Neuroprotective polysaccharides from Nerium indicum rescue cultured neurons from beta-amyloid peptides-induced apoptosis via different mechanisms

Abstract

Most of the polysaccharides purified from Chinese medicinal herbs showed anti-tumor and immune-stimulating effects. However, little is known about their effects on neuroprotection. Our previous study has demonstrated that polysaccharides (J2, J3 and J4) isolated from the flowers of Nerium indicum (Oleander) exert partial protection in cortical neurons stressed by beta-amyloid (Aβ) peptides. In this study, we have isolated and characterized a new polysaccharide from the flowers of N. indicum (named as J6) and aimed to investigate its neuroprotective effects against Aβ-induced apoptosis. Pretreatment of the polysaccharide J6 significantly decreased the activity of caspase-3 as well as the cytotoxicity triggered by Aβ peptides in a dose-dependent manner. In contrast to the activation of survival signaling such as Akt found in J2, J3 and J4 fractions, the newly synthesized J6 markedly inhibited Aβ peptide-stimulated phosphorylation of c-Jun N-terminal kinase (JNK-1) as determined by western-blot analysis. Taken together, the polysaccharides isolated from the flowers of N. indicum can serve as potential neuroprotective agents against neuronal death in Alzheimer’s disease. The differences in neuroprotective mechanisms may due to the compositions of these polysaccharides; it would be investigated in the future study.