Chitooligosaccharides Protect Against Copper-Induced Damage in Cultured Rat Cortical Neurons By Attenuating Intracelluar Reactive Oxygen Species Level

Alzheimer's disease (AD) is the most common form of senile dementia, a progressive neurodegenerative disease. A large number of evidence has suggests that dyshomeostasis of the redox-active biometals, such as copper and other metal ions, would lead to oxidative stress damage in neurons. The accumulated Copper in the AD brains could result in pro-oxidative stress and increase free radical production, which plays a key role in the pathology of AD. Chitooligosaccharides (COSs) are biodegradation product of chitosan and demonstrate diversely biological bioactivities. To explore the neuroprotective effects of COSs againt copper ions toxicity associate with pathology of AD, here we first report that protective effects of COSs (M.W. 1500, DD.90%) against Cu(II)-induced neurotoxicity in primary cultured rat cortical neurons. Cortical neurons were cultured at 37 °C for 7days then incubated more for 12 hours in culture medium without or with 0.4, 0.2, and 0.1mg/ml COSs, respectively. After removed the culture medium and the cultured cortical neurons were added fresh culture medium containing 50μM CuCl2, incubated for 48 hours at 37 °C in a humidified incubator. Cell viability were assayed by MTT, Hoechst 33342 assay and lactate dehydrogenase (LDH) assay, and the reactive oxygen species(ROS) levels were detected byROS assay based on the ROS-mediated conversion of nonfluorescent 2',7'-DCFH-DA into fluorescent DCFH. The toxicity of Cu(II) to cortical neurons was obviously attenuated in a concentration-dependent manner by COSs. The data derived from the LDH and Hoechst 33342 assay support the results from MTT assay well. The following ROS assay indicated that COSs prevent Cu(II)-induced the elevation of intracellular ROS. These findings suggest that COSs protect against Cu(II) induced neurotoxicity in primary cortical neurons by interfering with an increase in intracellular ROS. It will be helpful to further develop the usages of COSs in AD treatment.