Neuroprotective effects of alkaline extract of Lycium barbarum on beta-amyloid peptide neurotoxicity

Abstract

Lycium barbarum is a Chinese medical herb that has long been used for its anti-aging and eye-protective properties. Our laboratory has reported that water-soluble extract from L. barbarum exhibits neuroprotective effects against β-amyloid (Aβ) peptide neurotoxicity. We hypothesize that water-soluble extract is not the only extract eliciting neuroprotection. Therefore, we have examined other fractions from different extraction methods. Primary cortical neurons were prepared from embryonic day-17 Sprague-Dawley (SD) rats. The release of lactate dehydrogenase (LDH) and activity of caspase-3 were determined for neurotoxicity. Pretreatment of alkaline extract of Lycium barbarum (LBB) significantly reduced the release of LDH and the activity of caspase-3 triggered by Aβ peptide. “Wash-out” procedures did not reduce its neuroprotective effects, suggesting that it is less likely for the extract to bind directly to Aβ peptide in preventing its interaction to cell membrane. Loss of the cytoprotective properties after acidification of the extract suggests that the glycoconjugates are the major effective components. The two sub-fractions of LBB also showed neuroprotective effects as indicated by the reduction of LDH release and the activity of caspase-3. Western blot analysis demonstrated that B1 and B2 sub-fractions enhanced the phosphorylation of Akt. Taken together, our results suggest that fractions of alkaline extraction from Lycium barbarum attenuate Aβ peptide neurotoxicity and may serve as neuroprotective agents against AD.