VanWinkle W B, Snuggs M, Miller J C, Buja L M
Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston 77030.
Cell Motil Cytoskeleton. 1994;28(2):119-34. doi: 10.1002/cm.970280204.
Damage to the cardiac myocyte sarcolemma following any of several pathological insults such as ischemia (anoxia) alone or followed by reperfusion (reoxygenation), is most apparent as progressive sarcolemmal blebbing, an event attributed by many investigators to a disruption in the underlying cytoskeletal scaffolding. Scanning electron microscopic observation of tissue cultured rat neonatal cardiomyocytes indicates that exposure of these cells to the toxic aldehyde 4-hydroxynonenal (4-HNE), a free radical-induced, lipid peroxidation product, results in the appearance of sarcolemmal blebs, whose ultimate rupture leads to cell death. Indirect immunofluorescent localization of a number of cytoskeletal components following exposure to 4-HNE reveals damage to several, but not all, key cytoskeletal elements, most notably microtubules, vinculin-containing costameres, and intermediate filaments. The exact mechanism underlying the selective disruption of these proteins cannot be ascertained at this time. Colocalization of actin indicated that whereas elements of the cytoskeleton were disrupted by increasing length of exposure to 4-HNE, neither the striated appearance of the myofibrils nor the lateral register of neighboring myofibrils was altered. Monitoring systolic and diastolic levels of intracellular calcium ([Ca2+]i) indicated that increases in [Ca2+]i occurred after considerable cytoskeletal changes had already taken place, suggesting that damage to the cytoskeleton, at least in early phases of exposure to 4-HNE, does not involve Ca(2+)-dependent proteases. However, 4-HNE-induced cytoskeletal alterations coincide with the appearance of, and therefore suggest linkage to, sarcolemmal blebs in cardiac myocytes. Although free radicals produced by reperfusion or reoxygenation of ischemic tissue have been implicated in cellular damage, these studies represent the first evidence linking cardiomyocyte sarcolemmal damage to cytoskeletal disruption produced by a free radical product.
在诸如单独缺血（缺氧）或随后再灌注（复氧）等几种病理损伤中的任何一种之后，心肌细胞肌膜的损伤最明显地表现为进行性肌膜起泡，许多研究者将此现象归因于潜在细胞骨架支架的破坏。对组织培养的新生大鼠心肌细胞进行扫描电子显微镜观察表明，将这些细胞暴露于有毒醛类4-羟基壬烯醛（4-HNE），一种自由基诱导的脂质过氧化产物，会导致肌膜泡的出现，其最终破裂会导致细胞死亡。在暴露于4-HNE后，对一些细胞骨架成分进行间接免疫荧光定位显示，几种但并非所有关键细胞骨架元件受到损伤，最显著的是微管、含纽蛋白的肌节和中间丝。目前尚无法确定这些蛋白质选择性破坏的具体机制。肌动蛋白的共定位表明，虽然细胞骨架元件因暴露于4-HNE的时间延长而受到破坏，但肌原纤维的条纹外观和相邻肌原纤维的横向排列均未改变。监测细胞内钙（[Ca2+]i）的收缩期和舒张期水平表明，[Ca2+]i的升高发生在相当多的细胞骨架变化已经发生之后，这表明细胞骨架的损伤，至少在暴露于4-HNE的早期阶段，不涉及钙依赖性蛋白酶。然而，4-HNE诱导的细胞骨架改变与心肌细胞中肌膜泡的出现同时发生，因此表明两者存在联系。尽管缺血组织再灌注或复氧产生的自由基与细胞损伤有关，但这些研究首次证明了心肌细胞肌膜损伤与自由基产物导致的细胞骨架破坏之间的联系。
