PostDoc Fellowship: Shu Liu A Novel Mechanism by which iPLA2 Beta Links Vascular Injury and Restenosis

Due to the high morbidity and mortality of restenosis there is an urgent need to understand the molecular mechanism that underlies it and to identify new therapeutic targets to prevent post-angioplasty restenosis. With this long-term goal in mind, the application specifically tests the role of calcium independent phospholipase A2 beta (iPLA2 beta) in restenosis. iPLA2beta is a member of the phospholipase A2 superfamily with ubiquitous tissue distributions and diverse cellular functions. In particular, a requirement of iPLA2beta in cell proliferation has been demonstrated in vitro in a variety of cell types. Consistently, our preliminary data show that inhibiting iPLA2beta with inhibitor or genetic deletion diminished vascular smooth muscle cells (VSMC) proliferation. Moreover, we found that specific overexpression of iPLA2beta in smooth muscle cells in mice is sufficient to increase reactive oxygen species (ROS) production by NAD(P)H oxidase in vasculature. While this evidence is consistent with a potentially important role of iPLA2beta in restenosis, direct and definitive in vivo experimental evidence is lacking. We created a novel smooth muscle specific iPLA2beta transgenic mouse model (iPLA2beta-Tg) and obtained an iPLA2beta knockout mouse model (iPLA2beta-KO) from Dr. Turk to directly test the hypothesis that vascular injury-induced iPLA2beta activation/up-regulation leads to excess ROS production by NAD(P)H oxidase and VSMC proliferation and thereby significantly contributes to restenosis. Two specific aims are: 1) to test the hypothesis that iPLA2beta plays a critical role in wire-injury induced, NAD(P)H oxidase-mediated ROS production in vascular wall by using the iPLA2beta-Tg and iPLA2beta-KO mice; 2) to test the hypothesis that iPLA2beta plays a critical role in wire-injury induced VSMC proliferation and restenosis by using the iPLA2beta-Tg and iPLA2beta-KO mice. We will isolate femoral arteries from wire-injury and sham-operated mice at different time after wire injury. We will use real-time PCR and Western blot to determine NAD(P)H oxidase expression, HPLC and confocal microscopy to determine ROS production, Brdu and PCNA staining to determine VSMC proliferation, and elastin staining to determine neointima. Results from the proposed studies likely will elucidate molecular mechanisms underlying restenosis and lead to the identification of iPLA2beta as a potential novel therapeutic target for the prevention and treatment of the restenosis.