Abstract 19163: Implication of DNA Damage Signaling and Epigenetic Readers in Metabolic Disorder Observed in Vascular Wall of Ischemic Patients
Background: Coronary artery stenosis is characterized by coronary artery smooth muscle cell (CoASMC) proliferation and survival in detrimental conditions (increased inflammation, oxidized lipids, shear stress) known to cause DNA damage. In cancer, increased cell proliferation was attributed to DNA damage signaling activation secondary to mitochondrial/metabolic dysfunction. This leads to the upregulation of Poly(ADP)ribose-polymerase 1 (PARP-1), a critical enzyme acting as a DNA damage sensor, and the epigenetic reader Bromodomain-containing protein 4 (BRD4), both known to contribute to cell survival and proliferation. In light of these observations, we hypothesized that impaired mitochondria/metabolism triggers DNA damage signaling in coronary artery stenosis leading to CoASMC proliferation and thus vessel narrowing.
Method/Results: Primary cultured human CoASMC from patients with stenosis (n=3) exhibit signs of mitochondrial dysfunction including hyperpolarization (TMRM; n=3, p<0.05), downregulation metabolic sensors Sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor coactivator 1 (PGC1-α) expression (western blot (WB); n=3, p<0.05). These cells also exhibit enhanced glycolysis compared to control hCoASMC (Seahorse Bioscience XF24e; n=3, p<0.05). These mitochondrial/metabolic abnormalities enhance DNA damage signaling in human coronary arteries with stenosis (53BP1; n=8, p<0.05), as well as PARP-1 and BRD4 expression (WB; n=4, p<0.05) compared to control arteries. This pathogenic phenotype is also present in isolated hCoASMC issued from stenosis, as they have more DNA damage sites (γH2AX; n=5, p<0.05) and exhibit increased PARP-1 and BRD4 expression (WB; n=4, p<0.05) compared to control hCoASMC. PARP-1 and BRD4 activation in pathologic hCoASMC promote proliferation (Ki67; n=5, p<0.05) by downregulating cell cycle inhibitors p300 and p21 (WB; n=3, p<0.05), leading to cell survival (MTT assay; n=3, p<0.05). This pathological phenotype was reversed upon treatment with a PARP-1 (Veliparib, 10μM) or a BRD4 (JQ1, 1μM) inhibitor.
Conclusion: Our study suggests an important role for BRD4 signaling and metabolic disorder in coronary diseases and opens the door to new avenues of investigation and treatment.
Author Disclosures: J. Meloche: None. S. Henry: None. M. Le Guen: None. E. Charbonneau: None. S. Provencher: None. S. Bonnet: Research Grant; Modest; Bayer. Other Research Support; Modest; actellion. Honoraria; Modest; Merck.
- © 2014 by American Heart Association, Inc.