Abstract 16424: A Critical Role of Poly-ADP Ribose Polymerase 1 (PARP-1) in Human Pulmonary Arterial Hypertension
Background: Pulmonary arterial hypertension (PAH) is a vascular disease that is characterized by vascular lesions and obstructions of the distal pulmonary arteries (PA). This phenotype is associated with oxidative stress and inflammatory processes sustained by the activation of the transcription factor NFAT. Despite these unfavorable conditions known to promote DNA damage, PAH pulmonary artery smooth muscle cells (PASMC) are proliferative and resistant to apoptosis suggesting as in cancer cells an activation of the DNA repair machinery allowing PAH-PASMC to survive in these detrimental conditions. Poly-ADP ribose polymerase 1 (PARP-1) is the most important enzyme implicated in the detection and repair of single strand DNA breaks (SSB). In addition PARP-1 regulates cell survival, cell death and is implicated in transcriptional regulation of a number of genes involved in neoplasic processes and inflammation including NFAT. We hypothesized that PARP-1 activation is increased in PAH-PASMC contributing to their proliferation and survival and thus to pulmonary vascular remodeling.
Methods/results: Using human lung tissues (8 control vs 8 PAH) and primary cultured PASMC from distal PA of patients with (n=3) or without (n=5) PAH we demonstrated for the first time that the increase in oxidative stress (Kamiya assay; p<0.05) promotes SSB (8-hydroxy-desoxyguanosine and 53BP1 assays; p<0.05) in PAH-PASMC. Increased SSB triggers PARP-1 activation (qRT-PCR and immunofluorescence) in PAH-PASMCs allowing SSB repair and thus PAH-PASMC survival. Moreover, PARP-activation promotes NFATc2 activation by 24% promoting PAH-PASMC proliferation by 30% (PCNA) and resistance to apoptosis by 25% (TUNEL). Finally we showed that the clinically available PARP inhibitor ABT-888 reverses all these abnormalities and the PAH phenotype both in vitro and in vivo in rats with monocrotaline-induced PAH.
Conclusion: we demonstrated for the first time that the DNA repair machinery PARPs are etiologically implicated in PAH. Moreover we showed that the clinically available PARP-1 inhibitors might represent new therapeutic agent against PAH.
- © 2011 by American Heart Association, Inc.