Icariside II, a Phosphodiesterase-5 inhibitor, attenuates beta-amyloid-induced cognitive deficits via BDNF/TrkB/CREB Signaling

Abstract

Background/Aims: Icariside II (ICS II) is an active component from Epimedium brevicornum, a Chinese medicine extensively used in China. Our previous study has proved that ICS II protects against learning and memory impairments and neuronal apoptosis in the hippocampus induced by beta-amyloid 25-35 (Aβ 25-35 ) in rats. However, its in-depth underlying mechanisms remain still unclear. Hence this study was designed to explore the potential underlying mechanisms of ICS II by experiments with an in vivo model of Aβ 25-35 -induced cognitive deficits in rats combined with a neuronal-like PC12 cells injury in vitro model. Methods: The cognitive deficits was measured using Morris water maze test, and apoptosis, intracellular reactive oxygen species (ROS) and mitochondrial ROS levels were detected by TUNEL, DCFH-DA and Mito-SOX staining, respectively. Expression of Bcl-2, Bax, brain derived neurotrophic factor (BDNF), tyrosine receptor kinase B (TrkB), and cAMP response element binding (p-CREB) and active-Caspase 3 levels were evaluated by Western blot. Results: It was found that ICS II, a phosphodiesterase-5 inhibitor, significantly attenuated cognitive deficits caused by Aβ 25-35 injection in rats, and ICS II not only significantly enhanced the expression of BDNF and TrkB, but also activated CREB. Furthermore, ICS II also significantly abrogated Aβ 25-35 -induced PC12 cell injury, and inhibited Aβ 25-35 -induced intracellular reactive oxygen species (ROS) overproduction, as well as mitochondrial ROS levels. In addition, ICS II up-regulated the expressions of BDNF and TrkB consistent with the findings in vivo. ANA-12, a TrkB inhibitor, blocked the neuroprotective effect of ICS II on Aβ 25-35 -induced neuronal injury. Conclusion: ICS II mitigates Aβ 25-35 -induced cognitive deficits and neuronal cell injury by upregulating the BDNF/TrkB/CREB signaling, suggesting that ICS II can be used as a potential therapeutic agent for dementia, such as Alzheimer's disease.