Neuroprotective effects of salidroside against beta-amyloid-induced oxidative stress in SH-SY5Y human neuroblastoma cells

Beta-amyloid (Aβ) peptide, the hallmark of Alzheimer's disease (AD), invokes a cascade of oxidative damages to neurons and eventually leads to neuronal death. In this study, salidroside (Sald), an active compound isolated from a traditional Chinese medicinal plant, Rhodiola rosea L., was investigated to assess its protective effects and the underlying mechanisms against Aβ-induced oxidative stress in SH-SY5Y human neuroblastoma cells. Aβ25–35-induced neuronal toxicity was characterized by the decrease of cell viability, the release of lactate dehydrogenase (LDH), morphological alterations, neuronal DNA condensation, and the cleavage of poly(ADP-ribose) polymerase (PARP) by activated caspase-3. Pretreatment with salidroside markedly attenuated Aβ25–35-induced loss of cell viability and apoptosis in a dose-dependent manner. The mechanisms of salidroside protected neurons from oxidative stress included the induction of antioxidant enzymes, thioredoxin (Trx), heme oxygenase-1 (HO-1), and peroxiredoxin-I (PrxI); the downregulation of pro-apoptotic protein Bax and the upregulation of anti-apoptotic protein Bcl-XL. Furthermore, salidroside dose-dependently restored Aβ25–35-induced loss of mitochondrial membrane potential (MMP) as well as suppressed the elevation of intracellular reactive oxygen species (ROS) level. It was also observed that Aβ25–35 stimulated the phosphorylation of mitogen-activated protein (MAP) kinases, including c-Jun NH2-terminal kinase (JNK) and p38 MAP kinase, but not extracellular signal-regulated kinase1/2 (ERK1/2). Salidroside inhibited Aβ25–35-induced phosphorylation of JNK and p38 MAP kinase, but not ERK1/2. These results suggest that salidroside has protective effects against Aβ25–35-induced oxidative stress, which might be a potential therapeutic agent for treating or preventing neurodegenerative diseases.