Cell experiment:

The SH-SY5Y human neuroblastoma cell line is used in this study. The cells are routinely cultured in a mixture of Dulbecco's modified Eagle's medium (DMEM)/Ham's F12 containing 10% fetal bovine serum, 2 mM L-glutamine, antibiotic and antimycotic solution under a humidified atmosphere of 5% CO2-95% air at 37℃. The SH-SY5Y are plated in 96-well plates at 1×105 cells per well for the treatment with Aβ25-35 and the BAY 73-6691. Before experiments, freshly prepared Aβ25-35 peptide at 20 μM is added to the cells with or without exposure to different concentrations (50, 100, 150 and 200 μg/mL) of BAY 73-6691[1].

Animal experiment:

Male ICR mice (weighing 25 to 30 g) are used to induce the animal model of Alzheimer's disease (AD). All mice are housed in a temperature- and humidity-controlled room with a constant light-dark cycle (12 h/12 h) and are maintained on ad libitum food and water. BAY 73-6691 at different doses (0.3, 1 and 3 mg/kg) is consecutively injected (i.p.) once daily at 7:30 A.M on days 1 to 10 after injection of Aβ25-35 (day 0). Mice are divided into six groups: (I) sham, (II) Aβ, (III) Aβ+0.3 mg/kg BAY 73-6691, (IV) Aβ+1 mg/kg BAY 73-6691, (V) Aβ+3 mg/kg BAY 73-6691 and (VI) 3 mg/kg BAY 73-6691[1].

BAY 73-6691 is a potent, selective brain penetrant PDE9A inhibitor.

The BAY 73-6691 dose-dependently alleviates cell viability loss due to Aβ25-35 treatment. It is found that when SH-SY5Y cells are cultured by Aβ25-35, a high degree of cell apoptosis is observed, while additional stimulation with BAY 73-6691 causes attenuation of cell apoptosis. BAY 73-6691 dose-dependently attenuates oxidative stress induced by Aβ25-35, and BAY 73-6691 at 200 μg/mL almost neutralizes Aβ25-35-induced oxidative damage. The BAY 73-6691 attenuates Aβ25-35-induced increase of apoptosis cells[1].

BAY 73-6691 dose-dependently improves the acquisition performance in the Aβ25-35-injected mice on days 7 to 10 (day 7, F(5,54)=65.153; day 8, F(5,54)=62.340; day 9, F(5,54)=37.529; day 10, F(5,54)=38.624; P<0.001). BAY 73-6691 at 3 mg/kg can almost completely abolish the prolongation of escape-latency on days 9 to 10. BAY 73-6691 dose-dependently elevates the Aβ25-35-induced decrease of the dwell time on the 10th day post Aβ25-35 injection (day 10, F(5,54)=27.360, P<0.001). Results reveal that the Aβ25-35 injection and BAY 73-6691 treatment cause no influence on the swimming speed. Treatment with BAY 73-6691 does not cause detectable alteration of spatial memory in sham mice. BAY 73-6691 alleviates Aβ25-35-induced abnormalities of the above indices. The BAY 73-6691 causes no influence on the four indices mentioned above in sham mice. The BAY 73-6691 has no significant effect on the apoptosis of hippocampal neurons in sham mice[1].

[1]. Li J, et al. Protective effects of BAY 73-6691, a selective inhibitor of phosphodiesterase 9, on amyloid-β peptides-induced oxidative stress in in-vivo and in-vitro models of Alzheimer's disease. Brain Res. 2016 Jul 1;1642:327-335.