No abstract

Somatic DNA damage has been linked to coronary artery disease (CAD). However, whether genetic instability is linked to CAD per se or to concomitant potentially genotoxic metabolic and pharmacological factors remains still unclear. The aim of this study was to evaluate the determinants of somatic DNA damage in a large population of patients undergoing coronary angiography. A total of 278 in-hospital patients (215 men, age 61.8+/-0.7 years) were studied by using micronucleus assay (MN) in human lymphocytes, which is one of the most commonly used biomarker for somatic DNA damage. Significant CAD (>50% diameter stenosis) was present in 210 patients (179 men, age 62.3+/-0.7 years). Normal coronary arteries were observed in 68 patients (35 men, age 60.2+/-1.7 years). There were no significant differences between patients with and without CAD, but patients with multivessel disease had the highest MN levels (P=0.01). MN frequency was also found significantly higher in presence of type 2 diabetes (P<0.0001), dyslipidemia (P=0.048) and nitrate therapy (P=0.0002). A significant additive effect was also observed between diabetes and nitrate therapy (P=0.02). On multivariate logistic regression analysis, diabetes [odds ratio=6.8 (95% confidence interval, 3.2-14.5), P<0.0001] and nitrate therapy [odds ratio=2.4 (95% confidence interval, 1.3-4.7), P=0.01] remained the only significant determinants for the 50th percentile of MN (>12 per thousand). These results indicated that diabetes and, to a lesser extent, chronic nitrate therapy are major determinants of somatic DNA instability in patients with CAD. DNA damage might represent an additional pathogenetic dimension and a possible therapeutic target in the still challenging management of coronary artery disease concerning diabetics.

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality in industrialized countries. It is characterized by a progressive airflow limitation resulting from an abnormal inflammatory response of the lungs to inhaled gases and particles. Since oxidative stress is thought to play a role in COPD, and since increased oxidative stress is associated with chromosomal instability in several diseases, we investigated whether such relationship also exists in COPD. Whole blood lymphocytes from 49 COPD patients and 48 age- and sex-matched controls were cultivated in vitro and cytogenetic damage was evaluated by micronucleus (MN) and sister-chromatid-exchange (SCE) assays. In patients with COPD, MN frequency was not significantly different from that of controls. Similarly, SCE frequency did not differ in the two groups suggesting no disturbance in DNA replication. Unlike other diseases characterized by oxidative stress, COPD does not appear to be associated with DNA damage.

Myotonic Dystrophy type 1 (DM1) is one of the many inherited human diseases whose molecular defect is the expansion of a trinucleotide DNA sequence. DM1 shares with fragile X syndrome (FMR1), another “unstable triplet syndrome”, several molecular features not present in the remaining triplet diseases. As FMR1 is also characterised by chromosome instability at the site of the expanded triplet, lymphocytes from DM1 patients and healthy donors were cultured for micronucleus (MN) analysis, in order to verify if DM1 is also prone to chromosome instability. A FISH analysis was also carried out to detect the presence of centromeric sequences in the observed MN. The data indicate that DM1 patients present a percentage of centromere-positive MN significantly higher than controls, suggesting that chromosome loss is the main mechanism underlying the origin of the increased spontaneous instability. To further assess the proneness to instability of cells of DM1 patients, cultures from patients and controls were treated in vitro with growing concentrations of two different mutagens: colcemid, a “pure” aneugen compound whose target is tubulin, and mytomicin C, a strong clastogen. The results show that the patient group is significantly less sensitive to colcemid. These data, together with FISH analysis, suggest the presence, in DM1 patients, of an already damaged tubulin, which becomes no more sensitive to the effect of colcemid and which could be the main defect underlying the aneugenic effects in DM1.