Unstabilized DNA Breaks in Lymphocytes of Patients with Different Subsets of Systemic Sclerosis

Abstract

The clastogenic effects on DNA, proven by the presence of micronuclei (MN) and the protective cellular mechanisms normally used to stabilize DNA breaks were investigated in three subsets of patients with systemic sclerosis (SSc). The frequency of MN found in cultures of peripheral lymphocytes in patients with anticentromere and antitopoisomerase I antibodies was significantly higher than that in the control group. The group with anticentromere antibody showed a significantly higher frequency of MN than did the subjects with antitopoisomerase antibody (4.22% versus 2.34%, P < 0.001). Patients with anti-RNA polymerase III, instead, had a low prevalence of typical micronucleated cells (0.98%), not significantly different from that of the healthy controls (0.82%). Moreover, when MN was characterized for the presence or absence of DNA fragments with free 3'-OH ends by digoxigenin-dUTP (DIG-dUTP) using terminal deoxynucleotidil transferase, its frequency was found to be increased in the groups with anticentromere and antitopoisomerase I antibodies with respect to that in the controls. The increase was significantly higher in the lymphocytes of the patients with anticentromere than in those with antitopoisomerase I antibody (35% versus 20.08%, P < 0.001). Nonetheless, the prevalence of unstable DNA fragments in patients with anti-RNA polymerase III antibody was low (2.05%) and not significantly different from that of the control group (1.18%). Our results indicate that there is a clastogenic effect on DNA and an interference in the protective cellular mechanisms normally stabilizing DNA breaks only in some subsets of SSc patients.

Genotoxic Effect in Autoimmune Diseases Evaluated by the Micronucleus Test Assay: Our Experience and Literature Review

“…Furthermore, ACA positive patients showed the highest MN frequencies, which suggest a possible role of ACA in determining cytogenetic anomalies [ 31 ]. Confirming the results of this previous study, Majone and coworkers described in 2007 [ 43 ] a significantly higher frequency of MN in SSc patients who were positive for ACA compared to SSc patients who were positive for antitopoisomerase or anti-RNA polymerase III as well as healthy controls. More importantly, they examined the nature of chromosome damage within analyzed lymphocytes for the presence of MN.…”

Patients with Systemic Sclerosis Present Increased DNA Damage Differentially Associated with DNA Repair Gene Polymorphisms

“…The micronuclei represent losses of blocks of DNA or even whole chromosomes 14 , which may cause loss of regions that encode proteins important for adequate cell functioning 11,12,15,34,35,36 . One of the most important findings is the observation of an increased frequency of micronuclei in SSc peripheral blood lymphomononuclear cells.…”

Coherent Somatic Mutation in Autoimmune Disease

“…In SSc fibroblasts, increased sumoylation of TOP1 induces deficits in TOP1-mediated supercoiled-DNA relaxation [204] and disruption of TOP1 is known to cause chromosomal aberrations [203]. Inhibition of sumoylation improves TOP1 function in fibroblasts [203] and reduces fibrosis [205]. One interpretation of this data is that anti-TOP1 SSc is a sumoylation disorder.…”

“…Chromosomal abnormalities are found at high frequency in the lymphocytes of patients with anti-centromere or anti-TOP1 antibodies, but at normal frequency in patients with anti-RNAPIII antibodies [203]. In SSc fibroblasts, increased sumoylation of TOP1 induces deficits in TOP1-mediated supercoiled-DNA relaxation [204] and disruption of TOP1 is known to cause chromosomal aberrations [203]. Inhibition of sumoylation improves TOP1 function in fibroblasts [203] and reduces fibrosis [205].…”