iPLA2 as a Target in Vascular Inflammation, Neointima Formation, and Restenosis

描述（由申请人提供）：

DESCRIPTION (provided by applicant): Coronary heart disease is the single leading cause of death among men and women in the United States. Coronary revascularization, including coronary artery bypass graft (CABG) and percutaneous coronary intervention (PCI) is the most common modality in patients with coronary diseases. However, it is also among the most costly, and is often associated with a high incidence of restenosis. Although the rate of restenosis is significantly reduced with the use of bare-metal stent (BMS) and particularly with drug-eluting stent (DES), a persistently high rate of restenosis after BMS and an increased risk of in-stent thrombosis with DES have been encountered as significant limitations to the long-term efficacy of coronary revascularization. With a long-term goal of identifying novel therapeutic targets for coronary heart disease, the current application specifically investigates a potentially critical role of calcium independent phospholipase A2b (iPLA2b) in vascular inflammation, re-endothelialization, and neointima formation in a mouse femoral artery wire injury model. iPLA2b is a member of the phospholipase A2 superfamily that acts on phospholipids to produce a free fatty acid and a lysophospholipid. iPLA2b is expressed in vascular smooth muscle cells (VSMC) and is implicated in many human diseases. Whereas little is known about the role of other PLA2 in vascular injury-induced neointima formation, substantial evidence, including pharmacological inhibition, antisense oligonucleotide down- rgulation, genetic deletion, and smooth muscle-specific overexpression, consistently demonstrated that iPLA2b plays a critical role in vascular inflammation and neointima formation in a mouse carotid artery ligation model. To investigate whether targeting smooth muscle-specific iPLA2b is sufficient to reduce vascular inflammation and neointima formation, a femoral artery injury model that better mimics PCI was established, a novel tamoxifen-inducible smooth muscle-specific iPLA2b knockout mouse model (SM-iPLA2b-iKO) was developed, and the current proposal hypothesizes that activation of iPLA2b in VSMC by vascular injury plays a key role in wire injury-induced vascular inflammation, re-endothelialization, and neointima formation, thereby significantly contributing to the development of restenosis after coronary revascularization. Three Specific Aims are: 1) To test the hypothesis that smooth muscle-specific iPLA2b plays a critical role in the initiation of vascular inflammation, re-endothelialization, and neointima formation; 2) To determine the molecular mechanism that underlies wire injury-induced iPLA2b activation, vascular inflammation, and neointima formation; 3) To investigate whether post-wire injury molecular and genetic targeting iPLA2b has an effect on the progression of re-endothelialization, vascular inflammation, and neointima formation. To achieve this goal, a well established and most physiological relevant femoral artery wire injury model will be used in combination with several novel and established genetic animal models (SM- iPLA2b-iKO, SM-HIF-1a-iKO, and SM-iPLA2b-Tg/12/15-LO) to selectively inhibit or activate iPLA2b, HIF-1a, and 12/15-LO before and after wire injury. Injured and non-injured femoral arteries will be isolated and then subjected to molecular, immunohistological, and biochemical studies to determine the role of iPLA2b in vascular inflammation and neointima formation. Results from the proposed studies may modify the current paradigm that the initiation and early progression of vascular inflammation are largely attributed to coordinated interactions among monocytes/macrophages, leukocytes, and endothelial cells by providing the first direct experimental evidence that VSMC also play a critical role in these early key events. Importantly, results from the proposed studies will elucidate specific mechanisms that could lead to the identification of iPLA2b as a novel potential therapeutic target for the prevention and treatment of vascular inflammation, re- endothelialization, neointima formation, and restenosis.