Nox4 敲除不能预防心肌梗死后早期小鼠膈肌萎缩、收缩功能障碍或线粒体适应不良。
Nox4 Knockout Does Not Prevent Diaphragm Atrophy, Contractile Dysfunction, or Mitochondrial Maladaptation in the Early Phase Post-Myocardial Infarction in Mice.
机构信息
Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, USA.
Institute for Cardiovascular Physiology, Goethe University, Frankfurt, Germany.
出版信息
Cell Physiol Biochem. 2021 Aug 20;55(4):489-504. doi: 10.33594/000000400.
BACKGROUND/AIMS: Diaphragm dysfunction with increased reactive oxygen species (ROS) occurs within 72 hrs post-myocardial infarction (MI) in mice and may contribute to loss of inspiratory maximal pressure and endurance in patients.
METHODS
We used wild-type (WT) and whole-body Nox4 knockout (Nox4KO) mice to measure diaphragm bundle force in vitro with a force transducer, mitochondrial respiration in isolated fiber bundles with an O sensor, mitochondrial ROS by fluorescence, mRNA (RT-PCR) and protein (immunoblot), and fiber size by histology 72 hrs post-MI.
RESULTS
MI decreased diaphragm fiber cross-sectional area (CSA) (~15%, p = 0.015) and maximal specific force (10%, p = 0.005), and increased actin carbonylation (5-10%, p = 0.007) in both WT and Nox4KO. Interestingly, MI did not affect diaphragm mRNA abundance of MAFbx/atrogin-1 and MuRF-1 but Nox4KO decreased it by 20-50% (p < 0.01). Regarding the mitochondria, MI and Nox4KO decreased the protein abundance of citrate synthase and subunits of electron transport system (ETS) complexes and increased mitochondrial O flux (JO) and HO emission (JHO) normalized to citrate synthase. Mitochondrial electron leak (JHO/JO) in the presence of ADP was lower in Nox4KO and not changed by MI.
CONCLUSION
Our study shows that the early phase post-MI causes diaphragm atrophy, contractile dysfunction, sarcomeric actin oxidation, and decreases citrate synthase and subunits of mitochondrial ETS complexes. These factors are potential causes of loss of inspiratory muscle strength and endurance in patients, which likely contribute to the pathophysiology in the early phase post-MI. Whole-body Nox4KO did not prevent the diaphragm abnormalities induced 72 hrs post-MI, suggesting that systemic pharmacological inhibition of Nox4 will not benefit patients in the early phase post-MI.
背景/目的：在心肌梗死（MI）后 72 小时内，小鼠的膈肌功能障碍伴有活性氧（ROS）增加，这可能导致患者吸气最大压力和耐力丧失。
方法
我们使用野生型（WT）和全身 Nox4 敲除（Nox4KO）小鼠，通过力传感器测量体外膈肌束力，通过 O 传感器测量分离纤维束的线粒体呼吸，通过荧光测量线粒体 ROS，通过 RT-PCR 和免疫印迹测量 mRNA 和蛋白质，通过组织学测量纤维大小。
结果
MI 降低了膈肌纤维横截面积（CSA）（~15%，p = 0.015）和最大比力（10%，p = 0.005），并增加了肌球蛋白重链（actin）的羰基化（5-10%，p = 0.007）在 WT 和 Nox4KO 中均如此。有趣的是，MI 不影响膈肌肌萎缩蛋白/atrogin-1 和 MuRF-1 的 mRNA 丰度，但 Nox4KO 使其降低了 20-50%（p < 0.01）。关于线粒体，MI 和 Nox4KO 降低了柠檬酸合酶和电子传递系统（ETS）复合物亚基的蛋白丰度，并增加了线粒体 O 通量（JO）和 HO 发射（JHO）与柠檬酸合酶的归一化比值。ADP 存在时，Nox4KO 中的线粒体电子漏（JHO/JO）较低，而 MI 不改变其值。
结论
我们的研究表明，MI 后早期阶段导致膈肌萎缩、收缩功能障碍、肌球蛋白重链氧化，并降低柠檬酸合酶和线粒体 ETS 复合物亚基的水平。这些因素可能是患者吸气肌力量和耐力丧失的潜在原因，这可能导致 MI 后早期阶段的病理生理学变化。全身 Nox4KO 并不能预防 MI 后 72 小时引起的膈肌异常，这表明全身抑制 Nox4 的药理学方法不会使 MI 后早期阶段的患者受益。
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