AR1001 ameliorates Alzheimer’s disease pathology and symptoms by multi‐mechanisms

Abstract

Background The accumulation of amyloid‐b (Ab) in the brain is the primary pathological hallmark of Alzheimer’s disease (AD). Aggregated Ab is associated with cytotoxicity by a variety of mechanisms leading to neuronal apoptosis and synaptic impairments. Here, we present experimental evidence showing that AR1001, a highly selective and potent phosphodiesterase 5 (PDE5) inhibitor, acts as a polypharmacological agent for the treatment of AD by promoting neuronal cell survival and inhibiting Ab accumulation. Method The in vitro toxic effects of Ab were examined using the human neuroblastoma derived SH‐SY5Y cell line and mouse hippocampal neuronal HT‐22 cell line. Cell‐free Thioflavin T (ThT) fluorescence assay and SDS‐PAGE with PICUP (Photo‐Induced Cross‐Linking of Unmodified Proteins) of Ab plaques were employed to test inhibition of Ab aggregate formation and reduction of preformed oligomers and fibrils. To identify transcription factors responsible for inhibitory effects of AR1001 on Amyloid Precursor Protein (APP) / b‐site APP cleaving enzyme 1 (BACE1) expression, the Transcription Factor Profiling Plate Array was used to monitor the activation/inhibition of various transcription factors. 5XFAD transgenic mice were used to evaluate Ab42 induced neurodegeneration and amyloid plaque formation. NSE/APP‐C105 transgenic mice were used to test spatial and learning memory in the Morris water maze test and the passive avoidance test. Result AR1001 markedly increased cGMP levels and activated cGMP/cGMP‐dependent protein kinase/cAMP responsive element‐binding protein (CREB) cascade in Ab‐treated SH‐SY5Y cells, promoting neuronal cell survival. In Ab‐treated HT‐22 cells, downregulation of Glucocorticoid Receptor (GR) transcriptional activity by AR1001 was responsible for reduced expression of APP, BACE1 and Dickkopf‐1 (Dkk1). In addition, AR1001 disrupted pre‐formed Ab42 fibrils in vitro. Interestingly, AR1001 reduced deposition of Aβ plaques in 5XFAD transgenic mouse brain by activating the autophagic process. Finally, AR1001 significantly improved memory functions in NSE/APP‐C105 mice. Conclusion Our findings strongly support that AR1001 has benefits against the accumulation of Ab and cognitive deficits in AD mouse models. We have demonstrated that AR1001 serves as a polypharmacological agent to inhibit PDE5 activity, promoting cell survival, and downregulate GR activity, reducing APP/BACE1 expression.