1MeTIQ Provides Protection Against Aβ-Induced Reduction of Surface Expression of Synaptic Proteins and Inhibits H2O2-Induced Oxidative Stress in Primary Hippocampal Neurons

Alzheimer's disease (AD) is associated with increased brain levels of beta-amyloid (A beta) peptides, which readily self-aggregate into fibrils and oligomers that have particularly deleterious properties toward synapses of excitatory glutamatergic neurons. Here, we examined the neuroprotective effects of 1-methyl-1,2,3,4,-tetrahydroisoquinoline (1MeTIQ) against A beta-induced loss of synaptic proteins in cultured primary hippocampal neurons. Exposure of mature primary hippocampal neurons to 10 mu M synthetic A beta 1-40 over 72 h resulted in similar to 60 % reduction in the surface expression of NR1 subunit of the NMDA receptor (NMDAR), PSD-95, and synaptophysin, without causing neuronal death. Concomitant treatment with 500 mu M of 1MeTIQ, a low-affinity NMDAR antagonist significantly ameliorated the loss of synaptic protein markers. The neuroprotective properties of 1MeTIQ were compared with those of MK-801, which at 0.5 mu M concentration also prevented A beta 1-40-induced loss of synaptic proteins in primary neuronal cultures. Furthermore, we provide novel evidence demonstrating effectiveness of 1MeTIQ in reducing the level of reactive oxygen species (ROS) in primary neuronal culture system. As oxidative stress contributes importantly to neurodegeneration in AD, 1MeTIQ may provide a dual neuroproctective effect in AD both as a NMDARs antagonist and ROS formation inhibitor. 1MeTIQ occurs endogenously at low concentrations in the brain and its synthetic form readily penetrates the blood-brain barrier after the systemic administration. Our results highlight a possibility of the application of 1MeTIQ as a neuroprotective agent in AD-related neurodegeneration.