Nanotoxicology is an increasingly relevant field and sound paradigms on how inhaled nanoparticles (NPs) interact with organs at the cellular level, causing harmful conditions, have yet to be established. This is particularly true in the case of the cardiovascular system, where experimental and clinical evidence shows morphological and functional damage associated with NP exposure. Giving the increasing interest on cobalt oxide (Co3O4) NPs applications in industrial and bio-medical fields, a detailed knowledge of the involved toxicological effects is required, in view of assessing health risk for subjects/workers daily exposed to nanomaterials. Specifically, it is of interest to evaluate whether NPs enter cardiac cells and interact with cell function. We addressed this issue by investigating the effect of acute exposure to Co3O4-NPs on excitation-contraction coupling in freshly isolated rat ventricular myocytes. Patch clamp analysis showed instability of resting membrane potential, decrease in membrane electrical capacitance, and dose-dependent decrease in action potential duration in cardiomyocytes acutely exposed to Co3O4-NPs. Motion detection and intracellular calcium fluorescence highlighted a parallel impairment of cell contractility in comparison with controls. Specifically, NP-treated cardiomyocytes exhibited a dose-dependent decrease in the fraction of shortening and in the maximal rate of shortening and re-lengthening, as well as a less efficient cytosolic calcium clearing and an increased tendency to develop spontaneous twitches. In addition, treatment with Co3O4-NPs strongly increased ROS accumulation and induced nuclear DNA damage in a dose dependent manner. Finally, transmission electron microscopy analysis demonstrated that acute exposure did lead to cellular internalization of NPs. Taken together, our observations indicate that Co3O4-NPs alter cardiomyocyte electromechanical efficiency and intracellular calcium handling, and induce ROS production resulting in oxidative stress that can be related to DNA damage and adverse effects on cardiomyocyte functionality.

中文翻译：

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氧化钴纳米颗粒在大鼠心室肌细胞中诱导氧化应激并改变机电功能

纳米毒理学是一个日益相关的领域，关于吸入纳米粒子 (NP) 如何在细胞水平上与器官相互作用、导致有害条件的合理范式尚未建立。在心血管系统的情况下尤其如此，其中实验和临床证据显示与 NP 暴露相关的形态和功能损伤。鉴于对氧化钴 (Co3O4) NPs 在工业和生物医学领域的应用越来越感兴趣，需要详细了解所涉及的毒理学效应，以评估每天接触纳米材料的受试者/工人的健康风险。具体来说，评估 NPs 是否进入心脏细胞并与细胞功能相互作用是很有趣的。我们通过研究急性暴露于 Co3O4-NPs 对新鲜分离的大鼠心室肌细胞兴奋-收缩耦合的影响来解决这个问题。膜片钳分析表明，急性暴露于 Co3O4-NPs 的心肌细胞的静息膜电位不稳定，膜电容降低，动作电位持续时间呈剂量依赖性降低。与对照相比，运动检测和细胞内钙荧光突出了细胞收缩性的平行损伤。具体而言，NP 处理的心肌细胞在缩短的分数和缩短和再延长的最大速率方面表现出剂量依赖性降低，以及细胞溶质钙清除效率较低和发生自发性抽搐的趋势增加。此外，用 Co3O4-NPs 处理强烈增加 ROS 积累并以剂量依赖性方式诱导核 DNA 损伤。最后，透射电子显微镜分析表明，急性暴露确实导致 NPs 的细胞内化。总之，我们的观察表明 Co3O4-NPs 改变心肌细胞机电效率和细胞内钙处理，并诱导 ROS 产生，导致氧化应激，这可能与 DNA 损伤和对心肌细胞功能的不利影响有关。