Oxidized CaMKII in Atrial Fibrillation

描述(申请人提供)：我们的团队发现了一种通过氧化CaMKII调节域中成对的Met残基(281/282)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，锁定氧化的CaMKII(OX-CaMKII)进入持续活性构型。我们最近发现房颤患者的心房中OX-CaMKII的表达比对照组增加，这使得我们建立并验证了Ang II注射的小鼠模型，并增强了房颤的敏感性，以测试ROS和OX-CaMKII在房颤中的潜在作用。我们发现，血管紧张素转换酶基因和自发性房颤基因靶向表达血管紧张素转换酶基因的起搏诱发阵发性房颤小鼠与房颤患者相似，表现为心房OX-CaMKII增加。我们的建议将检验这一新的假设，即OX-CaMKII是一种关键的、但之前未被认识到的信号机制，用于驱动有利于房颤的心律失常事件，使用以下特定的目的。1.确定血管紧张素转换酶II对房颤的致心律失常作用是否需要增加OX-CaMKII。我们计划进行的实验将定位我们所提出的途径的假想的“上游”元件，并测量NADPH氧化酶、MSRA活性和CaMKII Met氧化对OX-CaMKII水平和房颤诱导的贡献。2.确定OX-CaMKII是否有利于房颤的发生。这一目标的研究将测试OX-CaMKII“下游”的分子和细胞机制，我们假设该机制可以解释OX-CaMKII通过增加SR钙摄取和释放、内向INCX和延迟后除极(DADS)来增加房颤的诱导。3.确定OX-CaMKII是否通过心房增大和纤维化参与房颤底物的形成。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)的表达而促进心律失常前房性重构。

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).