Abstract
AimRepetitive transcranial magnetic stimulation (rTMS) is a non-invasive and safe technique for treatment of central and peripheral nerve injury. In recent years, this technique has been widely used in clinic, and an increasing number of studies have reported its mechanisms. In this study, we investigated the mechanisms of rTMS-mediated autophagy flux in human bone mesenchymal stromal cells (BMSCs).MethodsA frequency of 50 Hz was employed. Cells were divided into five groups: (1) normal, (2) sham, (3) 0.5 T, (4) 1.0 T, and (5) 1.5 T. Cells were stimulated for 20 min/day. The levels of p62, LC3-II/I, phosphorylated extracellular signal-regulated kinase (p-ERK), ERK, phosphorylated-AKT (p-AKT), AKT, phosphorylated mammalian target of rapamycin (p-mTOR), mTOR, phosphorylated protein kinase A (p-PKA), PKA, phosphorylated epidermal growth factor receptor (p-EGFR), EGFR, Nanog, Oct4, Sox2, and NMDA receptor (NMDAR1) were investigated by western blotting. Intracellular calcium (Ca2+) levels were quantified by flow cytometry. p62 and LC3 expression was also assessed by immunofluorescence analysis.ResultsIn the 0.5 T group, rTMS increased the expression of LC3-II/I, p-ERK/ERK, and NMDAR1 and decreased the levels of p62 and p-mTOR/mTOR than in the normal group. The ratio of p-AKT/AKT, p-PKA/PKA, and p-EGFR/EGFR and the expression of Nanog, Oct4, and Sox2 remained unchanged. Immunofluorescence analysis revealed colocalization of p62 with LC3 puncta, and flow cytometry analysis displayed that Ca2+ levels were elevated. However, in the 1.0 and 1.5 T groups, no changes in the expression of these autophagy markers were observed.ConclusionIn the 0.5 T group, high-frequency rTMS can induce autophagy through NMDAR–Ca2+–ERK–mTOR signaling in BMSCs. In the 1.0 and 1.5 T groups, autophagy is not activated.
Highlights
Repetitive transcranial magnetic stimulation is widely used for the treatment of central nervous system (CNS) diseases and is based on the regulation of brain plasticity and electromagnetic induction (Matheson et al, 2016)
We investigated the mechanisms of Repetitive transcranial magnetic stimulation (rTMS)-mediated autophagy flux in human bone mesenchymal stromal cells (BMSCs)
In the 0.5 T group, rTMS increased the expression of LC3-II/I, phosphorylated extracellular signal-regulated kinase (p-ERK)/ERK, and NMDAR1 and decreased the levels of p62 and phosphorylated mammalian target of rapamycin (p-mTOR)/mTOR than in the normal group
Summary
Repetitive transcranial magnetic stimulation (rTMS) is widely used for the treatment of central nervous system (CNS) diseases and is based on the regulation of brain plasticity and electromagnetic induction (Matheson et al, 2016). The effects of rTMS are determined by various stimulatory parameters including stimulus intensity, stimulus frequency, and stimulus patterns. High-frequency rTMS (≥5 Hz) can facilitate cortical excitability, whereas lowfrequency rTMS (≤1 Hz) reduces cortical excitability (Shu et al, 2018). Previous studies found that rTMS could treat CNS disease, such as Parkinson’s disease and Alzheimer’s disease (Rabey and Dobronevsky, 2016; Yang et al, 2018). RTMS can intervene in various electrostatic processes, such as protein– protein interactions (To et al, 2018). The molecular mechanisms of these effects are not completely understood
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