DNA damage and repair in a model of rat vascular injury

Restenosis rates following vascular interventions still limit their long-term success. Oxidative stress plays a relevant role in this pathophysiological phenomenon, but less attention has been devoted to its effects on DNA damage and to the subsequent mechanisms of repair. In the present study, we analysed in a model of arteriotomy-induced stenosis in rat carotid arteries the time-dependent expression of DNA damage markers and of DNA repair genes, together with the assessment of proliferation and apoptosis indexes. The expression of the oxidative DNA damage marker 7,8-dihydro-8-oxo-2′-deoxyguanosine was increased at 3 and 7 days after arteriotomy, with immunostaining distributed in the injured vascular wall and perivascular tissue. Expression of the DNA damage marker phospho-H2A.X was less relevant, but increased from 4 h to 7 days after arteriotomy, with immunostaining prevalently present in the adventitia and, to a lesser extent, in medial smooth muscle cells at the injury site. RT (reverse transcription)–PCR indicated a decrease in eight out of 12 genes involved in the DNA repair machinery we selected from 4 h to 7 days after arteriotomy, with the exception of an increase in the Mutyh and Slk genes (P<0.05). Western blot analysis revealed a decrease in p53 and catalase at 3 days after arteriotomy (P<0.05). A maximal 7% of BrdU-positive cells in the endothelium and media occurred at 7 days after arteriotomy, whereas the apoptotic index peaked at 3 days after injury (P<0.05). In conclusion, our results highlight a persistent DNA damage, presumably related to a temporary decrease in the expression of the DNA repair machinery and of the antioxidant enzyme catalase, playing a role in stenosis progression.