Role for DNA Damage Signaling in Pulmonary Arterial Hypertension
Background—Pulmonary arterial hypertension (PAH) is associated with sustained inflammation known to promote DNA damage. Despite these unfavorable environmental conditions PAH pulmonary arterial smooth muscle cells (PASMC) exhibit, in contrast to healthy PASMC, a pro-proliferative and anti-apoptotic phenotype, sustained in time by the activation of miR-204, NFAT and HIF-1α. We hypothesized that PAH-PASMC have increased activation of Poly(ADP-ribose) polymerase-1 (PARP-1), a critical enzyme implicated in DNA repair, allowing proliferation despite the presence of DNA damaging insults, eventually leading to PAH.
Methods and Results—Human PAH distal pulmonary arteries and cultured PAH-PASMC exhibit increased DNA damage markers (53BP1 & γ-H2AX) as well as an overexpression of PARP-1 (immunoblot & activity assay), compared to healthy tissues/cells. Healthy PASMC treated with a clinically relevant dose of TNF-α harbored a similar phenotype, suggesting that inflammation induces DNA damage and PARP-1 activation in PAH. We also showed that PARP-1 activation accounts for miR-204 downregulation (qRT-PCR) and the subsequent activation of the transcription factors NFAT and HIF-1α in PAH-PASMC, previously shown to be critical for PAH in several models. These effects resulted in PASMC proliferation (Ki67, PCNA and WST1 assays) and resistance to apoptosis (TUNEL and AnnexinV assays). In vivo, the clinically available PARP inhibitor ABT-888 reversed PAH in two experimental rat models (Sugen/hypoxia and monocrotaline).
Conclusions—These results show for the first time that the DNA damage/PARP-1 signaling pathway is important for PAH development and provide a new therapeutic target for this deadly disease, with high translational potential.
- Received September 9, 2013.
- Revision received October 31, 2013.
- Accepted November 8, 2013.