BACKGROUND: Paeonol is a primary phenolic component of the Chinese medicinal herb Cortex moutan. Recent studies have shown that paeonol has anti-inflammatory, analgesic, and antioxidative effects as well as a significant cardioprotective effect against myocardial ischemia.OBJECTIVE: To investigate the protective effect of paeonol on β-amyloid 25-35-induced toxicity in PC12 cells and analyze its mechanism of action.DESIGN, TIME AND SETTING: A controlled repeated-measures cell-based study was performed in the Department of Pharmacology of Guangdong Medical College between September 2006 and December 2007.MATERIALS: Paeonol was supplied by Xuancheng Baicao Plant Industry and Trade Company, China.PC12 cells were a kind girl from Dr. Haitao Zhang at Guangdong Medical College. Β-amyloid 25-35was purchased from Sigma Company, USA. Lactate dehydrogenase (LDH) and malondialdehyde (MDA)kits were purchased from Nanjing Jiancheng Bioengineering Research Institute, China.METHODS: PC12 cells were maintained in Dulbeccos modified eagles medium (DMEM) supplemented with 100 mL/L heat-inactivated horse serum and 50 mL/L fetal bovine serum at 37℃ and cultured in an incubator with 5% CO2. The medium was renewed every other day. Batches of cells were assigned into three groups. (1) Paeonol group: cells were preincubated with different concentrations of paeonol (12, 25or 50 μ mol/L) for one hour and β-amyloid 25-35 was added to the medium; (2) control group: cells were cultured in DMEM supplemented with 100 mL/L heat-inactivated horse serum and 50 mL/L fetal bovine serum; and (3) β-amyloid 25-35 group: β-amyloid 25-35 was added to the medium.MAIN OUTCOME MEASURES: When PC12 cells in each group were cultured for 24 hours, the cell viability was determined using the MTT reduction assay, LDH release into the culture media was measured by 2,4-dinitrophenylhydrazine chromatometry and MDA content was measured using a thiobarbituric acid assay.RESULTS: When PC12 cells were treated with β -amyloid 25-35 (50 μ mol/L) for 24 hours, their viability was significantly lower compared with the control group (P < 0.01). When the cells were treated with paeonol for one hour prior to incubation with β -amyloid 25-35, their viability was significantly increased compared with the β -amyloid 25-35 group (P < 0.05-0.01), LDH activity and MDA level in the β -amyloid 25-35 group were significantly increased compared with the control group (P < 0.01). When the cells were treated with different concentrations of paeonot, LDH activity and MDA level in PC12 cells were significantly decreased compared with the β-amyloid 25-35 group (P < 0.01).CONCLUSION: Paeonol protects PC12 cells against β-amyloid 25-35-induced toxicity and the protective effect of paeonol is probably achieved through its antioxidative effects.