Roflumilast and tadalafil improve learning and memory deficits in intracerebroventricular Aβ1-42 rat model of Alzheimer's disease through modulations of hippocampal cAMP/cGMP/BDNF signaling pathway

Background Alzheimer's disease (AD) is the most prevalent age-dependent neurodegenerative disease characterized by progressive impairment of memory and cognitive functions. Cyclic nucleotides like cAMP and cGMP are well-known to play an important role in learning and memory functions. Enhancement of cAMP and cGMP levels in the hippocampus by phosphodiesterase (PDE) inhibitors might be a novel therapeutic approach for AD. Thus, the present study was planned to explore the therapeutic potential of roflumilast (RFM) and tadalafil (TDF) phosphodiesterase inhibitors in intracerebroventricular (ICV) A beta 1-42 induced AD in rats. Methods ICV A beta 1-42 was administered in rats followed by treatment with RFM (0.05 mg/kg) and TDF (0.51 mg/kg) for 15 days. Novel object recognition (NOR), and Morris water maze (MWM) test were performed during the drug treatment schedule. On the day, 22 rats were sacrificed, and hippocampus was separated for biochemical, neuroinflammation, and histopathological analysis. Results A beta 1-42 infused rats were induce behavioral impairment and increased AChE, BACE-1, A beta 1-42, GSK-3 beta, phosphorylated tau (p-Tau), pro-inflammatory cytokines (TNF-alpha, IL-1 beta, and IL-6) levels, oxidative stress (increased MDA, Nitrite and decreased GSH), histopathological changes, and reduced cAMP, cGMP, and BDNF levels. RFM and TDF significantly attenuated A beta 1-42 induced memory deficits and neuropathological alterations in the hippocampus. Conclusion The outcomes of the current study indicate that RFM and TDF lead to memory enhancement through upregulation of cAMP/cGMP/BDNF pathway, thus they may have a therapeutic potential in cognitive deficits associated with AD. Graphic abstract

Automated summary

The study explored the therapeutic potential of RFM and TDF phosphodiesterase inhibitors in treating AD induced by ICV Aβ1-42 in rats. RFM and TDF were found to significantly attenuate memory deficits and neuropathological alterations induced by Aβ1-42.