Effects of homocysteine and memantine on oxidative stress related TRP cation channels in in-vitro model of Alzheimer's disease.

Memantine (MEM) has been used to treat patients with Alzheimer' disease though inhibition of reactive oxygen species (ROS), Ca2+ entry and glutamate receptor. The Ca2+ permeable TRPA1, TRPM2 and TRPV1 channels are activated in the hippocampus by ROS, and antioxidant MEM as a potent TRPA1, TRPM2 and TRPV1 channel antagonist may reduce Aβ-induced oxidative stress and apoptosis in the neurons. In the current study, we investigated the neuroprotective properties of MEM in Aβ-induced hippocampal neuron cultures. Freshly isolated hippocampal neurons of mice were divided into eight groups as control, Aβ, Hcy, MEM, Aβ + Hcy, Aβ + Hcy + MEM, Aβ + MEM and Hcy + MEM. The neurons were exposed to incubated with Aβ (20 µM for 24 h), Hcy (250 µM for 30 min) and MEM (10 µM for 24 h). TRPA1, TRPM2 and TRPV1 of the eight groups were further stimulated by cinnamaldehyde, cumene hydyroperoxide and capsaicin, respectively although they were further inhibited by AP-18, N-(p-Amylcinnamoyl) anthranilic acid (ACA) and capsazepine (CPZ). The [Ca2+] concentration, apoptosis, caspase 3, caspase 9 activations, mitochondrial membrane depolarization and intracellular ROS production values in the neurons were higher in Aβ and Hcy groups than in control although they were lower in the MEM group than in Aβ and Hcy groups. The values were further decreased by MEM + AP-18, MEM + CPZ and MEM + ACA treatments as compared to MEM only. Aβ and Hcy-induced decrease of cell viability level was increased by MEM treatment although Aβ and Hcy-induced increase of caspase 3, caspase 9, PARP1, TRPA1, TRPM2 and TRPV1 expression levels were decreased by MEM treatments. In conclusion, TRPA1, TRPM2 and TRPV1 channels are involved in Aβ and Hcy-induced neuronal death, and modulation of the activity of these channels by MEM treatment may account for their neuroprotective activity against apoptosis, excessive ROS production, and Ca2+ entry.