Effect of Fe₃O₄-magnetic nanoparticles on acute exercise enhanced KCNQ₁ expression in mouse cardiac muscle

Lijie Liu¹, Baoan Chen², Feixiang Teng¹, Lijuan Shi¹, Nan Jing², Li Wang¹, Ningna Chen², Guohua Xia², Xiaomao Li³

¹Department of Physiology and Pharmacology, Medical School, Southeast University, Nanjing, People’s Republic of China; ²Department of Hematology, Affiliated Zhongda Hospital, Clinical Medical School, Southeast University, Nanjing, People’s Republic of China; ³Department of Physics, University of Saarland, Saarbruechen, Germany

Abstract: While the potential impact of magnetic nanoparticles (MNPs) has been widely explored in almost all medical fields, including cardiology, one question remains; that is whether MNPs interfere with cardiac physiological processes such as the expression and function of ion channels, especially in vivo. KCNQ₁ channels are richly expressed in cardiac myocytes and are critical to the repolarization of cardiac myocytes. In this study, we evaluated the effects of Fe₃O₄-magnetic nanoparticles (MNPs-Fe₃O₄) on the expression of KCNQ₁ in cardiac muscle of mice at rest and at different times following a single bout of swimming (SBS). Firstly, we demonstrated that the expression levels of KCNQ₁ channels are significantly up-regulated in mice following a SBS by means of reverse transcription polymerase chain reaction (RT-PCR) and western-blot. After treating mice with normal saline or pure MNPs-Fe₃O₄ separately, we studied the potential effect of MNPs-Fe₃O₄ on the expression profile of KCNQ₁ in mouse cardiac muscle following a SBS. A SBS increased the transcription of KCNQ₁ at 3 hours post exercise (3PE) 164% ± 24% and at 12 hours post exercise (12PE) by 159% ± 23% (P < 0.05), and up-regulated KCNQ₁ protein 161% ± 27% at 12PE (P < 0.05) in saline mice. In MNPs-Fe₃O₄ mice, KCNQ₁ mRNA increased by 151% ± 14% and 147% ± 12% at 3 and 12 PE, respectively (P < 0.05). Meanwhile, an increase of 152% ± 14% in KCNQ₁ protein was also detected at by 12PE. These results indicated that the administration of MNPs-Fe₃O₄ did not cause any apparent effects on the expression profile of KCNQ₁ in rested or exercised mice cardiac muscle. Our studies suggest a novel path of KCNQ₁ current adaptations in the heart during physical exercise and in addition provide some useful information for the biomedical application of MNPs which are imperative to advance nanomedicine.

Keywords: KCNQ₁, cardiac muscle, magnetic nanoparticles of Fe₃O₄