Protective Effects of Repetitive Transcranial Magnetic Stimulation Against Streptozotocin-Induced Alzheimer's Disease.

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation under investigation for treatment of a wide range of neurological disorders. In particular, the therapeutic application of rTMS for neurodegenerative diseases such as Alzheimer's disease (AD) is attracting attention. However, the mechanisms underlying the therapeutic efficacy of rTMS have not yet been elucidated, and few studies have systematically analyzed the stimulation parameters. In this study, we found that treatment with rTMS contributed to restoration of memory deficits by activating genes involved in synaptic plasticity and long-term memory. We evaluated changes in several intracellular signaling pathways in response to rTMS stimulation; rTMS treatment activated STAT, MAPK, Akt/p70S6K, and CREB signaling. We also systematically investigated the influence of rTMS parameters. We found an effective range of applications for rTMS and determined the optimal combination to achieve the highest efficiency. Moreover, application of rTMS inhibited the increase in cell death induced by hydrogen peroxide. These results suggest that rTMS treatment exerts a neuroprotective effect on cellular damage induced by oxidative stress, which plays an important role in the pathogenesis of neurological disorders. rTMS treatment attenuated streptozotocin (STZ)-mediated cell death and AD-like pathology in neuronal cells. In an animal model of sporadic AD caused by intracerebroventricular STZ injection, rTMS application improved cognitive decline and showed neuroprotective effects on hippocampal histology. Overall, this study will help in the design of stimulation protocols for rTMS application and presents a novel mechanism that may explain the therapeutic effects of rTMS in neurodegenerative diseases, including AD.

Synergistic apoptosis by combination of metformin and an O-GlcNAcylation inhibitor in colon cancer cells.

BACKGROUND: Although autophagy is an important mediator of metformin antitumor activity, the role of metformin in the crosstalk between autophagy and apoptosis remains unclear. The aim was to confirm the anticancer effect by inducing apoptosis by co-treatment with metformin and OSMI-1, an inhibitor of O-GlcNAcylation, in colon cancer cells. METHODS: Cell viability was measured by MTT in colon cancer cell lines HCT116 and SW620 cells. Co-treatment with metformin and OSMI-1 induced autophagy and apoptosis, which was analyzed using western blot, reverse transcription-polymerase chain reaction (RT-PCR) analysis, and fluorescence-activated cell sorting (FACS). Combined treatment with metformin and OSMI-1 synergistically inhibit the growth of HCT116 was confirmed by xenograft tumors. RESULTS: We showed that metformin inhibited mammalian target of rapamycin (mTOR) activity by inducing high levels of C/EBP homologous protein (CHOP) expression through endoplasmic reticulum (ER) stress and activating adenosine monophosphate-activated protein kinase (AMPK) to induce autophagy in HCT116 cells. Interestingly, metformin increased O-GlcNAcylation and glutamine:fructose-6-phosphate amidotransferase (GFAT) levels in HCT116 cells. Thus, metformin also blocks autophagy by enhancing O-GlcNAcylation, whereas OSMI-1 increases autophagy via ER stress. In contrast, combined metformin and OSMI-1 treatment resulted in continuous induction of autophagy and disruption of O-GlcNAcylation homeostasis, resulting in excessive autophagic flux, which synergistically induced apoptosis. Downregulation of Bcl2 promoted apoptosis via the activation of c-Jun N-terminal kinase (JNK) and CHOP overexpression, synergistically inducing apoptosis. The activation of IRE1α/JNK signaling by OSMI-1 and PERK/CHOP signaling by metformin combined to inhibit Bcl2 activity, ultimately leading to the upregulation of cytochrome c release and activation of caspase-3. CONCLUSIONS: In conclusion, combinatorial treatment of HCT116 cells with metformin and OSMI-1 resulted in more synergistic apoptosis being induced by enhancement of signal activation through ER stress-induced signaling rather than the cell protective autophagy function. These results in HCT116 cells were also confirmed in xenograft models, suggesting that this combination strategy could be utilized for colon cancer treatment.