Xanthoceraside attenuates amyloid β peptide_25–35-induced learning and memory impairments in mice

In Alzheimer's disease (AD), the deposition of amyloid peptides is invariably associated with oxidative stress and inflammatory responses. Xanthoceraside has anti-inflammatory and antioxidative activities. However, it remains unclear whether xanthoceraside improves amyloid beta (A beta)-induced neurotoxicity. The purpose of this study was to examine the effect of xanthoceraside on behavioral impairments, inflammatory responses, and oxidative stress induced by A beta peptide(25-35) (A beta(25-35)) in mice. The mice were treated orally with xanthoceraside (0.02, 0.08, or 0.32 mg/kg, once daily) after the intracerebroventricular injection of A beta(25-35) (day 0). Cognitive functions were evaluated in Y-maze (day 6) and novel object recognition tests (days 7 and 8). Inducible nitric oxide synthase (iNOS) and nitrotyrosine levels in the hippocampus were examined (day 9). The mRNA expressions of iNOS and interleukin-4 (IL-4) in the hippocampus were measured 2 h and 3 days after the A beta(25-35) injection by real-time reverse transcription-polymerase chain reaction. Xanthoceraside significantly attenuated behavioral impairments induced by A beta(25-35) in the Y-maze and novel object recognition tests. Repeated treatment with xanthoceraside significantly inhibited the increase in the expression of iNOS and nitrotyrosine in the hippocampus induced by A beta(25-35), which is associated with an enhanced expression of the IL-4 mRNA. These findings suggest that xanthoceraside attenuates memory impairments through amelioration of oxidative stress and inflammatory responses induced by A beta(25-35) and is a potential candidate for an AD treatment.