ABRTRACT (Project Summary) Abdominal aortic aneurysm (AAA) is categorized as a progressive weakening and dilation of the aortic wall resulting in chronic failure of the aortic wall and catastrophic rupture with mortality rates >80% resulting in the death of ~30,000 Americans and ~500,000 people worldwide. Known risk factors for AAA include tobacco use, hypertension, male gender, and cardiovascular disease, however, the underlying mechanisms of this disease are still poorly understood. Moreover, little progress has been made in identification of druggable targets to reduce AAA burden creating a void in patient care. Pharmaceuticals (statins, ACE inhibitors) against CVDs have had limited success in AAA patients and the only treatment option is invasive surgical intervention, pursued only when the risk of aneurysm rupture outweighs the risk of surgery. Recent evidence has emerged demonstrating that resident gut microbes in the human intestine can promote several cardiovascular diseases. Specifically, the meta-organismal produced metabolite trimethylamine N-oxide (TMAO) has repeatedly been linked to numerous cardiovascular and metabolic pathologies. Our previous work demonstrates that TMAO is associated with AAA status in two case/control cohorts. Furthermore, dietary choline increases circulating TMAO in a gut microbiome dependent manner to enhance AAA pathogenesis in murine models. The putative receptor for TMAO is the endoplasmic protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), known as an initiator of the unfolded protein response (UPR) and endoplasmic reticulum (ER) stress. PERK signaling temporally regulates autophagy, apoptosis, mitochondrial-ER contact points (MERCs), and mitochondrial function, processes that are all affiliated with AAA pathogenesis. Our preliminary data demonstrates that both in vivo choline-induced TMAO and ex vivo application of TMAO result in PERK-dependent ER-stress. Additionally, TMAO treatment induces loss of VSMC phenotype, increases apoptosis, and blunts autophagy in a PERK-dependent manner. Yet, the contribution of TMAO-mediated PERK activation in VSMCs to AAA initiation and progression remains uncertain. Thus, the overall goal of this proposal is to determine how the gut microbiome-derived metabolite TMAO contributes to the initiation and progression of AAA through its putative binding target PERK. Our two specific aims will (1) define the role of VSMC-specific PERK in TMAO-augmented AAA; and (2) determine the PERK- dependent detrimental mechanisms in VSMCs. Successful completion of this F32 research proposal will increase our understanding of the of the mechanisms by which TMAO-mediated PERK signaling exacerbates AAA initiation and progression in order to identify novel therapeutic targets for the prevention and treatment of AAA in patients. The experience gained from this proposal under the mentorship of Dr. Owens and my advisory committee at the University of Cincinnati will facilitate my transi...