Cytoprotective effects of Lycium barbarum on cultured neurons against reducing stress on the endoplasmic reticulum

Abstract

Lycium barbarum is a commonly used Chinese medicinal herb for nourishment of the eyes, liver and kidney. Studies have shown that extracts from L. barbarum process anti-aging and cytoprotective activities. Its extracts have been demonstrated to exhibit anti-oxidative effects in which oxidative stress is considered to contribute to aging processes. Many studies, therefore, explain the protective effects of L. barbarum as a result of its anti-oxidative activities. In this study, we demonstrated that L. barbarum is not solely an anti-oxidant. We used dithiothreitol (DTT) as reducing agent to trigger reducing stress in primary cultured neurons and in human neuroblastoma SH-SY5Y cell line. We found that extracts of L. barbarum (LBG) exerted cytoprotective effects on both types of cells by lowering the DTT-induced LDH release and activation of caspase-3. DTT is a well-known endoplasmic reticulum (ER)-stress inducer and can cause PKR-like ER kinase (PERK) activation. We found that LBG significantly attenuated the level of DTT-induced phosphor-PERK in primary neuronal cultures. Taken together, our study shows that L. barbarum can exhibit cytoprotective effects against reducing stress on the ER and is therefore not simply an antioxidant. Acknowledgement: This work is partly supported by HKU Strategic Research Theme on Healthy Aging, and HKU Seed Funding for Basic Research (2004–2005) to R.C.C.C.