Cyclooxygenase-2 modulates ER-mitochondria crosstalk to mediate superparamagnetic iron oxide nanoparticles induced hepatotoxicity: an in vitro and in vivo study

Abstract

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.

Keywords:

• Superparamagnetic iron oxide nanoparticles
• cyclooxygenase-2
• mitochondria-associated endoplasmic reticulum membranes
• interorganelle Ca²⁺ transfer
• hepatotoxicity

Disclosure statement

All authors declare that they have no conflicts of interest related to this study.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Nos. 81773465, 81573181, 81874272, and 81472997), the Natural Science Foundation of Fujian Province of China (Nos. 2014J01372 and 2015J01344), the Regional Demonstration of Marine Economy Innovative Development Project (No. 16PYY007SF17), and the Scientific Research Foundation of State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics (No. 2017ZY003).