TRPM2 Channel Inhibition Attenuates Amyloid β42-Induced Apoptosis and Oxidative Stress in the Hippocampus of Mice.

Abstract

Alzheimer's disease (AD) is characterized by the increase of hippocampal Ca2+ influx-induced apoptosis and mitochondrial oxidative stress (OS). The OS is a stimulator of TRPM2, although N-(p-amylcinnamoyl)anthranilic acid (ACA), 2-aminoethyl diphenylborinate (2/APB), and glutathione (GSH) are non-specific antagonists of TRPM2. In the present study, we investigated the protective roles of GSH and TRPM2 antagonist treatments on the amyloid β42 peptide (Aβ)-caused oxidative neurotoxicity and apoptosis in the hippocampus of mice with AD model. After the isolation of hippocampal neurons from the newborn mice, they were divided into five incubation groups as follows: control, ACA, Aβ, Aβ+ACA, and Aβ+GSH. The levels of apoptosis, hippocampus death, cytosolic ROS, cytosolic Zn2+, mitochondrial ROS, caspase-3, caspase-9, lipid peroxidation, and cytosolic Ca2+ were increased in the primary hippocampus cultures by treatments of Aβ, although their levels were decreased in the neurons by the treatments of GSH, PARP-1 inhibitors (PJ34 and DPQ), and TRPM2 blockers (ACA and 2/APB). The Aβ-induced decreases of cell viability, cytosolic GSH, reduced GSH, and GSH peroxidase levels were also increased in the groups of Aβ+ACA and Aβ+GSH by the treatments of ACA and GSH. However, the Aβ-caused changes were not observed in the hippocampus of TRPM2-knockout mice. In conclusion, the present data demonstrate that maintaining the activation of TRPM2 is not only important for the quenching OS and neurotoxicity in the hippocampal neurons of mice with experimental AD but also equally critical to the modulation of Aβ-induced apoptosis. The possible positive effects of GSH and TRPM2 antagonist treatments on the amyloid-beta (Aβ)-induced oxidative toxicity in the hippocampus of mice. The ADP-ribose (ADPR) is produced via the stimulation of PARP-1 in the nucleus of neurons. The NUT9 in the C terminus of TRPM2 channel acts as a key role for the activation of TRPM2. The antagonists of TRPM2 are glutathione (GSH), ACA, and 2/APB in the hippocampus. The Aβ incubation-mediated TRPM2 stimulation increases the concentration of cytosolic-free Ca2+ and Zn2+ in the hippocampus. In turn, the increased concentration causes the increase of mitochondrial membrane potential (ΔΨm), which causes the excessive generations of mitochondria ROS and the decrease of cytosolic GSH and GSH peroxidase (GSH-Px). The ROS production and GSH depletion are two main causes in the neurobiology of Alzheimer's disease. However, the effect of Aβ was not shown in the hippocampus of TRPM2-knockout mice. The Aβ and TRPM2 stimulation-caused overload Ca2+ entry cause apoptosis and cell death via the activations of caspase-3 (Casp/3) and caspase-9 (Casp/9) in the hippocampus. The actions of Aβ-induced oxidative toxicity were modulated in the primary hippocampus by the incubations of ACA, GSH, 2/APB, and PARP-1 inhibitors (PJ34 and DPQ). (↑) Increase. (↓) Decrease.