Anti-autophagic and anti-apoptotic effects of memantine in a SH-SY5Y cell model of Alzheimer's disease via mammalian target of rapamycin-dependent and -independent pathways

Abstract

Memantine non-competitively blocks the N-methyl-d-aspartate receptor in order to inhibit beta-amyloid (Aβ) secretion, and has been used to treat moderate-to-severe Alzheimer's disease (AD). However, the mechanisms underlying the role of memantine in the autophagy and apoptosis of neuronal cells in AD, as well as the association between neuronal autophagy and apoptosis have yet to be elucidated. The present study aimed to establish an AD cell model overexpressing the 695-amino-acid Swedish mutant of Aβ precursor protein (APP695swe) in order to observe the effects of memantine on the cell viability, autophagy and apoptosis of SH-SY5Y cells in the AD model, and to investigate the associated underlying mechanisms. A pcDNA3.1-APP695 plasmid was transfected into the SH-SY5Y cells. Reverse transcription-quantitative polymerase chain reaction and western blot analyses demonstrated that the AD cell model was successfully established. MTT assays demonstrated that memantine was able to upregulate neuronal cell survival, and acridine orange staining and flow cytometry demonstrated that memantine (5 µM) was able to inhibit neuronal autophagy and apoptosis. Following neuronal autophagy induction by rapamycin, cell apoptosis rates increased significantly. Further experiments revealed that memantine was able to upregulate the expression of signaling molecules phosphorylated (p)-phosphoinositide 3-kinase, p-Akt and p-mammalian target of rapamycin (mTOR), and also inhibited the phosphorylation of the B-cell lymphoma 2/Beclin-1 complex via mitogen-activated protein kinase 8. In conclusion, the results of the present study demonstrated that in the AD cell model, autophagy was able to promote apoptosis. Memantine exerted anti-autophagic and anti-apoptotic functions, and mTOR-dependent as well as-independent autophagic signaling pathways were involved in this process. Therefore, these results of the present study strongly supported the use of memantine as a potential therapeutic strategy for AD treatment.

Malathion increases apoptotic cell death by inducing lysosomal membrane permeabilization in N2a neuroblastoma cells: a model for neurodegeneration in Alzheimer’s disease

“… 33 However, following neuronal autophagy induction by rapamycin, the rate of apoptosis increased in another AD cell model, SH-SY5Y cells overexpressing the 695-amino-acid Swedish mutant of A β precursor protein (APP695swe), suggesting a pro-apoptotic function for autophagy. 34 In the latter APP695swe-transfected AD cell model, memantine (5 μ M) increased neuronal cell survival by inhibiting neuronal autophagy and apoptosis via both mammalian target of rapamycin-dependent and -independent autophagic signaling pathways. 34 In rotenone-treated SH-SY5Y cells, rotenone attenuated autophagic LC3 and beclin 1 levels, which were recovered by 1,25-dyhydroxyvitamin D 3 (calcitriol).…”

“… 34 In the latter APP695swe-transfected AD cell model, memantine (5 μ M) increased neuronal cell survival by inhibiting neuronal autophagy and apoptosis via both mammalian target of rapamycin-dependent and -independent autophagic signaling pathways. 34 In rotenone-treated SH-SY5Y cells, rotenone attenuated autophagic LC3 and beclin 1 levels, which were recovered by 1,25-dyhydroxyvitamin D 3 (calcitriol). 35 Rotenone-induced neurodegeneration involves initiation of autophagic flux before cells undergo apoptotic cell death.…”

Autophagy and Alzheimer’s Disease: From Molecular Mechanisms to Therapeutic Implications

“…According to recent meta-analysis it shows good tolerance and some efficacy in AD treatment ( Matsunaga et al, 2015b ). This effect may be in some extent mediated by memantine ability to influence autophagy in either mTOR-dependent or mTOR-independent manner ( Song G. et al, 2015 ).…”

Contribution of Lysosome and Sigma Receptors to Neuroprotective Effects of Memantine Against Beta-Amyloid in the SH-SY5Y Cells

“…34 In contrast, memantine has decreased autophagy in a cellular model of the AD. 15 The difference may be due to the dose of memantine and the cells used in these two experiments. However, there are limited data about the memantine effects on the lysosomal activity.…”

“… 14 The Aβ-induced over-activation of the NMDA receptors leads to the autophagy activation and neuronal apoptosis. 15 However, the contribution of lysosome inhibition to the neuroprotective effects of NMDA antagonists like memantine is elusive.…”