Poly (ADP) ribose synthetase inhibition reduces obliterative airway disease in rat tracheal allografts.

Background: Obliterative bronchiolitis (OB) is the major long-term complication affecting lung transplant recipients, and is characterized pathologically by chronic inflammatory and fibroproliferative airway disease. Based on studies revealing anti-inflammatory and anti-apoptotic properties of poly (ADP)-ribose synthetase (PARS) inhibitors, we hypothesized that their administration would be protective in a heterotopic model of experimental OB.

Methods: We transplanted rat tracheas from Brown-Norway donors into Lewis recipients, and treated 2 groups with a novel PARS inhibitor, INO-1001. One group received 14 days of treatment, whereas a second received delayed treatment beginning on Day 7 post-transplant. Tracheas were analyzed by light microscopy and computerized morphometry. Effects on cytokine transcription, nuclear transcription factor activation and cellular death were assessed by in situ hybridization for tumor necrosis factor-alpha (TNF-alpha), electromobility shift assays for nuclear factor-kappaB (NF-kappaB) and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays, respectively.

Results: PARS inhibition significantly decreased luminal obstruction (p < 0.001) and enhanced preservation of epithelial lining (p < 0.001) at 14 days post-transplant. Day 7 controls confirmed the development of an obstructive lesion in the lumen, averaging 28% occlusion. Delayed treatment (beginning on Day 7) arrested (p < 0.001) progression of the established lesion. Allograft airways treated with INO-1001 demonstrated attenuated NF-kappaB nuclear translocation, reduced transcription of TNF-alpha mRNA, and decreased cellular death on TUNEL and caspase 3 staining.

Conclusions: PARS inhibition is anti-inflammatory, protects against experimental OB, and is associated with enhanced preservation of respiratory epithelium and decreased cellular death. Delayed treatment with INO-1001 arrests progression of the lesion developed by Day 7. These studies suggest that activation of PARS plays a critical role in the development of airway obliterative disease.