5‐aminoisoquinolin‐1(2 H )‐one, a water‐soluble poly (ADP‐ribose) polymerase (PARP) inhibitor reduces the evolution of experimental periodontitis in rats

Background: Poly (ADP‐ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischaemia‐reperfusion and inflammation. Recent studies have demonstrated that PARP activation plays a crucial role in the pathogenesis of acute periodontal injury. Aim: We have investigated the effect of 5‐aminoisoquinolin‐1(2 H )‐one (5‐AIQ), a water‐soluble PARP inhibitor, in a rat model of periodontitis. Materials and Methods: Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day eight, the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis. Results and Conclusions: Ligation significantly induced an increased neutrophil infiltration and a positive staining for PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of 5‐aminoisoquinolin‐1(2 H )‐one (5‐AIQ) (5 mg/kg daily for eight days) significantly decreased all of the parameters of inflammation as described above. This suggests that inhibition of PARP may represent a novel approach for the treatment of periodontal disease.