Neuroprotective effects of icaritin against beta amyloid-induced neurotoxicity in primary cultured rat neuronal cells via estrogen-dependent pathway.

Beta-amyloid protein (Abeta) is the hallmark of pathogenic neurotoxins which contribute greatly to Alzheimer's disease (AD)-associated cascade including severe neuronal loss. In present study, icaritin, an active natural ingredient from a Chinese plant, Epimedium sagittatum maxim, was investigated to assess its neuroprotective effect against the toxicity induced with Abeta(25-35) in primary cultured rat cortical neuronal cells as well as the underlying mechanisms. Abeta(25-35) induced neuronal toxicity, characterized by decreased cell viability, lactate dehydrogenase (LDH) release, and neuronal DNA condensation, which is associated with both the loss of membrane potential and the alteration of the expression of Bcl-2 family proteins. The phenotype alternation induced by Abeta(25-35) could be reversed by icaritin. Furthermore, the neuroprotective effects of icaritin mentioned above were estrogen receptor dependent due to the blocking action induced by estrogen receptor antagonist ICI 182,780 and well matched binding affinity with estrogen receptor by a receptor-ligand docking experiment. mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor PD98059 weakened the protective effects, which implied mitogen-activated protein kinase/extracellular signal-regulated kinase pathway may also be involved in and partly contributed to the neuroprotective effects of icaritin.