Mechanisms of High Flow Induced Vasculopathy

描述(申请人提供)：血流增加会引起一系列血管反应，最早的反应是扩张性的，主要是内皮细胞介导的，随后是肌源性张力的发展(用于使血流恢复到基线)和对激动剂的反应增强。这种对收缩药物反应增强的机制尚不完全清楚，但可能涉及内皮细胞和血管平滑肌细胞中离子通道介导的信号转导。我们建立了一种幼猪离体肺叶高流量模型(通过主-肺吻合术建立)，导致临床肺动脉高压的新血管内膜增殖和早期反应性增强，其反应性似乎是内皮和L型钙通道依赖性的。我们的初步数据表明，持续的血流导致电压门控钙通道表达增加和一氧化氮合酶功能障碍，这可能有助于分流动脉的反应性增强。我们推测，显著增强内皮源性EETs的合成增加了L型钙通道的开放，并减少了钙激活的K通道在增加流量后对下层PAVSM的开放。这笔赠款的具体目的有三个：(I)我们将确定血管平滑肌细胞中的内皮第二信使信号通路包括PLC、EETs、NOS和Ca(L)以及Kca离子通道对高流量或基线流量下PAS的张力和反应性的贡献。(2)研究血流诱导的肺动脉内皮细胞eNOS表达及肺动脉血管平滑肌细胞钙(L)和KCA型离子通道表达的变化。(3)研究分流前后肺血管内皮细胞内皮细胞第二信使信号通路PLC、EETs、一氧化氮合酶、钙(L)门控和KCA通道活性的变化，以及EETs对分流前和非分流后肺动脉内皮细胞[Ca~(2+)]i的影响。这些研究应该提供关于高流量引起的血管病变背后的细胞机制的有价值的信息，这些疾病使一些临床上重要的疾病复杂化，如先天性心脏病的修复、肺切除术等。

DESCRIPTION (provided by applicant): Increased flow induces a series of vascular responses, the earliest of which are prodilatory and largely endothelial mediated, followed by the development of myogenic tone (which serves to return blood flow towards baseline) and enhanced reactivity to agonists. The mechanisms, which underlie this heightened response to contractile agents, are incompletely understood, but likely involve ion channel-mediated transduction of signals in endothelial and vascular smooth muscle cells. We have developed a model of high flow to isolated lung lobes of young pigs (created by an aorto-pulmonary anastomosis) which results in neointimal proliferation characteristic of clinical pulmonary hypertension and early enhanced reactivity which reactivity appears to be endothelial and L-type calcium channel dependent. Our preliminary data suggest that sustained flow results in increased expression of voltage-gated calcium channels and dysfunctions in NOS which may contribute to enhanced reactivity of shunted arteries. We hypothesize that acutely enhanced synthesis of endothelial-derived EETs increases opening of L-type calcium and decreases the opening of calcium activated K channels in subjacent PAVSMs following increased flow. The specific aims of the grant are threefold: (i) We will identify the contribution of the endothelial second messenger signaling pathways including PLC, EETs, NOS and Ca(L) and KCa ion channels in vascular smooth muscle cells to the tone and reactivity of PAs exposed to high or baseline flows. (2) We will characterize flow-induced changes in expression of eNOS levels in PAs as well as expression of Ca(L) and KCa type ion channels in pulmonary artery vascular smooth muscle cells. (3) We will examine flow-induced changes in activity of endothelial second messenger signaling cascades PLC, EETs, NOS, gating of Ca(L) and KCa channels in PAVSM, and effect of EETs on [Ca2+]i in PAVSMCs of shunted versus non-shunted pulmonary arteries. These studies should yield valuable information about cellular mechanisms which underlie high flow induced vasculopathy, which conditions complicate a number of clinically important conditions such as repair of congenital heart defects, pneumonectomies, and others.