Oxidized CaMKII in Atrial Fibrillation

描述（由申请人提供）：我们的研究小组确定了CaMKII通过CaMKII调控区域配对Met残基（281/282）氧化激活CaMKII的机制，并发现血管紧张素II （Ang II）输注导致心肌Met 281/282氧化，将氧化的CaMKII （ox- CaMKII）锁定为持续活性结构。我们最近发现，与对照组相比，房颤患者心房中ox-CaMKII的表达增加，这使我们开发并验证了一种输注Ang II和增强房颤敏感性的小鼠模型，以测试ROS和ox-CaMKII在房颤中的潜在作用。我们发现，输注Ang II的起搏诱导的阵发性房颤小鼠和血管紧张素转换酶基因靶向心肌表达和自发性房颤的小鼠，与房颤患者相似，心房ox-CaMKII表达增加。我们的建议将测试新的假设，即ox-CaMKII是一个关键的，但以前未被认识到的信号机制，它通过以下特定目的驱动有利于AF的心律失常事件。1. 确定ox-CaMKII的增加是否对Ang II对AF的促心律失常作用是必要的。计划中的实验将绘制我们提出的途径的假设“上游”元件，并测量NADPH氧化酶、MsrA活性和CaMKII Met氧化对ox-CaMKII水平和AF诱导的贡献。2. 确定ox-CaMKII是否有利于AF起始。本研究将测试ox-CaMKII“下游”的分子和细胞机制，我们假设这可以解释ox-CaMKII通过增加SR Ca2+摄取和释放、向内INCX和延迟后去极化（DADs）来增加AF诱导。3. 确定ox-CaMKII是否通过心房扩大和纤维化促进房颤底物的形成。这些实验将确定过量的ox-CaMKII是否通过促进基质金属蛋白酶（有利于心房扩大）、转化生长因子b1和心房肌细胞死亡（诱导反应性和修复性心房纤维化）的表达来促进心房重构。

DESCRIPTION (provided by applicant): Our group identified a mechanism for CaMKII activation by oxidation of paired Met residues (281/282) in the CaMKII regulatory domain, and found that angiotensin II (Ang II) infusion leads to myocardial Met 281/282 oxidation, locking oxidized CaMKII (ox- CaMKII) into a persistently active configuration. We recently found that expression of ox- CaMKII is increased in atria from AF patients compared to controls, leading us to develop and validate a mouse model of Ang II infusion and enhanced AF susceptibility to test the potential role of ROS and ox-CaMKII in AF. We found that Ang II-infused mice with pacing-induced paroxysmal AF and mice with gene targeted myocardial expression of angiotensin converting enzyme and spontaneous AF, resembled AF patients by showing increased atrial ox-CaMKII. Our proposal will test the novel hypothesis that ox-CaMKII is a critical, but previously unrecognized, signaling mechanism for driving proarrhythmic events that favor AF using the following specific aims. 1. Determine if increased ox-CaMKII is necessary for proarrhythmic effects of Ang II on AF. Experiments planned in the aim will map the hypothesized 'upstream' elements of our proposed pathway and measure the contribution of NADPH oxidase, MsrA activity and CaMKII Met oxidation on ox-CaMKII levels and AF induction. 2. Determine if ox-CaMKII favors AF initiation. Studies in this aim will test a molecular and cellular mechanism 'downstream' to ox-CaMKII that we hypothesize explains increased AF induction by ox-CaMKII through increased SR Ca2+ uptake and release, inward INCX and delayed afterdepolarizations (DADs). 3. Determine if ox-CaMKII contributes to AF substrate through atrial enlargement and fibrosis. These experiments will determine if excessive ox-CaMKII contributes to proarrhythmic atrial remodeling by promoting expression of matrix metalloproteinase (favoring atrial enlargement), transforming growth factor b1 and atrial myocyte death (inducing reactive and reparative atrial fibrosis).