The neuroprotective effects of tanshinone IIA on β-amyloid-induced toxicity in rat cortical neurons

Oxidative stress caused by amyloid β-peptide (Aβ) may play an important role in the pathogenesis of Alzheimer disease (AD). Aβ is known to be directly responsible for the production of reactive oxygen species (ROS) and induction of apoptosis. Tanshinone IIA (Tan IIA) is extracted from a traditional herbal medicine Salvia miltiorrhiza BUNGE, which has been shown to protect against oxidative stress and cell death. In this study, we investigated the neuroprotective effect of Tan IIA against Aβ_25-35-induced cell death in cultured cortical neurons. Exposure of cortical neurons to 30μM Aβ_25-35 caused a significant viability loss, cell apoptosis and decreased activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) as well as increased levels of malondialdehyde (MDA) production. In parallel, Aβ_25-35 significant increased the intracellular ROS elevation and decreased mitochondrial membrane potential (MMP). However, pretreatment of the cells with Tan IIA prior to Aβ_25-35 exposure suppressed these Aβ_25-35-induced cellular events noticeably. In addition, Tan IIA reduced the Aβ_25-35-induced increase of caspase-3 activity, and reduced cytochrome c translocation into the cytosol from mitochondria. Furthermore, Tan IIA also ameliorated the Aβ_25-35-induced Bcl-2/Bax ratio reduction in cortical neurons. Taken together, these data indicate that Tan IIA protected cultured cortical neurons against Aβ_25-35-induced neurotoxicity through its antioxidative potential. Our results strongly suggest that Tan IIA may be effective in treating AD associated with oxidative stress.