Chitooligosaccharides protect cultured hippocampal neurons against glutamate-induced neurotoxicity.

Chitooligosaccharides (COSs), the biodegradation product of chitosan, have demonstrated a diverse array of biological activities. Here we report the protective effect of COSs (M.W. 800) against glutamate-induced neurotoxicity in cultured hippocampal neurons. The cell viability assessments, together with Hoechst 33342 staining and flow cytometry for cell apoptosis analysis, indicated that glutamate (125 microM)-induced cell apoptosis in cultured hippocampal neurons was attenuated in a concentration-dependent manner by COSs pretreatment. After measurement with Fluo 4-AM, COSs were found to depress glutamate-induced elevation in intracellular calcium concentration (Ca(2+)). The enzymatic assay indicated that COSs antagonized glutamate-evoked activation of caspase-3. These results collectively suggest that COSs prevent cultured hippocampal neurons from glutamate-induced cell damage by interfering with an increase in Ca(2+) and inhibiting caspase-3 activity.