AbstractBackgroundNitric oxide/cGMP/CREB signaling is critical for learning and memory processes and is disturbed by Abeta amyoid and in Alzheimer’s disease. AR1001 is an inhibitor of phosphodiesterase (PDE)‐5, which degrades specifically cGMP, thus having a potential to reverse AD pathology.MethodFor the in vivo study, AR1001 was intraperitoneally administered (4 mg/kg/day) to APP‐C105 mice for 4 weeks. Then after behavioral tests (Morris‐water maze and passive avoidance tests) were done, hippocampal levels of Abeta1‐42 and p‐Tau (S199/202) were determined. In the in vitro study using human neuroblastoma SH‐SY5Y cells and mouse hippocampal HT‐22 cells, the effects of AR1001 on Abeta1‐42‐induced cytotoxicity and intracellular signaling were examined.ResultAR1001 markedly improved cognitive functions in both Morris‐water maze and passive avoidance tests and reduced hippocampal Abeta1‐42 and p‐Tau levels in the APP‐C105 mice. In the in vitro experiments, AR1001 inhibited Abeta1‐42‐induced cell death, mitochondrial membrane potential derangement, and apoptotic markers (cleaved caspase‐3 and cleaved PPAR) concentration‐dependently. AR1001 reversed Abeta1‐42‐induced decrease in phosphorylated CREB (p‐CREB), and NGF/BDNF expression. Further, AR1001 blocked Abeta1‐42‐induced pSer9‐GSK3beta decrease and p25/p35 increase. Interestingly, compared with sildenafil, vardenafil and tadalafil, AR1001 was more effective in inhibiting glucocorticoid receptor (GR) dimerization and Wnt antagonist Dickkopf‐1 (Dkk‐1) expression, and in enhancing Wnt3a expression.ConclusionAR1001 had protective effects both in vivo and in vitro models of AD. Furthermore, AR1001 showed more pronounced activity in the modulation of GR and Wnt signaling among the various PDE‐5 inhibitors. It is suggested that the multimodal activity of AR1001 contributes to the therapeutic effects of AR1001 observed in the phase 2 clinical trial in AD patients (NCT03625622).