Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) are central microdomains of the ER that interact with mitochondria. MAMs provide an essential platform for crosstalk between the ER and mitochondria and play a critical role in the local transfer of calcium (Ca2+) to maintain cellular functions. Despite the potential uses of superparamagnetic iron oxide nanoparticles (SPIO-NPs) in biomedical applications, the hepatotoxicity of these nanoparticles (NPs) is not well characterized and little is known about the involvement of MAMs in ER-mitochondria crosstalk. We studied SPIO-NPs-associated hepatotoxicity in vitro and in vivo. In vitro, human normal hepatic L02 cells were exposed to SPIO-NPs (2.5, 7.5, and 12.5 μg/mL) for 6 h and SPIO-NPs (12.5 μg/mL) was found to induce apoptosis. In vivo, SPIO-NPs induced liver injury when mice were intravenously injected with 20 mg/kg body weight SPIO-NPs for 24 h. Based on both in vitro and in vivo studies, we found that the structure and Ca2+ transport function of MAMs were perturbated and an accumulation of cyclooxygenase-2 (COX-2) in MAMs fractions was increased upon treatment of SPIO-NPs. The interaction between COX-2 and the components of MAMs, in terms of IP3R-GRP75-VDAC1 complex, was also revealed. Furthermore, the role of COX-2 in SPIO-NPs-associated hepatotoxicity was investigated by modifying the expression of COX-2. We demonstrated that COX-2 increases the structural and functional ER-mitochondria coupling and enhances the efficacy of ER-mitochondria Ca2+ transfer through the MAMs, thus sensitizing hepatocytes to a mitochondrial Ca2+ overload-dependent apoptosis. Taken together, our findings link SPIO-NPs-triggered hepatotoxicity with ER-mitochondria Ca2+ crosstalk which is mediated by COX-2 and provide mechanistic insight into the impact of interorganelle ER-mitochondria communication on hepatic nanotoxicity.

中文翻译：

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环氧合酶2调节ER-线粒体串扰以介导超顺磁性氧化铁纳米颗粒诱导的肝毒性：一项体外和体内研究。

线粒体相关的内质网（ERM）膜（ERM）是与线粒体相互作用的ER的中央微区。MAM为内质网和线粒体之间的串扰提供了必不可少的平台，并在钙（Ca2 +）的局部转移中发挥关键作用，以维持细胞功能。尽管超顺磁性氧化铁纳米粒子（SPIO-NPs）在生物医学应用中有潜在用途，但这些纳米粒子（NPs）的肝毒性尚未得到很好的表征，而关于MAM参与ER-线粒体串扰的知之甚少。我们在体外和体内研究了SPIO-NPs相关的肝毒性。在体外，将人类正常肝L02细胞暴露于SPIO-NPs（2.5、7.5和12.5μg/ mL）6 h，发现SPIO-NPs（12.5μg/ mL）可诱导细胞凋亡。体内，当小鼠静脉注射20 mg / kg体重的SPIO-NP达24小时时，SPIO-NPs会引起肝损伤。基于体外和体内研究，我们发现，经SPIO-NP处理后，MAMs的结构和Ca2 +转运功能受到干扰，并且MAMs组分中环氧合酶2（COX-2）的积累增加。还揭示了COX-2和MAM组件之间的相互作用，即IP3R-GRP75-VDAC1复合物。此外，通过修饰COX-2的表达，研究了COX-2在SPIO-NPs相关的肝毒性中的作用。我们证明，COX-2增加了结构和功能的ER-线粒体偶联，并增强了通过MAM传递ER-线粒体Ca2 +的功效，从而使肝细胞对线粒体Ca2 +超负荷依赖性细胞凋亡敏感。在一起