2*7 was also found to increase 5.26 (95% CI=1.07–25.76) times the risk of thyroid cancer. In conclusion, our results show that NAT2 polymorphisms play a significant role in thyroid cancer risk modulation.

Effects of cerium oxide nanoparticles on differentiated/undifferentiated human intestinal Caco-2 cells

Since ingestion constitute one of the main routes of nanoparticles (NPs) exposure, intestinal cells seems to be a suitable choice to evaluate their potential harmful effects. Caco-2u202fcells, derived from a human colon adenocarcinoma, have the ability to differentiate forming consistent cell monolayer structures. For these reasons Caco-2u202fcells, both in their undifferentiated or differentiated state, are extendedly used. We have used well-structured monolayers of differentiated Caco-2u202fcells, as a model of intestinal barrier, to evaluate potential harmful effects associated to CeO2NPs exposure via ingestion. Different parameters such as cell toxicity, monolayer integrity and permeability, cell internalization, translocation through the monolayer, and induction of DNA damage were evaluated. No toxic effects of CeO2NPs were observed, independently of the differentiated state of the Caco-2u202fcells. In the same way, no effects on the monolayer integrity/permeability were observed. Although important cell uptake was demonstrated in undifferentiated cells (by using confocal microscopy), CeO2NPs remained mostly attached to the apical membrane in the differentiated cells. In spite of this apparent lack of uptake in differentiated cells, translocation of CeO2NPs to the basolateral chamber was observed by using confocal microscopy. Finally no genotoxic effects were observed when the comet assay was used, although decreases in the levels of oxidized bases were observed, supporting the antioxidant role of CeO2NPs.

Micronuclei induced by alachlor, mitomycin-C and vinblastine in human lymphocytes: presence of centromeres and kinetochores and influence of staining technique

Antikinetochore antibodies and fluorescence in situ hybridization with an alphoid centromeric probe were applied to the cytokinesis-block micronucleus (MN) assay to study the suitability of these methodologies to detect clastogenic/aneugenic activity in isolated human lymphocytes. The chemicals selected for this study were the herbicide alachlor, the clastogen mitomycin-C (MMC), and the aneugen vinblastine sulphate (VBL). Furthermore, MN frequencies obtained from slides stained with May-Grünwald-Giemsa (MGG) and with the DNA fluorochrome 4,6-diamidino-2-phenylindole (DAPI) were compared to check if the DNA-specific DAPI facilitated a more accurate recording of MN than the unspecific MGG. The results showed that the detection of kinetochores (KC) or centromeres (CM) within MN are equally reliable and sensitive techniques to study the mode of action of clastogenic and aneugenic agents. The comparison of CM and KC detection in control cultures suggested that up to 17% of spontaneous chromosome-containing MN may be due to KC disruption, whereas the majority are caused by dysfunction in other components of the mitotic apparatus. Alachlor (7.5-20 micrograms/ml) and MMC (0.6 microM) acted as pure clastogens without aneugenic activity, inducing exclusively KC- and CM-negative MN. VBL produced primarily KC- and CM-positive MN, in accordance with its known mechanism of action. A comparison between CM and KC data in the VBL treatment suggested that some 7% of KC-containing MN may not be detected by the probe. The frequencies of MN were generally higher in slides stained with DAPI than in those stained with MGG, especially in controls and clastogen-treated cultures.(ABSTRACT TRUNCATED AT 250 WORDS)