Abstract 13824: Role for DNA Damage in the Etiology of 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 PASMCs a pro-proliferative and anti-apoptotic phenotype, sustained in time by the activation of miR-204, STAT3/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-PASMCs exhibit increased DNA damage markers (53BP1 & γ-H2AX) as well as an overexpression of PARP-1 (immunoblot & immunofluorescence), compared to tissues from healthy donors. Human PASMCs from healthy donors treated with a clinically relevant dose of etoposide (DNA damage inducer) or TNF-α, IL-6, PDGF (pro-PAH factors) harbored a similar phenotype, suggesting that pro-PAH factors induce damage to DNA leading to PARP-1 activation in PAH. We also showed that PARP-1 activation accounts for a STAT3-dependent miR-204 downregulation (qRT-PCR) and the subsequent upregulation and activation of the transcription factors NFAT and HIF-1α in PAH-PASMCs, previously shown to be critical for PAH in several models. These effects resulted in PASMC proliferation (PCNA & Ki67 assays) and resistance to apoptosis (AnnexinV and TUNEL assays). In vivo, increases in DNA damage by etoposide gavage enhanced monocrotaline-induced PAH (p<0.05, n=5), while the clinically available PARP inhibitor ABT-888 improved PAH in two experimental rat models (Sugen/hypoxia and monocrotaline, p<0.05; n=10 in each group).
Conclusion: These results show for the first time that the DNA damage/PARP-1 signaling pathway is important for the development of PAH and provide a new therapeutic target for this deadly disease, with high translational potential (as ABT-888 is currently in clinical phase II in cancer).
- © 2013 by American Heart Association, Inc.