The spatiotemporal expression profile of ATF3 determines the fate of smooth muscle cells in abdominal aortic aneurysm development

Background: Abdominal Aortic Aneurysm (AAA) is a catastrophic disease with little effective therapy, likely due to the limited understanding of the mechanisms underlying AAA development and progression. Activating transcription factor (ATF) 3 has been increasingly recognized as a key regulator of cardiovascular diseases. However, the role of ATF3 in AAA development and progression remains elusive. Methods: Genome-wide RNA sequencing analysis was performed on the aorta isolated from saline or Ang II-induced AAA mice, and ATF3 was identified as the potential key gene for AAA development. To examine the role of ATF3 in AAA development, vascular smooth muscle cell (VSMC)-specific ATF3 knockdown or overexpressed mice by recombinant adeno-associated virus serotype 9 (rAAV9) vectors carrying ATF3, or shRNA-ATF3 with SM22a promoter were used in AngII (angiotensin II) induced AAA mice. In human and murine VSMCs, gain or loss of function experiments were performed to investigate the role of ATF3 in VSMC proliferation and apoptosis. Results: In both AngII-induced AAA mice and AAA patients, the expression of ATF3 was reduced in aneurysm tissues but increased in aortic lesion tissues. The deficiency of ATF3 in VSMC promoted AAA formation in AngII-induced AAA mice. PDGFRB was identified as the target of ATF3, which mediated VSMC proliferation in response to TNF-alpha at the early stage of AAA. ATF3 suppressed the mitochondria-dependent apoptosis at the advanced stage by upregulating its direct target BCL2. Our ChIP results also demonstrated that the recruitment of NF?B1 and P300/BAF/H3K27ac complex to the ATF3 promoter induces ATF3 transcription via enhancer activation. NFKB1 inhibitor (Andrographolide) inhibits the expression of ATF3 by blocking the recruiters NFKB1 and ATF3-enhancer to the ATF3-promoter region, ultimately leading to AAA development. Conclusions: Our results demonstrate a previously unrecognized role of ATF3 in AAA development and progression, and ATF3 may serve as a novel therapeutic and prognostic marker for AAA. Overall design: Abdominal Aortic Aneurysm (AAA) Animal Models Angiotensin II (Ang II) (1,000 ng/kg/min, HY-13948, MedChemExpress, NJ, USA) was dissolved in normal saline and was infused using osmotic pumps (Alzet 2004, Durect Corporation, USA) for 4 weeks. Male mice (ApoE-/-,12 weeks old, about 20-25 g) were anesthetized, and the suprarenal abdominal aortas (identified between the last pair of intercostal arteries and the right renal branch) were harvested at 28 days after implantation surgery. The formation of aneurysm was determined by the abdominal aorta diameter increased by 50% or more. Any mouse that died prior to the study endpoint was subjected to autopsy, and aneurysm rupture was characterized by the presence of egress with blood clots outside the adventitia of the dilated aortic wall. Samples:Genome-wide RNA sequencing (RNAseq) analysis was performed on the aorta isolated from saline or Ang II-induced AAA mice. The aorta from AAA mice was further divided into the aortic lesion (non-aneurysm) section and the aneurysm section.